Compositions – Liquid crystal compositions
Patent
1997-03-18
1999-08-17
Wu, Shean C.
Compositions
Liquid crystal compositions
2522995, 152458, 264187, 428357, 428393, C09K 1952, B60C 912, D01F 202, B32B 2302
Patent
active
059389710
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to cellulose, liquid-crystal solutions having a base of cellulose, that is to say a high concentration of cellulose, as well as spun products of cellulose.
More particularly, the invention relates to liquid-crystal solutions having a base of cellulose when they are spinnable, that is to say solutions which can be spun in order to produce fibers of films having high mechanical properties.
It has been known for a long time that the production of liquid-crystal solutions is essential for the obtaining of fibers having high mechanical properties, as shown, in particular, by U.S. Pat. No. 3,767,756 relating to aramid fibers and U.S. Pat. No. 4,746,694 relating to fibers of aromatic polyesters.
Liquid-crystal solutions having a base of cellulose derivatives, as well as the fibers or films which can be obtained from these solutions have also been described in certain patents or patent applications.
U.S. Pat. Nos. 4,370,168 and 4,501,886 have, for instance, shown the existence of spinnable liquid-crystal solutions having a base of ethers or cellulose acetate dissolved in inorganic acids, which solutions make it possible to obtain fibers of high tensile strength and high modulus. The methods employed are, however, limited in their application by the following drawbacks: solutions of these derivatives; fibers, when possible, in order to obtain cellulose fibers; with the spinning, in the case of the acetates.
European Patent B 179,822 and the equivalent U.S. Pat. No. 4,839,113 describe the obtaining of liquid-crystal spinning solutions having a base of cellulose formate by reacting cellulose with formic acid and phosphoric acid. They also describe fibers of regenerated cellulose having high mechanical properties, obtained by regeneration of cellulose formate fibers. The processes used have numerous advantages. In particular, the use of the formate as derivative permits a derivation in situ (formylation and dissolution of the cellulose in the same solvent mixture) and a very rapid regeneration, on line with the spinning. These processes are nevertheless penalized by the recycling of a mixture of acids as well as of products of the regeneration.
Moreover, numerous attempts have been made to obtain liquid-crystal solutions of cellulose by dissolving the cellulose directly (no derivation and therefore suppression of the regeneration).
It has, for instance, been proposed to dissolve the cellulose in a mixture of N,N-dimethylacetamide (DMAC) and lithium chloride (LiCl), as described for example in U.S. Pat. No. 4,278,790. With such a system, it is not possible to obtain sufficiently concentrated solutions and their anisotropy is slight, so that it is not possible to obtain fibers which have high mechanical properties (see, for example J. Polym. Sci., Polym. Phys. Ed. 27:1477, 1989, and J. Appl. Polym. Sci. 51:583, 1994).
It has also been proposed to dissolve the cellulose directly in N-oxide tertiary amines, in particular the N-oxide of N-methylmorpholine, as described for example in U.S. Pat. No. 4,416,698. These solvents are poorly adapted to the use of highly concentrated solutions, a condition of concentration which moreover is necessary for the obtaining of a liquid-crystal phase since the temperature of use of these solutions is close to the degradation temperature of the solvent.
The Japanese patent application published under number 4-258 648 also describes solutions obtained by the direct dissolving of cellulose, some of these solutions being capable of presenting optical anisotropy under certain conditions. However, the solvent mixture proposed is formed of at least two acids, in particular sulfuric acid and phosphoric acid. The presence of two acids may result in serious complications upon recycling. Furthermore, the use of sulfuric acid entails the risk of leading to a sulfonation of the cellulose or to an extensive degradation of it, and therefore to more difficult spinning. There is also the risk of rapid corrosion of the equipment.
SUMMARY OF THE I
REFERENCES:
patent: 4370168 (1983-01-01), Kamide et al.
patent: 4839113 (1989-06-01), Villaine et al.
patent: 4926920 (1990-05-01), Gouttebessis et al.
WPI, Week 8849, Derwent Publications Ltd., London, GB; AN 88-351892 & SU 1397456 Synth. Resin, May 23, 1988.
WPI, Week 8822, Derwent Publications Ltd., London, GB; An 88-153465 & SU 1348396 Phys-Chem Problems, Oct. 30, 1987.
Patent Abstracts of Japan, vol. 17 No. 42, C-1020, JP 4258648, Cellulose Dope Sep. 14, 1992 and JP 910020067, Feb. 13, 1991.
Esnault Philippe
Huston Rima
Meraldi Jean-Paul
Urso Fabio
Michelin Recherche ET Technique S.A.
Wu Shean C.
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