Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1997-09-17
1999-01-05
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428393, D02G 300
Patent
active
058560041
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a cellulose filament yarn for industrial application with a breaking tenacity of higher than 600 mN/tex and containing more than 400 filaments.
Such a yarn is known from EP 0 220 642-A1, which publication discloses a cellulose yarn suitable for use as a reinforcing material in pneumatic tires. This yarn can be made by spinning an optically anisotropic solution of cellulose formate in phosphoric acid, followed by regeneration of the cellulose formate yarn. The resulting yarn has a morphology which appears to be built up of layers embedded in each other which surround the axis of the filament, and which besides varies pseudoperiodically along the axis of the filament. EP 0 179 822-A1 likewise discloses a cellulose yarn having a morphology with a similar pseudoperiodical variation along the axis of the filament. This morphology can be made visible with a polarisation microscope. According to the latter publication, the filaments of such a yarn have a sheath/core structure. According to WO 94/17136, the morphology is connected with the anisotropic solution from which the filaments are obtained. Sheath/core structures may give rise to high fibre fibrillation, especially in the case of fibres of great stiffness. As stated in WO 94/17136, this fibrillation can occur when such a filament is passed along a rough surface. This may give rise to processing problems, e.g., when processing a yarn made up of such filaments for use as a reinforcing material, for instance as the yarn is corded, when fibrillation can lead to the formation of fluff, which, in its turn, can lead to an irregular cord of lower cord strength being made.
U.S. Pat. No. 4,464,323 discloses a cellulose filament yarn of 40 filaments, the individual filaments having a high breaking tenacity (>1000 mN/tex). The filaments are made by spinning an anisotropic solution. However, since the number of filaments is very low and the preparative process for the yarn is so complex as to preclude production on an economically advantageous scale, the yarn is not suitable for use on an industrial scale.
It is clear from the above-mentioned publications that cellulose filaments of high strength can be obtained by spinning an anisotropic, cellulose-containing solution.
At the moment, the only commercially available cellulose yarns for industrial applications are those made via the viscose process. Such yarns generally contain 1000 or more filaments and have a breaking tenacity in the range of 400 to 550 mN/tex. Such yarns generally have a modulus of elasticity, characterised by their tenacity at an elongation of 1% (TASE 1%), of less than 100 mN/tex. These yarns are made by spinning an optically isotropic solution, and the morphology of the filaments does not vary pseudoperiodically along the axis of the filament.
For a number of applications of a cellulose yarn as a reinforcing material, the yarn is processed into a cord. Such cords usually contain two or three intertwined twisted yarns. In actual practice, the twist factor serves as a measure of the number of turns of a yarn in a cord structure. The twist factor can be calculated from the weight per unit length of the cord (the so-called linear density) and the number of turns in the cord per unit length. The twist factor increases as during cord manufacture from one and the same type of yarn the number of turns per unit length increases. When making a cord from twisted yarns, the yarns generally are intertwined in such a way as will result in the number of turns per unit length in the cord being the same as the number of turns per unit length in the yarn of which the cord is built up, with the proviso that the direction in which the twisted yarns are intertwined is opposite to the direction of twist of the yarns. In such a way a so-called symmetrical cord is formed. Alternatively, an asymmetrical cord can be formed.
It was found that the breaking force of a cord of cellulose yarns made in such a way decreases as the twist factor increases. However, the twist factor was also found to affe
REFERENCES:
patent: 4464323 (1984-08-01), O'Brien
patent: 4839113 (1989-06-01), Villaine et al.
patent: 4926920 (1990-05-01), Goattebessis et al.
patent: 5571468 (1996-11-01), Meraldi et al.
Broeren Egbert Wilhelmus Christinus
Elkink Frederik
Maatman Hendrik
Akzo Nobel nv
Edwards Newton
Morris Louis A.
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