Process for preparing cellulose fibers

Details Process for preparing cellulose fibers Process for preparing cellulose fibers

1999-06-25

2000-12-05

Tentoni, Leo B.

Plastic and nonmetallic article shaping or treating: processes

Forming continuous or indefinite length work

Shaping by extrusion

26421116, D01F 202

Patent

active

06156253&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention pertains to a process for producing fibres from an optically anisotropic solution containing cellulose and/or cellulose derivatives, inorganic acids of phosphorus, and water by extruding the solution through a non-corroding spinneret and coagulating the resulting extrudates in a coagulant.
2. Description of Related Art
Such a process is known, int. al., from WO 96/06208. As is described in this application, cellulose fibres can be obtained by spinning and coagulating an anisotropic solution of cellulose in a solvent containing phosphoric acid and/or its anhydrides and water. In this application it is stated to be advantageous to employ a non-corroding. spinneret when spinning such a solution, e.g., a spinneret made of an alloy containing gold and platinum. WO 96/06208 discloses various coagulants. WO 97/19207 discloses a process for producing cellulose fibres from an anisotropic solution containing cellulose formate. This application also states that it is advantageous to employ a non-corroding spinneret when spinning the solution, e.g., a spinneret made of an alloy containing gold and platinum. In the process described in said non-prepublished patent-application the extrudates are coagulated in acetone and washed and dried under low tension.
The processes described in the aforesaid patent applications are especially suitable for the production of cellulose fibres having very good mechanical properties. The obtained fibres have a breaking tenacity which is (much) higher than the breaking tenacity of, say, Cordenka.RTM., i.e., a tenacity in excess of 600 mN/tex. For that reason the fibres described are especially suitable for technical use, e.g., as reinforcement material in conveyor belts, V-belts, and car tyres.
A major drawback to the disclosed processes is that in order to obtain fibres having the aforementioned favourable mechanical properties, use is made of organic solvents as coagulant (e.g., acetone). However, the use of such solvents is not very desirable in view of explosions and/or fire, spinning machine,


SUMMARY OF THE INVENTION

The invention now provides a process for producing cellulose fibres from an optically anisotropic solution by extruding the solution through a non-corroding spinneret and coagulating the resulting extrudates in a coagulant which does not have the above-mentioned drawbacks.


DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention consists in that in a process of the known type mentioned in 20 the opening paragraph the coagulant is an at least 50 wt. % water-containing liquid comprising a phosphate salt which does not originate from the spinning solution.
It should be added that use of an aqueous solution containing water-soluble inorganic salts as a coagulation bath for regenerated cellulose was already known from JP-A-07 189019 and JP-A-60 209006. However, in both said prior art disclosures the cellulose is coagulated from an organic solvent and, optionally, water containing solution, which may require a totally different coagulation bath than a cellulose, phosphoric acid, and water-containing solution.
Not the slightest allusion is made in said prior art disclosures to the beneficial results that may be obtained by dissolving the cellulose in an inorganic solution, followed by coagulating in an at least 50 wt. % water-containing liquid comprising a phosphate salt which does not originate from the spinning solution.
In this patent application the term "fibres" refers to continuous filaments as well as short-length fibres (shorter than 100 mm, i.e. staple fibres) and fibres of greater length (>100 mm). The fibres can be bundled up into yarns, slivers or strands, or be processed to make fabrics or non-wovens.
The term "phosphoric acid" in the application refers to all inorganic acids of phosphorus and their mixtures. Orthophosphoric acid is the acid of pentavalent phosphorus, i.e. H.sub.3 PO.sub.4. Its anhydrous equivalent, i.e., the anhydride, is phosphorus pentoxide (P.sub.2 O5). In additio

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