Polyamide fiber and method for producing same

Abstract

The present invention provides a polyamide fiber in which the coefficient of kinetic friction (μd: Wet) between fibers when same are wet is suppressed in order to dramatically improve the long-term wear durability required for industrial materials used under severe conditions, especially marine ropes of recent years.　The polyamide fiber is characterized in that: the coefficient of kinetic friction (μd: Wet) between the fibers when same are wet is in the range of 0.060-0.225; and the ratio μd: Wet / μd: Dry (when wet / when dry) of the coefficient of kinetic friction between the fibers when same are wet and when same are dry is in the range of 0.67-1.15.

Description

Polyamide fiber and its manufacturing method

[0001] The present invention relates to polyamide fibers and a method for producing the same.

[0002] Polyamide fibers have excellent mechanical and chemical properties and are widely used in clothing and industrial applications, including ropes, airbags, tire cords, and nets, due to their high strength and elongation, high abrasion resistance, and high durability.

[0003] Among these, rope applications, particularly marine ropes for seabed mooring used on platforms (bases) for offshore oil fields and offshore wind power generation facilities, require rope strength, abrasion resistance, durability underwater (in wet conditions), and shock absorption to prevent damage to the moorings. Offshore wind power generation facilities require mooring ropes that have abrasion resistance and durability for a long period of 20 years or more, even when subjected to violent movement by waves and wind, and dramatically improving this long-term abrasion durability is a technical challenge.

[0004] Various synthetic fibers have been proposed as fibers for marine ropes. For example, Patent Document 1 proposes a blend of polybenzazole fiber and high-strength polyethylene fiber.

[0005] Furthermore, surface treatments of fibers or ropes have also been investigated with the aim of improving long-term wear resistance. Patent Document 2 discloses fibers and ropes in which an oil agent made of amino-modified silicone is applied to nylon threads, and also discloses a method for reducing the coefficient of static friction between fibers when dry.

[0006] Patent Document 3 discloses polyester fibers to which an oil agent is applied that reduces shedding and reduces the coefficient of static friction between fibers.

[0007] Japanese Unexamined Patent Publication No. 7-165164 Japanese Unexamined Patent Application No. 9-95877 Unexamined Japanese Patent Application No. 2012-72512

[0008] The synthetic fiber described in Patent Document 1 is high-strength, but suffers from low elongation, poor impact absorption for moorings, and high cost, resulting in performance and economic problems. In the rope manufacturing process described in Patent Document 2, a straight oil primarily composed of a fatty acid ester is applied to undrawn yarn immediately after melt spinning, and then a low-friction amino-modified silicone oil is applied immediately before winding after stretching and relaxation. However, when the oil is applied immediately before winding at high speed, the amount of low-friction oil applied is limited, resulting in uneven application and poor adhesion of the oil to the yarn. While the static friction coefficient between fibers in dry conditions is low, the static friction coefficient in wet conditions is high, posing issues with long-term wear durability in water. The oil described in Patent Document 3 reduces the static friction coefficient between fibers in wet conditions and shows some effectiveness, but quickly falls off when subjected to vibration or load in the ocean. Therefore, long-term wear durability remains an issue. Furthermore, polyester fibers have even lower durability due to their low elongation, and their low impact resistance poses a problem of heavy loads on moorings and ropes.

[0009] The present invention solves the above problems and aims to provide a polyamide fiber that has a dramatically improved long-term abrasion resistance in water, which is required for marine ropes in recent years, and has improved operability in the spinning process.

[0010] The present invention is the result of extensive research by the present inventors to solve the above-mentioned problems, and comprises the following features: (1) Polyamide fibers characterized in that the wet interfiber kinetic friction coefficient (μd:Wet) is in the range of 0.060 to 0.225, and the ratio of the wet interfiber kinetic friction coefficient to the dry interfiber kinetic friction coefficient (μd:Dry) (μd:Wet / μd:Dry) is in the range of 0.67 to 1.15; (2) The polyamide fibers according to (1) above characterized in that the wet interfiber static friction coefficient (μs:Wet) is in the range of 0.090 to 0.218, and the ratio of the wet interfiber static friction coefficient to the dry interfiber static friction coefficient (μs:Wet / μs:Dry) is in the range of 0.85 to 1.15. (3) The polyamide fiber according to (1) or (2), wherein the total amount of spinning oil attached to the polyamide fiber is 0.5% by mass to 2.8% by mass, the amount of silicone compound attached to the polyamide fiber is 0.3% by mass to 1.5% by mass, and the rate of silicone compound shedding after ultrasonic washing is 20% or less. (4) The polyamide fiber according to (1) or (2), wherein the fineness is 100 dtex to 4,000 dtex, the strength is 6.5 cN / dtex to 9.3 cN / dtex, and the elongation is 20.0% to 30.0%. (5) The method for producing the polyamide fiber according to (1), which includes a drawing step, and wherein a spinning oil containing a silicone compound is applied before the drawing step. (6) The polyamide fiber according to (1), which is used for marine ropes. (7) A marine rope made of the polyamide fiber according to (1).

[0011] The polyamide fiber of the present invention exhibits a low coefficient of dynamic friction between fibers even when wet, making it possible to provide a rope that is excellent in long-term abrasion resistance even under harsh conditions of use underwater. Furthermore, the polyamide fiber of the present invention reduces contamination of high-temperature drawing rollers during the spinning process (even when an oil agent that reduces the coefficient of static friction between fibers is applied), thereby improving productivity.

[0012] FIG. 1 is a schematic diagram of an apparatus for measuring the fiber-to-fiber friction coefficient of a sample.

[0013] The present invention will be described in detail below.

[0014] The polyamide fiber of the present invention is made of polyamide. Examples of polyamides used in the present invention include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polydodecanamide (nylon 12), polytetramethylene adipamide (nylon 46), polypentamethylene adipamide (nylon 56), polyhexamethylene sebacamide (nylon 610), polytetramethylene sebacamide (nylon 410), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polyxylylene phthalamide, and copolymers and blend polymers thereof. Among these, polymers selected from polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), and polyhexamethylene sebacamide (nylon 610), copolymer polyamides containing these polymers as the main components, and blend polymers thereof are preferred.

[0015] When a copolymerized polyamide is used, examples of copolymerization components include two or more selected from ε-caproamide, hexamethylene adipamide, tetramethylene adipamide, hexamethylene sebacamide, hexamethylene isophthalamide, tetramethylene terephthalamide, xylylene phthalamide, etc. Specifically, it is preferable that the copolymerized polyamide be a polymer selected from a copolymerized polyamide of nylon 6 and nylon 66, a copolymerized polyamide obtained by copolymerizing nylon 6 with polyalkylene glycol, dicarboxylic acid, amine, etc., and a blend polymer thereof.

[0016] The polyamide fiber in the present invention preferably contains 95% by weight or more, more preferably 97% by weight or more, of the polyamide component in the polymer, which allows the excellent durability of the polyamide to be fully exhibited.

[0017] Furthermore, additives such as weatherproofing agents, heat-resistant agents, and antioxidants can be added to the polyamide as needed, and the polyamide can be melt-spun. Some or all of the additives may be added during polymerization, or they may be mixed by other methods.

[0018] In addition, when producing high-strength polyamide fibers, it is preferable to use a polyamide resin used as a raw material after increasing its viscosity by solid-phase polymerization or the like.

[0019] The fineness of the polyamide fiber of the present invention is preferably 100 dtex to 4000 dtex, more preferably 700 dtex to 2000 dtex. By making it 100 dtex or more, it is possible to efficiently process it into a doubled and twisted yarn for a marine rope. On the other hand, by making it 4000 dtex or less, it is possible to adjust the fineness to the required fineness for doubling.

[0020] The single fiber fineness of the polyamide fiber of the present invention is preferably 4 dtex to 40 dtex, more preferably 5 dtex to 15 dtex. Polyamide fibers with a single fiber fineness of 4 dtex or more have good abrasion resistance against the drawing roll in the spinning process, and when the draw ratio is increased to obtain high-strength fibers, they can prevent fluffing and maintain good quality. On the other hand, a single fiber fineness of 40 dtex or less facilitates filament bundling. Furthermore, the polymer is well cooled in the spinning process, and a good form can be obtained even when winding at a high speed of 3,000 m / min or more, which allows for uniform drawing in the spinning process.

[0021] The strength of the polyamide fiber of the present invention is preferably 6.5 cN / dtex to 9.3 cN / dtex, more preferably 7.0 cN / dtex to 8.8 cN / dtex. By setting the strength in this range, the polyamide fiber has high mechanical properties even in water, and a highly durable rope can be provided.

[0022] The elongation of the polyamide fiber of the present invention is preferably 20% to 30%, more preferably 22% to 27%. In particular, when the strength is within the above-mentioned range and the elongation is within the above-mentioned range, a high-strength, high-quality polyamide fiber can be provided. Furthermore, a rope with excellent shock absorption properties in water can be provided.

[0023] The method for producing polyamide fibers of the present invention is a melt spinning method including a drawing step, in which a spinning oil containing a silicone compound is applied before the drawing step.

[0024] An example of the method for producing polyamide fibers according to the present embodiment will be described below. The method will be described using one embodiment of a spinning process (spinning method) for industrial nylon fibers as an example, but is not limited to this as long as the polyamide fibers of the present invention can be obtained.

[0025] First, a polymer melted in an extruder-type spinning machine is spun out from a spinneret. The spun polymer passes through a heating cylinder installed directly below the spinneret and is cooled and solidified by a cooling air device to form a yarn. Next, the yarn is converged by a yarn path control guide, after which a spinning oil is applied by an oiling device, and the yarn is wound around a group of godet rollers and taken up. The taken-up yarn is not wound up once, but is wound around multiple pairs of godet rollers rotating at high speed in sequence, and is drawn by the difference in the speed of the rollers. After multi-stage drawing in two or more stages, the yarn is relaxed and then wound up. Drawing is preferably performed by hot drawing at a temperature above the glass transition temperature, and the final drawing and heat setting temperature is preferably at a high temperature of 180°C or higher but lower than the melting point. The draw ratio is preferably in the range of 2 to 6 times, and the yarn is wound up into a cheese shape on a winding device at a winding speed of 1500 to 5000 m / min.

[0026] The device for applying the spinning oil is not particularly limited, but it is preferable to apply it before drawing in the spinning process using at least one oiling roller or guide oiling device. The spinning oil may be either a water-based emulsion containing a smoothing agent or a surfactant as the main component, or a non-aqueous treatment agent.

[0027] The spinning oil used in the present invention is preferably an aqueous emulsion containing a silicone compound and preferably a wax component. The aqueous emulsion is prepared by appropriately selecting and combining a lubricant, a surfactant, and other components such as an ester component, a polyether component, and additives.

[0028] Preferred examples of the silicone compound include dimethylpolysiloxane, amino-modified silicone, phenyl-modified silicone, and polyether-modified silicone. The blending amount in the spinning oil is preferably 3.0% by mass to 28.0% by mass, more preferably 4.0% by mass to 24.0% by mass. Examples of wax-based components include polyethylene wax, and the blending amount in the spinning oil is preferably 0.5% by mass to 5.0% by mass, more preferably 0.5% by mass to 4.0% by mass.

[0029] By applying a spinning oil containing the compound, which has been atomized by applying pressure using a high-pressure homogenizer, before the drawing step, it is possible to suppress the occurrence of stains on the roller surface and the associated occurrence of yarn breakage and fluff, even when the fiber is subjected to the subsequent hot drawing step.As a result, it is possible to produce polyamide fibers that satisfy the inter-fiber dynamic friction coefficient of the present invention, with good spinning operability.

[0030] The smoothing agent is preferably a divalent fatty acid ester compound or a divalent fatty acid ester compound containing ethylene oxide, and the molecular weight thereof is preferably 600 to 1000. Further, a divalent fatty acid ester compound containing 20% ​​by mass to 50% by mass of ethylene oxide is more preferred.

[0031] Examples of surfactants include alcohol alkylene oxide adduct ester compounds and alkylene oxide-containing higher alcohol alkylene oxide adducts. The molecular weight of the alcohol alkylene oxide adduct ester compound is preferably 1500 to 2500. The molecular weight of the alkylene oxide-containing higher alcohol alkylene oxide adduct is preferably 1000 to 2000. In the alkylene oxide-containing higher alcohol alkylene oxide adduct, the alkylene oxide content is preferably 5% to 20% by mass.

[0032] The total amount of oil applied to the polyamide fiber of the present invention is preferably 0.5% to 2.8% by mass, more preferably 0.5% to 2.3% by mass, and even more preferably 0.6% to 1.8% by mass. By adjusting the amount within this range, the coefficient of dynamic friction between fibers in the dry state (μd:Dry) can be reduced, a decrease in strength due to friction between fibers during rope production can be suppressed, and processability can be improved. In the production of polyamide fiber, from the viewpoint of yarn running stability when applying oil before the drawing process, the upper limit of the total amount of oil applied is 2.8% by mass or less.

[0033] The oil agent adhered to the polyamide fiber of the present invention contains a silicone compound. The amount of silicone compound adhered to the polyamide fiber is preferably 0.3% by mass to 1.5% by mass, more preferably 0.3% by mass to 1.2% by mass, and even more preferably 0.4% by mass to 1.0% by mass. By setting the amount of silicone compound adhered to 0.3% by mass or more, it is possible to reduce the coefficient of dynamic friction between wet fibers when the silicone compound dropout rate after water washing is within a specified range. By setting the amount of silicone compound adhered to 1.5% by mass or less, it is possible to reduce contamination on high-temperature drawing rollers during the spinning process.

[0034] Furthermore, the polyamide fiber of the present invention preferably has a silicone compound shedding rate (hereinafter referred to as "silicone shedding rate") of 20% or less after ultrasonic water washing. The silicone shedding rate is more preferably 18% or less, and even more preferably 16% or less. By setting the silicone shedding rate within this range, the silicone shedding rate can be reduced even when the rope is used underwater and is violently moved by waves and wind. This makes it possible to control the ratio of the dynamic friction coefficient between fibers in the dry and wet states (μd:Wet / μd:Dry), achieving a reduction in the dynamic friction coefficient between fibers in the wet state (μd:Wet), which was not possible with conventional polyamide fibers.

[0035] The polyamide fibers of the present invention have a wet interfiber dynamic friction coefficient (μd:Wet) of 0.060 to 0.225, and a ratio (μd:Wet / μd:Dry) of the wet interfiber dynamic friction coefficient (μd:Dry) to the dry interfiber dynamic friction coefficient (μd:Dry) of 0.67 to 1.15. The wet interfiber dynamic friction coefficient (μd:Wet) is preferably 0.080 to 0.210, more preferably 0.098 to 0.180. The ratio (μd:Wet / μd:Dry) of the dry interfiber dynamic friction coefficient (μd:Dry) to the wet interfiber dynamic friction coefficient (μd:Wet / μd:Dry) is preferably 0.75 to 1.10, more preferably 0.85 to 1.05. As is clear from known literature, when fibers are wetted with water, the interfiber sliding property generally deteriorates, and the wet interfiber friction coefficient is greater than the dry interfiber friction coefficient. In response to this, the inventors have conducted extensive research and discovered polyamide fibers that can exhibit low friction characteristics even when wet, comparable to the coefficient of dynamic friction between fibers when dry. This invention makes it possible to control the coefficient of dynamic friction between fibers when wet (μd:Wet) within the above range, dramatically improving long-term abrasion resistance. If the coefficient of dynamic friction between fibers when wet (μd:Wet) exceeds 0.225, improvement in long-term abrasion resistance in water cannot be achieved. If it is less than 0.060, the friction between the fiber and the drawing roller becomes too low, making it impossible to draw at a high ratio, and high-strength yarn cannot be obtained.

[0036] The polyamide fibers of the present invention have a wet inter-fiber static friction coefficient (μs:Wet) of 0.090 to 0.218, and a ratio (μs:Wet / μs:Dry) of the wet inter-fiber static friction coefficient (μs:Dry) to the dry inter-fiber static friction coefficient (μs:Dry) of 0.85 to 1.15. The wet inter-fiber static friction coefficient (μs:Wet) is preferably 0.100 to 0.200, and more preferably 0.110 to 0.190. The ratio (μs:Wet / μs:Dry) of the wet inter-fiber static friction coefficient (μs:Wet) to the dry inter-fiber static friction coefficient (μs:Dry) is preferably 0.90 to 1.10, and more preferably 0.92 to 1.03. By setting the values ​​in this range, a decrease in rope strength due to friction between fibers during use can be suppressed.

[0037] As a result of extensive research, the inventors have found that the amount of silicone compound attached can be increased by applying a spinning oil containing a silicone compound before drawing in the spinning process, rather than just before winding.Furthermore, they have found that applying the spinning oil to the fiber before the hot drawing process improves the ability of the oil to adhere to the fiber, thereby suppressing the rate of silicone compound removal after ultrasonic water washing and the coefficient of friction between wet fibers.

[0038] The polyamide fiber of the present invention exhibits excellent properties for use in marine ropes. Furthermore, the marine rope of the present invention can be produced using the polyamide fiber of the present invention by a known rope production method. Although the marine rope of the present invention is made from the polyamide fiber of the present invention, it may contain other fibers within a range that does not impair the properties, and may be a double or triple rope, with either layer being made of the polyamide fiber of the present invention.

[0039] The following examples will explain the present invention in more detail. However, the present invention is not limited to these examples. The definitions and measurement methods of the various properties in the present invention are as follows.

[0040] (1) Relative viscosity in sulfuric acid: 0.25 g of a sample was dissolved in 25 ml of 98% concentrated sulfuric acid, and the solution was measured using an Ostwald viscometer at a constant temperature of 25°C in a thermostatic bath. Relative viscosity in sulfuric acid = number of seconds it takes for the polymer solution to fall / number of seconds it takes for the sulfuric acid to fall. The relative viscosity was calculated from the ratio of the number of seconds it takes for the polymer solution to fall and the number of seconds it takes for the sulfuric acid to fall. The measurement was carried out five times, and the average value was calculated.

[0041] (2) Intrinsic viscosity IV: 8 g of a sample was dissolved in 100 ml of orthochlorophenol, and the solution specific viscosity ηr at 25°C was measured using an Ostwald viscometer. The intrinsic viscosity was calculated using the following approximate formula: IV = 0.0242ηr + 0.2634, where ηr = (t × d) / (t0 × d0), t: falling time of the solution, t0: falling time of orthochlorophenol, d: density of the solution, and d0: density of orthochlorophenol.

[0042] (3) Fineness: The corrected fineness was measured according to the method specified in JIS L1013 (2010) 8.3.1B method.

[0043] (4) Strength and elongation: Measured under the constant-rate elongation conditions specified in JIS L1013 (2010) 8.5.1 Standard Test. The sample was subjected to a Tensilon UCT-100 manufactured by Orientec Co., Ltd., with a grip distance of 25 cm and a pulling speed of 30 cm / min. The elongation was determined from the elongation at the point showing the maximum strength in the S-S curve.

[0044] (5) Ultrasonic water washing treatment: A 100 cm length of yarn was collected from the yarn sample and placed on a bobbin with holes. The yarn was subjected to ultrasonic water washing treatment by immersing it in a Sharp ultrasonic cleaner UT-605S (frequency: 35 kHz, output level: 50%) for 90 minutes while cooling the pure water (5 liters) to 30°C or less, and then air-drying it for 24 hours in a room at a temperature of 20°C ± 3°C and a humidity of 65% ± 5%.

[0045] (6) Amount of silicone compound attached and rate of removal: After wet decomposition of a yarn sample with sulfuric acid, the amount of silicone compound attached was calculated from the Si atom content by ICP analysis. Rate of silicone removal (%) = (W1 - W2) / W1 x 100 The amount of silicone compound attached to the yarn sample after spinning was W1, and the amount of silicone compound remaining on the yarn sample after ultrasonic water washing treatment by the method in (5) above was W2.

[0046] (7) Total amount of oil agent attached: 120 ml of n-hexane was added to 10 g of a yarn sample, and the mixture was shaken at room temperature for 10 minutes to extract the oil agent components into n-hexane. 100 ml of n-hexane after the oil agent component extraction was weighed and evaporated under vacuum, and the amount of oil agent component attached (W3) was calculated from the weight of the non-volatile content. The amount of silicone compound attached (W4) that could not be extracted with n-hexane was determined from the yarn sample after extraction using the method in (6) above. Total amount of oil agent attached = amount of oil agent component attached (W3) + amount of silicone compound attached (W4) The total amount of oil agent attached to the fiber was calculated using the above formula.

[0047] (8) Coefficient of dynamic friction between fibers in a dry state (μd: Dry): Measured using the device shown in Figure 1. A yarn sample was folded back on a bearing roller (diameter Φ11 mm) and crossed twice at a crossing angle of 30 degrees (twisting). The take-up roller speed was 40 m / min, and the speed of the yarn feed roller was adjusted so that the pulleys (pulley weight + load: 750 g) were balanced. The friction entry tension (T1) and friction exit tension (T2) were measured. Calculations were made using the following formula: Friction coefficient = (1 / πnβ) × ln(T2 / T1), where π = pi, n = 2 (twist count), and β = sin (crossing angle) = 0.50.

[0048] (9) Coefficient of dynamic friction between fibers in wet state (μd: Wet): Using the measurement method described in (8) above, the measurement was carried out with the intersection of the fibers immersed in pure water (1 liter / 25° C.) in a water tank.

[0049] (10) Coefficient of static friction between fibers in a dry state (μs: Dry): Using the measurement method described in (8) above, the friction entry tension (T1) and friction exit tension (T2) were measured at a take-up roller speed of 0.1 m / min.

[0050] (11) Coefficient of static friction between fibers in a wet state (μs: Wet): Using the measurement method described in (9) above, the friction entry tension (T1) and friction exit tension (T2) were measured at a take-up roller speed of 0.1 m / min with the intersection of the fibers immersed in pure water (1 liter / 25°C) in a water tank.

[0051] (12) Underwater / Abrasion-Breakage Evaluation: A yarn sample was folded back on a bearing roller (diameter Φ11 mm), crossed five times at a crossing angle of 30 degrees (twisting), and the number of strokes (breakage count) until the yarn broke was measured under a load of 500 g, a yarn stroke width of 50 mm, and a stroke count of 60 times / min. [Evaluation Criteria] S: Breakage count is 1000 or more A: Breakage count is 500 or more but less than 1000 B: Breakage count is 100 or more but less than 500 C: Breakage count is less than 100

[0052] (13) Operability Number of yarn breakages that occurred during spinning of 1 ton of polymer weight yarn. [Evaluation criteria] S: Less than 1 time A: 1 time or more but less than 3 times B: 3 times or more but less than 5 times C: 5 times or more.

[0053] (Examples 1 to 10) Polyamide 66 pellets obtained by a known liquid phase polymerization method were used. Copper iodide equivalent to 70 ppm of copper and potassium iodide equivalent to 1000 ppm of potassium were added to and adsorbed onto the polyamide 66 pellets, and polyamide 66 pellets were produced by a known solid phase polymerization method so as to have a sulfuric acid relative viscosity of 3.80.

[0054] The resulting nylon 66 pellets were fed to an extruder, and the discharge rate was adjusted using a metering pump to obtain a yarn having a fineness of 1,400 dtex. The spinning temperature was 295°C, and the yarn was spun through a spinneret with 204 holes. A heating cylinder was provided directly below the spinneret, and the spun yarn was passed through the high-temperature atmosphere of the heating cylinder and then cooled and solidified by blowing cold air at 20°C. An aqueous emulsion spinning oil having the composition shown in Tables 1 and 2 was applied to the cooled and solidified yarn using an oiling roller, and the yarn was wound around a spinning take-up roller to take up the spun yarn. The spinning oil had been previously atomized by applying pressure using a high-pressure homogenizer. The take-up yarn was then continuously hot-drawn in three stages without being taken up, to obtain a high-strength nylon 66 fiber having a fineness of 1,400 dtex and 204 filaments. The stretching ratio was changed so that the resulting strength would be the values ​​shown in Tables 1 and 2 below, the temperature of the final stretching roller was set to 230° C., and the film was wound up.

[0055] Example 11 The same procedure as in Example 1 was carried out except that polyamide 610 pellets obtained by a known liquid phase polymerization method were used, the spinning temperature was 280°C, and the final stretching roller temperature was 200°C.

[0056] Example 12 The same procedure as in Example 1 was carried out except that polyamide 6 pellets obtained by a known liquid phase polymerization method were used, the spinning temperature was 280°C, and the final stretching roller temperature was 200°C.

[0057]

[0058]

[0059] The physical properties of the polyamide fibers obtained in Examples 1 to 12 were evaluated, and the results are shown in Tables 1 and 2. As is clear from Tables 1 and 2, the polyamide fibers of the present invention have excellent friction durability in water due to a low coefficient of dynamic friction between fibers.

[0060] Comparative Examples 1 to 4 The same procedures as in Example 1 were carried out except that a water-based emulsion spinning oil having the composition shown in Table 3 was applied.

[0061] Comparative Example 5 The same procedure as in Comparative Example 1 was carried out except that polyamide 6 pellets obtained by a known liquid phase polymerization method were used, the spinning temperature was 280°C, and the final stretching roller temperature was 200°C.

[0062] (Comparative Example 6) The same procedure as in Comparative Example 1 was carried out, except that the post-treatment oil shown in Table 4 was additionally applied immediately before winding in the spinning process, i.e., after drawing, and the spinning oil was not subjected to high-pressure homogenizer treatment.

[0063] Comparative Examples 7 and 8 The same procedures as in Comparative Example 6 were carried out except that polyamide 6 pellets obtained by a known liquid phase polymerization method were used, the spinning temperature was 280°C, and the final stretching roller temperature was 200°C.

[0064] Comparative Example 9: Using polyethylene terephthalate pellets obtained by a known liquid-phase polymerization method, pellets having an intrinsic viscosity (IV) of 1.20 were prepared by a known solid-phase polymerization method. The same procedure as in Comparative Example 3 was carried out, except that the polyethylene terephthalate pellets were used, the spinning temperature was 300°C, and the spinning oil was not treated with a high-pressure homogenizer.

[0065]

[0066]

[0067] The polyamide fiber of the present invention exhibits a low coefficient of dynamic friction between fibers even when wet, and can provide a rope that has excellent long-term abrasion resistance even under harsh conditions of use underwater.

[0068] 1: Yarn 2: Yarn supply roller 3: Pulley 4: Load 5: Friction entry tension detector 6: Bearing roller 7: Water tank 8: Intersection angle 9: Friction exit tension detector 10: Take-up roller 11: Yarn suction device

Claims

1. A polyamide fiber characterized in that the coefficient of kinetic friction between fibers when wet (μd:Wet) is in the range of 0.060 to 0.225, and the ratio (μd:Wet / μd:Dry) of the coefficient of kinetic friction between fibers when wet to the coefficient of kinetic friction between fibers when dry (μd:Dry) is in the range of 0.67 to 1.

15.

2. Polyamide fiber according to claim 1, characterized in that the coefficient of static friction between fibers when wet (μs:Wet) is in the range of 0.090 to 0.218, and the ratio of the coefficient of static friction between fibers when wet to the coefficient of static friction between fibers when dry (μs:Wet / μs:Dry) is in the range of 0.85 to 1.

15.

3. Polyamide fiber according to claim 1 or 2, in which the total amount of spinning oil attached to the polyamide fiber is 0.5% by mass to 2.8% by mass, the amount of silicone compound attached to the polyamide fiber is 0.3% by mass to 1.5% by mass, and the drop-off rate of the silicone compound after ultrasonic water washing is 20% or less.

4. The polyamide fiber according to claim 1 or 2, which has a fineness of 100 dtex to 4000 dtex, a strength of 6.5 cN / dtex to 9.3 cN / dtex, and an elongation of 20.0% to 30.0%.

5. A method for producing polyamide fibers according to claim 1, characterized in that in the fiber production method having a drawing step, a spinning oil containing a silicone compound is applied before the drawing step.

6. Polyamide fiber according to claim 1, characterized in that it is used for marine ropes.

7. A marine rope made from the polyamide fiber of claim 1.

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