Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-10-31
2002-06-25
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C428S370000
Reexamination Certificate
active
06410139
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a splittable multi-component fiber of good splittability, a method for producing it, and a fibrous article comprising it. More precisely, the invention relates to a splittable multi-component fiber of good splittability favorable for use in the field of industrial materials for battery separators, wipers, filters, etc., and also in the field of sanitary materials for napkin, etc., and relates to a method for producing it, and a fibrous article comprising it.
BACKGROUND ART
Heretofore known is a method of using sea-island or splittable multi-component fibers for producing fine fibers. In the method of using sea-island multi-component fibers, a plurality of different components are combined and spun into multi-component fibers, and one component of the resulting multi-component fibers is dissolved and removed to give fine fibers. The method gives extremely fine fibers, but is uneconomical as requiring the step of dissolving and removing one component of the multi-component fibers. In the other method of using splittable multi-component fibers, a plurality of different resins are combined and spun into multi-component fibers, and the resulting multi-component fibers are split into a large number of fine fibers by applying physical stress to them or by processing them with a chemical reagent with which the resins constituting each fiber shrink to different degrees. Known are various types of multi-component fibers made from a plurality of different resins, including, for example, a combination of a polyester resin and a polyolefin resin, a combination of a polyester resin and a polyamide resin, a; combination of a polyamide resin and a polyolefin resin, etc. However, in the process of splitting the splittable multi-component fibers into fine fibers followed by further processing the resulting fine fibers to give non-woven fabrics and others, the step of splitting the multi-component fibers into fine fibers by processing them with high-pressure liquid jets takes a lot of time, and this is the rate-determining step for the subsequent step of processing the resulting fine fibers to give non-woven fabrics. In addition, the energy cost for the step of splitt ing the multi-component fibers into fine fibers is high. Moreover, the thus split fine fibers and fibrous articles comprising them inevitably contain different types of polymers, and, at present, their applications in the field of industrial materials that are required to be resistant to chemicals are limited.
On the other hand, in splittable multi-component fibers from a combination of a plurality of resins of the same type, for example, from a combination of polyolefin resins, that of polyester resins, or that of polyamide resins or the like, the constituent polymers are more highly miscible with each other, as compared with those in splittable multi-component fibers from a combination of a plurality of different types of resins such as that mentioned above. Therefore, the multi-component fibers of the former type need greater physical impact for splitting them into fine fibers. As a result, the multi-component fibers thus having received such greater physical impact will be split into uneven fibers, some of which are thick but some others are thin. Such uneven fibers are problematic in that non-woven fabrics made from them have a bad uniformity, and the line speed for processing them with high-pressure liquid jets must be significantly lowered. To that effect, the multi-component fibers are problematic and are not satisfactory.
To solve the problem, Japanese Patent Laid-Open No. 28922/1992 discloses a splittable multi-component fiber comprising a plurality of resins of the same type to which is added an organosiloxane or a modified organosiloxane. They say therein that the splittable multi-component fiber, though comprising polymers of the same type, can be readily split into fine fibers. The splittability of the multi-component fiber disclosed could be enhanced in some degree, but the fiber is still problematic in that the strength of fibrous articles (non-woven fabrics, etc.) comprising the split fibers is low and that the secondary workability of the fibrous articles is poor.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied so as to obtain splittable multi-component fibers free from the prior art problems noted above, and to obtain uniform fibrous articles comprising them. As a result, we have found that a splittable multi-component fiber comprising at least two thermoplastic resin components, in which one thermoplastic resin component is broken to form a partially conjugated part having been broken in the direction of the fiber axis (see
FIG. 2
) and/or a non-conjugated part (see
FIG. 3
) around the multi-component fiber, is readily splittable, and that a fibrous article comprising the splittable multi-component fibers has uniformity. We have also found that a splittable multi-component fiber comprising at least two polyolefin resin components and having a hollow with the individual constituent resin components being alternately radially aligned around the hollow in its cross section and with the percentage of its hollowness falling between 5 and 40%—in which the ratio of the mean length, W, of the outer peripheral arc of one constituent resin component to the mean thickness, L, of the component between the end of the hollow and the outer periphery of the fiber, W/L, falls between 0.25 and 2.5—is readily splittable, and that a fibrous article comprising the splittable multi-component fibers has fineness and uniformity. We have still found that a splittable multi-component fiber comprising at least two thermoplastic resin components—in which the constituent components are alternately aligned to be adjacent to each other in the direction of the fiber axis in the cross section of the fiber, the cross section is bent, curved or flattened, and the ratio of the major axis, L, of the cross section to the minor axis, W, thereof , L/W falls between 3 and 20—is readily splittable, and that a fibrous article and a piled fibrous article comprising the splittable multi-component fibers has fineness and uniformity. We have still found that a splittable multi-component fiber comprising at least two thermoplastic resin components—in which the constituent components are alternately aligned to be adjacent to each other in the direction of the fiber axis in the cross section of the fiber, the cross section is bent, curved or flattened, and the ratio of the major axis, L, of the cross section to the minor axis, W, thereof, L/W falls between 3 and 20—is readily splittable, and that a fibrous article and a laminated fibrous article comprising the splittable multi-component fibers has fineness and uniformity. On the basis of these findings, we have completed the present invention. As is obvious from the above-mentioned description, the object of the invention is to provide a splittable multi-component fiber capable of being readily split into fine fibers, a method for producing it, a fibrous article having uniformity that comprises the fiber, and a product comprising the article.
The invention is composed of a first aspect including the following (1) to (6), a second aspect including the following (7) to (21), a third aspect including the following (22) to (28), and a fourth aspect including the following (29) to (43).
(1). A splittable multi-component fiber comprising thermoplastic resin components (A) and (B) alternately aligned in its cross section, which is characterized in that the component (A) is formed continuously in the direction of the fiber axis, and the component (B) is so randomly formed that some of it is conjugated to the component (A) in the direction of the fiber axis to give a completely conjugated part and some others of it are broken in the direction of the fiber axis to give a partially conjugated part in which the area conjugated to the component (A) is smaller than that in the completely conjugated part and/or a non-conjugated part in which th
Kojima Mitsuru
Nishijima Masaru
Sakamoto Kazuyuki
Suzuki Masayasu
Tsutsui Toshihiko
Chisso Corporation
Edwards N.
Fay Sharpe Fagan Minnich & McKee LLP
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