Process for producing multilayer polytetrafluoroethylene porous

Details Process for producing multilayer polytetrafluoroethylene porous Process for producing multilayer polytetrafluoroethylene porous

1992-06-05

1993-07-06

Theisen, Mary Lynn

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

Stratified or layered articles

264119, 264122, 264127, 2642888, B29C 4706, B32B 526

Patent

active

052251314

ABSTRACT:
A process for producing a multilayer polytetrafluoroethylene porous membrane is disclosed, which process comprises at least two layers having different average pore diameters, the process comprising the steps of: filling the inside of a cylinder of an extruding mold distinctively with at least two kinds of polytetrafluoroethylene fine powders with each of which a liquid lubricant has been mixed; paste-extruding the powders to obtain a multilayer extrudate, which is then optionally rolled; removing the liquid lubricant from the multilayer extrudate or the rolled multilayer extrudate to obtain an unsintered multilayer structure; subsequently heating the unsintered multilayer structure at a temperature not lower than the melting point of sintered polytetrafluoroethylene to obtain a semisintered multilayer structure; and then stretching the semisintered multilayer structure at least monoaxially. A semisintered polytetrafluoroethylene multilayer structure capable of being used as an intermediate material for the above process is also disclosed.

REFERENCES:
patent: 4576861 (1986-03-01), Kato
patent: 5064593 (1991-11-01), Tamaru et al.
WO88/05687, WIPO, Aug. 1988.

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