Paint composition, kit, coating film, and method for forming a coating film

Abstract

A coating material composition comprising an organic polyisocyanate (A) and an acrylic polyol (B), wherein the organic polyisocyanate (A) includes a modified polyisocyanate (a), the modified polyisocyanate (a) is a reaction product between a polyisocyanate component (a1) and a polyol component (a2), or is a modification product of said reaction product, the polyisocyanate component (a1) includes an organic diisocyanate or a modification product thereof, the polyol component (a2) includes at least one that is selected from the group consisting of polytetramethylene glycols and polycarbonate polyols, and that has a number average molecular weight of 200-750, and the acrylic polyol (B) includes an acrylic polyol (b) that has a glass transition temperature of 5-30°C and that has a hydroxyl value more than 100 mgKOH / g but not more than 150 mgKOH / g.

Description

[Technical Field]

[0001] This disclosure relates to a paint composition, a kit, a paint film, and a method for forming a paint film. [Background technology]

[0002] Hard coating is a known method for forming a coating on the surface of plastic molded products that offers excellent scratch resistance, stain resistance, and other properties. Hard coating is a method for forming a coating with high crosslinking density and surface hardness. However, once a coating formed by hard coating is scratched, cracks will develop from that point. Furthermore, when hard-coated plastic molded products are used as exterior parts for automobiles, sand, pebbles, etc., can collide with the molded product while the vehicle is in motion, causing scratches such as fine dents on the surface (coated surface). In the case of hard coating, the problem of scratches on the coating surface can be avoided by increasing the thickness of the coating, but increasing the thickness of the coating reduces the aesthetic appeal and increases the weight of the exterior parts.

[0003] Therefore, instead of hard coat treatment, soft coat treatment, which forms a coating film using a coating composition that has the function of absorbing external forces and restoring scratches (hereinafter referred to as "self-healing properties"), is becoming popular. As a coating composition for soft coat treatment, for example, Patent Document 1 discloses a coating composition comprising a polycarbonate diol containing specific repeating units and terminal hydroxyl groups, wherein the average number of carbon atoms in the specific repeating units is 3.0 to 4.0, a polyol other than the polycarbonate diol, and an organic polyisocyanate. Patent Document 1 states that a coating film with high scratch recovery and stain resistance can be obtained with this coating composition. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-137840 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the coating film produced by the paint composition described in Patent Document 1 has a long scratch recovery time and its stain resistance is not entirely satisfactory.

[0006] One aspect of this disclosure is directed toward providing a coating film that has good stain resistance and excellent self-healing properties against scratches. Another aspect of this disclosure is directed toward providing a coating film that has good smoothness, stain resistance, and adhesion, and excellent self-healing properties against scratches. Another aspect of this disclosure is directed toward providing a paint composition that contributes to the production of the above coating film, a kit for preparing the paint composition, and a method for forming the above coating film. [Means for solving the problem]

[0007] Each aspect of this disclosure includes the embodiments shown in [1] to

[11] below.

[0008] [1] A paint composition comprising an organic polyisocyanate (A) and an acrylic polyol (B), wherein the organic polyisocyanate (A) comprises a modified polyisocyanate (a), the modified polyisocyanate (a) being a reaction product of a polyisocyanate component (a1) and a polyol component (a2) or a modified version thereof, the polyisocyanate component (a1) comprising an organic diisocyanate or a modified version thereof, the polyol component (a2) comprising at least one selected from the group consisting of polytetramethylene glycol and polycarbonate polyols having a number average molecular weight of 200 to 750, and the acrylic polyol (B) comprising an acrylic polyol (b) having a glass transition temperature of 5 to 30°C and a hydroxyl value greater than 100 mg KOH / g and less than or equal to 150 mg KOH / g.

[0009] [2] The paint composition according to [1], wherein the average number of functional groups of the modified polyisocyanate (a) is 4.0 to 6.0.

[0010] [3] The coating composition according to [1] or [2], wherein the polyisocyanate component (a1) contains at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0011] [4] The coating composition according to any one of [1] to [3], wherein the modified polyisocyanate (a) contains an allophanate-modified polyisocyanate.

[0012] [5] The coating composition according to [4], wherein the modified polyisocyanate (a) further contains an isocyanurate-modified polyisocyanate.

[0013] [6] The coating composition according to any one of [1] to [5], further containing a polydimethylsiloxane compound.

[0014] [7] The coating composition according to [6], wherein the silicon content in terms of SiO2 is 0.001 to 0.1% by mass based on the total amount of the organic polyisocyanate (A), the acrylic polyol (B), and the polydimethylsiloxane compound.

[0015] [8] The coating composition according to any one of [1] to [7], wherein the ratio of the number of moles of isocyanate groups in the isocyanate group-containing compound contained in the coating composition to the number of moles of hydroxyl groups in the hydroxyl group-containing compound contained in the coating composition is 0.8 to 1.3.

[0016] [9] A kit for preparing the coating composition according to any one of [1] to [8], comprising a first agent containing the organic polyisocyanate (A) and a second agent containing the acrylic polyol (B).

[0017]

[10] A coating film containing a cured product of the coating composition according to any one of [1] to [8].

[0018]

[11] A method for forming a coating film, comprising applying the coating composition according to any one of [1] to [8] onto a substrate and curing it. [Effects of the Invention]

[0019] According to one aspect of this disclosure, a coating film with good stain resistance and excellent self-healing properties against scratches can be provided. According to another aspect of this disclosure, a coating film with good smoothness, stain resistance, and adhesion, and excellent self-healing properties against scratches can be provided. According to another aspect of this disclosure, a paint composition that contributes to the production of the above-mentioned coating film, a kit for preparing the paint composition, and a method for forming the above-mentioned coating film can be provided. [Modes for carrying out the invention]

[0020] Exemplary embodiments for carrying out each aspect of this disclosure will be described in further detail. However, this disclosure is not limited to the following embodiments.

[0021] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, in numerical ranges described in this specification, the upper or lower limits of those ranges may be replaced with the values ​​shown in the examples. Also, the upper and lower limits described individually can be combined in any way. In this specification, "(meth)acrylic" means at least one of acrylic and its corresponding methacrylic.

[0022] <Paint composition> A coating composition according to one aspect of the present disclosure comprises an organic polyisocyanate (A) and an acrylic polyol (B), wherein the organic polyisocyanate (A) comprises a modified polyisocyanate (a), the modified polyisocyanate (a) being a reaction product of a polyisocyanate component (a1) and a polyol component (a2) or a modified version thereof, the polyisocyanate component (a1) comprising an organic diisocyanate or a modified version thereof, the polyol component (a2) comprising at least one selected from the group consisting of polytetramethylene glycol and polycarbonate polyols having a number average molecular weight of 200 to 750, and the acrylic polyol (B) comprising an acrylic polyol (b) having a glass transition temperature of 5 to 30°C and a hydroxyl value greater than 100 mg KOH / g and less than or equal to 150 mg KOH / g.

[0023] According to one aspect of the present disclosure, a coating film can be obtained that has good stain resistance and excellent self-healing properties against scratches. Furthermore, according to one aspect of the present disclosure, a coating film with good smoothness and adhesion can also be obtained. The details of the coating composition according to one aspect of the present disclosure and the components that may be included in the coating composition will be described below.

[0024] (Organic polyisocyanate (A)) Organic polyisocyanate (A) includes modified polyisocyanate (a). Modified polyisocyanate (a) is a reaction product of polyisocyanate component (a1) and polyol component (a2), or a modified version thereof.

[0025] The reaction product may be a urethane-modified polyisocyanate obtained by the reaction of a polyisocyanate component (a1) and a polyol component (a2), and may be an allophanate-modified polyisocyanate obtained by allophanate-modifying the urethane-modified polyisocyanate, or an isocyanurate-modified polyisocyanate obtained by isocyanurate-modifying the urethane-modified polyisocyanate.

[0026] Examples of modified products include block-modified products of the above reaction products. Block-modified products have a structure in which some of the isocyanate groups are modified with a blocking agent. The blocking agent prevents the reaction between the isocyanate groups and water and active hydrogen groups such as hydroxyl groups by blocking the isocyanate groups, thereby suppressing the progress of the reaction in the paint composition. Therefore, block-modified products can be easily converted into a single liquefaction. Modified polyisocyanate (a), which is a block-modified product, is a latent curing agent that reacts with active hydrogen groups when the blocking agent dissociates upon heating, and the isocyanate groups are reactivated. Details of the blocking agent will be described later. In the following description, allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate include block-modified allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate.

[0027] The modified polyisocyanate (a) preferably contains allophanate-modified polyisocyanate. By including allophanate-modified polyisocyanate in the modified polyisocyanate (a), it is possible to obtain a coating film that is flexible yet tough, a lower viscosity liquid state is possible, and the handling properties during painting are improved, as well as the self-healing properties of the coating film are further improved.

[0028] From the viewpoint of obtaining a more flexible and tough coating film, the modified polyisocyanate (a) may include both allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate. When the modified polyisocyanate (a) includes isocyanurate-modified polyisocyanate, the glass transition temperature of the resulting coating film (polyurethane resin in the coating film) increases. However, to lower the glass transition temperature, for example, by increasing the content of polycarbonate polyol-derived structures, the impairment of self-healing properties can be suppressed.

[0029] When the modified polyisocyanate (a) includes allophanate-modified polyisocyanate or isocyanurate-modified polyisocyanate, the fewer the number of urethane groups in the modified polyisocyanate (a), the higher the self-healing properties of the coating film. From this viewpoint, the modified polyisocyanate (a) does not need to substantially have urethane groups. The term "substantially lacking urethane groups" means that the modified polyisocyanate (a) does not exhibit proton nuclear magnetic resonance ( 1 This means that the content of urethane-modified polyisocyanate, as confirmed by the 1H-NMR spectrum, is 0.5 mol% or less, based on the total amount of allophanate-modified polyisocyanate, isocyanurate-modified polyisocyanate, and urethane-modified polyisocyanate.

[0030] The total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate in modified polyisocyanate (a) may be 80% by mass or more, or 90% by mass or more, or 100% by mass, based on the total mass of modified polyisocyanate (a), from the viewpoint of further improving the self-healing properties of the coating film.

[0031] When the modified polyisocyanate (a) includes allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate, the content of isocyanurate-modified polyisocyanate may be 30 mol% or less, 20 mol% or less, or 10 mol% or less, based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate, from the viewpoint of further improving the self-healing properties of the coating film. The content of isocyanurate-modified polyisocyanate may be 1 mol% or more, 2 mol% or more, or 3 mol% or more, based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate, from the viewpoint of further improving the stain resistance of the coating film. The content of isocyanurate-modified polyisocyanate may be 1 to 30 mol%, 2 to 20 mol%, or 3 to 10 mol%, from the viewpoint of the above. The above content is related to proton nuclear magnetic resonance ( 1This can be confirmed by 1H-NMR spectroscopy.

[0032] From the viewpoint of obtaining a coating film with superior self-healing properties, the average number of functional groups of the modified polyisocyanate (a) may be 4.0 or more, and may be 4.5 or more. From the viewpoint of viscosity, the average number of functional groups of the modified polyisocyanate (a) may be 6.0 or less, and may be 5.5 or less. From the above viewpoint, the average number of functional groups of the modified polyisocyanate (a) may be 4.0 to 6.0 or 4.5 to 5.5.

[0033] In this specification, the average number of functional groups of modified polyisocyanate (a) refers to the average number of isocyanate groups (-NCO) contained in one molecule of modified polyisocyanate (a). The average number of functional groups of modified polyisocyanate (a) can be calculated from the isocyanate group content (NCO content) and the number-average molecular weight of modified polyisocyanate (a). If the modified polyisocyanate (a) is a block-modified product, the average number of functional groups also includes the number of blocked isocyanate groups.

[0034] The NCO content of modified polyisocyanate (a) may be 13.0 to 23.0% by mass, and may also be 14.0% to 22.0% by mass or 15.0% to 21.0% by mass. When the NCO content of modified polyisocyanate (a) is 23.0% by mass or less, the self-healing properties of the coating film are further improved. When the NCO content of modified polyisocyanate (a) is 13.0% by mass or more, the stain resistance of the coating film is improved.

[0035] In this specification, the NCO content is the value measured by the method described in JIS K1603-1 (Test Method for Aromatic Isocyanates in Polyurethane Raw Materials). However, if the modified polyisocyanate (a) is a blocked modified product, the NCO content of the modified polyisocyanate (a) in an unblocked state (with the blocking agent dissociated) shall be measured.

[0036] The number-average molecular weight of the modified polyisocyanate (a) may be 500 to 8,000, and may also be 600 to 7,500 or 700 to 7,000. When the number-average molecular weight of the modified polyisocyanate (a) is 500 or more, the self-healing properties of the coating film are further improved. When the number-average molecular weight of the modified polyisocyanate (a) is 8,000 or less, the smoothness of the coating film is further improved, and the appearance of the coating film is further improved.

[0037] In this specification, the number-average molecular weight is the value measured using GPC (gel permeation chromatography) under the following conditions. However, if the modified polyisocyanate (a) is a blocked modified product, the number-average molecular weight of the modified polyisocyanate (a) in its unblocked state (with the blocking agent dissociated) shall be measured. [conditions] • Measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation) • Column: "TSKguardcolumn HXL-L" (manufactured by Tosoh Corporation) Particle size = 6 μm, Size = 6 mm ID × 30 cm × 4 pieces Carrier: Tetrahydrofuran (THF) • Detector: Parallax refraction Sample: 0.1% THF solution Calibration curve: Polystyrene

[0038] The viscosity of modified polyisocyanate (a) at 25°C may be 500 to 10000 mPa·s, and may also be 800 to 6000 mPa·s or 1000 to 3000 mPa·s. When the viscosity of modified polyisocyanate (a) at 25°C is within the above range, the film-forming properties are good, the smoothness of the film is further improved, and the appearance of the film is further improved. The viscosity of modified polyisocyanate (a) at 25°C is a value measured using a B-type viscometer.

[0039] Organic polyisocyanate (A) may contain one type of modified polyisocyanate (a) alone, or it may contain two or more types in combination. Furthermore, organic polyisocyanate (A) may contain organic polyisocyanates other than modified polyisocyanate (a) (for example, polyisocyanate component (a1) which is a reaction raw material), as long as the self-healing properties are not impaired. However, the content of modified polyisocyanate (a) in organic polyisocyanate (A) is preferably 80% by mass or more, more preferably 90% by mass, and even more preferably 100% by mass, based on the total mass of organic polyisocyanate (A). The content of free polyisocyanate component (a1) may be 1.0% by mass or less, based on the total mass of organic polyisocyanate (A).

[0040] Next, we will describe the polyisocyanate component (a1) and polyol component (a2), which are reaction raw materials for modified polyisocyanate (a), as well as the method for producing modified polyisocyanate (a).

[0041] [Polyisocyanate component (a1)] The polyisocyanate component (a1) is a component composed of an organic compound having multiple isocyanate groups, and includes organic diisocyanates or modified versions thereof. An organic diisocyanate is an organic compound having two isocyanate groups. Examples of organic diisocyanates include aromatic diisocyanates, aromatic aliphatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Modified versions may be modified versions of these organic diisocyanates. Examples of modified versions include allophanate-modified polyisocyanates, isocyanurate-modified polyisocyanates, uretdione-modified polyisocyanates, urethane-modified polyisocyanates, burette-modified polyisocyanates, uretoimine-modified polyisocyanates, and acylurea-modified polyisocyanates. The polyisocyanate component (a1) may be one selected from the above organic diisocyanates and modified forms, or it may be a mixture of two or more selected from the above organic diisocyanates and modified forms.

[0042] Examples of aromatic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate / 2,6-tolylene diisocyanate mixture, m-xylylene diisocyanate, p-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate mixture, and 4,4'-diphenyl Examples include diisocyanates, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate.

[0043] Examples of aromatic aliphatic diisocyanates include 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene or mixtures thereof, and ω,ω'-diisocyanato-1,4-diethylbenzene.

[0044] Examples of aliphatic diisocyanates include hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate.

[0045] Examples of alicyclic diisocyanates include isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate.

[0046] From the viewpoint of weather resistance of the coating film, organic diisocyanates are preferred, and it is more preferable to use at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates. Furthermore, from the viewpoint of weather resistance of the coating film, polyisocyanates without unsaturated bonds are preferred. That is, it is even more preferable to use at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates that do not have unsaturated bonds. Among these, hexamethylene diisocyanate is particularly preferred because it is easy to obtain and synthesize, and a coating film with even better adhesion and self-healing properties can be obtained.

[0047] The polyisocyanate component (a1) may contain polyisocyanates other than organic diisocyanates and their modified forms. However, the total amount of organic diisocyanates and their modified forms in the polyisocyanate component (a1) is preferably 80% by mass or more, more preferably 90% by mass, and even more preferably 100% by mass, based on the total mass of the polyisocyanate component (a1).

[0048] [Polyol component (a2)] The polyol component (a2) is a component composed of an organic compound having multiple hydroxyl groups. The polyol component (a2) includes at least one selected from the group consisting of polytetramethylene glycol and polycarbonate polyols, with a number average molecular weight of 200 to 750.

[0049] Polytetramethylene glycol is a compound having an oxytetramethylene group in its molecular skeleton and is mainly obtained by ring-opening polymerization of tetrahydrofuran. The number-average molecular weight of polytetramethylene glycol is 200 to 750, and may be 220 or more, 250 or more, 600 or less, 500 or less, or 220 to 600 or 250 to 500. The larger the number-average molecular weight of polytetramethylene glycol, the easier it is to improve the self-healing properties of the coating film, and the smaller the number-average molecular weight of polytetramethylene glycol, the easier it is to achieve good coating film smoothness and a good coating film appearance.

[0050] Polycarbonate polyols are compounds having multiple carbonate groups and multiple hydroxyl groups, and are mainly obtained from de-alcoholization or de-phenolization reactions of low molecular weight polyols (e.g., polyols with a molecular weight of 500 or less) and carbonate. Examples of polycarbonate polyols include compounds (reaction products) obtained from de-alcoholization or de-phenolization reactions of at least one compound selected from the group of compounds shown in (α) below and at least one compound selected from the group of compounds shown in (β) below. (α): Low molecular weight polyols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer diol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc. (β): Dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; alkylene carbonates such as ethylene carbonate and propylene carbonate; diaryl carbonates such as diphenyl carbonate, dinaphthyl carbonate, diantlyl carbonate, diphenanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate; and other carbonates.

[0051] As for polycarbonate polyols, those obtained from the de-alcoholization reaction of 1,6-hexanediol and dialkyl carbonate (reaction products of 1,6-hexanediol and dialkyl carbonate) are preferred from the viewpoint of further improving the stain resistance of the coating film.

[0052] The number-average molecular weight of the polycarbonate polyol is 200 to 750, and may be 220 or more, 250 or more, or 300 or more, and may be 600 or less, 500 or less, or 400 or less, and may be 220 to 600, 250 to 500, 300 to 750, or 200 to 400. The larger the number-average molecular weight of the polycarbonate polyol, the easier it is to improve the self-healing properties of the coating film, and the smaller the number-average molecular weight of the polycarbonate polyol, the easier it is to achieve good coating film smoothness and a good coating film appearance.

[0053] The polyol component (a2) may contain polyols other than polytetramethylene glycol and polycarbonate polyols (other polyols). In other words, the modified polyisocyanate (a) may be a reaction product of polyisocyanate component (a1) (e.g., organic diisocyanate or a modified thereof), at least one selected from the group consisting of polytetramethylene glycol and polycarbonate polyols having a number average molecular weight of 200 to 750, and another polyol. However, the content (total amount) of polytetramethylene glycol and polycarbonate polyol in the polyol component (a2) is preferably 80% by mass or more, more preferably 90% by mass, and even more preferably 100% by mass, based on the total mass of the polyol component (a2).

[0054] Other polyols include, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer diol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, pentaerythritol, and the like. The other polyols may be a single compound or a combination of two or more compounds.

[0055] Other polyols that can be used include polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, fluorinated polyols, and animal / vegetable oil-based polyols.

[0056] [Method for producing modified polyisocyanate (a)] Modified polyisocyanate (a) can be obtained, for example, through the following steps 1 to 4.

[0057] • Step 1: A polyisocyanate component (a1) and a polyol component (a2) are charged in amounts such that there is an excess of isocyanate groups relative to the hydroxyl groups, and an isocyanate group-terminated prepolymer I is obtained by urethane reaction. • Step 2: A catalyst is added to isocyanate-terminated prepolymer I, and allophanate conversion is carried out at 70-150°C to produce isocyanate-terminated prepolymer II. • Step 3: The reaction is stopped by adding a reaction stopper to the isocyanate group-terminated prepolymer II. • Step 4: Remove the free polyisocyanate component (a1) from the isocyanate group-terminated prepolymer II by thin-film distillation or solvent extraction to obtain modified polyisocyanate (a).

[0058] In steps 1 to 3 described above, the reaction is carried out under a nitrogen gas or dry air stream. Steps 1 to 3 may be carried out in the presence or absence of an organic solvent.

[0059] Various organic solvents that do not affect the reaction can be used as organic solvents. Examples of organic solvents include aliphatic hydrocarbons such as octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl isobutyl ketone and cyclohexanone; esters such as butyl acetate and isobutyl acetate; glycol ether esters such as ethylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate, and ethyl-3-ethoxypropionate; ethers such as dioxane; halogenated hydrocarbons such as methylene iodide and monochlorobenzene; and polar aproton solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphonylamide. These organic solvents may be used individually or in combination of two or more.

[0060] Next, a method for producing a modified polyisocyanate (a) according to one embodiment will be described in more detail, using as an example the manufacturing process of a modified polyisocyanate (a) that primarily promotes allophanate modification.

[0061] [Step 1: Process for producing isocyanate-terminated prepolymer I] In the first step, an isocyanate-terminated prepolymer I is produced by reacting a polyisocyanate component (a1) and a polyol component (a2). The amounts of polyisocyanate component (a1) and polyol component (a2) charged are such that there is an excess of isocyanate groups relative to hydroxyl groups.

[0062] The "amount in which isocyanate groups are in excess relative to hydroxyl groups" is defined as the number of moles of isocyanate groups in the polyisocyanate component (a1) (M' NCO ) and the number of moles of hydroxyl groups in the polyol component (a2) (M' OH ) Ratio R'(=M' NCO / M' OH The amount may be such that the ratio R' is between 6 and 40, and the amount may be such that the ratio R' is between 7 and 30. If the ratio R' is 6 or higher, the excess isocyanurate-modified polyisocyanate in the resulting modified polyisocyanate (a) can be further suppressed. If the ratio R' is 40 or lower, the increase in the amount of polyisocyanate containing urethane groups in the resulting modified polyisocyanate (a) is further suppressed, the decrease in the number of functional groups is further suppressed, and productivity and yield are further improved.

[0063] The reaction temperature for the polyisocyanate component (a1) and the polyol component (a2) (urethane reaction temperature) is, for example, 20 to 120°C, but may also be 20 to 100°C or 50 to 100°C. The reaction time for the urethane reaction varies depending on the presence and type of catalyst and the temperature, but is generally within 10 hours, but may also be 1 to 5 hours.

[0064] In the urethane reaction, known urethane catalysts can be used. Examples of urethane catalysts include organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate; and organic amines such as triethylenediamine and triethylamine, and their salts. These catalysts may be used individually or in combination of two or more.

[0065] [Step 2: Process for producing isocyanate-terminated prepolymer II] In the second step, an allophanate reaction is carried out after the urethane reaction in the first step to produce isocyanate-terminated prepolymer II. At this time, the allophanate reaction may be carried out simultaneously with (in parallel with) the urethane reaction, or after the completion of the urethane reaction.

[0066] When the urethane formation reaction and the allophanate formation reaction are carried out simultaneously (in parallel), the reactions should be carried out in the presence of both the urethane formation catalyst and the allophanate formation catalyst. On the other hand, when the allophanate formation reaction is carried out after the urethane formation reaction is completed, the urethane formation reaction should be carried out for a predetermined time in the presence of the urethane formation catalyst and in the absence of the allophanate formation catalyst, and then the allophanate formation reaction should be carried out by adding the allophanate formation catalyst.

[0067] As the allophanate catalyst, a known catalyst can be appropriately selected and used. For example, metal salts of carboxylic acids (metal salts of alkali metals such as lithium, sodium, and potassium; metal salts of alkaline earth metals such as magnesium, calcium, and barium; metal salts of other typical metals such as tin and lead; metal salts of transition metals such as manganese, iron, cobalt, nickel, copper, zinc, and zirconium; etc.) can be used. Examples of carboxylic acids include monocarboxylic acids and polycarboxylic acids.

[0068] Specific examples of allophanate catalysts include zirconium octoate. Allophanate catalysts may be used individually or in combination of two or more types.

[0069] The amount of allophanate catalyst used may be 0.001 to 0.1% by mass, or 0.005 to 0.03% by mass, relative to the total mass of the polyisocyanate component (a1) and the polyol component (a2). When the amount of allophanate catalyst used is 0.001% by mass or more, the allophanate reaction proceeds more easily, the amount of urethane-modified polyisocyanate byproducts is suppressed, and the decrease in the number of functional groups of the resulting polyisocyanate is further suppressed. Furthermore, when the amount of allophanate catalyst used is 0.1% by mass or less, storage stability is further improved.

[0070] The reaction temperature of the allophanatization reaction is preferably 70 to 150 °C, more preferably 90 to 130 °C. When the reaction temperature is 70 °C or higher, allophanate-modified polyisocyanate is more likely to be generated, and the amount of by-products of urethane-modified polyisocyanate is further suppressed, so that the decrease in the functional group number of the obtained polyisocyanate is further suppressed. Further, when the reaction temperature is 150 °C or lower, the by-products of isocyanurate-modified polyisocyanate are suppressed, and the self-healing property is further improved.

[0071] The allophanatization reaction is preferably carried out until the urethane group substantially disappears. Here, "the urethane group substantially disappears" means that the content of urethane-modified polyisocyanate confirmed by proton nuclear magnetic resonance ( 1 1H-NMR) spectrum is 0.5 mol% or less based on the total amount of allophanate-modified polyisocyanate, isocyanurate-modified polyisocyanate and urethane-modified polyisocyanate.

[0072] In the second step, mainly the allophanatization reaction proceeds. However, as described above, by adjusting the ratio R' (= M' NCO / M' OH ) in the first step, the isocyanuration reaction can also be partially advanced. For example, by setting the ratio R' to 10 or more, the content of isocyanurate-modified polyisocyanate (based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate) can be set to 30 mol% or less.

[0073] [Step 3: Reaction Stopping Step] In the third step, after the allophanatization reaction in the second step, a reaction terminator that deactivates the catalyst is added to stop the allophanatization reaction. The addition time of the reaction terminator may be after the completion of the allophanatization reaction (after the urethane group substantially disappears). However, in order to suppress the progress of side reactions, it is preferable to add the reaction terminator promptly after the completion of the allophanatization reaction.

[0074] As reaction stoppers, known compounds such as inorganic acids like phosphoric acid and hydrochloric acid, organic acids having sulfonic acid groups, sulfamic acid groups, etc., esters thereof, and acyl halides can be used. These may be used individually or in combination of two or more.

[0075] The amount of reaction stopper added varies depending on the type of catalyst, but may be 0.5 to 10 equivalents or 0.8 to 5.0 equivalents relative to the amount of catalyst added. Adding 0.5 equivalents or more of reaction stopper further improves the storage stability of the resulting modified polyisocyanate. Adding 10 equivalents or less of reaction stopper further suppresses discoloration. After the reaction is stopped, a purification step can be performed to remove the free, unreacted polyisocyanate component (a1).

[0076] [4th step: Purification step] In the fourth step, any free, unreacted polyisocyanate component (a1) present in the reaction mixture is removed. If an organic solvent was used in the reaction process, it can also be removed in this purification step.

[0077] It is preferable to remove the polyisocyanate component (a1) to a residual content of 1.0% by mass or less, and more preferably to a residual content of less than 1.0% by mass. When the residual content is 1.0% by mass or less, the odor is further reduced and the storage stability is further improved.

[0078] The removal of the polyisocyanate component (a1) is preferably carried out by thin-film distillation. Thin-film distillation can be performed, for example, by thin-film distillation under a high vacuum of 10 to 100 Pa at 120 to 140°C.

[0079] Although a method for producing modified polyisocyanate (a) according to one embodiment has been described above, the method for producing modified polyisocyanate (a) is not limited to the embodiment described above.

[0080] For example, in another embodiment, steps 2 to 4 may be omitted, and the isocyanate-terminated prepolymer I obtained in step 1 may be used as the modified polyisocyanate (a).

[0081] Furthermore, in another embodiment, for example, a step may be performed after the fourth step in which a portion of the isocyanate groups are modified (blocked) with a blocking agent. Examples of blocking agents include phenolic blocking agents such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, p-hydroxydiphenyl, t-butylphenol, o-isopropylphenol, o-sec-butylphenol, p-nonylphenol, pt-octylphenol, hydroxybenzoic acid, and hydroxybenzoic acid esters; lactam blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; active methylene blocking agents such as diethyl malonate, dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. Alcohol-based blocking agents such as ylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methoxymethanol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate and other glycolic acid esters; lactic acid esters such as lactic acid, methyl lactate, ethyl lactate, butyl lactate and other lactic acid esters; methylolurea, methylolmelamine, diacetone alcohol, ethylene chlorhydrin, ethylene bromhydrin, 1,3-dichloro-2-propanol, ω-hydroperfluoroalcohol, acetocyanhydrin and other alcohol-based blocking agents; mercaptan-based blocking agents such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol and other mercaptan-based blocking agents; acid amide-based blocking agents such as acetanilide, acetanisidide, acetoluid, acrylamide, methacrylamide, acetic acid amide, stearic acid amide, benzamide and other acid amide-based blocking agents; imide-based blocking agents such as succinimide, phthalimide, maleimide and other acid amide-based blocking agents;Examples of blockers include amine-based blockers such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazole-based blockers such as imidazole and 2-ethylimidazole; urea-based blockers such as urea, thiourea, ethyleneurea, ethylenethiourea, and 1,3-diphenylurea; carbamate-based blockers such as phenyl N-phenylcarbamate and 2-oxazolidone; imine-based blockers such as ethyleneimine and propyleneimine; oxime-based blockers such as formamidoxime, acetaldehyde, acetoxime, methyl ethyl ketoxime, diacetylmonoxime, benzophenone oxime, and cyclohexanone oxime; and sulfite-based blockers such as sodium bisulfite and potassium bisulfite. These blockers may be used individually or in combination of two or more types.

[0082] Furthermore, for example, by using an isocyanurate catalyst instead of an allophanate catalyst, isocyanurate modification may be primarily promoted. The degree of allophanate modification and isocyanurate modification depends on the selection of various catalysts and the above ratio R'(=M'). NCO / M' OH It can be adjusted by ( ).

[0083] (Acrylic polyol (B)) Acrylic polyol (B) contains acrylic polyol (b). Here, "acrylic polyol" means a polymer containing (meth)acrylic monomer as a monomer unit and having multiple hydroxyl groups.

[0084] Acrylic polyol (b) may be a homopolymer obtained by polymerizing one type of (meth)acrylic monomer, or it may be a copolymer obtained by copolymerizing two or more types of (meth)acrylic monomers. Acrylic polyol (b) may contain monomers other than (meth)acrylic monomer as monomer units, but from the viewpoint of achieving both a predetermined glass transition temperature and hydroxyl value, it is preferable to contain only (meth)acrylic monomer as monomer units.

[0085] Examples of homopolymers obtained by polymerizing one type of (meth)acrylic monomer include homopolymers of hydroxy (meth)acrylic acid compounds. Examples of copolymers obtained by copolymerizing two or more types of (meth)acrylic monomers include copolymers obtained by copolymerizing (meth)acrylic acid esters and hydroxy (meth)acrylic acid compounds.

[0086] Here, (meth)acrylic acid ester is at least one selected from the group consisting of acrylic acid esters and methacrylic acid esters. (Meth)acrylate hydroxy compound is at least one selected from the group consisting of acrylate hydroxy compounds and methacrylate hydroxy compounds, having one or more hydroxyl groups in its molecule that can act as reaction sites.

[0087] The glass transition temperature (Tg) of acrylic polyol (b) is 5 to 30°C. If the glass transition temperature of acrylic polyol (b) is below 5°C, the self-healing properties against repeated scratches and the stain resistance when used outdoors may decrease. Also, if the glass transition temperature of acrylic polyol (b) exceeds 30°C, the self-healing properties at room temperature (e.g., 5 to 35°C) and low temperatures (e.g., below 5°C) may decrease. From the viewpoint of improving the self-healing properties against repeated scratches and the stain resistance when used outdoors, the glass transition temperature of acrylic polyol (b) may be 10°C or higher or 15°C or higher. From the viewpoint of improving the self-healing properties at room temperature and low temperatures, the glass transition temperature of acrylic polyol (b) may be 25°C or lower or 20°C or lower. From the viewpoint of the above, the glass transition temperature of acrylic polyol (b) may be 10 to 25°C or 15 to 20°C. Polyols (b) having a glass transition temperature within the above range can be synthesized by adjusting the type and blending ratio of monomer components. For example, if the acrylic polyol (b) is a copolymer, the glass transition temperature can be estimated using Fox's formula, and the blending ratio of monomer components can be set to obtain acrylic polyols (b) having a glass transition temperature within the above range.

[0088] The glass transition temperature of the above acrylic polyol (b) can be determined by measuring the inflection point of the DSC in accordance with JIS K7121.

[0089] The hydroxyl value of acrylic polyol (b) is greater than 100 mg KOH / g and less than or equal to 150 mg KOH / g. If the hydroxyl value of acrylic polyol (b) falls outside this range, self-healing properties, stain resistance, and smoothness may decrease. From the viewpoint of better stain resistance and smoothness, the hydroxyl value of acrylic polyol (b) may be 120 mg KOH / g or more or 140 mg KOH / g or more. From the viewpoint of better self-healing properties, the hydroxyl value of acrylic polyol (b) may be 130 mg KOH / g or less or 110 mg KOH / g or less. From the viewpoint of the above, the hydroxyl value of acrylic polyol (b) may be 120-150 mg KOH / g, 140-150 mg KOH / g, 120-130 mg KOH / g, greater than 100 and less than or equal to 130 mg KOH / g, or greater than 100 and less than or equal to 110 mg KOH / g. The hydroxyl value of the above acrylic polyol (b) is the value measured according to the method in accordance with JIS K1557.

[0090] Acrylic polyol (b) can be obtained, for example, by polymerizing a mixture of (meth)acrylic monomer and a polymerization initiator by applying energy (such as ultraviolet light, electron beams, or thermal energy). In other words, acrylic polyol (b) can be a thermal polymer or a photopolymer. Acrylic polyol (b) may be a thermal polymer because it is more likely to become a polymer in which the polymerization and crosslinking reactions are completed.

[0091] Acrylic polyol (B) may contain acrylic polyol (b) alone, or in combination of two or more types. Furthermore, acrylic polyol (B) may contain acrylic polyol (b') other than acrylic polyol (b) (an acrylic polyol whose glass transition temperature and / or hydroxyl value are outside the above range).

[0092] The content of acrylic polyol (b') in acrylic polyol (B) may be 50% by mass or less (for example, 0 to 50% by mass), 30% by mass or less, or 10% by mass or less, based on the total mass of acrylic polyol (B), from the viewpoint of obtaining a coating film with better self-healing properties and stain resistance.

[0093] Next, we will describe (meth)acrylic acid esters and (meth)acrylic acid hydroxy compounds that can serve as reaction raw materials for acrylic polyol (b), as well as polymerization initiators.

[0094] [(meth)acrylic acid ester] Examples of (meth)acrylic acid esters include alkyl esters having an alkyl group with 1 to 20 carbon atoms. Examples of such (meth)acrylic acid esters include alkyl (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; cycloalkyl (meth)acrylic acid esters such as cyclohexyl (meth)acrylate (products of the esterification reaction between (meth)acrylic acid and alicyclic alcohols); and aryl (meth)acrylic acid esters such as phenyl (meth)acrylate and benzyl (meth)acrylate. Such (meth)acrylic acid esters may be used individually or in combination of two or more types.

[0095] [(meth)acrylate hydroxy compound] The (meth)acrylate hydroxy compounds have one or more hydroxyl groups in their molecule that can act as reaction sites with the polyisocyanate composition. Examples of (meth)acrylate hydroxy compounds include hydroxy acrylate compounds such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate, and pentaerythritol triacrylate; and hydroxy methacrylate compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate, and pentaerythritol trimethacrylate. These (meth)acrylate hydroxy compounds may be used individually or in combination of two or more.

[0096] [Polymerization initiator] Examples of polymerization initiators include thermal polymerization initiators and photopolymerization initiators. The polymerization initiator is selected appropriately depending on the polymerization method.

[0097] Examples of thermal polymerization initiators include peroxydicarbonates such as di-2-ethylhexylperoxydicarbonate; peroxyesters such as t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisopropyl carbonate, and t-hexylperoxyisopropyl carbonate; and peroxyketals such as di(t-butylperoxy)-2-methylcyclohexane, di(t-butylperoxy)3,3,5-trimethylcyclohexane, and di(t-butylperoxy)cyclohexane.

[0098] Examples of photopolymerization initiators include acetophenones such as acetophenone, methoxyacetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, α-hydroxy-α,α'-dimethylacetophenone, 2-hydroxy-2-cyclohexylacetophenone, and 2-methyl-1[4-(methylthio)phenyl]-2-monfolinopropanone-1; benzoin ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl butyl ether; Examples include ketones such as phenophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, N,N'-tetramethyl-4,4'-diaminobenzophenone, and 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone; thioxanthones such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone; phosphine oxides such as bisacylphosphine oxide and benzoylphosphine oxide; ketals such as benzyldimethylketal; and quinones such as camphane-2,3-dione and phenanthrenequinone.

[0099] (Polydimethylsiloxane compounds) The paint composition may contain a polydimethylsiloxane compound. Using a polydimethylsiloxane compound not only further improves the smoothness and stain resistance of the coating film, but also further improves scratch resistance while maintaining self-healing properties. Therefore, by using a polydimethylsiloxane compound, it is possible to achieve a high degree of both self-healing and scratch resistance even when the coating film obtained is a thin film with a thickness of less than 20 μm.

[0100] Here, polydimethylsiloxane compounds include not only polydimethylsiloxane (dimethylpolysiloxane) but also modified forms of polydimethylsiloxane. Examples of modified forms of polydimethylsiloxane include those derived from compounds that have at least one hydroxyl group in polydimethylsiloxane. Such modified forms have at least one hydroxyl group.

[0101] Examples of polydimethylsiloxane compounds include dimethylpolysiloxane-acrylic block copolymers having an acrylic portion, dimethylpolysiloxane-polyether block copolymers having a polyether portion, dimethylpolysiloxane-polyester block copolymers having a polyester portion, and dimethylpolysiloxane-polyether-polyester block copolymers having both a polyether and a polyester portion. Each of the above copolymers may have at least one hydroxyl group in its structure (in the acrylic portion, polyether portion, or polyester portion). Having at least one hydroxyl group in its structure allows the additive to react with the polyisocyanate, making it less likely for the additive to bleed out after film formation, thus improving stain resistance and providing excellent recoatability. Note that polydimethylsiloxane compounds having two or more hydroxyl groups and an acrylic block are not considered to be the above-mentioned acrylic polyol (B).

[0102] Examples of dimethylpolysiloxane-acrylic block copolymers include BYK-SILCLEAN3700 (manufactured by BYK Chemie Japan, number average molecular weight: 7600, silicon content (SiO2 equivalent): 1% by mass).

[0103] Examples of dimethylpolysiloxane-polyether block copolymers include BYK-377 (number average molecular weight: 1400, silicon content: 18% by mass), BYK-SILCLEAN3720 (number average molecular weight: 1100, silicon content: 17% by mass), BYK-9200 (number average molecular weight: 4600, silicon content: 36% by mass), BYK-9201 (number average molecular weight: 4100, silicon content: 20% by mass), BYK-9204 (number average molecular weight: 5700, silicon content: 26% by mass), BYK-9205 (number average molecular weight: 4800, silicon content: 37% by mass), BYK-9206 (number average molecular weight: 5400, silicon content: 34% by mass), BYK-9210 (number average molecular weight: 4200, silicon content: 14% by mass), and BYK-9211 (number average molecular weight: 49% by mass). 00, silicon content: 37% by mass), BYK-9215 (number average molecular weight: 4500, silicon content: 29% by mass), BYK-9230 (number average molecular weight: 6000, silicon content: 20% by mass) ), BYK-9241 (number average molecular weight: 6000, silicon content: 22% by mass), BYK-9242 (number average molecular weight: 10500, silicon content: 16% by mass), BYK-9247 (number average molecular weight: 10500, silicon content: 16% by mass) Examples include BYK-9420 (number average molecular weight: 2500, silicon content: 33% by mass), BYK-9001 (number average molecular weight: 6800, silicon content: 22% by mass), BYK-9004 (number average molecular weight: 6800, silicon content: 17% by mass), and BYK-9020 (number average molecular weight: 10500, silicon content: 17% by mass). All of the above products are manufactured by BYK Chemie Japan.

[0104] Examples of dimethylpolysiloxane-polyester block copolymers include BYK-370 (manufactured by Bic Chemie Japan, number average molecular weight: 2100, silicon content: 8% by mass).

[0105] Examples of dimethylpolysiloxane-polyether-polyester block copolymers include BYK-375 (manufactured by Bic Chemie Japan, number average molecular weight: 2200, silicon content: 15% by mass).

[0106] The number-average molecular weight of the polydimethylsiloxane compound may be 1,000 to 15,000, or 1,500 to 12,000 or 2,000 to 8,000. When the number-average molecular weight of the polydimethylsiloxane compound is 1,000 or more, the self-healing properties of the coating film are further improved. When the number-average molecular weight of the polydimethylsiloxane compound is 15,000 or less, the smoothness of the coating film is further improved, and the appearance of the coating film is further improved.

[0107] From the viewpoint of further improving the smoothness, slip resistance, stain resistance, and scratch resistance of the coating film, the silicon content of the polydimethylsiloxane compound may be 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, based on the total mass of the polydimethylsiloxane compound. From the viewpoint of further suppressing the occurrence of recoating and further suppressing the decrease in recoating ability, the silicon content of the polydimethylsiloxane compound may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 15% by mass or less, 10% by mass or less, or 5.0% by mass or less, based on the total mass of the polydimethylsiloxane compound. From the viewpoint of the above, the silicon content of the polydimethylsiloxane compound may be 0.1 to 50% by mass, 0.1 to 15% by mass, 0.5 to 45% by mass, 0.5 to 10% by mass, 1.0 to 40% by mass, or 1.0 to 5.0% by mass, based on the total mass of the polydimethylsiloxane compound. The silicon content mentioned above is an SiO2 equivalent value, measured by thermogravimetric-differential thermal analysis (TG-DTA).

[0108] Polydimethylsiloxane compounds may be used individually or in combination of two or more types.

[0109] The amount of polydimethylsiloxane compound added may be adjusted so that the silicon content in the paint composition (based on the total amount of organic polyisocyanate (A), acrylic polyol (B), and polydimethylsiloxane compound) falls within the range described below.

[0110] The polydimethylsiloxane compound may be added when mixing the acrylic polyol (B) and the organic polyisocyanate (A). For example, the organic polyisocyanate (A), acrylic polyol (B), and polydimethylsiloxane compound may be mixed and stirred during film formation. Furthermore, if the polydimethylsiloxane compound has at least one hydroxyl group, it may be incorporated into the organic polyisocyanate (A) by reacting it with the organic polyisocyanate beforehand. In other words, the organic polyisocyanate (A) (for example, modified polyisocyanate (a)) may be an organic polyisocyanate modified with the polydimethylsiloxane compound. In this case, the reaction solution obtained by the reaction of the polydimethylsiloxane compound and the organic polyisocyanate may be mixed and stirred with the acrylic polyol (B) during film formation and used.

[0111] (Other ingredients) Paint compositions may use various paint additives as needed. Examples of paint additives include those that provide leveling and stain resistance to the paint film, as well as those that further improve scratch resistance while maintaining self-healing properties. Paint additives make it easier to achieve both practical self-healing and scratch resistance, even when the paint film is thin. Examples of additives include antioxidants such as 2,6-di-tert-butyl-4-methylphenol, UV absorbers, pigments, dyes, solvents, flame retardants, hydrolysis inhibitors, lubricants, plasticizers, fillers, antistatic agents, dispersants, catalysts, storage stabilizers, and thickeners.

[0112] As catalysts, known urethane catalysts can be used. Examples include organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate, and organic amines such as triethylenediamine, triethylamine, diazabicycloundecene, and diazabicyclononene, and their salts. These catalysts may be used individually or in combination of two or more. The catalyst may also be incorporated when forming the coating film.

[0113] (M NCO / M OH ) The number of moles of hydroxyl groups in the hydroxyl group-containing compound contained in the paint composition (M OH The number of moles of isocyanate groups in the isocyanate group-containing compound contained in the paint composition (M) NCO The ratio R(=M) NCO / M OH From the viewpoint of further suppressing excess hydroxyl groups and further improving water resistance and heat resistance, and from the viewpoint of further suppressing a decrease in crosslink density and further improving durability (stain resistance, etc.) and mechanical strength of the coating film, the ratio R may be 0.8 or higher, and may be 0.9 or higher or 1.0 or higher. From the viewpoint of further suppressing excess isocyanate groups and suppressing the excessive generation of isocyanurate and urea groups and further improving the flexibility and self-healing properties of the coating film, the ratio R may be 1.3 or lower, and may be 1.2 or lower or 1.1 or lower. From the viewpoint of the above, the ratio R may be 0.8 to 1.3, 0.9 to 1.2, or 1.0 to 1.1.

[0114] From the same viewpoint as above, the ratio of the number of moles of isocyanate groups in the organic polyisocyanate (A) to the total number of moles of hydroxyl groups in the acrylic polyol (B) and hydroxyl groups in the polydimethylsiloxane compound may be 0.8 to 1.3.

[0115] (Silicon content) The silicon content in the paint composition, calculated as SiO2, is preferably 0.001 to 0.1% by mass, based on the total amount of organic polyisocyanate (A), acrylic polyol (B), and polydimethylsiloxane compound. When the silicon content is 0.001% by mass or more, the smoothness, slip resistance, stain resistance, and scratch resistance of the resulting coating film are further improved. When the silicon content is 0.1% by mass or less, the occurrence of paint repellency is further suppressed, and the decrease in recoatability is further suppressed. From the same viewpoint as above, the silicon content may be 0.002% by mass or more, 0.005% by mass or more, or 0.01% by mass or more, or 0.09% by mass or less, or 0.05% by mass or less. Note that "total amount of organic polyisocyanate (A), acrylic polyol (B), and polydimethylsiloxane compound" can be rephrased as "amount of total resin solids."

[0116] The above-mentioned paint composition can be prepared, for example, by mixing the above-mentioned organic polyisocyanate (A), the above-mentioned acrylic polyol (B), and optionally a polydimethylsiloxane compound and / or the above-mentioned additive, such that the ratio R and silicon content are within the above-mentioned range.

[0117] As described above, a coating composition according to one aspect of this disclosure can be used to obtain a coating film that exhibits both high self-healing properties and stain resistance. Furthermore, it is possible to obtain a coating film that is excellent not only in self-healing properties and stain resistance, but also in smoothness and adhesion. In particular, when using the polydimethylsiloxane compound, a thin coating film of less than 20 μm can be obtained that exhibits both high self-healing properties and stain resistance. For these reasons, a coating composition according to one aspect of this disclosure can be suitably used for forming surface coatings on automotive exterior materials, which require fine processability, high design quality, and lightweight exterior parts, as well as on plastic molded products.

[0118] Although a coating composition according to one aspect of the present disclosure has been described above, the coating composition and its manufacturing method are not limited to the above aspect. For example, the coating composition may contain, in place of the above-mentioned organic polyisocyanate (A) and polydimethylsiloxane compound, or in addition to the above-mentioned organic polyisocyanate (A) and polydimethylsiloxane compound, a reaction product of the above-mentioned organic polyisocyanate (A) and polydimethylsiloxane compound having at least one hydroxyl group.

[0119] <Kit> A kit according to one aspect of the present disclosure is a kit for preparing the above-described paint composition (paint composition preparation kit), and comprises, for example, a first agent containing the above-described organic polyisocyanate (A) and a second agent containing the above-described acrylic polyol (B). Here, the organic polyisocyanate (A) contained in the first agent includes a modified polyisocyanate which is a reaction product of an organic polyisocyanate and a polydimethylsiloxane compound having at least one hydroxyl group (for example, a reaction product of a reaction product of a polyisocyanate component (a1) and a polyol component (a2) or a modified version thereof, and a polydimethylsiloxane compound).

[0120] The paint composition preparation kit may further comprise other agents besides the first and second agents. These other agents may include, for example, the polydimethylsiloxane compound described above.

[0121] The first and second agents may be prepared so that the above-mentioned paint composition can be obtained by mixing them, or they may be prepared so that the above-mentioned paint composition can be obtained by mixing the first agent, the second agent, and other agents other than the first and second agents. For example, when preparing a paint composition containing the polydimethylsiloxane compound, the polydimethylsiloxane compound may be incorporated into the first agent and / or the second agent, or the polydimethylsiloxane compound may be incorporated into the other agent. The above-mentioned additives that may be included in the paint composition may be included in the first agent, the second agent, or the other agent.

[0122] When using the paint composition preparation kit, for example, the first agent, the second agent, and any other agent used may be mixed so that the ratio R is within the range described above.

[0123] <coating film> A coating film according to one aspect of this disclosure is a self-healing coating film and includes a cured product of the above-described coating composition. The coating film can exhibit self-healing properties within one hour, for example, at room temperature (e.g., 5 to 35°C) or by heating to 40 to 60°C. Furthermore, the coating film can exhibit good smoothness and good stain resistance under high humidity conditions. The inventors surmise that the smoothness is improved by improving drying properties and humidity resistance, and the stain resistance is improved by improving crosslinking density.

[0124] The cured product of the paint composition contains a polyurethane resin having a urethane structure produced by a urethane reaction between an organic polyisocyanate (A) and an acrylic polyol (B). The urethane structure contained in the polyurethane resin includes, in addition to the urethane group (-CONH-), reaction residues of the organic polyisocyanate (A) and reaction residues of the acrylic polyol (B), and optionally, reaction residues of a polydimethylsiloxane compound (a polydimethylsiloxane compound having at least one hydroxyl group).

[0125] The thickness of the coating film is, for example, 5 to 40 μm. The coating film may also be a thin film with a thickness of less than 20 μm. When the paint composition contains the above polydimethylsiloxane compound (or the reaction product of the above organic polyisocyanate (A) and a polydimethylsiloxane compound having at least one hydroxyl group), even if the thickness of the coating film is less than 20 μm (for example, 5 μm), it has good smoothness, stain resistance and adhesion, and excellent self-healing properties against scratches.

[0126] The coating film is typically formed on an adherend. That is, one aspect of this disclosure comprises an adherend and a coating film formed on the adherend. The adherend will be described later.

[0127] <Method for forming a coating film> A method for forming a coating film according to one aspect of this disclosure comprises applying the above-described coating composition onto a substrate and curing it. The details of the substrate are as described above.

[0128] Examples of adherends include molded articles and surface-treated articles of materials such as stainless steel, phosphated steel, zinc-plated steel, iron, copper, aluminum, brass, glass, acrylic polyol, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyetheretherketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, and SEBS resin. The surface-treated article may be a molded article (surface-treated molded article) of an olefin resin such as polyethylene or polypropylene that has undergone surface treatment such as corona discharge treatment.

[0129] The above-mentioned adherend may have other coatings on its surface that can serve as an intermediate layer. In other words, the paint composition may be applied directly to the surface of the molded body described above, or it may be applied on top of other coatings that have been applied as a base coat to the surface of the molded body described above. The other coatings may be a single layer or multiple layers.

[0130] The coating composition may be applied by methods such as spraying, brushing, or dipping. According to one embodiment of the coating composition of this disclosure, a coating film with excellent smoothness and self-healing properties can be obtained even with spray coating, which is susceptible to humidity.

[0131] The curing of the coating composition may be carried out, for example, by heating. The heating for curing may be the heating for drying. That is, when the coating composition contains a solvent, the coating composition may be cured simultaneously (in parallel) with the drying for removing the solvent. The heating temperature may be, for example, 60 to 150 °C. The heating time may be, for example, 1 to 10 hours.

Examples

[0132] Hereinafter, examples according to the present disclosure will be described, but the present disclosure is not construed as being limited to these examples

[0133] <Measurement of number average molecular weight> The number average molecular weight disclosed in this example is the value measured under the following conditions. [Conditions] · Measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation) · Column: "TSKguardcolumn HXL-L" (manufactured by Tosoh Corporation) Particle size = 6 μm, size = 6 mm ID × 30 cm × 4 pieces · Carrier: Tetrahydrofuran (THF) · Detector: Differential refraction · Sample: 0.1% THF solution · Calibration curve: Polystyrene

[0134] <Measurement of NCO content> The NCO content disclosed in this example is the value measured according to the method described in JIS K1603-1 (Test method for aromatic isocyanates as raw materials for polyurethanes).

[0135] <Measurement of viscosity> The viscosity disclosed in this example is the value obtained by measuring the viscosity at 25 °C with a No. 4 rotor using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model "DVL-BII type").

[0136] <Measurement of free HDI content> The free HDI content disclosed in this embodiment is a value calculated from the area ratio of the hexamethylene diisocyanate peak in the polyisocyanate composition by performing GPC (HLC-8120, manufactured by Tosoh).

[0137] <Measurement of silicon content> The silicon content disclosed in this embodiment is obtained by determining the mass remaining percentage after holding in a nitrogen atmosphere at 500°C for 30 minutes using thermogravimetric differential thermal analysis (TG-DTA), and then calculating the SiO2 equivalent value by assuming that the mass remaining percentage corresponds to the silica remaining percentage.

[0138] <Synthesis of Modified Polyisocyanates> (Synthesis Example 1) In a 1 L four-necked flask equipped with a stirrer, thermometer, condenser, and dropping funnel, 890 g of hexamethylene diisocyanate (manufactured by Tosoh Corporation, NCO content: 49.9% by mass, hereinafter referred to as "HDI") and 110 g of PTMG-250 (manufactured by BASF, polytetramethylene glycol, trade name: Poly THF250, number average molecular weight 250) were charged, and the urethane reaction was carried out at 80°C for 2 hours under a nitrogen stream. Subsequently, 0.05 g of zirconium octoate (trade name: Zirconyl octoate, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as "OctZr") was added, and the allophanate reaction was carried out at 110°C for 2 hours. After the NCO content reached 37.0% by mass, the reaction was terminated by adding 0.5 g of JP-508 (trade name, manufactured by Johoku Kagaku Kogyo Co., Ltd., acidic phosphate ester), and the reaction solution was cooled to room temperature. Unreacted HDI was removed from this reaction solution by thin-film distillation at 130°C and 0.04 kPa to obtain polyisocyanate P1.

[0139] Polyisocyanate P1 had an NCO content of 16.2% by mass, was a clear liquid, had a number-average molecular weight of 1,400, an average number of functional groups of 5.4 calculated from the NCO content and number-average molecular weight, a viscosity of 2,000 mPa·s at 25°C, and a free HDI content of 0.2% by mass. Polyisocyanate P1 mainly contains allophanate-modified polyisocyanate and a small amount of isocyanurate-modified polyisocyanate, as determined by proton nuclear magnetic resonance (MMU) testing. 1 This was confirmed by 1H-NMR spectroscopy. Furthermore, the content of isocyanurate-modified polyisocyanate was 2 mol%, based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate.

[0140] (Synthesis Example 2) In a 1 L four-necked flask equipped with a stirrer, thermometer, condenser, and dropping funnel, 880 g of HDI and 120 g of PCD-250 (polyhexamethylene polycarbonate diol, number average molecular weight 250) were charged, and the urethane reaction was carried out at 80°C for 2 hours under a nitrogen stream. Subsequently, 0.05 g of OctZr was added, and the allophanate reaction was carried out at 110°C for 2 hours. After the NCO content reached 35.9% by mass, the reaction was stopped by adding 0.05 g of JP-508, and the reaction mixture was cooled to room temperature. Unreacted HDI was removed from this reaction mixture by thin-film distillation at 130°C and 0.04 kPa to obtain polyisocyanate P2.

[0141] Polyisocyanate P2 had an NCO content of 15.9% by mass, was a clear liquid, had a number-average molecular weight of 1,350, an average number of functional groups of 5.1 calculated from the NCO content and number-average molecular weight, a viscosity of 4,000 mPa·s at 25°C, and a free HDI content of 0.2% by mass. Polyisocyanate P2 mainly contains allophanate-modified polyisocyanate and a small amount of isocyanurate-modified polyisocyanate, as determined by proton nuclear magnetic resonance (MMU) testing. 1This was confirmed by 1H-NMR spectroscopy. Furthermore, the content of isocyanurate-modified polyisocyanate was 2 mol%, based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate.

[0142] (Synthesis Example 3) In a 1 L four-necked flask equipped with a stirrer, thermometer, condenser, and dropping funnel, 870 g of HDI and 130 g of PCD-500 (polyhexamethylene polycarbonate diol, number average molecular weight 500) were charged, and the urethane reaction was carried out at 80°C for 2 hours under a nitrogen stream. Subsequently, 0.05 g of OctZr was added, and the allophanate reaction was carried out at 110°C for 2 hours. After the NCO content reached 39.1% by mass, the reaction was stopped by adding 0.05 g of JP-508, and the reaction mixture was cooled to room temperature. Unreacted HDI was removed from this reaction mixture by thin-film distillation at 130°C and 0.04 kPa to obtain polyisocyanate P3.

[0143] Polyisocyanate P3 had an NCO content of 13.2% by mass, a number-average molecular weight of 1,450, an average number of functional groups of 4.6 calculated from the NCO content and number-average molecular weight, a viscosity of 6,000 mPa·s at 25°C, and a free HDI content of 0.2% by mass. Polyisocyanate P3 mainly contains allophanate-modified polyisocyanate and a small amount of isocyanurate-modified polyisocyanate, as determined by proton nuclear magnetic resonance (MMU) testing. 1 This was confirmed by 1H-NMR spectroscopy. Furthermore, the content of isocyanurate-modified polyisocyanate was 3 mol%, based on the total amount of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate.

[0144] <Synthesis of acrylic polyol (B)> (Synthesis Example 4) 70 g of butyl acetate was placed in a 300 ml four-necked flask equipped with a stirrer, thermometer, condenser, and dropping funnel, and the temperature was raised to 120°C. Next, 38.0 g of methyl methacrylate (manufactured by Mitsubishi Gas Chemical Co., Ltd., hereinafter referred to as "MMA"), 26.0 g of butyl acrylate (manufactured by Nippon Shokubai Co., Ltd., hereinafter referred to as "BA"), 31.0 g of 2-hydroxyethyl acrylate (manufactured by [company name], hereinafter referred to as "2HEA"), 5.0 g of isovonyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., hereinafter referred to as "IBXA"), and 2 g of perbutyl O (manufactured by NOF Corporation, t-butylperoxy-2-ethylhexanoate) were added to the dropping funnel to prepare a mixture, which was then added dropwise to the reaction vessel over 4 hours. The reaction mixture was then maintained at 120°C for 1 hour. Next, 30 g of butyl acetate and 1 g of perbutyl O were added to a dropping funnel to prepare a mixture, which was then added dropwise to the reaction vessel over 1 hour. After that, the mixture was maintained at 120°C for 3 hours and then cooled to room temperature. This yielded a solution of acrylic polyol 1 (AP1).

[0145] The hydroxyl value of acrylic polyol 1 in AP1 was measured according to the method specified in JIS K1557, and was found to be 150.0 mg KOH / g. AP1 was a transparent liquid, its solid content (acrylic polyol 1 content) was 50% by mass, and its glass transition temperature (hereinafter referred to as "Tg") was 15°C.

[0146] (Synthesis examples 5-10) Using the raw materials and preparation ratios listed in Table 1, the same procedure as in Synthesis Example 4 was performed to obtain a solution of acrylic polyols 2-7 (AP2-7, solid content: 50% by mass).

[0147] [Table 1]

[0148] <Examples 1-10 and Comparative Examples 1-5> [Preparation of paint composition] The materials shown in Tables 2-3 were mixed in the amounts (unit: g) shown in Tables 2-3 to prepare paint compositions 1-15 for Examples 1-10 and Comparative Examples 1-5, respectively. In Tables 2-3, the ratio R represents the number of moles of hydroxyl groups in the hydroxyl group-containing compound contained in the paint composition (the sum of the number of moles of hydroxyl groups in the acrylic polyol and the number of moles of hydroxyl groups in the polydimethylsiloxane compound) [M OH [M] The number of moles of isocyanate groups in the isocyanate group-containing compound contained in the paint composition (the number of moles of isocyanate groups in organic polyisocyanate) NCO ] ratio [M NCO / M OH This indicates the following. Furthermore, the Si content in Tables 2-3 represents the silicon content in SiO2 equivalent in the paint composition measured by the method described above (based on the total amount of organic polyisocyanate, acrylic polyol, and polydimethylsiloxane compound).

[0149] [Preparation of coating film] Under the following conditions, each of the coating compositions 1 to 15 was applied to a substrate, and the coating compositions were cured to obtain the coating films of Examples 1 to 10 and Comparative Examples 1 to 5, respectively. The substrates used were either acrylic resin sheets (manufactured by Kuraray Co., Ltd., 2 mm thick) or thermoplastic polyurethane films. (Painting conditions) • Painting method: Use an applicator. ·Humidity condition: 50%RH ·Temperature conditions: 23℃ Drying (curing) conditions: Forced drying at 80°C for 5 hours. • Film thickness: Approximately 20 μm

[0150] <Rating> The following evaluation tests 1 to 4 were performed on the coating films obtained from Examples 1 to 10 and Comparative Examples 1 to 5. In evaluation tests 1, 3, and 4, coating films made using an acrylic resin plate (manufactured by Kuraray Co., Ltd., 2 mm thick) as the substrate were used, while in evaluation test 2, coating films made using a thermoplastic polyurethane film as the substrate were used.

[0151] (Evaluation test 1: Coating appearance (smoothness)) In accordance with JIS Z 8741, the gloss of the coating film at 60° was measured using a haze-gloss reflectometer (manufactured by BYK-Additives & Instruments), and the appearance of the coating film was evaluated according to the following evaluation criteria. An evaluation of A indicated that the coating film appearance was good. In this evaluation, a good coating film appearance also essentially means good smoothness. [Evaluation Criteria] A: Glossiness of 80% or higher • B: Glossiness less than 80%

[0152] (Evaluation test 2: Stain resistance) The surface of the paint film was contaminated with a black Sharpy marker, and then left to stand for 1 hour at a temperature of 23°C and a humidity of 50% RH. After standing, the contaminated surface of the paint film was wiped with gauze soaked in ethanol, and the color difference before and after contamination was calculated using spectro2guide (BYK-Gardner) with the following formula. Color difference=[(ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2 ] 1 / 2

[0153] The stain resistance was evaluated according to the following evaluation criteria. An evaluation of A indicated good stain resistance. [Evaluation Criteria] A: Color difference is less than 1 B: Color difference between 1 and less than 2 • C: Color difference of 2 or more

[0154] (Evaluation test 3: Self-healing properties) Under conditions of 23°C and 50% RH, the surface of the coating was scratched by rubbing it with a brass wire brush. The degree of scratch repair was observed visually, and the time it took for the scratches to completely heal was measured. A rating of A or B indicated good self-healing properties. [Evaluation Criteria] A: The wound will heal within 1 hour at room temperature. B: At room temperature, the wound will not heal within 1 hour, but when heated to 50°C, the scar will heal within 1 hour. • C: Whether at room temperature or heated to 50°C, the damage will not heal within one hour.

[0155] (Evaluation test 4: Adhesion) Adhesion tests were conducted using the cross-cut method in accordance with JIS 5600-5-6, and adhesion was evaluated according to the following evaluation criteria. An evaluation of A indicated good adhesion. [Evaluation Criteria] ·A: Classification 0~1 ·B: Classification 2~5

[0156] [Table 2]

[0157] [Table 3]

[0158] Details of each ingredient in Tables 2-3 are as follows: • Polyisocyanates P1-P3: Polyisocyanates P1-P3 synthesized in Synthesis Examples 1-3 • Polyisocyanate P4:HDI isocyanurate (product name: Coronate HXR, manufactured by Tosoh Corporation) • AP1~AP7: Solutions of acrylic polyols synthesized in synthesis examples 4~10 (AP1~AP7) • U-CAT SA102: (Manufactured by Sunapro Co., Ltd., urethane catalyst, 2-ethylhexanoate of DBU) • BYK-SILCLEAN3700: (Manufactured by BYK Chemie Japan, Dimethylpolysiloxane-acrylic block copolymer, Number average molecular weight: 7600, Silicon content (SiO2 equivalent): 1%)

Claims

1. It contains an organic polyisocyanate (A) and an acrylic polyol (B), The aforementioned organic polyisocyanate (A) includes modified polyisocyanate (a), The modified polyisocyanate (a) is a reaction product of a polyisocyanate component (a1) and a polyol component (a2), or a modified version thereof. The polyisocyanate component (a1) includes an organic diisocyanate or a modified version thereof. The polyol component (a2) comprises polytetramethylene glycol having a number average molecular weight of 200 to 750. A paint composition comprising acrylic polyol (b), wherein the acrylic polyol (B) has a glass transition temperature of 5 to 30°C and a hydroxyl value of 120 mg KOH / g or more and 150 mg KOH / g or less.

2. The coating composition according to claim 1, wherein the average number of functional groups of the modified polyisocyanate (a) is 4.5 to 6.

0.

3. The paint composition according to claim 1 or 2, wherein the polyisocyanate component (a1) comprises at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

4. The paint composition according to any one of claims 1 to 3, wherein the modified polyisocyanate (a) comprises at least one selected from the group consisting of allophanate-modified polyisocyanate and isocyanurate-modified polyisocyanate.

5. The paint composition according to claim 4, wherein the content of the isocyanurate-modified polyisocyanate is 1 to 30 mol%, based on the total amount of the allophanate-modified polyisocyanate and the isocyanurate-modified polyisocyanate.

6. A paint composition according to any one of claims 1 to 5, further comprising a polydimethylsiloxane compound.

7. SiO ２ The paint composition according to claim 6, wherein the converted silicon content is 0.001 to 0.1% by mass, based on the total amount of the organic polyisocyanate (A), the acrylic polyol (B), and the polydimethylsiloxane compound.

8. The paint composition according to any one of claims 1 to 7, wherein the ratio of the number of moles of isocyanate groups in the isocyanate group-containing compound contained in the paint composition to the number of moles of hydroxyl groups in the hydroxyl group-containing compound contained in the paint composition is 0.8 to 1.

3.

9. A kit for preparing a paint composition according to any one of claims 1 to 8, A kit comprising a first agent containing the organic polyisocyanate (A) and a second agent containing the acrylic polyol (B).

10. A coating film comprising a cured product of the coating composition according to any one of claims 1 to 8.

11. A method for forming a coating film, comprising applying a coating composition according to any one of claims 1 to 8 onto a substrate and curing it.

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