Abstract: A fusion bonded fiber product is made by compressing between heated dies a mat of moisture-containing fibers of the type that change irreversibly to an amorphous nonglassy state that permits fiber-to-fiber bonding at a characteristic critical temperature. The further compression of the partially compacted mat is stopped or slowed when the mat is a small multiple of the desired caliper for the bonded product for a period of time sufficient to vaporize the moisture content of the mat. During this time period, most of the vaporized moisture content of the mat is expelled as saturated steam through the mat surfaces while the temperature of the mat is still well below the critical temperature. Then, the compression of the mat is continued under continuous consolidation to the final density and caliper of the fusion bonded product while the mat is heated to a temperature above the critical temperature.

Abstract: A fusion bonded fiber product is made by compressing between heated dies a mat of moisture-containing fibers of the type that change irreversibly to an amorphous non glassy state that permits fiber-to-fiber bonding at a characteristic critical temperature. The further compression of the partially compacted mat is stopped when the mat is a small multiple of the desired caliper for the bonded product for a period sufficient to vaporize the moisture content of the mat. During this pause, most of the vaporized moisture content of the mat is expelled as saturated steam through the mat surfaces while the temperature of the mat is still well below the critical temperature. Then, the compression of the mat is continued under continuous consolidation to the final density and caliper of the fusion bonded product while the mat is heated to a temperature above the critical temperature.