Thermosetting resin sheet, vehicle, vehicle component, method for producing thermosetting resin sheet, and coating method

Abstract

The present invention provides a thermosetting resin sheet provided with at least one resin layer comprising a thermosetting resin composition, wherein the thermosetting resin composition contains a polyol resin and a melamine resin (B). Each of a vehicle and a vehicle component according to the present invention is coated using a thermosetting resin sheet according to the present invention. A method for producing a thermosetting resin sheet according to the present invention includes a step for forming a resin layer by applying a thermosetting resin composition onto a transfer layer and / or a protective layer. The present invention also provides a coating method in which an object to be coated is coated using a thermosetting resin sheet according to the present invention, the coating method including: a step for attaching the thermosetting resin sheet to the object to be coated; and a step for curing the thermosetting resin sheet attached to the object to be coated at a heating temperature of 120°C or lower. The present invention can provide: a thermosetting resin sheet that can be cured at a low heating temperature; a vehicle and a vehicle component each coated using the thermosetting resin sheet; a method for producing the thermosetting resin sheet; and a coating method using the thermosetting resin sheet.

Description

Thermosetting resin sheet, vehicle, vehicle parts, method for manufacturing thermosetting resin sheet, and painting method

[0001] The present invention relates to a thermosetting resin sheet, a vehicle and vehicle parts painted using the thermosetting resin sheet, a method for manufacturing the thermosetting resin sheet, and a painting method using the thermosetting resin sheet.

[0002] For furniture, steel plates, vehicle bodies, etc., painting and decoration are carried out from the viewpoints of design and durability. It is known that decoration is performed using a film such as a decorative film. As such a decorative film, for example, a thermosetting coating sheet mainly composed of an acrylic resin having a plurality of functional groups, a monomer having a plurality of functional groups as a crosslinking agent that reacts with an isocyanate group, and blocked isocyanate is known as the prior art (see Patent Document 1).

[0003] Japanese Patent No. 2688105

[0004] The thermosetting coating sheet described in Patent Document 1 is cured by heating the thermosetting coating sheet, and the blocking agent of the blocked isocyanate dissociates, and the thermosetting coating sheet is cured. However, the thermosetting coating sheet described in Patent Document 1 has a problem that the heating temperature during thermosetting is high and the material of the object to be painted is limited.

[0005] Therefore, an object of the present invention is to provide a thermosetting resin sheet that can be appropriately used as a coating sheet and can be cured at a low heating temperature, a vehicle and vehicle parts painted using the thermosetting resin sheet, a method for manufacturing the thermosetting resin sheet, and a painting method using the thermosetting resin sheet.

[0006] As a result of diligent research, the present inventors have found that the above problems can be solved by using melamine resin as a crosslinking agent contained in a thermosetting resin sheet, and have completed the present invention. That is, the present invention provides the following [1] to

[12] . [1] A thermosetting resin sheet comprising at least one resin layer made of a thermosetting resin composition, wherein the thermosetting resin composition comprises a polyol resin and a melamine resin (B). [2] The thermosetting resin sheet according to [1] above, wherein the polyol resin comprises at least one polyol resin selected from the group consisting of (meth)acrylic polyol resin and polyester polyol resin. [3] The thermosetting resin sheet according to [1] or [2] above, wherein the content of the melamine resin (B) in the thermosetting resin composition is 5 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the polyol resin contained in the thermosetting resin composition. [4] The thermosetting resin sheet according to any one of [1] to [3] above, wherein the weight-average molecular weight of the melamine resin (B) is 1,000 or more and 5,000 or less. [5] The thermosetting resin sheet according to any one of [1] to [4] above, wherein the thickness of the resin layer is 200 μm or less. [6] The thermosetting resin sheet according to any one of [1] to [5] above, wherein the polyol resin comprises a polyol resin (A) having a weight-average molecular weight of 100,000 or more and 1,000,000 or less. [7] The thermosetting resin sheet according to [6] above, wherein the polyol resin further comprises a polyol resin (C) having a weight-average molecular weight of 300 or more and 30,000 or less, and the polyol resin (C) is at least one polyol selected from the group consisting of (meth)acrylic polyol, polyester polyol, polycarbonate polyol and polycaprolactone polyol. [8] A thermosetting resin sheet according to any one of [1] to [7] above, wherein the thermosetting resin composition further comprises a blocked isocyanate. [9] A vehicle painted using the thermosetting resin sheet according to any one of [1] to [8] above.

[10] A vehicle part painted using the thermosetting resin sheet according to any one of [1] to [8] above.

[11] A method for producing a thermosetting resin sheet according to any one of [1] to [8] above, comprising the step of applying the thermosetting resin composition onto at least one of a transfer layer and a protective layer to form the resin layer.

[12] A painting method for applying paint to an object to be painted using a thermosetting resin sheet according to any one of [1] to [8] above, comprising the steps of attaching the thermosetting resin sheet to the object to be painted, and curing the thermosetting resin sheet attached to the object to be painted at a heating temperature of 120°C or lower.

[0007] According to the present invention, it is possible to provide a thermosetting resin sheet that can be appropriately used as a painting sheet and can be cured at a low heating temperature, a vehicle and vehicle parts painted using the thermosetting resin sheet, a method for manufacturing the thermosetting resin sheet, and a painting method using the thermosetting resin sheet.

[0008] [Thermosetting Resin Sheet] The thermosetting resin sheet of the present invention is a thermosetting resin sheet comprising at least one resin layer made of a thermosetting resin composition, wherein the thermosetting resin composition includes a polyol resin and a melamine resin (B). This allows the sheet to be used appropriately as a coating sheet and allows the thermosetting resin sheet to be cured at a low heating temperature.

[0009] (Resin Layer) The resin layer in the thermosetting resin sheet of the present invention consists of a thermosetting resin composition. The thermosetting resin composition includes a polyol resin and a melamine resin (B). Examples of polyol resins include (meth)acrylic polyol resin, polycarbonate polyol resin, polyester polyol resin, epoxy resin-modified polyol resin, and polycaprolactone polyol resin. These polyol resins can be used individually or in combination of two or more. In this specification, (meth)acrylic polyol resin may be simply referred to as "(meth)acrylic polyol" for convenience. The same applies to the other resins. The polyol resin preferably contains at least one of (meth)acrylic polyol resin and polyester polyol resin, and more preferably contains (meth)acrylic polyol resin. Details of these polyol resins will be explained later in the section on polyol resin (A) or polyol resin (C).

[0010] <Polyol Resin (A)> The polyol resin preferably includes a polyol resin (A) having a weight-average molecular weight of 100,000 or more and 1,000,000 or less. Examples of polyol resin (A) include (meth)acrylic polyol resin, polycarbonate polyol resin, polyester polyol resin, epoxy resin-modified polyol resin, etc., among which (meth)acrylic polyol resin and polyester polyol resin are preferred, and (meth)acrylic polyol resin is more preferred. These polyol resins (A) may be used individually or in combination of two or more.

[0011] In polyol resin (A), the number of hydroxyl groups is not particularly limited as long as there are two or more. Furthermore, polyol resin (A) may also have functional groups other than hydroxyl groups. Examples of functional groups other than hydroxyl groups include amino groups and carboxyl groups.

[0012] The polyol resin (A) preferably contains a plurality of functional groups, in particular a (meth)acrylic resin ((meth)acrylic polyol resin) having a plurality of hydroxyl groups. The (meth)acrylic resin may also have functional groups other than hydroxyl groups. Examples of functional groups other than hydroxyl groups include amino groups and carboxyl groups.

[0013] (Meth)acrylic resin is preferably an acrylic polymer obtained by polymerizing a monomer mixture containing a (meth)acrylic acid ester monomer and a monomer containing a hydroxyl group functional group. In such alkyl polymers, hydroxyl groups can be incorporated into the acrylic polymer by the hydroxyl group-containing monomer. (Meth)acrylic means methacrylic or acrylic, and the same applies to other similar terms.

[0014] Examples of the above-mentioned (meth)acrylic acid ester monomers include (meth)acrylic acid ester monomers that do not have functional groups, such as alkyl (meth)acrylates with an alkyl group having 1 to 18 carbon atoms, such as methyl (meth)acrylate and ethyl (meth)acrylate; (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate; and 2-ethoxyethyl (meth)acrylate.

[0015] The above-mentioned hydroxyl group-containing monomers are not particularly limited, and include (meth)acrylic acid ester monomers having hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate.

[0016] Furthermore, the monomer mixture may also contain monomers other than the above-mentioned (meth)acrylic acid ester monomers and hydroxyl group-containing monomers, such as monomers containing functional groups other than hydroxyl groups and styrene derivative monomers. By using monomers containing functional groups other than hydroxyl groups, such as amino groups and carboxyl groups, in addition to hydroxyl groups, functional groups other than hydroxyl groups can be introduced into the (meth)acrylic resin. Examples of amino group-containing monomers are not particularly limited, and include (meth)acrylic acid ester monomers having amino groups, such as 2-aminoethyl (meth)acrylate. Examples of carboxyl group-containing monomers are not particularly limited, such as (meth)acrylic acid. Examples of styrene derivative monomers are not particularly limited, such as styrene, α-methylstyrene, α-ethylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-ethoxystyrene, p-chlorostyrene, m-chlorostyrene, o-chlorostyrene, etc.

[0017] Furthermore, as the (meth)acrylic resin, a copolymer obtained by block or graft polymerization of the above-mentioned acrylic polymer with another monomer or polymer may be used. In this case, examples of other monomers or polymers include acrylic, styrene, maleic acid, imide, silicone, and fluorine monomers, or polymers of these monomers.

[0018] Polyester polyols include those obtained by polycondensation of a polyol and a polycarboxylic acid, and specifically, resins synthesized by esterification reactions from polybasic acids and polyhydric alcohols. Polybasic acids are, for example, compounds having two or more carboxyl groups in one molecule. Examples of polybasic acids include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, trimellitic acid, and pyromellitic acid. Anhydrides of these polybasic acids can also be used. These polybasic acids can be used individually or in combination of two or more. Polyhydric alcohols are, for example, compounds having two or more hydroxyl groups in one molecule. Examples of polyhydric alcohols include diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, and hydrogenated bisphenol A; polyols with a valency of three or higher, such as trimethylolpropane, trimethylolethane, glycerin, and pentaerythritol; and hydroxycarboxylic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolpentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid. These polyhydric alcohols can be used individually or in combination of two or more.

[0019] The weight-average molecular weight of the polyol resin (A) is preferably 100,000 or more and 1,000,000 or less, as described above. If the weight-average molecular weight of the polyol resin (A) is 100,000 or more, sheet molding of the thermosetting resin composition becomes easier. If the weight-average molecular weight of the polyol resin (A) is 1,000,000 or less, the thermosetting resin sheet becomes flexible, the ability of the thermosetting resin sheet to conform to the shape of the object to be coated becomes good, and it becomes easy to use as a sheet for coating. From this viewpoint, the weight-average molecular weight of the polyol resin (A) is more preferably 110,000 or more, even more preferably 120,000 or more, even more preferably 130,000 or more, even more preferably 140,000 or more, more preferably 900,000 or less, even more preferably 800,000 or less, even more preferably 700,000 or less, even more preferably 600,000 or less, more preferably 110,000 to 900,000, even more preferably 120,000 to 800,000, even more preferably 130,000 to 700,000, and even more preferably 140,000 to 600,000. In this specification, the weight-average molecular weight is measured by gel permeation chromatography (GPC) and is determined as a standard polystyrene equivalent value. The measurement conditions are as follows. Column: GPC LF-604 (Size: Inner diameter x Length: 6.0 mm x 150 mm) Flow rate: 0.3 mL / min Column temperature: 40°C Injection volume: 10 μL Detector: RI (Differential Refractive Index Detector) Mobile phase: THF Standard sample: Polystyrene Sample preparation solvent: THF Instrument: ACQUITY Advanced Polymer Chromatography (APC) system (Waters Corporation)

[0020] The hydroxyl value of the polyol resin (A) is preferably 120 mg KOH / g or less. When the hydroxyl value of the polyol resin (A) is 120 mg KOH / g or less, the adhesive strength of the resin layer to the adherend can be further increased. From this viewpoint, the hydroxyl value of the polyol resin (A) is more preferably 100 mg KOH / g or less, and even more preferably 90 mg KOH / g or less.

[0021] The hydroxyl value of the polyol resin (A) is preferably 10 mg KOH / g or more. When the hydroxyl value of the polyol resin (A) is 10 mg KOH / g or more, the hardness of the resin layer can be increased. From this viewpoint, the hydroxyl value of the polyol resin (A) is more preferably 15 mg KOH / g or more, and even more preferably 20 mg KOH / g or more.

[0022] From the above perspective, the hydroxyl value of the polyol resin (A) is preferably 10 mg KOH / g or more and 120 mg KOH / g or less, more preferably 15 mg KOH / g or more and 100 mg KOH / g or less, and even more preferably 20 mg KOH / g or more and 90 mg KOH / g or less.

[0023] Furthermore, the glass transition temperature (Tg) of the polyol resin (A) is preferably less than 90°C, more preferably 80°C or less, even more preferably 60°C or less, preferably -20°C or higher, more preferably 0°C or higher, and preferably -20°C or higher but less than 90°C, more preferably 0°C or higher but 80°C or lower, and even more preferably 0°C or higher but 60°C or lower. When the glass transition temperature of the polyol resin (A) is within the above range, it becomes easier to impart a certain level of tackiness and stretchability to the resin layer. In this specification, the glass transition temperature is a value determined by scanning calorimetry (DSC) in accordance with JIS K7121.

[0024] The content of polyol resin (A) in the polyol resin contained in the thermosetting resin composition is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, preferably 100% by mass or less, preferably 30% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, and even more preferably 50% by mass or more and 100% by mass or less.

[0025] <Melamine Resin (B)> The hydroxyl groups of the polyol resin (A) undergo a condensation reaction with the methylol groups of the melamine resin (B), causing the thermosetting resin composition to harden. Melamine resin (B) can be obtained by polycondensation of melamine and formaldehyde, or by a combination of methylation by formaldehyde and etherification by alcohol in melamine. The alcohol contains C １ ~C ８ These materials can be used. In addition, formalin-paraformaldehyde and butylformaldehyde-solution (butanol-formaldehyde-water) can be used as raw materials for formaldehyde. By selecting the reaction molar ratio, the ratio of methylol groups and ether groups, and the degree of polymerization can be changed. For example, lowering the molar ratio of formaldehyde and alcohol increases the number of methylene bonds and methyl ether bonds, which increases the weight-average molecular weight of the melamine resin. Specific examples of melamine resins include alkylated melamine resins such as methylolated melamine resin, iminomethylolated melamine resin, iminomethylolated melamine resin, methylated melamine resin, ethylated melamine resin, propylated melamine resin, butylated melamine resin, hexylated melamine resin, and octylated melamine resin; methylolalkylated melamine resins such as methylolmethylated melamine resin, methylolethylated melamine resin, methylolpropylated melamine resin, methylolbutylated melamine resin, methylolhexylated melamine resin, and methyloloctylated melamine resin; iminomethylolalkylated melamine resins such as iminomethylolmethylated melamine resin, iminomethylolethylated melamine resin, iminomethylolpropylated melamine resin, iminomethylolbutylated melamine resin, iminomethylolhexylated melamine resin, and iminomethyloloctylated melamine resin. Among these, iminomethylol alkylated melamine resin is preferred, and iminomethylol butylated melamine resin is more preferred. The above melamine resins may be used individually or in combination of two or more types.

[0026] The weight-average molecular weight of melamine resin (B) is preferably 500 to 5000. When the weight-average molecular weight of melamine resin (B) is within the above range, the thermosetting resin sheet can be cured at an even lower heating temperature, and the flexibility of the thermosetting resin sheet can be further improved. From this viewpoint, the weight-average molecular weight of melamine resin (B) is more preferably 600 or more, even more preferably 800 or more, even more preferably 1000 or more, more preferably 4000 or less, even more preferably 3000 or less, more preferably 600 to 4000, even more preferably 800 to 3000, and even more preferably 1000 to 3000.

[0027] The content of melamine resin (B) in the thermosetting resin composition is preferably 5 parts by mass or more and 80 parts by mass or less per 100 parts by mass of polyol resin contained in the thermosetting resin composition. When the content of melamine resin (B) is 5 parts by mass or more, it becomes even easier to cure the thermosetting resin sheet at a low temperature. Furthermore, when the content of melamine resin (B) is 80 parts by mass or less, the adhesion to the substrate after curing the thermosetting resin sheet becomes even better. From this viewpoint, the content of melamine resin (B) in the thermosetting resin composition is more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, even more preferably 50 parts by mass or less, more preferably 10 parts by mass or more and 70 parts by mass or less, even more preferably 20 parts by mass or more and 60 parts by mass or less, even more preferably 25 parts by mass or more and 55 parts by mass or less, and even more preferably 25 parts by mass or more and 50 parts by mass or less. If the polyol resin contained in the thermosetting resin composition is only polyol resin (A), the content of melamine resin (B) in the thermosetting resin composition is the content relative to 100 parts by mass of polyol resin (A). Furthermore, if the polyol resin contained in the thermosetting resin composition consists only of polyol resin (A) and polyol resin (C) described later, the content of melamine resin (B) in the thermosetting resin composition is the content relative to 100 parts by mass of the total of polyol resin (A) and polyol resin (C).

[0028] <Polyol Resin (C)> The polyol resin contained in the thermosetting resin composition may consist solely of the polyol resin (A) described above, but it may also contain polyol resins other than polyol resin (A). Specifically, the thermosetting resin composition may further contain polyol resin (C) having a weight-average molecular weight of 300 or more and 30,000 or less. By including polyol resin (C) in the thermosetting resin composition, it becomes easier to achieve a good balance of properties such as coating properties, curing properties, tackiness, and stretchability of the thermosetting resin sheet. Furthermore, it is possible to improve the wettability to the workpiece and increase the adhesive strength of the thermosetting resin sheet to the workpiece. From this viewpoint, the weight-average molecular weight of the polyol resin (C) is preferably 300 or more, more preferably 400 or more, even more preferably 500 or more, even more preferably 600 or more, even more preferably 800 or more, preferably 10000 or less, even more preferably 8000 or less, even more preferably 6000 or less, even more preferably 4000 or less, preferably 300 to 10000, even more preferably 400 to 8000, even more preferably 500 to 6000, even more preferably 600 to 4000, and even more preferably 800 to 4000.

[0029] Examples of polyol resin (C) include (meth)acrylic polyol, polyester polyol, polycarbonate polyol, and polycaprolactone polyol. These polyol resins can be used individually or in combination of two or more. Among these polyol resins, (meth)acrylic polyol and polycarbonate polyol are preferred, with (meth)acrylic polyol being more preferred. The (meth)acrylic polyol used as polyol resin (C) is an oligomer, and similar to the (meth)acrylic polyol resin in polyol resin (A) above, it is preferable to use a (meth)acrylic polyol having multiple hydroxyl groups. The polyol resin (C) above may be used individually or in combination of two or more.

[0030] When polyol resin (A) is a polyester polyol resin, it is preferable to use a polyester polyol resin as polyol resin (C). Examples of polyester polyol resins used as polyol resin (C) include those with a lower molecular weight than the polyester polyol resin that can be used as polyol resin (A). The weight-average molecular weight of this low molecular weight polyester polyol is preferably less than 3000.

[0031] The hydroxyl value of the polyol resin (C) is preferably 20 mg KOH / g or more, more preferably 40 mg KOH / g or more, even more preferably 60 mg KOH / g or more, preferably 500 mg KOH / g or less, more preferably 400 mg KOH / g or less, even more preferably 300 mg KOH / g or less, preferably 20 mg KOH / g or more and 500 mg KOH / g or less, more preferably 40 mg KOH / g or more and 400 mg KOH / g or less, and even more preferably 60 mg KOH / g or more and 300 mg KOH / g or less. If the thermosetting resin composition contains multiple types of polyol resin (C), it is preferable that the hydroxyl value of each polyol resin (C) be within the above range.

[0032] When the thermosetting resin composition contains polyol resin (C), the content of polyol resin (C) in the polyol resin contained in the thermosetting resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, preferably 5% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 50% by mass or less, and even more preferably 15% by mass or more and 45% by mass or less. In this case, the content of polyol resin (A) in the polyol resin contained in the thermosetting resin composition is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, preferably 25% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 35% by mass or more and 85% by mass or less.

[0033] The polyol resin content in the thermosetting resin composition is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 85% by mass or less, and even more preferably 40% by mass or more and 80% by mass or less. The thermosetting resin composition for forming the resin layer may be diluted with volatile components such as solvents as described later, but in this specification, the content (by mass) of each component in the resin layer or thermosetting resin composition means the value based on solid content excluding volatile components.

[0034] Within the limits that do not impede the effects of the present invention, the thermosetting resin composition may contain thermosetting resins other than polyol resins. Examples of thermosetting resins other than polyol resins include (meth)acrylic resins other than polyol resins, polycarbonate resins other than polyol resins, polyester resins other than polyol resins, epoxy resins other than polyol resins, and the like. These thermosetting resins can be used individually or in combination of two or more. The thermosetting resins other than polyol resins may have a weight-average molecular weight of less than 100,000 or greater than 1,000,000, or a weight-average molecular weight of 100,000 or more and 1,000,000 or less.

[0035] <Blocked Isocyanate> The thermosetting resin composition may contain a curing agent other than the melamine resin (B) described above, for example, a blocked isocyanate. The thermosetting resin composition can be further improved in curability by containing a blocked isocyanate. A blocked isocyanate is a compound in which isocyanate groups are blocked by a protecting group. When exposed to high temperatures, the protecting group (blocked portion) thermally dissociates and detaches, and a curing reaction occurs between the resulting isocyanate group and the polyol resin described above. A blocked isocyanate can be obtained, for example, by reacting an isocyanate compound having two or more isocyanate groups in one molecule with a blocking agent. The isocyanate compounds having two or more isocyanate groups in a single molecule are not particularly limited, but examples include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, or modified versions thereof. Examples of blocking agents include pyrazoles, phenols, oximes, lactams, malonic acid esters, and activated methylene compounds.

[0036] The content of blocked isocyanate in the thermosetting resin composition is preferably 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of polyol resin. When the content of blocked isocyanate is 5 parts by mass or more per 100 parts by mass of polyol resin, the thermosetting resin composition can be cured even more sufficiently. When the content of blocked isocyanate is 50 parts by mass or less per 100 parts by mass of polyol resin, it is possible to prevent a decrease in various physical properties of the thermosetting resin sheet. From this viewpoint, the content of blocked isocyanate is more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, more preferably 48 parts by mass or less, even more preferably 46 parts by mass or less, even more preferably 44 parts by mass or less, more preferably 10 parts by mass or more and 48 parts by mass or less, even more preferably 15 parts by mass or more and 46 parts by mass or less, and even more preferably 20 parts by mass or more and 44 parts by mass or less.

[0037] The thermosetting resin composition may contain, in addition to polyol resin (A) and melamine resin (B), polyol resin (C) and blocked isocyanate as needed, components appropriate to the performance required for the coating formed from the thermosetting resin sheet. For example, if the coating formed from the thermosetting resin sheet is a colored coating, it is preferable to include colorants such as pigments, dyes, and glossing agents in the thermosetting resin composition. If the coating formed from the thermosetting resin sheet is a heat-shielding coating, it is preferable to include a heat-shielding material in the thermosetting resin composition. Furthermore, the thermosetting resin composition may contain components other than those mentioned above, for example, other additives. Examples of additives include crosslinking agents, dispersants, inorganic fillers other than pigments and glossing agents, anti-aging agents, antioxidants, and rust inhibitors. In addition, the resin layer may consist of a clear layer as described later. Among these, it is preferable that the thermosetting resin composition contains at least a colorant. This results in a colored resin layer.

[0038] Pigments used as colorants include, but are not limited to, metal oxide pigments such as titanium dioxide and iron oxide; inorganic pigments such as carbon black, clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white; and organic pigments such as azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, benzimidazolon pigments, vat pigments, isoindoline pigments, isoindolinone pigments, metal chelate azo pigments, phthalocyanine pigments, indanthrone pigments, dioxane pigments, and indigo pigments. Known dyes can be used, including azo dyes, anthraquinone dyes, indigoid dyes, and stilbene dyes. The luminous agent is a compound that can impart luminosity to the resin layer and can impart the property of showing gloss when observed from multiple directions. The luminous material is not particularly limited, but examples include compounds in which a titanium oxide layer is provided on the surface of natural mica, synthetic mica, alumina flakes, glass flakes, etc. The thermosetting resin composition more preferably contains at least one of a pigment or a luminous material as a coloring agent, and even more preferably contains a pigment. It is also preferable for the thermosetting resin composition to contain both a pigment and a luminous material. The content of the coloring agent in the thermosetting resin composition is not particularly limited. For example, when the coloring agent is carbon black, the content of the coloring agent in the thermosetting resin composition is, for example, about 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, for example, about 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, for example, about 0.05% by mass or more and about 20% by mass or less, preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.3% by mass or more and 10% by mass or less. Furthermore, in addition to the above-mentioned additives such as colorants and heat-shielding materials, the thermosetting resin composition may also appropriately contain additives such as inorganic fillers, curing catalysts, curing accelerators, surface modifiers, defoamers, crosslinking agents, dispersants, anti-aging agents, and antioxidants.

[0039] The thermosetting resin sheet of the present invention may include a single resin layer or two or more resin layers. By providing two or more resin layers, various functions can be imparted to the coating formed from the resin layer. The two or more resin layers are preferably laminated continuously in the thickness direction.

[0040] When the thermosetting resin sheet includes a single resin layer, the resin layer is preferably made of the above-described thermosetting resin composition containing a polyol resin and a melamine resin. Further, the thermosetting resin composition may contain a blocked isocyanate, a colorant, and other additives in addition to these.

[0041] When the thermosetting resin sheet includes two or more resin layers, each resin layer is preferably made of the above-described thermosetting resin composition containing a polyol resin and a melamine resin. Further, at least one of the two or more resin layers may contain a colorant as described above to form a colored resin layer, may contain a heat insulating material to form a heat insulating layer, or may be a clear layer without substantially containing a colorant.

[0042] When the thermosetting resin sheet includes two or more resin layers, it is preferable that at least two of the two or more resin layers are a colored resin layer and a clear layer. In this case, the clear layer and the colored resin layer are preferably arranged in this order from the transfer layer side. With such a layer structure, when the thermosetting resin sheet is attached to the object to be coated, the colored resin layer and the clear layer are arranged in this order from the object to be coated side. By having at least one of the two or more resin layers be a colored resin layer, the object to be coated can be colored by the coating formed from the resin layer. Further, by providing a clear layer in addition to the colored resin layer, the colored resin layer can be protected or gloss can be imparted to the colored resin layer. The colored resin layer preferably contains a pigment as a colorant. Therefore, it is particularly preferable that the resin layer includes a clear layer and a colored resin layer.

[0043] The colored resin layer and the clear layer are each preferably made of the above-described thermosetting resin composition containing a polyol resin and a melamine resin. The thermosetting resin composition for the colored resin layer may contain a colorant as described above. The thermosetting resin composition for the colored resin layer may be adjusted so that the content of the colorant in the entire resin layer is within the above range. Further, the thermosetting resin composition for the colored resin layer contains a polyol resin (A), and preferably contains a polyol resin (C) in addition to the polyol resin (A).

[0044] On the other hand, the clear layer is a transparent layer and may have transparency such that the color of the colored resin layer can be visually recognized from the outside through the clear layer. For example, the transmittance of light with a wavelength of 450 nm may be 80% or more. The clear layer is preferably a coating film that does not contain a colorant, but may contain a small amount of a colorant as long as its function is not impaired. The thermosetting resin composition for the clear layer contains the polyol resin (A) as described above, but may or may not contain a polyol resin (C) in addition to the polyol resin (A).

[0045] Of course, when the thermosetting resin sheet includes two or more resin layers, it is not limited to the two-layer structure of the clear layer and the colored resin layer, and can have various laminated structures. It is also possible to provide two or more colored resin layers and one or more clear layers to form a structure of three or more layers, or to omit the clear layer and form a structure consisting of two colored resin layers. Also, two or more clear layers may be provided. Further, a heat insulating layer or the like may be provided between the clear layer and the colored resin layer to form a structure of three or more layers.

[0046] When the thermosetting resin sheet is a single layer, the thickness of the resin layer is not particularly limited, but for example, it is 200 μm or less, preferably 100 μm or less, for example, 5 μm or more, preferably 15 μm or more, for example, 5 μm or more and 200 μm or less, preferably 15 μm or more and 100 μm or less. Setting the thickness of the resin layer to be below the above upper limit makes it easier to improve curability. Also, setting it to be above the above lower limit makes it easier to improve various performances. When the thermosetting resin sheet has two or more resin layers, the total thickness of the resin layers is not particularly limited, but for example, it is 400 μm or less, preferably 200 μm or less, for example, 10 μm or more, preferably 30 μm or more, for example, 10 μm or more and 400 μm or less, preferably 30 μm or more and 200 μm or less. Setting the total thickness of the resin layers to be below the above upper limit makes it easier to improve curability. Also, setting it to be above the above lower limit makes it easier to improve various performances.

[0047] In the above explanation, it has been assumed that when a thermosetting resin sheet contains two or more resin layers, each resin layer consists of the specific thermosetting resin composition described above, which includes a polyol resin and a melamine resin (B). However, when a thermosetting resin sheet contains two or more resin layers, the other layers may consist of resin compositions other than the thermosetting resin composition described above, as long as at least one layer consists of the thermosetting resin composition described above.

[0048] (Transfer Layer) The thermosetting resin sheet of the present invention may include a transfer layer. The transfer layer is preferably laminated on at least one surface of the above-mentioned resin layer (a single resin layer or a laminate of two or more resin layers). The transfer layer protects the resin layer from scratches and the adhesion of foreign matter, and also serves as a support when the resin layer is attached to an object to be coated. The transfer layer is preferably moldable by vacuum forming and preferably machined.

[0049] The transfer layer is preferably formed from a resin film. Examples of resins used in the resin film include polyethylene resin, polyolefin resins such as polypropylene resin, and polyimide resin. Among these, it is more preferable to include polypropylene resin or polyethylene resin from the viewpoint of production cost and ease of handling, and it is even more preferable to include polypropylene resin or polyimide resin from the viewpoint of heat resistance.

[0050] The polypropylene resin may be homopropylene, or a copolymer of propylene such as random polypropylene and a small amount (e.g., 10% by mass or less) of another α-olefin. Examples of other α-olefins include chain-like α-olefins with 1 to 12 carbon atoms, such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, and 1-decene. The polyethylene resin may be low-density polyethylene (LDPE, density: 0.930 g / cm³). ３ (less than), medium-density polyethylene (MDPE, density: 0.930 g / cm³) ３ 0.942g / cm or more ３ (less than), high-density polyethylene (HDPE, density: 0.942 g / cm³) ３ Examples include the above, linear low-density polyethylene (LLDPE), and others.

[0051] The resin film constituting the transfer layer may be a single-layer film consisting of one layer, or a multilayer film consisting of two or more layers. Furthermore, in the resin film constituting the transfer layer, the resin contained in the resin film may be used alone, or two or more types may be used in combination. When two or more types of resin are used in combination, different types of resin may be used in each layer to form a multilayer film. Alternatively, a single-layer film may be formed by mixing two or more types of resin, or one or more layers in a multilayer film may be formed by mixing them.

[0052] The transfer layer may have at least one surface that has been treated with a release agent, such as a silicone-based release agent or a fluorine-based release agent. When the transfer layer is treated with a release agent, it is preferable that the treated surface constitutes the surface on the resin layer side. Treating the transfer layer with a release agent makes it easier to remove from the resin layer. However, the transfer layer does not need to be treated with a release agent as long as it can be removed from the resin layer.

[0053] The thickness of the transfer layer is not particularly limited, but is, for example, 10 μm or more, preferably 30 μm or more, more preferably 50 μm or more, for example 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, for example 10 μm or more and 500 μm or less, preferably 30 μm or more and 400 μm or less, more preferably 50 μm or more and 300 μm or less.

[0054] (Protective Layer) The thermosetting resin sheet of the present invention may be provided with a protective layer. The protective layer is a component that protects the resin layer from scratches and the adhesion of foreign matter. The protective layer is preferably laminated on at least one surface of the resin layer (a single resin layer or a laminate of two or more resin layers). Also, if a transfer layer is provided as described above, the protective layer is preferably provided on the surface of the resin layer opposite to the surface on which the protective layer is provided. The protective layer is preferably formed from a resin film. Examples of resins used for the resin film for the protective layer include thermoplastic resins. It is also preferable to use a resin whose tensile strength can be adjusted to the desired range described above. The protective layer is preferably moldable by vacuum forming and preferably can be processed by cutting. Specific examples of resins used for the resin film include polyolefin resins, polyester resins such as polybutylene terephthalate and polyethylene terephthalate, polyamide resins, polycarbonate resins, acrylic resins, fluororesins, flexible polyvinyl chloride resins, polymethylpentene resins, and tetrafluoroethylene resins. When using polyolefin resin, the same material as the transfer layer described above can be used. Among the above, polyester resin is preferred.

[0055] The resin film forming the protective layer may be a single-layer film consisting of one layer, or a multilayer film consisting of two or more layers. Furthermore, the resin contained in the resin film constituting the protective layer may be used alone, or two or more types may be used in combination. The resin film used for the protective layer may be a stretched resin film or an unstretched resin film, but an unstretched resin film is preferred. The protective layer may have at least one surface that has been treated with a release agent such as a silicone-based release agent or a fluorine-based release agent. When the protective layer is treated with a release agent, it is preferable that the treated surface constitutes the surface on the resin layer side. The protective layer is made easier to peel off from the resin layer by being treated with a release agent. However, the protective layer does not need to be treated with a release agent as long as it can be peeled off from the resin layer. The thickness of the protective layer is not particularly limited, but is, for example, 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, for example 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, for example 10 μm or more and 500 μm or less, preferably 20 μm or more and 400 μm or less, more preferably 30 μm or more and 300 μm or less.

[0056] (Method for Manufacturing Thermosetting Resin Sheets) The method for manufacturing thermosetting resin sheets is not particularly limited, but can be manufactured by known methods. For example, a thermosetting resin composition may be prepared, the prepared thermosetting resin composition may be applied to a transfer layer, and dried as necessary to form a resin layer. Alternatively, if the thermosetting resin sheet includes a protective layer, the thermosetting resin composition may be applied to the protective layer, dried as necessary to form a resin layer, and then a transfer layer may be laminated onto the resin layer formed on the protective layer to obtain a thermosetting resin sheet. When applying the thermosetting resin composition to the transfer layer or protective layer, the thermosetting resin composition may be appropriately diluted with a solvent. Examples of solvents include ethyl acetate, butyl acetate, and toluene. If the thermosetting resin sheet includes two or more resin layers, they may be formed by sequentially forming and laminating each resin layer. For example, if there is a clear layer and a colored resin layer, the clear layer and the colored resin layer may be laminated on the transfer layer in that order. Furthermore, if the thermosetting resin sheet includes a protective layer, the thermosetting resin sheet may be obtained by laminating a colored resin layer formed on the protective layer with a clear layer formed on the transfer layer.

[0057] [Painting Method] The following describes a painting method for applying paint to an object to be painted using the thermosetting resin sheet of the present invention. The painting method according to one embodiment of the present invention comprises the following first and second steps: First step: A step of attaching the thermosetting resin sheet to the object to be painted. Second step: A step of curing the thermosetting resin sheet.

[0058] (First Step) The first step is to attach a thermosetting resin sheet to the object to be painted. The object to which the thermosetting resin sheet is attached is not particularly limited, but examples include electrical appliances, automobiles, vehicles such as other transport equipment, vehicle parts of automobiles and other transport equipment, general merchandise, heavy machinery, ships, aircraft exterior materials, exterior walls or roofing materials of houses and buildings, bridges, steel frames, plants, wind turbine blades, etc. Examples of vehicle parts include interior materials for vehicles and exterior materials for vehicles. Among these, vehicles and vehicle parts are preferred, vehicle parts are more preferred, and exterior materials for vehicles are even more preferred. Examples of exterior materials for vehicles include hoods, roofs, door panels, bumpers, fuel filler panels, trunk lids, rear gates, etc. When the thermosetting resin sheet is attached to the exterior material of a vehicle, it may be attached to the exterior material attached to the vehicle body, or it may be attached to the exterior material before it is attached to the vehicle body. Furthermore, the material of the object to be painted is not particularly limited, but may be any of the following: resin material, inorganic material such as ceramic, painted steel plate, unpainted steel plate, steel material, etc. Among these, painted steel plate, unpainted steel plate, steel material, etc., are preferred.

[0059] The thermosetting resin sheet used in the first step is a sheet for forming a coating on the object to be coated. The thermosetting resin sheet comprises a resin layer and a transfer layer formed on one side of the resin layer. The resin layer is made of a thermosetting resin composition and can be cured by heating. The resin layer constitutes a part of the coating formed on the object to be coated. The resin layer may be a laminate with two or more layers as described above.

[0060] Before being applied to the object to be painted, a protective layer may be bonded to the other side of the resin layer of the thermosetting resin sheet. If a protective layer is bonded, the transfer-type thermosetting resin should have the protective layer peeled off from the resin layer before being applied to the object to be painted, exposing the resin layer, and then be applied to the object to be painted. The method of peeling off the protective layer is not particularly limited and may be done by a peeling device or by hand. Of course, the protective layer may be omitted in the thermosetting resin sheet.

[0061] In this process, a thermosetting resin sheet with the resin layer exposed is preferably attached to the object to be painted so that the resin layer is in contact with it. The method of attaching the thermosetting resin sheet to the object to be painted is not particularly limited; it may be done by hand using a squeegee or by using a laminating device. Since the resin layer is made of a thermosetting resin composition and is not yet cured at the time of attachment, it is easier to ensure a certain degree of flexibility. Therefore, the resin layer can adhere properly to the object to be painted and be temporarily fixed to the object with appropriate adhesive strength.

[0062] The thermosetting resin sheet may be pre-formed by vacuum forming, press forming, or compressed air forming, and shaped to correspond to the shape of the object to be painted. The shaped thermosetting resin sheet is then attached to the object to be painted. Pre-forming may be performed before peeling off the protective layer from the resin layer, or after peeling off the protective layer, if the thermosetting resin sheet has a protective layer. Pre-forming allows the thermosetting resin sheet to be easily attached to the object to be painted, even if the object has a complex shape. Of the above, pre-forming is preferably performed by vacuum forming. Pre-forming is preferably done by pressing the painting sheet to a jig or mold using vacuum forming, and then stretching the thermosetting resin sheet using the jig or mold to shape it to correspond to the surface shape of the object to be painted. Here, vacuum forming is preferably TOM forming. TOM stands for "Three Dimension Overlay Method," and applying TOM molding allows for the creation of complex shapes.

[0063] (Second Step) The second step is performed after the first step and cures the resin layer of the thermosetting resin sheet. In this step, the resin layer should be sufficiently cured to the point where it can be used as a coating.

[0064] Furthermore, in the second step, the thermosetting resin sheet, while attached to the object to be coated, is preferably heated using a heating device such as an oven or an infrared heater. The heating temperature is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, preferably 160°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, and even more preferably 120°C or lower, preferably 70°C to 160°C, more preferably 80°C to 150°C, even more preferably 90°C to 140°C, and even more preferably 90°C to 120°C. The heating time is, for example, 5 minutes to 300 minutes, preferably 10 minutes to 180 minutes.

[0065] The coating method of the present invention may further include a step of peeling the transfer layer from the resin layer. The transfer layer may be peeled off by a peeling device or by hand. The peeling of the transfer layer may be performed before the second step, after the second step, or in the middle of the second step, but it is preferable to perform it before the second step.

[0066] A step of spray painting may be included between the first and second steps.

[0067] For example, in one embodiment, first, a thermosetting resin sheet equipped with a transfer layer is attached to the object to be painted. The object to be painted may be, for example, a painted steel plate or an unpainted steel plate. Next, the transfer layer is peeled off. Then, spray painting is performed to form a spray coating layer on the thermosetting resin sheet and the areas of the object to be painted where the thermosetting resin sheet is not provided. The spray coating layer may be a clear coating layer or a colored coating layer, but a clear coating layer is preferred. The clear coating layer may be formed, for example, by a thermosetting resin composition for spray painting that does not contain a colorant. The colored coating layer may be formed, for example, by a thermosetting resin composition for spray painting that contains a colorant.

[0068] Subsequently, the thermosetting resin sheet is cured in the second step described above, and the spray coating layer is cured by baking or other means. For example, it is preferable to cure the thermosetting resin sheet and the spray coating layer by heating in the second step described above. In this embodiment, as described above, if the spray coating layer is a clear coating layer, the thermosetting resin sheet is preferably made of a colored resin layer, since a clear layer is not required.

[0069] In another embodiment, a thermosetting resin sheet with a transfer layer is attached to the object to be painted. Next, spray painting is performed to form a first coating layer on top of the transfer layer and on the parts of the object to be painted where the thermosetting resin sheet is not attached. Then, the transfer layer is peeled off. As a result, the first coating layer is provided only on the parts of the object to be painted where the thermosetting resin sheet is not attached. The first coating layer may be a clear coating layer or a colored coating layer, but a colored coating layer is preferred. The colored coating layer may be formed, for example, by a thermosetting resin composition for spray painting that contains a colorant. The clear coating layer may be formed, for example, by a thermosetting resin composition for spray painting that does not contain a colorant. The first coating layer may be formed by spraying the thermosetting resin composition for spray painting onto the object to be painted and pre-drying it.

[0070] Next, spray painting is performed to form a second coating layer on the thermosetting resin sheet and the first coating layer. The second coating layer may be a clear coating layer or a colored coating layer, but it is preferable that it be a clear coating layer. After that, the thermosetting resin sheet is cured by the second step described above, and the first and second coating layers are cured by baking or the like. For example, it is preferable to cure the resin sheet and the first and second coating layers by heating in the second step described above. In this embodiment, as described above, if the second coating layer is a clear coating layer, the thermosetting resin sheet is preferably made of a colored resin layer because a clear layer is not required.

[0071] [Vehicles and Vehicle Parts] The vehicles and vehicle parts of the present invention are painted using the thermosetting resin sheet of the present invention.

[0072] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0073] The measurement and evaluation methods in this embodiment are as follows: (Hardness of coating after baking) For the thermosetting resin sheet, after peeling off the protective layer, it was bonded to the steel plate via the resin layer, and then the transfer layer was peeled off. The resin layer bonded to the steel plate was hardened by heating at the heating temperature and heating time shown in Table 1. The pencil hardness of the obtained hardened product was measured on the surface in accordance with JIS K 5600-5-4 and evaluated according to the following evaluation criteria. In Example 13, resin layer B was bonded to a painted steel plate. <Evaluation Criteria> A: No scratches were made at HB pencil hardness. B: Scratches were made at HB pencil hardness, but no scratches were made at B pencil hardness. C: Scratches were made at B pencil hardness.

[0074] (Adhesion to baked-on painted plates) For the thermosetting resin sheet, after peeling off the protective layer, it was bonded to the steel plate via the resin layer, and then the transfer layer was peeled off. The resin layer bonded to the steel plate was cured by heating it at the heating temperature and heating time shown in Table 1. A cross-cut test was performed on the resin layer in accordance with JIS K 5600-5-6 and evaluated according to the following evaluation criteria. In Example 13, resin layer A was bonded to a painted steel plate. <Evaluation Criteria> A: Test result classification 0 to 1 B: Test result classification 2 C: Test result classification 3 or higher

[0075] The components of the transfer layer film, protective layer film, and resin layer used in the examples and comparative examples are as follows: <Transfer layer film> Unoriented cyclic polyolefin film (Toray Industries, Inc. "Decofit Q17CK", thickness 100 μm), tensile elongation at 100°C (MD = 1850%, TD = 1850%) <Protective layer film> Unoriented polyethylene terephthalate film (A-PET) (Nakamoto Pax Co., Ltd. "A-PET", thickness 200 μm), tensile elongation at 100°C (MD = 1200%, TD = 980%) <Polyol resin (A)> Polyol resin (1): Acrylic polyol resin, weight-average molecular weight 600,000, hydroxyl value 40 mg KOH / g, glass transition temperature 40°C, solid content concentration (NV) = 30% by mass (solvent: ethyl acetate) Polyol resin (2): Acrylic polyol resin, weight-average molecular weight 300,000, hydroxyl value 40 mg KOH / g, glass transition temperature 40°C, solids content (NV) = 30% by mass (solvent: ethyl acetate) Polyol resin (3): Acrylic polyol resin, weight-average molecular weight 150,000, hydroxyl value 40 mg KOH / g, glass transition temperature 40°C, solids content (NV) = 30% by mass (solvent: ethyl acetate) Polyol resin (4): Polyester polyol resin, weight-average molecular weight 150,000, hydroxyl value 40 mg KOH / g, glass transition temperature 40°C, solids content (NV) = 30% by mass <Melamine resin (B)> Iminomethylol butylated melamine resin, manufactured by Ornex Co., Ltd., trade name "CYMEL 202", solids content (NV) = 80% (solvent: ethyl acetate), reaction start temperature = 110°C <Blocked isocyanate> Hexamethylene diisocyanate-based blocked isocyanates (HDI-based), Blocking agent type: 3,5-Dimethylpyrazole (DMP), solids content (NV) = 70%, solvent is ethyl acetate, reaction start temperature = 120°C <Polyol resin (C)> Hydroxyl group-containing (meth)acrylic polymer: weight average molecular weight 2500, manufactured by Toagosei Co., Ltd. "ARUFON UH-2041", hydroxyl value 120 mg KOH / g, solids content (NV) = 100 mass%, glass transition temperature -50°C <Curing catalyst> Curing catalyst (1): Phosphate-based weak acid catalyst, manufactured by Ornex Co., Ltd., product name "CYCAT 296-9", solids content (NV) = 100 mass% Curing catalyst (2): Metal complex, manufactured by Kusumoto Kasei Co., Ltd., product name "XK-639", solids content (NV) = 100 mass% <Curing agent> Hexamethylene diisocyanate-based blocked isocyanate (HDI), blocking agent: 3,5-dimethylpyrazole (DMP), solids content (NV) = 70%, solvent: ethyl acetate, reaction initiation temperature = 120°C.

[0076] [Preparation of Thermosetting Resin Sheets] (Examples 1-12) Each component was added according to the formulation shown in Table 1, and ethyl acetate was added as a solvent to prepare a coating of thermosetting resin composition A with a solid content concentration of 30% by mass.

[0077] After coating the surface of the transfer layer film with a paint of thermosetting resin composition A using an applicator, a pre-drying process was carried out at a drying temperature of 60°C for 30 minutes, followed by a main drying process at a drying temperature of 90°C for 5 minutes to form a 50 μm thick resin layer A on the transfer layer. Then, a protective layer film was laminated onto the resin layer A on the transfer layer and laminated at 25°C to obtain a thermosetting resin sheet in which the transfer layer, resin layer A, and protective layer were laminated in that order. The above evaluation was performed using the obtained thermosetting resin sheet. The evaluation results are shown in Table 1.

[0078] (Example 13) Each component was added according to the formulation shown in Table 1, and ethyl acetate was added as a solvent to prepare paints of thermosetting resin composition A and paints of thermosetting resin composition B, with a solid content concentration of 30% by mass.

[0079] After coating the surface of the transfer layer film with a paint of thermosetting resin composition A using an applicator, a pre-drying process was carried out at a drying temperature of 60°C for 30 minutes, followed by a main drying process at a drying temperature of 90°C for 5 minutes to form a 50 μm thick resin layer A on the transfer layer. After coating the surface of resin layer A with a paint of thermosetting resin composition B using an applicator, a pre-drying process was carried out at a drying temperature of 60°C for 30 minutes, followed by a main drying process at a drying temperature of 90°C for 5 minutes to form a 50 μm thick resin layer B on resin layer A. Then, a protective layer film was laminated onto resin layer B on resin layer A and laminated at 25°C to obtain a thermosetting resin sheet in which the transfer layer, resin layer A, resin layer B, and protective layer were laminated in that order. The above evaluation was performed using the obtained thermosetting resin sheet. The evaluation results are shown in Table 1.

[0080]

[0081] In Examples 1 to 13, the thermosetting resin sheets contained a polyol resin and a melamine resin in at least one resin layer, allowing them to be cured at low heating temperatures, and even at low heating temperatures, the cured thermosetting resin sheets exhibited good adhesion. On the other hand, in Comparative Example 1, although the thermosetting resin sheet contained a polyol resin in its thermosetting resin composition, the crosslinking agent was a blocked isocyanate instead of a melamine resin, requiring a higher heating temperature to ensure adhesion to the substrate.

Claims

1. A thermosetting resin sheet comprising at least one resin layer made of a thermosetting resin composition, wherein the thermosetting resin composition comprises a polyol resin and a melamine resin (B).

2. The thermosetting resin sheet according to claim 1, wherein the polyol resin comprises at least one polyol resin selected from the group consisting of (meth)acrylic polyol resins and polyester polyol resins.

3. The thermosetting resin sheet according to claim 1, wherein the content of the melamine resin (B) in the thermosetting resin composition is 5 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the polyol resin contained in the thermosetting resin composition.

4. The thermosetting resin sheet according to claim 1, wherein the weight-average molecular weight of the melamine resin (B) is 1,000 or more and 5,000 or less.

5. The thermosetting resin sheet according to claim 1, wherein the thickness of the resin layer is 200 μm or less.

6. The thermosetting resin sheet according to claim 1, wherein the polyol resin comprises a polyol resin (A) having a weight-average molecular weight of 100,000 or more and 1,000,000 or less.

7. The thermosetting resin sheet according to claim 6, wherein the polyol resin further comprises a polyol resin (C) having a weight-average molecular weight of 300 or more and 30,000 or less, and the polyol resin (C) is at least one polyol selected from the group consisting of (meth)acrylic polyol, polyester polyol, polycarbonate polyol and polycaprolactone polyol.

8. The thermosetting resin sheet according to claim 1, wherein the thermosetting resin composition further comprises a blocked isocyanate.

9. A vehicle painted using the thermosetting resin sheet described in claim 1 or 2.

10. A vehicle part painted using the thermosetting resin sheet described in claim 1 or 2.

11. A method for producing a thermosetting resin sheet according to any one of claims 1 to 8, comprising the step of applying the thermosetting resin composition onto at least one of the transfer layer and the protective layer to form the resin layer.

12. A painting method for applying paint to an object to be painted using a thermosetting resin sheet according to any one of claims 1 to 8, comprising the steps of: attaching the thermosetting resin sheet to the object to be painted; and curing the thermosetting resin sheet attached to the object to be painted at a heating temperature of 120°C or lower.

Images