A high-strength MPP cable protection tube

Abstract

The invention discloses a high-strength MPP cable protection tube, belongs to the technical field of cable processing, and is used to solve the technical problem that the strength and flame retardant performance of the MPP cable protection tube in the prior art need to be further improved; the invention comprises: a flame retardant shielding layer, and an MPP layer wrapped outside the flame retardant shielding layer, wherein a modified cross-linking agent is prepared, and a modified polypropylene is radiatively cross-linked to form a complex spatial structure, zeolite is modified to obtain a modified foaming aid having a large number of active sites, and a foaming agent is filled inside the modified foaming agent to obtain a modified foaming agent, and the cross-linked polypropylene is fully foamed through the gas slow release effect of the internal pores, and the cross-linked polypropylene is used as a heterogeneous nucleation site to form a β crystal form, thereby improving the strength of the material, and the protective tube has excellent flame retardant performance through the synergistic cooperation between the hierarchical structures, and finally a high-strength MPP cable protection tube with high ring stiffness, wear resistance, flame retardancy and high electromagnetic shielding effectiveness is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of cable processing, and in particular to a high-strength MPP cable protection tube. Background Art

[0002] The improvement in strength and flame retardancy of MPP cable protection tubes reflects the higher requirements for safety and durability in power and communication projects. Initially, modified polypropylene materials had basic mechanical strength to meet conventional cable protection needs. As the construction environment became more complicated, projects gradually adopted glass fiber reinforcement and other technologies to improve the compression and impact resistance of pipes to adapt to more severe conditions. At the same time, in order to cope with fire hazards, the development of flame retardant technology is also crucial. By adding environmentally friendly flame retardants, the safety in high temperature and fire environments can be significantly improved. These improvements have made cable protection tubes widely used in power, communications and other fields.

[0003] Prior art CN111019242A discloses an impact-resistant, heat-resistant, flame-retardant MPP power pipe material, comprising the following components in parts by weight: 50-70 parts of polypropylene resin, 15-25 parts of heat-resistant filler, 1-4 parts of toughening agent and 10-25 parts of flame retardant, wherein the heat-resistant filler is a mixture of montmorillonite and talcum powder in a weight ratio of 1:3-1:5. The MPP power pipe prepared by the MPP power pipe material has the characteristics of strong impact resistance, good flame retardancy, high mechanical strength and good heat resistance, excellent comprehensive performance and stable processing and molding;

[0004] However, the above patent content is to melt-blend and extrude polypropylene resin and auxiliary materials to achieve the technical effects of impact resistance, heat resistance and flame retardancy. However, the polarity difference between polypropylene resin and auxiliary materials such as heat-resistant fillers can easily lead to poor compatibility between materials, making the interface bonding force between materials weak, resulting in the wear resistance and impact resistance of the pipe to be further improved, and the flame retardancy of the pipe only by adding a single flame retardant to the auxiliary materials needs to be further improved.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0006] The object of the present invention is to provide a high-strength MPP cable protection tube, which is used to solve the technical problem that the strength and flame retardant performance of the MPP cable protection tube in the prior art need to be further improved.

[0007] The object of the present invention can be achieved by the following technical solution: a high-strength MPP cable protection tube, comprising a flame-retardant shielding layer, and MPP layers are arranged on both the inner and outer sides thereof;

[0008] The MPP layer comprises the following raw material components in parts by weight: 80-100 parts of cross-linked polypropylene, 30-40 parts of modified foaming agent, 10-20 parts of plasticizer, 5-10 parts of filler, 3-5 parts of stabilizer, 3-5 parts of antioxidant, 3-5 parts of ultraviolet absorber and 3-5 parts of lubricant;

[0009] The flame retardant shielding layer (200) comprises the following raw material components in parts by weight: 80-100 parts of cross-linked polypropylene, 40-60 parts of ammonium polyphosphate, 10-20 parts of plasticizer, 5-10 parts of filler, 3-5 parts of stabilizer, 3-5 parts of antioxidant and 3-5 parts of lubricant.

[0010] Furthermore, the plasticizer is one or more of dioctyl phthalate, diisononyl phthalate and tributyl citrate; the filler is one or more of nano-silica particles, titanium dioxide and carbon black; the stabilizer is one or more of diphenyl (2,4-di-tert-butyl) pyran, bis (2,4-di-tert-butylphenyl) benzothiophene and 2,4-dichlorophenyl fluorinated benzophenone; the antioxidant is one or more of tri-tert-butyl hydroxyphenyl acrylate, tetramethyl dihydroxyphenyl acrylate and tri-tert-butyl hydroxyphenyl acrylate; the ultraviolet absorber is one or more of diphenyl triazolyl diphenyl triazoline, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole-4-one) and 2-hydroxy-4-methoxy butyl benzoate; the lubricant is one or more of calcium stearate, oxidized polyethylene wax and montan wax.

[0011] Further, the preparation method of cross-linked polypropylene comprises the following steps:

[0012] A1, adding modified polypropylene resin, dilauryl disulfide propionate and modified crosslinking agent into a twin-screw extruder for melt extrusion to obtain a crosslinked polypropylene precursor;

[0013] A2. Placing the cross-linked polypropylene precursor in an electron beam irradiation device to obtain cross-linked polypropylene after electron irradiation.

[0014] The reaction principle for preparing cross-linked polypropylene is as follows: under electron beam irradiation, high-energy electron beams directly act on the molecular chains of the cross-linked polypropylene precursor, causing the carbon-hydrogen bonds or carbon-carbon bonds in the molecular chains to be ionized or excited. The impact of high-energy electrons causes the molecules to produce free radicals, that is, highly active atoms or molecular fragments with unpaired electrons. These free radicals react with a large number of carbon-carbon double bonds in the modified cross-linking agent in a high-energy state, and finally cross-linked polypropylene is prepared.

[0015] Furthermore, in step A1, the amount ratio of modified polypropylene resin, dilauryl disulfide propionate and modified cross-linking agent is 40-50g:1-2g:5-8g, the temperature of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port is 170°C, 185, 185°C, 200°C, 200°C, 210°C, 210°C, the main engine speed of the twin-screw extruder is 120-160rpm, and the pressure is 80-120bar. In step A2, the operation of electron irradiation is: nitrogen protection is introduced into the electron irradiation device at a flow rate of 10-20L / min, and the electron beam energy is set to 2-3MeV, the power is 25-30kW, the radiation dose is 100-150kGy, and the conveyor belt speed is set to 2m / min.

[0016] Furthermore, the preparation method of the modified polypropylene resin is as follows: polypropylene, 1,3,5-triallyl cyanurate, m-trifluoromethylstyrene and azobisisobutyronitrile are added to a reaction kettle and stirred, the temperature of the reaction kettle is increased to 240-300° C., and the mixture is stirred for 2-4 hours to obtain the modified polypropylene resin.

[0017] The reaction equation for preparing modified polypropylene resin is:

[0018]

[0019] Where:

[0020] The reaction principle for preparing modified polypropylene resin is as follows: azobisisobutyronitrile is decomposed to generate free radicals, which react with double bonds to initiate polymerization between double bond monomers, and finally modified polypropylene is prepared.

[0021] Furthermore, the usage ratio of polypropylene, 1,3,5-triallyl cyanurate, m-trifluoromethylstyrene and azobisisobutyronitrile is 3-5 g: 5-8 g: 12-16 g: 0.8-1.2 g, and the stirring rate of the reactor is 120-160 rpm.

[0022] Furthermore, the preparation method of the modified cross-linking agent is as follows: N,N-dimethylformamide is added to a reactor and stirred, the temperature of the reactor is lowered to 0-5°C, tetrapropylene succinic acid is added to the reactor, and after being kept warm and stirred for 5-10 minutes, N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added dropwise to the reactor, and after being kept warm and stirred for 20-30 minutes, the temperature of the reactor is increased to room temperature, and melamine is continued to be added dropwise to the reactor, and the reactor is kept warm and stirred for 8-10 hours, and the modified cross-linking agent is obtained by post-treatment.

[0023] The reaction equation for preparing the modified crosslinking agent is:

[0024]

[0025] Where:

[0026] The reaction principle for preparing the modified crosslinking agent is as follows: tetrapropylene succinic acid is an organic acid with a dicarboxyl group. The carboxyl group is activated by adding N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide. N,N'-dicyclohexylcarbodiimide reacts with the carboxyl group to form an intermediate activated ester. N-hydroxysuccinimide enhances the stability of the intermediate product. N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added to the reactor under low temperature conditions. In this process, the activated carboxyl group is ready to react with the subsequently added melamine to form an amide bond. Melamine contains multiple amino groups and can undergo cross-linking reactions with multiple activated carboxyl groups to form a large number of cross-linked networks.

[0027] Furthermore, the stirring rate of the reactor is 80-120 rpm, and the amount ratio of N,N-dimethylformamide, tetrapropylene succinic acid, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide and melamine is 30-40 mL: 5-8 g: 0.8-1.2 g: 0.3-0.5 g: 4-6 g. Post-treatment includes: after the reactor is cooled to room temperature, the reaction solution is added to a rotary evaporator with a water bath temperature of 80-100 ° C, and the reduced pressure distillation is performed until no liquid is extracted to obtain a modified cross-linking agent.

[0028] Furthermore, the preparation method of the modified foaming agent is as follows: adding the modified foaming aid, ammonium bicarbonate, azodicarbonamide and dimethyl sulfoxide into a reactor and stirring, raising the temperature of the reactor to 40-50°C, stirring for 20-30 minutes, standing for 15-20 minutes, and post-treating to obtain the modified foaming agent.

[0029] The reaction principle for preparing the modified foaming agent is: after ammonium bicarbonate and azodicarbonamide are dissolved in dimethyl sulfoxide, dimethyl sulfoxide is immersed in the gaps of the modified foaming agent. After the solvent is volatilized, ammonium bicarbonate and azodicarbonamide are crystallized in the gaps to finally prepare the modified foaming agent.

[0030] Furthermore, the stirring rate of the reactor is 80-120 rpm, the dosage ratio of the modified foaming agent, ammonium bicarbonate, azodicarbonamide and dimethyl sulfoxide is 8-10 g: 1-2 g: 0.6-0.8 g: 30-40 mL, and the post-treatment includes: after the reactor is cooled to room temperature, the reaction liquid is added to a rotary evaporator with a water bath temperature of 80-100° C., and the reduced pressure distillation is performed until no liquid is extracted to obtain a modified foaming agent.

[0031] Further, the preparation method of the modified foaming aid is:

[0032] B1, adding ZSM-5 zeolite, ferric nitrate powder and deionized water into a reactor, stirring at room temperature for 2-3 hours, adding dilute nitric acid dropwise into the reactor during stirring, maintaining the pH value of the reactant system at 3-4, and post-treating to obtain modified zeolite;

[0033] B2. Place the modified zeolite in a muffle furnace and introduce nitrogen protection. The temperature of the muffle furnace is raised to 300°C at a heating rate of 5°C / min. After being kept warm for 2 hours, the temperature is raised to 550°C at a heating rate of 2°C / min. Oxygen is introduced at a gas flow rate of 50 mL / min. The temperature is kept warm for 4-6 hours to obtain oxidized zeolite.

[0034] B3. Add zeolite oxide and saturated hydrogen peroxide solution into a reactor and stir. Raise the temperature of the reactor to 40-50° C., keep warm and stir for 2-3 hours, and perform post-treatment to obtain a modified foaming aid.

[0035] The reaction principle for preparing the modified foaming aid is as follows: ZSM-5 zeolite is a molecular sieve with a regular pore structure and has exchangeable cations on its surface. In the first step, by mixing the zeolite with a ferric nitrate solution, in an acidic environment, the iron ions gradually replace part of the cations in the zeolite to form an iron-exchanged zeolite; by treating the metal-exchanged zeolite under oxygen and high temperature, the iron ions further undergo an oxidation reaction, and the temperature is raised to 300°C at a slower heating rate under nitrogen protection to remove moisture and organic matter adsorbed on the surface. In an oxygen environment, the temperature is raised to 550°C, and oxygen reacts with the iron ions in the iron-exchanged zeolite to generate iron oxide substances, thereby enhancing the oxidation catalytic activity of the material; the oxidized zeolite is reacted with a hydrogen peroxide solution, and hydrogen peroxide, as a strong oxidant, further modifies the surface of the zeolite to make it have higher surface activity.

[0036] Furthermore, in step B1, the amount ratio of ZSM-5 zeolite, ferric nitrate powder and deionized water is 8-10g:50-60g:100mL, the stirring rate of the reactor is 80-120rpm, and the post-treatment includes: after the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60°C for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified zeolite; in step B3, the amount ratio of oxidized zeolite and hydrogen peroxide solution is 5-8g:20-30mL, and the post-treatment includes: after the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60°C for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified foaming aid.

[0037] Furthermore, the preparation method of the MPP cable protection tube protective sleeve comprises the following steps:

[0038] S1. uniformly mixing cross-linked polypropylene, ammonium polyphosphate, a plasticizer, a filler, a stabilizer, an antioxidant and a lubricant to obtain a mixture;

[0039] S2, placing the copper mesh in a mold, adding the mixed material into a twin-screw extruder for melt extrusion to cast the copper mesh, and obtaining a flame retardant shielding layer after the material is cooled;

[0040] S3, cross-linked polypropylene, modified foaming agent, plasticizer, filler, stabilizer, antioxidant, UV absorber and lubricant are evenly mixed to obtain cable material, the flame retardant shielding layer is placed in a mold, the cable material is added into a twin-screw extruder for melt extrusion, and the inner and outer surfaces of the copper mesh are cast respectively, and the MPP layer is obtained after the material is cooled.

[0041] Furthermore, in step S1, the temperatures of the eight temperature zones of the twin-screw extruder from the feed port toward the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 120-160rpm, and the pressure is 80-120bar; in step S2, the temperatures of the eight temperature zones of the twin-screw extruder from the feed port toward the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 120-160rpm, and the pressure is 80-120bar.

[0042] The present invention has the following beneficial effects:

[0043] 1. During the combustion process of the flame-retardant shielding layer of the MPP cable protection tube prepared by the present invention, ammonium polyphosphate decomposes to produce ammonia and acidic substances. The acidic substances promote the carbonization of triazine rings in cross-linked polypropylene to generate a molten carbon layer. The released ammonia promotes the foaming of the carbon layer while reducing the oxygen content, further enhancing the flame retardancy of the carbon layer. The external organic material has a complex spatial segment structure, which cooperates with the internal copper mesh to further enhance the shielding effectiveness of the layer; in the process of preparing the MPP layer, the ammonium bicarbonate in the modified foaming agent decomposes at low temperature to produce gas to promote the low-temperature foaming of cross-linked polypropylene, and the azodicarbonamide decomposes at high temperature to produce gas. The modified foaming aid as a modified foaming agent carrier produces a large number of active sites after metal ion replacement, oxidation and peroxide cleaning, which improves its compatibility with organic materials and improves the wear resistance of the material. The large number of voids inside it provide a slow-release effect for gas release, making the material foam evenly and fully, and at the same time, as a heterogeneous nucleation center, it promotes the heterogeneous nucleation of cross-linked polypropylene to form β crystals, so that the mechanical properties of the MPP layer are further improved, and finally a high-strength MPP cable protection tube with high ring stiffness, wear resistance, flame retardancy and high electromagnetic shielding effectiveness is prepared.

[0044] 2. In the process of preparing the modified foaming agent of the present invention, zeolite is reacted with ferric nitrate, and iron ions enter the crystal structure of zeolite to enhance its catalytic activity. The introduction of iron ions can provide additional active sites in the foaming process of polypropylene, which is conducive to the formation of a more stable and uniform pore structure, and acidifies the surface of zeolite, so that the pores and active sites of zeolite are more suitable for subsequent catalytic and modified treatments; the surface of zeolite is further activated by high temperature and oxidative environment, and surface groups such as iron oxide formed in the oxidation process can further enhance the catalytic performance of zeolite and provide more stable nucleation points in the subsequent foaming process; more oxygen groups, such as peroxy groups and hydroxyl groups, are introduced into the surface of zeolite by soaking in hydrogen peroxide solution to enhance its activity. These groups help to generate more bubbles and improve the pore structure in the foaming process of polypropylene, so that more bubble nuclei are formed in the foaming process of polypropylene, and the uniformity and distribution of the pores are improved, thereby enhancing the performance of the foaming material.

[0045] 3. In the process of preparing cross-linked polypropylene, the present invention first prepares a modified cross-linking agent, which has a large number of triazine rings and excellent carbonization performance, so that the flame retardant performance of the material is further improved, and a complex spatial network structure is formed through low-temperature catalytic condensation, so that during the radiation cross-linking process, the modified polypropylene forms a complex spatial network structure, thereby improving the wear resistance of the material; the modified polypropylene is prepared by selecting a monomer with a large number of fluorine groups, triazine rings and a complex double bond structure. The complex double bond structure makes the modified polypropylene have a complex spatial network structure, which significantly improves the strength of the material. Compared with traditional polypropylene materials, its complex side chains and spatial structure significantly improve the performance of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 It is a structural schematic diagram of the present invention;

[0048] Figure 2 It is a schematic diagram of the internal structure analysis of the present invention;

[0049] In the figure: 100, MPP layer; 200, flame retardant shielding layer. DETAILED DESCRIPTION

[0050] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] The ZSM-5 zeolite used in the present invention is purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., and the product name is ZSM5;

[0052] The ammonium polyphosphate used in the present invention is purchased from Henan Tuoyuan Chemical Products Co., Ltd. Example 1

[0053] This embodiment is used to provide a method for preparing a high-strength MPP cable protection tube, comprising the following steps:

[0054] S1. Preparation of cross-linked polypropylene

[0055] Weigh: 3.0 g of polypropylene, 6.0 g of 1,3,5-triallyl cyanurate, 12.0 g of m-trifluoromethylstyrene, 0.8 g of azobisisobutyronitrile and 60.0 mL of N,N-dimethylformamide, add them into a reactor and stir, raise the temperature of the reactor to 100° C., keep the temperature for 2 hours, cool the reactor to room temperature, add the reaction liquid into a rotary evaporator with a water bath temperature of 80° C., and distill under reduced pressure until no liquid is produced to obtain a modified polypropylene resin;

[0056] Weigh: add 32.0 mL of N,N-dimethylformamide to a reactor and stir, lower the temperature of the reactor to 5°C, add 5.0 g of tetrapropylene succinic acid to the reactor, keep warm and stir for 5 minutes, drop 1.0 g of N,N'-dicyclohexylcarbodiimide and 0.3 g of N-hydroxysuccinimide to the reactor, keep warm and stir for 24 minutes, raise the temperature of the reactor to room temperature, continue to drop 4.0 g of melamine to the reactor, keep warm and stir for 8 hours, cool the reactor to room temperature, add the reaction solution to a rotary evaporator with a water bath temperature of 80°C, and distill under reduced pressure until no liquid is produced to obtain a modified cross-linking agent;

[0057] Weigh: 40.0 g of modified polypropylene resin, 1.2 g of dilauryl disulfide propionate and 5.0 g of modified crosslinking agent are added to a twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170° C., 185° C., 185° C., 200° C., 200° C., 210° C., 210° C., the main engine speed of the twin-screw extruder is 120 rpm, the pressure is 80 bar, and a cross-linked polypropylene precursor is obtained by melt extrusion;

[0058] The cross-linked polypropylene precursor was placed in an electron beam irradiation device, nitrogen was introduced at a flow rate of 10 L / min for protection, and the electron beam energy was set to 2 MeV, the power was 25 kW, the radiation dose was 100 kGy, and the conveyor belt speed was set to 2 m / min to obtain cross-linked polypropylene.

[0059] S2. Preparation of modified foaming agent

[0060] Weigh: 8.0 g ZSM-5 zeolite, 50.0 g ferric nitrate powder and 100.0 mL deionized water are added to a reactor and stirred at room temperature for 2 h. During the stirring process, dilute nitric acid is added dropwise to the reactor to maintain the pH of the reactant system at 3. After the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60° C. for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified zeolite;

[0061] The modified zeolite was placed in a muffle furnace, and nitrogen was introduced for protection. The temperature of the muffle furnace was raised to 300°C at a heating rate of 5°C / min, and after being kept warm for 2 hours, the temperature was raised to 550°C at a heating rate of 2°C / min, and oxygen was introduced at a gas flow rate of 50 mL / min. The temperature was kept warm for 4 hours to obtain oxidized zeolite.

[0062] Weigh: 5.0 g of zeolite oxide and 20.0 mL of saturated hydrogen peroxide solution are added to a reactor and stirred. The temperature of the reactor is raised to 40° C., the stirring rate is 120 rpm, and the mixture is stirred for 2 h. After the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60° C. for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified foaming aid;

[0063] Weigh: 8.0 g of modified foaming aid, 1.0 g of ammonium bicarbonate, 0.6 g of azodicarbonamide and 30.0 mL of dimethyl sulfoxide, add into a reactor and stir, raise the temperature of the reactor to 40°C, keep stirring for 20 min, let stand for 15 min, cool the reactor to room temperature, add the reaction solution into a rotary evaporator with a water bath temperature of 80°C, distill under reduced pressure until no liquid is extracted, and obtain a modified foaming agent.

[0064] S3. Preparation of MPP cable protection tube

[0065] Weigh: 80.0 g of cross-linked polypropylene, 40.0 g of ammonium polyphosphate, 12.0 g of dioctyl phthalate, 6.4 g of nano silicon dioxide particles, 3.6 g of diphenyl (2,4-di-tert-butyl) pyran, 3.6 g of tri-tert-butyl hydroxyphenyl acrylate, 3.6 g of diphenyl triazolyl diphenyl triazoline and 4.2 g of calcium stearate, and mix them uniformly to obtain a mixture;

[0066] The copper mesh is placed in a mold, and the mixture is added into a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185°C, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively. The main engine speed of the twin-screw extruder is 120rpm, and the pressure is 80bar. The copper mesh is cast by melt extrusion, and the flame-retardant shielding layer 200 is obtained after the material is cooled.

[0067] Weigh: 84.0g cross-linked polypropylene, 36.0g modified foaming agent, 12.0g dioctyl phthalate, 6.4g nano-silicon dioxide particles, 3.6g diphenyl (2,4-di-tert-butyl) pyran, 3.6g tri-tert-butyl hydroxyphenyl acrylate, 3.6g tri-tert-butyl hydroxyphenyl acrylate, 3.6g diphenyl triazolyl diphenyl triazoline and 4.2g calcium stearate, mix well to obtain cable material, and make flame retardant shielding layer 200 Put it into the mold, add the cable material into the twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 120rpm, the pressure is 80bar, and the inner and outer surfaces of the flame-retardant shielding layer are cast by melt extrusion, and the MPP layer 100 is obtained after the material is cooled. Example 2

[0068] This embodiment is used to provide a method for preparing a high-strength MPP cable protection tube, comprising the following steps:

[0069] S1. Preparation of cross-linked polypropylene

[0070] Weigh: 4.0 g of polypropylene, 5.4 g of triallyl 1,3,5-cyanurate, 14.4 g of m-trifluoromethylstyrene and 1.0 g of azobisisobutyronitrile, add them into a reactor and stir, raise the temperature of the reactor to 240° C., stir at a rate of 120 rpm, and keep stirring for 3 hours to obtain a modified polypropylene resin;

[0071] Weigh: add 36.0 mL of N,N-dimethylformamide to a reactor and stir, lower the temperature of the reactor to 3°C, add 6.4 g of tetrapropylene succinic acid to the reactor, keep warm and stir for 8 minutes, drop 1.0 g of N,N'-dicyclohexylcarbodiimide and 0.4 g of N-hydroxysuccinimide to the reactor, keep warm and stir for 20 minutes, raise the temperature of the reactor to room temperature, continue to drop 4.8 g of melamine to the reactor, keep warm and stir for 9 hours, cool the reactor to room temperature, add the reaction solution to a rotary evaporator with a water bath temperature of 90°C, and distill under reduced pressure until no liquid is produced to obtain a modified cross-linking agent;

[0072] Weigh: 48.0g of modified polypropylene resin, 1.6g of dilauryl disulfide propionate and 6.4g of modified crosslinking agent are added to a twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, 210°C, the main engine speed of the twin-screw extruder is 120rpm, the pressure is 100bar, and a cross-linked polypropylene precursor is obtained by melt extrusion;

[0073] The cross-linked polypropylene precursor was placed in an electron beam irradiation device, nitrogen was introduced at a flow rate of 20 L / min for protection, and the electron beam energy was set to 3 MeV, the power was 30 kW, the radiation dose was 150 kGy, and the conveyor belt speed was set to 2 m / min to obtain cross-linked polypropylene.

[0074] S2. Preparation of modified foaming agent

[0075] Weigh: 10.0 g ZSM-5 zeolite, 54.0 g ferric nitrate powder and 100.0 mL deionized water were added to a reactor and stirred at room temperature for 3 h. During the stirring process, dilute nitric acid was added dropwise to the reactor to maintain the pH of the reactant system at 4. After the reaction was completed, the reaction liquid was filtered to collect the filter cake, and the filter cake was placed in a drying oven at a temperature of 60° C. for vacuum drying until the filter cake had a constant weight, thereby obtaining a modified zeolite;

[0076] The modified zeolite was placed in a muffle furnace, and nitrogen was introduced for protection. The temperature of the muffle furnace was raised to 300°C at a heating rate of 5°C / min, and after being kept warm for 2 hours, the temperature was raised to 550°C at a heating rate of 2°C / min, and oxygen was introduced at a gas flow rate of 50 mL / min. The temperature was kept warm for 6 hours to obtain oxidized zeolite.

[0077] Weigh: 7.2 g of zeolite oxide and 24.0 mL of saturated hydrogen peroxide solution are added to a reactor and stirred. The temperature of the reactor is raised to 50° C., the stirring rate is 100 rpm, and the mixture is stirred for 3 hours at this temperature. After the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60° C. for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified foaming aid;

[0078] Weigh: 10.0 g of modified foaming aid, 2.0 g of ammonium bicarbonate, 0.7 g of azodicarbonamide and 36.0 mL of dimethyl sulfoxide, add into a reactor and stir, raise the temperature of the reactor to 50°C, keep stirring for 30 minutes, let stand for 20 minutes, cool the reactor to room temperature, add the reaction solution into a rotary evaporator with a water bath temperature of 100°C, distill under reduced pressure until no liquid is extracted, and obtain a modified foaming agent.

[0079] S3. Preparation of MPP cable protection tube

[0080] Weigh: 84.0 g of cross-linked polypropylene, 54.0 g of ammonium polyphosphate, 16.0 g of dioctyl phthalate, 8.0 g of nano silicon dioxide particles, 3.6 g of diphenyl (2,4-di-tert-butyl) pyran, 3.6 g of tri-tert-butyl hydroxyphenyl acrylate, 3.6 g of diphenyl triazolyl diphenyl triazoline and 4.2 g of calcium stearate, and mix them uniformly to obtain a mixture;

[0081] The copper mesh is placed in a mold, and the mixture is added into a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185°C, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively. The main engine speed of the twin-screw extruder is 160rpm, and the pressure is 120bar. The copper mesh is cast by melt extrusion, and the flame-retardant shielding layer 200 is obtained after the material is cooled.

[0082] Weigh: 96.0g cross-linked polypropylene, 36.0g modified foaming agent, 12.0g dioctyl phthalate, 8.4g nano-silicon dioxide particles, 3.6g diphenyl (2,4-di-tert-butyl) pyran, 3.6g tri-tert-butyl hydroxyphenyl acrylate, 4.2g tri-tert-butyl hydroxyphenyl acrylate, 4.2g diphenyl triazolyl diphenyl triazoline and 4.2g calcium stearate, mix well to obtain cable material, and make flame retardant shielding layer 200 Put it into the mold, add the cable material into the twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 160rpm, the pressure is 120bar, and the inner and outer surfaces of the flame retardant shielding layer are cast by melt extrusion, and the MPP layer 100 is obtained after the material is cooled. Example 3

[0083] This embodiment is used to provide a method for preparing a high-strength MPP cable protection tube, comprising the following steps:

[0084] S1. Preparation of cross-linked polypropylene

[0085] Weigh: 4.8 g of propylene, 7.2 g of triallyl 1,3,5-cyanurate, 14.4 g of m-trifluoromethylstyrene and 1.2 g of azobisisobutyronitrile, add into a reaction kettle and stir, raise the temperature of the reaction kettle to 300° C., stir at a rate of 160 rpm, keep warm and stir for 2 h, and obtain a modified polypropylene resin;

[0086] Weigh: add 36.0 mL of N,N-dimethylformamide to a reactor and stir, lower the temperature of the reactor to 0°C, add 7.2 g of tetrapropylene succinic acid to the reactor, keep warm and stir for 8 minutes, drop 1.0 g of N,N'-dicyclohexylcarbodiimide and 0.4 g of N-hydroxysuccinimide to the reactor, keep warm and stir for 24.0 minutes, raise the temperature of the reactor to room temperature, continue to drop 5.4 g of melamine to the reactor, keep warm and stir for 9 hours, cool the reactor to room temperature, add the reaction solution to a rotary evaporator with a water bath temperature of 90°C, and distill under reduced pressure until no liquid is produced to obtain a modified cross-linking agent;

[0087] Weigh: 48.0g of modified polypropylene resin, 1.6g of dilauryl disulfide propionate and 6.4g of modified crosslinking agent are added into a twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, 210°C, the main engine speed of the twin-screw extruder is 150rpm, the pressure is 100bar, and a cross-linked polypropylene precursor is obtained by melt extrusion;

[0088] The cross-linked polypropylene precursor was placed in an electron beam irradiation device, nitrogen was introduced at a flow rate of 15 L / min for protection, and the electron beam energy was set to 3 MeV, the power was 27 kW, the radiation dose was 125 kGy, and the conveyor belt speed was set to 2 m / min to obtain cross-linked polypropylene.

[0089] S2. Preparation of modified foaming agent

[0090] Weigh: 9.0 g ZSM-5 zeolite, 54.0 g ferric nitrate powder and 100.0 mL deionized water, add into the reactor, stir at room temperature for 3 h, add dilute nitric acid dropwise into the reactor during stirring, maintain the pH value of the reactant system at 4, after the reaction is completed, filter the reaction liquid to collect the filter cake, place the filter cake in a drying oven at 60 ° C for vacuum drying until the filter cake has a constant weight, and obtain the modified zeolite;

[0091] The modified zeolite was placed in a muffle furnace, and nitrogen was introduced for protection. The temperature of the muffle furnace was raised to 300°C at a heating rate of 5°C / min, and after being kept warm for 2 hours, the temperature was raised to 550°C at a heating rate of 2°C / min, and oxygen was introduced at a gas flow rate of 50 mL / min. The temperature was kept warm for reaction for 5 hours to obtain oxidized zeolite.

[0092] Weigh: 7.2 g of zeolite oxide and 24.0 mL of saturated hydrogen peroxide solution are added to a reactor and stirred. The temperature of the reactor is raised to 45° C., the stirring rate is 80 rpm, and the mixture is stirred for 3 hours at this temperature. After the reaction is completed, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at a temperature of 60° C. for vacuum drying until the filter cake has a constant weight, thereby obtaining a modified foaming aid;

[0093] Weigh: 9.0g of modified foaming aid, 1.6g of ammonium bicarbonate, 0.7g of azodicarbonamide and 36.0mL of dimethyl sulfoxide, add into the reactor and stir, raise the temperature of the reactor to 45.0°C, keep stirring for 24min, let stand for 16min, cool the reactor to room temperature, add the reaction solution into a rotary evaporator with a water bath temperature of 90°C, distill under reduced pressure until no liquid is produced, and obtain a modified foaming agent.

[0094] S3. Preparation of MPP cable protection tube

[0095] Weigh: 84.0 g of cross-linked polypropylene, 54.0 g of ammonium polyphosphate, 12.0 g of dioctyl phthalate, 8.4 g of nano silicon dioxide particles, 4.8 g of diphenyl (2,4-di-tert-butyl) pyran, 4.8 g of tri-tert-butyl hydroxyphenyl acrylate, 3.6 g of diphenyl triazolyl diphenyl triazoline and 3.6 g of calcium stearate, and mix them uniformly to obtain a mixture;

[0096] The copper mesh is placed in a mold, and the mixture is added into a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185°C, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively. The main engine speed of the twin-screw extruder is 150rpm, and the pressure is 100bar. The copper mesh is cast by melt extrusion, and the flame-retardant shielding layer 200 is obtained after the material is cooled.

[0097] Weigh: 96.0g cross-linked polypropylene, 36.0g modified foaming agent, 18.0g dioctyl phthalate, 7.2g nano-silicon dioxide particles, 4.8g diphenyl (2,4-di-tert-butyl) pyran, 4.8g tri-tert-butyl hydroxyphenyl acrylate, 4.8g tri-tert-butyl hydroxyphenyl acrylate, 4.8g diphenyl triazolyl diphenyl triazoline and 4.8g calcium stearate, mix well to obtain cable material, and make flame retardant shielding layer 200 Put it into the mold, add the cable material into the twin-screw extruder, the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185, 185°C, 200°C, 200°C, 210°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 150rpm, the pressure is 100bar, and the inner and outer surfaces of the flame-retardant shielding layer are cast by melt extrusion, and the MPP layer 100 is obtained after the material is cooled.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 3 is that step S1 is eliminated, and in step S3, an equal amount of polypropylene resin is used to replace cross-linked polypropylene.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 3 is that the radiation cross-linking step in step S1 is eliminated, and in step S3, an equal amount of modified polypropylene resin is used to replace the cross-linked polypropylene.

[0102] Comparative Example 3

[0103] The difference between this comparative example and Example 3 is that step S2 is eliminated, and in step S3, an equal amount of sodium bicarbonate powder is used to replace the modified foaming agent.

[0104] Performance Test:

[0105] The ring stiffness and flame retardant properties of the MPP cable protection tubes prepared in Examples 1-3 and Comparative Examples 1-3 were tested with reference to the standard DL / T 802.9-2018 "Technical Conditions for Conduits for Power Cables Part 9: High-Strength Polyvinyl Chloride Plastic Cable Conduits";

[0106] The volume wear of the MPP cable protection tubes prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 9867-2008 "Determination of wear resistance of vulcanized rubber or thermoplastic rubber (rotating roller abrasion machine method)";

[0107] The vertical burning rating of the MPP cable protection tubes prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 26526-2011 "Specification for Thermoplastic Elastomer Low Smoke Halogen-Free Flame Retardant Materials";

[0108] The anti-electromagnetic interference performance of the MPP cable protection tubes prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics".

[0109] The tensile yield stress of the MPP cable protection tubes prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 12670-2008 "Polypropylene (PP) Resin", as shown in the following table:

[0110]

[0111] Data Analysis:

[0112] Comparing and analyzing the data in Table 1 above, the ring stiffness (3%) of the MPP cable protection tube prepared by the present invention is 29 kPa, the limiting oxygen index is 39%, and the volume wear is 44 mm 3 , vertical combustion grade is V-0, electromagnetic shielding grade is SE-1, bending modulus is 41MPa and tensile yield stress is 1173MPa, all data are better than the comparative example;

[0113] Explanation analysis:

[0114] The invention prepares a modified polypropylene having a large number of fluorine groups and triazine rings, and obtains cross-linked polypropylene having a complex spatial structure by melt extrusion with a prepared modified cross-linking agent having a large number of olefins and then radiation cross-linking, and melt-casts the cross-linked polypropylene, ammonium polyphosphate and auxiliary materials into a copper mesh to obtain a flame-retardant shielding layer, and melt-casts the cross-linked polypropylene, a modified foaming agent and auxiliary materials into a flame-retardant shielding layer to obtain an MPP layer, and finally obtains an MPP cable protection tube;

[0115] During the combustion of the flame retardant shielding layer, ammonium polyphosphate decomposes to produce ammonia and acidic substances. The acidic substances promote the carbonization of triazine rings in cross-linked polypropylene to form a molten carbon layer. The released ammonia promotes the foaming of the carbon layer while reducing the oxygen content, further enhancing the flame retardancy of the carbon layer.

[0116] In the process of preparing the MPP layer, the ammonium bicarbonate in the modified foaming agent decomposes at low temperature to produce gas to promote the low-temperature foaming of cross-linked polypropylene, and the azodicarbonamide decomposes at high temperature to produce gas to promote the high-temperature foaming of cross-linked polypropylene. The modified foaming aid as a carrier of the modified foaming agent produces a large number of active sites after metal ion replacement, oxidation and peroxide cleaning, thereby improving its compatibility with organic materials. The large number of voids inside it provide a slow-release effect for gas release, so that the material foams evenly and fully, and at the same time, as a heterogeneous nucleation center, it promotes the heterogeneous nucleation of cross-linked polypropylene to form a β crystal, so that the mechanical properties of the MPP layer are further improved, and finally a high-strength MPP cable protection tube with high ring stiffness, wear resistance, flame retardancy and high electromagnetic shielding effectiveness is prepared.

[0117] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A high-strength MPP cable protection tube, characterized in that: It includes a flame retardant shielding layer, and MPP layers are provided on both the inner and outer sides thereof; The MPP layer comprises the following raw material components in parts by weight: 80-100 parts of cross-linked polypropylene, 30-40 parts of modified foaming agent, 10-20 parts of plasticizer, 5-10 parts of filler, 3-5 parts of stabilizer, 3-5 parts of antioxidant, 3-5 parts of ultraviolet absorber and 3-5 parts of lubricant; The flame retardant shielding layer comprises the following raw material components in parts by weight: 80-100 parts of cross-linked polypropylene, 40-60 parts of ammonium polyphosphate, 10-20 parts of plasticizer, 5-10 parts of filler, 3-5 parts of stabilizer, 3-5 parts of antioxidant and 3-5 parts of lubricant.

2. A high-strength MPP cable protection tube according to claim 1, characterized in that: The preparation method of the cross-linked polypropylene comprises the following steps: A1, adding modified polypropylene resin, dilauryl disulfide propionate and modified crosslinking agent into a twin-screw extruder for melt extrusion to obtain a crosslinked polypropylene precursor; A2. Place the cross-linked polypropylene precursor in an electron beam irradiation device to obtain cross-linked polypropylene after electron irradiation.

3. A high-strength MPP cable protection tube according to claim 2, characterized in that: In step A1, the amount ratio of modified polypropylene resin, dilauryl disulfide propionate and modified crosslinking agent is 40-50g:1-2g:5-8g, the temperature of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port is 170°C, 185, 185°C, 200°C, 200°C, 210°C, 210°C, the main engine speed of the twin-screw extruder is 120-160rpm, and the pressure is 80-120bar. In step A2, the operation of electron irradiation is: nitrogen protection is introduced into the electron irradiation device at a flow rate of 10-20L / min, and the electron beam energy is set to 2-3MeV, the power is 25-30kW, the radiation dose is 100-150kGy, and the conveyor belt speed is set to 2m / min.

4. A high-strength MPP cable protection tube according to claim 2, characterized in that: The preparation method of the modified polypropylene resin is as follows: polypropylene, 1,3,5-triallyl cyanurate, m-trifluoromethylstyrene and azobisisobutyronitrile are added into a reaction kettle and stirred, the temperature of the reaction kettle is increased to 240-300° C., and the reaction kettle is stirred for 2-4 hours to obtain the modified polypropylene resin.

5. A high-strength MPP cable protection tube according to claim 4, characterized in that: The usage ratio of polypropylene, 1,3,5-triallyl cyanurate, m-trifluoromethylstyrene and azobisisobutyronitrile is 3-5 g: 5-8 g: 12-16 g: 0.8-1.2 g, and the stirring rate of the reactor is 120-160 rpm.

6. A high-strength MPP cable protection tube according to claim 2, characterized in that: The preparation method of the modified crosslinking agent comprises the following steps: adding N,N-dimethylformamide to a reaction kettle and stirring, lowering the temperature of the reaction kettle to 0-5°C, adding tetrapropylene succinic acid to the reaction kettle, keeping warm and stirring for 5-10 minutes, dropping N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide into the reaction kettle, keeping warm and stirring for 20-30 minutes, raising the temperature of the reaction kettle to room temperature, continuously dropping melamine into the reaction kettle, keeping warm and stirring for 8-10 hours, and performing post-treatment to obtain the modified crosslinking agent.

7. A high-strength MPP cable protection tube according to claim 6, characterized in that: The stirring rate of the reaction kettle is 80-120 rpm, and the dosage ratio of N,N-dimethylformamide, tetrapropylene succinic acid, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide and melamine is 30-40 mL: 5-8 g: 0.8-1.2 g: 0.3-0.5 g: 4-6 g.

8. The high-strength MPP cable protection tube according to claim 1, characterized in that: The preparation method of the modified foaming agent is as follows: adding the modified foaming aid, ammonium bicarbonate, azodicarbonamide and dimethyl sulfoxide into a reaction kettle and stirring, raising the temperature of the reaction kettle to 40-50° C., stirring for 20-30 minutes, standing for 15-20 minutes, and post-treating to obtain the modified foaming agent.

9. A high-strength MPP cable protection tube according to claim 8, characterized in that: The stirring rate of the reaction kettle is 80-120 rpm, and the dosage ratio of the modified foaming agent, ammonium bicarbonate, azodicarbonamide and dimethyl sulfoxide is 8-10 g: 1-2 g: 0.6-0.8 g: 30-40 mL.

10. The high-strength MPP cable protection tube according to claim 8, characterized in that: The preparation method of the modified foaming aid is: B1, adding ZSM-5 zeolite, ferric nitrate powder and deionized water into a reactor, stirring at room temperature for 2-3 hours, adding dilute nitric acid dropwise into the reactor during stirring, maintaining the pH value of the reactant system at 3-4, and post-treating to obtain modified zeolite; B2. Place the modified zeolite in a muffle furnace and introduce nitrogen protection. The temperature of the muffle furnace is raised to 300°C at a heating rate of 5°C / min. After being kept warm for 2 hours, the temperature is raised to 550°C at a heating rate of 2°C / min. Oxygen is introduced at a gas flow rate of 50 mL / min. The temperature is kept warm for 4-6 hours to obtain oxidized zeolite. B3. Add zeolite oxide and saturated hydrogen peroxide solution into a reactor and stir. Raise the temperature of the reactor to 40-50° C., keep warm and stir for 2-3 hours, and perform post-treatment to obtain a modified foaming aid.

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