Polyamide multifilament and polyamide monofilament

Abstract

The purpose of the present invention is to provide a high-strength monofilament having stable product quality at a good processing yield from a polyamide multifilament having high strength and excellent filament separation properties, which is difficult to obtain in the prior art. The present invention is a polyamide multifilament characterized in that the number of tangles (A) (pieces / m) under low load tension conditions is greater than 0.3 and less than 3.0 and the ratio (A / B) of the number of tangles (A) under low load tension conditions to the number of tangles (B) (pieces / m) under high load tension conditions is 1.5 or more, and a polyamide monofilament obtained by dividing the polyamide multifilament. The single fiber fineness of the multifilament is 6 to 40 dtex, and the strength of the multifilament is 7.0 to 11.0 cN / dtex.

Description

Technical Field

[0001] The present invention relates to polyamide multifilaments and polyamide monofilaments. Background Art

[0002] Conventionally, as a method for efficiently producing monofilaments, a method called "splitting" has been proposed, in which a multifilament is separated to obtain a monofilament.

[0003] Various proposals have been made for obtaining monofilaments in a good processing yield using this method for processing polyester fibers (Patent Documents 1 to 3).

[0004] In recent years, the technology for splitting multifilament yarns has been widely used not only for clothing but also for general industrial applications, and its scope of application has continued to expand. In the field of aromatic polyamide fibers, proposals have been made to produce fine-denier aromatic polyamide multifilament yarns by splitting multiple multifilament yarns obtained by combining multiple yarns (Patent Documents 4 and 5).

[0005] Regarding high-strength polyamide fibers, it is described that since the single filaments of the multifilament yarn are not entangled with each other (entanglements), entanglement is not imparted to the original yarn, thereby successfully obtaining single filaments at a certain level of processing yield (Patent Document 6).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-277910

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-9341

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2001-279521

[0011] Patent Document 4: Japanese Patent Application Laid-Open No. 2004-011043

[0012] Patent Document 5: Japanese Patent Application Laid-Open No. 2015-098664

[0013] Patent Document 6: Japanese Patent Application Publication No. 2020-158906 Summary of the Invention

[0014] Problems to be solved by the invention

[0015] However, even if the "splitting" process of splitting multifilaments into single filaments is applied to conventional high-strength polyamide multifilaments, several problems still exist in terms of splitting processability and subsequent quality stability of the single filament products.

[0016] In the cases described in Patent Documents 1 to 3, most mother yarns have an elongation of 40% to 60%, and the monofilaments obtained by splitting them are limited to use in clothing.

[0017] For example, Patent Document 3 discloses that, in the entanglement method, by reducing the load tension applied to the stylus to less than 0.20 cN / dtex, the yarn separation property is improved, and there is a correlation between the load tension, i.e., the entanglement strength, and the yarn separation processability. However, the entanglement number ratio for different load tensions is not clear. In addition, it does not take into account the fact that the reduction in entanglement strength leads to a decrease in the bundledness of the single fibers constituting the multifilament yarn, which leads to untwisting during fiber package winding and the accompanying reduction in yarn separation processability. In particular, in the case of high-strength and high-stiffness fibers that can be used in industrial applications, there is a tendency for untwisting to occur more frequently during package winding, and the low bundledness of the single fibers has a significant impact on the yarn separation processability. Low yarn bundledness of the single fibers not only affects the yarn separation processability, but also easily causes uneven stretching between the single fibers, resulting in uneven physical properties of the single fibers after the yarn separation.

[0018] Furthermore, Patent Documents 4 and 5 are different from the case where a multifilament is divided into single yarns. Furthermore, although the number of entanglements is specified, the number of entanglements under different load tensions is not considered.

[0019] Furthermore, the technology described in Patent Document 6 cannot achieve a high yarn splitting yield that matches conventional polyester clothing applications, and has problems with stable yarn splitting processability and product quality stability of the physical properties of the single yarns after splitting.

[0020] In order to solve the above-mentioned problems, an object of the present invention is to provide a high-strength polyamide multifilament yarn having excellent splitting processability and a high-strength polyamide monofilament yarn having stable product quality obtained by splitting the multifilament yarn.

[0021] Means of solving problems

[0022] The present invention is the result of careful research to solve the above-mentioned problems, and includes the following configurations. (1) A polyamide multifilament yarn, wherein the number of entanglements A (pieces / m) under low load tension conditions is greater than 0.3 and less than 3.0, and the ratio A / B of the number of entanglements A under low load tension conditions to the number of entanglements B (pieces / m) under high load tension conditions is 1.5 or more, and the single fiber fineness of the multifilament yarn is 6 to 40 dtex and the strength is 7.0 to 11.0 cN / dtex. (2) The polyamide multifilament yarn according to (1) above, wherein the number of single fibers is 8 to 16 and the elongation is 20 to 35%. (3) The polyamide multifilament yarn according to (1) or (2) above, wherein the strength variation coefficient (CV value) of each single fiber constituting the multifilament yarn is less than 5.0. The fineness variation coefficient is less than 5.0. (4) The polyamide multifilament according to any one of (1) to (3), wherein the oil adhesion rate of each single fiber constituting the multifilament is less than 10.0. (5) The polyamide multifilament according to any one of (1) to (3), wherein the polyamide multifilament is used for splitting. (6) A polyamide monofilament obtained by splitting the polyamide multifilament according to any one of (1) to (3).

[0023] Effects of the Invention

[0024] According to the present invention, a high-strength polyamide multifilament with excellent splitting processability can be provided, and a high-strength monofilament with stable product quality can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [ Figure 1 ] Figure 1 This is a schematic diagram of the production process of the polyamide multifilament of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below.

[0027] As the raw material used for the polyamide multifilament of the present invention, there is no particular limitation as long as it is a polyamide such as the copolyamide of nylon 6, nylon 66, nylon 12, nylon 46, nylon 410, nylon 56, nylon 510, nylon 610, the copolyamide of nylon 6 and nylon 66, or the copolyamide in which nylon 6 is copolymerized with polyalkylene glycol, dicarboxylic acid, amine, etc. The polyamide multifilament of the present invention can contain, as required, an end-capping agent such as monocarboxylic acid, a matting agent such as titanium oxide, a polymerization catalyst such as a phosphorus compound, a heat-resistant agent, a copper compound, and an antioxidant such as a halide of an alkali metal or alkaline earth metal as well as a heat-resistant stabilizer as components other than the polyamide, but the polyamide component is preferably more than 95 wt %, more preferably more than 97 wt %. When the polyamide component is less than 95 wt %, the mechanical properties of the polyamide are reduced, so it is not preferred.

[0028] The polyamide multifilament yarn of the present invention needs to have an entanglement count A under low-load tension conditions of greater than 0.3 pcs / m and less than 3.0 pcs / m. It is preferably greater than 0.3 pcs / m and less than 2.5 pcs / m, and more preferably greater than 0.3 pcs / m and less than 2.0 pcs / m. The entanglement count A under low-load tension conditions referred to herein is measured using an automatic entanglement tester (e.g., the Rothschild Tangle Tester R-2072) capable of performing the same procedures as those described in JIS L1013 (2010) 8.15, under the conditions of a trip level of 0.17 cN / dtex, an initial tension of 0.05 cN / dtex, a measurement speed of 10 m / min, and a fiber length of 1000 m. This is, for example, the value obtained by the measurement described in the Examples. The present invention has discovered that, when the number of entanglements A under low load tension conditions is greater than 0.3 pcs / m and less than 3.0 pcs / m, by appropriately imparting bundledness between the individual fibers constituting the multifilament yarn, it is possible to suppress single-filament untwisting during yarn package winding and the associated breakage of yarns during the yarn separation process. In the present invention, when the number of entanglements under low load tension conditions is greater than 3.0 pcs / m, there are problems with deteriorating yarn separation during the yarn separation process due to excessive entanglement between the individual fibers, and uneven quality of the single fibers after separation due to tension concentration on the strongly entangled fibers. When the number of entanglements is less than 0.3 pcs / m, bundledness cannot be imparted between the individual fibers, resulting in untwisting during yarn package winding and causing breakage during the yarn separation process.

[0029] Furthermore, it is important that the ratio A / B of the number of entanglements A (pieces / m) under low load tension conditions to the number of entanglements B (pieces / m) under high load tension conditions in the polyamide multifilament of the present invention is 1.5 or greater. It is preferably 2.0 or greater, and more preferably 2.5 or greater. The number of entanglements B under high load tension conditions referred to in the present invention refers to the number of entanglements measured using an automatic entanglement tester (e.g., the R-2072 entanglement tester manufactured by Rothschild) capable of performing the same procedures as those described in JIS L1013 (2010) 8.15, under conditions of a detachment level of 0.51 cN / dtex, an initial tension of 0.05 cN / dtex, a measurement speed of 10 m / min, and a fiber length of 1000 m. This is, for example, the value obtained by the measurements described in the Examples. When the entanglement number ratio A / B is 1.5 or more, as in the present invention, it means that there are a large number of entanglements that can be detected under low load tension conditions but not under high load tension conditions. Such entanglements will slip over the entanglements of the single fibers under the tension during the splitting process, so that no breakage occurs, that is, they appear as "micro-entanglements", making this feature more prominent. By keeping within this entanglement number ratio, breakage during the splitting process caused by the entanglement of the single fibers can be reduced, and the single fibers can be given a degree of bundling that can suppress untwisting during the winding of the yarn package, so it is confirmed that it is related to the success rate of the splitting process. When the entanglement number ratio is less than 1.5, the entanglement between the single fibers is too strong, so the splitting properties in the splitting process are deteriorated, and the tension concentration on the single fibers with strong entanglements causes uneven quality of the single fibers after splitting.

[0030] The single fiber fineness of the polyamide multifilament yarn of the present invention is 6 to 40 dtex, preferably 7 to 37 dtex, and more preferably 8 to 34 dtex. A single fiber fineness greater than 40 dtex deteriorates the cooling efficiency during spinning, resulting in reduced yarn quality and an inability to achieve high strength suitable for industrial applications. A single fiber fineness less than 6 dtex is prone to entanglement between single fibers, making it difficult to control the entanglement ratio under the two tensions and to achieve a "micro-entangled" morphology.

[0031] The strength of the polyamide multifilament yarn of the present invention is 7.0 to 11.0 cN / dtex. Preferably, it is 7.5 to 9.5 cN / dtex. If the strength is within this range, high-strength single yarns can be obtained after the multifilament yarn is separated. A strength of less than 7.0 cN / dtex is insufficient for high-strength single yarns for industrial use. When attempting to obtain polyamide multifilament yarns with a strength greater than 11.0 cN / dtex, mechanical stretching at high ratios is required, which increases the incidence of burrs and the associated breakage of yarns during the separation process.

[0032] The polyamide multifilament yarn of the present invention preferably has an elongation of 20.0% to 35.0%, more preferably 22.0% to 35.0%. This range allows for a certain degree of tension during the splitting process, resulting in improved splitting properties. Furthermore, the toughness and work-to-break properties of the split single yarns can be increased, maintaining excellent durability. The strength (cN / dtex) and elongation (%) are values measured under the constant-speed tensile test conditions specified in JIS L1013 (1999) 8.5.1.

[0033] The polyamide multifilament yarn of the present invention preferably has 8 to 16 single fibers, more preferably 12 to 16. When producing single fibers of the same fineness, a larger number of single fibers increases the total polymer output, allowing for uniform spinning. Furthermore, the number of bobbins that can be used for splitting and winding using a conventional splitting machine is limited to 16. Therefore, by adjusting the number of single fibers to the specified number, a multifilament yarn can be converted into single fibers in a single splitting process.

[0034] The CV values of the strength and fineness of each single fiber constituting the polyamide multifilament yarn of the present invention are both less than 5.0. Preferably, they are both less than 4.0. More preferably, they are less than 3.5. By maintaining the CV values within these preferred ranges, a single fiber with stable product quality can be provided. The CV values of the strength and fineness of each single fiber (CV value) are obtained by measuring the strength and fineness of each single fiber after splitting the polyamide multifilament yarn at a splitting speed of 400 m / min and a splitting tension of 0.75 cN / dtex using the method described below, calculating the average value and standard deviation from the measured data, and using the following formula: CV value (%) = [standard deviation] / [average value] × 100. Furthermore, the CV value of the oil adhesion rate of each single fiber constituting the polyamide multifilament yarn of the present invention is preferably less than 10.0. More preferably, it is less than 8.0. Here, the CV value of the oil adhesion rate of each single fiber is the value obtained by measuring the oil adhesion rate of each single fiber after separating a polyamide multifilament at a separation speed of 400 m / min and a separation tension of 0.75 cN / dtex using the method described below. The average value and standard deviation of the measured data are calculated and then determined using the following formula: CV value = [Standard Deviation] / [Average Value] × 100. By keeping the CV value of the oil adhesion rate within the preferred range, the tensile tension applied during hot stretching becomes uniform across the single fibers, thus suppressing stretching unevenness. Furthermore, by uniformizing the friction between the single fibers during the separation process, the separation properties are improved. The oil used is not particularly limited, as long as it is a known oil.

[0035] Figure 1 This is a schematic diagram of a direct spinning and drawing apparatus preferably used in the present invention.

[0036] Below, Figure 1 Taking the polyamide multifilament of the present invention as an example, the production method will be described. However, the production method is not limited thereto as long as the polyamide multifilament of the present invention can be obtained.

[0037] First, polyamide raw material pellets serving as a raw material for the polyamide multifilament of the present invention are prepared. A known polymerization method can be used for the polymerization of polyamide.

[0038] The sulfuric acid relative viscosity (hereinafter referred to as viscosity) of the raw material pellets of the polyamide multifilament yarn of the present invention is preferably 2.5 to 3.9, more preferably 3.0 to 3.9. Within this range, a high-strength polyamide multifilament yarn with excellent spinnability can be obtained. The sulfuric acid relative viscosity is the value measured at 25°C using an Ostwald viscometer after dissolving a sample in 98% sulfuric acid.

[0039] Next, the polyamide pellets are supplied to an extrusion spinning machine and distributed to a spinning die by a metering pump for melt spinning. The spinning temperature is set to a value 50°C higher than the melting point of the polymer, and the polymer is preferably discharged from a spinning die 1 having 8 to 16 holes. It is preferably passed through a heating cylinder 2 that surrounds a range of 5 to 300 cm from just below the spinning die. As for the temperature in the heating cylinder, it is preferably in the range of -30°C to +30°C of the melting point of the polymer polyamide, and more preferably in the range of -15°C to +15°C. The spun filaments are not cooled immediately, but are slowly cooled by passing through a high-temperature environment surrounded by the above-mentioned heating cylinder, thereby relaxing the orientation of the melt-spun polyamide molecules, thereby improving the uniformity of the molecular orientation between single fibers, and thus achieving high strength of the polyamide multifilament.

[0040] Next, the unstretched yarn 5, which has passed through the high-temperature environment, is cooled and solidified by blowing air at 10 to 80°C, preferably 10 to 50°C, through a cross-flow cooling device 3. If the cooling air temperature exceeds 80°C, the fibers will sway more during spinning, causing collisions between individual fibers, which can deteriorate the spinning properties. A single-flow air cylinder is preferably used as the cross-flow cooling device.

[0041] Then, the obtained cooled filaments are oiled by an oiling device 4 including an oiling roller, and can be pulled by a drawing roller (1FR) 6 and wound after stretching. From the viewpoint of uniform oil adhesion, the oiling roller is preferably subjected to a pear skin finish. By using an oiling roller with a pear skin finish, the contact area between the filaments and the roller is increased, and the uneven oil adhesion rate between the single fibers can be reduced. The applied oil can be a known oil. In order to suppress the adhesion of the single fibers to the drawing roller (1FR) 6, the amount of the oil is preferably 0.3 to 1.5% by weight, and more preferably 0.5 to 1.0% by weight.

[0042] The spinning speed, defined by the rotational speed of the take-up roller (1FR) 6, is preferably 400 to 1200 m / min. A spinning speed of 400 m / min or higher provides a sufficient final production speed, resulting in excellent production efficiency and the ability to produce polyamide multifilament yarns at low cost. A spinning speed of 1200 m / min or lower is preferred because it prevents frequent yarn breakage and burrs.

[0043] The spun yarns obtained by the above-described method can be stretched, heat-treated, and wound up using known methods. Specifically, for a two-stage stretching process, the spun yarns drawn by the take-up roller (1FR) 6 are wound in the order of the feed roller (2FR) 7, the first stretching roller (1DR) 8, the second stretching roller (2DR) 10, and the relaxation roller (RR) 11, heat-treated, stretched, and wound up on a winder 13.

[0044] Pre-stretching is performed between 1FR and 2FR, first-stage stretching is performed between 2FR and 1DR, and second-stage stretching is performed between 1DR and 2DR. The 2FR temperature is set between -20°C and +20°C, the glass transition temperature of the polymer, and the 1DR temperature is set between 100°C and 225°C. Pre-stretching and first-stage stretching are preferably performed hot around the glass transition temperature. The remaining stretching and heat setting temperatures are generally preferably performed at elevated temperatures between -20°C and +20°C, the crystallization temperature of the polymer.

[0045] The combined draw ratio (hereinafter referred to as the draw ratio), defined as the draw ratio between the take-up roller (1FR) 6 and the second draw roller (2DR) 10, is preferably a high draw ratio to obtain high-strength polyamide multifilament. Within the fineness range described herein, a draw ratio of 3.5 to 5.0 is sufficient. Furthermore, the winding speed is typically preferably 1500 to 4500 m / min, more preferably 2000 to 4500 m / min. Furthermore, the winding tension is preferably 0.05 to 0.25 cN / dtex when wound into a roll (cheese-like) using a winding device.

[0046] Furthermore, to obtain a polyamide multifilament having the number of entanglements A and the entanglement ratio A / B specified in the present invention, it is effective to fluidize the filaments using a first entangling nozzle 9 between the first drawing roller (1DR) 8 and the second drawing roller (2DR) 10, and a second entangling nozzle 12 between the relax roller (RR) 11 and the winder 13, when winding the filaments into a polyamide multifilament package. In particular, when fluidizing the multifilaments under the specified winding tension, it is preferable to adjust the compressed air pressure of the second entangling nozzle 12 to 0.005 to 0.015 MPa / dtex per unit single fiber fineness, and more preferably 0.005 to 0.010 MPa / dtex.

[0047] By the above-described method, the polyamide multifilament yarn described in the present invention having high strength and good spinnability can be produced.

[0048] Furthermore, the polyamide multifilament obtained by the above method can be processed by a known yarn separation method to obtain high-strength polyamide monofilaments with stable product quality at a good processing yield.

[0049] Example

[0050] The present invention will be described in detail below with reference to the following examples. The definitions and determination methods of the various characteristics of the present invention are as follows.

[0051] (1) Sulfuric acid relative viscosity (ηr): Dissolve 0.25 g of polymer pellets or strands in 25 ml of 98% sulfuric acid and measure at 25°C using an Ostwald viscometer. Calculate the viscosity using the following formula. The measured value is the average of five samples. ηr = Flow time of the sample solution / Flow time of the sulfuric acid alone.

[0052] (2) Total fineness: The gross fineness was measured under a specified load of 0.045 cN / dtex using JIS L1013 (1999) 8.3.1 A method.

[0053] (3) Single fiber number: calculated according to the method of JIS L1013 (1999) 8.4.

[0054] (4) Single fiber fineness: calculated by dividing the total fineness by the number of single fibers.

[0055] (5) Strength, Tenacity, and Elongation: Measured under the constant-speed elongation conditions specified in the standard test of JIS L1013 (1999) 8.5.1. The specimens were measured using a "TENSILON" UCT-100 manufactured by Orientec, with a clamp spacing of 25 cm and a tensile speed of 30 cm / min. The strength was determined from the maximum strength in the S-S curve, and the elongation was determined from the elongation at the point showing the maximum strength in the S-S curve. The strength was determined by dividing the strength by the total fineness. For the multifilament specimen, samples were taken every 1 m in the longitudinal direction, and measurements were performed at 5 points. The average value was calculated from the measured data.

[0056] (6) Number of tangles: 1000 m of yarn was evaluated using a tangle tester R-2072 manufactured by Rothschild at a measurement speed of 10 m / min. The detachment level was set to 0.17 cN / dtex for the number of tangles A under low load tension conditions and 0.51 cN / dtex for the number of tangles B under high load tension conditions. The initial tension was set to 0.05 cN / dtex for both measurements.

[0057] (7) Ratio of the number of tangles under different load tensions A / B: Calculated by dividing the number of tangles A (pieces / m) measured in the above item (6) by the number of tangles B (pieces / m).

[0058] (8) Splitting Processability: 50 multifilament packages weighing 5.0 kg were split using a splitting machine KA-516OF manufactured by AIKI Riotec. The percentage of packages that could be split into single filaments without breakage was expressed as the full bobbin ratio (%). Splitting was performed at a splitting speed of 400 m / min and a splitting tension of 0.75 cN / dtex. S: Full bobbin ratio of 85% or more A: Full bobbin ratio of 70% or more and less than 85% B: Full bobbin ratio of 55% or more and less than 70% C: Full bobbin ratio of 30% or more and less than 55%.

[0059] (9) The variation rate of the fineness of each single fiber: The fineness of each single fiber obtained from the same package subjected to the splitting process under the conditions of the above-mentioned item (8) was measured in the same manner as in the above-mentioned item (2). The average value and standard deviation were calculated from the measured data. The variation rate was calculated using the following formula: Variation rate (%) = [Standard deviation] / [Average value] × 100 (10) The variation rate of the strength of each single fiber: The strength of each single fiber obtained from the same package subjected to the splitting process under the conditions of the above-mentioned item (8) was measured in the same manner as in the above-mentioned item (5). The average value and standard deviation were calculated from the measured data. The variation rate was calculated using the calculation formula described in the above-mentioned item (9).

[0060] (11) Coefficient of variation of the oil adhesion rate of each single fiber: The amount of oil adhesion of each single fiber obtained from the same package subjected to the filament separation process under the conditions of the aforementioned item (8) was measured by the hexane extraction method in accordance with JIS L1096 (2010) 8.32. The average value and standard deviation of the oil adhesion rate were calculated from the measured data, and the coefficient of variation was calculated using the calculation formula described in the aforementioned item (9).

[0061] (Example 1)

[0062] A 5% by weight aqueous solution of copper acetate as an antioxidant was added to nylon 66 pellets obtained through liquid-phase polymerization and mixed. 68 ppm of adsorbed copper was added relative to the weight of the polymer. Subsequently, a 50% by weight aqueous solution of adsorbed potassium iodide and a 20% by weight aqueous solution of potassium bromide were added in an amount such that the potassium content reached 0.1 parts by weight per 100 parts by weight of the polymer pellets. Solid-phase polymerization was carried out using a batch-type solid-phase polymerization apparatus to produce nylon 66 pellets with a sulfuric acid relative viscosity of 3.75. The resulting nylon 66 pellets were fed into an extruder with a diameter of 110 mm and melted at a melt temperature of 300°C. The molten polymer was distributed to a spinning pack by adjusting the discharge rate using a metering pump to produce multifilament yarns with a total fineness of 175 dtex. The molten polymer was then filtered through a 40 μm-diameter metal nonwoven filter within the spinning pack and spun through a die with 16 circular holes. A 15cm long heating cylinder was installed 3cm below the die surface and heated to a temperature of 250°C inside the cylinder. The temperature inside the cylinder refers to the air temperature at the center of the cylinder, 1cm from the inner wall. A single-flow air duct, blowing air from one direction, was installed directly below the heating cylinder. Cool air at 20°C was blown onto the yarn at a speed of 35m / min, cooling and solidifying it. The yarn was then lubricated by a pear-skinned oiling roller (oiling roller).

[0063] The undrawn yarn, to which an oil has been applied, is wound around a 1FR rotating at a surface speed of 850 m / min and then stretched at a combined draw ratio of 4.1. The drawn yarn is continuously tensioned at 5% between the drawing roller and the 2FR without temporary winding. The first stretching step is then performed at a rotational speed ratio of 2.80 times, followed by a second stretching step at a rotational speed ratio of 1.40 times, and is then wound at a speed of 3500 m / min. The roller surfaces of the 1FR and 2FR rollers are mirror-polished, while the 1DR, 2DR, and RR rollers are pear-skinned. The roller temperatures of the 1FR roller are non-heated, the 2FR rollers are 40°C, the 1DR rollers are 150°C, the 2DR rollers are 225°C, and the RR rollers are 150°C. Nylon 66 multifilament yarn is obtained through this melt spinning and stretching process. The entanglement treatment is performed by spraying high-pressure air perpendicularly to the running yarn within the entanglement applying device. Guides for combing and conveying the yarns were provided before and after the entangling nozzles. The pressure of the injected air was set to 0.30 MPa in the first entangling nozzle and to 0.10 MPa in the second entangling nozzle.

[0064] (Example 2)

[0065] The same procedure as in Example 1 was carried out except that the pressure of the second entangling nozzle was set to 0.07 MPa.

[0066] (Example 3)

[0067] The same procedure as in Example 1 was carried out except that the pressure of the second entangling nozzle was set to 0.13 MPa.

[0068] (Example 4)

[0069] The same procedure as in Example 1 was carried out except that the total fineness of the polyamide multifilament was set to 110 dtex and the yarn was produced by changing the draw ratio between 1DR and 2DR to a total draw ratio of 4.2.

[0070] (Example 5)

[0071] The same procedure as in Example 1 was carried out except that the total fineness of the polyamide multifilament was set to 350 dtex and the yarn was produced by changing the draw ratio between 1DR and 2DR to a total draw ratio of 4.5.

[0072] (Example 6)

[0073] The same procedure as in Example 1 was carried out except that a mirror-finished oil feed roller was used.

[0074] (Example 7)

[0075] The same procedure as in Example 1 was carried out except that the pressure of the first entangling nozzle was set to 0.00 MPa.

[0076] (Example 8)

[0077] Nylon 6 pellets with a relative viscosity of sulfuric acid of 3.30 were melt-spun at 270°C. The molten polymer was discharged by a metering pump in such a manner that a multifilament with a total fineness of 470 dtex could be obtained, and the molten polymer was spun through a die with 14 circular holes. The yarn was stretched at a comprehensive stretching ratio of 4.7 times and wound at a take-up speed of 2100 m / min. In addition, regarding the temperature of each roller, 1FR was non-heated, 2FR was 40°C, 1DR was 150°C, 2DR was 200°C, and RR was 150°C. Nylon 6 multifilament yarn was obtained by this melt spinning and stretching. Regarding the air pressure injected during the entanglement process, it was set to 0.20 MPa in the first entanglement nozzle and 0.20 MPa in the second entanglement nozzle. The rest was carried out in the same manner as in Example 1.

[0078] (Example 9)

[0079] The same procedures as in Example 8 were carried out except that the total fineness of the polyamide multifilament was set to 235 dtex and the yarn was produced at a total draw ratio of 4.5 times.

[0080] (Example 10)

[0081] The same procedure as in Example 1 was carried out except that nylon 410 pellets having a sulfuric acid relative viscosity of 3.60 were used.

[0082] (Example 11)

[0083] The same procedure as in Example 8 was carried out except that nylon 610 pellets having a sulfuric acid relative viscosity of 3.80 were used.

[0084]

[0085] The physical properties and yarn separation processability of the polyamide multifilaments obtained in Examples 1 to 11, as well as the coefficient of variation of the physical properties of the single yarns after separation, were evaluated. The results are shown in Table 1.

[0086] As can be seen from Table 1, the polyamide multifilament of the present invention achieves high strength and good splitting processability by controlling the ratio A / B between the low-load tension condition A and the high-load tension condition B within a predetermined range.

[0087] (Comparative Example 1)

[0088] The same procedure as in Example 1 was carried out except that the pressure of the second entangling nozzle was set to 0.00 MPa.

[0089] (Comparative Example 2)

[0090] The same procedure as in Example 1 was carried out except that the pressure of the second entangling nozzle was set to 0.25 MPa.

[0091] (Comparative Example 3)

[0092] The same procedure as in Example 1 was carried out except that the total fineness of the polyamide multifilament was set to 78 dtex and the pressure of the second entangling nozzle was set to 0.05 MPa.

[0093] (Comparative Example 4)

[0094] The same procedure as in Example 1 was carried out except that the total fineness of the polyamide multifilament was set to 700 dtex, the pressure of the second entangling nozzle was set to 0.25 MPa, the total stretching ratio was set to 4.5 times, and the winding speed was set to 2700 m / min.

[0095] (Comparative Example 5)

[0096] The yarn was produced in the same manner as in Example 1 except that the pressure of the second entangling nozzle was set to 0.00 MPa and the total stretching ratio was set to 2.7 times.

[0097] (Comparative Example 6)

[0098] The same procedure as in Example 8 was carried out except that the second entangling nozzle pressure was set to 0.00 MPa and the yarn was produced at a total draw ratio of 3.3 times.

[0099] (Reference Example 1)

[0100] Referring to Patent Document 6: Japanese Patent Application Laid-Open No. 2020-158906, the following polyamide multifilament yarn was produced and evaluated. Specifically, the same mirror-polished oil feed roller as used in Example 6 was used, the first and second entangling nozzles were omitted, and no entangling treatment was performed between 1DR and 2DR, and from RR to winding. The same procedures as in Example 1 were followed, except that the mirror-polished oil feed roller used for lubrication in this reference example was a commonly used oil feed roller.

[0101]

[0102] Table 2 shows the results of evaluation of the physical properties and yarn separation processability of the polyamide multifilaments obtained in Comparative Examples 1 to 6, and the coefficient of variation of the physical properties of the single yarns after separation.

[0103] It can be seen that in Comparative Example 1, where the polyamide multifilament was produced without performing an entangling treatment using the second entangling nozzle, the entanglement number A under low load tension conditions was very small. This indicates that in this case, due to the extreme loss of bundledness between the individual fibers, untwisting frequently occurred during package winding, affecting the processability of the polyamide multifilament yarn.

[0104] In Comparative Example 2, the second entangling nozzle pressure was set to 0.25 MPa, and the pressure per single fiber fineness was set to 0.023 MPa / dtex. In this case, the number of entanglements A under low load tension conditions was approximately the same as the number of entanglements B under high load tension conditions, indicating a normal entanglement pattern. The spinnability of this polyamide multifilament yarn was significantly deteriorated.

[0105] In Comparative Example 3, the total fineness of the polyamide multifilament was 78 dtex, and the single fiber fineness was 4.9 dtex. Furthermore, the second entangling nozzle pressure was set to 0.05 MPa, and the second entangling nozzle pressure per single fiber fineness was controlled to 0.010 MPa / dtex. In this case, while the number of entanglements A under low load tension conditions could be controlled within the range specified by the present invention, the number of entanglements B under high load tension conditions remained at the same value, failing to produce a "micro-entangled" morphology. Consequently, the processability of the polyamide multifilament yarn was affected.

[0106] In Comparative Example 4, the total fineness of the polyamide multifilament was 700 dtex and the single fiber fineness was 43.8 dtex. In this case, the cooling efficiency during spinning was deteriorated, so the quality of the raw yarn was reduced, and the strength level specified in the present invention could not be achieved.

[0107] Reference Example 1 corresponds to an example of producing polyamide multifilament yarn using the method described in the Examples of Reference Patent Document 6. In this case, due to the lack of entanglement treatment using the second entanglement nozzle, the bundling between the individual fibers was extremely poor, resulting in problems with yarn separation and the full tube ratio during filament separation. Furthermore, due to the use of a mirror-polished oil feed roller and the lack of entanglement treatment using the first entanglement nozzle, the coefficient of variation of the strength variation between individual fibers and the coefficient of variation of the oil adhesion ratio variation between individual fibers were significantly poor, resulting in problems with the stability of the product quality of this monofilament yarn.

[0108] Industrial applicability

[0109] The polyamide multifilament yarn of the present invention offers high strength and excellent splitting properties, while also suppressing variations in physical properties between individual fibers. This allows for the production of high-strength monofilament yarns with consistent product quality. This expands the application range of polyamide monofilament yarns and enhances the sophistication of existing monofilament products, such as sports yarns and mesh yarns.

[0110] Description of Reference Numerals

[0111] 1: Spinning die 2: Heating cylinder 3: Cross-flow cooling device 4: Oil supply device 5: Yarn 6: Pulling roller (1FR) 7: Yarn supply roller (2FR) 8: 1st stretching roller (1DR) 9: 1st entangling nozzle 10: 2nd stretching roller (2DR) 11: Relaxation roller (RR) 12: 2nd entangling nozzle 13: Winder

Claims

1. A polyamide multifilament yarn having an entanglement number A under low load tension conditions greater than 0.3 and less than 3.0, and a ratio (A / B) of the entanglement number A under low load tension conditions to the entanglement number B under high load tension conditions of greater than 1.5, wherein the multifilament yarn has a single fiber fineness of 6 to 40 dtex and a tenacity of 7.0 to 11.0 cN / dtex, and the units of the entanglement number A and the entanglement number B are pieces / m.

2. The polyamide multifilament according to claim 1, wherein the number of single fibers is 8 to 16 and the elongation is 20 to 35%. The polyamide multifilament according to claim 1 or 2, wherein the CV value of the uniformity variation rate of fineness of each single fiber constituting the multifilament is less than 5.0, and the CV value of the uniformity variation rate of strength is less than 5.

0. The polyamide multifilament according to any one of claims 1 to 3, wherein the CV value of the oil adhesion rate of each single fiber constituting the multifilament is less than 10.

0. The polyamide multifilament according to any one of claims 1 to 3, which is used for splitting. 6 . A polyamide monofilament obtained by dividing the polyamide multifilament according to claim 1 .

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