Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1997-08-22
2000-09-12
Dixon, Merrick
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
2642101, 2642905, 264187, 264203, D01D 512
Patent
active
061173789
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with a process for the production of cellulose fibers according to the amine-oxide process, as well as with cellulose fibers, in particular cellulose staple fibers.
BACKGROUND OF THE INVENTION
For some decades there has been a search for processes for the production of cellulose moulded bodies as a substitute for the viscose process, which is widely employed. An alternative which is interesting for its reduced environmental impact among other reasons, is to dissolve cellulose without derivatisation in an organic solvent and extrude from this solution moulded bodies such as fibers, films and membranes. Fibres thus extruded have been accorded by BISFA (The International Bureau for the Standardization of man made fibers) the generic name Lyocell. By an organic solvent, BISFA means a mixture of an organic chemical and water.
It has turned out that as an organic solvent, a mixture of a tertiary amine-oxide and water is particularly appropriate for the production of cellulose moulded bodies. As the amine-oxide, primarily N-methylmorpholine-N-oxide (NMMO) is used. Other amine-oxides are described e.g. in EP-A- 0 553 070. A process for the production of mouldable cellulose solutions is known e.g. from EP-A- 0 356 419. The production of cellulose moulded bodies using tertiary amine-oxides generally is referred to as amine-oxide process.
U.S. Pat. No. 4,246,221 describes an amine-oxide process for the production of cellulose solutions which are spun into filaments in a forming tool such as a spinneret and afterwards passed through a precipitation bath, wherein the cellulose is precipitated and water-containing, swollen filaments are obtained. These filaments may be processed to cellulose fibers and staple fibers in the conventional way, i.e. by washing and post-treatment. It is known that the cellulose fibers produced from amineoxide solutions according to the dry/wet spinning process have, in contrast to natural, crimped cellulose fibers such as cotton, an unlobed, round cross-section. When they are processed to yarns and plane fibre assemblies, the round cross-section and the relatively smooth surface may cause problems, as described e.g. in EP-A- 0 574 870. According to this patent application, these problems include a deficient adhesion of the fibers to each other when the spinning fibre is spun to yarns, an insufficient cover of the filament yarns and insufficient slippage resistance of the plane fibre assemblies produced from this fibre and filament yarns. To solve these problems, the above patent application proposes to extrude the amine-oxide solution through spinning holes having a cross-section which is not circular but shaped, for example Y-shaped. Thus, the Lyocell fibers get a Y-shaped section.
In Chemical Fibers International (CFI), volume 45, February 1995, pages 27 and 30, the microscopic illustration of four cellulose fibers all produced according to the amine-oxide process is shown. It is interesting that these fibers are not identical, although all of them are produced according to the amine-oxide process. The differences between the four fibers can be seen even under the microscope. In the literature cited it is not indicated how those skilled in the art may produce the different cellulose fibers, in other words no information is given to those skilled in the art how it is possible to make each of the fibers look different.
In Textilia Europe 6/94, pages 6ff, also a cellulose fibre produced according to the amine-oxide process is described, and again those skilled in the art are not given any clues about the details of the production. Based on other information, it can be gathered from this literature that the cellulose fibre, the production of which is not indicated, has a permanent crimp, but no more detailed information given as to what is meant by this and how the fibre may be crimped.
Crimped fibers are advantageous various reasons for, particularly for processing them into staple fibers. For instance, it is easier to card the fibers, since a certain adhesion of
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Declaration of Dieter Eichinger and attached Exhibits A-H.
Eibl Markus
Eichinger Dieter
Dixon Merrick
Lenzing Aktiengesellschaft
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