Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-04-16
2004-02-10
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C057S243000
Reexamination Certificate
active
06689461
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a false-twisted yarn of a polyester composite fiber, which can be used for knitted or woven fabrics.
BACKGROUND ART
In recent years there has been a strong demand for stretch knitted or woven fabrics exhibiting an excellent stretch performance and a wearable feel.
This demand has been met by the use of numerous stretchable knitted or woven fabrics obtained by mixing, for example, polyurethane fiber with polyester fiber or the like.
However, polyurethane fiber is problematic in that it is not easily dyed with polyester fiber disperse dyes and therefore requires a more complex dyeing process, while it also becomes brittle and loses its stretch properties with prolonged use.
It has been attempted to avoid such problems by investigating the use of a crimped yarn of polyester fiber instead of a polyurethane fiber.
Crimped yarn is a term including bulky yarn obtained by mechanical working of drawn yarn or partially oriented yarn (POY), and self-crimping yarn achieved by adhering two types of polymers in a side-by-side or eccentrical fashion and crimping them.
False twisted yarn is a typical type of bulky yarn of poly(trimethylene terephthalate) (hereunder, “PTT”). Such yarn is described in numerous published documents including Kohyo (National Patent Publication of Translated Version) No. 9-509225, Japanese Unexamined Patent Publication SHO No. 58-104216, Japanese Unexamined Patent Publication SHO No. 11-172536, Japanese Unexamined Patent Publication No. 2001-20136 and WO00/47507, and Chemical Fibers International, Vol.47, pp.72-74 (published 2/1997).
PTT false twisted yarn includes single heater stretch yarn obtained directly by crimping or draw crimping, and double heater set yarn obtained by further heat treatment of single heater stretch yarn.
Single heater stretch yarn has residual torque, and with further heat treatment the crimping is augmented and hardened to give false twisted yarn with latent crimpability. Double heater set yarn is obtained by development of crimps by thermosetting, and such textured yarn has low residual torque.
Single heater false twisted yarn having latent crimpability and a high crimp development property is normally used in woven fabrics, but when it resides in a woven fabric with strong binding force due to the fabric texture, or when it has been subjected to a strong load, it often fails to exhibit adequate crimping even if the cloth is subjected to heat treatment or other steps.
For example, when conventional PTT false twisted yarn is used as the warp yarn for a woven fabric, the strong binding force of the fabric texture prevents expression of adequate crimping and, therefore, a fabric with an excellent stretch property (or, stretchability) cannot be obtained.
Double heater false twisted yarn with dense crimping and few surface irregularities is commonly used for cloths such as knitted fabrics with relatively low texture binding force, but when conventional PTT false twisted yarn is used, stretchability is obtained but little of the free-movement property of cloths employing polyurethane fiber is exhibited.
On the other hand, side-by-side crimped yarn is a typical type of self-crimping yarn of PTT fiber, and the relevant prior art includes Japanese Examined Patent Publication SHO No. 43-19108, Japanese Unexamined Patent Publication No. 2000-239927, Japanese Unexamined Patent Publication No. 2000-256918, Japanese Unexamined Patent Publication No. 2001-55634, European Patent (EP) No. 1059372, Japanese Unexamined Patent Publication No. 2001-40537, Japanese Unexamined Patent Publication No. 2001-131837, Japanese Unexamined Patent Publication No. 2002-61031, Japanese Unexamined Patent Publication No. 2002-54029 and U.S. Pat. No. 6,306,499.
In these documents there is proposed either the use of PTT for at least one of the components, or else the use of PTT with different intrinsic viscosity for side-by-side or eccentric core-sheath two-component composite fiber (hereunder both collectively referred to as “PTT composite fibers”; PTT composite fiber is also called as PTT conjugate fiber). Such PTT composite fibers are characterized by having a soft feel and satisfactory crimp development property. The aforementioned prior art documents teach that such fibers have stretch properties and elongation recovery, and that these properties can be utilized for application in various stretch knitted or woven fabrics or bulky knitted or woven fabrics.
However, conventional PTT composite fibers have been found to have the following problems.
(i) Crimp Development Property
Because of the weak crimp development property of conventional PTT composite fibers, excellent stretchability cannot be obtained when they are used for woven fabrics with strong binding force due to the texture. That is, although adequate crimping is expressed in the absence of a load, adequate crimping cannot be expressed even with heat treatment in the presence of binding as exists in a woven fabric or under a load.
In order to compensate for the weak crimp development property and to express adequate stretchability, it has been necessary to first produce a wide knitted or woven fabric, and then release the binding or load during heat treatment, which results in significantly shrinkage of the fabric width. It cannot be denied that this method is economically disadvantageous because of the reduced cloth width.
When a conventional PTT composite fiber is used directly in a knitted or woven fabric, craping irregularities are produced on the surface of the cloth product, resulting in impaired surface quality. In order to improve the surface quality, twisting is carried out at 500-2000 turns/m but, although the surface craping is reduced with greater twisting such that the surface quality is improved to some degree, a drawback is that the crimpability is reduced.
Thus, while conventional PTT composite fibers exhibit stretch properties and an elongation recovery comparable to elastic fibers if heat treated in the absence of a load, when they are actually used in a cloth, their weak crimp development property limits their use for woven fabrics with strong fiber binding.
It has also been considered to combine false twisting with such polyester composite fibers in order to compensate for the weakness of the crimp development property of the fibers.
Publicly known poly(ethylene terephthalate) composite fibers, when subjected simply to false twisting, do not exhibit a crimpability exceeding false twisting of the individual component fibers of the composite fiber. (See, for example, “Filament Texturing Technology Manual” ed. by The Textile Machinery Society of Japan, p.190: 1976.)
Japanese Unexamined Patent Publication No. 2000-256918 discloses a technique whereby an eccentric core-sheath composite fiber comprising as one of the components PTT obtained by copolymerization of three-dimensional crosslinkable trifunctional components, is subjected to false twisting to develop crimps. This publication, however, merely mentions crimping of latent crimped yarn as one means of development, and neither discloses nor suggests an improvement in the crimp development property. Also, the PTT fiber obtained by copolymerization of crosslinking components disclosed in this publication has poor long-term spinning stability, and this has therefore hampered industrial operations. In addition, because of the effect of the crosslinking components, the breaking elongation of the false twisted yarn is less than 25%, resulting in more yarn breakage during false twisting and thus hampered industrial operation.
(ii) False Twisting Property
Surprisingly, it has been shown that for false twisting of conventional PTT composite fiber, yarn breakage increases during false twisting as the false twisting time proceeds.
When the cause of this was investigated, it was found to be that trimethylene terephthalate cyclic dimers in the fiber sublimate during false twisting and attach to, and accumulate on, the guides.
It is surmised that the lower degree of molecular orientation of side-by-side com
Abe Takao
Koyanagi Tadashi
Matsuo Teruhiko
Yamamoto Mitsuyuki
Asahi Kasei Kabushiki Kaisha
Edwards N.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
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