Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-08-17
2002-12-17
Edwards, Newton (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C264S130000, C264S210300, C264S211140
Reexamination Certificate
active
06495254
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polytrimethylene terephthalate fiber (hereinafter referred to as PTT fiber), which is a kind of polyester fiber, and a method for producing the same. Specifically, it relates to a so-called two-step method for producing PTT fiber wherein polytrimethylene terephthalate is melt-spun and once taken up as an undrawn fiber after which it is drawn to be the PTT fiber and the PTT fiber thus obtained has a high uniformity suitable for a clothing use. More specifically, it relates an atmospheric condition and a time period for maintaining the undrawn fiber in the above-mentioned method for producing the same.
BACKGROUND ART
Polyester fibers mainly composed of polyethylene terephthalate have widely been produced, all over the world, as synthetic fibers most suitable for clothing use, and the polyester fiber industry has already developed into a major industrial field.
On the other hand, PTT fiber has long been studied, but it has not yet reached full-scale industrial production because of a high price of trimethylene glycol which is one of raw materials thereof in the prior art. In this regard, a method has recently been invented, for producing trimethylene glycol at a low cost, whereby there is a possibility of industrialization.
PTT fiber is expected to be an epoch-making fiber having the advantages of polyester fiber and nylon fiber, and the application thereof has been studied for clothing use or carpet use in which the advantages thereof are desirable.
PTT fiber has long been known in the prior art and, for example, from Japanese Unexamined Patent Publications (Kokai) No. 52-5320 (A), No. 52-8123 (B), No. 52-8124 (C), NO. 58-104216 (D), J. Polymer Science: Polymer Physics Edition Vol., 14, 263 to 274 (1976) (E), and Chemical Fibers International Vol., 45, April (1995) 110 to 111 (F).
In these prior arts, PTT fiber is produced by a so-called two-step method and there is the following description in (D) which is technically similar to the present invention:
“Since PTT undrawn fiber produced by an ordinary production method, i.e., at a spinning rate of lower than 2000 m/min has extremely low degrees of orientation and crystallization and a glass transition point as low as 35° C., the properties thereof very quickly change with time whereby it is difficult to obtain PTT fiber having favorable properties because of the generation of fluff or neps during a drawing process.”
A method is proposed in (D) as a technique for avoiding this problem, wherein a spinning rate is 2000 m/min or higher, preferably 2500 m/min or higher to develop the degrees of orientation and crystallization and a drawing temperature is maintained in a range from 35 to 80° C. Also, there is an example in (D) wherein an undrawn fiber obtained at a spinning rate of 3,500 m/min is drawn after being left for 24 hours under the condition of 20° C. and 60% RH.
Although there is a description in (D) that the structure and physical properties of the undrawn fiber spun at a spinning rate lower than 2000 m/min significantly vary with time at a room temperature to directly disturb the drawing stability, there are neither descriptions nor suggestions of countermeasure for avoiding adverse effects caused by such a variation with time of the undrawn fiber obtained at a spinning rate of lower than 2000 m/min, not to speak of concrete means for suppressing such variation with time within a minimum limit to obtain a high quality fiber while maintaining a favorable drawing stability.
From the description of Examples in (D), PTT fiber resulted from the method of (D) has a toughness of 18 (cN/dtex)%
½
or less, from which it will be apparent that the mechanical property is poorer.
In a comparative example disclosed in (D), a description is seen in that an undrawn fiber spun at a spinning rate of 1200 m/min was left in the atmosphere at 20° C. and 60% RH, and thereafter drawn to be a drawn fiber having a toughness of as low as 18 (cN/dtex)%
½
, however, there is no description on the variation value of fiber size (U%) or the periodic fluctuation thereof.
As a result of studies according to the present inventors, it was found that when PTT fiber is produced by the two-step method wherein a spinning rate is 1900 m/min or less, a shrinkage of the resultant undrawn fiber varies with atmospheric temperature and time as shown in
FIGS. 1 and 2
. It was also found that if the variation of shrinkage with time is large, an undrawn fiber package transforms from a normal shape as shown in
FIG. 3A
to an abnormal shape as shown in
FIG. 3B
due to the shrinkage as the time lapses, and lengths of the undrawn fiber in the package are partially adhered to each other to disturb the smooth unwinding of the undrawn fiber, which results in the large fluctuation of unwinding tension and the generation of many yarn breakages or single-filament breakages to worsen the drawing stability. Note that, in
FIGS. 3A and 3B
, reference numeral
1
denotes the undrawn fiber and
2
denotes a bobbin for taking up the undrawn yarn.
Also, it was apparent that the drawn yarn obtained from the undrawn fiber wound in the package transformed due to the variation of shrinkage with time generally has a large variation value of fiber size, i.e., U%, and the periodic fluctuation thereof corresponding to a traverse width of a take-up winder for the undrawn fiber (2 to 5 m as converted to the drawn fiber) or integral times thereof (see FIGS.
4
A and
5
A). A knit or woven fabric made of such a drawn fiber having the large U% and the periodic fluctuation of fiber size is in general unevenly dyed to exhibit a periodic dyeing speck or luster which is apparently unsuitable for a clothing use in which the uniformity is the most important property.
Generally speaking, in the industrial production of synthetic fiber by the two-step method, maximally three or four days are required for completing the drawing after the undrawn fiber has been taken up, whereby influence of the variation in shrinkage with time is substantially inevitable. Accordingly, the industrial production of PTT fiber suitable for the clothing use is impossible under the condition wherein the variation in shrinkage with time is significant as in the above manner.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a high-quality PTT fiber suitable for clothing use obtained by a two-step method, which can be drawn in a stable manner (to result in a high yield), high in toughness and low in variation of fiber size, particularly in periodic fluctuation of fiber size, preferable for an apparel, excellent in quality, and a method for industrially producing such PTT fiber. A problem to be solved by the present invention is to suppress the shrinkage of the undrawn fiber with time as much as possible, to reduce the fluctuation of unwinding tension of the undrawn fiber and to eliminate the adverse effect on the drawing stability of the undrawn fiber and on the quality of the drawn fiber.
As a result of diligent study, the present inventors found the relationship between the atmospheric condition (temperature and relative humidity) in which PTT undrawn fiber is retained and the shrinkage variation of the undrawn fiber with time as well as the relationship between the atmospheric condition and the drawing stability or the quality of the drawn fiber. The present invention has completed based on such a knowledge.
That is, a first aspect of the present invention is a twisted or non-twisted PTT fiber high in uniformity, having an intrinsic viscosity in a range from 0.7 to 1.3, composed of 95 mol % or more of repeated units of trimethylene terephthalate and 5 mol % or less of repeated units of other ester, characterized in that a toughness of the fiber is 19 (cN/dtex)%
½
or more and a variation value of fiber size (U%) during the continuous measurement of the fiber size by an evenness tester is 1.5 or less as well as the fiber exhibits either one of characteristics defined by the following requisites (1), (2) and (3);
(1) a periodic va
Abe Takao
Azuma Youichiro
Matsuo Teruhiko
Asahi Kasei Kabushiki Kaisha
Edwards Newton
Finnegan, Henderson, Farabow, Garrett & Dunner, L.LP.
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