Polyamide yarn for false twist texturing and polyamide false twist texturing yarn

Abstract

To provide polyamide yarn for false twisting that make it possible to positively increase the false twisting temperature, and to provide false-twisted polyamide yarn having high crimping rates.SOLUTION: A polyamide yarn for false twisting has a shrinkage rate of 4.5-8.0% after dry-heated for 10 seconds at 200°C and also has a single yarn fineness of 5.0 dtex or less, the polyamide yarn mainly composed of polycaproamide (polyamide 6).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyamide yarn for false twist texturing, which is mainly made of polycaproamide and which exhibits high crimp performance when false twisted, and to a polyamide false twist texturized yarn. [Background technology]

[0002] Polyamide yarns and polyester yarns, which are synthetic fibers, are widely used in clothing and industrial applications due to their excellent mechanical and chemical properties. In particular, polyamide yarns are widely used in general clothing products due to their excellent touch and gloss. 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 fabrics, and therefore the texture such as softness and stretchability is improved, and the functions such as heat retention and water absorption are also improved 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 high crimp rate among false twisted yarns.

[0003] Patent Document 1 proposes a polyamide yarn for false twist texturing, with a single yarn fineness of 7 dtex or more and a filament count of 2 or 3. Because the single yarn fineness is large, it is possible to have a refreshing dry touch, but conversely, because the single yarn fineness is extremely large, it is difficult for the yarn to crimp, making it difficult to achieve tactile sensations such as softness and stretchability, and heat retention and water absorbency.

[0004] Generally, means for improving the crimp rate of false twisted yarn include a method of forcibly twisting the yarn, such as pin false twisting, and preferably a method of actively heating the yarn 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 (for example, polyhexamethylene adipamide (polyamide 66) in the case of polyamide) with a melting point that can withstand the false twisting temperature when the false twisting temperature is raised is used.

[0005] Patent Documents 2 and 3 propose polyamide yarns for false twist texturing with a single yarn fineness of 1.2 dtex or less. Because the single yarn fineness is small, it is possible to produce false twist texturing yarns with excellent tactile properties such as softness and stretchability, and rich functions such as heat retention and water absorbency. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-113531 A [Patent Document 2] JP 2009-84749 A [Patent Document 3] JP 2005-320655 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, from the viewpoint of imparting crimp performance, which is the most important characteristic of false twist textured yarn, in the examples of Patent Document 2, the resin used 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 melting point is lower than that of polyhexamethylene adipamide, so the false twist texture temperature cannot be actively increased. As a result, it is difficult to obtain false twist textured yarn with high crimp performance.

[0008] Furthermore, Patent Document 3 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.

[0009] An object of the present invention is to provide a polyamide yarn for false twist texturing that allows the false twist texturing temperature to be actively increased and exhibits high crimp performance even when polycaproamide is used, which was difficult to do with conventional techniques, and to provide said polyamide false twist texturized yarn. [Means for solving the problem]

[0010] 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) The polyamide yarn for false twisting according to (1) above, which has a relative viscosity of 2.9 to 3.4 in 98% sulfuric acid. 。 Effect of the Invention

[0011] By specifying the dry heat shrinkage rate of the polyamide yarn for false twisting of the present invention, the false twisting temperature can be actively increased even though the yarn is polycaproamide, and by specifying the single yarn fineness, the actual twist during false twisting can be stably imparted, so that a polyamide false twisted yarn with excellent crimp performance can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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 unit constituting the polycaproamide is handThe content of the other components is not particularly limited as long as they do not impair the effects of the present invention, and examples of the other components 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), polyhexamethylene dodecanoamide (polyamide 612), etc. 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.

[0013] 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 within this range, false twisting can be performed at a higher temperature (about 190°C with a contact type hot plate) than the normal false twisting temperature of 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 at the twisted portion, making it possible to introduce twist, but it is the amorphous distortion portion of the yarn that is subjected 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, which leads to yarn breakage during false twist processing. If the dry heat shrinkage is 4.5% or more, the amount of amorphous distortion of 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, the better, but in consideration of the properties of polycaproamide and the manufacturing process of polyamide yarn for false twist processing, it is difficult to obtain one exceeding 8.0%. The preferred range of the dry heat shrinkage is 5.0 to 8.0%.

[0014] 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 yarn lengthwise thickness unevenness (U%)), it is preferable that the single yarn fineness is 1.0 dtex or more.

[0015] 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 (about 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 introduced, thereby obtaining a false twisted yarn with high crimping performance.

[0016] 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, there is no generation of fuzz or single yarn breakage, so that a false twisted yarn with stable quality can be obtained. 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 polyamide yarn for false twisting, the phenomenon in which the yarn stretches during package winding, that is, so-called swelling, can be suppressed, so that the yarn layers do not shift in the package during winding, and stable winding is possible.

[0017] 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. When the strength at 15% elongation is 1.5 cN / dtex or more, the processing tension during false twisting can be stably increased, and thus a false twisted yarn with high crimping performance can be obtained. When 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 thus a false twisted yarn with high crimping performance can be obtained. In addition, there is no generation of fluff or single yarn breakage, and a false twisted yarn with stable quality can be obtained.

[0018] 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. However, 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.

[0019] The polyamide yarn for false twisting of the present invention can be obtained by a conventionally known melt spinning technique, and examples thereof 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: semi-stretched yarn), and its manufacturing method conforms to the POY method (high-speed spinning method).

[0020] 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, these can be preferably controlled by the 98% sulfuric acid relative viscosity and moisture content of the resin pellets, the drawing process, etc.

[0021] In the production of the polyamide yarn for false twisting of the present invention, the polycaproamide resin pellets used preferably have a relative viscosity in 98% sulfuric acid of 2.9 to 3.4. When the relative viscosity in 98% sulfuric acid is 2.9 or more, stress concentration on the spinning line between the spinneret and the take-up roller is alleviated, and the amorphous amount of the yarn can be ensured, and by setting an appropriate draw ratio between the take-up roller and the stretching roller, the amorphous strain amount of the yarn becomes sufficient, making it easy to control the dry heat shrinkage rate. When the relative viscosity in 98% sulfuric acid is 3.4 or less, the melt viscosity is suitable for melt spinning, so that the spinnability during melt spinning is improved, and stable production without yarn breakage is possible.

[0022] 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 in 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 a 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 in 98% sulfuric acid can be suppressed.

[0023] 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, and also in the false twisting polyamide yarn of the present invention, a quality-stable false twisting polyamide yarn without the occurrence of fluff or single yarn breakage can be obtained.

[0024] 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, but 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, it is possible to suppress the change in the 98% sulfuric acid relative viscosity when melting the polycaproamide resin pellets, and also suppress the generation of low polymer components (monomers, oligomers) during melting, thereby reducing the dirt of the discharge hole of the spinneret and enabling stable production without yarn breakage.

[0025] In the production of the polyamide yarn for false twist texturing 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, and the amorphous amount of the yarn can be secured, 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. 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 stretching rollers, but from the viewpoint of efficiently obtaining polyamide yarn for false twist texturing, it is preferable that the take-up speed is 2500 m / min or more.

[0026] The draw ratio is preferably 1.1 to 1.4 times. More preferably, it is 1.1 to 1.3 times. When 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, and the dry heat shrinkage can be easily controlled. When the draw ratio is 1.4 times or less, the elongation and the 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 twisting can be stably introduced, and a false twisted yarn having high crimping performance can be obtained. The draw ratio is preferably 1.1 to 1.4 times, and is a high draw ratio among POY methods, except for 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 polyamide yarn for false twisting 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 means a surface roughness of 0.5 to 0.9S, where the surface roughness is used as an index. Examples of mirror surface treatment methods include a method of coating a metal surface, a method of applying an abrasive to a soft cloth such as felt using a machine such as a buff motor or a router, a method of polishing the surface using a metal abrasive, and a method of dissolving and polishing the metal surface by passing a direct current through an electrolyte. Among these, a method of coating a 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, the surface of each roller is measured at any three points at least in the part in contact with the yarn at 1 cm intervals in the rotation direction, and the average value is used.

[0027] In the production of the polyamide yarn for false twist texturing of the present invention, the winding speed does not need to be particularly set as long as it is within a range in which an appropriate take-up speed and draw ratio can be set, but from the viewpoint of efficiently and stably obtaining the polyamide yarn for false twist texturing, it is preferably 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 twist texturing be efficiently obtained, but also the phenomenon in which the yarn elongates during package winding, that is, the so-called 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.

[0028] The polyamide false twist textured yarn obtained using the polyamide yarn for false twist texture 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 a woven fabric, the binding force between the yarns at the overlapping of the weave is strong, so that the tactile properties such as softness and stretchability are inferior to those of knitted fabrics, etc. In order to improve the tactile properties such as softness and stretchability in a woven fabric, spandex or false twist textured yarn, which has stretch recovery properties in the yarn itself, is preferably used.

[0029] The crimp rate of the polyamide false twist textured yarn of the present invention refers to the rate of recovery from stretching when the yarn is restrained. If the crimp rate is less than 25%, the woven fabric will have poor tactile properties such as softness and stretchability. If the crimp rate is more than 40%, the woven fabric will have too high elasticity, resulting in rough and hard tactile properties such as softness and stretchability, and poor surface quality of the woven fabric.

[0030] When the crimp rate of the polyamide false twist textured yarn of the present invention is 25% or more, the yarn has sufficient stretch 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 stretchability, 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%.

[0031] 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 draw-friction false twist texture device. An example is as follows. For example, the false twist textured polyamide yarn of the present invention, which is supplied to a draw-friction false twist texture device, is sent to a feed roller via a desired yarn guide and fluid treatment device. It is then guided to a draw roller through a heated false twist heater, a cooling plate, and a twisting body for draw-friction false twist, and wound up as a false twist textured yarn. As for the draw-friction false twist, the yarn may be subjected to friction false twist texture after drawing with a hot pin or hot plate before the feed roller of the draw-friction false twist texture device, or may be subjected to friction false twist texture while being drawn between the feed roller and the draw roller.

[0032] 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 the production cost, it is preferable to use the three-axis twister and the belt nip, which are friction false twist methods.

[0033] 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 shrinkage 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-fixed, and the set rate for polyamide is about 80 to 90%. Therefore, in order to obtain high shrinkage 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. is .

[0034] As for the cooling method, a cooling plate may be used, and examples thereof include air cooling and water cooling, but are not limited thereto. Taking into consideration efficiency and damage to the yarn, it is preferable to use a cooling plate.

[0035] The ratio (T2 / T1) of the twisting tension (T1) to the untwisting tension (T2) is preferably 0.7 to 1.0. When the ratio (T2 / T1) is 1.0 or less, that is, when the untwisting tension (T2) is small, the generation of fuzz, that is, single yarn breakage, can be suppressed, so that yarn breakage after twisting is reduced, stable stretch-friction false twist processing is possible, and the obtained false twist textured yarn is of excellent quality. By making the ratio (T2 / T1) 0.7 or more, poor untwisting can be suppressed, and high crimp can be obtained. EXAMPLES

[0036] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring the property values ​​in the examples are as follows.

[0037] (1)Dry heat shrinkage rate The measurements were performed using a TESTRITE thermal shrinkage oven (model MK3) (hereafter referred to as MK3). The yarn samples were doubled as necessary (for example, 3-ply yarn for 20 dtex, 2-ply yarn for 26 dtex), paralleled, and set in the MK3 so that the yarn samples were 50 dtex or more. When setting the yarn samples in the MK3, great care was taken not to touch the yarn samples as much as possible, and also not to pull the yarn samples as much as possible when doubled and paralleled. The initial weight of the yarn samples held by the measuring roller was adjusted to 0.05 cN / dtex relative to the yarn samples. After confirming that the yarn samples set in the MK3 had no slack, the yarn samples were pushed into the heater, and the shrinkage rate at the time the alarm was activated was accurately read from the scale of the MK3. The measurements were performed 10 times, and the average value was taken as the dry heat shrinkage rate. The heater temperature was set to 200°C, and the alarm activation timer was set to 10 seconds.

[0038] (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. The flow time (t2) of only 98% sulfuric acid was then measured. The ratio of t1 to t2, i.e., t1 / t2, was determined as the relative viscosity of 98% sulfuric acid.

[0039] (3) Total fineness, single yarn fineness A yarn sample was set on a measuring machine with a circumference of 1 m and rotated 250 times to make a looped skein. After drying in a hot air dryer (105±2°C x 60 minutes), the skein was weighed on a weighing scale and multiplied by the official moisture content to calculate the total fineness. The official moisture content was set to 4.5%. The single yarn fineness was calculated by dividing the calculated total fineness by the number of filaments.

[0040] (4) Strength at 15% elongation, strength, elongation The 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 calculated by dividing the stress when elongated to 57.5 cm by the total fineness. The strength was calculated by dividing the maximum point stress by the total fineness. The elongation was calculated by dividing the tensile length at which the maximum point stress was shown by 50 cm and multiplying this by 100. The strength at 15% elongation, strength, and elongation were all measured three times, and the average values ​​were calculated.

[0041] (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 the spool length L1 was measured after 2 minutes. Next, the initial load was removed in 25°C water, replaced with a new load equivalent to 0.09 cN / dtex, and the spool length L0 was measured after 2 minutes. The crimp rate was then calculated using the following formula. Crimp rate=[(L0-L1) / L0]×100(%) (6) Evaluation of the texture of tubular knitted fabric Two yarn samples were fed to a cylindrical knitting machine, and the yarn density was adjusted to 50 on the cylindrical knitting machine to produce a cylindrical knitted fabric. Five subjects were asked to pass the obtained cylindrical knitted fabric through their hands, and a questionnaire was given to each subject regarding the softness and stretchability of the fabric. When five subjects answered that the softness and stretchability were excellent, the rating was ◎, when four subjects answered ○, when three subjects answered △, and when two or less subjects answered ×.

[0042] (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 98% sulfuric acid relative viscosity of the resin pellets after the moisture content adjustment was 3.15. Magnesium oxide powder was added at a rate of 0.04 g (1 millimole of magnesium element) to 100 g of the polycaproamide resin pellets and dry-blended. This was melted at the melting temperature shown in Table 1, metered and transported by a gear pump, and discharged from a spinneret having the filament number group shown in Table 1 to form a thread. The thread was then cooled and solidified to room temperature by a uniflow chimney, and a water-containing oil agent was added by an oiling device, after which it was entangled by a fluid treatment device, and again a water-containing oil agent was added 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 taken up at the take-up speed shown in Table 1 to obtain a polyamide yarn for false twist texturing. The resulting polyamide yarn for false twist texturing was measured for total fineness, single yarn fineness, strength, elongation, strength at 15% elongation, relative viscosity in 98% sulfuric acid, and dry heat shrinkage. The results are shown in Table 1.

[0043] The obtained polyamide yarn for false twisting was subjected to simultaneous drawing and false twisting processing 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 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=13g / 16g=0.81 to obtain a polyamide false twist textured yarn of 22 dtex and 20 filaments. The crimp percentage of the obtained polyamide false twist textured yarn was measured. The results are shown in Table 1.

[0044] A tubular knitted fabric was produced from the obtained polyamide false twist textured yarn, and the softness and the feel of the stretchability were evaluated. The results are shown in Table 1. 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 the softness was slightly inferior.

[0045] Example 2 A polyamide yarn for false twist texturing of about 26 dtex was obtained by melt spinning in the same manner as in Example 1, except that the polycaproamide resin pellets containing 100 mol% of ε-caprolactam units after moisture content adjustment (100 ppm or less) had a 98% sulfuric acid relative viscosity of 2.90, and the polyamide yarn for false twist texturing had a 98% sulfuric acid relative viscosity of 2.96. 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.

[0046] The resulting polyamide yarn for false twisting was false twisted in the same manner as in Example 1 to obtain a polyamide false twisted yarn. The crimp percentage of the resulting polyamide false twisted yarn was measured. The results are shown in Table 1.

[0047] A tubular knitted fabric was made from the obtained polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

[0048] 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.

[0049] The obtained polyamide yarn for false twisting was false twisted 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, and untwisted yarn was occasionally observed. The crimp percentage of the obtained polyamide false twisted yarn was measured. The results are shown in Table 1.

[0050] A tubular knitted fabric was made from the obtained polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

[0051] (Reference example 1) The polyamide yarn for false twisting obtained in Comparative Example 1 was subjected to simultaneous draw-friction false twisting processing 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=11g / 10g=1.1, to obtain a polyamide false twist textured yarn of 22 dtex and 20 filaments. The crimp percentage of the obtained polyamide false twist textured yarn was measured. The results are shown in Table 1.

[0052] A tubular knitted fabric was made from the obtained polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

[0053] (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 rest of the process was 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.

[0054] The obtained polyamide yarn for false twisting was subjected to simultaneous drawing and false twisting processing 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 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=10g / 10g=1 to obtain a polyamide false twist textured yarn of 22 dtex and 20 filaments. The crimp percentage of the obtained polyamide false twist textured yarn was measured. The results are shown in Table 1.

[0055] A tubular knitted fabric was made from the obtained polyamide false twist textured yarn, and the softness and stretchability of the fabric were evaluated. The results are shown in Table 1.

[0056] [Table 1]

[0057] As is clear from the results in Table 1, the polyamide yarn for false twisting of the present invention, while being made of polycaproamide, exhibits extremely remarkable effects in comparison with conventional polyamide yarns for false twisting, such as the ability to actively raise the false twisting temperature and to obtain a polyamide false twisting yarn with excellent crimp performance.

Claims

1. The polyamide yarn for false twisting 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.

2. 2. Polyamide yarn for false twist texturing according to claim 1, which has a relative viscosity of 98% sulfuric acid of 2.9 to 3.4.

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