Process of making a porous PTFE membrane

Details Process of making a porous PTFE membrane Process of making a porous PTFE membrane

1997-05-16

1999-06-08

Tentoni, Leo B.

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

Autogenously or by activation of dry coated particles

264154, 264232, 2642358, 2642888, 2642902, B29C 6720

Patent

active

059102772

ABSTRACT:
A fine powder of polytetrafluoroethylene is mixed with a liquid lubricant, and the mixture is molded into an unsintered sheet by at least one of an extrusion method and a rolling method. The liquid lubricant is removed from the sheet by at least one of a heating method and an extrusion method. This sheet-form molding is stretched in the machine direction to produce a sheet-form polytetrafluoroethylene molding which, upon analysis with a differential scanning calorimeter, gives a crystal fusion curve having an endothermic peak in the temperature range of 345.+-.5 .degree. C. and which has a degree of crystallization of from 0.1 to 0.85 and a specific gravity of 1.4 or lower. The molding is then stretched in the transverse direction to produce a porous polytetrafluoroethylene (PTFE) membrane. The process is effective in producing, with good reproducibility, a useful porous PTFE membrane which has a high collection efficiency and a low pressure loss and is reduced in the leakage of coarse particles.

REFERENCES:
patent: 3953566 (1976-04-01), Gore
patent: 4596837 (1986-06-01), Yamamoto et al.
patent: 4902423 (1990-02-01), Bacino
Abstract of Japan 7-196,831 (Published Aug. 1, 1995).

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