JPH0653813B2 - Method for producing polytetrafluoroethylene resin composite composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polytetrafluoroethylene resin composite composition. More specifically, it relates to a method for producing a polytetrafluoroethylene resin composite composition comprising a polytetrafluoroethylene resin and another polymer substance.

[Conventional technology]

Heretofore, when a composite composition with other substances was produced using a polytetrafluoroethylene resin fine powder produced by an emulsion polymerization method, there was a problem in its dispersion. For example, even if you mix pigments and dyes with this resin fine powder,
Even if the mixture is shaken with stirring using a solvent or the like, the mixture formed therein is only in a non-uniform dispersed state that can be seen immediately by the eye. Similarly, in the case of mixing with other polymer substances, it is the actual situation that very good dispersion cannot be expected.

This is because polytetrafluoroethylene resin fine powder (fine powder) obtained by a commercially available emulsion polymerization method forms particles having an average particle size of about 500μ in which primary particles of about 0.3μ are aggregated, and this resin is also difficult to wet. It is considered that this is because the mixed components do not penetrate into the inside.

In order to improve these points, it is necessary to further finen the fine powder so that the average particle diameter is several tens μ or less, preferably several μ or less. However, the commonly used microparticulation methods, such as dry or wet milling, cause the disadvantages that the particles fuse together and form crystalline fibers by shearing. Such a thing is remarkable when kneading fine powder with an open roll, a kneader, etc. Therefore, it is difficult to obtain a good dispersion by such a method.

Further, as another method, it is also possible to disperse a dispersion which is in the order of primary particles in advance, but even if the dispersion is simply mixed by stirring by this method, the dispersion is fused and causes aggregation. Since it is granulated, an effective dispersed mixture cannot be obtained.

[Problems to be solved by the invention]

Therefore, the present inventors use the polytetrafluoroethylene resin dispersion forming the primary particle order as it is, in the latter method, the dispersion is fused at the time of mixing, and conditions under which agglomeration is not caused. As a result of repeated various investigations for obtaining, by mixing at a temperature below the fusion point of the dispersion or solution of the other polymer substance and the polytetrafluoroethylene resin, by forming a polytetrafluoroethylene resin composite composition, It has been found that this problem can be effectively solved.

[Means for solving problems]

Therefore, the present invention relates to a method for producing a polytetrafluoroethylene resin composite composition, wherein the production of the polytetrafluoroethylene resin composite composition comprises a dispersion or solution of polytetrafluoroethylene resin dispersion and other polymer substances. , And mixed at a temperature of 10 ° C. or lower, and then obtained as a solid product.

As the polytetrafluoroethylene resin dispersion, an aqueous dispersion itself produced by an emulsion polymerization method is generally used, but a fine powder of polytetrafluoroethylene resin is used as a halogenated hydrocarbon such as methylene chloride or trichlorotrifluoroethane. Add to a solvent or a solvent with which they are easily mixed such as a mixed solvent such as methyl ethyl ketone, and after impregnating these solvents into the powder, while cooling below the fusion point of the polytetrafluoroethylene resin, there are fluorine-based nonionic It can also be used as a mixed liquid in which a surfactant or the like is added, and the mixture is agitated with a homogenizer or the like to form fine particles.

As the other polymer substance mixed with this, various rubbers or resins are used depending on the intended use of the composite composition. For example, fluorocarbon rubber is used when chemical resistance, heat resistance, gas barrier property, etc. are required, and silicone polymer is used when used for oxygen-enriched membranes. Also, NBR, butyl rubber, polyimide resin, etc. are appropriately used.

These two are mixed at a temperature of about 10 ° C. or lower which is a temperature of about 15 ° C. (which also changes depending on the crystallinity) which is the fusion point of the polytetrafluoroethylene resin. If mixing is performed at a temperature higher than this, for example, at room temperature, fusion and agglomeration occur, and a molded product molded from this composite composition cannot have a homogeneous structure.

The solid product is obtained from the mixture by a reprecipitation method, a salt folding method, a drying method or the like depending on the properties of the dispersion, the solution or the like used.

The solid polytetrafluoroethylene resin composite composition is generally used in such a proportion that polytetrafluoroethylene resin accounts for about 20 to 80% by volume and other polymer substances account for about 80 to 20% by volume. In addition to this, various fillers, colorants,
A lubricant or the like is appropriately added for use.

〔The invention's effect〕

When mixing the polytetrafluoroethylene resin and the other polymer substance in the liquid medium, by maintaining the mixing temperature at 10 ° C. or less, it is possible to obtain a polytetrafluoroethylene resin composite composition in a good dispersed state. It is possible to obtain a molded product having a uniform porous structure by applying a suitable combination of means such as compression, extrusion, stretching, rolling and firing to the composite composition. Since such a molded product has not only the characteristics of polytetrafluoroethylene resin but also the shape retention and the reinforcing effect due to the uniform porous structure, it is possible to provide a highly functional composite material. .

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 Polytetrafluoroethylene resin (PTFE) powder
(Mitsui DuPont Fluorochemicals Teflon 6-J, average particle size of about 500μ) 132g, trichlorotrifluoroethane
(Manufactured product Freon TF) -Methyl ethyl ketone (1: 1) mixed solvent 480 ml was added, and the liquid temperature was cooled to 5 ° C. After adding 1.1 g of a fluorine-based nonionic surfactant (Asahi Glass Product Surflon S-381) to this, homogenizer (TK Homomixer manufactured by Tokushu Kika Kogyo Co., Ltd., pulverized with stirring, and 300 mesh bath (particle size 50 μm ) Was formed.

In this state, 260 ml of a methyl ethyl ketone solution containing 6 g of carbon black and 35 g of NBR (Perbunan N3807 NS, Bayer Japan) was added with stirring and the liquid temperature was 5 ° C.
After that, methanol was gradually added to reprecipitate and dried to obtain a black lump.

This black small lump polytetrafluoroethylene resin composite composition was pressed into a plate-like body having a thickness of 1 mm at 60 kgf / cm ² , and then rolled into a film having a thickness of 50 μ with a roll, while maintaining its stretched state. Pressed at 150 ° C.

Comparative Example 1 The treatment temperature of 5 ° C. in Example 1 was changed to room temperature (25 ° C.).

Comparing Example 1 and Comparative Example 1 described above, in the stage of the black small lumps, the white lumps in the lumps of Comparative Example 1 were white.
(Particle size of about 100 to 500 μ) was present, but such particles were not confirmed by observation with an optical microscope in the case of Example 1, and at the stage of the molded sample, the width of about 100 μ was found in the case of Comparative Example 1. Although many white streaks were confirmed, those of Example 1 could not be confirmed.

Example 2 220 g of PTFE dispersion (Teflon 30-J, a product of Mitsui DuPont Fluorochemicals) was used as a methyl-n-hexylketone solution of fluororubber (Viton GF manufactured by DuPont) whose liquid temperature was previously set to 5 ° C. (rubber 76.4 g). (Solution dissolved in 760 ml of solvent) is gradually added while gently stirring, and then ethanol is added to reprecipitate while maintaining the liquid temperature at 5 ° C.
It was washed several times with ethanol and dried.

The obtained polytetrafluoroethylene resin composite composition as a white powder was preformed into a cylindrical shape at 60 kgf / cm ² , and then extruded into a sheet having a thickness of 1 mm at an extrusion pressure of 3.6 ton / cm ² .
This was 100% stretched at a stretching rate of 3.5 cm / sec and pressed at 180 ° C. while maintaining the stretched state to obtain a sheet-like material having a thickness of 0.5 mm.

Comparative Example 2 The treatment temperature of 5 ° C. in Example 2 was changed to room temperature (25 ° C.).

Comparing Example 2 and Comparative Example 2 described above, in the mixing and reprecipitation stage, in Comparative Example 2, dispersion agglomeration was observed during mixing, and the reprecipitated substance did not become a powder but became a lump. At the stage of the molded sample, fluororubber was extracted with acetone, and the sample after the extraction was observed by a scanning electron microscope. As a result, the sample of Example 2 had a PTFE porous structure composed of a connecting part and a fiber part. However, a homogeneous product was not obtained from that of Comparative Example 2.

Example 3 183 g of PTFE dispersion (Teflon 30-J) was added to NBR latex (Nipol 15 manufactured by Nippon Zeon Co., Ltd.) whose liquid temperature was previously set to 5 ° C.
61) In 268 g, the mixture was gradually added with gentle stirring, and then methanol was added while maintaining the liquid temperature at 5 ° C. for reprecipitation, followed by washing with methanol for several times and then drying.

A sheet-like material having a thickness of 0.5 mm was molded from the obtained white powder polytetrafluoroethylene resin composite composition in the same manner as in Example 2, and the molded sample was subjected to NBR rubber extraction with methyl ethyl ketone to perform scanning electron scanning. When observed under a microscope, it was confirmed that it had a PTFE porous structure composed of a connecting portion and a fiber portion.

Example 4 257 g of PTFE dispersion (Teflon 30-J) was dissolved in polydimethylsiloxane (Toray Silicone product SH410) in methylene chloride solution (solution in which 30 g of polydimethylsiloxane was dissolved in 120 ml of solvent), the liquid temperature of which was previously set to 5 ° C. The mixture was gradually added with gentle stirring, and then methanol was added while maintaining the liquid temperature at 5 ° C. for reprecipitation, followed by washing with ethanol several times and drying.

The obtained white powder polytetrafluoroethylene resin composite composition was preformed, extruded and stretched in the same manner as in Example 2, and baked at 350 ° C. for 10 minutes while maintaining the stretched state,
A sheet having a thickness of 1 mm was obtained. When this molded sample was subjected to polydimethylsiloxane extraction with methyl ethyl ketone and observed by a scanning electron microscope, it was confirmed that it had a PTFE porous structure composed of a connecting part and a fiber part.

Claims (3)

[Claims] 1. A polytetrafluoroethylene resin characterized by being obtained as a solid after mixing a dispersion or solution of a polytetrafluoroethylene resin dispersion and another polymer substance at a temperature of 10 ° C. or lower. Method for producing composite composition. 2. The method for producing a polytetrafluoroethylene resin composite composition according to claim 1, wherein an aqueous dispersion produced by an emulsion polymerization method is used as the polytetrafluoroethylene resin dispersion. 3. As a polytetrafluoroethylene resin dispersion, a solvent that easily wets it is added to polytetrafluoroethylene resin fine powder, and the mixture is cooled to a temperature of 10 ° C. or lower in the presence of a fluorine-based nonionic surfactant. The method for producing a polytetrafluoroethylene resin composite composition according to claim 1, wherein a mixed solution which is made into fine particles is used.