JP2007231473A - Blended spun yarn and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blended spun yarn giving a cloth with good swell and touch feeling and without uneven dyeing on dyeing, and a method for producing the same. <P>SOLUTION: This blended spun yarn obtained by spinning a high shrinkage multifilament yarn A and a low shrinkage multifilament yarn B together is provided, wherein the high shrinkage multifilament yarn A is substantially composed of a synthetic fiber filament obtained by mainly using a thermoplastic polymer as a raw material, having a dry heat shrinkage of 10-45% at 180°C, excellent in stability over time of the dry heat shrinkage, and having a dry shrinkage changing rate [Kd(%)] satisfying formula (1): 0.0≤Kd(%)<5.0, and also the multifilament yarn B is composed of a synthetic fiber filament having a dry heat shrinkage and/or boiling water shrinkage substantially smaller than those of the high shrinkage multifilament yarn A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mixed fiber composite yarn and a method for producing the same. More specifically, a new high-shrinkage multifilament yarn and a low-shrinkage multifilament yarn that have small changes in heat shrinkage with time, good process stability and processability during blending, and excellent productivity. The present invention relates to a blended composite yarn that provides a fabric having a good swell and feel, and a method for industrially producing the blended composite yarn.

  In the synthetic fiber multifilament yarn represented by the polyester filament, when the multifilament yarn is used for clothing, various improvements have been made to improve the hard texture unique to the synthetic fiber. As one representative method, a method is known in which a plurality of fibers having different shrinkage rates are combined to form a mixed fiber composite yarn. This composite yarn is a low-shrinkable fiber with a low thermal shrinkage rate that appears on the surface of the yarn by subsequent heat treatment and greatly affects the texture and texture, or a self-stretched fiber that stretches itself by heat (hereinafter referred to as “low-shrinkage yarn”). And a yarn made of a high shrinkage fiber having a larger thermal shrinkage rate than the low shrinkage yarn (hereinafter referred to as “high shrinkage yarn”), and mainly high shrinkage by heating after forming the fabric. The yarn is heat-shrinked so that the fabric is swelled to give a good texture (for example, see Patent Document 1 and Patent Document 2 below).

  As a low shrinkage yarn constituting such a composite yarn, excellent properties such as texture, designability, dyeability, etc. are required. The appearance has been improved. On the other hand, as a high shrinkage yarn, there is a demand for a more versatile and economical yarn for the purpose of facilitating the combination with various types of low shrinkage yarns other than improving the drape of the fabric such as the elasticity and stiffness of the fabric. Has been. However, in high-shrinkage yarns, achieving both higher heat shrinkage and controllability of heat shrinkage is a required characteristic that has never been realized in the past, and has been regarded as a technically difficult task. .

  So far, in the production of high shrinkage yarns made from general-purpose polymer such as polyester, in order to increase the heat shrinkage rate, the method of adjusting the heat setting temperature to a low level and to obtain the desired heat shrinkage rate Methods such as incomplete stretching have been employed. However, the quality of the high shrinkage yarn obtained by lowering the heat setting temperature or incomplete drawing becomes more unstable, and it is easily affected by external factors after spinning, resulting in poor stability over time. For this reason, in order to obtain a good composite yarn with stable quality, it must be combined with a low shrink yarn immediately after the production of a high shrink yarn and heat set, and the high shrink yarn in the original yarn state for a certain period or more. It was not possible to select a storage method that could be stored or transported drastically.

  In other words, the conventional high shrinkage yarn has a shrinkage rate that changes with the passage of time and the shrinkage rate is not stable over time, so the time from yarn production to compounding should be shortened as much as possible, or from yarn production to compounding. It must always be kept at a certain time, and the storage time must be strictly managed. Since the management of the latter storage time is complicated, usually, a method is adopted in which a high-shrinkage yarn is quickly combined after the yarn production for the purpose of suppressing the defect rate in terms of quality control of the composite yarn.

  However, in such a method, there is a problem that a high shrinkage yarn has to be manufactured every time it is combined, and this is a great limitation in production. As described above, the high shrinkage yarn cannot be prepared in advance, and it is necessary to produce the yarn every time the composite yarn is manufactured, which is a fatal defect particularly for the high shrinkage yarn that requires economic efficiency.

  Further, conventionally, it has been necessary to make sure that the high shrinkage yarn side is heat-set when compositing. When heat setting is not performed at all from the production of a high shrinkage yarn, it is necessary to perform heat setting after forming the fabric. In fact, such a fabric can be manufactured stably only in a small amount. It was impossible except for production.

  As described above, the high shrinkage yarn has various problems in terms of the quality of the fabric using the composite yarn due to the variation in shrinkage due to its property. In other words, if high-shrinkage yarns with different yarn-making timings and variations in shrinkage rate are used and the composite yarns are manufactured under the same conditions, shrinkage spots will occur in the heat set after the formation of the subsequent fabric, and also due to dyeing. There was a problem that spotted spots (step spots) were observed and the quality of the product was lowered. Also, in order to avoid this problem, a composite yarn using a high-shrinkage yarn that has been heat-set so that the shrinkage rate is a certain value or less can not achieve the satisfactory fabric swell and texture. could not.

JP-A-1-250425 JP-A-7-207540

  The first object of the present invention is to use a synthetic fiber multifilament yarn having excellent shrinkage over time despite having a high shrinkage, in view of the above-mentioned problems of the prior art. A second object of the present invention is to provide a method for producing such a mixed fiber composite yarn.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by a novel mixed fiber composite yarn satisfying the following requirements, and have reached the present invention. .

  That is, the mixed fiber composite yarn of the present invention is a mixed fiber composite yarn obtained by mixing a high shrinkage multifilament yarn A and a low shrinkage multifilament yarn B, and the high shrinkage multifilament yarn A is a thermoplastic resin. The main raw material is a polymer, the dry heat shrinkage rate is 10 to 45% (preferably 20 to 40%), the dry heat shrinkage rate is excellent over time, and the change rate [Kd (%)] of the dry heat shrinkage rate is high. A synthetic fiber filament that satisfies the following mathematical formula (1) is substantially synthetic, and the low shrinkage multifilament yarn B is substantially smaller in dry heat shrinkage and / or boiling water shrinkage than the high shrinkage multifilament yarn A. It consists of fiber filaments.

  Here, Kd (%) represents the rate of change of the dry heat shrinkage rate (HDS) over time, and is a numerical value that can be viewed as an index of the heat shrinkage rate over time of the yarn. The Kd (%) indicates the dry heat shrinkage rate before and after the yarn for which the change rate of the dry heat shrinkage rate is left for 120 hours in the standard temperature and humidity state 2 of JIS Z-8703, respectively. Assuming that the previous dry heat shrinkage rate is HDSb and the dry heat shrinkage rate after standing is HDSa, the change rate [Kd (%)] of the dry heat shrinkage rate over 120 hours is calculated according to the following formula.

  The “dry heat shrinkage ratio” is obtained as follows. That is, the original length (L0) of a sample loaded with 110 mg per dtex is measured, and then left standing in an atmosphere of 180 ° C. for 30 minutes with no load. After the treatment, a load of 110 mg per dtex is again applied to the sample, the length (L1) after the treatment is measured, and the dry heat shrinkage is calculated by the following formula.

  Moreover, it is preferable that the high shrinkage filament yarn A constituting the mixed fiber composite yarn of the present invention also has a rate of change [Kw (%)] over 120 hours with respect to the boiling water shrinkage rate that satisfies the following formula.

  Here, Kw (%) represents the rate of change of boiling water shrinkage (BWS) with time, and is a numerical value that can be viewed as an indicator of the boiling water shrinkage of the yarn over time. This Kw (%) is the boiling water shrinkage ratio before and after leaving the yarn for which the boiling water shrinkage change is determined for 120 hours in the standard temperature and humidity state 2 of JIS Z-8703, respectively. Is BWSb, and the boiling water shrinkage after standing is BWSa. Specifically, 10 yarns of the yarn to be measured were collected, of which 5 were measured for initial boiling water shrinkage to be BWSa, and for the remaining 5 were subjected to aging treatment, the boiling water shrinkage was measured for BWSb. And For both BWSa and BWSb before and after the lapse of time, the average rate of each five is used, and the rate of change over 120 hours is calculated by the following formula.

  The “boiling water shrinkage ratio” is obtained as follows. That is, the original length (L0) of a sample loaded with 110 mg per dtex is measured, and then immersed in boiling water with no load for 15 minutes. After immersion in boiling water, the sample is again subjected to a load of 110 mg per dtex, the length after treatment (L2) is measured, and the boiling water shrinkage is calculated by the following equation.

  In such a mixed fiber composite yarn, the high shrinkage multifilament yarn A is a filament mainly composed of a polyester polymer obtained by copolymerizing isophthalic acid, dimethylisophthalic acid or both as a third component, and the boiling water shrinkage change [Kw %] Is preferably made of a polyester filament that simultaneously satisfies the above formulas (1) and (2).

  On the other hand, the low-shrinkage multifilament yarn B is preferably a polyethylene terephthalate multifilament that has been subjected to drawing heat treatment and has a boiling water shrinkage of 5% or more smaller than that of the high-shrinkage multifilament yarn A described above.

  The mixed fiber composite yarn of the present invention is one in which the constituent filaments (single fibers) of both the multifilament yarns are randomly entangled into a single yarn. This yarn may be twisted as necessary, or may be twisted in two or more.

  Such a mixed fiber composite yarn is a high-shrinkage multifilament yarn A used as a main raw material for producing a composite yarn obtained by mixing a high-shrinkage multifilament yarn A and a low-shrinkage multifilament yarn B. The dry heat shrinkage rate is 10 to 45%, and the change rate [Kd (%)] of the dry heat shrinkage rate and the change rate [Kw%] of the boiling water shrinkage rate are expressed by the following mathematical formulas (1) and (2). :

を同時に満足する合成繊維マルチフィラメントからなる高収縮マルチフィラメント糸Ａを使用し、これと、乾熱収縮率及び／又は沸水収縮率が高収縮マルチフィラメント糸Ａよりも実質的に小さい低収縮マルチフィラメント糸Ｂとのフィラメント同士を、空気攪乱流にて交絡させた後、１本の糸条として引き取ることを特徴とする方法により製造することが出来る。

And a high shrinkage multifilament yarn A comprising a synthetic fiber multifilament that simultaneously satisfies the above, and a low shrinkage multifilament having a dry heat shrinkage and / or boiling water shrinkage substantially lower than that of the high shrinkage multifilament yarn A The filaments with the yarn B can be entangled by air turbulent flow and then taken up as a single yarn, and can be produced by a method characterized by the following.

In this method, polyester multifilament undrawn yarn or partially oriented yarn (POY) is used as the high shrinkage multifilament yarn A at a magnification such that the birefringence (Δn) after drawing is 0.06 to 0.15. It is preferable to use cold-drawn multifilament yarns. Further, as the low shrinkage multifilament yarn B, it is preferable to use an oriented crystallized polyester multifilament yarn having a boiling water shrinkage rate of 5% or more smaller than that of the high shrinkage multifilament yarn A.
In the method of the present invention, it is preferable not to perform heat setting in the mixed fiber compounding step.

  The mixed fiber composite yarn of the present invention has a very small change in the heat shrinkage rate with time despite the high heat shrinkage rate of the high shrinkage yarn constituting it. Therefore, regardless of the production timing of the high shrinkage yarn, it can be combined with the low shrinkage yarn to produce a mixed fiber composite yarn having a stable quality.

  In particular, an undrawn yarn made of polyester copolymerized with isophthalic acid or a high shrink yarn obtained by cold drawing a partially oriented yarn (POY) has a special effect that the shrinkage can be arbitrarily selected depending on the drawing conditions. Therefore, when producing a composite yarn from this high shrinkage yarn and a general filament yarn that has been heat-set and has a low heat shrinkage rate, it is possible to eliminate the variation in quality over time as in the past, and to feel the muscular feeling due to dyeing. There is no swell and it can be set as the fabric which has a good texture and quality with a bulge.

  As is clear from the above description, the mixed fiber composite yarn of the present invention uses the above-described specific heat-shrinkable synthetic fiber multifilament yarn A (hereinafter referred to as “high-shrinkage yarn A”) as the high-shrinkage yarn. This is the biggest feature.

  The high shrinkage yarn A is a multifilament whose main raw material is a thermoplastic polymer, and has a dry heat shrinkage rate at 180 ° C. of 10 to 45%, preferably 20 to 40%, and a dry heat shrinkage rate. The stability over time is excellent, and the rate of change in dry heat shrinkage [Kd (%)] satisfies the above formula (1). When the rate of change in dry heat shrinkage [Kd (%)] is outside the above range, when using a yarn having a different yarn production time as a high shrinkage yarn, streaks occur at the stage of dyeing the composite yarn into a fabric. The object of the present invention cannot be achieved.

  The high shrinkage yarn A preferably has a boiling water shrinkage of 120% over time [Kw (%)] satisfying the above formula (2) in order to obtain a good composite yarn. Further, the boiling water shrinkage of the high shrink yarn A is preferably in the range of 10 to 45%, particularly 20 to 40%.

  As such a high shrinkage yarn A, the basic structural unit constituting the polymer is composed of ethylene terephthalate, and a low crystallinity copolymer containing 1 to 10 mol% of ethylene isophthalate and / or ethylene methyl isophthalate units in total. Those made of polyester are particularly suitable.

  The number of filaments and the fineness of the high shrinkage yarn A are appropriately selected according to the number of filaments and the fineness of the low shrinkage yarn B combined therewith. In general, the number of filaments of the high shrinkage yarn A is 10 to 50, particularly 15 to 30 is appropriate, and the total fineness is about 30 to 150 dtex, particularly 50 to 100 dtex. The single yarn fineness of the high shrink yarn A is preferably larger than that of the low shrink yarn B, and generally 1 to 5 dtex, particularly 3 to 4 tex is preferable.

  On the other hand, the constituent polymer of the low shrinkage yarn B can be arbitrarily selected, but is usually preferably a polyethylene terephthalate polyester. The number of filaments of the low shrinkage yarn B is 50 to 200, particularly 70 to 150, and the total fineness is 30 to 150 dtex, particularly 50 to 120 dtex. The single yarn fineness of the low shrinkage yarn B is preferably 0.1 to 1.5 dtex in consideration of the texture of the product.

  These high shrink yarn A and / or low shrink yarn B may contain stabilizers, matting agents, colorants, fillers, and other modifiers as necessary. Further, as long as the high shrinkage yarn A and / or the low shrinkage yarn B satisfy the above-mentioned conditions, a plurality of types of yarns may be used in combination. Further, the low shrinkage yarn may be composed of an easily dyeable polymer. The fiber cross-sectional shape of these high-shrinkage yarns A and / or low-shrinkage yarns B is not limited to a normal circular (round) cross-section, and is an irregular cross-section such as an ellipse, flat, tri-loval, multi-loval, hollow, etc. There is no problem.

Hereinafter, although the manufacturing method of the mixed fiber composite yarn which concerns on this invention is demonstrated, first, the suitable manufacturing method of the above high shrinkage yarn A is explained in full detail.
In the present invention, the polymer used as the raw material for the high shrinkage yarn A and the method for fiberizing the polymer are not particularly limited, but when the main purpose is to form a fabric for clothing by weaving or knitting, It is preferable to use a general-purpose thermoplastic polymer such as polyester. Among them, the main repeating unit constituting the polymer is ethylene terephthalate, and as the third component, isophthalic acid or dimethylisophthalic acid or both of them is 1 to the total aromatic dicarboxylic acid component constituting the polyester. Copolyesters copolymerized in a proportion of -10 mol% are optimal.

  This is melt-spun by a known method to obtain a polyester multifilament yarn, which is then cold-drawn 1.3 to 2.0 times, so that the birefringence (Δn) of the drawn filament is 0.00. It is optimal to use a yarn of 06 to 0.15.

  At this time, the polyester multifilament yarn before drawing is an undrawn yarn or partially oriented yarn (POY) having a birefringence (Δn) of 0.02 to 0.05 melt-spun at a spinning speed of 2500 to 3500 m / min. Is preferred.

  In the drawing process, it is necessary to perform cold drawing without applying heat to the yarn. Heating here is not preferable because the shrinkage after stretching decreases.

  As the low shrinkage multifilament yarn B (hereinafter referred to as the low shrinkage yarn B) combined with the high shrinkage yarn A, the dry heat shrinkage rate and / or boiling water shrinkage rate is substantially smaller than that of the high shrinkage yarn A. Yarn is used. For example, a general polyester filament yarn is heat set so that the dry heat shrinkage rate and the boiling water shrinkage rate are about 10% or less so that the heat shrinkage rate behavior is stabilized during use. Therefore, a general polyester filament yarn can be used as the low shrinkage yarn B and combined with the high shrinkage yarn A to obtain a mixed fiber composite yarn. Further, as the low shrinkage yarn B, a self-elongating yarn as described in Patent Document 1 may be used. In order to obtain a good mixed fiber composite yarn, the low heat shrinkage B has a dry heat shrinkage and a boiling water shrinkage of 5% or more smaller than that of the high shrinkage yarn A. In particular, the dry heat shrinkage is 5 to 35%. A low shrinkage yarn B having a boiling water shrinkage of 5 to 20% is particularly preferable.

  These high shrink yarn A and / or low shrink yarn B may contain a stabilizer, a matting agent, a colorant, and other modifiers as necessary. Further, as long as the high shrinkage yarn A and / or the low shrinkage yarn B satisfy the above-mentioned conditions, a plurality of types of yarns may be used in combination.

  In the production of the composite yarn according to the present invention, for example, using a device as shown in FIG. Then, a method is adopted in which the constituent filaments (single fibers) are randomly entangled and then taken up as a single composite yarn. In the mixed fiber compounding step, it is preferable to process each yarn with 1 to 3% overfeed. Moreover, it is preferable not to carry out heat setting in this mixed fiber compounding step. When heat is set here, the shrinkage rate is significantly reduced.

  The mixed fiber composite yarn thus obtained is made into a fabric such as a woven fabric or a knitted fabric, and then heat is applied in processes such as refining, dyeing and finishing, so that the high shrink yarn A in the composite yarn contracts to become a core yarn. The low shrinkage yarn B becomes a sheath yarn to form a swelled fabric having a good texture. That is, the low shrinkage yarn B is formed by weaving and knitting a composite yarn into a fabric, and when the fabric is heated by refining, dyeing, or other processes, its constituent filaments come out on the surface of the composite yarn and are so-called. It becomes a sheath thread. For this reason, you may make it give a special texture by making the constituent fiber of the low shrinkage yarn B into an irregular cross-section fiber, or making it a thin fiber. Moreover, you may comprise all or one part of the low shrinkage yarn B with the filament which consists of an easily dyeable polymer.

  After this mixed fiber composite yarn is made into a fabric such as woven fabric or knitted fabric, heat is applied in processes such as refining, dyeing, and finishing, so that the high shrinkage filament in the composite yarn contracts to become a core yarn, and low The shrink filament becomes a sheath yarn to form a swelled fabric with good texture.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the scope of the present invention is not limited by these.
[Examples 1-2]
<Manufacture of high shrinkage yarn>
The polyester polymer used for the high shrinkage yarn is made of polyethylene terephthalate copolymerized with 2.6 mol% of isophthalic acid (intrichlorophenol, intrinsic viscosity 0.61 at 35 ° C.) by a conventional method to form a chip. Prepared.

  The obtained chip was dried by a conventional method, and extruded at a melting temperature of 285 ° C. from a spinneret having 15 round cross-section discharge holes and a spinneret having 30 round cross-section discharge holes, Both are taken up at a termination speed of 3000 m / min, and are respectively 50 dtex / 15 fil, birefringence (Δn) 0.031 multifilament yarn and 100 dtex / 30 fil, birefringence (Δn) 0.033 multifilament yarn. I picked it up. Each multifilament yarn that has been chopped off is drawn by cold drawing with a draw machine set at a lower magnification than the breaking elongation of the original yarn, that is, the former is 1.35 times and the latter is 1.33 times. A highly shrinkable filament yarn (filament A) was obtained. The birefringence (Δn) of each filament yarn was 0.11 and 0.10. The heat shrink characteristics of these yarns are shown in Table 1 in the Filament A column of Examples 1 and 2.

<Manufacture of composite yarn>
On the other hand, two kinds of fully oriented polyester filament yarns (filaments B) having a fineness of 56 dtex / 72 fil and a fineness of 112 dtex / 144 fil after heat treatment were prepared (these heat shrink characteristics are also shown in Example 1, Table 1). (Shown in the filament B column of Example 2) and the above-mentioned high-shrinkage filament yarn A were mixed together and mixed to produce a composite yarn. As shown in Table 1, the blending method is carried out using a device shown in FIG. 1 by a conventional method using a blender equipped with an air entanglement device and adjusting the number of entangled yarns to the same number. A mixed yarn was obtained. That is, in the apparatus of FIG. 1, A is a core yarn (high shrinkage yarn), B is a sheath yarn (fully oriented polyester yarn in this embodiment), and both yarns supplied from the raw yarn supply roller 1 are After passing through the preheating roller 2, it was mixed with the compressed air entanglement device 3, taken up by the take-up roller 4, and wound up as a composite yarn 6 of the product. The overfeed rate between the raw yarn supply roller 1 and the take-up roller 4 was 2%. However, in Examples 1 and 2 and Comparative Examples 1 and 2, the heater was not used, and the set heater 5 was used only in Comparative Example 3.

<Production and Evaluation of Fabric>
At this time, for the purpose of subsequent evaluation of streaks, the yarn was separately produced by the same method and conditions based on the obtained mixed fiber composite yarn, and the time elapsed from the time of cold drawing to the fiber mixing was extended by 5 days. A mixed fiber composite yarn using the shrink yarn A (filament A) and the low shrink yarn (filament B) was prepared and used for forming a fabric by mixing with the above-mentioned standard mixed fiber composite yarn.

  By using a high shrinkage yarn (filament A) having a different number of days after the cold drawing to obtain a fabric by weaving into a plain weave by a conventional method, followed by boil-off, presetting, dyeing and final setting according to a conventional method. The intended fabric was obtained. In Example 1, the warp for warp was warped by twin yarn twisting, and in Example 2, the warp was used for warp by single yarn twist.

  The obtained fabric was subjected to a sensory test on the texture such as swelling. After that, quality tests such as fluff and dyeing were performed, and a comprehensive evaluation was performed along with process passability. The results shown in the column of Example 1 and Example 2 in Table 1 were obtained from the measurement of the properties of the respective raw yarns and the sensory test after the product became a fabric.

  The fabrics obtained in this example all have good processability for polymerization, yarn production, weaving, and dyeing, have no streaking due to the intended dyeing, and have a good texture and quality along with appropriate swelling. It was a fabric.

[Comparative Examples 1-2]
Except that polyethylene terephthalate not copolymerized with isophthalic acid was used as a polyester polymer as a raw material for the high shrinkage yarn (filament A), fabric formation was carried out through the same steps as in Examples 1 and 2. The results as shown in column 1 of Comparative Example 1 and Comparative Example 2 were obtained. That is, although the swelling of the fabric was good, the streaks were conspicuous and there was no value as a product.

[Comparative Example 3]
In the production of a high shrinkage yarn (filament A), instead of cold drawing, drawing was performed with a heat set of 180 ° C., and the other fabrics were formed through the same steps as in Comparative Example 2, and Comparative Examples in Table 1 The results shown in column 3 were obtained. That is, there was no swelling of the fabric and it was not worth the product.

The schematic side view which shows an example of the apparatus which manufactures a mixed fiber composite yarn using the multifilament yarn of this invention.

Explanation of symbols

A: High shrinkage yarn (core yarn)
B: Low shrinkage yarn (sheath yarn)
1: Raw yarn supply roller 2: Preheating roller 3: Compressed air entanglement device 4: Take-off roller 5: Set heater (only Comparative Example 3 is used)
6: Product composite yarn

Claims (6)

A composite yarn obtained by blending a high-shrinkage multifilament yarn A and a low-shrinkage multifilament yarn B, wherein the high-shrinkage multifilament yarn A is mainly made of a thermoplastic polymer and has a dry heat shrinkage of 10 to 10%. 45% and the rate of change in dry heat shrinkage [Kd (%)] is the following formula (1):
0.0 ≦ Kd (%) <5.0 (1)
[Kd (%) in the above formula (1) is the change in the dry heat shrinkage before and after the target synthetic fiber multifilament yarn was left for 120 hours in the standard temperature and humidity state 2 of JIS Z-8703. Represents a rate. ]
And the low shrinkage multifilament yarn B is composed of a synthetic fiber filament yarn having substantially lower dry heat shrinkage and / or boiling water shrinkage than the high shrinkage multifilament yarn A. Mixed fiber composite yarn characterized by this. The high shrinkage multifilament yarn A has a change rate [Kw%] in boiling water shrinkage of the following formula (2):
0.0 ≦ Kw (%) <5.0 (2)
[Kw (%) in the above formula (2) is the rate of change in the boiling water shrinkage before and after the target synthetic fiber multifilament yarn was allowed to stand for 120 hours in the standard temperature and humidity state 2 of JIS Z-8703. Represents. ]
The mixed fiber composite yarn according to claim 1, comprising a multifilament yarn satisfying   The thermoplastic polymer constituting the high-shrinkage multifilament yarn A is a polyester having ethylene terephthalate as a main repeating unit, and, as the third component, isophthalic acid or dimethylisophthalic acid or both are used as the total dicarboxylic acid of the polyester. The mixed fiber composite yarn according to claim 1 or 2, comprising a copolyester copolymerized in a range of 1 to 10 mol% of the component. In producing a composite yarn obtained by blending high-shrinkage multifilament yarn A and low-shrinkage multifilament yarn B, the high-shrinkage multifilament yarn A is mainly composed of a thermoplastic polymer and has a dry heat shrinkage of 10 The change rate [Kd (%)] of the dry heat shrinkage rate and the change rate [Kw%] of the boiling water shrinkage rate are ˜45% and the following mathematical formulas (1) and (2):
0.0 ≦ Kd (%) <5.0 (1)
0.0 ≦ Kw (%) <5.0 (2)
[However, Kd (%) and Kw (%) are as defined above. ]
And a high shrinkage multifilament yarn A comprising a synthetic fiber multifilament that simultaneously satisfies the above, and a low shrinkage multifilament having a dry heat shrinkage and / or boiling water shrinkage substantially lower than that of the high shrinkage multifilament yarn A A method for producing a mixed fiber composite yarn, wherein filaments with the yarn B are entangled with each other by an air turbulent flow and then taken up as a single yarn.   5. The polyester multifilament yarn that is cold-drawn at a magnification such that the birefringence (Δn) after drawing is 0.06 to 0.15 is used as the high-shrinkage multifilament yarn A. A manufacturing method for mixed fiber composite yarns.   The method for producing a mixed fiber composite yarn according to claim 4 or 5, wherein heat setting is not performed in the composite fiber compounding step.

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