JP2877421B2 - Film production method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a film from a polymer liquid crystal. More specifically, the present invention relates to a method for producing a high quality film having excellent surface properties and excellent mechanical properties from a polymer liquid crystal.

[Conventional technology]

When a film is produced from a polymer liquid crystal, a method of supplying humidified hot air in order to convert an optically anisotropic dope into optically isotropic is known. However, it has been found that a film having sufficiently satisfactory surface properties cannot be obtained in many cases when the film forming speed is increased industrially and isotropic and when the film thickness is increased.

[Problems to be solved by the invention]

It is an object of the present invention to provide a method for industrially producing a film from a polymer liquid crystal at high quality with excellent surface properties and mechanical performance with high productivity.

[Means for solving the problem]

The present inventor has conducted studies from various angles in order to solve the above-mentioned problems, and as a result, has reached the present invention.

If the film forming speed is increased or the film thickness is increased, it is necessary to supply high humidity and high temperature hot air to the cast optically anisotropic dope. In some cases, the surface of the rolled dope was disturbed or crystallized and precipitated, which was found to be a cause of deteriorating the surface properties of the film.

Then, while continuing various investigations on how to improve the surface properties of the film, surprisingly, by dividing the hot air zone and supplying hot air with different temperature and humidity, the high-speed productivity and the surface property of the film were improved. The inventors have found that it is possible to achieve both compatibility and production of a thick film and compatibility with the surface properties of the film, and have reached the present invention.

That is, the present invention is directed to casting an optically anisotropic dope of a polymer liquid crystal from a die onto a support surface while maintaining optical anisotropy, converting the dope to optically isotropic by humidification and heating, and then solidifying. In the method for producing a film to be formed, the above-mentioned humidifying and heating steps are divided into two or more steps, and gases having different humidity and temperature are supplied.

Hereinafter, in order to explain the present invention in more detail, poly-p-
For example, a polymer liquid crystal dope consisting of a concentrated sulfuric acid solution of phenylene terephthalamide (hereinafter abbreviated as PPTA) is cast from a slit die to produce a film. It should be understood that the techniques of the present invention are equally applicable to the law.

PPTA is virtually Which is conveniently produced from a conventionally known paraphenylenediamine and terephthaloyl chloride by a low-temperature solution polymerization method.

If the degree of polymerization of the polymer is too low, a film having good mechanical properties cannot be obtained.
A polymer having a degree of polymerization that gives a logarithmic viscosity ηinh of 4.5 or more (a value measured by dissolving 0.2 g of the polymer in 100 ml of sulfuric acid at 30 ° C.) is selected.

In the method of the present invention, it is necessary to first adjust the optically anisotropic liquid crystal doping of PPTA.

A suitable solvent for adjusting the dope used to form the PPTA film is sulfuric acid at a concentration of 95% by weight or more. With less than 95% sulfuric acid, dissolution is difficult or the dope after dissolution becomes abnormally high in viscosity. Chlorosulfuric acid, fluorosulfuric acid, phosphorus pentoxide, trihalogenated acetic acid and the like may be slightly mixed in the dope. Sulfuric acid can be 100% by weight or more, but a concentration of 98 to 100% by weight is preferably used from the viewpoint of the stability and solubility of the polymer.

The concentration of the polymer in the dope is preferably a concentration that exhibits optical anisotropy at room temperature (about 20 ° C. to 30 ° C.) or higher. Specifically, about 10% by weight or more, preferably about 10% by weight or more is used. Used at 11% by weight or more. At a polymer concentration lower than this, that is, a polymer concentration that does not show optical anisotropy at room temperature or higher, a molded PPTA film often does not have favorable mechanical performance. Although the upper limit of the polymer concentration of the dope is not particularly limited, it is usually 20% by weight or less, particularly a PPT having a high logarithmic viscosity ηinh.
The amount of A is preferably 18% by weight or less, more preferably 16% by weight or less.

The dope may contain, for example, ordinary additives such as a bulking agent, a brightening agent, an ultraviolet stabilizer, a heat stabilizer, an antioxidant, a pigment, a dissolution aid, and a lubricant.

Whether the dope is optically anisotropic or optically isotropic,
It can be examined by a known method, for example, a method described in Japanese Patent Publication No. 50-8474, but its critical point depends on the type of solvent, temperature, polymer concentration, degree of polymerization of polymer, non-solvent content and the like. Therefore, by examining these relationships in advance, an optically anisotropic dope is prepared, and the optically anisotropic dope can be changed into an optically isotropic by treating it under the condition of an optically isotropic dope.

The dope used in the present invention is to remove insoluble dust and foreign matter as much as possible prior to molding and solidification by filtration or the like, and to remove gases such as air generated or entrained during melting. preferable. Degassing can be performed after the dope is once prepared, or can be achieved under vacuum (reduced pressure) consistently from the stage of charging the raw materials for preparation. The dope can be prepared continuously or in batches.

The dope thus prepared is cast on a support surface from a die such as a slit die through a dope pipe while maintaining optical anisotropy, that is, as liquid crystal.

It is preferred that the support surface is completely cleaned and dried. The cast optically anisotropic dope is then converted into an optically isotropic dope.

An important point of the present invention is that the humidified and heated hot air is divided and supplied in order to obtain the optically isotropic dope. It is difficult to achieve both compatibility with the surface properties of the film, and compatibility with production of a thick film and its surface properties.

The present invention divides the process of humidification and heating into two or more,
First, the surface of the dope is made isotropic with low-humidity heated air to form a surface layer with good moisture permeability, and then the entire dope is cast at once with high-humidity heated air. The isotropic method is preferred.

However, other ways of thinking about the divided zones,
It may be performed under conditions.

The number of division zones used in the present invention is required to be two or more, specifically 2 to 10, preferably 2 to
There are five.

The casting dope on the support surface is then subjected to a solidification treatment. Water, aqueous sulfuric acid, aqueous sodium hydroxide, aqueous sodium sulfate, and the like, which can be used as the dope coagulating liquid, are preferably 20 to 70% by weight aqueous sulfuric acid. The temperature of the coagulating liquid is preferably set to 10 ° C or lower, more preferably 5 ° C or lower.

Since the coagulated film contains an acid as it is, it is necessary to wash and remove the acid component as much as possible in order to produce a film in which the mechanical performance is hardly reduced by heating. Specifically, it is desirable to remove the acid content to about 500 ppm or less. Water is usually used as the washing liquid. However, if necessary, warm water may be used, or after neutralization and washing with an aqueous alkali solution, washing with water or the like may be performed.

Washing is performed by, for example, running a film in a washing solution, spraying the washing solution, or the like.

The washed film may then be stretched if necessary in hot and humid conditions. Since the PPTA molecular chains can be oriented in the stretching direction by the stretching, the mechanical performance is improved.

Drying is performed under tension, under constant length, or while stretching slightly to limit shrinkage of the film. In order to dry while limiting shrinkage, for example, a method of drying with a tenter dryer, a method of drying by sandwiching between metal frames, and the like can be used. The method and temperature for drying are not particularly limited.

Examples Examples will be shown below, but these examples illustrate the present invention and do not limit the present invention.
Unless otherwise specified in the examples, parts or parts by weight are indicated.

The logarithmic viscosity ηinh was measured by dissolving 0.2 g of the polymer in 100 ml of 98% sulfuric acid and then at 30 ° C. by a conventional method. The viscosity of the dope was measured using a B-type viscometer at a rotation speed of 1 rpm. The thickness of the film is measured by a capacitance-type non-contact thickness gauge (manufactured by Ono Sokki
30mm in the center of the sample film using type CL-230)
Was measured at three points at 10 mm intervals, and the average value of five sheets was obtained. In the sample (MD) direction, the entire width of the sample film was first divided into five equal parts in the width direction, and further cut into 10 mm width × 10 cm length. Width (T
In the direction D), first, the entire width was cut at five points of 20 mm in the length direction, and 10 mm × 10 cm was further cut from the center.

The elongation and modulus were calculated using a constant-speed elongation type elongation measuring machine by cutting a film sample into a 100 mm × 10 mm rectangle, drawing a load-elongation curve five times at a measurement length of 30 mm and a pulling speed of 30 mm / min, and using this. It was done.

The surface roughness Ra (center line surface roughness) representing the surface properties of the film was measured with a Surfcom 550 type surface roughness meter (trade name, manufactured by Tokyo Seimitsu Co., Ltd.) (measuring length 4 mm, cutoff 0.8 mm).

Examples 1 to 3 A PPTA polymer having a logarithmic viscosity ηinh of 7.0 was dissolved at a sulfuric acid polymer concentration of 99.7% at a concentration of 12% to obtain a dope having optical anisotropy at 60 ° C. The viscosity of this dope measured at room temperature was 9500 poise. The dope was degassed under vacuum while maintaining the dope at about 60 ° C. to facilitate film formation. This degassed dope also had the same optical anisotropy as above, and had a viscosity of 4400 poise. The dope is passed through a filter from a tank, and guided to a die through a curved pipe of a gear pump 1.5 m. The tube is maintained at about 60 ° C.

Outside diameter 16.2mmφ, length 19 between slit die and curved tube
An 8-station static mixer made of polished stainless steel with a 4 mm surface 0.4S is installed. The static mixer and the slide die are also maintained at about 60 ° C.

The slip die has a slit of 0.15 mm in width and 300 mm in width, the base part is made of stainless steel, and the liquid contact part of the dope is made of tantalum with a thickness of about 7 mm and polished to 0.4 S did. An optically anisotropic dope was cast from the slit onto an endless belt made of tantalum, and then the casting dope was converted from optically anisotropic to optically isotropic. The endless belt made of tantalum softens the industrial water after performing filtration to cut the content of 1μ or more,
Further, a mirror-polished surface washed and dried with high-purity water having a conductivity of 0.2 μs / cm treated with a high-purity water treatment machine was used. At this time, the zone to be converted to optical isotropic is divided into three zones,
Blowing air of about 5% relative humidity and about 110 ° C into the zone,
Air having a relative humidity of about 20% and about 120 ° C. was blown to the second zone, and air having a relative humidity of about 40% and about 115 ° C. was blown to the third zone.

The isotropic dope was introduced into a 40% by weight sulfuric acid aqueous solution at −3 ° C. together with the belt to be coagulated.

Next, the coagulated film is peeled off from the belt.
After running in water and deoxidizing, run in neutralized solution.
Washed by running in water at ℃. The film after washing is stretched in the MD direction without drying, while changing the speed between the rolls, and then stretched in the TD direction using a tenter drier, and further stretched under constant length using a different tenter dryer for 200 mm. It dried with hot air at ° C.

The stretching conditions in the MD direction in the above wet state are 1.10, 1.2
Table 1 shows the results of measuring the physical properties of the sample manufactured at a speed of about 10 to 12 m / min, changing from 0 to 1.30 times (Examples 1 to 3).

Examples 4 to 6 When converting the optically anisotropic dope of Examples 1 to 3 into optically isotropic, the conditions were changed as follows.
A film was produced in the same manner as in Example 3.

The first zone is blown with air with a relative humidity of about 10% and a temperature of about 110 ° C, and the second zone with a relative humidity of about 45% and a temperature of about 120 ° C
Was blown, and the third zone was made isotropic without being used.

 Table 1 shows the results.

Comparative Examples 1 to 3 When converting the optically anisotropic dope of Examples 1 to 3 into an optically isotropic dope, the relative humidity in all zones was about 40%, and the relative humidity was about 115%.
Examples 1 to 3 except that the air was blown into the isotropic state.
A film was produced in exactly the same manner as described above. The result is the first
As shown in the table, the mechanical performance and surface properties of the film were considerably poor.

Examples 7 to 9 When converting the optically anisotropic dope of the operation of Examples 1 to 3 to optically isotropic, except that the conditions were changed as follows, the films were prepared in exactly the same manner as in Examples 1 to 3. Manufactured.

Air of about 10% relative humidity and about 110 ° C is blown to the first zone, air of about 30% relative humidity and about 120 ° C is blown to the second zone, and about 45% and about 120% of relative humidity is blown to the third zone. ° C air was blown.

Further, it was manufactured by changing the stretching conditions in the wet state to 1.10, 1.20, and 1.30 times (Examples 7 to 9) and changing the speed to 5 to 6 m / min.

 Table 2 shows the results.

Comparative Examples 4 to 6 When converting the optically anisotropic dope in the operation of Examples 1 to 3 into an optically isotropic dope, the relative humidity was about 45% for all zones,
A film was produced in exactly the same manner as in Examples 1 to 3, except that air at about 115 ° C was blown to make the film isotropic. As a result, as shown in Table 2, the mechanical performance and surface properties of the film were considerably poor.

[Effects of the Invention] According to the present invention, a film having excellent surface properties and mechanical performance can be obtained at a high speed, and the productivity is very good.

Even with a thick film of about 20 μ or more, a film having good surface properties can be obtained.

For this reason, the film obtained by the present invention is required to be used as an insulating material for electric equipment rotating at high speed, a magnetic tape, a flexible printed wiring board, an electric wire covering material, a filtration membrane, a capacitor film, an electric insulating film, a video printer tape, and the like. It can satisfy performance and is useful for packaging materials, plate making materials, photographic films and the like.

Claims (1)

(57) [Claims] 1. An optically anisotropic dope of a polymer liquid crystal is cast from a die onto a supporting surface while maintaining the optical anisotropy, and the dope is converted into an optically isotropic by humidification and heating, and then solidified. In the method for producing a film, the above humidifying and heating steps are divided into two or more steps, and gases having different humidity and temperature are supplied.