Composition for HDPE outer sheath, preparation method and application thereof, and power cable

Abstract

The invention provides a composition for an HDPE (high-density polyethylene) outer sheath, a preparation method, application and a power cable, and the composition comprises the following components in parts by weight: 100-120 parts of HDPE resin, 15-25 parts of polyurethane resin, 5-10 parts of modified nano cellulose aerogel, 1-3 parts of a modified cross-linking agent, 0.1-0.5 part of an antioxidant, 0.1-0.5 part of a light stabilizer and 0.5-2 parts of a lubricant. The modified nano-crystalline cellulose aerogel is nano-crystalline cellulose aerogel loaded with cerium oxide and ZIF-8 (Zinc Ionium Factor 8) nano-particles; the modified cross-linking agent is hyperbranched siloxane of which the tail end contains a maleic anhydride group and silicon hydroxyl. The composition provided by the invention has the advantages of light weight and good corrosion resistance and weather resistance, has excellent flame retardance and oxidation resistance, and can be applied to an outer sheath layer of a power cable.

Description

Technical Field

[0001] The invention belongs to the technical field of cable materials, and particularly relates to a composition for an HDPE outer sheath, a preparation method and application thereof, and a power cable. Background Art

[0002] Currently, cables serve as signal connections between various electrical appliances, instruments, and automatic devices. They are primarily used for signal transmission and control signals in control and monitoring interlocking circuits and protection circuits, and are widely used in various fields. In today's rapidly developing power transmission and distribution systems, efficient, safe, and durable cable products play a vital role. With technological advancements and the growing demand for electricity across various industries, cable performance requirements are becoming increasingly stringent. While ensuring the safety and reliability of power cables, there is an urgent need for lightweight materials. The desired materials are expected to have low density while maintaining high strength and insulation properties.

[0003] Currently, some lightweight materials, such as plastic foam, glass fiber reinforced composites, and carbon fiber reinforced composites, while meeting engineering requirements for lightweight materials to a certain extent, also have many shortcomings that require improvement and enhancement. Plastic foam has the advantage of low density, but its strength as a cable sheath is clearly insufficient. Glass fiber reinforced composites and carbon fiber reinforced composites have high strength, but their high density does not meet the requirements for lightweight and insulation. Therefore, these materials cannot meet the comprehensive performance requirements of high strength, safety, and low density in related fields. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a composition for HDPE outer sheath, a preparation method and application, and a power cable. The HDPE outer sheath composition provided by the present invention has the advantages of being lightweight, having good corrosion resistance and weather resistance, and at the same time has excellent flame retardant and antioxidant properties, and can be well applied to the outer sheath layer of power cables.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a composition for an HDPE outer sheath, comprising the following components, in parts by weight: 100-120 parts of HDPE (high-density polyethylene) resin, 15-25 parts of polyurethane resin, 5-10 parts of modified nanocellulose aerogel, 1-3 parts of modified crosslinking agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of light stabilizer, and 0.5-2 parts of lubricant;

[0007] The modified nanocellulose aerogel is a nanocellulose aerogel loaded with cerium oxide and ZIF-8 nanoparticles; and the modified crosslinking agent is a hyperbranched siloxane containing maleic anhydride groups and silanol groups at the ends.

[0008] The HDPE outer sheath in the present invention is synergistically toughened and modified by introducing polyurethane and modified nanocellulose aerogel into the raw materials for HDPE resin, and adding a modified cross-linking agent to replace the traditional coupling agent, thereby improving the mechanical properties of the material while also improving the flame retardant and antioxidant properties of the material.

[0009] The modified cross-linking agent provided by the present invention introduces maleic anhydride groups and silanol groups at the end. Maleic anhydride can react with HDPE by free radicals, and the silanol groups can condense with polyurethane. At the same time, the hyperbranched topological structure and dynamic covalent bonds are used to realize intelligent regulation of the HDPE / polyurethane interface, and a "HDPE-siloxane-polyurethane" gradient interface layer is dynamically formed at the processing temperature. In addition, the introduced silicon element synergistically flame retards and promotes carbonization, realizing the integration of in-situ interface reinforcement and flame retardant functions. Therefore, the modified cross-linking agent introduced by the present invention can not only increase and improve the mechanical properties of HDPE, but also improve its flame retardancy.

[0010] The modified nanocellulose aerogel provided by the present invention enhances the mechanical properties of the material through the nanofiber bridging effect. Its three-dimensional network forms a "skeleton structure" in the HDPE matrix, and the ZIF-8 particles act as cross-linking points to inhibit fiber slippage, thereby improving the mechanical properties of the material. At the same time, the microporous structure of ZIF-8 can selectively absorb UV-A (315-400nm) and the cellulose nanofibers scatter UV-B (280-315nm). CeO2 undergoes a reversible valence change (Ce 4+ +e - →Ce 3+ ) continuously consumes alkyl radicals generated by HDPE photodegradation, thereby improving the material's aging resistance. Furthermore, ZIF-8 pyrolysis releases ZnO nanoparticles, catalyzing the carbonization of cellulose to form a dense carbon layer. CeO2 promotes cross-linking of HDPE decomposition products, reducing the risk of melt dripping, thereby enhancing the material's flame retardancy. This invention, through the combination of biomass-templated MOF growth and rare earth defect chemistry, achieves the integrated "enhancement, aging resistance, and flame retardancy" functionality that traditional additives lack.

[0011] In the present invention, the HDPE resin 100-120 parts can be 100 parts, 102 parts, 105 parts, 108 parts, 120 parts, etc.; the polyurethane resin 15-25 parts can be 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, etc.; the modified nanocellulose aerogel 5-10 parts can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.; the modified crosslinking agent 1-3 parts can be 1 part, 1.2 parts, 1.5 parts, 1 .8 parts, 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, etc.; the antioxidant 0.1-0.5 parts can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.; the light stabilizer 0.1-0.5 parts can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.; the lubricant 0.5-2 parts can be 0.5 parts, 0.8 parts, 1 parts, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, etc.

[0012] Preferably, the preparation method of the modified nanocellulose aerogel comprises:

[0013] A1, nanocellulose, zinc source and ligand undergo in situ growth reaction in a mixed solvent to obtain a nanocellulose solution loaded with ZIF-8 nanoparticles;

[0014] A2. A solution of nanocellulose loaded with ZIF-8 nanoparticles is dried by supercritical drying to obtain an aerogel loaded with ZIF-8 nanoparticles;

[0015] A3. The aerogel is loaded with a cerium precursor and calcined to obtain the modified nanocellulose aerogel.

[0016] Preferably, step A1 comprises: mixing a nanocellulose suspension and a zinc source solution, adding a 2-methylimidazole solution to carry out an in-situ growth reaction, and obtaining a nanocellulose solution loaded with ZIF-8 nanoparticles.

[0017] Preferably, the concentration of the nanocellulose suspension is 0.5-2%, such as 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc.

[0018] Preferably, in the nanocellulose suspension, the diameter of the nanocellulose is 20-50 nm, such as 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc.

[0019] Preferably, the zinc source solution is a zinc nitrate solution, and the concentration of the zinc nitrate solution is 0.05-0.1M, such as 0.05M, 0.06M, 0.07M, 0.08M, 0.09M, 0.1M, etc.

[0020] Preferably, the mass ratio of the nanocellulose to the zinc nitrate is 10:(15-20), for example, 10:15, 10:16, 10:17, 10:18, 10:19, 10:20, etc.

[0021] Preferably, the molar ratio of zinc nitrate to 2-methylimidazole is 1:(3-5), such as 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0022] Preferably, the in situ growth reaction temperature is room temperature, the time is 20-24h, such as 20h, 21h, 22h, 23h, 24h, etc., and the pH value is 7.5-8.5, such as 7.5, 7.8, 8, 8.2, 8.5, etc.

[0023] Preferably, the supercritical method in step A2 includes: using supercritical CO2, drying at 35-45°C, for example, 35°C, 36°C, 38°C, 40°C, 42°C, 45°C, etc., and 8-12MPa (for example, 8, 9, 10, 11, 12) for 4-8h, for example, 4h, 5h, 6h, 7h, 8h, etc.

[0024] Preferably, step A3 is: the aerogel is impregnated with a cerium nitrate solution, vacuum-assisted infiltration for 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc., and then maintained at 300-400 ° C (for example, 300 ° C, 320 ° C, 350 ° C, 380 ° C, 400 ° C, etc.) in a nitrogen atmosphere for 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc., and finally treated in a hydrogen-containing atmosphere at 400-420 ° C (for example, 400 ° C, 405 ° C, 410 ° C, 415 ° C, 420 ° C, etc.) for 0.5-1 hour (for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1 hour, etc.) to obtain the modified nanocellulose aerogel.

[0025] Preferably, the method for preparing the modified nanocellulose aerogel further comprises:

[0026] Acetobacter xylinum is used to ferment and culture bacterial cellulose membranes, which are purified and then mixed with deionized water and homogenized to obtain nanocellulose suspensions.

[0027] Preferably, the purification method comprises immersing the bacterial cellulose membrane in an alkaline solution at 70-80°C (e.g., 70°C, 72°C, 75°C, 78°C, 80°C, etc.) for 1-3h (e.g., 1h, 1.5h, 2h, 2.5h, 3h, etc.) for purification.

[0028] Preferably, the preparation method of the modified cross-linking agent comprises:

[0029] B1, pentaerythritol triacrylate and γ-aminopropyltriethoxysilane react in the presence of a catalyst to obtain product I;

[0030] B2. After the product I reacts with maleic anhydride, it reacts with pentaerythritol tetrakis-3-mercaptopropionate to obtain the modified crosslinking agent.

[0031] Preferably, the molar ratio of pentaerythritol triacrylate, γ-aminopropyltriethoxysilane, maleic anhydride and pentaerythritol tetra-3-mercaptopropionate is 1:(2.5-3):(2.5-3):0.5, for example, 1:2.5:2.5:0.5, 1:2.5:2.6:0.5, 1:2.5:2.8:0.5, 1:2.5:3:0.5, 1:2.6:2.5:0.5, 1:2.8:2.5:0.5, 1:3:2.5:0.5, 1:2.6:2.6:0.5, 1:2.6:2.8:0.5, 1:2.6:3:0.5, 1:2.8:2.8:0.5, 1:3:3:0.5, etc.

[0032] Preferably, step B1 is: pentaerythritol triacrylate is dissolved in ethanol and heated, preferably to 55-65°C, for example, 55°C, 56°C, 58°C, 60°C, 62°C, 65°C, etc., and then γ-aminopropyltriethoxysilane and the catalyst are added dropwise to react. The reaction time is preferably 4-6h, for example, 4h, 4.2h, 4.5h, 5h, 5.5h, 6h, etc., to obtain a reaction solution containing product I.

[0033] Preferably, in step B1, the catalyst is dibutyltin dilaurate, and the added amount of the catalyst is preferably 2-4% of the mass of pentaerythritol triacrylate, for example, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0034] Preferably, step B2 is: after the reaction liquid is cooled, it is reacted with maleic anhydride, preferably for 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc., and then the temperature is increased to add pentaerythritol tetrakis-3-mercaptopropionate and a catalyst for reaction, preferably for 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc., and the solvent is removed to obtain the modified crosslinking agent.

[0035] Preferably, the cooling is to 45-55°C, such as 45°C, 48°C, 50°C, 52°C, 55°C, etc.

[0036] Preferably, the temperature is raised to 75-80°C, such as 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, etc.

[0037] Preferably, in step B2, the catalyst is dibutyltin dilaurate, and the amount of the catalyst added is preferably 2-4% of the mass of pentaerythritol tetrakis-3-mercaptopropionate, such as 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0038] Preferably, the antioxidant is selected from any one of antioxidant 1010, antioxidant 1076, antioxidant 168 and antioxidant DLTDP, or a combination of at least two thereof.

[0039] Preferably, the light stabilizer is selected from any one of hindered amine light stabilizers, benzotriazole ultraviolet absorbers, and benzophenone ultraviolet absorbers, or a combination of at least two thereof.

[0040] Preferably, the lubricant is selected from any one or a combination of at least two of calcium stearate, microcrystalline wax, polyethylene sodium, stearic acid monoglyceride or polydimethylsiloxane.

[0041] In a second aspect, the present invention provides a method for preparing the composition for HDPE outer sheath as described in the first aspect, the preparation method comprising:

[0042] After the HDPE resin, polyurethane resin and modified crosslinking agent are mixed for the first time, the modified nanocellulose aerogel is added for the second mixing, and finally the antioxidant, light stabilizer and lubricant are added for the third mixing to obtain the HDPE outer sheath composition.

[0043] Preferably, the temperature of the first mixing is 170-180°C, such as 170°C, 172°C, 175°C, 178°C, 180°C, etc., and the time is 4-6 min, such as 4 min, 4.2 min, 4.5 min, 5 min, 5.5 min, 6 min, etc.

[0044] Preferably, the temperature of the second mixing is 190-200°C, such as 190°C, 192°C, 195°C, 198°C, 200°C, etc., and the time is 8-10 min, such as 8 min, 8.5 min, 9 min, 9.5 min, 10 min, etc.

[0045] Preferably, the temperature of the third mixing is 140-150°C, such as 140°C, 142°C, 145°C, 148°C, 150°C, etc., and the time is 2-4 min, such as 2 min, 2.5 min, 3 min, 3.5 min, 4 min, etc.

[0046] In a third aspect, the present invention provides a use of the HDPE outer sheath composition as described in the first aspect in preparing a power cable.

[0047] In a fourth aspect, the present invention provides a power cable, comprising a cable core and a shielding layer and a sheath layer wrapped around the outside of the cable core, the sheath layer comprising a PVC (polyvinyl chloride, Polyvinyl Chloride) inner sheath layer, an aluminum wire armor layer and a HDPE outer sheath layer arranged from the inside to the outside, and the raw materials for preparing the HDPE outer sheath layer include the composition for HDPE outer sheath described in the first aspect.

[0048] Preferably, the shielding layer includes a first semi-conductive shielding layer, an XLPE (cross-linked polyethylene) insulating layer, a second semi-conductive shielding layer and a copper wire shielding layer arranged from the inside to the outside.

[0049] In a fifth aspect, the present invention provides a method for preparing the power cable according to the fourth aspect, the method comprising:

[0050] S1. Prepare the shielding layer, PVC inner sheath layer and aluminum wire armor layer on the outside of the cable core in sequence;

[0051] S2. The HDPE outer sheath composition described in the first aspect is coated on the outside of the aluminum wire armor layer to form an HDPE outer sheath layer to obtain the power cable.

[0052] Preferably, the cable core is prepared by twisting multiple aluminum conductors.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] In the present invention, aluminum wire armor and HDPE sheath are introduced into the power cable. The HDPE outer sheath layer is synergistically toughened and modified by introducing polyurethane and modified nanocellulose aerogel into the raw materials to modify the HDPE resin, and a modified cross-linking agent is added to replace the traditional coupling agent. While improving the mechanical properties of the material, the flame retardant and antioxidant properties of the material are also improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is the TG curve of the modified nanocellulose aerogel obtained in Preparation Example 1 of the present invention;

[0056] Figure 2 This is the infrared spectrum of the modified cross-linking agent obtained in Preparation Example 2 of the present invention;

[0057] Figure 3 This is a schematic structural diagram of a power cable according to an embodiment of the present invention;

[0058] Among them: 1-cable core; 2-first semi-conductive shielding layer; 3-XLPE insulation layer; 4-second semi-conductive shielding layer; 5-copper wire shielding layer; 6-PVC inner sheath layer; 7-aluminum wire armor layer; 8-HDPE outer sheath layer. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0060] Unless otherwise specified, the raw materials involved in the following specific embodiments of the present invention are all conventional materials in the art and can be purchased from commercial products. Some raw material information is as follows:

[0061] HDPE resin: purchased from Qilu Petrochemical;

[0062] Polyurethane resin: purchased from Jiangsu Huada New Materials Co., Ltd.

[0063] Hindered amine light stabilizer: Tinuvin 622 purchased from BASF;

[0064] Benzotriazole UV absorber: Tinuvin 328 purchased from BASF;

[0065] Benzophenone UV absorber: purchased from BASF UV-531;

[0066] Polyethylene sodium: purchased from Sichuan Wei Chemical;

[0067] Polydimethylsiloxane: purchased from Hubei Xingfa Chemical;

[0068] Microcrystalline wax: purchased from Jiangsu Taier New Materials Co., Ltd.

[0069] Preparation Example 1

[0070] This preparation example provides a method for preparing modified nanocellulose aerogel, as follows:

[0071] A1. Soak the bacterial cellulose membrane in 1M NaOH solution at 80°C for 2 h to remove residual bacteria and polysaccharide impurities. Mix the purified cellulose membrane with deionized water at a ratio of 1:100 and crush it into a nanofiber suspension with a diameter of 20-50 nm using a high-pressure homogenizer.

[0072] A2. Mix the nanocellulose suspension with 0.1M zinc nitrate solution in a volume ratio of 1:1 and ultrasonically disperse for 30 minutes to make Zn 2+ Adsorbed to the cellulose surface, slowly add 2-methylimidazole methanol solution to control the 2-methylimidazole and Zn 2+The molar ratio was 4:1, the pH value was adjusted to 8 with triethylamine, and the reaction was carried out at room temperature for 22 hours;

[0073] A3, after replacing the water content of the reaction solution obtained in A2 with ethanol in a gradient manner, the reaction solution was placed in a supercritical CO2 drying vessel and dried at 40°C and 10 MPa for 6 h to obtain nanocellulose aerogel;

[0074] A4. Immerse the aerogel in 0.05M cerium nitrate ethanol solution, vacuum-assisted infiltration for 2 h, and heat to 350 °C at 2 °C / min in a nitrogen atmosphere and hold for 2 h to make Ce 3+ It was converted into CeO2 nanoparticles and treated at 400℃ for 1h in a 5% H2 / Ar mixed gas to obtain modified nanocellulose aerogel.

[0075] Performance Test 1

[0076] The modified nanocellulose aerogel was subjected to thermogravimetric analysis. The heating program was: N2 atmosphere, 10℃ / min to 600℃. The obtained TG curve is shown in the figure. Figure 1 As shown:

[0077] As can be seen from the figure, at 100-150°C: adsorbed water is removed (weight loss <5%); 250-350°C: cellulose decomposition (weight loss of about 40%, maximum weight loss rate temperature: 315°C); 400-500°C: ZIF-8 skeleton collapses (weight loss of 60-65%, delayed by 50°C compared with pure ZIF-8); above 500°C, there is no more weight loss, and the final residual carbon rate is 35-40% (CeO2 catalytic carbonization effect). Therefore, it can be seen from the TG curve that the preparation method provided by the present invention prepares nanocellulose aerogel loaded with cerium oxide and ZIF-8 nanoparticles.

[0078] Preparation Example 2

[0079] This preparation example provides a method for preparing a modified cross-linking agent, as follows:

[0080] B1. Dissolve 0.02 mol of pentaerythritol triacrylate in 100 mL of ethanol, raise the temperature to 60°C under nitrogen protection, add 0.06 mol of γ-aminopropyltriethoxysilane and 0.2 g of dibutyltin dilaurate dropwise, and react for 5 h.

[0081] B2. Cool to 50°C, add 0.06 mol maleic anhydride, react for 4 h, and finally heat to 80°C, add 0.01 mol pentaerythritol tetrakis-3-mercaptopropionate and 0.15 g dibutyltin dilaurate, react for 4 h, remove ethanol by rotary evaporation, and dry in vacuo to obtain a modified crosslinker.

[0082] Performance Test 2

[0083] The prepared modified cross-linking agent was subjected to infrared spectroscopy analysis, and the obtained infrared spectrum was as follows: Figure 2 As shown:

[0084] As can be seen from the figure, 3350cm -1 The broad peak of silanol at 1720 cm indicates that some silanol groups are retained, which can provide active sites for subsequent condensation with polyurethane. -1 The peak at 1780 cm-1 is the characteristic peak of ester group C=O, which proves that it has a hyperbranched skeleton. -1 / 1850cm -1 The anhydride C=O characteristic peak is at the center. The characteristic double peak of the anhydride proves that the end group functionalization is complete and the MAH grafting is successful. The anhydride peak (1780 / 1850cm -1 ) and ester peak (1720cm -1 ) intensity ratio ≈1:3, further verifying the hyperbranched structure, 1080cm -1 It is the characteristic peak of Si-O-Si. The strong broad peak indicates that the siloxane is highly cross-linked to form a three-dimensional siloxane network. -1 -600cm -1 The multiple peaks at 400 nm are Si-C bending vibrations; therefore, the infrared spectrum shows that the preparation method provided by the present invention successfully prepares hyperbranched siloxane containing maleic anhydride groups and silanol groups at the ends.

[0085] Preparation Example 3

[0086] This preparation example provides a mixture for an HDPE outer sheath layer, comprising: 100 parts of HDPE resin, 25 parts of polyurethane resin, 5 parts of modified nanocellulose aerogel, 3 parts of a modified crosslinking agent, 0.1 parts of an antioxidant 1010, 0.5 parts of a benzophenone-based ultraviolet absorber, 0.2 parts of polyethylene sodium, and 0.3 parts of polydimethylsiloxane; the modified nanocellulose aerogel is prepared in Example 1; the modified crosslinking agent is prepared in Example 2;

[0087] The preparation method is as follows: HDPE, polyurethane resin and modified cross-linking agent are first kneaded at 180°C for 6 minutes, then modified nanocellulose aerogel is added, kneaded at 190°C for 8 minutes, and finally antioxidant 1010, benzophenone ultraviolet absorber, polyethylene sodium and polydimethylsiloxane are added, and kneaded at 150°C for 4 minutes to obtain a mixture.

[0088] Preparation Example 4

[0089] This preparation example provides a mixture for an HDPE outer sheath layer, comprising: 120 parts of HDPE resin, 15 parts of polyurethane resin, 10 parts of modified nanocellulose aerogel, 1 part of a modified crosslinking agent, 0.3 parts of an antioxidant 1076, 0.2 parts of an antioxidant DLTDP, 0.1 parts of a benzotriazole ultraviolet absorber, 1 part of calcium stearate, and 1 part of microcrystalline wax; the modified nanocellulose aerogel is prepared in Example 1; the modified crosslinking agent is prepared in Example 2;

[0090] The preparation method is as follows: HDPE, polyurethane resin and modified cross-linking agent are first kneaded at 180°C for 4 minutes, then modified nanocellulose aerogel is added, kneaded at 190°C for 10 minutes, and finally antioxidant 1076, antioxidant DLTDP, benzotriazole ultraviolet absorber, calcium stearate and microcrystalline wax are added, and kneaded at 150°C for 2 minutes to obtain a mixture.

[0091] Preparation Example 5

[0092] This preparation example provides a mixture for an HDPE outer sheath layer, comprising: 110 parts of HDPE resin, 20 parts of polyurethane resin, 8 parts of modified nanocellulose aerogel, 2 parts of a modified crosslinking agent, 0.2 parts of an antioxidant 1010, 0.1 parts of an antioxidant 168, 0.2 parts of a hindered amine light stabilizer, 0.6 parts of calcium stearate, and 0.6 parts of stearic acid monoglyceride; the modified nanocellulose aerogel is prepared in Example 1; the modified crosslinking agent is prepared in Example 2;

[0093] The preparation method is as follows: HDPE, polyurethane resin and modified cross-linking agent are first kneaded at 180°C for 5 minutes, then modified nanocellulose aerogel is added, kneaded at 190°C for 9 minutes, and finally antioxidant 1010, antioxidant 168, hindered amine light stabilizer, calcium stearate and stearic acid monoglyceride are added, and kneaded at 150°C for 3 minutes to obtain a mixture.

[0094] Comparative Preparation Example 1

[0095] This comparative preparation example provides a mixture for a HDPE outer sheath layer.

[0096] The difference from Preparation Example 5 is that in this comparative preparation example, no modified nanocellulose aerogel is added.

[0097] Comparative Preparation Example 2

[0098] This comparative preparation example provides a mixture for a HDPE outer sheath layer.

[0099] The difference from Preparation Example 5 is that in this comparative preparation example, no modified cross-linking agent is added.

[0100] Examples 1-3

[0101] This embodiment provides a power cable with high strength and light weight. Figure 3 As shown, the power cable includes a cable core 1, the outer side of the cable core is covered with a shielding layer and a sheath layer, the shielding layer includes a first semi-conductive shielding layer 2, an XLPE insulation layer 3, a second semi-conductive shielding layer 4 and a copper wire shielding layer 5 arranged from the inside to the outside, and the sheath layer includes a PVC inner sheath layer 6, an aluminum wire armor layer 7 and a HDPE outer sheath layer 8 arranged from the inside to the outside, and the mixture used for the HDPE outer sheath layer 8 is the mixture provided in Preparation Example 3-5.

[0102] The preparation method is:

[0103] S1. A plurality of aluminum conductors are twisted together by a stranding process to form a cable core, and then a first semi-conductive shielding layer, an XLPE insulation layer, a second semi-conductive shielding layer and a copper wire shielding layer, a PVC inner sheath layer and an aluminum wire armor layer are sequentially prepared;

[0104] S2. The mixed material is added to a twin-screw extruder, melt-blended, and then extruded and coated on the outer wall of the aluminum wire armor layer to form a HDPE outer sheath layer to obtain a power cable.

[0105] Comparative Example 1-2

[0106] This comparative example provides a power cable

[0107] The difference from Example 1 is that in this comparative example, the mixture used for the HDPE outer sheath layer is the mixture provided in Comparative Examples 1-4.

[0108] Performance Test 3

[0109] The performance test of the HDPE outer sheath layer of the power cable provided in Examples 1-3 and Comparative Examples 1-2 was performed as follows:

[0110] (1) Mechanical properties: Referring to GB / T 528-2009, the outer sheath layer was cut into 25 mm × 4 mm dumbbell-shaped tensile specimens and mechanical properties were tested using a universal testing machine at a tensile rate of 20 mm / min. The test results are shown in Table 1:

[0111] Table 1

[0112] sample Tensile strength / MPa <![CDATA[Impact strength (kJ / m 2 )]]> Elongation at break / % Example 1 23.6 29.1 716 Example 2 22.0 27.4 674 Example 3 24.2 30.5 695 Comparative Example 1 16.8 20.3 784 Comparative Example 2 17.6 22.5 702

[0113] It can be seen from the examples and performance tests that the HDPE outer sheath provided by the present invention introduces modified nanocellulose aerogel and a modified cross-linking agent, and the two synergistically toughen and modify, which can effectively improve the tensile strength and impact strength of the material; wherein, the hyperbranched structure end of the modified cross-linking agent contains maleic anhydride groups and silanol groups, which can be covalently bonded with HDPE and polyurethane respectively, and the modified nanocellulose aerogel enhances the mechanical properties of the material through the nanofiber bridging effect. The three-dimensional network of the nanocellulose aerogel forms a "skeleton structure" in the HDPE matrix, and the ZIF-8 particles serve as cross-linking points to inhibit fiber slippage, thereby improving the mechanical properties of the material.

[0114] (2) Flame retardant properties: The HDPE outer sheath layer was made into a standard specimen of 127×12.7×3.2 mm and subjected to horizontal and vertical (UL-94) burning test according to ASTM D3801-1996 standard. At the same time, the oxygen index test (LOI) was conducted according to ASTM D2863-70 standard. The test results are shown in Table 2:

[0115] Table 2

[0116] sample Limiting oxygen index / % UL94 Example 1 32.3 V-0 Example 2 31.7 V-0 Example 3 31.2 V-0 Comparative Example 1 24.5 V-1 Comparative Example 2 26.1 V-1

[0117] It can be seen from the examples and performance tests that the HDPE outer sheath provided by the present invention has a certain flame retardant effect by introducing modified nanocellulose aerogel and modified cross-linking agent. Among them, the three-dimensional siloxane network in the modified cross-linking agent provides a large amount of silicon element, which can synergistically flame retardant, promote carbonization, and improve the flame retardant properties of the material; ZIF-8 in the modified nanocellulose aerogel is pyrolyzed to release ZnO nanoparticles, catalyzing the carbonization of cellulose to form a dense carbon layer, and CeO2 promotes the cross-linking of HDPE decomposition products, reducing the risk of melt droplets, thereby improving the flame retardant properties of the material.

[0118] (3) Oxidation resistance test: The HDPE outer sheath material was cut into dumbbell-shaped tensile specimens of 25 mm × 4 mm. UV aging test was carried out in a UV weathering test chamber according to GB / T14522-2008. The samples were exposed for 8 h (irradiance of 0.76 W / m 2 The blackboard temperature was 50±3℃, spraying was performed for 0.25h, condensation was performed for 3.75h, and 12h was considered as one cycle. The sampling periods were 1d, 3d, 7d, 14d, 21d, and 28d. The tensile strength was tested according to GB / T528-2009. The tensile rate was 20mm / min. The tensile strength retention rate was calculated by comparing with the initial tensile strength. The results are shown in Table 3:

[0119] Table 3

[0120]

[0121] From the examples and performance tests, it can be seen that the HDPE outer sheath provided by the present invention can increase its thermal stability and antioxidant effect to a certain extent by introducing modified nanocellulose aerogel and modified crosslinking agent; wherein, the microporous structure of ZIF-8 in the modified nanocellulose aerogel selectively absorbs UV-A (315-400nm), the cellulose nanofibers scatter UV-B (280-315nm), and CeO2 changes through reversible valence (Ce 4+ +e - →Ce 3+ ) continuously consumes the alkyl radicals produced by the photodegradation of HDPE, thereby improving the anti-aging properties of the material.

[0122] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A composition for HDPE outer sheath, characterized in that: The composition comprises the following components in parts by weight: 100-120 parts of HDPE resin, 15-25 parts of polyurethane resin, 5-10 parts of modified nanocellulose aerogel, 1-3 parts of modified crosslinking agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of light stabilizer, and 0.5-2 parts of lubricant; The modified nanocellulose aerogel is a nanocellulose aerogel loaded with cerium oxide and ZIF-8 nanoparticles; and the modified crosslinking agent is a hyperbranched siloxane containing maleic anhydride groups and silanol groups at the ends.

2. The HDPE outer sheath composition according to claim 1, characterized in that The preparation method of the modified nanocellulose aerogel comprises: A1, nanocellulose, a zinc source and a ligand undergo an in situ growth reaction in a mixed solvent to obtain a nanocellulose solution loaded with ZIF-8 nanoparticles; A2. A solution of nanocellulose loaded with ZIF-8 nanoparticles is prepared by supercritical drying to obtain an aerogel loaded with ZIF-8 nanoparticles; A3. The aerogel is loaded with a cerium precursor and calcined to obtain the modified nanocellulose aerogel.

3. The HDPE outer sheath composition according to claim 2, characterized in that: Step A1 comprises: mixing a nanocellulose suspension and a zinc source solution, adding a 2-methylimidazole solution to carry out an in-situ growth reaction, and obtaining a nanocellulose solution loaded with ZIF-8 nanoparticles; Preferably, the concentration of the nanocellulose suspension is 0.5-2%; Preferably, in the nanocellulose suspension, the diameter of the nanocellulose is 20-50 nm; Preferably, the zinc source solution is a zinc nitrate solution, and the concentration of the zinc nitrate solution is 0.05-0.1M; Preferably, the mass ratio of the nanocellulose to the zinc nitrate is 10:(15-20); Preferably, the molar ratio of zinc nitrate to 2-methylimidazole is 1:(3-5); Preferably, the in situ growth reaction temperature is room temperature, the time is 20-24 hours, and the pH value is 7.5-8.5; Preferably, the supercritical method in step A2 comprises: using supercritical CO2, drying at 35-45°C and 8-12 MPa for 4-8 hours; Preferably, step A3 comprises: impregnating the aerogel with a cerium nitrate solution, vacuum-assisted infiltration for 1-3 hours, then maintaining the solution at 300-400° C. for 1-3 hours in a nitrogen atmosphere, and finally treating the solution at 400-420° C. for 0.5-1 hour in a hydrogen atmosphere to obtain the modified nanocellulose aerogel; Preferably, the method for preparing the modified nanocellulose aerogel further comprises: Acetobacter xylinum is used to ferment and culture bacterial cellulose membranes, which are purified and then mixed with deionized water and homogenized to obtain a nanocellulose suspension. Preferably, the purification method comprises immersing the bacterial cellulose membrane in an alkaline solution at 70-80° C. for 1-3 hours for purification.

4. The HDPE outer sheath composition according to any one of claims 1 to 3, characterized in that: The preparation method of the modified cross-linking agent comprises: B1, pentaerythritol triacrylate and γ-aminopropyltriethoxysilane react in the presence of a catalyst to obtain product I; B2, after reacting the product I with maleic anhydride, reacting with pentaerythritol tetrakis-3-mercaptopropionate to obtain the modified crosslinking agent; Preferably, the molar ratio of pentaerythritol triacrylate, γ-aminopropyltriethoxysilane, maleic anhydride and pentaerythritol tetrakis-3-mercaptopropionate is 1:(2.5-3):(2.5-3):0.5; Preferably, step B1 comprises: dissolving pentaerythritol triacrylate in ethanol and heating the mixture, preferably to 55-65° C., and then dropwise adding γ-aminopropyltriethoxysilane and a catalyst to react, preferably for 4-6 hours, to obtain a reaction solution containing product I; Preferably, in step B1, the catalyst is dibutyltin dilaurate, and the amount of the catalyst added is preferably 2-4% of the mass of pentaerythritol triacrylate; Preferably, step B2 comprises: after cooling the reaction solution, reacting with maleic anhydride, preferably for 3-5 hours, then heating and adding pentaerythritol tetrakis-3-mercaptopropionate and a catalyst, preferably for 3-5 hours, and removing the solvent to obtain the modified crosslinking agent; Preferably, the cooling is to 45-55°C; Preferably, the temperature is raised to 75-80°C; Preferably, in step B2, the catalyst is dibutyltin dilaurate, and the amount of the catalyst added is preferably 2-4% of the mass of pentaerythritol tetrakis-3-mercaptopropionate.

5. The HDPE outer sheath composition according to any one of claims 1 to 4, characterized in that: The antioxidant is selected from any one of antioxidant 1010, antioxidant 1076, antioxidant 168 or antioxidant DLTDP, or a combination of at least two thereof; Preferably, the light stabilizer is selected from any one or a combination of at least two of a hindered amine light stabilizer, a benzotriazole ultraviolet absorber or a benzophenone ultraviolet absorber; Preferably, the lubricant is selected from any one of calcium stearate, microcrystalline wax, polyethylene sodium, stearic acid monoglyceride or polydimethylsiloxane, or a combination of at least two thereof.

6. A method for preparing the composition for HDPE outer sheath according to any one of claims 1 to 5, characterized in that: The preparation method comprises: After mixing HDPE resin, polyurethane resin and modified cross-linking agent for the first time, adding modified nanocellulose aerogel for the second mixing, and finally adding antioxidant, light stabilizer and lubricant for the third mixing to obtain the HDPE outer sheath composition; Preferably, the temperature of the first mixing is 170-180°C and the time is 4-6 minutes; Preferably, the temperature of the second mixing is 190-200°C and the time is 8-10 minutes; Preferably, the temperature of the third mixing is 140-150° C., and the time is 2-4 minutes.

7. Use of the HDPE outer sheath composition according to any one of claims 1 to 5 in preparing a power cable.

8. A power cable, characterized in that: The power cable includes a cable core and a shielding layer and a sheath layer coated on the outside of the cable core. The sheath layer includes a PVC inner sheath layer, an aluminum wire armor layer and a HDPE outer sheath layer arranged from the inside to the outside. The raw materials for preparing the HDPE outer sheath layer include the HDPE outer sheath composition described in any one of claims 1 to 5.

9. The power cable according to claim 8, characterized in that The shielding layer comprises a first semi-conductive shielding layer, an XLPE insulating layer, a second semi-conductive shielding layer and a copper wire shielding layer which are arranged from the inside out.

10. A method for preparing a power cable according to claim 8 or 9, characterized in that: The preparation method comprises: S1. Prepare the shielding layer, PVC inner sheath layer and aluminum wire armor layer on the outside of the cable core in sequence; S2. The HDPE outer sheath composition according to any one of claims 1-5 is coated on the outside of the aluminum wire armor layer to form an HDPE outer sheath layer to obtain the power cable; Preferably, the cable core is prepared by twisting multiple aluminum conductors.

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