Patent ID: 6899790

Claim:
A process for producing high bulk cellulosic pulp exhibiting a durable elevated curl index comprising: (a) feeding a cellulosic pulp including Kraft fiber to a refining gap defined between opposed surfaces, at least one of the surfaces being rotatable with respect to its opposed surface; (b) concurrently heat-treating and convolving the cellulosic pulp including Kraft fiber in the refining gap at elevated temperature and pressure at high consistency under conditions selected so as to preclude substantial fibrillation and attendant paper strength and fiber bonding development, wherein said step of heat-treating and convolving said fiber has a duration of up to about 20 seconds; (c) recovering said pulp wherein the length weighted curl index of the treated fiber is at least about 20% higher than the length weighted curl index of the fiber prior to said heat treatment and convolving thereof, wherein said at least 20% elevation of said length weighted curl index of the treated fiber is a property of the fiber capable of persisting for at least 30 minutes in a disintegrator at 1% consistency at a temperature of 125° F.