JP7625820B2 - Polyamide yarn for false twist texturing and polyamide false twist texturing yarn - Google Patents

Description

The present invention relates to a polyamide yarn for false twist texturing, which is mainly made of polycaproamide and exhibits high crimping performance when false twist texturing is performed, and to a polyamide false twist texturing yarn.

Synthetic fibers such as polyamide and polyester yarns have excellent mechanical and chemical properties and are therefore widely used in clothing and industrial applications. In particular, polyamide yarns are widely used in general clothing products due to their excellent texture and luster. In particular, false twisted yarns are widely used in woven and knitted fabrics for clothing applications. In particular, false twisted yarns with a high crimp rate have a thicker texture when made into fabric, which not only improves the feel of the fabric, such as softness and stretchability, but also improves functions such as heat retention and water absorption compared to false twisted yarns with a normal crimp rate. For this reason, there is an extremely high market demand for false twisted yarns with a particularly high crimp rate.

Patent Document 1 proposes a polyamide yarn for false twist processing, with a single yarn fineness of 7 dtex or more and a filament count of 2 or 3. The large single yarn fineness makes it possible to have a refreshing dry touch, but on the other hand, the extremely large single yarn fineness makes it difficult for the yarn to crimp, making it difficult to achieve tactile properties such as softness and stretchiness, or heat retention and water absorbency.

In general, methods for improving the crimp rate of false twisted yarn include forced twisting such as pin false twisting, and preferably active heating during false twisting to a degree that does not melt the yarn (using a contact type hot plate, raising the processing temperature, etc.). For yarn design, a resin with a melting point that can withstand the false twisting temperature when the false twisting temperature is raised (for example, polyhexamethylene adipamide (polyamide 66) in the case of polyamide) is used.

Patent Document 2 and Patent Document 3 propose polyamide yarns for false twist processing with a single yarn fineness of 1.2 dtex or less. Because the single yarn fineness is small, it is possible to produce false twisted yarns that have excellent tactile properties such as softness and stretchability, and are rich in functions such as heat retention and water absorption.

JP 2003-113531 A JP 2009-84749 A JP 2005-320655 A

However, in terms of imparting crimping performance, which is the most important characteristic of false twist textured yarn, the resin used in the examples of Patent Document 2 is limited to polyhexamethylene adipamide. When using polycaproamide (polyamide 6), which is particularly suitable among polyamides in terms of thread formability and mechanical properties, the false twisting temperature cannot be actively increased because its melting point is lower than that of polyhexamethylene adipamide, and as a result, it is difficult to obtain false twist textured yarn with high crimping performance.

Patent Document 3 also uses polycaproamide in the examples, and the false twisting temperature is as high as 200°C. However, the false twisting machine (Teijin Seiki HTS-1500) shown in the examples is a non-contact hot plate, which is still insufficient in terms of actively heating the yarn, and as a result, it is difficult to obtain a false twisted yarn with high crimping performance.

The present invention aims to provide a polyamide yarn for false twisting that can actively increase the false twisting temperature and exhibit high crimping performance even when using polycaproamide, which was difficult to achieve with conventional technology, and to provide said polyamide false twisted yarn.

In order to achieve the above object, the present invention has the following configuration.
(1) A polyamide yarn for false twist texturing, which is made of polycaproamide containing 90 mol % or more of ε-caprolactam units, and which has a shrinkage rate of 4.5 to 8.0%, an elongation of 50 to 70%, and a single yarn fineness of 5.0 dtex or less after dry heat treatment at 200° C. for 10 seconds.
(2) A polyamide yarn for false twist texturing according to (1) above, having a relative viscosity of 98% sulfuric acid of 2.9 to 3.4 .

The polyamide yarn for false twisting of the present invention has a specified dry heat shrinkage rate, which allows the false twisting temperature to be actively increased, even though it is polycaproamide. In addition, by specifying the single yarn fineness, the actual twist during false twisting can be stably applied, making it possible to provide a polyamide false twisting yarn with excellent shrinkage performance.

The polyamide of the present invention is a resin in which a so-called hydrocarbon group is linked to the main chain via an amide bond, and is mainly composed of polycaproamide. The term "mainly" used here means that the ε-caprolactam units constituting the polycaproamide constitute 90 mol% or more. The other components are not particularly limited as long as they do not impair the effects of the present invention, and examples thereof include units of aminocarboxylic acid, dicarboxylic acid, diamine, etc., which are monomers constituting polyamides such as polydodecanoamide (polyamide 12), polyhexamethylene adipamide, polyhexamethylene sebacamide (polyamide 610), and polyhexamethylene dodecanoamide (polyamide 612). In addition to pigments such as titanium oxide and carbon black, conventionally known oxidation spinning agents, color inhibitors, antistatic agents, light resistance agents, flame retardants, moisture-absorbing resins, etc. may also be included.

The polyamide yarn for false twisting of the present invention has a shrinkage rate (dry heat shrinkage rate) of 4.5 to 8.0% after dry heat treatment at 200°C for 10 seconds. By setting the shrinkage rate in this range, false twisting can be performed at a higher temperature (about 190°C with a contact type hot plate) than the false twisting temperature of normal polycaproamide (about 170°C with a contact type hot plate), and as a result, a false twisted yarn with high shrinkage performance can be obtained. In false twisting, the yarn is heated and plasticized in the twisted portion, making it possible to introduce twist, but it is the amorphous distortion portion of the yarn that is subject to twist deformation. The dry heat shrinkage rate specified in the present invention is the amount of deformation of the amorphous distortion portion, and if this value is large, high shrinkage will occur when false twisting is performed at a high temperature. If the dry heat shrinkage rate is less than 4.5%, the amount of twist deformation will be small, resulting in low shrinkage performance. Furthermore, the melting and softening of the yarn progresses extremely, causing the yarn to become slack, leading to yarn breakage during false twist processing. If the dry heat shrinkage rate is 4.5% or more, the amount of amorphous distortion in the yarn is sufficient, making it possible to perform false twist processing at high temperatures (around 190°C with a contact type hot plate), resulting in a false twisted yarn with high shrinkage performance. Of course, the higher the dry heat shrinkage rate, the better, but considering the properties of polycaproamide and the manufacturing process of polyamide yarn for false twist processing, it is difficult to achieve a dry heat shrinkage rate of more than 8.0%. The preferred range for the dry heat shrinkage rate is 5.0 to 8.0%.

The polyamide yarn for false twisting of the present invention has a single yarn fineness of 5.0 dtex or less. By setting the single yarn fineness in this range, the flexibility of the yarn can be maintained and the actual twist during false twisting can be stably introduced, resulting in a false twisted yarn with high crimping performance. If the single yarn fineness exceeds 5.0 dtex, the flexibility of the yarn cannot be maintained and the actual twist during false twisting cannot be stably introduced, resulting in low crimping performance. From the viewpoint of obtaining a polyamide false twisted yarn with excellent crimping performance by actively increasing the false twisting temperature, it is not necessary to set a lower limit for the single yarn fineness, but from the viewpoint of obtaining a polyamide yarn for false twisting with good and stable quality (particularly strength and thickness unevenness (U%) in the longitudinal direction of the yarn), it is preferable that the single yarn fineness is 1.0 dtex or more.

The polyamide yarn for false twisting of the present invention preferably has a relative viscosity in 98% sulfuric acid of 2.9 to 3.4. If the relative viscosity in 98% sulfuric acid is 2.9 or more, the strength of the false twisted yarn can be maintained in addition to high crimping performance when false twisting is performed at a high temperature (approximately 190°C with a contact type hot plate). If the relative viscosity in 98% sulfuric acid is 3.4 or less, the flexibility of the yarn can be maintained and the actual twist during false twisting can be stably applied, resulting in a false twisted yarn with high crimping performance.

The polyamide yarn for false twisting of the present invention has an elongation of 50 to 70% . When the elongation is 50% or more, the flexibility of the yarn can be maintained and the actual twist during false twisting can be stably introduced, so that a false twisted yarn with high crimping performance can be obtained. In addition, a false twisted yarn with stable quality can be obtained without the occurrence of fluff or single yarn breakage. When the elongation is 70% or less, the processing tension during false twisting can be stably increased, so that a false twisted yarn with high crimping performance can be obtained. In addition, in the manufacturing process of the polyamide yarn for false twisting, the phenomenon of yarn elongation during package winding, so-called swelling, can be suppressed, so that the yarn layers do not shift in the package during winding, and stable winding is possible.

The polyamide yarn for false twisting of the present invention preferably has a strength at 15% elongation of 1.5 to 2.2 cN/dtex. If the strength at 15% elongation is 1.5 cN/dtex or more, the processing tension during false twisting can be stably increased, and a false twisted yarn with high shrinkage performance can be obtained. If the strength at 15% elongation is 2.2 cN/dtex or less, the flexibility of the yarn can be maintained and the actual twist during false twisting can be stably introduced, and a false twisted yarn with high shrinkage performance can be obtained. In addition, a false twisted yarn with stable quality can be obtained without the occurrence of fluff or single yarn breakage.

The total fineness and number of filaments of the polyamide yarn for false twisting of the present invention are not particularly limited as long as they do not impair the effects of the present invention, but when used as a clothing material, it is preferable that the total fineness is 10 to 240 dtex and the number of filaments is 2 to 150.

The polyamide yarn for false twisting of the present invention can be obtained by a conventionally known melt spinning method, and examples are as follows. For example, polycaproamide resin is melted, metered and transported by a gear pump, and discharged from a spinneret to form a yarn. The yarn is cooled to room temperature by blowing cooling air onto it using a yarn cooling device such as a chimney, oiled and bundled using an oiling device, entangled in a fluid treatment device, and if necessary, oiled and bundled again using an oiling device, passed through a take-up roller and a stretching roller, and stretched according to the ratio of the peripheral speeds of the take-up roller and the stretching roller. After stretching, the yarn is wound up using a winding device. The polyamide yarn for false twisting of the present invention is classified as a so-called partially oriented yarn (POY), and its manufacturing method conforms to the POY method (high-speed spinning method).

In order to control the dry heat shrinkage, elongation, and strength at 15% elongation of the polyamide yarn for false twisting of the present invention within the above ranges, they can be preferably controlled by the 98% sulfuric acid relative viscosity and moisture content of the resin pellets, the drawing process, etc.

In the production of the polyamide yarn for false twisting of the present invention, the polycaproamide resin pellets used preferably have a 98% sulfuric acid relative viscosity of 2.9 to 3.4. If the 98% sulfuric acid relative viscosity is 2.9 or more, stress concentration on the spinning line between the spinneret and the take-up rollers is alleviated, ensuring the amorphous amount of the yarn, and by setting an appropriate draw ratio between the take-up rollers and the stretching rollers, the amount of amorphous strain of the yarn becomes sufficient, making it easy to control the dry heat shrinkage rate. If the 98% sulfuric acid relative viscosity is 3.4 or less, the melt viscosity is suitable for melt spinning, improving spinnability during melt spinning and enabling stable production without yarn breakage.

In the production of the polyamide yarn for false twisting of the present invention, it is preferable to suppress the change in the relative viscosity of 98% sulfuric acid when melting the polycaproamide resin pellets. A preferred method for this is to adjust the moisture content of the polycaproamide resin pellets before feeding them into the melt spinning machine. The moisture content of the polycaproamide resin pellets varies depending on the spinning system, etc., but is preferably 1200 ppm or less. If the moisture content of the polycaproamide resin pellets is 1200 ppm or less, hydrolysis of polycaproamide is suppressed at the stage of melting the polycaproamide resin pellets, so that the change in the relative viscosity of 98% sulfuric acid can be suppressed.

As a method other than adjusting the moisture content of the polycaproamide resin pellets before being fed into the melt spinning machine, it is also possible to add an appropriate amount of a magnesium compound to the polycaproamide resin pellets. Preferred magnesium compounds are magnesium oxide and magnesium hydroxide. The amount of magnesium added is preferably 0.5 to 10 millimoles of magnesium element per 100 g of the polycaproamide resin pellets. If the amount of magnesium added is 0.5 millimoles or more, the polymerization reaction of polycaproamide is suppressed at the stage of melting the polycaproamide resin pellets, so that the change in the relative viscosity of 98% sulfuric acid can be suppressed. If the amount of magnesium added is 10 millimoles or less, the magnesium compound does not become a foreign matter, and stable production without an increase in the filtration pressure of the spinning pack is possible. In addition, the polyamide yarn for false twisting of the present invention can also obtain a polyamide yarn for false twisting that is free of fluff and single yarn breakage and has stable quality.

In the production of the polyamide yarn for false twisting of the present invention, the melting temperature of the polycaproamide resin pellets is not particularly limited as long as it does not impair the effects of the present invention. However, when using polycaproamide resin pellets with a 98% sulfuric acid relative viscosity of 2.9 to 3.4, it is preferable to melt them at 260 to 300°C. If the melting temperature is 260°C or higher, the melt viscosity becomes suitable for melt spinning, improving the spinnability during melt spinning and enabling stable production without yarn breakage. If the melting temperature is 300°C or lower, the change in the 98% sulfuric acid relative viscosity when melting the polycaproamide resin pellets can be suppressed, and the generation of low-polymer components (monomers, oligomers) during melting is also suppressed, reducing the fouling of the discharge holes of the spinneret and enabling stable production without yarn breakage.

In the production of the polyamide yarn for false twisting of the present invention, the take-up speed is preferably 4000 m/min or less, more preferably 3800 m/min or less. If the take-up speed is 4000 m/min or less, stress concentration on the spinning line between the spinneret and the take-up rollers is alleviated, ensuring the amorphous amount of the yarn, and by setting an appropriate draw ratio between the take-up rollers and the stretch rollers, the amount of amorphous strain of the yarn becomes sufficient, making it easy to control the dry heat shrinkage rate. There is no need to set a lower limit for the take-up speed as long as it is within a range where an appropriate draw ratio can be set between the take-up rollers and the stretch rollers, but from the viewpoint of efficiently obtaining polyamide yarn for false twisting, it is preferable that the take-up speed is 2500 m/min or more.

The draw ratio is preferably 1.1 to 1.4 times. More preferably, it is 1.1 to 1.3 times. If the draw ratio is 1.1 times or more, sufficient distortion can be imparted to the amorphous yarn secured between the spinneret and the take-up roller, making it easy to control the dry heat shrinkage. If the draw ratio is 1.4 times or less, the elongation and strength at 15% elongation are in a preferred range, and the flexibility of the yarn can be maintained, so that the actual twist during false twist processing can be stably applied, and a false twist textured yarn with high shrinkage performance can be obtained. Although the draw ratio is preferably 1.1 to 1.4 times, this is a high draw ratio among POY methods, excluding special fibers such as those with a single yarn fineness of 7 dtex or more described in Patent Document 1. This is to facilitate the control of the dry heat shrinkage in the false twisting polyamide yarn of the present invention, and from the viewpoint of obtaining the dry heat shrinkage stably without unevenness in the longitudinal direction of the yarn, it is preferable that the surfaces of the take-up roller and the draw roller are mirror-finished. The term "mirror surface" as used herein refers to a surface roughness of 0.5 to 0.9 S, where the surface roughness is used as an index. Examples of mirror surface treatment methods include coating the metal surface, applying an abrasive to a soft cloth such as felt using a machine such as a buffing motor or a router, polishing the surface using a metal abrasive, and dissolving and polishing the metal surface by passing a direct current through an electrolyte. Among these, the method of coating the metal surface with a coating material is preferred, and the coating material may be chromium, titanium, zinc, etc., with chromium being preferred from the standpoint of durability and cost. The surface roughness is a value measured according to JIS B0601 (1970) and is expressed as the sum of the peak height and valley depth. In the present invention, measurements are taken at three arbitrary points on the surface of each roller that contacts at least the yarn at 1 cm intervals in the direction of rotation, and the average value is used.

In the production of the polyamide yarn for false twisting of the present invention, the winding speed does not need to be set in particular as long as the appropriate take-up speed and draw ratio can be set within the range, but from the viewpoint of efficiently and stably obtaining polyamide yarn for false twisting, it is preferable that the winding speed is 3500 to 4500 m/min. More preferably, it is 3800 to 4200 m/min. If the winding speed is 3500 m/min or more, not only can the polyamide yarn for false twisting be efficiently obtained, but also the phenomenon in which the yarn elongates during package winding, that is, the phenomenon of swelling, can be suppressed, so that the yarn layer does not shift in the package during winding, and stable winding is possible. If the winding speed is 4500 m/min or less, the take-up speed is in an appropriate range from the viewpoint of the spinnability of the yarn, and stable production without yarn breakage is possible.

The polyamide false twist textured yarn obtained using the false twist textured polyamide yarn of the present invention has a crimp rate (CR2) of 25 to 40%. By setting it in this range, even when used in a woven fabric, the fabric will have excellent tactile properties such as softness and stretchability. In general, in the case of woven fabrics, the binding force between the yarns at the overlapping weave is strong, so that the tactile properties such as softness and stretchability are inferior to those of knitted fabrics. In order to improve the tactile properties such as softness and stretchability in woven fabrics, spandex or false twist textured yarns that have elasticity and recovery in the yarn itself are preferably used.

The shrinkage rate of the polyamide false twist textured yarn of the present invention refers to the rate of elasticity recovery when the yarn is restrained. If the shrinkage rate is less than 25%, the woven fabric will have poor tactile properties such as softness and stretchability. If the shrinkage rate exceeds 40%, the woven fabric will have too much elasticity, resulting in rough and hard tactile properties such as softness and stretchability, and poor surface quality of the woven fabric.

When the crimp rate of the polyamide false twist textured yarn of the present invention is 25% or more, the yarn has sufficient elasticity and recovery performance, and a woven fabric rich in texture such as softness and stretchability can be obtained. When the crimp rate is 40% or less, the yarn has appropriate elasticity, and the texture such as softness and stretchability does not become rough and hard, and a woven fabric with excellent surface quality can be obtained. The crimp rate of the polyamide false twist textured yarn of the present invention is preferably 30 to 40%.

The polyamide false twist textured yarn of the present invention can be obtained by a conventionally known false twist texture technique, and is preferably false twist textured in a stretch-friction false twist texture device. Examples are as follows. For example, the false twist textured polyamide yarn of the present invention supplied to the stretch-friction false twist texture device is sent to a supply roller via a desired yarn guide and fluid treatment device. It is then guided to a stretch roller through a heated false twist heater, a cooling plate, and a twisting body that performs stretch-friction false twist, and is wound up as a false twist textured yarn. As for the stretch-friction false twist, the yarn may be stretched by a hot pin or hot plate before the supply roller of the stretch-friction false twist texture device, and then the friction false twist texture may be applied, or the friction false twist texture may be applied while being stretched between the supply roller and the stretch roller.

The twisting method is not limited to the spindle method, the three-axis twister method, the belt nip method, etc. When it is desired to strengthen the crimp, it is preferable to use the spindle method, and when it is desired to increase the processing speed and reduce production costs, it is preferable to use the friction false twist method, the three-axis twister, or the belt nip.

The heating method is not limited. A high-temperature contact heater or a high-temperature non-contact heater may be used, but a high-temperature contact heater is preferred from the viewpoint of increasing the false twist processing temperature to obtain a polyamide false twist textured yarn with excellent crimping performance. In false twist processing, the yarn is heated to plasticize it, twisted, and cooled to set, and the molecules in the fiber are rearranged to relieve distortion, resulting in a yarn with the bending and twisting deformation fixed as it is, and twisting properties are imparted. This deformation is not 100% heat-set, and the set rate for polyamide is about 80 to 90%. Therefore, in order to obtain high crimping performance, it is necessary to apply heat firmly to the yarn with a high-temperature contact heater to rearrange the molecules in the fiber and relieve distortion. Therefore, a high-temperature contact heater is preferred, and the processing temperature (heater setting temperature with a contact type hot plate) is 183 to 200°C.

The cooling method can be, but is not limited to, using a cooling plate, air cooling, water cooling, etc., but it is preferable to use a cooling plate considering efficiency and damage to the yarn.

It is preferable that the ratio (T2/T1) of the twisting tension (T1) to the untwisting tension (T2) is 0.7 to 1.0. When the ratio (T2/T1) is 1.0 or less, i.e., when the untwisting tension (T2) is small, the generation of fuzz, i.e., single yarn breakage, can be suppressed, resulting in less yarn breakage after twisting, enabling stable stretch-friction false twist processing, and the resulting false twisted yarn is of excellent quality. By making the ratio (T2/T1) 0.7 or more, poor untwisting can be suppressed, resulting in high crimp.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. The measurement methods for the characteristic values in the examples are as follows.

(1) Dry heat shrinkage rate: The dry heat shrinkage rate was measured using a "thermal shrinkage oven (model MK3)" manufactured by TESTRITE Co., Ltd. (hereinafter referred to as MK3). The yarn sample was doubled as necessary so that the yarn was 50 dtex or more (for example, three doubled yarns for 20 dtex, two doubled yarns for 26 dtex), and then paralleled and set in the MK3. When setting the yarn sample in the MK3, great care was taken not to touch the yarn sample as much as possible, and also not to pull the yarn sample as much as possible when doubled and paralleled. The initial weight of the yarn sample held by the measuring roller was adjusted to 0.05 cN/dtex with respect to the yarn sample. After confirming that the yarn sample set in the MK3 had no slack, the yarn sample was pushed into the heater, and the shrinkage rate at the time of the alarm activation was accurately read from the scale of the MK3. The measurement was performed 10 times, and the average value was taken as the dry heat shrinkage. The heater temperature was set to 200° C., and the alarm activation timer was set to 10 seconds.

(2) Relative Viscosity of 98% Sulfuric Acid 0.25 g of sample was dissolved in 100 ml of 98% sulfuric acid to give 1 g, and the flow time (t1) was measured at 25°C using an Ostwald viscometer. Then, the flow time (t2) of only 98% sulfuric acid was measured. The ratio of t1 to t2, i.e., t1/t2, was determined as the relative viscosity of 98% sulfuric acid.

(3) Total fineness, single filament fineness A yarn sample was set on a measuring machine with a circumference of 1 m, rotated 250 times to make a looped skein, and dried in a hot air dryer (105±2°C x 60 minutes). The weight of the skein was measured on a weighing scale, and the total fineness was calculated by multiplying the weight by the official moisture content. The official moisture content was set to 4.5%. The single filament fineness was calculated by dividing the calculated total fineness by the number of filaments.

(4) Strength at 15% elongation, strength, elongation Yarn samples were measured using Orientec's "TENSILON" (model UCT-100) under the constant-speed elongation conditions specified in JIS L1013 (Testing methods for chemical fiber filament yarns, 2010). The gripping distance was 50 cm, and the pulling speed was 50 cm/min. The strength at 15% elongation was determined by dividing the stress when elongated to 57.5 cm by the total fineness. The strength was determined by dividing the maximum point stress by the total fineness. The elongation was determined by multiplying the tensile length at which the maximum point stress was shown by 50 cm by 100. The strength at 15% elongation, strength, and elongation were each measured three times, and the average values were calculated.

(5) Crimp rate (CR2)
The yarn sample was spooled, subjected to an initial load of 0.0018 cN/dtex, treated in 98°C water for 20 minutes, and air-dried for 24 hours. Next, the same initial load was applied in 25°C water, and after 2 minutes, The initial load was then removed in water at 25° C., and replaced with a new load equivalent to 0.09 cN/dtex. The skein length L0 was measured after 2 minutes. The crimp rate was calculated by the above.
Crimp rate = [(L0-L1)/L0] x 100 (%)
(6) Evaluation of the feel of tubular knitted fabric Two yarn samples were fed to a tubular knitting machine, and the yarn density was adjusted to 50 on the tubular knitting machine to produce a tubular knitted fabric. Five subjects were asked to try the knitted fabric on, and a questionnaire was given to each of them regarding the softness and stretchiness of the fabric. The number of subjects who answered that the softness and stretchiness of the fabric were excellent was given an excellent rating of 4. Cases with 1 person were marked with an O, cases with 3 people with a △, and cases with 2 or less people with an X.

(Examples 1, 3 to 6, Comparative Examples 2 to 4)
Polycaproamide resin pellets containing 100 mol% of ε-caprolactam units (no other copolymerization components) were dried to adjust the moisture content of the resin pellets to 100 ppm or less. The resin pellets after the moisture content adjustment had a relative viscosity in 98% sulfuric acid of 3.15. Magnesium oxide powder was added at a rate of 0.04 g (1 mmol of magnesium element) to 100 g of the polycaproamide resin pellets, and dry-blended. The mixture was melted at the melting temperature shown in Table 1, metered and transported by a gear pump, and discharged from a spinneret having the number of filaments shown in Table 1 to form a yarn. The yarn was then cooled and solidified to room temperature by a uniflow chimney, and was oiled with a water-containing oil by an oiling device, and was then entangled by a fluid treatment device, and was again oiled with a water-containing oil by an oiling device. For drawing, a mirror-finished take-up roller and a drawing roller (surface roughness of 0.5S, chrome-coated finish) were used. The take-up speed and draw ratio were as shown in Table 1. After drawing, the yarn was wound up at the winding speed shown in Table 1 to obtain a polyamide yarn for false twist texturing. The total fineness, single yarn fineness, strength, elongation, strength at 15% elongation, 98% sulfuric acid relative viscosity, and dry heat shrinkage of the obtained polyamide yarn for false twist texturing were measured. The results are shown in Table 1.

The resulting polyamide yarn for false twisting was subjected to simultaneous drawing and false twisting processing using a three-axis friction disk type drawing and friction false twisting device (IVF1205) at a processing temperature (heater setting temperature with a contact-type hot plate) of 198°C, a processing speed of 650 m/min, a draw ratio of 1.24, a D/Y ratio of 2.0, and T2/T1 = 13 g/16 g = 0.81, to obtain a 22 dtex, 20 filament polyamide false twisted yarn. The crimp rate of the resulting polyamide false twisted yarn was measured. The results are shown in Table 1.

A tubular knit fabric was made from the resulting polyamide false twist textured yarn and evaluated for softness and stretchiness. The results are shown in Table 1. Note that in Example 3, the single yarn fineness was 3.7 dtex, which was thicker than the other Examples (single yarn fineness was 1.1 dtex), and therefore the softness was slightly inferior.

Example 2
Melt spinning was carried out in the same manner as in Example 1, except that the polycaproamide resin pellets containing 100 mol% as ε-caprolactam units after moisture content adjustment (100 ppm or less) had a 98% relative viscosity in sulfuric acid of 2.90, and the polyamide yarn for false twist texturing had a 98% relative viscosity in sulfuric acid of 2.96, to obtain a polyamide yarn for false twist texturing of about 26 dtex. The total fineness, single yarn fineness, strength, elongation, strength at 15% elongation, 98% relative viscosity in sulfuric acid, and dry heat shrinkage of the obtained polyamide yarn for false twist texturing were measured. The results are shown in Table 1.

The obtained polyamide yarn for false twisting was subjected to the same false twisting process as in Example 1 to obtain a polyamide false twisted yarn. The crimp rate of the obtained polyamide false twisted yarn was measured. The results are shown in Table 1.

A tubular knit fabric was made from the resulting polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

(Comparative Example 1)
A polyamide yarn for false twisting was obtained by melt spinning in the same manner as in Example 1, except that the polycaproamide resin pellets containing 100 mol% ε-caprolactam units after moisture content adjustment (100 ppm or less) had a 98% sulfuric acid relative viscosity of 2.63, and the polyamide yarn for false twisting had a 98% sulfuric acid relative viscosity of 2.70. The total fineness, single yarn fineness, strength, elongation, strength at 15% elongation, 98% sulfuric acid relative viscosity, and dry heat shrinkage of the obtained polyamide yarn for false twisting were measured. The results are shown in Table 1. The dry heat shrinkage was a low value of 3.5%, less than 4.5%, and the crimp rate (CR2) of the false twisting yarn was a low 12.0%, resulting in poor stretchability.

The obtained polyamide yarn for false twisting was subjected to false twisting in the same manner as in Example 1 to obtain a polyamide false twisted yarn. The T2/T1 ratio was low at 0.64, and the obtained polyamide false twisted yarn had partial fusion and poor untwisting, with occasional untwisted yarn. The crimp rate of the obtained polyamide false twisted yarn was measured. The results are shown in Table 1.

A tubular knit fabric was made from the resulting polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

(Reference Example 1)
The false twist polyamide yarn obtained in Comparative Example 1 was subjected to a false twist simultaneous drawing process using a three-axis friction type friction disk type draw-friction false twisting device (IVF1205) at a processing temperature (heater setting temperature with a heating contact type hot plate) of 180°C, a processing speed of 630 m/min, a draw ratio of 1.23, a D/Y ratio of 2.0, and T2/T1 = 11 g/10 g = 1.1, to obtain a 22 dtex, 20 filament polyamide false twisted yarn. The crimp rate of the obtained polyamide false twisted yarn was measured. The results are shown in Table 1.

A tubular knit fabric was made from the resulting polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

(Reference Example 2)
The polyhexamethylene adipamide resin pellets were dried to adjust the moisture content of the resin pellets to 1100 ppm. The resin pellets after the moisture content adjustment had a relative viscosity in 98% sulfuric acid of 2.63. No magnesium compound was added, and the remaining steps were melt spun in the same manner as in Example 1 to obtain a polyamide yarn for false twist texturing. The total fineness, single yarn fineness, strength, elongation, strength at 15% elongation, relative viscosity in 98% sulfuric acid, and dry heat shrinkage of the obtained polyamide yarn for false twist texturing were measured. The results are shown in Table 1.

The obtained polyamide yarn for false twisting was subjected to simultaneous drawing and false twisting processing using a three-axis friction disk type drawing and friction false twisting device (IVF1205) at a processing temperature (heater setting temperature with a heating contact type hot plate) of 195°C, a processing speed of 630 m/min, a draw ratio of 1.25, a D/Y ratio of 2.2, and T2/T1 = 10 g/10 g = 1, to obtain a 22 dtex, 20 filament polyamide false twisted yarn. The crimp rate of the obtained polyamide false twisted yarn was measured. The results are shown in Table 1.

A tubular knit fabric was made from the resulting polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

As is clear from the results in Table 1, the false twist polyamide yarn of the present invention, while being made of polycaproamide, has extremely remarkable effects in comparison with conventional false twist polyamide yarns, such as being able to actively increase the false twist temperature and being able to obtain a polyamide false twist yarn with excellent crimping performance.

Claims (2)

A polyamide yarn for false twist processing, which is made of polycaproamide containing 90 mol % or more of ε-caprolactam units, and has a shrinkage rate of 4.5 to 8.0%, an elongation of 50 to 70%, and a single yarn fineness of 5.0 dtex or less after dry heat treatment at 200°C for 10 seconds. The polyamide yarn for false twist texturing according to claim 1, which has a relative viscosity in 98% sulfuric acid of 2.9 to 3.4.