Cross-linked polyester resin

Abstract

The present invention provides a cross-linked polyester resin that exhibits high strength at room temperature through dynamic covalent crosslinking that allows for bond exchange at high temperatures. Above its softening temperature, it is reprocessable and allows for inter-film adhesion and self-healing. Furthermore, even without the addition of an ester exchange catalyst, it exhibits softening behavior based on bond exchange in the ester exchange reaction, demonstrating self-adhesion, reformability, and damage repair properties. A cross-linked polyester resin is obtained by cross-linking a polyester resin having carboxyl groups on its side chains with an epoxy crosslinker having multiple epoxy groups. The epoxy crosslinker comprises an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups within the molecule, with the epoxyamine compound being present in an amount of 3 to 30 moles per 100 moles of carboxyl groups in the polyester resin having carboxyl groups on its side chains.

Description

Technical Field

[0001] The present invention relates to a polyester resin obtained by cross-linking a polyester resin having a carboxyl group on a side chain with an epoxy cross-linking agent having a plurality of epoxy groups. Background Art

[0002] Polyester resins are polycondensates synthesized through the dehydration condensation of polycarboxylic acids and polyols. Examples include linear polymers made from terephthalic acid or its ester-forming derivatives and ethylene glycol. Polyester resins offer excellent versatility and practicality, making them suitable for use as materials for films, sheets, fibers, and bottles. Furthermore, their excellent mechanical properties, weather resistance, and chemical resistance are expected to expand their use in a variety of applications, including electrical insulation, solar cells, and industrial components such as tire cord.

[0003] Such polyester resins are cross-linked with each other using a cross-linking agent and are also used as cross-linked polyester resins. For example, Patent Document 1 describes an adhesive composition containing a carboxyl-containing polymer compound, which maintains good adhesion to various plastic films, metals, and glass epoxy resins, while also having excellent high moisture and heat resistance, even with lead-free solder under high humidity. The carboxyl-containing polymer compound contains at least a polymer polyol (A), a polymer polyol (B) different from the polymer polyol (A), and tetracarboxylic dianhydride as copolymer components. In the examples of patent document 1, an example of an adhesive composition is disclosed: relative to 100 parts by mass of the solid content of a carboxyl-containing polymer compound (C1), 9 parts of YDCN-700-10 (phenolic varnish type epoxy resin) manufactured by Nippon Steel Chemicals & Materials Co., Ltd. and 0.1 part of TETRAD (registered trademark)-X (N,N,N',N'-tetraglycidyl-m-xylenediamine) manufactured by Mitsubishi Gas Chemical Co., Ltd. are added, and the solid content concentration is adjusted to 35% using methyl ethyl ketone to obtain an adhesive composition.

[0004] Patent Document 2 also describes an adhesive composition containing a carboxyl-containing polymer compound having similar properties to those of Patent Document 1. This adhesive composition comprises a carboxyl-containing polyester resin (A) and an epoxy resin (B), wherein the carboxyl-containing polyester resin (A) comprises a polymer polyol (A1), a polymer polyol (A2) different from the polymer polyol (A1), and tetracarboxylic dianhydride as copolymerization components. Patent Document 2 describes an adhesive composition in an example wherein 9 parts of YDCN-700-10 (a novolac-type epoxy resin) manufactured by Nippon Steel Chemicals & Materials Co., Ltd. and 0.1 parts of TETRAD (registered trademark)-X (N,N,N',N'-tetraglycidyl-m-xylenediamine) manufactured by Mitsubishi Gas Chemical Co., Ltd. are added to 100 parts by mass of the solid content of the carboxyl-containing polyester resin (A-1), and the solid content concentration is adjusted to 35% using methyl ethyl ketone.

[0005] The adhesive compositions described in Patent Documents 1 and 2 are excellent in moisture-heat resistance.

[0006] Patent Document 3 also describes a cross-linked polyester resin that exhibits self-adhesiveness, reshapeability, and damage repair properties. This cross-linked polyester resin is characterized by comprising a polymer backbone containing ester groups at multiple points, a polyester resin containing multi-point covalent crosslinks composed of ester groups and hydroxyl radicals, and an ester exchange catalyst. Because the cross-linked polyester resin described in Patent Document 3 is mixed with an ester exchange catalyst, the hydroxyl radicals, through the action of the nearby ester exchange catalyst, attack the CO bond of one of the multiple ester groups, initiating an ester exchange reaction, thereby achieving properties such as self-adhesiveness. The examples in Patent Document 3 disclose the use of zinc acetate as the ester exchange catalyst.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2018 / 105543

[0010] Patent Document 2: International Publication No. 2018 / 179707

[0011] Patent Document 3: International Publication No. 2020 / 045439 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] Because the zinc acetate used in the examples of Patent Document 3 is metallic, cross-linked polyester resins containing such zinc acetate are difficult to use in electrical applications. Therefore, there is a need for a cross-linked polyester resin that exhibits softening properties at high temperatures, self-adhesive properties, re-formability, and damage repairability, even without the addition of an ester exchange catalyst.

[0014] In response to this situation, the present invention aims to provide a cross-linked polyester resin that exhibits high strength at room temperature through dynamic covalent cross-linking that allows for bond exchange at high temperatures. It also exhibits reprocessability, inter-film adhesion, and self-healing properties above its softening temperature. Furthermore, even without the addition of a transesterification catalyst, the resin exhibits softening behavior due to bond exchange in the transesterification reaction, resulting in self-adhesion, reformability, and damage repair properties. Another object of the present invention is to provide a cross-linked polyester resin that, even when mixed with a transesterification catalyst, allows for lower processing temperatures while maintaining heat resistance.

[0015] Technical means to solve the problem

[0016] The present invention is as follows.

[0017] [1] A cross-linked polyester resin characterized in that it is a resin obtained by cross-linking a polyester resin having carboxyl groups on its side chains with an epoxy cross-linking agent having a plurality of epoxy groups, wherein the epoxy cross-linking agent comprises an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in its molecule, and the epoxyamine compound is present in an amount of 3 to 30 parts by mole relative to 100 parts by mole of the carboxyl groups in the polyester resin having carboxyl groups on its side chains.

[0018] [2] The cross-linked polyester resin according to [1] is characterized in that the molar ratio of the carboxyl group of the polyester resin having a carboxyl group on the side chain to the epoxy group of the epoxyamine compound, i.e., the carboxyl group:the epoxy group=1:0.125 to 1:1.2.

[0019] [3] The cross-linked polyester resin according to [1] or [2], wherein the tertiary amino group and the epoxy group contained in the epoxyamine compound constitute a diglycidylamino group.

[0020] [4] The cross-linked polyester resin according to any one of [1] to [3], wherein the molecular weight of the epoxyamine compound is 800 or less.

[0021] [5] A cross-linked polyester resin composition comprising an ester exchange catalyst and the cross-linked polyester resin according to any one of [1] to [4].

[0022] Effects of the Invention

[0023] In the present invention, a polyester resin having carboxyl groups on its side chains is crosslinked using an epoxy crosslinking agent containing an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups within the molecule. This results in a crosslinked polyester resin that exhibits softening behavior due to bond exchange during a transesterification reaction, even without the addition of a transesterification catalyst, due to the tertiary amino groups within the epoxyamine compound acting like a transesterification catalyst. This allows for self-adhesion, reshaping, and damage repair properties. Furthermore, the crosslinked polyester resin of the present invention may be a crosslinked polyester resin composition incorporating a transesterification catalyst. Even with the addition of a transesterification catalyst, the number of crosslinking points generated by the epoxyamine compound remains unchanged compared to when no transesterification catalyst is added, allowing for lower processing temperatures while maintaining heat resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [ Figure 1 ] Figure 1 The graph shows the results of measuring the change in the linear expansion coefficient of cross-linked polyester resin.

[0025] [ Figure 2 ] Figure 2 The graph shows the results of measuring the storage modulus (DMA) of cross-linked polyester resin. DETAILED DESCRIPTION

[0026] The present inventors conducted intensive research to provide a cross-linked polyester resin that exhibits softening behavior based on bond exchange in an ester exchange reaction without mixing with a metal-containing ester exchange catalyst, and exhibits self-adhesiveness, reformability, and damage repairability. They discovered that using an epoxy cross-linking agent containing an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as a cross-linking agent for cross-linking polyester resins, and mixing the epoxyamine compound in an amount of 3 to 30 mol parts relative to 100 mol parts of carboxyl groups in the polyester resin, can solve the above-mentioned problems, thereby completing the present invention.

[0027] The present invention is described in detail below.

[0028] The cross-linked polyester resin of the present invention is a polyester resin having carboxyl groups on its side chains, cross-linked with an epoxy cross-linking agent having multiple epoxy groups. The epoxy cross-linking agent includes an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in its molecule. The side chain here can be a structure having a carboxyl group on a branched substituent (e.g., an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, etc.) on the main chain of the aromatic polyester resin, or a structure having a carboxyl group directly on the aromatic polyester resin. The side chain is preferably a structure having a carboxyl group directly on the aromatic polyester resin. The polyester resin is cross-linked by reacting the two or more epoxy groups contained in the epoxyamine compound with the carboxyl groups on the side chains of the polyester resin. That is, the cross-linked polyester resin has ester groups and hydroxyl groups formed by the reaction of the carboxyl 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 cross-linking.

[0029] The epoxyamine compound may contain 2 or more epoxy groups, 3 or more epoxy groups, or 4 or more epoxy groups. The upper limit of the number of epoxy groups is not particularly limited, but is preferably 6 or less, more preferably 5 or less, for example.

[0030] Furthermore, epoxy amine compounds contain tertiary amino groups within their molecules. Tertiary amino groups function similarly to transesterification catalysts. By heating a cross-linked polyester resin, the hydroxyl groups within the cross-linked polyester resin, even without the addition of a transesterification catalyst, can attack the CO bonds of ester groups near the hydroxyl groups due to the action of the tertiary amino groups, causing bond exchange via a transesterification reaction and exhibiting softening behavior. However, if the epoxy amine compound contains only one tertiary amino group within the molecule, the transesterification reaction cannot proceed sufficiently, resulting in a lack of self-adhesion, reshapeability, and damage repair properties. Furthermore, even if a transesterification catalyst is added to actively promote the transesterification reaction, the number of crosslinking points generated by the epoxy amine compound according to the present invention remains unchanged compared to when no transesterification catalyst is added. This allows the cross-linked polyester resin to maintain its inherent heat resistance while lowering its softening temperature, thereby reducing processing temperature.

[0031] In the present invention, the epoxyamine compound contains two or more tertiary amino groups in the molecule. By containing two or more tertiary amino groups, softening behavior can be exhibited.

[0032] The epoxyamine compound is present in an amount of 3 to 30 mol parts per 100 mol parts of carboxyl groups in the polyester resin having carboxyl groups on its side chains. If the epoxyamine compound is reduced to less than 3 mol parts, the ratio of epoxy groups to carboxyl groups decreases, resulting in an excessively low crosslinking density and inability to cure. Therefore, the epoxyamine compound is present in an amount of 3 mol parts or more, preferably 5 mol parts or more, and more preferably 10 mol parts or more. However, if the epoxyamine compound exceeds 30 mol parts, the ratio of epoxy groups to carboxyl groups increases, and the excess epoxy groups self-polymerize, resulting in an excessively high crosslinking density. This is believed to reduce the mobility of the crosslinked polymer and increase the softening temperature. Therefore, the epoxyamine compound is present in an amount of 30 mol parts or less, preferably 28 mol parts or less, and more preferably 26 mol parts or less.

[0033] The number of carboxyl groups in each polyester resin polymer chain (hereinafter referred to as N COOH ) can be calculated as follows. For example, when the acid value of a polyester resin is A (mgKOH / g), since the molecular weight of KOH is 56.1 g / mol, the number of carboxyl groups per 1g of polyester resin with carboxyl groups on the side chains can be expressed as A / 56.1 (mmol / g). When the number average molecular weight of a polyester resin with carboxyl groups on the side chains is B (g / mol), the number of carboxyl groups in the polymer chain can be expressed as A / 56.1×B / 1000 (units), which is the number of carboxyl groups per polymer chain, N. COOH .

[0034] The tertiary amino group and epoxy group contained in the epoxyamine compound preferably constitute a diglycidylamino group as shown in the following formula: wherein * represents an atomic bond.

[0035] [Chemical Formula 1]

[0036]

[0037] The number of diglycidylamino groups contained in the epoxyamine compound molecule may be 1, but is preferably 2 or more. The presence of 2 or more diglycidylamino groups facilitates the softening behavior of bond exchange by the transesterification reaction. The number of diglycidylamino groups is preferably 3 or less, for example.

[0038] The diglycidylamino group may be bonded to an aliphatic hydrocarbon group having about 1 to 10 carbon atoms (hereinafter referred to as linker 1), an aromatic hydrocarbon ring having about 6 to 20 carbon atoms (hereinafter referred to as linker 2), or a group consisting of two or more aromatic hydrocarbon rings having about 6 to 20 carbon atoms bonded to an aliphatic hydrocarbon group having about 1 to 10 carbon atoms (hereinafter referred to as linker 3). The diglycidylamino group is preferably bonded to linker 2 or linker 3, and is particularly preferably bonded to an aromatic hydrocarbon ring (preferably a benzene ring).

[0039] Examples of epoxy amine compounds include N,N,N',N'-tetraglycidyl-m-xylenediamine and 4,4'-methylenebis(N,N-diglycidylaniline). N,N,N',N'-tetraglycidyl-m-xylenediamine is sold as the polyfunctional epoxy compound "TETRAD-X" by Mitsubishi Gas Chemical Co., Ltd. 4,4'-methylenebis(N,N-diglycidylaniline) is available from Tokyo Chemical Industry Co., Ltd. (TCI). One epoxy amine compound may be used alone, or two or more may be used.

[0040] The molecular weight of the epoxyamine compound is preferably 800 or less. A molecular weight of 800 or less allows the epoxyamine compound to enter between polyester chains, easily forming 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 greater.

[0041] In addition to the epoxyamine compound (hereinafter referred to as the first epoxyamine compound) described above, polyfunctional epoxy compounds other than the first epoxyamine compound (hereinafter referred to as other polyfunctional epoxy compounds) may also be used as epoxy crosslinking agents. Specifically, these other polyfunctional epoxy compounds are crosslinking agents that undergo a curing reaction with the carboxyl groups present in the side chains of the polyester resin to form crosslinks. Examples of these crosslinking agents include compounds containing two or more epoxy groups but no tertiary amino group in their molecules (hereinafter referred to as non-amine epoxy compounds) and compounds containing two or more epoxy groups and one tertiary amino group in their molecules (hereinafter referred to as second epoxyamine compounds). Using these other polyfunctional epoxy compounds together with the first epoxyamine compound facilitates the formation of three-dimensional crosslinks, thereby improving heat resistance.

[0042] 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 and phenol novolac epoxy resins can reduce crosslinking density and alleviate stress during peeling. Commercially available cresol novolac epoxy resins include, for example, YDCN-700 manufactured by Nippon Steel Chemicals & Materials Co., Ltd. Commercially available phenol novolac epoxy resins include, for example, EPICLON N-700A manufactured by DIC Corporation.

[0043] Epoxy resins having a dicyclopentadiene skeleton are rigid and have extremely low hygroscopicity, which can reduce crosslinking density and alleviate stress during peeling. Commercially available epoxy resins having a dicyclopentadiene skeleton include, for example, HP7200 series manufactured by DIC Corporation.

[0044] Examples of the second epoxyamine compound include triglycidyl-p-aminophenol (also known as N,N-diglycidyl-4-(glycidyloxy)aniline), etc. Commercially available triglycidyl-p-aminophenol includes, for example, jER630 manufactured by Mitsubishi Chemical Corporation.

[0045] These other polyfunctional epoxy compounds can be used alone or in combination of two or more.

[0046] The first epoxyamine compound is preferably present in an amount of 30 or more mol parts per 100 mol parts of the total epoxy crosslinking agent. The first epoxyamine compound is more preferably present in an amount of 50 or more mol parts, and even more preferably present in an amount of 80 or more mol parts. 100 mol parts is particularly preferred. As the epoxy crosslinking agent, only epoxyamine compounds having two or more epoxy groups and two or more tertiary amino groups in the molecule may be used.

[0047] (Polyester resin)

[0048] The polyester resin has a carboxyl group in the side chain, and the carboxyl group reacts with the epoxy group contained in the epoxy crosslinking agent to crosslink the polyester resin.

[0049] The polyester resin having a carboxyl group on its side chain may be either an aliphatic polyester or an aromatic polyester. From the perspective of improving self-adhesion, aliphatic polyesters are more preferred; from the perspective of improving heat resistance, aromatic polyesters are more preferred. A combination of aliphatic and aromatic polyesters may also be used. Furthermore, when a cross-linked polyester resin is used as an adhesive sheet or film for bonding a film substrate to a metal substrate, an aromatic polyester is more preferred over an aliphatic polyester as the polyester resin having a carboxyl group on its side chain.

[0050] The polyester resin having a carboxyl group on the side chain can be prepared by, for example, a method of polycondensing a polycarboxylic acid, a polyol and a dicarboxylic acid containing a nucleophilic reactive group (such as a thiol group), and then reacting the nucleophilic reactive group with an unsaturated carboxylic acid; a method of polycondensing a polycarboxylic acid, a polyol and an unsaturated polycarboxylic acid or an anhydride thereof, and then reacting the unsaturated group with a carboxylic acid having a nucleophilic reactive group.

[0051] The polycarboxylic acid may be mainly composed of a dicarboxylic acid (for example, 60 or more mol parts, preferably 80 or more mol parts, of the dicarboxylic acid relative to 100 mol parts of the polycarboxylic acid). Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phthalic 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 the polycarboxylic acid 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 provided as acid anhydrides in the polycondensation reaction.

[0052] Examples of the polyol include neopentyl glycol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 2,2-dimethyl-1,3-propylene glycol, 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-dimethyl-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. Aliphatic diols such as ethanol; polyether diols such as diethylene glycol, triethylene glycol, polyethylene glycol, polyalkylene glycol, and polytetramethylene glycol; alicyclic polyols such as 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanediols, and hydrogenated bisphenols; and diol-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 phthalic acid, and propylene glycol-modified phthalic acid. One or more of these can be used.

[0053] Examples of the dicarboxylic acid 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 having a thiol group, such as thiomalic acid.

[0054] Examples of the unsaturated carboxylic acid that reacts with the 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.

[0055] Examples of the unsaturated polycarboxylic acid include aliphatic α,β-unsaturated dicarboxylic acids having approximately 4 to 10 carbon atoms, such as maleic acid and fumaric acid.

[0056] Examples of the carboxylic acid having a nucleophilic reactive group that reacts with the unsaturated group of the unsaturated polycarboxylic acid include aliphatic monocarboxylic acids having about 2 to 10 carbon atoms and having a thiol group, such as mercaptoacetic acid and mercaptopropionic acid.

[0057] The molar ratio of the carboxyl groups of the polyester resin having carboxyl groups on its side chains to the epoxy groups of the first epoxyamine compound is preferably 1:0.125 to 1:1.2. The more preferred lower limit of the molar ratio is 1:0.3, and the more preferred upper limit is 1:1.1. The most preferred molar ratio is 1:1.

[0058] The number average molecular weight (Mn) of the polyester resin having carboxyl groups on its side chains is preferably 6,000 to 20,000, for example. A number average molecular weight of 6,000 or greater can improve heat resistance. The number average molecular weight is more preferably 6,500 or greater, and even more preferably 7,000 or greater. However, if the number average molecular weight of the polyester resin having carboxyl groups on its side chains is too high, 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.

[0059] The molecular weight dispersion index (PDI) of the polyester resin having a carboxyl group on the side chain is preferably 1.3 to 1.8. The molecular weight dispersion index can be calculated according to the following formula based on the weight average molecular weight (Mw) and the number average molecular weight (Mn).

[0060] PDI value = Mw / Mn

[0061] The PDI value is more preferably 1.4 or higher. However, if the PDI value is too high, the chain length will vary greatly, which will easily lead to strength variations. Therefore, the PDI value is preferably 1.8 or lower, and more preferably 1.7 or lower.

[0062] The number of carboxyl groups per polyester resin polymer chain (N COOH ) preferably 3 to 50. N COOH If the ratio is 3 or more, the carboxyl groups on the side chains of the polyester resin are cross-linked via epoxy cross-linking agents, thereby improving heat resistance. COOH It is more preferably 3.5 or more, and even more preferably 4 or more. COOH If it becomes too large, the polyester resin will become too hard and brittle due to excessive cross-linking. COOHIt is preferably 50 or less, more preferably 48 or less, and further preferably 45 or less.

[0063] The acid value of polyester resins having carboxyl groups on their side chains is preferably 5 mgKOH / g or higher. By setting the acid value to 5 mgKOH / g or higher, heat resistance can be improved. The acid value is more preferably 10 mgKOH / g or higher, and even more preferably 15 mgKOH / g or higher. However, if the acid value is too high, the crosslinking density becomes too high, resulting in excessive hardness, which may reduce adhesion. Therefore, the acid value is preferably 250 mgKOH / g or lower, more preferably 230 mgKOH / g or lower, and even more preferably 200 mgKOH / g or lower.

[0064] (Transesterification Catalyst)

[0065] The cross-linked polyester resin of the present invention may not contain a transesterification catalyst, but may contain a transesterification catalyst within a range that does not impair the effects of the present invention. By adding a transesterification catalyst, the transesterification reaction can be accelerated, thereby lowering the softening temperature and, consequently, the processing temperature, while maintaining the heat resistance of the cross-linked polyester resin.

[0066] As the transesterification catalyst, for example, zinc acetate, triphenylphosphine, trimethylamine, triethylamine, etc. can be used, and zinc acetate is preferably used among these. The transesterification catalyst may be used alone or in combination of two or more.

[0067] When a transesterification catalyst is mixed, the amount 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, per 100 parts by mole of the carboxyl groups of the polyester resin. The lower limit for the use of a mixed transesterification catalyst 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, per 100 parts by mole of the carboxyl groups of the polyester resin. When multiple transesterification catalysts are used, the total amount is shown.

[0068] (cross-linked polyester resin)

[0069] The softening temperature of the transesterification catalyst of the present invention for bond exchange by the transesterification reaction is preferably, for example, 155 to 300°C. For a cross-linked 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. For a cross-linked polyester resin without 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.

[0070] The change in linear expansion coefficient when heated from room temperature to 300°C under applied tension is measured. The softening temperature of the cross-linked polyester resin (cross-linked polyester resin composition) is the temperature at the inflection point of the linear expansion coefficient change curve. Specific implementation methods are described in detail in the Examples.

[0071] The glass transition temperature (Tg) of the cross-linked polyester resin (cross-linked polyester resin composition) of the present invention is preferably -50 to 150°C. A Tg of -50°C or higher ensures heat resistance. The Tg is more preferably -40°C or higher, and even more preferably -30°C or higher. However, if the Tg is too high, processing becomes difficult, so the Tg is preferably 150°C or lower. The Tg is more preferably 130°C or higher, and even more preferably 100°C or higher.

[0072] Next, the method for producing the cross-linked polyester resin according to the present invention will be described.

[0073] The cross-linked polyester resin of the present invention can be produced by known methods. For example, a method can be employed in which a polyester resin having carboxyl groups on its side chains and an epoxy cross-linking agent containing a first epoxyamine compound are dissolved in a solvent, the solvent is removed, and the mixture is heated under reduced pressure to effect cross-linking. The molar ratio of the carboxyl groups of the polyester resin having carboxyl groups on its side chains to the epoxy groups of the first epoxyamine compound is preferably 1:0.125 to 1:1.2. The more preferred lower limit of the molar ratio is 1:0.3, the more preferred upper limit is 1:1.1, and the most preferred molar ratio is 1:1.

[0074] The cross-linked polyester resin of the present invention has self-adhesive properties. The cross-linked polyester resins of the present invention can be stacked and laminated, and transesterification occurs at the interface of the cross-linked polyester resins by heating and pressing, so that the cross-linked polyester resins can be bonded to each other without using an adhesive.

[0075] The cross-linked polyester resin of the present invention has reshapeability. After being deformed into a predetermined shape, it can be heated in the deformed state to cause transesterification and reshape, and the predetermined shape can be maintained even after cooling.

[0076] The cross-linked polyester resin of the present invention has damage-repairing properties. Even if the surface is scratched by a knife, it can be heated to induce bond exchange through a transesterification reaction, thereby self-repairing. Therefore, the cross-linked polyester resin of the present invention can be used as the main component of a self-repairing material. For example, the self-repairing material can be used as a coating material.

[0077] The cross-linked polyester resin of the present invention can be used as a main component of a molding material. Specifically, the cross-linked polyester resin has excellent molding processability and extrusion moldability, making it useful as a molding material, for example, as a 3D printing material or a linear molding material.

[0078] Furthermore, cross-linked polyester resins can also be used as a material for a network structure. A network structure is a structure formed by connecting a portion of linear shaped bodies. The network structure can be produced by melting the cross-linked polyester resin, discharging the melt from a nozzle, and then allowing the melt to fuse and solidify.

[0079] The content of the cross-linked 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, further preferably 90% by mass or more, and may be 100% by mass.

[0080] The cross-linked polyester resin of the present invention is difficult to dissolve even when immersed in a solvent (particularly an organic solvent) and has excellent solvent resistance. Therefore, the cross-linked polyester resin can be suitably used as a laminate material, for example.

[0081] The cross-linked polyester resin of the present invention exhibits excellent room temperature storage stability. Specifically, even after storage at a predetermined temperature for a certain period of time, the gel fraction remains substantially unchanged. Furthermore, even after storage at a predetermined temperature for a certain period of time, the resin exhibits softening behavior comparable to that before storage.

[0082] Even in the cross-linked polyester resin of the present invention, when an aromatic polyester resin is used as the polyester resin having carboxyl groups on its side chains, the cross-linked polyester resin can be used, for example, as adhesive sheets, adhesive films, and molding materials. When used as an adhesive sheet or film, the cross-linked polyester resin of the present invention can be sandwiched between the desired adherends and heated. Heating causes bond exchange due to an ester exchange reaction, allowing the adherends to be bonded.

[0083] Examples of adherends include resin films and metal foils. Cross-linked polyester resins can be used as adhesives between resin films, between metal foils, or between resin films and metal foils. Examples of resin films include polyimide films, polyester films, and PET films. Examples of metal foils include copper foil, silver foil, and gold foil. The adhesiveness of the cross-linked aromatic polyester resin can be evaluated based on the 90° peel strength shown in the Examples.

[0084] Even when an aromatic polyester resin is used as the polyester resin having carboxyl groups on its side chains in the cross-linked polyester resin of the present invention, heating the cross-linked polyester resin to a temperature above the ester exchange activation temperature allows for bond exchange. However, when the cross-linked polyester resin is used as an adhesive material, heating the adhesive to a temperature above the ester exchange activation temperature makes it difficult to peel. Therefore, the cross-linked polyester resin can be used as a stick-and-peel adhesive material for patch applications. The peelability of the cross-linked polyester resin when heated to a high temperature can be evaluated based on the 90° peel strength measured during heating as described in the Examples.

[0085] In addition, although the application of the cross-linked polyester resin is described above, a cross-linked polyester resin composition containing a cross-linked polyester resin and an ester exchange catalyst can also be used in the same application.

[0086] 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.

[0087] Example

[0088] The following examples are given to better illustrate the present invention, but the present invention is not limited to the following examples. Of course, modifications can be made within the scope of the above and the following principles, and any of them are included in the technical scope of the present invention. Hereinafter, "parts" are expressed as "parts by mass."

[0089] A polyester resin having carboxyl groups on its side chains is cross-linked with an epoxy cross-linking agent having multiple epoxy groups to produce a cross-linked polyester resin. The polyester resin used is an aliphatic polyester resin or an aromatic polyester resin.

[0090] Production Example 1 (Aliphatic Polyester Resin A1)

[0091] A stirrer was prepared, and 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 trifluoromethanesulfonate were added to a 50 ml glass conical flask and stirred at 80°C until homogenized. After dissolution, the pressure in the conical flask was reduced to 5 mmHg over 30 minutes, and a polycondensation reaction was carried out at 80°C for 20 hours under a vacuum of 0.3 mmHg 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 10 ml of N,N-dimethylformamide (DMF) in a 20 ml eggplant-shaped flask. Then, 15 mol parts of acrylic acid and 2.1 mol parts of triethylamine as a catalyst were added, and the mixture was stirred at room temperature for 15 hours to allow Michael addition to occur between the thiol group of the thiomalic acid unit and the double bond of the acrylic acid. The resulting product was reprecipitated with methanol to prepare a polyester resin having carboxyl groups on its side chains. The resulting polyester resin is hereinafter referred to as aliphatic polyester resin A1.

[0092] Production Example 2 (Aromatic Polyester Resin B1)

[0093] Prepare a stirrer and add 25 mol parts of maleic acid, 25 mol parts of adipic acid, 50 mol parts of bis(2-hydroxyethyl)terephthalate (BHET), and 0.5 mol parts of scandium trifluoromethanesulfonate to a 50 ml glass conical flask. Stir at 100°C until homogenized. After dissolution, the pressure in the glass conical flask is reduced to 5 mmHg over 30 minutes, and a polycondensation reaction is carried out at 110°C for 4 hours under a vacuum of 0.3 mmHg or less. After the reaction, the contents are removed and cooled to obtain a polyester resin raw material. Next, in a 20 ml eggplant-shaped flask, 50 mol parts of the polyester resin raw material are dissolved in 10 ml of N,N-dimethylformamide (DMF). Then, 25 mol parts of thioglycolic acid and 1.6 mol parts of triethylamine as a catalyst are added. Stir at room temperature for 15 hours to allow the thioglycolic acid to undergo Michael addition to the maleic acid units of the polyester resin raw material via thiol groups. The resulting product was reprecipitated with acetone to prepare a polyester resin having an aromatic structure and carboxyl groups on its side chains. The resulting polyester resin is hereinafter referred to as aromatic polyester resin B1.

[0094] Production Example 3 (Aromatic Polyester Resin B2)

[0095] 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 ratio of maleic acid to bis(2-hydroxyethyl)terephthalate (BHET) was changed to that shown in Table 1. Next, thioglycolic acid was added to the polyester resin raw material in the same manner as in Production Example 2 to prepare a polyester resin having a carboxyl group on its side chain and an aromatic structure. The resulting polyester resin is hereinafter referred to as Aromatic Polyester Resin B2.

[0096] Production Example 4 (Aromatic Polyester Resin C1)

[0097] (1) Polymer polyol c1

[0098] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 135 parts by mole of terephthalic acid, 311 parts by mole of isophthalic acid, 5 parts by mole of trimellitic anhydride, 74 parts by mole of 2-methyl-1,3-propanediol, 417 parts by mole of 1,4-cyclohexanediol, and 0.2 parts by mole of tetrabutyl titanate were added. The temperature was gradually raised to 250°C, and an esterification reaction was carried out while distilled water was removed from the system. After the esterification reaction was completed, the pressure was gradually reduced to 10 mmHg for initial polymerization while the temperature was raised to 250°C. Later polymerization was further carried out at a pressure below 1 mmHg until the specified torque was reached. The reaction vessel was then returned to atmospheric pressure by introducing nitrogen, and 5 parts by mole of trimellitic anhydride was added. The reaction was continued at 220°C for 30 minutes to produce polymer polyol C1.

[0099] (2) Polymer polyol C2

[0100] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 390 parts by mole of terephthalic acid, 390 parts by mole of isophthalic acid, 440 parts by mole of ethylene glycol, 362 parts by mole of 2,2-dimethyl-1,3-propanediol, and 0.2 parts by mole of tetrabutyl titanate were added. The temperature was gradually raised to 250°C, and an esterification reaction was carried out while distilled water was removed from the system. After the esterification reaction was completed, the pressure was gradually reduced to 10 mmHg for initial polymerization while the temperature was raised to 250°C. Further, post-polymerization was carried out at a pressure below 1 mmHg until the specified torque was reached, yielding Polyol C2.

[0101] (3) Aromatic polyester resin C1

[0102] In a reaction vessel equipped with a stirrer, thermometer, and reflux line, 160 parts by mole of polymer polyol C1, 40 parts by mole of polymer polyol C2, 5.2 parts by mole of pyromellitic anhydride, and 200 parts by mole of toluene were added and dissolved by slowly raising the temperature to 80°C. After dissolution, 0.1 parts by mole of triethylamine was added as a reaction catalyst, and the temperature was slowly raised to 105°C and reacted for 24 hours. After confirming the completion of the reaction by infrared spectrophotometry (IR), 108 parts by mole of toluene was added for dilution, yielding a solution having a solids content of 40% of a polyester resin having carboxyl groups on its side chains. The polyester resin having carboxyl groups on its side chains is hereinafter referred to as aromatic polyester resin C1.

[0103] The compositions (molar ratios) of the aliphatic polyester resin A1 and the aromatic polyester resins B1 and B2 obtained in Production Examples 1 to 4 are shown in Table 1 below.

[0104] [Table 1]

[0105]

[0106] The number average molecular weight (Mn), molecular weight dispersion (PDI), number of carboxyl groups per polyester polymer chain (N) and the number of carboxyl groups per polyester polymer chain (N) were calculated for the obtained aliphatic polyester resin A1, aromatic polyester resin B1, B2 and C1. COOH ), and acid value, the results are shown in Table 1. The methods for obtaining these various properties are as follows.

[0107] (Number average molecular weight (Mn) and molecular weight dispersion (PDI))

[0108] An aliphatic polyester resin or aromatic polyester resin is dissolved in tetrahydrofuran to a concentration of approximately 0.5% by mass and filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm. However, if the resin is insoluble in tetrahydrofuran, N,N-dimethylformamide is used instead of tetrahydrofuran. The number average molecular weight (Mn) and weight average molecular weight (Mw) are measured by gel permeation chromatography using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate is 1 ml / min, and the column temperature is 30°C. Chromatographic columns used are KF-802, KF-804L, and KF-806L manufactured by Showa Denko. Monodisperse polystyrene is used as a standard substance (molecular weight standard). Low molecular weight compounds (such as oligomers) with a number average molecular weight of less than 1000 are not counted and are omitted. Based on the measured number average molecular weight (Mn) and weight average molecular weight (Mw), the molecular weight dispersion (PDI) is calculated from the following formula.

[0109] PDI value = Mw / Mn

[0110] (Acid value)

[0111] 0.2 g of an aliphatic polyester resin or aromatic polyester resin is dissolved in 20 ml of chloroform. Phenolphthalein is added to the solution as an indicator, and neutralization titration is performed using a 0.1 N potassium hydroxide ethanol solution. From this titration, the amount of potassium hydroxide consumed in neutralization (mgKOH) is converted to the amount per 1 g of the aliphatic polyester resin or aromatic polyester resin to calculate the acid value (mgKOH / g).

[0112] (The number of carboxyl groups per polyester polymer chain (N COOH ))

[0113] The number of carboxyl groups per polyester polymer chain (N COOH ) is calculated as follows. For example, if the acid value of a polyester resin with carboxyl groups on its side chains is A (mgKOH / g), the number of carboxyl groups per 1g of the polyester resin with carboxyl groups on its side chains can be expressed as A / 56.1 (mmol / g) because the molecular weight of KOH is 56.1 g / mol. If the number average molecular weight of the polyester resin with carboxyl groups on its side chains is B (g / mol), the number of carboxyl groups in the polymer chain can be expressed as A / 56.1×B / 1000 (units), which is the number of carboxyl groups per polymer chain, N. COOH .

[0114] In the following examples, the following epoxy crosslinking agents were used.

[0115] (1) Multifunctional epoxy compound "TETRAD-X" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd. (N,N,N',N'-tetraglycidyl-m-xylenediamine)

[0116] (2) 4,4'-methylenebis(N,N-diglycidylaniline)

[0117] (3) 1,4-Butanediol diglycidyl ether

[0118] (4) "jER630" (trade name) manufactured by Mitsubishi Chemical Corporation (triglycidyl p-aminophenol)

[0119] The multifunctional epoxy compounds "TETRAD-X" (trade name) and 4,4'-methylenebis(N,N-diglycidylaniline) manufactured by Mitsubishi Gas Chemical are both epoxyamine compounds with two tertiary amino groups and four epoxy groups in their molecules, and both have two diglycidylamino groups. "jER630" (trade name) manufactured by Mitsubishi Chemical is an epoxyamine compound with one tertiary amino group and three epoxy groups in its molecule, and one diglycidylamino group. 1,4-Butanediol diglycidyl ether is a multifunctional epoxy compound with two epoxy groups in its molecule but no tertiary amino group.

[0120] (Example 1)

[0121] Aliphatic polyester resin A1, serving as the polyester resin, and 4,4'-methylenebis(N,N-diglycidylaniline), serving as an epoxy crosslinker, were mixed at a molar ratio of 1:1 between the carboxyl groups of the polyester resin and the epoxy groups of the epoxyamine compound. Specifically, for every 100 moles of carboxyl groups in the aliphatic polyester resin A1, the epoxy groups of the 4,4'-methylenebis(N,N-diglycidylaniline) accounted for 25 moles. 10 parts by mass of the aliphatic polyester resin A1 and 1.3 parts by mass of 4,4'-methylenebis(N,N-diglycidylaniline) were dissolved in 10 parts by mass of tetrahydrofuran (THF). This solution was placed in a Teflon (registered trademark)-coated mold and heated to 40°C to volatilize the THF. The sample, after THF removal, was heated at 120°C under vacuum for 4 hours to produce a crosslinked polyester resin film (0.7 mm thick).

[0122] (Examples 2 to 8)

[0123] As shown in Table 2-1, a cross-linked polyester resin film (thickness 0.7 mm) was manufactured under the same manufacturing conditions as in Example 1, except that an aliphatic polyester resin A1, an aromatic polyester resin B1, B2 or C1 was used as the polyester resin; and a multifunctional epoxy compound "TETRAD-X" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd., or 4,4'-methylenebis(N,N-diglycidylaniline) was used as the epoxy cross-linking agent.

[0124] (Example 9)

[0125] Aromatic polyester resin C1 (polyester resin) and Mitsubishi Gas Chemical's multifunctional epoxy compound "TETRAD-X" (trade name) as an epoxy crosslinking agent were mixed at a molar ratio of 1:1 between the carboxyl groups in the polyester resin's side chains and the epoxy groups in the epoxyamine compound. Furthermore, a transesterification catalyst was added. Specifically, for every 100 molar parts of carboxyl groups in aromatic polyester resin C1, 25 molar parts of epoxy groups in "TETRAD-X" (trade name) were added, and 5 molar parts of zinc acetate as the transesterification catalyst were added. 10 parts by mass of these aromatic polyester resins 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). The two solutions were mixed and dissolved in a Teflon (registered trademark)-coated mold and then heated to 40°C to evaporate the solvent. The sample from which the solvent had been removed was heated at 120° C. under vacuum for 4 hours to obtain a cross-linked polyester resin film (thickness 0.7 mm).

[0126] (Examples 10 and 11)

[0127] As shown in Table 2-2, a cross-linked 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.

[0128] (Comparative Examples 1 and 3)

[0129] A cross-linked polyester resin film (thickness 0.7 mm) was manufactured under the same manufacturing conditions as in Example 7, except that 50 mol parts (0.30 mass parts) of 1,4-butanediol diglycidyl ether or 33 mol parts (0.27 mass parts) of "jER630" (trade name) was used instead of 25 mol parts of "TETRAD-X" (trade name) as an epoxy crosslinking agent.

[0130] (Comparative Examples 2 and 4)

[0131] A cross-linked polyester resin film (thickness 0.7 mm) was manufactured under the same manufacturing conditions as in Example 11, except that 50 mol parts (0.30 mass parts) of 1,4-butanediol diglycidyl ether or 33 mol parts (0.27 mass parts) of "jER630" (trade name) was used instead of 25 mol parts of "TETRAD-X" (trade name) as an epoxy cross-linking agent.

[0132] The compositions (in parts by mole) of the cross-linked polyester resin films obtained in Examples 1 to 11 and Comparative Examples 1 to 4 are shown in Table 2-1 and Table 2-2 below.

[0133]

[0134] The properties of the cross-linked polyester resin film shown in Table 3-1 and Table 3-2 below are the results of the following evaluations.

[0135] (Softening temperature)

[0136] The change in the linear expansion coefficient of a cross-linked polyester resin film was measured using the "TMA7100" manufactured by HITACHI. The initial distance between the clamps was 15 mm. To prevent the deflection of the test piece (a rectangle with a width of 4 mm × a length of 20 mm × a thickness of 0.7 mm) cut from the cross-linked polyester resin film, the test piece was heated from room temperature to 300°C at a heating rate of 10°C / min in a nitrogen atmosphere under a slight external tension (20 mN). The results of Example 11, Comparative Example 2, and Comparative Example 4 are as follows. Figure 1 As shown. The vertical axis represents the displacement of the linear expansion coefficient. Figure 1 In FIG, the solid line represents the result of Example 11, the dotted line represents the result of Comparative Example 2, and the dashed line represents the result of Comparative Example 4. The temperature at the inflection point of the linear expansion coefficient change curve is the softening temperature.

[0137] (Storage modulus (DMA))

[0138] The storage modulus (DMA) of the cross-linked polyester resin film was measured. The resin was placed in a dynamic viscoelasticity measuring device "DVA-200" manufactured by IT Measurement Control Co., Ltd., and the measurement frequency was set to 10 Hz. The resin was heated from room temperature to 200-300°C at a heating rate of 4°C / min to measure the storage modulus (DMA). In the measurement results, the results of Example 11, Comparative Example 2, and Comparative Example 4 are as follows: Figure 2 As shown. The vertical axis represents the storage modulus. Figure 2 In the graph, the solid line represents the result of Example 11, the dotted line represents the result of Comparative Example 2, and the dashed line represents the result of Comparative Example 4. The upper limit of the heating temperature is 290°C for Example 11, 200°C for Comparative Example 2, and 300°C for Comparative Example 4.

[0139] Depend on Figure 2 It is clear that no drastic change in storage modulus is observed in any of the resins before and after 200°C, so it is considered that the cross-linked structure is maintained at 200°C.

[0140] (Self-adhesive)

[0141] Two cross-linked polyester resin films (0.7 mm thick) were stacked at the same end. The films were heated to a temperature above their softening temperature, and then pressure was applied at 400 kPa in the stacking direction. This pressure was maintained for 2 hours to produce a laminated cross-linked polyester resin film. If the overlapping laminated portion adhered, the film was evaluated as having self-adhesion (○); if not, the film was evaluated as not having self-adhesion (×).

[0142] (Reformability)

[0143] A cross-linked polyester resin film (0.7 mm thick) was spirally wound around a spatula. Both ends of the film were secured to the spatula with tape and left at a 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 retained its curled shape even after removal from the spatula, it was evaluated as having re-formability (○). If it did not retain its curled shape and returned to a flat surface, it was evaluated as having no re-formability (×).

[0144] (Damage repair)

[0145] A cutter was used to inscribe a wound approximately 1 cm long and 0.1 mm deep on the surface of a cross-linked polyester film (0.7 mm thick). The film was then left at a high temperature (softening temperature + approximately 20°C) for 10 hours and then cooled to room temperature. If the wound on the cross-linked polyester film disappeared, the film was evaluated as having damage repairability (○); if the wound on the cross-linked polyester film did not disappear, the film was evaluated as having no damage repairability (×).

[0146] (Glass transition temperature Tg)

[0147] The cross-linked polyester resin films obtained in Examples and Comparative Examples were thermally analyzed using a DSC apparatus (Model: DSC7020) manufactured by Hitachi High-Tech Science Co., Ltd., by heating from -100°C to 300°C at a heating rate of 20°C / min in a nitrogen atmosphere to measure (Tg).

[0148] (90° peel strength)

[0149] A 20 mm long x 50 mm wide test piece was cut from the resulting cross-linked 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.). This PET film of the same type was then placed on top of the test piece to form a three-layer structure of "PET film / cross-linked polyester resin film / PET film." The layers were then bonded together in a hot press using pressure and heating at 170°C and 2 MPa for 280 seconds. The resulting laminate was used as a sample for 90° peel strength evaluation.

[0150] In addition, a polyimide film (PI, "apical" (registered trademark) manufactured by Kaneka Co., Ltd., thickness 12.5 μm) was used instead of the above-mentioned PET film. In addition, a 90° peel strength evaluation sample was prepared under the same conditions except that it had a three-layer structure of "PI / cross-linked polyester resin film / PI".

[0151] In addition, rolled copper foil (thickness 20 μm) and polyimide film (PI, "apical" (registered trademark) manufactured by Kaneka Co., Ltd., thickness 12.5 μm) were used instead of the above-mentioned PET film. In addition, the 90° peel strength evaluation sample was prepared under the same conditions except that it had a three-layer structure of "Cu / cross-linked polyester resin film / PI".

[0152] 90° peel strength was measured using an Autograph AG-Xplus manufactured by Shimadzu Corporation at 25°C and a tensile speed of 50 mm / min. Based on the measured 90° peel strength, the film's adhesiveness was evaluated according to the following criteria. The evaluation results are shown in Tables 3-1 and 3-2. Note that "-" indicates not tested.

[0153] <Evaluation Criteria>

[0154] ◎: 1.0N / mm or more

[0155] ○: 0.5N / mm or more, less than 1.0N / mm

[0156] △: 0.35N / mm or more, less than 0.5N / mm

[0157] ×: less than 0.35N / mm

[0158] (Formability)

[0159] The resulting cross-linked polyester resin film (0.7 mm thick) was cut into a 5 mm wide x 5 mm long sample and inserted into a mold made by cutting an 8 mm diameter circle from a 1 mm thick Teflon (registered trademark) sheet. The sample was then pressurized and heated using a hot press. The pressurization conditions were 4 MPa and the heating conditions were softening temperature + 30°C for 15 minutes.

[0160] The cross-linked polyester resin film sheet was evaluated as having good formability if it could be formed into the mold shape, and as having poor formability if it could not be formed. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" indicates that the evaluation was not conducted.

[0161] (Extrusion Formability)

[0162] 6 g of the obtained cross-linked polyester resin film (thickness 0.7 mm) was cut into samples of 5 mm width × 5 mm length, and was fed into a twin-screw extruder "MiniLab" manufactured by HAAKE at a cylinder temperature of 150° C. in three portions and extruded at a screw speed of 50 min. -1After sample addition, the kneaded product was kneaded for 5 minutes, and then extruded from the barrel. After kneading, a score of ◯ was given if the kneaded product could be discharged to form a linear molded article; a score of × was given if the kneaded product could not be discharged or a linear molded article could not be formed. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that in Examples 6 and 8, the extrusion moldability was evaluated at a cylinder temperature of 200°C. "-" indicates not tested.

[0163] (Storage stability at room temperature)

[0164] The room temperature storage stability of the obtained cross-linked polyester resin film was evaluated based on the change rate of the gel fraction and the softening behavior.

[0165] (1) Change rate of gel fraction

[0166] First, the gel fraction of the obtained cross-linked polyester resin film was measured. The gel fraction was measured by the following method.

[0167] 0.125 g of the obtained cross-linked 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 dried at 80°C for 1 hour in a vacuum dryer and the mass was measured. The gel fraction was determined by the following formula.

[0168] Gel fraction (%) = (weight of residual gel component after drying ÷ 0.125) × 100

[0169] Next, the cross-linked polyester resin film was stored at a constant temperature of 5°C, 25°C, or 40°C for 6 months. After 6 months, the gel fraction was measured using the above method. Based on the gel fraction at the start of storage and the gel fraction after 6 months, the rate of change in the gel fraction from the start of storage was calculated. The rate of change is expressed as the absolute value of the difference in gel fraction (%) before and after 6 months, as shown in the following formula.

[0170] Change rate = Gel fraction after 6 months of storage (%) - Gel fraction at the beginning of storage (%)

[0171] A change rate of less than 10% was evaluated as ○, a change rate of 10% to 25% was evaluated as △, and a change rate exceeding 25% was evaluated as ×. The evaluation results are shown in Tables 3-1 and 3-2 below. Note that "-" indicates that the test was not conducted.

[0172] (2) Softening behavior

[0173] The resulting cross-linked polyester resin film was stored at 25°C for 6 months and then evaluated for softening behavior due to bond exchange reactions using stress relaxation measurements. Stress relaxation tests were conducted using an MCR302 (manufactured by Anton Paar) at temperatures of 100°C, 150°C, and 180°C. The tests were conducted under a nitrogen atmosphere. The test pieces used were discs with a diameter of 8 mm and a thickness of 0.7 mm, cut from the cross-linked polyester resin film.

[0174] After 6 months of storage at 25°C, if the stress relaxation test at any of 100°C, 150°C, and 180°C showed softening behavior, a rating of ○ was given; if no softening behavior was shown at any of 100°C, 150°C, and 180°C, a rating of × was given. The evaluation results are shown in Tables 3-1 and 3-2 below. Stress relaxation after 6 months of storage at 25°C indicates that the softening characteristics based on bond exchange were maintained even after storage, and that there was no initial behavior or change during long-term storage at room temperature.

[0175] (Solvent resistance)

[0176] The resulting cross-linked polyester resin film (0.7 mm thick) was cut into 5 mm wide x 5 mm long samples, one sample per bottle, and placed in screw-type flasks. Three bottles were prepared for each standard. 3 ml of ethanol, dimethylformamide (DMF), or tetrahydrofuran (THF) was added, and the samples were allowed to stand at room temperature for 5 hours. After 5 hours of standing, if no change compared to before immersion was observed, the solvent resistance was evaluated as good (◎). If the sample swelled but did not dissolve, the solvent resistance was evaluated as good (○). If it 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 conducted.

[0177] (90° peel strength when heated)

[0178] The 90° peel strength during heating is measured for the "Cu / cross-linked polyester resin film / PI" in the above-mentioned 90° peel strength evaluation sample using a thermostatic chamber (manufactured by Shimadzu Corporation, THERMOSTATIC CHAMBER) at a softening temperature of the samples listed in Tables 3-1 and 3-2 of +30°C. For the measurement of the 90° peel strength, an autograph AG-Xplus manufactured by Shimadzu Corporation was used to measure at a softening temperature of each sample of +30°C at a tensile 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 the following Tables 3-1 and 3-2. Note that "-" means not implemented.

[0179] <Evaluation Criteria>

[0180] ◎: Less than 0.35N / mm

[0181] ○: 0.35N / mm or more, less than 0.5N / mm

[0182] △: 0.5N / mm or more, less than 1.0N / mm

[0183] ×: 1.0N / mm or more

[0184]

[0185]

[0186] The cross-linked polyester resin film (thickness 0.7 mm) obtained in Example 7 was cut into thin resin shapes (width 5 mm × length 5 mm × thickness 0.7 mm), melted at a temperature of 200°C, and discharged into cooling water at a single hole discharge rate of 1.0 g / min through circular solid small holes (orifices) with a hole diameter of 1.0 mm arranged at intervals of 4 mm on the effective surface of a nozzle with a width of 40 cm and a length of 4 cm, and solidified. Specifically, cooling water was arranged 10 cm below the discharge position, and a pair of traction conveyors with a width of 50 cm and a distance of 3 cm were arranged in parallel with a stainless steel endless net partially exposed to the water surface to be pulled, and the contact parts were welded while the two sides were sandwiched, and the net was introduced into cooling water at a speed of 1.0 m per minute to solidify. Then, it was dried in a hot air dryer at 70°C for 15 minutes and cut into the specified size. As a result, a film with a thickness of 3 cm and a density of 0.060 g / cm was obtained. 3 reticular structure.

[0187] The following inferences can be made from the results in Table 3-1 and Table 3-2.

[0188] The cross-linked polyester resins obtained in Examples 1 to 11 are all obtained by using an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as an epoxy cross-linking agent, and meet the requirements specified in the present invention. Even if an ester exchange catalyst is not mixed, Examples 1 to 8 can show a softening behavior based on the bond exchange caused by the ester exchange reaction, and obtain the characteristics of self-adhesion, re-formability, and damage repairability. The expression of re-formability is believed to be because the exchange of ester bonds is activated at high temperatures and is fixed into a new equilibrium mesh structure during the cooling process. The expression of damage repairability is believed to be because the exchange of ester bonds is activated at high temperatures, which promotes the rearrangement of molecular chains near the surface of the cross-linked polyester resin film. In addition, in Examples 1 to 8, because an ester exchange catalyst is not mixed, the cross-linked polyester resin film can be applied to materials surrounding electronic materials.

[0189] Examples 9-11 use an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in its molecule as an epoxy crosslinking agent, and a transesterification catalyst is added. Comparison of Examples 9-11 with Example 7 shows that increasing the amount of transesterification catalyst added leads to more active bond exchange via the transesterification reaction, and a tendency for the softening temperature to decrease while maintaining heat resistance. This demonstrates that the softening temperature can be adjusted based on the amount of transesterification catalyst added.

[0190] The cross-linked polyester resin films of Examples 1-11 exhibit excellent formability, extrudability, room temperature storage stability, and solvent resistance. Among these, the cross-linked polyester resin films of Examples 4-11, which use aromatic polyester resins as polyester resins having carboxyl groups on their side chains, exhibit high 90° peel strength and are therefore useful as adhesives. Furthermore, the cross-linked polyester resin films of Examples 4-11 exhibit low 90° peel strength when heated to a softening temperature + 30°C, indicating easy peeling.

[0191] On the other hand, the cross-linked polyester resin films obtained in Comparative Examples 1 to 4 all do not use an epoxyamine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule as an epoxy crosslinker, and therefore do not meet the requirements specified by the present invention. In Comparative Example 1, bond exchange via the transesterification reaction did not occur, and thus the film exhibited no self-adhesiveness, reshaping, or damage-healing properties. In Comparative Example 2, the addition of a transesterification catalyst further enhanced the bond exchange via the transesterification reaction, resulting in the film exhibiting self-adhesiveness, reshaping, and damage-healing properties. However, the softening temperature was relatively lower than that of Example 11, which contained an equivalent amount of transesterification catalyst. The epoxy crosslinker used in Comparative Example 3, despite having three epoxy groups in the molecule, only had one tertiary amino group, so bond exchange via the transesterification reaction did not proceed sufficiently, resulting in no self-adhesiveness, reshaping, or damage-healing properties. In Comparative Example 4, the addition of a transesterification catalyst further enhanced the bond exchange via the transesterification reaction, resulting in the film exhibiting self-adhesiveness, reshaping, and damage-healing properties. However, the softening temperature was relatively lower than that of Example 11 in which the same amount of the transesterification catalyst was mixed.

[0192] Next, the adhesive properties of the cross-linked polyester resin film (0.7 mm thick) obtained in Example 11 were evaluated by conducting 180° peel tests and shear tests using test pieces in which the cross-linked polyester resin film was sandwiched between PET film, PI film, or AI substrate. Specifically, the cross-linked 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 form Test Piece a. The cross-linked 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 form Test Piece b. The cross-linked polyester resin film obtained in Example 11 was sandwiched between two 1.5 mm thick AI substrates and held at 200°C for 1 hour to form Test Piece c.

[0193] The 180° peel test measured the maximum stress when one end of the laminated PET film or PI film was folded 180° in the plane of the test piece and then pulled to peel. The 180° peel test was not performed on Test piece c. The shear test measured the maximum shear force when the laminated PET film, PI film, or AI substrate was pulled in opposite directions in the plane of the test piece. The results are shown in Table 4 below.

[0194] [Table 4]

[0195] PET PI Al 180° peeling (N / mm) 0.9 1.4 - Shear force (N / mm) 15.2 3.5 0.7

[0196] As is clear from the results in Table 4, the cross-linked polyester resin film obtained in Example 11 can be used to bond PET film, PI film, and AI substrate.

Claims

1. A cross-linked polyester resin, characterized in that It is an aromatic polyester resin with carboxyl groups on the side chain, cross-linked with an epoxy cross-linking agent having multiple epoxy groups, and has a softening temperature of 155 to 300°C. The number of carboxyl groups N per polymer chain of the aromatic polyester resin is COOH 3 or more and 50 or less, The epoxy crosslinking agent comprises an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in the molecule, wherein the epoxy amine compound is present in an amount of 3 to 30 parts by mole relative to 100 parts by mole of the carboxyl group of the aromatic polyester resin having a carboxyl group on the side chain, and the epoxy amine compound is present in an amount of 80 parts by mole or more based on 100 parts by mole of the total epoxy crosslinking agent; The aromatic polyester resin having a carboxyl group on the side chain has a number average molecular weight of 6,000 to 16,000 and a molecular weight dispersion index (PDI) of 1.3 to 1.

8.

2. The cross-linked polyester resin according to claim 1, characterized in that The molar ratio of the carboxyl group of the aromatic polyester resin having a carboxyl group on the side chain to the epoxy group of the epoxyamine compound, that is, the carboxyl group:the epoxy group=1:0.125 to 1:1.

2.

3. The cross-linked polyester resin according to claim 1 or 2, characterized in that The tertiary amino group contained in the epoxy amine compound and the epoxy group constitute a diglycidylamino group.

4. The cross-linked polyester resin according to claim 1 or 2, characterized in that The molecular weight of the epoxyamine compound is 800 or less.

5. A cross-linked polyester resin composition, characterized in that Contains an ester exchange catalyst and the cross-linked polyester resin according to any one of claims 1 to 4.

Images