Aqueous polyurethane dispersion for waterproof breathable coatings

Abstract

An aqueous polyurethane dispersion comprises a polyurethane polymer obtainable by the reaction of an isocyanate-functional polyurethane prepolymer A) with an isocyanate-reactive component B), wherein the isocyanate-functional prepolymer A) is obtainable by the reaction of a mixture comprising: a polyol component comprising a polyester polyol obtainable by the reaction of a mixture comprising an aliphatic dicarboxylic acid and at least one diol selected from the group consisting of linear aliphatic diols and a branched aliphatic diols; and a polyisocyanate component comprising ≧50 weight-%, based on the total weight of polyisocyanates, of dicyclohexylmethane diisocyanate. The isocyanate-reactive component B) comprises a compound comprising sulfonate groups which is employed in an amount of ≧3.5 weight-% to ≦10 weight-%, based on the total weight of the polyol component, the polyisocyanate component and the isocyanate-reactive component B). The invention also concerns the use of such an aqueous polyurethane dispersion for coatings, a method of manufacturing a coated substrate and to a coated substrate.

Claims

1. An aqueous polyurethane dispersion comprising a polyurethane polymer obtained by the reaction of an isocyanate-functional polyurethane prepolymer A) with an isocyanate-reactive component B), wherein the isocyanate-functional prepolymer A) is obtained by the reaction of a mixture comprising: a polyol component comprising a polyester polyol obtained by the reaction of a mixture comprising adipic acid, 1,6-hexanediol and neopentyl glycol, wherein the molar ratio of 1,6 hexane diol to neopentyl glycol is in a range of ≧1.5:1 to ≦2.5:1; and a polyisocyanate component comprising ≧99 weight-% to ≦100 weight-%, based on the total weight of polyisocyanates, of dicyclohexylmethane diisocyanate; and wherein the isocyanate-reactive component B) comprises 2-[(2-aminoethyl)amino]ethanesulfonic acid and/or salts thereof, in an amount of ≧3.5 weight-% to ≦6 weight-%, based on the total weight of the polyol component, the polyisocyanate component and the isocyanate-reactive component B), and wherein the dispersion applied as a coating exhibits a water vapor transmission rate of ≧16800 g/m.sup.2/d to ≦22900 g/m.sup.2/d.

2. The dispersion according to claim 1, wherein the polyester polyol has a number-average molecular weight of ≧1000 g/mol to ≦2000 g/mol.

3. The dispersion according to claim 1, wherein the isocyanate-reactive component B) further comprises a polyamine chain extender in an amount of ≧5 weight-% to ≦15 weight-% based on the total weight of the isocyanate-reactive component B).

4. A method for the production of water vapor-permeable coatings comprising applying the aqueous polyurethane dispersion according to claim 1 to a substrate.

5. A method of manufacturing a coated substrate, comprising the steps of providing a substrate and coating the substrate with an aqueous polyurethane dispersion according to claim 1.

6. The method according to claim 5, further comprising the step of drying the aqueous polyurethane dispersion.

7. The method according to claim 5, wherein the substrate is selected from the group consisting of textiles, metal surfaces, glass surfaces, ceramic surfaces, concrete surfaces, stone surfaces, leather surfaces and synthetic polymer surfaces.

8. A coated substrate comprising a coating which comprises an aqueous or dried polyurethane dispersion according to claim 1.

9. The coated substrate according to claim 8, wherein the substrate is selected from the group consisting of textiles, metal surfaces, glass surfaces, ceramic surfaces, concrete surfaces, stone surfaces, leather surfaces and synthetic polymer surfaces.

10. The coated substrate according to claim 8, wherein the coating has a water vapor transmission rate of ≧16800 g/m.sup.2/d to ≦22900 g/m.sup.2/d.

11. The dispersion according to claim 1, wherein the polyisocyanate component is dicyclohexylmethane diisocyanate.

12. The dispersion according to claim 3, wherein the polyamine chain extender is ethylenediamine.

13. The dispersion according to claim 1, wherein the polyisocyanate component is dicyclohexylmethane diisocyanate, wherein the isocyanate-reactive component B) further comprises a polyamine chain extender in an amount of ≧5 weight-% to ≦15 weight-% based on the total weight of the isocyanate-reactive component B), and wherein the polyamine chain extender is ethylenediamine.

14. An aqueous polyurethane dispersion consisting of a polyurethane polymer obtained by the reaction of an isocyanate-functional polyurethane prepolymer A) with an isocyanate-reactive component B), wherein the isocyanate-functional prepolymer A) is obtained by the reaction of a mixture comprising: a polyol component comprising a polyester polyol obtained by the reaction of a mixture comprising adipic acid, 1,6-hexanediol and neopentyl glycol, wherein the molar ratio of 1,6 hexane diol to neopentyl glycol is in a range of ≧1.5:1 to ≦2.5:1; and a polyisocyanate component comprising ≧99 weight-% to ≦100 weight-%, based on the total weight of polyisocyanates, of dicyclohexylmethane diisocyanate; and wherein the isocyanate-reactive component B) comprises 2-[(2-aminoethyl)amino]ethanesulfonic acid and/or salts thereof, in an amount of ≧3.5 weight-% to ≦6 weight-%, based on the total weight of the polyol component, the polyisocyanate component and the isocyanate-reactive component B), and wherein the dispersion applied as a coating exhibits a water vapor transmission rate of ≧10000 g/m.sup.2/d to ≦25000 g/m.sup.2/d.

Description

EXAMPLES

(1) The present invention is illustrated by reference to examples, although these are not to be understood as being limiting. Unless stated otherwise, all of the quantitative data, fractions and percentages are based on the weight and the total amount or on the total weight of the compositions. Unless noted otherwise, all of the analytical measurements refer to measurements at temperatures of 23° C.

(2) The solids or solid-body contents were determined by heating a weighed sample at 125° C. to constant weight. At constant weight, the solid-body content is calculated by reweighing the sample.

(3) Unless expressly mentioned otherwise, NCO contents were determined volumetrically in accordance with DIN-EN ISO 11909. The control on free NCO groups was carried out by means of IR spectroscopy (band at 2260 cm.sup.−1)

(4) The stated viscosities were determined by means of rotary viscometry in accordance with DIN 53019 at 23° C. using a rotary viscometer from Anton Paar Germany GmbH, Ostfildern, Germany.

(5) The average particle sizes (the number-average is given) of the polyurethane dispersions were determined following dilution with deionized water by means of laser correlation spectroscopy (instrument: Malvern Zetasizer 1000, Malver Inst. Limited).

Glossary

(6) Diaminosulfonate: NH.sub.2—CH.sub.2CH.sub.2—NH—CH.sub.2CH.sub.2—SO.sub.3Na (sodium 2-[(2-aminoethyl)amino]-ethanesulfonate, 45% strength in water); amounts given in the examples relate to this 45 weight-% solution in water

(7) Desmophen® 2020/C2200: polycarbonate polyol, OH number 56 mg of KOH/g, number-average molecular weight 2000 g/mol (Bayer MaterialScience AG, Leverkusen, Germany)

(8) PolyTHF® 2000: polytetramethylene glycol polyol, OH number 56 mg of KOH/g, number-average molecular weight 2000 g/mol (BASF AG, Ludwigshafen, Germany)

(9) PolyTHF® 1000: polytetramethylene glycol polyol, OH number 112 mg of KOH/g, number-average molecular weight 1000 g/mol (BASF AG, Ludwigshafen, Germany)

(10) Polyether LB 25: monofunctional polyether based on ethylene oxide/propylene oxide of number-average molecular weight 2250 g/mol, OH number 25 mg of KOH/g (Bayer MaterialScience AG, Leverkusen, Germany)

(11) Desmodur® W: dicyclohexylmethane diisocyanate (H.sub.12-MDI)

Example 1 (Comparative Example)

(12) 987.0 g of PolyTHF® 2000, 375.4 g of PolyTHF® 1000, 761.3 g of Desmophen® C2200 and 44.3 g of polyether LB 25 were heated to 70° C. in a standard stirring apparatus. Then, a mixture of 237.0 g of hexamethylene diisocyanate and 313.2 g of isophorone diisocyanate was added and the mixture was stirred at 120° C. until the theoretical NCO value was reached. The finished prepolymer was dissolved with 4830 g of acetone and in so doing cooled to 50° C., and then a solution of 25.1 g of ethylenediamine, 116.5 g of isophoronediamine, 61.7 g of diaminosulfonate and 1030 g of water was metered in. The afterstirring time was 10 min. The mixture was then dispersed by adding 1250 g of water. The solvent was removed by distillation in vacuo.

(13) The resulting white dispersion had the following properties:

(14) Solids content: 61% Particle size (LCS): 312 nm

(15) Viscosity (viscometer, 23° C.): 241 mPas

(16) pH (23° C.): 7.15

Example 2 (Comparative Example)

(17) 450 g of PolyTHF® 1000 and 2100 g of PolyTHF® 2000 were heated to 70° C. Then, a mixture of 225.8 g of hexamethylene diisocyanate and 298.4 g of isophorone diisocyanate was added and the mixture was stirred at 100-115° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 5460 g of acetone at 50° C. and then a solution of 29.5 g of ethylenediamine, 143.2 g of diaminosulfonate and 610 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 1880 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(18) Solids content: 56%

(19) Particle size (LCS): 276 nm Viscosity: 1000 mPas

Example 3 (Comparative Example)

(20) 1649.0 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 291.7 g of hexamethylene diisocyanate were added and the mixture was stirred at 100-115° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 3450 g of acetone at 50° C. and then a solution of 16.8 g of ethylenediamine, 109.7 g of diaminosulfonate and 425 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 1880 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(21) Solids content: 42%

(22) Particle size (LCS): 168 nm

(23) Viscosity: 425 mPas

(24) pH: 7.07

Example 4 (Comparative Example)

(25) 340 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 60.1 g of hexamethylene diisocyanate were added and the mixture was stirred at 105° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 711 g of acetone at 50° C. and then a solution of 2.1 g of ethylenediamine, 32.4 g of diaminosulfonate and 104.3 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 1880 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(26) Solids content: 40%

(27) Particle size (LCS): 198 nm

(28) Viscosity: 700 mPas

(29) pH: 6.31

Example 5 (Comparative Example)

(30) 340 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 60.1 g of hexamethylene diisocyanate were added and the mixture was stirred at 105° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 711 g of acetone at 50° C. and then a solution of 46.9 g of diaminosulfonate and 129 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 477 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(31) Solids content: 33%

(32) Particle size (LCS): 168 nm

(33) Viscosity: 410 mPas

(34) pH: 7.3

Example 6 (Comparative Example)

(35) 318.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 74.5 g of isophorone diisocyanate were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 700 g of acetone at 50° C. and then a solution of 44.0 g of diaminosulfonate and 121 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 470 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(36) Solids content: 29%

(37) Particle size (LCS): 29 nm

(38) Viscosity: 450 mPas

(39) pH: 6.9

Example 7 (Comparative Example)

(40) 318.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 87.9 g of Desmodur® W were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 720 g of acetone at 50° C. and then a solution of 20.6 g of diaminosulfonate, 4.1 g of ethylene diamine and 87 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 520 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(41) Solids content: 40.2%

(42) Particle size (LCS): 172 nm

(43) Viscosity: 23 mPas

(44) pH: 8.7

Example 8

(45) 318.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 87.9 g of Desmodur® W were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 720 g of acetone at 50° C. and then a solution of 32.9 g of diaminosulfonate, 1.6 g of ethylene diamine and 102 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 520 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(46) Solids content: 40.5%

(47) Particle size (LCS): 148 nm

(48) Viscosity: 30 mPas

(49) pH: 7.3

Example 9

(50) 318.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 87.9 g of Desmodur® W were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 720 g of acetone at 50° C. and then a solution of 44.0 g of diaminosulfonate and 121 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 500 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(51) Solids content: 40.0%

(52) Particle size (LCS): 215 nm

(53) Viscosity: 48 mPas

(54) pH: 9.0

Example 10

(55) 318.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol were heated to 65° C. Then, 87.9 g of Desmodur® W were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 720 g of acetone at 50° C. and then a solution of 41.8 g of diaminosulfonate, 1.5 g of ethylene diamine and 127 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 480 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(56) Solids content: 39.4%

(57) Particle size (LCS): 149 nm

(58) Viscosity: 108 mPas

(59) pH: 8.9

Example 11

(60) 148.8 g of a polyester of adipic acid, hexanediol and neopentyl glycol with a number-average molecular weight of 1700 g/mol and 175.0 g of Desmophen® C 2200 were heated to 65° C. Then, 82.1 g of Desmodur® W were added and the mixture was stirred at 125° C. until the actual NCO value had dropped below the theoretical NCO value. The finished prepolymer was dissolved with 720 g of acetone at 50° C. and then a solution of 41.1 g of diaminosulfonate and 113 g of water was metered in. The afterstirring time was 15 min. The mixture was then dispersed by adding 500 g of water. The solvent was removed by distillation in vacuo and a storage-stable dispersion was obtained.

(61) Solids content: 40.9%

(62) Particle size (LCS): 182 nm

(63) Viscosity: <50 mPas

(64) pH: 8.5

Example 12 (Water Vapor Transmission Rate (WVTR) Testing)

(65) In a film casting instrument comprising two polished rolls, which was set to a precise distance, a release paper was inserted in front of the rear roll. The distance between the paper and the front roll was adjusted by means of a feeler gauge. This distance corresponds to the (wet) film thickness of the resulting coating, and was adjusted to the desired deposition for each coat. Coating could also be performed consecutively in several coats.

(66) The individual coats were applied by pouring the products (set to a viscosity of 4500 mPa s by addition of Borchi Gel ALA, Borchers, Langenfeld, Del.) onto the gap between the paper and the front roll and pulling the release paper vertically downwards, whereby the corresponding film was formed on the paper. If several coats were to be applied, each individual coat was dried and the paper inserted again.

(67) In order to determine the water vapor transmission rate (WVTR), a wet film of 150 μm was applied onto a release paper of the type VEZ matte. The film was dried at 50° C. for 10 minutes and at 150° C. for 3 minutes. WVTR was measured according to the publication DS 2109 TM1 of the British Textile Technology Group, Manchester, GB. The results are summarized in the following table.

(68) TABLE-US-00001 Film based on dispersion of WVTR example no. [g/m.sup.2/d]  1 2280 (comparative)  2 3750 (comparative)  3 2170 (comparative)  4 3060 (comparative)  5 3100 (comparative)  6 2300 (comparative)  7 2800 (comparative)  8 16800  9 22900 10 19800 11 21300

Example 13: Hydrostatic Pressure Test

(69) A film with a strength of 37.4 g/cm.sup.2 was prepared from example 8 according to DIN 53886. Measurement of the hydrostatic pressure test (ISO 811:1981) was done according to DIN EN 20811:1992 at 20° C. The result was that no leakage could be detected at hydrostatic pressures of 6000 mm.