Method for preparing a microporous film
AssigneeFirma Carl Freudenberg
InventorsDieter Groitzsch, Akinori Minami, Gerhard Schaut
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Abstract
A microporous, polymeric film is prepared by dissolving methylene-chloride-soluble, film-forming polymers completely in methylene chloride. Then an aqueous phase is prepared containing non-methylene-chloride-soluble, water-soluble thickeners and, if desired, additives, and brought to a viscosity of about 0.07 to 0.5 Pa s. The aqueous phase is then dispersed in the polymer solution and the resultant paste is spread onto a support material or intermediate support, the methylene chloride is evaporated, the resultant membrane is transferred to the actual support, and finally the water is removed by drying.
Claims20
A method for the preparation of a microporous membrane-like, polymeric film comprising:
- forming an aqueous phase without use of a precipitating or swelling agent, the aqueous phase having a viscosity of 0.07 to b 0.5 Pa.sup.. s as adjusted by being treated with 0.3 to 6 wt. % of a thickening agent soluble in water but not soluble in methylene chloride;
- emulsifying the aqueous phase in 5 to 15% methylene chloride solution of an at least one film forming thermoplastic polymer soluble in methylene chloride in a weight ration of polymer solution to aqueous phase of 90:10 to 60:40, the polymer solution having a viscosity of 0.1 to 1 Pa.sup.. s;
- spreading the polymer solution onto a support material to coat the support;
- volatizing the methylene chloride from the coated support;
- and
- removing water at a temperature of 100.degree. to 180.degree. C.
The method of clam 1 further comprising recovering the volatized methylene chloride.
The method of clam 1 wherein the thermoplastic polymer is a linear polyurethane.
The method of clam 1 wherein the thermoplastic polymer is a polyurethane resin.
Dependencies are inferred from the claim text.