(Meth)acrylic copolymer, coating material composition, coated article and method for forming multilayer coating film

A coating material composition comprising a (meth)acrylic copolymer (A) and a polyisocyanate compound or blocked polyisocyanate compound,

• wherein the (meth)acrylic copolymer has an acid value greater than 0 mgKOH/g and equal to or less than 80 mgKOH/g, and comprises:
• a macromonomer constituent unit (a), and
• a constituent unit (b) derived from a vinyl monomer,
• wherein the constituent unit (a) is present in a range of from 30 to 60% by mass with respect to a total mass of all constituent units of the (meth)acrylic copolymer (A),
• wherein the constituent unit (b) comprises a constituent unit derived a carboxyl group-comprising vinyl-based monomer,
• wherein the (meth)acrylic copolymer (A) comprises a mixture of constituent units having primary hydroxyl groups and secondary/tertiary hydroxyl groups and a content of the constituent unit having secondary/tertiary hydroxyl groups is greater than 50% by mass and equal to or less than 95% by mass with respect to the total mass of the constituent unit that has a hydroxyl group,
• wherein the (meth)acrylic copolymer (A) comprises no more than 30 parts by mass of a constituent unit having a primary hydroxyl group, with respect to 100 parts by mass of the constituent unit (a) and the constituent unit (b), and
• wherein a gel fraction of one day after coating is equal to or less than 70%,
• wherein a gel fraction of eight days after coating is equal to or greater than 80%, and
• wherein the macromonomer (a) is of formula (1)
• wherein, in formula (1),
• R is H, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, an optionally substituted aryl group, or an optionally substituted heterocyclic group,
• Z is a terminal group, and
• Q is a main chain part comprising two or more constituent units of formula (a′)
• wherein, in formula (a′),
• R1 is H, a methyl group, or CH2OH, and
• R2 is OR3, a halogen atom, COR4, COOR5, CN, CONR6R7, or R8, R3 to R7 each independently being H, an optionally substituted alkyl group, an optionally substituted alicyclic group, an optionally substituted aryl group, an optionally substituted heteroaryl group, an optionally substituted nonaromatic heterocyclic group, an optionally substituted aralkyl group, an optionally substituted alkaryl group, or an optionally substituted organosilyl group, substituent group(s) of each of these groups is at least one selected from the group consisting of a carboxylic acid group, a carboxylic acid ester group, an epoxy group, a hydroxy group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanato group, a sulfonic acid group, and a halogen atom, and
• R8 is an optionally substituted aryl group or an optionally substituted heteroaryl group, substituent group(s) of each of these groups being at least one selected from the group consisting of a carboxylic acid group, a carboxylic acid ester group, an epoxy group, a hydroxy group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanato group, a sulfonic acid group, an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted olefin group, and a halogen atom.

A coating material composition comprising a (meth)acrylic copolymer (A) and a polyisocyanate compound or blocked polyisocyanate compound,

• wherein the (meth)acrylic copolymer has an acid value greater than 0 mgKOH/g and equal to or less than 80 mgKOH/g, and comprises:
• a macromonomer constituent unit (a);
• and
• a constituent unit (b) derived from a vinyl monomer,
• wherein the constituent unit (a) is present in a range of from 30 to 60% by mass with respect to a total mass of all constituent units of the (meth)acrylic copolymer (A),
• wherein the constituent unit (b) comprises a constituent unit derived a carboxyl group-containing vinyl-based monomer,
• wherein the (meth)acrylic copolymer (A) comprises a mixture of constituent units having primary hydroxyl groups and secondary/tertiary hydroxyl groups and a content of the constituent unit having secondary/tertiary hydroxyl groups is greater than 50% by mass and equal to or less than 95% by mass with respect to the total mass of the constituent unit that has a hydroxyl group,
• wherein the (meth)acrylic copolymer (A) comprises no more than 30 parts by mass of a constituent unit having a primary hydroxyl group, with respect to 100 parts by mass of the constituent unit (a) and the constituent unit (b), and
• wherein a relationship between a gel fraction of one day after coating and a gel fraction of eight days after coating follows formula (I)
• 100≥GF8d−GF1d≥40 (I),
• GF8d being the gel fraction of eight days after coating and GF1d being the gel fraction of one day after coating, and
• wherein the macromonomer (A) is of formula (1)
• wherein, in formula (1),
• R is H, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, an optionally substituted aryl group, or an optionally substituted heterocyclic group,
• Z is a terminal group, and
• Q is a main chain part comprising two or more constituent units of formula (a′)
• wherein, in formula (a′),
• R1 is H, a methyl group, or CH2OH, and
• R2 represents OR3, a halogen atom, COR4, COOR5, CN, CONR6R7, or R8, R3 to R7 each independently being H, an optionally substituted alkyl group, an optionally substituted alicyclic group, an optionally substituted aryl group, an optionally substituted heteroaryl group, an optionally substituted nonaromatic heterocyclic group, an optionally substituted aralkyl group, an optionally substituted alkaryl group, or an optionally substituted organosilyl group, the substituent group(s) of each of these groups being at least one selected from the group consisting of a carboxylic acid group, a carboxylic acid ester group, an epoxy group, a hydroxy group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanato group, a sulfonic acid group, and a halogen atom, and
• R8 is an optionally substituted aryl group or an optionally substituted heteroaryl group, the substituent group(s) of each of these groups being at least one selected from the group consisting of a carboxylic acid group, a carboxylic acid ester group, an epoxy group, a hydroxy group, an alkoxy group, a primary amino group, a secondary amino group, a tertiary amino group, an isocyanato group, a sulfonic acid group, an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted olefin group, and a halogen atom.