Modified polyvinyl chloride composite material for cable and preparation method thereof

Abstract

The invention relates to the field of cables, and discloses a modified polyvinyl chloride composite material for cables and a preparation method thereof.The composite material comprises low-density polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer, nitrile rubber, modified graphene oxide, modified nano calcium carbonate and auxiliaries; the modified graphene oxide is prepared by reacting acylating chlorination of graphene oxide with an anti-aging derivative, the anti-aging derivative is prepared by reducing a benzoxazole-containing intermediate generated by a reaction of 2-amino-4-bromophenol and 4-cyanobenzaldehyde to obtain an aminated benzoxazole-containing intermediate, then the aminated benzoxazole-containing intermediate reacts with p-phenylenediamine, and then the product reacts with 3-(3, 4-dichlorophenyl)-1, 2, 3-triazole-3-one to obtain the anti-aging graphene oxide. 2, 5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride is subjected to a reaction to prepare the product. And the modified nano calcium carbonate is prepared by reacting phosphonitrilic chloride trimer with an amino silane coupling agent and 2-amino benzoxazole-5-borate and then grafting on the surface of the nano calcium carbonate. The composite material prepared by the invention has excellent flame retardance, heat resistance and long-acting oxidation resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and particularly relates to a modified polyvinyl chloride composite material for cables and a preparation method thereof. Background Art

[0002] Cable materials are polymer materials applied to the insulation and protection of wires and cables, and are mainly divided into several categories such as rubber, plastic, and nylon. Currently, the main organic polymer materials used for preparing cable materials are plastics and rubbers. Among them, plastics such as polyvinyl chloride plastics and cross-linked polyethylene plastics have poor flame retardancy; rubbers such as ethylene-propylene rubber materials and silicone rubber materials generally have general flame retardancy and mechanical properties. With the progress of power communication technology promoting the development and improvement of circuits, the occurrence of cable and wire fires not only affects the efficiency of data transmission, but may also cause environmental damage and production losses. Therefore, it is extremely important to adopt high-quality flame retardant cable materials for communication safety.

[0003] As a common thermoplastic, polyvinyl chloride is often used in the cable field due to its excellent mechanical properties and low thermal conductivity. The polyvinyl chloride molecular structure contains a large number of chlorine atoms, which makes polyvinyl chloride have inherent flame retardancy. However, during the processing of polyvinyl chloride, a large amount of processing aids (such as plasticizers, lubricants, stabilizers, and coupling agents, etc.) are often added to obtain a polyvinyl chloride material with excellent comprehensive properties. However, the addition of a large amount of aids destroys the inherent flame retardancy of polyvinyl chloride, making polyvinyl chloride flammable under high-temperature conditions. When polyvinyl chloride thermally degrades or burns, it will produce a large amount of hydrogen chloride gas and release toxic black smoke. Therefore, it is extremely important to adopt high-quality flame retardant polyvinyl chloride cable materials for communication and life safety.

[0004] In order to improve the flame retardancy of cable materials in the prior art, a large amount of inorganic flame retardants are often added. Since small molecule flame retardants have poor compatibility with materials, they will reduce the mechanical properties of materials, and will also make the viscosity, compatibility, and flexibility of polymer materials poor. In addition, in the prior art, by introducing non-reactive cyclotriphosphazene derivatives into cable materials in a physical blending manner, there is a problem of migration and exudation, and the stability of the properties of the obtained products is generally poor; in addition, existing cable materials often choose polyolefins. Although they have high dielectric strength, in actual application, the disadvantages of poor heat-oxygen aging resistance and poor high-temperature resistance of cable materials limit their further application. The prior art adds hindered phenol antioxidants and amine antioxidants, but small molecule antioxidants are easily volatilized and migrated during the processing and subsequent use of cable materials, and cannot ensure the long-term antioxidant performance of cable materials. Therefore, there are still difficulties in actual application. Summary of the Invention

[0005] To solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a modified polyvinyl chloride composite material for cables and its preparation method. By adding modified graphene oxide and modified nano-calcium carbonate, the composite material is endowed with excellent flame retardancy, heat resistance and long-term antioxidant properties.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A modified polyvinyl chloride composite material for cables, comprising the following raw materials in parts by weight: 40 - 70 parts of low-density polyethylene, 30 - 55 parts of polyvinyl chloride, 20 - 35 parts of ethylene-vinyl acetate copolymer, 10 - 20 parts of nitrile rubber, 3 - 8 parts of modified graphene oxide, 2 - 6 parts of modified nano-calcium carbonate, 0.5 - 2.5 parts of stabilizer, 1 - 2 parts of plasticizer, 1 - 3 parts of lubricant, 0.5 - 1 part of antioxidant; The modified graphene oxide is prepared by acyl chlorinating graphene oxide with thionyl chloride and then carrying out an acylation reaction with an anti-aging derivative. The anti-aging derivative is prepared by cyclizing 2-amino-4-bromophenol and 4-cyanobenzaldehyde to generate a benzoxazole-containing intermediate, which is reduced by hydrogen under the action of a Raney-Ni catalyst. After the prepared amino-containing benzoxazole intermediate undergoes a substitution reaction with p-phenylenediamine, it is then subjected to an acylation reaction with 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride; The modified nano-calcium carbonate is prepared by grafting a cyclotriphosphazene derivative onto the surface of nano-calcium carbonate through a chemical reaction. The cyclotriphosphazene derivative is prepared by substituting hexachlorocyclotriphosphazene with γ-aminopropyltriethoxysilane and 2-aminobenzoxazole-5-borate.

[0007] Preferably, the preparation method of the modified graphene oxide includes the following steps: (1) Take 2-amino-4-bromophenol and 4-cyanobenzaldehyde in a reactor, add triethylamine and samarium trifluoromethanesulfonate, then add a mixed solvent of ethanol and deionized water, and reflux at 70 - 80 °C under a nitrogen atmosphere for 10 - 12 h. After the reaction is completed, pour the reaction solution into deionized water, filter by suction, and purify with a silica gel chromatography column to prepare a benzoxazole-containing intermediate; (2) Take 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid in a reactor, add chloroform solvent, heat to 50 - 60 °C, slowly dropwise add thionyl chloride, and stir and react for 4 - 6 h. After the reaction is completed, remove the unreacted substances by rotary evaporation to prepare 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride; (3) Take the benzoxazole-containing intermediate and tetrahydrofuran in a reactor, stir and mix, then add a Raney-Ni catalyst, and then stir at room temperature under a hydrogen pressure for 4 - 5 h. After the reaction is completed, filter and concentrate to prepare an amino-containing benzoxazole intermediate; (4) Take the amino-functionalized benzoxazole intermediate, p-phenylenediamine, and triethylamine in a reactor, add tetrahydrofuran as a solvent, place it at 55 - 70 °C and stir for 2 - 4 h. After the reaction is completed, perform suction filtration, washing, and drying to prepare the modified amino-functionalized benzoxazole intermediate; (5) Take the modified amino-functionalized benzoxazole intermediate and anhydrous dichloromethane in a reactor, add 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride and triethylamine, stir and react for 8 - 12 h. After the reaction is completed, perform suction filtration, washing, and drying to prepare the anti-aging derivative; (6) Take graphene oxide and ultrasonically disperse it in thionyl chloride, heat it to 75 - 85 °C, stir and react for 2 - 6 h, then remove thionyl chloride. Ultrasonically disperse the obtained acyl-chlorinated graphene oxide in N,N-dimethylformamide, then add the anti-aging derivative, place it at 110 - 125 °C and reflux for 20 - 24 h. After the reaction is completed, perform suction filtration, washing, and drying to prepare the modified graphene oxide.

[0008] Preferably, in the step (4), the molar ratio of the amino-functionalized benzoxazole intermediate to p-phenylenediamine is 1:1 - 1.2.

[0009] Preferably, in the step (5), the molar ratio of the modified amino-functionalized benzoxazole intermediate to 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride is 1:1 - 1.2.

[0010] Preferably, the preparation method of the modified nano-calcium carbonate includes the following steps: A. Take hexachlorocyclotriphosphazene, tetrahydrofuran, and triethylamine in a reactor under a nitrogen atmosphere, stir to dissolve hexachlorocyclotriphosphazene, add a mixed solution of γ-aminopropyltriethoxysilane and tetrahydrofuran, place it at 40 - 55 °C and stir for 4 - 6 h, then add 2-aminobenzoxazole-5-borate, and continue to react for 8 - 12 h. After the reaction is completed, perform filtration, washing, and drying to prepare the cyclotriphosphazene derivative; B. Take nano-calcium carbonate and ultrasonically disperse it in a mixed solution of absolute ethanol and deionized water, then add the cyclotriphosphazene derivative, place it at 55 - 70 °C and stir for 4 - 8 h. After the reaction is completed, perform centrifugation, washing, and drying to prepare the modified nano-calcium carbonate.

[0011] Preferably, in the step A, the molar ratio of hexachlorocyclotriphosphazene, γ-aminopropyltriethoxysilane, and 2-aminobenzoxazole-5-borate is 1:1 - 1.2:5 - 5.1.

[0012] Preferably, the stabilizer is one of calcium-zinc stabilizer and organotin stabilizer.

[0013] Preferably, the plasticizer is one or a combination of more of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate.

[0014] Preferably, the lubricant is one of stearic acid, polyethylene wax, and oxidized polyethylene wax; the antioxidant is one or a combination of more of antioxidant 1010, antioxidant 168, antioxidant 1024, and antioxidant 1076.

[0015] A preparation method of a modified polyvinyl chloride composite material for cables comprises the following steps: weighing each raw material by weight parts, mixing low-density polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer, nitrile rubber, modified graphene oxide, modified nano calcium carbonate, plasticizer, stabilizer, lubricant, and antioxidant evenly to obtain a mixture, and putting the mixture into a twin-screw extruder for extrusion molding to prepare the modified polyvinyl chloride composite material for cables.

[0016] The beneficial effects of the present invention: The present invention utilizes the cyclization reaction of 2-amino-4-bromophenol and 4-cyanobenzaldehyde. After the amino group in the structure of 2-amino-4-bromophenol condenses with the aldehyde group in the structure of 4-cyanobenzaldehyde, the phenolic hydroxyl group in the structure of 2-amino-4-bromophenol attacks the formed cyano group to undergo intramolecular cyclization, generating a benzoxazole-containing intermediate. Then, the benzoxazole-containing intermediate is reduced by hydrogen under the action of a Raney-Ni catalyst to catalyze the hydrogenation of the introduced cyano group in its structure to generate a primary amine, thereby preparing an amino-functionalized benzoxazole intermediate. Then, the bromine atom in its structure undergoes a substitution reaction with the amino group at one end of the antioxidant p-phenylenediamine to prepare a modified amino-functionalized benzoxazole intermediate. Subsequently, it undergoes an acylation reaction with 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride to prepare an antioxidant derivative.

[0017] The present invention utilizes thionyl chloride to acyl-chlorinate graphene oxide and then undergoes an acylation reaction with the un-grafted amino group in the structure of the antioxidant derivative to prepare modified graphene oxide, thereby firmly bonding the hindered phenol antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid and the antioxidant p-phenylenediamine in the graphene oxide lamellar structure through strong chemical bonds, thereby restricting the volatilization and migration phenomenon of the antioxidant derivative in the cable material, and further realizing the long-term antioxidant performance of the cable material. Moreover, a highly heat-resistant benzoxazole group is introduced into the graphene oxide lamellar structure, improving the high-temperature resistance performance of the cable material. In addition, after the surface of graphene oxide is modified by the antioxidant derivative, the interlayer spacing of graphene oxide is increased, which is beneficial to the uniform dispersion of graphene oxide and avoids the performance defects caused by the aggregation of graphene oxide.

[0018] In the present invention, a substitution reaction occurs between the chlorine atoms in the structure of hexachlorocyclotriphosphazene and one molecule of γ-aminopropyltriethoxysilane. Subsequently, a substitution reaction occurs between the amino group in 2-aminobenzoxazole-5-borate and the remaining unreacted chlorine atoms in the hexachlorocyclotriphosphazene structure to prepare a cyclotriphosphazene derivative. Then, a condensation reaction occurs between the introduced silicon hydroxyl groups in the cyclotriphosphazene derivative structure and the hydroxyl groups on the surface of nano-calcium carbonate to prepare a modified nano-calcium carbonate. Thus, a cyclotriphosphazene derivative with the synergistic flame retardancy of N, P, and B elements and a high heat-resistant benzoxazole group is introduced onto the surface of nano-calcium carbonate, endowing the cable material with long-term flame retardancy and heat resistance. At the same time, the grafting reaction is beneficial to improving the lipophilicity of the nano-calcium carbonate surface, promoting the relatively uniform dispersion of nano-calcium carbonate in the cable material. Detailed implementation manners

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0020] Example 1 A preparation method of modified graphene oxide includes the following steps: (1) Take 2.1 g of 2-amino-4-bromophenol and 2.6 g of 4-cyanobenzaldehyde in a reactor, add 2 g of triethylamine and 0.6 g of samarium trifluoromethanesulfonate, then add a mixed solvent of 50 mL of ethanol and 50 mL of deionized water, and reflux at 75 °C for 12 h under a nitrogen atmosphere. After the reaction is completed, pour the reaction solution into deionized water, filter by suction, and purify with a silica gel chromatography column. The eluent is ethyl acetate - petroleum ether with a volume ratio of 1:9 to prepare a benzoxazole intermediate. (2) Take 2.8 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid in a reactor, add 30 mL of chloroform solvent, heat to 50 °C, slowly dropwise add 2 mL of thionyl chloride, and stir and react for 5 h. After the reaction is completed, remove the unreacted substances by rotary evaporation to prepare 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride. (3) Take 3 g of the benzoxazole intermediate and 50 mL of tetrahydrofuran in a reactor, stir and mix, then add 0.2 g of Raney-Ni catalyst, and then stir at room temperature under a hydrogen pressure of 0.3 MPa for 5 h. After the reaction is completed, filter and concentrate to prepare an amino-functionalized benzoxazole intermediate. (4) Take 3 g of the amino-functionalized benzoxazole intermediate, 1.1 g of p-phenylenediamine, and 1 g of triethylamine in a reactor, add 50 mL of tetrahydrofuran solvent, place it at 65 °C and stir for 3 h. After the reaction is completed, filter, wash, and dry to prepare the modified amino-functionalized benzoxazole intermediate; (5) Take 3.3 g of the modified amino-functionalized benzoxazole intermediate and 60 mL of anhydrous dichloromethane in a reactor, add 3.1 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride and 1 g of triethylamine, stir and react for 12 h. After the reaction is completed, filter, wash, and dry to prepare the anti-aging derivative; (6) Take 5 g of graphene oxide and ultrasonically disperse it in thionyl chloride. Heat it to 80 °C and stir for 4 h, then remove thionyl chloride. Ultrasonically disperse the obtained acyl chloride graphene oxide in 100 mL of N,N-dimethylformamide, then add 3.2 g of the anti-aging derivative, place it at 120 °C and reflux for 24 h. After the reaction is completed, filter, wash, and dry to prepare the modified graphene oxide.

[0021] Example 2 A method for preparing modified nano-calcium carbonate includes the following steps: A. In a nitrogen atmosphere, take 3.4 g of hexachlorocyclotriphosphazene, 50 mL of tetrahydrofuran, and 7 g of triethylamine in a reactor, stir to dissolve hexachlorocyclotriphosphazene, add a mixed solution of 2.2 g of γ-aminopropyltriethoxysilane and 10 mL of tetrahydrofuran, place it at 50 °C and stir for 4 h, then add 13 g of 2-aminobenzoxazole-5-borate, and continue to react for 12 h. After the reaction is completed, filter, wash, and dry to prepare the cyclotriphosphazene derivative; B. Take 5 g of nano-calcium carbonate and ultrasonically disperse it in a mixed solution of 90 mL of absolute ethanol and 10 mL of deionized water, then add 3.5 g of the cyclotriphosphazene derivative, place it at 65 °C and stir for 7 h. After the reaction is completed, centrifuge, wash, and dry to prepare the modified nano-calcium carbonate.

[0022] Example 3 A modified polyvinyl chloride composite material for cables includes the following raw materials by weight: 44 parts of low-density polyethylene, 32 parts of polyvinyl chloride, 21 parts of ethylene-vinyl acetate copolymer, 10 parts of nitrile rubber, 3 parts of the modified graphene oxide prepared in Example 1, 2.5 parts of the modified nano-calcium carbonate prepared in Example 2, 0.7 part of calcium-zinc stabilizer, 1 part of plasticizer dioctyl adipate, 1 part of lubricant stearic acid, 0.5 part of antioxidant 1010.

[0023] The preparation method of the modified polyvinyl chloride composite material for cable comprises the following steps: weighing each raw material by weight, uniformly mixing low-density polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer, nitrile rubber, modified graphene oxide, modified nano-calcium carbonate, plasticizer, stabilizer, lubricant and antioxidant to obtain a mixture, putting the mixture into a twin-screw extruder for extrusion molding, and preparing the modified polyvinyl chloride composite material for cable.

[0024] Example 4 A modified polyvinyl chloride composite material for cables comprises the following raw materials in parts by weight: 56 parts of low-density polyethylene, 43 parts of polyvinyl chloride, 30 parts of ethylene-vinyl acetate copolymer, 14 parts of nitrile rubber, 5 parts of modified graphene oxide prepared in Example 1, 4 parts of modified nano-calcium carbonate prepared in Example 2, 1.5 parts of calcium zinc stabilizer, 1.4 parts of plasticizer dimethyl phthalate, 2 parts of lubricant polyethylene wax, and 0.7 parts of antioxidant 1010.

[0025] The preparation method of the modified polyvinyl chloride composite material for the above-mentioned cable is the same as that in Example 3.

[0026] Example 5 A modified polyvinyl chloride composite material for cables comprises the following raw materials in parts by weight: 63 parts of low-density polyethylene, 50 parts of polyvinyl chloride, 32 parts of ethylene-vinyl acetate copolymer, 17 parts of nitrile rubber, 7 parts of modified graphene oxide prepared in Example 1, 5 parts of modified nano-calcium carbonate prepared in Example 2, 2 parts of calcium zinc stabilizer, 1.8 parts of plasticizer dioctyl phthalate, 2.5 parts of lubricant oxidized polyethylene wax, and 0.8 parts of antioxidant 1010.

[0027] The preparation method of the modified polyvinyl chloride composite material for the above-mentioned cable is the same as that in Example 3.

[0028] Comparative Example 1 A method for preparing modified nano calcium carbonate comprises the following steps: A. In a nitrogen atmosphere, 3.4 g of hexachlorocyclotriphosphazene, 50 mL of tetrahydrofuran and 7 g of triethylamine were placed in a reactor, and the hexachlorocyclotriphosphazene was dissolved by stirring. A mixed solution of 2.2 g of γ-aminopropyltriethoxysilane and 10 mL of tetrahydrofuran was added, and the mixture was stirred at 50° C. for 4 h. After the reaction was completed, the mixture was filtered, washed and dried to prepare a cyclotriphosphazene derivative; B. Take 5 g of nano-calcium carbonate and ultrasonically disperse it in a mixed solution of 90 mL of anhydrous ethanol and 10 mL of deionized water, then add 3.5 g of a cyclotriphosphazene derivative, stir and react at 65° C. for 7 hours. After the reaction is completed, centrifuge, wash and dry to prepare modified nano-calcium carbonate.

[0029] Comparative Example 2 A modified polyvinyl chloride composite material for cables comprises the following raw materials in parts by weight: 63 parts of low-density polyethylene, 50 parts of polyvinyl chloride, 32 parts of ethylene-vinyl acetate copolymer, 17 parts of nitrile rubber, 7 parts of graphene oxide, 5 parts of modified nano calcium carbonate prepared in Example 2, 2 parts of calcium-zinc stabilizer, 1.8 parts of plasticizer dioctyl phthalate, 2.5 parts of lubricant oxidized polyethylene wax, 0.8 part of antioxidant 1010.

[0030] The preparation method of the above-mentioned modified polyvinyl chloride composite material for cables is the same as that of Example 3.

[0031] Comparative Example 3 A modified polyvinyl chloride composite material for cables, comprising the following raw materials in parts by weight: 63 parts of low-density polyethylene, 50 parts of polyvinyl chloride, 32 parts of ethylene-vinyl acetate copolymer, 17 parts of nitrile rubber, 7 parts of modified graphene oxide prepared in Example 1, 5 parts of modified nano calcium carbonate prepared in Comparative Example 1, 2 parts of calcium-zinc stabilizer, 1.8 parts of plasticizer dioctyl phthalate, 2.5 parts of lubricant oxidized polyethylene wax, 0.8 part of antioxidant 1010.

[0032] The preparation method of the above-mentioned modified polyvinyl chloride composite material for cables is the same as that of Example 3.

[0033] Comparative Example 4 A modified polyvinyl chloride composite material for cables, comprising the following raw materials in parts by weight: 63 parts of low-density polyethylene, 50 parts of polyvinyl chloride, 32 parts of ethylene-vinyl acetate copolymer, 17 parts of nitrile rubber, 7 parts of modified graphene oxide prepared in Example 1, 5 parts of nano calcium carbonate, 2 parts of calcium-zinc stabilizer, 1.8 parts of plasticizer dioctyl phthalate, 2.5 parts of lubricant oxidized polyethylene wax, 0.8 part of antioxidant 1010.

[0034] The preparation method of the above-mentioned modified polyvinyl chloride composite material for cables is the same as that of Example 3.

[0035] Performance testing Perform performance testing on the composite materials prepared in Examples 3-5 and Comparative Examples 2-4: (1) Flame retardancy and heat resistance testing: The flame retardancy is tested by the limiting oxygen index test and the vertical burning test; the heat resistance is tested by a thermogravimetric analyzer. Under nitrogen protection, the temperature is raised from room temperature to 800 °C at a rate of 5 °C / min, and the initial decomposition temperature of the material is recorded. The data results are shown in Table 1.

[0036] Table 1 Test results of the flame retardancy of the samples

[0037] As can be seen from the data in Table 1, the composite materials prepared in Examples 3-5 of the present invention have excellent flame retardancy and heat resistance. Among them, in Comparative Example 2, graphene oxide was not modified, and the measured initial decomposition temperature was lower than that in Examples 3-5. The reason is that no highly heat-resistant benzoxazole groups were introduced into the structure of graphene oxide, resulting in a decrease in heat resistance. In Comparative Example 3, the modified nano-calcium carbonate component added did not graft 2-aminobenzoxazole-5-borate, and in Comparative Example 4, nano-calcium carbonate was not modified. The measured flame retardancy and heat resistance of Comparative Examples 3-4 were lower than those in Examples 3-5, and the decrease in flame retardancy in Comparative Example 4 was obvious, indicating that the grafting of cyclotriphosphazene derivatives greatly improved the flame retardancy and heat resistance of the composite materials.

[0038] (2)Mechanical property testing: The tensile strength and elongation at break were tested in accordance with GB / T 528-2009; the tear strength was tested in accordance with GB / T 529-2008, and the data results are shown in Table 2.

[0039] Table 2 Test results of the mechanical properties of the samples

[0040] As can be seen from the data in Table 2, the composite materials prepared in Examples 3-5 of the present invention and Comparative Example 3 have the characteristics of high tensile strength and being not easily broken. Among them, in Comparative Example 2, graphene oxide was not modified, and in Comparative Example 4, nano-calcium carbonate was not modified. The measured mechanical properties of Comparative Examples 2 and 4 were worse than those in Examples 3-5. The possible reason is that the agglomeration of graphene oxide and nano-calcium carbonate led to a decrease in mechanical properties.

[0041] (3)Heat-resistant oxygen aging property testing: The samples were placed in an air heat aging test chamber for high-temperature heat-oxygen aging at 100 °C. The aging cycle was divided into four test cycles of 3, 6, 12, and 24 days. Five samples were taken in each cycle, and the oxidation induction time of each sample was tested to evaluate the heat-resistant oxygen aging property of the samples. The data results are shown in Table 3.

[0042] Table 3 Test results of the heat-resistant oxygen aging properties of the samples

[0043] As can be seen from the data in Table 3, the composite materials prepared in Examples 3-5 of the present invention have a longer oxidation induction time, and still maintain a longer oxidation induction time after 24 days of heat-oxygen aging process, and have excellent heat-resistant oxygen aging properties. Among them, in Comparative Example 2, graphene oxide was not modified, and the measured oxidation induction time was significantly shorter than that in Examples 3-5. The reason is that no anti-aging derivatives were modified on the surface of graphene oxide, resulting in worse long-term heat-resistant oxygen aging properties than those in Examples 3-5.

[0044] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0045] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A modified polyvinyl chloride composite material for cables, characterized in that, It includes the following raw materials in parts by weight: 40-70 parts of low-density polyethylene, 30-55 parts of polyvinyl chloride, 20-35 parts of ethylene-vinyl acetate copolymer, 10-20 parts of nitrile rubber, 3-8 parts of modified graphene oxide, 2-6 parts of modified nano calcium carbonate, 0.5-2.5 parts of stabilizer, 1-2 parts of plasticizer, 1-3 parts of lubricant, and 0.5-1 part of antioxidant; The modified graphene oxide is prepared by acylating graphene oxide with thionyl chloride and then reacting with an antioxidant derivative. The antioxidant derivative is prepared by cyclizing 2-amino-4-bromophenol and 4-cyanobenzaldehyde to form a benzoxazole intermediate, reducing it with hydrogen under the action of a Raney-Ni catalyst, and then acylating the prepared amino-functionalized benzoxazole intermediate with p-phenylenediamine and then reacting with 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride; The modified nano calcium carbonate is prepared by grafting a cyclotriphosphazene derivative onto the surface of nano calcium carbonate through a chemical reaction. The cyclotriphosphazene derivative is prepared by substituting hexachlorocyclotriphosphazene with γ-aminopropyltriethoxysilane and 2-aminobenzoxazole-5-borate; 2. The modified polyvinyl chloride composite material for cables according to claim 1, wherein The preparation method of the modified graphene oxide includes the following steps: (1) Take 2-amino-4-bromophenol and 4-cyanobenzaldehyde in a reactor, add triethylamine and samarium trifluoromethanesulfonate, then add a mixed solvent of ethanol and deionized water, reflux at 70-80 °C under a nitrogen atmosphere for 10-12 h. After the reaction is completed, pour the reaction solution into deionized water, filter by suction, and purify with a silica gel chromatography column to obtain the benzoxazole intermediate; (2) Take 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid in a reactor, add chloroform solvent, heat to 50-60 °C, slowly dropwise add thionyl chloride, stir and react for 4-6 h. After the reaction is completed, remove the unreacted substances by rotary evaporation to obtain 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride; (3) Take the benzoxazole intermediate and tetrahydrofuran in a reactor, stir and mix, then add a Raney-Ni catalyst, and then stir at room temperature under a hydrogen pressure for 4-5 h. After the reaction is completed, filter and concentrate to obtain the amino-functionalized benzoxazole intermediate; (4) Take the amino-functionalized benzoxazole intermediate, p-phenylenediamine and triethylamine in a reactor, add tetrahydrofuran solvent, stir and react at 55-70 °C for 2-4 h. After the reaction is completed, filter by suction, wash, and dry to obtain the modified amino-functionalized benzoxazole intermediate; (5) Take the modified amino-functionalized benzoxazole intermediate and anhydrous dichloromethane in a reactor, add 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride and triethylamine, stir and react for 8-12 h. After the reaction is completed, filter by suction, wash, and dry to obtain the antioxidant derivative; (6) Graphene oxide was taken and ultrasonically dispersed in thionyl chloride. The temperature was raised to 75 - 85 °C, and after stirring and reacting for 2 - 6 h, thionyl chloride was removed. The obtained acyl chloride graphene oxide was ultrasonically dispersed in N,N - dimethylformamide, and then an antioxidant derivative was added. It was refluxed and reacted at 110 - 125 °C for 20 - 24 h. After the reaction was completed, it was filtered, washed, and dried to prepare modified graphene oxide.

3. The modified polyvinyl chloride composite material for cables according to claim 2, wherein, In the step (4), the molar ratio of the amino - containing benzoxazole intermediate to p - phenylenediamine is 1:1 - 1.

2.

4. The modified polyvinyl chloride composite material for cables according to claim 2, wherein In the step (5), the molar ratio of the modified amino - containing benzoxazole intermediate to 3 - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionyl chloride is 1:1 - 1.

2.

5. The modified polyvinyl chloride composite material for cables according to claim 1, wherein The preparation method of the modified nano - calcium carbonate includes the following steps: A. In a nitrogen atmosphere, hexachlorocyclotriphosphazene, tetrahydrofuran, and triethylamine were taken in a reactor, and stirred to dissolve hexachlorocyclotriphosphazene. A mixed solution of γ - aminopropyltriethoxysilane and tetrahydrofuran was added, and it was stirred and reacted at 40 - 55 °C for 4 - 6 h. Then 2 - aminobenzoxazole - 5 - borate was added and the reaction continued for 8 - 12 h. After the reaction was completed, it was filtered, washed, and dried to prepare a cyclotriphosphazene derivative. B. Nano - calcium carbonate was taken and ultrasonically dispersed in a mixed solution of absolute ethanol and deionized water, and then the cyclotriphosphazene derivative was added. It was stirred and reacted at 55 - 70 °C for 4 - 8 h. After the reaction was completed, it was centrifuged, washed, and dried to prepare modified nano - calcium carbonate.

6. The modified polyvinyl chloride composite material for cables according to claim 5, characterized in that, In the step A, the molar ratio of hexachlorocyclotriphosphazene, γ - aminopropyltriethoxysilane, and 2 - aminobenzoxazole - 5 - borate is 1:1 - 1.2:5 - 5.

1.

7. The modified polyvinyl chloride composite material for cables according to claim 1, wherein The stabilizer is one of calcium - zinc stabilizer and organotin stabilizer.

8. The modified polyvinyl chloride composite material for cables according to claim 1, wherein, The plasticizer is one or a combination of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate.

9. The modified polyvinyl chloride composite material for cables according to claim 1, characterized in that, The lubricant is one of stearic acid, polyethylene wax, and oxidized polyethylene wax; the antioxidant is one or a combination of antioxidant 1010, antioxidant 168, antioxidant 1024, and antioxidant 1076.

10. A method for preparing a modified polyvinyl chloride composite material for cables according to any one of claims 1 to 9, characterized in that, It includes the following steps: Weigh each raw material by weight parts. Low - density polyethylene, polyvinyl chloride, ethylene - vinyl acetate copolymer, nitrile rubber, modified graphene oxide, modified nano - calcium carbonate, plasticizer, stabilizer, lubricant, and antioxidant were kneaded evenly to obtain a mixture. The mixture was put into a twin - screw extruder and extruded into shape to prepare a modified polyvinyl chloride composite material for cables.

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