3870593 is referenced by 101 patents and cites 4 patents.

Porosity (preferably microporosity) can be introduced into a polymeric film by (1) dispersing finely divided particles of a non-hygroscopic inorganic salt such as calcium carbonate into a suitable polymer, e.g., by milling, (2) forming a film of the filled polymer, and (3) stretching the film to provide good porosity and water absorptive or transmissive characteristics. It is unnecessary to leach out the particles of the inorganic salt, and the resulting porous film is useful in laminates, adhesive tapes, gas permeable containers, first aid dressings, and the like even though it still contains these particles.

Stretch-oriented porous films and preparation and use thereof
Application Number
Publication Number
Application Date
April 29, 1974
Publication Date
March 11, 1975
Vander Louw John F
Elton Robert L
Alexander Sell Steldt & DeLaHunt
Minnesota Mining and Manufacturing Company
B29c 17/02
B32b 03/00
C08L 75/00
C08L 75/04
C09J 07/02
B29C 55/12
B29C 55/04
A61L 15/42
A61L 15/16
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