High-temperature resistant long-chain semi-aromatic polyamide resin, its preparation method, composition and molded articles

Abstract

This invention discloses a high-temperature resistant long-chain semi-aromatic polyamide resin, its preparation method, composition, and molded articles. The polymerizable monomers of the polyamide resin include a diamine monomer and a diacid monomer. The diamine monomer is selected from 1,13-tetanediamine and 1,5-pentanediamine, and the diacid monomer is selected from any one or a combination of two or more of terephthalic acid and its derivatives, wherein 1,5-pentanediamine accounts for 50-80% of the molar fraction of the diamine monomer. This polyamide resin has a melting point between 270 and 315°C and exhibits excellent color stability and melt flowability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a high-temperature resistant long-carbon-chain semi-aromatic polyamide. Background Technology

[0002] High-temperature resistant long-chain semi-aromatic polyamides refer to polyamides with melting points above 270℃, whose molecular backbone contains both aromatic ring structures and diamine or diacid monomer units with 10 or more carbon atoms. These mainly include PA10T, PA11T, PA12T, PA13T, and PA14T. Long-chain semi-aromatic nylons not only possess excellent heat resistance, mechanical properties, solvent and chemical resistance, good insulation, and low moisture absorption; they also exhibit good toughness and a low melting point (below 350℃: the temperature at which semi-aromatic nylon begins to decompose during processing is 350℃), resulting in good processability and high cost-effectiveness. The excellent comprehensive properties of long-chain semi-aromatic nylons have led to their widespread application in the automotive, aerospace, and electronics industries, with continuously increasing market demand. Patent CN104817693B discloses PA11T and its preparation method, utilizing a "one-pot" method in a rotary drum reactor. The reaction temperature throughout is kept below the melting point of PA11T, and the overall reaction time is controlled within 15 hours, producing a powder. This method is suitable for small-scale laboratory preparation, but scale-up production faces difficulties in powder discharge and storage. Furthermore, the PA11T prepared by this method has a relatively low viscosity (1.61–1.70), leading to deviations in mechanical properties. Patent CN112321820A discloses a preparation method for PA10T, PA12T, and PA14T, namely a one-step solid-state polymerization method. Throughout the reaction, the temperature is kept below the melting temperature of the materials. In addition, small balls are added during the reaction, which not only mix and stir but also collide with materials that may adhere to the inner wall of the equipment, preventing material sticking. This method produces a white powdered nylon, which also faces difficulties in powder discharge and storage if used for scale-up production. Its melting point, tensile strength, flexural strength, flexural modulus, heat distortion temperature, elongation at break, and notched impact strength are all good, and the overall quality of the product is very good.

[0003] Industrially, polyamide is typically produced by melt discharge and pelletizing, which requires the system temperature to be above the product's melting point. To achieve good melt flowability, the temperature usually needs to be 15-25°C above the melting point. However, in mass production, melt discharge usually takes 20-40 minutes. Maintaining the high temperature will cause the product's color to deteriorate as the discharge time increases. The degree of yellowing can reflect the degree of polymer degradation, further affecting the product's quality.

[0004] Carbon quantum dots (CQDs) are novel nanomaterials composed of dispersed, spherical carbon particles with extremely small sizes (below 10 nm) and fluorescent properties. CQDs possess numerous advantages, including excellent optical properties, good water solubility, low toxicity, environmental friendliness, wide availability of raw materials, low cost, and good biocompatibility. Since their initial discovery, many synthesis methods have been developed, including arc discharge, laser ablation, electrochemical synthesis, chemical oxidation, combustion, hydrothermal synthesis, microwave synthesis, and template methods. CQDs have wide applications, showing promising prospects in many fields such as medical imaging technology, environmental monitoring, chemical analysis, catalyst preparation, and energy development. Summary of the Invention

[0005] To address the shortcomings of existing technologies and products, this invention provides a high-temperature resistant long-carbon-chain semi-aromatic polyamide resin, its preparation method, composition, and molded articles.

[0006] The first aspect of this invention provides a high-temperature resistant long-chain semi-aromatic polyamide resin (hereinafter referred to as polyamide resin). The polymer monomers of the polyamide resin include a diamine monomer and a diacid monomer. The diamine monomer is selected from 1,13-tridecanediamine and 1,5-pentanediamine, and the diacid monomer is selected from any one or a combination of two or more of terephthalic acid and its derivatives, wherein 1,5-pentanediamine accounts for 50-80% of the molar fraction of the diamine monomer.

[0007] In a preferred embodiment of the present invention, the molar ratio of diamine monomer to diacid monomer is (1.005-1.1):1, more preferably (1.005-1.05):1, and more preferably (1.005-1.03):1.

[0008] In a preferred embodiment of the present invention, the molar fraction of 1,5-pentanediamine in the diamine monomer is 51-75%, more preferably 65-75%, more preferably 70-75%, for example 55%, 60%, 65%, 70% or 75%.

[0009] As a preferred embodiment of the present invention, the derivatives of terephthalic acid include, but are not limited to, any one or a combination of two or more of terephthaloyl chloride, dimethyl terephthalate and diethyl terephthalate.

[0010] As a preferred embodiment of the present invention, the high-temperature resistant long-carbon-chain semi-aromatic polyamide resin further contains carbon dots, the content of which is 50-1200 ppm, further 200-1200 ppm, further 400-1200 ppm, further 400-1000 ppm, and further 650-1000 ppm.

[0011] In a preferred embodiment of the present invention, the particle size of the carbon dots is 1-10 nm, and more specifically 5-10 nm.

[0012] In a preferred embodiment of the present invention, the functional groups on the surface of the carbon dots are carboxyl groups and hydroxyl groups.

[0013] As one embodiment of the present invention, the carbon dot surface may also contain a small amount of other functional groups besides hydroxyl and carboxyl groups. This is acceptable as long as it does not affect the properties of the high-temperature resistant long-chain semi-aromatic polyamide resin.

[0014] As one embodiment of the present invention, the carbon dots can be further modified, such as by doping with metal ions (e.g., sodium ions). This is acceptable as long as it does not affect the properties of the high-temperature resistant long-chain semi-aromatic polyamide resin.

[0015] This invention does not impose any particular restrictions on the source or preparation process of the carbon dots. For example, they can be commercially available, or refer to Yingran H, Ling DZ, Tai-Shung C.Na + Functionalized carbon quantum dotincorporated thin-film nanocomposite membranes for selenium and arsenic removal[J].Journal of Membrane Science,2018,564:483-491. Section 2.2 of this paper describes the preparation of carbon dots with hydroxyl and carboxyl functional groups on the surface.

[0016] As one embodiment of the present invention, the high-temperature resistant long-carbon-chain semi-aromatic polyamide resin includes diamine structural units and diacid structural units formed by the polymerization reaction of the diamine monomer and the diacid monomer, wherein the sum of the diamine structural units and the diacid structural units accounts for more than 97 wt% of the polyamide resin, and more preferably more than 99 wt%.

[0017] In one embodiment of the present invention, the polyamide resin contains additives.

[0018] As one embodiment of the present invention, the additives include, but are not limited to, any one or a combination of two or more of the following: capping agents, catalysts, flame retardants, antioxidants, ultraviolet absorbers, infrared absorbers, nucleating agents, fluorescent whitening agents, and antistatic agents.

[0019] In one embodiment of the present invention, the content of the additive is 0.01% to 3 wt%, more specifically 0.01% to 1.5 wt%.

[0020] As one embodiment of the present invention, the additive includes at least a capping agent, which includes any one or a combination of two or more organic monocarboxylic acids having 2 to 7 carbon atoms, such as any one or a combination of two of benzoic acid and acetic acid.

[0021] In one embodiment of the present invention, the ratio of the end-capping agent to the sum of the masses of the diamine monomer and the diacid monomer is (0.05-0.5):100, and more specifically (0.05-0.3):100.

[0022] As a preferred embodiment of the present invention, the melting point of the polyamide resin is 270-315°C, more specifically 285-315°C.

[0023] As a preferred embodiment of the present invention, the relative viscosity of the high-temperature resistant long-chain semi-aromatic polyamide resin is 2.2 to 2.6, and more preferably 2.35 to 2.45.

[0024] As a preferred embodiment of the present invention, the YI value of the high-temperature resistant long carbon chain semi-aromatic polyamide resin when held at a temperature 30°C higher than its melting point for 40 min is set as M, and the YI value when held for 0 min is set as N. The M / N ratio is 1 to 1.2, more preferably 1 to 1.1, and more preferably 1 to 1.05.

[0025] A second aspect of the present invention provides a method for preparing a high-temperature resistant long-chain semi-aromatic polyamide resin, characterized by comprising the following steps:

[0026] 1) The polyamide salt solution is concentrated by water displacement at 120-150°C under an inert gas or nitrogen atmosphere, and then the temperature is raised to 230-270°C and reacted at a pressure of 2.0-3.0 MPa for 0.5-2.5 h;

[0027] 2) Drain water to reduce the pressure in the reaction system to 0-0.1 MPa. The temperature of the reaction system is 285-335℃ when the pressure reduction ends. Then, evacuate to a vacuum degree below -0.02 MPa and maintain it for 0-300 seconds to obtain polyamide melt.

[0028] The polyamide salt is obtained by reacting a diamine monomer and a diacid monomer to form a salt.

[0029] In one embodiment, the method includes step a) prior to step 1): adding diamine monomer and diacid monomer to water, heating to 120–160°C, and optionally maintaining the temperature at 120–160°C for 0.5–2.5 h to form a polyamide salt solution.

[0030] In one embodiment, the wastewater concentration in step 1) is such that the concentration of the polyamide salt is 50 wt% to 80 wt%, and more specifically 60 wt% to 75 wt%.

[0031] In one embodiment, the reaction time in step 1) is 0.5 to 2 hours.

[0032] In one embodiment, step 2) involves draining water to reduce the pressure in the reaction system to 0-0.05 MPa, or further to 0-0.02 MPa.

[0033] In one embodiment, step 2) involves evacuating to a vacuum level of -0.05 MPa to -0.1 MPa.

[0034] In one embodiment, the vacuum holding time in step 2) is 0 to 90 seconds, further 5 to 90 seconds, and even further 5 to 30 seconds.

[0035] In one embodiment, the polyamide salt solution in step 1) contains additives and carbon dots.

[0036] In one embodiment, the additive is added at any stage of step a) and / or step 1). Preferably, the raw materials in step a) also include the additive. For example, the additive can be added during the preparation of the polyamide salt solution.

[0037] In one embodiment, carbon dots are added at any stage of step a) and / or step 1). Preferably, the raw materials in step a) also include carbon dots. For example, carbon dots can be added during the preparation of a polyamide salt solution.

[0038] In one embodiment, the raw materials in step a) further include carbon dots and additives. For example, carbon dots and additives can be added during the preparation of the polyamide salt solution.

[0039] The carbon dots and additives have the same limitations as described above.

[0040] In one embodiment, the method includes step 3): water-cooling and cutting polyamide melt into pellets to obtain polyamide resin.

[0041] A third aspect of the present invention is to provide a composition comprising the high-temperature resistant long-chain semi-aromatic polyamide resin described in any of the preceding claims.

[0042] A fourth aspect of the present invention is to provide a molded article prepared from a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0043] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0044] The reagents and raw materials used in this invention are all commercially available.

[0045] The positive and progressive effects of this invention are as follows:

[0046] Compared with the prior art, the implementation of the present invention has at least the following advantages:

[0047] 1. The high-temperature resistant long-chain semi-aromatic polyamide resin of the present invention can be obtained by one-step condensation polymerization process. The method is simple and easy to operate and has good industrialization prospects.

[0048] 2. Due to the extensive entanglement of long chains, long-chain polyamides are prone to melt flow defects, leading to longer melt discharge times and consequently, poor polymer color. Carbon dots, with their spherical structure and abundant hydroxyl and carboxyl groups on their surface, are introduced into long-chain polyamides in this invention. These carbon dots act as end-capping agents, reducing exposed terminal amino groups and thus minimizing weak points for high-temperature degradation. Furthermore, the spherical structure of the carbon dots provides self-lubrication, improving the melt flow of the long-chain polymer. The synergistic effect of introducing carbon dots enhances the color stability of the melt discharge of long-chain polyamides.

[0049] 3. Carbon dots are believed to form extremely strong hydrogen bonds. The introduction of ppm-level carbon dots can play a role in physical and chemical micro-crosslinking, which can improve the mechanical strength of the material and enhance its high-temperature resistance. It also has a high melting point. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] 1) Method for testing melting point:

[0052] According to standard ISO 11357-3, the heating rate is 20℃ / min.

[0053] 2) Relative viscosity η r Test method:

[0054] Ubbelohde viscometer concentrated sulfuric acid method: Accurately weigh 0.5±0.0002g of dried polyamide resin sample, add 50mL of concentrated sulfuric acid (96%) to dissolve it to obtain a polyamide solution, and measure and record the flow time t0 of concentrated sulfuric acid and the flow time t of polyamide solution in a constant temperature water bath at 25±0.02℃.

[0055] Formula for calculating relative viscosity number: Relative viscosity η r = t / t0.

[0056] 3) Yellow Index (YI value): Refer to HG / T3862-2006.

[0057] 4) Discharge rate: Measured in seconds, which is the time (in seconds) it takes for 100g of polyamide melt to flow out from the bottom valve of the reactor.

[0058] The antioxidant used in the examples and comparative examples is antioxidant H10, the catalyst is sodium hypophosphite, and the end-capping agent is benzoic acid or acetic acid. The carbon dots have carboxyl and hydroxyl functional groups on their surface and a particle size of 5–10 nm.

[0059] In the examples and comparative examples, "%" represents a mass percentage, and the amounts of antioxidants, catalysts, capping agents, and carbon dots are based on the sum of the masses of all diamine and diacid monomers.

[0060] The unit ppm represents a percentage by mass; 100 ppm = 0.01%.

[0061] The pressures described in the examples and comparative examples are all gauge pressures.

[0062] Example 1

[0063] 0.46 mol 1,13-tetanediamine, 0.55 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.13% benzoic acid, 550 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 135 °C under a nitrogen atmosphere and held at that temperature for 1 hour to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and maintained at 2.5 MPa for 1 hour. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 303 °C. A vacuum of -0.07 MPa was applied and maintained for 15 seconds to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0064] Example 2

[0065] 0.40 mol 1,13-tetanediamine, 0.62 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.12% benzoic acid, 600 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 140 °C under a nitrogen atmosphere and held at that temperature for 1 hour to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and maintained at 2.6 MPa for 1 hour. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 295 °C. A vacuum of -0.07 MPa was applied and maintained for 10 seconds to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0066] Example 3

[0067] 0.37 mol 1,13-tetanediamine, 0.66 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.11% benzoic acid, 650 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 140 °C under a nitrogen atmosphere and held at that temperature for 1 hour to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 135 °C. The solution was then concentrated by water displacement to a concentration of 70 wt%. The temperature was then raised again to 255 °C and maintained at 2.7 MPa for 1 hour. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 288 °C. A vacuum of -0.07 MPa was applied and maintained for 15 seconds to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0068] Example 4

[0069] 0.32 mol 1,13-tetanediamine, 0.70 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.10% benzoic acid, 700 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 145 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and maintained at 2.6 MPa for 1.5 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 297 °C. A vacuum of -0.08 MPa was applied and maintained for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0070] Example 5

[0071] 0.25 mol 1,13-tetanediamine, 0.76 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.09% benzoic acid, 750 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 150 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 60 wt%. The temperature was then raised again to 250 °C and maintained at 2.7 MPa for 1.2 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 329 °C. A vacuum of -0.07 MPa was applied and maintained for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0072] Example 6

[0073] 0.32 mol 1,13-tetanediamine, 0.70 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.10% benzoic acid, 50 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 145 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and the reaction was carried out at a pressure of 2.6 MPa for 1.5 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 297 °C. A vacuum of -0.08 MPa was applied and held for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0074] Example 7

[0075] 0.32 mol 1,13-tetanediamine, 0.70 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.10% acetic acid, 50 ppm carbon dots, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 145 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and maintained at 2.6 MPa for 1.5 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 297 °C. A vacuum of -0.08 MPa was applied and maintained for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0076] Comparative Example 1

[0077] 0.32 mol 1,13-tetanediamine, 0.70 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.10% benzoic acid, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 145 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and maintained at 2.6 MPa for 1.5 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 297 °C. A vacuum of -0.08 MPa was applied and maintained for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0078] Comparative Example 2

[0079] 0.32 mol 1,13-tetanediamine, 0.70 mol 1,5-pentanediamine, 1.00 mol terephthalic acid, 0.03% catalyst, 0.3% antioxidant, 0.10% acetic acid, and water were mixed evenly. The mixture was stirred at 80 rpm and heated to 145 °C under a nitrogen atmosphere and held at that temperature for 1 h to obtain a 50 wt% nylon salt solution. Heating was stopped, and the reaction system was cooled to 130 °C. The solution was then concentrated by water displacement to a concentration of 65 wt%. The temperature was then raised again to 250 °C and the reaction was carried out at a pressure of 2.6 MPa for 1.5 h. The pressure was then reduced by water displacement to 0 MPa. After the pressure reduction, the temperature of the reaction system was 297 °C. A vacuum of -0.08 MPa was applied and held for 10 s to obtain a polyamide melt. The polyamide melt was then water-cooled, stretched, and pelletized to obtain a high-temperature resistant long-chain semi-aromatic polyamide resin.

[0080] Table 1

[0081]

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-temperature-resistant long-carbon-chain semi-aromatic polyamide resin, characterized by, The polyamide resin comprises a diamine monomer and a diacid monomer, the diamine monomer is selected from 1,13-tridecanediamine and 1,5-pentanediamine, and the diacid monomer is selected from terephthalic acid and derivatives thereof, wherein the mole fraction of 1,5-pentanediamine in the diamine monomer is 50-80%; The polyamide resin contains carbon dots, and the content of the carbon dots is 50-1200 ppm.

2. The long carbon chain semi-aromatic polyamide resin having high heat resistance according to claim 1, wherein The mole fraction of 1,5-pentanediamine in the diamine monomer is 51-75%; and / or, The substance amount ratio of the diamine monomer to the diacid monomer is (1.005-1.1):1; and / or; The content of the carbon dots is 200-1200 ppm; and / or, The particle size of the carbon dots is 1-10 nm; and / or, The polyamide resin comprises diamine structural units and diacid structural units formed after polymerization of the diamine monomer and the diacid monomer, and the total of the diamine structural units and the diacid structural units accounts for more than 97% by weight of the polyamide resin; and / or, The polyamide resin contains an additive.

3. The long carbon chain semi-aromatic polyamide resin having high heat resistance according to claim 2, wherein The mole fraction of 1,5-pentanediamine in the diamine monomer is 65-75%; and / or, The substance amount ratio of the diamine monomer to the diacid monomer is (1.005-1.05):1; and / or; The content of the carbon dots is 400-1200 ppm; and / or, The particle size of the carbon dots is 5-10 nm; and / or, The total of the diamine structural units and the diacid structural units accounts for more than 99% by weight of the polyamide resin; and / or, The additive comprises any one or a combination of two or more of an end-capping agent, a catalyst, a flame retardant, an antioxidant, an ultraviolet absorber, an infrared absorber, a crystallization nucleating agent, an optical brightener, and an antistatic agent; and / or, The content of the additive in the polyamide resin is 0.01-3% by weight.

4. The long carbon chain semi-aromatic polyamide resin having high heat resistance according to claim 2, wherein The mole fraction of 1,5-pentanediamine in the diamine monomer is 70-75%; and / or, The substance amount ratio of the diamine monomer to the diacid monomer is (1.005-1.03):1; and / or; The content of the carbon dots is 400-1000 ppm; and / or, The content of the additive in the polyamide resin is 0.01-1.5% by weight.

5. The long carbon chain semi-aromatic polyamide resin of claim 1, wherein the long carbon chain semi-aromatic polyamide resin has a melting point of 300°C or higher. The content of the carbon dots is 650-1000 ppm; and / or, The melting point of the polyamide resin is 270-315℃; and / or, The relative viscosity of the polyamide resin is 2.2-2.

6.

6. The long carbon chain semi-aromatic polyamide resin of claim 1, wherein, The melting point of the polyamide resin is 285-315℃; and / or, The relative viscosity of the polyamide resin is 2.35-2.

45.

7. The long carbon chain semi-aromatic polyamide resin of claim 1, wherein the long carbon chain semi-aromatic polyamide resin has a melting point of 300°C or higher. The YI value of the polyamide resin when kept at a temperature 30℃ higher than the melting point for 40 min is set as M, and the YI value when kept for 0 min is set as N, and M / N is 1-1.

2.

8. The long carbon chain semi-aromatic polyamide resin of claim 7, wherein the long carbon chain semi-aromatic polyamide resin has a melting point of 300°C or higher. M / N is 1-1.

1.

9. The long carbon chain semi-aromatic polyamide resin of claim 7, wherein the long carbon chain semi-aromatic polyamide resin has a melting point of 300°C or higher. M / N is 1-1.

05.

10. A method for producing the high-temperature-resistant long-carbon-chain semi- aromatic polyamide resin described in any one of claims 1 to 9, characterized by, The method comprises the following steps: 1) draining and concentrating a solution of a polyamide salt at 120-150℃ under an inert gas or nitrogen atmosphere, and then increasing the temperature to 230-270℃, and reacting for 0.5-2.5 h under a pressure of 2.0-3.0 MPa; 2) draining and decompressing to reduce the pressure in the reaction system to 0-0.1 MPa, and then vacuumizing to a vacuum degree of -0.02 MPa or less, and maintaining for 0-300 s, to obtain a polyamide melt; The solution of the polyamide salt contains an additive and carbon dots.

11. The method of claim 10, wherein, The draining in step 1) is to concentrate the polyamide salt to a concentration of 50wt%-80wt%; and / or, The reaction in step 1) is for 0.5-2.5 h; and / or, The draining and decompressing in step 2) is to reduce the pressure in the reaction system to 0-0.05 MPa; and / or, The vacuumizing in step 2) is to a vacuum degree of -0.05 MPa to -0.1 MPa; and / or, The time for maintaining the vacuum in step 2) is 0-90 s.

12. The method of claim 10, wherein, The draining in step 1) is to concentrate the polyamide salt to a concentration of 60wt%-75wt%; and / or, The draining and decompressing in step 2) is to reduce the pressure in the reaction system to 0-0.02 MPa; and / or, The time for maintaining the vacuum in step 2) is 5-90 s.

13. The preparation method according to claim 10, characterized in that, The time for maintaining the vacuum in step 2) is 5-30 s.

14. The method of claim 10, wherein, The polyamide salt is obtained by reacting a diamine monomer and a diacid monomer; and / or, The method comprises a step a) before step 1): adding the diamine monomer and the diacid monomer into water, and heating to 120-160 ℃, and optionally maintaining at 120-160 ℃ for 0.5-2.5 h, to form a solution of the polyamide salt.

15. The preparation method according to claim 14, characterized in that, The additive is added at any stage of step a) and / or step 1); and / or, The carbon dots are added at any stage of step a) and / or step 1); and / or, The method comprises a step 3): water-cooling, drawing, and pelletizing the polyamide melt to obtain a polyamide resin.

16. A composition characterized in that, The composition comprises the high-temperature-resistant long-carbon-chain semi-aromatic polyamide resin according to any one of claims 1-9.

17. A molded product prepared by using the high-temperature-resistant long-carbon-chain semi-aromatic polyamide resin according to any one of claims 1-9 as a raw material.

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