JPS6228215A - Molding of fluoroplastic - Google Patents

Abstract

PURPOSE:To make the molding of fluoroplastic at elevated temperature unnecessary by a method wherein the product is molded by mixing water soluble low- boiling organic solvent with aqueous dispersions of fluoroplastic. CONSTITUTION:Five to three hundred percent by volume of water soluble low- boiling organic solvent, the boiling point of which is 160 deg.C or less, is added to 20-70% by weight of aqueous dispersion of polytetrafluoroethylene, tetrafluoroethylene or the like or their copolymer in order to obtain setting precipitate of fluoroplastic. The molding of the obtained setting precipitate of fluoroplastic is done at a temperature ranging from room temperature to 160 deg.C under elevated or reduced pressure. Powder can be blended with the aqueous dispersion. As for the powder, any powder will do provided that the powder is insoluble to water and the water soluble low-boiling organic solvent employed, such as various kinds of polymer, carbon black, fine glass powder or the like. A molded fluoroplastic product is obtained by simultaneously removing both the water in the aqueous dispersion and the organic solvent for setting precipitate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for molding a fluororesin and a powder containing the fluororesin.

Conventional technology Polytetrafluoroethylene (hereinafter abbreviated as PTFE) is known as a resin with excellent properties such as oxidation resistance and oil resistance, but it is well known that it has problems with its moldability. . For example, the method for molding PTFE is described in US Patent No. 259.
A method for molding fine powder is known as described in Japanese Patent No. 3582. The method described herein involves adding a high-boiling oily solvent to an aqueous dispersion and press-molding the coagulated viscous particles.

Problems to be Solved by the Present Invention However, in the above-described fine powder molding method, it is necessary to add a high-boiling point oily organic solvent to an aqueous dispersion and then coagulate it to remove water. There is a problem in that high temperature is required for its removal. Therefore, an object of the present invention is to provide a molding method that can mold PTFE by simultaneously removing water for an aqueous dispersion and an organic solvent for coagulation used in a fine powder molding method.

Fluororesin is also used as a binder for powder molding because it is an extremely stable substance, but a large amount of fluororesin is required to maintain the strength of the molded product, and in some cases powder There was also the problem of compromising its own performance. Therefore, another object of the present invention is to provide a mixture of powder and an aqueous dispersion of fluororesin, which can solve these problems and form a strong powder molded body even with a small amount of fluororesin. The purpose of this invention is to provide a molding method.

Means for Solving the Problems According to the present invention, there is provided a method for molding a fluororesin, which comprises adding a low boiling point water-soluble organic solvent to an aqueous dispersion of a fluororesin, mixing the mixture, and molding the mixture.

According to the present invention, a low-boiling water-soluble organic solvent is added to a mixture of an aqueous dispersion of a fluororesin, water, and a powder insoluble in the following low-boiling water-soluble organic solvents, and the mixture is molded. A method for molding powder is provided.

Functions and Effects of the Invention Fluororesins to which the present invention can be applied include, for example, PTFE,
Copolymer of tetrafluoroethylene and hexafluoropropylene,
A copolymer of tetrafluoroethylene and ethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl buttate, or a copolymer thereof, each in the form of an aqueous dispersion, is used. do. The concentration of fluororesin in the aqueous dispersion is not particularly limited, but is generally 20 to 70% by weight.

The low boiling point water-soluble organic solvent used in the method of the present invention means a water-soluble organic solvent with a boiling point of 160 ° C or less,
Specifically, for example, acetone, methanol, ethanol,
Examples include methyl ethyl ketone and methyl acetate. Two or more kinds of these organic solvents may be used. The proportion of the organic solvent used is not particularly limited, but is generally 5 to 300% by volume based on the aqueous dispersion.

If the amount of organic solvent used is too small, the molding strength of the molded product will be weak (on the contrary, if it is too large, it will be difficult to remove the organic solvent, which is not preferable).

The powder that can be molded by the method of the present invention may be any powder that is insoluble in water and the low-boiling water-soluble organic solvent used, and includes, for example, various polymers, carbon blanks, glass fine powder, inorganic compounds, organic Examples include powders of compounds, fungi, etc. Furthermore, there are no restrictions on the shape or dimensions of the powder, and the powder may be swollen by the solvent.

There is no particular limit to the mixing ratio of the powder and the aqueous dispersion of fluororesin, and it is generally determined by taking into account the strength of the final molded powder. Preferably, the solids content in the gel is between 1 and 20% by weight. If the amount of the aqueous dispersion is too small, the molding strength of the molded product will be weak, and if it is too large, the physical properties of the powder will be impaired, which is not preferable.

According to the present invention, after adding the low boiling point water-soluble organic solvent to the aqueous dispersion, it is necessary to mix the two intimately, for example by stirring well, and if the mixing is insufficient, the strength of the molded product will deteriorate. It falls and becomes brittle. For mixing, a known stirring method or other methods can be used, and the mixing time varies depending on the types of the fluororesin and the low-boiling organic solvent, but a few minutes to several hours is usually sufficient.

The well-mixed mixture of aqueous dispersion and organic solvent is shaped according to conventional methods.

The temperature during molding in the present invention is between room temperature and 160°C, and the pressure applied cannot be absolutely specified because it varies depending on the desired thickness and density of the molded product, and molding may be performed under reduced pressure. good.

The molding method according to the present invention can be applied to insoluble and infusible powders, powders that decompose at high temperatures, etc., does not impair the performance of the powder itself, and is extremely inexpensive.

In addition, when molding a fluororesin or a mixture of powder and fluororesin according to the present invention, for example, antioxidants,
Known additives such as ultraviolet absorbers and dyes may be added.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Example I 50% by volume of methyl alcohol was added to a 45% by weight aqueous dispersion of PTFE, stirred in a mortar for 5 minutes, and the resulting gel was pressure-molded at 40°C using a hot press. I got the film. 60°
The mixture was dried under reduced pressure at C to remove a small amount of residual solvent and water.

The obtained film was an extremely homogeneous, stiff white film.

Example 2 A film was molded in the same manner as in Example 1 except that acetone was used instead of methyl alcohol. The obtained film was a strong film similar to Example 1.

Example 3 A film was obtained by molding in the same manner as in Example 2, except that polychlorotrifluoroethylene was used instead of PTFE. The resulting film was stiffer and more homogeneous than Example 1.

Example 4 - PTFE for polyimide powder (particle size approximately 80 μm)
7% solids by weight of a 50% aqueous dispersion of
Added. Next, acetone was added to the aqueous dispersion in an amount of 75% by volume, and the mixture was stirred in a mortar for 5 minutes, and then pressure-molded at 40'C using a hot press to obtain a film. This film was dried under reduced pressure at 60°C to remove a small amount of residual solvent and water.

The obtained film was extremely homogeneous, and the bending strength of a small piece of 1 cm in diameter and 3 cm in length was measured and found to be 168 kg/crA.

Example 5 A Ketjen black film was produced in the same manner as in Example 1, except that in Example 4, Ketjen black (secondary particle size: 50 μm) was used instead of polyimide powder, and methyl alcohol was used instead of acetone. Obtained. The resulting film was extremely homogeneous and had a bending strength of 112 kg/cra similar to Example 4.

Example 6 A glycine film was obtained in the same manner as in Example 4, except that glycine powder (particle size: about 30 μm) was used instead of polyimide powder.

The obtained film was a homogeneous transparent body.

Comparative Example 1 An attempt was made to obtain a polyimide film in the same manner as in Example 4, except that acetone was not added, but the film was too weak to be molded.

Claims (1)

[Claims] 1. A method for molding a fluororesin, which comprises adding a low boiling point water-soluble organic solvent to an aqueous dispersion of a fluororesin, mixing the mixture, and molding the mixture. 2. Molding of a powder characterized by adding a low boiling point water soluble organic solvent to a mixture of an aqueous dispersion of a fluororesin, water, and a powder insoluble in the following low boiling point water soluble organic solvent, mixing, and molding. Method.