Nylon bushing and preparation method thereof
By adding HDI and a hydrophobic agent during the preparation of nylon bushings, the problems of insufficient wear resistance and water absorption of nylon bushings were solved, and the material properties were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGHAI HONGDE NEW MATERIAL TECH CO LTD
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-12
AI Technical Summary
Existing nylon bushings have low wear resistance and water absorption, which cannot meet the requirements for high performance.
By adding the modifier HDI (hexamethylene diisocyanate) during the preparation of nylon bushings, the molecular weight is increased and the material properties are improved by reacting with the amino or carboxyl groups at the end of the nylon chain. At the same time, a hydrophobic agent is added to reduce water absorption.
It improves the wear resistance of nylon bushings and reduces water absorption, thereby enhancing the material's frictional properties and dimensional stability.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of nylon material technology, specifically relating to a nylon bushing and its preparation method. Background Technology
[0002] Nylon bushings are cylindrical mechanical parts made primarily of nylon (polyamide, PA). Their core function is as a support and wear-resistant component, assembled within mechanical shafts and bores to reduce friction, minimize wear, and isolate vibration and noise. Thanks to the self-lubricating properties of nylon, they can operate in oil-free or low-oil conditions, exhibiting high wear resistance and lightweight properties. Simultaneously, they possess excellent corrosion resistance and electrical insulation, protecting the metal substrate, extending equipment life, and reducing maintenance costs. Widely used in automotive hinges, mechanical linkages, furniture hardware, and various transmission mechanisms, they are a high-performance and cost-effective engineering plastic component.
[0003] Currently, the nylon bushings commonly used in the market employ simplified processes to reduce costs, resulting in lower wear resistance and water absorption. Summary of the Invention
[0004] To address the aforementioned technical problems, the present invention aims to provide a nylon bushing and its preparation method, thereby improving the wear resistance and water absorption of the nylon bushing.
[0005] This invention provides a method for preparing a nylon bushing, the method comprising the following steps: 90-95 parts by weight of caprolactam were dehydrated, then heated and melted under vacuum, and dehydrated again, and then an inert gas was added. Add 0.25~1.2 parts by weight of catalyst and 4~8 parts by weight of No. 58 wax, and stir to mix; Add 1-3 parts by weight of hydrophobic agent and 0.3-1.2 parts by weight of hexamethylene diisocyanate and stir. Pour into a sealed bushing mold and cure.
[0006] In the production process of nylon, degradation reactions such as high temperature and hydrolysis cause the macromolecular chains of nylon to break, resulting in a decrease in molecular weight and viscosity. This invention addresses this by adding the modifying agent HDI (hexamethylene diisocyanate). HDI can simultaneously react with the amino or carboxyl groups at the ends of two broken nylon chains, reconnecting them and increasing the average molecular weight of the nylon. The chain-extending or cross-linking effect of HDI gives the material higher wear resistance and mechanical properties, while reducing water absorption.
[0007] Preferably, the dehydration of 90-95 parts by weight of caprolactam includes drying the caprolactam in a vacuum oven at 80°C-100°C for 4-6 hours.
[0008] In this scheme, the main raw materials are first dried to avoid residual moisture from adversely affecting subsequent anionic polymerization.
[0009] Preferably, the catalyst is NaOH, and the mass of NaOH is 0.25% to 1.2% of the caprolactam.
[0010] Preferably, before the step of adding 0.25-1.2 parts by weight of catalyst and 4-8 parts by weight of No. 58 wax and stirring and mixing, the preparation method further includes: Crush or cut the No. 58 wax into small particles.
[0011] In this method, No. 58 wax is crushed or cut into small particles to facilitate rapid melting and dispersion later.
[0012] Preferably, the heating and melting temperature is 125℃~135℃, and the duration is 20~30 minutes.
[0013] In this method, caprolactam is heated and melted under vacuum for 20-30 minutes. This allows the caprolactam to continue to remove trace amounts of water and air bubbles while it is in a molten state, at which point the liquid becomes clear and transparent.
[0014] Preferably, the step of adding 0.25-1.2 parts by weight of catalyst and 4-8 parts by weight of No. 58 wax, and stirring and mixing, includes: Add the catalyst to component A and stir for 5-10 minutes; Add the No. 58 wax and stir.
[0015] Preferably, the step of adding the hydrophobic agent and hexamethylene diisocyanate, stirring, injecting into a sealed bushing mold, and curing includes: The bushing mold is preheated to 160°C~180°C; Add a hydrophobic agent and hexamethylene diisocyanate and stir. Pour the mixture into a preheated sealing bushing mold and keep the mold warm for 15-30 minutes to cure and form the desired shape.
[0016] This method involves preheating the mold to prevent the injected mixture from solidifying upon contact with the low-temperature mold before anionic polymerization occurs. Simultaneously, the mold is sealed to prevent air from entering and causing material oxidation.
[0017] Preferably, the method further includes: Cool the bushing mold and remove the nylon bushing from the bushing mold.
[0018] Preferably, the method further includes: The bushing mold is heat-treated in an oil bath or oven at 100-120°C for 1-2 hours, and then cooled.
[0019] This method involves heat-treating the nylon bushing in an oil bath or oven at 100-120℃ for 1-2 hours, followed by slow cooling. This eliminates internal stress, improves crystallinity, and stabilizes dimensions.
[0020] Preferably, the method further includes: The bushing mold is boiled or steamed for 2-4 hours and then cooled.
[0021] This method involves boiling or steaming the nylon bushing for 2-4 hours to balance the moisture content, improve its resilience, and thus enhance its impact strength.
[0022] This invention provides a nylon bushing prepared by the above-described method, the nylon bushing comprising: 90-95 parts by weight of caprolactam, 1-3 parts by weight of hydrophobic agent, 4-8 parts by weight of No. 58 wax, 0.25-1.2 parts by weight of NaOH, and 0.3-1.2 parts by weight of hexamethylene diisocyanate. Detailed Implementation
[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments and examples. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.
[0024] Example 1 The method for preparing the nylon bushing in this embodiment is as follows: S1. Dry 90 parts by weight of caprolactam CPL in a vacuum oven at 80-100℃ for 4-6 hours to remove moisture from the raw material.
[0025] S2. Place the dried caprolactam into the reaction vessel, heat the vessel to 125-135℃ to completely melt the caprolactam (CPL) into a liquid, and turn on the vacuum system. Continue to remove trace amounts of moisture and air bubbles while the liquid is still molten for 20-30 minutes. At this point, the liquid will become clear and transparent. To avoid the influence of oxygen and moisture in the air, inert gas can be further introduced into the reaction vessel for protection.
[0026] S3. Add 0.25 parts by weight of the prepared catalyst NaOH (the catalyst also needs to be dried beforehand to avoid introducing moisture) and 4 parts by weight of No. 58 wax to the reactor, stir at high speed for 5-10 minutes to ensure that the substances are fully mixed.
[0027] S4. Next, add 1 part by weight of hydrophobic agent and 0.3 parts by weight of hexamethylene diisocyanate to the reactor, while continuing to stir rapidly to ensure uniform dispersion before gelation. Finally, quickly pour the uniformly mixed material into a nylon bushing mold preheated to 160°C. The nylon bushing mold must be well sealed to prevent air from entering and causing oxidation of the material. The material will quickly undergo anionic polymerization in the mold, completing polymerization and solidification within 15-30 minutes. At this time, maintain the mold temperature for 20-30 minutes to ensure complete reaction. Finally, demold the material; after opening the mold, the nylon bushing is obtained.
[0028] To further enhance the performance of nylon bushings, post-processing can be performed on the removed nylon bushings, including: Annealing: Heat-treat the product in an oil bath or oven at 100-120℃ for 1-2 hours, then cool slowly. This can eliminate internal stress, improve crystallinity, and stabilize dimensions.
[0029] Conditioning treatment: If the product requires high toughness, it can be boiled in water or steamed for 2-4 hours to balance the moisture and improve the impact strength.
[0030] As an example, in step S2, the catalyst NaOH and a small amount of dried CPL can be premixed in another small container to form a catalyst slurry, and then in step S3, the prepared catalyst slurry can be added to the reactor as a catalyst.
[0031] Example 2 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that in step S1, caprolactam is 92 parts by weight.
[0032] Example 3 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that in step S1, caprolactam is 93 parts by weight.
[0033] Example 4 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of caprolactam in step S1 is 95 parts by weight.
[0034] Example 5 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 0.4 parts by weight.
[0035] Example 6 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 0.6 parts by weight.
[0036] Example 7 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 0.8 parts by weight.
[0037] Example 8 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 1.0 parts by weight.
[0038] Example 9 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 1.2 parts by weight.
[0039] Example 10 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 1.2 parts by weight.
[0040] Example 11 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the wax No. 358 is 6 parts by weight in step S358.
[0041] Example 12 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the wax No. 358 is 8 parts by weight in step S358.
[0042] Example 13 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the hydrophobic agent in step S4 is 1 part by weight.
[0043] Example 14 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the hydrophobic agent in step S4 is 2 parts by weight.
[0044] Example 15 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the hydrophobic agent in step S4 is 3 parts by weight.
[0045] Example 15 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 0.3 parts by weight.
[0046] Example 16 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 0.5 parts by weight.
[0047] Example 17 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 0.7 parts by weight.
[0048] Example 18 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 0.9 parts by weight.
[0049] Example 19 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 1.1 parts by weight.
[0050] Example 20 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 1.2 parts by weight.
[0051] Comparative Example 1 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that in step S1, caprolactam is 90 parts by weight.
[0052] Comparative Example 2 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that in step S1, caprolactam is 96 parts by weight.
[0053] Comparative Example 3 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 0.1 parts by weight.
[0054] Comparative Example 4 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the catalyst NaOH in step S3 is 1.3 parts by weight.
[0055] Comparative Example 5 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the No. 58 wax is 3 parts by weight in step S3.
[0056] Comparative Example 6 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the weight of wax No. 58 is 9 parts in step S3.
[0057] Comparative Example 7 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the hydrophobic agent in step S4 is 0.5 parts by weight.
[0058] Comparative Example 8 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the hydrophobic agent in step S4 is 4 parts by weight.
[0059] Comparative Example 9 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 0.2 parts by weight.
[0060] Comparative Example 10 The preparation method of the nylon bushing in this embodiment is the same as in Example 1, except that the amount of hexamethylene diisocyanate in step S4 is 1.3 parts by weight.
[0061] Performance testing (1) Coefficient of friction Tensile testing was performed in accordance with GB / T 3960 standard.
[0062] (2) Water absorption The bending test was performed in accordance with GB / T 1034, which specifies the determination of water absorption of plastics.
[0063] The nylon bushings prepared in the above embodiments and comparative examples were subjected to the above performance tests, and the test results are shown in Table 1.
[0064] Table 1
[0065] As shown in Table 1: By adding the modified additive HDI to repair the molecular chain and seal the end groups of nylon, the tribological properties and water absorption properties of the material can be optimized simultaneously.
[0066] coefficient of friction The embodiments generally exhibit a lower coefficient of friction, with some optimized embodiments showing a coefficient of friction as low as 0.17, far lower than most comparative examples, indicating that the modified material surface is smoother and the friction performance is significantly improved.
[0067] Wear amount The wear amounts of the embodiments were generally lower and more stable, with most embodiments having wear amounts controlled within the range of 1.0–2.0 mg, which was significantly better than the comparative examples. This indicates that after the molecular chains were reconnected, the material structure was more compact and had stronger wear resistance.
[0068] Water absorption rate The water absorption rate of the examples was generally lower than that of the comparative examples. In some examples, the water absorption rate after 24 hours could be as low as 0.32%, indicating that the reaction of HDI with the amino and carboxyl groups at the end of the nylon chain effectively reduced the number of hydrophilic groups, reduced the water absorption rate of the material, and improved dimensional stability and water resistance.
[0069] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a nylon bushing, characterized in that, The preparation method includes the following steps: 90-95 parts by weight of caprolactam were dehydrated, then heated and melted under vacuum, and dehydrated again, and then an inert gas was added. Add 0.25~1.2 parts by weight of catalyst and 4~8 parts by weight of No. 58 wax, and stir to mix; Add 1-3 parts by weight of hydrophobic agent and 0.3-1.2 parts by weight of hexamethylene diisocyanate and stir. Pour into a sealed bushing mold and cure.
2. The preparation method according to claim 1, characterized in that, The process of dehydrating 90-95 parts by weight of caprolactam includes drying the caprolactam in a vacuum oven at 80°C-100°C for 4-6 hours.
3. The preparation method according to claim 1, characterized in that, The catalyst is NaOH, and the mass of NaOH is 0.25% to 1.2% of the caprolactam.
4. The preparation method according to claim 1, characterized in that, Before the step of adding 0.25-1.2 parts by weight of catalyst and 4-8 parts by weight of No. 58 wax and stirring and mixing, the preparation method further includes: Crush or cut the No. 58 wax into small particles.
5. The preparation method according to claim 1, characterized in that, The heating and melting temperature is 125℃~135℃, and the duration is 20~30 minutes.
6. The preparation method according to claim 1, characterized in that, The step of adding 0.25-1.2 parts by weight of catalyst and 4-8 parts by weight of No. 58 wax, and stirring and mixing, includes: Add the catalyst and stir for 5-10 minutes; Add the No. 58 wax and stir.
7. The preparation method according to claim 1, characterized in that, The steps of adding a hydrophobic agent and hexamethylene diisocyanate, stirring, injecting into a sealed bushing mold, and curing include: The bushing mold is preheated to 160°C~180°C; Add a hydrophobic agent and hexamethylene diisocyanate and stir. Pour the mixture into a preheated sealing bushing mold and keep the mold warm for 15-30 minutes to cure and form the desired shape.
8. The preparation method according to claim 1, characterized in that, The method further includes: Cool the bushing mold and remove the nylon bushing from the bushing mold.
9. The preparation method according to claim 8, characterized in that, The method further includes: The nylon bushing is heat-treated in an oil bath or oven at 100-120°C for 1-2 hours, and then cooled.
10. A nylon bushing, characterized in that, The nylon bushing is prepared by the method described in any one of claims 1 to 9.