Porous polyimide film production method and porous polyimide film produced using said method

Patent metadata

Field	Value
Publication number	US-10968328-B2
Application number	US-201716320415-A
Country	US
Kind code	B2
Filing date	Jul 25, 2017
Priority date	Jul 25, 2016
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The present invention pertains to a porous polyimide film production method and a porous polyimide film produced using said method, said method including: a step (1) in which a poly(amic acid) solution comprising 40%-97% by mass organic polar solvent and 3%-60% by mass poly(amic acid) having an intrinsic viscosity, comprising tetracarboxylic acid units and diamine units, of 1.0-3.0 is cast in film form and immersed in or caused to come in contact with a coagulating solvent having water as an essential component thereof, and a porous film of poly(amic acid) is produced; and a step (2) in which the porous film of poly(amic acid) obtained in said step is heat treated and imidized. Shrinkage in the film longitudinal direction and transverse direction after heat treatment is suppressed to no more than 8% for each direction and the speed of temperature increase in a temperature range of at least 200° C. during the heat treatment is at least 25° C./min.

First claim

The invention claimed is:

1. A method for producing a porous polyimide film, the method comprising the steps of:
(1) casting a poly(amic acid) solution consisting of 3 to 60% by mass of a poly(amic acid) having an limiting viscosity number of 1.0 to 3.0, the poly(amic acid) consisting of tetracarboxylic acid unit and diamine unit, and 40 to 97% by mass of an organic polar solvent into a film-like shape, and dipping in or bringing it into contact with a coagulating solvent comprising water as an essential component to prepare a porous film of poly(amic acid); and
(2) imidizing the porous film of a poly(amic acid) obtained in the step (1) by heat treatment, wherein each of the shrinkage ratios in the longitudinal direction and the transverse direction of the film after heat treatment is suppressed to 8% or lower, and the temperature rising rate in the temperature region of 200° C. or higher in the heat treatment is 25° C./min or higher,
wherein the porous polyimide film is a three-layer structure porous polyimide film having two surface layers (a) and (b), and a macrovoid layer sandwiched between the surface layers (a) and (b),
the macrovoid layer has partition walls bonded to the surface layers (a) and (b), and a plurality of macrovoids surrounded by the partition walls and the surface layers (a) and (b) and having a mean pore size in the film plane direction of from 10 to 500 μm,
the partition walls of the macrovoid layer have a thickness of 0.1 μm to 50 μm,
at least one partition walls have one or a plurality of pores communicating adjacent macrovoids,
each of the surface layers (a) and (b) has a thickness of 0.1 μm to 50 μm,
at least one of the surface layers (a) and (b) has a plurality of fine pores having an average pore diameter of more than 5 μm and not more than 200 μm, while the other has a plurality of fine pores having an average pore diameter of 0.01 μm to 200 μm;
the surface opening ratio of at least one of the surface layer is not less than 10%, while that of the other surface layer is not less than 5%;
the fine pores in the surface layers (a) and (b) communicate with the macrovoids; and
the porous polyimide film has a total film thickness of 5 μm to 500 μm, the Gurley value being not more than 20 sec/100 cc, and a porosity being 60% to 95%.

2. The method for producing a porous polyimide film-according to claim 1 , wherein the poly(amic acid) comprises at least one tetracarboxylic dianhydride selected from the group consisting of biphenyltetracarboxylic dianhydride and pyromellitic dianhydride; and at least one diamine selected from the group consisting of benzenediamine, diaminodiphenyl ether and bis(aminophenoxy)phenyl.

3. The method for producing a porous polyimide film-according to claim 1 or 2 , wherein the coagulating solvent comprising water as an essential component is water, or a mixed solution of 5% by mass or more and less than 100% by mass of water, and more than 0% by mass to 95% by mass or less, of an organic polar solvent.

4. The method for producing a porous polyimide film according to claim 1 or 2 , further comprising the step of subjecting at least one surface of the porous polyimide film obtained in the step (2) to plasma treatment.

5. A method for producing a porous polyimide film, the method comprising the steps of:
(1) casting a poly(amic acid) solution consisting of 3 to 60% by mass of a poly(amic acid) having an limiting viscosity number of 1.0 to 3.0, the poly(amic acid) consisting of tetracarboxylic acid unit and diamine unit, and 40 to 97% by mass of an organic polar solvent into a film-like shape, and dipping in or bringing it into contact with a coagulating solvent comprising water as an essential component to prepare a porous film of poly(amic acid);
(2) imidizing the porous film of a poly(amic acid) obtained in the step (1) by heat treatment, and
(3) subjecting at least one surface of the porous polyimide film obtained in the step (2) to plasma treatment,
wherein the porous polyimide film is a three-layer structure porous polyimide film having two surface layers (a) and (b), and a macrovoid layer sandwiched between the surface layers (a) and (b),
the macrovoid layer has partition walls bonded to the surface layers (a) and (b), and a plurality of macrovoids surrounded by the partition walls and the surface layers (a) and (b) and having a mean pore size in the film plane direction of from 10 to 500 μm,
the partition walls of the macrovoid layer have a thickness of 0.1 μm to 50 μm,
at least one partition walls have one or a plurality of pores communicating adjacent macrovoids,
each of the surface layers (a) and (b) has a thickness of 0.1 μm to 50 μm,
at least one of the surface layers (a) and (b) has a plurality of fine pores having an average pore diameter of more than 5 p.m and not more than 200 p.m, while the other has a plurality of fine pores having an average pore diameter of 0.01 μm to 200 μm;
the surface opening ratio of at least one of the surface layer is not less than 10%, while that of the other surface layer is not less than 5%;
the fine pores in the surface layers (a) and (b) communicate with the macrovoids; and
the porous polyimide film has a total film thickness of 5 μm to 500 μm, the Gurley value being not more than 20 sec/100 cc, and a porosity being 60% to 95%.

Assignees

• Ube Industries

Inventors

• Ohya Shusei
• Matsuo Makoto
• Fujii Yuuichi
• Bamba Keita

Classifications

• C08J7/123

  Treatment by wave energy or particle radiation (C08J7/18 takes precedence) · CPC title

• C08J2379/08

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

• C08J2201/0544

  the non-solvent being aqueous · CPC title

• C08G73/1067

  Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound · CPC title

• C08G73/1032

  characterised by the solvent(s) used · CPC title