Preparation method of high-temperature-resistant and low-hygroscopic copolymer nylon

Abstract

This invention relates to the field of functional nylon material research and development technology, and discloses a method for preparing high-temperature resistant and low-hygroscopic copolymer nylon. Specifically, the method involves: synthesizing a fluorinated hydrophobic silane crosslinking agent; using the fluorinated hydrophobic silane crosslinking agent and silane coupling agent KH-560 to perform surface modification treatment on montmorillonite nanosheets to obtain epoxy-functionalized hydrophobic modified montmorillonite; under melt shearing, the epoxy groups in the epoxy-functionalized hydrophobic modified montmorillonite undergo a ring-opening grafting reaction with the amino groups at the ends of the nylon 6 / 66 copolymer resin molecular chains to achieve a chemically bonded composite between the hydrophobic modified montmorillonite and the nylon 6 / 66 copolymer resin matrix, thus obtaining a high-temperature resistant and low-hygroscopic copolymer nylon. This copolymer nylon product has a water absorption rate of less than 1.0% and a heat distortion temperature greater than 110℃ after immersion in water at 23℃ for 24 hours, making it suitable for applications with stringent requirements for dimensional accuracy and performance stability, such as precision electronic appliances and high-precision transmission components.

Description

Technical Field

[0001] This invention relates to the field of functional nylon material research and development technology, specifically a method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon. Background Technology

[0002] Polyamide (commonly known as nylon) is a class of engineering plastics whose molecular backbone contains repeating amide groups (-CONH-). Nylon 6 (PA6, polycaprolactam) and Nylon 66 (PA66, polyhexamethylene adipamide) are the two most widely used aliphatic polyamides. PA6 has excellent toughness and processing fluidity, while PA66 exhibits a higher melting point and rigidity.

[0003] Nylon 6 / 66 copolymer is a nylon material produced by copolymerization of caprolactam and nylon 66 salt under specific conditions. The copolymerization structure disrupts the regular arrangement of the molecular chains, reducing the crystallinity and slowing the crystallization rate. This gives nylon 6 / 66 copolymer a wider processing window and better flexibility than homopolymers. Furthermore, by adjusting the ratio of the two components, the melting point and crystallization behavior of the copolymer can be controlled. It is widely used in the automotive industry, electronics, mechanical transmission, and transportation sectors.

[0004] Traditional nylon materials exhibit significant hygroscopicity due to the high density of amide groups in their molecular chains, which facilitates strong hydrogen bonding between the chains. For example, nylon 6 has an equilibrium water absorption rate of approximately 2.5-3.0% at 23°C and 50% relative humidity, with a saturated water absorption rate reaching 9-11%; nylon 66 has an equilibrium water absorption rate of approximately 2.0-2.8%, with a saturated water absorption rate reaching 8-10%. Nylon 6 / 66 copolymers, due to the disruption of molecular chain regularity in their copolymer structure, exhibit a significantly increased proportion of amorphous regions, allowing water molecules to penetrate more easily into the material's interior, making them more prone to hygroscopicity compared to homopolymers.

[0005] In humid environments, water molecules that penetrate the material can form hydrogen bonds with the NH and C=O groups of the amide groups in the nylon molecular chain, acting as a plasticizer. This increases the inter-chain spacing, leading to problems such as decreased mechanical properties, deteriorated dimensional stability, and reduced glass transition temperature. This severely limits its application in fields with stringent requirements for dimensional accuracy and performance stability, such as precision electronics and high-precision transmission components.

[0006] Studies have found that montmorillonite possesses a unique two-dimensional layered structure, which can reduce the moisture absorption rate of materials to some extent by extending the diffusion path of water molecules within the material (i.e., the labyrinth effect). However, conventional montmorillonite is a hydrophilic inorganic filler with poor interfacial compatibility with organic nylon matrices. Direct blending can lead to uneven dispersion and agglomeration of the filler, which not only fails to effectively block water molecule diffusion but may also become stress concentration points, resulting in a decline in the mechanical properties of the material.

[0007] In addition, introducing montmorillonite into nylon materials can improve their heat resistance. The nano-size effect and high specific surface area of ​​montmorillonite sheets can form a heat insulation barrier in the nylon matrix, which can delay heat transfer by physically blocking and restrict the thermal movement of polymer molecular chains, thereby improving the heat distortion temperature and thermal stability of the material. Summary of the Invention

[0008] To address the shortcomings of nylon 6 / 66 copolymers, such as high hygroscopicity, deterioration of mechanical properties and dimensional stability under humid conditions, this invention provides a method for preparing high-temperature resistant, low-hygroscopic copolymer nylon based on a technical strategy combining molecular structure design and interface regulation.

[0009] A method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon includes the following steps: Step 1: Synthesize a fluorinated hydrophobic silane crosslinking agent; Step 2: Surface modification of montmorillonite nanosheets was carried out using a fluorinated hydrophobic silane crosslinking agent and a silane coupling agent KH-560 to obtain epoxy-functionalized hydrophobic modified montmorillonite. Step 3: Under melt shearing, the epoxy groups in the epoxy-functionalized hydrophobically modified montmorillonite undergo a ring-opening grafting reaction with the amino groups at the ends of the nylon 6 / 66 copolymer resin molecular chains, thereby achieving a chemically bonded composite between the hydrophobically modified montmorillonite and the nylon 6 / 66 copolymer resin matrix, and obtaining a high-temperature resistant and low-hygroscopic copolymer nylon.

[0010] Preferably, the formulation of the high-temperature resistant and low-hygroscopic copolymer nylon is: 90-95wt% nylon 6 / 66 copolymer resin and 5-10wt% epoxy-functionalized hydrophobic modified montmorillonite.

[0011] Preferably, the preparation method of the fluorinated hydrophobic silane crosslinking agent is as follows: Using 1 molar equivalent of isophorone diisocyanate and 0.97-0.99 molar equivalents of perfluoroalkyl ethanol compound as raw materials, and DBTDL as catalyst, an addition reaction is carried out in anhydrous DMF solvent at 20℃-40℃, via the more reactive secondary alicyclic isocyanate group in isophorone diisocyanate and the hydroxyl group in perfluoroalkyl ethanol to generate an isocyanate intermediate; wherein, the perfluoroalkyl ethanol compound is one of 3,3,3-trifluoropropanol, pentafluoro-n-butanol, 3,3,4,4,5,5,5-heptafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-hexanol, 1H,1H,2H,2H-perfluoro-1-heptanol, and 1H,1H,2H,2H-perfluoro-1-octanol; Using 1 molar equivalent of 4-hydroxybenzylamine and 2.01-2.03 molar equivalents of 3-(acryloyloxy)propyltrimethoxysilane as raw materials, an addition reaction is carried out in anhydrous DMF solvent at 30℃-50℃, through which the amino group in 4-hydroxybenzylamine and the acryloyloxy group in 3-(acryloyloxy)propyltrimethoxysilane undergo an addition reaction to generate a phenolic bis(trimethoxysilane) intermediate. Using 1 molar equivalent of isocyanate-based intermediate and 1.01-1.03 molar equivalent of phenol-based bis(trimethoxysilane) intermediate as raw materials, and DBTDL as catalyst, a fluorinated hydrophobic silane crosslinking agent is generated by an addition reaction between the primary isocyanate group in the isocyanate-based intermediate and the phenolic hydroxyl group in the phenol-based bis(trimethoxysilane) intermediate in anhydrous DMF solvent at 50-70°C.

[0012] Preferably, the preparation method of the epoxy-functionalized hydrophobic modified montmorillonite is as follows: after hydrolyzing a fluorinated hydrophobic silane crosslinking agent and a silane coupling agent KH-560 into silanols in an aqueous organic solvent, the silanols are then subjected to a dehydration condensation reaction with montmorillonite nanosheets dispersed in an anhydrous organic solvent in the presence of an acidic catalyst, thereby grafting epoxy groups and fluorinated hydrophobic segments onto the surface of montmorillonite to obtain epoxy-functionalized hydrophobic modified montmorillonite.

[0013] Preferably, the mass ratio of the fluorinated hydrophobic silane crosslinking agent, the silane coupling agent KH-560, and the montmorillonite nanosheets in the epoxy functionalized hydrophobic modified montmorillonite is (1-3):(0.3-0.8):10.

[0014] Preferably, the montmorillonite nanosheets have a diameter of 2-5 μm and a thickness of 4-8 nm.

[0015] A high-temperature resistant and low-hygroscopic copolymer nylon was prepared according to the above method. The high-temperature resistant and low-hygroscopic copolymer nylon is composed of nylon 6 / 66 copolymer resin and epoxy functionalized hydrophobic modified montmorillonite. After soaking in water at 23°C for 24 hours, the water absorption rate is less than 1.0% and the heat distortion temperature is greater than 110°C.

[0016] Preferably, the high-temperature resistant, low-moisture-absorbing copolymer nylon is used to manufacture precision electronic and electrical components and / or high-precision transmission components.

[0017] Beneficial effects: This invention first designs and synthesizes fluorinated hydrophobic silane crosslinking agents (fluorinated hydrophobic silane crosslinking agents A-Ⅰ and A-Ⅱ), and then combines them with silane coupling agent KH-560 to perform surface modification treatment on montmorillonite. On the one hand, it stabilizes the grafting of fluorinated hydrophobic segments on the surface of montmorillonite, fundamentally improving the hydrophilic properties of montmorillonite, solving the problem of filler agglomeration, and endowing it with excellent hydrophobic and moisture-resistant properties. On the other hand, it introduces active epoxy reaction sites on the surface of montmorillonite, providing a basis for subsequent reactive composites with nylon matrix. By controlling the length of the fluorinated hydrophobic segments, the material properties can be optimized in a targeted manner. The only difference between the fluorinated hydrophobic silane crosslinking agents A-I and A-II is the length of the terminal fluorinated segments. The shorter fluorinated chain (A-I) has less steric hindrance, which is beneficial for the uniform dispersion of montmorillonite in the nylon matrix and the improvement of interfacial chemical bonding density, thus achieving a better mechanical reinforcement effect. The longer fluorinated chain (A-II) has a longer fluorinated carbon segment and lower surface energy, resulting in a more significant hydrophobic shielding effect and better low moisture absorption properties. By applying A-I and A-II respectively, targeted selection can be made according to the different requirements of mechanical and hydrophobic properties in actual application scenarios. Nylon 6 / 66 copolymer was premixed with modified montmorillonite with fluorinated hydrophobic segments and epoxy active sites on its surface, and then melt-composite through a twin-screw extruder to build a high-strength organic-inorganic interface bond through epoxy-terminated amino ring-opening reaction. This invention achieves synergistic effects through multiple modification mechanisms: fluorinated hydrophobic segments impart strong hydrophobicity to the micro-regions of the material, inhibiting the adsorption and penetration of water molecules; the two-dimensional layered structure of montmorillonite blocks the transfer of water molecules and heat; and the covalently bonded interface effectively eliminates interfacial voids between the matrix and the filler, avoiding interfacial water absorption defects, while achieving efficient stress transfer. The resulting copolymer nylon material significantly improves hygroscopicity while simultaneously enhancing mechanical and heat resistance properties. Compared to conventional nylon 6 / 66 copolymer resin, the copolymer nylon product prepared by this invention exhibits increased tensile strength by 10.8-12.6%, increased flexural strength by 8.1-9.0%, increased heat distortion temperature by 25.2-28.7℃ (reaching 114.6-118.1℃), increased water contact angle from 72.4° to 103.7-110.2°, and decreased moisture absorption rate from 4.0% to 0.5-0.9%. Detailed Implementation

[0018] Experimental example: The synthesis of a fluorinated hydrophobic silane crosslinking agent includes the following steps: Step 1: Using 1 molar equivalent of isophorone diisocyanate (CAS No. 4098-71-9) containing a hydrophobic alicyclic structure and 0.98 molar equivalent of perfluoroalkyl ethanol compound as raw materials, and DBTDL as catalyst, an addition reaction is carried out in anhydrous DMF solvent at 20℃-40℃, through the reaction of the more reactive secondary alicyclic isocyanate group in isophorone diisocyanate with the hydroxyl group in perfluoroalkyl ethanol, to generate an isocyanate intermediate with the following chemical structure: ; The perfluoroalkyl ethanol compounds may be made from the following raw materials: Perfluoromethylethanol (n=0,3,3,3-trifluoropropanol, CAS No. 2240-88-2): ; Perfluoroethyl ethanol (n=1, pentafluorobutanol, CAS number 54949-74-5): ; Perfluoropropyl ethanol (n=2,3,3,4,4,5,5,5-heptafluoro-1-pentanol, CAS No. 755-40-8): ; Perfluorobutylethanol (n=3, 1H,1H,2H,2H-perfluoro-1-hexanol, CAS No. 2043-47-2): ; Perfluoropentylethanol (n=4, 1H,1H,2H,2H-perfluoro-1-heptanol, CAS No. 185689-57-0): ; Perfluorohexylethanol (n=5, 1H,1H,2H,2H-perfluoro-1-octanol, CAS No. 647-42-7): ; Step 2: Using 1 molar equivalent of 4-hydroxybenzylamine (CAS No. 696-60-6) and 2.01 molar equivalents of 3-(acryloyloxy)propyltrimethoxysilane (CAS No. 4369-14-6) as raw materials, an addition reaction is carried out in anhydrous DMF solvent at 30℃-50℃ between the amino group in 4-hydroxybenzylamine and the acryloyloxy group in 3-(acryloyloxy)propyltrimethoxysilane to generate a phenolic bis(trimethoxysilane) intermediate, the chemical structural formula of which is: ; Step 3: Using 1 molar equivalent of isocyanate-based intermediate and 1.01 molar equivalent of phenol-based bis(trimethoxysilane) intermediate as raw materials, and DBTDL as catalyst, an addition reaction is carried out in anhydrous DMF solvent at 50-70°C between the primary isocyanate group in the isocyanate-based intermediate and the phenolic hydroxyl group in the phenol-based bis(trimethoxysilane) intermediate to generate a fluorinated hydrophobic silane crosslinking agent. Its chemical structural formula is as follows: ; This invention selects representative perfluoromethylethanol (n=0,3,3,3-trifluoropropanol) and perfluorohexylethanol (n=5,1H,1H,2H,2H-perfluoro-1-octanol) for research and development experiments: Research Experiment 1: Using a method for synthesizing fluorinated hydrophobic silane crosslinking agents, when perfluoromethyl ethanol is used in a perfluoroalkyl ethanol compound, a fluorinated hydrophobic silane crosslinking agent A-Ⅰ is synthesized, with the following chemical structural formula: ; The specific preparation steps of fluorinated hydrophobic silane crosslinking agent A-I are as follows: Under nitrogen protection, 2.2 g of isophorone diisocyanate, 1.1 g of 3,3,3-trifluoropropanol and 30 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature (25 °C) for 10 min. Then, 10 μL of LBTDL catalyst was added dropwise to the three-necked flask, the temperature was raised to 30 °C and stirred for 6 h. After cooling to room temperature, the solvent was removed by rotary evaporation under reduced pressure and dried under vacuum to obtain isocyanate-based intermediate I. Under nitrogen protection, 1.2 g of 4-hydroxybenzylamine and 20 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature (25 °C) for 10 min to dissolve. Then, 30 mL of anhydrous N,N-dimethylformamide solution containing 4.7 g of 3-(acryloyloxy)propyltrimethoxysilane was added dropwise to the three-necked flask. The mixture was heated to 40 °C and stirred for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation under reduced pressure and dried under vacuum to obtain phenolic bis(trimethoxysilane) intermediate. Under nitrogen protection, 1.7 g of isocyanate intermediate I, 3.0 g of phenolic bis(trimethoxysilane) intermediate and 50 mL of anhydrous N,N-dimethylformamide were added to a three-necked flask and stirred at room temperature (25 °C) for 10 min. Then, 20 μL of LBTDL catalyst was added dropwise to the three-necked flask, the temperature was raised to 60 °C and stirred for 5 h, the mixture was cooled to room temperature, the solvent was removed by rotary evaporation under reduced pressure, and the mixture was dried under vacuum to obtain fluorinated hydrophobic silane crosslinking agent A-I. Fluorohydrophobic silane crosslinking agent A-I is characterized as follows: 1H NMR (DMSO-d6, 400MHz) δ: 0.94(s, 3H), 0.99(s, 3H), 1.11(s, 3H), 1.61(s, 2H), 1.67-1.72(t, 4H) , 1.90-1.93(m, 4H), 2.33-2.41(m, 4H), 2.74-2.80(m, 6H), 3.20-3.33(m, 6H), 3.56(s, 18H), 3.66(s, 2H), 3.82-3.91(m, 1H), 4.09-4.17(m, 6H), 6. 60-6.62(d, 1H), 6.79-6.82(t, 1H), 7.07-7.09(d, 2H), 7.28-7.30(d, 2H); The elemental analysis results obtained by Vario EL Ⅲ elemental analyzer are as follows: experimental values ​​(theoretical values, %): C 51.71 (51.76), H 7.29 (7.38), N 4.50 (4.53); The actual and theoretical values ​​of C, H, and N in the elemental analysis results are within the error range. Combined with the proton NMR results, it is proven that the chemical structure of the fluorinated hydrophobic silane crosslinking agent A-I is consistent with the expectation.

[0019] Research Experiment 2: Using a method for synthesizing fluorinated hydrophobic silane crosslinking agents, when perfluoroalkyl ethanol compounds are used with perfluorohexyl ethanol, fluorinated hydrophobic silane crosslinking agent A-II is synthesized, with the following chemical structural formula: ; The specific preparation steps for fluorinated hydrophobic silane crosslinking agent A-II are as follows: The specific experimental steps for preparing isocyanate-based intermediate II differ from those for isocyanate-based intermediate I in Research and Development Experiment 1 only in that 3.6 g of 1H,1H,2H,2H-perfluoro-1-octanol is used instead of 1.1 g of 3,3,3-trifluoropropanol. The specific experimental steps for preparing the phenol-based bis(trimethoxysilane) intermediate are the same as those for the phenol-based bis(trimethoxysilane) intermediate in Experiment 1 of the research and development program. The specific experimental steps for preparing fluorinated hydrophobic silane crosslinking agent A-II differ from those for fluorinated hydrophobic silane crosslinking agent A-I in Experiment 1 only in that 2.9g of isocyanate-based intermediate II is used to replace 1.7g of isocyanate-based intermediate I. Fluorohydrophobic silane crosslinking agent A-II is characterized as follows: 1H NMR (DMSO-d6, 400MHz) δ: 0.95 (s, 3H), 0.99 (s, 3H), 1.10 (s, 3H), 1.67-1.72 (t, 6H), 1.89-1. 93(m, 4H), 2.33-2.41(m, 4H), 2.75-2.80(m, 6H), 3.21-3.34(m, 6H), 3. 56(s, 18H), 3.64(s, 2H), 3.81-3.90(m, 1H), 4.10-4.17(m, 6H), 6.60- 6.62(d, 1H), 6.81-6.84(t, 1H), 7.08-7.10(d, 2H), 7.28-7.29(d, 2H); The elemental analysis results obtained by Vario EL Ⅲ elemental analyzer are as follows: experimental values ​​(theoretical values, %): C 45.82 (45.87), H 5.79 (5.82), N 3.55 (3.57); The actual and theoretical values ​​of C, H and N in the elemental analysis results are within the error range. Combined with the proton NMR results, it is proven that the chemical structure of the fluorinated hydrophobic silane crosslinking agent A-II is consistent with the expectation.

[0020] Example 1: Preparation of epoxy-functionalized hydrophobic modified montmorillonite I: Montmorillonite nanosheets were surface-modified using a fluorinated hydrophobic silane crosslinking agent A-I and a silane coupling agent KH-560 (3-glycidyloxypropyltrimethoxysilane). The fluorinated hydrophobic silane crosslinking agent A-I and the silane coupling agent KH-560 were hydrolyzed into silanol groups in an aqueous organic solvent. These silanol groups then underwent a dehydration condensation reaction with montmorillonite nanosheets dispersed in an anhydrous organic solvent in the presence of an acidic catalyst. This process grafted epoxy groups and fluorinated hydrophobic segments onto the montmorillonite surface, yielding epoxy-functionalized hydrophobic modified montmorillonite I. The specific experimental steps for preparing epoxy-functionalized hydrophobically modified montmorillonite I are as follows: Dissolve 2g of fluorinated hydrophobic silane crosslinking agent A-Ⅰ and 0.5g of silane coupling agent KH-560 in 50mL of anhydrous methanol, add 5mL of deionized water, adjust the pH of the system to 5.5 using glacial acetic acid, and stir the reaction at room temperature for 3h to form a mixed hydrolysis solution of fluorinated hydrophobic silane crosslinking agent A-Ⅰ and silane coupling agent KH-560. 10g of sodium-based montmorillonite powder (particle size 2-5μm, thickness 4-8nm) was ultrasonically dispersed in 100mL of anhydrous methanol and stirred for 30min. Then, the above mixed hydrolysis solution was slowly added dropwise, the temperature was raised to 60℃ and stirred for 12h, centrifuged at 10000rpm for 10min, and washed twice with anhydrous methanol, once with deionized water, and once with anhydrous methanol. The mixture was then vacuum dried to obtain epoxy-functionalized hydrophobic modified montmorillonite I.

[0021] Example 2: Epoxy-functionalized hydrophobic modified montmorillonite II was prepared. The only difference between it and epoxy-functionalized hydrophobic modified montmorillonite I is that fluorinated hydrophobic silane crosslinking agent A-I is replaced by fluorinated hydrophobic silane crosslinking agent A-II.

[0022] Example 3: A high-temperature resistant, low-hygroscopic copolymer nylon was prepared using the following formulation: 94 wt% nylon 6 / 66 copolymer resin (model B230) and 6 wt% epoxy-functionalized hydrophobic modified montmorillonite. The preparation method involved a ring-opening grafting reaction between the epoxy groups in the epoxy-functionalized hydrophobic modified montmorillonite and the amino groups at the ends of the nylon 6 / 66 copolymer resin molecular chains under melt shear, achieving a chemically bonded composite between the hydrophobic modified montmorillonite and the nylon 6 / 66 copolymer resin matrix. The preparation steps are as follows: Step 1: Place the nylon 6 / 66 copolymer resin in a vacuum oven at 90℃ and dry for 12 hours to reduce the moisture content to below 0.1% to obtain the pretreated nylon 6 / 66 copolymer resin. Step 2: According to the formula of high temperature resistant and low moisture absorption copolymer nylon, add the pretreated nylon 6 / 66 copolymer resin and epoxy functionalized hydrophobic modified montmorillonite into a high-speed mixer, mix evenly under nitrogen atmosphere, mix speed 1500 r / min, mix time 5 min, and obtain premix. Step 3: The premixed material is added to the co-rotating parallel twin-screw extruder through the hopper for reactive melt blending and extrusion. After the extruded material is cooled, it is granulated by a pelletizer and vacuum dried to obtain high-temperature resistant and low-hygroscopic copolymer nylon. The process parameters for the twin-screw extruder are set as follows: preheating temperature 220℃, temperatures of zones 1-7 are 220℃, 230℃, 245℃, 255℃, 255℃, and 250℃ respectively, and rotation speed is 350r / min. Among them, when epoxy-functionalized hydrophobic modified montmorillonite I and epoxy-functionalized hydrophobic modified montmorillonite II are used respectively, high-temperature resistant and low-hygroscopic copolymer nylon I and high-temperature resistant and low-hygroscopic copolymer nylon II are prepared sequentially.

[0023] Comparative example: A montmorillonite-blended copolymer nylon was prepared with the following formulation: 94 wt% nylon 6 / 66 copolymer resin (model B230) and 6 wt% sodium-based montmorillonite powder. The preparation steps are as follows: Step 1: Place the nylon 6 / 66 copolymer resin in a vacuum oven at 90℃ and dry for 12 hours to reduce the moisture content to below 0.1% to obtain the pretreated nylon 6 / 66 copolymer resin. Step 2: According to the formula of high temperature resistant and low moisture absorption copolymer nylon, add the pretreated nylon 6 / 66 copolymer resin and sodium montmorillonite powder into a high-speed mixer, mix evenly under nitrogen atmosphere, mix speed 1500 r / min, mix time 5 min, and obtain premix; Step 3: The premixed material is fed into a co-rotating parallel twin-screw extruder through a hopper for physical melt blending and extrusion. After the extruded material is cooled, it is granulated by a pelletizer and vacuum dried to obtain montmorillonite blended copolymer nylon. The process parameters of the twin-screw extruder are set as follows: preheating temperature 220℃, temperatures of zones 1-7 are 220℃, 230℃, 245℃, 255℃, 255℃, and 250℃ respectively, and rotation speed is 350r / min.

[0024] Performance testing: The copolymer nylon sample and conventional nylon 6 / 66 copolymer resin (model B230) were placed in a vacuum oven at 90℃ and dried for 12 hours. The sample was then molded into test strips using an injection molding machine. The process parameters for the injection molding machine are set as follows: barrel temperature 250℃, nozzle temperature 255℃, mold temperature 80℃, injection pressure 60MPa, holding pressure 20MPa, plasticizing pressure 8MPa, screw speed 150r / min, injection time 5s, holding time 18s, and cooling time 25s. (1) Mechanical property testing: Tensile strength tests were conducted according to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics". Type 1B specimens (total length ≥ 150 mm, width of narrow parallel section 10 mm, gauge length 50 mm, thickness 4 mm) were used, and the test speed was 50 mm / min. The bending strength test was conducted according to GB / T 9341-2008 "Determination of bending properties of plastics". The sample size was 80mm×10mm×4mm (length×width×thickness), the standard span was 64mm (span-to-thickness ratio 16:1), and the test speed was 2mm / min. (2) Contact angle test: The water contact angle of the sample is tested by the droplet method using a contact angle measuring instrument; (3) Moisture absorption rate test: According to GB / T 1034-2008 "Determination of water absorption of plastics", the 60mm×60mm×2mm (length×width×thickness) sample was dried in an oven at 50℃ to constant weight. After being taken out and cooled to room temperature, it was weighed and recorded as the initial weight m0. Then, the dried sample was completely immersed in distilled water at 23℃ for 24 hours. It was then taken out with tweezers and the moisture on the surface of the sample was wiped dry with a clean dry cloth. The sample was weighed and recorded as the weight after moisture absorption m1. The moisture absorption rate of the sample was calculated. The specific method is as follows: Moisture absorption rate (%) = (m1 - m0) / m0 × 100%; (4) High temperature resistance test: According to GB / T 1634.2-2019 "Determination of load deformation temperature of plastics - Part 2: Plastics and hard rubber", an 80mm×10mm×4mm (length×width×thickness) sample was placed on a support with a span of 64mm, a load of 1.80MPa was applied, and the temperature was increased at a rate of 120℃ / h. The initial temperature was 25℃, and the temperature at which the bending deflection of the sample reached 0.34mm was recorded as the heat distortion temperature. The performance test results are shown in Table 1 below.

[0025] Table 1. Experimental results of the properties of high-temperature resistant, low-hygroscopic copolymer nylon The following conclusions can be drawn from the performance test data in Table 1: Conclusion 1: The copolymer nylon product prepared by the present invention using epoxy-functionalized hydrophobic modified montmorillonite has achieved significant improvements in mechanical properties and high-temperature resistance compared to conventional nylon 6 / 66 copolymer resin, and its hygroscopicity has also been significantly improved. Conclusion 2: By chemically incorporating epoxy-functionalized hydrophobic modified montmorillonite into a nylon matrix, effective stress transfer is achieved through high-strength interfacial chemical bonding, significantly improving the mechanical properties of the composite material (tensile strength increased by 10.8-12.6% and flexural strength increased by 8.1-9.0% compared to conventional nylon 6 / 66 copolymer resin). Among them, the epoxy-functionalized hydrophobic modified montmorillonite II prepared by fluorinated hydrophobic silane crosslinking agent A-II (containing long fluorine chain) has a slightly lower reinforcing effect than the epoxy-functionalized hydrophobic modified montmorillonite I prepared by fluorinated hydrophobic silane crosslinking agent A-I (containing short fluorine chain). The possible reason is that the increase of fluorinated chain segments in fluorinated hydrophobic silane crosslinking agent A-II brings a greater steric hindrance effect. At the same time, the increased flexibility of long fluorine chain segments may weaken the interface rigidity to a certain extent, thus having a slight negative impact on the load transfer efficiency. Conclusion 3: The introduction of fluorinated hydrophobic segments endows the copolymer nylon material with excellent hydrophobic properties, significantly reducing the surface energy and moisture absorption rate of the material. Compared with conventional nylon 6 / 66 copolymer resin, the water contact angle is increased by 31.3-37.8° and the moisture absorption rate is reduced by 77.5-87.5%. Among them, the fluorinated hydrophobic silane crosslinking agent A-II has a longer fluorinated chain segment and a more significant hydrophobic shielding effect, resulting in high-temperature resistant and low-hygroscopic copolymer nylon II exhibiting better moisture resistance. Conclusion 4: The heat distortion temperature of the copolymer nylon product prepared by this invention is >110℃, exhibiting excellent high-temperature resistance.

Claims

1. A process for the production of a high temperature resistant, low moisture absorbing copolymer nylon, characterized by, Includes the following steps: Step 1: Synthesize a fluorinated hydrophobic silane crosslinking agent, the chemical structural formula of which is: ； Step 2: Surface modification of montmorillonite nanosheets was carried out using a fluorinated hydrophobic silane crosslinking agent and a silane coupling agent KH-560 to obtain epoxy-functionalized hydrophobic modified montmorillonite. Step 3: Under melt shearing, the epoxy groups in the epoxy-functionalized hydrophobically modified montmorillonite undergo a ring-opening grafting reaction with the amino groups at the ends of the nylon 6 / 66 copolymer resin molecular chains, thereby achieving a chemically bonded composite between the hydrophobically modified montmorillonite and the nylon 6 / 66 copolymer resin matrix, and obtaining a high-temperature resistant and low-hygroscopic copolymer nylon.

2. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 1, characterized in that, The formulation of the high-temperature resistant, low-hygroscopic copolymer nylon is: 90-95wt% nylon 6 / 66 copolymer resin and 5-10wt% epoxy-functionalized hydrophobic modified montmorillonite.

3. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 1, characterized in that, The preparation method of the fluorinated hydrophobic silane crosslinking agent is as follows: Using 1 molar equivalent of isophorone diisocyanate and 0.97-0.99 molar equivalents of perfluoroalkyl ethanol compound as raw materials, and DBTDL as catalyst, an addition reaction is carried out in anhydrous DMF solvent at 20℃-40℃, via the more reactive secondary alicyclic isocyanate group in isophorone diisocyanate and the hydroxyl group in perfluoroalkyl ethanol to generate an isocyanate intermediate; wherein, the perfluoroalkyl ethanol compound is one of 3,3,3-trifluoropropanol, pentafluoro-n-butanol, 3,3,4,4,5,5,5-heptafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-hexanol, 1H,1H,2H,2H-perfluoro-1-heptanol, and 1H,1H,2H,2H-perfluoro-1-octanol; Using 1 molar equivalent of 4-hydroxybenzylamine and 2.01-2.03 molar equivalents of 3-(acryloyloxy)propyltrimethoxysilane as raw materials, an addition reaction is carried out in anhydrous DMF solvent at 30℃-50℃, through which the amino group in 4-hydroxybenzylamine and the acryloyloxy group in 3-(acryloyloxy)propyltrimethoxysilane undergo an addition reaction to generate a phenolic bis(trimethoxysilane) intermediate. Using 1 molar equivalent of isocyanate-based intermediate and 1.01-1.03 molar equivalent of phenol-based bis(trimethoxysilane) intermediate as raw materials, and DBTDL as catalyst, a fluorinated hydrophobic silane crosslinking agent is generated by an addition reaction between the primary isocyanate group in the isocyanate-based intermediate and the phenolic hydroxyl group in the phenol-based bis(trimethoxysilane) intermediate in anhydrous DMF solvent at 50-70°C.

4. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 3, characterized in that, When the perfluoroalkyl ethanol compound is 3,3,3-trifluoropropanol, the chemical structural formula of the fluorinated hydrophobic silane crosslinking agent prepared is: 。 5. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 3, characterized in that, When the perfluoroalkyl ethanol compound is 1H,1H,2H,2H-perfluoro-1-octanol, the chemical structural formula of the fluorinated hydrophobic silane crosslinking agent prepared is as follows: 。 6. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 1, characterized in that, The preparation method of the epoxy-functionalized hydrophobic modified montmorillonite is as follows: after hydrolyzing a fluorinated hydrophobic silane crosslinking agent and a silane coupling agent KH-560 into silanols in an aqueous organic solvent, the silanols are then reacted with montmorillonite nanosheets dispersed in an anhydrous organic solvent under the presence of an acidic catalyst to undergo a dehydration condensation reaction, thereby grafting epoxy groups and fluorinated hydrophobic segments onto the surface of montmorillonite to obtain epoxy-functionalized hydrophobic modified montmorillonite.

7. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 6, characterized in that, The mass ratio of the fluorinated hydrophobic silane crosslinking agent, silane coupling agent KH-560, and montmorillonite nanosheets in the epoxy functionalized hydrophobic modified montmorillonite is (1-3):(0.3-0.8):

10.

8. The method for preparing a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 7, characterized in that, The montmorillonite nanosheets have a diameter of 2-5 μm and a thickness of 4-8 nm.

9. A high-temperature resistant, low-hygroscopic copolymer nylon prepared by the method according to any one of claims 1-8, characterized in that, The high-temperature resistant and low-hygroscopic copolymer nylon is composed of nylon 6 / 66 copolymer resin and epoxy-functionalized hydrophobic modified montmorillonite. After being soaked in water at 23°C for 24 hours, the water absorption rate is less than 1.0%, and the heat distortion temperature is greater than 110°C.

10. The application of a high-temperature resistant, low-hygroscopic copolymer nylon according to claim 9, characterized in that, The high-temperature resistant, low-hygroscopic copolymer nylon is used to manufacture precision electronic and electrical components and / or high-precision transmission components.

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