Highly branched polymers as cross-linking agents in microcapsule wall

1. A microcapsule, comprising:

a capsule core and

a capsule wall,

wherein the capsule wall is obtained by a process comprising polymerizing, in a free-radical polymerization, an oil-in-water emulsion,

wherein the oil-in-water emulsion comprises the following monomers:

(I) 30 to 90% by weight based on the total weight of the monomers of at least one monomer (I) selected from the group consisting of a C 1 -C 24 -alkyl ester of acrylic acid or of methacrylic acid or of both, acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid,

(II) 10 to 70% by weight based on the total weight of the monomers of a monomer (II), which is an ethylenically unsaturated crosslinker, wherein at least 10% by weight, based on the total weight of the monomers (I), (II) and (III), is a highly branched polymeric crosslinker, and

(III) 0 to 30% by weight based on the total weight of the monomers of a monomer (III), which is a monounsaturated monomer, which is different from monomer (I); and

a hydrophobic core material.

2. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker is a hyperbranched polymer with a double bond content of from 0.1 to 10 mol/kg.

3. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker is a polyaddition product or polycondensation product.

4. The microcapsule of claim 1 , wherein the highly branched crosslinker is selected from the group consisting of a polycarbonate, a polyester, a polyether, a polyurethane, a polyurea, a polyamide, and mixtures thereof.

5. The microcapsule of claim 1 , wherein the highly branched crosslinker is a polyester, a polycarbonate, a polyurethane, or a mixture thereof.

6. The microcapsule of claim 1 , wherein

a total content of all monomer (I) is from 40 to 70% by weight based on the total weight of the monomers,

a total content of all monomer (II) is from 30% to 60% by weight based on the total weight of the monomers, wherein a total content of the highly branched polymeric crosslinker is at least 30% by weight based on the total weight of the monomers (I), (II) and (III), and

a total content of all monomer (III) is from 0 to 30%.

7. The microcapsule of claim 1 , wherein the free-radical polymerization is in the presence a protective colloid.

8. The microcapsule of claim 7 , wherein the protective colloid comprises a polyvinyl alcohol, a partially hydrolyzed polyvinyl acetate, a methylhydroxy(C 1 -C 4 )-alkylcellulose, or a mixture thereof.

9. The microcapsule of claim 1 , wherein the hydrophobic core material is at least one material selected from the group consisting of an aliphatic or aromatic hydrocarbon compound; a saturated or unsaturated C 6 -C 30 -fatty acid; a fatty alcohol; a C 6 -C 30 -fatty amine; a C 4 -C 30 -mono-, C 4 -C 30 -di-, or C 4 -C 30 -polyester; a primary, secondary or tertiary C 4 -C 30 -carboxamide; a fatty acid ester; a natural or synthetic wax; a halogenated hydrocarbon; a natural oil; a C 3 -C 20 -ketone; a C 3 -C 20 -aldehyde; a crosslinker; an adhesive resin; a tackifying resin; a fragrance; an aroma substance; an active compound; a dye; a color former; a catalyst; and an inhibitor.

10. A process for preparing a microcapsule, the process comprising:

forming a microcapsule which comprises capsule core and a capsule wall, wherein said forming comprises polymerizing, in a the free-radical polymerization, an oil-in-water emulsion,

wherein the oil-in-water emulsion comprises the following monomers:

(I) 30 to 90% by weight based on the total weight of the monomers of at least one monomer (I) selected from the group consisting of a C 1 -C 24 -alkyl ester of acrylic acid or of methacrylic acid or of both; acrylic acid; methacrylic acid; maleic acid; fumaric acid; and itaconic acid,

(II) 10 to 70% by weight based on the total weight of the monomers of a monomer (II), which is an ethylenically unsaturated crosslinker, wherein at least 10% by weight, based on the total weight of the monomers (I), (II) and (III), is a highly branched polymeric crosslinker, and

(III) 0 to 30% by weight based on the total weight of the monomers of a monomer (III), which is a monounsaturated monomer, which is different from monomer (I); and

a hydrophobic core material.

11. A latent heat storage material, comprising the microcapsule of claim 1 .

12. The microcapsule of claim 4 , wherein the highly branched crosslinker is at least one crosslinker selected from the group consisting of a poly(urea urethane), a poly(ether amine), a poly(ester amine), a poly(ether amide), a poly(ester amide), a poly(amidoamine), a poly(ester carbonate), a poly(ether carbonate), a poly(ether ester), and a poly(ether ester carbonate).

13. The process of claim 10 , wherein the oil-in-water emulsion further comprises a protective colloid.

14. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker has a molar mass distribution such that the width of the molar mass distribution is at least 1.1.

15. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker has a degree of branching per molecule of from 10 to 100%.

16. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker has at least 2 to 100, on number-average, ethylenically unsaturated end groups and/or side groups.

17. The microcapsule of claim 1 , wherein the highly branched polymeric crosslinker has a weight-average molecular weight Mw of from about 800 to 300 000.

18. The process of claim 10 , wherein the highly branched polymeric crosslinker has a molar mass distribution such that the width of the molar mass distribution is at least 1.1.

19. The process of claim 10 , wherein the highly branched polymeric crosslinker has a degree of branching per molecule of from 10 to 100%.

20. The process of claim 10 , wherein the highly branched polymeric crosslinker has at least 2 to 100, on number-average, ethylenically unsaturated end groups and/or side groups.

21. The process of claim 10 , wherein the highly branched polymeric crosslinker has a weight-average molecular weight Mw of from about 800 to 300 000.