High-temperature-resistant polyamide as well as preparation method and composition thereof

Abstract

The invention provides high-temperature-resistant polyamide and a preparation method thereof. The polyamide contains diamine units from pentamethylene diamine and hexamethylenediamine and diacid units from terephthalic acid and adipic acid, the diamine units from the pentamethylene diamine account for 50-80 mol% of all the diamine units, and the diacid units from the terephthalic acid account for 50-80 mol% of all the diacid units; and the melting point of the high-temperature-resistant polyamide is 270-310 DEG C. The polyamide has excellent mechanical properties, heat resistance, melt processability and dimensional stability.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a high temperature resistant polyamide material, a preparation method and a composition thereof. Background Art

[0002] The melting point of high-temperature resistant polyamide is generally above 270°C. It has excellent heat resistance and excellent mechanical properties and is widely used in electronic devices, automotive engine peripheral components, aerospace and other fields. Among them, polypentamethylene terephthalamide (PA5T for short) is a polyamide with excellent performance. It exhibits excellent mechanical strength because it also has a rigid benzene ring structure. The comprehensive performance of PA5T is similar to that of PA6T. Compared with PA6T, it has two major advantages. One is that its monomer diamine is obtained through biological fermentation and has lower carbon emissions; the other is that it can bypass the monopoly of foreign companies on hexamethylenediamine and avoid the problem of "stuck neck" of raw materials. Since the melting point of PA5T is higher than 350°C and melt processing is difficult, industry researchers will introduce other dibasic acid components through copolymerization modification to obtain polyamide resins with lower melting points (about 300°C). Chinese patent CN113999388A discloses a bio-based high temperature resistant nylon PA5T / 5I copolymer and its preparation method. The reaction time under high pressure is as long as 3 hours and the process is complicated. The impact toughness of the prepared copolyamide resin is poor, and the simply supported beam notched impact strength is only 4.5 kJ / m 2 , unable to meet the downstream terminal market demand for high-temperature polyamide.

[0003] Carbon nanotubes are aggregated into bundles due to van der Waals forces, which are prone to local twisting and entanglement. They are insoluble in water and common organic solvents, which limits the application of carbon nanotubes. In comparison, carboxyl-modified carbon nanotubes have better reactivity and solubility. The preparation methods of carboxyl-modified carbon nanotubes for reinforcing polyamide generally include solution blending, melt blending and in-situ blending. Among them, in-situ blending is suitable for industrial applications and can make the carboxyl-modified carbon nanotubes well dispersed in the base phase, and can improve the interface properties between the carboxyl-modified carbon nanotubes and the matrix, thereby improving the performance of polyamide. However, there is no report on the preparation of carboxyl-modified carbon nanotubes for reinforcing short carbon chain high temperature resistant polyamide by liquid phase in-situ polymerization process. Summary of the invention

[0004] In order to solve the deficiencies of the prior art and products, the present invention provides a high temperature resistant polyamide and a preparation method and composition thereof, which not only has a high melting point and can be used in environmental conditions with high temperature requirements, but also has excellent mechanical properties.

[0005] The first aspect of the present invention provides a high temperature resistant polyamide, which contains diamine units from pentamethylenediamine and hexamethylenediamine, and diacid units from terephthalic acid and adipic acid, wherein the diamine units from pentamethylenediamine account for 50 to 80 mol% of all diamine units, and the diacid units from terephthalic acid account for 50 to 80 mol% of all diacid units; the melting point of the high temperature resistant polyamide is 270 to 310°C.

[0006] The present invention sets a specific diamine and dibasic acid formula to obtain a polyamide temperature of up to 270°C or more, and the pentamethylenediamine used is preferably bio-based pentamethylenediamine, which is more in line with the policy regulations and sustainable development goals of carbon neutrality and carbon peak. The bio-based pentamethylenediamine described in the present invention refers to pentamethylenediamine synthesized from biomass-derived compounds such as glucose and lysine through enzyme reaction, yeast reaction or fermentation reaction in the monomer synthesis process. The bio-based content of bio-based pentamethylenediamine can be determined by a method for measuring the radioactive C14 content, such as the standard ASTM-D6866 method of the American Society for Testing and Materials.

[0007] Preferably, the polymerizable monomers of the polyamide include diamine monomers and diacid monomers, the diamine monomers are pentamethylenediamine and hexamethylenediamine, wherein the molar percentage of pentamethylenediamine in the diamine monomers is 50-80%, and the diacid monomers are terephthalic acid and adipic acid, wherein the molar percentage of terephthalic acid in the diacid monomers is 50-80%. Preferably, the molar ratio of the diamine monomers to the diacid monomers is 1-1.01:1.

[0008] Preferably, the pentamethylenediamine is 1,5-pentamethylenediamine, the adipic acid is 1,6-hexamethylenediamine, and the hexamethylenediamine is 1,6-hexamethylenediamine.

[0009] In one embodiment, the molar percentage of pentamethylenediamine to diamine monomers is 60% to 80%.

[0010] In one embodiment, the molar percentage of terephthalic acid in the diacid monomer is 60% to 80%.

[0011] In one embodiment, the molar ratio of the diamine monomer to the diacid monomer is (1.005-1.05):1, further (1.005-1.03):1.

[0012] Preferably, the diamine units derived from pentamethylenediamine account for 60 to 80 mol% of all diamine units, and the diacid units derived from terephthalic acid account for 60 to 80 mol% of all diacid units.

[0013] Preferably, the molar ratio of diamine units from pentamethylenediamine and hexamethylenediamine is 0.6-0.8:0.2-0.4, for example, 0.755:0.25, 0.725:0.28, 0.655:0.35, 0.605:0.40.

[0014] Preferably, the molar ratio of the diacid units from terephthalic acid and adipic acid is 0.6-0.8:0.2-0.4, for example, 0.75:0.25, 0.72:0.28, 0.65:0.35, 0.60:0.40.

[0015] Preferably, the molar ratio of the diamine units derived from pentamethylenediamine to the diacid units derived from terephthalic acid is 1-1.01:1.

[0016] In one embodiment, the viscosity of the polyamide is 120 to 150 mL / g, and further 130 to 150 mL / g.

[0017] In one embodiment, the viscosity fluctuation of the polyamide is 0-2.0 mL / g, further 0.1-1 mL / g, further 0.1-0.6 mL / g. The polyamide of the present invention can obtain lower viscosity fluctuation under specific preparation process conditions. The smaller the viscosity fluctuation of the polyamide, the more stable the material system.

[0018] Preferably, the polyamide further contains carboxylated carbon nanotubes, and the content of the carboxylated carbon nanotubes is 0.2 wt% to 4.5 wt%, further 0.4 wt% to 3.5 wt%, which is the mass percentage of the polyamide.

[0019] In one embodiment, the diameter of the carboxylated carbon nanotubes is 5 to 30 nm, and further 8 to 25 nm.

[0020] In one embodiment, the length of the carboxylated carbon nanotubes is 1 to 30 μm, and further 5 to 20 μm.

[0021] The carboxylated carbon nanotubes of the present invention can be obtained by commercial purchase. It is generally known to those skilled in the art that carboxylated carbon nanotubes are generally prepared by oxidation methods, such as concentrated sulfuric acid and concentrated nitric acid oxidation methods, and hydrogen peroxide oxidation methods. For example, carbon nanotubes are prepared by heating and refluxing in a mixed system of concentrated sulfuric acid (concentration 98%) and concentrated nitric acid (concentration 68%). The volume ratio of the concentrated sulfuric acid and concentrated nitric acid is generally (1-5): (1-5). The heating reflux reaction temperature is generally around 100°C, and the reaction time is generally 0.5-2h. The reaction process of the hydrogen peroxide oxidation method is, for example, referred to "Research on the Preparation of Carboxylated Carbon Nanotubes by Hydrogen Peroxide Oxidation", author Zhu Shukui, Su Xueli, published in "Journal of Analytical Science" December 2012, Vol. 28, No. 6.

[0022] As an embodiment of the present invention, the polyamide may further include additives. The content of the additives may be selected according to actual conditions. The additives include heat-capping agents, catalysts, stabilizers, antioxidants, fluorescent whitening agents, pigments, dyes, UV inhibitors, flame retardants, flow modifiers, organic fillers, inorganic fillers, silica powder, powder binders or combinations thereof, such as heat stabilizers and / or antioxidants. Wherein, the catalyst may be phosphoric acid, phosphorous acid, trimethyl phosphite, triphenyl phosphite, trimethyl phosphate, triphenyl phosphate, sodium hypophosphite, zinc hypophosphite, calcium hypophosphite, potassium hypophosphite or a combination thereof, such as sodium hypophosphite. The antioxidant is selected from one or more of hindered phenol antioxidants, hindered amine antioxidants and phosphite antioxidants; wherein, the hindered phenol antioxidant may be commercially available, preferably, the hindered phenol antioxidant is selected from antioxidant 1098 and / or antioxidant 1010, such as antioxidant 1098. Wherein, the phosphite antioxidant can be purchased commercially, preferably, the phosphite antioxidant is selected from antioxidant 168 and / or antioxidant S9228. Preferably, the antioxidant is selected from one or more of the commercially available antioxidant 168, antioxidant 1098, antioxidant 1010 and antioxidant S9228.

[0023] In one embodiment, the content of the additive is 0.01 wt % to 3 wt %.

[0024] In one embodiment, the tensile strength of the polyamide is 80 to 120 MPa, and further 90 to 120 MPa.

[0025] In one embodiment, the heat deformation temperature of the polyamide is 100 to 145°C, and further 120 to 140°C.

[0026] In one embodiment, the equilibrium water absorption of the polyamide is 2.5% or less, further 2.0% or less, further 0.5% to 1.8%.

[0027] A second aspect of the present invention provides a method for preparing a high temperature resistant polyamide, characterized in that it comprises the following steps:

[0028] 1) In an inert gas or nitrogen atmosphere, the polyamide salt solution is drained and concentrated at 120-140° C., then heated to 235-265° C., and reacted at a pressure of 1.9-3.3 MPa for 0.5-3 h;

[0029] 2) draining water and reducing pressure to reduce the pressure in the reaction system to 0-0.1 MPa, the temperature of the reaction system after the pressure reduction is 285-350°C, and then evacuating to a vacuum degree of less than -0.02 MPa, maintaining for 0-300 seconds, to obtain a melt;

[0030] The polyamide salt solution is obtained by mixing pentamethylenediamine, terephthalic acid, adipic acid, hexamethylenediamine and water.

[0031] In one embodiment, the temperature of the mixture of pentamethylenediamine, terephthalic acid, adipic acid, hexamethylenediamine and water is 60-100° C., and preferably the mixture is kept at 60-100° C. for 0.5-3 hours. The mixture is preferably stirred during mixing.

[0032] In one embodiment, the preparation method is carried out in a nitrogen atmosphere or an inert gas atmosphere.

[0033] In one embodiment, the drainage in step 1) is concentrated to a polyamide salt concentration of 40 wt % to 80 wt %, further 55 wt % to 70 wt %.

[0034] In one embodiment, the reaction time of step 1) is 0.5 to 2 hours.

[0035] In one embodiment, the water discharge and pressure reduction in step 2) reduces the pressure in the reaction system to 0-0.05 MPa, or further to 0-0.02 MPa.

[0036] In one embodiment, in step 2), the vacuum is evacuated to a vacuum degree of -0.05 MPa to -0.1 MPa.

[0037] In one embodiment, the time of maintaining the vacuum state in step 2) is 0 to 90 seconds, further 1 to 90 seconds, further 1 to 60 seconds.

[0038] In one embodiment, the polyamide salt solution in step 1) contains additives and / or carboxylated carbon nanotubes.

[0039] In one embodiment, carboxylated carbon nanotubes are added when preparing the polyamide salt solution or in step 1).

[0040] In one embodiment, the additive is added when preparing the solution of the polyamide salt or in step 1).

[0041] Preferably, the polyamide salt solution further comprises additives and carboxylated carbon nanotubes, that is, the additives and carboxylated carbon nanotubes are added during the preparation of the polyamide salt solution.

[0042] The additives and the carboxylated carbon nanotubes have the same definitions as described above.

[0043] In one embodiment, the method comprises step 3): water-cooling the melt to form strands and pelletize the melt to obtain the high temperature resistant polyamide.

[0044] The third aspect of the present invention is to provide a composition, the components of the composition include any of the above-mentioned high temperature resistant polyamides.

[0045] Compared with the prior art, the implementation of the present invention has at least the following advantages:

[0046] 1. The high temperature resistant polyamide of the present invention can be obtained by a one-step liquid phase condensation polymerization process, which is simple and easy to operate and has good industrial prospects.

[0047] 2. The present invention introduces adipic acid and hexamethylenediamine into the PA5T system. Under the premise of a specific component ratio, the irregular introduction of different methylene groups destroys the original polymer crystallization process, reduces the amide group density of the molecular chain, and reduces the melting point, degree of crystallization and water absorption. Therefore, compared with PA5T, the polyamide of the present invention has better melt processing performance and dimensional stability.

[0048] 3. The present invention further adds carboxylated carbon nanotubes, and the in-situ polymerization process improves the compatibility between the carboxylated carbon nanotubes and the polyamide matrix, solving the disadvantage that the carboxylated carbon nanotubes are easy to agglomerate. At the same time, the introduction of carboxylated carbon nanotubes enhances the heat resistance and mechanical properties of polyamide, reduces the equilibrium water absorption rate, and better meets the downstream market demand of high-temperature polyamide. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] 1) Melting point test method: refer to standard ISO 11357-3, heating rate: 20℃ / min.

[0051] 2) Viscosity number and viscosity number fluctuation test method: Use the concentrated sulfuric acid method with an Ubbelohde viscometer to accurately weigh 0.25g of the dried sample, add it to 50mL of concentrated sulfuric acid (96%) to dissolve, and measure and record the concentrated sulfuric acid flow time t0 and the sample solution flow time t in a 25°C constant temperature water bath. Viscosity number calculation formula: Viscosity number VN = (t / t0-1) / C; t-solution flow time; t0-solvent flow time; C-sample solution concentration (g / mL). Test 5 samples in parallel and calculate the average value as the sample viscosity (mL / g). Viscosity number fluctuation test: The difference between the maximum and minimum viscosity values ​​of the 5 samples tested in parallel.

[0052] 3) Tensile strength: refer to standard GB / T 1040.2-2006.

[0053] 4) Heat deformation temperature: refer to standard GB / T 1633-2000.

[0054] 5) Equilibrium water absorption: refer to standard ISO 62-2008.

[0055] The antioxidant used in the following examples and comparative examples is antioxidant 1098, the catalyst is sodium hypophosphite, and the 1,5-pentanediamine is bio-based pentamethylenediamine. Carboxylated carbon nanotubes: tube diameter 15nm, length 10μm, purchased from Nanjing Xianfeng Nanomaterial Technology Co., Ltd., model XFM03. In the examples and comparative examples, "%" represents mass percentage, and the amount of antioxidant, catalyst, and carboxylated carbon nanotubes is based on the sum of the masses of all diamines and diacid monomers. The pressures described in the examples and comparative examples are all gauge pressures.

[0056] Example 1

[0057] 0.755 mol of 1,5-pentanediamine, 0.75 mol of terephthalic acid, 0.25 mol of 1,6-hexanediamine, 0.25 mol of 1,6-hexanediamine, 0.03% of a catalyst, 0.3% of an antioxidant and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining the water and reducing the pressure, and the temperature of the reaction system was 325°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.07 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was subjected to stranding and pelletizing to obtain a high temperature resistant polyamide.

[0058] Example 2

[0059] 0.725 mol of 1,5-pentanediamine, 0.72 mol of terephthalic acid, 0.28 mol of 1,6-hexanediamine, 0.28 mol of 1,6-hexanediamine, 0.03% of a catalyst, 0.3% of an antioxidant and water were uniformly mixed, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining the water and reducing the pressure, and the temperature of the reaction system was 320°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.07 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was subjected to stranding and pelletizing to obtain a high temperature resistant polyamide.

[0060] Example 3

[0061] 0.755 mol 1,5-pentanediamine, 0.75 mol terephthalic acid, 0.25 mol 1,6-hexanediamine, 0.25 mol 1,6-hexanediamine, 0.03% catalyst, 0.3% antioxidant, 0.5% carboxylated carbon nanotubes and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and reacted for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining water, and the temperature of the reaction system was 325°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.08 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a high temperature resistant polyamide.

[0062] Example 4

[0063] 0.725 mol of 1,5-pentanediamine, 0.72 mol of terephthalic acid, 0.28 mol of 1,6-hexanediamine, 0.28 mol of 1,6-hexanediamine, 0.03% of a catalyst, 0.3% of an antioxidant, 1% of a carboxylated carbon nanotube and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining the water and reducing the pressure, and the temperature of the reaction system was 320°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.08 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a high temperature resistant polyamide.

[0064] Example 5

[0065] 0.655 mol 1,5-pentanediamine, 0.65 mol terephthalic acid, 0.35 mol 1,6-hexanediamine, 0.35 mol 1,6-hexanediamine, 0.03% catalyst, 0.3% antioxidant, 2% carboxylated carbon nanotubes and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining water, and the temperature of the reaction system was 305°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.08 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a high temperature resistant polyamide.

[0066] Example 6

[0067] 0.655 mol 1,5-pentanediamine, 0.65 mol terephthalic acid, 0.35 mol 1,6-hexanediamine, 0.35 mol 1,6-hexanediamine, 0.03% catalyst, 0.3% antioxidant, 0.5% carboxylated carbon nanotubes and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining water, and the temperature of the reaction system was 305°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.08 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a high temperature resistant polyamide.

[0068] Example 7

[0069] 0.605 mol of 1,5-pentanediamine, 0.60 mol of terephthalic acid, 0.40 mol of 1,6-hexanediamine, 0.40 mol of 1,6-hexanediamine, 0.03% of a catalyst, 0.3% of an antioxidant, and 3% of carboxylated carbon nanotubes were mixed uniformly with water, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining the water and reducing the pressure, and the temperature of the reaction system was 300°C after the pressure reduction was completed; the vacuum degree was evacuated to -0.08 MPa and maintained for 60 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a high temperature resistant polyamide.

[0070] Comparative Example 1

[0071] 0.655 mol of 1,5-pentanediamine, 0.65 mol of terephthalic acid, 0.35 mol of 1,6-hexanediamine, 0.35 mol of 1,6-hexanediamine, 0.03% of a catalyst, 0.3% of an antioxidant, 2% of carboxylated carbon nanotubes and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at the temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and the reaction was carried out for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining the water and reducing the pressure, and the temperature of the reaction system after the pressure reduction was completed was 305°C to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain polyamide.

[0072] Table 1

[0073]

[0074] As can be seen from Table 1, the polyamide of the present invention obtains a high-temperature resistant polyamide with a melting point of more than 270°C by setting a specific molar ratio of monomer raw materials, and the heat deformation temperature is all above 100°C, and the equilibrium water absorption rate is as low as less than 2.5%, which can be used in a wide range of high-temperature usage scenarios. The viscosity fluctuation of the polyamide obtained in Comparative Example 1 is relatively high due to the lack of a vacuuming step. In Examples 3-7, carboxylated carbon nanotubes are added, and the melting point of the polyamide changes slightly, but the tensile strength and heat deformation temperature are significantly improved, which will be more suitable for use in scenarios with higher requirements for material deformation at high temperatures.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 polyamide, characterized in that: It contains diamine units from pentamethylenediamine and hexamethylenediamine, and diacid units from terephthalic acid and adipic acid, Among them, the diamine units from pentamethylenediamine account for 50-80 mol% of all diamine units, and the diacid units from terephthalic acid account for 50-80 mol% of all diacid units; the melting point of the high temperature resistant polyamide is 270-310°C.

2. The high temperature resistant polyamide according to claim 1, characterized in that: The molar ratio of diamine units derived from pentamethylenediamine and hexamethylenediamine is 0.6-0.8:0.2-0.4; and / or the molar ratio of diacid units derived from terephthalic acid and adipic acid is 0.6-0.8:0.2-0.

4.

3. The high temperature resistant polyamide according to claim 1, characterized in that: The viscosity of the polyamide is 120-150 mL / g; and / or the viscosity fluctuation of the polyamide is 0-2.0 mL / g.

4. The high temperature resistant polyamide according to claim 1, characterized in that: The polyamide further contains carboxylation carbon nanotubes, and the content of the carboxylation carbon nanotubes is 0.2 wt% to 4.5 wt%, and further 0.4 wt% to 3.5 wt%.

5. The high temperature resistant polyamide according to any one of claims 1 to 4, characterized in that: The tensile strength of the polyamide is 80 to 120 MPa, further 90 to 120 MPa; and / or, The heat deformation temperature of the polyamide is 100 to 145° C., further 120 to 140° C.; and / or, The equilibrium water absorption of the polyamide is 2.5% or less, further 2.0% or less, further 0.5% to 1.8%.

6. A method for preparing the high temperature resistant polyamide according to any one of claims 1 to 5, characterized in that: The steps include: 1) In an inert gas or nitrogen atmosphere, the polyamide salt solution is drained and concentrated at 120-140° C., then heated to 235-265° C., and reacted at a pressure of 1.9-3.3 MPa for 0.5-3 h; 2) draining water and reducing pressure to reduce the pressure in the reaction system to 0-0.1 MPa, the temperature of the reaction system after the pressure reduction is 285-350°C, and then evacuating to a vacuum degree of less than -0.02 MPa, maintaining for 0-300 seconds, to obtain a melt; The polyamide salt solution is obtained by mixing pentamethylenediamine, terephthalic acid, adipic acid, hexamethylenediamine and water.

7. The method according to claim 6, characterized in that In step 2), the vacuum is evacuated to a vacuum degree of -0.05 MPa to -0.1 MPa; and / or, The time for maintaining the vacuum state in step 2) is 0 to 90 s, further 1 to 90 s, further 1 to 60 s.

8. The method according to claim 6, characterized in that The carboxylated carbon nanotubes and / or additives are added when preparing the solution of the polyamide salt or in step 1).

9. The method according to claim 8, characterized in that The additives include heat-capping agents, catalysts, stabilizers, antioxidants, fluorescent brighteners, pigments, dyes, UV-resistant agents, flame retardants, flow modifiers, organic fillers, inorganic fillers, silica powder, powder binders or combinations thereof.

10. A composition, characterized in that The components thereof include the high temperature resistant polyamide described in any one of claims 1 to 9.

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