WO2025156639A1 - Cut-resistant fiber and preparation method therefor - Google Patents

Abstract

A cut-resistant fiber and a preparation method therefor. The preparation method comprises the following steps: carrying out surface treatment on an inorganic fiber material, to improve the affinity of the inorganic fiber material to a polyethylene base material; mixing narrow-molecular-weight-distribution polyethylene obtained by polymerization using a single-site catalyst, the treated inorganic fiber material, and a processing aid to form a blend; feeding the obtained blend into a double-screw extruder for melt blending, and obtaining an undrawn fiber melt by means of a spinneret; carrying out high-temperature high-ratio drawing on the undrawn fiber melt at a drawing ratio of greater than 180 times until an inorganic fiber reaches a unidirectionally oriented state, and then cooling the inorganic fiber; and carrying out high-temperature multi-ratio drawing again on the cooled inorganic fiber to obtain a cut-resistant polyethylene composite fiber. Compared with the prior art, the preparation method solves the problems such as environmental pollution, high cost and tedious steps generated in conventional ultrahigh-molecular-weight polyethylene fiber preparation and modification carried out on this basis.

Description

Cut-resistant fiber and preparation method thereof Technical Field

The present invention relates to the technical field of polymer materials, in particular to a cut-resistant fiber and a preparation method thereof.

Background Art

With the rapid advancement of science and technology, the demand for specialty fibers in the engineering and technical community is growing. High-performance polyethylene fibers, characterized by their lightweight, high strength, long service life, wear resistance, high strength, moisture resistance, and corrosion resistance, are widely used in towing ropes, load-bearing ropes, rescue ropes, and cut-resistant gloves. In recent years, the use of high-performance fibers has gradually increased in the cut-resistant field, such as civilian and police cut-resistant gloves and military clothing. The demand for high-performance fibers with excellent cut-resistant properties is also increasing. Due to its low raw material cost and high strength and modulus, high-performance polyethylene fibers have gradually gained application in this field.

At present, the methods for polyethylene spinning used in the field of cut resistance can be mainly divided into three categories:

The first category includes methods disclosed in Chinese Patents CN200980146604, CN201410264678, International Application Publication No. WO2005/066401A1, and U.S. Patent No. 430577, in which high-molecular-weight polyethylene is first swelled and dissolved with a solvent and then extruded into polyethylene filaments. The filaments are then subjected to solvent extraction and drying to remove the solvent, and finally to multi-stage stretching to obtain high-strength and high-modulus polyethylene fibers. This type of method can produce high-strength and high-modulus ultra-high molecular weight polyethylene fiber products, which have excellent mechanical properties and relatively good cut resistance. The general cut resistance grade can reach EN388-2, making them the mainstream fiber raw material for cut-resistant products. However, ultra-high molecular weight polyethylene fibers are difficult to process, have complex production processes, and are expensive. Problems such as solvent volatilization and recovery during the production process are difficult to resolve, resulting in a significant impact on the environment. In addition, the cut resistance performance does not meet the requirements of products with high cut resistance requirements.

The second category, primarily encompassing those disclosed in Chinese patents CN106149085A, CN107326462A, and CN108315833A, further enhances the properties of ultra-high molecular weight polyethylene (UHMWPE) spinning. The main approach involves mixing nanomaterials and inorganic materials, such as graphene, nanosilica, carbon fiber, and glass fiber, into the UHMWPE raw material. This process then produces fiber products with high cut-resistant properties through a spinning process. While the fiber products produced by this method offer superior cut-resistant properties compared to UHMWPE fibers, the processing costs and complexity are extremely high. The main challenge is the difficulty of uniformly dispersing the nanoscale inorganic materials in the solvent while also preventing agglomeration within the fiber product. This requires demanding modification procedures such as emulsification and grafting of the inorganic and nanomaterials. Furthermore, the solvents mixed with the nanomaterials and inorganic materials are difficult to recycle, resulting in extremely high costs for waste solvent disposal.

The third category mainly includes Chinese patents CN201780040580.9, CN201880081866.6, CN201080007173.6, etc., which use inorganic fibers and polyethylene fibers to mix and knit to form wear-resistant fiber products. After these fiber products are made into gloves or fabrics, the inorganic fibers are easy to pierce out, affecting the comfort, and the mixing cost is also relatively high.

Summary of the Invention

The purpose of the present invention is to provide a cut-resistant fiber and a preparation method thereof in order to solve the above problems, thereby solving the problems of environmental pollution, high cost, and complicated steps caused by the preparation of traditional ultra-high molecular weight polyethylene fibers and their modification.

The purpose of the present invention is achieved through the following technical solutions:

A first aspect of the present invention provides a method for preparing a cut-resistant fiber, comprising the following steps:

S1: surface treating the inorganic fiber material to improve the affinity of the inorganic fiber material to the polyethylene base material;

S2: Mixing the narrow molecular weight distribution polyethylene obtained by polymerization with a single active site catalyst, the inorganic fiber material treated in S1, and a processing aid to form a blend;

S3: feeding the blend obtained in S2 into a twin-screw extruder for melt blending, and obtaining an undrawn fiber melt through a spinneret;

S4: stretching the unstretched fiber melt at a high ratio at a high temperature, with a stretching ratio greater than 180 times, until the inorganic fiber reaches a unidirectional orientation state, and then cooling;

S5: The inorganic fiber cooled in S4 is subjected to high-temperature multiple stretching again to obtain a cut-resistant polyethylene composite fiber.

Furthermore, the inorganic fiber comprises a mixture of one or more of carbon fiber, glass fiber, wollastonite fiber, and basalt fiber.

Furthermore, in S1, the aspect ratio of the inorganic fiber material is greater than 50.

Furthermore, in S1, the length of the inorganic fiber material ranges from 1 to 1500 μm, preferably from 300 to 1500 μm.

Furthermore, in S1, the diameter of the inorganic fiber material is 1-40 μm, preferably 5-25 μm.

Furthermore, in S1, the surface treatment is one or more of coupling agent treatment, surface chemical modification treatment, surface coating treatment, and plasma treatment.

Furthermore, in S1, the weight average molecular weight of the narrow molecular weight distribution polyethylene is between 150,000 and 1,000,000, and the molecular weight distribution is lower than 3.0.

Furthermore, in S3, the extrusion temperature of the twin-screw extruder is 160°C-240°C, and the spinneret temperature is 180°C-250°C.

Furthermore, in S4, the temperature during high-ratio stretching is 60°C-150°C.

Furthermore, in S4, the cooling temperature is 5°C-40°C, and the cooling medium is air or water.

Furthermore, in S5, the ratio of high-temperature multiple stretching is 5-20 times, and the temperature is 70°C-130°C.

A second aspect of the present invention provides a cut-resistant fiber obtained by the above preparation method.

The core concept of the present invention is:

The main reason why polyethylene melt spinning cannot currently form cut-resistant fibers is that the molecular weight of the fibers produced by melt spinning is relatively low. Low-molecular-weight polyethylene often has low wear resistance, which is detrimental to cut resistance. The present invention uses polyethylene with a weight-average molecular weight greater than 100,000 to first improve the wear resistance of the polyethylene base material. At the same time, the polyethylene molecular chain structure with a narrow molecular weight distribution is adopted, with the polyethylene molecular weight distribution being less than 3.0, further reducing the effect of low molecular weight on slippage or untangling between molecular chains, thereby improving the wear resistance and cut resistance of the polyethylene base material.

To further enhance the fiber's cut resistance, the present invention not only improves the wear resistance of the polyethylene base material but also melt-blends an inorganic fiber material with a narrow molecular weight distribution polyethylene. This invention leverages the high draw ratio of the narrow molecular weight distribution polyethylene melt. After the polyethylene melt is ejected from the spinneret, it is stretched at high speed, achieving a draw ratio of over 180 times. This fully orients the inorganic fiber material blended in the polyethylene melt, parallel to the fiber product's direction. This oriented inorganic fiber filler significantly enhances the fiber product's cut resistance.

This invention utilizes polyethylene raw materials with a reasonable molecular weight distribution and molecular weight range, and a targeted processing technology to uniformly disperse the inorganic fiber material within the polyethylene fiber and form an oriented structure, resulting in a polyethylene fiber product with cut-resistant properties. Compared with existing cut-resistant fibers and preparation methods, the cut-resistant fiber products of this patent have the following advantages:

1) No solvent is required during the spinning process, and there is no mixing or cooling process, which greatly simplifies the high-performance polyethylene fiber spinning process.

2) Greatly reduce the high production costs caused by solvent treatment and solvent recovery, and the process is more environmentally friendly.

3) The production process is in a solvent-free state, which greatly improves the safety factor of the production process.

4) The inorganic fiber processing method is simple, which reduces the processing steps and reduces the processing cost.

DETAILED DESCRIPTION

The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention. These modifications and improvements are all within the scope of protection of the present invention.

Any features such as preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution shall be deemed to be common technical features disclosed in the prior art.

The characterization data of the polyethylene raw materials in the examples were obtained by the following method:

The tensile properties test uses the methods and equipment in "ANSI/ISEA 2016" to test the cut resistance level of the finished yarn.

Example 1

Glass fiber (length 600 μm, diameter 10 μm), silane coupling agent KH560, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixing was performed for 1 minute each time, followed by a 30-second pause. The total mixing time was about 10 minutes to obtain the treated glass fiber.

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 2.8, a thousand carbon methyl groups less than 0.1, and a density of 0.945 g/ ^cm3 , obtained by polymerization using a late transition metal catalyst, was blended with treated glass fiber, antioxidant 1010, and zinc stearate in a ratio of 95:4.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw fiber was stretched multiple times at 80°C and then wound up. The stretching ratio was 400 times the extrusion rate. The cooling temperature and medium after stretching were 20°C air. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 7 times and the hot tunnel temperature was 100°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A5.

Example 2

Carbon fibers (1000 μm in length and 7 μm in diameter) and fluorine gas were placed in a sealed reactor. The fluorine gas pressure was 0.7-0.8 MPa and the temperature was 150°C. The reaction lasted for two hours to obtain surface-fluorinated carbon fibers.

Polyethylene with a weight average molecular weight of 150,000, Mw/Mn of 2.9, a thousand carbon methyl number of <0.1, and a density of 0.948 g/ ^cm3 obtained by metallocene catalyst polymerization was blended with fluorinated carbon fiber, fluororubber, antioxidant 1010, and antioxidant PS802 in a ratio of 95:4.5:0.1:0.2:0.2 to obtain a carbon fiber/polyethylene blend, and the blending time was 3 minutes.

The carbon fiber/polyethylene blend was fed into a screw extruder for melt extrusion. The twin-screw extruder had a temperature of 145°C to 190°C from the feed section to the discharge section, a rotation speed of 90 rpm, and an extrusion die aperture of 0.4 mm.

The extruded raw fiber was stretched multiple times at 60°C and then wound up. The stretching ratio was 300 times the extrusion rate. The cooling temperature and medium after stretching were 20°C water bath. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 8 times and the hot channel temperature was 110°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A5.

Example 3

Wollastonite fiber (length 300 μm, diameter 5 μm), titanate coupling agent JN-9, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixture was blended for 1 minute each time, then stopped for 30 seconds. The total mixing time was about 10 minutes to obtain the treated wollastonite fiber.

Polyethylene with a weight average molecular weight of 400,000, Mw/Mn of 2.9, a thousand carbon methyl number of <0.1, and a density of 0.941 g/ ^cm3 obtained by metallocene catalyst polymerization was blended with treated wollastonite fiber, stearic acid, calcium stearate, and antioxidant 1010 in a ratio of 94:5, 0.3, 0.4, and 0.3 for 3 minutes to obtain a raw material.

The raw materials were fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section was 145°C to 190°C, the speed was 110 rpm, and the aperture of the extrusion die was 1 mm.

The extruded raw yarn was stretched multiple times at 100°C and then wound up. The stretching ratio was 180 times the extrusion rate. The cooling temperature and medium after stretching were 40°C hot air. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 5 times and the hot tunnel temperature was 120°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A5.

Example 4

Basalt fiber (length 1500 μm, diameter 25 μm), aluminate coupling agent 411-C, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixing was performed for 1 minute each time, and then stopped for 30 seconds. The total mixing time was about 10 minutes to obtain the treated basalt fiber.

Polyethylene with a weight average molecular weight of 1 million, Mw/Mn of 2.7, a thousand carbon methyl number of less than 0.1, and a density of 0.943 g/ ^cm3 obtained by metallocene catalyst polymerization was blended with treated wollastonite fiber, stearic acid, calcium stearate, and antioxidant 1010 in a ratio of 94:5, 0.3, 0.4, and 0.3 for 3 minutes to obtain a raw material.

The raw materials were fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section was 145°C to 190°C, the speed was 200 rpm, and the aperture of the extrusion die was 5 mm.

The extruded raw yarn was stretched multiple times at 120°C and then wound up, with a stretching ratio of 200 times the extrusion rate. The wound fiber was then stretched again at high temperature multiple times, with a stretching ratio of 9 times and a hot tunnel temperature of 125°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A5.

Example 5

Carbon fibers (1000 μm in length and 20 μm in diameter) and fluorine gas were placed in a closed reactor. The fluorine gas pressure was 0.7-0.8 MPa and the temperature was 150°C. The reaction lasted for two hours to obtain surface-fluorinated carbon fibers.

Glass fiber, fluorinated carbon fiber, silane coupling agent KH560, liquid paraffin, and polyethylene wax are placed in a high-speed mixer in a ratio of 2:4:2:1:1 and mixed at high speed. The temperature is controlled between 70°C and 90°C. The mixture is blended for 1 minute each time, stopped for 30 seconds, and the mixing time is about 10 minutes in total to obtain the treated mixed fiber.

The polyethylene obtained by polymerization with a late transition metal catalyst having a weight average molecular weight of 400,000, Mw/Mn of 2.4, a thousand carbon methyl number of less than 0.1, and a density of 0.941 g/ ^cm3 was blended with the treated mixed fiber, stearic acid, calcium stearate, and antioxidant 1010 in a ratio of 94:5, 0.3, 0.4, and 0.3, and the blending time was 3 minutes to obtain the raw material.

The melt was fed into a screw extruder for melt extrusion. The temperature of the twin screw from the feeding section to the discharge section was 145°C to 200°C, the speed was 220 rpm, and the aperture of the extrusion die was 10 mm.

The extruded raw fiber was stretched multiple times at 150°C and then wound up, with a stretching ratio of 600 times the extrusion rate. The wound fiber was then stretched again at a high temperature multiple times, with a stretching ratio of 15 times and a hot tunnel temperature of 130°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A6.

Comparative Example 1

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 2.8, a kilo-carbon methyl number of less than 0.1, and a density of 0.945 g/ ^cm³ , obtained by polymerization using a late transition metal catalyst, was blended with antioxidant 1010 and zinc stearate in a ratio of 99.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw fiber was stretched multiple times at 80°C and then wound up. The stretching ratio was 400 times the extrusion rate. The cooling temperature and medium after stretching were 20°C air. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 7 times and the hot tunnel temperature was 100°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A1.

Comparative Example 2

Glass fiber, silane coupling agent KH560, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixture was blended for 1 minute each time, then stopped for 30 seconds. The total mixing time was about 10 minutes to obtain treated glass fiber.

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 2.8, a thousand carbon methyl groups less than 0.1, and a density of 0.945 g/ ^cm3 , obtained by polymerization using a late transition metal catalyst, was blended with treated glass fiber, antioxidant 1010, and zinc stearate in a ratio of 95:4.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw yarn was stretched multiple times at 80°C and then wound up. The stretching ratio was 40 times the extrusion rate. The cooling temperature and medium after stretching were 20°C air. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 7 times and the hot tunnel temperature was 100°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A3.

Comparative Example 3

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 2.8, a kilo-carbon methyl number of less than 0.1, and a density of 0.945 g/ ^cm³ , obtained by polymerization using a late transition metal catalyst, was blended with untreated glass fiber, antioxidant 1010, and zinc stearate in a ratio of 95:4.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw yarn was stretched multiple times at 80°C and then wound up. The stretching ratio was 180 times the extrusion rate, and the yarn broke.

Comparative Example 4

Glass fiber, silane coupling agent KH560, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixture was blended for 1 minute each time, then stopped for 30 seconds. The total mixing time was about 10 minutes to obtain treated glass fiber.

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 5.4, a thousand carbon methyl groups less than 0.1, and a density of 0.952 g/cm ³ , obtained by polymerization using a late transition metal catalyst, was blended with treated glass fiber, antioxidant 1010, and zinc stearate in a ratio of 95:4.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw yarn was stretched multiple times at 80°C and then wound up. The stretching ratio was 180 times the extrusion rate, and the yarn broke.

Comparative Example 5

Glass fiber, silane coupling agent KH560, liquid paraffin, and polyethylene wax were placed in a high-speed mixer at a ratio of 6:2:1:1 and mixed at high speed. The temperature was controlled between 70°C and 90°C. The mixture was blended for 1 minute each time, then stopped for 30 seconds. The total mixing time was about 10 minutes to obtain treated glass fiber.

Polyethylene having a weight average molecular weight of 150,000, an Mw/Mn ratio of 5.4, a thousand carbon methyl groups less than 0.1, and a density of 0.952 g/cm ³ , obtained by polymerization using a late transition metal catalyst, was blended with treated glass fiber, antioxidant 1010, and zinc stearate in a ratio of 95:4.5:0.2:0.3 for 3 minutes to obtain a raw material.

The raw materials are fed into a screw extruder for melt extrusion. The temperature of the twin-screw from the feeding section to the discharge section is 145°C to 180°C, the speed is 90 rpm, and the aperture of the extrusion die is 0.5 mm.

The extruded raw yarn was stretched multiple times at 80°C and then wound up. The stretching ratio was 30 times the extrusion rate. The cooling temperature and medium after stretching were 20°C air. The wound fiber was stretched multiple times again at high temperature. The stretching ratio was 4 times and the hot tunnel temperature was 100°C.

The fiber after high temperature multiple stretching is subjected to cut resistance test, and the cut resistance can reach A3.

Comparative Example 6

A method for preparing wear-resistant and cut-resistant ultra-high molecular weight polyethylene fiber comprises the following steps: adding 0.5 parts of silane KH550 coupling agent, 5 parts of nano-silica, 6 parts of basalt staple fibers, 0.2 parts of sodium stearate, 0.2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.8 parts of nano-dispersant VK-01 to 1000 parts of white oil; and treating the mixture in a high-speed rotary emulsifier at 8000 r/min for 4 hours at a temperature controlled at 60°C to form a mother liquor. 80 parts of a resin with a weight-average molecular weight of 4,000,000 and a molecular weight distribution of 5.6, an average particle size of 180 μm, a particle size distribution width (d90-d10)/d50 of 1.2, and a bulk density of 0.34 g/cm3, were added to a ball mill at 50°C. The mother liquor was then slowly added to the mill at a rate of 2 parts per minute and stirred to mix thoroughly. The mixture was then evacuated in a sealed container for 4 hours. The mixture was then wet-spun through a twin-screw extruder, metering pump, and spinning manifold. The fiber was then extracted, dried, drawn, and heat-stretched before being wound up. Testing revealed that the fiber had an A3 cut-resistant grade.

Table 1

As shown in the table above, blending polyethylene with treated inorganic fibers yields polyethylene fiber products with superior cut resistance compared to pure polyethylene, reaching A3 levels. Polyethylene with a weight-average molecular weight of 150,000 to 1,000,000 and a molecular weight distribution below 3.0, when blended with treated inorganic fibers, exhibits even better stretchability in the spinneret melt, reaching stretch ratios exceeding 180x. When the stretch ratio exceeds 180x in the melt, the fiber product's cut resistance is further enhanced, reaching A5-A6 levels.

The cut-resistant fiber prepared by this method is far superior to the method of preparing high-performance fibers by solution dissolution and current melt extrusion in terms of cost, process complexity and environmental protection, and its cutting performance is also better than that of ultra-high molecular weight polyethylene cut-resistant fiber products prepared by the solution method.

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 method for preparing a cut-resistant fiber, characterized by comprising the following steps: S1: surface treating the inorganic fiber material to improve the affinity of the inorganic fiber material to the polyethylene base material; S2: Mixing the narrow molecular weight distribution polyethylene obtained by polymerization with a single active site catalyst, the inorganic fiber material treated in S1, and a processing aid to form a blend; S3: feeding the blend obtained in S2 into a twin-screw extruder for melt blending, and obtaining an undrawn fiber melt through a spinneret; S4: stretching the unstretched fiber melt at a high ratio at a high temperature, with a stretching ratio greater than 180 times, until the inorganic fiber reaches a unidirectional orientation state, and then cooling; S5: The inorganic fiber cooled in S4 is subjected to high-temperature multiple stretching again to obtain a cut-resistant polyethylene composite fiber. The method for preparing a cut-resistant fiber according to claim 1, characterized in that in S1, the inorganic fiber comprises a mixture of one or more of carbon fiber, glass fiber, wollastonite fiber, and basalt fiber. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S1, the aspect ratio of the inorganic fiber material is greater than 50. The method for preparing a cut-resistant fiber according to claim 1, characterized in that in S1, the surface treatment is one or more of coupling agent treatment, surface chemical modification treatment, surface coating treatment, and plasma treatment. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S1, the weight average molecular weight of the narrow molecular weight distribution polyethylene is between 150,000 and 1,000,000, and the molecular weight distribution is less than 3.0. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S3, the extrusion temperature of the twin-screw extruder is 160°C-240°C, and the spinneret temperature is 180°C-250°C. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S4, the temperature during high-ratio stretching is 60°C-150°C. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S4, the cooling temperature is 5°C-40°C, and the cooling medium is air or water. The method for preparing a cut-resistant fiber according to claim 1, characterized in that, in S5, the high-temperature multiple stretching ratio is 5-20 times, and the temperature is 70°C-130°C. A cut-resistant fiber obtained by the preparation method according to any one of claims 1 to 9.