JP7176517B2 - Multifilament and its constituent monofilaments - Google Patents

Description

The present invention relates to a multifilament and a monofilament that constitutes it.

BACKGROUND ART Conventionally, polyethylene with an extremely high molecular weight, called ultra-high molecular weight polyethylene, has been used in many applications because of its excellent properties such as impact resistance. Among them, a manufacturing method (hereinafter referred to as , gel spinning method) is widely known as a high-strength, high-modulus fiber (for example, Patent Documents 1 and 2).

In addition, spinning is performed using a spinning solution in which ultra-high molecular weight polyethylene is uniformly dissolved in a volatile solvent, the solvent in the spun gel yarn is volatilized, then the gel yarn is cooled using an inert gas, and finally It is also known that a high-strength, high-modulus fiber can be produced by a dry spinning method such as drawing at a high magnification (for example, Patent Document 3).

Polyethylene fibers (multifilaments) having such high strength and high elastic modulus have been used in a wide range of fields in recent years. However, when polyethylene fibers with improved strength and elastic modulus are used in ropes and braids, for example, it becomes possible to design with fewer strands or with a lower fineness, making it possible to reduce the diameter of ropes and braids. However, there was a drawback that wear resistance deteriorated accordingly.

Therefore, in order to improve abrasion resistance, it is known to improve abrasion resistance by increasing the fineness of the monofilament (for example, Patent Documents 4 and 5).

Japanese Patent No. 4565324 Japanese Patent No. 4565325 Japanese Patent No. 4141686 Japanese patent publication "JP 2015-193960" Japanese published patent publication "Special table 2016-507662"

More than ever before, there is a demand for more resistance to abrasion even under overload conditions and further wear resistance. In addition, increasing the fineness of the monofilament greatly increases the bending rigidity and significantly decreases the flexibility. Cut-resistant gloves and fishing lines are the main uses of ultrahigh-molecular-weight polyethylene fibers. The operability at the time is remarkably deteriorated.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a multifilament or the like excellent in abrasion resistance and flexibility.

The present inventors have finally completed the present invention as a result of earnest studies. That is, the present invention is as follows.
(1) A multifilament composed of a polyethylene monofilament having an intrinsic viscosity [η] of 5.0 dL/g or more and 40.0 dL/g or less and having a repeating unit of ethylene, wherein the monofilament comprises (a (b) 15 dtex or more; and (c) JIS L
1095, wherein the number of reciprocating abrasions at break is 10000 times or more in an abrasion strength test measured at a load of 10 cN/dtex. (2) The multifilament conforms to JIS L 1095 and has a reciprocating wear count of 10,000 or more at break in an abrasion strength test measured at a load of 5 cN/dtex (1) The multifilament described in .
(3) The multifilament according to (1) or (2), wherein the monofilament has a tensile strength of 18 cN/dtex or more and an initial elastic modulus of 600 N/dtex or more.
(4) A monofilament constituting the multifilament according to any one of (1) to (3).

The present invention can provide a multifilament having excellent abrasion resistance and flexibility. The multifilament according to the present invention is resistant to rubbing and has excellent wear resistance even under overload conditions. This significantly increases product life. In addition, not only the amount of fluff generated by rubbing during use is greatly reduced, but also the amount of fluff generated during processing into products is reduced, thereby improving the working environment. Moreover, since the multifilament according to the present invention is excellent in flexibility, each product using the multifilament according to the present invention is excellent in workability and operability.

The present invention will be described in detail below.

〔polyethylene〕
The monofilaments constituting the multifilament according to the present invention are preferably composed of polyethylene whose repeating unit is substantially ethylene, and are preferably ultra-high molecular weight polyethylene composed of ethylene homopolymers. Moreover, as the polyethylene used in the present invention, not only homopolymers of ethylene but also copolymers of ethylene and a small amount of other monomers can be used as long as the effects of the present invention can be obtained. Other monomers include, for example, α-olefins, acrylic acid and its derivatives, methacrylic acid and its derivatives, vinylsilane and its derivatives, and the like. The high-molecular-weight polyethylene used in the present invention includes ultra-high-molecular-weight polyethylene composed of a homopolymer of ethylene, copolymers (copolymers of ethylene and other monomers (eg, α-olefin)), or homopolyethylene. and an ethylene copolymer, or a blend of homopolyethylene and other homopolymers such as α-olefins, which may be partially crosslinked, or partially methyl branched, ethyl branched, It may have butyl branches and the like. In particular, it is a copolymer with an α-olefin such as propylene and 1-butene, and even an ultra-high molecular weight polyethylene containing short-chain or long-chain branches at a rate of less than 20 per 1000 carbon atoms. good. Containing a certain amount of branching can provide stability in the production of the multifilament according to the present invention, especially in spinning and drawing, but if it contains 20 or more per 1000 carbon atoms, branching will conversely occur. An excessively large portion is not preferable because it is an obstacle to spinning and drawing. However, if the content of monomers other than ethylene is too high, it becomes a hindrance to stretching. Therefore, the content of monomers other than ethylene is preferably 5.0 mol % or less, more preferably 1.0 mol % or less, still more preferably 0.2 mol % or less, most preferably 0.2 mol % or less. 0 mol %, that is, a homopolymer of ethylene. In this specification, "polyethylene" includes not only homopolymers of ethylene but also copolymers of ethylene and a small amount of other monomers, unless otherwise specified. In addition, in the production of the multifilament according to the present invention, a polyethylene composition obtained by blending polyethylene with various additives described later as necessary can be used. shall also include things.

In addition, in the measurement of the intrinsic viscosity described later, if the intrinsic viscosity falls within the predetermined range described later, polyethylenes having different number average molecular weights and weight average molecular weights may be blended, and the molecular weight distribution (Mw / Mn) different polyethylenes may be blended. It may also be a blend of a branched polymer and a non-branched polymer.

[Weight average molecular weight]
As described above, the polyethylene used in the present invention is preferably ultra-high molecular weight polyethylene, and the weight-average molecular weight of ultra-high molecular weight polyethylene is preferably 490,000 to 6,200,000, more preferably 550 ,000 to 5,000,000, more preferably 800,000 to 4,000,000. If the weight-average molecular weight is less than 490,000, there is a risk that the multifilament will not have high strength and high elastic modulus even if the stretching step described later is performed. This is presumed to be because the number of molecular ends per cross-sectional area of the multifilaments increased due to the small weight average molecular weight, which acted as structural defects. On the other hand, when the weight average molecular weight exceeds 6,200,000, the tension during the drawing process becomes very large, causing breakage and making the production very difficult.

The weight-average molecular weight is generally determined by GPC measurement, but when the weight-average molecular weight is high like the polyethylene used in the present invention, the GPC measurement method is not suitable for reasons such as clogging of the column during measurement. It may not be easy to obtain. Therefore, regarding the polyethylene used in the present invention, instead of the GPC measurement method, "POLYMER HANDBOOK, Fourth Edition, J. Brandrup and EH Immergut, EA Grulke Ed., A JOHN WILEY & SONS, Inc Publication 1999", the weight average molecular weight is calculated from the value of the intrinsic viscosity described later.
Weight average molecular weight = ^5.365 x 104 x (intrinsic viscosity) 1.37

[Limiting viscosity]
The intrinsic viscosity of the polyethylene used in the present invention is 5.0 dL/g or more, preferably 8.0 dL/g or more, and 40.0 dL/g or less, preferably 30.0 dL/g or less, more preferably 25.0 dL/g or less. 0 dL/g or less. If the intrinsic viscosity is less than 5.0 dL/g, a high-strength multifilament may not be obtained. On the other hand, regarding the upper limit of the intrinsic viscosity, there is no particular problem as long as a high-strength multifilament can be obtained. The above range is preferred.

[Monofilament fineness]
The fineness of the monofilaments constituting the multifilament according to the present invention is preferably 15 dtex or more and 80 dtex or less, more preferably 16 dtex or more and 50 dtex or less, and still more preferably 17 dtex or more and 30 dtex or less. If the single filament fineness is less than 15 dtex, the abrasion resistance is lowered. Also, if the single yarn fineness exceeds 80 dtex, the strength of the multifilament will decrease, which is not preferable.

[Total fineness of multifilament]
The multifilament according to the present invention preferably has a total fineness of 18 dtex or more and 5000 dtex or less, more preferably 40 dtex or more and 3000 dtex or less, and still more preferably 60 dtex or more and 1000 dtex or less. If the total fineness is less than 18 dtex, the abrasion resistance will be significantly reduced, and the required performance will not be satisfied, for example, when cut resistant gloves or fishing lines are used. On the other hand, if the total fineness exceeds 5000 dtex, the flexibility is lowered, which is not preferable.

[Cross-sectional shape of monofilament]
The cross-sectional shape of the monofilaments constituting the multifilament according to the present invention is a flat shape with an aspect ratio of 2.0 or more. When the aspect ratio is 2.0 or more, the wear resistance of the monofilament and the multifilament formed therefrom (see Examples below) is improved. In addition, the upper limit of the aspect ratio of the monofilament is not particularly limited as long as the aspect ratio maintains the abrasion resistance of the multifilament according to the present invention, which will be described later.

Also, if the aspect ratio is less than 2.0, the bending rigidity of the monofilament is significantly reduced, and as a result, it is considered that the flexibility of the multifilament is reduced (worse). If the flexibility is reduced, the workability of gloves manufactured from multifilament and the workability and operability of fishing lines are significantly reduced. However, since the cross-sectional shape of the monofilaments constituting the multifilament according to the present invention is a flat shape with an aspect ratio of 2.0 or more, it is believed that the multifilament can be made to have excellent flexibility.

[Abrasion of monofilament]
In the abrasion test based on JIS L 1095, the monofilament constituting the multifilament according to the present invention has a reciprocating abrasion count of 10,000 or more, preferably 15,000 or more, until breakage under a load of 10 cN/dtex. It is preferably 30000 times or more. In addition, an upper limit is not specifically limited.

[Abrasion of multifilament]
In an abrasion test based on JIS L 1095, the multifilament according to the present invention has a reciprocating abrasion count of 10,000 or more, preferably 15,000 or more, and more preferably 30,000 times until breakage under a load of 5 cN/dtex. That's it. In addition, an upper limit is not specifically limited.

[Tensile strength]
The multifilament according to the present invention preferably has a tensile strength of 15 cN/dtex or more, more preferably 20 cN/dtex or more, and even more preferably 25 cN/dtex or more. The multifilament according to the present invention has the above-mentioned tensile strength even if the fineness of the monofilament is increased, and can be expanded to applications requiring wear resistance and dimensional stability that could not be developed with conventional multifilaments. can. A higher tensile strength is preferable, and the upper limit is not particularly limited. A method for measuring the tensile strength will be described later.

[Breaking elongation]
The multifilament according to the present invention preferably has a breaking elongation of 1.5% or more, more preferably 2.0% or more, further preferably 2.5% or more, preferably 8% or less, and more preferably 6% or less. 5% or less is more preferable. When the elongation at break is less than 1.5%, even a slight strain during use or processing into a product tends to cause single yarn breakage or fluffing, which is not preferable. On the other hand, if the elongation at break exceeds 8%, the dimensional stability is impaired, which is undesirable. A method for measuring the elongation at break will be described later.

[Initial elastic modulus]
The multifilament according to the present invention preferably has an initial elastic modulus of 500 cN/dtex or more and 2400 cN/dtex or less. If the multifilament has such an initial elastic modulus, it becomes difficult for the physical properties and shape to change due to external forces received during use of the product or during the process of manufacturing the product. The initial elastic modulus is more preferably 700 cN/dtex or more, still more preferably 900 cN/dtex or more, and more preferably 2000 cN/dtex or less, still more preferably 1800 cN/dtex or less. If the initial elastic modulus exceeds 2400 cN/dtex, the high elastic modulus impairs the flexibility of the yarn, which is not preferable. A method for measuring the initial elastic modulus will be described later.

〔Production method〕
As for the manufacturing method for obtaining the multifilament according to the present invention, it is preferable to use a gel spinning method. The method for producing the multifilament according to the present invention using the gel spinning method will be specifically described below. In addition, the method of manufacturing the multifilament according to the present invention is not limited to the following steps and numerical values.

<Dissolution process>
A polyethylene solution is prepared by dissolving high molecular weight polyethylene in a solvent. The solvent is preferably a volatile organic solvent such as decalin or tetralin, a solid at room temperature, or a non-volatile solvent. The concentration of polyethylene in the polyethylene solution is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. It is necessary to select the optimum concentration according to the intrinsic viscosity [η] of raw material polyethylene.

The concentration of polyethylene in the solution may vary depending on the properties of the solvent and the molecular weight and molecular weight distribution of the polyethylene. In particular, when using polyethylene with a very high molecular weight, for example, a measurement temperature of 135° C. and decalin as a solvent, and an intrinsic viscosity [η] of 14 dL/g or more, a polyethylene solution with a concentration of 50 wt % or more becomes highly viscous. , brittle breakage is likely to occur during spinning, making spinning very difficult. On the other hand, the drawback of using polyethylene solutions with concentrations of, for example, less than 0.5 wt % is that the yields are reduced and the costs of solvent separation and recovery are increased.

The polyethylene solution can be prepared in various ways, for example by suspending solid polyethylene in a solvent and then stirring at elevated temperature, or by mixing the suspension and using a twin-screw extruder equipped with a conveying section. can be manufactured by

<Spinning process>
The polyethylene solution prepared by high-temperature stirring or a twin-screw extruder is preferably 10°C or higher than the melting point of polyethylene using an extruder or the like, more preferably 20°C or higher than the melting point of polyethylene. More preferably, the extrusion is carried out at a temperature higher than the melting point of polyethylene by 30°C or more, and then supplied to a spinneret (spinning nozzle) using a metering feeder. The time for passing through the orifice of the spinneret is preferably 1 second or more and 8 minutes or less. If the time is less than 1 second, the flow of the polyethylene solution in the orifice is disturbed, and the polyethylene solution cannot be discharged stably, which is not preferable. Moreover, it is not preferable because the structure of the entire single yarn becomes non-uniform under the influence of turbulence in the flow of the polyethylene solution. On the other hand, if it exceeds 8 minutes, the polyethylene molecules are discharged without being oriented, and the spinning tension range per single yarn tends to be outside the above range, which is not preferable. Moreover, since the crystal structure of the obtained single yarn becomes non-uniform, it is not preferable because abrasion resistance cannot be expressed as a result.

Threads are formed by passing a polyethylene solution through a spinneret having a plurality of orifices arranged therein. When a polyethylene solution is spun to produce yarn, the temperature of the spinneret must be equal to or higher than the melting temperature of polyethylene, preferably 140°C or higher, more preferably 150°C or higher. The dissolution temperature of the polyethylene depends on the selected solvent, the concentration of the polyethylene solution, and the mass concentration of the polyethylene, of course the spinneret temperature should be below the thermal decomposition temperature of the polyethylene.

The polyethylene solution is preferably discharged from a spinneret having a diameter of 0.2 to 3.5 mm (more preferably a diameter of 1.0 to 2.5 mm) at a discharge rate of preferably 10.0 g/min/hole or more. If the discharge rate is 10.0 g/min/hole or less, the effect of deformation of the monofilament cross section due to drawing becomes small, so that the flatness of the monofilament becomes low and the flexibility of the fiber is impaired. More preferably, it is 12.0 g/min/hole or more. At that time, it is preferable to set the spinneret temperature to a temperature higher than the melting point of polyethylene by 10° C. or more and lower than the boiling point of the solvent used. In the temperature range near the melting point of polyethylene, the viscosity of the polymer is too high to allow rapid take-up. Further, if the temperature is higher than the boiling point of the solvent used, the solvent boils immediately after exiting the spinneret, which is not preferable because the yarn breaks immediately below the spinneret.

The extruded polyethylene solution is cooled with a previously rectified gas or liquid to form threads. The cooled yarn is preferably taken up at a speed of 800 m/min or less, more preferably 200 m/min or less. Air or an inert gas such as nitrogen or argon is used as the cooling gas. Further, water or the like is used as the liquid used in the present invention. At this time, the temperature of the gas or liquid used for cooling is preferably 5°C or higher and 60°C or lower, more preferably 10°C or higher and 30°C or lower. If the temperature of the gas or liquid used for cooling is out of this range, the tensile strength of the filament will be significantly reduced, resulting in reduced abrasion resistance, which is not preferable.

<Stretching process>
It is preferable that the cooled yarn passes through at least one or more stages of drawing process and is drawn 20 times or more and 400 times or less with respect to the discharge speed of the orifice. Moreover, it is preferable to stretch|stretch at the temperature below the melting point of polyethylene. When stretching is performed multiple times, the temperature during stretching is preferably increased in the subsequent stages, and the stretching temperature in the last stage of stretching is preferably 80°C or higher and 160°C or lower, more preferably 90°C or higher and 158°C. It is below. The conditions of the heating device may be set so that the yarn is drawn within the above drawing temperature range during drawing. At this time, the yarn temperature can be measured, for example, using an infrared camera (FLIR SC640 manufactured by FLIR Systems).

The drawing time of the undrawn yarn, that is, the time required for deformation of the multifilament is preferably 0.5 minutes or more and 20 minutes or less, more preferably 15 minutes or less, and still more preferably 10 minutes or less. If the deformation time of the multifilament exceeds 20 minutes, the molecular chains are relaxed during the drawing even if the manufacturing conditions other than the drawing time are set within a suitable range, which is not preferable because the strength of the monofilament is lowered.

〔others〕
In order to impart other functions, additives such as antioxidants and anti-reduction agents, pH adjusters, surface tension reducing agents, thickeners, humectants, and thickeners may be added during the production of the multifilament according to the present invention. Dyeing agents, preservatives, antifungal agents, antistatic agents, pigments, mineral fibers, other organic fibers, metal fibers, sequestering agents and the like may be added.

The multifilament of the present invention is suitably used for gloves, fishing lines, fiber-reinforced resin reinforcing materials, cement reinforcing materials, fiber-reinforced rubber reinforcing materials, medical sutures, artificial tendons, and the like. In addition, this polyethylene fiber is processed such as knitting and weaving to produce tapes, ropes, nets, material protective covers, sheets, strings for kites, bow strings, sail cloths, curtain materials, protective materials, bulletproof materials, artificial muscles, crafts, etc. Suitable for mechanical parts, battery separators and chemical filters. Furthermore, the multifilament of the present invention can be split into monofilaments for use. Of course, the multifilament of the present invention and the monofilament of the present invention are not limited to being used as the materials described above, and can be used as various materials.

EXAMPLES The present invention will be specifically described below by way of examples. However, the present invention is not limited to the following examples, and it is of course possible to make appropriate modifications within the scope that can be adapted to the gist of the preceding and following descriptions. included in the scope of

First, the measurement and evaluation of characteristic values performed on multifilaments (samples) produced in Examples and Comparative Examples described later will be described.

(1) Intrinsic viscosity The specific viscosity of various dilute solutions is measured using an Ubbelohde-type capillary viscosity tube in Decalin at 135°C, and the specific viscosity is divided by the concentration. The limiting viscosity was determined from the point of extrapolation to the origin of the straight line. At the time of measurement, 1 wt % of an antioxidant (trade name "Yoshinox BHT" manufactured by Yoshitomi Pharmaceutical Co., Ltd.) was added to the sample relative to the polymer, and the mixture was stirred and dissolved at 135°C for 24 hours to prepare a measurement solution.

(2) Fineness A sample was cut into 10 m lengths at five different positions, the mass was measured, and the average value was converted to 10000 m to obtain fineness (dtex).

(3) Fineness of Monofilament A sample was cut into 20 cm monofilaments at five different positions, the mass was measured, and the average value was converted to 10000 m to obtain the fineness (dtex).

(4) Tensile strength, elongation at break, and initial elastic modulus In accordance with JIS L 1013 8.5.1, using a universal testing machine (manufactured by Orientec Co., Ltd., "Tensilon Universal Material Testing Machine RTF-1310"), The strain-stress curve was measured under conditions of a sample length of 200 mm (length between chucks) and an elongation rate of 100 mm/min under conditions of an ambient temperature of 20° C. and a relative humidity of 65%. The tensile strength and elongation at break were obtained from the stress and elongation at break, and the initial elastic modulus was calculated from the tangent line giving the maximum slope near the origin of the curve. At this time, the initial load applied to the sample during measurement was 1/10 of the mass (g) per 10,000 m of the sample. The tensile strength, elongation at break, and initial elastic modulus were the average values of 10 measurements.

(5) Cross-Sectional Aspect Ratio of Monofilament The aspect ratio of a monofilament was determined by embedding it in an acrylic resin and using a microtome to prepare a cross section. An industrial microscope (Nikon ECLIPSE LV150NA) was used with a 20x objective lens, and images were acquired using a microscope digital camera (Nikon DXM1200). Next, using image analysis software "ImageJ", the lengths of the major axis and the minor axis of the fiber cross section were measured, and the average value was obtained to calculate the aspect ratio.

(6) Abrasion test Abrasion resistance was evaluated by an abrasion test based on method B for measuring abrasion strength among general spun yarn test methods (JIS L 1095). The measurement was carried out using a silk cohesive force tester manufactured by Asano Kikai Seisaku Co., Ltd. Using a hard steel of φ2.0 mm as a friction element, a load of 5 cN / dtex or 10 cN / dtex, an atmosphere temperature of 20 ° C., a friction speed of 115 times / min, a reciprocating distance of 2.5 cm, and a friction angle of 110 degrees. The number of times of friction until breakage was measured. The number of tests was set to 5 times, the data of the maximum number of times and the minimum number of times were excluded, and the average value of the remaining 3 measurements was expressed.

(Example 1)
A dispersion of decalin and ultra-high molecular weight polyethylene having an intrinsic viscosity of 18.0 dL/g was prepared so as to have a polyethylene concentration of 9.0% by mass. This blend polymer is supplied to an extruder, heated at 190° C. to gel, and extruded from a spinneret having an orifice diameter of φ1.5 mm and 4H at a nozzle surface temperature of 170° C. and a single hole discharge rate of 15.5 g/min. rice field.

The discharged yarn was cooled in a water-cooled bath at 15° C. while being taken up, and then taken up at a speed of 23 m/min to obtain an undrawn multifilament consisting of four monofilaments. Next, the unstretched multifilament was stretched 2.4 times while being dried by heating with hot air at 120°C. Subsequently, the multifilament was stretched 4.5 times with hot air at 140° C., and the intermediate stretched multifilament was immediately wound up in the stretched state. Further, the resulting intermediate drawn multifilament was drawn 2.9 times with hot air at 150° C. to make a total of 31 times. Table 1 shows the physical properties and evaluation results of the obtained multifilament.

(Example 2)
In Example 1, the same procedure as in Example 1 was carried out except that the cooling temperature of the yarn was 10° C., the draw ratio in the second stage drawing was 2.7 times, and the draw ratio in the third stage was 4.5 times. multifilament was obtained. Table 1 shows the physical properties and evaluation results of the obtained multifilament.

(Example 3)
In Example 1, the same procedure as in Example 1 was performed except that the heating temperature for gelation was 180° C., the single hole discharge amount was 20.0 g/min, and the draw ratio in the third stage was 4.0 times. A multifilament was obtained. Table 1 shows the physical properties and evaluation results of the obtained multifilament.

(Comparative example 1)
A multifilament was obtained in the same manner as in Example 2, except that the heating temperature for gelation was 220°C.

(Comparative example 2)
In Example 2, the heating temperature for gelation was 220° C., the draw ratio in the first stage drawing was 1.5 times, the draw ratio in the second stage drawing was 2.2 times, and the third stage drawing was performed. A multifilament was obtained in the same manner as in Comparative Example 2 except that the magnification was 1.7 times.

(Comparative Example 3)
A dispersion of decalin and ultra-high molecular weight polyethylene having an intrinsic viscosity of 18.0 dL/g was prepared so as to have a polyethylene concentration of 9.0% by mass. This blend polymer is supplied to an extruder, heated at 190° C. to gel, and extruded from a spinneret having an orifice diameter of φ0.8 mm and 30H at a nozzle surface temperature of 180° C. at a single hole discharge rate of 2.5 g/min. rice field.

The discharged yarn was cooled in a water-cooled bath at 20° C. while being taken up, and then taken up at a speed of 37 m/min to obtain an undrawn multifilament consisting of 30 monofilaments. Next, the unstretched multifilament was stretched 2.0 times while being dried by heating with hot air at 120°C. Subsequently, the film was stretched 5.0 times with hot air at 140° C., for a total of 10 times.

As can be seen from Table 1, in Examples 1 and 2, compared with Comparative Example 1, the aspect ratio of the cross section of the monofilament is 2.0 or higher. Since the materials of Examples 1 and 2 and Comparative Example 1 are the same, the section modulus of the monofilaments of Examples 1 and 2 are 0.78 times and 0.71 times lower than those of Comparative Example 1, respectively. It is considered that the flexibility of the multifilament is improved. Surprisingly, the wear resistance of Examples 1 and 2 is more than twice that of Comparative Example 1, which is a high wear resistance multifilament.

As can be seen from Table 2, in Examples 1 and 2, although the fineness of the monofilament is the same as in Comparative Example 1, abrasion resistance is significantly improved. Moreover, even when the single yarn fineness is high as in Example 3, the high abrasion resistance is maintained. On the other hand, Comparative Example 2, which has a low strength, and Comparative Example 3, which has a low monofilament fineness, show low abrasion resistance values.

The multifilament according to the present invention includes, for example, protective woven and knitted fabrics, tapes, ropes, nets, fishing lines, material protection covers, sheets, kite strings, bow strings, sail cloths, curtain materials, protective materials, bulletproof materials, medical It can be used for industrial materials such as sutures, artificial tendons, artificial muscles, fiber-reinforced resin reinforcing materials, cement reinforcing materials, fiber-reinforced rubber reinforcing materials, machine tool parts, battery separators, and chemical filters.

Claims (4)

A multifilament composed of monofilaments made of ultrahigh-molecular-weight polyethylene having an intrinsic viscosity [η] of 5.0 dL/g or more and 40.0 dL/g or less and having a repeating unit that is substantially ethylene,
The monofilament has (a) a flat shape with a ratio of the long side to the short side of the cross section perpendicular to the fiber axis direction of 2 or more, (b) 15 dtex or more, and (c) conforming to JIS L 1095. , wherein the number of reciprocating abrasions at breakage in an abrasion strength test measured at a load of 10 cN/dtex is 10,000 or more. 2. The multifilament according to claim 1, wherein the multifilament conforms to JIS L 1095 and has a reciprocating wear count of 10,000 or more at break in an abrasion strength test measured at a load of 5 cN/dtex. multifilament. 3. The multifilament according to claim 1, wherein the monofilament has a tensile strength of 18 cN/dtex or more and an initial elastic modulus of 600 N/dtex or more. A monofilament constituting the multifilament according to any one of claims 1 to 3.