PVC corrosion-resistant cable protection pipe and preparation process thereof

Abstract

The invention relates to the technical field of chlorinated polyvinyl chloride plastics, in particular to a PVC corrosion-resistant cable protection pipe and a preparation process thereof. The invention aims to solve the problem that the mechanical property and the corrosion resistance of the existing PVC cable protection pipe cannot be considered at the same time. Chlorinated polyvinyl chloride and polyvinyl chloride are subjected to hot mixing to obtain matrix resin, and the corrosion-resistant additive, the composite flame retardant, the flexibilizer and other additives are added to obtain the cable protection tube. The corrosion-resistant additive is obtained by grafting and modifying nano silicon dioxide with epoxy resin and premixing with an ethylene-vinyl alcohol copolymer; the composite flame retardant comprises core layers of nitrogen series, phosphorus series and inorganic hydroxides and a shell layer of an acrylate polymer, and is obtained through a core-shell reaction; the cable protection pipe is prepared through a multi-step mixing process; by introducing the core-shell structure and the corrosion-resistant auxiliary agent, efficient flame retardance and corrosion resistance are achieved, stress is buffered through the flexible shell layer, and the mechanical property of the material is maintained.

Description

Technical Field

[0001] The invention relates to the technical field of chlorinated polyvinyl chloride plastics, in particular to a PVC-based corrosion-resistant cable protection tube and a preparation process thereof. Background Art

[0002] Cable protection pipes are an indispensable infrastructure in power and communication projects, used to protect cables from mechanical damage and chemical corrosion from the external environment. In existing technologies, polyvinyl chloride is widely used to manufacture such pipes due to its low cost, easy processing and inherent flame retardancy. However, as the application environment becomes increasingly harsh, the performance defects of traditional polyvinyl chloride pipes are becoming increasingly prominent.

[0003] Insufficient mechanical properties are the main problem limiting the application of polyvinyl chloride in pipes; ordinary polyvinyl chloride materials themselves have the disadvantages of insufficient toughness and poor impact resistance. In addition, in order to meet fire safety requirements, a large amount of flame retardants usually need to be added to PVC. However, these inorganic or organic small molecule flame retardants have poor compatibility with the PVC matrix and are prone to agglomeration during the blending process, forming stress concentration points, seriously damaging the continuity of the matrix, and resulting in a significant decrease in the mechanical properties of the composite material.

[0004] Since cable protection pipes are often buried in the soil or exposed to industrial environments, they will inevitably come into contact with corrosive media such as acids, alkalis, and salts, and the demand for corrosion resistance is increasing. Although PVC itself is chemically resistant, the added ordinary fillers are usually hydrophilic on the surface, and the interface bonding with the hydrophobic PVC matrix is ​​weak, which can easily become a channel for the penetration of corrosive media. The corrosive media invade along this weak interface, causing the filler to separate from the matrix, accelerating the swelling, degradation and failure of the material, and leading to the loss of its protective function.

[0005] In summary, existing technologies utilize modification of PVC pipes to enhance their mechanical and corrosion resistance. However, simple physical blending or single modification methods fail to improve the overall performance of the material. Often, methods designed to enhance mechanical properties compromise compatibility, thereby reducing other material properties. In practical applications, the challenge of balancing mechanical and corrosion resistance persists, resulting in a reduced material lifespan due to insufficient overall performance.

[0006] Therefore, a PVC corrosion-resistant cable protection tube and its preparation process are proposed. Summary of the Invention

[0007] The present invention aims to provide a PVC-based corrosion-resistant cable protection tube and its preparation process. The present invention comprises the following steps: hot-mixing chlorinated polyvinyl chloride and polyvinyl chloride to obtain a base resin, and adding a corrosion-resistant additive, a composite flame retardant, a toughening agent, and other additives to obtain the cable protection tube; the corrosion-resistant additive is obtained by grafting modified nano-silica with an epoxy resin and premixing it with an ethylene-vinyl alcohol copolymer; the composite flame retardant comprises a core layer of nitrogen, phosphorus, and inorganic hydroxides and a shell layer of an acrylic polymer, obtained through a core-shell reaction; and the cable protection tube is prepared through a multi-step mixing process. The present invention achieves efficient flame retardancy and corrosion resistance through the core-shell structure and the introduction of the corrosion-resistant additive, while buffering stress through the flexible shell layer to maintain the mechanical properties of the material.

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

[0009] The present invention provides a PVC-based corrosion-resistant cable protection tube, comprising a base material, a corrosion-resistant additive, a composite flame retardant and additives;

[0010] The matrix material includes chlorinated polyethylene, polyvinyl chloride and calcium zinc complex stabilizer;

[0011] Corrosion-resistant additives include grafted nanoparticles and ethylene-vinyl alcohol copolymer;

[0012] The grafted nanoparticles include nanosilica, epoxy resin, and glycidoxypropyltrimethoxysilane;

[0013] The composite flame retardant includes melamine cyanurate, triphenyl phosphate, nano magnesium hydroxide, butyl acrylate, styrene and methyl methacrylate;

[0014] The additives include MBS, stearic acid, polyethylene wax, antimony trioxide and antioxidant 1010.

[0015] The present invention also provides a preparation process of a PVC-based corrosion-resistant cable protection tube, comprising the following preparation steps:

[0016] The base material and the corrosion-resistant additive are discharged into a cooling mixer in parts by mass, cooled to 60-70°C and stirred for 20 minutes, 20-30 parts of a composite flame retardant, 6-10 parts of MBS, 0.3-0.8 parts of stearic acid, 1-2 parts of polyethylene wax, 1-1.5 parts of antimony trioxide and 0.3-0.5 parts of an antioxidant 1010 are added, and stirred to obtain a mixture; the mixture is added into a twin-screw extruder and melt-extruded; the mixture is shaped by a vacuum sizing sleeve, and cooled by a spray water tank with the water temperature controlled at 15-20°C for 30-60 seconds; the mixture is then towed at a constant speed by a crawler tractor and cut to a set length by a planetary cutter to obtain a cable protection tube; the obtained cable protection tube is a PVC solid wall tube with a diameter ranging from 50-100 mm and a wall thickness distributed between 2-5 mm according to the diameter, and is cut to a set required length.

[0017] The temperatures of the melt extrusion zones are: 170-180°C in the feeding zone, 180-190°C in the compression zone, 190-195°C in the metering zone, 180-190°C in the die head, 20-35rpm in the main screw speed, and -0.06 to -0.08MPa in the vacuum exhaust degree.

[0018] Preferably, the preparation of the base material and the corrosion-resistant additive comprises the following steps:

[0019] By weight, 50-60 parts of chlorinated polyvinyl chloride, 40-50 parts of polyvinyl chloride and 5 parts of calcium zinc complex stabilizer are put into a high-speed mixer, and hot-mixed at 110-120° C. for 20-30 minutes to obtain a base material;

[0020] Calculated by weight, 3-8 parts of grafted nanoparticles and 5-10 parts of ethylene-vinyl alcohol copolymer are added into a high-speed mixer, and pre-mixed at 80-90° C. for 30-40 minutes to obtain a corrosion-resistant additive.

[0021] Preferably, the preparation of the grafted nanoparticles comprises the following steps:

[0022] Add 15 parts of epoxy resin E518 and 2 ml of triethylamine to the modified nano-silica, heat to 50-60°C, and carry out grafting reaction for 5-6 hours to obtain a reactant; separate the reactant, wash it with anhydrous ethanol three times, and vacuum dry it at 80°C for 12 hours to obtain grafted nanoparticles.

[0023] Preferably, the preparation of modified nano-silica comprises the following steps:

[0024] The method comprises the following steps: placing nano-silica in a vacuum drying oven and vacuum drying at 100° C. for 5 hours to obtain a dry raw material; adding 5-10 parts of glycidyloxypropyltrimethoxysilane to 10 ml of a 95% ethanol aqueous solution, adding acetic acid to adjust the pH value to 4-5, and stirring for 40 minutes to obtain a silane solution; ultrasonically dispersing 100 parts of the dry raw material in a 95% ethanol aqueous solution to prepare a dispersion with a mass concentration of 10%, ultrasonically dispersing for 30 minutes at an ultrasonic power of 200 W, slowly adding the silane solution under stirring, heating to 60-70° C., carrying out a modification reaction for 2-4 hours, separating and centrifuging, washing with deionized water three times, and vacuum drying at 80° C. for 10 hours to obtain the modified nano-silica.

[0025] Preferably, the preparation of the composite flame retardant comprises the following steps:

[0026] Under nitrogen protection, the monomer pre-emulsion is added dropwise to the core layer solution, the addition time is maintained at 2 hours, the temperature is controlled at 70-80°C, and the stirring speed is 500-600 rpm. After the dropwise addition is completed, the core-shell reaction is carried out for 4-6 hours to obtain a reaction product; the reaction product is cooled to room temperature, demulsified and filtered, washed alternately with deionized water and anhydrous ethanol 5-8 times, and vacuum dried at 70°C for 10 hours to obtain a composite flame retardant; the particle size of the composite flame retardant is 5-10 μm, and the shell coverage is 12-18%.

[0027] Preferably, the preparation of the monomer pre-emulsion and the core layer solution comprises the following steps:

[0028] Melamine cyanurate, triphenyl phosphate and nano-magnesium hydroxide were mixed, deionized water was added, and the mixture was placed in a high-speed blender and stirred at 1000 rpm for 30 minutes to obtain a suspension; ammonium persulfate was added to the suspension, the temperature was raised to 50-60°C, and an activation reaction was carried out for 1-2 hours to obtain a core layer solution; butyl acrylate, styrene and methyl methacrylate were mixed, deionized water and sodium lauryl sulfate were added, and the mixture was stirred at 200 rpm for 30 minutes to obtain a monomer pre-emulsion;

[0029] The mass ratio of melamine cyanurate, triphenyl phosphate and nano magnesium hydroxide is 1-2:1:1; the mass ratio of butyl acrylate, styrene and methyl methacrylate is 2-3:5-6:2-3.

[0030] Preferably, the chlorine content of chlorinated polyvinyl chloride is 65-69%, and the number average molecular weight is 80,000-100,000; the polyvinyl chloride is selected from high-density polyvinyl chloride, and the melt index is 0.5-2g / 10min; the ethylene content of ethylene-vinyl alcohol copolymer is 32-38mol%, and the melt index is 1-5g / 10min; the particle size of nano-silica is 20-30nm, and the epoxy group grafting rate is 10-15%; the number average molecular weight of polyethylene wax is 2000-4000, and the melting point is 100-110°C; the epoxy resin is E-51; and the particle size of nano-magnesium hydroxide is 40-80nm.

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

[0032] 1. This solution increases the chlorine content of the matrix by introducing chlorinated polyvinyl chloride, thereby enhancing intermolecular forces and rigid support. The composite flame retardant core-shell structure avoids agglomeration, with the rubber core absorbing impact energy and the glass shell improving compatibility to achieve a balance between rigidity and toughness. Nanoparticles reinforce the material through size effects, and their surface epoxy groups form chemical bonds with the matrix to optimize stress transfer. The hot mixing and premixing process ensures uniform dispersion of the additives to avoid stress concentration. Through the synergistic effect of multiple components, the protective tube has high tensile, bending and impact strength, and improved mechanical properties.

[0033] 2. The present invention generates non-flammable gas to dilute oxygen through the decomposition of melamine cyanurate, and triphenyl phosphate generates phosphorus-containing free radicals to cut off the combustion chain reaction. The two synergistically inhibit combustion in the gas phase; nano-magnesium hydroxide absorbs heat and decomposes to cool down and release water vapor, and forms a heat-insulating and oxygen-isolating barrier with the carbonization promoted by triphenyl phosphate, thereby achieving gas-solid two-phase flame retardancy; utilizing the multi-mechanism flame retardant effect, and at the same time introducing an in-situ polymerized acrylate shell to disperse the flame retardant at the submicron level, reducing the negative impact on mechanical properties while improving flame retardancy.

[0034] 3. The present invention constructs double protection through the synergistic effect of matrix modification and additives: chlorinated polyvinyl chloride enhances the interaction between matrix molecular chains by virtue of its high chlorine content, thereby improving chemical corrosion resistance; the grafted nanoparticles are uniformly dispersed after premixing, and their epoxy groups strengthen the interface bonding, extending the penetration path of the corrosive medium; ethylene-vinyl alcohol copolymer forms a polar barrier layer, which cooperates with the nanoparticles to form a composite network of chemical barriers and physical barriers, preventing the intrusion of media such as acids and alkalis, and significantly improving the corrosion resistance and stability of the protective tube in different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The changes in the acid strength retention rates of the cable protection tubes obtained in Example 10, Comparative Examples 1-3, and Comparative Examples 14-16 of the present invention are shown. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The KH560 of the present invention is glycidyloxypropyltrimethoxysilane; MBS is a terpolymer of methyl methacrylate, butadiene and styrene; MCA is melamine cyanurate; TPP is triphenyl phosphate; BA is butyl acrylate; St is styrene; and MMA is methyl methacrylate.

[0038] See also Figure 1 The present invention provides a PVC corrosion-resistant cable protection tube and its preparation process, and the technical solution is as follows:

[0039] Example 1

[0040] The method comprises the following steps: placing nano-silica in a vacuum drying oven and vacuum drying at 100° C. for 5 h to obtain a dry raw material; adding 8 parts of KH560 to 10 ml of a 95% ethanol aqueous solution, adding acetic acid to adjust the pH value to 4, and stirring for 40 min to obtain a silane solution; ultrasonically dispersing 100 parts of the dry raw material in a 95% ethanol aqueous solution to prepare a dispersion with a mass concentration of 10%, the ultrasonic dispersion time is 30 min, the ultrasonic power is 200 W, and the silane solution is slowly added under stirring, the temperature is raised to 70° C., the modification reaction is carried out for 3 h, the reaction is separated and centrifuged, the reaction is washed with deionized water 3 times, and the reaction is vacuum dried at 80° C. for 10 h to obtain modified nano-silica; adding 10 parts of epoxy resin E51 to the modified nano-silica and 2 ml of triethylamine, the temperature is raised to 60° C., and the reaction is grafted for 5 h to obtain a reactant; the reactant is separated, washed with anhydrous ethanol 3 times, and vacuum dried at 80° C. for 12 h to obtain grafted nanoparticles;

[0041] 60 parts of melamine cyanurate, 30 parts of triphenyl phosphate and 30 parts of nano magnesium hydroxide were mixed, 500 parts of deionized water were added, the mixture was placed in a high-speed stirrer, and stirred at 1000 rpm for 30 minutes to obtain a suspension; 0.5 parts of ammonium persulfate were added to the suspension, the temperature was raised to 50°C, and activation reaction was carried out for 2 hours to obtain a core layer solution; 6 parts of butyl acrylate, 10 parts of styrene and 4 parts of methyl methacrylate were mixed, 100 parts of deionized water and 0.2 parts of sodium lauryl sulfate were added, and the mixture was stirred at 200 rpm for 30 minutes to obtain a monomer pre-emulsion; under nitrogen protection, the monomer pre-emulsion was slowly added dropwise to the core layer solution, the dropping time was kept within 2 hours, the temperature was controlled at 70°C, and the stirring speed was 600 rpm. After the dropwise addition was completed, the core-shell reaction was carried out for 5 hours to obtain a reaction product; the reaction product was cooled to room temperature, demulsified and filtered, washed alternately with deionized water and anhydrous ethanol 5 times, and vacuum dried at 70°C for 10 hours to obtain a composite flame retardant.

[0042] 60 parts of chlorinated polyvinyl chloride, 40 parts of polyvinyl chloride and 5 parts of calcium zinc complex stabilizer are put into a high-speed mixer and hot-mixed at 110°C for 25 minutes to obtain a base material; 5 parts of grafted nanoparticles and 8 parts of ethylene-vinyl alcohol copolymer are added to the high-speed mixer and pre-mixed at 90°C for 40 minutes to obtain a corrosion-resistant additive; the base material and the corrosion-resistant additive are discharged into a cooling mixer, cooled to 60°C and stirred for 20 minutes, 25 parts of a composite flame retardant, 8 parts of MBS, 0.5 parts of stearic acid, 1.5 parts of polyethylene wax, 1.2 parts of antimony trioxide and 0.3 parts of antioxidant 1010 are added, and the mixture is stirred and mixed at 500 rpm for 30 minutes to obtain a mixture; the mixture is added to a twin-screw extruder and melt-extruded; the mixture is shaped by a vacuum sizing sleeve, and passed through a spray water tank with the water temperature controlled at 15°C, cooled and shaped for 40 seconds; then the mixture is towed at a constant speed by a crawler tractor and cut to a set length by a planetary cutter to obtain a cable protection tube.

[0043] Examples 2-5 refer to the preparation methods and parameter conditions of Example 1, with the differences shown in Table 1.

[0044] Table 1 Parameter changes of Examples 1-5

[0045]

[0046] Comparative Example 1 refers to Example 1, except that chlorinated polyvinyl chloride is not added and an equal amount of polyvinyl chloride is used.

[0047] Comparative Example 2 refers to Example 1, except that no grafted nanoparticles are added.

[0048] Comparative Example 3 refers to Example 1, except that the nano-silica is not grafted and modified with epoxy resin.

[0049] Comparative Example 4 refers to Example 1, except that no composite flame retardant is added.

[0050] Comparative Example 5 refers to Example 1, except that the composite flame retardant is not added through the core-shell structure but melt blended.

[0051] Comparative Example 6 refers to Example 1, except that no MBS is added.

[0052] Comparative Example 7 refers to Example 1, except that the base material is prepared without a hot mixing process and is directly melted and added.

[0053] Comparative Example 8 refers to Example 1, except that the grafted nanoparticles and the ethylene-vinyl alcohol copolymer are not premixed but directly melted and added.

[0054] Comparative Example 9 refers to Example 1, except that the hot mixing and blending process is not performed and melt extrusion is directly performed.

[0055] Experimental Example 1 Mechanical Strength Test

[0056] The cable protection tubes prepared in Examples 1-5 and Comparative Examples 1-9 were subjected to mechanical strength tests. The tensile strength was tested according to GB / T 1040.2-2006; the bending strength was tested according to GB / T 9341-2008; and the impact strength was tested according to GB / T 1843-2008. The test results are shown in Table 2.

[0057] Table 2 Test results of Examples 1-5 and Comparative Examples 1-9

[0058] Example Tensile strength / MPa Bending strength / MPa <![CDATA[Impact strength / kJ / m 2 > Example 1 45 65 22 Example 2 42 62 21 Example 3 43 64 20 Example 4 42 63 20 Example 5 46 60 21 Comparative Example 1 35 48 16 Comparative Example 2 32 45 18 Comparative Example 3 36 45 15 Comparative Example 4 42 56 17 Comparative Example 5 35 50 15 Comparative Example 6 42 58 12 Comparative Example 7 36 48 13 Comparative Example 8 37 51 14 Comparative Example 9 30 40 10

[0059] The results in Table 2 show that, in the comparative example, the mechanical properties of the cable protection tube obtained by adjusting the components and processes are significantly reduced compared with those in the embodiment; in comparative example 1, the lack of chlorinated polyvinyl chloride leads to a decrease in the rigidity and crosslinking density of the matrix resin, an increase in the slippage between the molecular chains, and a significant decrease in strength and toughness. Chlorinated polyvinyl chloride is a chlorinated modified product of polyvinyl chloride, with a higher chlorine content and a stronger intermolecular force. The matrix material formed by the blending of the two significantly improves the mechanical strength; the results of comparative examples 2-3 show that the physical reinforcement effect of nanoparticles is lacking, the stress concentration phenomenon is significant, and the nanoparticles The interfacial cross-linking effect of the particles is missing, and the overall strength of the material is reduced; the surface of unmodified nano-silica is hydrophilic, and has poor interfacial compatibility with the hydrophobic polyvinyl chloride matrix, which easily forms stress concentration points. KH560 provides a preliminary dispersion effect to avoid the agglomeration of nanoparticles. Epoxy resin grafting and ethylene-vinyl alcohol copolymer blending can further strengthen the filler-matrix interface through chemical bonding. The loss of this effect leads to particle shedding and a sudden drop in strength. In comparative examples 4-5, the absence of the composite flame retardant has little effect on the overall mechanical strength of the material. Although the damage to the matrix continuity caused by the flame retardant filler is reduced, the toughening effect of the core-shell structure disappears. , the strength is slightly reduced; however, if the flame retardant is not introduced through the core-shell structure, the nano-scale dispersion of the flame retardant cannot be achieved, and direct melt blending leads to serious agglomeration of the flame retardant particles, forming rigid filler defects, causing stress concentration, and greatly reducing the strength; the core-shell structure can buffer stress through the flexible shell layer, improve the compatibility of the filler and the matrix, and then form an interpenetrating network with the polyvinyl chloride matrix, enhance the interface bonding, and further improve the mechanical strength; in Comparative Example 6, MBS is used as an impact modifier, and its rubber phase can absorb impact energy and inhibit crack propagation. The absence of MBS leads to brittle fracture of the material, and the impact strength is greatly reduced. In addition, the The dispersed phase can enhance the continuity of the matrix, and its absence leads to a decrease in overall strength. The results of comparative examples 7-9 show that the mechanical strength of the material can be greatly improved by adjusting the process. The hot mixing process can evenly disperse the calcium zinc stabilizer and react with the polyvinyl chloride molecular chain, inhibiting the release of hydrochloric acid during processing and avoiding degradation. The premixing process can pre-form hydrogen bonds or physical entanglements between the polar resin and the grafted nanoparticles through mechanical shearing, thereby improving the blending compatibility. Direct blending and extrusion leads to severe segregation of components, agglomeration of nanoparticles, uneven distribution of flame retardants, and insufficient reaction of stabilizers. The matrix presents an "island structure" defect, and the mechanical strength is significantly reduced.

[0060] In summary, by introducing chlorinated polyvinyl chloride, the chlorine content in the matrix is ​​higher, the intermolecular force is stronger, and a rigid molecular chain structure is formed, which provides sufficient support and pressure resistance for the protective tube; at the same time, in the composite flame retardant, the introduction of the core-shell structure avoids the agglomeration of the flame retardant while achieving the rigidity and toughness balance of the material; its rubbery core structure acts as a stress concentration point, which can effectively absorb energy when impacted, causing the matrix to produce a large number of silver streaks and shear bands, thereby dissipating the impact energy, and its glassy shell structure ensures its compatibility with the matrix; finally, the size effect of the nanoparticles has an enhancing effect, and the epoxy groups on the surface form a strong chemical bond with the matrix, so that the stress can be effectively transferred from the flexible matrix to the rigid nanoparticles; the introduction of hot mixing and premixing processes ensures that the additives can reach a highly uniform dispersion state before melting, avoiding the occurrence of stress concentration points; through the synergistic effect between multiple components and processes, the overall mechanical strength of the material is improved.

[0061] Example 6 is the same as Example 1;

[0062] Examples 7-9 refer to the preparation methods and parameter conditions of Example 1, with the differences shown in Table 3.

[0063] Table 3 Parameter changes of Examples 6-9

[0064]

[0065] Comparative Example 4 refers to Example 1, except that no composite flame retardant is added.

[0066] Comparative Example 5 refers to Example 1, except that the composite flame retardant is not added through the core-shell structure but melt blended.

[0067] Comparative Example 10 refers to Example 1, except that only an equal amount of melamine cyanurate is used in the composite flame retardant.

[0068] Comparative Example 11 refers to Example 1, except that only an equal amount of triphenyl phosphate is used in the composite flame retardant.

[0069] Comparative Example 12 refers to Example 1, except that only an equal amount of nano-magnesium hydroxide is used in the composite flame retardant.

[0070] Comparative Example 13 refers to Example 1, except that no shell material is introduced into the composite flame retardant, and the flame retardant is directly melted and added.

[0071] Experimental Example 2 Flame retardant performance test

[0072] The cable protection tubes prepared in Examples 6-9, Comparative Examples 4-5, and Comparative Examples 10-13 were subjected to flame retardant performance tests. The limiting oxygen index was tested according to GB / T 2406.2-2009; the self-extinguishing time and vertical burning grade were tested according to GB / T 2408-2021. The test results are shown in Table 4.

[0073] Table 4 Test results of Examples 6-9, Comparative Examples 4-5, and Comparative Examples 10-13

[0074] Example Limiting oxygen index / % Vertical combustion level Self-extinguishing time / s Example 6 36 V-0 ≤10 Example 7 35 V-0 ≤10 Example 8 34 V-0 ≤10 Example 9 35 V-0 ≤10 Comparative Example 4 20 Burning dripping No self-extinguishing Comparative Example 5 26 V-2 30 Comparative Example 10 24 V-1 16 Comparative Example 11 23 V-1 18 Comparative Example 12 22 V-2 20 Comparative Example 13 25 V-2 25

[0075] The results in Table 4 show that the comparative example shows significantly reduced flame retardant performance compared with the embodiment by adjusting the dosage of the composite flame retardant component and the process; in comparative examples 4-5, after the flame retardant is missing, the cable protection tube material lacks the multi-component effect of melamine cyanurate inhibiting free radicals, triphenyl phosphate forming carbon to isolate oxygen, and nano magnesium hydroxide absorbing heat during combustion, resulting in intense combustion; the core-shell structure realizes nano-scale dispersion of the flame retardant through emulsion polymerization, and the shell layer and the polyvinyl chloride matrix form an interpenetrating network, which enhances the interface bonding and evenly distributes the flame retardant components, thereby improving the flame retardant performance; on the contrary, direct melt blending causes the flame retardant particles to agglomerate and cannot effectively contact the flame, and there are many interface defects, and heat is easily conducted to the matrix, weakening the flame retardant. Efficiency; Combined with Comparative Example 13, the missing shell layer leads to uneven dispersion of the flame retardant and a loose carbon layer. The gas generated by the decomposition of melamine cyanurate easily breaks through the carbon layer, and the cooling effect of nano-magnesium hydroxide cannot effectively cover the combustion area due to poor dispersion, which ultimately leads to a significant decrease in the flame retardant performance of the material; the introduction of the shell material is not only a dispersion carrier, but its polymer chain can also cooperate with triphenyl phosphate to form an expanded carbon layer during combustion, thereby enhancing the barrier effect; the results of Comparative Examples 10-12 show that the use of a single flame retardant, the lack of the melamine cyanurate gas phase flame retardant mechanism, the condensed phase carbonization effect of triphenyl phosphate, and the heat absorption of nano-magnesium hydroxide, the synergistic effect of multiple mechanisms of physical cooling, the flame retardant performance of the obtained cable protection tube material is greatly reduced.

[0076] In summary, melamine cyanurate decomposes during heating to produce non-combustible gases such as NH3 and N2 to dilute oxygen, while triphenyl phosphate decomposes to produce phosphorus-containing free radicals that can capture highly active free radicals in the combustion chain reaction. Through synergistic action, the combustible gas is diluted in the gas phase and the combustion chain reaction is cut off, achieving dual inhibition of dilution and capture; in addition, nano-magnesium hydroxide decomposes through endothermic decomposition, releasing water vapor to dilute oxygen, reducing the surface temperature of the material, and synergistically decomposing triphenyl phosphate to promote the dehydration and carbonization of the matrix to form a dense carbon layer, constructing a heat-insulating and oxygen-isolating barrier on the surface of the material, and further improving the flame retardant properties of the material through the simultaneous action of gas and solid phases and the complementary flame retardant mechanisms; at the same time, the in-situ polymerization method introduces an acrylic shell, which not only ensures that the flame retardant core can be evenly dispersed in the matrix in a submicron form, avoiding performance shortcomings caused by agglomeration, but also minimizes the negative impact of the flame retardant on the mechanical properties of the material, thereby improving the comprehensive performance of the protective tube.

[0077] Example 10 is the same as Example 1;

[0078] Examples 11-14 refer to the preparation method and parameter conditions of Example 1, with the differences shown in Table 5.

[0079] Table 5 Parameter changes of Examples 10-14

[0080]

[0081] Comparative Example 1 refers to Example 1, except that chlorinated polyvinyl chloride is not added and an equal amount of polyvinyl chloride is used.

[0082] Comparative Example 2 refers to Example 1, except that no grafted nanoparticles are added.

[0083] Comparative Example 3 refers to Example 1, except that the nano-silica is not grafted and modified with epoxy resin.

[0084] Comparative Example 8 refers to Example 1, except that the grafted nanoparticles and the ethylene-vinyl alcohol copolymer are not premixed but directly melted and added.

[0085] Comparative Example 14 refers to Example 1, except that the corrosion resistant additive is prepared without adding ethylene-vinyl alcohol copolymer.

[0086] Comparative Example 15 refers to Example 1, except that the nano-silica is not modified or grafted, but is directly blended and added.

[0087] Comparative Example 16 refers to Example 1, except that the nano-silica is not modified and is directly ring-opened grafted with the epoxy resin.

[0088] Experimental Example 3 Corrosion Resistance Test

[0089] The cable protection tubes prepared in Examples 10-14, Comparative Examples 1-3, Comparative Example 8, and Comparative Examples 14-16 were subjected to corrosion resistance tests. 3 cm test specimens were taken from the prepared protection tubes, and the tensile strength of the initial test specimens was measured according to GB / T 1040.2-2006. The specimens were then placed in 10% hydrochloric acid solution, 10% sodium hydroxide solution, and 5% sodium chloride solution, respectively, and allowed to stand at 25°C for 72 hours. After standing, the treated specimens were taken out, washed with deionized water, and dried at 50°C for 10 hours to obtain treated specimens. The tensile strength was measured according to GB / T 1040.2-2006, and the tensile strength retention rate was calculated. The test results are shown in Table 6. The acid strength retention rate of Example 10, Comparative Examples 1-3, and Comparative Examples 14-16 changes as shown in Table 6. Figure 1 shown.

[0090] Table 6 Test results of Examples 10-14, Comparative Examples 1-3, Comparative Example 8, Comparative Examples 14-16

[0091] Example Acid strength retention rate / % Alkaline strength retention rate / % Neutral strength retention rate / % Example 10 95.2 98.3 99.5 Example 11 94.9 97.8 99.4 Example 12 95.1 97.8 99.2 Example 13 94.8 98.2 99.5 Example 14 94.8 98.1 99.3 Comparative Example 1 82.6 86.4 93.2 Comparative Example 2 88.5 90.6 95.4 Comparative Example 3 80.6 80.5 90.8 Comparative Example 8 85.4 88.6 93.6 Comparative Example 14 87.3 89.5 94.6 Comparative Example 15 75.6 78.4 88.2 Comparative Example 16 83.5 84.2 91.5

[0092] From the results in Table 2, it can be seen that the cable protection tube obtained in the comparative example shows significantly reduced corrosion resistance compared with the embodiment due to the changes in components and processes; in comparative example 1, chlorinated polyvinyl chloride is not added, and only polyvinyl chloride is used. The density of polar groups in the molecular chain is reduced, and acid-base media can more easily penetrate into the gaps between the molecular chains, resulting in swelling and chain breakage, and reduced corrosion resistance. However, with the addition of chlorinated polyvinyl chloride, the interaction between the molecular chains is stronger due to the increase in chlorine content, and the electronegativity of chlorine atoms can inhibit the attack of acid-base media on CC bonds, thereby improving chemical corrosion resistance; from the results of comparative examples 2-3, it can be seen that the epoxy groups on the surface of the grafted nanoparticles can form hydrogen bonds or physical entanglements with the matrix, fill the micro-defects in the matrix, form a barrier effect, and prevent the corrosive medium from easily penetrating through the pores. In addition, epoxy resin grafting can graft epoxy segments to the surface of nano-silica through chemical bonding, thereby improving interface compatibility, blocking medium penetration, and preventing nanoparticle agglomeration. Defects become corrosion breakthroughs. In addition, the corrosion resistance of the epoxy resin itself can work synergistically with the nanoparticles. In Comparative Example 8, direct melt addition leads to uneven dispersion of the ethylene-vinyl alcohol copolymer and the grafted particles. The high barrier properties of the ethylene-vinyl alcohol copolymer and the filling effect of the nanoparticles cannot work synergistically, and local areas are easily damaged by corrosive media. Combined with Comparative Example 14, the ethylene-vinyl alcohol copolymer molecules form hydrogen bonds with the grafted nanoparticles through mechanical shearing during the premixing process, which promotes the uniform dispersion of the two in the matrix to form a nano-polymer composite barrier layer, further improving the corrosion resistance. In Comparative Examples 15-16, the unmodified nano-silica has high surface energy and is easy to agglomerate to form micron-level defects. At the same time, the interface bonding with the matrix is ​​weak, and the corrosive medium can quickly penetrate into the material through the gaps between the agglomerates. In addition, there is a lack of modified grafting steps, and the compatibility cannot be improved by interface modification, resulting in the nanoparticles becoming corrosion channels and accelerating material corrosion.

[0093] In summary, the present invention introduces chlorinated polyvinyl chloride and polyvinyl chloride as matrix materials, and utilizes the high chlorine content of chlorinated polyvinyl chloride to strengthen the intermolecular chain interaction force of the matrix and improve the corrosion resistance. The premixing process ensures that the grafted nanoparticles are evenly dispersed in the matrix, extending the penetration path of the corrosive medium. The epoxy groups on the surface enhance the interface bonding with the matrix, avoiding the penetration channel caused by the separation of the filler from the matrix. In addition, the micro-dispersed ethylene-vinyl alcohol copolymer phase forms a discontinuous barrier layer in the matrix. The synergistic effect of the two additives forms a nano-filler-polar barrier composite network, providing dual protection of chemical barrier and physical barrier, effectively blocking the invasion of corrosive media, and further improving the corrosion resistance.

[0094] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A PVC corrosion-resistant cable protection tube, characterized in that: The cable protection tube comprises a base material, a corrosion-resistant additive, a composite flame retardant and additives; Wherein, the matrix material comprises chlorinated polyethylene, polyvinyl chloride and calcium zinc complex stabilizer; The corrosion-resistant additive includes grafted nanoparticles and ethylene-vinyl alcohol copolymer; The grafted nanoparticles include nano-silica, epoxy resin and glycidyloxypropyltrimethoxysilane; The composite flame retardant comprises melamine cyanurate, triphenyl phosphate, nano magnesium hydroxide, butyl acrylate, styrene and methyl methacrylate; The auxiliary agents include MBS, stearic acid, polyethylene wax, antimony trioxide and antioxidant 1010.

2. A process for preparing the PVC corrosion-resistant cable protection tube according to claim 1, characterized in that: The preparation of the cable protection tube includes the following preparation steps: The base material and the corrosion-resistant additive are discharged into a cooling mixer, cooled and stirred to mix, a composite flame retardant, MBS, stearic acid, polyethylene wax, antimony trioxide and antioxidant 1010 are added, and stirred to mix to obtain a mixture; the mixture is added into a twin-screw extruder and melt-extruded; the mixture is shaped by a vacuum sizing sleeve and cooled and shaped by a spray water tank; the mixture is then towed at a constant speed by a crawler traction machine and cut to a set length by a planetary cutter to obtain the cable protection tube.

3. The preparation process of the PVC corrosion-resistant cable protection tube according to claim 2, characterized in that: The preparation of the base material and the corrosion-resistant additive comprises the following steps: Putting chlorinated polyvinyl chloride, polyvinyl chloride and calcium zinc complex stabilizer into a high-speed mixer and hot mixing to obtain the matrix material; Grafted nanoparticles and ethylene-vinyl alcohol copolymer are added into a high-speed mixer and pre-mixed to obtain the corrosion-resistant additive.

4. The process for preparing the PVC corrosion-resistant cable protection tube according to claim 3, characterized in that: The preparation of the grafted nanoparticles comprises the following steps: Epoxy resin E51 and triethylamine are added to the modified nano-silica to undergo grafting reaction to obtain a reactant; the reactant is separated, washed with anhydrous ethanol, and vacuum dried to obtain the grafted nanoparticles.

5. The process for preparing the PVC corrosion-resistant cable protection tube according to claim 4, characterized in that: The preparation of the modified nano-silica comprises the following steps: The method comprises the following steps: placing nano-silica in a vacuum drying oven and vacuum drying the nano-silica to obtain a dry raw material, adding glycidyloxypropyltrimethoxysilane to a 95% ethanol aqueous solution, adding acetic acid to adjust the pH value to acidic, and stirring to obtain a silane solution; ultrasonically dispersing the dry raw material in a 95% ethanol aqueous solution to prepare a dispersion with a mass concentration of 10%, adding the silane solution under stirring, subjecting the modified nano-silica to separation and centrifugation for reaction, washing with deionized water, and vacuum drying to obtain the modified nano-silica.

6. The process for preparing the PVC corrosion-resistant cable protection tube according to claim 2, characterized in that: The preparation of the composite flame retardant comprises the following steps: Under nitrogen protection, the monomer pre-emulsion is added dropwise to the core layer solution. After the addition is completed, a core-shell reaction is performed to obtain a reaction product. The reaction product is cooled to room temperature, demulsified and filtered, washed alternately with deionized water and anhydrous ethanol, and vacuum dried to obtain the composite flame retardant.

7. The process for preparing the PVC corrosion-resistant cable protection tube according to claim 6, characterized in that: The preparation of the monomer pre-emulsion and the core layer solution comprises the following steps: Melamine cyanurate, triphenyl phosphate and nano-magnesium hydroxide are mixed, deionized water is added, and the mixture is placed in a high-speed blender and stirred to obtain a suspension; ammonium persulfate is added to the suspension to perform an activation reaction to obtain the core layer solution; butyl acrylate, styrene and methyl methacrylate are mixed, deionized water and sodium lauryl sulfate are added, and the mixture is stirred to obtain the monomer pre-emulsion.

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