Aqueous 2K PUR systems
View Patent ↗The invention relates to aqueous two-component polyurethane systems comprising vinyl polymer polyol dispersions modified with reactive diluents, to a process for preparing them and to use as coating materials.
1. A process for preparing aqueous two-component polyurethane systems, comprising i) preparing a polyol component a) composed of a hydrophobic core polymer having a glass transition temperature of 40° to 100° C., on which a hydrophilic shell polymer having a glass transition temperature of from −100° to +25° C. has been grafted by aqueous-phase emulsion polymerization, ii) adding a hydroxyl-containing polyether component b) before, during or after the polymerization and iii) admixing a polyisocyanate component c) therewith.
2. The process of claim 1 , wherein no cosolvent is used.
3. The process of claim 1 , wherein said polyol component a) is prepared from
A) from 0 to 7% by weight of a monomer selected from the group consisting of acrylic acid, methacrylic acid, and mixtures thereof,
B) from 5 to 75% by weight of a monomer selected from the group consisting of methyl methacrylate, styrene, and mixtures thereof
C) from 3 to 40% by weight of a monomer selected from the group consisting of C 1-8 alkyl acrylates, C 2-8 alkyl methacrylates, and mixtures thereof,
D) from 2 to 74% by weight of a monomer selected from the group consisting of monohydroxy-functional alkyl acrylates, monohydroxy-functional alkyl methacrylates, and mixtures thereof,
E) from 0 to 30% by weight of other olefinically unsaturated monomers, the sum of the components being 100% by weight.
4. The process of claim 1 , wherein the polyether component b) comprises a polypropylene oxide polyol having a molecular weight of from 300 to 4000 g/mol.
5. The process of claim 1 , wherein the polyisocyanate component c) has a viscosity of from 5 to 12 000 mPas.
6. The process according of claim 1 , wherein components a), b) and c) are mixed manually or by the action of a stirrer, the proportions being chosen so as to give an NCO/OH equivalents ratio of from 0.2:1 to 5:1.
7. The aqueous two-component polyurethane system produced by the process of claim 6 .
8. A coating composition comprising the aqueous two-component polyurethane system of claim 7 .
9. The coating composition of claim 8 , further comprising an organic cosolvent in an amount of less than 2% by weight.
10. A process for producing coated substrates, comprising applying the composition of claim 7 to a substrate.
11. The coated substrate produced according to claim 10