Method for producing polyester resin composition

Abstract

To provide a production method of a polyester resin composition, which can produce the polyester resin composition having high concentration of inorganic particles in the polyester resin composition, and from which a biaxial oriented film having excellent characteristics of particle dispersibility and particle aggregation property can be produced.SOLUTION: In a production method of a polyester resin composition by supplying a polyester resin to a twin screw extruder including a plasticization section, a kneading section and a degasification section from a resin supply port side in this order, and adding particle dispersion slurry from an addition section set up on the kneading section into the twin screw extruder, the addition section is placed on a middle point in the longer direction of the twin screw extruder in the kneading section, or on the side closer to the plasticization section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a polyester resin composition. Specifically, it relates to a method for producing a polyester resin composition having a step of adding a slurry of particles to a polyester resin and kneading them.

Background Art

[0002] Biaxially oriented films of polyester resin have excellent physical and chemical properties and are used as base films for magnetic recording media and dielectrics for capacitors. Also, due to their excellent transparency, they are widely used in fields such as graphic arts, displays, and packaging materials. In order to improve the running properties of the polyester resin film, it is necessary to moderately roughen the surface of the film by making particles such as calcium carbonate present in the film, but it is desired that there are no uniform and large protrusions.

[0003] When synthesizing calcium carbonate particles, it is carried out in an aqueous solvent, so it is obtained as an aqueous slurry (Patent Document 1). However, this aqueous slurry has a high pH and contains synthetic impurities. In the case of commercially available particles, an ethylene glycol ("EG") slurry is known. As a step of adding these particles to a polyester resin, when adding the EG slurry to the esterification step, the dispersibility is poor. In the case of the polymerization step, if the particle concentration is not adjusted to a low concentration, the dispersibility deteriorates, but if it is made low, there is too much EG and the balance deteriorates, so the dispersion is still poor. When adding in other steps, since EG cannot be discharged, depolymerization occurs.

[0004] Patent Document 2 describes a method of adding an aqueous dispersion of particles to a biaxial kneader when producing a composition of a polyester resin and inorganic particles, but the blending amount of the particles is as low as 0.001 to 1.0% by weight with respect to the composition, and the particle concentration in the aqueous dispersion is 0.01 to 10% by weight.

[0005] Patent Document 3 describes a method of producing a polyester resin-inorganic particle composition (the blending amount of particles in the composition: 1 to 30% by weight) in which a slurry with a particle concentration of 5 to 80% by weight in an aqueous dispersion is spray-injected using the pressure difference with the inside of a kneader. However, when the polyester resin composition is made into a biaxially stretched film, it cannot be said that it is sufficient to improve the dispersibility and aggregability of the inorganic particles and the film properties.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a method for producing a polyester resin composition capable of producing a polyester resin composition having a high inorganic particle concentration in the polyester resin composition and having good properties, namely particle dispersibility and particle aggregability, when made into a biaxially stretched film.

Means for Solving the Problems

[0008] The present inventors have found that when kneading a polyester resin and an aqueous dispersion (aqueous slurry) of inorganic particles with a high concentration, by pressuring and spray-supplying the aqueous slurry to the first half of the kneading section in the kneader, when the polyester resin composition is made into a biaxially stretched film, a film with good inorganic particle dispersibility and no particle aggregation can be obtained, and based on this finding, the invention has been completed.

[0009] The gist of the present invention is as follows.

[0010] [1] A method for producing a polyester resin composition, which comprises supplying a polyester resin to a twin-screw extruder having a plasticizing section, a kneading section, and a degassing section in this order from the resin supply port side, and adding a particle dispersion slurry into the twin-screw extruder from an addition section provided in the kneading section, wherein the addition section is located at the middle in the longitudinal direction of the twin-screw extruder in the kneading section or on the plasticizing section side thereof.

[0011] [2] The method for producing a polyester resin composition according to [1], wherein the distance from the boundary between the plasticizing section and the kneading section to the addition section is within 40% of the length of the kneading section.

[0012] [3] The method for producing a polyester resin composition according to [1], wherein the distance from the boundary between the plasticizing section and the kneading section to the addition section is within 30% of the length of the kneading section. [Advantages of the Invention]

[0013] According to the method for producing a polyester resin composition of the present invention, a polyester resin composition having a high inorganic particle concentration in the polyester resin composition and good characteristics, i.e., in terms of particle dispersibility and particle aggregability, when formed into a biaxially stretched film can be produced. [Brief Description of the Drawings]

[0014]

Figure 1

[0015] In the present invention, a polyester resin composition is produced by supplying a polyester resin to a twin-screw extruder having a plasticizing section, a kneading section, and a degassing section in this order from the resin supply port side, and adding a particle dispersion slurry into the twin-screw extruder from an addition section provided in the kneading section.

[0016] [Polyester Resin] The polyester resin used in the present invention is not particularly limited and refers to a polyester obtained using aromatic dicarboxylic acids such as terephthalic acid and 2,6-naphthalenedicarboxylic acid or their esters and ethylene glycol as the main starting materials, but may contain other third components.

[0017] As the dicarboxylic acid component, for example, one or more of isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid can be used. Also, as the glycol component, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol can be used. The polyester resin of the present invention has 80 mol% or more of the repeating structural units as ethylene terephthalate units or ethylene-2,6-naphthalate units.

[0018] This polyester resin is supplied to a twin-screw extruder, and a particle dispersion slurry is injected into the kneading section and further kneaded and extruded to obtain a polyester resin composition.

[0019] [Particle dispersion slurry] <Particle> The particles for adding to the polyester used in the present invention are not particularly limited, and examples include calcium carbonate, silicon oxide, crosslinked organic polymer particles, talc, clay, kaolin, etc. Among them, synthetic calcium carbonate, spherical silicon oxide, crosslinked organic particles, etc. manufactured by a synthetic method and having a narrow particle size distribution are preferable. When used for film applications, the average particle diameter (d50) of the particles is preferably 0.05 to 3 μm. Also, when integrated from the large particle side, the ratio [d25 / d75] of the particle diameter (d25) at which the integrated weight of the particles is 25% to the particle diameter (d75) at which the integrated weight of the particles is 75% is preferably 2.2 or less, more preferably 2.0 or less, and even more preferably 1.8 or less.

[0020] <Concentration of particle dispersion slurry> The particle concentration in the particle dispersion slurry added to the twin-screw extruder is preferably about 10 to 60% by weight, particularly about 15 to 50% by weight.

[0021] <Amount of added particle dispersion slurry> The amount of the particle dispersion slurry added to the twin-screw extruder is preferably an amount such that the particle content in the produced polyester resin composition is 0.1 to 10.0% by weight, particularly 0.5 to 6.0% by weight, especially 1.0 to 5.0% by weight. In addition, in order to suppress the hydrolysis of the polyester resin, the amount of the added particle dispersion slurry is preferably in the range of 0.5 to 10% by weight based on the polyester resin.

[0022] <Medium of particle dispersion slurry> The medium is mainly water. The proportion of water in the medium is preferably 40% by weight or more.

[0023] Examples of the medium other than water include ethylene glycol derived from the slurry raw material.

[0024] The method for calculating the ethylene glycol concentration contained in the water slurry is as follows: The filtrate at the completion of the water slurry substitution described later is measured with a saccharimeter (manufactured by Atago Co., Ltd.) to obtain the Brix value. The ethylene glycol concentration (A) of the filtrate is calculated by A = 1.6153 * Brix value - 0.9458, and the ethylene glycol concentration (B) contained in the water slurry is calculated by B = (100 - particle concentration (C)) * (A / 100). The ethylene glycol concentration contained in the water slurry is preferably 5% by weight or less. The lower the ethylene glycol concentration in the slurry, the more preferable it is, but it takes a long time for solvent substitution to make it 2% by weight or less. If it exceeds 5% by weight, when added to the twin-screw extruder, the polyester resin tends to depolymerize due to ethylene glycol, and the intrinsic viscosity tends to decrease.

[0025] <Substitution of the medium of the slurry (raw material slurry) containing particles produced by the synthesis method> Particles produced by a synthesis method are usually obtained as a particle-containing slurry (hereinafter sometimes referred to as a raw material slurry) dispersed in a medium (water and / or organic solvent) used for particle synthesis. When the medium is water, the pH is high and undesirable impurities are mixed in. Also, as the organic solvent, methanol or the like is often used. These organic solvents are often solvents not used in the polyester resin manufacturing process and are not preferably added to the polyester resin.

[0026] Therefore, in the case of a raw material slurry in which the medium of the particle-containing slurry is water or an organic solvent, it is preferable to replace the medium with ethylene glycol. The method of replacing water or an organic solvent in the raw material slurry with ethylene glycol to obtain an ethylene glycol slurry is not particularly limited. For example, there are methods such as concentrating and drying the solvent solution to obtain a powder and then adding ethylene glycol, or directly adding ethylene glycol and performing concentration under reduced pressure to remove water or an organic solvent. However, as described in JP-A-6-269615, it is preferable to use a filter medium having a pore diameter (μm) preferably of d50×0.1 or more and d50×12 or less, and repeat concentration by filtration and dilution with ethylene glycol to obtain an ethylene glycol slurry.

[0027] <Replacement of ethylene glycol in ethylene glycol slurry with water> The ethylene glycol slurry obtained as described above or the ethylene glycol slurry of commercially available particles is converted into a water slurry by the following method. This is because the addition of the particle slurry can be performed even outside the polymerization process by making it a water slurry.

[0028] The medium replacement for converting the ethylene glycol slurry into a water slurry is preferably performed by repeating concentration by filtration and dilution with water using a filter medium having a pore diameter (μm) preferably of d50×0.1 or more and d50×12 or less.

[0029] <Filtration device used for medium replacement> The filtration device used for media replacement is composed of a slurry storage tank, a slurry circulation pump, a filter with filter media, a pressure gauge, a heat exchanger, etc., and a storage tank, etc. may be added as required. The material of the filter media is preferably made of ceramic in terms of corrosion resistance and solvent resistance, etc.

[0030] As the filtration method, there is a method called cross-flow filtration in which the liquid to be filtered is filtered while flowing on the surface of the membrane filter, and the deposited cake layer is kept to a minimum by the shear force due to the parallel flow, or a method called direct filtration in which the liquid to be filtered is directly filtered by the membrane filter. Either method can be used.

[0031] By subjecting the slurry to filtration treatment, it is separated into a medium as the filtrate and a concentrated slurry (particles + medium). Water is added to the concentrated slurry for dilution and then filtered again. By repeating this, the medium is gradually replaced with water. For example, water is added to a concentrated ethylene glycol slurry with a particle concentration of 40% by weight, diluted to a particle concentration of about 20% by weight, then filtered, and the same amount of water as the discharged filtrate is added to the concentrated slurry. By repeating this concentration and dilution operation, ethylene glycol is gradually replaced with water, and a slurry mainly composed of water can be obtained. By concentrating the slurry thus obtained, a slurry with the target concentration and mainly composed of water can be obtained.

[0032] If the pore diameter of the filter media used for the above concentration is less than d50×0.1 μm, the filtration rate is low, so it takes time for concentration, which is not preferable. If the pore diameter exceeds d50×12, particles also flow out together with the dispersed medium filtered during concentration by filtration, which is not preferable.

[0033] When starting to replace the dispersion medium, the slurry concentration is preferably a concentration that can maintain good dispersibility of the particles, and it varies depending on the type of particles and the particle size. In the case of synthetic calcium carbonate, spherical silicon oxide, and crosslinked organic polymer particles, the concentration at the start of replacement is usually in the range of 10 to 60% by weight, preferably 15 to 50% by weight. If the concentrated slurry concentration is less than 10% by weight, the efficiency tends to deteriorate, and if the slurry concentration exceeds 60% by weight, the particles may aggregate in the concentrated slurry.

[0034] [Twin-screw kneading extruder] For kneading, a twin-screw extruder (twin-screw kneading extruder) is used.

[0035] Figure 1 is a side view of a twin-screw kneading extruder. As is well known, this twin-screw kneading extruder rotates the screw in the barrel (cylinder) 1 by a driving device M to perform kneading and extrusion.

[0036] The polyester resin supplied from the polymer inlet 2 melts in the plasticizing section A and is transferred to the kneading section B. Then, from the slurry addition nozzle 3, the particle dispersion slurry is injected (preferably, press-fitted and sprayed) into the molten resin. After the molten resin and the slurry are mixed and kneaded, they are transferred to the degassing section C. By sucking the inside of the barrel 1 with a vacuum pump (not shown) connected to the vent port 4, water, which is the dispersion medium, is removed. The resin composition is extruded as a strand from the extrusion port at the end of the barrel 1, and then, although not shown in the figure, it is cut in water and pelletized.

[0037] The inner diameter of the barrel of the twin-screw kneading extruder is preferably 60 to 90 mm, particularly 65 to 85 mm, the length of the plasticizing section A is 400 to 1000 mm, particularly 500 to 900 mm, the length of the kneading section B is 400 to 1000 mm, particularly 500 to 900 mm, and the length of the degassing section C is about 400 to 1300 mm, particularly 500 to 1200 mm.

[0038] The boundary positions of the plasticizing section, kneading section, and degassing section are defined by the differences in the screws' blades within the barrel. As the screw pieces for the plasticizing section and the kneading section, a kneading disk is usually used, and as the screw piece for the degassing section, a full flight screw is usually used. The boundary position between the plasticizing section A and the kneading section B is defined by the switch of the blade from the kneading disk to the full flight screw. The combination of the screw pieces can be changed as appropriate.

[0039] [Position of the water slurry addition nozzle 3] The slurry addition nozzle 3 is arranged on the side closer to the plasticizing section A than the center in the longitudinal direction of the barrel of the kneading section B, that is, within 50% or less, preferably within 40% or less, more preferably within 30% or less from the upstream end of the kneading section B (the boundary between the plasticizing section A and the kneading section B).

[0040] [Kneading conditions] The cylinder temperature during kneading is 200 - 300 °C, particularly 220 - 290 °C, the screw rotation speed is 80 - 270 rpm, particularly 100 - 200 rpm, and the discharge rate is preferably about 80 - 180 kg / h, particularly 100 - 150 kg / h.

[0041] [Use and intrinsic viscosity of the polyester resin composition] From the polyester resin composition thus produced, films can be manufactured by various methods. As the molding method, known film manufacturing methods can be applied. For example, after melting at a temperature above the melting point of the polyester, a polyester sheet can be obtained by extrusion molding. Further, the obtained polyester sheet can be biaxially stretched to obtain a polyester film.

[0042] <Intrinsic viscosity of the polyester resin composition> The intrinsic viscosity of the polyester resin composition is preferably 0.50 dL / g or more, more preferably 0.52 dL / g or more. If this value is less than 0.50 dL / g, there may be a possibility that pelletization cannot be achieved. The upper limit is not particularly limited, but is preferably about 0.70 dL / g.

[0043] The measurement of the intrinsic viscosity of the polyester resin composition is carried out as follows: Approximately 0.25 g of the sample is dissolved in approximately 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (mass ratio 1 / 1) so that the concentration becomes 1.00 g / dL. After that, it is cooled to 30 °C, and at 30 °C, using a fully automatic solution viscometer (manufactured by Sentec, "DT553"), the dropping seconds of only the sample solution and the solvent are measured, and the intrinsic viscosity (IV) is calculated by the following formula. IV = ((1 + 4KHηsp)^0.5 - 1) / (2KHC) Here, ηsp = η / η0 - 1, where η is the dropping seconds of the sample solution, η0 is the dropping seconds of only the solvent, C is the sample solution concentration (g / dL), and KH is the Huggins constant. KH is adopted as 0.33. The dissolution conditions of the sample are 110 °C for 30 minutes.

Examples

[0044] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measurement methods and definitions of various physical properties and characteristics in the examples are as follows. In the examples and comparative examples, "parts" means "parts by weight".

[0045] [Measurement method] <Average particle diameter of inorganic particles contained in the slurry> 0.03 - 0.10 g of the slurry of inorganic particles is mixed with 200 ml of pure water and treated with a sample supply device incorporated with an ultrasonic disperser (manufactured by Microtrac Bel, "MICROTRAC SDC"), and the average particle diameter is measured using a laser diffraction particle size distribution meter (manufactured by Microtrac Bel, "MT-3000II"). The average particle diameter in this case is the particle diameter when the volume fraction reaches 50%.

[0046] <Particle concentration of inorganic particles contained in the slurry> 3.0 - 5.0 g of the slurry of inorganic particles is weighed into an aluminum dish, placed on a hot plate at 200 °C, and only the dispersion solvent is evaporated for 1 hour. Then, it is pre-cooled in a desiccator for 3 minutes and weighed again to obtain the particle concentration.

[0047] <Average particle diameter of inorganic particles (aggregated particles (secondary particles)) in the manufactured polyester resin composition> After adding 160 ml of a phenol-tetrachloroethane mixed solvent (weight ratio 2:3) to 3.2 g of the polyester resin composition, the mixture is stirred for 30 minutes while heating at 130°C to dissolve the polyester resin composition to form a slurry. After cooling the slurry to room temperature, the average particle diameter is measured using a laser diffraction particle size distribution analyzer (manufactured by Microtrac Bel Corporation, "MT-3000II"). The average particle diameter in this case is the particle diameter when the volume fraction reaches 50%.

[0048] <Evaluation of particle dispersibility in the polyester resin composition> From the particle size cumulative distribution obtained from the measurement results of the average particle diameter of the particles in the polyester resin composition, the ratio (volume basis, %) of particles with a particle diameter of 10 μm or more is calculated. The smaller the ratio, the better the particle dispersibility. When the ratio is 5.0% or less, it is rated as ◎ (excellent), when it is 5.1% or more and 10.0% or less, it is rated as ○ (good), when it is 10.1% or more and 15.0% or less, it is rated as △ (fair), and when it is 15.1% or more, it is rated as × (poor).

[0049] <Film property (number of large protrusions)> Measured using "Contour GT-X" (registered trademark) of Bruker AXS K.K., the maximum peak height Sp value is obtained from the obtained surface profile curve, and the number of Sp values of 400 nm or more in 36 screens is counted as the number of large protrusions. This value is preferably as small as possible. When it is 5 or less, it is rated as good (〇), and when it is 6 or more, it is rated as poor (×). (Foreign matter is counted as a large protrusion.)

[0050] [Method for preparing slurry] <Preparation of calcium carbonate slurry (I)> An ethylene glycol slurry of colloidal calcium carbonate particles with an average particle size d50 of 0.95 μm (manufactured by Maruo Calcium Co., Ltd., "MG-10". The particle concentration in the slurry was 40.0 wt%) 60 kg was added with 60 kg of pure water and diluted so that the particle concentration in the slurry became 20 wt% to obtain a slurry stock solution. Then, this slurry stock solution was concentrated by filtering it through a filtration device (a ceramic concentration filtration device equipped with a ceramic membrane with a pore diameter of 0.2 μm (Cefilt filtration device manufactured by NGK Filtec Co., Ltd.)). Every time 10 kg of filtrate was discharged from the filtration device, 10 kg of pure water was added to the concentrated slurry and diluted to return the particle concentration to 20 wt%. This concentration and dilution operation was repeated 15 times. Next, 60 kg of filtrate was discharged from the filtration device and concentrated so that the slurry concentration became about 40 wt%. The particle concentration in the obtained slurry was 41.8 wt%, and the ethylene glycol concentration in the slurry was 3.9 wt%. The dispersibility of calcium carbonate in the obtained slurry was good. This slurry was designated as calcium carbonate slurry (I).

[0051] <Preparation of Calcium Carbonate Slurry (II)> 25 kg of an ethylene glycol slurry of colloidal calcium carbonate particles with the same average particle size d50 of 0.95 μm as above was added with 25 kg of pure water and diluted so that the particle concentration in the slurry became 20 wt% to obtain a slurry stock solution. Then, it was concentrated by filtering it through the same ceramic concentration filtration device as above. Every time 10 kg of filtrate was discharged from the filtration device, the slurry stock solution was added with 10 kg of pure water and diluted to return the particle concentration to 20 wt%. This concentration and dilution operation was repeated 6 times. Next, 30 kg of filtrate was discharged from the filtration device and concentrated so that the slurry concentration became about 50 wt%. The particle concentration in the obtained slurry was 52.8 wt%, and the ethylene glycol concentration in the slurry was 2.8 wt%. The dispersibility of calcium carbonate in the obtained slurry was good. This slurry was designated as calcium carbonate slurry (II).

[0052] <Preparation of Calcium Carbonate Slurry (III)> An ethylene glycol slurry of colloidal calcium carbonate particles with an average particle size d50 of 0.68 μm (manufactured by Maruo Calcium Co., Ltd., "MG-7". The particle concentration in the slurry was 40.0% by weight) was used to prepare calcium carbonate slurry (III) in the same manner as in the case of calcium carbonate (II), except for this. The particle concentration in the obtained slurry was 50.5% by weight, and the ethylene glycol concentration in the slurry was 3.5% by weight. The dispersibility of calcium carbonate in the obtained slurry was good.

[0053] <Production of polyester resin> A continuous polymerization apparatus consisting of one stock solution preparation tank, two-stage esterification reaction tanks connected in series thereto, and three-stage melt polycondensation tanks connected in series to the second-stage esterification reaction tank was used. Terephthalic acid and ethylene glycol were continuously supplied to the stock solution preparation tank at a weight ratio of 100:45, and an ethylene glycol solution of ethyl acid phosphate was continuously added in an amount such that the content as phosphorus atoms in the produced polyester resin was 7 ppm by weight, and stirred and mixed to prepare a slurry-like stock solution. This slurry-like stock solution was continuously transferred to the first-stage esterification reaction tank and then to the second-stage esterification reaction tank to carry out the esterification reaction.

[0054] Next, an ethylene glycol solution of magnesium acetate tetrahydrate was added to this esterification reaction product in an amount such that the content as magnesium atoms in the produced polyester resin was 9 ppm by weight, and an ethylene glycol solution of tetra-n-butyl titanate was further added in an amount such that the content as titanium atoms in the produced polyester resin was 4.5 ppm by weight, and melt polycondensation was carried out in the first-stage polycondensation reaction tank and then in the second-stage polycondensation reaction layer.

[0055] Next, the polycondensation reaction was carried out in the second-stage polycondensation reaction tank and further in the third-stage polycondensation reaction tank at 277 °C, an absolute pressure of 0.2 kPa, and an average residence time of 1 hour.

[0056] The melt polycondensation reaction product taken out from the third-stage polycondensation reaction tank was extruded in a strand form from a die, cooled and solidified, and cut with a cutter to obtain polyester resin pellets with an average weight of 24 mg each. The intrinsic viscosity of these pellets was 0.560 dL / g.

[0057] Next, these melt polycondensation polyester resin pellets were continuously supplied into a stirring crystallizer maintained at about 160°C under a nitrogen atmosphere so that the residence time was about 60 minutes for crystallization, and then continuously supplied to a tower-type solid-phase polycondensation apparatus, where solid-phase polycondensation was carried out at 210°C for 18 hours under a nitrogen atmosphere.

[0058] The intrinsic viscosity of the obtained polyester resin was 0.700 dL / g.

[0059] [Example 1] A vented twin-screw extruder with the configuration shown in Fig. 1 (manufactured by AUTOMATIK, model "ZCM", screws rotating in the same direction, barrel inner diameter D: 71 mm, length of the plasticizing section A: 800 mm, length of the kneading section B: 600 mm, length of the degassing section C: 1000 mm, and the position of the nozzle 3 for slurry addition was 162 mm from the upstream of the kneading section B (27% of the length of the kneading section B)) was used.

[0060] The polyester resin manufactured as described above was charged from the polymer inlet 2 and kneaded at a cylinder temperature of 280°C, a screw rotation speed of 150 rpm, and a discharge rate of 120 kg / h. Also, calcium carbonate slurry (I) was injected from the nozzle 3. The slurry addition amount was adjusted so that the particle concentration in the polyester resin composition was 1.5% by weight. The vacuum degree of the vent port was set to -0.098 MPa for degassing. The extruded polyester resin composition was cut in water to form pellets. The intrinsic viscosity of these pellets was 0.534 dL / g. Table 1 shows the evaluation results of the calcium carbonate particle dispersibility and film properties of the obtained polyester resin composition.

[0061] [Example 2] The polyester resin composition was melt-kneaded and pelletized in the same manner as in Example 1, except that the addition amount of calcium carbonate slurry (I) was adjusted so that the particle concentration in the polyester resin composition was 2% by weight, and evaluation was performed. The results are shown in Table 1.

[0062] [Example 3] Using calcium carbonate slurry (II), the polyester resin composition was melt-kneaded and pelletized in the same manner as in Example 1, except that the addition amount was adjusted so that the particle concentration in the polyester resin composition was 3.6% by weight, and evaluation was performed. The results are shown in Table 1.

[0063] [Example 4] Using calcium carbonate slurry (III), the polyester resin composition was melt-kneaded and pelletized in the same manner as in Example 3, except that the addition amount of the calcium carbonate slurry was adjusted so that the particle concentration in the polyester resin composition was 2% by weight, and evaluation was performed. The results are shown in Table 1.

[0064] [Example 5] Using calcium carbonate slurry (III), the polyester resin composition was melt-kneaded and pelletized in the same manner as in Example 1, except that the addition amount was adjusted so that the particle concentration in the polyester resin composition was 4.7% by weight, and the discharge amount during melt-kneading was set to 100 kg / h, and evaluation was performed. The results are shown in Table 1.

[0065] [Reference Example 1] [Preparation of silica slurry] An ethylene glycol slurry of spherical silica particles with an average particle size d50 of 0.44 μm (manufactured by Nippon Shokubai Co., Ltd. "KE-E50". The particle concentration in the slurry was 20.0 wt%) was added with 25 kg of pure water to 25 kg, and diluted so that the particle concentration in the slurry became 10 wt% to obtain a slurry stock solution. Then, the slurry was concentrated by filtering it through the same ceramic concentration filtration device as above except that a ceramic membrane with a pore diameter of 0.1 μm was installed. Every time 10 kg of filtrate was discharged from the filtration device, 10 kg of pure water was added for dilution to return the particle concentration to 10 wt%. This concentration and dilution operation was repeated 6 times. Next, 37.5 kg of filtrate was discharged from the filtration device, and the slurry was concentrated so that the slurry concentration became about 40 wt%. The particle concentration in the obtained slurry was 38.9 wt%, and the ethylene glycol concentration in the slurry was 3.7 wt%. The dispersibility of silica in the obtained aqueous slurry was good.

[0066] Using this silica slurry, a polyester resin composition was melt-kneaded and pelletized in the same manner as in Example 1 except that the addition amount was adjusted so that the particle concentration in the polyester resin composition became 2 wt%, and evaluation was performed. The results are shown in Table 1.

[0067] [Comparative Example 1] Calcium carbonate slurry (I) was carried out in the same manner as in Example 1 except that it was changed to the calcium carbonate ethylene glycol slurry prepared in Reference Example 2 below, but the intrinsic viscosity decreased and strands could not be obtained.

[0068] [Reference Example 2] [Preparation of ethylene glycol slurry of calcium carbonate]< To 60 kg of an ethylene glycol slurry of colloidal calcium carbonate particles with an average particle size d50 of 0.95 μm (manufactured by Maruo Calcium Co., Ltd. "MG-10". The particle concentration in the slurry was 40.0 wt%), 60 kg of ethylene glycol was added and diluted to a particle concentration of 20 wt% in the slurry.

[0069] 100 parts by mass of dimethyl terephthalate and 65 parts by mass of ethylene glycol were charged into a transesterification reaction vessel equipped with a stirrer, a temperature increasing device, and a distillate separation column, and heated to 150 °C to melt the dimethyl terephthalate. Next, an ethylene glycol solution of magnesium acetate tetrahydrate was added so that 0.09 part by mass of magnesium acetate was added to the resulting polyester resin component. Then, the temperature was raised to 225 °C over 3 hours under normal pressure, and the mixture was stirred and held at 225 °C for 1 hour and 15 minutes while distilling off methanol to conduct a transesterification reaction, and the transesterification reaction was substantially completed to obtain a low-polymerized polyester (oligomer).

[0070] Next, the polyester oligomer was transferred to a polycondensation reaction vessel equipped with a stirrer, a temperature increasing device, and a pressure reducing device. Then, under stirring, an ethylene glycol slurry of colloidal calcium carbonate particles was added to the oligomer so that the particle concentration was 2.0% by weight based on the polyester resin component.

[0071] Next, an ethylene glycol solution of phosphoric acid was added to the oligomer so that the amount of phosphoric acid added was 0.03 part by mass based on the resulting polyester resin component, and an ethylene glycol solution of antimony trioxide was added as a polycondensation catalyst so that the amount of antimony trioxide added was 0.04 part by mass based on the resulting polyester resin component. Then, the pressure was reduced from 101.3 kPa to 0.4 kPa over 85 minutes and held at 0.4 kPa, and the temperature was raised from 225 °C to 280 °C over 2 hours and held at 280 °C for 1.5 hours to conduct a polycondensation reaction, obtaining a polyester resin composition having an intrinsic viscosity of 0.62 dL / g. As a result of film formation, coarse foreign matters were generated.

[0072] [Table 1] [Explanation of Symbols]

[0073] 1 Barrel 2 Polymer Inlet 3 Slurry Addition Nozzle 4 Vent ports

Claims

1. A method for producing a polyester resin composition by supplying a polyester resin to a twin-screw extruder having a plasticizing section, a kneading section, and a degassing section in this order from the resin supply port side, and adding a particle dispersion slurry into the twin-screw extruder from an addition section provided in the kneading section, wherein the addition section is a method for producing a polyester resin composition located on the plasticizing section side rather than the middle in the longitudinal direction of the kneading section of the twin-screw extruder, the distance from the boundary between the plasticizing section and the kneading section to the addition section is within 40% (excluding 0%) of the length of the kneading section, the proportion of water in the medium in the particle dispersion slurry is 40% by weight or more, and the ethylene glycol concentration in the particle dispersion slurry is 5% by weight or less A method for producing a polyester resin composition.

2. The method for producing a polyester resin composition according to Claim 1, wherein the distance from the boundary between the plasticizing section and the kneading section to the addition section is within 30% of the length of the kneading section.

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