WO2022209813A1

WO2022209813A1 - Polyamide multifilament

Info

Publication number: WO2022209813A1
Application number: PCT/JP2022/011230
Authority: WO
Inventors: 渡邉雄大; 渡邉勇太; 鯨井実月
Original assignee: 東レ株式会社
Priority date: 2021-03-29
Filing date: 2022-03-14
Publication date: 2022-10-06
Also published as: CN116964259A; EP4317550A1; JPWO2022209813A1; TW202237917A

Abstract

This polyamide multifilament has a total fineness of 4-100 dtex, a single filament fineness of 1.1-5.0 dtex, a strength-elongation product of 4.5-10.0 cN/dtex, a flatness (b/a) expressed by a major axis b and a minor axis a in a single filament cross section of 6.1-15.0, and a flatness CV value of 2.0 or less.　Provided is a polyamide multifilament having a flat cross-section and excellent practical durability of a knitted material or textile for clothing, and having a soft texture and an excellent aesthetic appearance.

Description

polyamide multifilament

The present invention relates to flat cross-section polyamide multifilaments suitable for woven and knitted fabrics in clothing applications. More particularly, the present invention relates to a polyamide multifilament that can provide a woven or knitted fabric with excellent softness, practical durability, and aesthetics when the flat cross-section polyamide multifilament of the present invention is used for clothing.

Synthetic fibers such as polyamide and polyester are widely used in clothing and industrial applications due to their excellent mechanical and chemical properties. In particular, polyamide fibers are widely used in general clothing such as stockings, innerwear, and sportswear due to their unique softness, high strength, abrasion resistance, color development, and hygroscopicity. .

Texture is one of the characteristics required for clothing products. A large number of flat yarns have been proposed as techniques for improving texture. For example, Patent Document 1 discloses oval or convex lens-shaped polyamide multifilament having a flatness of 1.5 to 5.0 and a fiber cross-sectional shape that is symmetrical with respect to the long axis, and a covering elastic yarn using the same. 2 proposes a covering elastic yarn having a single yarn fineness of 0.6 to 1.0 dtex and a cross-sectional shape symmetrical with respect to the long axis, and a stocking using the same. Further, in Patent Document 3, although it is used for airbags, the cross-sectional shape of the single yarn has a flattening ratio of 1.5 to 8, which is represented by the ratio a/b of the maximum major axis length a and the maximum minor axis length b. 0.0 synthetic fiber multifilament for both or one of warp and weft.

WO2020/105637 JP 2009-203563 A JP-A-2003-55861

The demand for texture has evolved with the times, and the pursuit of softness requires yarn with a higher degree of flatness. However, if the flatness is increased, the strength and abrasion resistance will decrease, resulting in a decrease in practical durability. Therefore, there has been a demand for a higher flatness while maintaining durability.

The flat cross-section polyamide multifilament described in Patent Document 1 is designed to minimize the spinneret hole in order to achieve high strength. This increases the variation in the strength and abrasion resistance, and causes fuzz, streaks, uneven gloss, and lacks aesthetics. In addition, even if the conditions described in Patent Document 1 are applied to Patent Document 2 to promote the relaxation of polymer orientation and lower the solidification point, such as keeping the atmosphere temperature under the die at a high temperature in order to increase the strength product, solidification A high degree of flatness could not be obtained in forming a flat cross section due to the decrease in the score, and the texture could not be differentiated. Furthermore, even if the flat cross-section polyamide multifilament described in Patent Document 3 is reduced in fineness in order to develop it for clothing applications, the slow cooling region is not appropriate and the cooling difference between single yarns is large, so the flatness, single yarn fineness, and raw yarn Variation in physical properties increases, strength and abrasion resistance decrease, fuzz, streaks, and uneven gloss occur, resulting in poor aesthetics.

The object of the present invention is to solve the above problems, and to provide a flat cross-section polyamide multifilament that is excellent in practical durability, soft touch and aesthetics for woven or knitted fabrics for clothing.

In order to solve the above problems, the present invention employs the following configuration.
(1) The total fineness is 4 to 100 dtex, the single yarn fineness is 1.1 to 5.0 dtex, the strength and elongation product is 4.5 to 10.0 cN / dtex, and the single yarn cross section is represented by the major diameter b and the minor diameter a. A polyamide multifilament having a flatness (b/a) of 6.1 to 15.0 and a flatness CV value of 2.0 or less.
(2) The polyamide multifilament according to (1) above, which has a flattening/smoothing rate of 1.5% or less.
Flatness smoothness (%) = (aM-am) / a × 100
(aM: maximum minor axis, am: minimum minor axis)
(3) A woven fabric comprising the polyamide multifilament described in (1) or (2) above.
(4) A knitted fabric comprising the polyamide multifilament described in (1) or (2) above.

The polyamide multifilament of the present invention is a polyamide multifilament characterized by high flatness, high strength and elongation product, and little variation in flatness between single filaments. Furthermore, the polyamide multifilament of the present invention can be used to obtain woven fabrics or knitted fabrics for clothing that are excellent in practical durability, soft touch, and aesthetics.

One embodiment of a production apparatus that can be preferably used in the method for producing a polyamide multifilament of the present invention Schematic cross-sectional model diagram showing a spinneret and a heating cylinder that can be preferably used in the method for producing a polyamide multifilament of the present invention. One embodiment of the ejection hole shape of a spinneret that can be preferably used in the method for producing a polyamide multifilament of the present invention One embodiment of the fiber cross-section of the polyamide multifilament of the present invention Hole arrangement of spinneret that can be preferably used in the method for producing polyamide multifilament of the present invention Hole arrangement of the spinneret used in Comparative Example 6

The present invention will be described in further detail below.

The polyamide constituting the polyamide multifilament of the present invention is a resin composed of a high molecular weight body in which a so-called hydrocarbon group is linked to the main chain via an amide bond, and such a polyamide is excellent in spinnability and mechanical properties. Polycaproamide (nylon 6) and polyhexamethylene adipamide (nylon 66) are mainly preferred, and polycaproamide (nylon 6) is more preferred because it is difficult to gel and has good spinning properties. 80 mol % of ε-caprolactam units constituting polycaproamide for polycaproamide and hexamethylenediammonium adipate units constituting polyhexamethylene adipamide for polyhexamethylene adipamide, respectively. or more, more preferably 90 mol % or more. Other components include, but are not limited to, polydodecanamide, polyhexamethyleneadipamide, polyhexamethyleneazelamide, polyhexamethylenesebacamide, polyhexamethylenedodecanamide, polymetaxylylene adipate. units of aminocarboxylic acid, dicarboxylic acid, diamine, etc., which are monomers constituting polyhexamethylene terephthalamide, polyhexamethylene isophthalamide, and the like.

Generally, titanium oxide is often used as a matting agent for polyamide multifilaments, but the polyamide of the present invention may also contain titanium oxide as a matting agent. The content of titanium oxide may be appropriately set within a range that does not impair the effects of the present invention, and the preferred range is 0 to 2% by weight. Moreover, various additives other than the above-described titanium oxide may be contained within a range that does not impair the effects of the present invention. Examples of these additives include stabilizers such as manganese compounds, heat-resistant agents, and flame retardants.

The polyamide multifilament of the present invention has a total fineness of 4 to 100 dtex and a single filament fineness of 1.1 to 5.0 dtex, and is mainly used for clothing applications that require a soft feel. By setting the total fineness in the range of 4 to 100 dtex, it is possible to obtain a clothing product excellent in soft feeling. If it is less than 4 dtex, the strength of the raw yarn is insufficient, the tear strength of the woven fabric and the burst strength of the knitted fabric are inferior, and the practical durability of the clothing product is impaired. Preferably, it is 70 dtex or less. Further, by setting the single yarn fineness in the range of 1.1 to 5.0 dtex, it is possible to obtain a clothing product excellent in soft feeling. If it is less than 1.1 dtex, fluff and pilling of woven and knitted fabrics are likely to occur, and the practical durability and aesthetics of clothing products are reduced. Preferably, it is 4.0 dtex or less.

The polyamide multifilament of the present invention has a strength and elongation product of 4.5 to 10.0 cN/dtex. Within this range, the fabric tear strength, the knit fabric burst strength, and the wear resistance are excellent, and the practical durability of the clothing product can be obtained. If it is less than 4.5, the practical durability of the clothing product is impaired. Preferably, it is 6.0 or more.

The polyamide multifilament of the present invention has a flatness (b/a) of 6.1 to 15.0, which is represented by the long diameter b and the short diameter a of the single filament cross section. The flatness referred to here is a line indicating the long diameter b, which is obtained by measuring the long diameter b of the single yarn cross section as shown in FIG. After drawing a straight line perpendicular to the major axis b from 5 points that divide the fiber into 6 equal parts, the line segment between the intersection points of the straight line and the fiber outline is the minor axis aN, and the five minor axes aN (a1, Flatness = b/a is calculated from the average value (minor axis a) of a2, a3, a4, a5). Flatness was measured for all filaments, and the average value was taken as the flatness referred to in the present invention. Also, of the minor axis aN, the maximum value is aM and the minimum value is am. By setting the flatness to such a range, the bending softness of the fibers is improved, and it is possible to obtain a clothing product that is superior in softness to the touch compared to the conventional technique, thereby achieving differentiation. If it is less than 6.1, it is not possible to obtain a clothing product that is soft to the touch and differentiated from the prior art. On the other hand, if it exceeds 15.0, the strength and elongation product will be lowered, and the tear strength of the fabric, the burst strength of the knitted fabric, and the wear resistance will be lowered, thus impairing the practical durability of the clothing product. It is preferably 7.0 to 14.0, more preferably 8.0 to 11.0.

The polyamide multifilament of the present invention has a flatness CV value of 2.0 or less. A flatness of 6.1 to 15.0 indicates a high flatness in terms of shape, so that it emits a strong luster due to the scattering and reflection of light. On the other hand, because of its shape, it is easy to bend and twist in the longitudinal direction. Therefore, the appearance of the fabric surface tends to look like streaks, and uneven gloss tends to occur. In addition, it has a very delicate shape that is prone to damage and fluffing at places where it is twisted and stressed. By setting the flatness CV value to 2.0 or less, a clothing product excellent in aesthetics can be obtained. The flatness CV value referred to here indicates the variation in flatness of each single yarn, and is a value obtained by dividing the standard deviation value of flatness of all filaments by the average value of flatness. Aesthetics is an expression that indicates the cleanness of the overall appearance of the surface of the fabric, free from product defects such as fluff, streaks, and gloss unevenness. If it exceeds 2.0, streaks, uneven luster, or fuzz may occur, or a combination thereof, resulting in poor aesthetics. In addition, the abrasion resistance is also inferior, impairing the practical durability of clothing products. It is preferably 1.5 or less.

The cross-sectional shape of the polyamide multifilament according to the embodiment of the present invention is not particularly limited as long as it has a flat shape, and the surface shape is not particularly limited. For example, a polyamide multifilament according to embodiments of the present invention may have a lens-shaped cross-section, a bean-shaped cross-section, a modified cross-section having 3-8 convexes and the same number of concaves. A particularly preferred form is the flat flat shape illustrated in FIG. 4(1).

The polyamide multifilament of the present invention preferably has a flatness smoothness of 1.5% or less. The flat smoothness ratio as used herein indicates the uniformity of the flat minor axis of the single yarn, and of the short diameter aN of the cross section of the single yarn, the maximum minor diameter aM and the minimum minor diameter am are expressed as (aM-am)/ax 100 was calculated, and the average value of all filaments was taken as the flatness/smoothness ratio. The smaller the number, the flatter the flatness of the cross section. The higher the number, the flatter the shape is, such as a lens-shaped cross section, a bean-shaped cross section, and an irregular cross-section with 3 to 8 convex parts and the same number of concave parts. It shows that it is a cross section. By setting the flatness/smoothness to 1.5% or less, a flat-type flat cross section with small irregularities as illustrated in FIG. 4 is obtained. By making the cross section of the flat type, when it is made into a woven fabric, the single yarns are easily laminated in the same direction, and the higher the flatness, the thinner the woven fabric, and the softer the texture is improved. In addition, the surface of the woven fabric becomes smooth, a strong glossy feeling is obtained, uneven gloss is suppressed, and aesthetics is improved. More preferably, it is 1.0% or less.

Next, one example of the method for producing the polyamide multifilament of the present invention will be specifically described. FIG. 1 shows one embodiment of a production apparatus preferably used in the method for producing polyamide multifilament of the present invention.

For the polyamide multifilament of the present invention, the polyamide is melted, the polyamide polymer is weighed and transported by a gear pump, and finally extruded from the discharge hole provided in the spinneret 1 to form each filament. As shown in FIG. 1, each filament discharged from the spinneret 1 in this way is surrounded by a gas supply device 2 for blowing out steam to suppress contamination of the spinneret over time, and for slow cooling. A heating cylinder 3 is provided as shown in FIG. After that, the multifilament is formed by applying an oil agent by the lubricating device 5 and by bundling each filament to form a multifilament. .

In the production of the polyamide multifilament of the present invention, it is preferable that the polyamide resin chips used have a relative viscosity of 2.5 to 4.0 in 98% sulfuric acid. The higher the 98% sulfuric acid relative viscosity, the easier it is to obtain a high flatness, while the higher the flatness, the lower the strength and elongation product. By setting it as such a range, the flatness and the strength and elongation product can be obtained. Also, from the viewpoint of spinning properties, if it is 3.5 or less, the extrusion pressure of the molten polymer during spinning and its rising speed over time can be suppressed, and an excessive load on production equipment and an extension of the spinneret replacement cycle can be achieved. , It is more preferable because productivity can be ensured. In the production of the polyamide multifilament of the present invention, the melting temperature is 20 ° C. higher than the melting point (Tm) of the polyamide (Tm + 20 ° C.) or higher, and 95 ° C. with respect to Tm. It is preferable to melt at a high temperature (Tm+95° C.) or lower. By setting the viscosity within such a range, the melt viscosity is suitable for melt spinning, so that stable spinning becomes possible.

In the production of the polyamide multifilament of the present invention, in order to achieve the desired flatness and flatness CV value, the spinneret ejection holes are optimized and the shear rate is set to an appropriate value. FIG. 3 shows one embodiment of the shape of the ejection holes of the spinneret. The discharge hole has a structure in which the circular holes at both ends are connected by slits, and in order to control the flatness to 6.1 to 15.0, the discharge hole width H (mm) of the spinneret 1 is minimized. do. In addition, in order to control the flatness CV value to 2.0 or less, the shear rate is lowered in order to reduce the stress applied to the polymer on the discharge hole wall (circumference). That is, the aspect ratio of the ejection hole (ejection hole length N/ejection hole width H shown in FIG. 3) is set to 15-30. By setting the thickness within such a range, it is possible to achieve both high and uniform flatness and excellent productivity. Preferably, the aspect ratio is 18-27.

Also, the discharge hole width H is set to 0.060 to 0.080 mm. More preferably, it is 0.065 to 0.075 mm. Flatness can be achieved by minimizing the width of the ejection hole within the range in which the polymer is stably ejected. Furthermore, in order to efficiently obtain a flat cross-section fiber that satisfies the single filament fineness, flatness, and flatness/smoothness of the present invention, the diameter D of the round hole shown in FIG. It is preferable that

However, the aspect ratio of the discharge holes is a high value of 15 to 30, and with such a discharge hole shape, differences in the cooling profile within each discharge hole and between each discharge hole are likely to occur. For this reason, variations between single yarns occur due to differences in the formation of fiber cross sections and differences in solidification points (flatness CV value increases). Therefore, it is possible to uniformize the cooling profile between the discharge holes and suppress the variation (flatness CV value) between the single yarns. FIG. 5 illustrates the case of an annular cooling device. The hole arrangement is such that a line segment connecting the center point of the mouthpiece and the length center point (N/2) of the discharge holes intersects perpendicularly with the line segment of the length of the discharge holes.

In the production of the polyamide multifilament of the present invention, in order to achieve the desired flatness and strength product, depending on the single filament fineness of the multifilament, a slow cooling area is installed under the spinneret to keep the ambient temperature at a high temperature. , After sufficiently accelerating the relaxation of the polymer orientation, it is rapidly solidified in the cooling zone to fix the cross-sectional shape of the fiber. FIG. 2 shows a schematic cross-sectional model diagram showing the spinneret and the heating tube.

In the production of the polyamide multifilament of the present invention, a heating cylinder 3 is provided above the cooling device 4 so as to surround each filament on its entire circumference. The orientation of the polyamide polymer discharged from the spinneret 1 can be improved by placing the heating cylinder 3 above the cooling device 4 and setting the atmospheric temperature in the heating cylinder within the range of 280 to 310°C. . A desired strength and elongation product can be achieved by promoting the relaxation of the orientation in the slow cooling zone from the mouthpiece surface to the bottom surface of the heating cylinder. If the heating cylinder is not installed, the slow cooling region is lost, and the orientation relaxation from the die surface to cooling is insufficient, so it is difficult to achieve the desired strength and elongation product.

The length L of the heating cylinder is preferably 30 to 80 mm, although it depends on the single filament fineness of the multifilament. By setting the length of the heating cylinder to 30 mm or more, the distance becomes sufficient to promote the relaxation of polymer orientation, and the desired strength and elongation product is achieved. A desired flatness is achieved by setting the thickness to 80 mm or less. More preferably, it is 40 to 70 mm.

Also, the heating cylinder is preferably multi-layered. In the total fineness range of the polyamide multifilament of the present invention, which is mainly used for clothing applications, if the temperature distribution in the heating cylinder is constant, the heat convection tends to be disturbed, and the solidification state of each filament. and become a factor that worsens U%. Therefore, by making the heating cylinder multi-layered and gradually lowering the temperature setting from the upper layer to the lower layer, it is possible to intentionally create a heat convection from the upper layer to the lower layer, creating a downdraft in the same direction as the accompanying flow of the yarn. , the turbulence of heat convection in the heating cylinder is suppressed, yarn swaying is small, and a multifilament with a small U% can be obtained. More preferably, the multilayer heating cylinder is composed of two or more layers, and the single layer length L1 of the multilayer heating cylinder is preferably in the range of 10 to 25 mm.

In the production of the polyamide multifilament of the present invention, it is important for the cooling device 4 to uniformly cool each single yarn, and cooling is performed by an annular cooling device. For example, an annular cooling device that blows rectified cooling air from the outer peripheral side toward the center or an annular cooling device that blows rectified cooling air from the center toward the outer periphery is used.

In the case of a uniflow cooling device that blows rectified cooling air from one direction, the flatness CV value increases due to the difference in cooling between the single yarn on the front side and the single yarn on the back side of the outlet.

In order to achieve the desired flatness, the solidification point of the polymer is raised. This is because the elastic force acting on the polymer is directed outward and acts in the direction that minimizes the surface area, thereby shortening the working time. That is, the solidification point of the polymer coming out of the lower surface of the heating cylinder and entering the cooling zone is brought as close to the upper end of the cooling zone as possible. The vertical distance LS from the lower surface of the spinneret to the upper end of the cooling air blowing portion of the cooling device 4 (hereinafter referred to as cooling start distance LS) is 30 to 100 mm.

Furthermore, in order to achieve the desired flatness CV value while maintaining high flatness, the polymer entering the cooling zone is rapidly cooled as uniformly as possible. The horizontal distance LF from the upper end of the cooling air blowing portion of the cooling device 4 to the yarn group (hereinafter referred to as the cooling start point-to-yarn distance LF) is 7 to 15 mm. By setting it to such a range, uniform cooling can be achieved by rectification, and since it is less susceptible to wind speed variations, a uniform flatness can be achieved. The base point of the yarn group is the farthest position from the cooling air blowing portion. L can be arbitrarily adjusted by the length of the heating cylinder and LF by the arrangement of the mouthpiece holes.

Also, from the viewpoint of the Nusselt heat exchange system, it is preferable to increase the cooling wind speed as an effective method of bringing the solidification point closer to the upper end. It is preferably in the range of .0 to 6.0 m/min. When the velocity is 4.0 m/min or more, the heat exchange rate of the polymer increases and the solidification point approaches the upper end surface of the cooling zone, thereby realizing the desired flatness. On the other hand, from the viewpoint of operability, 6.0 m/min or less is preferable. Also, the temperature of the cooling air in the cooling zone is also an important factor in heat exchange, and the temperature of the cooling air is preferably 20° C. or less. When the temperature is 20° C. or lower, the heat exchange rate of the polymer increases and the solidification point approaches the upper end surface of the cooling zone, thereby realizing the desired flatness.

In the production of the polyamide multifilament of the present invention, the position of the lubricating device 5, that is, the vertical distance Lg from the lower surface of the spinneret in FIG. It is preferably 800 to 1,500 mm, more preferably 1,000 to 1,300 mm, depending on the fineness and cooling efficiency of the filaments from the cooling device. When the length is 800 mm or more, the filament temperature drops to an appropriate level when the oil is applied, and when the length is 1500 mm or less, yarn sway due to downdraft is small, and a multifilament with a low U% can be obtained. In addition, when it is 1500 mm or less, the distance from the solidification point to the oiling position is shortened, which reduces the accompanying flow, and the spinning tension is reduced, which suppresses the spinning orientation, and the drawability is excellent, so the strength is high. It is preferable from the point of view of conversion. When the length is 800 mm or more, the bending of the yarn from the mouthpiece to the lubricating guide becomes appropriate, the influence of rubbing on the guide is less likely to occur, and the increase in strength is less reduced.

The present invention will be described in more detail below with reference to examples.

A. Strength and Elongation Product A fiber sample is measured according to JIS L1013 (2010) Tensile Strength and Elongation, and a tensile strength-elongation curve is drawn. As for the test conditions, the type of tester was a constant speed elongation type, the grip interval was 50 cm, and the tensile speed was 50 cm/min. When the tensile strength at break was smaller than the maximum strength, the maximum tensile strength and elongation at that time were measured.

The strength and strength/elongation product were determined by the following formulas.
Elongation = elongation at break (%)
Strength = tensile strength at break (cN) / fineness (dtex)
Strength and elongation product = {strength (cN / dtex)} × {elongation (%) + 100} / 100
B. A fiber sample is set on a measuring scale with a total fineness of 1.125 m/circumference, rotated 500 times to create a loop-shaped skein, dried with a hot air dryer (105 ± 2 ° C. x 60 minutes), and then weighed. The fineness was calculated from the value obtained by weighing the skein and multiplying it by the official moisture content. The official moisture content was 4.5%.

C. Sulfuric acid relative viscosity (ηr)
0.25 g of a polyamide chip sample was dissolved to 1 g in 100 ml of sulfuric acid having a concentration of 98% by mass, and the flowing time (T1) at 25° C. was measured using an Ostwald type viscometer. Subsequently, the flow-down time (T2) of sulfuric acid having a concentration of 98% by mass was measured. The ratio of T1 to T2, ie, T1/T2, was defined as the sulfuric acid relative viscosity.

D. Flatness Cut out a thin piece in the cross-sectional direction at an arbitrary position of the fiber, photograph the fiber cross-section of all filaments with a transmission microscope, print out at a magnification of 1000 (Mitsubishi Electric Co., Ltd. SCT-P66), and then use a scanner ( Epson's GT-5500WINS) was used to take in (black-and-white photographs, 400 dpi), and image processing software (WINROOF) was used while being magnified 1500 times on the display. Measure the major diameter b of the single yarn cross section, divide the line segment showing the major diameter b into 6 equal parts, draw a straight line perpendicular to the major diameter b from 5 points, and then draw a line segment between the intersection points of the straight line and the fiber outline. is the minor axis aN, and the flatness = b/a is calculated from the average value (minor axis a) of five measured minor axes aN. The flatness of all filaments was measured, and the numerical average of the obtained values was taken as the flatness.

E. Flatness CV value (%)
The flatness CV value was obtained by calculating the standard deviation of the flatness of all the filaments measured above and dividing it by the average value of the flatness.

F. Flatness/Smoothness For measurement of flatness, (aM-am)/a×100 is calculated for the maximum minor diameter aM and the minimum minor diameter am of the minor diameter aN of the single filament cross section, and the average value of all filaments is the flatness and smoothness. rate.

G. Fabric evaluation (a) Tear strength For the woven product produced by the same method as in Example 1, the tear strength was measured at any three points according to JIS L-1096 (2010) (8.17 A method). Mean values were measured. Four grades were evaluated according to the following criteria.
S: 4.5N or more A: 4.1N or less than 4.5N B: 3.7N or less than 4.1N C: less than 3.7N.

(b) Abrasion strength For the textile product produced by the same manufacturing method as in Example 1, measure the pilling abrasion strength at any three points according to JIS L-1076 (2012) (8.1.1 A method). and the average value was measured.
S: Grade 5 A: Grade 4 B: Grade 3 C: Grade 2 or lower Both tear strength and abrasion strength made SAB acceptable for durability.

(c) Feel The softness of the woven product produced by the same manufacturing method as in Example 1 was evaluated by inspectors (5 people) with extensive experience in evaluating the feel of the fabric. Then, a relative evaluation was made using a woven fabric prepared by the same manufacturing method as in Example 1 as a reference. The results were evaluated by each examiner, and the average value of the five examiners (rounded off to the nearest whole number) was 5 for S, 4 for A, 3 for B, and 1 to 2 for C. SAB was judged to have passed the texture.
5 points: very excellent 4 points: somewhat excellent 3 points: normal 2 points: somewhat inferior 1 point: inferior.

(d) Aesthetics Regarding the textile products produced by the same manufacturing method as in Example 1, inspectors (5 people) with extensive experience in appearance inspections comprehensively viewed the fabric without fluff, streaks, gloss unevenness, etc., which are product defects. The appearance of the surface was judged according to the following criteria. The results were evaluated by each examiner, and the average value of the five examiners (rounded off to the nearest whole number) was 5 for S, 4 for A, 3 for B, and 1 to 2 for C. SAB was considered aesthetically acceptable.
5 points: No fluff, streaks, or uneven gloss 4 points: No fluff or streaks 3 points: No fluff 2 points: No streaks 1 point: No uneven gloss.

[Example 1]
As a polyamide, nylon 6 chips having a sulfuric acid relative viscosity (ηr) of 3.3, a melting point of 225° C. and containing no titanium oxide were dried by a conventional method so as to have a moisture content of 0.03% by mass or less. The obtained nylon 6 chips were melted at a spinning temperature (melting temperature) of 298° C. and discharged from a spinneret (discharge rate: 39.2 g/min). The spinneret had 68 holes, 2 threads per spinneret, and as shown in FIG. , was used.

The spinning machine was spun using the spinning machine shown in FIG. A heating cylinder having a length of L50 mm was used, and the ambient temperature of the heating cylinder was set to 290°C. Each filament discharged from the spinneret is cooled from the outer circumference to the center with a cooling start distance LS of 60 mm, a cooling start point-to-yarn distance LF of 10 mm, a wind temperature of 18 ° C., and a wind speed of 5.0 m / min. The yarn was passed through an annular cooling device 4 to cool and solidify to room temperature. After that, the oil solution was applied at a position Lg of 1300 mm from the face of the nozzle, and each filament was bundled to form a multifilament. Convergence was imparted by injecting high-pressure air onto the running yarn in the device 6 . The pressure of the injected air was 0.2 MPa (flow rate 30 L/min). After that, it is drawn so that the drawing ratio between the take-up roller 7 and the drawing roller 8 is 1.8 times, and it is wound by the winder 9 at 3500 m/min. A nylon 6 multifilament was obtained.

The obtained multifilaments were used for warp and weft, and woven in a plain weave with a warp density of 188/2.54 cm and a weft density of 155/2.54 cm. The obtained gray fabric was dyed in the following (a) to (e) to obtain a fabric with a warp density of 200/2.54 cm and a weft density of 160/2.54 cm.
(a) Refining: Neugen WS 5 ml/L, sodium hydroxide 5 g/L, liquor ratio 1:50, 95°C x 60 minutes,
(b) Intermediate set: 180 ° C. x 1 minute (c) Dyeing: Acid dye (Nylosan Blue-GFL 167% (manufactured by Sandos) 1.0% owf, 98 ° C. x 60 minutes (d) Fixing treatment: Synthetic tannin (nylon Fix 501 (manufactured by Senka Co., Ltd.) 3 g/l, 80° C.×20 minutes (e) Finishing set: 200° C.×1 minute Table 1 shows the evaluation results of the obtained flat nylon 6 multifilament and woven fabric.

[Examples 2 and 3] [Comparative Examples 1 and 2]
A flat nylon 6 multifilament of 56 dtex and 34 filaments was obtained in the same manner as in Example 1 except that the heating cylinder length L and the cooling start distance LS were changed as shown in Table 1 to obtain a woven fabric. Table 1 shows the evaluation results.

[Examples 4 and 5]
A flat nylon 6 multifilament of 56 dtex and 34 filaments was obtained in the same manner as in Example 1 except that the sulfuric acid relative viscosity (ηr) of the polyamide was changed as shown in Table 1 to obtain a woven fabric. Table 1 shows the evaluation results.

[Examples 6 and 7] [Comparative Examples 3 and 4]
A flat nylon 6 multifilament of 56 dtex and 34 filaments was obtained in the same manner as in Example 1 except that the aspect ratio of the discharge hole of the spinneret shown in FIG. 3 was changed as shown in Table 2, and a woven fabric was obtained. Table 1 shows the evaluation results.

[Example 8]
The number of holes of the spinneret was 48, two threads per spinneret, and the aspect ratio of the ejection holes of the spinneret shown in FIG. A 78 dtex, 24 filament, flat nylon 6 multifilament was obtained in the same manner as in 1 to obtain a woven fabric.

[Example 9]
The number of holes of the spinneret was 48, two threads per spinneret, and the aspect ratio of the ejection holes of the spinneret shown in FIG. A 100 dtex, 24 filament, flat nylon 6 multifilament was obtained in the same manner as in 1 to obtain a woven fabric.

[Comparative Example 5]
A 56 dtex, 34 filament, and a flat nylon 6 multifilament were obtained in the same manner as in Example 1, except that the cooling device 4 was changed to a uniflow system that blows cooling rectified air in one direction to obtain a woven fabric. Table 2 shows the evaluation results.

[Comparative Example 6]
A nylon 6 multifilament of 56 dtex and 34 filaments was obtained in the same manner as in Example 1 except that the spinneret was changed to a hole arrangement in which the cooling air hit in parallel with the major axis direction of the flat cross section as shown in FIG. , a woven fabric was obtained. Table 2 shows the evaluation results.

[Comparative Examples 7 and 8]
A nylon 6 multifilament of 56 dtex and 34 filaments was obtained in the same manner as in Example 1 except that the cooling start point-to-yarn distance LF was changed as shown in Table 2 to obtain a woven fabric. Table 2 shows the evaluation results.

[Comparative Example 9]
A 56 dtex, 34 filament, flat nylon 6 multifilament was obtained in the same manner as in Example 1 except that the spinneret shown in FIG. Obtained. Table 2 shows the evaluation results.

1: Spinneret 2: Gas supply device 3: Heating cylinder 4: Cooling device 5: Lubricating device 6: Fluid nozzle device 7: Take-up roller 8: Stretching roller 9: Winding device L: Heating cylinder length LS: Cooling start distance LF: Cooling start point - yarn distance Lg: Oil supply position N: Discharge hole length H: Discharge hole width D: Round hole diameter a: Minor diameter of flat cross section b: Long diameter of flat cross section

Claims

The total fineness is 4 to 100 dtex, the single yarn fineness is 1.1 to 5.0 dtex, the strength and elongation product is 4.5 to 10.0 cN/dtex, and the flatness is expressed by the major diameter b and the minor diameter a of the single yarn cross section. A polyamide multifilament having a (b/a) of 6.1 to 15.0 and a flatness CV value of 2.0 or less.
2. The polyamide multifilament according to claim 1, wherein the flattening smoothness is 1.5% or less.
Flatness smoothness (%) = (aM-am) / a × 100
aM: maximum minor axis am: minimum minor axis
A fabric containing the polyamide multifilament according to claim 1 or claim 2.
A knitted fabric comprising the polyamide multifilament according to claim 1 or claim 2.