Process for the preparation of a cross-linked hydrogel

0001The present invention relates to a simplified process for the esterification of unsaturated acids with polyalcohols and use of the reaction mixtures thus obtainable.

0002Swellable hydrogel-forming polymers, so-called superabsorbents (SAP), are known from the prior art. These are networks of flexible hydrophilic polymers, which can be both ionic and nonionic in nature. These are able to absorb and bind aqueous liquids with the formation of a hydrogel and are therefore preferred for the production of tampons, diapers, sanitary napkins, incontinence articles, training underwear for children, shoe inserts and other hygiene articles in the absorption of body fluids. Superabsorbers are also used in other areas of technology in which liquids, in particular water or aqueous solutions, are absorbed. These areas are, for example, storage, packaging, transport (packaging material for water-sensitive articles such as Flower transport, shock protection); Food sector (transportation of fish, fresh meat; absorption of water, blood in fresh fish / meat packaging); Medicine (wound plasters, water-absorbent material for burn dressings or for other wetting wounds), cosmetics (carrier material for pharmaceutical chemicals and medicines, rheumatic plasters, ultrasound gel, cooling gel, cosmetic thickener, sun protection); Thickener for oil / water or Water / oil emulsions; Textiles (gloves, sports clothing, moisture regulation in textiles, shoe inserts); chemical-technical Applications (catalyst for org. Reactions, immobilization of large functional molecules (enzymes), adhesive for agglomerations, heat storage, filtration aids, hydrophilic component in polymer laminates, dispersants, plasticizers); Building and construction, installation (powder injection molding, clay-based plasters, vibration-inhibiting medium, tools for tunnel excavations in water-rich subsoil, cable sheathing); Water treatment, waste treatment, water separation (de-icing agents, reusable sandbags); Cleaning; Agricultural industry (irrigation, retention of melt water and dew precipitation, composting additive, protection of the forests from fungal / insect attack, delayed release of active substances in plants); in fire protection (flying sparks) (covering houses or Covering house walls with SAP Gel, since the water has a very high heat capacity, can prevent ignition; Spraying SAP gel in case of fires such as forest fires); Coextrusion agents in thermoplastic polymers (hydrophilization of multilayer films); Production of foils and thermoplastic molded articles that can absorb water (e.g. Films for rain and condensation water for agriculture); Films containing SAP for keeping fruit and vegetables fresh, which can be packed in moist films; the SAP stores water released from the fruit and vegetables without the formation of condensation drops and partially releases the water back to the fruit and vegetables, so that neither rotting nor withering occurs; SAP polystyrene coextrudates e.g. for food packaging such as meat, fish, poultry, fruit and vegetables); Carrier substance in active ingredient formulations (pharmaceuticals, crop protection). The superabsorbents are usually located in the so-called. absorbent core, which includes, among other materials, fibers (cellulose fibers) which, as a kind of liquid reservoir, temporarily store the spontaneously applied amounts of liquid and ensure good drainage of body fluids in the absorbent core to the superabsorbent.

0003The current trend in diaper construction is to produce thinner constructions with a reduced proportion of cellulose fibers and an increased proportion of hydrogel. With the trend towards ever thinner diaper constructions, the requirement profile for the water-swellable hydrophilic polymers has changed significantly over the years. While the very high swelling capacity was initially the focus at the beginning of the development of highly absorbent hydrogels, it was later shown that the ability of the superabsorbent to transfer and distribute liquids is also of crucial importance. It has been shown that conventional superabsorbents swell strongly on the surface when wetted with liquid, so that the liquid transport into the interior of the particle is made very difficult or is completely prevented. This peculiarity of the superabsorbent is also referred to as "gel blocking". Due to the higher loading of the hygiene article (polymer per unit area), the polymer must not form a barrier layer for subsequent liquid when swollen. If the product has good transport properties, optimal use of the entire hygiene article can be guaranteed. The phenomenon of gel blocking is thus prevented, which in extreme cases leads to the escape of the liquid, the so-called Leakage of the hygiene article leads. Fluid transfer and distribution is therefore critical in the initial absorption of body fluids.

0004Hydrogels, for example, have good transport properties and, when swollen, have a high gel strength. Gels with only low gel strength can be deformed under an applied pressure (body pressure), clog pores in the superabsorbent / cellulose fiber absorbent body and thereby prevent further fluid absorption. Increased gel strength is generally achieved through higher crosslinking, which, however, reduces the retention of the product. Surface post-crosslinking is an elegant method of increasing gel strength. In this process, dried superabsorbers with average crosslinking density are subjected to additional crosslinking. The surface postcrosslinking increases the crosslinking density in the shell of the superabsorbent particles, as a result of which the absorption under pressure is raised to a higher level. While the absorption capacity in the superabsorbent shell decreases, the core of the superabsorbent particles has an improved absorption capacity compared to the shell due to the presence of movable polymer chains, so that the shell structure ensures improved liquid transmission without the effect of gel blocking occurring. It is entirely desirable that the total capacity of the superabsorbent is not used spontaneously, but rather with a time delay. Since urine is usually applied to the hygiene article several times, the absorption capacity of the superabsorbent does not need to be exhausted after the first disposition.

0005Hydrophilic, highly swellable hydrogels are in particular polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethyl cellulose, partially crosslinked polyalkylene oxide or natural products which are swellable in aqueous liquids, such as guar derivatives. Such hydrogels are used as products absorbing aqueous solutions for the production of diapers, tampons, sanitary napkins and other hygiene articles, but also as water-retaining agents in agricultural horticulture.

0006In order to improve the application properties, such as Rewet in the diaper and AUL, hydrophilic, highly swellable hydrogels are generally surface or gel crosslinked. This postcrosslinking is known per se to the person skilled in the art and is preferably carried out in the aqueous gel phase or as surface postcrosslinking of the ground and sieved polymer particles.

0007Out <patcit id="pcit0001" dnum="WO9321237A"><text>WO 93/21237</text></patcit> are (meth) acrylates of alkoxylated polyvalent C₂ - C₁₀-Hydrocarbons known as crosslinkers. These can be used as mixtures with by-products from the manufacturing process.

0008A disadvantage of these compounds is that complex cleaning operations are required for at least partial separation of starting materials and by-products - the crosslinking agents used in the document mentioned have an acrylic acid content of less than 0.1% by weight.

0009The production of such higher (meth) acrylic acid esters by acid-catalyzed esterification of (meth) acrylic acid with the corresponding alcohols in the presence of an inhibitor / inhibitor system and, if appropriate, a solvent, such as benzene, toluene, cyclohexane, is generally known.

0010Since, as is well known, the formation of the ester from (meth) acrylic acid and alcohol is based on an equilibrium reaction, in order to achieve economic conversions, an input material is generally used in excess and / or the esterification water formed and / or the target ester are removed from the equilibrium.

0011Therefore, in the preparation of the higher (meth) acrylic acid esters, the water of reaction is generally removed and an excess of (meth) acrylic acid is usually used.

0012<patcit id="pcit0002" dnum="US4187383A"><text>US 4 187 383</text></patcit> describes an esterification process of (meth) acrylic acid with organic polyols at a reaction temperature of 20 to 80 ° C with an equivalent excess of 2 to 3: 1.

0013A disadvantage of this process is that the low reaction temperature means that the reaction times are up to 35 hours and the excess acid in the reaction mixture is removed by neutralization with subsequent phase separation.

0014<patcit id="pcit0003" dnum="WO200114438A"><text>WO 2001/14438</text></patcit> (<nplcit id="ncit0001" npl-type="d"><text>Derwent Abstract No. 2001-191644 / 19</text></nplcit>) and <patcit id="pcit0004" dnum="WO200110920A"><text>WO 2001/10920</text></patcit> (<nplcit id="ncit0002" npl-type="c"><text>Chemical Abstracts 134: 163502</text></nplcit>) describe processes for the esterification of (meth) acrylic acid with polyalkylene glycol monoalkyl ethers in a ratio of 3: 1 - 50: 1 in the presence of acids and polymerization inhibitors and, after deactivation of the acid catalyst, copolymerization of the residue from (meth) acrylic acid ester and (meth) acrylic acid at pH 1.5 - 3.5, and its use as a cement additive.

0015A disadvantage of this process is that it is limited to polyalkylene glycol monoalkyl ethers, that the catalyst has to be deactivated and that such copolymers cannot be used as crosslinking agents for hydrogels since they only have one functionality.

0016The object was to simplify the production process for substances which can be used as radical crosslinkers for superabsorbers.

0017The object is achieved by a method for producing an ester F of a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B, comprising the steps<ul id="ul0001" list-style="none" compact="compact"><li>a) reacting a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D and, if appropriate, a solvent E which forms an azeotrope with water to form an ester F,</li><li>b) optionally removing at least part of the water formed in a) from the reaction mixture, it being possible for b) to take place during and / or after a),</li><li>f) optionally neutralizing the reaction mixture,</li><li>h) if a solvent E was used, optionally removing this solvent by distillation and / or</li><li>i) stripping with a gas which is inert under the reaction conditions, where<ul id="ul0002" list-style="dash" compact="compact"><li>the polyalcohol A has at least two hydroxyl functions,</li><li>the molar excess of the ethylenically unsaturated carboxylic acid B to the polyalcohol A per hydroxyl group to be esterified in A is at least 1.05: 1 and</li><li>the optionally neutralized carboxylic acid B contained in the reaction mixture obtained after the last step essentially remains in the reaction mixture.</li></ul></li></ul>

0018The molar excess of B to A (depending on the hydroxyl group to be esterified in polyalcohol A) is at least 1.05: 1, preferably at least 1.1: 1, particularly preferably at least 1.25: 1, very particularly preferably at least 1.5: 1 and in particular at least 2.5: 1.

0019In a preferred embodiment, B is in an excess of, for example, greater than 5: 1, preferably greater than 10: 1, particularly preferably greater than 20: 1, very particularly preferably greater than 50: 1, in particular greater than 75: 1 and especially greater than 100 : 1 used.

0020The esterification products thus obtainable can be used as radical crosslinkers in hydrogels essentially without further purification, in particular without substantial removal of the excess of carboxylic acid B and the content of esterification catalyst C.

0021Unless otherwise stated, crosslinking in this document means radical crosslinking (gel crosslinking, internal crosslinking, crosslinking of linear or weakly crosslinked polymer). This crosslinking can take place via free-radical or cationic polymerization mechanisms or other, for example Michael addition, transesterification or transesterification mechanisms, preferably by free-radical polymerization.

0022Aqueous liquid-absorbing hydrogel-forming polymers are preferably those with an absorption of distilled water of at least their own weight, preferably 10 times their own weight, this absorption is preferably also achieved under a pressure of 0.7 psi.

0023Polyalcohols A which can be used according to the invention are compounds which have at least two hydroxyl functions (—OH), preferably at least three, particularly preferably three to ten, very particularly preferably three to six and in particular three to four.

0024The polyalcohols can be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted with functional groups.

0025As a rule, the polyalcohols have two to 50 carbon atoms and preferably three to 40.

0026Unless stated otherwise, the molecular weight of the polyalcohols which can be used is generally less than 5000 g / mol, preferably less than 2500 g / mol, particularly preferably less than 1500 g / mol, very particularly preferably less than 1000 g / mol and in particular less than 800 g / mol.

0027Preferred polyalcohols A are polyols, functionalized polyols, alkoxylated polyols, sugar alcohols, partially alkoxylated sugar alcohols, polyetherols, polyesterols, at least partially alkoxylated polyesterols and at least partially saponified, alkoxylated polyesterols.

0028Examples of polyols are trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, pentaerythritol, glycerol, 1,2-ethylene glycol, 1,2-propylene glycol, 2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, Hydroquinone, bisphenol A, bisphenol F, bisphenol B, 2,2-bis (4-hydroxycyclohexyl) propane, 1,1-, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 1,2-, 1 , 3- or 1,4-cyclohexanediol, but-2-ene-1,4-diol and but-2-in-1,4-diol.

0029The polyols can also carry additional functionalities such as ether functions (-O-), carboxyl functions (-COOH) or C.₁-C₄-Alkyloxycarbonyl functions (ester groups), where C₁-C₄Alkyl in this document means methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl or tert-butyl.

0030Examples of such functionalized polyols are ditrimethylolpropane, dipentaerythritol, dimethylolpropionic acid, dimethylolbutyric acid, trimethylolacetic acid, hydroxypivalic acid and the 2-hydroxyethyl or C₁-C₄-Alkyl esters of these acids. Preferred polyols are those of the formula (I):<chemistry id="chem0001" num="0001"><img file="EP1516010B1_D0001.tif" /></chemistry>

0031Mean in it<dl id="dl0001" compact="compact"><dt>R¹, R²</dt><dd>independently of one another hydrogen, C₁ - C₁₀Alkyl, preferably C₁ - C₄-Alkyl, C₁ - C₁₀-Hydroxyalkyl, preferably hydroxy-C₁ - C₄-Alkyl, carboxyl or C₁ - C₄-Alkyloxy-carbonyl, preferably hydrogen, hydroxymethyl and C₁ - C₄-Alkyl and particularly preferably hydroxymethyl and C₁ - C₄-Alkyl.</dd></dl>

0032The alkyl radicals can each be straight-chain or branched.

0033Examples of R¹ and R² are hydrogen, methyl, ethyl, <i>iso</i>Propyl, n-propyl, n-butyl, <i>iso</i>-Butyl, sec-butyl, <i>tert</i>-Butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, hydroxymethyl, carboxyl, methoxycarbonyl, ethoxycarbonyl or n-butoxycarbonyl, preferably hydrogen, hydroxymethyl, methyl and ethyl, particularly preferably hydroxymethyl, methyl and Ethyl.

0034Particularly preferred polyhydric alcohols of the formula (I) are trimethylolbutane, trimethylolpropane, trimethylolethane, neopentylglycol, pentaerythritol, 2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-propanediol, dimethylolpropionic acid, dimethylolpropionic acid methyl ester, Dimethylolpropionic acid ethyl ester, dimethylolbutyric acid, dimethylolbutyric acid methyl ester or dimethylolbutyric acid ethyl ester, neopentyl glycol, trimethylol propane, pentaerythritol and dimethylol propionic acid are preferred, neopentyl glycol, trimethylolpropane and pentaerythritol and in particular trimethylolpropane and pentaerythritol are very particularly preferred.

0035Examples of sugar alcohols are sorbitol, mannitol, maltitol, isomalt, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol and dulcitol (galactitol).

0036Examples of polyetherols are poly-THF with a molecular weight between 162 and 2000, preferably between 162 and 1458, particularly preferably between 162 and 1098, very particularly preferably between 162 and 738 and in particular between 162 and 378, poly-1,3-propanediol and Poly-1,2-propanediol with a molecular weight between 134 and 1178, preferably between 134 and 888, particularly preferably between 134 and 598 and very particularly preferably between 134 and 308, Polyethylene glycol with a molecular weight between 106 and 898, preferably between 106 and 458, particularly preferably from 106 to 400, very particularly preferably between 106 and 235 and in particular diethylene glycol, triethylene glycol and tetraethylene glycol.

0037Examples of suitable polyesterols are those which can be prepared by esterifying polycarboxylic acids, preferably dicarboxylic acids, with the abovementioned polyols.

0038The starting materials for such polyesterols are known to the person skilled in the art. Preferably can be used as polycarboxylic acids, oxalic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid or tetrahydrophthalic acid, their isomers and hydrogenation products, and esterifiable derivatives, such as anhydrides or dialkyl esters, for example C₁-C₄Alkyl esters, preferably methyl, ethyl or n-butyl esters, of the acids mentioned.

0039Suitable hydroxyl-bearing carboxylic acids or lactones are 4-hydroxybenzoic acid, 6-hydroxy-2-naphthalic acid, pivalolactone or ε-caprolactone. Suitable polyols are the above-mentioned polyfunctional alcohols, preferably neopentyl glycol, trimethylolpropane, trimethylolethane, pentaerythritol, dimethylolpropionic acid or dimethylolbutyric acid.

0040Preferred examples of such polyesterols are those of the formula (IIIa-c)<chemistry id="chem0002" num="0002"><img file="EP1516010B1_D0002.tif" /></chemistry>wherein<dl id="dl0002"><dt>R¹, R²</dt><dd>have the meanings given above and</dd><dt>Y</dt><dd>a straight-chain or branched, optionally substituted alkylene group having 2 to 20 carbon atoms or an optionally substituted cycloalkylene or arylene group having 6 to 12 carbon atoms or a single bond</dd></dl>mean.

0041Examples of Y are a single bond, methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, cis-1,2 -Ethenylene, trans-1,2-ethenylene, 1,2-, 1,3- or 1,4-phenylene, 1,2-cyclohex-1-enylene, 1,2-, 1,3- or 1,4 -Cyclohexylene, 4-carboxy-1,2-phenylene, 2-carboxy-1,4-phenylene or 1-carboxy-2,4-phenylene.

0042Preferred groups Y are 1,2-ethylene, 1,4-butylene and 1,2-, 1,3-or 1,4-phenylene.

0043Of course, due to the production process, there are usually mixtures in which lower and higher oligomers can also be present.

0044In a further preferred embodiment, reaction mixtures of at least partially saponified polyesterols are used as polyalcohols A for the preparation of the ester F.

0045For this purpose, the polyesterols described above, for example, are at least partially saponified with a suitable base and then, if appropriate after separating off the basic constituents remaining in the reaction mixture, esterified with the carboxylic acid B.

0046Suitable bases are, for example, NaOH, KOH, Ca (OH)₂, Milk of lime, na₂CO₃ or K₂CO₃, for example as a solid, solution or suspension, preferably in the form of a 10-50% strength by weight solution, particularly preferably in the form of a 20-40% strength by weight aqueous solution.

0047The saponification, ie the cleavage of the ester groups contained in the polyesterol, is carried out, for example, at least 10% based on the ester groups in the starting compound, preferably at least 25%, particularly preferably at least 50%, very particularly preferably at least 75% and in particular at least 90%.

0048If basic constituents, such as, for example, the basic salt of the carboxylic acid, are to be removed from the reaction mixture, this can be done, for example, via ion exchangers, for example acidic or strongly acidic ion exchangers.

0049The reaction mixture is then acidified and esterified with the carboxylic acid B as described.

0050Polyester (meth) acrylates can be in several stages or in one stage, such as in <patcit id="pcit0005" dnum="EP279303A"><text>EP-A 279 303</text></patcit> described, can be prepared from (meth) acrylic acid, polycarboxylic acid and polyol.

0051Also usable as polyalcohols are alkoxylated polyols and polyesterols which can be obtained by reacting a polyol or polesterol with at least one alkylene oxide.

0052Reaction mixtures containing such compounds of the formula VII can also be prepared according to the invention.         R⁸- (O (CH (R¹⁰) CH (R¹⁰)O)_y-C (= O) -R⁹)_x     (VII), wherein<dl id="dl0003" compact="compact"><dt>R⁸</dt><dd>a polyvalent, straight chain or branched C₂-C₁₀-Alkyl radical,</dd><dt>R⁹</dt><dd>independently of one another a straight-chain or branched C₂-C₁₀Alkenyl radical,</dd><dt>R¹⁰</dt><dd>independently of one another hydrogen or methyl,</dd><dt>x</dt><dd>independently a positive integer of 2 or greater and</dd><dt>y</dt><dd>is independently a number from 3 to 8 for x = 2 and a number from 2 to 7 for x = 3 or greater.</dd></dl>

0053The underlying alcohol to be esterified has the formula VIIa         R⁸- (O (CH (R¹⁰) CH (R¹⁰)O)_y-H)_x     (VIIa), where R⁸, R¹⁰, x and y are as defined above.

0054The compounds of the formula (VII) are generally polyhydric alcohols VIIa which have 2 to 10 carbon atoms and are alkoxylated with between 2 and 8 alkylene oxide units per hydroxyl group and whose terminal hydroxyl group in each alkylene oxide chain is esterified with an unsaturated carboxylic acid or its ester having 2 to 10 carbon atoms is. The starting alcohol is preferably a polyhydric alcohol having 3 to 6 carbon atoms and preferably carrying 2 to 4 hydroxyl groups. The starting alcohol is particularly preferably trimethylolpropane, glycerol, pentaerythritol, 1,3-propanediol, propylene glycol, 1,4-butanediol or butylene glycol. Trimethylolpropane, glycerol and pentaerythritol are very particularly preferred as starting alcohol.

0055Suitable alkylene oxides are, for example, ethylene oxide, propylene oxide, isobutylene oxide, vinyloxirane and / or styrene oxide.

0056The alkylene oxide chain can preferably be composed of ethylene oxide, propylene oxide and / or butylene oxide units. Such a chain can be composed of a species of an alkylene oxide or a mixture of alkylene oxides. If a mixture is used, the different alkylene oxide units can be present statistically or as blocks or blocks of individual species. Preferred alkylene oxide is ethylene oxide, propylene oxide or a mixture thereof, particularly preferred is ethylene oxide or propylene oxide and very particularly preferably ethylene oxide. Thus, a radical R is preferred¹⁰ per alkylene oxide unit is hydrogen and the other is methyl or hydrogen, both radicals R being particularly preferred¹⁰ Hydrogen.

0057The preferred number of alkylene oxide units in each chain is dependent on the number of chains.

0058The esterifying agent is a straight-chain or branched ethylenically unsaturated carboxylic acid or its esters having 2 to 10 carbon atoms, preferably an ethylenically unsaturated carboxylic acid having 2 to 4 and particularly preferably a 2 to 3 carbon atoms, very particularly preferably acrylic acid, methacrylic acid or their esters, in particular acrylic acid .

0059The compounds of the formula VII are frequently present as a mixture of compounds which are described by this formula and by-products of the production process.

0060Among these compounds VII, particular preference is given to the hydroxyl groups up to six times, particularly preferably the up to four times and very particularly preferably the four times ethoxylated compounds, hereinafter referred to as compounds VIIb. These have increased hydrolysis stability.

0061Compounds VII, each per hydroxyl group, are equally preferred<ul id="ul0003" list-style="dash" compact="compact"><li>for x = 2 more than eight times, particularly preferably more than ten times, very particularly preferably more than twelve times and in particular at least 15 times, respectively</li><li>for x = 3 or greater than seven times, particularly preferably more than nine times, very particularly preferably more than twelve times and in particular at least 15 times ethoxylated, hereinafter referred to as compounds VIIc, since these generally have an increased solubility in water.</li></ul>

0062Compounds VII are also conceivable in which values ​​of 0, 1 or 2 can assume values ​​for x = 2 y and values ​​of 0 or 1 for x = 3 y.

0063Mixtures of the compounds VIIb and VIIc are particularly advantageous, for example those with a weight ratio VIIb: VIIc of 10:90 to 90:10, preferably 20:80 to 80:20, particularly preferably 30:70 to 70:30 and very particularly preferably from 40:60 to 60:40.

0064Preferred examples of such alkoxylated polyols are the alkoxylation products (IIa), (IIb) or (IIc) of polyols of the formula (I),<chemistry id="chem0003" num="0003"><img file="EP1516010B1_D0003.tif" /></chemistry>wherein<dl id="dl0004"><dt>R¹, R²</dt><dd>have the meanings given above,</dd><dt>k, l, m, q</dt><dd>independently of one another each represent an integer from 1 to 10, preferably 1 to 5, particularly preferably 3 to 5 and in particular 4 and</dd><dt>every X_i</dt><dd>for i = 1 to k, 1 to l, 1 to m and 1 to q can be selected independently of one another from the group - CH_2-CH_2-O-, -CH_2-CH (CH₃) -O-, -CH (CH₃) -CH_2-O-, -CH_2-C (CH₃)_2-O-, -C (CH₃)_2-CH₂-O-, -CH_2-CHVin-O-, -CHVin-CH_2-O-, -CH_2-CHPh-O- and -CHPh-CH_2-O-, preferably from the group -CH_2-CH_2-O-, -CH_2-CH (CH₃) -O- and -CH (CH₃) -CH_2-O-, and particularly preferably -CH_2-CH_2-O-,</dd></dl>where Ph is phenyl and Vin is vinyl.

0065These are preferably one to five times, particularly preferably three to five times and very particularly preferably four times ethoxylated, propoxylated or mixed ethoxylated and propoxylated and in particular exclusively ethoxylated neopentyl glycol, trimethylolpropane, trimethylolethane or pentaerythritol.

0066Of these, particularly preferred are those polyhydric alcohols of the formula (IIb).

0067Equally preferred is one to 20 times, preferably one to ten times, particularly preferably two to ten times, very particularly preferably two to five times, in particular three to five times and especially three to four times alkoxylated, preferably ethoxylated, propoxylated or mixed-ethoxylated-propoxylated and particularly preferred ethoxylated glycerin (calculated here in exceptional cases in mol of alkoxy groups per mol of glycerol).

0068The degrees of alkoxylation given relate in each case to the average degree of alkoxylation.

0069The number average molecular weight M_n the alkoxylated polyols is preferably not more than 1000 g / mol, particularly preferably not more than 800 g / mol and very particularly preferably not more than 550 g / mol.

0070The information on the number average and weight average molecular weight M_n and M_w refer here to gel permeation chromatography measurements, using polystyrene as the standard and tetrahydrofuran as the eluent. The method is in<nplcit id="ncit0003" npl-type="b"><text>Analytiker Taschenbuch Vol. 4, pages 433 to 442, Berlin 1984</text></nplcit> described.

0071Examples of alkoxylated sugar alcohols are those compounds which can be obtained from sugar alcohols, for example from the sugar alcohols listed above, by alkoxylation, for example with the alkylene oxides listed above, preferably with ethylene oxide and / or propylene oxide and very particularly preferably with ethylene oxide.

Examples of this are

0072<ul id="ul0004" list-style="dash"><li>the tetrols listed, which are on average 2 to 30 times, preferably 2 to 20 times, particularly preferably 3 to 10 times and in particular 3, 4, 5, 6, 7 or 8 times alkoxylated per mol of sugar alcohol,</li><li>the pentols listed, which are on average 3 to 35 times, preferably 3 to 28 times, particularly preferably 4 to 20 times and in particular 4, 5, 6, 7, 8, 9 or 10 times alkoxylated per mole of sugar alcohol,</li><li>Higher sugar alcohols, which on average are alkoxylated 4-50 times, preferably 6-40 times, particularly preferably 7-30 times, very particularly preferably 8-20 times and in particular 10-15 times per mole of sugar alcohol.</li></ul>

0073Preferred alkoxylated sugar alcohols are those in which at least one hydroxyl group of the sugar alcohol is not alkoxylated.

0074Preferred examples of alkoxylated polesterols are those of the formula (IVa-c)<chemistry id="chem0004" num="0004"><img file="EP1516010B1_D0004.tif" /></chemistry>wherein<dl id="dl0005" compact="compact"><dt>R¹, R², Y</dt><dd>have the meanings given above,</dd><dt>k, l, m, q, r, s</dt><dd>independently of one another each represent an integer from 1 to 30, preferably 1 to 20, particularly preferably 1 to 10 and in particular 1 to 5 and</dd><dt>every X_i</dt><dd>for i = 1 to k, 1 to l, 1 to m, 1 to q, 1 to r and 1 to s can be selected independently of one another from the group -CH_2-CH₂-O-, -CH_2-CH (CH₃) -O-, -CH (CH₃) -CH_2-O-, -CH_2-C (CH₃)₂-O-, -C (CH₃)_2-CH_2-O-, -CH_2-CHVin-O-, -CHVin-CH_2-O-, -CH_2-CHPh-O- and -CHPh-CH_2-O-, preferably from the group -CH_2-CH_2-O-, -CH_2-CH (CH₃) -O- and -CH (CH₃) -CH_2-O-, and particularly preferably -CH_2-CH_2-O-,</dd></dl>where Ph is phenyl and Vin is vinyl, mean.

0075These are preferably unalkoxylated or one to ten times, particularly preferably two to five times ethoxylated, propoxylated or mixed ethoxylated and propoxylated neopentyl glycol, trimethylolpropane, trimethylolethane or pentaerythritol enhanced with adipic acid, phthalic acid, terephthalic acid or isophthalic acid.

0076The reaction of the alcohols with an alkylene oxide is known per se to the person skilled in the art. Possible implementation forms can be found in<nplcit id="ncit0004" npl-type="b"><text>Houben-Weyl, Methods of Organic Chemistry, 4th edition, 1979, Thieme Verlag Stuttgart, ed. Heinz Kropf, Volume 6 / 1a, Part 1, pages 373 to 385</text></nplcit>.

0077If mixed alkoxylated alcohols are used, the different alkoxy groups contained therein can be in a molar ratio of, for example, 0.05-20: 1, preferably 0.1-10: 1 and particularly preferably 0.2-5: 1.

0078No particular demands are placed on the viscosity of the polyalcohols which can be used according to the invention, except that they should be able to be pumped without problems at a temperature of up to approximately 80 ° C., they should preferably have a viscosity below 1000 mPas, preferably below 800 mPas and very particularly preferably below 500 mPas.

0079If trihydric or higher polyalcohols are used as the polyalcohols in the esterification, it can be advantageous for their use according to the invention as radical crosslinking agents to merely partially esterify the polyalcohols. This means that in the case of an n-valent polyalcohol only at least 2 of the n hydroxyl groups are esterified with the carboxylic acid B.

0080For n = 3 the degree of esterification is at least 2, for n = 4 at least 2, preferably at least 2.5 and particularly preferably at least 3, for n = 5 or greater at least 2, preferably at least 3 and particularly preferably at least 4.

0081In such a case, the stoichiometric excess of carboxylic acid B to be used is calculated to the desired degree of esterification, that is, for example, 2 / n times the molar excesses given above. The esterification can of course also be terminated, for example by cooling or dilution, when the desired degree of esterification has been reached.

0082Ethylenically unsaturated carboxylic acids B which can be used according to the invention are those compounds which have at least one carboxyl group (-COOH), preferably one, and at least one, preferably one, ethylenically unsaturated group.

0083The carboxylic acids which can be used according to the invention can be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted with functional groups.

0084As a rule, the carboxylic acids have three to ten carbon atoms, preferably three to five and particularly preferably three to four.

0085Examples of ethylenically unsaturated carboxylic acids B are acrylic acid, methacrylic acid, ethacrylic acid, maleic acid including its anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, vinyl acetic acid, allylacetic acid or crotonic acid.

0086Preferred carboxylic acids B are α, β-unsaturated carboxylic acids.

0087Methacrylic acid and acrylic acid, referred to in this document as (meth) acrylic acid, are particularly preferred, and acrylic acid is very particularly preferred.

0088Esterification catalysts C which can be used according to the invention are sulfuric acid, aryl or alkylsulfonic acids or mixtures thereof. Examples of arylsulfonic acids are benzenesulfonic acid; para-toluenesulfonic acid or dodecylbenzenesulfonic acid, examples of alkylsulfonic acids are methanesulfonic acid, ethanesulfonic acid or trifluoromethanesulfonic acid. Strongly acidic ion exchangers or zeolites can also be used as esterification catalysts. Sulfuric acid and ion exchangers are preferred.

0089Polymerization inhibitors D which can be used according to the invention are, for example, phenols such as alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert.-butyl-2,4-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol , 4-tert-butyl-2,6-dimethylphenol, or 2,2'-methylene-bis- (6-tert-butyl-4-methylphenol), 4,4'-oxydiphenyl, 3,4-methylenedioxydiphenol ( Sesame oil), 3,4-dimethylphenol, hydroquinone, pyrocatechol (1,2-dihydroxybenzene), 2- (1'-methylcyclohex-1'-yl) -4,6-dimethylphenol, 2- or 4- (1'-phenyl-eth- 1'-yl) phenol, 2-tert-butyl-6-methylphenol, 2,4,6-tris-tert-butylphenol, 2,6-di-tert-butylphenol, 2,4-di-tert.- butylphenol, 4-tert-butylphenol, nonylphenol [11066-49-2], octylphenol [140-66-9], 2,6-dimethylphenol, bisphenol A, bisphenol F, bisphenol B, bisphenol C, bisphenol S, 3, 3 ', 5,5'-tetrabromobisphenol A, 2,6-di-tert-butyl-p-cresol, Koresin® from BASF AG, 3,5-di-tert-butyl-4-hydroxybenzoic acid methyl ester, 4-tert-butylpyrocatechol, 2-hydroxybenzyl alcohol, 2-methoxy-4-methylphenol, 2,3,6-trimethylphenol, 2,4, 5-trimethylphenol, 2,4,6-trimethylphenol, 2-isopropylphenol, 4-isopropylphenol, 6-isopropyl-m-cresol, n-octadecyl-β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate , 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-tert butyl-4-hydroxybenzyl) benzene, 1,3,5, -Tris- (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5, -Tris- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl isocyanurate, 1,3,5-tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate or pentaerythritol tetrakis [β- (3,5, -di-tert- butyl-4-hydroxyphenyl) propionate], 2,6-di-<i>tert</i>.-butyl-4-dimethylaminomethyl-phenol, 6-<i>sec</i>.-Butyl-2,4-dinitrophenol, Irganox® 565, 1141, 1192, 1222 and 1425 from Ciba Specialty Chemicals, 3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid octadecyl ester, 3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid hexadecyl ester, 3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid octyl ester, 3-thia-1,5-pentanediol-bis - [(3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecanediol-bis - [(3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecanediol-bis - [(3'-<i>tert</i>.-Butyl-4'-hydroxy-5'-methylphenyl) propionate], 1,9-nonanediol-bis - [(3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionate], 1,7-heptanediamine bis [3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid amide], 1,1-methanediamine bis [3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid amide], 3- (3 ', 5'-di-<i>tert</i>.-Butyl-4'-hydroxyphenyl) propionic acid hydrazide, 3- (3 ', 5'-dimethyl-4'-hydroxyphenyl) propionic acid hydrazide, bis (3-<i>tert</i>.-Butyl-5-ethyl-2-hydroxy-phen-1-yl) methane, bis (3,5-di-<i>tert</i>.-Butyl-4-hydroxy-phen-1-yl) methane, bis [3- (1'-methylcyclohex-1'-yl) -5-methyl-2-hydroxy-phen-1-yl] methane, bis ( 3-<i>tert</i>.-Butyl-2-hydroxy-5-methyl-phen-1-yl) methane, 1,1-bis (5-<i>tert</i>.-Butyl-4-hydroxy-2-methyl-phen-1-yl) ethane, bis (5-<i>tert</i>.-Butyl-4-hydroxy-2-methyl-phen-1-yl) sulfide, bis (3-th<i>r</i>t-butyl-2-hydroxy-5-methyl-phen-1-yl) sulfide, 1,1-bis (3,4-dimethyl-2-hydroxy-phen-1-yl) -2-methylpropane, 1, 1-bis (5-<i>tert</i>.-Butyl-3-methyl-2-hydroxy-phen-1-yl) butane, 1,3,5-tris [1 '- (3 ", 5" -di<i>tert</i>.-Butyl-4 "-hydroxyphen-1" -yl) meth-1'-yl] -2,4,6-trimethylbenzene, 1,1,4-tris (5'-<i>tert</i>.-Butyl-4'-hydroxy-2'-methyl-phen-1'-yl) butane, aminophenols, such as para-aminophenol, nitrosophenols, such as para-nitrosophenol, p-nitroso-o-cresol, alkoxyphenols, for example 2-methoxyphenol (guaiacol, pyrocatechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-tert-butyl-4 -methoxyphenol, 3,5-di-tert-butyl-4-hydroxyanisole, 3-hydroxy-4-methoxybenzyl alcohol, 2,5-dimethoxy-4-hydroxybenzyl alcohol (syringa alcohol), 4-hydroxy-3-methoxybenzaldehyde (vanillin), 4 -Hydroxy-3-ethoxybenzaldehyde (ethylvanillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin), 1- (4-hydroxy-3-methoxyphenyl) ethanone (acetovanillon), eugenol, dihydroeugenol, isoeugenol, tocopherols, such as, for example, α-, β-, γ-, δ- and ε-tocopherol, tocol, α-tocopherol hydroquinone, and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), quinones and hydroquinones such as hydroquinone or hydroquinone monomethyl ether, 2.5 -Di-<i>tert</i>.-Butyl hydroquinone, 2-methyl-p-hydroquinone, 2,3-dimethyl hydroquinone, trimethyl hydroquinone, 4-methyl catechol, tert-butyl hydroquinone, 3-methyl pyrocatechol, benzoquinone, 2-methyl-p-hydroquinone, 2,3-dimethyl hydroquinone, trimethyl 3-methylcatechol, 4-methylcatechol, tert-butylhydroquinone, 4-ethoxyphenol, 4-butoxyphenol, hydroquinone monobenzyl ether, p-phenoxyphenol, 2-methylhydroquinone, 2,5-di-tert-butylhydroquinone, tetramethyl-p-benzoquinone, Diethyl 1,4-cyclohexanedione-2,5-dicarboxylate, phenyl-p-benzoquinone, 2,5-dimethyl-3-benzyl-p-benzoquinone, 2-isopropyl-5-methyl-p-benzoquinone (thymoquinone), 2 , 6-diisopropyl-p-benzoquinone, 2,5-dimethyl-3-hydroxy-p-benzoquinone, 2,5-dihydroxyp-benzoquinone, embelin, tetrahydroxy-p-benzoquinone, 2,5-dimethoxy-1,4-benzoquinone , 2-amino-5-methyl-p-benzoquinone, 2,5-bisphenylamino-1,4-benzoquinone, 5,8-dihydroxy-1,4-naphthoquinone, 2-anilino-1,4, naphthoquinone, anthraquinone, N , N-dimethylindoaniline, N, N-diphenyl-p-benzoquinone diimine, 1,4-benzoquinone dioxime, Coerulignon, 3,3'-di-tert-butyl-5,5'-dimethyldiphenoquinone, p-rosolic acid (aurine), 2,6-di-tert -butyl-4-benzylidene-benzoquinone, 2,5-di-tert-amylhydroquinone, N-oxyls such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2, 6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4, 4 ', 4 "tris (2,2,6,6-tetramethyl-piperidine-N-oxyl) phosphite, 3-oxo-2,2,5,5-tetramethyl-pyrrolidine-N-oxyl, 1-oxyl-2,2,6,6-tetramethyl-4-methoxypiperidine, 1-oxyl-2,2,6,6- tetramethyl-4-trimethylsilyloxypiperidine, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate, 1- Oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl- (4-tert-butyl) benzoate, bis (1-oxyl -2,2,6,6-tetramethylpiperidin-4-yl) succinate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate, 1,10-decanedioic acid bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) ester, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -n -butylmalonate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) isophthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) terephthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) hexahydroterephthalate, N, N'- Bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipinamide, N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam, N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecylsuccinimide, 2,4,6-tris- [N-butyl-N- (1-oxyl-2,2,6, 6-tetramethylpiperidin-4-yl] triazine, N, N'-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N'-bis-formyl-1,6-diaminohexane , 4,4'-ethylene-bis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) aromatic amines such as phenylenediamines, N, N-diphenylamine, N-nitrosodiphenylamine, nitrosodiethylaniline, N, N '-Dialkyl-para-phenylenediamine, where the alkyl radicals can be the same or different and each independently consist of 1 to 4 carbon atoms and can be straight-chain or branched, for example N, N'-di-iso-butyl-p-phenylenediamine, N, N'-di-iso- propyl-p-phenylene diamine, Irganox 5057 from Ciba Specialty Chemicals, N, N'-di-iso-butyl-p-phenylene diamine, N, N'-di-iso-propyl-p-phenylene diamine, p-phenylene diamine, N-phenyl p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-isopropyl-N-phenyl-p-phenylenediamine, N, N'Di-sec-butyl-p-phenylenediamine (Kerobit® BPD from BASF AG), N-Phenyl-N'-isopropyl-p-phenylenediamine (Vulkanox® 4010 from Bayer AG), N- (1,3- Dimethylbutyl) -N'-phenyl-p-phenylenediamine, N-phenyl-2-naphthylamine, imoinodibenzyl, N, N'-diphenylbenzidine, N-phenyltetraaniline, acridone, 3-hydroxydiphenylamine, 4-hydroxydiphenylamine, hydroxylamines such as N, N-diethylhydroxylyl , Urea derivatives such as urea or thiourea, phosphorus-containing compounds such as triphenylphosphine, triphenylphosphite, Hypophosphorous acid or triethyl phosphite, sulfur-containing compounds such as diphenyl sulfide, phenothiazine or metal salts, such as copper, manganese, cerium, nickel, chromium chloride, dithiocarbamate, sulfate, salicylate or acetate or mixtures thereof. The phenols and quinones mentioned are preferred; hydroquinone, hydroquinone monomethyl ether, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl-phenol, 2,6-di-tert.- are particularly preferred. Butyl-4-methylphenol, 2,4-di-tert-butylphenol, triphenylphosphite, hypophosphorous acid, CuCl₂ and guaiacol, hydroquinone and hydroquinone monomethyl ether are very particularly preferred.

0090Hydroquinone monomethyl ether, hydroquinone, and alkylphenols, optionally in combination with tripehnyl phosphite and / or hypophosphorous acid, are particularly preferred.

0091To further support the stabilization, an oxygen-containing gas, preferably air or a mixture of air and nitrogen (lean air) can be present.

0092Among the stabilizers listed, preference is given to those which are aerobic, ie those which require the presence of oxygen to develop their full inhibitory action.

0093Solvents E which can be used according to the invention are in particular those which are suitable for the azeotropic removal of the water of reaction, if desired, in particular aliphatic, cycloaliphatic and aromatic hydrocarbons or mixtures thereof.

0094Preferably n-pentane, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene or xylene are used. Cyclohexane, methylcyclohexane and toluene are particularly preferred.

0095For the esterification, the preparation and / or work-up methods of polyhydric alcohols known to the person skilled in the art can be used, for example those mentioned at the beginning or those in <patcit id="pcit0006" dnum="DE19941136A"><text>DE-A 199 41 136</text></patcit>, <patcit id="pcit0007" dnum="DE3843843A"><text>DE-A 38 43 843</text></patcit>, <patcit id="pcit0008" dnum="DE3843854A"><text>DE-A 38 43 854</text></patcit>, <patcit id="pcit0009" dnum="DE19937911A"><text>DE-A 199 37 911</text></patcit>, <patcit id="pcit0010" dnum="DE19929258A"><text>DE-A 199 29 258</text></patcit>, <patcit id="pcit0011" dnum="EP331845A"><text>EP-A 331 845</text></patcit>, <patcit id="pcit0012" dnum="EP554651A"><text>EP 554 651</text></patcit> or <patcit id="pcit0013" dnum="US4187383A"><text>US 4 187 383</text></patcit> described.

0096In general, the esterification can be carried out as follows:

0097The esterification apparatus consists of a stirred reactor, preferably a reactor with a circulation evaporator and an attached distillation unit with a condenser and phase separation vessel.

0098The reactor can be, for example, a reactor with double-wall heating or / and internal heating coils. A reactor with an external heat exchanger and natural or forced circulation, that is to say using a pump, particularly preferably natural circulation, in which the recycle stream is brought about without mechanical aids, is preferably used.

0099The reaction can of course also be carried out in a plurality of reaction zones, for example a reactor cascade composed of two to four, preferably two to three, reactors.

0100Suitable circulation evaporators are known to the person skilled in the art and are described, for example, in R. Billet, Verdampfertechnik, HTB-Verlag, Bibliographisches Institut Mannheim, 1965, 53. Examples of circulation evaporators are shell-and-tube heat exchangers, plate heat exchangers, etc.

0101Of course, several heat exchangers can also be present in the circulation.

0102The distillation unit is of a type known per se. This can be a simple distillation, which may be equipped with a splash guard, or a rectification column. In principle, all common internals come into consideration as column internals, for example floors, packings and / or fillings. Of the trays, bubble trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred, of the fillings those with rings, spirals, saddle bodies or braids are preferred.

0103As a rule, 5 to 20 theoretical floors are sufficient.

0104The condenser and the separation vessel are of conventional construction.

0105Carboxylic acid B and polyalcohol A are generally used in the esterification a) in a molar excess, as indicated above, based on the hydroxyl groups of the alcohol. The excess used can be up to approximately 1000: 1, if desired.

0106The above-mentioned esterification catalysts C are suitable.

0107They are generally used in an amount of 0.1-5% by weight, based on the esterification mixture, preferably 0.5-5%, more preferably 1-4% and very particularly preferably 2-4% by weight.

0108If necessary, the esterification catalyst can be removed from the reaction mixture using an ion exchanger. The ion exchanger can be added directly to the reaction mixture and then filtered off, or the reaction mixture can be passed over an ion exchange bed.

0109The esterification catalyst is preferably left in the reaction mixture. However, if the catalyst is an ion exchanger, this is preferably removed, for example by filtration.

0110To further support the stabilization, an oxygen-containing gas, preferably air or a mixture of air and nitrogen (lean air) can be present.

0111This oxygen-containing gas is preferably metered into the bottom region of a column and / or into a circulation evaporator and / or passed through the reaction mixture and / or over it.

0112The polymerization inhibitor (mixture) D (as mentioned above) is used in a total amount of 0.01-1% by weight, based on the esterification mixture, preferably 0.02-0.8, particularly preferably 0.05-0.5% by weight %.

0113The polymerization inhibitor (mixture) D can be used, for example, as an aqueous solution or as a solution in a starting material or product.

0114b) The water of reaction formed in the reaction can be distilled off during or after the esterification a), this process being able to be supported by a solvent which forms an azeotrope with water.

0115The solvents listed above are suitable as solvent E for azeotropic removal of the water of reaction, if desired.

0116It is preferred to carry out the esterification in the presence of a solvent.

0117The amount of solvent used is 10-200% by weight, preferably 20-100% by weight, particularly preferably 30-100% by weight, based on the sum of polyalcohol and carboxylic acid B.

0118However, it is also conceivable to carry out without an entrainer, such as in the <patcit id="pcit0014" dnum="DE3843854A1"><text>DE-A1 38 43 854</text></patcit>, Column 2, line 18 to column 4, line 45, but in contrast to this with the stabilizers mentioned above.

0119If the water contained in the reaction mixture is not removed via an azeotroping solvent, it is possible to remove it by stripping with an inert gas, preferably an oxygen-containing gas, particularly preferably with air or lean air, for example as in US Pat <patcit id="pcit0015" dnum="DE3843843A"><text>DE-A 38 43 843</text></patcit> described.

0120The reaction temperature of the esterification a) is generally 40-160 ° C., preferably 60-140 ° C. and particularly preferably 80-120 ° C. The temperature can remain the same or rise in the course of the reaction, but is preferably raised in the course of the reaction. In this case the final temperature of the esterification is 5 - 30 ° C higher than the initial temperature. The temperature of the esterification can be determined and regulated by varying the solvent concentration in the reaction mixture, as in<patcit id="pcit0016" dnum="DE19941136A"><text>DE-A 199 41 136</text></patcit> and the German application with the file number <patcit id="pcit0017" dnum="DE10063175"><text>100 63 175.4</text></patcit> described.

0121If a solvent is used, it can be distilled off from the reaction mixture via the distillation unit attached to the reactor.

0122The distillate can either be removed or, after condensation, fed into a phase separator. The aqueous phase obtained in this way is generally discharged, the organic phase can be fed as reflux into the distillation unit and / or be passed directly into the reaction zone and / or into a circulation evaporator, as in the German patent application with the file number 100 63 175.4 described.

0123When used as reflux, the organic phase, as in the <patcit id="pcit0018" dnum="DE19941136A"><text>DE-A 199 41 136</text></patcit> described, can be used to control the temperature in the esterification.

0124The esterification a) can be carried out without pressure, but also under overpressure or underpressure, preferably under normal pressure.

0125The reaction time is generally 2 to 20 hours, preferably 4 to 15 hours and particularly preferably 7 to 12 hours.

0126The order in which the individual reaction components are added is not essential according to the invention. All components can be mixed and then heated, or one or more components can not be or only partially and only added after heating.

0127The composition of the carboxylic acid B which can be used is not restricted and, in the case of crude (meth) acrylic acid, can have, for example, the following components:<tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="30mm" /><tbody><row><entry>(Meth) acrylic acid</entry><entry>90 - 99.9% by weight</entry></row><row><entry>acetic acid</entry><entry>0.05 - 3% by weight</entry></row><row><entry>Propionic acid</entry><entry>0.01 - 1% by weight</entry></row><row><entry>Diacrylic acid</entry><entry>0.01 - 5% by weight</entry></row><row><entry>water</entry><entry>0.05 - 5% by weight</entry></row><row><entry>Carbonyl-containing</entry><entry>0.01 - 0.3% by weight</entry></row><row><entry>Inhibitors</entry><entry>0.01-0.1% by weight</entry></row><row><entry>Maleic acid (anhydride)</entry><entry>0.001 - 0.5% by weight</entry></row></tbody></tgroup></table></tables>

0128The crude (meth) acrylic acid used is generally stabilized with 200-600 ppm phenothiazine or other stabilizers in amounts which enable comparable stabilization. The term carbonyl-containing is understood here to mean, for example, acetone and lower aldehydes, such as, for example, formaldehyde, acetaldehyde, crotonaldehyde, acrolein, 2- and 3-furfural and benazaldehyde.

0129Crude (meth) acrylic acid is understood here to mean the (meth) acrylic acid-containing mixture which is obtained after absorption of the reaction gases from propane / propene / acrolein or isobutane / isobutene / methacrolein oxidation in an absorption medium and subsequent separation of the absorption medium or by fractionation Condensation of the reaction gases is obtained.

0130Of course, pure (meth) acrylic acid can also be used, for example with the following purity:<tables id="tabl0002" num="0002"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="37mm" /><colspec colnum="2" colname="col2" colwidth="32mm" /><tbody><row><entry>(Meth) acrylic acid</entry><entry>99.7 - 99.99% by weight</entry></row><row><entry>acetic acid</entry><entry>50 - 1000 ppm by weight</entry></row><row><entry>Propionic acid</entry><entry>10th - 500 ppm by weight</entry></row><row><entry>Diacrylic acid</entry><entry>10th - 500 ppm by weight</entry></row><row><entry>water</entry><entry>50 - 1000 ppm by weight</entry></row><row><entry>Carbonyl-containing</entry><entry>1 - 500 ppm by weight</entry></row><row><entry>Inhibitors</entry><entry>1 - 300 ppm by weight</entry></row><row><entry>Maleic acid (anhydride)</entry><entry>1 - 200 ppm by weight</entry></row></tbody></tgroup></table></tables>

0131The pure (meth) acrylic acid used is generally stabilized with 100-300 ppm hydroquinone monomethyl ether or other storage stabilizers in amounts which enable comparable stabilization.

0132Pure or pre-purified (meth) acrylic acid is generally understood to mean (meth) acrylic acid, the purity of which is at least 99.5% by weight and which is essentially free of the aldehydic, other carbonyl-containing and high-boiling components.

0133The distilled off aqueous phase of the condensate, if present, separated off via the attached column, which can generally contain 0.1-10% by weight of carboxylic acid B, for example (meth) acrylic acid, is separated off and discharged. The carboxylic acid contained therein, for example (meth) acrylic acid with an extractant, preferably the solvent optionally used in the esterification, for example with cyclohexane, can advantageously be at a temperature between 10 and 40 ° C. and a ratio of aqueous phase to extractant of 1: 5 - 30, preferably 1:10 - 20, extracted and returned to the esterification.

0134To further support the circulation, an inert gas, preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) can be passed into the circulation, through or over the reaction mixture, for example in amounts of 0.1-1. preferably 0.2-0.8 and particularly preferably 0.3-0.7 m3 / m3h, based on the volume of the reaction mixture.

0135The course of the esterification a) can be followed by tracking the amount of water discharged and / or the decrease in the carboxylic acid concentration in the reactor.

0136The reaction can be ended, for example, as soon as 90% of the theoretically expected amount of water has been discharged through the solvent, preferably at least 95% and particularly preferably at least 98%.

0137The end of the reaction can be determined, for example, by essentially no further water of reaction being removed via the entrainer. If carboxylic acid B is discharged together with the water of reaction, its proportion can be determined, for example, by back-titration of an aliquot of the aqueous phase.

0138Removal of the reaction water can be dispensed with, for example, if the carboxylic acid B is used in a high stoichiometric excess, for example of at least 1.5: 1, preferably at least 2.5: 1 and very particularly preferably at least 5: 1. In this case, a substantial part of the amount of water formed remains in the reaction mixture. During or after the reaction, only the proportion of water which is determined by the volatility at the temperature applied is removed from the reaction mixture and, in addition, no measures are taken to separate off the water of reaction formed. For example, at least 10% by weight of the water of reaction formed can remain in the reaction mixture, preferably at least 20% by weight, particularly preferably at least 30% by weight, very particularly preferably at least 40 and in particular at least 50% by weight.

0139c) After the esterification has ended, the reactor mixture can be cooled in a customary manner to a temperature of from 10 to 30 ° C. and, if appropriate, by adding solvent, which can be the same as or different from the solvent which may be used for the azeotropic removal of water any target ester concentration can be set.

0140In a further embodiment, the reaction can be stopped with a suitable diluent G and to a concentration of, for example, 10-90% by weight, preferably 20-80%, particularly preferably 20 to 60%, very particularly preferably 30 to 50% and in particular approximately Diluted 40%, for example to reduce the viscosity.

0141It is important that an essentially homogeneous solution is formed after dilution.

0142This is preferably done only relatively shortly before use in the production of the hydrogel, for example not more than 24 hours beforehand, preferably not more than 20, particularly preferably not more than 12, very particularly preferably not more than 6 and in particular not more than 3 hours before.

0143The diluent G is selected from the group consisting of water, a mixture of water with one or more water-soluble organic solvents or a mixture of water with one or more single or multi-functional alcohols, for example methanol and glycerol. The alcohols preferably carry 1, 2 or 3 hydroxyl groups and preferably have between 1 to 10, in particular up to 4, carbon atoms. Primary and secondary alcohols are preferred.

0144Preferred alcohols are methanol, ethanol, isopropanol, ethylene glycol, 1,2-propanediol or 1,3-propanediol.

0145d) If necessary, the reaction mixture can be decolorized, for example by treatment with activated carbon or metal oxides, such as, for example, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, boron oxide or mixtures thereof, in amounts of, for example, 0.1-50% by weight, preferably 0.5 to 25% by weight, particularly preferably 1-10% by weight at temperatures of, for example, 10 to 100 ° C., preferably 20 to 80 ° C. and particularly preferably 30 to 60 ° C.

0146This can be done by adding the powdered or granular decolorizing agent to the reaction mixture and subsequent filtration, or by passing the reaction mixture over a bed of the decolorizing agent in the form of any suitable moldings.

0147The reaction mixture can be decolorized at any point in the workup process, for example at the stage of the crude reaction mixture or after prewashing, neutralization, washing or solvent removal, if appropriate.

0148The reaction mixture can also be subjected to a prewash e) and / or a neutralization f) and / or a postwash g), preferably only a neutralization f). If necessary, neutralization f) and prewash e) can also be interchanged in the order.

0149Carboxylic acid B, for example (meth) acrylic acid and / or catalyst C, can be at least partially recovered from the aqueous phase of the washes e) and g) and / or neutralization f) by acidification and extraction with a solvent and used again.

0150For prewashing or afterwashing e) or g), the reaction mixture is washed in a washing apparatus with a washing liquid, for example water or a 5-30% by weight, preferably 5-20, particularly preferably 5-15% by weight sodium chloride, potassium chloride -, Ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline, treated.

0151The ratio of the reaction mixture to the washing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.

0152The washing or neutralization can be carried out, for example, in a stirred tank or in other conventional apparatus, for example in a column or mixer-settler apparatus.

0153In terms of process engineering, all extraction and washing processes and apparatuses known per se can be used for washing or neutralization in the process according to the invention, for example those which are described in <nplcit id="ncit0005" npl-type="b"><text>Ullmann's Encyclopedia of Industrial Chemistry, 6th ed, 1999 Electronic Release, chapter: Liquid - Liquid Extraction - Apparatus</text></nplcit>, are described. For example, these can be single-stage or multi-stage, preferably single-stage extractions, as well as those in cocurrent or countercurrent mode, preferably countercurrent mode.

0154Sieve plate or packed or packed columns, stirred tanks or mixer-settlers, and pulsed columns or those with rotating internals are preferably used.

0155The prewash e) is preferably used when metal salts, preferably copper or copper salts, are used as inhibitors (with).

0156After-washing g) can be advantageous for removing base or salt traces from the reaction mixture neutralized in f).

0157For the neutralization f), the optionally prewashed reaction mixture, which may still contain small amounts of catalyst and the main amount of excess carboxylic acid, for example (meth) acrylic acid, can have a 5-25, preferably 5-20, particularly preferably 5-15% by weight aqueous solution of a base, such as, for example, alkali metal or alkaline earth metal oxides, hydroxides, carbonates or hydrogen carbonates, preferably sodium hydroxide solution, potassium hydroxide solution, sodium hydrogen carbonate, sodium carbonate, Potassium hydrogen carbonate, calcium hydroxide, lime milk, ammonia, ammonia water or potassium carbonate, to which 5-15% by weight of sodium chloride, potassium chloride, ammonium chloride or ammonium sulfate may be added, particularly preferably neutralized with sodium hydroxide solution or sodium hydroxide solution. The degree of neutralization is preferably 10 to 80 mol%, preferably 20 to 80 mol%, particularly preferably 40 to 80 mol%, based on the monomers containing acid groups. This neutralization can take place before and / or during the polymerization, preferably before the polymerization.

0158The base is added in such a way that the temperature in the apparatus does not rise above 60 ° C., preferably between 20 and 35 ° C., and the pH is 4-13. The heat of neutralization is preferably dissipated by cooling the container with the aid of internal cooling coils or via double-wall cooling.

0159The ratio of the reaction mixture to the neutralizing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.

0160The statements made above apply to the apparatus.

0161h) If a solvent is present in the reaction mixture, this can essentially be removed by distillation. Any solvent present is preferably removed from the reaction mixture after washing and / or neutralization, but if desired this can also be done before washing or neutralization.

0162For this purpose, an amount of storage stabilizer, preferably hydroquinone monomethyl ether, is added to the reaction mixture such that, after removal of the solvent, 100-500, preferably 200-500 and particularly preferably 200-400 ppm thereof are contained in the target ester (residue).

0163The main amount of solvent is removed by distillation, for example, in a stirred tank with double-wall heating and / or internal heating coils under reduced pressure, for example at 20-700 mbar, preferably 30-500 and particularly preferably 50-150 mbar and a temperature of 40-80 ° C . Of course, the distillation can also be carried out in a falling film or thin film evaporator. For this purpose, the reaction mixture is passed through the apparatus, preferably several times in a circuit, under reduced pressure, for example at 20-700 mbar, preferably 30-500 and particularly preferably 50-150 mbar and a temperature of 40-80 ° C.

0164An inert gas, preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) can advantageously be introduced into the distillation apparatus, for example 0.1-1, preferably 0.2-0.8 and particularly preferably 0, 3 - 0.7 m3 / m3h, based on the volume of the reaction mixture.

0165The residual solvent content in the residue after the distillation is generally less than 5% by weight, preferably 0.5-5% and particularly preferably 1 to 3% by weight.

0166The separated solvent is condensed and preferably reused.

0167If necessary, solvent stripping i) can be carried out in addition to or instead of the distillation.

0168For this purpose, the target ester, which still contains small amounts of solvent, is heated to 50-90 ° C., preferably 80-90 ° C., and the remaining amounts of solvent are removed with a suitable gas in a suitable device. A vacuum can also be created to assist.

0169Suitable apparatuses are, for example, columns of a type known per se which have the usual internals, for example trays, beds or directional packs, preferably beds. In principle, all common internals come into consideration as column internals, for example trays, packings and / or packing elements. Of the bottoms, bell bottoms, sieve bottoms, valve bottoms, Thormann bottoms and / or dual-flow bottoms are preferred; of the fillings are those with rings, spirals, saddle bodies, Raschig, Intos or Pall rings, Barrel or Intalox saddles, Top-Pak etc. or braids, preferred.

0170A falling film, thin film or wiping film evaporator, such as a Luwa, Rotafilm or Sambay evaporator, which can be equipped, for example, with a demister as a splash guard, is also conceivable here.

0171Suitable gases are gases which are inert under the stripping conditions, preferably oxygen-containing gases, particularly preferably air or mixtures of air and nitrogen (lean air) or water vapor, in particular those which are heated to 50 to 100.degree.

0172The amount of stripping gas is, for example, 5-20, particularly preferably 10-20 and very particularly preferably 10 to 15 m3 / m3h, based on the volume of the reaction mixture.

0173If necessary, the ester can be subjected to filtration j) at any stage of the work-up process, preferably after washing / neutralization and, if appropriate, solvent removal, in order to remove traces of salts and any decolorizing agent present.

0174In a conceivable embodiment, the esterification a) of the polyalcohol A with the carboxylic acid B is carried out in a molar excess of at least 5: 1 as mentioned above in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D without a solvent which forms an azeotrope with water.

0175In a preferred embodiment, the excess carboxylic acid B is essentially not separated off, ie only the proportion of carboxylic acid B which is determined by the volatility at the temperature applied is removed from the reaction mixture, and no measures are taken to separate off the carboxylic acid carried out, such as distillative, rectificative, extractive, such as washing, absorptive, such as Transfer over activated carbon or over ion exchangers, and / or chemical steps, such as trapping the carboxylic acid with epoxides.

0176The carboxylic acid B contained in the reaction mixture is preferably not more than 75% by weight, particularly preferably not more than 50% by weight, very particularly preferably not more than 25% by weight, in particular not more than 10% by weight and especially not more separated as 5% by weight from the reaction mixture, based on the carboxylic acid B present in the reaction mixture after the end of the reaction. In a particularly preferred embodiment, step b) can be dispensed with, so that only the proportion of water of reaction and carboxylic acid B which is determined by the volatility at the temperature applied is removed from the reaction mixture. This can preferably be prevented by essentially complete condensation.

0177Furthermore, the esterification catalyst C used essentially remains in the reaction mixture.

0178The reaction mixture obtainable in this way preferably has an acid number in accordance with. DIN EN 3682 from at least 25 mg KOH / g reaction mixture, particularly preferably from 25 to 80 and very particularly preferably from 25 to 50 mg KOH / g.

0179Prewashing or postwashing e) or g) is preferably dispensed with, only one filtration step j) can be useful.

0180The reaction mixture can then be diluted in step c), in which case it is preferably converted to the hydrogel within 6 hours, particularly preferably within 3 hours. It can preferably be neutralized in a step f).

0181The sequence of steps c), j) and f) is arbitrary.

0182The invention also relates to a mixture of substances<ul id="ul0005" list-style="dash" compact="compact"><li>at least one ester F, obtainable by one of the esterification processes described above,</li><li>Carboxylic acid B and</li><li>Diluent G.</li></ul>

0183May be included as further components<ul id="ul0006" list-style="dash" compact="compact"><li>Esterification catalyst C in protonated or unprotonated form,</li><li>Polymerization inhibitor D as well</li><li>optionally solvent E, if such was used in the esterification.</li></ul>

0184The mixture of substances can optionally be neutralized and have a pH, as listed under f) above.

0185When the mixture of substances is neutralized, at least some of the carboxylic acids B are converted into their water-soluble alkali metal, alkaline earth metal or ammonium salts.

0186Preferred mixture contains<ul id="ul0007" list-style="dash" compact="compact"><li>Ester F in the substance mixture 0.1 to 40% by weight, particularly preferably 0.5 to 20, very particularly preferably 1 to 10, in particular 2 to 5 and especially 2 to 4% by weight,</li><li>Carboxylic acid B 0.5-99.9% by weight, particularly preferably 0.5-50% by weight, very particularly preferably 1-25, in particular 2-15 and especially 3 to 5% by weight,</li><li>Esterification catalyst C 0-10% by weight, particularly preferably 0.02</li><li>5, very particularly preferably 0.05-2.5% by weight and in particular 0.1-1% by weight,</li><li>Polymerization inhibitor D 0-5% by weight, particularly preferably 0.01</li><li>1.0, very particularly preferably 0.02-0.75, in particular 0.05-0.5 and especially 0.075-0.25% by weight,</li><li>Solvent E 0-10% by weight, particularly preferably 0-5% by weight, very particularly preferably 0.05-1.5% by weight and in particular 0.1-0.5% by weight, with the proviso that the total is always 100% by weight % is, as well</li><li>optionally diluent G ad 100% by weight.</li></ul>

0187The reaction mixtures and mixtures according to the invention obtainable by the above process can be used<ul id="ul0008" list-style="dash" compact="compact"><li>as radical crosslinker of water-absorbing hydrogels,</li><li>as starting material for the production of polymer dispersions,</li><li>as starting material for the production of polyacrylates (except hydrogels),</li><li>as paint raw material or</li><li>as a cement additive.</li></ul>

0188Particularly suitable for use as radical crosslinkers of water-absorbing hydrogels are those mixtures according to the invention which have a water solubility (at 25 ° C. in distilled water) of at least 5% by weight, preferably at least 10% by weight, particularly preferably at least 20% by weight, very particularly preferably at least 30 % By weight and in particular of at least 50% by weight.

0189k) The reaction mixture from the esterification, including its work-up steps, as far as they are carried out, for example the reaction mixture from f), or, if f) is omitted, from b), or, if b) is dispensed with, the reaction mixture from a ) can optionally be mixed with additional monoethylenically unsaturated compounds N which do not carry acid groups but can be copolymerized with the hydrophilic monomers M, can then be polymerized to produce water-absorbing hydrogels in the presence of at least one radical initiator K and optionally at least one graft base L.

Can be advantageous

0190l) the reaction mixture from k) is post-crosslinked.

0191Hydrophilic monomers M suitable for producing k) these hydrophilic, highly swellable hydrogels are, for example, polymerizable acids, such as acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, vinylsulfonic acid, vinylphosphonic acid, maleic acid including its anhydride, fumaric acid, itaconic acid, citraconic acid, Mesaconic acid, glutaconic acid, aconitic acid, allylsulfonic acid, sulfoethyl acrylate, sulfomethacrylate, sulfopropyl acrylate, Sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropylsulfonic acid, 2-hydroxy-3-methacryloxypropylsulfonic acid, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2methylpropanesulfonic acid, 2-acrylamido-2-methylpropanephosphonic acid as well as their amides, hydroxyalkyl esters and ammonium group-containing and amino group groups . The monomers can be used alone or as a mixture with one another. Furthermore, water-soluble N-vinylamides or diallyldimethylammonium chloride. Preferred hydrophilic monomers are compounds of the formula V.<chemistry id="chem0005" num="0005"><img file="EP1516010B1_D0005.tif" /></chemistry>wherein<dl id="dl0006" compact="compact"><dt>R³</dt><dd>Hydrogen, methyl or ethyl,</dd><dt>R⁴</dt><dd>the group -COOR⁶, a sulfonyl group or phosphonyl group, one with a (C₁-C₄) Alkyl alcohol esterified phosphonyl group or a group of formula VI</dd></dl><chemistry id="chem0006" num="0006"><img file="EP1516010B1_D0006.tif" /></chemistry><dl id="dl0007" compact="compact"><dt>R⁵</dt><dd>Hydrogen, methyl, ethyl or a carboxyl group,</dd><dt>R⁶</dt><dd>Hydrogen, amino or hydroxy- (C₁-C₄) Alkyl and</dd><dt>R⁷</dt><dd>mean a sulfonyl group, a phosphonyl group or a carboxyl group.</dd></dl>

0192Examples of (C₁-C₄) - Alkyl alcohol are methanol, ethanol, n-propanol or n-butanol.

0193Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid.

0194To optimize properties, it can be useful to use additional monoethylenically unsaturated compounds N which do not carry acid groups but can be copolymerized with the monomers bearing acid groups. These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acid, e.g. B. acrylamide, methacrylamide and N-vinylformamide, N-vinyl acetamide, N-methyl-vinyl acetamide, acrylonitrile and methacrylonitrile. Other suitable compounds are, for example, vinyl esters of saturated C₁- to C₄-Carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers with at least 2 carbon atoms in the alkyl group, such as. B. ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C₃- to C₆-Carboxylic acids, e.g. B. esters from monovalent C₁- to C₁₈Alcohols and acrylic acid, methacrylic acid or maleic acid, half esters of maleic acid, e.g. B. maleic acid mono-methyl ester, N-vinyl lactams such as N-vinyl pyrrolidone or N-vinyl caprolactam, acrylic acid and methacrylic acid esters of alkoxylated monohydric, saturated alcohols, e.g. B. alcohols with 10 to 25 carbon atoms, which have been reacted with 2 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol, and monoacrylic acid esters and monomethacrylic acid esters of polyethylene glycol or polypropylene glycol, the molar masses (M._n) of the polyalkylene glycols can be, for example, up to 2000. Other suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene or tert-butylstyrene.

0195These monomers not carrying acid groups can also be used in a mixture with other monomers, e.g. B. Mixtures of vinyl acetate and 2-hydroxyethyl acrylate in any ratio. These monomers not carrying acid groups are added to the reaction mixture in amounts between 0 and 50% by weight, preferably less than 20% by weight.

0196The crosslinked (co) polymers preferably consist of monoethylenically unsaturated monomers bearing acid groups, which are optionally converted into their alkali metal or ammonium salts before or after the polymerization, and from 0 to 40% by weight, based on their total weight, of no monoethylenically unsaturated monomers bearing acid groups.

0197The production of (meth) acrylic acid-containing (co) polymers, polyacrylic acids and superabsorbers has been described many times and is therefore sufficiently well known, see for example "<nplcit id="ncit0006" npl-type="b"><text>Modern Superabsorbent Polymer Technology ", FL Buchholz and AT Graham, Wiley-VCH, 1998</text></nplcit>.

0198Preferred hydrogels are those obtained by crosslinking polymerization or copolymerization of acid-bearing monoethylenically unsaturated monomers M or their salts.

0199In the process for postcrosslinking, the starting polymer is treated with a postcrosslinker and preferably postcrosslinked and dried during or after the treatment by increasing the temperature, the crosslinker preferably being contained in an inert solvent. Inert solvents are understood to mean those which in the reaction do not essentially react either with the starting polymer or with the postcrosslinker. Preferred solvents are those which more than 90%, preferably more than 95%, particularly preferably more than 99%, in particular more than 99.5%, do not react chemically with the starting polymer or postcrosslinker.

0200Preferred for post-crosslinking 1) and drying m) is the temperature range between 30 and 250 ° C., in particular 50-200 ° C., and the range between 100-180 ° C. is very particularly preferred. The surface postcrosslinking solution is preferably applied by spraying onto the polymer in suitable spray mixers. Following the spraying, the polymer powder is thermally dried, and the crosslinking reaction can take place both before and during the drying. It is preferred to spray on a solution of the crosslinking agent in reaction mixers or mixing and drying systems such as, for example, Lödige mixers, BEPEX mixers, NAUTA mixers, SHUGGI mixers or PROCES-SALL. Fluidized bed dryers can also be used.

0201Drying can take place in the mixer itself, by heating the jacket or by blowing in warm air. A downstream dryer such as a tray dryer, a rotary kiln or a heatable screw is also suitable. However, azeotropic distillation, for example, can also be used as the drying process. The preferred residence time at this temperature in the reaction mixer or dryer is less than 60 minutes, particularly preferably less than 30 minutes.

0202The above processes are preferred, the starting polymer being a polymeric acrylic acid or a polyacrylate, in particular a polymeric acrylic acid or a polyacrylate, which have been obtained via radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinking agent has been used.

0203Such processes are preferred in which the substance mixture containing free radical crosslinking agent, ie the ester F, and diluent G in a ratio of 0.1-20% by weight, in particular 0.5-10% by weight, based on the mass of the starting polymer becomes.

0204Such processes are preferred in which the radical crosslinker is used in a dosage of 0.01-5.0% by weight, preferably 0.02-3.0% by weight, very particularly preferably 0.03-2.5% by weight, in particular 0.05 - 1.0 and especially 0.1 to 0.75% by weight based on the starting polymer is used.

0205The invention also relates to polymers produced by one of the abovementioned processes and their use in hygiene articles, packaging materials and in nonwovens, and to the use of an abovementioned mixture of substances for the production of crosslinked or heat-crosslinkable polymers, in particular in paints and varnishes.

0206The hydrophilic, highly swellable hydrogels (starting polymers) to be used are, in particular, polymers of (co) polymerized hydrophilic monomers M, graft (co) polymers of one or more hydrophilic monomers M on a suitable graft base L, crosslinked cellulose or starch ethers or swellable in aqueous liquids Natural products, such as guar derivatives. These hydrogels are known to the person skilled in the art and are described, for example, in<patcit id="pcit0019" dnum="US4286082A"><text>U.S. 4,286,082</text></patcit>, <patcit id="pcit0020" dnum="DE2706135C"><text>DE-C-27 06 135</text></patcit>, <patcit id="pcit0021" dnum="US4340706A"><text>US 4,340,706</text></patcit>, <patcit id="pcit0022" dnum="DE3713601C"><text>DE-C-37 13 601</text></patcit>, <patcit id="pcit0023" dnum="DE2840010C"><text>DE-C-28 40 010</text></patcit>, <patcit id="pcit0024" dnum="DE4344548A"><text>DE-A-43 44 548</text></patcit>, <patcit id="pcit0025" dnum="DE020780A4"><text>DE-A40 20 780</text></patcit>, <patcit id="pcit0026" dnum="DE4015085A"><text>DE-A-40 15 085</text></patcit>, <patcit id="pcit0027" dnum="DE3917846A"><text>DE-A-39 17 846</text></patcit>, <patcit id="pcit0028" dnum="DE3807289A"><text>DE-A-38 07 289</text></patcit>, <patcit id="pcit0029" dnum="DE3533337A"><text>DE-A-35 33 337</text></patcit>, <patcit id="pcit0030" dnum="DE3503458A"><text>DE-A-35 03 458</text></patcit>, <patcit id="pcit0031" dnum="DE4244548A"><text>DE-A-42 44 548</text></patcit>, <patcit id="pcit0032" dnum="DE4219607A"><text>DE-A-42 19 607</text></patcit>, <patcit id="pcit0033" dnum="DE4021847A"><text>DE-A-40 21 847</text></patcit>, <patcit id="pcit0034" dnum="DE3831261A"><text>DE-A-38 31 261</text></patcit>, <patcit id="pcit0035" dnum="DE3511086A"><text>DE-A-35 11 086</text></patcit>, <patcit id="pcit0036" dnum="DE3118172A"><text>DE-A-31 18 172</text></patcit>, <patcit id="pcit0037" dnum="DE3028043A"><text>DE-A-30 28 043</text></patcit>, <patcit id="pcit0038" dnum="DE4418881A"><text>DE-A-44 18 881</text></patcit>, <patcit id="pcit0039" dnum="EP0801483A"><text>EP-A-0 801 483</text></patcit>, <patcit id="pcit0040" dnum="EP0455985A"><text>EP-A-0 455 985</text></patcit>, <patcit id="pcit0041" dnum="EP0467073A"><text>EP-A-0 467 073</text></patcit>, <patcit id="pcit0042" dnum="EP0312952A"><text>EP-A-0 312 952</text></patcit>, <patcit id="pcit0043" dnum="EP0205874A"><text>EP-A-0 205 874</text></patcit>, <patcit id="pcit0044" dnum="EP0499774A"><text>EP-A-0 499 774</text></patcit>, <patcit id="pcit0045" dnum="DE2612846A"><text>DE-A 26 12 846</text></patcit>, <patcit id="pcit0046" dnum="DE4020780A"><text>DE-A-40 20 780</text></patcit><patcit id="pcit0047" dnum="EP0205674A"><text>EP-A-0 20 5674</text></patcit>, <patcit id="pcit0048" dnum="US5145906A"><text>US 5,145,906</text></patcit>, <patcit id="pcit0049" dnum="EP0530438A"><text>EP-A-0 530 438</text></patcit>, <patcit id="pcit0050" dnum="EP0670073A"><text>EP-A-0 670 073</text></patcit>, <patcit id="pcit0051" dnum="US4057521A"><text>US4 057 521</text></patcit>, <patcit id="pcit0052" dnum="US4062817A"><text>U.S. 4,062,817</text></patcit>, <patcit id="pcit0053" dnum="US4525527A"><text>US 4,525,527</text></patcit>, <patcit id="pcit0054" dnum="US4295987A"><text>U.S. 4,295,987</text></patcit>, <patcit id="pcit0055" dnum="US5011892A"><text>US 5,011,892</text></patcit>, <patcit id="pcit0056" dnum="US4076663A"><text>U.S. 4,076,663</text></patcit> or <patcit id="pcit0057" dnum="US4931497A"><text>U.S. 4,931,497</text></patcit>. Highly swellable hydrogels from a manufacturing process as in<patcit id="pcit0058" dnum="WO0138402A"><text>WO 01/38402</text></patcit> described, as well as inorganic-organic hybrid highly swellable hydrogels as in <patcit id="pcit0059" dnum="DE19854575"><text>DE 198 54 575</text></patcit> described. The content of the aforementioned patent documents, in particular the hydrogels produced by the processes, are expressly part of the present disclosure.

0207Suitable graft bases L for hydrophilic hydrogels, which can be obtained by graft copolymerization of olefinically unsaturated acids, can be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, and hydrophilic polyesters.

0208The water-absorbing polymer can be obtained by radical graft copolymerization of acrylic acid or acrylate onto a water-soluble polymer matrix. Suitable water-soluble polymer matrices include, but are not limited to, alginates, polyvinyl alcohol, and polysaccharides such as starch. A polyfunctional ethylenically unsaturated radical crosslinking agent is used in the graft copolymerization according to the invention.

0209The water-absorbing polymer can be an organic-inorganic hybrid polymer composed of a polymeric acrylic acid or a polyacrylate on the one hand and a silicate, aluminate or aluminosilicate on the other hand. In particular, polymeric acrylic acid or polyacrylate can be used which have been obtained via free-radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinking agent has been used and in the production process of which a water-soluble silicate or soluble aluminate or mixtures of the two has been used.

0210Preferred hydrogels are in particular polyacrylates, polymethacrylates and those in <patcit id="pcit0060" dnum="US4931497A"><text>U.S. 4,931,497</text></patcit>, <patcit id="pcit0061" dnum="US5011892A"><text>US 5,011,892</text></patcit> and <patcit id="pcit0062" dnum="US5041496A"><text>U.S. 5,041,496</text></patcit> described graft polymers. Very particularly preferred hydrogels are those in<patcit id="pcit0063" dnum="WO0138402A"><text>WO 01/38402</text></patcit> Kneading polymers described and the in <patcit id="pcit0064" dnum="DE19854575"><text>DE 198 545 75</text></patcit> described hybrid organic-inorganic hydrogels based on polyacrylates.

0211The substances produced according to the invention and usable as radical crosslinkers in hydrogels can be used alone or in combination with other crosslinkers, for example internal or surface crosslinkers, for example the following:

0212Suitable crosslinkers are in particular methylenebisacryl or methacrylamide, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or triacrylate, e.g. B. butanediol or ethylene glycol diacrylate or methacrylate and trimethylolpropane triacrylate and allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl ester, polyallyl ester, tetraallyloxyethane, triallyl amine, tetraallyl ethylenediamine, allyl ester of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in <patcit id="pcit0065" dnum="EP0343427A"><text>EP-A-0 343 427</text></patcit> are described. However, hydrogels which are prepared using polyallyl ethers as crosslinkers and by acidic homopolymerization of acrylic acid are particularly preferred in the process according to the invention. Suitable crosslinkers are pentaerythritol tri- and tetraallyl ether, polyethylene glycol diallyl ether, monoethylene glycol diallyl ether, glycerol di and triallyl ether, polyallyl ether based on sorbitol, and ethoxylated variants thereof. Other particularly preferred crosslinkers are the polyethylene glycol diacrylates, ethoxylated derivatives of trimethylolpropane triacrylate, for example Sartomer SR 9035, and ethoxylated derivatives of glycerol diacrylate and glycerol triacrylate. Mixtures of the above crosslinking agents can of course also be used.

0213Hydrogels which are prepared as radical crosslinkers with an ester F prepared according to the invention are very particularly preferred.

0214The water-absorbing polymer is preferably a polymeric acrylic acid or a polyacrylate. This water-absorbing polymer can be prepared by a process known from the literature. Polymers which contain crosslinking comonomers are preferred (0.001-10 mol%), but very particularly preferred are polymers which have been obtained by free-radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinker has been used.

0215The hydrophilic, highly swellable hydrogels can be produced by polymerization processes known per se. Polymerization in aqueous solution by the so-called gel polymerization method is preferred. As mentioned above, dilute, preferably aqueous, particularly preferably 15 to 50% by weight aqueous solutions of one or more hydrophilic monomers and, if appropriate, a suitable graft base L in the presence of a radical initiator, preferably without mechanical mixing, using the Trommsdorff-Norrish effect (<nplcit id="ncit0007" npl-type="s"><text>Macromol. Chem. 1, 169 (1947</text></nplcit>)), polymerized. The polymerization reaction can be carried out in the temperature range between 0 ° C. and 150 ° C., preferably between 10 ° C. and 100 ° C., both under normal pressure and under elevated or reduced pressure. As usual, the polymerization can also be carried out in a protective gas atmosphere, preferably under nitrogen. To initiate the polymerization high-energy electromagnetic radiation or the usual chemical polymerization initiators K can be used, e.g. B. organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, azo compounds such as azodiisobutyronitrile and inorganic peroxy compounds such as (NH₄)₂S₂O₈, K₂S₂O₈ or H₂O₂.

0216You can optionally in combination with reducing agents such as ascorbic acid, sodium bisulfite, and iron (11) sulfate or redox systems, which contain as a reducing component an aliphatic and aromatic sulfinic acid, such as benzenesulfinic acid and toluenesulfinic acid or derivatives of these acids, such as. B. Mannich adducts of sulfinic acids, aldehydes and amino compounds, as in the<patcit id="pcit0066" dnum="DE1301566C"><text>DE-C-1 301 566</text></patcit> are used. By heating the polymer gels for several hours in the temperature range from 50 ° to 130 ° C., preferably from 70 ° to 100 ° C., the quality properties of the polymers can be improved still further.

0217The gels obtained are neutralized to 0-100 mol%, preferably 25-100 mol%, and particularly preferably 50-85 mol%, based on the monomer used, it being possible to use the customary neutralizing agents, preferably alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal carbonates, but particularly preferably sodium hydroxide, sodium carbonate and sodium hydrogen carbonate.

0218The neutralization is usually achieved by mixing in the neutralizing agent as an aqueous solution or preferably also as a solid. For this purpose, the gel is mechanically comminuted, for example using a meat grinder, and the neutralizing agent is sprayed on, sprinkled on or poured on, and then carefully mixed in. For this purpose, the gel mass obtained can be minced several times for homogenization. The neutralized gel mass is then dried with a belt or roller dryer until the residual moisture content is preferably below 10% by weight, in particular below 5% by weight.

0219However, the polymerization itself can also be carried out by any of the other methods described in the literature. In particular, the neutralization of the acrylic acid can also be carried out before the polymerization, as described in step f) above. The polymerization can then be carried out continuously or batchwise in a belt reactor known to the person skilled in the art or in a kneading reactor. When the polymerization is carried out in a belt reactor, initiation by means of electromagnetic radiation, preferably by means of UV radiation, or alternatively initiation using a redox initiator system is particularly preferred. The combination of both initiation methods is also very particularly preferred: electromagnetic radiation and chemical redox initiator system simultaneously.

0220n) The dried hydrogel can then be ground and sieved, roller mills, pin mills or vibrating mills usually being used for grinding. The preferred particle size of the sieved hydrogel is preferably in the range 45-1000 μm, preferably 45-850 μm, particularly preferably 200-850 μm, and very particularly preferably 300-850 μm. These areas preferably contain 80% by weight of the particles, in particular 90% by weight of the particles. The size distribution can be determined using established laser methods.

0221The present invention furthermore relates to crosslinked hydrogels which contain at least one hydrophilic monomer M in copolymerized form and are crosslinked with an ester F of a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B. The ester can be according to the invention or in a manner known in the art are produced, preferably in a manner according to the invention.

0222Compounds as described above can be used as esters F. Polyalcohols A and ethylenically unsaturated carboxylic acids B are also those as described above.

0223Preferred esters F are those in which the polyalcohol A is selected from the list polyol which has at least one ether, carboxyl or C as additional functionality₁ - C₄-Alkyloxycarbonylfunktion has, sugar alcohols, partially alkoxylated sugar alcohols, polyesterols, at least partially alkoxylated polyesterols and at least partially saponified, alkoxylated polyesterols, as described in each case above.

0224Those esters F in which the polyalcohol A is selected from the list of ditrimethylolpropane, dipentaerythritol, dimethylolpropionic acid and dimethylolbutyric acid are particularly preferred.

0225Further preferred esters F are those of the formula VII, as defined above, in which y is independent of one another<ul id="ul0009" list-style="dash" compact="compact"><li>for x = 2 a number greater than 8, preferably more than 10, particularly preferably more than 12 and in particular at least 15 and</li><li>for x = 3 or greater, a number greater than 7, preferably more than 9, particularly preferably more than 12 and in particular at least 15.</li></ul>

0226Likewise preferred are esters F of formula VII, as defined above, in which y is independently up to 6, particularly preferably up to 4 and very particularly preferably 4.

0227It is also possible to use esters F of the formula VII, as defined above, in which values ​​of 0, 1 or 2 can be assumed for x = 2 y and values ​​of 0 or 1 for x = 3 y.

0228The polyalcohols A described by the formula VII in the esters F, which are used as crosslinkers in the hydrogels mentioned above, can each be ethoxylated, propoxylated or mixed, ethoxylated and propoxylated and in particular exclusively ethoxylated, ie R¹⁰ in formula VII can mean, for example, independently of one another hydrogen and / or methyl and in particular exclusively hydrogen.

0229Particularly preferred esters F of formula VII are those esters F of a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B, the polyalcohol A being one to three to four times ethoxylated glycerol per glycerol or one trimethylolpropane or pentaerythritol four times ethoxylated per hydroxyl group .

0230The CRC value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 15, in particular 16, 18, 20, 22, 24 or higher, particularly preferably 25 in particular at 26, 27, 28, 29, particularly preferably at 30, 31, 32, 33, 34, 35, 36, 37 or higher.

0231The AUL 0.7 psi value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 8, in particular 9, 10, 11, 12, 13, 14 or higher , particularly preferably 15, in particular 16, 17, 18, 19 or higher, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26, 27, 28 or higher.

0232The AUL-0.5psi value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 8, in particular 9, 10, 11, 12, 13, 14 or higher, particularly preferred for 15, in particular for 16, 17, 18, 19 or higher, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26, 27, 28 or higher.

0233Use and use of the hydrogel-forming polymers according to the invention

0234The present invention further relates to the use of the above-mentioned hydrogel-forming polymers in hygiene articles, comprising

0235(P) an upper liquid-permeable cover (Q) a lower liquid impervious layer (R) a core located between (P) and (Q), containing 10-100% by weight of the hydrogel-forming polymer according to the invention 0 - 90% by weight of hydrophilic fiber material preferably 20-100% by weight of the hydrogel-forming polymer according to the invention, 0-80% by weight of hydrophilic fiber material more preferably 30-100% by weight of the hydrogel-forming polymer according to the invention, 0 - 70% by weight of hydrophilic fiber material even more preferably 40-100% by weight of the hydrogel-forming polymer according to the invention, 0-60% by weight of hydrophilic fiber material more preferably 50-100% by weight of the hydrogel-forming polymer according to the invention 0-50% by weight of hydrophilic fiber material particularly preferably 60-100% by weight of the hydrogel-forming polymer according to the invention, 0 - 40% by weight of hydrophilic fiber material particularly preferably 70-100% by weight of the hydrogel-forming polymer according to the invention, 0-30% by weight of hydrophilic fiber material extremely preferably 80-100% by weight of the hydrogel-forming polymer according to the invention, 0-20% by weight of hydrophilic fiber material most preferably 90-100% by weight of the hydrogel-forming polymer according to the invention, 0 - 10% by weight of hydrophilic fiber material (S) optionally a tissue layer and immediately above and below the core (R) (T) optionally a receiving layer located between (P) and (R).

0236The percentages are to be understood such that at 10-100% by weight, 11, 12, 13, 14, 15, 16, 17, 18, 19 to 100% by weight of the hydrogel-forming polymer according to the invention and all the intermediate% - Data (eg 12.2%) are possible and correspondingly hydrophilic fiber material from 0 to 89, 88, 87, 86, 85, 83, 82, 81% by weight and percentages in between (eg 87.8%) are possible are. If there are other materials in the core, the percentages of polymer and fiber decrease accordingly. The analog applies to the preferred ranges, for example 81, 82, 83, 84, 85, 86, 87, 88, 89% by weight for the hydrogel-forming polymer according to the invention and correspondingly 19, 18, 17, 16 , 15, 14, 13, 12, 11% by weight of the fiber material are present. Thus, in the preferred range 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 to 100% by weight of hydrogel-forming polymer according to the invention, in the more preferred range 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 to 100% by weight of hydrogel-forming polymer according to the invention, in the even more preferred range 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 to 100% by weight % hydrogel-forming polymer according to the invention, in the more preferred range 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 up to 100% by weight of hydrogel-forming polymer according to the invention, in the particularly preferred range 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 to 100% by weight of hydrogel-forming polymer according to the invention, in the particularly preferred range Range 70, 71, 71, 72, 73, 74, 75, 76, 77, 78, 79 to 100% by weight of hydrogel-forming polymer according to the invention and in the most preferred range 90, 91, 92, 93, 94, 95 , 96, 97, 98, 99 or 100 wt .-% hydrogel-forming polymer according to the invention.

0237Hygiene articles mean incontinence pads and incontinence pants for adults as well as diapers for babies.

0238The liquid-permeable cover (P) is the layer that has direct skin contact. The material for this consists of conventional synthetic or semi-synthetic fibers or films of polyester, polyolefins, rayon or natural fibers such as cotton. In the case of non-woven materials, the fibers are usually to be connected using binders such as polyacrylates. Preferred materials are polyester, rayon and their blends, polyethylene and polypropylene. Examples of liquid permeable layers are described in <patcit id="pcit0067" dnum="WO9957355A1"><text>WO 99/57355 A1</text></patcit>, <patcit id="pcit0068" dnum="EP1023883A2"><text>EP 102 388 3 A2</text></patcit>.

0239The liquid-impermeable layer (Q) usually consists of a film made of polyethylene or polypropylene.

0240In addition to the hydrogel-forming polymer according to the invention, the core (R) contains hydrophilic fiber material. Hydrophilic is understood to mean that aqueous liquids are rapidly distributed over the fiber. Usually the fiber material is cellulose, modified cellulose, rayon, polyester such as polyethylene terephthalate. Cellulose fibers such as cellulose are particularly preferred. The fibers generally have a diameter of 1 to 200 μm, preferably 10 to 100 μm. In addition, the fibers have a minimum length of 1 mm.

0241The structure and shape of diapers is generally known and is described, for example, in WO 95/26 209 p. 66 line 34 to p. 69 line 11, <patcit id="pcit0069" dnum="DE19604601A1"><text>DE 196 04 601 A1</text></patcit>, <patcit id="pcit0070" dnum="EP0316518A"><text>EP-A-0 316 518</text></patcit> and <patcit id="pcit0071" dnum="EP0202127A"><text>EP-A-0 202 127</text></patcit> described. Generally, diapers and other hygiene items are also in<patcit id="pcit0072" dnum="WO0065084A"><text>WO 00/65084</text></patcit>, especially on pages 6-15, <patcit id="pcit0073" dnum="WO0065348A"><text>WO 00/65348</text></patcit>, especially on pages 4 - 17, <patcit id="pcit0074" dnum="WO0035502A"><text>WO 00/35502</text></patcit>, especially pages 3-9, <patcit id="pcit0075" dnum="DE19737434"><text>DE 19737434</text></patcit>, <patcit id="pcit0076" dnum="WO988439A"><text>WO 98/8439</text></patcit> described. Sanitary articles for feminine hygiene are described in the following references. The hydrogel-forming polymers according to the invention which absorb aqueous liquids can be used there. Literature for feminine hygiene:<patcit id="pcit0077" dnum="WO9524173A"><text>WO 95/24173</text></patcit>: Absorption Article for Controlling Odor, <patcit id="pcit0078" dnum="WO9111977A"><text>WO 91/11977</text></patcit>: Body Fluid Odor Control, <patcit id="pcit0079" dnum="EP389023A"><text>EP 389023</text></patcit>: Absorbent Sanitary Articles, <patcit id="pcit0080" dnum="WO9425077A"><text>WO 94/25077</text></patcit>: Odor Control Material, <patcit id="pcit0081" dnum="WO9701317A"><text>WO 97/01317</text></patcit>: Absorbent Hygienic Article, <patcit id="pcit0082" dnum="WO9918905A"><text>WO 99/18905</text></patcit>, <patcit id="pcit0083" dnum="EP834297A"><text>EP 834297</text></patcit>, <patcit id="pcit0084" dnum="US5762644A"><text>US 5,762,644</text></patcit>, <patcit id="pcit0085" dnum="US5895381A"><text>US 5,895,381</text></patcit>, <patcit id="pcit0086" dnum="WO9857609A"><text>WO 98/57609</text></patcit>, <patcit id="pcit0087" dnum="WO2000065083A"><text>WO 2000/065083</text></patcit>, <patcit id="pcit0088" dnum="WO2000069485A"><text>WO 2000/069485</text></patcit>, <patcit id="pcit0089" dnum="WO2000069484A"><text>WO 2000/069484</text></patcit>, <patcit id="pcit0090" dnum="WO2000069481A"><text>WO 2000/069481</text></patcit>, <patcit id="pcit0091" dnum="US6123693A"><text>US 6,123,693</text></patcit>, <patcit id="pcit0092" dnum="EP1104666A"><text>EP 1104666</text></patcit>, <patcit id="pcit0093" dnum="WO2001024755A"><text>WO 2001/024755</text></patcit>, <patcit id="pcit0094" dnum="WO2001000115A"><text>WO 2001/000115</text></patcit>, <patcit id="pcit0095" dnum="EP105373A"><text>EP 105373</text></patcit>, <patcit id="pcit0096" dnum="WO2001041692A"><text>WO 2001/041692</text></patcit>, <patcit id="pcit0097" dnum="EP1074233A"><text>EP 1074233</text></patcit>. Tampons are described in the following writings:<patcit id="pcit0098" dnum="WO9848753A"><text>WO 98/48753</text></patcit>, <patcit id="pcit0099" dnum="WO9841179A"><text>WO 98/41179</text></patcit>, <patcit id="pcit0100" dnum="WO9709022A"><text>WO 97/09022</text></patcit>, <patcit id="pcit0101" dnum="WO9846182A"><text>WO 98/46182</text></patcit>, <patcit id="pcit0102" dnum="WO9846181A"><text>WO 98/46181</text></patcit>, <patcit id="pcit0103" dnum="WO2001043679A"><text>WO 2001/043679</text></patcit>, <patcit id="pcit0104" dnum="WO2001043680A"><text>WO 2001/043680</text></patcit>, <patcit id="pcit0105" dnum="WO2000061052A"><text>WO 2000/061052</text></patcit>, <patcit id="pcit0106" dnum="EP1108408A"><text>EP 1108408</text></patcit>, <patcit id="pcit0107" dnum="WO2001033962A"><text>WO 2001/033962</text></patcit>, <patcit id="pcit0108" dnum="DE200020662"><text>DE 200020662</text></patcit>, <patcit id="pcit0109" dnum="WO2001001910A"><text>WO 2001/001910</text></patcit>, <patcit id="pcit0110" dnum="WO2001001908A"><text>WO 2001/001908</text></patcit>, <patcit id="pcit0111" dnum="WO2001001909A"><text>WO 2001/001909</text></patcit>, <patcit id="pcit0112" dnum="WO2001001906A"><text>WO 2001/001906</text></patcit>, <patcit id="pcit0113" dnum="WO2001001905A"><text>WO 2001/001905</text></patcit>, <patcit id="pcit0114" dnum="WO200124729A"><text>WO 2001/24729</text></patcit>. Incontinence articles are described in the following writings: Disposable Absorbent Article for Incontinent Individuals:<patcit id="pcit0115" dnum="EP311344A"><text>EP 311344</text></patcit> Description pp. 3 - 9; Disposable Absorbent Article:<patcit id="pcit0116" dnum="EP850623A"><text>EP 850623</text></patcit>; Absorbent Article:<patcit id="pcit0117" dnum="WO9526207A"><text>WO 95/26207</text></patcit>; Absorbent Article:<patcit id="pcit0118" dnum="EP894502A"><text>EP 894502</text></patcit>; Dry Laid Fibrous Structure:<patcit id="pcit0119" dnum="EP850616A"><text>EP 850 616</text></patcit>; <patcit id="pcit0120" dnum="WO9822063A"><text>WO 98/22063</text></patcit>; <patcit id="pcit0121" dnum="WO9749365A"><text>WO 97/49365</text></patcit>; <patcit id="pcit0122" dnum="EP903134A"><text>EP 903134</text></patcit>; <patcit id="pcit0123" dnum="EP887060A"><text>EP 887060</text></patcit>; <patcit id="pcit0124" dnum="EP887059A"><text>EP 887059</text></patcit>; <patcit id="pcit0125" dnum="EP887058A"><text>EP 887058</text></patcit>; <patcit id="pcit0126" dnum="EP887057A"><text>EP 887057</text></patcit>; <patcit id="pcit0127" dnum="EP887056A"><text>EP 887056</text></patcit>; <patcit id="pcit0128" dnum="EP931530A"><text>EP 931530</text></patcit>; <patcit id="pcit0129" dnum="WO9925284A"><text>WO 99/25284</text></patcit>; <patcit id="pcit0130" dnum="WO9848753A"><text>WO 98/48753</text></patcit>. Feminine hygiene and incontinence articles are described in the following writings: Catamenial Device:<patcit id="pcit0131" dnum="WO9322998A"><text>WO 93/22998</text></patcit> Description pp. 26 - 33; Absorbent Members for Body Fluids:<patcit id="pcit0132" dnum="WO9526209A"><text>WO 95/26209</text></patcit> Description pp. 36 - 69; Disposable Absorbent Article:<patcit id="pcit0133" dnum="WO9820916A"><text>WO 98/20916</text></patcit> Description pp. 13 - 24; Improved composite absorbent structures:<patcit id="pcit0134" dnum="EP306262A"><text>EP 306262</text></patcit> Description pp. 3 - 14; Body Waste Absorbent Article:<patcit id="pcit0135" dnum="WO9945973A"><text>WO 99/45973</text></patcit>. These references and the references there are hereby expressly included in the disclosure of the invention.

0242The hydrogel-forming polymers according to the invention are outstandingly suitable as absorbents for water and aqueous liquids, so that they can advantageously be used as water-retaining agents in agricultural horticulture, as filtration aids and particularly as absorbent components in hygiene articles such as diapers, tampons or sanitary napkins.

Storage and fixation of the highly swellable hydrogels according to the invention

0243In addition to the highly swellable hydrogels described above, the absorbent composition according to the present invention contains compositions which contain or to which the highly swellable hydrogels are fixed. Any composition is suitable which can absorb the highly swellable hydrogels and which can also be integrated into the absorption layer. A large number of such compositions are already known and have been described in detail in the literature. A composition for incorporating the highly swellable hydrogels can e.g. B. be a fiber matrix consisting of a cellulose fiber mixture (air-laid web, wet laid web) or synthetic polymer fibers (meltblown web, spunbonded web), or else a mixed fiber structure made of cellulose fibers and synthetic fibers. Possible fiber materials are described in detail in the following chapter. The process of an air-laid web is described, for example, in<patcit id="pcit0136" dnum="WO9828478A"><text>WO 98/28 478</text></patcit>. Furthermore, open-pore foams or the like can be used to install highly swellable hydrogels.

0244Alternatively, such a composition can be created by fusing two individual layers, one or better a plurality of chambers being formed which contain the highly swellable hydrogels. Such a chamber system is described in detail in<patcit id="pcit0137" dnum="EP0615736A1"><text>EP 0 615 736 A1</text></patcit> P. 7 line 26 ff.

0245In this case, at least one of the two layers should be permeable to water. The second layer can be either water permeable or water impermeable. Tissues or other fabrics, closed or open-cell foams, perforated films, elastomers or fabrics made of fiber material can be used as layer material. If the absorbent composition consists of a composition of layers, the layer material should have a pore structure whose pore dimensions are small enough to retain the highly swellable hydrogel particles. The above examples for the composition of the absorbent composition also include laminates of at least two layers, between which the highly swellable hydrogels are installed and fixed.

0246In general, there is the possibility of fixing hydrogel particles within the absorbent core to improve the so-called dry and wet integrity. Dry and wet integrity means the ability to incorporate highly swellable hydrogels into the absorbent composition in such a way that they can withstand external forces both in the wet and in the dry state and there is no displacement or leakage of highly swellable polymer. The effects of force are to be understood above all as mechanical loads, such as occur in the course of movement when the hygiene article is worn, or the weight load under which the hygiene article is particularly exposed to incontinence. There are a multitude of possibilities for fixing which are known to the person skilled in the art. Examples such as fixation by heat treatment, addition of adhesives, thermoplastics, binder materials are listed in WO 95/26 209 p. 37 line 36 to p. 41 Line 14. Said passage is therefore part of this invention. Methods for increasing wet strength can also be found in<patcit id="pcit0138" dnum="WO200036216A1"><text>WO 2000/36216 A1</text></patcit>.

0247Furthermore, the absorbent composition can consist of a carrier material, such as. B. consist of a polymer film on which the highly swellable hydrogel particles are fixed. The fixation can be done on one or both sides. The carrier material can be water-permeable or water-impermeable.

0248In the above compositions of the absorbent composition, the highly swellable hydrogels are used in a weight fraction of 10 to 100% by weight, preferably 20-100% by weight, more preferably 30-100% by weight, even more preferably 40-100% by weight, more preferably 50-100% by weight, particularly preferably 60-100% by weight, particularly preferably 70-100% by weight, most preferably 80-100% by weight and most preferably 90-100% by weight based on the total weight of the composition and the highly swellable hydrogels incorporated.

Fibrous materials of the absorbent composition

0249The structure of the present absorbent composition according to the invention is based on a variety of fiber materials which are used as fiber networks or matrices. Included in the present invention are both fibers of natural origin (modified or unmodified) and synthetic fibers.

0250Patent WO 95/26 209 p. 28 line 9 to p. 36 line 8 gives a detailed overview of examples of fibers which can be used in the present invention. Said passage is therefore part of this invention.

0251Examples of cellulosic fibers include those commonly used in absorbent products such as fleece pulp and cotton type pulp. The materials (softwood or hardwood), manufacturing processes such as chemical pulp, semi-chemical pulp, chemothermal mechanical pulp (CTMP) and bleaching processes are not particularly limited. For example, natural cellulose fibers such as cotton, flax, silk, wool, jute, ethyl cellulose and cellulose acetate are used.

0252Suitable synthetic fibers are made from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylic compounds such as ORLON^®, Polyvinyl acetate, polyethyl vinyl acetate, soluble or insoluble polyvinyl alcohol. Examples of synthetic fibers include thermoplastic polyolefin fibers such as polyethylene fibers (PULPEX^®), Polypropylene fibers and polyethylene-polypropylene two-component fibers, polyester fibers, such as polyethylene terephthalate fibers (DACRON^® or KO-DEL^®), Copolyester, polyvinyl acetate, polyethyl vinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides, copolyamides, polystyrene and copolymers of the abovementioned polymers, and also two-component fibers made of polyethylene terephthalate-polyethylene-isophthalate copolymer, polyethyl vinyl acetate / polypropylene, polyethylene / polyester, copolyester / polypropylene / Polyester, polyamide fibers (nylon), polyurethane fibers, polystyrene fibers and polyacrylonitrile fibers. Polyolefin fibers, polyester fibers and their two-component fibers are preferred. Also preferred are heat-adhesive two-component fibers made of shell-core type and side-by-side type made of polyolefin because of their excellent dimensional stability after liquid absorption.

0253The synthetic fibers mentioned are preferably used in combination with thermoplastic fibers. During heat treatment, the latter partly migrate into the matrix of the existing fiber material and thus represent connection points and renewed stiffening elements when cooling. In addition, the addition of thermoplastic fibers means an expansion of the existing pore dimensions after the heat treatment has taken place. In this way it is possible to continuously increase the proportion of thermoplastic fibers towards the cover sheet by continuously metering in thermoplastic fibers during the formation of the absorption layer, which results in an equally continuous increase in pore sizes. Thermoplastic fibers can be formed from a large number of thermoplastic polymers which have a melting point of less than 190 ° C., preferably between 75 ° C. and 175 ° C. At these temperatures, no damage to the cellulose fibers is yet to be expected.

0254The lengths and diameters of the synthetic fibers described above are not particularly limited, and in general any fiber with a length of 1 to 200 mm and a diameter of 0.1 to 100 denier (grams per 9,000 meters) can be preferably used. Preferred thermoplastic fibers have a length of 3 to 50 mm, particularly preferred a length of 6 to 12 mm. The preferred diameter of the thermoplastic fiber is between 1.4 and 10 decitex, particularly preferably between 1.7 and 3.3 decitex (grams per 10,000 meters). The shape is not particularly limited, and examples include fabric-like, narrow cylinder-like, cut / split yarn-like, staple fiber-like and continuous fiber-like.

0255The fibers in the absorbent composition according to the invention can be hydrophilic, hydrophobic or a combination of both. According to the definition of<nplcit id="ncit0008" npl-type="b"><text>Robert F. Gould in the publication "Contact Angle, Wettability, and Adhesion", American Chemical Society (1964</text></nplcit>) A fiber is said to be hydrophilic if the contact angle between the liquid and the fiber (or its surface) is smaller than 90 °, or if the liquid tends to spread spontaneously on the same surface. As a rule, both processes are coexistent. Conversely, a fiber is said to be hydrophobic if a contact angle of greater than 90 ° is formed and no spreading is observed.

0256Hydrophilic fiber material is preferably used. It is particularly preferred to use fiber material that is weakly hydrophilic on the body side and most hydrophilic in the region around the highly swellable hydrogels. In the manufacturing process, the use of layers of different hydrophilicity creates a gradient that channels the impinging liquid to the hydrogel, where the absorption ultimately takes place.

0257Suitable hydrophilic fibers for use in the absorbent composition according to the invention are, for example, cellulose fibers, modified cellulose fibers, rayon, polyester fibers such as, for. B. polyethylene terephthalate (DACRON^®), and hydrophilic nylon (HYDROFIL^®). Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, such as treating thermoplastic fibers obtained from polyolefins (such as polyethylene or polypropylene, polyamides, polystyrenes, polyurethanes, etc.) with surfactants or silica. However, cellulose fibers are preferred for reasons of cost and availability.

0258The highly swellable hydrogel particles are embedded in the fiber material described. This can be done in a variety of ways, e.g. B. builds up an absorption layer in the form of a matrix with the hydrogel material and the fibers, or by embedding highly swellable hydrogels in layers of fiber mixture, where they are ultimately fixed, whether by adhesive or lamination of the layers.

0259The liquid-absorbing and distributing fiber matrix can consist of synthetic fiber or cellulose fiber or a mixture of synthetic fiber and cellulose fiber, the mixing ratio of (100 to 0) synthetic fiber: (0 to 100) cellulose fiber being able to vary. The cellulose fibers used can also be chemically stiffened to increase the dimensional stability of the hygiene article.

0260The chemical stiffening of cellulose fibers can be achieved in different ways. On the one hand, fiber stiffening can be achieved by adding suitable coatings to the fiber material. Such additives include, for example, polyamide-epichlorohydrin coatings (Kymene^® 557 H, Hercoles, Inc. Wilmington Delaware, USA), polyacrylamide coatings (described in <patcit id="pcit0139" dnum="US3556932A"><text>U.S. Patent 3,556,932</text></patcit> or as a commercial product of the Parez brand^® 631 NC, American Cyanamid Co., Stamford, CT, USA), melamine-formaldehyde coatings and polyethyleneimine coatings.

0261The chemical stiffening of cellulose fibers can also be done by chemical reaction. So z. B. the addition of suitable crosslinking substances bring about a crosslinking that takes place within the fiber. Suitable crosslinking substances are typical substances that are used to crosslink monomers. Including, but not limited to, are C₂-C₈ Dialdehydes, C₂-C₈ Monoaldehydes with acid functionality, and especially C₂-C₉ Polycarboxylic acids. Specific substances from this series are, for example, glutaraldehyde, glyoxal, glyoxylic acid, formaldehyde and citric acid. These substances react with at least 2 hydroxyl groups within a single cellulose chain or between two adjacent cellulose chains within a single cellulose fiber. The crosslinking stiffens the fibers, which are given greater dimensional stability through this treatment. In addition to their hydrophilic character, these fibers have uniform combinations of stiffening and elasticity. This physical property makes it possible to maintain the capillary structure even with simultaneous contact with liquid and compression forces and to prevent premature collapse.

0262Chemically crosslinked cellulose fibers are known and in <patcit id="pcit0140" dnum="WO9111162A"><text>WO 91/11162</text></patcit>, <patcit id="pcit0141" dnum="US3224926A"><text>U.S. Patent 3,224,926</text></patcit>, <patcit id="pcit0142" dnum="US3440135A"><text>U.S. Patent 3,440,135</text></patcit>, <patcit id="pcit0143" dnum="US3932209A"><text>U.S. Patent 3,932,209</text></patcit>, <patcit id="pcit0144" dnum="US4035147A"><text>U.S. Patent 4,035,147</text></patcit>, <patcit id="pcit0145" dnum="US4822453A"><text>U.S. Patent 4,822,453</text></patcit>, <patcit id="pcit0146" dnum="US4888093A"><text>U.S. Patent 4,888,093</text></patcit>, <patcit id="pcit0147" dnum="US4898642A"><text>U.S. Patent 4,898,642</text></patcit> and <patcit id="pcit0148" dnum="US5137537A"><text>U.S. Patent 5,137,537</text></patcit> described. The chemical crosslinking stiffens the fiber material, which is ultimately reflected in the improved dimensional stability of the entire hygiene article. The individual layers are by methods known to those skilled in the art, such as. B. fused together by heat treatment, adding hot melt adhesives, latex binders, etc.

Manufacturing process of the absorbent composition

0263The absorbent composition is composed of compositions which contain highly swellable hydrogels and the highly swellable hydrogels which are present in or fixed to said compositions.

0264Examples of processes with which an absorbent composition is obtained, which for example consist of a carrier material to which hydrogels which are highly swellable on one or both sides are fixed, are known and included, but not limited to, by the invention.

0265Examples of processes with which an absorbent composition is obtained which consists, for example, of highly swellable hydrogels (c) embedded in a fiber material mixture of synthetic fibers (a) and cellulose fibers (b), the mixing ratio of (100 to 0) synthetic fibers : (0 to 100) cellulose fiber may vary include (1) a process in which (a), (b) and (c) are mixed simultaneously, (2) a process in which a mixture of (a) and (b ) is mixed into (c), (3) a process in which a mixture of (b) and (c) is mixed with (a), (4) a process in which a mixture of (a) and (c ) is mixed into (b), (5) a process in which (b) and (c) are mixed and (a) is metered in continuously, (6) a process, in which (a) and (c) are mixed and (b) is metered in continuously, and (7) a method in which (b) and (c) are mixed separately in (a). Of these examples, methods (1) and (5) are preferred. The device used in this method is not particularly limited, and a conventional device known to those skilled in the art can be used.

0266The correspondingly produced absorbent composition can optionally be subjected to a heat treatment, so that an absorption layer with excellent dimensional stability in the moist state results. The heat treatment method is not particularly limited. Examples include heat treatment by supplying hot air or infrared radiation. The temperature during the heat treatment is in the range from 60 ° C. to 230 ° C., preferably between 100 ° C. and 200 ° C., particularly preferably between 100 ° C. and 180 ° C.

0267The duration of the heat treatment depends on the type of synthetic fiber, its quantity and the speed of manufacture of the hygiene article. Generally, the duration of the heat treatment is between 0.5 seconds to 3 minutes, preferably 1 second to 1 minute.

0268The absorbent composition is generally provided, for example, with a liquid-permeable top layer and a liquid-impervious bottom layer. Leg cuffs and adhesive tapes are then attached, thus completing the hygiene article. The materials and types of the permeable top layer and impermeable bottom layer, as well as the leg ends and adhesive tapes are known to the person skilled in the art and are not particularly restricted. Examples of this can be found in <patcit id="pcit0149" dnum="WO9526209A"><text>WO 95/26 209</text></patcit>.

0269The advantage of the present invention resides in the fact that the esters F which can be used as crosslinkers do not have to be purified after their preparation, in particular that the carboxylic acid B, for example acrylic acid, does not have to be separated off, since this is generally a monomer for the preparation of the hydrogels.

Experimental part

0270Unless otherwise stated, ppm and percentages used in this document relate to percentages by weight and ppm.

0271The process according to the invention is explained in more detail by the following example.

Examples

Manufacture of raw acrylate esters as superabsorbent crosslinkers

0272In the examples, the superabsorbent crosslinkers are prepared by esterifying polyetherols with acrylic acid, the water being separated off in an azeotropic distillation. Esterification catalyst is sulfuric acid in the examples. The reactants are presented together with a stabilizer mixture consisting of hydroquinone monomethyl ether, triphenyl phosphite and hypophosphorous acid in the examples in methylcyclohexane as an entrainer. The reaction mixture is then heated to about 98 ° C until the azeotropic distillation begins. During the azeotropic distillation, the temperature in the reaction mixture rises. The amount of water separated off is determined. The distillation is stopped when at least the theoretical amount of water has been removed. The entrainer is then removed in a vacuum distillation. The product is cooled and used as a crosslinker in the production of superabsorbents.

0273The conversion and yield of the reaction are not precisely determined, since the water separated off in the esterification also contains acrylic acid and acrylic acid is also removed during the vacuum distillation of the entrainer. The crude ester also contains free acrylic acid, which is titrated together with the catalyst (acid number).

0274Unless otherwise stated, all quantities are parts by weight.

Preparation of the ester

0275Acid numbers were acc. DIN EN 3682 determined.

Example 1 (polyethylene glycol 400 diacrylate)

0276740 Parts of polyethylene glycol with an average molecular weight of approximately 400 (Pluriol 400®, BASF AG) were esterified with 320 parts of acrylic acid and 5 parts of sulfuric acid in 354 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid were added as auxiliaries. 65 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 50.4 mg KOH / g and was adjusted to an acid number of 99 mg KOH / g by adding 72 parts of acrylic acid. The viscosity of the slightly yellowish product (iodine color number 1) was 91 mPas.

Example 2 (Polyethylene Glycol 600 Diacrylate)

0277810 Parts of polyethylene glycol with an average molecular weight of about 600 (Pluriol® 600, BASF AG) were esterified with 234 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid were added as auxiliaries. 40 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 54 mg KOH / g and was adjusted to 100 mg KOH / g by adding 70 parts of acrylic acid. The viscosity of the slightly yellowish product was 100 mPas.

Example 3 (approx. 3-fold, ie TMP triacrylate ethoxylated once per hydroxyl group)

0278579 Parts of triple ethoxylated trimethylolpropane are esterified with 562 parts of acrylic acid and 5 parts of sulfuric acid in 380 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid are added as auxiliaries. 125 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 38 mg KOH / g. The viscosity of the almost colorless product (iodine color number 0-1) is 200 mPas.

Example 4 (approx. 7 times per molecule of TMP ethoxylated TMP triacrylate)

0279681 Parts of 7-fold ethoxylated trimethylolpropane (Polyol TP 70 @, Perstorp) were esterified with 414 parts of acrylic acid and 5 parts of sulfuric acid in 365 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid were added as auxiliaries. 102 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 26 mg KOH / g and was adjusted to 99 mg KOH / g by adding 105 parts of acrylic acid. The viscosity of the almost colorless product (iodine color number 0-1) was 73.2 mPas.

Example 5 (approx. 15 times per molecule of TMP ethoxylated TMP triacrylate)

0280750 Parts of 15-fold ethoxylated trimethylolpropane (Emulan® TE15, BASF AG) were esterified with 216 parts of acrylic acid and 5 parts of sulfuric acid in 322 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid were added as auxiliaries. 44 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 36 mg KOH / g. The viscosity of the almost colorless product (iodine color number 0-1) was 324 mPas.

Example 6 (approx. 20 times per molecule of TMP ethoxylated TMP triacrylate)

0281830 Parts of approximately 20-fold ethoxylated trimethylolpropane were esterified with 216 parts of acrylic acid and 5 parts of sulfuric acid in 345 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid were added as auxiliaries. 44 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 36 mg KOH / g and was adjusted to 101 mg KOH / g by adding 96 parts of acrylic acid. The viscosity of the almost colorless product (iodine color number 0-1) was 324 mPas.

Example 7 (approx. 3 times per glycerol molecule of ethoxylated glycerol triacrylate)

0282561 Parts of approximately 3-fold ethoxylated glycerol are esterified with 605 parts of acrylic acid and 5 parts of sulfuric acid in 390 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 130 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 30 mg KOH / g. The viscosity of the almost colorless product (iodine color number 0-1) is 380 mPas.

Example 8 (approx. 5-fold per glycerol molecule of ethoxylated glycerol triacrylate)

0283940 Parts of about 5-fold ethoxylated glycerol (Lupranol® VP9209, BASF Schwarzheide GmbH) were esterified with 670 parts of acrylic acid and 6 parts of sulfuric acid in 500 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid were added as auxiliaries. 44 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 29 mg KOH / g.

Example 9 (approx. 9-fold per glycerol molecule of ethoxylated glycerol triacrylate)

0284704 Parts of about 9-fold ethoxylated glycerol (Lutron® HF1, BASF AG) were esterified with 363 parts of acrylic acid and 5 parts of sulfuric acid in 356 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid were added as auxiliaries. 76 parts of water were removed before the entrainer was removed by vacuum distillation. The product was cleaned using K300 filters. The acid number was 71 mg KOH / g and was adjusted to an acid number of 100 mg KOH / g by adding 8 parts of acrylic acid. The viscosity of the almost colorless product (iodine color number 0-1) was 113 mPas.

Example 10 (approx. 5-fold per molecule of pentaerythritol ethoxylated pentaerytrithol tetraacrylate)

0285382 Parts of about 5-fold ethoxylated pentaerytrithol are esterified with 348 parts of acrylic acid and 5 parts of sulfuric acid in 180 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 72 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 35 mg KOH / g. The viscosity of the dark colored product (iodine color number cannot be determined) is 280 mPas.

Example 11 (approx. 13 times per molecule of ethoxylated dipentaerytrithol)

0286545 Parts of about 13-fold ethoxylated dipentaerytrithol (DPP 130 from Perstorp AB) are esterified with 585 parts of acrylic acid and 5 parts of sulfuric acid in 400 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 130 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 45 mg KOH / g. The viscosity of the slightly colored product (iodine color number 1-2) is 1600 mPas.

Example 12 (approx. 4 times per molecule of ethoxylated sorbitol acrylate)

0287490 Parts of approximately 4-fold ethoxylated sorbitol are esterified with 444 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of toluene. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 96 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 45 mg KOH / g. The viscosity of the dark colored product (iodine color number 3-4) is 990 mPas.

Example 13 (approx. 6 times per molecule of ethoxylated sorbitol acrylate)

0288601 Parts of about 6-fold ethoxylated sorbitol are esterified with 444 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of cyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 96 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 45 mg KOH / g. The viscosity of the dark colored product (iodine color number 2-3) is 700 mPas.

Example 14 (approx. 8 times per molecule of ethoxylated sorbitol acrylate)

0289689 Parts of approximately 8-fold ethoxylated sorbitol are esterified with 444 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of toluene. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 100 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 45 mg KOH / g. The viscosity of the dark colored product (iodine color number 5) is 700 mPas.

Example 15 (approx. 10 times per molecule of ethoxylated sorbitol acrylate)

0290788 Parts of approximately 8-fold ethoxylated sorbitol are esterified with 444 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of toluene. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added as auxiliaries. 106 parts of water are separated off before the entrainer is removed by vacuum distillation. The product is cleaned using K300 filters. The acid number is 45 mg KOH / g. The viscosity of the dark colored product (iodine color number 10-15) is 500 mPas.

Example 16 (approx. 13 times per molecule of ethoxylated sorbitol hexaacrylate)

0291625 Parts of approximately 13-fold ethoxylated sorbitol were esterified with 518 parts of acrylic acid and 5 parts of sulfuric acid in 381 parts of methylcyclohexane. 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid were added as auxiliaries. 116 parts of water were removed before the entrainer was removed by vacuum distillation. The product is cleaned using K300 filters. The acid number was 78 mg KOH / g. The viscosity of the dark colored product (iodine color number not determinable) was 406 mPas.

Production of hydrogels

0292To determine the quality of the surface crosslinking, the dried hydrogel can be examined using the following test methods.

Test methods

a) Centrifuge Retention Capacity (CRC Centrifuge Retention Capacity)

0293This method determines the free swellability of the hydrogel in the tea bag. To determine the CRC, 0.2000 ± 0.0050 g of dried hydrogel (grain fraction 106 - 850 µm) are weighed into a 60 x 85 mm tea bag, which is then sealed. The tea bag is placed in an excess of 0.9% by weight saline solution (at least 0.83 1 saline solution / 1 g polymer powder) for 30 minutes. The tea bag is then centrifuged at 250 g for 3 minutes. The amount of liquid is determined by weighing the centrifuged tea bag.

b) Absorption under pressure (AUL Absorbency Under Load) (0.7 psi)

0294The measuring cell for determining the AUL 0.7 psi is a plexiglass cylinder with an inner diameter of 60 mm and a height of 50 mm, which has a glued-on stainless steel sieve bottom with a mesh size of 36 µm on the underside. The measuring cell also includes a plastic plate with a diameter of 59 mm and a weight, which can be placed together with the plastic plate in the measuring cell. The weight of the plastic plate and the total weight are 1345 g. To carry out the determination of the AUL 0.7 psi, the weight of the empty plexiglass cylinder and the plastic plate is determined and noted as Wo. Then 0.900 ± 0.005 g of hydrogel-forming polymer (particle size distribution 150 - 800 µm) is weighed into the plexiglass cylinder and distributed as evenly as possible on the stainless steel sieve plate. Then the plastic plate is carefully placed in the plexiglass cylinder and the entire unit is weighed; the weight is called W_a written down. Now the weight is placed on the plastic plate in the plexiglass cylinder. In the middle of the Petri dish with a diameter of 200 mm and a height of 30 mm, a ceramic filter plate with a diameter of 120 mm and a porosity of 0 is placed and enough 0.9% by weight sodium chloride solution is filled in that the liquid surface with the filter plate surface closes without the surface of the filter plate being wetted. Then a round filter paper with a diameter of 90 mm and a pore size &lt;20 µm (S&amp;S 589 black tape from Schleicher &amp; Schüll) is placed on the ceramic plate. The plexiglass cylinder containing the hydrogel-forming polymer is now placed with the plastic plate and weight on the filter paper and left there for 60 minutes. After this time, the complete unit is removed from the Petri dish from the filter paper and then the weight is removed from the Plexiglas cylinder. The plexiglass cylinder containing swollen hydrogel is weighed out together with the plastic plate and the weight as W_b written down.

0295The absorption under pressure (AUL) is calculated as follows: <maths id="math0001"><math display="block"><mi>AUL</mi><mspace width="1em" /><mn mathvariant="normal">0</mn><mo mathvariant="normal">,</mo><mn mathvariant="normal">7</mn><mspace width="1em" /><mi>psi</mi><mspace width="1em" /><mfenced open="[" close="]"><mi mathvariant="normal">G</mi><mo mathvariant="normal">/</mo><mi mathvariant="normal">G</mi></mfenced><mo mathvariant="normal">=</mo><mfenced open="[" close="]"><msub><mi mathvariant="normal">W</mi><mi mathvariant="normal">b</mi></msub><mo mathvariant="normal">-</mo><msub><mi mathvariant="normal">W</mi><mi mathvariant="normal">a</mi></msub></mfenced><mo mathvariant="normal">/</mo><mfenced open="[" close="]"><msub><mi mathvariant="normal">W</mi><mi mathvariant="normal">a</mi></msub><mo mathvariant="normal">-</mo><msub><mi mathvariant="normal">W</mi><mn mathvariant="normal">0</mn></msub></mfenced></math><img file="EP1516010B1_D0007.tif" /></maths>

0296The AUL 0.5psi is measured analogously with lower pressure.

0297c) The fraction extractable after 16 h (Extract. 16 h) was determined analogously to that in <patcit id="pcit0150" dnum="EP811636A1"><text>EP-A1 811 636</text></patcit>, P. 13, line 1 to line 19.

Example 18-27:

Preparation of the base polymer

0298In a laboratory kneader (Werner and Pfleiderer LUK 8.0 K2), 6 kg of a 40% by weight aqueous acrylic acid solution which had been neutralized to 77 mol% with sodium hydroxide were placed.

0299The types specified in Table 1 were added as crosslinkers in the amounts specified therein, based in each case on the acrylic acid used. Then 0.28% by weight of sodium persulfate and 0.0056% by weight of ascorbic acid, based in each case on the acrylic acid monomer used, were added as the polymerization initiator.

0300The reaction started and the temperature of the kneading jacket was adjusted so that the heat of reaction was not dissipated through the jacket. This results in an almost adiabatic heating of the reaction mixture, with the polymerization taking place with stirring. At the end of the reaction, the temperature is maintained for about an hour. Then a fine-crumbly gel could be emptied.

0301The gel was dried for 3 hours at 160 ° C. in a circulating air cabinet, ground with a laboratory roller mill, and sieved at 100-850 micrometers. This is the normal base polymer of Table 1.

0302Alternatively, the gel was first tempered for 6 hours at 90 ° C. in a sealed plastic bag, and only then was it dried for 3 hours at 160 ° C. in a circulating air cabinet, ground with a laboratory roller mill, and finally sieved at 100-850 micrometers. This is the hydrolyzed base polymer of Table 1.

Post-crosslinking:

0303The dry normal base polymer powder was mixed with a solution of 0.06% by weight of ethylene glycol diglycidyl ether (Nagase, Japan), 3.43% by weight of water and 1.47% by weight of 1,2-propanediol, based in each case on the polymer used Sprayed stirring homogeneously. The moist powder was then heated in a drying cabinet at 150 ° C. for 60 minutes. It was then sieved again at 850 micrometers to remove agglomerates. The properties of this post-crosslinked polymer were determined and are listed in Table 1.<tables id="tabl0003" num="0003"><table frame="all"><title>Table 1</title><tgroup cols="9"><colspec colnum="1" colname="col1" colwidth="18mm" /><colspec colnum="2" colname="col2" colwidth="21mm" /><colspec colnum="3" colname="col3" colwidth="27mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="18mm" /><colspec colnum="6" colname="col6" colwidth="18mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><colspec colnum="8" colname="col8" colwidth="14mm" /><colspec colnum="9" colname="col9" colwidth="18mm" /><thead><row><entry valign="top">example</entry><entry valign="top">Crosslinker</entry><entry valign="top">Amount used</entry><entry valign="top">solubility</entry><entry namest="col5" nameend="col6" align="left" valign="top"><b>Base polymer</b></entry><entry namest="col7" nameend="col9" align="left" valign="top">Post-crosslinked polymer</entry></row></thead><tbody><row rowsep="0"><entry /><entry /><entry /><entry /><entry>CRC</entry><entry>Extract. 16h</entry><entry>CRC</entry><entry>AUL 0.7 psi</entry><entry>Extract. 16h</entry></row><row rowsep="0"><entry>18</entry><entry>Product from example 1</entry><entry>0,44%</entry><entry>Clear</entry><entry>36,2</entry><entry>9,9%</entry><entry>27,9</entry><entry>25,8</entry><entry>7,2%</entry></row><row rowsep="0"><entry>19</entry><entry>Product from example 9</entry><entry>0,50%</entry><entry>Clear</entry><entry>31,0</entry><entry>7,5%</entry><entry>29,2</entry><entry>25,8</entry><entry>7,2%</entry></row><row rowsep="0"><entry>20</entry><entry>Product from example 4</entry><entry>0,50%</entry><entry /><entry>35,4</entry><entry>9,4%</entry><entry>29,9</entry><entry>25,8</entry><entry>6,1%</entry></row><row rowsep="0"><entry>21</entry><entry>Product from example 5</entry><entry>0,50%</entry><entry /><entry>38,1</entry><entry>13,8%</entry><entry>32,8</entry><entry>24,7</entry><entry>11,6%</entry></row><row><entry>22</entry><entry>Product from example 6</entry><entry>0,50%</entry><entry /><entry>35,3</entry><entry>10,0%</entry><entry>31,2</entry><entry>26,4</entry><entry>8,0%</entry></row></tbody></tgroup></table></tables>

0304The solubility of the crosslinker is determined by adding the crosslinker to the reaction mixture at room temperature. The assessment is done visually. The following scale is used Clear = complete clear solution Cloudy = clear cloudiness in the solution that can be observed with the naked eye Drop = floating of the crosslinker in drop form The other products according to the invention can be implemented analogously.