Anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material and preparation method thereof

Abstract

The invention discloses an anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material and a preparation method thereof, and relates to the technical field of optical cable sheaths. According to the invention, vinyl phosphonate and styrene are subjected to a polymerization reaction to obtain a flame-retardant elastomer; and mixing the matrix resin, the flame-retardant elastomer, the flexibilizer, the filler, the stabilizer, the dispersant and the coloring agent, banburying, and carrying out melt extrusion to obtain the anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material. The sheath material has the advantages of low smoke, no halogen, environmental protection, excellent flame retardation and cracking resistance, and considerable application prospect.

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, are increasingly being used in a wider range of applications, and the performance requirements for optical cables are also 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] Although traditional optical cable sheath materials have good flame retardant and mechanical properties, they are mainly based on polyvinyl chloride resin, which will produce a large amount of toxic smoke and corrosive gases when burned, posing a great safety hazard. In recent years, with the enhancement of environmental awareness and the improvement of fire safety requirements, low-smoke halogen-free flame retardant sheath materials have gradually become the mainstream choice of optical cable sheath materials.

[0004] However, the existing low-smoke halogen-free flame-retardant sheath materials still have some shortcomings. For example, the common low-smoke halogen-free flame-retardant sheath materials currently mainly achieve flame retardancy by adding inorganic flame retardants. In order to achieve the ideal flame retardant effect, it is often necessary to mix and add a large amount of inorganic flame retardants. Simply physically mixing and adding inorganic flame retardants may result in poor flame retardant durability due to the migration or precipitation of inorganic flame retardants. In addition, the large amount of inorganic flame retardants added will also affect other properties of the material, such as reducing the processing fluidity of the material, resulting in difficulties in extrusion molding, and affecting production efficiency.

[0005] The Chinese patent application with publication number CN 116462896A discloses a low-smoke, halogen-free, flame-retardant sheath material for optical cables and a preparation method thereof. The sheath material for optical cables prepared in the 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, 2-amino-5-pyridine carboxylic acid lanthanum and 4,4'-dihydroxybenzophenone lanthanum, 2-amino-5-pyridine carboxylic acid lanthanum and 4,4'-dihydroxybenzophenone lanthanum can prevent the catalytic degradation of hydrogen chloride gas on the sheath material and increase the thermal stability of the sheath material; the modified graphite is modified with polyvinyl pyrrolidone to help improve the dispersibility, and under high temperature conditions, it not only plays a flame retardant role, but also can absorb the generated hydrogen chloride gas, and cooperates with 2-amino-5-pyridine carboxylic acid lanthanum and 4,4'-dihydroxybenzophenone lanthanum to treat hydrogen chloride.

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

[0007] In view of the deficiencies of the prior art, the present application provides a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material and a preparation method thereof, wherein a flame-retardant elastomer is obtained by polymerization of vinyl phosphonate and styrene; and the base resin, flame-retardant elastomer, toughening agent, filler, stabilizer, dispersant and colorant are mixed, kneaded and melt-extruded to obtain the crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material. The sheath material is low-smoke and halogen-free, very environmentally friendly, and has excellent flame retardant and crack-resistant properties, and has considerable application prospects.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, the sheath material comprising a base resin and a flame-retardant elastomer; the flame-retardant elastomer is obtained by polymerization reaction of vinyl phosphonate and styrene.

[0009] In a second aspect, the present application provides a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, comprising: 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, stirring at a second set temperature and for 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 into 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 according to a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture; adding the mixture into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed mixture; The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at the fifth set temperature, and the mixed material after banburying is cooled and pelletized to obtain sheath material particles.

[0010] Beneficial technical effects: The present application obtains a flame retardant elastomer by polymerization reaction of vinyl phosphonate and styrene; and then the base resin, flame retardant elastomer and other additives are mixed, kneaded and melt extruded to obtain the anti-cracking low-smoke halogen-free optical cable flame retardant sheath material. The vinyl phosphonate segment embedded in the flame retardant elastomer through polymerization reaction will not migrate or precipitate, and the vinyl phosphonate segment has good compatibility with the organic base resin, the combination is more uniform and tight, and the anti-cracking performance is enhanced. Moreover, the vinyl phosphonate segment decomposes at high temperature to generate acidic substances such as phosphoric acid, which can catalyze the dehydration reaction of the polystyrene segment in the flame retardant elastomer, thereby promoting the formation of a flame retardant carbon layer. In addition, the vinyl phosphonate segment also decomposes at high temperature to generate free radicals such as PO· and HPO·, which can capture H· and OH· free radicals in the flame and inhibit the combustion chain reaction; and the vinyl phosphonate segment decomposes at high temperature to produce non-combustible gases (such as H2O, CO2, etc.) that can dilute the concentration of combustible gases, further inhibit combustion and reduce smoke. In addition, all raw materials of the flame-retardant sheath material of the optical cable prepared in the present application are halogen-free and very environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the process of producing crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material. DETAILED DESCRIPTION

[0012] 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 part 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 creative work are within the scope of protection of this application.

[0013] In this application, the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit the application.

[0014] 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.

[0015] In addition, if the terms “first” or “second” appear in the present application, they are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0016] In a first aspect, the present application provides a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, the sheath material comprising a base resin and a flame-retardant elastomer; the flame-retardant elastomer is obtained by polymerization reaction of vinyl phosphonate and styrene.

[0017] In a specific embodiment, the base resin includes one or more of polyethylene, polypropylene and EVA.

[0018] In one embodiment, the structure of the vinyl phosphonate comprises: ; Wherein, R includes any one of methyl and ethyl.

[0019] In a specific embodiment, the structure of the flame retardant elastomer is as follows, comprising: ; Wherein, R includes any one of a methyl group and an ethyl group; a is an integer in the range of 70 to 100; b is an integer in the range of 200 to 300; and c is an integer in the range of 70 to 100.

[0020] In a specific embodiment, the sheath material further includes a toughening agent, a filler, a stabilizer, a dispersant and a colorant.

[0021] In a specific embodiment, in the sheath material, the mass ratio of base resin, flame retardant elastomer, toughening agent, filler, stabilizer, dispersant and colorant is (50~70): (10~20): (2~10): (10~20): (1~5): (1~5): (1~2).

[0022] 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.

[0023] In a specific embodiment, the filler includes one or more of talc, kaolin, mica powder and calcium carbonate.

[0024] In a specific embodiment, the stabilizer includes at least one of 2,6-di-tert-butyl-p-cresol and dilauryl thiodipropionate.

[0025] In a specific embodiment, the dispersant includes one or more of glyceryl stearate, n-butyl stearate and n-butyl palmitate.

[0026] In a specific embodiment, the colorant includes one or more of titanium dioxide, iron oxide, phthalocyanine blue and carbon black.

[0027] In a second aspect, the present application provides a method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, such as Figure 1 As shown, including: 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, stirring at a second set temperature and for 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 into 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 according to a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture; adding the mixture into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed mixture; The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at the fifth set temperature, and the mixed material after banburying is cooled and pelletized to obtain sheath material particles.

[0028] In a specific embodiment, during the preparation of the flame retardant elastomer, all raw materials are subjected to a water removal treatment.

[0029] In a specific embodiment, the solvent includes any one of toluene and xylene.

[0030] In a specific embodiment, the initiator includes any one of n-butyl lithium and sec-butyl lithium.

[0031] In a specific embodiment, the terminator includes any one of ethanol and isopropanol.

[0032] In a specific embodiment, the mass ratio of the solvent, styrene, vinyl phosphonate, initiator and terminator is (30-40): (20-30): (35-45): (0.1-1): (1-3).

[0033] 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.

[0034] In a specific implementation, the first setting time is 30 to 60 minutes; the second setting time is 60 to 90 minutes; the third setting time is 20 to 60 minutes; the fourth setting time is 10 to 20 minutes; the fifth setting time is 5 to 15 minutes; and the sixth setting time is 10 to 30 minutes.

[0035] The following will specifically describe 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.

[0036] Embodiment 1: 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: 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; 2. Add 42.5 g of vinyl phosphonate to the reactor and stir at 80 °C for 75 min; 3. Add 10 g of styrene to the reactor again and stir at 80 °C for 40 min; 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; 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 stearyl glyceride and 1 g of titanium dioxide into a high-speed mixer according to mass proportion, and mix at 90° C. for 10 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 130°C for 20 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 155° C., cool and pelletize to obtain sheath material particles.

[0037] Embodiment 2: 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: 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; 2. Add 39.2 g of vinyl phosphonate to the reactor and stir at 85 °C for 80 min; 3. Add 12.5 g of styrene to the reactor again and stir at 85 °C for 50 min; 4. Add 3 g of isopropanol into the reactor, stir at 85°C for 18 min, and dry the material to obtain a flame retardant elastomer; 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 mass proportion, and mix at 95° C. for 12 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 135°C for 25 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 158° C., cool and pelletize to obtain sheath material particles.

[0038] Embodiment 3: 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: 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; 2. Add 37.9 g of vinyl phosphonate to the reactor and stir at 75 °C for 70 min; 3. Add 11 g of styrene to the reactor again and stir at 75 °C for 30 min; 4. Add 1.5 g of ethanol to the reactor, stir at 75°C for 12 min, and dry the material to obtain a flame retardant elastomer; 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 mass proportion, and mix at 85° C. for 8 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 125°C for 15 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 152° C., cool and pelletize to obtain sheath material particles.

[0039] Embodiment 4: 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: 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; 2. Add 41 g of vinyl phosphonate to the reactor and stir at 90 °C for 90 min; 3. Add 13 g of styrene to the reactor again and stir at 90 °C for 60 min; 4. Add 2 g of isopropanol to the reactor, stir at 90°C for 20 min, and dry the material to obtain a flame retardant elastomer; 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 mass proportion, and mix at 100 ° C for 15 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 140°C for 30 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 160° C., cool and pelletize to obtain sheath material particles.

[0040] Embodiment 5: 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: 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 min; 2. Add 38 g of vinyl phosphonate to the reactor and stir at 82 °C for 85 min; 3. Add 12 g of styrene to the reactor again and stir at 82 °C for 45 min; 4. Add 1.3 g of ethanol to the reactor, stir at 82°C for 16 min, and dry the material to obtain a flame retardant elastomer; 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 mass proportion, and mix at 92° C. for 14 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 132°C for 22 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 156° C., cool and pelletize to obtain sheath material particles.

[0041] Embodiment 6: 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: 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; 2. Add 37 g of vinyl phosphonate to the reactor and stir at 88 °C for 88 min; 3. Add 15 g of styrene to the reactor again and stir at 88 °C for 55 min; 4. Add 2.5 g of isopropanol to the reactor, stir at 88°C for 19 min, and dry the material to obtain a flame retardant elastomer; 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 mass proportion, and mix at 98° C. for 13 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 138°C for 28 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 150° C., cool and pelletize to obtain sheath material particles.

[0042] Comparative Example 1: A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps: 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; 2. Add 42.5 g of 1,4-butadiene to the reactor and stir at 80 °C for 75 min; 3. Add 10 g of styrene to the reactor again and stir at 80 °C for 40 min; 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; 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 stearyl glyceride and 1 g of titanium dioxide into a high-speed mixer according to mass proportion, and mix at 90° C. for 10 min to obtain a mixture; 6. Add the mixture into an internal mixer and mix at 130°C for 20 minutes to obtain a mixed mixture; 7. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 155° C., cool and pelletize to obtain sheath material particles.

[0043] Comparative Example 2: A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps: 1. Add 55.8 g EVA, 16 g aluminum hydroxide, 6 g maleic anhydride grafted polypropylene, 16 g mica powder, 2.5 g 2,6-di-tert-butyl-p-cresol, 2.5 g n-butyl palmitate and 1.2 g phthalocyanine blue into a high-speed mixer according to mass proportion, and mix at 85° C. for 8 min to obtain a mixture; 2. Add the mixture into an internal mixer and mix at 125°C for 15 minutes to obtain a mixed mixture; 3. Add the mixed material after banburying into a twin-screw extruder, melt-extrude the mixed material after banburying at 152°C, and obtain sheath material particles after cooling and pelletizing.

[0044] Comparative Example 3: A method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material comprises the following steps: 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 mass proportion, and mix at 98° C. for 13 min to obtain a mixture; 2. Add the mixture into an internal mixer and mix at 138°C for 28 minutes to obtain a mixed mixture; 3. Add the mixed material after banburying into a twin-screw extruder, melt and extrude the mixed material after banburying at 150°C, and obtain sheath material particles after cooling and pelletizing.

[0045] 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, and the test method followed GB / T1040.3-2006.

[0046] A vertical combustion test was performed on the sheath prepared by the sheath material of the present application, and its flame retardant grade was evaluated based on the measured vertical combustion level. The test method complied with GB / T2408-2008.

[0047] The sheath prepared by the sheath material of the present application is subjected to a smoke density test to evaluate its low smoke characteristics, and the test method complies with GB / T8323.2-2008.

[0048] The above 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".

[0049] Table 1 Performance test results of the sheaths prepared from the sheath materials prepared in the embodiments and comparative examples

[0050] It can be seen from Table 1 that the tensile strength, elongation at break, smoke density and vertical burning level of Examples 1-6 are better than those of Comparative Examples 1-3 as a whole.

[0051] This is because the vinyl phosphonate segments embedded in the flame retardant elastomers in Examples 1 to 6 through polymerization reactions will not migrate or precipitate like flame retardants added by ordinary physical mixing, and the vinyl phosphonate segments have good compatibility with the organic matrix resin, and the combination is more uniform and tight, and the anti-cracking performance is enhanced. Moreover, the vinyl phosphonate segments decompose at high temperatures to generate acidic substances such as phosphoric acid, which can catalyze the dehydration reaction of the polystyrene segments in the flame retardant elastomer, thereby promoting the formation of a flame retardant carbon layer. In addition, the vinyl phosphonate segments also decompose at high temperatures to generate free radicals such as PO· and HPO·, which can capture H· and OH· free radicals in the flame and inhibit the combustion chain reaction; and the vinyl phosphonate segments decompose at high temperatures to produce non-combustible gases (such as H2O, CO2, etc.) that can dilute the concentration of combustible gases, further inhibit combustion and reduce smoke.

[0052] In addition, all raw materials used in Examples 1 to 6 are halogen-free and very environmentally friendly.

[0053] In Comparative Example 1, no vinyl phosphonate chain 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 chain 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.

[0054] The above results show and describe the basic principles and main features of the present application as well as the advantages of the present application.

[0055] Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present application. Without departing from the spirit and scope of the present application, the present application may have various changes and improvements, and these changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection sought in the present application is defined by the equivalents of the attached claims.

Claims

1. A crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material, characterized in that: The sheath material comprises a base resin and a flame retardant elastomer; the flame retardant elastomer is obtained by polymerization reaction of vinyl phosphonate and styrene.

2. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 1, characterized in that: 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.

3. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 1, characterized in that: The structure of the flame retardant elastomer comprises: ； Wherein, R includes any one of a methyl group and an ethyl group; a is an integer in the range of 70 to 100; b is an integer in the range of 200 to 300; and c is an integer in the range of 70 to 100.

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

5. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 4, 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).

6. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 4, 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.

7. The anti-cracking low-smoke halogen-free optical cable flame-retardant sheath material according to claim 4, 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.

8. The method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material according to any one of claims 1 to 7, characterized in that: The following steps are involved: 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, stirring at a second set temperature and for 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 into 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 according to a mass ratio, and mixing at a third set temperature for a fifth set time to obtain a mixture; adding the mixture into an internal mixer, and performing internal mixing at a fourth set temperature for a sixth set time to obtain a mixed mixture; The mixed material after banburying is added into a twin-screw extruder, and the mixed material after banburying is melt-extruded at the fifth set temperature, and the mixed material after banburying is cooled and pelletized to obtain sheath material particles.

9. The method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material according to claim 8, characterized in that: 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).

10. The method for preparing a crack-resistant low-smoke halogen-free optical cable flame-retardant sheath material according to claim 8, 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 setting time is 30~60min; the second setting time is 60~90min; the third setting time is 20~60min; the fourth setting time is 10~20min; the fifth setting time is 5~15min; the sixth setting time is 10~30min.

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