JPH10338757A - Polyester film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject low oligomeric polyester film that is excellent in long-term heat resistance and in productivity and can be used for motor insulation for refrigerator or a variety of electric insulation uses by using a non-liquid crystal polymer and a polyester copolymer. SOLUTION: This objective polyester film comprises (A) <=0.5 wt.%, preferably <=0.35 wt.% of a non-liquid crystal polyester (this polyester is mainly constituted with an aromatic dicarboxylic acid, an alicyclic carboxylic acid or an aliphatic dicarboxylic acid and diols and (B) 0.01-5 wt.%, preferably 0.1-1 wt.% of a polyester copolymer bearing mesogen groups in the main chain (a polyester copolymer comprising aromatic oxycarbonyl units and aromatic dioxy units) and has <=140 deg.C, preferably <=130 deg.C of the heat-up crystallization temperature, 0.6-2.5 dl/g (preferably 0.8-1.5 dl/g of intrinsic viscosity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyester film. More specifically, the present invention relates to a polyester film having excellent long-term heat resistance, high productivity, and low oligomers, which is used for motor insulation applications such as refrigerators and various electrical insulation applications.

[0002]

2. Description of the Related Art In general, polyester films used for electrical insulation have a high molecular weight, so that the driving current value during extrusion and the filtration pressure are increased, so that the discharge amount per unit time is increased to improve productivity. It was difficult to do. Further, since polyester is decomposed at the time of extrusion, it has been difficult to obtain a film having low oligomer and excellent long-term heat resistance.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyester film having a long-term heat resistance, a low oligomer and excellent productivity in order to overcome the above-mentioned problems in the prior art. .

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have added a copolymerized polyester (B) having a mesogen group in the main chain to a non-liquid crystalline polyester (A), The relationship between the thermal properties, long-term heat resistance, amount of oligomer, etc. and the composition, melt viscosity, and amount of the copolymerized polyester (B) to be added was intensively studied. as a result,
The specific copolyester (B) is added to the non-liquid crystalline polyester (A) and biaxially stretched so that the total stretching ratio in the machine direction and transverse direction is 9 to 15 times. And the first stage heat treatment is at least 205 ° C.
When the final heat treatment is performed at a temperature lower than the melting point of the non-liquid crystalline polyester (A) at 120 to 180 ° C., the crystallization temperature of the non-liquid crystalline polyester (A) is lowered and the non-liquid crystalline polyester (A) It has been found that the copolymer polyester (B) dispersed in (1) increases the adhesion between the (A) phase and the (B) phase, or that a film having excellent long-term heat resistance can be obtained, and has completed the present invention. . That is, the polyester film of the present invention comprises a non-liquid crystalline polyester (A)
And a copolymer polyester (B) containing a mesogen group in the main chain, and the film has a heated crystallization temperature of 140
The invention is based on a polyester film having an intrinsic viscosity of 0.6 to 2.5 dl / g or less and a method for producing the same.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a typical non-liquid crystalline polyester (A) constituting the polyester film of the present invention, an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol are mainly used. Polyester as a component. As the aromatic dicarboxylic acid component, for example, terephthalic acid, isophthalic acid, phthalic acid,
1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,
4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid and the like can be used, and among them, terephthalic acid, phthalic acid, 2,6- Naphthalenedicarboxylic acid can be used. As the alicyclic dicarboxylic acid component, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components are 1
Only one kind may be used, or two or more kinds may be used in combination. Further, an oxyacid such as hydroxyethoxybenzoic acid may be partially copolymerized. As the diol component, for example, ethylene glycol, 1,2-propanediol,
1,3-propanediol, neopentyl glycol,
1,3-butanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2, 2′-bis (4′-β-hydroxyethoxyphenyl) propane or the like can be used, and among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol, etc. are preferably used. And particularly preferably, ethylene glycol or the like can be used. These diol components may be used alone or in combination of two or more. In addition, polyesters may include other compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, monofunctional compounds such as 2,4-dioxybenzoic acid, lauryl alcohol, and phenyl isocyanate. It may be copolymerized within the range of the shape.

Among these, the average molecular weight of the polyalkylene glycol or polyether dicarboxylic acid is preferably from 400 to 40,000, more preferably 60 to 40,000.
0 to 20,000, more preferably 1,000 to 10,000
It is. Of course, a copolymer comprising a plurality of aromatic dibasic acids and a plurality of glycols may be used.

The non-liquid crystalline polyester (A) used in the present invention may contain, if necessary, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a dye, a fatty acid ester, a wax, etc. Or an antifoaming agent such as polysiloxane. In addition, clay, mica, titanium oxide, calcium carbonate, carion, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina, zirconia, etc., for imparting lubricity, abrasion resistance and scratch resistance Inorganic particles, acrylic acid, organic particles containing styrene, etc. as components, or so-called internal particles precipitated by a catalyst or the like added at the time of polyester polymerization reaction, or containing a surfactant. be able to.

The copolymer polyester (B) containing a mesogen group (liquid crystalline structural unit) in the main chain used in the present invention is:
It is a melt-moldable polymer and may be a liquid crystalline polyester or a non-liquid crystalline polyester. Specifically, it is a copolymer polyester comprising a structural unit selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, an aromatic dicarbonyl unit, an alkylenedioxy unit and the like.

Preferred examples of the copolymerized polyester (B) used in the present invention include the following (I), (II) and (III)
And a copolymerized polyester comprising the structural unit of (IV),
At least one selected from copolymerized polyesters composed of structural units (I), (III) and (IV) and copolymerized polyesters composed of structural units (I), (II) and (IV) is used. Can be

[0010]

Embedded image (However, R ₁ in the formula is

Embedded image And R ₂ is

Embedded image R ₃ represents one or more groups selected from

Embedded image Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit [(II) + (III
)] And the structural unit (IV) are substantially equimolar. ) The structural unit (I) is p-hydroxybenzoic acid and / or
Or a structural unit of a polyester formed from 6-hydroxy-2-naphthoic acid, wherein the structural unit (II) is 4, 4 ′
-Dihydroxybiphenyl, 3,3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydro The structural unit formed from an aromatic dihydroxy compound selected from xinaphthalene, 2,2'-bis (4-hydroxyphenyl) propane and 4,4'-dihydroxydiphenyl ether, and the structural unit (III) was formed from ethylene glycol. Structural unit, structural unit (IV)
Is terephthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
Selected from 1,2-bis (phenoxy) ethane-4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid and 4,4'-diphenyletherdicarboxylic acid The structural units formed from the aromatic dicarboxylic acids are shown below.

In the case of the copolymerized polyester comprising the above structural units (I), (II) and (IV), R ₁ is

Embedded image And R ₂ is

Embedded image And at least one selected from the R ₃

Embedded image Those which are at least one kind selected from

In the case of a copolymerized polyester comprising the above structural units (I), (II) and (IV), R ₁ is

Embedded image And R ₃ is

Embedded image Is particularly preferred.

The structural units (I), (II) and (II)
In the case of the copolymerized polyester consisting of I) and (IV), R ₁ is

Embedded image And R ₂ is

Embedded image And R ₃ is

Embedded image Is particularly preferred.

In the present invention, the copolymerization amount is calculated from the molar ratio of repeating structural units capable of forming a polymer, and is expressed in mol%. In the case of the preferred copolymerized polyester, the structural unit (I), the structural unit (II) + (IV), and the structural unit (III)
And (IV) are repeating structural units capable of forming a polymer, and the copolymerization amount can be calculated from the copolymerization molar ratio. Structural units (I), (II) + (IV), (III) + (I
Although the copolymerization molar ratio of V) is arbitrary, when the copolymerization amount of the mesogen group is 5 to 95 mol%, the polymer is dispersed in the non-liquid crystalline polyester, and the long-term heat resistance becomes good. When the copolymerization amount of the structural units (I) and (II) + (IV), which are mesogen groups, is lower than 5 mol%, it is difficult to obtain the effect of suppressing shear heat generation in the extrusion step by improving the fluidity of the polymer, and foreign substances are not easily obtained. And the amount of oligomer increases. Further, if it is higher than 95 mol%, the dispersibility decreases, and the long-term heat resistance deteriorates.
It becomes difficult to obtain an excellent film for electrical insulation.

When the copolymerization amount of the mesogen group is reduced, the ability to form an anisotropic molten phase, ie, liquid crystallinity, is weakened, but the compatibility with the non-liquid crystalline polyester (A) is increased. The dispersibility is improved, and the long-term heat resistance of the film is improved. However, if the copolymerization amount of the mesogen group is lower than 5 mol%, the liquid crystallinity becomes too weak, and it becomes difficult to obtain a film having good long-term heat resistance intended in the present invention, which is not preferable.

From the above, it is preferable that the copolymerized polyester (B) of the present invention has the following copolymerization amount.

In the case of a copolymerized polyester comprising the above structural units (I), (II), (III) and (IV), [(I) with respect to the above structural unit [(I) + (II) + (III)] ) + (II)] is preferably from 5 to 95% by mole, more preferably from 15 to 80% by mole, and still more preferably from 20 to 70% by mole. In addition, the structural unit [(I) +
(II) + (III)] has a molar fraction of 95
-5 mol% is preferable, 85-20 mol% is more preferable, and 80-30 mol% is still more preferable. Also,
The molar ratio of the structural units (I) / (II) is preferably from 75/25 to 95/5 from the viewpoint of fluidity, more preferably from 7/25 to 95/5.
8/22 to 93/7. The number of moles of the structural unit (IV) is substantially equal to the total number of moles of the structural unit [(II) + (III)].

In the case of a copolymerized polyester comprising the structural units (I), (III) and (IV), the structural unit (I) is 5 to 95 mol% of [(I) + (III)].
Is preferably 15 to 80 mol%, and more preferably 20 to 70 mol%. Structural unit (IV)
Is substantially equimolar to the structural unit (III).

Further, in the case of the copolymerized polyester comprising the above structural units (I), (II) and (IV), the copolymerized polyester is not used alone, but is used for the structural units (I), (II), (III) and (IV)
And / or a blend polymer of a copolymerized polyester composed of the structural units (I), (III) and (IV).
Also in the case of this blend polymer, as described above,
The molar fraction of [(I) + (II)] to the structural unit [(I) + (II) + (III)] is preferably from 5 to 95 mol%, more preferably from 15 to 80%, even more preferably from 20 to 20 mol%. ~ 70 mol%.

The term "substantially" in the above description means that the number of the terminal groups of the polyester can be increased to either the carboxyl group terminal or the hydroxyl terminal group, if necessary. This is because the number of moles of the structural unit (IV) is not completely equal to the total number of moles of the structural unit [(II) + (III)].

In the polycondensation of the preferred copolymerized polyester, 3,3'-diphenyldicarboxylic acid, 2,2,
Aromatic dicarboxylic acids such as' -diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecandioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, Aromatic diols such as 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, 1,4-butanediol,
1,6-hexanediol, neopentyl glycol,
Aliphatic, alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and m
-Hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 2,6-hydroxynaphthoic acid, and p-aminophenol, p-aminobenzoic acid, etc. are further copolymerized in a small proportion that does not impair the object of the present invention. be able to.

The method for producing the copolymerized polyester in the present invention is not particularly limited, and it can be produced according to a polycondensation method of various polyesters.

For example, in the method for producing the above-mentioned preferably used copolymerized polyester, the structural unit (III)
When the compound does not contain (1) and (2), the following (3) production method is preferable when the compound contains the structural unit (III).

(1) p-acetoxybenzoic acid and 4,
A method of producing from a diacylated aromatic dihydroxy compound such as 4'-diacetoxybiphenyl, 4,4'-diacetoxybenzene and an aromatic dicarboxylic acid such as terephthalic acid by a deacetic acid polycondensation reaction.

(2) p-hydroxybenzoic acid and 4,
A method of reacting an aromatic dihydroxy compound such as 4'-dihydroxybiphenyl and hydroquinone, and an aromatic dicarboxylic acid such as terephthalic acid with acetic anhydride to acylate a phenolic hydroxyl group, followed by a deacetic acid polycondensation reaction.

(3) Polyester polymers such as polyethylene terephthalate, oligomers or bis (β-
(Hydroxyethyl) terephthalate or the like, in the presence of bis (β-hydroxyethyl) ester of an aromatic dicarboxylic acid, by the method of (1) or (2).

Although these polycondensation reactions proceed without a catalyst, it is sometimes preferable to add a metal compound such as stannous acetate, tetrabutyl titanate, potassium acetate and sodium acetate, antimony trioxide and metallic magnesium. .

The polyester film of the present invention is required to have a heated crystallization temperature of 140 ° C. or less. It is preferably at most 135 ° C, more preferably at most 130 ° C. If the temperature-rise crystallization temperature is higher than 140 ° C., it is considered that some interaction between the non-liquid crystalline polyester and the copolymerized polyester is reduced, and the long-term heat resistance is deteriorated.

The polyester film of the present invention needs to have an intrinsic viscosity [η] of 0.6 to 2.5 (dl / g), preferably 0.7 to 2 (dl / g), and more preferably 0.7 to 2 (dl / g). Preferably, it is 0.8 to 1.5 (dl / g). When the intrinsic viscosity [η] is less than 0.6 (dl / g), it is difficult to obtain a film having good long-term heat resistance, and the amount of oligomer (cyclic trimer) tends to increase. Is not preferred. On the other hand, the intrinsic viscosity is 2.5
It is difficult to substantially form a film larger than (dl / g).

The method for producing the polyester film of the present invention is not particularly limited, but the non-liquid crystalline polyester (A)
And a resin composition comprising a copolymerized polyester (B) containing a mesogen group in the main chain is melt-extruded into a sheet and then biaxially stretched so that the total stretching ratio in the longitudinal and transverse directions is 9 to 15 times. After stretching, it is preferable to perform heat treatment in multiple stages. Surprisingly, long-term heat resistance is improved when the heat treatment is performed at another stage. The multi-step heat treatment may be performed in either a temperature increasing step or a temperature decreasing step, but is preferably performed in a temperature decreasing step. Particularly preferred is a manufacturing method in which the first-stage heat treatment is performed at 205 ° C. or higher and lower than the melting point of the non-liquid crystalline polyester (A), and the final-stage heat treatment is performed at 120 to 180 ° C. The total stretching ratio in the machine direction and transverse direction is 9
If it is smaller than twice, exceeds 15 times, or heat treatment is performed in only one stage, the long-term heat resistance deteriorates, and thus it is not preferable to use as an electrical insulating material.

The copolyester (B) in the present invention
Is not particularly limited, but has a melt viscosity of 0.1 to 100 P
a · sec, preferably 0.1 to 15 Pa · sec or less, more preferably 0.1 to 3 Pa · sec. A low-viscosity copolymerized polyester (B), that is, a copolymerized polyester that increases the melt viscosity ratio (melt viscosity of non-liquid crystalline polyester (ηA) / melt viscosity of copolymerized polyester (ηB)) is preferable. The lower the viscosity of the non-liquid crystalline polyester, the better the dispersion of the copolymerized polyester, the lower the oligomers, and the better the long-term heat resistance (the elongation at break is required to decrease to half that before heat treatment). Time) can be effectively achieved. The melt viscosity ratio is not particularly limited, but is preferably at least 5 or more, more preferably 10 or more, and more preferably 50 or more.
The number is particularly preferably 200 or more. According to the findings of the present inventors, it is most preferably 200 or more and 100,000 or less.

The copolymerized polyester having such a low melt viscosity and particularly suitably used for achieving the object of the present invention includes the structural units (I), (II) and (II).
It is a copolymerized polyester consisting of I) and (IV).

The polyester film of the present invention is not particularly limited, but when the polyester film is heat-treated in an atmosphere of 200 ° C., the elongation at break in the longitudinal direction and the width direction of the film is reduced to half that before the heat treatment. Is preferably 20 hours or more. Preferably 25
The time is at least 30 hours, more preferably at least 30 hours. The polyester film of the present invention is often used at a high temperature, and the time required for the elongation at break to be reduced to half of that before heat treatment is less than 20 hours, for example, when used for a motor portion, It deteriorates during long-term use, and cannot be used.

The content of the non-liquid crystalline polyester (A) cyclic trimer in the polyester film of the present invention is as follows:
Although not particularly limited, it is 0.5% by weight or less, more preferably 0.4% by weight or less, and particularly preferably 0.35% by weight.
It is as follows. When the content of the cyclic trimer is more than 0.5% by weight, when used as an electrical insulating film, the cyclic trimer precipitates on the motor during long-term use,
Problems such as accumulation and becoming unusable may occur.

The amount of the copolyester (B) added to the polyester film of the present invention is not particularly limited, but is 0.01 to 5% by weight, preferably 0.05 to 3% by weight, and more preferably 0.1 to 3% by weight. A range of 1% by weight is good.
If the addition amount is less than 0.01% by weight, it becomes difficult to obtain a film having good long-term heat resistance. On the other hand, if it exceeds 5% by weight, the surface of the polyester film becomes very rough and the surface roughness becomes large. It is not preferable as an electrically insulating film because it is easy to work and the processing characteristics are easily deteriorated.

The dispersibility of the copolymerized polyester (B) in the polyester film of the present invention also varies depending on the screw used during melt extrusion. In the present invention, the screw may be a screw having any shape, such as full flight and barrier flight, but promotes the dispersion of the copolymerized polyester and improves the long-term heat resistance of the film.
In order to reduce the haze value, it is preferable to use various mixing type screws having a ratio (L / D) of the length (L) to the diameter (D) of the screw of 20 or more. The mixing type screw is a screw having a mixing part at a screw compression part, a measuring part or an intermediate position between them, for example, a fluted barrier, a dalmage,
A screw having a unimelt, a multi-pin, or the like is used.

The form of dispersion of the copolymerized polyester (B) in the polyester film is not particularly limited, but is preferably a dispersion form such as a skin core type, a sea-island type, a multilayer type, a fiber type, a spherical shape, and an oblate spherical shape. The average dispersion diameter of the copolymerized polyester (B) is not particularly limited, but is preferably 2 μm or less,
More preferably 0.5 μm or less, most preferably 0.1 μm.
3 μm or less. If the average dispersion diameter is larger than 2 μm, the long-term heat resistance of the polyester film tends to decrease, which is not preferable. When the domains of the copolymerized polyester are oblate, the aspect ratio (L / D) of the long axis to the uniaxial of the oblong domains is not particularly limited, but is 2.
0 or less, more preferably 10 or less, and most preferably 5
It is as follows.

The polyester film of the present invention is not particularly limited. In addition to the non-liquid crystalline polyester (A) and the copolymerized polyester (B), polyethylene terephthalate may be used as a compatibilizer for the non-liquid crystalline polyester and the copolymerized polyester. (Hereinafter referred to as “PET”) and a copolymer of p-hydroxybenzoic acid (hereinafter referred to as “PHB”), a copolymer of polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as “PEN”) and PHB, and the like. A compound or the like may be contained. It is preferable to add a compatibilizer because the dispersibility of the copolymerized polyester (B) is improved and the long-term heat resistance is easily improved. PET / PHB copolymer, P
The ratio of PET and PEN of the EN / PHB copolymer is not particularly limited, but is preferably 50 to 50 from the viewpoint of compatibility.
Preferably it is 95 mol%. The content of the compatibilizer in the polyester film is not particularly limited, but is preferably 1 to 50% of the content of the copolymerized polyester (B).

The polyester film of the present invention is not particularly limited, but is a film in which the above composition is biaxially oriented. A uniaxial or non-oriented film is not preferable because long-term heat resistance becomes poor.

The polyester film of the present invention is not particularly limited, but is usually a film having a thickness of 1000 μm or less, preferably 3 to 500 μm, more preferably 5 to 500 μm.
The range is from 0 to 300 μm.

The polyester film of the present invention may be blended with another polymer as long as the object of the present invention is not impaired.

The polyester film of the present invention may be a single film, but may have another polymer layer, such as polyester,
Polyolefin, polyamide, polyvinylidene chloride, acrylic polymer, etc. may be laminated.

The polyester film of the present invention is particularly effective for electrical insulation, but can also be used for magnetic recording media, capacitors, photographs, packaging, drawings, ribbons and the like.

Next, a preferred example of the method for producing a polyester film of the present invention will be shown and described, but the present invention is not necessarily limited thereto.

First, as a method for producing the non-liquid crystalline polyester, various methods can be adopted in this field. For example, a direct esterification reaction of terephthalic acid and a small amount of other dicarboxylic acid components with ethylene glycol and a small amount of other glycol components, or a transesterification reaction with a glycol component when a dialkyl ester of a dicarboxylic acid component is used. By heating this under reduced pressure to remove the excess glycol component, a chip of non-liquid crystalline polyester (A) having an intrinsic viscosity of about 0.5 can be obtained. At this time, it is preferable to use a transesterification catalyst or a polymerization reaction catalyst, or to add a stabilizer, if necessary. It is preferable to use an antimony compound as the polymerization catalyst and to use a phosphorus compound as the stabilizer. Antimony trioxide or the like is used as the antimony compound. As the phosphorus compound, a phosphonate such as dimethylphenylphosphonate is used. The polymerization temperature is preferably as low as possible as long as the polymerization state can be maintained. Of course, a coloring inhibitor, an antioxidant, a crystal nucleating agent, a lubricant, a stabilizer, an antiblocking agent, an ultraviolet absorber, an antifoaming agent, an antistatic agent and the like may be added. This chip is subjected to solid phase polymerization under reduced pressure. In case of solid phase polymerization, 1
After pre-crystallization at a temperature of 80 ° C. or lower, 190 to 25
Solid phase polymerization is performed at 0 ° C. under a reduced pressure of about 1 mmHg for 10 to 100 hours to increase the intrinsic viscosity.

A non-liquid crystalline polyester chip (A) and a copolymerized polyester chip (B) having a mesogen group in the main chain at a predetermined ratio are put into a vacuum dryer, and are subjected to reduced pressure in order to suppress hydrolysis. After sufficiently drying at 180 ° C. for 10 hours, the mixture is supplied to a melt extruder and extruded while being degassed to suppress the decomposition of polyester, and is extruded into a sheet from a slit die at a draft ratio of 5 to 100, and is then cast. The above is cooled and solidified to form an unstretched film.

Before being put into the vacuum dryer, the copolymerized polyester (B) may be dispersed in the raw material of the non-liquid crystalline polyester (A). As a method for dispersing the copolymerized polyester in the non-liquid crystalline polyester raw material, first, the non-liquid crystalline polyester chip and the copolymerized polyester chip are mixed and melted using a vented twin-screw extruder while sealing with nitrogen. Extrusion and kneading of the copolymerized polyester into the non-liquid crystalline polyester are preferably performed, and it is effective to perform the kneading a plurality of times. As the screw used at this time, a BM type screw is preferable from the viewpoint of mixing strength.

It is also preferable to reduce the dispersion diameter by pulverizing the copolymerized polyester chip before mixing it with the non-liquid crystalline polyester chip. For example, into a crusher, put the same amount of copolyester chips and dry ice,
It is also effective to form a film by rotating at a high speed, pulverizing, classifying, collecting a liquid crystalline polyester having a small dispersion diameter, mixing with a polyester chip and performing melt extrusion.

Next, the unstretched film is biaxially stretched,
Biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. Further, after performing these stretching, re-longitudinal stretching and re-lateral stretching may be performed. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction is performed first in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more stages, and a method in which the total longitudinal stretching ratio is 3 to 7 times is a stretching failure. Desirable without. The longitudinal stretching speed is 5000 to 30
A range of 0000% / min is preferred.

Next, stretching in the width direction is performed. As the stretching method in the width direction, for example, a method using a stenter is preferable. The stretching ratio in the width direction is 3 to 7 times, and the stretching speed is 1000.
Perform in the range of ２０20,000% / min. Further, if necessary, re-longitudinal stretching and re-lateral stretching are performed. As the stretching conditions in that case, the stretching in the longitudinal direction is 90 to 180 ° C., and the stretching ratio is 1.
The stretching is performed at a stretching temperature of 90 to 180 ° C in the width direction and a stretching ratio of 1.1 to 2 times in the width direction.

Next, the biaxially oriented film is heat-treated and wound into a roll on a winder. The heat treatment conditions in this case may be any of a fixed length, a relaxed state, and a finely stretched state.
It is preferable that the heat treatment in the final stage is performed at 120 ° C. to 180 ° C. at a temperature of 5 ° C. or higher, lower than the melting point of the non-liquid crystalline polyester (A), and the processing time is 0.5 to 60 seconds for each stage. Further, it is also preferable to perform a relaxation treatment in the heat treatment step.

[0052]

[Methods for measuring physical properties and evaluating effects]

(1) Intrinsic viscosity [η] It was measured in orthochlorophenol at 25 ° C. In addition,
When the copolymerized polyester was not dissolved in orthochlorophenol, the measurement was performed after removing the polymer by centrifugation.

(2) Average Dispersion Diameter and Aspect Ratio of Copolyester (B) The polyester film is cut in the vertical, horizontal and thickness directions, and the cut surface is cut using a transmission electron microscope to obtain a copolymer 100%. Observe and ask for the individual. The aspect ratio is the ratio (L / D) of the length (L) of the longest direction of the copolymerized polyester and the length (D) of the thickest portion perpendicular to the longest direction, and the average dispersion diameter is D.

(3) Melt viscosity (Pa · sec) Under the condition of melting point (Tm) + 15 ° C., the shear rate is 1000 (1).
/ Mm), nozzle diameter 0.5mmφ, nozzle length 1
The value is a value measured by a height type flow tester using a 0 mm nozzle. The unit is expressed in Pa · sec. Here, the melting point (Tm) refers to an endothermic peak temperature (Tm1) observed when a polymer that has been polymerized is measured from room temperature under a heating condition of 40 ° C./min in differential scanning calorimetry.
After holding at a temperature of Tm1 + 20 ° C. for 5 minutes, once cooling to room temperature under a temperature-lowering condition of 20 ° C./min, and then measuring again at a temperature rising condition of 20 ° C./min, an endothermic peak temperature (Tm2) observed. Refers to the peak.

(4) Heating Crystallization Temperature (° C.) A polyester sample (5 mg) was placed in an aluminum pan using a “robot” differential scanning calorimeter (RDC220) manufactured by Seiko Electronic Industry Co., Ltd. Hold for one minute and then quench using liquid nitrogen. Next, the temperature was raised at a rate of 10 ° C./min, and the temperature of the crystallization exothermic peak from the glassy state was defined as the temperature rise crystallization temperature.

(5) Oligomer content (cyclic trimer) 100 mg of a polymer was dissolved in 1 ml of orthochlorophenol, and the solution was subjected to liquid chromatography (model 8500, VARIAN
And the ratio to the polymer (shown in% by weight).

(6) Long-term heat resistance Measured according to UL746B. Specifically, the polyester film before heat treatment is cut out in the longitudinal direction and the width direction, and the elongation at break is measured with a “Tensilon” tensile tester, and the initial elongation at break is first determined. Next, the cut film is heat-treated in a heating oven under an atmosphere of 200 ° C.
The time required for the elongation at break in the longitudinal and width directions to decrease to half of the initial elongation at break is determined.

[0058]

Next, embodiments of the present invention will be described based on examples.

Example 1 As a non-liquid crystalline polyester (A), an intrinsic viscosity of 0.7
(Dl / g) polyethylene terephthalate (PET)
Raw materials were used. As the copolymerized polyester (B), a copolymerized polyester (melting point: 265)
° C, liquid crystal starting temperature 240 ° C, melt viscosity 1.5 Pa · s)
Was used.

[Copolymer Polyester Raw Material A] p-hydroxybenzoic acid copolymer molar ratio 72.5 4,4′-dihydroxybiphenyl 7.5 ethylene glycol 20.0 terephthalic acid 27.5 98% by weight of PET, copolymer polyester After mixing at 2% by weight, the mixture was dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, fed to an extruder, and melted at 285 ° C. while being deaerated. The polymer is filtered using a high-precision filter having a filtration accuracy of removing a foreign substance of 80 μm or more with a probability of 95%, and then a molten sheet is extruded from a T-die die at a draft ratio of 10 and cast by an electrostatic application method. Was wound around a casting drum having a surface temperature of 25 ° C. and solidified by cooling to prepare an unstretched film ([η] = 0.65) containing 0.5% by weight of the copolymerized polyester (B). The discharge amount of the extruder was adjusted to adjust the total thickness.

This unstretched film was stretched 3.4 times in the longitudinal direction at a temperature of 95 ° C. This stretching was performed in four stages with a peripheral speed difference between two sets of rolls. This uniaxially stretched film was stretched 3.5 times in the width direction at 135 ° C. using a tenter. This film was heated at a first heat treatment temperature of 225 ° C.
The heat treatment temperature at the final stage is 155 ° C and the thickness is 250μ.
m of biaxially oriented PET film was wound by a winder. The temperature rise crystallization temperature of this film is 133 ° C.,
The average dispersion diameter of the copolymerized polyester in the film is 0.5
μm.

Table 1 shows the properties of this polyester film.
As shown in Table 2, it was excellent in long-term heat resistance and was a low oligomer.

Example 2 In the same manner as in Example 1, a PET chip ([η] = 0.9) raw material was used as the non-liquid crystalline polyester. As the copolyester (B), a copolyester (melting point: 208 ° C., liquid crystal onset temperature: 190 ° C., melt viscosity: 1 Pa · sec) polycondensed from the following raw materials was used. A stretched film ([η] = 0.84) was made.

[Copolymerized Polyester Raw Material B] p-Hydroxybenzoic acid Copolymerization molar ratio 42.5 4,4′-dihydroxybiphenyl 7.5 Ethylene glycol 50.0 Terephthalic acid 57.5 3.3 in the longitudinal direction at
It was stretched twice. This stretching is the difference in peripheral speed between two sets of rolls.
This was performed in four stages. This uniaxially stretched film was stretched 3.4 times in the width direction at 105 ° C. using a tenter. This film was subjected to a first heat treatment temperature of 210 ° C., a second heat treatment temperature of 150 ° C., a final heat treatment of 130 ° C., and a 125 μm-thick biaxially oriented PET film was wound by a winder. The heat-up crystallization temperature of this film is 1
The temperature was 34 ° C., and the average dispersion diameter of the copolymerized polyester in the film was 0.2 μm.

Table 1 shows the properties of this polyester film.
As shown in Table 2, it was excellent in long-term heat resistance and was a low oligomer.

Example 3 As the copolymerized polyester (B), a copolymerized polyester (melting point: 215 ° C., liquid crystal onset temperature: 195 ° C., melt viscosity: 10 Pa · sec) obtained by polycondensation from the following raw materials was used.

[Copolymerized polyester raw material C] p-hydroxybenzoic acid copolymerization molar ratio 32.5 4,4'-dihydroxybiphenyl 7.5 ethylene glycol 60.0 terephthalic acid 67.5 In the same manner as in Example 1, Then, an unstretched film ([η] = 0.76) containing 5% by weight of a copolymerized polyester was prepared using the PET chip and the copolymerized polyester chip.

This unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 93 ° C. This stretching was performed in four stages with a peripheral speed difference between two sets of rolls. This uniaxially stretched film was stretched 3.4 times in the width direction at 105 ° C. using a tenter. This film is subjected to a first stage heat treatment temperature of 220 ° C.
The final heat treatment temperature is 150 ° C and the thickness is 250μ.
m of biaxially oriented PET film was wound by a winder. The temperature rise crystallization temperature of this film is 131 ° C.,
The average dispersion diameter of the copolymerized polyester in the film is 0.1
It was 5 μm.

Table 1 shows the properties of this polyester film.
As shown in Table 2, it was excellent in long-term heat resistance and was a low oligomer.

Example 4 The copolyester used in Example 1 was kneaded once with a PET chip ([η] = 0.8), and a PET chip ([η) containing 2% by weight of the copolyester (B) was used. ] =
0.77) was obtained. This chip and PET chip ([η]
= 0.8) at a ratio of 25/75% by weight to obtain an unstretched film ([η] = 0.74) containing 0.5% by weight of the copolymerized polyester.

A film was formed in the same manner as in Example 1 and had a thickness of 250 μm.
Was obtained. The heated crystallization temperature of this film was 135 ° C., and the average dispersion diameter of the copolymerized polyester in the film was 0.3 μm.

Table 1 shows the properties of this polyester film.
As shown in Table 2, it was excellent in long-term heat resistance and was a low oligomer.

Comparative Example 1 A biaxial film having a thickness of 250 μm was formed in the same manner as in Example 1 except that the copolyester (B) was not used, and the heat treatment was performed in one stage at a heat treatment temperature of 225 ° C. Oriented PE
A T film was obtained. The heat-up crystallization temperature of this film is 1
58 ° C.

Table 1 shows the properties of this polyester film.
As shown in Table 2, the long-term heat resistance was insufficient, and the amount of oligomer was also increased.

Comparative Example 2 A biaxially oriented PET film was produced in the same manner as in Example 1 except that the amount of the copolyester was changed to 0.005% by weight and the heat treatment temperature was set to 225 ° C. in one stage. I got

Examples 5 to 7, Comparative Examples 3 to 5 Polyester films were formed by changing the type of non-liquid crystalline polyester, the intrinsic viscosity, the composition of the copolymerized polyester, the amount added, the melt viscosity, and the heat treatment method. The properties of the obtained film were as shown in Tables 1 and 2. When the polyester film is within the scope of the present invention, it has excellent long-term heat resistance and is a low oligomer, but when the properties of the polyester film deviate from the range of the present invention, the long-term heat resistance is insufficient and the amount of oligomer increases. Film.

[0077]

[Table 1]

[Table 2]

[0078]

According to the present invention, there is provided a film comprising a non-liquid crystalline polyester (A) and a copolymerized polyester (B) having a mesogen group in the main chain, wherein the film has a temperature-induced crystallization temperature of 14%.
A polyester film having an intrinsic viscosity of 0.6 dl / g or more at 0 ° C. or less has excellent long-term heat resistance, is a low oligomer, and is suitable as a polyester film for electrical insulation.

Claims (11)

[Claims] 1. A film comprising a non-liquid crystalline polyester (A) and a copolymerized polyester (B) containing a mesogen group in a main chain, wherein the film has a temperature-rise crystallization temperature of 14
A polyester film having an intrinsic viscosity of 0.6 to 2.5 dl / g or more at 0 ° C. or less. 2. When the polyester film is heat-treated in an atmosphere of 200 ° C., the time required for the elongation at break in the longitudinal direction and the width direction of the film to be reduced to half that before the heat treatment is 20 to 20,000 hours. 2. The method according to claim 1, wherein
Polyester film according to 1. 3. The film has an intrinsic viscosity of 0.7 to 2 dl /
3. The polyester film according to claim 1, wherein g is g. 4. The polyester film according to claim 1, wherein the copolymer polyester (B) has a melt viscosity of 0.1 to 100 Pa · sec. 5. The polyester film according to claim 1, wherein the copolymerization amount of the mesogen group in the copolymerized polyester (B) is from 5 mol% to 95 mol%. 6. The polyester film according to claim 1, wherein the polyester film contains 0.01 to 5% by weight of the copolymerized polyester (B). 7. The copolymerized polyester (B) is a copolymerized polyester comprising the following structural units (I), (III) and (IV) and a copolymerized polyester comprising the structural units (I), (II) and (IV). Polymerized polyester, (I), (II), (II
The polyester film according to any one of claims 1 to 6, wherein the polyester film is at least one selected from copolymerized polyesters comprising the structural units (I) and (IV). Embedded image (However, R ₁ in the formula is R ₂ represents one or more groups selected from Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit [(II) + (II
I)] and the structural unit (IV) are substantially equimolar. ) 8. The polyester film according to claim 1, wherein the non-liquid crystalline polyester (A) has a cyclic trimer content of 0.1 to 0.5% by weight. Polyester film according to 1. 9. The non-liquid crystalline polyester (A) is polyethylene terephthalate or polyethylene-2,6-
The polyester film according to any one of claims 1 to 8, wherein the polyester film is at least one selected from the group consisting of naphthalenedicarboxylates and modified products thereof. 10. An electrically insulating material comprising the polyester film according to claim 1. 11. A resin composition comprising a non-liquid crystalline polyester (A) and a copolymerized polyester (B) containing a mesogen group in the main chain is melt-extruded into a sheet and then subjected to total stretching in the machine and transverse directions. The film is biaxially stretched so that the magnification becomes 9 to 15 times, and then heat treatment is performed in multiple stages, and the first stage heat treatment is performed at 205 ° C. or more at a non-liquid crystalline polyester (A).
Wherein the final heat treatment is performed at 120 to 180 ° C.