Flexible EVA cable sheath material and preparation method thereof

Abstract

The invention relates to the technical field of cable materials, and provides a flexible EVA cable sheath material and a preparation method thereof. The cable sheath material is prepared from the following raw materials in parts by weight: 25 to 50 parts of ethylene-vinyl acetate copolymer EVA, 15 to 30 parts of ultra-low density polyethylene, 2 to 10 parts of grafted EVA, 2 to 10 parts of flame retardant, 2 to 10 parts of polydopamine modified montmorillonite-boron nitride fiber composite material, 0.5 to 3 parts of flexibilizer, 0.2 to 1 part of silicone and 0.2 to 1 part of organopolysiloxane. A grafting monomer for grafting EVA comprises maleic anhydride and / or an acrylate compound; the polydopamine modified montmorillonite-boron nitride fiber composite material is prepared from montmorillonite, boron nitride fibers, hydroxylated lignin, dopamine hydrochloride and polyethyleneimine through a reaction. Various functional raw materials are compounded, and the obtained cable sheath has good flexibility, flame retardance, thermal deformation resistance, aging resistance and mechanical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, in particular to a flexible EVA cable sheath material and a preparation method thereof. Background Art

[0002] A cable is a conductor that transmits power or information from one point to another. Its manufacturing process typically involves first insulating one or more conductors with a sheath to form a single wire. Two or more insulated wires are then twisted into pairs, and these pairs are then twisted into a cable core. The core is then covered with a shield and sheath, ultimately creating the power or information transmission cable. As a means of transmitting power and information, wires and cables are widely used in various fields, including transportation, industrial mining, and electrical communications.

[0003] During use, cables require an insulating, flame-retardant sheath. The quality of this sheath significantly impacts cable performance. To maintain cable flexibility, the sheath must also be flexible. Traditional flexible cable sheaths are made from a low-smoke, halogen-free material. These materials are based on polyolefin resin, with inorganic flame retardants, fillers, antioxidants, lubricants, and other additives added in appropriate proportions. This low-hardness product is then extruded and plasticized through a screw extruder. However, existing low-hardness products present several challenges, including thermal deformation and a need for improved flame retardancy. Summary of the Invention

[0004] The present invention aims to solve at least one of the above technical problems and provides a flexible EVA cable sheath material and a preparation method thereof.

[0005] The present invention provides a flexible EVA cable sheath material, comprising the following raw materials in parts by weight: 25-50 parts of ethylene-vinyl acetate copolymer, 15-30 parts of ultra-low density polyethylene, 2-10 parts of grafted EVA, 2-10 parts of flame retardant, 2-10 parts of polydopamine-modified montmorillonite-boron nitride fiber composite material, 0.5-3 parts of toughening agent, 0.2-1 parts of silicone, and 0.2-1 parts of organopolysiloxane;

[0006] The grafting monomer of the grafted EVA includes one or two of maleic anhydride or acrylic ester compounds;

[0007] The polydopamine modified montmorillonite-boron nitride fiber composite material is prepared by reacting montmorillonite, boron nitride fiber, hydroxylated lignin, dopamine hydrochloride and polyethyleneimine.

[0008] Compared to polyethylene, EVA reduces high crystallinity and improves toughness, impact resistance, filler compatibility, and heat sealing properties due to the introduction of vinyl acetate monomer into the molecular chain. EVA is also water-resistant, corrosion-resistant, soft, and elastic. Ultra-low-density polyethylene (ULDPE) has excellent tensile strength, impact strength, and tear strength, as well as good thermal properties, insulation, and corrosion resistance. By blending ULDPE with EVA, the present invention improves the strength, flexibility, and low-temperature heat sealing properties of cable sheathing materials.

[0009] Polydopamine modified montmorillonite-boron nitride fiber composite material is prepared by reacting montmorillonite, boron nitride fiber, hydroxylated lignin, dopamine hydrochloride, and polyethyleneimine. Montmorillonite is composed of layered silicate with the structural formula (Al, Mg)2〔SiO 10(OH)2·n H2O has a large aspect ratio. After treatment, it can be dispersed in the EVA cable sheath material to form a composite material with partially or completely intercalated and exfoliated layered silicates, which has a toughening effect. When the cable burns, montmorillonite acts as a skeleton and promotes the carbonization of polymers such as EVA and polyethylene. After combustion, a dense carbon shell is formed. The carbon shell has a certain strength, which can prevent the sheath from dripping after combustion, effectively slowing or inhibiting the spread of combustion. The carbonized layer can also cut off the overflow of combustible gases, inhibit further temperature rise of the polymer resin, and hinder the thermal decomposition of the polymer to produce combustible gases, thereby further enhancing the overall flame retardancy. Boron nitride fiber has good thermal stability, wear resistance, and strong chemical stability. It can be used as a reinforcing agent for cable sheaths to increase mechanical properties. After modifying the surfaces of montmorillonite and boron nitride fibers, polydopamine introduces a large number of amino and hydroxyl groups, simultaneously activating the surfaces of the montmorillonite and boron nitride fibers. Polyethyleneimine is then grafted onto the fibers to introduce amino groups. This modification improves the affinity between the montmorillonite, boron nitride fibers, and the EVA organic interface, significantly enhancing the tensile strength, fracture toughness, flame retardancy, insulation, and thermal stability of the EVA cable sheathing material. The catechol groups in polydopamine impart excellent surface adhesion, enabling the material to adhere to various substrates through hydrogen and chemical bonding. Polydopamine also absorbs ultraviolet light, providing UV protection. Lignin, an aromatic polymer widely found in plants, contains a large number of conjugated structures such as benzene rings and carbonyl groups, as well as phenolic hydroxyl groups. It exhibits excellent antioxidant and UV resistance, scavenging free radicals generated by inorganic particles due to light exposure, and improving the aging resistance of the EVA cable sheath. Hydroxylated lignin, obtained through hydroxylation, can control lignin's molecular weight and increase its hydroxyl content, thereby improving lignin's reactivity and compatibility with EVA, reducing lignin aggregation in EVA, and enhancing the mechanical properties of EVA cable sheaths. It can also impart long-term UV resistance and biodegradability to EVA cable sheaths. Hydroxylated lignin can also act as a surfactant, improving the antistatic properties and flexibility of EVA cable sheaths. Polydopamine-modified montmorillonite-boron nitride fiber composites can significantly enhance the flexibility, mechanical properties, flame retardancy, heat deformation resistance, and aging resistance of EVA cable sheaths.

[0010] Grafted EVA can improve the compatibility and adhesion between ethylene-vinyl acetate copolymer, ultra-low density polyethylene matrix and inorganic interface, improve the dispersibility and compatibility of inorganic substances, ensure the overall compatibility and heat deformation resistance of the material, thereby improving the flame retardancy of the cable sheath, increasing the oxygen index, and significantly improving the mechanical properties and thermal properties of the material.

[0011] Silicone refers to an organosilicon compound containing silicon-oxygen (Si-O) bonds, preferably in the form of solid silicone particles. Silicone can improve the wear resistance of EVA sheaths, extending their service life; increase their flexibility and elasticity, maintaining good performance even at low temperatures; improve their thermal stability, maintaining stability even at high temperatures; improve their surface properties, such as increasing the smoothness and anti-stick properties of molded sheaths to reduce friction; and enhance their UV resistance, extending their service life in outdoor environments. Organopolysiloxanes can improve the compatibility and adhesion between organic polymers and inorganic materials, enhancing structural strength.

[0012] The present invention uses a variety of functional raw materials for compounding, and the obtained cable sheath material has good flexibility, flame retardancy, heat deformation resistance, aging resistance and mechanical properties.

[0013] Preferably, the content of vinyl acetate in the ethylene-vinyl acetate copolymer EVA is 10-50 wt%, and the density of the ultra-low density polyethylene is 0.898-0.910 g / cm 3 .

[0014] Preferably, the flame retardant includes one or both of an inorganic flame retardant and a cyclotriphosphazene flame retardant;

[0015] The toughening agent includes polyethylene-octene co-elastomer and cellulose. Cellulose molecules are polar, and the interaction between molecular chains is strong, which can improve the compatibility and adhesion between organic and inorganic materials. The polyethylene-octene co-elastomer and cellulose synergistically increase toughness, giving the material the required ultra-low hardness.

[0016] Preferably, the weight proportions of the raw materials in the polydopamine-modified montmorillonite-boron nitride fiber composite material are: 10-30 parts of montmorillonite, 5-25 parts of boron nitride fiber, 3-18 parts of hydroxylated lignin, 2-15 parts of dopamine hydrochloride, and 2-10 parts of polyethyleneimine.

[0017] Preferably, the weight proportions of the raw materials in the grafted EVA are: 80-100 parts of EVA, 0.5-5 parts of SEBS, 0.5-5 parts of grafting monomer, and 0.1-0.5 parts of initiator.

[0018] Preferably, the initiator for grafting EVA includes dicumyl peroxide or benzamide peroxide.

[0019] Another object of the present invention is to provide a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0020] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0021] Montmorillonite and boron nitride fiber are dispersed in an ethanol aqueous solution, a NaOH solution is added to adjust the pH to alkaline, the temperature is raised and stirred to react, the resulting solid is separated, and the modified montmorillonite-boron nitride fiber is obtained after washing;

[0022] Modified montmorillonite-boron nitride fiber, hydroxylated lignin, and dopamine hydrochloride are dispersed in a Tris buffer solution, ultrasonically treated for 0.5-1 hour, stirred and reacted at 30-60°C for 6-12 hours, solids are separated, polyethyleneimine solution is added to the solids, stirred and reacted for 0.5-2 hours, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0023] S2. Mix ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene (ULDPE), grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite, toughening agent, silicone, and organopolysiloxane according to parts by weight, and knead at 130-180° C.

[0024] S3, extruding and granulating through an extruder to obtain a flexible EVA cable sheath material.

[0025] Preferably, in step S1:

[0026] The temperature of the reaction is 50-80°C and the time is 0.5-2h;

[0027] The polyethyleneimine solution was added and stirred, and the reaction temperature was 30-50°C.

[0028] Preferably, in step S2:

[0029] The preparation method of grafted EVA is as follows: dissolve the grafting monomer and initiator in acetone, then sprinkle them on the EVA matrix, stir evenly, then sprinkle SEBS on the EVA matrix, wait for the acetone to completely evaporate, and then extrude and granulate at 160-200℃;

[0030] The mixing time is 0.5-2h.

[0031] Preferably, in step S3:

[0032] The extrusion includes primary extrusion and secondary extrusion. The temperature of the primary extrusion is 110-150°C, and the temperature of the secondary extrusion is 80-110°C.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention uses a variety of functional raw materials for compounding, and the resulting cable sheath has good flexibility, flame retardancy, heat deformation resistance, aging resistance and mechanical properties. The polydopamine-modified montmorillonite-boron nitride fiber composite material, after being modified by polydopamine and grafted with polyethyleneimine, improves the affinity of montmorillonite, boron nitride fiber and EVA organic interface, and greatly improves the tensile strength, fracture toughness, flame retardancy, insulation and thermal stability of the EVA cable sheath material; montmorillonite has the effect of increasing toughness and flame retardancy; boron nitride fiber has good thermal stability and wear resistance, strong chemical stability, and can be used as a reinforcing agent to increase the mechanical properties of the cable sheath; polydopamine also has excellent surface adhesion and UV protection, and hydroxylated lignin can increase the mechanical properties of the EVA cable sheath, and improve antistatic properties and softness. Silicone can improve the wear resistance, flexibility and elasticity, thermal stability, surface properties and aging resistance of the EVA sheath. Grafted EVA can improve the compatibility and adhesion between the polyolefin matrix and the inorganic flame retardant interface, ensure the overall compatibility and heat deformation resistance of the material, and significantly improve the flame retardancy, mechanical properties and thermal properties of the material.

[0035] 2. The preparation method of the present invention is simple and convenient, and is suitable for large-scale promotion and application. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0037] The equipment and chemical reagents used in the embodiments of the present invention are all commercially available.

[0038] In the following examples: the organopolysiloxane is an organopolysiloxane coupling agent with a density of 0.9-1.2 g / cm 3 The kinematic viscosity at 25°C is 5-30 cst. Silicone is solid silicone particles.

[0039] Example 1

[0040] A flexible EVA cable sheath material comprises the following raw materials in parts by weight: 50 parts of ethylene-vinyl acetate copolymer (EVA), 15 parts of ultra-low-density polyethylene (ULDPE), 10 parts of grafted EVA, 10 parts of magnesium hydroxide, 10 parts of a polydopamine-modified montmorillonite-boron nitride fiber composite, 2 parts of a polyethylene-octene co-elastomer (product model: Mitsui Chemicals DF805), 1 part of cellulose, 1 part of silicone, and 1 part of an organopolysiloxane methyltrimethoxysilane. The vinyl acetate content in the ethylene-vinyl acetate copolymer (EVA) is 50% by weight, and the density of the ULDPE is 0.898-0.910 g / cm 3 .

[0041] The present embodiment provides a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0042] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0043] 30 parts of montmorillonite and 25 parts of boron nitride fiber were dispersed in an ethanol aqueous solution, and NaOH solution was added to adjust the pH to 7.5-8.0. The mixture was heated to 50°C and stirred for 2 hours. The solid was separated and washed to obtain modified montmorillonite-boron nitride fiber.

[0044] The modified montmorillonite-boron nitride fiber obtained above, 18 parts of hydroxylated lignin, and 15 parts of dopamine hydrochloride were dispersed in a Tris buffer solution, ultrasonically treated for 1 hour, stirred and reacted at 30°C for 12 hours, and then 10 parts of polyethyleneimine were added, stirred and reacted at 50°C for 2 hours, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0045] S2, the preparation method of grafted EVA is as follows: take 5 parts of maleic anhydride and 0.5 parts of dicumyl peroxide initiator and dissolve them in acetone, then evenly sprinkle them on 100 parts of EVA substrate, stir evenly, then evenly sprinkle 5 parts of SEBS on the EVA substrate, wait for the acetone to completely evaporate, and then extrude and granulate at 160°C;

[0046] S3, mixing ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene, grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite material, toughening agent, silicone, and methyltriacetoxysilane according to parts by weight, and kneading at 130° C. for 2 h;

[0047] S4. Extruding the product twice through an extruder and granulating the product, wherein the temperature of the first extrusion is 150° C. and the temperature of the second extrusion is 110° C., to obtain a flexible EVA cable sheath material.

[0048] Example 2

[0049] A flexible EVA cable sheath material comprises the following raw materials in parts by weight: 25 parts ethylene-vinyl acetate copolymer (EVA), 30 parts ultra-low-density polyethylene (ULDPE), 2 parts grafted EVA, 2 parts hexaphenoxycyclotriphosphazene flame retardant, 2 parts polydopamine-modified montmorillonite-boron nitride fiber composite, 0.2 parts polyethylene-octene co-elastomer (product model: Dow GA1000R), 0.3 parts cellulose, 0.2 parts silicone, and 0.2 parts organopolysiloxane. The vinyl acetate content in the ethylene-vinyl acetate copolymer (EVA) is 10% by weight, and the density of the ULDPE is 0.898-0.910 g / cm 3 .

[0050] The present embodiment provides a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0051] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0052] 10 parts of montmorillonite and 5 parts of boron nitride fiber were dispersed in an ethanol aqueous solution, and a NaOH solution was added to adjust the pH to 8.5-9.5. The mixture was heated to 80°C and stirred for 0.5 h. The solid was separated and washed to obtain modified montmorillonite-boron nitride fiber.

[0053] The modified montmorillonite-boron nitride fiber obtained above, 3 parts of hydroxylated lignin, and 2 parts of dopamine hydrochloride were dispersed in a Tris buffer solution, ultrasonically treated for 0.5 h, stirred and reacted at 60°C for 6 h, and then 2 parts of polyethyleneimine were added, stirred and reacted at 30°C for 0.5 h, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0054] S2, the preparation method of grafted EVA is as follows: take 0.5 parts of triglyceride of acrylic acid and 0.1 parts of initiator benzamide peroxide and dissolve them in acetone, then evenly sprinkle them on 80 parts of EVA substrate, stir evenly, then evenly sprinkle 0.5 parts of SEBS on the EVA substrate, wait for the acetone to completely evaporate, and then extrude and granulate at 200°C;

[0055] S3, mixing ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene, grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite material, toughening agent, silicone, and organopolysiloxane according to parts by weight, and kneading at 180° C. for 0.5 h;

[0056] S4. Extruding the product twice through an extruder and granulating the product. The temperature of the first extrusion is 110° C., and the temperature of the second extrusion is 80° C. to obtain a flexible EVA cable sheath material.

[0057] Example 3

[0058] A flexible EVA cable sheath material comprises the following raw materials in parts by weight: 37 parts of ethylene-vinyl acetate copolymer (EVA), 23 parts of ultra-low-density polyethylene (ULDPE), 6 parts of grafted EVA, 3 parts of a cyclotriphosphazene-PMMH-6 polymer flame retardant, 2 parts of aluminum hydroxide, 6 parts of a polydopamine-modified montmorillonite-boron nitride fiber composite, 1 part of a polyethylene-octene co-elastomer (product model: Mitsui Chemicals DF805), 0.8 parts of cellulose, 0.6 parts of silicone, and 0.6 parts of vinyl trisbutyl ketoxime silane. The vinyl acetate content in the ethylene-vinyl acetate copolymer (EVA) is 30% by weight, and the density of the ULDPE is 0.898-0.910 g / cm 3 .

[0059] The present embodiment provides a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0060] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0061] 20 parts of montmorillonite and 15 parts of boron nitride fiber were dispersed in an ethanol aqueous solution, and a NaOH solution was added to adjust the pH to 8.5-9.0. The mixture was heated to 60°C and stirred for 1 hour. The solid was separated and washed to obtain modified montmorillonite-boron nitride fiber.

[0062] The modified montmorillonite-boron nitride fiber obtained above, 10 parts of hydroxylated lignin, and 8 parts of dopamine hydrochloride were dispersed in a Tris buffer solution, ultrasonically treated for 1 hour, stirred and reacted at 45°C for 8 hours, and then 6 parts of polyethyleneimine were added, stirred and reacted at 40°C for 1 hour, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0063] S2, the preparation method of grafted EVA is as follows: 2 parts of maleic anhydride, 1 part of triglyceride of acrylic acid and 0.25 parts of dicumyl peroxide (initiator) are dissolved in acetone, and then evenly sprinkled on 100 parts of EVA substrate, stirred evenly, and then 2.5 parts of SEBS are evenly sprinkled on the EVA substrate. After the acetone is completely volatilized, extrusion and granulation are performed at 180°C;

[0064] S3, mixing ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene, grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite material, toughening agent, silicone, and organopolysiloxane according to parts by weight, and kneading at 150° C. for 1 hour;

[0065] S4. Extruding the material twice through an extruder and granulating the material, wherein the temperature of the first extrusion is 130° C. and the temperature of the second extrusion is 100° C., to obtain a flexible EVA cable sheath material.

[0066] Example 4

[0067] A flexible EVA cable sheath material comprises the following raw materials in parts by weight: 30 parts of ethylene-vinyl acetate copolymer (EVA), 26 parts of ultra-low-density polyethylene (ULDPE), 8 parts of grafted EVA, 4 parts of a cyclotriphosphazene-PMMH-6 polymer flame retardant, 4 parts of a polydopamine-modified montmorillonite-boron nitride fiber composite, 0.5 parts of a polyethylene-octene co-elastomer (product model: Mitsui Chemicals DF805), 0.5 parts of cellulose, 0.4 parts of silicone, and 0.75 parts of methyl tributylidene silane. The vinyl acetate content in the ethylene-vinyl acetate copolymer (EVA) is 20% by weight, and the density of the ULDPE is 0.898-0.910 g / cm 3 .

[0068] The present embodiment provides a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0069] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0070] 15 parts of montmorillonite and 20 parts of boron nitride fiber were dispersed in an ethanol aqueous solution, and a NaOH solution was added to adjust the pH to 8.0-8.5. The mixture was heated to 70°C and stirred for 1 hour. The solid was separated and washed to obtain modified montmorillonite-boron nitride fiber.

[0071] The modified montmorillonite-boron nitride fiber obtained above, 15 parts of hydroxylated lignin, and 10 parts of dopamine hydrochloride were dispersed in a Tris buffer solution, ultrasonically treated for 45 minutes, stirred and reacted at 40°C for 9 hours, and then 8 parts of polyethyleneimine were added, stirred and reacted at 45°C for 1 hour, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0072] S2, the preparation method of grafted EVA is as follows: take 1 part of maleic anhydride, 0.5 parts of trimethylolpropane triacrylate and 0.2 parts of initiator benzamide peroxide and dissolve them in acetone, then evenly sprinkle them on 90 parts of EVA substrate, stir evenly, then evenly sprinkle 1.5 parts of SEBS on the EVA substrate, wait for the acetone to completely evaporate, and then extrude and granulate at 170°C;

[0073] S3, mixing ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene, grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite material, toughening agent, silicone, and organopolysiloxane according to parts by weight, and kneading at 140° C. for 1.5 h;

[0074] S4. Extruding the product twice through an extruder and granulating the product. The temperature of the first extrusion is 120° C., and the temperature of the second extrusion is 90° C. to obtain a flexible EVA cable sheath material.

[0075] Example 5

[0076] A flexible EVA cable sheath material comprises the following raw materials in parts by weight: 43 parts of ethylene-vinyl acetate copolymer (EVA), 20 parts of ultra-low-density polyethylene (ULDPE), 4 parts of grafted EVA, 3 parts of magnesium hydroxide, 5 parts of hexaphenoxycyclotriphosphazene, 8 parts of polydopamine-modified montmorillonite-boron nitride fiber composite, 1.5 parts of polyethylene-octene co-elastomer (product model: Dow GA1000R), 1 part of cellulose, 0.7 parts of silicone, and 0.4 parts of phenyltributylanoxime silane. The vinyl acetate content in the ethylene-vinyl acetate copolymer (EVA) is 40% by weight, and the density of the ULDPE is 0.898-0.910 g / cm 3 .

[0077] The present embodiment provides a method for preparing a flexible EVA cable sheath material, comprising the following steps:

[0078] S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material:

[0079] 25 parts of montmorillonite and 10 parts of boron nitride fiber were dispersed in an ethanol aqueous solution, and a NaOH solution was added to adjust the pH to 8.5-9.0. The mixture was heated to 65°C and stirred for 1.5 hours. The solid was separated and washed to obtain modified montmorillonite-boron nitride fiber.

[0080] The modified montmorillonite-boron nitride fiber obtained above, 7 parts of hydroxylated lignin, and 5 parts of dopamine hydrochloride were dispersed in a Tris buffer solution, ultrasonically treated for 0.5 h, stirred and reacted at 50°C for 8 h, and then 4.5 parts of polyethyleneimine were added, stirred and reacted at 40°C for 1 h, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material;

[0081] S2. Preparation method of grafted EVA: dissolve 2.5 parts of maleic anhydride, 1.5 parts of 1,6-hexanediol diacrylate and 0.4 parts of initiator dicumyl peroxide or benzamide peroxide in acetone, and then evenly sprinkle them on 100 parts of EVA substrate, stir evenly, and then evenly sprinkle 3.5 parts of SEBS on the EVA substrate. After the acetone is completely volatilized, granulate by extrusion at 190°C.

[0082] S3, mixing ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene, grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite material, toughening agent, silicone, and organopolysiloxane according to parts by weight, and kneading at 170° C. for 1 hour;

[0083] S4. Extruding the material twice through an extruder and granulating the material, wherein the temperature of the first extrusion is 140° C. and the temperature of the second extrusion is 100° C., to obtain a flexible EVA cable sheath material.

[0084] Comparative Example 1

[0085] Except for removing the polydopamine-modified montmorillonite-boron nitride fiber composite material, the rest was the same as in Example 3.

[0086] Comparative Example 2

[0087] The montmorillonite in the polydopamine-modified montmorillonite-boron nitride fiber composite material was removed, and the rest was the same as in Example 3.

[0088] Comparative Example 3

[0089] The boron nitride fibers in the polydopamine-modified montmorillonite-boron nitride fiber composite material were removed, and the rest were the same as in Example 3.

[0090] Comparative Example 4

[0091] The hydroxylated lignin in the polydopamine-modified montmorillonite-boron nitride fiber composite material was removed, and the rest was the same as in Example 3.

[0092] Comparative Example 5

[0093] The polydopamine modification step is removed. The difference between this comparative example and Example 3 is that in step S1, after the modified montmorillonite-boron nitride fiber is prepared, the modified montmorillonite-boron nitride fiber is directly reacted with polyethyleneimine, and hydroxylated lignin and dopamine hydrochloride are not used. The rest is the same as Example 3.

[0094] Comparative Example 6

[0095] The polydopamine modification and polyethyleneimine grafting steps were removed, and the modified montmorillonite-boron nitride fiber obtained in step S1 was directly substituted for the polydopamine-modified montmorillonite-boron nitride fiber composite material. The rest was the same as in Example 3.

[0096] Table 1

[0097]

[0098]

[0099] As can be seen from the data in Table 1, compared with Comparative Examples 1-6: The cable sheath materials of Examples 1-5 have good flexibility, mechanical strength, flame retardancy and heat deformation resistance, with a tensile strength greater than 14MPa, an elongation at break greater than 380%, an oxygen index greater than 40%, and a strength and elongation change rate of less than 25% after heat aging (110°C*20 days); this indicates that the polydopamine-modified montmorillonite-boron nitride fiber composite material has a significant effect on the performance of EVA cable sheath materials. Among them, montmorillonite has a greater effect on flame retardancy, with the oxygen index of Comparative Example 2 reduced to 32.7%; boron nitride fiber has a greater effect on mechanical properties, with the tensile strength and elongation at break of Comparative Example 3 reduced to 9.3MPa and 288%, respectively. The present invention adopts a combination of multiple functional materials, and the synergistic effect of each component jointly promotes the performance improvement of EVA cable sheath materials.

[0100] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flexible EVA cable sheath material, characterized in that: The invention comprises the following raw materials in parts by weight: 25-50 parts of ethylene-vinyl acetate copolymer, 15-30 parts of ultra-low density polyethylene, 2-10 parts of grafted EVA, 2-10 parts of flame retardant, 2-10 parts of polydopamine-modified montmorillonite-boron nitride fiber composite material, 0.5-3 parts of toughening agent, 0.2-1 parts of silicone, and 0.2-1 parts of organopolysiloxane; The grafting monomer of the grafted EVA includes one or two of maleic anhydride or acrylic ester compounds; The polydopamine modified montmorillonite-boron nitride fiber composite material is prepared by reacting montmorillonite, boron nitride fiber, hydroxylated lignin, dopamine hydrochloride and polyethyleneimine.

2. A flexible EVA cable sheath material according to claim 1, characterized in that: The content of vinyl acetate in the ethylene-vinyl acetate copolymer EVA is 10-50 wt%, and the density of the ultra-low density polyethylene is 0.898-0.910 g / cm 3 .

3. A flexible EVA cable sheath material according to claim 1, characterized in that: The flame retardant includes one or two of an inorganic flame retardant and a cyclotriphosphazene flame retardant; The toughening agent includes polyethylene octene co-elastomer and cellulose.

4. A flexible EVA cable sheath material according to claim 1, characterized in that: The weight proportions of the raw materials in the polydopamine-modified montmorillonite-boron nitride fiber composite material are: 10-30 parts of montmorillonite, 5-25 parts of boron nitride fiber, 3-18 parts of hydroxylated lignin, 2-15 parts of dopamine hydrochloride, and 2-10 parts of polyethyleneimine.

5. The flexible EVA cable sheath material according to claim 1, characterized in that: The weight proportions of the raw materials in the grafted EVA are: 80-100 parts of EVA, 0.5-5 parts of SEBS, 0.5-5 parts of grafting monomer, and 0.1-0.5 parts of initiator.

6. A flexible EVA cable sheath material according to claim 5, characterized in that: The initiator includes dicumyl peroxide or benzamide peroxide.

7. A method for preparing a flexible EVA cable sheath material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Preparation of polydopamine modified montmorillonite-boron nitride fiber composite material: Montmorillonite and boron nitride fiber are dispersed in an ethanol aqueous solution, a NaOH solution is added to adjust the pH to alkaline, the temperature is raised and stirred to react, the resulting solid is separated, and the modified montmorillonite-boron nitride fiber is obtained after washing; Modified montmorillonite-boron nitride fiber, hydroxylated lignin, and dopamine hydrochloride are dispersed in a Tris buffer solution, ultrasonically treated for 0.5-1 hour, stirred and reacted at 30-60°C for 6-12 hours, solids are separated, polyethyleneimine solution is added to the solids, stirred and reacted for 0.5-2 hours, and dried to obtain a polydopamine-modified montmorillonite-boron nitride fiber composite material; S2. Mix ethylene-vinyl acetate copolymer (EVA), ultra-low density polyethylene (ULDPE), grafted EVA, flame retardant, polydopamine-modified montmorillonite-boron nitride fiber composite, toughening agent, silicone, and organopolysiloxane according to parts by weight, and knead at 130-180° C. S3, extruding and granulating through an extruder to obtain a flexible EVA cable sheath material.

8. The method for preparing a flexible EVA cable sheath material according to claim 7, characterized in that: In the step S1: The temperature of the reaction is 50-80°C and the time is 0.5-2h; The polyethyleneimine solution was added and stirred, and the reaction temperature was 30-50°C.

9. The method for preparing a flexible EVA cable sheath material according to claim 7, characterized in that: In the step S2: The preparation method of grafted EVA is as follows: dissolve the grafting monomer and initiator in acetone, then sprinkle them on EVA, stir evenly, then sprinkle SEBS on EVA, wait for the acetone to completely evaporate, and then extrude and granulate at 160-200℃; The mixing time is 0.5-2h.

10. The method for preparing a flexible EVA cable sheath material according to claim 7, characterized in that: In the step S3: The extrusion includes primary extrusion and secondary extrusion. The temperature of the primary extrusion is 110-150°C, and the temperature of the secondary extrusion is 80-110°C.

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