Polyamide 46 Multifilament

Abstract

This polyamide multifilament is characterized in that after heat treatment at a strength of 6.0-9.0 cN / dtex, an elongation of 15-30%, and 120 °C for 24 hours, an elongation rate (E'10) after 10 times of tensioning in a room temperature environment is less than 2.5%, and a difference (E'10-E'1) between an elongation rate (E'1) after the heat-treated fiber is tensioned one time in the room temperature environment and the elongation rate (E'10) after 10 times of tensioning is less than 0.60%.　Provided is a polyamide multifilament having high strength, high thermal dimensional stability, and excellent stretchability.

Description

[Technical field]

[0001] The present invention relates to polyamide 46 multifilaments. [Background technology]

[0002] Multifilaments produced using aliphatic polyamides are high-strength polyamide multifilaments that have superior properties such as high strength and high elongation compared to multifilaments made from other materials.

[0003] One of the applications of high-strength polyamide multifilaments is industrial belt cords. In particular, polyamide 66 is widely used for belt cords because it has a high melting point and high strength among polyamides, yet is inexpensive. Compared to polyamide 66, polyamide 46 has an even higher melting point and high heat resistance, and therefore has excellent thermal dimensional stability, making it a suitable material for belt cords. A technology for improving strength by improving spinning and drawing conditions (Patent Document 1) has been disclosed. Alternatively, a technology for improving thermal dimensional stability (Patent Documents 2 and 3) has also been disclosed, and there have been inventions to further improve the properties of polyamide 46 as a belt cord. However, although some technologies for improving the strength and thermal dimensional stability of polyamide 46 multifilaments have been reported, there have been almost no disclosures of technologies for improving stretchability, and furthermore, there has been no disclosure at all of a technology for improving stretchability while maintaining thermal dimensional stability, that is, a technology for achieving both thermal dimensional stability and stretchability.

[0004] Stretchability is a useful property not only for belt cords, but also for sewing threads, and if stretchability can be exhibited, particularly at high temperatures, the range of application in various applications will be expanded. As a method for imparting stretchability to polyamide multifilament, for example, a method has been disclosed in which a semi-oriented polyamide multifilament is used as a sheath thread and taslan-processed with a polyamide multifilament core thread (Patent Document 4). However, such conventional stretchability-producing technology results in a raw yarn design that impairs strength, making it difficult to apply to industrial applications that require high strength.

[0005] That is, the prior art does not provide a polyamide 46 multifilament that has all of high strength, high thermal dimensional stability, and excellent stretchability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 59-88910 [Patent Document 2] Japanese Patent Application Publication No. 59-76914 [Patent Document 3] Japanese Patent Application Publication No. 1-168914 [Patent Document 4] JP 2002-249943 A Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to solve the above problems and to provide a polyamide 46 multifilament having high strength, high thermal dimensional stability and excellent stretchability. [Means for solving the problem]

[0008] In order to achieve the above object, the polyamide monofilament of the present invention has the following configuration.

[0009] That is, it is a polyamide 46 multifilament characterized by having a strength of 6.0 to 9.0 cN / dtex, an elongation of 15 to 30%, an elongation (E'10) after heat treatment at 120°C for 24 hours and then tensile testing 10 times in a room temperature environment of less than 2.5%, and a difference (E'10-E'1) between the elongation (E'1) after the heat-treated fiber is tensile tested once in a room temperature environment and the elongation (E'10) after tensile testing 10 times in a room temperature environment of less than 0.60%.

[0010] In addition, the preferable conditions are that the difference (E10-E1) between the elongation percentage after one stretch at room temperature (E1) and the elongation percentage after ten stretches at room temperature (E10) is less than 0.70%, the heat shrinkage percentage at 120°C is 0.5 to 2.0%, the relative viscosity of sulfuric acid is 3.0 to 5.0, and the total fineness is 300 dtex to 2300 dtex.

[0011] The polyamide 46 multifilament of the present invention is produced by melt spinning polyamide 46 and drawing the spun undrawn yarn in multiple stages, the multiple stages including at least a first stage drawing and a final stage drawing, and the final stage drawing is performed at a draw ratio of 1.00 to 1.10. Furthermore, the polyamide 46 multifilament is produced by melting the polyamide 46 in a vacuum during melt spinning. Effect of the Invention

[0012] According to the present invention, as described below, it is possible to provide a polyamide 46 multifilament having high strength, high thermal dimensional stability and excellent stretchability. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of the manufacturing process of the polyamide 46 multifilament of the present invention (the melting process is omitted). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The polyamide 46 multifilament of the present invention will be described below.

[0015] In order to achieve the above object, the polyamide 46 multifilament of the present invention is made of a polyamide resin. As the polyamide resin, a polyamide resin whose main component is polyamide 46 is preferable. In particular, it is more preferable to use a polyamide resin whose main component is 98% by mass or more of polyamide 46, excluding additives described later, from the total mass, and it is even more preferable to use only polyamide 46. It is also possible to use polyamide 46 copolymerized with other polyamides, and polyamide 6, polyamide 66, polyamide 610, and polyamide 612 can be used as polyamides used for copolymerization. In addition, it may be a mixture of polyamide 46 and other polyamides. By using polyamide 46, which has a high melting point, as the main component, a multifilament with high heat resistance can be produced.

[0016] It is preferable to add 250 to 7000 ppm, preferably 500 to 5000 ppm, of heat-resistant agents such as conventional inorganic and organic copper salts, copper compounds such as simple copper metal, amine compounds, mercapto compounds, phosphorus compounds, and hindered phenol compounds to the polyamide resin. These may be used alone or in combination. If the amount of these heat-resistant agents is less than 250 ppm, the suppression of thermal deterioration of the polymer is limited, and the strength and elongation of the filament at high temperatures decreases. On the other hand, if more than 7000 ppm of heat-resistant agents are added, the strength and elongation of the fiber tends to be impaired.

[0017] The sulfuric acid relative viscosity of polyamide 46, which is the raw material of the polyamide 46 multifilament of the present invention, is preferably 3.0 to 5.0, more preferably 3.5 to 5.0. If the sulfuric acid relative viscosity exceeds the above range, it contributes to deterioration of spinnability and tends to frequently cause yarn breakage and fluffing during drawing. If the sulfuric acid relative viscosity is less than 3.5, the molecular chain of the polyamide is short, so that the stretchability and thermal dimensional stability required for the above-mentioned applications cannot be expressed. The sulfuric acid relative viscosity refers to a value measured by the method described in the Examples section.

[0018] The polyamide 46 multifilament of the present invention preferably has a fineness of 300 to 2300 dtex, more preferably 400 to 1700 dtex. If the fineness is less than 200 dtex, the fineness is too small, and there is a high possibility that fuzz will be generated during hot drawing of the multifilament after melt spinning. If the fineness is more than 2300 dtex, not only will it be difficult to use it as a sewing thread, but the uniform cooling during spinning will deteriorate, resulting in a decrease in the quality of the raw yarn, and the strength and durability of the belt may decrease.

[0019] The number of single fibers in the polyamide 46 multifilament of the present invention is preferably 30 to 350, more preferably 50 to 250. If the number is less than this range, the single fiber fineness becomes thick, the cooling efficiency during melt spinning becomes low, and the flexibility of the multifilament tends to be lost. On the other hand, if the number is more than this range, the single fiber fineness becomes thin, and fluff tends to be easily generated.

[0020] The strength of the polyamide 46 multifilament of the present invention must be 6.0 to 9.0 cN / dtex, and more preferably 7.0 to 9.0 cN / dtex. This strength range is also a property required for polyamide multifilaments when used in many products, and it has been discovered that this range is essential for obtaining polyamide 46 multifilaments that have both thermal dimensional stability and stretchability. The strength refers to a value measured by the method described in the Examples section.

[0021] The elongation (breaking elongation) of the polyamide 46 multifilament of the present invention must be 15 to 30%, and more preferably 18 to 30%. If it is in this range, the belt can absorb shock by stretching when a load is applied to the belt, and the durability of the belt can be maintained. The elongation is a value measured by the method described in the Examples section.

[0022] The cross-sectional shape of the single fiber of the polyamide 46 multifilament of the present invention is not particularly limited. Various cross-sectional shapes can be adopted, including a round cross-section, flat, polygonal, Y-shaped, X-shaped, and other irregular shapes, and hollow. A mixture of multiple cross-sectional shapes is also acceptable.

[0023] The polyamide 46 multifilament of the present invention preferably has a difference (E10-E1) between the elongation percentage after one stretch at room temperature (E1) and the elongation percentage after ten stretches at room temperature (E10) of less than 0.70%. More preferably, it is less than 0.60%. If it exceeds this range, the hysteresis loss becomes too large for use as a belt cord, and the belt tension decreases with each use time, so that the product may not be suitable for medium to long-term use. The repeated tensile test and the method for calculating the elongation percentage are described in the Examples section.

[0024] The elongation (E'10) of the fiber after 24 hours of treatment at 120°C and 10 times of tension at room temperature must be less than 2.5%, more preferably less than 2.0%. Furthermore, the difference (E'10-E'1) between the elongation (E'1) after one tension at room temperature and the elongation (E'10) after 10 times of tension at room temperature must be less than 0.60%, more preferably less than 0.50%. During use of the belt, the temperature of the belt and the cord becomes high due to the load, friction, and usage environment. Therefore, if the difference between these elongations is too high, the tension of the belt will decrease over time in the temperature range from room temperature to high temperatures. The 24 hours of treatment at 120°C, the repeated tension test, and the method of calculating the elongation will be described in the Examples section.

[0025] The heat shrinkage of the polyamide 46 multifilament of the present invention at 120°C is preferably 0.5 to 2.0%, more preferably 0.5 to 1.7%. If the heat shrinkage is below this range, tension is not generated against the temperature rise caused by friction during belt driving, and the multifilament may lose its stretchability. If the heat shrinkage exceeds this range, the thermal dimensional stability may be impaired.

[0026] Hereinafter, one embodiment of the method for producing the polyamide 46 multifilament of the present invention will be described.

[0027] The polyamide 46 multifilament of the present invention is preferably produced by melt spinning, and as described above, the relative viscosity in sulfuric acid of the nylon 46 resin used in melt spinning is preferably 3.0 to 5.0, more preferably 3.5 to 5.0. Within this range, a high-strength nylon 46 multifilament can be stably obtained with good spinnability.

[0028] An outline of one embodiment of the method for producing the polyamide 46 multifilament of the present invention is shown in FIG. 1 (the melting step is not shown).

[0029] The polyamide 46 resin is melted, kneaded and spun in an extruder-type spinning machine, and the melting is preferably performed in a vacuum environment. In the vacuum environment, the pressure at the resin supply port of the extruder is preferably less than 5 kPa, more preferably less than 3 kPa. Unlike other aliphatic polyamides that thicken when melted and produce high molecular weight substances, polyamide 46 has the property of decomposing when melted and producing low molecular weight substances. The decomposition mechanism can be broadly divided into thermal decomposition, oxidative decomposition, and hydrolysis, and melting under vacuum eliminates water and oxygen in the air, limiting the decomposition mechanism to thermal decomposition only, making it possible to suppress the decomposition of the resin. By suppressing the decomposition during melting, the molecular weight of the resin constituting the multifilament can be maintained high, and a highly crystallized polyamide 46 multifilament can be formed, thereby producing a product that has both stretchability and thermal dimensional stability.

[0030] The spinning temperature is set to 10 to 50°C higher than the melting point of the polymer, and melt spinning is performed from a spinneret 1 having a plurality of holes, preferably 30 to 350, more preferably 50 to 250. It is preferable to surround the area of ​​5 to 300 cm from directly below the spinneret with a heating cylinder 2, and pass the melt-spun yarn through a high-temperature atmosphere at -30 to +30°C relative to the melting point. The high-temperature atmosphere through which the yarn is passed is more preferably -15 to +15°C relative to the melting point. By gradually cooling the spun yarn through the high-temperature atmosphere surrounded by the heating cylinder without immediately cooling it, the orientation of the melt-spun polyamide 46 molecules is relaxed, and the uniformity of the molecular orientation between the single fibers can be improved, so that the strength of the polyamide 46 filament can be increased. On the other hand, if the yarn is immediately cooled without passing through a high-temperature atmosphere, the orientation of the undrawn yarn is increased, and the variation in the degree of orientation between the single fibers becomes large. If such an undrawn yarn is hot-drawn, there is a possibility that a high-strength polyamide 46 multifilament cannot be obtained as a result.

[0031] The undrawn yarn that has passed through the above steps is cooled and solidified by blowing air at 10 to 80°C, preferably 10 to 50°C, onto it using a cross-flow cooling device 3. If the cooling air temperature is less than 10°C, a large cooling device is required, which is not preferable. If the cooling air temperature exceeds 80°C, a large amount of air is required, which increases the shaking of the single fibers, causing collisions between the single fibers, etc., which causes deterioration of spinnability.

[0032] The cooled and solidified undrawn yarn is then preferably drawn in multiple stages, particularly in two or three stages. In the case of three-stage drawing, as specifically illustrated in FIG. 1, first, an oil is applied to the cooled and solidified undrawn yarn by an oiling device 4, and the yarn is taken up by a take-up roller (1FR) 6. The take-up roller is usually unheated. The yarn is then wound in the order of a yarn feed roller (2FR) 7, a first draw roller (1DR) 8, a second draw roller (2DR) 9, a third draw roller (3DR) 10, and a relaxation roller (RR) 11, and is subjected to a heat treatment and a draw treatment, and is then taken up by a winder 12. It is preferable that the surface of 2FR is a mirror finish, and the surfaces of 1DR, 2DR, 3DR, and RR are matte finish.

[0033] The first stage of stretching is performed between the 2FR and the 1DR, with the temperature of the 2FR (roller surface temperature) being 30-50°C and the temperature of the 1DR being 100-225°C. The second stage of stretching is performed between the 1DR and the 2DR, with the temperature of the 2DR (roller surface temperature) being 150-230°C. The third stage of stretching is performed between the 2DR and the 3DR, with the temperature of the 3DR (roller surface temperature) being 180-240°C.

[0034] Here, in the production of the polyamide 46 multifilament of the present invention, it is important that the draw ratio in the third drawing step, i.e., the final drawing step, is 1.00 to 1.10, and it is more preferable that the draw ratio is 1.00 to 1.05. By performing drawing under these conditions, not only can the crystallinity be increased, but also the orientation of the non-crystalline part can be maintained. Therefore, it is possible to provide a multifilament that exhibits high strength, thermal dimensional stability, and high stretchability. If the draw ratio is greater than the above range, the orientation of the non-crystalline part of the molecular chain becomes high, which deteriorates the thermal dimensional stability, and if the generation of fluff becomes significant, the strength tends to be impaired. If the draw ratio is lower than 1.00, the tension decreases, which may cause large yarn swaying and make spinning difficult.

[0035] In this manner, the polyamide 46 multifilament of the present invention can be obtained. EXAMPLES

[0036] [Relative viscosity of sulfuric acid] 1 g of a sample was dissolved in 100 ml of 98% sulfuric acid, and the viscosity was measured at 25° C. using an Ostwald viscometer. The average value of two measurements was used.

[0037] [Multifilament fineness] Measured according to JIS L1090 ​​(1999).

[0038] [Fiber strength and elongation] The tensile strength and elongation measured according to the method of JIS L1013 (1999) were regarded as the strength and elongation. The measurements were performed using a Tensilon tensile tester manufactured by Orientec Co., Ltd. under the conditions of a test length of 250 mm and a tensile speed of 300 mm / min. The measurements were performed three times for each sample, and the average values ​​were calculated.

[0039] [Elongation after repeated tensile testing at room temperature] A fiber having a test length of 250 mm was clamped in the chuck of a Tensilon tensile tester manufactured by Orientec Co., Ltd. in an environment of 25°C, and pulled at a speed of 300 mm / min until a load of 2.0 cN / dtex was reached, and then the operation of returning to the original chuck gap at a speed of 300 mm / min was repeated a specified number of times. The elongation at which a load of 0.1 cN / dtex was indicated at the specified number of return operations in the repeated tensile test was defined as the elongation after repeated tensile tests. That is, the elongation at which a load of 0.1 cN / dtex was indicated when the fiber was pulled once and returned to the original chuck gap after the pulling and return operations were repeated nine times was defined as E10.

[0040] [120℃ 24 hour treatment] In a 25℃ environment, a fiber with a test length of 250 mm is clamped in the chuck of an A&D Tensilon tensile testing machine RTG-1250, and an A&D high and low temperature environmental chamber TLF-3R / F / GS is set, and the fiber is treated at 120℃ for 24 hours.

[0041] [Elongation after repeated tensile testing at room temperature after 24 hours at 120℃] Remove the yarn from the high and low temperature environmental chamber, and in a 25℃ environment, subject a 250 mm test length of fiber to repeated tension using an A&D Tensilon tensile testing machine RTG-1250, in the same manner as in [Elongation after repeated tensile tests in a room temperature environment], and calculate the elongation.

[0042] [Heat shrinkage rate at 120℃] A test piece of fiber with a length of 250 mm was treated at 120°C for 2 minutes using a TST2 manufactured by Lenzing Instrument, and the fiber shrinkage rate ({(length before treatment - length after treatment) / length before treatment} x 100 (%)) was measured before and after the treatment.

[0043] [Spinning] Polyamide 46 was melt-spun, and the spun undrawn yarn was drawn in multiple stages, and drawn at least in the first drawing stage and the final drawing stage, in which the yarn was produced according to the following Examples and Comparative Examples, and the yarn breakage and amount of fluff were evaluated as follows. Yarn breakage is a state in which the yarn breaks during production, making it impossible to produce. A: The number of yarn breakages per hour is less than 0.1, and the number of fuzz particles per 10,000 m is less than 1. B: The number of yarn breakages per hour is 0.1 or more, or the number of fuzz particles per 10,000 m is 1 or more. C: The thread breaks frequently, making it impossible to harvest raw thread.

[0044] Example 1 (Manufacturing method of polyamide 46 multifilament) The manufacturing process shown in FIG. 1 was used.

[0045] Polyamide 46 resin ("Stanyl" (registered trademark), melting point 292°C) with a sulfuric acid relative viscosity of 3.9 was melted at 305°C under vacuum using an extruder-type spinning machine. The molten polymer was measured with a gear pump so that the total fineness was 940 dtex, and then filtered with a 20μ metal nonwoven fabric filter in a spinning pack and spun from a nozzle with 136 round holes. A heating cylinder with a length of 15 cm was installed 3 cm below the nozzle surface, and the atmosphere inside the cylinder was heated to 300°C, so that the spun yarn passed through an atmosphere of 300°C. The atmosphere temperature inside the cylinder refers to the air temperature at the center of the heating cylinder length, 1 cm away from the inner wall.

[0046] A uniflow chimney that blows air from one direction was installed directly below the heating barrel, and cold air at 20°C was blown onto the yarn after it passed through the heating barrel at a speed of 35 m / min to cool and solidify it, after which an oiling device was used to apply oil to the yarn.

[0047] The undrawn yarn to which the oil agent was applied was wound around the 1FR rotating at a surface speed of 600 m / min, and then drawn at a total draw ratio of 4.70. The drawn yarn was continuously stretched by 5% between the take-up roller and the 2FR without being wound up, and then the first stage drawing was performed at a rotation speed ratio of 3.27, then the second stage drawing was performed at a rotation speed ratio of 1.30, and finally the third stage drawing was performed at a rotation speed ratio of 1.05, and then the yarn was wound up at a speed of 2600 m / min. The roller surfaces of the 1FR and 2FR were mirror-finished, and the 1DR, 2DR, 3DR, and RR were matte-finished. The roller temperatures of the 1FR were unheated, the 2FR was 80°C, the 1DR was 175°C, the 2DR was 180°C, the 3DR was 230°C, and the RR was 150°C. A nylon 46 multifilament was obtained by such melt spinning and drawing (Table 1).

[0048] The physical properties of the resulting fibers were evaluated and are shown in Table 2.

[0049] Example 2 The same procedure as in Example 1 was carried out, except that the third-stage draw ratio (final draw ratio) during spinning of the nylon 46 multifilament was set to 1.00.

[0050] Example 3 The same procedures as in Example 1 were carried out except that the molten polymer was metered by a gear pump during melt spinning so that the fineness would be 1,400 dtex, and a spinneret having 204 round holes was used.

[0051] Example 4 The same procedure as in Example 1 was carried out except that during melt spinning, the molten polymer was metered using a gear pump so that the fineness was 470 dtex, a 72-hole round nozzle was used, and drawing was performed at a total draw ratio of 4.20 times.

[0052] Example 5 The same procedure as in Example 1 was carried out except that two-stage drawing was performed and the final draw ratio was 1.08 times.

[0053] Comparative Example 1 The same procedure as in Example 1 was carried out except that the final stretching ratio was 1.25 times.

[0054] Comparative Example 2 The same procedure as in Example 1 was carried out except that the final stretching ratio was 0.90 times.

[0055] Comparative Example 3 The same procedure as in Example 1 was carried out, except that melt spinning using an extruder-type spinning machine was carried out under normal pressure.

[0056] Comparative Example 4 The same procedure as in Example 4 was carried out, except that the molten polymer was metered by a gear pump during melt spinning so that the fineness was 235 dtex.

[0057] Comparative Example 5 The same procedure as in Example 1 was repeated, except that a polyamide 66 polymer having a relative viscosity in sulfuric acid of 3.7 was melt-spun at 280° C. under vacuum using an extruder-type spinning machine.

[0058] Comparative Example 6 The same procedure as in Example 1 was carried out except that a polyamide 6 polymer having a relative viscosity in sulfuric acid of 3.7 was melt-spun at 260° C. under vacuum using an extruder-type spinning machine.

[0059] [Table 1]

[0060] [Table 2]

[0061] The production conditions in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1, and the evaluation results of the physical properties of the obtained polyamide 46 multifilaments are shown in Table 2.

[0062] As is clear from Table 2, the polyamide 46 multifilament of the present invention has high strength, high thermal dimensional stability, and exhibits superior stretchability.

[0063] On the other hand, the multifilaments of Comparative Examples 5 and 6, which are conventional technologies, have high strength but low stretchability, making it impossible to maintain tension when made into belt cords or sewing threads.

[0064] Furthermore, as in Comparative Example 3, melting under normal pressure causes the polymer to decompose, making it impossible to obtain a high-strength multifilament, and furthermore, the low crystallinity results in poor stretchability.

[0065] Furthermore, when producing a high-strength polyamide 46 multifilament, if the draw ratio in the final drawing step exceeds 1.1 as in Comparative Example 1, crystallization does not occur and the thermal dimensional stability or stretchability deteriorates. On the other hand, in Comparative Example 2, the draw ratio in the final drawing step is less than 1.0, so yarn breakage occurs frequently and it is difficult to collect raw yarn. [Industrial Applicability]

[0066] The polyamide 46 multifilament of the present invention is not only strong and durable, but also has high heat resistance, high thermal dimensional stability, and excellent stretchability, so that when used as a belt cord, the belt does not require an autotensioner, and the overall cost of the belt drive unit can be reduced. In addition, by taking advantage of the advantages of the polyamide 46 multifilament, that is, high strength and high stretchability, it can also be used as a sewing thread for clothing for sports applications, etc. [Explanation of symbols]

[0067] 1: Spinneret 2: Heating cylinder 3: Cross-flow cooling device 4: Refueling device 5: Thread 6: Take-up roller (1FR) 7: Yarn feeding roller (2FR) 8: First stretching roller (1DR) 9: Second drawing roller (2DR) 10: Third stretching roller (3DR) 11: Relaxation roller (RR) 12: Winder

Claims

1. A polyamide 46 multifilament characterized in that 98% or more by mass, excluding additives, is made of polyamide 46 resin, the total fineness is 300-2300 dtex, the strength is 7.0-9.0 cN / dtex, the elongation is 18-30%, the heat shrinkage at 120°C is 0.5-2.0%, the elongation (E'10) after heat treatment at 120°C for 24 hours and then 10 stretches at room temperature is less than 2.5%, and the difference (E'10-E'1) between the elongation (E'1) after the heat-treated fiber is stretched once at room temperature and the elongation (E'10) after 10 stretches is less than 0.60%.

2. The polyamide 46 multifilament according to claim 1, characterized in that the difference (E10-E1) between the elongation percentage after one tensile test at room temperature and the elongation percentage after ten tensile tests at room temperature is less than 0.70%.

3. The polyamide 46 multifilament according to claim 1 or 2, characterized in that the relative viscosity of the polyamide 46 in sulfuric acid is 3.0 to 5.

0.

4. 3. A method for producing a polyamide 46 multifilament, comprising melting polyamide 46 under vacuum to perform melt spinning, and then multi-stage drawing of the spun undrawn yarn, characterized in that the multi-stage drawing comprises at least a first-stage drawing and a final drawing, and in the final drawing, drawing is performed at a draw ratio of 1.00 to 1.10 between rollers set at different temperatures.

Images