Unsaturated long carbon chain polyamides, mercapto-olefin microcrosslinking pieces, and methods of making and using

Abstract

Unsaturated long-chain polyamide, mercaptoene micro-crosslinked components, preparation methods, and applications, wherein the repeating structural unit of the unsaturated long-chain polyamide comprises: —NH—(CH2). a —NH—CO—(CH2) p —CH=CH—(CH2) q —CO—; and the residual carbon-carbon double bond content is 0.20–0.80 mmol / g. The thiol-based micro-crosslinked parts are mainly formed by co-extrusion granulation, thermoplastic molding, and post-curing of the unsaturated long-chain polyamide, multifunctional thiol compounds, and free radical initiators. This invention also discloses their preparation methods and applications. The polyamide of this invention has controllable residual C=C content and combines melt processability with resistance to media, wear resistance, and dimensional stability. The crosslinked parts of this invention have melt processability, low crosslinking density, heat / media resistance, low friction, scratch resistance, dimensional stability, and good mechanical properties. The method of this invention is simple, and the reaction conditions are mild.

Description

Technical Field

[0001] This invention specifically relates to an unsaturated long-chain polyamide, a mercaptoene micro-crosslinked component, its preparation method, and its application. Background Technology

[0002] Long-chain aliphatic polyamides (such as PA10,10, PA12,12, etc.) have low water absorption and good chemical resistance due to their high crystallinity and low polarity, and are widely used in oil and gas transportation, cable sheathing, pipes, and moving parts. However, these materials have a high coefficient of surface friction, and surface scratch resistance and low friction performance often rely on external lubricants or surface coatings. This results in problems such as easy migration and precipitation of lubricants, easy wear of coatings, difficulty in maintaining low friction and scratch resistance during long-term service, insufficient durability, and poor reprocessability.

[0003] CN101200541A discloses a long-chain dicarboxylic acid type polyamide resin and its preparation method, which utilizes long alkyl chains to improve water resistance, heat resistance, and mechanical properties. However, the polyamide backbone obtained by this technical solution has a conventional linear amide structure, and the system does not have controllable active sites that can be used for "secondary reaction / post-curing" after molding, making it difficult to maintain the thermoplastic processing window.

[0004] CN113651956A discloses a method for preparing ultra-high toughness branched polyamide copolymers and the resulting polyamide copolymers, which are suitable for melt blending toughening, extrusion, blown film and other fields. However, this type of "branching / network structure regulation" mainly occurs in the polymerization stage, making it difficult to achieve two-stage regulation of "first linear processable molding, then controllable curing in the in-process stage".

[0005] In existing technologies, post-crosslinking of polyamides using methods such as irradiation and peroxide crosslinking can improve surface properties and heat resistance to some extent. However, on the one hand, it usually leads to problems such as high gel fraction, significantly reduced melt flowability, and difficulty in remelting and processing the material, thus limiting recycling and secondary processing. On the other hand, introducing unsaturated diacid monomers and crosslinking systems during the polymerization stage to provide reactive sites has potential, but if significant crosslinking occurs during polymerization, it will destroy the linear structure, resulting in uncontrollable batch crosslinking, and making it difficult to precisely control the molecular weight and processing window.

[0006] CN109265677A discloses a method for preparing high-temperature resistant transparent polyamide, aiming to improve the heat resistance and transparency of polyamide. However, this technical solution focuses on the transparency / heat resistance target and does not provide a controllable reaction site design and content control for post-curing after molding. Therefore, it is difficult to achieve a synergistic improvement in thermoplastic processability and long-term low friction, scratch resistance and durability stability of the product.

[0007] CN101392063A discloses a polydimethylsiloxane-polyamide multi-block thermoplastic elastomer, which achieves properties such as softness, resilience, and wear resistance through the condensation polymerization of diamine / diacid with diamine-terminated polydimethylsiloxane. However, this technical solution relies on the soft segments of siloxane to achieve elasticity and partial wear resistance, and the material system is not consistent with the engineering application scenarios of long-chain polyamides, which require "low polarity, low water absorption, media resistance, and melt processing."

[0008] Therefore, there is an urgent need to find an unsaturated long-chain polyamide that can maintain low water absorption, chemical resistance, and low-temperature toughness, with controllable residual C=C content, melt processability, media resistance, abrasion resistance, and dimensional stability. It should also have controllable crosslinking points and low crosslinking density, and improve heat / media resistance, low friction, scratch resistance, dimensional stability, and mechanical properties while maintaining melt processability. Furthermore, it should be a simple preparation method with a clear process window, mild reaction conditions, good repeatability, and suitability for large-scale production. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide an unsaturated long carbon chain polyamide that maintains low water absorption, chemical resistance and low temperature toughness, has controllable residual C=C content, and has melt processability, media resistance, strength retention, wear resistance and dimensional stability.

[0010] The further technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a mercaptoene micro-crosslinked part and its application, which has controllable introduction of crosslinking points, melt processability, low crosslinking density, heat / media resistance, low friction, scratch resistance, good dimensional stability and mechanical properties.

[0011] The technical problem to be further solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing unsaturated long carbon chain polyamide and mercaptoene micro-crosslinked parts with simple process, clear process window, mild reaction conditions, good repeatability and suitable for large-scale production.

[0012] The technical solution adopted by this invention to solve its technical problem is as follows: an unsaturated long-chain polyamide, whose repeating structural unit includes: —NH—(CH2). a —NH—CO—(CH2) p —CH=CH—(CH2) q —CO—, where a is an integer from 10 to 12, p and q are integers satisfying p+q=14; and the residual carbon-carbon double bond content is 0.20 to 0.80 mmol / g.

[0013] The inventive concept of this unsaturated long-chain polyamide is as follows: while maintaining the high strength, heat resistance, and processability of the polyamide backbone, a structural system of "low-polarity long-chain backbone + latent reaction sites" is constructed by introducing long methylene segments and a small number of embedded carbon-carbon double bonds into the dicarboxylic acid segments. This type of structure has universal advantages: on the one hand, the long methylene segments can reduce the polarity of the molecular chain and the density of hydrogen bonds, improve the material's water absorption sensitivity and media permeability, and generally help improve hydrolysis resistance, chemical media resistance, and dimensional stability, while reducing surface friction tendency; on the other hand, the polyamide matrix can still maintain good crystallinity and mechanical framework support, enabling the material to possess strength, toughness, and heat resistance in engineering processing and service scenarios. More importantly, the C=C retained on the chain serves as a designable "reaction window," providing a universal chemical anchor for subsequent mild secondary reactions after molding, such as mercapto-olefin addition micro-crosslinking and surface / interface functionalization, thereby realizing the path of "thermoplastic processing first, followed by directional strengthening and upgrading."

[0014] Furthermore, the limitation on the residual carbon-carbon double bond content in this invention is mainly based on the need to strike a balance between "post-curing reaction efficiency" and "thermoplastic processability / long-term stability": when the residual C=C content is too low, there are insufficient effective reaction sites to participate in post-curing, making it difficult to form sufficient micro-crosslinks / structural fixation, resulting in insignificant improvements in wear resistance, scratch resistance, media resistance, and creep resistance brought about by post-curing, and making it more prone to problems such as "adding a post-curing system but the effect is unstable or not repeatable"; when the residual C=C content is too high, side reactions or undesirable crosslinking (such as inter-chain reactions caused by thermal oxidation and increased tendency to gel) are more likely to occur during polymerization and processing, which may lead to decreased melt fluidity, narrowed processing window, and increased surface defects in the product; at the same time, it is also more likely to cause excessively high crosslink density in the post-curing stage, resulting in adverse consequences such as material embrittlement, decreased elongation, increased risk of stress cracking, and poor recycling and reprocessing performance. Therefore, by controlling the residual C=C within the above range, sufficient and stable reaction sites can be provided for subsequent controllable post-curing while ensuring melt processing and molding, thus achieving repeatability and engineering adaptability of performance improvement.

[0015] The technical solution adopted by this invention to further solve its technical problem is as follows: a method for preparing unsaturated long-chain polyamide, comprising the following steps: (1) Add water to an unsaturated dicarboxylic acid, heat and stir to dissolve, then add an aqueous solution of a diamine and continue stirring to obtain a homogeneous disalt solution; (2) The binary salt solution obtained in step (1) is placed in a closed reaction vessel. Under the protection of an inert atmosphere, the temperature is slowly raised to dehydrate and pre-condensation is carried out. Then, the pressure is reduced and the melt is discharged. The melt is water-cooled, stretched, and granulated. It is then vacuum dried and cooled to obtain unsaturated long carbon chain polyamide.

[0016] The inventive concept of this invention is as follows: This invention uses an unsaturated diacid as the acid component and polycondenses it with a diamine in a stoichiometric ratio to obtain an aliphatic long carbon chain copolymer polyamide. No mercapto compounds or free radical initiators are added during the pressure pre-condensation and decompression polycondensation processes. By controlling the polycondensation time, temperature, and end-group balance, the residual C=C content of the obtained linear long carbon chain polyamide is controlled, which ensures sufficient reactive sites while avoiding excessive residual double bonds that could lead to easy over-crosslinking in the subsequent process.

[0017] Preferably, in step (1), the equivalence ratio of the carboxyl group in the unsaturated diacid to the amino group in the diamine, Eq(COOH) / Eq(NH2), is 1.000–1.010:1 (more preferably 1.001–1.006:1, and even more preferably 1.001–1.004:1). The stoichiometric ratio in the polycondensation system directly determines the degree of polymerization and the type of end groups: a stoichiometric ratio close to 1 yields higher molecular weight and stable melt rheology; a slightly acidic composition can compensate for the loss of the diamine during dehydration / gasification and suppress excessive amino end groups. If Eq(COOH) / Eq(NH2) < 1.000, indicating an excess of amino groups, it will lead to limited polymerization degree, lower molecular weight, insufficient melt strength, and increased end-group activity, easily causing processing / performance fluctuations. If Eq(COOH) / Eq(NH2) > 1.010, indicating an excess of acid groups, it will similarly limit the degree of polymerization and increase oligomers and carboxyl end groups, leading to rheological instability and decreased mechanical and hydrothermal durability. In the equivalence ratio Eq(COOH) / Eq(NH2), Eq(COOH) is the amount of carboxyl groups in the unsaturated diacid; Eq(NH2) is the amount of amino groups in the diamine; the ratio of the two is defined as Eq(COOH) / Eq(NH2).

[0018] Preferably, in step (1), the mass ratio of the unsaturated diacid to water is 0.25–1.00:1 (more preferably 0.35–0.80:1). Water mainly serves as a wetting / dissolving and heat transfer medium during the salt production stage. The amount of water used ensures that the diacid is fully dispersed and uniformly neutralized with the diamine, avoiding local high concentrations that could lead to clumping or premature condensation.

[0019] Preferably, in step (1), the heating and stirring temperature for dissolving is 70–80°C. The temperature inside the reactor during the feeding process is controlled to not exceed 90°C to avoid premature polycondensation caused by localized overheating.

[0020] Preferably, in step (1), the mass concentration of the diamine aqueous solution is 15-50 wt% (more preferably 20-35 wt%). If the concentration is too low, too much water will be introduced, leading to increased dehydration load and polycondensation fluctuations in the subsequent process; if the concentration is too high, the solution viscosity will increase or the risk of crystallization will increase, which may easily cause deviations in feeding and uneven neutralization, thereby causing instability in molecular weight distribution and processing rheology.

[0021] Preferably, in step (1), the temperature for continued stirring is 60-80°C and the time is 20-60 min.

[0022] Preferably, in step (1), the unsaturated dicarboxylic acid includes C18:1 aliphatic unsaturated dicarboxylic acids, etc. The unsaturated dicarboxylic acid has a long methylene segment and an embedded C=C structure, which can reduce water absorption sensitivity and improve media stability without significantly increasing the polarity of the system. At the same time, the C=C can serve as a latent reaction site for subsequent functionalization / post-curing reactions.

[0023] More preferably, the C18:1 aliphatic unsaturated dicarboxylic acid includes one or more of 9-octadecenoic acid (ODDA), 10-octadecenoic acid, or 11-octadecenoic acid.

[0024] Preferably, in step (1), the diamine includes C10-C12 straight-chain diamines, etc. The diamine has structural characteristics of long methylene segments, a flexible main chain, and low polarity.

[0025] More preferably, the C10-C12 straight-chain diamine includes one or more of 1,12-diaminododecane (DMD), 1,10-decanediamine (DAD), or 1,11-diaminoundecane.

[0026] Preferably, in step (2), the slow heating dehydration means: heating to 160-180°C at a rate of 0.5-3.0°C / min (more preferably 1-2°C / min) for dehydration. During the dehydration process, water vapor is discharged and an inert atmosphere is introduced to maintain a pressure of 0.5-1.5 MPa until the water is discharged and the reactants are in a viscous melt state.

[0027] Preferably, in step (2), the pre-condensation refers to: first heating to 240-250°C at a rate of 0.5-3.0°C / min (more preferably 1-2°C / min), then introducing an inert atmosphere to maintain the pressure inside the reactor at 0.5-1.5MPa, and stirring at a speed of 20-60r / min, and pre-condensing for 1.5-2.5h.

[0028] Preferably, in step (2), the reduced-pressure polymerization refers to: first venting and evacuating the air, reducing the absolute pressure to ≤400 Pa within 10–20 min, and then reducing the pressure and polymerizing at 240–250 °C for 10–60 min (more preferably 20–50 min). Reduced-pressure polymerization can further increase the polymer molecular weight and adjust the end-group balance. When the torque or melt viscosity reaches the set range, heating and evacuation are stopped.

[0029] Preferably, in step (2), the vacuum drying temperature is 60 to 100°C, the vacuum degree is -0.06 to -0.10 MPa, and the time is 6 to 10 hours.

[0030] Preferably, in step (2), or after vacuum drying, solid-phase polycondensation is carried out under an inert atmosphere. Solid-phase polycondensation is used as a means of optimizing performance and processing stability. Its purpose is to further increase the molecular weight and reduce oligomer and end-group fluctuations under mild conditions below the melting point after melt polycondensation, thereby improving the melt strength and processing stability of the resin.

[0031] Preferably, the solid-phase polycondensation is performed at a temperature of 150–170°C for 1–6 hours. Under these solid-phase polycondensation conditions, segment diffusion is restricted, and an inert atmosphere is used to reduce the risk of adverse side reactions at residual C=C sites.

[0032] Preferably, in step (2), the inert atmosphere includes one or more of nitrogen, argon, or helium.

[0033] The technical solution adopted by the present invention to further solve its technical problem is as follows: a thiol micro-crosslinked part is mainly made by blending, extruding, granulating, thermoplastic molding and free radical initiator of the unsaturated long carbon chain polyamide, multifunctional thiol compound and free radical initiator and then performing post-curing treatment.

[0034] The invention of the thiol-ene micro-crosslinked component is based on the following concept: using unsaturated long-chain polyamide containing C=C sites as the matrix, a multifunctional thiol compound is introduced after molding, and a thiol-ene addition reaction is triggered under free radical initiation conditions to construct a small number of thioether bond crosslinking points between the chains, thereby forming a low-crosslinking density micro-crosslinked network. By controlling Eq(SH) / Eq(C=C) and post-curing conditions, the number of crosslinking points can be adjusted, achieving both structural constraints on chain slippage and surface damage propagation, and avoiding embrittlement and non-recyclability caused by high crosslinking. This invention, while maintaining the inherent low water absorption, chemical resistance, and low-temperature toughness of long-chain polyamide, introduces controllable thiol-ene micro-crosslinking, achieving a comprehensive performance balance between low friction, scratch resistance, media resistance, and thermoplastic recyclability.

[0035] Preferably, the amounts of the multifunctional thiol compound and the free radical initiator are respectively equivalent to 0.05–2.50% (more preferably 0.20–2.00%) and 0.05–0.50% (more preferably 0.10–0.35%) of the mass of the unsaturated long-chain polyamide. This range of amounts ensures that the conversion rate and crosslinking density of the thiol-ene reaction are within the micro-crosslinking window. If the amount of the multifunctional thiol compound is too low, the reaction will be insufficient; if the amount is too high, gelation / flowability will decrease and recycling processability will be weakened. If the amount of the free radical initiator is too low, curing will be incomplete; if the amount is too high, side reactions such as chain transfer will easily occur, causing fluctuations in structure and properties.

[0036] Preferably, the equivalence ratio of thiol groups in the multifunctional thiol compound to the residual carbon-carbon double bonds in the unsaturated long-chain polyamide, Eq(SH) / Eq(C=C), is 0.05–0.40:1 (more preferably 0.06–0.30:1, and even more preferably 0.08–0.25:1). Under the synergistic control of the residual C=C content and its thiol equivalence ratio, the present invention constructs a sparse three-dimensional cross-linked network with a low gel fraction in the long-chain polyamide matrix. This network significantly inhibits surface plastic deformation and micro-cutting, reduces the dynamic friction coefficient, and improves scratch resistance. On the other hand, it does not form a continuous high-density gel structure, thereby maintaining melt fluidity and melt reprocessability, so that the material still has a good processing window in injection molding, extrusion, and other molding processes, as well as in recycling and reprocessing. In the equivalence ratio Eq(SH) / Eq(C=C), Eq(SH) is the amount of substance of the mercapto compound multiplied by its functionality; Eq(C=C) is the amount of substance of residual C=C in the linear resin; the ratio of the two is defined as Eq(SH) / Eq(C=C).

[0037] Preferably, the multifunctional thiol compound includes one or more of trimethylolpropane tris(3-mercaptopropionate) (TMPMP), 1,6-hexanedithiol, or pentaerythritol tetra(3-mercaptopropionate).

[0038] Preferably, the free radical initiator includes one or more of the following: phosphooxy photoinitiator, azobisisobutyronitrile, or benzoyl peroxide.

[0039] The technical solution adopted by the present invention to further solve its technical problem is as follows: a method for preparing mercaptoene micro-crosslinked parts, comprising the following steps: (1) After drying the unsaturated long carbon chain polyamide, it is added to a twin-screw extruder with a multifunctional thiol compound and a free radical initiator for co-extrusion granulation to obtain a masterbatch containing post-curing components; (2) After drying the masterbatch containing the post-curing component obtained in step (1), thermoplastic molding is performed to obtain the molded part; (3) Place the molded part obtained in step (2) in an inert atmosphere and perform post-curing treatment to obtain mercaptoene micro-crosslinked part.

[0040] The inventive concept of this invention is as follows: after setting the ratio of multifunctional thiol compounds and unsaturated long carbon chain polyamides according to the ratio of thiol groups to C=C bonds, they are introduced into the curing window. Under the action of an initiator, short-term thiol-ene post-curing is carried out to construct a sparse micro-crosslinked network with a low gel fraction, thereby achieving a comprehensive improvement in low friction, scratch resistance and media resistance while maintaining thermoplastic reprocessability.

[0041] Preferably, in step (1), or before adding to the twin-screw extruder, dry mixing is performed first.

[0042] Preferably, in step (1), the barrel temperature of the blend extrusion granulation is 200-230°C, the die head temperature is 230-240°C, and the screw speed is 100-250 rpm (more preferably 150-220 rpm).

[0043] Preferably, in step (2), the thermoplastic molding includes injection molding, extrusion or blow molding, etc.

[0044] Preferably, the injection molding conditions are: the injection molding machine barrel temperature is 200-230℃, the screw speed is 100-250rpm (more preferably 100-200rpm), and the mold temperature is 40-80℃.

[0045] Preferably, the extrusion conditions are: extruder barrel temperature of 200-220°C, die head temperature of 205-225°C, screw speed of 20-80 rpm, sizing, and cooling.

[0046] Preferably, the blow molding conditions are: the blow molding melt temperature is 200-230°C, the die head temperature is 205-235°C, the blow pressure is 0.2-0.8 MPa, and the mold temperature is 20-60°C.

[0047] Preferably, in steps (1) and (2), the drying refers to drying with hot air or vacuum at 70-90°C for 8-12 hours until the moisture content is ≤0.10wt%. Drying is required before thermoplastic molding to reduce the impact of water absorption on processing and performance.

[0048] Preferably, in step (3), the post-curing treatment includes thermal activation and / or photoactivation treatment, etc.

[0049] Preferably, in step (3), the temperature of the thermal activation treatment is 140–180°C (more preferably 150–165°C), the time is 5–30 min (more preferably 8–20 min), until the mass fraction of the gel is 0.5–5.0 wt% (more preferably 1–4 wt%, even more preferably 1.5–3.8 wt%). During the post-curing process, the residual C=C in the system undergoes a thiol-ene addition reaction with the thiol groups under the initiation of the initiator, forming a sparse cross-linked network. When the gel fraction of the thiol-ene micro-crosslinked part obtained after post-curing is 0.5–5.0 wt%, it can still maintain its melt processability.

[0050] Preferably, in step (3), the inert atmosphere includes one or more of nitrogen, argon, or helium.

[0051] The inert atmosphere used in this invention is a high-purity atmosphere with a purity of ≥99.999%.

[0052] The technical solution adopted by the present invention to further solve its technical problem is as follows: the application of mercaptoene micro-crosslinked parts, that is, applying the mercaptoene micro-crosslinked parts or their products to pipes, cable sheaths, low-friction wear-resistant parts or sports equipment parts, etc.

[0053] The beneficial effects of this invention are as follows: (1) The unsaturated long carbon chain polyamide of the present invention, while maintaining low water absorption, chemical resistance and low temperature toughness, introduces and controls residual C=C sites, so that the material has both stable melt processability and mild post-curing reactivity after molding, realizing the two-stage regulation of "first thermoplastic molding and then controllable strengthening", and provides repeatable reaction sites for subsequent thiol-ene micro-crosslinking, thereby improving the product's resistance to media, wear resistance and dimensional stability; (2) The thiol-ene micro-crosslinked parts of the present invention adopt the segmented strategy of “preparing linear unsaturated long carbon chain polyamide first, and then curing it after micro-crosslinking with thiol-ene”, that is, retaining the reactive olefin bonds in the polymerization stage and triggering micro-crosslinking with a small dose after molding. This avoids the irreversible processing problem caused by batch crosslinking in the polymerization stage, so that the long chain polyamide can obtain more durable low friction and scratch resistance while maintaining thermoplastic reprocessability, and maintain good mechanical strength in long-term medium and humid heat environment; (3) Under the synergistic control of residual C=C content and its thiol equivalent ratio, the present invention constructs a sparse three-dimensional cross-linked network with low gel fraction. The obtained thiol micro-cross-linked parts have a dynamic friction coefficient of 0.20 to 0.28 under dry conditions and 23°C, and the scratch grade is improved by 0.7 to 1.8 grades compared with the uncured sample. The water absorption rate of the obtained thiol micro-cross-linked parts after being placed at 23°C and 50% relative humidity for 168 hours is ≤1.08wt%, achieving a comprehensive balance of low friction, scratch resistance, media resistance and mechanical properties. (4) Compared with traditional irradiation crosslinking or high gelation degree crosslinking schemes, the method of the present invention only requires short-term thermal / photoactive activation followed by curing, without the need for electron beam or high-dose irradiation equipment. The process is simple and can be scaled up directly on existing polyamide injection molding and extrusion production lines. The process window is clear, the reaction conditions are mild, and the repeatability is good. It is suitable for the large-scale application of cable sheaths, oil and gas / chemical media conveying pipes, as well as low-friction transmission components and sports equipment components. Detailed Implementation

[0054] The present invention will be further described below with reference to the embodiments.

[0055] The 9-octadecenoic acid (ODDA) used in the embodiments and comparative examples of this invention has a purity ≥98% and a moisture content ≤0.3%; 1,12-diaminododecane or 1,10-decanediamine (DAD) has a purity ≥99.0% and a moisture content ≤0.2%, calculated based on the density of 30 wt% 1,12-diaminododecane aqueous solution, 30 wt% 1,10-decanediamine aqueous solution being 0.95 g / mL, and the density of 50 wt% 1,12-diaminododecane aqueous solution being 0.92 g / mL; the inert atmosphere used in the embodiments and comparative examples of this invention is a high-purity atmosphere with a purity ≥99.999%; the raw materials or chemical reagents used in the embodiments of this invention, unless otherwise specified, are obtained through conventional commercial channels.

[0056] The relevant data involved in the embodiments of this invention are detected by the following methods: Residual C=C content: using 1 HNMR can be used to quantify the allyl hydrogen signal in long-chain polyamides (using CDCl3 or DMSO-d6 as solvent), expressed as mmol / g, and can be verified by iodometric titration. End-group titration: Carboxyl groups were titrated using the KOH / benzyl alcohol method; amino groups were titrated using the HClO4 / glacial acetic acid potentiometric titration method. Gel fraction: According to ASTM D2765 standard, N,N-dimethylformamide (DMF) was used for extraction at 150°C for 8 hours. The dry weight of the sample after extraction was determined and expressed as the dry basis residual mass fraction.

[0057] Example 1 of unsaturated long carbon chain polyamide The repeating structural unit of the unsaturated long-chain polyamide is: —NH—(CH2) 12 —NH—CO—(CH2)7—CH=CH—(CH2)7—CO—; The residual carbon-carbon double bond content was 0.52 mmol / g.

[0058] Example 1: Preparation method of unsaturated long carbon chain polyamide (1) 1500g of deionized water was added to 1000g (3.20mol) of 9-octadecenoic acid placed in a glass-lined reactor. After heating and stirring to dissolve at 75℃, 2243mL of 30wt% 1,12-diaminododecane aqueous solution was added. The Eq(COOH) / Eq(NH2) ratio was 1.003. The mixture was stirred at 80℃ for 45min to obtain a homogeneous binary salt solution. (2) Place the binary salt solution obtained in step (1) in a sealed reactor. Under the protection of a high-purity nitrogen atmosphere, slowly heat up to dehydrate: heat up to 170℃ at a rate of 1.0℃ / min for dehydration. During the dehydration process, open the exhaust valve on the top of the reactor to discharge water vapor, and introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0MPa until the water is drained and the reactants are in a viscous melt state. Then perform pre-condensation: heat up to 245℃ at a rate of 1.5℃ / min, and then introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0MPa in the reactor. After pre-condensation for 2.0 h at a stirring speed of 40r / min, perform decompression polymerization: first exhaust the gas and evacuate the vacuum, and reduce the absolute pressure to ≤300℃ within 15 min. Pa, then at 245℃, reduce compression and polymerize for 30 min, discharge the melt, water-cool and stretch into strips, cut into pellets, vacuum dry at 80℃ and -0.10MPa for 8 h, cool, and obtain unsaturated long carbon chain polyamide 1.

[0059] Examples 1-1 to 1-3 of thiol-based micro-crosslinked components The thiol-based micro-crosslinked component is formed by extruding and granulating 100 parts by weight of unsaturated long-chain polyamide 1 with 0.553 parts by weight, 1.036 parts by weight, and 1.589 parts by weight of trimethylolpropane tris(3-mercaptopropionate) and 0.30 parts by weight of phosphono-oxygen photoinitiator, followed by thermoplastic molding and post-curing treatment; wherein the equivalent ratio of the thiol group in trimethylolpropane tris(3-mercaptopropionate) to the residual carbon-carbon double bond in unsaturated long-chain polyamide 1, Eq(SH) / Eq(C=C), are 0.08, 0.15, and 0.23, respectively.

[0060] Preparation methods of mercaptoene micro-crosslinked components: Examples 1-1 to 1-3 (1) 100 parts by weight of unsaturated long carbon chain polyamide 1 was dried with hot air at 80°C for 10 hours until the moisture content was ≤0.10wt%. Then, it was added to the main feed port of a twin-screw extruder and mixed with 0.553 parts by weight, 1.036 parts by weight, 1.589 parts by weight of trimethylolpropane tris(3-mercaptopropionate) and 0.30 parts by weight of phosphonic photoinitiator added to the side feed port of the twin-screw extruder. The mixture was blended, extruded and granulated at the following temperatures: 210°C, 215°C, 220°C, 225°C and 230°C in the barrel, 235°C at the die head, and 180 rpm at the screw speed. The result was a masterbatch containing post-curing components. (2) The masterbatch containing post-curing components obtained in step (1) is dried with hot air at 80°C for 8 hours until the moisture content is ≤0.10wt%. Then it is added to the injection molding machine and injection molded at the following temperatures: 205°C, 210°C, 215°C, 220°C and 225°C in the barrel, 150 rpm in the screw speed and 60°C in the mold temperature. (3) The molded parts obtained in step (2) are placed in a nitrogen-filled oven with a high-purity nitrogen atmosphere and subjected to post-curing heat activation treatment at 160°C for 10 min until the mass fraction of the gel is 1.6 wt%, 3.2 wt%, and 4.6 wt%, respectively, to obtain mercaptoene micro-crosslinked parts 1-1 to 1-3.

[0061] Application Examples of Thiothene Micro-Crosslinked Components 1-1 to 1-3 The injection-molded mercaptoene micro-crosslinked parts 1-1 to 1-3 are applied to low-friction and wear-resistant components (including gears, sliders, bushings, or guide bushings).

[0062] Example 2 of unsaturated long carbon chain polyamide The repeating structural unit of the unsaturated long-chain polyamide is: —NH—(CH2) 10 —NH—CO—(CH2)7—CH=CH—(CH2)7—CO—; The residual carbon-carbon double bond content was 0.48 mmol / g.

[0063] Example 2: Preparation method of unsaturated long carbon chain polyamide (1) 1500 g of deionized water was added to 1000 g (3.2 mol) of 9-octadecenoic acid placed in a glass-lined reactor. After heating and stirring to dissolve at 75 °C, 1927 mL of 30 wt% 1,10-decanediamine aqueous solution was added. The Eq(COOH) / Eq(NH2) ratio was 1.004. The mixture was stirred at 80 °C for 45 min to obtain a homogeneous binary salt solution. (2) Place the binary salt solution obtained in step (1) in a sealed reactor. Under the protection of a high-purity nitrogen atmosphere, slowly heat up to dehydrate: heat up to 170℃ at a rate of 1.0℃ / min for dehydration. During the dehydration process, open the exhaust valve on the top of the reactor to discharge water vapor, and introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0 MPa until the water is drained and the reactants are in a viscous melt state. Then perform pre-condensation: heat up to 240℃ at a rate of 1.5℃ / min, and then introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0 MPa in the reactor. After pre-condensation for 2.0 h at a stirring speed of 40 r / min, perform decompression polymerization: first exhaust the gas and evacuate the vacuum, and reduce the absolute pressure to ≤400 within 15 min. Pa, then at 245℃, reduce compression and polymerize for 30 min, discharge the melt, water-cool and stretch into strips, cut into pellets, vacuum dry at 80℃ and -0.10MPa for 8 h, cool, and obtain unsaturated long carbon chain polyamide 2.

[0064] Example 2 of mercaptoene micro-crosslinked component The thiol-based micro-crosslinked component is formed by extruding and granulating 100 parts by weight of unsaturated long-chain polyamide 2, 0.361 parts by weight of 1,6-hexanedithiol and 0.10 parts by weight of benzoyl peroxide, followed by thermoplastic molding and post-curing treatment; wherein, the equivalent ratio of the thiol group in 1,6-hexanedithiol to the residual carbon-carbon double bond in unsaturated long-chain polyamide 2, Eq(SH) / Eq(C=C), is 0.10.

[0065] Example 2: Preparation method of thiol-based micro-crosslinked components (1) 100 parts by weight of unsaturated long carbon chain polyamide 2 were dried with hot air at 80°C for 10 h until the moisture content was ≤0.10wt%, and then added to the main feed port of the twin-screw extruder. 0.361 parts by weight of 1,6-hexanedithiol and 0.10 parts by weight of benzoyl peroxide were added to the side feed port of the twin-screw extruder. The barrel temperature was 200°C, 205°C, 210°C, 215°C, 220°C and 225°C respectively, the die head temperature was 230°C and the screw speed was 180 rpm. The mixture was then extruded and granulated to obtain a masterbatch containing post-curing components. (2) The masterbatch containing post-curing components obtained in step (1) is dried with hot air at 80°C for 8 hours until the moisture content is ≤0.10wt%. Then it is added to a twin-screw extruder. The barrel temperature is 200°C, 205°C, 210°C, 215°C and 220°C respectively, the die head temperature is 225°C and the screw speed is 40 rpm. The extrusion, sizing and cooling are carried out to obtain the molded pipe. (3) The molded tube obtained in step (2) is placed in a nitrogen-filled oven with a high-purity nitrogen atmosphere and subjected to post-curing heat activation treatment at 150°C for 15 min until the mass fraction of the gel is 2.5 wt%, thus obtaining mercaptoene micro-crosslinked part 2.

[0066] Application Example 2 of Thiolene Micro-Crosslinked Components The extruded mercaptoene micro-crosslinked component 2 is applied to fluid transport pipes (including coolant pipes, fuel pipes or pneumatic pipes) or cable sheaths.

[0067] Examples 3-1 to 3-5 of unsaturated long-chain polyamides The repeating structural units of the unsaturated long-chain polyamide are all: —NH—(CH2) 12 —NH—CO—(CH2)7—CH=CH—(CH2)7—CO—; The residual carbon-carbon double bond contents were 0.20 mmol / g, 0.35 mmol / g, 0.50 mmol / g, 0.65 mmol / g, and 0.80 mmol / g, respectively.

[0068] Preparation methods of unsaturated long-chain polyamides: Examples 3-1 to 3-5 (1) 2000 g of deionized water was added to 1000 g (3.20 mol) of 9-octadecenoic acid placed in a glass-lined reactor. After heating and stirring to dissolve at 80°C, 1391 mL of 50 wt% 1,12-diaminododecane aqueous solution was added. The Eq(COOH) / Eq(NH2) ratio was 1.002. The mixture was stirred for 20 min at 60°C to obtain a homogeneous binary salt solution. (2) Place the binary salt solutions obtained in step (1) into a sealed reaction vessel. Under the protection of a high-purity nitrogen atmosphere, slowly heat up to dehydrate: heat up to 175℃ at a rate of 1.0℃ / min for dehydration. During the dehydration process, open the exhaust valve on the top of the vessel to discharge water vapor and introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0 MPa until the water is drained and the reactants are in a viscous melt state. Then perform pre-condensation: heat up to 245℃ at a rate of 1.5℃ / min, then introduce a high-purity nitrogen atmosphere to maintain a pressure of 1.0 MPa in the vessel. After pre-condensation for 2.2 h at a stirring speed of 40 r / min, perform decompression polymerization: first exhaust the gas and evacuate the vacuum, then reduce the absolute pressure to ≤300 within 15 min. Pa, and then subjected to decompression polymerization at 250℃, 248℃, 245℃, 243℃, and 240℃ for 60min, 45min, 30min, 20min, and 15min respectively, the melt was discharged, water-cooled, stretched, and pelletized, and then vacuum dried at 80℃ and -0.10MPa for 8h. Among them, Examples 3-1 to 3-4 were placed under a high-purity nitrogen atmosphere and subjected to solid-state polycondensation at 165℃, 160℃, 158℃, and 155℃ for 6h, 4h, 2h, and 1h respectively, and then cooled to obtain unsaturated long carbon chain polyamides 3-1 to 3-4 respectively. Example 3-5 was directly cooled to obtain unsaturated long carbon chain polyamide 3-5.

[0069] Examples 3-1 to 3-5 of thiol-based micro-crosslinked components The thiol-based micro-crosslinked component is made by extruding and granulating 100 parts by weight of unsaturated long-chain polyamides 3-1 to 3-5 with 0.399 parts by weight, 0.697 parts by weight, 0.996 parts by weight, 1.295 parts by weight, and 1.594 parts by weight of trimethylolpropane tris(3-mercaptopropionate) and 0.30 parts by weight of phosphooxy photoinitiator, respectively, followed by thermoplastic molding and post-curing treatment; wherein, the equivalent ratio Eq(SH) / Eq(C=C) of the thiol group in trimethylolpropane tris(3-mercaptopropionate) to the residual carbon-carbon double bond in unsaturated long-chain polyamides 4-1 to 4-5 is 0.15.

[0070] Preparation methods of mercaptoene micro-crosslinked components: Examples 3-1 to 3-5 The only difference between the method examples 3-1 to 3-5 of the present invention and the method for preparing mercaptoene micro-crosslinked parts examples 1-2 is that in step (1), the components and weight parts of the mercaptoene micro-crosslinked parts examples 3-1 to 3-5 are used for co-extrusion granulation. In step (2) of embodiments 3-5 of the present invention, the material is added to a blow molding machine and blow molded at a melt temperature of 220°C, a die head temperature of 225°C, a blow pressure of 0.5 MPa, and a mold temperature of 40°C to obtain a molded part. In step (3), post-curing heat activation treatments were performed at 150℃ for 18 min, 16 min, 14 min, 12 min, and 10 min, respectively, until the mass fraction of the gel was 0.9 wt%, 1.8 wt%, 3.0 wt%, 3.9 wt%, and 4.7 wt%, respectively. Examples 1-2 illustrate the preparation methods of the Yutong mercaptoene micro-crosslinked components.

[0071] Application Examples of Thiothene Micro-Crosslinked Components 3-1 to 3-5 The injection-molded mercaptoene micro-crosslinked parts 3-1 to 3-4 were respectively applied to low-friction wear-resistant components (including gears, sliders, bushings or guide bushings). The blow-molded mercaptoene micro-crosslinked parts 3-5 are applied to sports equipment components.

[0072] Comparative Example 1 The only difference between this comparative example and the preparation methods of the thiol-ene micro-crosslinked components in Examples 1-2 is that in step (1), unsaturated long-chain polyamide 1 is replaced with saturated long-chain polyamide, and in step (3), the material of Comparative Example 1 is finally obtained; the only difference between the preparation method of the saturated long-chain polyamide and the preparation method of the unsaturated long-chain polyamide in Example 1 is that in step (1), 1000 g (3.20 mol) 9-octadecenoic acid is replaced with 602 g (3.20 mol) disebaic acid, and the residual C=C≈0 in the obtained saturated long-chain polyamide. The rest is the same as the preparation methods of the thiol-ene micro-crosslinked components in Examples 1-2.

[0073] Comparative Example 2 The only difference between this comparative example and the preparation methods of the mercaptoene micro-crosslinked parts in Examples 1-2 is that in step (1), the unsaturated long-chain polyamide 1 is replaced with the unsaturated long-chain polyamide that is mistakenly crosslinked during the polymerization stage, and no phospho-oxygen photoinitiator is added, resulting in the material of Comparative Example 2. The only difference between the preparation method of the unsaturated long-chain polyamide that is mistakenly crosslinked during the polymerization stage and the preparation method of the unsaturated long-chain polyamide in Example 1 is that in step (1), 0.30 parts by weight of phospho-oxygen photoinitiator is added together with the 1,12-diaminododecane aqueous solution. The rest is the same as the preparation methods of the mercaptoene micro-crosslinked parts in Examples 1-2.

[0074] To facilitate comparison of the mercaptoene micro-crosslinked parts obtained in Examples 1-3 of the present invention, the relationship between the residual C=C content, Eq(SH) / Eq(C=C) equivalent ratio, and gel fraction in the materials obtained in Comparative Examples 1 and 2 is listed together as shown in Table 1.

[0075]

[0076] As shown in Table 1, Examples 1-3 of this invention, by not adding thiol compounds and initiators during the polymerization stage of long-chain polyamides, ensured that C=C in the unsaturated diacids was not consumed in large quantities during the polycondensation process, and avoided the crosslinking problem during polymerization, as seen in Comparative Example 2. This provided a controllable reaction site basis for subsequent post-curing of thiol-ene. The post-curing of Examples 1-3 of this invention controlled the Eq(SH) / Eq(C=C) ratio within the range of 0.05-0.40, and by controlling the amount of thiol and post-curing conditions, the gel fraction of the thiol-ene micro-crosslinked parts was kept within the low gel micro-crosslinking window of 0.5-5.0 wt%, forming a controllable micro-crosslinked structure. This achieved a controllable improvement in low friction, scratch resistance, and media resistance while maintaining thermoplastic processability, thus meeting the requirements of this invention for "processability and controllable micro-crosslinking structure" of the thiol-ene micro-crosslinked parts. In Examples 1-1 to 1-3 of this invention, under the condition of a residual C=C content of 0.52 mmol / g, the gel fraction increased with the increase of the Eq(SH) / Eq(C=C) equivalence ratio, indicating that the degree of micro-crosslinking can be controllably adjusted within a low gelation window by adjusting the equivalence ratio. In Examples 3-1 to 3-4 of this invention, under the condition of Eq(SH) / Eq(C=C) = 0.15, only the residual C=C content of the linear resin was changed, verifying the correspondence between "reactive site content - degree of micro-crosslinking (gel fraction)". The relationship is that the gel fraction increases with the increase of residual C=C content. In summary, this invention, through the synergistic design of the residual C=C content of linear resin and the post-curing equivalent ratio, keeps the formation of the mercapto-ene micro-crosslinked network and the gel fraction within a controllable range. Thus, while maintaining the thermoplastic reprocessability and the inherent low water absorption properties of long-chain polyamide, it provides a stable structural basis for obtaining mercapto-ene micro-crosslinked parts with comprehensive properties such as low friction, scratch resistance and media resistance. It is suitable for applications such as pipes, cable sheaths and low friction wear-resistant parts. As can be seen from the comparison between Examples 3-3 and Examples 1-2 of the present invention, the further solid-state polycondensation of unsaturated long-chain polyamides in Examples 3-3 can adjust the molecular weight / processability, but does not have a significant impact on the gel fraction. In practical applications, whether solid-state polycondensation is required can be selected according to the specific molding process, thus broadening the scope of application of the method of the present invention.

[0077] Comparative Example 1, due to the absence of C=C in the linear resin, has almost zero sites available for the thiol-ene reaction. Even with the addition of thiol compounds / initiators, it is difficult to form a gel, verifying the importance of residual double bonds. Comparative Example 2, due to the addition of an initiator during the polymerization stage, premature crosslinking occurred, resulting in a gel fraction as high as 15.8%, far exceeding the upper limit set by this invention. This led to a significant decrease in melt flowability and processing difficulties during melt extrusion and injection molding, and the molded products were difficult to subsequently undergo controllable thiol-ene post-curing.

[0078] To evaluate the thiol-based micro-crosslinked parts obtained in Examples 1-3 of this invention, the dynamic friction, scratch, media aging, and water absorption properties of the materials obtained in Comparative Examples 1 and 2 were tested according to the following methods, and the test results are shown in Table 2.

[0079] 1) Coefficient of dynamic friction: The coefficient of dynamic friction was tested according to ASTM D1894 standard at 23°C under dry conditions, with steel-strip pairing and a 200g load. 2) Scratch grade: The scratches on the sample surface are graded and evaluated according to DIN 55656 / ISO 1518 standards, and the results are expressed as the grade improvement value relative to the uncured sample. 3) Tensile strength retention rate: The sample was immersed in a medium of 50±2℃ and ethylene glycol / deionized water = 50 / 50 (mass ratio) for 500h for aging. After rinsing with deionized water and drying, it was placed at 23±2℃ for 24h. Then the tensile strength was tested according to ISO 527. 4) Salt spray strength retention rate after 500 hours: The test was conducted under neutral salt spray conditions according to ISO 9227, with a salt spray solution of 5 wt% NaCl, a test temperature of 35±2℃, and continuous spraying for 500 hours. After removal, the solution was rinsed with deionized water, dried, and placed at 23±2℃ for 24 hours. Then, the tensile strength was tested according to ISO 527. 5) Water absorption rate: The sample was placed at 23℃ and 50% relative humidity for 168 hours, and the mass change before and after water absorption was measured. The water absorption rate was expressed as a mass fraction.

[0080]

[0081] From Tables 1 and 2, we can see that: Friction reduction and scratch resistance: The low-gel micro-crosslinked networks constructed in Examples 1 and 2 of this invention under controlled residual C=C and Eq(SH) / Eq(C=C) conditions can effectively suppress surface plastic deformation and micro-cutting, achieving significant friction reduction and scratch resistance effects. In contrast, Comparative Example 1, due to the absence of C=C sites in the resin backbone that can participate in thiol-ene addition, did not form an effective gel, with a gel fraction close to 0, resulting in limited improvement in friction and scratch performance. Although Comparative Example 2 contains unsaturated dicarboxylic acid, the addition of an initiator during the polymerization stage caused the residual C=C to drop to 0.10 mmol / g, and a high gelation rate was observed. Therefore, its dynamic friction coefficient, scratch performance, and long-term media aging performance were all inferior to those of Examples 1 and 2 of this invention. Resistance to media and environment: The tensile strength retention rate and the strength retention rate after aging in ethylene glycol at 50℃ for 500h and salt spray for 500h of the present invention are both better than those of comparative examples 1 and 2. This indicates that the sparse cross-linked network formed under low gelation conditions in the present invention not only does not weaken the media resistance advantage of the long carbon chain polyamide itself, but also plays a certain supporting role in long-term mechanical retention. The mechanism is that the post-curing of mercapto-ene introduces a small number of sulfide cross-linking points between the chains, which provides moderate constraint on molecular chain slippage and stress relaxation, and reduces the strength decay caused by chain segment rearrangement, microcrack initiation and propagation during media aging. At the same time, the cross-linking points can improve the stability of the network structure, making it easier for the mercapto-ene micro-cross-linked parts to maintain the mechanical synergy of crystalline and amorphous phases in humid heat / salt spray environment, thus exhibiting a higher strength retention level. Water absorption and dimensional stability: The water absorption rates of Examples 1 and 2 of this invention are in the same low range as those of Comparative Examples 1 and 2, which is significantly better than many conventional PA6 / PA66 systems. However, Comparative Example 2 has lost its good processability due to excessive crosslinking. This indicates that this invention maintains the inherent low water absorption and dimensional stability of long-chain polyamides while introducing a micro-crosslinked network. The mechanism is that the long methylene segments in the main chain of long-chain polyamides reduce the density and polarity of the amide groups, making it difficult for water molecules to enter in large quantities and form stable swelling. The micro-crosslinking of the mercaptoene micro-crosslinked parts of this invention mainly fixes the network structure in a "point-like" manner between chains through a small number of thioether bonds. This does not introduce a large number of strong hydrophilic groups and can also inhibit chain segment rearrangement and volume expansion after water absorption, thereby helping to maintain low water absorption and dimensional stability, while maintaining melt processability.

[0082] A comparison of Examples 3-3 and Examples 1-2 shows that although Examples 3-3 further subjected the unsaturated long-chain polyamide to solid-state polycondensation, the residual C=C content and Eq(SH) / Eq(C=C) content of both are very close. Therefore, their micro-crosslinking degree and performance indicators such as dynamic friction, scratch grade improvement, and strength retention are similar. This indicates that the further solid-state polycondensation of the unsaturated long-chain polyamide mainly acts on the further polycondensation of the linear resin end groups to increase the molecular weight and optimize melt rheology and processing stability. Its effect is mainly reflected in processing indicators such as IV, MFR, melt viscosity, or extrusion / injection molding process stability, and does not necessarily lead to significant differences in the above performance indicators.

Claims

1. An unsaturated long-chain polyamide, characterized in that: Its repeating structural unit includes: —NH—(CH2) a —NH—CO—(CH2) p —CH=CH—(CH2) q —CO—, where a is an integer from 10 to 12, p and q are integers satisfying p+q=14; and the residual carbon-carbon double bond content is 0.20 to 0.80 mmol / g.

2. A method for preparing the unsaturated long-chain polyamide as described in claim 1, characterized in that, Includes the following steps: (1) Add water to an unsaturated dicarboxylic acid, heat and stir to dissolve, then add an aqueous solution of a diamine and continue stirring to obtain a homogeneous disalt solution; (2) The binary salt solution obtained in step (1) is placed in a closed reaction vessel. Under the protection of an inert atmosphere, the temperature is slowly raised to dehydrate and pre-condensation is carried out. Then, the pressure is reduced and the melt is discharged. The melt is water-cooled, stretched, and granulated. It is then vacuum dried and cooled to obtain unsaturated long carbon chain polyamide.

3. The method for preparing unsaturated long-chain polyamide according to claim 2, characterized in that: In step (1), the equivalent ratio of the carboxyl group in the unsaturated diacid to the amino group in the diamine, Eq(COOH) / Eq(NH2), is 1.000–1.010:1; the mass ratio of the unsaturated diacid to water is 0.25–1.00:1; the heating and stirring temperature for dissolving is 70–80°C; the mass concentration of the diamine aqueous solution is 15–50 wt%; and the stirring temperature for continued stirring is 60–80°C for 20–60 minutes. min; the unsaturated dicarboxylic acid includes a C18:1 aliphatic unsaturated dicarboxylic acid; the C18:1 aliphatic unsaturated dicarboxylic acid includes one or more of 9-octadecenoic acid, 10-octadecenoic acid, or 11-octadecenoic acid; the diamine includes a C10-C12 straight-chain diamine; the C10-C12 straight-chain diamine includes one or more of 1,12-diaminododecane, 1,10-decanediamine, or 1,11-diaminoundecane.

4. The method for preparing unsaturated long-chain polyamide according to claim 2 or 3, characterized in that: In step (2), the slow heating dehydration refers to: heating to 160-180℃ at a rate of 0.5-3.0℃ / min for dehydration, during which water vapor is discharged and an inert atmosphere is introduced to maintain a pressure of 0.5-1.5MPa until the water is completely discharged and the reactants are in a viscous melt state; the pre-condensation refers to: first heating to 240-250℃ at a rate of 0.5-3.0℃ / min, then introducing an inert atmosphere to maintain a pressure of 0.5-1.5MPa inside the reactor, and pre-condensing at a stirring speed of 20-60r / min for 1.5-2.5h; the reduced-pressure polymerization refers to: first venting and evacuating, reducing the absolute pressure to ≤400Pa within 10-20min, and then reducing the pressure for 10-60h at 240-250℃. The vacuum drying temperature is 60–100°C, the vacuum degree is -0.06–-0.10 MPa, and the time is 6–10 h; or after vacuum drying, it is placed under an inert atmosphere for solid-phase polycondensation; the solid-phase polycondensation temperature is 150–170°C, and the time is 1–6 h; the inert atmosphere includes one or more of nitrogen, argon, or helium.

5. A mercaptoene micro-crosslinking component, characterized in that: It is mainly composed of unsaturated long carbon chain polyamide as described in claim 1, multifunctional thiol compound and free radical initiator, blended, extruded and granulated, thermoplastic molded and then post-cured.

6. The mercaptoene micro-crosslinking component according to claim 5, characterized in that: The amounts of the polyfunctional thiol compound and the free radical initiator are respectively equivalent to 0.05-2.50% and 0.05-0.50% of the mass of the unsaturated long-chain polyamide; the equivalent ratio of the thiol group in the polyfunctional thiol compound to the residual carbon-carbon double bond in the unsaturated long-chain polyamide, Eq(SH) / Eq(C=C), is 0.05-0.40:1; the polyfunctional thiol compound includes one or more of trimethylolpropane tris(3-mercaptopropionate), 1,6-hexanedithiol, or pentaerythritol tetra(3-mercaptopropionate); the free radical initiator includes one or more of phosphonooxy photoinitiators, azobisisobutyronitrile, or benzoyl peroxide.

7. A method for preparing a thiol-based micro-crosslinked component as described in claim 5 or 6, characterized in that, Includes the following steps: (1) After drying the unsaturated long carbon chain polyamide of claim 1, it is added to a twin-screw extruder with a multifunctional thiol compound and a free radical initiator for co-extrusion granulation to obtain a masterbatch containing post-curing components; (2) After drying the masterbatch containing the post-curing component obtained in step (1), thermoplastic molding is performed to obtain the molded part; (3) Place the molded part obtained in step (2) in an inert atmosphere and perform post-curing treatment to obtain mercaptoene micro-crosslinked part.

8. The method for preparing the thiol-based micro-crosslinked component according to claim 7, characterized in that: In step (1), or before adding to the twin-screw extruder, dry mixing is performed first; the barrel temperature of the co-extrusion granulation is 200-230℃, the die temperature is 230-240℃, and the screw speed is 100-250rpm; in step (2), the thermoplastic molding includes injection molding, extrusion, or blow molding; the injection molding conditions are: the injection molding machine barrel temperature is 200-230℃, the screw speed is 100-250rpm, and the mold temperature is 40-80℃; the extrusion conditions are: the extruder barrel temperature is 200-220℃, the die temperature is 205-225℃, the screw speed is 20-80rpm, sizing, and cooling; the blow molding conditions are: the blow molding melt temperature is 200-230℃, the die temperature is 205-235℃, and the blow pressure is 0.2-0.

8. MPa, mold temperature is 20~60℃; in steps (1) and (2), the drying refers to drying with hot air or vacuum at 70~90℃ for 8~12h until the moisture content is ≤0.10wt%.

9. The method for preparing the thiol-based micro-crosslinked component according to claim 7 or 8, characterized in that: In step (3), the post-curing treatment includes thermal activation and / or photoactivation. The thermal activation treatment is performed at a temperature of 140–180°C for 5–30 min until the mass fraction of the gel is 0.5–5.0 wt%; the inert atmosphere includes one or more of nitrogen, argon, or helium.

10. An application of the mercaptoene microcrosslinker as described in claim 5 or 6, characterized in that: The mercaptoene micro-crosslinked component or its product as described in claim 5 or 6 may be applied to pipes, cable sheaths, low-friction wear-resistant parts, or sports equipment parts.

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