A high-strength direct-buried optical cable and its preparation method

Abstract

The present invention discloses a high-strength direct-buried optical cable and a preparation method thereof, comprising at least one reinforcement member, at least one cable core twisted around the reinforcement member and filled with a water-blocking cable paste, a water-blocking tape layer coated outside the cable core, an inner sheath coated outside the water-blocking tape layer, an armor layer coated outside the inner sheath, and a high-strength outer sheath coated outside the armor layer, wherein the cable core is composed of a loose tube filled with a water-blocking fiber paste and at least one optical fiber accommodated in the loose tube; wherein, by weight, the high-strength outer sheath comprises the following raw materials: 80-85 parts of high-density polyethylene, 15-20 parts of nylon 612, 8-12 parts of a compatibilizer, 15-20 parts of modified silica, 1-3 parts of an antioxidant, and 0.7-1.1 parts of a lubricant. The high-strength direct-buried optical cable has excellent high strength, aging resistance, and wear resistance, and significantly extends the service life and transmission reliability of the optical cable.

Description

Technical Field

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

[0002] Optical cables, the backbone infrastructure for high-speed data transmission in the modern information society, must ensure long-term, stable operation of their fragile optical fibers in diverse and complex environments. Direct-buried optical cables, due to their direct underground installation, are subject to the combined effects of soil pressure, rock abrasion, groundwater erosion, and temperature fluctuations. Therefore, an ideal direct-buried optical cable must possess excellent comprehensive performance, including superior crush resistance to withstand the static pressure of soil and rock, strong strength and puncture resistance to withstand unexpected external forces during construction or geological activities, good abrasion resistance to prevent surface wear during pipeline routing and ground movement, and excellent low-temperature toughness to prevent brittle cracking during installation or use in cold regions. The outermost sheath is the first and most important physical barrier to achieve these properties. Its mechanical strength and long-term environmental tolerance directly determine the reliability and service life of the entire optical cable line.

[0003] Currently, the outer sheath of direct-buried optical cables is commonly made of high-density polyethylene (HDPE). While HDPE offers cost-effectiveness and excellent basic insulation properties, its inherent flaws are becoming increasingly prominent when meeting increasingly stringent comprehensive performance requirements. On the one hand, the mechanical strength of conventional HDPE sheaths, particularly strength and puncture resistance, is insufficient, making it difficult to fully meet the protection requirements of high-grade direct-buried optical cables in complex geological environments. On the other hand, and perhaps even more significant, is the long-term aging of the material. Traditional small-molecule antioxidants have been used to enhance HDPE's aging resistance. However, these small-molecule additives lack a strong chemical bond with the polymer matrix. Over long periods of burial, they migrate into the environment due to concentration gradients (e.g., being pumped out by groundwater) or evaporate due to temperature fluctuations. This causes their effective concentration in the material to decrease year by year, ultimately losing their protective properties. This leads to premature embrittlement and cracking of the cable sheath, significantly shortening the effective service life of communication lines.

[0004] Chinese patent application CN114924370A discloses an anti-termite, wear-resistant direct-buried optical cable and its preparation method, relating to the field of optical cable technology. The invention first prepares an inner sheath layer with styrene nonanoate and polypropylene; then, aminophenyl alanine, methoxybenzaldehyde propionate, and polylactic acid are mixed to form a mesogenic metaporphyrin and a helical molecular chain with an azobenzene cholesteric liquid crystal as a template to form an outer sheath layer; finally, the inner and outer sheath layers are sequentially wrapped around the cable core layer, and a nickel hypophosphite-based optical impregnation coupling roller-pressing process is performed to form a phosphate ester, vanillylamide nonanoate, and metallic nickel layer, resulting in an anti-termite, wear-resistant direct-buried optical cable. The anti-termite, wear-resistant direct-buried optical cable prepared by this invention exhibits excellent toughness, tensile strength, flame retardancy, anti-termite properties, and wear resistance. Chinese patent application CN108761688A discloses a micro-flexible armored direct-buried and pipeline optical cable and an optical cable production process, which relates to the field of communication equipment technology. The micro-flexible armored direct-buried and pipeline optical cable provided by the invention includes: an optical fiber, a first water-blocking layer, a micro-bundle tube, a second water-blocking layer, a stainless steel protective layer, a reinforcement layer, and a sheath; the number of optical fibers is multiple, the micro-bundle tube is arranged outside the multiple optical fibers, the first water-blocking layer is arranged between the optical fiber and the micro-bundle tube, the second water-blocking layer is wrapped around the outside of the micro-bundle tube, the stainless steel protective layer is wrapped around the outside of the second water-blocking layer, and the stainless steel protective layer, reinforcement layer, and sheath are wrapped and arranged in sequence from the inside to the outside. The micro-flexible armored direct-buried and pipeline optical cable provided by the invention alleviates technical problems in related technologies such as large optical cable size and poor flexibility. However, none of the above patents solve problems such as cracking of direct-buried optical cables due to aging during long-term burial. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a high-strength direct-buried optical cable and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A high-strength direct-buried optical cable comprises at least one strength member, at least one cable core twisted around the strength member and filled with water-blocking jelly, a water-blocking tape layer wrapped around the cable core, an inner sheath wrapped around the water-blocking tape layer, an armor layer wrapped around the inner sheath, and a high-strength outer sheath wrapped around the armor layer, wherein the cable core comprises a loose tube filled with water-blocking jelly and at least one optical fiber accommodated in the loose tube.

[0008] The high-strength outer sheath is made of the following raw materials, calculated by weight: 80-85 parts of high-density polyethylene, 15-20 parts of nylon 612, 8-12 parts of a compatibilizer, 15-20 parts of modified silica, 1-3 parts of an antioxidant, and 0.7-1.1 parts of a lubricant.

[0009] In the present invention, a specifically formulated HDPE / nylon 612 alloy matrix is ​​used in the outer sheath, and modified silica is creatively introduced, so that the final optical cable outer sheath not only has excellent mechanical strength, wear resistance and processing fluidity, but also achieves high strength, aging resistance and wear resistance of the optical cable through the functional design of modified silica, significantly extending the service life and transmission reliability of the optical cable.

[0010] Preferably, the preparation method of the modified silicon dioxide comprises the following steps:

[0011] S1, adding nano-silica to an ethanol aqueous solution, then adding γ-glycidyloxypropyltrimethoxysilane, stirring to react, filtering, washing, and drying after the reaction is completed to obtain pretreated silica;

[0012] S2, adding the pretreated silica in step S1 to DMF, followed by adding 6-mercaptopyridine-3-carboxylic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine, and reacting at a constant temperature. After the reaction is completed, filtering, washing, and drying to obtain organic silica;

[0013] S3. Add the organic silica prepared in step S2 to toluene, and then add erucamide, 4-tert-butylstyrene, and azobisisobutyronitrile, and heat to react. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0014] In the present invention, the modified silica uses nano-silica as a skeleton, which has a huge specific surface area and can provide sufficient reaction sites and an interaction area with the matrix at a relatively small addition amount. At the same time, its inherent high hardness and high modulus provide basic rigidity and strength for the sheath material. The nano-silica is reacted with γ-glycidyloxypropyltrimethoxysilane to introduce epoxy groups on the surface of the nano-silica, which not only facilitates subsequent reactions but also improves the interfacial compatibility between the filler and the sheath material substrate.

[0015] Preferably, the mass ratio of the pretreated silica, 6-mercaptopyridine-3-carboxylic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine in step S2 is 90-100:8-12:10-15:1-2.

[0016] Preferably, the isothermal reaction in step S2 is carried out at a temperature of 60-70° C. and for a time of 3-5 h.

[0017] In the present invention, the carboxyl group in 6-mercaptopyridine-3-carboxylic acid is activated by an N'-dicyclohexylcarbodiimide / 4-dimethylaminopyridine system, causing it to react with the epoxy group on the pretreated silica, thereby introducing 6-mercaptopyridine-3-carboxylic acid on the silica by chemical bonding. The sulfur- and nitrogen-containing pyridine ring structure in 6-mercaptopyridine-3-carboxylic acid can capture free radicals and passivate harmful metal ions, thereby giving the sheath material excellent long-term thermal and oxygen stability and weather resistance. At the same time, the mercapto group it carries is also conducive to the subsequent reactions.

[0018] Preferably, in step S3, the mass ratio of the organic silica, erucamide, 4-tert-butylstyrene, and azobisisobutyronitrile is 90-100:4-6:5-8:0.5-0.8, and the heating reaction temperature is 70-80° C. and the reaction time is 2-3 h.

[0019] In the present invention, organic silica is reacted with erucamide and 4-tert-butylstyrene through a mercapto-ene reaction, so that erucamide and 4-tert-butylstyrene are simultaneously introduced into the silica. Erucamide has a long hydrophobic fatty chain similar to the structure of polyethylene and can be physically entangled and embedded in the molecular chain of HDPE. Through the "physical anchoring" effect, the filler is firmly fixed in the matrix, greatly improving the interfacial bonding force, thereby significantly improving the strength and toughness of the sheath material. At the same time, erucamide itself is also a lubricant, which can improve processing fluidity and reduce the friction coefficient during optical cable laying. The rigid benzene ring and bulky tert-butyl group in 4-tert-butylstyrene can form a strong physical anchoring and mechanical interlocking effect at the interface between the filler and the HDPE matrix, greatly enhancing the interfacial bonding force, thereby significantly improving the tensile strength and modulus of the outer sheath.

[0020] Preferably, the compatibilizer is maleic anhydride grafted POE.

[0021] Preferably, the antioxidant is one or more of antioxidant 168, antioxidant 1098, and antioxidant 1010; and the lubricant is silicone masterbatch.

[0022] Preferably, the preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, compatibilizer, modified silica, antioxidant, and lubricant according to the formula amount, adding them to a high-speed mixer, mixing them evenly, then adding the mixture to a twin-screw extruder, and extruding and granulating at 220-250°C to obtain the product.

[0023] The present invention also protects a method for preparing the high-strength direct-buried optical cable as described above, comprising the following steps:

[0024] Step 1: Making colored optical fibers: coloring the bare optical fibers into colored optical fibers of different colors;

[0025] Step 2: Making the cable core: Using a secondary coating extruder to form a loose tube, and filling the loose tube with colored optical fibers of different colors and water-blocking paste, and winding them to form a single cable core;

[0026] Step 3: Cable the multiple cable cores together: Cable the strength members and the multiple cable cores together in a stranding machine, with the strength members located in the center and the multiple cable cores located outside the strength members. At the same time, fill the gaps between the multiple cable cores with water-blocking cable paste.

[0027] Step 4: Make the inner sheath and armor layer: Wrap the water-blocking tape around the cable core to form a water-blocking tape layer, then extrude and coat the high-density polyethylene material around the water-blocking tape layer to form an inner sheath, and then apply a layer of corrugated steel tape or wrap a layer of steel wire around the outer surface of the inner sheath to form a metal armor layer;

[0028] Step 5: Making a high-strength outer sheath layer: Extruding a high-strength outer sheath over the armor layer using an extruder to obtain the high-strength direct-buried optical cable.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The high-strength direct-buried optical cable provided by the present invention adopts a specially formulated HDPE / nylon 612 alloy matrix in the outer sheath and creatively introduces modified silica, so that the final optical cable outer sheath not only has excellent mechanical strength, wear resistance and processing fluidity, but also, through the functional design of modified silica, multiple functional groups such as aging resistance, reinforcement, volume expansion and lubrication are synergistically integrated on its surface, thereby achieving precise control of the interface between the filler and the polymer matrix at the nanoscale; this enables the modified silica to be evenly distributed in the sheath matrix with excellent dispersibility and strong interfacial bonding force, significantly enhancing the mechanical properties, environmental stress cracking resistance and long-term thermal oxidation stability of the sheath material, and ultimately giving the direct-buried optical cable excellent tensile strength, wear resistance and weather resistance, and can effectively resist the erosion of complex underground environments and mechanical damage during installation, significantly extending the service life and transmission reliability of the optical cable.

[0031] (2) The high-strength direct-buried optical cable provided by the present invention incorporates modified silica, which integrates three organic groups with different functions on the surface of the same nanofiller through multi-step chemical reactions; with nano-silica as the substrate, 6-mercaptopyridine-3-carboxylic acid, erucamide, and 4-tert-butylstyrene are grafted in sequence, and this structure firmly anchors the functional components on the silica. The sulfur- and nitrogen-containing heterocyclic structure of 6-mercaptopyridine-3-carboxylic acid gives the material excellent aging resistance and potential biological inertness; the long carbon chain structure in erucamide acts as a molecular lubricant, improving the processing fluidity of the material and increasing the surface smoothness of the sheath; the rigid benzene ring and the large tert-butyl structure in 4-tert-butylstyrene act as an efficient physical anchor point, significantly enhancing the interfacial bonding between the filler and the HDPE matrix; these three functional groups are firmly bound to the silica surface through covalent bonds, and their synergistic effect makes silica have multiple roles such as a reinforcing body, a stabilizer, and a processing aid, greatly improving the comprehensive performance improvement effect of the outer sheath.

[0032] (3) The high-strength direct-buried optical cable provided by the present invention adopts a HDPE / nylon 612 blend system and a specific maleic anhydride grafted POE compatibilizer formula, which effectively improves the mechanical properties of the outer sheath; nylon 612 is used as a reinforcing phase, and its inherent high rigidity, high wear resistance and low water absorption rate significantly improve the sheath's ability to resist soil extrusion, rock scratching and creep; the maleic anhydride grafted POE compatibilizer improves the interfacial bonding force of the two phases by forming an effective "molecular bridge" at the interface of HDPE and nylon, inhibits phase separation, and enables the reinforcement effect of nylon to be fully exerted, ultimately giving the optical cable outer sheath excellent tensile strength, puncture resistance and aging resistance, meeting the application requirements of high-strength direct burial. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the high-strength direct-buried optical cable of the present invention.

[0034] In the figure, 1. reinforcement; 2. cable core; 3. loose tube; 4. optical fiber; 5. water-blocking tape layer; 6. inner sheath; 7. armor layer; 8. high-strength outer sheath; 9. water-blocking cable grease. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0037] The brand of the high-density polyethylene is Borealis HE3366; the brand of the nylon 612 is Evonik Degussa DX9323; the particle size of the nano-silica is 200-300 nm; the brand of the maleic anhydride-grafted POE is Mitsui MA8510, and the grafting rate is 1%.

[0038] Example 1

[0039] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0040] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 83 parts of high-density polyethylene, 17 parts of nylon 612, 10 parts of maleic anhydride grafted POE, 18 parts of modified silica, 2 parts of antioxidant 1098, and 0.9 parts of silicone masterbatch.

[0041] The preparation method of the modified silicon dioxide comprises the following steps:

[0042] S1. Add 85 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 55°C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0043] S2, adding 95g of the pretreated silica in step S1 to 1.5L of DMF, followed by adding 10g of 6-mercaptopyridine-3-carboxylic acid, 13g of N,N'-dicyclohexylcarbodiimide, and 1.5g of 4-dimethylaminopyridine, and reacting at 65°C for 4h. After the reaction is completed, filtering, washing, and drying to obtain organic silica;

[0044] S3. Add 95 g of the organic silica in step S2 to 1.5 L of toluene, and then add 5 g of erucamide, 7 g of 4-tert-butylstyrene, and 0.7 g of azobisisobutyronitrile. React at 75° C. for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0045] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1098, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0046] Example 2

[0047] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0048] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 80 parts of high-density polyethylene, 20 parts of nylon 612, 12 parts of maleic anhydride grafted POE, 15 parts of modified silica, 1 part of antioxidant 1010, and 0.7 parts of silicone masterbatch.

[0049] The preparation method of the modified silicon dioxide comprises the following steps:

[0050] S1. Add 80 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 7 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 50°C for 4 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0051] S2, adding 90g of the pretreated silica in step S1 to 1.5L of DMF, followed by adding 8g of 6-mercaptopyridine-3-carboxylic acid, 10g of N,N'-dicyclohexylcarbodiimide, and 1g of 4-dimethylaminopyridine, and reacting at 60°C for 5h. After the reaction is completed, filtering, washing, and drying to obtain organic silica;

[0052] S3. Add 90 g of the organic silica in step S2 to 1.5 L of toluene, and then add 6 g of erucamide, 5 g of 4-tert-butylstyrene, and 0.5 g of azobisisobutyronitrile. React at 70° C. for 3 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0053] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1010, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0054] Example 3

[0055] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0056] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 85 parts of high-density polyethylene, 15 parts of nylon 612, 12 parts of maleic anhydride grafted POE, 20 parts of modified silica, 3 parts of antioxidant 168, and 1.1 parts of silicone masterbatch.

[0057] The preparation method of the modified silicon dioxide comprises the following steps:

[0058] S1. Add 90 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 10 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 60° C. for 3 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0059] S2. Add 100 g of the pretreated silica in step S1 to 1.5 L of DMF, followed by 12 g of 6-mercaptopyridine-3-carboxylic acid, 15 g of N,N'-dicyclohexylcarbodiimide, and 2 g of 4-dimethylaminopyridine. The mixture is reacted at 70° C. for 3 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain organic silica.

[0060] S3. Add 100 g of the organic silica in step S2 to 1.5 L of toluene, and then add 6 g of erucamide, 5 g of 4-tert-butylstyrene, and 0.8 g of azobisisobutyronitrile. React at 80° C. for 2 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0061] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 168, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0062] Comparative Example 1

[0063] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0064] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 83 parts of high-density polyethylene, 17 parts of nylon 612, 10 parts of maleic anhydride grafted POE, 18 parts of modified silica, 2 parts of antioxidant 1098, and 0.9 parts of silicone masterbatch.

[0065] The preparation method of the modified silicon dioxide comprises the following steps:

[0066] S1. Add 85 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 55°C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0067] S2, adding 95g of the pretreated silica in step S1 to 1.5L of DMF, followed by adding 10g of 6-mercaptopyridine-3-carboxylic acid, 13g of N,N'-dicyclohexylcarbodiimide, and 1.5g of 4-dimethylaminopyridine, and reacting at 65°C for 4h. After the reaction is completed, filtering, washing, and drying to obtain organic silica;

[0068] S3. Add 95 g of the organic silica in step S2 to 1.5 L of toluene, then add 5 g of erucamide and 0.7 g of azobisisobutyronitrile, and react at 75° C. for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0069] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1098, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0070] Compared with Example 1, this comparative example does not introduce 4-tert-butylstyrene into the modified silica.

[0071] Comparative Example 2

[0072] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0073] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 83 parts of high-density polyethylene, 17 parts of nylon 612, 10 parts of maleic anhydride grafted POE, 18 parts of modified silica, 2 parts of antioxidant 1098, and 0.9 parts of silicone masterbatch.

[0074] The preparation method of the modified silicon dioxide comprises the following steps:

[0075] S1. Add 85 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 55°C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0076] S2, adding 95g of the pretreated silica in step S1 to 1.5L of DMF, followed by adding 10g of 6-mercaptopyridine-3-carboxylic acid, 13g of N,N'-dicyclohexylcarbodiimide, and 1.5g of 4-dimethylaminopyridine, and reacting at 65°C for 4h. After the reaction is completed, filtering, washing, and drying to obtain organic silica;

[0077] S3. Add 95 g of the organic silica in step S2 to 1.5 L of toluene, and then add 7 g of 4-tert-butylstyrene and 0.7 g of azobisisobutyronitrile. React at 75° C. for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0078] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1098, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0079] Compared with Example 1, erucamide was not introduced into the modified silica in this comparative example.

[0080] Comparative Example 3

[0081] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0082] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 83 parts of high-density polyethylene, 17 parts of nylon 612, 10 parts of maleic anhydride grafted POE, 18 parts of modified silica, 2 parts of antioxidant 1098, and 0.9 parts of silicone masterbatch.

[0083] The preparation method of the modified silicon dioxide comprises the following steps:

[0084] S1. Add 85 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 55°C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0085] S2. Add 95 g of the pretreated silica in step S1 to 1.5 L of DMF, followed by adding 10 g of 6-mercaptopyridine-3-carboxylic acid, 13 g of N,N'-dicyclohexylcarbodiimide, and 1.5 g of 4-dimethylaminopyridine. The mixture is reacted at a constant temperature of 65°C for 4 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain modified silica.

[0086] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1098, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0087] Compared with Example 1, erucamide and 4-tert-butylstyrene were not introduced into the modified silica in this comparative example.

[0088] Comparative Example 4

[0089] A high-strength direct-buried optical cable comprises at least one strength member 1, at least one cable core 2 twisted around the strength member 1 and filled with a water-blocking jelly 9, a water-blocking tape layer 5 wrapped around the cable core, an inner sheath 6 wrapped around the water-blocking tape layer, an armor layer 7 wrapped around the inner sheath 6, and a high-strength outer sheath 8 wrapped around the armor layer 7, wherein the cable core 2 is composed of a loose tube 3 filled with a water-blocking jelly and at least one optical fiber 4 housed in the loose tube 3.

[0090] Among them, the high-strength outer sheath is made of the following raw materials, calculated by weight: 83 parts of high-density polyethylene, 17 parts of nylon 612, 10 parts of maleic anhydride grafted POE, 18 parts of modified silica, 2 parts of antioxidant 1098, and 0.9 parts of silicone masterbatch.

[0091] The preparation method of the modified silicon dioxide comprises the following steps:

[0092] S1. Add 85 g of nano-silica to 1 L of ethanol-water solution (volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, and stir at 55°C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated silica;

[0093] S2. Add 95 g of pretreated silica in step S1 to 1.5 L of toluene, then add 5 g of erucamide, 7 g of 4-tert-butylstyrene, and 0.7 g of azobisisobutyronitrile, and react at 75° C. for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain modified silica.

[0094] The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, maleic anhydride grafted POE, modified silica, antioxidant 1098, and silicone masterbatch according to the formula amount, adding the mixture into a high-speed mixer, mixing evenly, then adding the mixture into a twin-screw extruder, and extruding and granulating at 240° C. to obtain the outer sheath.

[0095] Compared with Example 1, this comparative example does not introduce 6-mercaptopyridine-3-carboxylic acid into the modified silica.

[0096] The high-strength outer sheaths prepared in Examples 1-3 and Comparative Examples 1-4 were prepared into strips and subjected to performance testing. Tensile strength and elongation at break were measured according to GB / T 2951.11-2008, "General Test Methods for Insulation and Sheathing Materials of Electric and Optical Cables - Part 11: General Test Methods for Thickness and Dimensional Measurements - Mechanical Properties." Aging tests were conducted according to GB / T 2951.12-2008, "General Test Methods for Insulation and Sheathing Materials of Electric and Optical Cables - Part 12: General Test Methods for Thermal Aging." The aging temperature was 100°C ± 2°C, the air exchange rate was 15 times per hour, and the test duration was 360 hours. The tensile strength and elongation retention of the high-strength outer sheaths before and after aging were measured. The test results are shown in Table 1.

[0097] Table 1 Performance test results of each group of high-strength outer sheaths

[0098]

[0099] As can be seen from Table 1 above, the high-strength outer sheath prepared by the present invention has excellent mechanical properties. At the same time, after thermal oxidation aging, it also has a good strength retention rate, which can give the optical cable excellent tensile strength, puncture resistance and aging resistance, and meet the application requirements of high-strength direct burial of optical cables.

[0100] The above content is a further detailed description of the present invention in combination with specific implementation examples. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

[0101] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-strength direct-buried optical cable, characterized in that: The invention comprises at least one strength member (1), at least one cable core (2) twisted around the strength member (1) and filled with water-blocking cable paste (9), a water-blocking tape layer (5) wrapped around the cable core, an inner sheath (6) wrapped around the water-blocking tape layer, an armor layer (7) wrapped around the inner sheath (6), and a high-strength outer sheath (8) wrapped around the armor layer (7), wherein the cable core (2) is composed of a loose tube (3) filled with water-blocking fiber paste and at least one optical fiber (4) accommodated in the loose tube (3); The high-strength outer sheath is made of the following raw materials, calculated by weight: 80-85 parts of high-density polyethylene, 15-20 parts of nylon 612, 8-12 parts of compatibilizer, 15-20 parts of modified silica, 1-3 parts of antioxidant, and 0.7-1.1 parts of lubricant. The preparation method of the modified silicon dioxide comprises the following steps: S1, adding nano-silica to an ethanol aqueous solution, then adding γ-glycidyloxypropyltrimethoxysilane, stirring and reacting to obtain pretreated silica; S2, adding the pretreated silica to DMF, followed by adding 6-mercaptopyridine-3-carboxylic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine, and reacting at a constant temperature to obtain organic silica; S3. Adding organic silica to toluene, and then adding erucamide, 4-tert-butylstyrene, and azobisisobutyronitrile, and heating to react to obtain modified silica.

2. The high-strength direct-buried optical cable according to claim 1, characterized in that: In step S1, the mass ratio of nano-silica to γ-glycidyloxypropyltrimethoxysilane is 80-90:7-10, the stirring reaction temperature is 50-60° C., and the time is 3-4 hours.

3. The high-strength direct-buried optical cable according to claim 1, characterized in that: The mass ratio of the pretreated silica, 6-mercaptopyridine-3-carboxylic acid, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine in step S2 is 90-100:8-12:10-15:1-2.

4. The high-strength direct-buried optical cable according to claim 1, characterized in that: The isothermal reaction in step S2 is carried out at a temperature of 60-70° C. for 3-5 hours.

5. The high-strength direct-buried optical cable according to claim 1, characterized in that: In step S3, the mass ratio of the organic silica, erucamide, 4-tert-butylstyrene, and azobisisobutyronitrile is 90-100:4-6:5-8:0.5-0.8, and the heating reaction temperature is 70-80° C. and the reaction time is 2-3 hours.

6. The high-strength direct-buried optical cable according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted POE.

7. The high-strength direct-buried optical cable according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 168, antioxidant 1098, and antioxidant 1010; and the lubricant is silicone masterbatch.

8. The high-strength direct-buried optical cable according to claim 1, characterized in that: The preparation method of the high-strength outer sheath comprises the following steps: weighing high-density polyethylene, nylon 612, a compatibilizer, modified silica, an antioxidant, and a lubricant according to the formula, adding the mixture into a high-speed mixer, and mixing them evenly; then adding the mixture into a twin-screw extruder, and extruding and granulating at 220-250° C. to obtain the outer sheath.

9. A method for preparing a high-strength direct-buried optical cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Making colored optical fibers: coloring the bare optical fibers into colored optical fibers of different colors; Step 2: Making the cable core: Using a secondary coating extruder to form a loose tube, and filling the loose tube with colored optical fibers of different colors and water-blocking paste, and winding them to form a single cable core; Step 3: Cable the multiple cable cores together: Cable the strength members and the multiple cable cores together in a stranding machine, with the strength members located in the center and the multiple cable cores located outside the strength members. At the same time, fill the gaps between the multiple cable cores with water-blocking cable paste. Step 4: Make the inner sheath and armor layer: Wrap the water-blocking tape around the cable core to form a water-blocking tape layer, then extrude and coat the high-density polyethylene material around the water-blocking tape layer to form an inner sheath, and then apply a layer of corrugated steel tape or wrap a layer of steel wire around the outer surface of the inner sheath to form a metal armor layer; Step 5: Making a high-strength outer sheath layer: Extruding a high-strength outer sheath over the armor layer using an extruder to obtain the high-strength direct-buried optical cable.

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