JP2000239501A - Polyethylene naphthalate composition - Google Patents

Abstract

(57) [Problem] To have excellent tear resistance and high Young's modulus,
Further, to provide a film having both excellent hue and transparency, and a polyethylene naphthalate composition capable of providing a fiber having improved bending fatigue resistance while maintaining high strength and hydrolysis resistance. . SOLUTION: 90-99% by weight of polyethylene naphthalate having naphthalenedicarboxylic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component, and aromatic polyesters 1-10 having a glass transition temperature in a range of 130-200 ° C. % By weight with a polymer blend.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene naphthalate composition, and more particularly, to a film having excellent tear resistance and mechanical strength, excellent knot strength,
The present invention relates to a polyethylene naphthalate composition capable of forming a fiber having a tensile strength.

[0002]

2. Description of the Related Art Polyethylene naphthalate has excellent mechanical properties and chemical properties, especially from properties such as high strength, high Young's modulus, dimensional stability, hydrolysis resistance, heat resistance and gas barrier properties. Widely used for films, fibers and the like.

However, since polyethylene naphthalate has a rigid molecular structure, molded articles have various problems. For example, in the case of polyethylene naphthalate film, delamination (delamination) easily occurs in the film. The delaminated part may be whitened,
Further, since the tear resistance of the film is low, there is a problem in that tearing occurs in the production process of the biaxially stretched film.

[0004] Polyethylene naphthalate fibers are used for tire cords and canvases because of their high strength, high elastic modulus and hydrolysis resistance. However, due to their low elongation and toughness, fatigue resistance, especially bending fatigue, is low. Physical properties such as friction and fatigue are extremely low, and are not suitable for long-term use.

To solve these problems, for example, Japanese Patent Application Laid-Open No. 8-104742 and Japanese Patent Application Laid-open No.
In Japanese Patent Application Laid-Open Publication No. H11-264, a technique of copolymerizing a bisphenol compound with polyethylene naphthalate is proposed. However, this technique can reduce the delamination and fatigue resistance, which are the drawbacks of polyethylene naphthalate, but on the contrary, the high strength and high Young's modulus characteristics of polyethylene naphthalate are impaired, and fundamental modification is required. Has not been reached.

[0006] The applicant of the present invention has disclosed in Japanese Patent Laid-Open No. 10-33060.
In JP-A No. 4 (1994), a composition was proposed in which a polyalkylene naphthalate was mixed with a polyimide having a glass transition temperature equal to or lower than the glass transition temperature of the polyalkylene naphthalate. The composition has significantly improved moldability, improved crystallinity, no problems such as bleed-out after molding, and good weather resistance and delamination resistance. However, since polyimide is expensive, there is a problem in terms of cost.

On the other hand, Japanese Patent No. 2505436 proposes to use an anisotropic polyester as a rigid polyester for improvement by a polymer blend of polyethylene naphthalate and a rigid different polyester.

According to the method described in this publication, the anisotropy polyester is copolymerized with polyethylene terephthalate or polyethylene naphthalate to increase the compatibility at the time of blending and to improve the Young's modulus and dimensional stability of the blended polymer. You can. However, when the anisotropic polyester is finally blended with polyethylene naphthalate, the micro-dispersed part by weight of the anisotropic polyester causes delamination and has not been fundamentally modified.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to provide excellent tear resistance and high Young's modulus, and to further provide excellent hue and transparency. Another object of the present invention is to provide a polyethylene naphthalate composition capable of providing a film having both the above characteristics and a fiber having improved bending fatigue resistance while maintaining high strength and hydrolysis resistance.

[0010]

Means for Solving the Problems In view of the above prior art, the present inventors have conducted intensive studies to develop polyethylene naphthalate having improved tear resistance and flex fatigue resistance, and as a result, a specific aromatic compound was obtained. It has been found that blending a polyester can solve the above-mentioned problems of the prior art, and has completed the present invention.

That is, an object of the present invention is to provide 90 to 99% by weight of polyethylene naphthalate having naphthalenedicarboxylic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component, and aromatic polyesters 1 to 1.
A polyethylene naphthalate composition obtained by polymer blending 0% by weight with a polyethylene naphthalate composition, wherein the aromatic polyester has a glass transition temperature in the range of 130 to 200 ° C. be able to.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, a main component of polyethylene naphthalate is polyethylene naphthalate in which a main dicarboxylic acid component is naphthalenedicarboxylic acid and a main glycol component is ethylene glycol. Here, “main” means that the component accounts for 90 mol% or more.

Examples of the naphthalenedicarboxylic acid include 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid is preferred.

In the present invention, it is preferable that the copolymerization amount of the diethylene glycol component in the polyethylene naphthalate is 3 mol% or less based on the total glycol component.

The diethylene glycol component is not added and copolymerized in the form of diethylene glycol or its ester-forming derivative as a copolymer component during the copolymer production reaction, but is produced as a by-product during the production reaction. It is polymerized.

When the copolymerization amount of the diethylene glycol component is 3 mol% or less, the effect of improving tear resistance and bending fatigue as a fiber when formed into a film becomes large, but the crystallinity is impaired, so that mechanical properties are impaired. It is not preferable because the strength is greatly reduced.

The polyethylene naphthalate used in the present invention may contain other dicarboxylic acid at a ratio of not more than 10 mol%, preferably not more than 5 mol% of the total amount of all dicarboxylic acid components, as long as the effects of the present invention are not impaired. The components may be copolymerized. Other dicarboxylic acid components include, for example, terephthalic acid, isophthalic acid, phthalic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfondicarboxylic acid, benzophenonedicarboxylic acid, phenylindanedicarboxylic acid, 5-sulfoxyisophthalic acid metal salt, -Aromatic dicarboxylic acids such as sulfonium isophthalic acid phosphonium salt; and aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid. These may be used alone or in combination of two or more.

The polyethylene naphthalate used in the present invention may contain other glycol components in an amount of, for example, 10 mol% or less, preferably 5 mol% or less of the total amount of all glycol components, as long as the effects of the present invention are not impaired. It may be copolymerized. Other glycol components include, for example, aliphatic glycols such as propylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentylene glycol, polyethylene glycol, cyclohexanediol, and cyclohexanedimethanol. , O-xylylene glycol, m-xylylene glycol, p-xylylene glycol, 1,4
-Bis (2-hydroxyethoxy) benzene, 1,4-
Bis (2-hydroxyethoxyethoxy) benzene,
4,4'-bis (2-hydroxyethoxy) biphenyl, 4,4'-bis (2-hydroxyethoxyethoxy) biphenyl, 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane, 2,2 -Bis [4-
(2-Hydroxyethoxyethoxy) phenyl] propane, 1,3-bis (2-hydroxyethoxy) benzene, 1,3-bis (2-hydroxyethoxyethoxy)
Benzene, 1,2-bis (2-hydroxyethoxy) benzene, 1,2-bis (2-hydroxyethoxyethoxy) benzene, 4,4′-bis (2-hydroxyethoxy) diphenylsulfone, 4,4′-bis Aromatic glycols such as (2-hydroxyethoxyethoxy) diphenylsulfone, hydroquinone, 2,2-bis (4-hydroxyphenyl) propane, resorcinol, catechol, dihydroxynaphthalene, dihydroxybiphenyl, and diphenols such as dihydroxydiphenylsulfone. No. These may be used alone or in combination of two or more.

The molecular structure of the polyethylene naphthalate used in the present invention is substantially a linear structure. However, as long as the effects of the present invention are not impaired, for example, 2 mol% or less, preferably 1 mol%, based on all acid components. % Or less, a polycarboxylic acid or polyhydroxy compound having three or more functional groups, for example, trimellitic acid or pentaerythritol may be copolymerized.

In producing the polyethylene naphthalate of the present invention, the dicarboxylic acid component containing naphthalene dicarboxylic acid and / or a lower alkyl ester thereof as a main component and the glycol component containing ethylene glycol as a main component are polycondensed. It can be produced by reacting.

Preferably, the lower alkyl ester of naphthalenedicarboxylic acid is transesterified with ethylene glycol, and after the transesterification reaction is completed, the resulting reaction product is subjected to polycondensation.

The lower alkyl ester of naphthalenedicarboxylic acid includes, for example, dimethyl ester, diethyl ester and dipropyl ester. Preferably, it is a dimethyl ester.

The aromatic polyester used in the present invention must have a glass transition point of 130 to 200 ° C. When the glass transition point is 130 ° C. or lower, the tear resistance of the film and the bending fatigue of the fiber are not improved, which is not preferable. On the other hand, if the temperature exceeds 200 ° C., the difference in glass transition point with polyethylene naphthalate is too large, and the kneadability at the time of blending is undesirably reduced. The glass transition point is preferably from 135 to 190 ° C.,
It is more preferable that the temperature is 180 ° C.

In the present invention, the glass transition point is from 130 to
As the aromatic polyester in the range of 200 ° C., for example, an aromatic polyester containing a repeating unit represented by the following structural formula (a) or (b) in an amount of 70 mol% or more based on all repeating units of the aromatic polyester Can be mentioned.

[0025]

Embedded image

[0026]

Embedded image

In the above structural formula (a), the main dicarboxylic acid component is a terephthalic acid component and / or 4,4'-diphenyldicarboxylic acid component, and the main glycol component is 2,2 '-[9H-fluorene-9-ylidenebis ( 4,1-phenyleneoxy)] bis [ethanol] component.

The above-mentioned structural formula (b) is obtained from a 4,4′-diphenyldicarboxylic acid component as a main dicarboxylic acid component and a 2,2 ′-[sulfonylbis (p-phenyleneoxy)] bisethanol component as a main glycol component. Polyester.

Here, when the repeating units represented by the structural formulas (a) and (b) in the aromatic polyester of the present invention are 70 mol% or more based on all repeating units of the aromatic polyester, It is particularly preferable because the tear resistance when formed into a film and the bending fatigue resistance when formed into a fiber are further improved. The repeating unit is 75 mol%
More preferably, it is at least 80 mol%.

In order to produce the aromatic polyester represented by the structural formula (a), the terephthalic acid and / or
Or a lower alkyl ester thereof and 4,4'-diphenyldicarboxylic acid and / or a lower alkyl ester thereof, and 2,2 '-[9H-fluoren-9-ylidenebis (4,1-phenyleneoxy)] bis [ethanol]. Is subjected to a direct esterification reaction or transesterification reaction, and after the completion of the direct esterification reaction or transesterification reaction, the resulting reaction product can be produced by polycondensation, but the direct esterification reaction or transesterification reaction is promoted. For example, a method in which a lower glycol such as ethylene glycol is excessively added to directly perform an esterification reaction or a transesterification reaction to remove an excessive lower glycol component during polycondensation is preferably used. When the aromatic polyester represented by the structural formula (b) is produced, 4,4′-diphenyldicarboxylic acid and / or a lower alkyl ester thereof and 2,2 ′-[sulfonylbis (p- Phenyleneoxy)] bisethanol and a direct esterification reaction or transesterification reaction, and after completion of the direct esterification reaction or transesterification reaction, the resulting reaction product may be subjected to polycondensation.

In preparing the polyethylene naphthalate composition of the present invention, the polyethylene naphthalate and the aromatic polyester are blended in a weight ratio of polyethylene naphthalate to polyethylene naphthalate based on the total weight of the polyethylene naphthalate composition. The weight ratio with the aromatic polyester may be 90:10 to 99: 1, and the blending method is not particularly limited.

For example, a method in which an aromatic polyester is added before the completion of the polymerization reaction of polyethylene naphthalate to form chips, a method in which polyethylene naphthalate and aromatic polyester are supplied to a melt kneader such as a uniaxial or biaxial kneader and kneaded. It is also possible to preferably use a method of forming chips, a method of melting and kneading at the time of spinning or film formation, and a method of spinning and forming a film as it is. When using a melt kneader, it may be melt kneaded in a state of chip blending in advance,
The polymer to be blended may be quantitatively fed into the kneader using a kneader provided with a quantitative feeder and melt-kneaded.

The intrinsic viscosity of the polyethylene naphthalate composition according to the present invention is not particularly limited, but it is determined in a phenol / tetrachloroethane mixed solvent (weight ratio 6: 4) at 35 ° C.
It is preferable that the intrinsic viscosity measured in the above is in the range of 0.4 to 1.2, and when it is in this range, the mechanical strength and moldability when the composition is formed into a molded product is further increased. Can be compatible. The intrinsic viscosity is, in particular, 0.5 to
It is preferably within the range of 1.1.

The polyethylene naphthalate composition of the present invention may contain, if necessary, a lubricant, a pigment, a dye, an antioxidant, a light stabilizer, as long as the object of the present invention is achieved.
Additives such as a heat stabilizer, a light-shielding agent, a matting agent and the like can be blended.

There is no particular limitation on the production of fibers using the polyethylene naphthalate composition of the present invention, and it can be produced by a conventionally known method for producing ordinary polyester fibers. , A method of continuous drawing without winding the undrawn yarn once, a method of melt-spinning at a spinning speed of 5,000 m / min or more, and omitting the drawing process. After the undrawn yarn is cooled and solidified in the above, a method of drawing in a heating medium or under contact heating such as a heating roller or by a non-contact type heater is adopted. Further, at the time of melt spinning, a hydrolysis inhibitor such as carbodiimide and a chain extender such as bisoxazoline may be added.

The drawing temperature when the fiber of the present invention is drawn into a drawn yarn may be set to a glass transition point of polyethylene naphthalate or higher and a glass transition point of aromatic polyester or lower. Although it depends on the respective glass transition points of phthalate and aromatic polyester, it is preferably carried out at 125 ° C. to 150 ° C., and the obtained drawn yarn has a Young's modulus of 1900 to 4
000 kg / mm ² and knot strength of 3.5 to 1
0.0 g / De.

In order to produce a film using the polyethylene naphthalate composition of the present invention, a conventionally known film forming method can be used. For example, the composition is melted, extruded into a sheet, and then cooled with a cooling drum. The film can be produced by cooling to obtain an unstretched film, and then stretching the unstretched film in the biaxial direction, heat-setting, and if necessary, heat-relaxing. At this time, since the surface characteristics, density, and heat shrinkage of the film vary depending on the stretching conditions and other manufacturing conditions, the film is formed by appropriately selecting the conditions as needed.

The stretching temperature at the time of stretching the film of the present invention to produce a biaxially oriented film may be set at a glass transition point of polyethylene naphthalate or higher and a glass transition point of aromatic polyester or lower. Depends on the respective glass transition points of polyethylene naphthalate and aromatic polyester, but is substantially 125 ° C.
To 150 ° C., and the obtained biaxially oriented film has a biaxial Young's modulus of 500
２０００2000 kg / mm ² , and the tear strength is within the range of the following formula.

[0039]

(Equation 2)

[0040]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by these examples. In addition, each value in an Example was calculated | required by the following method.

(1) Intrinsic viscosity: Measured in a phenol / tetrachloroethane (weight ratio 6: 4) mixed solvent at 35 ° C. according to a conventional method.

(2) Content of diethylene glycol (DEG): The polymer was decomposed using hydrazine hydrate and subjected to gas chromatography (“263-7” manufactured by Hitachi, Ltd.).
0 ").

(3) Strong elongation, knot strength (fiber): JIS
The measurement was performed according to the method described in L1070.

(4) Young's modulus (film): JIS K
According to the method described in 7127, the Young's modulus in the machine direction (MD) and the transverse direction (TD) was measured.

(5) Tear strength (film): JIS K
According to the method described in 7128, the measurement was carried out for the tear strength in the machine direction (MD) and the transverse direction (TD).

Reference Example 1 Production of aromatic polyester (a): 50 parts by weight of dimethyl terephthalate, 101.6 parts by weight of 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, ethylene glycol 32 0.5 parts by weight and 0.35 parts by weight of tetrabutoxytitanate as a catalyst were charged into a reaction vessel equipped with a distillation apparatus, and the reaction product was placed in a nitrogen gas atmosphere at 150 ° C.
The temperature was raised from 220 ° C. to 220 ° C., and a transesterification reaction was performed for 200 minutes. After completion of the transesterification reaction, the transesterification reaction product was transferred to a reaction vessel equipped with a stirrer, a nitrogen inlet, a reduced pressure port, and a distillation apparatus and heated to 260 ° C., and at normal pressure for about 5 minutes at 15 to 20 mmHg. About 30 minutes, 0.1m
The temperature was raised to 285 ° C. at mHg to carry out a polycondensation reaction, and after reaching a predetermined melt viscosity, chips were formed by a conventional method. The glass transition temperature of the obtained aromatic polyester (a) is 1
At 51 ° C., the intrinsic viscosity was 0.41.

Reference Example 2 Production of aromatic polyester (b): 70 parts by weight of dimethyl 4,4'-diphenyldicarboxylate, 4,4'-bis (2-hydroxyethoxy) diphenyl sulfone
9 parts by weight, 32.5 parts by weight of ethylene glycol, and 0.35 part by weight of tetrabutoxytitanate as a catalyst were charged into a reaction vessel equipped with a distillation apparatus, and the temperature of the reaction product was raised from 150 ° C. to 220 ° C. under a nitrogen gas atmosphere. Then 200
The transesterification was performed for minutes. After completion of the transesterification reaction, the transesterification reaction product was stirred, a nitrogen inlet,
Transfer to a reaction vessel heated to 260 ° C. equipped with a decompression port and a distillation apparatus, about 5 minutes at normal pressure, about 30 at 15-20 mmHg.
Then, the temperature was raised to 285 ° C. at 0.1 mmHg to perform a polycondensation reaction, and after reaching a predetermined melt viscosity, chips were formed by a conventional method. The glass transition temperature of the obtained polyester was 142 ° C., and the intrinsic viscosity was 0.45.

Example 1 Production of polyethylene naphthalate composition: naphthalene-
100 parts by weight of 2,6-dicarboxylic acid dimethyl ester,
After subjecting 60 parts by weight of ethylene glycol to a transesterification reaction using 0.03 parts by weight of manganese acetate tetrahydrate as a transesterification catalyst according to a conventional method, 0.023 parts by weight of trimethyl phosphate is added, and substantially The transesterification was terminated.

Then, 0.024 parts by weight of antimony trioxide was added, and a polycondensation reaction was subsequently carried out in a conventional manner under a high temperature and high vacuum. 2.5 parts by weight of Group A polyester (a) was added to obtain a polyethylene naphthalate composition having an intrinsic viscosity of 0.61 dl / g and a DEG copolymerization amount of 1.3 mol%.

Yarn production: A pellet of this polyethylene naphthalate composition was dried at 180 ° C. for 3 hours, and had a pore size of 0.27.
Melt spinning was performed at 310 ° C. using a die having 6 mm holes, and the spinning was performed at 400 m / min. This undrawn yarn is drawn 6 times on a supply roller heated to 150 ° C., and then heat-treated at a constant length on a hot plate heated to 240 ° C.
A drawn yarn of 0 de / 6 fill was obtained. Table 1 shows the properties of the obtained drawn yarn.

Film formation: The pellets of the polyethylene naphthalate composition were dried at 180 ° C. for 3 hours, then supplied to an extruder popper, melted at a melting temperature of 300 ° C., and passed through a 1 mm slit die at a surface temperature of 40 ° C. It was extruded on a rotating cooling drum to obtain an unstretched film. The unstretched film thus obtained is preheated at 120 ° C., and the IR at 900 ° C. from 15 mm above between low-speed and high-speed rolls.
The film was heated by a heater and stretched 3.6 times in the machine direction, then supplied to a stenter, and stretched 4.6 times in the transverse direction at 140 ° C. The obtained biaxially oriented film was heat-set at a temperature of 210 ° C. for 5 seconds to obtain a biaxially oriented film having a thickness of 10 μm. Table 1 shows the properties of the obtained biaxially oriented film.

[Embodiment 2] In Embodiment 1, reference example 1
The same operation was carried out except that the amount of the polyester prepared in the above was changed to 5 parts by weight, and the intrinsic viscosity was 0.60 dl /.
g, a polyethylene naphthalate composition having a DEG copolymerization amount of 1.3 mol%. The obtained polyethylene naphthalate composition was formed into a thread and a film in the same manner as in Example 1. Table 1 shows the results.

Example 3 The same procedure as in Example 1 was repeated except that 2.5 parts by weight of the polyester prepared in Reference Example 2 was added as the aromatic polyester to obtain an intrinsic viscosity of 0.61 dl / g. Thus, a polyethylene naphthalate composition having a DEG copolymerization amount of 1.4 mol% was obtained. The obtained polyethylene naphthalate composition was formed into a thread and a film in the same manner as in Example 1. Table 1 shows the results.

Example 4 Using 100 parts by weight of dimethyl naphthalene-2,6-dicarboxylate and 60 parts by weight of ethylene glycol, and using 0.03 parts by weight of manganese acetate tetrahydrate as a transesterification catalyst, in a conventional manner. After transesterification according to the following procedure, trimethyl phosphate was added.
023 parts by weight was added to substantially terminate the transesterification reaction.

Then, 0.024 parts by weight of antimony trioxide was added, and a polycondensation reaction was carried out by a conventional method under a high temperature and a high vacuum, followed by an intrinsic viscosity of 0.62 and a DEG copolymerization amount of 1.2 mol. % Of polyethylene naphthalate homopolymer and 2.5 parts by weight of the aromatic polyester produced by the procedure of Reference Example 1 were melt-kneaded at 300 ° C. for 12 minutes under a high vacuum using a vented twin-screw extruder. A polyethylene naphthalate composition having an intrinsic viscosity of 0.60 dl / g and a DEG copolymerization amount of 1.2 mol% was obtained. The obtained polyethylene naphthalate composition was subjected to spinning in the same manner as in Example 1,
A film was formed. Table 1 shows the results.

COMPARATIVE EXAMPLE 1 The same procedure as in Example 1 was repeated except that no aromatic polyester was added, to obtain a polyethylene resin having an intrinsic viscosity of 0.62 dl / g and a DEG copolymerization amount of 1.2 mol%. A phthalate homopolymer was obtained.
The obtained polyethylene naphthalate homopolymer was formed into a thread and a film in the same manner as in Example 1. Table 1 shows the results.

[Comparative Example 2] In Example 1, the aromatic polyester had an intrinsic viscosity of 0.65 and a DEG amount of 1.1.
The same operation was performed except that 2.5 parts by weight of polyethylene terephthalate was added in an amount of 0.62 mol%.
A polyethylene naphthalate composition having a dl / g of 1.2 mol% of the DEG copolymer was obtained. The obtained polyethylene naphthalate composition was formed into a thread and a film in the same manner as in Example 1. Table 1 shows the results.

[0058]

[Table 1]

As is clear from Table 1, the fibers and films comprising the polyethylene naphthalate composition of the present invention had high knot strength and delamination resistance while maintaining high strength and high Young's modulus.

[0060]

Industrial Applicability The polyethylene naphthalate composition of the present invention has excellent tear resistance and high Young's modulus, a film having both excellent hue and transparency, and high strength and hydrolysis resistance. Fiber with improved flex fatigue resistance can be formed while maintaining the same, the obtained fiber can be suitably used for tire cord, canvas, etc., and the film can be used for photographic film, magnetic film, insulation It can be suitably used for a wide range of applications such as film applications.

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Claims (7)

[Claims] 1. A polyethylene blend obtained by polymer blending 90 to 99% by weight of polyethylene naphthalate having naphthalene dicarboxylic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component, and 1 to 10% by weight of an aromatic polyester. A phthalate composition, wherein the aromatic polyester has a glass transition temperature of 130 to 20.
A polyethylene naphthalate composition, which is in the range of 0 ° C. 2. The polyethylene naphthalate composition according to claim 1, wherein the aromatic polyester is a polyester containing at least 70 mol% of a repeating unit represented by the following structural formula (a) based on all repeating units. Embedded image 3. The polyethylene naphthalate composition according to claim 1, wherein the aromatic polyester is a polyester containing a repeating unit represented by the following structural formula (b) in an amount of 70 mol% or more based on all repeating units. Embedded image 4. A fiber obtained by subjecting a fiber formed by melt-spinning the polyethylene naphthalate composition according to claim 1 to a glass transition temperature of polyethylene naphthalate or higher and a glass transition temperature of aromatic polyester or lower. 5. A Young's modulus of 1900 to 4000 kg / m.
m ² and the knot strength is 3.5 to 10.0 g / De.
The fiber according to claim 4, which is: 6. A film formed by melt-forming the polyethylene naphthalate composition according to claim 1 and biaxially stretching the glass transition temperature of the polyethylene naphthalate to the glass transition temperature of the aromatic polyester or lower. the film. 7. The film according to claim 6, wherein the Young's modulus in the biaxial direction of the film is 500 to 2000 kg / mm ² , and the tear strength satisfies the following equation. (Equation 1)