JPS648733B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a raw thread for sewing thread, and more particularly to a raw thread for sewing thread that has excellent high-speed sewing properties. In recent years, sewing speeds using sewing machines have been increasing rapidly, and there has been a demand for sewing threads that have physical properties that can withstand this speed. However, during high-speed sewing where the reciprocating speed of the needle reaches 4000 times/min, the temperature of the needle rises to nearly 250°C, so when conventional polyester thread is used as sewing thread, a precursor phenomenon of melting occurs in the polyester filament. There was a problem in that this caused a significant decrease in strength. In order to solve this problem, measures such as cooling the sewing machine needle and improving the finishing oil for the sewing machine thread have been considered, but no satisfactory results have been obtained yet. The inventors of the present invention have made extensive studies to solve these problems, and as a result, have found that the precursor melting phenomenon of the polyester filament can be suppressed by blending polyamide, and have arrived at the present invention. That is, the present invention provides a filament yarn consisting of a melt mixture of a polyester having ester terephthalate as a main repeating unit and a melt-spun polyamide, in which the polyamide is present in the filament in an amount of 0.25 to 25% by weight; The elongation of the yarn
35% or less, shrinkage rate after boiling water treatment is 3% or less,
This raw thread for sewing thread has an excellent strength retention rate, characterized by having a strength retention rate (I) of at least 30% when subjected to dry heat constant length heat treatment at 250°C for 60 minutes. However, the strength retention rate (I) is defined as below. I=ST _A /ST _O ×100 (%) ST _A : Yarn strength after constant dry heat treatment at 250° C. for 60 minutes ST _O : Yarn strength before heat treatment The present invention will be further explained. The raw thread for sewing thread of the present invention is (i) a filament yarn made of a molten mixture of polyester and 0.25 to 25% by weight of polyamide, and (ii) has an elongation of 35% or less and does not shrink when treated with boiling water. (iii) The strength retention rate (I) of conventional polyester yarn is at most 10% when heat-treated with dry heat constant length for 60 minutes in an oven set at 250℃. On the other hand, the polyester yarn of the present invention shows a value of at least 30%, usually 50 to 70%. It is not yet clear why the polyester yarn of the present invention has much better heat deterioration resistance than conventional polyester yarn, but in the case of conventional polyester yarn, when the temperature becomes high and approaches the melting point of polyester, The thermal movement of the polyester molecular chains in the crystalline part intensifies, causing melting of the microcrystalline part, partial melting and recrystallization of the quasi-crystalline part, and the fiber structure, which is characterized by being extremely strong in the uniaxial direction, collapses. , the strength is significantly reduced. On the other hand, in polyester filaments blended with polyamide, when subjected to severe heat, the polyamide molecular chains that melt before the polyester penetrate into the amorphous part of the polyester layer and become entangled with the polyester molecular chains in this amorphous part. Since the thermal motion of the polyester molecular chains is restricted, it is presumed that the structural change due to heat treatment is smaller than that of conventional polyester filaments. The polyester referred to in the present invention is mainly polyethylene terephthalate, but it may be copolymerized with the addition of 15 mol% or less of a third component, such as various dicarboxylic acids, dioxy compounds, etc. It may also contain known additives. However, the intrinsic viscosity (value determined from the viscosity of an o-chlorophenol solution at 35°C) of these polyesters is generally preferably from 0.50 to 0.95. If the intrinsic viscosity is less than 0.50, the strength required for a sewing thread tends to be insufficient, while if it exceeds 0.95, the spinning condition tends to deteriorate. On the other hand, the polyamide to be blended with the polyester may be any polyamide that can be melt-spun, and may be a blend of several types of polyamides with different chemical structures, or a copolymer with a third component. Among them, nylon 6 or nylon 66 is preferred. In the present invention, these polyamides must be dispersed in the filament in an amount of 0.25 to 25% by weight, preferably 0.5 to 5% by weight. here,
If it is less than 0.25%, there will be almost no improvement in heat deterioration resistance, and if it exceeds 25%, the melt spinnability will deteriorate rapidly and the strength and elongation of the resulting yarn will be abnormally low, so-called It becomes what is called a weak thread and cannot be used as sewing thread. Further, such filament yarns must have an elongation of 35% or less and a shrinkage rate of 3% or less when treated with boiling water (100° C., 30 minutes). here,
If the elongation exceeds 35% or the shrinkage rate exceeds 3%, the internal structure of the filament will be relaxed during processing steps such as twisting and setting into sewing thread, resulting in a loss of 5% to 10% of the sewing thread. The modulus at % elongation decreases, resulting in deterioration of puckering properties. When spinning such raw thread for sewing thread, blending of polyester and polyamide can be carried out by any method. For example, polyamide may be mixed at the end of the polyester polymerization process, or polyester and polyamide may be individually polymerized and formed into chips or flakes, then mixed, melted, cooled, and chipped again. Furthermore, it can also be achieved by mixing polyester and polyamide in the form of chips and then immediately melt-spinning the mixture. However, in this case, it is preferable to use a screw type extruder in order to increase the degree of kneading of both polymers. Both polymers blended in this way are spun using normal equipment, and further stretched to an elongation of 35% or less, and a shrinkage rate of 3% or less when treated with boiling water (100°C, 30 minutes). It is necessary to set the heat to . The polyester yarn of the present invention can be made into a sewing thread as a flat yarn, a woolly textured yarn or a staple fiber through ordinary processes. At this time, it is possible to use the polyester yarn of the present invention in combination with other sewing thread threads other than the present invention by means such as blending or doubling. full amount
It is preferable to use 30% by weight or more. Since the sewing thread using the polyester thread of the present invention described above has excellent heat deterioration resistance, high-speed sewing is possible without cooling the sewing machine needle or using special oil as in conventional sewing machines. . The present invention will be explained below with reference to Examples. Example 1 Polyethylene terephthalate with an intrinsic viscosity of 0.64
97.5% by weight and 2.5% by weight of nylon 6 with an intrinsic viscosity of 1.0 were mixed in the form of chips, dried at 160°C for 4 hours, and then melted and kneaded in a 25mm diameter screw type melt extruder to create a spinneret with a 0.35mm diameter discharge hole. The material was then discharged, cooled and solidified using a normal cooling air stream, treated with an oil agent, and then wound up at a speed of 1000 m/min. Next, this spun yarn was drawn 3.9 times at a preheating temperature of 85° C., and then heat-treated for constant length at 210° C. to obtain a drawn yarn of 70 de/24 fils. This drawn yarn was heated for a fixed length of 60 minutes in a hot air circulation oven set at 250°C. Strength and elongation of drawn yarn,
The following table shows the shrinkage rate, the strength after heating, and the strength retention rate during the heating.

[Table] The drawn yarn (polyester yarn) of the present invention is
It shows excellent strength retention even when heat treated near the melting point, such as 250°C. This drawn yarn (polyester yarn) was first-twisted, three yarns were combined, then top-twisted, and then dyed at 130°C to obtain a sewing thread. Using this sewing thread, polyester 65
When four layers of 35% rayon plain fabric (weighing 150 g/cm ² ) were sewn together at a sewing speed of 4500 rpm, the sewing thread did not break within 1 minute. On the other hand, for comparison, the strength and elongation of a polyester yarn obtained by spinning and drawing heat treatment using polyethylene terephthalate that does not contain nylon 6 under the same conditions as in the above example and constant length at 250°C for 60 minutes are shown. The strength and strength retention rate when heated are shown in the table below.

[Table] A sewing test was conducted in the same manner as in Example 1 above using sewing threads made by twisting three of these drawn threads (polyester threads) and dyeing them at 130°C. The thread broke. Example 2 A drawn yarn of 70 de/24 fils was obtained by spinning yarn in the same manner as in Example 1, except that polyethylene terephthalate with an intrinsic viscosity of 0.64 and nylon 6 with an intrinsic viscosity of 1.0 were mixed in chip form at various ratios as shown in the table below. Ta. This drawn yarn was heated for 60 minutes in a hot air circulation oven set at 250°C. The strength retention rate upon heating is also shown in the following table.

[Table] No.1 and No.7 are polyester or nylon 6
This is a case of a single yarn, and the strength retention rate of each obtained drawn yarn is extremely low. Also, No. 6 has too little blending ratio of nylon 6.
No. 2 shows almost no improvement in the strength retention of the drawn yarn. On the other hand, No. 6, in which the blending ratio of nylon 6 is too high, has an effect of improving the strength retention of the obtained drawn yarn, but the spinning condition is poor. On the other hand, in Nos. 3 to 5, the spinnability was good and the effect of improving the strength retention of the drawn yarn was sufficiently large. Example 3 Polyethylene terephthalate with intrinsic viscosity 0.64
Thread spinning was carried out in the same manner as in Example 1, except that 97.5% by weight and 2.5% by weight of nylon 66 having an intrinsic viscosity of 1.12 were mixed to obtain a drawn yarn of 70 de/24 fils. This drawn yarn
When heated for 60 minutes in a hot air circulation oven set at 250°C, the strength retention rate was 42%, indicating an improvement in the strength retention rate of the drawn yarn.

Claims (1)

[Scope of Claims] 1. A filament yarn made of a melt mixture of a polyester having ethylene terephthalate as a main repeating unit and a melt-spun polyamide, wherein the filament contains 0.25 to 25% of the polyamide.
% by weight, on the other hand, the elongation of the yarn is 35% or less, the shrinkage rate by boiling water treatment is 3% or less, and at 250 ° C.
Strength retention rate (I) when subjected to constant dry heat treatment for 60 minutes
This raw yarn for sewing thread has an excellent strength retention rate of at least 30%. However, the strength retention rate (I) is defined as below. I = ST _A / ST _O × 100 (%) ST _A : Yarn strength after constant dry heat treatment at 250°C for 60 minutes ST _O : Yarn strength before heat treatment 2 The intrinsic viscosity of the polyester is 0.50 to 0.95. A raw thread for sewing thread according to claim 1. 3. The raw thread for sewing thread according to claim 1, wherein the amount of the polyamide added is 0.5 to 5% by weight. 4. The raw yarn for sewing thread according to claim 1 or 3, wherein the polyamide is nylon 6. 5. The raw yarn for sewing thread according to claim 1 or 3, wherein the polyamide is nylon 66.