JPH09323347A - Polyester film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the modulus of rigidity of liquid crystalline polyester fiber and eliminate its surface defect and further, reduce its oligomer quantity buy blending non-liquid crystalline polyester and liquid crystalline polyester with a specific wt.% of fluidization promoter which reduces a filtration pressure at least in a specific value during the passage of these polymer through filter. SOLUTION: In a method for manufacturing a film by filtering a polymer after extruding it in a molten state from an extruder, the molten polymer is extruded from the extruder which blends non-liquid crystalline polyester and liquid crystalline polyester with one wt.% of addition of fluidization promoter which reduces a filter pressure by at least 10% to be filtered into a film, Further, the non liquid crystalline polyester and the liquid crystalline polyester are blended with the fluidization prompter which is a low molecular weight liquid crystalline polyester of the monopolymer or the copolymer type with a number average molecular weight of 1000-15000 to obtain the film. Thus it is possible to inhibit the shape relaxation of the liquid crystalline polyester fiber and consequently, enhance its modules in torsion and eliminate its surface defect, and further reduce it oligomer quantity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a film in which physical properties and quality of a conventional polyester film are significantly improved,
Specifically, the present invention relates to a polyester film having high rigidity, toughness, low surface defects / oligomer content, high quality, and excellent electrical characteristics.

[0002]

2. Description of the Related Art As one method of increasing the rigidity, a method of increasing the degree of molecular orientation by improving drawing is generally well performed. As another method, international publication WO87-
As represented by JP-A-05919, JP-B-37577, JP-A-57-25354, and the like, a compound having a high rigidity such as a liquid crystalline polyester is finely dispersed in a non-liquid crystalline polyester, There is a method to reinforce.

[0003]

However, if the molecules are excessively oriented in order to increase the rigidity, film breakage during stretching is unavoidable, and there is a limit to the practical improvement of the rigidity.

The method of reinforcing and strengthening the liquid crystalline polyester becomes remarkable when the morphology of the liquid crystalline polyester can be controlled into a fibrous shape, and the liquid crystalline polyester fiber is used in the film forming process. However, there is a problem that it is not always effective because the shape relaxation occurs. That is, the liquid crystalline polyester melt immediately after being extruded from an extruder that gives a high shear rate of 100 sec ⁻¹ or more often has a fibrous form,
After that, when the shear rate is reduced to 10 sec- ¹ or less, for example, by passing through a filter, even if it is a fiber shape immediately after extrusion, the shape is changed to a spherical shape, and as a result, as expected, However, there was a problem in that the improvement of the rigidity was not recognized. Further, by extruding a non-liquid crystalline polyester having a high intrinsic viscosity, to form a film, when trying to obtain a film having excellent mechanical properties, the filtration pressure rises when passing through the filter to become large, making extrusion difficult, When the temperature of the filter part is raised to avoid this point, the polymer is thermally decomposed and the degree of polymerization is lowered, so that the mechanical strength is low and only a low quality polyester film can be obtained.
Especially for magnetic recording media, it is necessary to remove foreign substances in the polymer as much as possible to smooth the film surface.Therefore, since a very fine filter is used, the filtration pressure rise is large compared to other applications, and the surface It was difficult to obtain a film having a smooth surface and high mechanical strength.

An object of the present invention is to provide a non-liquid crystalline polyester and a liquid crystalline polyester with a fluidity promoter to overcome the problems of increase in filtering pressure when passing through a filter and relaxation of the shape of the liquid crystalline polyester fiber, thereby improving rigidity. It is to provide a high-quality polyester film having a high rate and a small amount of surface defects and oligomers.

[0006]

In order to solve the above-mentioned problems, the present inventors have made extensive studies on additives to a composite of a non-liquid crystalline polyester and a liquid crystalline polyester. As a result, the fluidity promoter that reduces the filter filtration pressure by 10% or more by adding 1% by weight is not only effective in reducing the filter filtration pressure, but also, surprisingly, relaxes the shape of the liquid crystalline polyester fiber. That is, the decrease in L / D is also suppressed, and as a result, a high quality polyester film having a high rigidity and a small amount of surface defects and oligomers can be obtained, and the intrinsic viscosity obtained by the film formation is 0.
Absolute molecular weight of 1000 to 1000 in films of 6 or more
It was found that 0 to 15% by weight of non-liquid crystalline polyester molecules were contained, and the present invention was completed.

That is, the present invention provides a non-liquid crystalline polyester (A) and a liquid crystalline polyester (B) in a method for producing a polyester film by melt-extruding a polymer with an extruder and then filtering with a filter. A polymer is melt-extruded by a method for producing a polyester film or by an extruder, which is characterized by blending a fluidity promoter (C) which reduces filter filtration pressure by 10% or more by adding 1% by weight to form a film. Then, in the method for producing a polyester film by filtration with a filter, a non-liquid crystalline polyester (A) and a liquid crystalline polyester (B), a low molecular weight non-liquid crystalline polyester having a number average molecular weight of 1,000 to 15,000, homopolymerized or copolymerized. And a method for producing a polyester film, characterized by blending a fluidity promoter (C) It is an essential more obtained polyester film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystalline polyester (B) used in the present invention has melt moldability having a mesogenic group in the main chain,
In addition, it is a liquid crystal forming polyester. Examples thereof include polyesters that form an anisotropic melt phase composed of structural units selected from aromatic oxycarbonyl units, aromatic dioxy units, aromatic dicarbonyl units, alkylenedioxy units, and the like.

Examples of preferred liquid crystalline polyesters used in the present invention include liquid crystalline polyesters having the following structural units (I), (II), (III) and (IV),
One or more selected from liquid crystalline polyesters composed of structural units (I), (III) and (IV) and liquid crystalline polyesters composed of structural units (I), (II) and (IV). Used.

[0010]

Embedded image (However, R1 in the formula is

Embedded image And R2 is

[Chemical 6] Represents one or more groups selected from

[Chemical 7] 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 above structural unit (I) is the structural unit of the polyester produced from p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid,
Is 4,4'-dihydroxybiphenyl, 3,3 ',
5,5′-tetramethyl-4,4′-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone,
Phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2′-bis (4-hydroxyphenyl) propane and 4,4′-
A structural unit generated from an aromatic dihydroxy compound selected from dihydroxydiphenyl ether, a structural unit (III) is a structural unit generated from ethylene glycol, and a structural unit (IV) is terephthalic acid, isophthalic acid,
4,4'-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-
4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid and 4,
Each of the structural units formed from an aromatic dicarboxylic acid selected from 4′-diphenyl ether dicarboxylic acid is shown.

Further, in the case of the liquid crystal polyester comprising the above structural units (I), (II) and (IV), R1 is

Embedded image And R2 is

Embedded image R3 is one or more selected from

Embedded image Those which are at least one kind selected from

In the case of a liquid crystal polyester composed of the above structural units (I), (III) and (IV), R1 is

Embedded image And R3 is

[Chemical 12] Is particularly preferred.

The above structural units (I), (II) and (II
In the case of liquid crystal polyester consisting of (I) and (IV),
R1

Embedded image And R2 is

Embedded image And R3 is

Embedded image Is particularly preferred.

The above-mentioned structural units (I), (II), (III) and (IV) may be copolymerized in any amount, but in view of fluidity and compatibility with the non-liquid crystalline polyester, Is preferred.

The above structural units (I), (II) and (IV)
In the case of a liquid crystalline polyester consisting of, the structural unit (I) is preferably 15 to 90 mol% of [(I) + (II)], more preferably 50 to 80 mol%, and 55 to 75.
Molar% is most preferred. Structural unit (IV) is structural unit (I
It is substantially equimolar to I).

In the case of a liquid crystalline polyester composed of the structural units (I), (III) and (IV), the structural unit (I) is 30 to 95 mol% of [(I) + (III)]. Is preferred, 40-80 mol% is more preferred, and 50
~ 75 mol% is most preferred. The structural unit (IV) is substantially equimolar to the structural unit (III).

Further, the structural units (I), (II),
In the case of the liquid crystalline polyester composed of (III) and (IV), the molar fraction of [(I) + (II)] with respect to the above structural unit [(I) + (II) + (III)] is 40 to 85. Mol%
Is preferable, and 60-80% is more preferable. Further, the molar fraction of (III) with respect to the structural unit [(I) + (II) + (III)] is preferably 60 to 15 mol%, more preferably 40 to 20 mol%. Further, the molar ratio of the structural units (I) / (II) is preferably from 75/25 to 95 / from the viewpoint of fluidity.
5, more preferably 78/22 to 93/7. Further, the number of moles of the structural unit (IV) is the structural unit [(II)
+ (III)].

The term "substantially" in the above description means that the number of the terminal groups of the polyester may be either carboxylxyl group terminals or hydroxyl terminal groups, 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)].

When polycondensing the above preferred liquid crystalline polyester, in addition to the components constituting the structural units (I) to (IV), 3,3'-diphenyldicarboxylic acid, 2,2 '
-Aromatic dicarboxylic acids such as diphenyldicarboxylic acid,
Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, 4,4'-dihydroxydiphenylsulfone, 4,4 ' -Dihydroxydiphenyl sulfide, aromatic diol such as 4,4'-dihydroxybenzophenone, 1,4-butanediol, 1,
6-hexanediol, neopentyl glycol, 1,
Aliphatic and alicyclic diols such as 4-cyclohexanediol, 1,4-cyclohexanedimethanol and aromatic hydroxycarboxylic acids such as m-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, and p-aminophenol, p-amino Benzoic acid and the like can be further copolymerized in a small proportion within a range that does not impair the object of the present invention.

The method for producing the liquid crystalline polyester in the present invention is not particularly limited and can be produced, for example, according to the following polycondensation method of polyester.

In the above-mentioned method for producing a liquid crystalline polyester which is preferably used, the following (1) and (2) are used when the structural unit (III) is not contained, and the following (3) is used when the structural unit (III) is contained. The manufacturing method is preferred.

(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) In the presence of (1) or (2) in the presence of a polyester polymer such as polyethylene terephthalate, an oligomer or a bis (β-hydroxyethyl) ester of an aromatic dicarboxylic acid such as bis (β-hydroxyethyl) terephthalate. The method of manufacturing by the method of.

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

In the present invention, a low-viscosity liquid crystalline polyester, that is, a liquid crystalline polyester for increasing the melt viscosity ratio (melt viscosity of non-liquid crystalline polyester (η _A ) / melt viscosity of liquid crystalline polyester (η _B )) is preferable. . This is because the object of the present invention, in particular, the suppression of heat generation by shearing in the extrusion step can be achieved more effectively as in the case where a low-viscosity liquid crystalline polyester is added to the non-liquid crystalline polyester.
The melt viscosity ratio needs to be at least 5 or more, preferably 10 or more, more preferably 50 or more, and particularly preferably 500 or more. According to the knowledge of the present inventors, this melt viscosity ratio (η _A / η _B ) is 500 or more, 1
Most preferably, it is at most 0,000. Therefore, the melt viscosity of the liquid crystalline polyester depends on the melt viscosity of the non-liquid crystalline polyester to be used, but is 200 Pa.s under the conditions of the melting point of the non-liquid crystalline polyester forming the matrix + 15 ° C. and the shear rate of 100 sec ^−1. Should be less than a second,
Preferably 50 Pa · sec or less, more preferably 10 P
It is a second or less. Liquid crystal polyesters having such a low melt viscosity and which can be particularly preferably used for achieving the object of the present invention include structural units (I), (II),
A liquid crystalline polyester composed of (III) and (IV). This liquid crystalline polyester is particularly effective in finely dispersing it in the non-liquid crystalline polyester to enhance the quality and characteristics of the polyester film.

The form of dispersion of the liquid crystalline polyester in the polyester film may be any form such as skin-core type, sea-island type, multi-layer type and fiber type, and is not particularly limited, but in the case of the present invention, the liquid crystalline polyester is It is preferably finely dispersed in a fibrous state in the polyester film. In this case, the diameter of the liquid crystalline polyester fiber is 3
It is less than or equal to μm, preferably less than or equal to 1 μm, more preferably less than or equal to 0.5 μm, and particularly preferably less than or equal to 0.2 μm. The aspect ratio (L / D), which is the ratio of the fiber length (L) and the fiber diameter (D) of the liquid crystalline polyester fiber, is 1
It is 0 or more, preferably 50 or more, more preferably 100 or more, still more preferably 150 or more. The amount of the liquid crystalline polyester added is not particularly limited, but is preferably 0.1 to 40% by weight, preferably 0.3 to 20% by weight, and more preferably 0.5 to 10% by weight based on the total weight of the polymer. If the amount added is less than 0.1% by weight, it is difficult to obtain a high-strength film, and if it exceeds 40% by weight, the surface of the polyester film becomes very rough, which is not preferable.

Typical examples of the non-liquid crystalline polyester (A) used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polycyclohexane dimethylene terephthalate, and their copolyesters. Examples include coalescing. Of course, polyesters having an ether component in the main chain, for example, copolymers of diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol and the like may be used.

In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate having an intrinsic viscosity of 0.6 or more, preferably 0.8 or more, more preferably 1.2 or more, still more preferably 1.4 or more are preferable. According to the knowledge of the present inventors, polyethylene terephthalate and polyethylene-2,6-naphthalate having an intrinsic viscosity of 1.4 or more and 2.5 or less are most preferable. Non-liquid crystalline polyester (A)
When the intrinsic viscosity of is large, the melt viscosity ratio (η _A / η _B )
Becomes larger and the difference in molecular weight from the fluidity promoter (C) also becomes larger, and as a result, suppression of shearing heat generation in the extruder and reduction of filter filtration pressure can be effectively realized. Further, in this case, the liquid crystalline polyester is finely dispersed in the film, the L / D of the liquid crystalline polyester fiber formed at this time is increased, and its shape relaxation is suppressed, so that the rigidity of the film is increased, It is preferable for obtaining the polyester film of the present invention. The solid phase polymerization method is most preferably used as a means for obtaining such a non-liquid crystalline polyester having a high intrinsic viscosity. The melting point of the non-liquid crystalline polyester is preferably equal to or higher than that of the liquid crystalline polyester because the liquid crystalline polyester is easily finely dispersed in a fibrous state in the non-liquid crystalline polyester.

The fluidity promoter (C) used in the present invention is
It is not particularly limited as long as it is a polymer or an oligomer which has a melt moldability and can reduce the filter filtration pressure by 10% or more by adding 1% by weight, but the number average molecular weight is from 1000 to 15
000 low molecular weight compounds are desirable. A compound that reduces the filter filtration pressure by less than 10% even if added in an amount of 1% by weight cannot suppress the shape relaxation of the liquid crystal polyester fiber, and the addition of such a compound gives the polyester film aimed at by the present invention. It is not preferable because it is not available

The number average molecular weight of the low molecular weight compound is preferably 3,000 to 12,000, more preferably 5,000 to 10,000. Number average molecular weight is 1
The non-liquid crystalline polyester of 5000 or more has a small effect of reducing the filtering pressure, and the aspect ratio L of the liquid crystalline polyester fiber is L.
This is not preferable because it reduces / D. Further, it is not preferable to use an oligomer having a number average molecular weight of 1000 or less, because the problem of bleeding out occurs during film formation.

Further, the fluidity promoter (C), that is, the low molecular weight compound, of the present invention preferably has a solubility parameter difference with the non-liquid crystalline polyester (A) of 2 MPa ^1/2 or less. Preferably 1.5 or less,
It is more preferably 1 or less, and particularly preferably 0.5 or less. The solubility parameter referred to in the present invention is a value calculated by the atomic group contribution method, for example, Van Krevelen,
"Properties of Polymers", T
third complete Revised E
It can be calculated by the method described in the section, ELSEVIER (1990). Regarding the parameters of each atomic group,
Various proposals have been made, and calculation may be performed by any method, but Hoftizer-Van Krevelen, H
The method of Oy, Small, Fedors et al. can be preferably used.

The amount of the low molecular weight compound added is not particularly limited, but the non-liquid crystalline polyester molecule having a molecular weight of 1,000 to 10,000 is contained in the film having a non-liquid crystalline polyester having an intrinsic viscosity of 0.6 or more in an amount of 1 to 15% by weight. It is preferable that the amount is an appropriate amount necessary for the addition, and the total weight of the polymer is 0.0
It is 1 to 10% by weight, more preferably 0.2 to 8% by weight, particularly preferably 0.5 to 5% by weight. 0.0
Whether the amount is less than 1% by weight or the amount is more than 10% by weight, a molecular weight of 10 or less is obtained in a film having an intrinsic viscosity of 0.6 or more.
0 to 10000 non-liquid crystalline polyester molecules 1 to 1
It is not preferable because it is difficult to set the content in the range of 5% by weight. If the addition amount is less than 0.01% by weight, the filtering pressure reducing effect is extremely small, and if the addition amount is more than 10% by weight, it becomes difficult to obtain a film having a high intrinsic viscosity. At the same time that the dispersed diameter of the liquid crystalline polyester increases, the aspect ratio L of the liquid crystalline polyester fiber
/ D also becomes small, and it is difficult to obtain the effects of the present invention such as improvement in mechanical properties and quality of the film.

As a specific example of the fluidity accelerator (C) which can be preferably used in the present invention, a homopolymerized or copolymerized low molecular weight non-liquid crystalline polyester is used, and a typical example thereof is an intrinsic viscosity of 0. 2 to 0.6 of polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polycyclohexane dimethylene terephthalate, and copolymers and oligomers thereof are used. Of course, a polyester having an ether component in the main chain, for example, those obtained by copolymerizing diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol, etc., may be used in a small amount as long as the effect of the present invention is not impaired. That is, it may be one obtained by copolymerizing about 5% or less of mesogenic groups. Further, these low molecular weight non-liquid crystalline polyesters are preferably compounds in which the molecular terminals are non-polarized so that the non-liquid crystalline polyester (A) is difficult to hydrolyze. It is also preferable to blend two or more low molecular weight non-liquid crystalline polyesters of the present invention.

In the polyester film of the present invention, a plasticizer, insofar as the effect of the present invention is not impaired,
A weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a coloring agent, a conductive agent, etc. may be added.

The polyester film of the present invention may be a single film, but other polymer layers such as polyester,
Polyolefin, polyamide, polyvinylidene chloride, acrylic polymer, etc. may be laminated. Especially when the polyester layer is thinly laminated on the surface layer, the thickness of the laminated portion (M)
Is smaller than the average diameter (N) of the particles contained in the laminated portion (M <N), preferably 1/1000 of M.
It is possible to obtain a film excellent in running property, slipperiness, and smoothness by setting the ratio to ½, more preferably 1/100 to 1/10, and especially for magnetic recording in which surface characteristics are important. It is preferable as a base film.

Further, in the case of a laminated film having three or more layers made of polyester, productivity and quality can be improved by mixing the recovered raw material in the central layer. Such particles include silicon oxide, magnesium oxide, calcium carbonate, titanium oxide, aluminum oxide,
Crosslinked polyester, crosslinked polystyrene, mica, talc, kaolin and the like are used, but not limited to these.

The polyester film of the present invention may be an unstretched or unoriented film, but when it is a uniaxially or biaxially oriented and heat-set oriented film by a known method, it has high elasticity, toughness, heat resistance and low oligomer. , The effects such as electrical characteristics are more prominently exhibited.

Next, a method for producing the polyester film of the present invention will be described, but the present invention is not limited to such an example.

Here, an example in which polyethylene terephthalate is used as the non-liquid crystal polyester (A) is shown, but the production conditions differ depending on the polyester used. Esterified from terephthalic acid and ethylene glycol, or
Bis-β-hydroxyethyl terephthalate (BHT) is obtained by transesterification of dimethyl terephthalate and ethylene glycol. Next, while transferring the BHT to the polymerization tank, the polymerization reaction is advanced by heating to 280 ° C. under vacuum. Here, a polyester having an intrinsic viscosity of about 0.5 is obtained. The obtained polyester is subjected to solid-state polymerization in a pellet form under reduced pressure. If solid phase polymerization is used,
After pre-crystallizing at a temperature of 0 ° C or less, 190-250
The liquid crystal polyester (B) to be used is solid-state polymerized under reduced pressure of about 1 mmHg at 10 ° C. for 10 to 50 hours and has a melt viscosity of 5
The degree of polymerization is increased so that it becomes more than double.

Next, the high-viscosity polyethylene terephthalate, the liquid crystalline polyester (B) and the fluidity accelerator,
For example, a raw material obtained by blending a low molecular weight non-liquid crystalline polyester having a number average molecular weight of 1,000 to 15,000, a raw material obtained by melting these once and uniformly mixing them, and further, a raw material recovered from the film of the present invention alone or appropriately in the above 2 After vacuum-drying a raw material obtained by mixing three kinds of raw materials at 180 ° C. for 3 hours or more, the raw material is fed to an extruder heated to 280 ° C. under a nitrogen stream or under vacuum so that the intrinsic viscosity does not decrease. The film is formed by the method of. Of course, at this time,
The shear rate in the extruder is 20 sec ^-1 or more, preferably 50
The higher the ^{value of} sec ⁻¹ or more, the smaller the dispersion diameter of the liquid crystalline polyester (B) in the extruder, and the greater the effect of the present invention with a small amount of the fluidity promoter (C), which is preferable, but the shear rate is 300 seconds. ^If it is larger than ^-1 , it is not preferable because the polymer is thermally decomposed by shearing heat generation.

Further, foreign matters are removed by using a filter such as a sintered metal, a porous ceramics, a sand or a metal net. At this time, the average shear rate when passing through the filter is 1
It is as low as 0 sec ⁻¹ or less, and the pressure during filtration does not become remarkably low when only the liquid crystalline polyester is added, but the addition of the fluidity promoter (C) of the present invention reduces the pressure during filtration. It becomes possible to reduce to a practical range. T
The draft ratio at the time of extrusion into a sheet by a die is preferably 10 to 200, more preferably 15 to 100 to reduce the fibrous dispersion diameter of the liquid crystal polyester, and further to reduce the fiber length (L). The aspect ratio (L / D), which is the ratio of the diameter (D), is preferably 10 to 100.
The value can be uniformly increased to 0, more preferably 100 to 700, and further preferably 150 to 500. After that, the sheet-shaped cast film is heated by a heating roll group at 80 to 150 ° C., stretched in the longitudinal direction by 2 to 7 times in one stage or in multiple stages of two or more stages, and cooled by a cooling roll group at 20 to 50 ° C. To do.

Then, the film is guided to a tenter and, while holding both ends of the film with clips, the film is heated in a hot air atmosphere heated to 80 to 150 ° C. and stretched 2 to 6 times in the transverse direction.

Subsequently, the film is heat-set at a temperature of 150 to 250 ° C. Heat fixation may be done under tension,
Further, in order to further improve the thermal dimensional stability, relaxation in the width direction is also preferably performed. Further, if necessary, re-longitudinal stretching and / or re-transverse stretching can be performed before heat setting.

[0046]

[Methods for measuring physical properties and evaluating effects]

(1) Intrinsic viscosity It is a value measured at a concentration of 0.1 g / ml in orthochlorophenol at 25 ° C. Since the liquid crystalline polyester does not dissolve in orthochlorophenol, the measurement was performed after removing the polymer by centrifugation.

(2) Melt viscosity Using a high and low flow tester, a shear rate of 1 at 280 ° C.
Measure the value at 00 seconds- ¹ . The unit is represented by [Pa · sec].

(3) Young's modulus A sample was set in a Tensilon type tensile tester (manufactured by Orientec Co., Ltd.) so that the width was 10 mm and the length between chucks was 100 mm, and the sample was pulled in an atmosphere of 23 ° C. and 65% RH. The tensile test was performed at a speed of 200 mm / min to obtain the value.

(4) Fish eye (FE) A film of 10 cm ² was placed under crossed Nicol polarized light, and a portion of the entire image in which the surrounding color was different and the major axis was 10 μm or more was selected. I counted. The unit is shown in pieces / cm ² .

(5) Oligomer amount 100 mg of the polymer was dissolved in 1 ml of o-chlorophenol and subjected to liquid chromatography (model 8500 VAR).
(Manufactured by IAN). It is expressed in% by weight with respect to the polymer.

(6) Fiber Diameter and Aspect Ratio of Liquid Crystalline Polyester The film was dissolved using orthochlorophenol,
Unmelted liquid crystalline polyester is separated by centrifugation,
Using a scanning microscope, liquid crystalline polyester fiber 100
Observe and ask for the individual. The aspect ratio is the ratio (L / D) of the length (L) in the longest direction of the liquid crystalline polyester fiber and the length (D) of the thickest portion which is orthogonal to it. Further, D is the fiber diameter.

(7) Filter filtration pressure and reduction degree of filter filtration pressure The experimental apparatus is shown in FIG. Gear pump (manufactured by Kawasaki Heavy Industries, 1.
6 cc / rotation), filter (manufactured by Nippon Seisen Co., Ltd., leaf disc filter NF-140: 65 mm diameter, 80)
Using a Toshiba 30 mm small single-screw extruder (L / D = 22) equipped with a μm cut sintered filter) and a pressure gauge, pressures PA and PB before and after the filter were measured under the following conditions.

[Extrusion Conditions] Screw rotation speed: 52 rpm Screw measuring section shear rate: 109 sec- ¹ Polymer discharge rate: 3.6 kg / hr Extruder set temperature: Feeding section 265 ° C. Compressing section 280 ° C. Measuring section 280 ° C. Gear pump Part 280 ° C filter part 280 ° C gear pump discharge rate: 1.6kg / hr

The degree R of reduction of filter pressure was calculated by the following formula.

R = [(P ₀ -P ₁ ) / P ₀ ] × 100 P ₀ : Filtering pressure (pressure difference: when no fluidity promoter is added)
P _A -P _B) P _1: filtration pressure of adding the fluidity accelerator (pressure difference: P
_A- P _B )

(8) Number average molecular weight and absolute molecular weight Analysis was requested to Toray Research Center Co., Ltd. and measured by gel per chromatography (GPC).

[0057]

EXAMPLES The present invention will be described based on examples and comparative examples.

Example 1 As an amorphous polyester, an intrinsic viscosity of 0.8 (dl /
The polyethylene terephthalate raw material of g) was used. As the liquid crystalline polyester, a liquid crystalline polyester (melting point 265 ° C., liquid crystal starting temperature 240
C., melt viscosity 23 Pa · sec) was used.

[Liquid Crystalline Polyester Raw Material 1] Hydroxybenzoic Acid Copolymerization Molar Ratio 72.5 4, 4′-Dihydroxybiphenyl 7.5 Ethylene Glycol 20.0 Terephthalic Acid 27.5

As the fluidity promoter, low molecular weight polyethylene terephthalate having a number average molecular weight of 8000 was used. The polyethylene terephthalate, liquid crystal polyester and fluidity promoter are dried and the mixture is heated to 150 mm.
Supplied to a single-screw extruder and at 285 ° C, shear rate 100 seconds
After melt-mixing and weighing at ^-1 , shear rate 10 sec ^{-1 in the} fiber sintered stainless metal filter (10 μm cut)
After that, it was extruded into a sheet shape from a T die die at a draft ratio of 50, and was contact-cooled and solidified while applying an electrostatic charge to a cooling drum kept at 25 ° C. The cast film was stretched 4 times at 110 ° C. with a longitudinal roll type stretching machine to increase the birefringence to 0.13, introduced into a tenter, stretched 4 times at 100 ° C., and then once cooled to 60 ° C. Then, it was heat-set at 200 ° C. to obtain a biaxially oriented film having a thickness of 8 μm. Table 2 shows the characteristics thus obtained and the degree of reduction in filter filtration pressure during melt extrusion. By forming a film using a fluidity promoter that reduces the filter filtration pressure by 10% or more when 1% by weight is added, a high-quality film having a high Young's modulus and a small amount of fish eyes and oligomers was obtained. The film has a non-liquid crystalline polyester with an intrinsic viscosity of 0.75 and a molecular weight of 1,000 to 1,000.
It contained 11.0% by weight of non-liquid crystalline polyester molecules of 0, and had excellent properties as a film for various applications such as magnetic recording media and electrical insulation.

Examples 2 and 3 A biaxially oriented film was obtained in the same manner as in Example 1, except that polyethylene terephthalate raw materials having different intrinsic viscosities were used as the non-liquid crystal polyester. When a raw material having a high intrinsic viscosity is used, the effect of the fluidity promoter becomes more remarkable, the dispersion diameter of LCP becomes small, and the L / D becomes large, and a high Young's modulus higher than that in Example 1 is obtained. A quality film was obtained. These films had a high intrinsic viscosity and contained 5 to 7% by weight of non-liquid crystalline polyester molecules having a molecular weight of 1,000 to 10,000.

Examples 4 to 9 Films were obtained in the same manner as in Example 3 except that the amount of the fluidity promoter used, the number average molecular weight and the type of polymer were changed. As shown in the table, when the fluidity promoter having the constitution of the present invention was used, a film having high Young's modulus and high quality was obtained. Incidentally, these films had a high intrinsic viscosity and contained non-liquid crystalline polyester molecules having a molecular weight of 1,000 to 10,000 in the range of 3 to 15% by weight.

Comparative Examples 1 and 2 Comparative Examples 1 and 2 show the results of film formation as in Example 1 or 3 except that the fluidity accelerator was not used. When the fluidity promoter is not added, the effect of the liquid crystal polyester cannot be maximized and the high Young's modulus,
It was not possible to obtain a high quality film. Further, the obtained film contained 10% by weight or more of non-liquid crystalline polyester molecules having a molecular weight of 1,000 to 10,000.

Comparative Example 3 A film was formed in the same manner as in Example 3 except that low molecular weight polypropylene having a number average molecular weight of 8000 was used as the fluidity promoter. When PP having a solubility parameter difference of 2 or more from the non-liquid crystalline polyester is added, 1% by weight is added.
The addition reduced the filter filtration pressure by less than 10%, and it was not possible to obtain a high Young's modulus and high quality film. In this case, the obtained film has a molecular weight of 1
000-10,000 non-liquid crystalline polyester molecules 15
It was contained by weight% or more.

Comparative Examples 4 to 7 Comparative Examples 4 and 5 are cases where the amount of the fluidity promoter added is outside the range of the present invention, and Comparative Examples 6 and 7 are cases where the number average molecular weight is outside the range of the present invention. Other conditions were exactly the same as in Example 3 to obtain a biaxially oriented film. As shown in the table, in the case of these comparative examples, a film having high Young's modulus and quality as in Example 3 was not obtained, and the obtained film contained non-liquid crystalline polyester molecules having a molecular weight of 1,000 to 10,000. The content was 15% by weight or more.

[0066]

[Table 1]

[Table 2]

[Table 3]

[0067]

INDUSTRIAL APPLICABILITY According to the present invention, a composite comprising an amorphous polyester, a liquid crystalline polyester and a fluidity promoter is used as a film, the rigidity of the film is increased, and surface defects and oligomers of the film are reduced to improve the quality. It has been improved and can be widely used for various film applications such as magnetic recording, electrical insulation, heat-sensitive transfer ribbon, and heat-sensitive stencil printing.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an extrusion experimental apparatus used for evaluation of a filter pressure and a reduction degree of the filter pressure of the present invention.

[Explanation of symbols]

 1:30 mm compact single screw extruder (L / D = 22) 2: Single pipe 3: Gear pump 4: Filter 5: Bleed port 6: Filter upstream pressure gauge 7: Filter downstream pressure gauge 81: Extruder supply thermoelectric Pair 82: Extruder compression section thermocouple 83: Extruder metering section thermocouple 84: Gear pump section thermocouple 85: Filter section thermocouple

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Claims (14)

[Claims] 1. A method for producing a polyester film, comprising melt-extruding a polymer with an extruder and then filtering it with a filter to add a non-liquid crystalline polyester (A), a liquid crystalline polyester (B) and 1% by weight. A method for producing a polyester film, which comprises blending a fluidity promoter (C) for reducing the filter filtration pressure by 10% or more to form a film. 2. A non-liquid crystalline polyester (A), a liquid crystalline polyester (B), and a number average molecular weight of 1,000 in a method for producing a polyester film by melt-extruding a polymer with an extruder and then filtering with a filter. ~ 15,000
1. A method for producing a polyester film, which comprises blending a fluidity promoter (C) which is a low molecular weight non-liquid crystalline polyester homopolymerized or copolymerized with the above to form a film. 3. The method for producing a polyester film according to claim 1, wherein the non-liquid crystalline polyester (A) has an intrinsic viscosity of 0.6 or more. 4. A non-liquid crystalline polyester (A), a liquid crystalline polyester (B), and a number average molecular weight of 1000 to 1500.
A polyester film comprising a fluidity promoter (C) having an absolute molecular weight of 10 in the polyester film.
0 to 10000 non-liquid crystalline polyester molecules 1 to 1
A polyester film containing 5% by weight. 5. The fluidity accelerator (C) is a fluidity accelerator having a solubility parameter difference with the non-liquid crystalline polyester (A) of 2 MPa ^1/2 or less. Polyester film. 6. The polyester film according to claim 4, wherein the fluidity-enhancing agent (C) is a homo- or copolymerized non-liquid crystalline polyester. 7. The polyester film according to any one of claims 4 to 6, wherein the fluidity promoter (C) is contained in the polyester film in an amount of 0.01 to 10% by weight. 8. The polyester according to any one of claims 4 to 7, wherein the melt viscosity ratio (ηA / ηB) of the non-liquid crystal polyester (A) and the liquid crystal polyester (B) is 5 or more. the film. 9. A liquid crystalline polyester (B) comprising a liquid crystalline polyester comprising structural units (I), (III) and (IV) below, and a liquid crystal comprising structural units (I), (II) and (IV). Polyester, (I), (II), (II
The polyester film according to any one of claims 4 to 8, which is at least one selected from liquid crystalline polyesters composed of the structural units I) and (IV). Embedded image (Where R1 in the formula is R1 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) + (III
)] And the structural unit (IV) are substantially equimolar. ) 10. The polyester film according to claim 4, wherein the polyester film contains the liquid crystalline polyester (B) in an amount of 0.1 to 40% by weight. 11. The polyester film according to claim 4, wherein the non-liquid crystalline polyester (A) has an intrinsic viscosity of 0.6 or more. 12. The non-liquid crystalline polyester (A) is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate and modified products thereof, according to any one of claims 4 to 11. Or the described polyester film. 13. The polyester film according to claim 4, wherein the polyester film is a uniaxially or biaxially oriented film. 14. A liquid crystalline polyester (B) is finely dispersed in a fibrous state in a film, and an aspect ratio (L / D) which is a ratio of the length (L) and the diameter (D) of the fiber is 10. It is above, The polyester film in any one of Claims 4-13 characterized by the above-mentioned.