Polyester composition and method for producing the same

Abstract

To provide a polyester composition which prevents calcium carbonate particles from aggregated and turned into a coarse foreign matter, and is excellent in hydrolysis resistance, and a method for producing the same.MEANS FOR ACHIEVING THE PURPOSE: A polyester composition contains calcium carbonate particles and a phosphorus atom (element), and satisfies the following expressions (I) and (II). Expression (I): 0.2≤R≤0.8. Expression (II): 0.38 / R2≤P1. In the expressions, R is a volume average diameter (μm) of the calcium carbonate particles, and P1 is a phosphorus atom (element) content contained in isolated particles obtained by isolated from the polyester composition by the following method (wt.%: weight ratio to isolated particles). (Isolation method: The isolation method adds dichloromethane to a solid content obtained by centrifugally separating a polyester composition at centrifugal acceleration of 40,900 G and 20°C for one hour after dissolved at 150°C for one hour in o-chlorophenol, centrifugally separates the solid content under the same condition, and obtains a solid content. The isolation method adds dichloromethane to the obtained solid content again, and centrifugally separates the solid content under the same condition. A solid content obtained by performing centrifugal separation with the dichloromethane three times in total is determined as isolated particles.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polyester composition and a method for producing the same.

Background Art

[0002] Polyester is excellent in mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and is used in various applications. Among polyesters, polyethylene terephthalate (hereinafter referred to as PET) is particularly widely used in applications that require high quality, such as optical films and release films, because of its excellent transparency and processability. As a method for improving transportability and releasability, a technique is known in which an appropriate amount of particles is blended into polyester to form fine protrusions on the film surface. In general release films, smoothness is required such that when a release object is provided on the release film while maintaining the releasability, the defects of the release film are not transferred to the release object. Further, in the release of a liquid crystal polarizing plate, since the release film is subjected to a cross-nicol inspection while being bonded to the polarizing plate, it is desired to reduce foreign matter in the release film so as not to inhibit the cross-nicol inspection.

[0003] However, due to the activity of the particles themselves, there are problems that the particles are denatured and become foreign substances at high temperatures, and the amount of COOH terminal groups in the polyester composition increases, resulting in poor hydrolysis resistance.

[0004] In response to these problems, studies have been conducted as shown in the following documents. In Patent Document 1 and Patent Document 2, it is described that the hydrolysis resistance is improved by containing an alkali metal phosphate in a polyester resin. Patent Document 3 discloses a technique for providing a polyester composition excellent in particle dispersibility and heat resistance by using surface-treated particles.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 WO2014 / 021095 Gazette Patent Document 2 Japanese Unexamined Patent Application Publication No. 2013-189521 Patent Document 3 Japanese Unexamined Patent Application Publication No. Hei 8-143756 Summary of the Invention Problems to be Solved by the Invention

[0006] As in the prior art described above, there was a problem that suppression of the foreignization of particles was insufficient only by improving the hydrolysis resistance of the polyester composition. And if only the foreignization of particles was suppressed, thermal decomposition and hydrolysis during polyester melting could not be prevented. Further, simply using surface-treated particles could not suppress the decomposition reaction of the polyester. That is, with the conventional techniques for improving hydrolysis resistance and surface treatment of particles, it was impossible to achieve both the hydrolysis resistance of the polyester composition and the stabilization of the particles.

[0007] An object of the present invention is to provide a polyester composition that suppresses aggregation and coarsening of calcium carbonate particles and has excellent hydrolysis resistance, and a method for producing the same. Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, a polyester composition that suppresses aggregation and coarsening of calcium carbonate particles and has excellent hydrolysis resistance, and a method for producing the same were found, and the present invention was achieved. The object of the present invention is achieved by the following means. (1) A polyester composition containing calcium carbonate particles and a phosphorus atom (element), Composed of phosphoric acid and an alkali metal phosphate, satisfying the following formulas (I), (II), (V), and (VI). 0.2 ≦ R ≦ 0.8 (I) 0.38 / R 2 ≦ P 1 (II) Content of free calcium atoms (elements) ≦ 5 ppm (V) 0.01 ppm ≤ sodium atom (element) content (weight ratio to the polyester composition) ≤ 30 ppm or less (VI) R: volume average diameter (μm) of calcium carbonate particles P 1 : phosphorus atom (element) content (wt%: weight ratio to the isolated particles) contained in the isolated particles obtained by isolating from the polyester composition by the following method (Isolation method: Dissolve the polyester composition in o-chlorophenol at 150 °C for 1 hour, then centrifuge at a centrifugal acceleration of 40900 G at 20 °C for 1 hour. Add dichloromethane to the obtained solid content and centrifuge under the same conditions to obtain a solid content. Add dichloromethane to the obtained solid content again and perform centrifugation under the same conditions. The solid content obtained by performing centrifugation with dichloromethane a total of 3 times is used as the isolated particles.) (Content of free calcium atoms (elements): The content of calcium atoms (elements) in the polymer obtained by dissolving the polyester composition in o-chlorophenol at 150 °C for 1 hour, then centrifuging at a centrifugal acceleration of 40900 G at 20 °C for 1 hour, collecting the obtained supernatant solution by decantation, adding acetone to precipitate, collecting the precipitate by filtration, and drying in vacuo at 150 °C for 12 hours.) (2) The polyester composition according to (1), wherein the calcium atom (element) content is 100 ppm (weight ratio to the polyester composition) or more. (3) The polyester composition according to (1), wherein the increase amount ΔCOOH of carboxylic acid end groups before and after heat and moisture treatment at 155 °C for 4 hours under saturated steam is 80 eq / t or less. (4) The polyester composition according to (1), wherein the polyester is polyethylene terephthalate. (5) A method for producing a polyester composition, in which a dicarboxylic acid or dicarboxylic acid ester and a diol are subjected to an esterification reaction or transesterification reaction, and then a polycondensation reaction is carried out to produce the polyester composition. Before the end of the polycondensation reaction, calcium carbonate particles and a compound containing a mixed solution of phosphoric acid and an alkali metal phosphate are added as a mixed slurry, and the polyester composition satisfies the following formulas (III), (IV), (VII). 0.2 ≤ R ≤ 0.8 (III) 0.38 / R 2 ≤P 2 (IV) 0.01 ppm ≤ sodium atom (element) content (weight ratio to the polyester composition) ≤ 30 ppm or less (VII) R: volume average diameter (μm) of calcium carbonate particles P 2 : amount of phosphorus atom (element) added as a mixed slurry (wt%: weight ratio to calcium carbonate) (6) The method for producing a polyester composition according to (5), wherein the addition amount of calcium carbonate particles is 100 ppm or more as calcium atoms (element) (weight ratio to the polyester composition). (7) The method for producing a polyester composition according to (5), wherein the polyester is polyethylene terephthalate.

Advantages of the Invention

[0009] The polyester composition obtained by the present invention suppresses aggregation and coarsening of calcium carbonate particles and is excellent in hydrolysis resistance.

Modes for Carrying Out the Invention

[0010] The present invention will be described in detail below.

[0011] The polyester composition of the present invention is a polyester composition containing calcium carbonate particles and phosphorus atoms (element) and satisfying the following formulas (I) and (II). 0.2 ≤ R ≤ 0.8 (I) 0.38 / R 2 ≤P 1 (II) R: volume average diameter (μm) of calcium carbonate particles P 1 : phosphorus atom (element) content (wt%: weight ratio to the isolated particles) contained in the isolated particles obtained by isolating from the polyester composition by the following method The polyester composition of the present invention contains calcium carbonate particles, and the volume average diameter R of the particles needs to be 0.2 μm or more and 0.8 μm or less (the above formula (II)). The method for measuring the volume average diameter is to subject the polyester composition to plasma treatment to expose the particles, and use a Hitachi field emission scanning electron microscope (model number S-4000) and a Nidec SEM-IMAGEANALYZER (model number Rudex AP) to perform measurements at a magnification of 5000 times for 20 or more fields of view. The equivalent circle diameter is measured from at least 200 particles and calculated by assuming a pseudo-stereoscopic spherical shape. The lower limit of the volume average diameter R is preferably 0.4 μm or more. By setting it above the above lower limit, it is possible to provide a polyester composition without particle aggregation. Also, the volume average diameter affects the surface physical properties when the polyester composition is processed into a film. Larger volume average diameter particles are a factor in the formation of coarse protrusions on the film surface. Therefore, by setting the volume average diameter below the above upper limit, it is possible to obtain a film with reduced coarse protrusions.

[0012] Moreover, the polyester composition of the present invention needs to contain a phosphorus atom (element). By containing a phosphorus atom (element), hydrolysis resistance can be imparted to the polyester composition. Further, by protecting the surface of calcium carbonate particles with a phosphorus compound, particle aggregation is less likely to occur even when subjected to a thermal history, etc., and it becomes possible to provide a polyester composition having good particle dispersibility.

[0013] The phosphorus atom (element) content P contained in the isolated particles obtained by isolating from the polyester composition of the present invention 1 (wt%: weight ratio to the isolated particles) needs to satisfy the following formula. 0.38 / R 2 ≦P 1 (II) Here, P 1 The upper limit is preferably 2.5 wt% or less. By setting it within the above range, it becomes possible to provide a polyester composition in which aggregation of particles is suppressed without inhibiting the polymerization reaction of the polyester. Isolation of the particles from the polyester composition is carried out by the following method. That is, after dissolving 1 g of the polyester composition in 10 ml of o-chlorophenol at 150°C for 1 hour, centrifugation is performed at a centrifugal acceleration of 40900 G and 20°C for 1 hour. After separation, the supernatant is removed by decantation, dichloromethane is added to the obtained solid content, the precipitate is stirred, and then centrifuged under the same conditions to obtain a solid content. Dichloromethane is added again to the obtained solid content, the precipitate is stirred, and then centrifugation is performed under the same conditions. The solid content obtained by performing the centrifugation with dichloromethane a total of three times is used as the isolated particles. Calcium carbonate particles are mixed and added with a phosphorus compound, and the phosphorus compound adheres to the particle surface. Since the phosphorus compound adhering to this surface has the effect of protecting the particles, addition according to the surface area of the particles is required. By containing a phosphorus atom (element) that satisfies formula (II), the surface of the particles can be effectively protected, and aggregation and coarsening of the particles can be suppressed.

[0014] The polyester composition of the present invention preferably contains 100 ppm or more of calcium atoms (element) based on the weight of the polyester composition. By containing calcium atoms (element) of not less than the above lower limit, the transportability and releasability when the polyester composition is processed into a film become good.

[0015] The content of free calcium atoms (elements) in the polyester composition of the present invention is preferably 10 ppm or less, more preferably 5 ppm or less, based on the weight of the polyester composition. The free calcium content means, as described in the examples in detail, after dissolving 1 g of the polyester composition in 10 ml of o-chlorophenol at 150 °C for 1 hour, centrifuging at a centrifugal acceleration of 40900 G at 20 °C for 1 hour, collecting the supernatant solution by decantation, adding acetone thereto to precipitate, and recovering by filtration, it is the calcium content in the polymer from which the obtained particles have been removed. In a film containing calcium carbonate particles, free calcium is generated from the calcium carbonate particles due to the heat history during film formation or the like. This generated free calcium forms a by-product with the polyester composition and causes aggregation of the particles and formation of coarse foreign substances. By protecting the surface of the calcium carbonate particles with a sufficient amount of a phosphorus compound, the release of calcium from the calcium carbonate particles can be prevented. By suppressing the amount of free calcium below the above upper limit, it becomes possible to suppress the aggregation of calcium carbonate particles.

[0016] Moreover, the polyester composition of the present invention preferably contains sodium atoms (elements) in an amount of 0.01 ppm or more and 30 ppm or less based on the weight of the polyester composition. By setting it within the above range, the hydrolysis resistance becomes good, and furthermore, the surface protection of the calcium carbonate particles can be effectively carried out.

[0017] The hydrolysis resistance of the polyester composition of the present invention is evaluated by the value of ΔCOOH. ΔCOOH is the increase amount of COOH end groups when subjected to hydrothermal treatment at 155 °C for 4 hours under saturated water vapor. The smaller the value of ΔCOOH, the better the hydrolysis resistance. In the polyester composition of the present invention, ΔCOOH is preferably 80.0 or less. When the value of ΔCOOH is 80.0 or less, the hydrolysis resistance is good, and the decomposition of the polyester that causes aggregation of the particles can be suppressed. The value of ΔCOOH is more preferably 70.0 or less, and even more preferably 60.0 or less.

[0018] Next, the method for producing the polyester composition of the present invention will be described. The method for producing the polyester composition of the present invention uses dicarboxylic acid or its ester and diol as the main raw materials, and consists of the following two-step process. That is, the first step is composed of (A) an esterification reaction or (B) a transesterification reaction, and the second step is composed of (C) a polycondensation reaction that follows.

[0019] As the raw materials for producing the polyester composition of the present invention, dicarboxylic acid or dicarboxylic acid ester and diol can be used, and it is also possible to use a combination of two or more kinds.

[0020] Examples of the dicarboxylic acid of the present invention include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyl 4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, malonic acid, dimer acid, etc. The dicarboxylic acid ester refers to the lower alkyl esters, acid anhydrides, acyl chlorides, etc. of the dicarboxylic acids described above, and methyl esters, ethyl esters, hydroxyethyl esters, etc. are preferably used. A more preferred embodiment of the dicarboxylic acid or dicarboxylic acid ester in the present invention is terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, or their alkyl esters in that a polyester composition with a high melting point and easy to process into films, fibers, etc. can be obtained.

[0021] Examples of the diol of the present invention include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, and neopentyl glycol; alicyclic diols such as cyclohexanedimethanol, cyclohexaneethanol, norbornanedimethanol, norbornaneethanol, tricyclodecanedimethanol, tricyclodecaneethanol, decalindimethanol, and decalineethanol, which are saturated alicyclic primary diols; saturated heterocyclic primary diols containing cyclic ethers such as isosorbide; and other various alicyclic diols such as cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexyl)propane, 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentanediol, 4-cyclopentene-1,3-diol, and adamantanediol; and aromatic cyclic diols such as paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9'-bis(4-hydroxyphenyl)fluorene. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used as long as the effects of the present invention are not impaired. Ethylene glycol is preferred in terms of being able to fully achieve the effects of the present invention and being able to obtain a polyester composition that is easy to process into films, fibers, etc.

[0022] In the production method of the present invention, among the steps of the first stage, (A) the esterification reaction step is a step of subjecting a dicarboxylic acid and a diol to an esterification reaction at a predetermined temperature, reacting until a predetermined amount of water distills off, and obtaining a low polymer. When obtaining a low polymer by an esterification reaction, from the viewpoints of esterification reactivity and heat resistance, the molar ratio of the diol to the dicarboxylic acid (diol / dicarboxylic acid) before the start of the esterification reaction is preferably in the range of 1.05 or more and 1.40 or less. More preferably, it is 1.05 or more and 1.30 or less, and still more preferably, it is 1.05 or more and 1.20 or less. By setting the range as described above, since it has good reactivity and can suppress the generation of by-products such as dimers of the diol, the heat resistance can be improved.

[0023] Also, (B) the transesterification reaction step is a step of subjecting a dicarboxylic acid ester and a diol to a transesterification reaction, reacting until a predetermined amount of alcohol distills off, and obtaining a low polymer. When obtaining a low polymer by a transesterification reaction, from the viewpoints of reactivity and heat resistance, the molar ratio of the diol to the dicarboxylic acid ester (diol / dicarboxylic acid ester) is preferably in the range of 1.7 or more and 2.3 or less. By setting the range as described above, the transesterification reaction can proceed efficiently, and since the by-production of dimers of the diol can be suppressed, the heat resistance can be improved.

[0024] Among the steps of the second stage, (C) the polycondensation reaction is a step of obtaining a polyester composition from the low polymer obtained by (A) the esterification reaction or (B) the transesterification reaction.

[0025] Also, batch polymerization, semi-continuous polymerization, and continuous polymerization can be applied to the production method of the present invention.

[0026] In the method for producing the polyester composition of the present invention, as the catalyst (A) used in the esterification reaction, compounds such as manganese, cobalt, zinc, titanium, and calcium may be used. However, from the viewpoints of thermal decomposition and generation of foreign substances in the polycondensation reaction stage, it is preferable to carry out the esterification reaction without a catalyst. Here, in the (A) esterification reaction, even without a catalyst, the reaction proceeds sufficiently due to the autocatalytic action of the carboxylic acid. Further, as the catalyst (B) used in the transesterification reaction, known transesterification catalysts can be used. Examples of the transesterification catalyst include organic manganese compounds, organic magnesium compounds, organic calcium compounds, organic cobalt compounds, organic lithium compounds, etc. Specifically, there are carbonates, acetates, benzoates, oxides, hydroxides, etc., but it is not limited thereto.

[0027] Also, as the catalyst (C) used in the polycondensation reaction, known polycondensation catalysts can be used. For example, compounds such as antimony, titanium, aluminum, tin, and germanium compounds can be mentioned. Examples of the antimony compound include antimony oxides, antimony carboxylates, and antimony alkoxides. Examples of the titanium compound include titanium chelate complexes, titanium alkoxides, and titanium oxides obtained by hydrolysis of titanium alkoxides.

[0028] Examples of the aluminum compound include aluminum carboxylates, aluminum alkoxides, aluminum chelate compounds, and basic aluminum compounds.

[0029] Examples of the tin compound include tin compounds having an alkyl group and tin compounds having a hydroxyl group.

[0030] Examples of the germanium compound include germanium oxides and germanium alkoxides.

[0031] The above metal compounds may be hydrates. Among these, from the viewpoints of polymerization time and economy, it is preferable to use an antimony compound as the polycondensation reaction catalyst. In the method for producing the polyester composition of the present invention, calcium carbonate particles and a compound containing a phosphorus atom (element) are added as a mixed slurry, and it is necessary to satisfy the following formulas (III) and (IV). 0.2 ≦ R ≦ 0.8 (III) 0.38 / R 2 ≦ P 2 (IV) R: Volume average diameter (μm) of calcium carbonate particles P 2 : Amount of phosphorus atom (element) added as a mixed slurry (wt%: weight ratio to calcium carbonate).

[0032] In the method for producing the polyester composition of the present invention, the volume average diameter R of the calcium carbonate particles to be added needs to be 0.2 μm or more and 0.8 μm or less. Preferably, it is 0.4 μm or more as the lower limit. By setting it to be not less than the above lower limit, it is possible to provide a polyester composition with excellent particle dispersibility. Further, the volume average diameter affects the surface physical properties when the polyester composition is processed into a film, and particles with a large volume average diameter are a factor in forming coarse protrusions on the film surface. Therefore, by setting the volume average diameter to be not more than the above upper limit, it is possible to obtain a film with reduced coarse protrusions.

[0033] Regarding the polyester composition of the present invention, the addition amount P of the compound containing a phosphorus atom (element) 2 needs to be mixed with the calcium carbonate particles so as to satisfy the following formula (IV) with respect to the volume average diameter R of the calcium carbonate particles and added to the polyester composition. 0.38 / R 2 ≦ P 2 (IV) P 2 The upper limit of is preferably 3.0 wt% or less. By setting it within the above range, it is possible to provide a polyester composition in which particle aggregation is suppressed without inhibiting the polymerization reaction. The amount of phosphorus added is 0.38 / R with respect to the volume average diameter R of the calcium carbonate particles2 If it is less than that, the surface of the particles cannot be sufficiently protected, which may cause particle aggregation and coarsening. As the phosphorus compound, phosphoric acid, trimethyl phosphate, ethyldiethylphosphonoacetate, phosphorous acid, etc. can be used, and it is also possible to use a plurality of phosphorus compounds in combination. It is particularly preferable that this phosphorus compound is phosphoric acid. By adding the phosphorus compound, the surface of the calcium carbonate particles can be effectively protected, and further, the hydrolysis resistance can be imparted to the polyester composition.

[0034] Also, in the method for producing the polyester composition of the present invention, it is preferable to add sodium atoms (elements) so as to be 0.01 ppm or more and 30 ppm or less based on the weight of the polyester composition. By setting it within the above range, the hydrolysis resistance becomes good, and further, the surface protection of the calcium carbonate particles can be effectively performed.

[0035] The compound containing sodium atoms (elements) is not particularly limited. For example, sodium phosphates, hydroxides, acetates, carbonates, nitrates, chlorides, etc. can be mentioned. From the viewpoint of hydrolysis resistance, it is more preferable that it is a sodium phosphate salt. Examples of the sodium phosphate salt include sodium dihydrogen phosphate, disodium hydrogen phosphate, and trisodium phosphate. Sodium dihydrogen phosphate is particularly preferable from the viewpoint of hydrolysis resistance. Also, a plurality of sodium phosphate salts may be used in combination.

[0036] Also, it is preferable to use the above sodium phosphate salt in combination with a compound containing other phosphorus atoms (elements). It is particularly preferable to mix as a buffer solution composed of a sodium phosphate salt and phosphoric acid. By mixing a buffer solution composed of a sodium phosphate salt and phosphoric acid with the calcium carbonate particle slurry, the surface of the calcium carbonate particles can be coated, and it becomes possible to suppress the elution of calcium from the surface of the calcium carbonate particles due to heating during melt molding such as polycondensation reaction and film formation.

[0037] In the method for producing the polyester composition of the present invention, the calcium carbonate particles and the compound containing a phosphorus atom (element) may be added at any stage of the (A) esterification reaction or (B) transesterification reaction step, followed by the (C) polycondensation reaction step. However, by adding after mixing the calcium carbonate particles and the compound containing a phosphorus atom (element) before the end of the polycondensation reaction, the amount of COOH terminal groups can be reduced and the hydrolysis resistance can be improved, and further a polyester composition having good particle dispersibility can be obtained.

[0038] Further, the compound containing the phosphorus atom (element) may be used in combination with other alkali metal compounds. For example, by using potassium hydroxide in combination, the melt specific resistance of the polyester required for electrostatic coating film formation can be reduced, and the moldability can be improved.

[0039] In the method for producing the polyester composition of the present invention, when carried out via the (A) esterification reaction, from after the esterification reaction until the calcium carbonate particles and the compound containing a phosphorus atom (element) are added as a mixed slurry, it is preferable to carry out additional addition of a glycol component such as ethylene glycol. The low molecular weight product of the polyester composition obtained by the esterification reaction has a higher degree of polymerization than the low molecular weight product obtained by the transesterification reaction, so calcium carbonate particles and sodium phosphate salts are difficult to disperse and foreign matter formation is likely to occur. Therefore, by additionally adding a glycol such as ethylene glycol and once reducing the degree of polymerization by depolymerization, the formation of foreign matter can be suppressed.

[0040] This additional added glycol such as ethylene glycol is preferably 0.05 times mole or more and 0.5 times mole or less based on all acid components. More preferably, it is 0.1 times mole or more and 0.3 times mole or less. By setting it within the above range, the formation of foreign matter of the alkali metal phosphate can be suppressed without causing a delay in the polymerization time due to a temperature drop in the polymerization system.

[0041] When adding a compound containing calcium carbonate particles and phosphorus atoms (elements), in terms of particle dispersibility, it is preferably added as a slurry. When adding as a slurry, since it is preferable that the particles and the dispersion solvent are sufficiently mixed, it is preferably mixed for at least 10 seconds or more. The mixing may be carried out using a stirring device such as a stirrer or a magnetic stirrer. Also, the particle dispersion solvent is preferably the same as the diol of the polyester composition, and in the case of PET, it is particularly preferable to use ethylene glycol.

[0042] During and after the addition of the calcium carbonate particles and the compound containing phosphorus atoms (elements), it is preferable to stir the reaction system. By stirring, the additives can be more uniformly dispersed.

[0043] Also, in the method for producing the polyester composition of the present invention, in order to obtain a high molecular weight polyester composition, solid phase polymerization may be carried out. The solid phase polymerization is not particularly limited in terms of the apparatus and method, but is carried out by heat-treating the polyester composition in an inert gas atmosphere or under reduced pressure. The inert gas may be any gas that is inert to the polyester composition, and examples thereof include nitrogen, helium, and carbon dioxide gas. However, nitrogen is preferably used from the viewpoint of economy. Also, under reduced pressure conditions, it is advantageous to make the vacuum higher because the time required for the solid phase polymerization reaction can be shortened. Specifically, it is preferable to maintain a pressure of 110 Pa or less.

[0044] Hereinafter, specific examples of the method for producing the polyester composition in the present invention will be given, but the present invention is not limited thereto.

[0045] A slurry of terephthalic acid and ethylene glycol (1.15 times the molar amount of terephthalic acid) is gradually added to an esterification reactor charged with bis-hydroxyethyl terephthalate (BHT) dissolved at 250 °C, and the esterification reaction is allowed to proceed. The temperature in the reaction system is controlled to be 245 to 250 °C, and the esterification reaction is terminated when the reaction rate reaches 95%.

[0046] The esterification reactant at 255°C thus obtained is transferred to a polymerization apparatus, and a polycondensation catalyst, an additional amount of ethylene glycol, and a mixed slurry of calcium carbonate particles and a compound containing a phosphorus atom (element) are added. During these operations, it is preferable to maintain the temperature inside the reaction system at 240 - 255°C so that the esterified product does not solidify.

[0047] Thereafter, while gradually raising the temperature inside the polymerization apparatus to 290°C, the pressure inside the polymerization apparatus is gradually reduced from atmospheric pressure to 250 Pa or less to distill out ethylene glycol. The reaction is terminated when a predetermined stirring torque is reached, the pressure inside the reaction system is returned to atmospheric pressure with nitrogen gas, and the molten polyester is discharged in a strand shape into cold water and cut to obtain a polyester composition.

[0048] The polyester composition obtained in the present invention can be molded by a known molding process method and can be processed into various products such as films, fibers, bottles, injection molded products, and the like.

[0049] When processing the polyester composition of the present invention into various products, one or more additives such as colorants including pigments and dyes, lubricants, antistatic agents, flame retardants, ultraviolet absorbers, antibacterial agents, nucleating agents, plasticizers, mold release agents, etc. can be added within a range that does not impair the effects of the present invention.

[0050] The polyester composition of the present invention is excellent in hydrolysis resistance and particle dispersibility, and there are few decomposition foreign substances and aggregated foreign substances of particles generated during melt molding and processing steps. Therefore, it can be used as various products such as films, fibers, bottles, injection molded products, etc., and in particular, it can be used for high-quality films such as optical films and release films.

[0051] As the film, it may be a single-layer film composed of the polyester composition of the present invention or a laminated film having at least one layer of the polyester composition of the present invention. Particularly in the case of a laminated film, a laminated film having a layer made of the polyester composition of the present invention on at least one surface is preferable. When the layer made of the polyester composition of the present invention exists on the film surface, aggregation foreign matters and coarse protrusions derived from particles can be suppressed.

[0052] The molded article produced from the polyester composition of the present invention is excellent in thermal stability and color tone, and thus is useful as agricultural materials, horticultural materials, fishery materials, civil engineering and construction materials, stationery, medical supplies, automobile parts, electrical and electronic parts or other applications. Particularly, in the case of a biaxially stretched film, it is suitable for a release process film and an optical film.

Examples

[0053] The present invention will be described in more detail with reference to the following examples. The physical property values in the examples were measured by the following methods. The methods described below describe the measurement methods for the case of a single component of the polyester composition of the present invention. In the case of a molded article composed of a plurality of resins such as a laminated film, the resin of each layer is isolated by scraping and analyzed. Although the method of measuring the amount of COOH terminal groups (unit: eq / t refers to equivalent / t) of the polyester composition is described, in the case of a molded article composed of a plurality of resins such as a laminated film, each layer of resin is isolated by scraping and analyzed. Also, Example 4, Example 9, and Example 10 are to be read as reference examples.

[0054] (1) Amount of COOH terminal groups in the polyester composition (unit: eq / t refers to equivalent / t) Measured by the method of Maurice (literature M.J. Maurice, F. Huizinga, Anal. Chem. Acta, 22, 363 (1960)). That is, 0.5 g of the polyester resin composition is weighed with an accuracy within 0.001 g. 50 ml of a solvent obtained by mixing o-cresol / chloroform at a mass ratio of 7 / 3 is added to the sample, and the mixture is heated. After the internal temperature reaches 90°C, heating and stirring are carried out for 20 minutes to dissolve it. Also, only the mixed solvent is separately heated in the same manner as a blank solution. The solution is cooled to room temperature, and titration is performed using a potentiometric titrator with a 1 / 50N potassium hydroxide methanol solution. Also, titration is similarly carried out for the blank solution of only the mixed solvent. The amount of COOH terminal groups in the polyester resin composition was calculated by the following formula. Amount of COOH terminal groups (eq / t) = {(V1 - V0) × N × f} × 1000 / S Here, V1 is the volume of the titrant in the sample solution (mL), V0 is the volume of the titrant in the blank solution (mL), N is the normality of the titrant (N), f is the factor of the titrant, and S is the mass of the polyester resin composition (g).

[0055] (2) Quantification of alkali metal atoms (elements) in the polyester composition (unit: ppm) 1 g of the polyester composition is placed in a platinum dish and completely ashed at 700°C for 1.5 hours. Next, the ash is dissolved in 20 mL of 0.25N hydrochloric acid aqueous solution, and pure water is added to make it a 0.1N hydrochloric acid aqueous solution, which is used as a measurement sample, and quantification is carried out by atomic absorption spectrometry (manufactured by Hitachi, Ltd.: Polarized Zeeman Atomic Absorption Photometer Model 180 - 80, Flame: Acetylene - Air).

[0056] (3) Quantification of Ca atoms (elements) and P atoms (elements) in the polyester composition (unit: ppm) 7 g of the polyester composition is molded into a cylindrical shape with a melt press machine, and quantification is carried out using a fluorescence X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation.

[0057] (4) Content of free calcium atoms (elements) in the polyester composition (unit: ppm) 30 g of the polyester composition was added to 300 mL of o-chlorophenol and dissolved at 150 °C for 1 hour. After that, centrifugation was performed at a centrifugal acceleration of 40900 G at 20 °C for 1 hour. The obtained supernatant solution was collected by decantation, 500 mL of acetone was added thereto for precipitation, the precipitate was collected by filtration, and quantification was performed by the analysis method of (3) on the product vacuum-dried at 150 °C for 12 hours. A centrifuge manufactured by HITACHI, himac CR20G (rotor: R19A) was used.

[0058] (5) Isolation of calcium carbonate particles from the polyester composition and measurement of the phosphorus element (atom) content in the isolated particles (unit: wt%) 30 g of the polyester composition was added to 300 mL of o-chlorophenol and dissolved at 150 °C for 1 hour. After that, centrifugation was performed at 18000 rpm (40900 G) at 20 °C for 1 hour. 300 mL of dichloromethane was added to the obtained solid content and the precipitate was stirred, followed by centrifugation at a centrifugal acceleration of 40900 G at 20 °C for 1 hour to obtain a solid content. 300 mL of dichloromethane was added again to the obtained solid content and the precipitate was stirred, followed by centrifugation under the same conditions. The solid content obtained by performing centrifugation with dichloromethane a total of 3 times was used as the isolated particles. The phosphorus atom (element) content in the isolated particles was measured using an ICP emission spectroscopic analyzer (PS3520VDDII manufactured by Hitachi High-Technologies Corporation). A centrifuge manufactured by Hitachi, himac CR20G (rotor: R19A) was used.

[0059] (6) Measurement of the particle volume average diameter in the polyester composition (unit: μm) The polyester composition was subjected to plasma treatment, and the particle volume average diameter was measured using a field emission scanning electron microscope manufactured by Hitachi (model number S-4000) and a SEM-IMAGE ANALYZER manufactured by Nidec (model number Rudex AP). When analyzing the particle diameter, measurements were performed at a magnification of 5000 times for 20 or more fields of view. The equivalent circle diameter was measured from at least 200 particles, and it was regarded as a pseudo-stereoscopic sphere to calculate the volume average particle diameter.

[0060] (7) Heat treatment of the polyester composition and evaluation of aggregation and coarsening of particles The polyester composition is pre-treated by vacuum drying at 150°C for 3 hours and then at 180°C for 7.5 hours, heated and melted at 300°C for 10 hours under a nitrogen flow, and then rapidly cooled in water. The volume average particle diameter of the obtained composition is calculated by the method described in (6) above, and the ratio (volume average diameter after heating / volume average diameter before heating) divided by the volume average diameter before heat treatment calculated in (6) is evaluated as an index of particle aggregation and coarsening (◎ and 〇 are regarded as passing). ◎: 1.2 or less 〇: 1.2 to 1.5 ×: 1.5 or more.

[0061] (8) Evaluation of hydrolysis resistance (ΔCOOH) of polyester composition The polyester composition is subjected to a hydrothermal treatment at 155°C for 4 hours under saturated steam, and the amount of increase in COOH end groups (ΔCOOH = COOH after treatment - COOH before treatment) is calculated by measuring the amount of COOH end groups before and after the treatment. The treatment apparatus used was a PRESSER COOKER 306SIII (manufactured by HIRAYAMA MANUFACTURING CO., LTD.).

[0062] (9) Preparation of biaxially oriented film and measurement of three-dimensional roughness [Production of PET-A] A slurry composed of 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol (1.15 times the molar amount relative to terephthalic acid) was gradually added to an esterification reactor charged with 105 parts by weight of BHT melted at 250°C, and the esterification reaction was allowed to proceed. The temperature in the reaction system was controlled to be 245 - 250°C, and the esterification reaction was terminated when the reaction rate reached 95% to obtain BHT. 105 parts by weight (equivalent to 100 parts by weight of PET) of BHT in a molten state was charged from the esterification reactor into a polymerization apparatus, and the temperature was set to 255°C. An ethylene glycol solution of manganese acetate tetrahydrate (40 ppm as Mn atoms (element) relative to the weight of the polyester composition), an ethylene glycol slurry of antimony trioxide (100 ppm as Sb atoms (element) relative to the weight of the polyester composition), and phosphoric acid (35 ppm as P atoms (element) relative to the weight of the polyester composition) were added thereto. Then, the temperature inside the polymerization apparatus was gradually raised to 290°C, and the pressure was reduced from normal pressure to 250 Pa or less, and the polymerization reaction was carried out until a predetermined stirring torque was exhibited at 290°C. After the completion of the polymerization reaction, the pressure inside the reaction system was returned to normal pressure with nitrogen gas, and the molten polyester inside the polymerization apparatus was discharged in a strand form into a water tank for cooling and then cut to obtain a pelletized polyester composition (intrinsic viscosity 0.62).

[0063] [Production of Biaxially Oriented Film] 50 parts by weight of PET-A and 50 parts by weight of the polyester composition of the present invention were blended so as to be 50 parts by weight, and dried under reduced pressure at 160 ° C for 2 hours, and then introduced into an extruder for the A layer. Further, 100 parts by weight of PET-A as the resin constituting the B layer was dried under reduced pressure at 160 ° C for 2 hours, and then introduced into an extruder for the B layer. Each raw material was melted at 280 ° C in the extruder, and joined and laminated with a layer joining block, and a two-layer laminate having a lamination ratio of A layer / B layer of 2 / 12.5 was formed. It was extruded onto a casting drum having a surface temperature of 25 ° C, and a laminated sheet having a two-layer structure was produced while applying an electrostatic charge. Subsequently, the sheet was preheated with a group of heated rolls, then stretched 3.5 times in the longitudinal direction at a temperature of 90 ° C, and then cooled with a group of rolls at a temperature of 25 ° C to obtain a uniaxially oriented film. While gripping both ends of the obtained uniaxially oriented film with clips, it is stretched 4.0 times in the width direction perpendicular to the longitudinal direction in a heating zone at a temperature of 110 ° C in a tenter. Subsequently, heat fixation is carried out at a temperature of 230 ° C for 10 seconds in a heat treatment zone in the tenter. Next, after uniformly cooling slowly in a cooling zone, it is wound up to obtain a biaxially oriented polyester film having a thickness of 25 μm.

[0064] [Measurement of 3D Roughness of Biaxially Oriented Film] The obtained biaxially oriented polyester film was cut out into a 10 cm square, and using a non-contact optical roughness measuring instrument (NewView7300 manufactured by Zygo), with a 50-fold objective lens, the measurement area was 139 μm × 104 μm, and 40-field measurements were performed by randomly changing the location. At this time, the sample was set so that the particle-containing layer became the observation surface. Using a band-pass filter with a wavelength of 1.65 to 50 μm by the surface analysis software MetroPro built into the measuring instrument, the arithmetic mean roughness Ra (unit: nm) was determined. Evaluation was carried out according to the following criteria as an index of Ra required for the optical release film, and ◎ and ○ were regarded as passing. ◎: Less than 15.5 ○: 15.5 or more and less than 17.0 ×: 17.0 or more.

[0065] (Example 1) Into an esterification reactor charged with 105 parts by weight of BHT melted at 250°C, a slurry consisting of 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol (1.15 times the molar amount relative to terephthalic acid) was gradually added to proceed with the esterification reaction. The temperature in the reaction system was controlled to be 245 - 250°C, and the esterification reaction was terminated when the reaction rate reached 95% to obtain BHT. 105 parts by weight (equivalent to 100 parts by weight of PET) of BHT in a molten state was charged from the esterification reactor into the polymerization apparatus, and the temperature was set to 255°C. An ethylene glycol solution of manganese acetate tetrahydrate (24 ppm as Mn atoms (element) relative to the weight of the polyester composition), and an ethylene glycol slurry of antimony trioxide (255 ppm as Sb atoms (element) relative to the weight of the polyester composition) were added. Then, 5 parts by weight of ethylene glycol (0.15 times the molar amount relative to the terephthal component) was additionally added to promote depolymerization, and then ethylene glycol solutions of phosphoric acid (49 ppm as P atoms (element) relative to the weight of the polyester composition) and disodium hydrogen phosphate dihydrate (16 ppm as Na atoms (element) and 23 ppm as P atoms (element) relative to the weight of the polyester composition)) and an ethylene glycol slurry with a calcium carbonate particle concentration of 20 wt% (volume average diameter 0.8 μm) were all mixed, and the mixture stirred for 60 seconds to form a homogeneous slurry was added. (1 part by weight as calcium carbonate). Thereafter, the temperature inside the polymerization apparatus was gradually raised to 290°C, and the pressure was reduced from normal pressure to 250 Pa or less, and the polymerization reaction was carried out until a predetermined stirring torque was exhibited at 290°C. After the polymerization reaction was completed, the inside of the reaction system was returned to normal pressure with nitrogen gas, and the molten polyester inside the polymerization apparatus was discharged in a strand form into a water tank for cooling and then cut to obtain a pellet-shaped polyester composition. The properties of the obtained polyester composition are shown in Table 1. The polyester composition obtained in Example 1 had no particle aggregation or formation of coarse foreign substances and was also excellent in hydrolysis resistance, so it had physical properties suitable for optical films and release films.

[0066] (Examples 2 - 4, Comparative Examples 1 - 2) A polyester composition was obtained in the same manner as in Example 1, except that the volume average diameter of the calcium carbonate particles and the addition amount of the compound containing a phosphorus atom (element) were changed as shown in Table 1. The properties of the obtained polyester composition are shown in Table 1.

[0067] [Table 1]

[0068] The polyester compositions obtained in Examples 2 to 4 had no particle aggregation or formation of coarse foreign substances and were excellent in hydrolysis resistance, and thus had physical properties suitable for optical films and release films. The polyester composition obtained in Comparative Example 1 had a small volume average diameter of the calcium carbonate particles, particle aggregation was observed, and it was unacceptable. The polyester composition obtained in Comparative Example 2 had a large volume average diameter of the calcium carbonate particles, and coarse protrusions were formed when molded into a film, and it was unacceptable.

[0069] (Examples 5 to 8, Comparative Example 3) A polyester composition was obtained in the same manner as in Example 1, except that the addition amount of the compound containing a phosphorus atom (element) was changed as shown in Table 2. The properties of the obtained polyester composition are shown in Table 2.

[0070] [Table 2]

[0071] In the polyester compositions obtained in Examples 5 to 8, the volume average diameter after heat treatment slightly increased due to the increase in the phosphorus atom (element), but there was no particle aggregation or formation of coarse foreign substances, and they were excellent in hydrolysis resistance, and thus had physical properties suitable for optical films and release films. The polyester composition obtained in Comparative Example 3 had a small addition amount of the compound containing a phosphorus atom (element), a small phosphorus atom (element) content in the calcium carbonate particles isolated from the polyester composition, particle aggregation and formation of coarse foreign substances occurred, and the hydrolysis resistance was also poor and it was unacceptable.

[0072] (Examples 9 - 10, Comparative Example 4) A polyester composition was obtained in the same manner as in Example 1, except that the types of compounds containing phosphorus element (atoms) were changed as shown in Table 3. The properties of the obtained polyester composition are shown in Table 3. In the polyester compositions obtained in Examples 9 - 10, although some particle aggregation was observed due to the difference in acidity of the phosphorus species used, they had excellent hydrolysis resistance and had physical properties suitable for optical films and release films. In the polyester composition obtained in Comparative Example 4, only phosphoric acid was mixed with and added to calcium carbonate particles, calcium ions eluted from the calcium carbonate particles, the content of free calcium atoms (elements) increased, and the content of phosphorus atoms (elements) in the isolated particles was also low.

[0073] (Examples 11 - 12) A polyester composition was obtained in the same manner as in Example 1, except that the addition amounts of calcium carbonate particles and the compounds containing phosphorus atoms (elements) were changed as shown in Table 3. The properties of the obtained polyester composition are shown in Table 3. In the polyester compositions obtained in Examples 11 - 12, although some aggregation and formation of coarse foreign matter were observed as the addition amount of particles increased, they had physical properties suitable for optical films and release films.

[0074] (Example 13) 101.0 parts by weight of dimethyl terephthalate and 64.6 parts by weight of ethylene glycol (2 times the molar amount of dimethyl terephthalate) were each weighed and charged into a transesterification reactor. After dissolving the contents at 150 °C, an ethylene glycol solution of manganese(II) acetate tetrahydrate (24 ppm as Mn atoms (element) based on the weight of the polyester composition) and an ethylene glycol slurry of antimony trioxide (255 ppm as Sb atoms (element) based on the weight of the polyester composition) were added and stirred. Methanol was distilled off while raising the temperature to 240 °C, and when a predetermined amount of methanol had distilled off, the transesterification reaction was terminated. Then, the reaction product was transferred to a polymerization reactor, and an ethylene glycol solution of phosphoric acid (49 ppm as P atoms (element) based on the weight of the polyester composition) and disodium hydrogen phosphate dihydrate (16 ppm as Na atoms (element) and 23 ppm as P atoms (element) based on the weight of the polyester composition) and an ethylene glycol slurry with a calcium carbonate particle concentration of 20 wt% were all mixed, and the mixture obtained by stirring for 60 seconds to form a homogeneous slurry was added. (1 part by weight as calcium carbonate). After the addition, the temperature inside the polymerization reactor was gradually raised to 290 °C, and the pressure was reduced from normal pressure to 250 Pa or less, and the polymerization reaction was carried out until a predetermined stirring torque was shown at 290 °C. After the polymerization reaction was completed, the pressure inside the reaction system was returned to normal pressure with nitrogen gas, and the molten polyester inside the polymerization reactor was discharged in a strand form into a water tank for cooling and then cut to obtain a pellet-shaped polyester composition. The properties of the obtained polyester composition are shown in Table 3. The polyester composition obtained in Example 14 had no particle aggregation or formation of coarse foreign substances and was excellent in hydrolysis resistance, so it had physical properties suitable for optical films and release films.

[0075] (Comparative Example 5) In the same manner as in Example 1, 105 parts by weight (equivalent to 100 parts by weight of PET) of BHT was charged in a molten state from an esterification reactor to a polymerization apparatus, and the temperature was set to 255°C. An ethylene glycol solution of manganese acetate tetrahydrate (24 ppm as Mn atoms (elements) based on the weight of the polyester composition) and an ethylene glycol slurry of antimony trioxide (255 ppm as Sb atoms (elements) based on the weight of the polyester composition) were added. Then, 5 parts by weight of ethylene glycol (0.15 times the molar ratio of the terephthal component) was additionally added to proceed with depolymerization. Next, a mixed ethylene glycol solution of phosphoric acid (49 ppm as P atoms (elements) based on the weight of the polyester composition) and sodium dihydrogen phosphate dihydrate (16 ppm as Na atoms (elements) and 23 ppm as P atoms (elements) based on the weight of the polyester composition) was added. After adding the phosphorus compound, an ethylene glycol slurry with a calcium carbonate particle concentration of 20 wt% was added (1 part by weight as calcium carbonate). Then, the temperature inside the polymerization apparatus was gradually raised to 290°C, and the pressure was reduced from normal pressure to 250 Pa or less, and the polymerization reaction was carried out until a predetermined stirring torque was exhibited at 290°C. After completion of the polymerization reaction, the inside of the reaction system was returned to normal pressure with nitrogen gas, and the molten polyester inside the polymerization apparatus was discharged in a strand form into a water tank, cooled, and then cut to obtain a pellet-shaped polyester composition. In the obtained polyester composition, the surface of the particles could not be protected by the phosphorus compound, there were many free calcium components, and the particle shape could not be maintained by heat treatment, so particle aggregation occurred, and the three-dimensional roughness when processed into a biaxially oriented film was unqualified.

[0076]

Table 3

Claims

1. A polyester composition containing calcium carbonate particles and phosphorus atoms (elements), prepared using phosphoric acid and an alkali metal phosphate, and satisfying the following formulas (I), (II), (V), and (VI). 0.2 ≤ R ≤ 0.8 (I) 0.38 / R ２ ≤ P １ (II) Free calcium atom (element) content ≤ 5 ppm (V) 0.01 ppm ≤ Sodium atom (element) content (weight ratio to the polyester composition) ≤ 30 ppm or less (VI) R: Volume average diameter (μm) of calcium carbonate particles P １ : The phosphorus atom (element) content (wt%: weight ratio to the isolated particles) contained in the isolated particles obtained by isolating from the polyester composition by the following method (Isolation method: Dissolve the polyester composition in o-chlorophenol at 150 °C for 1 hour, then centrifuge at a centrifugal acceleration of 40900 G at 20 °C for 1 hour. Add dichloromethane to the obtained solid content, centrifuge under the same conditions, and obtain a solid content. Add dichloromethane to the obtained solid content again and perform centrifugation under the same conditions. The solid content obtained by performing centrifugation with dichloromethane a total of 3 times is used as the isolated particles.) (The free calcium atom (element) content is the calcium atom (element) content in the polymer obtained by dissolving the polyester composition in o-chlorophenol at 150 °C for 1 hour, then centrifuging at a centrifugal acceleration of 40900 G at 20 °C for 1 hour, collecting the obtained supernatant solution by decantation, adding acetone to precipitate, collecting the precipitate by filtration, and vacuum drying at 150 °C for 12 hours.)

2. The polyester composition according to claim 1, wherein the calcium atom (element) content is 100 ppm (weight ratio to the polyester composition) or more.

3. The polyester composition according to claim 1, wherein the increase amount ΔCOOH of carboxylic acid end groups before and after heat and humidity treatment at 155 °C for 4 hours under saturated steam is 80 eq / t or less.

4. The polyester composition according to claim 1, wherein the polyester is polyethylene terephthalate.

5. When producing a polyester composition by subjecting a dicarboxylic acid or dicarboxylic acid ester and a diol to an esterification reaction or transesterification reaction and then a polycondensation reaction, a compound containing a mixed solution of calcium carbonate particles and phosphoric acid and an alkali metal phosphate is added as a mixed slurry before the end of the polycondensation reaction, and a method for producing a polyester composition satisfying the following formulas (III), (IV), and (VII). 0.2 ≤ R ≤ 0.8 (III) 0.38 / R ２ ≤ P ２ (IV) 0.01 ppm ≤ Sodium atom (element) addition amount (weight ratio to the polyester composition) ≤ 30 ppm or less (VII) R: Volume average diameter of calcium carbonate particles (μm) P ２ : Amount of phosphorus atoms (element) added as a mixed slurry (wt%: weight ratio to calcium carbonate)

6. The method for producing a polyester composition according to claim 5, wherein the addition amount of calcium carbonate particles is 100 ppm or more as calcium atoms (element) (weight ratio based on the polyester composition).

7. The method for producing a polyester composition according to claim 5, wherein the polyester is polyethylene terephthalate.

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