Polyethylene fibers and products containing said fibers

Abstract

The present invention provides: a polyethylene fiber which has excellent cut resistance, while having almost or completely no residual solvent; and a product which uses this fiber. A polyethylene fiber which is characterized by containing hard particles that have an average breadth of 18 μm or less, while having an aspect ratio of from 3 to 100.

Description

[Technical Field]

[0001] The present invention relates to polyethylene fibers and products containing the fibers. [Background technology]

[0002] Traditionally, natural fibers such as cotton and common organic fibers have been used as cut-resistant materials. Furthermore, gloves knitted from these fibers have been widely used in fields requiring cut resistance. Therefore, knitted or woven fabrics made from spun yarns of high-strength fibers such as aramid fibers have been devised to provide cut resistance. However, these have been unsatisfactory in terms of shedding and durability. Meanwhile, as an alternative, attempts have been made to improve cut resistance by combining metallic fibers with organic or natural fibers. However, the addition of metallic fibers results in a stiff texture and loss of flexibility.

[0003] As a technique for solving the above problems, for example, ultra-high molecular weight polyethylene fibers that have excellent cut resistance due to the yarn containing a plurality of hard fibers with an average diameter of up to 25 μm are known (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2010-507026 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, ultra-high molecular weight polyethylene is spun by a solution spinning method. Although high-strength polyethylene fibers can be obtained by this manufacturing method, not only is productivity low, but large-scale ventilation equipment is required to recover the solvent during yarn production. In addition, leaching of the solvent remaining in the polyethylene fibers becomes an issue, limiting the uses of the polyethylene fibers.

[0006] The present invention has been made to solve the problems of the prior art. That is, an object of the present invention is to provide a polyethylene fiber that has excellent cut resistance and leaves little or no solvent residue, and a product using the fiber. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention has the following configuration.

[0008] 1. Polyethylene fibers characterized by having an aspect ratio of 3 or more and 100 or less and containing hard particles with an average short diameter of 18 μm or less. 2. The polyethylene fiber according to 1 above, wherein the intrinsic viscosity [η] of the polyethylene is 0.8 dL / g or more and less than 8.0 dL / g. 3. Polyethylene fiber according to 1. or 2. above, wherein the weight-average molecular weight of the polyethylene is 40,000 or more and 900,000 or less. 4. The polyethylene fiber according to any one of the above items 1 to 3, wherein the hard particles are metal, silicon compound, or mineral. 5. The polyethylene fiber according to any one of 1. to 4. above, wherein the hard particles contain 20% by mass or more of SiO2. 6. The polyethylene fiber according to any one of 1. to 5. above, wherein the hard particles have an average minor axis of 1.0 μm or more. 7. The polyethylene fiber according to any one of 1. to 6. above, which contains 2% by mass or more of the hard particles. 8. A product comprising the polyethylene fiber described in any one of 1. to 7. above. 9. The product according to claim 8, wherein the product is a cut-resistant woven or knitted fabric. 10. The product according to 8. or 9. above, wherein the product is a glove. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide polyethylene fibers that have excellent cut resistance and leave little or no solvent residue, and products using said fibers. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to polyethylene fibers containing hard particles. The present invention will be described in detail below.

[0011] <Polyethylene fiber> The polyethylene fiber of the present invention preferably has an intrinsic viscosity [η] of 0.8 dL / g or more and less than 8.0 dL / g, more preferably 1.0 dL / g or more and 6.0 dL / g or less, even more preferably 1.2 dL / g or more and less than 4.9 dL / g, and particularly preferably 1.5 dL / g or more and 2.5 dL / g or less.

[0012] By setting the intrinsic viscosity at 0.8 dL / g or higher, the number of structural defects in the fiber can be reduced by reducing the number of polyethylene molecular end groups. This can improve the mechanical properties of the fiber, such as strength and modulus, as well as cut resistance. Furthermore, by setting the intrinsic viscosity to less than 8.0 dL / g, clogging of the filtration filter during the spinning process due to the hard particles added can be suppressed, improving productivity. Furthermore, setting the intrinsic viscosity to less than 8.0 dL / g facilitates spinning using the melt spinning method, eliminating the need for solution spinning methods such as gel spinning. When using the melt spinning method, no solvent is used during production, which reduces the impact on workers and the environment. Furthermore, since there is no residual solvent in the finished fiber, there is no problem of residual solvent leaching, and the use applications of polyethylene fibers are not limited.

[0013] The polyethylene fiber of the present invention preferably has a weight-average molecular weight (Mw) of 40,000 or more and 900,000 or less. By setting Mw to 40,000 or more, the number of structural defects in the fiber can be reduced by reducing the number of polyethylene molecular end groups. This improves the mechanical properties of the fiber, such as strength and modulus, as well as cut resistance. Furthermore, by setting Mw to 900,000 or less, spinning by melt spinning becomes easier, eliminating the need for solution spinning, such as gel spinning. This is advantageous in terms of reducing production costs and simplifying the work process. Mw is more preferably 60,000 or more, even more preferably 80,000 or more, more preferably 700,000 or less, even more preferably 500,000 or less, and particularly preferably 350,000 or less. Mw can be calculated from the intrinsic viscosity in dL / g using the following formula: Intrinsic viscosity=4.6×10 -4 ×Mw 0.73

[0014] Furthermore, the polyethylene of the present invention may be a copolymer of ethylene with a small amount of other monomers, such as α-olefins, acrylic acid and its derivatives, methacrylic acid and its derivatives, or vinylsilane and its derivatives. Alternatively, the polyethylene may be a blend of these copolymers, a copolymer of an ethylene homopolymer with the above copolymer, or a blend of an ethylene homopolymer with a homopolymer of another α-olefin. In particular, using a copolymer with an α-olefin such as propylene or butene-1 to contain a certain amount of short- or long-chain branching is more preferable in producing the polyethylene fiber of the present invention, since this provides stability in spinning and drawing. However, an excessive content of components other than ethylene can actually hinder drawing. Therefore, from the perspective of obtaining polyethylene fibers with high strength and high modulus, the proportion of components other than ethylene in the entire polyethylene fiber, on a monomer basis, is preferably 0.2 mol % or less, more preferably 0.1 mol % or less. Of course, the polyethylene of the present invention may be composed solely of ethylene.

[0015] The polyethylene fiber of the present invention may have a core-sheath structure, and may have an irregular shape such as a star shape, a triangle shape, or a hollow shape.

[0016] <Hard particles> The polyethylene fiber of the present invention contains hard particles. In the present invention, "hard particles" refers to particles that are difficult to aggregate in the polymer (polyethylene fiber). In the present invention, the major axis of the hard particle refers to the length at the position where the length of the hard particle is at its maximum (the length of the maximum diameter), and the minor axis of the hard particle refers to the width perpendicular to the major axis, specifically the length at the position where the length is at its maximum in the direction perpendicular to the length L of the major axis at the maximum position (the major axis of the hard particle).

[0017] The average value of the major axis lengths of the hard particles used in the present invention (hereinafter referred to as the average major axis length) is preferably 25 μm or more, more preferably 45 μm or more, and even more preferably 80 μm or more. The average major axis length of the hard particles used in the present invention is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. The methods for measuring the major axis length of the hard particles and calculating the average major axis length will be described in detail in the Examples section below. The average major axis length is calculated by measuring the major axis length of each of 10 hard particles and averaging the measurements.

[0018] The average minor axis of the hard particles used in the present invention (hereinafter referred to as the average minor axis) is 18 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. If the average minor axis of the hard particles exceeds 18 μm, the filtration filter will clog during spinning, significantly reducing fiber productivity, particularly stretchability. Furthermore, if the average minor axis of the hard particles exceeds 18 μm, melt spinning will be difficult. The average minor axis of the hard particles used in the present invention is preferably 1.0 μm or more, more preferably 3.0 μm or more, and even more preferably 5.0 μm or more. If the average minor axis of the hard particles is less than 1.0 μm, the specific surface area will increase and the hard particles will aggregate, potentially causing clogging during spinning. The methods for measuring the minor axis of the hard particles and calculating the average minor axis will be described in detail in the Examples section below. The average minor axis is calculated by measuring the minor axis of each of 10 hard particles and averaging the measurements.

[0019] The aspect ratio of the hard particles used in the present invention is 3 or more and 100 or less. If the aspect ratio is less than 3, cut resistance will be poor. If the aspect ratio exceeds 100, melt spinning will be difficult. The aspect ratio is preferably 5 or more and 70 or less, more preferably 7 or more and 50 or less, and particularly preferably 9 or more and 30 or less. Here, the aspect ratio of the hard particles is a value calculated based on JIS8900-1 (i.e., an index representing the shape of a particle defined by the major axis / minor axis in a microscopic image of the particle). The methods for measuring and calculating the aspect ratio of hard particles will be described in detail in the Examples section below. The aspect ratio of each of 10 hard particles is calculated from the major axis and minor axis of each particle, and the average value of the aspect ratios of the 10 hard particles is taken as the aspect ratio of the hard particles.

[0020] The average particle size of the hard particles used in the present invention is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. The average particle size of the hard particles used in the present invention is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 135 μm or less, and particularly preferably 100 μm or less. By making the average particle size of the hard particles 10 μm or more, cut resistance can be improved. Furthermore, by making the average particle size of the hard particles 300 μm or less, clogging of the filtration filter during spinning can be suppressed, improving productivity. The average particle size of the hard particles is determined by calculating the average major axis and average minor axis using the method described above, and the average value of the average major axis and average minor axis is taken as the average particle size.

[0021] Specific examples of hard particles used in the present invention include metals, silicon compounds, minerals, and the like. One or more of these may be used. Here, examples of the metals include aluminum, tungsten, iron, titanium, chromium, zinc, manganese, nickel, copper, silver, and gold, as well as compounds of these metals. The silicon compounds are not particularly limited as long as they contain silicon, and examples include silica, glass, and silicon carbide. Examples of the minerals include quartz, rock wool, and iron oxide. Rock wool is a material (mineral fiber) produced by rapidly cooling a material primarily composed of rock or blast furnace slag melted in a melting furnace. For example, slag wool produced from a material primarily composed of blast furnace slag is also included.

[0022] The hard particles used in the present invention preferably contain an aluminum compound or a silicon compound, and more preferably contain an aluminum compound and a silicon compound.

[0023] The aluminum compound is not particularly limited as long as it is a compound containing aluminum, but Al2O3 is preferred. The silicon compound is not particularly limited as long as it is a compound containing silicon, and examples include silica, glass, and silicon carbide. However, silica and / or glass are preferred, and glass is more preferred. Silica and glass are distinguished mainly by their SiO2 content. Silica is essentially composed of SiO2 alone, and the SiO2 content of silica is generally 95 mass% or more. In contrast, the main component of glass is generally SiO2, and may also contain Al2O3, B2O3, P2O5, etc. The shape of the glass used in the present invention is not particularly limited, but glass fiber is preferred.

[0024] The hard particles preferably contain 5% by mass or more of an aluminum compound, more preferably 10% by mass or more, and preferably 40% by mass or less, and more preferably 30% by mass or less. The hard particles preferably contain 20% by mass or more of a silicon compound, more preferably 30% by mass or more, and preferably 70% by mass or less, and more preferably 60% by mass or less. In particular, the hard particles preferably contain 20% by mass or more of SiO2, more preferably 30% by mass or more, and even more preferably 50% by mass or more, and preferably 70% by mass or less, and more preferably 60% by mass or less.

[0025] The hard particles used in the present invention may be used as they are, or may be surface-modified with a group such as dimethyl, epoxy, hexyl, phenyl, methacryl, vinyl, or isocyanate.

[0026] The content of hard particles in the entire polyethylene fiber of the present invention is 2% by mass or more, preferably 3% by mass or more, preferably 20% by mass or less, and more preferably 10% by mass or less. By making the content of hard particles 2% by mass or more, the frequency of contact between the hard particles present in the fiber and the blade increases, making it easier to achieve the effect of improving cut resistance.

[0027] When spinning the polyethylene fiber of the present invention, the hard particles may be used as a master batch in which they are kneaded in advance with polyethylene, or may be used alone.

[0028] The polyethylene fiber of the present invention may contain additives such as antioxidants, lubricants, antistatic agents, peroxides, pigments, dyes, and dispersants in addition to the hard particles.

[0029] <Manufacturing method of polyethylene fiber> The polyethylene fiber of the present invention can be produced, for example, by melt spinning. By using the melt spinning method, polyethylene fibers containing little or no residual solvent can be obtained. Specifically, the residual solvent in the polyethylene fiber is preferably 20 ppm or less, and more preferably 10 ppm or less.

[0030] Identifying the type of residual solvent contained in polyethylene fibers and measuring the amount of residual solvent in polyethylene fibers can be performed by two measurement methods: i) concentrating the components eluted by Soxhlet extraction with chloroform using an evaporator and performing qualitative and quantitative analysis by nuclear magnetic resonance (NMR), or ii) measuring by gas chromatography. When the boiling point of the residual solvent exceeds 350°C, it is preferable to measure the amount of residual solvent by the former qualitative and quantitative analysis using NMR, while when the boiling point of the residual solvent is 350°C or lower, it is preferable to measure the amount of residual solvent using the latter gas chromatography. Detailed measurement methods for i) and ii) above will be described later. In this specification, the amount of residual solvent is measured by the above two measurement methods, and the larger value is taken as the amount of residual solvent in the polyethylene fiber.

[0031] On the other hand, when gel spinning, which is one of the methods for producing ultra-high molecular weight polyethylene fibers using a solvent (solution spinning), is used, high-strength polyethylene fibers can be obtained, but the use of solvents has a significant impact on the health of manufacturing workers and the environment, and the solvent remaining in the fibers has a significant impact on the health of product users. Furthermore, gel spinning also has the problem of low productivity.

[0032] The method for producing the polyethylene fiber of the present invention using the melt spinning method will be specifically described below. Note that the method for producing the polyethylene fiber of the present invention is not limited to the following steps and numerical values.

[0033] The polyethylene resin and powdered hard particles are blended and melt-extruded using an extruder or the like at a temperature, for example, 10°C or higher, preferably 50°C or higher, and more preferably 80°C or higher, above the melting point of the polyethylene resin. The resulting mixture is then supplied to a spinning nozzle (spinneret) using a constant-rate feeder at a temperature, for example, 80°C or higher, preferably 100°C or higher, above the melting point of the polyethylene resin. The pressure of the inert gas supplied to the extruder is preferably 0.001 MPa or higher and 0.8 MPa or lower, more preferably 0.05 MPa or higher and 0.7 MPa or lower, and even more preferably 0.1 MPa or higher and 0.5 MPa or lower. The resulting mixture is then extruded at a rate of 0.1 g / min or higher through a spinning nozzle having a diameter of, for example, 0.3 mm or higher and 2.5 mm or lower, preferably 0.5 mm or higher and 1.5 mm or lower. The linear extrusion speed of the molten resin from the spinning nozzle is preferably 10 cm / min or higher and 120 cm / min or lower. The linear extrusion speed is more preferably 20 cm / min or more and 110 cm / min or less, and even more preferably 30 cm / min or more and 100 cm / min or less.

[0034] Next, the extruded yarn is cooled to 5 to 40°C and then wound up at 50 m / min or more. The resulting undrawn yarn is then drawn at least once at a temperature below the melting point of the undrawn yarn. Specifically, the drawing process is preferably carried out in two or more stages. The initial drawing temperature is preferably below the crystal dispersion temperature of the undrawn yarn, more preferably 80°C or less, and even more preferably 75°C or less. Next, the undrawn yarn is preferably drawn at a temperature above the crystal dispersion temperature and below the melting point, more preferably at 90°C or more and below the melting point.

[0035] The crystal dispersion temperature is a temperature measured by the following method. First, the solid viscoelastic modulus is measured using a solid viscoelasticity measuring device (TA Instruments, "DMA Q800"). The measured solid viscoelastic modulus is analyzed using "TA Universal Analysis" (TA Instruments). The measurement start temperature is -140°C, the measurement end temperature is 140°C, and the heating rate is 1.0°C / min. The strain is 0.04%, and the initial load at the start of the measurement is 0.05 cN / dtex. The measurement frequency is 11 Hz. Next, the loss modulus is calculated based on the obtained solid viscoelastic modulus, and the temperature dispersion is determined from the low temperature side. The loss modulus values ​​are plotted logarithmically on the vertical axis and temperature on the horizontal axis, and the peak value of the loss modulus that appears on the highest temperature side is taken as the crystal dispersion temperature.

[0036] The total stretching ratio is preferably 6 times or more, more preferably 8 times or more, and even more preferably 10 times or more. The total stretching ratio is preferably 30 times or less, more preferably 25 times or less, and even more preferably 20 times or less. When multi-stage stretching is employed, for example, when two-stage stretching is performed, the stretching ratio in the first stage is preferably 1.05 times or more and 4.00 times or less, and the stretching ratio in the second stage is preferably 2.5 times or more and 15 times or less.

[0037] <Products containing polyethylene fibers> Examples of products containing the polyethylene fiber of the present invention include woven and knitted fabrics, which can be suitably used as cut-resistant woven and knitted fabrics, gloves, vests, etc. For example, gloves can be obtained by putting the polyethylene fiber of the present invention on a knitting machine. Alternatively, the polyethylene fiber of the present invention can be put on a loom to obtain a fabric, which can then be cut and sewn into gloves.

[0038] The gloves thus obtained can be used as they are, but if necessary, they can be coated with a resin to impart anti-slip properties. Examples of the resin used here include, but are not limited to, urethane-based and ethylene-based resins.

[0039] As will be seen from the examples described later, the polyethylene fiber of the present invention has excellent cut resistance. Therefore, products using the polyethylene fiber of the present invention are suitable for use not only in the above-mentioned woven and knitted fabrics such as gloves and vests, but also in tapes, ropes, nets, fishing lines, material protection covers, sheets, kite lines, bowstrings, sailcloths, and curtain materials. Of course, the products using the polyethylene fiber of the present invention are not limited to these.

[0040] Furthermore, because the polyethylene fiber of the present invention has high cut resistance, it is suitable for use as a material making use of this cut resistance, for example, a fiber-reinforced resin reinforcement, a cement reinforcement, a fiber-reinforced rubber reinforcement, or a protective material that is expected to be subjected to environmental changes, a bulletproof material, a medical suture, an artificial tendon, an artificial muscle, a fiber-reinforced resin reinforcement, a cement reinforcement, a fiber-reinforced rubber reinforcement, a machine tool part, a battery separator, a chemical filter, etc. Of course, the polyethylene fiber of the present invention is not limited to these materials and can be used as a variety of materials.

[0041] This application claims the benefit of priority to Japanese Patent Application No. 2020-120057, filed on July 13, 2020. The entire content of the specification of Japanese Patent Application No. 2020-120057, filed on July 13, 2020, is incorporated herein by reference. [Example]

[0042] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present invention.

[0043] First, the measurements and evaluations of the characteristic values ​​performed on the fibers (fiber samples) and tubular knitted fabrics (knitted fabric samples) using the fibers produced in the examples and comparative examples described below will be described.

[0044] (1) Intrinsic viscosity [η] The intrinsic viscosity was measured using a Ubbelohde capillary viscometer with decalin heated to 135°C as the solvent. Specifically, the specific viscosity of various dilute solutions was measured, and the intrinsic viscosity was determined from the extrapolated point to the origin of the line obtained by least-squares approximation of the viscosity versus concentration. To measure the specific viscosity, the fiber sample was divided or cut into approximately 5 mm lengths, and 1% by mass of an antioxidant (Yoshinox BHT (registered trademark), manufactured by Yoshitomi Pharmaceutical Co., Ltd.) was added to the polymer. The solution was then stirred and dissolved at 135°C for 4 hours to prepare the measurement solution.

[0045] (2) Average major and minor diameters of hard particles The average major and minor diameters of the hard particles were determined using scanning electron microscope (SEM) photographs. The fiber sample was placed in a crucible and burned until it turned into ash and carbonaceous material. It was then placed in an electric furnace and heated above the polyethylene decomposition temperature. Once the carbonaceous material was completely ash, the sample was allowed to cool in a desiccator to obtain the ash content. SEM photographs of the ash were taken, and the major axis (maximum major diameter) and minor axis (maximum minor diameter) of each of 10 randomly selected hard particles were measured. The maximum minor diameter was defined as the length at the maximum point in the direction perpendicular to the maximum major diameter. The average major diameter was determined by averaging the maximum major diameters of the 10 hard particles, and the average minor diameter was determined by averaging the maximum minor diameters of the 10 hard particles. Due to the high hardness of the hard particles, their shape is unlikely to change even when heated.

[0046] (3) Aspect ratio of hard particles The aspect ratio of the hard particles was determined using SEM photographs. Specifically, each fiber sample prepared using the method described below was placed in a crucible and burned until it turned into ash and carbonaceous material. Then, it was placed in an electric furnace and heated above the decomposition temperature of polyethylene. Once the carbonaceous material had completely turned to ash, it was allowed to cool in a desiccator to room temperature to obtain the ash. SEM photographs of the ash thus obtained were taken, and the major axis (maximum long diameter) and minor axis (maximum short diameter) of each of 10 randomly selected hard particles were measured. The aspect ratio of each particle was calculated by dividing the maximum major diameter by the maximum short diameter. The maximum short diameter was defined as the length at the position where the length was greatest in the direction perpendicular to the maximum major diameter. The average aspect ratio of the 10 hard particles was then used as the aspect ratio of the hard particles. Due to their high hardness, it is believed that the shape of hard particles does not change even when heated.

[0047] (4) Hard particle content The hard particle content was determined by ash content measurement based on JIS-2272. 1.0 g of fiber sample was placed in a crucible and burned until it turned into ash and carbonaceous material, then placed in an electric furnace and heated at a temperature above the decomposition temperature of polyethylene. After the carbonaceous material had completely turned to ash, the sample was allowed to cool in a desiccator and its mass was measured to determine the ash content. The hard particle content was calculated based on the resulting ash content and the mass ratio of the ash content to the total fiber weight.

[0048] (5) Cut resistance (coupe test) Cut resistance was measured using a Coupe Tester (manufactured by Sodemat) in accordance with the European standard EN388. Specifically, polyethylene fibers prepared by the methods described below were used, and a circular knitting machine manufactured by Shima Seiki Mfg. Co., Ltd. was used to knit fabrics with a basis weight of 350 g / m. 2 ±35g / m 2 The index value of the obtained cylindrical knitted fabric in a coupe tester was calculated as follows to evaluate the cut resistance.

[0049] Here, aluminum foil was provided on the sample stage of the above-mentioned device, and the knitted fabric sample was placed on this. Next, a circular blade provided on the device was rotated in the opposite direction to the running direction and run over the sample. When the knitted fabric sample was cut, the circular blade came into contact with the aluminum foil, causing electricity to flow, thereby detecting the completion of the cut resistance test. While the circular blade was operating, a counter attached to the device continued counting, and the value was recorded.

[0050] In this test, the basis weight was approximately 380 g / m 2 A plain woven cotton fabric was used as a blank, and the cut resistance of the knitted fabric samples was evaluated. Testing began with the blank, and blank and knitted fabric sample tests were alternately conducted, with the knitted fabric sample tested five times, and finally a sixth blank test completed one set of tests. Ten sets of the above tests were conducted, and the average index value of the ten sets was used as a proxy evaluation of cut resistance. A higher index value indicates better cut resistance.

[0051] The index value is calculated by the following formula: K = (count value of cotton cloth before sample test + count value of cotton cloth after sample test) / 2 Index value = (sample count value + K) / K

[0052] The cutter used to evaluate cut resistance was a 45mm diameter rotary cutter for L-type blades manufactured by OLFA Corporation. The material was SKS-7 tungsten steel, with a blade thickness of 0.3 mm. The test load was set to 5N.

[0053] In this example, the index value obtained in Comparative Example 4 was set to a cut resistance of 100, which was used as the reference value, and the cut resistance of the other Examples 1 to 8, Comparative Examples 1 to 3, and Comparative Example 9 was expressed as a relative ratio to Comparative Example 4. For example, the cut resistance of Example 1 was 120, which means that when the cut resistance of Comparative Example 4 was set to 100%, a high cut resistance of 120% (1.2 times) was obtained.

[0054] (6) Cut resistance (ISO test) Cut resistance was measured using the RGI TDM-100 in accordance with ISO13997 "Protective clothing - Mechanical properties - Test method for cut resistance against sharp objects." The cut direction was set at a 45-degree angle.

[0055] (7) Residual solvent amount After removing the oil from each polyethylene fiber produced by the method described below using a 1:1 mixture of hexane and ethanol, the residual solvent content in the polyethylene fiber was measured by two measurement methods: i) Soxhlet extraction with chloroform, concentrating the eluted components in an evaporator, and qualitatively and quantitatively analyzing them by NMR, and ii) measurement by gas chromatography. The larger of the residual solvent amounts measured by the two measurement methods was taken as the residual solvent content in the polyethylene fiber. The residual solvent content in the polyethylene fibers of Examples 1 to 8 produced by melt spinning was all 1 ppm or less. On the other hand, the residual solvent content in the polyethylene fiber of Comparative Example 9 produced by solution spinning was 50 ppm. [i) NMR measurement] BRUKER AVANCE NEO 600 1 The results were obtained by analysis using H-NMR (solvent: CDCl3, frequency: 600 MHz). [ii) Gas chromatography method] Using a Shimadzu GCMS Thermal Desorption System TD-20, the mixture was heated at 80°C for 10 minutes under a helium stream (50 ml / min). The generated gas was collected by cooling in a Tenax-TA adsorption tube, desorbed by heating, and analyzed using a Shimadzu GCMS-QP2010Ultra gas chromatograph mass spectrometer GC / MS under the following conditions: <Analysis conditions> Sample heating temperature: 80°C x 10 min Column: RESTEK Rxi-1ms (Shimadzu GLC, length 60 m, inner diameter 0.32 mm, film thickness 0.25 μm) Column linear velocity: 35 cm / sec Split ratio: 50:1 Column oven temperature: 50°C for 2 minutes, then increase the temperature to 320°C at 15°C / min, and hold for 15 minutes. Mass measurement range (m / z): 35 to 500

[0056] Example 1 A blend polymer was prepared by mixing 97% by mass of polyethylene pellets with an intrinsic viscosity of 1.9 dL / g and 3% by mass of rock wool (hard particles) with an average major axis of 125 μm and an average minor axis of 7 μm. The blend polymer was fed into an extruder, melted at 280°C, and extruded through a 30-hole spinneret with a φ0.8 mm orifice diameter at a nozzle face temperature of 288°C at a single-hole throughput rate of 0.32 g / min.

[0057] The extruded yarn was passed through a 10 cm warming zone and then cooled by quenching at 18°C ​​at 0.5 m / sec. After that, it was wound into a cheese shape at a spinning speed of 80 m / min to obtain an undrawn yarn. The undrawn yarn was then wound between two drive rolls at a draw ratio of 3x, and then heated with hot air at 100°C to obtain a drawn yarn at the maximum draw ratio at which it could be stably drawn. The drawn yarns were doubling to obtain a total of 880 dtex ± 88 dtex to obtain the polyethylene fiber of Example 1. Using the obtained polyethylene fiber, a tubular knitted fabric was produced using the above method, and its cut resistance was evaluated. The results are shown in Table 1. In this and the following examples and comparative examples, the drawn yarns were doubling to obtain the desired dtex, but in some cases, they were also separated.

[0058] Examples 2 to 8 Polyethylene fibers and tubular knitted fabrics were obtained and their cut resistance was evaluated in the same manner as in Example 1, except that the polymer, hard particles, and spinning speed used were changed to those shown in Table 1. The results are shown in Table 1.

[0059] [Table 1]

[0060] (Comparative Examples 1 to 4) Polyethylene fibers and tubular knitted fabrics were obtained and their cut resistance was evaluated in the same manner as in Example 1, except that the polymer, hard particles, and spinning speed used were changed to those shown in Table 2. The results are shown in Table 2.

[0061] (Comparative Examples 5 to 8) An attempt was made to produce polyethylene fibers in the same manner as in Example 1, except that the polymer, hard particles, and spinning speed used were the same as those in Example 1, but the conditions shown in Table 2 were changed. However, in Comparative Examples 5 and 6, the viscosity of the molten material was too high to extrude, and in Comparative Examples 7 and 8, clogging occurred during spinning, and an undrawn yarn could not be obtained in any of the Comparative Examples. These results are shown in Table 2.

[0062] (Comparative Example 9) Ultra-high molecular weight polyethylene with an intrinsic viscosity of 27.0 dL / g was dissolved in decalin at a concentration of 9% by mass. The resulting solution was fed into a twin-screw extruder with a 25 mm screw diameter and a gear pump. The solution was heated to 180°C. The solution was pumped through a spinneret containing 64 holes, each with a diameter of 1 mm. The resulting filaments were stretched 80 times overall and dried in a hot air oven. After drying, the filaments were bundled to form a yarn and wound onto a bobbin. The stretched yarns were combined to a total thickness of 880 dtex ± 88 dtex to obtain the polyethylene fiber of Comparative Example 9. A tubular knitted fabric was produced using the resulting polyethylene fiber using the method described above, and its cut resistance was evaluated. The results are shown in Table 2.

[0063] (Comparative Example 10) An attempt was made to produce polyethylene fibers in the same manner as in Comparative Example 9, except that the intrinsic viscosity of the ultra-high molecular weight polyethylene was changed to 1.9 dL / g, but spinning was not possible and polyethylene fibers could not be produced. The results are shown in Table 2.

[0064] [Table 2]

[0065] As can be seen from Table 1, the tubular knitted fabrics made from the polyethylene fibers of Examples 1 to 8, specifically polyethylene fibers having an aspect ratio of 3 to 100 and containing hard particles with an average minor axis of 18 μm or less, have high index values, i.e., high levels of cut resistance. Thus, a comparison of Examples 1 to 8 and Comparative Examples 1 to 10 above shows that polyethylene fibers satisfying the requirements of the present invention are fibers that have excellent cut resistance and leave little or no solvent residue.

[0066] Although the embodiments and examples of the present invention have been described above, the embodiments and examples disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0067] The polyethylene fiber of the present invention has high cut resistance and can be used to make cut-resistant woven or knitted fabrics that take advantage of this cut resistance, such as gloves and vests. Furthermore, the polyethylene fiber alone can be used for industrial materials such as tapes, ropes, nets, fishing lines, material protective covers, sheets, kite lines, bowstrings, sailcloth, curtain materials, protective materials, bulletproof materials, medical sutures, artificial tendons, artificial muscles, fiber-reinforced resin reinforcements, cement reinforcements, fiber-reinforced rubber reinforcements, machine tool parts, battery separators, and chemical filters. Thus, the polyethylene fiber of the present invention can exhibit excellent performance and be widely applicable, making it a great contribution to industry.

Claims

1. A polyethylene fiber characterized in that it contains hard particles having an aspect ratio of 3 or more and 100 or less, an average particle diameter of 10 μm or more, and an average minor axis of 1.0 to 18 μm, and has an intrinsic viscosity [η] of 0.8 dL / g or more and less than 8.0 dL / g, and the hard particles are metals, silicon compounds, or minerals.

2. 2. The polyethylene fiber according to claim 1, wherein the weight average molecular weight of the polyethylene is 40,000 or more and 900,000 or less.

3. The hard particles contain SiO ２ The polyethylene fiber according to claim 1 or 2, comprising 20% ​​by mass or more of the following:

4. The polyethylene fiber according to any one of claims 1 to 3, containing 2% by mass or more of the hard particles.

5. A product comprising the polyethylene fiber according to any one of claims 1 to 4.

6. 6. The article of claim 5, wherein the article is a cut-resistant woven or knitted fabric.

7. 7. The article of claim 5 or 6, wherein the article is a glove.

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