Radiation-curable water-dispersible polyurethane (meth)acrylates

Abstract

The present invention relates to radiation-curable, water-dispersible polyurethane (meth)acrylates, to coating compositions comprising the latter, to the use thereof and to the process for production thereof.

Claims

1. A radiation-curable, water-dispersible urethane (meth)acrylate (A) essentially formed from (a) at least one (cyclo)aliphatic di- and/or polyisocyanate, (b1) at least one (cyclo)aliphatic diol having a molar mass of less than 700 g/mol, (b2) at least one polyester diol having a weight-average molar mass Mw of 700 to 2000, wherein 5 to 35 mol %, based on the total isocyanate functions in (a), of hydroxyl functions in the sum total of (b1) and (b2), (c) at least one compound (c) having at least one isocyanate-reactive group and at least one free-radically polymerizable unsaturated group, wherein component (c) is selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-butane-1,4-diol monoacrylate, 3-butane-1,4-diol monoacrylate, 1,2-diacrylate of glycerol, 1,3-diacrylate of glycerol, trimethylolpropane diacrylate, pentaerythrityl triacrylate, ditrimethylolpropane triacrylate and dipentaerythrityl pentaacrylate, wherein 20 to 80 mol %, based on the total isocyanate functions in (a), of hydroxyl functions in the sum total of (c), (d) at least one compound having at least one isocyanate-reactive group and at least one acid group, wherein 20 to 60 mol %, based on the total isocyanate functions in (a), of hydroxyl functions in the sum total of (d), (e) at least one base of an alkali metal for at least partial neutralization of the acid groups of component (d), wherein 60 to 100 mol %, based on acid functions in (d), of in the sum total of base (e), (f) optionally at least one monoalcohol having exactly one hydroxyl function, or at least one mono- and di-C1-C4-alkylamine, wherein 0 to 30 mol %, based on the total isocyanate functions in (a), of hydroxyl or amino functions which react with isocyanate in the sum total of base (f), (g) at least one monofunctional polyalkylene oxide polyether alcohol wherein 0.5 to 10 mol %, based on the total isocyanate functions in (a), of hydroxyl functions in the sum total of (g) with the proviso that the sum total in components (b), (c), (d), and (g) is 70 to 100 mol % of isocyanate-reactive groups based on total isocyanate functions in (a)).

2. The urethane (meth)acrylate according to claim 1, wherein component (a) is a mixture of a cycloaliphatic or aliphatic monomeric diisocyanate (a1) and a polyisocyanate (a2) based on a cycloaliphatic or aliphatic monomeric diisocyanate.

3. The urethane (meth)acrylate according to claim 2, wherein component (a1) is selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, 2,4-di(isocyanatocyclohexyl)methane, and 4,4-di(isocyanatocyclohexyl)methane.

4. The urethane (meth)acrylate according to claim 2, wherein the polyisocyanate (a2) is a polyisocyanate having isocyanurate groups, uretdione diisocyanate, polyisocyanate having biuret groups, polyisocyanate having urethane or allophanate groups.

5. The urethane (meth)acrylate according to claim 2, wherein the polyisocyanate (a2) is a compound of the formula ##STR00004## in which R5 is a divalent alkylene radical which has 2 to 12 carbon atoms and may optionally be substituted by C1- to C4-alkyl groups and/or be interrupted by one or more oxygen atoms, R6 is a divalent alkylene radical or cycloalkylene radical which has 2 to 20 carbon atoms and may optionally be substituted by C1- to C4-alkyl groups and/or be interrupted by one or more oxygen atoms, R7 is hydrogen or methyl, and X is a positive number having a statistical average of 2 to 6.

6. The urethane (meth)acrylate according to claim 1, wherein component (b1) is selected from the group consisting of ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol, butane-2,3-diol, pentane-1,2-diol, pentane-1,3-diol, pentane-1,4-diol, pentane-1,5-diol, pentane-2,3-diol, pentane-2,4-diol, hexane-1,2-diol, hexane-1,3-diol, hexane-1,4-diol, hexane-1,5-diol, hexane-1,6-diol, hexane-2,5-diol, heptane-1,2-diol, heptane-1,7-diol, octane-1,8-diol, octane-1,2-diol, nonane-1,9-diol, decane-1,2-diol, decane-1,10-diol, dodecane-1,2-diol, dodecane-1,12-diol, 1,5-hexadiene-3,4-diol, neopentyl glycol, 2-butyl-2-ethylpropane-1,3-diol, 2-methylpentane-2,4-diol, 2,4-dimethylpentane-2,4-diol, 2-ethylhexane-1,3-diol, 2,5-dimethylhexane-2,5-diol, 2,2,4-trimethylpentane-1,3-diol, pinacol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol.

7. The urethane (meth)acrylate according to claim 1, wherein component (b2) is a polyester diol having a weight-average molar mass Mw of 700 to 2000 g/mol and an acid number to DIN 53240 of not more than 20 mg KOH/g.

8. The urethane (meth)acrylate according to claim 1, wherein component (d) is dimethylolpropionic acid.

9. The urethane (meth)acrylate according to claim 1, wherein component (f) is present and is a mono-, di-C1-C4-alkylamine, mono- or dialkanolamine.

10. The urethane (meth)acrylate according to claim 1, wherein component (f) is present and is selected from the group consisting of diethylamine, di-n-butylamine, ethanolamine, propanolamine, N,N-dipropanolamine and N,N-diethanolamine.

11. An aqueous coating composition comprising the urethane (meth)acrylate according to claim 1, optionally a low molecular weight (meth)acrylate (B) which is soluble or dispersible in an aqueous dispersion of the urethane (meth)acrylate (A), optionally a pigment, and optionally a photoinitiator.

12. An article of wood, paper, textile, leather, fleece, plastics surfaces, glass, ceramic, mineral building materials, cement blocks, fiber cement boards, metals or coated metals, coated by the coating composition according to claim 11.

13. A printing ink comprising the coating composition according to claim 11.

14. A method comprising printing on polycarbonate, polyethylene, polypropylene, polyamide, polyethylene terephthalate (PET), or paper with the printing ink according to claim 13.

15. An aqueous dispersion comprising the urethane (meth)acrylate of claim 1, wherein the aqueous dispersion is capable of storage for 10 days at a temperature of 40? C. without sedimentation.

16. An aqueous dispersion comprising the urethane (meth)acrylate of claim 1, wherein the aqueous dispersion is capable of storage for 30 days at a temperature of 40? C. without gelation.

17. The aqueous dispersion comprising the urethane (meth)acrylate of claim 15, wherein the aqueous dispersion is capable of storage for 30 days at a temperature of 40? C. without gelation.

Description

EXAMPLE 1

(1) In a stirred tank, 69 parts dimethylolpropionic acid, 19 parts neopentyl glycol, 144 parts Lupraphen? VP 9327 (BASF SE; polyester diol based on adipic acid, isophthalic acid and cyclohexanedimethanol, having a mean OH number of 140 mgKOH/g), 29 parts 2-hydroxyethyl acrylate, 62 parts Pluriol?A1020E (BASF SE; methanol-started polyethylene glycol having a mean OH number of 50 mgKOH/g) and 1 part Kerobit? TBK (BASF SE; 2,6-di-t-butylcresol) were homogenized in 350 parts acetone, followed by parallel metered addition, within 20 min, of 463 parts Laromer? LR 9000 (BASF SE; unsaturated polyisocyanate based on 2-hydroxyethyl acrylate and hexamethylene diisocyanate having an isocyanate equivalent weight of about 290 g/mol) and parts hexamethylene diisocyanate. The reaction mixture was heated to 65? C. and left to react down to a residual isocyanate content of 0.9% by weight of NCO. After dilution of the prepolymer obtained with 300 parts acetone, the residual isocyanate content was converted by reaction with 25 parts diethanolamine. After neutralization of the reaction mixture with 203 parts 10% sodium hydroxide solution in water and dispersion by addition of 1200 parts water, the acetone was distilled off to obtain a dispersion having 39% by weight solids, a pH of 7.5, a viscosity of 300 mPa.Math.s and a weight-average molecular weight of 12 000 g/mol.

COMPARATIVE EXAMPLE 1 (TRIETHYLAMINE NEUTRALIZATION)

(2) In a stirred tank, 41 parts dimethylolpropionic acid, 11 parts neopentyl glycol, 86 parts Lupraphen? VP 9327 (BASF SE; polyester diol based on adipic acid, isophthalic acid and cyclohexanedimethanol, having a mean OH number of 140 mgKOH/g), 17 parts 2-hydroxyethyl acrylate, 37 parts Pluriol?A1020E (BASF SE; methanol-started polyethylene glycol having a mean OH number of 50 mgKOH/g) and 0.5 part Kerobit? TBK (BASF SE; 2,6-di-t-butylcresol) were homogenized in 210 parts acetone, followed by parallel metered addition, within 20 min, of 278 parts Laromer? LR 9000 (BASF SE; unsaturated polyisocyanate based on 2-hydroxyethyl acrylate and hexamethylene diisocyanate having an isocyanate equivalent weight of about 290 g/mol) and 21 parts hexamethylene diisocyanate. The reaction mixture was heated to 65? C. and left to react down to a residual isocyanate content of 0.9% by weight of NCO. After dilution of the prepolymer obtained with 200 parts acetone, the residual isocyanate content was converted by reaction with 14 parts diethanolamine. After neutralization of the reaction mixture with 32 parts triethylamine in water and dispersion by addition of 810 parts water, the acetone was distilled off to obtain a dispersion having 39% by weight solids, a pH of 7.4, a viscosity of 1100 mPa.Math.s and a weight-average molecular weight of 23 000 g/mol.

COMPARATIVE EXAMPLE 2 (NO PLURIOL A1020E AND TRIETHYLAMINE NEUTRALIZATION)

(3) In a stirred tank, 44 parts dimethylolpropionic acid, 12 parts neopentyl glycol, 92 parts Lupraphen? VP 9327 (BASF SE; polyester diol based on adipic acid, isophthalic acid and cyclohexanedimethanol, having a mean OH number of 140 mgKOH/g), 23 parts 2-hydroxyethyl acrylate and 0.5 part Kerobit? TBK (BASF SE; 2,6-di-t-butylcresol) were homogenized in 210 parts acetone, followed by parallel metered addition, within 20 min, of 296 parts Laromer? LR 9000 (BASF SE; unsaturated polyisocyanate based on 2-hydroxyethyl acrylate and hexamethylene diisocyanate having an isocyanate equivalent weight of about 290 g/mol) and 22 parts hexamethylene diisocyanate. The reaction mixture was heated to 65? C. and left to react down to a residual isocyanate content of 0.9% by weight of NCO. After dilution of the prepolymer obtained with 200 parts acetone, the residual isocyanate content was converted by reaction with 17 parts diethanolamine. After neutralization of the reaction mixture with 33 parts triethylamine and dispersion by addition of 810 parts water, the acetone was distilled off to obtain a dispersion having 39% by weight solids, a pH of 7.6, a viscosity of 3300 mPa.Math.s and a weight-average molecular weight of 38 000 g/mol.

(4) Properties:

(5) TABLE-US-00001 Comparative Comparative Example 1 example 1 example 2 pH.sup.(1), 7.5 7.4 7.6 Viscosity, mPa .Math. s.sup.(1) 300 1100 3300 (t = 0 d, 25? C.) pH.sup.(1) 7.3 6.5 6.2 Viscosity, mPa .Math. s.sup.(1) 260 900 3150 (t = 30 d, T = 25? C.) pH.sup.(1) 7.2 5.5 (sediment) 5.1 (sediment) Viscosity, mPa .Math. s.sup.(1) 230 330 600 (t = 10 d, T = 40? C.) pH.sup.(1) 7.0 gelated gelated Viscosity, mPa .Math. s.sup.(1) 210 (t = 30 d, T = 40? C.) .sup.(1)Property of the dispersion produced

(6) It can be seen that the inventive dispersion, even after storage over a prolonged period, retains its stability, whereas the dispersions according to the comparative examples lose their properties.