Coating materials that are to be applied onto articles to be coated, such as automobile bodies, must have excellent film performance including mar resistance, and must also produce an excellent outer appearance for the coating films. The types of scuffing damage that can occur include scuffing damage by car washing and scratching damage by coins or keys, which are known to have different damage mechanisms, and resistance to both kinds of damage is desirable. On the other hand, increasing viscosity or precipitation that may occur during storage of a coating material can make its application difficult, and therefore storage stability is also required for coating materials.
PTL 1, for example, discloses a coating composition comprising (A) a polyol compound with 3 or more hydroxyl groups in the molecule and having a hydroxyl value in the range of 110 to 700 mgKOH/g and a number-average molecular weight in the range of 200 to 1,800, (B) a polyisocyanate compound, and (C) a resin-coated silica particle dispersion, wherein the resin-coated silica particle dispersion (C) is a resin-coated silica particle dispersion obtained by reacting (c1) silica particles having a polymerizable unsaturated group with (c2) a polymerizable unsaturated monomer in a mass ratio of (c1):(c2)=20:80 to 90:10, and the content of the resin-coated silica particle dispersion (C) is in the range of 5 to 75 mass % based on the total solid content of the polyol compound (A), the polyisocyanate compound (B) and the resin-coated silica particle dispersion (C). This coating composition, however, while having excellent resistance to car washing scuff damage, has been less satisfactory in terms of resistance to scratch marks by coins and keys, and storage stability.
Moreover, PTL 2 discloses a coating composition comprising (A) silica particles having the surfaces modified by a specific hydrolyzable silane compound (a), and (B) a binder component. This coating composition, however, while having excellent resistance to car washing scuff damage, has been less satisfactory in terms of resistance to scratch marks by coins and keys, and storage stability.
PTL 3 discloses a coating composition comprising (A) a hydroxyl group-containing acrylic resin which is a copolymer of monomer components comprising (a) 25 to 50 mass % of a hydroxyl group-containing polymerizable unsaturated monomer, (b) 5 to 30 mass % of an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer of 6 to 20 carbon atoms and (c) 20 to 70 mass % of another polymerizable unsaturated monomer, (B) a polyisocyanate compound comprising an aliphatic diisocyanate wherein the isocyanurate trimer content is 30 to 70 mass %, the uretdione dimer content is 3 to 30 mass % and the multimer content of other tri- or greater polymers is 0 to 67 mass %, based on the total amount of the polyisocyanate compound, and (C) polysiloxane-modified silica particles with a mean primary particle size of 1 to 40 nm. This coating composition, however, while having excellent resistance to car washing scuff damage, has been less satisfactory in terms of resistance to scratch marks by coins and keys, and storage stability.
PTL 4 discloses a coating composition comprising as essential components, (I) a colloidal silica-containing acrylic-based resin obtained by copolymerization of (a) colloidal silica that is modified with a hydrolyzable alkoxysilyl group-containing unsaturated monomer and evenly dispersed in an organic solvent, (b) a specific polysiloxane-based macromonomer, (c) a hydroxyl group-containing unsaturated monomer and if necessary (d) another unsaturated monomer, and (II) a curing agent. However, this coating composition, while having excellent resistance to car washing scuff damage, has been less satisfactory in terms of resistance to scratch marks by coins and keys, and storage stability.
PTL 5 discloses composite microparticles having an organic polymer integrated with inorganic fine particles, the composite microparticles containing an ethylenic unsaturated group. However, when the inorganic fine particles are used in a coating material, although they provide excellent resistance to car washing scuff damage, they have been less satisfactory in terms of resistance to scratch marks by coins and keys, and storage stability.
PTL 6 discloses organic polymer-composite inorganic fine particles having an organic polymer immobilized on the surfaces of inorganic fine particles, the organic polymer including a perfluoroalkyl and/or silicone group. However, when the inorganic fine particles are used in a coating material, although they provide excellent resistance to pencil scratch marks, they have been less satisfactory in terms of car washing scuff damage and storage stability.