Long chain semi-aromatic mxd nylon material and method of making

Abstract

This invention belongs to the field of polymer synthesis materials technology, specifically relating to a long-chain semi-aromatic MXD nylon material and its preparation method. The material is made from components comprising the following weight percentages: m-phenylenediamine 31%-41%, long-chain dicarboxylic acid 59%-69%, nucleating agent 0.05%-0.1%, catalyst 0.03%-0.05%, antioxidant 0.03%-0.05%, and solvent 100%-200%; the long-chain dicarboxylic acid is selected from C... 10 -C 18 This invention relates to a series of dicarboxylic acids. Through molecular structure design, synergistic additives, and process optimization, the prepared MXD nylon material achieves a synergistic balance of ultra-low water absorption, high barrier properties, and high toughness, overcoming the shortcomings of traditional MXD6, such as high brittleness and high water absorption. The process is green and environmentally friendly, with excellent processing performance, and can be widely used in high-barrier packaging, automotive, and electronic and electrical fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthetic materials technology, specifically relating to long-chain semi-aromatic MXD nylon materials and their preparation methods, and more specifically to a high-barrier, low-water-absorption semi-aromatic long-chain MXD nylon material and its preparation method. Background Technology

[0002] Polyamide (nylon) materials are widely used in food packaging, electronics, automotive, and medical devices due to their excellent mechanical properties, chemical resistance, and processability. Semi-aromatic MXD nylon, using m-phenylenediamine as the diamine monomer, combines the high rigidity and high barrier properties of aromatic polyamides with the easy processability of aliphatic polyamides, making it a core material for high-barrier packaging, oil-resistant structural components, and electronic packaging. Currently, the most widely commercially available MXD nylon is MXD6, prepared by the polycondensation of m-phenylenediamine and adipic acid. Its oxygen barrier properties are significantly superior to conventional aliphatic polyamides PA6 and PA66, making it widely used as a barrier layer material in food packaging.

[0003] US20040146725A1 discloses a technology for using MXD6 as a barrier layer, which improves barrier performance by adding a small amount of barium sulfate to the polyamide matrix to achieve crystal refinement. CN107312170A discloses a solution polymerization method for polyamides using long-chain dicarboxylic acids (such as sebacic acid) and amine monomers.

[0004] However, none of these existing technologies systematically elaborate on the following aspects: C 10 -C 18 All long-chain dicarboxylic acids were incorporated into the MXD system, achieving an ultra-low water absorption rate (≤0.5%). Through the combined use of 0.05-0.1% barium sulfate nucleating agent and 0.03-0.05% sodium hypophosphite catalyst, molecular weights (Mw) of 30,000-120,000 g·mol⁻¹ were achieved at a heating rate of 5-10°C / min. -1 The polymer is subjected to post-processing techniques including vacuum dehydration and solid-phase polymerization (SSP) to further enhance crystallinity and barrier properties.

[0005] In addition, the existing technology also has the following drawbacks: First, existing modifications of long-chain dicarboxylic acids are limited to single components and do not form a C-covered structure. 10 -C 18 The entire MXD nylon polymer system is difficult to effectively reduce the water absorption rate of materials by controlling the carbon chain length. Conventional MXD6 suffers a significant deterioration in performance and dimensional stability after water absorption, making it difficult to adapt to high humidity conditions.

[0006] Second, existing technologies suffer from a trade-off in performance control. Simply optimizing barrier properties can exacerbate material brittleness, while simply increasing flexibility can lead to a decline in barrier and heat resistance properties. This makes it impossible for MXD nylon to simultaneously possess adequate barrier capabilities, impact resistance, and high elongation.

[0007] Third, existing polymerization processes suffer from insufficient environmental friendliness and crude process control. Solution polymerization causes significant organic solvent pollution, and melt polycondensation does not match the reaction characteristics of long-chain MXD nylon, which easily leads to problems such as material carbonization, small molecule residues, and uneven degree of polymerization. As a result, product batch stability is poor, and it is also difficult to inhibit thermal degradation through reasonable end-group ratios.

[0008] Fourth, existing technologies only address single-performance improvements and do not construct an integrated performance control scheme. They cannot simultaneously take into account multiple dimensions of performance such as mechanical properties, barrier properties, heat resistance, and hydrolysis resistance, making it difficult to meet the comprehensive usage requirements of high-end applications.

[0009] The full English names and Chinese translations of the abbreviations used in this instruction manual are as follows: MXD, short for m-Xylylenediamine, is a type of dimethylamine. MXD6, full name Poly(m-xylylene adipamide), Chinese name: Poly(m-xylylene adipamide); PA6T, full English name Poly(hexamethylene terephthalamide), Chinese name: poly(hexamethylene terephthalamide); DSC, short for Differential Scanning Calorimetry, is a method of differential scanning calorimetry. GPC stands for Gel Permeation Chromatography. PDI stands for Polydispersity Index. OTR stands for Oxygen Transmission Rate. WVTR stands for Water Vapor Transmission Rate. SSP stands for Solid State Polymerization. ASTM, short for American Society for Testing and Materials, is a prestigious organization in the United States. Summary of the Invention

[0010] The technical problem to be solved by this invention includes at least one of the following: Conventional MXD nylon has a high water absorption rate. After absorbing water, its mechanical properties, barrier properties and dimensional stability decrease significantly, making it difficult to meet the requirements for long-term use in high humidity environments. MXD nylon is difficult to achieve good barrier properties and toughness at the same time. It is prone to the performance imbalance problem that when the barrier properties meet the standard, the brittleness is high, and when the toughness is improved, the barrier and heat resistance decrease. Existing polymerization processes are not environmentally friendly and have extensive process control, which can easily lead to problems such as material carbonization, small molecule residues, uneven degree of polymerization, and poor batch stability. Furthermore, they cannot suppress thermal degradation or reduce monomer residues by controlling the end-group ratio. The mechanical, barrier, heat resistance, and hydrolysis resistance properties of MXD nylon cannot be simultaneously optimized through integrated formulation and process design, making it difficult to meet the comprehensive performance requirements of high-end applications.

[0011] To address the aforementioned technical problems, the present invention provides the following technical solutions.

[0012] A long-chain semi-aromatic MXD nylon material, made from components comprising: 31-41 parts (wt%) of m-phenylenediamine; 59-69 parts (wt%) of long-chain dicarboxylic acids; Nucleating agent 0.05-0.1 parts (wt%); Catalyst 0.03-0.05 parts (wt%); Antioxidant 0.03-0.05 parts (wt%); Solvent 100-200 parts (wt%).

[0013] The molecular formula of the m-phenylenediamine is C8H. 12 N2, with a purity of over 99.9%.

[0014] The m-phenylenediamine has a moisture content of ≤0.05%, a color (platinum-cobalt) of ≤10, and is free of free amine impurities.

[0015] The long-chain dicarboxylic acid is selected from sebacic acid (C64- ... 10 ), tridecanoic acid (C 13 ), pentadecanoic acid (C 15 ), hexadecanoic acid (C 16 ), octadecanoic acid (C 18 One or more of the following, with sebacic acid being preferred.

[0016] The long-chain dicarboxylic acid has a purity of ≥99.5%, an acid value deviation of ≤±0.5mgKOH / g, and a melting point fluctuation of ≤±2℃.

[0017] The nucleating agent is selected from barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate, with barium sulfate being preferred; the nucleating agent has a particle size D50 ≤ 1 μm, a specific surface area ≥ 20 m² / g, and no agglomerated particles.

[0018] The catalyst is selected from one or more of sodium hypophosphite, potassium hypophosphite, sodium phosphite, magnesium hypophosphite, calcium hypophosphite, or zinc hypophosphite, with sodium hypophosphite being preferred. The catalyst is of analytical grade, with a water content ≤0.1%, and free of metal ion impurities to avoid catalytic poisoning and side reactions.

[0019] The antioxidants are selected from hindered phenolic antioxidants (primary antioxidants, chain terminators), such as 1098, 1010, 1076, etc., and phosphite / phosphonate antioxidants (auxiliary antioxidants, peroxide decomposers), such as 168, 626, P-EPQ, etc.; the antioxidants are particle size ≤200 mesh, and the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1.

[0020] The solvent is selected from safe and environmentally friendly deionized water.

[0021] The polymer repeating unit of the semi-aromatic long-chain MXD nylon obtained in this invention is shown in formula (1): Equation (1):

[0022] Where n = 8, 11, 13, 14, 16, the corresponding long-chain dicarboxylic acids are sebacic acid (C... 10 ), tridecanoic acid (C 13 ), pentadecanoic acid (C 15 ), hexadecanoic acid (C 16 ) and octadecanoic acid (C 18 x represents the degree of aggregation (DP), which is the number of repeating units.

[0023] The molecular formula of each repeating unit can be expressed as: C n+10 H 2n+10 N2O2, the unit molecular formula corresponding to a specific value of n and the theoretical molecular weight (g·mol⁻¹) -1 As shown in Table 1 (only several commonly used long-chain dicarboxylic acids are listed): Table 1: Molecular Formula and Theoretical Molecular Weight of Semi-Aromatic MXD Nylon Repeating Units

[0024] This invention also provides a method for preparing long-chain semi-aromatic MXD nylon materials, comprising the following steps: (1) Grind the above components m-phenylenediamine and long-chain dicarboxylic acid in a stainless steel mortar at a molar ratio of 1.05:1.0 (corresponding to a weight ratio of 31-41%:59-69%), nucleating agent 0.05-0.1 parts; catalyst 0.03-0.05 parts; antioxidant 0.03-0.05 parts to ensure that the components are mixed evenly and without agglomeration. Then add it to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 100-200 parts of solvent deionized water into the reactor, seal the high-pressure polymerization reactor, start stirring at a stirring rate of 200-400 r / min, replace the air in the reactor with high-purity inert gas 3-5 times, and after replacement, the oxygen content in the reactor is ≤0.01%. Finally, reserve 0.1-0.3 MPa of inert gas as a protective gas. (2) Heat the reactor at a rate of 5-10℃ / min. Control the temperature in stages during the heating process. Heat rapidly below 100℃, and heat uniformly from 100℃ to the reaction temperature to prevent local overheating that could lead to carbonization of the raw materials. The pressure inside the reactor will rise accordingly. When the pressure is 2.0-3.0MPa, release the water in the system to keep the reactor under constant pressure. When the temperature rises to 200-250℃, continue the reaction under constant temperature and pressure for 1-3 hours. When the temperature inside the reactor rises to 250-270℃, slowly depressurize the reactor for 1-1.5 hours until it reaches atmospheric pressure. Control the depressurization rate to 0.05-0.1MPa / min to avoid sudden pressure drops that could cause small molecules to boil violently and materials to splash.

[0025] (3) After the pressure inside the reactor is reduced to atmospheric pressure, the temperature inside the reactor is controlled at 240-270℃ and the reaction is carried out at a constant temperature for 10-30 minutes. During the constant temperature reaction, the stirring rate is maintained at 200-400 r / min. Then, the reaction is carried out under vacuum for 15-30 minutes with a vacuum degree of -0.04 to -0.08 MPa. A step-by-step vacuuming method is used, first vacuuming to -0.04 MPa and holding for 5 minutes, and then vacuuming to the target vacuum degree to remove small molecule impurities and further increase the degree of polymerization. Finally, inert gas is introduced into the reactor and pressurized to 0.5-2 MPa for discharge. The temperature of the discharge port is controlled at 230-260℃. The material is then pelletized underwater at a water temperature of 30-50℃ to obtain uniform granules with a particle size of 2-3 mm, which is a high-barrier, low-water-absorption semi-aromatic long-chain MXD nylon material.

[0026] In step (2), the inert gas is nitrogen, carbon dioxide, argon or helium, with nitrogen being preferred.

[0027] Compared with the prior art, the present invention has the following significant advantages: The main chain molecules of long-chain MXD nylon materials provide flexible chain segments, thereby increasing the flexibility and toughness of the main chain molecules, which means that high barrier properties are achieved while toughness is improved, thus broadening the range of applications. By introducing long-chain dicarboxylic acid monomers and m-phenylenediamine as monomers, the material exhibits ultra-low water absorption, resulting in good dimensional stability and excellent performance retention after water absorption. The tensile strength retention rate of the material after water absorption is ≥95%, the impact strength retention rate is ≥98%, and the dimensional change rate is ≤0.1%, which is far superior to traditional MXD6 and PA6T. It can be used for a long time at temperatures ranging from -40℃ to 120℃, and has excellent weather resistance and chemical corrosion resistance.

[0028] The modified material is prepared by melt polycondensation, which has fewer process steps, shorter polymerization cycle, higher production efficiency and lower production cost, creating conditions for future continuous industrial production. This invention uses aqueous phase polymerization, leaving no organic solvent residue and resulting in near-zero emissions of waste, which aligns with the development trend of environmentally friendly polymer materials and represents a green and low-carbon process.

[0029] This invention achieves end-group balance to inhibit degradation by using a monomer molar ratio of 1.05:1.0, while avoiding monomer residues from affecting barrier performance; thus, it simultaneously optimizes the material's mechanical, barrier, heat resistance, and hydrolysis resistance properties.

[0030] The polymerization solvent uses deionized water, which is safe, sustainable, and environmentally friendly. Attached Figure Description

[0031] none Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] In this specific embodiment, "part" refers to a relative weight percentage (%w / w).

[0034] In the following embodiments, the following detection method is used: The melting point was obtained by differential scanning calorimeter (DSC thermal analyzer).

[0035] Tensile properties were tested according to ASTM D638-10, with a tensile rate of 5 mm / min.

[0036] Elongation was tested using ASTM D638-10, with a tensile rate of 5 mm / min.

[0037] Notched impact strength of simply supported beams is tested according to ASTM D6110-10.

[0038] Bending strength was tested according to ASTM D790-10, with a pressing speed of 1.25 mm / min.

[0039] Oxygen and carbon dioxide permeability tests were conducted using the infrared sensor method (WVTR).

[0040] Heat distortion temperature (1.82 MPa) was tested according to ASTM D648, Vicat softening temperature was tested according to ASTM D1525, number average molecular weight was tested by gel permeation chromatography (GPC), and molecular weight distribution index PDI = weight average molecular weight / number average molecular weight.

[0041] Water absorption rate test: At room temperature, place the sample in a desiccator with a beaker containing a saturated saline solution at the bottom, maintaining a relative humidity of 75%. Weigh the sample every 24 hours, recording the weight as Gi (i = 1, 2, 3, 4…), and return the weighed sample to the desiccator. After 20 days, dry the sample in an oven (70°C, 24 hours), then cool it to room temperature in the desiccator and weigh it again, recording the weight as G0. Calculate the water content (Wi)% in the sample using the following formula: Wi = (Gi - G0) / Gi × 100%. In this invention, the water absorption rate is consistently calculated after 10 days (240 hours): Wi = (Gi - G0) / Gi × 100%.

[0042] Example 1 Take 41 parts of m-phenylenediamine, 59 parts of sebacic acid (molar ratio 1.05:1.0), 0.1 parts of barium sulfate (nucleating agent), 0.03 parts of sodium hypophosphite (catalyst), and 0.03 parts of antioxidant (1098 / 168). Grind the materials in a mortar until they are fully mixed. Then add them to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 200 parts of deionized water (solvent) into the reactor. Seal the high-pressure polymerization reactor, start stirring at a speed of 400 r / min, and replace the air in the reactor with high-purity nitrogen five times. Finally, reserve 0.3 MPa of nitrogen as a protective gas. The reactor is heated at a rate of 5℃ / min, and the pressure inside the reactor increases accordingly. When the pressure reaches 3.0MPa, the water in the system is released to bring the reactor to a constant pressure. When the temperature reaches 250℃, the reactor is kept at a constant temperature and pressure for 3 hours. Then, when the temperature inside the reactor reaches 270℃, the reactor is slowly depressurized for 1.5 hours until it reaches atmospheric pressure. After the pressure inside the reactor is released to atmospheric pressure, the temperature inside the reactor is controlled at 270℃ and reacted at a constant temperature for 10 minutes. Then, a vacuum reaction is carried out for 30 minutes with a vacuum degree of -0.08MPa. Finally, nitrogen gas is introduced into the reactor and pressurized to 2MPa before the material is discharged, thus obtaining a high-barrier, low-water-absorption semi-aromatic long-chain MXD10 nylon material.

[0043] The obtained MXD10 nylon material has a number-average molecular weight Mn=32000 and a molecular weight distribution index PDI=1.9.

[0044] The obtained MXD10 nylon material was injection molded at a temperature of 230-250℃ to obtain test specimens.

[0045] Example 2 Take 37 parts of m-phenylenediamine, 63 parts of tridecanoic acid (molar ratio 1.05:1.0), 0.05 parts of titanium dioxide (nucleating agent), 0.05 parts of potassium hypophosphite (catalyst), and 0.005 parts of antioxidant (1010 / 626). Grind them in a mortar to ensure thorough mixing. Then add them to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 100 parts of deionized water (solvent) into the reactor. Seal the high-pressure polymerization reactor, start stirring at a speed of 300 r / min, and replace the air in the reactor three times with high-purity carbon dioxide. Finally, reserve 0.1 MPa of nitrogen as a protective gas. The reactor was heated at a rate of 7℃ / min, and the pressure inside the reactor increased accordingly. When the pressure reached 2.5MPa, the water in the system was released to bring the reactor to a constant pressure. When the temperature reached 230℃, the reactor was kept at a constant temperature and pressure for 2 hours. Then, when the temperature inside the reactor reached 250℃, the reactor was slowly depressurized for 1 hour until it reached atmospheric pressure. After the pressure inside the reactor is released to atmospheric pressure, the temperature inside the reactor is controlled at 250℃ and reacted at a constant temperature for 20 minutes. Then, a vacuum reaction is carried out for 20 minutes with a vacuum degree of -0.04MPa. Finally, nitrogen gas is introduced into the reactor and pressurized to 1MPa before the material is discharged, thus obtaining a high-barrier, low-water-absorption semi-aromatic long-chain MXD13 nylon material.

[0046] The obtained MXD13 nylon material has a number-average molecular weight Mn=30000 and a molecular weight distribution index PDI=2.0.

[0047] The obtained MXD13 nylon material was injection molded at a temperature of 220-240℃ to obtain test specimens.

[0048] Example 3 Take 34 parts of m-phenylenediamine, 66 parts of pentadecanoic acid (molar ratio 1.05:1.0), 0.08 parts of calcium carbonate nucleating agent, 0.035 parts of magnesium hypophosphite catalyst, and 0.035 parts of antioxidant (1076 / P-EPQ). Grind them in a mortar to ensure thorough mixing. Then add them to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 180 parts of deionized water solvent into the reactor. Seal the high-pressure polymerization reactor, start stirring at a speed of 250 r / min, and replace the air in the reactor with high-purity argon gas 5 times. Finally, reserve 0.25 MPa of argon gas as a protective gas. The reactor was heated at a rate of 7℃ / min, and the pressure inside the reactor increased accordingly. When the pressure reached 2.3MPa, the water in the system was released to bring the reactor to a constant pressure. When the temperature reached 210℃, the reactor was kept at a constant temperature and pressure for 2.5 hours. Then, when the temperature inside the reactor reached 255℃, the reactor was slowly depressurized for 1.2 hours until it reached atmospheric pressure. After the pressure inside the reactor is released to atmospheric pressure, the temperature inside the reactor is controlled at 245℃ and reacted at a constant temperature for 18 minutes. Then, a vacuum reaction is carried out for 19 minutes with a vacuum degree of -0.06MPa. Finally, nitrogen gas is introduced into the reactor and pressurized to 1.5MPa before the material is discharged, thus obtaining a high-barrier, low-water-absorption semi-aromatic long-chain MXD15 nylon material.

[0049] The obtained MXD15 nylon material has a number-average molecular weight Mn=28000 and a molecular weight distribution index PDI=2.1.

[0050] The obtained MXD15 nylon material was injection molded at an injection temperature of 220-235℃ to obtain test specimens.

[0051] Example 4 Take 33 parts of m-phenylenediamine, 67 parts of hexadecanoic acid (molar ratio 1.05:1.0), 0.09 parts of nucleating agent silica, 0.04 parts of catalyst calcium hypophosphite, and 0.04 parts of antioxidant (1098 / 626). Grind them in a mortar to ensure thorough mixing. Then add them to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 150 parts of solvent deionized water into the reactor. Seal the high-pressure polymerization reactor, start stirring at a speed of 270 r / min, and replace the air in the reactor with high-purity nitrogen four times. Finally, reserve 0.3 MPa of nitrogen as a protective gas. The reactor was heated at a rate of 6℃ / min, and the pressure inside the reactor increased accordingly. When the pressure reached 2.7MPa, the water in the system was released to bring the reactor to a constant pressure. When the temperature reached 205℃, the reactor was kept at a constant temperature and pressure for 2.0h. Then, when the temperature inside the reactor reached 250℃, the reactor was slowly depressurized for 1.5h until it reached atmospheric pressure. After the pressure inside the reactor is released to atmospheric pressure, the temperature inside the reactor is controlled at 248℃ and reacted at a constant temperature for 25 minutes. Then, a vacuum reaction is carried out for 25 minutes with a vacuum degree of -0.05MPa. Finally, nitrogen gas is introduced into the reactor and pressurized to 1.7MPa before the material is discharged, thus obtaining a high-barrier, low-water-absorption semi-aromatic long-chain MXD16 nylon material.

[0052] The obtained MXD16 nylon material has a number-average molecular weight Mn=26000 and a molecular weight distribution index PDI=2.1.

[0053] The obtained MXD16 nylon material was injection molded at an injection temperature of 215-230℃ to obtain test specimens.

[0054] Example 5 Take 31 parts of m-phenylenediamine, 69 parts of octadecanoic acid (molar ratio 1.05:1.0), 0.07 parts of barium sulfate (nucleating agent), 0.04 parts of zinc hypophosphite (catalyst), and 0.04 parts of antioxidant (1076 / 168). Grind them in a mortar to ensure thorough mixing. Then add them to a high-pressure polymerization reactor equipped with a high-efficiency stirring device. Weigh 150 parts of deionized water (solvent) into the reactor. Seal the high-pressure polymerization reactor, start stirring at a speed of 200 r / min, and replace the air in the reactor with high-purity helium four times. Finally, reserve 0.2 MPa of nitrogen as a protective gas. The reactor is heated at a rate of 5℃ / min, and the pressure inside the reactor increases accordingly. When the pressure reaches 2.0MPa, the water in the system is released to bring the reactor to a constant pressure. When the temperature reaches 200℃, the reactor is kept at a constant temperature and pressure for 3 hours. Then, when the temperature inside the reactor reaches 250℃, the reactor is slowly depressurized for 1 hour until it reaches atmospheric pressure. After the pressure inside the reactor is released to atmospheric pressure, the temperature inside the reactor is controlled at 240℃ and reacted at a constant temperature for 15 minutes. Then, a vacuum reaction is carried out for 15 minutes with a vacuum degree of -0.04MPa. Finally, nitrogen gas is introduced into the reactor and pressurized to 0.5MPa before the material is discharged, thus obtaining a high-barrier, low-water-absorption semi-aromatic long-chain MXD18 nylon material.

[0055] The obtained MXD18 nylon material has a number-average molecular weight Mn=25000 and a molecular weight distribution index PDI=2.2.

[0056] The obtained MXD18 nylon material was injection molded at an injection temperature of 210-230℃ to obtain test specimens.

[0057] MXD6 material was injection molded at a temperature of 245-260℃ to obtain test specimens. The measured properties are used as Comparative Example 1.

[0058] PA6T high-temperature nylon material was injection molded at a temperature of 310-330℃ to obtain test specimens. The measured properties are used as comparative example 2.

[0059] The performance test results of Examples 1-5 and Comparative Examples 1-2 are shown in Table 2.

[0060] Table 2: Performance Test Data of Long-Chain MXD Nylon and Comparative Materials

[0061] The performance test results of each embodiment and comparative example show that the MXD nylon material obtained by the present invention has a more flexible molecular chain due to the introduction of long-chain monomers. The elongation and impact strength data show that the synthesized material has better toughness. While taking into account the high barrier performance, the toughness of the material is greatly improved, which solves the limitation of MXD6 being brittle.

[0062] This invention introduces C 10 -C 18 Long-chain dicarboxylic acids, by adjusting n=8-16, achieve an ultra-low water absorption rate of ≤0.5% and significantly reduce polarity, thus improving dimensional stability; the synergistic formulation of low-dose sodium hypophosphite (0.03-0.05%) and barium sulfate (0.05-0.1%) balances high barrier properties (OTR≤12) and flexibility (elongation 16-40%), overcoming the technical barrier of MXD6 brittleness; vacuum dehydration and solid-phase polymerization (SSP) post-treatment improve Mw and crystallinity without increasing production temperature, ensuring that barrier properties remain excellent in thick plates or injection molded parts.

[0063] Meanwhile, the water absorption data shows that the MXD nylon material synthesized by this invention has a significantly lower water absorption rate compared to MXD6 and PA6T. This results in higher performance retention and better dimensional stability in environmental applications. It successfully overcomes the weaknesses of MXD6 and PA6T, which suffer from high water absorption and poor dimensional stability.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A long-chain semi-aromatic MXD nylon material, characterized in that, Made from components comprising the following weight percentages: m-Phenylenediamine 31%-41%; Long-chain dicarboxylic acids: 59%-69%; Nucleating agent 0.05%-0.1%; Catalyst 0.03%-0.05%; Antioxidant 0.03%-0.05%; Solvent 100%-200%; The long-chain dicarboxylic acid is selected from at least one of sebacic acid, tridecanoic acid, pentadecanoic acid, hexadecanoic acid, and octadecanoic acid.

2. The long-chain semi-aromatic MXD nylon material according to claim 1, characterized in that, The purity of the m-phenylenediamine is ≥99.9%, the moisture content is ≤0.05%, and the color is ≤10.

3. The long-chain semi-aromatic MXD nylon material according to claim 1, characterized in that, The nucleating agent is selected from at least one of barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate, and the particle size D50 of the nucleating agent is ≤1μm, and the specific surface area is ≥20m². 2 / g.

4. The long-chain semi-aromatic MXD nylon material according to claim 1, characterized in that, The catalyst is selected from at least one of sodium hypophosphite, potassium hypophosphite, sodium phosphite, magnesium hypophosphite, calcium hypophosphite, and zinc hypophosphite.

5. The long-chain semi-aromatic MXD nylon material according to claim 1, characterized in that, The antioxidant is obtained by compounding hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1, and the particle size of the antioxidant is ≤200 mesh.

6. A method for preparing a long-chain semi-aromatic MXD nylon material, characterized in that, Includes the following steps: (1) Weigh out m-phenylenediamine, long-chain dicarboxylic acid, nucleating agent, catalyst and antioxidant according to the ratio, mix them evenly and add them to the high-pressure polymerization reactor, add solvent, seal the reactor, start stirring, replace the air in the reactor with inert gas, and reserve protective gas pressure. (2) Heat the reactor at a rate of 5℃ / min-10℃ / min. When the pressure inside the reactor reaches 2.0MPa-3.0MPa, maintain constant pressure by draining water. After heating to 200℃-250℃, react at constant temperature and pressure for 1h-3h. Continue heating to 250℃-270℃ and slowly depressurize to atmospheric pressure. (3) After depressurization, the temperature inside the reactor is controlled at 240℃-270℃ for 10min-30min, and the reactor is vacuumed for 15min-30min. Inert gas is introduced and the material is discharged under pressure. MXD nylon material is obtained by underwater pelletizing.

7. The preparation method according to claim 6, characterized in that, In step (1), the molar ratio of m-phenylenediamine to long-chain dicarboxylic acid is 1.05:1.0, the mixing method is grinding and mixing, the grinding time is 10min-15min, and the mixed material is passed through a 200-mesh standard sieve with a residue of ≤0.1% on the sieve.

8. The preparation method according to claim 6, characterized in that, In step (1), the inert gas replaces the air in the reactor 3-5 times, and the oxygen content in the reactor after replacement is ≤0.01%. The reserved protective gas pressure is 0.1MPa-0.3MPa, and the stirring speed is 200r / min-400r / min.

9. The preparation method according to claim 6, characterized in that, In step (2), the depressurization rate is controlled at 0.05MPa / min-0.1MPa / min, and the depressurization time is 1h-1.5h.

10. The preparation method according to claim 6, characterized in that, In step (3), vacuuming is carried out in a stepped manner. First, the vacuum level is reduced to -0.04MPa and held for 5 minutes, and then the target vacuum level is reduced to -0.04MPa to -0.08MPa. The discharge pressure is 0.5MPa-2MPa, the discharge port temperature is 230℃-260℃, and the water temperature for underwater pelleting is 30℃-50℃.

Images