polyethylene fibers

Abstract

Provided is a polyethylene fiber that is high in strength and excellent in creep resistance. The present invention is an ultrahigh molecular weight polyethylene fiber characterized by being an ultrahigh molecular weight polyethylene fiber that contains ethyl branches in side chains, and by the ratio {(C2H5 / 1000C) / (elongation stress)} of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) to the elongation stress (MPa) of the aforementioned polyethylene fiber being 2 to 30 branches per 1000 carbon atoms per MPa, and by the polyethylene fiber containing two or more kinds of ultrahigh molecular weight polyethylenes that differ in average molecular weight, molecular weight distribution, or number of ethyl branches, the two or more kinds of ultrahigh molecular weight polyethylenes being ultrahigh molecular weight polyethylenes that have undergone ethylene polymerization in the presence of a Ziegler catalyst, one of the two or more kinds of ultrahigh molecular weight polyethylenes being an ultrahigh molecular weight polyethylene that has ethyl branches, and the other being an ultrahigh molecular weight polyethylene that does not have ethyl branches.

Description

[0001] This application is a divisional application of the application filed on May 13, 2020, with application number 202080033818.7 and invention title "Polyethylene Fiber". Technical Field

[0002] This invention relates to a novel high-strength polyethylene fiber, which can be widely used in industry for the following purposes: high-performance textiles such as various sportswear, bulletproof vests / protective clothing / protective gloves; various rope products such as anchor ropes / mooring ropes, yacht ropes, and construction ropes; various braided products such as fishing lines and blind cables; further chemical filters, battery separators, or tent curtain materials; and synthetic reinforcing fibers for sports such as helmets and skis, and for speaker cones. Background Technology

[0003] High-strength polyethylene fibers are known to be obtained, for example, by using ultra-high molecular weight polyethylene as a raw material and employing a so-called "gel spinning method" to obtain previously unseen high-strength / high-modulus fibers that have undergone super-stretching (e.g., Patent Document 1), and are already widely used in industry. These high-strength polyethylene fibers possess extremely excellent high strength / high modulus of elasticity, but there is a market desire to improve upon the shortcomings stemming from their raw materials. For example, the primary structure of ultra-high molecular weight polyethylene, the raw material for high-strength polyethylene fibers, is extremely simple, and therefore lacks hydrogen bonds between molecular chains, making it prone to slippage between molecular chains. Consequently, if a load is applied continuously for a long time, the fiber elongation, or creep elongation, increases. As a result, its application is limited in applications requiring prolonged load application, such as weaving, twisting, fishing lines, ropes, and nets.

[0004] To address the aforementioned issues, for example, Patent Documents 2 and 3 have proposed polyethylene fibers with ethyl side chains, etc. However, ethyl side chains significantly impede tensile strength, thus limiting the number of side chains required to maintain high strength and productivity, failing to achieve the high creep characteristics levels expected by the market in recent years.

[0005] Therefore, for example, Patent Document 4 discloses an ultra-high molecular weight polyethylene fiber that improves both creep life and strength properties, but further improvements in properties are required.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Publication No. 60-47922

[0009] Patent Document 2: Japanese Patent Application Publication No. 6-280111

[0010] Patent Document 3: International Publication No. 2017 / 102618

[0011] Patent Document 4: Japanese Patent No. 6069676 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] The present invention was made against the background of the above-mentioned prior art problems, and its object is to provide: polyethylene fiber with high strength and extremely excellent creep resistance.

[0014] Solution for solving the problem

[0015] The inventors conducted in-depth research to solve the aforementioned problems, and as a result, completed this invention. That is, the invention is as described below.

[0016] [1] An ultra-high molecular weight polyethylene fiber, characterized in that it is an ultra-high molecular weight polyethylene fiber containing ethyl branches in its side chains.

[0017] The ratio of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) in the aforementioned polyethylene fiber to the elongation stress (MPa) of the aforementioned polyethylene fiber {(C2H5 / 1000C) / (elongation stress)} is 2 to 30 per 1000 carbon atoms / MPa.

[0018] [2] According to the ultra-high molecular weight polyethylene fiber described in [1] above, in the creep test at a test temperature of 70°C and a test load of 6.6 g / dtex,

[0019] The creep rate is 9.0 × 10⁻⁶. -8 sec -1 the following,

[0020] The elongation rate was less than 2.7% 24 hours after the start of the measurement.

[0021] The elongation rate was less than 5.0% 96 hours after the start of the measurement, and

[0022] The time required for the elongation to reach 3.0% is more than 30 hours.

[0023] [3] The ultra-high molecular weight polyethylene fiber according to [1] or [2] above, wherein the number of ethyl branches (C2H5 / 1000C) per 1000 carbon atoms exceeds 1.1.

[0024] [4] The ultra-high molecular weight polyethylene fiber according to any one of [1] to [3] above, wherein,

[0025] For polyethylene fibers, differential scanning calorimetry (DSC) was used to measure the temperature at a rate of 10°C / min, increasing the temperature from 30°C to 200°C (first increase), holding at 200°C for 5 minutes, then decreasing the temperature from 200°C to 30°C at a rate of 10°C / min, holding at 30°C for 5 minutes, and then increasing the temperature from 30°C to 200°C at a rate of 10°C / min (second increase).

[0026] The peak melting point temperature of the aforementioned polyethylene fiber during the first heating step is below 141°C.

[0027] The heat generated during the second heating process, up to the peak temperature of the aforementioned polyethylene fiber, within the range of 70°C to 150°C, is less than 134 J / g.

[0028] [5] The ultra-high molecular weight polyethylene fiber according to any one of [1] to [4] above has a tensile strength of 20 cN / dtex or higher.

[0029] [6] Braided tape, twisted yarn, fishing line, rope or net, comprising any one of the above [1] to [5] ultra-high molecular weight polyethylene fibers.

[0030] The effects of the invention

[0031] The polyethylene fiber of this invention has high strength and excellent creep resistance, therefore, it can be widely used in braiding, twisting, fishing lines, ropes, nets and other applications. Attached Figure Description

[0032] Figure 1 A diagram illustrating the state of the specimen during installation and during creep measurement.

[0033] Figure 2 A diagram illustrating the state of the measurement during creep testing. Detailed Implementation

[0034] In order to provide ultra-high molecular weight polyethylene fibers with high strength and excellent creep resistance, the inventors conducted research based on the structure of Patent Document 4.

[0035] Specifically, Patent Document 4 discloses an ultra-high molecular weight polyethylene fiber containing ethyl branches, wherein the ratio of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) to the elongation stress ES of the ultra-high molecular weight polyethylene polymer satisfies 1.00 to 3.00 mm. 2At / N, the creep life under a load of 600 MPa at a temperature of 70°C must be at least 125 hours. Here, "elongation stress of the polymer" refers to the stress required to elongate 600% within 10 minutes when various loads are applied and the polymer is stretched to 600% elongation at a specified temperature (150°C) for a test sample that has been compressed and molded into a specific shape. In the aforementioned Patent Document 4, the elongation stress of the polymer is measured based on ISO 11542-2A.

[0036] In addition, in the aforementioned Patent Document 4, the number of ethyl branches per 1000 carbon atoms is preferably 0.40 to 1.10. In the examples, polyethylene with an ethyl branch number of 0.69 or 1.05 is used.

[0037] However, according to the research results of the inventors, when the ratio of the number of ethyl branches per 1000 carbon atoms to the elongation stress of the polyethylene fiber was set to 2 to 30 per 1000 carbon atoms per MPa, and controlled to exceed the upper limit of Patent Document 4, it was unexpectedly found that the strength and creep resistance (especially the strength) were further improved compared to Patent Document 4. It was thus discovered that the number of ethyl branches per 1000 carbon atoms can be increased, preferably controlled to be more than 1.1 per 1000 carbon atoms, thus completing the present invention.

[0038] It should be noted that the following changes were made in this invention when studying elongation stress.

[0039] First, since the present invention cannot measure elongation stress according to the ISO standard as described in Patent Document 4 above, the elongation stress is measured using a method similar to that ISO standard (changing the load from a clamp to a chuck and changing the measurement environment from a liquid phase (e.g., inside silicone oil) to a gas phase. Details are described in the Examples section below).

[0040] Furthermore, in this invention, in order to more accurately grasp the characteristics of the fiber, the elongation stress of the polyethylene fiber itself is measured instead of the elongation stress of the polymer as described in Patent Document 4 above. According to the research results of the inventors, the elongation stress of the polymer has a good correlation with the intrinsic viscosity of the fiber. Therefore, the composition {(C2H5 / 1000C) / (elongation stress of the polymer) ratio} of Patent Document 4, which focuses on the polymer, can be related to the composition {(C2H5 / 1000C) / (elongation stress of the fiber) ratio} of this invention, which focuses on the fiber.

[0041] Polyethylene fibers that meet the above characteristics exhibit minimal deformation even when exposed to tension for extended periods in harsh environments such as outdoor applications, such as ropes and nets. This significantly improves the product's lifespan and benefits both economic efficiency and environmental protection.

[0042] The structure of the present invention will now be described in detail.

[0043] [Polyethylene fiber]

[0044] As described above, the polyethylene fiber of the present invention is characterized by being an ultra-high molecular weight polyethylene fiber containing ethyl branches in its side chains. The ratio of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) in the aforementioned polyethylene fiber to the elongation stress of the aforementioned polyethylene fiber {(number of ethyl branches) / (elongation stress); unit: branches / 1000 carbon atoms / MPa. Hereinafter, it is sometimes abbreviated as "ratio of ethyl branches to elongation stress"} is 2 to 30 branches / 1000 carbon atoms / MPa. This ratio is set to ensure the desired high strength and creep resistance. If the ratio is less than 2 branches / 1000 carbon atoms / MPa, the creep resistance decreases. On the other hand, if the ratio is greater than 30 branches / 1000 carbon atoms / MPa, the tensile strength decreases.

[0045] The above ratio is preferably 2.5 to 25 carbon atoms per 1000 carbon atoms per MPa, and more preferably 3.0 to 20 carbon atoms per 1000 carbon atoms per MPa.

[0046] The above ratio can be controlled according to the intrinsic viscosity of the raw material polyethylene. For example, if raw material polyethylene with very low intrinsic viscosity is used, the intrinsic viscosity in the fiber becomes smaller, and therefore the elongation stress also becomes smaller. As a result, the above ratio becomes larger (see Comparative Example 3 in Table 1 below).

[0047] Here, the "number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C); hereinafter sometimes simply referred to as the number of ethyl branches" constituting the above ratio is preferably more than 1.1. This is because the above-mentioned polyethylene fibers can effectively prevent the slippage of polyethylene molecules, thus exhibiting excellent creep resistance.

[0048] It should be noted that in the aforementioned Patent Document 4, in addition to the number of ethyl branches, the number of butyl branches is also specified. However, according to the research results of the inventors, polyethylene fibers with butyl branches are difficult to process. Therefore, in this invention, only the number of ethyl branches is specified.

[0049] The number of ethyl branches (unit: branches per 1000 carbon atoms) is preferably greater than 1.1, more preferably greater than 1.10, even more preferably greater than 1.3, and even more preferably greater than 1.5. From the viewpoint of creep resistance, there is no particular upper limit. If the number of ethyl branches increases, the tensile strength decreases, and the desired high-strength fiber cannot be obtained. Therefore, 20 or less is preferred, more preferably 15 or less, and even more preferably 10 or less.

[0050] Here, the number of ethyl branches mentioned above refers to the number of ethyl branches contained in the polyethylene fiber.

[0051] The polyethylene fiber of the present invention exhibits excellent creep resistance. Here, "excellent creep resistance" means that, in a creep test at a test temperature of 70°C and a test load of 6.6 g / dtex, it satisfies all of the characteristics described below (i) to (iv).

[0052] (i) The creep rate is 9.0 × 10⁻⁶. -8 sec -1 the following,

[0053] (ii) The elongation rate is less than 2.7% 24 hours after the start of the measurement.

[0054] (iii) The elongation rate is less than 5.0% 96 hours after the start of the measurement, and

[0055] (iv) The time required for the elongation to reach 3.0% is more than 30 hours.

[0056] The polyethylene fibers of the present invention preferably have a tensile strength of 20 cN / dtex or higher. This is because the aforementioned polyethylene fibers have high strength and high elastic modulus, and therefore can be widely used in industry. More preferably, the tensile strength is 25 cN / dtex or higher, and even more preferably, the tensile strength is 30 cN / dtex or higher. There is no particular limitation on the upper limit of tensile strength, but it is technically difficult to industrially produce polyethylene fibers with a tensile strength exceeding 60 cN / dtex. Hereinafter, tensile strength is sometimes abbreviated as strength. The initial elastic modulus is preferably 500 cN / dtex or higher. More preferably, the initial elastic modulus is 600 cN / dtex or higher, and even more preferably, the initial elastic modulus is 700 cN / dtex or higher. There is no particular limitation on the upper limit of the initial elastic modulus, but if it exceeds 2000 cN / dtex, it is prone to unevenness and monofilament breakage during molding and processing into tapes and ropes, and is therefore not preferred. The elongation at break is preferably 3.0% or higher. More preferably, the elongation at break is 3.2% or higher, and even more preferably, the elongation at break is 3.4% or higher. There is no particular upper limit to the elongation at break, but it is preferred to be below 7.0%. If the elongation at break is below 3.0%, it is prone to unevenness and single filament breakage during molding and processing into tapes or ropes, so it is not preferred. If the elongation at break is above 7.0%, it is technically difficult to industrially produce polyethylene fibers with tensile strength within the above range.

[0057] The polyethylene fibers of this invention have excellent strength and creep resistance, and are therefore suitable for applications where they are exposed to tension for extended periods in harsh environments, such as braiding, twisting, fishing lines, ropes, nets, etc.

[0058] For the aforementioned polyethylene fibers, differential scanning calorimetry (DSC) was used to measure the melting point peak temperature at 141°C or lower when the temperature was increased from 30°C to 200°C at a rate of 10°C / min (first heating). The aforementioned polyethylene fibers exhibit excellent tensile properties, and sufficiently high strength / modulus of elasticity can be obtained even when alkyl side chains are present. It can be considered that the temperature of the melting point peak at the first heating indicates the contribution of the alkyl side chains in the polyethylene fibers as steric hindrance. That is, it can be considered that the alkyl side chains act as steric hindrance, resulting in disordered crystal structure, lower melting temperature, and prevention of polyethylene molecule slippage, thus exhibiting excellent creep characteristics. Furthermore, the temperature of the melting point peak at the first heating is preferably not lower than 125°C. If the melting point peak temperature is lower than 125°C, the tensile properties improve, but the molecular weight is low, or crystallization is insufficient; therefore, sometimes sufficient strength / modulus of elasticity is not obtained. More preferably, it is 130°C or higher, and even more preferably 132°C or higher.

[0059] Furthermore, for the aforementioned polyethylene fibers, the heat generated during the second heating phase, within the range of 70°C to 150°C up to the melting point peak temperature, is below 134 J / g. It can be assumed that this heat generated during the second heating phase reflects the number of alkyl side chains in the raw polyethylene material.

[0060] The peak temperature of the first heating and the heat in the second heating, based on differential scanning calorimetry (DSC), are specifically the values ​​measured as follows: For polyethylene fibers, using differential scanning calorimetry (DSC), the temperature is increased from 30°C to 200°C at a rate of 10°C / min (first heating), held at 200°C for 5 minutes, then decreased from 200°C to 30°C at a rate of 10°C / min, held at 30°C for 5 minutes, and then increased from 30°C to 200°C at a rate of 10°C / min (second heating).

[0061] [Raw material: polyethylene]

[0062] As described above, the number of ethyl branches in the polyethylene fiber of the present invention is preferably more than 1.1 (unit: branches / 1000 carbon atoms). By increasing the number of ethyl branches in this way, the ratio of the number of ethyl branches to the elongation stress of the polyethylene fiber is controlled in the range of 2 to 30 branches / MPa, resulting in polyethylene fibers with excellent tensile strength and creep resistance. Patent Document 4, mentioned above, does not disclose any method for improving strength and creep resistance by increasing the number of ethyl branches as in the present invention.

[0063] The polyethylene used in this invention can be constructed in a manner that controls the number of ethyl branches in the polyethylene fibers to fall within the aforementioned range. For example, the following polyethylene raw materials are recommended. As shown in the examples described later, when using any type of polyethylene raw material, it is determined that when the number of ethyl branches preferably exceeds 1.1 (unit: branches / 1000 carbon atoms), the desired properties are obtained.

[0064] (i) A blend of ultra-high molecular weight polyethylene (UHMWPE) polymerized with ethylene in the presence of a Ziegler catalyst and UHMWPE polymerized with ethylene in the presence of a metallocene catalyst.

[0065] (ii) Polyethylene (blended) containing two or more types of ultra-high molecular weight polyethylene with different average molecular weights and ethyl branch numbers.

[0066] (iii) Raw material polyethylene (non-blended) formed from individual ultra-high molecular weight polyethylene polymerized in the presence of a Ziegler catalyst or individual ultra-high molecular weight polyethylene polymerized in the presence of a metallocene catalyst.

[0067] In (i) and (iii) above, either or both of the ultra-high molecular weight polyethylene polymerized with ethylene in the presence of a Ziegler catalyst and the ultra-high molecular weight polyethylene polymerized with ethylene in the presence of a metallocene catalyst may have ethyl branches.

[0068] Furthermore, the above (ii) is a scheme in which two or more kinds of raw materials of polyethylene with different average molecular weight, molecular weight distribution or number of ethyl branches are blended and used together, thereby ensuring polyethylene fibers with excellent tensile properties, high strength and high elastic modulus (refer to Examples 2 to 7 in Table 1 below).

[0069] Here, "polyethylenes with different average molecular weights" refers to polyethylene with a large average molecular weight (hereinafter referred to as "H polyethylene") and polyethylene with a small average molecular weight (hereinafter referred to as "L polyethylene"), preferably having an intrinsic viscosity difference of about 2.0 dL / g or more. More preferably, it is 3.0 dL / g or more. Based on the research results of the present inventors, it has been determined that L polyethylene is beneficial for tensile strength, while H polyethylene is beneficial for high strength. Through the effect of L polyethylene, even with a large number of alkyl side chains (ethyl branches in this invention), sufficient tensile strength can be obtained, and the high strength capability of H polyethylene can be fully utilized.

[0070] The difference in intrinsic viscosity between H-polyethylene and L-polyethylene is preferably 15.0 dL / g or less, more preferably 10.0 dL / g or less. This is because, as mentioned above, a smaller average molecular weight improves tensile properties, while a larger proportion of L-polyethylene tends to make it difficult to obtain high-strength fibers.

[0071] In (i) or (ii) above, the number of blended materials is not particularly limited, for example, it can be 2, 3 or 4 types. However, if it is considered to ensure the desired creep resistance and high strength mechanical properties, and to improve molding processability, it is preferable to blend two or more (preferably 2) types of polyethylene raw materials with different average molecular weights, molecular weight distributions or ethyl branch numbers.

[0072] In contrast, (iii) above is not a scheme involving blending multiple raw material polyethylenes as described in (i) or (ii) above, but rather a scheme using a single ultra-high molecular weight polyethylene obtained in the presence of a Ziegler catalyst or a metallocene catalyst (see Example 1 in Table 1 below). According to the experimental results of the inventors, even the non-blending scheme described in (iii) above can yield polyethylene fibers with the desired creep resistance and high strength. However, it was determined that the blending scheme described in (i) or (ii) above can further increase the draw ratio using the first drawing filament described below, resulting in polyethylene fibers with even higher tensile strength. Patent Document 4 does not disclose any use of the raw material polyethylenes described in (i) to (iii) above.

[0073] The following is a detailed description of each plan.

[0074] Regarding (i)

[0075] The polyethylene raw material used in this invention, as described in (i), can be a blend of ultra-high molecular weight polyethylene (hereinafter referred to as "Ziegler polyethylene") polymerized with ethylene in the presence of a Ziegler catalyst and ultra-high molecular weight polyethylene (hereinafter referred to as "metallocene polyethylene") polymerized with ethylene in the presence of a metallocene catalyst. In this case, it is recommended to use Ziegler polyethylene as the polyethylene with a large average molecular weight (H polyethylene) and metallocene polyethylene as the polyethylene with a small average molecular weight (L polyethylene). This is because the wide molecular weight distribution of Ziegler polyethylene is beneficial for the high molecular weight component to function as H polyethylene, i.e., high strength. On the other hand, this is because metallocene polyethylene has a narrow molecular weight distribution compared to Ziegler polyethylene, which is beneficial for the low molecular weight component to function as L polyethylene, i.e., improved tensile strength. As a result, polyethylene fibers with excellent tensile strength and high elastic modulus can be obtained.

[0076] To achieve high tensile strength, Ziegler polyethylene is preferred to be without ethyl branches, and metallocene polyethylene is preferred to have ethyl branches only. This is because it is known that branches hinder tensile strength and make high strength difficult. As mentioned above, due to the influence of average molecular weight and molecular weight distribution, metallocene polyethylene with ethyl branches exhibits excellent tensile strength and is therefore preferred.

[0077] To obtain the polyethylene fiber of the present invention, the blending ratio of H polyethylene and L polyethylene can be appropriately adjusted considering the difference in the number of ethyl side chains and intrinsic viscosity of each polymer. For example, it is preferable to blend H polyethylene to L polyethylene in a ratio of H polyethylene:L polyethylene (by weight) of 10 to 90:90 to 10. From the viewpoint of uniform blending of the two polymers, it is ideal to blend them in a ratio of 30 to 70:70 to 30, which is even more preferred.

[0078] Regarding (ii)

[0079] The polyethylene used in this invention, as described in (ii), can be obtained by ethylene polymerization of two or more ultra-high molecular weight polyethylenes with different average molecular weights in the presence of a Ziegler catalyst or a metallocene catalyst. The fibers formed from this ultra-high molecular weight polyethylene also exhibit excellent tensile properties and tensile strength.

[0080] The above (ii) is preferably obtained by ethylene polymerization mainly in the presence of a Ziegler catalyst. It can be inferred that, as mentioned above, the polyethylene obtained in the presence of a Ziegler catalyst has a large molecular weight distribution, and the range of molecular weight repetition among polyethylenes with different average molecular weights is large, ensuring the continuity of the molecular weight distribution. Therefore, the processing conditions for processing the raw material into fibers are wide.

[0081] Regarding (iii)

[0082] The polyethylene used in this invention, as described in (iii) above, can be a single ultra-high molecular weight polyethylene formed by ethylene polymerization in the presence of a Ziegler catalyst or a metallocene catalyst [unlike (i) and (ii) above, which are non-blended]. Fibers formed from this ultra-high molecular weight polyethylene also exhibit excellent tensile strength.

[0083] Of these, for the same reasons as (ii) above, it is preferred that the ethylene is polymerized primarily in the presence of a Ziegler catalyst.

[0084] [Manufacturing method of polyethylene fiber]

[0085] Next, a preferred method for manufacturing the polyethylene fiber of the present invention will be described.

[0086] [Raw material: polyethylene]

[0087] The polyethylene fiber of the present invention preferably uses ultra-high molecular weight polyethylene as the raw material polyethylene.

[0088] In this invention, the index of "ultra-high molecular weight" is represented by intrinsic viscosity [η].

[0089] Specifically, the intrinsic viscosity [η] of this raw material polyethylene is 5.0 dL / g or more and 40.0 dL / g or less. More preferably, it is 8.0 dL / g or more and 35.0 dL / g or less; even more preferably, it is 10.0 dL / g or more and 30.0 dL / g or less; and even more preferably, it is 12.0 dL / g or more and 30.0 dL / g or less. If the intrinsic viscosity is less than 5.0 dL / g, the tensile strength of the final polyethylene fiber becomes lower, and sometimes the desired high-strength polyethylene fiber (e.g., tensile strength of 20 cN / dtex or more) cannot be obtained. On the other hand, if the intrinsic viscosity is greater than 40.0 dL / g, the tensile properties decrease, and sometimes the desired high-strength fiber cannot be obtained.

[0090] In addition, the raw material polyethylene contains ethyl groups (ethyl branches) in its side chains, and the preferred range of the number of ethyl branches is as described above.

[0091] When using polyethylene from two or more raw materials, ethyl groups may be present on the side chains of any one or both.

[0092] The polyethylene fibers of the present invention are preferably manufactured by gel spinning. Specifically, the manufacturing method preferably includes the following steps: a dissolution step of dissolving raw polyethylene in a solvent to form a polyethylene solution; a spinning step of discharging the polyethylene solution from a nozzle at a temperature above the melting point of the raw polyethylene and cooling the discharged filaments with a refrigerant; a drying step of removing solvent from the discharged undrawn filaments; a drawing step of drawing; and a winding step of winding the drawn filaments. Each step will be described below.

[0093] [Dissolving process]

[0094] First, it is recommended to prepare a polyethylene solution by dissolving high molecular weight polyethylene as the raw material. For example, volatile organic solvents such as decahydronaphthalene and tetrahydronaphthalene, and non-volatile solvents such as alkanes can be used as solvents for the polyethylene raw material. The concentration of polyethylene in the polyethylene solution is preferably 0.5% by mass or more and 40% by mass or less, more preferably 2.0% by mass or more and 30% by mass or less, and even more preferably 3.0% by mass or more and 20% by mass or less. If the polyethylene concentration is less than 0.5% by mass, the production efficiency becomes very poor. On the other hand, if the polyethylene concentration is greater than 40% by mass, it may sometimes be difficult to discharge from the nozzle described later in the gel spinning process due to the very large molecular weight.

[0095] [Spinning process]

[0096] The aforementioned polyethylene solution is extruded using an extruder or similar device at a temperature above the melting point of the raw polyethylene (preferably at a temperature 10°C or higher). The solution is then supplied to the spinning nozzle using a metering device. The polyethylene solution is then forced through and discharged from the spinning nozzle, which consists of multiple orifices, thereby forming filaments (gel filaments). This process continues until the temperature of the spinneret is set below the thermal decomposition temperature of the raw polyethylene. It should be noted that extrusion is performed at a temperature 10°C or higher than the melting point of the raw polyethylene.

[0097] Next, the discharged gel filaments are cooled in a cooling medium while being collected. Cooling methods can include, for example, dry quenching based on inert gases such as air or nitrogen, or wet / dry quenching using a miscible liquid or an immiscible liquid such as water.

[0098] [Drying / Stretching Process]

[0099] The filaments (undrawn filaments) collected in the spinning process described above are continuously or temporarily wound up and then subjected to a drying / drawing process. The purpose of the drying process is to remove the solvent. In the case of volatile solvents, this removal can be carried out in a heated atmosphere or using heated rollers. Examples of heated atmospheres include inactive gases such as air and nitrogen, water vapor, and liquid media. Alternatively, non-volatile solvents can be used, in which case extraction methods using extractants can be employed. Examples of extractants include chloroform, benzene, heptane, nonane, decane, ethanol, and higher alcohols.

[0100] In the subsequent stretching process, it is preferable to stretch the unstretched yarn while it is heated, such that the yarn speed at the exit of the stretching process is several times that at the inlet. Stretching can be performed in one pass or in multiple passes, preferably one to three passes. The stretching process can be performed in a hot medium atmosphere or using heated rollers. Examples of hot mediums include inactive gases such as air and nitrogen, water vapor, and liquid media.

[0101] Here, regarding the stretching temperature, it is determined that stretching at a temperature 1.0 to 10.0°C lower than that of the polyethylene raw material without ethyl branches improves stretchability and ultimately improves fiber strength. This is believed to be mainly because the melting point is lower when the side chains of the polyethylene raw material contain ethyl branches. Specifically, depending on the number of ethyl branches in the polyethylene fiber, stretching is preferably performed at a temperature of 130 to 150°C. Ideally, stretching is further preferably performed at a temperature of 132 to 148°C.

[0102] This application claims priority based on Japanese Patent Application No. 2019-091508, No. 2019-091509, filed May 14, 2019, and Japanese Patent Application No. 2019-195992, filed October 29, 2019. The entire contents of the descriptions of Japanese Patent Application No. 2019-091508, No. 2019-091509, and No. 2019-195992, filed May 14, 2019, are incorporated herein by reference.

[0103] Example

[0104] The following examples illustrate the present invention in detail. However, the present invention is not limited to the following examples and can be implemented by modifications that conform to the foregoing / hereafter described spirit, all of which are included within the protection scope of the present invention. Unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "% by mass".

[0105] The various properties of the polyethylene fibers in the following examples were measured and evaluated according to the following criteria.

[0106] (1) Intrinsic viscosity

[0107] The specific viscosity of various dilute solutions of decahydronaphthalene was determined using an Ubbelohde capillary viscometer at 135°C. The viscosity was plotted as concentration, and the intrinsic viscosity was determined by extrapolating the line obtained using the least squares approximation to the origin. The test solution was prepared as follows: 1% by mass of an antioxidant (manufactured by API Corporation, "Yoshinox (registered trademark) BHT") was added to the sample and stirred at 135°C for 4 hours to dissolve.

[0108] (2) Number of ethyl branches

[0109] 250 mg of each sample was collected and dissolved in o-dichlorobenzene + p-dichlorobenzene-d4 (7 vol% + 3 vol%) at 145 °C. C-NMR was determined at 120 °C. 13 The number of ethyl branches can be estimated using C-NMR spectroscopy using the following methods.

[0110] When the ethylene chain peak of polyethylene is set to 30 ppm, a peak originating from the ethyl side chain is detected near 34 ppm. When the integral value of the ethylene chain peak is set to 1000, and the integral value of the 34 ppm peak is set to A, the number of ethyl side chains can be calculated as A / 2 (chains / 1000C).

[0111] (3) Elongation stress

[0112] In this invention, the elongation stress of ultra-high molecular weight polyethylene (UHMW) molding materials is determined by performing pressure molding and elongation stress tests, based on Annex A (specifying) of the ISO standard "JIS K 6936-2:2007, Plastics - Materials for Molding and Extrusion of Ultra-High Molecular Weight Polyethylene (PE-UHMW) - Part 2: Methods for Preparing Test Pieces and Methods for Determining Properties," which is essentially the same as the aforementioned standard. As mentioned earlier, the main difference between the JIS K 6936-2:2007 method and the method of this invention lies in the following aspects: the load is changed from a clamp to a chuck, and the measurement environment is changed from a liquid phase (e.g., inside silicone oil) to a gas phase.

[0113] Specifically, first, the sample is cleaned with acetone and then pressed and molded under the following conditions to produce a sheet-like test piece.

[0114] Molding temperature: 210℃; Preheating conditions: 15 minutes at 5MPa; Full molding conditions: 30 minutes at 10MPa; Average cooling rate: 15℃ / min; Molded part removal temperature: below 40℃; Testing machine used: Electric heating press manufactured by Otake Machinery Industry Co., Ltd.

[0115] Using the obtained test piece, the elongation stress was measured under the following conditions.

[0116] For the test pieces, a pressure-molded product was machined (the shape of the test piece is referenced from Figure 3, Annex A, JIS K 6936-2:2007). Six test pieces were used, with a clamp spacing of 20 mm. The test temperature was 150℃±2℃ (in the gas phase). The testing machine used was an Autograph AG-I 100kN precision universal testing machine manufactured by Shimadzu Corporation (with a load sensor capacity of 1kN). The test load was set such that the time required for the parallel narrow portion of the test piece to reach 600% elongation fell within the range of 1 to 20 minutes. Six different loads (in MPa) were applied using different weights. Based on the results from the six test pieces, the horizontal axis was set as the measurement time (in minutes), and the vertical axis as the stress (in MPa). The estimated tensile stress required to reach 600% elongation within 10 minutes was calculated, and this estimated tensile stress was used as the elongation stress (in MPa).

[0117] (4) Fineness

[0118] The sample was cut into 10m pieces at 5 different locations, and its weight was measured. The fineness (dtex) was calculated by averaging the values ​​of the 5 pieces.

[0119] (5) Tensile strength, elongation at break and initial elastic modulus

[0120] These properties were determined according to JIS L1013 8.5.1.

[0121] Specifically, using "Tensilon" manufactured by Orient Technology Co., Ltd., strain-stress curves were obtained under the conditions of a sample length of 200 mm (length between chucks), an elongation rate of 100 mm / min, an atmosphere temperature of 20℃, and a relative humidity of 65%. The tensile strength (cN / dtex) was calculated from the stress at the fracture point of the obtained curve, and the elongation at break was calculated from the elongation.

[0122] In addition, the elastic modulus (cN / dtex) is calculated from the tangent of the maximum gradient near the origin of the provided curve.

[0123] These characteristic values ​​are expressed as the average of 10 measurements. It should be noted that the initial load applied to the sample during the measurement is set to 1 / 10 of the mass (g) of each 10,000m sample.

[0124] (6) Differential Scanning Calorimetry (DSC)

[0125] The experiment was conducted using a TA Instruments DSCQ100 instrument. The sample was cut into pieces less than 3-5 mm thick, and approximately 2 mg was filled / sealed into an aluminum dish. An empty aluminum dish was used as a reference. Under nitrogen atmosphere, the temperature was increased from 30°C to 200°C at a rate of 10°C / min (first heating). The temperature was held at 200°C for 5 minutes, then decreased from 200°C to 30°C at a rate of 10°C / min, held at 30°C for 5 minutes, and finally increased from 30°C to 200°C at a rate of 10°C / min (second heating). The heating DSC curve was then calculated. From this heating DSC curve, the endothermic peak temperature at the first heating was taken as the melting point peak temperature in the first heating. Furthermore, the heat of fusion [unit: J / g] in the range of 70°C to 150°C during the second heating was taken as the heat in the second heating.

[0126] (7) Creep resistance

[0127] like Figure 1 and Figure 2 As shown, one end of the free end of the specimen is fixed, a specified load is applied to the other free end, and the portion between the two ends of the specimen is heated to a specified temperature. The creep is measured by reading the change in the specimen at each measurement time. The specific measurement method is described below.

[0128] Prepare a metal plate (70.0 cm in length, with a mirror-finished surface) that can be heated to a specified temperature (70°C in this embodiment) and maintained at that temperature.

[0129] The sample is placed on the aforementioned metal plate without being twisted, so that they are in contact.

[0130] like Figure 1 As shown, one side of the free end of the above-mentioned sample is fixed to the part protruding from the metal plate, and an initial load (load of 0.2 g / dtex) is applied to the other free end protruding from the metal end.

[0131] For the sample on the aforementioned metal plate, mark two locations at intervals of 50.0 cm along the sample length. Then, remove the initial load and install the specified load (6.6 g / dtex). Next, as... Figure 2 As shown, the lid was closed from the top to maintain heat (the lid and sample did not contact each other) without contacting the sample on the metal plate, and the creep measurement began. The lid was opened every hour from the start of the measurement until 5 hours, then every 12 hours, and at 24 and 96 hours, and the distance between the initially marked intervals was read. Specific measurement times were as follows: starting from the start of the measurement, measurements were taken at 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 17 hours (5 hours + 12 hours), 24 hours, 29 hours (17 hours + 12 hours), 41 hours (29 hours + 12 hours), 53 hours (41 hours + 12 hours), 65 hours (53 hours + 12 hours), 77 hours (65 hours + 12 hours), 89 hours (77 hours + 12 hours), 96 hours, 101 hours (89 hours + 12 hours), 113 hours (101 hours + 12 hours), 125 hours (113 hours + 12 hours), and thereafter every +12 hours.

[0132] The creep was measured until the sample broke.

[0133] Here, the elongation ε of the sample at a certain time t is... i (mm) represents the marking spacing L on the sample at time t. (t) The difference between the marking spacing L0 (50.0 cm) of the initially marked specimen and the elongation (strain) ε is the amount of strain. i (t)(%) is shown below.

[0134] ε i (t)(%)=(L (t) -L0)×100 / L0

[0135] Furthermore, the creep rate τ (1 / s) is defined as the change in the length of the sample every 1 second, and the creep rate τ at each measurement time interval. i As shown below.

[0136] τ i (1 / second)=(ε) i -ε i-1 ) / (t i -t i-1 )×1 / 100

[0137] As described above, the distance between the marks is measured from the start of the measurement until the sample breaks, and the creep rate τ at each measurement time is recorded. i Plotted on a logarithmic scale, its minimum value is taken as the creep rate of the measured sample.

[0138] Furthermore, the time taken before the visible sample fracture is read is taken as the measured creep life of the sample. That is, the time taken to read the final sample length is taken as the creep life. It should be noted that in this embodiment, if the creep life measured in this way reaches 509 hours or more, it is judged that the creep life is much longer than that of the prior art, and no further measurement is performed. The creep life at this time is recorded as "more than 509 hours".

[0139] (Example 1)

[0140] In this embodiment, polyethylene fibers are made from polyethylene raw material formed by the aforementioned (iii) ethylene polymerization of ultra-high molecular weight polyethylene in the presence of a Ziegler catalyst.

[0141] Specifically, the polymerization uses a Ziegler catalyst, and ultra-high molecular weight polyethylene (A) with an intrinsic viscosity of 15.6 dL / g and 3.4 ethyl side chains per 1000 carbon atoms is mixed with decahydronaphthalene (decahydronaphthalene) as a solvent at a ratio of 9:91 (by weight) to form a slurry liquid.

[0142] The resulting slurry-like liquid is dissolved in a twin-screw extruder equipped with a mixing and conveying section, and the resulting polyethylene solution is discharged from a spinneret at a spinneret surface temperature of 175°C and a single-orifice discharge rate of 3.0 g / min. The spinneret has 16 orifices with a diameter of 0.8 mm.

[0143] Next, the discharged filaments are collected and cooled using a 20°C water-cooling bath with the nozzle 1.5 cm above the water surface at a speed of 80.0 m / min, forming 16 monofilaments of unstretched multifilaments (gel filaments). These unstretched multifilaments are then continuously dried and stretched to 1.5 times their original length in hot air at 110°C, and further stretched to 2.7 times their original length in hot air at 140°C, resulting in the first stretched filament with a total stretch ratio of 4.0 times.

[0144] The first drawn filament was further drawn to 2.3 times its original length in hot air at 141°C, and the drawn multifilament was immediately wound up in the drawn state.

[0145] The resulting stretched multifilament has 3.4 ethyl branches per 1000°C, an elongation stress of 0.24 MPa, and a ratio of 14.2 ethyl branches per MPa to elongation stress.

[0146] In addition, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 62 dtex, tensile strength 33 cN / dtex, initial elastic modulus 796 cN / dtex, and elongation at break 4.7%. The creep test results are as follows: creep rate 7.5 × 10⁻⁶. -10 sec -1 The elongation rate was 1.5% 24 hours after the start of the test, 1.5% 96 hours after the start of the test, and the time until the elongation rate reached 3.0% was more than 509 hours (the elongation rate was 1.7% at 509 hours). The creep life was more than 509 hours. The DSC results of this fiber sample are as follows: the melting point peak temperature at the first heating was 136℃, and the heat generated during the second heating was 124 J / g.

[0147] (Example 2)

[0148] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more ultra-high molecular weight polyethylenes with different average molecular weights that have undergone ethylene polymerization in the presence of a Ziegler catalyst, as described in (ii) above.

[0149] Specifically, in Example 1 above, ultra-high molecular weight polyethylene (A) with an intrinsic viscosity of 15.6 dL / g and 3.4 ethyl side chains per 1000 carbon atoms, ultra-high molecular weight polyethylene (B) with an intrinsic viscosity of 20.0 dL / g and no ethyl side chains, and decahydronaphthalene were mixed in a weight ratio of 5.3:3.7:91.0 to obtain a slurry-like liquid. The first drawing filament was then drawn to 2.8 times its original length in hot air at 145°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above.

[0150] The resulting stretched multifilament has 2.0 ethyl branches per 1000°C, an elongation stress of 0.26 MPa, and a ratio of 7.7 ethyl branches per MPa to elongation stress.

[0151] In addition, the physical properties of the above-mentioned stretched multifilament are as follows: fineness 47 dtex, tensile strength 36 cN / dtex, initial elastic modulus 1094 cN / dtex, and elongation at break 4.1%. The creep test results are as follows: creep rate 8.7 × 10⁻⁶. -9 sec -1The elongation rate was 1.5% 24 hours after the start of the test, 2.2% 96 hours after the start of the test, and the time to reach 3.0% elongation was 173 hours, with a creep life of over 509 hours. The DSC results of the fiber sample are as follows: the melting point peak temperature during the first heating was 139℃, and the heat generated during the second heating was 123 J / g.

[0152] (Example 3)

[0153] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more ultra-high molecular weight polyethylenes with different average molecular weights that have undergone ethylene polymerization in the presence of a Ziegler catalyst, as described in (ii) above.

[0154] Specifically, in Example 1 above, ultra-high molecular weight polyethylene (C) with an intrinsic viscosity of 17.0 dL / g and 2.0 ethyl side chains per 1000 carbon atoms polymerized using a Ziegler catalyst, ultra-high molecular weight polyethylene (B) with an intrinsic viscosity of 20.0 dL / g and no ethyl side chains polymerized using a Ziegler catalyst, and decahydronaphthalene (decahydronaphthalene) were mixed in a weight ratio of ultra-high molecular weight polyethylene (C): ultra-high molecular weight polyethylene (B): decahydronaphthalene = 6.8:2.2:91.0 to obtain a slurry-like liquid. The first drawing filament was then drawn to 3.0 times its original length in hot air at 145°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above.

[0155] The resulting stretched multifilament has an ethyl branch number of 1.5 per 1000°C, an elongation stress of 0.34 MPa, and an ethyl branch number to elongation stress ratio of 4.4 per MPa.

[0156] In addition, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 45 dtex, tensile strength 39 cN / dtex, initial elastic modulus 1214 cN / dtex, and elongation at break 3.9%. The creep test results are as follows: creep rate 4.9 × 10⁻⁶. -9 sec -1 The elongation rate was 1.0% 24 hours after the start of the test, 1.3% 96 hours after the start of the test, and the time to reach 3.0% elongation was 437 hours, with a creep life of over 509 hours. The DSC results of the fiber sample are as follows: the melting point peak temperature during the first heating was 140℃, and the heat during the second heating was 130 J / g.

[0157] (Example 4)

[0158] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more ultra-high molecular weight polyethylenes with different average molecular weights that have undergone ethylene polymerization in the presence of a Ziegler catalyst, as described in (ii) above.

[0159] Specifically, in Example 1 above, the liquid composition is changed to a slurry-like liquid, wherein the slurry-like liquid is a mixture of ultra-high molecular weight polyethylene (D) polymerized using a Ziegler-based catalyst, having an intrinsic viscosity of 18.0 dL / g and 2.9 ethyl side chains per 1000 carbon atoms, ultra-high molecular weight polyethylene (B) polymerized using a Ziegler-based catalyst, having an intrinsic viscosity of 20.0 dL / g and no ethyl side chains, and decahydronaphthalene (decahydronaphthalene) in the form of ultra-high molecular weight polyethylene (D): ultra-high molecular weight polyethylene. (B): Decahydronaphthalene = 6.2:2.8:91.0 (weight ratio) was mixed. The take-up speed of the spinneret was changed to 60.0 m / min. The unstretched multifilament was dried in hot air at 110°C and stretched to 1.5 times. It was then continuously stretched to 3.3 times in hot air at 140°C to obtain a first stretched filament with a total stretch ratio of 5.0 times. The first stretched filament was stretched in hot air at 145°C. Otherwise, the stretched multifilament was obtained in the same manner as in Example 1 above.

[0160] The resulting stretched multifilament has 2.0 ethyl branches per 1000°C, an elongation stress of 0.41 MPa, and a ratio of 4.8 ethyl branches per MPa to elongation stress.

[0161] In addition, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 63 dtex, tensile strength 35 cN / dtex, initial elastic modulus 1048 cN / dtex, and elongation at break 4.0%. The creep test results are as follows: creep rate 4.8 × 10⁻⁶. -8 sec -1 The elongation rate was 2.5% 24 hours after the start of the test, 4.6% 96 hours after the start of the test, and the time to reach 3.0% elongation was 53 hours. The creep life was over 245 hours. The DSC results of the fiber sample are as follows: the melting point peak temperature at the first heating was 139℃, and the heat during the second heating was 123J / g.

[0162] (Example 5)

[0163] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more types of ultra-high molecular weight polyethylene with different average molecular weights, namely, ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst and ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a metallocene catalyst, or ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst.

[0164] Specifically, in Example 1 above, the liquid composition was changed to a slurry. The slurry was made by mixing ultra-high molecular weight polyethylene (E) with a metallocene catalyst, intrinsic viscosity of 16.3 dL / g, and 7.0 ethyl side chains per 1000 carbon atoms, with ultra-high molecular weight polyethylene (B) with a Ziegler catalyst, intrinsic viscosity of 20.0 dL / g, and no ethyl side chains, and decahydronaphthalene (decahydronaphthalene) in a weight ratio of 2.6:6.4:91.0. The first drawing filament was then drawn to 3.5 times its original length in hot air at 145°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above.

[0165] The resulting stretched multifilament has 2.0 ethyl branches per 1000°C, an elongation stress of 0.48 MPa, and a ratio of 4.2 ethyl branches per MPa to elongation stress.

[0166] In addition, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 40 dtex, tensile strength 38 cN / dtex, initial elastic modulus 1255 cN / dtex, and elongation at break 3.7%. Creep test results are as follows: creep rate 1.1 × 10⁻⁶. -9 sec -1 The elongation rate was 1.4% 24 hours after the start of the test, 2.0% 96 hours after the start of the test, and the time to reach 3.0% elongation was 233 hours, with a creep life of over 509 hours. The DSC results of the fiber sample are as follows: the melting point peak temperature during the first heating was 140℃, and the heat generated during the second heating was 128 J / g.

[0167] (Example 6)

[0168] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more types of ultra-high molecular weight polyethylene with different average molecular weights, namely, ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst and ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a metallocene catalyst, or ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst.

[0169] Specifically, in Example 1 above, the liquid composition was changed to a slurry. The slurry was made by mixing ultra-high molecular weight polyethylene (F) with a metallocene catalyst, intrinsic viscosity of 16.8 dL / g, and 2.9 ethyl side chains per 1000 carbon atoms, with ultra-high molecular weight polyethylene (B) with a Ziegler catalyst, intrinsic viscosity of 20.0 dL / g, and no alkyl side chains, and decahydronaphthalene (decahydronaphthalene) in a weight ratio of ultra-high molecular weight polyethylene (F): ultra-high molecular weight polyethylene (B): decahydronaphthalene = 4.7:4.3:91.0. The first drawing filament was drawn to 2.5 times its original length in hot air at 145°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above.

[0170] The resulting stretched multifilament has an ethyl branch number of 1.5 per 1000°C, an elongation stress of 0.36 MPa, and an ethyl branch number to elongation stress ratio of 4.2 per MPa.

[0171] In addition, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 50 dtex, tensile strength 35 cN / dtex, initial elastic modulus 989 cN / dtex, and elongation at break 4.4%. The creep test results are as follows: creep rate 3.1 × 10⁻⁶. -8 sec -1 The elongation rate was 2.4% 24 hours after the start of the test, 3.6% 96 hours after the start of the test, and the time to reach 3.0% elongation was 53 hours, with a creep life of 353 hours. The DSC results of the fiber sample are as follows: the melting point peak temperature at the first heating was 139℃, and the heat generated during the second heating was 121 J / g.

[0172] (Example 7)

[0173] In this embodiment, polyethylene fibers are produced using polyethylene raw materials of two or more types of ultra-high molecular weight polyethylene with different average molecular weights, namely, ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst and ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a metallocene catalyst, or ultra-high molecular weight polyethylene containing ethylene polymerized in the presence of a Ziegler catalyst.

[0174] Specifically, in Example 1 above, the following slurry-like liquid was used instead: ultra-high molecular weight polyethylene (F) with an intrinsic viscosity of 16.8 dL / g and 2.9 ethyl side chains per 1000 carbon atoms polymerized using a metallocene catalyst, ultra-high molecular weight polyethylene (B) with an intrinsic viscosity of 20.0 dL / g and no alkyl side chains polymerized using a Ziegler catalyst, and decahydronaphthalene (decahydronaphthalene) were mixed in a weight ratio of ultra-high molecular weight polyethylene (F): ultra-high molecular weight polyethylene (B): decahydronaphthalene = 6.2:2.8:91.0. The spinneret collection speed was changed to 100.0 m / min, and the first drawn filament was drawn in hot air at 145°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above. The resulting drawn multifilament has an ethyl branch number of 2.0 per 1000°C, an elongation stress of 0.32 MPa, and an ethyl branch number to elongation stress ratio of 6.3 per MPa. Furthermore, the physical properties of the above-mentioned drawn multifilament are as follows: fineness 46 dtex, strength 33 cN / dtex, initial elastic modulus 842 cN / dtex, and elongation at break 4.5%. Creep test results are as follows: creep rate 1.2 × 10⁻⁶. -8 sec -1 The elongation rate was 1.5% 24 hours after the start of the test, 1.8% 96 hours after the start of the test, and the time until the elongation rate reached 3.0% was more than 353 hours, with a creep life of 389 hours. The DSC results of this fiber sample are as follows: the melting point peak temperature at the first heating was 139℃, and the heat during the second heating was 118J / g.

[0175] (Comparative Example 1)

[0176] Toyobo Co., Ltd.'s ultra-high molecular weight polyethylene fiber "Izanas Grade SK777" has an ethyl branch number of 0.0 per 1000°C, an elongation stress of 0.58 MPa, and an ethyl branch number to elongation stress ratio of 0.0 per MPa. Its physical properties are as follows: fineness 1775 dtex, tensile strength 35 cN / dtex, initial modulus of elasticity 1190 cN / dtex, and elongation at break 3.6%.

[0177] The creep resistance is as follows: creep rate is 3.6 × 10⁻⁶. -6 sec -1The time until the elongation reached 3.0% was 2 hours, and the creep life was 17 hours. It should be noted that fracture was confirmed 24 hours after the start of the measurement; therefore, the elongation could not be measured 24 hours after the start of the measurement. Similarly, the elongation could not be measured 96 hours after the start of the measurement. Therefore, the creep resistance of Comparative Example 1 was worse than any of the examples described above. The DSC results of this fiber sample are as follows: the melting point peak temperature at the first heating was 146°C, and the heat generated during the second heating was 146 J / g.

[0178] (Comparative Example 2)

[0179] In Example 1 above, the ultra-high molecular weight polyethylene (A) was replaced with ultra-high molecular weight polyethylene (G) polymerized using a Ziegler catalyst, having an intrinsic viscosity of 20.0 dL / g and 0.5 ethyl side chains per 1000 carbon atoms, and the first drawing filament was drawn to 2.8 times its original length in hot air at 148°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above.

[0180] The resulting drawn multifilament has an ethyl branch number of 0.5 per 1000°C, an elongation stress of 0.41 MPa, and an ethyl branch number to elongation stress ratio of 1.2 per MPa. Its physical properties are as follows: fineness 48 dtex, tensile strength 36 cN / dtex, initial elastic modulus 1125 cN / dtex, and elongation at break 3.8%.

[0181] The creep resistance is as follows: creep rate is 2.8 × 10⁻⁶. -7 sec -1 The elongation rate was 4.7% 24 hours after the start of the test, 13.5% 96 hours after the start of the test, and the time to reach 3.0% elongation was 17 hours, with a creep life of 101 hours. Therefore, the creep resistance of Comparative Example 2 was worse than any of the examples described above. The DSC results of this fiber sample are as follows: the melting point peak temperature at the first heating was 142°C, and the heat generated during the second heating was 135 J / g.

[0182] (Comparative Example 3)

[0183] In Example 1 above, the ultra-high molecular weight polyethylene (A) was replaced with ultra-high molecular weight polyethylene (E) polymerized using a metallocene catalyst, having an intrinsic viscosity of 16.3 dL / g and 7.0 ethyl side chains per 1000 carbon atoms; ultra-high molecular weight polyethylene (H) polymerized using a Ziegler catalyst, having an intrinsic viscosity of 11.4 dL / g and no ethyl side chains was replaced with ultra-high molecular weight polyethylene (E): ultra-high molecular weight polyethylene (H): ultra-high molecular weight naphthalene = 7.7:1.3:91.0 (weight ratio), and the first drawn filament was stretched to 1.5 times its original length in hot air at 140°C. Otherwise, the drawn multifilament was obtained in the same manner as in Example 1 above. The drawn multifilament thus obtained had an ethyl branch number of 6.0 per 1000°C, an elongation stress of 0.14 MPa, and an ethyl branch number to elongation stress ratio of 42.9 per MPa. The physical properties are as follows: fineness is 89 dtex, tensile strength is 19 cN / dtex, initial elastic modulus is 323 cN / dtex, and elongation at break is 4.6%. The maximum draw ratio for drawing from the first drawn yarn to the drawn multifilament is 1.5 times, and it is impossible to increase the draw ratio above this.

[0184] The fiber properties of Comparative Example 3 were worse than those of any of the examples described above; therefore, creep resistance was not evaluated. Furthermore, DSC measurements were not performed.

[0185] [Table 1]

[0186]

[0187] Explanation of reference numerals in the attached figures

[0188] 1. Sample

[0189] 2. Metal plate

[0190] 3. Load

[0191] 4. Fixed end of the specimen

[0192] 5. Cover

Claims

1. A type of ultra-high molecular weight polyethylene fiber, characterized in that, It is an ultra-high molecular weight polyethylene fiber with ethyl side chains. The ratio of the number of ethyl branches per 1000 carbon atoms in the polyethylene fiber (C2H5 / 1000C) to the elongation stress (MPa) of the polyethylene fiber {(C2H5 / 1000C) / (elongation stress)} is 2~30 per 1000 carbon atoms / MPa. The polyethylene fiber contains two types of ultra-high molecular weight polyethylene with different average molecular weights and ethyl branch numbers. The intrinsic viscosity difference between the two types of ultra-high molecular weight polyethylene is greater than 2.0 dL / g. For the two types of ultra-high molecular weight polyethylene, the ultra-high molecular weight polyethylene with a smaller average molecular weight has ethyl branches, while the ultra-high molecular weight polyethylene with a larger average molecular weight does not have ethyl branches.

2. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The intrinsic viscosity of the two types of ultra-high molecular weight polyethylene is above 5.0 dL / g and below 40.0 dL / g. The intrinsic viscosity difference between the two types of ultra-high molecular weight polyethylene is greater than 2.0 dL / g and less than 15.0 dL / g.

3. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, In the creep test at a temperature of 70℃ and a load of 6.6 g / dtex, The creep rate is 9.0 × 10⁻⁶. -8 sec -1 the following, The elongation rate was less than 2.7% 24 hours after the start of the measurement. The elongation rate was less than 5.0% 96 hours after the start of the measurement, and The time required for the elongation to reach 3.0% is more than 30 hours.

4. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) exceeds 1.

1.

5. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, For polyethylene fibers, differential scanning calorimetry (DSC) was used to measure the temperature at a rate of 10°C / min, increasing the temperature from 30°C to 200°C (first increase), holding at 200°C for 5 minutes, then decreasing the temperature from 200°C to 30°C at a rate of 10°C / min, holding at 30°C for 5 minutes, and then increasing the temperature from 30°C to 200°C at a rate of 10°C / min (second increase). The peak melting point temperature of the polyethylene fiber during the first heating process is below 141°C. The heat generated during the second heating process, up to the peak temperature of the polyethylene fiber in the range of 70°C to 150°C, is less than 134 J / g.

6. The ultra-high molecular weight polyethylene fiber according to claim 1 has a tensile strength of 20 cN / dtex or higher.

7. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The ratio of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) to the elongation stress (MPa) of the polyethylene fiber {(C2H5 / 1000C) / (elongation stress)} is 3.0~20 per 1000 carbon atoms / MPa.

8. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The ratio of the number of ethyl branches per 1000 carbon atoms (C2H5 / 1000C) to the elongation stress (MPa) of the polyethylene fiber {(C2H5 / 1000C) / (elongation stress)} is 4.4~7.7 per 1000 carbon atoms / MPa.

9. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The number of ethyl branches (C2H5 / 1000C) per 1000 carbon atoms in the polyethylene fiber is 1.3 or more and 15 or less.

10. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The number of ethyl branches (C2H5 / 1000C) per 1000 carbon atoms in the polyethylene fiber is more than 1.5 and less than 10.

11. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The number of ethyl branches (C2H5 / 1000C) per 1000 carbon atoms in the polyethylene fiber is 1.5 or more and 2.0 or less.

12. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The number of ethyl branches (C2H5 / 1000C) per 1000 carbon atoms in the ultra-high molecular weight polyethylene with ethyl branches is 2.0 or more and 7.0 or less.

13. The ultra-high molecular weight polyethylene fiber according to claim 5, wherein, The peak melting point temperature of the polyethylene fiber during the first heating process is above 125°C.

14. The ultra-high molecular weight polyethylene fiber according to claim 5, wherein, The peak melting point temperature of the polyethylene fiber during the first heating process is above 130°C.

15. The ultra-high molecular weight polyethylene fiber according to claim 5, wherein, The peak melting point temperature of the polyethylene fiber during the first heating process is above 132°C.

16. The ultra-high molecular weight polyethylene fiber according to claim 2, wherein, The intrinsic viscosity is above 12.0 dL / g and below 30.0 dL / g. The difference in intrinsic viscosity is greater than 2.0 dL / g and less than 10.0 dL / g.

17. The ultra-high molecular weight polyethylene fiber according to claim 2, wherein, The intrinsic viscosity is above 15.6 dL / g and below 18.0 dL / g. The difference in intrinsic viscosity is greater than 2.0 dL / g and less than 4.4 dL / g.

18. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The tensile strength of the polyethylene fiber is above 30 cN / dtex and below 60 cN / dtex.

19. The ultra-high molecular weight polyethylene fiber according to claim 18, wherein, The lower limit of the tensile strength is above 35 cN / dtex.

20. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The initial elastic modulus of the polyethylene fiber is above 500 cN / dtex and below 2000 cN / dtex.

21. The ultra-high molecular weight polyethylene fiber according to claim 20, wherein, The lower limit of the initial elastic modulus is above 700 cN / dtex.

22. The ultra-high molecular weight polyethylene fiber according to claim 20, wherein, The lower limit of the initial elastic modulus is above 1048 cN / dtex.

23. The ultra-high molecular weight polyethylene fiber according to claim 1, wherein, The polyethylene fiber has a breaking elongation of 3.0% or more and 7.0% or less.

24. The ultra-high molecular weight polyethylene fiber according to claim 23, wherein, The lower limit of the elongation at break is 3.2% or higher.

25. The ultra-high molecular weight polyethylene fiber according to claim 23, wherein, The lower limit of the elongation at break is 3.4% or higher.

26. The ultra-high molecular weight polyethylene fiber according to claim 23, wherein, The lower limit of the elongation at break is 3.9% or higher.

27. Braided tapes, twisted yarns, fishing lines, ropes, or nets comprising ultra-high molecular weight polyethylene fibers as described in any one of claims 1 to 26.

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