Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2003-08-15
2004-11-02
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000, C057S210000, C057S211000
Reexamination Certificate
active
06811872
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a filament machine sewing thread capable of forming uniform stitches while leaving gloss of filaments and having good high-speed sewability.
BACKGROUND ART
Filament machine sewing threads have been used for various kinds of sewing because of gloss as compared with that of machine sewing threads comprising spun yarns, uniform stitches and a high machine sewing thread strength; however, the filament machine sewing threads have disadvantages in that sewability in back stitching and zigzag chain stitching readily causing untwisting is inferior to that of the spun yarn machine sewing threads.
As for causes thereof, it is thought that drawing is carried out while applying a high thermal history using a polymer having a higher intrinsic viscosity than that of conventional polymers in order to retain the machine sewing thread strength which is a feature of the filament machine sewing threads at a high value, and that the torque of the primary and final twists applied in the subsequent step of forming the machine sewing threads is thereby not sufficiently set even after dyeing of the machine sewing threads to cause untwisting and the formation of stitches is not successful when carrying out the back stitching and zigzag chain stitching.
In order to solve the problems, JP-A 5-106134 (hereunder, JP-A means “Japanese Unexamined Patent Publication”) discloses that a machine sewing thread having excellent sewability is obtained by forming a composite from two kinds of filament yarns having a difference in elongation of 20% or above and forming loops or slacknesses with the high-elongation yarn. In the machine sewing thread, however, there are problems that separation of the two kinds of filament yarns occurs and a bias is caused in the form of stitches to deteriorate uniformity or a difference in dyeability is conspicuous when the machine sewing thread is dyed.
JP-A 9-78335 discloses a filament machine sewing thread obtained by spinning and combining a filament yarn having a high birefringence with a filament yarn having a low birefringence and arranging the filament yarn having the low birefringence in a sheath part. The machine sewing thread has problems that the strength is lowered, the thread slips down from a bobbin, smooth thread feed cannot be made, breakage sometimes occurs and handleability is bad as compared with that of conventional filament machine sewing threads because only the difference in birefringence is utilized.
It is an object of the present invention to improve disadvantages caused by the formation of loops or slacknesses as described above and to provide a filament machine sewing thread capable of forming uniform stitches while leaving the gloss of filaments and having good high-speed sew ability.
DISCLOSURE OF THE INVENTION
As a result of intensive studies made to achieve the objects, the present inventors have found out that a desired filament machine sewing thread is obtained by suitably controlling the intrinsic viscosity [&eegr;]
F
and elongation of the filaments constituting the spun combined filament yarn within specific ranges. Thus, according to the invention, there is provided a filament machine sewing thread comprising a spun combined filament yarn in which polyester filaments A
1
having an intrinsic viscosity [&eegr;]
F
within the range of 0.7 to 1.2 and polyester filaments B having a lower intrinsic viscosity [&eegr;]
F
than that of the polyester filaments A by 0.2 to 0.7 and a higher elongation than that of the polyester filaments A are combined in a spinning stage.
BEST MODE FOR CARRYING OUT THE INVENTION
The mode for carrying out the invention will initially be detailed hereinafter.
In the present invention, the filament machine sewing thread is obtained by the so-called spinning filament combining method for simultaneously spinning polyester filaments A and polyester filaments B, then doubling the filaments A and B and simultaneously winding the doubled filaments.
Specifically, methods for leading polyester polymers different in intrinsic viscosity to the same spinneret, extruding the polyester polymers from separate discharge holes without mixing and winding the filaments together using a usual conjugate spinning machine or the like or methods for individually extruding the respective polymers from individually independent spinnerets, then doubling the filaments and winding the doubled filaments or the like can be adopted. In short, any methods may be used when both the filaments are united before completing the winding after the spinning.
Examples of the polyester used in the present invention include polyethylene terephthalate (hereinafter abbreviated to PET), polypropylene terephthalate, polybutylene terephthalate and the like. PET is most preferably exemplified.
It is necessary that the intrinsic viscosity of the polyester filaments A is high from aspects of heat resistance, abrasion resistance and strength, and it is necessary that the intrinsic viscosity [&eegr;]
F
of the spun filaments is within the range of 0.7 to 1.2. When the intrinsic viscosity exceeds 1.2, a large-scaled apparatus is required for polymerization and the cost is increased.
A polyester having a lower intrinsic viscosity [&eegr;]
F
than the intrinsic viscosity [&eegr;]
F
of the low-elongation filaments by 0.2 to 0.7 is used as the polyester filaments B. This is because the intrinsic viscosity of polyester filaments B is reduced to keep the polyester filaments B in a state of scarcely producing a thermal stress and the polyester filaments A having the residual torque is embraced with the polyester filaments B to thereby prevent the torque of the machine sewing thread from developing when carrying out the back stitching and zigzag stitching. In order to prevent the torque from developing, a difference in intrinsic viscosity of 0.2 or above is required. When the difference exceeds 0.7, the tenacity of the polyester filament filaments A becomes too low and breakage of single filaments occurs when sewing is carried out by a sewing machine to cause disturbance of stitches and lowering of uniformity. The difference in intrinsic viscosity is preferably 0.3 to 0.6.
The elongation of the polyester filaments B may be higher than that of the polyester filaments A; however, the elongation is usually higher for polyester filaments having a lower intrinsic viscosity when the same spinning conditions are adopted.
In the present invention, it is preferably that the polyester filaments contain an orientation inhibitor.
The orientation inhibitor herein refers to a substance having actions of inhibiting the orientation of the polyester filaments B and increasing the elongation. Specifically, examples of the orientation inhibitor include polystyrene polymers, polymethacrylate polymers or polymethylpentene polymers and the like; however, the orientation inhibitor is not limited to the polymers.
Optional methods can be adopted as a method for including the orientation inhibitor. For example, the orientation inhibitor may be included in a polymerization process of PET or the polymers may be melt mixed with PET, extruded, cooled, then cut and formed into chips. Further, both in a chip state are mixed and then directly melt spun.
The content of the orientation inhibitor is preferably 0.5 to 8.0% by weight based on the total weight of the filaments. When the content is lower than 0.5% by weight, effects on increase in elongation are not sufficiently produced. On the other hand, when the content exceeds 8.0% by weight, the strength of the filaments is extremely lowered and single filament breakage sometimes occurs even at low-speed rotation of a sewing machine. The content of the orientation inhibitor is preferably 0.5 to 5.0% by weight.
As mentioned above, the spinning filament combining method is adopted in the present invention. This is because it is necessary to adopt a spinning and winding method so as to mix the polyester filaments A with the polyester filaments B of the order of si
Higaki Masahiro
Kasaoka Katsuyuki
Nakayama Genji
Oobora Kenji
Edwards N.
Sughrue & Mion, PLLC
Teijin Limited
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