Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-07-30
2004-01-06
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C206S392000
Reexamination Certificate
active
06673443
ABSTRACT:
TECHNICAL FIELDS
The present invention relates to a pirn of a conjugate fiber formed from two types of polyesters, and method for producing the same.
BACKGROUND ART
Poly(ethylene terephthalate) (hereinafter abbreviated to PET) fibers are mass-produced around the world as synthetic fibers most suitable for clothing applications, and the production thereof has become a large industries.
Poly(trimethylene terephthalate) (hereinafter abbreviated to PTT) fibers are known from the prior art technologies such as those disclosed in the following references: J. polymer Science: polymer Physics Edition, Vol. 14 (1976) p 263-274; Chemical Fibers International, Vol. 45, April (1995) p 110-111; Japanese Unexamined Patent Publication (Kokai) No. 52-5320; Japanese Unexamined Patent Publication (Kokai) No. 52-8123; Japanese Unexamined Patent Publication (Kokai) No. 52-8124; WO 99/2716; and WO 00/22210.
The references to the prior art technologies describe that when PTT fibers show appropriate breaking elongation, thermal stress and boil-off shrinkage, knitted or woven fabrics, in which the PTT fibers are used, can manifest a low elastic modulus and a soft feel. The references also describe that such PTT fibers are appropriate to clothing such as underwear, outerwear, sportswear, leg wear, lining cloth and swimwear.
On the other hand, a side-by-side type or eccentric sheath-core type conjugate fiber is known as a fiber to which bulkiness can be imparted without false twisting.
A conjugate fiber, for at least one component of which a PTT is used or for both components of which two respective PTTs differing from each other in intrinsic viscosity are used (hereinafter referred to as polyester-based conjugate fiber), is known as a conjugate fiber having a soft feel specific to PTT. For example, such conjugate fibers are described in the following references: Japanese Examined Patent Publication (Kokoku) No. 43-19108; Japanese Unexamined Patent Publication (Kokai) No. 11-189923; Japanese Unexamined Patent Publication (Kokai) No. 2000-239927; Japanese Unexamined Patent Publication (Kokai) No. 2000-256918; Japanese Unexamined Patent Publication (Kokai) No. 2001-55634; EP 1059372; Japanese Unexamined Patent Publication (Kokai) No. 2001-40537; Japanese Unexamined Patent Publication (Kokai) No. 2001-131837; Japanese Unexamined Patent Publication (Kokai) No. 2002-61031; Japanese Unexamined Patent Publication (Kokai) No. 2002-54029; Japanese Unexamined Patent Publication (Kokai) No. 2002-88586; U.S. Pat. No. 6,306,499 and WO 01/53573. These references describe that a polyester-based conjugate fiber characteristically has a soft feel and a good development of crimp, and that the fiber can be applied to various stretch knitted or woven fabrics or bulky knitted or woven fabrics by utilizing these properties.
In the production of synthetic fibers such as polyamide and polyester fibers, drawn fibers have heretofore been obtained by a two-stage system comprising melt spinning a polymer, winding an undrawn fiber, and drawing the undrawn fiber. WO 00/22210 as mentioned above describes the technology. Although the winding shape of the drawn fiber thus wound by the two-stage system can be a cheese shape or a pirn shape, it is generally a pirn shape.
A fiber wound in a pirn shape is used for preparing a knitted or woven fabric without further processing. Alternatively, the fiber is false twisted for the purpose of imparting bulkiness and stretchability to the fabric, and then used for preparing a knitted or woven fabric.
False twisting a fiber wound in a pirn shape is hindered by the unwindability of the fiber, from the pirn, or by yarn breakage during false twisting, and pin false twisting in which the false twisting rate is 100 m/min at the most has been adopted. The false twisting method disclosed in WO 00/22210 mentioned above also belongs to this category. However, in order to reduce the processing cost in recent years, even the pin false twisting must be conducted at a rate of 150 m/min or more, and adoption of high-speed false twisting at a rate of from 200 to 700 m/min in which a disc or belt is used has been required.
According to investigations by the present inventors, high-speed false twisting of a polyester-based conjugate fiber pirn differs from false twisting of a PET fiber in that it has the following problems: (a) yarn breakage takes place during unwinding; (b) yarn breakage takes place on a false twisting heater; and (c) uneven dyeing of a false-twisted yarn occurs. In particular, when industrial production is taken into consideration, it has become evident that the problems are manifested in a pirn holding a large amount of yarn.
(a) Yarn Breakage during Unwinding
Because a PTT fiber is excellent in elastic recovery, the drawing stress a yarn suffers during drawing remains as a shrinkage force when the yarn is wound into a drawn yarn pirn, and the drawn yarn pirn is tightly wound. The tight winding of a drawn yarn pirn becomes more significant when the period from directly after winding the yarn in a pirn shape to until the yarn is actually supplied to false twisting is longer and the winding amount is larger.
A drawn yarn pirn that is tightly wound has a high winding hardness. When a yarn is to be unwound from such a drawn yarn pirn, the unwinding tension greatly fluctuates in the longitudinal direction of the yarn, and an extraordinary high tension is produced, in some cases, to cause yarn breakage.
(b) Yarn Breakage on False Twisting Heater
A proper false twisting temperature range of a polyester-based conjugate fiber is extremely narrow in comparison with a PET fiber, and the fiber must be false twisted at heater temperature of from 150 to 180° C. When the heater temperature is lower than 150° C., the crimp of the false twisted yarn flows in a knitting or weaving stage or a dyeing stage, or the like disadvantageous phenomenon takes place. The crimpability of the false-twisted yarn is deteriorated, and a practically usable processed yarn is hardly obtained. On the other hand, when the heater temperature exceeds 180° C., yarn breakage tends to take place on the heater. That is, because the thermal shrinkage characteristics of the drawn yarn provided to false twisting greatly influence the false twisting ability, strict selection of the thermal shrinkage characteristics is particularly important to the polyester-based conjugate fiber.
(c) Uneven Dyeing of False-Twisted Yarn
The false-twisted yarn obtained by false twisting a polyester-based conjugate fiber tends to produce uneven dyeing in comparison with the false-twisted yarn obtained by false twisting a fiber of PTT alone. The reason is thought to be as follows though it is not clear. The fluctuation of the unwinding tension described in (a) or manifestation of the crimp a polyester-based conjugate fiber makes the contact resistance of the yarn to guides of the false twisting machine significant. As a result, the fluctuation of a tension during false twisting becomes significant to produce nonuniformity in a yarn that influences the dyeing quality of false twisting.
The problems as mentioned above of false twisting a polyester-based conjugated fiber have not been anticipated from a knowledge concerning a PET fiber. The problems have been elucidated for the first time from the research by the present inventors. The above references of the prior art technologies neither disclose nor suggest practical problems on an industrial production scale in such false twisting. It is needless to say that methods of solving the problems have never been known.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a polyester-based conjugate fiber pirn excellent in high-speed false twisting ability though the pirn is obtained by a two-stage method. More specifically, an object of the present invention is to provide a polyester-based conjugate fiber pirn that shows good unwindability even in high-speed false twisting, that produces neither yarn breakage nor fluff formation during false twisting even at a high heater temperature and that,
Abe Takao
Koyanagi Tadashi
Asahi Kasei Kabushiki Kaisha
Edwards N.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
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