Use of thinnings and other low specific gravity wood for lyocell pulps

• US 6,686,039 B2
• Filed: 01/02/2003
• Issued: 02/03/2004
• Est. Priority Date: 02/24/1999
• Status: Expired due to Term

• Current Assignee: International Paper Company
• Original Assignee: Weyerhaeuser Company (Weyerhauser)
• Inventors: Robarge, Kent, Persinger, W. Harvey Jr., Sealey, James E. II, Luo, Mengkui
• Primary Examiner(s): Kelly, Cynthia H.
• Assistant Examiner(s): GRAY, JILL M
• Application Number:
  US10/336,389
• Publication Number:
  US 20030186054A1
• Time in Patent Office: 397 Days
• Field of Search: 428/357, 428/359, 428/393, 162/157.1, 162/157.6, 162/150
• US Class Current: 428/393
• CPC Class Codes: C08B 1/00 Preparatory treatment of cellulose for making derivatives thereof , e.g. pre-treatment, pre-soaking, activation
• CPC Class Codes: D01D 5/098 with simultaneous stretching
• CPC Class Codes: D01D 5/18 by means of rotating spinnerets
• CPC Class Codes: D01F 2/00 Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
• CPC Class Codes: D21C 3/02 with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
• CPC Class Codes: D21C 9/004 inorganic compounds
• CPC Class Codes: D21C 9/10 Bleaching ; Apparatus therefor
• CPC Class Codes: Y10T 428/29 Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
• CPC Class Codes: Y10T 428/2904 Staple length fiber
• CPC Class Codes: Y10T 428/2933 Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2965 Cellulosic

Abstract

The use of low specific gravity wood from thinning operations, for example, will produce a lower brownstock viscosity for a given kappa number target. A differential of 200-cP falling ball pulp viscosity has been detected from Kraft cooks of low and high specific gravity wood. Using low specific gravity wood can reduce the bleach stage temperature and the chemical dose needed in the bleach plant to produce lyocell pulp specifications. Low specific gravity wood also increases the ability to reduce pulp viscosity to very low levels without increasing the copper number of the pulp or the concentration of carbonyl in the pulp above acceptable levels.

Claims

1. A pulp, comprising:

at least 7% by weight hemicellulose;

a viscosity less than 32 cP

a copper number less than 2;

a weighted average fiber length less than 2.7 mm; and

a coarseness less than 23 mg/100 m.

2. The pulp of claim 1, further comprising a combined copper, manganese, and iron content less than 20 ppm.

3. The pulp of claim 1, further comprising a total metal content less than 300 ppm.

4. The pulp of claim 1, further comprising a silicon content less than 50 ppm.