Irradiation crosslinking low-smoke halogen-free flame retardant material and preparation method thereof

Abstract

The invention relates to the technical field of cable materials, and particularly discloses an irradiation crosslinking low-smoke halogen-free flame-retardant material and a preparation method thereof. The irradiation crosslinking low-smoke halogen-free flame retardant material is prepared from the following raw materials: 80 to 105 parts of polyolefin resin, 60 to 70 parts of stearic acid coated magnesium hydroxide, 6 to 10 parts of hyperbranched polyphosphate, 5 to 8 parts of zinc borate, 8 to 10 parts of glycidyl methacrylate grafted POE (Polyolefin Elastomer), 2 to 3 parts of triallyl isocyanurate and 1 to 2 parts of silicone master batch. According to the invention, the components have better dispersion uniformity and interface bonding effect, and maintain higher flame retardant property. The irradiation crosslinking low-smoke halogen-free flame retardant material with relatively excellent mechanical property and flame retardant property can be prepared by adopting the raw materials in a limited ratio and the preparation method.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, in particular to a radiation cross-linked low-smoke halogen-free flame retardant and a preparation method thereof. Background Art

[0002] The rapid development of power, communications, rail transit, and new energy sectors has placed higher demands on cable safety, environmental friendliness, and durability. While traditional polyvinyl chloride (PVC) or halogen-containing flame-retardant cable materials are relatively low-cost, they can release large amounts of toxic and corrosive gases in fires, creating secondary hazards. They also produce large amounts of thick smoke during combustion, severely impacting evacuation and firefighting efforts. Therefore, the industry urgently needs to develop low-smoke, halogen-free, flame-retardant cable materials with excellent mechanical properties and weather resistance.

[0003] In the related art, a phosphorus-nitrogen composite highly flame-retardant radiation-cross-linked halogen-free and low-smoke cable material is disclosed, which includes the following raw materials in parts by weight: 85-95 parts of polyolefin, 5-15 parts of compatibilizer, 80-100 parts of inorganic flame retardant, and 20-50 parts of organic phosphorus-nitrogen flame retardant; wherein the polyolefin is selected from one or more of thermoplastic elastomer, metallocene linear low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer; and the compatibilizer is maleic anhydride grafted polyethylene.

[0004] However, due to the high filling ratio of inorganic flame retardants and organic phosphorus nitrogen flame retardants, the inorganic flame retardants have strong scattering and absorption effects on electron beams, and the irradiation dose needs to be greatly increased to achieve uniform cross-linking. Excessive doses can easily lead to uneven cross-linking networks after irradiation, which may cause a significant decrease in the mechanical properties of the material. Summary of the Invention

[0005] In order to improve the mechanical properties of radiation-crosslinked low-smoke halogen-free flame retardant, the present application provides a radiation-crosslinked low-smoke halogen-free flame retardant and a preparation method thereof.

[0006] In the first aspect, the present application provides a radiation cross-linked low-smoke halogen-free flame retardant material, which adopts the following technical solution:

[0007] A radiation-crosslinked low-smoke halogen-free flame retardant comprises the following raw materials in parts by weight: 80-105 parts of polyolefin resin, 60-70 parts of stearic acid-coated magnesium hydroxide, 6-10 parts of hyperbranched polyphosphate, 5-8 parts of zinc borate, 8-10 parts of glycidyl methacrylate grafted POE, 2-3 parts of triallyl isocyanurate, and 1-2 parts of silicone masterbatch.

[0008] In a specific embodiment, methyl methacrylate-butadiene-styrene copolymer is also included.

[0009] In a specific embodiment, tetraethoxysilane is also included.

[0010] In a specific embodiment, triphenyl borate is also included.

[0011] In a specific embodiment, halloysite nanotubes and a silane coupling agent are also included.

[0012] In a specific embodiment, the polyolefin resin includes metallocene linear low density polyethylene, ethylene-octene copolymer and ethylene-vinyl acetate copolymer in a weight ratio of (5-6):(2-3):1.

[0013] In a second aspect, the present application provides a method for preparing a radiation-crosslinked low-smoke halogen-free flame retardant, which adopts the following technical solution:

[0014] A method for preparing a radiation-crosslinked low-smoke halogen-free flame retardant material comprises the following steps:

[0015] The hyperbranched polyphosphate is mixed with zinc borate to obtain a flame retardant;

[0016] Adding polyolefin resin from zone I of the twin-screw extruder, adding flame retardant and silicone masterbatch from zone II of the twin-screw extruder, adding stearic acid-coated magnesium hydroxide from zone III of the twin-screw extruder, adding glycidyl methacrylate grafted POE from zone IV of the twin-screw extruder, adding triallyl isocyanurate from zone IV of the twin-screw extruder, extruding and granulating to obtain ready-to-use granules;

[0017] The prepared particles are pre-irradiated under nitrogen protection at a dose of 30-40 kGy; and then subjected to a main irradiation curing treatment at a dose of 70-80 kGy to obtain an irradiated cross-linked material.

[0018] The radiation cross-linked material is allowed to stand under hot air circulation to obtain a radiation cross-linked low-smoke halogen-free flame retardant.

[0019] In a specific embodiment, the screw speed of the twin-screw extruder is 200-250 r / min.

[0020] In a specific embodiment, the temperature zones of the twin-screw extruder are set as follows: zone I 150-160°C, zone II 165-170°C, zone III 170-175°C, zone IV 175-180°C, and die head 170-175°C.

[0021] In a specific embodiment, the stearic acid-coated magnesium hydroxide is prepared according to the following steps:

[0022] Magnesium hydroxide is dispersed in an ethanol / water mixed solvent, a silane coupling agent is added, the mass ratio of magnesium hydroxide to the silane coupling agent is 100:(2-3), and the mixture is stirred evenly. Stearic acid is added, the temperature is raised to 78-82°C, the reaction is carried out for 0.8-1.2 hours, and the mixture is filtered and dried to obtain stearic acid-coated magnesium hydroxide; the mass ratio of magnesium hydroxide to stearic acid is (98-102):1.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. The present application adopts a limited ratio of polyolefin resin, stearic acid-coated magnesium hydroxide, hyperbranched polyphosphate, zinc borate, glycidyl methacrylate grafted POE, triallyl isocyanurate and silicone masterbatch, so that each component has better dispersion uniformity and interface bonding effect, and maintains high flame retardant properties.

[0025] 2. This application uses raw materials with limited ratios and preparation methods to prepare radiation-crosslinked low-smoke halogen-free flame retardant materials with excellent mechanical properties and flame retardant properties. DETAILED DESCRIPTION

[0026] Unless otherwise specified, the raw materials used in this application are all commercially available. Among them, ethylene-octene copolymer was purchased from Mitsui Chemicals of Japan, with the brand name PH6201VP18IY. Hyperbranched polyphosphate was purchased from Shanghai Ziyi Reagent Factory. Glycidyl methacrylate grafted POE was purchased from Dongguan Suda Plastic Raw Materials Co., Ltd., with the brand name PX2250. Triallyl isocyanurate was purchased from Hubei Wanbicot Biomedicine Co., Ltd. The model of silicone masterbatch is Dow Corning MB50-004. The model of stearic acid is Indonesia Sven 1801. The model of metallocene linear low-density polyethylene is AT6101. The brand name of ethylene-vinyl acetate copolymer is 18J3. Methyl methacrylate-butadiene-styrene copolymer was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd. Tetraethoxysilane was purchased from Mattwell (Shandong) New Materials Co., Ltd. Triphenylborate was purchased from Hunan Huateng Pharmaceutical Co., Ltd. Halloysite nanotubes were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0027] The present application is further described in detail below with reference to the following examples and comparative examples.

[0028] Example

[0029] Example 1

[0030] This example provides a radiation-crosslinked low-smoke, halogen-free flame retardant. The following raw materials are used: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate-grafted polyurethane (POE), 2.5 kg of triallyl isocyanurate, and 1.5 kg of silicone masterbatch. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 5.5:2.5:1.

[0031] The stearic acid-coated magnesium hydroxide of the present embodiment was prepared as follows:

[0032] Magnesium hydroxide was dispersed in an ethanol / water mixed solvent with a volume concentration of 70%, and a silane coupling agent KH560 was added, with a mass ratio of magnesium hydroxide to silane coupling agent KH560 of 100:2.5. The temperature was raised to 60° C. and stirred for 2 hours. Stearic acid was added, the temperature was raised to 80° C. and reacted for 1 hour. The mixture was filtered and dried to obtain stearic acid-coated magnesium hydroxide; the mass ratio of magnesium hydroxide to stearic acid was 100:1.

[0033] This embodiment also provides a method for preparing a radiation-crosslinked low-smoke halogen-free flame retardant material, which comprises the following steps:

[0034] According to the above ratio, the hyperbranched polyphosphate and zinc borate were added into a high-speed mixer and mixed at 500 r / min for 3 minutes to obtain a flame retardant.

[0035] Ethylene-octene copolymer was added to Zone I of the twin-screw extruder, where plasticization was completed. Flame retardant and silicone masterbatch were added to Zone II. Stearic acid-coated magnesium hydroxide was added from the middle side feed port of Zone III at a feed rate of 20 kg / h. Volatiles were removed at the end of Zone III. Glycidyl methacrylate-grafted POE was injected from the front end of Zone IV. Triallyl isocyanurate was added from the end of Zone IV via a liquid injection pump at an injection pressure of 0.8 MPa. Extrusion granulation was then performed to obtain the pellets for use.

[0036] The spare particles were pre-irradiated with an electron accelerator under nitrogen protection at a dose of 35 kGy. The particles were then subjected to a main irradiation curing treatment at a dose of 75 kGy to obtain an irradiated cross-linked material.

[0037] The irradiation cross-linked material was placed under hot air circulation at 80° C. for 24 hours to obtain a irradiation cross-linked low-smoke halogen-free flame retardant.

[0038] The screw speed of the twin-screw extruder is 230 r / min.

[0039] The temperature zones of the twin-screw extruder are set as follows: zone I 150-160°C, zone II 165-170°C, zone III 170-175°C, zone IV 175-180°C, and die head 170-175°C.

[0040] Example 2

[0041] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 80 kg of ethylene-octene copolymer, 70 kg of stearic acid-coated magnesium hydroxide, 10 kg of hyperbranched polyphosphate, 8 kg of zinc borate, 10 kg of glycidyl methacrylate grafted POE, 3 kg of triallyl isocyanurate, and 2 kg of silicone masterbatch.

[0042] Example 3

[0043] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 105 kg of ethylene-octene copolymer, 60 kg of stearic acid-coated magnesium hydroxide, 5 kg of hyperbranched polyphosphate, 5 kg of zinc borate, 8 kg of glycidyl methacrylate grafted POE, 2 kg of triallyl isocyanurate, and 1 kg of silicone masterbatch.

[0044] Example 4

[0045] The only difference between this embodiment and embodiment 1 is that the ethylene-octene copolymer is replaced by an equal amount of polyolefin resin. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 4:1:1.

[0046] Example 5

[0047] The only difference between this embodiment and embodiment 1 is that the ethylene-octene copolymer is replaced by an equal amount of polyolefin resin. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 5:2:1.

[0048] Example 6

[0049] The only difference between this embodiment and embodiment 1 is that the ethylene-octene copolymer is replaced by an equal amount of polyolefin resin. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 5.5:2.5:1.

[0050] Example 7

[0051] The only difference between this embodiment and embodiment 1 is that the ethylene-octene copolymer is replaced by an equal amount of polyolefin resin. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 6:3:1.

[0052] Example 8

[0053] The only difference between this embodiment and embodiment 1 is that the ethylene-octene copolymer is replaced by an equal amount of polyolefin resin. The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer, and ethylene-vinyl acetate copolymer in a weight ratio of 7:4:1.

[0054] Example 9

[0055] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, and 5 kg of methyl methacrylate-butadiene-styrene copolymer.

[0056] In the preparation method of radiation cross-linked low-smoke halogen-free flame retardant:

[0057] Ethylene-octene copolymer and methyl methacrylate-butadiene-styrene copolymer are added from zone I of the twin-screw extruder, and plasticization is completed in zone I.

[0058] Example 10

[0059] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, and 5 kg of tetraethoxysilane.

[0060] In the preparation method of radiation cross-linked low-smoke halogen-free flame retardant:

[0061] Glycidyl methacrylate grafted POE was injected from the front end of Zone IV of the twin-screw extruder, and triallyl isocyanurate and tetraethoxysilane were added from the end of Zone IV of the twin-screw extruder via a liquid injection pump at an injection pressure of 0.8 MPa. Extrusion granulation was then performed to obtain the ready-to-use granules.

[0062] Example 11

[0063] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, and 6 kg of triphenyl borate.

[0064] In the preparation method of radiation cross-linked low-smoke halogen-free flame retardant:

[0065] According to the above ratio, hyperbranched polyphosphate, triphenylborate and zinc borate were added into a high-speed mixer and mixed at 500 r / min for 3 minutes to obtain a flame retardant.

[0066] Example 12

[0067] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, 5 kg of methyl methacrylate-butadiene-styrene copolymer, 5 kg of tetraethoxysilane, and 6 kg of triphenylborate.

[0068] The preparation method of the radiation cross-linked low-smoke halogen-free flame retardant material of this embodiment is as follows:

[0069] According to the above ratio, hyperbranched polyphosphate, triphenylborate and zinc borate were added into a high-speed mixer and mixed at 500 r / min for 3 minutes to obtain a flame retardant.

[0070] Ethylene-octene copolymer and methyl methacrylate-butadiene-styrene copolymer were added to Zone I of the twin-screw extruder, and plasticization was completed in Zone I. Flame retardants and silicone masterbatch were added to Zone II of the twin-screw extruder. Stearic acid-coated magnesium hydroxide was added from the middle side feed port of Zone III of the twin-screw extruder at a feed rate of 20 kg / h. Volatile matter was removed at the end of Zone III. Glycidyl methacrylate-grafted POE was injected from the front end of Zone IV of the twin-screw extruder. Triallyl isocyanurate and tetraethoxysilane were added from the end of Zone IV of the twin-screw extruder via a liquid injection pump at an injection pressure of 0.8 MPa. Extrusion granulation was then performed to obtain the pellets for use.

[0071] The spare particles were pre-irradiated with an electron accelerator under nitrogen protection at a dose of 35 kGy. The particles were then subjected to a main irradiation curing treatment at a dose of 75 kGy to obtain an irradiated cross-linked material.

[0072] The irradiation cross-linked material was placed under hot air circulation at 80° C. for 24 hours to obtain a irradiation cross-linked low-smoke halogen-free flame retardant.

[0073] Example 13

[0074] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant material uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, 8 kg of halloysite nanotubes, and 0.2 kg of silane coupling agent KH560.

[0075] In the preparation method of radiation cross-linked low-smoke halogen-free flame retardant:

[0076] According to the above ratio, halloysite nanotubes and silane coupling agent are first mixed uniformly, and then added into a high-speed mixer together with hyperbranched polyphosphate and zinc borate, and mixed at 500 r / min for 3 minutes to obtain a flame retardant.

[0077] Example 14

[0078] The only difference between this embodiment and Example 1 is that the radiation cross-linked low-smoke halogen-free flame retardant material uses the following raw materials: 92 kg of ethylene-octene copolymer, 65 kg of stearic acid-coated magnesium hydroxide, 8 kg of hyperbranched polyphosphate, 6.5 kg of zinc borate, 9 kg of glycidyl methacrylate grafted POE, 2.5 kg of triallyl isocyanurate, 1.5 kg of silicone masterbatch, methyl methacrylate-butadiene-styrene copolymer, tetraethoxysilane, triphenyl borate, 8 kg of halloysite nanotubes, and 0.2 kg of silane coupling agent KH560.

[0079] The preparation method of the radiation cross-linked low-smoke halogen-free flame retardant material of this embodiment is as follows:

[0080] According to the above ratio, halloysite nanotubes and silane coupling agent are first mixed uniformly, and then added into a high-speed mixer together with hyperbranched polyphosphate and zinc borate, and mixed at 500 r / min for 3 minutes to obtain a flame retardant.

[0081] Ethylene-octene copolymer and methyl methacrylate-butadiene-styrene copolymer were added to Zone I of the twin-screw extruder, and plasticization was completed in Zone I. Flame retardants and silicone masterbatch were added to Zone II of the twin-screw extruder. Stearic acid-coated magnesium hydroxide was added from the middle side feed port of Zone III of the twin-screw extruder at a feed rate of 20 kg / h. Volatile matter was removed at the end of Zone III. Glycidyl methacrylate-grafted POE was injected from the front end of Zone IV of the twin-screw extruder. Triallyl isocyanurate and tetraethoxysilane were added from the end of Zone IV of the twin-screw extruder via a liquid injection pump at an injection pressure of 0.8 MPa. Extrusion granulation was then performed to obtain the pellets for use.

[0082] The spare particles were pre-irradiated with an electron accelerator under nitrogen protection at a dose of 35 kGy. The particles were then subjected to a main irradiation curing treatment at a dose of 75 kGy to obtain an irradiated cross-linked material.

[0083] The irradiation cross-linked material was placed under hot air circulation at 80° C. for 24 hours to obtain a irradiation cross-linked low-smoke halogen-free flame retardant.

[0084] Example 15

[0085] The only difference between this embodiment and Example 1 is that the stearic acid-coated magnesium hydroxide of this embodiment is prepared according to the following steps:

[0086] Magnesium hydroxide was dispersed in an ethanol / water mixed solvent with a volume concentration of 70%, a silane coupling agent was added, the mass ratio of magnesium hydroxide to the silane coupling agent was 100:2, the temperature was raised to 60°C and stirred for 2 hours, stearic acid was added, the temperature was raised to 78°C and reacted for 1.2 hours, and the mixture was filtered and dried to obtain stearic acid-coated magnesium hydroxide; the mass ratio of magnesium hydroxide to stearic acid was 98:1.

[0087] Example 16

[0088] The only difference between this embodiment and Example 1 is that the stearic acid-coated magnesium hydroxide of this embodiment is prepared according to the following steps:

[0089] Magnesium hydroxide was dispersed in an ethanol / water mixed solvent with a volume concentration of 70%, a silane coupling agent was added, the mass ratio of magnesium hydroxide to the silane coupling agent was 100:3, the temperature was raised to 60° C. and stirred for 2 hours, stearic acid was added, the temperature was raised to 82° C. and reacted for 0.8 hours, and the mixture was filtered and dried to obtain stearic acid-coated magnesium hydroxide; the mass ratio of magnesium hydroxide to stearic acid was 102:1.

[0090] Example 17

[0091] The only difference between this embodiment and embodiment 1 is that the screw speed of the twin-screw extruder is 200 r / min.

[0092] Example 18

[0093] The only difference between this embodiment and embodiment 1 is that the screw speed of the twin-screw extruder is 250 r / min.

[0094] Example 19

[0095] The only difference between this embodiment and embodiment 1 is that the dose of pre-irradiation is 30 kGy and the dose of main irradiation is 70 kGy.

[0096] Example 20

[0097] The only difference between this embodiment and embodiment 1 is that the dose of pre-irradiation is 40 kGy and the dose of main irradiation is 80 kGy.

[0098] Comparative Example

[0099] Comparative Example 1

[0100] The only difference between this comparative example and Example 1 is that the stearic acid-coated magnesium hydroxide is replaced by an equal amount of magnesium hydroxide.

[0101] Comparative Example 2

[0102] The only difference between this comparative example and Example 1 is that an equal amount of magnesium hydroxide is used to replace the hyperbranched polyphosphate.

[0103] Comparative Example 3

[0104] The only difference between this comparative example and Example 1 is that the glycidyl methacrylate grafted POE is replaced by an equal amount of ethylene-octene copolymer.

[0105] Comparative Example 4

[0106] The only difference between this comparative example and Example 1 is that an equal amount of ethylene-octene copolymer is used to replace triallyl isocyanurate.

[0107] Comparative Example 5

[0108] The only difference between this comparative example and Example 1 is that the silicone masterbatch is replaced by an equal amount of ethylene-octene copolymer.

[0109] Performance testing

[0110] For Examples 1-20 and Comparative Examples 1-5, the following performance tests were performed:

[0111] According to GB / T 1040.1-2018 “Determination of tensile properties of plastics Part 1: General principles”, the tensile strength of the radiation-cross-linked low-smoke halogen-free flame retardant materials of each embodiment and comparative example was tested.

[0112] According to GB / T 1843-2008 “Determination of Izod Impact Strength of Plastics”, the notched impact strength of the radiation-cross-linked low-smoke halogen-free flame retardant materials of the embodiments and comparative examples was tested.

[0113] According to GB / T 2951.21-2008, the thermal elongation of the radiation cross-linked low-smoke halogen-free flame retardant material of each embodiment and comparative example was tested under the condition of 200° C.×15 min.

[0114] According to GB / T 2406.2-2009, the oxygen index of the radiation-crosslinked low-smoke halogen-free flame retardant fuel of each embodiment and comparative example was tested.

[0115] The results are shown in Table 1.

[0116] Table 1

[0117]

[0118] Combining Example 1 and Comparative Examples 1-5 and Table 1, it can be seen that compared with Example 1, the tensile strength of Comparative Examples 1-5 is less than 16 MPa, and the notched impact strength is less than 20 kj / m 2 , the thermal elongation under the conditions of 200℃×15min is greater than 100%. This shows that the technical solution of Example 1 can better improve the mechanical properties of the material. This may be because the stearic acid-coated magnesium hydroxide used in the technical solution of Example 1, the stearic acid layer improves the compatibility with polyolefins, and compared with magnesium hydroxide, it has better dispersibility, making the stress of the material more dispersed. The P=O bond at the branched end of the hyperbranched polyphosphate catalyzes the dehydration of MH into carbon, and cross-links itself to form a tough POC carbon layer. Zinc borate and the decomposition products of the hyperbranched polyphosphate generate borophosphate glass, which closes the micropores of the carbon layer. Triallyl isocyanurate is cross-linked with the polyolefin molecular chain, and the epoxy group of POE grafted with glycidyl methacrylate can react with the surface hydroxyl group of the flame retardant to enhance the interface bonding effect. Therefore, the raw material ratio and preparation method of Example 1 can improve the mechanical properties of the material. Moreover, the oxygen index of the material is greater than 35%, and it has excellent flame retardant properties.

[0119] Combining Examples 1-8 and Table 1, it can be seen that compared with Example 1, the tensile strength of Examples 2-8 is greater than 16 MPa, and the notched impact strength is greater than 2020 kj / m 2, the thermal elongation under the conditions of 200℃×15min is less than 100%, and the oxygen index is greater than 35%. This shows that the mechanical properties of the material can be improved by adopting the technical solutions of Examples 1-8, and the material maintains excellent flame retardant properties. It can be seen from Examples 1 and 4-8 that the mechanical properties and flame retardant properties of the materials prepared in Examples 5-7 are better, which shows that the polyolefin resin compounded with metallocene linear low-density polyethylene, ethylene-octene copolymer and ethylene-vinyl acetate copolymer can further improve the mechanical properties and flame retardant properties of the material. This may be because the high crystallinity of metallocene linear low-density polyethylene provides mechanical strength, and the narrow molecular weight distribution improves processability. The octene side chains of the ethylene-octene copolymer form physical crosslinking points, which synergistically toughen the triallyl isocyanurate chemical crosslinking network and can improve flexibility. The polar groups of the ethylene-vinyl acetate copolymer improve the compatibility of the flame retardant, and the high VA content is conducive to crosslinking. The three work together to further improve the mechanical properties and flame retardant properties of the material.

[0120] Combining Examples 1, 9-14 and Table 1, it can be seen that compared to Example 1, the tensile strength and notched impact strength of Examples 9-14 are significantly increased, and the thermal elongation at 200°C × 15min changes little and is less than 100%. The oxygen index is greater than 35%. This shows that the addition of methyl methacrylate-butadiene-styrene copolymer, tetraethoxysilane, triphenylborate, halloysite nanotubes or silane coupling agent can further improve the mechanical properties of the material. Moreover, the mechanical properties and flame retardant properties of Example 14 are significantly improved. This shows that the synergistic use of methyl methacrylate-butadiene-styrene copolymer, tetraethoxysilane, triphenylborate, halloysite nanotubes and silane coupling agent can simultaneously improve the mechanical properties and flame retardant properties of the material. This may be because triphenylborate and hyperbranched polyphosphate synergistically catalyze ceramicization and increase the amount of residual carbon. Tetraethoxysilane helps cross-linking, methyl methacrylate-butadiene-styrene has a toughening effect and can absorb impact energy, halloysite nanotubes can bridge cracks, and silane coupling agents can improve the interface bonding effect between halloysite nanotubes and other materials.

[0121] Combining Examples 1, 15-20, and Table 1, it can be seen that the tensile strength, notched impact strength, and thermal elongation at 200°C x 15 min of Examples 15-20 are similar to those of Example 1. Furthermore, the oxygen index is greater than 35%. This indicates that the process conditions of Examples 15-20 can also improve the mechanical properties of the material. This may be because, at the screw speed of this application, shear force and thermal degradation can be balanced, which, under the temperature partitioning of this application, facilitates the dispersion of the flame retardant while preventing premature decomposition of triallyl isocyanurate. Within the irradiation value range of this application, better crosslinking uniformity can be achieved, preventing molecular chain breakage.

[0122] In summary, this application can break through the contradiction of "high flame retardancy-low mechanical properties" of traditional halogen-free flame retardant materials by limiting the raw material ratio and preparation method, and improve the mechanical properties of radiation-crosslinked low-smoke halogen-free flame retardant materials.

[0123] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A radiation cross-linked low-smoke halogen-free flame retardant, characterized in that: The invention comprises the following raw materials in parts by weight: 80-105 parts of polyolefin resin, 60-70 parts of stearic acid-coated magnesium hydroxide, 6-10 parts of hyperbranched polyphosphate, 5-8 parts of zinc borate, 8-10 parts of glycidyl methacrylate grafted POE, 2-3 parts of triallyl isocyanurate and 1-2 parts of silicone masterbatch.

2. The radiation cross-linked low-smoke halogen-free flame retardant according to claim 1, characterized in that: Also included are methyl methacrylate-butadiene-styrene copolymers.

3. The radiation cross-linked low-smoke halogen-free flame retardant according to claim 2, characterized in that: Also included is tetraethoxysilane.

4. The radiation cross-linked low-smoke halogen-free flame retardant according to claim 3, characterized in that: Also included are triphenyl borate esters.

5. The radiation cross-linked low-smoke halogen-free flame retardant according to claim 1, characterized in that: Also included are halloysite nanotubes and silane coupling agents.

6. The radiation cross-linked low-smoke halogen-free flame retardant according to claim 1, characterized in that: The polyolefin resin comprises metallocene linear low-density polyethylene, ethylene-octene copolymer and ethylene-vinyl acetate copolymer in a weight ratio of (5-6):(2-3):

1.

7. A method for preparing the radiation cross-linked low-smoke halogen-free flame retardant according to any one of claims 1 to 6, characterized in that: The steps include: The hyperbranched polyphosphate is mixed with zinc borate to obtain a flame retardant; Adding polyolefin resin from zone I of the twin-screw extruder, adding flame retardant and silicone masterbatch from zone II of the twin-screw extruder, adding stearic acid-coated magnesium hydroxide from zone III of the twin-screw extruder, adding glycidyl methacrylate grafted POE from zone IV of the twin-screw extruder, adding triallyl isocyanurate from zone IV of the twin-screw extruder, extruding and granulating to obtain ready-to-use granules; The prepared particles are pre-irradiated under nitrogen protection at a dose of 30-40 kGy; and then subjected to a main irradiation curing treatment at a dose of 70-80 kGy to obtain an irradiated cross-linked material. The radiation cross-linked material is allowed to stand under hot air circulation to obtain a radiation cross-linked low-smoke halogen-free flame retardant.

8. The method for preparing the radiation cross-linked low-smoke halogen-free flame retardant according to claim 7, characterized in that: The screw speed of the twin-screw extruder is 200-250r / min.

9. The method for preparing the radiation cross-linked low-smoke halogen-free flame retardant according to claim 7, characterized in that: The temperature zones of the twin-screw extruder are set as follows: zone I 150-160°C, zone II 165-170°C, zone III 170-175°C, zone IV 175-180°C, and die head 170-175°C.

10. The method for preparing the radiation cross-linked low-smoke halogen-free flame retardant according to claim 7, characterized in that: The stearic acid-coated magnesium hydroxide is prepared according to the following steps: dispersing magnesium hydroxide in an ethanol / water mixed solvent, adding a silane coupling agent, wherein the mass ratio of magnesium hydroxide to the silane coupling agent is 100:(2-3), stirring evenly, adding stearic acid, heating to 78-82° C., reacting for 0.8-1.2 hours, filtering and drying to obtain stearic acid-coated magnesium hydroxide; the mass ratio of magnesium hydroxide to stearic acid is (98-102):1.

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