International Paper Company

Leo N Nelli

Vacheslav M Yasnovsky

Dinkar G Wagle

The stiffness of multi-ply paper and board products is increased by dewatering the base ply on the papermaking machine to a consistency of at least about 8% prior to application of the next ply. The desired laminating consistency is more readily achieved through the use of pulp which has been subjected to a heat treatment process comprising heating the pulp at a temperature in the range of 170.degree. C. to 250.degree. in the presence of water for at least about 0.1 minutes, which reduces the water retention valve of the pulp. The heat treated pulp also produces a stiffer multi-ply product in its own right, which augments the stiffness advantage connected with attainment of higher laminating consistencies.

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Wallkill, NY, United States of America

Leo N Nelli