JPS6233931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a polyester film. More specifically, the present invention relates to a method for forming a film by melt extrusion of a polyester having the property of forming an optically anisotropic melt.

Conventionally, polyester that has the property of forming an optically anisotropic melt has been produced by simply melt-spinning the polyester molecules, which can be highly oriented in the fiber axis direction.
It is well known to provide fibers with high Young's modulus.

However, the melt of such polyester is
When used to form sheets or films using the die method, the resulting film has excellent dimensional stability and heat resistance in the machine axis direction, probably because orientation occurs in the discharge direction when passing through the slit of the die. However, these properties are insufficient in the direction perpendicular to these, and the non-uniformity of the properties in both axial directions has been a major obstacle in practical use.

The present inventors have conducted repeated research on a method for obtaining a polyester film or sheet that does not have such drawbacks from a polyester that has the property of forming an optically anisotropic melt, and have finally arrived at the method of the present invention.

That is, when forming a film by melt-extruding a polyester having the property of forming an optically anisotropic melt through a slit, the present invention provides a polyester melt having a melt viscosity of at least 1000 poise at 360° C. and a shear rate of 100 sec ^-1 . This is a polyester film forming method characterized in that the melt is extruded while passing through a slit while applying shear stress in a direction perpendicular to the discharge direction at a shear rate that is at least twice the shear rate in the discharge direction.

In the method of the present invention, the polyester that has the property of forming an optically anisotropic melt refers to a polyester that has the property of allowing polarized light to pass through an optical system in which the polymer in a molten state is equipped with crossed polarizers at 90°C.

Such polyesters include, for example, 1 terephthalic acid, diphenyl ether-4,
Such as 4'-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenooxyethane-4,4'-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, transcyclohexane-1,4-dicarboxylic acid, etc. Symmetric aromatic dicarboxylic acid or symmetric alicyclic dicarboxylic acid; methyl terephthalic acid,
Methoxyterephthalic acid, chlorterephthalic acid, bromoterephthalic acid, diphenyl ether-2,2'-dimethyl-4,4'-dicarboxylic acid,
Diphenooxyethane-2,2'-dichloro-
4,4'-dicarboxylic acid, transcyclohexane-1-methyl-1,4-dicarboxylic acid, etc., the symmetrical aromatic dicarboxylic acids or alicyclic dicarboxylic acids mainly substituted with lower alkyl, lower alkoxy or halogen nuclei, etc. As an acid component, symmetrical dioxyaromatic compounds such as hydroquinone, 4,4'-dioxydiphenyl, 4,4'-dioxydiphenyl ether, bis(4-oxyphenoxy)ethane, etc.; chlorohydroquinone , bromohydroquinone, methylhydroquinone, ethylhydroquinone, 2,
2'-dimethyl-4,4'-dioxydiphenyl,
3,3'-dimethoxy-4,4'-dioxydiphenyl ether, bis(2-chloro-4-oxyphenoxy)ethane and the like, lower alkyl, lower alkoxy or halogen-substituted derivatives of the symmetrical dioxyaromatic compounds, etc. Homopolyester or copolyester derived from the main diol component (hereinafter referred to as polyester A), 2 P-oxybenzoic acid, 4-oxydiphenyl-4'-carboxylic acid, 3-chloro-4-oxybenzoic acid, 3- Methoxy-4-oxybenzoic acid, 3-ethoxy-4-oxybenzoic acid, 2
-Methyl-4-oxybenzoic acid, 3-methyl-
Copolyesters (hereinafter referred to as Polyester B) can be mentioned.

The acid components that can be copolymerized with polyester A include oxycarboxylic acids, which are the main components of polyester B, as well as isophthalic acid,
Diphenyl ether-3,3'-dicarboxylic acid, diphenooxyethane-3,3'-dicarboxylic acid, naphthalene-1,6-dicarboxylic acid, m-oxybenzoic acid, 5-methylisophthalic acid, 5-chloroisophthalic acid acid, 4-methylisophthalic acid, 5-tertiary
butyl isophthalic acid, diphenyl ether
4,4'-dichloro-3,3'-dicarboxylic acid, diphenyl-3,4'-dimethyl-4,3'-dicarboxylic acid, diphenooxyethane-2,2'-dibromo-
3,3'-dicarboxylic acid, naphthalene-2,7-dichloro-1,6-dicarboxylic acid, 4-ethoxy-3-oxybenzoic acid, cyclohexane carbonate
Examples include aromatic dicarboxylic acids such as 1,3-dicarboxylic acids, aromatic oxycarboxylic acids, and alicyclic dicarboxylic acids.

On the other hand, examples of the acid component that can be copolymerized with polyester B include the main acid component of polyester A and the copolymerizable acid component.

Diol components that can be copolymerized with polyester A include resorcinol, 3,3'-dioxydiphenyl, 3,3'-dioxydiphenyl ether,
1,6-dioxynaphthalene, bis(3-hydroxyphenoxy)ethane, 2,2-bis(4-
hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 4
-chlorresorcin, 4-ethoxyresorcin, 4-bromoresorcin, 4,4'-dimethoxy-3,3'-dioxydiphenyl, 4,4'-dimethyl-3,3'-dioxydiphenyl, 4 , 4'-dimethoxy-3,3'-dioxydiphenyl ether, 2,4'-dichloro-3,3'-dioxydiphenyl ether, 2,5-dichloro-1,6-dihydroxynaphthalene, 2, 2'-dibrome-3,
Aromatic dioxy compounds such as 3′-dioxydiphenooxyethane or lower alkyl thereof,
Lower alkoxy or halogen nucleus substituted product, ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol, 2-ethyl-2
- Aliphatic glycols and alicyclic glycols having 10 or less carbon atoms, such as methyltrimethylene glycol, cyclohexane-1,4-dimethanol, etc.; 1,
4-bis(β-hydroxyethoxy)benzene, 1,3-bis(β-hydroxyethoxy)
Benzene, 4,4'-bis(β-hydroxyethoxy)diphenyl, 4,4'-bis(β-hydroxyethoxy)diphenyl ether, 4,4'-bis(β-hydroxyethoxy)diphenyl sulfone , 2,2-(bisβ-hydroxyethoxyphenyl)propane and other dioxyaromatic compound derivatives.

Next, examples of the diol component that can be copolymerized with polyester B include the main diol component of polyester A or the copolymerized diol component.

Preferably, the polyester used in the method of the present invention has 50 para-oriented aromatic groups in the main chain of the polyester.
The polyester contains at least 60 mol%, more preferably 60 to 85 mol%, and has a softening point of 150 to 380°C (preferably 200 to 350°C). Here, a para-oriented aromatic group refers to a divalent bonding group of an aromatic group coaxially opposite to the aromatic ring, such as a 1,4-phenylene group, or a 1,5-naphthalene group, a 2,6-naphthalene group, etc. Refers to residues arranged in opposite directions on parallel axes, such as groups. If there are too many para-oriented aromatic groups, the film tends to split easily during film formation.

Specific examples of preferred polyesters used in the method of the present invention include (1) p-oxybenzoic acid and terephthalic acid, isophthalic acid, diphenooxyethane-4,4'-dicarboxylic acid, diphenyl ether-4,4 '-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, and carbonic acid, and one or more selected from the group consisting of hydroquinone, chloro Consists of an ester with one or more dioxyaromatic compounds selected from the group consisting of hydroquinone, methylhydroquinone, 4,4'-dioxydiphenyl, and 4,4'-dioxyphenyl ether Copolyester; (2) Terephthalic acid, diphenyl ether-4,
The group consisting of 4'-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenooxyethane-4,4'-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid and transcyclohexane-1,4-dicarboxylic acid one or more selected from the group consisting of hydroquinone, chlorohydroquinone, methylhydroquinone, 4,4'-dioxydiphenyl, and 4,4'-dioxyphenyl ether; Homopolyesters or copolyesters composed of esters with two or more types; (3) Copolyesters composed of esters of terephthalic acid, isophthalic acid, and chlorohydroquinone and/or methylhydroquinone; (4) Terephthalic acid, diphenyl- One or more selected from the group consisting of 4,4'-dicarboxylic acid, diphenooxyethane-4,4'-dicarboxylic acid, and naphthalene-2,6-dicarboxylic acid, and chlorohydroquinone and/or methyl Copolyester composed of an ester of hydroquinone and resorcin; (5) from the group consisting of p-oxybenzoic acid and terephthalic acid, diphenooxyethane-4,4'-dicarboxylic acid, and naphthalene-2,6-dicarboxylic acid; Copolyester composed of ester of one or more selected species and ethylene glycol; (6) terephthalic acid and/or naphthalene-2,
Examples include copolyesters composed of esters of 6-dicarboxylic acid and chlorohydroquinone and/or methylhydroquinone and ethylene glycol.

More preferred polyesters in the method of the present invention are polyesters (1) to (4) that do not contain aliphatic or alicyclic glycol, and polyester (1) is particularly preferred. The above polyester can be produced by a conventionally known method. For example, an aromatic dicarboxylic acid and/or an alicyclic dicarboxylic acid and a lower fatty acid ester of a dioxyaromatic compound (for example, acetate, etc.) may be used together with an aromatic oxycarboxylic acid ester (for example, acetate, etc.) as necessary. Polymerize by heating; If necessary, combine the aryl ester of aromatic dicarboxylic acid and/or alicyclic dicarboxylic acid (for example, phenyl ester, etc.) with the dioxyaromatic compound; etc.) and/or diaryl carbonate (for example, diphenyl carbonate, etc.); Aromatic dicarboxylic acid and/or alicyclic dicarboxylic acid and dioxyaromatic compound are optionally combined with aromatic oxycarboxylic acid. For example, the reaction mixture is reacted with a diaryl carbonate such as diphenyl carbonate, and the reaction mixture is then heated and polymerized.

Terephthalic acid, diphenooxyethane-4,
A polyester of an aromatic dicarboxylic acid such as 4'-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, etc. and an aliphatic or alicyclic glycol such as ethylene glycol or cyclohexane-1,4-dimethanol; A lower fatty acid ester (for example, acetic acid ester, etc.) of the aromatic dicarboxylic acid and the dioxyaromatic compound such as methylhydroquinone or chlorohydroquinone, or (b)
The aromatic oxycarboxylic acid, such as p-oxybenzoic acid, and a lower fatty acid ester (eg, acetate) are polymerized by heating.

There are other methods. In these polymerization methods, conventionally known transesterification of lithium acetate, sodium acetate, sodium carbonate, magnesium acetate, zinc oxide, manganese acetate, ammothine trioxide, stannous acetate, titanium tetrabutoxide, lead oxide, etc. is carried out as necessary. A small proportion of catalyst can be added to accelerate the reaction. In addition, the polymerization of the polyester is carried out under normal pressure or reduced pressure (usually 100 to 0.01
mmHg), by a melt polymerization method at a temperature of 200°C or higher and 380°C or lower. Preferably, in order to obtain a high polymer suitable for the method of the present invention, a polyester obtained by a melt polymerization method under reduced pressure is processed at a temperature below its softening point (for example, at a temperature of 100 to 5°C below the softening point) under reduced pressure or under a stream of inert gas. Further solid phase polymerization can be performed.

In the method of the present invention, the intrinsic viscosity of the polyester is preferably 0.8 or more, more preferably 1.0 or more. In addition, the melt of this polymer has a melt viscosity of at least 1000 at 360°C and a shear rate of 100 sec ^-1.
Poise, even 1000 to 400000 poise, especially 10000
~300000 poise is preferred. If the viscosity is too low, the film tends to split during film formation, which is undesirable.

In the method of the present invention, the polyester is preferably melt-extruded at a temperature above the flow initiation temperature of the polyester, for example at a temperature of 240 to 400°C, preferably 260 to 380°C. At this time, the gap between the slits can be freely selected depending on the desired thickness of the film. This slit gap is usually 0.001~10
mm, preferably in the range of 0.02 to 2 mm.

In the method of the present invention, the land length of the slit is not particularly limited, but is usually selected from a range of 5 times or more, more preferably 10 to 50 times, the slit width.

In the method of the present invention, shear stress is applied to the polyester melt in a direction perpendicular to the discharge direction while it passes through a slit during melt extrusion. The method of applying shear stress is not particularly limited, but it can be applied, for example, by moving one or both members forming the slit in the direction in which it is desired to apply shear stress. In the method of the present invention, the shearing force is at least twice, preferably at least 5 times, particularly preferably at least 10 times, and up to 100 times, the shear rate in the discharge direction of the polyester melt. If this shear rate is too low, the desired effect will not be fully achieved.

The polyester film obtained by the method of the present invention has excellent stretchability and can be stretched at a high magnification in at least one direction. The stretching is preferably carried out immediately after extruding the polyester melt through the slit. It can also be carried out in the same manner as conventional stretching methods. The polyester film or sheet obtained by the method of the present invention is preferably 2 times or more (in the case of biaxial stretching, the area magnification is 2 times to 100 times).
times), particularly preferably 3 times or more (in the case of biaxial stretching, the area magnification is 3 times to 100 times) in the machine axis direction (or in both directions, i.e., the machine axis direction and the width direction perpendicular to the machine axis) Stretch to. By such stretching, not only can a transparent film be obtained, but also a film having better dimensional stability, heat resistance and mechanical properties can be obtained. In this case, the stretching in the machine axis direction is preferably carried out at the same time as the polyester melt is discharged from the slit, and the stretching in the direction perpendicular to the machine axis is carried out either 1) at the same time as the discharge, or 2) in the machine axis direction at the same time as the discharge. After the stretching, the stretching may be carried out at, for example, 180°C or higher.

The polyester film or sheet obtained by the above method itself has excellent dimensional stability, heat resistance, and mechanical properties, but it can be further heat treated at a temperature of, for example, 180°C or higher and lower than the softening point of polyester. It is preferable to do so. Of course in this case 0.01
In particular, dimensional stability can also be improved by heat treating under tension or relaxation for ~10 minutes, or by treating the polyester film or sheet under conditions that cause the polyester to undergo inherent polymerization.

According to the method of the present invention, an industrially useful polyester film or sheet with little thickness unevenness can be obtained from a polyester having the property of forming an optically anisotropic melt by a melt film forming method.

In addition, in the present invention, the flow start temperature of polyester is determined when approximately 1 g of polyester is heated to a diameter of 1 mm and a length of 5 mm.
The polymer is placed in a high-performance flow tester equipped with a cap with mm-sized holes, and heated at a rate of about 10°C per minute from room temperature under a pressure of 100 kg/cm ² to soften the polymer and begin to flow out from the cap. Defined as temperature.

Further, the shear rate (γa) and the apparent melt viscosity (ηa) are measured at the measurement temperature using the Koka type flow tester as described above, and are calculated by the following formula.

γa=4Q/πr ³ ηa=πpr ⁴ /8lQ [where, Q: discharge amount (cc/sec), r: capillary radius (cm), P: extrusion pressure (dyne/cm ² ), l;
Capillary Length (cm)] Next, the method of the present invention will be explained with reference to Examples.
In addition, the intrinsic viscosity (ηinh) in the examples is for polymer 50
mg was dissolved in 10 ml of p-chlorophenol, and the relative viscosity (ηr) was determined at 50°C and calculated using the following formula.

ηinh=lnηr/0.5 Example 1 and Comparative Example 1 115 parts of phenyl p-oxybenzoate, 114 parts of diphenyl isophthalate and 42 parts of hydroquinone together with 0.089 part of stannous acetate at a temperature of 280 to 290°C;
The reaction was carried out by heating for 3 hours under normal pressure, and then the pressure was gradually reduced to 310°C, and the absolute pressure was 20°C.
The reaction was carried out for 50 minutes under mmHg. The obtained polymer had an intrinsic viscosity of 1.02, a flow initiation temperature of 295°C, and an apparent melt viscosity of 380 at a shear rate of 1000 sec ^-1 .
It was poise.

This polymer was ground into 12-24 meshes and heated to 250°C.
Solid phase polymerization was carried out under reduced pressure of 0.01 mmHg for 10 hours. The obtained high polymer was heated at 360℃ and a shear rate of 100sec ¹ .
It showed a melt viscosity of 78,000 poise.

This high polymer is melted at 360°C and extruded at a speed of 0.5 m/min using a film forming device equipped with a ring die with a diameter of 150 mm, a slit width of 0.5 mm, and a land length of 30 mm. The cylindrical film was wound up at a speed of 4 m/min. During this time, the outer ring die was rotated at a speed of 12 times/min, and the pressure inside the cylindrical film was adjusted so that the diameter of the cylindrical film after being discharged was approximately constant. The obtained film is transparent and has Young's modulus in the longitudinal direction, strength, and elongation, respectively.
700Kg/mm ² , 20Kg/mm ² and 4%, and the transverse Young's modulus, strength and elongation are 300Kg/mm ² and 15, respectively.
Kg/mm ² and 8%. Furthermore, this film
The shrinkage rate after being held at 250°C for 5 minutes was 1% or less in both the vertical and horizontal directions, and it had extremely excellent dimensional stability.

For comparison, the above-mentioned high polymer was melted at 360°C, and a T-shaped material with a length of 100 mm, a slit width of 0.5 mm, and a land length of 30 mm was prepared.
The polymer was extruded at a speed of 0.5 m/min using a film-forming device with a die, and the film was then wound up at a speed of 5 m/min.

The obtained film was transparent, and the Young's modulus strength and elongation in the machine direction were 1500 Kg/mm ² , 30 Kg/mm ² and 2%, respectively, while the Young's modulus, strength and elongation in the transverse direction were 100 Kg/mm ² , respectively. , 1Kg/mm ² and 4%.

Furthermore, when the high degree of polymerization polyester used in Example 1 and Comparative Example 1 was placed on the sample stage of a polarizing microscope equipped with a heating cell and its melting state at 360°C was observed, the field of view was bright even under crossed nicol conditions, and it was optically stable. It was confirmed that it has the property of forming an anisotropic melt.

Claims (1)

[Claims] 1. When forming a film by melt-extruding a polyester having the property of forming an optically anisotropic melt through a slit, a polyester melt having a melt viscosity of at least 1000 poise at 360° C. and a shear rate of 100 sec ^-1 is 1. A method for forming a polyester film, which comprises extruding the polyester while applying shear stress in a direction perpendicular to the discharge direction at a shear rate that is at least twice the shear rate in the discharge direction while passing through a slit.