JPS62257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester sewing thread that has excellent sewability, particularly eliminates the problem of skipped stitches, and improves the quality of sewn products. In recent years, synthetic fiber sewing threads, especially polyester spun sewing threads, have been rapidly gaining popularity due to their high strength, uniform quality, cost benefits, etc. However, they are inferior in sewability compared to traditional cotton Katan threads. In particular, it has the disadvantage of frequently causing skipped stitches,
This has caused problems in terms of sewing efficiency and quality. As a result of extensive research into the phenomenon of stitch skipping of sewing thread, the inventor of the present invention found that in order to improve stitch skipping, the key is how to form a large and stable loop made with a sewing machine needle during sewing. It has been found that the physical properties of the sewing thread, such as the modulus during initial elongation and the torque properties of the sewing thread, are the dominant factors in the formation of the sewing thread. That is,
The modulus of sewing thread at its initial elongation is related to the amount of strain against the stress applied to the needle thread during sewing; if the modulus is small, it becomes unstable due to the elasticity of elongation during loop formation, and the loop also becomes smaller. Sewing thread is repeatedly stretched and sewn in during the sewing process, but if the torque at that time is strong, the needle thread loop will twist, making it impossible to stably pass the bobbin thread through the looper, resulting in skipped stitches. will occur. Conventional polyester spun sewing thread has a much lower modulus at initial elongation than cotton Katan yarn, and attempts have been made to reduce the breaking elongation of sewing thread in an attempt to improve stitch skipping. The modulus value at the initial elongation that results in the No consideration was given to torque properties, and in some cases the torque properties after repeated stretching were quite strong, which was the reason why sufficient results could not be achieved in the past in improving skipped stitches. An object of the present invention is to provide a polyester spun sewing thread which has excellent sewability, has almost no skipped stitches, maintains its quality as a sewing thread, and does not reduce the quality of sewn products. To this end, the present invention has the following configuration.
That is, in the present invention, 85 mol% or more of the repeating unit is composed of ethylene terephthalate, and the average fiber length is
A sewing thread made by twisting and twisting multiple spun single yarns of polyester fiber with a diameter of 35 to 51 mm.
Elongation under g/d load is 7.3% or less and 1.5
This polyester spun sewing thread is characterized by having a torque of 6 times/10 cm or less after repeatedly applying a load of g/d 20 times, and a heat shrinkage rate of 4.5% or less when dry heated at 160°C. The present invention improves the modulus of polyester fibers, increases the bulk density of the yarn, increases the contribution of the modulus of the polyester fibers to the yarn, and dramatically improves the modulus of the resulting plied and twisted yarn during initial elongation. This is intended to improve sewability and, in particular, to prevent skipped stitches. below,
The present invention will be explained in detail. The polyester fiber constituting the polyester spun sewing thread according to the present invention is one in which 85 mol% or more of its repeating units consist of ethylene terephthalate, and in particular, a polyester fiber manufactured from terephthalic acid or its functional derivative and ethylene glycol. The main target is 15% of terephthalic acid or its functional derivatives as the acid component.
Replacement by up to less than mol % of at least one bifunctional acid selected from e.g. isophthalic acid, adipic acid, sebacic acid or their functional derivatives, or replacing a part of the ethylene glycol as glycol component with 15 It also includes copolymerized polyester fibers substituted with at least one kind selected from dihydric alcohols such as diethylene glycol and propylene glycol in an amount of less than mol %. In addition, staples with an average fiber length of 35 to 51 mm were limited from the viewpoint of heat resistance, fiber properties such as modulus, and morphological slip properties such as fraying, and when multiple spun yarns were combined. Twisting is also done from the same point of view. Next, the reason why the elongation at a load of 1.5 g/d is 7.3% or less is as follows. The stress that needle thread receives during sewing varies depending on sewing conditions such as the sewing material and sewing machine rotation speed, but generally it is 0.8 to 1.5 g/d.
It is thought that a loop is formed after a certain degree of impact stress is applied, and it is important that the modulus of the sewing thread is large when the impact stress is applied, and the elongation at a load of 1.5 g/d is 7.3. If it exceeds %,
This is because the needle thread loop becomes unstable due to the rebound elasticity caused by the stretching of the sewing thread, and the formed loop also becomes smaller, making skipped stitches more likely to occur. Note that the elongation at a load of 1.5 g/d refers to the elongation at a constant speed extension type tensile tester with a sample length of 20 cm and a tensile speed.
1.5 from the stress-strain curve when pulled at 20cm/min
It refers to the measured elongation rate under g/d stress. Methods to increase the modulus of sewing thread include using polyester fibers that have been made highly modulus by stretching them at high temperatures and high ratios, or by using a combination of methods such as twisting and then stretching them at high temperatures and high ratios and then heat-treating them. However, in order to dramatically improve the modulus in the initial elongation according to the present invention, after the dyed and twisted yarn is stretched at high temperature and high magnification,
Furthermore, it is preferable to stabilize the yarn structure by sufficiently heat setting the yarn under some relaxation. Further, the torque of the sewing thread after applying a load of 1.5 g/d 20 times is usually 6 times/10 cm or less, but preferably 5 times/10 cm or less. This corresponds to the degree of torque balance of the sewing thread after receiving the impact stress during sewing as mentioned above, and when the torque exceeds 6 times/10cm, the needle thread loop becomes twisted and becomes stable. This is because there are cases where the pattern is not formed, and the occurrence of skipped stitches cannot be completely prevented. The torque referred to here is determined by using a constant-speed elongation tensile tester, fixing both ends of a 40cm sample length, repeatedly applying a load of 1.5g/d 20 times at a tensile speed of 100cm/min, and then applying the repeated load. This is the value expressed by the number of twists per 10 cm when a 40 cm thread is turned into a single ring and a load of 1/30 g/d is applied. In order to obtain a yarn with the minimum torque when repeatedly loaded, the number of twists of the spun single yarn of polyester fiber and the number of twists of the plied yarn applied in the opposite direction to the twisting direction of the spun single yarn should be adjusted. A method of setting the balance appropriately and stabilizing it even after repeated elongation by heat treatment is applied. In order to properly balance the number of twists, it is preferable to set the ratio of the twist coefficient K ₂ of the combined twisted yarn to the twist coefficient K ₁ of the spun single yarn in the range of 1.0≦K ₂ /K ₁ ≦1.5. As for the heat treatment conditions for stabilizing the balance, it is effective to add some stretching and heat set for 0.5 seconds or more at a temperature range of 20 to 40°C lower than the melting point of the polyester fiber. Furthermore, dry heat 160 of the sewing thread according to the present invention
The heat shrinkage rate at °C is 4.5% or less, more preferably 3% or less. This is to prevent the sewn product from shrinking when subjected to heat treatment such as ironing after sewing or when washed, to prevent puckering and to prevent a significant deterioration in the quality of the sewn product. In order to increase the modulus of the sewing thread, a method is generally adopted in which polyester fibers are stretched at a high magnification, but the heat shrinkage rate tends to be high, so it is necessary to perform sufficient heat treatment to reduce the heat shrinkage. It is preferable to hold it down. As described above, the polyester spun sewing thread according to the present invention not only completely eliminates the problem of skipped stitches, which is a drawback of conventional polyester sewing threads, but also maintains a stable sewing condition and improves the tension during sewing. It has remarkable effects such as a drastic reduction in breakage, fewer thread breakages, and much cleaner stitches than conventional sewing thread. Example A polyethylene terephthalate chip with an intrinsic viscosity of 0.635 (measured at 30°C in a solvent of phenol/tetrachloroethane - 3/2) was melted at a temperature of 290°C, and discharged through a nozzle with a pore diameter of 0.3 mm and 460 holes for a distance of 1000 m. Stretching temperature after spinning at winding speed of /min
It was stretched at 200°C, a stretching ratio of 4.0, and a stretching speed of 130 m/min, and was crimped with a crimper and cut into 44 mm. The obtained polyester fiber staple had a fineness of 1.2 d, a tenacity of 7.2 g/d, an elongation of 18.5%, an initial tensile resistance value (according to JISL1073) of 60 g/d, and a heat shrinkage rate of 3.1% when dry heated at 160°C. Ta. This polyester fiber was spun under normal spinning conditions to obtain a spun yarn with a twist coefficient of 3.5 and a count of Ne60' ^S. After that, three of the spun yarns were aligned, and a normal combination was applied to increase the bulk density of the twisted yarn. A tension of 70 g, which is 2 to 3 times the twisting tension, was applied and the spun yarn was twisted in the opposite direction to the single yarn twisting with a twist coefficient of 4.7. Thereafter, the resulting twisted yarn was wound into cheese, and the yarn was dyed with a disperse dye at 130° C. for 30 minutes, and then heat-treated using a two-stage heat setter at various stretching temperatures and stretching ratios shown in the table. However, the length of the first stage heater is 0.6m, and the length of the second stage heater is 1.0m.
The winding speed of the yarn after heat treatment was 50 m/min in each case. However, the meanings of the symbols for sewing thread physical properties in the table are as follows. *1: Elongation under 1.5g/d load (%), *2: Torque after applying 1.5g/d load 20 times (times/10cm), *3: 160℃×
Dry heat shrinkage rate (%) for 30 minutes (according to JISL1073)

[Table] The stitch skipping evaluation of the sewability test in the table was performed using a cotton fabric with a fabric weight of 250 g/m ² at a speed of 4000 rpm using a double chainstitch sewing machine after applying the heat treatment shown in the table and applying 3% by weight of silicone oil. This was done by visual judgment of the occurrence of skipped stitches when 1000 m of two sheets were sewn in a straight line. ◎ is excellent, 〇 is good, △ is fair, and × is poor. Sewing threads having an elongation ST1.5 of 7.3% or less under a load of 1.5 g/d are Nos. 2 to 6, and these are the sewing threads of the present invention. As described above, the sewing thread of the present invention had a reduced occurrence of skipped stitches compared to the conventional sewing thread (No. 1) that was not heat-treated. Among these, Nos. 4 to 6 in particular have a low torque after 20 repetitions of a 1.5 g/d load, so there is almost no problem with skipped stitches, the seams are extremely clean, and there is almost no thread breakage during sewing. It was boring.

Claims (1)

[Claims] 1 Sewing thread made by twisting together multiple spun single yarns of polyester fibers in which 85 mol% or more of the repeating units are composed of ethylene terephthalate and the average fiber length is 35 to 51 mm, and when loaded at 1.5 g/d The elongation of the sewing thread is 7.3% or less, and the torque of the sewing thread after applying a load of 1.5 g/d 20 times is 6 times/10 cm.
The following is a polyester spun sewing thread characterized by a heat shrinkage rate of 4.5% or less under dry heat at 160°C.