AQUEOUS URETDIONE GROUP-CONTAINING COMPOSITIONS AND METHOD FOR PRODUCING SAME

Abstract

The invention relates to aqueous uretdione group-containing compositions comprising or consisting of (A) at least one uretdione group-containing curing agent based on aliphatic, cycloaliphatic, aliphatic and/or aromatic polyisocyanates which do not contain chemically bonded hydrophilating groups; (B) at least one polyacrylate copolymer; (C) optionally solvents; and (D) optionally auxiliary agents and additives; wherein the quantity ratio of the components (A) and (B) is measured such that the molar ratio of the NCO groups of the curing agent (A), said groups being provided in the form of uretdione, to the NCO reactive groups of the polyacrylate copolymer (B) equals 3.0:0.5 to 0.5:3.0, and A and B are provided as a physical mixture. The invention additionally relates to a method for producing a polyurethane layer using the aqueous uretdione group-containing composition according to the invention, to the polyurethane layer obtained therefrom, and to a substrate which is coated with or adhered to the polyurethane layer.

Claims

1. An aqueous uretdione group-containing compositions comprising: (A) at least one uretdione group-containing curing agent based on one or more of aliphatic, cycloaliphatic, araliphatic, and aromatic polyisocyanates that contains no chemically-bonded hydrophilizing groups; (B) at least one polyacrylate copolymer; (C) optionally, solvents; and (D) optionally, auxiliaries and additives; wherein the quantitative ratio of the at least one uretdione group-containing curing agent (A) and the at least one polyacrylate copolymer (B) is such that the molar ratio of the NCO groups of the curing agent (A) present as uretdione to NCO-reactive groups of the polyacrylate copolymer (B) is 3.0:0.5 to 0.5:3.0, and wherein (A) and (B) are present as a mixture.

2. The composition as claimed in claim 1, wherein the at least one uretdione group-containing curing agent (A) was obtained by reacting a monomeric isocyanate comprising at least one monomeric isocyanate selected from the group consisting of tetramethylene diisocyanate, cyclohexane-1,3-diisocyanate and cyclohexane-1,4-diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, dicyclohexylmethane-2,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, tetramethylxylylene diisocyanate, triisocyanatononane, toluene diisocyanate, diphenylmethane-2,4-diisocyanate, diphenylmethane-4,4-diisocyanate, triphenylmethane-4,4-diisocyanate, naphthylene-1,5-diisocyanate, and mixtures thereof.

3. The composition as claimed in claim 1, wherein hydroxyl-containing monomers or polymers are used as starting materials for the at least one uretdione group-containing curing agent (A).

4. The composition as claimed in claim 1, wherein the at least one uretdione group-containing curing agent (A) has a free NCO content of less than 5% by weight and a content of uretdione groups of 1% to 18% by weightcalculated as C.sub.2N.sub.2O.sub.2, molecular weight 84 g/mol.

5. The composition as claimed in claim 1, wherein the aqueous composition has an acid value of 1 to 100 mg KOH/g.

6. The composition as claimed in claim 1, wherein the at least one polyacrylate copolymer is obtained by reacting a mixture of free-radically polymerizable monomers (M), comprising (M1) hydroxyl- and carboxyl-free (meth)acrylic esters having C1 to C12 hydrocarbon radicals in the alcohol moiety; (M2) hydroxyl-functional, free-radically polymerizable monomers; (M3) carboxyl-functional, free-radically polymerizable monomers; (M4) optionally, vinyl esters of aliphatic carboxylic acids; (M5) optionally, at least one cycloaliphatic ester of (meth)acrylic acid and/or vinylaromatics.

7. The composition as claimed in claim 1, wherein the at least one polyacrylate copolymer (B) has an OH content greater than 1% by weightcalculated as OH groups based on the solids content, molecular weight 17 g/moland a number-average molecular weight Mn of 500 to 20 000 g/mol.

8. The composition as claimed in claim 1, wherein the solvent is selected from the group consisting of acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, xylene, solvent naphtha, propylene glycol mono-n-butyl ether, dipropylene glycol dimethyl ether, methoxypropyl acetate, dibasic esters, and mixtures thereof.

9. The composition as claimed in claim 1, wherein the auxiliaries and additives are selected from the group consisting of leveling agents, light stabilizers, catalysts, fillers, and pigments or mixtures thereof.

10. The composition as claimed in claim 1, wherein the sum of the proportions by weight of (A), (B), and (D) is 30% to 60% by weight based on the solids content of the total aqueous composition.

11. A process for producing a polyurethane layer comprising the steps of i) providing an aqueous uretdione group-containing composition as claimed in claim 1; ii) applying to a substrate the composition obtained in i) to produce a mixture; iii) drying the mixture from step ii), and iv) curing the mixture from step iii) by heating to from 40 C. to 180 C. for up to 180 minutes.

12. The process as claimed in claim 11, wherein the aqueous uretdione group-containing composition was obtained by mixing the uretdione group-containing curing agent (A) with the at least one polyacrylate copolymer (B) in the absence of water to form a mixture, and subsequently dispersing the mixture with water.

13. A polyurethane layer obtained by a process as claimed in claim 11.

14. A substrate coated or bonded with the polyurethane layer as claimed in claim 13.

Description

EXAMPLES

[0117] Raw Materials Employed:

[0118] Dowanol PnB: propylene glycol mono-n-butyl ether, from Dow

[0119] Peroxan DB: di-tert-butyl peroxide from Pergan.

[0120] Solvent Naphtha 100: an aromatic solvent, CAS: 64 742-95-6, from Azelis.

[0121] Veova 9: Versatic acid vinyl ester from Momentive.

[0122] Analytical Methods Used:

[0123] All viscosity measurements were carried out using a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) in accordance with DIN EN ISO 3219:1994-10.

[0124] NCO contents were determined titrimetrically in accordance with DIN EN ISO 11909:2007-05.

[0125] OH values were determined titrimetrically in accordance with DIN EN ISO 4629-2:2015-02.

[0126] The determination of acid values titrimetrically in accordance with DIN EN ISO 2114:2002-06.

[0127] Solids contents were determined in a circulating-air oven in accordance with DIN EN ISO 3251:2008-06, method B.

[0128] Average particle sizes (MPS) were determined using a Zetasizer Nano from Malvern (DE) in accordance with DIN ISO 13321:2004-10.

[0129] pH determinations were carried out using a pH meter in accordance with DIN ISO 976:2008-07 in a 1:4 dilution with distilled water.

[0130] Residual monomer contents were measured in accordance with DIN EN ISO 10283 by gas chromatography with an internal standard.

[0131] Pendulum hardness was measured on a standardized coil test plate (coil coating blackCS 200570, from Heinz Zanders Prf-Blech-Logistik) in accordance with DIN EN ISO 1522:2007-04 using a Knig pendulum.

[0132] Chemical resistance was measured on a standardized coil test plate (coil coating blackCS 200570, from Heinz Zanders Prf-Blech-Logistik). A cotton pad soaked in the test substance (xylene or water) was laid on the coating surface and covered with a watch glass. After the specified contact time, the cotton pad soaked in test substance was removed and the contact site dried off and immediately examined. Softening and discoloration of the coating surface were assessed. The assessment was made in accordance with DIN EN ISO 4628-1 as follows:

[0133] 0 no, i.e. no noticeable damage

[0134] 1 very few areas of damage, i.e. small, just about significant number

[0135] 2 a few areas of damage, i.e. small, but significant number

[0136] 3 moderate number of areas of damage

[0137] 4 considerable number of areas of damage

[0138] 5 very many areas of damage

[0139] Unless explicitly described otherwise, all percentages refer to percentages by weight.

[0140] Preparation of a Uretdione Group-Containing Crosslinker (Crosslinker 1, Preparation Example)

[0141] To 1000 g (4.50 mol) of isophorone diisocyanate (IPDI) were successively added at room temperature under dry nitrogen, with stirring, 10 g (1%) of triisodecyl phosphite and 20 g (2%) of 4-dimethylaminopyridine (DMAP) as catalyst. After 20 h, the reaction mixture, which had an NCO content of 28.7%, corresponding to a degree of oligomerization of 21.8%, was freed of volatiles, without prior addition of a catalyst poison, with the aid of a thin-film evaporator at a temperature of 160 C. and a pressure of 0.3 mbar.

[0142] This yielded a light yellow uretdione polyisocyanate having a free NCO group content of 17.0%, a monomeric IPDI content of 0.4%, and a viscosity of more than 200 000 mPas.

[0143] 337 g of 1,4-butanediol, 108 of 2-ethylhexanol, and 569 g of -caprolactone were mixed at room temperature under dry nitrogen, 0.3 g of tin(II) octoate was added, and the mixture was stirred at 160 C. for 5 h and then cooled to room temperature. To this mixture was then added, over a period of 30 min, 1850 g of the above-described uretdione group-containing polyisocyanate based on IPDI, which was warmed to 80 C. The reaction mixture was stirred at a temperature of max. 100 C. until the NCO content of the reaction mixture had fallen to a value of 0.8% after 7 to 8 h. The reaction mixture was solidified by pouring it onto a metal sheet, comminuted, and then dissolved in Dowanol PnB to give a solution with a solids content of 60% by weight.

Examples 1 to 4

Example 1

[0144]

TABLE-US-00001 TABLE 1 Weight (g) Component 1 DOWANOL PnB 1567 Component 2 PEROXAN DB 33 DOWANOL PnB 33 Component 3 METHYL METHACRYLATE 1243 HYDROXYETHYL METHACRYLATE 2419 n-BUTYL METHACRYLATE 592 n-BUTYL ACRYLATE 723 ISOBORNYL METHACRYLATE 1701 BUTANEDIOL MONOACRYLATE 836 STYRENE 573 Component 4 PEROXAN DB 140 DOWANOL PnB 140 Component 5 BUTANEDIOL MONOACRYLATE 296 METHYL METHACRYLATE 449 HYDROXYETHYL METHACRYLATE 467 n-BUTYL ACRYLATE 379 ACRYLIC ACID 316 Component 6 PEROXAN DB 33 DOWANOL PnB 60 Total amount 12000

[0145] Component 1 from table 1 was weighed into a stirring apparatus under nitrogen and heated to 138 C. Component 2 was then metered in evenly at 138 C. over a period of 20 minutes. After this, component 3 and component 4 were immediately metered in evenly at 138 C. in parallel over a period of 4 h 30 min. At the end of the addition, the reaction mixture was held at 138 C. for 30 min. Finally, component 5 and component 6 were metered in evenly at 138 C. in parallel over a period of 1 h 30 min. At the end of the addition, the reaction mixture was held at 138 C. for a further 1 h. After cooling, a pale yellowish, highly viscous polyacrylate solution was obtained. 500 g of this solution was weighed into a stirring apparatus under nitrogen and heated to 70 C. After homogenizing, 567 g of the 60% solution of crosslinker 1 in Dowanol PnB was added and the mixture was homogenized again at 70 C. for 30 min, followed by addition of a mixture of 21.5 g of triethanolamine and 4.3 g of dimethylethanolamine. The mixture was stirred at 70 C. for a further 30 min and then 463 g of distilled water was stirred in to the mixture. Fine adjustment of the viscosity to approx. 2000 mPas afforded a dispersion having the following properties:

TABLE-US-00002 Solids content 43.7% by weight Acid value (100%) 13 mg KOH/g OH content (100%, calculated) 2.8% by weight Average particle size 230 nm Viscosity 2030 mPas pH 7.5 The dispersion remained stable at 23 C. for 10 months.

Example 2

[0146] 500 g of polyacrylate solution from example 1 was weighed into a stirring apparatus under nitrogen and heated to 70 C. After homogenizing, 283 g of the 60% solution of crosslinker 1 in Dowanol PnB was added and the mixture was homogenized again at 70 C. for 30 min, followed by addition of a mixture of 21.5 g of triethanolamine and 4.3 g of dimethylethanolamine. The mixture was stirred at 70 C. for a further 30 min and then 407 g of distilled water was stirred into it. Fine adjustment of the viscosity to approx. 2000 mPas afforded a dispersion having the following properties:

TABLE-US-00003 Solids content 41.7% by weight Acid value (100%) 16.6 mg KOH/g OH content (100%, calculated) 3.6% by weight Average particle size 175 nm Viscosity 2360 mPas pH 7.5 The dispersion remained stable at 23 C. for 10 months.

Example 3

[0147]

TABLE-US-00004 TABLE 2 Weight (g) Component 1 SOLVENT NAPHTHA 100 900 BUTYLGLYCOL 648 Component 2 PEROXAN DB 33 BUTYLGLYCOL 33 Component 3 METHYL METHACRYLATE 3669 HYDROXYETHYL METHACRYLATE 1816 n-BUTYL ACRYLATE 2603 Component 4 PEROXAN DB 139 BUTYLGLYCOL 139 Component 5 METHYL METHACRYLATE 520 HYDROXYETHYL METHACRYLATE 734 n-BUTYL ACRYLATE 408 ACRYLIC ACID 245 Component 6 PEROXAN DB 33 BUTYLGLYCOL 80 Total amount 12000

[0148] Component 1 from table 2 was weighed into a stirring apparatus under nitrogen and heated to 138 C. Component 2 was then metered in evenly at 138 C. over a period of 20 minutes. After this, component 3 and component 4 were immediately metered in evenly at 138 C. in parallel over a period of 4 h 30 min. At the end of the addition, the reaction mixture was held at 138 C. for 30 min. Finally, component 5 and component 6 were metered in evenly at 138 C. in parallel over a period of 1 h 30 min. At the end of the addition, the reaction mixture was held at 138 C. for a further 1 h. After cooling, a pale yellowish, highly viscous polyacrylate solution was obtained to 100 C., the reaction mixture was transferred to the appropriate container(s).

[0149] 552 g of this solution was weighed into a stirring apparatus under nitrogen and heated to 70 C. After homogenizing, 471 g of the 60% solution of crosslinker 1 in Dowanol PnB was added and the mixture was homogenized again at 70 C. for 30 min, followed by addition of 14.6 g of dimethylethanolamine. The mixture was stirred at 70 C. for a further 30 min and then 466 g of distilled water was stirred in. Fine adjustment of the viscosity to approx. 2000 mPas afforded a stable dispersion having the following properties:

TABLE-US-00005 Solids content 46.1% by weight Acid value (100%) 16.3 mg KOH/g OH content (100%, calculated) 2.1% by weight Average particle size 225 nm Viscosity 1110 mPas pH 8.2 The dispersion remained stable at 23 C. for 5 months.

Example 4

[0150]

TABLE-US-00006 TABLE 3 Weight (g) Component 1 DOW ANOL PnB 3438 Component 2 PEROXAN DB 33 DOWANOL PnB 33 Component 3 STYRENE 570 METHYL METHACRYLATE 1566 HYDROXYETHYL METHACRYLATE 1601 n-BUTYL ACRYLATE 341 ISOBORNYL METHACRYLATE 1520 n-BUTYL METHACRYLATE 1208 VEOVA 9 1251 Component 4 PEROXAN DB 118 DOWANOL PnB 321 Total amount 12000

[0151] Component 1 from table 3 was weighed into a stirring apparatus under nitrogen and heated to 148 C. Component 2 was then metered in evenly at 148 C. over a period of 20 minutes. After this, component 3 and component 4 were immediately metered in evenly at 148 C. in parallel over a period of 6 h. At the end of the addition, the reaction mixture was held at 148 C. for 60 min. After cooling to 80 C., the polyacrylate solution was transferred to the appropriate container(s).

TABLE-US-00007 TABLE 4 Raw material Weights Component 1 Polyacrylate solution from table 3 1993 Component 2 PEROXAN DB 36 DOWANOL PnB 36 72 Component 3 2-ETHYLHEXYL ACRYLATE 377 HYDROXYETHYL ACRYLATE 1931 n-BUTYL METHACRYLATE 1308 ISOBORNYL METHACRYLATE 2951 n-BUTYL ACRYLATE 338 BUTANEDIOL MONOACRYLATE 555 Component 4 PEROXAN DB 129 DOWANOL PnB 154 Component 5 METHYL METHACRYLATE 533 HYDROXYETHYL ACRYLATE 799 n-BUTYL ACRYLATE 411 METHACRYLIC ACID 333 Component 6 PEROXAN DB 36 DOWANOL PnB 80 Total amount 12000

[0152] Component 1 from table 4 was weighed into a stirring apparatus under nitrogen and heated to 144 C. Component 2 was then metered in evenly at 144 C. over a period of 20 minutes. After this, component 3 and component 4 were immediately metered in evenly at 144 C. in parallel over a period of 4 h 30 min. At the end of the addition, the reaction mixture was held at 144 C. for 5 min. Finally, component 5 and component 6 were metered in evenly at 144 C. in parallel over a period of 1 h 30 min. At the end of the addition, the reaction mixture was held at 144 C. for a further 1 h. After cooling, a pale yellowish, highly viscous polyacrylate solution was obtained.

[0153] 304 g of this solution was weighed into a stirring apparatus under nitrogen and heated to 70 C. After homogenizing, 385 g of the 60% solution of crosslinker 1 in Dowanol PnB was added and the mixture was homogenized again at 70 C. for 30 min, followed by addition of 11 g of dimethylethanolamine. The mixture was stirred at 70 C. for a further 30 min and then 324 g of distilled water was stirred into it. Fine adjustment of the viscosity to approx. 2000 mPas afforded a dispersion having the following properties:

TABLE-US-00008 Solids content 42.6% by weight Acid value (100%) 18 mg KOH/g OH content (100%, calculated) 2.5% by weight Average particle size 287 nm Viscosity 2030 mPas pH 8.7 The dispersion remained stable at 23 C. for 5 months.

[0154] Tests of Coating Properties:

[0155] Clearcoats were produced from the preceding examples 1 to 4. (all weights in g):

TABLE-US-00009 TABLE 5 Inventive examples 5 to 8 Example 5 6 7 8 1 10.00 2 10.00 3 10.00 4 10.00

[0156] The dispersions were homogenized in a SpeedMixer at 2000 rpm for 1 minute applied to a metal coil test plate in a layer thickness of 180 m (wet) using a coating blade. The plates with the applied wet coatings were for 5 min at room temperature, baked for 30 min at 180 C., and then stored for 24 hours at room temperature. The performance of the stored films was assessed (table 6).

TABLE-US-00010 TABLE 6 Tests of the coating properties of the inventive examples 5-8 Example 5 6 7 8 Appearance of the coating (visual examination) clear, glossy clear, glossy clear, glossy silk-matt Film thickness (dry, ) 60 50 50 40 Pendulum hardness (s) 188 196 189 204 Resistance to xylene (5 minutes) 3 2 3 2 Deionized water (1 hour) 1 0-1 0-1 0-1

[0157] As can be seen from table 6, the uretdione-containing dispersions of the invention afford hard and resistant coatings. Both glossy and silk-matt coatings can be produced from the uretdione-containing dispersions of the invention.