Bio-based semi-aromatic polyamide pa9t materials and low temperature methods of making

Abstract

The application belongs to the technical field of polymer material synthesis, and discloses a bio-based semi-aromatic polyamide PA9T material and a low-temperature preparation method thereof. The application adopts a low-temperature polymerization process, introduces potassium compounds as activators under a low-temperature process, has good adaptability with a low-temperature polymerization system, can promote the forward movement of a polycondensation reaction balance, and improves polymerization efficiency. Meanwhile, in cooperation with sulfide or hydroxyl amine antioxidants, stable thermal oxygen protection is exerted under a low-temperature condition, and the stability of a polymerization process and the high quality of a product are synergistically ensured. The pressure maintaining temperature is reduced to 160-210 DEG C, the final polymerization temperature is reduced to 250-280 DEG C, compared with a traditional high-temperature process of 290-320 DEG C, the reaction temperature is significantly reduced, the thermal decomposition of monomers and the thermal degradation of polymers are effectively inhibited, the side reactions such as amide exchange are reduced, the product molecular weight distribution is narrow, the PDI can be controlled below 2.05, and the batch stability is good.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, and in particular to bio-based semi-aromatic polyamide PA9T material and its low-temperature preparation method. Background Technology

[0002] Bio-based semi-aromatic polyamide PA9T is a high-performance engineering plastic formed by the condensation polymerization of nonyldiamine and terephthalic acid. It combines the processability of aliphatic polyamides with the heat resistance of aromatic polyamides, and is widely used in electronics, automotive manufacturing, and precision instruments. However, the industrial preparation of existing PA9T materials still faces many technical bottlenecks.

[0003] Currently, PA9T polymerization generally adopts a high-temperature and high-pressure melt polycondensation process. Due to the high rigidity and high melting point of semi-aromatic polyamide molecular chains, the polymerization process needs to be carried out at a relatively high temperature. High temperature conditions not only consume a lot of energy, but also easily cause monomer decomposition, polymer thermal degradation and side reactions, resulting in a widening of molecular weight distribution, fluctuation of end group content and deterioration of material color. At the same time, high temperature places stringent requirements on the temperature and pressure resistance of equipment.

[0004] Existing processes typically rely on phosphorus- or tin-containing compounds as polycondensation catalysts to accelerate the reaction. These catalysts leave some residue in the polymer matrix after the reaction, and this residue is prone to catalytic thermal oxidative degradation during high-temperature processing and long-term service, leading to decreased melt stability and reduced mechanical properties, thus limiting the application of PA9T in high-end precision parts manufacturing.

[0005] To improve the mechanical properties and heat resistance of pure linear PA9T, the industry has attempted to construct micro-crosslinked structures through chemical crosslinking modification. However, PA9T synthesis takes place in a high-temperature, high-pressure hydrothermal environment, and the crosslinking agent is prone to side reactions such as hydrolysis, self-polymerization, or premature crosslinking, leading to gel formation, uncontrolled reaction, and product quality fluctuations. At the same time, although the introduction of crosslinked structures can improve strength, it often sacrifices melt flowability, and the precise control of crosslinking density is difficult, resulting in poor industrial reproducibility.

[0006] In addition, the pretreatment process of the existing PA9T one-step process usually needs to be carried out under heating and pressurization conditions. This process is not only energy-intensive, but the increased temperature also exacerbates the risk of amine component volatilization and loss, which can easily lead to monomer ratio deviation and affect the degree of polymerization and product batch stability.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The present invention aims to solve at least one of the above technical problems, and provides a bio-based semi-aromatic polyamide PA9T material and a low-temperature preparation method thereof.

[0009] To achieve the above objectives, the first technical solution adopted by the present invention is as follows: The bio-based semi-aromatic polyamide PA9T material is prepared by one-step melt polymerization of monomer nonanediamine and monomer terephthalic acid in a molar ratio of 1 to 1.05:1 in the presence of antioxidants, end-capping agents, activators and deionized water. The amount of antioxidant added is 0.05% to 0.2% of the total mass of the monomers; The amount of the capping agent added is 0.05% to 0.3% of the total molar amount of the monomer; The activator is potassium chloride and / or potassium bromide, and the amount added is 0.05-0.2% of the total molar amount of the monomer; The amount of deionized water added is 80-100% of the total mass of the monomers.

[0010] Preferably, the antioxidant is a thioether compound or a hydroxyamine compound.

[0011] Preferably, the thioether compound is DLTDP and / or DSTDP; the hydroxyamine compound is Revonox420 and / or Genox EP.

[0012] Preferably, the capping agent is a compound containing only one carboxyl group, including at least one of benzoic acid, cyclohexanecarboxylic acid, and acetic acid.

[0013] The second technical solution adopted in this invention is: A low-temperature preparation method for bio-based semi-aromatic polyamide PA9T materials includes: The monomer nonanediamine, monomer terephthalic acid, antioxidant, capping agent, activator and deionized water are mixed evenly; the resulting mixture is treated under an inert gas atmosphere at room temperature and pressure for 30 to 90 minutes. Heat to 160–210℃, pressurize to 1.0–1.5 MPa, and maintain the temperature and pressure for 1–3 hours; Continue heating to 250–280℃ and then uniformly depressurize to atmospheric pressure within 30–90 minutes; Maintain a constant temperature and evacuate for 30–90 minutes; After vacuuming is completed, the temperature is raised to 290℃, and inert gas is introduced to achieve a slight positive pressure of 0.1 to 0.3 MPa before discharging.

[0014] Preferably, the ambient temperature and pressure treatment time is 60 minutes.

[0015] Preferably, the heat preservation and pressure maintenance are carried out at 180℃ and 1.2MPa for 3 hours.

[0016] Preferably, the temperature is further increased to 260°C and the pressure is uniformly reduced to atmospheric pressure within 60 minutes; the vacuuming time is 90 minutes.

[0017] Preferably, the micro-positive pressure is 0.2 MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a low-temperature polymerization process, introducing potassium compounds as activators at low temperatures. These compounds exhibit good compatibility with the low-temperature polymerization system, promoting a positive shift in the polycondensation equilibrium and improving polymerization efficiency. Simultaneously, the use of thioether or hydroxylamine antioxidants provides stable thermo-oxidative protection under low-temperature conditions, synergistically ensuring the stability of the polymerization process and the high quality of the product. The holding temperature is reduced to 160-210℃, and the final polymerization temperature is reduced to 250-280℃. Compared to the traditional high-temperature process of 290-320℃, the reaction temperature is significantly lowered, effectively inhibiting monomer thermal decomposition and polymer thermal degradation, reducing side reactions such as amide exchange, resulting in a narrow molecular weight distribution of the product, with PDI controllable below 2.05, and good batch-to-batch stability.

[0019] This invention does not use traditional phosphorus-based or tin-based polycondensation catalysts such as sodium hypophosphite and stannous chloride. There are no phosphorus or tin elements remaining in the reaction system, which fundamentally eliminates the risk of thermal oxidation and catalytic degradation caused by catalyst residue. It significantly improves the long-term thermal stability and melt processing stability of the material and avoids yellowing and performance degradation problems during high-temperature processing and service.

[0020] This invention employs a room temperature and pressure pretreatment process, eliminating the need for additional heating and pressurization, significantly reducing energy consumption in the pretreatment stage and simplifying equipment requirements. Under inert gas protection, the monomers are dissolved and initially contacted through thorough stirring, effectively suppressing the volatilization loss of amine components, ensuring the accuracy of monomer ratios, and improving raw material utilization and product yield, with a yield that can stably reach over 93%. Attached Figure Description

[0021] Figure 1 This refers to the bio-based semi-aromatic polyamide PA9T prepared in Example 1 of this invention; Figure 2 The tensile strength curve of bio-based semi-aromatic polyamide PA9T. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The first embodiment of the present invention provides a bio-based semi-aromatic polyamide PA9T material, which is prepared by one-step melt polymerization of monomer nonanediamine and monomer terephthalic acid in a molar ratio of 1 to 1.05:1 in the presence of antioxidant, end-capping agent, activator and deionized water; The amount of antioxidant added is 0.05% to 0.2% of the total mass of the monomers; The amount of the capping agent added is 0.05% to 0.3% of the total molar amount of the monomer; The activator is potassium chloride and / or potassium bromide, and the amount added is 0.05-0.2% of the total molar amount of the monomer; The amount of deionized water added is 80-100% of the total mass of the monomers.

[0024] The monomers used in this invention are nonyldiamine and terephthalic acid. Nonyldiamine, as a bio-based aliphatic diamine monomer, can be obtained from renewable resources such as castor oil through chemical conversion; terephthalic acid, as an aromatic dicarboxylic acid monomer, imparts rigidity and heat resistance to the polymer chain segments. The two form a semi-aromatic polyamide molecular chain through a condensation reaction, which is a conventional monomer combination for preparing PA9T in this field.

[0025] The molar ratio of nonadiamine to terephthalic acid is preferably 1 to 1.03:1, more preferably 1.01:1. This ratio range is a conventional choice in the preparation of semi-aromatic polyamides in the art. A small excess of nonadiamine can compensate for the possible loss of amine components due to volatilization during polymerization, ensuring the stoichiometric balance of the reactive groups.

[0026] The antioxidant is a thioether compound or a hydroxylamine compound, and the amount of antioxidant added is preferably 0.05% of the total mass of the monomer. Thioether compounds such as DLTDP (dilauryl thiodipropionate) and DSTDP (distearate thiodipropionate) are commonly used long-acting heat stabilizers in the art; hydroxylamine compounds such as Revonox 420 and Genox EP are known high-efficiency antioxidants in the art. The specific selection and dosage of the above antioxidants are within the scope that can be routinely determined by those skilled in the art based on the polymerization temperature and product performance requirements. In the low-temperature polymerization system of the present invention, DLTDP or Revonox 420 is preferred.

[0027] The capping agent is a compound containing only one carboxyl group, including at least one of benzoic acid, cyclohexanecarboxylic acid, and acetic acid, preferably acetic acid. The amount of capping agent added is preferably 0.1% of the total molar amount of the monomer. Monocarboxylic acid capping agents are molecular weight regulators routinely used by those skilled in the art in the synthesis of semi-aromatic polyamides, and their selection and dosage can be routinely adjusted according to the target molecular weight and end-group content.

[0028] The activator is preferably potassium chloride, and the amount added is preferably 0.15% of the total molar amount of the monomer.

[0029] It is important to note that traditional phosphorus- or tin-based catalysts accelerate polymerization by participating in or promoting the chemical process of amidation. After the reaction, they often remain in the polymer as decomposition products or complexes, leading to catalyst residue defects. In contrast, the potassium compounds in this invention maintain their ionic form before and after the reaction, ultimately dispersing ionicly within the polymer matrix without introducing impurities such as phosphorus or tin.

[0030] Under the low-temperature process of this invention, chloride ions can reversibly form NH…Cl with amino groups. - Hydrogen bonding, although it temporarily weakens the nucleophilicity of the corresponding amino group, can competitively break the solvation binding of water molecules on the amino group, releasing more free amino groups that can participate in the reaction. Potassium ions and chloride ions together construct local high ion concentration microregions, increasing the effective collision probability between carboxyl groups and amino groups. At the same time, chloride ions act as proton transfer mediators, accelerating the migration of water molecules, a byproduct of polycondensation, from the reaction site, inhibiting the reverse hydrolysis reaction, and promoting the forward shift of the polymerization equilibrium. After the reaction, potassium chloride is dispersed in the polymer in ionic form.

[0031] More importantly, this activation effect is ion-specific: when the same molar amount of sodium salt (such as sodium chloride) is used as a substitute, the polymerization efficiency decreases significantly, and the molecular weight and mechanical properties of the product deteriorate markedly. This indicates that the effect of potassium ions is not a simple ionic strength effect, but is related to the specific ionic radius of potassium ions, their hydration characteristics, and their interaction with polyamide segments.

[0032] The preferred amount of deionized water added is 80% of the total mass of the monomers. The amount of solvent used is a parameter that can be routinely determined by those skilled in the art based on the reactor volume, material concentration, and stirring efficiency.

[0033] The second embodiment of the present invention provides a low-temperature preparation method for bio-based semi-aromatic polyamide PA9T material, comprising: The monomer nonanediamine, monomer terephthalic acid, antioxidant, capping agent, activator and deionized water are mixed evenly; the resulting mixture is treated under an inert gas atmosphere at room temperature and pressure for 30 to 90 minutes. Heat to 160–210℃, pressurize to 1.0–1.5 MPa, and maintain the temperature and pressure for 1–3 hours; Continue heating to 250–280℃ and then uniformly depressurize to atmospheric pressure within 30–90 minutes; Maintain a constant temperature and evacuate for 30–90 minutes; After vacuuming is completed, the temperature is raised to 290℃, and inert gas is introduced to achieve a slight positive pressure of 0.1 to 0.3 MPa before discharging.

[0034] This method employs a one-step melt polymerization process, in which monomers, additives, and solvents are added to the reactor at once. The entire process of raw material dissolution, prepolymerization, melt polymerization, and post-processing is completed continuously in one reaction device, eliminating the need for prepolymer separation, pulverization, and long-term solid-phase polymerization steps in traditional prepolymerization and solid-phase thickening processes.

[0035] The mixed material is then treated under an inert gas atmosphere at room temperature and pressure (25℃, 101KPa) for a preferred time of 60 minutes.

[0036] This invention achieves complete dissolution and initial contact of monomers under ambient temperature and pressure conditions. Under the protection of an inert gas (such as nitrogen), nonanediamine and terephthalic acid are thoroughly stirred to form a nylon salt solution in deionized water, effectively suppressing the oxidation loss of the amine component at room temperature. The advantages of this pretreatment method are: no additional heating and pressurization energy consumption is required, significantly reducing energy consumption and equipment requirements in the pretreatment stage; it also avoids the risk of amine volatilization loss due to temperature increases, which helps maintain the accuracy of the monomer ratio.

[0037] In the low-temperature pressure-holding polymerization stage, preferably, the pretreated material is heated to 180°C and pressurized to 1.2 MPa, and then kept at the same temperature and pressure for 3 hours.

[0038] Under a closed, pressurized environment, water remains in a liquid state, allowing the monomers to fully contact and undergo an amidation reaction to form oligomers. The holding temperature of this invention is significantly lower than the 200–250°C typically used in existing technologies. At this low temperature, the presence of potassium-based activators effectively inhibits the thermal decomposition of monomers and side reactions, while simultaneously promoting the steady formation of amide bonds.

[0039] After the heat preservation and pressure holding are completed, preferably, the material is heated to 260°C and then depressurized to normal pressure at a uniform rate within 60 minutes.

[0040] As the temperature rises, moisture evaporates from the system, naturally increasing the pressure. By controlling the opening of the pressure relief valve, the pressure is gradually reduced to atmospheric pressure within a set time, preventing material boiling or entrainment caused by a sudden pressure drop. Simultaneously, the polymer undergoes gradual dehydration and molecular weight increase. The final polymerization temperature (250–280℃) helps reduce high-temperature thermal degradation and maintains the regularity of the polymer molecular structure.

[0041] Keeping the temperature constant, the vacuuming time is preferably 90 minutes. Under high vacuum conditions, residual trace amounts of moisture and low-molecular-weight volatiles in the system are effectively removed, driving the polymerization equilibrium towards higher molecular weight and significantly increasing the degree of polymerization. At lower reaction temperatures, the molecular chain growth rate is relatively slow; by extending the vacuum dehydration time, the kinetic limitations caused by low temperature can be fully compensated, ensuring that the target molecular weight is reached.

[0042] Since the melting point of PA9T products is typically in the range of 275–300°C, raising the material temperature to 290°C ensures that the system is in a fully molten, viscous flow state, facilitating subsequent fiber drawing and pelletizing operations. Micro-positive pressure (preferably 0.2 MPa) discharge effectively prevents material oxidation caused by backflow of air, while providing a stable discharge driving force. Post-discharge processing steps such as fiber drawing, pelletizing, and drying are standard procedures in the preparation of polyamide chips, and this invention does not impose any special limitations on them.

[0043] The following provides several examples and comparative examples to illustrate the preparation and properties of bio-based semi-aromatic polyamide PA9T materials in detail.

[0044] Example 1 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 260℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 60 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0045] The slices of bio-based semi-aromatic polyamide PA9T prepared in this embodiment are shown below. Figure 1 As shown.

[0046] Example 2 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 90% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 260℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 60 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 60 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.1MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0047] Example 3 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.05% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 2h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 260℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 30 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0048] Example 4 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.05:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.2% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.5MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 280℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 60 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0049] Example 5 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.05% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 100% of the total mass of monomers. The monomers, additives and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 90 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 160℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 260℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 30 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0050] Example 6 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.1% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 1h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 260℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 90 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.3MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0051] Example 7 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.3% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.05% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 60 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.2MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 280℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 60 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 30 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0052] Example 8 The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material in this embodiment is as follows: (1) The molar ratio of nonanediamine to terephthalic acid is 1.01:1. The amount of antioxidant DLTDP added is 0.2% of the total mass of monomers, the amount of end-capping agent acetic acid added is 0.2% of the total molar mass of monomers, the amount of activator potassium chloride added is 0.15% of the total molar mass of monomers, and the amount of deionized water added is 80% of the total mass of monomers. The monomers, auxiliaries and solvents are added together into a high-temperature and high-pressure reactor. The reactor is closed, and the air inside the reactor is replaced three times with nitrogen. The stirring is turned on and the stirring speed is set to 80 r / min. The mixture is continuously dissolved for 30 min to achieve uniform mixing. (2) After the monomer and additives are fully dissolved in the solvent, set the temperature inside the reactor to 180℃ and continue to heat up at a constant rate. At this time, the pressure inside the reactor will continue to increase with the increase of temperature and time. When the pressure inside the reactor reaches 1.0MPa, open the pressure relief valve and start heat preservation and pressure preservation. After the pressure preservation time reaches 3h, stop heat preservation and pressure preservation and enter the pressure relief stage. (3) Set the reactor temperature to 250℃ and adjust the opening and closing of the pressure relief valve to uniformly reduce the pressure inside the reactor to atmospheric pressure within 60 minutes. After the pressure inside the reactor drops to atmospheric pressure, turn on the vacuum pump to start vacuuming to remove small molecule impurities and further increase the degree of polymerization. The vacuuming time is 90 minutes. After the vacuuming is completed, set the reactor temperature to 290℃ again and fill the reactor with nitrogen to make the pressure inside the reactor reach a slight positive pressure of 0.2MPa. Then open the discharge valve to start discharging. After drawing, pelletizing and drying, PA9T material chips are obtained.

[0053] Comparative Example 1 Compared with Example 1, the only difference is that potassium chloride is not added; the other raw materials and process parameters are the same as in Example 1.

[0054] Comparative Example 2 Compared with Example 1, the only difference is that potassium chloride is replaced with an equal amount of sodium chloride, while the other raw materials and process parameters are the same as in Example 1.

[0055] Comparative Example 3 Compared with Example 1, the only difference is that the holding temperature is increased from 180°C to 210°C, while the other raw materials and process parameters are the same as in Example 1.

[0056] The performance of the bio-based semi-aromatic polyamide PA9T materials prepared in the above examples and comparative examples was tested, and the results are shown in Tables 1 and 2.

[0057] The testing methods are as follows: density was determined according to ISO 1183-1 / -2 / -3; water absorption was determined at 23℃ for 24h; melt index was determined according to ISO 1133-1 / -2; tensile strength and elongation at break were determined according to GB / T 1040.2-2022; flexural strength was determined according to GB / T 9341-2008; notched impact strength was determined according to ISO 179-1; molecular weight distribution (PDI) was determined according to ISO 16014-1 / -4; relative viscosity was determined according to the sample preparation and solvent conditions of ISO 307:2019, using an Ubbelohde viscometer to measure the outflow time of a 0.25 g / dL PA9T concentrated sulfuric acid (mass fraction 96%~98%) solution and pure solvent at (25±0.1)℃, according to η. r = t / t0 is calculated, where η r The viscosity is relative, t is the solution outflow time, and t0 is the solvent outflow time; melting point, glass transition temperature, and crystallization temperature are determined according to ISO 11357-3 and ISO 11357-2; terminal amines are determined by potentiometric titration (trifluoroethanol system) as specified in GB / T 38138-2019; yield is calculated as the ratio of the mass of the obtained product to the theoretical yield.

[0058] Table 1 .

[0059] Table 2 .

[0060] Compared to Example 1, the experimental results of Comparative Example 1 demonstrate that the absence of potassium chloride at low temperatures prevents the polymerization reaction from proceeding effectively, and an activator is essential. The experimental results of Comparative Example 2 demonstrate that sodium ions cannot replace potassium ions in their activating effect, and the activating effect of potassium compounds exhibits ion specificity. The experimental results of Comparative Example 3 demonstrate that in the system of this invention, a low-temperature holding pressure condition of 180°C is superior to 210°C; excessively high temperatures are detrimental to obtaining high molecular weight, narrowly distributed products.

[0061] The comparison of the above comparative examples and embodiments shows that the combination of potassium compound activator, low temperature pressure holding and long vacuum in the present invention is not a simple superposition of factors, but a synergistic effect: under low temperature conditions, potassium compounds effectively promote the condensation reaction by improving the ionic environment and mass transfer conditions of the system; while appropriate low temperature avoids thermal degradation side reactions, and with sufficient vacuum dehydration time, high molecular weight, narrow distribution and high performance PA9T product are finally obtained.

[0062] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A bio-based semi-aromatic polyamide PA9T material, characterized in that, It is prepared by one-step melt polymerization of monomer nonanediamine and monomer terephthalic acid in a molar ratio of 1-1.05:1 in the presence of antioxidant, end-capping agent, activator and deionized water; The amount of antioxidant added is 0.05% to 0.2% of the total mass of the monomers; The amount of the capping agent added is 0.05% to 0.3% of the total molar amount of the monomer; The activator is potassium chloride and / or potassium bromide, and the amount added is 0.05-0.2% of the total molar amount of the monomer; The amount of deionized water added is 80-100% of the total mass of the monomers.

2. The bio-based semi-aromatic polyamide PA9T material as described in claim 1, characterized in that, The antioxidant is a thioether compound or a hydroxyamine compound.

3. The bio-based semi-aromatic polyamide PA9T material as described in claim 2, characterized in that, The thioether compounds are DLTDP and / or DSTDP; the hydroxyamine compounds are Revonox 420 and / or Genox EP.

4. The bio-based semi-aromatic polyamide PA9T material as described in claim 1, characterized in that, The capping agent is a compound containing only one carboxyl group, including at least one of benzoic acid, cyclohexanecarboxylic acid, and acetic acid.

5. The low-temperature preparation method of the bio-based semi-aromatic polyamide PA9T material according to any one of claims 1-4, characterized in that, include: The monomer nonanediamine, monomer terephthalic acid, antioxidant, capping agent, activator and deionized water are mixed evenly; the resulting mixture is treated under an inert gas atmosphere at room temperature and pressure for 30 to 90 minutes. Heat to 160–210℃, pressurize to 1.0–1.5 MPa, and maintain the temperature and pressure for 1–3 hours; Continue heating to 250–280℃ and then uniformly depressurize to atmospheric pressure within 30–90 minutes; Maintain a constant temperature and evacuate for 30–90 minutes; After vacuuming is completed, the temperature is raised to 290℃, and inert gas is introduced to achieve a slight positive pressure of 0.1 to 0.3 MPa before discharging.

6. The low-temperature preparation method according to claim 5, characterized in that, The ambient temperature and pressure treatment time is 60 minutes.

7. The low-temperature preparation method according to claim 5, characterized in that, The heat preservation and pressure holding were carried out at 180℃ and 1.2MPa for 3 hours.

8. The low-temperature preparation method according to claim 5, characterized in that, The temperature is further increased to 260°C and then uniformly reduced to atmospheric pressure within 60 minutes; the vacuuming time is 90 minutes.

9. The low-temperature preparation method according to claim 5, characterized in that, The micro-positive pressure is 0.2 MPa.

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