Polyolefin coating composition and primer

Abstract

Provided is a coating composition which exhibits good adhesion and good storage stability. A coating film formed on a polyolefin resin substrate has excellent high-pressure vehicle washing resistance, chemical resistance, and oil immersion resistance. Specifically provided is a coating composition which is characterized by containing a modified polyolefin (A) having a glass transition temperature of-30 DEG C or higher and a (meth) acrylic resin (B) containing a polymer of a radically polymerizable compound (b1), the radical polymerizable compound (b1) contains a polyfunctional (meth) acrylate, the glass transition temperature of the (meth) acrylic resin (B) is 0 DEG C or higher, and the hydroxyl value of the (meth) acrylic resin (B) is 5-150 mgKOH / g.

Description

Technical Field

[0001] The present invention relates to a polyolefin-based coating composition and a primer coating. Background Art

[0002] Resin materials such as polyolefins and ABS are lightweight and have excellent properties, so they are used in a wide range of applications. Especially in automotive applications, in the vehicle body lightweighting for energy conservation, resin substrates such as polyolefins and ABS are becoming popular. On these resin substrates, coatings are applied to the surface mainly for design and protection purposes. When applying coatings, a primer coating is pre-coated to improve the adhesion between the top coating film and the resin substrate. However, since polyolefins are generally non-polar and have low adhesion to coating films, primers using modified polyolefin resins with excellent adhesion are particularly applied to automotive exterior parts.

[0003] In recent years, the cases of washing cars and removing snow by spraying high-temperature and high-pressure warm water have increased, and the requirement for the coating film not to peel off even when spraying warm water at higher pressures and higher temperatures than before has been increasing day by day. There is a need for a coating that has excellent high-pressure car wash resistance for polyolefin substrates.

[0004] In response to this, the present applicant proposed in Patent Document 1 a coating composition containing a modified polyolefin resin having a glass transition temperature of -30°C or higher and a specific acrylic resin. The coating composition containing the above-mentioned modified polyolefin resin and specific acrylic resin has chemical resistance and high-pressure car wash resistance to polyolefin substrates, and the storage stability of the coating is also good.

[0005] Moreover, polyolefin substrates have excellent heat aging resistance and weather resistance, and their use range has been broadened as a substitute material for polar rubbers used in rubber parts. Especially in parts used for automotive applications, since there are many parts that come into contact with lubricating oil, working oil, grease, or gasoline, one of the required characteristics of the coatings applied to these parts is oil immersion resistance. Coatings using modified polyolefin resins with excellent adhesion are composed of hydrocarbons and are non-polar, so it is difficult to satisfy oil immersion resistance. Therefore, there has long been a need for a coating that has excellent high-pressure car wash resistance on polyolefin substrates and fully exhibits oil immersion resistance.

[0006] For example, Patent Document 2 discloses a coating resin obtained by polymerizing a mixture of chlorinated polyolefin having a chlorine content of 50% by mass or less and an ethylenic monomer, which can form a coating film having various excellent properties such as solvent resistance, oil resistance, and adhesion, and proposes a coating resin composition having excellent storage stability. Prior Art Documents Patent Documents

[0007] Patent Document 1: International Publication No. WO 2022 / 054727 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-201236 Summary of the Invention Problems to be Solved by the Invention

[0008] However, in a modified resin in which an acrylic polymer chain is partially grafted onto a polyolefin, although the storage stability is excellent, the adhesion to the polyolefin substrate decreases, and it cannot be said to have sufficient high-pressure car wash resistance and oil immersion resistance.

[0009] The present invention has been completed in view of the above background circumstances, and provides a coating composition that is excellent in high-pressure car wash resistance, chemical resistance, and oil immersion resistance to a polyolefin substrate, exhibits good adhesion, and has good storage stability, and a primer containing the composition. Technical Means for Solving the Problems

[0010] The present inventors have found that a coating composition obtained by mixing a modified polyolefin resin having a glass transition temperature of -30°C or higher and a (meth)acrylic resin having a glass transition temperature of 0°C or higher and an acid value of 5 to 150 mgKOH / g can solve the above problems, and thus completed the present invention. The above (meth)acrylic resin contains a polymer of a radically polymerizable compound, and the radically polymerizable compound contains a polyfunctional (meth)acrylate.

[0011] The present invention includes, for example, the subject matters described in the following items.

[0012] [1] A coating composition, characterized in that it contains a modified polyolefin (A) and a (meth)acrylic resin (B), The modified polyolefin (A) has a glass transition temperature of -30°C or higher, The (meth)acrylic resin (B) contains a polymer of a radically polymerizable compound (b1), and the radically polymerizable compound (b1) contains a polyfunctional (meth)acrylate, The (meth)acrylic resin (B) has a glass transition temperature of 0°C or higher, The (meth)acrylic resin (B) has a hydroxyl value of 5 to 150 mgKOH / g. Effects of the Invention

[0013] According to the present invention, it is possible to provide a coating composition that is excellent in high-pressure car wash resistance, chemical resistance, and oil immersion resistance to a polyolefin substrate, exhibits good adhesion, and has good storage stability, and a primer containing the composition. Detailed Description of the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] <Modified polyolefin (A)> The modified polyolefin (A) used in the present invention is a modified product of a polyolefin resin.

[0016] The polyolefin resin may be a polymer of a single α-olefin or a copolymer of two or more α-olefins. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, etc. When the polyolefin resin is a copolymer, the polyolefin resin may be a random copolymer or a block copolymer.

[0017] From the viewpoint of exhibiting sufficient adhesion to a non-polar resin substrate, etc., the polyolefin resin is preferably polypropylene and a propylene-α-olefin copolymer, and among them, polypropylene (propylene homopolymer), ethylene-propylene copolymer, propylene-1-butene copolymer, and propylene-ethylene-butene copolymer are preferred.

[0018] The ratio of the propylene component to the α-olefin component in the propylene-α-olefin copolymer is not limited, and in 100 mol% of the structural units, it preferably contains 50 mol% or more of the structural units derived from propylene, and more preferably contains 70 mol% or more. When the structural units derived from propylene are contained within the above range, it is easy to maintain the adhesion to the polyolefin substrate.

[0019] The weight average molecular weight (Mw) of the modified polyolefin (A) is preferably in the range of 20,000 to 180,000. More preferably in the range of 40,000 to 150,000. Further preferably in the range of 60,000 to 120,000. When it is less than 20,000, there is a case where the cohesion weakens and the adhesiveness deteriorates. On the other hand, when it exceeds 180,000, there is a possibility that the solubility in the solvent decreases, the compatibility with the (meth)acrylic resin (B) decreases, and the storage stability of the coating decreases.

[0020] The modified polyolefin (A) is preferably crystalline. Since it is crystalline, compared with non-crystalline, its cohesion is strong, and its adhesiveness, water resistance, heat resistance, and chemical resistance are excellent, so it is useful.

[0021] The crystallinity described in the present invention means that using a differential scanning calorimeter (hereinafter also referred to as DSC. Manufactured by TA Instrument Japan, Q-2000), heating from -100°C to 250°C at 10°C / min., and a clear melting peak appears during this heating process. The melting point is measured using DSC, heating and melting the resin at a rate of 10°C / min., cooling and resinifying, and the value measured by the peak temperature of the melting peak during the second heating and melting.

[0022] The melting point (Tm) of the modified polyolefin (A) is preferably 40 °C or higher, more preferably 50 °C or higher, and still more preferably 60 °C or higher. In addition, it is preferably 120 °C or lower, more preferably 100 °C or lower, and still more preferably 90 °C or lower. When it is lower than 40 °C, the cohesion decreases and the high-pressure car wash resistance deteriorates. When it exceeds 120 °C, the solubility in the solvent decreases and the storage stability of the coating material deteriorates.

[0023] The glass transition temperature (hereinafter referred to as Tg) of the modified polyolefin (A) is -30 °C or higher. It is preferably -25 °C or higher, and more preferably -20 °C or higher. When Tg is -30 °C or higher, even when high-pressure and high-temperature warm water is sprayed in the high-pressure car wash resistance test, the adhesion between the substrate and the coating film is good, the coating film is hardly affected, and the high-pressure car wash resistance becomes good. The upper limit of the glass transition temperature (Tg) of the modified polyolefin (A) in the present application is not particularly limited, but from the viewpoint of the performance of the coating film made from the coating composition, it is, for example, 50 °C or lower.

[0024] The polyolefin resin may also be a polyolefin resin using a bio-derived raw material instead of a polyolefin resin derived from petroleum. The bio-derived polyolefin resin refers to a polyolefin resin produced from biological resources (biomass). Biological resources are formed from renewable bio-derived organic resources other than fossil resources, and are produced from raw materials such as crops, plants, microorganisms, agricultural waste, and discarded food. Compared with the case of using petroleum-derived raw materials, since renewable resources can be used, carbon dioxide emissions can be reduced and the environment can be protected.

[0025] The polyolefin using a bio-derived raw material preferably contains at least a propylene structural unit. In addition, the biomass degree of the polyolefin resin is 25% or higher, preferably 27% or higher, and more preferably 30% or higher. The upper limit is 100% or lower, and there is no particular limitation. The biomass degree of the total carbon can be calculated from the carbon isotope content of mass number 14 measured according to ASTM D6866.

[0026] The modified polyolefin (A) is not particularly limited, and preferably includes at least one of an acid-modified polyolefin (a1) and an acid-modified chlorinated polyolefin (a2).

[0027] The mass ratio of the modified polyolefin (A) in the total solid components of the coating composition is preferably 5% by mass or more and 80% by mass or less. At this time, the coating film made from the coating composition can maintain higher adhesion. The mass ratio of the modified polyolefin (A) in the total solid components of the coating composition is more preferably 10% by mass or more and 70% by mass or less, and further preferably 20% by mass or more and 60% by mass or less. In addition, the total solid components referred to herein mean the total amount of the total components excluding components such as solvents volatilized from the coating composition during the production of the coating film.

[0028] <Acid-modified polyolefin (a1)> In the present invention, the acid-modified polyolefin (a1) is not limited, and is preferably obtained by modifying at least one of polymers and copolymers of α-olefins with an acid, and more preferably a substance obtained by grafting at least one of α,β-unsaturated carboxylic acids and their acid anhydrides.

[0029] As at least one of α,β-unsaturated carboxylic acids and their acid anhydrides, for example, maleic acid, itaconic acid, citraconic acid, and acid anhydrides thereof can be mentioned. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. As maleic anhydride which is further preferred, specifically, maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc. can be mentioned. These acid-modified polyolefins can be used alone or in combination of two or more.

[0030] As a method for producing the acid-modified polyolefin (a1), there is no particular limitation, and for example, a radical linking and branching reaction (that is, a reaction in which a radical species is generated for a polymer as a main chain, and the radical species is used as a polymerization initiation point to cause graft polymerization of an unsaturated carboxylic acid and an acid anhydride) can be mentioned.

[0031] When a polyolefin resin is modified with an acid to produce the acid-modified polyolefin (a1), a radical initiator can also be used. The radical polymerization initiator is a compound that can generate radicals by heat or light. As the radical initiator, there is no particular limitation, and an organic peroxide is preferably used. As the organic peroxide, peroxides such as di-tert-butyl phthalate peroxide, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl perbenzoate, tert-butyl 2-ethylhexanoate peroxide, tert-butyl tert-pentanoate peroxide, methyl ethyl ketone peroxide, di-tert-butyl peroxide, lauroyl peroxide, etc. can be mentioned; azo nitriles such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), etc.

[0032] With respect to 100% by mass of the acid-modified polyolefin, the amount of acid modification of the acid-modified polyolefin (a1) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.5% by mass or more. In addition, it is preferably 30% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less. Outside the above ranges, the adhesiveness to the polyolefin substrate may decrease.

[0033] The acid value of the acid-modified polyolefin (a1) is preferably 4 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g, and still more preferably 6 to 30 mgKOH / g. When the acid value is less than 4 mgKOH / g, there is a possibility that the crosslinking reaction with the crosslinking agent contained in the topcoat layer is insufficient. On the other hand, when it exceeds 40 mgKOH / g, there is a possibility that the storage stability of the coating decreases.

[0034] <Acid-modified chlorinated polyolefin (a2)> The acid-modified chlorinated polyolefin (a2) used in the present invention is not limited. For example, it is preferably obtained by chlorinating the above acid-modified polyolefin (a1).

[0035] As a method for producing the acid-modified chlorinated polyolefin (a2), there is no particular limitation. For example, it can be obtained by dissolving the acid-modified polyolefin (a1) in a halogenated hydrocarbon such as chloroform and introducing chlorine.

[0036] From the viewpoints of solution stability and adhesiveness, with respect to 100% by mass of the acid-modified chlorinated polyolefin, the lower limit of the chlorine content of the acid-modified chlorinated polyolefin (a2) is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. In particular, when it is an acid-modified homopolypropylene, if within the above range, it exhibits good adhesive strength to the polyolefin substrate. The upper limit is preferably 40% by mass or less, more preferably 35% by mass or less, and still more preferably 30% by mass or less. When exceeding the above upper limit value, the crystallinity of the acid-modified chlorinated polyolefin may decrease and the adhesive strength may decrease.

[0037] <(Meth)acrylic resin (B)> In the present invention, "(meth)acrylate" means "acrylate or methacrylate", and "(meth)acrylic acid" means "acrylic acid or methacrylic acid".

[0038] (Meth)acrylic resin (B) contains a polymer of a radically polymerizable compound (b1). The radically polymerizable compound (b1) can be a compound having appropriate radical reactivity. For example, the radically polymerizable compound (b1) is a compound having at least 1 ethylenically unsaturated bond in the molecule.

[0039] The radically polymerizable compound (b1) contains a polyfunctional (meth)acrylate. Therefore, the crosslinking density of the acrylic resin (B) increases, and excellent oil immersion resistance can be exhibited.

[0040] The number of functional groups of the polyfunctional (meth)acrylate is preferably in the range of 2 to 6, more preferably 2 to 3. When it exceeds 6, it tends to increase viscosity, and there is a possibility that the storage stability deteriorates.

[0041] Examples of the polyfunctional (meth)acrylate include alkane diol di(meth)acrylates such as 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and dimethylol tricyclodecane di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate and bisphenol F ethylene oxide-modified di(meth)acrylate; polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, urethane di(meth)acrylate, and epoxy di(meth)acrylate. There is no particular limitation on the polyfunctional methacrylate having three or more functional groups. Examples thereof include dipentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, di(tris(hydroxymethyl)propane) tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and other ethylene oxide-modified (meth)acrylates; isocyanuric acid ethylene oxide-modified tri(meth)acrylate, ε-caprolactone-modified tri(acryloyloxyethyl) isocyanurate, and other isocyanuric acid-modified tri(meth)acrylates; pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol tri(meth)acrylate toluene diisocyanate urethane prepolymer, dipentaerythritol penta(meth)acrylate hexamethylene diisocyanate urethane prepolymer, and other urethane methacrylates. These can be used alone or in combination of two or more. Among these, 2-functional or 3-functional (meth)acrylates are preferred, and 1,6-hexanediol dimethacrylate and trimethylolpropane trimethacrylate are particularly preferred.

[0042] In the radically polymerizable compound (b1) constituting the (meth)acrylic resin (B), the polyfunctional (meth)acrylate is preferably contained in an amount of 0.1 to 5% by mass. More preferably, it is 0.2 to 4% by mass, and still more preferably, it is 0.5 to 3% by mass. When the content rate of the polyfunctional (meth)acrylate is less than 0.1% by mass, there is a case where the oil immersion resistance is not sufficiently exhibited. On the other hand, when the content rate of the polyfunctional (meth)acrylate exceeds 5% by mass, there is a case where particles are generated in the (meth)acrylic resin or when it is made into a coating composition.

[0043] In addition, the radically polymerizable compound (b1) preferably contains a radically polymerizable compound having a hydroxyl group. At this time, the adhesion to polar substrates such as polycarbonate substrates and ABS substrates can be improved. In addition, by having crosslinking points, it can crosslink with coatings and substrates for topcoats, and the adhesion to topcoat coatings and substrates can also be improved.

[0044] Examples of the radically polymerizable compound having a hydroxyl group include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, polyethylene glycol - polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc. These can be used alone or in combination of two or more.

[0045] For the radically polymerizable compound having a hydroxyl group, it is preferably contained in the radically polymerizable compound (b1) constituting the (meth)acrylic resin (B) in an amount of 0.5 to 40% by mass. More preferably, it is 3 to 30% by mass, and still more preferably, it is 7 to 20% by mass. By being 0.5% by mass or more, the high-pressure car wash resistance and oil immersion resistance are liable to become good, and it is easy to maintain good adhesion to polar substrates such as polycarbonate substrates and ABS substrates. By being 40% by mass or less, the water resistance is liable to become better, and it is easy to maintain good compatibility between the modified polyolefin (A) and the (meth)acrylic resin (B), and it is easy to maintain good storage stability of the coating.

[0046] The radically polymerizable compound (b1) may also include at least one of (meth)acrylate having an alkoxymethyl group and (meth)acrylate having an alkoxyethyl group. At this time, while it is easy to maintain good compatibility between the modified polyolefin (A) and the (meth)acrylic resin (B), the adhesion to polar substrates such as polycarbonate substrates and ABS substrates can be improved. In addition, the adhesion to the coating used in the topcoat can also be improved.

[0047] Specific examples of the (meth)acrylate having an alkoxymethyl group include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, propoxymethyl (meth)acrylate, butoxymethyl (meth)acrylate, etc.; specific examples of the (meth)acrylate having an alkoxyethyl group include 2-methoxyethyl (meth)acrylate, 1-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 1-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 1-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 1-butoxyethyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-(2-butoxyethoxy)ethyl (meth)acrylate, [2-(2-methoxyethoxy)ethoxy]ethyl (meth)acrylate, etc. Among these, in order to obtain good adhesion, it is preferable to use (meth)acrylate esters of alkoxymethyl or alkoxyethyl having 5 or less carbon atoms such as methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, propoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 1-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 1-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 1-propoxyethyl (meth)acrylate.

[0048] The (meth)acrylate having an alkoxymethyl group and the (meth)acrylate having an alkoxyethyl group are preferably contained in the radically polymerizable compound (b1) constituting the (meth)acrylic resin (B) in an amount of 1 to 55% by mass. More preferably, it is 3 to 50% by mass, and still more preferably, it is 5 to 40% by mass. By being 1% by mass or more, it is easy to keep the adhesion to polar substrates such as polycarbonate substrates and ABS substrates in a good state. By being 55% by mass or less, it is easy to keep the compatibility between the modified polyolefin (A) and the (meth)acrylic resin (B) in a good state, and it is easy to keep the storage stability of the coating in a good state.

[0049] As the radically polymerizable compound (b1), by containing at least one of the (meth)acrylate having an alkoxymethyl group and the (meth)acrylate having an alkoxyethyl group and a radically polymerizable compound having a hydroxyl group, it is possible to seek a balance between the compatibility with the modified polyolefin and the crosslinking reaction, and it is easy to obtain a coating composition having excellent adhesion and water resistance to both non-polar substrates and polar substrates and excellent storage stability.

[0050] As the radical polymerizable compound (b1) other than the above, examples thereof include: (meth)acrylic acid alkyl ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, docosyl (meth)acrylate; (meth)acrylate compounds having an alicyclic structure such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate; ethylenically unsaturated monomers having a carboxyl group such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, cinnamic acid; ethylenically unsaturated monomers having an acid anhydride group such as maleic anhydride, itaconic anhydride, citraconic anhydride; (meth)acrylate compounds having an aromatic ring such as benzyl (meth)acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate; ethylenically unsaturated monomers having an amino group such as (meth)acrylic acid dimethylaminoethyl ester, (meth)acrylic acid diethylaminoethyl ester, (meth)acrylic acid tert-butylaminoethyl ester, (meth)acrylic acid methylethylaminoethyl ester, dimethylaminostyrene, diethylaminostyrene, (meth)acrylic acid pentamethyldecyl ester, (meth)acrylic acid tetramethyldecyl ester; ethylenically unsaturated monomers containing an epoxy group such as glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate; ethylenically unsaturated monomers containing an alkoxysilyl group such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane; ethylenically unsaturated monomers containing a polyoxyethylene group such as mono(polyethylene glycol) (meth)acrylate, mono(polyethylene glycol / polypropylene glycol) (meth)acrylate, mono(methoxypolyethylene glycol) (meth)acrylate;Ethylenically unsaturated monomers containing an amide group such as (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-bis(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-bis(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-bis(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-bis(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-bis(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, diacetone (meth)acrylamide; aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, indene; (meth)acrylonitrile, acrylmorpholine, etc. These can be used alone or in combination of two or more. In addition, the radically polymerizable compound (b1) is not limited to the compounds shown above.;

[0051] The radically polymerizable compound (b1) may also contain a chain transfer agent. A chain transfer agent is a radical polymerization regulator that can react with the end of a growing polymer chain during radical polymerization to stop the growth of the polymer while generating a new polymerization-initiating radical. There is no particular limitation on the chain transfer agent, and examples thereof include mercaptans such as n-dodecyl mercaptan (lauryl mercaptan), 2-ethylhexyl mercaptoacetate, 2,4-diphenyl-4-methyl-1-pentene, 2-mercaptoethanol, 2,3-dimercapto-1-propanol, glycidyl mercaptan; allyl compounds such as allyl acetate, α-methylstyrene dimer, and allyl carbinol, etc.

[0052] When obtaining a polymer from the radically polymerizable compound (b1), a radical initiator may also be used. A radical initiator is a compound capable of generating radicals by heat or light. Examples of radical initiators include: organic peroxide radical initiators such as di-tert-butyl phthalate peroxide, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl benzoate peroxide, tert-butyl 2-ethylhexanoate peroxide, tert-butyl tert-pentanoate peroxide, methyl ethyl ketone peroxide, di-tert-butyl peroxide, lauroyl peroxide, etc.; azo nitrile radical initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), etc.

[0053] The radically polymerizable compound (b1) may also contain a biomass-derived (meth)acrylic monomer component. The biomass-derived (meth)acrylic monomer component is composed of biomass-derived (meth)acrylic acid, biomass-derived alkanol, and an ester of biomass-derived or non-biomass-derived (meth)acrylic acid. Examples of the biomass-derived alkanol include biomass ethanol, alkanols derived from plant raw materials such as palm oil, palm kernel oil, coconut oil, etc. When the number of carbon atoms of the biomass-derived alkanol is 3 or more, the alkanol may be linear or may have a branched chain.

[0054] The glass transition temperature (Tg) of the (meth)acrylic resin (B) is 0 °C or higher. The Tg of the (meth)acrylic resin (B) is preferably 2 °C or higher, more preferably 10 °C or higher. Therefore, water resistance and high-pressure car wash resistance can be imparted to the coating film formed from the coating composition. In addition, there is no particular limitation on the upper limit of the Tg of the (meth)acrylic resin (B) in the present application. From the viewpoint of the processability of the film-forming process of the coating film prepared from the coating composition, it is, for example, 150 °C or lower.

[0055] The Tg of the (meth)acrylic resin (B) is a value calculated theoretically from the composition ratio of the radically polymerizable monomer (b1) and is a value calculated using the following calculation formula (FOX formula). 1 / Tg = C1 / Tg1 + C2 / Tg2 + ··· + Cn / Tgn: (FOX formula) [In the above calculation formula (Fox formula), Cn is the mass fraction of each of the n monomers, Tgn is the glass transition temperature of each homopolymer of the n monomers, and n is the type of monomer used as the radically polymerizable monomer (b1), expressed as a positive integer. That is, it is the calculation formula when obtaining the (meth)acrylic resin (B) by polymerization of n monomers. The unit of the glass transition temperature in the above calculation formula (Fox formula) is the absolute temperature "K", and the value obtained by converting this calculated value to the Celsius temperature "°C" is used as the glass transition temperature of the (meth)acrylic resin (B).]

[0056] The Tg of the homopolymer of the monomer can use the values described in the literature. As such literature, for example, the following literature can be referred to: the (meth)acrylate catalog of Kyoeisha Chemical Co., Ltd., the acrylate catalog of Mitsubishi Chemical Corporation, and "New Polymer Library 7, Introduction to Synthetic Resins for Coatings" written by Kyozo Kitaoka, published by Polymer Publishing Society in 1997, pages 168 - 169.

[0057] In addition, as the radically polymerizable monomer (b1), when there are monomers with unknown glass transition temperatures, such as special monomers and polyfunctional monomers, in a small amount, only the monomers with clear glass transition temperatures are used to obtain the glass transition temperature of the (meth)acrylic resin (B).

[0058] The weight - average molecular weight (Mw) of the (meth)acrylic resin (B) is preferably 1,000 or more, more preferably 5,000 or more, and further preferably 10,000 or more. In addition, it is preferably 100,000 or less, more preferably 50,000 or less. When the weight - average molecular weight is less than 1,000, the cohesion sometimes decreases and the high - pressure car wash resistance deteriorates. On the other hand, when it exceeds 100,000, the storage stability of the coating sometimes decreases.

[0059] The hydroxyl value of the (meth)acrylic resin (B) is 5 - 150 mgKOH / g. The hydroxyl value of the (meth)acrylic resin (B) is preferably 10 - 100 mgKOH / g, more preferably 20 - 80 mgKOH / g. When it is less than 5 mgKOH / g, the cross - linking reaction is insufficient, the adhesion decreases, and the high - pressure car wash resistance and oil immersion resistance decrease. On the other hand, when it exceeds 150 mgKOH / g, the water resistance decreases, and the storage stability of the coating decreases due to hydrogen bonding and cross - linking reactions.

[0060] The acid value of the (meth)acrylic resin (B) is preferably 0.1 to 30 mgKOH / g. The acid value of the (meth)acrylic resin (B) is more preferably 1 to 25 mgKOH / g, further preferably 2 to 20 mgKOH / g, and particularly preferably 3 to 15 mgKOH / g. At this time, the close adhesion to polar substrates such as polycarbonate substrates and ABS substrates can be improved. In addition, by having crosslinking points, it can crosslink with the coatings and substrates used for topcoats, and the close adhesion to topcoat coatings and substrates can also be improved. In addition, the high-pressure car wash resistance and oil immersion resistance are also excellent, especially the chemical resistance such as volatile oil resistance and vaporized oil resistance is excellent. When the acid value exceeds 30 mgKOH / g, the water resistance and the storage stability of the coating composition may decrease. In addition, the "acid value" refers to the number of mg of potassium hydroxide required to neutralize 1 g of the solid component of the (meth)acrylic resin (B).

[0061] The hydroxyl value of the (meth)acrylic resin (B) represents a value in terms of solid component conversion, and can be evaluated according to the pyridine - acetyl chloride method of JIS K 0070 - 1992. In addition, the acid value of the (meth)acrylic resin (B) represents a value in terms of solid component conversion, and can be evaluated according to the potentiometric titration method of JIS K 0070 - 1992.

[0062] With respect to 100 parts by mass of the modified polyolefin (A), the content of the (meth)acrylic resin (B) is preferably 25 parts by mass or more. More preferably, it is 50 parts by mass or more, and further preferably 100 parts by mass or more. At this time, the high-pressure car wash resistance is good, the compatibility between the modified polyolefin (A) and the (meth)acrylic resin (B) is good, and good coating storage stability can be obtained. When it is less than 25 parts by mass, the close adhesion to polar substrates such as polycarbonate substrates and ABS substrates may decrease. In addition, it is preferably 900 parts by mass or less, more preferably 450 parts by mass or less, and further preferably 300 parts by mass or less. When it exceeds 900 parts by mass, the close adhesion to polyolefin substrates decreases, and the high-pressure car wash resistance and oil immersion resistance become poor.

[0063] The mass ratio of the (meth)acrylic resin (B) in the total solid component of the coating composition is preferably 5% by mass or more and 80% by mass or less. At this time, the coating film made from the coating composition can maintain higher close adhesion. The mass ratio of the modified polyolefin (A) in the total solid component of the coating composition is more preferably 10% by mass or more and 70% by mass or less, and further preferably 20% by mass or more and 60% by mass or less. In addition, the total solid component described here refers to the total amount of the total components after removing components such as solvents that volatilize during the process of forming a coating film from the coating composition.

[0064] <Solvent (C)> In the present invention, the coating composition may also contain a solvent (C). The solvent (C) is used for purposes such as adjusting the viscosity of the coating composition, adjusting the coatability, and adjusting the film-forming property. As the solvent (C), there is no limitation as long as it can dissolve the acid-modified polyolefin (A) and the (meth)acrylic resin (B). As the hydrocarbon solvent (C1), examples include aromatic hydrocarbon solvents such as toluene, xylene, and Solvesso (registered trademark) 100; aliphatic hydrocarbon solvents such as hexane and heptane; and alicyclic hydrocarbon solvents such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane. One or more of these can be preferably used. Among them, xylene and cyclohexane are preferred. Particularly preferred is a combination of xylene, Solvesso (registered trademark) 100, methylcyclohexane, and cyclohexane.

[0065] Relative to 100 parts by mass of the modified polyolefin (A), it is preferably to contain 200 parts by mass or more of the hydrocarbon solvent (C1), more preferably 300 parts by mass or more, and further preferably 400 parts by mass or more. In addition, it is preferably 3,000 parts by mass or less, more preferably 2,000 parts by mass or less, and further preferably 1,000 parts by mass or less. By setting it within the above range, it is easy to exhibit excellent storage stability of the coating composition.

[0066] The solvent (C) also preferably contains the hydrocarbon solvent (C1), and further contains at least one of an ester solvent (C2) and a ketone solvent (C3). In this case, it is easy to obtain an anti-tackifying effect and exhibit excellent storage stability of the coating composition.

[0067] Examples of the ester solvent (C2) include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, and amyl acetate. Among them, ethyl acetate and butyl acetate are preferred. Examples of the ketone solvent (C3) include acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Among them, methyl ethyl ketone is preferred. It is also a preferred mode to combine two or more of the ester solvent (C2) and the ketone solvent (C3).

[0068] Relative to the total amount of 100 parts by mass of the modified polyolefin (A) and the (meth)acrylic resin (B), the content of the ester solvent (C2) and the ketone solvent (C3) is preferably 20 parts by mass or more, more preferably 50 parts by mass or more. In addition, it is preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and further preferably 200 parts by mass or less.

[0069] The content (mass ratio) of the ester solvent (C2), the ketone solvent (C3), and the hydrocarbon solvent (C1) is preferably (C2 + C3):(C1) = 5:95 to 95:5, more preferably 10:90 to 92:8, and further preferably 15:85 to 90:10.

[0070] In the coating composition of the present invention, as the solvent (C), an alcohol-based solvent (C4) may also be contained. Since the alcohol-based solvent (C4) has a high polarity, the effects of viscosity adjustment and thickening inhibition are better, and excellent storage stability of the coating composition can be exhibited. In addition, the solid content concentration can be increased, which can contribute to the reduction of the solvent usage amount. Examples of the alcohol-based solvent (C4) include: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, etc. In 100% by mass of the solvent (C), the content of the alcohol-based solvent (C4) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still preferably 5% by mass or less, and more preferably 3% by mass or less.

[0071] Relative to the total amount of 100 parts by mass of the modified polyolefin (A) and the (meth)acrylic resin (B), the content of the alcohol-based solvent (C4) is preferably 1 part by mass or more, more preferably 5 parts by mass or more. In addition, it is still preferably 50 parts by mass or less, and more preferably 30 parts by mass or less.

[0072] <Pigment> The coating composition of the present invention may contain a pigment. As the pigment, for example, a coloring pigment, a extender pigment, a conductive pigment, etc. can be used.

[0073] Examples of the coloring pigment include: titanium oxide, carbon black, chrome yellow, loess, Hansa yellow, pigment yellow, chrome orange, permanent orange, permanent red, fast violet, methyl violet lake, navy blue, cobalt blue, phthalocyanine blue, pigment green, naphthol green, aluminum paste, etc. These can be used alone or in combination of two or more.

[0074] Examples of the extender pigment include: barium sulfate, talc, silica, calcium carbonate, etc. These can be used alone or in combination of two or more.

[0075] As the conductive pigment, if it can impart conductivity to the coating film, there is no particular limitation, and any shape of particulate, flaky, fibrous (including whisker) can be used. Examples of the conductive pigment include: conductive carbon, carbon nanotubes, carbon nanofibers, tin oxide doped with silver, nickel, copper, graphite, aluminum, antimony, tin oxide doped with phosphorus, needle-like titanium oxide with a surface coated with tin oxide / antimony, antimony oxide, zinc antimonate, indium tin oxide, etc. These can be used alone or in combination of two or more.

[0076] When the coating composition of the present invention contains a pigment, its content is preferably 50 to 700 parts by mass, more preferably 75 to 350 parts by mass, based on 100 parts by mass of the modified polyolefin (A).

[0077] <(Solvent-based) Coating Composition> The coating composition of the present invention is composed of a modified polyvinyl chloride (A) and a (meth)acrylic resin (B), and the coating composition of the present invention can be provided by dilution as needed.

[0078] Within the range that does not impair the effects of the present invention, the coating composition proposed in the present invention may also contain an alkyd resin, a polyurethane resin, a tackifier, etc. These can also be all manufactured from biomass-derived raw materials.

[0079] The coating composition of the present invention is preferably a solvent-based coating composition in essence. As the solvent (C), it is preferred to contain a hydrocarbon solvent (C1) and an alcohol solvent (C4), and further contain at least one of an ester solvent (C2) and a ketone solvent (C3). When the total solvent in the coating composition is 100% by mass, the total of the hydrocarbon solvent (C1), the ester solvent (C2), the ketone solvent (C3), and the alcohol solvent (C4) is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, and it has no influence even if it is 100% by mass. When it is essentially a solvent-based coating composition, it is easy to exhibit excellent water resistance and high-pressure car wash resistance.

[0080] The viscosity during coating of the above coating composition is not particularly limited, and it is preferably in the range of 10 to 300 mPa·sec, more preferably in the range of 15 to 200 mPa·sec. At this time, it is more suitable from the viewpoints of good coating processability and the appearance of the finished product.

[0081] The coating composition of the present invention may also contain a curing agent within the range that does not impair the effects of the present invention. As the curing agent, a blocked isocyanate or an epoxy-based curing agent is preferred. For the blocked isocyanate, it can be made into a one-component coating composition by previously masking the isocyanate group with a blocking agent, and it can be heat-cured when the coating film is formed.

[0082] <Primer> The coating composition of the present invention can be used as a primer for coating the surface of a polyolefin substrate. As the polyolefin substrate, it can be a well-known polyolefin substrate such as polypropylene, polyethylene, ethylene-propylene copolymer, etc., and a polypropylene substrate is preferred. The coating composition of the present invention can be used as a primer for coating the surface of a polar substrate. As the polar substrate, for example, well-known plastic-based polar substrates such as ABS and polycarbonate can be cited, and an ABS substrate is preferred. Examples of the coated article obtained from the coating composition of the present invention include: structures, metal products, plastic products, rubber products, etc. More specifically, examples include: automotive outer panels, automotive parts (such as parts of the vehicle body, bumpers, spoilers, rearview mirrors, wheels, fenders, radiator grilles, interior materials, etc., parts of various materials), etc. The coating composition of the present invention can be used as a colored or colorless clear paint, or can be made into a colored paint. In addition, a top coat can be further formed in advance on the coating film composed of the coating composition of the present invention. Examples of the top coat include acrylic resins and the like. As a method of further forming a top coat on the coating film composed of the coating composition of the present invention, for example, there is a method of top-coating a primer on the entire surface or a part of the substrate, starting from placing the coating film at an appropriate room temperature or starting from heating and then drying or curing it, and then coating the top coat, etc. The coating method of the coating composition of the present invention is not particularly limited, and known methods such as brush coating, spraying, dipping, etc. can be used. <Examples>

[0083] Hereinafter, the present invention will be specifically described based on examples, and the present invention is not limited to these examples. "Parts" that exist alone in the examples or comparative examples represent parts by mass. In addition, the measurement / evaluation methods used in the present invention are as described below.

[0084] Measurement method <Measurement of acid value of modified polyolefin (A)> The acid value (mgKOH / g) of the modified polyolefin (A) in the present invention is a value calculated according to the following formula using FT-IR (manufactured by Shimadzu Corporation, FT-IR8200PC), with the coefficient (f) obtained from the calibration curve made from the chloroform solution of maleic anhydride (manufactured by Tokyo Chemical Industry) and the absorbance (I) of the stretching peak (1780 cm-1) of the carbonyl group (C=O) of succinic anhydride in the acid-modified polyolefin solution. Acid value (mgKOH / g) = [Absorbance (I) × (f) × 2 × Molecular weight of potassium hydroxide × 1000 (mg) / Molecular weight of succinic anhydride] Molecular weight of succinic anhydride: 100.07 Molecular weight of potassium hydroxide: 56.11

[0085] <Measurement of weight-average molecular weight (Mw) of modified polyolefin (A) and (meth)acrylic resin (B)> The weight-average molecular weights of the modified polyolefin (A) and the (meth)acrylic resin (B) in the present invention are the values measured by a gel permeation chromatograph Alliance e2695 manufactured by Waters K.K. Japan (hereinafter referred to as GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, chromatographic column: Shodex KF-806 + KF-803, column temperature: 40 °C, flow rate: 1.0 ml / minute, detector: photodiode array detector (wavelength 254 nm = ultraviolet light)).

[0086] <Measurement of Tm and Tg of Modified Polyolefin (A)> The measurement of Tm and Tg according to DSC in the present invention are the values measured according to JIS K7121-2012. Using a DSC measuring device (manufactured by Seiko Instruments Inc.), after maintaining and heating about 5 mg of the sample in a molten state at 150 °C for 10 minutes, cooling is carried out at a rate of 10 °C / minute, and after stably maintaining at -50 °C, further heating is carried out at a rate of 10 °C / minute to 150 °C, and the melting peak temperature is measured to obtain the values of Tm and Tg. Here, Tg refers to the midpoint glass transition temperature.

[0087] <Chlorine Content of Modified Polyolefin (A)> The chlorine content of the acid-modified chlorinated polyolefin (a2) can be measured by titration according to JIS K-7229-1995.

[0088] <Production Example of Acid-Modified Polyolefin (A-1)> Add 100 parts by mass of a propylene-butene copolymer (76 mol% propylene component and 24 mol% 1-butene component) polymerized by a metallocene catalyst, 150 parts by mass of toluene, 4 parts by mass of maleic anhydride, and 10 parts by mass of di-tert-butyl peroxide to a 1 L autoclave, and react at 140 °C for 3 hours. Then, it is injected into a container filled with a large amount of methyl ethyl ketone to precipitate the resin. After that, unreacted substances, etc. are removed by centrifugation to obtain a maleic anhydride-grafted acid-modified propylene / 1-butene copolymer. Then, it is dried under reduced pressure at 50 °C for 5 hours to obtain an acid-modified propylene-butene copolymer (acid value 6 mgKOH / g, weight-average molecular weight 30,000, Tm 70 °C, Tg -20 °C). The acid-modified polyolefin synthesized by this production example is designated as A-1.

[0089] Except that the di-tert-butyl peroxide is changed to 6 parts by mass, the operation is carried out in the same manner as in Production Example 1 to obtain an acid-modified propylene / 1-butene copolymer (acid value 6 mgKOH / g, weight-average molecular weight 160,000, Tm 70 °C, Tg -20 °C). The acid-modified polyolefin synthesized by this production example is designated as A-2.

[0090] Except for changing the charged amount of maleic anhydride to 38 parts by mass, by operating in the same manner as in Production Example 1, an acid-modified propylene / 1-butene copolymer (acid value: 36 mgKOH / g, weight-average molecular weight: 30,000, Tm: 70°C, Tg: -20°C) was obtained. The acid-modified polyolefin synthesized by this production example was designated as A-3.

[0091] Except for changing the charged amount of maleic anhydride to 38 parts by mass and changing di-tert-butyl peroxide to 5 parts by mass, by operating in the same manner as in Production Example 1, an acid-modified propylene / 1-butene copolymer (acid value: 36 mgKOH / g, weight-average molecular weight: 160,000, Tm: 70°C, Tg: -20°C) was obtained. The acid-modified polyolefin synthesized by this production example was designated as A-4.

[0092] <Production Example of Acid-Modified Chlorinated Polyolefin (A-5)> To a 1 L autoclave equipped with a stirrer, 100 parts by mass of a propylene-ethylene copolymer (98 mol% propylene component and 2 mol% ethylene component), 150 parts by mass of toluene, 10 parts by mass of maleic anhydride, and 4 parts by mass of di-tert-butyl peroxide were added. After heating to 140°C, stirring was further continued for 3 hours. Thereafter, the resulting reaction solution was cooled and then poured into a container filled with a large amount of methyl ethyl ketone to precipitate the resin. Thereafter, unreacted substances and the like were removed by centrifugation to obtain a maleic anhydride-grafted acid-modified propylene-ethylene copolymer. Thereafter, by drying under reduced pressure at 70°C for 5 hours, a maleic anhydride-modified propylene-ethylene copolymer was obtained. Thereafter, 100 parts by mass of the maleic anhydride-modified propylene-ethylene copolymer and 1700 parts by mass of chloroform were charged into a 2 L glass-lined reaction kettle and sealed. While stirring the liquid in the reaction kettle, heating was carried out, and dissolution was carried out at a kettle internal temperature of 120°C for 1 hour. After cooling the kettle internal temperature to 110°C, 0.5 part by mass of tert-butyl 2-ethylhexanoate peroxide was added, and 70 parts by mass of chlorine gas was introduced. The kettle internal temperature was cooled to 60°C, and 1400 parts by mass of chloroform was distilled off. Thereafter, by drying, a maleic anhydride-modified chlorinated propylene-ethylene copolymer (A-5, acid value: 15 mgKOH / g, chlorine content: 20% by mass, weight-average molecular weight: 90,000, Tm: 70°C, Tg: 5°C) was obtained.

[0093] <Preparation Example of Modified Polyolefin Solution> To a 1000 ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer, 280 parts by mass of cyclohexane and 120 parts by mass of xylene relative to 100 parts by mass of A-1 were charged. While stirring, the temperature was raised to 70°C, and by stirring for 1 hour, a 20% by mass solid content solution of A-1 was obtained.

[0094] Solutions of A-2 to A-5 were obtained by dissolving A-2 to A-5 in the same manner as the A-1 solution.

[0095] Into a 1000 ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer, 280 parts by mass of cyclohexane and 120 parts by mass of xylene were charged relative to 100 parts by mass of a modified polyolefin (copolymer of ethylene, ethyl acrylate, and maleic anhydride, acid value 15 mgKOH / g-resin, weight-average molecular weight 100,000, Tm 60 °C, Tg -40 °C). While stirring, the temperature was raised to 70 °C, and by stirring for 1 hour, an A-6 solution was obtained.

[0096] <Production Example of (Meth)acrylic Resin (B-1)> First, a mixed solution composed of 10 parts by mass of 2-ethoxyethyl methacrylate (EEMA), 45 parts by mass of 2-ethylhexyl methacrylate (EHMA), 34 parts by mass of isobornyl methacrylate (IBOMA), 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 0.1 part by mass of trimethylolpropane trimethacrylate (TMPMA), 1 part by mass of methacrylic acid (MAA), 3 parts by mass of α-methylstyrene dimer, 4.5 parts by mass of PERBUTYL O as a polymerization initiator, and 36.5 parts by mass of butyl acetate (BA) as a solvent was prepared. Next, 113.5 parts by mass of butyl acetate (BA) was charged into a 500 ml four-necked flask equipped with a water-cooled reflux condenser and a stirrer, and degassed thoroughly with nitrogen. The internal temperature was raised to 90 °C. Then, the prepared mixed solution was dropped through a dropping funnel for 3 hours for polymerization. After the dropping was completed, by further heating and curing for 5 hours, a (meth)acrylic resin B-1 with a solid content of 40% (hydroxyl value 43 mgKOH / g, acid value 6.5 mgKOH / g, Tg 40 °C, weight-average molecular weight 12,000) was prepared.

[0097] Except that the radically polymerizable compounds and solvents were changed as shown in Table 1, (meth)acrylic resins B-2 to B-18 were prepared in the same manner. In addition, 2-methoxyethyl methacrylate was denoted as MEMA, 1,6-hexanediol dimethacrylate was denoted as HDOMA, and xylene was denoted as XL.

[0098] [Table 1]

[0099] <Coating Composition> The coating composition as shown in Example 1 was prepared as follows. 40 parts by mass of xylene was added to 500 parts by mass of Solution A-1 (100 parts by mass of A-1), and further pigments in the mass ratios shown in Table 2 were added until the evaluation by a grindometer became 10 μm or less, and a pigment dispersion was prepared by dispersion using a bead mill. To this pigment dispersion, Solution B-2 was added until the (meth)acrylic resin B-2 became 100 parts by mass, and then a solvent of cyclohexane, methyl ethyl ketone, and butyl acetate was mixed until the ratio shown in Table 2, to obtain the coating composition as shown in Example 1.

[0100] According to the method as shown in Example 1, the coating compositions as shown in Examples 2 to 21 were prepared by mixing the components shown in Tables 2 and 3. An ester-based solvent (C2), a ketone-based solvent (C3), and an alcohol-based solvent (C4) were added to the pigment dispersion.

[0101] According to the method as shown in Example 1, the coating compositions as shown in Comparative Examples 1 to 5 were prepared by mixing the components shown in Table 3. An ester-based solvent (C2), a ketone-based solvent (C3), and an alcohol-based solvent (C4) were added to the pigment dispersion.

[0102] Evaluation method <Coating stability test> Regarding the coating stability of the coating composition prepared according to the example or comparative example, the following items were evaluated.

[0103] The viscosity (flow time) of the coating composition prepared in the example or comparative example was measured using a Ford cup (No. 4, 25 °C). The coating composition was allowed to stand at -5 °C and 50 °C for 10 days, and the appearance and viscosity of the coating composition were evaluated. Evaluation criteria A: No particles or gelation, and the increase in the flow time (viscosity increase) was within 1 second compared to the viscosity before the test. B: No particles or gelation, and the increase in the flow time (viscosity increase) exceeded 1 second and was within 5 seconds compared to the viscosity before the test. C: Although there were no particles or gelation, the increase in the flow time (viscosity increase) exceeded 5 seconds compared to the viscosity before the test. D: Particles or gelation occurred, and the increase in the flow time (viscosity increase) exceeded 5 seconds compared to the viscosity before the test.

[0104] Production of test coated plates With respect to 100 parts by mass of the coating composition obtained in the examples or comparative examples, the solvent composition during coating was prepared by mixing 30 parts by mass of xylene and 30 parts by mass of toluene. Hereinafter, the prepared coating composition is referred to as a diluted coating composition.

[0105] A polypropylene (PP) substrate (10 cm × 10 cm) or an ABS substrate (10 cm × 10 cm) was degreased with isopropanol as a test panel. The above-prepared diluted coating composition was spray-coated on the test panel to a dry film thickness of 10 μm. On the diluted coating composition layer of the above test panel, as a colored primer, Retan (registered trademark) PG white (trade name, manufactured by Kansai Paint Co., Ltd.) was spray-coated to a dry film thickness of 50 μm. Thereafter, it was heated in an oven at 80 °C for 30 minutes to obtain a test coated panel having a laminated coating film. Using this test coated panel, various coating film performance tests shown below were carried out.

[0106] <Coating film performance test> Regarding the test coated panel prepared as described above, evaluation tests were carried out for the following items.

[0107] (1) Initial adhesion On the coated surfaces of each test coated panel of the PP substrate and the ABS substrate, cuts were made with a knife until reaching the substrate, and 100 squares of 1 mm × 1 mm in size were cut out. A transparent adhesive tape was attached to its surface, and the operation of quickly peeling off the tape at 20 °C and replacing it with a new tape and peeling it off again was repeated a total of 3 times, and the evaluation was carried out according to the following criteria. Evaluation criteria A: No peeling occurred even after repeating 5 times. B: Peeling occurred at the 5th time. C: Peeling occurred at the 4th time. D: Peeling occurred at the 1st - 3rd time.

[0108] (2) Water resistance After each test coated panel of the PP substrate and the ABS substrate was left standing in an atmosphere of 25 °C for 36 hours, it was immersed in warm water at 40 °C for 10 days. After confirming the change in the coating film, the adhesion evaluation was carried out according to the method shown in (1), and the evaluation was carried out according to the following criteria. A: The appearance was completely unchanged, and no peeling occurred even after repeating 5 times. B: The appearance was completely unchanged, but peeling occurred at the 5th time. C: The appearance was completely unchanged, but peeling occurred at the 4th time. D: Foaming occurred, and peeling occurred at the 1st - 3rd time.

[0109] (3) Gasohol resistance (chemical resistance) At 20°C, each test coated plate of the PP substrate was immersed in a test solution with a gasoline / ethanol weight ratio of 90 / 10, and the coated surface state of swelling and peeling after 120 minutes was observed and evaluated according to the following criteria. Evaluation Criteria A: Completely no abnormality. B: Swelling with a diameter less than 1 mm or peeling with a diameter less than 1 mm occurs. C: Swelling with a diameter of 1 mm or more and less than 3 mm or peeling with a diameter of 1 mm or more and less than 3 mm occurs. D: Swelling with a diameter of 3 mm or more or peeling with a diameter of 3 mm or more occurs.

[0110] (4) High-pressure car wash resistance test (high-pressure cleaning resistance) Using a cutter, incisions were made on the painted surface of each test coated plate of the PP substrate until reaching the substrate, and 100 squares with a size of 1 mm × 1 mm were cut out. The distance between the coated plate and the spray nozzle was 10 cm, the angle was 90°, and the coated plate was placed in such a way that the sprayed water was directly facing the crosscut part. At this time, warm water with a water temperature of 80°C and a water pressure of 80 bar was continuously sprayed for 1 minute. The state of the coating film after spraying was observed and evaluated according to the following criteria. A: Completely no peeling. B: Less than 1% of the coating film on the coated plate peeled off. C: 1% or more and less than 10% of the coating film on the coated plate peeled off. D: 10% or more of the coating film on the coated plate peeled off.

[0111] (5) Oil immersion resistance test Based on the test alcohol-added fuel liquid specified in ISO1817, a test solution was prepared. The test solution contained 25.35% by mass of 2,2,4-trimethylpentane, 42.25% by mass of toluene, 12.68% by mass of diisobutene, 15.0% by mass of methanol, 4.22% by mass of ethanol, 0.5% by mass of water, and 20 ppm of formic acid. Using a cutter, incisions were made on the test coated plate until reaching the substrate, and 100 squares with a size of 1 mm × 1 mm were cut out. It was immersed in this test solution at 25°C for 120 minutes, and then the coated surface state of swelling and peeling of the coating film was observed and evaluated according to the following criteria. Evaluation Criteria A: Completely no peeling. B: One or more and less than 5 peelings or swellings occur. C: Five or more and less than 10 peelings or swellings occur. D: Ten or more peelings or swellings occur.

[0112] In each of the examples and comparative examples, the results of the evaluation tests conducted according to the above coating stability test and film properties test are shown in Tables 2 and 3 below. The numerical values of the modified polyolefin (A) and (meth)acrylic resin (B) in Tables 2 and 3 are values converted to solid content.

[0113] [Table 2]

[0114] [Table 3]

[0115] As shown in Tables 2 and 3, it is known that the coating compositions prepared in Examples 1 to 21 exhibit good adhesion to polyolefin substrates and ABS substrates, have excellent storage stability, and have excellent high-pressure wash resistance, ethanol gasoline resistance, and oil immersion resistance of the films formed on non-polar substrates. For the coating composition prepared in Comparative Example 1, since the (meth)acrylic resin does not have a hydroxyl group and an acid value and does not contain a polyfunctional (meth)acrylate, the crosslinking points of the film are few, and the adhesion to the ABS substrate is generally poor, and the high-pressure wash resistance and oil immersion resistance are poor. For the coating composition prepared in Comparative Example 2, since the Tg of the (meth)acrylic resin is lower than 0 °C, the water resistance and oil immersion resistance are slightly poor, and the ethanol gasoline resistance and high-pressure wash resistance are poor. For the coating composition prepared in Comparative Example 3, since the (meth)acrylic resin does not contain a polyfunctional (meth)acrylate, the oil immersion resistance is poor. For the coating composition prepared in Comparative Example 4, since the hydroxyl value of the (meth)acrylic resin exceeds 150 mgKOH / g, the water resistance and coating stability are poor. For the coating composition prepared in Comparative Example 5, since the Tg of the modified polyolefin is lower than -30 °C, the film properties and coating stability are both poor.

[0116] The present invention provides an invention in the following manner. [1] A coating composition, characterized by containing a modified polyolefin (A) and a (meth)acrylic resin (B), wherein the glass transition temperature of the modified polyolefin (A) is -30 °C or higher, the (meth)acrylic resin (B) contains a polymer of a radically polymerizable compound (b1), and the radically polymerizable compound (b1) contains a polyfunctional (meth)acrylate, the glass transition temperature of the (meth)acrylic resin (B) is 0 °C or higher, the hydroxyl value of the (meth)acrylic resin (B) is 5 to 150 mgKOH / g. [2] The coating composition according to [1], wherein the polyfunctional (meth)acrylate is bifunctional and / or trifunctional. [3] The coating composition according to [1] or [2], wherein the content of the polyfunctional (meth)acrylate in the radically polymerizable compound (b1) is 0.1 to 5% by mass. [4] The coating composition according to any one of [1] to [3], wherein the radically polymerizable compound (b1) constituting the (meth)acrylic resin (B) includes at least one of a (meth)acrylate having an alkoxymethyl group and a (meth)acrylate having an alkoxyethyl group. [5] The coating composition according to any one of [1] to [4], wherein the content of the (meth)acrylate having an alkoxymethyl group and the (meth)acrylate having an alkoxyethyl group in the radically polymerizable compound (b1) is 1 to 55% by mass. [6] The coating composition according to any one of [1] to [5], wherein the acid value of the (meth)acrylic resin (B) is 0.1 to 30 mgKOH / g. [7] The coating composition according to any one of [1] to [6], characterized in that the modified polyolefin (A) includes at least one of an acid-modified polyolefin (a1) and an acid-modified chlorinated polyolefin (a2). [8] The coating composition according to any one of [1] to [7], wherein the acid value of the modified polyolefin (A) is 4 to 40 mgKOH / g. [9] The coating composition according to any one of [1] to [8], wherein the weight average molecular weight of the modified polyolefin (A) is 20,000 to 180,000.

[10] The coating composition according to any one of [1] to [9], wherein the content of the (meth)acrylic resin (B) is 25 to 900 parts by mass with respect to 100 parts by mass of the modified polyolefin (A).

[11] The coating composition according to any one of [1] to

[10] , which contains a solvent (C), and the solvent (C) contains a hydrocarbon solvent (C1), and 200 to 3000 parts by mass of the hydrocarbon solvent (C1) is contained with respect to 100 parts by mass of the modified polyolefin (A).

[12] The coating composition according to any one of [1] to

[11] , which contains a solvent (C), and the solvent (C) contains a hydrocarbon solvent (C1), and further contains at least one of an ester solvent (C2) and a ketone solvent (C3).

[13] The coating composition according to

[11] or

[12] , wherein the solvent (C) further contains an alcohol solvent (C4).

[14] An undercoat for a polyolefin substrate, which contains the coating composition described in any one of [1] to

[13] .

[15] An undercoat for an ABS substrate, which contains the coating composition described in any one of [1] to

[13] .

Claims

1. A coating composition, characterized in that, Containing a modified polyolefin (A) and a (meth)acrylic resin (B), The glass transition temperature of the modified polyolefin (A) is -30°C or higher. The (meth)acrylic resin (B) contains a polymer of a radically polymerizable compound (b1), and the radically polymerizable compound (b1) includes a polyfunctional (meth)acrylate. The glass transition temperature of the (meth)acrylic resin (B) is 0°C or higher. The hydroxyl value of the (meth)acrylic resin (B) is 5 to 150 mgKOH / g.

2. The coating composition according to claim 1, wherein the polyfunctional (meth)acrylate is bifunctional and / or trifunctional.

3. The coating composition according to claim 1, wherein the content of the polyfunctional (meth)acrylate in the radically polymerizable compound (b1) is 0.1 to 5% by mass.

4. The coating composition according to claim 1, wherein the radically polymerizable compound (b1) constituting the (meth)acrylic resin (B) contains at least one of a (meth)acrylate having an alkoxymethyl group and a (meth)acrylate having an alkoxyethyl group.

5. The coating composition according to claim 1, wherein the content of the (meth)acrylate having an alkoxymethyl group and the (meth)acrylate having an alkoxyethyl group in the radically polymerizable compound (b1) is 1 to 55% by mass.

6. The coating composition according to claim 1, wherein the acid value of the (meth)acrylic resin (B) is 0.1 to 30 mgKOH / g.

7. The coating composition according to claim 1, characterized in that, The modified polyolefin (A) includes at least one of an acid-modified polyolefin (a1) and an acid-modified chlorinated polyolefin (a2).

8. The coating composition according to claim 1, wherein the acid value of the modified polyolefin (A) is 4 to 40 mgKOH / g.

9. The coating composition according to claim 1, wherein the weight average molecular weight of the modified polyolefin (A) is 20,000 to 180,000.

10. The coating composition according to claim 1, wherein the content of the (meth)acrylic resin (B) relative to 100 parts by mass of the modified polyolefin (A) is 25 to 900 parts by mass.

11. The coating composition according to claim 1, which contains a solvent (C), and the solvent (C) contains a hydrocarbon solvent (C1), and relative to 100 parts by mass of the modified polyolefin (A), it contains 200 to 3000 parts by mass of the hydrocarbon solvent (C1).

12. The coating composition according to claim 1, which contains a solvent (C), and the solvent (C) contains a hydrocarbon solvent (C1), and further contains at least one of an ester solvent (C2) and a ketone solvent (C3).

13. The coating composition according to claim 11, wherein the solvent (C) further contains an alcohol solvent (C4).

14. An undercoat for a polyolefin substrate, which contains the coating composition according to any one of claims 1 to 13.

15. An undercoat for an ABS substrate, which contains the coating composition according to any one of claims 1 to 13.

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