| abstract |
IN A PROCESS FOR PRODUCING MOISTURE PERMEABLE POLYMER FILMS BY COATING POLYMER SOLUTION ON A SUBSTRATE, COAGULATING WITH A NON-SOLVENT WHICH IS MISCIBLE WITH THE POLYMER SOLVENT, AND WASHING TO REMOVE THE SOLVENT, THE IMPROVEMENT COMPRISING FACILITATING THE WASHING BY INCORPORATING IN THE POLYMER SOLUTION A PARTICULATE SOLID MATERIAL, THE PARTICLES OF WHICH HAVE DIMENSIONS SUCH THAT THE SMALLEST DIMENSIONS OF THE PARTICLES ARE AT LEAST 0.1 MICRON AND THE LARGEST DIMENSIONS ARE NOT IN EXCESS OF 300 MICRONS. SUITABLE MATERIALS ARE, E.G. CALCIUM CARBONATE, MAGNESIUM CARBONATE, IRON OXIDE, TITANIUM OXIDE, MILLED PULP AND CELLULOSE CRYSTALLITE. |