POLYTETRAFLUOROETHYLENE MOLDED ARTICLE AND METHOD FOR ITS PRODUCTION

摘要

A method for producing fired polytetraferuoroethylene molded article having a cylindrical form wherein a polytetraferuoroethylene powder is subjected to a compression molding to prepare a pre-compression molded material having a cylindrical form, a mandrel is placed through the central hole of the pre-compression molded material, and the pre-compression molded material is suspended in a horizontal position by supporting the mandrel and then fired, characterized in that the mandrel used has an outer diameter (Dm) which is the same as or greater than the central hole diameter (cD) of the pre-compression molded material after the firing; a large fired porous polytetraferuoroethylene molded article and a wide fired porous polytetraferuoroethylene sheet; and a gas-permeable film and a cushion sheet comprising the above sheet. The method has allowed the firing of a large polytetraferuoroethylene molded article to be carried out while suppressing the deformation of the article and also allowed the firing of a large porous polytetraferuoroethylene molded article which has been difficult to be fired by a conventional method.