High-temperature-resistant nylon multilayer co-extrusion film and preparation method thereof
Patent Information
- Application Number
- CN202610995149.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-06
- Publication Date
- 2026-09-25
AI Technical Summary
[0008]本发明针对现有技术中传统尼龙真空袋膜耐高温性能不足、热氧老化稳定性差及吸湿率高的技术缺陷，提供一种兼具耐高温、优异耐热氧老化性能、低吸水率的尼龙多层共挤膜及其制备方法，通过功能单体的分子结构设计、反应性熔融共混原位接枝及多层共挤功能分层设置的协同策略，实现疏水抗氧组分与耐高温增强组分在聚酰胺基体中的化学键合锚固与纳米级分散
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Abstract
Description
Technical Field
[0001] This invention relates to the field of vacuum bag film technology for aerospace manufacturing, specifically to a high-temperature resistant nylon multilayer co-extruded film and its preparation method. Background Technology
[0002] Carbon fiber reinforced resin matrix composites (CFRPs) have become a core material for manufacturing the main load-bearing structures of aircraft (such as fuselages and wings) due to their high specific strength, high specific modulus, and excellent fatigue properties. Among them, autoclave molding is the mainstream method for achieving high-quality curing of high-performance carbon fiber prepreg components.
[0003] In the autoclave molding process, vacuum bag film is one of the key auxiliary materials. Its main function is to form a sealed vacuum system on the surface of the prepreg layer. By evacuating the vacuum, interlayer gas and volatiles are removed. Under the combined action of the pressure inside the autoclave (usually 0.5-0.8MPa) and the curing temperature (120-180℃ for epoxy system, 200-250℃ and above for bismaleimide BMI and polyimide PI system), the resin is ensured to fully wet the fibers and densify them, suppressing defects such as porosity and delamination, and finally obtaining high-quality parts with high fiber volume fraction and low porosity.
[0004] Currently, polyamide (also known as nylon, such as PA6 / PA66) has become the preferred material for vacuum bag films due to its low air permeability, high strength and toughness, excellent processing performance and cost advantages, and can meet the curing requirements of most epoxy resin systems below 180°C.
[0005] However, with the increasing demands for heat resistance in structural components of next-generation aircraft, and the trend towards higher temperatures (≥200℃) and longer curing cycles in autoclave curing processes, traditional nylon vacuum bag films have significant shortcomings. For example, conventional PA6 / PA66 nylon bag films exhibit significant degradation in mechanical properties under conditions above 180-190℃, in the presence of oxygen, and under pressure, resulting in softening, creep, and even rupture, making it difficult to meet the process requirements of high-temperature resin systems such as BMI.
[0006] Although polyimide (PI) bags and films can withstand temperatures above 400°C, their low elongation, narrow processing window, complex molding process, and extremely high cost make them unsuitable for large-scale, low-cost production in the civil aviation sector.
[0007] Studies have found that nylon materials are prone to thermal oxidative degradation in high-temperature, aerobic environments, manifesting as molecular chain breakage and a sharp decline in mechanical properties. This can easily cause the vacuum bag film to rupture or fail to seal during the curing cycle, leading to component scrapping and even posing safety risks to the autoclave. Furthermore, nylon molecular chains contain a large number of amide groups, which can form hydrogen bonds with water molecules, giving nylon strong hygroscopic properties. High moisture content causes the nylon vacuum bag film to vaporize during the autoclave heating stage. This not only disrupts vacuum stability but also affects the resin curing reaction, inducing porosity or resin-rich defects on the component surface, severely weakening the interlaminar shear strength and resistance to damp heat of the composite material. Summary of the Invention
[0008] This invention addresses the shortcomings of traditional nylon vacuum bag films in terms of insufficient high-temperature resistance, poor thermo-oxidative aging stability, and high moisture absorption. It provides a nylon multilayer co-extruded film with high-temperature resistance, excellent thermo-oxidative aging resistance, and low water absorption, as well as its preparation method. Through a synergistic strategy of functional monomer molecular structure design, reactive melt blending in-situ grafting, and multilayer co-extrusion functional layering, the chemical bonding and anchoring of hydrophobic antioxidant components and high-temperature resistant reinforcing components in the polyamide matrix and their nanoscale dispersion are achieved.
[0009] A high-temperature resistant nylon multilayer co-extruded film, wherein the high-temperature resistant nylon multilayer co-extruded film is a three-layer symmetrical co-extruded structure consisting of a low moisture absorption and antioxidant outer layer, a high-temperature resistant middle layer, and a low moisture absorption and antioxidant inner layer; The formulation of the low moisture absorption and antioxidant outer and inner layers is: 50-70wt% copolyamide 6 / 66 resin and 30-50wt% low moisture absorption and heat-resistant oxygen aging resistant PA masterbatch; The formulation of the high-temperature resistant intermediate layer is: 50-70wt% copolyamide 6 / 66 resin and 30-50wt% high-temperature resistant PA masterbatch; The low moisture absorption, heat resistance, and oxygen aging resistant PA masterbatch is prepared by reactive melt blending and extrusion of epoxy functionalized hindered phenolic hydrophobic modifier and copolymer polyamide 6 / 66 resin. The high-temperature resistant PA masterbatch is obtained by reactive melt blending and extrusion of epoxy functionalized montmorillonite filler and copolymer polyamide 6 / 66 resin; Both the epoxy-functionalized hindered phenolic hydrophobic modifier and the epoxy-functionalized montmorillonite filler are covalently bonded to the polyamide molecular chain through the ring-opening reaction of the epoxy group with the end group of the polyamide molecular chain. Preferably, the formulation of the low moisture absorption, heat resistance, and oxygen aging resistant PA masterbatch is: 85-95wt% copolyamide 6 / 66 resin and 5-15wt% epoxy functionalized hindered phenolic hydrophobic modifier. Preferably, the formulation of the high-temperature resistant PA masterbatch is: 85-95wt% copolymer polyamide 6 / 66 resin and 5-15wt% epoxy functionalized montmorillonite filler.
[0010] Preferably, the epoxy-functionalized montmorillonite filler is prepared by surface modification of 8-15 parts by weight of sodium-based montmorillonite with 0.5-1.5 parts by weight of silane coupling agent KH560.
[0011] Preferably, the sodium-based montmorillonite has a sheet diameter of 3-8 μm and a thickness of 5-15 nm.
[0012] Preferably, the mass ratio of the low moisture absorption and antioxidant outer layer, the high temperature resistant intermediate layer, and the low moisture absorption and antioxidant inner layer in the high temperature resistant nylon multilayer co-extruded film is (1.5-3):(4-7):(1.5-3).
[0013] Preferably, the thickness of the high-temperature resistant nylon multilayer co-extruded film is 50-100 μm.
[0014] A method for preparing a high-temperature resistant nylon multilayer co-extruded film includes the following steps: Step 1: Premix the copolymer polyamide 6 / 66 resin with epoxy functionalized hindered phenolic hydrophobic modifier, and then perform reactive melt blending extrusion at a temperature of 210-255℃ using a co-rotating twin-screw extruder. Granulate and dry to obtain a low moisture absorption, heat-resistant, and oxygen-aging resistant PA masterbatch. Step 2: Premix the copolymer polyamide 6 / 66 resin with epoxy-functionalized montmorillonite filler, and then perform reactive melt blending extrusion at a temperature of 230-295℃ using a co-rotating twin-screw extruder. Granulate and dry the mixture to obtain high-temperature resistant PA masterbatch. Step 3: Prepare the raw materials according to the formula of high temperature resistant nylon multilayer co-extruded film. Put the raw materials of each layer into the hoppers of the three screw extruders of the three-layer co-extruded film blow molding unit. The molten resin is combined at the die head through the distributor, extruded and blown by the die head, cooled and wound up to obtain high temperature resistant nylon multilayer co-extruded film.
[0015] Preferably, the process parameters of the screw extruder corresponding to the low moisture absorption and antioxidant outer layer and inner layer are set as follows: the temperatures of zones 1-3 are 205-215℃, 220-240℃, and 250-260℃, respectively, and the rotation speed is 50-70 r / min. Preferably, the process parameters of the screw extruder corresponding to the high-temperature resistant intermediate layer are set as follows: the temperatures of zones 1-3 are 225-240℃, 260-270℃, and 285-295℃, respectively, and the rotation speed is 70-90 r / min.
[0016] Preferably, the preparation method of the epoxy functionalized hindered phenolic hydrophobic modifier is as follows: Using 1 molar equivalent of oleylamine and 0.95-0.99 molar equivalents of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane as raw materials, an alkenyl secondary amine intermediate is generated by the addition reaction between the -NH2 functional group of oleylamine and the acryloyloxy group of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane. Using 1 molar equivalent of an alkenyl secondary amine intermediate and 1.01-1.05 molar equivalents of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid as raw materials, under the promotion of DCC condensing agent, the -NH- functional group of the alkenyl secondary amine intermediate undergoes an amidation reaction with the carboxyl functional group of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid via DMAP catalysis to generate an alkenyl hindered phenolic intermediate; In the m-chloroperoxybenzoic acid / dichloromethane system, an epoxidation reaction is carried out through the alkenyl functional group of the alkenyl hindered phenolic intermediate to generate an epoxy-functionalized hindered phenolic hydrophobic modifier.
[0017] Application of a high-temperature resistant nylon multilayer co-extruded film in aerospace manufacturing materials, wherein the high-temperature resistant nylon multilayer co-extruded film is used as a vacuum bag film in the autoclave curing process of aerospace composite materials. Beneficial effects
[0018] This invention uses oleylamine as a synthetic raw material. First, it introduces a hydrophobic siloxane chain through a primary amino-acryloyloxy addition reaction with (3-acryloyloxypropyl)tris(trimethylsiloxy)silane. The resulting secondary amine intermediate undergoes an amidation reaction with 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in a DCC / DMAP catalytic system to graft hindered phenolic antioxidant groups. Finally, the alkenyl group in oleylamine is epoxidized by m-chloroperoxybenzoic acid, integrating the epoxy group (reactive grafting site), hindered phenolic group (antioxidant function), and long-chain alkyl / siloxane group (hydrophobic function) into a single molecular structure to obtain an epoxy-functionalized hindered phenolic hydrophobic modifier. Epoxy-functionalized montmorillonite filler was prepared by surface modification of sodium-based montmorillonite using silane coupling agent KH560. Epoxy-functionalized hindered phenolic hydrophobic modifier and epoxy-functionalized montmorillonite filler were respectively reacted and melt-blended with polyamide 6 / 66 resin and extruded. By utilizing the ring-opening grafting reaction between epoxy groups and polyamide molecular chain end groups (-NH2 / -COOH), low moisture absorption, heat-resistant and oxygen-aging resistant PA masterbatch and high temperature resistant PA masterbatch were obtained. A three-layer co-extrusion blow molding process is used to prepare a high-temperature resistant nylon multilayer co-extruded film. The film has a low moisture absorption and heat-resistant oxygen aging resistant PA masterbatch on the surface layer to form a double-sided hydrophobic and oxygen-resistant protective barrier, and a high-temperature resistant PA masterbatch in the middle layer to provide the main mechanical support and high-temperature dimensional stability. The film exhibits a longitudinal tensile strength change rate of <15% after 24 hours of heat-oxidation aging at 180℃, a heat distortion temperature of >220℃, and a moisture absorption rate of <1.0wt% after 24 hours of underwater at 25℃. It can be used as a vacuum bag film in the curing process of aerospace composite materials. Detailed Implementation Example 1:
[0019] A high-temperature resistant nylon multilayer co-extruded film I, the film structure and the raw material formulation and dosage of each film layer are shown in Table 1; Table 1 Experimental formulation of high-temperature resistant nylon multilayer co-extruded film I
[0020] Among them, the type of the copolyamide 6 / 66 resin is C40LN 09, and the amino content is 50.8 meq / kg; The formulation of the low moisture absorption, heat resistance, and oxygen aging resistant PA masterbatch is: 90wt% copolymer polyamide 6 / 66 resin and 10wt% epoxy functionalized hindered phenolic hydrophobic modifier. The formulation of the high-temperature resistant PA masterbatch is: 90wt% copolyamide 6 / 66 resin and 10wt% epoxy functionalized montmorillonite filler; The preparation steps of the epoxy functionalized hindered phenolic hydrophobic modifier are as follows: Step 1: Synthesis of the secondary amine intermediate: Using 1 molar equivalent of oleylamine (CAS No. 112-90-3) and 0.97 molar equivalents of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane (CAS No. 17096-12-7) as raw materials, an alkenyl secondary amine intermediate is generated through an addition reaction between the -NH2 functional group of oleylamine and the acryloyloxy group of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane. The synthesis process is as follows: Under nitrogen protection, 2.7 g of oleylamine and 20 mL of anhydrous N,N-dimethylformamide are added to a three-necked flask and stirred at room temperature until completely dissolved. Then, [the solution is added to...] 20 mL of anhydrous N,N-dimethylformamide solution containing 4.0 g of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane was added dropwise to a three-necked flask. The mixture was heated to 45 °C and stirred for 10 h. The reaction was monitored by TLC (ethyl acetate / petroleum ether = 1:5) until complete. The mixture was cooled to room temperature, extracted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the filtrate was collected. Ethyl acetate was removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1:8 to 1:5 gradient elution), the solvent was removed by rotary evaporation under reduced pressure, and the product was dried under vacuum to obtain a secondary amine intermediate with the following chemical structure: ; Step 2, Synthesis of the Alkenyl Hindered Phenolic Intermediate: Using 1 molar equivalent of an alkenyl secondary amine intermediate and 1.03 molar equivalent of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (antioxidant 1310, CAS No. 20170-32-5) as raw materials, under the promotion of DCC (N,N'-dicyclohexylcarbodiimide) condensing agent, the -NH- functional group of the alkenyl secondary amine intermediate undergoes an amidation reaction with the carboxyl functional group of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid via DMAP (4-dimethylaminopyridine) catalysis to generate the alkenyl hindered phenolic intermediate. The synthesis process is as follows: Under nitrogen protection, 1.9 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 1.5 g of DCC condensing agent, and 0.2 g of 4-dimethylaminopyridine are added... Pyridine and 30 mL of anhydrous dichloromethane were added to a three-necked flask and stirred at room temperature for 10 min. Then, 40 mL of anhydrous dichloromethane solution containing 4.5 g of the alkenyl secondary amine intermediate was added dropwise to the flask. The mixture was stirred at room temperature for 24 h, and the reaction was monitored by TLC (ethyl acetate / petroleum ether = 1:3) until complete. The mixture was filtered to remove DCU dicyclohexylurea formed by DCC activation of the carboxyl group. The filter cake was washed twice with dichloromethane, and the filtrate was collected. The filtrate was washed successively with saturated sodium bicarbonate and saturated brine, dried with anhydrous sodium sulfate, filtered, and the filtrate was collected. Dichloromethane was removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (elution with ethyl acetate / petroleum ether = 1:4 to 1:2 gradient), the solvent was removed by rotary evaporation under reduced pressure, and the product was dried under vacuum to obtain the alkenyl hindered phenolic intermediate, whose chemical structure is as follows: ; Step 3: Synthesis of epoxy-functionalized hindered phenolic hydrophobic modifier: In the m-chloroperoxybenzoic acid / dichloromethane system, an epoxidation reaction is carried out through the alkenyl functional group of the alkenyl hindered phenolic intermediate to generate an epoxy-functionalized hindered phenolic hydrophobic modifier. The synthesis process is as follows: Under nitrogen protection, 4.0 g of the alkenyl hindered phenolic intermediate and 40 mL of anhydrous dichloromethane are added to a three-necked flask, stirred and dissolved at room temperature for 30 min, and cooled to 0 °C in an ice-salt bath. Then, 0.9 g of m-chloroperoxybenzoic acid is added in four batches at 10 min intervals. After stirring at 0℃ for 30 min, the ice-salt bath was removed, and the mixture was slowly raised to room temperature with continued stirring for 5 h. The reaction was monitored by TLC (ethyl acetate / petroleum ether = 1:3) until complete. The mixture was washed successively with saturated sodium bicarbonate and saturated brine, dried with anhydrous sodium sulfate, filtered, and the filtrate was collected. Dichloromethane was removed by rotary evaporation under reduced pressure. The crude product was purified by silica gel column chromatography (eluting with ethyl acetate / petroleum ether at a gradient of 1:5 to 1:2), the solvent was removed by rotary evaporation under reduced pressure, and the product was dried under vacuum to obtain an epoxy-functionalized hindered phenolic hydrophobic modifier with the following chemical structure: ; The 1H NMR characterization of the epoxy-functionalized hindered phenolic hydrophobic modifier is as follows: 1 H NMR (DMSO-d6, 400MHz) δ: 0.13 (s, 27H), 0.52-0.54 (t, 2H), 0.87-0.90 (t, 3H), 1.22-1.40 (m, 22H), 1.44 (s, 18H), 1.52-1.67 (m, 6H), 1.77-1.83 (m, 2H), 2.59- 2.64(m, 4H), 2.85-2.88(t, 2H), 3.21-3.26(m, 2H), 3.32-3.35(t, 2H), 3.56-3.59(t, 2H), 4.11-4.14(t, 2H), 6.36(s, 1H), 7.01(s, 2H); The preparation steps of epoxy-functionalized montmorillonite filler are as follows: Dissolve 1 part by weight of silane coupling agent KH560 (3-(2,3-epoxypropoxy)propyltrimethoxysilane) in 10 parts by weight of methanol, add 1 part by weight of deionized water and 0.1 part by weight of glacial acetic acid, and stir at room temperature for 2 hours to hydrolyze the trimethoxysilyl group into silanol groups, forming a hydrolysate solution of silane coupling agent KH560; Add 10 parts by weight of sodium-based montmorillonite powder (sheet diameter 3-8 μm, thickness 5- The 15nm silane coupling agent was ultrasonically dispersed in 100 parts by weight of methanol. The hydrolysis solution of the above-mentioned silane coupling agent KH560 was slowly added dropwise. The mixture was heated to 40°C and stirred for 8 hours to allow the silanol groups to undergo a dehydration condensation reaction with the hydroxyl groups on the surface of montmorillonite, thereby grafting the epoxy functional groups onto the surface of montmorillonite. The mixture was cooled to room temperature, centrifuged at 8000 rpm for 15 minutes, washed three times with methanol, and vacuum dried at 80°C for 12 hours to obtain the epoxy-functionalized montmorillonite filler. Example 2:
[0021] A method for preparing a high-temperature resistant nylon multilayer co-extruded film I includes the following steps: Step 1: Preparation of low moisture absorption and heat-resistant oxygen aging resistant PA masterbatch: Copolymer polyamide 6 / 66 resin was dried in a vacuum oven at 100℃ for 8 hours to reduce the moisture content to below 0.1%. 90 parts by weight of the dried copolymer polyamide 6 / 66 resin was fully premixed with 10 parts by weight of epoxy functionalized hindered phenolic hydrophobic modifier. The mixture was then fed into a co-rotating twin-screw extruder through the main feed port and subjected to reactive melt blending extrusion under a high-shear screw configuration. After the extruded material was cooled, it was granulated by a pelletizer and then vacuum dried at 80℃ for 4 hours to obtain low moisture absorption and heat-resistant oxygen aging resistant PA masterbatch. During the melt blending extrusion process, the epoxy groups in the epoxy-functionalized hindered phenolic hydrophobic modifier undergo a ring-opening grafting reaction with the end groups (-NH2 / -COOH) of the copolymer polyamide 6 / 66 resin molecular chain in the melt shear field, thereby achieving chemical bonding and uniform dispersion of the epoxy-functionalized hindered phenolic hydrophobic modifier in the copolymer polyamide 6 / 66 resin matrix. The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 210℃, Zone 2 220℃, Zone 3 235℃, Zone 4 240℃, Zone 5 250℃, Zone 6 255℃, Zone 7 (distillation head) 250℃; Preheating temperature 210℃; Screw speed 200r / min; Step 2, Preparation of high-temperature resistant PA masterbatch: Copolymer polyamide 6 / 66 resin was dried in a vacuum oven at 100℃ for 8 hours to reduce the moisture content to below 0.1%. 90 parts by weight of the dried copolymer polyamide 6 / 66 resin was fully premixed with 10 parts by weight of epoxy functionalized montmorillonite filler and fed into a co-rotating twin-screw extruder through the main feed port. Reactive melt blending extrusion was carried out under a high-shear screw configuration. After the extruded material was cooled, it was granulated by a pelletizer and then vacuum dried at 80℃ for 4 hours to obtain high-temperature resistant PA masterbatch. During the melt blending extrusion process, the epoxy groups on the surface of the epoxy-functionalized montmorillonite filler undergo a ring-opening grafting reaction with the end groups (-NH2 / -COOH) of the copolymer polyamide 6 / 66 resin molecular chain in the melt shear field, thereby achieving chemical bonding and uniform dispersion of the montmorillonite filler in the copolymer polyamide 6 / 66 resin matrix. The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 230℃, Zone 2 250℃, Zone 3 265℃, Zone 4 280℃, Zone 5 290℃, Zone 6 295℃, Zone 7 (distillation head) 290℃; Preheating temperature 230℃; Screw speed 300r / min; Step 3, Preparation of high-temperature resistant nylon multilayer co-extruded film I: According to the formula of high-temperature resistant nylon multilayer co-extruded film I, the raw materials of each layer are fed into the hoppers of the three screw extruders of the three-layer co-extrusion film blow molding unit. The molten resin is combined at the die head through the distributor, and then extruded and blown by the die head. The die head temperature is 260℃, the blow ratio is 2.8, and the traction speed is 6.0m / min. After cooling and winding, a high-temperature resistant nylon multilayer co-extruded film I with a thickness of 80μm is obtained. The process parameters for the screw extruders corresponding to the first and third layers are set as follows: the temperatures of zones 1-3 are 210℃, 230℃, and 255℃, respectively, and the rotation speed is 60r / min. The process parameters for the screw extruder corresponding to the second layer are set as follows: the temperatures of zones 1-3 are 230℃, 265℃, and 295℃, respectively, and the rotation speed is 80r / min. Example 3:
[0022] A high-temperature resistant nylon multilayer co-extruded film II, the film structure and the raw material formulation and dosage of each film layer are shown in Table 2; Table 2 Experimental formulation of high-temperature resistant nylon multilayer co-extruded film II
[0023] The preparation method of a high-temperature resistant nylon multilayer co-extruded film II is the same as that of the high-temperature resistant nylon multilayer co-extruded film I in Example 2, and a high-temperature resistant nylon multilayer co-extruded film II with a thickness of 80 μm is obtained. Example 4:
[0024] A high-temperature resistant nylon multilayer co-extruded film III, the film structure and the raw material formulation and dosage of each film layer are shown in Table 3; Table 3 Experimental formulation of high-temperature resistant nylon multilayer co-extruded film III
[0025] The preparation method of a high-temperature resistant nylon multilayer co-extruded film III is the same as that of the high-temperature resistant nylon multilayer co-extruded film I in Example 2, and a high-temperature resistant nylon multilayer co-extruded film III with a thickness of 80 μm is obtained. Comparative Example 1:
[0026] The nylon multilayer co-extruded film a was prepared, and its film structure and the raw material formulation and dosage of each film layer are shown in Table 4. Table 4 Experimental formulation of nylon multilayer co-extruded film a
[0027] The preparation method of nylon multilayer co-extruded film a is as follows: the raw materials are prepared according to the formula of nylon multilayer co-extruded film a, and the raw materials of each layer are respectively fed into the hoppers of the three screw extruders of the three-layer co-extruded film blow molding unit. The molten resin is combined at the die head through the distributor, and then extruded and blown by the die head. The die head temperature is 240℃, the blow ratio is 2.8, the traction speed is 6.0m / min, cooled and wound up to obtain nylon multilayer co-extruded film a with a thickness of 80μm. The process parameters for the screw extruders corresponding to the first, second, and third layers are all set as follows: the temperatures of zones 1-3 are 210℃, 230℃, and 255℃, respectively, and the rotation speed is 60r / min. Comparative Example 2:
[0028] Nylon multilayer co-extruded film b was prepared. Its film structure and the raw material formulation and dosage of each film layer are shown in Table 5. Table 5 Experimental formulation of nylon multilayer co-extruded film b
[0029] The preparation method of nylon multilayer co-extruded film b is as follows: Step 1: Preparation of hydrophobic / antioxidant blended PA masterbatch: Copolymer polyamide 6 / 66 resin was dried in a vacuum oven at 100℃ for 8 hours to reduce the moisture content to below 0.1%. 90 parts by weight of the dried copolymer polyamide 6 / 66 resin and 10 parts by weight of a compound composition consisting of oleylamine, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (the molar ratio of oleylamine, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid was fully premixed and fed into a co-rotating twin-screw extruder through the main feed port. Melt blending extrusion was performed under a high-shear screw configuration. After cooling, the extruded material was granulated by a pelletizer and then vacuum dried at 80℃ for 4 hours to obtain the hydrophobic / antioxidant blended PA masterbatch. The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 210℃, Zone 2 220℃, Zone 3 235℃, Zone 4 240℃, Zone 5 250℃, Zone 6 255℃, Zone 7 (distillation head) 250℃; Preheating temperature 210℃; Screw speed 200r / min; Step 2, Preparation of montmorillonite blended PA masterbatch: Copolymer polyamide 6 / 66 resin was dried in a vacuum oven at 100℃ for 8 hours to reduce the moisture content to below 0.1%. 90 parts by weight of the dried copolymer polyamide 6 / 66 resin was fully premixed with 10 parts by weight of sodium-based montmorillonite powder and fed into a co-rotating twin-screw extruder through the main feed port. The extruded material was melt-blended and extruded under a high-shear screw configuration. After cooling, the extruded material was granulated by a pelletizer and then vacuum-dried at 80℃ for 4 hours to obtain montmorillonite blended PA masterbatch. The temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 230℃, Zone 2 250℃, Zone 3 265℃, Zone 4 280℃, Zone 5 290℃, Zone 6 295℃, Zone 7 (distillation head) 290℃; Preheating temperature 230℃; Screw speed 300r / min; Step 3, Preparation of Nylon Multilayer Co-extruded Film b: According to the formula of Nylon Multilayer Co-extruded Film b, the raw materials of each layer are fed into the hoppers of the three screw extruders of the three-layer co-extruded film blow molding unit. The molten resin is combined at the die head through the distributor, and then extruded and blown through the die head. The die head temperature is 260℃, the blow ratio is 2.8, and the traction speed is 6.0m / min. After cooling and winding, a Nylon Multilayer Co-extruded Film b with a thickness of 80μm is obtained. The process parameters for the screw extruders corresponding to the first and third layers are set as follows: the temperatures of zones 1-3 are 210℃, 230℃, and 255℃, respectively, and the rotation speed is 60r / min. The process parameters for the screw extruder corresponding to the second layer are set as follows: the temperatures of zones 1-3 are 230℃, 265℃, and 295℃, respectively, and the rotation speed is 80r / min. Performance testing:
[0030] I. Mechanical property testing: (1) Longitudinal tensile strength before thermo-oxidative aging: According to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the specimen was cut into strips with a length of 150 mm, a width of 15 mm and a gauge length of 50 mm along the longitudinal direction (MD). After adjusting at 25℃ and 50%RH for 24 h, the specimen was fixed on the fixture of the universal testing machine and subjected to tensile testing at a tensile rate of 50 mm / min. The longitudinal tensile strength of the specimen was recorded. (2) Longitudinal tensile strength after 24h of thermo-oxidative aging at 180℃: First, cut the sample into strips with a length of 150mm, a width of 15mm, and a gauge length of 50mm. Then, vertically suspend the strips in the effective working area of the forced ventilation thermo-aging chamber with a spacing of ≥10mm. Treat the sample at 180℃ for 24h with an air exchange rate of 30 times / h. After that, according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", adjust the sample at 25℃ and 50%RH for 24h and fix it on the fixture of the universal testing machine. Perform a tensile test at a tensile rate of 50mm / min. Record the longitudinal tensile strength of the sample and calculate the rate of change of longitudinal tensile strength of the sample after 24h of thermo-oxidative aging at 180℃. The specific method is as follows: Change rate of longitudinal tensile strength (%) = (Longitudinal tensile strength before thermo-oxidative aging - Longitudinal tensile strength after 24 hours of thermo-oxidative aging at 180℃) / Longitudinal tensile strength before thermo-oxidative aging × 100%; II. High Temperature Resistance Test: According to standard GB / T 1634.2-2019 "Determination of load deflection temperature of plastics - Part 2: Plastics and hard rubber", multilayer films were stacked and hot-pressed into sheet samples of 80mm×10mm×4mm. The samples were placed flat on a support with a span of 64mm, and a load of 0.45MPa was applied. The temperature was increased at a rate of 120℃ / h, with an initial temperature of 25℃. The temperature at which the bending deflection of the sample reached 0.34mm was recorded as the heat deflection temperature (HDT). III. Moisture Absorption Rate Test: Following the GB / T 1034-2008 standard "Determination of Water Absorption of Plastics", a 60mm × 60mm (length × width) sample was dried in an oven at 50℃ until constant weight. After cooling to room temperature, the sample was weighed and recorded as the initial weight. The dried sample was then completely immersed in distilled water (water temperature controlled at 25℃) for 24 hours. It was then removed with tweezers, and the surface moisture was absorbed using absorbent filter paper. The sample was weighed and recorded as the weight after moisture absorption. The moisture absorption rate of the sample was calculated. The specific method is as follows: Moisture absorption rate (%) = (weight of sample after moisture absorption - initial weight of sample) / initial weight of sample × 100%; The performance test results are shown in Table 6 below.
[0031] Table 6. Performance test results of high-temperature resistant nylon multilayer co-extruded film
[0032] The following conclusions can be drawn from the test data in Table 6: Conclusion 1: The high-temperature resistant nylon multilayer co-extruded film product prepared by the present invention using the independently developed low moisture absorption heat-resistant and oxygen-aging resistant PA masterbatch and high temperature resistant PA masterbatch has a longitudinal tensile strength change rate of <15% and a heat distortion temperature of >220℃ after 24 hours of heat-oxidation aging at 180℃. Compared with Comparative Example 1 without modification and Comparative Example 2 with simple blending modification, it has achieved significant improvement in high temperature resistance and heat-oxidation aging resistance. Conclusion 2: The high-temperature resistant nylon multilayer co-extruded film prepared by this invention has a moisture absorption rate of <1.0wt% after being kept in water at 25℃ for 24 hours, which is significantly improved compared with Comparative Example 1 and Comparative Example 2.
Claims
1. A high-temperature resistant nylon multilayer co-extruded film, characterized in that, The high-temperature resistant nylon multilayer co-extruded film has a three-layer symmetrical co-extruded structure consisting of a low-moisture-absorbing and antioxidant outer layer, a high-temperature resistant middle layer, and a low-moisture-absorbing and antioxidant inner layer. The formulation of the low moisture absorption and antioxidant outer and inner layers is: 50-70wt% copolyamide 6 / 66 resin and 30-50wt% low moisture absorption and heat-resistant oxygen aging resistant PA masterbatch. The formulation of the high-temperature resistant intermediate layer is: 50-70wt% copolyamide 6 / 66 resin and 30-50wt% high-temperature resistant PA masterbatch; The low moisture absorption, heat resistance, and oxygen aging resistant PA masterbatch is prepared by reactive melt blending and extrusion of epoxy functionalized hindered phenolic hydrophobic modifier and copolymer polyamide 6 / 66 resin. The high-temperature resistant PA masterbatch is obtained by reactive melt blending and extrusion of epoxy functionalized montmorillonite filler and copolymer polyamide 6 / 66 resin; Both the epoxy-functionalized hindered phenolic hydrophobic modifier and the epoxy-functionalized montmorillonite filler are covalently bonded to the polyamide molecular chain through the ring-opening reaction of epoxy groups with the end groups of the polyamide molecular chain. The chemical structural formula of the epoxy-functionalized hindered phenolic hydrophobic modifier is as follows: 。 2. The high-temperature resistant nylon multilayer co-extruded film according to claim 1, characterized in that, The formulation of the low moisture absorption, heat resistance, and oxygen aging resistant PA masterbatch is: 85-95wt% copolyamide 6 / 66 resin and 5-15wt% epoxy functionalized hindered phenolic hydrophobic modifier. The formulation of the high-temperature resistant PA masterbatch is: 85-95wt% copolymer polyamide 6 / 66 resin and 5-15wt% epoxy-functionalized montmorillonite filler.
3. The high-temperature resistant nylon multilayer co-extruded film according to claim 1, characterized in that, The epoxy-functionalized montmorillonite filler is prepared by surface modification of 8-15 parts by weight of sodium-based montmorillonite with 0.5-1.5 parts by weight of silane coupling agent KH560.
4. The high-temperature resistant nylon multilayer co-extruded film according to claim 3, characterized in that, The sodium-based montmorillonite flakes have a diameter of 3-8 μm and a thickness of 5-15 nm.
5. The high-temperature resistant nylon multilayer co-extruded film according to claim 1, characterized in that, The mass ratio of the low moisture absorption and antioxidant outer layer, the high temperature resistant middle layer, and the low moisture absorption and antioxidant inner layer in the high temperature resistant nylon multilayer co-extruded film is (1.5-3):(4-7):(1.5-3).
6. The high-temperature resistant nylon multilayer co-extruded film according to claim 1, characterized in that, The thickness of the high-temperature resistant nylon multilayer co-extruded film is 50-100 μm.
7. A method for preparing a high-temperature resistant nylon multilayer co-extruded film according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Premix the copolymer polyamide 6 / 66 resin with epoxy functionalized hindered phenolic hydrophobic modifier, and then perform reactive melt blending extrusion at a temperature of 210-255℃ using a co-rotating twin-screw extruder. Granulate and dry to obtain a low moisture absorption, heat-resistant, and oxygen-aging resistant PA masterbatch. Step 2: Premix the copolymer polyamide 6 / 66 resin with epoxy-functionalized montmorillonite filler, and then perform reactive melt blending extrusion at a temperature of 230-295℃ using a co-rotating twin-screw extruder. Granulate and dry the mixture to obtain high-temperature resistant PA masterbatch. Step 3: Prepare the raw materials according to the formula of high temperature resistant nylon multilayer co-extruded film. Put the raw materials of each layer into the hoppers of the three screw extruders of the three-layer co-extruded film blow molding unit. The molten resin is combined at the die head through the distributor, extruded and blown by the die head, cooled and wound up to obtain high temperature resistant nylon multilayer co-extruded film.
8. The method for preparing a high-temperature resistant nylon multilayer co-extruded film according to claim 7, characterized in that, The process parameters of the screw extruder corresponding to the low moisture absorption and antioxidant outer and inner layers are set as follows: the temperatures of zones 1-3 are 205-215℃, 220-240℃, and 250-260℃, respectively, and the rotation speed is 50-70 r / min. The process parameters of the screw extruder corresponding to the high-temperature resistant intermediate layer are set as follows: the temperatures of zones 1-3 are 225-240℃, 260-270℃, and 285-295℃, respectively, and the rotation speed is 70-90 r / min.
9. The method for preparing a high-temperature resistant nylon multilayer co-extruded film according to claim 7, characterized in that, The preparation method of the epoxy functionalized hindered phenolic hydrophobic modifier is as follows: Using 1 molar equivalent of oleylamine and 0.95-0.99 molar equivalents of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane as raw materials, an alkenyl secondary amine intermediate is generated by the addition reaction between the -NH2 functional group of oleylamine and the acryloyloxy group of (3-acryloyloxypropyl)tris(trimethylsiloxy)silane. Using 1 molar equivalent of an alkenyl secondary amine intermediate and 1.01-1.05 molar equivalents of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid as raw materials, under the promotion of DCC condensing agent, the -NH- functional group of the alkenyl secondary amine intermediate undergoes an amidation reaction with the carboxyl functional group of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid via DMAP catalysis to generate an alkenyl hindered phenolic intermediate; In the m-chloroperoxybenzoic acid / dichloromethane system, an epoxidation reaction is carried out through the alkenyl functional group of the alkenyl hindered phenolic intermediate to generate an epoxy-functionalized hindered phenolic hydrophobic modifier.
10. The application of a high-temperature resistant nylon multilayer co-extruded film according to any one of claims 1-6 in aerospace manufacturing materials, characterized in that, The high-temperature resistant nylon multilayer co-extruded film is used as a vacuum bag film in the autoclave curing process of aerospace composite materials.