Patent ID: 6875308

Claim:
In a method of making a permeable fibrous mat on a wet process mat machine in which an aqueous slurry containing glass fibers is continuously deposited onto the top surface of a moving permeable forming belt, partially dewatered, followed by drying the wet web to produce a dry non-woven fibrous mat, the improvement comprising applying a foam or froth onto the wet web after said web has been partially dewatered, the foam or froth having a high percentage of air having a blow ratio of at least about 12, the foam forming less than 5 milliliters of liquid in the bottom of an Imhoff cone after 16 hours from the time of filling the cone to a one liter mark and a viscosity of at least about 200 centipoise, and applying said foam at a rate to produce a dry, mat having a coating on one face, the mat having a permeability of at least about 200 CFM/sq. ft.