Process for making lyocell fiber from sawdust pulp

• US 6,861,023 B2
• Filed: 04/23/2002
• Issued: 03/01/2005
• Est. Priority Date: 08/23/1996
• Status: Expired due to Term

• Current Assignee: International Paper Company
• Original Assignee: Weyerhaeuser Company (Weyerhauser)
• Inventors: Luo, Mengkui, Wester, Brian, Persinger, W. Harvey Jr., Sealey, James E. II
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US10/128,975
• Publication Number:
  US 20030025252A1
• Time in Patent Office: 1,043 Days
• Field of Search: 264/187, 264/203, 162/9, 162/65, 162/79, 162/90
• US Class Current: 264/187
• 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 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/2933 Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2965 Cellulosic

Abstract

A process for making lyocell fibers including the steps of pulping raw material in a digester to provide an alkaline pulp, wherein the raw material includes sawdust in an amount greater than 0% up to 100%; contacting the alkaline pulp including cellulose and at least about 7% hemicellulose under alkaline conditions with an amount of an oxidant sufficient to reduce the average degree of polymerization of the cellulose to the range of from about 200 to about 1100 without substantially reducing the hemicellulose content or substantially increasing the copper number of the pulp; and forming fibers from the pulp.

Claims

1. A process for making lyocell fibers comprising the steps of:

(a) pulping raw material in a digester to provide an alkaline pulp, wherein the raw material comprises sawdust in an amount greater than 0% up to 100%;

(b) contacting the alkaline pulp comprising cellulose and at least about 7% hemicellulose under alkaline conditions with an amount of an oxidant sufficient to reduce the average degree of polymerization of the cellulose to the range of from about 200 to about 1100 without substantially reducing the hemicellulose content or substantially increasing the copper number of the pulp; and

(c) forming fibers from the pulp treated in accordance with step (b).

2. The process of claim 1, wherein the oxidant is selected from the group consisting of a chemical with a peroxide group, oxygen, hydrogen peroxide, chlorine dioxide, ozone, and combinations thereof.

3. The process of claim 1, wherein the reduction in the average degree of polymerization of the cellulose occurs in the presence of a ratio of magnesium to transition metals of less than about 50%.

4. The process of claim 1, wherein the hemicellulose content is reduced less than about 15%.

5. The process of claim 1, wherein the copper number increases less than about 25%.

6. The process of claim 1, wherein the contacting step occurs in the substantial absence of an inhibitor to the degradation of the cellulose by the oxidant.

7. The process of claim 1, wherein the alkaline pulp and oxidant are contacted at a pH greater than about 8.0.

8. The process of claim 1, further comprising a step of dissolving the pulp after step (b) in a solvent for forming into a spinnable dope, wherein the pulp is readily dissolved in NMMO monohydrate within 10 minutes using the test of Example 3.