JPH09207151A - Production of film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve film forming stability by improving the thickness irregularity of a film at a welded part when a belt welded along its peripheral direction is used and reducing the meandering of the belt. SOLUTION: In a method for producing a film by casting a polymer soln. on a support to mold the same, an endless belt having at least one welded part 2 along the peripheral direction thereof and characterized by that the flatness of the welded part is 1/150 or less and the length deviation of both end parts of the belt is 1% or less of the average length of the belt is used as the support.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a solution film-forming film using an endless belt as a support.

[0002]

2. Description of the Related Art When an organic polymer becomes a molten state by applying a temperature higher than its melting point, it is discharged as a molten film from a die and molded into a film. Polymers with a temperature higher than the decomposition temperature will decompose before melting, so dissolve the polymer in a suitable solvent, cast the polymer solution thus obtained on a support, and then remove the solvent. It is formed into a film by the film method. Examples of films formed by such a solution film forming method include cellulose, vinyl acetate, aromatic polyamide, and aromatic polyimide films.

The polymer solution cast on the support requires time for removing the solvent and adjusting the orientation until it has self-holding property, but it generally takes a long time and therefore the support is required. An endless belt is used as the above (as an example of aromatic polyamide, Japanese Patent Laid-Open No. 4-139229).

[0004]

The material of the belt that can be used may be limited depending on the film to be formed. For example, there are cases where only a specific material can be used due to corrosiveness, adhesiveness, etc., and the width of the belt that can be produced is inevitably determined due to the restrictions of the belt manufacturing equipment. However, from the viewpoint of productivity, it is preferable to produce a wide film with a wide belt, but for this purpose, a method of widening the belt by welding along the circumferential direction (longitudinal direction) is adopted. . However, if the precision of the welded portion is poor, there are problems that the unevenness of the thickness of the film formed is deteriorated, and the running property of the belt and the stability of the film formation are poor.

An object of the present invention is to solve such a problem,
It is an object of the present invention to provide a method for producing a film which has good thickness unevenness even when a wide film is formed and enables stable film formation.

[0006]

In order to solve the above problems, the method for producing a film of the present invention is a method for producing a film in which a polymer solution is cast on a support to form a film.
The support has at least one welded portion along the circumferential direction of the belt, the flatness of the welded portion is 1/150 or less, and the length deviation of both end portions of the belt is the average length of the belt. The method is characterized by using an endless belt having a thickness of 1% or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The film referred to in the present invention is a solution film-forming film formed by casting a solution containing a polymer and a solvent as main components from a die onto a support. The type of solvent is not particularly limited as long as it dissolves the polymer. The concentration of the polymer in the solution depends on the kind of the polymer, but is generally 3 to 50% by weight, and in the solution, other than the polymer and the solvent, depending on the purpose, a lubricant, a plasticizer, and a conductive material Particles, antioxidants, and other additives may be blended. As the polymer, aromatic polyamide,
Aromatic polyimide, polyarylate, polycarbonate, cellulose polymers such as cellulose diacetate and cellulose triacetate, vinyl acetate and polyvinyl alcohol can be used.

The form of the support used in the production of the film of the present invention is an endless belt. As the material,
There are iron, stainless steel (SUS), nickel, titanium, tantalum, copper, hastelloy and the like. Further, the surface of the belt may be plated or surface-treated with chromium, gold, silver, nickel or the like, if necessary, in order to improve corrosion resistance, hardness, decrease in adhesiveness and the like. Examples of the surface treatment include forming a thin film of oxide hydrate of chromium, forming a silicone or fluorine film.

It is preferable that the thickness of the belt is 0.5 to 3 mm because the flatness is good. More preferably 1
It is 2.5 mm. Further, the width is preferably wide from the viewpoint of productivity, and 1 to 6 m is preferable in use. It is preferable that the width of the belt can be made as wide as possible at the time of manufacturing the belt, but when it is not possible due to the restrictions of the ingot, rolling machine, etc., widen the material of a certain width by welding along the circumferential direction (longitudinal direction). Is done. The flatness of the weld along the circumferential direction needs to be 1/150 or less. It is more preferably 1/300 or less. If it is larger than this, the unevenness of the thickness of the film is deteriorated due to the welded portion,
The belt running may be affected.

Further, usually, at least one weld portion for endlessness exists. Or, depending on the size of the belt required and the size of the belt material that can be manufactured,
In some cases, more than one place is required. The flatness of this weld is also 1 /
It is preferably 150 or less. More preferably 1 /
It is 300 or less.

The length deviation at both ends of the belt must be 1% or less of the average length of the belt. Preferably 0.5
% Or less, more preferably 0.2% or less. If it is more than 1%, the meandering of the belt becomes large and it becomes difficult to stabilize the running.

1 to 4 show examples of the structure of the endless belt. 1 and 2 show an endless belt 1 in which a welded portion 2 along the belt circumferential direction is provided at one location in the belt width direction. FIG. 3 shows an endless belt in which two welded portions 2 along the belt circumferential direction are provided at two positions in the belt width direction. FIG. 4 shows the endless belt 1 in which the welding portion 2 along the belt circumferential direction is provided at one location, but the welding portions 3 extending in the belt width direction are provided at a plurality of locations. Further, the present invention includes the case where there are three or more welded portions along the belt circumferential direction, and is not limited to the illustrated one.

The casting of the film is preferably performed 35 mm or more inside the end portion of the belt. More preferably, the inner side is 50 mm or more. Outside this, the stability of the film formation deteriorates due to the influence of vibration of the belt and the like.

In the film of the present invention, when the polymer is an aromatic polyamide or an aromatic polyimide, the effect of the present invention is great and it is preferable. Although the thickness of the film to be formed is not limited, it is generally 1 to 100 μm. Especially 10μ
When the film is thinner than m, the influence of the welded portion of the belt becomes large, so that the effect of the present invention becomes relatively large.

The method for producing the film of the present invention will be described below by taking the case of an aromatic polyamide film as an example, but the invention is not limited thereto. First, in the production of aromatic polyamide polymer, when it is obtained from acid chloride and diamine, in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF). , Solution polymerization or interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride is by-produced.When neutralizing this, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate and lithium carbonate, and ethylene oxide,
Organic neutralizing agents such as propylene oxide, ammonia, triethylamine, triethanolamine, diethanolamine are used. The reaction between the isocyanate and the carboxylic acid is performed in an aprotic organic polar solvent in the presence of a catalyst.

These polymer solutions may be used directly as a film-forming stock solution, or the polymer may be isolated once and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to prepare a film-forming stock solution. Good.

In order to form fine irregularities on the surface of the film, it is preferable to add particles. The method of adding the particles includes a method in which the particles are sufficiently slurried in a solvent in advance and then added as a solvent for polymerization or a solvent for dilution, and a method in which the particles are directly added after preparing a film-forming stock solution.

A higher polymer concentration is desirable because it leads to improved productivity, but from the viewpoint of a realistic process, it is 3-5.
It is within the range of 0%.

The film-forming stock solution prepared as described above is used to form a film by a solution film-forming method. The solution film-forming method includes a dry method, a dry-wet method, and a wet method, but any method may be used as long as it uses an endless belt and is not particularly limited.

The case of forming a film by a dry-wet method will be explained as an example. First, the above solution is extruded from the spinneret onto an endless belt to form a thin film, and then the solvent is scattered from the thin film layer until the thin film has a self-holding property. To do.

The film thus cast on the support is dried by a method such as hot air, support heating or infrared heating to remove the solvent. Room temperature ~
The boiling point of the solvent + 20 ° C., within the range of 60 minutes, preferably from room temperature to the boiling point of the solvent.

The film that has undergone the dry process is introduced into the wet process, where the solvent and impurities contained in the film are removed. This bath is generally composed of an aqueous medium and may contain an organic solvent, an inorganic salt or the like in addition to water. However, the water content is generally 30% or more, preferably 50% or more, and the bath temperature is usually 0 to 100 ° C.

The film that has gone out of the wet process is further dried and heat-treated to become a film. 200 to 4 as temperature
At 50 ° C., the processing time is 1 second or more and 60 minutes or less.

The film formed as described above may be stretched during the film forming process for the purpose of improving the thickness unevenness and mechanical properties. As for the draw ratio, the longitudinal draw ratio is 0.95 to 2
Fold (longitudinal stretching ratio is defined as a value obtained by dividing the winding speed by the casting speed), and an area ratio of 0.8 to 4 times (an area ratio is an area of the film before stretching and an area of the film before stretching). It is preferable to be in the range of local thickness unevenness and mechanical properties, and more preferably, the longitudinal stretching ratio is 1.05 to 1.5 times, and the area ratio is 1.1 to 1.3. Double.

By winding the film obtained as described above, an aromatic polyamide film is obtained.

The method of measuring each characteristic and the method of evaluating the effect in the present invention are as follows. (1) Flatness The flatness is measured by the method shown in FIG. FIG. 5 is a diagram showing an example for obtaining the flatness of the welded portion when the back surface of the welded portion of the belt forms a recess, and the back surface portion of the belt welded portion is parallel to the width direction of the belt. It is a thickness direction schematic sectional drawing. FIG. 6 is a diagram showing an example for obtaining the flatness of the welded portion when the back surface of the welded portion of the belt forms a convex portion. The back surface portion of the belt welded portion is parallel to the width direction of the belt. It is a schematic cross-sectional view in the thickness direction. Apply a tension of 1 kg / mm ^{2 in} the longitudinal direction of the belt,
A ruler 4 is applied to the back surface side of the belt of the welded portion at a right angle to the welding direction, and h is measured with a gap gauge. The length L of the non-flat portion is obtained and expressed as h / L. 10 points are measured in the belt circumferential direction, and the average value is shown. If there are multiple welds, calculate the average of them.

(2) Length deviation at both ends of the belt The length of the belt is obtained at both ends (A1 and A2) and arithmetically averaged to obtain the average belt length. The difference between the lengths of both ends is calculated and divided by the average length of the belt. | A1-A2 | / [(A1 + A2) / 2]

(3) Unevenness of Film Thickness The film is sampled so that the film-formed portion on the welded portion along the circumferential direction of the belt is included, and the film is measured in the film width direction (TD direction) with an electronic micro-thickness gauge. When the thickness of the film formed at the welded portion of the belt is within 20% of the thickness of the portion other than the welded portion, it is evaluated as ◯, and when larger than that, it is evaluated as x.

(4) Running property of belt A film was formed using the belt shown in the example, and when the meandering amount of the belt per 10 hours was within 20 mm, it was ○, when it was from 20 to 30 mm, Δ, and it was larger. The case was marked with x.
The meandering control was performed by moving the shaft of one of the drums supporting the belt to change the tensions at the left and right ends of the belt.

(5) Film-forming stability Film-forming stability was evaluated as ◯ when the film could be formed without breaking the film for 10 hours or more, and as x when the film was less than that.

[0031]

【Example】

Example 1 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component and 4,4′-diaminodiphenyl ether corresponding to 15 mol% were dissolved in N-methylpyrrolidone (NMP), and this was dissolved in this. Polymerization was completed by adding 2-chloroterephthalic acid chloride corresponding to 99.7 mol% and stirring for 4 hours. 0.05μ to this
The m-diameter silica was added at 0.2% by weight based on the polymer. This was neutralized with lithium carbonate, and then ammonia water was diluted with NMP and added to give a polymer concentration of 10.
An aromatic polyamide solution having 8% by weight and a solution viscosity of 4000 poise (30 ° C.) was obtained.

This polymer solution was passed through a 1 μm-cut filter and then cast from a die onto an endless belt. The belt is made of nickel and has an overall width of 1.2 m.
With respect to the width, it is welded at one location along the circumferential direction (longitudinal direction) at the center (the one having a width of 0.6 m is welded by the welding method of FIG. 1). There is only one endless weld.
The surface to be cast is mirror-polished, and the belt has a thickness of 1 mm and a length of 10 m. Other conditions are as shown in Table 1.

The casting position was set so as to be 50 mm from both ends of the belt (referred to as A side and B side, respectively). The solvent was dried on this belt at 130 ° C. until it was self-retaining, and the film was continuously peeled from the belt at a speed of 6 m / min. Next, the film is introduced into a water tank at 50 ° C. to extract the residual solvent and the inorganic salts produced by neutralization, and the water is dried and heat-treated in a tenter at 300 ° C. for 1 minute to give a 5 μm-thick aromatic salt. A polyamide film was obtained. In the meantime, the film was stretched 1.1 times and 1.2 times in the longitudinal direction and the width direction, respectively. As shown in Table 1, the film formation of this film was very stable, and the belt did not meander. Further, the uneven thickness of the film at the weld along the circumferential direction was also good.

Example 2 The belt used is made of SUS304, has a width of 2.2 m, a thickness of 1.6 mm and a length of 30 m. 1.1 as shown in FIG.
Two pieces of m width are welded, and the flatness, length deviation, etc. are as shown in Table 1. Example 1 on this belt
The film was formed by using the same polymer solution as described above. The solvent was evaporated from the cast film at 140 ° C. at 15 m / min, and the self-supporting film was continuously peeled from the belt. Next, the film was introduced into a water tank at 40 ° C. to extract the residual solvent and the inorganic salt generated by the neutralization, and to extract 300 more
Water was dried and heat-treated in a tenter at 1 ° C for 1 minute to obtain an aromatic polyamide film having a thickness of 5 µm. During this period, the film was stretched 1.2 times and 1.3 times in the longitudinal direction and the width direction, respectively. The film of this film was very stable, and the belt did not meander. The thickness unevenness of the film at the welded portion in the circumferential direction of the belt was good.

Example 3 The belt used was made of SUS316 and had a width of 2.4 m, a thickness of 1.6 mm and a length of 30 m. As shown in FIG. 3, there are two welds, and three 0.8 m wide materials are welded along the circumferential direction. A polymer solution was cast onto this belt in the same manner as in Example 2 to form a film, but as shown in Table 1, the film formation was very stable, and the belt did not meander. The thickness unevenness of the film at the welded portion in the circumferential direction of the belt was good.

Example 4 The belt used was made of tantalum and had a width of 1.2 m, a thickness of 1.3 mm and a length of 10 m. As shown in FIG. 4, welding is performed by welding five plates having a length of 2 m and a width of 0.6 m in the length direction, and further welding at one place in the width direction. The flatness was 1/800 at the weld along the circumferential direction. A film was formed using this belt in the same manner as in Example 1, but as shown in Table 1, the uneven thickness of the film at the welded portion of the belt was good. Further, the running property of the belt and the film forming property were excellent.

Comparative Examples 1 to 3 Films having the same width and length as those of Example 2 were used to form films using the same polymer solution as that of Example 2. In Comparative Example 1, the thickness unevenness was large in the portion corresponding to the welded portion along the circumferential direction, and the running property of the belt was also somewhat unstable due to the influence of the flatness of the welded portion. In Comparative Examples 2 and 3, the results are as shown in Table 1, respectively, and none were satisfactory.

[0038]

[Table 1]

[0039]

When the belt cannot be widened due to the constraints of the manufacturing equipment, the belt can be widened by welding along the circumferential direction, but the accuracy of the welded portion is poor. Therefore, there is no belt that can be practically used in terms of quality and film forming stability. However, by using the belt of the present invention, it becomes possible to form a wide film with good thickness unevenness of the film, and the meandering of the belt is small, which enables stable film formation for a long time. In particular, when it is used for forming a film of an aromatic polyamide film, the thickness unevenness of the film required for a magnetic recording medium, which is its main use, is extremely excellent, and good electromagnetic conversion characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a belt having one welded portion along the circumferential direction of the belt.

FIG. 2 is a side view of the belt of FIG.

FIG. 3 is a plan view showing an example of a belt having two welded portions along the circumferential direction of the belt.

FIG. 4 is a plan view showing an example of a belt having one welded portion along the circumferential direction of the belt and several welded portions extending in the width direction.

FIG. 5 is a view showing an example for obtaining the flatness of the welded portion when the back surface of the welded portion of the belt forms a recess,
It is a thickness direction schematic sectional drawing parallel to the width direction of a belt about the back surface part of this belt welding part.

FIG. 6 is a view showing an example for obtaining the flatness of the welded portion when the back surface of the welded portion of the belt forms a convex portion,
It is a thickness direction schematic sectional drawing parallel to the width direction of a belt about the back surface part of this belt welding part.

[Explanation of symbols]

 1 Belt 2 Welded part (extending along the circumferential direction) 3 Welded part (extending in the width direction) 4 Ruler

Claims (5)

[Claims] 1. A method for producing a film in which a polymer solution is cast on a support to form a film, wherein the support has at least one weld along the circumferential direction of the belt. A method for producing a film, wherein an endless belt having a flatness of 1/150 or less and a length deviation of both end portions of the belt of 1% or less of an average length of the belt is used. 2. The method for producing a film according to claim 1, wherein the flatness of the weld along the circumferential direction of the belt is 1/300 or less. 3. The method for producing a film according to claim 1, wherein the length deviation of both ends of the belt is 0.5% or less of the average length of the belt. 4. The method for producing a film according to claim 1, wherein the film is cast inward by 35 mm or more from the end of the belt. 5. The method for producing a film according to claim 1, wherein the film is an aromatic polyamide film or an aromatic polyimide film.