Method for producing porous polyimide film

Patent metadata

Field	Value
Publication number	US-10177357-B2
Application number	US-201515509247-A
Country	US
Kind code	B2
Filing date	Sep 7, 2015
Priority date	Sep 10, 2014
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

Provided is a method for producing a porous polyimide film with which it is possible to suppress the occurrence of curling in the polyimide-fine particle composite film obtained by firing the unfired composite film. The method for producing a porous polyimide film of the present invention includes, in the following order: forming an unfired composite film using a varnish that contains a resin including polyamide acid and/or polyimide, fine particles, and a solvent; immersing the unfired composite film in a solvent including water; firing the unfired composite film to obtain a polyimide-fine particle composite film; and removing the fine particles from the polyimide-fine particle composite film.

First claim

The invention claimed is:

1. A method for producing a porous polyimide film, the method comprising, in the following order:
applying a varnish onto a surface of a support, the varnish comprising a resin including polyamide acid and/or polyimide, fine particles, and a first solvent;
drying the varnish thus applied to form an unfired composite film;
peeling the unfired composite film off from the support;
immersing the unfired composite film into a second solvent including water;
firing the unfired composite film to obtain a polyimide-fine particle composite film; and
removing the fine particles from the polyimide-fine particle composite film.

2. The method according to claim 1 , further comprising, between the immersing and the firing, pressing the unfired composite film after the immersing.

3. The method according to claim 1 , further comprising, between the immersing and the firing, drying the unfired composite film after the immersing.

4. The method according to claim 1 , wherein said drying the varnish thus applied is carried out under atmosphere or vacuum conditions at a temperature from 1° C. to 100° C.

5. The method according to claim 1 , wherein the unfired composite film formed by said drying contains a residual amount of the first solvent before immersing it into the second solvent, and wherein said immersing the unfired composite film into the second solvent including water is to reduce the residual amount of the first solvent from the unfired composite film.

6. The method according to claim 1 , wherein the first solvent is at least one member selected from the group consisting of nitrogen-containing polar solvents, lactone polar solvents, dimethyl sulfoxide, acetonitrile, fatty acid esters, ethers, and phenol solvents, and
wherein the second solvent including water is a solvent including not less than 50% by mass of water.

7. The method according to claim 1 , wherein said immersing the unfired composite film into the second solvent including water is carried out at a temperature from 5° C. to 60° C.

8. The method according to claim 1 , wherein the surface of the support is one of a surface of a substrate or a surface of a lower film that is formed on the substrate and is different from the unfired composite film.

9. The method according to claim 8 , wherein the lower film is another unfired composite film formed by applying another varnish comprising a resin including polyamide acid and/or polyimide, fine particles, and a solvent, and drying the another varnish thus applied.

Assignees

• Tokyo Ohka Kogyo Co Ltd

Inventors

• Tobari Mitsuharu
• Kawamura Yoshitsugu
• Ishikawa Kaoru
• Sugawara Tsukasa

Classifications

• C08G73/10 Primary

  Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors · CPC title

• B01D67/0023

  by inducing porosity into non porous precursor membranes · CPC title

• B32B5/16

  characterised by features of a layer formed of particles, e.g. chips, powder {or granules (layer formed of natural mineral particles B32B19/00; layer being formed of wood fibres, chips or particles B32B21/02)} · CPC title

• B32B27/281

  comprising polyimides · CPC title

• B32B5/022

  Non-woven fabric · CPC title