3844865 is referenced by 58 patents and cites 5 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.

Title
Method of making stretch-oriented porous films
Application Number
05/260,321
Publication Number
3844865
Application Date
June 6, 1972
Publication Date
October 29, 1974
Inventor
Vander Louw John F
Elton Robert L
Agent
Alexander Sell Steldt & DeLaHunt
Assignee
Minnesota Mining and Manufacturing Company
IPC
B32b 05/16
B29c 17/02
C08L 75/00
C08L 75/04
B29C 55/12
B29C 55/04
A61L 15/42
A61L 15/16
View Original Source