A high-temperature resistant nylon PA6T / 66 copolymer and its preparation method

Abstract

This invention belongs to the field of polymer materials and discloses a high-temperature resistant nylon PA6T / 66 copolymer and its preparation method. The raw materials for preparation include terephthalic acid, adipic acid, 1,6-hexanediamine, a branching agent, a capping agent, a catalyst, and demineralized water. The molar ratio of terephthalic acid to adipic acid is (5:5) to (10:0); the ratio of the amount of 1,6-hexanediamine to the total molar amount of terephthalic acid and adipic acid is (1.015 to 1.050):1; the amount of the branching agent is 0.05% to 0.5% of the total molar amount of terephthalic acid, adipic acid, and 1,6-hexanediamine; and the amount of the capping agent is 0.5% to 1.5% of the total mass of terephthalic acid, adipic acid, and 1,6-hexanediamine. The high-temperature resistant nylon PA6T / 66 copolymer of the present invention incorporates a high-temperature resistant branching agent, which is introduced into the main chain of the nylon molecular chain. After prepolymerization and solid-phase thickening, the high-temperature resistant nylon prepared has a relatively high viscosity, and while possessing excellent mechanical properties, it also has better toughness and melt flowability, and better processing performance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically, it relates to a high-temperature resistant nylon PA6T / 66 copolymer and its preparation method. Background Technology

[0002] Semi-aromatic nylons are a class of high-performance polyamide materials that contain both aliphatic and aromatic units in their main chain, combining the flexibility of aliphatic nylons with the heat resistance and mechanical strength of aromatic nylons. The aliphatic units provide flexibility and processability, while the aromatic units enhance heat resistance, mechanical strength, and chemical stability.

[0003] Semi-aromatic nylons possess excellent heat resistance, with glass transition temperatures (Tg) exceeding 100℃; they exhibit low deformability, shrinkage, and creep, and are relatively dimensionally stable; their mechanical properties are superior to those of general aliphatic nylons; they have low water absorption, with minimal impact on product dimensions and mechanical properties after water absorption; they possess excellent electrical insulation properties, as well as outstanding arc resistance and tracking resistance; they also exhibit good solvent and corrosion resistance; a low coefficient of linear expansion, low warpage, and good processability. Semi-aromatic nylons can be widely used in automotive, electronics, and industrial materials fields, and future research will further improve their performance and environmental friendliness.

[0004] While semi-aromatic high-temperature resistant nylons possess excellent properties, they still present certain challenges in terms of processability, cost, performance, and environmental impact. For instance, the melting point of semi-aromatic nylons typically exceeds 300°C, requiring high-temperature equipment for processing, which increases energy consumption and equipment costs. Furthermore, semi-aromatic high-temperature resistant nylons have high melt viscosity and poor flowability, making it difficult to fill molds during injection molding or extrusion. Although they exhibit high strength and rigidity, their toughness is relatively poor, making them prone to brittle fracture. Finally, semi-aromatic nylons are difficult to biodegrade, potentially causing environmental pollution upon disposal.

[0005] Chinese Patent Publication No. CN109575273A discloses a high-temperature resistant semi-aromatic copolymer nylon and its preparation method. The nylon comprises the following components in parts by weight: 80-100 parts of terephthalic acid, 40-50 parts of isophthalic acid, 10-15 parts of adipic acid, 90-120 parts of hexamethylenediamine, 0.1-0.3 parts of catalyst, 0.05-0.2 parts of nucleating agent, 0.5-2.5 parts of end-capping agent, 0.25-0.6 parts of anti-yellowing agent, and 80-120 parts of deionized water. The synthesized semi-aromatic copolymer nylon has a melting point of about 300±20℃, which is lower than the thermal decomposition temperature, and can be directly melt-extruded.

[0006] Chinese patent CN102477219A discloses a semi-aromatic high-temperature resistant nylon and its preparation method. The method involves adding 75-95 parts of nylon salt, 0.2-0.8 parts of end-capping agent, 0.1-0.6 parts of catalyst, 0.5-1 parts of antioxidant, 0.1-0.5 parts of lubricant, and 30-50 parts of deionized water to a stirred high-pressure polymerization reactor. The high-temperature resistant nylon prepolymer synthesized in the high-pressure stirred reactor is then melt-extruded twice using a twin-screw extruder. This improves the devolatilization efficiency, shortens the thickening time, and allows for the smooth discharge of high-viscosity polymer from the reactor. Using different extrusion temperatures prevents high-temperature degradation of the prepolymer.

[0007] Chinese patent CN118325071A discloses a method for preparing bio-based semi-aromatic high-temperature resistant nylon PA5T / 56. Using PTA terephthalic acid and 1,5-pentanediamine as raw materials, the method involves copolymerization with adipic acid, the addition of antioxidants and whitening agents, followed by salt formation, prepolymerization, and solid-phase thickening to ultimately produce bio-based semi-aromatic high-temperature resistant nylon PA5T / 56. This technology utilizes biomass as a partial source of raw materials, reducing dependence on petroleum resources, and the material is biodegradable.

[0008] The existing industrially produced semi-aromatic nylon varieties mainly include the following: PA6T, PA9T, PA10T, PA12T, PA6I / 6T, PA6T / 6I, PA6T / 66, and PA6T / XT. PA6T / 66 is a copolymer of hexamethylenediamine (HMDA), terephthalic acid (TPA), and adipic acid (AA). It has excellent heat resistance and mechanical properties and is often used in electronics, automobiles, and other fields. However, its toughness and melt flowability need further improvement.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The technical problem to be solved by this invention is to overcome at least one of the shortcomings of the prior art and provide a high-temperature resistant nylon PA6T / 66 copolymer and its preparation method. The high-temperature resistant nylon PA6T / 66 copolymer prepared by this invention has excellent mechanical properties, good toughness, good flowability, and superior processing performance. In addition, the preparation method is simple, easy to implement, convenient for large-scale production and further promotion, and has a wide range of applications.

[0011] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0012] This invention provides a high-temperature resistant nylon PA6T / 66 copolymer, the raw materials for which include terephthalic acid, adipic acid, 1,6-hexanediamine, a branching agent, a capping agent, a catalyst, and demineralized water, wherein:

[0013] The molar ratio of terephthalic acid to adipic acid is (5:5) to (10:0);

[0014] The ratio of the amount of 1,6-hexanediamine to the total molar amount of terephthalic acid and adipic acid is (1.015–1.050):1;

[0015] The amount of the branching agent used is 0.05 to 0.5% of the total molar amount of terephthalic acid, adipic acid, and 1,6-hexanediamine;

[0016] The amount of the capping agent is 0.5 to 1.5% of the total mass of terephthalic acid, adipic acid and 1,6-hexanediamine.

[0017] As a preferred embodiment, the ratio of the amount of 1,6-hexanediamine to the total molar amount of terephthalic acid and adipic acid is (1.015–1.025):1.

[0018] As a preferred embodiment, the amount of the branching agent is 0.05 to 0.2% of the total molar amount of terephthalic acid, adipic acid, and 1,6-hexanediamine.

[0019] Experiments have shown that increasing the amount of branching agent within a certain range helps to further improve the toughness of high-temperature resistant nylon, while also increasing its melt flow index. However, if the amount of branching agent added is too high, exceeding 0.5% of the total molar amount of terephthalic acid, adipic acid, and 1,6-hexamethylenediamine, it will affect the polymerization. This is because excessively high terminal carboxyl groups will result in an excessively low relative viscosity of the polymer.

[0020] In a further embodiment, the branching agent is citrate amide prepared from citric acid and amino acids.

[0021] In this invention, citrate amide is added as a branching agent to the raw materials of the high-temperature resistant nylon PA6T / 66 copolymer. Citrate amide is prepared from citric acid and amino acids. Citric acid is a tribasic acid that can react with long-chain amino acids via amidation. Citric acid and amino acids are linked through amide bonds (-CONH-), yielding a novel star-shaped branching agent. On one hand, the terminal carboxyl group of the branching agent can further react with the terminal amino groups of the high-temperature nylon to increase the spacing between the high-temperature nylon molecular chains, making it easier to detangle during processing, thus improving its fluidity and processing performance. On the other hand, the introduction of long-chain amino acids into the nylon molecular chain also improves the flexibility of the high-temperature nylon molecular chain, thereby enhancing the toughness of the nylon copolymer.

[0022] In a further embodiment, the molar ratio of citric acid to amino acids is 1:3.

[0023] Preferably, the amino acid is selected from one or more of aspartic acid, asparagine, glutamic acid, lysine, and arginine.

[0024] A further approach involves preparing citrate amide by heating a reaction of citric acid and amino acids in an organic solvent.

[0025] In a further embodiment, the organic solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide, and dichloroethane.

[0026] A further approach involves heating the reaction in the presence of a carboxyl activator to prepare citrate amide.

[0027] In a further embodiment, the carboxyl activator is selected from at least one of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and dicyclohexylcarbodiimide.

[0028] A further proposed approach involves heating the reaction at a temperature of 80-120℃ for a reaction time of 1-4 hours.

[0029] As an alternative implementation method, the preparation method of citrate amide includes: adding citric acid and amino acids in a molar ratio of 1:3 to N,N-dimethylformamide (DMF), heating to 80-120°C in the presence of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, reacting for 1-4 hours, and then filtering and drying to obtain citrate amide.

[0030] In a further embodiment, the capping agent is selected from one or more of acetic acid, propionic acid, cyclohexylcarboxylic acid, and benzoic acid.

[0031] In a further embodiment, the catalyst is selected from one or more of phosphoric acid, sodium hypophosphite, triphenyl phosphate, and sodium pyrophosphate.

[0032] In a further embodiment, the notched impact strength of the high-temperature resistant nylon PA6T / 66 copolymer is 5.5–7 kJ / m. 2 Tensile strength is 90–105 MPa; flexural strength is 130–155 MPa; melt flow index is 70–85 g / 10 min.

[0033] This invention provides a method for preparing the high-temperature resistant nylon PA6T / 66 copolymer, comprising the following steps:

[0034] (1) Preparation of PA6T / 66 salt: Terephthalic acid, adipic acid and deionized water are mixed and stirred until the system becomes a white suspension. The temperature is raised; nitrogen gas is introduced, branching agent, end-capping agent and 1,6-hexanediamine are added, the pH value of the solution is adjusted, the temperature is kept warm and stirring is continued to obtain PA6T / 66 salt solution.

[0035] (2) Preparation of PA6T / 66 prepolymer: Add catalyst to PA6T / 66 salt solution; replace with nitrogen to remove air, pressurize, heat and stir to carry out prepolymerization reaction to obtain PA6T / 66 prepolymer;

[0036] S3: Solid-phase final polycondensation: The prepolymer undergoes a solid-phase final polycondensation reaction under nitrogen protection to obtain the PA6T / 66 copolymer.

[0037] In a further step, in step (1), the temperature is raised to 65℃~75℃;

[0038] In a further step, in step (1), the pH of the solution is adjusted to 7.2–7.5;

[0039] In a further step, in step (1), keep warm and continue stirring for 0.5h to 2h.

[0040] In a further embodiment, in step (2), the amount of catalyst added is 0.01 to 0.5% of the mass of the PA6T / 66 salt solution;

[0041] In a further step, the conditions for the prepolymerization reaction in step (2) include:

[0042] First, heat to 180℃~190℃ and react for 0.5h~2h, while maintaining a stable pressure of 0.5~1.0MPa through drainage.

[0043] Continue heating to 200℃~240℃, pressure 1.8~3.0MPa, reaction for 1h~4h;

[0044] Continue heating to 250℃~280℃, react for 1~3 hours, and then reduce to normal pressure to obtain PA6T / 66 prepolymer.

[0045] In the preparation method of this invention, the prepolymer reaction is carried out using a programmed staged temperature increase method. This allows for controllable molecular weight of the prepolymer, resulting in a high-temperature resistant nylon resin that maintains excellent mechanical properties while exhibiting good flowability. This solves the problem of poor flowability in high-temperature resistant nylon, which is detrimental to subsequent processing. If a direct temperature increase method is used, the prepolymerization reaction of the nylon salt cannot be effectively controlled, leading to excessively rapid molecular weight growth and uneven molecular weight distribution, thus affecting its mechanical properties.

[0046] In a further embodiment, in step (3), the conditions for the solid-phase final polycondensation reaction include: under nitrogen protection, the reaction temperature is 230-280℃, and the reaction time is 5-8h, to obtain PA6T / 66 copolymer;

[0047] In a further embodiment, the solid-phase polycondensation reaction is carried out in a solid-phase thickening reaction bed or a vacuum drum.

[0048] A further scheme yielded a PA6T / 66 copolymer with a relative viscosity of 1.85–2.85.

[0049] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0050] 1. The high-temperature resistant nylon PA6T / 66 copolymer prepared by this invention incorporates citrate amide as a branching agent in the raw materials. This branching agent is simple to prepare, has a high yield, and can be effectively introduced into the main chain of the high-temperature resistant nylon molecular chain through copolymerization, improving the flexibility of the molecular chain and the toughness of the high-temperature resistant nylon PA6T / 66 copolymer. Furthermore, its introduction can increase the spacing between the high-temperature resistant nylon molecular chains, making it easier for the high-temperature resistant nylon to untangle during processing, thus improving its melt flowability and processability.

[0051] In addition, experiments have shown that increasing the amount of branching agent added within a certain range helps to further improve its toughness; at the same time, the melt index increases, which is beneficial for subsequent processing.

[0052] 2. In the preparation method of high-temperature resistant nylon of the present invention, a programmed stage heating method is adopted in the prepolymerization reaction. In this way, the molecular weight of the prepolymer can be controlled, and the prepared high-temperature resistant nylon resin has good fluidity while maintaining excellent mechanical properties, thus solving the problem of poor fluidity of high-temperature resistant nylon, which is not conducive to subsequent processing.

[0053] 3. The method for preparing high-temperature resistant nylon provided by this invention has simple operation steps and easy-to-control conditions, which is conducive to large-scale production and market promotion and application, and has broad prospects and application fields. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0055] The methods for testing relative viscosity, melting point, and mechanical properties in the embodiments of the present invention are as follows:

[0056] 1. Relative viscosity test conditions: The phase viscosity of the solution after dissolving the high-temperature resistant nylon in 98% concentrated sulfuric acid is...

[0057] For viscosity, the test temperature was 25℃, the concentration was 0.01g / ml, and the test was conducted according to ISO 307 standard.

[0058] 2. Melting point test: Using the DSC method, weigh 5-8 mg of sample, heat it to 400 °C at 20 °C / min under a nitrogen atmosphere, hold for 5 min, then cool it back to room temperature at a rate of 20 °C / min, and then heat it to 400 °C at a rate of 10 °C / min. The endothermic peak temperature at this point is the melting point of the polymer.

[0059] 3. Mechanical property testing: The prepared high-temperature resistant nylon injection molded test strips were tested for tensile strength according to GB / T1040.2 standard, flexural strength and flexural modulus according to GB / T9341-2008 standard, and simply supported beam impact strength according to GB / T1043.1 standard.

[0060] 4. Melt flow index: Tested according to ISO1133, test temperature 330℃, weight 5kg.

[0061] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0062] In the following examples, the preparation method of citrate amide includes: adding citric acid and amino acids in a molar ratio of 1:3 to N,N-dimethylformamide (DMF), heating to 80-120°C in the presence of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, reacting for 1-4 hours, and then filtering and drying to obtain citrate amide.

[0063] Example 1

[0064] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0065] S1: Preparation of PA6T / 66 salt: 99.60 kg (600 mol) terephthalic acid, 58.5 kg (400 mol) adipic acid and deionized water were mixed and stirred until the system formed a white suspension. The temperature was raised to 65℃~75℃. Nitrogen gas was introduced, and 0.5 kg (1 mol) citrate amide (the reaction product of citrate-lysine), 0.3 kg benzoic acid and 118 kg (1016 mol) 1,6-hexanediamine were added. The pH of the solution was adjusted to 7.2~7.5. The solution was kept at this temperature and stirred for 0.5 h~2 h to obtain PA6T / 66 salt solution.

[0066] S2: In a polymerization reactor, add PA6T / 66 salt solution, 0.14 kg sodium hypophosphite, and demineralized water. Then, purge the air in the reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, and react at 180°C for 1.5 h. Drain the water to maintain a stable pressure. Continue heating to 225°C, maintain a pressure of 2.2 MPa, and react for 3 h. Continue heating to 275°C and react for 2 h to obtain PA6T / 66 prepolymer.

[0067] S3: The PA6T / 66 copolymer prepared in S2 was fed into a vacuum drum for solid-state polymerization at a temperature of 260℃ and a residence time of 3h to obtain the high-temperature resistant PA6T / 66 copolymer.

[0068] Example 2

[0069] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0070] S1: Preparation of PA6T / 66 salt: 116.2 kg (700 mol) terephthalic acid, 43.9 kg (300 mol) adipic acid and deionized water were mixed and stirred until the system formed a white suspension. The temperature was raised to 65℃~75℃. Nitrogen gas was introduced, and 0.5 kg (1 mol) citrate amide (the reaction product of citrate-lysine), 0.3 kg benzoic acid and 118 kg (1016 mol) 1,6-hexanediamine were added. The pH of the solution was adjusted to 7.2~7.5. The solution was kept at this temperature and stirred for 0.5 h~2 h to obtain PA6T / 66 salt solution.

[0071] S2: In a polymerization reactor, add PA6T / 66 salt solution, 0.14 kg sodium hypophosphite, and demineralized water. Then, purge the air in the reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, and react at 180°C for 1.5 h. Drain the water to maintain a stable pressure. Continue heating to 225°C, maintain a pressure of 2.2 MPa, and react for 3 h. Continue heating to 275°C and react for 2 h to obtain PA6T / 66 prepolymer.

[0072] S3: The PA6T / 66 copolymer prepared in S2 was fed into a vacuum drum for solid-state polymerization at a temperature of 260℃ and a residence time of 3h to obtain the high-temperature resistant PA6T / 66 copolymer.

[0073] Example 3

[0074] This embodiment uses the following steps to prepare high-temperature resistant nylon:

[0075] S1: Preparation of PA6T / 66 salt: 83 kg (500 mol) terephthalic acid, 73.1 kg (500 mol) adipic acid and deionized water were mixed and stirred until the system formed a white suspension. The temperature was raised to 65℃~75℃. Nitrogen gas was introduced, and 1 kg (1.5 mol) citrate amide (the reaction product of citrate-arginine), 0.3 kg benzoic acid and 119 kg (1025 mol) 1,6-hexanediamine were added. The pH of the solution was adjusted to 7.2~7.5. The solution was kept at this temperature and stirred for 0.5 h~2 h to obtain PA6T / 66 salt solution.

[0076] S2: In a polymerization reactor, add PA6T / 66 salt solution, 0.14 kg sodium hypophosphite, and demineralized water. Then, purge the air in the reactor with inert gas N2, pressurize to 0.8 MPa, heat and stir, and react at 180°C for 1.5 h. Drain the water to maintain a stable pressure. Continue heating to 225°C, maintain a pressure of 2.2 MPa, and react for 3 h. Continue heating to 275°C and react for 2 h to obtain PA6T / 66 prepolymer.

[0077] S3: The PA6T / 66 copolymer prepared in S2 was fed into a vacuum drum for solid-state polymerization at a temperature of 260℃ and a residence time of 3h to obtain the high-temperature resistant PA6T / 66 copolymer.

[0078] Example 4

[0079] The formulation and process are the same as in Example 1, except that the amount of citrate amide (the reaction product of citrate-lysine) is 1 kg (2 mol).

[0080] Example 5

[0081] The formulation and process are the same as in Example 1, except that step S3 is a solid-state polymerization reaction, the temperature is 280°C, and the residence time is 8 hours.

[0082] Example 6

[0083] The formulation and process are the same as in Example 1, except that the amount of benzoic acid added is changed to 0.6 kg.

[0084] Comparative Example 1

[0085] The formulation and process are the same as in Example 1, except that citrate amide (the reaction product of citrate-lysine) is not added.

[0086] Comparative Example 2

[0087] The formulation and process are the same as in Example 1, except that 1 mol of citrate amide (the reaction product of citrate-lysine) is replaced with 1 mol of trimesic acid.

[0088] Comparative Example 3

[0089] The formulation is the same as in Example 1, except that step (1) does not use a staged heating method. The high-temperature resistant nylon is prepared using the following steps:

[0090] Steps S1 and S3 are the same as in Example 1, and step S2 includes:

[0091] In a polymerization reactor, PA6T / 66 salt solution, 0.14 kg sodium hypophosphite and demineralized water were added. The air in the polymerization reactor was replaced with inert gas N2. The pressure was increased to 0.8 MPa, heated and stirred, and the temperature was raised to 275 °C. The pressure was maintained at 2.2 MPa and the reaction was carried out for 5 hours to obtain PA6T / 66 prepolymer.

[0092] Table 1. Test results of high-temperature resistant nylon prepared in the examples and comparative examples.

[0093]

[0094]

[0095] Results analysis:

[0096] As can be seen from Table 1, the high-temperature resistant nylon PA6T / 66 copolymer prepared in the embodiments of the present invention introduces citrate amide into the main chain of the high-temperature nylon PA6T / 66 molecular chain, which improves the flexibility of the molecular chain and thus increases the notched impact strength.

[0097] Compared with Example 1, Example 4 increased the content of the branching agent, which helps to further improve its toughness.

[0098] Compared to Example 1, Example 6 increased the content of the capping agent, which helped to reduce the relative viscosity of the PA6T / 66 copolymer and improve processability.

[0099] Compared with Example 1, Example 5 increased the temperature and time of solid-state polycondensation, which can increase the relative viscosity of PA6T / 66 copolymer, but the melt index decreased significantly, which is not conducive to subsequent processing.

[0100] Terephthalic acid and hexamethylenediamine undergo condensation polymerization to form PA6T, while adipic acid and hexamethylenediamine further condense to form PA66. As shown in Table 1, compared to Example 2, the amount of adipic acid used in Example 3 is increased, meaning the content of PA66 is increased. With increasing PA66 content, the polymer melting point decreases. This is because as the PA66 content increases, the rigid structure of the benzene ring decreases, thus lowering the melting point. As the PA66 content in the polymer increases, tensile strength gradually decreases, flexural strength decreases, and notched impact strength increases. This is because as the PA66 content increases, the content of benzene rings in the copolymer backbone decreases, the content of rigid chains decreases, and the proportion of flexible chains increases, thus decreasing strength and increasing toughness.

[0101] Compared with Example 1, no branching agent citric acid-lysine was added in Comparative Example 1. The tensile strength and flexural strength of the copolymer did not change much, but the notched impact strength and melt index decreased. This is because the addition of the branching agent introduced flexible segments into the PA6T / 66 chain segment, which improved the impact resistance of the polymer. At the same time, the special structure of the branching agent made the spacing between the high-temperature nylon molecular chains larger, making it easier to untangle during processing and improving its fluidity.

[0102] In Comparative Example 2, the addition of the same molar ratio of pyromellitic acid resulted in a decrease in both the notched impact strength and melt index of the polymer. This is because the side chain of pyromellitic acid is relatively short. After its addition, the melt index can be slightly increased compared to Comparative Example 1, but its impact strength is not significantly affected.

[0103] In Comparative Example 3, instead of using a stepped heating process, the temperature was directly raised to 275°C for a high-temperature, high-pressure reaction to form a prepolymer. Its mechanical properties decreased significantly. This is because the stepped heating polymerization process effectively controlled the prepolymerization reaction of the nylon salt by controlling the temperature and pressure at different polymerization stages, inhibiting salt decomposition and achieving a controlled polymerization reaction of the polyamide salt solution. This ensured a stable and controllable increase in polymer viscosity. In contrast, the direct heating process would lead to a wider molecular weight distribution in the polymer, resulting in decreased mechanical properties.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high temperature resistant nylon PA6T / 66 copolymer, characterized in that, The preparation raw materials include terephthalic acid, adipic acid, 1,6 hexanediamine, branching agent, end-capping agent, catalyst and desalted water, wherein: The molar ratio of the terephthalic acid to the adipic acid is (5:5)~(10:0), and the adipic acid is not 0; The ratio of the amount of the 1,6 hexanediamine to the total moles of the terephthalic acid and the adipic acid is (1.015~1.050):1; The amount of the branching agent is 0.05~0.5% of the total moles of the terephthalic acid, the adipic acid and the 1,6 hexanediamine; The amount of the end-capping agent is 0.5~1.5% of the total mass of the terephthalic acid, the adipic acid and the 1,6 hexanediamine; The branching agent is citric acid amide prepared from citric acid and amino acid, the molar ratio of the citric acid to the amino acid is 1:3, and the amino acid is selected from one or more of aspartic acid, asparagine, glutamic acid, lysine and arginine; The preparation method of the high-temperature-resistant nylon PA6T / 66 copolymer comprises the following steps: (1) preparation of PA6T / 66 salt: terephthalic acid, adipic acid and desalted water are mixed and stirred until the system is a white suspension, and then heated; nitrogen is introduced, and a branching agent, an end-capping agent and 1,6 hexanediamine are added, the pH value of the solution is adjusted, and the solution is heated and continuously stirred to obtain a PA6T / 66 salt solution; (2) preparation of PA6T / 66 prepolymer: a catalyst is added to the PA6T / 66 salt solution; nitrogen is introduced to remove air, and the solution is pressurized and heated and stirred to perform prepolymerization, thereby obtaining a PA6T / 66 prepolymer; (3) solid-phase final polycondensation: the prepolymer is subjected to solid-phase final polycondensation under the protection of nitrogen to obtain a PA6T / 66 copolymer. In step (2), the prepolymerization conditions comprise: firstly, heating to 180~190℃, reacting for 0.5~2h, draining water and keeping the pressure stable at 0.5~1.0 MPa; continuously heating to 200~240℃, reacting for 1~4h under a pressure of 1.8~3.0 MPa; continuously heating to 250~280℃, reacting for 1~3h, and then reducing to normal pressure to obtain the PA6T / 66 prepolymer.

2. The high temperature resistant nylon PA6T / 66 copolymer according to claim 1, characterized in that, The end-capping agent is selected from one or more of acetic acid, propionic acid, cyclohexane carboxylic acid and benzoic acid.

3. The high temperature resistant nylon PA6T / 66 copolymer according to claim 1, characterized in that, The catalyst is selected from one or more of phosphoric acid, sodium hypophosphite, triphenyl phosphate and sodium pyrophosphate.

4. High temperature resistant nylon PA6T / 66 copolymer according to any one of claims 1-3, characterized in that, The notched impact strength of the high-temperature-resistant nylon PA6T / 66 copolymer is 5.5-7 kJ / m 2 ; the tensile strength is 90-105 MPa; the bending strength is 130-155 MPa; and the melt index is 70-85 g / 10min.

5. A process for the production of a high temperature resistant nylon PA6T / 66 copolymer as claimed in any one of claims 1 to 4, characterized in that, The preparation method comprises the following steps: (1) preparation of PA6T / 66 salt: terephthalic acid, adipic acid and desalted water are mixed and stirred until the system is a white suspension, and then heated; nitrogen is introduced, and a branching agent, an end-capping agent and 1,6 hexanediamine are added, the pH value of the solution is adjusted, and the solution is heated and continuously stirred to obtain a PA6T / 66 salt solution; (2) preparation of PA6T / 66 prepolymer: a catalyst is added to the PA6T / 66 salt solution; nitrogen is introduced to remove air, and the solution is pressurized and heated and stirred to perform prepolymerization, thereby obtaining a PA6T / 66 prepolymer; (3) solid-phase final polycondensation: the prepolymer is subjected to solid-phase final polycondensation under the protection of nitrogen to obtain a PA6T / 66 copolymer.

6. The production method according to claim 5, characterized by, In step (1), the temperature is heated to 65~75℃.

7. The preparation method according to claim 5, characterized in that, In step (1), the pH value of the solution is adjusted to 7.2~7.

5.

8. The preparation method according to claim 5, characterized in that, In step (1), the temperature is kept constant and the stirring is continued for 0.5h-2h.

9. The method of any one of claims 5-8, wherein, In step (2), the catalyst is added in an amount of 0.01-0.5% of the mass of the PA6T / 66 salt solution.

10. The method of any one of claims 5-8, wherein, In step (2), the conditions for the prepolymerization include: First, the temperature is raised to 180-190℃, the reaction is carried out for 0.5h-2h, and the water is drained to keep the pressure stable at 0.5-1.0 MPa; Then, the temperature is continuously raised to 200-240℃, the pressure is 1.8-3.0 MPa, and the reaction is carried out for 1h-4h; Then, the temperature is continuously raised to 250-280℃, the reaction is carried out for 1-3h, and the pressure is reduced to normal pressure, to obtain the PA6T / 66 prepolymer.

11. The method of making according to any one of claims 5-8, wherein, In step (3), the conditions for the solid-phase final polycondensation reaction include: under nitrogen protection, the reaction temperature is 230-280℃, and the reaction time is 5h-8h, to obtain the PA6T / 66 copolymer.

12. The method of making according to any one of claims 5-8, wherein, In step (3), the solid-phase final polycondensation reaction is carried out in a solid-phase tackifying reaction bed or a vacuum drum.

13. The method of making according to any one of claims 5-8, wherein, In step (3), the high-temperature resistant nylon is dissolved with concentrated sulfuric acid with a concentration of 98%, the test temperature is 25℃, the concentration is 0.01g / ml, the test is carried out according to the ISO307 standard, and the relative viscosity of the obtained PA6T / 66 copolymer is 1.85-2.85.

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