Patent ID: 9616391
Date: 2017-04-11
CPC Classifications: B01D,B29C,B29K,B29L,C08L,D06P

Claim:
1. A black porous polytetrafluoroethylene membrane comprising a porous polytetrafluoroethylene membrane dyed black having a porous structure, wherein the porous structure has voids formed between fibrils of polytetrafluoroethylene, which are fibers of the polytetrafluoroethylene, as pores in the porous structure, a whiteness of a principal surface of the black porous polytetrafluoroethylene membrane as measured according to JIS L 1015 (Hunter method) is in a range from 18.0 to 23.0%, and the whiteness of the principal surface falls within a range from 18.0 and 25.0% after heating at 350° C. for 1 minute.