A method for preparing ultra-high molecular weight polyethylene fiber

Abstract

The invention discloses a method for preparing ultra-high molecular weight polyethylene fiber, comprising the following steps: step A: dispersing ultra-high molecular weight polyethylene powder and processing aid in a solvent to obtain a mixed raw material; step B: preheating the mixed raw material and sending it into a twin-screw extruder for spinning to obtain a polyethylene sol colloidal filament bundle; step C: placing the polyethylene sol colloidal filament bundle in cold water for cooling and squeezing out water to obtain a frozen gel filament; step D: pre-stretching the frozen gel filament, placing it in an extractant for extraction at room temperature, and washing, evaporating and drying in sequence after the extraction to obtain an ultra-high molecular weight polyethylene fiber precursor; step E: stretching the ultra-high molecular weight polyethylene fiber precursor to obtain an ultra-high molecular weight polyethylene fiber. The invention can solve the problem of poor fluidity during the current ultra-high molecular weight polyethylene processing, and prepare polyethylene fibers with excellent creep resistance and ideal mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene fiber preparation, and more specifically to a method for preparing ultra-high molecular weight polyethylene fiber. Background Art

[0002] Ultra High Molecular Weight Polyethylene Fiber (UHMWPE), also known as high-strength high-modulus polyethylene fiber, is a fiber spun from polyethylene with a molecular weight between 1 million and 5 million. The density of the fiber is usually between 0.920 and 0.964 g / cm 3 Because ultra-high molecular weight polyethylene fiber has the advantages of high specific strength and high specific modulus, as well as resistance to acid and alkali corrosion and good wear resistance, it is widely used in the preparation of protective materials in the fields of aerospace, medical equipment, etc., as well as in the preparation of ship anchor ropes, etc.

[0003] However, the chemically inactive property of ultra-high molecular weight polyethylene fiber also has disadvantages: since ultra-high molecular weight polyethylene fiber has a highly symmetrical methylene structure, its surface lacks polar groups and has low surface energy, which makes ultra-high molecular weight polyethylene fiber have high crystallinity and orientation; although this can make it have excellent mechanical strength, on the other hand, it also leads to the disadvantages of ultra-high molecular weight polyethylene fiber such as poor heat resistance and easy creep. In particular, its poor creep resistance seriously limits its application.

[0004] In order to improve the performance of ultra-high molecular weight polyethylene fibers, cross-linking modification, nanoparticle addition modification, and addition of other fibers with good creep resistance are commonly used for modification. Although these methods can improve the disadvantage of ultra-high molecular weight polyethylene fibers being prone to creep to a certain extent, they also have many defects. For example, cross-linking under high temperature or high radiation conditions will lead to a decrease in the mechanical strength of ultra-high molecular weight polyethylene fibers, while UV cross-linking, nanoparticle addition modification, and addition of other fibers with good creep resistance are usually ineffective, difficult to operate, and have high costs, making them difficult to industrialize.

[0005] In addition, the mechanical strength of ultra-high molecular weight polyethylene fiber is related to the molecular weight of the polyethylene raw material used: the higher the molecular weight of the polyethylene raw material, the better the mechanical strength of the polyethylene fiber obtained, but as the molecular weight of the polyethylene raw material increases, its viscosity increases, the fluidity is poor, and the processing difficulty increases. In order to reduce the processing difficulty of ultra-high molecular weight polyethylene, flow modifiers or low molecular weight polyethylene are usually added to polyethylene during the processing process, but the polyethylene fiber prepared by this method does not fully utilize the structural characteristics between high molecular weight polyethylene molecular chains, and the flow modifier is prone to uneven dispersion and aggregation in polyethylene with high viscosity, resulting in unsatisfactory strength of the polyethylene fiber products actually obtained. Summary of the invention

[0006] To this end, the technical problem to be solved by the present invention is to provide a method for preparing ultra-high molecular weight polyethylene fibers, which can solve the problem of poor fluidity during current ultra-high molecular weight polyethylene processing and prepare polyethylene fibers with excellent creep resistance and ideal mechanical properties.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for preparing ultra-high molecular weight polyethylene fiber comprises the following steps:

[0009] Step A: dispersing ultra-high molecular weight polyethylene powder and a processing aid in a solvent to obtain a mixed raw material;

[0010] Step B: preheating the mixed raw material and sending it into a twin-screw extruder for spinning to obtain a polyethylene sol colloidal filament bundle;

[0011] Step C: placing the polyethylene sol colloidal filament bundle in cold water to cool it and then squeezing out the water to obtain frozen gel filaments;

[0012] Step D: After pre-stretching the jelly filaments, the jelly filaments are placed in an extractant for extraction at room temperature, and after the extraction is completed, the jelly filaments are washed, evaporated and dried in sequence to obtain ultra-high molecular weight polyethylene fiber precursors;

[0013] Step E: drawing the ultra-high molecular weight polyethylene fiber precursor to obtain the ultra-high molecular weight polyethylene fiber.

[0014] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, in step A: the ultra-high molecular weight polyethylene powder is obtained by crushing the ultra-high molecular weight polyethylene raw material and passing it through a 100-mesh sieve; the relative molecular mass of the ultra-high molecular weight polyethylene raw material is 3 million to 5 million.

[0015] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, the catalyst used for catalyzing the synthesis of ultra-high molecular weight polyethylene raw materials is a manganese-based catalyst and a boron compound.

[0016] The above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, the method for preparing a manganese-based catalyst comprises the following steps: mixing manganese chloride, sodium thiocyanate and methanol and stirring them evenly at room temperature, then adding benzyltriphenylphosphonium chloride and continuing to stir, and filtering to obtain a filtrate after the reaction is completed; evaporating the filtrate under reduced pressure to obtain a solid product, which is the manganese-based catalyst.

[0017] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, the molar ratio of manganese chloride to sodium thiocyanate is 1:20-50; the mass ratio of manganese chloride to methanol is 1-2:1; the amount of benzyl triphenyl phosphonium chloride added is 4-6 times the mass of manganese chloride; manganese chloride, sodium thiocyanate and methanol are mixed and stirred at room temperature for 1-2 hours, benzyl triphenyl phosphonium chloride is added and stirred for 1-1.5 hours; the temperature of reduced pressure evaporation is 25-35°C.

[0018] The above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, the method for preparing boron compound is: tetraoctylphosphine chloride solution and octyl substituted sodium malonate borate solution are fully stirred and mixed at room temperature, and then continued to stir and heat to react; the mixed reaction liquid obtained after the reaction is mixed with dichloromethane to extract an organic phase; the organic phase is rotary evaporated and dried to obtain a boron compound.

[0019] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, the molar concentration of the tetraoctylphosphine chloride solution is 0.5-0.8 mol / L, the molar concentration of the octyl substituted sodium malonate borate solution is 0.3-0.5 mol / L; the volume ratio of the tetraoctylphosphine chloride solution to the octyl substituted sodium malonate borate solution is 1:1-1.5; the volume ratio of the mixed reaction liquid to dichloromethane during extraction is 1:1-3; the stirring time at room temperature is 20-50 min; the heating reaction is stirred for 8-10 hours, and the heating reaction temperature is 50-65°C; the rotary evaporation temperature is 50-60°C, the drying temperature is 60-70°C, and the drying time is 8-12 hours.

[0020] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, in step A, the processing aid is prepared by mixing tert-butylhydroquinone, dibutylhydroxytoluene and tri(2,4-di-tert-butylphenyl)phosphite in a mass ratio of 1:1-1.5:2-5, and the solvent is white oil; the processing aid is 2-3% of the mass of the ultra-high molecular weight polyethylene powder; and the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed raw material is 8-16wt%.

[0021] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, in step B, the preheating temperature of the mixed raw materials is 40-60°C, and the spinning temperature of the twin-screw extruder is 180-210°C; in step C, the cold water cooling temperature is 5-10°C.

[0022] In the above-mentioned method for preparing ultra-high molecular weight polyethylene fiber, in step D, the extractant is dichloromethane; the pre-stretching temperature is 100-130°C, and the stretching multiple of the pre-stretching is 3-5 times; the drying temperature is 40-50°C; in step E, the stretching temperature is 130-150°C, the number of stretching times is 3-5 times, and the stretching multiple of each stretching is 5-15 times.

[0023] The technical solution of the present invention achieves the following beneficial technical effects:

[0024] When preparing ultra-high molecular weight polyethylene fibers, the present invention uses ultra-high molecular weight polyethylene with a molecular weight of 3 million to 5 million prepared by a manganese-based catalyst and a boron compound as a raw material, adds tert-butylhydroquinone, dibutylhydroxytoluene and tris(2,4-di-tert-butylphenyl)phosphite as processing aids, and optimizes the solution spinning preparation process to obtain ultra-high molecular weight polyethylene fibers with strong creep resistance and good mechanical properties.

[0025] The present invention uses a mixture of a manganese-based catalyst and a boron compound as a catalyst to catalyze the preparation of an ultra-high molecular weight polyethylene raw material, and finally prepares a polyethylene raw material with a molecular weight in the range of 3 million to 5 million, and the polyethylene raw material has the advantages of low viscosity, good processing fluidity, and appropriate branching degree. The present invention uses homemade polyethylene as a raw material, and when it is processed into polyethylene fiber by a solution spinning method, its crystallinity and orientation are reduced to a certain extent, and polyethylene fibers with strong creep resistance and ideal mechanical properties can be prepared, and its creep resistance is enhanced.

[0026] Compared with the manganese-based catalyst and boron compound in the prior art, the manganese-based catalyst and boron compound prepared by the method of the present invention are used in combination to catalyze ethylene to generate ultra-high molecular weight polyethylene with a higher degree of branching and a narrower molecular weight distribution, so that the ultra-high molecular weight polyethylene has better fluidity when processed into polyethylene fibers, and there is no need to add additional flow modifiers or lower molecular weight polyethylene raw materials to improve the fluidity of the ultra-high molecular weight polyethylene, which is conducive to processing to obtain ultra-high molecular weight polyethylene fibers with ideal mechanical properties and creep resistance. DETAILED DESCRIPTION

[0027] Example 1

[0028] The method for preparing ultra-high molecular weight polyethylene fiber in this embodiment comprises the following steps:

[0029] Step A: dispersing ultra-high molecular weight polyethylene powder and a processing aid in a solvent to obtain a mixed raw material; the processing aid is prepared by mixing tert-butyl hydroquinone, dibutyl hydroxytoluene and tris (2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:1.5:4, and the solvent is white oil; the processing aid is 2% of the mass of the ultra-high molecular weight polyethylene powder; the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed raw material is 10wt%; the ultra-high molecular weight polyethylene powder is obtained by crushing an ultra-high molecular weight polyethylene raw material and passing it through a 100-mesh sieve; the relative molecular mass of the ultra-high molecular weight polyethylene raw material is 3 million to 5 million; the catalyst used for catalyzing the synthesis of the ultra-high molecular weight polyethylene raw material is a manganese-based catalyst and a boron compound;

[0030] The preparation method of the manganese-based catalyst comprises the following steps:

[0031] Manganese chloride, sodium thiocyanate and methanol are mixed and stirred at room temperature for 2 hours, the molar ratio of manganese chloride to sodium thiocyanate is 1.5:1; the mass ratio of manganese chloride to methanol is 1:20; the amount of benzyl triphenyl phosphonium chloride added is 4 times the mass of manganese chloride; then benzyl triphenyl phosphonium chloride is added and stirring is continued for 1.5 hours, and after the reaction is completed, a filtrate is obtained by filtering; the filtrate is placed at 35°C for reduced pressure evaporation to obtain a solid product, which is a manganese-based catalyst.

[0032] The preparation method of the boron compound is:

[0033] The tetraoctylphosphine chloride solution and the octyl substituted sodium malonic acid borate solution are fully stirred and mixed at room temperature in a volume ratio of 1:1.5 for 30 min, the molar concentration of the tetraoctylphosphine chloride solution is 0.8 mol / L, and the molar concentration of the octyl substituted sodium malonic acid borate solution is 0.5 mol / L; then continue to stir and heat to react, the heating reaction temperature is 60°C, and the heating reaction is stirred for 8 hours; after the reaction is completed, the mixed reaction liquid is mixed with dichloromethane to extract an organic phase; during the extraction, the volume ratio of the mixed reaction liquid to dichloromethane is 1:2; the organic phase is rotary evaporated at 55°C and then dried at 65°C for 12 hours to obtain a boron compound.

[0034] The method for preparing ultra-high molecular weight polyethylene raw materials by catalyzing manganese-based catalysts and boron compounds is as follows: first, a polymerization kettle is replaced with high-purity nitrogen for no less than three times, and then n-hexane, a co-catalyst (MAO or triethylaluminum) and a catalyst (manganese-based catalyst and a boron compound are mixed in a mass ratio of 1:1) are added to the polymerization kettle, wherein the initial mass concentration of the co-catalyst is 1.0 mg / L, and the initial mass concentration of the catalyst is 1.5 mg / L in the reaction system; the temperature of the polymerization kettle is increased to 60°C, and ethylene is introduced to make its pressure reach 0.5 MPa, and the polymerization reaction is carried out for 1 hour at the temperature and pressure, and after the reaction is completed, the temperature is lowered, the material is discharged and dried, and the ultra-high molecular weight polyethylene raw material is obtained.

[0035] Step B: preheating the mixed raw material to 50° C. and then feeding it into a twin-screw extruder for spinning, the spinning temperature of the twin-screw extruder is 200° C., to obtain a polyethylene sol colloidal filament bundle;

[0036] Step C: placing the polyethylene sol colloidal filament bundle in cold water at a temperature of 5° C. to cool it and then squeezing out the water to obtain frozen gel filaments;

[0037] Step D: After pre-stretching the gel filaments (pre-stretching temperature is 130° C., and the pre-stretching stretching ratio is 5 times), the gel filaments are placed in dichloromethane for extraction at room temperature, and after the extraction is completed, the gel filaments are washed, evaporated and dried (drying temperature is 45° C.) in sequence to obtain ultra-high molecular weight polyethylene fiber precursors;

[0038] Step E: The ultra-high molecular weight polyethylene fiber precursor is stretched for multiple times, the stretching temperature is 130° C., the number of stretching times is 5 times, and the stretching multiple of each stretching is 8 times; thus, the ultra-high molecular weight polyethylene fiber is obtained.

[0039] During the processing of the ultra-high molecular weight polyethylene fiber of this embodiment, the ultra-high molecular weight polyethylene has good fluidity and is easy to process, and less waste is generated during the processing.

[0040] Example 2

[0041] The method for preparing ultra-high molecular weight polyethylene fiber in this embodiment comprises the following steps:

[0042] Step A: dispersing ultra-high molecular weight polyethylene powder and a processing aid in a solvent to obtain a mixed raw material; the processing aid is prepared by mixing tert-butyl hydroquinone, dibutyl hydroxytoluene and tri(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:1:2, and the solvent is white oil; the processing aid is 3% of the mass of the ultra-high molecular weight polyethylene powder; the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed raw material is 15wt%; the ultra-high molecular weight polyethylene powder is obtained by crushing an ultra-high molecular weight polyethylene raw material and passing it through a 100-mesh sieve; the relative molecular mass of the ultra-high molecular weight polyethylene raw material is 3 million to 5 million; the catalyst used for catalyzing the synthesis of the ultra-high molecular weight polyethylene raw material is a manganese-based catalyst and a boron compound; the boron compound is trialkyl boron; the preparation method of the manganese-based catalyst comprises the following steps:

[0043] Manganese chloride, sodium thiocyanate and methanol are mixed and stirred at room temperature for 1 hour, the molar ratio of manganese chloride to sodium thiocyanate is 1:1; the mass ratio of manganese chloride to methanol is 1:30; the amount of benzyl triphenyl phosphonium chloride added is 5 times the mass of manganese chloride; then benzyl triphenyl phosphonium chloride is added and stirring is continued for 1 hour, and after the reaction is completed, a filtrate is obtained by filtering; the filtrate is placed at 25°C and evaporated under reduced pressure to obtain a solid product, which is a manganese-based catalyst.

[0044] The method for preparing ultra-high molecular weight polyethylene raw material catalyzed by manganese-based catalyst and boron compound is the same as that in Example 1.

[0045] Step B: preheating the mixed raw material to 60° C. and then feeding it into a twin-screw extruder for spinning, the spinning temperature of the twin-screw extruder being 210° C. to obtain a polyethylene sol colloidal filament bundle;

[0046] Step C: placing the polyethylene sol colloidal filament bundle in cold water at a temperature of 10° C. to cool it and then squeezing out the water to obtain frozen gel filaments;

[0047] Step D: pre-stretching the gel filaments (pre-stretching temperature is 100° C., and the pre-stretching stretching ratio is 3 times), and then extracting them in dichloromethane at room temperature. After the extraction, washing, evaporation and drying (drying temperature is 50° C.) are carried out in sequence to obtain ultra-high molecular weight polyethylene fiber precursors;

[0048] Step E: The ultra-high molecular weight polyethylene fiber precursor is stretched for multiple times, the stretching temperature is 150° C., the number of stretching times is 3 times, and the stretching multiple of each stretching is 12 times; thus, the ultra-high molecular weight polyethylene fiber is obtained.

[0049] During the processing of the ultra-high molecular weight polyethylene fiber in this embodiment, the ultra-high molecular weight polyethylene has good fluidity and is easy to process. Less waste is generated during the processing, but it is more than that in Example 1.

[0050] Example 3

[0051] The method for preparing ultra-high molecular weight polyethylene fiber in this embodiment comprises the following steps:

[0052] Step A: dispersing ultra-high molecular weight polyethylene powder and a processing aid in a solvent to obtain a mixed raw material; the processing aid is prepared by mixing tert-butyl hydroquinone, dibutyl hydroxytoluene and tris (2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:2:5, and the solvent is white oil; the processing aid is 2.5% of the mass of the ultra-high molecular weight polyethylene powder; the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed raw material is 8wt%; the ultra-high molecular weight polyethylene powder is obtained by crushing an ultra-high molecular weight polyethylene raw material and passing it through a 100-mesh sieve; the relative molecular mass of the ultra-high molecular weight polyethylene raw material is 3 million to 5 million; the catalyst used for catalyzing the synthesis of the ultra-high molecular weight polyethylene raw material is a manganese-based catalyst, and the preparation method of the manganese-based catalyst comprises the following steps:

[0053] Manganese chloride, sodium thiocyanate and methanol are mixed and stirred at room temperature for 2 hours, the molar ratio of manganese chloride to sodium thiocyanate is 1.5:1; the mass ratio of manganese chloride to methanol is 1:50; the amount of benzyl triphenyl phosphonium chloride added is 6 times the mass of manganese chloride; then benzyl triphenyl phosphonium chloride is added and stirring is continued for 1 hour, and after the reaction is completed, a filtrate is obtained by filtering; the filtrate is placed at 35°C and evaporated under reduced pressure to obtain a solid product, which is a manganese-based catalyst.

[0054] The method for preparing ultra-high molecular weight polyethylene raw material by catalysis of manganese-based catalyst is the same as that in Example 1, except that the catalyst is a manganese-based catalyst.

[0055] Step B: preheating the mixed raw material to 40° C. and then feeding it into a twin-screw extruder for spinning, the spinning temperature of the twin-screw extruder being 180° C. to obtain a polyethylene sol colloidal filament bundle;

[0056] Step C: placing the polyethylene sol colloidal filament bundle in cold water at a temperature of 8° C. to cool it and then squeezing out the water to obtain frozen gel filaments;

[0057] Step D: After pre-stretching the gel filaments (pre-stretching temperature is 120° C., and the pre-stretching stretching ratio is 5 times), the gel filaments are placed in dichloromethane for extraction at room temperature, and after the extraction is completed, they are washed, evaporated and dried (drying temperature is 50° C.) in sequence to obtain ultra-high molecular weight polyethylene fiber precursors;

[0058] Step E: The ultra-high molecular weight polyethylene fiber precursor is stretched for multiple times, the stretching temperature is 150° C., the number of stretching times is 4 times, and the stretching multiple of each stretching is 10 times; thus, the ultra-high molecular weight polyethylene fiber is obtained.

[0059] During the processing of the ultra-high molecular weight polyethylene fiber of this embodiment, the ultra-high molecular weight polyethylene has good fluidity and is easy to process. Less waste is generated during the processing, but slightly more than that in Example 2.

[0060] Example 4

[0061] The difference between this embodiment and embodiment 1 is that the processing aid is a mixture of tert-butylhydroquinone, dibutylhydroxytoluene and tris(2,4-di-tert-butylphenyl)phosphite in a mass ratio of 1:3:1. The ultra-high molecular weight polyethylene fiber of this embodiment has good fluidity and is easy to process, and the waste generated during the processing is less than that of embodiment 1.

[0062] The creep elongation and tensile strength of the ultra-high molecular weight polyethylene fiber were measured respectively by the method in GB / T19975-2005. When the creep elongation was measured, the load was 50% and the test temperature was 70° C. After testing, the creep elongation and breaking strength of the ultra-high molecular weight polyethylene fibers prepared in Examples 1 to 4 are shown in the following table.

[0063] Table 1

[0064] Test items Example 1 Example 2 Example 3 Example 4 Fiber creep elongation (%) 1.03％ 1.32％ 1.60％ 1.25％ Fiber breaking strength (CN / dtex) 47.9 44.7 43.2 40.4

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing ultra-high molecular weight polyethylene fiber, characterized in that: The steps include: Step A: dispersing ultra-high molecular weight polyethylene powder and a processing aid in a solvent to obtain a mixed raw material; the processing aid is prepared by mixing tert-butyl hydroquinone, dibutyl hydroxytoluene and tris (2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:1 to 1.5:2 to 5, and the solvent is white oil; the processing aid is 2 to 3% of the mass of the ultra-high molecular weight polyethylene powder; the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed raw material is 8 to 16wt%; Step B: preheating the mixed raw material and sending it into a twin-screw extruder for spinning to obtain a polyethylene sol colloidal filament bundle; Step C: placing the polyethylene sol colloidal filament bundle in cold water to cool it and then squeezing out the water to obtain frozen gel filaments; Step D: After pre-stretching the jelly filaments, the jelly filaments are placed in an extractant for extraction at room temperature, and after the extraction is completed, the jelly filaments are washed, evaporated and dried in sequence to obtain ultra-high molecular weight polyethylene fiber precursors; Step E: drawing the ultra-high molecular weight polyethylene fiber precursor to obtain the ultra-high molecular weight polyethylene fiber; The catalyst used in the synthesis of ultra-high molecular weight polyethylene raw materials is a manganese-based catalyst and a boron compound; The preparation method of the manganese-based catalyst comprises the following steps: mixing manganese chloride, sodium thiocyanate and methanol and stirring them evenly at room temperature, then adding benzyl triphenylphosphonium chloride and continuing stirring, filtering to obtain a filtrate after the reaction is completed; evaporating the filtrate under reduced pressure to obtain a solid product, which is the manganese-based catalyst; The preparation method of the boron compound comprises: fully stirring and mixing a tetraoctylphosphine chloride solution and an octyl substituted sodium malonate borate solution at room temperature, and then continuing to stir and heat to react; mixing the mixed reaction liquid obtained after the reaction is completed with dichloromethane to extract an organic phase; rotary evaporating the organic phase and drying it to obtain the boron compound; The method for preparing ultra-high molecular weight polyethylene raw materials by catalysis of manganese-based catalysts and boron compounds is as follows: first, a polymerization kettle is replaced with high-purity nitrogen for no less than three times, and then n-hexane, a co-catalyst and a catalyst are added into the polymerization kettle, wherein the co-catalyst is MAO or triethylaluminum, and the catalyst is a manganese-based catalyst and a boron compound, and the manganese-based catalyst and the boron compound are mixed in a mass ratio of 1:1, and in the reaction system, the initial mass concentration of the co-catalyst is 1.0 mg / L, and the initial mass concentration of the catalyst is 1.5 mg / L; the temperature of the polymerization kettle is increased to 60°C, and ethylene is introduced to make its pressure reach 0.5 MPa, and the polymerization reaction is carried out for 1 hour at the temperature and pressure maintained, and after the reaction is completed, the material is cooled, discharged and dried to obtain the ultra-high molecular weight polyethylene raw material.

2. The method for preparing ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step A, the ultra-high molecular weight polyethylene powder is obtained by crushing the ultra-high molecular weight polyethylene raw material and passing it through a 100-mesh sieve; the relative molecular mass of the ultra-high molecular weight polyethylene raw material is 3 million to 5 million.

3. The method for preparing ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The molar ratio of manganese chloride to sodium thiocyanate is 1-2:1; the mass ratio of manganese chloride to methanol is 1:20-50; the amount of benzyl triphenyl phosphonium chloride added is 4-6 times the mass of manganese chloride; manganese chloride, sodium thiocyanate and methanol are mixed and stirred at room temperature for 1-2 hours, benzyl triphenyl phosphonium chloride is added and stirring is continued for 1-1.5 hours; the temperature of reduced pressure evaporation is 25-35°C.

4. The method for preparing ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The molar concentration of the tetraoctylphosphonium chloride solution is 0.5-0.8 mol / L, and the molar concentration of the octyl substituted sodium malonic acid borate solution is 0.3-0.5 mol / L; the volume ratio of the tetraoctylphosphonium chloride solution to the octyl substituted sodium malonic acid borate solution is 1:1-1.5; during extraction, the volume ratio of the mixed reaction solution to dichloromethane is 1:1-3; The stirring and mixing time at room temperature is 20 to 50 minutes; the heating reaction is stirred for 8 to 10 hours, and the heating reaction temperature is 50 to 65°C; the rotary evaporation temperature is 50 to 60°C, the drying temperature is 60 to 70°C, and the drying time is 8 to 12 hours.

5. The method for preparing ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step B, the preheating temperature of the mixed raw materials is 40-60°C, and the spinning temperature of the twin-screw extruder is 180-210°C; in step C, the cooling temperature of cold water is 5-10°C.

6. The method for preparing ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step D, the extracting agent is dichloromethane; the pre-stretching temperature is 100-130°C, and the stretching ratio of the pre-stretching is 3-5 times; the drying temperature is 40-50°C; in step E, the stretching temperature is 130-150°C, the stretching times are 3-5 times, and the stretching ratio of each stretching is 5-15 times.