Cross-linked polyester resin

Abstract

Provided is a crosslinked polyester resin that exhibits self-adherence, remoldability, and a damage repair capacity. Due to dynamic covalent bond crosslinking that is capable of bond exchange at elevated temperatures, the crosslinked polyester resin exhibits high strength at room temperature, but at and above softening temperature is capable of reprocessing, film-to-film adherence, and self-repair. Moreover, even without the addition of a transesterification catalyst, the crosslinked polyester resin exhibits a softening behavior attributable to bond exchange by a transesterification reaction.　The crosslinked polyester resin is a resin in which a polyester resin having the carboxy group in side chain position is crosslinked by an epoxy crosslinking agent that has a plurality of epoxy groups. The epoxy crosslinking agent contains an epoxyamine compound that has at least two tertiary amino groups and at least two epoxy groups in the molecule, and the epoxyamine compound is used at 3-30 parts by mole per 100 parts by mole of the carboxy group in the polyester resin having the carboxy group in side chain position.

Description

[Technical Field]

[0001] The present invention relates to a polyester resin in which a polyester resin having a carboxy group in a side chain is crosslinked with an epoxy-based crosslinking agent having a plurality of epoxy groups. [Background technology]

[0002] Polyester resins are polycondensates synthesized by dehydration condensation of polycarboxylic acids and polyalcohols, and examples thereof include linear polymers produced from terephthalic acid or its ester-forming derivatives and ethylene glycol. Polyester resins are versatile and practical, and are suitable for use as materials for films, sheets, fibers, bottles, and the like. Furthermore, due to their excellent mechanical properties, weather resistance, and chemical resistance, polyester resins are expected to be used in a variety of applications in the future, including electrical insulation, solar cells, and industrial parts such as tire cords.

[0003] Such polyester resins are also used as cross-linked polyester resins by cross-linking polyester resins with a cross-linking agent. For example, Patent Document 1 describes an adhesive composition containing a carboxylic acid group-containing polymer compound that maintains good adhesion to various plastic films, metals, and glass epoxy, while also exhibiting excellent moist heat resistance and being compatible with lead-free soldering under high humidity. This carboxylic acid group-containing polymer compound contains at least a polymer polyol (A), a polymer polyol (B) different from the polymer polyol (A), and a tetracarboxylic acid dianhydride as copolymerization components. An example of an adhesive composition disclosed in Patent Document 1 is one obtained by adding 9 parts of YDCN-700-10 (novolac epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd. and 0.1 parts of TETRAD (registered trademark)-X (N,N,N',N'-tetraglycidyl-m-xylylenediamine) manufactured by Mitsubishi Gas Chemical Company, Inc. as epoxy resins to 100 parts solids of a carboxylic acid group-containing polymer compound (C1), and adjusting the solids concentration to 35% using methyl ethyl ketone.

[0004] Patent Document 2 also describes an adhesive composition containing a carboxylic acid group-containing polymer compound with properties similar to those of Patent Document 1. This adhesive composition contains a carboxylic acid group-containing polyester resin (A) and an epoxy resin (B), in which the carboxylic acid group-containing polyester resin (A) contains, as copolymerization components, a polymer polyol (A1), a polymer polyol (A2) different from the polymer polyol (A1), and a tetracarboxylic acid dianhydride. An example of an adhesive composition in Patent Document 2 describes an adhesive composition obtained by adding 9 parts of YDCN-700-10 (a novolac epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd. and 0.1 parts of TETRAD®-X (N,N,N',N'-tetraglycidyl-m-xylylenediamine) manufactured by Mitsubishi Gas Chemical Company, Inc. to 100 parts solids of the carboxylic acid group-containing polyester resin (A-1), and adjusting the solids concentration to 35% using methyl ethyl ketone.

[0005] The adhesive compositions described in Patent Documents 1 and 2 have excellent resistance to moist heat.

[0006] Patent Document 3 describes a cross-linked polyester resin that exhibits self-adhesion, remoldability, and scratch repair. This cross-linked polyester resin is characterized by a polymer backbone containing multiple ester bonds, a polyester resin containing multiple covalently cross-linked moieties containing ester bonds and free OH groups, and a transesterification catalyst. The cross-linked polyester resin described in Patent Document 3 contains a transesterification catalyst. A free OH group attacks the CO bond of one of the many nearby ester bonds due to the action of the nearby transesterification catalyst, resulting in a transesterification reaction, resulting in properties such as self-adhesion. Patent Document 3 also discloses an example in which zinc acetate is used as the transesterification catalyst. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 105543 [Patent Document 2] International Publication No. 2018 / 179707 [Patent Document 3] International Publication No. 2020 / 045439 Summary of the Invention [Problem to be solved by the invention]

[0008] Because the zinc acetate used in the examples of Patent Document 3 is a metal, it has been difficult to apply such crosslinked polyester resins containing zinc acetate to electrical materials. Therefore, there is a demand for crosslinked polyester resins that exhibit softening properties at high temperatures without the addition of a transesterification catalyst, and that also exhibit self-adhesiveness, remoldability, and scratch repair properties.

[0009] The present invention has been made in light of the above-mentioned circumstances, and its object is to provide a crosslinked polyester resin that has high strength at room temperature due to dynamic covalent crosslinking that allows bond exchange at high temperatures, but that is capable of reprocessing, film adhesion, and self-repair above the softening temperature, and that exhibits softening behavior due to bond exchange due to transesterification reaction even without the addition of a transesterification catalyst, and that exhibits self-adhesion, remoldability, and scratch repair properties. Another object of the present invention is to provide a crosslinked polyester resin that can be processed at a low temperature while maintaining heat resistance, even when a transesterification catalyst is added. [Means for solving the problem]

[0010] The present invention is as follows. [1] A crosslinked polyester resin, characterized in that the polyester resin has a carboxy group in the side chain and is crosslinked with an epoxy-based crosslinking agent having a plurality of epoxy groups, and the epoxy-based crosslinking agent contains an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule, and the epoxy amine compound is contained in an amount of 3 to 30 molar parts per 100 molar parts of the carboxy group of the polyester resin having a carboxy group in the side chain. [2] The crosslinked polyester resin according to [1], wherein the molar ratio of the carboxy group of the polyester resin having a carboxy group in a side chain to the epoxy group of the epoxy amine compound is 1:0.125 to 1:1.2, i.e., the carboxy group:the epoxy group. [3] The crosslinked polyester resin according to [1] or [2], wherein the tertiary amino group and the epoxy group contained in the epoxy amine compound constitute a diglycidyl amino group. [4] The crosslinked polyester resin according to any one of [1] to [3], wherein the molecular weight of the epoxyamine compound is 800 or less. [5] A crosslinked polyester resin composition comprising a transesterification catalyst and the crosslinked polyester resin according to any one of [1] to [4]. [Effects of the Invention]

[0011] In the present invention, a polyester resin having carboxyl groups in its side chains is crosslinked with an epoxy-based crosslinking agent containing an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in its molecule. As a result, the tertiary amino groups contained in the epoxyamine compound molecule act as a transesterification catalyst, and a crosslinked polyester resin exhibits softening behavior due to bond exchange caused by a transesterification reaction even without the addition of a transesterification catalyst, thereby providing a crosslinked polyester resin that exhibits self-adhesiveness, remoldability, and scratch repair properties. Furthermore, the crosslinked polyester resin of the present invention may be a crosslinked polyester resin composition containing a transesterification catalyst. Even when a transesterification catalyst is added, the number of crosslinking points formed by the epoxyamine compound remains unchanged compared to when a transesterification catalyst is not added, allowing for lower processing temperatures while maintaining heat resistance. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a graph showing the results of measuring the change in the linear expansion coefficient of a crosslinked polyester resin. [Figure 2] FIG. 2 is a graph showing the results of measuring the storage modulus (DMA) of a crosslinked polyester resin. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present inventors have conducted extensive research with the aim of providing a crosslinked polyester resin that exhibits softening behavior due to bond exchange through a transesterification reaction without the addition of a metal-containing transesterification catalyst, and that exhibits self-adhesion, remoldability, and scratch repair. As a result, they have found that the above-mentioned problems can be solved by using an epoxy-based crosslinking agent containing an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as a crosslinking agent that crosslinks polyester resins, and by compounding the epoxyamine compound in an amount ranging from 3 to 30 molar parts per 100 molar parts of carboxyl groups in the polyester resin, thereby completing the present invention.

[0014] The present invention will be described in detail below.

[0015] The crosslinked polyester resin according to the present invention is a resin in which a polyester resin having carboxy groups in its side chains is crosslinked with an epoxy-based crosslinking agent having multiple epoxy groups. The epoxy-based crosslinking agent contains an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule. The side chain may have a structure in which a carboxy group is present on a substituent (e.g., an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, etc.) branched from the main chain of the aromatic polyester resin, or a structure in which a carboxy group is present directly on the aromatic polyester resin. The side chain preferably has a structure in which a carboxy group is present directly on the aromatic polyester resin. The polyester resin is crosslinked by the reaction of two or more epoxy groups contained in the epoxyamine compound with the carboxy groups on the side chains of the polyester resin. That is, the crosslinked polyester resin has an ester group and a hydroxyl group formed by the reaction of the carboxy groups on the side chains of the polyester resin with the epoxy groups of the epoxyamine compound. The heat resistance of the polyester resin is improved by crosslinking.

[0016] The number of epoxy groups contained in the epoxy amine compound may be 2 or more, may be 3 or more, or may be 4 or more. The upper limit of the number of epoxy groups is not particularly limited, but is, for example, preferably 6 or less, more preferably 5 or less.

[0017] Furthermore, the epoxy amine compound contains a tertiary amino group within the molecule. The tertiary amino group acts similarly to a transesterification catalyst. By heating the crosslinked polyester resin, the hydroxyl groups present in the crosslinked polyester resin attack the CO bonds of the ester groups present near the hydroxyl groups through the action of the tertiary amino group, resulting in bond exchange via transesterification, resulting in softening behavior, even without the addition of a transesterification catalyst. However, if there is only one tertiary amino group within the epoxy amine compound molecule, the transesterification reaction does not proceed sufficiently, resulting in a lack of self-adhesiveness, remoldability, and scratch repair properties. Furthermore, even if a transesterification catalyst is added to actively promote the transesterification reaction, according to the present invention, the number of crosslinking points by the epoxy amine compound remains unchanged compared to when a transesterification catalyst is not added. This allows the crosslinked polyester resin to maintain its heat resistance while lowering its softening temperature and processing temperature.

[0018] In the present invention, the number of tertiary amino groups contained in the molecule of the epoxy amine compound is set to at least 2. By containing at least two tertiary amino groups, softening behavior can be exhibited.

[0019] The epoxy amine compound is used in an amount of 3 to 30 molar parts per 100 molar parts of carboxy groups in the polyester resin having carboxy groups in its side chains. If the amount of epoxy amine compound is less than 3 molar parts, the ratio of epoxy groups to carboxy groups will be low, resulting in too low a crosslink density and preventing curing. Therefore, the amount of epoxy amine compound is 3 molar parts or more, preferably 5 molar parts or more, and more preferably 10 molar parts or more. However, if the amount of epoxy amine compound exceeds 30 molar parts, the ratio of epoxy groups to carboxy groups will be high, and the excess epoxy groups will self-polymerize, resulting in too high a crosslink density. This is thought to result in a decrease in the mobility of the crosslinked polymer and an excessively high softening temperature. Therefore, the amount of epoxy amine compound is 30 molar parts or less, preferably 28 molar parts or less, and more preferably 26 molar parts or less.

[0020] The number of carboxyl groups per polymer chain of polyester resin (hereinafter referred to as NCOOH The acid value (sometimes expressed as ) can be calculated using the following method. For example, if the acid value of a polyester resin is A (mgKOH / g), the molecular weight of KOH is 56.1 g / mol, so the number of moles of carboxy groups per 1 g of polyester resin having carboxy groups on the side chains can be expressed as A / 56.1 (mmol / g). If the number average molecular weight of a polyester resin having carboxy groups on the side chains is B (g / mol), the number of carboxy groups in the polymer chain can be expressed as A / 56.1 x B / 1000 (numbers), which is the number of carboxy groups per polymer chain, N COOH Let's say.

[0021] The tertiary amino group and epoxy group contained in the epoxyamine compound preferably constitute a diglycidylamino group represented by the following formula: In the formula, * represents a bond.

[0022] [ka]

[0023] The number of diglycidylamino groups contained in the molecule of the epoxy amine compound may be one, but preferably two or more. By containing two or more diglycidylamino groups, softening behavior due to bond exchange by transesterification reaction is easily exhibited. The number of diglycidylamino groups is preferably, for example, three or less.

[0024] The diglycidylamino group may be bonded to an aliphatic hydrocarbon having about 1 to 10 carbon atoms (hereinafter referred to as linking group 1), may be bonded to an aromatic hydrocarbon ring having about 6 to 20 carbon atoms (hereinafter referred to as linking group 2), or may be bonded to a group in which two or more aromatic hydrocarbon rings having about 6 to 20 carbon atoms are bonded to an aliphatic hydrocarbon having about 1 to 10 carbon atoms (hereinafter referred to as linking group 3). The diglycidylamino group is preferably bonded to linking group 2 or linking group 3, and it is particularly preferable that the diglycidylamino group is bonded to an aromatic hydrocarbon ring (preferably a benzene ring).

[0025] Examples of epoxy amine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 4,4'-methylenebis(N,N-diglycidylaniline). N,N,N',N'-tetraglycidyl-m-xylylenediamine is commercially available from Mitsubishi Gas Chemical Company, Inc. as a multifunctional epoxy compound "TETRAD-X." 4,4'-methylenebis(N,N-diglycidylaniline) is available from Tokyo Chemical Industry Co., Ltd. (TCI). One type of epoxy amine compound may be used, or two or more types may be used.

[0026] The molecular weight of the epoxyamine compound is preferably 800 or less. When the molecular weight is 800 or less, the epoxyamine compound penetrates between polyester chains, facilitating the formation of three-dimensional crosslinks and improving heat resistance. The molecular weight of the epoxyamine compound is more preferably 700 or less, and even more preferably 600 or less. The lower limit of the molecular weight of the epoxyamine compound is, for example, 250 or more.

[0027] In addition to the above-mentioned epoxy amine compound (hereinafter referred to as the "first epoxy amine compound"), a polyfunctional epoxy compound other than the first epoxy amine compound (hereinafter referred to as the "other polyfunctional epoxy compound") may also be used as the epoxy-based crosslinking agent. Specifically, the other polyfunctional epoxy compound may be a crosslinking agent that undergoes a curing reaction with carboxyl groups in the side chains of the polyester resin to form a crosslink. The crosslinking agent may be a compound having two or more epoxy groups in its molecule but not a tertiary amino group in its molecule (hereinafter referred to as the "non-amine epoxy compound"), or a compound having two or more epoxy groups and one tertiary amino group in its molecule (hereinafter referred to as the "second epoxy amine compound"). The use of the other polyfunctional epoxy compound together with the first epoxy amine compound facilitates the formation of three-dimensional crosslinks, improving heat resistance.

[0028] Examples of non-amine epoxy compounds include cresol novolac epoxy resins, phenol novolac epoxy resins, and epoxy resins having a dicyclopentadiene skeleton. The use of cresol novolac epoxy resins or phenol novolac epoxy resins can reduce the crosslink density and alleviate stress during peeling. Examples of commercially available cresol novolac epoxy resins include YDCN-700 manufactured by Nippon Steel Chemical & Material Co., Ltd. Examples of commercially available phenol novolac epoxy resins include EPICLON N-700A manufactured by DIC Corporation.

[0029] Epoxy compounds having a dicyclopentadiene skeleton have extremely low moisture absorption due to the rigidity of the dicyclopentadiene skeleton, and can reduce the crosslink density and relieve stress during peeling. Commercially available epoxy compounds having a dicyclopentadiene skeleton include, for example, the HP7200 series manufactured by DIC Corporation.

[0030] Examples of the second epoxyamine compound include triglycidyl para-aminophenol (also known as N,N-diglycidyl-4-(glycidyloxy)aniline). Commercially available triglycidyl para-aminophenol products include jER630 manufactured by Mitsubishi Chemical Corporation.

[0031] These other polyfunctional epoxy compounds can be used alone or in combination of two or more.

[0032] When the total amount of the epoxy crosslinking agent is 100 parts by mole, the amount of the first epoxy amine compound is preferably 30 parts by mole or more. The amount of the first epoxy amine compound is more preferably 50 parts by mole or more, and even more preferably 80 parts by mole or more. The amount of the first epoxy amine compound is particularly preferably 100 parts by mole, and it is preferable to use only an epoxy amine compound having two or more epoxy groups and two or more tertiary amino groups in the molecule as the epoxy crosslinking agent.

[0033] (polyester resin) The polyester resin has a carboxy group in the side chain, and the polyester resin is crosslinked by the reaction of this carboxy group with the epoxy group contained in the epoxy-based crosslinking agent.

[0034] The polyester resin having a carboxy group in the side chain may be an aliphatic polyester or an aromatic polyester. From the viewpoint of improving self-adhesion, it is more preferable to use an aliphatic polyester, and from the viewpoint of improving heat resistance, it is more preferable to use an aromatic polyester, and aliphatic polyesters and aromatic polyesters may be used in combination. Furthermore, when the crosslinked polyester resin is used as an adhesive sheet or adhesive film for adhering a film substrate or a metal substrate, it is preferable to use an aromatic polyester rather than an aliphatic polyester as the polyester resin having a carboxy group in the side chain.

[0035] A polyester resin having a carboxy group in the side chain can be prepared, for example, by polycondensing a polycarboxylic acid, a polyhydric alcohol, and a dicarboxylic acid containing a nucleophilic reactive group (such as a thiol group), followed by reacting the nucleophilic reactive group with an unsaturated carboxylic acid, or by polycondensing a polycarboxylic acid, a polyhydric alcohol, and an unsaturated polycarboxylic acid or an anhydride thereof, followed by reacting the unsaturated group with a carboxylic acid having a nucleophilic reactive group.

[0036] The polycarboxylic acid may be primarily composed of a dicarboxylic acid (for example, 60 or more molar parts, preferably 80 or more molar parts of dicarboxylic acid per 100 molar parts of polycarboxylic acid). Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phenylenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and dimer acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalic acid, and 1,2-cyclohexenedicarboxylic acid; and unsaturated group-containing dicarboxylic acids such as fumaric acid, maleic acid, and terpene-maleic acid adducts. One or more of these dicarboxylic acids may be used. Examples of polycarboxylic acids include tricarboxylic acids and tetracarboxylic acids such as trimellitic acid, pyromellitic acid, and 3,3',4,4'-benzophenonetetracarboxylic acid. These tricarboxylic acids and tetracarboxylic acids are preferably subjected to the polycondensation reaction as acid anhydrides.

[0037] Examples of polyhydric alcohols include aliphatic glycols such as neopentyl glycol, ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,6-hexanediol, 4-methyl-1,7-heptanediol, 2-methyl-1,8-octanediol, 4-methyl-1,8-octanediol, 4-propyl-1,8-octanediol, and 1,9-nonanediol; diethylene glycol, Examples of suitable polyether glycols include triethylene glycol, polyethylene glycol, polyolefin glycol, and polytetramethylene glycol; alicyclic polyols such as 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane glycols, and hydrated bisphenols; and glycol-modified aromatic dicarboxylic acids such as ethylene glycol-modified terephthalic acid (e.g., bis-2-hydroxyethyl terephthalate (BHET)), propylene glycol-modified terephthalic acid, ethylene glycol-modified isophthalic acid, propylene glycol-modified isophthalic acid, ethylene glycol-modified orthophthalic acid, and propylene glycol-modified orthophthalic acid. One or more of these may be used.

[0038] Examples of dicarboxylic acids containing a nucleophilic reactive group include dicarboxylic acids containing a thiol group as a reactive group, such as aliphatic dicarboxylic acids having about 4 to 10 carbon atoms and a thiol group, such as thiomalic acid.

[0039] Examples of unsaturated carboxylic acids that react with a nucleophilic reactive group include aliphatic α,β-unsaturated monocarboxylic acids having about 3 to 10 carbon atoms, such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid.

[0040] Examples of unsaturated polycarboxylic acids include aliphatic α,β-unsaturated dicarboxylic acids having about 4 to 10 carbon atoms, such as maleic acid and fumaric acid.

[0041] Examples of carboxylic acids having a nucleophilic reactive group that reacts with the unsaturated group of an unsaturated polycarboxylic acid include aliphatic monocarboxylic acids having about 2 to 10 carbon atoms and a thiol group, such as thioglycolic acid and mercaptopropionic acid.

[0042] The molar ratio of the carboxy groups of the polyester resin having carboxy groups in its side chains to the epoxy groups of the first epoxyamine compound is preferably 1:0.125 to 1:1.2 (carboxy groups:epoxy groups). The lower limit of the molar ratio is more preferably 1:0.3, and the upper limit is more preferably 1:1.1. The molar ratio is most preferably 1:1.

[0043] The number average molecular weight (Mn) of the polyester resin having a carboxy group in the side chain is preferably, for example, 6,000 to 20,000. When the number average molecular weight of the polyester resin having a carboxy group in the side chain is 6,000 or more, heat resistance can be improved. The number average molecular weight is more preferably 6,500 or more, and even more preferably 7,000 or more. However, if the number average molecular weight of the polyester resin having a carboxy group in the side chain is too large, it becomes too hard and brittle. Therefore, the number average molecular weight is preferably 20,000 or less, more preferably 19,000 or less, and even more preferably 18,000 or less.

[0044] The molecular weight dispersity (PDI) of the polyester resin having a carboxy group in the side chain is preferably 1.3 to 1.8. The molecular weight dispersity can be calculated using the following formula based on the weight average molecular weight (Mw) and the number average molecular weight (Mn). PDI value = Mw / Mn

[0045] The PDI value is preferably 1.4 or higher. However, if the PDI value is too high, the chain length will vary, which will lead to variations in strength. Therefore, the PDI value is preferably 1.8 or lower, more preferably 1.7 or lower.

[0046] The number of carboxyl groups per polymer chain of polyester resin (N COOH ) is preferably 3 to 50. COOH When N is 3 or more, the carboxyl groups on the side chains of the polyester resin are crosslinked with the epoxy crosslinking agent, improving heat resistance. COOH is more preferably 3.5 or more, and even more preferably 4 or more. COOH If N becomes too large, the polyester resin will be excessively cross-linked, making it too hard and brittle. COOH is preferably 50 or less, more preferably 48 or less, and even more preferably 45 or less.

[0047] The acid value of the polyester resin having a carboxy group in the side chain is preferably 5 mgKOH / g or more. By setting the acid value to 5 mgKOH / g or more, heat resistance can be improved. The acid value is more preferably 10 mgKOH / g or more, and even more preferably 15 mgKOH / g or more. However, if the acid value is too high, the crosslinking density may become too high, resulting in hardness and reduced adhesiveness. Therefore, the acid value is preferably 250 mgKOH / g or less, more preferably 230 mgKOH / g or less, and even more preferably 200 mgKOH / g or less.

[0048] (Transesterification catalyst) The crosslinked polyester resin of the present invention does not need to contain a transesterification catalyst, but may be a crosslinked polyester resin composition containing a transesterification catalyst within a range that does not impair the effects of the present invention. By incorporating a transesterification catalyst, the transesterification reaction can be promoted, thereby lowering the softening temperature while maintaining the heat resistance of the crosslinked polyester resin itself, and thereby lowering the processing temperature.

[0049] Examples of the transesterification catalyst that can be used include zinc acetate, triphenylphosphine, trimethylamine, and triethylamine, and among these, zinc acetate is preferred. One or more types of transesterification catalysts may be used.

[0050] When a transesterification catalyst is blended, it is preferably 30 parts by mole or less, more preferably 28 parts by mole or less, and even more preferably 25 parts by mole or less, relative to 100 parts by mole of carboxy groups in the polyester resin. When a transesterification catalyst is blended, the lower limit is, for example, preferably 1 part by mole or more, more preferably 2 parts by mole or more, and even more preferably 3 parts by mole or more, relative to 100 parts by mole of carboxy groups in the polyester resin. When multiple types of transesterification catalysts are used, this refers to the total amount.

[0051] (crosslinked polyester resin) The crosslinked polyester resin of the present invention preferably has a softening temperature resulting from bond exchange due to a transesterification reaction of, for example, 155 to 300° C. In the case of a crosslinked polyester resin composition containing a transesterification catalyst, the softening temperature is, for example, preferably 155° C. or higher, more preferably 160° C. or higher, and even more preferably 165° C. or higher. In the case of a crosslinked polyester resin not containing a transesterification catalyst, the softening temperature is, for example, preferably 175° C. or higher, more preferably 180° C. or higher, and even more preferably 190° C. or higher.

[0052] The softening temperature of a crosslinked polyester resin (crosslinked polyester resin composition) is determined by measuring the change in linear expansion coefficient when heated from room temperature to 300°C under tension, and the temperature at the inflection point of the linear expansion coefficient change curve is used. A specific measurement method will be described in detail in the Examples section.

[0053] The crosslinked polyester resin (crosslinked polyester resin composition) of the present invention preferably has a glass transition temperature (Tg) of -50 to 150°C. A Tg of -50°C or higher ensures heat resistance. Tg is more preferably -40°C or higher, and even more preferably -30°C or higher. However, if Tg is too high, processing becomes difficult, so Tg is preferably 150°C or lower. Tg is more preferably 130°C or lower, and even more preferably 100°C or lower.

[0054] Next, a method for producing the crosslinked polyester resin according to the present invention will be described.

[0055] The crosslinked polyester resin of the present invention can be produced by known methods. For example, a polyester resin having carboxy groups in its side chains and an epoxy-based crosslinking agent containing a first epoxyamine compound are dissolved in a solvent, the solvent is removed, and the mixture is heated under reduced pressure to crosslink the polyester resin. The molar ratio of the carboxy groups in the polyester resin having carboxy groups in its side chains to the epoxy groups in the first epoxyamine compound is preferably 1:0.125 to 1:1.2 (carboxy groups:epoxy groups). The lower limit of the molar ratio is more preferably 1:0.3, the upper limit is more preferably 1:1.1, and the most preferably 1:1.

[0056] The crosslinked polyester resin of the present invention has self-adhesive properties, and when the crosslinked polyester resins of the present invention are laminated together and heated and pressurized, transesterification occurs at the interface of the crosslinked polyester resins, allowing the crosslinked polyester resins to be bonded together without the use of an adhesive.

[0057] The crosslinked polyester resin of the present invention is remoldable; after being deformed into a predetermined shape, it is heated in the deformed state, causing transesterification, allowing it to be remolded, and even when cooled, it retains the predetermined shape.

[0058] The crosslinked polyester resin of the present invention has scratch-repairing properties, and even if the surface is scratched with a cutter knife or the like, heating causes bond exchange through an ester exchange reaction, resulting in self-repair. Therefore, the crosslinked polyester resin of the present invention can be used as a main component of a self-repairing material. As a self-repairing material, it can be used, for example, as a material for paint.

[0059] The crosslinked polyester resin of the present invention can be used as a main component of a molding material. That is, the crosslinked polyester resin has good moldability and extrusion moldability, and is therefore useful as a molding material, and can be used, for example, as a material for 3D printers or a material for filamentous moldings.

[0060] The crosslinked polyester resin can also be used as a material for a network structure. A network structure is a structure in which parts of filamentous molded bodies are connected to each other. The network structure can be produced by melting the crosslinked polyester resin, discharging the molten material from a nozzle, and solidifying the discharged material while welding it together.

[0061] The content of the crosslinked polyester resin in the solid content of the self-adhesive, self-repairing material, or molding material is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass.

[0062] The crosslinked polyester resin of the present invention is hardly dissolved even when immersed in a solvent (particularly an organic solvent), and therefore has good solvent resistance, and can therefore be suitably used as a laminating material, for example.

[0063] The crosslinked polyester resin of the present invention has good storage stability at room temperature. That is, even when stored at a predetermined temperature for a predetermined period of time, the gel fraction hardly changes. Furthermore, even when stored at a predetermined temperature for a predetermined period of time, the resin exhibits softening behavior equivalent to that before storage.

[0064] Among the crosslinked polyester resins of the present invention, when an aromatic polyester resin is used as the polyester resin having a carboxy group in a side chain, the crosslinked polyester resin can be used, for example, as an adhesive sheet, adhesive film, or molding material. When used as an adhesive sheet or adhesive film, the crosslinked polyester resin of the present invention can be sandwiched between the bonded members to be bonded and heated. By heating, bond exchange occurs due to an ester exchange reaction, allowing the bonded members to be bonded to each other.

[0065] Examples of the adherend include resin films and metal foils, and the crosslinked polyester resin can be used as an adhesive between resin films, between metal foils, or between a resin film and a metal foil. Examples of the resin film include polyimide film, polyester film, and PET film. Examples of the metal foil include copper foil, silver foil, and gold foil. The adhesiveness of the crosslinked aromatic polyester resin can be evaluated based on the 90° peel strength shown in the examples.

[0066] Among the crosslinked polyester resins of the present invention, when an aromatic polyester resin is used as the polyester resin having a carboxyl group in the side chain, the crosslinked polyester resin becomes capable of bond exchange when heated above its ester bond exchange activation temperature (softening temperature). Therefore, when the crosslinked polyester resin is used as an adhesive material, the adhesive becomes easily peeled by heating the adhesive above its ester bond exchange activation temperature. Therefore, the crosslinked polyester resin can be used as a material for adhesives for repair applications that can be applied and removed. The peelability of the crosslinked polyester resin when heated to a high temperature can be evaluated based on the 90° peel strength when heated, as shown in the examples.

[0067] Although the applications of the crosslinked polyester resin have been described above, a crosslinked polyester resin composition containing a crosslinked polyester resin and a transesterification catalyst can also be used for the same applications.

[0068] This application claims the benefit of priority based on Japanese Patent Application No. 2020-174536, filed on October 16, 2020. The entire contents of the specification of Japanese Patent Application No. 2020-174536 are incorporated herein by reference. [Example]

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples, and it is of course possible to carry out the present invention with modifications within the scope of the above and below-described aims, all of which are included in the technical scope of the present invention. Hereinafter, "parts" means "parts by mass."

[0070] A crosslinked polyester resin was produced by crosslinking a polyester resin having a carboxyl group in the side chain with an epoxy-based crosslinking agent having multiple epoxy groups. The polyester resin was either an aliphatic polyester resin or an aromatic polyester resin.

[0071] Production Example 1 (Aliphatic Polyester Resin A1) A 50ml glass flask equipped with a stirrer was charged with 15 mol parts of thiomalic acid, 35 mol parts of adipic acid, 50 mol parts of 1,5-pentanediol, and 0.5 mol parts of scandium triflate, and the mixture was stirred at 80°C to homogenize. After dissolution, the pressure in the glass flask was reduced to 5mmHg over 30 minutes, and then the polycondensation reaction was carried out at 80°C for 20 hours under a vacuum of 0.3mmHg or less. After the reaction, the contents were removed and cooled to obtain a polyester resin raw material. Next, 70 mol parts of the polyester resin raw material were dissolved in 10ml of N,N-dimethylformamide (DMF), and then 15 mol parts of acrylic acid and 2.1 mol parts of triethylamine as a catalyst were added. The mixture was stirred at room temperature for 15 hours to induce Michael addition between the thiol group of the thiomalic acid unit and the double bond of the acrylic acid. This was then reprecipitated in methanol to prepare a polyester resin with carboxyl groups in the side chains. The obtained polyester resin is hereinafter referred to as aliphatic polyester resin A1.

[0072] Production Example 2 (Aromatic Polyester Resin B1) A 50 ml glass flask equipped with a stirrer was charged with 25 mol parts maleic acid, 25 mol parts adipic acid, 50 mol parts bis-2-hydroxyethyl terephthalate (BHET), and 0.5 mol parts scandium triflate, and the mixture was stirred at 100°C to homogenize. After dissolution, the pressure in the glass flask was reduced to 5 mmHg over 30 minutes, and then the polycondensation reaction was carried out at 110°C under a vacuum of 0.3 mmHg or less for 4 hours. After the reaction, the contents were removed and cooled to obtain a polyester resin raw material. Next, 50 mol parts of the polyester resin raw material were dissolved in 10 ml of N,N-dimethylformamide (DMF), and then 25 mol parts thioglycolic acid and 1.6 mol parts triethylamine as a catalyst were added. The mixture was stirred at room temperature for 15 hours, allowing the thioglycolic acid to undergo Michael addition via the thiol group to the maleic acid units of the polyester resin raw material. This was reprecipitated with acetone to prepare a polyester resin having a carboxyl group in the side chain and an aromatic structure, hereinafter referred to as aromatic polyester resin B1.

[0073] Production Example 3 (Aromatic Polyester Resin B2) A polyester resin raw material was produced in the same manner as in Production Example 2, except that adipic acid was not added and the charging ratio of maleic acid and bis-2-hydroxyethyl terephthalate (BHET) was changed as shown in Table 1. Next, a polyester resin having a carboxy group in the side chain and an aromatic structure was prepared by adding thioglycolic acid to the polyester resin raw material in the same manner as in Production Example 2. The obtained polyester resin is hereinafter referred to as aromatic polyester resin B2.

[0074] Production Example 4 (Aromatic Polyester Resin C1) (1) High molecular weight polyol c1 A reactor equipped with a stirrer, thermometer, and outflow condenser was charged with 135 mol parts of terephthalic acid, 311 mol parts of isophthalic acid, 5 mol parts of trimellitic anhydride, 74 mol parts of 2-methyl-1,3-propanediol, 417 mol parts of 1,4-cyclohexanediol, and 0.2 mol parts of tetrabutyl titanate. The temperature was gradually raised to 250 ° C., and the esterification reaction was carried out while removing the distilled water from the system. After the esterification reaction was completed, the pressure was gradually reduced to 10 mmHg while performing initial polymerization, and the temperature was raised to 250 ° C., and then post-polymerization was carried out until the specified torque was reached at 1 mmHg or less. Nitrogen was then introduced into the reactor, the pressure was returned to normal, and 5 mol parts of trimellitic anhydride were added. The reaction was carried out at 220 ° C. for 30 minutes to obtain polymer polyol c1. (2) High molecular weight polyol c2 A reactor equipped with a stirrer, thermometer, and outflow cooler was charged with 390 moles of terephthalic acid, 390 moles of isophthalic acid, 440 moles of ethylene glycol, 362 moles of 2,2-dimethyl-1,3-propanediol, and 0.2 moles of tetrabutyl titanate, and the temperature was gradually raised to 250 ° C., and an esterification reaction was carried out while removing the distilled water from the system. After the esterification reaction was completed, initial polymerization was carried out while gradually reducing the pressure to 10 mmHg, and the temperature was raised to 250 ° C., and then post-polymerization was carried out at 1 mmHg or less until a predetermined torque was reached, yielding high molecular weight polyol c2. (3) Aromatic polyester resin C1 In a reaction vessel equipped with a stirrer, thermometer, and reflux condenser, 160 parts of polymer polyol c1, 40 parts of polymer polyol c2, 5.2 parts of pyromellitic anhydride, and 200 parts of toluene were charged and dissolved while gradually increasing the temperature to 80 ° C. After dissolution, 0.1 parts of triethylamine was added as a reaction catalyst, and the temperature was gradually increased to 105 ° C. and the reaction was allowed to proceed for 24 hours. After confirming the completion of the reaction by infrared spectroscopy (IR), 108 parts of toluene was added to dilute the mixture, thereby obtaining a solution with a solids concentration of 40% of a polyester resin having a carboxy group in the side chain. The polyester resin having a carboxy group in the side chain is hereinafter referred to as aromatic polyester resin C1.

[0075] The compositions (molar ratios) of the aliphatic polyester resin A1 and aromatic polyester resins B1 and B2 obtained in Production Examples 1 to 4 are shown in Table 1 below.

[0076] [Table 1]

[0077] The obtained aliphatic polyester resin A1 and aromatic polyester resins B1, B2, and C1 were analyzed for number average molecular weight (Mn), polydispersity index (PDI), and number of carboxyl groups per polymer chain of the polyester resin (N COOH The results are shown in Table 1. The methods for determining these various properties are as follows.

[0078] (Number average molecular weight (Mn) and polydispersity index (PDI)) Aliphatic or aromatic polyester resins were dissolved in tetrahydrofuran to a concentration of approximately 0.5% by mass and filtered through a 0.5 μm pore size polytetrafluoroethylene membrane filter to prepare samples. However, if the resin was insoluble in tetrahydrofuran, N,N-dimethylformamide was used instead. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by gel permeation chromatography using a differential refractometer as the detector and tetrahydrofuran as the mobile phase. The flow rate was 1 mL / min and the column temperature was 30°C. Showa Denko KF-802, KF-804L, and KF-806L columns were used. Monodisperse polystyrene was used as the standard (molecular weight standard). Low-molecular-weight compounds (oligomers, etc.) with a number-average molecular weight of less than 1,000 were not counted and were omitted. The molecular weight dispersity index (PDI) was calculated based on the measured number-average molecular weight (Mn) and weight-average molecular weight (Mw) using the following formula: PDI value = Mw / Mn

[0079] (acid number) 0.2 g of aliphatic polyester resin or aromatic polyester resin was dissolved in 20 ml of chloroform, and phenolphthalein was added to this solution as an indicator, followed by neutralization titration with a 0.1 N potassium hydroxide ethanol solution. From the titration amount, the number of mg of potassium hydroxide (mg KOH) consumed for neutralization was converted into the amount per 1 g of aliphatic polyester resin or aromatic polyester resin to calculate the acid value (mg KOH / g).

[0080] (Number of carboxyl groups per polymer chain of polyester resin (N COOH )) Number of carboxyl groups per polymer chain (N COOH ) was calculated using the following method. For example, when the acid value of a polyester resin having carboxy groups in the side chains is A (mgKOH / g), the number of moles of carboxy groups per 1 g of polyester resin having carboxy groups in the side chains can be expressed as A / 56.1 (mmol / g) because the molecular weight of KOH is 56.1 g / mol. When the number average molecular weight of a polyester resin having carboxy groups in the side chains is B (g / mol), the number of carboxy groups in the polymer chain can be expressed as A / 56.1 × B / 1000 (numbers), which is the number of carboxy groups per polymer chain, N COOH It was decided.

[0081] In the following examples, the following epoxy crosslinking agents were used: (1) "TETRAD-X" (trade name) multifunctional epoxy compound (N,N,N',N'-tetraglycidyl-m-xylylenediamine) manufactured by Mitsubishi Gas Chemical Company, Inc. (2) 4,4'-methylenebis(N,N-diglycidylaniline) (3) 1,4-butanediol diglycidyl ether (4) "jER630" (trade name) (triglycidyl paraaminophenol) manufactured by Mitsubishi Chemical Corporation

[0082] The multifunctional epoxy compound "TETRAD-X" (trade name) manufactured by Mitsubishi Gas Chemical Company, Inc. and 4,4'-methylenebis(N,N-diglycidylaniline) are both epoxy amine compounds with two tertiary amino groups and four epoxy groups in the molecule, and both have two diglycidylamino groups. "jER630" (trade name) manufactured by Mitsubishi Chemical Corporation is a multifunctional epoxy compound with one tertiary amino group and three epoxy groups in the molecule, and one diglycidylamino group. 1,4-Butanediol diglycidyl ether is a multifunctional epoxy compound with two epoxy groups in the molecule but no tertiary amino groups.

[0083] Example 1 Aliphatic polyester resin A1 was used as the polyester resin, and 4,4'-methylenebis(N,N-diglycidylaniline) was used as the epoxy crosslinker. The molar ratio of the carboxyl groups of the polyester resin to the epoxy groups of the epoxy amine compound was 1:1. Specifically, for 100 molar parts of the carboxyl groups of the aliphatic polyester resin A1, the epoxy groups of 4,4'-methylenebis(N,N-diglycidylaniline) were 25 molar parts. 10 parts by weight of the aliphatic polyester resin A1 and 1.3 parts by weight of the 4,4'-methylenebis(N,N-diglycidylaniline) were dissolved in 10 parts by weight of tetrahydrofuran (THF). The solution was placed in a Teflon®-coated mold and heated to 40°C to remove the THF by evaporation. The THF-removed sample was heated at 120°C under vacuum for 4 hours to obtain a crosslinked polyester resin film (0.7 mm thick).

[0084] Examples 2 to 8 As shown in Table 2-1, a crosslinked polyester resin film (thickness 0.7 mm) was produced under the same production conditions as in Example 1, except that aliphatic polyester resin A1, aromatic polyester resin B1, B2, or C1 was used as the polyester resin, and the polyfunctional epoxy compound "TETRAD-X" (trade name) manufactured by Mitsubishi Gas Chemical Company, Inc. or 4,4'-methylenebis(N,N-diglycidylaniline) was used as the epoxy crosslinking agent.

[0085] Example 9 Aromatic polyester resin C1 was used as the polyester resin, and Mitsubishi Gas Chemical Company, Inc.'s multifunctional epoxy compound "TETRAD-X" (trade name) was used as the epoxy crosslinker. A transesterification catalyst was also added. The molar ratio of the carboxyl groups on the side chains of the polyester resin to the epoxy groups of the epoxy amine compound was 1:1. Specifically, the carboxyl groups of aromatic polyester resin C1 were 100 parts by mole, the epoxy groups of "TETRAD-X" (trade name) were 25 parts by mole, and zinc acetate was used as the transesterification catalyst at 5 parts by mole. Ten parts by mass of aromatic polyester resin C1 and 0.27 parts by mass of "TETRAD-X" (trade name) were dissolved in 10 parts by mass of tetrahydrofuran (THF), and 0.03 parts by mass of zinc acetate was dissolved in 1 part by mass of dimethylformamide (DMF). These two solutions were mixed and dissolved in a Teflon-coated mold. The mixture was then heated to 40°C to evaporate and remove the solvent. The sample from which the solvent had been removed was heated at 120°C for 4 hours under vacuum conditions to obtain a crosslinked polyester resin film (thickness 0.7 mm).

[0086] (Examples 10 and 11) As shown in Table 2-2, a crosslinked polyester resin film (thickness: 0.7 mm) was produced under the same production conditions as in Example 9, except that the amount of the transesterification catalyst was changed.

[0087] (Comparative Examples 1 and 3) A crosslinked polyester resin film (thickness 0.7 mm) was produced under the same production conditions as in Example 7, except that 50 molar parts (0.30 parts by mass) of 1,4-butanediol diglycidyl ether or 33 molar parts (0.27 parts by mass) of "jER630" (trade name) was used instead of 25 molar parts of "TETRAD-X" (trade name) as an epoxy-based crosslinking agent.

[0088] (Comparative Examples 2 and 4) A crosslinked polyester resin film (thickness 0.7 mm) was produced under the same production conditions as in Example 11, except that 50 molar parts (0.30 parts by mass) of 1,4-butanediol diglycidyl ether or 33 molar parts (0.27 parts by mass) of "jER630" (trade name) was used instead of 25 molar parts of "TETRAD-X" (trade name) as an epoxy-based crosslinking agent.

[0089] The compositions (parts by mole) of the crosslinked polyester resin films obtained in Examples 1 to 11 and Comparative Examples 1 to 4 are shown in Tables 2-1 and 2-2 below.

[0090] [Table 2-1]

[0091] [Table 2-2]

[0092] The properties of the crosslinked polyester resin films shown in Tables 3-1 and 3-2 below were evaluated as follows.

[0093] (Softening temperature) The change in the linear expansion coefficient of the crosslinked polyester resin film was measured using a Hitachi "TMA7100." The initial jig distance was 15 mm. To prevent deflection, test pieces (rectangles measuring 4 mm wide x 20 mm long x 0.7 mm thick) cut from the crosslinked polyester resin film were heated from room temperature to 300°C at a heating rate of 10°C / min under a nitrogen gas atmosphere with a constant tension (20 mN). Of the measurement results, those for Example 11, Comparative Example 2, and Comparative Example 4 are shown in Figure 1. The vertical axis represents the change in linear expansion coefficient. In Figure 1, the solid line represents the results for Example 11, the dotted line represents the results for Comparative Example 2, and the dash-dotted line represents the results for Comparative Example 4. The temperature at the inflection point of the linear expansion coefficient change curve was determined as the softening temperature.

[0094] (Storage Modulus (DMA)) The storage modulus (DMA) of the crosslinked polyester resin film was measured. The storage modulus (DMA) was measured by setting the resin in a dynamic viscoelasticity measuring device "DVA-200" manufactured by IT Measurement & Control Co., Ltd., setting the measurement frequency to 10 Hz, and heating the resin from room temperature to 200-300°C at a heating rate of 4°C / min. Of the measurement results, the results of Example 11, Comparative Example 2, and Comparative Example 4 are shown in Figure 2. The vertical axis represents the storage modulus. In Figure 2, the solid line represents the results of Example 11, the dotted line represents the results of Comparative Example 2, and the dashed-dotted line represents the results of Comparative Example 4. The upper limit of the heating temperature was 290°C for Example 11, 200°C for Comparative Example 2, and 300°C for Comparative Example 4.

[0095] As is clear from FIG. 2, no sudden change in storage modulus was observed around 200°C for any of the resins, which suggests that the crosslinked structure was maintained at 200°C.

[0096] (Self-adhesive) Two cross-linked polyester resin films (0.7 mm thick) were stacked end-to-end, heated to a temperature above their softening temperature, pressed in the lamination direction at 400 kPa, and held in this state for two hours to produce a laminated cross-linked polyester resin film. If the overlapping laminated parts adhered, it was evaluated as having self-adhesion (◯), and if they did not adhere, it was evaluated as not having self-adhesion (×).

[0097] (Remoldability) A cross-linked polyester resin film (0.7 mm thick) was spirally wrapped around a spatula, and both ends of the film were fixed to the spatula with tape. The film was then left at high temperature (softening temperature + approximately 20°C) for 2 hours. After cooling to room temperature, the tape was removed and the cross-linked polyester resin film was removed from the spatula. If the cross-linked polyester resin film maintained its wrapped shape even after being removed from the spatula, it was evaluated as remoldable (◯); if it could not maintain its wrapped shape and returned to a flat shape, it was evaluated as not remoldable (×).

[0098] (Scratch repair) A scratch approximately 1 cm long and 0.1 mm deep was made on the surface of a crosslinked polyester resin film (0.7 mm thick) with a cutter. The film was left at a high temperature (softening temperature + approximately 20°C) for 10 minutes and then allowed to cool to room temperature. If the scratch on the crosslinked polyester resin film disappeared, it was evaluated as having scratch repairability (◯); if the scratch on the crosslinked polyester resin film did not disappear, it was evaluated as not having scratch repairability (×).

[0099] (glass transition temperature Tg) The crosslinked polyester resin films obtained in the examples and comparative examples were subjected to thermal analysis using a DSC apparatus (Model: DSC7020) manufactured by Hitachi High-Tech Science Corporation in a nitrogen atmosphere by heating from -100°C to 300°C at a heating rate of 20°C / min, to measure the glass transition temperature (Tg).

[0100] (90° peel strength) A test piece measuring 20 mm long x 50 mm wide was cut from the resulting crosslinked polyester resin film (0.7 mm thick). The cut test piece was placed on a 25 μm thick PET film (manufactured by Toyobo Co., Ltd.), and another PET film of the same type was placed on top of the test piece to create a three-layer structure of "PET film / crosslinked polyester resin film / PET film." The layers were then bonded together by heating and pressurizing at 170°C, 2 MPa, and 280 seconds in a heat press. The resulting laminate was used as a sample for evaluating 90° peel strength.

[0101] In addition, a sample for evaluating 90° peel strength was prepared under the same conditions except that a polyimide film (PI, "Apical" (registered trademark) manufactured by Kaneka Corporation, thickness 12.5 μm) was used instead of the above PET film, resulting in a three-layer structure of "PI / crosslinked polyester resin film / PI."

[0102] In addition, a sample for evaluating 90° peel strength was prepared under the same conditions except that a rolled copper foil (thickness: 20 μm) and a polyimide film (PI, "Apical" (registered trademark) manufactured by Kaneka Corporation, thickness: 12.5 μm) were used instead of the above PET film, resulting in a three-layer structure of "Cu / crosslinked polyester resin film / PI."

[0103] The 90° peel strength was measured using a Shimadzu Autograph AG-Xplus at 25°C and a pulling speed of 50 mm / min. Based on the measured 90° peel strength, the adhesiveness of the film was evaluated according to the following criteria. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" means that the test was not performed. <Evaluation criteria> ◎:1.0N / mm or more ○: 0.5N / mm or more and less than 1.0N / mm △: 0.35N / mm or more and less than 0.5N / mm ×: Less than 0.35N / mm

[0104] (Moldability) The resulting crosslinked polyester resin film (0.7 mm thick) was cut into a 5 mm wide x 5 mm long sample and placed in a mold. The mold was made by cutting an 8 mm diameter circle out of a 1 mm thick Teflon (registered trademark) sheet. The film was then pressurized and heated in a heat press. The pressure was 4 MPa, and the heating conditions were softening temperature + 30°C for 15 minutes.

[0105] The crosslinked polyester resin film piece was evaluated as ◯ if it could be molded into the mold shape, and as × if it could not be molded. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" means that it was not performed.

[0106] (Extrusion moldability) 6 g of the obtained cross-linked polyester resin film (thickness 0.7 mm) was cut into a sample of 5 mm wide x 5 mm long, and the sample was fed into a twin-screw extruder "MiniLab" manufactured by HAAKE in three batches at a barrel temperature of 150 °C and a screw rotation speed of 50 min -1After the sample was completely charged, the mixture was kneaded for 5 minutes, and then extruded from the barrel. After kneading, if the mixture could be discharged and a filamentous molded product was obtained, the extrusion moldability was evaluated as ◯, and if the mixture could not be discharged and a filamentous molded product was not obtained, the extrusion moldability was evaluated as ×. The evaluation results are shown in Tables 3-1 and 3-2 below. In Examples 6 and 8, the barrel temperature was changed to 200°C to evaluate the extrusion moldability. "-" means that the experiment was not carried out.

[0107] (room temperature storage stability) The room temperature storage stability of the resulting crosslinked polyester resin film was evaluated based on the rate of change in gel fraction and softening behavior.

[0108] (1) Change in gel fraction First, the gel fraction of the resulting crosslinked polyester resin film was measured by the following method.

[0109] 0.125 g of the resulting crosslinked polyester resin film was weighed and immersed in 25 mL of methyl ethyl ketone at room temperature for 2 hours. The remaining gel component was then dried in a vacuum dryer at 80°C for 1 hour and its mass was measured. The gel fraction was calculated using the following formula: Gel fraction (%) = (weight of remaining gel component after drying ÷ 0.125) × 100

[0110] Next, the crosslinked polyester resin film was stored at a constant temperature of 5°C, 25°C, or 40°C for 6 months, and the gel fraction was measured using the method described above after 6 months. The rate of change from the gel fraction at the start of storage was calculated based on the gel fraction at the start of storage and the gel fraction after 6 months of storage. The rate of change was expressed as the absolute value of the difference in gel fraction (%) before and after 6 months, as shown in the following formula. Change rate = gel fraction (%) after 6 months - gel fraction (%) at the start of storage

[0111] A change rate of less than 10% was evaluated as ○, a change rate of 10% to 25% was evaluated as △, and a change rate of more than 25% was evaluated as ×. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" means that the test was not carried out.

[0112] (2) Softening behavior The obtained crosslinked polyester resin film was stored at 25°C for 6 months, and the presence or absence of softening behavior due to bond exchange reaction was evaluated by stress relaxation measurement. For stress relaxation measurement, MCR302 (manufactured by Anton Paar) was used, and stress relaxation tests were performed at temperatures of 100°C, 150°C, and 180°C. The tests were performed in a N2 gas atmosphere. The test specimens used were disk-shaped samples with a diameter of 8 mm and a thickness of 0.7 mm cut out from the above crosslinked polyester resin film.

[0113] After storage at 25°C for six months, samples that showed softening behavior when stress relaxation tests were performed at any of the temperatures of 100°C, 150°C, and 180°C were evaluated as ○, and samples that showed no softening behavior when stress relaxation tests were performed at any of the temperatures of 100°C, 150°C, and 180°C were evaluated as ×. The evaluation results are shown in Tables 3-1 and 3-2 below. The fact that stress relaxation was observed after storage at 25°C for six months indicates that the softening properties due to bond exchange were maintained even after storage, and that there was no change from the initial behavior during long-term storage at room temperature.

[0114] (Solvent resistance) The resulting crosslinked polyester resin film (0.7 mm thick) was cut into 5 mm wide x 5 mm long samples, and three samples were placed in each screw bottle, one per bottle, for each level. 3 mL of ethanol, dimethylformamide (DMF), or tetrahydrofuran (THF) was added to each bottle and the bottle was left standing at room temperature for 5 hours. After 5 hours of standing, if there was no change from before immersion, the solvent resistance was evaluated as excellent (◎); if the sample swelled but did not dissolve, the solvent resistance was evaluated as good (○); if the sample dissolved, the solvent resistance was evaluated as poor (×). The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" indicates that the test was not performed.

[0115] (90° peel strength when heated) The 90° peel strength during heating was measured for the "Cu / crosslinked polyester resin film / PI" sample from the 90° peel strength evaluation samples above, using a thermostatic chamber (Shimadzu Corporation, Thermostatic Chamber) at a temperature 30°C above the softening temperature of each sample listed in Tables 3-1 and 3-2. The 90° peel strength was measured using a Shimadzu Corporation Autograph AG-Xplus at a temperature 30°C above the softening temperature of each sample, at a pulling speed of 50 mm / min. Based on the measured 90° peel strength during heating, the peelability of the laminate was evaluated according to the following criteria. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" indicates that the test was not performed. <Evaluation criteria> ◎: Less than 0.35N / mm ○: 0.35N / mm or more and less than 0.5N / mm △: 0.5N / mm or more and less than 1.0N / mm ×: 1.0N / mm or more

[0116] [Table 3-1]

[0117] [Table 3-2]

[0118] The crosslinked polyester resin film obtained in Example 7 was chopped into fine resin shapes (5 mm wide x 5 mm long x 0.7 mm thick), melted at 200°C, and extruded into cooling water at a single-hole discharge rate of 1.0 g / min through a 40 cm wide x 4 cm long nozzle with 1.0 mm diameter round solid orifices arranged at 4 mm intervals across its effective nozzle surface. The film was then solidified. Specifically, cooling water was placed 10 cm below the discharge position, and the film was drawn onto a pair of parallel 50 cm wide stainless steel endless nets spaced 3 cm apart by a pair of take-up conveyors, each partially above the water surface. The nets were then fused together at the contact points, sandwiched between the two sides, and drawn into the cooling water at a speed of 1.0 m / min for solidification. The resulting film was then dried in a hot air dryer at 70°C for 15 minutes and cut to the desired size. The resulting film had a thickness of 3 cm and a density of 0.060 g / cm.3 A network structure of this size was obtained.

[0119] The results of Tables 3-1 and 3-2 can be considered as follows.

[0120] The crosslinked polyester resins obtained in Examples 1 to 11 were all obtained using an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as an epoxy-based crosslinking agent, and thus satisfied the requirements of the present invention. In Examples 1 to 8, even without the addition of a transesterification catalyst, softening behavior due to bond exchange caused by the transesterification reaction was observed, and self-adhesiveness, remoldability, and scratch repair properties were obtained. The remoldability was probably due to the activation of ester bond exchange at high temperatures, which was then fixed into a new equilibrium network structure during cooling. The scratch repairability was probably due to the activation of ester bond exchange at high temperatures, which promoted rearrangement of molecular chains near the surface of the crosslinked polyester resin film. Furthermore, since no transesterification catalyst was added in Examples 1 to 8, the crosslinked polyester resin film can be used as a material for electronics and related applications.

[0121] In Examples 9 to 11, an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule was used as the epoxy crosslinking agent, and a transesterification catalyst was also added. Comparing Examples 9 to 11 with Example 7, it was confirmed that the addition of a transesterification catalyst and an increase in the amount of the catalyst activated the bond exchange due to the transesterification reaction, resulting in a tendency for the softening temperature to decrease while maintaining heat resistance. In other words, it was found that the softening temperature could be adjusted based on the amount of the transesterification catalyst added.

[0122] The crosslinked polyester resin films of Examples 1 to 11 were excellent in moldability, extrusion moldability, room temperature storage stability, and solvent resistance. Among these, the crosslinked polyester resin films of Examples 4 to 11, which used aromatic polyester resins as polyester resins having carboxy groups in their side chains, had high 90° peel strength and were useful as adhesives. Furthermore, the crosslinked polyester resin films of Examples 4 to 11 had low 90° peel strength when heated to the softening temperature + 30°C, indicating that they were easily peeled.

[0123] On the other hand, the crosslinked polyester resins obtained in Comparative Examples 1 to 4 did not use an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as the epoxy crosslinking agent, and therefore did not satisfy the requirements of the present invention. In Comparative Example 1, bond exchange due to the transesterification reaction did not proceed, and the properties of self-adhesion, remoldability, and scratch repair were not exhibited. In Comparative Example 2, the addition of a transesterification catalyst activated bond exchange due to the transesterification reaction, and the properties of self-adhesion, remoldability, and scratch repair were exhibited. However, compared to Example 11, which contained the same amount of transesterification catalyst, the softening temperature was relatively low. The epoxy crosslinking agent used in Comparative Example 3 had three epoxy groups in the molecule, but only one tertiary amino group, so bond exchange due to the transesterification reaction did not proceed sufficiently, and the properties of self-adhesion, remoldability, and scratch repair were not exhibited. In Comparative Example 4, a transesterification catalyst was added to the example of Comparative Example 3, which activated the bond exchange due to the transesterification reaction, resulting in the development of self-adhesion, remoldability, and scratch repair properties. However, compared to Example 11, which contained the same amount of transesterification catalyst, the softening temperature was relatively lower.

[0124] Next, a 180° peel test and a shear test were performed using test pieces prepared by sandwiching the crosslinked polyester resin film (0.7 mm thick) obtained in Example 11 between a PET film, a PI film, or an Al substrate to evaluate the adhesiveness of the crosslinked polyester resin film. Specifically, the crosslinked polyester resin film obtained in Example 11 was sandwiched between two 100 μm-thick PET films and pressed at 180°C and 20 MPa for 10 minutes to obtain test piece a. The crosslinked polyester resin film obtained in Example 11 was sandwiched between two 25 μm-thick PI films and pressed at 180°C and 20 MPa for 10 minutes to obtain test piece b. The crosslinked polyester resin film obtained in Example 11 was sandwiched between two 1.5 mm-thick Al substrates and held at 200°C for 1 hour to obtain test piece c.

[0125] In the 180° peel test, the maximum stress was measured when one edge of the bonded PET or PI film was folded back 180° along the planar direction of the test specimen and peeled away. The 180° peel test was not performed on test specimen c. In the shear test, the bonded PET film, PI film, or Al substrate was pulled in opposite directions along the planar direction of the test specimen, and the maximum shear force was measured. The measurement results are shown in Table 4 below.

[0126] [Table 4]

[0127] As is clear from the results in Table 4, it was found that the crosslinked polyester resin film obtained in Example 11 can be used to bond PET films, PI films, and Al substrates.

Claims

1. a crosslinked polyester resin obtained by crosslinking a polyester resin having a carboxy group in a side chain with an epoxy-based crosslinking agent having a plurality of epoxy groups; The epoxy-based crosslinking agent includes an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule, the epoxy amine compound is 80 parts by mole or more when the total amount of the epoxy crosslinking agent is 100 parts by mole, the epoxy amine compound is present in an amount of 3 to 30 parts by mole relative to 100 parts by mole of the carboxy group of the polyester resin having a carboxy group in a side chain, The crosslinked polyester resin has a softening temperature of 155 to 300°C.

2. 2. The crosslinked polyester resin according to claim 1, wherein a molar ratio of a carboxy group of the polyester resin having a carboxy group in a side chain to an epoxy group of the epoxy amine compound is 1:0.125 to 1:1.2, where the molar ratio is the carboxy group:the epoxy group.

3. 3. The crosslinked polyester resin according to claim 1, wherein the tertiary amino group and the epoxy group contained in the epoxy amine compound constitute a diglycidyl amino group.

4. 4. The crosslinked polyester resin according to claim 1, wherein the molecular weight of the epoxyamine compound is 800 or less.

5. A crosslinked polyester resin composition comprising a transesterification catalyst and the crosslinked polyester resin according to any one of claims 1 to 4.

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