WO2025189698A1 - Creep-resistant high-performance polyethylene fiber and preparation thereof and use thereof - Google Patents

Abstract

The present invention relates to a creep-resistant high-performance polyethylene fiber and preparation thereof and a use thereof. The preparation process of the polyethylene fiber comprises: carrying out high-temperature extrusion on a polyethylene resin raw material and an auxiliary agent by means of a screw extruder to obtain polyethylene unstretched protofilaments, said polyethylene resin raw material being obtained by polymerization using a single-site polyethylene catalyst, directly carrying out high-ratio stretching on the polyethylene unstretched protofilaments under a heat preservation condition, and then continuously carrying out high-temperature multi-ratio thermal stretching and winding, to obtain a creep-resistant high-performance polyethylene fiber, i.e., a target product. Compared with the prior art, the present invention solves the problem that the creep performance of an ultra-high molecular weight polyethylene fiber is poorly improved due to the use of a solvent during preparation, the preparation process of the obtained fiber product is simple, and by using the structural characteristics of the resin raw material, the creep resistance is further improved.

Description

A creep-resistant high-performance polyethylene fiber and its preparation and application Technical Field

The invention belongs to the technical field of polyethylene fiber material preparation, and relates to a creep-resistant high-performance polyethylene fiber and its preparation and application.

Background Art

High-performance polyethylene fibers offer the advantage of high strength and are suitable for use in high-end fiber products, with applications in medicine, fishing, and protective equipment. However, because high-performance polyethylene fiber molecules lack side chains, hydrogen bonds are absent between fiber molecules, and van der Waals forces act solely as dispersion forces, the intermolecular forces acting on high-performance polyethylene fibers are minimal, making them susceptible to intermolecular slippage and creep. These poor creep properties limit their use in applications requiring prolonged loads, such as fishing ropes. Therefore, there is a need to improve the creep resistance of fibers and expand their application in high-end products.

Patent CN109824961B provides a method for preparing cut-resistant and creep-resistant ultra-high molecular weight polyethylene fibers. This technology uses high-speed shear blending to disperse modified graphene and silane coupling agent-modified silicon carbide whiskers in ultra-high molecular weight polyethylene powder. The resulting powder premix is then evenly dispersed in a spinning solution under ultrasonic conditions, and the cut-resistant and creep-resistant ultra-high molecular weight polyethylene fibers are spun. While this technology improves the dispersibility of inorganic fillers to some extent, it suffers from the long preparation time of the modifier and insufficient improvement in creep resistance.

Chinese patents CN113502556B and CN105442100A use irradiation to obtain cross-linked ultra-high molecular weight polyethylene fibers. This method requires the use of a high-energy irradiation device, which is not conducive to industrial production and has poor control over the degree of cross-linking.

Chinese patent CN111172607B discloses a highly creep-resistant ultra-high molecular weight polyethylene fiber and its preparation method. This patent adds linear α-olefins during the polymerization of ultra-high molecular weight polyethylene resin to increase the branching degree of the ultra-high molecular weight polyethylene resin. The obtained polyethylene resin has a branch content of 10 to 1000 per 100,000 carbon atoms in the skeleton. The ultra-high molecular weight polyethylene fiber is prepared by gel spinning. The resulting fiber product has improved creep resistance. This method starts from the spinning raw material and introduces branches during the polymerization process. The process is simple and has This is beneficial for industrial production. However, the patented gel spinning process is complex and costly, and the creep resistance of the fiber product is poorly improved.

Summary of the Invention

The purpose of the present invention is to provide a creep-resistant high-performance polyethylene fiber and its preparation and application, which solves the problem that the creep performance of ultra-high molecular weight polyethylene fiber is poorly improved due to the use of solvents. The preparation process of the obtained fiber product is simple, and the structural characteristics of the resin raw material are utilized to further improve the creep resistance.

The purpose of the present invention can be achieved by the following technical solutions:

One of the technical solutions of the present invention provides a method for preparing creep-resistant high-performance polyethylene fiber, which comprises taking polyethylene resin raw material and additives and extruding polyethylene unstretched precursor yarn at high temperature through a screw extruder, then directly stretching the polyethylene unstretched precursor yarn at high times under heat preservation conditions, and then continuing to perform high-temperature multiple-times hot stretching and winding to obtain creep-resistant high-performance polyethylene fiber, which is the target product.

Furthermore, the polyethylene resin raw material is a copolymer of ethylene and an α-olefin comonomer having more than 3 carbon atoms, with a weight average molecular weight of 100,000-600,000, a molecular weight distribution of less than 3, an average branching content of 1-25 per 1000 carbon atoms, a density greater than 0.91 g/cm ³ , and a melt index (MI) of 0.01-10 g/10 min at 21.6 kg load and 190° C.

Furthermore, the polyethylene resin raw material is prepared by the following method:

A solvent, a single-site catalyst, a co-catalyst, ethylene, hydrogen, and a comonomer are added to a reactor protected by an inert gas and free of water and oxygen. A polymerization reaction is carried out at high temperature to produce a polyethylene resin raw material with a certain degree of branching. The solvent is added to dissolve the ethylene monomer and simultaneously disperse the catalyst, comonomer, and the resulting polyethylene. The solvent can be, for example, n-hexane.

Furthermore, the reactor is a slurry tank reactor, a slurry loop reactor, a gas phase fluidized bed reactor or a combination of the above reactors.

Furthermore, the amount of the comonomer added is 0.1% to 5% of the molar amount of ethylene, specifically 0.1%, 5%, 1%, 2%, etc.

Furthermore, the amount of hydrogen added satisfies its concentration of 0 to 100 ppm, wherein when the amount of hydrogen added is 0 ppm, it indicates that no hydrogen is added. Here, hydrogen is added to adjust the molecular weight of polyethylene and does not affect creep resistance.

Furthermore, the molar ratio of the co-catalyst to the single-active-site catalyst is (0.01-1000):1. Specifically, it can be 0.01:1, 1000:1, 0.1:1, 1:1, 10:1, 100:1, and the like.

Furthermore, the single-active-site catalyst can be a metallocene polyethylene catalyst, a transition metal catalyst, etc. Such as the metallocene catalyst tetramethylcyclopentadienyl zirconocene dichloride (TMCP), the Schiff base single-active-site catalyst bis[N-cyclohexyl-(3-tert-butyl salicylaldimine)] zirconium dichloride (FI), the ActivCAT catalyst produced by GRACE, the new generation of post-metallocene catalysts jointly researched and developed by Mitsui Chemicals of Japan and Dow Chemical Company of the United States, etc. The single-active-site catalyst here belongs to the conventional catalyst known in the art, and itself does not belong to the innovative protection point of the present invention.

The cocatalyst is triethylaluminum, triisobutylaluminum or methylaluminoxane.

Furthermore, the comonomer is one or more α-olefins having a carbon number greater than or equal to 3, preferably one or more of propylene, butene, hexene, octene or 4-methyl-1-pentene.

Furthermore, the polymerization reaction temperature is 70-90° C., the pressure is 0.8-1 MPa, and the time is 1-3 hours.

Furthermore, the additive comprises a mixture of an antioxidant and a surface lubricant, with the mass ratio of antioxidant to surface lubricant being 1:0.2 to 1:5; the additive addition amount is 0.05% to 5% of the polyethylene resin raw material. Furthermore, the antioxidant is one or more of 2,6-di-tert-butyl-p-cresol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate;

The surface lubricant is one or more of titanate, fluororubber, stearate or aluminate compounds.

Furthermore, the high stretching ratio is 5-50 times, and the holding temperature is 60-140°C.

Furthermore, the high-temperature multiple thermal stretching ratio is 2-20 times, and the stretching temperature is 70-130°C.

A second technical solution of the present invention provides a creep-resistant high-performance polyethylene fiber, which is prepared by any of the preparation methods described above.

A third technical solution of the present invention provides an application of a creep-resistant high-performance polyethylene fiber in the preparation of creep-resistant polyethylene fiber products.

The present invention adopts a single active center catalyst, and the resin raw material obtained by polymerization has the characteristics of narrow molecular weight distribution and uniform distribution of branches on the polyethylene long chain molecules with narrow molecular weight distribution after copolymerization. As shown in Figures 1 and 2, the narrow molecular weight distribution polyethylene of the present invention has branches introduced by copolymerization evenly distributed in the polyethylene long chain with the entire molecular weight distribution; while the wide molecular weight distribution polyethylene obtained by polymerization using existing Ziegler Natta (ZN) and chromium-based catalysts has branches introduced by copolymerization with a larger number of short branches in the low molecular weight part and a smaller number of short branches in the high molecular weight part. The increase in branch content is believed to improve the creep resistance of the fiber. The present invention has found through research that the uniformity of branch distribution is a key factor in further improving creep resistance. Single-active center catalysts can obtain better copolymerization performance and more uniform short branch distribution than Ziegler Natta catalysts. Thousand-carbon methyl Compared with polyethylene polymerized with a single-active-site catalyst and polyethylene polymerized with a comparable number of Ziegler-Natta and chromium-based catalysts, the fiber products of polyethylene polymerized with a single-active-site catalyst have better creep resistance.

The present invention also found that the creep resistance of fibers is related to the molecular weight and molecular weight distribution of the resin raw material. A higher molecular weight indicates better creep resistance in the resulting fibers, while the low molecular weight fraction of broad molecular weight distribution polyethylene reduces creep resistance. Compared to the creep resistance of polyethylene fibers with the same weight-average molecular weight but different molecular weight distributions, which have not been copolymerized, narrow molecular weight distribution polyethylene exhibits superior creep resistance.

In addition, compared with ultra-high molecular weight polyethylene, the present invention uses a polyethylene resin raw material with a molecular weight of 100,000-600,000. The resin raw material has a low molecular weight and good processing performance. The introduction of side chains still has good processing performance. Solvent disentanglement is not required during the spinning process, and fiber products can be directly prepared through melt extrusion and drawing processes. Ultra-high molecular weight polyethylene fiber products require solvent disentanglement for fiber spinning, so solvent residues will be generated in the fibers. The solvent residues significantly reduce the creep resistance of existing ultra-high molecular weight polyethylene fibers. The present invention uses a melt spinning process for processing to obtain fiber products without solvent residues. Compared with the current ultra-high molecular weight polyethylene fibers, the fiber product spinning process of the present invention also has creep resistance advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of molecular weight and branching distribution of narrow molecular weight distribution polyethylene;

Figure 2 is a schematic diagram of the molecular weight and branching distribution of broad molecular weight distribution polyethylene.

DETAILED DESCRIPTION

The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

In the following examples, the metallocene polyethylene catalyst used was produced by Grace Company (WR Grace & Co. 101B catalyst.

The transition metal polyethylene catalyst was synthesized in the laboratory using the following methods:

Synthesis of carrier Mg1:

Add n(methanol):n(original carrier Mg(OH) ₂ )=10:1 into the reaction flask, heat to 100°C, add diisobutyl phthalate, n(diisobutyl phthalate):n(original carrier Mg(OH) ₂ )=1:1, stir at high speed, stirring speed 500 rpm, react for 4 hours, after the reaction is completed, quickly press the resulting mixture into a large The solution was fixed in n-hexane at -15°C to obtain a solid.

The obtained solid was placed in a nitrogen atmosphere and heated to 60° C. for 5 hours to obtain the desired carrier Mg1 with an average particle size of 150 μm and a specific surface area of 450 m ² /g.

Catalyst loading: The above-mentioned transition metal titanium complex (prepared according to CN 202010061212.6) (33.6 mg, 50 mol, 673 g/mol) was dissolved in 10 mL of toluene, and triethylaluminum (0.1 mL, 100 mol, 1.0 mol/L) was added and stirred at room temperature for 30 minutes to obtain a catalyst solution; the carrier Mg1 (1.0 g) was added and stirred at room temperature for 1 hour. The mixture was filtered, washed with toluene, and dried in vacuo to obtain the supported catalyst C1.

The structure of the transition metal titanium complex is as follows:

Test method for fiber creep resistance: The creep resistance of the fiber was tested using the method of GB/T199752005. The creep test conditions were: 40% load, 20 cm clamp distance, and 60 min constant force stretching.

Unless otherwise specified, the remaining raw materials or processing techniques are conventional commercially available raw materials or processing techniques in the art.

Example 1:

The polyethylene polymerization reaction is carried out in a 2L batch reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After the gas replacement is completed, nitrogen is introduced, and n-hexane, metallocene catalyst, and co-catalyst triethylaluminum and methylaluminoxane are pressed into the replaced reactor through nitrogen. The amount of n-hexane added is 1.5L, the amount of catalyst added is 0.2g, the amount of triethylaluminum added is 0.5g, and the amount of methylaluminoxane added is 0.3g. Ethylene is introduced, and the set pressure is maintained at 0.9MPa. The reactor is opened for stirring and the reactor is gradually heated by heat transfer oil. When the reactor is heated to 80°C, the reaction is maintained for 2h. 1% of octene monomer is added at the beginning of the reaction (that is, 1% of the molar amount of ethylene, the same below). After the reaction is completed, the entry of ethylene gas is turned off, and the upper layer of n-hexane is removed after cooling with cooling water. The product is taken out to obtain a weight average molecular weight of 400,000, Mw/Mn of 2.5, and A polyethylene resin raw material having a short chain branch number (SCB) of 10, a density of 0.932 g/cm ³ , and an MI of 2.8 g/10 min.

The polyethylene resin raw material obtained by polymerization, antioxidant 1010, stearic acid and calcium stearate are fed into a screw extruder for melt extrusion. The amounts of antioxidant 1010, stearic acid and calcium stearate are 0.2%, 0.3% and 0.4% of the mass of the polyethylene resin raw material, respectively. The extruded raw yarn is subjected to high-multiple stretching and winding at a heat preservation condition of 100°C, with a stretching ratio of 20 times. The wound fiber is subjected to high-temperature multiple stretching and winding, with a stretching ratio of 5 times and a stretching temperature of 100°C. After winding, creep-resistant high-performance polyethylene fiber is obtained.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 0.322%.

Example 2:

The polyethylene polymerization reaction is carried out in a 2L batch reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After the gas replacement is completed, nitrogen is introduced, and n-hexane, metallocene catalyst, and co-catalyst triisobutylaluminum and methylaluminoxane are pressed into the replaced reactor through nitrogen. The amount of n-hexane added is 1.5L, the amount of catalyst added is 0.2g, the amount of triethylaluminum added is 0.5g, and the amount of methylaluminoxane added is 0.3g. Ethylene is introduced, and the set pressure is maintained at 0.9MPa. The reactor is turned on for stirring and the reactor is gradually heated by heat transfer oil. When the reactor is raised to 78°C, the reaction is maintained for 2h. 4% of octene monomer is added at the beginning of the reaction. After the reaction is completed, the entry of ethylene gas is turned off, and the upper layer of n-hexane is removed after cooling with cooling water, and the product is taken out. A polyethylene resin raw material having a weight average molecular weight of 400,000, Mw/Mn of 2.5, a thousand-carbon short chain branch number SCB of 20, a density of 0.925 g/cm ³ , and an MI of 3.5 g/10 min was obtained.

The polyethylene resin raw material obtained by polymerization, antioxidant 1076, stearic acid and calcium stearate are fed into a screw extruder for melt extrusion. The amounts of antioxidant 1076, stearic acid and calcium stearate are 0.2%, 0.3% and 0.4% of the polyethylene mass, respectively. The extruded raw yarn is subjected to high-multiple stretching and winding at a heat preservation condition of 120°C, with a stretching ratio of 40 times. The wound fiber is subjected to high-temperature multiple stretching and winding, with a stretching ratio of 8 times and a stretching temperature of 90°C. After winding, creep-resistant high-performance polyethylene fiber is obtained.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 0.210%.

Example 3:

Polyethylene polymerization was carried out in a 2L batch reactor. First, the polymerization reactor was purged with nitrogen several times to remove the air in the reactor, and then purged with ethylene several times. After the gas replacement was completed, nitrogen was introduced, and n-hexane, transition metal catalyst, co-catalyst triethylaluminum, and methylaluminoxane were pressed into the reactor after the replacement through nitrogen. The amount of n-hexane added was 1.5L, the amount of catalyst added was 0.2g, the amount of triethylaluminum added was 0.5g, and the amount of methylaluminoxane added was 0. 0.3g of oxane was added. Ethylene was introduced, maintaining the set pressure at 0.8MPa. The reactor was stirred and gradually heated with thermal oil. After reaching 85°C, the reaction was maintained for 2 hours. 0.5% of butene monomer was added at the beginning of the reaction. After the reaction was completed, the ethylene gas was turned off. After cooling with cooling water, the upper layer of n-hexane was removed and the product was removed to obtain a polyethylene resin raw material with a weight-average molecular weight of 200,000, an Mw/Mn ratio of 2, a number of 1,000 carbon short chain branches (SCB) of ⁵ , a density of 0.933g/cm³, and an MI of 5.4g/10min.

The polyethylene resin obtained by polymerization, along with antioxidant 1010, calcium stearate, and titanate, were fed into a screw extruder for melt extrusion. The amounts of antioxidant 1010, calcium stearate, and titanate were 0.2%, 0.2%, and 0.2% of the polyethylene mass, respectively. The extruded raw yarn was subjected to high-stretching and winding at 80°C with a draw ratio of 5. The wound fiber was then subjected to high-temperature multiple stretching and winding at a draw ratio of 20 and a draw temperature of 100°C to obtain creep-resistant high-performance polyethylene fiber.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 0.605%.

Example 4:

The polyethylene polymerization reaction is carried out in a 2L intermittent reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After the gas replacement is completed, nitrogen is introduced, and n-hexane, transition metal catalyst, and co-catalyst triethylaluminum and methylaluminoxane are pressed into the replaced reactor through nitrogen. The amount of n-hexane added is 1.5L, the amount of catalyst added is 0.2g, the amount of triethylaluminum added is 0.5g, and the amount of methylaluminoxane added is 0.3g. Ethylene is introduced, and the set pressure is maintained at 1MPa. The reactor is turned on for stirring and the reactor is gradually heated by heat transfer oil. After the reactor is heated to 73°C, the reaction is maintained for 2h. 3% propylene monomer and 2% 4-methyl-1-pentene are added at the beginning of the reaction. After the reaction, the ethylene gas was turned off, and after cooling with cooling water, the upper n-hexane layer was removed and the product was taken out to obtain a polyethylene resin raw material with a weight average molecular weight of 600,000, Mw/Mn of 1.5, a thousand-carbon short chain branch number SCB of 25, a density of 0.915 g/ ^cm3 , and an MI of 1.7 g/10min.

The polyethylene raw material obtained by polymerization, antioxidant 1076 and zinc stearate are fed into a screw extruder for melt extrusion. The dosage of antioxidant 1076 and zinc stearate is 0.2% and 0.4% of the polyethylene mass, respectively. The extruded raw yarn is subjected to high-multiple stretching and winding at a heat preservation condition of 130°C, with a stretching ratio of 30 times. The wound fiber is subjected to high-temperature multiple stretching and winding, with a stretching ratio of 15 times and a stretching temperature of 120°C. After winding, creep-resistant high-performance polyethylene fiber is obtained.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 0.105%.

Comparative Example 1:

A polyethylene resin was prepared using the same method as in Example 1, except that no comonomer was added during the polymerization process. The resulting polyethylene resin had a weight-average molecular weight of 400,000, an Mw/Mn ratio of 2.5, a 1,000-carbon short chain branch (SCB) ratio of 0.05, a density of 0.940 g/cm ³ , and an MI of 0.3 g/10 min. The resulting polyethylene resin was melt-spun and stretched using the same method as in Example 1 to produce polyethylene fibers.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 4.852%.

Comparative Example 2:

The resin raw material used in Example 1 was used in a solvent spinning method to prepare a spinning solution with a mass percentage of 8wt% of polyethylene resin raw material and paraffin oil for gel spinning. The spinning pre-swelling treatment temperature was 90°C and the pre-swelling treatment time was 1h. A high-temperature extrusion and stretching process similar to that of Example 1 was used to feed the polymerized polyethylene resin raw material, antioxidant 1010, stearic acid, and calcium stearate into a screw extruder for melt extrusion. The amounts of antioxidant 1010, stearic acid, and calcium stearate were 0.2%, 0.3%, and 0.4% of the mass of the polyethylene resin raw material, respectively. The extruded raw yarn was subjected to high-multiple stretching and winding at a heat preservation condition of 80°C, with a stretching ratio of 20 times. The wound fiber was subjected to high-temperature multiple stretching and winding, with a stretching ratio of 5 times and a stretching temperature of 100°C, to obtain polyethylene fiber.

The prepared fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant force tensile test, and the creep rate was 3.021%.

Comparative Example 3:

Polyethylene polymerization is carried out in a 2L batch reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After the gas replacement is completed, nitrogen is introduced, and n-hexane, ZN catalyst (for the preparation of ZN catalyst, see Example 1 of patent CN1223268A) and co-catalyst triisobutylaluminum are pressed into the replaced reactor through nitrogen. 1.5L of n-hexane is added, 0.2g of catalyst is added, and 0.8g of triethylaluminum is added. Ethylene is introduced, maintaining the set pressure of 0.9MPa, the reactor is opened for stirring and the reactor is gradually heated by thermal oil. After the reactor is raised to 80°C, the reaction is maintained for 2h. 1% of octene monomer is added at the beginning of the reaction. After the reaction is completed, the ethylene gas is turned off, the upper layer of n-hexane is removed after cooling with cooling water, and the product is taken out. The obtained weight-average molecular weight was 400,000, Mw/Mn was 5.5, the number of short chain branches (SCB) was 10, the density was 0.938 g/cm ³ , and the MI was 6.7 g/10 min. A fiber product was prepared using the method of Example 1. The obtained fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant tension. The creep rate was 4.593%.

Comparative Example 4:

Polyethylene polymerization is carried out in a 2L batch reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After completing the gas replacement, nitrogen is introduced, and n-hexane and chromium catalyst (for the preparation of chromium catalysts, see Example 1 of patent CN102942643A) and co-catalyst triisobutylaluminum are pressed into the replaced reactor by nitrogen. 1.5L of n-hexane is added, 0.2g of catalyst is added, and 0.8g of triethylaluminum is added. Ethylene is introduced, and the set pressure is maintained at 0.8MPa. The reactor is opened for stirring and the reactor is gradually heated by thermal oil. After the reactor is raised to 80°C, the reaction is maintained for 2h. 1% of butene monomer is added in the early stage of the reaction. After the reaction is completed, the ethylene gas is turned off, and the upper n-hexane is removed after cooling with cooling water, and the product is taken out. The obtained weight-average molecular weight was 200,000, Mw/Mn was 8.8, the number of short chain branches (SCB) was 5, the density was 0.945 g/cm ³ , and the MI was 8.5 g/10 min. A fiber product was prepared using the method of Example 1. The obtained fiber was subjected to a creep test under the conditions of 40% load, 20 cm clamp distance, and 60 min constant tension. The creep rate was 6.266%.

Comparative Example 5:

The polyethylene polymerization reaction is carried out in a 2L batch reactor. First, the polymerization reactor is replaced with nitrogen several times to remove the air in the reactor, and then replaced with ethylene several times. After the gas replacement is completed, nitrogen is introduced, and n-hexane, transition metal catalyst, and co-catalyst triethylaluminum and methylaluminoxane are pressed into the replaced reactor through nitrogen. The amount of n-hexane added is 1.5L, the amount of catalyst added is 0.2g, the amount of triethylaluminum added is 0.5g, and the amount of methylaluminoxane added is 0.3g. Ethylene is introduced, and the set pressure is maintained at 0.8MPa. The reactor is turned on for stirring and the reactor is gradually heated by heat transfer oil. After the reactor is heated to 85°C, the reaction is maintained for 2h. At the beginning of the reaction, 0.5% butene monomer and 50ppm hydrogen are added. After the reaction, the ethylene gas was turned off, and after cooling with cooling water, the upper n-hexane layer was removed and the product was taken out to obtain a polyethylene resin raw material with a weight average molecular weight of 150,000, Mw/Mn of 2, a thousand-carbon short chain branch number SCB of 5, a density of 0.942 g/ ^cm3 , and an MI of 4.1 g/10min.

The polyethylene resin raw material obtained by polymerization in this comparative example was blended with the polyethylene resin raw material obtained in Example 3 at a mass ratio of 1:1. The blended raw materials were melt-spun and stretched using the method of Example 3 to obtain polyethylene fibers.

The resulting fiber was tested for creep resistance under conditions of 40% load, 20cm clamping distance, and 60 minutes of constant-force tension, yielding a creep rate of 1.550%. This indicates that blending raw materials with weight-average molecular weights of 200,000 and 150,000 broadens the molecular weight distribution and deteriorates creep resistance.

Comparative Example 6:

The polyethylene resin raw material was prepared by referring to Example 1, except that the reaction pressure was adjusted to 1 MPa and the reaction temperature was adjusted to 50°C, so that the weight average molecular weight of the polyethylene resin raw material obtained was 1.5 million, Mw/Mn was 2.5, and the carbon short The number of branches SCB is 10.

The fiber product was prepared by the same direct melt extrusion and drawing process as in Example 1. Melt fracture occurred during the high-magnification drawing and winding process under heat preservation conditions, and no fiber product could be obtained.

Table 1 Performance data of each embodiment and comparative example

As shown in the table above, the high-performance polyethylene fiber provided by the present invention has a creep rate of less than 1.0%, significantly superior to fibers produced from polyethylene resins with a broad molecular weight distribution and within the same molecular weight range. Conventional ultra-high molecular weight polyethylene fibers produced using solution spinning currently have a creep rate of 3.2% to 3.8%. The fibers of the present invention have a creep rate superior to conventional ultra-high molecular weight polyethylene fibers. Furthermore, they are significantly superior to ultra-high molecular weight polyethylene fibers produced using solvents in terms of cost, process complexity, and environmental friendliness.

The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims (10)

A preparation method for creep-resistant high-performance polyethylene fiber is characterized in that a single-active-center polyethylene catalyst is used to polymerize a polyethylene resin raw material and an additive, and polyethylene unstretched precursor is extruded at high temperature through a screw extruder. The polyethylene unstretched precursor is then directly stretched at a high ratio under heat preservation conditions, and then continuously subjected to high-temperature multiple-fold hot stretching and winding to obtain creep-resistant high-performance polyethylene fiber, which is the target product. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 1 is characterized in that the polyethylene resin raw material is a copolymer of ethylene and an α-olefin comonomer having a carbon number greater than or equal to 3, has a weight-average molecular weight of 100,000 to 600,000, a molecular weight distribution of less than 3, an average branching content of 1 to 25 per 1000 carbon atoms, a density greater than 0.91 g/cm ³ , and a melt index (MI) of 0.01 to 10 g/10 min at 190° C. under a load of 21.6 kg. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 1 or 2, wherein the polyethylene resin raw material is prepared by the following method: Solvent, single-active-site catalyst, co-catalyst, ethylene, hydrogen and comonomer are added into a reactor that is free of water and oxygen and protected by inert gas, and polymerization reaction is carried out at high temperature to obtain polyethylene resin raw material with a certain degree of branching. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 3, wherein the amount of the comonomer added is 0.1% to 5% of the molar amount of ethylene; The amount of hydrogen added is such that its concentration is 0 to 100 ppm. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 3, wherein the molar ratio of the co-catalyst to the single-active-site catalyst is (0.01-1000):1; The co-catalyst is triethylaluminum, triisobutylaluminum or methylaluminoxane; The comonomer is one or more α-olefins having a carbon number greater than or equal to 3, specifically one or more of propylene, butene, hexene, octene or 4-methyl-1-pentene; The polymerization reaction temperature is 70-90°C, the pressure is 0.8-1 MPa, and the time is 1-3 hours. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 1, wherein the auxiliary agent comprises a mixture of an antioxidant and a surface lubricant, and the mass ratio of the antioxidant to the surface lubricant is 1:0.2 to 1:5; The amount of additive added is 0.05%-5% of the mass of the polyethylene resin raw material. The method for preparing a creep-resistant high-performance polyethylene fiber according to claim 1 is characterized in that The high stretching ratio is 5-50 times and the holding temperature is 60-140°C; The high-temperature multiple thermal stretching ratio is 2-20 times, and the stretching temperature is 70-130°C. A creep-resistant high-performance polyethylene fiber is prepared by the preparation method according to any one of claims 1 to 7. Use of the creep-resistant high-performance polyethylene fiber according to claim 8 in the preparation of creep-resistant polyethylene fiber products. A method for improving the creep resistance of polyethylene fibers is characterized in that a single-active-center polyethylene catalyst is first used for polymerization to obtain a polyethylene resin raw material, which is then extruded with an additive through a screw extruder at high temperature to obtain polyethylene unstretched filaments, which is then directly subjected to high-multiple stretching under heat-insulating conditions, followed by high-temperature multiple hot stretching and winding to complete the process.