PROCESS FOR THE SUPERFICIAL TREATMENT OF A NON-WOVEN AND VERY AERATED FIBROUS FILTER LAYER FORMING AN ELECTRET, AND ITS APPLICATION TO FILTERS AND ESPECIALLY RESPIRATORY MASKS

摘要

The process of the invention consists in smoothing the or each fluffy surface of the layer by exerting a slight friction under low pressure so that the projecting fibers are flattened on the subjacent fibrous mass without the latter being compressed, the friction being exerted at a softening temperature such that the superficial fibers are welded together to form a skin or porous glaze. The smoothing is preferably effected by means of a metal mass whose temperature is between 115 DEG and 150 DEG C. This process may be applied to the outer face of a filtering breathing mask constituted by an envelope made of this fibrous material covering a relatively rigid porous shell for protection of the skin; it may also be applied to at least one of the faces of filtering layers equipping filters of any type.