Curable coating composition

1. A method for forming an acrylic emulsion comprising:

emulsion copolymerization of monomers comprising an acrylic monomer having an epoxy group (a-1), an acrylic monomer having a hydroxyl group (a-2) using a reactive emulsifier having an unsaturated double bond in the molecule (D) and a polymerization initiator having an imidazole group and/or an imidazoline group (b-3) in the presence of a silane compound having an epoxy group and an alkoxy group in the molecule (c-1).

2. The method according to claim 1 , wherein the acrylic emulsion is produced by the emulsion copolymerization under the condition of pH 5 to 10.

3. The method according to claim 1 , wherein the acrylic emulsion is produced by the emulsion copolymerization in an aqueous medium in the presence of an acrylic polymer (E).

4. The method according to claim 3 , wherein the acrylic polymer (E) is produced by the emulsion copolymerization of at least two unsaturated monomers comprising an unsaturated monomer having at least one epoxy group (a-1) and an unsaturated monomer having a carboxyl group (a-4) in an aqueous medium using a reactive emulsifier having an unsaturated double bond in the molecule (D) and a polymerization initiator having an imidazole group and/or imidazoline group (b-3), the number of moles of (a-1) is equal to or smaller than that of (a-4).

5. The method according to claim 3 , wherein the acrylic polymer (E) is produced by the emulsion copolymerization of an unsaturated monomer comprising a compound having at least two unsaturated double bonds in the molecule in an aqueous medium using a reactive emulsifier having an unsaturated double bond in the molecule (D) and a polymerization initiator having an imidazole group and/or imidazoline group (b-3).

6. An acrylic emulsion produced according to the process of claim 1 .

7. A curable coating composition comprising an acrylic resin having an epoxy group and a hydroxyl group in the side chain (A), a compound having an amino group having a molecular weight of not greater than 1000 (B), and a silane compound having an epoxy group or amino group in the molecule (C), the silane compound (C) being contained in an amount of from 0.02 to 500% by weight based on the total amount of the acrylic resin (A) and the compound having an amino group (B), wherein the compound having an amino group (B) is represented by general formula (I) (b-1):

wherein:

X represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms which has at least one substituent selected from the group consisting of A, B and C, a group having a benzene skeleton which may be substituted by a hydroxyl group and/or an alkyl group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 10 carbon atoms;

each of A, B and C is independently a group represented by the general formula (II) or (III):

 wherein each of R 1 , R 2 , R 4 , R 5 , R 6 , R 7 and R 8 independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; each of R 3 and R 9 independently represents an alkylene group having 1 to 10 carbon atoms or a carbonyl group; and

each of p, q and r is an integer of 0 to 1, provided that at least one of p, q and r is 1.

8. A curable coating composition comprising an acrylic resin having an epoxy group and a hydroxyl group in the side chain (A), a compound having an amino group having a molecular weight of not greater than 1000 (B), and a silane compound having an epoxy group or amino group in the molecule (C), the silane compound (C) being contained in an amount of from 0.02 to 500% by weight based on the total amount of the acrylic resin (A) and the compound having an amino group (B), wherein the compound having an amino group (B) is a compound having an imidazole group and/or an imidazoline group (b-2).

9. The curable coating composition according to claim 7 , wherein the acrylic resin (A) is prepared by polymerization using a polymerization initiator having an imidazole group and/or an imidazoline group (b-3).

10. A magnesium alloy having thereon a coat film formed with the curable coating composition of claim 7 , but having no chromate conversion film.

11. A magnesium alloy having thereon a coat film formed with the curable coating composition of claim 8 , but having no chromate conversion film.

12. An aluminum alloy having thereon a coat film comprising the curable coating composition of claim 7 , but having no chromate conversion film.

13. An aluminum alloy having thereon a coat film comprising the curable coating composition of claim 8 , but having no chromate conversion film.