JP5696808B1 - Multifilament - Google Patents

Abstract

The present invention provides a multifilament that can be processed into a product in a wide temperature range and that is excellent in dimensional stability and wear resistance. A multifilament composed of five or more single yarns, wherein the multifilament has an intrinsic viscosity [η] of 5.0 dL / g or more and 40.0 dL / g or less, and the repeating unit is substantially equal. Polyethylene, which is ethylene, is included. According to JIS L 1095, the number of reciprocating wear at break in the wear strength test measured with a load of 5 cN / dtex is 1000 times or more and measured with a load of 10 cN / dtex. The multi-filament is characterized in that the number of reciprocating wear at the time of fracture in the applied wear strength test is 100 times or more. [Selection figure] None

Description

  The present invention relates to a multifilament excellent in dimensional stability and wear resistance.

  Conventionally, polyethylene having a very high molecular weight called ultra-high molecular weight polyethylene has been used for many applications because it has good properties such as impact resistance. Among them, a polyethylene gel solution in which ultra high molecular weight polyethylene is dissolved in an organic solvent is made into a fibrous gel body by rapidly cooling after extrusion from an extruder, and a production method (hereinafter referred to as “continuous stretching”) while removing the organic solvent from the gel body. Ultra high molecular weight polyethylene fibers manufactured by the gel spinning method are widely known as high-strength and high-modulus fibers (for example, Patent Document 1 and Patent Document 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 with an inert gas, and finally It is also known that high-strength and high-modulus fibers can be produced by a dry spinning method such as drawing at a high magnification (for example, Patent Document 3).

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

Japanese Patent No. 4565324 Japanese Patent No. 4565325 Japanese Patent No. 4141686

  An object of the present invention is to provide a multifilament that can be processed into a product in a wide temperature range and is excellent in dimensional stability and wear resistance.

  The present inventors have found that a multifilament having excellent wear resistance, high strength and high elastic modulus can be obtained by bringing the crystal structure of the entire single yarn (monofilament) as close to uniform as possible, and completed the present invention. It came to do.

The multifilament according to the present invention comprises 5 or more single yarns, and the multifilament has an intrinsic viscosity [η] of 5.0 dL / g or more and 40.0 dL / g or less, and the repeating unit is substantially ethylene. It contains polyethylene is, conformity to JIS L 1095, reciprocating abrasion times at break in the measured abrasion strength test load as 5 cN / dtex is characterized in that at least 1000 times. In addition, the multifilament according to the present invention preferably has 100 or more reciprocating wear times at break in a wear strength test measured in accordance with JIS L 1095 with a load of 10 cN / dtex.

  The fineness of the single yarn is preferably 3 dtex or more and 40 dtex or less.

The multifilament of the present invention preferably has a thermal stress maximum value of 0.20 cN / dtex or more. Further, the coefficient of variation CV defined by the following formula (1) of the initial elastic modulus is preferably 30% or less.
Coefficient of variation CV (%) = (standard deviation of initial elastic modulus of the single yarn) / (average value of initial elastic modulus of the single yarn) × 100 (1)

  The multifilament of the present invention preferably has a thermal stress at 120 ° C. of 0.15 cN / dtex or more. Moreover, it is preferable that the heat shrinkage rate at 70 ° C. is 0.20% or less and the heat shrinkage rate at 120 ° C. is 3.0% or less. Further, it is preferable that the tensile strength is 18 cN / dtex or more and the initial elastic modulus is 600 cN / dtex or more.

  The method for producing a multifilament of the present invention includes a dissolving step in which the polyethylene is dissolved in a solvent to obtain a polyethylene solution, the polyethylene solution is discharged from a nozzle at a temperature equal to or higher than the melting point of the polyethylene, and the discharged yarn is 10 ° C. Spinning process for cooling with a refrigerant of 60 ° C. or lower, stretching process for removing solvent from discharged undrawn yarn, and winding process for winding with a tension of 5 cN / dtex or lower at 50 ° C. or lower The number of stretching in the stretching step is 1 to 3 times, the stretching ratio is 7.0 to 60 times, and the total stretching time is 0.5 to 20 minutes. To do.

The multifilament according to the present invention can be processed into products in a wide temperature range. When the product is used, changes in mechanical properties such as thermal stress, thermal contraction rate, initial elastic modulus over a wide temperature range. Is small and excellent in dimensional stability.
In addition, it is resistant to rubbing even under overload conditions and has excellent wear resistance. This significantly improves the product life. Further, not only the amount of fluff generated due to rubbing during use is greatly reduced, but also the amount of fluff generated during processing into a product is reduced, so that the working environment is improved.
Therefore, the multifilament according to the present invention is a protective woven or knitted fabric that utilizes cut resistance, tape, rope, net, fishing line, material protective cover, sheet, kite thread, bowstring, sailcloth, curtain material, protection Excellent as industrial materials such as materials, bulletproof materials, medical sutures, artificial tendons, artificial muscles, fiber reinforced resin reinforcing materials, cement reinforcing materials, fiber reinforced rubber reinforcing materials, machine tool parts, battery separators, chemical filters, etc. It exhibits performance and design and can be applied widely.

  Hereinafter, polyethylene used for the production of the multifilament according to the present invention, and the physical properties and production method of the multifilament according to the present invention will be described.

〔polyethylene〕
The multifilament according to the present invention preferably contains polyethylene whose repeating unit is substantially ethylene, and more preferably ultrahigh molecular weight polyethylene made of a homopolymer of ethylene. The polyethylene used in the present invention can use not only a homopolymer of ethylene but also a copolymer of ethylene and a small amount of other monomers as long as the effects of the present invention are obtained. Examples of other monomers include α-olefin, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, vinylsilane and derivatives thereof, and the like. Examples of the high molecular weight polyethylene used in the present invention include ultra high molecular weight polyethylene composed of ethylene homopolymers, copolymers (copolymers of ethylene and other monomers (for example, α-olefin)), or homopolyethylene. It may be a blend of ethylene and an ethylene copolymer, or a blend of homopolyethylene and other homopolymers such as α-olefin, partially crosslinked, or partially methyl branched, ethyl branched, It may have a butyl branch or the like. Particularly, it is a copolymer with an α-olefin such as propylene and 1-butene, and it is an ultrahigh molecular weight polyethylene in which a short chain or a long chain branch is contained at a ratio of less than 20 per 1000 carbon atoms. Good. Inclusion of a certain amount of branching can give stability in spinning and drawing, especially in the production of the multifilament according to the present invention. However, when more than 20 carbon atoms are contained, the branching is reversed. It is not preferable that there are too many parts because it becomes a hindrance factor during spinning and drawing. However, when there is too much content of monomers other than ethylene, it becomes an obstruction factor of extending | stretching on the contrary. Therefore, it is preferable that monomers other than ethylene are 5.0 mol% or less in a monomer unit, More preferably, it is 1.0 mol% or less, More preferably, it is 0.2 mol% or less, Most preferably, it is 0.00. 0 mol%, that is, a homopolymer of ethylene. In the present specification, “polyethylene” includes not only ethylene homopolymers but also copolymers of ethylene and a small amount of other monomers, unless otherwise specified. In addition, for the production of the multifilament according to the present invention, a polyethylene composition in which various additives to be described later are blended with polyethylene as necessary can be used, and “polyethylene” in the present specification includes such a polyethylene composition. Include objects.

  Further, in the measurement of the intrinsic viscosity described later, if the intrinsic viscosity falls within a predetermined range described later, polyethylenes having different number average molecular weights and weight average molecular weights may be blended, or the molecular weight distribution (Mw / Mn). Different polyethylenes may be blended. Further, it may be a blend of a branched polymer and an unbranched polymer.

<Weight average molecular weight>
As described above, the polyethylene used in the present invention is preferably ultra high molecular weight polyethylene, and the ultra high molecular weight polyethylene preferably has a weight average molecular weight of 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, the multifilament may not have a high strength and a high elastic modulus even if the stretching step described later is performed. This is presumed to be due to the fact that since the weight average molecular weight is small, the number of molecular ends per cross-sectional area of the multifilament increases, which acts as a structural defect. On the other hand, if the weight average molecular weight exceeds 6,200,000, the tension during the stretching process becomes very large, causing breakage, which makes it very difficult to produce.

The weight average molecular weight is generally determined by the GPC measurement method. However, when the weight average molecular weight is high as in the polyethylene used in the present invention, the GPC measurement method may cause a column clogging at the time of measurement. There is a risk that it cannot be easily obtained. Therefore, for the polyethylene used in the present invention, instead of the GPC measurement method, “POLYMER HANDBOOK, Fourth Edition, J. Brandrup and E. H. Immergut, E. A. Gulke Ed., A JOHN WILEY & Sons, Inc. By using the following formula described in “1999”, the weight average molecular weight is calculated from the value of the intrinsic viscosity described later.
Weight average molecular weight = 5.365 × 10 ⁴ × (intrinsic viscosity) ^1.37

<Intrinsic 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, 40.0 dL / g or less, preferably 30.0 dL / g or less, more preferably 25. 0 dL / g or less. When the intrinsic viscosity is less than 5.0 dL / g, a high-strength multifilament may not be obtained. On the other hand, the upper limit of the intrinsic viscosity is not particularly problematic as long as a high-strength multifilament can be obtained. However, if the intrinsic viscosity of polyethylene is too high, it becomes difficult to produce a multifilament because the workability is lowered. It is preferable that it is the above-mentioned range.

[Single yarn fineness]
The multifilament according to the present invention preferably has a single yarn fineness of 3 dtex or more and 40 dtex or less, more preferably 5 dtex or more and 30 dtex or less, and further preferably 6 dtex or more and 20 dtex or less. When the single yarn fineness is 3 dtex or more, high wear resistance is exhibited. On the other hand, when the single yarn fineness exceeds 40 dtex, the strength of the multifilament is lowered, which is not preferable.

[Total fineness of multifilament]
The multifilament according to the present invention preferably has a total fineness of 15 dtex or more and 7000 dtex or less, more preferably 30 dtex or more and 5000 dtex or less, and further preferably 40 dtex or more and 3000 dtex or less. When the total fineness is 15 dtex or more, high wear resistance is exhibited. On the other hand, when the total fineness exceeds 7000 dtex, the strength of the multifilament is lowered, which is not preferable.

[Number of single yarns]
The multifilament according to the present invention is composed of 5 or more single yarns, preferably 10 or more single yarns, more preferably 15 or more.

〔wear〕
For the multifilament according to the present invention, the surface of the multifilament is washed with hexane and ethanol at room temperature, and after the surface of the multifilament is dried, a wear test based on JIS L 1095 is performed. As a result, the load is 5 cN / dtex. The number of times until breakage is 1000 times or more, preferably 1500 times or more, more preferably 3000 times or more. In addition, although an upper limit is not specifically limited, It is preferable that it is 300000 times or less. Further, the number of times until fracture when the load is 10 cN / dtex is 100 times or more, preferably 150 times or more, more preferably 200 times or more, and particularly preferably 300 times or more. In addition, although an upper limit is not specifically limited, It is preferable that it is 100,000 times or less.

[Thermal stress]
In the multifilament according to the present invention, the maximum value of thermal stress in TMA (mechanical thermal analysis) measurement is preferably 0.20 cN / dtex or more and 5.0 cN / dtex or less, more preferably 0.25 cN / dtex. As described above, it is 3.0 cN / dtex or less. When the maximum value of thermal stress is less than 0.20 cN / dtex, the elastic modulus of the multifilament may be lowered, which is not preferable. Moreover, since the dimensional change will become large when the thermal stress maximum value exceeds 5.0 cN / dtex, it is not preferable.
In the multifilament according to the present invention, the temperature at which the thermal stress maximum value in TMA (mechanical thermal analysis) measurement is preferably 120 ° C. or higher, more preferably 130 ° C. or higher. When the temperature is less than 120 ° C., the dimensional change becomes large when stored at a high temperature or when the product is washed with hot water.
In the multifilament according to the present invention, the thermal stress at 120 ° C. in TMA (mechanical thermal analysis) measurement is preferably 0.15 cN / dtex or more and 0.5 cN / dtex or less, more preferably 0.17 cN. / Dtex or more and 0.4 cN / dtex or less. When the thermal stress at 120 ° C. is less than 0.15 cN / dtex, the elastic modulus of the multifilament may be lowered, which is not preferable.

[Heat shrinkage]
The multifilament according to the present invention preferably has a heat shrinkage rate at 70 ° C. of 0.20% or less, more preferably 0.18% or less, and still more preferably 0.15% or less. Although a minimum is not specifically limited, It is preferable that it is 0.01% or more. In addition, the multifilament according to the present invention preferably has a heat shrinkage rate at 120 ° C. of 3.0% or less, more preferably 2.9% or less, and further preferably 2.8% or less. Although a minimum is not specifically limited, It is preferable that it is 0.01% or more. In addition, the heat shrinkage rate at 70 ° C. or 120 ° C. of the multifilament refers to the heat shrinkage rate in the longitudinal direction of the multifilament at 70 ° C. or 120 ° C.

[Tensile strength]
The multifilament according to the present invention has a tensile strength of 18 cN / dtex or more, preferably 20 cN / dtex or more, more preferably 21 cN / dtex or more. The multifilament according to the present invention has the above-described tensile strength even when the single yarn fineness is increased, and can be developed to applications that require wear resistance and dimensional stability that cannot be developed with conventional multifilaments. it can. Higher tensile strength is preferred, and the upper limit is not particularly limited. For example, multifilaments having a tensile strength exceeding 85 cN / dtex are technically and industrially difficult to produce. The method for measuring the tensile strength will be described later.

[Elongation at break]
The multifilament according to the present invention has an elongation at break of preferably 3.0% or more, more preferably 3.4% or more, further preferably 3.7% or more, preferably 7.0% or less, 6.0% The following is more preferable, and 5.0% or less is more preferable. When the elongation at break is less than 3.0%, it is not preferable because breakage of single yarn or generation of fluff is likely to occur with a slight distortion when the product is used or processed into the product. On the other hand, if the elongation at break exceeds 7.0%, the dimensional stability is impaired, which is not preferable. 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 600 cN / dtex or more and 1500 cN / dtex or less. If the multifilament has such an initial elastic modulus, physical properties and shape changes are less likely to occur due to external forces received during use of the product or during processing of the product. The initial elastic modulus is more preferably 650 cN / dtex or more, further preferably 680 cN / dtex or more, more preferably 1400 cN / dtex or less, still more preferably 1300 cN / dtex or less, particularly preferably 1200 cN / dtex or less. If the initial elastic modulus exceeds 1500 cN / dtex, the suppleness of the yarn is impaired by the high elastic modulus, which is not preferable. A method for measuring the initial elastic modulus will be described later.

[Coefficient of variation of initial elastic modulus of single yarn constituting multifilament]
About the initial elastic modulus of the single yarn constituting the multifilament according to the present invention, the coefficient of variation CV defined by the following formula (1) is preferably 30% or less, more preferably 25% or less, More preferably, it is 20% or less. If the coefficient of variation CV representing the variation in the initial elastic modulus of the single yarn exceeds 30%, it is not preferable because not only the strength of the multifilament composed of the single yarn is lowered but also the wear resistance is deteriorated. In addition, although a minimum is not specifically limited, It is preferable that it is 0.5% or more.
Coefficient of variation CV (%) = (standard deviation of initial elastic modulus of the single yarn) / (average value of initial elastic modulus of the single yarn) × 100 (1)

[Crystal structure of single yarn]
The single yarn used in the present invention preferably has a structure in which the crystal structure inside the single yarn is almost uniform throughout the cross section (vertical surface in the longitudinal direction). That is, the single yarn used in the present invention has a ratio of the diffraction peak intensity of the (200) plane to the diffraction peak intensity of the (110) plane (hereinafter referred to as peak intensity ratio) in the measurement using the X-ray beam described later. When measured over the entire cross section of the single yarn, the difference between the maximum value and the minimum value is preferably 0.22 or less, more preferably 0.20 or less, and still more preferably 0.18 or less. When the difference between the maximum value and the minimum value of the peak intensity ratio exceeds 0.22, it indicates that the uniformity of the crystal structure of the entire cross section is insufficient, and a multi-layer consisting of a single yarn having a non-uniform crystal structure Filaments are not preferred because they tend to have low wear resistance. The lower limit of the difference between the maximum value and the minimum value of the peak intensity ratio is not particularly limited, but about 0.01 is sufficient. Hereinafter, a method for measuring the peak strength ratio in the single yarn and how to obtain the difference between the maximum value and the minimum value of the peak strength ratio will be described.

  The crystal structure inside the single yarn can be confirmed by an X-ray analyzer using an X-ray beam having a half width smaller than the diameter of the single yarn. The diameter of the single yarn can be determined with an optical microscope or the like. When the cross section of the single yarn is an ellipse or the like, the distance connecting the two most distant points existing on the outer periphery of the single yarn is the diameter, and the midpoint of the two points is the center of the single yarn. It is preferable to use an X-ray beam having a half width of 30% or less of the diameter of the single yarn, and more preferably an X-ray beam having a half width of 10% or less of the diameter of the single yarn.

  The difference between the maximum value and the minimum value of the peak intensity ratio is obtained by the following method. The peak intensity ratio is measured at equal intervals from the center of the single yarn to a position near the outer periphery of the single yarn (hereinafter referred to as the outermost point), the maximum value and the minimum value of the peak strength ratio are determined, and the difference is obtained. The outermost point is preferably a point separated from the center of the single yarn by 30% or more of the diameter, and more preferably 35% or more of the diameter. The number of measurement points of the peak intensity ratio from the center of the single yarn to the outermost point is preferably 3 or more, and more preferably 5 or more. The interval is preferably smaller than the half width of the X-ray beam, and the interval is more preferably 90% or less of the half width of the X-ray beam.

  The peak strength ratio is preferably 0.01 or more and 0.48 or less, more preferably 0.08 or more and 0.40 or less, and further preferably 0.15 or more and 0.35 or less at any measurement point inside the single yarn. It is. When there is a measurement point where the peak intensity ratio exceeds 0.48, the crystals inside the single yarn are extremely grown in the a-axis direction of the orthorhombic unit cell, and the crystal structure of the entire cross section A multifilament made of a single yarn having a non-uniform crystal structure indicates that the uniformity is insufficient.

Regarding the peak intensity ratio, the coefficient of variation CV ′ defined by the following formula (2) is preferably 50% or less, more preferably 40% or less, and still more preferably 30% or less. If the coefficient of variation CV ′ exceeds 50%, the uniformity of the crystal structure of the entire cross section is insufficient. The lower limit of the coefficient of variation CV ′ is not particularly limited, but is preferably 1% or more.
Coefficient of variation CV ′ (%) = (standard deviation of peak strength ratio of single yarn) / (average value of peak strength ratio of single yarn) × 100 (2)

  The degree of crystal orientation in the axial direction (longitudinal direction) of the single yarn (hereinafter referred to as crystal orientation) is also measured at equal intervals from the center of the single yarn to the outermost point using the X-ray beam as in the case of the peak intensity ratio. I do. The degree of crystal orientation is preferably 0.950 or more and more preferably 0.960 or more at any measurement point inside the single yarn. If there is a measurement point having a degree of crystal orientation of less than 0.950, it is not preferable because the wear resistance of such a multifilament made of a single yarn may be lowered. The upper limit of the degree of crystal orientation is not particularly limited, but it is substantially difficult to obtain a single yarn exceeding 0.995.

  Further, the difference between the maximum value and the minimum value of the degree of crystal orientation can be obtained in the same manner as the difference between the maximum value and the minimum value of the peak intensity ratio. The difference between the maximum value and the minimum value of the peak intensity ratio is preferably 0.010 or less, and more preferably 0.007 or less. A single yarn in which the difference between the maximum value and the minimum value of the degree of crystal orientation exceeds 0.010 has a non-uniform crystal structure, so that the wear resistance of a multifilament made of such a single yarn may be reduced. This is not preferable. The lower limit of the difference between the maximum value and the minimum value of the degree of crystal orientation is not particularly limited, but about 0.001 is sufficient.

〔Production method〕
The production method for obtaining the multifilament according to the present invention is preferably based on a gel spinning method. Specifically, the method for producing a multifilament according to the present invention includes a dissolving step in which polyethylene is dissolved in a solvent to form a polyethylene solution, and the polyethylene solution is discharged from a nozzle at a temperature equal to or higher than the melting point of the polyethylene. A spinning process in which the yarn is cooled with a refrigerant of 10 ° C. or more and 60 ° C. or less, a stretching process in which the solvent is removed from the discharged undrawn yarn, and winding that is wound at 50 ° C. or less with a tension of 5 cN / dtex or less. It is preferable to provide a taking process.

<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 room temperature solid or a non-volatile solvent. The polyethylene concentration in the polyethylene solution is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less. There is a need to select an optimal concentration according to the intrinsic viscosity [η] of polyethylene as a raw material.

  Various methods can be used as the method for producing the polyethylene solution. For example, the polyethylene solution can be obtained by using a twin screw extruder or by suspending solid polyethylene in a solvent and stirring at a high temperature. Can be produced. At this time, it is preferable that the mixing condition is 1 minute or more and 80 minutes or less in a temperature range of 150 ° C. or more and 200 ° C. or less. If it is less than 1 minute, mixing may be incomplete, which is not preferable. On the other hand, when the time in the temperature range of 150 ° C. or higher and 200 ° C. or lower exceeds 80 minutes, the polyethylene molecule breaks or crosslinks so much that the spinning range is exceeded. However, it is difficult to produce a multifilament having both high strength, high elastic modulus and dimensional stability even if a multifilament composed of at least five is manufactured. Depending on the molecular weight and concentration of the polymer, mixing at a temperature exceeding 200 ° C. is required, but the mixing time at a temperature exceeding 200 ° C. is preferably 30 minutes or less. When the time exceeds 30 minutes, the polyethylene molecule breaks or crosslinks so much that the spinning range is exceeded. Therefore, a multifilament composed of at least 5 single yarns having a single yarn fineness of 3 dtex or more is manufactured. However, it is difficult to make a multifilament having both high strength, high elastic modulus and dimensional stability. In addition, the above-mentioned range in which spinning is possible means that spinning at 10 m / min or more is possible, and the spinning tension at that time is 0.01 cN or more and 300 cN or less per single yarn.

<Spinning process>
The polyethylene solution prepared by high-temperature stirring or a twin screw extruder is preferably at a temperature higher by 10 ° C. or higher than the melting point of polyethylene by using an extruder or the like, more preferably at a temperature higher by 20 ° C. or higher than the melting point of polyethylene. More preferably, extrusion is performed at a temperature 30 ° C. or more higher than the melting point of polyethylene, and then, it is supplied to a spinneret (spinning nozzle) using a quantitative supply device. The time for passing through the orifice of the spinneret is preferably 1 second or more and 8 minutes or less. When the time is less than 1 second, the flow of the polyethylene solution in the orifice is disturbed, which is not preferable because the polyethylene solution cannot be stably discharged. Further, it is not preferable because the structure of the whole single yarn becomes non-uniform under the influence of the disturbance of the flow of the polyethylene solution. On the other hand, if it exceeds 8 minutes, the polyethylene molecules are ejected with little orientation, and the spinning tension range per single yarn tends to be out of the above range, which is not preferable. Further, since the crystal structure of the obtained single yarn becomes non-uniform, it is not preferable because the wear resistance cannot be expressed as a result.

  A thread is formed by passing a polyethylene solution through a spinneret in which a plurality of orifices are arranged. When a yarn is produced by spinning a polyethylene solution, the temperature of the spinneret needs to be equal to or higher than the melting temperature of polyethylene, preferably 140 ° C or higher, and more preferably 150 ° C or higher. The melting temperature of the polyethylene depends on the solvent selected, the concentration of the polyethylene solution, and the mass% of the polyethylene, and of course the spinneret temperature is below the thermal decomposition temperature of the polyethylene.

  Next, the polyethylene solution is preferably discharged at a discharge rate of 0.1 g / min or more from a spinneret having a diameter of 0.2 to 3.5 mm (more preferably, a diameter of 0.5 to 2.5 mm). 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 and cannot be taken up at a fast speed. Further, a temperature higher than the boiling point of the solvent to be used is not preferable because the solvent boils immediately after leaving the spinneret, and yarn breakage frequently occurs immediately below the spinneret. Note that the spinneret is provided with five or more orifices so that the multifilament is composed of five or more single yarns. Preferably there are 7 or more orifices.

  On the spinneret surface side (polyethylene solution discharge side), the same number of pores (one end of the orifice) for discharging the polyethylene solution as the number of orifices are formed. The discharge amount of the polyethylene solution from each pore Is preferably as uniform as possible, and for this purpose, it is preferable that the temperature difference between the pores is small. Specifically, the coefficient of variation CV ″ of discharge amount in each pore ((standard deviation of discharge amount in all pores provided in the spinneret) / (average of discharge amount in all pores provided in the spinneret) Value) × 100) is preferably 20% or less, more preferably 18% or less. In order to obtain the above coefficient of variation CV ″, the difference between the maximum temperature and the minimum temperature of the pores is 10 ° C. It is preferable that it is below, More preferably, it is 8 degrees C or less. The method for reducing the difference between the maximum temperature and the minimum temperature of the pores is not particularly limited, but it is preferable that the spinneret is shielded so as not to come into direct contact with the outside air. For example, the spinneret is shielded from heat insulating glass. A method of shielding from the outside air with a plate is mentioned. The difference between the maximum temperature and the minimum temperature of the pores is reduced by minimizing the difference between the distance between the shielding plate and the pore closest to the shielding plate and the distance between the shielding plate and the pore farthest from the shielding plate. Can be reduced.

  The atmosphere until the yarn discharged from the pores is cooled by the refrigerant after being discharged from the pores is not particularly limited, but is preferably filled with an inert gas such as nitrogen or helium. .

  Next, the discharged yarn is preferably taken up at a speed of 800 m / min or less while being cooled with a cooling medium, and more preferably 200 m / min or less. At this time, it is preferable that the temperature of a cooling medium is 10-60 degreeC, More preferably, it is 12 degreeC or more and 35 degrees C or less. If the refrigerant temperature is out of this range, the tensile strength of the multifilament is greatly decreased as the single yarn fineness increases, which is not preferable. The cause is considered as follows. In order to maintain high strength and high elastic modulus even when the single yarn fineness is increased, it is preferable to make the crystal structure of the entire single yarn as uniform as possible. However, if the temperature of the cooling medium is too low, the cooling near the center of the cross section of the single yarn cannot catch up with the cooling near the outer surface of the single yarn, and the crystal structure of the entire single yarn becomes non-uniform. Also, if the temperature of the cooling medium is too high, the difference between the cooling rate near the center of the cross section of the single yarn and the cooling rate near the outer surface of the single yarn becomes small, but the time required for cooling becomes long. The structural change occurs in the spun undrawn yarn, and the crystal structure tends to differ between the vicinity of the center of the cross section of the single yarn and the vicinity of the outer surface of the single yarn. For this reason, the strength of the single yarn is lowered, and the strength of the multifilament is also lowered. The cooling medium may be either a miscible liquid that is miscible with the solvent of the polyethylene solution or an immiscible liquid such as water that is immiscible with the solvent of the polyethylene solution.

  The time from the end of cooling to the removal of the solvent present in the yarn is preferably shorter, that is, it is preferable to remove the solvent immediately after cooling. Details of the removal of the solvent will be described later. The time required for removing the solvent is preferably within 10 hours, more preferably within 2 hours, and even more preferably within 30 minutes until the amount of the solvent remaining in the multifilament becomes 10% or less. is there. When the time required for removing the solvent exceeds 10 hours, the difference between the crystal structure formed near the center of the cross section of the single yarn and the crystal structure formed near the outer surface of the single yarn becomes large, This is not preferable because the crystal structure becomes non-uniform.

<Extension process>
The unstretched yarn taken up in the spinning process is continuously or once wound, and then the stretching process is performed. In the drawing process, the undrawn yarn obtained by cooling is drawn several times in a heated state. Stretching may be performed only once or divided into a plurality of times, but is preferably 1 time or more and 3 times or less. Further, the undrawn yarn may be stretched by one or more stages after being heat-dried. The stretching step may be performed in a heat medium atmosphere or using a heating roller. Examples of the medium include air, an inert gas such as nitrogen, water vapor, and a liquid medium.

  Although it is necessary to remove the solvent from the undrawn yarn, the solvent may be drawn while removing the solvent, or the solvent removal may be performed separately from the drawing step. As the solvent removal means, the heating method described above may be used in the case of a volatile solvent, but the extraction method using an extractant or the like may be used in the case of using a non-volatile solvent. As the extractant, for example, chloroform, benzene, trichlorotrifluoroethane (TCTFE), hexane, heptane, nonane, decane, ethanol, higher alcohol and the like can be used.

The draw ratio of the undrawn yarn is preferably 7.0 times or more and 60 times or less, more preferably 8.0 times or more and 55 times as the total draw ratio regardless of whether the drawing process is a single stage or a multi-stage. It is not more than twice, more preferably not less than 9.0 times and not more than 50 times. Moreover, it is preferable to extend | stretch at the temperature below the melting | fusing point of polyethylene. When stretching a plurality of times, it is preferable to increase the temperature at the time of stretching as it progresses to the later stage, and the stretching temperature at 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 as follows. What is necessary is just to set the conditions of a heating apparatus so that a thread | yarn may become in the range of the said extending | stretching temperature at the time of extending | stretching. At this time, the temperature of the yarn can be measured using, for example, 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 further preferably 10 minutes or less. If the deformation time of the multifilament exceeds 20 minutes, the molecular chain relaxes during stretching even if the production conditions other than the stretching time are within a suitable range, which is not preferable because the strength of the single yarn decreases.

The deformation rate during stretching is preferably 0.001 s ^-1 or more and 0.8 s ^-1 or less. More preferably, 0.01s ^-1 or more and 0.1s ^-1 or less. The deformation rate can be calculated from the draw ratio of the multifilament, the drawing speed, and the length of the drawing section. That is, deformation rate (s ⁻¹ ) = stretching speed / {stretching section · (stretching ratio−1)}. If the deformation rate is too high, the multifilament breaks before reaching a sufficient draw ratio, which is not preferable. Also, if the deformation rate of the multifilament is too slow, the molecular chain relaxes during stretching, so a high-strength, high-modulus multifilament cannot be obtained, and the tensile strength when the braid is made into a braid In addition, the initial elastic modulus is low, which is not preferable.

<Winding process>
The stretched yarn is preferably wound up within 10 minutes from the end of stretching, more preferably within 8 minutes, and even more preferably within 5 minutes. The drawn yarn is preferably wound with a tension of 0.001 cN / dtex or more and 5 cN / dtex or less, more preferably 0.05 cN / dtex or more and 3 cN / dtex or less. By winding with the time and tension within the above range, it is possible to wind in a state in which the residual strain in the cross-sectional direction in the multifilament is maintained. If the tension during winding is less than 0.001 N / dtex, the residual strain becomes small and the stress distribution in the cross-sectional direction becomes unstable. As a result, in each single yarn constituting the multifilament, Difference in residual strain is developed. Further, if the winding tension is larger than 5.0 cN / dtex, the single yarn constituting the multifilament is likely to be broken, which is not preferable.

  Moreover, it is preferable that the temperature at the time of winding is 50 degrees C or less, More preferably, they are 5 degreeC or more and 45 degrees C or less. When the temperature at the time of winding exceeds 50 ° C., there is a possibility that the residual strain fixed in the above cooling process may be relaxed, which is not preferable.

[Others]
In order to provide other functions, when producing the multifilament according to the present invention, an additive such as an antioxidant or an antioxidant, a pH adjuster, a surface tension reducing agent, a thickener, a humectant, a thickener. 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 according to the present invention is a protective woven or knitted fabric utilizing cut resistance, tape, rope, net, fishing line, material protective cover, sheet, kite thread, bowstring, sail cloth, curtain material, protective material, It can be used for industrial materials such as bulletproof materials, medical 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.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

  The measurement of the characteristic value of the multifilament in each of the following examples and comparative examples was performed as follows.

(1) Intrinsic viscosity The solvent was decalin at a temperature of 135 ° C., and the specific viscosities of various dilute solutions were measured using an Ubbelohde capillary viscosity tube. The intrinsic viscosity was determined from the extrapolation point to the origin of the straight line obtained by the least square approximation from the plot with respect to the concentration of the diluted solution viscosity. In measurement, the sample was divided or cut into a length of about 5 mm, and 1% by mass of an antioxidant (“Yoshinox (registered trademark) BHT” manufactured by API Corporation) was added to the sample at 135 ° C. The measurement solution was prepared by stirring and dissolving for 4 hours.

(2) Weight average molecular weight The weight average molecular weight was calculated from the intrinsic viscosity value measured by the method (1) using the following formula.
Weight average molecular weight = 5.365 × 10 ⁴ × (intrinsic viscosity) ^1.37

(3) Tensile strength, breaking elongation, and initial elastic modulus Measured in accordance with JIS L 1013 8.5.1. Universal testing machine (Orientec Co., Ltd., “Tensilon Universal Material Testing Machine RTF-1310 The strain-stress curve was measured under the conditions of an ambient temperature of 20 ° C. and a relative humidity of 65% under the conditions of a sample length of 200 mm (length between chucks) and an elongation rate of 100 mm / min. The tensile strength and elongation at break were calculated from the stress and elongation at the breaking point, and the initial elastic modulus was calculated from the tangent that gave the maximum gradient near the origin of the curve. At this time, the initial load applied to the sample during measurement was set to 1/10 of the mass (g) per 10000 m of multifilament. In addition, the average value of 10 times of measured values was used for tensile strength, breaking elongation, and initial elastic modulus.

(4) Coefficient of variation CV
The initial elastic modulus of each single yarn constituting the sample is measured by the above measurement method, and (standard deviation of the initial elastic modulus of the single yarn constituting the multifilament) / (the initial elastic modulus of the single yarn constituting the multifilament) The value of (average value) × 100 was calculated and used as the coefficient of variation CV (%).

(5) Thermal shrinkage The sample was cut into 70 cm and marked at 10 cm positions from both ends, that is, so that the sample length was 50 cm. Next, the sample was heated at a temperature of 70 ° C. for 30 minutes using a hot air circulation type heating furnace in a state of being hung on a jig so that no load was applied to the sample. Thereafter, the sample was taken out from the heating furnace, sufficiently cooled to room temperature, and then the length of the position where the sample was initially marked was measured. The thermal shrinkage rate was obtained from the following formula. In addition, the average value of the measured value of 2 times was used for the heat shrinkage rate.
Thermal contraction rate (%) = 100 × (sample length before heating−sample length after heating) / (sample length before heating)
Further, the temperature for heating for 30 minutes was changed from 70 ° C. to 120 ° C., and the thermal shrinkage at 120 ° C. was measured in the same manner as described above.

(6) Thermal stress A thermal stress strain measuring device (manufactured by Seiko Instruments Inc., “TMA / SS120C”) was used for measurement. A sample was prepared to have a length of 20 mm, the initial load was 0.01764 cN / dtex, the temperature was raised from room temperature (20 ° C.) to the melting point at a temperature rising rate of 20 ° C./min, and the thermal stress at 120 ° C. was measured. The thermal stress and the temperature at which the thermal shrinkage is maximized were measured.

(7) Fineness The sample was cut into 20 cm single yarns at 5 different positions, the mass was measured, and the average value was converted to 10000 m to obtain the fineness (dtex).

(8) Abrasion test Abrasion resistance was evaluated by an abrasion test based on the B method in which the sample was adjusted to about 220 dtex and the abrasion strength was measured in a general spun yarn test method (JIS L 1095). The measurement was carried out using a yarn binding force testing machine manufactured by Asano Machinery Manufacturing Co., Ltd. Using a hard steel of 2.0 mmφ as a friction element, testing was performed at a load of 5 cN / dtex or 10 cN / dtex, an ambient temperature of 20 ° C., a friction speed of 115 times / minute, a reciprocating distance of 2.5 cm, and a friction angle of 110 degrees. The number of times of friction was measured. When the load was 5 cN / dtex and when the load was 10 cN / dtex, the number of reciprocating frictions until the sample was cut due to wear was measured. The number of tests was 7, and the data of the maximum number and the minimum number were excluded, and the average value of the remaining five measurements was expressed.

(9) Peak intensity ratio inside single yarn Crystal size and orientation evaluation were measured using X-ray diffraction method. As an X-ray source, a large synchrotron radiation facility SPring-8 was used as an X-ray source, and a BL03 hatch was used. The wavelength of the X-ray used is λ = 1.0 mm. The X-ray size was adjusted so that the distance connecting the two most distant points existing on the outer periphery of the X-ray cross section was 7 μm or less. The sample was placed on an XYZ stage so that the single yarn axis was vertical, so that the X-rays were perpendicular to the axial direction of the sample. The stage was moved slightly so that the midpoint of the distance connecting the two most distant points existing on the outer periphery of the X-ray cross section was located at the center of the stage. Since the X-ray intensity is very high, the sample is damaged if the exposure time of the sample is too long. Therefore, the exposure time during X-ray diffraction measurement was set to be within 30 seconds. Under these measurement conditions, beams were applied at substantially equal intervals from the center of the single yarn to the vicinity of the outer periphery of the single yarn, and X-ray diffraction patterns at each location were measured. Specifically, the center of the single yarn, the point 2.5 μm away from the center, the point 5.0 μm away, the point 7.5 μm away, etc. X-ray diffraction patterns were measured at 2.5 μm intervals up to the vicinity. For example, in the case of a single yarn having a diameter of 32 μm (radius 16 μm), the center, a point 2.5 μm away from the center, a point 5.0 μm away, a point 7.5 μm away, a point 10.0 μm away, 12.5 μm away The X-ray diffraction pattern was measured at a total of 7 points including 15.0 μm apart. X-ray diffraction patterns were recorded using a flat panel placed at a position 67 mm away from the sample. From the recorded image data, the peak intensity ratio was determined from the peak intensity values derived from orthorhombic (110) and orthorhombic (200) from the diffraction profile in the equator direction.

(10) Degree of crystal orientation inside the single yarn As in the above (9), the X-ray source was measured at the large synchrotron radiation facility SPring-8. The degree of crystal orientation was determined from the azimuth diffraction profile using the following formula from the half-value width of the orthorhombic (110) orientation distribution function.
Degree of crystal orientation = (180− (half width of (110) plane)) / 180

  Regarding the degree of crystal orientation, the center of the single yarn, the point 2.5 μm away from the center, the point 5.0 μm away, the point 7.5 μm away, etc. Measurement was performed at intervals of 2.5 μm to the vicinity of the outer periphery. For example, in the case of a single yarn having a diameter of 32 μm (radius 16 μm), the center, a point 2.5 μm away from the center, a point 5.0 μm away, a point 7.5 μm away, a point 10.0 μm away, 12.5 μm away A total of 7 points were measured including the points 15.0 μm apart.

Example 1
A dispersion of ultrahigh molecular weight polyethylene having an intrinsic viscosity of 18.0 dL / g, a weight average molecular weight of 2,900,000, and a melting point peak of 134 ° C. and decalin was prepared so as to have a polyethylene concentration of 11.0% by mass. This dispersion was made into a solution with an extruder with a residence time in the temperature range of 205 ° C. being 8 minutes, and the polyethylene solution was discharged from the spinneret at a spinneret surface temperature of 180 ° C. at a single-hole discharge rate of 4.5 g / min. The number of orifices formed in the spinneret was 15, and the orifice diameter was φ1.0 mm. The fine hole for discharging the yarn (one end of the orifice) formed on the surface of the spinneret is shielded so as not to come into direct contact with the outside air. Specifically, the spinneret is a shield plate made of heat insulating glass having a thickness of 10 mm. Was shielded from the open air. The distance between the shielding plate and the pore closest to the shielding plate was 40 mm, and the distance between the shielding plate and the pore farthest from the shielding plate was 60 mm. Further, the difference between the maximum temperature and the minimum temperature of the pores is 3 ° C., and the variation coefficient CV ″ of the ejection amount in each pore ((standard deviation of the ejection amount in 15 pores) / (15 pores) The average value of the discharge amount) x 100) was 8%, and was cooled with a water-cooled bath at 20 ° C. while taking out the discharged yarn, and then taken out at a speed of 70 m / min. An unstretched multifilament made of yarn was obtained, and then the unstretched multifilament was stretched 4.0 times while being heated and dried with hot air at 120 ° C. Subsequently, it was stretched to 2.7 times with hot air at 150 ° C. The stretched multifilament was immediately wound up in the stretched state, the total stretch ratio was 10.8 times, the total stretch time was 4 minutes, and the deformation rate during stretching was 0.0300 sec ^-1 . The temperature at the time of winding is 3 The winding tension was 0.100 cN / dtex at 2 ° C. The time from the end of drawing at 150 ° C. to the winding time was 2 minutes. Table 2 shows the physical properties and evaluation results.

(Example 2)
In Example 1, the dispersion was made into a solution by using an extruder with a residence time in the temperature range of 205 ° C. of 8 minutes, the single-hole discharge amount of the polyethylene solution was 5.0 g / min, and the pores farthest from the shielding plate The distance between the maximum temperature and the minimum temperature of the pore is 4 ° C., the variation coefficient CV ″ of the discharge amount in each pore is 11%, the spinning speed is 60 m / min, and the draw ratio in hot air at 150 ° C. A multifilament was obtained in the same manner as in Example 1 except that 2.5 times (the total draw ratio was 10.0 times), the total draw time was 6 minutes, and the deformation rate at the time of drawing was 0.0200 sec- ¹ . Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Example 3)
In Example 1, the distance from the farthest pore from the shielding plate is 45 mm, the difference between the highest temperature and the lowest temperature of the pore is 2 ° C., the variation coefficient CV ″ of the discharge amount in each pore is 6%, and winding A multifilament was obtained in the same manner as in Example 1 except that the tension at the time was 0.200 cN / dtex and the time from the start of drawing to winding was 12 minutes. Table 2 shows the physical properties and evaluation results of the multifilaments.

Example 4
In Example 1, the residence time in the temperature range of 205 ° C. is 11 minutes, the draw ratio in hot air at 150 ° C. is 2.5 times (total draw ratio is 10.0 times), the total draw time is 5 minutes, Example except that the deformation rate was 0.0240 sec ⁻¹ , the temperature when winding the drawn yarn was 40 ° C., the tension during winding was 0.030 cN / dtex, and the time from the start of drawing to winding was 5 minutes. A multifilament was obtained in the same manner as in Example 1. Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Example 5)
In Example 1, the residence time in the temperature range of 205 ° C. is 18 minutes, the draw ratio in hot air at 120 ° C. is 4.5 times, and the draw ratio in hot air at 150 ° C. is 2.2 times (total draw ratio is 9.9). Times), a multifilament was obtained in the same manner as in Example 1 except that the total stretching time was 5 minutes and the deformation rate during stretching was 0.0240 sec-1. Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Comparative Example 1)
In Example 1, the residence time in the temperature range of 205 ° C. was 32 minutes, the single-hole discharge rate was 1.0 g / min, and no heat insulating glass shielding plate having a thickness of 10 mm was provided. Difference of 12 ° C., discharge coefficient variation CV ″ in each pore is 23%, stretch ratio in hot air at 120 ° C. is 3.0 times, stretch ratio in hot air at 150 ° C. is 2.3 times (total stretch ratio) Multifilaments were obtained in the same manner as in Example 1, except that the number was 6.9 times) Table 1 shows the production conditions of the multifilaments, and Table 2 shows the physical properties and evaluation results of the obtained multifilaments.

(Comparative Example 2)
In Example 1, a multifilament was obtained in the same manner as in Example 1 except that the discharged yarn was cooled with a water-cooled bath at 65 ° C. and an undrawn yarn was obtained under a spinning speed of 10 m / min. Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Comparative Example 3)
In Example 1, a multifilament was obtained in the same manner as in Example 1 except that the total stretching time was 25 minutes and the deformation rate during stretching was 0.0005 sec ⁻¹ . Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Comparative Example 4)
In Example 1, the draw ratio in hot air at 120 ° C. is 3.5 times, the draw ratio in hot air at 150 ° C. is 2.0 times (the total draw ratio is 7.0 times), and the temperature at which the drawn yarn is wound up A multifilament was obtained in the same manner as in Example 1 except that the temperature was 70 ° C. and the tension during winding was 0.008 cN / dtex. Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

(Comparative Example 5)
Similar to the production method described in Japanese Patent No. 4141686 (Patent Document 3), an intrinsic viscosity of 21.0 dL / g, a weight average molecular weight of 3,500,000, and an ultrahigh molecular weight polyethylene having a melting point peak of 135 ° C. A slurry mixture of 90% by mass of decalin is supplied to a screw-type kneader to make a solution with a residence time in the temperature range of 230 ° C. of 11 minutes, and the polyethylene solution is discharged from the spinneret at a surface temperature of the spinneret of 170 ° C. It discharged at 1.4 g / min. The number of orifices formed in the spinneret was 96, and the orifice diameter was φ0.7 mm. The difference between the maximum temperature and the minimum temperature of the pores is 12 ° C., and the variation coefficient CV ″ of the discharge amount in each pore ((standard deviation of the discharge amount in 96 pores) / (discharge in 96 pores) The average value of the amount) × 100) was 24% Nitrogen gas at 100 ° C. was discharged from the slit orifice for gas supply installed just under the spinneret to the discharged yarn at an average wind speed of 1.2 m / The spray was sprayed as evenly as possible in seconds to positively evaporate the decalin on the fiber surface, and immediately after that, it was cooled with an air flow set at 30 ° C. while taking up the discharged yarn, and then downstream of the spinneret. An unstretched multifilament consisting of 96 single yarns was obtained at a speed of 75 m / min with a Nelson roller installed in 1. At this point, the mass of the solvent contained in the yarn was discharged from the spinneret. At the time The unstretched multifilament was then stretched 4.0 times while being heated and dried with hot air at 100 ° C. in a heating oven. In a heating oven, it was stretched 4.0 times with hot air at 149 ° C., and the stretched multifilament was immediately wound up in the stretched state, the total stretching ratio was 16.0 times, the total stretching time was 8 minutes, and deformation during stretching The speed was 0.0200 sec ⁻¹ , the temperature during winding of the stretched multifilament was 30 ° C., and the tension during winding was 0.100 cN / dtex, the time from the end of stretching at 149 ° C. to the winding. The production conditions of the multifilament are shown in Table 1, and the physical properties and evaluation results of the obtained multifilament are shown in Table 2.

(Comparative Example 6)
A dispersion of ultrahigh molecular weight polyethylene having an intrinsic viscosity of 11.0 dL / g, a weight average molecular weight of 1,400,000, and a melting point peak of 131 ° C. and liquid paraffin was prepared so that the polyethylene concentration was 14.0% by mass. did. This dispersion was made into a solution in an extruder at a residence time in the temperature range of 220 ° C. of 39 minutes, and the polyethylene solution was discharged from the spinneret at a spinneret surface temperature of 170 ° C. at a single hole discharge rate of 2.0 g / min. The number of orifices formed in the spinneret was 48, and the orifice diameter was φ1.0 mm. The difference between the maximum temperature and the minimum temperature of the pores is 13 ° C., and the variation coefficient CV ″ of the ejection amount in each pore ((standard deviation of the ejection amount in 48 pores) / (ejection in 48 pores) The average value of the amount) × 100) was 22%, cooled by a water-cooled bath at 20 ° C. while taking out the discharged yarn, and then taken up at a speed of 35 m / min, consisting of 48 single yarns. Next, the unstretched multifilament was passed through n-decane at 80 ° C. to remove liquid paraffin, and then the unstretched multifilament was heated and dried with hot air at 120 ° C. Then, the film was stretched 3.0 times with hot air at 150 ° C., and the stretched multifilament was immediately wound up in the stretched state, the total stretching ratio was 18.0 times, and the total stretching time. 9 minutes during stretching The form speed was 0.0400sec ^-1. Stretched coiling temperature 30 ° C. at the time of multi-filament, until the winding tension during winding a drawn ends at .150 ° C. which was 0.100cN / dtex The time was 2 minutes, Table 1 shows the production conditions of the multifilament, and Table 2 shows the physical properties and evaluation results of the obtained multifilament.

  According to the present invention, it is possible to provide a multifilament that can be processed into a product in a wide temperature range and that is excellent in dimensional stability and wear resistance. The multifilament according to the present invention is a protective woven or knitted fabric utilizing cut resistance, tape, rope, net, fishing line, material protective cover, sheet, kite thread, bowstring, sail cloth, curtain material, protective material, It can be applied to industrial materials such as bulletproof materials, medical 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 (8)

A multifilament composed of 5 or more single yarns,
The multifilament is
The intrinsic viscosity [η] is 5.0 dL / g or more and 40.0 dL / g or less, the repeating unit is ethylene, and other monomers other than ethylene are 5.0 mol% or less in monomer units ,
Initial elastic constant of 600 cN / dtex or more, conforming to JIS L 1095, Ri der reciprocating abrasion times above 1000 at break in the measured abrasion strength test load as 5 cN / dtex,
A multifilament, wherein the coefficient of variation CV of a single yarn defined by the following formula (1) of the initial elastic modulus is 30% or less .
Coefficient of variation CV (%) = (standard deviation of initial elastic modulus of the single yarn) / (average value of initial elastic modulus of the single yarn) × 100 (1)   2. The multifilament according to claim 1, wherein the number of reciprocating wear at break in a wear strength test measured with a load of 10 cN / dtex in accordance with JIS L 1095 is 100 times or more.   The multifilament according to claim 1 or 2, wherein the fineness of the single yarn is 3 dtex or more and 40 dtex or less.   The multifilament according to any one of claims 1 to 3, wherein the maximum value of thermal stress is 0.20 cN / dtex or more. The multifilament according to any one of claims 1 to 4 , wherein the thermal stress at 120 ° C is 0.15 cN / dtex or more. The multifilament according to any one of claims 1 to 5 , wherein a heat shrinkage rate at 70 ° C is 0.20% or less and a heat shrinkage rate at 120 ° C is 3.0% or less. Multifilament according to any one of claims 1-6 the tensile strength of 18cN / dtex or more. It is a manufacturing method of the multifilament according to any one of claims 1 to 7 ,
A dissolving step of dissolving the polyethylene in a solvent to obtain a polyethylene solution;
A spinning process in which the polyethylene solution is discharged from a nozzle at a temperature equal to or higher than the melting point of the polyethylene, and the discharged yarn is cooled with a refrigerant of 10 ° C. or higher and 60 ° C. or lower;
A stretching step of stretching while removing the solvent from the discharged unstretched yarn;
A winding step of winding at a tension of 5 cN / dtex or less at 50 ° C. or less,
The stretching times in the stretching step is at most three times or more times, the draw ratio is less 60 times 7.0 times state, and are a total of less 20 minutes 0.5 minutes extension time period,
A plurality of pores for discharging the polyethylene solution is formed in the nozzle, and the maximum value of the temperature difference between the pores when discharging the polyethylene solution is 10 ° C. or less. Manufacturing method.