JPH05279506A - Production of porous material - Google Patents

Abstract

PURPOSE:To produce a porous material which is based on a powder blend of a 1:1 alternating copolymer of polytetrafluoroethylene/vinylidene fluoride with hexafluoroisobutylene and has a thickness of 50mum or lower and an excellent compression resistance. CONSTITUTION:After the thermal treatment at 346-326 deg.C, streching at 346 deg.C or lower and quenching are conducted in the process for producing a porous material based on a powder blend of a 1:1 alternating copolymer of polytetrafluoroethylene/vinylidene fluoride with hexafluoroisobutylene by paste extrusion.

Description

Detailed Description of the Invention

[0001]

OBJECT OF THE INVENTION The present invention relates to a method for producing a porous body, and particularly to a 1: 1 alternating copolymer powder of polytetrafluoroethylene (hereinafter abbreviated as PTFE) / vinylidene fluoride and hexafluoroisobutylene (hereinafter referred to as CM-X). (Abbreviated) The present invention relates to a method for producing a blend type porous body.

[0002]

2. Description of the Related Art A heat treatment condition for obtaining a molded product of a thinner and stronger polytetrafluoroethylene porous body by using a material of polytetrafluoroethylene alone is obtained by using a clear regulation. Japanese Patent Fair 2-796
The technology disclosed in No. 7 is very high in industrial value. That is, the technique disclosed in Japanese Examined Patent Publication No. 2-7967 discloses that "a green compact obtained by paste extrusion of polytetrafluoroethylene has a melting point of the fine powder or less and is obtained from the fine powder. After heat treatment at a temperature not lower than the melting point of the molded product, no change in the endothermic peak of the fine powder on the crystal melting diagram by a differential scanning calorimeter is caused and the specific gravity of the molded product becomes 2.0 or more. The method for producing a polytetrafluoroethylene porous body is characterized in that the powder is stretched at a temperature equal to or lower than the melting point of the powder.

However, even with this technique, there is a large limit in meeting the difficult problem of reducing the thickness and at the same time not lowering the compressive strength, and a thin polytetrafluoroethylene porous body is practically used. It is a non-negligible obstacle to the application of.

Even if this problem is solved by another method, the basic physical properties of a polymer called polytetrafluoroethylene, such as excellent heat resistance, chemical inertness, and a minimum level of refractive index, Surface tension and dielectric constant,
If it does not retain a high degree of electrical insulation, its application will be very narrow, and it will be considerably less important. That is, there is a demand for a method of producing a porous body having a small thickness and excellent compression resistance while maintaining the basic physical properties of PTFE as much as possible.

[0005]

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art, to have a thin thickness of 50 μm or less and to have excellent compression resistance, and to retain the basic physical properties of polytetrafluoroethylene. It is intended to provide a method for producing a PTFE / CM-X powder blend type porous body.

[0006]

The gist of the present invention is to use a 1: 1 alternating copolymer powder blend system blend of polytetrafluoroethylene / vinylidene fluoride and hexafluoroisobutylene as the material of the polytetrafluoroethylene porous body. And in the manufacturing method, there were two points that heat treatment conditions were used so as to obtain a thin polytetrafluoroethylene porous body having excellent lateral strength.
By combining these two, it is possible to obtain a thin porous body having excellent compression resistance while maintaining the basic physical properties of polytetrafluoroethylene.

As PTFE, fine powder separated from a dispersion produced by emulsion polymerization and having a particle diameter of about 20 μm to 500 μm is used. A 1: 1 alternating copolymer of vinylidene fluoride and hexafluoroisobutylene (trade name: CM-X, Montecatini Co., Montefluos Department) is currently a product of Pilot Plant Steel and has a coating grade (particle size 20 μm). Compression molding grade (particle size 20-800μm) and dispersion (solid content 25% and 45%, particle size 0.1-0.2μ)
There are 3 types of m). Of these, coating grades are suitable for the blends of this invention. There is no particular limitation on the blending ratio of CM-X. The extrusion aid for paste extrusion may be a conventional petroleum solvent such as Isopar E and Isopar M (Esso Chemicals) or Sumoy P-55 (Matsumura Oil Co., Ltd.).

With respect to the blending amount of the extrusion aid, depending on the blending ratio of CM-X, the larger the blending ratio of CM-X, the smaller the blending ratio. C
In the case of the MX blend, it is more difficult to obtain an extrudate having a good appearance and no cracks by paste extrusion than in the case of using PTFE alone. The suitability of the wet treatment is extremely important.

PTFE / obtained by these methods
The heat treatment conditions for the CM-X powder blend type unsintered molded product and the stretching conditions necessary for making it porous are described in JP-B-2-7967.
Almost the same as that described in No. 346 ° C-3
It is heat-treated in the temperature range of 26 ° C., stretched at a temperature of 346 ° C. or lower, and then rapidly cooled.

What is particularly important in making the PTFE / CM-X powder blend system porous is quenching immediately after stretching at a temperature of 346 ° C. or lower, or without this, fracture of the blend porous body may occur. is there.

Polyflon TFE Fine Powder F-10
3 (Daikin Industrial Products) and CM-X Powder Coating Grade 0, 5, 10, 15, 30, 46, 50, 7
A 5% powder blend sample was compounded and for each sample, as an extrusion aid, Smoyl p-55 (bp31
4 to 373 ° C.) was uniformly mixed at 15%, and after stirring and shaking well so that PTFE was not fibrillated, it was allowed to stand at RT for 24 hours.
It was left for h. A billet is preformed from these and a thickness of 0.1 to 300 is obtained at a temperature of 300 ° C. or less using a die for tape.
Paste extrusion molding was performed on a tape having a width of 0.5 mm and a width of 10 mm.

This tape was heat-treated and stretched under various conditions as shown in Table 1 to form a porous tape having a thickness of 25 μm and a porosity of 80%. The permanent deformation rate (%) was measured by applying a 50 gf load for 5 minutes and then removing at RT by an area of 1 cm ² ).

From these results, it can be seen that the thin film of the porous body made of the PTFE / CM-X powder blend system has excellent compression resistance.

[0014]

[Table 1]

[0015]

As described above, according to the present invention, the thickness is 50 μm or less, the compression resistance is excellent, and the PT
It is possible to manufacture a PTFE / CM-X powder blend type porous body which retains the basic physical properties of FE, and its industrial value is extremely large.

Claims (1)

[Claims] 1. A 1: 1 ratio of polytetrafluoroethylene / vinylidene fluoride and hexafluoroisobutylene.
A method of molding an alternating copolymer powder blend type porous body by paste extrusion, comprising heat-treating at a temperature range of 346 ° C to 326 ° C, stretching at a temperature of 346 ° C or less, and then rapidly cooling. A method for producing a 1: 1 alternating copolymer powder blend type porous body of polytetrafluoroethylene / vinylidene fluoride and hexafluoroisobutylene.