Method for forming porous PTFE layer
A method for forming a porous PTFE layer includes steps of: combining one or at least two unburned porous PTFE films and a support body that can withstand a heating condition in the following process (a rod or plate shaped support body made of mesh or the like is preferable) by using a predetermined means in such a manner that a slip can be prevented in a heating treatment in the following process; and heating the matter resulted from the above process at a temperature of at least 150° C. and less than the melting point of the PTFE film for the range of 5-120 minutes (preferably at a temperature in the range of the melting point of a thermoplastic resin fiber to 320° C. for the range of 10-60 minutes in the case in which the thermoplastic resin fiber or the like is used in the process).
1. A method for forming a porous PTFE layer, comprising the steps of:
(1) winding one or at least two stretched unburned porous PTFE films around a rod shaped support body that can withstand a heating condition in a following process (2) and combining the PTFE film and the rod shaped support body by bonding the PTFE film and the rod shaped support body to each other using a binder resin; and
carrying out the heating treatment in the process (2) at a temperature in a range of the melting point of the used binder resin up to 320° C. for a time of 10 to 60 minutes.
2. The method for forming a porous PTFE layer as defined in claim 1 , wherein the binder resin is a binder resin containing tetrafluoroethylene hexafluoropropylene copolymer (FEP), or tetrafluoroethylene perfluoro alkoxyethylene copolymer (PFA), and the heating treatment in the process (2) is carried out at a temperature in the range of 200 to 320° C. for the range of 10 to 60 minutes.
3. The method for forming a porous PTFE layer as defined in claim 1 , wherein the rod shaped support body is made of a mesh, a non woven fiber, a braided rope, or a woven fabric.