A fluorine-containing wear-resistant polyoxymethylene composition, its preparation method and application

Abstract

The present invention relates to the technical field of polymer materials, and in particular to a fluorine-containing wear-resistant polyoxymethylene composition, a preparation method and an application thereof. The fluorine-containing wear-resistant polyoxymethylene composition comprises: 100 parts of a polyoxymethylene polymer containing terminal hydroxyl groups, 0.05 - 10 parts of an isocyanate compound, 2 - 25 parts of polytetrafluoroethylene, 0.05 - 2 parts of a lubricant and 0.05 - 1 part of an antioxidant; the functionality of the isocyanate compound is ≥3. In the present invention, adding the isocyanate compound can react with the polyoxymethylene polymer containing terminal hydroxyl groups, improve the stability of the polytetrafluoroethylene-filled polyoxymethylene (POM) system, and thus reduce the formaldehyde release amount of POM; the added isocyanate compound can increase the surface hardness of the fluorine-containing wear-resistant polyoxymethylene composition, and can also penetrate into the PTFE molecular chains to reduce the internal frictional force between the PTFE molecular chains, thereby reducing the friction coefficient and wear of the polyoxymethylene system.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a fluorine-containing wear-resistant polyoxymethylene composition, a preparation method thereof, and an application thereof. Background Art

[0002] Polyoxymethylene (POM) is a highly crystalline linear thermoplastic polymer, which has excellent mechanical properties, wear resistance, self-lubrication, oil resistance, chemical resistance, creep resistance, low water absorption, and can maintain its mechanical, chemical, and electrical properties within a relatively wide temperature range. It is an engineering plastic with excellent comprehensive properties and is widely used in industries such as automobiles, electronics, and household appliances.

[0003] POM is mainly composed of (-CH2-O-) chain segments, with a small amount of (-CH2CH2O-) or (-CH2CH2CH2CH2O-) chain segments mixed therein, and the end groups are macromolecules with methoxy ether or hydroxyethyl ether structures. This results in that during the melt processing, POM is prone to chain scission under the action of heat and oxygen, and this thermal decomposition is autocatalytic, releasing a large amount of formaldehyde. Especially in materials that use molybdenum disulfide to improve the wear resistance of POM, molybdenum disulfide will accelerate the decomposition of POM, generating more formaldehyde. Therefore, in the invention and creation of polyoxymethylene compositions, the inhibition of formaldehyde release is an important aspect; especially for fluorine-containing wear-resistant polyoxymethylene, due to the addition of fluorine compounds, it will affect the stability of the polyoxymethylene molecular chain, and other components need to be added to improve its stability.

[0004] Currently, many methods for improving the thermal stability of polyoxymethylene have been proposed. In various schemes, additives that can react with degradation gases such as formaldehyde generated by thermal degradation, such as amines, amides, and hydrazines, are mainly used. For example, Japanese Unexamined Patent Publication No. Hei 10-1592 describes adding acrylamide and a boric acid compound to a polyoxymethylene resin; Japanese Unexamined Patent Publication No. Sho 59-213752 describes adding alanine to a polyoxymethylene resin. However, the added additives have the property of thermal instability, which is likely to cause the polymer to turn yellow and easily exude in the polymer, resulting in the formation of precipitates in the mold. Therefore, the improvement of the thermal stability of polyoxymethylene is limited.

[0005] DuPont of the United States has published multiple patents on the thermal stability of polyoxymethylene. The main idea is to add amide substances to absorb the formaldehyde gas generated during the processing, thereby reducing formaldehyde release and stabilizing the polymer processing. For example, in Chinese Patent CN87102759, a hydroxyl-containing compound ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVA), and copolyamide are used to achieve stable polyoxymethylene processing and reduce formaldehyde release. In Chinese Patent CN201680008580, polyacrylamide, copolyamide, EVOH, and allantoin are introduced to reduce formaldehyde release. In Chinese Patent CN201480068593, by controlling the dosages of polyacrylamide and copolyamide, formaldehyde release and mold fouling are controlled, and a certain amount of creep is achieved simultaneously.

[0006] However, the principles adopted in these patented methods are all to react the added substances with the generated formaldehyde molecules to reduce the formaldehyde content finally present in the product, so as to obtain a lower test result in the formaldehyde release test. At present, there is no solution to study the internal factors that generate formaldehyde molecules and fundamentally solve the formaldehyde release problem during POM decomposition. Moreover, heat, oxygen, acidic substances, and shear will all accelerate the generation of formaldehyde molecules. Therefore, there is an urgent need for a fluorine-containing wear-resistant polyoxymethylene composition with low formaldehyde release and its preparation method. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a fluorine-containing wear-resistant polyoxymethylene composition, its preparation method and application. The fluorine-containing wear-resistant polyoxymethylene composition of the present invention has the advantages of good wear resistance and low formaldehyde release at the same time.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] First objective, the present invention provides a fluorine-containing wear-resistant polyoxymethylene composition, comprising the following components in parts by weight:

[0010] 100 parts of a polyoxymethylene polymer containing terminal hydroxyl groups, 0.05 - 10 parts of an isocyanate compound, 2 - 25 parts of polytetrafluoroethylene, 0.05 - 2 parts of a lubricant, and 0.05 - 1 part of an antioxidant;

[0011] The functionality of the isocyanate compound ≥ 3; preferably, the functionality of the isocyanate compound is 3 - 4.

[0012] In the present invention, by adding a polyfunctional isocyanate compound (functionality ≥ 3) to the system, the polyfunctional isocyanate compound reacts with a polyoxymethylene polymer containing terminal hydroxyl groups, which can improve the stability of the polytetrafluoroethylene-filled polyoxymethylene (POM) system in the preparation of a fluorine-containing wear-resistant polyoxymethylene composition system, thereby reducing the formaldehyde release amount of POM; the polyfunctional isocyanate compound can penetrate into the polytetrafluoroethylene (PTFE) molecular chains, reducing the internal friction force between the PTFE molecular chains, thereby reducing the friction coefficient and wear of the polyoxymethylene system. By adjusting the addition amounts of the polyfunctional isocyanate compound and polytetrafluoroethylene, the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition can be synergistically increased.

[0013] When the functionality of the isocyanate compound is ≥ 3, it can eliminate the terminal hydroxyl groups in the POM molecular chains and further connect multiple POM molecular chains together, thereby increasing the hardness of POM (when the functionality of the isocyanate compound is 2, it cannot increase the hardness of POM), and improving the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition.

[0014] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the weight part of the isocyanate compound is 0.5 - 2 parts.

[0015] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the weight part of the polytetrafluoroethylene is 10 - 20 parts.

[0016] The present invention optimizes the weight parts of the isocyanate compound and polytetrafluoroethylene. The isocyanate compound can better penetrate into the PTFE molecular chains, reducing the internal friction force between the PTFE molecular chains, thereby reducing the friction coefficient and wear of the fluorine-containing wear-resistant polyoxymethylene composition system, and the hardness of the prepared fluorine-containing wear-resistant polyoxymethylene composition is also relatively high, with better comprehensive performance.

[0017] By introducing a polyfunctional isocyanate compound into the fluorine-containing wear-resistant polyoxymethylene composition, through the reaction activity of the isocyanate compound, it can react with the terminal hydroxyl groups of POM, thereby reducing the formaldehyde release amount of the fluorine-containing wear-resistant polyoxymethylene composition.

[0018] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the isocyanate compound includes at least one of trimers of 4,4'-methylenebis(phenyl isocyanate), isophorone diisocyanate, 1,6-hexamethylene diisocyanate, 2,4-toluene diisocyanate or 2,6-toluene diisocyanate. The isocyanate compound is preferably a trimer of isophorone diisocyanate.

[0019] When the isocyanate compound is selected from the above substances, it can react with the terminal hydroxyl groups in the POM molecular chain and further connect multiple POM molecular chains together, thereby improving the surface hardness of POM and the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition.

[0020] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the D50 particle size of the polytetrafluoroethylene is 2-10 μm.

[0021] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the weight-average molecular weight of the polytetrafluoroethylene is at least 100,000, and preferably, the weight-average molecular weight of the polytetrafluoroethylene is 100,000-200,000.

[0022] The D50 particle size and molecular weight of polytetrafluoroethylene have a great influence on the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition. When polytetrafluoroethylene with the above particle size and molecular weight is selected, the friction coefficient and wear of the fluorine-containing wear-resistant polyoxymethylene composition can be reduced.

[0023] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the polyoxymethylene polymer containing terminal hydroxyl groups is a homopolymer composed of formaldehyde monomers represented by formula (I), or a copolymer composed of formaldehyde monomers represented by formula (I) and monomers represented by formula (II), or a mixture of the above homopolymers and copolymers;

[0024] Formula (I): -(-CH2O-)-; Formula (II): [(CX1X2) a O];

[0025] X1 and X2 are the same or different and are each independently selected from the following groups: hydrogen, alkyl or aryl, and a is an integer of 2 to 6.

[0026] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the homopolymer is a homopolymer formed by chemical reaction with an ester group or an ether group at the end; the copolymer is a copolymer that is not completely capped but has free hydroxyl ends in the copolymer monomer units, or a copolymer capped with an ether group.

[0027] Preferably, the polyoxymethylene polymer containing terminal hydroxyl groups has a melt index of 2-50 g / 10 min under the test conditions of 190 °C and 2.16 kg according to the ISO 1133-2011 standard.

[0028] As a preferred embodiment of the fluorine-containing wear-resistant polyoxymethylene composition of the present invention, the lubricant is a stearamide lubricant; the antioxidant is a phenolic antioxidant.

[0029] Selecting a phenolic antioxidant can improve the thermal stability of the fluorine-containing wear-resistant polyoxymethylene composition.

[0030] Preferably, the phenolic antioxidant is at least one of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 2,5-di-tert-butyl-4-hydroxybenzyl dimethylamine, diethyl 3,5-di-tert-butyl-4-hydroxybenzyl phosphate, stearyl 3,5-di-tert-butyl-4-hydroxybenzyl phosphate, 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distearyl-thiotriazolylamine, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylglycidyl allyl ether)-1,3,5-triazine, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythrityl-tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3,5-dimethyl-4-hydroxyphenyl)propionate], ditrimethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] or 2,2'-thiodiethyl-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0031] Among them, the phenolic antioxidant is preferably a compound of ditrimethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine. For example, the phenolic antioxidant is a compound of Irganox@245 and Irganox@1098 (the ratio is 2:1).

[0032] Second objective, the present invention also provides a preparation method of the above-mentioned fluorine-containing wear-resistant polyoxymethylene composition, which includes the following steps:

[0033] 1) According to the ratio, add the polyoxymethylene polymer with terminal hydroxyl groups, isocyanate compound, polytetrafluoroethylene, lubricant and antioxidant into a premixer and mix to obtain a premix;

[0034] 2) Add the premix into a twin-screw extruder, melt and extrude at 180°C to 200°C, cool and pelletize to obtain the fluorine-containing wear-resistant polyoxymethylene composition.

[0035] Third objective, the present invention also provides the application of the above-mentioned fluorine-containing wear-resistant polyoxymethylene composition in automobiles, electronic and electrical appliances, and household electrical products.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention provides a fluorine-containing wear-resistant polyoxymethylene composition, a preparation method and an application thereof. An isocyanate compound with a functionality ≥ 3 is added to the preparation system of the fluorine-containing wear-resistant polyoxymethylene composition. Due to the reactive activity of the isocyanate compound, the isocyanate compound can react with the polyoxymethylene polymer containing terminal hydroxyl groups, which can improve the stability of the polytetrafluoroethylene-filled polyoxymethylene (POM) system, thereby reducing the formaldehyde release amount of POM; the added isocyanate compound can increase the surface hardness of the fluorine-containing wear-resistant polyoxymethylene composition, and can also penetrate into the polytetrafluoroethylene (PTFE) molecular chain, reducing the internal friction force between the PTFE molecular chains, thereby reducing the friction coefficient and wear of the polyoxymethylene system. By adjusting the addition amounts of the polyfunctional isocyanate compound and polytetrafluoroethylene, the present invention can synergistically increase the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition, and the fluorine-containing wear-resistant polyoxymethylene composition is not easily precipitated. Detailed Embodiments

[0038] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0039] In the following examples and comparative examples, unless otherwise specified, the experimental methods used are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0040] The sources of raw materials used in the following examples and comparative examples are as follows:

[0041] POM resin: grade POM KP20, copolymer POM level, melt index 9 g / 10 min (190 °C / 2.16 kg), Ticona GmbH, Germany.

[0042] POM resin: grade POM MC90, copolymer polyoxymethylene resin, melt index 9 g / 10 min (190 °C / 2.16 kg), Kaifeng Longyu Chemical Co., Ltd.

[0043] Isocyanate compound:

[0044] Isocyanate compound 1: grade VESTANAT T 1890 / 100, trimer of isophorone diisocyanate, functionality of NCO is 3 - 4, produced by Evonik Degussa GmbH;

[0045] Isocyanate compound 2: grade MDI-100, 4,4'-diphenylmethane diisocyanate, functionality of NCO is 2, produced by Wanhua Chemical Group Co., Ltd.;

[0046] Polytetrafluoroethylene (PTFE):

[0047] Grade: GR-C0410H, D50 particle size: 2 - 3μm, molecular weight: 100,000, produced by Zhejiang Gore New Materials Co., Ltd.;

[0048] Grade: GR-C04W20, D50 particle size: 3 - 5μm, molecular weight: 100,000, produced by Zhejiang Gore New Materials Co., Ltd.;

[0049] Grade: GR-C04W40M, D50 particle size: 8 - 10μm, molecular weight: 200,000, produced by Zhejiang Gore New Materials Co., Ltd.;

[0050] Grade: GR-C04W70, D50 particle size: 20 - 40μm, molecular weight: 100,000, produced by Zhejiang Gore New Materials Co., Ltd.;

[0051] Grade: GR-C0420H, D50 particle size: 3 - 5μm, molecular weight: 30,000, produced by Zhejiang Gore New Materials Co., Ltd.;

[0052] Grade: GR-C0420L, D50 particle size: 3 - 5μm, molecular weight: 800,000, produced by Zhejiang Gore New Materials Co., Ltd.

[0053] Lubricant: Grade: EBS B50, ethylene bisstearamide, produced by Guangzhou Runfeng Chemical Co., Ltd.;

[0054] Antioxidant: The antioxidant is a compound of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine (ratio 2:1). The trade name of triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] is Irganox 245, produced by BASF Germany; the trade name of N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine is Irganox1098, produced by BASF Germany.

[0055] The performance tests of the products in the examples and comparative examples are as follows:

[0056] The flexural strength and flexural modulus tests are carried out according to the ISO 178 - 2019 standard. The specimen size is 80mm * 10mm * 4mm, and the test speed is 2mm / min. The test equipment is an electronic tensile testing machine of Zwick Company, Germany.

[0057] The Rockwell hardness test standard is ISO 2039.1 - 2001. The specimen size is 60mm * 60mm * 4mm, and the test equipment is an Aolongxin touch screen digital display plastic Rockwell hardness tester of Shanghai Aolongxingdi Testing Equipment Co., Ltd.

[0058] The formaldehyde emission was measured according to the VDA 275 test standard, and the specific process is as follows:

[0059] The polyoxymethylene resin was injection-molded at an injection temperature between 190 - 200 °C to produce a product with dimensions of 100 mm * 100 mm * 2 mm, and then cut into a product with dimensions of 100 mm * 40 mm * 2 mm. The injection-molded sample was fixed in a 1-liter polyethylene bottle containing 50 ml of distilled water, ensuring that the specimen did not come into contact with the water. Then the bottle was sealed and baked in an oven at 60 °C for 3 hours. Subsequently, 10 ml of the aqueous solution was sampled from the polyethylene bottle, 10 ml of a standard solution of acetylacetone and 10 ml of ammonium acetate were added, and after standing for a period of time, the coloration degree of the water in the bottle was analyzed using a UV spectrophotometer, and then the formaldehyde content was calculated.

[0060] The friction coefficient and specific wear rate were tested according to the JIS K7218 standard. The counter-material was S45C steel, the friction mode was the pin-on-disk mode, the linear velocity was 0.8 m / s, and the load was 4 KG.

[0061] The components (in parts by weight) of the fluorine-containing wear-resistant polyoxymethylene compositions of Examples 1 - 13 and Comparative Examples 1 - 8 are shown in Tables 1 - 2. The preparation method of the fluorine-containing wear-resistant polyoxymethylene composition is as follows:

[0062] According to the ratio, a polyoxymethylene polymer with terminal hydroxyl groups, PTFE, an isocyanate compound, a lubricant, and an antioxidant were added to a premixer and mixed for 1 - 2 min to obtain a premix. Then the premix was added to a twin-screw extruder and melt-extruded at 180 °C - 200 °C, with the main machine speed of 300 - 400 revolutions per minute, and cooled and pelletized to obtain the fluorine-containing wear-resistant polyoxymethylene composition. Among them, the temperature of Zone 1 was controlled at 180 - 190 °C, the temperature of Zone 2 was 180 - 190 °C, the temperature of Zone 3 was 180 - 190 °C, the temperature of Zone 4 was 180 - 190 °C, the temperature of Zone 5 was 180 - 190 °C, the temperature of Zone 6 was 180 - 190 °C, the temperature of Zone 7 was 190 - 200 °C, the temperature of Zone 8 was 190 - 200 °C, and the temperature of Zone 9 was 190 - 200 °C.

[0063] Table 1 Formulation and performance test results of fluorine-containing wear-resistant polyoxymethylene compositions (Examples 1 - 13)

[0064]

[0065]

[0066] Table 2 Formulation and performance test results of fluorine-containing wear-resistant polyoxymethylene compositions (Comparative Examples 1 - 8)

[0067]

[0068]

[0069] According to the data in Table 1 and Table 2, comparing Examples 1-5 with Comparative Example 2, adding an isocyanate compound to the preparation system of the fluorine-containing wear-resistant polyoxymethylene composition can effectively reduce the formaldehyde release amount of the fluorine-containing wear-resistant polyoxymethylene composition. Due to the reactivity of the isocyanate compound, the isocyanate compound can react with the polyoxymethylene polymer containing terminal hydroxyl groups, which can improve the stability of the polytetrafluoroethylene-filled polyoxymethylene (POM) system, thereby achieving the reduction of the formaldehyde release amount of the fluorine-containing wear-resistant polyoxymethylene composition. Moreover, the hardness of the fluorine-containing wear-resistant polyoxymethylene composition is also increased.

[0070] Comparing Examples 1-5 with Comparative Example 8, when the functional group of the isocyanate compound is 2, only the formaldehyde release amount can be reduced; when the functionality of the isocyanate compound ≥ 3, both the formaldehyde release amount and the specific wear rate can be reduced.

[0071] In Examples 3, 6-9, with the increase in the weight fraction of polytetrafluoroethylene, the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition can be increased. When the weight fraction of polytetrafluoroethylene is between 10-20 parts, the comprehensive performance of the prepared fluorine-containing wear-resistant polyoxymethylene composition is better.

[0072] Comparing Example 3, Examples 10-11 with Comparative Examples 4-6, when the particle size of polytetrafluoroethylene is not within the range of 2-10 μm and the weight-average molecular weight of polytetrafluoroethylene is not between 100,000 and 200,000, the specific wear rate of the prepared fluorine-containing wear-resistant polyoxymethylene composition is relatively high, and the wear resistance of the fluorine-containing wear-resistant polyoxymethylene compositions in Comparative Examples 4-6 is inferior to that of Examples 3, 10-11.

[0073] Comparing Example 3 with Comparative Example 1, the present invention simultaneously adds a polyfunctional isocyanate compound and polytetrafluoroethylene, which can synergistically increase the wear resistance of the fluorine-containing wear-resistant polyoxymethylene composition, and the formaldehyde release amount of the fluorine-containing wear-resistant polyoxymethylene composition is also relatively low.

[0074] Comparing Example 3 with Comparative Example 3, when the weight fraction of polytetrafluoroethylene in the present invention exceeds 2-25 parts, although the friction coefficient and wear of the prepared fluorine-containing wear-resistant polyoxymethylene composition are lower, its strength will decrease, and the comprehensive performance is inferior to that of the examples of the present invention.

[0075] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A fluorine-containing wear-resistant polyoxymethylene composition, characterized in that, Comprising the following components in parts by weight: 100 parts of a polyoxymethylene polymer containing terminal hydroxyl groups, 0.5 - 10 parts of an isocyanate compound, 15 - 25 parts of polytetrafluoroethylene, 0.05 - 2 parts of a lubricant, and 0.05 - 1 part of an antioxidant; The functionality of the isocyanate compound is ≥3; The D50 particle size of the polytetrafluoroethylene is 2 - 10 μm, and the weight-average molecular weight is 100,000 - 200,000.

2. The fluorine-containing wear-resistant polyoxymethylene composition according to claim 1, wherein The weight parts of the isocyanate compound are 0.5 - 2 parts.

3. The fluorine-containing wear-resistant polyoxymethylene composition according to claim 1, wherein The isocyanate compound includes at least one of trimers of 4,4'-methylenebis(phenyl isocyanate), isophorone diisocyanate, 1,6-hexamethylene diisocyanate, 2,4-toluene diisocyanate, or 2,6-toluene diisocyanate.

4. The fluorine-containing wear-resistant polyoxymethylene composition according to claim 1, characterized in that The polyoxymethylene polymer containing terminal hydroxyl groups is a homopolymer composed of formaldehyde monomers represented by formula (I), or a copolymer composed of formaldehyde monomers represented by formula (I) and monomers represented by formula (II), or a mixture of the above homopolymer and copolymer; Formula (I): -(-CH2O-)-; Formula (II): [(CX1X2) a O]; X1 and X2 are the same or different and are each independently selected from the following groups: hydrogen, alkyl, or aryl, and a is an integer from 2 to 6.

5. The fluorine-containing wear-resistant polyoxymethylene composition according to claim 1, characterized in that The lubricant is a stearamide lubricant; the antioxidant is a phenolic antioxidant.

6. A method for preparing a fluorine-containing wear-resistant polyoxymethylene composition according to any one of claims 1-5, characterized in that, Comprising the following steps: 1) According to the ratio, add the polyoxymethylene polymer containing terminal hydroxyl groups, isocyanate compound, polytetrafluoroethylene, lubricant, and antioxidant into a premixer and mix to obtain a premix; 2) Add the premix into a twin-screw extruder, melt and extrude at 180°C - 200°C, cool and pelletize to obtain the fluorine-containing wear-resistant polyoxymethylene composition.

7. Use of the fluorine-containing wear-resistant polyoxymethylene composition according to any one of claims 1 - 5 in gear components, rearview mirror rotating shafts, and automotive pedal mechanisms.

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