Polyamide resin as well as preparation method and application thereof

Abstract

The invention provides polyamide resin as well as a preparation method and application thereof. In the polyamide resin, the carboxyl content is less than or equal to 35 mol / t, and the amino content is less than or equal to 50 mol / t. According to the present invention, the polyamide resin has characteristics of good thermal retention stability, yellowing resistance, high relative viscosity and good fluidity, can be used in the high-temperature molding process, and can meet the requirements of the automobile part field, the electrical and electronic part field, the sliding part field and the like on the resin.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering plastics, and specifically relates to a polyamide resin and a preparation method and application thereof. Background Art

[0002] Polyamide is a polymer formed by the ring-opening polymerization of cyclic lactam or the condensation of dibasic acid and diamine. Common polyamides are represented by nylon 6 and nylon 66. Nylon 6 and nylon 66 are widely used in automotive parts, electronic and electrical parts, sliding parts and other fields due to their excellent heat resistance, chemical resistance, and easy processing and molding.

[0003] The common molding methods of polyamide resin are injection molding and extrusion molding. Regardless of which molding method is used, the resin melt is required to stay in the molding equipment at high temperature for a period of time. However, since polyamide resin contains a certain amount of terminal amino groups and terminal carboxyl groups, the terminal carboxyl groups tend to be acidic under high temperature conditions and act as a catalyst, resulting in accelerated degradation of the resin at high temperatures, and ultimately the performance of the molded product is reduced.

[0004] In order to reduce the influence of carboxyl groups, there are two commonly used methods: adding alkaline inorganic substances and adding amino end-capping agents to reduce the acidity of the resin. Although alkaline inorganic substances can reduce the content of carboxyl groups under certain circumstances, the addition of inorganic substances will inhibit the crystallization between polyamide molecular chains and weaken the performance of polyamide. In addition, during the use of injection molded products, the precipitation of inorganic substances will cause further decline in product performance. The addition of amino end-capping agents can easily lead to excessive amino content in polyamide resins. During the heating process, the resin will turn yellow and gel under the influence of free radicals.

[0005] Therefore, developing a polyamide resin that has good heat retention stability, yellowing resistance, high relative viscosity and good fluidity is an urgent problem to be solved in the art. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a polyamide resin and a preparation method and application thereof. The polyamide resin has good thermal retention stability and yellowing resistance, and at the same time, the polyamide resin also has a high relative viscosity and good fluidity, can be used in high-temperature molding processes, and meets the requirements of the automotive parts field, the electrical and electronic parts field, the sliding parts, etc. for resins.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a polyamide resin, wherein the carboxyl content of the polyamide resin is ≤35 mol / t and the amino content of the polyamide resin is ≤50 mol / t.

[0009] In the present invention, the carboxyl content in the polyamide resin is within a specific range, which can reduce the degradation of the polyamide resin during molding. When retained under high temperature conditions, the viscosity of the polyamide resin can also remain stable, and excellent fluidity is exhibited during the molding process; the amino content is within a specific range, which is beneficial to improving the yellowing resistance of the resin, and can also further improve the thermal retention stability of the polyamide resin.

[0010] In the present invention, the carboxyl content is ≤35 mol / t, for example, it can be 1 mol / t, 2 mol / t, 4 mol / t, 6 mol / t, 8 mol / t, 10 mol / t, 11 mol / t, 12 mol / t, 13 mol / t, 14 mol / t, 15 mol / t, 16 mol / t, 17 mol / t, 18 mol / t, 19 mol / t, 20 mol / t, 21 mol / t, 22 mol / t, 23 mol / t, 24 mol / t, 25 mol / t, 26 mol / t, 27 mol / t, 28 mol / t, 29 mol / t, 30 mol / t, 32 mol / t, 34 mol / t, 35 mol / t or the range between any of the above values.

[0011] Preferably, the carboxyl content of the polyamide resin is 5 to 30 mol / t, and more preferably the carboxyl content is 12 to 25 mol / t.

[0012] In the present invention, when the carboxyl content in the polyamide resin is within a specific range, the heat retention stability and yellowing resistance of the polyamide resin are better; when the carboxyl content is too low, the relative amino content increases, which easily leads to yellowing of the resin; when the carboxyl content is high, the polyamide resin is easily degraded during molding and has poor heat retention stability.

[0013] In the present invention, the amino content in the polyamide resin is ≤50 mol / t, for example, it can be 1 mol / t, 2 mol / t, 4 mol / t, 6 mol / t, 8 mol / t, 10 mol / t, 11 mol / t, 12 mol / t, 13 mol / t, 14 mol / t, 15 mol / t, 16 mol / t, 17 mol / t, 18 mol / t, 19 mol / t, 20 mol / t, 21 mol / t, 22 mol / t, 23 mol / t, 24 mol / t, 25 mol / t, 26 mol / t, 27 mol / t, 28 mol / t, 29 mol / t, 30 mol / t, 32 mol / t, 34 mol / t, 36 mol / t, 38 mol / t, 40 mol / t, 42 mol / t, 44 mol / t, 46 mol / t, 48 mol / t, 50 mol / t or the range between any of the above values.

[0014] Preferably, the amino content in the polyamide resin is 20 to 45 mol / t, and more preferably, the amino content is 25 to 40 mol / t.

[0015] In the present invention, when the amino content in the polyamide resin is within a specific range, the heat retention stability and yellowing resistance of the polyamide resin are better; when the amino content is too low, the relative carboxyl content increases and the heat retention stability of the resin is poor; when the amino content is high, the resin is prone to yellowing.

[0016] Preferably, the molecular structure of the polyamide resin comprises a diamine structural unit and a dibasic acid structural unit; and the dibasic acid structural unit comprises at least a succinic acid structural unit.

[0017] In the present invention, the succinic acid structural unit includes a bio-based succinic acid structural unit or a petroleum-based succinic acid structural unit. Based on the consideration of carbon reduction and environmental protection, the bio-based succinic acid structural unit is preferred.

[0018] Preferably, the molar percentage of the succinic acid structural unit in the dibasic acid structural unit is ≥10%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or any range between the above values; more preferably, the molar percentage of the succinic acid structural unit is ≥50%.

[0019] Preferably, the dibasic acid structural unit further includes at least one of an adipic acid structural unit, an azelaic acid structural unit, a sebacic acid structural unit, a furandicarboxylic acid structural unit or a terephthalic acid structural unit.

[0020] Preferably, the diamine structural unit includes C4 to C12 aliphatic diamine structural units, for example, C4, C5, C6, C7, C8, C9, C10, C11, C12 aliphatic diamine structural units, illustratively including but not limited to butanediamine structural units, pentamethylenediamine structural units, hexamethylenediamine structural units, heptamethylenediamine structural units, octanediamine structural units, nonanediamine structural units, decanediamine structural units, undecanediamine structural units, dodecanediamine structural units, etc.

[0021] Preferably, the diamine structural unit includes at least one of a pentamethylenediamine structural unit, a hexamethylenediamine structural unit or a decamethylenediamine structural unit.

[0022] Preferably, the polyamide resin contains succinimide terminal groups in its molecular structure.

[0023] Preferably, based on the molar content of the dibasic acid structural units as 100%, the molar percentage of the structural units containing succinimide terminal groups is ≤2.2%, for example, it can be 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, 2.1% or the range between any of the above values; more preferably, the molar percentage of the structural units containing succinimide terminal groups is 1.15-1.55%, and particularly preferably, the molar percentage of the structural units containing succinimide terminal groups is 1.2-1.4%.

[0024] In the present invention, by partially converting the terminal carboxyl groups of succinic acid into succinimide terminal groups and controlling the content of the succinimide terminal groups within a specific range, the carboxyl content in the polyamide resin can be reduced without adding an end-capping agent, and the heat retention stability of the polyamide resin can be improved, while ensuring that the relative viscosity of the polyamide resin is still at a relatively high level to meet the use requirements; if the content of the succinimide terminal groups is too little, the carboxyl content is high and the heat retention stability is poor; if the content is too high, the viscosity is low and a high molecular weight polyamide resin cannot be obtained.

[0025] In the present invention, because succinic acid will undergo a side reaction at high temperature to generate succinimide, the content of succinimide terminal groups is related to the content of succinic acid and the solid phase thickening process. By regulating the succinic acid content and the temperature of the solid phase thickening, the content of succinimide terminal groups can be controlled within a specific range.

[0026] Preferably, the molecular structure of the polyamide resin further comprises an acylpiperidine terminal group.

[0027] In the present invention, the acyl piperidine terminal group is formed by piperidine and a carboxyl group.

[0028] Preferably, the molar content of the dibasic acid structural unit is 100%, and the molar percentage of the structural unit containing the acyl piperidine terminal group is 0.5-2.5%, for example, it can be 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, 2.2%, 2.5% or the range between any of the above values; further preferably, the molar percentage of the structural unit containing the acyl piperidine terminal group is 0.8-1.8%.

[0029] In the present invention, on the basis of forming succinimide, acyl piperidine terminal groups are further formed, which can further reduce the carboxyl content and improve the thermal retention stability of the polyamide resin; if the acyl piperidine terminal group content is too high, the amino content is high and the resin is prone to yellowing.

[0030] Preferably, the melting point of the polyamide resin is ≥260°C, for example, it can be 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C, 305°C, 310°C, 312°C, 314°C, 316°C, 320°C or ranges between any of the above values, more preferably 264-312°C.

[0031] Preferably, according to standard GB / T 12006.1-1989, the relative viscosity of the polyamide resin is ≥1.95, for example, it can be 1.95, 1.96, 1.97, 1.98, 1.99, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.6, 2.7, 2.8, 2.9, 3 or a range between any of the above values, more preferably a relative viscosity ≥2, and particularly preferably a relative viscosity of 2 to 3.

[0032] Preferably, after the polyamide resin is heat treated at 300° C. for 30 min, the difference between the initial relative viscosity and the relative viscosity after heat treatment is ≤0.17, for example, it may be 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16 or any range between the above values.

[0033] In the present invention, the initial relative viscosity refers to the relative viscosity of the polyamide resin before heat treatment.

[0034] Preferably, the polyamide resin has a flow length of an Archimedean spiral of 2.5 mm thickness at a temperature of 320° C. and a pressure of 50 MPa. For example, it may be 302 mm, 304 mm, 306 mm, 308 mm, 310 mm, 312 mm, 314 mm, 315 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm, 380 mm, 400 mm, 420 mm, 440 mm, 460 mm, 480 mm, 500 mm, 520 mm, 540 mm, 560 mm, 580 mm, 600 mm, 620 mm, 640 mm, 660 mm, 680 mm, 700 mm or a range between any of the above values.

[0035] In a second aspect, the present invention provides a method for preparing the polyamide resin according to the first aspect, the preparation method comprising the following steps:

[0036] The diamine and the dibasic acid are pre-reacted and solid phase viscosity is increased to obtain the polyamide resin.

[0037] Preferably, the raw materials for the pre-reaction further include piperidine.

[0038] Preferably, the added molar amount of piperidine is 0.5-4.5% of the total molar amount of the dibasic acid, for example, it can be 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5% or the range between any of the above values.

[0039] Preferably, the pre-reaction material further comprises a catalyst and / or a solvent.

[0040] Preferably, the mass of the catalyst accounts for 0.02-0.3% of the total mass of the diamine and the dibasic acid, for example, it can be 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3% or the range between any of the above values.

[0041] In the present invention, the catalyst includes but is not limited to hypophosphite, zinc isooctanoate, phosphoric acid, boric acid, organic sulfonic acid and the like.

[0042] Preferably, the mass of the solvent accounts for 20-40% of the total mass of the system, for example, it may be 20%, 25%, 30%, 35%, 40% or any range between the above values.

[0043] In the present invention, the total mass of the system refers to the total mass of the diamine, the dibasic acid, the catalyst, the solvent and the optional piperidine.

[0044] In the present invention, the solvent includes water.

[0045] Preferably, the pre-reaction is carried out in the presence of a protective atmosphere; the protective atmosphere includes but is not limited to nitrogen, argon, etc.

[0046] Preferably, the pre-reaction temperature is 200-220° C. and the time is 0.5-2 h.

[0047] In the present invention, the specific steps of the pre-reaction include: mixing and stirring a diamine, a dibasic acid, a catalyst, a solvent and optional piperidine, heating to 190-220° C. within 1-4 hours in the presence of a protective atmosphere, keeping the temperature for 0.5-2 hours, and then continuing to heat to 210-240° C., discharging the material when the pressure reaches more than 2.8 MPa, and then vacuum drying at 60-100° C. for 12-30 hours to obtain a prepolymer product.

[0048] Preferably, the temperature of the solid phase viscosity enhancement is 225-275°C, for example, it can be 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 260°C, 270°C or any range between the above values; the pressure is 30-70Pa, for example, it can be 30Pa, 35Pa, 40Pa, 45Pa, 50Pa, 55Pa, 60Pa, 65Pa, 70Pa or any range between the above values; the time is 5-11h, for example, it can be 5h, 6h, 8h, 10h, 11h or any range between the above values.

[0049] In the present invention, during the solid phase viscosity increasing process, the relative viscosity of the material is measured according to the standard GB / T 12006.1-1989, and the solid phase viscosity increasing process is stopped until the relative viscosity changes by ≤0.01.

[0050] In a third aspect, the present invention provides a product produced by high temperature molding, wherein the material of the product includes the polyamide resin according to the first aspect.

[0051] In the present invention, the high temperature molding includes but is not limited to injection molding, extrusion molding, etc.; the products include but are not limited to automobile parts, electrical and electronic parts, sliding parts, etc.

[0052] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The polyamide resin provided by the present invention controls the carboxyl and amino contents within a specific range, thereby improving the heat retention stability of the polyamide resin and resisting yellowing; at the same time, the polyamide resin also has a high relative viscosity and good fluidity, can be used in a high-temperature molding process, and meets the requirements for resins in the fields of automotive parts, electrical and electronic parts, sliding parts, etc. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0056] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art; the reagents used in the present invention can be purchased commercially, and the reagents used are as follows:

[0057] Succinic acid: Bio-based succinic acid, Kingfa Science & Technology Co., Ltd., purity >99%.

[0058] Other dibasic acids: adipic acid, azelaic acid, sebacic acid, furandicarboxylic acid, terephthalic acid, etc. are all commercially available with a purity of ≥97%.

[0059] Diamines: pentamethylenediamine, hexamethylenediamine, and decamethylenediamine, which are commercially available and have a purity of ≥97%.

[0060] Sodium hypophosphite: analytical grade, purchased from Sigma-Aldrich.

[0061] Piperidine: analytical grade, purchased from Sigma-Aldrich.

[0062] In the present invention, the carboxyl content in the polyamide resin is tested using a ZD-2 fully automatic potentiometric titrator from Shanghai Yidian Scientific Instrument Co., Ltd. The specific method includes: taking 0.5 g of polyamide resin in a container, adding 50 mL of o-cresol thereto, refluxing to dissolve, and titrating the terminal carboxyl content with a calibrated KOH solution (concentration of 0.05 mol / L).

[0063] The amino content in the polyamide resin was tested using a ZD-2 fully automatic potentiometric titrator from Shanghai Yidian Scientific Instrument Co., Ltd. The specific method included: taking 0.5 g of polyamide resin in a container, adding 50 mL of phenol thereto, refluxing to dissolve, and titrating the terminal amino content with a calibrated HCL solution (concentration of 0.04 mol / L).

[0064] The content of succinimide terminal groups in polyamide resin refers to the molar percentage of structural units containing succinimide terminal groups, and is expressed in terms of 13 The specific steps include: weighing 30 mg of polyamide resin, dissolving it in 0.6 mL of a mixed solvent of hexafluoroisopropanol and deuterated chloroform (hexafluoroisopropanol and deuterated chloroform volume ratio of 1:2), and then using the AVANCEⅢ500 nuclear magnetic resonance spectrometer of Bruker Company of Germany to measure the polyamide resin. 13 C NMR; 13C NMR can obtain the signal peak area of ​​the carbonyl group of the succinimide terminal group and integrate it, which is recorded as A1; obtain the signal peak area of ​​the carbonyl group of the dibasic acid and integrate it, which is recorded as A2; the molar percentage of the structural unit containing the succinimide terminal group = A1 / A2×100%.

[0065] In Tables 1 to 3, the molar content of the acylpiperidine terminal group refers to the molar content of the structural unit containing the acylpiperidine terminal group in the dibasic acid structural unit, which is determined by the molar percentage of piperidine in the total molar content of the dibasic acid monomer.

[0066] In the present invention, the molar contents of the diamine structural unit and the dibasic acid structural unit in the molecular structure of the polyamide resin are calculated based on the molar contents of the diamine monomer and the dibasic acid monomer. For example, if the molar content of succinic acid in the dibasic acid is 10%, then the molar content of succinic acid structural units in the dibasic acid structural units in the molecular structure of the polyamide resin is 10%.

[0067] Examples 1 to 10, Comparative Examples 1 to 4

[0068] Examples 1 to 10 and Comparative Examples 1 to 4 respectively provide a polyamide resin, wherein the contents of amino, carboxyl, succinimide terminal groups, and acylpiperidine terminal groups in the polyamide resin are as shown in Tables 1 to 3; the composition of the diamines in the polyamide resin is as shown in Tables 1 to 3, taking the total molar amount of the diamine structural unit as 100%; the composition of the dibasic acid in the polyamide resin is as shown in Tables 1 to 3, taking the total molar amount of the dibasic acid structural unit as 100%. Wherein, " / " indicates that the component is not present in the formula; the acylpiperidine terminal group is prepared by adding piperidine externally, and the acylpiperidine terminal group content refers to the content of the terminal group formed by the added piperidine and the carboxyl group.

[0069] The preparation method of the polyamide resin comprises:

[0070] In a pressure autoclave equipped with magnetic coupling stirring, a condenser, a gas phase port, a feed port, and a pressure explosion-proof port, diamine and dibasic acid are added according to the formula amount, and then sodium hypophosphite, deionized water and piperidine in the formula amount are added thereto; the weight of sodium hypophosphite is 0.1% of the weight of other materials except deionized water, and the weight of deionized water is 30% of the total weight of the materials; vacuum is evacuated and filled with high-purity nitrogen as a protective gas, and the temperature is raised to 210° C. within 2 hours under stirring, the reaction mixture is stirred at 210° C. for 1 hour, and then the temperature of the reactants is raised to 230° C. under stirring; the material is discharged when the pressure reaches more than 2.8 MPa, and vacuum dried at 80° C. for 24 hours to obtain a prepolymer product; the prepolymer product is solid-phase thickened for 5 to 10 hours under 225 to 275° C. and 50 Pa vacuum conditions, and the solid-phase thickening time of all embodiments and comparative examples is less than 10 hours to reach the reaction end point, that is, the polyamide resin is obtained; the specific solid-phase thickening temperature and time are shown in Tables 1 to 3.

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075]

[0076] Table 3

[0077]

[0078] Performance Testing

[0079] (1) Relative viscosity ηr0: Referring to the standard GB / T 12006.1-1989, the specific test method is: measuring the relative viscosity ηr0 of a polyamide resin with a concentration of 1 g / dL in 98% concentrated sulfuric acid at 25±0.01°C; the greater the relative viscosity, the higher the molecular weight obtained.

[0080] (2) Thermal retention stability: The polyamide resin was kept at 300°C for 30 min under nitrogen conditions and its relative viscosity ηr was measured. 30 ,ηr0 and ηr 30 The smaller the difference Δηr, the better the thermal retention stability.

[0081] (3) Flowability: The flow length of a 2.5 mm thick Archimedean spiral was measured at 320°C and an injection pressure of 50 MPa.

[0082] (4) Melting point: Tested in accordance with GB / T 19466-2004; DSC test was performed using Netzsch-DSC 200F3 from Netzsch, Germany. According to GB / T 19466-2004, the melting point of the polymer was tested under nitrogen atmosphere, flow rate of 50 mL / min, and heating rate of 20°C / min.

[0083] (5) b value: The yellowness of polyamide resin was measured according to ASTM D6290-2019 standard using a HunterLab yellow index meter.

[0084] The specific test results are shown in Table 4.

[0085] Table 4

[0086]

[0087] As can be seen from Table 4, the polyamide resin provided by the present invention controls the carboxyl and amino contents within a specific range, can improve the heat retention stability of the polyamide resin, and is resistant to yellowing; at the same time, the polyamide resin also has a high relative viscosity and good fluidity; the relative viscosity of the polyamide resin is ≥1.95, and the value of the relative viscosity decrease after maintaining the temperature at 300°C for 30 minutes is ≤0.16, and the b value is <2.5; under the conditions of a temperature of 320°C and an injection pressure of 50MPa, the flow length of a 2.5mm thick Archimedean spiral is ≥304mm; the melting point of the polyamide resin is ≥264°C.

[0088] It can be seen from the comparative examples that if the carboxyl content in the polyamide resin is too high, the thermal retention stability is poor and the fluidity is poor; if the amino content is too high, the thermal retention stability is reduced and the resin is prone to yellowing.

[0089] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polyamide resin, characterized in that The carboxyl content of the polyamide resin is ≤35 mol / t, and the amino content is ≤50 mol / t.

2. The polyamide resin according to claim 1, characterized in that The carboxyl content of the polyamide resin is 5 to 30 mol / t, preferably 12 to 25 mol / t; Preferably, the amino content in the polyamide resin is 20 to 45 mol / t, and more preferably, the amino content is 25 to 40 mol / t.

3. The polyamide resin according to claim 1 or 2, characterized in that The molecular structure of the polyamide resin comprises a diamine structural unit and a dibasic acid structural unit; the dibasic acid structural unit comprises at least a succinic acid structural unit; Preferably, the molar percentage of the succinic acid structural unit in the dibasic acid structural unit is ≥10%, more preferably the molar percentage of the succinic acid structural unit is ≥50%; Preferably, the dibasic acid structural unit further comprises at least one of an adipic acid structural unit, an azelaic acid structural unit, a sebacic acid structural unit, a furandicarboxylic acid structural unit or a terephthalic acid structural unit; Preferably, the diamine structural unit comprises a C4-C12 aliphatic diamine structural unit; Preferably, the diamine structural unit includes at least one of a pentamethylenediamine structural unit, a hexamethylenediamine structural unit or a decamethylenediamine structural unit.

4. The polyamide resin according to any one of claims 1 to 3, characterized in that The molecular structure of the polyamide resin contains succinimide terminal groups; Preferably, based on the molar content of the dibasic acid structural unit as 100%, the molar percentage of the structural unit containing the succinimide terminal group is ≤2.2%, and more preferably the molar percentage of the structural unit containing the succinimide terminal group is 1.15-1.55%.

5. The polyamide resin according to any one of claims 1 to 4, characterized in that The molecular structure of the polyamide resin also includes an acylpiperidine terminal group; Preferably, based on 100% molar content of the dibasic acid structural unit, the molar content of the structural unit containing the acylpiperidine terminal group is 0.5-2.5%, and more preferably, the molar content of the structural unit containing the acylpiperidine terminal group is 0.8-1.8%.

6. The polyamide resin according to any one of claims 1 to 5, characterized in that The melting point of the polyamide resin is ≥260°C; Preferably, according to standard GB / T 12006.1-1989, the relative viscosity of the polyamide resin is ≥1.95, more preferably the relative viscosity is ≥2; Preferably, after the polyamide resin is heat-treated at 300° C. for 30 minutes, the difference between the initial relative viscosity and the relative viscosity after the heat treatment is ≤0.17; Preferably, the polyamide resin has a flow length of an Archimedean spiral of 2.5 mm thickness ≥ 302 mm under the conditions of a temperature of 320° C. and a pressure of 50 MPa.

7. A method for preparing a polyamide resin according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: The diamine and the dibasic acid are pre-reacted and solid phase viscosity is increased to obtain the polyamide resin.

8. The preparation method according to claim 7, characterized in that: The raw materials of the pre-reaction also include piperidine; Preferably, the pre-reaction material further comprises a catalyst and / or a solvent; Preferably, the mass of the catalyst accounts for 0.02-0.3% of the total mass of the diamine and the dibasic acid; Preferably, the mass of the solvent accounts for 20-40% of the total mass of the system.

9. The preparation method according to claim 7 or 8, characterized in that: The pre-reaction is carried out in the presence of a protective atmosphere; Preferably, the pre-reaction temperature is 200-220°C and the time is 0.5-2h; Preferably, the temperature of the solid phase viscosity enhancement is 225-275° C., the pressure is 30-70 Pa, and the time is 5-11 hours.

10. A product obtained by high temperature molding, characterized in that: The material of the product comprises the polyamide resin according to any one of claims 1 to 6.

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