PURPOSE: To improve physical properties such as impregnating ability, compressive strength, heat resistivity, etc., with low relative dielectric constant by constituting a wet paper for lamination which is dried and integrated from a wooden pulp and a meta aromatic polyamide fiber pulp spread in a film shape.
CONSTITUTION: After suspending a meta aromatic polyamide fiber pulps into water at its concentration lower than that of a wooden pulp, respective pulps are dissociated and dispersed from each other with a pulper or the like. The obtained slurry is transferred to a refiner, a clearance between a stator and a roter is adjusted such that it gradually narrows from a normal value so as to crash the pulps to pieces and spread them in a film shape. This is mixed in a precrushed wooden pulp slurry by an amount of 35 to 90% of the total weight and is made to a wet paper by a conventional method. An oil impregnated or gas impregnated electrical insulating pressboard can be produced by heating and pressing so as to dry and integrate it after plural sheets of the wet paper are laminated.
ITO HITOMI
MURATA MAMORU
