Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-07-06
2001-02-06
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
06183865
ABSTRACT:
TECHNICAL FIELD
The present invention relates to regenerated cellulosic fibers which are produced by the use of a spinning dope of cellulose dissolved in a solvent containing N-methylmorpholine N-oxide (hereinafter abbreviated to NMMO) and to a process for producing the same. More particularly, it relates to a technique of manufacturing regenerated cellulosic fibers with a hollow or non-circular cross section, which have excellent dyeability, luster and feeling as well as improved resistance to fibrillation.
BACKGROUND ART
Methods for producing regenerated cellulosic fibers by the use of an NMMO-containing solvent have been known for a long time, as disclosed in JP-B 57-11566 and JP-B 60-28848, for example. The conventional methods of production utilizing the above solvent, however, have a serious drawback that the resulting regenerated cellulosic fibers are liable to cause fibrillation, which has become a hindrance to their general application. In spite of such a drawback, these methods have recently attracted attention again because they are environmentally friendly and are useful from an economical point of view and the resulting regenerated fibers have good physical properties to a certain extent as compared with the rayon process.
As for the above problem of fibrillation, many studies for solving the problem have been made, and some patent applications have been filed, as seen from JP-A 8-501356, JP-A 7-508320, and JP-A 8-49167, for example. In actual cases, however, these studies have not yet reached to the level that satisfactory effects can be obtained on a practical scale.
In the case where the regenerated cellulosic fibers produced by the use of the above solvent are applied to the filed of clothing or the like, it is believed that the formation of a hollow or non-circular cross section is useful for improving the luster or feeling of these fibers themselves or when they are made into woven or knitted fabrics. Notwithstanding, no studies have been made so far on the regenerated cellulosic fibers with a hollow or non-circular cross section produced by the use of an NMMO-containing solvent.
Furthermore, no one has considered using cellulose materials for the purpose of making a contribution to the preservation of global environment nor utilizing cellulose materials containing hemicellulose and lignin in large quantities.
The present invention has been made under the above circumstances with the objects of overcoming the problem of fibrillation which is found as a drawback of regenerated cellulosic fibers produced by the use of an NMMO-containing solvent as described above, as well as, in particular, of providing regenerated cellulosic fibers having excellent physical properties, feeling, dyeability and other properties for use in clothing, and of establishing a process of manufacture ensuring their stable production.
DISCLOSURE OF INVENTION
The regenerated cellulosic fiber of the present invention, which can overcome the above problem, is as follows:
(1) A regenerated cellulosic fiber which is produced by the use of a spinning dope of cellulose dissolved in a solvent containing N-methyl-morpholine N-oxide, the cellulose contained in the fiber having an average degree of polymerization of 400 or lower, and 5% to 30% by weight of the cellulose having a degree of polymerization of 500 or higher. The regenerated cellulosic fiber of the present invention exhibits excellent physical properties and appearance properties such as luster, and further have quite excellent resistance to fibrillation; it can therefore find wide applications for use in clothing.
The process for producing regenerated cellulosic fibers of the present invention is as follows:
(2) A process for producing regenerated cellulosic fibers by the use of a spinning dope of cellulose dissolved in an NMMO-containing solvent, characterized in that spinning is carried out by a dry spinneret wet spinning method under the conditions that the average degree of polymerization of cellulose contained in the spinning dope is held to 400 or lower and 5% to 30% by weight of the cellulose is adjusted to a degree of polymerization of 500 or higher. With the use of this process, the resulting fibers can have improved resistance to fibrillation.
The embodiments of the present invention may include the following examples.
A regenerated cellulosic fiber as described above in (1), wherein the regenerated cellulosic fiber contains lignin in an amount of 1% to 10% by weight based on the total weight of the cellulose.
A regenerated cellulosic fiber as described above in (1), wherein the regenerated cellulosic fiber has a hemicellulose content of 3% to 15% by weight based on the weight of the regenerated cellulosic fiber.
A regenerated cellulosic fiber as described above in (1), wherein the fiber has a hollow cross section.
A regenerated cellulosic fiber as described above in (1), wherein the fiber has a degree of non-circular cross section of 1.2 or higher.
A process for producing regenerated cellulosic fibers as described above in (2), wherein the spinning dope has a cellulose concentration of 10% to 25% by weight.
A process of production as described above in (2), wherein the spun filament extruded from a spinneret is cooled by a cooling gas before the spun filament is immersed in a coagulation bath.
A process of production as described in (2), wherein the spinneret has a non-circular or C-shaped cross section.
A process of production as described above in (2), wherein the spinneret has an approach portion with a taper angle of 10 to 45 degrees toward a nozzle tip.
The present invention will hereinafter be explained in detail.
The present inventors have gone on with their studies for solving the above problem from different points of view for the purpose of preventing fibrillation which is a drawback of the prior art as described above, particularly found in the regenerated cellulosic fibers produced by the use of an NMMO-containing solvent. As a result, they have found a new fact which has not been recognized so far by any person skilled in the art, i.e., when regenerated cellulosic fibers are produced by the use of the above solvent, the use of a special spinning dope which will cause a pseudo-liquid-crystalline phenomenon in the spinning step can give regenerated cellulosic fibers only causing quite low fibrillation.
They have further gone on with their studies and finally discovered that the degree of polymerization of cellulose dissolved in the spinning dope is very important to the occurrence of a pseudo-liquid-crystalline phenomenon as described above in the spinning step, which may be achieved by the use of a mixed cellulose solution having a specified average degree of polymerization of the cellulose and containing high molecular weight cellulose and low molecular weight cellulose at a specified ratio; when spinning is carried out by the use of such a mixed cellulose solution as a spinning dope, high-quality regenerated cellulosic fibers only causing quite low fibrillation and further having a hollow cross section can be obtained with reliability and ease. The term “pseudo-liquid-crystalline phenomenon” as used herein refers to a phenomenon that there occurs the transition of cellulose, similarly to the case of liquid crystal, in the fluidizing or stretching field during spinning.
Thus the present invention is characterized in that in the production of regenerated cellulosic fibers by a spinning method using a spinning dope of cellulose dissolved in an NMMO-containing solvent, both the average degree of polymerization of the cellulose dissolved in the spinning dope and the content of high molecular weight cellulose are specified so that a pseudo-liquid-crystalline phenomenon is allowed to occur in the spinning step.
More specifically, the average degree of polymerization of cellulose dissolved in the spinning dope should be held to 400 or lower, and the content of high molecular weight cellulose with a degree of polymerization of 500 or higher in the cellulose should be limited in the range of 5% to 30% by weight. It see
Kobayashi Hisato
Tanaka Yoshikazu
Yabuki Kazuyuki
Edwards N
Kenyon & Kenyon
Toyo Boseki Kabushiki Kaisha
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