Aqueous dispersion and aqueous coating composition, and process of forming coating film

An aqueous dispersion (X) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b2) in the presence of starch and/or modified starch (a) to obtain a reaction product, radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (b1) in the presence of the reaction product to obtain an acrylic modified starch (A), and then dispersing the acrylic modified starch (A) in an aqueous medium,

• wherein, the radical polymerizable unsaturated monomer mixture (b1) consists of:
• less than 5% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer,
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and
• 0-95% by mass of other radical polymerizable unsaturated monomers,
• the radical polymerizable unsaturated monomer mixture (b2) consists of:
• 5-95% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer,
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and
• 0-90% by mass of other radical polymerizable unsaturated monomers, and
• the acid value of the acrylic modified starch (A) is in the range of 10-150 mgKOH/g.

An aqueous dispersion (Y) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (d1) in the presence of a radical polymerizable unsaturated group-containing starch and/or modified starch (c) to obtain a reaction product, radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (d2) in the presence of the reaction product to obtain an acrylic modified starch (C), and then dispersing the acrylic modified starch (C) in an aqueous medium,

• wherein, the radical polymerizable unsaturated monomer mixture (d1) comprises:
• 5-95% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, and
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer,
• the radical polymerizable unsaturated monomer mixture (d2) comprises:
• less than 5% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, and
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer, and
• the acid value of the acrylic modified starch (C) is in the range of 10-150 mgKOH/g.

An aqueous dispersion (Y) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (d2) in the presence of a radical polymerizable unsaturated group-containing starch and/or modified starch (c) to obtain a reaction product, radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (d1) in the presence of the reaction product to obtain an acrylic modified starch (C), and then dispersing the acrylic modified starch (C) in an aqueous medium,

• wherein, the radical polymerizable unsaturated monomer mixture (d2) comprises:
• less than 5% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, and
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer,
• the radical polymerizable unsaturated monomer mixture (d1) comprises:
• 5-95% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, and
• 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer, and
• the acid value of the acrylic modified starch (C) is in the range of 10-150 mgKOH/g.

A process of forming a coating film comprising the steps of:

• coating a substrate with an aqueous coating composition (I) to form a base coating film,
• coating the base coating film with an active energy radiation curable coating composition (II), and then
• irradiating it with an active energy radiation,
• wherein the aqueous coating composition (I) is an aqueous coating composition comprising an aqueous dispersion (Z) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (f1), consisting of less than 5% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and 5-95% by mass of other radical polymerizable unsaturated monomers, in the presence of starch and/or modified starch (e) to obtain a reaction product, radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (f2) consisting of 5-95% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and 0-90% by mass of other radical polymerizable unsaturated monomers, in the presence of the reaction product, to obtain an acrylic modified starch (E) with an acid value in the range of 10-150 mgKOH/g, and then dispersing the acrylic modified starch (E) in an aqueous medium, and
• the active energy radiation curable coating composition (II) is an active energy radiation curable coating composition comprising a saccharide and/or derivative thereof with an acryloyl group, and a photopolymerization initiator.

A process of forming a coating film that comprises the steps of:

• coating a substrate with an aqueous coating composition (I) to form a base coating film,
• coating the base coating film with an active energy radiation curable coating composition (II), and then
• irradiating it with an active energy radiation,
• wherein the aqueous coating composition (I) is an aqueous coating composition comprising an aqueous dispersion (Z) obtained by radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (f2), consisting of 5-95% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and 0-90% by mass of other radical polymerizable unsaturated monomers, in the presence of starch and/or modified starch (e) to obtain a reaction product, radical polymerization reaction of a radical polymerizable unsaturated monomer mixture (f1) consisting of less than 5% by mass of a carboxyl group-containing radical polymerizable unsaturated monomer, 5-95% by mass of a hydroxyl group-containing radical polymerizable unsaturated monomer and 5-95% by mass of other radical polymerizable unsaturated monomers, in the presence of the reaction product, to obtain an acrylic modified starch (E) with an acid value in the range of 10-150 mgKOH/g, and then dispersing the acrylic modified starch (E) in an aqueous medium, and
• the active energy radiation curable coating composition (II) is an active energy radiation curable coating composition comprising a saccharide and/or derivative thereof with an acryloyl group, and a photopolymerization initiator.