Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1997-08-22
1999-07-06
Raimund, Christopher
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
26421113, 26421114, 1062002, 1062003, 1062021, 139420B, 66202, D01F 200
Patent
active
059194120
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is concerned with a new cellulose moulded body and a process for the production of this cellulose moulded body. Particularly, the present invention is concerned with a new cellulose fibre and a new cellulose film having a predetermined tendency to fibrillation.
For the purposes of the present specification and claims, the term "moulded body" means particularly fibres and films. In the following, the term "fibres" means fibres, films and also other moulded bodies.
As an alternative to the viscose process, in recent years there has been described a number of processes wherein cellulose, without forming a derivative, is dissolved in an organic solvent, a combination of an organic solvent and an inorganic salt, or in aqueous saline solutions. Cellulose fibres made from such solutions have received by BISFA (The International Bureau for the Standardisation of man made Fibres) the generic name Lyocell. As Lyocell, BISFA defines a cellulose fibre obtained by a spinning process from an organic solvent. By "organic solvent", BISFA understands a mixture of an organic chemical and water.
The present invention is concerned with a specific process for the production of a cellulose fibre of the Lyocell type, wherein a cellulose solution is extruded across an air gap into an aqueous precipitation bath. In the following, this process will be referred to as amine-oxide process, wherein a tertiary amine-oxide, particularly N-methylmorpholine-N-oxide (NMMO), is used as a solvent. Such a process is described for instance in U.S. Pat. No. 4,246,221 and provides fibres which exhibit a high tensile strength, a high wet-modulus and a high loop strength.
A typical feature of the Lyocell fibres is their pronounced tendency to fibrillate when wet. Fibrillation means the breaking off of the fibre in longitudinal direction at mechanical stress in a wet condition, so that the fibre gets hairy, furry. The reason for fibrillation may be that the fibres consist of fibrils which are arranged in the longitudinal direction of the fibre axis and that there is only little crosslinking between these.
WO 92/14871 describes a process for the production of a fibre having a reduced tendency to fibrillation. The reduced tendency to fibrillation is achieved by providing all the baths with which the fibre is contacted before the first drying with a maximum pH value of 8,5.
WO 92/07124 also describes a process for the production of a fibre having a reduced tendency to fibrillation wherein the freshly spun, i.e. never dried fibre is treated with a polymer that can be made cationic. As such a polymer, a polymer having imidazole and azetidine groups is mentioned. Additionally, there may be carried out a treatment with an emulsifiable polymer, such as polyethylene or polyvinylacetate, or a crosslinking with glyoxal.
In a lecture given by S. Mortimer at the CELLUCON conference in 1993 in Lund, Sweden, it was mentioned that the tendency to fibrillation rises as drawing is increased.
There have been published already some methods to reduce the tendency to fibrillation of Lyocell fibres:
Thus from WO 95/02082 of the applicant it is known that fibrillation may be reduced by certain combinations of spinning parameters.
Moreover, it is known that the fibrillation properties of Lyocell fibres may be improved by chemical crosslinking. Thus, e.g. EP-A-0 538 977 describes crosslinking of Lyocell fibres with chemical reagents able to react with cellulose in the never dried state, i.e. when the fibre is produced, as well as in the dried state, i.e. substantially during the textile finishing of the plane fibre assemblies.
It is known further that the tendency to fibrillation of Lyocell fibres may be reduced by crosslinking them with glyoxal (M. Dube and R. H. Blackwell, TAPPI Proceedings; International Dissolving and Specialty Pulps, pages 111-119; 1983).
Crosslinking Lyocell fibres during their textile finishing has the main drawback for the finishing operator of requiring additional steps which cause additional costs.
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Firgo Heinrich
Mulleder Eduard
Seidl Sigrid
Lenzing Aktiengesellschaft
Raimund Christopher
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