A flame-retardant high-strength optical cable and its preparation method

Abstract

The present invention discloses a flame-retardant high-strength optical cable and a preparation method thereof, including at least one reinforcing member, at least one cable core distributed outside the reinforcing member, an inner sheath coated outside the cable core, and a flame-retardant outer sheath coated on the inner sheath. Wherein the cable core is composed of at least one optical fiber and a loose tube; wherein, by weight, the flame-retardant outer sheath is made of the following raw materials: 80-90 parts of polypropylene, 10-20 parts of nylon 6, 3-6 parts of compatibilizer, 20-25 parts of modified flame retardant, 1-3 parts of antioxidant, 0.5-1 part of lubricant, and 5-10 parts of modified glass fiber. The optical cable has excellent flame-retardant performance, good mechanical properties, simple structure, easy preparation, long service life, and good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical cables, and particularly relates to a flame-retardant high-strength optical cable and a preparation method thereof. Background Art

[0002] In recent years, due to the rapid development of China's communication business, while people's demand for optical cable products is increasing continuously, safety and health issues have always attracted the attention of producers and users, and have gradually become the key focus of current social production. Communication optical cables are the communication lifelines of the country and society, and also an important cornerstone of the modern information society. Their safety issues must not be ignored. Although good mechanical and transmission performance are the basic requirements for optical fiber and optical cable products, for optical cables laid indoors in high-rise buildings and used in some special occasions such as power, mining, subway, and tunnel, clear requirements for flame-retardant performance are also put forward. Therefore, it is crucial to improve the flame-retardant performance of optical cables.

[0003] Flame-retardant optical cables are a new type of optical cables that can delay ignition and slow down the speed of fire spread. After the flame-retardant optical cable is out of the influence range of an open flame, the combustion flame will quickly and automatically go out, which can avoid further fire damage. Through continuous investment in recent years, researchers and producers have successively developed various optical cable flame-retardant technologies suitable for different usage occasions.

[0004] Although there are various optical cables on the market now, the performance of most sheath materials is still not very ideal. In order to improve the flame-retardant performance of optical cables and enhance their use safety, most manufacturers often add halogen-free flame-retardant materials to the sheath material to achieve the flame-retardant effect. Excessive addition of inorganic halogen-free flame-retardant materials will lead to poor fluidity during the mixing and molding of the polymer matrix, uneven dispersion of the halogen-free flame-retardant materials, which will not only seriously affect the microstructure and apparent performance of the sheath material, but also reduce the mechanical properties of the optical cable sheath.

[0005] Chinese Patent Application No. CN201510340282.4 discloses a low-smoke and halogen-free flame retardant material for drop wire optical cable and its preparation method. The low-smoke and halogen-free flame retardant material contains a polyolefin substrate and a compatibilizer. Based on 100 parts by total weight of the polyolefin substrate and the compatibilizer, the weight ratio of the polyolefin substrate to the compatibilizer is 80 - 90 parts by weight : 10 - 20 parts by weight. And based on 100 parts by weight of the polyolefin substrate and the compatibilizer, the low-smoke and halogen-free flame retardant material for drop wire optical cable further contains the following components in parts by weight: 0.5 - 2 parts of antioxidant; 140 - 180 parts of inorganic flame retardant; 1 - 5 parts of lubricant; 1 - 4 parts of coupling agent; and 0 - 8 parts of halogen-free masterbatch. However, a large amount of inorganic flame retardant is added, and the improvement of the mechanical properties of the sheath material, especially the bending property, tensile property, etc., is limited. Chinese Patent Application No. CN201810790986.5 discloses a highly flame retardant cable material and its preparation method. The highly flame retardant cable material includes the following raw materials: low-density polyethylene, ethylene-vinyl acetate copolymer, modified aluminum hypophosphite, moroxydine, ethylene glycol monostearate, polypropylene wax, photocatalyst, aluminum-magnesium alloy powder, antioxidant. The modified aluminum hypophosphite is composed of aluminum hypophosphite, methylene diisocyanate, phenyl silicone oil, and polyimide in a mass ratio of 6:2:9:1. The obtained cable material has excellent aging resistance, antibacterial property, corrosion resistance, flame retardancy, and mechanical properties. However, there is still room for improvement in its mechanical properties.

[0006] Therefore, there is a need for a flame retardant high-strength optical cable that can have excellent flame retardant performance and good mechanical properties, especially can be unaffected in a fire and will not become an extended combustion material, ensuring stable signal transmission. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a flame retardant high-strength optical cable and its preparation method. The prepared optical cable has excellent flame retardant performance, and at the same time has good mechanical properties, and has a simple structure, is easy to prepare, has a long service life, and has good application prospects.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A flame retardant high-strength optical cable includes at least one strengthening member (1), at least one cable core (2) distributed outside the strengthening member (1), an inner sheath (5) covering the cable core, and a flame retardant outer sheath (6) covering the inner sheath. Wherein the cable core (2) is composed of at least one optical fiber (4) and a loose tube (3);

[0010] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 80-90 parts of polypropylene, 10-20 parts of nylon 6, 3-6 parts of compatibilizer, 20-25 parts of modified flame retardant, 1-3 parts of antioxidant, 0.5-1 part of lubricant, and 5-10 parts of modified glass fiber.

[0011] Preferably, the preparation method of the modified flame retardant includes the following steps:

[0012] S1. Add sepiolite powder to deionized water, then add γ-aminopropyltriethoxysilane, and react at 80-90 °C for 4-6 h. After the reaction is completed, continue to add glutaric anhydride DMF solution and stir to react. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite.

[0013] S2. Add DOPO to toluene, stir and dissolve it, then add 4,4'-dihydroxybenzophenone, and carry out a heating reaction. After the reaction is completed, add the carboxylated sepiolite and concentrated phosphoric acid obtained in step S1, and carry out a constant-temperature reaction. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite. The specific reaction process is as follows:

[0014]

[0015]

[0016] S3. Add 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and DMF to a flask, stir evenly, then add the modified sepiolite, and react at 100-110 °C for 5-8 h under nitrogen protection. During the reaction, add triethylamine dropwise every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant. The specific reaction process is as follows:

[0017]

[0018] Preferably, in step S1, the mass ratio of the sepiolite powder, γ-aminopropyltriethoxysilane, and glutaric anhydride DMF solution is 30:10-15:25-50, and the mass fraction of glutaric anhydride in the glutaric anhydride DMF solution is 20%; the temperature of the stirring reaction is 40-50 °C, and the reaction time is 2-3 h.

[0019] Preferably, in step S2, the mass ratio of DOPO, 4,4'-dihydroxybenzophenone, carboxylated sepiolite, and concentrated phosphoric acid is 20-30:10-15:30-40:50-60, and the mass fraction of the concentrated phosphoric acid is 85%; the temperature of the heating reaction is 100-130 °C, the time is 4-7 h, the temperature of the constant-temperature reaction is 60-70 °C, and the time is 3-5 h.

[0020] Preferably, the mass ratio of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine, DMF, and modified sepiolite in step S3 is 10-15:200-300:30-40.

[0021] Preferably, the preparation method of the modified glass fiber includes the following steps: At room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane to 400 g of absolute ethanol, stir for 5-6 h, then add ammonia water with a mass fraction of 10%, adjust the pH to 9-10, stir for 30 min, then add 100 g of glass fiber, stir for 10-15 h, and after the reaction is completed, dry at 60 °C to obtain it.

[0022] Preferably, the compatibilizer is maleic anhydride grafted polypropylene; the lubricant is one or more of oxidized polyethylene wax, low molecular weight polyethylene wax, lignite wax, or calcium stearate.

[0023] Preferably, the antioxidant is one or more of antioxidant 168, antioxidant 1098, and antioxidant 1010.

[0024] Preferably, the preparation method of the flame-retardant outer sheath includes the following steps: Weigh polypropylene, nylon 6, compatibilizer, modified flame retardant, antioxidant, lubricant, and modified glass fiber according to the formula amount, add them to a high-speed mixer, mix evenly, and then add the mixture to a twin-screw extruder and extrude and pelletize at 210-250 °C to obtain it.

[0025] The present invention also protects a preparation method of the flame-retardant high-strength optical cable, including the following steps:

[0026] Step 1, making colored optical fibers: Color the bare optical fibers into colored optical fibers of different colors;

[0027] Step 2, making a cable core: Form a loose tube through a secondary coating extruder, and place colored optical fibers of different colors into the loose tube and wind them to form a single cable core;

[0028] Step 3, stranding multiple cable cores: Stranding the strengthening member and multiple cable cores in a stranding machine to form a cable, with the strengthening member located in the center and multiple cable cores located outside the strengthening member;

[0029] Step 4, making an inner sheath: Extrude and coat low-density polyethylene or medium-density polyethylene or high-density polyethylene material on the multiple cable cores formed in step 3 to form an inner sheath;

[0030] Step 5, making a flame-retardant outer sheath layer: Extrude and coat a flame-retardant outer sheath on the inner sheath through an extruder to obtain the flame-retardant high-strength optical cable.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The flame-retardant high-strength optical cable provided by the present invention is formed by reacting polypropylene and nylon 6 as resin raw materials, and simultaneously adding a compatibilizer, a modified flame retardant, an antioxidant, a lubricant, and modified glass fibers; the compatibilizer can improve the compatibility between polypropylene and nylon 6, improve the mechanical properties of the flame-retardant outer sheath, and thus improve the strength and toughness of the optical cable; the modified flame retardant and the modified glass fibers can synergistically improve the flame-retardant performance of the flame-retardant outer sheath. During the combustion process of the polymer, DOPO in the modified flame retardant can participate in the reaction to form a carbon layer, improving the carbonization rate of the polymer. At the same time, the silicon element in the modified glass fibers will improve the thermal stability of the carbon layer, enabling it to fully play the role of heat insulation and gas barrier, so that the flame-retardant outer sheath has excellent flame-retardant effects.

[0033] (2) The flame-retardant high-strength optical cable provided by the present invention is added with a modified flame retardant using sepiolite as a carrier. Sepiolite is a magnesium silicate clay mineral with a porous fibrous morphological structure. This structure endows it with excellent properties such as adsorption, catalysis, and barrier properties, and the fibrous structure enables it to have good dispersibility in the polymer. First, sepiolite is carboxylated to introduce carboxyl groups on its surface, which is beneficial for subsequent reactions. Subsequently, DOPO reacts with 4,4'-dihydroxybenzophenone, and the P-H bond in DOPO can react with the C=O bond in 4,4'-dihydroxybenzophenone to obtain an intermediate product, increasing the phosphorus-containing groups in 4,4'-dihydroxybenzophenone. Then, carboxylated sepiolite is added to introduce grafted intermediate products on the surface of sepiolite. Finally, 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine reacts with the modified sepiolite, using triethylamine as an acid-binding agent to introduce triazine groups into sepiolite, increasing the nitrogen content in the modified flame retardant. The nitrogen and phosphorus in the modified flame retardant can form a nitrogen-phosphorus-silicon synergistic flame-retardant system with the silicon in sepiolite. 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine can delay the volatilization loss of DOPO in the condensed phase and release non-combustible gases including ammonia and nitrogen, further improving the flame-retardant effect.

[0034] (3) The flame-retardant high-strength optical cable provided by the present invention is added with modified glass fibers. Tetraethyl orthosilicate and polydimethylsiloxane are used to modify the glass fibers, generating organic-inorganic hybrids on the glass fibers, increasing the surface roughness of the glass fibers, enabling better physical and mechanical interlocking between the surface of the glass fibers and the polymer. Moreover, both the modified glass fibers and the polymer are hydrophobic, increasing their compatibility and improving the mechanical properties of the flame-retardant outer sheath. At the same time, due to the introduction of silicon elements on the surface of the glass fibers, the silicon content in the flame-retardant sheath is increased, further improving the flame-retardant performance of the optical cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic structural diagram of the flame-retardant high-strength optical cable of the present invention.

[0036] In the figure, 1 is a strengthening member; 2 is a cable core; 3 is a loose tube; 4 is an optical fiber; 5 is an inner sheath; 6 is a flame-retardant outer sheath. Specific embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] The polypropylene is purchased from Suzhou Xindezhi New Materials Co., Ltd., and the grade is Hanwha Totalpetrochemical HJ730; the nylon 6 is purchased from Shanghai Fuchen Plastic Raw Materials Co., Ltd., and the grade is Ube 1013B of Japan; the sepiolite powder is purchased from Shijiazhuang Mayue Building Materials Co., Ltd., and the mesh number is 325 mesh; the glass fiber is purchased from Hebei Wensheng New Materials Technology Co., Ltd., the fiber diameter is 8-12 μm, and the length is 50-60 μm; the polydimethylsiloxane is purchased from Wuhan Shu'er Biotechnology Co., Ltd., which is hydroxyl-terminated polydimethylsiloxane, CAS No.: 70131-67-8, and the viscosity is 60-70 cs; the maleic anhydride grafted polypropylene is purchased from Dongguan Taotao Plastic Raw Materials Co., Ltd., and the grafting rate is 1.5%.

[0039] Example 1

[0040] A flame-retardant high-strength optical cable includes at least one strengthening member 1, at least one cable core 2 distributed outside the strengthening member 1, an inner sheath 5 covering the cable core, and a flame-retardant outer sheath 6 covering the inner sheath, wherein the cable core 2 is composed of at least one optical fiber 4 and a loose tube 3;

[0041] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 1098, 0.8 part of oxidized polyethylene wax, and 7 parts of modified glass fiber.

[0042] The preparation method of the modified flame retardant includes the following steps:

[0043] S1. Add 30 g of sepiolite powder to deionized water, then add 13 g of γ-aminopropyltriethoxysilane, and react at 85 °C for 5 h. After the reaction is completed, continue to add 40 g of a glutaric anhydride DMF solution with a mass fraction of 20%, and stir and react at 45 °C for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite;

[0044] S2. Add 25 g of DOPO to 500 mL of toluene, stir and dissolve it, then add 13 g of 4,4'-dihydroxybenzophenone, and react at 120 °C for 5 h. After the reaction is completed, add 35 g of the carboxylated sepiolite obtained in step S1 and 55 g of concentrated phosphoric acid with a mass fraction of 85%, and react at a constant temperature of 65 °C for 4 h. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite;

[0045] S3. Add 13 g of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and 250 g of DMF to a flask, stir evenly, then add 35 g of modified sepiolite, and react at 105 °C for 7 h under nitrogen protection. During the reaction, add triethylamine every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0046] The preparation method of the modified glass fiber includes the following steps: At room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane to 400 g of absolute ethanol, stir for 5.5 h, then add ammonia water with a mass fraction of 10% to adjust the pH to 10, stir for 30 min, then add 100 g of glass fiber, stir for 13 h, and after the reaction is completed, dry at 60 °C to obtain it.

[0047] The preparation method of the flame-retardant outer sheath includes the following steps: Weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 1098, oxidized polyethylene wax, and modified glass fiber according to the formula amount, add them to a high-speed mixer, mix evenly, and then add the mixture to a twin-screw extruder and extrude and pelletize at 240 °C to obtain it.

[0048] Example 2

[0049] A flame-retardant high-strength optical cable includes at least one strengthening member 1, at least one cable core 2 distributed outside the strengthening member 1, an inner sheath 5 covering the cable core, and a flame-retardant outer sheath 6 covering the inner sheath, wherein the cable core 2 is composed of at least one optical fiber 4 and a loose tube 3;

[0050] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 168, 0.8 part of low molecular weight polyethylene wax, and 7 parts of modified glass fiber.

[0051] The preparation method of the modified flame retardant includes the following steps:

[0052] S1. Add 30 g of sepiolite powder to deionized water, then add 10 g of γ-aminopropyltriethoxysilane, react at 80 °C for 6 h. After the reaction is completed, continue to add 25 g of a 20% glutaric anhydride DMF solution, stir and react at 40 °C for 3 h. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite.

[0053] S2. Add 20 g of DOPO to 500 mL of toluene, stir and dissolve, then add 10 g of 4,4'-dihydroxybenzophenone, react at 100 °C for 7 h. After the reaction is completed, add 30 g of the carboxylated sepiolite obtained in step S1 and 50 g of 85% concentrated phosphoric acid, react at a constant temperature of 60 °C for 5 h. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0054] S3. Add 10 g of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and 200 g of DMF to a flask, stir evenly, then add 30 g of modified sepiolite, react at 100 °C for 8 h under nitrogen protection. During the reaction, add triethylamine every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0055] The preparation method of the modified glass fiber includes the following steps: At room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane to 400 g of absolute ethanol, stir for 5 h, then add 10% ammonia water to adjust the pH to 9, stir for 30 min, then add 100 g of glass fiber, stir for 10 h. After the reaction is completed, dry at 60 °C to obtain it.

[0056] The preparation method of the flame-retardant outer sheath includes the following steps: Weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 168, low molecular weight polyethylene wax, and modified glass fiber according to the formula amount, add them to a high-speed mixer, mix evenly, then add the mixture to a twin-screw extruder, and extrude and pelletize at 240 °C to obtain it.

[0057] Example 3

[0058] A flame-retardant high-strength optical cable, comprising at least one reinforcing member 1, at least one cable core 2 distributed outside the reinforcing member 1, an inner sheath 5 covering the cable core, and a flame-retardant outer sheath 6 covering the inner sheath, wherein the cable core 2 is composed of at least one optical fiber 4 and a loose tube 3;

[0059] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 1010, 0.8 part of lignite wax, and 7 parts of modified glass fiber.

[0060] The preparation method of the modified flame retardant includes the following steps:

[0061] S1. Add 30 g of sepiolite powder to deionized water, then add 12 g of γ-aminopropyltriethoxysilane, react at 85 °C for 5 h. After the reaction is completed, continue to add 35 g of a 20% glutaric anhydride DMF solution, stir and react at 45 °C for 3 h. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite;

[0062] S2. Add 25 g of DOPO to 500 mL of toluene, stir and dissolve, then add 12 g of 4,4'-dihydroxybenzophenone, react at 110 °C for 6 h. After the reaction is completed, add 35 g of the carboxylated sepiolite obtained in step S1 and 55 g of 85% concentrated phosphoric acid, react at a constant temperature of 65 °C for 4 h. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite;

[0063] S3. Add 13 g of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and 250 g of DMF to a flask, stir evenly, then add 35 g of modified sepiolite, react at 105 °C for 6 h under nitrogen protection. During the reaction, add triethylamine every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0064] The preparation method of the modified glass fiber includes the following steps: At room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane to 400 g of absolute ethanol, stir for 6 h, then add 10% ammonia water to adjust the pH to 10, stir for 30 min, then add 100 g of glass fiber, stir for 12 h. After the reaction is completed, dry at 60 °C to obtain it.

[0065] The preparation method of the flame-retardant outer sheath comprises the following steps: Weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 1010, oxidized polyethylene wax, lignite wax, and modified glass fiber according to the formula amounts, add them to a high-speed mixer, mix evenly, and then add the mixture to a twin-screw extruder to extrude and pelletize at 240 °C to obtain the product.

[0066] Example 4

[0067] A flame-retardant high-strength optical cable includes at least one strengthening member 1, at least one cable core 2 distributed outside the strengthening member 1, an inner sheath 5 covering the cable core, and a flame-retardant outer sheath 6 covering the inner sheath. Wherein, the cable core 2 is composed of at least one optical fiber 4 and a loose tube 3;

[0068] Wherein, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 1098, 0.8 part of calcium stearate, and 7 parts of modified glass fiber.

[0069] The preparation method of the modified flame retardant comprises the following steps:

[0070] S1. Add 30 g of sepiolite powder to deionized water, then add 15 g of γ-aminopropyltriethoxysilane, react at 90 °C for 4 h. After the reaction is completed, continue to add 50 g of a 20% glutaric anhydride DMF solution, stir and react at 50 °C for 2 h. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite;

[0071] S2. Add 30 g of DOPO to 500 mL of toluene, stir and dissolve it, then add 15 g of 4,4'-dihydroxybenzophenone, react at 130 °C for 4 h. After the reaction is completed, add 40 g of the carboxylated sepiolite obtained in step S1 and 60 g of 85% concentrated phosphoric acid, react at 70 °C for 3 h under constant temperature. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite;

[0072] S3. Add 15 g of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and 300 g of DMF to a flask, stir evenly, then add 40 g of modified sepiolite, react at 110 °C for 5 h under nitrogen protection. During the reaction, add triethylamine every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0073] The preparation method of the modified glass fiber comprises the following steps: at room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane into 400 g of absolute ethanol, stir for 6 h, then add ammonia water with a mass fraction of 10%, adjust the pH to 9, stir for 30 min, then add 100 g of glass fiber, stir for 15 h, and after the reaction is completed, dry at 60 °C to obtain the product.

[0074] The preparation method of the flame-retardant outer sheath comprises the following steps: weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 1098, calcium stearate, and modified glass fiber according to the formula amount, add them into a high-speed mixer, mix evenly, and then add the mixture into a twin-screw extruder, and extrude and pelletize at 240 °C to obtain the product.

[0075] Comparative Example 1

[0076] A flame-retardant high-strength optical cable comprises at least one strengthening member 1, at least one cable core 2 distributed outside the strengthening member 1, an inner sheath 5 coated outside the cable core, and a flame-retardant outer sheath 6 coated outside the inner sheath, wherein the cable core 2 is composed of at least one optical fiber 4 and a loose tube 3;

[0077] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 1098, 0.8 part of oxidized polyethylene wax, and 7 parts of glass fiber.

[0078] The preparation method of the modified flame retardant comprises the following steps:

[0079] S1. Add 30 g of sepiolite powder into deionized water, then add 13 g of γ-aminopropyltriethoxysilane, react at 85 °C for 5 h, after the reaction is completed, continue to add 40 g of a 20% glutaric anhydride DMF solution, stir and react at 45 °C for 2.5 h, and after the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite;

[0080] S2. Add 25 g of DOPO into 500 mL of toluene, stir and dissolve, then add 13 g of 4,4'-dihydroxybenzophenone, react at 120 °C for 5 h, after the reaction is completed, add 35 g of the carboxylated sepiolite obtained in step S1 and 55 g of 85% concentrated phosphoric acid, react at a constant temperature of 65 °C for 4 h, and after the reaction is completed, filter, wash, and dry to obtain modified sepiolite;

[0081] S3. Add 13 g of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and 250 g of DMF into a flask. After stirring evenly, add 35 g of modified sepiolite. Under nitrogen protection, react at 105 °C for 7 h. During the reaction, add triethylamine dropwise every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0082] The preparation method of the flame-retardant outer sheath includes the following steps: Weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 1098, oxidized polyethylene wax, and glass fiber according to the formula amount, add them to a high-speed mixer, mix evenly, and then add the mixture to a twin-screw extruder and extrude and pelletize at 240 °C to obtain the product.

[0083] Comparative Example 2

[0084] A flame-retardant high-strength optical cable includes at least one strengthening member 1, at least one cable core 2 distributed outside the strengthening member 1, an inner sheath 5 covering the cable core, and a flame-retardant outer sheath 6 covering the inner sheath. The cable core 2 is composed of at least one optical fiber 4 and a loose tube 3.

[0085] Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 85 parts of polypropylene, 15 parts of nylon 6, 5 parts of maleic anhydride grafted polypropylene, 22 parts of modified flame retardant, 2 parts of antioxidant 1098, 0.8 part of oxidized polyethylene wax, and 7 parts of modified glass fiber.

[0086] The preparation method of the modified flame retardant includes the following steps:

[0087] S1. Add 30 g of sepiolite powder into deionized water, then add 13 g of γ-aminopropyltriethoxysilane, and react at 85 °C for 5 h. After the reaction is completed, continue to add 40 g of a 20% glutaric anhydride DMF solution, stir and react at 45 °C for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite.

[0088] S2. Add 25 g of DOPO into 500 mL of toluene, stir and dissolve it, then add 13 g of 4,4'-dihydroxybenzophenone, and react at 120 °C for 5 h. After the reaction is completed, add 35 g of the carboxylated sepiolite obtained in step S1 and 55 g of 85% concentrated phosphoric acid, and react at a constant temperature of 65 °C for 4 h. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

[0089] The preparation method of the modified glass fiber comprises the following steps: at room temperature, 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane are added to 400 g of absolute ethanol, stirred for 5.5 h, then ammonia water with a mass fraction of 10% is added to adjust the pH to 10, stirred for 30 min, then 100 g of glass fiber is added, stirred for 13 h, and after the reaction is completed, it is dried at 60 °C to obtain the product.

[0090] The preparation method of the flame-retardant outer sheath comprises the following steps: weigh polypropylene, nylon 6, maleic anhydride grafted polypropylene, modified flame retardant, antioxidant 1098, oxidized polyethylene wax, and modified glass fiber according to the formula amount, add them to a high-speed mixer, mix evenly, then add the mixture to a twin-screw extruder, and extrude and pelletize at 240 °C to obtain the product.

[0091] The flame-retardant outer sheaths prepared in Examples 1-4 and Comparative Examples 1-2 are made into specimens for performance testing. The tensile strength and elongation at break are tested in accordance with GB / T 2951.11-2008 "General test methods for insulating and sheathing materials of cables and optical cables - Part 11: General test methods - Measurement of thickness and overall dimensions, mechanical properties". Oxygen index test: The single vertical burning test is carried out in accordance with GB / T18380.11-2022 "Fire tests on cables and optical cables under fire conditions - Part 11: Test on a single insulated wire or cable - Vertical flame spread test - Apparatus". The oxygen index is tested in accordance with the method of GB / T 2406.2-2009 "Plastics - Determination of burning behavior by the oxygen index - Part 2: Room temperature test". The test results are shown in Table 1 below:

[0092] Table 1

[0093] Tensile strength / MPa Elongation at break / % Vertical burning test Oxygen index / % Example 1 28.3 381 Passed by 35.4 Example 2 27.2 358 Passed by 35.1 Example 3 27.5 367 Passed by 34.8 Example 4 27.9 384 Passed by 35.3 Comparative example 1 23.1 256 Passed by 31.2 Comparative example 2 26.8 359 Failed to pass 28.6

[0094] As can be seen from Table 1 above, the flame-retardant outer sheath prepared by the present invention has good flame-retardant performance and mechanical properties, and finally can improve the flame-retardant performance and mechanical properties of the optical cable, making the flame-retardant high-strength optical cable have good application prospects.

[0095] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flame-retardant high-strength optical cable, characterized in that, It includes at least one reinforcing member (1), at least one cable core (2) distributed outside the reinforcing member (1), an inner sheath (5) covering the cable core, and a flame-retardant outer sheath (6) covering the inner sheath. The cable core (2) is composed of at least one optical fiber (4) and a loose tube (3). Among them, by weight, the flame-retardant outer sheath is made of the following raw materials: 80 - 90 parts of polypropylene, 10 - 20 parts of nylon 6, 3 - 6 parts of compatibilizer, 20 - 25 parts of modified flame retardant, 1 - 3 parts of antioxidant, 0.5 - 1 part of lubricant, and 5 - 10 parts of modified glass fiber. Among them, the preparation method of the modified flame retardant includes the following steps: S1. Add sepiolite powder to deionized water, then add γ-aminopropyltriethoxysilane, react at 80 - 90 °C for 4 - 6 h. After the reaction is completed, continue to add glutaric anhydride DMF solution and carry out stirring reaction. After the reaction is completed, filter, wash, and dry to obtain carboxylated sepiolite. S2. Add DOPO to toluene, stir and dissolve it, then add 4,4'-dihydroxybenzophenone, and carry out heating reaction. After the reaction is completed, add the carboxylated sepiolite and concentrated phosphoric acid obtained in step S1, and carry out constant-temperature reaction. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite. S3. Add 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine and DMF to a flask, stir evenly, then add the modified sepiolite, and react at 100 - 110 °C for 5 - 8 h under nitrogen protection. During the reaction, add triethylamine every 1 h to adjust the pH of the reaction solution to 7. After the reaction is completed, filter, wash, and dry to obtain the modified flame retardant.

2. The flame-retardant high-strength optical cable according to claim 1, characterized in that In step S1, the mass ratio of the sepiolite powder, γ-aminopropyltriethoxysilane, and glutaric anhydride DMF solution is 30:10 - 15:25 - 50, and the mass fraction of glutaric anhydride in the glutaric anhydride DMF solution is 20%; the temperature of the stirring reaction is 40 - 50 °C, and the reaction time is 2 - 3 h.

3. The flame-retardant high-strength optical cable according to claim 1, characterized in that, In step S2, the mass ratio of DOPO, 4,4'-dihydroxybenzophenone, carboxylated sepiolite, and concentrated phosphoric acid is 20 - 30:10 - 15:30 - 40:50 - 60, and the mass fraction of the concentrated phosphoric acid is 85%; the temperature of the heating reaction is 100 - 130 °C, the time is 4 - 7 h, the temperature of the constant-temperature reaction is 60 - 70 °C, and the time is 3 - 5 h.

4. The flame-retardant high-strength optical cable according to claim 1, characterized in that, In step S3, the mass ratio of 2,4-dichloro-6-(4-methoxyphenyl)-1,3,5-triazine, DMF, and modified sepiolite is 10 - 15:200 - 300:30 - 40.

5. The flame-retardant high-strength optical cable according to claim 1, characterized in that, The preparation method of the modified glass fiber includes the following steps: At room temperature, add 20 g of tetraethyl orthosilicate and 10 g of polydimethylsiloxane to 400 g of absolute ethanol, stir for 5 - 6 h, then add ammonia water with a mass fraction of 10% to adjust the pH to 9 - 10, stir for 30 min, then add 100 g of glass fiber, stir for 10 - 15 h, and after the reaction is completed, dry at 60 °C to obtain it.

6. The flame-retardant high-strength optical cable according to claim 1, wherein The compatibilizer is maleic anhydride grafted polypropylene; the lubricant is one or more of oxidized polyethylene wax, low molecular weight polyethylene wax, lignite wax or calcium stearate.

7. The flame-retardant high-strength optical cable according to claim 1, characterized in that, The antioxidant is one or more of antioxidant 168, antioxidant 1098, antioxidant 1010.

8. The flame-retardant high-strength optical cable according to claim 1, wherein, The preparation method of the flame-retardant outer sheath comprises the following steps: weighing polypropylene, nylon 6, compatibilizer, modified flame retardant, antioxidant, lubricant and modified glass fiber according to the formula amount, adding them into a high-speed mixer, mixing evenly, and then adding the mixture into a twin-screw extruder to extrude and pelletize at 210-250 °C to obtain the product.

9. A method for preparing a flame-retardant high-strength optical cable according to any one of claims 1-8, characterized in that, Comprising the following steps: Step 1, making colored optical fibers: coloring bare optical fibers into colored optical fibers of different colors; Step 2, making a cable core: forming a loose tube through a secondary coating extruder, placing colored optical fibers of different colors into the loose tube, and winding to form a single cable core; Step 3, stranding multiple cable cores: stranding the strengthening member and multiple cable cores in a stranding machine to form a cable, with the strengthening member located in the center and multiple cable cores located outside the strengthening member; Step 4, making an inner sheath: extruding and coating a low-density polyethylene or medium-density polyethylene or high-density polyethylene material on the multiple cable cores formed in Step 3 to form an inner sheath; Step 5, making a flame-retardant outer sheath layer: extruding and coating a flame-retardant outer sheath on the inner sheath through an extruder to obtain the flame-retardant high-strength optical cable.

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