Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1996-06-21
1998-10-27
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
264203, D01F 202
Patent
active
058274634
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a process for the manufacture of cellulose moulded bodies in which cellulose is dissolved in a mixture of a tertiary amine oxide and a non-solvent. The solution of cellulose is extruded via a moulding tool thereby forming filaments which are conveyed through an air gap into a precipitation bath while being drawn.
In the course of the last decades, as a result of environmental problems concerning the established viscose process for the manufacture of cellulosic fibres, intensive effort was invested in providing alternative more environment friendly processes. One particularly interesting possibility which has crystallized in the last couple of years is the dissolving of cellulose without the development of a derivative in an organic solvent and extruding moulded bodies from this solution. Spun fibres of this type received the generic name Lyocell from BISFA (The International Bureau for the Standardization of Man-Made Fibres) whereby a mixture of an organic chemical and water is meant by an organic solvent.
It has been shown that a mixture of tertiary amine oxide and water are excellent as an organic solvent for the manufacture of Lyocell fibres. In the main, N-methyl morpholine-N-oxide (NMMO) is used as the amine oxide. Other suitable amine oxides are disclosed in EP-A 553 070. Processes for the manufacture of cellulosic moulded bodies from a solution of cellulose in a mixture of NMMO and water are for example disclosed in U.S. Pat. No. 4,246,221. Fibres manufactured in this way are characterised by a high fibre tenacity in the conditioned and wet state, a high wet modulus and a high loop strength.
A special characteristic of these fibres is their high tendency to fibrillation, particularly when under stress in a wet state such as for example during a washing operation. Whilst this property is absolutely desirable for certain fibre applications and produces interesting effects, the usefulness regarding other ends such as for example in textiles, which should show wash resistance, is reduced.
Therefore, no effort was spared in the attempt to reduce fibrillation behaviour using certain measures.
In PCT-WO 92/07124, the suggestion was made to treat a freshly spun, not yet dried, fibre with the solution of a polymer containing several cationic sites.
According to EP-A-538977, the fibres, which can be freshly spun or already dried, are treated with an aqueous solution which contains a chemical reagent with 2 to 6 functional groups able to react with cellulose.
PCT-WO 94/09191 suggests that the functional groups of a chemical reagent, with which the fibres are treated, are electrophilic C=C double compounds and other reactive groups for cellulose.
These suggestions have in common that a reduction in fibrillation tendency of the fibres is achieved by chemically modifying the fibre by the addition of cationic compounds to the hydroxyl groups, which display a negative potential, and on the other hand, by the development of covalent bonds of the cellulose with the reactive groups of the compounds with the resultant crosslinking of the fibrils.
Other papers such as the pending application AT 1348/93 from the applicant, are concerned with the possibility of likewise reducing the tendendy to fibrillation by deliberately varying spinning parameters such as the output, length of the air gap, drawing and air humidity in the air gap.
Surprisingly it has been found that an effective reduction in fibrillation tendency can be achieved when the precipitation bath, into which the fibre is led via an air gap following extrusion whilst being drawn, is basically made up of a non-aqueous solvent for the tertiary amine oxide, in particular NMMO, whereby the molecular weight of the non-aqueous solvent is larger than that of the tertiary amine oxide.
Normally cellulosic fibres are spun from a solution in a tertiary amine oxide into an aqueous precipitation bath.
SU-1 224 362 A on the other hand, describes a process for the manufacture of cellulose fibres with a spinning bath which
REFERENCES:
patent: 4246221 (1981-01-01), McCorsley
Romanov et al., Khim. Volokna, 1, p. 29 (1989).
Romanov et al., Khim. Volokna, 4, p. 33 (1989).
Romanov et al., Khim. Volokna, 1, p. 27 (1988).
Quenin, "Precipitation de la, cellulose a partirde solutions dans les oxydes d amines tertiares: application au filage", Dissertation Grenoble (1985).
Dube et al.,. "Precipitation and crystallization of cellulose from amine oxide solutions", TAPPI Proc. International and Dissolving Specialty Pulps, Boston (1983).
Weigel et al., "Challenges in Cellulosic Man-Made Fibres", Viscose Chemistry Seminar, Stockholm (1994) Seminar, Stockholm (1994).
English Translation of Austrian Patent Application 1348/93.
English Abstract of European Published Application No. EP 553070.
English Abstract of German Patent No. DD 255,711.
German Translation of Romanov et al. Khim, Volokna, 4, p. 33.
Lenzing Aktiengesellschaft
Tentoni Leo B.
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