Drawn yarn package and production method therefor

Details Drawn yarn package and production method therefor Drawn yarn package and production method therefor

2003-01-03

2004-03-23

Edwards, N. (Department: 1774)

Food or edible material: processes, compositions, and products

Inhibiting chemical or physical change of food by contact...

Treating liquid material

C428S395000, C264S103000, C264S130000, C264S211120, C264S211140, C206S392000

Reexamination Certificate

active

06709689

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a package of poly(trimethylene terephthalate) drawn yarn obtained by a direct spin-draw process, and a method for producing the same.
BACKGROUND ART
Poly(ethylene terephthalate) (hereinafter referred to as PET) fibers are mass-produced around the world as synthetic fibers most suitable for clothing applications, and the production thereof has become a large industry.
Poly(trimethylene terephthalate) (hereinafter referred to as PTT) fibers are known in the prior art as disclosed in the following references: (A) J. Polymer Science: Polymer Physics Edition, Vol. 14 p 263-274 (1976); (B) Chemical Fibers International, Vol. 45, p110-111 April (1995); (C) Chemical Fibers International, Vol. 47, p72 February (1997); and (D) WO 99/27168.
The references (A) and (B) of the prior art describe the fundamental properties of the stress-elongation characteristics of PTT fibers, and suggest that the fibers are suitable for clothing and carpet applications because the PTT fibers show small initial modulus and, in comparison with nylon and PET fibers, they are excellent in elastic recovery.
Moreover, the reference (C) of the prior art describes a direct spin-draw process. The reference (D) of the prior art describes PTT fibers obtained by a direct spin-draw process; it describes that when the PTT fibers show appropriate breaking elongation, thermal stress and boil-off shrinkage, knitted or woven fabrics for which the PTT fibers are used can manifest a low elastic modulus and a soft feeling. The reference (D) of the prior art further describes that such PTT fibers are appropriate to clothing such as innerwear, outerwear, sportswear, hosiery, lining cloth and swimwear.
The reference (D) of the prior art discloses as follows. A drawn yarn obtained by a direct-spin draw process significantly shrinks during and after winding, and the end surfaces of the resultant package come to have a swollen shape called bulging. As a result, a good package is hard to obtain. Moreover, even taking a package having such a bulging shape out of the winder becomes difficult.
The investigation by the present inventors has elucidated that the package of drawn yarn obtained by a direct spin-draw process has problems to be explained below other than those described by the above references of prior art.
a. Formation of High Edges and Pressing
A PTT drawn yarn is very sensitive to temperature and humidity. Specifically, heat generated from the motor itself of the winder during winding is transferred to the package through the bobbin axis, and the package temperature rises. Moreover, heat generated by friction between the package and the contact roll also raises the package temperature. As a result, the drawn yarn in the package shrinks.
The shrinkage of the drawn yarn is not produced substantially in both edge portions of the wound package having high hardness. It is produced in the other portion, namely, in only a drawn yarn wound in the central portion. As a result, the package comes to have a high edge winding shape during winding. When the package has a high edge shape, the edge portions alone are subsequently contacted with the contact roll, and frictional heat generation increasingly concentrates in the edge portions with an increase in a winding amount. Consequently, a package wound in such a manner to have a given winding diameter not only has a high edge winding form but is also in a state in which drawn yarns wound in each edge portion are pressed by the heat.
A study by the present inventors has clarified that such shrinkage of a drawn yarn caused by heat generation of the package is greatly influenced by dry thermal shrinkage stress of the drawn yarn.
b. Aging During Storage
A package of drawn yarn produced is seldom provided to the subsequent processing immediately, and is usually used after a storing period from one month to one year. Moreover, the storage temperature reaches a temperature as high as from about 30 to 40° C. when it is hot.
When the package is stored over a long period of time at such high temperature, the PTT drawn yarn shrinks resulting in package tightening and, as a result, a high edge and bulging shapes are made more significant. Moreover, the PTT drawn yarn wound in the edge portions of the package has a high density as the filaments thereof were adhered each other due to shrinkage.
FIG. 1
is a view schematically showing a package having a normal winding shape.
FIG. 2
is a view schematically showing a package deformed to have a high edge. In addition, the reference numerals
20
,
21
in
FIG. 1
designate a bobbin and a package, respectively; the signs &agr;, &bgr; in
FIG. 2
designate the diameter of the edge portion and the diameter of the central portion, respectively.
c. High Speed Unwindability
For lining cloth and innerwear applications, a plain weave fabric the structure of which is represented by taffeta, twill, or the like, and a warp knitted fabric such as tricot are employed. Because a PTT drawn yarn is used without further processing such as false twisting in these fabrics, fibers are regularly arranged in the fabrics. As a result, there is the problem that fine defects present in the fibers remain intact and tend to be manifested as qualitative defects such as “warp streaks”, “tight pick”, or “uneven dyeing.”
As cost competition has become severe in recent years, the processing rate is made high even in the weaving or knitting stage in order to correspond to the competition. For example, the rate of warping that is a stage of preparing the warp yarn of a woven fabric is made as high as from 500 to 1,000 m/min, while the rate was formerly from 100 to 200 m/min. The industrial weaving rate of a weft yarn with a weaving machine is currently from 800 to 1,500 m/min.
When a drawn yarn is unwound at high speed from a package of PTT drawn yarn having been stored at high temperature over a long period of time, yarn breakage increases, and unwinding tension fluctuation corresponding to a yarn length from one end surface to the opposite one of the package is generated. When a difference between the maximum and the minimum value of the tension fluctuation (hereinafter referred to as an unwinding tension difference) is large, qualitative defects are formed in the woven or knitted fabric.
FIG. 3
is a chart showing the fluctuation of an unwinding tension observed when a drawn yarn is unwound at high speed from a package having a good winding shape as shown in FIG.
1
.
FIG. 4
is a chart showing the fluctuation of an unwinding tension observed when a drawn yarn is unwound at high speed from a package having a high edge winding shape as shown in FIG.
2
.
In
FIGS. 3 and 4
, the abscissa indicates a yarn length of a drawn yarn and the ordinate indicates an unwinding tension (g).
Although the reference (D) of the prior art mentioned above proposes the solution of package tightening during winding and reduction of bulging, it does not refer to the formation of a high edge and pressing caused by heat generation of a package during winding, package tightening caused by aging, and problems produced by the package tightening when the package is unwound at high speed.
The reference (D) of the prior art describes that a weight of the yarn wound into a package must be made 2 kg or less, and discloses an embodiment of a package having a winding width as long as 300 mm, and a winding weight of from 1 to 1.5 kg (corresponding to a winding diameter of 130 mm). However, when a package having such a small winding amount is unwound at high speed, replacement of an old package with a new one must be frequently conducted. The use of such a package is therefore industrially disadvantageous. Moreover, because the winding width is large, there is the problem that the unwinding tension difference between one end surface and the other end one of a yarn length in the package is large. The reference (D) of the prior art describes only one embodiment of a package having a wound yarn in an amount of 5 kg. Because the dry thermal shrinkage stress of the yarn

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