Adhesive composition, adhesive sheet, laminate provided with adhesive sheet, laminate provided with cured sheet, and method for producing laminate provided with cured sheet

Abstract

The present invention provides an adhesive composition that is suitable for forming a cured sheet which exhibits sufficient adhesive strength for practical use and in which said adhesive strength can easily be lowered by contact with alcohol (specifically, at least one type of compound classified as an alcohol). This adhesive composition includes a polyamide P. The melt viscosity of the polyamide P at 160°C is 2000 Pa∙s or less. The included quantity of a crosslinking agent in the adhesive composition is 2.5 parts by mass or less per 100 parts by mass of the polyamide P.

Description

Adhesive composition, adhesive sheet, laminate with adhesive sheet, laminate with cured sheet, and method for manufacturing laminate with cured sheet

[0001] The present invention relates to an adhesive composition, an adhesive sheet, a laminate comprising an adhesive sheet, a laminate comprising a cured sheet, and a method for producing a laminate comprising a cured sheet.

[0002] Adhesives such as adhesive sheets are used to bond components together. As an example, the components can be bonded together by placing an adhesive sheet between the components and forming a cured sheet from the adhesive sheet. The cured sheet can be formed, for example, by heating the adhesive sheet to melt it, and then cooling it as necessary to harden the molten adhesive sheet.

[0003] Examples of materials for the cured sheet (or adhesive sheet) include adhesive compositions containing polyamide (see Patent Document 1). When an adhesive composition containing polyamide is used, the cured sheet formed from the adhesive composition tends to have excellent heat resistance and chemical resistance.

[0004] Japanese Patent Application Publication No. 7-62318

[0005] In recent years, a technology has been developed that reduces the adhesive strength of a cured sheet at the appropriate time to separate components. This technology makes it possible to recover and reuse components, and to easily repair or replace them. Furthermore, its use for temporary adhesion in manufacturing processes may improve productivity.

[0006] Possible means for reducing the adhesive strength of a cured sheet include applying a stimulus by heating, applying a voltage, irradiating with light, immersing in a liquid, etc. In particular, if the adhesive strength of a cured sheet could be reduced by simply contacting it with an alcohol such as ethanol without using an acid or base, work safety would be greatly improved.

[0007] Patent Document 1 discloses an adhesive composition that uses alcohol-soluble nylon as the polyamide. However, according to the investigations of the present inventors, the adhesive composition of Patent Document 1 has a composition adjusted so that it does not dissolve in alcohol after curing.

[0008] Therefore, an object of the present invention is to provide an adhesive composition suitable for forming a cured sheet that exhibits practically sufficient adhesive strength and whose adhesive strength can be easily reduced by contact with an alcohol (more specifically, at least one compound classified as an alcohol).

[0009] The present invention provides an adhesive composition containing a polyamide, wherein the polyamide has a melt viscosity of 2000 Pa·s or less at 160°C, and the amount of a crosslinking agent blended is 2.5 parts by mass or less per 100 parts by mass of the polyamide.

[0010] The present invention further provides an adhesive sheet comprising the above adhesive composition.

[0011] The present invention further provides a laminate comprising: a resin sheet; and the adhesive sheet described above disposed on the resin sheet.

[0012] The present invention further provides a laminate comprising: a substrate; and a cured sheet disposed on the substrate and formed from an adhesive composition containing a polyamide, wherein the peel strength between the substrate and the cured sheet is 6.0 N / 20 mm or greater; and the ratio M2 / M1 determined by the following test is 40% or less. Test: A portion of the cured sheet is scraped off to obtain a test piece. The test piece is immersed in ethanol for 72 hours in an atmosphere at 60°C. The ratio M2 / M1, which is the mass M2 (g) of the test piece after immersion in ethanol to the mass M1 (g) of the test piece before immersion in ethanol, is determined.

[0013] The present invention further provides a method for producing a laminate including the cured sheet described above, the method comprising forming the cured sheet on the substrate.

[0014] According to the present invention, it is possible to provide an adhesive composition suitable for forming a cured sheet that exhibits practically sufficient adhesive strength and whose adhesive strength can be easily reduced by contact with an alcohol (more specifically, at least one compound classified as an alcohol).

[0015] Fig. 1 is a cross-sectional view schematically showing an adhesive sheet according to one embodiment of the present invention; Fig. 2 is a cross-sectional view schematically showing a laminate including an adhesive sheet; Fig. 3 is a cross-sectional view schematically showing a laminate including a cured sheet; Fig. 4 is a view for explaining an example of a method for manufacturing a laminate including a cured sheet; Fig. 5 is a cross-sectional view schematically showing a modified example of a laminate including a cured sheet.

[0016] An adhesive composition according to a first aspect of the present invention is an adhesive composition containing a polyamide, wherein the polyamide has a melt viscosity of 2000 Pa s or less at 160°C, and the amount of a crosslinking agent blended is 2.5 parts by mass or less per 100 parts by mass of the polyamide.

[0017] In a second aspect of the present invention, for example, in the adhesive composition according to the first aspect, the melt viscosity is 1000 Pa·s or more.

[0018] In a third aspect of the present invention, for example, the adhesive composition according to the first or second aspect contains at least one selected from the group consisting of the crosslinking agent, a reactive agent other than the crosslinking agent, and a plasticizer.

[0019] In a fourth aspect of the present invention, for example, in the adhesive composition according to any one of the first to third aspects, the amount of the crosslinking agent blended is 0.01 parts by mass or more per 100 parts by mass of the polyamide.

[0020] In a fifth aspect of the present invention, for example, in the adhesive composition according to any one of the first to fourth aspects, the weight average molecular weight of the polyamide is 10,000 to 30,000.

[0021] In a sixth aspect of the present invention, for example, in the adhesive composition according to any one of the first to fifth aspects, the polyamide has a piperazine skeleton.

[0022] In a seventh aspect of the present invention, for example, in the adhesive composition according to any one of the first to sixth aspects, the polyamide is soluble in at least one compound classified as an alcohol.

[0023] In an eighth aspect of the present invention, for example, in the adhesive composition according to any one of the first to seventh aspects, the crosslinking agent is an epoxy-based crosslinking agent.

[0024] An adhesive sheet according to a ninth aspect of the present invention comprises the adhesive composition according to any one of the first to eighth aspects.

[0025] In a tenth aspect of the present invention, for example, the adhesive sheet according to the ninth aspect has a thickness of 5 to 200 μm.

[0026] A laminate according to an eleventh aspect of the present invention comprises: a resin sheet; and an adhesive sheet according to the ninth or tenth aspect, disposed on the resin sheet.

[0027] In a twelfth aspect of the present invention, for example, in the laminate according to the eleventh aspect, the resin sheet has a surface that has been subjected to a release treatment.

[0028] A thirteenth aspect of the present invention provides a laminate comprising: a substrate; and a cured sheet disposed on the substrate and formed from an adhesive composition containing polyamide; wherein the peel strength between the substrate and the cured sheet is 6.0 N / 20 mm or more; and the ratio M2 / M1 determined by the following test is 40% or less. Test: A portion of the cured sheet is scraped off to obtain a test piece. The test piece is immersed in ethanol for 72 hours in an atmosphere at 60°C. The ratio M2 / M1 of the mass M2 (g) of the test piece after immersion in ethanol to the mass M1 (g) of the test piece before immersion in ethanol is determined.

[0029] In a fourteenth aspect of the present invention, for example, in the laminate according to the thirteenth aspect, the surface roughness of the substrate is 25 μm or less.

[0030] In a fifteenth aspect of the present invention, for example, in the laminate according to the thirteenth or fourteenth aspect, the cured sheet has a tensile modulus of elasticity of 1 to 50 MPa.

[0031] A manufacturing method according to a sixteenth aspect of the present invention is the method for manufacturing a laminate according to any one of the thirteenth to fifteenth aspects, the manufacturing method including forming the cured sheet on the substrate.

[0032] In a seventeenth aspect of the present invention, for example, in the manufacturing method according to the sixteenth aspect, an adhesive sheet containing the adhesive composition is heated while being in contact with the substrate, and the cured sheet is formed from the adhesive sheet.

[0033] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0034] <Embodiment of Adhesive Composition> The adhesive composition of this embodiment contains polyamide P. The melt viscosity of the polyamide P at 160°C is 2000 Pa s or less. Furthermore, the amount of crosslinking agent in the adhesive composition is 2.5 parts by mass or less per 100 parts by mass of polyamide P. In this specification, the phrase "the amount of crosslinking agent is 2.5 parts by mass or less per 100 parts by mass of polyamide P" includes embodiments in which the adhesive composition does not contain a crosslinking agent (the amount of crosslinking agent is 0 parts by mass). The adhesive composition of this embodiment is typically a hot-melt adhesive.

[0035] According to the investigations of the present inventors, by adjusting the melt viscosity of polyamide P and the amount of crosslinking agent to fall within the above-mentioned ranges, it is possible to form a cured sheet that exhibits practically sufficient adhesive strength and whose adhesive strength can be easily reduced by contact with alcohol (more specifically, at least one compound classified as an alcohol).

[0036] (Polyamide) As described above, polyamide P has a melt viscosity of 2000 Pa s or less at 160°C. The melt viscosity of polyamide P can be determined by the following method. First, a sheet (thickness 1 mm) composed only of polyamide P is prepared by molding or the like. This sheet is punched out to prepare a test piece with a diameter of 25 mm. This test piece is sandwiched between parallel plates and set in a commercially available viscoelasticity measuring device (for example, ARES-G2 manufactured by TA Instruments). The test piece is heated to 160°C to melt. In this state, the parallel plates are rotated, and the melt viscosity is measured at a frequency of 0.1 Hz.

[0037] The melt viscosity of polyamide P at 160°C can be considered the initial melt viscosity when an adhesive sheet containing the adhesive composition is heated to 160°C. If this melt viscosity is 2000 Pa s or less, the adhesive sheet is easily melted by heating, and the adhesive sheet easily conforms to the surface of the adherend (substrate). In particular, if the surface of the substrate is uneven, part of the heated adhesive sheet is likely to penetrate into the recesses in the surface of the substrate. When a cured sheet is formed from the adhesive sheet while the adhesive sheet conforms to the surface of the substrate, the cured sheet tends to exhibit adhesive strength sufficient for practical use.

[0038] The melt viscosity of polyamide P at 160°C is 2000 Pa s or less as described above, and may be 1800 Pa s or less, 1600 Pa s or less, 1500 Pa s or less, 1400 Pa s or less, or even 1300 Pa s or less. From the viewpoint of handleability, the lower limit of the melt viscosity of polyamide P may be, for example, 1000 Pa s or more, 1100 Pa s or more, or even 1200 Pa s or more.

[0039] Polyamide P is preferably soluble in at least one compound classified as an alcohol. In this specification, "polyamide P is soluble in at least one compound classified as an alcohol" means that 5 g or more of polyamide P can be dissolved in 100 g of at least one compound classified as an alcohol within 24 hours at 60°C. Polyamide P is more preferably soluble in at least one compound classified as a lower alcohol having 5 or less carbon atoms. Examples of lower alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and n-pentanol. Polyamide P is particularly preferably soluble in ethanol.

[0040] The polyamide P preferably has a piperazine skeleton (more specifically, a structural unit A containing a piperazine skeleton). The piperazine skeleton not only improves the solubility of the polyamide P in alcohol, but is also suitable for reducing the melt viscosity of the polyamide P. The polyamide P containing a piperazine skeleton also tends to reduce the tensile modulus of elasticity of a cured sheet formed from the adhesive composition. The structural unit A containing a piperazine skeleton is preferably represented by the following formula (1):

[0041] In formula (1), R 1 ~R 4 are each independently a hydrogen atom or an arbitrary substituent. The arbitrary substituent is not particularly limited, and examples thereof include hydrocarbon groups. Examples of the hydrocarbon group include alkyl groups such as methyl, ethyl, and propyl groups. 1 ~R 4 are preferably all hydrogen atoms.

[0042] In formula (1), R 5 is an optional linking group. The optional linking group is, for example, a divalent hydrocarbon group. The divalent hydrocarbon group may be linear, branched, or cyclic. The divalent hydrocarbon group may have, for example, 1 to 20 carbon atoms, 3 to 15 carbon atoms, or even 4 to 10 carbon atoms. Examples of the divalent hydrocarbon group include alkylene groups such as butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group.

[0043] In polyamide P, the content of structural unit A containing a piperazine skeleton is, for example, 1 wt% or more, and may be 10 wt% or more, 30 wt% or more, 50 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or even 95 wt% or more. Polyamide P may be composed essentially of structural unit A. Note that polyamide P does not need to contain structural unit A as long as the melt viscosity of polyamide P at 160°C is 2000 Pa s or less.

[0044] The polyamide P may contain a structural unit B different from the structural unit A. The structural unit B may be represented by the following formula (2).

[0045] In formula (2), R 6 and R 7 are each independently an optional linking group. 6 and R 7 may be the same or different. The optional linking group is, for example, a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those described above for formula (1).

[0046] The content of the structural unit B in the polyamide P is not particularly limited and is, for example, 1 wt % to 99 wt %. The polyamide P may not contain the structural unit B. Note that the polyamide P may be composed essentially of the structural unit B only, as long as the melt viscosity of the polyamide P at 160°C is 2000 Pa s or less.

[0047] Polyamide P may be composed of only a single type of structural unit, but preferably contains multiple types of structural units. Polyamide P containing multiple types of structural units tends to have high solubility in alcohol. For example, polyamide P may contain multiple types of structural unit A, or may contain both structural unit A and structural unit B.

[0048] The weight-average molecular weight (Mw) of polyamide P may be, for example, 40,000 or less, 35,000 or less, 30,000 or less, or even 25,000 or less. The smaller the weight-average molecular weight of polyamide P, the lower the melt viscosity of polyamide P tends to be. The lower limit of the weight-average molecular weight of polyamide P may be, for example, 10,000 or more, 15,000 or more, or even 20,000 or more. The weight-average molecular weight of polyamide P is preferably 10,000 to 30,000, more preferably 20,000 to 30,000. The weight-average molecular weight of polyamide P can be calculated from the obtained chromatogram (chart) by measuring the molecular weight distribution of polyamide P using a gel permeation chromatograph (GPC) equipped with a refractive index detector (RID), and using a calibration curve based on standard polymethyl methacrylate.

[0049] As the polyamide P (particularly the polyamide P containing the structural unit A), commercially available products such as Platamid M1276 and Platamid H2519 manufactured by Arkema can be used.

[0050] The ratio of the mass (g) of polyamide P to the mass (g) of the total solid content of the adhesive composition is, for example, 50 wt % or more, and may be 70 wt % or more, 80 wt % or more, 90 wt % or more, or even 95 wt % or more. The adhesive composition may contain only polyamide P as the solid content. The adhesive composition may contain, together with polyamide P, another polyamide different from polyamide P (a polyamide having a melt viscosity at 160°C of more than 2000 Pa s), but preferably does not contain such a polyamide.

[0051] (Crosslinking Agent) The crosslinking agent is a compound having two or more reactive sites with polyamide P. The crosslinking agent tends to reduce the crystallinity of the cured sheet formed from the adhesive composition, thereby reducing the tensile modulus. The crosslinking agent is preferably capable of reacting with polyamide P (specifically, functional groups contained in polyamide P) and forming a chemical bond through the reaction. Examples of functional groups contained in polyamide P include carboxyl groups, amino groups, and amide groups. The crosslinking agent preferably contains two or more functional groups capable of reacting with functional groups contained in polyamide P.

[0052] Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based crosslinking agent, a thiol-based crosslinking agent, an unsaturated-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, a metal chelate-based crosslinking agent, and a peroxide-based crosslinking agent. Epoxy-based crosslinking agents and peroxide-based crosslinking agents are preferred, and epoxy-based crosslinking agents are particularly preferred. The crosslinking agents can be used alone or in combination of two or more.

[0053] The isocyanate crosslinking agent is a compound having one or more isocyanate groups in one molecule. Examples of the isocyanate crosslinking agent include carbodiimide-modified isocyanates (for example, Carbodilite V-05 manufactured by Nisshinbo).

[0054] The epoxy crosslinking agent is a compound having two or more epoxy groups per molecule. The number of epoxy groups contained in the epoxy crosslinking agent is preferably 3 to 5 per molecule. Examples of the epoxy crosslinking agent include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (e.g., TETRAD-C manufactured by Mitsubishi Gas Chemical Company, Inc.) and bisphenol-A-diglycidyl ether (e.g., jER828 manufactured by Mitsubishi Chemical Corporation).

[0055] As described above, the amount of crosslinking agent in the adhesive composition is 2.5 parts by mass or less, and may be 2.0 parts by mass or less, 1.8 parts by mass or less, 1.5 parts by mass or less, 1.3 parts by mass or less, 1.0 parts by mass or less, or even 0.8 parts by mass or less, per 100 parts by mass of polyamide P. When a cured sheet is formed using an adhesive composition in which the amount of crosslinking agent is adjusted to a low value, contacting the cured sheet with alcohol tends to reduce the adhesive strength of the cured sheet. The amount of crosslinking agent may be, for example, 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, or even 0.3 parts by mass or more, per 100 parts by mass of polyamide P, from the viewpoint of improving the adhesive strength of the cured sheet during use and reducing the tensile modulus of the cured sheet. However, in some cases, the adhesive composition may not contain a crosslinking agent. That is, the amount of crosslinking agent in the adhesive composition may be 0 parts by mass per 100 parts by mass of polyamide P.

[0056] (Reactant Other Than Crosslinking Agent) The adhesive composition may contain a reactant other than a crosslinking agent. The reactant other than a crosslinking agent (hereinafter sometimes simply referred to as "reactant") is a compound having one reactive site with polyamide P. However, the reactant may also be a compound that reacts with itself to form a chemical bond. The reactant tends to reduce the crystallinity of the cured sheet formed from the adhesive composition, thereby reducing the tensile modulus. The reactant is preferably capable of reacting with polyamide P (more specifically, functional groups contained in polyamide P) and forming a chemical bond through the reaction. The reactant preferably contains one functional group that can react with a functional group contained in polyamide P.

[0057] Examples of the reactant include epoxy-based reactants, amine-based reactants, thiol-based reactants, unsaturated-based reactants, oxazoline-based reactants, aziridine-based reactants, carbodiimide-based reactants, metal chelate-based reactants, peroxide-based reactants, etc. The reactants can be used alone or in combination of two or more.

[0058] In the adhesive composition, the amount of the reactant blended is preferably 1 to 20 parts by mass per 100 parts by mass of polyamide P. The adhesive composition may not contain a reactant. That is, the amount of the reactant blended in the adhesive composition may be 0 part by mass per 100 parts by mass of polyamide P.

[0059] (Plasticizer) The adhesive composition may contain a plasticizer. The plasticizer is compatible with polyamide P and can adjust the melt viscosity of the adhesive composition and the tensile modulus of a cured sheet formed from the adhesive composition. Examples of plasticizers include alcohols (higher alcohols, polyhydric alcohols, phenols, etc.), hydroxybenzoic acid esters, aromatic sulfonamides, and phosphate esters. These plasticizers are commonly used as plasticizers for polyamides. However, the plasticizer is not limited to the above-mentioned ones and may also be polyesters, polycarboxylic acid esters, epoxies, etc. The plasticizers can be used alone or in combination of two or more.

[0060] Examples of alcohols include polyhydric alcohols such as hexylene glycol and glycerin; and phenols such as β-naphthol, dibenzylphenol, and octylcresol. Examples of hydroxybenzoic acid esters include hydroxybenzoic acid alkyl esters such as p-hydroxybenzoic acid octyl ester, p-hydroxybenzoic acid heptyl ester, and p-hydroxybenzoic acid 2-ethylhexyl ester. Examples of aromatic sulfonamides include N-methylbenzenesulfonamide, N-butylbenzenesulfonamide, p-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, and N-cyclohexyl-p-toluenesulfonamide. Examples of phosphate esters include triphenyl phosphate and tricresyl phosphate. Examples of polycarboxylic acid esters include dimethyl phthalate.

[0061] The plasticizer preferably hardly volatilizes when the adhesive composition is heated to 160°C, and as an example, is preferably a compound having a melting point of 200°C or higher.

[0062] In the adhesive composition, the blend amount of the plasticizer is preferably 1 to 20 parts by mass per 100 parts by mass of polyamide P. When the blend amount of the plasticizer is 1 part by mass or more per 100 parts by mass of polyamide P, the plasticity of the cured sheet formed from the adhesive composition tends to be sufficiently improved. When the blend amount of the plasticizer is 20 parts by mass or less per 100 parts by mass of polyamide P, bleeding out of the plasticizer is suppressed. Note that the adhesive composition does not have to contain a plasticizer. That is, the blend amount of the plasticizer in the adhesive composition may be 0 parts by mass per 100 parts by mass of polyamide P.

[0063] The adhesive composition preferably contains at least one selected from the group consisting of a crosslinking agent, a reactive agent other than a crosslinking agent, and a plasticizer, which tends to reduce the crystallinity of the cured sheet formed from the adhesive composition, thereby reducing the tensile modulus.

[0064] (Other Components) The adhesive composition may further contain other components in addition to the components described above. Examples of other components include solvents, silane coupling agents, pH adjusters, viscosity adjusters (thickeners, etc.), leveling agents, release adjusters, softeners, fillers, colorants (pigments, dyes, etc.), surfactants, antistatic agents, preservatives, antioxidants, UV absorbers, antioxidants, and light stabilizers. From the viewpoint of storage stability, the adhesive composition preferably does not contain a silane coupling agent such as an epoxy silane. In particular, since epoxy silanes may self-react in an environment where water is present, the adhesive composition preferably does not contain an epoxy silane.

[0065] Examples of the solvent include water; alcohols such as methanol, ethanol, and isopropyl alcohol (IPA); ketones such as methyl ethyl ketone; esters; aliphatic, alicyclic, and aromatic hydrocarbons; halogenated hydrocarbons; amides such as dimethylformamide; sulfoxides such as dimethyl sulfoxide; and ethers such as dimethyl ether and tetrahydrofuran. The solvents may be used alone or in combination of two or more. The adhesive composition may contain a mixed solvent of water and an alcohol such as ethanol as the solvent.

[0066] The solvent content in the adhesive composition is not particularly limited and is, for example, 60% by mass to 99% by mass. However, in some cases, the solvent content may be less than 60% by mass. The adhesive composition may not contain a solvent. The solids concentration of the adhesive composition may be, for example, 1% by mass to 40% by mass, 10% by mass to 35% by mass, or even 15% by mass to 30% by mass.

[0067] <Embodiment of Adhesive Sheet> Fig. 1 is a cross-sectional view schematically showing an adhesive sheet 1 of this embodiment. The adhesive sheet 1 contains the adhesive composition described above. Specifically, the adhesive sheet 1 has the same composition as the adhesive composition except that it does not contain a solvent. However, the adhesive sheet 1 may contain a small amount of solvent derived from the adhesive composition. Note that when the adhesive composition contains a crosslinking agent, the crosslinking agent is typically present in an unreacted state in the adhesive sheet 1. The adhesive sheet 1 of this embodiment is typically a hot-melt adhesive sheet.

[0068] The thickness of the adhesive sheet 1 is, for example, 0.1 μm or more, and may be 0.5 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, or even 10 μm or more. The upper limit of the thickness of the adhesive sheet 1 is not particularly limited, and may be, for example, 2000 μm or less, 1000 μm or less, 500 μm or less, 200 μm or less, 100 μm or less, 50 μm or less, or even 30 μm or less. The thickness of the adhesive sheet 1 is preferably 5 to 200 μm. In this case, the adhesive sheet 1 tends to have sufficient adhesiveness for practical use and to be lightweight and flexible.

[0069] Next, a method for producing an adhesive sheet 1 will be described with reference to Figures 1 and 2. First, a resin sheet 5 shown in Figure 2 is prepared. The resin sheet 5 is typically a release sheet. The resin sheet 5 may be a non-silicone resin sheet or a silicone resin sheet.

[0070] Examples of non-silicone resin sheets include fluorine-based resin sheets (e.g., Nitoflon manufactured by Nitto Denko Corporation), polyester-based resin sheets, polymethylpentene-based resin sheets (e.g., Opulent (registered trademark) manufactured by Mitsui Chemicals Tocello), polystyrene-based resin sheets (e.g., Eudis (registered trademark) manufactured by Kurabo Industries, Ltd.), polyamide-based resin sheets, polyolefin-based resin sheets, etc. More specifically, examples include unstretched polyamide 6, unstretched polyamide 66, biaxially oriented polyamide 6, biaxially oriented polyamide 66, biaxially oriented polypropylene, biaxially oriented polyethylene terephthalate, biaxially oriented polybutylene terephthalate, easily molded polyethylene terephthalate, cast-molded polytetrafluoroethylene, unstretched extruded tetrafluoroethylene-ethylene copolymer (ETFE), unstretched extruded tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), unstretched extruded tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and laminates having these as the main layer.

[0071] The resin sheet 5 preferably has a surface 5a that has been subjected to a release treatment. The release treatment can be performed, for example, by applying a release agent to the surface 5a and then curing the applied release agent. Examples of the release agent that can be used include a silicone-based release agent.

[0072] From the viewpoint of shape conformability, the thickness of the resin sheet 5 is, for example, 1 μm to 1000 μm, and may be 10 μm to 200 μm, 15 μm to 100 μm, or even 20 μm to 50 μm.

[0073] The resin sheet 5 preferably has high heat resistance and is not easily melted by heating. For example, the resin sheet 5 preferably has a melting point of 200° C. or higher.

[0074] Next, an adhesive composition is applied onto the resin sheet 5 (specifically, onto the release-treated surface 5a of the resin sheet 5) to prepare a coating film. The adhesive composition can be applied by a known method, such as a method of dipping the resin sheet 5 into the adhesive composition, a method of brushing the adhesive composition onto the resin sheet 5, a method using various coaters, a spray coating method, or a method of applying an extruded, molten adhesive composition onto the resin sheet 5.

[0075] Next, the resulting coating film can be dried as needed to form the adhesive sheet 1. The coating film may be dried by heat treatment. The heating temperature of the coating film is preferably higher than the boiling point of the solvent contained in the adhesive composition, and is, for example, 80°C or higher, and may be 100°C or higher. The heating temperature of the coating film is preferably lower than the reaction initiation temperature of the crosslinking agent contained in the adhesive composition, and is, for example, 150°C or lower, and may be 120°C or lower. The heating time of the coating film is not particularly limited, and is, for example, 1 minute to 1 hour.

[0076] According to the above manufacturing method, adhesive sheet 1 is formed on resin sheet 5. In another aspect, the present invention provides a laminate (first laminate) 10 including resin sheet 5 and adhesive sheet 1 disposed on resin sheet 5. In first laminate 10, adhesive sheet 1 is preferably in direct contact with surface 5a of resin sheet 5 that has been subjected to a release treatment.

[0077] <Embodiment of Laminate> As shown in FIG. 3 , a laminate (second laminate) 20 of this embodiment includes a substrate 6 and a cured sheet 2 disposed on the substrate 6. The substrate 6 is an adherend for the cured sheet 2 and is a member different from the release sheet. The cured sheet 2 is formed from an adhesive composition containing polyamide P. Specifically, the cured sheet 2 is formed from an adhesive sheet 1 containing the above-described adhesive composition. When the adhesive sheet 1 contains a crosslinking agent derived from the adhesive composition, it is preferable that the crosslinking agent in the cured sheet 2 is in a state where it has reacted with the polyamide P, forming a crosslinked product of the polyamide P. Note that when the adhesive sheet 1 does not contain a crosslinking agent, the composition of the cured sheet 2 is almost the same as the composition of the adhesive sheet 1. Even in this case, the sheet disposed on the substrate 6 (adherend) will be referred to as the "cured sheet" for convenience in this specification to distinguish it from the adhesive sheet 1.

[0078] In the second laminate 20, the peel force F between the substrate 6 and the cured sheet 2 is 6.0 N / 20 mm or more. Furthermore, the ratio M2 / M1 determined by the following test is 40% or less. When the peel force F and the ratio M2 / M1 are within the above ranges, the cured sheet 2 exhibits adhesive strength sufficient for practical use, and tends to be easily reduced by contact with alcohol. Test: A portion of the cured sheet 2 is scraped off to obtain a test piece. The test piece is immersed in ethanol for 72 hours in an atmosphere at 60°C. The ratio M2 / M1, which is the mass M2 (g) of the test piece after immersion in ethanol to the mass M1 (g) of the test piece before immersion in ethanol, is determined.

[0079] The peel force F between the substrate 6 and the cured sheet 2 can be measured by the following method. First, a test laminate is prepared in which a cured sheet 2 measuring 80 mm long x 80 mm wide is placed between two substrates 6 measuring 100 mm long x 100 mm wide. The test laminate can be prepared, for example, by placing the above-mentioned adhesive sheet 1 between the two substrates 6 and forming the cured sheet 2 from this adhesive sheet 1. The cured sheet 2 can be formed by the method described below for the production method of the second laminate 20. As an example, the cured sheet 2 can be formed from the adhesive sheet 1 by heat pressing at 160°C for 1 minute.

[0080] Next, the test laminate is cut into a strip measuring 100 mm long x 20 mm wide to prepare a test specimen. The size of the bonded portion of the test specimen with the cured sheet 2 is 80 mm long x 20 mm wide. Next, the test specimen is placed in a commercially available tensile tester (e.g., TG-10kN manufactured by MinebeaMitsumi Inc.). At this time, two chucks are used to grip the ends of the two substrates 6 included in the test specimen. Next, a T-peel test according to Japanese Industrial Standards (JIS) K6854-3:1999 is performed at a peel rate of 50 mm / min to peel the two substrates 6 apart. The peel force at this time can be considered as the peel force F between the substrate 6 and the cured sheet 2. The T-peel test is performed in an atmosphere at 23°C.

[0081] The peel force F between the substrate 6 and the cured sheet 2 is 6.0 N / 20 mm or more as described above, and may be 7.0 N / 20 mm or more, 8.0 N / 20 mm or more, 9.0 N / 20 mm or more, 10.0 N / 20 mm or more, 11.0 N / 20 mm or more, or even 11.5 N / 20 mm or more. The greater the peel force F, the greater the adhesive strength of the cured sheet 2, and the more likely peeling between the substrate 6 and the cured sheet 2 is to be suppressed. The upper limit of the peel force F is not particularly limited and may be, for example, 50 N / 20 mm or less, or 20 N / 20 mm or less.

[0082] Specifically, the ratio M2 / M1 can be determined by the following method. First, a portion of the cured sheet 2 of the second laminate 20 is scraped off to obtain a test piece (small piece). This test piece is precisely weighed to determine its mass M1 (g). The mass M1 is adjusted to, for example, approximately 0.1 g. Next, the test piece is wrapped in a porous tetrafluoroethylene sheet (for example, "NTF1122" manufactured by Nitto Denko Corporation, average pore size 0.2 μm) and tied with kite string to obtain a measurement sample. The porous tetrafluoroethylene sheet and kite string to be used are precisely weighed in advance, and their total mass M3 (g) is determined.

[0083] Next, the measurement sample is placed in a container (for example, a 50 mL container filled with ethanol) containing a sufficient amount of ethanol relative to the mass M1 of the test piece, and the measurement sample is immersed in the ethanol. This container is left to stand at 60°C for 72 hours. Next, the measurement sample is removed from the container and dried to remove the ethanol from the measurement sample. The measurement sample can be dried, for example, by transferring the measurement sample to an aluminum cup, setting it in a dryer, and heating it at 130°C for 2 hours. The measurement sample after drying is accurately weighed, and the mass M4 (g) is determined. Based on the obtained results, the ratio M2 / M1 can be calculated using the following formula. In the formula below, mass M4 - total mass M3 corresponds to the mass M2 of the test piece after immersion in ethanol. Ratio M2 / M1 = 100 x (M4 - M3) / M1

[0084] As described above, the ratio M2 / M1 is 40% or less, and may be 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 8% or less, 5% or less, or even 3% or less. The lower the ratio M2 / M1, the easier it is to reduce the adhesive strength of the cured sheet 2 by contacting the cured sheet 2 with alcohol, which tends to make it easier to remove the cured sheet 2 from the substrate 6. The lower limit of the ratio M2 / M1 is not particularly limited and may be, for example, 0.1% or more, or 1% or more.

[0085] (Cured Sheet) The thickness of the cured sheet 2 is, for example, 0.1 μm or more, and may be 0.5 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, or even 10 μm or more. The upper limit of the thickness of the cured sheet 2 is not particularly limited and may be, for example, 2000 μm or less, 1000 μm or less, 500 μm or less, 200 μm or less, 100 μm or less, 50 μm or less, or even 30 μm or less. The thickness of the cured sheet 2 is preferably 5 to 200 μm. In this case, the cured sheet 2 tends to have sufficient adhesiveness for practical use and is lightweight and flexible. The thickness of the cured sheet 2 may be the same as the thickness of the adhesive sheet 1 before curing.

[0086] The tensile modulus of cured sheet 2 is preferably 100 MPa or less, and may be 80 MPa or less, 50 MPa or less, 40 MPa or less, 30 MPa or less, 25 MPa or less, or even 20 MPa or less. The lower the tensile modulus of cured sheet 2, the easier the cured sheet 2 deforms and the greater its flexibility tends to be. When the tensile modulus of cured sheet 2 is low, the peel force F tends to be easier to adjust to a higher value. The lower limit of the tensile modulus of cured sheet 2 is not particularly limited and may be, for example, 1 MPa or more, 5 MPa or more, or even 10 MPa or more. When the tensile modulus of cured sheet 2 is 1 MPa or more, cohesive failure of cured sheet 2 is suppressed, making it easier to adjust the peel force F to a higher value. The tensile modulus of cured sheet 2 is preferably 1 to 50 MPa.

[0087] The tensile modulus of cured sheet 2 can be determined by the following method. First, a 20 μm-thick flat film made of the same material as cured sheet 2 is punched out to prepare a dumbbell-shaped No. 3 test specimen. The above-mentioned flat film can be prepared, for example, by heating a 20 μm-thick adhesive sheet 1 at 160°C for 1 minute. The shape of the test specimen (dumbbell-shaped No. 3) is specified in JIS K6251:2017. Next, the test specimen is placed in a commercially available tensile tester (e.g., TG-10kN manufactured by MinebeaMitsumi Inc.), and a tensile test is performed under conditions of an initial chuck distance of 70 mm and a tensile speed of 50 mm / min. Based on the obtained results, a stress-strain curve is created, and the tensile modulus is determined from the slope of the elastic deformation region. The above tensile test is performed in an atmosphere at 23°C.

[0088] The heat of fusion of the cured sheet 2 is preferably 50 J / g or less, and may be 40 J / g or less, 30 J / g or less, or even 25 J / g or less. The smaller the heat of fusion of the cured sheet 2, the lower the tensile modulus of the cured sheet 2, and the easier it is to adjust the peel force F to a larger value. The lower limit of the heat of fusion of the cured sheet 2 may be, for example, 10 J / g or more, 15 J / g or more, or even 20 J / g or more.

[0089] The heat of fusion of the cured sheet 2 can be determined by the following method. First, a portion of the cured sheet 2 is scraped off to obtain a test piece (small piece) of approximately 5 mg. The test piece is placed in an aluminum pan and subjected to differential scanning calorimetry (DSC) measurement using a DSC device. In the DSC measurement, the temperature is first increased from 0°C to 200°C at a heating rate of 10°C / min. Next, the temperature is decreased to 0°C at a heating rate of 10°C / min, and then increased again from 0°C to 200°C at a heating rate of 10°C / min. The heat of fusion can be calculated from the results of the second heating in the DSC measurement.

[0090] The crystallinity of the cured sheet 2 is preferably 30% or less, and may be 25% or less, 20% or less, 15% or less, or even 13% or less. The lower the crystallinity of the cured sheet 2, the lower the tensile modulus of the cured sheet 2, and the easier it is to adjust the peel force F to a larger value. The lower limit of the crystallinity of the cured sheet 2 is, for example, 1% or more, and may be 5% or more, or even 10% or more. The crystallinity of the cured sheet 2 is determined by the heat of fusion ΔH of a polyamide with a crystallinity of 100%. 100 The ratio ΔHm / ΔH of the heat of fusion ΔHm (J / g) of the cured sheet 2 to the heat of fusion ΔHm (J / g) of the cured sheet 2 100 means.

[0091] (Substrate) As described above, the substrate 6 is the adherend of the cured sheet 2. It is preferable that the surface of the substrate 6 (particularly the surface in contact with the cured sheet 2) has irregularities. For example, the surface roughness of the substrate 6, expressed in terms of the arithmetic mean roughness Ra defined in JIS B0601:2013, may be, for example, 1 μm or more, 3 μm or more, or even 5 μm or more. The greater the surface roughness of the substrate 6, the easier it is to adjust the peel force F between the substrate 6 and the cured sheet 2 to a larger value. The upper limit of the surface roughness (arithmetic mean roughness Ra) of the substrate 6 is not particularly limited and may be, for example, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or even 10 μm or less. Furthermore, with the above-described adhesive composition containing polyamide P, it is easy to adjust the peel force F between the substrate 6 and the cured sheet 2 to a large value even if the surface roughness (arithmetic mean roughness Ra) of the substrate 6 is 25 μm or less. The surface roughness of the substrate 6 can be measured using a commercially available laser microscope.

[0092] The substrate 6 preferably has a porous structure. The unevenness present on the surface of the substrate 6 may be due to the porous structure. The pores contained in the porous structure are preferably continuous pores formed in a three-dimensional continuous manner. The substrate 6 may have through-holes penetrating the substrate 6, or may have independent pores. The substrate 6 may be non-porous in some cases.

[0093] The substrate 6 is not particularly limited and may be, for example, a fiber structure. Examples of the fiber structure include base fabrics such as woven fabrics and nonwoven fabrics. The fibers contained in the fiber structure may be long fibers. A substrate 6 containing long fibers tends to have a smaller surface roughness than a substrate containing short fibers. The substrate 6 may also contain short fibers in some cases. Note that the substrate 6 does not have to be a fiber structure and may be, for example, a foam.

[0094] The material of the substrate 6 is not particularly limited, and examples thereof include resin, rubber, metal, glass, ceramics, paper, etc. Examples of resins include polyesters such as polyethylene terephthalate, and polyamides such as nylon.

[0095] The thickness of the substrate 6 is not particularly limited, and is, for example, 1 μm to 1000 μm.

[0096] (Method for Producing Second Laminate) A method for producing the second laminate 20 of this embodiment includes, for example, forming a cured sheet 2 on a substrate 6. The cured sheet 2 can be formed, for example, by the following method. First, the above-described adhesive sheet 1 containing the adhesive composition is prepared. More specifically, a first laminate 10 is prepared in which the adhesive sheet 1 is placed on a resin sheet 5. Next, as shown in FIG. 4 , the adhesive sheet 1 of the first laminate 10 is brought into contact with the substrate 6. This results in a laminate 25 having the substrate 6, adhesive sheet 1, and resin sheet 5 in this order.

[0097] Next, cured sheet 2 is formed from adhesive sheet 1 while adhesive sheet 1 is in contact with substrate 6. As an example, cured sheet 2 is preferably formed from adhesive sheet 1 by heating adhesive sheet 1. Specifically, adhesive sheet 1 is melted by heating. Cured sheet 2 can be formed by cooling and curing the molten adhesive sheet 1 as necessary. Note that if adhesive sheet 1 contains a crosslinking agent derived from the adhesive composition, heating adhesive sheet 1 may cause a crosslinking reaction of polyamide P by the crosslinking agent to proceed.

[0098] The heating temperature of the adhesive sheet 1 is, for example, 150°C to 200°C, and preferably about 160°C. The heating time of the adhesive sheet 1 is not particularly limited, and is, for example, 1 second to 1 hour. The heating method of the adhesive sheet 1 is not particularly limited, and methods such as oven heating, infrared heating, high-frequency heating, and hot pressing can be used. The molten adhesive sheet 1 can be cooled, for example, by leaving it at room temperature (25°C).

[0099] Next, the resin sheet 5 is peeled off from the cured sheet 2, and the resin sheet 5 is removed. In this way, a second laminate 20 including the cured sheet 2 and the substrate 6 is obtained.

[0100] As described above, when polyamide P having a melt viscosity of 2000 Pa s or less at 160°C is used, adhesive sheet 1 is easily melted by heating it, and adhesive sheet 1 easily conforms to the surface of substrate 6. In particular, if the surface of substrate 6 is uneven, part of heated adhesive sheet 1 is likely to penetrate into the recesses in the surface of substrate 6. When cured sheet 2 is formed from adhesive sheet 1 while adhesive sheet 1 conforms to the surface of substrate 6, cured sheet 2 tends to exhibit adhesive strength sufficient for practical use.

[0101] The method for producing the second laminate 20 is not limited to the method described above. The second laminate 20 can also be produced by the following method. First, the above-described adhesive composition is applied to the surface of the substrate 6 to form a coating film on the substrate 6. The resulting coating film is dried to form the adhesive sheet 1. Examples of methods for applying the adhesive composition and conditions for drying the coating film include those described above for the adhesive sheet 1. Next, the second laminate 20 can be produced by forming a cured sheet 2 from the adhesive sheet 1 by the method described above.

[0102] (Method for Disassembling Second Laminate) In the second laminate 20, the adhesive strength of the cured sheet 2 is likely to decrease when it comes into contact with alcohol (more specifically, at least one compound classified as an alcohol). As an example, the cured sheet 2 can be easily removed from the second laminate 20 by contacting the cured sheet 2 with alcohol. In other words, the alcohol can disassemble the second laminate 20. By disassembling the second laminate 20, the substrate 6 can be recovered and reused.

[0103] The cured sheet 2 can be brought into contact with the alcohol by, for example, immersing the second laminate 20 in the alcohol. A lower alcohol having 5 or less carbon atoms (especially ethanol) is preferably used as the alcohol. The alcohol may be heated while the second laminate 20 is immersed in the alcohol. The heating temperature of the alcohol is, for example, 40°C or higher, or may be 50°C or higher, or even 60°C or higher. The heating temperature of the alcohol is preferably equal to or lower than the boiling point of the alcohol used. The immersion time of the second laminate 20 in the alcohol is not particularly limited and may be, for example, 1 minute to 100 hours.

[0104] <Modifications of Laminate> The second laminate 20 described above may include two substrates 6. The second laminate 21 in Fig. 5 includes substrate 6a and substrate 6b. The cured sheet 2 is disposed between substrate 6a and substrate 6b, and the cured sheet 2 is in direct contact with each of substrate 6a and substrate 6b.

[0105] The base material 6a and the base material 6b may have the same structure and material as each other or may have different structures and materials. Examples of the structure and material of the base material 6a and the base material 6b include those described above.

[0106] The second laminate 21 can be produced, for example, by placing an adhesive sheet 1 between a substrate 6 a and a substrate 6 b and forming a cured sheet 2 from this adhesive sheet 1. The cured sheet 2 can be formed by the method described above.

[0107] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0108] Example 1 First, a polyamide having a piperazine skeleton (Platamid M1276, manufactured by Arkema, weight-average molecular weight 21,000) was prepared. Next, 100 parts by mass of the polyamide and 0.5 parts by mass of an epoxy-based crosslinking agent (TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.) were dissolved in a mixed solvent of water and ethanol (temperature: 60°C) to obtain an adhesive composition of Example 1. The mixed solvent had a mass ratio of water to ethanol of 24 / 136. The adhesive composition was a solution with a solids concentration of 20% by mass.

[0109] (Examples 2 to 3 and Comparative Examples 1 to 3) Adhesive compositions of Examples 2 to 3 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the type of polyamide and the amount of crosslinking agent were changed as shown in Table 1.

[0110] <Evaluation of Polyamide> [Melt Viscosity] The melt viscosity of the polyamides used in the Examples and Comparative Examples was measured at 160° C. by the method described above. The viscoelasticity measuring device used was an ARES-G2 manufactured by TA Instruments.

[0111] <Evaluation of Cured Sheets> [Preparation of Adhesive Sheets] Adhesive sheets were prepared using the adhesive compositions of the Examples and Comparative Examples by the following method. First, an applicator was used to apply the adhesive composition to a resin sheet (release sheet: CA1 manufactured by Fujiko Co., Ltd.) having a release-treated surface to prepare a coating film. This coating film was placed in a thermostatic dryer and dried at 100°C for 5 minutes. This produced an adhesive sheet with a thickness of 20 μm. The thickness of the adhesive sheet was measured using a dial gauge (GC-9 manufactured by Peacock Co., Ltd.).

[0112] [Tensile Modulus] First, the adhesive sheet was heated at 160°C for 1 minute to produce a flat film (cured sheet) with a thickness of 20 µm. The cured sheet was punched out to produce a dumbbell-shaped No. 3 test piece. A tensile test was performed using this test piece according to the method described above to determine the tensile modulus. A TG-10kN tensile tester manufactured by MinebeaMitsumi Inc. was used.

[0113] [Ratio M2 / M1] First, a cured sheet was prepared using the method described above for the tensile modulus. Next, a portion of the cured sheet was scraped off to obtain a test piece (small piece). The mass M1 of this test piece was approximately 0.1 g. Next, the test piece was wrapped in a porous tetrafluoroethylene sheet (trade name "NTF1122", manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm and tied with kite string to prepare a measurement sample. The measurement sample was placed in a 50 mL container filled with ethanol and immersed in the ethanol. This container was left to stand at 60°C for 72 hours. Next, the measurement sample was removed from the container and transferred to an aluminum cup. This cup was placed in a dryer and dried at 130°C for 2 hours to remove the ethanol from the measurement sample. The dried measurement sample was precisely weighed to determine the mass M4. Based on the mass M1 (g), the mass M4 (g), and the total mass M3 (g) of the porous tetrafluoroethylene sheet and kite string, the ratio M2 / M1 was calculated using the following formula: Ratio M2 / M1 = 100 × (M4 - M3) / M1

[0114] [Peel Force F] First, the above adhesive sheet having a length of 80 mm and a width of 80 mm was placed between two sheets of long-fiber base fabric (manufactured by Standard Test Piece Co., Ltd., polyester fabric taffeta long fiber, ENE5070-150-3) having a length of 100 mm and a width of 100 mm. The long-fiber base fabric was a woven fabric with a surface roughness (arithmetic mean roughness Ra) of 8.94 μm. Next, a cured sheet was formed from the adhesive sheet by heat pressing at 160°C for 1 minute, thereby producing a test laminate. This test laminate was cut into a strip having a length of 100 mm and a width of 20 mm to prepare a test specimen. A T-peel test was performed on the test specimen under the above-mentioned conditions to determine the peel force F between the long-fiber base fabric and the cured sheet.

[0115] [Heat of fusion and crystallinity] For Examples 1 and 3, the heat of fusion and crystallinity of the cured sheets were determined. Specifically, a cured sheet was first prepared from the adhesive sheet using the method described above for the tensile modulus. Next, a portion of the cured sheet was scraped off to obtain a test piece (small piece) weighing approximately 5 mg. This test piece was subjected to DSC measurement using the method described above, and the heat of fusion was calculated. Furthermore, the heat of fusion ΔH of polyamide with a crystallinity of 100% was calculated.100 The ratio of the heat of fusion of the cured sheet ΔHm (J / g) to the heat of fusion of the cured sheet ΔHm (J / g) 100 The heat of fusion ΔH of polyamide with a crystallinity of 100% was calculated. 100 The heat of fusion of nylon 6 (190 J / g) was used as the heat of fusion.

[0116]

[0117] The abbreviations in Table 1 are as follows: M1276: Polyamide having a piperazine skeleton (Platamid M1276, manufactured by Arkema, weight-average molecular weight 21,000) H2519: Polyamide having a piperazine skeleton (Platamid H2519, manufactured by Arkema, weight-average molecular weight 26,000) CM8000: Polyamide not having a piperazine skeleton (Amilan CM8000, manufactured by Toray Industries, Inc., weight-average molecular weight 41,300) TETRAD-C: Epoxy-based crosslinking agent (TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.)

[0118] As can be seen from Table 1, the cured sheets formed from the adhesive compositions of the Examples, which contained a polyamide having a melt viscosity at 160°C of 2000 Pa s or less and in which the amount of crosslinking agent was adjusted to 2.5 parts by mass or less per 100 parts by mass of polyamide, had sufficiently high peel strengths F. From these results, it can be inferred that the cured sheets of the Examples exhibit adhesive strengths sufficient for practical use.

[0119] Furthermore, the cured sheets of the Examples had a low ratio M2 / M1. From these results, it is presumed that the adhesive strength of the cured sheets of the Examples can be easily reduced by contact with alcohol (especially ethanol).

[0120] As can be seen from the results of Comparative Examples 1 and 2, when a polyamide with a melt viscosity of more than 2000 Pa s at 160°C was used, it was difficult to adjust the peel force F of the cured sheet to a high value. This result is presumably due to the adhesive sheet not being sufficiently compatible with the surface of the long-fiber base fabric when heated.

[0121] As can be seen from the results of Comparative Example 3, the ratio M2 / M1 was very high in cured sheets formed from adhesive compositions containing more than 2.5 parts by mass of crosslinking agent per 100 parts by mass of polyamide. It is estimated that the adhesive strength of the cured sheet of Comparative Example 3 is hardly reduced even when it comes into contact with alcohol.

[0122] According to a cured sheet formed from the adhesive composition of the present embodiment, the adhesive strength can be reduced at an appropriate time, allowing the members to be easily disassembled from each other.

Claims

1. An adhesive composition comprising a polyamide, the polyamide having a melt viscosity of 2000 Pa·s or less at 160°C, and a crosslinking agent being blended in an amount of 2.5 parts by mass or less per 100 parts by mass of the polyamide.

2. The adhesive composition according to claim 1, wherein the melt viscosity is 1000 Pa·s or more.

3. The adhesive composition according to claim 1, which contains at least one selected from the group consisting of the crosslinking agent, a reactant other than the crosslinking agent, and a plasticizer.

4. The adhesive composition according to claim 1, wherein the amount of the crosslinking agent is 0.01 parts by mass or more per 100 parts by mass of the polyamide.

5. The adhesive composition according to claim 1, wherein the weight average molecular weight of said polyamide is 10,000 to 30,000.

6. The adhesive composition according to claim 1, wherein the polyamide has a piperazine skeleton.

7. The adhesive composition according to claim 1, wherein the polyamide is soluble in at least one compound classified as an alcohol.

8. The adhesive composition according to claim 1, wherein the crosslinking agent is an epoxy-based crosslinking agent.

9. An adhesive sheet comprising the adhesive composition according to any one of claims 1 to 8.

10. The adhesive sheet according to claim 9, having a thickness of 5 to 200 μm.

11. A laminate comprising: a resin sheet; and the adhesive sheet according to claim 9, disposed on the resin sheet.

12. The laminate according to claim 11, wherein the resin sheet has a surface that has been subjected to a release treatment.

13. A laminate comprising: a substrate; and a cured sheet disposed on the substrate and formed from an adhesive composition containing a polyamide, wherein the peel strength between the substrate and the cured sheet is 6.0 N / 20 mm or more; and the ratio M2 / M1 determined by the following test is 40% or less. Test: A part of the cured sheet is scraped off to obtain a test piece. The test piece is immersed in ethanol for 72 hours in an atmosphere at 60°C. The ratio M2 / M1 of the mass M2 (g) of the test piece after immersion in ethanol to the mass M1 (g) of the test piece before immersion in ethanol is determined.

14. The laminate according to claim 13, wherein the surface roughness of the substrate is 25 μm or less.

15. The laminate according to claim 13, wherein the cured sheet has a tensile modulus of elasticity of 1 to 50 MPa.

16. A method for producing a laminate according to any one of claims 13 to 15, comprising forming the cured sheet on the substrate.

17. The method of claim 16, further comprising heating an adhesive sheet containing the adhesive composition while the adhesive sheet is in contact with the substrate to form the cured sheet from the adhesive sheet.

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