JP2013173870A - Polyester resin, and polyester film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester excellent in dimensional stability to temperature change, and heat resistance.SOLUTION: A polyester has an acid component composed of a 2,6-naphthalenedicarboxylic acid component (component A) and an aromatic or alicyclic dicarboxylic acid component (component B) different from the component A, and a glycol component composed of an ethylene glycol component (component C) and an aliphatic dimerdiol component (component D), wherein the molar ratio of the component A and the component B is in the range of 80:20 to 95:5; the molar ratio of the component C and the component D is in the range of 75:25 to 95:5; the molar ratio of the component B (component B) bonding with the component C and the component B (component B) bonding with the component D is in the range of 15:85 to 40:60; and the intrinsic viscosity is ≥0.55.

Description

  The present invention relates to a polyester resin using an aromatic dicarboxylic acid and ethylene glycol as main components and an aromatic or alicyclic dicarboxylic acid and an aliphatic dimer diol as copolymerization components, and a 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.

  On the other hand, Patent Documents 1 to 4 propose that dimer acid or aliphatic polyester is incorporated in a part of the repeating unit, but actually the melting point and glass transition temperature are drastically lowered, and the heat resistance and the like are high. The required applications were only strictly limited in their development.

Japanese Patent Publication No.57-48577 Japanese Patent Publication No.54-15913 JP-A-4-91123 Japanese Patent No. 3110168

  An object of the present invention is to have excellent heat stability such as glass transition temperature (Tg) and melting point (Tm) necessary for practical use while having excellent dimensional stability against humidity change, and formability such as film formation. Another object of the present invention is to provide a polyester also having a polyester film and a polyester film using the same.

  As a result of diligent research to solve the above-mentioned problems, the present inventors incorporated a specific aliphatic polyester into a polyester composed of an aromatic dicarboxylic acid and ethylene glycol, and further controlled the bonding state within a specific range. Thus, the inventors have found that the above problems can be solved, and have reached the present invention.

Thus, according to the present invention, the acid component comprises a 2,6-naphthalenedicarboxylic acid component (component A) and an aromatic or alicyclic dicarboxylic acid component (component B) different from component A, and the glycol component is ethylene. A polyester comprising a glycol component (component C) and an aliphatic dimer diol component (component D),
The molar ratio of component A to component B is in the range of 80:20 to 95: 5, the molar ratio of component C to component D is in the range of 75:25 to 95: 5, and is bonded to component C Polyester having an intrinsic viscosity of 0.55 or more in which the molar ratio of Component B (Component B _C ) to Component B (Component B _D ) bonded to Component D is in the range of 15:85 to 40:60 A resin and a polyester film using the resin are provided.

According to the present invention, as a preferred embodiment of the present invention, the proportion of component C (component C _A ) bonded only to component A is 90 mol% or more based on the number of moles of component C. The molar ratio of component D (component D _A ) bound to component A to component D (component D _B ) bound to component B is in the range of 40:60 to 5:95, There are also provided a polyester resin further comprising at least one of using a low molecular weight precursor composed of Component B and Component D having an average molecular weight of 1,500 to 10,000, and a polyester film using the same.

  According to the present invention, a polyester having excellent low water absorption and heat resistance sufficient for practical use can be obtained, and since it has low water absorption, by forming it into a film, dimensional stability against humidity change can be obtained. An excellent polyester film can be provided.

  In describing the polyester and polyester film of the present invention, component A, component B, component C and component D will be described first.

<Component A>
Component A in the present invention is a 2,6-naphthalenedicarboxylic acid component. By using this, the object of the present invention can be achieved in terms of mechanical properties and heat resistance.

<Component B>
Component B in the present invention is an aromatic or alicyclic dicarboxylic acid component different from component A, and specific examples include a terephthalic acid component, an isophthalic acid component, and a 1,4-cyclohexanedicarboxylic acid component.

<Component C>
Component C in the present invention is an ethylene glycol component.

<Component D>
Component D in the present invention is an aliphatic dimer diol component. Dimer diol is a diol having about 36 carbon atoms in which dimer acid, which is a known dibasic acid obtained by an intermolecular polymerization reaction of unsaturated fatty acid, is hydrogenated in the presence of a catalyst, and the carboxylic acid portion of dimer acid is alcohol. Is the main component. The industrial production process of dimer acid is almost standardized in the industry, dimerization of unsaturated fatty acid having 11 to 22 carbon atoms or its lower alcohol ester with clay catalyst etc., and by-product such as trimer acid and monomer acid Obtained after removal of material. Specific examples of the dimer diol include Pripol 2033 manufactured by Croda.

<Polyester>
In the polyester of the present invention, the acid component mainly comprises the component A and the component B, and the glycol component mainly comprises the component C and the component D.
In the present invention, the molar ratio of Component A to Component B is in the range of 80:20 to 95: 5. By being in the said range, heat resistance and the dimensional stability with respect to a humidity change can be expressed highly. The lower limit of the preferred molar ratio of Component A to Component B is 85:15, and the upper limit is 93: 7.

  Moreover, in this invention, the molar ratio of the said component C and the component D is the range of 75: 25-95: 5. By being in the said range, heat resistance and the dimensional stability with respect to a humidity change can be expressed highly. The lower limit of the preferred molar ratio of component C to component D is 80:20, and the upper limit is 92: 8.

By the way, one of the features of the present invention is that, as described above, a small amount of component B and component D are copolymerized, but the ratio of component B and component D being directly bonded is extremely high. Therefore, the heat resistance is further enhanced. That is, in the polyester of the present invention, the molar ratio of the ratio of component B bonded to component _C (component B _C ) to component B bonded to component D (component B _D ) is 15 in terms of molar ratio. : It is necessary from the point of heat resistance that it is the range of 85-40: 60. The molar ratio of the preferred component _{B C} and component _{B D} is 20: 80 to 35: a 65. Such a coupling state can be adjusted by employing a manufacturing method described later.

Further, the polyester of the present invention, from the viewpoint of heat resistance, the proportion of the components is bound only with the component A C (Component C _A) is preferably 90 mol% or more. The upper limit is not particularly limited based on the number of moles of Component C, but 95 mol% or less, and more preferably 98 mol% or less is preferable because the transesterification reaction or the like may not be excessively suppressed.

Furthermore, the polyester of the present invention has a molar ratio of component D (component D _A ) bonded to component A and component D (component D _B ) bonded to component B from the viewpoint of heat resistance. 40:60 to 5:95. The molar ratio of the preferred component _{D A} and component _{D B} is 50: 50-30: 70. Such a coupling state can be adjusted by employing a manufacturing method described later.

The polyester of 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 a polyetherimide or a liquid crystalline resin. It is good. In the case of copolymerization, from the viewpoint of heat resistance, it is preferably less than 10 mol%, more preferably less than 5 mol%, based on the number of moles of all acid components.
The polyester of the present invention preferably has an intrinsic viscosity measured at 35 ° C. using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60) at 0.4 to 1. It is 5 dl / g, More preferably, it is the range of 0.5-1.3 dl / g.

  The polyester of the present invention preferably has a melting point measured by DSC in the range of 200 to 280 ° C, further in the range of 220 to 270 ° C, particularly in the range of 240 to 260 ° C, from the viewpoint of film forming property. When the melting point exceeds the above upper limit, when melt extrusion is performed, the fluidity is inferior, and the 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 and the like of the aromatic polyester are easily impaired.

  The polyester resin of the present invention preferably has a glass transition temperature (hereinafter sometimes referred to as Tg) measured by DSC of 65 ° C. or higher from the viewpoint of heat resistance. The upper limit is preferably 140 ° C. or less from the viewpoint of film forming properties. The minimum of preferable Tg is 70 degreeC, Furthermore, it is 80 degreeC. Moreover, the upper limit of preferable Tg is 120 degreeC. Such melting point and glass transition temperature can be adjusted by the types and ratios of component A, component B, component C, and component D, the bonding state of components A to D by the production method described later, and control of by-products. .

<Production method of polyester>
Below, the manufacturing method of polyester in this invention is demonstrated below.
First, ingredients A to D are prepared. Specifically, aromatic dicarboxylic acid or an ester-forming derivative thereof as a raw material for component A, aromatic or alicyclic dicarboxylic acid or an ester-forming derivative thereof as a raw material for component B, and ethylene glycol as a raw material for component C As an ingredient D, an aliphatic dimer diol is prepared. Then, the raw materials of these components A to D may be subjected to a polycondensation reaction via an esterification reaction or a transesterification reaction. However, it is difficult to obtain the above-described composition and bonding state by simply mixing and reacting the raw materials of components A to D at a desired ratio from the beginning. A case where dimethyl terephthalate is used as dimethyl naphthalenedicarboxylate and component B will be described as an example.

  First, a polyester precursor E in which two ethylene glycols are added to 2,6-naphthalenedicarboxylic acid by transesterifying dimethyl 2,6-naphthalenedicarboxylate with excess ethylene glycol to obtain the above-mentioned bonded state. (Ethylene glycol adduct of 2,6-naphthalenedicarboxylic acid) is prepared.

  In addition, dimethyl terephthalate and aliphatic dimer diol are transesterified to produce a low molecular weight substance F such as a polyester precursor, two or more linked dimers and trimers. These can be adjusted by the molar ratio of the aliphatic dimer diol and dimethyl terephthalate used.

  As the reaction temperature for producing the polyester precursor, when the glycol component is ethylene glycol, it is preferably carried out at the boiling point or higher, 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., dialalkylene glycol as a side reaction product is likely to be generated. By this transesterification reaction, a reactant as a polyester precursor is obtained.

  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. The low molecular weight precursor F can be easily obtained by further reducing the pressure in the reactor. The number average molecular weight of the low molecular weight precursor F is preferably in the range of 1,500 to 10,000. When the ratio is lower than the lower limit, the above-described bonding ratio of each component cannot be reached, and when the ratio is higher than the upper limit, the polycondensation reactivity with the polyester precursor E is deteriorated.

  And it can manufacture by carrying out the polycondensation reaction until this polyester precursor E and the polyester low molecular weight precursor F become desired molecular weight. Here, the polycondensation reaction will be described. First, the polycondensation temperature is in the range from a temperature higher than the melting point of the polymer to be obtained and 230 to 280 ° C. or lower, more preferably 5 ° C. higher than the melting point to 30 ° C. higher than the melting point. 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 copolymerized aromatic polyester resin having a high degree of polymerization.

  Examples of the polycondensation catalyst include metal compounds containing at least one metal element. The polycondensation catalyst can also be used in the esterification 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, etc. Among them, a titanium compound is particularly preferable because it exhibits high activity in both the esterification reaction and the 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 copolymerized aromatic polyester.

  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 orthoester or condensed orthoester, titanium orthoester or condensed orthoester and hydroxycarboxylic acid A reaction product comprising a titanium orthoester or a condensed orthoester, a hydroxycarboxylic acid and a phosphorus compound, a titanium orthoester or a condensed orthoester Both polyhydric alcohol having two hydroxyl groups, 2-hydroxycarboxylic acid or the like reaction product consisting of a base and the like.

  In addition, the polyester of the present invention can be produced by the method as described above. For example, a polyester having a higher ratio of component B and component D than the target is prepared, and a polyester having a lower ratio of component B and component D is prepared. These may be melt-kneaded to obtain a polyester having a desired composition, and by doing so, polyesters having different ratios of Component A, Component B, Component C and Component D are produced with high production efficiency. You can also

<Polyester film>
The polyester film of the present invention can be obtained by melt-forming the aforementioned polyester and extruding it into a sheet.
The polyester film of the present invention is preferably an oriented polyester film stretched in at least one direction in the film surface direction in order to express excellent dimensional stability, and is further stretched in both the film forming direction and the width direction. More preferably, it is a biaxially oriented polyester film.

  By the way, the polyester film of the present invention is composed of the above-described polyester of the present invention, but in the range not inhibiting the effects of the present invention, other thermoplastic polymers, stabilizers such as ultraviolet absorbers, antioxidants, plasticizers, Lubricants (particles, waxes, etc.), flame retardants, mold release agents, pigments, nucleating agents, fillers or glass fibers, carbon fibers, layered silicates and the like may be blended as necessary to form a polyester resin composition. 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. In particular, from the viewpoint of increasing the heat resistance, it can be said that it is a preferable embodiment to contain a glass transition temperature and the like.

  As described above, the polyester film of the present invention is preferably an oriented polyester film that has been stretched in the film forming direction or the width direction to increase the molecular orientation in that direction, and can be produced by the following method, for example. It is preferable because the Young's modulus is easily improved while maintaining the film forming property.

  First, the polyester of the present invention described above, or a polyester having a large amount of component (A) and component (C) and a polyester resin having a large amount of component B and component D before being melt kneaded, are dried, and the polyester resin is dried. Is supplied to an extruder heated to a melting point (Tm: ° C.) to (Tm + 50) ° C., and extruded from a die such as a T die, for example. 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 stretched. At this time, care is taken so that the transesterification reaction does not proceed excessively during melt-kneading. It is preferable that the cooling by the cooling drum be performed very quickly. 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.

In the case of biaxial stretching, the stretching method 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, 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. The film is stretched 3 to 10 times at a temperature of (Tg + 10) to (Tg + 50) ° C., 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. for 1 to 20 seconds, and further 1 to 15 It is preferable to carry out a second heat fixing treatment.
The thickness of the polyester film may be appropriately selected according to the application to be used, but when used for the base film of the magnetic recording medium, it is preferably 10 μm or less, more preferably 8 μm or less, and the lower limit of the thickness is not particularly limited, but 1 μm or more. Further, 3 μm or more is preferable.

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.
In addition, the above-mentioned biaxially oriented polyester film is used as a base film, and 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. be able to.

  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 the melting point were measured by DSC (TA Instruments Co., Ltd., trade name: DSC2920) at a sample weight of 20 mg and a heating rate of 10 ° C / min.

(3) Number average molecular weight The polymer was dissolved in HFIP (hexafluoroisopropanol) and measured by GPC (Shodex GPC-101). The number average molecular weight was determined in terms of polystyrene.

(4) Copolymerization amount 20 mg of a sample was dissolved in 0.6 mL of a mixed solvent of deuterated trifluoroacetic acid: deuterated chloroform = 1: 1, and a ¹ H-NMR spectrum (JEOL A600 manufactured by JEOL Ltd.) was measured at room temperature. The proportion of the copolymerization amount was estimated from the NMR spectrum.

(5) Water absorption rate The obtained film was dried in a thermostat kept at 50 ± 2 ° C. for 24 ± 1 hours, allowed to cool in a desiccator, and put in a container containing ion exchange water at 23 ± 2 ° C. Immerse in the complete immersion solution for 24 hours. After taking out the film sample, the surface was wiped with a clean dry cloth, the weight change before and after immersion was divided by the weight before immersion, and the water absorption was measured.

(6) Ratio of (Component B _C ) (Component B _D ) (Component C _A ) (Component D _A ) and (Component D _B ) About 20 mg of the polymerized polymer was deuterated with trifluoroacetic acid: deuterated chloroform = 1: 1. mixture is dissolved in a solvent 0.6 mL, it was measured at room temperature ¹ H-NMR spectrum (JEOL JEOL A600). Than spectrum of NMR, we estimated component _{B C, B D, C A} , D A, the ratio of _{D B.}

(7) Film forming property Under the conditions described in Example 1, the film was formed by stretching in the vertical direction and the horizontal direction, and it was observed whether the film could be stably formed. Evaluation was made according to the following criteria.
○: Stable film formation for 1 hour or more ×: Cutting occurs within 1 hour, and stable film formation is not possible

[Reference Example 1]
Dimethyl terephthalate at a molar ratio of 1: 1.25 and pripol 2033 (manufactured by Croda) as an aliphatic dimer diol were charged into a reactor, and manganese acetate (30 mmol% based on the number of moles of dimethyl terephthalate) was further added as a catalyst. Heated to 180 ° C., melted and stirred. The reaction was advanced while the temperature inside the reaction vessel was slowly raised to 235 ° C., and the methanol produced was distilled out of the reaction vessel. When the distillation of methanol was completed, phenylphosphonic acid (40 mmol% based on the number of moles of dimer acid) was added as a phosphorus compound to complete the esterification reaction. Subsequently, after 5 minutes, antimony trioxide was added as a polycondensation catalyst (20 mmol% based on the number of moles of dimer acid), heated to 280 ° C., and the degree of vacuum was gradually increased to obtain polyester low molecular weight precursor F1. Created.

[Reference Example 2]
A polyester low molecular weight precursor F2 was prepared in the same manner as in Reference Example 1 except that dimethylcyclohexanedicarboxylate and pripol 2033 (manufactured by Claude) were charged into the reactor at a molar ratio of 1: 1.22.

[Reference Example 3]
A polyester low molecular weight precursor F3 was prepared in the same manner as in Reference Example 1, except that dimethyl terephthalate and dipol diol Pripol 2033 (manufactured by Croda) were charged into the reactor at a molar ratio of 1: 1.05.

[Reference Example 4]
A polyester low molecular weight precursor F4 was prepared in the same manner as in Reference Example 1, except that dimethyl terephthalate at a molar ratio of 1: 2 and pripol 2033 (manufactured by Croda) as a dimer diol were charged into the reactor.

[Example 1]
A transesterification vessel was charged with dimethyl 2,6-naphthalenedicarboxylate, ethylene glycol, and manganese acetate (30 mmol% based on the number of moles of dimethyl 2,6-naphthalenedicarboxylate), heated to 150 ° C., melted and stirred. . The reaction was advanced while the temperature inside the reaction vessel was slowly raised to 235 ° C., and the methanol produced was distilled out of the reaction vessel. When the distillation of methanol was completed, phenylphosphonic acid (50 mmol% based on the number of moles of 2,6-naphthalenedicarboxylic acid) was added as a phosphorus compound to complete the transesterification reaction (hereinafter abbreviated as EI reaction). Subsequently, after 5 minutes, antimony trioxide was added as a polycondensation catalyst (20 mmol% based on the number of moles of dimethyl 2,6-naphthalenedicarboxylate) and heated to 240 ° C. to distill some ethylene glycol. Thus, a polyester precursor E1 was prepared.
The polyester precursor E1 and the polyester low molecular weight precursor F1 thus obtained were transferred to a polycondensation apparatus having a stirring blade inside. At this time, the polyester low molecular weight precursor F1 was charged so as to be 20 wt% of dimethyl 2,6-naphthalenedicarboxylate. Then, after dissolving and stirring for 10 minutes, the reaction temperature was allowed to reach 290 ° C. over 35 minutes while gradually increasing the degree of vacuum. While maintaining this temperature, the degree of vacuum was kept at 40 Pa, and a polycondensation reaction (abbreviated as PN reaction) was performed. The intrinsic viscosity of the obtained polyester was 0.61 dl / g. The polymer properties of the obtained polyester are shown in Table 1.
The polyester thus obtained is supplied to an extruder and extruded from a die at 300 ° C. (average residence time: 20 minutes) onto a cooling drum having a temperature of 55 ° C. while rotating in a molten state. It was. And between two sets of rollers with different rotation speeds along the film forming direction, the film is heated from above with an IR heater so that the film surface temperature becomes Tg + 25 ° C., and stretching in the longitudinal direction (film forming direction) A uniaxially stretched film was obtained at a magnification of 3.5. Then, this uniaxially stretched film is led to a stenter, a transverse stretching temperature Tg + 30 ° C., a transverse stretching ratio of 3.5 times, heat setting treatment (at 205 ° C. for 10 seconds) and cooling, and a biaxially stretched film having a thickness of 4.5 μm. Got.
Table 1 shows the properties of the obtained biaxially oriented polyester film and the polyester resin constituting it.

[Example 2]
The same operation as in Example 1 was performed except that the preparation with the polyester low molecular weight F1 was changed to 40 wt% of dimethyl 2,6-naphthalenedicarboxylate. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

[Example 3]
The same operation as in Example 1 was performed except that F2 was used in place of the polyester low molecular weight precursor F1 and the addition amount was changed. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

[Comparative Example 1]
The same operation as in Example 1 was performed except that the addition timing of the polyester precursor F1 was changed to the beginning of the transesterification reaction of the polyester precursor E1 in Example 1 and the addition amount was changed. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

[Comparative Example 2]
The same operation as in Example 1 was performed except that the amount of the polyester precursor F1 was changed to F3 and the addition amount was changed. The polycondensation reaction did not proceed, and a high-viscosity polymer could not be obtained, and film formation could not be performed. The obtained polymer physical properties are shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was performed except that the polyester precursor F1 was changed to F4 and the addition amount was changed. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

[Comparative Example 4]
The same operation as in Example 1 was performed except that the addition amount was changed. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

[Comparative Example 5]
When the polyester precursor F1 is polymerized, the precursor F3 is polymerized using 1,4-butanediol instead of 1,6-hexanediol. The same operation as in Example 1 was performed except that the polyester precursor F3 was used instead of the polyester precursor F1. Table 1 shows the polymer properties obtained and the properties of the biaxially stretched film.

In Table 1, the detected amount of component A is an aromatic dicarboxylic acid component, component B is a dimethyl terephthalate or cyclohexane dicarboxylic acid component, component D is a dimer diol component, component C is an ethylene glycol component, DEG is a diethylene glycol component, component B _C Is a component B that is coupled to component C, component B _D is a component B that is coupled to component D, component C _A is a component C that is coupled only to component A, and component C _B is also coupled to component B Component C, Component D _A are Component D bonded to Component A, Component DB _B is Component D bonded to Component B, and Tg is a glass transition temperature.

  The polyester of the present invention and the polyester film using the same have excellent dimensional stability that cannot be achieved by conventional polyethylene terephthalate and polyethylene-2,6-naphthalate, and are particularly required for dimensional stability. It can be suitably used as a base film for high-density magnetic recording media.

Claims (5)

The acid component comprises a 2,6-naphthalenedicarboxylic acid component (component A) and an aromatic or alicyclic dicarboxylic acid component (component B) different from component A, and the glycol component is an ethylene glycol component (component C). A polyester comprising an aliphatic dimer diol component (component D),
The molar ratio of component A to component B is in the range of 80:20 to 95: 5, the molar ratio of component C to component D is in the range of 75:25 to 95: 5, and is bonded to component C Polyester having an intrinsic viscosity of 0.55 or more in which the molar ratio of Component B (Component B _C ) to Component B (Component B _D ) bonded to Component D is in the range of 15:85 to 40:60 resin. The polyester resin according to claim 1, wherein the proportion of component C (component C _A ) bonded only to component A is 90 mol% or more based on the number of moles of component C. The molar ratio of component D (component D _A ) bonded to component A to component D (component D _B ) bonded to component B is in the range of 40:60 to 5:95. Or the polyester resin in any one of 2.   The polyester resin according to any one of claims 1 to 3, wherein a low molecular weight precursor comprising component B and component D having a number average molecular weight of 1,500 to 10,000 is used.   The polyester film which consists of a polyester resin in any one of Claims 1-4.