JP2006001992A - Polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene terephthalate resin composition whose molding such as film or fiber has a smooth surface durable enough for practical use and a high Young's modulus. <P>SOLUTION: Needle-shaped calcium silicate particles having an average diameter (D) of 0.01-1.0 μm, an average length (L) of 0.1-10 μm and an average aspect ratio (L/D) of 4-50 are dispersed in the polyethylene terephthalate resin composition in an amount of 0.1-20 wt.% of the weight of the composition. The biaxially oriented polyethylene terephthalate is obtained by using the composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyethylene terephthalate resin composition and a polyethylene terephthalate film using the same. More specifically, the present invention relates to a polyethylene terephthalate resin composition capable of obtaining a high Young's modulus polyethylene terephthalate film or polyethylene terephthalate fiber and a polyethylene terephthalate film using the same.

  Polyethylene terephthalate resin is used for films, fibers and the like because it has excellent moldability and mechanical properties.

  In particular, polyethylene terephthalate film is used as a base film for magnetic recording media. For the base film of magnetic recording media, for example, it is required that the magnetic recording medium can be made thin by data storage or the like to increase the length of the magnetic recording medium in the same volume, and the recording density can be further increased. ing. In order to satisfy this requirement, the base film must have a high Young's modulus and excellent surface flatness. High Young's modulus is also required for polyester fibers.

  As a method for improving the strength and dimensional stability of a polyester resin, a polyester resin composition containing fibrous wollastonite and a plate-like filler has been proposed (Japanese Patent Laid-Open No. 6-128466). A polyester composition in which a glass fiber having a specific fiber length is blended in a high proportion with polyalkylene terephthalate has been proposed (Japanese Patent Laid-Open No. 1-144452).

  However, polyester films obtained from these polyester resins have a rough surface and cannot be used for base films that require flatness such as magnetic recording media. In addition, when these polyester resins are used for the production of polyester fibers, there are problems such as frequent yarn breakage during spinning.

  In addition to this, a polyester resin containing carbon nanotubes has also been proposed (Japanese Patent Laid-Open No. 2003-82202), but the problem is that the surface of the resulting film is too rough and the yarn is frequently broken during spinning. was there.

JP-A-6-128466 Japanese Unexamined Patent Publication No. 1-144452 JP 2003-82202 A

  An object of the present invention is to solve the above-mentioned problems of the prior art, and provide a polyethylene terephthalate resin composition capable of providing a molded article such as a film or fiber having a high Young's modulus and surface flatness, and two using the same. It is to provide an axially oriented polyethylene terephthalate film.

As a result of repeated studies to solve the above problems, the present inventors have found that the problem can be solved by blending calcium silicate particles having a specific shape in a specific ratio with polyester having ethylene terephthalate as a main repeating unit. The present invention has been reached.
The present invention for solving the above problems is described below.

  [1] A polyethylene terephthalate resin composition containing 0.1 to 20% by weight of calcium silicate particles, wherein the calcium silicate particles have an average diameter (D) of 0.01 to 1.0 μm and an average length (L ) 0.1 to 10 μm and an average aspect ratio (L / D) of 4 to 50 acicular calcium silicate particles, and the temperature rise crystallization temperature (Tci) of the resin composition by a differential scanning calorimeter is 125. Polyethylene terephthalate resin composition in a range of ˜165 ° C.

  [2] The polyethylene terephthalate resin composition according to [1], wherein the calcium silicate particles are zonotolite particles.

  [3] A biaxially oriented polyethylene terephthalate film comprising the polyethylene terephthalate resin composition according to [1].

  [4] The biaxially oriented polyethylene terephthalate film according to [3], wherein the Young's modulus of at least one of the film forming direction and the width direction is in the range of 6 to 15 GPa.

  [5] The biaxially oriented polyethylene terephthalate film according to [3] or [4], which has a thickness of 2 to 10 μm.

  The polyethylene terephthalate resin composition of the present invention can be molded into a film, fiber, or the like using the composition, thereby obtaining a molded product having excellent surface flatness and a high Young's modulus. In particular, a biaxially oriented polyethylene terephthalate film having surface flatness and high Young's modulus can be obtained from the polyethylene terephthalate resin composition of the present invention, and its industrial value is extremely high.

Hereinafter, the present invention will be described in detail.
[Polyethylene terephthalate resin composition]
The polyethylene terephthalate (hereinafter, sometimes referred to as PET) resin composition of the present invention includes PET having calcium silicate particles as the main repeating unit of ethylene terephthalate, and the calcium silicate particles in the PET resin composition. The content ratio needs to be 0.1 to 20% by weight. By including calcium silicate particles in the PET resin composition at the above ratio, the Young's modulus and surface smoothness of a PET molded product obtained using the PET resin composition can be made excellent.

  The content ratio of PET in the PET resin composition is in the range of 80 to 99.9% by weight. The component of the PET resin composition may be only PET and calcium silicate particles, but the content ratio of PET and calcium silicate particles is in the above range and does not hinder the effects of the present invention. For example, the additive etc. which are mentioned later may be contained.

  Moreover, it is necessary that the temperature rising crystallization temperature (Tci) measured by the differential scanning calorimeter (DSC) of the PET resin composition of this invention is 125-165 degreeC. The Tci was obtained by increasing the temperature of the PET resin composition from 20 ° C. by DSC to 300 ° C. at a rate of temperature increase of 20 ° C./min. It is the temperature rising crystallization peak temperature (unit: ° C) observed at the time.

  If Tci is out of the above range, crystallization is slow as in the case of conventional PET resin compositions, or crystallization is too fast, so the effect of improving Young's modulus by acicular calcium silicate particles is poor, and dimensional stability Performance may be degraded, and the flatness of the surface may be impaired. In order to make Tci within the above range, it is effective to contain calcium silicate particles in the PET resin composition and adjust the amount depending on the amount and shape of the PET resin composition.

[PET]
The PET in the present invention contains ethylene terephthalate as the main repeating unit. This PET may be a homopolymer of ethylene terephthalate, and ethylene terephthalate copolymerized at a ratio of 20 mol% or less within the range in which components other than the components constituting ethylene terephthalate do not impair the effects of the present invention. A copolymer may also be used.

  In the PET of the present invention, 80 mol% or more of all dicarboxylic acid components are terephthalic acid, and 80 mol% or more of all glycol components are ethylene glycol. More preferably, in PET, 85 mol% or more of all dicarboxylic acid components are terephthalic acid, and 85 mol% or more of all glycol components are ethylene glycol. Furthermore, it is particularly preferable that 90 mol% or more of all dicarboxylic acid components are terephthalic acid and 90 mol% or more of all glycol components are ethylene glycol.

  When PET is a copolymer, the copolymer component is, for example, succinic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium dicarboxylic acid as a dicarboxylic acid component, or glycol. Examples of the component include alkylene glycol such as trimethylene glycol, diethylene glycol, propylene glycol, and 1,4-butanediol, and 1,4-cyclohexanedimethanol. In addition, these copolymerization components may use not only 1 type but 2 or more types together. These copolymer components are used in a range of less than 20 mol% of the total dicarboxylic acid component and / or less than 20 mol% of the total diol component.

  The intrinsic viscosity of PET in the present invention is preferably 0.4 dl / g to 0.8 dl / g at 35 ° C. in an orthochlorophenol solvent, more preferably 0.5 dl / g to 0.7 dl / g. is there. When the intrinsic viscosity is less than 0.4 dl / g, the mechanical strength required when the PET resin composition of the present invention is used for each product after it is formed into a film may be insufficient. On the other hand, when the intrinsic viscosity exceeds 0.8 dl / g, productivity at the time of melt kneading in the melt polymerization step and the film forming step may be impaired.

  The PET resin composition of the present invention can contain organic or inorganic inert particles as a lubricant in order to improve the film winding property, film transportability, and the like when the film is produced.

[Acicular calcium silicate particles]
In the present invention, acicular calcium silicate particles are blended in the PET resin composition in order to increase the Young's modulus of a molded product such as a film or fiber and to smooth the surface of the molded product.

  According to the study by the present inventors, a film in which specific acicular calcium silicate particles are dispersed in PET and stretched in a biaxial direction, or a fiber stretched in a uniaxial direction is surprisingly acicular. It has been found that a higher strength is exhibited under the same film forming or yarn forming conditions as compared with a film or fiber made of PET in which calcium silicate particles are not dispersed.

  In order to express the above effects, it is necessary to blend calcium silicate particles having a specific shape described below in a specific ratio.

  That is, the calcium silicate particles in the present invention have an average diameter (D) of 0.01 to 1.0 μm, an average length (L) of 0.01 to 10 μm, and an average aspect ratio (L / D) of 4 to 50. Needle-like calcium silicate particles. Moreover, the ratio in the PET resin composition of acicular calcium silicate particle | grains needs to be 0.1 to 20 weight%. In addition, the ratio in a PET resin composition here means the ratio in the PET resin composition which comprises the whole film, when a molded article is a single layer film, and a molded article consists of two or more layers. In the case of a laminated film, it means the ratio in the PET resin composition constituting the layer containing acicular calcium silicate particles.

  When the average diameter (D) of the acicular calcium silicate particles is less than the lower limit, sufficient improvement of Young's modulus of the molded product cannot be realized. On the other hand, if the average diameter (D) exceeds the upper limit, the film surface becomes rough, and when the magnetic recording medium is formed, the electromagnetic conversion characteristics of the magnetic recording medium are deteriorated. For the above reasons, the average diameter (D) of the acicular calcium silicate particles is preferably in the range of 0.01 to 0.5 μm, particularly 0.01 to 0.1 μm when used for a film.

  When the average length (L) of the acicular calcium silicate particles is less than the lower limit, a sufficient improvement in Young's modulus of the molded product cannot be realized. On the other hand, if the average length (L) exceeds the upper limit, the film surface becomes rough and the magnetic conversion characteristics deteriorate when the magnetic recording medium is obtained. For the above reasons, the average length (L) of the acicular calcium silicate particles is preferably 0.01 to 5 μm.

  In addition, when using the PET resin composition of this invention for manufacture of PET film, the average length (L) of acicular calcium-silicate particle | grains is 0.01-3 micrometers, Especially the range which is 0.01-1.0 micrometer. It is particularly preferred that

  When the average aspect ratio (L / D) of the acicular calcium silicate particles is less than the lower limit, sufficient improvement of Young's modulus of the molded product cannot be realized. On the other hand, if the average aspect ratio (L / D) exceeds the upper limit, the dispersion of the acicular calcium silicate particles tends to be non-uniform, and a sufficient improvement in Young's modulus of the molded product cannot be realized. For the above reasons, the average aspect ratio (L / D) of the acicular calcium silicate particles is preferably in the range of 4 to 30, particularly 4 to 20.

  When the amount of acicular calcium silicate particles added in the PET resin composition is less than 0.1% by weight, a sufficient improvement in Young's modulus of a molded article such as a film or fiber cannot be realized. On the other hand, when the addition amount exceeds 20% by weight, the effect of acicular calcium silicate particles becomes saturated. Further, the film forming and yarn manufacturing process becomes unstable. For the above reasons, the content of acicular calcium silicate particles in the PET resin composition is preferably in the range of 0.1 to 10% by weight, particularly 0.1 to 5% by weight.

  The acicular calcium silicate particles are not particularly limited as long as they satisfy the above-described characteristics, but are preferably zonotrite particles because the effects of the present invention are easily exhibited.

  Thus, the PET resin composition of the present invention can be advantageously applied to biaxially oriented PET films and oriented PET fibers. That is, by selecting and stretching the shape of the acicular calcium silicate particles within the scope of the present invention, the strength and dimensional stability of the molded product can be expressed to a higher degree.

[Method for producing PET resin composition]
The PET resin composition of the present invention is obtained by dispersing needle-shaped calcium silicate particles having the above-mentioned shape in a molten PET so that the content ratio in the PET resin composition is 0.1 to 20% by weight. be able to.

  The method of dispersing acicular calcium silicate particles in PET includes, for example, a method of adding acicular calcium silicate particles as a slurry in which ethylene glycol is dispersed in a PET manufacturing process, uniaxial or biaxial kneading extrusion Using a machine, add needle-like calcium silicate particles directly to PET obtained by polycondensation and knead and disperse, and create high-concentration needle-like calcium silicate particle-containing PET by any of the above methods. A method of obtaining a PET resin composition having an arbitrary concentration by mixing and kneading with PET not containing particles using a uniaxial or biaxial kneading extruder can be preferably used. At this time, in order to improve the dispersibility of acicular calcium silicate, it is preferable to use a dispersion treatment such as homogenization or sand grinder and a filtration treatment with a filtration filter in combination.

  Particularly preferably, since acicular calcium silicate particles can be uniformly dispersed, PET containing a high concentration of acicular calcium silicate particles is mixed and kneaded with PET containing no particles using a uniaxial or biaxial kneading extruder. In this method, a PET resin composition having an arbitrary concentration is obtained.

[Biaxially oriented PET film]
The biaxially oriented PET film of the present invention is composed of the PET resin composition of the present invention, and the film forming direction (hereinafter sometimes referred to as the longitudinal direction) and the in-plane direction (hereinafter referred to as the width direction or lateral direction) perpendicular thereto. PET film oriented in the biaxial direction. If it is not oriented in the biaxial direction, the Young's modulus improvement effect by the acicular calcium silicate particles cannot be obtained.

  The biaxially oriented PET film of the present invention contains acicular calcium silicate particles in a proportion of 0.1 to 20% by weight in the PET resin composition constituting the film. The acicular calcium silicate particles may be contained in the entire film, but when the film is a laminated film of two or more layers, at least one of the layers contains acicular calcium silicate particles. Good. For example, a two-layer structure of a layer not containing acicular calcium silicate particles and a layer containing acicular calcium silicate particles (acicular calcium silicate particle-containing layer), acicular calcium silicate-containing layers and both surfaces thereof A three-layer structure in which layers containing no acicular calcium silicate particles are laminated, a three-layer structure in which acicular calcium silicate particle-containing layers are laminated on both surfaces of a layer not containing acicular calcium silicate particles, and Examples of these layer structures include a layer structure of three or more layers in which a layer not containing acicular calcium silicate particles or a layer containing acicular calcium silicate particles is further provided.

  When the PET film of the present invention is used as a base fill of a magnetic recording medium, the surface roughness (Ra) of at least one exposed surface of the film is preferably 0.1 to 10 nm. When the surface roughness exceeds the upper limit, when a magnetic layer is provided on the surface to form a magnetic tape, the surface of the magnetic layer becomes rough and electromagnetic conversion characteristics deteriorate, which is not preferable. On the other hand, when the surface roughness is less than the lower limit, the slipping property between the film and the film is lowered, and the winding property of the film is deteriorated. This surface roughness is more preferably 0.5 to 5 nm for the above reason.

  As a means for providing such a surface roughness to the PET film of the present invention, in addition to adjusting the type, shape, size and amount of acicular calcium silicate particles contained in the PET film, inert particles are further added. It can be added and adjusted depending on the kind, shape, size and addition amount of the inert particles. Moreover, it can adjust also by the surface treatment which forms fine unevenness | corrugation in the at least one surface of the biaxially oriented PET film of this invention, for example, the coating process of a slippery coating agent. As the inert fine particles, for example, inorganic fine particles (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.) containing the elements of Periodic Tables IIA, IIB, IVA, and IVB, silicone resins, crosslinks Examples thereof include fine particles made of a polymer having high heat resistance such as polystyrene. When the inert fine particles are contained in the PET film, the average particle diameter of the fine particles is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.8 μm. The content of the inert fine particles is preferably 0.05 to 0.5% by weight, more preferably 0.1 to 0.3% by weight, in the PET resin composition constituting the PET film. Further, two or more kinds of inert particles having different kinds, shapes, or sizes may be used in combination.

  The biaxially oriented PET film of the present invention preferably has a Young's modulus of at least 6 GPa in at least one of the film forming direction and the width direction. If the Young's modulus in the longitudinal direction and the transverse direction are both below the lower limit, for example, when PET film is used as the base film of a magnetic recording medium tape, the dimensional stability is impaired due to changes in tension and changes in temperature and humidity. Therefore, problems such as track misalignment are likely to occur. Moreover, the effect by adding the acicular calcium silicate particle | grains becomes difficult to express. For the above reasons, the Young's modulus of any one of the PET films is more preferably 8 GPa or more, and particularly preferably 10 GPa or more.

  That is, the Young's modulus in the longitudinal direction of the PET film is preferably 6 GPa or more, more preferably 8 GPa or more, and particularly preferably 10 GPa or more, since the dimensional change in the width direction due to the tension change in the longitudinal direction of the magnetic tape can be suppressed. On the other hand, the Young's modulus in the lateral direction is preferably 6 GPa or more, more preferably 8 GPa or more, and particularly preferably 10 GPa or more because the change in the width direction of the magnetic tape due to temperature and humidity changes can be suppressed.

  In addition, although the upper limit of the Young's modulus in the vertical direction and the horizontal direction is not particularly limited, it is usually preferably 15 GPa or less because sufficient Young's modulus can be imparted in the orthogonal direction.

  The sum of the Young's modulus in the vertical and horizontal directions of the PET film is preferably 10 GPa or more, more preferably 13 GPa or more, and particularly preferably 15 GPa or more. Such a high Young's modulus can be obtained by the addition of acicular calcium silicate particles at a lower magnification than conventional films not containing acicular calcium silicate particles. The upper limit of the sum of the Young's modulus in the vertical direction and the horizontal direction is not particularly limited, but is usually at most 20 GPa.

  The thickness of the PET film of the present invention is appropriately designed according to the application to be used, and in particular when used for a base film of a magnetic recording medium tape, it should be 2 to 10 μm, further 3 to 8 μm, particularly 4 to 6 μm. Is preferred. If the thickness is less than the above lower limit, the tape strength is insufficient, and the tape width shrinks due to the tension at the start of running, and the track and the magnetic head are misaligned. If the thickness exceeds the upper limit, the length of the tape stored in the cartridge becomes short, and a desired storage capacity cannot be obtained.

[PET film production method]
The PET film of the present invention can be produced, for example, according to the following method.
First, a PET resin pellet containing a high concentration of acicular calcium silicate particles and a PET resin pellet containing no acicular calcium silicate particles are mixed at a predetermined ratio, and after drying, for example, a melting temperature of 260 ° C. to The film is extruded through a T-die from an extruder at 310 ° C. into a film shape, cast on a cooling drum, and cooled and solidified to produce an unstretched film. This unstretched film is stretched in the longitudinal direction at a temperature of 3 to 8 times at a temperature of 60 to 140 ° C., and then stretched in the transverse direction at a temperature of 70 to 140 ° C. and a magnification of 3 to 7 times. A film can be obtained. If necessary, longitudinal and / or transverse stretching may be divided into two or more stages (longitudinal multi-stage stretching, longitudinal-horizontal-vertical three-stage stretching, longitudinal-horizontal-vertical-horizontal 4). Step stretching, etc.). Moreover, you may implement by simultaneous biaxial stretching. The total draw ratio in producing the biaxially oriented PET film is preferably 10 to 35 times, more preferably 12 to 30 times as the area draw ratio. The biaxially oriented PET film is preferably heat-set at a temperature of 140 to 250 ° C after biaxial stretching, and particularly preferably heat-set at 180 to 230 ° C. The heat setting time is preferably 1 to 60 seconds.

  Further, when the biaxially oriented PET film of the present invention is a laminated film, two extruders are used, and at least one of them is fed with a pellet containing acicular calcium silicate particles and melted to form two layers or multiple layers Extruded as a laminated film from a die to produce a laminated unstretched film. Further, the laminated unstretched film can be produced by performing the same operation as in the case of the single-layer PET film.

[Magnetic recording medium]
The biaxially oriented PET film of the present invention has excellent Young's modulus, dimensional stability, flatness, slipperiness, winding property and the like. Since it has such characteristics, the PET film of the present invention is preferably used as a base film for high-density magnetic recording media, particularly as a base film for digital recording type magnetic machine recording media.

  A magnetic recording medium using the biaxially oriented PET film of the present invention as a base film can be obtained, for example, by the following method. That is, a magnetic layer is formed on one side surface (the flat side surface in the case of a laminated film) of a PET film, or iron, cobalt, chromium, or these as a main component by a method such as vacuum deposition, sputtering, or ion plating. A ferromagnetic metal thin film layer made of an alloy or oxide is formed, and a protective layer such as diamond-like carbon (DLC) or a fluorine-containing carboxylic acid-based lubricant layer is formed on the surface of the thin film layer according to the purpose, application, and necessity. A magnetic recording medium can be prepared by sequentially providing a backcoat layer on the surface opposite to the magnetic layer.

[PET fiber]
In the case of producing PET fibers using the PET resin composition of the present invention, the production method can adopt a known method as appropriate, but in order to develop the Young's modulus improvement effect by the acicular calcium silicate particles, it is uniaxial direction. It is necessary to have molecular orientation in the (spinning direction). In order to increase the molecular orientation, it is effective to increase the spinning speed or increase the draw ratio.

  Hereinafter, the present invention will be further described based on examples. Various physical property values and characteristics in the present invention are measured and defined as follows.

(1) Young's modulus Using a tensile tester “Tensilon” manufactured by Toyo Baldwin Co., Ltd., the film was placed in a room adjusted to a temperature of 20 ° C. and a humidity of 50%. From the tangent of the rising portion of the resulting load-elongation curve, the length is cut to 15 cm, the chuck is 100 mm, the film is pulled in the film forming direction and the width direction at a chart speed of 500 mm / min, and the chart speed is 500 mm / min. The Young's modulus in the film forming direction and the width direction is calculated.

(2) Average diameter and length of acicular calcium silicate particles The diameter and length of the acicular calcium silicate particles in the PET resin composition were observed with a transmission electron microscope (TEM), and 100 acicular shapes were obtained. Obtained by averaging the measurement results of calcium silicate particles.

(3) Average particle diameter of inert particles Measured using a CP-50 type Centrifugular Particle Size Analyzer manufactured by Shimadzu Corporation. The particle size corresponding to 50 mass percent is read from the cumulative curve of the particle size and the abundance of each particle size calculated based on the centrifugal sedimentation curve obtained, and this value is taken as the average particle size. To do.

(4) Surface roughness of the film (centerline average roughness: Ra)
Centerline average roughness (Ra) is measured according to JIS-B601. In the present invention, a stylus type surface roughness meter (SURFCORDER SE, 30C) manufactured by Kosaka Laboratory Ltd. is used to measure and obtain under the following conditions.
(A) Radius tip radius: 2 μm
(B) Measurement pressure: 30 mg
(C) Cutoff: 0.08mm
(D) Measurement length: 8.0 mm
(E) How to summarize data: The same sample is repeatedly measured 6 times, the largest value is removed, and the center line average roughness (Ra) is obtained as an average value using the remaining five data. When the surface roughness (Ra) of the center line exceeds 10 nm, the surface is too rough, and it is determined that it cannot be used as a magnetic recording medium.

(5) Intrinsic viscosity This is a value measured in orthochlorophenol at 25 ° C. The unit is dl / g.

(6) Temperature rising crystallization temperature (Tci)
A sample of 10 mg was mounted on a differential scanning calorimeter (TAM, Thermal Analyst model 2200), and this sample was heated to 300 ° C. at a heating rate of 20 ° C./min, and then rapidly cooled to 20 ° C. to obtain an amorphous sample Get. Using this amorphous sample, the crystallization exothermic peak observed when the temperature is raised to 300 ° C. at 20 ° C./min is defined as the temperature rise crystallization temperature (Tci, unit ° C.).

[Example 1]
170 ° C. polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.60 containing 3.0% by weight of acicular calcium silicate particles (zonotolite particles) having an average diameter of 0.05 μm and an average length of 0.4 μm After drying for 3 hours, it is supplied to an extruder hopper, melted at 280 ° C., and rapidly cooled and solidified on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 30 ° C. using a T-type extrusion die, An unstretched film made of a polyethylene terephthalate resin composition was obtained.

This unstretched film is preheated to 75 ° C., further heated by an infrared heater with a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls, stretched 5.0 times in the longitudinal direction, rapidly cooled, and then Was supplied to a stenter and stretched 4.5 times in the transverse direction at 120 ° C. Subsequently, the film was heat-fixed at 225 ° C. for 3 seconds to obtain a biaxially oriented polyethylene terephthalate film having a thickness of 4.5 μm.
The properties of the obtained polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film are shown in Table 1.

[Example 2]
Polyethylene terephthalate resin composition for layer A containing polyethylene terephthalate having an intrinsic viscosity of 0.60 and containing 3.0% by weight of acicular calcium silicate particles (zonotolite particles) having an average diameter of 0.05 μm and an average length of 0.4 μm The polyethylene terephthalate resin composition for layer B, in which 0.01% by weight of spherical silica particles having an average particle size of 0.1 μm is contained in polyethylene terephthalate having an intrinsic viscosity of 0.60, is dried at 170 ° C. for 3 hours. On a casting drum that is supplied to an extruder hopper, melted at a melting temperature of 280 ° C., and layer A and layer B are laminated using a multi-manifold coextrusion die, and the surface finish is maintained at 0.3 S and the surface temperature is 60 ° C. And solidified rapidly to obtain a laminated unstretched film. The thickness of each layer is 60% for the A layer and 40% for the B layer.

  The laminated unstretched film thus obtained is preheated to 75 ° C., and further heated by an infrared heater having a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls to 5.5 times in the longitudinal direction. Stretched, quenched, and then fed to the stenter, stretched 4.2 times in the transverse direction at 120 ° C, 1.14 times in the transverse direction at 170 ° C, and stretched 4.8 times in the total transverse direction. did. Subsequently, the film was heat-fixed at 225 ° C. for 3 seconds to obtain a laminated biaxially oriented polyethylene terephthalate film having a thickness of 4.5 μm. The properties of the obtained polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film are shown in Table 1.

[Examples 3 to 5]
A polyethylene terephthalate resin composition and a biaxially oriented polyethylene terephthalate film were obtained in the same manner as in Example 1 except that the acicular calcium silicate particles and the addition amount thereof were changed as shown in Table 1. The properties of the obtained polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film are shown in Table 1.

[Comparative Example 1]
170 ° C. polyethylene terephthalate containing 0.02% by weight of calcium carbonate particles having an average particle diameter of 0.6 μm and 0.2% by weight of silica particles having an average particle diameter of 0.1 μm without adding acicular calcium silicate particles After being dried for 3 hours, a polyethylene terephthalate resin composition and a biaxially oriented polyethylene terephthalate film having a thickness of 4.5 μm were obtained in the same manner as in Example 1 except that it was supplied to an extruder hopper. The properties of the obtained polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film are shown in Table 1.

[Comparative Examples 2 to 4 and Example 6]
A polyethylene terephthalate resin composition and a biaxially oriented film having a thickness of 4.5 μm were obtained in the same manner as in Example 1 except that the acicular calcium silicate particles were changed as shown in Table 1. The properties of the obtained polyethylene terephthalate resin composition and biaxially oriented polyethylene terephthalate film are shown in Table 1.

  PET in Table 1 indicates polyethylene terephthalate, and the content indicates the particle content in the resin composition. The diameters of calcium carbonate and silica are average particle diameters, and the shape is almost spherical.

Claims (5)

  A polyethylene terephthalate resin composition containing 0.1 to 20% by weight of calcium silicate particles, wherein the calcium silicate particles have an average diameter (D) of 0.01 to 1.0 μm and an average length (L) of 0. The temperature rising crystallization temperature (Tci) of the polyethylene terephthalate resin composition, which is a needle-like calcium silicate particle having an average aspect ratio (L / D) of 4 to 50 and measured by a differential scanning calorimeter, is 1 to 10 μm. A polyethylene terephthalate resin composition having a temperature range of 125 to 165 ° C.   The polyethylene terephthalate resin composition according to claim 1, wherein the calcium silicate particles are zonotolite particles.   A biaxially oriented polyethylene terephthalate film comprising the polyethylene terephthalate resin composition according to claim 1.   The biaxially oriented polyethylene terephthalate film according to claim 3, wherein the Young's modulus of at least one of the film forming direction and the width direction of the film is in the range of 6 to 15 GPa.   The biaxially oriented polyethylene terephthalate film according to claim 3, which has a thickness of 2 to 10 μm.