(meth)acrylic esters of polyalkoxylated trimethylolpropane

Translation of description of equivalent WO 03104302 A1

(Meth) acrylic esters of polyalkoxylated trimethylolpropane

description

The present invention relates to novel (meth) acrylic esters of polyalkoxylated trimethylolpropane, a simplified process for the preparation of these esters and use of the reaction mixtures thus obtainable.

Swellable hydrogel-forming polymers, known as superabsorbent (super Absorbing polymer, 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 aqueous liquids to form a hydrogel and to bind and are therefore preferred for the production of tampons, diapers, sanitary napkins, incontinence products, train- ing underwear for children, insoles and other hygiene articles for the absorption of body fluids. Superabsorbents are also used in other fields of technology where fluids, especially water or aqueous solutions, are absorbed. These areas include for example storage, packaging, transportation (packaging material for water-sensitive products such as flower transportation, shock protection); Food sector (transportation of fish, fresh meat; absorption of water, blood in FrischfischAFIeisch packs); Medicine (wound plasters, water-absorbent material for burn dressings or for other weeping wounds), cosmetics (carrier material for pharmaceuticals and medicaments, rheumatic plasters, ultrasound gel, cooling gel, cosmetic thickeners, sunscreen); Thickeners for oil / water or water / oil emulsions; Textiles (gloves, sportswear, moisture regulation in textiles, shoe inserts); chemical process industry. Applications (catalyst for organic reactions, immobilization of large functional molecules (enzymes), Adhe- siv for agglomerations, heat storage media, filtration aids, hydrophilic component in polymer laminates, dispersants, liquefiers.); Building and construction, installation (powder injection molding, clay plasters, vibration inhibiting medium, assistants in relation to tunneling in water-rich ground, cable sheathing); Water treatment, waste treatment, water removal (deicers, reusable sandbags); Cleaning; Agriculture industry (irrigation, retention of meltwater and dew precipitates, composting additive, protection of forests against fungal / insect infestation, delayed release of active ingredients to plants); fire protection (flying sparks) (covering houses or covering house walls with SAP gel, since water has a very high heat capacity, ignition can be prevented; spraying of SAP gel in fires such as forest fires); Coextrusion agent in thermoplastic polymers (hydrophilization of multilayer films); Production of films and thermoplastic moldings capable of absorbing water (eg storing rain and dew agricultural films); SAP-containing films for keeping fresh fruit and vegetables which can be packed in moist films; the SAP stores water discharged from fruits and vegetables without forming condensation droplets and returns the water partial to the fruits and vegetables again, so that neither fouling nor wilting occurs; SAP polystyrene coextrudates for example for food packaging such as meat, fish, poultry, fruits and vegetables); Carrier substance in active ingredient formulations (drugs, crop protection). In the hygiene articles, superabsorbents are generally positioned in an. Absorbent core which comprises as other materials, including fibers (cellulose fibers), the way as a kind of liquid that spontaneously applied liquid insults amounts between schenspeichem and efficient channelization of the body fluids in the absorbent core to ensure the superabsorbent.

The current trend in diaper design is toward ever thinner constructions having a reduced cellulose fiber content and an increased hydrogel. With the trend toward ever thinner diaper constructions the requirements profile has changed significantly to the water-swellable hydrophilic polymers over the years. While at the beginning of the development of highly absorbent hydrogels it was initially solely the very high swellability on which interest focused later shown that the ability of the superabsorbent to fluid transmission and distribution of crucial importance. It has been found that conventional superabsorbents on the

swell surface on wetting with liquid strong, so that the liquid transport is very difficult into the particle interior or completely prevented. This trait of superabsorbents is also referred to as "gel blocking". The greater amount of the hygiene article (polymer per unit area), the polymer in the swollen state must not form a barrier layer to subsequent fluid. A product having good transportation properties, an optimal utilization of the entire hygiene article can be ensured. The phenomenon of gel blocking, thereby preventing the leading in extreme cases to the escape of liquid, the so-called. Leakage of the hygiene article. Fluid transmission and distribution is thus to the initial absorption of body fluids is crucial.

Good transportation properties are possessed for example by hydrogels having high gel strength in the swollen state. Gels lacking in strength are deformable under an applied pressure (body pressure), clog the pores in the SAP / cellulose fiber absorbent and so prevent continued absorption of fluid. Enhanced gel strength is usually achieved by increasing the cross-linking, which, however, the retention of the product is reduced. An elegant way to enhance gel strength is surface postcrosslinking is., In this process, dried superabsorbents are subjected to out-average crosslinking density of an additional crosslinking. By Surface post increases the crosslink density in the sheath of the superabsorbent particle, whereby the absorption under pressure load to a higher level. Whereas the absorption capacity decreases in the superabsorbent particle sheath, the core of the superabsorbent particles by the presence of mobile polymer chains improved compared to the shell absorption capacity, so that shell construction an improved fluid transmission is ensured without the the gel blocking effect. It is perfectly desirable for the total capacity of the superabsorbent is exhausted not spontaneously but at different times. Since the hygiene article is generally repeatedly insulted usually with urine, the absorption capacity of the superabsorbent should sensibly not be exhausted after the first disposition.

Hydrophilic, highly swellable hydrogels are in particular polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable grafting base, crosslinked cellulose loose-or starch ethers, crosslinked carboxymethylcellulose, partially crosslinked polyalkylene oxide or swellable in aqueous fluids natural products, for example guar derivatives. Such hydrogels are not, however, used as aqueous solutions absorbing products to produce diapers, tampons, sanitary napkins and other hygiene as water-retaining agents in market gardening.

To improve their performance characteristics, such as diaper rewet and AUL, are hydrophilic, highly swellable hydrogels are generally surface or gel postcrosslinked. This postcrosslinking is known in the art per se and is preferably carried out in the aqueous gel phase or as surface post the ground and classified polymer particles.

EP 238050 discloses as possible Innenvernetzerfür superabsorbent two- or three times with acrylic or methacrylic acid esterified adducts of ethylene oxide and / or propylene oxide on trimethylolpropane.

Commercially available for example from Sartomer (Exton, PA, USA) is under the indicated trade names trimethylolpropane (SR 351), three times just ethoxylated trimethylolpropane triacrylate (SR 454), three times doubly ethoxylated trimethylolpropane (SR 499), thrice triply ethoxylated trimethylolpropane (SR 502 ), three times five times ethoxylated trimethylolpropane (SR 9035) and a total of 20 times ethoxylated trimethylolpropane (SR 415). Propoxylated trimethylolpropane triacrylates are pane under the trade names SR 492 (three times 1 PO per TMP) and CD 501 (three times 2 PO per TMP) available. WO 93/21237 discloses (meth) acrylates of alkoxylated polyhydric C₂ - C₁₀known as crosslinking hydrocarbons -. Were used Trimethylpropanver- netzer, the SR 351, SR 454, SR 502, SR 9035 and SR 415 correspond. These crosslinkers have 0, 3, 9, 15 or 20 EO units per TMP. Advantageously, according to WO 93/212373 times 2 to 7 EO units per TMP, especially 3 times 4 to 6 EO units per TMP.

A disadvantage of these compounds is that for at least partial removal of starting materials and by-products - the crosslinkers used in the reference cited have an acrylic acid content of less than 0.1% by weight - consuming cleaning operations are required.

Ethoxylated trimethylolpropane tri (meth) acrylates are mentioned in the patent literature repeatedly as internal crosslinkers, wherein only the commercially available from Sartomer TMP derivatives are used, for example in WO 98/47951 Trimethylolpropane- triethoxylat triacrylate in WO 01/41818 Sartomer # 9035 as called highly ethoxylated trimethylol propane triacrylate (HeTMPTA) and in WO 01/56625 SR 9035 and SR-492nd

The preparation 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 optionally a solvent, such as benzene, toluene, cyclohexane, is generally known.

As is well known, acrylic acid formation of the ester of (meth) and alcohol is an equilibrium reaction based, is to obtain economical conversions, a starting material generally used in excess and / or remove the esterification water formed and / or the target ester from the equilibrium.

Therefore, the water of reaction from the production of the higher (meth) acrylic acid ester is typically employed and usually an excess of (meth) acrylic acid.

US 4 187383 describes an esterification process of (meth) acrylic acid with organic polyols see at a reaction temperature of 20 to 80 ° C with an equivalent excess of 2 to 3: 1.

A disadvantage of this method is that amount to the low reaction temperature, the reaction times up to 35 hours and the excess is acid in the reaction mixture is removed by neutralization followed by phase separation. WO 2001/14438 (. Derwent Abstract No. 2001-191644 / 19) and WO 2001/10920 (Chemical Abstracts 134: 163502) describe processes for esterifying (meth) acrylic acid with Polyalkylenglykolmonoalkylethem in the ratio 3: 1 - 50: 1 in Ge - presence of acids and polymerization inhibitors and, after deactivation of the acidic catalyst, copolymerization of the residue from acrylic acid ester (meth) acrylates and (meth) acrylic acid at pH 1, 5 to 3.5, and its use as a cement additive.

A disadvantage of this method is that it is limited to Poiyalkylenglykolmonoalkylether that the catalyst must be deactivated and that such Copo lymerisate can not be used as crosslinkers for hydrogels since they only have one functionality.

The object was to provide further compounds which can be used as radical kalvernetzer for polymers, especially for superabsorbents and to simplify the manufacturing process for substances that are used as Radikalvemetzer for superabsorbents.

The object is achieved by the provide of an ester F of the formula

<img id="imgf000007_0001" he="47" wi="141" file="imgf000007_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" /> EO is O-CH2-CH2,

PO is independently O-CH2-CH (CH3) - or O-CH (CH3) -CH2-,

n1, n2, n3 are independently 4,5 or 6,

n1 + n2 + n3 is 14, 15 or 16,

m1, m2, m3 are independently 1, 2 or 3, m1 + m2 + m3 is 4, 5 or 6,

R1, R2, R3 are independently H or CH3.

The EO and PO units have been incorporated in such a way that polyethers and not peroxides.

Ester F Preference is given above wherein n1 + n2 + n3 is equal to 15th

Particularly preferred esters F as defined above wherein n1 = n2 = n3 =. 5

In addition, preference is given to esters F as defined above wherein m1 + m2 + m3 is equal to 5.

Furthermore, particular preference to esters F as defined above wherein m1 = m2 = 2 and m3 =. 1

Very particular preference is given to esters F are identical with the R1, R2 and R3, especially when R1, R2 and R3 are H.

The further object is achieved by a process for preparing an ester F of alkoxylated trimethylolpropane with (meth) acrylic acid, comprising the steps of

a) reacting alkoxylated trimethylolpropane with (meth) acrylic acid in pres- ence of at least one esterification catalyst C and of at least one polymerization inhibitor D and optionally one forms an azeotrope with water solvent E to form an ester F, b) optionally removing at least a part of in a ) resulting water from the reaction mixture, b), during and / or after a) take place, f) optionally, neutralizing the reaction mixture, h) optionally removing a solvent e was used, if this solvent by distillation and / or i) stripping with an under the reaction conditions, inert gas.

is preferred here

the molar excess of (meth) acrylic acid to alkoxylated trimethylolpropane 3.15: 1, and remains contained in the reaction mixture obtained after the last step, where appropriate neutralized (meth) acrylic acid substantially in the reaction mixture.

(Meth) acrylic acid is meant in the present invention, methacrylic acid, acrylic acid or mixtures of methacrylic acid and acrylic acid. Acrylic acid is preferred.

When the ester F is desired in pure form, it can be purified by known Auftrennungsverfah- reindeer.

The molar excess of (meth) acrylic acid to alkoxylated trimethylolpropane is at least 3.15: 1, preferably at least 3.3: 1, more preferably at least 3.75: 1, most preferably at least 4.5: 1 and particularly at least 7, 5: 1.

In a preferred embodiment, (meth) acrylic acid, for example, greater than 15 in an excess of 1, preferably greater than 30: 1, more preferably greater than 60: 1, most preferably greater than 150: 1, in particular greater than 225: 1 and especially greater than 300: 1.

The esterification products thus obtainable can essentially acrylic acid without further purification, specifically without substantial removal of the excess of (meth) and the content of esterification catalyst C, are used as radical crosslinkers in hydrogels.

Undercrosslinking is in this document, unless otherwise stated, the radical crosslinking (gel crosslinking, internal crosslinking, crosslinking of linear or lightly crosslinked polymer) understood. This crosslinking can by radical or cationic polymerization mechanisms or other, for example Michael addition, esterification or transesterification mechanisms, preferably by radical polymerization.

Hydrogel-forming polymers are preferably capable of absorbing distilled water of at least the net weight, preferably 10 times their own weight, this absorption is preferably achieved even under a pressure of 0.7 psi.

Applicable according to invention alkoxylated trimethylolpropane have the structure as shown in Formula II <img id="imgf000010_0001" he="38" wi="120" file="imgf000010_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" /> specified, wherein EO, PO, n1, n2, n3, m1, m2, m3 have the meanings given in the esters.

The reaction of trimethylolpropane with an alkylene oxide is known to the skilled worker. Possible ways of conducting can be found in Houben-Weyl, Methods of Organic Chemistry, 4th Edition, 1979, Thieme Verlag Stuttgart, ed. Heinz Kropf, Volume 6/1 a, part 1, pages 373-385.

For the preparation of compounds of formula II, for example, is first reacted with the trimethylol propane EO and then subsequently reacted with PO.

This can be done in which about 77 g of trimethylolpropane with 0.5 g of KOH, 45% is placed in water, in an autoclave and together at 80 ° C and reduced pressure (about 20 mbar) is dewatered. Then, at 120 to 130 ° C, the corresponding amount is added to propylene oxide and allowed to react at this temperature under elevated pressure. The reaction is complete when no further change in pressure is observed. It is then stirred for a further 30 min at 120 ° C. Then the appropriate amount of Ethyienoxid at 145 to 155 ° C is added over time at increased pressure and likewise allowed to react. After flushing with inert gas and cooling to 60 ° C, the catalyst is separated off by addition of sodium pyrophosphate and subsequent filtration.

The viscosity of the inventively employable polyols not described are special made claims, except that they should be readily pumpable at a temperature up to about 80 ° C, preferably they should have a viscosity below 1000 mPas, preferably below 800 mPas and most preferably below 500 mPas.

According Useful esterification catalysts C are sulfuric acid, aryl or alkyl sulfonic acids or mixtures thereof. Examples of arylsulphonic are benzenesulfonic acid, para-toluene sulfonic acid or dodecyl benzene sulfonic acid, examples of alkyl sulfonic acids are methanesulfonic acid or trifluoromethane sulfonic acid. Strongly acidic ion exchangers or zeolites are useful as esterification catalysts. Preferably sulfuric acid and ion exchangers are.

According to the invention usable polymerization inhibitors D are, for example, phenols such as alkylphenols le, for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl phenol, 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-Methylendioxydiphenol (sesame oil), 3,4-dimethyl phenol, hydroquinone, catechol (1, 2-dihydroxybenzene), 2- (1'

Methyl-cyclohex-1'-yl) -4,6-dimethylphenol, 2- or 4- (1'-phenyl-eth-1^.-yl) phenol, 2-tert-ButyI-6-methyl-phenol, 2,4,6-tris-tert-butylphenol, 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 4-tert-ButyIphenol, nonylphenol [11066-49-2], octyl phenol [140-66-9], 2,6-dimethyl phenol, bisphenol A, bisphenol F, bisphenol B, bisphenol C, bisphenol S, 3,3 \ 5,5'-tetrabromobisphenol A, 2,6-di-tert-butyl-p-cresol, Koresin® BASF AG, 3,5-di-tert-butyl-4-hydroxybenzoate, 4-tert-butylcatechol, 2- hydroxybenzyl alcohol, 2-methoxy-4-methylphenol, 2,3,6-trimethylphenol, 2,4,5-trimethylphenol, 2,4,6-trimethylphenol, 2-lsopropylphenol, 4-lsopropylphenol, 6- isopropyl-m-cresol, n-octadecyl-beta (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-butyI -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 [beta- (3,5-di-tert-butyI-4-hydroxyphenyl) - propionate], 2,6-di-te / τ.-butyl-4-dimethylaminomethyl-phenol, 6-se /c.-Butyl-2,4- dinitrophenol, Irganox® 565, 1141, 1192, 1222 and 1425 from Ciba specialty Chemicals, 3- (3 ', 5^l-di-Tert-butyl-4^.-hydroxyphenyl) propionate, 3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionsäurehexadecylester, 3- (3', 5'-di-terf.-butyl-4'-hydroxyphenyl) propionsäureoctylester , 3-thia-1 _l5-pentanediol-bis - [(3 ', 5^.-di-tert-butyl-4^l- Hydroxyphenyl) propionate], 4,8-dioxa-1, 11 -undecandiol-bis - [(3^., 5'-di-TE.-Butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1, 11-undecandiol-bis - [(3^.-fe / τ.-butyl-4^.-hydroxy-5'-methylphenyl) propionate], l .θ-nonanediol bis ^ S'.δ'-di-fetϊ. butyW--hydroxyphenyl) propionate], 1_l7-heptanediamine-bis [3- (3^., 5^.di-fert.-butyl-4^l- Hydroxyphenyl) propionamide], 1, 1 -Methandiamin-bis [3- (3 ', 5'-di-butyl-4'-hydroxyphenyl ferf.-) propionamide], 3- (3', 5^.-di-te /.-butyl-4'-hydroxyphenyl) propionic acid hydrazide, 3- (3 ', 5'-di-methyl-4'-hydroxyphenyl) propionic acid hydrazide, bis (3-fe / f.-butyl-5-ethyl -2-hydroxy-phen-1-yl) methane, bis (3,5-di --- ert.-butyl-4-hydroxy-phen-1 -yl) methane, bis [3- (1 '-methylcyclohex- 1 '-yl) -5-methyl-2-hydroxy-phen-1 -yl] methane, bis (3-ferf.-butyl-2-hydroxy-5-methyl-phen- 1 -yl) methane, 1, 1 -bis (5-fert.-butyl-4-hydroxy-2-methyl-phen-1 -yl) ethane, bis (5-fe /.-butyl 4-hydroxy-2-methyl-phen-1-yl) sulfide, bis (3-te / t-butyl-2-hydroxy-5-methyl-phen-1 - yl) sulfide, 1, 1 -bis (3, 4-dimethyl-2-hydroxy-phen-1-yl) -2-methyl propane, 1, 1 -bis (5-te / t-butyl-3-methyl-2-hydroxy-phen-1 -yl) -butane, 1, 3,5-tris [1 '- (3 ", 5" -di-fert.-butyl-4' hydroxy-phen-1 '-yl) -meth-1' -yl ^ Aδ-trimethylbenzene, 1 , 1, 4-tris (5^.th /.-butyl-4^.-hydroxy-2'-methyl-phen-1'-yl) butane, aminophenols, for example para-aminophenol, nitrosophenols, such as para-nitrosophenol, p-nitroso-o-cresol, alkoxyphenols, for example, 2- Methoxyphenoi (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, 2,5-dimethoxy-4-hydroxybenzyl alcohol (Syringaalkohol), 4- hydroxy-3-methoxybenzaldehyde (vanillin), 4-hydroxy-3-ethoxybenzaIdehyd (Ethylva- nillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin ), 1 - (4-hydroxy-3-methoxy-phenyl) ethanone (acetovanillone), eugenol, Dihydroeugenol, isoeugenol, tocopherols such as alpha-, beta-, gamma-, delta- and epsilon-tocopherol, tocol, alpha- Tocopherolhydrochinon, 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-fe-t-butylhydroquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 4-methylcatechol, tert-butyl hydroquinone, 3-methylcatechol, benzoquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 3-methylcatechol, 4-

Methylcatechol, tert-butylhydroquinone, 4-ethoxyphenol, 4-butoxyphenol, hydro- chinonmonobenzylether, p-phenoxyphenol, 2-methyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 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-dihydroxy-p-benzoquinone, Embelin, tetra- hydroxy-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 benzoquinonediimine, 1, 4-benzoquinone dioxime, Coerulignon, S.S'-di-tert-butyl-δ.δ¹- Dimethyldiphenochinon, p-rosolic acid (Aurin), 2,6-di-tert-butyl-4-benzylidene-benzoquinone, 2,5-di-tert-amylhydroquinone, N-oxyls such as 4-hydroxy-2,2,6 , 6- tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl₁ 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-pyrrolidin-N-oxyl, 1 -oxyl ^^ -methoxypiperidin. E.ö-tetramethyl ^, 1 -oxyl-2,2,6,6-tetramethyl-4-trimethylsilyloxypiperidin, ethylhexanoate 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2, 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-butyl malonate, 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) -hexahydroterephthalat, N, N'-bis (1 -oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -adipinamid, N- (1-2,2,6,6-tetramethylpiperidin -OxyI -4-yl) caprolactam, N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) - dodecylsuccinimid, 2,4,6-tris- [N-butyl-N- (1- oxyl 2.2₎6,6-tetramethylpiperidin-4-yl] triazine, N, N'-bis (1 -oxyl-tetramethylpiperidin ^ .θ.e ^ -y -N.N'-bis-formyl-l, 6- diaminohexane, 4, 4^.-Ethylenbis (1-oxyl-2,2,6,6-tetramethyIpiperazin-3-one) aromatic amines such as phenylenediamines, N, N-diphenylamine, N-nitroso-diphenylamine, nitroso diethylaniline, N, N'-dialkyl-para-phenylenediamine wherein the alkyl groups may be the same or different and each independently consist of 1-4 carbon atoms and may be straight or branched, for example N, N'-di- / so-butyl-p-phenylenediamine, N, N'-di- feo-propyl-p-phenylenediamine, Irganox 5057 from Ciba specialty Chemicals, N, N'-di- / so-butyl-p-phenylenediamine, N, N'-di- / so-propyl-p-phenylenediamine, p-phenylenediamine , N-phenyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-isopropyl-N-phenyl-p-phenylenediamine, N, N'Di-sec-butyl-p-phenylenediamine (the BPD Kerobit® BASF AG), N-phenyl-N'-isopropyl-p-phenylenediamine (Vulkanox 4010 by Bayer AG), N- (1, 3-DimethylbutyI) -N'-phenyl-p-phenylenediamine, N-phenyl-2- naphthylamine, Imoinodibenzyl, N, N'-diphenylbenzidine, N Phenyltetraanilin, acridone, 3-hydroxydiphenylamine, 4-hydroxydiphenylamine, hydroxy lamine as NN-diethylhydroxylamine, urea derivatives such as urea oderThio- urea, phosphorus-containing compounds such as triphenylphosphine, triphenyl phosphite, hypophosphorous acid or triethyl phosphite, sulfur-containing compounds such as diphenyl sulfide, phenothiazine or metal salts, wiebeispielsweise copper, manganese, cerium, nickel, chromium

chloride, dithiocarbamate, sulfate, acetate or salicylate, or mixtures thereof. Preferably, the mentioned phenols and quinones are particularly preferred are hydroquinone, hydroquinone monomethyl ether, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl-phenol, 2,6-di-tert .-butyl-4-methylphenol, 2,4-di-tert-butylphenol, triphenyl phosphite, hypophosphorous acid, CuCl₂ and guaiacol, very particular preference to hydroquinone and hydroquinone.

Particularly preferred are hydroquinone, hydroquinone and alkylphenols, optionally in combination with Tripehnylphosphit and / or hypophosphorous acid. Very particularly preferred are α-tocopherol (vitamin E), SS-tocopherol, y-tocopherol, δ-tocopherol or, optionally in combination with triphenyl phosphite and / or hypophosphorous acid.

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

Among the recited stabilizers, preferred are those which are aerobic, ie, those that require to develop their inhibiting effect, the presence of oxygen.

According to the invention usable solvents E are particularly those suitable for azeotropic removal of the water of reaction, if desired, are suitable, especially a--aliphatic, cycloaliphatic and aromatic hydrocarbons or mixtures thereof.

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

For the esterification the conventional preparation and / or work-up process can be applied of polyols, such as the aforementioned or in DE-A 19941 136, DE-A 3843843, DE-A 3843 854, DE-A 19937911, DE -A 19929258, EP-A 331 845, EP 554 651 or US 4,187,383 described.

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

The esterification apparatus comprises a stirred reactor, preferably a reactor with circulatory evaporator and an added distillation unit with condenser and phase separation vessel.

The reactor may be for example a reactor with jacketed heating and / or internal heating coils. Preferably, a reactor having an external heat exchanger and natural or forced circulation, ie, using a pump, more preferably natural circulation where circulation is accomplished without mechanical aids. Of course, the reaction in several reaction zones, for example a reactor cascade consisting of two to four, preferably two or three reactors can be performed.

Suitable circulatory evaporators are known to one skilled in the art and described for example in R. Billet, evaporator technology, HTB-Verlag, Bibliographical Institute Mannheim, 1965, 53. Examples of circulation it evaporates are tube heat exchangers, plate heat exchangers, etc.

Of course there may be in circulation, several heat exchangers.

The distillation unit is of per se known type. It may be a simple distillation unit which is optionally equipped with a splash guard, or a rectification column. Useful column internals include in principle all common internals, for example trays, structured packings and / or dumped. Among the trays cap trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred dumped packings are those of rings, coils, saddles or braids.

Typically 5 to 20 theoretical plates are sufficient.

The condenser and the separator vessel are of conventional design.

(Meth) acrylic acid and alkoxylated trimethylolpropane are used in the esterification a) usually in a molar excess as indicated above. The excess used can be up to about 3000: 1, if desired.

Useful esterification catalysts C include those recited above question.

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

If necessary, the esterification from the reaction mixture are removed by means of an ion exchanger. The ion exchanger can be added directly into the reaction mixture and then filtered off or the reaction mixture can be passed through an ion exchanger. Preferably, the esterification catalyst is left in the reaction mixture. If, however, the catalyst is an ion exchanger, it is preferably removed, for example by filtration.

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

This 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 about this.

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

The polymerization inhibitor (mixture) D may be used for example as an aqueous solution or as a solution in a reactant or product.

b) The water of reaction formed during the reaction can be distilled off during or after the esterification of a), whereby this process can be supported by a forming an azeotrope with water.

Suitable solvents E for azeotropic removal of the water of reaction, if desired, include the compounds recited above.

Preference is given to carrying out the esterification in the presence of a solvent.

The amount of solvent used is from 10 to 200% by weight, preferably 20-100% by weight, particularly preferably 30 to 100% by weight based on the sum of alcoholic xyliertem trimethylolpropane, and (meth) acrylic acid.

However, conceivable is an operation without entrainer, for example, in DE-A1 3,843,854, col. 2, line 18 to column. 4, line 45 is described, however, in contrast with the stabilizers mentioned above.

If the water contained in the reaction mixture is not removed via an azeotrope-forming solvent, it is possible by stripping with an inert gas, preferably more preferably to remove an oxygen containing gas, air or lean air, for example, as described in DE-A 3843 843 described. The reaction temperature for the esterification a) is generally at 40-160 ° C, preferably 60-140 ° C and more preferably 80-120 ° C. The temperature may remain constant during the reaction or increase, preferably it is raised in the course of the reaction. In this case, the final temperature of the esterification by 5 - 30 ° C higher than the initial temperature. The temperature for the esterification can be determined and controlled by varying the solvent concentration in the reaction mixture as described in DE-A 19941 136 and the German application with the file reference 100 63 175.4.

If a solvent is used, this can be distilled on the reactor distillation unit added from the reaction mixture.

The distillate may selectively be removed or, after condensation, fed sentrennapparat in a phase. The aqueous phase thus obtained is discharged normally, the organic phase can be recycled as reflux into the distillation unit and / or directly into the reaction zone and / or fed into a circulatory evaporator as described in the German patent application with the file reference 100 63 175.4 described.

When used as reflux, the organic phase, as described in DE-A 19941 136, are used to control the temperature in the esterification.

The esterification a) can pressure, at elevated pressure or vacuum are carried out, preferably under normal pressure.

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

The order of addition of the individual reaction components is measured inventive concept is not essential. It can be presented mixed all components and then heated, or can not, one or more components or only partially submitted and added only after heating.

The usable (meth) acrylic acid is not restricted in its composition and may comprise for example the following components:

(Meth) acrylic acid, from 90 to 99.9% by weight

Acetic acid 0.05 to 3% by weight

Propionic acid 0.01 to 1% by weight

Diacrylate 0.01 to 5 wt% Water from 0.05 to 5% by weight of carbonyl-containing from 0.01 to 0.3% by weight inhibitors from 0.01 to 0.1 wt% of maleic acid (anhydride) from 0.001 to 0.5 wt%

The raw used (meth) acrylic acid is generally stabilized with 200-600 ppm of phenothiazine or other stabilizers in amounts which permit comparable stabilization. Under the Ausfruck Carbonylics here, for example, acetone and lower aldehydes, such as formaldehyde, acetaldehyde, crotonaldehyde, acrolein, 2- and 3-furfural and Benazaldehyd understood.

Crude (meth) acrylic acid here refers to the (meth) understood acrylic acid mixture which is obtained or is obtained after absorption of the reaction gases of the propane / propene / acrolein relationship, isobutane / isobutene / methacrolein oxidation in an absorbent and subsequent removal of the absorbent is recovered by fractional condensation of the reaction gases.

Of course, even pure (meth) acrylic acid are used with such sweise following purity:

(Meth) acrylic acid, from 99.7 to 99.99% by weight

Acetic 50-1000 ppm

Propionic 10-500 ppm

Diacrylic 10-500 ppm

Water 50-1000 ppm

Carbonylics 1-500 ppm

Inhibitors 1-300 ppm

Maleic acid (anhydride) 1-200 ppm

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

Under pure or prepurified (meth) acrylic acid is generally (meth) acrylic acid whose purity is at least. 99.5% by weight and which is substantially free of aldehydic, other carbonylic and high-boiling components.

The during esterification distilled aqueous phase of about the attached column, if available, of the condensate removed, which generally 0.1 - may contain wt% (meth) acrylic acid 10, is separated and discharged. Advantageously contained therein (meth) acrylic acid with an extractant, preferably the solvent used in the esterification, for example cyclohexane, at a temperature between 10 and 40 ° C and a ratio of aqueous ger phase to extractant of 1: 5 - 30, 20 are extracted and recycled to the esterification - 10: preferably the first

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

The course of the esterification a) can be followed by monitoring the amount of water quantity and / or the decrease in the carboxylic acid concentration in the reactor are the.

The reaction may for example be terminated as soon as 90% of the theoretically expected amount of water has been carried out by the solvent, preferably at least 95% and more preferably at least 98%.

Completion of the reaction may for example be determined by the fact that substantially no further water of reaction is Removes over the entraining agent. ; If (meth) acrylic acid together with the reaction water discharged, their proportion is, for example, by back-titration of an aliquot of the aqueous phase determinable.

On removal of the reaction Waser example, can be dispensed with if the (meth) acrylic acid is used in a high stoichiometric excess, for example of at least 4.5: 1, preferably at least 7.5: 1 and most preferably at least 15: 1. In this case, there remains a substantial part of the amount of water formed in the reaction mixture. During or after the reaction, only the amount of water is removed from the reaction mixture, which is determined by the volatility at the employed temperature, and are also no measures for removing the water of reaction formed. For example, at least 10 wt% of the remaining water of reaction formed in the reaction mixture, preferably at least 20%, more preferably at least 30% by weight, most preferably at least 40 and especially at least 50% by weight. c) After completion of the esterification, the reactor mixture may be cooled in a conventional manner to a temperature of 10 to 30 ° C and optionally by adding solvent, which may be the same as any solvent used for the azeotropic removal of water or another, a any desired ester concentration can be adjusted.

In 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 about 40%, for example to reduce the viscosity.

It is important that forms an essentially homogeneous solution after dilution.

This preferably takes place only relatively shortly before use in the preparation of the hydrogel, for example not more than 24 hours before, preferably not more than 20, more preferably not more than 12, most preferably not more than 6 and especially not more than 3 hours ago.

The diluent G is selected from the group consisting of water, a mixture of water with one or more unlimited water-soluble organic solvent or a mixture of water with one or more simple or polyfunctional alcohols, eg methanol and glycerol. The alcohols preferably bear 1, 2 or 3 hydroxyl groups and preferably have from 1 to 10, in particular up to 4 carbon atoms. Preference is given to primary and secondary alcohols.

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

d) If necessary, the reaction mixture may be decolorized, for example by treatment with activated carbon or metal oxides, such as alumina, Siliciumo- oxide, magnesium oxide, zirconium oxide, boron oxide or mixtures thereof, in amounts of for example 0.1 to 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 are subjected.

This can by addition of powdery or granular decolorizing agent to the reaction mixture and subsequent filtration or by passing the reaction mixture used via a bed of the decolorizer in the form of any desired suitable moldings.

The discoloration of the reaction mixture can take place at any point in the work-up procedure, entfemung example at the stage of the crude reaction mixture or after any prewash, neutralization, wash or solvent.

The reaction mixture may further be subjected to a prewash e) and / or a neutralization on f) and / or a subsequent wash g), preferably merely to a neutralization f). Optionally can be interchanged neutralization f) and prewash e) in order also.

From the aqueous phase of the washes e) and g) and / or neutralization f) may con- tained (meth) acrylic acid and / or catalyst C recovered at least partially by acidification and extraction with a solvent and be used again.

For preliminary or subsequent wash e) or g) the reaction mixture is prepared in a Waschap- with a washing liquid, for example water or a 5-30% strength by weight, preferably 5-20, more preferably 5-15 wt% aqueous sodium chloride , potassium chloride, ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline treated.

The ratio of reaction mixture to wash liquor is generally from 1: 0,1 - 1, preferably 1: 0,2 - 0,8, more preferably from 1: 0.3 to 0.7.

The wash or neutralization can be for example in a stirred vessel or in other conventional apparatus, for example in a column or mixer-settler apparatus, performed.

Technically all known extraction and washing processes and apparatus can be used for washing or neutralization in the process of the invention, for example those described in Ullmann's Encyclopedia of Industrial Chemistry, 6th ed, 1999 Electronic Release, Chapter: Liquid - Liquid Extraction - Apparatus are described. For example, these can be single or multistage, preferably single-stage, extractions and those in cocurrent or countercurrent mode, preferably counter its current driving fashion. Preferably sieve tray or randomly packed columns, stirred vessels or mixer-settler apparatuses and also pulsed columns or columns are having rotating internals.

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

A subsequent wash g) may be the removal of base or salt traces from the neutralized in f) the reaction mixture is advantageous.

For neutralization, f) can be optionally pre-washed reaction mixture, which may still contain acrylic acid, small amounts of catalyst and the main amount of excess (meth) with a 5-25, preferably 5-20, particularly preferably 5-15% by weight aqueous solution of a Base such as alkali or alkaline earth metal oxides, hydroxides, carbonates or bicarbonates, preferably sodium hydroxide solution, sodium bicarbonate, sodium carbonate, potassium hydrogen carbonate, calcium hydroxide, lime, ammonia, ammonia water or potassium carbonate, optionally 5-15 wt% sodium chloride, potassium chloride, ammonium chloride or ammonium sulfate may be added, more preferably with sodium hydroxide or caustic soda-sodium chloride solution, are neutralized. The degree of neutralization is preferably 5 to 60 mol%, preferably monomers 10 to 40 mol%, particularly preferably 20 to 30 mol%, based on the acid groups. This neutralization can take place before and / or during the polymerization, preferably before the polymerization.

The addition of the base takes place 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 of 4-13 is. The dissipation of the heat of neutralization is preferably carried out by cooling the vessel with the aid of internal cooling coils or via Doppelwandküh- ment.

The ratio of reaction mixture to neutralizing liquor is generally from 1: 0,1 - 1, preferably 1: 0,2 - 0,8, more preferably from 1: 0.3 to 0.7.

With regard to the apparatus, the above statements.

h) If a solvent is present in the reaction mixture, so it can be removed by distillation substantially. Preferably, any solvent after washing and / or neutralization of the reaction mixture is optionally removed, if desired, this can also take place prior to the wash or neutralization.

For this, the reaction mixture with an amount of storage stabilizer, preferably hydroquinone described offset that after removal of the solvent 100 - 500, preferably 200-500 and more preferably 200-400 ppm thereof in the target ester (residue) are included.

The distillative removal of the main amount of solvent is effected for example in a stirred tank with jacketed heating and / or internal heating coils under reduced pressure, for example at 20-700 mbar, preferably 30 to 500 and more preferably 50-150 mbar and a temperature 40-80 ° C ,

Of course, can also take place in a falling-film or thin-film evaporator distillation. For this purpose, the reaction mixture is, preferably several times in a circuit, under reduced pressure, for example at 20 to 700 mbar, preferably 30 to 500 and particularly preferably 50-150 mbar and a temperature of 40-80 ° C through the apparatus.

An inert gas, preferably an oxygen-containing gas, more preferably air or a mixture of air and nitrogen (air) are introduced into the distillation apparatus, for example, 0.1 - 1. preferably 0,2 - 0,8, and more preferably 0, 3 to 0.7 m³/ m³h, based on the volume of the reaction mixture.

The residual solvent content in the residue after distillation is generally below 5% by weight, preferably 0.5 - 5% or more preferably 1 to 3% by weight.

The separated solvent is condensed and preferably reused.

If necessary, in addition to or instead of a distillation Lösungsmittelstrip- i) pung be performed.

For this, the target ester, which still contains small amounts of solvent, at 50 - 90 ° C, preferably 80 - heated to 90 ° C and the remaining amounts of solvent removed with a suitable gas in a suitable apparatus. To support can optionally also be a vacuum.

Suitable apparatuses are, for example, columns of per se known type, which have the customary internals, for example trays, dumped packing or structured packing, preferably dumped. Useful column internals are in principle all gängi- gen internals, for example trays, structured packings and / or random packing. Among the trays cap trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred; among the dumped packings are those of rings, coils, saddles, Raschig, Intos or Pall rings, barrel or Intalox saddles, Top-Pak, etc. or braids.

Another possibility here is a falling-film, thin-film or wiped film evaporator, such as a Luwa, Rotafiim- or Sambay evaporator, which may be splash-protection, for example with a demister.

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

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

If necessary, the ester at any stage of the proceedings Aufarbeitungsverfah-, preferably after washing / neutralization and any effected solvent removal filtration j) are subjected to remove precipitated traces of salts and any decolorizing.

In one conceivable embodiment, the esterification a) of alkoxylated tri is propane with the (meth) acrylic acid in an above-mentioned molar Ü surplus of at least 15: 1 in a presence of at least one esterification catalyst C and of at least one polymerization inhibitor D without water Aze otrop forming solvent.

The used in excess (meth) acrylic acid is not removed in a preferred embodiment, essentially, that it is only that fraction of (methacrylic acid removed from the reaction mixture, which is determined by the volatility at the employed temperature, and are also no measures for separation the carboxylic acid performed, such as distillation, rectification tive, extractive, such as washes, absorptive, such as being passed over activated carbon or ion exchangers, and / or chemical steps such as scavenging of the carboxylic acid with epoxides.

Preferably, the reaction mixture contained in the (meth) acrylic acid is not more than 75% by weight, particularly preferably not more than 50% by weight, very particularly preferably given to not more than 25 wt%, in particular not more than 10%, and especially not more than 5% by weight from the reaction mixture separated off, based on the contained end of the reaction in the reaction mixture (meth) acrylic acid. In a particularly preferred embodiment, to dispense with the step b), is so removed that only acid the amount of water of reaction and (methacrylic) from the reaction mixture, which is determined by the volatility at the employed temperature. This can preferably be prevented by substantially complete condensation.

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

The reaction mixture thus obtainable preferably has an acid value gem. DIN EN 3682 of at least 25 mg KOH / g of reaction mixture, particularly preferably from 25 to 80 and very particularly preferably from 25 to 50 mg KOH / g.

On a preliminary or subsequent wash e) or g) is preferably omitted; merely a filtration step j) may be useful.

Then the reaction mixture in step c) can be diluted, in this

Case, it is preferably implemented within 6 hours, more preferably within 3 hours to form the hydrogel. Preferably it can be neutralized in a step f).

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

The invention also relates to a composition of matter comprising

at least one ester F, obtainable by one of the esterification process described above,

(Meth) acrylic acid and diluent G.

Further components may be included

Esterification catalyst C in protonated or unprotonated form,

Polymerization inhibitor D and optionally solvent E, if such was used in the Versterung. The mixture may optionally be neutralized and have a pH as listed above under f).

When the mixture is neutralized, as a part of the (meth) acrylic acid is at least in their water-soluble alkali metal, alkaline earth metal or ammonium salts.

Preferred mixture contains at

Ester F in a fraction from 0.1 to 40 wt .-%, particularly preferably 0.5 to 20, very particularly preferably 1 to 10, in particular 2 to 5 and especially from 2 to 4

Wt .-%,

Monomer M 0.5 to 99.9% by weight, particularly preferably 0.5 to 50% by weight, very particularly preferably 1 - 25, in particular 2 - 15 and especially 3 to 5% by weight, the esterification catalyst C 0 - 10% by weight, particularly preferably from 0.02 to 5, most preferably 0.05 to 2.5% by weight and in particular 0.1 to 1% by weight,

Polymerization inhibitor D 0-5 wt%, particularly preferably 0.01 to 1, 0, very particularly preferably 0.02 to 0.75, in particular 0.05 to 0.5 and especially from 0.075 to 0.25% by weight, solvent E 0 - 10% by weight, more 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 sum is always 100% by weight, and optionally a diluent G ad 100% by weight.

The reaction mixtures obtainable by the above method and the inventive mixtures can be used

as radical of water-absorbing hydrogels, as a starting material for the manufacture of polymer dispersions, as a starting material for producing polyacrylates (apart from hydrogels), - as a paint raw material or as a cement additive.

For use as radical of water-absorbing hydrogels such compositions of the invention are particularly useful, the sensitivity (at 25 ° C in distilled water) of at least 0.5 percent by a solubility in water.%, Preferably at least 1 wt.%, More preferably at least 2 percent. %, even more preferably at least 5 wt.%, particularly preferably at least 10 wt.%, very particularly preferably at least 20 wt.% and in particular of at least 30 wt.% exhibit. k) The reaction mixture from the esterification, including workup steps, so far as these are passed through, for example, the reaction mixture from f), respectively, if they are not f), from b), or, if they are not b), the reaction mixture from a ), may optionally be added with additional monoethylenically unsaturated compounds N which do not bear an acid group but are copolymerizable with the hydrophilic monomers M, then at least one radical initiator K and optionally at least one grafting base L can be polymerized to produce water-absorbing hydrogels in the presence ,

Advantageously

I) the reaction mixture from k) postcrosslinked.

For preparing k) these hydrophilic, highly swellable hydrogels suitable hydrophilic le monomers M are, for example, polymerizable acids such as acrylic acid, methacrylic acid, ethacrylic acid, α-chloro acrylic acid, maleic acid, Maiein- 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, Sulfomethacrylat, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropyIsulfonsäure, 2-hydroxy-3-methacryl-oxypropylsulfonsäure, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido 2methylpropansulfonsäure, 2- acrylamido-2-methylpropane and also their amides, hydroxyalkyl esters and amino- or ammonio-containing esters and amides. The monomers can be used alone or in mixture with one another. Furthermore water-soluble N-vinylamides or Diallyidimethyl- ammonium chloride. Preferred hydrophilic monomers are compounds of the formula V

<img id="imgf000027_0001" he="21" wi="23" file="imgf000027_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

wherein

R³ Hydrogen, methyl or ethyl,

R⁴ the group -COOR⁶, A sulfonyl or phosphonyl group, one with a (CC₄) Alkyl alcohol esterified phosphonyl group or a group of the formula VI <img id="imgf000028_0001" he="20" wi="38" file="imgf000028_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

R⁵ Hydrogen, methyl, ethyl or a carboxyl group, R⁶ Hydrogen, amino or hydroxy- (C₁-C₄) Alkyl and R⁷ a sulfonyl group, a phosphonyl group or a carboxyl group.

Examples of (CrC) - alkyl alcohol are methanol, ethanol, n-propanol or n-butanol.

Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid, especially acrylic acid.

To optimize properties, it can be sensible to use additional monoethylenically cally unsaturated compounds N which do not bear an acid group but are copolymerizable with the monomers bearing acid groups. These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acid, eg. As acrylamide, methacrylamide and N-vinylformamide, N-vinylacetamide, N-methyl-vinylacetamide, acrylonitrile and methacrylonitrile. Other suitable compounds are, for example, vinyl esters of saturated C to C carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers having at least 2 carbon atoms in the alkyl kylgruppe such. As ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C₃- To C₆Carboxylic acids, eg., Esters of monovalent C ^ -C₁₈-Al- alcohols and acrylic acid, methacrylic acid or maleic acid, monoesters of maleic acid, z. B. Maieinsäuremono-methyl ester, N-vinyl lactams such as N-vinylpyrrolidone or N-vinylcaprolactam, acrylic and methacrylic esters of alkoxylated monohydric saturated alcohols, for. example from alcohols having 10 to 25 carbon atoms which have been reacted with 2 to 200 mol ethylene oxide and / or propylene oxide per mole of alcohol, as well as motor noacrylsäureester and monomethacrylic esters of polyethylene glycol or polypropylene glycol, the molar masses (M_n) Of the polyalkylene glycols, for example, to be able to 2000th Further suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene te or t-butyl.

This without acid groups monomers can be used in a mixture with other monomers, eg., Mixtures of vinyl acetate and 2-hydroxyethyl acrylate in any proportion. This no monomers bearing acid groups to the reaction mixture in quantities of between 0 and 50 wt .-%, preferably less than 20 wt .-% was added. Preferably, the cross-linked (co) polymers of acid-group-containing monoethylenically unsaturated monomers, which are optionally converted before or after the polymerization in their alkali or ammonium salts, and from 0 - 40% by weight based on their total weight no acid-functional monoethylenically unsaturated monomers.

The production, testing and use of (meth) acrylic acid (co) polymers, polyacrylic acids and superabsorbers has been widely described and therefore is well known, see for example "Modern Superabsorbent Polymer Technology", FL Buchholz and AT Graham, Wiley-VCH, 1998, or in Markus Frank "superabsorbents" in Ullmann's Handbook of Industrial Chemistry band 352,003th

Preferred hydrogels are obtained polymerization of acid-functional monoethylenically unsaturated monomers M or salts thereof by crosslinking polymerization or copolymerization are.

The polymers obtainable are characterized by an improved saponification index (VSI).

In the method for post-crosslinking the starting polymer is treated with a postcrosslinker and, preferably, post-crosslinked during or after the treatment by raising the temperature, and dried, wherein the crosslinker is preferably contained in an inert solvent. Inert solvents are understood to be the reaction in the reaction either with the starting polymer or with the postcrosslinker. Preferred are such solvents, of which more than 90%, preferably more than 95%, particularly preferably more than 99%, react in particular more than 99.5% chemically with the starting polymer or cross-linker. Are

Postcrosslinking I) and drying m) where the temperature range between 30 and 250 ° C, particularly 50-200 ° C, is very particularly preferably the

Range between 100-180 ° C. The application of the Oberflächennachvemetzungslö- solution is preferably applied by spraying the polymer in suitable spray mixers. Following spraying, the polymer powder is thermally dried, and the crosslinking reaction can take place both before and during drying. Preference is given to spraying a solution of the crosslinker in reaction mixers or mixing and drying systems such as Lödige mixers, BEPEX mixers, NAUTA mixers, SHUGGI mixer or PROCESSALL. Moreover, fluidized bed dryers can be used. Drying may take place in the mixer itself, by heating the jacket or blowing in warm air. Equally suitable is a downstream dryer such as a tray dryer, a rotary kiln, or a heatable screw. But it may also be eg as a drying process azeotropic distillation. The preferred residence time at this temperature in the reaction mixer or dryer is below 60 min., More preferably below 30 min.

Preferably the above processes wherein the starting polymer is a polymeric acrylic acid or a polyacrylate, especially a polymeric acrylic acid or a polyacrylate obtained by free-radical polymerization using a multi-functional ethylenically unsaturated radical crosslinker are.

such methods are preferred in which the composition of matter containing radical crosslinkers, ie the ester F, and diluents G in a ratio of 0.1 - 10 wt .-% used based on the mass of the starting polymer - 20 wt .-%, in particular 0.5 becomes.

Such processes are preferred in which the free-radical in a dose of 0.01 -. 5.0% by weight, preferably 0.02 - 3.0 wt%, most preferably 0.03 -.. 2.5% by weight, in particular 0.05 -. 1, 0, and specifically from 0.1 to 0.75 weight% based on the

Starting polymer.

The invention also provides polymers prepared according to any one of the above method and their use in hygiene articles, packaging materials and nonwovens, as well as the use of an abovementioned composition of matter for the preparation of crosslinked or crosslinkable by heat treating polymers, in particular in paints and coatings.

The case to be used hydrophilic, highly swellable hydrogels (Ausgangspoiyme- re) are in particular polymers of (co) polymerized hydrophilic monomers M,

Graft (co) polymers of one or more hydrophilic monomers M on a suitable grafting L, crosslinked starch ethers or swell in aqueous fluids natural products, for example guar derivatives. These hydrogels are known to the expert and described for example in US-4286082, DE-C-2706 135, US 4,340,706, DE-C-37 13 601, DE-C-2 840 010, DE-A-4344548,

DE-A4020780, DE-A-4015085, DE-A-3917846, DE-A-3807289, DE-A-3533337, DE-A-3503458, DE-A-4244548, DE-A-4219607, DE-A- 4021847, DE-A-3831261, DE-A-3511086, DE-A-3118172, DE-A-3028043, DE-A-4418881, EP-A-0801483, EP-A-0455985, EP-A-0467073, EP-A-0312952, EP-A-0205874, EP-A-0499774, DE-A 2612846, DE-A-4020780 EP-A-0205674, US-5145906, EP-A-0530438, EP-A-0670073, US4057521, US 4,062,817, US 4,525,527, US 4,295,987, US 5011 892, US 4076 663 or US 4931 497. Also particularly suitable highly swellable hydrogels from a manufacturing process as described in WO 01/38402 described, and inorganic-organic hybrid highly swellable hydrogels as described in DE 198 54 575 described. The contents of the aforementioned patent documents, in particular, the hydrogels prepared by the process, are expressly part of the present disclosure.

Suitable grafting bases L for hydrophilic hydrogels tion by graft copolymerization of olefinically unsaturated acids are available, may be natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and also other polysaccharides and oligosaccharides, polyalkylene oxides, especially polyethylene oxides and polypropylene oxides, and also hydrophilic polyesters.

The water-absorbing polymer can be obtained by free-radical graft copolymerization of acrylic acid or acrylate onto a water-soluble polymer matrix. Suitable water-soluble polymer matrices are, for example, but not exclusively, alginates, polyvinyl alcohol and polysaccharides such as starch. Graft copolymerization for the purposes of the invention utilizes a polyfunctional ethylenically of unsaturated radical crosslinker.

The water-absorbing polymer may be other, an organic-inorganic hybrid polymer formed from a polymeric acrylic acid or polyacrylate on the one hand and a silicate, aluminate or aluminosilicate. In particular, polymeric acrylic acid or polyacrylate can be used, which were obtained by radical polymerization and where a polyfunctional ethylenically unsaturated radical crosslinker and in which manufacturing process a water-soluble silicate or soluble aluminate or mixture has been used by both.

Preferred hydrogels are in particular polyacrylates, polymethacrylates and also the

US 4931 497, US 5011 graft described 892 and US 5041 496th Very particularly preferred hydrogels are the kneader described in WO 01/38402 and those described in DE 19854575 hybrid organic-inorganic hydrogels based on polyacrylates.

The inventively prepared, are useful as radical in hydrogels, may be used alone or in combination with other crosslinkers, for example internal or surface, such as the following: Particularly suitable crosslinkers are methylenebisacrylamide or methacrylamide, acrylate esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or Triacry- lat, z. B. butanediol or ethylene and also trimethylolpropane triacrylate and allyl compounds such as allyl (meth) triallyl, ma- leinsäurediallylester, polyallyl, tetraallyloxyethane, triallylamine, Tetraallylethylen- diamine, allyl esters of phosphoric acid and also vinylphosphonic acid derivatives as described for example in EP-A-0,343,427th Suitable crosslinkers are pentaerythritol rythritoltri- tetraallyl, polyethylene glycol diallyl ether, monoethylene glycol diallyl, triallyl and Glyceroldi-, polyallyl ethers based on sorbitol, and also ethoxylated variants thereof. Particularly preferred crosslinkers are the

Polyethylene glycol diacrylates, ethoxylated derivatives of trimethylolpropane for example Sartomer SR 9035, and also ethoxylated derivatives of glycerol and glycerol rintriacrylat. Of course, mixtures of the above crosslinkers. Very particular preference is given to such hydrogels which are prepared using an inventively prepared esters F as radical.

The water-absorbing polymer is preferably a polymeric acrylic acid or a polyacrylate. This water-absorbing polymer can be by one NEM known from the literature. Preference is given to polymers which comprise crosslinking comonomers (0.001 to 10 mol%), but most preference is given to polymers which were obtained by radical polymerization and when I where a polyfunctional ethylenically unsaturated radical crosslinker.

The hydrophilic, highly swellable hydrogels can be prepared by per se known polymerization process. Preference is given to polymerization in aqueous solution by the process known as gel polymerization. Here are diluted as stated above, preferably aqueous, particularly preferably 15 to 50% by weight aqueous solutions of one or more hydrophilic monomers and optionally of a suitable grafting base L in the presence of a radical initiator, preferably without mechanical mixing, utilizing the Trommsdorff Norrish effect ( Makromol. Chem. 1, 169 (1947)) polymerized. The polymerization reaction can in the temperature range between 0 ° C and 150 ° C, preferably between 10 ° C and 100 ° C, not only at atmospheric pressure but also at elevated or reduced

Printing to be performed. As is customary, the polymerization can also in a protective gas atmosphere, preferably under nitrogen, are executed. To initiate the polymerization energy electromagnetic rays or the customary chemical polymerization K as can be used, eg. Organic Pe- roxide such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, azo compounds such as azodiisobutyronitrile, and inorganic compounds such as peroxides (NH₄)₂S₂O_8th, K₂S₂O_8th or H₂O₂,

You can optionally acid in combination with reducing agents such as ascorbic, sodium, and iron (II) sulfate or redox systems where. Reducing component is an aliphatic and aromatic sulfinic acid, such as benzene acid with toluenesulfinic acid or derivatives of these acids, such example, Mannich adducts of sulfinic acid, aldehydes, and amino compounds, such as are described in DE-C-1301566, may be used. For several hours Nachhei- the polymer gels zen in the temperature range 50 ° to 130 ° C, preferably 70 ° to 100 ° C, the quality properties of the polymers can be further improved.

The gels obtained are to 0 - 100 mol%, preferably to 25 - 100 mol%, and most preferably 50 - 85 mol% neutralized, based on monomer used, for which the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal, more preferably sodium hydroxide, sodium carbonate and sodium bicarbonate.

Typically, the neutralization by mixing in the neutralizing agent as an aqueous solution or else preferably as a solid. The gel is mechanically comminuted, for example by means of a meat grinder, and the neutralizing agent is sprayed, sprinkled or poured on and then carefully mixed in. The gel mass obtained can be repeatedly minced for homogenization to. The neutralized gel mass is then dried until the residual moisture content is preferably below 10 wt .-%, especially below 5 with a belt or drum dryer wt .-%.

The polymerization as such can also be carried out by any other process described in the literature. In particular, the neutralization of the acrylic acid can also be carried out prior to the polymerization, as described above in step f). The polymerization can then be carried out continuously or discontinuously in a known to the expert belt reactor or a kneading reactor. In carrying out the polymerization in a belt reactor, initiation by electromagnetic radiation, preferably by UV radiation, or alternatively, the initiation with a redox initiator is especially preferred. Most preferably, the combination of two methods of initiation: electromagnetic radiation and chemical redox initiator system simultaneously. n) The dried hydrogel can then be ground and sieved, typically including roll mills, pin mills or swing mills for the grinding. The preferred particle size of the sieved hydrogel is preferably in the range 45 - 1000 .mu.m, preferably 45-850 .mu.m, more preferably 200-850 microns, and most preferably at 300-850 microns, also the range of 150 to 850 .mu.m is particularly preferably, especially the range 150 to 700 microns. These ranges preferably 80 wt .-% of the particles, in particular 90 wt .-% of the particles. The size distribution can be determined using established laser methods.

The present invention further provides crosslinked hydrogels, which are included crosslinked and at least one hydrophilic monomer M in copolymerized form with an ester F of alkoxylated trimethylolpropane acid with (meth) acrylic. The esters can be provided according to the invention or in a known manner in the art produced, preferably the inventive manner.

As the ester F include compounds, as described above.

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

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

The AUL 0,5psi value [g / g] of the hydrogel-forming polymers of the invention can be measured by the methods indicated in the description and is preferably above 8, especially 9, 10, 11, 12, 13, 14 or higher, particularly preferably at 15, in particular at 16, 17, 18, 19, or higher, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26, 27, 28, or higher.

The saponification index VSI of the hydrogel forming polymers according to the invention can by the methods indicated in the description can be measured and is preferably less than 10, in particular 9.5, 9, or 8.5 or less, particularly described preferably less than 8, in particular 7.5, 7, 6.5, 6, 5.5 or lower, even more preferably less than 5, in particular 4.4, 4 or lower.

Application and use of hydrogel-forming polymers of the invention

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

(P) an upper liquid-permeable cover (Q) a fluid-impervious backsheet

(R) a core positioned between (P) and (Q) and comprising

10-100 wt .-% of the hydrogel-forming polymer

0 - 90 wt .-% of hydrophilic fiber material preferably 20-100 wt .-% of the hydrogel-forming polymer 0 - 80 wt .-% of hydrophilic fiber material more preferably 30-100 wt .-% of the hydrogel-forming polymer, 0 - 70 wt .-% of hydrophilic fiber material even more preferably 40 - 100 weight .-% of the hydrogel-forming polymer, 0 - 60 wt .-% of hydrophilic fiber material more preferably 50 - 100 weight .-% of the hydrogel-forming polymer 0 - 50 wt .-% of hydrophilic fiber material particularly preferably 60 - 100 weight .-% of the hydrogel-forming polymer, 0 - 40 wt .-% of hydrophilic fiber material particularly preferably 70 - 100 weight .-% of the inventive hydrogel forming polymer, 0 - 30 wt .-% of hydrophilic fiber material extremely preferably 80 - 100 weight .-% of the inventive hydrogel forming polymer, 0 - 20 wt .-% of hydrophilic fiber material most preferably 90-100 wt .-% of the hydrogel-forming polymer, 0 - 10 wt .-% of hydrophilic fiber material (S) optionally one positioned directly above and below the core (R) to tissue layer and (D) optionally one between (P) and (R) to acquisition layer.

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

Hygiene articles are not only incontinence pads and incontinence briefs for adults but also diapers for infants.

In the liquid-permeable cover (P) is the layer which has direct contact with skin. Its material comprises customary synthetic or semisynthetic fibers or films of polyesters, polyolefins, rayon or natural fibers such as cotton. For non-woven materials the fibers are to be joined usually by binders such as polyacrylates. Preferred materials are polyesters, rayon and blends thereof, polyethylene and polypropylene. Examples of liquid-pervious layers are described in WO 99/57355 A1, EP 102 388 A2 3.

The liquid-impervious layer (Q) is generally a sheet of polyethylene or polypropylene.

The core (R) includes not only the hydrogel-forming polymer according to the invention of hydrophilic fiber material. By hydrophilic is meant that aqueous fluids spread quickly over the fiber. Usually, the fiber material cellulose is loose, modified cellulose, rayon, polyester such as polyethylene. Especially preferred are cellulose fibers such as pulp. The fibers typically have a diameter 1-200 microns, preferably 10-100 microns. Moreover, the fibers have a minimum length of 1 mm. The structure and the form of diapers is generally known and for example, in WO 95/26 209 page 66 line 34 to page 69 line 11, DE 196 04 601 A1, EP-A-0316518 and EP-A-0 202 127. described. Generally, nappies and other sanitary products also in WO 00/65084, especially at pages 6-15, WO 00/65348, in particular, pages 4 - 17, WO 00/35502, particularly pages 3-9, DE 19737434, WO 98/8439 described. Hygiene articles for feminine hygiene are described in the following references. The absorbing aqueous fluids hydrogel-forming polymers can be used there. References feminine hygiene: WO 95/24173: Absorption Articie for Controlling Odour, WO 91/11977: Body Fluid Odour Control, EP 389023: Absorbent Sanitary Articles, WO 94/25077: Odour Control Material, WO 97/01317: Absorbent Hygienic Articie, WO 99/18905, EP 8342^~97, US 5,762,644, US 5,895,381, WO 98/57609, WO 2000/065083, WO 2000/069485, WO 2000/069484, WO 2000/069481, US 6,123,693, EP 1104666, WO 2001/024755, WO 2001/000115, EP 105373, WO 2001/041692, EP 1074233. tampons are described in the following references: WO 98/48753, WO 98/41179, WO 97/09022, WO

98/46182, WO 98/46181, WO 2001/043679, WO 2001/043680, WO 2000/061052, EP 1108408, WO 2001/033962, DE 200 020 662, WO 2001/001910, WO 2001/001908, WO 2001/001909, WO 2001/001906, WO 2001/001905, WO 2001/24729. Incontinence products are described in the following publications: Disposable Absorbent Articie for Incon- continent Individuais: EP 311344 Description P. 3 - 9; Disposable Absorbent Articie: EP 850 623; Absorbent Articie: WO 95/26207; Absorbent Articie: EP 894 502; Dry Laid Fibrous Structure: EP 850 616; WO 98/22063; WO 97/49365; EP 903 134; EP 887 060; EP 887 059; EP 887058; EP 887 057; EP 887 056; EP 931 530; WO 99/25284; WO 98/48753. Feminine care and incontinence articles are described in the following references: Catamenial Device: WO 93/22998 description P. 26 - 33; Absorbent Members for Body Fluids: WO 95/26209 description P. 36 - 69; Disposable Absorbent Articie: WO 98/20916 description P. 13 - 24; Improved Composite Absorbent Structures: EP 306262 Description P. 3 - 14; Body Waste Absorbent Articie: WO 99/45973. These references and the references therein, are hereby expressly in the disclosure of the invention involved.

The hydrogel-forming polymers of the invention are very useful as absorbents for water and aqueous fluids, so that they can advantageously be used as a water retainer in market gardening, as Filtrationshilfs- medium and particularly as an absorbent component in hygiene articles such as diapers, tampons or sanitary napkins.

Incorporation and Fixation of the highly swellable hydrogels according to the invention In addition to the above-described highly swellable hydrogels, the absorbent composition of the present invention compositions before, which include highly swellable hydrogels or to which they are fixed. Any construction is suitable that is capable of accommodating highly swellable hydrogels and can also be integrated into the absorption layer. A variety of such compositions is already known and described in detail in the literature. A construction for installing the highly swellable hydrogels can be for. Example a fiber matrix consisting of a cellulose fiber mixture (airlaid web, wet laid web) or of synthetic polymer fibers (meltblown web, spunbonded web), or else of a fiber blend of cellulose fibers and synthetic fibers. Possible fiber materials are described in detail in subsequent chapters. The process of an air-laid web is described for example in WO 98/28478. Furthermore, open-celled foams or the like to install highly swellable hydrogels are used.

Alternatively, the result of fusing two individual layers, such a construction in which one or better a multiplicity of chambers which contain the highly swellable hydrogels. Such a chamber system is described in detail in EP 0615736 A1 page 7 line 26 ff.

In this case, at least one of the two layers should be water pervious. The second layer may either be water pervious or water impervious. The layer material can Tissues or other fabric, closed or open-celled foams, perforated films, elastomers or fabrics composed of fiber material. When the absorbent composition consists of a construction 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 of construction of the absorbent composition also include laminates of at least two layers with a, between the see are installed and fixed the highly swellable hydrogels.

Generally it is possible, hydrogel particles within the absorbent Gores to improve the so-called. Dry and wet integrity to fix. Dry and wet integrity describes the ability composition install highly swellable hydrogels such in the absorbent feed that they withstand external forces not only in the wet and in the dry state and there are no dislocations or leakage of highly swellable polymer. The forces mainly mechanical loads are to be understood as they occur in the course of movement while wearing the hygiene article or else the weight pressure on the hygienic tissues, especially in the case of incontinence is. In order to fix it are a number of possibilities th, which are known in the art. Examples such as fixation by heat treatment, addition of adhesives, thermoplastics, binder materials are noted in WO 95/26209 page 37 line 36 to page 41 line 14. The cited passage is thus part of this invention. Methods for enhancing wet strength are also found in WO 2000/36216 A1.

Furthermore, the absorbent composition may comprise a carrier material, such. As a polymer film on which the highly swellable hydrogel particles are fixed. Fixation can both one made on both sides are the. The carrier material may be water-pervious or water-impervious.

The above constructions of the absorbent composition incorporate the highly swellable hydrogels at a weight fraction of 10 to 100% by weight, preferably 20-100 wt .-%, more preferably 30-100 wt .-%, more preferably 40-100 wt .-%, more preferably 50-100 wt .-%, particularly preferably 60 to 100 wt .-%, particularly preferably 70 to 100 wt .-%, even more preferably 80 to 100 wt .-% and most preferably 90-100 wt .-% based built on the total weight of the composition and the highly swellable hydrogels.

Fiber Materials of the Absorbent Composition

The structure of the present invention the absorbent composition is based on a variety of fibrous materials which are used as a fiber network or matrices. With enclosed by the present invention includes both fibers natüriiehen origin (modified or unmodified) but also synthetic fibers.

A detailed overview of examples of fibers which can be used in the present invention is patent WO 95/26209 page 28 line 9 to page 36 line 8. The cited passage is thus part of this invention.

Examples of cellulose fibers include those which are customarily used in absorption products, such as fluff pulp and cellulose of the cotton type. The materials (soft- or hardwoods), production processes such as chemical pulp, semi-chemical pulp, chemi-mechanical pulp (CTMP) and bleaching processes are not particularly limited. So For example, natural cellulose fibers such as cotton, flax, silk, wool, jute, ethylcellulose and cellulose acetate are used.

Suitable synthetic fibers are produced from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylic compounds such as ORLON^®. Polyvinylaeetat, polyethyl, soluble or insoluble polyvinyl alcohol. Examples of synthetic fibers include thermoplastic polyolefin fibers, such as polyethylene fibers (PULPEX^®), Polypropylene fibers and polyethylene-polypropylene bicomponent fibers, polyester fibers, polyethylene terephthalate fibers, such as (DAC RON^® or KODEL^®), Copolyesters Polyvinylaeetat, polyethyl, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides, copolyamides, polystyrene and copolymers of the aforementioned polymers and also bicomponent fibers composed of polyethylene terephthalate-polyethylene isophthalate copolymer Polyethylvinylace- did polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester, polyamide fibers (nylon), polyurethane fibers, polystyrene fibers and polymer a lyacrylnitrilfasem. Preferably, polyolefin fibers, polyester fibers and bicomponent fibers. Further preferred in the heat are adhesive bicomponent fibers composed of polyolefin of the core-sheath type and side-by-side type on account of their excellent dimensional stability following fluid absorption.

The synthetic fibers mentioned are preferably used in combination with thermoplastic fibers. In the heat treatment, the latter migrate to some extent into the matrix of the fiber material present and so constitute the cooling bond sites and renewed stiffening elements. In addition, the addition means thermo-plastic fibers have an extension of the present pore dimensions after the heat treatment. In this way it is possible to continuously increase by continuous addition of thermoplastic fibers during the formation of the absorption layer the fraction of thermoplastic fibers to the cover sheet, whereby a similarly continuous increase in the pore sizes. Thermoplastic fibers can be formed from a variety 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 can be expected.

Lengths and diameters of synthetic fibers described above are not particularly restricted, and generally any fiber having a length of 1 to 200 mm and a diameter of 0.1 to 100 denier (grams per 9000 meters) can be preferably used. Preferred thermoplastic fibers have a length of 3 to 50 mm, especially preferred a length of 6 to 12 mm. The preferred diameter for the thermoplastic fiber is between 1, 4 and 10 decitex, more preferably between 1, 7 and 3.3 decitex (grams per 10,000 meters). The shape is not particularly limited, and examples include woven types, narrow cylindrical types, cut / chopped yarn types, staple fiber types and continuous fibrous one. The fibers in the absorbent composition of the invention can be hydrophilic, hydrophobic or a combination of both. According to the definition of Robert F. Gould in the publication "Contact angle, wettability and adhesion", American Chemical Society (1964), a fiber is referred to as hydrophilic, when the contact angle between the liquid and the fiber (or the fiber surface) is less than 90 °, or when the liquid tends to spread spontaneously on the same surface. The two processes are generally coexistent. Conversely, a fiber is referred to as hydrophobic when a contact angle is formed from greater than 90 ° and no spreading is observed.

Preferred hydrophilic fiber material is used. Especially preferred fiber material gets used, which is most hydrophilic weakly hydrophilic on the body side and in the region around the highly swellable hydrogels. In the manufacturing process a gradient is generated through the use of layers of different hydrophilicity, which channels impinging fluid to the hydrogel, where it is ultimately absorbed.

Suitable hydrophilic fibers for use in the absorbent composition of the invention include for example cellulose fibers, modified cellulose fibers, rayon, polyester fibers such. As polyethylene terephthalate (DACRON^®), And hydrophilic nylon (HYDROFIL^®). Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, such as the treatment of thermoplastic fibers derived from polyolefins (such. As polyethylene or polypropylene, polyamides, polystyrenes, polyurethanes, etc.) with surfactants or silica. For cost reasons, however, cellulose fibers are preferable to, and for reasons of availability.

The highly swellable hydrogel particles are embedded into the fiber material described. This can be done in many ways, by z. B. with the hydro gel material and the fibers together to create an absorbent layer in the form of a matrix, or by incorporating highly swellable hydrogels into fiber mixture layers, where they are ultimately fixed, whether by means of adhesive or lamination of the layers.

The fluid and -distributing fiber matrix may consist of synthetic fiber or cellulosic fiber or a mixture of synthetic fiber and cellulosic fiber, wherein the mixing ratio of (100 to 0) synthetic fiber: (0 to 100) cellulose fiber may vary. The cellulosic fibers used may be chemically stiffened to increase the dimensional stability of the hygiene article. The chemical stiffening of cellulose fibers can be achieved in different ways. Firstly, a fiber stiffening is by adding suitable coatings / 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 US Patent No. 3,556,932 or as a product of brand Parez^® NC 631, American Cyanamid Co., Stamford, CT, USA), melamine-formaldehyde coatings, and coatings having a polyethyleneimine.

The chemical stiffening of cellulose fibers can also be effected by chemical reaction. Thus, for. Example, the addition of suitable crosslinker effect crosslinking taking place within the fiber. Suitable crosslinker substances are typical substances used for crosslinking monomers. With included, but not limited thereto, are C₂-C_8th Dialdehydes, C₂-C_8th Monoalde- hyde having acid functionality and in particular C₂-C₉ Polycarboxylic. Specific substances from this series are for example glutaraldehyde, glyoxal, Glyoxylsäu- acid, formaldehyde and citric acid. These substances react with at least 2 hydroxyl groups within any one cellulose chain or between two adjacent cellulose chains within any one cellulose fiber. Through the networking takes place Verteif clothes the fibers formed by this treatment a greater

Dimensional stability bestowed get. In addition to their hydrophilic character, these fibers exhibit uniform combinations of stiffening and elasticity. This physical property makes it possible to retain the capillary structure even under simultaneous contact with fluid and compressive forces and to prevent pre- mature collapsing.

Chemically crosslinked cellulose fibers are known and described in WO 91/11162, US Patent 3,224,926, US Patent 3,440,135, US Patent 3,932,209, US Patent 4,035,147, US Patent 4,822,453, US Patent 4,888,093, US Patent 4,898,642 and US Patent 5,137,537 described. The chemical crosslinking imparts stiffening to the fiber material, which is ultimately reflected in improved dimensional stability for the entire hygiene article. The individual layers are so joined together by methods known to those skilled in such. As by heat treatment, addition of hot-melt adhesives, latex binders.

Manufacturing method of the absorbent composition

The absorbent composition is composed of constructions which contain highly swellable hydrogels and the highly swellable hydrogels which are present in said constructions or fixed thereto. Examples of methods by which to obtain an absorbent composition comprising for example, a carrier material, are fixed on one or both sides highly swellable hydrogels are known and joined by the invention used, but not limited thereto.

Examples of methods by which to obtain an absorbent Zusammensetzng, for example, of a fiber material blend of synthetic fibers (a) and cellulose fibers (b) embedded in highly swellable hydrogels (c), wherein the mixing ratio of (100 to 0) synthetic fiber : (0 to 100) cellulose fiber can vary, include (1) a method in which (a), (b) and (c) are mixed simultaneously, (2) a method in which a mixture of (a) and ( b) is blended in (c), (3) a method in which a mixture of (b) and (c) is mixed with (a), (4) a method in which a mixture of (a) and ( c) is mixed into (b), (5) a process are mixed at the (b) and (c) and (a) is continuously metered, (6) are mixed, a method in which (a) and (c) and (b) is metered in continuously, and (7) a method which may be blended separately in (a) in which (b) and (c), a. Of these examples, the AV Ahren (1) and (5) preferred. The apparatus used in this process is not particularly limited and any customary to the person skilled known device can be used.

The absorbent composition obtained can optionally be subjected to a heat treatment, so that an absorption layer having excellent dimensional stability in the moist state. The method for Hitzebehand- treatment is not particularly limited. Examples include heat treatment by feeding hot air or infrared irradiation. The temperature in the heat treatment is in the range 60 ° C to 230 ° C, preferably between 100 ° C and 200 ° C, more preferably between 100 ° C and 180 ° C.

The duration of the heat treatment depends on the type of synthetic fiber, the quantity and the rate of production of the hygiene article. In general, the duration of the heat treatment range from 0.5 second to 3 minutes, preferably 1 second to 1 minute.

The absorbent composition is generally provided for example with a liquid-pervious topsheet and a liquid impermeable backsheet. Furthermore, leg cuffs and adhesive tabs are attached and so completed the hygiene article. The materials and types of pervious topsheet and impervious backsheet and of the leg cuffs and adhesive are known in the art and not particularly limited. Examples can be found in WO 95/26 209th

The advantage of the present invention resides in that as crosslinking agents usable ester F after its manufacture does not have to be purified, especially that no acrylic acid, the (meth), preferably acrylic acid, must be removed, since this is usually a monomer for preparing the hydrogels represents.

experimental part

In this font used ppm and percentage data relate, unless indicated otherwise, percentages by weight and ppm.

The inventive method is explained in more detail by the following example.

Examples

Preparation of acrylate Rohestem as Superabsorbervemetzer

The preparation of Superabsorbervemetzer done in the examples by esterification ^• tion of alkoxylated trimethylolpropane with acrylic acid wherein the removal of the water takes place in azeotroped. Esterification catalyst is sulfuric acid in the examples. The reactants are charged together with a stabilizer mixture consisting of hydroquinone, triphenylphosphite and hypophosphorous acid in the examples in methylcyclohexane as entrainer. The reaction mixture is then heated to about 98 ° C to the azeotropic distillation begins. During the azeotropic distillation, the temperature increases in the reaction mixture. The amount of water removed is determined. Distillation is discontinued when at least the theoretical amount of water was separated.

Subsequently, the entraining agent is removed in a vacuum distillation. The product is cooled and used as crosslinkers in superabsorbent production.

Conversion and yield of the reaction is not precisely determined because the resterung in Ve- separated water also contains acrylic acid and also during the vacuum distillation of the entrainer acrylic acid is removed. Similarly, the crude ester still contains free acrylic acid which is titrated together with the catalyst (acid number).

All amounts are, unless otherwise indicated, by weight. Preparation of the ester

Acid numbers were. DIN EN 3682 determined.

Example 1 Preparation of the alkoxylated trimethylolpropane

77 g of trimethylolpropane are mixed with 0.5 g of KOH, 45% presented in water, in an autoclave and together at 80 ° C and reduced pressure (about 20 mbar) drained. Then at 120 to 130 ° C. 167 g of propylene oxide are added and allowed to react under elevated pressure temperature at this temperature. The reaction is complete when no further change in pressure is observed. It is then stirred for 30 minutes at about 120 ° C. Then 379 g of ethylene oxide are metered in at 145 to 155 ° C for extended periods at elevated pressure and likewise allowed to react. After flushing with inert gas and cooling to 60 ° C, the catalyst is pyrophosphate by addition of sodium and subsequent filtration separated.

Example 2 Preparation of the acrylic acid ester

887 parts of an approximately 5-fold propoxylated and 15x ethoxylated trimethylolpropane (according to Example 1) is esterified with 216 parts of acrylic acid and 5 parts of sulfuric acid in 345 parts of methylcyclohexane. Auxiliaries 3 parts of hydroquinone monomethyl ether, 1 part of triphenyl phosphite and 1 part of hypophosphorous acid. Were removed before the entrainer is removed by vacuum distillation 44 parts of water. The product is purified through K300 filter. The acid number is determined. By the addition of 96 parts of acrylic acid, the viscosity is adjusted. The viscosity of the almost colorless product (iodine color 0-1) is about 320 mPas.

The preparation of hydrogels

To determine the quality of the surface cross-linking the dried hydrogel can be investigated by the following test methods.

test Methods

a) Centrifuge Retention Capacity (CRC Centrifuge Retention Capacity)

This method measures the free swellability of the hydrogel in a teabag. To determine CRC, 0.2000 * 0.0050 g of dried hydrogel (particle size fraction 106-850 .mu.m) are weighed into a 60 x 85 mm in size tea bag is sealed subsequently. The teabag is placed for 30 minutes in an excess of 0.9 given. wt% sodium chloride solution (at least 0.831 saline solution / 1 g of polymer powder). The teabag is then centrifuged for 3 minutes at 250 g. The determination of the amount of liquid by weighing the centrifuged teabag.

b) absorption under load (AUL Absorbency Under Load) (0.7 psi)

The measuring cell for determining AUL 0.7 psi is a Plexiglass cylinder having an inner diameter of 60 mm and a height of 50 mm, which has a glued stainless steel sieve bottom having a mesh size of 36 microns at the bottom. The measuring cell further includes a plastic plate having a diameter of 59 mm and a weight which can be placed together in the plastic plate in the measuring cell. The weight of Piastikplatte and the weight totals 1345 g. To perform the determining AUL 0.7 psi is determined the weight of the empty Plexiglas cylinder and of the plastic plate and a W₀ written down. 0.900^* 0.005 g of hydrogel-forming polymer (particle size distribution 150-800 .mu.m) is weighed into the Plexiglas cylinder and distributed very uniformly over the stainless steel sieve bottom. The plastic plate is then carefully placed in the Plexiglas cylinder and weighed the entire unit; the weight is as W_a written down. The weight is then placed on the plastic plate in the Plexiglas cylinder. In the middle of a Petri dish with a diameter of 200 mm and a height of 30 mm, a ceramic filter plate is placed with a diameter of 120 mm and a porosity 0 and sufficient 0.9 wt.% Sodium chloride solution filled that the liquid surface with the filter plate surface closes without the surface of the filter plate being wetted. A round filter paper having a diameter of 90 mm and a pore size &lt;20 microns (S &amp; S 589 Black from Schleicher &amp; Schull) is placed on the ceramic plate. The containing hydrogel-forming polymer Plexiglas cylinder is then placed with plastic plate and weight on the filter paper and left there for 60 minutes. After this period, the complete unit from the petri dish is removed from the filter paper and then removed the weight from the Plexiglas cylinder. The swollen hydrogel containing Plexiglas cylinder is weighed together with the plastic plate and the weight recorded as W_b written down.

Absorbency under load (AUL) is calculated as follows:

AUL 0.7 psi [g / g] = [W_b-W_a] / [W_a-W₀]

The AUL 0,5psi is measured analogously a lower pressure. c) The determination of the extractable content after 16 h (Extract. 16h) was carried out analogously as described in EP-A1 811 636, page 13, line 1 to line 19 described.

d) method for the determination of residual contents of crosslinkers in hydrogels

To determine the content of unreacted Restvemetzer extracting these Restvemetzer initially by a double extraction from the dried hydrogel. These are weighed 0.400 g of dry hydrogel and 40 g 0.9 wt.% Saline solution in a sealable and centrifugable ampoule. For this one adds 8 ml dichloromethane, closes the vial, and is then allowed to shake for 60 minutes. The vial is then immediately 5 minutes zentrif ugiert at 1500 rpm, so that the organic phase is clearly separated from the aqueous phase.

In a second vial to be analyzed, 50 ul of monoethylene glycol, and add not more than 5 - 6 ml of Dichlormethanextracts, the weight of the extract is measured at 0,001 g. At 50-55 ° C then the dichloromethane is evaporated and the residue after cooling with 2 ml of methanol-water mixture was added (50 parts by volume). It is shaken for 10 min and then filtered through a 0.45 micron PTFE filter.

The sample thus obtained is separated by means of liquid phase chromatography and analyzed by mass spectrometry. Quantification is against a dilution series of the same cross-linker used.

and as a pre-column is a Zorbax Eclipse XDB-C 8 (12.5 x 4.6 mm - 5 microns) - as a chromatography column Zorbax Eclipse XDB C-8 (5 micron 150 x 4.6 mm) is used. As eluent a methanol / water mixture (75/25) is used.

The gradient is as follows:

<img id="imgf000047_0001" he="44" wi="90" file="imgf000047_0001.tif" img-format="tif" img-content="table" orientation="portrait" inline="yes" />

Flow 1 ml / min at 1600 psi pressure.

The injection volume is 20 ul.

Typical analysis time is 14 min for the samples. Detection is by mass spectrometry, for example in the range 800 - 1300 m / z (fill scan, positive). The device works with APCI (atmospheric pressure chemical ionization, positive ionization). To optimize the capillary temperature to 180 ° C, the set current to 80 ml / min APCI vaporizer temperature to 450 ° C, source current to 5.0 uA, and the gas.

The individual settings have to be specially made for each crosslinker. In addition one determined by an appropriate calibration of the crosslinking agent, the later relevant for evaluating characteristic peaks. In general, the main peak is selected.

The calculation of the residual crosslinker is then as follows:

CONCp_r0be = A_sample x x CONCstd VF / A_std

CONCpro_be: is wanted residual crosslinker in dry hydrogel in mg / kg

CONCS_td : Is wanted residual crosslinker in the calibration solution in mg / kg

APROBE: is peak area of ​​extract sample of dried hydrogel

A_Hours : Is peak area of ​​calibrating solution

VF is the dilution factor:

VF = M_DCM X Msolv / (Mp_rif_e XM_Ext_raot)

MDCM is weight of dichloromethane for extraction

Mpro s is weight of dry hydrogel

Msoivist weighing methanol-water mixture + monoethylene glycol

Mεxtract is weight of dichloromethane extract

Using calibration (several points for example in the range 0 - 50 ppm) is to ensure that the determination is carried out in the linear region. e) saponification index VSI

The comminuted gel is then further treated in two different ways:

Workup Method 1:

The comminuted gel is homogeneously dispersed on sieve-bottomed trays in a thin layer and then 24 hours at 80 ^SC dried in vacuo. This drying is very gentle and is therefore the optimal standard of comparison.

The dried hydrogel is then ground and the sieve fraction 300-600 micrometers is isolated.

Workup Method 2:

The comminuted gel is initially in a sealed plastic bag at 90⁹C for 24 h annealed. Then it is homogeneously dispersed on sieve-bottomed trays in a thin layer and for 24 hours at 80⁹C dried in vacuo. This drying simulates the drying conditions which occur in typical manufacturing facilities, which usually limit the drying performance and the throughput because of the associated quality drop.

The dried hydrogel is ground and the sieve fraction 300-600 micrometers is isolated.

The hydrogels obtained by the two methods of working up are characterized by determination of the tea bag capacity (CRC) as well as the content of extractables after 16 hours, and as to the content of unreacted Restvemetzer. In addition, the moisture content is determined and if it is more than 1% by weight, it will be taken into account mathematically in the determination of these properties. Typically, the moisture content is about 5 wt.%.

From the measured values ​​then determining the saponification ungsindex (VSI) of the crosslinking agent in the gel, which is calculated as follows:

VSI = 0.5 x (CRC₂ - CRCI) + 0.5 x (Extractable₂ - Extractable_!)

The subscripts denote here the workup method 1 or 2. The comparison seifungsindex is therefore greater, the more increases the teabags capacity by operating the drying and the more the proportion of extractables increases thereby. Both posts are equally weighted.

It is generally advantageous to use crosslinkers whose saponification index is as small as possible. The ideal cross-linker has a VSI of zero. The use of such crosslinking agents allows the performance of the operating dryers without sacrificing quality to technically achievable maximum increase. The reason is that the set during the polymerization crosslinking - and hence the properties of the end product - no longer by hydrolysis during drying changed.

Example 3 Preparation of superabsorbent using the acrylic acid ester of Example 2 and other Innenvemetzer example a

sodium acrylate solution in 1465 g of distilled water - in an acid-resistant plastic tray 305 g of acrylic acid and 3204 g of a 37.3% by weight are.. For this purpose 12.2 g TMP-15EO triacrylate as a crosslinking agent and 0.61 g are added as initiators V-50 (2,2'-Azobisamidino- dihydrochloride) and 3.05 g of sodium persulfate. The initiators are advantageously predissolved in a part of the make-up water. The batch is stirred for a few minutes.

Then allowed to approximately 30 min of nitrogen gas bubbled through the covered with plastic film solution in the tub to remove the oxygen and distribute the crosslinkers homogeneously. Finally one adds dissolved 0.244 g of hydrogen peroxide in 5 g of water and 0.244 g of ascorbic acid dissolved in 5 g of water are added. The start temperature at the beginning of the reaction to 11 - 13^Sbe C. The thickness of the reaction solution is approximately 6 cm. After a few minutes the reaction starts, allowed adiabatically react and leaves the thermally insulated tray thermally yet for no longer than 30 minutes are before the gel is worked up.

To work up the gel, the gel block is initially broken into pieces and then crushed by a meat grinder with 6 mm hole disc.

The comminuted gel is then further treated in two different ways:.

Workup Method 1:

The comminuted gel is homogeneously dispersed on sieve-bottomed trays in a thin layer and then 24 hours at 80⁹C dried in vacuo. This drying is very gentle and is therefore the optimal standard of comparison. The dried hydrogel is then ground and the sieve fraction 300-600 micrometers is isolated.

Workup Method 2:

The comminuted gel is initially in a sealed plastic bag at 90⁹C for 24 h annealed. Then it is homogeneously dispersed on sieve-bottomed trays in a thin layer and for 24 hours at 80⁹C dried in vacuo. This drying simulates the drying conditions which occur in typical manufacturing facilities, which usually limit the drying performance and the throughput because of the associated quality drop. The dried hydrogel is ground and the sieve fraction 300-600 micrometers is isolated.

be made following further examples in analogy to Example A:

Tab. 1

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The properties achieved these hydrogels are summarized in Tab. 2:

Extractable crosslinking extractable crosslinking

Ex CRC 1 CRC 2 VSI bare 16h 1 residual 1 bare 16h 2 residual content 2

[G / g] [wt.%] [Ppm] [g / g] [wt.%] [Ppm] a TMP-3 EO 36.6 4.4 857 70.6 44.2 1302 36.9 b TMP 15EO 29.7 2.8 51 43.1 12.6 20 11 6 c TMP-20EO 30.3 2.9 29 41 1 13.1 14 10.5

TMP 5PO

29.7 2.7 18 38.7 11 0 &lt;10 8.7

15EO

Example 4a Preparation of a superabsorbent using the acrylic acid ester of Example 2

In a Lödige plowshare kneader VT 5R-MK (5 l volume) is 388 g of deionized water, 173.5 g of acrylic acid, 2033.2 g of a 37.3 wt.% Strength Natriumacrylatlö- solution (100 mol% neutralized) and 5 submitted 90 g of crosslinking agent prepared in example 2 trimethylolpropane 5 PO 15 EO-triacrylate and blanketed for 20 minutes with nitrogen sparging. Then by adding (dilute aqueous solutions) of 2.112 g of sodium persulfate, 0.045 g ascorbic acid and hydrogen peroxide 0.126 g starts at about 23 ° C. After initiation, the temperature of the heating jacket of the reaction temperature is adjusted in the reactor by means of regulation. The crumbly gel eventually obtained is then dried in a convection oven at 160 ° C for about 3 hours. Followed by grinding and screened to 300-850 microns. The hydrogel obtained is afterwards oberflächennachvemetzt.

Example 4b: Procedure similar to Example 4, only the quantity of crosslinking agent is increased to 12 g.

Example 5a (Comparison Example) The implementation is fully analogous to that of Example 4a, however, the crosslinker is used trimethylolpropane 15 EO 5 PO triacrylate. The gel obtained is lumpy and must be comminuted before drying even with a meat grinder.

Example 5b (comparison example): Procedure analogous to Example 5a, only the use amount of the crosslinking agent is increased to 12 g.

postcrosslinking:

The dry base polymer powder from Example 4 + 5 is treated with a solution of 0.10 wt.% Ethylene glycol (Nagase, Japan), 3.43 wt.% Water and 1, 47 wt.% Propane-1, 2 -jeweils based on employed polymer sprayed homogeneously stirring.

The wet powder is then annealed in an oven at 150 C for 60 min. Thereafter, again sieved at 850 microns to remove agglomerates. The properties of this postcrosslinked polymer are determined.

The properties of the post-crosslinked polymers of Examples 4 and 5 as well as other variants are summarized in Table 3:

<img id="imgf000053_0001" he="61" wi="157" file="imgf000053_0001.tif" img-format="tif" img-content="table" orientation="portrait" inline="yes" /> As the crosslinking agent used in Example 4a and 4b performs apparent to product properties such as are typical for modern superabsorbents.

The crosslinkers in 5a and 5b also leads only to very tough and poorly processable gels, which can be difficult to prepare in the kneader.