JP5346881B2 - Copolymerized aromatic polyester and biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymerized aromatic polyester which, compared with polyethylene-2,6-naphthalenedicarboxylate or the like, can exhibit a lower humidity expansion coefficient if at the same Young's modulus, and has excellent dimensional stability with respect to an environmental change, and to provide a biaxially oriented polyester film using the copolymerized aromatic polyester. <P>SOLUTION: The copolymerized aromatic polyester is characterized in that: the main aromatic dicarboxylic acid components are aromatic dicarboxylic acid components expressed by formulae (I) and (II); the main glycol component is a glycol component expressed by formula (III); and the acid components expressed by the formula (I) are copolymerized in the range of 2 to 20 mol% based on the number of moles in the total aromatic dicarboxylic acid component äin the formulae (I), (II) and (III), R<SP POS="POST">1</SP>denotes a 2 to 8C alkylene group; R<SP POS="POST">2</SP>denotes a phenylene group or a naphthalenediyl group; and R<SP POS="POST">3</SP>denotes a 2 to 8C (cyclo)alkylene group}. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a novel copolymerized aromatic polyester obtained by copolymerizing a 4 ', 4 "-(alkylenedioxy) di-biphenyl-4-carboxylic acid component, 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 for high-density magnetic recording media. It is used. However, the demand for dimensional stability in high-density magnetic recording media and the like in recent years is increasing, and further improvement of characteristics is required.

  In order to answer such a request, Japanese Patent Laid-Open No. 5-212787 (Patent Document 1), International Publication No. 99/29488 (Patent Document 2), International Publication No. 00/76749 (Patent Document 3) It has been proposed to reduce the humidity expansion coefficient in the tape width direction by selecting the film production conditions. However, since the methods proposed in these methods are achieved only by optimizing the stretching conditions and the subsequent heat setting treatment conditions, the polyester is a polar polymer and is therefore susceptible to humidity. The solution to the problem was still inadequate.

JP-A-5-212787 International Publication No. 99/29488 pamphlet International Publication No. 00/76749

  The object of the present invention is to provide a novel copolymerized aromatic polyester having excellent dimensional stability against environmental changes, which can express a lower coefficient of humidity expansion with the same Young's modulus than polyethylene-2,6-naphthalenedicarboxylate, etc. And providing a biaxially oriented polyester film using the same.

  In a biaxially oriented polyester film, 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, the Young's modulus is not increased as much as possible, and there is a limit in terms of film forming properties and securing the Young's modulus in the orthogonal direction. For this reason, we have earnestly studied whether a film having an expansion coefficient for lower temperature and humidity can be obtained with the same Young's modulus, and as a result, the 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component is co-used. It has been found that, when polymerized, the same Young's modulus can exhibit a lower humidity expansion coefficient, and the present invention has been achieved.

（上記式（Ｉ）、（ＩＩ）、（ＩＩＩ）中の、Ｒ^１は炭素数２〜８のアルキレン基であり、Ｒ^２はフェニレン基またはナフタレンジイル基であり、Ｒ^３は炭素数２〜８の（シクロ）アルキレン基を示す。）で表される酸成分が共重合されている共重合芳香族ポリエステルが提供される。 Thus, according to the present invention, the main aromatic dicarboxylic acid component is an aromatic dicarboxylic acid component represented by the following formulas (I) and (II), and the main glycol component is a glycol component represented by the following formula (III):
In the range of 2 to 20 mol% based on the number of moles of the wholly aromatic dicarboxylic acid component, the following formula (I)

(In the above formulas (I), (II) and (III), R ¹ is an alkylene group having 2 to 8 carbon atoms, R ² is a phenylene group or a naphthalenediyl group, and R ³ is 2 to 2 carbon atoms. 8 (cyclo) alkylene group) is provided, and a copolymerized aromatic polyester in which an acid component is copolymerized is provided.

According to the present invention, as a preferred embodiment of the present invention, the acid component represented by the formula (I) is a 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylic acid component. The aromatic dicarboxylic acid component represented by the formula (II) is a 2,6-naphthalenedicarboxylic acid component or a terephthalic acid component, and the glycol component represented by the formula (III) is an ethylene glycol component. A copolymerized aromatic polyester comprising at least one of the following is also provided.
Furthermore, according to the present invention, there is also provided a biaxially oriented polyester film having at least one layer formed from the above-described copolymerized aromatic polyester of the present invention.

Since the copolymerized aromatic polyester of the present invention can express a lower coefficient of humidity expansion when compared with the conventional polyester and the same Young's modulus, it can be provided in a molded article such as a film that can obtain excellent dimensional stability against environmental changes. it can.
Therefore, according to the present invention, there is provided a film suitable for a use in which a high degree of dimensional stability in consideration of the influence of humidity is required, in particular, a base film of a high-density magnetic recording medium, and by using the film of the present invention. Also, a high-density magnetic recording medium having excellent dimensional stability can be provided.

<Aromatic polyester>
The copolymerized aromatic polyester of the present invention comprises an aromatic dicarboxylic acid component and a glycol component.
First, as the 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component represented by the specific structural formula (I), R ¹ has 2 to 8 carbon atoms. An alkylene group, preferably 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylic acid component, 4 ′, 4 ″-(trimethylenedioxy) di-biphenyl-4 -Carboxylic acid component, 4 ', 4''-(butyleneoxy) di-biphenyl-4-carboxylic acid component, and the like. Among these, in terms of the effect of the present invention, in the above general formula (I) R ¹ having an even number of carbon atoms is preferable, and a 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylic acid component is particularly preferable.

  Next, specific examples of the aromatic dicarboxylic acid component represented by the formula (II) include a terephthalic acid component, an isophthalic acid component, a 2,6-naphthalenedicarboxylic acid component, and a 2,7-naphthalenedicarboxylic acid component. Can be mentioned. Among these, from the viewpoint of the effect of the present invention, a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component that are relatively easy to improve physical properties such as mechanical strength are preferable, and a 2,6-naphthalenedicarboxylic acid component is particularly preferable. .

  Finally, examples of the glycol component represented by the formula (III) include an ethylene glycol component, a trimethylene glycol component, a tetramethylene glycol component, and a cyclohexanedimethanol component. Among these, from the viewpoint of the effect of the present invention, an ethylene glycol component that is relatively easy to improve physical properties such as mechanical strength is preferable.

  The copolymerized aromatic polyester of the present invention is a copolymer component known per se, for example, an aliphatic dicarboxylic acid component, an alicyclic dicarboxylic acid component, and the above-mentioned formula (III), as long as the effects of the present invention are not impaired. An acid component or alcohol component having a trifunctional or higher functional group such as an alkylene glycol component, a hydroxycarboxylic acid component, or trimellitic acid that does not correspond to the above may be copolymerized. Preferably, based on the number of moles of the aromatic dicarboxylic acid component constituting the copolymerized aromatic polyester, the total number of moles of the aromatic dicarboxylic acid component represented by the above formulas (I) and (II) and the above formula ( It is preferable that the number of moles of the glycol component represented by III) occupy 90 mol% or more, more preferably 95 mol% or more.

  By the way, the feature of the present invention is that 4 ′, 4 ″ − represented by the above formula (I) is in the range of 2 mol% or more and 20 mol% or less based on the number of moles of the wholly aromatic dicarboxylic acid component. (Alkylenedioxy) di-biphenyl-4-carboxylic acid component is copolymerized. When the proportion of the 4 ', 4 "-(alkylenedioxy) di-biphenyl-4-carboxylic acid component is less than the lower limit, the effect of reducing the humidity expansion coefficient is difficult to be exhibited. On the other hand, when the upper limit is exceeded, film-forming properties are impaired, it is difficult to improve mechanical properties such as Young's modulus by stretching, it is difficult to lower the coefficient of thermal expansion, and in severe cases it breaks during film-forming processes such as stretching. Resulting in. Surprisingly, the effect of reducing the humidity expansion coefficient by the 4 ', 4 "-(alkylenedioxy) di-biphenyl-4-carboxylic acid component is efficiently expressed even in a relatively small amount. From such a viewpoint, the lower limit of the content ratio of a preferable 4 ', 4 "-(alkylenedioxy) di-biphenyl-4-carboxylic acid component is preferably 3 mol% or more, and more preferably 5 mol% or more. On the other hand, the upper limit of the copolymerized aromatic polymer is preferably 15 mol% or less because the copolymerized aromatic polymer has high crystallinity, and stretching becomes difficult as the amount of copolymerization increases.

  By making a copolymerized aromatic polyester obtained by copolymerizing such a specific amount of 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component, both temperature expansion coefficient and humidity expansion coefficient are obtained. Both of them can produce a low-molded product such as a film.

  The amount of copolymerization of the 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component is adjusted by adjusting the composition of the raw materials so that the desired copolymerization amount is obtained in the polymerization stage, As the acid component, a polymer having a large amount of copolymerization of the 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component and a polymer not copolymerized or a polymer having a small amount of copolymerization are prepared. And it can adjust by carrying out transesterification by melt-kneading so that it may become a desired amount of copolymerization.

  The copolymerized aromatic polyester of the present invention may be blended with known additives and other resins as long as they do not impair the effects of the present invention. Additives include stabilizers such as UV absorbers, antioxidants, plasticizers, lubricants, flame retardants, mold release agents, pigments, nucleating agents, fillers or glass fibers, carbon fibers, layered silicates, etc. And may be appropriately selected according to the requirements of the intended use. Examples of other resins include aliphatic polyester resins, polyamide resins, polycarbonates, ABS resins, liquid crystal resins, polymethyl methacrylate, polyamide elastomers, polyester elastomers, polyether imides, and polyimides.

<Film>
The biaxially oriented polyester film of the present invention is obtained by melt-forming the above-mentioned copolymerized aromatic polyester and extruding it into a sheet shape, which may be referred to as the longitudinal direction, longitudinal direction, or MD direction. And it can produce by extending | stretching to the direction (henceforth a width direction, a horizontal direction, or TD direction) orthogonal to it. In addition, the biaxially oriented polyester film of the present invention may have at least one layer formed of the above-described copolymerized aromatic polyester of the present invention, and may be laminated with a film layer of the same kind of polymer. It may be laminated with the film layer. In addition, a laminated structure can be appropriately adopted according to the purpose.

By the way, the biaxially oriented polyester film of the present invention has a temperature expansion coefficient (αt) in at least one direction in the plane direction of the film of 14 × 10 ⁻⁶ / ° C. or less from the viewpoint of exhibiting excellent dimensional stability. Preferably there is. Preferably, the temperature expansion coefficient (αt) in the width direction of the film is equal to or less than the upper limit of the temperature expansion coefficient in at least one direction of the film, for example, by matching with the direction of the film for which dimensional stability is most required. It can be expressed in a film that can obtain excellent dimensional stability against changes. The lower limit of the preferred temperature expansion coefficient (αt) is −10 × 10 ⁻⁶ / ° C. or higher, particularly −7 × 10 ⁻⁶ / ° C. or higher, and the upper limit is 10 × 10 ⁻⁶ / ° C. or lower, particularly 7 × 10. ^{It is -6} degrees C or less. In addition, for example, when a magnetic recording tape is used, it can exhibit excellent dimensional stability against dimensional changes due to changes in the temperature and humidity of the atmosphere, so the direction satisfying the temperature expansion coefficient is the width direction of the biaxially oriented polyester film. Preferably there is.

In addition, the biaxially oriented polyester film of the present invention has a Young's modulus of at least 4.5 GPa or more in a direction in which the temperature expansion coefficient is 14 × 10 ⁻⁶ /% RH or less in at least one direction of the film surface direction. The upper limit is not particularly limited, but is usually about 12 GPa. A particularly preferable Young's modulus is in the range of 5 to 11 GPa, particularly 6 to 10 GPa. If it is out of this range, it may be difficult to achieve the above-mentioned αt and αh, or the mechanical characteristics may be insufficient. Such Young's modulus can be adjusted by the blend or copolymer composition described above and the stretching described below. In addition, the biaxially oriented polyester film of the present invention has at least one direction in the film surface direction, such as when used for a base film of a magnetic tape, preferably in a direction in which the temperature expansion coefficient is 14 × 10 ⁻⁶ /% RH or less. The humidity expansion coefficient is preferably 0 (× 10 ⁻⁶ /% RH) or less, and the lower limit is not particularly limited, but usually about 1 (× 10 ⁻⁶ /% RH) is preferable. Outside this range, the dimensional change with respect to the humidity change increases. Such a humidity expansion coefficient can be adjusted by the blend or copolymerization composition described above and the stretching described below.

As for the direction in which the temperature expansion coefficient is 14 × 10 ⁻⁶ or less, it is sufficient that at least one direction, preferably the width direction is satisfied as described above. Of course, the direction orthogonal to the width direction also preferably satisfies the same temperature expansion coefficient, humidity expansion coefficient, Young's modulus, and the like from the viewpoint of dimensional stability.

<Method for producing aromatic polyester resin>
The production method of the copolymerized aromatic polyester of the present invention will be described in detail.
As the 4 ′, 4 ″-(alkylenedioxy) di-biphenyl-4-carboxylic acid component represented by the above structural formula (I), it is preferable to use an alkyl ester, particularly from the viewpoint of handleability. Preference is given to using 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylic acid ethyl ester. 4 ′, 4 ″-(Ethylenedioxy) di-biphenyl-4-carboxylic acid ethyl ester is obtained by reacting 4′-hydroxybiphenyl-4-carboxylic acid ethyl ester with dihaloethane in an anhydrous polar solvent in the presence of potassium carbonate. Can be obtained.

  In addition, the copolymerized aromatic polyester of the present invention is obtained by reacting 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylic acid and its alkyl ester derivative with, for example, ethylene glycol to obtain a polyester precursor. To manufacture. In that case, it can also be made to react with other aromatic dicarboxylic acid components, for example, 2,6-naphthalenedicarboxylic acid, terephthalic acid or ester-forming derivatives thereof. And it can manufacture by superposing | polymerizing the polyester precursor obtained in this way in presence of a polymerization catalyst, You may give a solid phase polymerization etc. as needed. The intrinsic viscosity measured at 35 ° C. using a mixed solvent of aromatic polyester P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60) thus obtained is 0.4. From the viewpoint of the effect of the present invention, it is preferably in the range of -1.5 dl / g, more preferably in the range of 0.5-1.2 dl / g.

  The reaction temperature for producing the polyester precursor is preferably in the range of 190 ° C. to 250 ° C., and is carried out under normal pressure or under pressure. If it is lower than 190 ° C., the reaction does not proceed sufficiently, and if it is higher than 250 ° C., it is a side reaction product. Diethylene glycol is easily generated.

  In the reaction step for producing a polyester precursor, a known esterification or transesterification reaction catalyst may be used. For example, manganese acetate, zinc acetate, alkali metal compounds, alkaline earth metal compounds, titanium compounds and the like can be mentioned. A titanium compound that can suppress high surface protrusions when formed into a film is preferred.

  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 polymer and not higher than 230 to 300 ° 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 100 Pa or less.

  Examples of the polycondensation catalyst include metal compounds containing at least one metal element. The polycondensation catalyst can also be used in an esterification reaction or a transesterification reaction. 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, and the like. As described above, particularly when a titanium compound is used, a high protrusion on the surface due to the influence of the residual metal used in the catalyst when a film is formed. It is preferable to use this because it is suppressed.

  These catalysts may be used alone or in combination. The amount of the catalyst is preferably 0.001 to 0.1 mol%, more preferably 0.005 to 0.05 mol%, based on the number of moles of the repeating unit of the aromatic polyester.

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

  And, as described above, the copolymerized aromatic polyester of the present invention may be polymerized so as to be a copolymerized aromatic polyester having a desired copolymerization amount. The above aromatic polyesters having different copolymerization amounts may be prepared, melted and kneaded, and blended so as to obtain a desired copolymerization amount.

<Method for producing biaxially oriented polyester film>
The biaxially oriented polyester film of the present invention is obtained by stretching in the film forming direction and the width direction to increase the molecular orientation in each direction. For example, the following method maintains the film forming property. However, it is preferable because the Young's modulus is increased and the temperature expansion coefficient and the humidity expansion coefficient are easily reduced.

  First, using the above-mentioned copolymerized aromatic polyester of the present invention as a raw material, after drying this, it is supplied to an extruder heated to a melting point (Tm: ° C.) to (Tm + 50) ° C. of the aromatic polyester, For example, it is 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 achieve αt, αh, Young's modulus, etc. defined in the present invention, it is necessary to facilitate the subsequent stretching, and the polyester polymer of the present invention tends to have a high crystallization rate. From such a viewpoint, it is preferable that the cooling by the cooling drum be performed 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.

As the biaxial stretching, those known per se can be adopted, and sequential biaxial stretching or simultaneous biaxial stretching may be employed.
Here, a manufacturing method of sequential biaxial stretching in which longitudinal stretching, lateral stretching, and heat treatment are performed in this order will be described as an example. First, in the first longitudinal stretching, the glass transition temperature (Tg: ° C.) to (Tg + 40) ° C. of the copolymerized aromatic polyester is stretched 3 to 8 times, and then in the transverse direction at a higher temperature than the previous longitudinal stretching. It is stretched 3 to 8 times at a temperature of (Tg + 10) to (Tg + 50) ° C., and further at a temperature below the melting point of the copolymerized aromatic polyester as a heat treatment and at a temperature of (Tg + 50) to (Tg + 150) ° C. for 1 to 20 seconds. Furthermore, it is preferable to heat-set for 1 to 15 seconds.

  In polyalkylene-1,2-diphenoxyethane-4,4′-dicarboxylate, the temperature at which crystallization starts was too low, and it was difficult to perform sufficient stretching at the above temperature. The biaxially oriented polyester film of the invention can be stretched by copolymerizing not only the 4,4 ′-(alkylenedioxy) bisbenzoic acid component but also the aromatic dicarboxylic acid represented by the formula (II). It becomes.

  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, when the biaxially oriented polyester film of the present invention is a laminated film, two or more types of molten polyester are laminated in a die and then extruded into a film, preferably the melting point (Tm: ° C.) to (Tm + 70) of each polyester. ) Extrude at a temperature of ° C. or extrude two or more types of molten polyester from a die, laminate them, quench and solidify them to form a laminated unstretched film, and then perform biaxial stretching and Heat treatment may be performed. Further, when providing the above-mentioned coating layer, a desired coating solution is applied to one or both sides of the unstretched film or the uniaxially stretched film, and then the biaxial stretching and the same method as in the case of the single-layer film are performed. It is preferable to perform a heat treatment.

  According to the present invention, the above biaxially oriented polyester film 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. It can be used as a magnetic recording tape for data storage.

  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) Purity of diethyl 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylate 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylate was converted to N- After dissolving in methyl-2-pyrrolidone, measurement was performed using a solvent (dimethylformamide / H ₂ O) with a high performance liquid chromatograph (LC6A type, manufactured by Shimadzu Corporation).
The main peak area was determined by dividing the total peak area excluding the solvent-derived peak.

(2) Intrinsic viscosity The intrinsic viscosity of the obtained copolymerized aromatic polyester and film was measured at 35 ° C by dissolving the polymer using a mixed solvent of P-chlorophenol / tetrachloroethane (40/60 weight ratio). Asked.

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

(4) Copolymerization amount For the acid component, 50 mg of a sample was dissolved in 140 ml of a mixed solution of p-chlorophenol: heavy tetrachloroethane = 3: 1 (volume ratio) at 140 ° C., and 400 MHz ¹³ C-NMR (Hitachi Electronics) Manufactured by JEOL A600) at 140 ° C., and the amount of each acid component was measured.

(5) 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.

(6) 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 and the width direction of the film would be the measurement direction, respectively, set in TMA3000 manufactured by Vacuum Riko, and under a nitrogen atmosphere (0% RH) , Pre-treat at 60 ° C. for 30 minutes, and then 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. 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.

(7) 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 and the width direction of the film would be the measurement direction, set in TMA3000 manufactured by Vacuum Riko, and a humidity of 30% under a nitrogen atmosphere at 30 ° C. The length of each sample at RH and humidity 70% RH is measured, and the 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.

[Reference example]
100 parts by weight of 4′-hydroxybiphenyl-4-carboxylic acid, 250 parts by weight of ethanol and 30 parts by weight of concentrated sulfuric acid were charged into a reactor equipped with a stirrer and a reflux condenser, and reacted at 75 ° C. for 12 hours. The reaction product was cooled, filtered, and thoroughly rinsed with ion exchange water. Thereafter, the reaction product was added again to 300 parts by weight of ethanol, the temperature was raised, the crystal was recrystallized and dried under reduced pressure.
80 parts by weight of ethyl 4′-hydroxybiphenyl-4-carboxylate obtained above, 70 parts by weight of potassium carbonate, 95 parts by weight of dibromoethane and 400 parts by weight of ethanol were charged into a reactor equipped with a stirrer and a reflux condenser. The reaction was performed at 75 ° C. for 24 hours. The reaction product was cooled, filtered, rinsed three times with ion-exchanged water, and finally washed with ethanol. After drying under reduced pressure, 450 parts by weight of N-methyl-2-pyrrolidone was added to 50 parts by weight of the reaction product in the reactor described above and dissolved at 125 ° C. After cooling and recrystallization, filtration, repeated washing with ion exchange water, finally washing with methanol, drying under reduced pressure, 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4 -White crystals of diethyl carboxylate were obtained. The purity of diethyl 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylate was 98.9%.

[Example 1]
Diethyl 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylate obtained in Reference Example 5 kg (9.8 mol), 27.5 kg of 2,6-naphthalenedicarboxylic acid dimethyl ester (112. 7 mol) and 16.5 kg of ethylene glycol were charged into a reaction vessel equipped with a stirrer, a rectifying column and a condenser, and the temperature was raised to 150 ° C. Thereafter, 7.5 g (10 mmol%) of a reaction product (titanium trimellitic acid) obtained by reacting titanium tetrabutoxide and trimellitic anhydride at a molar ratio of 1: 2 at 175 ° C. for 4 hours was added to the whole reaction vessel. Was heated with nitrogen at a pressure of 0.20 MPa, and the internal temperature was increased to 250 ° C. with the pressure kept constant as the reaction proceeded. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, 4.6 g (17 mmol%) of triethylphosphonoacetate is added, and 0.05 kg of silica particles having an average particle size of 0.5 μm are added as an ethylene glycol slurry. did. And the excess ethylene glycol was driven out.
The obtained reaction product is transferred to a polymerization reaction tank. In the polymerization reaction tank, a polycondensation reaction is carried out while slowly raising the temperature from 250 ° C. and reducing the pressure, and finally a predetermined polymerization is performed at 290 ° C. and 50 Pa. Polycondensation was carried out until the temperature reached 1, thereby producing a copolymerized aromatic polyester 1.
The properties of the obtained copolyester 1 are shown in Table 1.

The aromatic polyester 1 thus obtained was supplied to an extruder and extruded from a die at 295 ° C. onto a cooling drum having a rotating temperature of 40 ° C. in a molten state 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 4.0. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.5 times in the transverse direction (width direction) at 140 ° C., and then heat-fixed at 200 ° C. for 5 seconds, and biaxially stretched with a thickness of 10 μm. A film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 2]
Aromatic polyester 1 obtained in the same manner as in Example 1 was supplied to an extruder and extruded from a die at 295 ° C. in a molten state onto a cooling drum at a temperature of 30 ° C. and rotated into a sheet 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 4.0. 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 5.0 times, and then heat-fixed at 200 ° C. for 3 seconds to be biaxially stretched with a thickness of 10 μm. A film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 3]
3 Kg (5.9 mol) of diethyl 4 ', 4''-(ethylenedioxy) di-biphenyl-4-carboxylate obtained in Reference Example, 27.4 Kg of 2,6-naphthalenedicarboxylic acid dimethyl ester (112. 3 mol) and 15.4 kg of ethylene glycol were charged into a reaction vessel equipped with a stirrer, a rectifying column and a cooler, and the temperature was raised to 150 ° C. Thereafter, 7.2 g (10 mmol%) of a reaction product (titanium trimellitic acid) obtained by reacting titanium tetrabutoxide and trimellitic anhydride at a molar ratio of 1: 2 at 175 ° C. for 4 hours was added. Heating was performed with nitrogen at a pressure of 0.20 MPa, and the internal temperature was increased to 250 ° C. with the pressure kept constant as the reaction proceeded. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, 4.5 g (17 mmol%) of triethylphosphonoacetate is added, and 0.05 kg of silica particles having an average particle size of 0.5 μm are added as an ethylene glycol slurry. did. And the excess ethylene glycol was driven out. Thereafter, copolymerized aromatic polyester 3 was produced in the same manner as in Example 1.

The sheet was supplied to an extruder and extruded from a die at 295 ° C. in a molten state onto a cooling drum having a rotating temperature of 30 ° 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 4.0. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.5 times in the transverse direction (width direction) at 140 ° C., and then heat-fixed at 200 ° C. for 5 seconds, and biaxially stretched with a thickness of 10 μm. A film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Example 4]
9 kg (17.6 mol) of diethyl 4 ′, 4 ″-(ethylenedioxy) di-biphenyl-4-carboxylate obtained in Reference Example, 24.3 kg of 2,6-naphthalenedicarboxylic acid dimethyl ester (99. 6 mol), 16.7 kg of ethylene glycol was charged into a reaction vessel equipped with a stirrer, a rectifying column and a cooler, and the temperature was raised to 150 ° C. Thereafter, 7.2 g (10 mmol%) of a reaction product (titanium trimellitic acid) obtained by reacting titanium tetrabutoxide and trimellitic anhydride at a molar ratio of 1: 2 at 175 ° C. for 4 hours was added. Heating was performed with nitrogen at a pressure of 0.20 MPa, and the internal temperature was increased to 250 ° C. with the pressure kept constant as the reaction proceeded. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, 4.5 g (17 mmol%) of triethylphosphonoacetate is added, and 0.05 kg of silica particles having an average particle size of 0.5 μm are added as an ethylene glycol slurry. did. And the excess ethylene glycol was driven out. Thereafter, copolymerized aromatic polyester 4 was produced in the same manner as in Example 1.

The sheet was supplied to an extruder and extruded from a die at 295 ° C. in a molten state onto a cooling drum having a rotating temperature of 30 ° 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 4.0. Then, this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.5 times in the transverse direction (width direction) at 140 ° C., and then heat-fixed at 200 ° C. for 3 seconds to be biaxially stretched with a thickness of 10 μm. A film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 1]
An intrinsic viscosity of 0.62 dl / g is obtained by subjecting dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol to an esterification reaction and a transesterification reaction in the presence of titanium tetrabutoxide, followed by a polycondensation reaction. Polyethylene-2,6-naphthalate 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 265 ° 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 characteristics of the obtained biaxially oriented polyester 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 10 μm thick biaxially stretched film.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 3]
14 Kg (27.5 mol) of diethyl 4 ', 4''-(ethylenedioxy) di-biphenyl-4-carboxylate obtained in Reference Example, 15.7 Kg of 2,6-naphthalenedicarboxylic acid dimethyl ester (64. 3 mol) and 14.8 kg of ethylene glycol were charged into a reaction vessel equipped with a stirrer, a rectifying column and a cooler, and the temperature was raised to 150 ° C. Thereafter, 6.7 g (12 mmol%) of a reaction product (titanium trimellitic acid) obtained by reacting titanium tetrabutoxide and trimellitic anhydride at a molar ratio of 1: 2 at 175 ° C. for 4 hours was added. Heating was performed with nitrogen at a pressure of 0.20 MPa, and the internal temperature was increased to 250 ° C. with the pressure kept constant as the reaction proceeded. Thereafter, the pressure in the reaction vessel is slowly returned to normal pressure, 4.1 g (20 mmol%) of triethylphosphonoacetate is added, and 0.05 kg of silica particles having an average particle size of 0.5 μm are added as an ethylene glycol slurry. did. And the excess ethylene glycol was driven out. Thereafter, a copolymerized aromatic polyester 5 was obtained in the same manner as in Example 1 except that the polycondensation temperature was changed to 300 ° C. The copolymer aromatic polyester 5 had a melting point of 271 ° C. and a glass transition temperature of 105 ° C.

  The copolymerized aromatic polyester 5 thus obtained was fed to an extruder and extruded from a die at 300 ° C. in a molten state onto a cooling drum having a temperature of 40 ° C. during rotation 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. When it was carried out at a magnification of 3.0, crystallization progressed too much and became white and could not be further stretched in the transverse direction.

  In Table 1, NA is 2,6-naphthalenedicarboxylic acid component, EBPA is 4,4 '-(ethylenedioxy) di-biphenyl-4-carboxylic acid component, intrinsic viscosity, melting point and glass transition temperature are film states. The value of the copolymerized aromatic polyester at, MD indicates the film forming direction, and TD indicates the width direction of the film.

  The copolymerized aromatic polyester of the present invention and the biaxially oriented polyester film obtained therefrom have a lower coefficient of humidity expansion than the conventional polyethylene terephthalate and polyethylene-2,6-naphthalate, if they have the same Young's modulus. It can be suitably used as a base film for applications requiring excellent dimensional stability, for example, a high-density magnetic recording medium.

Claims (5)

The main aromatic dicarboxylic acid component is an aromatic dicarboxylic acid component represented by the following formulas (I) and (II), and the main glycol component is a glycol component represented by the following formula (III):
A copolymerized aromatic polyester in which an acid component represented by the following formula (I) is copolymerized in a range of 2 to 20 mol% based on the number of moles of the wholly aromatic dicarboxylic acid component.

(In the above formulas (I), (II) and (III), R ¹ is an alkylene group having 2 to 8 carbon atoms, R ² is a phenylene group or a naphthalenediyl group, and R ³ is 2 to 2 carbon atoms. 8 represents a (cyclo) alkylene group.)   The copolymerized aromatic polyester according to claim 1, wherein the acid component represented by the formula (I) is a 4 ', 4 "-(ethylenedioxy) di-biphenyl-4-carboxylic acid component.   The copolymerized aromatic polyester according to claim 1, wherein the aromatic dicarboxylic acid component represented by the formula (II) is a 2,6-naphthalenedicarboxylic acid component or a terephthalic acid component.   The copolymer aromatic polyester according to claim 1, wherein the glycol component represented by the formula (III) is an ethylene glycol component.   A biaxially oriented polyester film having at least one layer formed from the copolymerized aromatic polyester according to claim 1.