Method for producing air-permeable composite sheet
It is an objective of the present invention to provide a method for producing an air-permeable composite sheet which has excellent mechanical strength and compression resistance as well as PTFE's innate property such as air-permeability, water repellency, heat resistance and chemical resistance; and a filter and a fabrics material containing the air-permeable composite sheet produced by the method as a constituent material. The method for producing an air-permeable composite sheet according to the present invention is characterized in comprising steps of filling pores of a porous PTFE sheet with a hardenable material solution; hardening or semi-hardening the porous PTFE sheet filled with the hardenable material solution; and expanding the hardened or semi-hardened porous PTFE sheet.
1. A filter comprising an air-permeable composite sheet produced by a method comprising:
filling pores of a porous PTFE sheet with a hardenable material solution;
hardening or semi-hardening the porous PTFE sheet filled with the hardenable material solution; and
expanding the hardened or semi-hardened porous PTFE sheet to yield the air-permeable composite sheet,
wherein the permeability of the air-permeable composite sheet exceeds the permeability of the porous PTFE sheet.
2. A fabric material comprising an air-permeable composite sheet produced by a method comprising:
filling pores of a porous PTFE sheet with a hardenable material solution;
hardening or semi-hardening the porous PTFE sheet filled with the hardenable material solution; and
expanding the hardened or semi-hardened porous PTFE sheet to yield the air-permeable composite sheet.
wherein continuous holes penetrate the air-permeable composite sheet.
3. The fabric of claim 2 , further comprising re-hardening the expanded porous PTFE sheet.
4. The fabric of claim 2 , wherein expanding the hardened or semi-hardened porous PTFE sheet comprises setting the expanding ratio to not less than 1.1 times and not more than 20 times.
5. The fabric of claim 2 , wherein the hardenable material comprises a silicon alkoxide.
6. The filter of claim 1 , further comprising re-hardening the expanded porous PTFE sheet.
7. The filter of claim 1 , wherein expanding the hardened or semi-hardened porous PTFE sheet comprises setting the expanding ratio to not less than 1.1 times and not more than 20 times.
8. The filter of claim 1 , wherein the hardenable material comprises a silicon alkoxide.