FLUORINE-CONTAINING POLYMER, COATING COMPOSITION, METHOD FOR PRODUCING COATED ARTICLE, AND COATED ARTICLE

1 . A fluorine-containing polymer having repeating units derived from

(a) a fluorine-containing monomer,

(b) a fluorine-free non-crosslinkable monomer, and

(c) a fluorine-free crosslinkable monomer,

wherein the fluorine-containing monomer (a) is a compound represented by formula:

CH 2 ═C(-X)—C(═O)—Y—Z—Rf   (a-I)

wherein X is a hydrogen atom, a monovalent organic group or a halogen atom,

Y is —O— or —NH—,

Z is a direct bond or a divalent organic group,

Rf is a fluoroalkyl group having 1 to 20 carbon atoms, and

wherein the fluorine-free non-crosslinkable monomer (b) comprises

(b1) a cyclic hydrocarbon group-containing monomer and

(b2) a low Tg monomer, a homopolymer of which has a glass transition temperature (Tg) of lower than 0° C.

2 . The fluorine-containing polymer according to claim 1 , wherein in the fluorine-containing monomer (a) represented by formula (a-I), X is a hydrogen atom and the number of carbon atoms of Rf is 1 to 6.

3 . The fluorine-containing polymer according to claim 1 , wherein in the cyclic hydrocarbon group-containing monomer (b1), the cyclic hydrocarbon group has 4 to 30 carbon atoms.

4 . The fluorine-containing polymer according to claim 1 , wherein in the monomer (b1), the cyclic hydrocarbon group is at least one selected from the group consisting of a cyclohexyl group, a t-butylcyclohexyl group, an adamantyl group, a 2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a bornyl group, an isobornyl group, a norbornyl group, a dicyclopentanyl group, a dicyclopentenyl group, a benzyl group, a phenyl group, a naphthyl group, a 2-t-butylphenyl group, and residues obtained by removing one or more hydrogen atoms from these groups.

5 . The fluorine-containing polymer according to claim 1 ,

wherein the monomer (b2) is a monomer, a homopolymer of which has a glass transition temperature of lower than 0° C., and is represented by formula:

CH 2 ═CX 2 —C(═O)—Y 2 —Z 2   (b2-I)

wherein X 2 is a hydrogen atom, a monovalent organic group or a halogen atom,

Y 2 is —O— or —NH—, and

Z 2 is a linear or branched chain aliphatic hydrocarbon group having 1 to 30 carbon atoms.

6 . The fluorine-containing polymer according to claim 1 ,

wherein the fluorine-free crosslinkable monomer (c) is a compound represented by formula:

CH 2 ═CX 3 —C(═O)—Y 3 —Z 3 —W 3   (c-I)

wherein X 3 is a hydrogen atom, a methyl group or a halogen atom,

Y 3 is a direct bond, —O— or —NH—,

Z 3 is a direct bond or a divalent organic group, and

W 3 is a hydroxyl group, an epoxy group, a chloromethyl group, a blocked isocyanate group, an amino group, a carboxyl group, a hydrazide group or a melamine group.

7 . The fluorine-containing polymer according to claim 6 , wherein the fluorine-free crosslinkable monomer (c) comprises both of

a compound of formula (c-I) wherein Z 3 is a linear or branched chain alkylene group having 1 to 20 carbon atoms and W 3 is a hydroxyl group, and

a compound of formula (c-I) having a carboxyl group.

8 . The fluorine-containing polymer according to claim 1 , wherein an amount of the fluorine-containing monomer (a) is 30% by weight or less with respect to the polymer.

9 . The fluorine-containing polymer according to claim 1 , wherein an amount of the fluorine-free non-crosslinkable monomer (b) is 10 to 75% by weight with respect to the polymer, and an amount of the fluorine-free crosslinkable monomer (c) is 10 to 75% by weight with respect to the polymer.

10 . The fluorine-containing polymer according to claim 1 , wherein a weight ratio of the monomer (b1) and the monomer (b2) is 100:5 to 100:100.

11 . A coating composition, comprising

(1) the fluorine-containing polymer according to claims 1 , and

(2) a liquid medium.

12 . The coating composition according to claim 11 , comprising

(4) a curing agent,

wherein the curing agent (4) is a polyisocyanate compound, and an equivalent ratio (NCO/OH) of an isocyanate group in the polyisocyanate compound to a hydroxyl group in the fluorine-containing polymer is 0.5 to 2.5.

13 . A method for producing a coated article, comprising coating an article with the coating composition according to claim 11 .

14 . A coated article having a coating film having a thickness of 30 μm or less formed from the coating composition of claim 11 .