Polyester resin composition and molded article

Abstract

To provide a polyester resin composition which can be collected and recycled without separating from a PET bottle and can satisfy the physical properties of products such as various containers, specifically, flexibility, slipperiness, heat resistance or the like.SOLUTION: There is provided a polyester resin composition which comprises a polyester containing a dicarboxylic acid unit including a terephthalic acid unit and a dimer acid unit and a diol unit including a polyalkylene glycol unit and a 1,4-butanediol unit as main constitutional units, wherein the polyester resin composition comprises 0.05 pts.wt. or more and 4.0 pts.wt. or less of a fatty acid amide having 8 to 22 carbon atoms based on 100 pts.wt. of the polyester, the content of the 1,4-butanediol unit in the polyester is 20 wt.% or more and the content of the dimer acid unit in the polyester is 0.5 wt.% or more and 5 wt.% or less and the content of the polyalkylene glycol unit in the polyester is 1 wt.% or more and 30 wt.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester resin composition. More specifically, the present invention relates to a polyester resin composition that can be collected and recycled without separating it from PET bottles and that has the physical properties, specifically flexibility, slipperiness, heat resistance, etc., required for products such as various containers, and a molded article made from the polyester resin composition. [Background technology]

[0002] Polyesters, such as polyethylene terephthalate (PET), have excellent mechanical strength, chemical stability, gas barrier properties, aroma retention, and hygiene. Furthermore, molded articles such as containers can be recovered, washed, crushed, and remolded. Therefore, they are widely used as environmentally friendly, recyclable packaging containers. However, polyesters have poor flexibility, and improvements have been sought.

[0003] Patent Document 1 proposes a polyester that contains terephthalic acid units and a specific amount of dimer acid units as dicarboxylic acid units, and ethylene glycol units and a specific amount of polyalkylene glycol units as diol units, as a polyester that can obtain molded articles that are excellent in flexibility and transparency, is free from the problem of loss of transparency during storage, and can obtain transparent molded articles even when the obtained molded articles are recovered, crushed, and then melt-molded again, resulting in polyesters with excellent recyclability.

[0004] On the other hand, various containers such as food containers and beverage containers are required to have flexibility (bending properties), slipperiness, heat resistance (heat deformation resistance), etc. depending on their use and application. Conventionally, polyolefins and polystyrenes have been used for containers that require such physical properties. That is, the PET currently used for PET bottles is hard and lacks flexibility, making it unable to undergo elastic deformation when released from the mold. For example, it cannot be used for products with a reverse tapered portion due to poor release properties. On the other hand, highly flexible PET has poor slipperiness, and when such PET containers are stacked for transportation, they are difficult to separate when removed, and in severe cases, the containers may even break. Furthermore, since PET also has poor slipperiness (is difficult to slide) with objects that are relatively hard to deform, it is difficult to handle. Furthermore, flexible PET has the problem of insufficient heat resistance, resulting in significant deformation at high temperatures.

[0005] For these reasons, polyolefins and polystyrenes have conventionally been used as molding materials in applications requiring flexibility, slipperiness, and heat resistance. However, polyolefin and polystyrene containers cannot be melt-molded together with PET bottles and other PET containers. In other words, because they are not compatible with PET, the molded products obtained by melt-molding with PET are opaque and cannot be reused. For this reason, polyolefin and polystyrene containers must be collected separately from PET bottles.

[0006] For these reasons, there is a need for the development of molding materials that can be collected and recycled without separating them from PET containers such as PET bottles, and that also have excellent flexibility, slipperiness, and heat resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-24951 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned conventional circumstances, an object of the present invention is to provide a polyester resin composition that can be collected and recycled without separating it from PET bottles and that satisfies the physical properties required for products such as various containers, specifically flexibility, slipperiness, heat resistance, etc., and to provide a molded article using this polyester resin composition. [Means for solving the problem]

[0009] As a result of intensive research by the present inventors to solve the above-mentioned problems, they found that the above-mentioned problems can be solved by a polyester resin composition containing a polyester containing, as main constituent units, dicarboxylic acid units including terephthalic acid units and dimer acid units, and diol units including polyalkylene glycol units and 1,4-butanediol units, wherein the polyester contains dimer acid units, 1,4-butanediol units, and polyalkylene glycol units in a predetermined ratio, and a predetermined amount of a specific fatty acid amide, and thus arrived at the present invention.

[0010] That is, the present invention provides the following.

[0011] [1] A polyester resin composition comprising a polyester containing, as main structural units, dicarboxylic acid units including terephthalic acid units and dimer acid units, and diol units including polyalkylene glycol units and 1,4-butanediol units, wherein the polyester contains 0.05 to 4.0 parts by weight of a fatty acid amide having 8 to 22 carbon atoms per 100 parts by weight of the polyester, the content of 1,4-butanediol units in the polyester is 20% by weight or more, the content of dimer acid units in the polyester is 0.5 to 5% by weight, and the content of polyalkylene glycol units in the polyester is 1 to 30% by weight.

[0012] [2] The polyester resin composition according to [1], wherein the polyalkylene glycol is polyethylene glycol having a weight-average molecular weight of 4,000 or less.

[0013] [3] The polyester resin composition according to [1] or [2], wherein the fatty acid amide is erucic acid amide.

[0014] [4] A molded article using the polyester resin composition according to any one of [1] to [3]. [Effects of the Invention]

[0015] According to the present invention, a polyester resin composition is provided which has excellent compatibility with PET for PET bottles, can be collected and recycled without separating it from PET containers such as PET bottles (hereinafter, this physical property may be referred to as "recyclability"), and also has excellent flexibility, slipperiness, and heat resistance. The polyester resin composition of the present invention has excellent flexibility, and therefore can be molded with good moldability even into a shape having a reverse tapered portion. Furthermore, since it has excellent slipperiness, it is easy to handle during transportation. Furthermore, the polyester resin composition of the present invention has excellent heat resistance and is resistant to deformation even under high temperature conditions. Therefore, the polyester resin composition of the present invention can be used as a molding material for various containers and the like for which polyolefins or polystyrenes have conventionally been used, and the waste materials can be easily recovered and recycled together with PET products. DETAILED DESCRIPTION OF THE INVENTION

[0016] The best mode for carrying out the present invention will be described in detail below, but the explanation of the constituent elements described below is a representative example of an embodiment of the present invention, and the present invention is not limited to these contents.

[0017] [Polyester resin composition] The polyester resin composition of the present invention is a polyester resin composition containing a polyester containing, as main structural units, dicarboxylic acid units including terephthalic acid units and dimer acid units, and diol units including polyalkylene glycol units and 1,4-butanediol units, The polyester contains 0.05 parts by weight or more and 4.0 parts by weight or less of a fatty acid amide having 8 to 22 carbon atoms per 100 parts by weight of the polyester, the content of 1,4-butanediol units in the polyester is 20% by weight or more, the content of dimer acid units in the polyester is 0.5% by weight or more and 5% by weight or less, The polyester is characterized in that the content of polyalkylene glycol units in the polyester is 1% by weight or more and 30% by weight or less.

[0018] In order to be recycled together with PET bottles, the material must have the physical properties to produce transparent molded products when mixed with PET bottles and melt-molded. Additionally, for various applications, the material must have elastic deformation properties that allow it to be released from the mold even at reverse tapered sections, a low coefficient of friction, and minimal deformation in high-temperature environments. The present invention solves the above-mentioned problems by providing a dimer acid copolymer polyester that is compatible with PET and contains polyalkylene glycol units to make it soft and elastically deformable, a lubricant to make it slippery, and 1,4-butanediol to promote crystallization and thereby impart heat resistance.

[0019] In the present invention, the term "unit" refers to a repeating unit introduced into a polyester derived from a compound (monomer) used as a raw material for producing the polyester. For example, a terephthalic acid unit refers to a unit introduced into a polyester derived from terephthalic acid or an ester-forming derivative thereof (hereinafter, these will be referred to as "terephthalic acid components." Similarly, a dicarboxylic acid or an ester-forming derivative thereof used to introduce a dicarboxylic acid unit will also be referred to as "dicarboxylic acid component.") The same applies to a dimer acid unit, a dicarboxylic acid unit, and an isophthalic acid unit. On the other hand, the polyalkylene glycol unit refers to a repeating unit that is derived from the polyalkylene glycol used as a raw material for producing the polyester and that is introduced into the polyester, and the same applies to 1,4-butanediol units, ethylene glycol units, and diol units. Furthermore, the term "main structural unit" refers to a repeating unit that accounts for 60% by weight or more, particularly 70 to 100% by weight, of all structural units that constitute the polyester. The constituent units such as the dicarboxylic acid units and the diol units in the polyester are 1 It can be quantified by measuring the H-NMR spectrum.

[0020] In the present invention, the respective structural units constituting the polyester are not limited to those all contained in a single polyester, but may be contained in separate polyesters and then contained in the polyester resin composition of the present invention. That is, the polyester contained in the polyester resin composition of the present invention may be a copolymer polyester containing all of terephthalic acid units, dimer acid units, polyalkylene glycol units, and 1,4-butanediol units, or may be a blend of a copolymer polyester containing terephthalic acid units and / or dimer acid units and polyalkylene glycol units, and a copolymer polyester containing terephthalic acid units and / or dimer acid units and 1,4-butanediol units, or a blend of a polyester containing terephthalic acid units and 1,4-butanediol units, and a polyester containing dimer acid units and polyalkylene glycol units, or may be a blend of polyesters containing one or more of the units contained as essential structural units in the polyester resin composition of the present invention, such that the contents of 1,4-butanediol units, dimer acid units, and polyalkylene glycol units are as described above. The polyester resin composition of the present invention may also contain a polyester that does not contain any of a terephthalic acid unit, a dimer acid unit, a polyalkylene glycol unit, and a 1,4-butanediol unit.

[0021] Hereinafter, the polyester contained in the polyester resin composition of the present invention may be referred to as the "polyester of the present invention." As described above, the polyester of the present invention may consist of only a single polyester, or may be a blend of two or more polyesters.

[0022] [Dicarboxylic acid unit] The dicarboxylic acid units constituting the polyester of the present invention contain terephthalic acid units and dimer acid units, and the content of the dimer acid units in the polyester is 0.5% by weight or more and 5% by weight or less. The dicarboxylic acid units according to the present invention may contain isophthalic acid units or the like as dicarboxylic acid units other than terephthalic acid and dimer acid.

[0023] <Terephthalic acid unit> The content of terephthalic acid units in the polyester of the present invention is not particularly limited, but is preferably 40% by weight or more and 80% by weight or less, and particularly preferably 45% by weight or more and 70% by weight or less. If the content of terephthalic acid units in the polyester is too low, the heat resistance may be poor. On the other hand, if the content of terephthalic acid units in the polyester is too high, the content of dimer acid units may be relatively low, which may result in poor recyclability and slip properties.

[0024] Examples of the terephthalic acid component used as a raw material for introducing terephthalic acid units into polyester include terephthalic acid and its esters and halides having an alkyl group having about 1 to 4 carbon atoms. These terephthalic acid components may be used alone or in combination of two or more.

[0025] <Dimer acid unit> The content of dimer acid units in the polyester of the present invention is 0.5% by weight or more and 5% by weight or less, preferably 1% by weight or more and 4.5% by weight or less, and more preferably 1% by weight or more and 4% by weight or less. If the content of dimer acid units in the polyester is too low, the recyclability and slip properties of the polyester may be reduced. On the other hand, if the content of dimer acid units in the polyester is too high, the recyclability of the polyester may be reduced.

[0026] In the present invention, dimer acid refers to a dimer of an unsaturated aliphatic carboxylic acid having 16 or more carbon atoms or a hydrogenated product thereof. This dimer acid can be obtained by dimerizing or hydrogenating a mixture of unsaturated aliphatic carboxylic acids having 16 or more carbon atoms (e.g., unsaturated aliphatic carboxylic acids mainly composed of linoleic acid or oleic acid) extracted from non-petroleum raw materials such as soybean oil, rapeseed oil, beef tallow, or tall oil. When dimer acid is obtained using such a production method, it contains impurities such as over-reacted trimers and unreacted unsaturated aliphatic carboxylic acids. Since these impurities can cause bleed-out and gelation in polyesters, it is preferable to minimize their amount. Furthermore, dimer acid contains an unsaturated bond, and if used as is, there is a possibility that a branching reaction will proceed during polymerization or that the color tone of the resulting polyester will be deteriorated. Therefore, it is preferable that the dimer acid component used as a production raw material for introducing dimer acid units into polyester is hydrogenated. The dimer acid component used as a raw material for producing the polyester may be one kind or a mixture of two or more kinds.

[0027] <Isophthalic acid unit> When the polyester of the present invention contains isophthalic acid units as dicarboxylic acid units other than terephthalic acid units and dimer acid units, the content of isophthalic acid units in the polyester is preferably 5% by weight or less, more preferably 3% by weight or less. If the content of isophthalic acid units in the polyester exceeds the upper limit, the crystallinity of the resulting molded article tends to decrease, resulting in a decrease in heat resistance.

[0028] Examples of isophthalic acid components used as a manufacturing raw material for introducing isophthalic acid units into polyester include isophthalic acid and its esters and halides having an alkyl group having about 1 to 4 carbon atoms. These isophthalic acid components may be used alone or in combination of two or more.

[0029] <Other dicarboxylic acid units> The polyester of the present invention may contain dicarboxylic acid units other than terephthalic acid units, dimer acid units, and isophthalic acid units, for example, in an amount of 10% by weight or less in terms of the content in the polyester, as long as the effects of the present invention are not impaired. Examples of other dicarboxylic acid components used as manufacturing raw materials to introduce other dicarboxylic acid units into polyesters include aromatic dicarboxylic acids such as phthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, and dodecadicarboxylic acid, as well as esters and halides of these compounds having an alkyl group having about 1 to 4 carbon atoms. These compounds may be used alone or in combination of two or more.

[0030] [Diol unit] The diol units constituting the polyester of the present invention contain polyalkylene glycol units and 1,4-butanediol units, and are characterized in that the content of polyalkylene glycol units in the polyester is 1% by weight to 30% by weight and the content of 1,4-butanediol units is 20% by weight or more. The diol units according to the present invention may contain diol units other than polyalkylene glycol units and 1,4-butanediol units, such as ethylene glycol units, diethylene glycol units, and 1,4-cyclohexanedimethanol units.

[0031] <Polyalkylene glycol unit> The content of polyalkylene glycol units in the polyester of the present invention is 1% by weight or more and 30% by weight or less, preferably 2% by weight or more and 27% by weight or less, and more preferably 3% by weight or more and 25% by weight or less. If the content of polyalkylene glycol units in the polyester is too low, flexibility will be insufficient, while if it is too high, the resulting molded product may become cloudy during storage or the transparency of the recycled molded product may be impaired.

[0032] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol block copolymers, polytetramethylene glycol, and polyhexamethylene glycol. Of these, polyethylene glycol and polytetramethylene glycol are preferred from the viewpoint of resin transparency and flexibility.

[0033] As the polyalkylene glycol, polyethylene glycol having a weight average molecular weight of 4000 or less is preferred from the viewpoint of good compatibility with PET. If the molecular weight of the polyalkylene glycol is equal to or less than the upper limit, cloudiness can be prevented and a transparent polyester can be obtained. However, if the molecular weight of the polyalkylene glycol is too small, the melting point of the polyester becomes too low. Therefore, in the case of polyethylene glycol, its weight-average molecular weight is preferably 500 or more, more preferably 1000 or more and 2000 or less. When the weight average molecular weight of the polyethylene glycol is within the above range, a transparent polyester is obtained in the molten state, and when blended with PET for PET bottles, the transparency of the recycled molded product is less likely to be affected. Here, the weight average molecular weight of polyethylene glycol is a value determined by size exclusion chromatography (SEC).

[0034] These polyalkylene glycols may be used alone or in combination of two or more.

[0035] <1,4-butanediol unit> The content of 1,4-butanediol units in the polyester of the present invention is 20% by weight or more, preferably 22% by weight or more, and more preferably 24% by weight or more. When the content of 1,4-butanediol units in the polyester is equal to or more than the above lower limit, a polyester excellent in recyclability, heat resistance, slip properties, etc. can be obtained. On the other hand, the content of 1,4-butanediol units in the polyester of the present invention is preferably 32% by weight or less, more preferably 29% by weight or less. When the content of 1,4-butanediol units in the polyester is the above upper limit or less, a polyester with excellent flexibility can be obtained.

[0036] <Ethylene glycol unit and diethylene glycol unit> The polyester of the present invention may contain ethylene glycol units and / or diethylene glycol units as diol units other than 1,4-butanediol units and polyalkylene glycol units.

[0037] When the polyester of the present invention contains ethylene glycol units, the content of the ethylene glycol units in the polyester is preferably 0.5% by weight or more and 5% by weight or less, and more preferably 1% by weight or more and 4% by weight or less. When the content of the ethylene glycol units in the polyester is in this range, the recyclability of the polyester tends to be good and the heat resistance tends to be improved.

[0038] When the polyester of the present invention contains diethylene glycol units, the content of diethylene glycol units in the polyester is preferably 0.1 to 1% by weight, more preferably 0.1 to 0.9% by weight. When the content of ethylene glycol units in the polyester is in this range, the recyclability of the polyester is improved, and the transparency of molded articles obtained by blending the polyester with PET tends to be improved.

[0039] The amount of diethylene glycol units in the polyester can be controlled by adjusting the amount of diethylene glycol used as a raw material during polyester production. In addition, diethylene glycol units in polyesters may be formed by dehydration bonding of two molecules of ethylene glycol used as a raw material during polyester production, forming diethylene glycol, which is then incorporated into the polyester as diethylene glycol units. To control this, for example, increasing the molar ratio of the diol component containing ethylene glycol used as a raw material to the dicarboxylic acid component used as a raw material may promote the diethylene glycol dimerization and tend to increase the amount of diethylene glycol. Furthermore, when the esterification reaction is carried out in the presence of a metal hydroxide such as sodium hydroxide or an alkali component such as tetraethylammonium hydroxide, the diethylene glycol dimerization tends to be suppressed and the amount of diethylene glycol units tends to decrease.

[0040] <Other diol units> The polyester of the present invention may contain diol units other than the above-mentioned 1,4-butanediol units, polyalkylene glycol units, ethylene glycol units and diethylene glycol units, for example, in a proportion of 10% by weight or less in the polyester, as long as the effects of the present invention are not impaired.

[0041] Examples of other diol components that can be used as raw materials for introducing other diol units into polyesters include aliphatic diols such as trimethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, and 2-ethyl-2-butyl-1,3-propanediol; 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanedimethylol, and 2,5-norbolone; Examples of suitable diols include alicyclic diols such as nandimethylol, aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid, as well as ethylene oxide adducts or propylene oxide adducts of 2,2-bis(4'-hydroxyphenyl)propane, dimer diol, etc. These may be used alone or in combination of two or more.

[0042] [Other building blocks] The polyester of the present invention may contain up to 10% by weight of other structural units than the dicarboxylic acid units and diol units. Other constituent components used as manufacturing raw materials for introducing other constituent units into the polyester are not particularly limited, and examples thereof include hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, and p-β-hydroxyethoxybenzoic acid, monofunctional components such as stearyl alcohol, heneicosanol, octacosanol, benzyl alcohol, stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid, and trifunctional or higher polyfunctional components such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetetracarboxylic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, and sugar esters. These may be used alone or in combination of two or more.

[0043] [Intrinsic viscosity] The intrinsic viscosity (IV) of the polyester of the present invention is preferably 0.40 dL / g to 1.20 dL / g, more preferably 0.45 dL / g to 1.15 dL / g, and even more preferably 0.48 dL / g to 1.10 dL / g. When the intrinsic viscosity is within the above range, it becomes possible to obtain a polyester with excellent moldability without deteriorating productivity.

[0044] The intrinsic viscosity of the polyester is measured by the method described below. Approximately 0.25 g of sample was dissolved in approximately 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (1 / 1 by weight) to a concentration of 1.00 g / dL, and then cooled to 30°C. At 30°C, the dropping time of the sample solution and the solvent alone was measured using a fully automatic solution viscometer (DT553, manufactured by Sentec Co., Ltd.), and the intrinsic viscosity (IV) was calculated using the following formula. IV=((1+4K H η sp ) 0.5 -1) / (2K H C) where η sp =η / η0-1, where η is the time it takes for the sample solution to fall, η0 is the time it takes for the solvent alone to fall, C is the concentration of the sample solution (g / dL), and K H is Huggins' constant. K H The sample dissolution conditions are 110°C for 30 minutes. If the material is properly dried and molded, the IV retention rate after molding will be approximately 90 to 95%.

[0045] The intrinsic viscosity of the polyester can be adjusted to fall within the above-mentioned preferred range in the polyester production method described below, for example, by optimizing the amount of catalyst or vaporizing agent added, or by adjusting the temperature, pressure, and reaction time during polycondensation to their optimum ranges.

[0046] [Method for producing polyester] The polyester of the present invention can be produced by using, as production raw materials, a dicarboxylic acid component containing a terephthalic acid component such as terephthalic acid and an ester-forming derivative thereof as a production raw material for introducing a terephthalic acid unit, a dimer acid component as a production raw material for introducing a dimer acid unit, and, if necessary, an isophthalic acid component such as isophthalic acid and an ester-forming derivative thereof as a production raw material for introducing an isophthalic acid unit, and a diol component containing polyalkylene glycol, 1,4-butanediol, and, if necessary, ethylene glycol, etc., and subjecting these dicarboxylic acid components and diol components to an esterification or transesterification reaction, directly as a polyester containing terephthalic acid units, dimer acid units, polyalkylene glycol units, and 1,4-butanediol units. However, when taking into consideration factors such as reactivity and ease of control of the content of each structural unit, it is preferable to use multiple polyesters containing some of the essential structural units of the polyester of the present invention and melt-knead them to obtain the polyester of the present invention, as described below.

[0047] (1) Polyethylene terephthalate containing dimer acid units (a polyester containing dimer acid units, terephthalic acid units, and ethylene glycol units; hereinafter, sometimes referred to as "polyester I") and polybutylene terephthalate containing polyalkylene glycol units (a polyester containing polyalkylene glycol units, terephthalic acid units, and 1,4-butanediol units; hereinafter, sometimes referred to as "polyester II") are melt-kneaded. (2) Polyethylene terephthalate containing dimer acid units (polyester I), polybutylene terephthalate containing polyalkylene glycol units (polyester II), and polyethylene terephthalate not containing dimer acid units or polyalkylene glycol units (polyester containing terephthalic acid units and ethylene glycol units; hereinafter, sometimes referred to as "polyester III") are melt-kneaded. (3) Polybutylene terephthalate containing dimer acid units (a polyester containing dimer acid units, terephthalic acid units, and 1,4-butanediol units; hereinafter, sometimes referred to as "Polyester IV") and polyethylene terephthalate containing polyalkylene glycol units (a polyester containing terephthalic acid units, polyalkylene glycol units, and ethylene glycol units; hereinafter, sometimes referred to as "Polyester V") are melt-kneaded. (4) Polybutylene terephthalate containing dimer acid units (polyester IV), polyethylene terephthalate containing polyalkylene glycol units (polyester V), and polyethylene terephthalate containing neither dimer acid units nor polyalkylene glycol units (polyester III) are melt-kneaded. (5) Polyethylene terephthalate not containing dimer acid units and polyalkylene glycol units (polyester III) and polyester containing dimer acid units and polyalkylene glycol units (hereinafter sometimes referred to as "polyester VI") are melt-kneaded. (6) Polyethylene terephthalate containing dimer acid units (polyester I), polyethylene terephthalate containing polyalkylene glycol units (polyester V), and polybutylene terephthalate containing neither dimer acid units nor polyalkylene glycol units (polyester VII) are melt-kneaded.

[0048] The above methods (1) to (6) may be used in combination of two or more. In any case, the polyester of the present invention can be easily produced by melt-kneading two or more of Polyesters I to VII so as to have the predetermined dimer acid unit content, polyalkylene glycol unit content, and 1,4-butanediol unit content.

[0049] The physical properties and production method of the polyesters I to VII are not particularly limited as long as they can be melt-kneaded to obtain the polyester of the present invention.

[0050] The method for producing the polyester of the present invention is not particularly limited, and a conventional method can be applied. For example, the polyester can be produced through a process including the steps of: mixing a dicarboxylic acid component containing terephthalic acid or an ester-forming derivative thereof, and, if necessary, isophthalic acid or an ester-forming derivative thereof, with a diol component containing 1,4-butanediol or ethylene glycol in a predetermined ratio under stirring to form a raw material slurry; heating the raw material slurry under normal pressure or under pressure to cause an esterification reaction to form a polyester oligomer (hereinafter sometimes referred to as an "oligomer"); adding a dimer acid or an ester-forming derivative thereof and a polyalkylene glycol to the obtained oligomer; gradually reducing the pressure and heating in the presence of an ester exchange catalyst or the like to cause a melt polycondensation reaction to obtain a polyester; and, if necessary, further subjecting the obtained polyester to a solid-state polycondensation reaction.

[0051] The dimer acid or its ester-forming derivative and the polyalkylene glycol can be added to either the raw material slurry or the oligomer.

[0052] Examples of the transesterification catalyst include antimony compounds such as diantimony trioxide; germanium compounds such as germanium dioxide and germanium tetroxide; titanium compounds such as titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate; dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, and triisobutyltin. Examples of suitable catalysts include tin compounds such as tin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannoic acid, ethylstannoic acid, and butylstannoic acid; magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, and magnesium hydrogen phosphate; and calcium compounds such as calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide, and calcium hydrogen phosphate. These catalysts can be used alone or in combination of two or more.

[0053] In addition, during polyester production, it is preferable to use a stabilizer together with the transesterification catalyst. Examples of stabilizers include orthophosphoric acid, polyphosphoric acid, pentavalent phosphorus compounds such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(triethylene glycol) phosphate, ethyl diethylphosphonoacetate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol acid phosphate, and trivalent phosphorus compounds such as phosphorous acid, hypophosphorous acid, and diethyl phosphite, trisdodecyl phosphite, trisnonyldecyl phosphite, and triphenyl phosphite. Of these, trivalent phosphorus compounds are generally more reducing than pentavalent phosphorus compounds, and the metal compound added as a polycondensation catalyst may be reduced and precipitated, causing the generation of foreign matter, so pentavalent phosphorus compounds are preferred.

[0054] The reaction pressure in the melt polycondensation reaction is preferably 0.001 kPa to 1.33 kPa in absolute pressure, and the reaction temperature is preferably 220°C to 280°C, more preferably 230°C to 260°C. The solid-phase polycondensation reaction is carried out under reduced pressure or in an inert gas atmosphere, and the reaction temperature is preferably 180° C. to 220° C. The reaction time of the solid-phase polycondensation reaction is preferably 5 hours to 100 hours. By setting the melt polycondensation reaction conditions and solid phase polycondensation reaction conditions as described above, it is possible to obtain a polyester having a desired intrinsic viscosity.

[0055] When the polyester of the present invention is produced using two or more of the polyesters I to VII described above, the polyesters may be kneaded in a molten state and pelletized, or the two or more polyester pellets may be dry-mixed after pelletizing the polyesters and then melt-kneaded. The polyester pellets may be melt-kneaded in advance and then molded, or they may be melt-kneaded in a molding machine and molded. The temperature during melt-kneading is usually about 240 to 300°C.

[0056] [Fatty acid amide] The polyester resin composition of the present invention contains 0.05 parts by weight or more and 4.0 parts by weight or less of a fatty acid amide having 8 to 22 carbon atoms per 100 parts by weight of the polyester of the present invention. If the carbon number of the fatty acid amide is 7 or less, the melting point tends to be low and the heat resistance tends to be poor. On the other hand, if the carbon number of the fatty acid amide is 23 or more, the effect of improving the slip property is insufficient. For this reason, in the present invention, fatty acid amides having 8 to 22 carbon atoms, preferably 14 to 22 carbon atoms, are used.

[0057] The fatty acid amide may be either saturated or unsaturated, but from the viewpoint of hygiene, unsaturated fatty acid amides are preferred, and specific examples include known unsaturated fatty acid amides such as erucic acid amide, oleic acid amide, brassidic acid amide, elaidic acid amide, etc. These unsaturated fatty acid amides may be used alone or in combination of two or more. Among these unsaturated fatty acid amides, erucic acid amide and oleic acid amide are preferred because they have high melting points and excellent heat resistance, and erucic acid amide is more preferred.

[0058] If the content of the fatty acid amide in the polyester resin composition of the present invention is 0.05 parts by weight or more relative to 100 parts by weight of the polyester of the present invention, the effect of improving slipperiness due to the inclusion of the fatty acid amide can be sufficiently obtained. If the content of the fatty acid amide is too high, recyclability deteriorates, and the transparency of recycled molded products obtained by blending with crushed molded products is poor. Therefore, in the polyester resin composition of the present invention, the content of the fatty acid amide is preferably 0.05 to 4 parts by weight, more preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the polyester of the present invention.

[0059] [Other ingredients] The polyester resin composition of the present invention may further contain, depending on its intended use, a crystal nucleating agent other than the fatty acid amide, an antioxidant, a coloring inhibitor, a pigment, a dye, an ultraviolet absorber, a release agent, a lubricant, a flame retardant, an antistatic agent, inorganic and / or organic particles, etc., within a range that does not impair the effects of the polyester of the present invention. The content of these other components in the polyester resin composition of the present invention is preferably 5% by weight or less, for example, 0.1 to 5% by weight, in the polyester resin composition of the present invention.

[0060] [Uses of polyester resin composition] The polyester resin composition of the present invention is excellent in recyclability, flexibility, slipperiness, and heat resistance. Therefore, it is useful for food containers with complex shapes that require flexibility, slipperiness, heat resistance, and recyclability, such as being collected and recycled together with PET bottles, as well as for protective sheets and films for such containers. For example, as a food container, the polyester resin composition of the present invention can be injection molded into a container having an opening and a lid for the container. Furthermore, the polyester resin composition of the present invention can be injection molded into a preform, the preform can be stretch-blow molded or extrusion molded into a parison, and the parison can be blow molded into a container such as a bottle or a tube. Such containers are useful for solid foods, beverages, and liquid seasonings such as soy sauce, sauces, mirin, dressings, and mayonnaise. The polyester of the present invention can be extruded into a sheet, and the sheet can be formed into a desired shape by vacuum forming or the like to form a container, which is useful as a beverage cup or its lid, a tray or container for food such as fried foods or prepared foods, etc. Furthermore, the sheet can be stretched into a film or the like to be used as a food packaging material or a protective film for the inner and outer surfaces of a tray or container. [Example]

[0061] 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 as long as it does not depart from the gist of the invention.

[0062] [Quantitative determination of each dicarboxylic acid unit and each diol unit in polyester] The amounts of the dicarboxylic acid units and diol units in the polyesters used in the following Examples and Comparative Examples were determined by the following method. Approximately 20 mg of polyester (pellets or a mixture thereof) was dissolved in 0.75 mL of a mixed solvent of deuterated chloroform / deuterated hexafluoroisopropanol (weight ratio 7 / 3), and 25 μL of deuterated pyridine was added to prepare a sample solution. The sample solution was placed in an NMR sample tube with an outer diameter of 5 mm, and analyzed at room temperature using a nuclear magnetic resonance spectrometer (Bruker "AVANCE400"). 1 The 1 H-NMR spectrum was measured to determine the proportions of each dicarboxylic acid unit and diol unit in the polyester.

[0063] [Production Example 1: Production of Polyester 1 (Polybutylene Terephthalate)] A transesterification reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and distillation tube was charged with 64.1 parts by weight of dimethyl terephthalate, 1,4-butanediol (hereinafter referred to as 1.4BG) in an amount equivalent to 1.2 times the molar ratio of dimethyl terephthalate, and tetrabutyl titanate as a catalyst. The amount was calculated as titanium metal, and the resulting polymer was 33 ppm. The 1,4BG solution was added. The liquid temperature in the vessel was then maintained at 150 ° C for 60 minutes, after which it was heated to 210 ° C over 90 minutes and held at 210 ° C for 30 minutes. During this time, the resulting methanol was distilled off, and the transesterification reaction was carried out for a total of 180 minutes. Fifteen minutes before the end of the transesterification reaction, magnesium acetate tetrahydrate dissolved in 1,4BG was added, followed by the addition of a hindered phenol antioxidant (Ciba-Geigy's "Irganox 1010") as a 1,4BG slurry. Subsequently, tetrabutyl titanate was added as a 1,4BG solution. The mixture was then transferred to a polycondensation reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, distillation tube, and vacuum exhaust port, and the polycondensation reaction was carried out under reduced pressure. The polycondensation reaction was carried out by gradually reducing the pressure in the reactor from atmospheric pressure to 0.4 kPa over 85 minutes and then maintaining the reaction temperature at 0.4 kPa or less. The reaction temperature was maintained at 210°C for 15 minutes from the start of pressure reduction, then increased to the maximum temperature of 240°C over 45 minutes, maintained at this temperature for 1 hour, and then controlled to a final temperature of 235°C. The reaction was terminated when the specified stirring torque (corresponding to an IV of 1.20 dL / g) was reached. The polycondensation reaction took 150 minutes (the polycondensation reaction time was measured as the time from the start of pressure reduction to the time the pressure was restored with nitrogen). The tank was then restored to a reduced pressure with nitrogen and then pressurized to withdraw the polymer. The temperature of the heat medium in the die during withdrawal was set to 230°C, and the polymer was withdrawn from the die in the form of strands. The strands were then cooled in a cooling water tank and cut with a cutter to obtain pellets of polyester 1. The contents of each component in polyester 1 were as follows, and the intrinsic viscosity was 1.20 dL / g. Terephthalic acid units: 67.3% by weight 1,4-butanediol units: 32.7% by weight

[0064] [Production Example 2: Production of Polyester 2 (Polyester Containing Polyethylene Glycol Units)] A transesterification reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and distillation tube was charged with 64.1 parts by weight of dimethyl terephthalate, 36.8 parts by weight of 1,4-butanediol (hereinafter referred to as 1.4BG), 30 parts by weight of polyethylene glycol (weight average molecular weight 2000), and tetrabutyl titanate as a catalyst, converted to titanium metal, and added as a 1,4BG solution to a concentration of 33 ppm relative to the polymer produced. Next, the liquid temperature in the vessel was maintained at 150 ° C for 60 minutes, then increased to 210 ° C over 90 minutes and held at 210 ° C for 30 minutes. During this time, the transesterification reaction was carried out for a total of 180 minutes while distilling off the produced methanol. Fifteen minutes before the end of the transesterification reaction, magnesium acetate tetrahydrate dissolved in 1,4BG was added, followed by the addition of a hindered phenol antioxidant (Ciba-Geigy's "Irganox 1010") as a 1,4BG slurry. Subsequently, tetrabutyl titanate was added as a 1,4BG solution. The mixture was then transferred to a polycondensation reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, distillation tube, and vacuum exhaust port, and the polycondensation reaction was carried out under reduced pressure. The polycondensation reaction was carried out by gradually reducing the pressure in the reactor from atmospheric pressure to 0.4 kPa over 85 minutes and then maintaining the reaction temperature at 0.4 kPa or less. The reaction temperature was maintained at 210°C for 15 minutes from the start of pressure reduction, then increased to the maximum temperature of 240°C over 45 minutes, maintained at this temperature for 1 hour, and then controlled to a final temperature of 235°C. The reaction was terminated when the specified stirring torque (corresponding to an IV of 1.20 dL / g) was reached. The polycondensation reaction took 150 minutes (the polycondensation reaction time was measured as the time from the start of pressure reduction to the time the pressure was restored with nitrogen). The tank was then restored to a reduced pressure with nitrogen and then pressurized to withdraw the polymer. The temperature of the heat medium in the die during withdrawal was set to 230°C, and the polymer was withdrawn from the die in the form of strands. The strands were then cooled in a cooling water tank and cut with a cutter to obtain pellets of polyester 2. The contents of each component in polyester 2 were as follows, and the intrinsic viscosity was 1.20 dL / g. Terephthalic acid units: 47.1% by weight Polyethylene glycol units: 30.0% by weight 1,4-butanediol units: 22.9% by weight

[0065] [Production Example 3: Production of Polyester 3 (Polyester Containing Dimer Acid Units)] Terephthalic acid and isophthalic acid were charged in amounts that would account for 58.5% by weight and 3.3% by weight, respectively, in the polyester after polymerization, and ethylene glycol was charged in an amount that was 1.2 times the molar ratio of the total amount of terephthalic acid and isophthalic acid to the total amount of terephthalic acid and isophthalic acid to an esterification reactor equipped with a stirrer, a temperature raising device, and a distillate separation column, and the temperature was kept at 250°C and the pressure was kept at 0.90 kg / cm. 2 The esterification reaction was carried out for 4 hours at 250°C under normal pressure, followed by 4 hours of esterification reaction to obtain a polyester oligomer. Next, the oligomer was transferred to a polycondensation reaction tank equipped with a distillation pipe and a stirrer, and a hydrogenated dimer acid having 36 carbon atoms ("Pripol 1009" manufactured by Croda Japan) was added in an amount that would result in 17.4% by weight of the polyester after polymerization. Furthermore, an ethylene glycol solution of germanium dioxide was added as a catalyst, and an ethylene glycol solution of orthophosphoric acid was added as a stabilizer. While maintaining the temperature inside the polycondensation reaction tank at 280°C, the pressure was reduced to 0.13 kPa over 2 hours, and then the reaction was carried out at the same pressure for 3 hours, after which the reaction system was returned to normal pressure to terminate the reaction. The obtained polyester was withdrawn as a strand from the bottom of the polycondensation reaction tank, immersed in water, and then cut with a cutter to obtain pellets of polyester 3. The contents of each component of polyester 3 were as follows, and the intrinsic viscosity was 0.67 dL / g. Terephthalic acid units: 58.5% by weight Isophthalic acid units: 3.3% by weight Dimer acid unit: 17.4% by weight Ethylene glycol units: 18.8% by weight Diethylene glycol units: 2.0% by weight

[0066] [Polyethylene terephthalate for PET bottles] As polyethylene terephthalate for PET bottles for compatibility evaluation, polyethylene terephthalate resin "BK2180" manufactured by Mitsubishi Chemical Indonesia (hereinafter referred to as "PET for compatibility evaluation") was prepared. The content of each component in this PET for compatibility evaluation was as follows, and the intrinsic viscosity was 0.83 dL / g. Terephthalic acid units: 75.3% by weight Isophthalic acid units: 1.3% by weight Ethylene glycol units: 22.2% by weight Diethylene glycol units: 1.2% by weight

[0067] [Evaluation method] <Recyclability (compatibility with PET used in PET bottles)> The molded plate samples obtained in each example and comparative example were crushed using a crusher (Horai Corporation's V-360 V-type crusher, screen hole diameter 8 mm), and 400 g of the crushed product was mixed with 1600 g of the aforementioned PET for compatibility evaluation in a stainless steel can. The mixture was then dried in a vacuum dryer at 60°C for 72 hours. The dried mixture was injection-molded into molded plates (hereinafter referred to as "recycled molded plates") using an injection molding machine (Nissei Plastic Industrial Co., Ltd.'s FE80S12ASE) under the following conditions: Molding temperature: 280°C (cylinder setting) Mold temperature: 20°C (chiller water setting temperature) Molded plate weight: 80g (total weight including plate, runner, and sprue) Mold filling time: 1.5 seconds Pressure retention time: 13.5 seconds Cooling time: 90 seconds Forming plate dimensions: 110mm wide with steps of 3-7mm thickness, starting from the runner side, 7mm thick for 20mm, then 6mm thick for 20mm, then 5mm thick for 20mm, then 4mm thick for 20mm, and finally 3mm thick for 30mm, 110mm x 110mm (runner and sprue not included) The haze of a 3 mm thick portion of this recycled molded plate was measured using a haze meter ("NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd.). The smaller the haze, the better the transparency and the better the compatibility with PET for PET bottles. A measured haze of 6% or less was rated as "good" and a haze of more than 6% was rated as "bad".

[0068] <Flexibility (bending properties of molded plate)> Test pieces measuring 10 mm wide x 60 mm long x 1 mm thick were cut out from the molded plate samples obtained in each of the Examples and Comparative Examples, and subjected to a constant speed bending test under the following conditions using the following bending tester. Toyo Seiki Manufacturing Co., Ltd. Bending tester: Bendgraph II Model: B Distance between fulcrums: 16mm Test speed: 1mm / min In this constant speed bending test, the smaller the load at a given displacement, the more excellent the flexibility. A load of 0.14 kgf or less at a displacement of 0.2 mm was rated as "good", and a load exceeding 0.14 kgf was rated as "poor".

[0069] <Sliding properties (sliding properties with hard materials)> Using the molded plate samples obtained in each example and comparative example, horizontal resistance was measured in a constant load horizontal friction test under the following conditions using Shinto Scientific's "Tribogear TYPE14DR," and the dynamic friction coefficient was determined by dividing the average horizontal resistance between the friction element's travel distance of 0.3 cm and 0.7 cm by the applied load. Friction element: 2mm diameter sapphire ball stylus Applied load: 1kgf Movement speed: 1cm / sec Drag measurement: 0.01 seconds / times The smaller the dynamic friction coefficient measured in the constant load horizontal friction test of the molded plate sample, the better the slipperiness is judged to be. In a constant load horizontal friction test of a molded plate sample, a load of 1 kgf was applied to the friction element and the test was conducted at 1 cm / sec. When the coefficient of dynamic friction of the friction element over a travel distance of 0.3 to 0.7 cm was 0.10 or less, it was evaluated as passing (○), and when it exceeded 0.10 it was evaluated as failing (×).

[0070] <Heat resistance (heat deformation resistance)> Using the molded plate samples obtained in each example and comparative example, a constant load temperature rise test was carried out under the following conditions using Seiko Instruments Inc.'s "TMA / SS6100", and the temperature at which the needle penetration depth became 0.1 mm was evaluated. Evaluation temperature: Room temperature to 120°C Heating rate: 5°C / min Probe: needle probe (tip diameter 1 mm) Measurement load: 0.5N The higher the temperature at which the needle penetration depth reaches 0.1 mm in the constant load temperature rise test of the above molded plate sample, the more excellent the heat resistance is judged to be. If this temperature was 70°C or higher, it was rated as a pass (◯), and if it was less than 70°C, it was rated as a fail (×).

[0071] [Example 1] 65% by weight of polyester 1, 25% by weight of polyester 2, and 10% by weight of polyester 3 were used, blended in the form of pellets, and dried in a vacuum dryer at 60° C. for 72 hours. The proportions of each polyester structural unit contained in the blend, calculated from this blend weight ratio, are shown in Table 1. The dried pellets were placed in a stainless steel can with a seal gasket, and a powder lubricant (erucic acid amide "Diamid (registered trademark) L-200" manufactured by Mitsubishi Chemical Corporation) was added in an amount equivalent to 0.5% by weight of the dried pellets. The can was then sealed and thoroughly stirred. The obtained polyester resin composition was injection molded into a molded plate (hereinafter referred to as a "molded plate sample") using an injection molding machine ("FE80S12ASE" manufactured by Nissei Plastic Industrial Co., Ltd.) under the following conditions. Molding temperature: 260°C (cylinder setting) Mold temperature: 20°C (chiller water setting temperature) Molded plate weight: 40g (total weight including plate, runner, and sprue) Mold filling time: 1 second Pressure retention time: 14 seconds Cooling time: 20 seconds Forming plate dimensions: 1mm thick, 110mm x 110mm (excluding runners and sprues)

[0072] The obtained molded plate samples were subjected to the above-mentioned evaluations, and the results are shown in Table 1.

[0073] [Examples 2 to 4, Comparative Examples 1 to 5] Molded plate samples were produced and evaluated in the same manner as in Example 1, except that the blend amounts of Polyesters 1 to 3 and the blend amount of erucic acid amide were changed as shown in Table 1. The proportions of each polyester structural unit contained in the blend and the evaluation results are shown in Table 1. The details of "BK2180" used in Comparative Example 3 are as follows. Mitsubishi Chemical Indonesia BK-PET "BK2180" Terephthalic acid units: 75.3% by weight Isophthalic acid units: 1.3% by weight Ethylene glycol units: 22.2% by weight Diethylene glycol units: 1.2% by weight Intrinsic viscosity: 0.83dL / g

[0074] In Table 1, the abbreviations for each structural unit are as follows: TPA: Terephthalic acid IPA: Isophthalic acid DA: Dimer acid BG: 1,4-butanediol EG: Ethylene glycol DEG: Diethylene glycol PEG: polyethylene glycol

[0075] [Table 1]

[0076] Table 1 shows that the polyester resin composition of the present invention, which is obtained by adding erucic acid amide in a predetermined ratio to a polyester containing terephthalic acid units, dimer acid units, polyalkylene glycol units, and 1,4-butanediol units, wherein the contents of the 1,4-butanediol units, dimer acid units, and polyalkylene glycol units fall within the ranges specified in the present invention, is excellent in all of recyclability, flexibility, slip properties, and heat resistance. In contrast, Comparative Examples 1 to 4, which do not contain erucic acid amide, are inferior in any of these physical properties. That is, Comparative Example 1 does not contain erucic acid amide, and has a large dynamic friction coefficient and poor slipperiness. Comparative Examples 2 and 3 do not contain erucic acid amide or polyalkylene glycol units, which are softening components, and are therefore inferior in softness. Comparative Example 3 does not contain 1,4-butanediol units and is also poor in heat resistance. Comparative Example 4 does not contain erucic acid amide or dimer acid units and is poor in recyclability and slipperiness. Comparative Example 5, in which the amount of erucic acid amide added was too large, was inferior in recyclability.

Claims

1. A polyester resin composition comprising a polyester containing, as main structural units, dicarboxylic acid units including terephthalic acid units and dimer acid units, and diol units including polyalkylene glycol units and 1,4-butanediol units, The polyester contains a fatty acid amide having 8 to 22 carbon atoms in an amount of 0.05 parts by weight or more and 4.0 parts by weight or less based on 100 parts by weight of the polyester, the content of 1,4-butanediol units in the polyester is 20% by weight or more; the content of dimer acid units in the polyester is 0.5% by weight or more and 5% by weight or less, The polyester resin composition has a polyalkylene glycol unit content of 1% by weight or more and 30% by weight or less.

2. 2. The polyester resin composition according to claim 1, wherein the polyalkylene glycol is polyethylene glycol having a weight average molecular weight of 4,000 or less.

3. 3. The polyester resin composition according to claim 1, wherein the fatty acid amide is erucic acid amide.

4. A molded article using the polyester resin composition according to any one of claims 1 to 3.

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