High whiteness high molecular weight bio-based pa46 particles comprising nylon 46 powder and applications thereof

Abstract

This invention provides a high-whiteness, high-molecular-weight bio-based PA46 particle containing nylon 46 powder and its applications, relating to the field of polymer materials technology. The nylon 46 powder is prepared by synergistically controlling the composition of the prepolymer through primary and secondary salt formation, followed by a method of pulsed instantaneous steam introduction during gradient heating. This method effectively avoids yellowing of the product, resulting in a pure white powder. Simultaneously, the gradient heating step of this application effectively maintains the continuous polycondensation reaction, achieving a significant increase in molecular weight and uniformity of molecular weight distribution. Using this powder as raw material, this application melt-blends two homogeneous nylon 46 powders prepared using the same process but with different molecular weights in a specific ratio, and synergistically adds a high-temperature resistant antioxidant and a temperature-resistant chain extender to obtain high-whiteness, high-molecular-weight bio-based PA46 particles, which can be widely used in the preparation of industrial products.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a nylon 46 powder containing high-whiteness, high-molecular-weight bio-based PA46 particles and its applications. Background Technology

[0002] Nylon 46 is a new type of engineering plastic with excellent comprehensive properties. It has a high melting point of 295℃ and excellent heat resistance; it also possesses a variety of other properties such as light weight, high strength, wear resistance, radiation resistance, fatigue resistance, flame retardancy, aging resistance, dimensional stability, excellent dielectric properties, and resistance to chemical media. Therefore, it has broad application prospects in industries such as machinery, automobiles, and electrical appliances. For example, in the machinery industry, it can be used to manufacture gears, bearings, seals, and gaskets; in the automotive industry, it can be used to manufacture engine parts, oil pump housings, and intake manifolds; and in the electrical appliance industry, it can be used to manufacture switches, sockets, and motor insulation materials.

[0003] However, the synthesis of nylon 46 presents significant polymerization challenges. Deviations in reaction conditions can easily lead to lower degrees of polymerization and molecular weight in the prepolymer, making it difficult to increase the molecular weight of the final product. For example, prior art CN115850692A discloses a high-temperature resistant nylon and its preparation method and application, which uses a one-pot method to prepare the high-temperature resistant nylon, but the intrinsic viscosity of the final product is only around 2, and the molecular weight is relatively low.

[0004] Meanwhile, in the solid-state polycondensation stage, existing technologies generally face the challenge of balancing color control and energy consumption. Currently, a large portion of solid-state polycondensation is carried out under a nitrogen atmosphere and directly heated to high temperatures, easily causing nylon 46 to turn brown, limiting its application in products with high color requirements. Some processes also involve solid-state polycondensation under a continuous atmosphere of water vapor and nitrogen, but process control is difficult, energy consumption is too high, and it does not meet current energy-saving and low-carbon requirements. For example, CN119751850A discloses a method for producing nylon 46, using butanediamine and organic dicarboxylic acids as raw materials, through a three-step process of salt formation, pre-polycondensation, and solid-state post-polycondensation. However, this process requires continuous water vapor during the solid-state polycondensation stage, and the final product is nylon 46 powder. This process not only significantly increases energy consumption and equipment investment costs but also adds additional processing steps for downstream enterprises (such as drying and pre-granulation), which is detrimental to improving industrialization efficiency.

[0005] In summary, the existing technology still has the following problems in the preparation of nylon 46 particles: (1) Solid-phase polycondensation easily leads to oxidation and yellowing of the product, resulting in insufficient whiteness; (2) It is difficult to increase the molecular weight and the distribution is uneven; (3) Poor processing and molding stability, making it difficult to directly and efficiently extrude ultra-high molecular weight powder; (4) The overall process has high energy consumption, long procedures, and large equipment investment, making it difficult to achieve energy-saving and large-scale production.

[0006] Therefore, it is both necessary and urgent to research and develop a method for preparing nylon 46 particles that can simplify the preparation process, reduce energy consumption and investment costs, avoid yellowing of the product, improve molecular weight and molecular weight distribution uniformity, and be suitable for large-scale production.

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

[0008] The primary objective of this invention is to provide a nylon 46 powder that has the advantages of high whiteness, high molecular weight and uniform distribution, and can be used directly for subsequent processing without drying.

[0009] The second objective of this invention is to provide high-whiteness, high-molecular-weight bio-based PA46 particles.

[0010] A third objective of this invention is to provide an application of the above-mentioned nylon 46 powder or the above-mentioned high-whiteness, high-molecular-weight bio-based PA46 particles.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a nylon 46 powder, which is prepared by a method comprising the following steps: Butylene diamine is added to a dicarboxylic acid solution to form a salt in the first stage, then butylene diamine is added again to form a salt in the second stage, followed by prepolymerization to obtain a prepolymer. The prepolymer is subjected to solid-phase polycondensation with gradient heating in an inert gas atmosphere, and water vapor is instantaneously introduced in a pulsed manner during the heating process.

[0012] Furthermore, the solid-state polycondensation includes: (A) Under the protection of an inert gas, the prepolymer is loaded into a reaction vessel and the temperature is programmed to rise. When the temperature reaches 220-250°C, saturated water vapor with a pressure of 0.05-0.15 MPa is introduced instantaneously in a pulsed manner. Each introduction time is 10-30 seconds. The total introduction time of water vapor in the solid-phase polycondensation stage is 1-10 minutes, and the water vapor flow rate is 1 L / min-9 L / min. (B) Subsequently, a gradient heating polycondensation reaction was carried out at temperatures of 200–230°C, 240–260°C and 270–280°C.

[0013] Furthermore, the gradient temperature polycondensation reaction in step (B) includes: The residence time was controlled at 1.0 to 1.5 h under stirring at 50 rpm and 200–230 °C; then the reaction temperature was controlled at 240–260 °C and the residence time was controlled at 1.0 to 1.5 h; then the reaction temperature was controlled at 270–280 °C and the residence time was controlled at 1 to 4 h. Preferably, when the residence time of the polycondensation section at 270-280°C is 4-8 hours, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 4.8, and the molecular weight is 52000 g / mol-58000 g / mol. Preferably, when the residence time of the polycondensation stage at 270-280°C is 1-3 hours, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 2.8, and the molecular weight is 22000g / mol-30000g / mol.

[0014] The present invention provides a high whiteness, high molecular weight bio-based PA46 particle, wherein the PA46 particle comprises a matrix resin and antioxidants and chain extenders dispersed therein; The matrix resin is formed by melt blending a first nylon component and a second nylon component, wherein the first nylon component and the second nylon component are the aforementioned nylon 46 powder; The first nylon component and the second nylon component are obtained from the same prepolymer through the same solid-state polycondensation process, the only difference being the residence time in the 270–280℃ heat preservation section; the first nylon component is obtained by heat preservation at 270–280℃ for 4 to 8 hours, and the second nylon component is obtained by heat preservation at 270–280℃ for 1 to 3 hours.

[0015] Furthermore, the whiteness of the first nylon component is 80-95, the relative viscosity is 4.8, and the molecular weight is 52000g / mol-58000g / mol; The second nylon component has a whiteness of 80-95, a relative viscosity of 2.8, and a molecular weight of 22000g / mol-30000g / mol.

[0016] Furthermore, the mass ratio of the first nylon component to the second nylon component is (50%–90%):(10%–50%).

[0017] Furthermore, the antioxidant is a high-temperature resistant antioxidant, and its addition amount is 0.1% to 0.8% of the total mass of the first nylon powder and the second nylon powder; The high-temperature resistant antioxidant is selected from one or more of antioxidant 1098, antioxidant 168, antioxidant 9228, antioxidant 626, potassium iodide, and copper iodide.

[0018] Furthermore, the chain extender is a heat-resistant chain extender, and its addition amount is 0.1% to 0.5% of the total mass of the first nylon powder and the second nylon powder; The heat-resistant chain extender is selected from one or more of TNK-30, SMA, ADR-4400, ADR-4370 and ADR-4368.

[0019] Furthermore, the PA46 particles have a whiteness of 75-90, a relative viscosity of 3-3.9, and a molecular weight distribution index of 1.2-1.8.

[0020] The present invention relates to the application of the above-mentioned nylon 46 powder or the above-mentioned high whiteness, high molecular weight bio-based PA46 particles in the preparation of industrial products.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The nylon 46 powder provided in this application is prepared by synergistic regulation of the prepolymer composition through primary and secondary salt formation, followed by pulsed instantaneous introduction of water vapor during gradient heating. This method effectively avoids the yellowing of the product and yields a white powder. Furthermore, the gradient heating step of this application effectively maintains the continuous polycondensation reaction, resulting in a significant increase in molecular weight and uniformity of molecular weight distribution.

[0022] The high-whiteness, high-molecular-weight bio-based PA46 particles provided by this invention are achieved by melting and blending two nylon 46 powders that are homologous and produced by the same process but have different molecular weights. This effectively solves the problems of poor feeding, excessive melting torque, and local overheating degradation when directly processing ultra-high molecular weight PA46. The first nylon component provides a high molecular weight skeleton, while the second nylon component acts as a flow carrier to promote uniform melting and heat transfer. Under the action of a chain extender, the two components achieve efficient molecular chain connection, ultimately obtaining PA46 particles with high whiteness, high molecular weight, uniform molecular weight distribution, and excellent processing stability.

[0023] The nylon 46 powder or high-whiteness, high-molecular-weight bio-based PA46 particles provided by this invention can be widely used to prepare industrial products with high requirements for heat resistance, dimensional stability, mechanical strength and whiteness. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1This is a schematic diagram of the preparation process of high whiteness, high molecular weight bio-based PA46 particles provided in Example 1. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0027] According to one aspect of the present invention, a nylon 46 powder is obtained by a method comprising the following steps: Butylene diamine is added to a dicarboxylic acid solution to form a salt in the first stage, then butylene diamine is added again to form a salt in the second stage, followed by prepolymerization to obtain a prepolymer. The prepolymer is subjected to solid-phase polycondensation with gradient heating in an inert gas atmosphere, and water vapor is instantaneously introduced in a pulsed manner during the heating process.

[0028] The nylon 46 powder provided in this application is prepared by synergistic regulation of the prepolymer composition through primary and secondary salt formation, followed by pulsed instantaneous introduction of water vapor during gradient heating. This method effectively avoids the yellowing of the product and yields a white powder. Furthermore, the gradient heating step of this application effectively maintains the continuous polycondensation reaction, resulting in a significant increase in molecular weight and uniformity of molecular weight distribution.

[0029] In a preferred embodiment of the present invention, the solid-phase polycondensation includes: (A) Under the protection of an inert gas, the prepolymer is loaded into a reaction vessel and the temperature is programmed to rise. When the temperature reaches 220℃~250℃, saturated water vapor with a pressure of 0.05~0.15 MPa is introduced instantaneously in a pulsed manner. Each introduction time is 10~30 s. The total introduction time of water vapor in the solid-phase polycondensation stage is 1~10 min, and the water vapor flow rate is 9 L / min. (B) Subsequently, a gradient heating polycondensation reaction was carried out at temperatures of 200–230°C, 240–260°C and 270–280°C.

[0030] As a preferred embodiment, the solid-phase polycondensation process of this application precisely triggers pulsed saturated water vapor intervention within the crystallization phase transition temperature range of 220℃ to 250℃. Combined with defined pressure, time, and flow rate parameters, an instantaneous and controllable micro-wetting environment is formed on the powder surface, effectively inhibiting oxidative yellowing and maintaining polycondensation activity. Then, through three-stage gradient heating polycondensation at 200~230℃, 240~260℃, and 270~280℃, the molecular chains gradually grow in an orderly manner, further increasing the molecular weight, optimizing the uniformity of molecular weight distribution, and enhancing the thermal stability and batch consistency of the product.

[0031] It should be noted that the mechanism by which this application achieves high whiteness, high molecular weight, and uniform distribution of nylon 46 powder lies in the following: at the temperature point where the polymer crystallinity changes, the instantaneous introduction of trace amounts of water vapor can rapidly form a localized "micro-wetting" environment on the surface of the powder particles. On the one hand, this preferentially and reversibly capsulates the active groups (such as amino groups) at the ends of the polymer chains, selectively inhibiting the oxidative degradation chain reaction initiated by the terminal amino groups (the main yellowing pathway), rather than hindering the condensation reaction. On the other hand, the instantaneous thermal shock it brings helps to disperse powder agglomerates caused by static electricity, promoting the uniformity of heat and mass transfer. Compared with continuous water vapor (which easily leads to hydrolysis) or simple inert gas protection (which has limited effect on inhibiting oxidative yellowing), the method of this application achieves an unexpected balance, greatly saving energy. It is the key to achieving both high whiteness (low yellowing) and high molecular weight with uniform molecular weight distribution in the product.

[0032] In a preferred embodiment of the present invention, the gradient heating polycondensation reaction in step (B) includes: The residence time was controlled at 1.0 to 1.5 h under stirring at 50 rpm and 200–230 °C; then the reaction temperature was controlled at 240–260 °C and the residence time was controlled at 1.0 to 1.5 h; then the reaction temperature was controlled at 270–280 °C and the residence time was controlled at 1 to 4 h. As a preferred embodiment, the gradient heating polycondensation process of this application controls the reaction in stages within three temperature ranges: 200–230°C, 240–260°C, and 270–280°C, and with appropriate residence time, so that the polycondensation reaction is gradually promoted from slow to strong. This is not only conducive to the effective removal of small molecule by-products, but also avoids local overheating and degradation caused by excessively vigorous reaction in the high-temperature stage. In particular, by controlling the residence time in the 270-280℃ range, flexible control of the molecular weight and whiteness of the final product can be achieved, obtaining nylon 46 powders with different molecular weight levels but all possessing high whiteness and good molecular weight distribution uniformity. This provides a raw material basis for subsequent compounding and preparation of high-performance PA46 particles with structural matching and complementary properties.

[0033] Preferably, when the residence time of the polycondensation stage at 270-280°C is 4 hours, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 4.8, and the molecular weight is 52000g / mol-58000g / mol. Preferably, when the residence time of the polycondensation stage at 270-280°C is 1 hour, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 2.8, and the molecular weight is 22000g / mol-30000g / mol.

[0034] According to one aspect of the present invention, a high-whiteness, high-molecular-weight bio-based PA46 particle, said PA46 particle comprising a matrix resin and antioxidants and chain extenders dispersed therein; The matrix resin is formed by melt blending a first nylon component and a second nylon component, wherein the first nylon component and the second nylon component are the aforementioned nylon 46 powder; The first nylon component and the second nylon component are obtained from the same prepolymer through the same solid-state polycondensation process, the only difference being the residence time in the 270–280℃ heat preservation section; The first nylon component was prepared by heating at 270–280℃ for 4 to 8 hours, and the second nylon component was prepared by heating at 270–280℃ for 1 to 3 hours.

[0035] The high-whiteness, high-molecular-weight bio-based PA46 particles provided by this invention are achieved by melting and blending two nylon 46 powders that are homologous and produced by the same process but have different molecular weights. This effectively solves the problems of poor feeding, excessive melting torque, and local overheating degradation when directly processing ultra-high molecular weight PA46. The first nylon component provides a high molecular weight skeleton, while the second nylon component acts as a flow carrier to promote uniform melting and heat transfer. Under the action of a chain extender, the two components achieve efficient molecular chain connection, ultimately obtaining PA46 particles with high whiteness, high molecular weight, uniform molecular weight distribution, and excellent processing stability.

[0036] In a preferred embodiment of the present invention, the whiteness of the first nylon component is 80-95, the relative viscosity is 4.8, and the molecular weight is 52000g / mol-58000g / mol; The second nylon component has a whiteness of 80-95, a relative viscosity of 2.8, and a molecular weight of 22000g / mol-30000g / mol.

[0037] It should be noted that this application employs a synergistic processing strategy of "dual-viscosity powder compounding". The low-viscosity powder (the second nylon component) exhibits even lower viscosity and better flowability in the initial melting stage, rapidly melting and encapsulating high-viscosity powder particles in the extruder's melting section. It acts as a "flowability carrier" and "heat transfer medium," significantly reducing the initial melting torque and processing temperature requirements of ultra-high viscosity materials, thus preventing localized overheating and degradation. Simultaneously, due to their identical chemical structures and excellent compatibility, a uniform network structure is reconstructed in the melt under the action of a chain extender. The molecular weight of the final product is not significantly reduced by the addition of the low-viscosity component; instead, it is ensured by improved processing stability. This compounding approach of "promoting high viscosity with low viscosity and synergistic homogenization" solves the technical bottleneck of the difficulty in directly extruding ultra-high viscosity PA46.

[0038] In a preferred embodiment of the present invention, after the solid-phase polycondensation experiment, the nylon 46 powder does not need to be dried (because the powder remains inside the vacuum drum, isolating it from air). It is first premixed with a specific ratio of high-temperature resistant antioxidant and heat-resistant chain extender using a high-speed mixer to ensure uniform dispersion. High-molecular-weight and slightly lower-molecular-weight PA46 powders are fed into two separate feed ports, with the feed rate adjusted to ensure synchronous discharge. The premixing additive is added from the side feed port to ensure efficient integration with the material. After the material is melted, blended, chain-extended, and devolatilized in an extruder, it is then pelletized and dried underwater to produce high-whiteness, high-molecular-weight nylon 46 particles with a uniform molecular weight distribution on a large scale.

[0039] The preparation method described in this application effectively alleviates the difficulties in improving feed flowability and the need for targeted screw configuration design in existing two-component compounding processes. It not only simplifies the process and reduces energy consumption, but more importantly, it avoids the potential pre-oxidation and pre-reaction consumption of chain extenders during the preheating stage that might result from pre-granulation. The chain extension reaction is more controllable and efficient when carried out in the extruder melt, contributing to precise control of the final molecular weight and uniform and stable product performance.

[0040] In a preferred embodiment of the present invention, the mass ratio of the first nylon component to the second nylon component is (50% to 90%):(10% to 50%).

[0041] In a preferred embodiment of the present invention, the antioxidant is a high-temperature resistant antioxidant, and its addition amount is 0.1% to 0.8% of the total mass of the first nylon powder and the second nylon powder; The high-temperature resistant antioxidant is selected from one or more of antioxidant 1098, antioxidant 168, antioxidant 9228, antioxidant 626, potassium iodide, and copper iodide.

[0042] In a preferred embodiment of the present invention, the chain extender is a heat-resistant chain extender, and its addition amount is 0.1% to 0.5% of the total mass of the first nylon powder and the second nylon powder; The heat-resistant chain extender is selected from one or more of TNK-30, SMA, ADR-4400, ADR-4370 and ADR-4368.

[0043] In a preferred embodiment of the present invention, the PA46 particles have a whiteness of 75-90, a relative viscosity of 3-3.9, and a molecular weight distribution index of 1.2-1.8.

[0044] According to one aspect of the present invention, the application of the above-described nylon 46 powder or the above-described high-whiteness, high-molecular-weight bio-based PA46 particles in the preparation of industrial products.

[0045] The nylon 46 powder or high-whiteness, high-molecular-weight bio-based PA46 particles provided by this invention can be widely used to prepare industrial products with high requirements for heat resistance, dimensional stability, mechanical strength and whiteness.

[0046] The technical solution of the present invention will be further described below with reference to the embodiments.

[0047] Example 1 Figure 1 This is a schematic diagram of the preparation process of high-whiteness, high-molecular-weight bio-based PA46 particles provided in this embodiment.

[0048] A method for preparing high-whiteness, high-molecular-weight bio-based PA46 particles includes the following steps: (1) Preparation of nylon salt (low-temperature high-pressure salt): 10 mol of adipic acid powder was added to a reaction vessel, followed by deionized water at 15 °C (1.5 times the mass of adipic acid), and then methanol was added to make the mass ratio of deionized water to methanol 1:1. Under stirring, 10.2 mol of liquid butanediamine was slowly added dropwise to the mixture at a rate of 2 wt% / min. After the addition was complete, nitrogen gas was introduced into the reaction vessel, pressurized to 8 MPa, and the reaction temperature was controlled at 25 °C. The reaction was maintained at this temperature for 90 min to obtain a 20% nylon salt solution.

[0049] (2) Prepolymerization: The pressure of the obtained nylon salt solution was slowly reduced to atmospheric pressure, and then 0.1 mol% (based on the amount of adipic acid) of butanediamine was added at 55 ℃ and 0.7 MPa nitrogen pressure to carry out a secondary salt formation reaction. After the reaction was completed, the system temperature was raised to 135 ℃, the vent valve was opened, and methanol and some water were removed at a constant temperature for 15 min. Then the temperature was raised to 200 ℃ and the pressure was increased to 1.1 MPa to carry out a pre-condensation reaction for 80 min. After the reaction was completed, the prepolymer powder was discharged by spraying.

[0050] (3) Solid-phase polycondensation of high molecular weight nylon 46 powder: The obtained prepolymer powder was loaded into a vacuum drum, and nitrogen gas was introduced (flow rate of 4 L / min). Simultaneously, the vacuum pump was turned on to maintain a slight positive pressure in the system and to remove air. The mixture was stirred at 50 rpm, and the temperature was increased according to the program. When the temperature reached 240 °C, saturated water vapor at a pressure of 0.05 MPa was instantaneously introduced in a pulsed manner, with each pulse lasting 12 seconds and the interval automatically controlled by the system. The total introduction time was 3 minutes, and the water vapor flow rate was 9 L / min. Subsequently, the temperature was stabilized at 225 °C (first temperature segment) and the reaction was maintained at this temperature for 1.2 h. Then, the temperature was increased to 255 °C (second temperature segment) and the reaction was maintained at this temperature for 1.2 h. Finally, the temperature was increased to 275 °C (third temperature segment) and the reaction was maintained at this temperature for 4 h. After the reaction was completed, heating was stopped, and the mixture was allowed to cool naturally to room temperature under nitrogen protection to obtain high molecular weight nylon 46 powder. The powder is white, undried, and kept in an airtight environment throughout the process.

[0051] (4) Solid-phase polycondensation of low molecular weight nylon 46 powder: Using the same equipment, atmosphere, heating program and pulse steam parameters as in step (3), only the holding time of the third temperature segment (275 °C) was shortened from 4 h to 1 h; the rest of the steps were the same as in step (3) to obtain low molecular weight nylon 46 powder. The powder is also white, and it has not undergone drying treatment and has been kept in an air-isolated state throughout the process.

[0052] (5) Integrated direct extrusion and granulation: The high molecular weight nylon 46 powder (80 wt%) obtained in step (3) and the low molecular weight nylon 46 powder (20 wt%) obtained in step (4) are respectively fed into two independent feed ports of a twin-screw extruder; wherein the length-to-diameter ratio (L / D) of the twin-screw extruder is 42:1, and the screw configuration includes a strong conveying section and a distribution mixing section; In a high-speed mixer, 0.5 wt% of a high-temperature resistant antioxidant (antioxidant 1098 and antioxidant 626 mixed at a mass ratio of 3:4) and 0.4 wt% of a heat-resistant chain extender (ADR-4400) are premixed for 10 min to ensure uniform dispersion. The premixed additive is precisely injected into the middle and rear part of the melting section (about 30 L / D from the feed port) through the side feed port of the extruder. After the material is melted, plasticized, blended, chain extended, and vacuum devolatilized in the extruder, it is granulated underwater and dried with hot air to obtain high-whiteness, high-molecular-weight bio-based PA46 particles. The PA46 particles are cylindrical particles with a diameter of 1.6~1.8 mm and a length of 3~3.3 mm.

[0053] It should also be noted that the present invention does not impose any special restrictions on the specific process steps of the compounding extrusion, such as melt plasticizing, blending, chain extension reaction, vacuum devolatilization, underwater pelletizing, and hot air drying. Conventional process conditions in the field can be used, as long as the cylindrical PA46 particles that meet the above size requirements are finally obtained.

[0054] Example 2 The only difference between this embodiment and embodiment 1 is that in step (3), the pressure of the pulsed steam is adjusted to 0.05 MPa and the time of each injection is adjusted to 10 s. All other process parameters and equipment conditions are exactly the same as in embodiment 1.

[0055] Example 3 The only difference between this embodiment and embodiment 1 is that in step (3), the pressure of the pulsed steam is adjusted to 0.15 MPa and the time for each injection is adjusted to 30 s. All other process parameters and equipment conditions are exactly the same as in embodiment 1.

[0056] Example 4 Except for step (5) integrated direct extrusion and granulation, in which “the amount of high molecular weight nylon 46 powder added in step (3) is 90 wt% and the amount of low molecular weight nylon 46 powder added in step (4) is 10 wt%”, the rest of this embodiment is the same as in embodiment 1.

[0057] Example 5 Except for step (5) integrated direct extrusion and granulation, in this embodiment, "the amount of high molecular weight nylon 46 powder added in step (3) is 50 wt%, and the amount of low molecular weight nylon 46 powder added in step (4) is 50 wt%", the rest is the same as in embodiment 1.

[0058] Example 6 Except for step (5) integrated direct extrusion and granulation, in this embodiment, "the amount of high molecular weight nylon 46 powder added in step (3) is 30 wt%, and the amount of low molecular weight nylon 46 powder added in step (4) is 70 wt%", the rest is the same as in embodiment 1.

[0059] Comparative Example 1 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that in step (3), the flow rate of water vapor is 1 L / min. The rest is the same as in Example 1.

[0060] Comparative Example 2 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that in step (3), the flow rate of water vapor is 20 L / min. The rest is the same as in Example 1.

[0061] Comparative Example 3 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that water vapor is continuously introduced in step (3).

[0062] Comparative Example 4 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that in step (3), the temperature is directly raised to 275°C to carry out a constant-temperature polycondensation reaction.

[0063] Comparative Example 5 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that the selection of the high-temperature resistant antioxidant in step (5) is different.

[0064] In this comparative example, copper iodide and potassium iodide (mass ratio 3:4) were used as high-temperature antioxidants to replace the high-temperature antioxidants in Example 1.

[0065] Comparative Example 6 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that the heat-resistant chain extender in Example 1 is replaced with an equal amount of heat-resistant chain extender (ADR-4370).

[0066] The rest is the same as in Example 1.

[0067] Comparative Example 7 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that no heat-resistant chain extender is added in this comparative example.

[0068] Comparative Example 8 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that the high molecular weight nylon 46 powder and the low molecular weight nylon 46 powder in step (5) are placed in the air for 1 hour and then conveyed to a twin-screw extruder.

[0069] The rest is the same as in Example 1.

[0070] Comparative Example 9 This comparative example provides a method for preparing PA46 particles. The only difference between this comparative example and Example 1 is that in step (3), water vapor is not introduced, but only an inert gas is introduced.

[0071] Experimental Example 1 To systematically verify the comprehensive effect of the technical solution of the present invention in solving the four major technical problems of oxidation and yellowing, molecular weight increase, processing stability and energy saving, PA46 particles prepared by Examples 1-6 and Comparative Examples 1-12 were selected and their performance was tested according to the following standard methods, and the results are summarized in the table below.

[0072] All tests were performed under the same environmental conditions (temperature 23±2℃, humidity 50±5%RH). Each group of samples was measured three times, and the average value was taken.

[0073] The specific testing methods are as follows: Relative viscosity: Referring to ISO 307 standard: First, vacuum dry the PA46 sample at 105℃ for 2-4 hours. Accurately weigh 0.5000g of the dried sample, dissolve it in 90% sulfuric acid and bring the volume to 100mL. After the sample is completely dissolved and transparent, place the Ubbelohde viscometer, pure formic acid solvent and the test solution in a constant temperature water bath at 25.0±0.1℃ for at least 15 minutes to equilibrate. Measure the outflow time of the pure solvent and the solution in the viscometer separately. Perform three parallel measurements with a range not exceeding 0.4s and take the average value. The ratio of the solution outflow time to the solvent outflow time is the relative viscosity.

[0074] Whiteness: First, turn on the whiteness meter to preheat, and complete the instrument calibration using the matching standard white plate and black tube; take dry and sieved PA46 prepolymer powder, and evenly fill it into the sample cell to a depth of ≥6mm. Use a clean glass plate to gently press and scrape it flat to ensure that the surface is flat, free of bubbles and cracks, and completely opaque; place the sample cell on the instrument sample stage, and measure the blue light whiteness (R457) under 45 / 0 optical conditions. Test the same sample in parallel 3 times, changing the sample loading position and scraping it flat again each time. Take the arithmetic mean of the 3 results as the final whiteness value, and the result is accurate to 0.1.

[0075] Molecular weight distribution index: Referring to GB / T 36214.1 and OECD 118 standards: First, the PA46 sample was vacuum dried at 105℃ for 2 hours. Accurately weighed and dissolved in hexafluoroisopropanol as solvent at 100℃ until completely transparent, preparing a 2 mg / mL solution. This solution was then filtered through a 0.45 μm organic filter membrane to remove impurities. The high-temperature GPC system was started, using hexafluoroisopropanol as the mobile phase. The column temperature was set to 80℃ and the flow rate to 1.0 mL / min. A differential refractive index (RI) detector was used. After the baseline stabilized, a lgM–elution volume correction curve was established using a narrow-distribution polystyrene (PS) standard. Subsequently, the sample solution was injected for separation and detection. Chromatographic data were collected, and the number-average molecular weight (Mn), weight-average molecular weight (Mw), Z-average molecular weight (Mz), and polydispersity index (PMI) were calculated by the workstation. = Mw / Mn), and generate a molecular weight distribution curve.

[0076] See Table 1 for specific test results.

[0077] Table 1:

[0078] As can be seen from the table above, the final Nylon 46 products prepared by the process of the present invention in Examples 1-5 all maintained their whiteness, relative viscosity, and molecular weight distribution within the target range, and were significantly better than the comparative examples and existing technologies. In Example 6, the relative viscosity of the final product was lower because the content of low molecular weight Nylon 46 powder was higher than that of high molecular weight Nylon 46 powder.

[0079] As can be seen from the data of Examples 1-5 and Comparative Example 1, under the same conditions, the amount of water introduced in a short time during the solid-phase polycondensation process is insufficient, which leads to the rapid evaporation of water vapor and the inability to effectively suppress the side reactions in the reaction system. Consequently, the powder after solid-phase polycondensation appears slightly yellow, and ultimately the PA46 particles after extrusion granulation are slightly yellow.

[0080] As can be seen from the data of Examples 1-5 and Comparative Example 2, when other conditions are the same, if too much water is introduced in a short time during the solid-phase polycondensation process, and this part of the water vapor is not removed in time, it will come into full contact with the material, eventually causing the material to become damp, which greatly hinders the increase of polymer molecular weight.

[0081] As can be seen from the data of Examples 1-5 and Comparative Example 3, excessive water vapor will clog the filter screen for a long time, causing nylon 46 powder to stick to the wall surface. Water vapor cannot be discharged in time, which will eventually lead to product hydrolysis and a significant decrease in the relative viscosity of the product particles after extrusion granulation.

[0082] The data from Examples 1-5 and Comparative Example 4 show that the absence of a gradient heating stage hinders the increase of polymer molecular weight; this may be because gradient heating is more conducive to the contact and discharge of water vapor with the material.

[0083] As can be seen from the data of Examples 1-5 and Comparative Example 5, under the same conditions, after replacing the organic antioxidant with the copper salt antioxidant, the PA46 particles extruded and granulated are slightly yellow, but the relative viscosity increases to 4.0. This indirectly confirms that the copper salt antioxidant is effective in inhibiting the degradation of PA46 and maintaining the molecular weight, but it will cause the product to be yellowish.

[0084] Data from Examples 1-5 and Comparative Example 6 show that, under the same conditions, when the heat-resistant chain extender used in the PA46 extrusion granulation process was replaced from ADR-4400 to ADR-4370 of the same series, the relative viscosity of the resulting PA46 particles was 3.6. This result indicates that ADR-4370 can still effectively perform chain extension under the current process system. Through the reaction of the epoxy groups in its molecular structure with the amino groups at the ends of the PA46 molecular chains, it achieves chain extension and cross-linking, thereby enabling the product to reach the target relative viscosity level and meeting the basic requirements for melt strength in subsequent processing. It also reflects the differences between ADR-4370 and ADR-4400 in terms of reactivity and molecular weight distribution, resulting in slightly different chain extension efficiencies and a slightly lower relative viscosity than the product modified with ADR-4400.

[0085] As can be seen from the data of Examples 1-5 and Comparative Example 7, when other conditions remain the same, the relative viscosity of the PA46 particles obtained without the use of the heat-resistant chain extender in the PA46 extrusion granulation process is 3.2, which fully demonstrates that the selected heat-resistant chain extender plays a key role in the PA46 processing system.

[0086] As can be seen from the data of Examples 1-5 and Comparative Example 8, when other conditions remain the same, if the mixture is left to stand in the air for 1 hour after all materials are mixed, Nylon 46 will quickly absorb moisture from the air due to its strong hygroscopicity. This will lead to the following problems in the subsequent extrusion process: the moisture will vaporize at high temperature to produce bubbles, which will destroy the continuity of the PA46 molecular chain. At the same time, the moisture will cause the PA46 molecular chain to undergo hydrolysis and degradation, resulting in a decrease in molecular weight. Ultimately, the relative viscosity of the PA46 particles after extrusion granulation is only 3.0, which is significantly lower than that of the product processed in the dry state, directly affecting the melt strength and subsequent molding and processing performance of the material.

[0087] As can be seen from the data of Examples 1-5 and Comparative Example 9, even without the introduction of water vapor, the nylon color significantly turned yellow, indicating that water vapor can effectively control the side reactions during the solid-phase polycondensation process.

[0088] In summary, by controlling the amino acid molar ratio and using low-temperature, high-pressure salt formation, with methanol and water as a mixed solvent, and by adding butanediamine during the prepolymerization stage, a salt-forming reaction was carried out again at 55°C and 0.7 MPa. During solid-phase polycondensation, a gradient heating method was used, and at the inflection point of the heating, water vapor was introduced in a micro-pressure, instantaneous pulsed manner to obtain a high-molecular-weight, uniformly distributed, white PA46 particle.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nylon 46 powder characterized in that, The nylon 46 powder is prepared by a method comprising the following steps: Butylene diamine is added to a dicarboxylic acid solution to form a salt in the first stage, then butylene diamine is added again to form a salt in the second stage, followed by prepolymerization to obtain a prepolymer. The prepolymer is subjected to solid-phase polycondensation with gradient heating in an inert gas atmosphere, and water vapor is instantaneously introduced in a pulsed manner during the heating process.

2. The nylon 46 powder of claim 1, wherein, The solid-phase polycondensation includes: (A) Under the protection of inert gas, the prepolymer is loaded into the reaction vessel and the temperature is programmed to rise. When the temperature rises to 220℃~250℃, saturated water vapor with a pressure of 0.05~0.15 MPa is introduced instantaneously in the form of pulses. Each introduction time is 10~30 s. The total introduction time of water vapor in the solid phase polycondensation stage is 1~10 min, and the water vapor flow rate is 1L / min~9 L / min. (B) Subsequently, a gradient heating polycondensation reaction was carried out at temperatures of 200–230°C, 240–260°C and 270–280°C.

3. The nylon 46 powder of claim 2, wherein, The gradient heating polycondensation reaction in step (B) includes: The residence time was controlled at 1.0 to 1.5 h under stirring at 50 rpm and 200–230 °C; then the reaction temperature was controlled at 240–260 °C and the residence time was controlled at 1.0 to 1.5 h; then the reaction temperature was controlled at 270–280 °C and the residence time was controlled at 1 to 4 h. Preferably, when the residence time of the polycondensation section at 270-280°C is 4-8 hours, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 4.8, and the number-average molecular weight is 52000 g / mol-58000 g / mol. Preferably, when the residence time of the polycondensation stage at 270-280°C is 1-3 hours, the whiteness of the nylon 46 powder is 80-95, the relative viscosity is 2.8, and the molecular weight is 22000g / mol-30000g / mol.

4. A high whiteness high molecular weight bio-based PA 46 particle characterized in that, The PA46 particles comprise a matrix resin and antioxidants and chain extenders dispersed therein; The matrix resin is formed by melt blending a first nylon component and a second nylon component, wherein the first nylon component and the second nylon component are nylon 46 powder as described in any one of claims 1 to 3; The first nylon component and the second nylon component are obtained from the same prepolymer through the same solid-state polycondensation process, the only difference being the residence time in the 270–280℃ heat preservation section; the first nylon component is obtained by heat preservation at 270–280℃ for 4h to 8h, and the second nylon component is obtained by heat preservation at 270–280℃ for 1h to 3h.

5. The high- brightness high molecular weight bio-based PA 46 particles according to claim 4, characterized in that, The first nylon component has a whiteness of 80-95, a relative viscosity of 4.8, and a number-average molecular weight of 52000 g / mol-58000 g / mol; The second nylon component has a whiteness of 80-95, a relative viscosity of 2.8, and a molecular weight of 22000g / mol-30000g / mol.

6. The high-whiteness, high-molecular-weight bio-based PA46 particles according to claim 5, characterized in that, The mass ratio of the first nylon component to the second nylon component is (50%~90%):(10%~50%).

7. The high-whiteness, high-molecular-weight bio-based PA46 particles according to claim 4, characterized in that, The antioxidant is a high-temperature resistant antioxidant, and its addition amount is 0.1% to 0.8% of the total mass of the first nylon component and the second nylon component; The high-temperature resistant antioxidant is selected from one or more of antioxidant 1098, antioxidant 168, antioxidant 9228, antioxidant 626, copper iodide, and potassium iodide.

8. The high-whiteness, high-molecular-weight bio-based PA46 particles according to claim 4, characterized in that, The chain extender is a heat-resistant chain extender, and its addition amount is 0.1% to 0.5% of the total mass of the first nylon component and the second nylon component; The heat-resistant chain extender is selected from one or more of TNK-30, SMA, ADR-4400, ADR-4370 and ADR-4368.

9. The high-whiteness, high-molecular-weight bio-based PA46 particles according to claim 4, characterized in that, The PA46 particles have a whiteness of 75-90, a relative viscosity of 3-3.9, and a molecular weight distribution index of 1.2-1.

8.

10. The application of the nylon 46 powder according to any one of claims 1 to 3 or the high whiteness, high molecular weight bio-based PA46 particles according to any one of claims 4 to 9 in the automotive, electronics and electrical and industrial machinery fields.

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