Flake- or sliver-like porous structure of polymeric material and process of producing same, and process of producing sheet-like structure therefrom

Flake- or sliver-like porous structures of a polymeric material heavily loaded with a finely divided inorganic substance are prepared by spurting a mixture of the polymeric and finely divided inorganic components in a solvent. The products have many fine, irregular voids. The thickness of walls forming such voids is 5 mu or less. The products are especially useful for producing sheet-like structures therefrom by beating and/or refining them followed by general paper making procedures. The sheets, when calendered, have a high initial modulus and improved dimensional stability.