Aqueous polyurethane dispersion comprising a terephthalic acid polyester

Abstract

The present invention relates to an aqueous polyurethane dispersion obtainable by the reaction of at least: (A) one polyisocyanate with two or more isocyanate groups, (B) one polyester component comprising (B1) a polyesterpolyol with a mean molecular weight of 300 to 900 g/Mol, having structural units derived from terephthalic acid, (C) one ionic group introducing compound with at least one sulphonate and/or carboxylate group and at least one isocyanate reactive group, (D) one diol with a mean molecular weight of 62 to 400 g/Mol, (E) one polyol with a mean molecular weight of 62 to 400 g/Mol, having three or more hydroxyl groups, (F) one amino functional and/or aminohydroxyl functional compound, its use to coat a substrate and a coating obtained by using the dispersion.

Claims

1. An aqueous polyurethane dispersion obtained by the reaction of at least: (A) 30 to 60% per weight of one polyisocyanate with two or more isocyanate groups, (B) 15 to 50% per weight of one polyester component comprising (B1) a polyesterpolyol with a weight average molecular weight of 300 to 900 g/Mol, comprises structural units derived from derived from 3-methyl-1,5 pentandiol, (C) 1.5 to 8% per weight of one ionic group introducing compound with at least one sulphonate and/or carboxylate group and at least one isocyanate reactive group, (D) 1 to 8% per weight of one diol with a weight average molecular weight of 62 to 400 g/Mol, (E) 0.1 to 4% per weight of one polyol with a weight average molecular weight of 62 to 400 g/Mol, having three or more hydroxyl groups, (F) 0.5 to 12% per weight of one amino functional and/or aminohydroxyl functional compound, wherein the sum of all percentages adds up to 100.

2. The dispersion according to claim 1, wherein the weight average molecular weight of the polyesterpolyol (B1) is 400 to 800.

3. The dispersion according to claim 1, wherein the polyol component (B) additionally comprises a polyesterpolyol (B2) with a weight average molecular weight of 1000 to 4000 g/Mol, having structural units derived from terephthalic acid.

4. The dispersion according to claim 3, wherein the weight average molecular weight of the polyesterpolyol (B2) is 1500 to 3500.

5. The dispersion according to claim 3, wherein the polyesterpolyol (B2) comprises structural units derived from 3-methyl-1,5 pentandiol.

6. The dispersion according to claim 3, wherein the ratio between the polyesterpolyol (B1) and the polyesterpolyol (B2) is between 100:0 to 40:60.

7. The dispersion according to claim 1, wherein the polyisocyanate (A) has two isocyanate groups.

8. The dispersion according to claim 1, wherein the ionic group introducing compound (C) comprises N-(2-aminoethyl)-2-aminoethane sulphonate and/or dimethylol propionic acid.

9. The dispersion according to claim 1, wherein the diol (D) comprises one or more compounds selected from the group consisting of ethanediol, di-ethyleneglycol, tri- ethyleneglycol, tetraethyleneglycol, 1,2-propanediol, di-propyleneglycol, tri-propyleneglycol, tetrapropyleneglycol, 1,3-propanediol, butanediol-1,4, butanedio-1,3, butanediol-2,3, pentanedio-1,5, hexanedio-1,6, 2,2-dimethyl-1,3-propanediol, 1,4-dihydroxycyclohexane, 1,4-dimethylolcyclohexane, octanedio-1,8, decanediol-1,10, dodecanediol-1,12, neopentylglycol, 1,4-cyclohexanediol, 1,4-cyclohexane-dimethanol, 1,4-, 1,3-, 1,2-dihydroxybenzene, 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol (A)), and 3-Methyl-1,5-pentandiol.

10. The dispersion according to claim 1, wherein the polyol (E) comprises one or more compounds selected from the group consisting of trimethylolpropane, glycerine, pentaerythrite, and dipenthaerytrite.

11. The dispersion according to claim 1, wherein the amino functional and/or aminohydroxyl functional compound (F) comprises one or more compounds selected from the group consisting of 1,2-ethanediamine, 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, diethylenetriamine, diethanolamine, ethanolamine, N-(2-hydroxyethyl)-ethylenediamine and N,N-bis(2-hydroxyethyl)-ethylenediamine.

12. A method comprising coating a substrate with the dispersion according to claim 1.

13. A coating obtained by applying the dispersion according to claim 1.

14. The dispersion according to claim 1, wherein the polyisocyanate (A) comprises one or more compounds selected from the group consisting of hexamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 4,4′-diisocyanato-dicyclohexyl-methane, and 4,4′-diisocyanato-dicyclohexylpropane-(2,2).

Description

EXAMPLE 1

(1) Formulations I-1 and I-2 (invention) and C-1 to C-3 (comparative), based on the dispersions 1, 2 (inventive) and 4 to 6, respectively, were prepared by addition of 32% of N-Methyl-2-pyrrolidoneand (based on Dispersion). Formulations were then prepared as free films of type 5 A, in accordance with DIN EN ISO 527-3 with the drying condition of first 10 minutes at room temperature, then 16 hours at 60° C. Dried films were then subjected to the following tests.

(2) TABLE-US-00001 I-1 I-2 C-1 C-2 C-3 Dispersion I II III IV V E-Module (MPa) 820 960 555 630 300 Elongation at break (%) 128 93 180 155 166
The films prepared from formulations according to the invention (I-1 and I-2) showed improved mechanical properties compared to the films prepared from formulations C-1 to C-3, such as a significant improved E-Module and at the same time lower Elongation at break.

EXAMPLE 2

(3) Formulations I-1 and I-2 (invention) and C-1 to C-3 (comparative) were prepared by addition of 32% of N-Methyl-2-pyrrolidoneand (based on Dispersion). Formulations were then doctor-bladed onto the aluminum substrate so that the dried film thickness was approximately 15 μm. The films were dried first for 10 minutes at room temperature, then for 16 hours at 60° C. Dried films were then subjected to the following tests.

(4) TABLE-US-00002 I-1 I-2 C-1 C-2 C-3 Dispersion I II III IV V dynamic friction 770 790 850 990 1040 power [N] dynamic friction 0.385 0.395 0.425 0.495 0.520 coefficient μ.sub.D
The films prepared from formulations according to the invention (I-1 and I-2) showed also lower dynamic friction power and a lower dynamic friction coefficient compared to the films prepared from formulations C-1 to C-3. Lower friction power on the surface leads to improved surface properties of the coatings such as an improved Rub resistance (see also example 4).

EXAMPLE 3

(5) Formulations I-1 and I-2 (invention) and C-1 to C-3 (comparative) were prepared by addition of 32% of N-Methyl-2-pyrrolidoneand (based on Dispersion). Formulations were then doctor-bladed onto the glass substrate so that the dried film thickness was approximately 15 μm. The films were dried first for 10 minutes at room temperature, then for 16 hours at 60° C. Dried films were then subjected to the following tests.

(6) TABLE-US-00003 I-1 I-2 C-1 C-2 C-3 Dispersion I II III IV V Micro hardness (N/mm.sup.2) 240 110 66 78 66 Measured only at the surface with the minimum penetration depth Micro hardness (N/mm.sup.2) 160 68 45 60 45 Measured with the penetration depth of 1 μm
The films prepared from formulations according to the invention (I-1 and I-2) showed improved Micro hardness compared to the films reared from formulations C-1 to C-3.

EXAMPLE 4

(7) Formulations I-1 and I-2 (invention) and C-1 to C-3 (comparative) were prepared by addition of 32% of N-Methyl-2-pyrrolidoneand (based on Dispersion). Formulations were then doctor-bladed onto the glass (or ABS) substrate so that the dried film thickness was approximately 15 μm. The films were dried first for 10 minutes at room temperature, then for 16 hours at 60° C. Dried films were then subjected to the following tests.

(8) TABLE-US-00004 I-1 I-2 C-1 C-2 C-3 Dispersion I II III IV V Pencil hardness H H HB HB HB On glass König pendulum hardness (s) 209 211 196 155 188 On glass Ethanol rubbing test 220 100 80 22 60 Double rubs on ABS
The films prepared from formulations according to the invention (I-1 and I-2) showed improved mechanical properties in combination with improved coating properties compared to the films prepared from formulations C-1 to C-3, such as higher hardness in combination with a significantly improved Rub resistance.

EXAMPLE 5

(9) Further formulations C-4 (comparative) and I-3 (invention) were prepared according to the following tables. Amounts given are in weight-parts, unless specified otherwise.

(10) TABLE-US-00005 C-4 I-3 Dispersion 3 88.11 Dispersion 7 86.86 Byk ® 028 1.00 1.04 Byk ® 346 0.20 0.24 Butyl di-glycol/water (1:1) 11.94 Butyl di-glycol 10.60 Solid content (%) 31.83 34.40 Cosolvent content/Dispersion (%) 6.87 12.03

EXAMPLE 6

(11) The formulations of example 5 were subjected to the tests as outlined in the following tables. Formulations were doctor-bladed onto the glass (for pendulum hardness), and pinewood substrates (for chemical resistance) in a thickness of 200 μm. The films were dried first at room temperature, unless specified otherwise. Dried films were then subjected to the following tests.

(12) TABLE-US-00006 C-4 I-3 König pendulum hardness (s) 16 h at 50° C. 142 159 Chemical resistance Drying condition: 67 h, 40° C. water resistance - 5 h Immediately 5 5 After recovery 5 5 Pure EtOH resistance - 5 h Immediately 1 2 After recovery 1 2-3 Double rubs with MEK <5 >100
The films prepared from the formulation according to the invention (I-3) showed improved mechanical properties in combination with improved coating properties on wood compared to the films prepared from formulation C-4, such as high hardness in combination with a significantly improve Rub resistance and resistance against ethanol.