Method of manufacturing highly-airtightened porous paper

A method of manufacturing highly-airtightened porous paper, the method comprising the steps of:

• manufacturing wet paper web from minute cellulose which is used as a raw material and has a diameter of 1 .mu.m or less, said cellulose principally comprising fibrils;
• and
• drying the wet paper web while voids in the wet paper web are retained by replacing the moisture remaining in the wet paper web with a solvent which is compatible with water and has a surface tension less than that of water, so that highly-airtightented porous paper having a thickness not exceeding 100 .mu.m and airtightness of 1000 sec/100 cc or more is formed.

A method of manufacturing highly-airtightened porous paper, the method comprising the steps of:

• manufacturing wet paper web from minute cellulose which is used as a raw material and has a fiber diameter of 1 .mu.m or less, said cellulose principally comprising fibrils;
• and
• drying the wet paper web while voids in the wet paper web are retained by freeze-drying the moisture remaining in the wet paper web, so that highly-airtightened porous paper having a thickness not exceeding 100 .mu.m and an airtightness of 1000 sec/100 cc or more is formed.

A method of manufacturing highly-airtightened porous paper, the method comprising the steps of:

• manufacturing wet paper web from minute cellulose which is dispersed in an organic solvent and has a fiber diameter of 1 .mu.m or less, said cellulose principally comprising fibrils;
• and
• drying the wet paper web while voids in the wet paper web are retained by evaporating the organic solvent remaining in the wet paper web, so that highly-airtightened porous paper having a thickness not exceeding 100 .mu.m and an airtightness of 1000 sec/100 cc or more is formed.

A method of manufacturing highly-airtightened porous paper, the method comprising the steps of:

• manufacturing wet paper web from minute cellulose which is used as a raw material and has a diameter of 1 .mu.m or less, said cellulose principally comprising fibrils and whose fibers have been beaten to a value of 700 ml or less measured by a modified CSF;
• and
• drying the wet paper web while voids in the wet paper web are retained to form a highly-airtightened porous paper having a thickness not exceeding 100 .mu.m and an airtightness of 1000 sec/100 cc or more.