A microporous membrane is described comprising at least two layers, wherein each layer is characterized by nodes interconnected by fibrils, the layers are bonded by means of plastic flow at temperatures below the melting point of either membrane material, and the pore architecture is formed in situ by...http://www.google.co.uk/patents/US20020045041?utm_source=gb-gplus-sharePatent US20020045041 - Microporous membrane with a stratified pore structure created in situ and process
