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

TECHNICAL FIELD

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

[0002] Polyamide fibers are excellent in mechanical properties and chemical properties, and thus are widely used in clothing applications and industrial applications. In industrial applications, polyamide fibers are suitably used for ropes, airbags, tire cords, nets, and the like because of their high tenacity and elongation properties, high abrasion resistance, and high durability.

[0003] Among them, in rope applications, particularly marine ropes for submarine mooring, used in platforms (bases) for marine oil fields and offshore wind power generation facilities, are required to have rope tenacity, abrasion resistance, and durability in the sea (wet condition), and impact absorbency for preventing moored objects from being damaged. In the offshore wind power generation facilities, a mooring rope having abrasion resistance durability for a long period of 20 years or more in a state of being vigorously moved by waves and wind has been required, and the dramatic improvement of the long-term abrasion durability thereof is a technical object.

[0004] Conventionally, various synthetic fibers have been proposed as marine rope fibers. For example, Patent Document 1 proposes a mixed fiber of a polybenzazole fiber and a high-tenacity polyethylene fiber.

[0005] In addition, for the purpose of improving long-term abrasion durability, surface treatment of fibers or ropes has also been studied. Patent Document 2 discloses a fiber and a rope in which an oil agent containing amino-modified silicone is applied to nylon yarns, and also discloses a method for reducing the fiber-to-fiber static friction coefficient in a dry condition.

[0006] Patent Document 3 discloses a polyester fiber to which an oil agent that is less likely to be removed and reduces a fiber-to-fiber static friction coefficient is applied.PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Laid-open Publication No. H7-165164 Patent Document 2: Japanese Patent Laid-open Publication No. H9-95877 Patent Document 3: Japanese Patent Laid-open Publication No. 2012-72512 SUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The synthetic fiber described in Patent Document 1 has high tenacity, but has low elongation, low impact absorbency to moored objects, and high cost, and thus has problems in terms of performance and economy. In the production of the rope described in Patent Document 2, a straight oil agent containing a fatty acid ester as a main component is applied to an undrawn yarn immediately after melt spinning, and then a low-friction amino-modified silicone oil agent is applied immediately before winding after a drawing / relaxation treatment. However, in the application of an oil agent immediately before winding in a high speed state, the adhesion amount of the low-abrasion oil agent is limited, and there is uneven adhesion of the oil agent, and fixing performance of the oil agent to the yarn is low. Therefore, although the fiber-to-fiber static friction coefficient in a dry condition is low, the static friction coefficient in a wet condition is high, thus posing a problem in long-term abrasion durability in water. The oil agent described in Patent Document 3 reduces the fiber-to-fiber static friction coefficient in a wet condition and exhibits some effect, but is removed immediately when vibration or a load in the sea is applied. Therefore, there remains a problem in long-term abrasion durability. In addition, polyester fibers, which have low elongation, exhibit low durability and also low impact acuteness, and thus have a problem that a large load is applied to the moored objects or the ropes.

[0009] The present invention has been made to solve the above problems, and an object of the present invention is to provide a polyamide fiber having dramatically improved long-term abrasion durability in water required for recent marine ropes, and improved yarn productivity in a yarn making process.SOLUTIONS TO THE PROBLEMS

[0010] The present invention has been intensively studied by the present inventors in order to solve the above problems, and has the following configuration. (1) A polyamide fiber having a fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) of 0.060 to 0.225, and a ratio (µd: Wet / µd: Dry) of the fiber-to-fiber dynamic friction coefficient in a wet condition to a fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry) of 0.67 to 1.15. (2) The polyamide fiber according to (1), having a fiber-to-fiber static friction coefficient in a wet condition (µs: Wet) of 0.090 to 0.218, and a ratio (µs: Wet / µs: Dry) of the fiber-to-fiber static friction coefficient in a wet condition to a fiber-to-fiber static friction coefficient in a dry condition of 0.85 to 1.15. (3) The polyamide fiber according to (1) or (2), wherein a total adhesion amount of a spinning oil to the polyamide fiber is 0.5 mass% to 2.8 mass%, an adhesion amount of a silicone compound to the polyamide fiber is 0.3 mass% to 1.5 mass%, and a removal rate of the silicone compound after ultrasonic water washing is 20% or less. (4) The polyamide fiber according to (1) or (2), wherein the polyamide fiber has a fineness of 100 dtex to 4000 dtex, a tenacity of 6.5 cN / dtex to 9.3 cN / dtex, and an elongation of 20.0% to 30.0%. (5) A method for producing the polyamide fiber according to (1), including a drawing process, wherein a spinning oil containing a silicone compound is applied before the drawing process. (6) The polyamide fiber according to (1), wherein the polyamide fiber is for a marine rope. (7) A marine rope including the polyamide fiber according to (1). EFFECTS OF THE INVENTION

[0011] The polyamide fiber of the present invention exhibits a low fiber-to-fiber dynamic friction coefficient even in a wet condition, and can provide a rope excellent in long-term abrasion durability even under severe use conditions in the sea. In the polyamide fiber of the present invention, the contamination of the high-temperature drawing roll is reduced in the yarn making process (even when an oil agent for reducing the fiber-to-fiber static friction coefficient is applied), and the productivity thereof is improved.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is a schematic view of an apparatus for measuring a fiber-to-fiber friction coefficient of a sample.EMBODIMENTS OF THE INVENTION

[0013] Hereinafter, the present invention will be described in detail.

[0014] The polyamide fiber of the present invention is made of polyamide. Examples of the polyamide 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, copolymers thereof, and blend polymers thereof. Among them, polymers selected from polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), and polyhexamethylene sebacamide (nylon 610), copolymerized polyamides mainly composed of these polymers, and blend polymers thereof are preferable.

[0015] When the copolymerized polyamide is used, examples of the copolymerization component include two or more selected from ε-caproamide, hexamethylene adipamide, tetramethylene adipamide, hexamethylene sebacamide, hexamethylene isophthalamide, tetramethylene terephthalamide, and xylylene phthalamide. Specifically, the polyamide fiber of the present invention is preferably made of a polymer selected from a copolymerized polyamide of nylon 6 and nylon 66, a copolymerized polyamide obtained by copolymerizing nylon 6 with a polyalkylene glycol, a dicarboxylic acid, an amine, or the like, and a blend polymer thereof.

[0016] In the polyamide fiber in the present invention, the content of the polyamide component in the polymer is preferably 95 wt% or more, and more preferably 97 wt% or more. When the content of the polyamide component is 95 wt% or more, good durability of the polyamide is sufficiently exhibited.

[0017] Furthermore, additives such as a weathering agent, a heat resistance agent, and an antioxidant can be added to the polyamide as necessary, and melt spinning can be performed. Some or all of the additives may be added during polymerization, or may be mixed by other methods.

[0018] In addition, in the case of producing a polyamide fiber having high tenacity, it is preferable that the viscosity of the polyamide resin used as a raw material is increased 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, and more preferably 700 dtex to 2000 dtex. When the fineness of the polyamide fiber is 100 dtex or more, the polyamide fiber is formed into a doubled and twisted yarn as a marine rope and processed into a product with high efficiency. On the other hand, when the fineness of the polyamide fiber is 4000 dtex or less, it is possible to adjust the fineness to a required fineness and combine the yarns.

[0020] The single fiber fineness of the polyamide fiber of the present invention is preferably 4 dtex to 40 dtex, and more preferably 5 dtex to 15 dtex. The polyamide fiber having a single fiber fineness of 4 dtex or more has good abrasion resistance with drawing rolls in the yarn making process, and can maintain good quality by preventing fluff when the drawing ratio is increased to obtain high-tenacity fibers. On the other hand, when the single fiber fineness is 40 dtex or less, the filaments are easily converged. In addition, the polymer is cooled well in the spinning process, and the form can be favorable even when the yarn is wound up at a high speed of 3000 m / min or more at which uniform drawing can be performed in the yarn making process.

[0021] The tenacity of the polyamide fiber of the present invention is preferably 6.5 cN / dtex to 9.3 cN / dtex, and more preferably 7.0 cN / dtex to 8.8 cN / dtex. Within such a range, a polyamide fiber having high mechanical properties even in water can be obtained, thus making it possible to provide a highly durable rope.

[0022] The elongation of the polyamide fiber of the present invention is preferably 20% to 30%, and more preferably 22% to 27%. In particular, when the tenacity is in the above range and the elongation is in the range, a polyamide fiber having high tenacity and high quality can be provided. Furthermore, a rope having excellent impact absorbency in water can be provided.

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

[0024] Hereinafter, an example of a method for producing a polyamide fiber according to the present embodiment will be described. An aspect of a yarn making process (yarn making method) of industrial nylon fibers will be described as an example, but the present invention is not limited thereto as long as the polyamide fiber of the present invention can be obtained.

[0025] First, a polymer melted in an extruder type spinning machine is spun from a spinneret. The spun polymer passes through a heating hood provided immediately below the spinneret, and is cooled and solidified by a cold air device to form a thread. Then, the thread is converged by a yarn guide, and then the spinning oil is applied to the thread by an oiling device. The thread is then wound around and taken up by a group of godet rolls. The take-up thread is wound around a plurality of pairs of godet rolls sequentially rotating at a high speed without being wound up once, and is drawn by the speed difference of the rolls. After performing multi-stage drawing in two or more stages, the drawn yarn is relaxed and wound up. It is preferable that hot drawing is performed at a temperature equal to or higher than the glass transition temperature, and final drawing and heat setting are performed at a high temperature of 180°C or higher and lower than the melting point. It is preferable that drawing is performed at a drawing ratio of 2 to 6 times, and the drawn yarn is wound up into a cheese shape with 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 the spinning oil before drawing in the yarn making process using at least one or more oiling rolls or a guide oil feeding device. The spinning oil may be either an aqueous emulsion containing a lubricant and a surfactant as a main component, or a nonaqueous treatment agent containing a lubricant and a surfactant as a main component.

[0027] The spinning oil in the present invention is preferably an aqueous emulsion. The spinning oil contains a silicone compound, and preferably further contains a wax-based component. The aqueous emulsion is prepared by appropriately selecting and combining a lubricant, a surfactant, and an ester component, a polyether component, an additive and the like, which are used as other components.

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

[0029] By applying, before the drawing process, a spinning oil prepared by applying pressure to a spinning oil containing the compound with a high-pressure homogenizer to convert particles into fine particles, generation of dirt on the surfaces of the rolls, yarn breakage associated with the dirt, and generation of fluff can be suppressed even when the thread is subjected to the subsequent hot drawing process. As a result, a polyamide fiber satisfying the fiber-to-fiber dynamic friction coefficient of the present invention can be produced with good yarn productivity in the yarn making.

[0030] The lubricant 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. Furthermore, the lubricant is preferably a divalent fatty acid ester compound containing 20 mass% to 50 mass% of ethylene oxide.

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

[0032] The total adhesion amount of the oil agent in the polyamide fiber of the present invention is preferably 0.5 mass% to 2.8 mass%, more preferably 0.5 mass% to 2.3 mass%, and still more preferably 0.6 mass% to 1.8 mass%. Within such a range, the fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry) can be reduced, a decrease in tenacity due to friction between fibers in the production of the rope can be suppressed, and furthermore, process passability can be enhanced. In the production of the polyamide fiber, the upper limit of the total adhesion amount of the oil agent is 2.8 mass% or less from the viewpoint of stability of yarn travelling when the oil agent is applied before the drawing process.

[0033] The oil agent adhered to the polyamide fiber of the present invention contains a silicone compound. The adhesion amount of the silicone compound to the polyamide fiber is preferably 0.3 mass% to 1.5 mass%, more preferably 0.3 mass% to 1.2 mass%, and still more preferably 0.4 mass% to 1.0 mass%. By setting the adhesion amount of the silicone compound to 0.3 mass% or more, the fiber-to-fiber dynamic friction coefficient in a wet condition can be lowered when the removal rate of the silicone compound after water washing falls within a prescribed range. By setting the adhesion amount of the silicone compound to 1.5 mass% or less, dirt on the high-temperature drawing roll in the yarn making process can be reduced.

[0034] Furthermore, the polyamide fiber of the present invention preferably has a removal rate of the silicone compound after ultrasonic water washing (hereinafter, abbreviated as silicone removal rate) of 20% or less. The silicone removal rate is more preferably 18% or less, and still more preferably 16% or less. Within such a range, the silicone removal rate can be reduced even in a state in which the rope is vigorously moved by the waves and wind when used in water. Therefore, the ratio (µd: Wet / µd: Dry) between the fiber-to-fiber dynamic friction coefficient in a dry condition and the fiber-to-fiber dynamic friction coefficient in a wet condition can be controlled, and suppression of the fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet), which cannot be achieved by conventional polyamide fibers, can be achieved.

[0035] In the polyamide fiber of the present invention, the fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) is 0.060 to 0.225, and the ratio (µd: Wet / µd: Dry) of the fiber-to-fiber dynamic friction coefficient in a wet condition to the fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry) is 0.67 to 1.15. The fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) is preferably 0.080 to 0.210, and more preferably 0.098 to 0.180. The ratio (µd: Wet / µd: Dry) between the fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry) and the fiber-to-fiber dynamic friction coefficient in a wet condition is preferably 0.75 to 1.10, and more preferably 0.85 to 1.05. As can be seen from known documents, in general, when fibers are wet with water, slippage between the fibers deteriorates, and the fiber-to-fiber friction coefficient in a wet condition is larger than the fiber-to-fiber friction coefficient in a dry condition. In view of this fact, the inventors conducted intensive studies and have found a polyamide fiber capable of exhibiting low friction properties equivalent to the fiber-to-fiber dynamic friction coefficient in a dry condition even in a wet condition. According to the present invention, the fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) can be controlled within the above range, and long-term abrasion durability has been dramatically improved. When the fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) exceeds 0.225, an improvement in long-term abrasion durability in water cannot be achieved. When the fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) is less than 0.060, the friction between the fibers and the drawing rolls becomes too low. As a result, drawing at a high magnification cannot be performed, and a high-tenacity yarn cannot be obtained.

[0036] In the polyamide fiber of the present invention, the fiber-to-fiber static friction coefficient in a wet condition (µs: Wet) is 0.090 to 0.218, and the ratio (µs: Wet / µs: Dry) of the fiber-to-fiber static friction coefficient in a wet condition to the fiber-to-fiber static friction coefficient in a dry condition (µs: Dry) is 0.85 to 1.15. The fiber-to-fiber static friction coefficient in a wet condition (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 fiber-to-fiber static friction coefficient in a wet condition (µs: Wet) to the fiber-to-fiber static friction coefficient in a dry condition (µs: Dry) is preferably 0.90 to 1.10, and more preferably 0.92 to 1.03. Within such a range, it is possible to suppress a decrease in rope tenacity due to abrasion between fibers when the rope is used.

[0037] As a result of intensive studies, the inventors have found that the adhesion amount of the silicone compound can be increased by applying a spinning oil containing a silicone compound not immediately before winding, but before drawing in the yarn making process. Furthermore, the inventors have found that, by applying the spinning oil to fibers and then subjecting the fibers to a hot drawing process, the fixing performance of the oil agent to the fibers is improved, and the removal rate of the silicone compound after ultrasonic water washing and the fiber-to-fiber friction coefficient in a wet condition are reduced.

[0038] The polyamide fiber of the present invention exhibits excellent properties for a marine rope. The marine rope of the present invention can be produced by a known rope production method using the polyamide fiber of the present invention. The marine rope of the present invention is made of the polyamide fiber of the present invention, but may be used in the form of containing other fibers as long as the properties thereof are not impaired. The marine rope of the present invention may be a double rope or a triple rope, and one layer of these ropes may be made of the polyamide fiber of the present invention.EXAMPLES

[0039] Hereinafter, aspects of the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to the examples. The definition and measurement method of each property in the present invention are as follows.

[0040] (1) Relative viscosity in sulfuric acid: In 25 ml of 98% concentrated sulfuric acid, 0.25 g of a sample was dissolved. Measurement was performed using an Oswald viscometer under a constant temperature of a 25°C thermostatic chamber. The relative viscosity was determined from the ratio of the dropping time of the polymer solution to the dropping time of sulfuric acid. The measurement was performed five times, and the average was taken. (2) Intrinsic viscosity IV: In 100 ml of ortho-chlorophenol, 8 g of a sample was dissolved, and the relative viscosity ηr of the solution at 25°C was measured with an Ostwald viscometer. The intrinsic viscosity was calculated from the following approximate formula: IV = 0.0242 ηr + 0.2634 where ηr = (t × d) / (t0 × d0) t: dropping time of solution t0: dropping time of ortho-chlorophenol d: density of solution d0: density of ortho-chlorophenol. (3) Fineness: According to a method defined in JISL1013 (2010) 8.3.1, method B, the fineness based on corrected mass was measured as the fineness. (4) Tenacity and elongation: The tenacity and elongation were measured under the conditions of constant rate extension defined in JIS L 1013 (2010) 8.5.1, Standard Time Test. A sample was measured using "TENSILON" UCT-100 manufactured by ORIENTEC CORPORATION, at a distance between chucks of 25 cm and a tensile speed of 30 cm / min. The elongation was determined from the elongation at the point showing the maximum tenacity in an S-S curve. (5) Ultrasonic water washing treatment: A 100 cm thread was collected from a yarn sample on a perforated bobbin, and immersed in an ultrasonic cleaner UT-605S (frequency: 35 KHz, output level: 50%) manufactured by Sharp Corporation for 90 minutes while cooling the pure water so that the temperature of pure water (5 liters) was 30°C or lower, to perform ultrasonic water washing treatment. Then, the thread was naturally dried in a room at a temperature of 20°C±3°C and a humidity of 65%±5% for 24 hours. (6) Adhesion amount and removal rate of silicone compound: A yarn sample was subjected to wet decomposition with sulfuric acid, and then the adhesion amount of the silicone compound was calculated from the Si atom content by ICP analysis. Silicone removal rate % = W 1 − W 2 / W 1 × 100 The adhesion amount of the silicone compound adhered to the yarn sample after yarn making was defined as W1. The adhesion amount of the silicone compound remaining in the yarn sample after ultrasonic water washing treatment by the method described in (5) was defined as W2. (7) Total adhesion amount of oil agent: To 10 g of a yarn sample, 120 ml of n-hexane is added, and the mixture is shaken at room temperature for 10 minutes, to thereby extract the oil agent component into n-hexane. Then, 100 ml of n-hexane after extraction of the oil agent component was weighed and then evaporated under vacuum. The adhesion amount of the oil agent component (W3) was determined from the weight of the nonvolatile component. The adhesion amount of the silicone compound (W4) that could not be extracted with n-hexane was determined by the method described in (6) from the yarn sample after extraction. The total adhesion amount of the oil agent in the fiber was calculated from the above formula. (8) Fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry): Measurement was performed using the apparatus shown in Fig. 1. A yarn sample was folded back with a bearing roll (diameter Φ11 mm) and crossed (twisted) twice such that the crossing angle was 30 degrees. The take-up roll speed was 40 m / min, and the supply roll speed was adjusted so that the system of the pulley (pulley weight + load: 750 g) was in equilibrium. The inlet tension (T1) and the outlet tension (T2) were measured. The friction coefficient was calculated by the following formula: Friction coefficient = 1 / πnβ × ln T 2 / T 1 where π = circular constant, n = 2 (number of twists), and β = sin (crossing angle) = 0.50. (9) Fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet): Using the measurement method described in (8), measurement was performed while the portion where the fibers were crossed was immersed in pure water (1 liter / 25°C) in a water tank. (10) Fiber-to-fiber static friction coefficient in a dry condition (µs: Dry): Using the measurement method described in (8), the inlet tension (T1) and the outlet tension (T2) were measured at a take-up roll speed of 0.1 m / min. (11) Fiber-to-fiber static friction coefficient in a wet condition (µs: Wet): Using the measurement method described in (9), the inlet tension (T1) and the outlet tension (T2) were measured at a take-up roll speed of 0.1 m / min while the portion where the fibers were crossed was immersed in pure water (1 liter / 25°C) in a water tank. (12) Abrasion and breakage test in water: A yarn sample was folded back with a bearing roll (diameter Φ11 mm) and crossed (twisted) 5 times such that the crossing angle was 30 degrees. The number of strokes (number of cycles to breakage) until the yarn was broken was measured under the conditions such that the load was 500 g, the stroke width of the yarn was 50 mm, and the number of strokes was 60 times / min. [Criteria for determination]

[0041] S: The number of cycles to breakage is 1000 or more. A: The number of cycles to breakage is 500 or more and less than 1000. B: The number of cycles to breakage is 100 or more and less than 500. C: The number of cycles to breakage is less than 100. (13) Yarn productivity

[0042] Number of yarn breakages occurred during yarn making for 1 ton of yarn on a polymer weight basis.[Criteria for determination]

[0043] S: less than 1 time A: 1 time or more and less than 3 times B: 3 times or more and less than 5 times C: 5 times or more. (Examples 1 to 10)

[0044] Polyamide 66 pellets obtained by a known liquid phase polymerization method were used. Copper(I) iodide in an amount corresponding to 70 ppm as copper and potassium iodide in an amount corresponding to 1000 ppm as potassium were added to and adsorbed to the polyamide 66 pellets, and polyamide 66 pellets were prepared by a known solid phase polymerization method such that the relative viscosity in sulfuric acid was 3.80.

[0045] The obtained nylon 66 pellets were supplied to an extruder, and the discharge amount was adjusted by a metering pump so that a thread having a fineness of 1400 dtex was obtained. Spinning was performed at a spinning temperature of 295°C through a spinneret having 204 holes. A heating hood was provided immediately below the spinneret, and the spun yarn was passed through a high-temperature atmosphere of the heating hood, and then cooled and solidified by blowing cold air at 20°C. Each of the spinning oils of aqueous emulsions having the compositions shown in Tables 1 and 2 was applied to the cooled and solidified thread with an oiling roll. The spun thread was wound around and taken up by a take-up roll for the spun yarn. As the spinning oil, a spinning oil in which particles therein are formed into fine particles by applying pressure to the spinning oil with a high-pressure homogenizer in advance was applied. Then, the take-up thread was continuously hot-drawn in three stages without being wound up once to obtain high-tenacity nylon 66 fibers of 1400 dtex and 204 filaments. The drawing ratio was changed so that the obtained tenacity had the values shown in Tables 1 and 2 below, the temperature of the final drawing roll was set to 230°C, and the yarn was wound up.(Example 11)

[0046] 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 drawing roll temperature was 200°C.(Example 12)

[0047] 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 drawing roll temperature was 200°C.[Table 1]

[0048] [Table 1]Examples123456Polymer typeN66N66N66N66N66N66Spinning oilLubricant [parts]50.050.050.050.050.054.0Surfactant [parts]25.025.025.025.022.026.0Silicone compound [parts] (Amino-modified silicone)13.013.013.013.016.08.0Wax-based component [parts] (Polyethylene wax)2.02.02.02.03.02.0other additives [parts]10.010.010.010.09.010.0Homogenizer treatmentYesYesYesYesYesYesPost-treatment oilLubricant [parts]------Surfactant [parts]------Silicone compound [parts] (Amino-modified silicone)------Wax-based component [parts] (Polyethylene wax)------Other additives [parts]------Total adhesion amount of oil agent in fiberAfter yarn making [mass%]1.621.202.002.601. 611.63After ultrasonic water washing [mass%]0.800.630.941.140.860.77Adhesion amount of silicone compound in fiberW1: after yarn making [mass%]0.680.500.841.090.760.65W2: after ultrasonic water washing [mass%]0.610.450.750.950.670.59Silicone removal rate [%] (W1 - W2) / W1 × 10010101113129Fiber-to-fiber dynamic friction coefficientDry condition (µd: Dry)0.1390.1700.1110.0710.1330.141Wet condition (µd: Wet)0.1190.1430.0940.0730.1030.128· Yarn speed 40 m / minRatio: wet condition / dry condition (µd: wet / µd: Dry)0.8560.8410.8471.0280.7740.908· Inlet tension: 750 gFiber-to-fiber static friction coefficientDry condition (µs: Dry)0.1640.1850.1490.1290.1610.165Wet condition (µs: Wet)0.1520.1580.1390.1280.1410.156· Yarn speed 0.1 m / minRatio: wet condition / dry condition (µs: wet / µs: Dry)0.9270.8540.9330.9920.8760.945· Inlet tension: 750 gPhysical propertiesFineness [dtex]140014001400140014001400Tenacity [cN / dtex]8.58.58.58.58.28.6Elongation [%]23.423.523.323.323.223.4Abrasion and breakage test in waterSSSSSSYarn productivitySSSASS [Table 2]

[0049] [Table 2]Examples789101112Polymer typeN66N66N66N66N610N6Spinning oilLubricant [parts]49.049.058.058.050.050.0Surfactant [parts]19.019.026.026.025.025.0Silicone compound [parts] (Amino-modified silicone)23.023.05.05.013.013.0Wax-based component [parts] (Polyethylene wax)3.03.01.01.02.02.0Other additives [parts]7.07.010.010.010.010.0Homogenizer treatmentYesYesYesYesYesYesPost-treatment oilLubricant [parts]------Surfactant [parts]------Silicone compound [parts] (Amino-modified silicone)------Wax-based component [parts] (Polyethylene wax)------Other additives [parts]------Total adhesion amount of oil agent in fiberAfter yarn making [mass%]2.600.802.600.801.571. 60After ultrasonic water washing [mass%]1.300.571.040.450.770.78Adhesion amount of silicone compound in fiberW1: after yarn making [mass%]1.380.420.960.300.660.67W2: after ultrasonic water washing [mass%]1.120.380.860.270.590.60Silicone removal rate [%] (W1 - W2) / W1 × 100191010101110Fiber-to-fiber dynamic friction coefficientDry condition (µd: Dry)0.0680.1920.0770.2030.1360.149Wet condition (µd: Wet)0.0700.1550.0880.1940.1280.156· Yarn speed 40 m / minRatio: wet condition / dry condition (µd: Wet / µd: Dry)1.0290.8071.1430.9560.9411.047· Inlet tension: 750 gFiber-to-fiber static friction coefficientDry condition (µs: Dry)0.1280.1910.1320.1960.1620.169Wet condition (µs: Wet)0.1280.1670.1380.1880.1530.167· Yarn speed 0.1 m / minRatio: wet condition / dry condition (µs: Wet / µs: Dry)1.0000.8741.0450.9590.9440.988· Inlet tension: 750 gPhysical propertiesFineness [dtex]140014001400140014001400Tenacity [cN / dtex]8.18.38.58.58.68.4Elongation [%]22.823.423.223.822.623.5Abrasion and breakage test in waterSSSASSYarn productivityASASSS

[0050] The results of evaluating the physical properties of the polyamide fibers obtained in Examples 1 to 12 are shown in Tables 1 and 2. As is apparent from Tables 1 and 2, the polyamide fiber of the present invention is excellent in abrasion durability in water by reducing the fiber-to-fiber dynamic friction coefficient.(Comparative Examples 1 to 4)

[0051] The same procedure as in Example 1 was carried out except that each of the spinning oils of aqueous emulsions having the compositions shown in Table 3 was applied.(Comparative Example 5)

[0052] 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 drawing roll temperature was 200°C.(Comparative Example 6)

[0053] 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 yarn making process, that is, after drawing, and the spinning oil was not subjected to a high-pressure homogenizer treatment.(Comparative Examples 7 and 8)

[0054] The same procedure as in Comparative Example 6 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 drawing roll temperature was 200°C.(Comparative Example 9)

[0055] 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 subjected to a high-pressure homogenizer treatment.[Table 3]

[0056] [Table 3]Comparative Examples12345Polymer typeN66N66N66N66N6Spinning oilLubricant [parts]60.060.068.045.060.0Surfactant [parts]33.033.024.020.033.0Silicone compound [parts] (Amino-modified silicone)2.02.00.030.02.0Wax-based component [parts] (Polyethylene wax)1.01.00.02.01.0other additives [parts]5.05.08.03.05.0Homogenizer treatmentYesYesYesYesYesPost-treatment oilLubricant [parts]-----Surfactant [parts]-----Silicone compound [parts] (Amino-modified silicone)-----Wax-based component [parts] (Polyethylene wax)-----Other additives [parts]-----Total adhesion amount of oil agent in fiberAfter yarn making [mass%]0.811.200.852.641.20After ultrasonic water washing [mass%]0.290.340.171.330.34Adhesion amount of silicone compound in fiberW1: after yarn making [mass%]0.130.190.001.580.19W2: after ultrasonic water washing [mass%]0.120.170.001.170.17Silicone removal rate [%] (W1 - W2) / W1 × 100811-2611Fiber-to-fiber dynamic friction coefficientDry condition (µd: Dry)0.2350.2250.2940.0650.256Wet condition (µd: Wet)0.2590.2380.3810.0580.263· Yarn speed 40 m / minRatio: wet condition / dry condition (µd: Wet / µd: Dry)1.1021.0581.2960.8921.027· Inlet tension: 750 gFiber-to-fiber static friction coefficientDry condition (µs: Dry)0.2130.2080.2430.1260.229Wet condition (µs: Wet)0.2180.2020.2630.1240.212· Yarn speed 0.1 m / minRatio: wet condition / dry condition (µs: wet / µs: Dry)1.0230.9711.0820.9840.926· Inlet tension: 750 gPhysical propertiesFineness [dtex]14001400140014001400Tenacity [cN / dtex]8.48.38.38.38.3Elongation [%]23.823.823.523.623.8Abrasion and breakage test in waterCBCSCYarn productivitySSACS [Table 4]

[0057] [Table 4]Comparative Examples6789Polymer typeN66N6N6PETspinning oilLubricant [parts]68.068.068.068.0Surfactant [parts]24.024.024.024.0Silicone compound [parts] (Amino-modified silicone)0.00.00.00.0Wax-based component [parts] (Polyethylene wax)0.00.00.00.0Other additives [parts]8.08.08.08.0Homogenizer treatmentNoNoNoNoPost-treatment oilLubricant [parts]484848-Surfactant [parts]262626-Silicone compound [parts] (Amino-modified silicone)121212-Wax-based component [parts] (Polyethylene wax)222-Other additives [parts]101010-Total adhesion amount of oil agent in fiberAfter yarn making [mass%]0.830.801.600.75After ultrasonic water washing [mass%]0.230.230.250.17Adhesion amount of silicone compound in fiberW1: after yarn making [mass%]0.170.160.640.00W2: after ultrasonic water washing [mass%]0.060.060.080.00silicone removal rate [%] (W1 - W2) / W1 × 100656388-Fiber-to-fiber dynamic friction coefficientDry condition (µd: Dry)0.2120.2130.1430.222Wet condition (µd: Wet)0.2880.3050.2780.301- Yarn speed 40 m / minRatio: wet condition / dry condition (µd: Wet / µd: Dry)1.3581.4321.9441.356- Inlet tension: 750 gFiber-to-fiber static friction coefficientDry condition (µs: Dry)0.2010.2020.1660.206Wet condition (µs: Wet)0.2300.2390.2220.236- Yarn speed 0.1 m / minRatio: wet condition / dry condition (µs: wet / µs: Dry)1.1441.1831.3371.146- Inlet tension: 750 gPhysical propertiesFineness [dtex]1400140014001400Tenacity [cN / dtex]8.38.38.48.5Elongation [%]23.622.822.314.8Abrasion and breakage test in waterCCCCYarn productivitySSSS INDUSTRIAL APPLICABILITY

[0058] The polyamide fiber of the present invention exhibits a low fiber-to-fiber dynamic friction coefficient even in a wet condition, and can provide a rope excellent in long-term abrasion durability even under severe use conditions in the sea.DESCRIPTION OF REFERENCE SIGNS

[0059] 1: Thread 2: Supply roll 3: Pulley 4: Load 5: Inlet tension detector 6: Bearing roll 7: Water tank 8: Crossing angle 9: Outlet tension at friction detector 10: Take-up roll 11: Thread suction device

Claims

1. A polyamide fiber having a fiber-to-fiber dynamic friction coefficient in a wet condition (µd: Wet) of 0.060 to 0.225, and a ratio (µd: Wet / µd: Dry) of the fiber-to-fiber dynamic friction coefficient in a wet condition to a fiber-to-fiber dynamic friction coefficient in a dry condition (µd: Dry) of 0.67 to 1.15.

2. The polyamide fiber according to claim 1, having a fiber-to-fiber static friction coefficient in a wet condition (µs: Wet) of 0.090 to 0.218, and a ratio (µs: Wet / µs: Dry) of the fiber-to-fiber static friction coefficient in a wet condition to a fiber-to-fiber static friction coefficient in a dry condition of 0.85 to 1.15.

3. The polyamide fiber according to claim 1 or 2, wherein a total adhesion amount of a spinning oil to the polyamide fiber is 0.5 mass% to 2.8 mass%, an adhesion amount of a silicone compound to the polyamide fiber is 0.3 mass% to 1.5 mass%, and a removal rate of the silicone compound after ultrasonic water washing is 20% or less.

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

5. A method for producing the polyamide fiber according to claim 1, comprising a drawing process, wherein a spinning oil containing a silicone compound is applied before the drawing process.

6. The polyamide fiber according to claim 1, wherein the polyamide fiber is for a marine rope.

7. A marine rope comprising the polyamide fiber according to claim 1.

Images