JP2009149808A - Polyester resin composition, and biaxially oriented film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin composition giving such a film as to be slight in voids developed around particles included therein, even if highly oriented in order to bring the film to low coefficients of thermal and humidity expansion. <P>SOLUTION: The polyester resin composition includes a polyester composed of an acid component and a glycol component and particles 0.1-5 μm in areal circle-equivalent average size with the ratio of its major axis to minor axis being 1.1-3. In this composition, the acid component consists of a 6,6'-(alkylenedioxy)di-2-naphthoic acid component and a phenyljiene-or naphthalenediyl-dicarboxylic acid component, with the proportion of the former being within the range of 5-80 mol% based on the number of moles of the total acid component, and the glycol component consists of a 2-4C alkylene glycol component. A biaxially oriented film using the above polyester resin composition is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyester resin composition copolymerized with 6,6 '-(alkylenedioxy) di-2-naphthoic acid and a film using the same.

  Aromatic polyesters typified by polyethylene terephthalate and polyethylene-2,6-naphthalate have excellent mechanical properties, dimensional stability and heat resistance, and thus are widely used for films and the like. In particular, polyethylene-2,6-naphthalate has mechanical properties, dimensional stability, and heat resistance superior to those of polyethylene terephthalate, so that it is used in demanding applications such as a base film for high-density magnetic recording media. in use. However, the demand for dimensional stability in high-density magnetic recording media and the like in recent years is increasing, and further characteristics, reduction of temperature expansion coefficient and humidity expansion coefficient are required.

By the way, both the humidity expansion coefficient and the temperature expansion coefficient are very closely related to the Young's modulus, and generally lower as the Young's modulus is higher. However, in order to increase the Young's modulus, it is necessary to perform stretching at a higher magnification and at a lower temperature. For example, peeling occurs at the interface between the particles and the polymer contained to make the film easy to handle, and voids called voids are generated. Occurs. This tendency is likely to occur with irregularly shaped particles that tend to have large variations in stress at the interface with the polymer.
For this reason, the Young's modulus is not increased as much as possible, and a film having an expansion coefficient with respect to lower temperature and humidity is required for the same Young's modulus.

  On the other hand, Patent Documents 1 to 4 are obtained from diethyl-6,6 ′-(alkylenedioxy) di-2-naphthoate, which is an ester compound of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid. Polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate has been proposed. According to this publication, polyethylene-6,6 '-(ethylenedioxy) di-2-naphthoate which is crystalline and has a melting point of 294 ° C. is specifically presented.

However, since polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate presented in these patent documents has a very high melting point and very high crystallinity, it should be formed into a film or the like. Then, there was a problem that the fluidity in the molten state was poor and the extrusion became non-uniform, or even when trying to stretch after extrusion, crystallization progressed and the film would break when stretched at a high magnification. Moreover, when the Example of patent document 3 was seen, there also existed a problem that the temperature expansion coefficient was high although the humidity expansion coefficient was low.
Therefore, polyethylene terephthalate as well as polyethylene-2,6-naphthalate and films such as those disclosed in Patent Document 3 are not sufficient for the demands of dimensional stability in recent magnetic recording media and the like. There was a need for improvement.

JP-A-60-135428 JP-A-60-212420 JP 61-145724 A JP-A-6-145323

  The object of the present invention is to have excellent dimensional stability when formed into a film and the like, and even if the film is stretched at a high magnification in order to enhance dimensional stability, the ratio of the length of the major axis to the minor axis contained Is to provide a polyester composition having small voids called voids generated around particles having a specific shape of 1.1 to 3.0, and a biaxially oriented film using the polyester composition.

  The present inventors surprisingly found that when a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is used as a copolymerization component, polyalkylene-6,6 ′-(alkylenedioxy) di- The present inventors have found that a film having excellent characteristics of both 2-naphthoate and the aromatic polyester which is a copolymerization partner thereof can be obtained. And compared with the conventional polyethylene terephthalate and polyethylene-2,6-naphthalate, the stress at the time of extending | stretching is very low, and the ratio of the length of the above-mentioned major axis and minor axis is 1.1-3.0. It was found that a film with smaller voids can be obtained with a film having the same Young's modulus even when particles having a shape are contained, and the present invention has been achieved.

  Thus, according to the present invention, the acid component consists of the following structural formulas (I) and (II), and the ratio of the following structural formula (I) is in the range of 5 to 80 mol% based on the number of moles of the total acid component. And the polyester having the glycol component represented by the following structural formula (III), the area circle equivalent average diameter is 0.1 to 5 μm, and the ratio of the major axis to the minor axis length is 1. .1-3 particles are provided.

（上記構造式（Ｉ）中のＲ_１は炭素数１〜１０のアルキレン基を、上記構造式（ＩＩ）中のＲ_２はフェニレン基またはナフタレンジイル基、上記構造式（ＩＩＩ）中のＲ_３は炭素数２〜４のアルキレン基を示す。）

(R ₁ in the structural formula (I) is an alkylene group having 1 to 10 carbon atoms, R ₂ in the structural formula (II) is a phenylene group or a naphthalenediyl group, and R ₃ in the structural formula (III). Represents an alkylene group having 2 to 4 carbon atoms.)

According to the invention, the content of the particles is in the range of 0.01 to 10% by weight based on the weight of the polyester composition, and the particles are composed of calcium carbonate, kaolin, clay, and aluminum silicate. There is also provided a polyester composition comprising at least one of at least one inorganic particle selected from the group.
Furthermore, according to this invention, the biaxially oriented film which consists of the polyester resin composition of the above-mentioned this invention is also provided.

  According to the present invention, while maintaining the characteristic that the excellent coefficient of humidity expansion of polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate is small, the film-forming property can be highly enhanced, As a result, a polyester composition having surprisingly low dimensional stability, which has a low temperature expansion coefficient which cannot be predicted from the prior art, can be obtained, and the polyester composition has a characteristic of extremely low stretching stress. Therefore, when trying to make a biaxially oriented film, even if particles having a ratio of the major axis to the minor axis of 1.1 to 3 are contained, voids generated in the periphery thereof are extremely reduced. be able to.

  Therefore, according to the present invention, there is provided a film suitable for a base film of a high-density magnetic recording medium, particularly for applications that require high dimensional stability and excellent surface flatness in consideration of the influence of humidity and temperature. If the film of the present invention is used, a high-density magnetic recording medium having excellent dimensional stability can be provided.

<Polyester composition>
In the polyester forming the polyester composition of the present invention, the acid component consists of the structural formula (I) and the structural formula (II), and the glycol component consists of the structural formula (III).

Specific examples of the acid component represented by the structural formula (I) are those in which R ₁ is an alkylene group having 1 to 10 carbon atoms, and preferably 6,6 ′-(ethylenedioxy) di -2-naphthoic acid component, 6,6 ′-(trimethylenedioxy) di-2-naphthoic acid component and 6,6 ′-(butyleneoxy) di-2-naphthoic acid component, etc. from the viewpoint of the effect of the present invention is preferable among them, those carbon atoms of an even number of R1 in the general formula (I), in particular the number of carbon atoms in R ₁ are 2 6,6 '- (ethylenedioxy) di - A 2-naphthoic acid component is preferred.

  Examples of the acid component represented by the structural formula (II) include a terephthalic acid component, an isophthalic acid component, a 2,6-naphthalenedicarboxylic acid component, and a 2,7-naphthalenedicarboxylic acid component. Among these, a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component are preferable from the viewpoint of mechanical properties, and a 2,6-naphthalenedicarboxylic acid component is particularly preferable.

  Specific examples of the glycol component represented by the structural formula (III) include an ethylene glycol component, a trimethylene glycol component, a tetramethylene glycol component, and the like. The mol% or more is preferably an ethylene glycol component, and more preferably 95 to 100 mol% is an ethylene glycol component.

  By the way, one of the characteristics of the present invention is that the 6,6 ′-(alkylenedioxy) di-2-naphthoate represented by the above structural formula (I) in the range of 5 to 80 mol% of the acid component of the polyester. The acid component is copolymerized. If the ratio of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is less than the lower limit, the stretching stress tends to be high, and the effect of suppressing the voids of the present invention by copolymerization and the effect of reducing the humidity expansion coefficient are manifested. It is hard to be done. On the other hand, the upper limit is preferably 80 mol% or less, and more preferably less than 50 mol% from the viewpoint of moldability. Surprisingly, the effect of suppressing voids and the effect of reducing the coefficient of humidity expansion by the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component are expressed very efficiently in a small amount, and below the upper limit. The humidity expansion coefficient equivalent to or lower than that of the film described in the example of Patent Document 3 has already been achieved in this part, and the effect from the viewpoint of the humidity expansion coefficient is saturated even when added above the upper limit. It can be said. From such a viewpoint, the upper limit of the copolymerization amount of the preferred 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is 45 mol% or less, further 40 mol% or less, and further 35 mol% or less. In particular, it is 30 mol% or less, and the other lower limit is 5 mol% or more, further 7 mol% or more, still more 10 mol% or more, particularly 15 mol% or more.

  By using a polyester obtained by copolymerizing such a specific amount of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, a molded product having a small void and a small temperature expansion coefficient and humidity expansion coefficient, For example, a film etc. can be manufactured.

  The aromatic polyester in the present invention may be copolymerized with other copolymerization components known per se within a range not impairing the effects of the present invention, or may be blended with polyetherimide or liquid crystalline resin. Also good.

  Next, the polyester according to the present invention preferably has a melting point measured by DSC in the range of 200 to 260 ° C., further in the range of 210 to 255 ° C., particularly in the range of 220 to 253 ° C. from the viewpoint of film forming property. When the melting point exceeds the above upper limit, when molding by melt extrusion, it is necessary to make the temperature higher to increase the fluidity, and it tends to be thermally deteriorated, and on the other hand, if the melting temperature is lowered, the fluidity is inferior, Discharge is likely to be non-uniform. On the other hand, when the ratio is less than the above lower limit, the film forming property is excellent, but the mechanical properties of the polyester are easily impaired. In general, when other acid components are copolymerized to lower the melting point, the mechanical properties and the like are also lowered at the same time. However, excellent mechanical properties and the like can be exhibited because the film-forming property is improved. In addition, in order to obtain the same Young's modulus, stretching at a higher magnification is required, but voids can be extremely suppressed even when stretching at such a high stretching ratio.

  Further, the polyester in the present invention has a glass transition temperature (hereinafter sometimes referred to as Tg) measured by DSC in the range of 90 to 119 ° C, more preferably in the range of 95 to 118 ° C, particularly in the range of 100 to 117 ° C. It is preferable from the viewpoint of heat resistance and dimensional stability. Such a melting point and glass transition temperature can be adjusted by controlling the type and amount of copolymerization component, dialalkylene glycol as a byproduct.

  By the way, the polyester composition of the present invention is an area circle in which the ratio of the major axis to the minor axis length is 1.1 to 3 in order to achieve both transportability and surface flatness when formed into a film or the like. It is necessary to contain particles having an equivalent average diameter of 0.1 to 5 μm. When the ratio of the major axis to the minor axis is in the above range, the effect of suppressing voids according to the present invention is easily exhibited, and there are also advantages such as the formation of protrusions of various shapes without using a plurality of particles. . In addition, the long axis and the short axis in the present invention are the length of the longest axis and the length of the shortest axis, respectively, when the particles are viewed with an operation electron microscope described later.

  The lower limit of the preferred area circle equivalent average diameter in the present invention is 0.15 μm or more, further 0.2 μm or more, particularly 0.3 μm or more. If the average diameter equivalent to the area circle is less than the lower limit, the particles are very small and are not easily affected by voids, and the effect of improving the runnability and winding property when made into a film is hardly exhibited. Of course, the polyester composition of the present invention only needs to contain particles having an area circle equivalent average diameter in the above range, and does not preclude containing particles having an area circle equivalent average diameter of less than the above lower limit. In addition, the upper limit of the area circle equivalent average diameter is 5 μm or less from the viewpoint of suppression of dropout of particles, etc., and when used as a film, it is preferably 3 μm or less, particularly when used as a magnetic recording medium, 1 μm or less. Preferably there is.

  The content of the particles in the present invention is at least 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, from the viewpoint of improving the handleability of the obtained molded product. . The upper limit is not particularly limited, but it is preferably 10% by weight or less when used as a normal film, particularly 1% by weight or less when used as a film for a magnetic recording medium.

  Examples of the particles having an area circle equivalent average diameter of 0.1 to 5 μm in which the ratio of the major axis to minor axis length used in the present invention is 1.1 to 3 include calcium carbonate, kaolin, clay, and aluminum silicate. Inorganic particles consisting of are preferably exemplified. Of course, the polyester resin composition and film of the present invention need only contain particles as described above, and are not limited to a single-component system, and may be a combination of two or more types or a multi-component system.

<Molded product>
The polyester composition of the present invention can be formed into a film by melting and forming into a sheet. When used as a base film such as a magnetic tape, it is preferable that at least one direction in the film surface direction has a high Young's modulus of 6.0 GPa or more so that the base film does not stretch due to stress applied to the film. In addition, by providing a film that can obtain such a high Young's modulus, usually a large amount of voids are likely to be generated, but in the present invention such voids can be suppressed, and the humidity expansion coefficient and the temperature expansion coefficient are reduced. Reduction can be achieved. Preferred Young's modulus is 5.1 to 11 GPa in the longitudinal direction of the film, more preferably 5.2 to 10 GPa, particularly 5.5 to 9 GPa, and 5 to 11 GPa in the width direction of the film, more preferably 6 to 10 GPa, particularly 7 It is in the range of -10 GPa.

<Method for producing polyester composition>
Below, the manufacturing method of the polyester composition in this invention is explained in full detail.
First, ester 6,6 ′-(alkylenedioxy) di-2-naphthoic acid or an ester-forming derivative thereof such as 2,6-naphthalenedicarboxylic acid or terephthalic acid or an ester-forming derivative thereof and ethylene glycol, for example. The polyester precursor is produced by the reaction of esterification or transesterification. The polyester precursor thus obtained may be polymerized in the presence of a polymerization catalyst, and solid phase polymerization or the like may be performed as necessary. The intrinsic viscosity measured at 35 ° C. using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60) of the polyester thus obtained is 0.4 to 1. 0.5 dl / g, and more preferably in the range of 0.5 to 1.3 dl / g is preferable from the viewpoints of handleability and mechanical properties. Two types of polymers having different proportions of the above structural formulas (I) and (II) can be prepared and melt kneaded so that the proportions of the above structural formulas (I) and (II) are aimed. Good.

  Further, in the step of producing the above-mentioned polyester precursor, the ethylene glycol component is used in an amount of 1.1 to 6 times, further 2 to 5 times, particularly 3 to 5 times the number of moles of the total acid component. From the point of view, it is preferable.

  The reaction temperature for producing the polyester precursor is preferably at or above the boiling point of ethylene glycol, particularly preferably in the range of 190 ° C to 250 ° C. When the temperature is lower than 190 ° C., the reaction does not proceed sufficiently. When the temperature is higher than 250 ° C., diethylene glycol as a side reaction product is likely to be generated. In addition, the reaction can be performed under normal pressure, but the reaction may be performed under pressure in order to further increase productivity. More specifically, the reaction pressure is 10 to 200 kPa in absolute pressure, the reaction temperature is usually 150 to 250 ° C., preferably 180 to 230 ° C., the reaction time is 10 to 10 hours, preferably 30 to 7 minutes. It is preferable to be performed for less than an hour. A reaction product as a polyester precursor is obtained by this esterification reaction or transesterification reaction.

  In the reaction step for producing the polyester precursor, a known esterification or transesterification reaction catalyst may be used. For example, an alkali metal compound, an alkaline earth metal compound, a titanium compound, and the like can be given.

  Next, the polycondensation reaction will be described. First, the polycondensation temperature is in the range of a temperature not lower than the melting point of the obtained polyester and not higher than 230 to 280 ° C, more preferably not lower than 5 ° C and higher than the melting point by 30 ° C. The polycondensation reaction is usually preferably performed under a reduced pressure of 50 Pa or less. If it is higher than 50 Pa, the time required for the polycondensation reaction becomes long, and it becomes difficult to obtain a copolyester having a high degree of polymerization.

  Examples of the polycondensation catalyst include metal compounds containing at least one metal element. In addition, you may use together a polycondensation catalyst as a catalyst of esterification reaction or transesterification. Examples of the metal element include titanium, germanium, antimony, aluminum, nickel, zinc, tin, cobalt, rhodium, iridium, zirconium, hafnium, lithium, calcium, and magnesium. More preferable metals are titanium, germanium, antimony, aluminum, tin, etc. Among them, titanium compounds are particularly preferable because they exhibit high activity in both esterification reaction, transesterification reaction and polycondensation reaction. .

  These catalysts may be used alone or in combination. The amount of the catalyst is preferably 0.001 to 0.5 mol%, more preferably 0.005 to 0.2 mol%, based on the number of moles of the repeating unit of the copolyester.

  Specific examples of the titanium compound as the polycondensation catalyst include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and the like. Eltitanate, tetrabenzyl titanate, lithium oxalate titanate, potassium oxalate titanate, ammonium oxalate titanate, titanium oxide, titanium condensed orthoester, titanium orthoester or reaction product of condensed orthoester and hydroxycarboxylic acid, titanium A reaction product comprising an orthoester or condensed orthoester, a hydroxycarboxylic acid and a phosphorus compound, an orthoester or condensed orthoester of titanium and at least two hydroxyl groups Polyhydric alcohols having 2-hydroxy carboxylic acid, or a reaction product comprising a base and the like.

  By the way, the addition method of the aforementioned particles is not particularly limited, and a known addition method can be employed. For example, a method of adding particles in the state of a glycol slurry in the polymerization reaction stage, a method of melt-kneading particles with a kneading extruder to the obtained polymer, and the like can be mentioned. From the viewpoint of particle dispersibility, a particle master polymer of a polyester composition containing particles at a high concentration is prepared by adding particles in a glycol slurry state in the polymerization reaction stage, and the particle master polymer contains particles. It is preferred to dilute with no polyester.

  The polyester composition of the present invention includes other thermoplastic polymers, stabilizers such as ultraviolet absorbers, antioxidants, plasticizers, lubricants, flame retardants, mold release agents, and pigments, as long as the effects of the present invention are not impaired. Further, a nucleating agent, a filler or glass fiber, carbon fiber, layered silicate, etc. may be blended as necessary. Examples of other types of thermoplastic polymers include aliphatic polyester resins, polyamide resins, polycarbonates, ABS resins, polymethyl methacrylate, polyamide elastomers, polyester elastomers, polyetherimides, polyimides, and the like.

<Film production method>
The polyester composition of the present invention is used as a raw material, dried, and then supplied to an extruder heated to a temperature of the melting point (Tm: ° C.) to (Tm + 50) ° C. of the polyester composition. Extrude into a sheet. In addition, the polyester composition of the present invention to be used is not limited to one type, for example, a polymer having a large proportion of the above structural formula (I) and a polymer having a large amount of the above structural formula (II) are prepared. They may be used by being melt-kneaded so that the ratio of the formulas (I) and (II) is within the target range. By adopting such a method, the above structural formulas (I) and (II) The ratio can be arbitrarily and easily changed. The extruded sheet can be rapidly cooled and solidified with a rotating cooling drum or the like to form an unstretched film, and the unstretched film can be biaxially stretched to obtain a biaxially oriented film.

  In addition, from the viewpoint of facilitating the later-described stretching, it is preferable to perform cooling with a cooling drum very quickly, not at a high temperature of 80 ° C. as described in Patent Document 4, but at a low temperature of 20-60 ° C. It is preferable to do so. By performing at such a low temperature, crystallization in the state of an unstretched film is suppressed, and subsequent stretching can be performed more smoothly.

Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching.
Here, a manufacturing method in which longitudinal stretching, lateral stretching, and heat treatment are performed in this order by sequential biaxial stretching will be described as an example. First, the first longitudinal stretching is performed at a glass transition temperature (Tg: ° C.) to (Tg + 40) ° C. of polyester at 3 to 8 times, and then at a higher temperature than the previous longitudinal stretching (Tg + 10) in the transverse direction. It is preferable that the film is stretched 3 to 8 times at a temperature of (Tg + 50) ° C., and further heat-treated at a temperature not higher than the melting point of the polymer and at a temperature of (Tg + 50) to (Tg + 150) ° C. for 1 to 20 seconds. The heat setting time is preferably 1 to 15 seconds.

Normally, when the stretch ratio is increased, the film-forming stability is impaired, but the polyester composition according to the present invention has very high stretchability, so there is no such problem, and in particular, the stretch ratio is higher. Therefore, it is particularly useful for a thin film having a thickness of 10 μm or less, more preferably 8 μm or less. The lower limit of the thickness of the film is not particularly limited, but is usually about 1 μm, preferably 3 μm.
In the above description, sequential biaxial stretching has been described. However, simultaneous biaxial stretching in which longitudinal stretching and lateral stretching are simultaneously performed can also be produced. For example, the stretching ratio and the stretching temperature described above may be referred to.

  When the biaxially oriented film is a laminated film, two or more types of molten polyester compositions are laminated in a die and then extruded into a film, preferably the melting point (Tm: ° C.) to (Tm + 70) of each polyester composition. ) Extrude at a temperature of ° C. or extrude two or more molten polyester compositions from a die, laminate them, quench and solidify them into a laminated unstretched film, Stretching and heat treatment may be performed. At this time, it is not necessary that all the film layers are the polyester composition of the present invention, and it is sufficient that at least one film layer is made of the polyester composition of the present invention. In addition, a coating layer may be provided on the surface of the biaxially oriented film. In that case, a desired coating solution is applied to one side or both sides of the unstretched film or the uniaxially stretched film described above, and after that, Biaxial stretching and heat treatment are preferably performed in the same manner as in the case.

  According to the present invention, a biaxially oriented film made of the polyester composition of the present invention is used as a base film, a nonmagnetic layer and a magnetic layer are formed in this order on one side, and a backcoat layer is formed on the other side. Thus, a magnetic recording tape can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the present invention, the characteristics were measured and evaluated by the following methods.

(1) Intrinsic viscosity The intrinsic viscosity of the obtained polyester was measured at 35 ° C by dissolving the polymer using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio). And asked.

(2) Glass transition point and melting point Glass transition point and melting point were measured by DSC (TA Instruments Co., Ltd., trade name: Thermal lyst 2100) at a heating rate of 20 ° C / min.

(3) Copolymerization amount For the glycol component, 10 mg of a sample was dissolved in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1 (volume ratio) at 80 ° C., and isopropyl was added. amine was added, measured at 80 ° C. at ¹ 600M after thorough mixing H-NMR (Hitachi Denshi Ltd. JEOL A600), were measured each glycol component amount.
As for the aromatic dicarboxylic acid component, 50 mg of a sample was dissolved in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1 at 140 ° C., and 400 M ¹³ C-NMR ( Hitachi Electron JEOL A600) was measured at 140 ° C., and the amount of each acid component was measured.

(4) Young's modulus The obtained film was cut out with a sample width of 10 mm and a length of 15 cm, and a universal tensile testing device (product name: manufactured by Toyo Baldwin, trade name: 100 mm between chucks, tensile speed 10 mm / min, chart speed 500 mm / min). Pull with Tensilon). The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.

(5) Temperature expansion coefficient (αt)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the width direction of the film was a measurement direction, set in TMA3000 manufactured by Vacuum Riko, and pretreated at 60 ° C. for 30 minutes in a nitrogen atmosphere (0% RH). Then, the temperature is lowered to room temperature. Thereafter, the temperature is raised from 25 ° C. to 70 ° C. at 2 ° C./min, the sample length at each temperature is measured, and the temperature expansion coefficient (αt) is calculated from the following equation. In addition, the measurement direction is the longitudinal direction of the sample cut out, the measurement was performed 5 times, and the average value was used.
αt = {(L ₆₀ −L ₄₀ )} / (L ₄₀ × ΔT)} + 0.5
Here, L ₄₀ in the above formula is the sample length (mm) at 40 ° C., L ₆₀ is the sample length (mm) at 60 ° C., ΔT is 20 (= 60-40) ° C., 0.5 Is the temperature expansion coefficient (× 10 ⁻⁶ / ° C.) of quartz glass.

(6) Humidity expansion coefficient (αh)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the width direction of the film would be the measurement direction, set in TMA3000 manufactured by Vacuum Riko, and a humidity of 30% RH and a humidity of 70% under a nitrogen atmosphere at 30 ° C. The length of each sample in RH is measured, and a humidity expansion coefficient is calculated by the following equation. In addition, the measurement direction is the longitudinal direction of the cut out sample, the measurement was performed 5 times, and the average value was αh.
αh = (L ₇₀ −L ₃₀ ) / (L ₃₀ × ΔH)
Here, L ₃₀ in the above formula is a sample length (mm) when 30% RH, L ₇₀ is a sample length (mm) when 70% RH, ΔH: 40 (= 70-30)% RH is there.

(7) Area circle equivalent average diameter (μm) of particle and ratio of major axis to minor axis A sample film piece is fixed to a sample table for a scanning electron microscope, and a sputtering apparatus manufactured by JEOL Ltd. (JFC-1100) Ion etching treatment is performed on the film surface under the following conditions using a type ion etching apparatus. The condition is that a sample is placed in a bell jar, the degree of vacuum is increased to a vacuum state of about 10 ⁻³ Torr, and ion etching is performed at a voltage of 0.25 kV and a current of 12.5 mA for about 10 minutes. Furthermore, with the same apparatus, the film surface was sputtered with gold, observed with a scanning electron microscope at 5,000 to 10,000 times, and the area equivalent circle diameter of each particle was measured with Luzex 500 manufactured by Japan Regulator Co., Ltd. Asked.
The ratio of the long axis to the short axis is determined by using the image analysis processing apparatus Luzex 500 (manufactured by Nippon Regulator Co., Ltd.), reading the length of the longest axis on the projection plane as the length of the long axis, and the other shortest axis. Was obtained as the length of the short axis, and the length of the long axis was divided by the length of the short axis.
The above measurement was carried out for 100 particles, and the average value was taken as the area diameter equivalent diameter of the particles and the ratio of the major axis to the minor axis.

(8) Content of particles Select a solvent that dissolves the polyester resin and does not dissolve the particles, dissolves the polyester resin composition, and then centrifuges the particles from the polyester resin to obtain a ratio (% by weight) to the total weight of the particles. Is the particle content. When particles having a major axis / minor axis length ratio of less than 1.1 coexist, the above-mentioned “(7) Particle area circle equivalent diameter (μm)” and major axis / minor axis ratio The content was calculated from the abundance ratio of each particle on the basis of the measurement results.

(9) Measurement of void ratio A sample film piece is fixed on a sample stage for a scanning electron microscope, and the surface of the film is subjected to the following conditions using a sputtering apparatus (JFC-1100 type ion etching apparatus) manufactured by JEOL Ltd. Ion etching treatment is performed. The condition is that a sample is placed in a bell jar, the degree of vacuum is increased to a vacuum state of about 10 ⁻³ Torr, and ion etching is performed at a voltage of 0.25 kV and a current of 12.5 mA for about 10 minutes. Further, using the same apparatus, the film surface was sputtered with gold, observed with a scanning electron microscope at a magnification of 20,000 times, and image analysis processing was performed from the obtained image with a Luzex 500 manufactured by Japan Regulator Co., Ltd. Extract the boundary where void boundaries can be confirmed, obtain the particle area and void area for each particle, and calculate the void ratio according to the following definition.
Void ratio = (particle area + void area) / particle area This measurement was performed on 100 particles, and the average value was defined as the void ratio. The smaller the void ratio, the smaller the void and the better.

[Example 1]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was carried out to give an intrinsic viscosity of 0.66 dl / g, 73 mol% of the acid component being 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component being 6,6 ′-(alkylenedioxy). A polyester composition was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were ethylene glycol components and 2 mol% were diethylene glycol components. In addition, in the polyester composition, before the polycondensation reaction, calcium carbonate particles shown in Table 1 were contained so as to be 0.2% by weight based on the weight of the resin composition to be obtained. The aromatic polyester had a melting point of 240 ° C. and a glass transition temperature of 117 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 50 ° C. to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 135 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 6.2. And this uniaxially stretched film is led to a stenter, stretched at 140 ° C. in the transverse direction (width direction) at a stretching ratio of 6.3 times, then heat-set at 200 ° C. for 10 seconds, and biaxially stretched with a thickness of 6 μm. A film was obtained.
Table 1 shows the characteristics of the obtained polyester resin composition and biaxially oriented film.

[Examples 2 to 5]
In Example 1, instead of calcium carbonate particles, as shown in Table 1, the same operation was repeated except that the particle type and content were changed.
Table 1 shows the characteristics of the obtained polyester resin composition and biaxially oriented film.

[Example 6]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was carried out, the intrinsic viscosity was 0.72 dl / g, 94 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 6 mol% of the acid component was 6,6 ′-(ethylenedioxy). A polyester composition was obtained in which 99 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 1 mol% was a diethylene glycol component. The polyester composition contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 255 ° C., and the glass transition temperature was 119 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 60 ° C. to form an unstretched film. Then, between the two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 140 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.3 times. Then, this uniaxially stretched film is guided to a stenter, stretched in the transverse direction (width direction) at 140 ° C. at a stretch ratio of 4.0 times, and then heat-set at 200 ° C. for 10 seconds, and biaxially stretched with a thickness of 8 μm A film was obtained.
The characteristics of the obtained biaxially oriented film are shown in Table 1.

[Example 7]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was carried out, the intrinsic viscosity was 0.77 dl / g, 80 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 20 mol% of the acid component was 6,6 ′-(ethylenedioxy). An aromatic polyester in which 99 mol% of the di-2-naphthoic acid component and glycol component was an ethylene glycol component and 1 mol% of a diethylene glycol component was obtained. The aromatic polyester contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 252 ° C., and the glass transition temperature was 116 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 50 ° C. to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 135 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.5. Then, this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.3 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 210 ° C. for 10 seconds, and biaxially stretched with a thickness of 6 μm. A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Example 8]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was performed, and the intrinsic viscosity was 0.77 dl / g, 65 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 35 mol% of the acid component was 6,6 ′-(ethylenedioxy). An aromatic polyester in which 98 mol% of the di-2-naphthoic acid component and glycol component was an ethylene glycol component and 2 mol% was a diethylene glycol component was obtained. The aromatic polyester contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 247 ° C., and the glass transition temperature was 116 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 50 ° C. to form an unstretched film. Then, between the two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 140 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.5. Then, this uniaxially stretched film is guided to a stenter, stretched at 140 ° C. in the transverse direction (width direction) at a stretch ratio of 6.0 times, and then heat-set at 210 ° C. for 10 seconds to be biaxially stretched with a thickness of 7 μm A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Example 9]
Esterification and transesterification of dimethyl terephthalate, 6,6 '-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol in the presence of titanium tetrabutoxide, followed by polycondensation reaction And the intrinsic viscosity is 0.73 dl / g, 65 mol% of the acid component is terephthalic acid component, 35 mol% of the acid component is 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, glycol component An aromatic polyester having 98.5 mol% of ethylene glycol component and 1.5 mol% of diethylene glycol component was obtained. The aromatic polyester contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 233 ° C., and the glass transition temperature was 91 ° C.

The aromatic polyester thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a temperature of 40 ° C. while rotating in a molten state to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 110 ° C., and stretching in the longitudinal direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 4.0. And this uniaxially stretched film is led to a stenter, stretched at 120 ° C. in the transverse direction (width direction) at a stretch ratio of 4.5 times, and then heat-fixed at 210 ° C. for 3 seconds to be biaxially stretched with a thickness of 10 μm A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Example 10]
Esterification and transesterification of dimethyl terephthalate, 6,6 '-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol in the presence of titanium tetrabutoxide, followed by polycondensation reaction And the intrinsic viscosity is 0.68 dl / g, 80 mol% of the acid component is terephthalic acid component, 20 mol% of the acid component is 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, glycol component An aromatic polyester having 98 mol% of ethylene glycol component and 2 mol% of diethylene glycol component was obtained. The aromatic polyester contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 230 ° C., and the glass transition temperature was 85 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 30 ° C. to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 105 ° C., and stretching in the longitudinal direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.0. Then, this uniaxially stretched film is guided to a stenter, stretched at 115 ° C. in the transverse direction (width direction) at a stretch ratio of 5.0 times, and then heat-fixed at 210 ° C. for 3 seconds to be biaxially stretched with a thickness of 10 m. A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Example 11]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was carried out, the intrinsic viscosity was 0.70 dl / g, 70 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 30 mol% of the acid component was 6,6 ′-(alkylenedioxy). An aromatic polyester in which 98 mol% of the di-2-naphthoic acid component and glycol component was an ethylene glycol component and 2 mol% was a diethylene glycol component was obtained. The aromatic polyester contained calcium carbonate particles as shown in Table 1 before the polycondensation reaction. The melting point of this polyester composition was 268 ° C., and the glass transition temperature was 101 ° C.

The polyester composition thus obtained was supplied to an extruder and extruded from a die at 300 ° C. in a molten state onto a cooling drum having a rotating temperature of 50 ° C. to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 135 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 4.0. And this uniaxially stretched film is led to a stenter, stretched at 140 ° C. in the transverse direction (width direction) at a stretching ratio of 3.8 times, then heat-set at 200 ° C. for 10 seconds, and biaxially stretched with a thickness of 10 μm. A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Comparative Example 1]
Dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol are subjected to an esterification reaction and a transesterification reaction in the presence of titanium tetrabutoxide, followed by a polycondensation reaction to obtain an intrinsic viscosity of 0.62 dl / g. Polyethylene-2,6-naphthalate in which 1.5 mol% of the glycol component was a diethylene glycol component was obtained. The polyethylene-2,6-naphthalate contains silica particles having an average particle diameter of 0.5 μm before the polycondensation reaction so that the amount is 0.2% by weight based on the weight of the resin composition obtained. Contained. This polyethylene-2,6-naphthalate had a melting point of 270 ° C. and a glass transition temperature of 120 ° C.

The polyethylene-2,6-naphthalate thus obtained was supplied to an extruder and extruded from a die at 300 ° C. in a molten state onto a cooling drum at a temperature of 60 ° C. during rotation to form an unstretched film. . Then, between the two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 140 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 3.0. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.3 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 200 ° C. for 10 seconds to be biaxially stretched with a thickness of 10 μm. A film was obtained.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Comparative Example 2]
In Comparative Example 1, the stretching temperature in the film forming direction is 140 ° C., the stretching ratio in the film forming direction is 4.0 times, the stretching temperature in the width direction is 140 ° C., and the stretching ratio in the width direction is 4.0 times. The same operation was repeated except that the heat setting treatment temperature was changed to 200 ° C. to obtain a biaxially stretched film.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Comparative Example 3]
In Comparative Example 1, the stretching temperature in the film forming direction is 140 ° C., the stretching ratio in the film forming direction is 4.5 times, the stretching temperature in the width direction is 140 ° C., and the stretching ratio in the width direction is 3.4 times. The same operation was repeated except that the heat setting treatment temperature was changed to 200 ° C. to obtain a biaxially stretched film.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

[Comparative Example 4]
In Comparative Example 3, the same operation was repeated except that the particle type and content to be contained were changed as shown in Table 1.
The properties of the obtained polyester composition and biaxially oriented film are shown in Table 1.

  In Table 1, the ENA component is a 6,6 '-(ethylenedioxy) di-2-naphthoic acid component, MD is the film forming direction, TD is the film width direction, and d is the area circle equivalent average diameter.

  The polyester composition of the present invention has excellent dimensional stability that cannot be achieved with conventional polyethylene terephthalate, polyethylene-2,6-naphthalate, and polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate. Therefore, it can be suitably used as a base film of a high-density magnetic recording medium, in particular, in applications where dimensional stability is required.

Claims (4)

The acid component comprises the following structural formulas (I) and (II), and the proportion of the following structural formula (I) is in the range of 5 to 80 mol% based on the number of moles of the total acid component, and the glycol component Having the following structural formula (III), particles having an area circle equivalent average diameter of 0.1 to 5 μm and a ratio of the major axis to the minor axis length of 1.1 to 3 A polyester composition comprising:

(R ₁ in the structural formula (I) is an alkylene group having 1 to 10 carbon atoms, R ₂ in the structural formula (II) is a phenylene group or a naphthalenediyl group, and R ₃ in the structural formula (III). Represents an alkylene group having 2 to 4 carbon atoms.)   The polyester composition according to claim 1, wherein the content of the particles is in the range of 0.01 to 10% by weight based on the weight of the polyester composition.   The polyester composition according to claim 1, wherein the particles are at least one inorganic particle selected from the group consisting of calcium carbonate, kaolin, clay, and aluminum silicate.   A biaxially oriented film comprising the polyester resin composition according to claim 1.