Crosslinked polyolefin material, preparation method thereof and cable material

Abstract

The invention discloses a cross-linked polyolefin material, which is prepared from the following ingredients in parts by weight: 10 to 20 parts of EVA (Ethylene Vinyl Acetate), 5 to 10 parts of LDPE (Low-Density Polyethylene), 5 to 15 parts of POE (Polyolefin Elastomer), 5 to 15 parts of silane grafted POE, 70 to 140 parts of compound inorganic flame retardants and 1 to 5 parts of compound cross-linking agents. The easy-crosslinking polyolefin material provided by the invention has excellent easy crosslinking property and physical and mechanical properties.

Description

Technical Field

[0001] The invention relates to the field of sheath materials, and in particular to a cross-linked polyolefin material and a preparation method thereof, and a cable material. Background Art

[0002] At present, low-smoke halogen-free materials are widely used in the wire and cable industry, especially in the construction industry and photovoltaic field. However, the construction of the domestic construction and photovoltaic fields has been basically completed, and the market demand has dropped seriously, leading to intensified market competition. Despite this, there is still room for optimization of low-smoke halogen-free materials in the formulation field. Common low-smoke halogen-free polyolefin materials must be cross-linked before they can be widely used. For most low-voltage application fields, radiation cross-linking and ultraviolet light cross-linking can meet the use requirements. However, external light radiation cross-linking has a greater dependence on the color and thickness of the material, so the wide range and convenience of use are far less than radiation cross-linking. At present, the radiation dose of domestic low-smoke halogen-free materials is generally between 8-14M, and the processing speed still has a lot of room for improvement. Therefore, it is very necessary to develop an easy-to-radiate cross-linked polyolefin material with low thermal elongation, high flame retardancy and high mechanical properties. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a cross-linked polyolefin material and a preparation method thereof, and a cable material, aiming to solve the problems of the current cross-linked polyolefin material having high thermal elongation, large irradiation dose, high flame retardancy and poor physical and mechanical properties.

[0004] To achieve the above object, the present invention provides a cross-linked polyolefin material and a preparation method thereof, and a cable material.

[0005] A cross-linked polyolefin material, characterized in that the ingredients of the cross-linked polyolefin material, measured in parts by weight, include: 10-20 parts of EVA, 5-10 parts of LDPE, 5-15 parts of POE, 5-15 parts of silane-grafted POE, 70-140 parts of a compounded inorganic flame retardant, and 1-5 parts of a compounded cross-linking agent.

[0006] Optionally, the composite cross-linking agent is obtained by mixing hydroxylated graphene oxide, a cross-linking agent and a catalyst.

[0007] Optionally, the hydroxylated graphene oxide is obtained by subjecting graphene oxide to a chemical reduction treatment, and the particle size of the hydroxylated graphene oxide is 0.1-0.3 um.

[0008] Optionally, the graphene oxide is prepared by a Hummers method.

[0009] Optionally, the crosslinking agent includes at least one of TAIC (triallyl isocyanurate), TMPTMA (trimethylolpropane trimethacrylate), PDM, ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), N,N′-phenyl bismaleimide (PDM or HVA-2), zinc diacrylate (ZDA), and zinc dimethacrylate (ZDMA).

[0010] Optionally, the catalyst is an organic tin catalyst, including at least one of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin didodecylsulfide, dibutyltin laurate maleate, and dibutyltin diacetate.

[0011] Optionally, the weight ratio of the hydroxylated graphene oxide, the cross-linking agent and the catalyst is (10-40): (10-40): (1-3).

[0012] Optionally, the melt index of the EVA is 2-8 g / min, and the content of vinyl acetate is 18%-50%; the melt index of the LDPE is 1-10 g / min; the melt index of the POE is 0.2-20 g / min, and the grafting rate of the silane-grafted POE is ≥1%, and the melt index is 0.2-20 g / min.

[0013] Optionally, the silane monomer in the silane-grafted POE is at least one of vinylmethyldiethoxysilane and vinyltri(2-methylethoxy)silane.

[0014] Optionally, the compound inorganic flame retardant is prepared by compounding antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion.

[0015] Optionally, the compound inorganic flame retardant is compounded by antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion, wherein the proportion of antimony trioxide, aluminum hydroxide and magnesium hydroxide is (10-20): (30-60): (30-60).

[0016] Optionally, the ingredients of the cross-linked polyolefin material also include at least one of a carbon former, an antioxidant and a lubricant; wherein, the ingredients are calculated by weight, the carbon former is 2-4 parts, the antioxidant is 0.1-1 part, and the lubricant is 1-3 parts.

[0017] In order to achieve the above object, the present invention also provides a method for preparing a cross-linked polyolefin material, comprising the following steps:

[0018] The hydroxylated graphene oxide, the cross-linking agent and the catalyst are fully mixed to obtain a composite cross-linking agent;

[0019] EVA, LDPE, POE, silane-grafted POE, inorganic flame retardant, carbon forming agent, antioxidant, i.e. lubricant are mixed evenly, and extruded and granulated to obtain granules; the granules and the compound cross-linking agent are stirred evenly, and the cross-linked polyolefin material is obtained by drying.

[0020] Optionally, the compound cross-linking agent is prepared by first dissolving hydroxylated graphene oxide and a cross-linking agent in an organic solvent, stirring after ultrasonication to fully disperse them, adding a catalyst, fully mixing to form a uniform mixture, and then drying to obtain the compound cross-linking agent.

[0021] Optionally, the organic solvent includes at least one of alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, ethers, ketones and diol derivatives.

[0022] In order to achieve the above object, the present invention also provides a cable material, which is applied to cables and comprises the above cross-linked polyolefin material.

[0023] Beneficial effects of the present invention: The present invention prepares a cross-linked polyolefin material, in which EVA, LDPE, POE, silane-grafted POE and inorganic flame retardants are used as main substrates. EVA introduces vinyl acetate monomer into its molecular chain, thereby reducing high crystallinity and improving toughness, impact resistance, filler compatibility and heat sealing performance. LDPE is a polymer polymerized from ethylene monomers, and its molecular structure has a large number of short branches, so that LDPE has lower crystallinity and higher flexibility. POE, silane-grafted POE, compound cross-linking agent and other additives are used as the main components of the cross-linked polyolefin material. The components cooperate and synergize with each other to form a specific resin matrix, so that obvious cross-linking effect can be obtained under low radiation doses. The compound cross-linking agent becomes the key to obtaining easily cross-linked cross-linked polyolefin materials. The hydroxylated graphene oxide and silane-grafted POE in the compound cross-linking agent undergo a cross-linking reaction under the action of a catalyst to form a first-type cross-linked network. The first-type cross-linked network has a strong The cross-linked network is formed, but its cross-linking reaction proceeds extremely slowly and the corresponding cross-linking degree cannot be reached within a limited time. Therefore, the double bonds in the cross-linking agent become the key to the second type of cross-linked network. The double bonds can be opened during irradiation to increase the connection with other resin substrates, such as EVA, POE, LDPE, silane-grafted POE, etc., and can serve as a bridge to connect the substrate and the first type of cross-linked network. The two complement each other, thereby achieving a cross-linked polyolefin material that can reduce the irradiation dose and achieve a sufficiently high degree of cross-linking within a specified time, so that the cable material can ensure the original good mechanical properties of the cross-linked polyolefin, and improve the flame retardancy and physical and mechanical properties of the cross-linked polyolefin material. The compound cross-linking agent added to the cross-linked polyolefin material has little effect on the performance of the cross-linked polyolefin material, and does not require a very high addition amount to obtain excellent cross-linking performance and physical and mechanical properties. Adding a small amount to the formula can play a good auxiliary cross-linking effect in the irradiation cross-linking process. At the same time, the specific resin compounding significantly improves the cross-linking degree and mechanical strength of the cross-linked polyolefin cable material. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0025] Unless defined otherwise, all technical and scientific terms used herein have the common meaning in the art to which the claimed subject matter belongs.

[0026] In order to facilitate the understanding of this embodiment, the symbols, instruments and terms are explained below:

[0027] EVA: Ethylene Vinyl Acetate Copolymer, ethylene-vinyl acetate copolymer, is a copolymer of ethylene and vinyl acetate. Due to the introduction of vinyl acetate monomer into the molecular chain, EVA reduces the high crystallinity and improves toughness, impact resistance, filler solubility and heat sealing properties. It is widely used in foaming shoe materials, functional shed films, packaging molds, hot melt adhesives, wires and cables, toys and other fields.

[0028] LDPE: Low Density Polyethylene, the lightest variety of polyethylene resin, is milky white, tasteless, odorless, non-toxic, and matte waxy particles. It has good softness, extensibility, electrical insulation, transparency, easy processing, and certain air permeability. It has good chemical stability and is resistant to alkali and general organic solvents.

[0029] POE: Polyolefin Elastomer, is a cross-linked polyolefin with the dual properties of plastic and rubber. It is synthesized using metallocene catalysts and has excellent physical and mechanical properties and a wide range of processing applications.

[0030] At present, low-smoke halogen-free materials are widely used in the wire and cable industry, especially in the construction industry and photovoltaic field. However, the construction of the domestic construction and photovoltaic fields has been basically completed, and the market demand has dropped seriously, leading to intensified market competition. Despite this, there is still room for optimization of low-smoke halogen-free materials in the formulation field. Common low-smoke halogen-free polyolefin materials must be cross-linked before they can be widely used. For most low-voltage application fields, radiation cross-linking and ultraviolet light cross-linking can meet the use requirements. However, external light radiation cross-linking has a greater dependence on the color and thickness of the material, so the wide range and convenience of use are far less than radiation cross-linking. At present, the radiation dose of domestic low-smoke halogen-free materials is generally between 8-14M, and the processing speed still has a lot of room for improvement. Therefore, it is very necessary to develop an easy-to-radiate cross-linked polyolefin material with low thermal elongation, high flame retardancy and high mechanical properties.

[0031] To solve the above problems, the present invention proposes a cross-linked polyolefin material, comprising: 10-20 parts of EVA, 5-10 parts of LDPE, 5-15 parts of POE, 5-15 parts of silane-grafted POE, 70-140 parts of a compounded inorganic flame retardant, and 1-5 parts of a compounded cross-linking agent.

[0032] The invention prepares a cross-linked polyolefin material. In the invention, EVA, LDPE, POE, silane-grafted POE and inorganic flame retardant are used as main substrates. Vinyl acetate monomer is introduced into the molecular chain of EVA, thereby reducing high crystallinity and improving toughness, impact resistance, filler compatibility and heat sealing performance. LDPE is a polymer polymerized from ethylene monomers, and has a large number of short branches in its molecular structure, so that LDPE has low crystallinity and high flexibility. POE, silane-grafted POE, compound cross-linking agent and other additives are used as main components of the cross-linked polyolefin material. The components cooperate and synergize with each other to form a specific resin matrix, so that an obvious cross-linking effect can be obtained under a low radiation dose. The compound cross-linking agent becomes the key to obtaining an easily cross-linked cross-linked polyolefin material. Hydroxylated graphene oxide and silane-grafted POE in the compound cross-linking agent undergo a cross-linking reaction under the action of a catalyst to form a first-class cross-linked network. The first-class cross-linked network has a strong cross-linked network. However, its cross-linking reaction proceeds extremely slowly and the corresponding degree of cross-linking cannot be achieved within a limited time. Therefore, the double bonds in the cross-linking agent become the key to the second type of cross-linking network. The double bonds can be opened during irradiation to increase the connection with other resin substrates, such as EVA, POE, LDPE, silane-grafted POE, etc., and can serve as a bridge to connect the substrate and the first type of cross-linking network. The two complement each other, thereby achieving a cross-linked polyolefin material that can reduce the irradiation dose and achieve a sufficiently high degree of cross-linking within a specified time, so that the cable material can ensure the original good mechanical properties of the cross-linked polyolefin, and improve the flame retardancy and physical and mechanical properties of the cross-linked polyolefin material. The compound cross-linking agent added to the cross-linked polyolefin material has little effect on the performance of the cross-linked polyolefin material, and does not require a very high addition amount to obtain excellent cross-linking performance and physical and mechanical properties. Adding a small amount in the formula can play a good auxiliary cross-linking effect in the irradiation cross-linking process. At the same time, the specific resin compounding significantly improves the cross-linking degree and mechanical strength of the cross-linked polyolefin cable material.

[0033] Furthermore, the composite cross-linking agent is obtained by mixing hydroxylated graphene oxide, a cross-linking agent and a catalyst.

[0034] The composite cross-linking agent is prepared by combining hydroxylated graphene oxide, a cross-linking agent and an organic tin catalyst, wherein the hydroxylated graphene oxide can serve as a first type of cross-linking network in the composite cross-linking agent under the action of the catalyst, and during the reaction process, double bonds can be opened during irradiation to increase the connection with other resins, that is, the cross-linking agent can serve as a second type of cross-linking network in the composite cross-linking agent, which makes up for the slow cross-linking reaction of the hydroxylated graphene oxide to a certain extent, and the first type of cross-linking network and the second type of cross-linking network in the composite cross-linking agent work together to obtain a composite cross-linking agent with high cross-linking degree and rapid reaction.

[0035] Furthermore, hydroxylated graphene oxide is obtained by chemically reducing graphene oxide, and the particle size of hydroxylated graphene oxide is 0.1-0.3 um.

[0036] Hydroxylated graphene oxide is obtained by hydroxylation modification of graphene oxide. Hydroxyl functional groups are introduced into the surface of graphene oxide, changing its surface properties and chemical properties, giving it new functions and application potential.

[0037] In some embodiments, the particle size of hydroxylated graphene oxide is preferably 0.2 um.

[0038] Furthermore, graphene oxide is prepared by the Hummers method.

[0039] The basic principle of the Hummers method is to oxidize graphite under strong acidic conditions to obtain graphene oxide, so that the graphite is oxidized and peeled off into single-layer or multi-layer graphene oxide. This method is easy to operate, does not require complicated equipment and conditions, and is suitable for large-scale production.

[0040] Further, the crosslinking agent includes at least one of TAIC (triallyl isocyanurate), TMPTMA (trimethylolpropane trimethacrylate), PDM, ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), N,N′-phenyl bismaleimide (PDM or HVA-2), zinc diacrylate (ZDA), and zinc dimethacrylate (ZDMA).

[0041] The cross-linking agent contains double bonds, which are the key to the second type of cross-linking network. The double bonds can be opened during irradiation to increase the connection with other resin substrates, such as PP, SEBS, POE, etc., and can serve as a bridge to connect the substrate and the first type of cross-linking network. The two complement each other, thereby achieving a cross-linked polyolefin material that can reduce the irradiation dose and achieve a sufficiently high degree of cross-linking within the specified time, so that the cable material can ensure good mechanical properties.

[0042] In some embodiments, the cross-linking agent is preferably TAIC.

[0043] Furthermore, the catalyst is an organic tin catalyst, including at least one of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin didodecylsulfide, dibutyltin laurate maleate, and dibutyltin diacetate.

[0044] Organotin catalysts are metal organic compounds formed by the direct combination of tin and carbon elements. Because the effect of steric hindrance on catalytic activity decreases with increasing temperature, replacing the smaller steric hindrance groups with larger steric hindrance alkyl groups can make organotin compounds have higher stability, resistance to hydrolysis and delayed catalytic activity.

[0045] In some embodiments, the catalyst is preferably dibutyltin dilaurate.

[0046] Furthermore, the weight ratio of hydroxylated graphene oxide, cross-linking agent and catalyst is (10-40): (10-40): (1-3).

[0047] In some embodiments, the weight ratio of hydroxylated graphene oxide, crosslinking agent and catalyst is preferably 10:40;3.

[0048] Furthermore, the weight ratio of hydroxylated graphene oxide, cross-linking agent and catalyst is (20-40): (20-40): (2.5-3).

[0049] Increasing the proportions of hydroxylated graphene oxide, crosslinking agent and catalyst can further improve the crosslinking-promoting performance of the composite crosslinking agent.

[0050] In some embodiments, the weight ratio of hydroxylated graphene oxide, cross-linking agent and catalyst is preferably 40:40:3.

[0051] Furthermore, the melt index of EVA is 2-8 g / min, and the content of vinyl acetate is 18%-50%; the melt index of LDPE is 1-10 g / min; the melt index of POE is 0.2-20 g / min, and the grafting rate of silane-grafted POE is ≥1%, and the melt index is 0.2-20 g / min.

[0052] In some embodiments, the vinyl acetate content is preferably 30%.

[0053] Furthermore, the silane monomer in the silane-grafted POE is at least one of vinylmethyldiethoxysilane and vinyltri(2-methylethoxy)silane.

[0054] In some embodiments, the silane monomer in the silane-grafted POE is preferably vinylmethyldiethoxysilane.

[0055] Furthermore, the compound inorganic flame retardant is compounded by antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion.

[0056] In some embodiments, the compound inorganic flame retardant is compounded from antimony trioxide, aluminum hydroxide and magnesium hydroxide.

[0057] Antimony trioxide is a common flame retardant, but a single flame retardant is often difficult to meet the complex and changing flame retardant requirements. It can be used in combination with aluminum-magnesium inorganic flame retardants to improve the flame retardant effect.

[0058] Furthermore, the compound inorganic flame retardant is compounded by antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion, wherein the proportion of antimony trioxide, aluminum hydroxide and magnesium hydroxide is (10-20): (30-60): (30-60).

[0059] In some embodiments, the ratio of antimony trioxide, aluminum hydroxide and magnesium hydroxide is preferably 10:50:40.

[0060] Furthermore, the ingredients of the cross-linked polyolefin material also include at least one of a carbon former, an antioxidant and a lubricant; wherein, the ingredients are calculated by weight, 2-4 parts of the carbon former, 0.1-1 parts of the antioxidant, and 1-3 parts of the lubricant.

[0061] The charring agent can form a char layer to prevent heat transfer and oxygen diffusion, thereby achieving a flame retardant effect. During the combustion process, the charring agent can be dehydrated by the dehydrating agent and carbonized to form a porous char layer. This char layer can prevent heat conduction and oxygen diffusion between the polymer and the heat source, reduce the decomposition temperature of the polymer, and prevent the diffusion of volatile combustible components; antioxidants can effectively reduce the oxidation rate of materials during processing and use by capturing free radicals, decomposing peroxides and complexing metal ions, thereby delaying or preventing oxidation or auto-oxidation processes, protecting plastic products from oxidation, and thus extending their service life; lubricants can significantly reduce the viscosity of cable materials, which helps the processing and production process of cable materials, and can also reduce the internal friction of cable materials during processing, thereby reducing energy consumption.

[0062] In some embodiments, the carbon-forming agent includes but is not limited to at least one of magnesium hydroxide and aluminum hydroxide, montmorillonite, and nanoclay carbon-forming agents, and the carbon-forming agent is preferably magnesium hydroxide.

[0063] In some embodiments, the antioxidant includes but is not limited to at least one of a hindered phenol antioxidant, a hindered amine antioxidant, and a phosphate antioxidant. The antioxidant is preferably antioxidant 1010.

[0064] In some embodiments, the lubricant includes but is not limited to at least one of PE wax, PVC lubricant and slip agent, and the lubricant is preferably PE wax.

[0065] In order to solve the above problems, the present invention also provides a method for preparing a cross-linked polyolefin material, comprising the following steps:

[0066] S1: hydroxylated graphene oxide, a cross-linking agent and a catalyst are fully mixed to obtain a composite cross-linking agent;

[0067] S2: EVA, LDPE, POE, silane-grafted POE, inorganic flame retardant, carbon forming agent, antioxidant, i.e. lubricant are mixed evenly, and extruded and granulated to obtain granules; the granules and the compounded cross-linking agent are stirred evenly, and a cross-linked polyolefin material is obtained by drying.

[0068] In some embodiments, extrusion granulation is achieved by a twin-screw extruder.

[0069] In some embodiments, the mixing and melting is carried out in an internal mixer, and the temperature of the internal mixer is raised to 140° C.-150° C.

[0070] In some embodiments, the temperature of the thermoplastic elastomer material obtained by extrusion pelletization is 130°C-140°C.

[0071] Furthermore, the hydroxylated graphene oxide and the cross-linking agent are first dissolved in an organic solvent, stirred after ultrasonication to fully disperse them, and then a catalyst is added, and a uniform mixture is formed after sufficient mixing, and then dried to obtain a composite cross-linking agent.

[0072] Furthermore, the organic solvent includes at least one of alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, ethers, ketones and diol derivatives.

[0073] In some embodiments, the organic solvent is preferably anhydrous ethanol.

[0074] In order to solve the above problems, the present invention also provides a cable material, which is applied to cables and includes the above cable material.

[0075] The present invention is explained below through specific examples and data.

[0076] Embodiment 1:

[0077] 40 parts of hydroxylated graphene oxide, 40 parts of a cross-linking agent and 3 parts of a catalyst are mixed to obtain a composite cross-linking agent.

[0078] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 10 parts of POE metallocene ethylene octene copolymer, 10 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 1 part of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0079] Embodiment 2:

[0080] The preparation method is the same as that of Example 1, except that:

[0081] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 10 parts of POE metallocene ethylene octene copolymer, 10 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 2 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0082] Embodiment 3:

[0083] The preparation method is the same as that of Example 1, except that:

[0084] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 10 parts of POE metallocene ethylene octene copolymer, 10 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0085] Embodiment 4:

[0086] The preparation method is the same as that of Example 1, except that:

[0087] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0088] Embodiment 5:

[0089] The preparation method is the same as that of Example 1, except that:

[0090] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 15 parts of POE metallocene ethylene octene copolymer, 5 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0091] Embodiment 6:

[0092] 40 parts of hydroxylated graphene oxide, 40 parts of a cross-linking agent and 3 parts of a catalyst are mixed to obtain a composite cross-linking agent.

[0093] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0094] Embodiment 7:

[0095] 40 parts of hydroxylated graphene oxide, 10 parts of a cross-linking agent and 3 parts of a catalyst are mixed to obtain a composite cross-linking agent.

[0096] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0097] Embodiment 8:

[0098] 40 parts of hydroxylated graphene oxide, 40 parts of a cross-linking agent and 1 part of a catalyst are mixed to obtain a composite cross-linking agent.

[0099] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and extruded and granulated to obtain granules; the granules and 5 parts of a compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0100] Comparative Example 1:

[0101] 40 parts of hydroxylated graphene oxide, 40 parts of a cross-linking agent and 3 parts of a catalyst are mixed to obtain a composite cross-linking agent.

[0102] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 50 parts of aluminum hydroxide, 50 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and extruded and granulated to obtain granules; the granules and 3 parts of compound cross-linking agent are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0103] Comparative Example 2:

[0104] 15 parts of EVA ethylene-vinyl acetate copolymer, 5 parts of LDPE linear low-density polyethylene, 5 parts of POE metallocene ethylene octene copolymer, 15 parts of silane-grafted POE silane-grafted metallocene ethylene octene copolymer, 10 parts of antimony trioxide, 50 parts of aluminum hydroxide, 40 parts of magnesium hydroxide, 2 parts of carbon former, 0.5 parts of antioxidant and 2 parts of lubricant are mixed evenly, and the mixture is subjected to banburying, extrusion and granulation to obtain granules; the granules and 3 parts of hydroxylated graphene oxide are stirred evenly, and a cross-linked polyolefin material for cables with high flame retardancy and high cross-linking degree is obtained by drying.

[0105] The components and important preparation variables of Examples 1-8 and Comparative Examples 1-2 are summarized in Table 1.

[0106] Table 1 Components of Examples 1-8 and Comparative Examples 1-2 of the present invention

[0107]

[0108] According to the provisions of GB / T 1040.2, EN-50264-3-1:2008 and GB / T2406.2, the cross-linked polyolefin materials in the above Examples 1-8 and Comparative Examples 1-2 were tested for tensile strength, elongation at break, thermal elongation, degree of cross-linking and oxygen index, and the test results were recorded in the following Table 2:

[0109] Table 2 Performance test table of Examples 1-8 of the present invention and Comparative Examples 1-2

[0110]

[0111] According to the above test results, it can be seen that in Examples 1-3, as the number of compound cross-linking agents increases, the tensile strength gradually increases, the elongation at break gradually decreases, the thermal elongation decreases regularly, and the degree of cross-linking increases, indicating that the degree of cross-linking of the samples of Examples 1-3 increases with the increase in the number of compound cross-linking agents, and the irradiation dose remains unchanged. The greater the degree of cross-linking of the material, the greater the force between molecules, and the smaller the thermal elongation value. The thermal elongation of the samples of Examples 1-3 also proves that the force between molecules increases, and the thermal elongation value decreases, proving that the first type of cross-linking network of the compound cross-linking agent has a strong cross-linking network. At the same time, the second type of cross-linking network increases the connection with other resin substrates. The two complement each other, thereby achieving a cross-linked polyolefin material that can reduce the irradiation dose and reach a sufficiently high degree of cross-linking within a specified time. Adding a small amount of compound cross-linking agent to the formula can play a good auxiliary cross-linking effect in the irradiation cross-linking process, thereby improving the cross-linking degree and mechanical strength of the cross-linked polyolefin cable material. In Examples 4 and 5, the content of the compound cross-linking agent in the overall substrate is indirectly increased by reducing the added amounts of POE and silane-grafted POE. However, unlike Example 4, the silane-grafted POE in Example 5 is a component of the first type of cross-linking network in the compound cross-linking agent. When the amount of silane-grafted POE is reduced, the first type of cross-linking network cannot form a sufficient degree of cross-linking, and its degree of cross-linking is low, which is 70%. Therefore, its thermal elongation is also increased to 108%, indicating that in the compound cross-linking agent, the first type of cross-linking network and the second type of cross-linking network complement each other and are indispensable. In Examples 6-8, the proportions of hydroxylated graphene oxide, crosslinking agent and organotin catalyst in the composite crosslinking agent were changed. In Example 6, the proportion of hydroxylated graphene oxide was 10, in Example 7, the proportion of crosslinking agent was 10, and in Example 8, the proportion of organotin catalyst was 1. It can be seen from Table 2 that when the proportion of any of the three in the composite crosslinking agent is too low, the crosslinking degree of the obtained crosslinked polyolefin material cannot obtain a regular thermal elongation performance. In Comparative Example 1, the flame retardant is lacking, and its flame retardant performance is relatively poor, and it cannot pass the flame retardant test. The tensile strength and crosslinking degree of Comparative Example 2 are significantly lower than those of Examples 1-8, and the thermal extension directly breaks, indicating that its crosslinking degree is relatively low. In summary, the crosslinked polyolefin cable material proposed in the present invention has good mechanical properties and flame retardant properties, and is easy to irradiate and crosslink, and is particularly suitable for the manufacture of various wires and cables in the field of industrial electrical appliances.

[0112] The invention verifies that the crosslinking degree of the crosslinked polyolefin material is improved by adding a compound crosslinking agent, so that the crosslinked polyolefin material has excellent physical and mechanical properties, has extremely high industrial value, and can be widely used and promoted.

[0113] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A cross-linked polyolefin material, characterized in that: The ingredients of the cross-linked polyolefin material, measured in parts by weight, include: EVA 10-20 parts, LDPE 5-10 parts, POE5-15 parts, Silane grafted POE 5-15 parts, Compound inorganic flame retardant 70-140 parts, Compound cross-linking agent 1-5 parts.

2. The cross-linked polyolefin material according to claim 1, characterized in that: The composite cross-linking agent is obtained by mixing hydroxylated graphene oxide, a cross-linking agent and a catalyst.

3. The composite cross-linking agent according to claim 2, characterized in that The hydroxylated graphene oxide is obtained by subjecting graphene oxide to chemical reduction treatment, and the particle size of the hydroxylated graphene oxide is 0.1-0.3 um.

4. The composite cross-linking agent according to claim 3, characterized in that The graphene oxide is prepared by the Hummers method.

5. The composite cross-linking agent according to claim 2, characterized in that The crosslinking agent includes at least one of TAIC (triallyl isocyanurate), TMPTMA (trimethylolpropane trimethacrylate), PDM, ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), N,N′-phenyl bismaleimide (PDM or HVA-2), zinc diacrylate (ZDA), and zinc dimethacrylate (ZDMA).

6. The composite cross-linking agent according to claim 2, characterized in that The catalyst is an organic tin catalyst, including at least one of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dilaurate, di(dodecylsulfide) dibutyltin, dibutyltin laurate maleate, and dibutyltin diacetate.

7. The composite cross-linking agent according to claim 2, characterized in that The weight ratio of the hydroxylated graphene oxide, the crosslinking agent and the catalyst is (10-40): (10-40): (1-3).

8. The cross-linked polyolefin material according to claim 1, characterized in that: The melt index of the EVA is 2-8 g / min, and the content of vinyl acetate is 18%-50%; the melt index of the LDPE is 1-10 g / min; the melt index of the POE is 0.2-20 g / min, and the grafting rate of the silane-grafted POE is ≥1%, and the melt index is 0.2-20 g / min.

9. The cross-linked polyolefin material according to claim 8, characterized in that: The silane monomer in the silane-grafted POE is at least one of vinylmethyldiethoxysilane and vinyltri(2-methylethoxy)silane.

10. The cross-linked polyolefin material according to claim 1, characterized in that: The compound inorganic flame retardant is prepared by compounding antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion.

11. The cross-linked polyolefin material according to claim 10, characterized in that: The compound inorganic flame retardant is compounded by antimony trioxide, aluminum hydroxide and magnesium hydroxide in a certain proportion, wherein the proportion of antimony trioxide, aluminum hydroxide and magnesium hydroxide is (10-20): (30-60): (30-60).

12. The cross-linked polyolefin material according to claim 1, characterized in that: The ingredients of the cross-linked polyolefin material also include at least one of a carbon former, an antioxidant and a lubricant; wherein, in terms of weight, the carbon former is 2-4 parts, the antioxidant is 0.1-1 parts, and the lubricant is 1-3 parts.

13. A method for preparing a cross-linked polyolefin material, characterized in that: The following steps are involved: The hydroxylated graphene oxide, the cross-linking agent and the catalyst are fully mixed to obtain a composite cross-linking agent; EVA, LDPE, POE, silane-grafted POE, inorganic flame retardant, carbon forming agent, antioxidant, i.e. lubricant are mixed evenly, and extruded and granulated to obtain granules; the granules and the compound cross-linking agent are stirred evenly, and the cross-linked polyolefin material is obtained by drying.

14. The method for preparing a cross-linked polyolefin material according to claim 13, characterized in that: The compound cross-linking agent is prepared by first dissolving hydroxylated graphene oxide and a cross-linking agent in an organic solvent, stirring them after ultrasonication to fully disperse them, adding a catalyst, fully mixing them to form a uniform mixture, and then drying them to obtain the compound cross-linking agent.

15. The method for preparing a cross-linked polyolefin material according to claim 14, characterized in that: The organic solvent includes at least one of alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, ethers, ketones and diol derivatives.

16. A cable material, characterized in that: Applied to cables, comprising the cross-linked polyolefin material as claimed in any one of claims 1 to 13.

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