Peelable coating composition and multilayer coating film formation method

Abstract

To provide a peelable coating composition which enables formation of a coating film that is excellent in adhesion to a base material and peelability after thermal loading.SOLUTION: A peelable coating composition contains (A) a crystalline polyester resin, wherein a maximum value of a phase difference between a stress curve and a strain curve at a temperature of 80 to 150°C, which is determined by dynamic viscoelasticity measurement under the conditions of a temperature rise rate of 10°C / min and a frequency of 1 Hz, is 45° or more. The peelable coating composition has a minimum value of complex viscosity at a temperature of 80 to 150°C, which is determined by dynamic viscoelasticity measurement under the conditions of a temperature rise rate of 10°C / min and a frequency of 1 Hz, of 10,000 Pa s or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a peelable coating composition and a method for forming a multi-layer coating film. [Background technology]

[0002] Forming a peelable coating film as a protective coating on the surface of vehicles such as automobiles and trains makes it easier to remove the coating film from substrates such as aluminum materials and resin members, making it possible to repaint deteriorated coating films or reduce the impurity concentration when recycling substrates.

[0003] For example, a vehicle can be protected and decorated by applying a peelable coating composition to the surface of the vehicle and then applying a colored coating and / or a clear coating thereon. In addition, when repainting or recycling of the substrate is desired, the peelable coating film can be removed for recycling.

[0004] The peelable coating film is required to have properties that make it difficult to peel off during normal use, yet can be easily peeled off when desired.

[0005] Patent Document 1 describes that an adhesive composition comprising a tacky polymer and at least one crystalline polymer selected from the group consisting of crystalline polycarbonate and 1,9-nonanediol-containing crystalline polyester polyol can provide a heat-peelable, heat-activated adhesive that maintains or improves a relatively high adhesive strength over a long period of time and has improved reliability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication 2003-213237 Summary of the Invention [Problem to be solved by the invention]

[0007] In the technique described in Patent Document 1, although the adhesive composition obtained has excellent long-term adhesive strength, the peelability after thermal loading is sometimes insufficient.

[0008] An object of the present invention is to provide a peelable coating composition that can form a coating film that has excellent adhesion to a substrate and excellent peelability after thermal loading. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned object can be achieved by a peelable coating composition containing a crystalline polyester resin (A), which has a maximum phase difference of 45° or more between the stress curve and the strain curve within a temperature range of 80 to 150°C, as determined by dynamic viscoelasticity measurement at a heating rate of 10°C / min and a frequency of 1 Hz.

[0010] That is, the present invention provides the following <1> ~ <5> It is related to. <1> (A) A peelable coating composition comprising a crystalline polyester resin, A peelable coating composition in which the maximum phase difference between the stress curve and the strain curve within a temperature range of 80 to 150°C is 45° or more, as determined by dynamic viscoelasticity measurement at a heating rate of 10°C / min and a frequency of 1 Hz. <2> The minimum complex viscosity within the temperature range of 80 to 150°C, as determined by dynamic viscoelasticity measurement at a heating rate of 10°C / min and a frequency of 1Hz, is 10,000 Pa·s or less. <1> The peelable coating composition according to claim 1. <3> Step (I-1): Applying a coating to the object to be coated <1> or <2> a step of applying the peelable coating composition according to claim 1 to form a peelable coating film; Step (I-2): A method for forming a multilayer coating film, comprising the step of applying a colored coating composition onto the peelable coating film formed in step (I-1) to form an uncured colored coating film. <4> Step (II-1): Applying a coating to the object to be coated <1> or <2> a step of applying the peelable coating composition according to claim 1 to form a peelable coating film; Step (II-2): A method for forming a multilayer coating film, comprising the step of applying a clear coat paint composition onto the peelable coating film formed in step (II-1) to form an uncured clear coat coating film. <5> The peelable coating film can be peeled from the substrate by heating at a temperature in the range of 80 to 150°C. <3> or <4> The method for forming a multilayer coating film according to claim 1. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a peelable coating composition that can form a coating film that has excellent adhesion to a substrate and excellent peelability after thermal loading. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below, but these are examples of preferred embodiments, and the present invention is not limited to these details.

[0013] [Removable coating composition] The peelable coating composition of the present invention is a peelable coating composition containing a crystalline polyester resin (A), and is a peelable coating composition in which the maximum phase difference between the stress curve and the strain curve within a temperature range of 80 to 150°C is 45° or more, as determined by dynamic viscoelasticity measurement at a heating rate of 10°C / min and a frequency of 1 Hz.

[0014] In this specification, the phase difference between the stress curve and the strain curve within a temperature range of 80 to 150°C, which is determined by dynamic viscoelasticity measurement, can be measured, for example, using a rheometer having a temperature control mechanism that can adjust the temperature of the measurement section within a range of -70 to 200°C, according to the following measurement procedures (1) to (4). (1) The paint is dried and filled into a molding die to form pellets with a diameter of 10 mm and a thickness of 0.5 mm. (2) The pellet is placed on a parallel plate connected to a measuring device. (3) The measuring section is heated to 200°C, cooled to 50°C and kept constant for 1 hour to crystallize the crystalline polyester in the coating composition. (4) Then, the sample is cooled to -70°C, and dynamic viscoelasticity measurement is started at a frequency of 1 Hz. The temperature dependency of dynamic viscoelasticity is measured while the temperature is increased to 200°C at a rate of 10°C / min.

[0015] From the viewpoint of the releasability of the coating film formed after thermal loading, the peelable coating composition of this embodiment has a maximum phase difference between the stress curve and the strain curve in the temperature range of 80 to 150°C, as determined by dynamic viscoelasticity measurement at a temperature rise rate of 10°C / min and a frequency of 1 Hz, of 45° or more, preferably in the range of 80 to 90°, and more preferably in the range of 85 to 90°.

[0016] Furthermore, from the viewpoint of the releasability of the coating film formed after thermal loading, the strippable coating composition of the present invention preferably has a minimum complex viscosity of 10,000 Pa·s or less, more preferably 10 to 10,000 Pa·s, and even more preferably 10 to 1000 Pa·s, within a temperature range of 80 to 150°C, as determined by dynamic viscoelasticity measurement at a heating rate of 10°C / min and a frequency of 1 Hz.

[0017] The complex viscosity in the temperature range of 80 to 150° C. in this specification can be measured using a rheometer, in the same way as the phase difference between the stress curve and the strain curve obtained from the dynamic viscoelasticity measurement.

[0018] The complex viscosity in the temperature range of 80 to 150° C. in this specification can be measured by the same measurement procedure as the measurement procedure for the phase difference between the stress curve and the strain curve obtained from the dynamic viscoelasticity measurement.

[0019] [Crystalline polyester resin (A)] The crystalline polyester resin (A) can usually be produced by an esterification reaction or transesterification reaction between an acid component and an alcohol component. The term "crystalline" means that the resin exhibits a clear melting point when measured with a differential scanning calorimeter.

[0020] The acid component may be any compound that is commonly used as an acid component in the production of polyester resins, such as an aliphatic polybasic acid, an alicyclic polybasic acid, or an aromatic polybasic acid.

[0021] The aliphatic polybasic acids are generally aliphatic compounds having two or more carboxyl groups per molecule, acid anhydrides of the aliphatic compounds, and esters of the aliphatic compounds. Examples of the aliphatic polybasic acids include aliphatic polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid, citric acid, and butanetetracarboxylic acid; anhydrides of the aliphatic polycarboxylic acids; and esters of the aliphatic polycarboxylic acids with lower alkyls having about 1 to 4 carbon atoms. The aliphatic polybasic acids can be used alone or in combination of two or more.

[0022] The alicyclic polybasic acids are generally compounds having one or more alicyclic structures and two or more carboxyl groups per molecule, acid anhydrides of the compounds, and esters of the compounds. The alicyclic structures are mainly 4- to 6-membered ring structures. Examples of the alicyclic polybasic acids include alicyclic polycarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 1,3,5-cyclohexanetricarboxylic acid; anhydrides of the alicyclic polycarboxylic acids; and esters of the alicyclic polycarboxylic acids with lower alkyls having about 1 to 4 carbon atoms. The alicyclic polybasic acids can be used alone or in combination of two or more.

[0023] The aromatic polybasic acids are generally aromatic compounds having two or more carboxyl groups per molecule, acid anhydrides of the aromatic compounds, and esters of the aromatic compounds, and examples thereof include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, trimellitic acid, and pyromellitic acid; anhydrides of the aromatic polycarboxylic acids; and esters of the aromatic polycarboxylic acids with lower alkyls having about 1 to 4 carbon atoms. The aromatic polybasic acids can be used alone or in combination of two or more.

[0024] Acid components other than the aliphatic polybasic acids, alicyclic polybasic acids, and aromatic polybasic acids may also be used. Examples of such acid components include, but are not limited to, fatty acids such as coconut oil fatty acids, cottonseed oil fatty acids, hempseed oil fatty acids, rice bran oil fatty acids, fish oil fatty acids, tall oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, tung oil fatty acids, rapeseed oil fatty acids, castor oil fatty acids, dehydrated castor oil fatty acids, and safflower oil fatty acids; monocarboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexanoic acid, and 10-phenyloctadecanoic acid; and hydroxycarboxylic acids such as lactic acid, 3-hydroxybutanoic acid, and 3-hydroxy-4-ethoxybenzoic acid. These acid components may be used alone or in combination.

[0025] As the alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be suitably used. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol, 1,6-pentanediol, 1,7-pentanediol, 1,8-pentanediol, 1,9-pentanediol, 2,10-pentanediol, 2,11-pentanediol, 2,12-pentanediol, 2,13-pentanediol, 2,14-pentanediol, 2,15-pentanediol, 2,16-pentanediol, 2,17-pentanediol, 2,18-pentanediol, 2,19-pentanediol, 2,20-pentanediol, 2,21-pentanediol, 2,22-pentanediol, 2,23-pentanediol, 2,24-pentanediol, 2,25-pentanediol, 2,26-pentanediol, 2,27-pentanediol, 2,28-pentanediol, 2,29 ... hexanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol dihydric alcohols such as hydroxypivalic acid neopentyl glycol ester, hydrogenated bisphenol A, hydrogenated bisphenol F, and dimethylolpropionic acid; polylactone diols obtained by adding a lactone compound such as ε-caprolactone to these dihydric alcohols; ester diol compounds such as bis(hydroxyethyl) terephthalate; polyether diol compounds such as alkylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, polybutylene glycol, and polytetramethylene ether glycol; trihydric or higher alcohols such as glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris(2-hydroxyethyl)isocyanuric acid, sorbitol, and mannite; polylactone polyol compounds obtained by adding a lactone compound such as ε-caprolactone to these trihydric or higher alcohols; and fatty acid esters of glycerin.

[0026] Furthermore, alcohol components other than the above polyhydric alcohols can also be used. Examples of such alcohol components include, but are not limited to, monoalcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, stearyl alcohol, and 2-phenoxyethanol; and alcohol compounds obtained by reacting a monoepoxy compound such as propylene oxide, butylene oxide, or "Cardura E10P" (trade name, manufactured by HEXION, a glycidyl ester of synthetic highly branched saturated fatty acid) with an acid.

[0027] The method for producing the polyester resin is not particularly limited, and the polyester resin can be produced according to a conventional method.

[0028] The melting point of the crystalline polyester resin (A) is preferably within a range of 60 to 150°C, more preferably within a range of 70 to 120°C, and even more preferably within a range of 80 to 100°C, from the viewpoints of the adhesion of the coating film to the substrate and the peelability after thermal loading.

[0029] In this specification, the melting point is determined by measuring the calorific value of a 10 mg sample at a heating rate of 20° C. / min using a differential scanning calorimeter.

[0030] As the differential scanning calorimeter, for example, DSC8230 (manufactured by Rigaku Corporation) can be used.

[0031] The number average molecular weight of the crystalline polyester resin (A) is preferably within a range of 10,000 to 100,000, more preferably within a range of 10,000 to 80,000, and even more preferably within a range of 10,000 to 50,000, from the viewpoints of adhesion of the coating film to the substrate and peelability after thermal loading.

[0032] In this specification, the average molecular weight is a value calculated from a chromatogram measured by gel permeation chromatography using the molecular weight of standard polystyrene as a reference. The gel permeation chromatograph used was an "HLC8120GPC" (manufactured by Tosoh Corporation). Four columns were used: "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, trade names). The analysis was performed under the following conditions: mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 mL / min, and detector: RI.

[0033] In the peelable coating composition of this embodiment, the content of the crystalline polyester resin (A) is preferably in the range of 50 to 100 mass %, more preferably in the range of 70 to 100 mass %, and even more preferably in the range of 80 to 100 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoints of adhesion of the coating film to the substrate and peelability after thermal loading.

[0034] In this specification, the term "solid content" refers to non-volatile components such as resins, curing agents, and pigments that remain after drying for 1 hour at 110° C. The solid content can be determined, for example, by weighing a sample into a heat-resistant container such as an aluminum foil cup, spreading the sample on the bottom of the container, drying it for 1 hour at 110° C., and weighing the mass of the components remaining after drying.

[0035] In this specification, the term "solid content concentration" refers to the mass ratio of the solid content in the composition. Therefore, the solid content concentration of the composition can be calculated by, for example, weighing 1.0 g of the composition into a heat-resistant container such as an aluminum foil cup, spreading the composition on the bottom of the container, drying at 110°C for 1 hour, weighing the mass of the components remaining in the composition after drying, and determining the ratio of the mass of the components remaining after drying to the total mass of the composition before drying.

[0036] [Other ingredients] The peelable coating composition of this embodiment may further contain, as necessary, other additives commonly used in the field of coatings, such as resins other than the crystalline polyester resin (A), curing agents, ultraviolet absorbers, light stabilizers, solvents (organic solvents, water), pigments, catalysts, dehydrating agents, antioxidants, surface conditioners, antifoaming agents, emulsifiers, surfactants, antifouling agents, wetting agents, thickeners, dyes, scratch resistance improvers, gloss adjusters, etc.

[0037] Examples of resins other than the crystalline polyester (A) include non-crystalline polyester resins, polyolefin resins, and acrylic resins.

[0038] The amorphous polyester resin can be generally produced by an esterification reaction or a transesterification reaction between an acid component and an alcohol component. The term "amorphous" means that the resin does not exhibit a clear melting point when measured with a differential scanning calorimeter.

[0039] As the acid component, the acid components exemplified for the crystalline polyester resin (A) can be used.

[0040] As the alcohol component, the alcohol components exemplified for the crystalline polyester resin (A) can be used.

[0041] When the peelable coating composition of the present embodiment contains the amorphous polyester resin, the content of the amorphous polyester resin is preferably in the range of 1 to 30 mass %, more preferably in the range of 1 to 20 mass %, and even more preferably in the range of 1 to 10 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoints of adhesion to the substrate and releasability after thermal loading.

[0042] As the acrylic resin, any known acrylic resin that has been conventionally used can be used.

[0043] The acrylic resin can be produced, for example, by copolymerizing polymerizable unsaturated monomers by a method known per se, such as solution polymerization in an organic solvent or emulsion polymerization in water.

[0044] As the polymerizable unsaturated monomer, for example, the following monomers (i) to (xxi) can be used: These polymerizable unsaturated monomers can be used alone or in combination of two or more. (i) Alkyl or cycloalkyl (meth)acrylates: for example, 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, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like. (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc. (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc. (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (v) Aromatic ring-containing polymerizable unsaturated monomers: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, and the like. (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc. (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, and the like. (viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group. (ix) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (x) Carboxyl group-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc. (xi) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, adducts of glycidyl (meth)acrylate with amine compounds, and the like. (xii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (xiii) Epoxy group-containing polymerizable unsaturated monomers: glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, etc. (xiv) (meth)acrylates having a polyoxyethylene chain with an alkoxy group at the molecular terminal. (xv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc. (xvi) Polymerizable unsaturated monomers having a phosphoric acid group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene)glycol (meth)acrylate, acid phosphooxypoly(oxypropylene)glycol (meth)acrylate, etc. (xvii) Polymerizable unsaturated monomers having an ultraviolet-absorbing functional group: 2-hydroxy-4(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, and the like. (xviii) Light-stable polymerizable unsaturated monomers: 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, etc. (xix) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc. (xx) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc. (xxi) Hydroxyl group-containing polymerizable unsaturated monomers: monoesters of (meth)acrylic acid with dihydric alcohols having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid with dihydric alcohols having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and (meth)acrylates having a polyoxyethylene chain terminated with a hydroxyl group. However, monomers that fall under the category of "(xvii) polymerizable unsaturated monomers having an ultraviolet-absorbing functional group" are excluded from the above "hydroxyl group-containing polymerizable unsaturated monomers," even if they have a hydroxyl group.

[0045] When the peelable coating composition of the present embodiment contains the acrylic resin, the content of the acrylic resin is preferably in the range of 1 to 30 mass %, more preferably in the range of 1 to 20 mass %, and even more preferably in the range of 1 to 10 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoints of adhesion to the substrate and removability after thermal loading.

[0046] The polyolefin resin can be either a polyolefin or a modified polyolefin. Examples of polyolefins include polyolefins obtained by (co)polymerizing one or more olefins having 2 to 10 carbon atoms, such as ethylene, propylene, butylene, and hexene. Modified polyolefins include unsaturated carboxylic acid or acid anhydride modified products, acrylic modified products, and chlorinated products of the polyolefins, as well as modified polyolefins obtained by combining these modifications.

[0047] The unsaturated carboxylic acid or acid anhydride-modified polyolefin can be produced, for example, by graft polymerizing an unsaturated carboxylic acid or its acid anhydride onto a polyolefin according to a method known per se. Examples of unsaturated carboxylic acids or their acid anhydrides that can be used for modification include aliphatic carboxylic acids having 3 to 10 carbon atoms and containing at least one, preferably one, polymerizable double bond per molecule. Specific examples include (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, and maleic anhydride. The amount of the unsaturated carboxylic acid or its acid anhydride grafted onto the polyolefin can be varied depending on the desired physical properties of the modified polyolefin, but is generally preferably within the range of 1 to 20 mass%, more preferably 1.5 to 15 mass%, and even more preferably 2 to 10 mass%, based on the solids weight of the polyolefin.

[0048] The acrylic-modified polyolefin can be produced by graft polymerizing at least one acrylic unsaturated monomer onto a polyolefin by a known suitable method. Examples of acrylic unsaturated monomers that can be used for this acrylic modification include C1-C (meth)acrylic acid monomers 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, nonyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. 20 Alkyl esters; C1 to C6 of (meth)acrylic acid such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate 21 Examples include hydroxyalkyl esters; other (meth)acrylic monomers such as (meth)acrylic acid, glycidyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, and further styrene, and these can be used either alone or in combination of two or more.

[0049] Acrylic modification of polyolefins can be carried out, for example, by first reacting an acrylic unsaturated monomer, such as glycidyl (meth)acrylate, that is reactive with the carboxyl groups in the unsaturated carboxylic acid or acid anhydride-modified polyolefin produced as described above to introduce a polymerizable unsaturated group into the polyolefin, and then (co)polymerizing the polymerizable unsaturated group with the acrylic unsaturated monomer, either alone or in combination of two or more. The amount of the acrylic unsaturated monomer used in the acrylic modification of polyolefins can be varied depending on the desired physical properties of the modified polyolefin, but is generally preferably 30% by mass or less, more preferably 0.1 to 20% by mass, and even more preferably 0.15 to 15% by mass, based on the solids weight of the resulting modified polyolefin.

[0050] The chlorinated polyolefin can be produced by chlorinating the polyolefin. The chlorination of the polyolefin can be carried out, for example, by blowing chlorine gas into an organic solvent solution or dispersion of the polyolefin or its modified product, and the reaction temperature is preferably 50 to 120°C. The chlorine content in the chlorinated polyolefin (solid content) can be varied depending on the desired physical properties of the chlorinated polyolefin, but is preferably 35 mass% or less, more preferably 10 to 30 mass%, and even more preferably 12 to 25 mass% based on the solid content weight of the chlorinated polyolefin.

[0051] When the peelable coating composition of the present embodiment contains the polyolefin resin, the content of the polyolefin resin is preferably in the range of 1 to 30 mass %, more preferably in the range of 1 to 20 mass %, and even more preferably in the range of 1 to 10 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoints of adhesion to the substrate and removability after thermal loading.

[0052] The curing agent is a compound capable of reacting with the crosslinkable functional group in the crystalline polyester resin (A) to cure the peelable coating composition. The curing agent can be used alone or in combination of two or more kinds.

[0053] The strippable coating composition of the present invention preferably does not contain the above-mentioned curing agent, from the viewpoint of the strippability of the coating film formed after thermal loading.

[0054] Examples of the curing agent include polyisocyanate compounds, blocked polyisocyanate compounds, polycarbodiimide compounds, amino resins, epoxy group-containing compounds, carboxyl group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds.

[0055] As the ultraviolet absorber, conventionally known ones can be used, for example, benzotriazole-based absorbers, triazine-based absorbers, salicylic acid derivative-based absorbers, benzophenone-based absorbers, etc. The ultraviolet absorber may also have a polymerizable unsaturated group.

[0056] Specific examples of the benzotriazole-based absorbents include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, Examples include 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2-{2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl}benzotriazole, and 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole.

[0057] Specific examples of the triazine-based absorbents include 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-isooctyloxyphenyl)-1,3,5-triazine, 2-[4((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.

[0058] Specific examples of the salicylic acid derivative-based absorbents include phenyl salicylate, p-octylphenyl salicylate, and 4-tert-butylphenyl salicylate.

[0059] Specific examples of the benzophenone-based absorbent include 4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, and naphthalene. Examples include thorium 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 5-chloro-2-hydroxybenzophenone, resorcinol monobenzoate, 2,4-dibenzoylresorcinol, 4,6-dibenzoylresorcinol, hydroxydodecylbenzophenone, and 2,2'-dihydroxy-4(3-methacryloxy-2-hydroxypropoxy)benzophenone.

[0060] Commercially available examples of the ultraviolet absorber include "TINUVIN 1130," "TINUVIN 900," "TINUVIN 928," "TINUVIN 384-2," "TINUVIN 479," "TINUVIN 477," "TINUVIN 405," "TINUVIN 400" (product names manufactured by BASF, TINUVIN is a registered trademark), and "RUVA 93" (product name manufactured by Otsuka Chemical Co., Ltd.).

[0061] When the peelable coating composition of this embodiment contains the above-mentioned ultraviolet absorber, the content of the ultraviolet absorber is preferably in the range of 0.1 to 10 mass %, more preferably in the range of 0.2 to 5.0 mass %, and even more preferably in the range of 0.3 to 3.0 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoint of the weather resistance of the coating film to be formed, etc.

[0062] The light stabilizer is used as a radical chain inhibitor that captures active radical species generated during the deterioration process of the coating film, and examples thereof include light stabilizers of hindered amine compounds.

[0063] Examples of the hindered amine compound include bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(N-methyl-2,2,6,6-tetramethyl-4-piperidinyl)sebacate, 4-benzoyloxy-2,2',6,6'-tetramethylpiperidine, bis(1,2,2,6,6-pentamethyl-4-piperidyl){[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}butylmalonate, Examples of light stabilizers include, but are not limited to, monomeric types such as methyl methyl ether, oligomeric types such as poly{[6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)iminol]}, and polyester bond types such as a polyesterification product of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and succinic acid. Also usable as the light stabilizer are known polymerizable light stabilizers.

[0064] Examples of commercially available light stabilizers include "TINUVIN 123," "TINUVIN 152," "TINUVIN 249," and "TINUVIN 292" (product names manufactured by BASF, TINUVIN is a registered trademark), "HOSTAVIN 3058" (product name manufactured by Clariant, Hostavin is a registered trademark), and "ADK STAB LA-82" (product name manufactured by ADEKA CORPORATION, ADK STAB is a registered trademark).

[0065] When the peelable coating composition of this embodiment contains the above-mentioned light stabilizer, the content of the light stabilizer is preferably in the range of 0.1 to 10 mass %, more preferably in the range of 0.2 to 7.5 mass %, and even more preferably in the range of 0.3 to 5.0 mass %, based on the total resin solid content of the peelable coating composition, from the viewpoint of the weather resistance of the coating film to be formed, etc.

[0066] Examples of the solvent that can be used include organic solvents, water, etc. Examples of the organic solvent include ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as ethyl acetate, butyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate; ether-based solvents such as tetrahydrofuran, dioxane, and dimethoxyethane; glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; aromatic solvents such as toluene, xylene, and "Swasol 1000" (trade name, high-boiling point petroleum solvent, manufactured by Cosmo Oil Co., Ltd.); and aliphatic hydrocarbon-based solvents such as hexane and heptane.

[0067] When the strippable coating composition of this embodiment contains the above-mentioned solvent, the content of the solvent is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 10 to 97 parts by mass, and even more preferably in the range of 15 to 95 parts by mass, based on the total resin solid content of the strippable coating composition.

[0068] Examples of the pigment include luster pigments, color pigments, extender pigments, etc. The pigments can be used alone or in combination of two or more.

[0069] Examples of the above-mentioned bright pigments include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, glass flakes, aluminum oxide, mica, aluminum oxide coated with titanium oxide and / or iron oxide, and mica coated with titanium oxide and / or iron oxide.

[0070] Examples of the color pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments, and heat-shielding pigments.

[0071] Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white.

[0072] When the peelable coating composition of the present embodiment contains the above-mentioned pigment, the content of the pigment is preferably in the range of 0.1 to 40 mass %, more preferably in the range of 0.2 to 30 mass %, and even more preferably in the range of 0.3 to 20 mass %, based on the total resin solid content of the peelable coating composition.

[0073] The optimum viscosity of the strippable coating composition of this embodiment varies depending on the coating composition, but for example, the viscosity after 1 minute at 60 rpm measured with a Brookfield viscometer at a temperature of 20°C (sometimes referred to herein as the "B60 value") is preferably in the range of 100 to 3000 mPa·s, more preferably in the range of 300 to 2000 mPa·s, and even more preferably in the range of 500 to 1500 mPa·s. The viscometer used here is "LVDV-I" (trade name, Brookfield, Brookfield viscometer).

[0074] In addition, in the above, the coating solids concentration of the peelable coating composition of the present invention is usually preferably in the range of 3 to 100 mass%, more preferably in the range of 5 to 80 mass%, and even more preferably in the range of 7 to 50 mass%.

[0075] The peelable coating composition of the present invention may be either a one-component coating or a multi-component coating, but is preferably a one-component coating from the viewpoints of excellent productivity since there is no need for a coating mixing step and simplification of maintenance of coating machines.

[0076] [Multi-layer coating film formation method] The peelable coating composition of the present invention can be used to form a peelable coating film when forming a multilayer coating film containing a peelable coating film and a colored coating film on a substrate. In this case, the coating film formation method can be carried out according to Method I below. <Method I> Step (I-1): A step of applying a peelable coating composition to an object to be coated to form a peelable coating film; Step (I-2): A method for forming a multilayer coating film, comprising the step of applying a colored coating composition onto the peelable coating film formed in step (I-1) to form an uncured colored coating film.

[0077] Examples of substrates include outer and inner panels of automobile bodies such as passenger cars, trucks, motorcycles and buses; automobile parts; and outer panels of household electrical appliances such as mobile phones and audio equipment.

[0078] The material of these substrates is not particularly limited. Examples include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

[0079] The peelable coating composition can be applied to a substrate by a known method, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. Of these, air spray coating and rotary atomization coating are preferred. Furthermore, such coating methods can be carried out in one or several batches until the desired film thickness is obtained.

[0080] The amount of the peelable coating composition to be applied is preferably an amount that results in a coating film having a dry thickness of 1 to 100 μm, more preferably an amount that results in a coating film having a dry thickness of 1 to 80 μm, and even more preferably an amount that results in a coating film having a dry thickness of 1 to 60 μm, from the viewpoints of the adhesion of the coating film to be formed and the peelability after thermal loading.

[0081] After forming the peelable coating film in the step (I-1), the peelable coating film may be further heated and / or air-dried, if necessary, to dry the peelable coating film.

[0082] The heating can be carried out by known means, for example, a drying oven such as a hot air oven, an electric oven, or an infrared induction heating oven. When the heating is carried out, the heating temperature is preferably within the range of 45 to 180°C, more preferably within the range of 50 to 170°C, and even more preferably within the range of 55 to 160°C. The heating time is not particularly limited, but is preferably within the range of 10 to 90 minutes, and more preferably within the range of 20 to 75 minutes.

[0083] The colored coating composition can be a coating prepared by mixing a base resin such as an acrylic resin, polyester resin, alkyd resin, urethane resin, or epoxy resin having a crosslinkable functional group such as a carboxyl group or a hydroxyl group, an amino resin such as a melamine resin or a urea resin, or a curing agent such as an optionally blocked polyisocyanate compound, together with a pigment, a thickener, and other optional components.

[0084] The method for applying the colored coating composition is not particularly limited, but a wet coating film can be formed by, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coating, or other coating methods. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating or rotary atomization coating is particularly preferred. The amount of the colored coating composition applied is usually preferably an amount that results in a cured film thickness of 5 to 40 μm, more preferably an amount that results in a cured film thickness of 7 to 35 μm, and even more preferably an amount that results in a cured film thickness of 10 to 30 μm.

[0085] In <Method I>, after forming the peelable coating film and colored coating film in the steps (I-1) and (I-2), a colored coating film and / or a clear coat coating film different from the colored coating film formed in step (I-2) may be further formed, if necessary.

[0086] In addition, in <Method I>, after forming the peelable coating film and the uncured colored coating film in the steps (I-1) and (I-2), the formed multilayer coating film may be heated, if necessary, to dry and / or cure the peelable coating film and the uncured colored coating film.

[0087] The heating can be carried out by known means, for example, a drying oven such as a hot air oven, an electric oven, or an infrared induction heating oven. When the heating is carried out, the heating temperature is preferably within the range of 45 to 180°C, more preferably within the range of 50 to 170°C, and even more preferably within the range of 55 to 160°C. The heating time is not particularly limited, but is preferably within the range of 10 to 90 minutes, and more preferably within the range of 20 to 75 minutes.

[0088] The peelable coating composition of the present invention can also be used to form a peelable coating film when forming a multilayer coating film containing a peelable coating film and a clear coat coating film on a substrate. In this case, the coating film formation method can be carried out according to Method II below. <Method II> Step (II-1): A step of applying the peelable coating composition according to claim 1 or 2 to a substrate to form a peelable coating film; Step (II-2): A method for forming a multilayer coating film, comprising the step of applying a clear coat paint composition onto the peelable coating film formed in step (II-1) to form an uncured clear coat coating film.

[0089] Examples of substrates include outer and inner panels of automobile bodies such as passenger cars, trucks, motorcycles and buses; automobile parts; and outer panels of household electrical appliances such as mobile phones and audio equipment.

[0090] The material of these substrates is not particularly limited. Examples include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

[0091] The peelable coating composition can be applied to a substrate by a known method, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc. Of these, air spray coating and rotary atomization coating are preferred. Furthermore, such coating methods can be carried out in one or several batches until the desired film thickness is obtained.

[0092] The amount of the peelable coating composition to be applied is preferably an amount that results in a coating film having a dry thickness of 1 to 100 μm, more preferably an amount that results in a coating film having a dry thickness of 1 to 80 μm, and even more preferably an amount that results in a coating film having a dry thickness of 1 to 60 μm, from the viewpoints of the adhesion of the coating film to be formed and the peelability after thermal loading.

[0093] After forming the peelable coating film in the step (II-1), the peelable coating film may be further heated and / or air-dried, if necessary, to dry the peelable coating film.

[0094] The heating can be carried out by known means, for example, a drying oven such as a hot air oven, an electric oven, or an infrared induction heating oven. When the heating is carried out, the heating temperature is preferably within the range of 45 to 180°C, more preferably within the range of 50 to 170°C, and even more preferably within the range of 55 to 160°C. The heating time is not particularly limited, but is preferably within the range of 10 to 90 minutes, and more preferably within the range of 20 to 75 minutes.

[0095] As the clear coat paint composition, any known thermosetting clear paint composition can be used. Examples of the thermosetting clear paint composition include organic solvent-based thermosetting paint compositions containing a base resin having a crosslinkable functional group and a curing agent, aqueous thermosetting paint compositions, and powder thermosetting paint compositions. Among them, from the viewpoint of the finished appearance of the multilayer coating film formed, organic solvent-based thermosetting paint compositions containing a base resin having a crosslinkable functional group and a curing agent are preferred.

[0096] Examples of crosslinkable functional groups possessed by the base resin include carboxyl groups, hydroxyl groups, epoxy groups, and alkoxysilyl groups. Types of base resins include acrylic resins, polyester resins, alkyd resins, urethane resins, epoxy resins, and fluororesins. Examples of curing agents include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl group-containing compounds, carboxyl group-containing resins, epoxy group-containing resins, and epoxy group-containing compounds.

[0097] Preferred combinations of base resin / curing agent for the above clear coat paint composition include hydroxyl group-containing resin / polyisocyanate compound, carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / blocked polyisocyanate compound, and hydroxyl group-containing resin / melamine resin, with hydroxyl group-containing resin / polyisocyanate compound being more preferred.

[0098] The clear coat paint composition may be a one-component paint or a multi-component paint such as a two-component urethane resin paint.

[0099] Furthermore, the above-mentioned clear coat paint composition may contain coloring pigments, luster pigments, dyes, etc., as needed, to the extent that transparency is not impaired, and may further contain extender pigments, ultraviolet absorbers, light stabilizers, antifoaming agents, thickeners, rust inhibitors, surface conditioners, etc., as appropriate.

[0100] The application method of the clear coat paint composition is not particularly limited, but a wet coating film can be formed by, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coating, or other coating methods. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating or rotary atomization coating is particularly preferred. The amount of application of the clear coat paint composition is usually preferably an amount that results in a cured film thickness of 10 to 70 μm, more preferably an amount that results in a cured film thickness of 20 to 50 μm.

[0101] Furthermore, when air spray coating, airless spray coating, or rotary atomization coating is performed, it is preferable to adjust the viscosity of the clear coating composition appropriately using a solvent such as an organic solvent so that it falls within a viscosity range suitable for the coating, typically a viscosity range of about 15 to 60 seconds, particularly about 20 to 50 seconds, at 20°C using a Ford Cup No. 4 viscometer.

[0102] Furthermore, in <Method II>, after forming the peelable coating film and the uncured clear coat coating film in the steps (II-1) and (II-2), the formed multilayer coating film may be heated, if necessary, to dry and / or cure the peelable coating film and the uncured clear coat coating film.

[0103] The heating can be carried out by known means, for example, a drying oven such as a hot air oven, an electric oven, or an infrared induction heating oven. When the heating is carried out, the heating temperature is preferably within the range of 45 to 180°C, more preferably within the range of 50 to 170°C, and even more preferably within the range of 55 to 160°C. The heating time is not particularly limited, but is preferably within the range of 10 to 90 minutes, and more preferably within the range of 20 to 75 minutes.

[0104] The peelable coating film of this embodiment is a coating film that is difficult to peel off during normal use, and can be peeled off by heating when desired.

[0105] From the viewpoint of reducing energy consumption during heating, the temperature during the heating is preferably within a range of 80 to 150°C, more preferably within a range of 80 to 145°C, and even more preferably within a range of 80 to 130°C. [Example]

[0106] Hereinafter, this embodiment will be described in more detail with reference to Production Examples, Examples, and Comparative Examples. Note that these Production Examples, Examples, and Comparative Examples are merely illustrative and are not intended to limit the scope of the present invention. In the Production Examples, Examples, and Comparative Examples, "parts" and "%" are based on mass unless otherwise specified. Furthermore, the film thickness of the coating film is based on the cured coating film.

[0107] Preparation of a Removable Coating Composition Example 1 100 parts (solid content: 100 parts) of Byron GA6400 (trade name, manufactured by Toyobo MC Co., Ltd., crystalline polyester resin, melting point: 96°C, solid content: 100%) and 900 parts of cyclohexanone were uniformly mixed to obtain a peelable coating composition (E-1) with a solid content of 10%.

[0108] Comparative Example 1 A comparative coating composition (C-1) was obtained in the same manner as the peelable coating composition (E-1) of Example 1, except that the coating composition was as shown in Table 1 below.

[0109] [Measurement of the maximum phase difference between the stress curve and the strain curve within the temperature range of 80 to 150°C and the minimum complex viscosity within the temperature range of 80 to 150°C] The coating composition was dried and filled into a molding die to form pellets with a diameter of 10 mm and a thickness of 0.5 mm. The resulting pellets were then placed on the measurement platform of a rheometer, and the measurement section was heated to 200°C. The measurement section was then cooled to -70°C, and dynamic viscoelasticity measurement was initiated under the conditions described below. Temperature dependence was measured while the temperature was raised to 200°C at a rate of 10°C / min. Parallel plates with a diameter of 8 mm were used in the measurement. The maximum phase difference between the stress curve and the strain curve within a temperature range of 80 to 150°C and the minimum complex viscosity within a temperature range of 80 to 150°C, obtained from the measurement data, are shown in Table 1.

[0110] [Measurement conditions] Apparatus: ARES-G2 rheometer (TA Instruments) Measurement: Dynamic viscoelasticity, strain dependency control, ·Measurement temperature: -70℃~200℃, Measurement gap: 0.4mm, Frequency: 1Hz

[0111] Preparation of test painted panels Each of the coating compositions obtained in Example 1 and Comparative Example 1 was applied to aluminum material A5052 to a dry film thickness of 5 μm, dried at 120°C for 30 minutes, and left to stand at room temperature for 1 day to form a peelable coating film. Onto the peelable coating film, "Epomarine GX" (trade name, epoxy-based colored coating, manufactured by Kansai Paint Co., Ltd.) was applied to a dry film thickness of 60 μm, dried at 40°C for 1 hour, and left to stand at room temperature for 1 day to form a cured colored coating film. Next, "Retan PG80" (trade name, urethane-based topcoat, manufactured by Kansai Paint Co., Ltd.) was applied to the colored coating film to a cured film thickness of 50 μm, dried at 40°C for 1 hour, and left to stand at room temperature for 1 day to prepare a test coated plate.

[0112] Peelability after heat load (80℃) One hundred 2mm x 2mm cross-hatched patterns were made on the coating surface of each test panel in accordance with JIS K 5600-5-6 (1990). Each test panel was then heated with a heat gun (Makita) for 30 seconds to bring the coating temperature to 80°C, and adhesive tape was applied to the surface and rapidly peeled off five times in a peel test. The remaining cross-hatched coating was examined after the peel test, and adhesion was evaluated according to the following criteria. A, B, and C were considered acceptable. The evaluation results are shown in Table 1. A: The number of cross-hatched coating films remaining after one peel test is 0. B: After one peel test, the grid pattern coating film remains, but after five peel tests, the number of remaining grid pattern coating films is zero. C: The number of remaining cross-hatched coating films after 5 peel tests is 1 or more and less than 21, D: The number of remaining cross-hatched coating films after 5 peel tests is 21 or more and less than 51, E: The number of remaining grid-like coating films after five peel tests was 51 or more.

[0113] Peelability after heat load (100°C) One hundred 2mm x 2mm cross-hatched patterns were made on the coating surface of each test panel in accordance with JIS K 5600-5-6 (1990). Each test panel was then heated with a heat gun (Makita) for 30 seconds to bring the coating temperature to 100°C, and adhesive tape was applied to the surface and rapidly peeled off five times in a peel test. The remaining cross-hatched coating was examined after the peel test, and the adhesion was evaluated according to the following criteria. A, B, and C were considered acceptable. The evaluation results are shown in Table 1. A: The number of cross-hatched coating films remaining after one peel test is 0. B: After one peel test, the grid pattern coating film remains, but after five peel tests, the number of remaining grid pattern coating films is zero. C: The number of remaining cross-hatched coating films after 5 peel tests is 1 or more and less than 21, D: The number of remaining cross-hatched coating films after 5 peel tests is 21 or more and less than 51, E: The number of remaining grid-like coating films after five peel tests was 51 or more.

[0114] Peelability after heat load (140℃) One hundred 2mm x 2mm cross-hatched patterns were made on the coating surface of each test panel in accordance with JIS K 5600-5-6 (1990). Each test panel was then heated with a heat gun (Makita) for 30 seconds to bring the coating temperature to 140°C, and adhesive tape was applied to the surface and rapidly peeled off five times in a peel test. The remaining cross-hatched coating was examined after the peel test, and the adhesion was evaluated according to the following criteria. A, B, and C were considered acceptable. The evaluation results are shown in Table 1. A: The number of cross-hatched coating films remaining after one peel test is 0. B: After one peel test, the grid pattern coating film remains, but after five peel tests, the number of remaining grid pattern coating films is zero. C: The number of remaining cross-hatched coating films after 5 peel tests is 1 or more and less than 21, D: The number of remaining cross-hatched coating films after 5 peel tests is 21 or more and less than 51, E: The number of remaining grid-like coating films after five peel tests was 51 or more.

[0115] Adhesion at 23°C At 23°C, 100 2mm x 2mm grids were made on the surface of each test panel in accordance with JIS K 5600-5-6 (1990), and adhesive tape was applied to the surface. After the tape was quickly peeled off, the remaining grid film was examined and the adhesion was evaluated according to the following criteria. A, B, and C were considered acceptable. The evaluation results are shown in Table 1. A: 100 square grid coatings remain. B: The number of remaining grid patterns is 99 or less, or more than 95, C: The number of remaining grid patterns is 94 or less, more than 90, D: The number of remaining grid coating films is 89 or less, more than 50, E: The number of remaining grid-like coating films is 49 or less.

[0116] [Table 1]

[0117] The components listed in the table are as follows: (Note 1) "Vylon GM380": Product name, manufactured by Toyobo MC Co., Ltd., crystalline polyester resin, melting point 138°C, solids concentration 100%.

Claims

1. (effect:) (A) A strippable coating composition comprising a crystalline polyester resin, A peelable coating composition in which the maximum phase difference between the stress curve and the strain curve within a temperature range of 80 to 150°C is 45° or more, as determined by dynamic viscoelasticity measurement at a temperature rise rate of 10°C / min and a frequency of 1 Hz.

2. 2. A peelable coating composition according to claim 1, wherein the minimum value of the complex viscosity within a temperature range of 80 to 150°C, as determined by dynamic viscoelasticity measurement at a temperature rise rate of 10°C / min and a frequency of 1 Hz, is 10,000 Pa s or less.

3. (effect:) Step (I-1): A step of applying the peelable coating composition according to claim 1 or 2 to a substrate to form a peelable coating film; Step (I-2): A method for forming a multilayer coating film, comprising the step of applying a colored coating composition onto the peelable coating film formed in step (I-1) to form an uncured colored coating film.

4. (effect:) Step (II-1): A step of applying the peelable coating composition according to claim 1 or 2 to a substrate to form a peelable coating film; Step (II-2): A method for forming a multilayer coating film, comprising the step of applying a clear coat paint composition onto the peelable coating film formed in step (II-1) to form an uncured clear coat coating film.

5. 5. The method for forming a multilayer coating film according to claim 3, wherein the peelable coating film can be peeled from the substrate by heating at a temperature in the range of 80 to 150°C.

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