A low-temperature impact-resistant flame-retardant silicon core tube and preparation method thereof

Abstract

The present application relates to the technical field of flame-retardant pipes, and in particular to a low-temperature impact-resistant flame-retardant silicon core pipe and a preparation method thereof. The low-temperature impact-resistant flame-retardant silicon core pipe comprises an inner layer and an outer layer, and the outer layer comprises the following raw materials in parts by weight: 70-90 parts of high-density polyethylene resin, 15-25 parts of star-shaped SBS, 3-5 parts of maleic anhydride grafted high-density polyethylene, 6-10 parts of inorganic flame retardant, 10-15 parts of elastic flame-retardant microspheres, 0.1-0.5 parts of antioxidant, 0.4-0.8 parts of antibacterial agent, 2-4 parts of carbon fiber, 1-3 parts of dispersant and 1-3 parts of silane coupling agent; the invention has the advantages of improving the mechanical properties of the pipe while improving its flame retardant properties.

Description

Technical Field

[0001] The present application relates to the technical field of flame-retardant pipes, and in particular to a low-temperature, impact-resistant, flame-retardant silicon core pipe and a preparation method thereof. Background Art

[0002] Silicone core pipe is a new type of composite pipe with silicone solid lubricant on the inner wall. It has good sealing performance, chemical corrosion resistance, low engineering cost, and is widely used in optical cable communication network systems such as highways and railways. Silicone core pipes need to have flame retardant properties to protect internal cables. With climate change and industry development, electronic equipment needs to adapt to more complex environments, especially to improve the impact resistance of flame-retardant silicon core pipes in extremely cold and low temperatures, so that they can adapt to line deployment in extremely cold areas.

[0003] Among them, high-density polyethylene (HDPE) has the advantages of light weight, low toxicity, high electrical insulation performance, good chemical resistance and easy processing, and is widely used to make the outer layer of silicon core pipes. However, high-density polyethylene is easy to burn and releases harmful gases when burning. Adding flame retardants to HDPE can effectively improve the flame retardant properties of the pipe. However, although traditional halogenated flame retardants have good flame retardant effects, they release a large amount of harmful gases and corrosive smoke during use, polluting the environment. Adding inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide has the advantages of low cost and non-toxicity, but when the amount of flame retardant added is large, it is easy to cause the mechanical properties of the pipe to decrease, especially in extremely cold areas, the mechanical properties of the pipe will decrease more significantly, which is not conducive to practical application. Summary of the invention

[0004] In order to improve the mechanical properties of the pipe while improving its flame retardant properties, the present application provides a low-temperature impact-resistant flame retardant silicon core pipe and a preparation method thereof.

[0005] In the first aspect, the present application provides a low-temperature impact-resistant flame-retardant silicon core tube, which adopts the following technical solution:

[0006] A low-temperature impact-resistant flame-retardant silicon core tube, comprising an inner layer and an outer layer, wherein the outer layer comprises the following raw materials in parts by weight: 70-90 parts of high-density polyethylene resin, 15-25 parts of star-shaped SBS, 3-5 parts of maleic anhydride grafted high-density polyethylene, 6-10 parts of inorganic flame retardant, 10-15 parts of elastic flame-retardant microspheres, 0.1-0.5 parts of antioxidant, 0.4-0.8 parts of antibacterial agent, 2-4 parts of carbon fiber, 1-3 parts of dispersant and 1-3 parts of silane coupling agent;

[0007] The preparation method of the elastic flame-retardant microspheres is as follows:

[0008] S1. Add 2-3 parts by weight of nickel oxide powder and 3-6 parts by weight of a silane coupling agent containing a double bond to an ethanol aqueous solution to obtain modified nickel oxide; under a nitrogen atmosphere, add modified nickel oxide, 18-22 parts by weight of vinyl triisopropoxy silane, 3-6 parts by weight of styrene and 0.6-0.9 parts by weight of double-terminated vinyl polydimethylsiloxane to 90-110 parts by weight of DMF, stir until completely dissolved, then add 0.008 parts by weight of an initiator, heat to 65-75°C, stir to react for 3.5-5h, then add 1.5-2.5 parts by weight of a small molecule cross-linking agent and 0.004 parts by weight of an initiator, stir to react for 8-15h, and obtain a mixed solution;

[0009] S2, separating the mixed liquid obtained in S1 into solid and liquid, washing, and drying to obtain elastic flame-retardant microspheres.

[0010] By adopting the above technical solution, by adding inorganic flame retardant aluminum hydroxide, aluminum hydroxide can decompose at high temperature to produce water vapor, oxygen and aluminum oxide and other substances, among which aluminum oxide can form a layer of insoluble oxide layer on the surface of the material, thereby forming a protective layer, which plays the role of heat insulation, oxygen isolation, heat absorption, etc., and can effectively slow down the combustion speed; and this layer of oxide can also prevent the fire source from spreading inward, improving the flame retardant effect. Nickel oxide is added here. Nickel oxide can play a certain flame retardant effect. The inventor found through experiments that the addition of nickel oxide can make the aluminum oxide layer more ductile, so that nickel oxide and aluminum oxide form a fluid film layer under the action of high temperature, which can increase the flame retardant surface, thereby making the flame retardant effect better, and the two also have a synergistic effect.

[0011] By wrapping the organosilicon elastomer on the surface of nickel oxide particles, the organosilicon on the surface of nickel oxide particles is prepared by adding different cross-linking agents at different stages of the polymerization process to make the internal cross-linking degree lower and the external cross-linking degree higher, so as to form elastic flame-retardant microspheres with higher elasticity. After being applied to the flame-retardant silicon core tube, it can be buffered to a large extent under the action of external force. In addition, on the one hand, the compatibility between nickel oxide and the system can be improved. The melting point of the organosilicon elastomer is relatively high. It will not melt during the production process of the flame-retardant silicon core tube and can still maintain its elasticity. This feature can make the flame-retardant silicon core tube have a certain buffer when subjected to external force, thereby improving the impact resistance of the silicon core tube; on the other hand, the organosilicon elastomer, as an organosilicon resin, forms an inert gas or barrier layer at high temperature to prevent oxygen from diffusing to the combustion surface. The organosilicon elastomer can form carbon layers of different densities based on different degrees of internal and external cross-linking to improve flame retardancy, and coexists with aluminum hydroxide to form continuous flame retardant points, making the flame retardant silicon core tube more flame retardant.

[0012] Therefore, through the selection of raw materials and the addition of proportions, the mechanical properties of the silicone core tube can be improved while taking into account the flame retardant properties. At -50°C, the tensile properties of the silicone core tube are reduced by 5-9%, and the impact strength is reduced by 4-7%. Its low temperature resistance is also excellent, which greatly improves the application potential of flame retardant silicone core tubes.

[0013] Preferably, the particle size of the nickel oxide powder is ≤100 nm.

[0014] By adopting the above technical solution, as the particle size of nickel oxide gradually increases, its tensile strength and impact resistance gradually decrease, so its particle size should not be too large.

[0015] Preferably, the double bond-containing silane coupling agent is one or more of vinyl triethoxysilane, acryloxymethyl trimethoxysilane, 7-octenyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl triisopropoxysilane and vinyl trisbutyl ketoxime silane.

[0016] Preferably, the double bond-containing silane coupling agent is acryloxymethyltrimethoxysilane.

[0017] By adopting the above technical scheme, the technical effect of the present application can be obtained by selecting the silane coupling agent containing double bonds within this range. The inventors have found through experiments that selecting acryloxymethyltrimethoxysilane as the silane coupling agent containing double bonds can achieve better low-temperature impact resistance. This may be due to the participation of nickel oxide in in-situ polymerization and encapsulation based on the modification of the silane coupling agent containing double bonds. When the molecular chain length of the silane coupling agent is too long, it is easy to cause poor encapsulation effect, while when the molecular chain length is too short, the increased internal cross-linking degree affects the elastic structure with low internal cross-linking degree and high external cross-linking degree. Therefore, the selection of a suitable silane coupling agent containing double bonds takes into account both the encapsulation effect and elasticity, thereby obtaining a better impact resistance effect.

[0018] Preferably, the small molecule cross-linking agent is divinylbenzene, trivinylbenzene or trivinylsilane.

[0019] By adopting the above technical solution, small molecule cross-linking agents can be selected within this range, and are listed one by one in the embodiments.

[0020] Preferably, the particle size of the inorganic flame retardant is 800-3000 mesh.

[0021] By adopting the above technical solution, based on the dispersion effect and production cost considerations, the particle size range of 800-3000 mesh is the best choice.

[0022] Preferably, the elastic flame-retardant microspheres are added in an amount of 15 parts by weight, and the inorganic flame retardant is added in an amount of 8 parts by weight.

[0023] By adopting the above technical solution and further optimizing the addition amount of elastic flame retardant microspheres and inorganic flame retardants, the flame retardant microspheres and inorganic flame retardants form more reasonable continuous flame retardant points in the system and the mechanical properties of the flame retardant silicon core tube are optimized.

[0024] Preferably, the inorganic flame retardant is aluminum hydroxide or magnesium hydroxide.

[0025] By adopting the above technical solution, both aluminum hydroxide and magnesium hydroxide can produce a metal oxide barrier layer at high temperature, and can achieve a synergistic effect with nickel oxide and silicone elastomer. Although magnesium hydroxide was not experimented in the examples, it is theoretically achievable.

[0026] In a second aspect, the present application provides a method for preparing a low-temperature impact-resistant flame-retardant silicon core tube, using the following technical solution:

[0027] A method for preparing a low-temperature impact-resistant flame-retardant silicon core tube comprises the following steps:

[0028] S1. Heat the raw materials of the inner layer to 115-125° C., stir and mix, and obtain the raw materials of the inner layer;

[0029] S2, heating the raw materials of the outer layer to 125-135° C., stirring and mixing, to obtain the outer layer raw materials;

[0030] S4, heating and melting the outer layer raw material and the inner layer raw material respectively, and extruding and compounding them simultaneously at 165-180° C. to obtain a silicon core tube blank;

[0031] S5. The silicon core tube blank is subjected to vacuum shaping, cooling, pulling and coiling processes to obtain a flame retardant silicon core tube.

[0032] By adopting the above technical scheme, the preparation method of the present application is relatively conventional, does not require special processes or equipment modifications, and the qualified rate of the obtained products is 98% or above, which is suitable for large-scale production.

[0033] In summary, the present application includes at least one of the following beneficial technical effects:

[0034] 1. By adding inorganic flame retardant aluminum hydroxide, aluminum hydroxide can decompose at high temperature to produce aluminum oxide, which can form an insoluble oxide layer on the surface of the material, thereby forming a protective layer, which plays a role in heat insulation, oxygen isolation, and heat absorption, and can effectively slow down the combustion rate; nickel oxide can have a certain flame retardant effect while making the aluminum oxide layer more ductile, so that nickel oxide and aluminum oxide form a fluid film layer under the action of high temperature, which can increase the flame retardant surface, thereby making the flame retardant effect better, and the two also have a synergistic effect. When the silicone on the surface of nickel oxide particles is prepared, its internal cross-linking degree is low and its external cross-linking degree is high, so that elastic flame retardant microspheres with higher elasticity can be formed. After being applied to the flame retardant silicon core tube, it can provide a large degree of buffering under the action of external force. Moreover, on the one hand, the compatibility between nickel oxide and the system can be improved. The melting point of the silicone elastomer is relatively high, and it can still maintain its elasticity in the flame-retardant silicone core tube system, so that the flame-retardant silicone core tube can have a certain buffer when subjected to external force, thereby improving the impact resistance of the silicone core tube; on the other hand, as a silicone resin, the silicone elastomer forms an inert gas or barrier layer at high temperature to prevent oxygen from diffusing to the combustion surface, thereby strengthening the synergistic effect between nickel oxide and aluminum hydroxide and making its flame retardant performance stronger.

[0035] 2. The limiting oxygen index of the flame-retardant silicon core tube prepared in the present application is 30.1% or above, and the maximum can reach 34.7%; the tensile strength is 31.2MPa or above, and the maximum can reach 42.4MPa; at the same time, its impact strength is between 48.1-59.1kJ / m2; it can be seen that the flame-retardant silicon core tube prepared in the present application has strong flame retardant properties, and at the same time, its mechanical properties are excellent, and at low temperatures, the reduction is small, which can meet the needs of extremely cold areas. DETAILED DESCRIPTION

[0036] The present application is further described in detail below in conjunction with the specific contents.

[0037] The raw materials in the preparation examples and embodiments of the present application can all be purchased commercially, among which the double-terminal vinyl polydimethylsiloxane has a viscosity of 1000 at 25°C; the dispersant is a polymer dispersant FS-4310; the antioxidant is an antioxidant 1076; the antibacterial agent is a silver ion antibacterial agent with a CAS number of 7440-22-4; the carbon fiber is purchased from Japan Toray Carbon Fiber T300-3K-40B carbon fiber; the brand of maleic anhydride grafted high-density polyethylene is Fusabond E100, and the grafting rate is 0.5-1%; the brand of high-density polyethylene is 8008H, the melt flow rate is 8g / 10min, and the flexural elasticity is 37MPa; the processing grade of star-shaped SBS is injection molding grade, with a brand of 3411; the model of polydimethylsiloxane is German Wacker silicone oil AK100; the grade of ammonium tripolyphosphate is industrial grade, with a CAS number of 2022-22-17.

[0038] Preparation Example 1

[0039] An elastic flame-retardant microsphere, the preparation method of which is as follows:

[0040] S1. Add 2.5g of nickel oxide powder and 5g of vinyl triethoxysilane to an ethanol aqueous solution (ethanol / water volume ratio 1 / 1), heat to 80°C for reaction for 2h, filter, wash and dry to obtain modified nickel oxide; under nitrogen atmosphere, add the modified nickel oxide prepared above, 20g of vinyl triisopropoxysilane, 5g of styrene and 0.8g of double-terminal vinyl polydimethylsiloxane to 100g of DMF, stir until completely dissolved, then add 0.008g of initiator, heat to 65°C, stir for reaction for 4h, then add 2g of divinylbenzene and 0.004g of initiator, stir for reaction for 10h to obtain a mixed solution; wherein, the particle size of the nickel oxide powder is 20nm; the initiator is azobisisobutyronitrile;

[0041] S2. The mixed solution obtained in S1 is subjected to solid-liquid separation, and the solid is washed with DMF, then washed with ethanol, and dried to obtain elastic flame-retardant microspheres.

[0042] Preparation Example 2

[0043] An elastic flame-retardant microsphere, which is different from Preparation Example 1 in that the particle size of the nickel oxide powder is 50 nm, and the remaining steps are the same as Preparation Example 1.

[0044] Preparation Example 3

[0045] An elastic flame-retardant microsphere, which is different from Preparation Example 1 in that the particle size of the nickel oxide powder is 100 nm, and the remaining steps are the same as Preparation Example 1.

[0046] Preparation Example 4

[0047] A kind of elastic flame retardant microspheres, which are different from those in Preparation Example 1 in that an equal amount of acryloxymethyltrimethoxysilane is used to replace vinyltriethoxysilane, and the remaining steps are the same as those in Preparation Example 1.

[0048] Preparation Example 5

[0049] An elastic flame-retardant microsphere, which is different from Preparation Example 1 in that 7-octenyltrimethoxysilane is used in an equal amount to replace vinyltriethoxysilane, and the remaining steps are the same as Preparation Example 1. Example 1

[0050] A low-temperature impact-resistant flame-retardant silicon core tube has a double-layer structure, including an inner layer and an outer layer, the thickness of the inner layer is 2.0 mm, and the thickness of the outer layer is 2.5 mm; the raw materials and the amounts of the raw materials of the outer layer and the inner layer are shown in Table 1, and the preparation method is as follows:

[0051] S1. High-density polyethylene resin, star-shaped SBS, maleic anhydride grafted high-density polyethylene, polydimethylsiloxane, propyltrimethoxysilane and ammonium tripolyphosphate are mixed, heated to 120° C., and stirred for 30 minutes to obtain an inner layer raw material;

[0052] S2, mixing high-density polyethylene resin, star-shaped SBS, maleic anhydride grafted high-density polyethylene, inorganic flame retardant, elastic flame retardant microspheres, antioxidant, antibacterial agent, dispersant and propyltrimethoxysilane, heating to 130° C., stirring and mixing for 1 hour, to obtain an outer layer raw material;

[0053] S4, heating and melting the outer layer raw material prepared in S2 and the inner layer raw material prepared in S1 respectively, and extruding and compounding them simultaneously at 170° C. to obtain a silicon core tube blank;

[0054] S5. The silicon core tube blank prepared in S3 is processed through vacuum shaping, cooling, pulling and coiling to obtain a φ32 / 26 flame-retardant silicon core tube.

[0055] The elastic flame-retardant microspheres are prepared by the method of Preparation Example 1; the inorganic flame retardant is aluminum hydroxide, and its average particle size is 2000 mesh; and the length of the carbon fiber is 1 cm.

[0056] Table 1 Raw materials and their usage in Example 1 (kg)

[0057] Example 2

[0058] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that its elastic flame-retardant microspheres come from Preparation Example 2, and the remaining steps are the same as Example 1.

[0059] Example 3

[0060] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that its elastic flame-retardant microspheres come from Preparation Example 3, and the remaining steps are the same as Example 1.

[0061] Example 4

[0062] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the amount of elastic flame-retardant microspheres added is 10 kg, and the remaining steps are the same as those of Example 1.

[0063] Example 5

[0064] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the amount of elastic flame-retardant microspheres added is 20 kg, and the remaining steps are the same as those of Example 1.

[0065] Example 6

[0066] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the amount of aluminum hydroxide added is 6 kg, and the remaining steps are the same as Example 1.

[0067] Example 7

[0068] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the amount of aluminum hydroxide added is 10 kg, and the remaining steps are the same as Example 1.

[0069] Example 8

[0070] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the average particle size of its aluminum hydroxide is 800 meshes, and the remaining steps are the same as Example 1.

[0071] Example 9

[0072] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the average particle size of its aluminum hydroxide is 3000 mesh, and the remaining steps are the same as Example 1.

[0073] Example 10

[0074] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that its elastic flame-retardant microspheres come from Preparation Example 4, and the remaining steps are the same as Example 1.

[0075] Embodiment 11

[0076] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that its elastic flame-retardant microspheres come from Preparation Example 5, and the remaining steps are the same as Example 1.

[0077] Comparative Example 1

[0078] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the elastic flame-retardant microspheres added to its outer layer raw material are replaced by aluminum hydroxide of equal mass, and the remaining steps are the same as Example 1.

[0079] Comparative Example 2

[0080] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the aluminum hydroxide added to its outer layer raw material is replaced by elastic flame-retardant microspheres of equal mass, and the remaining steps are the same as Example 1.

[0081] Comparative Example 3

[0082] A low-temperature, impact-resistant, flame-retardant silicon core tube, which is different from Example 1 in that the elastic flame-retardant microspheres added to the outer layer raw material are replaced by an equal amount of nickel oxide powder with a particle size of 20 nm, and the remaining steps are the same as Example 1.

[0083] Comparative Example 4

[0084] A low-temperature impact-resistant flame-retardant silicon core tube, which is different from Example 1 in that the preparation method of its elastic flame-retardant microspheres is as follows:

[0085] S1. Add 2.5 g of nickel oxide powder and 5 g of vinyl triethoxysilane to an ethanol aqueous solution (ethanol / water volume ratio 1 / 1), heat to 80°C for reaction for 2 h, filter, wash, and dry to obtain modified nickel oxide; under a nitrogen atmosphere, add the modified nickel oxide prepared above, 20 g of vinyl triisopropoxysilane, 5 g of styrene, and 2.5 g of divinylbenzene to 100 g of DMF, stir until completely dissolved, then add 0.008 g of an initiator, the initiator is azobisisobutyronitrile, heat to 65°C, stir to react for 14 h, and obtain a mixed solution; wherein the particle size of the nickel oxide powder is 20 nm;

[0086] S2. The mixed solution obtained in S1 is subjected to solid-liquid separation, and the solid is washed with DMF, then washed with ethanol, and dried to obtain elastic flame-retardant microspheres.

[0087] Performance testing

[0088] Flame-retardant silicon core tubes were prepared according to the preparation methods of Examples 1-11 and Comparative Examples 1-4, and then tested according to the following test method. The test results are shown in Tables 2 and 3.

[0089] Limiting oxygen index: tested using JF-3 limiting oxygen index instrument;

[0090] Tensile strength: Tested in accordance with the test standard GB / T 8804.3-2003 "Thermoplastic pipe tensile properties test Part 3: Polyolefin pipe";

[0091] Impact resistance: Test with reference to the method described in GB / T1043-79 “Rigid Plastic Simply Supported Beam Impact Test Method”.

[0092] Low temperature resistance: After the test samples were kept at -50°C for 24 hours, their tensile strength and impact strength were tested, as shown in Table 3.

[0093] Table 2 Test results of Examples 1-11 and Comparative Examples 1-4

[0094]

[0095] Table 3 Low temperature resistance test results of Examples 1-11

[0096]

[0097] The flame-retardant silicon core tubes of Examples 1-11 of the present application have a tensile property reduced by 5-9% and an impact strength reduced by 4-7% at -50°C.

[0098] It can be seen from the test data of Examples 1-11 and Comparative Examples 1-4, as well as Table 2, that the limiting oxygen index of the flame-retardant silicon core tube prepared in the present application is 30.1% or more, and the maximum can reach 34.7%; the tensile strength is 31.2MPa or more, and the maximum can reach 42.4MPa; at the same time, the impact strength is 48.1-57.1kJ / m 2 It can be seen that the flame retardant silicon core tube prepared in the present application has strong flame retardant properties, and its mechanical properties are excellent, and at low temperatures, its reduction is small, which can meet the needs of extremely cold areas.

[0099] By adding inorganic flame retardant aluminum hydroxide, aluminum hydroxide can decompose at high temperature to produce water vapor, oxygen and aluminum oxide and other substances, wherein aluminum oxide can form a layer of insoluble oxide layer on the surface of the material, thereby forming a protective layer, which plays the role of heat insulation, oxygen isolation, heat absorption, etc., and can effectively slow down the combustion speed; and this layer of oxide can also prevent the fire source from spreading inward, improving the flame retardant effect. Nickel oxide is added here. While nickel oxide can play a certain flame retardant effect, the inventor has found through experiments that the addition of nickel oxide can make the aluminum oxide layer more ductile, so that nickel oxide and aluminum oxide form a fluid film layer under the action of high temperature, which can increase the flame retardant surface, thereby making the flame retardant effect better, and the two also have a synergistic effect. It can be seen from the test data of Example 1 and Comparative Examples 1-2 that only adding aluminum hydroxide or nickel oxide is not as good as adding two substances at the same time. The flame retardant performance can also be verified.

[0100] Furthermore, due to the addition of inorganic fillers, nickel oxide and aluminum hydroxide, the tensile strength and impact strength of the flame retardant silicon core tube are poor, especially at low temperatures, the mechanical properties are difficult to meet the use requirements. By wrapping the organosilicon elastomer on the surface of the nickel oxide particles, first, the compatibility between nickel oxide and the system can be improved. The melting point of the organosilicon elastomer is relatively high. During the production process of the flame retardant silicon core tube, it will not melt and can still maintain its elasticity. This feature can make the flame retardant silicon core tube have a certain buffer when subjected to external force, thereby improving the impact strength of the silicon core tube; second, the organosilicon elastomer, as an organosilicon resin, forms an inert gas or barrier layer at high temperature to prevent oxygen from diffusing to the combustion surface, thereby strengthening the synergistic effect between nickel oxide and aluminum hydroxide, making it more flame retardant. This can be verified by the test data of Example 1 and Comparative Example 3.

[0101] The present application is designed that the organic silicon on the surface of the nickel oxide particles has a low internal crosslinking degree and a high external crosslinking degree during preparation, thereby forming elastic flame-retardant microspheres with higher elasticity. After being applied to the flame-retardant silicon core tube, it can provide a relatively large buffer under the action of external force. This can be verified by the test data of Example 1 and Comparative Example 4.

[0102] It can be seen from the test data of Examples 1-3 that as the particle size of nickel oxide gradually increases, its tensile strength and impact resistance gradually decrease, so its particle size should not be too large. Combined with Examples 4-5, on the basis of a certain nickel oxide particle size, when the addition amount of elastic flame-retardant microspheres is gradually increased, its limiting oxygen index is improved, but its tensile strength shows a decreasing trend, and the impact resistance is gradually improved; under comprehensive conditions, the addition amount of 8kg is the optimal addition amount. At this addition amount, combined with Examples 6-7, when the addition amount of aluminum hydroxide is large, it is also not conducive to the mechanical properties of the flame-retardant silicon core tube.

[0103] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A low temperature impact resistant flame retardant silicon core tube, characterized in that: It comprises an inner layer and an outer layer, wherein the outer layer comprises the following raw materials in parts by weight: 70-90 parts of high-density polyethylene resin, 15-25 parts of star-shaped SBS, 3-5 parts of maleic anhydride grafted high-density polyethylene, 6-10 parts of inorganic flame retardant, 10-15 parts of elastic flame retardant microspheres, 0.1-0.5 parts of antioxidant, 0.4-0.8 parts of antibacterial agent, 2-4 parts of carbon fiber, 1-3 parts of dispersant and 1-3 parts of silane coupling agent; The preparation method of the elastic flame-retardant microspheres is as follows: S1. Add 2-3 parts by weight of nickel oxide powder and 3-6 parts by weight of a silane coupling agent containing a double bond to an ethanol aqueous solution to obtain modified nickel oxide; under a nitrogen atmosphere, add modified nickel oxide, 18-22 parts by weight of vinyl triisopropoxy silane, 3-6 parts by weight of styrene and 0.6-0.9 parts by weight of double-terminated vinyl polydimethylsiloxane to 90-110 parts by weight of DMF, stir until completely dissolved, then add 0.008 parts by weight of an initiator, heat to 65-75°C, stir to react for 3.5-5h, then add 1.5-2.5 parts by weight of a small molecule cross-linking agent and 0.004 parts by weight of an initiator, stir to react for 8-15h, and obtain a mixed solution; S2, separating the mixed solution obtained in S1 into solid and liquid, washing, and drying to obtain elastic flame-retardant microspheres; The small molecule cross-linking agent is divinylbenzene, trivinylbenzene or trivinylsilane; The inorganic flame retardant is aluminum hydroxide or magnesium hydroxide.

2. The low-temperature impact-resistant flame-retardant silicon core tube according to claim 1, characterized in that: The particle size of the nickel oxide powder is ≤100 nm.

3. The low-temperature impact-resistant flame-retardant silicon core tube according to claim 1, characterized in that: The double bond-containing silane coupling agent is one or more of vinyl triethoxysilane, acryloxymethyl trimethoxysilane, 7-octenyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane, vinyl triisopropoxysilane and vinyl trisbutyl ketoxime silane.

4. The low-temperature impact-resistant flame-retardant silicon core tube according to claim 1, characterized in that: The particle size of the inorganic flame retardant is 800-3000 meshes.

5. The low-temperature impact-resistant flame-retardant silicon core tube according to claim 1, characterized in that: The elastic flame-retardant microspheres are added in an amount of 15 parts by weight, and the inorganic flame retardant is added in an amount of 8 parts by weight.

6. A method for preparing the low-temperature impact-resistant flame-retardant silicon core tube according to any one of claims 1 to 5, characterized in that: It includes the following steps: S1. Heat the raw materials of the inner layer to 115-125° C., stir and mix, and obtain the raw materials of the inner layer; S2, heating the raw materials of the outer layer to 125-135° C., stirring and mixing, to obtain the outer layer raw materials; S4, heating and melting the outer layer raw material and the inner layer raw material respectively, and extruding and compounding them simultaneously at 165-180° C. to obtain a silicon core tube blank; S5. The silicon core tube blank is subjected to vacuum shaping, cooling, pulling and coiling processes to obtain a flame retardant silicon core tube.

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