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Process for preparing chemical paper pulps by cooking, intermediate grinding and a final alkaline peroxide delignification

  • US 4,787,959 A
  • Filed: 11/18/1987
  • Issued: 11/29/1988
  • Est. Priority Date: 07/29/1977
  • Status: Expired due to Fees
First Claim
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1. A process of making chemical paper pulps by delignification of lignin-cellulose material which comprises:

  • (a) subjecting the lignin-cellulose material to a first cooking stage performed in the presence of an aqueous sodium hydroxide solution containing between about 10 and 30% of sodium hydroxide by weight of the dry initial material and at a temperature between about 150° and

    180°

    C. until the yield of cooked material is between about 50 and 60% by weight of the dry initial material to partially delignify the material;

    (b) grinding the material thus treated; and

    (c) subjecting the material thus ground to a second cooking stage performed at a temperature in the range of from about 90°

    C. to 120°

    C. in the presence of an aqueous solution of a peroxide, sodium hydroxide and a peroxide stabilizing agent which is present in an amount sufficient to slow but not prevent the decomposition of the peroxide into oxidizing species and wherein the amount of peroxide is between about 0.1 and 10% by weight of the dry ground material and the amount of sodium hydroxide is between about 1 and 10% by weight of the dry ground material, for a sufficient time to further delignify the material, the combination of steps (a), (b) and (c) removing at least about 80% of the lignin from the material, thus forming a chemical paper pulp.

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