Method for producing polyester resin, method for reducing tetrahydrofuran in polyester resin, molded article, method for producing molded article, and method for reducing tetrahydrofuran in molded article

Abstract

To provide a polyester resin having a reduced THF content and a method for producing the same.SOLUTION: The polyester resins contain a first copolymer having acid components containing terephthalic acids of 50mol% or more and dimer acids of 2 to 50mol% of the total amount of the acid components, and alcohol components containing 1, 4-butanediol of 50mol% or more of the total amount of the alcohol components, and the reduction ratio of the THF outgas generation amount of the following numerical expression (1) is 99.78% or more. In the equation, the "amount of THF outgas generated before heating" and the "amount of THF outgas generated after heating" are values measured by head space gas chromatography after resins before and after heating at 120 °C. for 12 hours under the pressure of the 280Pa are sealed in bottles and held at 150 °C. for 1 hour.SELECTED DRAWING: None

Description

Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2023-140521, filed on August 30, 2023, and incorporates all of the contents of that Japanese application by reference. [Technical Field]

[0002] The present disclosure relates to a polyester resin and a method for producing the same, as well as a molded article and a method for producing the same. [Background technology]

[0003] Polybutylene terephthalate (sometimes referred to as "PBT" in this disclosure) and polybutylene naphthalate (sometimes referred to as "PBN" in this disclosure) are used in a variety of applications, such as electrical and electronic equipment components, automotive components, and packaging materials.

[0004] When PBT and PBN are produced, tetrahydrofuran (sometimes referred to as "THF" in this disclosure) remains as a by-product in the produced resin. The remaining THF is released as outgassing. The released THF outgassing can adversely affect the processing of electrical and electronic equipment components, reduce the durability of automotive components, and contaminate packaged items. Furthermore, THF outgassing can also be harmful to the health of workers.

[0005] In the automobile interior trim described in Patent Document 1, a copolymer of ethene and (2-ethyl)hexyl acrylate is mixed with PBT to reduce the amount of THF outgassing.

[0006] In Patent Document 2, a biaxially stretched film containing modified PBT, which is obtained by copolymerizing PBT with polytetramethylene glycol, and polyethylene terephthalate is used to reduce the amount of THF outgassing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2022-543761 [Patent Document 2] International Publication No. 2011 / 162198 Summary of the Invention [Problem to be solved by the invention]

[0008] The THF content in PBT cannot be reduced by the method described in Patent Document 1. The modified PBT described in Patent Document 2 generates 220 μg / g or more of THF outgassing, and the reduction in the THF content is insufficient.

[0009] Therefore, there is a demand for polyester resins with a reduced THF content. [Means for solving the problem]

[0010] According to a first aspect of the present disclosure, there is provided a polyester resin that is a first copolymer obtained by polymerizing acid components including 50 mol% or more of an aromatic dicarboxylic acid component and 2 mol% to 50 mol% of a dimer acid component, based on the total amount of the acid components, and an alcohol component including 50 mol% or more of a 1,4-butanediol component, based on the total amount of the alcohol components. When the first copolymer is heated at 150°C for 1 hour, 1 μg or less of tetrahydrofuran is generated per 1 g of the first copolymer.

[0011] According to a second aspect of the present disclosure, there is provided a method for producing a polyester resin, including: a first step of preparing a first copolymer obtained by polymerizing acid components including 50 mol% or more of an aromatic dicarboxylic acid component and 2 mol% to 50 mol% of a dimer acid component, based on the total amount of the acid components, and alcohol components including 50 mol% or more of a 1,4-butanediol component, based on the total amount of the alcohol components; and a second step of heat-treating the first copolymer at a temperature of 66°C or higher and a melting point of the first copolymer or lower, under a pressure of 4,000 Pa or lower.

[0012] According to a third aspect of the present disclosure, there is provided a molded article containing the polyester resin according to the first aspect.

[0013] According to a fourth aspect of the present disclosure, there is provided a molded article comprising 5% by mass to 70% by mass of the polyester resin according to the first aspect and 30% by mass to 95% by mass of a second copolymer. The second copolymer is a polyester resin containing at least one alcohol component selected from the group consisting of 1,4-butanediol and polytetramethylene glycol. When the molded article is heated at 150°C for 1 hour, 50 μg or less of tetrahydrofuran is generated per 1 g of the molded article.

[0014] A fifth aspect of the present disclosure provides a method for producing a molded product, including: a first step of preparing a first copolymer obtained by polymerizing acid components including 50 mol% or more of an aromatic dicarboxylic acid component and 2 mol% to 50 mol% of a dimer acid component relative to the total amount of the acid components, and an alcohol component including 50 mol% or more of a 1,4-butanediol component relative to the total amount of the alcohol components; a second step of heat-treating the first copolymer at a temperature of 66°C or higher and a melting point of the first copolymer at a pressure of 4,000 Pa or lower; and a third step of molding a mixture of 5% to 95% by mass of the first copolymer and 5% to 95% by mass of the second copolymer. The second copolymer is a polyester resin including at least one alcohol component selected from the group consisting of 1,4-butanediol and polytetramethylene glycol. [Effects of the Invention]

[0015] The polyester resin of the present disclosure has a low residual THF content. Therefore, the amount of THF outgassing to which workers are exposed when using the polyester resin of the present disclosure can be reduced. Furthermore, deterioration in the quality of applied products due to the generation of THF outgassing from the polyester resin can be suppressed. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a flowchart illustrating a method for producing a polyester resin according to the present disclosure. [Figure 2] FIG. 2 is a flowchart showing a method for producing a molded article according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] According to a preferred embodiment of the first aspect, when the first copolymer that has not been subjected to a heat treatment at 50°C or higher is heated at 150°C for 1 hour, tetrahydrofuran is generated in an amount of 1 μg or less per 1 g of the copolymer.

[0018] According to a preferred embodiment of the first aspect, when the first copolymer is heated at 150° C. for 1 hour, the amount of tetrahydrofuran generated is 0.5 μg or less per 1 g of the copolymer.

[0019] According to a preferred embodiment of the first aspect, the acid component comprises a terephthalic acid component and a dimer acid component, or a 2,6-naphthalenedicarboxylic acid component and a dimer acid component. The alcohol component comprises a 1,4-butanediol component.

[0020] According to a preferred embodiment of the first aspect, the dimer acid component has at least one carbon atom selected from the group consisting of 44 and 36 carbon atoms.

[0021] According to a preferred embodiment of the second aspect, the heat treatment is carried out for 6 to 100 hours.

[0022] According to a preferred embodiment of the second aspect, the second step is carried out before the first copolymer is heat-treated to 50° C. or higher.

[0023] According to a preferred embodiment of the second aspect, the acid component comprises a terephthalic acid component and a dimer acid component, or a 2,6-naphthalenedicarboxylic acid component and a dimer acid component, and the alcohol component comprises a 1,4-butanediol component.

[0024] According to a preferred embodiment of the second aspect, the dimer acid component has at least one carbon atom selected from the group consisting of 44 and 36 carbon atoms.

[0025] According to a preferred embodiment of the fourth aspect, the second copolymer generates 150 μg to 600 μg of tetrahydrofuran per 1 g of polyester resin when heated at 150° C. for 1 hour.

[0026] According to a preferred embodiment of the fourth aspect, the molded article has at least one shape selected from the group consisting of a sheet shape, a film shape, and a container shape.

[0027] According to preferred embodiments of the third and fourth aspects, there is provided a member for an electric / electronic device, which includes the molded article of the third and fourth aspects.

[0028] According to preferred embodiments of the third and fourth aspects, there are provided automobile members including the molded articles of the third and fourth aspects.

[0029] According to preferred embodiments of the third and fourth aspects, there is provided a packaging material including the molded article of the third and fourth aspects.

[0030] According to a preferred embodiment of the fifth aspect, in the third step, the mixture is formed into at least one shape selected from the group consisting of a sheet shape, a film shape, and a container shape.

[0031] In the present specification and claims, each acid component and each alcohol component may also include its derivatives. For example, an acid component may also include a derivative of the acid component (e.g., an ester).

[0032] A polyester resin according to a first embodiment of the present disclosure will be described. The polyester resin referred to in the present disclosure also includes molded articles thereof (for example, polyester films, containers, packaging, etc.). In the present disclosure, the polymer may also include copolymers composed of two or more types of monomer components, and cross-linked polymers (crosspolymers).

[0033] The polyester resin of the present disclosure can be in various forms, such as pellets, sheets, films, containers, and packaging.

[0034] The pellets are obtained by cutting the produced strand-shaped polyester resin into particles. The mass of 100 pellets can be, for example, 2 g to 3 g.

[0035] In this disclosure, a sheet refers to a molded product having a shape that is thinner than the dimensions in other directions. In this disclosure, a film refers to a molded product having an extremely thin shape obtained by subjecting a sheet to a heat-stretching process.

[0036] Hereinafter, the total amount of a component may refer to the total number of moles of the monomers that form the basis of that component.

[0037] The polyester resin according to the first embodiment is a first copolymer obtained by polymerizing (A) an acid component and (B) an alcohol component, and has PBT or PBN as its main structure.

[0038] In the present disclosure, the (A) acid component may include a polycarboxylic acid component, which is a compound having multiple carboxy groups and / or a derivative thereof, and the (B) alcohol component may include a polyol component, which is a compound having multiple hydroxy groups (a polyhydroxy compound) and / or a derivative thereof.

[0039] [(A) Acid component] The (A) acid component includes an aromatic dicarboxylic acid component and a dimer acid component. Examples of aromatic dicarboxylic acid components include terephthalic acid components, isophthalic acid components, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 1,4-naphthalenedicarboxylic acid components, 2,6-naphthalenedicarboxylic acid components, 4,4'-diphenyldicarboxylic acid components, 9,9-bis(2-carboxyethyl)fluorene components, etc. Among these, terephthalic acid components and 2,6-naphthalenedicarboxylic acid components are particularly preferred.

[0040] The aromatic dicarboxylic acid component can be, for example, 50 mol% or more, 55 mol% or more, 60 mol% or more, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more relative to the total amount of component (A). If the aromatic dicarboxylic acid component is less than 50 mol%, the properties of the resulting polyester resin will be lost. The aromatic dicarboxylic acid component can be, for example, 98 mol% or less, 95 mol% or less, 92 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, or 65 mol% or less relative to the total amount of component (A).

[0041] Dimer acid is a dicarboxylic acid compound obtained by dimerizing unsaturated fatty acids having 10 to 30 carbon atoms. The dimer acid is at least one selected from the group consisting of dimeric dicarboxylic acids having 36 and 44 carbon atoms obtained by dimerizing unsaturated fatty acids having 18 carbon atoms, such as oleic acid and linoleic acid, and unsaturated fatty acids having 22 carbon atoms, such as erucic acid, and their ester-forming derivatives. Dimer acids in which the unsaturated double bonds remaining after dimerization are saturated by hydrogenation are called hydrogenated dimer acids. Hydrogenated dimer acids are preferred in terms of reaction stability, flexibility, impact resistance, and the like. Dimer acids are typically obtained as a mixture of compounds having a linear branched structure, an alicyclic structure, and the like. The contents of these compounds vary depending on the production process, but are not particularly limited. Among these, dimer acids having 44 carbon atoms are preferred because they can significantly reduce the amount of THF outgassing.

[0042] The dimer acid component may be, for example, 2 mol% or more, 5 mol% or more, 8 mol% or more, 10 mol% or more, 15 mol% or more, 20 mol% or more, 25 mol% or more, 30 mol% or more, or 35 mol% or more relative to the total amount of component (A). If the dimer acid component is less than 2 mol%, the amount of THF outgassing from the polyester resin will be large. The dimer acid component is preferably 50 mol% or less relative to the total amount of component (A). The dimer acid component may be, for example, 45 mol% or less, 40 mol% or less, 35 mol% or less, 30 mol% or less, 25 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, or 5 mol% or less relative to the total amount of component (A). If the dimer acid component exceeds 50 mol%, the heat resistance of the polyester resin will be reduced.

[0043] The (A) acid component may contain an acid component other than an aromatic dicarboxylic acid component and a dimer acid component, as long as the essential properties of the polyester resin of the present disclosure are not altered. Examples of other acid components include aliphatic dicarboxylic acid components such as succinic acid, glutaric acid, adipic acid, pyremic acid, suberic acid, azelaic acid, and sebacic acid; and alicyclic dicarboxylic acid components such as 1,2-, 1,3-, and 1,4-cyclohexanedicarboxylic acid and 1,4-, 1,5-, 2,6-, and 2,7-decahydronaphthalenedicarboxylic acid. These acid components may be used alone or in combination of two or more.

[0044] In the acid component of the first copolymer, the total amount of the aromatic dicarboxylic acid component and the dimer acid component can be 100 mol % relative to the total amount of the component (A).

[0045] [(B) Alcohol component] (B) The alcohol component includes a 1,4-butanediol component.

[0046] The 1,4-butanediol component is preferably 50 mol% or more, more preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more, based on the total amount of component (B). The 1,4-butanediol component can be 95 mol% or less, 90 mol% or less, or 85 mol% or less, based on the total amount of component (B). The 1,4-butanediol component can be 100 mol% based on the total amount of component (B). If the 1,4-butanediol component is less than 50 mol%, the properties of PBT or PBN will be lost.

[0047] The (B) alcohol component may contain components other than the 1,4-butanediol component, provided that the essential properties of the polyester resin of the present disclosure are not altered. Examples of other alcohol components include ethylene glycol, 1,4-cyclohexanedimethanol, propylene glycol, hexanediol, octanediol, decanediol, ethylene oxide-added bisphenol A, ethylene oxide-added bisphenol S, and trimethylolpropane. These alcohol components may be used alone or in combination of two or more.

[0048] The polyester resin of the present disclosure may contain known additives to the extent that the essential properties of the polyester resin of the present disclosure are not altered. Examples of additives that can be used include polymerization catalysts, antistatic agents, UV absorbers, heat stabilizers, light stabilizers, release agents, antioxidants, lubricants, plasticizers, pigments, and dyes.

[0049] The amount of THF outgassing from the polyester resin according to the first embodiment is 1 μg or less (1 ppm or less) per gram of polyester resin when the polyester resin is heated at 150°C for 1 hour in a state where it has not been subjected to a melting treatment after production, for example, in the form of pellets, preferably 0.8 μg or less, more preferably 0.5 μg or less, even more preferably 0.4 μg or less, particularly preferably 0.3 μg or less, even more particularly preferably 0.2 μg or less, and even more particularly preferably 0.1 μg or less.

[0050] The amount of THF outgassing from the polyester resin according to the first embodiment is even lower in a molded state, such as a sheet formed by melt extrusion of pellets, or a film formed by heat-stretching a sheet, than in a pellet state. For example, when heated at 150°C for 1 hour, the amount of THF outgassing from the molded product can be 0.2 μg or less (0.2 ppm or less), preferably 0.1 μg or less (0.1 ppm or less), and more preferably below the detection limit, per 1 g of the molded product.

[0051] The amount of THF outgassing generated from the polyester resin of the present disclosure can be measured, for example, by a headspace method.

[0052] The polyester resin of the present disclosure has a reduced amount of THF outgassing. This can reduce environmental pollution and adverse effects on worker health. Furthermore, it can prevent quality degradation of products using the polyester of the present disclosure due to THF outgassing.

[0053] For example, when the polyester resin of the present disclosure is used as a release agent in semiconductor manufacturing, the amount of THF outgassing is small, thereby improving the adhesion between the base film and the release layer. Furthermore, in the semiconductor manufacturing process, the interference with the soldering process due to THF outgassing can be reduced. Furthermore, the adverse effect of THF outgassing on the quality of the semiconductor itself can also be reduced.

[0054] The polyester resin of the present disclosure exhibits little bleed-out, excellent stability over time, and moldability, and therefore can be used in a wide range of molding materials, such as electrical and electronic equipment components, automotive components, and packaging materials.

[0055] The polyester resin of the present disclosure has excellent transparency and flexibility, as well as high heat resistance.

[0056] The polyester resin according to the first embodiment can be mixed with other polyester resins and used as a modifier for reducing the amount of THF outgassing. For example, as shown in the third and fourth embodiments described below, by molding a mixture of a polyester resin containing THF and the polyester resin according to the first embodiment to produce a molded product, the amount of THF outgassing from the molded product can be reduced.

[0057] In the polyester resin of the present disclosure, the molecular structure, crystalline structure, etc. may be unknown, and it may be impossible or impractical to directly identify the polyester resin of the present disclosure by its composition, structure, properties, etc. In such cases, it should be permitted to identify the polyester resin of the present disclosure by its manufacturing method.

[0058] As a second embodiment of the present disclosure, a method for producing a polyester resin according to the first embodiment will be described below. Fig. 1 shows a flowchart of the method for producing a polyester resin according to the second embodiment.

[0059] The method for producing a polyester resin according to the second embodiment can include a first step (S11) of preparing a first copolymer, and a second step (S12) of heat-treating the first copolymer obtained in the first step under reduced pressure.

[0060] The first copolymer prepared in the first step may be a commercially available polyester resin having the composition shown in the first embodiment. Hereinafter, a method for producing the first copolymer (polyester resin) as the first step will be described.

[0061] The first step is a step of polymerizing a monomer. That is, it is a step of polycondensing an acid and an alcohol. The polymerization in the first step is not particularly limited and can be carried out by a known polymerization method using a known catalyst. The method for producing the polyester resin before the second step may be either a method of direct esterification using an unsubstituted polycarboxylic acid as a starting material or a method of carrying out a transesterification reaction using an esterified product such as dimethyl ester as a starting material. In direct esterification, the temperature at which the polymerization reaction is carried out is high, resulting in decomposition of 1,4-butanediol and increased generation of THF outgas. Therefore, it is preferable to carry out a transesterification reaction using an esterified product of a polycarboxylic acid. When producing the polyester resin before the second step, in order to obtain a sufficient reaction rate, it is desirable to carry out a transesterification reaction under normal pressure using a known catalyst in the first step, and then carry out a polycondensation reaction under reduced pressure in the subsequent second step using a known catalyst.

[0062] The acid and alcohol used as raw materials for the polyester resin can be the above-mentioned compounds. The amounts of the acid and alcohol used can be appropriately determined depending on the contents of the acid component and alcohol component.

[0063] The transesterification reaction can be carried out, for example, by charging each compound used as a polymerization raw material and various other copolymerization components used as necessary into a reaction vessel equipped with a heater, a stirrer, and a distillation tube, adding a reaction catalyst, and raising the temperature while stirring under an inert gas atmosphere at normal pressure, and distilling off by-products such as methanol produced by the reaction. The reaction temperature can be 150°C to 230°C, preferably 160°C to 220°C. The reaction time can be about 3 to 7 hours.

[0064] It is desirable to use at least one metal compound as a catalyst for the transesterification reaction. Preferred metal elements include sodium, potassium, calcium, titanium, lithium, magnesium, manganese, zinc, tin, and cobalt. Among these, titanium compounds are preferred because they have high reactivity and produce a good color tone for the resulting resin. The amount of the transesterification catalyst used is preferably 5 ppm to 1,000 ppm, more preferably 10 ppm to 100 ppm, based on the polyester resin produced.

[0065] After the transesterification reaction is complete, it is desirable to add a phosphorus compound in an amount equal to or greater than the transesterification catalyst to further advance the esterification reaction. For example, it is desirable to carry out a transesterification reaction using an ester compound of terephthalic acid and 1,4-butanediol, and then add erucic acid together with the phosphorus compound to advance the esterification reaction, thereby producing a polyester resin. Examples of phosphorus compounds include phosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trimethyl phosphite, triethyl phosphite, and tributyl phosphite. Of these, trimethyl phosphate is particularly preferred. The addition rate of the phosphorus compound can be 5 ppm to 1,000 ppm, preferably 20 ppm to 100 ppm, based on the polyester resin produced.

[0066] Following the transesterification reaction, a polycondensation reaction can be further carried out until the desired molecular weight is achieved. The polycondensation reaction can be carried out, for example, by adding a polymerization catalyst to a reaction vessel containing the product obtained after the transesterification reaction, and then gradually increasing the temperature and reducing the pressure inside the reaction vessel. The pressure inside the vessel can be reduced from atmospheric pressure to 0.4 kPa or less, preferably 0.2 kPa or less. The temperature inside the vessel is increased from 220°C to 230°C, and finally to 220°C to 240°C, preferably 228°C to 235°C. After reaching a predetermined torque, the reaction product can be extruded from the bottom of the vessel and recovered. Typically, the reaction product is extruded into water in the form of a strand, cooled, and cut to obtain a pelletized polyester resin.

[0067] It is desirable to use at least one metal compound as a catalyst for the polycondensation reaction. Preferred metal elements include titanium, germanium, antimony, and aluminum. Among these, titanium compounds and germanium compounds are particularly preferred for producing optical resins because they are highly reactive and produce resins with excellent transparency and color tone. Titanium compounds are particularly reactive and less expensive than germanium compounds. Furthermore, titanium is not classified as a heavy metal, so titanium compounds can reduce environmental impact. The addition rate of the polymerization catalyst is preferably 30 ppm to 1,000 ppm, more preferably 50 ppm to 500 ppm, relative to the polyester resin to be produced.

[0068] The polyester resin of the present disclosure may be appropriately blended with various additives, such as antioxidants, heat stabilizers, lubricants, antistatic agents, plasticizers, UV absorbers, and pigments, depending on the application and molding purpose. These additives may be blended in either the polymerization reaction step or the processing and molding step. Examples of antioxidants include hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. Hindered phenol-based antioxidants are particularly preferred, with a preferred content of approximately 100 ppm to 5,000 ppm. When forming a melt-extrusion film, metal salts, such as magnesium acetate, calcium acetate, and magnesium chloride, may be added to stabilize the electrostatic adhesion of the cooling roll.

[0069] After the polycondensation reaction, a solid-state polymerization reaction may be carried out, which can increase the intrinsic viscosity of the polyester resin.

[0070] Next, in the second step, the polyester resin obtained in the first step is heat-treated under reduced pressure.

[0071] The pressure during the heat treatment is preferably 4,000 Pa or less, more preferably 3,000 Pa or less, even more preferably 2,000 Pa or less, even more preferably 1,000 Pa or less, particularly preferably 500 Pa or less, more particularly preferably 400 Pa or less, even more particularly preferably 300 Pa or less, most preferably 200 Pa or less, and even most preferably 100 Pa or less.

[0072] The heat treatment temperature is preferably 66°C or higher, more preferably 70°C or higher. The heat treatment temperature can be 80°C or higher, 90°C or higher, 100°C or higher, or 110°C or higher. The heat treatment temperature is preferably the melting point of the polyester resin or lower, more preferably 150°C or lower. If the heat treatment temperature exceeds the melting point of the resulting polyester resin, fusion of the polyester resin occurs.

[0073] The heat treatment time can be, for example, 6 hours or more, 10 hours or more, 20 hours or more, 30 hours or more, 40 hours or more, or 50 hours or more. The heat treatment time can be, for example, 100 hours or less, 90 hours or less, 80 hours or less, 70 hours or less, 60 hours or less, 50 hours or less, 40 hours or less, 30 hours or less, or 20 hours or less.

[0074] When the heat treatment temperature in the second step is less than 100° C., the heat treatment time is 20 hours or more, preferably 30 hours or more, more preferably 40 hours or more, and even more preferably 50 hours or more. When the heat treatment temperature in the second step is 100° C. or more, the heat treatment time is 6 hours or more, preferably 8 hours or more, and more preferably 10 hours or more.

[0075] In the second step, the polyester resin can be heat-treated in the form of pellets obtained in the first step, or in the form of a molded product such as a film. The second step is preferably carried out continuously from the first step in the form of pellets. By carrying out the heat treatment at an early stage, the risk of workers being exposed to THF outgassing can be reduced, and the decrease in mechanical strength and hydrolysis of the polyester resin due to THF outgassing can be suppressed. Furthermore, when the polyester resin of the present disclosure is blended with a resin with low resistance to THF outgassing, such as polypropylene or polycarbonate, adverse effects on the blended resin can be reduced.

[0076] The method for producing the polyester film of the present disclosure will be described.

[0077] The polyester film of the present disclosure can be produced according to a general polyester film production method. For example, a polyester resin is melted, and the non-oriented polyester is extruded into a sheet. The non-oriented polyester is stretched in the running direction at a temperature equal to or higher than the glass transition temperature by utilizing a roll speed difference, and then stretched in the width direction using a tenter and heat-treated. The thickness of the non-oriented polyester before stretching can be set taking into account the desired final polyester film thickness, stretching ratio, retardation of the resulting polyester film, etc.

[0078] According to the method for producing a polyester resin according to the second embodiment, a polyester resin that generates a small amount of THF outgassing during molding can be produced. In particular, the THF content in the polyester resin can be reduced before molding. This reduces the adverse effects of THF outgassing on workers handling the polyester resin of the present disclosure. Furthermore, it reduces the adverse effects of THF outgassing on products that use the polyester resin of the present disclosure.

[0079] A molded article according to a third embodiment of the present disclosure will be described.

[0080] The molded article according to the third embodiment of the present disclosure is a molded article containing a first copolymer, which is the polyester resin according to the first embodiment, and a second copolymer. The molded article can have at least one shape selected from the group consisting of a sheet shape, a film shape, and a container shape.

[0081] The above description is applicable to the polyester resin according to the first embodiment.

[0082] The second copolymer is a polyester resin having an acid component (C) and an alcohol component (D). The component (D) includes at least one selected from the group consisting of a 1,4-butanediol component and a polytetramethylene glycol component.

[0083] In the present disclosure, the (C) acid component may include a polycarboxylic acid component, which is a compound having multiple carboxy groups and / or a derivative thereof, and the (D) alcohol component may include a polyol component, which is a compound having multiple hydroxy groups (a polyhydroxy compound) and / or a derivative thereof.

[0084] [(C) Acid component] The (C) acid component includes at least one selected from the group consisting of a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component.

[0085] When the terephthalic acid component is the main component of component (C), the terephthalic acid component can be, for example, 50 mol% or more, 55 mol% or more, 60 mol% or more, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more relative to the total amount of component (C). If the terephthalic acid component is less than 50 mol%, the properties of polybutylene terephthalate will be lost. The terephthalic acid component can be, for example, 98 mol% or less, 95 mol% or less, 92 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, or 65 mol% or less relative to the total amount of component (C). Component (C) can be 100 mol% terephthalic acid component.

[0086] When 2,6-naphthalenedicarboxylic acid is the main component of component (C), the 2,6-naphthalenedicarboxylic acid component can be, for example, 50 mol% or more, 55 mol% or more, 60 mol% or more, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more relative to the total amount of component (C). If the 2,6-naphthalenedicarboxylic acid component is less than 50 mol%, the properties of polybutylene naphthalate are lost. The naphthalenedicarboxylic acid component can be, for example, 98 mol% or less, 95 mol% or less, 92 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, 70 mol% or less, or 65 mol% or less relative to the total amount of component (C). Component (C) can be 100 mol% 2,6-naphthalenedicarboxylic acid component.

[0087] The acid component (C) may contain an acid component other than a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component, as long as the essential properties of the polyester resin of the present disclosure are not altered. Examples of other acid components include aromatic dicarboxylic acid components such as isophthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 9,9-bis(2-carboxyethyl)fluorene; aliphatic dicarboxylic acid components such as succinic acid, glutaric acid, adipic acid, pyremic acid, suberic acid, azelaic acid, and sebacic acid; and alicyclic dicarboxylic acid components such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, and 2,7-decahydronaphthalenedicarboxylic acid. These acid components may be used alone or in combination.

[0088] The total amount of the (C) acid component consisting of at least one of a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component and other acid components can be 100 mol %.

[0089] [(D) Alcohol component] The (D) alcohol component includes at least one selected from the group consisting of a 1,4-butanediol component and a polytetramethylene glycol component.

[0090] The 1,4-butanediol component is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more, based on the total amount of component (D). The 1,4-butanediol component can be 95 mol% or less, 90 mol% or less, or 85 mol% or less, based on the total amount of component (D). The 1,4-butanediol component can be 100 mol% based on the total amount of component (D). If the 1,4-butanediol component is less than 80 mol%, the properties of PBT or PBN will be lost.

[0091] The polytetramethylene glycol component may be 5 mol% or more, 10 mol% or more, or 15 mol% or more, based on the total amount of component (D).The polytetramethylene glycol component may be 30 mol% or less, 25 mol% or less, 20 mol% or less, 15 mol% or less, or 10 mol% or less, based on the total amount of component (D).

[0092] When component (D) contains a polytetramethylene glycol component, the remainder of component (D) can be a 1,4-butanediol component.

[0093] The (D) alcohol component may contain alcohol components other than a 1,4-butanediol component and a polytetramethylene glycol component, as long as the essential properties of the polyester resin of the present disclosure are not altered. Examples of other alcohol components include an ethylene glycol component, a 1,4-cyclohexanedimethanol component, a propylene glycol component, a hexanediol component, an octanediol component, a decanediol component, an ethylene oxide-added bisphenol A component, an ethylene oxide-added bisphenol S component, and a trimethylolpropane component. These other alcohol components may be used alone or in combination of two or more.

[0094] Examples of the second copolymer include polybutylene terephthalate, polybutylene naphthalate, polybutylene terephthalate copolymerized with isophthalic acid, polybutylene terephthalate copolymerized with polytetramethylene glycol, and polyethylene terephthalate copolymerized with polytetramethylene glycol.

[0095] The amount of THF outgassing from the second copolymer can be 100 μg or more or 200 μg or more per 1 g of the second copolymer when the second copolymer (polyester resin) has not been subjected to a heat treatment at 50° C. or higher since its production and is in a state before being mixed with the first copolymer, for example, when the second copolymer is in the form of pellets. The amount of THF outgassing from the second copolymer can be 3,000 μg or less or 2,000 μg or less per 1 g of the second copolymer when the second copolymer (polyester resin) has not been subjected to a heat treatment at 50° C. or higher since its production and is in the state before being mixed with the first copolymer, for example, when the second copolymer is in the form of pellets. The second copolymer preferably generates 150 μg to 600 μg of tetrahydrofuran per 1 g of the second copolymer when heated at 150° C. for 1 hour.

[0096] In the molded article according to the third embodiment, the content of the first copolymer may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, relative to the mass of the molded article according to the third embodiment. The content of the first copolymer may be 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, relative to the mass of the molded article according to the third embodiment.

[0097] In the molded article according to the third embodiment, the second copolymer may be present in an amount of 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more relative to the mass of the molded article according to the third embodiment. The second copolymer may be present in an amount of 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or more relative to the mass of the molded article according to the third embodiment.

[0098] In the molded article according to the third embodiment, the total amount of the first copolymer and the second copolymer can be 100% by mass.

[0099] The amount of THF outgassing from the molded body according to the third embodiment, when the molded body is heated at 150°C for 1 hour, is 50 μg or less (50 ppm or less) per gram of molded body, preferably 40 μg or less, more preferably 30 μg or less, even more preferably 20 μg or less, particularly preferably 10 μg or less, even more particularly preferably 5 μg or less, and most preferably below the detection limit.

[0100] The molded article according to the third embodiment may contain known additives to the extent that they do not change the essential properties of the molded article according to the third embodiment. Examples of additives that can be used include polymerization catalysts, antistatic agents, ultraviolet absorbers, heat stabilizers, light stabilizers, mold release agents, antioxidants, lubricants, plasticizers, pigments, and dyes.

[0101] The molded article according to the third embodiment exhibits reduced THF outgassing even when a second copolymer containing a large amount of THF is mixed in. When a second copolymer containing at least one selected from the group consisting of 1,4-butanediol and polytetramethylene glycol is produced by a conventional method, it will contain by-produced THF. However, when the first copolymer and the second copolymer are mixed and molded, the THF can be removed during molding. This reduces the amount of THF outgassing from the molded article according to the third embodiment.

[0102] The molded article according to the third embodiment can be used, for example, as a member for electric / electronic devices, a member for automobiles, or a packaging material.

[0103] Examples of electrical and electronic equipment components include release films used in the production of various electrical and electronic equipment components; protective films used in various electrical and electronic equipment components; and various electrical and electronic equipment molded products such as switches, touch panels, sensors, and connectors.

[0104] Examples of automotive parts include interior parts such as instrument panels, consoles, door trims, headrests, tool boxes, luggage boxes, and sun visors; exterior parts such as bumpers, rear spoilers, front lids, and fenders; decorative films for interior and exterior parts; and protective films for interior and exterior parts.

[0105] Examples of packaging materials include various packaging films for container packaging, food packaging, pharmaceutical packaging, industrial chemical packaging, precision electronic component packaging, and agricultural chemical packaging.

[0106] As a fourth embodiment of the present disclosure, a method for manufacturing a molded product according to the third embodiment will be described. A method for producing a molded article according to a fourth embodiment of the present disclosure includes a first step of preparing a first copolymer obtained by polymerizing an acid component containing 50 mol% or more of an aromatic dicarboxylic acid component and 2 mol% to 50 mol% of a dimer acid component relative to the total amount of acid components, and an alcohol component containing 50 mol% or more of a 1,4-butanediol component relative to the total amount of alcohol components; a second step of heat-treating the first copolymer at a temperature of 66°C or higher and a melting point of the first copolymer under a pressure of 4,000 Pa or lower; and a third step of molding a mixture of 5% to 95% by mass of the first copolymer and 5% to 95% by mass of the second copolymer.

[0107] The first step and the second step are the same as the first step and the second step in the method for producing a polyester resin according to the second embodiment. The second copolymer is a polyester resin containing at least one alcohol component selected from the group consisting of a 1,4-butanediol component and a polytetramethylene glycol component.

[0108] The molding method used in the third step may be a known molding method such as injection molding, blow molding, extrusion molding, lamination, etc. The molded product may have at least one shape selected from the group consisting of a sheet shape, a film shape, and a container shape.

[0109] When the molded body obtained in the third step is heated at 150° C. for 1 hour, the amount of tetrahydrofuran generated is preferably 50 μg or less per 1 g of the molded body. The second copolymer preferably generates 150 μg to 600 μg of tetrahydrofuran per 1 g of the second copolymer when heated at 150° C. for 1 hour.

[0110] FIG. 2 shows a flowchart of the method for producing a molded body according to the fourth embodiment.

[0111] The method for producing a molded article according to the fourth embodiment can include the steps of preparing a first copolymer (S21), heat-treating the first copolymer under reduced pressure (S22), preparing a second copolymer (S23), and mixing the first copolymer and the second copolymer (S24). That is, the method for producing a molded article according to the fourth embodiment can include the step of mixing the first copolymer, which is the polyester resin according to the first embodiment, with the second copolymer. The order of steps S21 to S23 does not matter.

[0112] The method for producing the polyester resin according to the second embodiment is used as the method for producing the first copolymer.

[0113] The second copolymer can be produced by a known production method depending on the composition, or the second copolymer may be a commercially available product.

[0114] The method may include a step of producing a molded article by heating and melting the mixture of the first copolymer and the second copolymer at a temperature of, for example, 200° C. or higher, or 220° C. or higher. Examples of the molded article include a sheet, a film, a container, and the like.

[0115] According to the method for producing a molded article according to the fourth embodiment, even if the second copolymer contains THF, the THF can be removed during molding of the mixture with the first copolymer, making it possible to produce a molded article with a low THF outgassing even when the base polyester resin has a high THF content. [Example]

[0116] The polyester resin and its manufacturing method, as well as the molded article and its manufacturing method according to the present disclosure, will be described below with reference to examples. However, the polyester resin and its manufacturing method, as well as the molded article and its manufacturing method according to the present disclosure, are not limited to the following examples. The polyester resin composition was analyzed by NMR using the following method.

[0117] <Method for Analyzing Polyester Resin Composition by NMR> An FT-NMR apparatus (DPX400 type) manufactured by Bruker BioSpin was used. The polyester resin was dissolved in deuterated chloroform, mixed with tetramethylsilane as a standard, and the proton NMR spectrum was measured. The resin composition was calculated from the NMR spectrum.

[0118] [Test Examples 1 to 10] In Test Examples 1 to 10, as the acid, 100 mol% of dimethyl terephthalate or a mixture containing 100 mol% in total of dimethyl terephthalate and dimer acid which is a dimer of C22 erucic acid (manufactured by Croda, Pripol1004) or dimer acid which is a dimer of C18 unsaturated fatty acid (manufactured by Croda, Pripol1009), and as the alcohol, 100 mol% of 1,4-butanediol was charged into a reactor equipped with a stirrer, a rectification column, and a methanol distillation condenser. After dissolving the mixture in a solvent at 190 °C, 35 ppm of tetra-n-butoxytitanium was added, the temperature was raised from 190 °C to 225 °C over 3 hours, and a transesterification reaction was carried out while distilling the generated methanol out of the system. After completion of the transesterification reaction, the temperature was gradually raised from 225 °C to 235 °C over 60 minutes, and the pressure was gradually reduced from normal pressure to 0.2 kPa to terminate the reaction at a predetermined viscosity, and then it was extruded into cooling water and pelletized using a strand cutter. Tables 1 and 2 show the charged compositions of each test example and the polyester resin compositions analyzed by NMR. The intrinsic viscosity of the obtained polymer was 0.65 to 2.0 dl / g.

[0119] [Test Examples 11 to 13] In Test Examples 11 to 13, a polyester resin obtained by copolymerizing polybutylene terephthalate with polytetramethylene glycol was prepared. The manufacturing method was the same as that of Test Examples 1 to 10 except for the different compositions. Table 3 shows the charged compositions of each test example and the polyester resin compositions analyzed by NMR.

[0120] [Test Examples 14 to 21] In Test Examples 14 to 21, the production method was the same as in Test Examples 1 to 10, except that 100 mol% in total of dimethyl 2,6-naphthalenedicarboxylate and dimer acid (manufactured by Croda, Pripol 1004), which is a dimer of C22 erucic acid, was used as the acid. Table 4 shows the charging composition of each test example and the polyester resin composition analyzed by NMR.

[0121] Next, the obtained pellets were heat-treated under the conditions shown in Tables 1 to 4. The heating in Test Example 6 was carried out under atmospheric pressure in a nitrogen atmosphere. The melting point of the polyester resin before the heat treatment was measured as follows. Also, the amount of THF outgas generated was measured as follows, and the reduction rate of the amount of THF outgas generated was calculated as follows.

[0122] <Measurement of melting point> Using 10 mg of the polyester resin, the melting point Tm was determined from the DSC curve measured at a heating rate of 10 °C / min using a scanning differential calorimeter DSC (manufactured by Perkin Elmer, DSC7).

[0123] <Measurement of the amount of THF outgas generated and calculation of the reduction rate of the amount of THF outgas generated> The amount of THF outgas generated was measured for the polyester resin before the heat treatment and the heat-treated polyester resin. The heat-treated polyester resin was not the polyester resin itself for which the amount of THF outgas generated was measured before the heat treatment, but the same lot of polyester resin as before the heat treatment. The polyester resin was cryogenically pulverized to a powder of 30 to 50 mesh, 20 mg was sealed in a 25 ml vial, and it was held at 150 °C for 1 hour. Using a gas chromatograph GC-14A manufactured by Shimadzu Corporation, the amount of THF outgas generated was measured by headspace gas chromatography. The detection limit of the amount of THF outgas generated is 0.1 μg (0.1 ppm) per 1 g of the polyester resin.

[0124] The reduction rate of the amount of THF outgas generated was calculated by the following formula. Reduction rate of THF outgassing amount (%) = {(THF outgassing amount before heat treatment - THF outgassing amount after heat treatment) / THF outgassing amount before heat treatment} × 100

[0125] The abbreviations used in Tables 1 to 5 are as follows: TPA: Terephthalic acid component DA(C44): Dimer acid component with 44 carbon atoms DA(C36): Dimer acid component with 36 carbon atoms NDCA: 2,6-naphthalenedicarboxylic acid component BD: 1,4-butanediol component PTMG: Polytetramethylene glycol component

[0126] [Table 1]

[0127] [Table 2]

[0128] [Table 3]

[0129] [Table 4]

[0130] From the results of Tables 1 to 4, in Test Example 1, in which neither dimer acid nor polytetramethylene glycol was used as a monomer, the reduction in the amount of THF outgassing was small. Also, in Test Examples 11 to 13, in which polytetramethylene glycol was used as a monomer, the reduction in the amount of THF outgassing was small. On the other hand, in Test Examples 2 to 10, in which dimer acid was used as a monomer, the amount of THF outgassing was significantly reduced. In particular, by heating under reduced pressure, the amount of THF outgassing was reduced to nearly the detection limit. In Test Example 6, in which heat treatment was performed under atmospheric pressure, the heating time was 10 times that of Test Example 3, but the amount of THF outgassing could not be reduced to the same extent as in Test Example 3. In Test Examples 4 and 5, the amount of THF outgassing was reduced even at a heating temperature of 70°C. The amount of THF outgassing was reduced more effectively with a dimer acid having 44 carbon atoms than with a dimer acid having 36 carbon atoms. Furthermore, in Test Examples 15 to 21, in which 2,6-naphthalenedicarboxylic acid and dimer acid were used as monomers, the amount of THF outgassing could be significantly reduced, similar to Test Examples 2 to 10.

[0131] [Test Examples 22-25] The polyester resins in pellet form of Test Examples 3 and 8 were heat-treated and then molded into a 100 μm-thick sheet, and the amount of THF outgassing was measured. The sheet was molded using a T-die extruder, a common method for manufacturing polyester sheets, by melt extrusion at the molding temperature shown in Table 5, and then wound around a cast roll temperature-controlled at 20°C to obtain a sheet-like molded product. The method for measuring the amount of THF outgassing was the same as in Test Examples 1 to 21. In Table 5, "undetectable" indicates that the amount was below the detection limit.

[0132] [Table 5] From the results in Table 5, regardless of the molding temperature, no THF outgassing could be confirmed from the polyester resin in film form.

[0133] [Test Examples 26-47] The copolymers of Test Examples 2, 3, 7, 8, and 11 to 13 after heat treatment (referred to as "first copolymer" in Table 6) and the polybutylene terephthalate of Test Example 1 after heat treatment (referred to as "second copolymer" in Table 5) were mixed and molded into sheets. The amount of THF outgassing was measured for the molded sheets. No heat treatment at 50°C or higher was performed after molding before measurement. Table 6 shows the mixing ratio (mass ratio) of the first copolymer to the second copolymer and the amount of THF outgassing.

[0134] For sheet molding, the first copolymer and the second copolymer were mixed in the mass ratio shown in Table 6, melt-extruded at 250°C using a T-die extruder, which is a common method for producing polyester sheets, and wound around a cast roll whose temperature was controlled at 20°C to obtain a sheet-like molded product. In test examples in which the two copolymers were not mixed, sheets were similarly formed using a single copolymer.

[0135] [Table 6]

[0136] From the results in Table 6, in Test Example 26, the amount of THF outgassing could not be reduced when polybutylene terephthalate alone was formed into a sheet. Furthermore, in Test Examples 39 to 47, the amount of THF outgassing remained high even when a mixture of a polyester resin containing a polytetramethylene glycol component and polybutylene terephthalate was formed into a sheet. On the other hand, in Test Examples 27 to 38, the amount of THF outgassing could be significantly reduced when a polyester resin containing a dimer acid component was formed into a sheet. Even when polybutylene terephthalate contained a high amount of THF, such as 50% by mass or more, the amount of THF outgassing could be reduced during sheet formation.

[0137] [Test Examples 48-63] The copolymers of Test Examples 15 to 21 after heat treatment (referred to as "first copolymer" in Table 7) and the polybutylene naphthalate of Test Example 14 after heat treatment (referred to as "second copolymer" in Table 7) were mixed and molded into sheets. The amount of THF outgassing was measured for the molded sheets. No heat treatment at 50°C or higher was performed after molding before measurement. Table 7 shows the mixing ratio (mass ratio) of the first copolymer to the second copolymer and the amount of THF outgassing.

[0138] [Table 7]

[0139] From the results in Table 7, in Test Example 48, when polybutylene naphthalate alone was formed into a sheet, the amount of THF outgassing could not be reduced. Furthermore, in Test Examples 49 to 63, when a polyester resin containing a dimer acid component was formed into a sheet, the amount of THF outgassing could be significantly reduced. Even when polybutylene naphthalate contained a large amount of THF, such as 50% by mass or more, the amount of THF outgassing could be reduced during sheet formation.

[0140] The polyester resin and its manufacturing method of the present disclosure have been described based on the above embodiments and examples, but are not limited to the above embodiments and examples, and can include various modifications, changes, and improvements to each disclosed element (including elements described in the claims, specification, and drawings) within the scope of the present invention and based on the basic technical idea of ​​the present invention. Furthermore, various combinations, substitutions, and selections of each disclosed element are possible within the scope of the claims of the present invention.

[0141] Further objects, purposes and modes (including modifications) of the present invention will become apparent from the entire disclosure of the present invention including the claims.

[0142] With respect to numerical ranges set forth herein, unless otherwise specified, any numerical value or range falling within that range should be construed as being specifically set forth herein.

[0143] Some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes. Each supplementary note may be combined with each claim in the claims. [Appendix 1] A method of use in which the polyester resin according to the first embodiment is added to a polyester resin containing at least one alcohol component selected from the group consisting of 1,4-butanediol and polytetramethylene glycol. [Industrial Applicability]

[0144] The polyester resin and its manufacturing method, as well as the molded article and its manufacturing method of the present disclosure, can be applied to various molded articles, and can be particularly suitably applied to components for electric and electronic devices, components for automobiles, packaging materials, and the like.

Claims

1. an acid component containing 50 mol% or more of a terephthalic acid component and 2 mol% to 50 mol% of a dimer acid component relative to the total amount of the acid component; an alcohol component containing 50 mol% or more of a 1,4-butanediol component relative to the total amount of the alcohol component; A polyester resin comprising a first copolymer having: A polyester resin characterized in that the reduction rate of tetrahydrofuran (THF) outgas generation, represented by the following mathematical formula (1), is 99.78% or more. Reduction rate (%) of THF outgassing amount={(THF outgassing amount before heat treatment−THF outgassing amount after heat treatment) / THF outgassing amount before heat treatment}×100 Formula (1) In the formula (1), the "amount of THF outgassing before heat treatment" and the "amount of THF outgassing after heat treatment" are values ​​measured by headspace gas chromatography after freeze-pulverizing the polyester resin before and after heat treatment at 120°C for 12 hours under a pressure of 280 Pa, passing the resulting powder through a 30 to 50 mesh filter, sealing 20 mg of the resulting powder in a 25 ml vial, and holding the powder at 150°C for 1 hour.

2. 2. The polyester resin according to claim 1, wherein the amount of THF outgassed after heat treatment is 1 μg or less per 1 g of the polyester resin.

3. 2. The polyester resin according to claim 1, wherein the amount of THF outgassed after heat treatment is 0.5 μg or less per 1 g of the polyester resin.

4. 2. The polyester resin according to claim 1, wherein the amount of THF outgassing before heat treatment is 219 μg to 464 μg per 1 g of the polyester resin.

5. the acid component contains 60 mol % to 90 mol % of a terephthalic acid component and 10 mol % to 40 mol % of a dimer acid component, based on the total amount of the acid component; 2. The polyester resin according to claim 1, wherein the alcohol component contains 80 mol % or more of a 1,4-butanediol component based on the total amount of the alcohol component.

6. The polyester resin according to claim 1 , wherein the dimer acid component has at least one carbon atom selected from the group consisting of 44 and 36 carbon atoms.

7. a first step of preparing a first copolymer according to any one of claims 1 to 6; a second step of heat-treating the first copolymer at a temperature of 66°C or higher and a melting point of the first copolymer under a pressure of 4,000 Pa or lower; A method for producing a polyester resin, comprising:

8. The method for producing a polyester resin according to claim 7, wherein the heat treatment is carried out for 6 to 100 hours.

9. The method for producing a polyester resin according to claim 7 , wherein the second step is carried out before the first copolymer is heat-treated to 50° C. or higher.

10. A molded article comprising the polyester resin according to any one of claims 1 to 6.

11. 5% by mass to 70% by mass of the polyester resin according to any one of claims 1 to 6; 30% to 95% by weight of a second copolymer, the second copolymer is a polyester resin having an acid component containing a terephthalic acid component in an amount of 80 mol% or more relative to the total amount of the acid component, and at least one alcohol component selected from the group consisting of a 1,4-butanediol component and a polytetramethylene glycol component; A molded body, wherein the amount of tetrahydrofuran generated when the molded body is heated at 150°C for 1 hour is 50 µg or less per 1 g of the molded body.

12. 12. The molded article according to claim 11, wherein the amount of tetrahydrofuran generated when the second copolymer is heated at 150° C. for 1 hour is 150 μg to 600 μg per 1 g of the second copolymer.

13. A member for electric / electronic devices, an automobile part, or a packaging material, comprising the molded article according to claim 10.

14. A member for electric / electronic devices, an automobile part, or a packaging material, comprising the molded article according to claim 11.

15. a first step of preparing a first copolymer according to any one of claims 1 to 6; a second step of heat-treating the first copolymer at a temperature of 66°C or higher and a melting point of the first copolymer under a pressure of 4,000 Pa or lower; a third step of molding a mixture of 5% to 95% by weight of the first copolymer and 5% to 95% by weight of the second copolymer; the second copolymer is a polyester resin having an acid component containing a terephthalic acid component in an amount of 80 mol% or more relative to the total amount of acid components, and at least one alcohol component selected from the group consisting of a 1,4-butanediol component and a polytetramethylene glycol component.

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