The Chemithon Corporation

Brooks Rand, Ltd.

Albert Brucato

Richard J Brooks

The tearing strength of paper is improved by providing a furnish in which the fiber content is predominantly refined fiber with a minor amount, preferably 2 to 10 wt. %, of added unrefined fiber having incorporated therein a heat activatable bonding agent, particularly starch. The bonding agent adheres to and coats the added fiber without chemically reacting with the fiber. A cationic material, particularly polyethyleneimine, is premixed with the raw starch to cause it to adhere to the added fiber. During heat drying of the formed paper the starch is gelatinized to effect enhanced bonding of the added fiber.

Method of making paper having improved tearing strength

An additive comprising an anionic organic surface active agent is incorporated into mechanical or thermomechanical pulp at an elevated temperature and pressure. The additive causes dispersion of lignin and retards redeposition of lignin so that the bursting strength of the paper formed from the pulp is improved. The preferred additives are higher molecular weight anionic organic polyelectrolytes or polymers, particularly polymeric sulfonates. Further improvement in bursting strength is achieved by the wet end addition of a cationic organic polyelectrolyte or polymer, with or without starch. Lower molecular weight anionic organic detergents can also be used but should be rinsed from the pulp before forming paper.

Strength of paper from mechanical or thermomechanical pulp

Waste newsprint is defibered in an aqueous bath to which is added a deinking agent. The resulting slurry or pulp is rinsed, drained and formed into paper sheets. The deinking agent is a C.sub.14 to C.sub.20 alpha olefin sulfonate or a mixture of C.sub.18 alpha olefin sulfonate and a non-ionic detergent, depending upon the conditions of the deinking bath.

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Albert Brucato