Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2003-06-26
2004-08-03
Edwards, N (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S370000, C428S374000, C428S395000, C264S103000, C264S172130, C264S211140
Reexamination Certificate
active
06770365
ABSTRACT:
TECHNICAL FIELD
The present invention relates to polytrimethylene terephthalate filament yarn and to a process for its production. More specifically, the invention relates to polytrimethylene terephthalate filament yarn capable of being produced by high-speed spinning with high productivity, and having high residual elongation as well as excellent draw/false twisting workability, and to a process for its production.
BACKGROUND ART
For melt spinning of polyester filament yarn, maximizing the polymer discharge volume from the spinneret is a very effective means for improving productivity. Recently it has become one of the most preferred strategies in the fiber industry from the standpoint of reducing yarn production costs.
The typical means hitherto employed for improving productivity has been to increase the spinning take-up speed to thereby increase the discharge volume from the spinneret. In this method, however, the high take-up speed results in a higher degree of molecular orientation of the spun fibers such that the obtained spun fibers have lower residual elongation. When this happens, needless to mention, the suitable draw ratio in the subsequent draw/false twisting step is lower, leading to a situation in which the effect of increased discharge volume by the greater take-up speed is offset by the reduced draw factor in the drawing step.
One means of solving this problem is disclosed in Japanese Examined Patent Publication SHO No. 63-32885, as a method in which the addition polymer of an unsaturated monomer is added to a polyester as a filament elongation enhancer, so that the residual elongation of the spun fibers can be increased without offsetting the increased discharge volume. This method is in fact effective for improving residual elongation, for applications involving polyethylene terephthalate fiber as the most common type of polyester fiber. However, when the present inventors attempted to apply this solution means to polytrimethylene terephthalate, it was found that problems unique to polytrimethylene terephthalate occur and prevent polytrimethylene terephthalate filament yarn with high residual elongation and high productivity being obtained. That is, when polytrimethylene terephthalate filament yarn is produced using the filament elongation enhancer described in Japanese Examined Patent Publication SHO No. 63-32885, the filament elongation enhancer simply forms particle-like lumps in the melt spun polymer flow, thereby inhibiting the draft of the spun yarn and often resulting in yarn breakage. Also, it was found that as the molecular orientation unique to polytrimethylene terephthalate increases, the rapidly increasing thermal stress is relaxed and the tightening force on the bobbin increases due to relaxation of the wound filament stress, such that after winding is complete the bobbin cannot be removed from the winder holder and the filament package edges tend to swell, a phenomenon known as bulging. The obtained polytrimethylene terephthalate filament yarn also fails to consistently exhibit satisfactory processability in the draw/false twisting steps which are carried out subsequently.
On the other hand, Japanese Unexamined Patent Publication HEI No. 11-269719 proposes means whereby the residual elongation of spun fibers can be maintained at a conventional level while improving the winding property, which means involves high-speed spinning of polyester filaments containing an added filament elongation enhancer, wherein the filament elongation enhancer used has more limited properties. However, the present inventors found that when the means described in Japanese Unexamined Patent Publication HEI No. 11-269719 is applied for melt spinning of polytrimethylene terephthalate, the filament elongation enhancer fails to adequately exhibit its prescribed function, and it is not possible to avoid frequent yarn breakage during the spun yarn winding, or the swelling of the filament package edges known as bulging. In this case as well, the obtained polytrimethylene terephthalate filament yarn failed to consistently exhibit satisfactory processability in the draw/false twisting steps carried out subsequently.
In recent years, various production techniques and processing techniques have been developed for polytrimethylene terephthalate filament yarn. Among such techniques, one method whose application to polytrimethylene terephthalate has been attempted is known as “co-spinning”, wherein two types of polyesters with different melt properties are separately melted and discharged and then simultaneously wound up onto the same filament package to produce polyester composite yarn comprising two types of undrawn yarn with different properties.
However, when polytrimethylene terephthalate fiber is subjected to co-spinning with a polyester fiber such as polyethylene terephthalate at a spinning speed of, for example, 3000 m/min or greater, as the thermal stress due to the elastic recovery characteristic of the polytrimethylene terephthalate is higher than that of other polyesters, wind-up stress is produced on the polytrimethylene terephthalate fibers during winding, while the other polyester lacks winding tension due to weaker elastic recovery, such that sagging of the other polyester fibers in relation to the polytrimethylene terephthalate fibers occurs. It is difficult to evenly wind two running fiber groups, in such a state, onto the same package simultaneously.
For spinning of polytrimethylene terephthalate fibers or co-spinning thereof with polyester fibers other than polytrimethylene terephthalate in the relatively low spinning speed range of 1,000 to 1,500 m/min, both have a low level of thermal stress, and therefore the difference in stress relaxation is not significant and simultaneously winding of the two can be accomplished. However, as the glass transition temperature (Tg) of polytrimethylene terephthalate is close to room temperature, at 30 to 40° C., the properties of the composite yarn undergo alteration, within a few hours on several days, resulting in frequent yarn breakage during the draw/false twisting steps, and producing a poor-quality drawn/false twisted yarn product that exhibits considerable fluff or dye spots. In addition, because of the excessively low degree of orientation of the composite yarn, fused yarn breakage and incomplete untwisting tend to be problems in the draw/false twisting heater, and stable false twisting cannot be accomplished for this reason.
Thus, the prior art has included no knowledge of polytrimethylene terephthalate filament yarn produced by high-speed spinning, wherein the polytrimethylene terephthalate filament yarn has excellent draw/false twisting properties, and exhibits high residual elongation and high productivity, or of a process for its production.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide polytrimethylene terephthalate filament yarn obtained by high-speed spinning, which exhibits high productivity, high residual elongation, and excellent suitability for filament processing such as draw/false twist working, as well as a process for its production.
Upon much diligent research directed toward solving the problems explained above, the present inventors have found that when a filament elongation enhancer with a specific heat deformation temperature is used, it ceases to function as a stress concentrator and instead exhibits a function as a spinning stress carrier for the spun filaments, and as a result, the filament elongation enhancer becomes oriented along the fiber axis direction and finely dispersed in the fibers when they are drawn, thereby lowering the thermal stress and allowing release of tightening tension and improvement in residual elongation to be simultaneously achieved.
The polytrimethylene terephthalate filament yarn of the present invention comprises polytrimethylene terephthalate filaments from which a filament yarn is formed, and a filament elongation enhancing agent particles dispersed and contained in the filaments, in a content of 0.5 to 4.0% by mass based on the m
Iohara Koichi
Yoshimura Mie
Edwards N
Sughrue & Mion, PLLC
Teijin Limited
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