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EP-3950862-B1 - COATING COMPOSITION AND COATING FILM

EP3950862B1EP 3950862 B1EP3950862 B1EP 3950862B1EP-3950862-B1

Inventors

  • TAKAHASHI, KENICHI
  • ASAI, Akiko
  • KIMURA, KAZUYA
  • MUTO, KAZUAKI
  • TANIGAWA, Masashi

Dates

Publication Date
20260506
Application Date
20200327

Claims (10)

  1. A paint composition that forms a self-repairable, polysiloxane-modified polyhydroxyurethane-crosslinked, coating film, the paint composition comprising: a polysiloxane-modified polyhydroxyurethane resin; and as a curing agent, a polyisocyanate compound comprising two or more isocyanate groups in a molecule, wherein the polysiloxane-modified polyhydroxyurethane resin has repeating units represented by the following formula (1), wherein a crosslinked coating film formed with the polysiloxane-modified polyhydroxyurethane resin has a 20% modulus at 25°C of 10 MPa or less, measured according to the method identified in the specification: wherein X represents a direct bond, or a C1-30 aliphatic hydrocarbon group, a C4-40 alicyclic hydrocarbon group, a C6-40 aromatic hydrocarbon group, or a Si1-300 dimethyl siloxane group, and these groups optionally have, in a structure thereof, any bond selected from the group consisting of an ether bond, an amino bond, a sulfonyl bond, an ester bond, and a urethane bond, or a hydroxy group, a halogen atom, or a polyalkylene glycol chain having a number of repeating units of 1 to 30 and containing C2-6 alkylene; Y represents a C1-15 aliphatic hydrocarbon group, a C4-15 alicyclic hydrocarbon group, or a C6-15 aromatic hydrocarbon group, and these groups optionally have, in a structure thereof, an ether bond or a sulfonyl bond, or a hydroxy group or a halogen atom; and each of Z independently represents at least any one of structures selected from the group consisting of the following formulas (2) to (5), and two or more structures selected from the group consisting of these formulas (2) to (5) are optionally mixed in the repeating units and between the repeating units: wherein R represents a hydrogen atom or a methyl group; and, irrespective of whatever formula is selected, an uncombined bond on the right side forms a chemical bond with an oxygen atom, and an uncombined bond on the left side forms a chemical bond with X or forms a chemical bond with an uncombined bond on the left side of the other Z when X is a direct bond, provided that the polysiloxane-modified polyhydroxyurethane resin has at least a repeating unit of formula (1) wherein X represents a Si1-300 dimethyl siloxane group.
  2. The paint composition according to claim 1, wherein the polysiloxane-modified polyhydroxyurethane resin is a synthetic of a polysiloxane compound having at least two cyclic carbonate groups, the polysiloxane compound represented by the following formula (6), and a component comprising a diamine: wherein M represents a C1-30 aliphatic hydrocarbon group, a C4-40 alicyclic hydrocarbon group, or a C6-40 aromatic hydrocarbon group, and these groups optionally have, in a structure thereof, any bond selected from the group consisting of an ether bond, an amino bond, a sulfonyl bond, an ester bond, and a urethane bond, or a hydroxy group, a halogen atom, or a polyalkylene glycol chain having a number of repeating units of 1 to 30 and containing C2-6 alkylene; and n represents a number of 1 to 300.
  3. The paint composition according to claim 1 or 2, wherein the polysiloxane-modified polyhydroxyurethane resin has a polysiloxane content of 0.1 to 10.0% on a mass basis.
  4. The paint composition according to any one of claims 1 to 3, wherein part or the whole of a urethane bond contained in the polysiloxane-modified polyhydroxyurethane resin is an addition reaction product of a five-membered cyclic carbonate group, being a reaction product of an epoxy group and carbon dioxide, and an amino group, and a ratio of an -O-CO- structure in the addition reaction product, derived from the carbon dioxide, in the polysiloxane-modified polyhydroxyurethane resin is 1 to 20% by mass.
  5. The paint composition according to any one of claims 1 to 4, wherein the repeating units represented by the formula (1) comprise a unit such that X represents a chemical structure represented by the following formula (7): wherein A represents a chemical structure derived from a polyisocyanate; B represents a chemical formula derived from a polyol; and m represents any one of 1 to 6.
  6. The paint composition according to any one of claims 1 to 5, wherein the polysiloxane-modified polyhydroxyurethane resin has a 20% modulus at 25°C of 0.3 to 9.5 MPa, measured according to the method identified in the specification.
  7. The paint composition according to any one of claims 1 to 6, wherein the polyisocyanate compound has an NCO content of 3 to 35% in terms of a solid content.
  8. The paint composition according to any one of claims 1 to 7, wherein a ratio (NCO/OH) of a number of moles of an isocyanate group (NCO) of the polyisocyanate compound to a number of moles of a hydroxy group (OH) of the polysiloxane-modified polyhydroxyurethane resin is 0.2 to 1.1.
  9. The paint composition according to any one of claims 1 to 8, further comprising a urethane-curing catalyst.
  10. A paint film obtained by curing the paint composition according to any one of claims 1 to 9 having been applied.

Description

Technical Field The present invention relates to a paint composition containing a polysiloxane-modified polyhydroxyurethane resin as an essential component, and a paint film formed from the composition, and in more detail, relates to a paint composition capable of forming a paint film excellent in self-repairability. The present invention relates to a technique that can provide a self-repairable paint that can be more excellent in terms of countermeasure for environmental problems as compared to existing materials which have been used as a self-repairable paint. Background Art In the past, coating with a paint in which a resin component is contained is applied on a surface of a substrate, such as a plastic, paper, a metal, a fiber, glass, and wood, for the purpose of protecting the substrate from a scratch due to friction, denaturation due to heat, contamination due to adhesion of dusts and water, and the like, and maintaining beauty and design. Plastic substrates, such as an ABS resin and polycarbonate, have been used for various industrial products, such as electronic devices and automobile parts, especially for the purpose of reducing weight. Products need to be protected from a large number of scratches and contamination, which occur incidentally on the surfaces of the products during transportation and assembly of the products, especially during the use thereof, and therefore coating the surface of a plastic substrate is important. In coating materials at the time when the coating is applied, adhesiveness to various substrates, resistance to a scratch, resistance to contamination due to chemicals or the like, and so on are required according to the purpose of applying the coating. Among others, in the coating that is based on a dark color, such as black and dark blue, and has glossy feeling, a small scratch or slight dirt which occurred on a paint film is likely to be conspicuous to be a cause for impairing the beauty in terms of appearance, and therefore resistance to a scratch and dirt is particularly required. Examples of the means for making it difficult for the scratch or dirt on the paint film to occur includes a method of applying hard coat on a plastic substrate with an ultraviolet ray-curable resin or the like. For example, Patent Literature 1 discloses a paint composition capable of forming a paint film that exhibits excellent scratch resistance, hardness, appearance, adhesiveness, and resistance to a composition containing an ultraviolet ray absorber or the like to a plastic substrate in a one-coat-one-bake coating process. However, there is a problem that the paint film, when scratched strongly with a metal brush or the like, is broken, and scratch traces are left. As a method for solving such a problem, a paint composition capable of forming a self-repairable paint film, on which a scratch that has occurred disappears in a short time, on surfaces of various substrates has been proposed in recent years. For example, a polyurethane paint composition that uses a particular polyol, contains, as a basic composition, an allophanate-modified isocyanate compound substantially free of an isocyanurate group, and is capable of forming a paint film that is flexible and excellent in toughness has been proposed in Patent Literature 2. On the other hand, as a novel polyurethane-based material, development of a polyhydroxyurethane resin that is a polyurethane-based material having a hydroxy group in the chemical structure has progressed in recent years (see, for example, Patent Literature 3). The polyhydroxyurethane resin has a hydroxy group in the main chain thereof, thus can easily form a thermosetting film by crosslinking reaction, further, can be produced using carbon dioxide as a raw material, and therefore has also been attracting attention as an environmentally compatible resin. In addition, the polyhydroxyurethane resin has a strong tendency to have characteristics of being hard and brittle, and therefore utilization in special applications, such as barrier coating, where a conventional polyurethane resin cannot be used has been devised (see Patent Literature 4). Patent literature 5 relates to a thermoplastic polyolefin resin skin material having a thermoplastic polyolefin resin sheet, and either of a top coat layer directly formed on the sheet or a top coat layer formed through a primer layer formed on the sheet, and the top coat layer mainly consists of a five-membered ring annular carbonate polysiloxane compound and a polysiloxane-modified polyhydroxy polyurethane resin derived from a reaction with an amine compound. Patent literature 6 relates to a five-membered cyclocarbonate polysiloxane compound, which is produced by reacting an epoxy-modified polysiloxane compound and carbon dioxide Citation List Patent Literature Patent Literature 1: Japanese Patent No.5692481Patent Literature 2: Japanese Patent No. 4707013Patent Literature 3: Japanese Patent Laid-Open No. 2006-9001Patent Literature 4: Ja