Adhesive film for deep drawing base material attachment, adhesive layer, deep drawing laminate, and deep drawn body

Abstract

Provided is an adhesive film in which an adhesive layer is laminated on a resin film, which is suitable for use in adhering a draw-formed base material, and which has an adhesive layer that is easily stretched and difficult to break during drawing, and is difficult to separate from an adherend. Provided is an adhesive layer that is laminated on a resin film used to produce the above-described adhesive film, which is an adhesive layer that is easily stretched and difficult to break during draw forming, and is difficult to separate from an adherend. An adhesive film in which an adhesive layer is laminated on a resin film, the adhesive layer containing a crosslinked polyester resin (C) having a structure in which a side chain carboxyl group of a polyester resin (A) having a carboxyl group in a side chain is crosslinked by an epoxy crosslinking agent (B) having a plurality of epoxy groups in a molecule, and a transesterification catalyst (D), is an adhesive film for adhering a draw-formed base material.

Description

Technical Field

[0001] The present invention relates to an adhesive film for bonding with a deep-forming substrate, an adhesive layer laminated on a resin film for making the adhesive film, a deep-forming laminate formed by bonding the adhesive film with the deep-forming substrate, and a deep-forming body obtained from the deep-forming laminate. Background Technology

[0002] As a method for protecting or decorating the surfaces of interior and exterior automotive parts, appliance parts, building material parts, etc., a known method is to apply a coating to the surface of the part and then allow it to dry and cure by heating. However, since the coating used in this process uses volatile organic solvents, there is a problem of volatile organic solvent emissions.

[0003] Besides coating, vacuum forming is known as a method for decorating (modifying) the surface of a molded body. Vacuum forming refers to a lamination method in which a modifying film is stretched while being heated and softened, the space on the substrate side of the modifying film is depressurized, and pressure is applied to the space on the opposite side of the modifying film as needed, thereby forming the modifying film along a molded body that has been shaped into a three-dimensional form. A modifying film for this vacuum forming method is disclosed in Patent Document 1, and a cured adhesive for the vacuum forming method is disclosed in Patent Document 2.

[0004] [Existing Technical Documents]

[0005] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent No. 5708153

[0007] [Patent Document 2] Japanese Patent No. 7081214 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] Vacuum forming, which involves separately forming the substrate and bonding the modifying film, makes it difficult to control the positioning of the modifying film on the formed substrate. Furthermore, in vacuum forming, strength is required to prevent deformation or warping even under high pressure during forming, limiting its applicability. Therefore, if the substrate is drawn after bonding the substrate and the modifying film, forming can be performed after precisely determining the position of the modifying film relative to the substrate, thus making proper positioning easier. However, if the modifying film is bonded to the substrate and then drawn, the adhesive often detaches due to substrate deformation, causing the modifying film to peel off, or the deformation of the modifying film mismatches with the substrate deformation, resulting in wrinkles on the modifying film. This makes forming while maintaining the position of the modifying film technically challenging.

[0010] The object of the present invention is to provide an adhesive film having an adhesive layer laminated on a resin film, which is used to bond with a deep-forming substrate, and has an adhesive layer that is easy to stretch and difficult to break during deep-forming, and difficult to detach from the adhered body. Another object of the present invention is to provide an adhesive layer laminated on a resin film used to make the above-mentioned adhesive film, which is easy to stretch and difficult to break during deep-forming, and difficult to detach from the adhered body. Furthermore, another object of the present invention is to provide a laminate in which a resin film is bonded to a deep-forming substrate via an adhesive layer, which has good adhesion between the deep-forming substrate and the resin film, and the resin film is difficult to peel off from the deep-forming substrate even during deep-forming, and a deep-formed body obtained from this laminate.

[0011] [Methods used to solve problems]

[0012] The present invention is described below.

[0013] [1] An adhesive film for bonding a deep-drawing substrate is an adhesive film having an adhesive layer laminated on a resin film, the adhesive layer containing a crosslinked polyester resin (C) having a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on the side chain by an epoxy crosslinking agent (B) having multiple epoxy groups in the molecule, and an ester exchange catalyst (D).

[0014] [2] The adhesive film described in [1], wherein the epoxy crosslinking agent (B) comprises an aliphatic epoxy compound.

[0015] [3] The adhesive film described in [1] or [2], wherein the epoxy crosslinking agent (B) comprises an epoxy amine compound having a tertiary amino group in the molecule.

[0016] [4] The adhesive film described in [3] wherein the epoxy amine compound has one or more epoxides formed by the tertiary amino group bonded to the epoxy group via an alkylene group having 1 to 4 carbon atoms.

[0017] [5] The adhesive film described in any one of [1] to [4] contains 30 to 60 moles of the epoxy crosslinking agent (B) relative to 100 moles of the carboxyl groups of the polyester resin (A).

[0018] [6] The adhesive film described in any one of [1] to [5] contains 1 to 70 moles of the transesterification catalyst (D) relative to 100 moles of the carboxyl groups of the polyester resin (A).

[0019] [7] The adhesive film described in any one of [1] to [6], wherein the polyester resin (A) is a substance endowed with carboxyl groups by reacting a high molecular weight polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component and a polycarboxylic acid component with three or more functions.

[0020] [8] The adhesive film described in [7], wherein the polymer polyol (a) comprises two or more polymer polyols with different number average molecular weights (Mn).

[0021] [9] An adhesive layer laminated on a resin film and used to form an adhesive film for bonding deep-drawing substrates, comprising an adhesive layer having a crosslinked polyester resin (C) having a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on the side chain by an epoxy crosslinking agent (B) having multiple epoxy groups in the molecule, and an ester exchange catalyst (D).

[0022]

[10] The adhesive layer described in [9] has the following properties: at 170°C and 250°C, the stress at 100% elongation in the length direction is less than 1 MPa; at 170°C and 250°C, the stress at 200% elongation in the length direction is less than 1 MPa; and at 170°C and 250°C, the elongation at break is more than 100% and less than 1200%.

[0023]

[11] The adhesive layer described in [9] or

[10] , wherein the polyester resin (A) is a substance endowed with carboxyl groups by reacting a polymeric polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component and a polycarboxylic acid component with three or more functions.

[0024]

[12] The adhesive layer described in

[11] , wherein the polymer polyol (a) comprises two or more polymer polyols with different number average molecular weights (Mn).

[0025]

[13] A laminate for deep forming, which is formed by bonding a deep forming substrate with an adhesive film described in any one of [1] to [8].

[0026]

[14] A deep-drawn body obtained from a deep-drawn laminate as described in

[13] .

[0027] [The effects of the invention]

[0028] According to the present invention, an adhesive layer that is easily stretched and difficult to break during deep drawing can be provided, as well as an adhesive film having the adhesive layer and suitable for bonding with a deep drawing substrate. Furthermore, according to the present invention, a laminate formed by bonding a deep drawing substrate and a resin film via the aforementioned adhesive layer can be provided, wherein the deep drawing substrate and the resin film of the laminate exhibit good adhesion, and the resin film is difficult to peel off from the deep drawing substrate even during deep drawing. Additionally, according to the present invention, a deep-formed body obtained from the aforementioned laminate can be provided, wherein the resin film of the deep-formed body does not peel off, and the appearance design is satisfactory. Detailed Implementation

[0029] The adhesive film of this invention is a film in which an adhesive layer is laminated on a resin film for bonding to a deep-forming substrate. The key feature is that the adhesive layer contains: a crosslinked polyester resin (C) having a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on its side chains with an epoxy crosslinking agent (B) having multiple epoxy groups within the molecule; and an ester exchange catalyst (D). By crosslinking the carboxyl groups of the side chains of the polyester resin (A) with an epoxy crosslinking agent (B) having multiple epoxy groups within the molecule, both high crosslinking density and high flowability at high temperatures can be achieved in the presence of the ester exchange catalyst (D). As a result, an adhesive layer that is easy to stretch during deep forming and difficult to break can be achieved. When the adhesive film having this adhesive layer is bonded to a deep-forming substrate, the adhesion between the deep-forming substrate and the resin film becomes excellent, and the resin film is difficult to peel off from the deep-forming substrate even during deep forming. The invention will now be described.

[0030] (A) Polyester resins with carboxyl groups in the side chains

[0031] Polyester resin (A) has carboxyl groups in its side chains (hereinafter also referred to as branched structures). Additionally, polyester resin (A) has intramolecular ester bonds. The structure of polyester resin (A) [hereinafter sometimes simply referred to as polyester resin (A)] having carboxyl groups in its side chains can be a structure where carboxyl groups are present on branched substituents (e.g., aliphatic hydrocarbon groups, aromatic hydrocarbon groups, alicyclic hydrocarbon groups, etc.) on the polyester resin main chain, or a structure where carboxyl groups are present directly on the polyester resin main chain; preferably, a structure where carboxyl groups are present directly on the polyester resin main chain.

[0032] The number-average molecular weight (Mn) of the polyester resin (A) is preferably 5,000 to 50,000. By keeping the number-average molecular weight (Mn) of the polyester resin (A) within the above range, the acid value of the polyester resin (A) can be easily controlled. The number-average molecular weight (Mn) of the polyester resin (A) is more preferably 10,000 to 25,000, and even more preferably 12,000 to 20,000.

[0033] The acid value of the polyester resin (A) is preferably 5 to 40 mg KOH / g. By making the acid value of the polyester resin (A) 5 mg KOH / g or higher, sufficient crosslinking occurs between it and the epoxy crosslinking agent (B), improving the heat resistance of the adhesive layer. By making the acid value of the polyester resin (A) 40 mg KOH / g or lower, the crosslinking density is optimized, the molecular motion is not inhibited, ester bond exchange easily occurs, stress relief or softening becomes sufficient, and the adhesion becomes good. The acid value of the polyester resin (A) is more preferably 7 to 30 mg KOH / g, and even more preferably 10 to 20 mg KOH / g.

[0034] The glass transition temperature of the polyester resin (A) is preferably 0 to 110°C, more preferably 5 to 85°C, even more preferably 10 to 65°C, and particularly preferably 10 to 45°C.

[0035] In order to make polyester resin (A) have a branched structure and become a substance with side chains, the copolymer component used as its raw material can also have a branched structure.

[0036] Polyester resin (A) can be manufactured by reacting a polycarboxylic acid component with a polyol component. It can be a substance obtained by adding a monomer with a carboxyl group to a polyester with a reaction site obtained by reacting a polycarboxylic acid component with a polyol component. Preferably, it is a substance that is endowed with a carboxyl group by reacting a high molecular weight polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component with three or more functions (copolymerization).

[0037] (a) High molecular weight polyols

[0038] Polymer polyol (a) can be a polymer of polycarboxylic acid components and polyol components (polymer polyester polyol). In addition, polymer polyol (a) can contain polycarboxylic acid components with more than three functions or polyol components with more than three functions.

[0039] (Polycarboxylic acid components)

[0040] As a polycarboxylic acid component for use in high molecular weight polyols (a), aromatic dicarboxylic acid components and / or polycarboxylic acid components other than aromatic dicarboxylic acid components may be used, preferably at least aromatic dicarboxylic acid components.

[0041] From the viewpoint of improving the cohesiveness and strength of the resin, aromatic dicarboxylic acid components are preferred as polycarboxylic acid components for use in high molecular weight polyols (a). Examples of aromatic dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, and 2,2'-biphenyl dicarboxylic acid. Additionally, aromatic dicarboxylic acids with sulfonic acid groups, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonnaphthalene-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid, as well as their metal salts, ammonium salts, and other aromatic dicarboxylic acids with sulfonate groups, can also be used. These can be used alone or in mixtures of two or more. Among these, terephthalic acid, isophthalic acid, and mixtures thereof are preferred.

[0042] Examples of polycarboxylic acid components other than aromatic dicarboxylic acids include, for instance, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and their anhydrides; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, and dimer acids; dicarboxylic acids containing unsaturated bonds such as fumaric acid, maleic acid and their anhydrides; thiomalic acid with a thiol group in its molecular structure; and 2,5-furandicarboxylic acid (FDCA) from biomass sources. These can be used alone or in combination of two or more.

[0043] (Polyol components)

[0044] As the polyol component used in the high molecular weight polyol (a), a diol component is preferred. Examples of diol components include aliphatic diols, alicyclic diols, aromatic diols, or diols containing ether bonds.

[0045] Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol (DMH), neopentyl glycol hydroxypentanoate, dimethylolheptane, and 2,2,4-trimethyl-1,3-pentanediol.

[0046] Examples of alicyclic diols include, for example, 1,4-cyclohexanediol, 1,4-cyclohexanediethanol, tricyclodecanediol, tricyclodecanediethanol, spirocyclodiol, hydrogenated bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, and dimerized diols.

[0047] Examples of aromatic diols include terephthalic acid, isophthalic acid, o-phthalic acid, p-hydroxyphenylethanol, 1,4-benzenediol, ethylene oxide adducts of 1,4-benzenediol, bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts, which are diols obtained by adding 1 to several moles of ethylene oxide or propylene oxide to the two phenolic hydroxyl groups of bisphenols. Alternatively, diol-modified aromatic dicarboxylic acids can be used. Specific examples include ethylene glycol-modified terephthalic acid (BHET), propylene glycol-modified terephthalic acid, ethylene glycol-modified isophthalic acid, propylene glycol-modified isophthalic acid, ethylene glycol-modified phthalic acid, and propylene glycol-modified phthalic acid. Other examples of diol-modified aromatic dicarboxylic acids include diol-modified aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, 2,2'-biphenyl dicarboxylic acid, 5-hydroxyisophthalic acid, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonnaphthalene-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid, sulfoterephthalic acid and / or their metal salts, ammonium salts, etc., having sulfonic acid groups or sulfonate groups.

[0048] Examples of diols containing ether bonds include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct.

[0049] These can be used alone or in combination of two or more. Among these, aliphatic diols are preferred, and ethylene glycol, 2-methyl-1,3-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,6-hexanediol are more preferred.

[0050] (Polycarboxylic acid components with 3 or more functions)

[0051] Examples of compounds that are trifunctional or higher polycarboxylic acid components used in high molecular weight polyols (a) include trimellitic acid, pyromellitic acid, ethylene glycol bis(triptyltrimethylamine), glyceryl tri(triptyltrimethylamine), trimellitic anhydride, pyromellitic tetracarboxylic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). These can be used alone or in mixtures of two or more. Among these, trimellitic anhydride is preferred.

[0052] (Polyols with 3 or more functions)

[0053] Examples of polyols with three or more functions used in high molecular weight polyols (a) include glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, etc. These can be used alone or in combination of two or more.

[0054] High molecular weight polyols (a) may include, for example, hydroxycarboxylic acid compounds with hydroxyl and carboxyl groups in their molecular structure, such as 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, and 4,4-bis(p-hydroxyphenyl)valeric acid.

[0055] The number average molecular weight (Mn) of the high molecular weight polyol (a) is preferably 1,000 to 30,000, more preferably 2,000 to 25,000, and even more preferably 3,000 to 20,000.

[0056] The polymeric polyol (a) may contain two or more polymeric polyols with different number-average molecular weights (Mn). When the polymeric polyol (a) contains two or more polymeric polyols with different number-average molecular weights (Mn), it may contain a long-chain polymeric polyol (a1) with a number-average molecular weight (Mn) of 7000 or more and a short-chain polymeric polyol (a2) with a number-average molecular weight (Mn) of 1000 or more but less than 7000. By containing two or more polymeric polyols with different number-average molecular weights (Mn), the heat resistance of the adhesive layer can be improved. For example, the long-chain molecules of the long-chain polymeric polyol (a1) block contribute to heat resistance; on the other hand, by introducing the short-chain polymeric polyol (a2) block, a sufficient amount of carboxylic acid can be introduced to impart heat resistance. Furthermore, there is no particular upper limit to the number-average molecular weight (Mn) of the long-chain polymeric polyol (a1), for example, it may be 20000 or less.

[0057] When the polymeric polyol (a) comprises both long-chain polymeric polyol (a1) and short-chain polymeric polyol (a2), the amount of short-chain polymeric polyol (a2) is preferably 5 to 50 parts by mass relative to a total of 100 parts by mass of both long-chain and short-chain polymeric polyols (a1 and a2). By keeping the polymerization ratio of long-chain and short-chain polymeric polyols (a1 and a2) within the above range, the heat resistance of the adhesive layer can be improved. More preferably, the amount of short-chain polymeric polyol (a2) is 10 to 40 parts by mass relative to a total of 100 parts by mass of both long-chain and short-chain polymeric polyols (a1 and a2), and even more preferably, 20 to 30 parts by mass.

[0058] When the polymeric polyol (a) comprises a long-chain polymeric polyol (a1) and a short-chain polymeric polyol (a2), the polymerization amount of the long-chain polymeric polyol (a1), based on 100% by mass of the polymeric polyol (a), is preferably 50 to 90% by mass. By keeping the polymerization amount of the long-chain polymeric polyol (a1) in the polymeric polyol (a) within the above range, the heat resistance and adhesion of the adhesive layer are improved because the polymerization amounts of the short-chain polymeric polyol (a2) and the polycarboxylic acid components with 3 or more functions are balanced. The polymerization amount of the long-chain polymeric polyol (a1), based on 100% by mass of the polymeric polyol (a), is more preferably 60 to 85% by mass, and even more preferably 70 to 80% by mass.

[0059] (Polycarboxylic acid components with 3 or more functions)

[0060] Polycarboxylic acid components with three or more functions that react (polymerize) with high molecular weight polyols (a) are not particularly limited as long as they are compounds with three or more carboxyl groups within the molecule. Carboxyl groups can form anhydride groups within the molecule; in this case, one anhydride group is counted as two carboxyl groups.

[0061] Examples of polycarboxylic acid components with three or more functions include trimellitic acid, pyromellitic acid, ethylene glycol bis(triptamine), glyceryl tri(triptamine), trimellitic anhydride, pyromellitic tetracarboxylic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). These can be used alone or in mixtures of two or more. Among these, pyromellitic tetracarboxylic anhydride is preferred.

[0062] Regarding the amount of polycarboxylic acid components with three or more functions in the adhesive layer, relative to 100 moles of polyester resin (A), the polycarboxylic acid components with three or more functions can be 0.1 to 3 moles, more preferably 0.3 to 2 moles, and even more preferably 0.5 to 1.5 moles.

[0063] Regarding the polymerization ratio of the high molecular weight polyol (a) and the polycarboxylic acid component with three or more functions in the polyester resin (A), the polycarboxylic acid component with three or more functions is preferably 0.5 to 10 parts by mass relative to 100 parts by mass of the high molecular weight polyol (a), more preferably 1 to 8 parts by mass, and even more preferably 2 to 5 parts by mass. By making the polymerization ratio of the polycarboxylic acid component with three or more functions above the above-mentioned lower limit, the crosslinking amount becomes sufficient, and the heat resistance of the adhesive layer is improved. By making the polymerization ratio of the polycarboxylic acid component with three or more functions below the above-mentioned upper limit, the crosslinking density is not too high, ester bond exchange is easily achieved, softening becomes sufficient, and the adhesion is improved.

[0064] The acid value of the high molecular weight polyol (a) is preferably 0.1 to 20 mg KOH / g, more preferably 0.2 to 15 mg KOH / g, and even more preferably 0.3 to 10 mg KOH / g.

[0065] When the polyol (a) comprises a long-chain polyol (a1) and a short-chain polyol (a2), the acid value of the long-chain polyol (a1) is preferably 1 to 20 mg KOH / g, more preferably 2 to 15 mg KOH / g, and even more preferably 3 to 10 mg KOH / g. The acid value of the short-chain polyol (a2) is preferably 0.1 to 10 mg KOH / g, more preferably 0.2 to 8 mg KOH / g, and even more preferably 0.3 to 5 mg KOH / g.

[0066] The glass transition temperature of the polymeric polyol (a) is preferably -10 to 100°C, more preferably 0 to 80°C, and even more preferably 5 to 60°C.

[0067] When the polyol (a) comprises a long-chain polyol (a1) and a short-chain polyol (a2), the glass transition temperature of the long-chain polyol (a1) is preferably -10 to 60°C, more preferably -5 to 30°C, and even more preferably 0 to 15°C. The glass transition temperature of the short-chain polyol (a2) is preferably 5 to 100°C, more preferably 20 to 90°C, and even more preferably 30 to 80°C.

[0068] (Reaction catalyst)

[0069] When manufacturing polyester resin (A), a reaction catalyst can be used within a range that does not impair the aforementioned effects. Examples of reaction catalysts include, for instance, imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, or 1-cyanoethyl-2-ethyl-4-methylimidazole; triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, N,N-diisopropylethylamine, N,N-dimethylaminopyridine, 1,8-diazabicyclo(5,4,0)-undecene-7, and 1,5-diazabicyclo(4,3,0). Tertiary amines such as non-5-ene or 6-dibutylamino-1,8-diazabicyclo(5,4,0)undec-7-ene, and compounds in which these tertiary amines are prepared as amine salts using phenol, octanoic acid, or quaternized tetraphenylborate, etc.; quaternary ammonium salts such as tetramethylammonium bromide, tetraethylammonium bromide, tetra-n-butylammonium bromide, tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, and tetra-n-butylammonium hydroxide. These can be used alone or in mixtures of two or more. Among these, tertiary amines and compounds in which these tertiary amines are prepared as amine salts using phenol, octanoic acid, or quaternized tetraphenylborate, etc., are preferred, and triethylamine is more preferred.

[0070] (B) Epoxy crosslinking agent

[0071] Epoxy crosslinking agents (B) are epoxy compounds with multiple epoxy groups within their molecules. That is, epoxy compounds have two or more epoxy groups within their molecules. Epoxy compounds may contain oxygen atoms or sulfur atoms within their molecules as needed.

[0072] By using epoxy compounds, the heat resistance of the adhesive layer can be improved due to the ease with which three-dimensional crosslinking can be formed. Furthermore, by crosslinking the side chain carboxyl groups of the polyester resin (A) with epoxy compounds, both high crosslinking density and high-temperature fluidity can be achieved in the presence of an ester exchange catalyst (D). As a result, an adhesive layer that is easy to stretch during deep drawing and difficult to break can be achieved while ensuring heat resistance.

[0073] The number of epoxy groups in the molecule of the epoxy compound is preferably 2 to 4, more preferably 2 or 3, and even more preferably 2.

[0074] Aliphatic epoxides can be used as epoxides. Aliphatic epoxides are compounds composed of aliphatic saturated hydrocarbon groups and epoxy groups, and may contain oxygen atoms or sulfur atoms within the molecule as needed. Examples of aliphatic epoxides include compounds in which multiple epoxy-containing groups are bonded to an aliphatic saturated hydrocarbon group via oxygen or sulfur atoms. Examples of epoxy-containing groups include epoxy groups, glycidyl groups, etc.

[0075] Examples of epoxy compounds include, for example, polytetramethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, and bisphenol S diglycidyl ether. These can be used alone or in mixtures of two or more. Among these, 1,4-butanediol diglycidyl ether is preferred.

[0076] The epoxy crosslinking agent (B) can be an epoxy amine compound having multiple epoxy groups within the molecule and further having a tertiary amino group. That is, as the epoxy crosslinking agent (B), an epoxy amine compound having multiple epoxy groups and one or more tertiary amino groups within the molecule can be used, which is an epoxy compound having multiple epoxy groups within the molecule. The epoxy amine compound may contain oxygen atoms and sulfur atoms within the molecule as needed.

[0077] By crosslinking the carboxyl groups of the side chains of polyester resin (A) with an epoxy amine compound, both high crosslinking density and high high-temperature fluidity can be achieved in the presence of an ester exchange catalyst (D). As a result, an adhesive layer that is easy to stretch and difficult to break during deep drawing can be achieved while ensuring heat resistance. Furthermore, the tertiary amino group of the epoxy amine compound, like the ester exchange catalyst (D), exhibits ester exchange catalysis. Upon heating the adhesive layer, the hydroxyl groups contained in the adhesive layer attack the C=O bonds of the ester groups near the hydroxyl groups through the action of the tertiary amino group, resulting in bond exchange based on the ester exchange reaction, which can exhibit stress-relieving behavior.

[0078] The number of epoxy groups in the epoxide amine compound is preferably 2 to 4, more preferably 3 or 4. The number of tertiary amino groups in the epoxide amine compound can be 2 or more, preferably 3 or less.

[0079] The epoxide amine compound may have one or more epoxide amino groups formed by bonding a tertiary amino group to an epoxy group via an alkylene group having 1 to 4 carbon atoms. The alkylene group used to link the tertiary amino group and the epoxy group has more preferably 3 or fewer carbon atoms, further preferably 2 or fewer, and particularly preferably 1. One epoxy group may be bonded to the nitrogen atom of the tertiary amino group via an alkylene group having 1 to 4 carbon atoms, or two epoxy groups may be bonded via an alkylene group having 1 to 4 carbon atoms; preferably, it is a diepoxide amino group with two epoxy groups bonded via an alkylene group having 1 to 4 carbon atoms.

[0080] The number of epoxidized amino groups in the molecule of an epoxidized amine compound can be two or more, three or more, five or fewer, or four or fewer. That is, the number of epoxidized amino groups in the molecule of an epoxidized amine compound can be two to five, or three or four. The number of diepoxidized amino groups in the molecule of an epoxidized amine compound can be one, two, or three, preferably one or two, and more preferably two diglycidylamino groups.

[0081] Epoxidamine compounds have an aromatic ring, to which a dicyclic amino group may be bonded. The number of dicyclic amino groups bonded to the aromatic ring can be one, two, or preferably three or less. When the epoxidamine compound has an aromatic ring, a dicyclic amino group may be bonded to the aromatic ring via an alkylene group having 1 to 4 carbon atoms. The alkylene group used to connect the aromatic ring and the dicyclic amino group more preferably has 3 or less carbon atoms, further preferably 2 or less, and particularly preferably 1. When the epoxidamine compound has an aromatic ring, the number of aromatic rings can be one, two, or preferably three or less. When the epoxidamine compound has two or more aromatic rings, the aromatic rings may be directly bonded to each other, or two or more aromatic rings may be bonded via an alkylene group having 1 to 4 carbon atoms.

[0082] Examples of epoxide amine compounds include, for instance, 4-(ethylene oxide-2-ylmethoxy)-N,N-bis(ethylene oxide-2-ylmethyl)aniline (hereinafter sometimes referred to as triglycidyl-p-aminophenol), N,N,N',N'-tetraglycidyl-m-phenylenediamine, and 4,4'-methylenebis(N,N-diglycidylaniline). These can be used alone or in mixtures of two or more. Among these, triglycidyl-p-aminophenol is preferred.

[0083] As an epoxy-based crosslinking agent (B), epoxy compounds and epoxy amine compounds can be used separately or in combination.

[0084] Regarding the amount of epoxy crosslinking agent (B) in the adhesive layer, relative to 100 moles of carboxyl groups in the polyester resin (A), the amount of epoxy crosslinking agent (B) can be 30 to 60 moles. By keeping the amount of epoxy crosslinking agent (B) in the adhesive layer within the above range, the crosslinking density becomes appropriate, and stress relief in the crosslinked adhesive layer can be achieved. In the adhesive layer, the amount of epoxy crosslinking agent (B) relative to 100 moles of carboxyl groups in the polyester resin (A) is more preferably 25 to 58 moles, and even more preferably 30 to 55 moles.

[0085] (C) Cross-linked polyester resin

[0086] Crosslinked polyester resin (C) is a resin having a structure formed by crosslinking the side chain carboxyl groups of polyester resin (A) with an epoxy crosslinking agent (B) having multiple epoxy groups in the molecule. The side chain carboxyl groups of polyester resin (A) can be crosslinked by an epoxy compound having multiple epoxy groups in the molecule, or by an epoxy amine compound having multiple epoxy groups and one or more tertiary amino groups in the molecule, or by both an epoxy compound having multiple epoxy groups but no tertiary amino groups in the molecule and an epoxy amine compound having multiple epoxy groups and one or more tertiary amino groups in the molecule.

[0087] (D) Ester exchange catalyst

[0088] The transesterification catalyst (D) is a transesterification catalyst for the ester groups in the polyester resin (A). By including the transesterification catalyst (D) in the adhesive layer, the crosslinked polyester resin (C) can form dynamic covalent crosslinks that can undergo bond exchange at high temperatures. As a result, it has high strength at room temperature, and above the transesterification activation temperature, in addition to being able to bond resin films or deep-drawing substrates, it also exhibits stress relief. The adhesive film (modified film) easily deforms in accordance with the deformation of the substrate during deep drawing.

[0089] Examples of transesterification catalysts (D) include zinc acetate, anhydrous zinc acetate, zinc acetylacetonate (II), aluminum acetylacetonate (III), triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 1,8-diazabicyclo[5.4.0]undec-7-ene. These can be used alone or in mixtures of two or more. Among these, anhydrous zinc acetate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0090] Regarding the molar ratio of the transesterification catalyst (D) in the adhesive layer, it is preferably 1 to 70 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A). By keeping the molar ratio of the transesterification catalyst (D) in the adhesive layer within the above range, stress relief in the crosslinked adhesive layer can be achieved. The molar ratio of the transesterification catalyst (D) in the adhesive layer is more preferably 3 to 65 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A), and even more preferably 5 to 60 molar parts.

[0091] The adhesive layer can be manufactured by mixing a polyester resin (A) with carboxyl groups on its side chains, an epoxy crosslinking agent (B), and an ester exchange catalyst (D), heating the mixture, and then performing a crosslinking reaction via an epoxy ring-opening reaction. The heating temperature is preferably 80–200°C, more preferably 85–180°C, and even more preferably 90–150°C. The heating time depends on the heating temperature, but is preferably 30 minutes to 10 hours, more preferably 1 to 8 hours, and even more preferably 2 to 5 hours.

[0092] The reaction between polyester resin (A) and epoxy crosslinking agent (B) can be carried out in the absence of a solvent or in the presence of an organic solvent. When using an organic solvent, there are no particular limitations as long as the organic solvent does not react with either polyester resin (A) or epoxy crosslinking agent (B). Examples include aromatic organic solvents such as toluene and xylene, aliphatic organic solvents such as heptane and octane, ketone solvents such as methyl ethyl ketone, ether solvents such as tetrahydrofuran and diethyl ether, and amide solvents such as dimethylformamide, N-methylpyrrolidone, and N,N-dimethylformamide. These can be used alone or in mixtures of two or more. Among these, aromatic organic solvents, ketone solvents, and amide solvents are preferred.

[0093] In the crosslinked polyester resin (C), the ratio of polyester resin (A) having carboxyl groups in its side chains to the epoxy crosslinking agent (B) can be determined based on the molar ratio of functional groups between the carboxyl groups in the side chains of the polyester resin (A) and the epoxy groups in the epoxy crosslinking agent (B). From the viewpoint of crosslinking reaction efficiency and stress relief in the crosslinked polyester resin (C) after crosslinking, the ratio of carboxyl groups in the polyester resin (A) to epoxy groups in the epoxy crosslinking agent (B) (carboxyl groups:epoxy groups) is preferably 100:50 to 100:150 (molar parts), more preferably 100:80 to 100:120 (molar parts).

[0094] (Adhesive film)

[0095] The adhesive film is a substance in which an adhesive layer is laminated on a resin film, comprising a cross-linked polyester resin (C) with a structure formed by cross-linking the side chain carboxyl groups of a polyester resin (A) having carboxyl groups in the side chain with an epoxy cross-linking agent (B) having multiple epoxy groups in the molecule, and an ester exchange catalyst (D).

[0096] Examples of materials that can be used as resin films include, for example, polyester resins, polyamide resins, polyimide resins, polyamide-imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluoropolymers. Among these, polyester resins are preferred.

[0097] For example, according to conventional methods, an adhesive film with an adhesive layer laminated on the surface of a resin film can be obtained by coating and drying a coating solution containing the aforementioned epoxy crosslinking agent (B) having multiple epoxy groups in its molecule, polyester resin (A) having carboxyl groups in its side chains, and transesterification catalyst (D). Furthermore, after drying, if a release substrate is adhered to the adhesive layer, it can be wound without transfer to the back of the resin film, resulting in excellent operability. Simultaneously, since the adhesive layer is protected, it has excellent storage properties and is easy to use. As a release substrate, examples include a coating layer (single or double-sided) of clay, polyethylene, polypropylene, or other sealing fillers provided on the surface (single or double-sided) of high-quality paper, kraft paper, roll paper, glassine paper, etc., and a silicone-based, fluorinated, or alkyd-based release agent coated on the coating layer. In addition, examples can be given of various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as substances coated with the above-mentioned release agent on films such as polyethylene terephthalate and polyethylene naphthalate.

[0098] There is no particular limitation on the method of applying the above coating liquid to the resin film. For example, methods such as using a comma coating machine, a lip coating machine, a die coating machine, or a reverse roller coating machine can be cited.

[0099] (Adhesive layer)

[0100] This invention also includes an adhesive layer laminated on a resin film for use in forming an adhesive film for bonding deep-drawing substrates. The adhesive layer is a substance containing a crosslinked polyester resin (C) with a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on its side chains with an epoxy crosslinking agent (B) having multiple epoxy groups within the molecule, and an ester exchange catalyst (D). The thickness of the adhesive layer can be appropriately varied as needed, for example, preferably 0.01 to 0.8 mm. By making the thickness of the adhesive layer 0.01 mm or more, sufficient adhesive strength can be obtained.

[0101] Preferably, the stress of the adhesive layer at 100% elongation in the longitudinal direction is 1 MPa or less at both 170°C and 250°C. Therefore, even if a laminate formed by bonding a deep-drawn substrate and a resin film via this adhesive layer is deep-drawn, the resin film is difficult to peel off from the deep-drawn substrate. More preferably, the stress of the adhesive layer at 100% elongation in the longitudinal direction at 170°C is 0.8 MPa or less, and even more preferably 0.5 MPa or less. More preferably, the stress of the adhesive layer at 250°C at 100% elongation in the longitudinal direction is 0.5 MPa or less, and even more preferably 0.3 MPa or less.

[0102] Preferably, the stress of the adhesive layer at 200% elongation in the length direction is 1 MPa or less at both 170°C and 250°C. Therefore, even if a laminate formed by bonding a deep-drawn substrate and a resin film via this adhesive layer is deep-drawn, the resin film is difficult to peel off from the deep-drawn substrate. More preferably, the stress of the adhesive layer at 200% elongation in the length direction at 170°C is 0.8 MPa or less, and even more preferably 0.5 MPa or less. More preferably, the stress of the adhesive layer at 200% elongation in the length direction at 250°C is 0.5 MPa or less, and even more preferably 0.3 MPa or less.

[0103] The adhesive layer preferably has an elongation at break of 100% to 1200% at 170°C and 250°C. Therefore, even if a laminate formed by bonding a deep-drawn substrate and a resin film via this adhesive layer is deep-drawn, the resin film is difficult to peel off from the deep-drawn substrate. The elongation at break of the adhesive layer at 170°C is more preferably 110–1180%, and even more preferably 120–1150%. The elongation at break of the adhesive layer at 250°C is more preferably 105–1180%, and even more preferably 110–1150% or less.

[0104] The adhesive layer is particularly preferably subjected to stresses of less than 1 MPa when the length is 100% elongated at 170°C and 250°C, stresses of less than 1 MPa when the length is 200% elongated at 170°C and 250°C, and elongation at break of more than 100% and less than 1200% at 170°C and 250°C.

[0105] (Layered structure)

[0106] This invention also includes a laminate formed by bonding the aforementioned adhesive film to a deep-drawing substrate, which is preferably used for deep drawing. The deep-drawing laminate is a substance formed by stacking a resin film, an adhesive layer, and a deep-drawing substrate in that order. Examples of deep-drawing substrates include metal substrates such as metal sheets and resin substrates such as film-like resins. Examples of metal substrate materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, platings, and metals treated with zinc or chromium compounds. Examples of resin substrate materials include polyester resins, polyamide resins, polyimide resins, polyamide-imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluoropolymers. Among these, from the viewpoint of adhesion strength and durability to the adhesive layer of the adhesive film, metal substrates are preferred, and SUS, copper, and aluminum are more preferred.

[0107] The conditions for bonding the deep-drawn substrate to the adhesive film are preferably a temperature that is, for example, 15°C or higher than the softening temperature of the adhesive layer. Specifically, for example, it is preferably 185°C or higher.

[0108] (Deep-drawn parts)

[0109] The present invention also includes a deep-formed article obtained from the above-described deep-forming laminate. When the above-described deep-forming laminate is deep-formed, since the adhesive layer and the resin film deform in accordance with the deformation of the deep-forming substrate, no peeling or wrinkling of the resin film occurs in the deep-formed article, and a deep-formed article with good appearance design can be obtained.

[0110] This application claims the benefit of priority based on Japanese Patent Application No. 2024-23115, filed on February 19, 2024. The entire contents of the description of the aforementioned Japanese Patent Application No. 2024-23115 are incorporated herein by reference.

[0111]

Example

[0112] The present invention will be described in more detail below with examples, but the present invention is not limited to the following examples. Of course, it can also be implemented by making changes within the scope of the foregoing and the following description, and all of them are included in the technical scope of the present invention.

[0113] First, long-chain high-molecular-weight polyols (a1) and short-chain high-molecular-weight polyols (a2) were copolymerized with polycarboxylic acid components with more than three functions to produce a polyester resin (A) with carboxyl groups on the side chain.

[0114] (a1) Long-chain high molecular weight polyols

[0115] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 30 moles of terephthalic acid, 69 moles of isophthalic acid, and 1 mole of trimellitic anhydride (as polycarboxylic acids) and 15 moles of 2-methyl-1,3-butanediol, 85 moles of 1,6-hexanediol, and 0.2 moles of tetrabutyl titanate (as polyols) were added. The mixture was slowly heated to 250°C while removing distilled water from the system to carry out esterification. After esterification, the pressure was slowly reduced to 10 mmHg while initial polymerization was carried out, and the temperature was raised to 250°C. Later polymerization was then carried out at a pressure below 1 mmHg until the specified torque was reached. The pressure was then restored to atmospheric pressure with nitrogen, and 1 mole of trimellitic anhydride (as a polycarboxylic acid with more than three functions) was added. The reaction was carried out at 220°C for 30 minutes to obtain a long-chain high-molecular-weight polyol (a1-1). The composition of the obtained long-chain high molecular weight polyol (a1-1) is shown in Table 1.

[0116] (a2) Short-chain high molecular weight polyols

[0117] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 50 moles of terephthalic acid and 50 moles of isophthalic acid (as polycarboxylic acids), 55 moles of ethylene glycol and 45 moles of 2,2-dimethyl-1,3-propanediol (as polyols), and 0.2 moles of tetrabutyl titanate were added. The mixture was slowly heated to 250°C while removing distilled water from the system to carry out an esterification reaction. After the esterification reaction, the pressure was slowly reduced to 10 mmHg while initial polymerization was carried out, and the temperature was raised to 250°C. Later polymerization was then carried out at a pressure below 1 mmHg until the specified torque was reached, thereby obtaining a short-chain high-molecular-weight polyol (a2-1). The composition of the obtained short-chain high-molecular-weight polyol (a2-1) is shown in Table 1.

[0118] For the obtained long-chain high-molecular-weight polyols (a1-1) and short-chain high-molecular-weight polyols (a2-1), the number-average molecular weight (Mn), acid value, and glass transition temperature were determined by the following steps. These physical properties are shown in Table 1.

[0119] (i) Number-average molecular weight (Mn)

[0120] The obtained long-chain polyol (a1-1) or short-chain polyol (a2-1) was dissolved or diluted in tetrahydrofuran to a concentration of approximately 0.5% by mass. The solution was then filtered through a 0.5 μm PTFE membrane filter and used as the sample for analysis. The number-average molecular weight was determined by gel permeation chromatography using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was set to 1 mL / min, and the column temperature to 30 °C. Monodisperse polystyrene was used as the molecular weight standard. The number-average molecular weight was calculated after excluding the fraction with a molecular weight less than 1000.

[0121] (ii) Acid value

[0122] Dissolve 0.2 g of the obtained long-chain polyol (a1-1) or short-chain polyol (a2-1) in 20 ml of chloroform. Using phenolphthalein as an indicator, perform neutralization titration with 0.1 N potassium hydroxide (KOH) ethanol solution. Based on the titration volume, convert the mg of KOH consumed in neutralization to the amount per 1 g of long-chain polyol (a1-1) or short-chain polyol (a2-1), and calculate the acid value (mgKOH / g).

[0123] (iii) Glass transition temperature

[0124] Five mg of the obtained long-chain polyol (a1-1) or short-chain polyol (a2-1) was placed in an aluminum dish, sealed with a lid, and used as the sample for analysis. Using a Seiko Electronics Co., Ltd. differential scanning calorimeter (DSC220 type), the sample was held at 250°C for 5 minutes, then rapidly cooled with liquid nitrogen. Subsequently, the sample was heated from -100°C to 300°C at a heating rate of 20°C / min. The inflection point of the obtained curve was taken as the glass transition temperature.

[0125] Table 1

[0126]

[0127] (A) Polyester resins with carboxyl groups in the side chains

[0128] In a reaction vessel equipped with a stirrer, thermometer, and reflux pipe, 80 parts by mass of long-chain polyol (a1-1), 20 parts by mass of short-chain polyol (a2-1), 2.6 parts by mass of pyromellitic anhydride (a polycarboxylic acid component with more than three functions), and 100 parts by mass of toluene were added. The mixture was slowly heated to 80°C while being dissolved in toluene. After dissolution, 0.05 parts by mass of triethylamine was added as a reaction catalyst, and the mixture was slowly heated to 105°C and reacted for 24 hours. After the reaction was confirmed to be complete by infrared spectroscopy (IR), 54 parts by mass of toluene was added for dilution, thereby obtaining a solution of polyester resin (A-1) containing carboxyl groups in the side chain with a solid concentration of 40% by mass. The composition of the obtained polyester resin (A-1) containing carboxyl groups in the side chain is shown in Table 2.

[0129] Table 2

[0130]

[0131] Next, an adhesive layer was fabricated using the obtained polyester resin (A-1), epoxy crosslinking agent (B), and transesterification catalyst (D).

[0132] The following compound was used as an epoxy crosslinking agent (B).

[0133] Epoxide (B-1): As 1,4-butanediol diglycidyl ether (hereinafter, sometimes referred to as BDE), "Epogosei (registered trademark) BD" manufactured by Yokkaichi Synthetic Co., Ltd. was used. 1,4-Butanediol diglycidyl ether has two epoxy groups in its molecule.

[0134] Epoxyamine compound (B-2): As triglycidyl-p-aminophenol, "jER630" manufactured by Mitsubishi Chemical Corporation was used. Triglycidyl-p-aminophenol has 3 epoxy groups and 1 tertiary amino group in its molecule.

[0135] Epoxy compound (B-3): As a phenolic varnish-type epoxy resin, "YCDN-700-10" manufactured by JITCO Chemicals & Materials was used. "YCDN-700-10" is a multifunctional epoxy resin with an epoxy equivalent of 198 to 210.

[0136] The following compound was used as an ester exchange catalyst (D).

[0137] The transesterification catalyst (D-1) used was anhydrous zinc acetate (Zn(OAc)2) manufactured by Fujifilm and Kojun Chemical Co., Ltd.

[0138] The transesterification catalyst (D-2) used was 1,5,7-triazabicyclo[4.4.0]dec-5-ene (hereinafter sometimes referred to as TBD) manufactured by Tokyo Chemical Industry Co., Ltd.

[0139] (Example 1)

[0140] Solution 1, containing 25.5% by mass of solids, is prepared by dissolving the polyester resin (A-1) in toluene in a specific molar ratio of carboxyl groups to epoxy groups (B-1). The amount of epoxy group (B-1) is set to 50 moles relative to 100 moles of carboxyl groups in the polyester resin (A-1). Solution 2, containing 8.3% by mass of solids, is prepared by dissolving the transesterification catalyst (D-1) in N,N-dimethylformamide. Solution 1 and solution 2 are mixed in a specific molar ratio of carboxyl groups to transesterification catalyst (D-1) to prepare a coating liquid 1 containing 20% ​​by mass of solids. The amount of transesterification catalyst (D-1) is set to 20 moles relative to 100 moles of carboxyl groups in the polyester resin (A-1).

[0141] Next, the obtained coating liquid 1 was coated onto the resin film and dried to produce an adhesive film 1 consisting of a resin film and an adhesive layer 1. As the resin film, a PET film (Toyobo G2000, 38 μm thick) with surface treatments including plasma treatment and corona treatment was used. Coating liquid 1 was coated onto the surface of the PET film. The coating of coating liquid 1 was performed using a coater; the required amount of liquid was dropped onto the surface of the PET film, and then uniformly coated onto the surface of the PET film using a coater with a 200 μm gap. The PET film coated with coating liquid 1 was heat-treated at 100°C for 3 hours to produce the adhesive film 1 consisting of a PET film and an adhesive layer 1. The dried film thickness of the adhesive layer 1 in the obtained adhesive film 1 was approximately 0.025 mm. The physical properties of the obtained adhesive layer 1 were evaluated.

[0142] Peel the PET film from adhesive film 1, remove adhesive layer 1, and cut a test piece with a length of 250 mm and a width of 10 mm from adhesive layer 1. Use a tensile testing machine (TENSILON universal testing machine manufactured by ORIENTEC Co., Ltd.) with the initial tensile clamp spacing set to 20 mm and stretch the test piece in the length direction at a tensile speed of 20 mm / min to conduct a tensile test. The tensile test is performed by placing the test piece in a constant temperature bath set to 170°C or 250°C and preheating for 30 seconds. The loads applied to the film when the test piece elongates by 100% (i.e., when the clamp spacing becomes 40 mm) and when the test piece elongates by 200% (i.e., when the clamp spacing becomes 60 mm) are read. Divide the read loads by the cross-sectional area of ​​the test piece before the tensile test (film thickness × 10 mm) to obtain the values ​​as the stress at 100% elongation and the stress at 200% elongation, respectively.

[0143] In addition, the elongation at fracture of the test piece was measured, and the elongation at fracture was calculated according to the following formula. Where Lo represents the length of the test piece before the test, and L represents the length of the test piece at fracture.

[0144] Elongation at break (%) = 100 × (L - Lo) / Lo

[0145] As a reference experiment, the test piece was not placed in the constant temperature bath, and a tensile test was performed at room temperature (25℃). The stress at 100% elongation and the stress at 200% elongation were calculated.

[0146] Table 3 below shows the stress of adhesive layer 1 when it is 100% elongated in the length direction at 25℃, 170℃ or 250℃, the stress of adhesive layer 1 when it is 200% elongated in the length direction at 25℃, 170℃ or 250℃, and the elongation at break of adhesive layer 1 at 170℃ or 250℃.

[0147] Next, the adhesive film 1 is bonded to the deep-forming substrate to manufacture the deep-forming laminate 1, and the adhesion between the PET film and the GA steel sheet, as well as the deep-forming properties of the deep-forming laminate 1, are evaluated. Specifically, an alloyed hot-dip galvanized steel sheet (hereinafter sometimes referred to as GA steel sheet) is used as the deep-forming substrate. The GA steel sheet is placed on the heating table of the laminator, preheated at 185°C for 5 minutes, and then the laminator is started. The GA steel sheet is fed at a speed of 9.0 m / min. The adhesive film 1 is supplied relative to the GA steel sheet such that the alloyed hot-dip galvanized layer of the GA steel sheet contacts the adhesive layer 1 of the adhesive film 1. Utilizing the preheating of the GA steel sheet, the GA steel sheet is laminated at a lamination pressure of 3 bar. After passing through the lamination rollers, it is immersed in a water bath for cooling, thus manufacturing the deep-forming laminate 1. The laminator is an original machine with a continuous structure for the steel sheet heating table and lamination rollers. The laminate structure of the deep drawing laminate 1 is PET film / adhesive layer / GA steel plate.

[0148] For the obtained deep-drawing laminate 1, the adhesion between the PET film and the GA steel sheet was evaluated. Adhesion was evaluated through a peel test, in which one end of the PET film was folded back 180° along the surface of the deep-drawing laminate 1, and the load during peeling was measured. The width of the test piece was set to 20 mm, and the stretching speed of the PET film was set to 100 mm / min. Adhesion was evaluated based on the measured load according to the following criteria. The evaluation results are shown in Table 3 below.

[0149] (Evaluation Criteria)

[0150] The case where the load per 20 mm width of PET film exceeds 10 N is evaluated as having particularly excellent adhesion, and is described as A in Table 3.

[0151] The PET film with a load of 5 to 10 N per 20 mm width is evaluated as having excellent adhesion, and is described as B in Table 3.

[0152] The case where the load per 20 mm width of PET film is less than 5 N is evaluated as poor adhesion, and is described as C in Table 3.

[0153] Next, the resulting laminate 1 for deep forming was subjected to deep forming. The formability of the laminate 1 was evaluated by visually observing whether the PET film followed the deformation of the GA steel sheet. A Kawasaki Yuko Co., Ltd. hydraulic press "DPD-1500" was used as the deep forming machine. The deep forming process involved setting the pressing pressure to 100 tons, visually observing whether cracking, bubbling, or wrinkling occurred in the PET film or adhesive layer 1, and evaluating the results according to the following criteria. The evaluation results are shown in Table 3 below.

[0154] (Evaluation Criteria)

[0155] The condition where neither the PET film nor the adhesive layer 1 cracked, bubbled, or wrinkled was evaluated as having exceptionally excellent deep-drawing formability, and is described as A in Table 3.

[0156] If either the PET film or the adhesive layer 1 experiences cracking, bubbling, or wrinkling, it is considered to have good deep-drawing formability, and is described as B in Table 3.

[0157] If either the PET film or the adhesive layer 1 experiences two or more of the following conditions—cracking, bubbling, and wrinkling—it is considered to have poor deep-drawing formability, and is described as C in Table 3.

[0158] (Example 2)

[0159] Except that the temperature at which the GA steel sheet was preheated on the heating platen of the laminator in Example 1 was changed from 185°C to 200°C, the laminate 2 for deep forming was manufactured under the same conditions as in Example 1. The adhesion between the PET film and the GA steel sheet, as well as the deep forming properties, were evaluated for the resulting laminate 2 for deep forming under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0160] (Example 3)

[0161] Except that the temperature at which the GA steel sheet was preheated on the heating platen of the laminator in Example 1 was changed from 185°C to 230°C, the laminate 3 for deep forming was manufactured under the same conditions as in Example 1. The adhesion between the PET film and the GA steel sheet, as well as the deep forming properties, were evaluated for the resulting laminate 3 for deep forming under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0162] (Example 4)

[0163] Except that the 20 moles of transesterification catalyst (D-1) used in Example 1 relative to 100 moles of carboxyl groups of polyester resin (A) were replaced with 20 moles of transesterification catalyst (D-2), the coating liquid 4 was prepared under the same conditions as in Example 1. Next, the obtained coating liquid 4 was coated onto the resin film under the same conditions as in Example 1 and allowed to dry, thus producing an adhesive film 4 consisting of a resin film and an adhesive layer 4. The dried film thickness of the adhesive layer 4 in the obtained adhesive film 4 was approximately 0.353 mm. The physical properties of the obtained adhesive layer 4 were evaluated under the same conditions as in Example 1. Next, except that the temperature of the GA steel sheet preheated on the heating table of the laminator was changed from 185°C to 200°C, the deep-drawing laminate 4 was prepared under the same conditions as in Example 1. The adhesion between the PET film and the GA steel sheet, as well as the deep-drawing properties, were evaluated for the obtained deep-drawing laminate 4 under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0164] (Example 5)

[0165] Except that the 20 moles of transesterification catalyst (D-1) used in Example 1 relative to 100 moles of carboxyl groups of polyester resin (A) were replaced with 50 moles, the coating liquid 5 was prepared under the same conditions as in Example 1. Next, the obtained coating liquid 5 was coated onto a resin film under the same conditions as in Example 1 and allowed to dry, thus producing an adhesive film 5 consisting of a resin film and an adhesive layer 5. The dried film thickness of the adhesive layer 5 in the obtained adhesive film 5 was approximately 0.017 mm. The physical properties of the obtained adhesive layer 5 were evaluated under the same conditions as in Example 1. Next, a deep-drawing laminate 5 was prepared under the same conditions as in Example 1, except that the preheating temperature of the GA steel sheet on the heating table of the laminator was changed from 185°C to 200°C. The adhesion between the PET film and the GA steel sheet, as well as the deep-drawing properties, were evaluated for the obtained deep-drawing laminate 5 under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0166] (Example 6)

[0167] Except that the 50 moles of epoxy compound (B-1) used in Example 1 relative to 100 moles of carboxyl groups of polyester resin (A) were replaced with 33 moles of epoxy amine compound (B-2), the coating liquid 6 was prepared under the same conditions as in Example 1. Next, the obtained coating liquid 6 was coated onto a resin film under the same conditions as in Example 1 and allowed to dry, thus producing an adhesive film 6 consisting of a resin film and an adhesive layer 6. The dried film thickness of the adhesive layer 6 in the obtained adhesive film 6 was approximately 0.487 mm. The physical properties of the obtained adhesive layer 6 were evaluated under the same conditions as in Example 1. Next, except that the temperature of the GA steel sheet preheated on the heating table of the laminator was changed from 185°C to 200°C, the deep-drawing laminate 6 was prepared under the same conditions as in Example 1. The adhesion between the PET film and the GA steel sheet, as well as the deep-drawing properties, were evaluated for the obtained deep-drawing laminate 6 under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0168] (Example 7)

[0169] Except that the 50 moles of epoxy compound (B-1) used in Example 1 relative to 100 moles of carboxyl groups of polyester resin (A) were replaced with 47 moles, and 2 moles of epoxy amine compound (B-2) were also used, and the 20 moles of transesterification catalyst (D-1) were replaced with 10 moles, the coating liquid 7 was prepared under the same conditions as in Example 1. Next, the obtained coating liquid 7 was coated onto the resin film under the same conditions as in Example 1, and allowed to dry, thus producing an adhesive film 7 consisting of the resin film and the adhesive layer 7. The physical properties of the obtained adhesive layer 7 were evaluated under the same conditions as in Example 1. Next, except that the temperature of the GA steel sheet preheated on the heating table of the laminator was changed from 185°C to 200°C, the deep-drawing laminate 7 was prepared under the same conditions as in Example 1. The adhesion between the PET film and the GA steel sheet, as well as the deep-drawing properties, were evaluated for the obtained deep-drawing laminate 7 under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0170] (Comparative Example 1)

[0171] A solution 11 with a solid content of 25.5% by mass was prepared by dissolving the polyester resin (A-1) in toluene in a specific molar ratio of carboxyl groups (molar equivalents) to epoxy groups (B-1). The amount of epoxy compound (B-1) was set to 50 molar parts relative to 100 molar parts of carboxyl groups of polyester resin (A-1). Next, the obtained solution 11 was coated onto a resin film under the same conditions as in Example 1 and allowed to dry to produce an adhesive film 11 consisting of a resin film and an adhesive layer 11. The physical properties of the obtained adhesive layer 11 were evaluated under the same conditions as in Example 1. Next, a deep-drawing laminate 11 was manufactured under the same conditions as in Example 1, except that the temperature of the GA steel sheet preheated on the heating table of the laminator was changed from 185°C to 200°C. The adhesion between the PET film and the GA steel sheet, as well as the deep-drawing properties, were evaluated for the obtained deep-drawing laminate 11 under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0172] (Comparative Example 2)

[0173] A solution 12 with a solid content of 25.5% by mass was prepared by dissolving the polyester resin (A-1) in toluene in a specific molar ratio of carboxyl groups (molar equivalent) to epoxy compounds (B-3) (phenolic varnish-type epoxy resin). The amount of phenolic varnish-type epoxy resin was set to 65 molar parts relative to 100 molar parts of carboxyl groups of polyester resin (A-1). Next, the obtained solution 12 was coated onto a resin film under the same conditions as in Example 1 and allowed to dry, thereby producing an adhesive film 12 consisting of a resin film and an adhesive layer 12. The physical properties of the obtained adhesive layer 12 were evaluated under the same conditions as in Example 1. Next, a laminate 12 for deep drawing was manufactured under the same conditions as in Example 1, except that the temperature of the GA steel sheet preheated on the heating table of the laminator was changed from 185°C to 200°C. For the resulting laminate 12 for deep drawing, the adhesion between the PET film and the GA steel sheet, as well as the deep drawing properties, were evaluated under the same conditions as in Example 1. The evaluation results are shown in Table 3 below.

[0174] Table 3

[0175]

[0176] As can be clearly seen from Table 3, Examples 1 to 7 are examples using adhesive films that meet the requirements specified in this invention. The adhesive layer contained in the adhesive film is easy to stretch and difficult to break during deep drawing. Therefore, the laminate formed by bonding the GA steel sheet and the PET film via this adhesive layer has good adhesion between the GA steel sheet and the PET film, and even during deep drawing, the PET film is difficult to peel off from the GA steel sheet. On the other hand, Comparative Examples 1 and 2 are examples using adhesive films that do not meet the requirements specified in this invention. The adhesive layer contained in the adhesive film is difficult to stretch and easy to break during deep drawing. Therefore, the laminate formed by bonding the GA steel sheet and the PET film via this adhesive layer has poor adhesion between the GA steel sheet and the PET film, and the PET film peels off from the GA steel sheet during deep drawing.

Claims

1. An adhesive film for bonding deep-drawn substrates, comprising an adhesive layer laminated on a resin film, characterized in that, The adhesive layer contains a crosslinked polyester resin (C) having a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on the side chain by an epoxy crosslinking agent (B) having multiple epoxy groups in the molecule, and an ester exchange catalyst (D).

2. The adhesive film according to claim 1, wherein, The epoxy crosslinking agent (B) comprises an aliphatic epoxy compound.

3. The adhesive film according to claim 1, wherein, The epoxy crosslinking agent (B) comprises an epoxy amine compound having a tertiary amino group within the molecule.

4. The adhesive film according to claim 3, wherein, The epoxide amine compound has one or more epoxide amines formed by the bonding of the tertiary amine to the epoxide via an alkylene group having 1 to 4 carbon atoms.

5. The adhesive film according to claim 1, wherein, The epoxy crosslinking agent (B) contains 30 to 60 moles of the carboxyl group relative to 100 moles of the polyester resin (A).

6. The adhesive film according to claim 1, wherein, The transesterification catalyst (D) contains 1 to 70 moles of the carboxyl group relative to 100 moles of the polyester resin (A).

7. The adhesive film according to claim 1, wherein, The polyester resin (A) is a substance that is endowed with carboxyl groups by reacting a high molecular weight polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component and a polycarboxylic acid component with three or more functions.

8. The adhesive film according to claim 7, wherein, The high molecular weight polyol (a) contains two or more high molecular weight polyols with different number average molecular weights Mn.

9. An adhesive layer laminated on a resin film and used to form an adhesive film for bonding deep-drawn substrates, characterized in that, An adhesive layer comprising a crosslinked polyester resin (C) having a structure formed by crosslinking the carboxyl groups of a polyester resin (A) having carboxyl groups on the side chain by an epoxy crosslinking agent (B) having multiple epoxy groups in the molecule, and an ester exchange catalyst (D).

10. The adhesive layer according to claim 9, wherein, At 170℃ and 250℃, the stress at 100% elongation in the longitudinal direction is below 1MPa. At 170℃ and 250℃, the stress at 200% elongation in the length direction is below 1MPa. At 170℃ and 250℃, the elongation at break is above 100% and below 1200%.

11. The adhesive layer according to claim 9, wherein, The polyester resin (A) is a substance that is endowed with carboxyl groups by reacting a high molecular weight polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component and a polycarboxylic acid component with three or more functions.

12. The adhesive layer according to claim 11, wherein, The high molecular weight polyol (a) contains two or more high molecular weight polyols with different number average molecular weights Mn.

13. A laminate for deep drawing, which is formed by bonding a deep drawing substrate with an adhesive film according to any one of claims 1 to 8.

14. A deep-drawn article obtained from the deep-drawn laminate of claim 13.

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