In the context of usability tests with users, patients and doctors, we have made the experience among others, that the “standard” inner nonwoven does not optimally meet the requirements: Men must always be shaved, as minimal beard stubble sticks to the face it is not possible to wear the mask for long periods without fiber accumulation it is difficult to talk freely for long periods as there are fiber particles in the mouth the mask often collapses when breathing i.e. the dimensional stability is suboptimal. 

 For this purpose, we have developed a interior nonwoven that meets these requirements. The new developt nonwoven is a bico-fine fiber nonwoven consisting of polyethylene and polypropylene fibers. We use the different melting points of the thermoplastics polyethylene and polypropylene.

Polyethylene begins to melt at 105°C and polypropylene slightly higher i.e. it generally begins to melt at approx. 165°C. We make this temperature difference to our advantage i.e. after many tests, DACH has calendered this special nonwoven mixture with a special roller system and a defined high temperature i.e. the different sides of the nonwoven run around the rollers on two heated metal rollers which are arranged in an S-shape (see picture 1) one above the other (roller width is several meters long and diameter of the rollers approx. 90 cm). 

In addition, the two rollers press the nonwoven together in such a way that the low-melting polyethylene fiber melts a little bit and becomes compacted, thinner, soft, smooth and without sticking out fibers on the surface thanks to this special technique.