JP6044309B2 - Polyethylene tape, polyethylene split yarn and method for producing them - Google Patents

Description

  The present invention relates to a polyethylene tape and a polyethylene split yarn that have small changes in mechanical properties over a wide temperature range and are excellent in dimensional stability.

  Conventionally, high-performance textiles such as various sports clothing, various safety items such as bulletproof / protective clothing and protective gloves; various rope products such as tag ropes, mooring ropes, yacht ropes and construction ropes; various braided products such as fishing lines and blind cables ; Net products such as fishing nets and ball-proof nets; Reinforcing materials for various non-woven fabrics used for chemical filters and battery separators; curtain materials for tents; for sports such as helmets and skis; for composites such as speaker cones and prepregs High-strength fibers and tapes are used in a wide range of industries such as reinforcing fibers;

  As a high-strength fiber used in these applications, for example, Patent Document 1 discloses a polyethylene fiber having a high elastic modulus, which is produced by dissolving an ultrahigh molecular weight polyethylene in a solvent to form a solution and using a so-called gel spinning method. It is disclosed. However, since the polyethylene fiber is produced using an organic solvent, there is a problem that the working environment is deteriorated when the polyethylene fiber is produced. In addition, after use as a product, in applications that are used indoors and outdoors, a trace amount of organic solvent remaining in the polyethylene fiber causes a burden on the environment, which is a problem.

  As an invention that solves the above problems, for example, Patent Document 2 proposes a polyethylene fiber using a melt spinning method using high molecular weight polyethylene as a raw material. The polyethylene fiber obtained by the means has a smaller number average molecular weight and weight average molecular weight of polyethylene used than the polyethylene fiber used in the gel spinning method. Moreover, although it is estimated that the difference in a manufacturing method is a factor, the said melt spinning method can obtain the polyethylene fiber which has high elongation and a high shrinkage rate. Such polyethylene fibers exhibit excellent performance for applications that actively heat shrink. On the other hand, when performing post-processing that requires heating and heating (for example, heat treatment during resin coating), it is an important characteristic that the heat shrinkage rate and heat shrinkage stress near 100 ° C. are small. Polyethylene fiber having a high shrinkage ratio has a large change in mechanical properties before and after post-processing, and also tends to cause a change in mechanical properties when the product is used over a long period of time or at high temperatures. It is difficult to obtain a product with

  As an invention for solving the above problems, for example, Patent Document 3 proposes a polyethylene tape obtained by rolling and molding ultrahigh molecular weight polyethylene without using a solvent. However, in the polyethylene tape obtained by this production method, the mechanical properties easily change and the dimensional change also occurs in an environment exceeding the crystal dispersion temperature of polyethylene or due to a load applied during product processing. Therefore, the product processing conditions for making a structure such as a rope, a net or a woven or knitted fabric are limited. Also, when a load is applied during use of the final product, it is used under high tension, such as fiber reinforced plastic, concrete reinforced wire, rope, etc., or used in applications where the environmental temperature changes greatly during use. In this case, mechanical property changes and dimensional changes are easily generated, and it is difficult to maintain product performance.

JP 2001-73224 A JP 2003-55833 A Special table 2011-515643 gazette

The present invention is a polyethylene tape that has little change in mechanical properties over a wide temperature range, is excellent in dimensional stability, can be selected in a wide temperature range, and can be used in a wide temperature range after product processing. And the provision of polyethylene split yarn. In the present specification, the polyethylene tape has a belt-like shape, a width of 2.1 mm or more and 50 mm or less, and a thickness of 2 μm or more and 2 mm or less, and a polyethylene split yarn is a fiber shape and has a width and thickness. Indicates 3 mm or less.
In addition, the present invention has a small change in mechanical properties over a wide temperature range, is excellent in dimensional stability, can be selected in a wide temperature range, and can be used in a wide temperature range after product processing. Another object of the present invention is to provide a method for producing a polyethylene tape and a polyethylene split yarn.

  As a result of earnest research, the present inventors have completed the present invention, paying attention to the monoclinic and orthorhombic ratio, crystallinity, higher order structure of polyethylene, and the like of polyethylene tape and polyethylene split yarn.

The polyethylene tape and the polyethylene split yarn according to the present invention include polyethylene whose intrinsic viscosity [η] is 5.0 dL / g or more and 32.0 dL / g or less and whose repeating unit is substantially an ethylene chain. The ratio is 0.1% to 30%, and the orthorhombic ratio is 40% to 99%.
The crystallinity in the tape or split yarn is preferably 65% or more.
The polyethylene preferably has a weight average molecular weight (Mw) of 490,000 to 6,200,000 and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) of 6.0 or less.
The polyethylene tape preferably has a tensile strength of 0.8 GPa or higher and an initial elastic modulus of 20 GPa or higher, and the polyethylene split yarn has a tensile strength of 8 cN / dtex or higher and an initial elastic modulus of 200 cN / dtex or higher. Is preferred.
The residual solvent concentration in the polyethylene tape and polyethylene split yarn is preferably 1000 ppm or less.
The polyethylene split yarn preferably includes a single yarn having a single yarn fineness of 0.5 dtex or more and 1000 dtex or less.
The polyethylene tape is produced by compressing polyethylene having an intrinsic viscosity [η] of 5.0 dL / g or more and 32.0 dL / g or less and a substantially repeating ethylene chain at a temperature of 100 ° C. or more and 145 ° C. or less. A compressing step, a rolling step in which the polyethylene compressed in the compressing step is rolled at a temperature of 120 ° C. or higher and 145 ° C. or lower, and a polyethylene rolled in the rolling step is stretched one or more steps in a temperature range of 20 ° C. or higher and 160 ° C. or lower. Then, in the temperature range of 80 ° C. or higher and 170 ° C. or lower, the film was stretched in a stretching step of stretching from 0.01 seconds to 30 minutes at a stretching ratio of from 0.85 times to 6.0 times, and a stretching step. A winding step of winding the polyethylene with a winding tension of 5.0 cN / dtex or less in a state where polyethylene is cooled to a temperature of 60 ° C. or less.
The method for producing a polyethylene split yarn comprises a cutting step for cutting the polyethylene tape produced by the above production method.
In the present invention, not only polyethylene tape and polyethylene split yarn, but also a braided string including polyethylene tape or polyethylene split yarn, twisted yarn, woven or knitted fabric, a cut tape characterized by cutting the polyethylene tape into 1 mm or more and 10 cm or less, Also included are cut fibers obtained from polyethylene split yarns.

The polyethylene tape and polyethylene split yarn according to the present invention have little change in mechanical properties such as heat shrinkage stress, heat shrinkage rate and storage elastic modulus over a wide temperature range during product processing and product use, and dimensional stability. It is also excellent. As a product, not only as polyethylene tape and polyethylene split yarn, but also braided string, twisted yarn, woven / knitted fabric, rope, net, fishing line, material protective cover, sheet, kite yarn using the polyethylene tape or polyethylene split yarn according to the present invention, Bowstring, sailcloth, curtain material, protective material, bulletproof material, medical suture, artificial tendon, artificial muscle, fiber reinforced resin reinforcing material, cement reinforcing material, fiber reinforced rubber reinforcing material, machine tool parts, battery separator, chemical As an industrial material such as a filter, it exhibits excellent performance and design and can be widely applied.
In addition, the production method according to the present invention produces a tape by a rolling method that does not use a solvent, in order to avoid adverse effects on production workers and the environment. Furthermore, a split yarn is produced by cutting the tape. At this time, by precisely controlling the winding tension in the drawing process and further in the winding process after the heat treatment, the change in mechanical properties over a wide temperature range is small, and the polyethylene tape and polyethylene split have excellent dimensional stability. Yarn can be obtained.

  Hereinafter, the physical properties of polyethylene used for the production of the polyethylene tape and polyethylene split yarn according to the present invention, and the physical properties and production methods of the polyethylene tape and polyethylene split yarn according to the present invention will be described.

〔polyethylene〕
The polyethylene used in the present invention preferably has a substantially repeating ethylene unit. In addition, not only ethylene homopolymers but also copolymers of ethylene and a small amount of other monomers can be used 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. In addition, the polyethylene used in the present invention is a copolymer (a copolymer of ethylene and another monomer (for example, α-olefin)), a blend of homopolyethylene and an ethylene copolymer, It may be a blend of homopolyethylene and other homopolymers such as α-olefin, and may have partial crosslinking, partial methyl branching, ethyl branching, butyl branching and the like. Further, it may be a blend of polyethylenes having different weight average molecular weights, or a blend of polyethylenes having different molecular weight distributions (Mw / Mn). Further, it may be a blend of a branched polymer and an unbranched polymer. At this time, if the amount of branching or crosslinking in the tape or split yarn is increased, the creep resistance of the product is improved. However, if the amount of branching is too large, breakage will occur frequently during the stretching process described later, so the amount of crosslinking or amount of branching is increased. It is preferable to adjust according to the required performance of the product to be used.

However, when there is too much content of monomers other than ethylene, it becomes an obstruction factor of extending | stretching on the contrary. Therefore, from the viewpoint of obtaining a high-strength polyethylene tape and polyethylene split yarn, other monomers such as α-olefin are preferably 5.0 mol% or less, more preferably 1.0 mol% or less, in terms of monomer units. More preferably, it is 0.2 mol% or less, and even more preferable is 0.0 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. Further, as a raw material for tapes and split yarns, a polyethylene composition in which various additives described later are blended with polyethylene as necessary can be used, and “polyethylene” in the present specification includes such a polyethylene composition. Shall.
The intrinsic viscosity of the polyethylene used in the present invention is 5.0 dL / g or more, preferably 6.0 dL / g or more, more preferably 8.0 dL / g in the state of a polyethylene tape or polyethylene split yarn. The above is 32.0 dL / g or less, preferably 27.0 dL / g or less, more preferably 22.0 dL / g or less. Even with ultra high molecular weight polyethylene having an intrinsic viscosity of 5.0 dL / g or more, it becomes easy to produce a film, a polyethylene tape, and a polyethylene split yarn obtained from the polyethylene tape by a rolling method described later, so-called gel. There is no need to make yarn by spinning. Therefore, it is advantageous in terms of suppressing the manufacturing cost and simplifying the work process. Furthermore, since no solvent is used during production, there is no adverse effect of the solvent on workers and the environment, and there is almost no residual solvent in the product, so there is no adverse effect of the solvent on the product user. When the intrinsic viscosity is 5.0 dL / g or more, the number of structural defects in the polyethylene tape and the polyethylene split yarn can be reduced due to the decrease in the molecular end groups of the polyethylene. Therefore, the tensile strength, initial elastic modulus, and the like of the polyethylene tape and polyethylene split yarn can be improved, and the mechanical properties and wear resistance can be improved. A method for measuring the intrinsic viscosity will be described later.

The weight average molecular weight of the polyethylene used in the present invention is preferably 490,000 to 6,200,000, more preferably 550,000 to 5 in a state of a polyethylene tape or a polyethylene split yarn. 1,000,000, more preferably 800,000 to 4,000,000. When the weight average molecular weight is less than 490,000, not only can the film be stretched at a high magnification in the rolling process and the stretching process described later, but the polyethylene tape and the polyethylene split yarn can be obtained even if heat treatment is performed at the last stage in the stretching process. Does not become high strength, high elastic modulus. This is presumed to be due to the fact that since the molecular weight was small, the number of molecular ends per cross-sectional area of the polyethylene tape or polyethylene split yarn increased, which acted as a structural defect. On the other hand, if the weight average molecular weight exceeds 6,200,000, the tension during the rolling process and the stretching process becomes very large, causing breakage, which makes it very difficult to produce.
The ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) is 6.0 or less, preferably 5.5 or less, more preferably 5.0 or less. When Mw / Mn exceeds 6.0, a polymer having a very large molecular weight is likely to be contained, the tension during the rolling process and the stretching process described later is increased, and yarn breakage frequently occurs in the process, which is not preferable. The ratio (Mw / Mn) is preferably 1.0 or more, more preferably 1.1 or more, and still more preferably 1.5 or more. The measuring method of a weight average molecular weight and a number average molecular weight is mentioned later.
In addition, when manufacturing a polyethylene tape and a polyethylene split yarn using the homopolymer of ethylene, it is preferable that the intrinsic viscosity of a raw material homopolyethylene, a weight average molecular weight, and Mw / Mn are in the range as described above.

[Ratio of monoclinic and orthorhombic crystals, crystallinity]
The polyethylene tape and the polyethylene split yarn have a monoclinic crystal ratio of 0.1% to 30%, preferably 0.5% to 29.5%, more preferably 2.0% as the internal structure. It is 29% or less. Furthermore, the ratio of orthorhombic crystals is 40% or more and 99% or less, preferably 45% or more and 96% or less, and more preferably 50% or more and 95% or less. Although the mechanism in the relationship between the internal structure of the polyethylene tape and polyethylene split yarn and the physical property retention ratio is not clear, the deformation during the rolling process described later, the heat treatment conditions at the final stage of the stretching process, and the control of the winding tension, By containing a small amount of the monoclinic component in the internal structure within the above range, good physical property retention is exhibited. If the monoclinic crystal ratio is more than 30%, the retention rate of the storage elastic modulus tends to be difficult to maintain the range described later. The reason is not clear, but it seems that the crystal structure of monoclinic crystal is more unstable than that of orthorhombic crystal.

  In addition, due to the presence of monoclinic crystals within the above range, the polyethylene tape and the polyethylene split yarn exhibit excellent wear resistance characteristics. Although the details are not clear, it is possible to have a certain amount of monoclinic crystal in the polyethylene tape and polyethylene split yarn rather than the orthorhombic crystal structure in which the polyethylene tape and polyethylene split yarn are all stable. The monoclinic crystal plays a role of a cushion, and is presumed to be able to disperse the energy given from the object to be worn. A method for measuring the ratio of monoclinic crystal and orthorhombic crystal will be described later.

  The crystallinity of the polyethylene tape and the polyethylene split yarn is preferably 65% or more, more preferably 75% or more, and still more preferably 80% or more. When the crystallinity is less than 65%, the tensile strength and initial elastic modulus of the polyethylene tape and polyethylene split yarn are decreased, which is not preferable. The upper limit of the crystallinity is not particularly limited, but if it exceeds 99%, the retention rate of knot strength and hook strength is lowered, which is not preferable for applications requiring knotting or hooking. A method for measuring the crystallinity will be described later.

[Tensile strength]
The polyethylene tape according to the present invention preferably has a tensile strength of 0.8 GPa or more. By having such a tensile strength, the polyethylene tape according to the present invention can be developed to applications that could not be developed by a general-purpose polyethylene tape obtained by a conventional melt molding method. The tensile strength is more preferably 1.5 GPa or more, and still more preferably 2.0 GPa or more. Higher tensile strength is preferable, and the upper limit is not particularly limited. For example, it is technically and industrially difficult to obtain a tape having a tensile strength of 6.0 GPa or more by the rolling method. A method for measuring the tensile strength will be described later.

  The polyethylene split yarn according to the present invention preferably has a tensile strength of 8 cN / dtex or more. Since the polyethylene split yarn according to the present invention has such a tensile strength, it can be developed to applications that cannot be developed with a general-purpose polyethylene split yarn obtained by a conventional melt molding method. The tensile strength is more preferably 15 cN / dtex or more, and still more preferably 22 cN / dtex or more. Higher tensile strength is preferred, and the upper limit is not particularly limited. For example, it is technically and industrially difficult to produce a split yarn having a tensile strength of 60 cN / dtex or more by the rolling method.

[Initial elastic modulus]
The polyethylene tape according to the present invention preferably has an initial elastic modulus of 20 GPa or more and 220 GPa or less. If the polyethylene tape has such an initial elastic modulus, a change in mechanical properties and a change in shape are less likely to occur with respect to an external force applied during product or product processing. The initial elastic modulus is more preferably 40 GPa or more, further preferably 50 GPa or more, particularly preferably 90 GPa or more, more preferably 190 GPa or less, still more preferably 180 GPa or less. Obtaining a tape having an initial elastic modulus exceeding 220 GPa is difficult in terms of industrial production due to frequent tearing and breakage. A method for measuring the tensile strength and the initial elastic modulus will be described later.

  The polyethylene split yarn according to the present invention preferably has an initial elastic modulus of 200 cN / dtex or more and 2200 cN / dtex or less. If the polyethylene split yarn has such an initial elastic modulus, it becomes difficult for a change in mechanical properties or a change in shape to occur due to an external force applied during product or product processing. The initial elastic modulus is more preferably 300 cN / dtex or more, further preferably 400 cN / dtex or more, particularly preferably 500 cN / dtex or more, more preferably 1900 cN / dtex or less, still more preferably 1600 cN / dtex or less. Obtaining a polyethylene split yarn having an initial elastic modulus exceeding 2200 cN / dtex is difficult for industrial production because fuzz and breakage frequently occur. A method for measuring the initial elastic modulus will be described later.

[Residual solvent concentration]
The residual solvent concentration in the polyethylene tape and polyethylene split yarn is preferably 1000 ppm or less, more preferably 500 ppm or less, still more preferably 200 ppm or less, and most preferably 0 ppm (there is no residual solvent). Examples of the residual solvent include hydrocarbon solvents such as decalin (decahydronaphthalene) and paraffin. A method for measuring the residual solvent concentration will be described later.

[Heat shrinkage stress / heat shrinkage rate]
The polyethylene tape and polyethylene split yarn according to the present invention preferably have a maximum heat shrinkage temperature of 100 ° C. or higher, more preferably 110 ° C. or higher, and still more preferably 115 ° C. or higher in TMA (mechanical thermal analysis) measurement. The maximum heat shrinkage stress in TMA measurement is preferably 2.0 cN / dtex or less, more preferably 1.8 cN / dtex or less, and still more preferably 1.4 cN / dtex or less. In addition, the polyethylene tape and the polyethylene split yarn are characterized by a small dimensional difference from the room temperature region to the crystal dispersion temperature region because the residual strain is small near room temperature. Therefore, the heat shrinkage stress at 50 ° C. in TMA measurement is preferably 0.20 cN / dtex or less, more preferably 0.15 cN / dtex or less, and the heat shrinkage stress at 80 ° C. is 0.50 cN / dtex or less. It is preferable that it is 0.45 cN / dtex or less.
The polyethylene tape and polyethylene split yarn according to the present invention preferably have a heat shrinkage rate at 100 ° C. of 5.0% or less, more preferably 4.5% or less, and still more preferably 4.0% or less. is there. The heat shrinkage rate of the polyethylene tape at 100 ° C. refers to the heat shrinkage rate in the longitudinal direction of the polyethylene tape at 100 ° C.

[Storage modulus]
The polyethylene tape and the polyethylene split yarn preferably have a high storage elastic modulus retention over a wide temperature range. Specifically, the storage elastic modulus at 100 ° C. is preferably 20% or more of the storage elastic modulus at 30 ° C., more preferably 35% or more, and still more preferably 40% or more. Polyethylene tape and polyethylene split yarn having a high storage elastic modulus retention rate even under a dynamic load are less affected by environmental changes even under a high temperature environment for 24 hours or more, and exhibit a good physical property retention rate. Hereinafter, the “good physical property retention rate” indicates that the thermal shrinkage rate at 100 ° C. is −5.0% or more and 5.0% or less. Note that the value of the thermal contraction rate is negative when it is thermally expanded. In addition, during post-processing in which resin coating or the like is performed on a polyethylene tape or polyethylene split yarn, the higher the storage modulus retention rate, the lower the mechanical properties after post-processing can be suppressed. In addition, even if the product is used under high tension, such as reinforced plastic material, concrete reinforcement, rope, etc., and depending on the environment at the time of use, the product performance accompanying environmental changes Can be reduced. A method for measuring the storage elastic modulus will be described later.

[Other physical properties]
The width of the polyethylene tape is preferably 15 mm or less, and the thickness of the polyethylene tape is preferably 1 mm or less, more preferably 200 μm or less.

  The polyethylene split yarn preferably has a single yarn fineness of 0.5 dtex or more and 1000 dtex or less, more preferably 2 dtex or more and 800 dtex or less, and further preferably 5 dtex or more and 500 dtex or less.

〔Production method〕
About the manufacturing method which obtains the polyethylene tape and polyethylene split yarn which concern on this invention, it is preferable by the following rolling forming methods. Another method for producing ultra-high molecular weight polyethylene fibers using a solvent is the gel spinning method. Although the gel spinning method provides high strength, it is not only low in productivity but also manufactured by using a solvent. The impact on workers' health and the environment, and the solvent remaining in the fiber has a great impact on the health of product users.

In the method for producing a polyethylene tape and a polyethylene split yarn according to the present invention, it is preferable to perform rolling and stretching. Specifically, the method for producing a polyethylene tape or polyethylene split yarn according to the present invention includes a compression step of compressing polyethylene, a rolling step of rolling polyethylene compressed in the compression step, and a polyethylene rolled in the rolling step. It is preferable to include a stretching process for stretching and a winding process for winding the polyethylene stretched in the stretching process. Moreover, in the manufacturing method of the polyethylene split yarn which concerns on this invention, it is preferable to provide the cutting process which cut | disconnects the polyethylene tape wound by the winding process.
In the compression step, polyethylene (for example, polyethylene powder) is compressed. The pressure at this time is 50 N / cm ² or more and 15,000 N / cm ² or less. Preferably 100 N / cm ² or more, 8,000N / cm ² or less, more preferably, 400 N / cm ² or more and 6,000N / cm ² or less. The temperature at the time of compression is 100 ° C. or higher and 145 ° C. or lower, preferably 110 ° C. or higher and 142 ° C. or lower, more preferably 120 ° C. or higher and 140 ° C. or lower. When the pressure is less than 50 N / cm ² or the temperature during compression is lower than 100 ° C., the polymer particles are only crushed, and the polymer particles are hardly entangled between the polymer particles. Becomes weak and is not preferable. Further, when the pressure exceeds 15,000 N / cm ² , the polyethylene molecular chain is broken, so that not only the tensile strength of polyethylene obtained by compression is reduced, but also the compression apparatus becomes large, and the productivity is increased. It is not preferable also from a viewpoint. When the compression temperature exceeds 145 ° C., the entanglement between the polyethylene molecular chains becomes large, and it is not preferable because it cannot be stretched at a high magnification in the rolling process and the stretching process described later.
The compression time in the compression step is 0.5 second to 40 minutes, preferably 5 seconds to 15 minutes, and more preferably 10 seconds to 10 minutes. When the compression time is less than 0.5 seconds, peeling occurs between the polymer particles, which is not preferable. On the other hand, if the compression time exceeds 40 minutes, the polyethylene molecular chain in the obtained polyethylene is broken, resulting in a decrease in tensile strength due to a decrease in molecular weight.

  In the rolling process and the stretching process, it is preferable to heat the polyethylene between the feed roll and the take-up roll and perform rolling and stretching in the running direction (MD direction) with a speed difference between the feed roll and the take-up roll. However, in order to prevent cutting in the middle of the process, it is preferable to carry out at this stage below the melting temperature of polyethylene. For this heating, any of liquid heating, hot plate, hot air heating, infrared heating, dielectric heating and the like can be used. Further, if necessary, a heating medium such as steam can be introduced into the feed roll or the take-up roll. The polyethylene molded on the hot plate may be heated by direct contact.

  The rolling temperature in the rolling step is 120 ° C. or higher and 145 ° C. or lower, preferably 125 ° C. or higher and 143 ° C. or lower, more preferably 128 ° C. or higher and 141 ° C. or lower. Moreover, it is preferable that ratio of the length in the longitudinal direction of the polyethylene after rolling with respect to the polyethylene before rolling in a rolling process is 1.5 times or more and 30 times or less.

  In the stretching process, stretching is preferably performed in two or more stages. When extending | stretching in 2 steps or more, it is preferable that the temperature at the time of extending | stretching is so high that it progresses to a back | latter stage. When stretching is performed in two or more stages, the stretching temperature in the initial stretching (for example, the first stage stretching) is 20 ° C. or higher and 160 ° C. or lower, preferably 60 ° C. or higher and 150 ° C. or lower, more preferably 80. It is ℃ or more and 148 ℃ or less. In the case of one-time stretching, the stretching temperature is preferably not less than the crystal dispersion temperature of polyethylene and not more than the melting point of polyethylene. The crystal dispersion temperature of polyethylene is a value obtained by the measurement method described later. In addition, the preferable conditions of time and temperature in the last stage when extending | stretching in 2 steps or more are mentioned later.

  The draw ratio in the drawing step is preferably 4 times or more, more preferably 5 times or more, and still more preferably 6 times or more. The total ratio of the rolling ratio in the rolling process and the stretching ratio in the stretching process (the ratio of the length in the longitudinal direction to the polyethylene before the rolling process of polyethylene after the end of the last stage of the stretching process) should be 10 times or more and 550 times or less. Is more preferably 15 times or more and 400 times or less, still more preferably 20 times or more and 280 times or less. In each stage of the rolling process and the stretching process, the rolling ratio or the stretching ratio may be less than 1 time (the length becomes shorter than before the process starts).

  Further, when it is desired to further improve the storage elastic modulus of the polyethylene tape and the polyethylene split yarn, the time required to form an unstretched molded product, that is, the time required from the start of the rolling process to the end of the last stage of the stretching process (hereinafter, It is preferable to control the molding time). The molding time is preferably within 40 minutes, more preferably within 25 minutes, and even more preferably within 20 minutes. When the molding time exceeds 40 minutes, a predetermined monoclinic and orthorhombic ratio cannot be obtained in the polyethylene tape and the polyethylene split yarn.

  By shortening the molding time, the ratio of monoclinic crystal and orthorhombic crystal can be set within a predetermined range. Although details of this mechanism have not been clarified, it is presumed that when the molding time is longer than 40 minutes, orthorhombic crystals having a stable crystal structure are also subjected to deformation stress, and the ratio of orthorhombic crystals decreases. By increasing the ratio of orthorhombic crystals, the change in storage modulus over a wide temperature range is reduced, and further, the change in mechanical properties can be reduced even when used for a long time at a relatively high temperature. Become. Although the molding time may be short, since it is necessary to give a predetermined temperature to the tape, it takes 0.1 second or longer, preferably 1 second or longer, more preferably 10 seconds or longer.

  In the present invention, as described above, the heat treatment method of the polyethylene tape and the polyethylene split yarn in the last stage of the stretching process, that is, the heat treatment temperature and the heat treatment time for stretching in the last stage of the stretching process are important. Further, the winding tension and the winding temperature in the winding process are also important. By precisely controlling the heat treatment conditions in the last stage of the stretching process, the winding tension in the winding process, etc., the heat shrinkage rate at 100 ° C. can be made 5.0% or less.

The stretching temperature in the last stage stretching (heat treatment temperature when stretching in the last stage) is preferably not less than the crystal dispersion temperature of polyethylene and not more than 170 ° C., specifically, 80 ° C. to 170 ° C. is preferable. The upper limit of the drawing temperature in the last drawing is preferably the melting point of polyethylene.
Further, the draw ratio in the last stage of the drawing step is preferably 0.85 times or more and 6.0 times or less, more preferably 0.90 times or more and 4.0 times or less, and further preferably 0.95 times or more and 3.0 times. It is as follows. When the draw ratio in the last stage is less than 0.85, the tape and split yarn in the process are loosened, and the tension becomes unstable, which is not preferable. On the other hand, if the draw ratio in the last stage exceeds 6.0 times, it is not preferable because breakage occurs due to excessive tension.
At this time, the last stage time of the stretching step (heat treatment time when stretching in the last stage) is preferably 0.01 seconds to 30 minutes. Preferably, it is 0.02 seconds or more and 20 minutes or less, and more preferably 0.04 seconds or more and 10 minutes or less. When the time is shorter than 0.01 seconds, heat treatment cannot be sufficiently performed, and a desired storage elastic modulus retention rate and heat shrinkage rate cannot be obtained. On the other hand, if it exceeds 30 minutes, the time for applying heat is too long, so that the tensile strength or the initial elastic modulus is lowered.
The tension applied to polyethylene in the last stage is preferably 15 cN / dtex or less, more preferably 5 cN / dtex or less, and still more preferably 1 cN / dtex or less. In the last stage, when the heat treatment is performed at a temperature lower than the crystal dispersion temperature of polyethylene, the residual stress inside the polyethylene cannot be sufficiently removed. The heating method during the heat treatment in the last stage is not particularly limited. A known method such as a hot roller, a radiant panel, a steam jet, or a hot pin is recommended, but is not limited thereto.

  In the heat treatment at the final stage of the stretching step, it is preferable to set the three factors of the heat treatment temperature, the heat treatment time, and the heat treatment tension within the above ranges. When the heat treatment time is shorter than the above range, or when the heat treatment temperature is lower than the above range, the ratio of monoclinic crystals in the obtained molded product increases, or the fluctuation of the storage elastic modulus due to the temperature influence increases. Tend. In addition, when the heat treatment temperature is higher than the above range or when the tension during the heat treatment is larger than the above range, the polyethylene tends to break during the last step of the stretching step, or the initial elastic modulus of the obtained molded product There is a tendency to decrease.

The winding tension in the winding process is preferably 5.0 cN / dtex or less, more preferably 4.0 cN / dtex or less, and still more preferably 3.5 cN / dtex or less. When the winding tension exceeds 5.0 cN / dtex, excessive residual stress is applied to the inside of the polyethylene tape and the polyethylene split yarn. As a result, the heat shrinkage rate at 100 ° C. exceeds 5.0%, or the maximum heat shrinkage stress in TMA (mechanical thermal analysis) exceeds 2.0 cN / dtex, which is not preferable. In addition, the heat shrinkage stress in the region from the room temperature assumed as the product's use environment temperature to the vicinity of the crystal dispersion temperature of polyethylene also increases, causing changes in mechanical properties and dimensional changes due to environmental changes. And the use temperature range of the final product is limited.
The winding temperature in the winding process is preferably 60 ° C. or lower. More preferably, it is 55 degrees C or less, More preferably, it is 50 degrees C or less. When the temperature is higher than 60 ° C., the temperature becomes close to the crystal dispersion temperature of polyethylene, so that residual stress tends to occur inside the resulting product, and dimensional changes and mechanical property changes tend to occur after commercialization, which is not preferable. . In addition, the heat shrinkage stress increases in the temperature range from the room temperature that is assumed as the product's use environment temperature to the crystal dispersion temperature of polyethylene, and mechanical properties and dimensional changes are likely to occur due to environmental changes. It is not preferable because restrictions such as processing conditions and the use temperature range of the final product are likely to occur.
In the cutting step, for example, a polyethylene split yarn can be obtained by passing the polyethylene tape obtained in the winding step through a splitter.

In order to provide other functions, additives such as antioxidants, anti-reduction agents, PH adjusters, surface tension reducing agents, thickeners, moisturizers, thickening agents, antiseptics, antifungal agents, electrification Inhibitors, pigments, mineral fibers, other organic fibers, metal fibers, sequestering agents and the like may be used.
In addition, braided strings, twisted yarns, woven and knitted fabrics containing polyethylene tape or polyethylene split yarn, cut tape obtained by cutting polyethylene tape into 1 mm or more and 10 cm or less, cut fiber obtained from polyethylene split yarn, and the like can also be produced. In addition, in this specification, a cut fiber refers to what cut the polyethylene split yarn into 1 mm or more and 10 cm or less.

  Synthetic fibers such as polyester, nylon, and acrylic, natural fibers such as cotton and hair, and regenerated fibers such as rayon, etc. may be used at a ratio of 70% by mass or less of braided yarn, twisted yarn, and woven or knitted fabric.

The polyethylene tape and the polyethylene split yarn according to the present invention include a rope, a safety rope, a net, a ball-proof net, a fishnet net, a fishing line, a meat thread, a material protective cover, a sheet, a kite thread, a bowstring, a sailcloth, a curtain. It can be used for materials.
The above uses may require various colors or design properties depending on the purpose while maintaining the mechanical properties. Conventionally, post-processing for coating a resin containing an inorganic pigment or an organic pigment has often been performed (see, for example, JP-A No. 2004-308047), but the polyethylene tape and polyethylene split yarn according to the present invention are used. Therefore, it can be used without damaging the original texture of the material.

  In addition, the polyethylene tape and polyethylene split yarn according to the present invention have little change in mechanical properties and excellent dimensional stability over a wide temperature range, and therefore fiber reinforcement that requires heating in the post-processing step. Suitable for resin reinforcing materials, cement reinforcing materials, fiber reinforced rubber reinforcing materials, or protective materials, bulletproof materials, medical sutures, artificial tendons, artificial muscles, machine tool parts, battery separators, chemical filters, etc. Can be used.

  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 characteristic values of polyethylene tape and polyethylene split yarn in each of the following examples and comparative examples were measured as follows. In the following, the “length” of the sample refers to the length of the sample in the longitudinal direction.

(1) Intrinsic viscosity The specific viscosity of various dilute solutions was measured using an Ubbelohde capillary viscosity tube with decalin at a temperature of 135 ° C. 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. For measurement, the sample was divided or cut into lengths of about 5 mm, and 1% by mass of an antioxidant (“Yoshinox (registered trademark) BHT” manufactured by API Corporation) was added to the polymer at 135 ° C. The measurement solution was prepared by stirring and dissolving for 4 hours.

(2) Weight average molecular weight Mw, number average molecular weight Mn, and Mw / Mn
The weight average molecular weight Mw, the number average molecular weight Mn, and Mw / Mn were measured by gel permeation chromatography (GPC). As a GPC device, “GPC 150C ALC / GPC” (manufactured by Waters) is used, and as a column, one “GPC UT802.5” (manufactured by SHODEX) and two “UT806M” (manufactured by SHODEX) are used. As a differential refractometer (RI detector). The measurement solvent used was o-dichlorobenzene, and the column temperature was 145 ° C. The sample concentration was 1.0 mg / ml, and 200 microliters were injected for measurement. The calibration curve of molecular weight is created using a polystyrene sample with a known molecular weight by the universal calibration method.

(3) Tensile strength and initial elastic modulus Universal tester (Orientec Co., Ltd., “Tensilon Universal Material Tester RTF-1310”), sample length 200 mm (length between chucks), elongation rate 100% / min. The strain-stress curve was measured at an ambient temperature of 20 ° C. and a relative humidity of 65%, and the tensile strength was calculated from the stress and elongation at the breaking point, and the initial elastic modulus was calculated from the tangent line that gave the maximum gradient near the origin of the curve. At this time, the initial load applied to the sample at the time of measurement was set to 1/10 of the mass (g) per 10,000 m of fiber, and the tensile strength and the initial elastic modulus were average values of 10 measurements. did.

(4) Thermal contraction rate The sample was cut into 70 cm and marked at 10 cm positions from both ends, that is, the sample length was 50 cm. Next, the sample was heated at a temperature of 100 ° C. for 30 minutes using a hot air circulation type heating furnace while 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)

(5) Thermal contraction stress A thermal stress strain measuring device (manufactured by Seiko Instruments Inc., “TMA / SS120C”) was used for the measurement. In the case of a tape, a sample is prepared so that the length is 20 mm, the width is 2 mm, and in the case of a split yarn, the length is 20 mm and the fineness is 100 dtex, an initial load of 0.01764 cN / dtex is applied, and the temperature rising rate is 20 ° C./min. The maximum heat shrinkage stress and the heat shrinkage stress at 50 ° C. and 80 ° C. were measured.

(6) Storage elastic modulus For measurement of storage elastic modulus at 100 ° C and 30 ° C, a solid viscoelasticity measuring apparatus (manufactured by TA Instruments, "DMA Q800") was used. In order to prevent slippage between the sample of the tape and split yarn and the device chuck or single yarn breakage during measurement, sandwich both ends of the sample with cardboard using adhesive and double-sided tape, and between the chucks that sandwich the sample Adjustment was made so that the mass was 100 g when the distance was 10 mm and the measurement sample width was 10,000 m. As a result, the presence of cardboard between the sample and the apparatus chuck in the measurement makes it possible to suppress slippage at the apparatus chuck and single yarn variations. The measurement start temperature was −10 ° C., the measurement end temperature was 140 ° C., and the rate of temperature increase was 1.0 ° C./min. The amount of strain was 0.04%, and the initial load at the start of measurement was 0.05 cN / dtex. The measurement frequency was 11 Hz. For analysis of the measured data, “TA Universal Analysis” (manufactured by TA Instruments) was used. At this time, the retention rate of the storage elastic modulus was obtained from the following equation.
Storage modulus retention rate (%) = 100 × [(storage modulus at 100 ° C.) / (Storage modulus at 30 ° C.)]

(7) Crystal dispersion temperature Similarly to the above (6), data was measured using a solid viscoelasticity measuring apparatus (TA Instruments, "DMA Q800"), and analysis of the measured data “TA Universal Analysis” (manufactured by TA Instruments) was used. The measurement start temperature was −140 ° C., the measurement end temperature was 140 ° C., and the rate of temperature increase was 1.0 ° C./min. The strain amount was 0.04%, and the initial load at the start of measurement was 0.05 cN / dtex. The measurement frequency was 11 Hz. The loss elastic modulus was calculated, the temperature dispersion was obtained from the low temperature side, the value of the loss elastic modulus was logarithmically plotted on the vertical axis, the horizontal axis was plotted with temperature, and the peak value appearing on the highest temperature side was defined as the crystal dispersion temperature.

(8) Residual solvent concentration Gas chromatography (manufactured by Shimadzu Corporation) was used to measure the residual solvent concentration in the sample. A 10 mg sample was set on a glass insert at the gas chromatography inlet. The inlet was heated above the boiling point of the solvent, and the solvent volatilized by heating was introduced into the column by nitrogen purge. The column temperature was set to 40 ° C. and the solvent was trapped for 5 minutes. Next, measurement was started after the column temperature was raised to 80 ° C. From the obtained peak, the residual solvent concentration was determined.

(9) Crystallinity Data was measured using a differential scanning calorimeter (TA Instruments, “DSC measuring device”), and “TA Universal Analysis” was used for analysis of the measured data. (TA Instruments, Inc.) was used. The sample was cut to 5 mg or less, and about 2 mg was filled and enclosed in an aluminum pan. A similar empty aluminum pan was used as a reference. The measurement was performed under a temperature range of 50 ° C. to 200 ° C. under an inert gas and the rate of temperature increase was about 10 ° C./min. The baseline of the obtained temperature rising DSC curve was corrected, the peak area was divided by the sample mass, the measured heat of fusion was calculated, and the crystallinity was determined from the following formula.
Crystallinity (%) = 100 × (measured heat of fusion (J / g)) / (293 (J / g))

(10) Ratio measurement of monoclinic crystal, orthorhombic crystal, etc. The ratio of the crystal component was determined by solid high resolution ¹³ C-NMR. Specifically, it was measured at room temperature using “AVANCE400WB” (manufactured by Bruker Biospin). Magnetic field strength and spin rate were measured at 9.4 T and 4 kHz, respectively. Dipolar decoupling (DD) / MAS was used as the measurement pulse. The sample was cut into strips and filled into the rotor. The DD / MAS spectrum was measured by a single pulse method (DD / MAS method) with a waiting time of 4300 seconds and a spectrum reflecting all components. Waveform separation was performed as monoclinic, orthorhombic and amorphous components from the low magnetic field side. The ratio was determined from the monoclinic, orthorhombic and amorphous components and the area ratio of each peak.

Example 1
The ultra-high molecular weight homopolyethylene powder having an intrinsic viscosity of 14 dL / g, a weight average molecular weight of 1,500,000, and Mw / Mn of 1.9 was heated to 121 ° C. and compression-molded at 550 N / cm ² for 9 minutes. Ultra high molecular weight homopolyethylene powder is produced by the method described in JP-A-2005-29775. Next, the obtained molded body was supplied between a pair of rolls rotating in the opposite direction at the same vertical speed of 1 m / min adjusted to a surface temperature of 140 ° C., and rolled four times to obtain a film. Thereafter, the obtained film was passed through a slitter to form a tape, and stretched 2.5 times at 145 ° C. between the heating rollers (first-stage stretching). Next, a stretched tape was obtained by stretching 2.5 times at 151 ° C. (second stage stretching). Subsequently, the obtained stretched tape was subjected to a heat treatment for 2 minutes under the conditions of 152 ° C., a tension of 1.5 cN / dtex, and a 1.1-fold stretching (last-stage stretching). The total time required from the start of rolling to the end of the last stage drawing was 19 minutes. Thereafter, the film was wound at 28 ° C. with a tension of 3.2 cN / dtex to obtain a polyethylene tape having a width of 5 mm and a thickness of 60 μm. Next, a polyethylene split yarn was obtained by passing the obtained polyethylene tape through a splitter (having a protrusion of 32 threads / inch on the edge of a hexagonal bar). Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Example 2)
In Example 1, a polyethylene tape was prepared in the same manner as in Example 1 except that the draw ratio in the final drawing was 1.8 times, the heat treatment time was 0.06 minutes, and the tension was changed to 3.0 cN / dtex. Obtained. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

Example 3
In Example 1, a polyethylene tape was obtained in the same manner as in Example 1 except that the drawing temperature in the final drawing was changed to 154 ° C., the heat treatment time was changed to 4.0 minutes, and the tension was changed to 1.2 cN / dtex. . Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

Example 4
In Example 1, the draw ratio in the second stage drawing is 3.0 times, the tension in the last stage drawing is 3.0 cN / dtex, the time required from the start of rolling to the end of the last stage drawing is 15 minutes, in the winding step A polyethylene tape was obtained in the same manner as in Example 1 except that the winding temperature was 35 ° C. and the winding tension was changed to 1.2 cN / dtex. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Example 5)
In Example 1, an ultrahigh molecular weight polyethylene powder having an intrinsic viscosity of 18 dL / g, a weight average molecular weight of 2,400,000, and Mw / Mn of 4.5 is heated to 132 ° C. and compression molded at 650 N / cm ^2. In the same manner as in Example 1, except that the rolling ratio in the rolling process was 2.5 times, the stretching ratio in the first stage stretching was 3.0 times, and the tension in the last stage stretching was changed to 3.0 cN / dtex. A polyethylene tape having a width of 8 mm and a thickness of 60 μm was obtained. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Comparative Example 1)
In Example 1, the stretching temperature in the last stage stretching was 149 ° C., the stretching ratio was 1.5 times, the heat treatment time was 0.005 seconds, and the tension was changed to 16.6 cN / dtex. A polyethylene tape was obtained in the same manner. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Comparative Example 2)
In Example 1, a polyethylene tape was obtained in the same manner as in Example 1 except that the winding temperature in the winding process was changed to 32 ° C. and the winding tension was changed to 5.3 cN / dtex. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Comparative Example 3)
In Example 1, a high-density high molecular weight polyethylene powder having an intrinsic viscosity of 2.2 dL / g, a weight average molecular weight of 150,000, and Mw / Mn of 2.9 is used, and the rolling ratio in the rolling process is 2.5 times. Polyethylene tape in the same manner as in Example 1, except that the draw ratio in the stage drawing was 3.0 times, the drawing time in the last stage drawing was 0.005 seconds, and the winding tension was changed to 5.2 cN / dtex. Got. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

(Comparative Example 4)
In Example 1, the stretching time in the last stage stretching was 32 minutes, the time required from the start of rolling to the end of the last stage stretching was 48 minutes, and the winding tension in the winding process was changed to 2.1 cN / dtex. In the same manner as in Example 1, a polyethylene tape was obtained. Further, a polyethylene split yarn was obtained from the obtained polyethylene tape in the same manner as in Example 1. Table 1 shows the physical properties and evaluation results of the obtained polyethylene tape and polyethylene split yarn.

  According to the present invention, it is possible to provide a polyethylene tape and a polyethylene split yarn having a small change in mechanical properties over a wide temperature range and excellent in dimensional stability. In addition, braided strings, twisted yarns, woven and knitted fabrics, ropes, nets, fishing lines, material protective covers, sheets, kite yarns, bowstrings, sailcloths, curtain materials, protective materials, bulletproofs using polyethylene tape and polyethylene split yarn as products. It can be applied to industrial materials such as 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 (21)

The intrinsic viscosity [η] is 5.0 dL / g or more and 32.0 dL / g or less, the repeating unit is an ethylene chain, and the other monomer other than ethylene includes polyethylene having a monomer unit of 5.0 mol% or less. A polyethylene tape having a monoclinic crystal ratio of 0.1% to 30% and an orthorhombic crystal ratio of 40% to 99%.   The polyethylene tape according to claim 1, wherein the degree of crystallinity in the tape is 65% or more.   The polyethylene has a weight average molecular weight (Mw) of 490,000 to 6,200,000 and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) of 6.0 or less. 2. The polyethylene tape according to 2.   The polyethylene tape according to any one of claims 1 to 3, which has a tensile strength of 0.8 GPa or more and an initial elastic modulus of 20 GPa or more.   The polyethylene tape according to any one of claims 1 to 4, wherein the residual solvent concentration in the tape is 1000 ppm or less.   A braid comprising the polyethylene tape according to any one of claims 1 to 5.   A twisted yarn comprising the polyethylene tape according to any one of claims 1 to 5.   A woven or knitted fabric comprising the polyethylene tape according to any one of claims 1 to 5.   A cut tape, wherein the polyethylene tape according to any one of claims 1 to 5 is cut into 1 mm or more and 10 cm or less. The intrinsic viscosity [η] is 5.0 dL / g or more and 32.0 dL / g or less, the repeating unit is an ethylene chain, and the monomer other than ethylene is 100 % of polyethylene having a monomer unit of 5.0 mol% or less. A compression step of compressing at a temperature of from ℃ to 145 ℃,
A rolling step of rolling the polyethylene compressed in the compression step at a temperature of 120 ° C. or higher and 145 ° C. or lower;
The polyethylene rolled in the rolling step is stretched one or more steps in a temperature range of 20 ° C. or more and 160 ° C. or less, and then in a temperature range of 80 ° C. or more and 170 ° C. or less with a draw ratio of 0.85 times or more and 6.0 times or less. A stretching step of stretching in 0.01 seconds or more and 30 minutes or less;
In a state where the polyethylene stretched in the stretching step is cooled to a temperature of 60 ° C. or lower, and a winding step of winding with a winding tension of 5.0 cN / dtex or less ,
The intrinsic viscosity [η] is 5.0 dL / g or more and 32.0 dL / g or less, the repeating unit is an ethylene chain, and the other monomer other than ethylene includes polyethylene having a monomer unit of 5.0 mol% or less. And a method for producing a polyethylene tape having a monoclinic crystal ratio of 0.1% to 30% and an orthorhombic crystal ratio of 40% to 99% . The intrinsic viscosity [η] is 5.0 dL / g or more and 32.0 dL / g or less, the repeating unit is an ethylene chain, and the other monomer other than ethylene includes polyethylene having a monomer unit of 5.0 mol% or less. A polyethylene split yarn having a monoclinic crystal ratio of 0.1% to 30% and an orthorhombic crystal ratio of 40% to 99%.   The polyethylene split yarn according to claim 11, wherein the crystallinity in the split yarn is 65% or more.   The polyethylene split yarn according to claim 11 or 12, comprising a single yarn having a single yarn fineness of 0.5 dtex or more and 1000 dtex or less.   The polyethylene has a weight average molecular weight (Mw) of 490,000 to 6,200,000, and a ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight (Mn) of 6.0 or less. 14. The polyethylene split yarn according to any one of items 13.   The polyethylene split yarn according to any one of claims 11 to 14, having a tensile strength of 8 cN / dtex or more and an initial elastic modulus of 200 cN / dtex or more.   The polyethylene split yarn according to any one of claims 11 to 15, wherein the residual solvent concentration in the split yarn is 1000 ppm or less.   A braid comprising the polyethylene split yarn according to any one of claims 11 to 16.   A twisted yarn comprising the polyethylene split yarn according to any one of claims 11 to 16.   A woven or knitted fabric comprising the polyethylene split yarn according to any one of claims 11 to 16.   A cut fiber obtained from the polyethylene split yarn according to any one of claims 11 to 16.   The manufacturing method of the polyethylene split yarn characterized by including the cutting process of cut | disconnecting the polyethylene tape manufactured by the manufacturing method of Claim 10.