Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-04-05
2001-07-17
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S364000
Reexamination Certificate
active
06261689
ABSTRACT:
The invention relates to fibers made of cellulose derivatives and to fibers made of cellulose regenerated from these derivatives.
“Cellulose derivatives” is here understood to mean, in a known way, the compounds formed, as a result of chemical reactions, by substitution of the hydroxyl groups of cellulose, these derivatives also being known as substitution derivatives. “Regenerated cellulose” is understood to mean a cellulose obtained by a regeneration treatment carried out on a cellulose derivative.
The invention more particularly relates to fibers made of cellulose formate and to fibers made of cellulose regenerated from this formate, and to the methods for producing such fibers.
Fibers made of cellulose formate and fibers made of cellulose regenerated from this formate have been described in particular in International Patent Application WO 85/05115 (PCT/CH85/00065), filed by the Applicant Company, or in the equivalent Patent EP-B-179,822 and U.S. Pat. No. 4,839,113. These documents describe the production of spinning solutions based on cellulose formate by reaction of cellulose with formic acid and phosphoric acid. These solutions are optically anisotropic, that is to say that they exhibit a liquid crystal state. These documents also describe the cellulose formate fibers obtained by spinning these solutions, according to the so-called dry-jet-wet spinning technique, and the cellulose fibers obtained after a regeneration treatment of these formate fibers.
In comparison with conventional cellulose fibers, such as rayon or viscose fibers, or with other conventional non-cellulose fibers, such as nylon or polyester fibers, for example, all spun from optically isotropic liquids, the cellulose fibers of Application WO 85/05115 are characterized by a much more orderly structure, due to the liquid crystal nature of the spinning solutions from which they emerge. They thus exhibit very high mechanical properties in extension, in particular very high tenacity and modulus values, but, on the other hand, are characterized by rather low values of elongation at break, these values being on average between 3% and 4% and not exceeding 4.5%.
However, greater values of elongation at break may be desirable when such fibers are used in certain technical applications, in particular as components for reinforcing a tire, in particular a tire carcass casing.
The first aim of the invention is to provide fibers made of cellulose formate and fibers made of regenerated cellulose which, in comparison with the fibers of Application WO 85/05115, exhibit a significantly improved elongation at break and high properties of energy at break.
The second aim of the invention is to produce the above improvements without decreasing the tenacity of the fibers, which is a major advantage of the invention.
Another aim of the invention is to produce fibers made of regenerated cellulose, from cellulose formate, the resistance to fatigue of which, in particular with respect to tires, is substantially improved in comparison with that of the fibers made of regenerated cellulose of the abovementioned Application WO 85/05115.
The fiber made of cellulose formate of the invention is characterized by the following relationships:
Ds
≧2;
Te
>45;
Mi
>800;
ELb
>6;
Eb
>13.5,
Ds being the degree of substitution of the cellulose as formate groups (in %), Te being its tenacity in cN/tex, Mi being its initial modulus in cN/tex, ELb being its elongation at break in % and Eb being its energy at break in J/g.
The fiber made of cellulose of the invention, regenerated from cellulose formate, is characterized by the following relationships:
0
<D
S
<2;
T
E
>60;
M
I
>1000;
EL
B
>6;
E
B
>17.5,
D
S
being the degree of substitution of the cellulose as formate groups (in %), T
E
being its tenacity in cN/tex, M
I
being its initial modulus in cN/tex, EL
B
being its elongation at break in % and E
B
being its energy at break in J/g.
The fiber made of cellulose formate and the fiber made of regenerated cellulose above are both obtained by virtue of novel and specific methods which constitute other subjects of the invention.
The spinning method of the invention, in order to obtain the fiber made of cellulose formate of the invention, which consists in spinning a solution of cellulose formate in a solvent based on phosphoric acid, according to the so-called dry-jet-wet spinning method, is characterized in that the stage of coagulation of the fiber and the stage of neutral washing of the coagulated fiber are both carried out in acetone.
The regeneration method of the invention, in order to obtain the fiber made of regenerated cellulose of the invention, which consists in passing a fiber made of cellulose formate into a regenerating medium, in washing it and then in drying it, is characterized in that the regenerating medium is an aqueous sodium hydroxide (NaOH) solution in which the sodium hydroxide concentration, recorded as Cs, is greater than 16% (% by weight).
The invention additionally relates to the following products:
reinforcing assemblies each containing at least one fiber in accordance with the invention, for example cables, plied yarns or multifilament fibers twisted on themselves, it being possible for such reinforcing assemblies to be, for example, hybrids, that is to say composites, containing components of different natures, optionally not in accordance with the invention;
articles reinforced by at least one fiber and/or one assembly in accordance with the invention, these articles being, for example, rubber or plastic articles, for example plies, belts, pipes or tires, in particular tire carcass casings.
The invention will easily be understood with the help of the description and the non-limiting examples which follow.
REFERENCES:
patent: 4370168 (1983-01-01), Kamide et al.
patent: 4839113 (1989-06-01), Villaine et al.
patent: 5571468 (1996-11-01), Meraldi et al.
patent: 5585181 (1996-12-01), Meraldi et al.
patent: 5587238 (1996-12-01), Meraldi et al.
patent: 6139959 (2000-10-01), Meraldi et al.
Aubry Jean-Claude
Cizek Vlastimil
Meraldi Jean-Paul
Ribiere Joel
Schneider Andre
BakerBotts L.L.P.
Edwards N.
Michelin Recherche ET Technique S.A.
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