HK1246374B - Hygroscopic core-sheath conjugate yarn and production method therefor - Google Patents

Description

Hygroscopic core-sheath composite yarn and method for producing the same

Technical Field

The present invention relates to a hygroscopic core-sheath composite yarn having excellent hand feel.

Background Art

Synthetic fibers made of thermoplastic resins such as polyamide and polyester are widely used in clothing and industrial applications due to their excellent strength, chemical resistance, heat resistance, and the like.

Polyamide fibers, in particular, offer unique properties such as softness, high tensile strength, color development when dyed, and high heat resistance, as well as excellent hygroscopicity, making them widely used in underwear, sportswear, and other applications. However, compared to natural fibers such as cotton, polyamide fibers lack sufficient hygroscopicity and exhibit issues such as airtightness and stickiness, resulting in inferior comfort compared to natural fibers. This presents a problem.

Against this backdrop, synthetic fibers that exhibit excellent moisture absorption and release properties to prevent airtightness and stickiness, and have comfort properties close to those of natural fibers, are desired primarily for underwear and sportswear applications.

Therefore, the method of adding hydrophilic compounds to polyamide fibers is generally the most studied method. For example, Patent Document 1 proposes a method of improving moisture absorption performance by blending polyvinyl pyrrolidone, a hydrophilic polymer, with polyamide and spinning the blended fibers.

On the other hand, active research has been conducted to achieve both hygroscopic performance and mechanical properties by making the fiber structure into a core-sheath structure, with a core made of a highly hygroscopic thermoplastic resin and a sheath made of a thermoplastic resin with excellent mechanical properties.

For example, Patent Document 2 describes a core-sheath composite fiber consisting of a core and a sheath, wherein the core is not exposed on the fiber surface. The core is a polyether block amide copolymer having a 6-nylon hard segment and a 6-nylon resin as a sheath. The area ratio of the core to the sheath in the fiber cross section is 3/1 to 1/5.

Furthermore, Patent Document 3 describes a core-sheath type composite fiber having excellent hygroscopicity, wherein a polyetheresteramide is arranged in the core portion and a polyamide is arranged in the sheath portion, and exhibits high hygroscopicity. The core-sheath type composite fiber is characterized in that it is a core-sheath type composite fiber having a thermoplastic resin as the core portion and a fiber-forming polyamide resin as the sheath portion, the main component of the thermoplastic resin forming the core portion is polyetheresteramide, and the ratio of the core portion is 5 to 50% by weight of the total weight of the composite fiber.

Furthermore, Patent Document 4 describes a composite fiber having moisture absorption and release properties, characterized by having a polyamide or polyester sheath component and a thermoplastic water-absorbent resin formed from a cross-linked polyethylene oxide as a core component. This document describes a highly moisture-absorbent core-sheath composite fiber in which a highly moisture-absorbent, water-insoluble modified polyethylene oxide is provided in the core and a polyamide is provided in the sheath.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 9-188917

Patent Document 2: International Publication No. 2014/10709

Patent Document 3: Japanese Patent Application Laid-Open No. 6-136618

Patent Document 4: Japanese Patent Application Laid-Open No. 8-209450

Summary of the Invention

Problems to be solved by the invention

However, although the fiber described in Patent Document 1 has moisture absorption and desorption properties close to those of natural fibers, it cannot fully satisfy this performance, and achieving higher moisture absorption and desorption properties is a problem.

Furthermore, while the core-sheath composite fibers described in Patent Documents 2 to 4 have moisture absorption and release properties comparable to or superior to those of natural fibers, the core deteriorates with repeated use, resulting in a decrease in moisture absorption performance. Furthermore, the texture of these fabrics, when fabricated, is soft, comparable to that of nylon, which is insufficient. A softer texture than existing products is highly desired.

Methods for solving problems

The present invention aims to overcome the above-mentioned problems of the prior art and to provide a core-sheath composite yarn having high hygroscopicity and achieving comfort exceeding that of natural fibers, washing durability sufficient to withstand the hygroscopicity of actual use, and a soft hand feel that has not been achieved before.

In order to solve the above-mentioned problems, the present invention includes the following means.

(1) A hygroscopic core-sheath composite yarn, wherein the core polymer is a polyetheresteramide copolymer, the sheath polymer is a polyamide, and the boiling water shrinkage is 6 to 11%.

(2) The hygroscopic core-sheath composite yarn according to (1), wherein the elongation is 60 to 90%.

(3) A false twisted yarn formed from the hygroscopic core-sheath composite yarn described in (1) or (2).

(4) A fabric comprising the hygroscopic core-sheath composite yarn according to (1) or (2) in at least a portion of the fabric.

(5) A method for producing a hygroscopic core-sheath composite yarn according to (1) or (2), wherein the yarn discharged from the spinneret is cooled and solidified by cooling air, and then the yarn is applied with an aqueous solution and/or an emulsion oil twice, and then wound up, wherein the time interval between the first stage application and the second stage application is 20 msec or longer.

Effects of the Invention

According to the present invention, a core-sheath composite yarn can be provided that has high hygroscopicity and can achieve comfort exceeding that of natural fibers, washing durability that can withstand the hygroscopicity of actual use, and a soft feel that has not been achieved before.

DETAILED DESCRIPTION

The core-sheath composite yarn of the present invention utilizes a polyamide for the sheath and a thermoplastic polymer with high hygroscopicity for the core. The thermoplastic polymer with high hygroscopicity in the core refers to a polymer having a ΔMR of 10% or greater, measured in pellet form. Examples include polyetheresteramide copolymers, polyvinyl alcohol, and cellulosic thermoplastic resins. Polyetheresteramide copolymers are preferred due to their thermal stability, compatibility with the polyamide in the sheath, and excellent peel resistance. By creating such a core-sheath composite yarn, a yarn with high ΔMR can be achieved, resulting in a textile with excellent hygroscopicity and comfort. ΔMR is an indicator of humidity regulation, expressed as the difference in moisture absorption at an internal temperature and humidity of 30°C x 90% RH, typically during light to moderate work or light to moderate exercise, and at an external temperature and humidity of 20°C x 65% RH. A higher ΔMR corresponds to higher hygroscopicity and greater wear comfort.

A polyetheresteramide copolymer is a block copolymer having ether, ester, and amide bonds within the same molecular chain. More specifically, it is a block copolymer obtained by polycondensing one or more polyamide components (A) selected from lactams, aminocarboxylic acids, and salts of diamines and dicarboxylic acids, with a polyetherester component (B) formed from a dicarboxylic acid and a polyoxyalkylene glycol.

The polyamide component (A) includes lactams such as ε-caprolactam, lauryl lactam, and undecanolactam; ω-aminocarboxylic acids such as aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid; and nylon salts of diamine-dicarboxylic acids which are precursors of nylon 66, nylon 610, nylon 612, and the like. The preferred polyamide-forming component is ε-caprolactam.

The polyetherester component (B) is composed of a dicarboxylic acid having 4 to 20 carbon atoms and a polyoxyalkylene glycol. Examples of the dicarboxylic acid having 4 to 20 carbon atoms include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. These can be used singly or in combination of two or more. Preferred dicarboxylic acids are adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid, and isophthalic acid. Examples of the polyoxyalkylene glycol include polyethylene glycol, poly(1,2- and 1,3-propylene glycol), poly(1,4-butylene glycol), and poly(1,6-hexanediol). Polyethylene glycol, which has excellent hygroscopic properties, is particularly preferred.

The number average molecular weight of the polyoxyalkylene glycol is preferably 300 to 10,000, more preferably 500 to 5,000. A molecular weight of 300 or greater is preferred because it is less likely to scatter outside the system during the polycondensation reaction and results in a fiber with stable moisture absorption properties. A molecular weight of 10,000 or less is also preferred because it produces a uniform block copolymer and stabilizes the spinning properties.

The molar ratio of the polyetherester component (B) is preferably 20 to 80%. A molar ratio of 20% or more is preferred because good hygroscopicity is achieved. A molar ratio of 80% or less is also preferred because good dyeing fastness and washing durability are achieved.

As such a polyetheresteramide copolymer, "MH1657" and "MV1074" manufactured by Alkema Corporation are commercially available.

Examples of polyamides used in the sheath include nylon 6, nylon 66, nylon 46, nylon 9, nylon 610, nylon 11, nylon 12, and nylon 612, or copolymers containing these with compounds having functional groups capable of forming amides, such as laurolactam, sebacic acid, terephthalic acid, isophthalic acid, and 5-sodium sulfoisophthalate. Nylon 6, nylon 11, nylon 12, nylon 610, and nylon 612 have a small difference in melting point from the polyetheresteramide copolymer, which can suppress thermal degradation of the polyetheresteramide copolymer during melt spinning and are therefore preferred from the perspective of yarn-forming properties. Nylon 6, which has excellent dyeability, is particularly preferred.

Various additives such as light-reducing agents, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, crystal nucleating agents, fluorescent brighteners, antistatic agents, hygroscopic polymers, carbon, etc. can be copolymerized or mixed with the polyamide of the sheath portion of the present invention as needed, with the total additive content being between 0.001 and 10% by weight.

The core-sheath composite yarn of the present invention requires a boiling water shrinkage of 6-11%. By keeping this within this specified range, false-twisted yarns, when subsequently made into textiles, can achieve a soft feel not previously achieved with nylon. If the boiling water shrinkage is less than 6%, the core-sheath composite yarn crystallizes before false twisting. Even if crimps are applied during false twisting, the crimps cannot be compressed, failing to achieve a sense of expansion or a soft feel. Furthermore, if the boiling water shrinkage exceeds 11%, the shrinkage is excessive, resulting in a stiff feel to the textile. A more preferred range for the boiling water shrinkage is 6-10%, and even more preferably, 7-9.5%.

To achieve a boiling water shrinkage of 6-11%, in addition to producing the core-sheath composite yarn described above, it is preferable to apply an oil in two stages during yarn production. Oiling is essential to improve yarn smoothness and bundling properties. Applying an aqueous solution or emulsion to the cooled and solidified yarn, allowing it to stand for a certain period, and then applying the emulsion again can easily reduce the boiling water shrinkage. This is believed to be because the first stage of application simultaneously supplies water to the yarn, causing crystallization. The second stage of oiling ensures smoothness and bundling properties. A time interval of 20 msec or longer between the first and second stages of application is preferred, as it facilitates controlling the boiling water shrinkage within the specified range of the present invention. While a longer time interval is preferred, extending the application interval requires a longer process step, so it is best to set the interval based on efficient production. It should be noted that the yarn spinning speed is 3000 m/min, and when the difference between the oil application positions in the first and second stages is 1.5 m, the application interval is 30 msec. Furthermore, setting the yarn tension during oil application within the range of 0.15 to 0.40 cN/dtex promotes yarn orientation, thereby enabling the boiling water shrinkage to fall within this specified range, which is preferred. It should be noted that the yarn tension is measured from the first stage to the second stage. Furthermore, the core-sheath composite yarn of the present invention preferably has an elongation of 60 to 90%. To improve flexibility, a false twisting process may be used. Due to this false twisting process, an elongation of 60 to 90% minimizes the change in curl over time and the decrease in curl during repeated stretching, further improving the yarn's flexibility, which is preferred.

The total fineness, number of single fibers (in the case of long fibers), length, and number of crimps (in the case of short fibers) of the core-sheath composite yarn of the present invention are not particularly limited, and the cross-sectional shape can be formed into any desired shape depending on the intended use of the resulting fabric. Considering use as a long fiber material for clothing, the total fineness of the multifilament yarn is preferably 5 dtex or greater and 235 dtex or less, and the number of single fibers is preferably 2 or greater and 144 or less. Furthermore, the cross-sectional shape is preferably circular, triangular, flat, Y-shaped, star-shaped, eccentric, or laminated.

The ratio of the core portion of the core-sheath composite yarn of the present invention is preferably 20 to 80 parts by weight, more preferably 30 to 70 parts by weight, relative to 100 parts by weight of the composite yarn. Within this range, a good ΔMR is achieved and processability during false twisting is improved.

The polyamide pellets used in the sheath portion of the present invention preferably have a sulfuric acid relative viscosity of 2.3 to 3.3, more preferably 2.6 to 3.3. This range not only facilitates maintaining the boiling water shrinkage within the specified range but also improves the washing durability of ΔMR, making it easier to achieve comfortable textiles.

The polyetheresteramide copolymer pellets used in the core of the present invention preferably have an o-chlorophenol relative viscosity (OCP relative viscosity) of 1.2 or higher and 2.0 or lower. An o-chlorophenol relative viscosity of 1.2 or higher is preferred because it not only applies optimal stress to the sheath during spinning, but also crystallizes the polyamide in the sheath, facilitating control of boiling water shrinkage, but also improves the washing durability of ΔMR.

In addition to the preferred production methods described above, the core-sheath composite yarn of the present invention can also be obtained by known melt spinning and composite spinning methods, as exemplified below.

For example, the polyamide (sheath) and polyetheresteramide copolymer (core) are melted separately, metered and transported using a gear pump, and then formed into a composite stream with a core-sheath structure using conventional methods. The stream is then discharged from the spinneret and cooled to room temperature by blowing cooling air through a yarn cooling device such as a chimney. The yarn is then lubricated in two stages using the aforementioned method and passed through take-up rollers. The circumferential speed of the take-up rollers is preferably 3000-3900 m/min. The yarn that has passed through the take-up rollers is preferably stretched at a ratio of 1.0-1.1 times and passed through stretching rollers. The winding tension is then adjusted to achieve the desired packaged form, and the yarn is then wound using a winder (winding device).

The core-sheath composite yarn obtained by the present invention achieves enhanced softness and a unique hand feel through false twisting. False twisting can be performed using known techniques such as friction, pinning, and band clamping. Friction is preferred for cost considerations, while pinning is preferred for crimping performance. In either process, the elongation after false twisting is preferably set to 25-40% to account for the temporal crimping behavior, false twisting properties, and subsequent weaving and knitting. Heat setting at 140-170°C is preferred for optimal crimping and to minimize temporal changes.

The core-sheath composite yarn of the present invention is preferably used for fabrics and clothing. The fabric form can be selected from woven fabrics, knitted fabrics, non-woven fabrics, etc. according to the purpose, and clothing is also included. In addition, as clothing, various clothing products such as underwear and sportswear can be produced.

Example

The present invention will be further described in detail with reference to the following examples. It should be noted that the methods for measuring the characteristic values in the examples are as follows.

(1) Relative viscosity of sulfuric acid

Dissolve 0.25 g of a sample in 100 ml of 98% by weight sulfuric acid to make 1 g. Use an Ostwald viscometer to measure the flow time (T1) at 25°C. Next, measure the flow time (T2) of the 98% by weight sulfuric acid alone. The ratio of T1 to T2, or T1/T2, is defined as the relative viscosity of sulfuric acid.

(2) Orthochlorophenol relative viscosity (OCP relative viscosity)

Dissolve 0.5 g of the sample in 100 ml of o-chlorophenol to obtain 1 g. Use an Ostwald viscometer to measure the flow time (T1) at 25°C. Next, measure the flow time (T2) of the o-chlorophenol alone. The ratio of T1 to T2, or T1/T2, is defined as the OCP relative viscosity.

(3) Fineness

The fiber sample was placed on a gauge at 1.125 m/s and rotated 200 times to form a circular hank. The hank was then dried in a hot air dryer (105 ± 2°C for 60 minutes). The hank mass was then weighed on a scale and multiplied by the official moisture regain to calculate the fineness. The official moisture regain for core-sheath composite yarn is 4.5% by weight.

(4) Strength and elongation

Fiber samples were measured using "TENSILON" (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. under the constant-rate elongation conditions specified in JIS L1013 (Test Methods for Chemical Fibers, 2010). Elongation was determined from the elongation at the point showing maximum strength on the tensile strength-elongation curve. Strength was determined by dividing the maximum strength by the fineness. Ten measurements were performed, and the average values were used as strength and elongation.

(5) Boiling water shrinkage

The fiber was made into a hank and the sample length S0 was measured under a load of 0.09 cN/dtex. Then, the sample was treated in boiling water for 15 minutes without a load and air-dried. After treatment, the sample length S1 was measured under a load of 0.09 cN/dtex and calculated according to the following formula.

Boiling water shrinkage = (S0-S1)/S0×100% (1)

(6) Stretch recovery rate (CR)

The recovery rate from stretch (CR) is an index showing the crimp properties of false twisted yarn.

The false-twisted yarn was formed into a hank, free-treated in 90°C water for 20 minutes, and air-dried. Next, a load of 0.0018 cN/dtex was applied in 25°C water, and the hank length L1 was measured 2 minutes later. Similarly, the 0.0018 cN/dtex load was removed and a load of 0.09 cN/dtex was applied in water. The hank length L0 was measured 2 minutes later and calculated using the following formula.

CR＝(L0-L1)/L0×100％ (2)

(7)ΔMR

A circular knitted fabric was produced using a circular knitting machine with a stitch density of 50. If the fiber's gross fineness was low, the yarns fed to the circular knitting machine were appropriately combined so that the total fineness of the fibers fed was 50 to 100 dtex. If the total fineness exceeded 100 dtex, the yarn was fed to the circular knitting machine with a single yarn and the stitch density adjusted to 50, as described above. Approximately 1 to 2 g of this circular knitted fabric was weighed in a weighing bottle and dried at 110°C for 2 hours. The weight (W0) was then measured after the material was dried at 20°C and 65% relative humidity for 24 hours. The weight (W65) was then measured after the material was stored at 30°C and 90% relative humidity for 24 hours. The weight (W90) was then calculated using the following formula.

MR1＝[(W65-W0)/W0]×100% (3)

MR2＝[(W90-W0)/W0]×100% (4)

ΔMR＝MR2-MR1 (5)

(8) ΔMR after washing

The circular knitted fabric was repeatedly washed 20 times by the method described in No. 103 of Appendix 1 of JIS L0217 (1995), and then the above-described ΔMR (moisture absorption and release) was measured and calculated.

The case where ΔMR was 7.0% or more was evaluated as S, and the case where ΔMR was 5.0% or more and less than 7.0% was evaluated as A.

(9) ΔMR retention after washing

As an indicator of the change in ΔMR before and after washing, the ΔMR retention rate after washing was calculated using the following formula.

ΔMR after washing/ΔMR before washing × 100 (6)

The evaluation was S when the ΔMR retention was 95% or higher, and A when the ΔMR retention was 90% or higher but less than 95% and had washing durability and was judged to provide good comfort when worn. Other evaluations were C.

(10) Fabric feel

Using the core-sheath composite yarn of the present invention and 22 dtex polyurethane elastic yarn, a bare weight plain fabric was produced using a 28G single circular knitting machine. The fabric was scoured, heat-set, dyed, and final-set to obtain a fabric. Separately, a standard nylon 6 false-twisted yarn (CR 26%) of 44 dtex/26F was prepared and a bare weight plain knit fabric was produced in the same manner as above. The hand of the resulting fabrics was compared and evaluated. S and A were considered acceptable.

S: Compared with fabrics made of ordinary nylon 6, it exhibits much better softness.

A: Compared with ordinary nylon 6 fabric, it is more flexible.

C: Equivalent to a fabric made of ordinary nylon 6.

(11) Comprehensive evaluation

If the evaluations of ΔMR after washing, ΔMR retention after washing, and fabric feel were all rated S, in addition to good hygroscopic comfort, the softness was also excellent, and the overall evaluation was also rated S. If all the above evaluations were A or higher, the overall evaluation was rated A, and if any one of the items was C, the overall evaluation was rated C.

(12) Tension measurement

The tension value was measured using a tension meter and an FT-R pickup sensor manufactured by Toray Engineering Co., Ltd.

Regarding the yarn tension during the first stage of lubrication application, the tension value was measured between the first and second stage lubrication devices, and the value obtained by dividing the tension value by the fineness was calculated (cN/dtex).

Regarding the winding tension, the tension value (cN) was measured between the second roller and the winder.

[Example 1]

A polyetheresteramide copolymer (MH1657, manufactured by Alkema, o-chlorophenol relative viscosity: 1.69) containing nylon 6 as the polyamide component and polyethylene glycol with a molecular weight of 1500 as the polyether component (polyoxyalkylene glycol) at a molar ratio of approximately 76% was used as the core. Nylon 6 with a sulfuric acid relative viscosity of 2.71 and an amino terminal group content of 5.95× ^10⁻⁵ mol/g was used as the sheath. The fibers were melted at 270°C and spun from a concentric core-sheath composite nozzle at a core/sheath ratio (parts by weight) of 50/50. The amino terminal group content was adjusted during polymerization using hexamethylenediamine and acetic acid.

The gear pump speed was selected to achieve a total fineness of 57 dtex for the resulting core-sheath composite yarn, with the discharge rates of the core and sheath components set at 19.6 g/min, respectively. The yarn discharged from the nozzle was cooled and solidified using a yarn cooling device. The first stage of lubrication was then applied using a 1% emulsion lubricant using an oiling device. The yarn tension at this stage was 0.30 cN/dtex. A second stage lubrication device was installed 2.0 m downstream of the first stage lubrication, applying a 15% emulsion lubricant. The yarn was then taken up using a first roller rotating at 3,500 m/min, followed by a second roller rotating at the same speed. The yarn was then wound using this winder, with the circumferential speed adjusted to 3,430 m/min to achieve a winding tension of 5 cN. The interval between the first and second stages of lubrication application was 34 msec. The physical properties of the obtained core-sheath composite yarn are shown in Table 1. The obtained core-sheath composite yarn had a boiling water shrinkage of 8.5% and an elongation of 75%.

This core-sheath composite yarn was processed using a friction-type false twisting machine at a processing ratio of 1.3, a processing speed of 400 m/min, and a heater temperature of 150°C to obtain a 44 dtex/26F false twisted yarn with an elongation of 34%. It should be noted that these false twisting conditions are common to both the Examples and Comparative Examples.

Evaluation of the resulting false-twist yarn revealed a ΔMR of 12.1% and a post-wash ΔMR of 11.8%, indicating a ΔMR retention of 98%. This demonstrates excellent moisture absorption and release, as well as excellent washing durability. The fabric also had an excellent feel, surpassing the softness of conventional nylon. Therefore, the overall rating was S.

[Example 2]

Spinning was performed under the following conditions: the speeds of the first and second rollers were set at 3,200 m/min, and the positional relationship between the first and second stages was set at 2.0 m, the same as in Example 1. Specifically, spinning was performed with the lubricant application interval set at 38 msec. The winder speed was adjusted to achieve a take-up tension of 5 cN, as in Example 1. Furthermore, the polymer discharge rate was adjusted to achieve a false-twisted yarn fineness of 44 dtex. The physical properties of the resulting core-sheath composite yarn are shown in Table 1: a boiling water shrinkage of 7.2% and an elongation of 81%.

False twisting was carried out in the same manner as in Example 1, except that the processing ratio was set to 1.35 times so that the elongation of the false twisted yarn would be 35%, thereby obtaining a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn exhibited excellent post-wash ΔMR (11.2%) and ΔMR retention (97%), demonstrating excellent moisture absorption and release, as well as excellent wash durability. The fabric also had an excellent hand feel, surpassing the softness of conventional nylon. Therefore, it received an overall rating of S.

[Example 3]

The draw ratio was set to 1.05. Specifically, spinning was performed at 3,500 m/min for the first roll and 3,675 m/min for the second roll. The intervals between lubricant application were the same as in Example 1, and other conditions were set based on the same considerations as in Example 1. The physical properties of the resulting core-sheath composite yarn are shown in Table 1: boiling water shrinkage was 9.5% and elongation was 66%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was adjusted so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn exhibited very good moisture absorption and desorption properties and wash durability, with a ΔMR of 12.8% and a ΔMR retention of 98% after washing. Meanwhile, the fabric felt slightly rough due to the higher boiling water shrinkage of the core-sheath composite yarn compared to Example 1, but exhibited superior softness compared to fabrics made with standard nylon 6. Therefore, the overall evaluation was rated A.

[Example 4]

Spinning was performed with a core/sheath ratio (parts by weight) of 30/70, a first roller and a second roller at 3,000 m/min, and an oil application interval of 40 msec. The physical properties of the resulting core-sheath composite yarn are shown in Table 1: a boiling water shrinkage of 6.1% and an elongation of 69%.

False twisting was carried out in the same manner as in Example 1, except that the processing ratio was adjusted so that the elongation of the false twisted yarn became 35%. False twisting was carried out in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twist yarn had a post-wash ΔMR of 7.2% and a ΔMR retention of 91%, demonstrating very good moisture absorption and desorption properties. While the ΔMR retention was slightly lower, likely due to the lower roller speed than in Example 1, affecting the orientation of the core-sheath composite yarn, the yarn exhibited excellent wash durability and moisture absorption and desorption properties. Regarding the fabric's feel, the lower boiling water shrinkage compared to Example 1 resulted in slightly weaker crimp and a slightly less bulging feel, but it exhibited superior softness compared to fabrics made from standard nylon 6. Therefore, the overall evaluation was rated A.

[Example 5]

Conditions were changed to a core/sheath ratio (parts by weight) of 20/80. Furthermore, the first and second rollers were both running at 3,800 m/min, and the second stage of oil application was performed 1.25 m downstream of the first stage. Specifically, spinning was performed with an interval of 20 msec between oil applications. The physical properties of the resulting core-sheath composite yarn are shown in Table 1. The shorter interval resulted in a slightly higher boiling water shrinkage of 10.8% and an elongation of 58%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn had a post-wash ΔMR of 5.9% and a ΔMR retention of 98%, demonstrating excellent moisture absorption and desorption properties and very good washing durability. Meanwhile, the fabric felt slightly rough due to the higher boiling water shrinkage of the core-sheath composite yarn compared to Example 1, but exhibited superior softness compared to fabrics made with standard nylon 6. Therefore, the overall evaluation was rated A.

[Example 6]

Spinning was performed in the same manner as in Example 1 except that nylon 6 having a sulfuric acid relative viscosity of 3.30 and an amino terminal group content of 4.78×10 ^-5 mol/g was used as the sheath. The properties of the resulting core-sheath composite yarn are shown in Table 1: boiling water shrinkage was 9.3% and elongation was 70%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn exhibited excellent post-wash ΔMR (ΔMR) of 12.2% and ΔMR retention of 99%, demonstrating excellent moisture absorption and release, as well as excellent wash durability. The fabric also had an excellent feel, surpassing the softness of conventional nylon. Consequently, the overall rating was rated S.

[Example 7]

Spinning was performed in the same manner as in Example 1 except that nylon 6 having a sulfuric acid relative viscosity of 2.40 and an amino terminal group content of 3.95×10 ^-5 mol/g was used as the sheath. The properties of the resulting core-sheath composite yarn are shown in Table 1: boiling water shrinkage was 6.7% and elongation was 84%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twist yarn had a post-wash ΔMR of 9.2% and a ΔMR retention of 93%, demonstrating very good moisture absorption and desorption properties. While the ΔMR retention was slightly lower, presumably due to the lower relative viscosity of sulfuric acid compared to Example 1, affecting the orientation of the core-sheath composite yarn, the yarn nonetheless exhibited excellent moisture absorption and desorption properties and washing durability. Furthermore, the fabric's hand felt slightly less crimped and slightly less bulgy due to its lower boiling water shrinkage than in Example 1, but exhibited superior softness compared to fabrics made of standard nylon 6. Therefore, the overall evaluation was rated A.

[Comparative Example 1]

Nylon 6 with a sulfuric acid relative viscosity of 2.15 and an amino terminal group content of 4.70× ^10⁻⁵ mol/g was used as the sheath. The speeds of the first and second rollers were set at 4,000 m/min, and the positional relationship between the first and second stages was set at 2.0 m, similar to Example 1. Spinning was performed under the above conditions, with the oil application interval being 30 msec. The physical properties of the resulting core-sheath composite yarn are shown in Table 2: a boiling water shrinkage of 11.5% and an elongation of 68%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twist yarn had a post-wash ΔMR of 7.5% and a ΔMR retention of 70%, indicating poor washing durability of moisture absorption and release. Furthermore, the fabric felt harsh and rough due to a higher boiling water shrinkage than in the Examples, resulting in a feel comparable to that of fabric made from standard nylon 6. Therefore, the overall evaluation was rated C.

[Comparative Example 2]

Spinning was performed under the aforementioned conditions, with the speed of the first and second rollers set at 4,200 m/min and the positional relationship between the first and second stages maintained at 2.0 m, similar to Example 1. Specifically, spinning was performed with the lubricant application interval set at 7 msec. The physical properties of the resulting core-sheath composite yarn are shown in Table 2: boiling water shrinkage was 14.5% and elongation was 70%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn exhibited very good moisture absorption and desorption, as well as excellent washing durability, with a ΔMR of 10.6% and a ΔMR retention of 96% after washing. However, the fabric had a strong sense of roughness due to a higher boiling water shrinkage than in the Examples, resulting in a feel comparable to that of fabric made of conventional nylon 6. This resulted in a C rating. Therefore, the overall rating was C.

[Comparative Example 3]

Spinning was carried out in the same manner as in Example 1 except that the second roll speed was 3,465 m/min and the second roll surface temperature was 130°C. The physical properties of the obtained core-sheath composite yarn are shown in Table 2: boiling water shrinkage was 5.2% and elongation was 70%.

False twisting was performed in the same manner as in Example 1, except that the processing ratio was set so that the elongation of the false twisted yarn became 35%. False twisting was performed in the same manner as in Example 1 to obtain a false twisted yarn of 44 dtex/26F.

The resulting false-twisted yarn exhibited very good moisture absorption and release, as well as excellent washing durability, with a ΔMR of 11.5% and a ΔMR retention of 96% after washing. On the other hand, the fabric's feel was comparable to that of fabrics made of standard nylon 6, as the boiling water shrinkage was lower than that of the examples, resulting in crystallization of the core-sheath composite yarns. This lack of crimp compression and a lack of expansion resulted in a feel comparable to that of fabrics made of standard nylon 6. Therefore, the overall evaluation was rated C.

[Table 1]

[Table 2]

Industrial Application Possibilities

The core-sheath composite yarn of the present invention can have high hygroscopicity and washing durability that can withstand the hygroscopicity in actual use, and can also achieve a soft feel.

Claims (5)

1. A hygroscopic core-sheath composite filament, wherein the core polymer is a polyether ester amide copolymer, the sheath polymer is polyamide, and the boiling water shrinkage rate is 6-11%. 2. The hygroscopic core-sheath composite filament according to claim 1 has an elongation of 60-90%. 3. A false-twist yarn formed from the hygroscopic core-sheath composite yarn as described in claim 1 or 2. 4. A fabric having, at least in a portion of the fabric, the hygroscopic core-sheath composite yarn as described in claim 1 or 2. 5. A method for manufacturing the hygroscopic core-sheath composite filament as described in claim 1 or 2, In the manufacturing method, the filament discharged from the spinneret is cooled and solidified by cooling air, and then an aqueous solution and/or emulsion oil are applied to the filament twice, followed by winding, wherein the time interval between the application of the first stage and the second stage is more than 20 msec.