International Paper Company

Sanjay Patnaik

Thomas E Amidon

Paul Hart

Narendra R Srivatsa

Jean J Renard

M C Matthew

A method for enhancing the deposition and retention of particulate filler on papermaking fibers. In a first vessel, there is formed a slurry of papermaking fibers and in a second vessel there is formed a slurry of lime or its equivalent. The fiber slurry is at a consistency of not greater than about 5%. These separately formed slurries are thereafter combined with a gaseous precipitant in a flow reactor and under conditions whereby the gaseous precipitant is subjected to rapid shear and calcium carbonate is deposited in situ on the fibers. Unexpectedly, the reaction time for the formation and deposition of the calcium carbonate filler is very rapid. Control over the pH of the reactants in the reactor is achieved through the sequence of introduction of the reactants to the reactor. Also, through selection of the molar ratio of the gaseous precipitant and lime, the morphology of the calcium carbonate crystals may be controlled.

Process for enhanced deposition and retention of particulate filler on

A high level of calcium carbonate filler is added to secondary fiber pulp by in situ attachment to the secondary fibers. The secondary fiber pulp is mixed with an alkaline salt such as calcium oxide or calcium hydroxide and contacted with a reaction gas such as carbon dioxide in a gas-liquid contactor apparatus through efficient mixing in order to precipitate filler material such as calcium carbonate crystal complexes on the secondary fibers. The resulting pulp products have comparable or, in some cases, better brightness, cleanliness, and other sheet properties as compared to filler addition by conventional methods.

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Westwood, NJ, United States of America

Sanjay Patnaik