JPH0679736A - Method for manufacturing polysulphone resin film - Google Patents

Abstract

PURPOSE:To ensure that an excellent cast film free from air bubble entrainment by adjusting the moisture content of polysulphone resin solution to a level of 2wt.% max and thereby improving wettability to a support during casting. CONSTITUTION:A polysulphone resin solution 3 is cast to a support consisting of a stainless belt 1 by a comma roll 5, and thus a polysulphone resin film is formed. This solution 3 is adjusted by a molecular sieve so that the moisture content is reduced to 0.2wt.%. Consequently, wettability to a belt 1 is improved and air 2 is no longer entrained so that a bubble nucleus 4 is not formed. Therefore, the thickness accuracy of the film obtained by peeling it off after drying is enhanced, and the polysulphone resin film has superior smoothness, high transparency and satisfactory appearance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polysulfone resin film, and more particularly to a method for producing a cast film excellent in appearance, smoothness, thickness accuracy and transparency with high productivity.

[0002]

2. Description of the Related Art At present, there are two methods for producing a polysulfone resin film, a melt cast film forming method and a solution cast film forming method. The melt-cast film forming method is, for example, as described in JP-A-52-147662, a polysulfone-based resin melted by heat is extruded from a mold into a film and cast (cast) on the surface of a support. ) And cool to obtain a film.

The film obtained by this melt cast film forming method has an insufficient appearance quality of the film due to fish eyes whose cores are molten residues and foreign substances, and adversely affects transparency and smoothness. Further, in terms of thickness accuracy, it does not exceed the mechanical accuracy of the mold, which is not sufficient.

The solution cast film forming method is described in, for example, Japanese Patent Laid-Open No.
As described in JP-A-111511, a resin is dissolved in a solvent, and a solution such as a comma coater, a lip coater, a doctor blade coater, a bar coater, and a roll coater is used to form a stainless belt, a stainless drum, a plastic film, or the like. It is a method of obtaining a film by casting on a support and then evaporating the solvent to separate it from the support.

When a film is produced by this solution cast film forming method, the solid content of the solution to be cast is 10
Since it is not 0%, when the cast solution is dried, the solvent evaporates and the thickness becomes thin. Therefore, a product obtained by multiplying the variation in thickness due to the mechanical precision of the various coaters described above by the solid content ratio becomes the variation in the thickness of the film after drying, and the thickness precision is improved. Therefore, it is possible to manufacture a film having higher thickness accuracy than the former melt cast film forming method. In addition, since it is possible to cast with a viscosity lower than that in the molten state, it is possible to remove foreign substances with a filter having a smaller retained particle size, which is more advantageous in terms of appearance and smoothness than the melt cast film formation method. is there.

[0006]

Even when a polysulfone-based resin film is produced by a solution cast film forming method having such an advantage, the polysulfone-based resin is changed to a good solvent such as methylene chloride, 1,2-dichloroethane or chlorobenzene. When dissolved, the polysulfone-based resin solution becomes water repellent. For this reason, the wettability of the polysulfone-based resin solution with respect to the stainless steel belt, the stainless steel drum, which is the support when casting, and the stainless steel, chromium, polyester, glass, fluororesin and the like which are the surface materials of the plastic film is low. Therefore, in the actual film formation, as shown in FIG. 1, when the solution 3 is cast on the support 1, it is easy to entrain the air 2, and the entrained air becomes the foaming nuclei 4 in the step of evaporating the solvent and casting. Impairs the appearance, smoothness, and thickness accuracy of the film. Also,
All of these good solvents are low boiling point solvents, and foaming is likely to occur in the drying process after casting on the above-mentioned support, and appearance, smoothness, and thickness accuracy are likely to be impaired. It becomes necessary to reduce the above, and the productivity is remarkably reduced.

This phenomenon also occurs when a poor solvent such as acetone or a plasticizer is added to the solution in addition to the polysulfone resin and the good solvent, depending on the purpose. In order to generate it, it is necessary to examine the coating method or conditions that do not generate foam nuclei.

The object of the present invention is to improve the wettability of the polysulfone-based resin solution with the surface of the support during the production by the solution cast film forming method, and to improve the appearance, smoothness and thickness accuracy by the solution cast film forming method. It is to provide a method for producing an excellent polysulfone-based resin film.

[0009]

Means for Solving the Problems As a result of extensive studies on the above problems, the present inventor has found that when a polysulfone-based resin film is produced by a solution cast film-forming method, the water content in the polysulfone-based resin solution is a support. The inventors of the present invention have found that they contribute to the wetting with the present invention.

That is, the gist of the present invention is that when a polysulfone-based resin film is produced by a solution cast film forming method, the water content in the polysulfone-based resin solution is adjusted to 0.2% by weight or less. A method for producing a polysulfone-based resin film, characterized in that the film is obtained by casting and drying the solution.

The polysulfone resin used in the present invention has a sulfone group in a repeating unit, which is represented by polysulfone which is a co-condensation polymer of 4,4'-dichlorodiphenylsulfone and a sodium salt of bisphenyl A. The aromatic polysulfone-based polymer and the like.

The solid content concentration of the polysulfone-based resin in the polysulfone-based resin solution used in the solution cast film forming method is a solution viscosity of 2000 to 100000 cp.
In the case of a polysulfone resin having a concentration of s, that is, a weight average molecular weight in terms of styrene of 7 × 10 ⁴ , it is preferably 20 to 40% by weight.

The water content of the polysulfone resin solution is preferably 0.2% by weight or less. More preferably,
It is preferably 0.03% by weight or more and 0.2% by weight or less. 0.
If it exceeds 2% by weight, a problem occurs in the solution stability of the polysulfone-based resin, the solution becomes cloudy, the film becomes cloudy even after casting and drying, and the transparency is impaired. This causes problems with the smoothness and thickness accuracy of the film. When the content is 0.03% by weight or less, a slight amount of foaming may occur depending on the manufacturing conditions, which is not a problem in practical use.

The solvent in the polysulfone resin solution is a good solvent such as methylene chloride, 1,2-dichloroethane or chlorobenzene, or a mixture of this good solvent with a poor solvent, a plasticizer or the like depending on the purpose. It is a thing.

The water content of the polysulfone resin solution described in the present invention means the water content with respect to the total amount of good solvent, poor solvent, plasticizer and the like.

The poor solvent described here is preferably one which has poor compatibility with the polysulfone resin and good compatibility with methylene chloride and does not cause coloring. For example,
Acetone, tetrahydrofuran, methyl ethyl ketone,
A poor solvent such as hexane can be used, and two or more kinds of poor solvents may be mixed and used.

The plasticizer is preferably one which has good compatibility with the polysulfone resin, does not cause phase separation or bleed-out, and does not cause coloring. For example, phthalic acid-based, phosphoric acid-based, adipic acid-based, citric acid-based, glycolic acid-based plasticizers can be used, and dicyclohexyl phthalate, butylbenzyl phthalate, tricresyl phosphate, methylphthalyl / ethyl glycolate, etc. can be used. It is preferable, and two or more kinds of plasticizers may be mixed and used.

As a support for casting the polysulfone-based resin solution, a metal such as a stainless belt or a stainless drum, a synthetic resin film such as a polyethylene terephthalate film, or the like can be used, and the surface thereof is a sintered body such as glass or the like. It may be covered with a fluororesin or the like, or may be subjected to a mold release treatment with silicon or a fluororesin.

By using a comma coater, a lip coater, a doctor blade coater, a roll coater, etc., the polysulfone-based resin solution having the adjusted water content is cast on the support, dried, and then peeled from the support.
It is possible to obtain a polysulfone-based resin film that has good thickness accuracy, high smoothness and transparency, and has no defective appearance.

[0020]

[Function] By adjusting the water content in the solution in the case of producing a polysulfone-based resin film by the solution cast film forming method, the wettability to the support at the time of casting the solution is improved, and the inclusion of bubbles is eliminated, It is possible to produce a cast film that has no foam nuclei and is not clouded, that is, has excellent appearance, smoothness, and thickness accuracy.

[0021]

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the method for producing the polysulfone-based resin film of the present invention is not limited to the following Examples.

Example 1 Polysulfone resin having a weight average molecular weight of 7 × 10 ⁴ in terms of styrene, which was dried at 140 ° C. for 7 hours and had a water content of 0.001% by weight, had a water content of 0.01% by a molecular sieve. Dissolved in methylene chloride reduced to 20% and further added water to obtain a solid content of 25% by weight, water content of 0.2% by weight
A solution was prepared so that This solution was cast on a polyethylene terephthalate film by a roll coater so that the thickness after drying would be 100 μm, and dried to produce a film. Table 1 shows the results of evaluation of the number of defects due to foaming after drying and the presence or absence of white turbidity.

Example 2 A solution was prepared with the same polysulfone resin and methylene chloride as in Example 1 so that the solid content was 30% by weight and the water content was 0.1% by weight, and the obtained solution was the same as in Example 1. A film was prepared on and evaluated. The results are shown in Table 1.

Example 3 A mixed solvent of methylene chloride: acetone = 97: 3 (weight ratio) was prepared from the same methylene chloride as in Example 1 and acetone whose water content was reduced to 0.03% by weight with a molecular sieve. Then, the same polysulfone resin as in Example 1 was dissolved in the mixed solvent, and water was further added to obtain a solid content of 30% by weight.
A solution was prepared to have a water content of 0.03% by weight, and a film was produced in the same manner as in Example 1 using the obtained solution.
An evaluation was made. The results are shown in Table 1.

Example 4 The same polysulfone resin as in Example 1 and methylene chloride were used to prepare a solution having a solid content of 30% by weight and a water content of 0.02% by weight. A film was prepared on and evaluated. The results are shown in Table 1.

Example 5 The same polysulfone resin solution as in Example 1 was cast on a stainless steel plate coated with glass by a lip coater so that the thickness after drying was 100 μm, and the film obtained after drying was the same as in Example 1. Was evaluated. The results are shown in Table 1.

Comparative Example 1 The same polysulfone resin as in Example 1 and methylene chloride were used to prepare a solution having a solid content of 30% by weight and a water content of 0.25% by weight. A film was prepared on and evaluated. The results are shown in Table 1.

[0028]

[Table 1]

From Table 1, it can be seen that the films of Examples had almost no defects due to foaming and no clouding.
On the other hand, the film of the comparative example has many defects due to foaming, and the film is opaque and not transparent.

[0030]

EFFECTS OF THE INVENTION According to the present invention, when a polysulfone-based resin film is produced by a solution cast film forming method, the wettability with a support is improved by adjusting the water content in the polysulfone-based resin solution, and foam nuclei are generated. And a white turbidity can be prevented, and a cast film excellent in appearance, smoothness, and thickness accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a solution casting process by roll coating using comma rolls. 1 Support 2 Entrained Air 3 Polysulfone Resin Solution 4 Foaming Core 5 Comma Roll

Claims (9)

[Claims] 1. When a polysulfone-based resin film is produced by a solution cast film forming method, a solution prepared so that the water content in the polysulfone-based resin solution is 0.2% by weight or less is cast and dried. A method for producing a polysulfone-based resin film, which comprises obtaining a film by 2. The method for producing a polysulfone film according to claim 1, wherein the solvent of the polysulfone-based resin solution is methylene chloride. 3. The method for producing a polysulfone resin film according to claim 1, wherein a poor solvent is mixed in the solvent of the polysulfone resin solution. 4. The method for producing a polysulfone resin film according to claim 1, wherein a plasticizer is mixed in a solvent of the polysulfone resin solution. 5. The poor solvent contained in the solvent of the polysulfone-based resin solution is acetone.
The method for producing a polysulfone-based resin film according to 1. 6. The method for producing a polysulfone-based resin film according to claim 5, wherein the amount of acetone contained in the solvent of the polysulfone-based resin solution is 1 to 30% by weight based on the total amount of the solvent. 7. The polysulfone-based resin solution according to claim 1, wherein the polysulfone-based resin solution is cast on a support made of a metal or a synthetic resin film when the film is produced by the solution cast film forming method. Method for producing resin film. 8. The method for producing a polysulfone-based resin film according to claim 7, wherein the surface of the support used for producing the film by the solution cast film formation method is coated with a sintered body. 9. The method for producing a polysulfone-based resin film according to claim 7, wherein the surface of the support when the film is produced by the solution cast film forming method is subjected to a mold release treatment.