JP2702752B2 - Film manufacturing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a film from a polymer liquid crystal, and more particularly, to a method for producing a film from a polymer liquid crystal having excellent surface properties.
The present invention relates to a method for producing a high-quality film having excellent mechanical performance without unevenness in thickness.

(Prior Art) Attempts have been made to obtain a high-performance polymer film using the easy orientation property of a polymer liquid crystal. However, since the polymer liquid crystal is easily oriented in the direction of the force, a special device is required for the production of a film that requires a balance between vertical and horizontal properties. In practice, for example, a method using a conical mandrel, an inflation method, a method of applying a shear in the lateral direction, a method of once converting a liquid crystal into a non-liquid crystal and then solidifying the liquid crystal.

By these methods, the problem of the balance between the vertical and horizontal properties of the film was basically solved, and a film having excellent mechanical performance was obtained. Due to the non-uniformity of the flow of the polymer liquid crystal, the uneven thickness and poor surface smoothness are caused.
This was a major drawback in the practical application of the film.

(Problems to be solved by the invention) An object of the present invention is to provide a polymer liquid crystal having excellent surface properties,
An object of the present invention is to provide a method for industrially producing a high-quality film having excellent mechanical performance without unevenness in thickness.

(Means for Solving the Problems) The present inventors have conducted studies from various angles in order to solve the above-mentioned problems. It was found out that there was unevenness in the flow direction of the polymer liquid crystal in the cross-sectional direction inside the pipe and inside the die based on the unique thixotropic property of the polymer.

Then, in order to reduce the unevenness of the thickness of the film, the dispersion of the shear stress history in the cross-sectional direction of the pipe accumulated in the course of the flow of the polymer liquid crystal in the pipe is eliminated and made uniform, and then guided to the die. The present inventors have found that it is effective to distribute the flow, and that the surface roughness of the film can be improved by doing so, and arrived at the present invention.

That is, the present invention is a method for producing a film, which comprises using a static mixing stirrer at the entrance of a die in producing a film from a liquid crystal polymer.

In the present invention, the polymer liquid crystal is a thermotropic,
The invention is not limited to either lyotropic liquid crystal, and can be applied to any type of polymer liquid crystal of nematic, cholesteric, and smectic. Examples of such a high-molecular liquid crystal include aromatic polyester, aromatic polyazomethine, hydroxypropylcellulose (thermotropic liquid crystal), aromatic polyamide-strong acid solution, hydroxypropylcellulose-water solution, cellulose derivative-acid or organic compound. Solvent solution, polybenzobisthiazole-acid solution,
Polybenzobisoxazole-acid solution (the above is lyotropic liquid crystal).

Next, the present invention is not particularly limited with respect to such a discharge molding method from a polymer liquid crystal. For example,
Extrusion from a ring-shaped die and vertical / horizontal balance by the inflation method, vertical / horizontal balance by casting on a conical mandrel, or non-liquid crystal extruded from a so-called T-die The method can be applied to a method of obtaining a vertical / horizontal balance by solidifying and then solidifying, or a method of obtaining a vertical / horizontal balance by extruding from a T-die and then applying lateral shearing. The point is to improve the unevenness of the thickness of the film caused by the unevenness of the flow rate of the dope of the polymer liquid crystal. Therefore, the present invention is not restricted by the method for keeping the vertical and horizontal balance of the film.

The most important feature of the present invention is that a static mixing stirrer (so-called static mixer) is used at the entrance of the die in producing a film from the above-mentioned polymer liquid crystal.

The static mixing stirrer is called by various names. In short, the mixing in the fluid is performed by splitting and twisting by an element installed in the pipe.

The surface material of the blade of the stationary mixing stirrer is preferably gold, platinum, silver, tantalum, stainless steel, etc., which is excellent in acid corrosion resistance.
Alloys of any of these compositions may be used, and these noble metals may be mixed with other metals in amounts up to about 20% by weight.

For example, in the case of a polymer liquid crystal using a highly corrosive strong acid as a solvent, it is desirable to have excellent corrosion resistance.

It is desirable that the surfaces of the blades of the static mixing and stirring device used in the present invention are finished to a mirror surface, and that the more the elements of the static mixing and stirring device are combined, the better the mixing is.

The direction of the blades of the static mixing stirrer at the connection between the static mixing stirrer and the die is closely related to the production of a film having less unevenness in thickness, and if the die is a slit die, it is connected to the slit die. It is desirable to install them in parallel.

Hereinafter, in order to explain the present invention in more detail, poly (p
Taking a polymer liquid crystal dope comprising a concentrated sulfuric acid solution of phenylene terephthalamide (hereinafter abbreviated as PPTA) as an example, a case where a film is produced from a slit die will be described. It should be understood that the technique of the present invention can be similarly applied to the film forming method.

PPTA is virtually And 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 obtained by dissolving 0.2 g of the polymer in 100 ml of sulfuric acid and measuring at 30 ° C.) is selected.

In the method of the present invention, first, it is necessary to prepare an optically anisotropic dope (liquid crystal dope) of PPTA.

A suitable solvent for preparing the dope used to mold the PPTA film is sulfuric acid at a concentration of 95% by weight or more. With less than 95% sulfuric acid, it is difficult to dissolve, 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 from the viewpoints of polymer stability and solubility, etc.
A concentration of 100100% by weight is preferably used.

The concentration of the polymer in the dope is preferably room temperature (about 20 ° C. to 30 ° C.) or more than that which exhibits optical anisotropy at a temperature higher than that. Specifically, about 10% by weight or more, preferably Used at about 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, the molded PP
TA films often do not have favorable mechanical properties. Although the upper limit of the polymer concentration of the dope is not particularly limited, it is usually not more than 20% by weight,
The content is preferably 18% by weight or less, more preferably 16% by weight or less, based on PTA.

The dope may contain ordinary additives, for example, extenders, delusterants, ultraviolet stabilizers, heat stabilizers, antioxidants, pigments, dissolution aids, lubricants and the like.

Whether the dope is optically anisotropic or optically isotropic can be determined by a known method, for example, a method described in Japanese Patent Publication No. 50-8474, but its critical point is determined by the type of solvent, temperature, and polymer. It depends on the concentration, the degree of polymerization of the polymer, the content of the non-solvent, etc.
By making an optically anisotropic dope and changing the condition to be an optically isotropic dope, it is possible to change from optically anisotropic to optically isotropic.

In the dope used in the present invention, as much as possible, insoluble dust and foreign substances are removed by filtration or the like prior to molding and solidification, and gas such as air generated or entrained during melting is removed. Preferably. Degassing can be performed after the dope is once prepared, or can be achieved by performing it under vacuum (reduced pressure) consistently from the stage of charging the raw materials for preparation. The preparation of the dope can be performed continuously or batchwise.

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

An important point of the present invention is to insert a static mixing stirrer between the dope piping and the slit die to make the flow of the dope uniform, and without using this stirrer, the unevenness of the film thickness is not reduced.

It is important that the surface of the blade of the static mixing stirrer of the present invention is polished to a mirror surface, specifically, a mirror surface finished with Rmax of 0.8S or less, more preferably 0.4S or less. .

The dope cast on the support surface converts the dope from optically anisotropic to optically isotropic prior to solidification.

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

Until then, the solidified film contains acid. In order to manufacture a film in which the mechanical properties are hardly reduced by heating, it is necessary to wash and remove the acid part as much as possible. Specifically, it is desirable to remove the acid content to about 500 ppm or less. Water is usually used as a washing liquid,
If necessary, it may be washed with water or the like after warm water or neutralized and washed with an aqueous alkali solution. The cleaning is performed by, for example, running the film in the cleaning liquid or spraying the cleaning liquid.

The washed film can then be stretched in the wet state, if necessary, but the stretching can orient the PPTA molecular chains in the stretching direction, thereby improving the mechanical properties.

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

(Examples) Examples will be shown below, but these examples are intended to explain the present invention and do not limit the present invention.
In the examples, unless particularly limited, the values are parts by weight or% by weight. Logarithmic viscosity ηinh is 98% sulfuric acid 100ml and polymer 0.
2 g was dissolved and measured at 30 ° C. by a conventional method. The viscosity of the dope is
It was measured at a rotation speed of 1 rpm using a B-type viscometer. The thickness of the film is calculated from the average value of the thickness at 10 measurement points at 1 cm intervals in the film width direction using a capacitance-type non-contact thickness gauge (type CL-230, manufactured by Ono Sokki Co., Ltd.). And the thickness unevenness is (maximum value−minimum value) / average value ×
Calculated from 100. For the elongation and moyduras, a film sample is measured at 100 mm x 10 mm
, And a load-elongation curve was drawn five times at a measurement length of 30 mm and a tensile speed of 30 mm / min, and was calculated from this.

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 manufactured by Tokyo Seimitsu Co., Ltd. (measuring length 4 mm, cut-off 0.8 mm).

Examples 1 to 3 A PPTA polymer having a η inh of 5.3 was dissolved in 99.6% sulfuric acid at a polymer concentration of 12% to obtain a dope having optical anisotropy at 60 ° C. When the viscosity of this dope was measured at room temperature, it was 9200 poise. The dope was degassed under vacuum while keeping the dope at about 60 ° C. to facilitate film formation. Also in this case, it had the same optical anisotropy as above, and the viscosity was 4200 poise. The dope passes through a filter from the tank, and passes through a gear pump to a 1.5-meter curved tube reaching the die.

Outer diameter 16.2mmφ, length 194m between slit die and curved pipe
An 8-station static mixer made of polished stainless steel having a surface of 0.4 m and a slit die is also maintained at about 60 ° C.

The slit die has a slit with a gap of 0.15 mm × width of 300 mm, the base part is made of stainless steel, and the liquid contact part of the dope is
An object made of tantalum having a thickness of about 7 mm and polished to 0.4S was used. From this slit, it is cast on an endless belt made of mirror-polished tantalum, and the relative humidity of about 45% is applied to about 13%.
Blowing air at 0 ° C to make the casting dope optically isotropic,
Along with the belt, it was introduced into a 25% by weight aqueous solution of sulfuric acid at −2 ° C. to solidify. Next, the coagulated film was peeled off from the belt and washed by running in warm water at about 40 ° C. The washed film was stretched with a tenter without drying, and then dried with a different tenter at 200 ° C. and hot air under a constant length.

Table 1 shows the results of sampling under different stretching conditions in the wet state.

Comparative Examples 1 to 3 The static mixer was removed from the devices of Examples 1 to 3, and films were produced in exactly the same manner. As a result, as shown in Table 1, although the mechanical performance of the film was quite inferior, the thickness unevenness and the surface property were considerably poor.

(Effect of the Invention) The film obtained by the method of the present invention has no thickness unevenness,
Good surface properties and good mechanical properties can be obtained.

For this reason, the film obtained by the present invention has the required performance of insulating materials and magnetic tapes for high-speed rotating electrical equipment, magnetic tapes, flexible printed wiring boards, wire covering materials, filtration membranes, capacitor films, electric insulating films, video printer tapes, and the like. Can satisfy, packaging material, plate making material,
It is also useful for photographic films.

Claims (1)

(57) [Claims] 1. A method of producing a film from a polymer liquid crystal, comprising using a static mixing stirrer at the entrance of a die.