A crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material and its preparation method

Abstract

This application discloses a crack-resistant, low-smoke, halogen-free optical cable flame-retardant sheathing material and its preparation method, relating to the field of optical cable sheathing technology. This application utilizes a polymerization reaction between vinyl phosphonate and styrene to produce a flame-retardant elastomer. A base resin, flame-retardant elastomer, toughening agent, filler, stabilizer, dispersant, and colorant are then mixed, kneaded, and melt-extruded to produce the crack-resistant, low-smoke, halogen-free optical cable flame-retardant sheathing material. This sheathing material is low-smoke, halogen-free, environmentally friendly, and exhibits excellent flame retardancy and crack resistance, offering promising application prospects.

Description

Technical Field

[0001] The present application relates to the technical field of optical cable sheaths, and in particular to a crack-resistant, low-smoke, halogen-free optical cable flame-retardant sheath material and a preparation method thereof. Background Art

[0002] With the rapid development of the information age, optical cables, as an important carrier of information transmission, have seen their application areas continuously expand, and the performance requirements for optical cables have also been increasing. Among them, the performance of the optical cable sheath material, as the first barrier to protect the optical fiber, directly affects the service life and safety of the optical cable.

[0003] While traditional optical cable sheathing materials offer excellent flame retardancy and mechanical properties, they are primarily based on polyvinyl chloride (PVC) resins, which produce large amounts of toxic smoke and corrosive gases when burned, posing a significant safety hazard. In recent years, with growing environmental awareness and heightened fire safety requirements, low-smoke, halogen-free, flame-retardant sheathing materials have gradually become the mainstream choice for optical cable sheathing.

[0004] However, existing low-smoke, halogen-free, flame-retardant sheathing materials still have some shortcomings. For example, currently common low-smoke, halogen-free, flame-retardant sheathing materials mainly achieve flame retardancy through the addition of inorganic flame retardants. To achieve the desired flame retardant effect, large amounts of inorganic flame retardants are often required to be mixed and added. Simply physically adding inorganic flame retardants can lead to poor flame retardant durability due to migration or precipitation of the inorganic flame retardants. Furthermore, the addition of large amounts of inorganic flame retardants can affect other material properties, such as reducing the material's processing fluidity, making extrusion molding difficult, and affecting production efficiency.

[0005] Chinese patent application CN 116462896A discloses a low-smoke, halogen-free, flame-retardant sheathing material for optical cables and its preparation method. The sheathing material prepared in this application includes the following raw materials: polyethylene resin, polypropylene resin, filler, plasticizer, flame retardant, composite stabilizer, antioxidant, lubricant, and compatibilizer. The composite stabilizer includes modified expanded graphite, lanthanum 2-amino-5-pyridinecarboxylate, and lanthanum 4,4'-dihydroxybenzophenone. Lanthanum 2-amino-5-pyridinecarboxylate and lanthanum 4,4'-dihydroxybenzophenone prevent catalytic degradation of the sheathing material by hydrogen chloride gas, increasing its thermal stability. Modified graphite with polyvinyl pyrrolidone improves its dispersibility. At higher temperatures, it not only provides a flame retardant effect but also absorbs generated hydrogen chloride gas, synergistically treating hydrogen chloride with lanthanum 2-amino-5-pyridinecarboxylate and lanthanum 4,4'-dihydroxybenzophenone.

[0006] However, this solution still achieves the flame retardant effect by physically mixing and adding inorganic flame retardants, and the flame retardant performance is not specifically reflected. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this application provides a crack-resistant, low-smoke, halogen-free, flame-retardant sheathing material for optical cables and its preparation method. A flame-retardant elastomer is obtained by polymerization of vinyl phosphonate and styrene. A base resin, flame-retardant elastomer, toughening agent, filler, stabilizer, dispersant, and colorant are then mixed, kneaded, and melt-extruded to produce the crack-resistant, low-smoke, halogen-free, and flame-retardant sheathing material. This sheathing material is low-smoke, halogen-free, environmentally friendly, and exhibits excellent flame retardancy and crack resistance, offering promising application prospects.

[0008] To achieve the above objectives, this application adopts the following technical solutions:

[0009] The present application provides a flame-retardant sheath material for crack-resistant low-smoke halogen-free optical cables, characterized in that the sheath material comprises a base resin and a flame-retardant elastomer; the flame-retardant elastomer is obtained by polymerization of vinyl phosphonate and styrene; the base resin comprises one or more of polyethylene, polypropylene, and EVA; the structure of the vinyl phosphonate comprises:

[0010] ;

[0011] Wherein, R includes any one of methyl and ethyl;

[0012] The structure of the flame retardant elastomer comprises:

[0013] ;

[0014] Wherein, R includes any one of methyl and ethyl; a is an integer in the range of 70 to 100; b is an integer in the range of 200 to 300; c is an integer in the range of 70 to 100;

[0015] The preparation method of the crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0016] Adding a solvent, styrene and an initiator into a reactor protected by nitrogen, and stirring at a first set temperature for a first set time;

[0017] Adding vinyl phosphonate to the reactor and stirring at a second set temperature and a second set time;

[0018] Add an equal amount of styrene to the reactor again, and stir at the second set temperature for a third set time;

[0019] Adding a terminator to the reactor, stirring at the second set temperature for a fourth set time, and drying the discharged material to obtain a flame retardant elastomer;

[0020] adding a base resin, a flame retardant elastomer, a toughening agent, a filler, a stabilizer, a dispersant, and a colorant into a high-speed mixer in a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture;

[0021] adding the mixed material into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed material;

[0022] The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at a fifth set temperature, and then cooled and pelletized to obtain sheath material pellets;

[0023] The solvent includes any one of toluene and xylene; the initiator includes any one of n-butyl lithium and sec-butyl lithium; the terminator includes any one of ethanol and isopropanol; the mass ratio of the solvent, styrene, vinyl phosphonate, initiator and terminator is (30-40): (20-30): (35-45): (0.1-1): (1-3).

[0024] Beneficial technical effects:

[0025] This application utilizes a polymerization reaction between vinyl phosphonate and styrene to produce a flame-retardant elastomer. A base resin, flame-retardant elastomer, and other additives are then mixed, kneaded, and melt-extruded to produce the crack-resistant, low-smoke, halogen-free optical cable flame-retardant sheathing material. The vinyl phosphonate segments embedded in the flame-retardant elastomer through the polymerization reaction do not migrate or precipitate. Furthermore, the vinyl phosphonate segments exhibit excellent compatibility with the organic base resin, resulting in a more uniform and tight bond and enhanced crack resistance. Furthermore, the vinyl phosphonate segments decompose at high temperatures to produce acidic substances such as phosphoric acid, which catalyze the dehydration reaction of the polystyrene segments in the flame-retardant elastomer, thereby promoting the formation of a flame-retardant char layer. Furthermore, the vinyl phosphonate segments also decompose at high temperatures to produce free radicals such as PO and HPO. These free radicals can capture H and OH radicals in flames, inhibiting the combustion chain reaction. Furthermore, the decomposition of the vinyl phosphonate segments at high temperatures also produces non-combustible gases (such as H₂O and CO₂), which can dilute the concentration of combustible gases, further inhibiting combustion and reducing smoke production. In addition, all raw materials of the flame-retardant sheath material of the optical cable prepared in this application are halogen-free and very environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the process of producing crack-resistant low-smoke halogen-free optical cable flame-retardant sheath materials. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] In this application, the terms used in this application are for the purpose of describing specific embodiments only and are not intended to be limiting of the application.

[0029] As used in this application, the singular forms "for," "or," "an," "any," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0030] The present application provides a flame-retardant sheath material for crack-resistant low-smoke halogen-free optical cables, characterized in that the sheath material comprises a base resin and a flame-retardant elastomer; the flame-retardant elastomer is obtained by polymerization of vinyl phosphonate and styrene; the base resin comprises one or more of polyethylene, polypropylene, and EVA; the structure of the vinyl phosphonate comprises:

[0031] ;

[0032] Wherein, R includes any one of methyl and ethyl;

[0033] The structure of the flame retardant elastomer comprises:

[0034] ;

[0035] Wherein, R includes any one of methyl and ethyl; a is an integer in the range of 70 to 100; b is an integer in the range of 200 to 300; c is an integer in the range of 70 to 100;

[0036] The preparation method of the crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material is as follows Figure 1 As shown, the following steps are included:

[0037] Adding a solvent, styrene and an initiator into a reactor protected by nitrogen, and stirring at a first set temperature for a first set time;

[0038] Adding vinyl phosphonate to the reactor and stirring at a second set temperature and a second set time;

[0039] Add an equal amount of styrene to the reactor again, and stir at the second set temperature for a third set time;

[0040] Adding a terminator to the reactor, stirring at the second set temperature for a fourth set time, and drying the discharged material to obtain a flame retardant elastomer;

[0041] adding a base resin, a flame retardant elastomer, a toughening agent, a filler, a stabilizer, a dispersant, and a colorant into a high-speed mixer in a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture;

[0042] adding the mixed material into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed material;

[0043] The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at a fifth set temperature, and then cooled and pelletized to obtain sheath material pellets;

[0044] The solvent includes any one of toluene and xylene; the initiator includes any one of n-butyl lithium and sec-butyl lithium; the terminator includes any one of ethanol and isopropanol; the mass ratio of the solvent, styrene, vinyl phosphonate, initiator and terminator is (30-40): (20-30): (35-45): (0.1-1): (1-3).

[0045] In a specific embodiment, the sheathing material further includes a toughening agent, a filler, a stabilizer, a dispersant and a colorant.

[0046] In a specific embodiment, the first set temperature is 50-70°C; the second set temperature is 70-90°C; the third set temperature is 80-100°C; the fourth set temperature is 120-140°C; and the fifth set temperature is 150-160°C.

[0047] In a specific embodiment, the first setting time is 30-60 minutes; the second setting time is 60-90 minutes; the third setting time is 20-60 minutes; the fourth setting time is 10-20 minutes; the fifth setting time is 5-15 minutes; and the sixth setting time is 10-30 minutes.

[0048] In a specific embodiment, in the sheath material, the mass ratio of the base resin, the flame retardant elastomer, the toughening agent, the filler, the stabilizer, the dispersant and the colorant is (50~70): (10~20): (2~10): (10~20): (1~5): (1~5): (1~2).

[0049] In a specific embodiment, the toughening agent includes one or more of silicone rubber, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, and maleic anhydride grafted EVA.

[0050] In a specific embodiment, the filler includes one or more of talc, kaolin, mica powder and calcium carbonate.

[0051] In one embodiment, the stabilizer includes at least one of 2,6-di-tert-butyl-p-cresol and dilauryl thiodipropionate.

[0052] In a specific embodiment, the dispersant includes one or more of glyceryl stearate, n-butyl stearate, and n-butyl palmitate.

[0053] In a specific embodiment, the colorant includes one or more of titanium dioxide, iron oxide, phthalocyanine blue and carbon black.

[0054] In a specific embodiment, during the preparation of the flame retardant elastomer, all raw materials are subjected to a water removal treatment.

[0055] The following will describe in detail a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material and a preparation method thereof provided by the present application in combination with different embodiments.

[0056] Example 1:

[0057] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0058] 1. Add 35 g toluene, 10 g styrene and 0.5 g n-butyl lithium into a nitrogen-protected reactor and stir at 60 ° C for 45 min;

[0059] 2. Add 42.5 g of vinyl phosphonate to the reactor and stir at 80 ° C for 75 minutes;

[0060] 3. Add 10 g of styrene to the reactor again and stir at 80 °C for 40 min;

[0061] 4. Add 2 g of ethanol to the reactor, stir at 80°C for 15 min, and dry the material to obtain a flame retardant elastomer;

[0062] 5. Add 60 g of polyethylene, 15 g of flame retardant elastomer, 5 g of silicone rubber, 15 g of talc, 2 g of 2,6-di-tert-butyl-p-cresol, 2 g of glyceryl stearate and 1 g of titanium dioxide into a high-speed mixer according to the mass ratio, and mix at 90° C. for 10 min to obtain a mixture;

[0063] 6. Add the mixture into an internal mixer and mix at 130°C for 20 minutes to obtain a mixed mixture;

[0064] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material after banburying at 155°C, cool and pelletize to obtain sheath material particles.

[0065] Example 2:

[0066] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0067] 1. Add 32 g of xylene, 12.5 g of styrene and 0.8 g of sec-butyl lithium into a nitrogen-protected reactor and stir at 65 ° C for 50 min;

[0068] 2. Add 39.2 g of vinyl phosphonate to the reactor and stir at 85 ° C for 80 minutes;

[0069] 3. Add 12.5 g of styrene to the reactor again and stir at 85 °C for 50 min;

[0070] 4. Add 3 g of isopropyl alcohol to the reactor, stir at 85°C for 18 minutes, and dry the material to obtain a flame retardant elastomer;

[0071] 5. Add 50 g of polypropylene, 18 g of flame retardant elastomer, 8 g of maleic anhydride grafted polyethylene, 16.5 g of kaolin, 3 g of dilauryl thiodipropionate, 3 g of n-butyl stearate and 1.5 g of iron oxide into a high-speed mixer according to the mass ratio, and mix at 95° C. for 12 min to obtain a mixture;

[0072] 6. Add the mixture into an internal mixer and mix at 135°C for 25 minutes to obtain a mixed mixture;

[0073] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 158°C, cool and pelletize to obtain sheath material particles.

[0074] Example 3:

[0075] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0076] 1. Add 38 g toluene, 11 g styrene and 0.6 g n-butyl lithium into a nitrogen-protected reactor and stir at 55 °C for 40 min;

[0077] 2. Add 37.9 g of vinyl phosphonate to the reactor and stir at 75 ° C for 70 minutes;

[0078] 3. Add 11 g of styrene to the reactor again and stir at 75 °C for 30 min;

[0079] 4. Add 1.5 g of ethanol to the reactor, stir at 75 ° C for 12 minutes, and dry the material to obtain a flame retardant elastomer;

[0080] 5. Add 55.8 g of EVA, 16 g of flame retardant elastomer, 6 g of maleic anhydride grafted polypropylene, 16 g of mica powder, 2.5 g of 2,6-di-tert-butyl-p-cresol, 2.5 g of n-butyl palmitate, and 1.2 g of phthalocyanine blue into a high-speed mixer according to the mass ratio, and mix at 85° C. for 8 min to obtain a mixture;

[0081] 6. Add the mixture into an internal mixer and mix at 125°C for 15 minutes to obtain a mixed mixture;

[0082] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 152°C, cool and pelletize to obtain sheath material particles.

[0083] Example 4:

[0084] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0085] 1. Add 30 g of xylene, 13 g of styrene and 1 g of sec-butyl lithium into a nitrogen-protected reactor and stir at 70 ° C for 60 min;

[0086] 2. Add 41 g of vinyl phosphonate to the reactor and stir at 90 ° C for 90 minutes;

[0087] 3. Add 13 g of styrene to the reactor again and stir at 90 ° C for 60 minutes;

[0088] 4. Add 2 g of isopropyl alcohol to the reactor, stir at 90°C for 20 min, and dry the material to obtain a flame retardant elastomer;

[0089] 5. Add 55 g of polyethylene, 20 g of flame retardant elastomer, 5 g of maleic anhydride grafted EVA, 10 g of calcium carbonate, 5 g of dilauryl thiodipropionate, 3 g of glyceryl stearate and 2 g of carbon black into a high-speed mixer according to the mass ratio, and mix at 100 ° C for 15 min to obtain a mixture;

[0090] 6. Add the mixture into an internal mixer and mix at 140°C for 30 minutes to obtain a mixed mixture;

[0091] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 160°C, cool and pelletize to obtain sheath material particles.

[0092] Example 5:

[0093] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0094] 1. Add 36 g toluene, 12 g styrene and 0.7 g n-butyl lithium into a nitrogen-protected reactor and stir at 58 ° C for 55 minutes;

[0095] 2. Add 38 g of vinyl phosphonate to the reactor and stir at 82 °C for 85 min;

[0096] 3. Add 12 g of styrene to the reactor again and stir at 82 °C for 45 min;

[0097] 4. Add 1.3 g of ethanol to the reactor, stir at 82°C for 16 minutes, and dry the material to obtain a flame retardant elastomer;

[0098] 5. Add 52 g of polypropylene, 17 g of flame retardant elastomer, 7 g of silicone rubber, 14.2 g of talc, 4 g of 2,6-di-tert-butyl-p-cresol, 4 g of n-butyl stearate, and 1.8 g of titanium dioxide into a high-speed mixer according to the mass ratio, and mix at 92° C. for 14 min to obtain a mixture;

[0099] 6. Add the mixture into an internal mixer and mix at 132°C for 22 minutes to obtain a mixed mixture;

[0100] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material after banburying at 156°C, cool and pelletize to obtain sheath material particles.

[0101] Example 6:

[0102] like Figure 1 As shown, a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0103] 1. Add 30 g of xylene, 15 g of styrene and 0.5 g of sec-butyl lithium into a nitrogen-protected reactor and stir at 68 ° C for 58 min;

[0104] 2. Add 37 g of vinyl phosphonate to the reactor and stir at 88 °C for 88 min;

[0105] 3. Add 15 g of styrene to the reactor again and stir at 88 °C for 55 min;

[0106] 4. Add 2.5 g of isopropyl alcohol to the reactor, stir at 88°C for 19 minutes, and dry the material to obtain a flame retardant elastomer;

[0107] 5. Add 63 g of EVA, 16 g of flame retardant elastomer, 5 g of maleic anhydride grafted polyethylene, 11 g of kaolin, 1.5 g of dilauryl thiodipropionate, 1.5 g of n-butyl palmitate, and 2 g of iron oxide into a high-speed mixer according to the mass ratio, and mix at 98° C. for 13 min to obtain a mixture;

[0108] 6. Add the mixture into an internal mixer and mix at 138°C for 28 minutes to obtain a mixed mixture;

[0109] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 150°C, cool and pelletize to obtain sheath material particles.

[0110] Comparative Example 1:

[0111] A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0112] 1. Add 35 g toluene, 10 g styrene and 0.5 g n-butyl lithium into a nitrogen-protected reactor and stir at 60 ° C for 45 min;

[0113] 2. Add 42.5 g of 1,4-butadiene to the reactor and stir at 80°C for 75 minutes;

[0114] 3. Add 10 g of styrene to the reactor again and stir at 80 °C for 40 min;

[0115] 4. Add 2 g of ethanol to the reactor, stir at 80°C for 15 min, and dry the material to obtain a flame retardant elastomer;

[0116] 5. Add 60 g of polyethylene, 15 g of flame retardant elastomer, 5 g of silicone rubber, 15 g of talc, 2 g of 2,6-di-tert-butyl-p-cresol, 2 g of glyceryl stearate and 1 g of titanium dioxide into a high-speed mixer according to the mass ratio, and mix at 90° C. for 10 min to obtain a mixture;

[0117] 6. Add the mixture into an internal mixer and mix at 130°C for 20 minutes to obtain a mixed mixture;

[0118] 7. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material after banburying at 155°C, cool and pelletize to obtain sheath material particles.

[0119] Comparative Example 2:

[0120] A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0121] 1. Add 55.8 g of EVA, 16 g of aluminum hydroxide, 6 g of maleic anhydride-grafted polypropylene, 16 g of mica powder, 2.5 g of 2,6-di-tert-butyl-p-cresol, 2.5 g of n-butyl palmitate, and 1.2 g of phthalocyanine blue into a high-speed mixer according to the mass ratio, and mix at 85° C. for 8 min to obtain a mixture;

[0122] 2. Add the mixture into an internal mixer and mix at 125°C for 15 minutes to obtain a mixed mixture;

[0123] 3. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 152°C, cool and pelletize to obtain sheath material particles.

[0124] Comparative Example 3:

[0125] A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps:

[0126] 1. Add 63 g of EVA, 16 g of vinyl phosphonate, 5 g of maleic anhydride-grafted polyethylene, 11 g of kaolin, 1.5 g of dilauryl thiodipropionate, 1.5 g of n-butyl palmitate, and 2 g of iron oxide into a high-speed mixer according to the mass ratio, and mix at 98° C. for 13 min to obtain a mixture;

[0127] 2. Add the mixture into an internal mixer and mix at 138°C for 28 minutes to obtain a mixed mixture;

[0128] 3. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material at 150°C, cool and pelletize to obtain sheath material particles.

[0129] The tensile strength and elongation at break of the sheath prepared from the sheath material of the present application were tested to evaluate its anti-cracking properties. The test method complies with GB / T1040.3-2006.

[0130] A vertical combustion test was performed on the sheath prepared from the sheath material of the present application, and its flame retardancy was evaluated based on the measured vertical combustion level. The test method complied with GB / T2408-2008.

[0131] The sheath prepared by the sheath material of the present application was subjected to a smoke density test to evaluate its low smoke characteristics. The test method complies with GB / T8323.2-2008.

[0132] The test results are shown in Table 1. The test results fully meet the performance requirements of the National Standard of the People's Republic of China GB / T32129-2015 "Halogen-free and low-smoke flame-retardant cable materials for wires and cables".

[0133] Table 1 Performance test results of sheaths made from sheath materials prepared in Examples and Comparative Examples

[0134]

[0135] As shown in Table 1, the tensile strength, elongation at break, smoke density and vertical burning level of Examples 1 to 6 are generally better than those of Comparative Examples 1 to 3.

[0136] This is because the vinyl phosphonate segments embedded in the flame-retardant elastomers of Examples 1-6 through polymerization do not migrate or precipitate like flame retardants added through conventional physical mixing. Furthermore, the vinyl phosphonate segments have excellent compatibility with the organic matrix resin, resulting in a more uniform and tight bond and enhanced crack resistance. Furthermore, the vinyl phosphonate segments decompose at high temperatures to produce acidic substances such as phosphoric acid, which catalyze the dehydration reaction of the polystyrene segments in the flame-retardant elastomer, thereby promoting the formation of a flame-retardant char layer. Furthermore, the vinyl phosphonate segments also decompose at high temperatures to produce free radicals such as PO· and HPO·. These free radicals can capture H· and OH· radicals in the flame, inhibiting the combustion chain reaction. Furthermore, the decomposition of the vinyl phosphonate segments at high temperatures also produces non-combustible gases (such as H2O and CO2), which can dilute the concentration of combustible gases, further inhibiting combustion and reducing smoke production.

[0137] In addition, all raw materials used in Examples 1 to 6 are halogen-free and very environmentally friendly.

[0138] In Comparative Example 1, no vinyl phosphonate segment was introduced, and no inorganic flame retardant was added by physical means. Instead, vinyl phosphonate was replaced by 1,4-butadiene. Therefore, although the mechanical properties of the sheath material prepared therefrom were slightly better than those of other comparative examples, the flame retardancy was the worst. In Comparative Example 2, an inorganic flame retardant was added by physical means. Therefore, although the flame retardancy of the sheath material prepared therefrom was slightly better than that of Comparative Example 1, the mechanical properties were the worst compared with those of other comparative examples. In Comparative Example 3, no vinyl phosphonate segment was introduced by polymerization reaction, but vinyl phosphonate was directly added by physical means. Therefore, the flame retardancy was better in the comparative example, but the mechanical properties were moderate.

[0139] The above results show and describe the basic principles and main features of this application as well as the advantages of this application.

[0140] Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. Such changes and improvements are intended to fall within the scope of the present application. The scope of protection claimed in the present application is defined by the equivalents of the appended claims.

Claims

1. A crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, characterized in that: The sheath material includes a base resin and a flame retardant elastomer; the flame retardant elastomer is obtained by polymerization of vinyl phosphonate and styrene; the base resin includes one or more of polyethylene, polypropylene and EVA; the structure of the vinyl phosphonate includes: ； Wherein, R includes any one of methyl and ethyl; The structure of the flame retardant elastomer comprises: ； Wherein, R includes any one of methyl and ethyl; a is an integer in the range of 70 to 100; b is an integer in the range of 200 to 300; c is an integer in the range of 70 to 100; The preparation method of the crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps: Adding a solvent, styrene and an initiator into a reactor protected by nitrogen, and stirring at a first set temperature for a first set time; Adding vinyl phosphonate to the reactor and stirring at a second set temperature and a second set time; Add an equal amount of styrene to the reactor again, and stir at the second set temperature for a third set time; Adding a terminator to the reactor, stirring at the second set temperature for a fourth set time, and drying the discharged material to obtain a flame retardant elastomer; adding a base resin, a flame retardant elastomer, a toughening agent, a filler, a stabilizer, a dispersant, and a colorant into a high-speed mixer in a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture; adding the mixed material into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed material; The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at a fifth set temperature, and then cooled and pelletized to obtain sheath material pellets; The solvent includes any one of toluene and xylene; the initiator includes any one of n-butyl lithium and sec-butyl lithium; the terminator includes any one of ethanol and isopropanol; the mass ratio of the solvent, styrene, vinyl phosphonate, initiator and terminator is (30-40): (20-30): (35-45): (0.1-1): (1-3).

2. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 1, characterized in that: The sheath material further comprises a toughening agent, a filler, a stabilizer, a dispersant and a colorant.

3. The method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material according to claim 1, characterized in that: The first set temperature is 50~70℃; the second set temperature is 70~90℃; the third set temperature is 80~100℃; the fourth set temperature is 120~140℃; the fifth set temperature is 150~160℃; the first set time is 30~60min; the second set time is 60~90min; the third set time is 20~60min; the fourth set time is 10~20min; the fifth set time is 5~15min; and the sixth set time is 10~30min.

4. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 2, characterized in that: In the sheath material, the mass ratio of the base resin, the flame retardant elastomer, the toughening agent, the filler, the stabilizer, the dispersant and the colorant is (50-70): (10-20): (2-10): (10-20): (1-5): (1-5): (1-2).

5. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 2, characterized in that: The toughening agent includes one or more of silicone rubber, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene and maleic anhydride grafted EVA; the filler includes one or more of talc powder, kaolin, mica powder and calcium carbonate.

6. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 2, characterized in that: The stabilizer includes at least one of 2,6-di-tert-butyl-p-cresol and dilauryl thiodipropionate; the dispersant includes one or more of glyceryl stearate, n-butyl stearate and n-butyl palmitate; and the colorant includes one or more of titanium dioxide, iron oxide, phthalocyanine blue and carbon black.

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