Method for bleaching wood fibers

Inactive Publication Date: 2006-04-20
HUANG QIANG +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0004] The problem addressed by this invention is to find a safer and more

Problems solved by technology

However, there are hazards associated with handling these r

Method used

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[0008] All percentages are expressed as weight percentages, unless specified otherwise. The term “Pre-mix” (PMX) refers to a process in which borohydride and bisulfite are mixed prior to addition to the wood fibers.

[0009] Dithionite ion, also referred to as hydrosulfite, can be produced by the reaction between bisulfite and borohydride ions, according to the following theoretical equation:

BH4−+8HSO3−+H+→4S2O4−2+B(OH)3+5H2O

The yield is somewhat less than 100% due to competing reactions, including that of borohydride with water, but is most often better than 85%. Since the exact mechanism of the reaction has not been fully characterized, this invention is not limited to reduction by dithionite ion, and other species present in the reaction mixture also may act as reducing agents. When the amount of bisulfite is at 8 moles per mole of borohydride, the theoretical reaction proceeds to completion. Without wishing to be bound by theory, it is believed that use of more than the theoret...

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Abstract

A method for bleaching wood fibers with a mixture of sodium borohydride and sodium bisulfite followed by peroxide bleaching in the same vessel.

Description

CROSS REFERENCE TO RELATED PATENT APPLICATIONS [0001] This is a non-provisional application of prior pending U.S. Provisional Application Ser. No. 60 / 619,154 filed on Oct. 15, 2004.BACKGROUND [0002] This invention relates generally to a method for bleaching wood fibers with mixture of sodium borohydride and sodium bisulfite followed by peroxide bleaching. [0003] Combinations of reductive and oxidative bleaching have been used to bleach wood fibers. For example, WO 01 / 59205 discloses a method for bleaching mechanical and chemithermomechanical pulp by pre-bleaching the pulp with a reductive bleaching agent, followed by peroxide bleaching reinforced with borohydride. The reductive agents mentioned in this reference are hydrosulfite, borohydride, hydrazine and formamidine sulfinic acid (FAS). However, there are hazards associated with handling these reductive agents, alone and / or in combination with peroxide. [0004] The problem addressed by this invention is to find a safer and more eff...

Claims

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Application Information

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IPC IPC(8): D21C3/00D21C3/04D21C3/02
CPCD21C9/1084D21C9/163
Inventor HUANG, QIANGGODA, RANGANAMMARCROWLEY, THOMAS ROBERT
Owner HUANG QIANG
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