AQUEOUS SELF-CROSSLINKABLE POLYURETHANE DISPERSIONS

Abstract

The present invention relates to polyester polyols (1) carrying at least one keto-type C═O group derived from HO—C(═O)—L.sup.1—C(═O)—R.sup.1 (1i) or from a derivative thereof, wherein L.sup.1 is a linking group and R.sup.1 is selected from the group consisting of C.sub.1-20-alkyl, C.sub.5-8-cycloalkyl, C.sub.6-10-aryl and C.sub.7-20-aralkyl, to aqueous polyurethane dispersions (PUD) comprising at least one polyurethane (2) carrying at least one keto-type C═O group, water, and optionally at least one organic solvent (4), wherein the at least one polyurethane (2) carrying at least one keto-type C═O group comprises units derived from at least one polyester polyol (1), to aqueous self-crosslinkable polyurethane dispersions (SC-PUD) comprising at least one polyurethane (2) carrying at least one keto-type C═O group, at least one compound (3) carrying at least two keto-type C═O group reactive groups, water, and optionally at least one organic solvent (4), wherein the at least one polyurethane (2) carrying at least one keto-type C═O group comprises units derived from at least one polyester polyol (1), to aqueous self-crosslinkable polyurethane coating composition comprising the aqueous self-crosslinkable polyurethane dispersion (SC-PUD) optionally at least one organic solvent (5), at least one coating composition additive (6), optionally at least one polymer (7) different from the polyurethane (2), and optionally at least one monomer (8) carrying at least one olefinically unsaturated group, to substrate coated with the aqueous self-crosslinkable polyurethane coating composition, and to a process for coating the substrate with the aqueous self-crosslinkable polyurethane coating composition.

Claims

1.-19. (canceled)

20. A polyester polyols carrying at least one keto-type C═O group derived from HO—C(═O)—L.sup.1—C(═O)—R.sup.1 or from a derivative thereof, wherein L.sup.1 is a linking group and R.sup.1 is selected from the group consisting of C.sub.1-20-alkyl, C.sub.5-8-cycloalkyl, C.sub.6-10-aryl and C.sub.7-20-aralkyl.

21. The polyester polyol of claim 20 comprising units derived from 5 to 50 weight % of HO—C(═O)—l.sup.1—C(═O)—R.sup.1 (1i) or derivative thereof, wherein L.sup.1 is a linking group and R.sup.1 is selected from the group consisting of C.sub.1-20-alkyl, C.sub.5-8-cycloalkyl, C.sub.6-10-aryl and C.sub.7-20-aralkyl, 5 to 60 weight % of at least one diacid (1ii) or derivative thereof, 0 to 30 weight % of at least one polyacid (1iii) carrying at least three COOH groups or derivative thereof, 5 to 50 weight % of at least one diol (1iv), 5 to 50 weight % of at least one polyol (1v) carrying at least three OH groups and 0 to 20 weight % of at least compound (lvi) comprising at least one epoxy group, based on the weight of the sum of (1i), (1ii), (1iii), (1iv) (1v) and (1vi).

22. The polyester polyol of claim 20, wherein L.sup.1 is a linking group and R.sup.1 is C.sub.1-10-alkyl.

23. The polyester polyol of claim 22 wherein L.sup.1 is C.sub.1-10-alkylene group and R.sup.1 is C.sub.1-6-alkyl.

24. The polyester polyol of claim 23, wherein L.sup.1 is C.sub.1-6-alkylene group and R.sup.1 is C.sub.1-4-alkyl.

25. The polyester polyol of claim 20, wherein the keto-type C═O group-density is in the range of 0.01 to 4 mmol keto-type C═O groups/g polyester polyol.

26. An aqueous polyurethane dispersion comprising at least one polyurethane carrying at least one keto-type C═O group, and optionally at least one organic solvent, wherein the at least one polyurethane carrying at least one keto-type C═O group comprises units derived from at least one polyester polyol of claim 20.

27. The aqueous polyurethane dispersion of claim 26 comprising 5 to 90 weight % of at least one polyurethane carrying at least one keto-type C═O group, 20 to 95 weight % of water, and 0 to 5 weight % of organic solvent, based on the weight of the at least one polyurethane, water and organic solvent, wherein the at least one polyurethane carrying at least one keto-type C═O group comprises units derived from the at least one polyester polyol.

28. An aqueous self-crosslinkable polyurethane dispersion comprising at least one polyurethane carrying at least one keto-type C═O group, at least one compound carrying at least two keto-type C═O group reactive groups, water, and optionally at least one organic solvent, wherein the at least one polyurethane carrying at least one keto-type C═O group comprises units derived from the at least one polyester polyol of claim 20.

29. The aqueous self-crosslinkable polyurethane dispersion of claim 28 comprising 5 to 90 weight % of at least one polyurethane carrying at least one keto-type C═O group, 0.01 to 20 weight % of at least one compound carrying at least two keto-type CO=group reactive groups, and 20 to 95 weight % of water, and 0 to 5 weight % of organic solvent, based on the total weight of the dispersion, wherein the at least one polyurethane carrying at least one keto-type C═O group comprises units derived from the at least one polyester polyol.

30. The aqueous self-crosslinkable polyurethane dispersion of claim 28, wherein the polyurethane carrying at least one keto-type C═O group comprises units derived from the at least one polyester polyol, at least one polymeric polyol (2i) different from the at least one polyester polyol, at least one polyol (2ii) having a molecular weight of below 400 g/mol, at least one polyol (2iii) carrying at least one acidic group or a salt thereof, optionally at least one alcohol or polyol (2iv) carrying at least one olefinically unsaturated group at least one polyisocyanate (2v), at least one polyamine (2vi) carrying at least two amino groups independently selected from the group consisting of primary and secondary amino groups, and optionally at least one compound carrying at least one olefinically unsaturated group and no NCO reactive groups (2vii).

31. The aqueous self-crosslinkable polyurethane dispersion of claim 28, wherein the polyurethane (2) carrying at least one keto-type C═O group comprises units derived from 1 to 40 weight % of the at least one polyester polyol, 5 to 70 weight % of at least one polymeric polyol (2i) different from the at least one polyester polyol, 1 to 30 weight % of at least one polyol (2ii) having a molecular weight of below 400 g/mol, 0.5 to 20 weight % of at least one polyol (2iii) carrying at least one acidic group or a salt thereof, 0 to 30 weight % of at least one alcohol or polyol (2iv) carrying at least one olefinically unsaturated group, 10 to 80 weight % of at least one polyisocyanate (2v), 0.1 to 10 weight % of at least one polyamine (2vi) carrying at least two amino groups independently selected from the group consisting of primary and secondary amino groups, and 0 to 20 weight % of at least one compound (2vii) carrying at least one olefinically unsaturated group and no NCO reactive groups, based on the weight of the sum of (1), (2i) (2ii), (2iii), (2iv), (2v), (2vi) and (2vii).

32. The aqueous self-crosslinkable polyurethane dispersion of claim 28, wherein compound (3) is a compound carrying at least two keto-type C═O group reactive groups selected from the group consisting of —C(50 O)—N(R.sup.2)H—NH.sub.2 and —N(R.sup.2)—NH.sub.2, wherein R.sup.2 is selected from the group consisting of hydrogen, C.sub.1-20-alkyl, C.sub.5-8-cycloalkyl, C.sub.6-10-aryl and C.sub.7-20-aralkyl.

33. The aqueous self-crosslinkable polyurethane dispersion of claim 28, wherein compound (3) is a compound carrying at least two keto-type C═O group reactive groups, which are —C(═O)—N(R.sup.2)—NH.sub.2groups, wherein R.sup.2 is selected from the group consisting of hydrogen, C.sub.1-20-alkyl, C.sub.5-8-cycloalkyl, C.sub.6-10-aryl and C.sub.7-20-aralkyl.

34. An aqueous self-crosslinkable polyurethane coating composition comprising the aqueous self-crosslinkable polyurethane dispersion (SC-PUD) of claim 28 optionally at least one organic solvent (5), at least one coating composition additive (6), optionally at least one polymer (7) different from the polyurethane (2), and optionally at least one monomer (8) carrying at least one olefinically unsaturated group.

35. The aqueous self-crosslinkable polyurethane coating composition of claim 34 comprising 50 to 99 weight % of the aqueous self-crosslinkable polyurethane dispersion, 0 to 10 weight % of at least an organic solvent, 0.1 to 10 weight % of at least one coating composition additive, 0 to 50 weight % of at least one polymer different from the polyurethane, and 0 to 40 weight % 0 of at least one monomer carrying at least one olefinically unsaturated group, based on the total weight of the aqueous self-crosslinkable polyurethane coating composition.

36. A substrate coated with the aqueous self-crosslinkable polyurethane coating composition of claim 34.

37. The substrate of claim 36, wherein the substrate is wood.

38. A process for coating a substrate of claim 36, comprising applying the aqueous self-crosslinkable polyurethane coating composition to a substrate.

Description

EXAMPLES

Example 1

Preparation of Polyester Polyols 1a Carrying at Least One Keto-Type C═O Group

[0424] A mixture of 36.45 kg levulinic acid and 23.64 kg 1,4-cyclohexane dimethanol (cis/trans mixture) was melted at 60° C. 50.98 kg adipic acid and 39.33 kg trimethylolpropane were added and the reaction mixture was heated under stirring and inert atmosphere at 100° C. until a clear solution was obtained (approximately 4 hours). A solution of 0.045 kg titanium (IV) butoxide in 500 mL methylethylketone was added. The reaction mixture was heated under stirring to 160° C. and kept for 3 hours at this temperature. Vacuum (300 mbar) was applied, and the reaction mixture was heated under stirring at 200° C. until an acid number of 10 mg KOH/g was reached (approximately 12 hours). The vacuum was disrupted, and the reaction mixture was cooled to 170° C. 4.78 kg Cardura E1OP (neodecanoic acid, 2,3-epoxypropyl ester) was added and the reaction mixture was heated under stirring at 170° C. until an acid number of 2 mg KOH/g was reached (approximately 6 hours), and then cooled to 90° C. to yield keto polyester polyol 1a (number average molecular weight: 2700 g/mol, OH-functionality: 4, acid number: 3 mg KOH/g, keto-type C═O group-density: 0.205 mmol/g keto polyester polyol 1a).

Example 2

[0425] Preparation of an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2a) comprising polyurethane 2a carrying at least one keto-type C═O group, and adipic acid dihydrazide (ADDH) (3a)

[0426] 47,6 g dimethylolpropionic acid (DMPA), 230 g of a polyester diol formed from adipic acid, isophthalic acid, 1,6-hexandiol, number average molecular weight Mn: 2000 g/mol, OH number: 56 mg KOH/g, 100 g of polyester polyol 1a of example 1, 74.8 g 1,4-butandiol and 100 g acetone were mixed at 65° C. 366.3 g isophorone diisocyanate was added, the temperature was increased to 90° C., and the reaction mixture was allowed to react for 2 hours. The mixture was diluted with 790 g acetone, and the NCO content was measured (1.46%). 3.9 g isophorone diamine (IPDA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 33.3 g diethanolethylamine (DEEA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 1400 g Water was added to the reaction mixture under rapid stirring to obtain a dispersion of the polyurethane in water. 10.5 g diethylenetriamine (DETA) was added and the reaction mixture was allowed to react for 15 min. Acetone was removed by distillation. Then, 110 g of a solution of adipic acid dihydrazide (ADDH) (12 wt % ADDH in water) was added to the dispersion to obtain an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2a) comprising polyurethane 2a and adipic acid dihydrazide (ADDH) (3a) (solid content: 37 wt %, viscosity at 23° C.: 80-200 mPas, pH: 7.5-8.5, minimum film forming temperature: 19° C., particle size: 100 nm).

Example 3

[0427] Preparation of an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2b) comprising polyurethane 2b carrying at least one keto-type C═O group, and adipic acid dihydrazide (ADDH) (3a)

[0428] 43,89 g dimethylolpropionic acid (DMPA), 265 g of a polyester diol formed from adipic acid, isophthalic acid, 1,6-hexandiol, MW: 2000 g/mol, OH number: 56 mg KOH/g, 100 g of polyester polyol 1a of example 1, 73,35 g 1,4-butandiol and 100 g acetone were mixed at 65° C. 356,31 g isophorone diisocyanate was added, the temperature was increased to 90° C., and the reaction mixture was allowed to react for 2 hours. The mixture was diluted with 800 g acetone, and the NCO content was measured (1.27%). 3.91 g isophorone diamine (IPDA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 34,57 g diethanolethylamine (DEEA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 1600 g Water was added to the reaction mixture under rapid stirring to obtain a dispersion of the polyurethane in water. 9.1 g diethylenetriamine (DETA) was added and the reaction mixture was allowed to react for 15 min. Acetone was removed by distillation. Then, 110 g of a solution of adipic acid dihydrazide (ADDH) (12 wt % ADDH in water) was added to the dispersion to obtain an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2b) comprising polyurethane 2b and adipic acid dihydrazide (ADDH) (3a) (solid content: 37 wt %, viscosity at 23° C.: 80-200 mPas, pH: 7.5-8.5, minimum film forming temperature: 15-17° C., particle size ˜100 nm).

Example 4

[0429] Preparation of an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2c) comprising polyurethane 2c carrying at least one keto-type C═O group, and adipic acid dihydrazide (ADDH) (3a)

[0430] 40.2 g dimethylolpropionic acid (DMPA), 300 g of a polyester diol formed from adipic acid, isophthalic acid, 1,6-hexandiol, MW: 2000 g/mol, OH number: 56 mg KOH/g, 100 g of the polyester polyol 1a of example 1, 72.0 g 1,4-butandiol and 100 g acetone were mixed at 65° C. 346,6 g isophorone diisocyanate was added, the temperature was increased to 90° C., and the reaction mixture was allowed to react for 2 hours. The mixture was diluted with 800 g acetone, and the NCO content was measured (1.16%). 4.0 g isophorone diamine (IPDA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 36.1 g diethanolethylamine (DEEA) was added to the mixture and the reaction mixture was allowed to react for 5 min. 1600 g Water was added to the reaction mixture under rapid stirring to obtain a dispersion of the polyurethane in water. 7.75 g diethylenetriamine (DETA) was added and the reaction mixture was allowed to react for 15 min. Acetone was removed by distillation. Then, 110 g of a solution of adipic acid dihydrazide (ADDH) (12 wt % ADDH in water) was added to the dispersion to obtain an aqueous self-crosslinkable polyurethane dispersion (SC-PUD2c) comprising keto polyurethane 2c and adipic acid dihydrazide (ADDH) (solid content: 37 wt%, viscosity at 23° C.: 80-200 mPas, pH: 7.5-8.5, minimum film forming temperature: 11-14° C., particle size ˜100 nm).

Examples 5

[0431] Preparation of matting coating compositions comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 5 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 4/1

[0432] The pH of 93.4 weight parts of the aqueous self-crosslinkable polyurethane dispersion SC-PUD2a of example2, SC-PUD2b of example 3 and SC-PUD 2c of example 4, respectively, was adjusted to 8.5 using N,N-dimethylaminoethanol (DMEA), 1.0 weight parts Acematt®TS 100 (pyrogenic silicic acid), 4.0 weight parts Dowanol™DpnB (slow-evaporating, hydrophobic glycol ether), 1.0 weight parts Dowanol™ DPM (dipropylene glycol methyl ether), 0.3 weight parts Hydropalat® WE 3221 (silicone surfactant) and 0.3 weight parts FoamStar® ST 2454 were added and mixed at room temperature.

Comparative Example 5

[0433] A comparative matting coating composition was prepared in analogy to the matting coating compositions of example 5, but using NeoRez® R-2180 (DSM Coating Resins LLC, aliphatic, self-cross-linking, water-based polyurethane, acid value: 0, solid content: 38.0 wt %, viscosity at 23° C.: 25-150 mPas, pH: 7.4-8.4) instead of SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively.

Example 6

[0434] Preparation of a matting coating composition comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 3 weight % organic solvent organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 4/1

[0435] The pH of 95.4 weight parts of the aqueous self-crosslinkable polyurethane dispersion SC-SUD2a of example2, SC-PUD2b of example 3and SC-PUD 2c of example 4, respectively, was adjusted to 8.5 using N,N-dimethylaminoethanol (DMEA), 1.0 weight parts Acematt®TS 100 (pyrogenic silicic acid), 2.4 weight parts Dowanol™DpnB (slow-evaporating, hydrophobic glycol ether), 0.6 weight parts Dowanol™ DPM (dipropylene glycol methyl ether), 0.3 weight parts Hydropalat® WE 3221 (silicone surfactant) and 0.3 weight parts FoamStar® ST 2454 were added and mixed at room temperature.

Comparative Example 6

[0436] A comparative matting coating composition was prepared in analogy to the matting coating compositions of example 6, but using NeoRez® R-2180 (DSM Coating Resins LLC, aliphatic, self-cross-linking, water-based polyurethane, acid value: 0, solid content: 38.0 wt %, viscosity at 23° C.: 25-150 mPas, pH: 7.4-8.4) instead of SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively.

Example 7

[0437] Preparation of matting coating compositions comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 5 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 1/4

[0438] The pH of 93.4 weight parts of the aqueous self-crosslinkable polyurethane dispersion SC-PUD2a of example2, SC-PUD2b of example 3and SC-PUD 2c of example 4, respectively, was adjusted to 8.5 using N,N-dimethylaminoethanol (DMEA), 1.0 weight parts Acematt®TS 100 (pyrogenic silicic acid), 1.0 weight parts Dowanol™DpnB (slow-evaporating, hydrophobic glycol ether), 4.0 weight parts Dowanol™ DPM (dipropylene glycol methyl ether), 0.3 weight parts Hydropalat® WE 3221 (silicone surfactant) and 0.3 weight parts FoamStar® ST 2454 were added and mixed at room temperature.

Comparative Example 7

[0439] A comparative matting coating composition was prepared in analogy to the matting coating compositions of example 7, but using NeoRez® R-2180 (DSM Coating Resins LLC, aliphatic, self-cross-linking, water-based polyurethane, acid value: 0, solid content: 38.0 wt %, viscosity at 23° C.: 25-150 mPas, pH: 7.4-8.4) instead of SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively.

Example 8

[0440] Preparation of matting coating compositions comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 3 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 1/4

[0441] The pH of 95.4 weight parts of the aqueous self-crosslinkable polyurethane dispersion SC-PUD2a of example2, SC-PUD2b of example 3 and SC-PUD 2c of example 4, respectively, was adjusted to 8.5 using N,N-dimethylaminoethanol (DMEA), 1.0 weight parts Acematt®TS 100 (pyrogenic silicic acid), 0.6 weight parts Dowanol™DpnB (slow-evaporating, hydrophobic glycol ether), 2.4 weight parts Dowanol™ DPM (dipropylene glycol methyl ether), 0.3 weight parts Hydropalat® WE 3221 (silicone surfactant) and 0.3 weight parts FoamStar® ST 2454 (defoamer) were added and mixed at room temperature.

Comparative Example 8

[0442] A comparative matting coating composition was prepared in analogy to the matting coating compositions of example 8, but using NeoRez® R-2180 (DSM Coating Resins LLC, aliphatic, self-cross-linking, water-based polyurethane, acid value: 0, solid content: 38.0 wt %, viscosity at 23° C.: 25-150 mPas, pH: 7.4-8.4) instead of SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively.

Example 9

[0443] Analysis of the film forming behaviour of the matting coating compositions of examples 5 to 8 and comparative examples 5 to 8 on absorbing parquet wood substrates

[0444] The surface of parquet wood board samples (30×15 cm) were polished using sandpaper (grain size 150). 1.8 g of a wood stain (Loba ProColor, 900005 Black, Lobadur) was applied on the surface of each wood board sample using a metal spatula. The wood board samples were allowed to dry over the weekend at room temperature (approximately 60 hours).

[0445] The coated wood board samples were then conditioned under the conditions described in tables 1 and 2 for 24 hours before the matting coating compositions were applied.

[0446] The matting coating compositions were applied on the wood board samples using a film applicator to yield a 120 μm thick film, which was allowed to dry for 5 hours under the conditions described in tables 1 and 2. Then, the matting coating compositions were applied a second time to yield a new 120 μm thick film, which was allowed to dry overnight (approximately 12 h), again under the conditions described in tables 1 and 2 The surface of wood board samples was polished lightly using sandpaper (grain size 150), and the matting coating compositions were applied a third time to yield a new 120 μm thick film, which was allowed to dry for 7 days, again under the conditions described in tables 1 and 2.

[0447] The coated wood board samples were treated with water for 24 hours in laboratory atmosphere, and the coating layer formed from the matting coating compositions was analyzed directly after the water treatment by visual inspection. The film formation behaviour of the coating compositions was ranked from score 1 (worst film formation) to score 5 (best film formation). [0448] Score 1: microcrack “networks” overall the surface [0449] Score 2: mostly groups of microcrack “networks” [0450] Score 3: small single microcracks, first groups of microcrack “networks” [0451] Score 4: small single microcracks [0452] Score 5: homogeneous, crack-free film

[0453] The scores for the coating compositions of examples 5 and 6 and comparative examples 5 and 6 are summarized in table 1.

TABLE-US-00001 TABLE 1 Comp Comp Ex. 5 ex 5 Ex 6 ex 6 SC-PUD SC- SC- SC- NeoRez ® SC- SC- SC- NeoRez ® PUD 2a PUD2b PUD2c R-2180 PUD2a PUD2b PUD2c R-2180 DpnB/DPM (4/1) [wt %] T r.h. 5 5 5 5 3 3 3 3 [° C.] [%] Score 23 50 5 5 5 5 nd nd nd nd 23 20 nd 5 5 nd nd nd 4 nd 21 50 5 5 5 nd nd nd 4 nd 17 50 5 5 5 4 4 4 4 2 15 50 5 5 5 4 4 nd nd nd 13 80 5 5 5 4 4 4 4 2 13 50 5 5 5 3 4 5 5 1 10 80 5 5 5 3 3 4 4 2 nd = not determined. r.h. = relative humidity.

[0454] Table 1 shows that the film formation behavior at temperatures from 21 to 23° C. and at 20 to 50% relative humidities, and after 24 h water treatment of the dryed film, of the inventive coating compositions of example 5 comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 5 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 4/1 is ranked with the highest score (score 5) and is comparable to the film forming behavior of comparative coating composition of comparative example 5 comprising the aqueous dispersion NeoRez® R-2180 (DSM Coating Resins LLC).

[0455] Table 1 shows that the film formation behavior at temperatures from 10 to 17° C. and at 50 to 80% relative humidities, and after 24 h water treatment of the dryed film, of the inventive coating compositions of example 5 comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 5 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 4/1 is ranked with the highest score (score 5) and is better than the film forming behavior of comparative coating composition of comparative example 5 comprising the aqueous dispersion NeoRez® R-2180 (DSM Coating Resins LLC).

[0456] Table 1 also shows that the film formation behaviour at temperatures from 10 to 17° C. and at 50 to 80% relative humidities, and after 24 h water treatment of the dryed film, of the inventive coating compositions of example 6 comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and only 3 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio 4/1 is slightly worse than that of the inventive coating compositions of example 5 comprising 5 weight % organic solvent, but much better than that of comparative coating composition of comparative example 6 comprising the aqueous dispersion NeoRez® R-2180 (DSM Coating Resins LLC) and 3 weight % organic solvent.

[0457] The scores for the coating compositions of examples 7 and 8 and comparative examples 7 and 8 are summarized in table 2.

TABLE-US-00002 TABLE 2 Comp Comp Ex 7 ex 7 Ex 8 ex 8 SC-PUD SC- SC- SC- NeoRez ® SC- SC- SC- NeoRez ® PUD 2a PUD2b PUD2c R-2180 PUD2a PUD2b PUD2c R-2180 DpnB/DPM (1/4) [wt %] T r.h. 5 5 5 5 3 3 3 3 [° C.] [%] Score 17 50 5 5 5 4 4 5 5 2 13 80 5 5 5 4 3 4 4 3 13 50 5 5 5 4 4 5 4 1 10 80 5 5 5 3 4 4 4 2

[0458] Table 2 shows that the film formation behavior at temperatures from 10 to 17° C. and at 50 to 80% relative humidities, and after 24 h water treatment of the dryed film, of the inventive coating compositions of example 7 comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and 5 weight % organic solvent mixture Dowanol ™DpnB/Dowanol™ DPM in a weight ratio 1/4 is ranked with the highest score (score 5) and is better than the film forming behavior of comparative coating composition of comparative example 7 comprising the aqueous dispersion NeoRez® R-2180 (DSM Coating Resins LLC).

[0459] Table 2 also shows that the film formation behaviour at temperatures from 10 to 17° C. and at 50 to 80% relative humidities, and after 24 h water treatment of the dryed film, of the inventive coating compositions of example 8 comprising the aqueous self-crosslinkable polyurethane dispersions SC-PUD2a, SC-PUD2b and SC-PUD2c of examples 2, 3 and 4, respectively, and only 3 weight % organic solvent mixture Dowanol™DpnB/Dowanol™ DPM in a weight ratio ¼ is slightly worse than that of the inventive coating compositions of example 7 comprising 5 weight % organic solvent, but much better than that of comparative coating composition of comparative example 8 comprising the aqueous dispersion NeoRez® R-2180 (DSM Coating Resins LLC) and 3 weight % organic solvent.