Use of alkoxysilylamines as curing agents for acetoacetate or acetoacetamide groups-containing resin precursors.

The invention relates to the use of certain alkoxysilylamines as hardeners for plastic precursors containing acetoacetate or acetoacetamide groups and a method for producing coatings on any substrates or for impregnating natural stone or concrete using coating or impregnating agents based on a corresponding two-component -Binding agent.

It is known that polyacetoacetates or polyacetoacetamides react spontaneously with polyamines to form crosslinked products (US Pat. No. 3,668,183). However, the corresponding systems have a pot life that is too short for the practical application of the reaction. By blocking the polyamines with carbonyl compounds, it is possible to produce stable mixtures. The mixture is activated and cross-linked only when exposed to moisture.

It has now surprisingly been found that polyacetoacetates or polyacetoacetamides can be reacted with alkoxysilanes containing amino groups to give polyenamines which ensure a long processing time and crosslink without the action of atmospheric moisture. The latter is advantageous, for example, for coatings with a layer thickness> 50 μ.

It could not have been foreseen that the water formed in the enamine formation by reaction of the polyacetoacetate or polyacetoacetamide with the aminosilane would not immediately lead to siloxane linkages and thereby cause a spontaneous crosslinking of the polymer, which would also have a practical application would result in a too short pot life. Surprisingly, however, this is not the case; rather, mixtures of plastic precursors of the type described below with acetoacetate and / or acetoacetamide groups with aminosilanes of the type described below generally have a pot life of at least 30 minutes, the reaction time of the polyacetoacetate or of the polyacetoacetamide with the aminosilane in a gradual reaction leads to the crosslinking of the plastic precursors with the formation of siloxane structures. It is of particular advantage here that the intermediate water is formed "on the spot", so that a perfect hardening of thick layers of lacquer is guaranteed, since the hardening reaction does not depend on contact with atmospheric moisture.

The invention relates to the use of<ul id="ul0001" list-style="none"><li>a) a primary amino group and an alkoxysilane group containing organic compounds</li></ul> as a hardener for<ul id="ul0002" list-style="none"><li>b) a total of at least two acetoacetate and / or acetoacetamide groups per molecule having plastic precursors.</li></ul>

According to the invention, any organic compounds which have a trialkoxysilyl group and a primary amine amino group per molecule are in principle suitable as hardener a). Preferred hardeners a) are compounds of the formula (I)         H₂N-R-Si (OR ') ₃ (I) used for which<dl id="dl0001"><dt>R</dt><dd>represents an aliphatic hydrocarbon radical having 2 to 6 carbon atoms, with the proviso that at least two carbon atoms are arranged between the nitrogen and the silicon atom, and</dd><dt>R '</dt><dd>represents an alkyl radical having 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms and particularly preferably a methyl radical.</dd></dl>

These amino-functional silanes can be prepared by known methods (W. Noll, "Chemistry and Technology of Silicones", Verlag Chemie GmbH, Weinheit 1968).

2-Aminohexyl- or 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-aminobutyltrimethoxysilane and / or 4-aminobutyltriethoxysilane are particularly preferably used.

The plastic precursors b) are polymers of the molecular weight range Mn from 400 to 25,000, preferably 700 to 15,000, which have a total of at least two acetoacetate and / or acetoacetamide groups per molecule. Polymers of the stated molecular weight range are particularly preferably used which contain at least two acetoacetate structural units of the formula (II) per molecule<chemistry id="chem0001" num="0001"><img file="EP0483583A2_D0001.tif" /></chemistry> with a total content of such structural units in the polymers of 1 to 55, preferably 8 to 40% by weight.

Such "polyacetoacetates" or "polyacetoacetamides" are known in principle (eg US Pat. No. 3,668,183). They are produced, for example, by reacting the corresponding polymers containing hydroxyl groups and / or amino groups with alkyl acetoacetates or with diketene.

Another possibility for the production of these plastic precursors is the copolymerization of olefinically unsaturated monomers such as styrene, acrylic acid and / or alkyl methacrylate and the like. with unsaturated acetoacetate-functional monomers, which in turn are accessible, for example, by reacting hydroxyalkyl acrylates or methacrylates with diketene.

However, the plastic precursors b) are preferably prepared by modifying hydroxyl and / or amino groups, preferably exclusively compounds having hydroxyl groups as functional groups, with diketene at, for example, 80 to 150 ° C., optionally with the use of suitable solvents such as xylene.

Starting compounds suitable for the production of the plastic precursors b) are, for example, the polyhydroxyl compounds of the molecular weight range Mn 200 to approximately 25,000, preferably 500 to approximately 7,000, known per se from polyurethane chemistry. These molecular weight data are approximate values. The molecular weight of these starting materials naturally corresponds to the molecular weight of the plastic precursors b) used according to the invention minus the molecular weight of the acetoacet groups.

The molecular weight Mn of higher molecular weight polyols, polyamines or plastic precursors b) used according to the invention (molecular weight greater than approx. 5000) can be determined using the membrane osmometry method. The molecular weight of the corresponding, comparatively low molecular weight compounds (molecular weight below 5000) can be calculated arithmetically from the stoichiometry of the starting materials used in the preparation of the compounds or from the functionality and the content of functional groups, or determined by vapor pressure osmometry.

Suitable starting compounds for the production of the plastic precursors b) are, for example, the polyhydroxy polyesters known per se from polyurethane chemistry, in particular those of the molecular weight range Mn 200 to 3000 from polybasic carboxylic acids such as adipic acid, phthalic acid, Tetrahydrophthalic acid or hexahydrophthalic acid or mixtures of such polycarboxylic acids with monobasic acids such as benzoic acid or stearic acid with excess amounts of polyhydric alcohols such as, for example, ethylene glycol, propylene glycol, 1,6-hexanediol, trimethylolpropane, glycerol, neopentyl glycol and / or pentaerythritol.

Also suitable are the polyhydroxy polyethers known per se from polyurethane chemistry, in particular of the molecular weight range 200 to 25,000 and a (mean) hydroxyl functionality of 2 to 6, preferably 2 to 3, as are obtainable in a manner known per se by alkoxylation of suitable starter molecules . The latter polyhydric alcohols or mixtures thereof are suitable as starter molecules. For alkoxylation, preference is given to using ethylene oxide and / or propylene oxide, optionally in a mixture and / or in any order.

Also suitable are the hydroxyl group-containing polyacrylates known from polyurethane coating technology, in particular those of the molecular weight range Mn 1000 to 15,000 with a hydroxyl group content of 1 to 10% by weight. These compounds are prepared in a manner known per se by copolymerization of olefinically unsaturated monomers with the use of hydroxyl-containing olefinically unsaturated monomers. Suitable monomers are, for example, acrylic acid and / or methacrylic acid alkyl esters with 1 to 6 carbon atoms in the alkyl radical, such as, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate or n-hexyl methacrylate and / or styrene. Suitable hydroxy-functional monomers are, for example, hydroxyalkyl esters of acrylic acid or methacrylic acid with 2 to 6 carbon atoms in the hydroxyalkyl radical, such as, for example, hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl or 6-hydroxyhexyl acrylate or methacrylate.

Also suitable, however, are less preferred are the aminopolyethers known per se from polyurethane chemistry, for example those as recommended in EP-A-00 81 701 for the production of molded plastics.

In the use according to the invention, the hardeners a) and the plastic precursors b) are preferably used in a quantity ratio which corresponds to an equivalent ratio of primary amino groups of the hardener a) to acetoacetate or acetoacetamide groups of the plastic precursors b) of 0.5: 1 to 1: 1, preferably 0.8: 1 to 1: 1.

The combinations of plastic precursors b) and hardeners a) according to the invention represent valuable two-component binders for coating agents for any substrates or impregnating agents, in particular for natural stone or concrete.

The invention accordingly also relates to a process for the production of coatings on any substrates using a coating composition which contains a two-component binder and the auxiliaries and additives customary in coating technology, characterized in that the two-component binder consists of<ul id="ul0003" list-style="none"><li>a) a hardener of the formula (I)         H₂N-R-Si (OR ') ₃ (I) in combination with</li><li>b) with at least one polymer of the molecular weight range Mn 400 to 25,000, which has at least two structural units of the formula (II) per molecule<chemistry id="chem0002" num="0002"><img file="EP0483583A2_D0002.tif" /></chemistry> contains from 1 to 55% by weight of such structural units, based on the weight of the polymer,</li></ul> there, the proportions of components a) and b) correspond to a molar ratio of compounds of formula (I) to structural units of formula (II) of 0.5: 1 to 1: 1 and wherein<dl id="dl0002"><dt>R</dt><dd>represents an aliphatic hydrocarbon radical having 2 to 6 carbon atoms, with the proviso that at least two carbon atoms are arranged between the nitrogen and the silicon atom, and</dd><dt>R '</dt><dd>represents an alkyl radical having 1 to 4 carbon atoms.</dd></dl>

The invention finally also relates to a method for impregnating natural stone or concrete for the purpose of preservation using an impregnating agent which, in addition to conventional auxiliaries and additives, contains a two-component binder, characterized in that the two-component binder consists of<ul id="ul0004" list-style="none"><li>a) a hardener of the formula (I)         H₂N-R-Si (OR ') ₃ (I) in combination with</li><li>b) with at least one polymer in the molecular weight range Mw 400 to 25,000, which has at least two structural units of the formula (II) per molecule<chemistry id="chem0003" num="0003"><img file="EP0483583A2_D0003.tif" /></chemistry> contains from 1 to 55% by weight of such structural units, based on the weight of the polymer,</li></ul> consists in which the proportions of components a) and b) correspond to a molar ratio of compounds of formula (I) to structural units of formula (II) of 0.5: 1 to 1: 1 and wherein R and R 'have the meaning just mentioned .

In the processes according to the invention for the production of coatings or impregnations, the combinations of hardener a) and plastic precursor b) described, optionally already using solvents of the type known per se from coating technology, are used as two-component binders.

Suitable solvents which can be used in the coating or impregnating agents and which may already be used in the preparation of the binder combinations are, for example, ethanol, propanol, butanol, methoxyethanol, methoxypropanol, methoxypropyl acetate, dimethoxyethane, toluene, xylene, benzyl acetate and mixtures thereof.

In general, the solids content of the coating or impregnating agents according to the invention is 10 to 80% by weight.

The coating or impregnating agents may themselves contain, in addition to the solvents mentioned by way of example, other auxiliaries and additives known per se. These include, for example, leveling aids, fillers or pigments.

The coating compositions of the invention generally have a pot life of at least 30 minutes as a 50% solution after combining the essential binder components a) and b).

In the production of coatings, the coating compositions according to the invention are preferably used in dry film thicknesses of 5 to 200 μm. Suitable substrates are in particular metal, stone, glass, plastic and wood.

When using the combinations according to the invention from the individual components a) and b) as impregnating agents, in particular for natural stone or concrete, the combinations according to the invention are preferably used in a 15 to 50% strength by weight solution in the solvents mentioned by way of example.

The following examples serve to explain the invention further, without limiting it.

Examples

Manufacture of plastic precursors:

Plastic precursor I:

170 g of a polyacrylate resin of molecular weight Mn 10,000, produced by copolymerization of 70 parts by weight of methyl methacrylate, 15 parts by weight of n-butyl acrylate and 15 parts by weight of hydroxyethyl methacrylate, are dissolved in n-butyl acetate to give a 50% by weight solution . 8.4 g of diketene are then added to this solution and the mixture is then heated to 100 ° C. for 1 hour with stirring. The reaction mixture is then stirred for a further 8 hours at 120 to 130 ° C. and then freed from the solvent. The pale yellow resin isolated in this way contains 9 g of acetoacetate groups per 100 g (determined by potentiometric titration of the acidic methylene groups with 0.1 N KOH).

Plastic precursor II:

215.5 g of a polyhydroxy polyester (0.25 mol OH), made from 12 parts by weight of trimethylolpropane, 10 parts by weight of pentaerythritol, 21 parts by weight of benzoic acid, 28 parts by weight of phthalic acid and 20 parts by weight of one Commercial, branched C₁₈ fatty acid (®Unimac 5680 from Unilever) are 60 wt .-% dissolved in xylene. Then this solution is mixed with 21 g of diketene. The further reaction and processing takes place in analogy to plastic precursor I. The resulting yellow resin contains 14 g of acetoacetate groups per 100 g.

example 1

33 3.5 g of 3-aminopropyltriethoxysilane are added to g of the plastic precursor I, dissolved in 33 g of n-butyl acetate, and applied to a degreased sheet. The reaction mixture is gelled after 4 hours. The coating is dry and tack-free after 15 minutes. The coating withstands more than 100 double strokes with a cotton ball soaked in methyl ethyl ketone. The pendulum hardness according to König (DIN 53 157) is 140 s (23 ° C / 50% relative humidity).

Example 2

33 2.8 g of 3-aminopropyltrimethoxysilane are added to g of the plastic precursor I, dissolved in 33 g of n-butyl acetate, and applied to a degreased sheet. The reaction mixture gelled after one hour. The coating resists approx. 70 double strokes with a cotton ball soaked in methyl ethyl ketone. The pendulum hardness according to König (DIN 53 157) is 120 s (23 ° C / 50% relative humidity).

Example 3

20 g of the plastic precursor II, dissolved in 33 g of n-butyl acetate, are mixed with 5 g of 3-aminopropyltrimethoxysilane and applied to a degreased sheet. The reaction mixture is gelled after 45 minutes. The coating is dry and tack-free after one hour.

The coating withstands more than 100 double strokes with a cotton ball soaked in methyl ethyl ketone. The pendulum hardness according to König (DIN 53 157) is 80 s (23 ° C / 50% relative humidity).