A polyamide resin, a method for preparing the same, and an application thereof

Abstract

This invention provides a polyamide resin, its preparation method, and its applications. The polyamide resin has a carboxyl content ≤35 mol / t and an amino content ≤50 mol / t. The polyamide resin exhibits good thermal retention stability and resistance to yellowing. Furthermore, it possesses high relative viscosity and good flowability, enabling it to be used in high-temperature molding processes and meeting the resin requirements of the automotive parts, electrical and electronic parts, and sliding parts industries.

Description

Technical Field

[0001] This invention belongs to the field of engineering plastics technology, specifically relating to a polyamide resin, its preparation method, and its application. Background Technology

[0002] Polyamides are polymers formed by the ring-opening polymerization of cyclic lactams or by the condensation of diacids and diamines. Common polyamides are represented by nylon 6 and nylon 66. Due to their excellent heat resistance, chemical resistance, and ease of processing, nylon 6 and nylon 66 are widely used in automotive parts, electronic and electrical components, and sliding parts.

[0003] Common molding methods for polyamide resins include injection molding and extrusion molding. Regardless of the method, the resin melt must remain in the molding equipment at a high temperature for a period of time. However, because polyamide resins contain a certain amount of terminal amino and carboxyl groups, the terminal carboxyl groups tend to be acidic under high-temperature conditions, acting as a catalyst. This accelerates the degradation of the resin at high temperatures, ultimately leading to a decline in the performance of the molded product.

[0004] To reduce the influence of carboxyl groups, two common methods are added: alkaline inorganic substances and amino-termining agents, thereby reducing the acidity of the resin. While alkaline inorganic substances can reduce the carboxyl content to some extent, their addition inhibits crystallization between polyamide molecular chains, weakening the polyamide's performance. Furthermore, during use, the precipitation of inorganic substances in the injection-molded product can further degrade its performance. On the other hand, the addition of amino-termining agents can easily lead to excessively high amino content in the polyamide resin. During heating, under the influence of free radicals, the resin may yellow and gel.

[0005] Therefore, developing a polyamide resin with good thermal retention stability, resistance to yellowing, high relative viscosity, and good flowability is an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polyamide resin, its preparation method, and its applications. The polyamide resin exhibits good thermal retention stability and resistance to yellowing. Furthermore, it possesses high relative viscosity and good flowability, enabling it to be used in high-temperature molding processes and meeting the resin requirements of the automotive parts, electrical and electronic components, and sliding parts industries.

[0007] To achieve this objective, the present invention adopts the following technical solution:

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

[0009] In this 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 held at high temperature, the viscosity of the polyamide resin can also remain stable, and it exhibits excellent flowability during molding. 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 this invention, the carboxyl content is ≤35 mol / t, and can be, for example, 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 any range between the above values.

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

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

[0013] In this invention, the amino content in the polyamide resin is ≤50 mol / t, and can be, for example, 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 any range between the above values.

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

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

[0016] Preferably, the molecular structure of the polyamide resin includes diamine structural units and diacid structural units; the diacid structural units include at least succinic acid structural units.

[0017] In this 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 succinic acid structural units in the dicarboxylic acid structural units 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 succinic acid structural units is ≥50%.

[0019] Preferably, the dicarboxylic acid structural unit further includes at least one of adipic acid structural unit, azelaic acid structural unit, sebacic acid structural unit, furanyl dicarboxylic acid structural unit, or terephthalic acid structural unit.

[0020] Preferably, the diamine structural unit includes C4 to C12 aliphatic diamine structural units, such as C4, C5, C6, C7, C8, C9, C10, C11, and C12 aliphatic diamine structural units. Exemplarily, it includes, but is not limited to, butanediamine, pentanediamine, hexanediamine, heptamethamine, octanediamine, nonanediamine, decanediamine, undecanediamine, and dodecanediamine structural units.

[0021] Preferably, the diamine structural unit includes at least one of a pentanediamine structural unit, a hexanediamine structural unit, or a decanediamine structural unit.

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

[0023] Preferably, based on the molar content of the dicarboxylic acid structural unit as 100%, the molar percentage of the structural unit containing the succinimide terminal group 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 any range between the above values; more preferably, the molar percentage of the structural unit containing the succinimide terminal group is 1.15-1.55%, and particularly preferably, the molar percentage of the structural unit containing the succinimide terminal group is 1.2-1.4%.

[0024] In this invention, by converting the succinic acid terminal carboxyl group into a succinimide terminal group and controlling the succinimide terminal group content within a specific range, the carboxyl content in the polyamide resin can be reduced without the need for external capping agents, thereby improving the thermal retention stability of the polyamide resin. At the same time, the relative viscosity of the polyamide resin is still kept at a high level to meet the application requirements. If the succinimide terminal group content is too low and the carboxyl content is high, the thermal retention stability will be poor; if the content is too high, the viscosity will be low, and high molecular weight polyamide resin cannot be obtained.

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

[0026] Preferably, the polyamide resin further contains acylpiperidine terminal groups in its molecular structure.

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

[0028] Preferably, based on the molar content of the dicarboxylic acid structural unit as 100%, the molar percentage of the structural unit containing the acylpiperidine terminal group is 0.5% to 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 any range between the above values; more preferably, the molar percentage of the structural unit containing the acylpiperidine terminal group is 0.8% to 1.8%.

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

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

[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 any range of the above values, more preferably the relative viscosity is ≥2, and particularly preferably the relative viscosity is 2 to 3.

[0032] 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 heat treatment is ≤0.17, for example, it can be 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16 or any of the above values.

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

[0034] Preferably, the polyamide resin, under conditions of 320°C and 50MPa, has a 2.5mm thick Archimedean spiral flow length ≥302mm, for example, it can be 302mm, 304mm, 306mm, 308mm, 310mm, 312mm, 314mm, 315mm, 320mm, 330mm, 340mm, 350mm, 360mm, 380mm, 400mm, 420mm, 440mm, 460mm, 480mm, 500mm, 520mm, 540mm, 560mm, 580mm, 600mm, 620mm, 640mm, 660mm, 680mm, 700mm or any range between 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 method comprising the following steps:

[0036] The polyamide resin is obtained by pre-reacting a diamine with a diacid to increase the viscosity of the solid phase.

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

[0038] Preferably, the added molar amount of piperidine is 0.5% to 4.5% of the total molar amount of the dicarboxylic 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 any range of the above values.

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

[0040] Preferably, the mass of the catalyst accounts for 0.02 to 0.3% of the total mass of the diamine and diacid, 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 any range of the above values.

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

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

[0043] In this invention, the total mass of the system refers to the total mass of the diamine, diacid, catalyst, solvent, and optionally piperidine.

[0044] In this 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 hours.

[0047] In this invention, the specific steps of the pre-reaction include: mixing and stirring a diamine, a diacid, a catalyst, a solvent, and optionally piperidine; heating to 190–220°C within 1–4 hours under a protective atmosphere; holding at that temperature for 0.5–2 hours; continuing to heat to 210–240°C; discharging at a pressure of 2.8 MPa or higher; and then vacuum drying at 60–100°C for 12–30 hours to obtain the prepolymer product.

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

[0049] In this invention, during the solid-phase viscosity enhancement process, the relative viscosity of the material is measured according to standard GB / T 12006.1-1989, and the solid-phase viscosity enhancement is stopped when the relative viscosity change is ≤0.01.

[0050] Thirdly, the present invention provides an article formed by high-temperature molding, the material of which includes the polyamide resin according to the first aspect.

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

[0052] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The polyamide resin provided by this invention, by controlling the content of its carboxyl and amino groups within a specific range, can improve the thermal retention stability of the polyamide resin and resist yellowing; at the same time, the polyamide resin also has high relative viscosity and good flowability, which can be used in high-temperature molding processes and meet the requirements of resins in the fields of automotive parts, electrical and electronic parts, sliding parts, etc. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field; all reagents used in this invention are commercially available, and the reagents used are as follows:

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

[0058] Other dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, furanyl dicarboxylic acid, and terephthalic acid, are all commercially available and have a purity of ≥97%.

[0059] Diamines: Pentylene diamine, hexanediamine, and decanediamine, all sourced from commercially available sources, with a purity of ≥97%.

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

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

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

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

[0064] The content of succinimide terminal groups in polyamide resins refers to the molar percentage of structural units containing succinimide terminal groups, expressed as... 13 The test was performed using C NMR. The specific steps included: weighing 30 mg of polyamide resin, dissolving it in 0.6 mL of a mixed solvent of hexafluoroisopropanol and deuterated chloroform (hexafluoroisopropanol to deuterated chloroform volume ratio 1:2), and then measuring the polyamide resin using a Bruker AVANCEⅢ500 NMR spectrometer (Germany). 13 C NMR; via 13C NMR can obtain the signal peak area of ​​the carbonyl group of the succinimide terminal group, and integrate it, denoted as A1; obtain the signal peak area of ​​the carbonyl group of the dicarboxylic acid, and integrate it, denoted as A2; the molar percentage of the structural unit containing the succinimide terminal group = A1 / A2 × 100%.

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

[0066] In this invention, the molar content of diamine structural units and diacid structural units in the molecular structure of the polyamide resin is calculated based on the molar content of diamine monomers and diacid monomers. For example, if the molar content of succinic acid in diacids is 10%, then the molar content of succinic acid structural units in diacid structural units in the molecular structure of the polyamide resin is 10%.

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

[0068] Examples 1-10 and Comparative Examples 1-4 each provide a polyamide resin. The contents of amino, carboxyl, succinimide, and acylpiperidine terminal groups in the polyamide resin are shown in Tables 1-3. The composition of the diamines in the polyamide resin is shown in Tables 1-3, based on a total molar amount of 100% for the diamine structural units. The composition of the diacids in the polyamide resin is shown in Tables 1-3, based on a total molar amount of 100% for the diacid structural units. " / " indicates that the component is not present in the formulation. The acylpiperidine terminal groups are prepared by externally adding piperidine, and the content of the acylpiperidine terminal groups refers to the content of the terminal groups formed by the externally added piperidine and carboxyl groups.

[0069] The method for preparing the polyamide resin includes:

[0070] Diamine and diacid were added to a pressure vessel equipped with a magnetic coupling stirrer, condenser, gas inlet, feed inlet, and pressure explosion-proof port according to the formula. Then, sodium hypophosphite, deionized water, and piperidine of the formula amount were added. The weight of sodium hypophosphite was 0.1% of the weight of the other ingredients except deionized water, and the weight of deionized water was 30% of the total weight of the ingredients. High-purity nitrogen was introduced as a protective gas under vacuum. The temperature was raised to 210°C within 2 hours under stirring. The reaction mixture was stirred at 210°C for 1 hour, and then the temperature of the reactants was raised to 230°C under stirring. The material was discharged when the pressure reached above 2.8 MPa and vacuum dried at 80°C for 24 hours to obtain the prepolymer product. The prepolymer product was solid-phase thickened under 225-275°C and 50 Pa vacuum conditions for 5-10 hours. The solid-phase thickening time for all examples and comparative examples reached the reaction endpoint within ≤10 hours, thus obtaining the polyamide resin. The specific solid-phase thickening temperature and time are shown in Tables 1-3.

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075]

[0076] Table 3

[0077]

[0078] Performance testing

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

[0080] (2) Thermal retention stability: The polyamide resin was kept under nitrogen atmosphere at 300℃ for 30 min, 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 Archimedes spiral was measured at 320 °C and 50 MPa injection pressure.

[0082] (4) Melting point: Tested according to GB / T 19466-2004 standard; DSC test was performed using Netzsch-DSC 200F3 model from Netzsch GmbH, Germany. According to GB / T 19466-2004 standard, 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 using a HunterLab yellow index meter in accordance with ASTM D6290-2019 standard.

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

[0085] Table 4

[0086]

[0087] As shown in Table 4, the polyamide resin provided by this invention, by controlling its carboxyl and amino content within a specific range, can improve the thermal retention stability of the polyamide resin and enhance its resistance to yellowing. Simultaneously, the polyamide resin also exhibits high relative viscosity and good flowability. The relative viscosity of the polyamide resin is ≥1.95, and the decrease in relative viscosity after maintaining a temperature of 300℃ for 30 minutes is ≤0.16, with a b-value <2.5. Under conditions of a temperature of 320℃ 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℃.

[0088] As can be seen from the comparative examples, the polyamide resin has too high a carboxyl content, resulting in poor thermal retention stability and poor flowability; the amino content is too high, which reduces thermal retention stability and makes the resin prone to yellowing.

[0089] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 within the protection scope of the present invention.

Claims

1. A polyamide resin, characterized in that, The polyamide resin has a carboxyl content of 12-24 mol / t and an amino content of 28-40 mol / t. The polyamide resin contains succinimide terminal groups in its molecular structure; Based on a molar content of 100% for the dicarboxylic acid structural unit, the molar percentage of the structural unit containing the succinimide terminal group is 1.15~1.55%; The polyamide resin has a molecular structure that includes diamine structural units and diacid structural units; the diacid structural units include at least succinic acid structural units, and the molar percentage of succinic acid structural units in the diacid structural units is ≥55%.

2. The polyamide resin according to claim 1, characterized in that, The dicarboxylic acid structural unit further includes at least one of adipic acid structural unit, azelaic acid structural unit, sebacic acid structural unit, furanyl dicarboxylic acid structural unit, or terephthalic acid structural unit.

3. The polyamide resin according to claim 1, characterized in that, The diamine structural unit includes C4~C12 aliphatic diamine structural units.

4. The polyamide resin according to claim 3, characterized in that, The diamine structural unit includes at least one of a pentanediamine structural unit, a hexanediamine structural unit, or a decanediamine structural unit.

5. The polyamide resin according to claim 1, characterized in that, The polyamide resin also contains acylpiperidine terminal groups in its molecular structure.

6. The polyamide resin according to claim 5, characterized in that, With the molar content of the dicarboxylic acid structural unit being 100%, the molar percentage of the structural unit containing the acylpiperidine terminal group is 0.5~2.5%.

7. The polyamide resin according to claim 6, characterized in that, With the molar content of the dicarboxylic acid structural unit being 100%, the molar percentage of the structural unit containing the acylpiperidine terminal group is 0.8~1.8%.

8. The polyamide resin according to claim 1, characterized in that, The polyamide resin has a melting point ≥260℃.

9. The polyamide resin according to claim 1, characterized in that, According to standard GB / T 12006.1-1989, the relative viscosity of the polyamide resin is ≥1.

95.

10. The polyamide resin according to claim 9, characterized in that, According to standard GB / T 12006.1-1989, the relative viscosity of the polyamide resin is ≥2.

11. The polyamide resin according to claim 1, characterized in that, 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.

12. The polyamide resin according to claim 1, characterized in that, The polyamide resin has a flow length of ≥302mm for a 2.5mm thick Archimedean spiral under the conditions of 320℃ and 50MPa.

13. A method for preparing a polyamide resin according to any one of claims 1 to 12, characterized in that, The preparation method includes the following steps: The polyamide resin is obtained by pre-reacting a diamine with a diacid to increase the viscosity of the solid phase.

14. The preparation method according to claim 13, characterized in that, The raw materials for the pre-reaction also include piperidine.

15. The preparation method according to claim 13, characterized in that, The pre-reacted materials also include catalysts and / or solvents.

16. The preparation method according to claim 15, characterized in that, The catalyst accounts for 0.02 to 0.3% of the total mass of the diamine and dicarboxylic acid.

17. The preparation method according to claim 15, characterized in that, The solvent accounts for 20-40% of the total mass of the system.

18. The preparation method according to claim 13, characterized in that, The pre-reaction is carried out in the presence of a protective atmosphere.

19. The preparation method according to claim 13, characterized in that, The pre-reaction temperature is 200~220℃, and the time is 0.5~2h.

20. The preparation method according to claim 13, characterized in that, The solid-phase thickening process is carried out at a temperature of 225~275℃, a pressure of 30~70Pa, and a time of 5~11h.

21. A product obtained by high-temperature molding, characterized in that, The material of the article includes the polyamide resin according to any one of claims 1 to 12.

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