Preparation method of reactive antioxidant grafted modified nylon 6 and film thereof

Abstract

The invention discloses a preparation method of reactive antioxidant grafted modified nylon 6 and a film thereof, and belongs to the technical field of nylon modification. A reactive antioxidant containing a hindered phenol structure and nylon 6 are subjected to melt chemical grafting to form a covalent bond combined nylon 6-antioxidant system, and hindered phenol provides hydrogen atoms and can be combined with free radicals generated in the aging process, so that the chain reaction of the hindered phenol is terminated, and phenoxy free radicals with low activity are formed by the hindered phenol. According to the invention, the reactive antioxidant grafted modified nylon 6 is further processed into a film product, and the nylon 6 film product prepared by the method has the advantages of less antioxidant migration, aging resistance, high mechanical property retention rate and the like.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a reaction-type antioxidant grafted modified nylon 6 and a film thereof, and belongs to the technical field of nylon modification. BACKGROUND

[0002] Nylon 6 (PA6) is one of general-purpose thermoplastic engineering plastics, contains amide groups (-CONH-) in the structure, can form hydrogen bonds between molecular chains, is easy to crystallize, has excellent mechanical properties, corrosion resistance, self-lubricating properties and other characteristics, and is widely used in the fields of machinery, aerospace, electronics, electrical appliances and packaging. However, in the process of PA6 molding and product use, the strong polar amide groups contained in PA6 will be broken under the combined action of light, heat and oxygen, affecting the weather resistance of nylon 6. In the process of thermal oxidation aging of nylon 6, free radicals and oxygen generate peroxide radicals and hydroperoxide, the hydroperoxide decomposes to generate alkoxy, and the molecular chain undergoes complex oxidation and chain scission reaction, seriously damaging the chemical structure and physical properties of the nylon 6, causing the discoloration, hardening, embrittlement and degradation of mechanical properties of the product, resulting in the decrease of the quality of the nylon product and the shortening of the service life. Nylon 6 film is more prone to aging under the action of heat and oxygen in the production and use process, affecting the mechanical properties, thermal stability and other properties of the film, and leading to the decrease of the service life of the film.

[0003] Nylon is a polymer sensitive to free radicals and prone to degradation, and the service life of most nylon products is mainly controlled by its antioxidant capacity. Antioxidants can delay or prevent the degradation and aging of materials in the oxidation process, and are essential components of nylon materials. Commonly used antioxidants for nylon include antioxidant 1098, 1010, 1076 and 1035, etc. However, these antioxidants are all small molecule antioxidants of the additive type, and their melting points are significantly lower than the processing temperature of nylon, showing poor thermal stability in the process of nylon processing or use, and being easy to migrate and precipitate, resulting in loss. Therefore, it is necessary to introduce antioxidant components into the molecular chain of nylon through a chemical modification method to prepare weather-resistant nylon 6 and its film. The method of introducing antioxidant components into the molecular chain of nylon can be grafting reaction of reaction-type antioxidant with nylon, and co-polycondensation of reaction-type antioxidant with synthetic nylon monomers.

[0004] The patent with publication number CN113956496A discloses a method for preparing a novel two-dimensional nylon 6 antioxidant. Copper salt antioxidants have antioxidant effects in nylon 6 films, but have obvious shortcomings, such as causing color contamination, migration and precipitation, catalyzing the degradation of nylon, complex processing, high cost, and being unsuitable for food contact materials, which limits their application in high transparency and high safety fields. The patent with publication number CN110452378A discloses a 4-maleimide diphenylamine and ethylenediamine copolymer antioxidant and a method for modifying nylon 6 composite materials. The 4-maleimide diphenylamine and ethylenediamine copolymer antioxidant is not easily volatile and precipitated during processing, but it has poor compatibility with the matrix and is not uniformly dispersed. The patent with publication number CN119321004A discloses a method for preparing an anti-aging nano-titanium dioxide modified nylon 6 fiber. The butyl nitrile rubber macromolecule and the tert-butyl phenol anti-aging small molecule are covalently grafted on the surface of nano-titanium dioxide. Nano-titanium dioxide and butyl nitrile rubber can absorb and disperse stress, and tert-butyl phenol can absorb free radicals generated during the oxidation process of the nylon 6 matrix. This improves the dispersity of the composite nylon 6 fiber and enhances its comprehensive performance such as mechanical properties and oxidation resistance. However, mixed organic solvents are used in the preparation process and inorganic nanomaterials are added. The introduction of inorganic nanoparticles also has the disadvantages of reduced transparency, complex processing, and possibly weakened mechanical properties.

[0005] Weather-resistant nylon 6 films can be widely used in photovoltaic backsheet films, agricultural long-life films, automotive films, and high-performance industrial packaging films. They have excellent heat-oxidative aging resistance, ultraviolet resistance, high mechanical strength, and good barrier properties, and are suitable for long-term use in outdoor and extreme environments. Such materials are often modified by copolymerization, nanocomposite, or multilayer co-extrusion processes to meet the application requirements of high weather resistance and high performance.

[0006] Graft copolymer is a kind of macromolecular material formed by chemically grafting one or more polymer side chains onto the main chain polymer, which has the performance of both main chain and side chain. Its main advantages are to improve the compatibility between polymers, enhance thermal and oxidative stability, improve mechanical properties, achieve functional modification, and effectively reduce the migration of additives. Through grafting, materials can be endowed with flame retardant, antioxidant, ultraviolet resistant, antistatic and other properties, and are suitable for food packaging, medical, film materials and high-performance engineering plastics and other fields. The application of graft copolymerization in the preparation of weather-resistant nylon 6 can effectively solve the problems of easy migration, easy failure and short service life of ordinary blended antioxidants. There are some literature reports on weather-resistant nylon 6 materials at home and abroad. Shi et al. (J. Therm. Anal. Calorim., 2015, 119: 1747-1757) developed a new type of reactive antioxidant (HP-Cl), which was grafted onto the PA6 main chain with a high grafting rate by reactive extrusion. Due to the in-situ stabilization of the reactive antioxidant, PA6-g-HP exhibits excellent thermal stability and anti-migration performance. Jiang et al. (J. Appl. Polym. Sci., 2021, 138: e51184) successfully synthesized two kinds of polymeric antioxidants PCN and PPN by free radical copolymerization and blended them with nylon 6 material. The high molecular weight antioxidant protects the PA6 molecular chain from breaking, improves the thermal degradation activation energy and thermal stability of PA6, and prolongs its service life. Li et al. (Ind. Eng. Chem. Res., 2017, 56: 13715-13724) prepared GO-HP hybrid materials by grafting HP on the surface of graphene oxide (GO), and then prepared PA6 / GO-HP nanocomposites by melt processing. The addition of GO makes PA6 change from γ crystal form to more stable α crystal form, and the OIT value, thermal degradation characteristic temperature and activation energy of PA6 / GO-HP nanocomposites are significantly improved, and GO-HP has a synergistic thermal and oxidative stabilization effect on PA6. The preparation of the above weather-resistant nylon 6 materials uses inorganic nanoparticles, high molecular weight antioxidants and nylon 6 matrix blending, which will migrate to the surface of the material or even precipitate from the material due to weak intermolecular forces and poor compatibility during processing or use, affecting the preparation of thin film materials and weakening the antioxidant effect. Grafting method is a chemical grafting reaction on long-chain macromolecules to introduce antioxidant groups, which is relatively simple in preparation method and stable in reaction process, but the amount of antioxidant grafted onto the polymer is limited, which restricts its antioxidant effect.

[0007] In summary, although there are some reports on the preparation of weather-resistant nylon 6 and its film material, the mainstream method is still to load antioxidants on the nylon 6 matrix material or to increase the molecular weight of the added antioxidants to reduce the physical loss during processing and use, increase the long-term stability of the polymer; by compounding two antioxidants or synthesizing multifunctional antioxidants, the heat-oxidative aging resistance of the polymer is improved. By copolymerization (random, graft or block copolymerization, etc.), it is expected to introduce heat-oxidative aging resistant and ultraviolet resistant structural units or functional groups into the main chain or side chain of nylon 6, so as to prepare nylon 6 and its film products with excellent and long-lasting weather resistance. SUMMARY

[0008] In order to solve the problems of poor compatibility of the added antioxidant with the nylon 6 resin, easy migration and precipitation during processing or long-term use, and reduction of antioxidant efficiency and weather resistance of the nylon 6, the application provides a reaction-type antioxidant grafted modified nylon 6 and its film and a preparation method thereof.

[0009] The technical scheme of the application is as follows:

[0010] The application first provides a preparation method of a reaction-type antioxidant grafted modified nylon 6, wherein the modified nylon 6 is prepared by mixing and melt grafting 100 parts of nylon 6, 0.05-1 part of an initiator and 0.1-2 parts of a reaction-type antioxidant. Preferably, the mixing and melt grafting process is that the above-mentioned materials are uniformly mixed in a high-speed mixer, then added into a twin-screw extruder, and the modified nylon 6 is prepared by melt reaction, extrusion, traction, granulation and drying. The reaction-type antioxidant contains a vinyl unsaturated group and a hindered phenol structure with antioxidant activity, and the modified nylon 6 is obtained by grafting the reaction-type antioxidant on the molecular chain of the nylon 6.

[0011] Further preferably, the reaction-type antioxidant is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester or 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid-3-butene-1-ester.

[0012] Further preferably, the modified nylon 6 is prepared by 100 parts of nylon 6, 0.05-1 part of an initiator and 0.5-2 parts of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester.

[0013] Further preferably, the modified nylon 6 is prepared by 100 parts of nylon 6, 0.05-1 part of an initiator and 0.5-1.5 parts of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid-3-butene-1-ester.

[0014] According to an embodiment of the present application, the initiator is cumene hydroperoxide or di-tert-butyl cumyl peroxide. The initiator is further preferably cumene hydroperoxide.

[0015] The modified nylon 6 is made of 100 parts of nylon 6, 0.05-1 parts of cumene hydroperoxide and 0.1-2 parts of the reactive antioxidant by mass fraction. Preferably, the modified nylon 6 is made of 100 parts of nylon 6, 0.2-0.8 parts of cumene hydroperoxide and 0.1-2 parts of the reactive antioxidant by mass fraction. Further preferably, the modified nylon 6 is made of 100 parts of nylon 6, 0.1-0.6 parts of di-tert-butyl cumyl peroxide and 0.1-2 parts of the reactive antioxidant by mass fraction.

[0016] The preparation method of the modified nylon 6 is as follows: the nylon granules, the initiator and the reactive antioxidant are fully mixed in a high-speed mixer, and then the mixture is subjected to melt grafting reaction, extrusion, traction, granulation, drying and obtaining of the grafted modified nylon 6 through a double-screw extruder under the conditions of a temperature of 180-250°C and a rotation speed of 60-100 rpm. Preferably, the temperature of each section of the double-screw extruder from the main feeding port to the head is 180-200°C, 210-220°C, 220-230°C, 230-240°C, 240-250°C and 240-250°C, and the screw rotation speed is 60-100 rpm.

[0017] The present application also provides a preparation method of the grafted modified nylon 6 film of the reactive antioxidant, which is to add the modified nylon 6 into a single-screw extruder, melt, extrude and cool and draw through a casting machine to obtain the modified nylon 6 film.

[0018] Further, the operation of the method in the single-screw and the casting machine is as follows: after the grafted copolymer granules are fully dried, the granules are subjected to melt, extrusion, stretching, cooling and winding through a casting machine under the conditions of a temperature of 180-250°C, a cooling roll temperature of 60-120°C and a linear speed of the casting roll A, the casting roll B and the traction roll of 1.5-3 m / min. More preferably, the temperature of each section of the single-screw extruder from the feeding port to the head is 180-200°C, 220-230°C, 230-240°C and 240-250°C, and the screw rotation speed is 20-40 rpm.

[0019] The present application has the following beneficial effects: the present application introduces a reaction antioxidant monomer containing a hindered phenol structure on the molecular chain of nylon 6 through a melt grafting reaction, realizes chemical grafting of the antioxidant on the polymer chain, and effectively solves the technical problems of easy migration, easy failure, short service life and the like of the traditional additive antioxidant. Hindered phenolic antioxidants are widely used in the anti-aging modification of polymers due to their excellent free radical scavenging ability, but the traditional method mixes them into the base polymer in a physical way, which is easy to migrate to the material surface or even precipitate from the material due to the weak intermolecular force during processing or use, resulting in weakening or even disappearance of the antioxidant effect, and seriously affecting the long-term stability and service life of the material.

[0020] The reaction antioxidant monomer used in the present application contains both an unsaturated functional group that can participate in polymerization and a hindered phenol structure with antioxidant activity, and can realize copolymerization grafting on the molecular chain under melt and initiation conditions. This chemical grafting method makes the antioxidant part of the polymer backbone, and the grafted antioxidant is uniformly distributed in the polymer chain, ensuring the overall antioxidant property of the material rather than just the surface, eliminating the migration and precipitation of the antioxidant during subsequent processing and use, and significantly improving the long-term stability and durability of the material in complex environments such as thermal oxygen, light oxygen and wet oxygen.

[0021] In summary, the present application not only fundamentally improves the stability and durability of the antioxidant in nylon 6, but also avoids environmental pollution and product failure problems that may be caused by antioxidant migration, providing reliable material protection for long-period application of high-performance nylon in the fields of automobiles, electrical, electronic, military, film and the like, and has broad industrial application prospects and important engineering value. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The UV-visible absorption spectrum of the sample of the reaction antioxidant grafted nylon 6 with or without initiator under the condition of reaction is shown.

[0023] Figure 2 The reaction mechanism diagram of the reaction antioxidant grafted modified nylon 6 is shown. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below.

[0025] The following examples are used to further illustrate the present application, and the purpose is to illustrate the present application and should not be interpreted as limiting the scope of the present application. The following uses parts by weight and percentage by weight unless otherwise specified.

[0026] The raw materials used in the present application are all conventional commercially available products unless otherwise specified; the methods used in the present application are all conventional methods in the art unless otherwise specified.

[0027] The embodiments of the present application are further described in the following examples.

[0028] Example 1 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100℃ for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 1.6 g of cumene hydroperoxide and 2 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 180℃, 210℃, 220℃, 230℃, 240℃, 240℃, the screw rotation speed was 70 rpm / min, and the feeding speed was 3.6 Hz; the melt blending grafting reaction was carried out under the above conditions to obtain an antioxidant grafted nylon 6 wire, which was cut into particles in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 200℃, 230℃, 230℃, 240℃, the screw rotation speed was 25 rpm / min, the linear speeds of the casting roller A, the casting roller B, and the traction roller were all 1.6 m / min, and the temperature of the cooling roller was 80℃; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0029] Example 2 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100℃ for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 1.6 g of cumene hydroperoxide and 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 180℃, 210℃, 220℃, 230℃, 240℃, 240℃, the screw rotation speed was 80 rpm / min, and the feeding speed was 4.2 Hz; the melt blending grafting reaction was carried out under the above conditions to obtain an antioxidant grafted nylon 6 wire, which was cut into particles in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 200℃, 230℃, 230℃, 240℃, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roller A, the casting roller B, and the traction roller were all 2.2 m / min, and the temperature of the cooling roller was 90℃; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0030] Example 3 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 2.4 g of cumene hydroperoxide and 6 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C, the screw rotation speed was 84 rpm / min, and the feeding speed was 4.2 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 200°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.5 m / min, and the temperature of the cooling roll was 100°C; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0031] Example 4 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 4 g of cumene hydroperoxide and 8 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 185°C, 210°C, 225°C, 235°C, 250°C, and 250°C, the screw rotation speed was 100 rpm / min, and the feeding speed was 5 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 180°C, 230°C, 240°C, and 250°C, the screw rotation speed was 40 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 3 m / min, and the temperature of the cooling roll was 120°C; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0032] Example 5 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 0.2 g of cumene hydroperoxide and 0.4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; a twin-screw extruder was used to perform a melt blending grafting reaction under the following conditions: the temperatures of the sections from the main feeding port to the die head were 185°C, 210°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 60 rpm / min, and the feeding speed was 3.2 Hz, to obtain an antioxidant grafted nylon 6 wire, which was cut into particles in a pelletizer to prepare nylon 6 grafting material pellets; a single-screw extruder was used to perform melt extrusion, drawing, cooling, and winding under the following conditions: the temperatures of the sections from the feeding port to the die head were 180°C, 230°C, 230°C, and 240°C, the screw rotation speed was 20 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 1.5 m / min, and the temperature of the cooling roll was 60°C, to obtain a nylon 6 film material.

[0033] Example 6 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 0.2 g of di-tert-butyl cumyl peroxide and 0.4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid-3-buten-1-yl ester in a high-speed mixer; a twin-screw extruder was used to perform a melt blending grafting reaction under the following conditions: the temperatures of the sections from the main feeding port to the die head were 190°C, 220°C, 223°C, 235°C, 240°C, and 240°C, the screw rotation speed was 60 rpm / min, and the feeding speed was 3.2 Hz, to obtain an antioxidant grafted nylon 6 wire, which was cut into particles in a pelletizer to prepare nylon 6 grafting material pellets; a single-screw extruder was used to perform melt extrusion, drawing, cooling, and winding under the following conditions: the temperatures of the sections from the feeding port to the die head were 200°C, 230°C, 230°C, and 240°C, the screw rotation speed was 20 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 1.5 m / min, and the temperature of the cooling roll was 60°C, to obtain a nylon 6 film material.

[0034] Example 7 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 1.2 g of dicumyl peroxide and 2 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-butene-1-ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 190°C, 215°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 75 rpm / min, and the feeding speed was 3.6 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 180°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.4 m / min, and the temperature of the cooling roll was 75°C; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0035] Example 8 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 1.2 g of dicumyl peroxide and 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-butene-1-ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 190°C, 215°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 80 rpm / min, and the feeding speed was 4 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 190°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.5 m / min, and the temperature of the cooling roll was 90°C; the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0036] Example 9 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 2 g of dicumyl peroxide and 6 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-buten-1-yl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 190°C, 215°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 90 rpm / min, and the feeding speed was 4.5 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 180°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.7 m / min, and the temperature of the cooling roll was 90°C; and the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0037] Example 10 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 4 g of dicumyl peroxide and 8 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-buten-1-yl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 190°C, 215°C, 225°C, 235°C, 245°C, and 250°C, the screw rotation speed was 100 rpm / min, and the feeding speed was 4.8 Hz; the melt blending and grafting reaction was carried out under the above conditions to obtain antioxidant grafted nylon 6 strands, which were pelletized in a pelletizer to prepare nylon 6 grafting material pellets; the temperature of each section of the single-screw extruder from the feeding port to the die head was 180°C, 230°C, 240°C, and 250°C, the screw rotation speed was 40 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 3 m / min, and the temperature of the cooling roll was 100°C; and the nylon 6 grafting material pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0038] Comparative Example 1 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; a twin-screw extruder had temperatures of 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C at the respective sections from the main feeding port to the die head, the screw rotation speed was 60 rpm / min, and the feeding speed was 3.2 Hz; the nylon 6 pellets were melt blended under the above conditions to obtain nylon 6 strands without antioxidant but after twin-screw processing, and the nylon 6 strands were cut into pellets in a pelletizer to prepare nylon 6 pellets; a single-screw extruder had temperatures of 200°C, 230°C, 230°C, and 240°C at the respective sections from the feeding port to the die head, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.2 m / min, and the temperature of the cooling roll was 60°C; and the nylon 6 pellets prepared above were melt-extruded, drawn, cooled, and wound to obtain a pure nylon 6 film.

[0039] Comparative Example 2 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was uniformly mixed with 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid octadecyl ester (antioxidant 1076) in a high-speed mixer; a twin-screw extruder had temperatures of 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C at the respective sections from the main feeding port to the die head, the screw rotation speed was 80 rpm / min, and the feeding speed was 4.2 Hz; the nylon 6 and the antioxidant were melt blended under the above conditions to obtain nylon 6 blend strands, and the nylon 6 blend strands were cut into pellets in a pelletizer to prepare nylon 6 blend pellets; a single-screw extruder had temperatures of 200°C, 230°C, 230°C, and 240°C at the respective sections from the feeding port to the die head, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.2 m / min, and the temperature of the cooling roll was 80°C; and the nylon 6 blend pellets prepared above were melt-extruded, drawn, cooled, and wound to obtain a nylon 6 film material.

[0040] Comparative Example 3 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 8 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl octadecyl ester (antioxidant 1076) in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C, the screw rotation speed was 90 rpm / min, and the feeding speed was 4.5 Hz; the antioxidant and nylon 6 blend was obtained under the above conditions by melt blending reaction, and the nylon 6 blend pellets were prepared by cutting in a pelletizer; the temperature of each section of the single-screw extruder from the feeding port to the die was 200°C, 230°C, 230°C, and 240°C, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.2 m / min, and the temperature of the cooling roll was 105°C; and the nylon 6 film material was obtained by melting, extruding, stretching, cooling, and winding the nylon 6 blend pellets prepared above.

[0041] Comparative Example 4 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamidomethyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C, the screw rotation speed was 80 rpm / min, and the feeding speed was 4.2 Hz; the antioxidant and nylon 6 blend was obtained under the above conditions by melt blending reaction, and the nylon 6 blend pellets were prepared by cutting in a pelletizer; the temperature of each section of the single-screw extruder from the feeding port to the die was 200°C, 230°C, 230°C, and 240°C, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.2 m / min, and the temperature of the cooling roll was 80°C; and the nylon 6 film material was obtained by melting, extruding, stretching, cooling, and winding the nylon 6 blend pellets prepared above.

[0042] Comparative Example 5 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-buten-1-ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 180°C, 210°C, 220°C, 230°C, 240°C, and 240°C, the screw rotation speed was 80 rpm / min, and the feeding speed was 4.2 Hz; the above-mentioned materials were melt blended under the above-mentioned conditions to obtain an antioxidant and nylon 6 blend thread, which was cut into particles in a pelletizer to prepare nylon 6 blend pellets; the temperature of each section of the single-screw extruder from the feeding port to the die was 180°C, 230°C, 230°C, and 240°C, the screw rotation speed was 30 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.2 m / min, and the temperature of the cooling roll was 80°C; the nylon 6 blend pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0043] Comparative Example 6 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 1.6 g of cumene hydroperoxide and 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid octadecyl ester (antioxidant 1076) in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 185°C, 215°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 90 rpm / min, and the feeding speed was 4.5 Hz; the above-mentioned materials were melt blended under the above-mentioned conditions to obtain an antioxidant and nylon 6 blend thread, which was cut into particles in a pelletizer to prepare nylon 6 blend pellets; the temperature of each section of the single-screw extruder from the feeding port to the die was 190°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.4 m / min, and the temperature of the cooling roll was 80°C; the nylon 6 blend pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0044] Comparative Example 7 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 1.2 g of dicumyl peroxide and 4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl octadecyl ester (antioxidant 1076) in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 185°C, 215°C, 225°C, 235°C, 240°C, and 240°C, the screw rotation speed was 90 rpm / min, and the feeding speed was 4.5 Hz; the melt blending reaction was carried out under the above conditions to obtain an antioxidant and nylon 6 blend wire, which was cut into particles in a pelletizer to prepare nylon 6 blend pellets; the temperature of each section of the single-screw extruder from the feeding port to the die was 190°C, 230°C, 230°C, and 240°C, the screw rotation speed was 35 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 2.4 m / min, and the temperature of the cooling roll was 80°C; the nylon 6 blend pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0045] Comparative Example 8 400 g of nylon 6 pellets were dried in a vacuum drying oven at 100°C for 12 h to remove moisture therefrom; the dried nylon 6 was mixed with 4.8 g of cumene hydroperoxide and 12 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl acrylamide methyl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die was 200°C, 215°C, 225°C, 235°C, 240°C, and 250°C, the screw rotation speed was 100 rpm / min, and the feeding speed was 5 Hz; the melt blending reaction was carried out under the above conditions to obtain an antioxidant and nylon 6 blend wire, which was cut into particles in a pelletizer to prepare nylon 6 blend pellets; the temperature of each section of the single-screw extruder from the feeding port to the die was 190°C, 230°C, 240°C, and 250°C, the screw rotation speed was 40 rpm / min, the linear speeds of the casting roll A, the casting roll B, and the traction roll were all 3 m / min, and the temperature of the cooling roll was 120°C; the nylon 6 blend pellets prepared above were melted, extruded, stretched, cooled, and wound to obtain a nylon 6 film material.

[0046] Comparative Example 9 400 g of nylon 6 pellets were dried in a vacuum oven at 100℃ for 12 h to remove the moisture therefrom; the dried nylon 6 was mixed with 4.8 g of dicumyl peroxide and 12 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid-3-buten-1-yl ester in a high-speed mixer; the temperature of each section of the twin-screw extruder from the main feeding port to the die head was 200℃, 215℃, 225℃, 235℃, 240℃, and 250℃, the screw rotation speed was 100 rpm / min, and the feeding speed was 5 Hz; the antioxidant and nylon 6 blend was obtained under the above conditions, and the nylon 6 blend pellets were prepared by cutting in a pelletizer; the temperature of each section of the single-screw extruder from the feeding port to the die head was 190℃, 230℃, 240℃, and 250℃, the screw rotation speed was 40 rpm / min, the linear speeds of the casting roller A, the casting roller B, and the traction roller were all 3 m / min, and the temperature of the cooling roller was 120℃; and the nylon 6 film material was obtained by melting, extruding, stretching, cooling, and winding the nylon 6 blend pellets.

[0047] The nylon 6 film material prepared by casting in the examples and comparative examples was cut into a rectangular shape of 10×5 cm, and the thickness of the film sample was 90-100 μm. In order to simulate the influence of ultraviolet light, temperature, humidity, and other factors on the material during long-term use in the natural environment, the film was placed in an ultraviolet aging accelerated test box for weather resistance evaluation test, and the aging method was in accordance with GB / T 16422.3-2022 laboratory light source exposure test method: fluorescent ultraviolet lamp. The film sample was taken out after aging for 10 days and 20 days, respectively, and subjected to infrared testing, thermogravimetric analysis, and melting and crystallization behavior analysis.

[0048] The purification process of the reactive antioxidant grafted nylon 6 in the present embodiment was as follows: 5 g of the dried grafted polymer was weighed into a 100 ml single-neck flask, 40 ml of formic acid solution was added, and the flask was placed in an oil bath at 100℃ for heating and dissolution. After 2 h of condensation reflux under magnetic stirring, the heating was stopped, and the reaction solution was poured into 400 ml of acetone solution while hot. After stirring, the solution was allowed to stand until it cooled and became thick, and then it was subjected to suction filtration. The precipitate obtained by suction filtration was washed with acetone 3 times and placed in a vacuum drying oven for drying to constant weight, thereby removing the homopolymer, monomer, and initiator impurities in the grafted polymer, and obtaining the purified grafted polymer.

[0049] The design strategy, advantages, process, and performance of the present application are further described below.

[0050] As Figure 1The figure shows the UV-Vis absorption spectrum of the sample of the grafting of the reactive antioxidant to nylon 6 in the presence or absence of an initiator. The hindered phenol structure of the reactive antioxidant has strong UV absorption at 275-280 nm, while the nylon 6 sample has no UV absorption in this wavelength range. In the presence of an initiator (each example), the reactive antioxidant undergoes a melt grafting reaction in the twin screw, and after purification, there is still obvious UV absorption at 275-280 nm, indicating that the reactive antioxidant is successfully grafted to nylon 6. When no initiator is added (Comparative Examples 4 and 5), the reactive antioxidant and nylon 6 only undergo physical blending in the twin screw, and after purification, the reactive antioxidant is eluted by the solvent, so the sample has almost no UV absorption at 275-280 nm.

[0051] As shown in Figure 2 , the reaction mechanism of the chemical grafting of the reactive antioxidant to nylon 6 is shown. The reactive antioxidant used in the application not only contains a hindered phenol structure, which has excellent free radical scavenging ability, but also introduces an alkenyl controllable reactive group, which undergoes a chemical grafting reaction with the polymer main chain under the conditions of an initiator and high temperature, and has both stability and reactivity. By optimizing the process parameters such as temperature and shear force, the reactive antioxidant is efficiently grafted to the nylon 6 main chain without using a solvent by using a twin-screw melt processing technology, greatly simplifying the process flow and taking into account environmental protection and industrial feasibility. This design strategy solves the problem of strong migration and poor durability of traditional physical blending antioxidants from the molecular structure level, ensuring the long-term effectiveness and low migration of the antioxidant in the material system, and the prepared film material has excellent thermal-oxidative stability, anti-aging ability and surface migration inhibition ability, which is suitable for the automotive, electrical and outdoor engineering fields with extremely high requirements for material stability, and shows good application prospects and industrialization potential.

[0052] After aging for 0 days, 10 days and 20 days, the nylon 6 film samples were tested by infrared spectroscopy. The Nicolet iS50 infrared spectrometer was used, the scanning range was 4000-500 cm -1 , the resolution was 4 cm -1 , the scanning times were 32, and the data acquisition and processing were performed using the OMNIC software of the infrared spectrometer. The absorption peak of N-H (3296 cm -1 ) was selected as the characteristic peak, and the absorption peak of methylene-CH2- (2860 cm -1 ) was selected as the reference peak. Table 1 lists the relative retention rate of N-H functional groups of the examples and comparative examples with the change of aging time.

[0053] Table 1 - Relative retention rate of N-H functional groups of nylon 6 with change of aging time

[0054]

[0055] The nylon 6 film samples after aging for 0 days, 10 days, 20 days were tested by differential scanning calorimetry, using a DSC 214 Polyma differential scanning calorimeter, all DSC tests were carried out under the protection of nitrogen, the heating and cooling rate was 10℃ / min, Table 2 lists the crystallinity of the nylon 6 after different aging time of the examples and comparative examples.

[0056] Table 2 - Crystallinity of nylon 6 after different aging time

[0057]

[0058] The nylon 6 film samples after aging for 0 days, 10 days, 20 days were tested by mechanical property, according to GB / T 1040.1-2018 standard using UTM4304 type universal testing machine to test the mechanical properties of the material, the sample was dumbbell type, the effective tensile length was 15mm, the width was 3mm, the thickness was 0.1mm, the tensile rate was 10mm / min, 5 groups were measured and the average value was taken. Table 3 lists the tensile strength of the examples and comparative examples after different aging time.

[0059] Table 3 - Tensile strength of nylon 6 after different aging time

[0060]

[0061] In the present application, with the change of the addition amount of reactive or blended antioxidant, the nylon 6 composite film material presents a certain dose-dependent trend in the aspects of anti-aging performance, crystallization behavior and mechanical properties. Specifically, when the antioxidant is added in the range of 0.1% to 2% by mass fraction, it can effectively inhibit the thermal-oxidative degradation and free radical chain scission of polyamide molecular chain during high-temperature processing and ultraviolet aging, thereby slowing down the downward trend of the relative retention rate of functional groups, crystallinity and tensile strength. The addition of antioxidant in this stage enhances the stability of the main chain at the molecular level, maintains the good crystal structure of the polymer, and is beneficial to the maintenance of the comprehensive performance of the material. However, when the addition amount of antioxidant is further increased to more than 2%, the mechanism of action changes. Excessive reactive antioxidant may cause excessive grafting or chaotic segment structure, which interferes with the regularity of polymer chain and crystallization behavior, and reduces the crystallinity. At the same time, the unreacted or aggregated antioxidant residues in the material may become a source of structural defects, which weakens the mechanical properties of the material. In addition, for blended antioxidants (such as antioxidant 1076), at high addition amount, the compatibility may decrease, the migration may increase, or the processing degradation side reaction may occur, and the crystallinity and tensile strength may decrease. It is shown that there is an optimal concentration range for the addition of antioxidant, and excessive use may cause adverse effects. Based on the test results of the relative retention rate of functional groups, crystallinity and tensile strength, the order of thermal-oxidative aging resistance is: reactive antioxidant grafted nylon 6 > added antioxidant blended with nylon 6 > pure nylon 6, which shows that the reactive antioxidant forms a covalent bond with the polymer main chain through grafting reaction, which not only prevents the migration or precipitation of antioxidant, but also significantly improves the stability and service life of the material.

[0062] Finally, the above examples are used to illustrate the technical solutions described in the present application, but not to limit the technical solutions described in the present application. Those skilled in the art can modify or equivalently replace the present application on the basis of the present application, but all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered in the scope of claims of the present application.

Claims

1. A method for preparing reactive antioxidant-grafted modified nylon 6, characterized in that, include: 100 parts by weight of nylon 6, 0.05-1 parts by weight of initiator and 0.1-2 parts by weight of reactive antioxidant are mixed evenly and added to a twin-screw extruder. Modified nylon 6 is obtained by melt reaction, extrusion, traction, pelletizing and drying. The reactive antioxidant contains vinyl unsaturated groups and a hindered phenolic structure with antioxidant activity. The modified nylon 6 is obtained by grafting the reactive antioxidant onto the molecular chain of nylon 6.

2. The method for preparing a reactive antioxidant grafted modified nylon 6 according to claim 1, characterized in that, The reactive antioxidant is methyl acrylamide 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or 3-butene-1-ester 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

3. The method for preparing a reactive antioxidant grafted modified nylon 6 according to claim 1, characterized in that, The initiator is cumene hydroperoxide or di-tert-butyl cumene hydroperoxide.

4. The method for preparing a reactive antioxidant grafted modified nylon 6 according to claim 3, characterized in that, The initiator is cumene hydroperoxide.

5. The method for preparing a reactive antioxidant grafted modified nylon 6 according to claim 1, characterized in that, The temperature of the melt reaction in the twin-screw extruder is 180~250℃.

6. The method for preparing a reactive antioxidant grafted modified nylon 6 according to claim 1, characterized in that, The temperatures of the twin-screw extruder from the main feed port to the die head are: 180~200℃, 210~220℃, 220~230℃, 230~240℃, 240~250℃, and 240~250℃; the screw speed is 60~100 rpm.

7. A method for preparing a reactive antioxidant-grafted modified nylon 6 film, characterized in that, Modified nylon 6 prepared by the method according to any one of claims 1-6 is added to a single screw extruder and melted, extruded, and cooled and drawn in a casting machine to obtain a modified nylon 6 film.

8. The method for preparing reactive antioxidant-grafted modified nylon 6 film according to claim 7, characterized in that, The temperatures of each section of the single-screw extruder from the feed port to the die head are: 180~200℃, 220~230℃, 230~240℃, and 240~250℃, and the screw speed is 20~40 rpm.

9. The method for preparing reactive antioxidant-grafted modified nylon 6 film according to claim 7, characterized in that, The casting machine includes casting roll A, casting roll B, traction roll and cooling roll. The linear speed of each roll is 1.5~3m / min and the temperature of the cooling roll is 60~120℃.

Images