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Treatment of wood chips with an alkali metal borohydride solution followed by mechanical defibration

  • US 3,981,765 A
  • Filed: 12/17/1974
  • Issued: 09/21/1976
  • Est. Priority Date: 07/30/1969
  • Status: Expired due to Term
First Claim
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1. A chemi-mechanical process for making an unbleached pulp with yield of at least 85% and brightness in excess of 60 G.E. with good color stability and high strength characteristics for papermaking purposes, the steps comprising in sequence:

  • a. providing a lignocellulosic material in the form of wood chips having a thickness in the range between 1/16 and 1/8 inch, and a dryness between 50 to 90%,b. impregnating the chips at a temperature from room temperature to 50°

    C with an alkaline solution comprised of an aqueous solution of sodium hydroxide and an alkali metal borohydride in an amount from 0.1 to 2.0% by weight of the chips and with a ratio of solution to chips of 2;

    1 to 20;

    1, said alkaline solution having an alkalinity, based on the Na22 O content of the alkaline material, from 3.5% to not in excess of 16%, by weight, and having a pH in excess of 13,c. heating the alkaline borohydride-impregenated chips at a temperature not greater than 150°

    C for at time between 15 minutes to 30 minutes to provide semi-cooked chips,d. separating said semi-cooked chips from the solution, ande. defiberizing the separated semi-cooked chips to mechanically separate the fibers of the chips into an unbleached pulp having said brightness, yield, and strength characteristics.

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