JP5694865B2 - Polyester composition, method for producing the same, and biaxially oriented polyester film - Google Patents

Description

  The present invention relates to a polyester composition of poly-1,4-cyclohexanedimethylene terephthalate and polyethylene-2,6-naphthalate, a method for producing the same, and a biaxially oriented polyester 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 such as a high-density magnetic recording tape. It is used. However, demands for dimensional stability in high-density magnetic recording tapes and the like in recent years are increasing, and further improvement of characteristics, for example, high dimensional stability against environmental changes such as temperature and humidity is required. .

  By the way, in Patent Document 1, it is possible to obtain a biaxially oriented polyester film having a low humidity expansion coefficient by using poly (1,4-cyclohexanedimethylene terephthalate) (hereinafter abbreviated as PCT). Document 2 discloses that the tear strength can be improved by blending PCT and polyethylene terephthalate. Furthermore, Patent Document 3 discloses that heat resistance can be improved by blending PCT and polyethylene-2,6-naphthalenedicarboxylate.

  However, when PCT and polyethylene-2,6-naphthalene dicarboxylate are blended, the compatibility between these polymers is poor, and the surface of the biaxially oriented polyester film obtained by blending has a large surface density and high density magnetic properties. It was a level that could not be used as a base film such as a recording tape.

JP-A-60-85437 Japanese Patent Laid-Open No. 60-203422 Japanese Patent Laid-Open No. 2-191638

  An object of the present invention is to provide a polyester composition capable of having dimensional stability and surface flatness against an environmental change that is extremely excellent in at least one direction when it is used as a film, and a biaxially oriented polyester film using the same. It is to provide.

As a result of diligent research to solve the above-mentioned problems, the present inventors mainly used polyethylene-2,6-naphthalate, which is poorly compatible with the above-mentioned polyester having poly (1,4-cyclohexanedimethylene terephthalate) as a main component. When a specific proportion of polyester as a component is blended and a specific phosphorus compound is used as a compatibilizer, the surface roughness of the film is maintained while having a very small temperature expansion coefficient and humidity expansion coefficient in a specific direction. The present inventors have found that a biaxially oriented polyester film excellent in processability can be obtained and the present invention has been achieved.
Thus, according to the present invention, the following polyester composition, method for producing the polyester composition, and biaxially oriented polyester film are provided.

（式（Ｉ）中、ｍは１または２、ｎは１２〜２５の整数を表す。）
で表されるリン化合物を含有するポリエステル組成物。
（２） ポリエステル（Ａ）は、酸成分がテレフタル酸成分と２，６−ナフタレンジカルボン酸成分とで、それらのモル比が１００：０〜７０：３０の範囲で、グリコール成分が１，４−シクロヘキサンジメタノール成分とエチレングリコール成分とで、両者のモル比が１００：０〜９５：５の範囲である上記（１）記載のポリエステル組成物。
（３） 式（Ｉ）で表されるリン化合物の含有量が、ポリエステル組成物の重量を基準として、０．０５〜１．５０重量％である上記（１）記載のポリエステル組成物。
（４） １，４−シクロヘキサンジメチレンテレフタレートを主たる繰り返し単位とするポリエステル（Ａ）と、エチレン−２，６−ナフタレンジカルボキシレートを主たる繰り返し単位とするポリエステル（Ｂ）とを、ポリエステル（Ａ）とポリエステル（Ｂ）との重量比が４０：６０〜９０：１０の範囲で、上記式（Ｉ）で表されるリン化合物の存在下でブレンドするポリエステル組成物の製造方法。
（５） 上記（１）〜（３）のいずれかに記載のポリエステル組成物からなる二軸配向ポリエステルフィルム。
（６） フィルムの製膜方向に直交する方向（幅方向）における温度膨張係数が１０ｐｐｍ／℃以下である上記（５）記載の二軸配向ポリエステルフィルム。
（７） 磁気テープのベースフィルムに用いる上記（５）または（６）のいずれかに記載の二軸配向ポリエステルフィルム。 (1) A polyester composition obtained by blending a polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit and a polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit. Because
The weight ratio of polyester (A) to polyester (B) is in the range of 40:60 to 90:10, and the following formula (I)

(In formula (I), m represents 1 or 2, and n represents an integer of 12 to 25.)
The polyester composition containing the phosphorus compound represented by these.
(2) Polyester (A) has an acid component of a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component in a molar ratio of 100: 0 to 70:30, and a glycol component of 1,4- The polyester composition according to the above (1), wherein the molar ratio of the cyclohexanedimethanol component and the ethylene glycol component is in the range of 100: 0 to 95: 5.
(3) The polyester composition according to the above (1), wherein the content of the phosphorus compound represented by the formula (I) is 0.05 to 1.50% by weight based on the weight of the polyester composition.
(4) A polyester (A) comprising a polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit and a polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit. And a polyester (B) in a weight ratio of 40:60 to 90:10, and a method for producing a polyester composition comprising blending in the presence of a phosphorus compound represented by the above formula (I).
(5) A biaxially oriented polyester film comprising the polyester composition according to any one of (1) to (3) above.
(6) The biaxially oriented polyester film according to the above (5), wherein the temperature expansion coefficient in a direction (width direction) perpendicular to the film forming direction of the film is 10 ppm / ° C. or less.
(7) The biaxially oriented polyester film according to any one of (5) and (6), which is used for a base film of a magnetic tape.

According to the present invention, polyethylene-2,6-dicarboxylate is present in a specific ratio while having compatibility with polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit, The film can be highly stretched to highly orient molecular chains in the direction in which dimensional stability against changes is required, and the resulting film can also have a high degree of surface flatness.
Therefore, by making the polyester composition of the present invention into a biaxially oriented polyester film and having a temperature expansion coefficient in the width direction of 10 ppm / ° C. or less, it can be suitably used as a base film of a magnetic tape, and its industrial value. Is extremely expensive.

The aromatic polyester in the present invention will be described in detail.
In the polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit in the present invention, 70 mol% or more of the total acid component is a terephthalic acid component, and other acid components include an isophthalic acid component, Examples include 2,6-naphthalenedicarboxylic acid component, 2,7-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, diphenyldicarboxylic acid, and the like. Among these, in order to improve the compatibility with the polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit, a 2,6-naphthalenedicarboxylic acid component is particularly preferable as a copolymerization component. . The copolymerization amount of the 2,6-naphthalenedicarboxylic acid component is preferably in the range of 0 to 30 mol%, more preferably in the range of 5 to 25 mol%, based on the number of moles of the total acid component of the polyester (A). . Polyester (A) has a 1,4-cyclohexanedimethanol component in which 80 mol% or more of the total glycol components are other components, and other glycol components include ethylene glycol components, propylene glycol components, 1,4-butanediol. Examples thereof include a component and a neopentyl glycol component. Among these, ethylene glycol is preferable. The proportion of the 1,4-cyclohexanedimethanol component in the total glycol component is preferably in the range of 95 to 100 mol%, more preferably 98 to 100 mol%.

Further, in the present invention, the polyester (B) having ethylene-2,6-naphthalenedicarboxylate as the main repeating unit is such that 85 mol% or more of all repeating units is ethylene-2,6-naphthalene from the viewpoint of mechanical properties. Polyesters composed of dicarboxylate units are preferred. Of course, a copolymer obtained by copolymerizing the other third component within a range not impairing the effects of the present invention, for example, 15 mol% or less, preferably 10 mol% or less, with respect to all repeating units of the aromatic polyester. It may be. The third component (copolymerization component) includes fats such as terephthalic acid, 2,7-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid and other aromatic dicarboxylic acids, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, etc. Examples include alicyclic dicarboxylic acids such as aliphatic dicarboxylic acids and cyclohexanedicarboxylic acids, and glycols such as trimethylene glycol, diethylene glycol, tetramethylene glycol, and cyclohexanedimethanol, and these may be used alone or in combination of two or more. May be.
Such polyesters (A) and (B) can each be produced by a method known per se, charged with raw materials so as to have a desired composition, and subjected to a polycondensation reaction via an ester exchange reaction or an esterification reaction. Can be manufactured.

  By the way, the polyester composition of this invention melt-kneads the above-mentioned polyester (A) and polyester (B). The molar ratio of the 1,4-cyclohexanedimethanol component and the ethylene glycol component and the molar ratio of the terephthalic acid component and the 2,6-naphthalenedicarboxylic acid component in the polyester composition are 40:60 to 90:10, respectively. Preferably, it is in the range of 65:35 to 88:12. By melt-kneading so as to achieve such a molar ratio, it is possible to perform highly-stretching that highly orients molecular chains in a direction that requires dimensional stability against environmental changes, and that stretch is also performed to a high degree. Sufficient mechanical properties necessary for workability and the like can also be provided in a direction perpendicular to the direction. If the amount of 1,4-cyclohexanedimethanol component or terephthalic acid component increases excessively, mechanical properties and heat resistance are likely to be impaired, while the amount of ethylene glycol component and 2,6-naphthalenedicarboxylic acid component excessively increase. If it becomes, it will become difficult to reduce a humidity expansion coefficient.

  Moreover, when the polyester composition of this invention melt-kneads polyester (A) and polyester (B), it is necessary to add the specific phosphorus compound represented by following formula (I).

  In formula (I), m represents an integer of 1 or 2, and n represents an integer of 12 to 25. When n is smaller than 12, after being added to the polyester, it tends to be scattered out of the system due to sublimation or the like, and the effect is less likely to appear, and when n is larger than 25, the reactivity with the polyester is decreased. The effect on is difficult to appear.

  The content of the phosphorus compound of formula (I) is preferably in the range of 0.05 to 1.50% by weight, more preferably in the range of 0.2 to 1.2% by weight, based on the weight of the polyester composition. Is more preferable. From such a viewpoint, the content of the phosphorus compound to be contained is preferably in the range of 100 to 1200 ppm, particularly in the range of 250 to 1000 ppm in terms of the amount of phosphorus element based on the weight of the polyester composition. When the amount of the phosphorus compound to be contained is in the above range, the surface roughness of the obtained biaxially oriented polyester film can be effectively flattened. Further, by using the phosphorus compound represented by the formula (I) as a compatibilizing agent, there is also an advantage that a site that has not been a product generated in the film forming step can be suitably reused. This is because the phosphorus compound of the formula (I) contained as a compatibilizing agent suppresses the progress of transesterification between the polyester (A) and the polyester (B), and has the same dimensional stability as that which does not include a reuse site. This is considered to be because a biaxially oriented polyester film having physical properties can be obtained.

  The polyester composition of the present invention may contain a resin or a functional agent known per se as long as the effects of the present invention are not impaired. As the resin to be blended, polyetherimide, liquid crystalline resin, and the like are preferable because the heat resistance and the like of the obtained film are easily improved.

Next, the biaxially oriented polyester film of the present invention will be described.
The biaxially oriented polyester film of the present invention is made of the above-described polyester composition, and is stretched in the film forming direction and the width direction. The laminated structure is not particularly limited, and may be a single layer film or a laminated film having two or more layers. In the case of a laminated film, at least one layer may be the biaxially oriented polyester film of the present invention.

Hereinafter, the preferable aspect of the biaxially-oriented polyester film of this invention is demonstrated.
In the biaxially oriented polyester film of the present invention, the Young's modulus is preferably 4 GPa or more, more preferably 5 GPa or more, and particularly preferably 5.5 GPa or more in either the film forming direction or the width direction. If the Young's modulus is less than 4 GPa in any direction, it is difficult to reduce the temperature expansion coefficient. In particular, when used as a base film for a magnetic recording tape, the direction in which the Young's modulus is increased is preferably the width direction of the biaxially oriented polyester film because track deviation and the like can be suppressed.
Moreover, when using it for magnetic tapes, it is preferable that both the film forming direction and the width direction Young's modulus of a film are 2.4 GPa or more from a viewpoint of reducing the elongation at the time of use.

  In order to obtain a film having such a high Young's modulus in a specific direction and a practically necessary Young's modulus in any direction, a polyester resin containing the above-mentioned specific amount of 1,4-cyclohexanedimethylene terephthalate component is used. In addition, when the film is highly stretched in the direction in which the Young's modulus is desired to be increased, and when the Young's modulus in a specific direction is further desired to be increased, the stretching in the direction orthogonal to the direction in which the Young's modulus is desired to be increased.

  By the way, the biaxially oriented polyester film of the present invention preferably has a temperature expansion coefficient (αt) of at least 10 ppm / ° C. in at least one direction, preferably the width direction of the film, from the viewpoint of exhibiting excellent dimensional stability. . When the temperature expansion coefficient in at least one direction of the film is 10 ppm / ° C. or less, excellent dimensional stability against environmental changes can be exhibited. The lower limit of the temperature expansion coefficient is not limited, but is usually −15 ppm / ° C. The preferred temperature expansion coefficient (αt) is in the range of −10 to 10 ppm / ° C., more preferably −7 to 7 ppm / ° C., particularly preferably −5 to 6 ppm / ° C. It is preferable because it can exhibit excellent dimensional stability against dimensional changes.

  Further, the biaxially oriented polyester film of the present invention has a humidity expansion coefficient of at least one direction, preferably the film width direction, in the range of 1 to 7 ppm /% RH, preferably 3 to 5 ppm /% RH. When a magnetic recording tape is used, it is preferable because it can exhibit excellent dimensional stability against dimensional changes due to changes in atmospheric humidity.

  The thickness of the biaxially oriented polyester film of the present invention is not particularly limited, but when used for a magnetic tape, the total film thickness is in the range of 2 to 15 μm, more preferably in the range of 3 to 8 μm, particularly in the range of 3.5 to 5 μm. Preferably there is. If this thickness exceeds the upper limit, the film thickness becomes too thick. For example, when used for a magnetic recording medium, the tape length to be put in the cassette is shortened and a sufficient magnetic recording capacity cannot be obtained.

  The biaxially oriented polyester film of the present invention is in the range of 1 to 20 nm, more preferably 2 to 15 nm, depending on the use of the surface roughness (Ra) of at least one surface from the relationship between flatness and running properties. It is preferable. In particular, when used as a base film of a magnetic recording medium, at least one surface preferably has a surface roughness (Ra) in the range of 1 to 10 nm. When the surface roughness (Ra) exceeds the upper limit, the flatness is poor, and for example, when used as a base film of a magnetic recording medium, output characteristics, electromagnetic conversion characteristics, etc. tend to be poor. On the other hand, when the surface roughness (Ra) is less than the lower limit, the running property tends to be poor.

  Further, the biaxially oriented polyester film of the present invention has a 10-point average roughness (Rz) of at least one surface of 10 to 400 nm, more preferably 15 to 300 nm, depending on the relationship between flatness and runnability. It is preferable that it exists in the range. In particular, when used as a base film of a magnetic recording medium, the 10-point average roughness (Rz) of at least one surface is preferably in the range of 20 to 200 nm. When the 10-point average roughness (Rz) exceeds the upper limit, flatness is poor, and when used as a base film of a magnetic recording medium, for example, output characteristics and electromagnetic conversion characteristics tend to be poor. On the other hand, when the 10-point average roughness (Rz) is less than the lower limit, the running property tends to be poor.

  By the way, in order to give the above-mentioned surface properties to the biaxially oriented polyester film of the present invention, it is preferable to contain 0.01% by weight or more of particles having an average particle diameter of 50 nm or more. If the average particle size or content is less than the lower limit, it becomes difficult to produce the above surface properties by forming protrusions with particles. Examples of the particles to be included include particles having small particle size variations. From such a viewpoint, the particles to be contained preferably have a relative standard deviation of 0.5 or less, more preferably 0.45 or less, and particularly preferably 0.40 or less when the particle size distribution is observed. Such particles can be adjusted by selecting particles with relatively little variation as described later, or by removing coarse particles by filtration with a filter or the like. In addition, in order to reduce the aforementioned Ra, in addition to using a specific phosphorus compound as a compatibilizing agent, the particle diameter of the particles to be contained may be reduced or the content may be reduced, while the other Ra is increased. For this purpose, the particle size of the particles to be contained may be increased or the content may be reduced. In order to reduce Rz, in addition to using a specific phosphorus compound as a compatibilizing agent, it is possible to reduce the ratio of particles having a large particle size among the particles to be contained.

  The particles to be included in such a film include (1) heat-resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, Particles made of crosslinked polyester), (2) metal oxides (for example, aluminum oxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide, zirconium oxide, etc.), metal carbonates (for example, magnesium carbonate, Inorganic such as calcium carbonate), metal sulfates (eg calcium sulfate, barium sulfate etc.), carbon (eg carbon black, graphite, diamond etc.) and clay minerals (eg kaolin, clay, bentonite etc.) Is it a compound And (3) externally added particles in which different materials are added in the form of particles such as core-shell type composite particles using, for example, a core and a shell, in addition to the range not impairing the effects of the present invention or ( 4) Internally precipitated particles formed by precipitation of a catalyst and the like can be mentioned. Among these, at least one kind of particles selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, a crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide, kaolin and clay is particularly preferable. At least one kind of particles selected from the group consisting of silicone resin, cross-linked acrylic resin, cross-linked polyester, cross-linked polystyrene, and silicon dioxide (excluding porous silica etc.) reduces the variation in particle size. It is preferable because it is easy. Of course, these may be used in combination of two or more.

  The average particle size of preferred particles is in the range of 50 to 1000 nm, more preferably 80 to 800 nm, and particularly in the range of 50 to 600 nm and further 80 to 400 nm when used as a magnetic recording medium. The preferred particle content is 0.01 to 0.5% by weight, more preferably 0.03 to 0.45% by weight, based on the weight of the film, particularly 0.01 to 0 when used as a magnetic recording medium. .4% by weight, and further 0.05 to 0.35% by weight.

Next, a method for producing the biaxially oriented polyester film of the present invention will be described, but the present invention is not limited thereto.
First, the biaxially oriented polyester film of the present invention is obtained by melt-forming the above-described polyester composition, extruding it into a sheet, and stretching it in the film forming direction and the width direction.

  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 composition used is 0.5 for polyester (A). -1.1 dl / g, more preferably in the range of 0.6-1.0 dl / g, and the polyester (B) is in the range of 0.4-1.0 dl / g, further 0.5-0.7 dl / g. It is preferable from the point of the effect of this invention that it exists in a range. If the intrinsic viscosity is equal to or higher than the upper limit, the viscosity becomes too high, and it becomes difficult to extrude the resin from the extruder during film formation. On the other hand, if the intrinsic viscosity is less than the lower limit, the film becomes brittle and stretching becomes difficult.

  The biaxially oriented polyester film of the present invention is preferably one in which the molecular orientation in each direction is enhanced by stretching in the film forming direction and the width direction. For example, it can be produced by the following method. It is preferable because the Young's modulus is easily improved while maintaining the properties.

  First, the above-mentioned polyester composition or a plurality of polyesters (A) and (B) having the composition are used as raw materials, dried, and then heated to a melting point of the polyester resin when formed into a film or a temperature of (Tm + 50) ° C. Then, the sheet is fed into an extruded machine and extruded into a sheet form from a die such as a T die. The extruded sheet is rapidly cooled and solidified with a rotating cooling drum or the like to form an unstretched film, and the unstretched film is further biaxially stretched.

  In order to make the aforementioned Young's modulus, αt, and αh within the preferable ranges, it is necessary to facilitate the subsequent stretching. From such a viewpoint, it is preferable to perform cooling with a cooling drum very quickly. . From such a viewpoint, it is preferable to carry out at a low temperature of 20 to 60 ° C. 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, the sequential biaxial stretching will be described by taking, as an example, a manufacturing method in which stretching is performed in the film forming direction and the width direction and heat treatment is performed in this order. First, stretching in the first film forming direction is performed at a glass transition temperature (Tg: ° C.) to (Tg + 40) ° C. of the polyester at 2 to 8 times, and then in the width direction is the same as the previous film forming direction. It is stretched 3 to 10 times at a temperature of (Tg + 10) to (Tg + 50) ° C., which is higher than that, and further treated as a heat treatment at a temperature below the melting point of the polymer and at a temperature of (Tg + 50) to (Tg + 150) ° C. It is preferable to perform heat setting treatment for 1 second, and further for 1 to 15 seconds. The heat treatment may be relaxed or stretched in the film forming direction or the width direction as desired, but the range is preferably -5 to 5% based on the length before the heat treatment. .

In addition, when melting | fusing point and glass transition temperature of polyester in the said film forming differ by polyester (A) and (B), the higher melting | fusing point and glass transition temperature are meant.
Although the above description has been described for sequential biaxial stretching, the biaxially oriented polyester film of the present invention can be produced by simultaneous biaxial stretching in which longitudinal stretching and lateral stretching are simultaneously performed, for example, the stretching ratio and stretching temperature described above, etc. Should be referred to.

  Further, as described above, the biaxially oriented polyester film of the present invention is not limited to a single layer film and may be a laminated film. In that case, at least one film layer is the biaxially oriented polyester film of the present invention. I need it. As a method of making such a laminated film, for example, two or more types of molten polyester are laminated in a die and then extruded into a film, preferably at a temperature of the melting point (Tm: ° C.) to (Tm + 70) ° C. of each polyester. Extrude or laminate after extruding two or more types of molten polyester from a die, quench and solidify to make a laminated unstretched film, then biaxially stretch and heat treatment in the same manner as in the case of the above-mentioned single layer film .

In addition, the biaxially oriented polyester film of the present invention may be provided with a coating layer known per se in order to improve adhesion and slipperiness. When providing a coating layer, apply the desired coating solution on one or both sides of the unstretched film or uniaxially stretched film, and then perform biaxial stretching and heat treatment in the same manner as in the case of the single-layer film described above. Just do it.
In the biaxially oriented polyester film of the present invention thus obtained, a nonmagnetic layer and a magnetic layer are formed in this order on one surface, and a backcoat layer is formed on the other surface, so that LTO or the like is formed. The linear recording type 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 The glass transition point and melting point were measured by DSC (TA Instruments Co., Ltd., trade name: Thermal lyst 2100) at a sample weight of 10 mg and a heating rate of 10 ° C / min.

(3) 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 apparatus (product name: 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.

(4) Temperature expansion coefficient (αt)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the film forming direction or the width direction of the film would be the measurement direction, set in TMA3000 manufactured by Vacuum Riko, and under a nitrogen atmosphere (0% RH) at 60 ° C. For 30 minutes and then let it cool 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. The measurement direction is the longitudinal direction of the cut sample.
αt = {(L60−L40)} / (L40 × ΔT)} + 0.5
Here, L40 in the above formula is a sample length (mm) at 40 ° C., L60 is a sample length (mm) at 60 ° C., ΔT is 20 (= 60-40) ° C., and 0.5 is quartz. It is a temperature expansion coefficient (ppm / ° C.) of glass.

(5) Humidity expansion coefficient (αh)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the film forming direction or the width direction of the film would be the measurement direction, set in TMA3000 manufactured by Vacuum Riko, and a humidity of 20% RH in a nitrogen atmosphere at 30 ° C. The length of each sample at a humidity of 80% RH is measured, and the humidity expansion coefficient is calculated by the following equation. The measurement direction is the longitudinal direction of the cut sample.
αh = (L80−L20) / (L20 × ΔH)
Here, L20 in the above formula is the sample length (mm) at 20% RH, L80 is the sample length (mm) at 80% RH, and ΔH: 60 (= 80-20)% RH.

(6) Film surface roughness Measured using a non-contact type three-dimensional surface roughness meter (manufactured by ZYGO: New View 5022) at a measurement magnification of 10 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm2). The center plane average roughness (Ra) and 10-point average roughness (Rz) are determined by the surface analysis software MetroPro built in the roughness meter.

(7) Copolymerization amount As for the glycol component, 10 mg of a sample was dissolved at 80 ° C. in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1 (volume ratio). Added isopropylamine, measured at 80 ° C. at after thorough mixing ¹ H-NMR (JEOL JEOL A600), were measured each glycol component amount.
As for the aromatic dicarboxylic acid component, 50 mg of a sample was dissolved at 140 ° C. in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1, and ¹³ C-NMR (Japan) It measured at 140 degreeC in electronic JEOL A600), and each acid component amount was measured.

(8) Measurement of phosphorus compound content A polymer sample is heated and melted to prepare a circular disk, measured using a Rigaku fluorescent X-ray apparatus 3270, and quantified based on the weight of the polyester composition. It was. And the content of the phosphorus compound contained was calculated from the amount of phosphorus element.

Reference Example 1 Preparation of Polyester A-1 Dimethyl terephthalate (DMT), dimethyl 2,6-naphthalenedicarboxylate (NDC), 1,4-cyclohexanedimethanol (CHDM), ethylene glycol (EG) A reaction vessel equipped with a stirrer, a rectifying column and a cooler was charged so that the molar ratio (DMT: NDC) / (CHDM: EG) would be 80: 20 / (99: 1). Tetrahydrate was added at 40 mmol% (based on the total acid content), and a transesterification reaction was performed. Then, phenylphosphonic acid was reacted at 50 mmol% (based on the total acid content), and then titanium tetrabutoxide and trimellitic anhydride were reacted at a molar ratio of 1: 2 at 175 ° C. for 4 hours (trimellitic acid). Titanium) 40 mmol% (based on the total acid content) was added and polycondensed at 290 ° C. to obtain polyester A-1 having an intrinsic viscosity of 0.680, a glass transition temperature of 95 ° C. and a melting point of 262 ° C.

Reference Example 2 Preparation of Polyester A-2 Polyester A-1 prepared in Reference Example 1 was crystallized with a dryer at 180 ° C. for 6 hours, and then charged into a tumbler-type reactor for 18 hours at 225 ° C. Condensation was performed to obtain polyester A-2 having an intrinsic viscosity of 0.905.

[Reference Example 3] Preparation of Polyester A-3 Dimethyl terephthalate (DMT), dimethyl isophthalate (DMI), and 1,4-cyclohexanedimethanol (CHDM) were each in a molar ratio (DMT: DMI) / (CHDM: EG) was charged into a reaction vessel equipped with a stirrer, a rectifying column and a cooler so that (90:10) / (99.5: 0.5), and manganese acetate tetrahydrate was added as a catalyst there. 40 mmol% (based on the total acid content) was added to conduct a transesterification reaction. Then, phenylphosphonic acid was reacted at 50 mmol% (based on the total acid content), and then titanium tetrabutoxide and trimellitic anhydride were reacted at a molar ratio of 1: 2 at 175 ° C. for 4 hours (trimellitic acid). Titanium) 40 mmol% (based on the total acid content) was added and polycondensed at 290 ° C. to obtain polyester A-3 having an intrinsic viscosity of 0.680, a glass transition temperature of 84 ° C. and a melting point of 270 ° C.

Reference Example 4 Preparation of Polyester A-4 In Reference Example 3, after the transesterification reaction, silica having an average particle size of 0.3 μm was added with ethylene glycol slurry so that the silica concentration in the polymer was 0.2 wt%. Subsequently, polycondensation was performed to obtain polyester A-4 having an intrinsic viscosity of 0.665, a glass transition temperature of 84 ° C., and a melting point of 271 ° C.

[Reference Example 5] Preparation of polyester B-1 Dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol were mixed in a stirrer so that the respective molar ratio (NDC: EG) was 100: 100. A reaction vessel equipped with a rectifying column and a condenser was charged, and 30 mmol% of manganese acetate tetrahydrate (based on the total acid content) was added thereto as a catalyst to conduct a transesterification reaction. Thereafter, 40 mmol% of trimethyl phosphate (based on the total acid content) and 20 mmol% of antimony trioxide (based on the total acid content) were added and polycondensed at 290 ° C. to obtain an intrinsic viscosity of 0.610. Polyester B-1 was obtained.

Reference Example 6 Preparation of Polyester B-2 In Reference Example 4, after the transesterification, silica having an average particle size of 0.3 μm was added with an ethylene glycol slurry so that the silica concentration in the polymer was 1 wt%, and then continued. Polycondensation was performed to obtain polyester B-2 having an intrinsic viscosity of 0.600.

[Example 1]
In each case, 80% by weight of dried polyester A-1, 6.7% by weight of polyester B-1 and 13.3% by weight of polyester B-2 were mixed, and as a compatibilizer, ADK STAB AX-71 (manufactured by ADEKA Corporation: After mixing 0.7% by weight of a mixture of dioctadecyl phosphate and monooctadecyl phosphate) to polyester, it was melt extruded at 300 ° C and cooled on a quenching drum maintained at 25 ° C. Got. Then, between two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated to 110 ° C., and stretching in the longitudinal direction (film forming direction) is performed at a draw ratio of 3.0 times. And a uniaxially stretched film was obtained. Then, this uniaxially stretched film is led to a stenter, and a transverse stretch temperature of 115 ° C. and a transverse stretch ratio of 6.5 times, heat setting treatment (180 ° C. for 10 seconds) and cooling are performed to obtain a 10 μm thick biaxially stretched film. It was. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 2]
In Example 1, the polyester A-1 was 86.7% by weight, the polyester B-1 was 10% by weight, the polyester B-2 was 13.3% by weight, and the transverse stretch ratio was 5.8 times. In the same manner as in Example 1, a 10 μm biaxially stretched film was obtained. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 3]
A 10 μm biaxially stretched film was obtained in the same manner as in Example 1 except that the amount of the compatibilizing agent was changed in Example 1. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 4]
In Example 1, polyester A-2 was used instead of polyester A-1, and the weight was 80% by weight of polyester A-2, 6.7% by weight of polyester B-1, and 13.3% by weight of polyester B-2. Other conditions were the same as in Example 1, and a 10 μm biaxially stretched film was obtained. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 5]
In Example 1, polyester A-3 was used in place of polyester A-1, and 80% by weight of polyester A-3, 6.7% by weight of polyester B-1 and 13.3% by weight of polyester B-2, and the transverse draw ratio Was made 6.3 times. Other conditions were the same as in Example 1, and a 10 μm biaxially stretched film was obtained. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 6]
In Example 5, Polyester A-3 was used instead of Polyester A-1, and it was set as 70% by weight of Polyester A-3, 16.7% by weight of Polyster B-1 and 13.3% by weight of Polyester B-2. Other conditions were the same as in Example 5, and a 10 μm biaxially stretched film was obtained. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 1]
A biaxially stretched film having a thickness of 10 μm was obtained in the same manner as in Example 1 except that no compatibilizer was added. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 2]
A biaxially stretched film having a thickness of 10 μm was obtained in the same manner as in Example 5 except that no compatibilizer was added. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 3]
In Example 1, the same operation was repeated except that the polyester A-1 was 50% by weight, the polyester B-1 was 36.7% by weight, and the polyester B-2 was 13.3% by weight. The draw ratio in the direction was 2.5 times, and the draw ratio in the transverse direction was 5.5 times. Other conditions were the same as in Example 1, and a 14 μm biaxially stretched film was obtained. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 4]
After mixing 86.7% by weight of Polyster B-1 and 13.3% by weight of Polyester B-2, an unstretched film was obtained by melt extrusion at 300 ° C. and cooling on a quenching drum maintained at 60 ° C. And between two sets of rollers with different rotational speeds along the film forming direction, the film surface temperature is heated to 130 ° C., and stretching in the longitudinal direction (film forming direction) is performed at a draw ratio of 5 times. A uniaxially stretched film was obtained. And this uniaxially stretched film is led to a stenter, a transverse stretching temperature of 125 ° C., a transverse stretching ratio of 6 times, heat setting treatment (180 ° C. for 10 seconds) and cooling are performed to obtain a biaxially stretched film having a thickness of 4.5 μm. It was. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 5]
A biaxially stretched film having a thickness of 11 μm was obtained in the same manner as in Example 1 except that only the polyester A-4 was used and the stretch ratio was 3.0 times and 5.0 times. The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 6]
In Example 1, instead of ADK STAB AX-71 (manufactured by ADEKA Corporation: a mixture of dioctadecyl phosphate and monooctadecyl phosphate), ADK STAB PEP-36 (manufactured by ADEKA: 3,9- (2, 6-di-tert-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane) A biaxially stretched film was obtained.

[Comparative Example 7]
In Example 1, 1,3-PBO (manufactured by Mikuni Pharmaceutical Co., Ltd .: 2,2′-) instead of Adeka Stab AX-71 (manufactured by ADEKA Co., Ltd .: mixture of dioctadecyl phosphate and monooctadecyl phosphate) A biaxially stretched film having a thickness of 10 μm was obtained in the same manner as in Example 1 except that (1,3-phenylene) bis-2-oxazoline) was used.

  In Table 1, MD means the film forming direction, and TD means the width direction.

  The polyester composition of the present invention can be provided in a biaxially oriented polyester film that can provide excellent dimensional stability that cannot be achieved with conventional polyethylene terephthalate, polyethylene-2,6-naphthalate, and the like. Therefore, it can be suitably used as a base film for high-density magnetic recording media, in particular, where dimensional stability and surface flatness are required.

Claims (7)

A polyester composition obtained by blending polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit and polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit. ,
A polyester composition characterized in that the weight ratio of the polyester (A) to the polyester (B) is in the range of 40:60 to 90:10 and contains a phosphorus compound represented by the following formula (I).

(In formula (I), m represents 1 or 2, and n represents an integer of 12 to 25.)   Polyester (A) has an acid component of a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component in a molar ratio of 100: 0 to 70:30, and a glycol component of 1,4-cyclohexanedimethanol. The polyester composition according to claim 1, wherein the molar ratio of the component to the ethylene glycol component is in the range of 100: 0 to 95: 5.   The polyester composition according to claim 1, wherein the content of the phosphorus compound represented by the formula (I) is 0.05 to 1.50 wt% based on the weight of the polyester composition. A polyester (A) having 1,4-cyclohexanedimethylene terephthalate as a main repeating unit and a polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main repeating unit are combined with a polyester (A) and a polyester ( A method for producing a polyester composition, comprising blending in the presence of a phosphorus compound represented by the following formula (I) in a weight ratio with B) of 40:60 to 90:10.

(In formula (I), m represents 1 or 2, and n represents an integer of 12 to 25.)   The biaxially oriented polyester film which consists of a polyester composition in any one of Claims 1-3. The coefficient of thermal expansion in the direction perpendicular to the film forming direction (width direction) is 10 ppm / ° C.
The biaxially oriented polyester film according to claim 5, wherein:   The biaxially oriented polyester film according to claim 5, which is used for a base film of a magnetic tape.