Method for producing crosslinkable polyester composition

Abstract

Provided is a method for producing a crosslinkable polyester composition, with which a polyester able to contain bond exchange type dynamic covalent bonds in the future can be provided in a condition having favorable workability in a simple manner. Also provided is a cured product having bond exchange type dynamic covalent bonds from the crosslinkable polyester composition having favorable workability. Also provided is a method for producing the cured product from the crosslinkable polyester composition having favorable workability. Also provided is a molded body containing the crosslinkable polyester composition having favorable workability.　The method for producing a crosslinkable polyester composition includes a step for kneading a copolyester in a heated molten state with a polyfunctional epoxy compound having a plurality of epoxy groups and a transesterification catalyst. The molded body contains a crosslinkable polyester composition which contains: a copolyester; a polyfunctional epoxy compound having a plurality of epoxy groups; and a transesterification catalyst. The crosslinkable polyester composition has a gel fraction of less than 30%, and is in the form of a rod, a yarn, a granule or flake.

Description

Method for producing crosslinkable polyester composition

[0001] The present invention relates to a method for producing a crosslinkable polyester composition, a method for producing a crosslinkable polyester composition, and a molded article containing the crosslinkable polyester composition.

[0002] Polyesters are polycondensates synthesized by dehydration condensation of polycarboxylic acids and polyalcohols, and examples thereof include polymers produced from terephthalic acid or its ester-forming derivatives and ethylene glycol. Polyesters are excellent in versatility and practicality and are suitably used, for example, as materials for films, sheets, fibers, bottles, and the like. Due to their excellent mechanical properties, weather resistance, and chemical resistance, polyesters 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 polyesters are also used as crosslinked polyesters by crosslinking polyesters with a crosslinking agent. Conventional crosslinked polyesters could not be remolded because the polyesters were crosslinked by covalent bonds. In contrast, in recent years, attention has been focused on crosslinked polyesters in which the polyesters are crosslinked by bond-exchange type dynamic covalent bonds. When crosslinked polyesters are crosslinked by bond-exchange type dynamic covalent bonds, further heating causes a bond exchange reaction, making them remoldable.

[0004] As an example of the production of crosslinked polyesters crosslinked by bond-exchange dynamic covalent bonds, for example, Non-Patent Document 1 describes a method in which polyethylene terephthalate (PET), a diglycidyl ether of bisphenol A, and 2,2-bis(hydroxymethyl)-2,2',2''-nitrilotriethanol (BIS-TRIS) are heated to 240 to 270°C using a twin-screw extruder, melted, and kneaded to produce pellets, and the resulting pellets are post-cured at 205°C for 10 hours under vacuum. Furthermore, Non-Patent Document 2 describes a method in which polybutylene terephthalate (PBT), a diglycidyl ether of bisphenol A, and zinc acetylacetonate hydrate are heated to 270°C using a twin-screw extruder, melted, and kneaded, and the resulting melt is injected into a test piece-shaped mold at 200°C and held therein. Meanwhile, in Non-Patent Document 3, the present inventors disclose a method for producing a bond exchange resin film with a gel fraction of approximately 100%, in which a mixture of an amorphous polyester resin, 4,4'-methylenebis(N,N-diglycidylaniline), and 1,8-diazabicyclo[5.4.0]-7-undecene is mixed in the presence of THF, followed by casting and vacuum drying to remove the THF, and then the solid is heated at 200°C for 24 hours.

[0005] Jianfan Qiu, et al. , Macromolecules. 2021, 54(2), 703-712. L. Farge, et al. , Macromolecules. 2021, 54(4), 1838-1849. Mikihiro Hayashi, et al. , Journal of Materials Chemistry A, 2022, 34(10), 17406-17414.

[0006] The polyethylene terephthalate described in Non-Patent Document 1 and the polybutylene terephthalate described in Non-Patent Document 2 are both crystalline, and therefore require high temperatures when heated, melted, and kneaded using a twin-screw extruder, resulting in crosslinking already occurring when extruded from the twin-screw extruder. As a result, the extrudates have poor fluidity and processability. On the other hand, in Non-Patent Document 3, a mixture containing an amorphous polyester resin is mixed in the presence of THF, requiring a large amount of solvent. Furthermore, after the mixture is prepared, it takes approximately 24 hours to remove THF and dry the mixture, leaving room for improvement before it can be used as an industrial production method.

[0007] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to provide a method for producing a crosslinkable polyester composition that can easily provide a polyester that may have bond-exchange type dynamic covalent bonds in the future in a state of good processability. Another object of the present invention is to provide a cured product (crosslinked polyester composition) having bond-exchange type dynamic covalent bonds from the crosslinkable polyester composition with good processability. Another object of the present invention is to provide a method for producing the cured product (crosslinked polyester composition) from the crosslinkable polyester composition with good processability. Another object of the present invention is to provide a molded article containing the crosslinkable polyester composition with good processability.

[0008] The present invention is as follows: [1] A method for producing a crosslinkable polyester composition, comprising a step of kneading a heat-molten copolymerized polyester with a polyfunctional epoxy compound having multiple epoxy groups and a transesterification catalyst. [2] A method for producing a crosslinkable polyester composition according to [1], comprising a step of molding the mixture into a predetermined shape after the kneading. [3] A method for producing a crosslinkable polyester composition according to [1] or [2], wherein the copolymerized polyester is an amorphous polyester. [4] A method for producing a crosslinkable polyester composition according to any one of [1] to [3], wherein the copolymerized polyester contains a first unit consisting of ethylene terephthalate or butylene terephthalate and further contains at least one component selected from the following group as an acid component and / or alcohol component: Acid component: terephthalic acid, isophthalic acid, sebacic acid Alcohol component: ethylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol [5] A method for producing a crosslinkable polyester composition according to any one of [1] to [4], wherein the transesterification catalyst does not contain a hydroxyl group. [6] A method for producing a crosslinkable polyester composition according to any one of [1] to [5], wherein the kneading is carried out at a temperature equal to or lower than the glass transition temperature (Tg) of the copolymer polyester + 120°C. [7] A method for producing a crosslinkable polyester composition according to any one of [1] to [6], wherein the kneading is carried out in a solvent-free state. [8] A method for producing a crosslinkable polyester composition according to any one of [1] to [7], wherein the kneading is carried out using a twin-screw kneading extruder. [9] A method for producing a crosslinkable polyester composition according to [8], wherein a sheet- or film-shaped molded article containing the crosslinkable polyester composition is extruded from the twin-screw kneading extruder.

[10] A method for producing a crosslinkable polyester composition by the method according to any one of [1] to [9], and then heating the crosslinkable polyester composition to crosslink it.

[11] A method for producing a crosslinkable polyester composition according to

[10] , wherein the crosslinking of the crosslinkable polyester composition is carried out by heating it at a temperature higher than the kneading temperature.

[12] A method for producing a crosslinked polyester composition according to

[10] or

[11] , wherein the crosslinking of the crosslinkable polyester composition is carried out by heating at a temperature of 120°C to 250°C for at least 1 hour.

[13] A molded article comprising a crosslinkable polyester composition comprising a copolymer polyester, a polyfunctional epoxy compound having multiple epoxy groups, and a transesterification catalyst, the crosslinkable polyester composition being rod-like, thread-like, granular, or flake-like, and having a gel fraction of less than 30%.

[14] A molded article comprising a crosslinkable polyester composition comprising a copolymer polyester, a polyfunctional epoxy compound having multiple epoxy groups, and a transesterification catalyst, the crosslinkable polyester composition being sheet-like or film-like, the gel fraction of which is less than 30%, and having a thickness of 20 μm or more.

[15] A molded article comprising the crosslinkable polyester composition according to

[13] or

[14] , the gel fraction of which is 30% or more after heating at a temperature of 120°C to 250°C for 3 hours.

[0009] According to the present invention, since a copolymerized polyester is kneaded with a multifunctional epoxy compound having multiple epoxy groups and a transesterification catalyst, the kneaded product can have bond-exchange dynamic covalent bonds in the future. Moreover, since this kneaded product is kept in a non-crosslinked state (i.e., a crosslinkable state) while being heated and kneaded, it can have good processability. If a crosslinkable polyester composition is produced by such a method, bond-exchange dynamic covalent bonds can be introduced by subsequent heating, and crosslinked polyesters having bond-exchange dynamic covalent bonds can be easily provided. When a crosslinkable polyester is crosslinked by bond-exchange dynamic covalent bonds, a bond exchange reaction occurs by further heating even after crosslinking, making it possible to reshape the polyester.

[0010] FIG. 1A shows GPC chromatograms obtained by measuring crosslinkable polyester compositions 1 and 2 obtained in Examples 1 and 2, and copolymer polyester A1. FIG. 1B shows GPC chromatograms obtained by measuring comparative crosslinkable polyester compositions 1 and 2 obtained in Comparative Examples 1 and 2, and copolymer polyester A1. FIG. 1C shows GPC chromatograms obtained by measuring comparative crosslinkable polyester composition 3 obtained in Comparative Example 3, and copolymer polyester A1. FIG. 2A shows an isothermal, time-resolved viscoelastic spectrum measured for crosslinkable polyester composition 1 obtained in Example 1. FIG. 2B shows an isothermal, time-resolved viscoelastic spectrum measured for crosslinkable polyester composition 2 obtained in Example 2. FIG. 2C shows an isothermal, time-resolved viscoelastic spectrum measured for comparative crosslinkable polyester composition 1 obtained in Comparative Example 1. FIG. 2D shows an isothermal, time-resolved viscoelastic spectrum measured for comparative crosslinkable polyester composition 3 obtained in Comparative Example 3. FIG. 3 is a graph showing the relationship between heating time and the gel fraction calculated for samples obtained by heating crosslinkable polyester compositions 1 and 2. Fig. 4 shows a stress relaxation spectrum measured for a sample obtained by heating crosslinkable polyester composition 1. Fig. 5A shows a photograph of the state before heating when a remolding test was performed using a test piece cut out from a sample obtained by heating crosslinkable polyester composition 1 at 180°C for 3 hours. Fig. 5B shows a photograph of the state after heating when a remolding test was performed using a test piece cut out from a sample obtained by heating crosslinkable polyester composition 1 at 180°C for 3 hours.

[0011] The method for producing a crosslinkable polyester composition according to an embodiment of the present invention is characterized by including a step of kneading a copolymerized polyester in a heated and molten state with a polyfunctional epoxy compound having multiple epoxy groups and a transesterification catalyst. In this specification, the term "crosslinkable polyester composition" refers to a composition containing a polyester before crosslinking, which has crosslinkability and undergoes crosslinking via an epoxy ring-opening reaction or a bond exchange reaction upon heating. Furthermore, a crosslinkable polyester composition obtained by heating the polyester to crosslink the polyesters is called a crosslinked polyester composition.

[0012] (Copolymer Polyester) The copolymer polyester used in the embodiment of the present invention may be an aliphatic polyester, an aromatic polyester, or a combination of an aliphatic polyester and an aromatic polyester.

[0013] The copolymerized polyester can be prepared, for example, by a method in which an acid component, an alcohol component, and a dicarboxylic acid containing a nucleophilic reactive group (e.g., a thiol group) are polycondensed, followed by reacting the nucleophilic reactive group of the dicarboxylic acid with an unsaturated carboxylic acid; or a method in which an acid component, an alcohol component, and an unsaturated polycarboxylic acid or an anhydride thereof are polycondensed, followed by reacting the unsaturated group of the unsaturated polycarboxylic acid with a carboxylic acid having a nucleophilic reactive group.

[0014] As the acid component, it is preferable to use a dicarboxylic acid as the main component (for example, preferably 60 molar parts or more, more preferably 80 molar parts or more, of the dicarboxylic acid per 100 molar parts of the acid component). Examples of dicarboxylic acids that can be used include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic 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. It is preferable to use at least one selected from the group consisting of aromatic dicarboxylic acids and aliphatic dicarboxylic acids as the acid component. As the acid component, for example, tricarboxylic acids and tetracarboxylic acids such as trimellitic acid, pyromellitic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, etc. may be used. The tricarboxylic acids and tetracarboxylic acids are preferably subjected to the polycondensation reaction as acid anhydrides.

[0015] Examples of the alcohol component include aliphatic glycols such as 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; polyether glycols such as diethylene glycol and triethylene glycol; polyethylene glycol; Polyalkylene glycols such as polytetramethylene glycol; alicyclic polyols such as 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane glycols, and hydrogenated bisphenols; 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; alkylene oxide adducts of phenols such as ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A; and the like may also be used. The alcohol component may be one of these, or two or more may be used. It is preferable to use an aliphatic glycol as the alcohol component.

[0016] The copolymer polyester preferably contains a first unit made of, for example, ethylene terephthalate or butylene terephthalate, and further contains at least one component selected from the following group as an acid component and / or alcohol component: Acid component: terephthalic acid, isophthalic acid, sebacic acid Alcohol component: ethylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol

[0017] As the dicarboxylic acid containing a nucleophilic reactive group, for example, a dicarboxylic acid containing a thiol group as the nucleophilic reactive group may be used, and it is preferable to use an aliphatic dicarboxylic acid having a thiol group and about 4 to 10 carbon atoms, such as thiomalic acid.

[0018] As the unsaturated carboxylic acid that reacts with the nucleophilic reactive group of the dicarboxylic acid, for example, an aliphatic α,β-unsaturated monocarboxylic acid having about 3 to 10 carbon atoms, such as acrylic acid, methacrylic acid, crotonic acid, or isocrotonic acid, may be used.

[0019] As the unsaturated polycarboxylic acid, for example, an aliphatic α,β-unsaturated dicarboxylic acid having about 4 to 10 carbon atoms, such as maleic acid or fumaric acid, may be used.

[0020] As the carboxylic acid having a nucleophilic reactive group that reacts with the unsaturated group of the unsaturated polycarboxylic acid, for example, an aliphatic monocarboxylic acid having a thiol group and about 2 to 10 carbon atoms, such as thioglycolic acid or mercaptopropionic acid, may be used.

[0021] The number-average molecular weight (Mn) of the copolymer polyester is preferably, for example, 6,000 to 50,000. Having a number-average molecular weight (Mn) of 6,000 or more can improve heat resistance. The number-average molecular weight (Mn) is more preferably 6,500 or more, and even more preferably 7,000 or more. However, if the number-average molecular weight (Mn) of the copolymer polyester becomes too large, the viscosity increases, making it difficult to flow and knead. Therefore, the number-average molecular weight (Mn) is preferably 50,000 or less, more preferably 40,000 or less, even more preferably 28,000 or less, and particularly preferably 25,000 or less. That is, the number-average molecular weight (Mn) of the copolymer polyester is, for example, more preferably 6,500 to 40,000, even more preferably 7,000 to 28,000, and particularly preferably 7,000 to 25,000.

[0022] The acid value of the copolymer polyester is, for example, preferably 0.1 to 5 mgKOH / g, more preferably 0.3 to 3 mgKOH / g, and even more preferably 0.5 to 2.0 mgKOH / g. The higher the acid value, the more crosslinking points there are, and the more heat resistance there is improved.

[0023] The glass transition point (Tg) of the copolymer polyester is preferably, for example, -15 to 130°C. Having a glass transition point (Tg) of 130°C or less improves the fluidity of the crosslinkable polyester composition. This facilitates lowering the heating temperature when kneading the copolymer polyester with a polyfunctional epoxy compound having multiple epoxy groups and an ester exchange catalyst. Although the polyester is prone to crosslinking, this crosslinking can be suppressed, making it easier to improve the fluidity of the kneaded mixture. The glass transition point (Tg) of the copolymer polyester is more preferably 100°C or less, and even more preferably 80°C or less. While the lower limit of the glass transition point (Tg) of the copolymer polyester is not particularly limited, from the viewpoint of mechanical properties after curing, it is preferably, for example, -15°C or higher, more preferably 1°C or higher, and even more preferably 3°C or higher. That is, the glass transition point (Tg) of the copolymer polyester is more preferably 1 to 100°C, and even more preferably 3 to 80°C.

[0024] The copolymerized polyester is preferably an amorphous polyester. Amorphous polyester refers to a polyester that does not have a clear melting point. By using an amorphous polyester, it becomes easier to lower the heating temperature when kneading the copolymerized polyester with a multifunctional epoxy compound having multiple epoxy groups and a transesterification catalyst.

[0025] (Multifunctional Epoxy Compound) The multifunctional epoxy compound having multiple epoxy groups used in the present invention refers to an epoxy compound containing two or more epoxy groups in the molecule. The number of functional groups (epoxy groups) contained in the multifunctional epoxy compound may be three or more, or four or more, and more preferably four or more. The upper limit of the number of epoxy groups is not particularly limited, but may be, for example, six or less, or five or less. That is, the number of functional groups (epoxy groups) contained in the multifunctional epoxy compound is preferably two to six, more preferably three to five, and even more preferably four to five.

[0026] Examples of polyfunctional epoxy compounds that can be used include bisphenol A diglycidyl ether (hereinafter sometimes referred to as DGEBA) and 4,4'-methylenebis(N,N-diglycidylaniline). Bisphenol A diglycidyl ether is a bifunctional epoxy compound containing two epoxy groups in the molecule. 4,4'-methylenebis(N,N-diglycidylaniline) is a tetrafunctional epoxy compound containing four epoxy groups in the molecule. One or more of these polyfunctional epoxy compounds may be used.

[0027] The amount of the polyfunctional epoxy compound is, for example, preferably 5 parts by mass or more, more preferably 8 parts by mass or more, even more preferably 10 parts by mass or more, and preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the copolymerized polyester. When multiple types of polyfunctional epoxy compounds are used, the amount refers to the total amount. That is, the amount of the polyfunctional epoxy compound is preferably 5 to 20 parts by mass, more preferably 8 to 18 parts by mass, and even more preferably 10 to 15 parts by mass, relative to 100 parts by mass of the copolymerized polyester.

[0028] (Transesterification Catalyst) The transesterification catalyst used in the embodiment of the present invention may be a basic catalyst, an acid catalyst, or an inorganic salt catalyst (Lewis acid catalyst). Examples of basic catalysts that may be used include 1,8-Diazabicyclo[5.4.0]-7-undecene (1,8-diazabicyclo[5.4.0]-7-undecene, hereinafter sometimes referred to as DBU), 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (1,5,7-triazabicyclo[4.4.0]dec-5-ene, hereinafter sometimes referred to as TBD), and 1-Methylimidazole. Examples of acid catalysts that may be used include p-Toluenesulfonic Acid. As the inorganic salt catalyst, for example, zinc acetate, tin(II) 2-ethylhexanoate, etc. may be used. As the transesterification catalyst, one of these may be used, or two or more of them may be used.

[0029] The amount of the transesterification catalyst is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the copolymerized polyester. The lower limit of the amount of the transesterification catalyst is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the copolymerized polyester. When multiple types of transesterification catalysts are used, the total amount refers to the total amount. That is, the amount of the transesterification catalyst is preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of the copolymerized polyester.

[0030] The transesterification catalyst is preferably a catalyst that does not contain a hydroxyl group. By using a catalyst that does not contain a hydroxyl group, alcoholysis is less likely to occur, and the gel fraction of the crosslinked polyester composition can be increased.

[0031] The kneading is carried out in a heated and molten state of the copolymerized polyester. By kneading the heated and molten copolymerized polyester with a multifunctional epoxy compound having multiple epoxy groups and a transesterification catalyst, the carboxy groups contained in the copolymerized polyester react with the epoxy groups contained in the multifunctional epoxy compound, resulting in a crosslinkable polyester composition. If decomposition of the polyester occurs during kneading, the carboxy groups and hydroxyl groups generated at both ends of the decomposed chain react with the epoxy groups, resulting in a high molecular weight. The obtained crosslinkable polyester composition is a composition containing a crosslinkable polyester that may have bond-exchange type dynamic covalent bonds in the future, and has good processability.

[0032] The kneading is preferably carried out at a temperature equal to or lower than the glass transition temperature (Tg) of the copolymer polyester + 120°C. Kneading within this temperature range can prevent the copolymer polyester from crosslinking during kneading. The kneading is more preferably carried out at a temperature equal to or lower than the glass transition temperature (Tg) of the copolymer polyester + 120°C and 250°C.

[0033] The kneading time is not particularly limited, but is preferably, for example, 2 minutes or more. Kneading for 2 minutes or more allows for uniform kneading. The kneading time is more preferably 3 minutes or more. However, longer kneading times result in poor productivity. Therefore, the upper limit of the kneading time is preferably, for example, 1 hour or less. The kneading time is more preferably 30 minutes or less, and even more preferably 15 minutes or less. That is, the kneading time is preferably 2 minutes to 1 hour, more preferably 3 minutes to 30 minutes, and even more preferably 3 minutes to 15 minutes.

[0034] The kneading is preferably carried out in an inert gas atmosphere, for example, nitrogen gas.

[0035] The kneading is preferably carried out in a solvent-free state, which eliminates the need to remove the solvent from the crosslinkable polyester composition obtained by kneading (i.e., eliminates the need to dry the crosslinkable polyester composition), thereby enabling production in a short time and industrial production.

[0036] The number-average molecular weight (Mn) of the crosslinkable polyester composition obtained by kneading is preferably, for example, 6,000 to 50,000. A number-average molecular weight (Mn) of 6,000 or more of the crosslinkable polyester composition can improve heat resistance. The number-average molecular weight (Mn) is more preferably 6,500 or more, and even more preferably 7,000 or more. However, if the number-average molecular weight (Mn) of the crosslinkable polyester composition becomes too large, the viscosity increases, making it difficult to flow and knead. Therefore, the number-average molecular weight (Mn) is preferably 50,000 or less, more preferably 40,000 or less, even more preferably 28,000 or less, and particularly preferably 25,000 or less. That is, the number-average molecular weight (Mn) of the crosslinkable polyester composition is more preferably 6,500 to 40,000, even more preferably 7,000 to 28,000, and particularly preferably 7,000 to 25,000.

[0037] The molecular weight distribution of the crosslinkable polyester composition is preferably, for example, 1.5 to 3. The molecular weight distribution can be calculated based on the weight average molecular weight (Mw) and the number average molecular weight (Mn) using the following formula: Molecular weight distribution = Mw / Mn

[0038] The molecular weight distribution of the crosslinkable polyester composition is more preferably 1.8 or more. However, if the molecular weight distribution of the crosslinkable polyester composition is too large, the chain length will vary widely, and the strength of the crosslinkable polyester composition will tend to vary. The molecular weight distribution of the crosslinkable polyester composition is more preferably 2.8 or less. That is, the molecular weight distribution of the crosslinkable polyester composition is more preferably 1.8 to 2.8.

[0039] The method for producing a crosslinkable polyester composition according to an embodiment of the present invention may further include a step of forming the kneaded mixture into a predetermined shape such as a film, sheet, granules, flakes, rod, or thread.

[0040] For example, it is preferable to use an extrusion molding machine for kneading, and it is more preferable to use a twin-screw kneading extruder. When using a twin-screw kneading extruder, it is preferable to extrude a molded article containing the crosslinkable polyester composition in the form of granules, flakes, rods, threads, sheets, or films from the twin-screw kneading extruder. A molded article containing the crosslinkable polyester composition in the form of a sheet or film may be used, for example, as an adhesive sheet or adhesive film. A molded article containing the crosslinkable polyester composition in the form of a sheet or film is sandwiched between substrates (adherends) to be bonded and heated, causing a bond exchange reaction, which allows the substrates to be bonded to each other.

[0041] The material of the substrate (adherend) is not particularly limited, and may be, for example, wood, glass, resin, metal, or a composite thereof. The form of the substrate is not particularly limited, and may be, for example, a film, sheet, foil, or plate. Examples of the substrate that can be used include a resin film, a metal foil, and a metal plate. Examples of the resin film that can be used include a polyimide film, a polyester film, and a PET film. Examples of the metal foil that can be used include copper foil, silver foil, and gold foil. Examples of the metal plate that can be used include an aluminum plate, a stainless steel plate, a steel plate, and an iron plate. A molded article containing a crosslinkable polyester composition may be used as an adhesive between the same or different types of substrates described above, and may be used, for example, as an adhesive between resin films, between metal foils, or between a resin film and a metal foil.

[0042] A molded article containing a crosslinkable polyester composition according to another embodiment of the present invention comprises a copolymerized polyester, a polyfunctional epoxy compound having multiple epoxy groups, and a transesterification catalyst, and is characterized by having a gel fraction of less than 30% and being in the form of a rod, thread, granule, or flake. Because the molded article containing the crosslinkable polyester composition has a gel fraction of less than 30%, it has excellent processability.

[0043] Another embodiment of a molded article containing a crosslinkable polyester composition according to the present invention comprises a copolymerized polyester, a polyfunctional epoxy compound having multiple epoxy groups, and a transesterification catalyst, and is characterized by a gel fraction of less than 30% and a film thickness of 20 μm or more. The gel fraction of the molded article containing the crosslinkable polyester composition is less than 30%, resulting in excellent processability. The film thickness of the molded article containing the crosslinkable polyester composition may be 20 μm to 3 mm, 0.1 mm to 2 mm, or 0.5 mm to 1.5 mm. A molded article containing the crosslinkable polyester composition in a sheet or film form may be used, for example, as an adhesive sheet or adhesive film. By sandwiching a sheet or film-like molded article containing the crosslinkable polyester composition between substrates (adherends) to be bonded and heating it, crosslinking occurs via an epoxy ring-opening reaction or a bond exchange reaction, allowing the substrates to be bonded together. The substrates may be those described above.

[0044] The gel fraction of a molded article containing the crosslinkable polyester composition is preferably 30% or more by heating at a temperature of 120°C to 250°C for 3 hours, more preferably 40% or more by heating at a temperature of 120°C to 250°C for 6 hours, and even more preferably 50% or more by heating at a temperature of 120°C to 250°C for 12 hours.

[0045] Molded articles containing the crosslinkable polyester composition according to the embodiment of the present invention have good processability, and by heating a molded article containing this crosslinkable polyester composition for 3 hours at a temperature exceeding the kneading temperature during production of the crosslinkable polyester composition, specifically at a temperature of 120°C (particularly above 120°C) to 250°C, a cured article (crosslinked polyester composition) with a gel fraction of 30% or more can be obtained. By heating a molded article containing the crosslinkable polyester composition, polyesters contained in the crosslinkable polyester composition are crosslinked by an epoxy ring-opening reaction or a bond-exchange type dynamic covalent bond, thereby obtaining a cured article (crosslinked polyester composition). Further heating of the crosslinked polyester composition (cured article) obtained by crosslinking the crosslinkable polyester composition causes a bond-exchange reaction, making it possible to reshape the composition.

[0046] Next, a method for producing a crosslinked polyester composition according to another embodiment of the present invention will be described. The crosslinked polyester composition according to an embodiment of the present invention is a cured product of the above-mentioned crosslinkable polyester composition, and can be produced by heating and crosslinking the crosslinkable polyester composition. That is, the method for producing a crosslinked polyester composition includes a step of kneading a copolymerized polyester in a heated and molten state with a multifunctional epoxy compound having multiple epoxy groups and a transesterification catalyst, and a step of heating and crosslinking the crosslinkable polyester composition obtained through the above step.

[0047] When producing a crosslinked polyester composition, it is preferable to heat the crosslinkable polyester composition at a temperature higher than the kneading temperature during production of the crosslinkable polyester composition, specifically, it is preferable to heat at a temperature of 120°C to 250°C. The heating temperature is more preferably 130°C or higher, even more preferably 140°C or higher, and more preferably 240°C or lower, even more preferably 230°C or lower. That is, the heating temperature is more preferably 130°C to 240°C, even more preferably 140°C to 230°C. The heating time is not necessarily determined as long as it is a time that allows crosslinking to proceed sufficiently, but is, for example, about 10 minutes to about 10 hours, and may be shorter or longer than this. The heating time may be 1 hour or more, or may be 1 hour to 10 hours.

[0048] The crosslinked polyester composition has remoldability, and after being deformed into a predetermined shape, by heating in the deformed state, a bond exchange reaction occurs, and the composition is remolded, and the predetermined shape is maintained even after cooling. The heating temperature may be, for example, 120°C to 250°C, 130°C to 240°C, or 140°C to 230°C.

[0049] The crosslinked polyester composition has good moldability and extrusion moldability, and therefore may be used, for example, as a molding material. The crosslinked polyester composition may be used, for example, as a material for a 3D printer or a material for a network structure. The network structure is a structure in which linear bodies made of the crosslinked polyester composition are fused at their intersections to form a network. The shape of the linear bodies is not particularly limited, and the interior of the linear body may be either solid or hollow, and the cross-sectional shape of the linear body may be either circular or irregular.

[0050] The crosslinked polyester composition may be used, for example, as an adhesive sheet or adhesive film. When used as an adhesive sheet or adhesive film, the crosslinked polyester composition is sandwiched between substrates (adhered members) to be bonded, and heated to cause an epoxy ring-opening reaction or a bond exchange reaction, thereby bonding the substrates together. The substrates may be those described above.

[0051] This application claims the benefit of priority based on Japanese Patent Application No. 2023-115347, filed on July 13, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-115347 are incorporated herein by reference.

[0052] 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."

[0053] A crosslinkable polyester composition was produced by kneading a polyfunctional epoxy compound having a plurality of epoxy groups and an ester exchange catalyst with a copolymerized polyester in a heated and molten state.

[0054] As the copolymer polyester, copolymer polyester A1 or copolymer polyester A2 manufactured by Toyobo Co., Ltd., which had been thoroughly dried in advance, was used. Copolymer polyester A1 and copolymer polyester A2 were prepared by the following procedure.

[0055] (Copolymer Polyester A1) A reactor equipped with a stirrer, thermometer, and distillation condenser was charged with 50 mol of terephthalic acid, 20 mol of isophthalic acid, 30 mol of sebacic acid, 58 mol of ethylene glycol, 42 mol of 2,2-dimethyl-1,3-propanediol, and 0.2 mol of tetrabutyl titanate, and the temperature was gradually raised to 250°C. An esterification reaction was carried out while removing the distilled water from the system. After completion of the esterification reaction, reduced pressure initial polymerization was carried out while gradually reducing the pressure to 10 mmHg, and the temperature was raised to 250°C. Further, post-polymerization was carried out at 1 mmHg or less until a predetermined torque was reached, thereby obtaining copolymer polyester A1. The composition of copolymer polyester A1 is shown in Table 1 below.

[0056] (Copolymer Polyester A2) A reactor equipped with a stirrer, thermometer, and distillation condenser was charged with 50 moles of terephthalic acid, 50 moles of isophthalic acid, 50 moles of ethylene glycol, 50 moles of 2,2-dimethyl-1,3-propanediol, and 0.2 moles of tetrabutyl titanate, and the temperature was gradually raised to 250°C. An esterification reaction was carried out while removing the distilled water from the system. After completion of the esterification reaction, initial polymerization was carried out while gradually reducing the pressure to 10 mmHg, and the temperature was raised to 250°C. Further, final polymerization was carried out at 1 mmHg or less until a predetermined torque was reached, thereby obtaining copolymer polyester A2. The composition of copolymer polyester A2 is shown in Table 1 below.

[0057] Copolymer polyester A1 and copolymer polyester A2 are linear amorphous polyesters that do not have a crosslinkable functional group in the side chain.

[0058] Next, the acid value (mg KOH / g) and glass transition temperature (°C) of the copolymer polyesters A1 and A2 were measured by the following procedure, and are shown in Table 1 below. (Acid Value) 0.2 g of the copolymer polyester 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 ethanolic potassium hydroxide 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 copolymer polyester, and the acid value (mg KOH / g) was calculated. (Glass Transition Temperature) Using a DSC7020 (manufactured by Hitachi HighTech Co., Ltd.), the acid value was measured at 200°C from -50°C to 200°C. ２ The glass transition temperature (Tg) was determined by measuring the heat flow rate in a gas atmosphere at a temperature change rate of 10° C. / min.

[0059]

[0060] The number-average molecular weight (Mn) of the copolymer polyesters A1 and A2 was measured by the following procedure. (Number-Average Molecular Weight (Mn) The copolymer polyester was dissolved in dimethylformamide (DMF) to a concentration of approximately 0.5% by mass, and the solution was filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm to prepare a measurement sample. The number-average molecular weight (Mn) was measured by gel permeation chromatography using DMF containing LiBr (0.05% by mass) as the mobile phase and a differential refractometer as the detector. The flow rate was 0.5 mL / min and the column temperature was 40°C. The columns used were Showa Denko KF-803, KF-804L, and KF-805L. Monodisperse polymethyl methacrylate was used as the standard substance (molecular weight standard). Low-molecular-weight compounds (oligomers, etc.) with a number-average molecular weight (Mn) of less than 1,000 were not counted and were omitted.

[0061] The number average molecular weight (Mn) of copolymer polyester A1 was 27,267 and the weight average molecular weight (Mw) was 50,559, and the number average molecular weight (Mn) of copolymer polyester A2 was 23,604 and the weight average molecular weight (Mw) was 44,018.

[0062] The polyfunctional epoxy compounds used were 4,4'-methylenebis(N,N-diglycidylaniline) and bisphenol A diglycidyl ether. 4,4'-methylenebis(N,N-diglycidylaniline) is a tetrafunctional epoxy compound with four epoxy groups. Bisphenol A diglycidyl ether (DGEBA) is a difunctional epoxy compound with two epoxy groups.

[0063] The transesterification catalysts used were 1,8-Diazabicyclo[5.4.0]-7-undecene (DBU), 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), or zinc acetate. 1,8-Diazabicyclo[5.4.0]-7-undecene, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene, and zinc acetate are all catalysts that do not contain hydroxyl groups.

[0064] Example 1 A crosslinkable polyester composition was produced by kneading 100 parts of copolymer polyester A1 in a heated and melted state with 10 parts of 4,4'-methylenebis(N,N-diglycidylaniline) and 2.5 parts of DBU. Kneading was carried out in a solvent-free state using a twin-screw kneader [Haake (trademark) MiniLab] manufactured by Thermo Fisher Scientific. Kneading was carried out under the conditions of a temperature of 120°C, a rotation speed of 50 rpm, and a nitrogen gas atmosphere for 5 minutes. The obtained crosslinkable polyester composition is hereinafter referred to as crosslinkable polyester composition 1.

[0065] (Example 2) A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that the amount of 4,4'-methylenebis(N,N-diglycidylaniline) in Example 1 was changed to 20 parts. The obtained crosslinkable polyester composition is hereinafter referred to as crosslinkable polyester composition 2.

[0066] Comparative Example 1 A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 4,4'-methylenebis(N,N-diglycidylaniline) was not used. The resulting crosslinkable polyester composition is hereinafter referred to as comparative crosslinkable polyester composition 1.

[0067] Comparative Example 2 A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 4,4'-methylenebis(N,N-diglycidylaniline) was not used and the amount of DBU was changed to 5 parts. The resulting crosslinkable polyester composition is hereinafter referred to as comparative crosslinkable polyester composition 2.

[0068] Comparative Example 3 A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that DBU was not used. The resulting crosslinkable polyester composition is hereinafter referred to as comparative crosslinkable polyester composition 3.

[0069] (Example 3) A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 100 parts of copolymer polyester A2 was used instead of 100 parts of copolymer polyester A1 in Example 1. The obtained crosslinkable polyester composition is hereinafter referred to as crosslinkable polyester composition 3.

[0070] (Example 4) A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 2.5 parts of zinc acetate was used instead of 2.5 parts of DBU in Example 1. The obtained crosslinkable polyester composition is hereinafter referred to as crosslinkable polyester composition 4.

[0071] Comparative Example 4 A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 100 parts of polybutylene terephthalate (PBT) was used instead of 100 parts of copolymer polyester A1, and the kneading temperature was changed to 270°C. Polybutylene terephthalate is a crystalline polyester. The obtained crosslinkable polyester composition is hereinafter referred to as comparative crosslinkable polyester composition 4.

[0072] Comparative Example 5 A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 100 parts of polybutylene terephthalate (PBT) was used instead of 100 parts of copolymer polyester A1, 1 part of DGEBA was used instead of 10 parts of 4,4'-methylenebis(N,N-diglycidylaniline), and the kneading temperature was changed to 270°C. The obtained crosslinkable polyester composition is hereinafter referred to as comparative crosslinkable polyester composition 5.

[0073] (Example 5) A crosslinkable polyester composition was produced under the same conditions as in Example 1, except that 10 parts of DGEBA was used instead of 10 parts of 4,4'-methylenebis(N,N-diglycidylaniline) in Example 1. The obtained crosslinkable polyester composition is hereinafter referred to as crosslinkable polyester composition 5.

[0074] The compositions (parts) of the crosslinkable polyester compositions 1 to 5 obtained in Examples 1 to 5 and the comparative crosslinkable polyester compositions 1 to 5 obtained in Comparative Examples 1 to 5 are shown in Table 2 below.

[0075]

[0076] Next, the GPC chromatograms of the crosslinkable polyester composition and the comparative crosslinkable polyester composition were measured by the following procedure to determine the number average molecular weight (Mn) and molecular weight distribution (Mw / Mn).

[0077] [Number-Average Molecular Weight (Mn) and Molecular Weight Distribution (Mw / Mn)] The GPC chromatogram of the crosslinkable polyester composition was measured using size exclusion chromatography. The crosslinkable polyester composition was dissolved in dimethylformamide to a concentration of approximately 0.2% by mass, and used as the measurement sample. The GPC chromatogram was measured using dimethylformamide containing 0.05% by mass of lithium bromide as the mobile phase, a Shimadzu RID-20A detector, and a Shimadzu LC-20AD pump system, and the number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined. The flow rate was 1.0 mL / min, and the column temperature was 40°C. Shodex K-803, K-804, and K-805 columns were used. Polymethyl methacrylate was used as the reference material (molecular weight standard). The molecular weight distribution (Mw / Mn) was calculated based on the number average molecular weight (Mn) and weight average molecular weight (Mw). The results are shown in Table 2. In Table 2, "-" indicates that the GPC chromatogram was not measured.

[0078] GPC chromatograms measured for crosslinkable polyester compositions 1 and 2 are shown in Figure 1A. Curve E1 in Figure 1A shows the results for crosslinkable polyester composition 1, and curve E2 shows the results for crosslinkable polyester composition 2. GPC chromatograms measured for comparative crosslinkable polyester compositions 1 and 2 are shown in Figure 1B. Curve CE1 in Figure 1B shows the results for comparative crosslinkable polyester composition 1, and curve CE2 shows the results for comparative crosslinkable polyester composition 2. GPC chromatograms measured for comparative crosslinkable polyester composition 3 are shown in Figure 1C. Curve CE3 in Figure 1C shows the results for comparative crosslinkable polyester composition 3. Figures 1A to 1C also show GPC chromatograms measured for copolymer polyester A1. Curve A1 in Figures 1A to 1C shows the results for copolymer polyester A1. In Figures 1A to 1C, the horizontal axis represents elution time (minutes), and the vertical axis represents differential refractive index.

[0079] The results of Examples 1 and 2 shown in FIG. 1A indicate that crosslinkable polyester compositions 1 and 2 have a longer elution time than copolymer polyester A1, indicating a lower molecular weight. Furthermore, the elution curves of crosslinkable polyester compositions 1 and 2 appear on the shorter side than copolymer polyester A1, indicating that components with slightly increased molecular weights were also produced by kneading. These results indicate the presence of a 4,4'-methylenebis(N,N-diglycidylaniline) component that reacts with the decomposed polyester. The results of Comparative Examples 1 and 2 shown in FIG. 1B indicate that comparative crosslinkable polyester compositions 1 and 2 have a longer elution time than copolymer polyester A1, indicating a lower molecular weight. These results demonstrate that DBU induces decomposition of the polyester main chain during kneading. The results of Comparative Example 3 shown in FIG. 1C indicate that comparative crosslinkable polyester composition 3 did not exhibit significant changes in molecular properties compared to copolymer polyester A1. The results show that no decomposition of 4,4'-methylenebis(N,N-diglycidylaniline) was observed during kneading, and no reaction with epoxy groups occurred.

[0080] Next, the adhesive properties of crosslinkable polyester compositions 3 and 4 were evaluated. Crosslinkable polyester compositions 3 and 4 were sandwiched between Teflon (registered trademark) sheets and pressed in a heat press at 180°C and 2 MPa for 2 minutes to form a sheet. Two aluminum pieces were prepared as substrates, and crosslinkable polyester compositions 3 and 4 were sandwiched between the two aluminum pieces. The two pieces were pressed in a heat press at 180°C and 2 MPa for 5 minutes, and then heated in an oven at 180°C for 3 hours to obtain test piece a. Two polyethylene terephthalate films (PET films) were prepared as substrates, and crosslinkable polyester compositions 3 and 4 were sandwiched between the two PET films. The two pieces were pressed in a heat press at 180°C and 2 MPa for 5 minutes, and then heated in an oven at 180°C for 3 hours to obtain test piece b. The heated test pieces a and b were allowed to cool to room temperature, and then touched with the hand to evaluate whether the substrates were adhered.

[0081] As a result of the evaluation, when crosslinkable polyester composition 3 was used, adhesion was achieved to both the aluminum piece and the PET film. When crosslinkable polyester composition 4 was used, adhesion was achieved to both the aluminum piece and the PET film.

[0082] Next, the crosslinkable polyester composition or the comparative crosslinkable polyester composition was heated and the change in viscoelasticity was measured to investigate the crosslinking reaction. Specifically, the crosslinkable polyester composition or the comparative crosslinkable polyester composition was heated and subjected to isothermal time-resolved viscoelasticity measurement according to the following procedure.

[0083] [Isothermal time-resolved viscoelasticity measurement] The crosslinkable polyester composition or the comparative crosslinkable polyester composition was heated at 180°C for 3 hours, and isothermal time-resolved viscoelasticity measurement was performed. In the isothermal time-resolved viscoelasticity measurement, the change in storage modulus (G') and the change in loss modulus (G'') with respect to heating time were measured. The measurement device used was an MCR102 manufactured by Anton Paar. The jig used was an aluminum disposable jig with a diameter of 8 mm. The test specimen had a diameter of 8 mm and a thickness of approximately 0.5 mm. The measurement was performed in a nitrogen gas atmosphere.

[0084] The isothermal, time-resolved viscoelastic spectrum measured for crosslinkable polyester composition 1 is shown in Figure 2A. The isothermal, time-resolved viscoelastic spectrum measured for crosslinkable polyester composition 2 is shown in Figure 2B. The isothermal, time-resolved viscoelastic spectrum measured for comparative crosslinkable polyester composition 1 is shown in Figure 2C. The isothermal, time-resolved viscoelastic spectrum measured for comparative crosslinkable polyester composition 3 is shown in Figure 2D. In Figures 2A to 2D, the horizontal axis represents time (seconds), and the vertical axis represents storage modulus (G') or loss modulus (G'').

[0085] In measurements at constant temperature and frequency, the progress of the crosslinking reaction during heating can be tracked based on the storage modulus (G') and loss modulus (G''). At temperatures well above the glass transition temperature of the crosslinkable polyester composition, if crosslinking is insufficient, G'' > G', but as crosslinking progresses with heating, G' increases, and after a certain time has passed, G' = G''. The time at which G' = G'' can be simply determined as the gelation time, and the time scale for crosslinking progress under certain temperature conditions can be evaluated. As heating time continues, G'' < G', and in this region, crosslinking can be considered to have progressed sufficiently.

[0086] As is clear from FIG. 2A , the crosslinkable polyester composition 1 showed a significant increase in G' over time, reaching the gel point where G' = G'' approximately 100 seconds after the start of heating. This result indicates that decomposition of the copolymer polyester A1 chains and the reaction with 4,4'-methylenebis(N,N-diglycidylaniline) progressed, resulting in the formation of a network structure. In this system, hydroxyl groups and carboxylic acid groups produced by decomposition react with 4,4'-methylenebis(N,N-diglycidylaniline), causing an epoxy ring-opening reaction, and further, a bond exchange reaction occurs between the hydroxyl groups produced by the epoxy ring-opening reaction and the chains of copolymer polyester A1, which is thought to lead to network growth.

[0087] As is clear from FIG. 2B , G' of crosslinkable polyester composition 2 increased over time, and reached the gel point, where G' = G'', approximately 1,000 seconds after the start of heating. This result indicates that decomposition of the copolymer polyester A1 chains and reaction with 4,4'-methylenebis(N,N-diglycidylaniline) progressed, resulting in the formation of a network structure. In this system, hydroxyl groups and carboxylic acid groups produced by decomposition react with 4,4'-methylenebis(N,N-diglycidylaniline), causing an epoxy ring-opening reaction, and further, a bond exchange reaction occurs between the hydroxyl groups produced by the epoxy ring-opening reaction and the chains of copolymer polyester A1, which is thought to lead to network growth.

[0088] 2A and 2B, it can be seen that the amount of 4,4'-methylenebis(N,N-diglycidylaniline) blended affects the time it takes for gelation to progress. It is believed that gelation progresses in a short period of time when the blending amount of 4,4'-methylenebis(N,N-diglycidylaniline) is 10 parts. Furthermore, after heating at 180°C for 3 hours, the storage modulus (G') of Crosslinkable Polyester Composition 1 was 0.81 MPa, and the storage modulus (G') of Crosslinkable Polyester Composition 2 was 0.013 MPa.

[0089] As is clear from these results, the amount of 4,4'-methylenebis(N,N-diglycidylaniline) added affects the crosslink density of the crosslinked polyester composition. It is believed that the crosslink density increases when the amount of 4,4'-methylenebis(N,N-diglycidylaniline) added is 10 parts.

[0090] 2C, the loss modulus (G") of the comparative crosslinkable polyester composition 1 remained almost constant over time, but the storage modulus (G') decreased over time. The comparative crosslinkable polyester composition 1 is an example that does not contain a polyfunctional epoxy compound having multiple epoxy groups, and this indicates that the polyester is slowly decomposed during heating due to the action of DBU.

[0091] 2D, the loss modulus (G") of comparative crosslinkable polyester composition 3 remained almost constant over time, but the storage modulus (G') increased over time. Comparative crosslinkable polyester composition 3 is an example that does not contain a transesterification catalyst, and it was found that the molecular weight of the polyester gradually increased during heating due to the reaction between copolymer polyester A1 and 4,4'-methylenebis(N,N-diglycidylaniline).

[0092] As is clear from FIGS. 2C and 2D, no gel point where G'=G'' was detected, and it is believed that the crosslinking reaction did not proceed even when heated at 180°C.

[0093] Next, the crosslinkable polyester composition or the comparative crosslinkable polyester composition was heated, and the gel fraction of the resulting sample (crosslinked polyester composition) was measured.

[0094] [Measurement of gel fraction] Crosslinkable polyester compositions 1 and 2 were heated at 180°C to prepare samples (crosslinked polyester compositions). The heating time was 3, 6, 12, or 24 hours. The obtained samples were immersed in a solvent (tetrahydrofuran) for 24 hours, and the procedure of exchanging the solvent was repeated three times. After the three cycles, the samples were taken out and dried in vacuum, and then the dry weight (m ｄ The initial weight (m ｉ ) compared with the gel fraction (f ｇｅｌ ) was calculated based on the following formula: ｇｅｌ (%) = m ｄ / m ｉ ×100

[0095] Furthermore, crosslinkable polyester compositions 3 to 5 and comparative crosslinkable polyester compositions 4 and 5 were heated at 180°C, and the gel fractions of the resulting samples (crosslinked polyester compositions) were calculated. The heating time was 3 hours, 6 hours, or 12 hours. For comparative crosslinkable polyester compositions 4 and 5, samples were prepared under the same conditions as above, except that hexafluoroisopropanol (HFIP) was used instead of tetrahydrofuran as the solvent in which the heated samples were immersed, and the gel fractions were calculated.

[0096] The calculated gel fractions are shown in Table 2. In Table 2, the results of measuring the gel fraction of the crosslinkable polyester composition itself before heating are also shown in the column for heating time 0 hours. In the examples in which DBU was used as the transesterification catalyst, the weight of DBU was calculated based on the initial weight (m ｉ ) was excluded.

[0097] The gel fractions calculated for Samples 1 and 2 (Crosslinked Polyester Compositions 1 and 2) produced from Crosslinkable Polyester Compositions 1 and 2 are shown in Figure 3. In Figure 3, the horizontal axis represents the heating time (hours) and the vertical axis represents the gel fraction (%). In Figure 3, ● (black circle) represents the result for Sample 1 obtained by heating Crosslinkable Polyester Composition 1, and ▲ (black triangle) represents the result for Sample 2 obtained by heating Crosslinkable Polyester Composition 2.

[0098] As is clear from FIG. 3 , heating crosslinkable polyester composition 1 at 180°C for 3 hours yielded crosslinked polyester composition 1 with a high gel fraction of 85-90%. However, extending the heating time beyond 3 hours did not significantly change the gel fraction of the resulting crosslinked polyester composition 1. Heating crosslinkable polyester composition 2 at 180°C for 3 hours yielded crosslinked polyester composition 2 with a gel fraction of approximately 30%. The gel fraction of crosslinked polyester composition 2 remained at approximately 30%, indicating slower crosslinking compared to Example 1. This result is consistent with the results of the viscoelasticity measurement described above. Although the gel fraction of crosslinkable polyester composition 2 increased with increasing heating time, the gel fraction of crosslinked polyester composition 2 remained at approximately 55% even after 24 hours of heating. From these results, it was found that the amount of 4,4'-methylenebis(N,N-diglycidylaniline) is an important factor in the progress of crosslinking of the crosslinkable polyester composition, affects the gel fraction of the crosslinked polyester composition, and that the gel fraction of the crosslinked polyester composition increases when the amount of 4,4'-methylenebis(N,N-diglycidylaniline) is set to 10 parts.

[0099] Next, for crosslinkable polyester composition 1, samples (crosslinked polyester compositions) were prepared under the same conditions as above, except that the heating temperature was 120°C, 140°C, or 160°C instead of 180°C, and the heating time was 3 hours, and the gel fractions were measured. The measured gel fractions are shown in Table 3.

[0100]

[0101] As is clear from Tables 2 and 3, when the crosslinkable polyester composition 1 obtained in Example 1 was heated at 180°C for 3 hours, a crosslinked polyester composition having a gel fraction of 85 to 90% was obtained, whereas when the heating temperature was lowered, the gel fraction of the crosslinked polyester composition decreased.

[0102] Next, the crosslinkable polyester composition 1 was heated to crosslink it, and the bond exchange properties of the resulting sample (crosslinked polyester composition) were evaluated based on the results of stress relaxation measurement and remolding test.

[0103] [Stress Relaxation Measurement] For the stress relaxation measurement, an MCR102 manufactured by Anton Paar was used as the measuring device. A disposable aluminum jig with a diameter of 8 mm was used as the jig. A test piece was prepared using a sample (crosslinked polyester composition) obtained by heating the crosslinkable polyester composition 1 at 180°C for 3 hours. The test piece had a diameter of 8 mm and a thickness of approximately 0.5 mm. The measurement temperature was 170°C, 180°C, 190°C, or 200°C. The measurement was carried out in a nitrogen gas atmosphere. The measured stress relaxation spectrum is shown in Figure 4. In Figure 4, the horizontal axis represents time (seconds) and the vertical axis represents the initial stress (σ ０ ) normalized by stress (σ / σ ０ The curves shown in FIG. 4 show the results of measurements at 190° C., 180° C., 170° C., and 160° C., in that order from the left.

[0104] As is clear from FIG. 4, significant stress relaxation was observed, and this result confirmed the progress of bond exchange via a bond exchange reaction at high temperatures.

[0105] [Remolding Test] In the remolding test, a flat test piece (film thickness 1 mm) cut into a strip shape from a sample (crosslinked polyester composition) obtained by heating Crosslinkable Polyester Composition 1 at 180°C for 3 hours was wrapped around a glass tube, both ends of which were secured with tape, and fixed to a spatula, as shown in Figure 5A. The test piece fixed to the spatula was heated in an oven at 180°C for 1 hour. After heating for 1 hour, the test piece was allowed to cool to room temperature, and the tape was removed. The test piece was fixed into a curved shape as shown in Figure 5B. The curved test piece did not return to its original flat shape even when heated with a hair dryer. The remolding of the sample is thought to be due to the activation of bond exchange at the high temperature of 180°C, which caused the elasticity to be lost, and a new network structure to be fixed after cooling.

[0106] From the above results, it is believed that by heating the sample (crosslinked polyester composition) at 180°C, the formation of a crosslinked structure and the introduction of bond exchange properties were confirmed, and material conversion from the crosslinkable polyester composition was achieved.

Claims

1. A method for producing a crosslinkable polyester composition, comprising the step of kneading a multifunctional epoxy compound having a plurality of epoxy groups and an ester exchange catalyst with a heated and molten copolymer polyester.

2. A method for producing the crosslinkable polyester composition according to claim 1, further comprising a step of forming the composition into a predetermined shape after the kneading.

3. The method for producing a crosslinkable polyester composition according to claim 1, wherein the copolyester is an amorphous polyester.

4. The method for producing a crosslinkable polyester composition according to claim 1, wherein the copolyester contains a first unit consisting of ethylene terephthalate or butylene terephthalate, and further contains at least one component selected from the following group as an acid component and / or alcohol component: Acid component: terephthalic acid, isophthalic acid, sebacic acid Alcohol component: ethylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol.

5. The method for producing a crosslinkable polyester composition according to claim 1, wherein the transesterification catalyst is a catalyst that does not contain a hydroxyl group.

6. The method for producing a crosslinkable polyester composition according to claim 1, wherein the kneading is carried out at a temperature equal to or lower than the glass transition temperature (Tg) of the copolymer polyester + 120°C.

7. The method for producing a crosslinkable polyester composition according to claim 1, wherein the kneading is carried out in a solvent-free state.

8. The method for producing a crosslinkable polyester composition according to claim 1, wherein the kneading is carried out using a twin-screw kneading extruder.

9. The method for producing a crosslinkable polyester composition according to claim 8, wherein a sheet- or film-shaped molded article containing the crosslinkable polyester composition is extruded from the twin-screw kneading extruder.

10. A method for producing a crosslinked polyester composition, comprising producing a crosslinkable polyester composition by the method of claim 1, and then heating the crosslinkable polyester composition to crosslink it.

11. The method for producing a crosslinked polyester composition according to claim 10, wherein the crosslinking of the crosslinkable polyester composition is carried out by heating at a temperature exceeding the kneading temperature.

12. The method for producing a crosslinked polyester composition according to claim 10, wherein the crosslinking of the crosslinkable polyester composition is carried out by heating at a temperature of 120°C to 250°C for 1 hour or more.

13. A molded article comprising a crosslinkable polyester composition which comprises a copolymer polyester, a polyfunctional epoxy compound having a plurality of epoxy groups, and an ester exchange catalyst, has a gel fraction of less than 30%, and is in the form of a rod, thread, granule, or flake.

14. A molded article comprising a crosslinkable polyester composition which comprises a copolymer polyester, a polyfunctional epoxy compound having multiple epoxy groups, and an ester exchange catalyst, and which is in the form of a sheet or film having a gel fraction of less than 30% and a thickness of 20 μm or more.

15. A molded article comprising the crosslinkable polyester composition according to claim 13 or 14, which has a gel fraction of 30% or more after heating at a temperature of 120°C to 250°C for 3 hours.

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