Flame-retardant and high-temperature-resistant CPVC cable protection pipe and preparation method thereof

Abstract

This invention discloses a flame-retardant and high-temperature resistant CPVC cable protection pipe and its preparation method, belonging to the field of pipe preparation. It addresses the technical problem that the flame-retardant and high-temperature resistance properties of existing CPVC cable protection pipes need further improvement. Specifically, it comprises the following components by weight: 80-100 parts CPVC, 8-15 parts flame-retardant modified eugenol, 1-3 parts mercapto-modified graphene oxide, 2-5 parts modified reactive anti-aging agent, and 1-3 parts excipients. This invention utilizes a peroxide-initiated in-situ mercapto-olefin click crosslinking reaction between flame-retardant modified eugenol, mercapto-modified graphene oxide, and the modified reactive anti-aging agent to successfully construct a three-dimensional inorganic-organic hybrid network within the CPVC matrix, significantly improving the flame-retardant, high-temperature resistance, thermo-oxidative aging resistance, and mechanical strength of the CPVC cable protection pipe.

Description

Technical Field

[0001] This invention relates to the field of pipe manufacturing, specifically to a flame-retardant and high-temperature resistant CPVC cable protection pipe and its manufacturing method. Background Technology

[0002] Chlorinated polyvinyl chloride (CPVC) is widely used as a protective conduit for high-voltage and ultra-high-voltage underground cables in urban power grids due to its excellent electrical insulation, corrosion resistance, and high mechanical strength. In recent years, with the continuous increase in power grid transmission capacity, cables are subjected to severe Joule heating during full-load or overload operation, resulting in the conduit being exposed to a high-temperature baking environment for a long time. This harsh service condition places more stringent requirements on the Vicat softening temperature, long-term heat and oxygen aging resistance, and flame retardant and smoke suppression performance of CPVC conduits. If the high-temperature structural rigidity of the conduit is insufficient or the flame retardant system fails, it is very easy to cause the conduit to deform and collapse, or even cause the underground cable fire to spread.

[0003] To improve the heat resistance and flame retardancy of CPVC pipes, physical blending modification is commonly used. Commonly used modifying materials include adding small-molecule phosphorus / nitrogen flame retardants, inorganic rigid nanofillers, and compounding hindered phenolic or phosphite antioxidants. Although these conventional methods can improve the flame retardancy or heat resistance of the material to a certain extent in the early stages, their modification mechanism mostly relies on the simple physical dispersion of additives in the matrix. There is an urgent need to find a new modification strategy that can solve the material defects at the molecular structure level.

[0004] Currently, traditional small-molecule flame retardants and anti-aging agents lack chemical bonding with the CPVC matrix. During high-temperature extrusion processing and long-term heat service, they are prone to thermal volatilization or migration to the pipe surface, resulting in a sharp decline in the long-term flame retardant performance and resistance to thermo-oxidative aging. Secondly, inorganic nanofillers, due to their extremely high surface energy, are prone to agglomeration in polymer melts. This severe macroscopic phase separation forms dense stress concentration points inside the matrix, leading to a significant deterioration in the impact toughness of the pipe. Furthermore, physical fillers cannot effectively limit the thermal creep and slippage of CPVC macromolecular chains under high-temperature conditions, resulting in a low ring stiffness retention rate of the pipe at high temperatures.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a flame-retardant and high-temperature resistant CPVC cable protection pipe and its preparation method, so as to solve the technical defects mentioned in the background art.

[0007] The objective of this invention can be achieved through the following technical solution: a flame-retardant and high-temperature resistant CPVC cable protection pipe, comprising the following components by weight: 80-100 parts CPVC, 8-15 parts flame-retardant modified eugenol, 1-3 parts mercapto-modified graphene oxide, 2-5 parts modified reactive anti-aging agent and 1-3 parts auxiliary materials.

[0008] The flame-retardant modified eugenol was prepared by the following steps:

[0009] A1. Place eugenol, potassium carbonate and acetone in a reaction vessel and stir. Add tetrabutylammonium bromide. Heat the reaction vessel to 55-65℃. Add epichlorohydrin and keep the reaction at the temperature for 2-4 hours. Post-treatment yields epoxy-modified eugenol.

[0010] A2. Epoxy-modified eugenol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine were placed in a reaction vessel under nitrogen atmosphere and stirred. The reaction vessel was heated to 120-130℃ and stirred for 2-4 hours. The flame-retardant modified eugenol was obtained after post-treatment.

[0011] Further, in step A1, the ratio of eugenol, potassium carbonate, acetone, tetrabutylammonium bromide, and epichlorohydrin is 1-2g:1.6-1.8g:15-25mL:0.03-0.05g:1-2g. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filtrate and one volume of ethyl acetate are added to a separatory funnel. Then, three volumes of saturated brine are added to the concentrate, and the mixture is washed 1-3 times. The organic phase is transferred to a rotary evaporator at a temperature of 50-60℃, and the mixture is evaporated under reduced pressure until no liquid is collected. The mixture is then transferred to a vacuum drying oven at a temperature of 50-60℃ and dried for 4-6 hours to obtain epoxy-modified eugenol.

[0012] Further, in step A2, the weight ratio of the epoxy-modified eugenol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine is 1.6-2.6:1.6-2.6:0.05-0.10. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, 5 mL of tetrahydrofuran is added to completely dissolve the product, and then the solution is slowly added dropwise to 50 mL of n-hexane under vigorous stirring to precipitate the product. After standing, the product is filtered, the filter cake is washed with n-hexane 1-3 times, transferred to an oven at 80-90℃, and dried for 10-12 h to obtain flame-retardant modified eugenol.

[0013] Furthermore, the thiol-modified graphene oxide is prepared by the following steps:

[0014] B1. Place graphene oxide and tetrahydrofuran in a reaction vessel at 0-5℃ and stir for 30-60 min. Add cyanuric chloride and sodium carbonate and stir at low temperature for 3-5 h. After post-treatment, obtain cyanuric chloride-grafted graphene oxide.

[0015] B2. Place cyanuric chloride-grafted graphene oxide and N,N-dimethylformamide in a nitrogen-protected reactor and stir. Add sodium hydrosulfide and triethylamine. Heat the reactor to 50-60℃ and maintain the temperature for 4-6 hours. Post-treatment yields thiol-modified graphene oxide.

[0016] Further, in step B1, the ratio of graphene oxide, tetrahydrofuran, cyanuric chloride, and sodium carbonate is 2-4g:400-500mL:10-12g:4-6g. The post-processing steps include: after the reaction is completed, the reaction solution is centrifuged, the precipitate is washed 2-4 times with tetrahydrofuran, and then the precipitate is transferred to a Soxhlet extractor and extracted with tetrahydrofuran as solvent for 6-8 hours. After extraction, the precipitate is transferred to a vacuum drying oven at 60-80℃ and dried to constant weight to obtain cyanuric chloride-grafted graphene oxide.

[0017] Further, in step B2, the ratio of cyanuric chloride-grafted graphene oxide, N,N-dimethylformamide, sodium hydrosulfide, and triethylamine is 4.5-5.5g:250-350mL:1-2g:0.2-0.7g. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water and ethanol, transferred to a freeze-drying oven at -60℃, and freeze-dried for 20-24h to obtain thiol-modified graphene oxide.

[0018] Furthermore, the preparation method of the modified reactive anti-aging agent is as follows: salicylaldehyde and ethanol are placed in a reaction vessel and stirred evenly, allylamine is slowly added dropwise, the reaction vessel is heated to 50-60℃, and the reaction is carried out with stirring for 2-4 hours. The modified reactive anti-aging agent is then obtained through post-treatment.

[0019] Furthermore, the ratio of salicylaldehyde, ethanol, and allylamine is 1-2g:5-15mL:0.4-0.9g. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 40-60℃, the low-boiling-point solvent is removed by rotary evaporation under reduced pressure, and then transferred to a vacuum drying oven at a temperature of 60-70℃ for drying for 4-6 hours to obtain the modified reactive anti-aging agent.

[0020] The present invention also proposes a method for preparing flame-retardant and high-temperature resistant CPVC cable protection pipe, comprising the following steps: adding CPVC, flame-retardant modified eugenol, mercapto-modified graphene oxide, modified reactive anti-aging agent and auxiliary materials into a high-speed mixer, premixing and reacting at 120-140℃ for 10-20 min, then transferring to a twin-screw extruder for melt extrusion, pelletizing and extrusion molding to obtain CPVC cable protection pipe.

[0021] Furthermore, the processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 160-170℃, plasticizing section 170-180℃, homogenizing section 180-190℃, die head temperature 185-195℃, screw speed 30-50 r / min, the auxiliary materials being lubricant, heat stabilizer and initiator in a mass ratio of 1:1:0.2, the lubricant being one or more of stearic acid, polyethylene wax and calcium stearate, the heat stabilizer being one or two of methyltin mercaptan and epoxidized soybean oil, and the initiator being dicumyl peroxide.

[0022] The present invention has the following beneficial effects:

[0023] 1. This invention initiates the process by pyrolysis of dicumyl peroxide, which promotes intrinsic mercapto-olefin click crosslinking of allyl-terminated flame-retardant modified eugenol, modified reactive anti-aging agent, and mercapto-modified graphene oxide during melt extrusion. This constructs a covalently bonded three-dimensional organic-inorganic network in situ within the matrix. Since the functional additives are all crosslinked and anchored to the graphene network nodes, the migration and precipitation of small molecule additives during long-term use at high temperatures are completely suppressed. At the same time, this rigid network effectively restricts the high-temperature creep and slippage of CPVC matrix molecular chain segments, achieving a significant synergistic leap in the heat aging resistance, tensile strength, and ring stiffness retention rate of the pipe.

[0024] 2. In this invention, the internal nano-hybrid network fully releases the intertwined synergistic effect of condensed phase and gas phase flame retardancy. The sterically hindered phosphorus-containing flame retardant groups and the Schiff base nitrogen-rich skeleton synergistically trigger the PN synergistic flame retardant effect during thermal degradation, catalyzing the rapid dehydrogenation and carbonization of the matrix. At this time, the two-dimensional graphene sheets exert a labyrinthine barrier effect, forming a physical barrier with the generated continuous and dense cross-linked carbon layer, which effectively delays heat conduction and the escape of combustible gases, giving the pipe excellent limiting oxygen index and high-temperature carbon retention rate.

[0025] 3. This invention also improves the rigidity and flame-retardant heat resistance of the material while taking into account the impact resistance of the matrix. The flexible long-chain structure of modified eugenol and the Schiff base anti-aging agent act as soft segments inside the molecule, while the rigid graphene sheets act as hard nodes, forming a spatial network heterogeneous microphase separation structure in the matrix, which greatly optimizes the stress transmission path. When subjected to external impact, this unique network can induce microcracks and absorb a large amount of impact energy, effectively avoiding the severe embrittlement caused by the direct addition of inorganic nanoparticles and improving the true impact rate of the pipe. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The CPVC used in this invention was purchased from Wuhan Mengqi Technology Co., Ltd., with a chlorine content of 65-68% and a particle size of 40-60 mesh.

[0028] The graphene oxide used in this invention was purchased from Jiangxi Shuobang New Material Technology Co., Ltd., with a sheet diameter of 1-10μm, an oxygen content of 30-50%, and a thickness of 8-20nm.

[0029] Example 1

[0030] This embodiment provides a method for preparing flame-retardant modified eugenol, including the following steps:

[0031] Step I: Preparation of epoxy-modified eugenol

[0032] Weigh out 10g of eugenol, 16g of potassium carbonate, and 150mL of butanone and place them in a reaction vessel and stir. Add 0.3g of tetrabutylammonium bromide, heat the reaction vessel to 55℃, add 10g of epichlorohydrin, and keep the reaction at this temperature for 2 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, add the filtrate and one volume of ethyl acetate to a separatory funnel, add three volumes of saturated brine to the concentrate, wash once, transfer the organic phase to a rotary evaporator at 50℃, evaporate under reduced pressure until no liquid is collected, transfer to a vacuum drying oven at 50℃ and dry for 4 hours to obtain epoxy-modified eugenol.

[0033] Step II: Preparation of flame-retardant modified eugenol

[0034] Weigh out 16g of epoxy-modified eugenol, 16g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 0.5g of triphenylphosphine and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and heat it to 120℃. Keep the mixture at this temperature and stir for 2 hours. After the reaction is complete, let the reaction system cool to room temperature and add 50mL of tetrahydrofuran to completely dissolve the product. Then, under vigorous stirring, slowly add the solution dropwise to 500mL of n-hexane to precipitate the product. After standing, filter the solution and wash the filter cake once with n-hexane. Transfer the filter cake to an oven at 80℃ and dry it for 10 hours to obtain flame-retardant modified eugenol.

[0035] The phenolic hydroxyl groups of eugenol are deprotonated by potassium carbonate and a phase transfer catalyst, resulting in nucleophilic substitution of epichlorohydrin and dehydrochlorination, thus preparing epoxy-modified eugenol. Subsequently, under the catalysis of triphenylphosphine, the PH bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes nucleophilic ring-opening addition to the epoxy group, covalently grafting phosphorus-containing flame-retardant functional groups onto the eugenol skeleton to obtain flame-retardant modified eugenol.

[0036] The epoxidation reaction introduces highly reactive epoxy groups into the eugenol skeleton, providing precise covalent grafting sites for subsequent functionalization modifications. Further nucleophilic ring-opening addition firmly anchors the sterically hindered phosphorus-containing flame-retardant groups, constructing an intrinsic flame-retardant structure with both high thermal stability and non-migratory properties. The terminal allyl group retained in this hybrid molecule serves as an active reaction site for in-situ click crosslinking with the matrix during subsequent processing, further improving the mechanical strength of the pipe.

[0037] Example 2

[0038] This embodiment provides a method for preparing flame-retardant modified eugenol, including the following steps:

[0039] Step I: Preparation of epoxy-modified eugenol

[0040] Weigh out 15g of eugenol, 17g of potassium carbonate, and 200mL of butanone and place them in a reaction vessel and stir. Add 0.4g of tetrabutylammonium bromide, heat the reaction vessel to 60℃, add 15g of epichlorohydrin, and keep the reaction at this temperature for 3h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, add the filtrate and one volume of ethyl acetate to a separatory funnel, add three volumes of saturated brine to the concentrate, wash twice, transfer the organic phase to a rotary evaporator at 55℃, evaporate under reduced pressure until no liquid is collected, transfer to a vacuum drying oven at 55℃ and dry for 5h to obtain epoxy-modified eugenol.

[0041] Step II: Preparation of flame-retardant modified eugenol

[0042] Weigh out 21g of epoxy-modified eugenol, 21g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 7.5g of triphenylphosphine and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 125℃. Keep the mixture at this temperature and stir for 3 hours. After the reaction is complete, let the reaction system cool to room temperature and add 50mL of tetrahydrofuran to completely dissolve the product. Then, under vigorous stirring, slowly add the solution dropwise to 500mL of n-hexane to precipitate the product. After standing, filter the solution and wash the filter cake twice with n-hexane. Transfer the filter cake to an oven at 80℃ and dry it for 11 hours to obtain flame-retardant modified eugenol.

[0043] Example 3

[0044] This embodiment provides a method for preparing flame-retardant modified eugenol, including the following steps:

[0045] Step I: Preparation of epoxy-modified eugenol

[0046] Weigh out 20g of eugenol, 18g of potassium carbonate, and 250mL of butanone and place them in a reaction vessel and stir. Add 0.5g of tetrabutylammonium bromide and heat the reaction vessel to 65℃. Add 20g of epichlorohydrin and keep the reaction vessel at this temperature for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature and filter it. Add the filtrate and one volume of ethyl acetate to the separatory funnel, then add three volumes of saturated brine to the concentrate. Wash the mixture three times. Transfer the organic phase to a rotary evaporator at 60℃ and evaporate under reduced pressure until no liquid is collected. Transfer the evaporator to a vacuum drying oven at 60℃ and dry for 6 hours to obtain epoxy-modified eugenol.

[0047] Step II: Preparation of flame-retardant modified eugenol

[0048] Weigh out 26g of epoxy-modified eugenol, 26g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 1g of triphenylphosphine and place them in a reaction vessel under nitrogen atmosphere. Stir the reaction vessel and heat it to 130℃. Keep it at this temperature and stir for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature and add 50mL of tetrahydrofuran to completely dissolve the product. Then, under vigorous stirring, slowly add the solution dropwise to 500mL of n-hexane to precipitate the product. After standing, filter the solution and wash the filter cake three times with n-hexane. Transfer the filter cake to an oven at 90℃ and dry it for 12 hours to obtain flame-retardant modified eugenol.

[0049] Example 4

[0050] This embodiment provides a method for preparing thiol-modified graphene oxide, including the following steps:

[0051] Step ①: Preparation of cyanuric chloride-grafted graphene oxide

[0052] Weigh 20g of graphene oxide and 4000mL of tetrahydrofuran and place them in a reaction vessel at 0℃. Stir for 30min, add 100g of cyanuric chloride and 40g of sodium carbonate, and stir at low temperature for 3h. After the reaction is complete, centrifuge the reaction solution, wash the precipitate twice with tetrahydrofuran, and then transfer the precipitate to a Soxhlet extractor. Extract with tetrahydrofuran as solvent for 6h. After extraction, transfer to a vacuum drying oven at 60℃ and dry to constant weight to obtain cyanuric chloride-grafted graphene oxide.

[0053] Step 2: Preparation of thiol-modified graphene oxide

[0054] Weigh 45g of cyanuric chloride-grafted graphene oxide and 2500mL of N,N-dimethylformamide and place them in a reaction vessel under nitrogen atmosphere and stir. Add 10g of sodium hydrosulfide and 2g of triethylamine. Heat the reaction vessel to 50℃ and keep it at that temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with deionized water and ethanol, transfer it to a freeze dryer at -60℃ and freeze dry for 20h to obtain mercapto-modified graphene oxide.

[0055] At low temperature and under sodium carbonate binding acid, the hydroxyl groups on the surface of graphene oxide undergo nucleophilic substitution of cyanuric chloride, and the triazine ring is covalently grafted onto the graphene framework. Further, under the promotion of triethylamine, the mercapto anion of sodium hydrosulfide undergoes secondary nucleophilic substitution of the carbon-chlorine bond on the triazine ring, removing the chloride ion and bonding an active mercapto group, thus obtaining mercapto-modified graphene oxide.

[0056] The grafted triazine ring provides a nitrogen-rich framework, which, together with the two-dimensional barrier effect of graphene, promotes high-temperature charring of the matrix. The further bonded active thiol groups act as coupling donors during the melt extrusion period, and undergo thiol-alkene click reactions with the allyl groups in the system, constructing a three-dimensional organic-inorganic hybrid network in situ in the matrix, thereby enhancing the thermal stability and flame retardant properties of the pipe.

[0057] Example 5

[0058] This embodiment provides a method for preparing thiol-modified graphene oxide, including the following steps:

[0059] Step ①: Preparation of cyanuric chloride-grafted graphene oxide

[0060] Weigh 30g of graphene oxide and 4500mL of tetrahydrofuran and place them in a reaction vessel at 3℃. Stir for 45min, add 110g of cyanuric chloride and 50g of sodium carbonate, and stir at low temperature for 4h. After the reaction is complete, centrifuge the reaction solution, wash the precipitate three times with tetrahydrofuran, and then transfer the precipitate to a Soxhlet extractor. Extract with tetrahydrofuran as solvent for 7h. After extraction, transfer to a vacuum drying oven at 70℃ and dry to constant weight to obtain cyanuric chloride-grafted graphene oxide.

[0061] Step 2: Preparation of thiol-modified graphene oxide

[0062] Weigh out 50g of cyanuric chloride-grafted graphene oxide and 3000mL of N,N-dimethylformamide and place them in a reaction vessel under nitrogen atmosphere and stir. Add 15g of sodium hydrosulfide and 5g of triethylamine. Heat the reaction vessel to 55℃ and keep it at that temperature for 5h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with deionized water and ethanol, transfer it to a freeze dryer at -60℃ and freeze dry for 22h to obtain mercapto-modified graphene oxide.

[0063] Example 6

[0064] This embodiment provides a method for preparing thiol-modified graphene oxide, including the following steps:

[0065] Step ①: Preparation of cyanuric chloride-grafted graphene oxide

[0066] Weigh 40g of graphene oxide and 5000mL of tetrahydrofuran and place them in a reaction vessel at 5℃. Stir for 60min, add 120g of cyanuric chloride and 60g of sodium carbonate, and stir at low temperature for 5h. After the reaction is complete, centrifuge the reaction solution and wash the precipitate 4 times with tetrahydrofuran. Then transfer the precipitate to a Soxhlet extractor and extract with tetrahydrofuran as solvent for 8h. After extraction, transfer to a vacuum drying oven at 80℃ and dry to constant weight to obtain cyanuric chloride-grafted graphene oxide.

[0067] Step 2: Preparation of thiol-modified graphene oxide

[0068] Weigh out 55g of cyanuric chloride-grafted graphene oxide and 3500mL of N,N-dimethylformamide and place them in a reaction vessel under nitrogen atmosphere and stir. Add 20g of sodium hydrosulfide and 7g of triethylamine. Heat the reaction vessel to 60℃ and keep it at that temperature for 6h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake 4 times with deionized water and ethanol, transfer it to a freeze dryer at -60℃ and freeze dry for 24h to obtain mercapto-modified graphene oxide.

[0069] Example 7

[0070] This embodiment provides a method for preparing flame-retardant and high-temperature resistant CPVC cable protection tubing, including the following steps:

[0071] Step 1: Preparation of modified reactive anti-aging agent

[0072] Weigh 10g of salicylaldehyde and 50mL of ethanol and place them in a reaction vessel. Stir well and slowly add 4g of allylamine. Heat the reaction vessel to 50℃ and keep it at this temperature while stirring for 2 hours. After the reaction is complete, wait for the reaction system to cool to room temperature. Transfer the reaction solution to a rotary evaporator at 40℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Then transfer it to a vacuum drying oven at 60℃ and dry for 4 hours to obtain the modified reactive anti-aging agent.

[0073] Step 2: Preparation of CPVC cable protection tubing

[0074] Calcium stearate, methyltin mercaptan, and diisopropylbenzene peroxide are mixed evenly in a mass ratio of 1:1:0.2 to obtain the excipients for later use.

[0075] Weigh out the following by weight: 80 parts CPVC, 8 parts flame-retardant modified eugenol prepared in Example 1, 1 part mercapto-modified graphene oxide prepared in Example 4, 2 parts modified reactive anti-aging agent and excipients, add them to a high-speed mixer, premix and react at 120°C for 10 min, then transfer to a twin-screw extruder, melt extrude, pelletize, and extrude to obtain CPVC cable protection pipe.

[0076] The processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 160℃, plasticizing section 170℃, homogenizing section 180℃, die head temperature 185℃, and screw speed 30r / min.

[0077] Salicylic aldehyde condenses and dehydrates with allylamine to generate a Schiff base containing an imine structure, thus preparing a modified reactive anti-aging agent with terminal allyl groups. Further, during melt extrusion, dicumyl peroxide thermally decomposes to release free radicals, which initiate a mercapto-alkene click reaction between mercapto-modified graphene oxide and the olefin double bonds on modified eugenol and the modified reactive anti-aging agent, thereby constructing a hybrid crosslinked network in situ within the CPVC cable protection pipe matrix.

[0078] The synthesized Schiff base endows the system with anti-thermal and oxidative aging activity, and the terminal allyl group provides reactive anchoring sites. The further initiated click crosslinking covalently bonds the anti-aging agent and flame retardant to the graphene nodes. The in-situ constructed three-dimensional hybrid network completely inhibits the migration and precipitation of functional additives, and synergistically enhances the flame retardant performance and high-temperature stability of the pipe by strongly restricting the high-temperature slippage of the matrix molecular chain segments.

[0079] Example 8

[0080] This embodiment provides a method for preparing flame-retardant and high-temperature resistant CPVC cable protection tubing, including the following steps:

[0081] Step 1: Preparation of modified reactive anti-aging agent

[0082] Weigh 15g of salicylaldehyde and 100mL of ethanol and place them in a reaction vessel. Stir well and slowly add 6.5g of allylamine. Heat the reaction vessel to 52℃ and keep it at this temperature while stirring for 3 hours. After the reaction is complete, wait for the reaction system to cool to room temperature. Transfer the reaction solution to a rotary evaporator at 50℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Then transfer it to a vacuum drying oven at 65℃ and dry for 5 hours to obtain the modified reactive anti-aging agent.

[0083] Step 2: Preparation of CPVC cable protection tubing

[0084] Calcium stearate, methyltin mercaptan, and diisopropylbenzene peroxide are mixed evenly in a mass ratio of 1:1:0.2 to obtain the excipients for later use.

[0085] Weigh out the following by weight: 90 parts CPVC, 12 parts flame-retardant modified eugenol prepared in Example 2, 2 parts mercapto-modified graphene oxide prepared in Example 5, 3.5 parts modified reactive anti-aging agent and excipients, add them to a high-speed mixer, premix and react at 130°C for 15 min, then transfer to a twin-screw extruder, melt extrude, pelletize, and extrude to obtain CPVC cable protection pipe.

[0086] The processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 165℃, plasticizing section 175℃, homogenizing section 185℃, die head temperature 190℃, and screw speed 40r / min.

[0087] Example 9

[0088] This embodiment provides a method for preparing flame-retardant and high-temperature resistant CPVC cable protection tubing, including the following steps:

[0089] Step 1: Preparation of modified reactive anti-aging agent

[0090] Weigh 20g of salicylaldehyde and 150mL of ethanol and place them in a reaction vessel. Stir well and slowly add 9g of allylamine. Heat the reaction vessel to 60℃ and keep it at this temperature while stirring for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature. Transfer the reaction solution to a rotary evaporator at 60℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Then transfer it to a vacuum drying oven at 70℃ and dry for 6 hours to obtain the modified reactive anti-aging agent.

[0091] Step 2: Preparation of CPVC cable protection tubing

[0092] Calcium stearate, methyltin mercaptan, and diisopropylbenzene peroxide are mixed evenly in a mass ratio of 1:1:0.2 to obtain the excipients for later use.

[0093] Weigh out the following by weight: 100 parts CPVC, 15 parts flame-retardant modified eugenol prepared in Example 3, 3 parts mercapto-modified graphene oxide prepared in Example 6, 5 parts modified reactive anti-aging agent and excipients, add them to a high-speed mixer, premix and react at 140°C for 20 min, then transfer to a twin-screw extruder, melt extrude, pelletize, and extrude to obtain CPVC cable protection pipe.

[0094] The processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 170℃, plasticizing section 180℃, homogenizing section 190℃, die head temperature 195℃, and screw speed 50r / min.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 9 is that, in step (2) when preparing the CPVC cable protection pipe, epoxy-modified eugenol is used in an equal amount to replace flame-retardant modified eugenol.

[0097] Comparative Example 2

[0098] The difference between this comparative example and Example 9 is that the modified reactive anti-aging agent was omitted in step (2) when preparing the CPVC cable protection pipe.

[0099] Comparative Example 3

[0100] The difference between this comparative example and Example 9 is that, in step (2) when preparing the CPVC cable protection pipe, cyanuric chloride-grafted graphene oxide is used in an equal amount to replace the mercapto-modified graphene oxide.

[0101] Performance testing:

[0102] Limiting oxygen index: The limiting oxygen index of the CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested according to the standard GB / T 2406.2-2009 "Determination of flammability by oxygen index method for plastics - Part 2: Room temperature test". The sample size was 80mm×10mm×4mm and the test temperature was 23℃±2℃.

[0103] TGA carbon residue rate: The TGA carbon residue rate of CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 33047.1-2016 "Thermogravimetric Analysis (TG) of Plastics Polymers - Part 1: General Rules". The test conditions were nitrogen atmosphere, heating rate of 10℃ / min, and test temperature range from room temperature to 800℃. The mass retention rate after holding at 800℃ for 10 min was taken as the carbon residue rate.

[0104] Vicat softening temperature: The Vicat softening temperature of the CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 1633-2000 "Determination of Vicat softening temperature (VST) of thermoplastic plastics". The test conditions were: Method B, 50N load, heating rate 50℃ / h, and needle penetration depth 1mm.

[0105] Ring stiffness: The ring stiffness of the CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 9647-2015 "Determination of ring stiffness of thermoplastic pipes". The sample length was 300mm±10mm, the compression rate was (5±1)mm / min, and the ring stiffness was calculated by taking the load when the diameter deformation was 3%.

[0106] Drop hammer impact: The CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 were tested for drop hammer impact according to the standard GB / T 14152-2001 "Test method for resistance to external impact of thermoplastic pipes - clockwise rotation method". The test conditions were: sample length 200mm ± 10mm, conditioned in a 0℃ water bath for at least 1h, and characterized by the true impact rate.

[0107] High-temperature resistance retention rate test: The CPVC cable protection pipes prepared in Examples 7-9 and Comparative Examples 1-3 were placed in a heat aging test chamber at 100℃±2℃ and subjected to heat aging treatment for 168h according to GB / T 7141-2008 "Plastics Heat Aging Test Method". The tensile strength retention rate was tested according to GB / T 1040.2-2022 "Determination of tensile properties of plastics Part 2: Test conditions for molding and extruded plastics", the limiting oxygen index retention rate was tested according to GB / T 2406.2-2009, and the ring stiffness retention rate was tested according to GB / T9647-2015. The specific data are shown in Table 1.

[0108] Table 1 - Performance Test Data for Each Sample

[0109]

[0110] Data Analysis:

[0111] A comparative analysis of the above tables shows that the CPVC cable protection pipe prepared by this invention has an oxygen limiting index of up to 49.6%, a carbon residue rate of 35.4% at 800℃, a Vicat softening temperature of 126.9℃, and a maximum ring stiffness of 23.5 kN / m. 2 The actual impact rate of the drop hammer impact test was 3.8%, and the tensile strength, limiting oxygen index, and ring stiffness retention rates after thermal aging reached 94.8%, 98.2%, and 95.7%, respectively, all of which were superior to the comparative example.

[0112] In the extrusion process, this invention initiates an in-situ thiol-alkene click crosslinking reaction between functionalized flame-retardant modified eugenol, thiol-modified graphene oxide, and active groups on modified reactive anti-aging agents via peroxide. This successfully constructs a three-dimensional inorganic-organic hybrid network within the CPVC matrix, effectively inhibiting the migration and precipitation of additives and restricting chain segment slippage. This significantly improves the flame retardancy, high-temperature resistance, thermo-oxidative aging resistance, and mechanical strength of CPVC cable protection pipes.

[0113] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame-retardant and high-temperature resistant CPVC cable protection conduit, characterized in that, It includes the following components by weight: 80-100 parts CPVC, 8-15 parts flame-retardant modified eugenol, 1-3 parts mercapto-modified graphene oxide, 2-5 parts modified reactive anti-aging agent and 1-3 parts excipients; The flame-retardant modified eugenol was prepared by the following steps: A1. Place eugenol, potassium carbonate and acetone in a reaction vessel and stir. Add tetrabutylammonium bromide. Heat the reaction vessel to 55-65℃. Add epichlorohydrin and keep the reaction at the temperature for 2-4 hours. Post-treatment yields epoxy-modified eugenol. A2. Epoxy-modified eugenol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine were placed in a reaction vessel under nitrogen atmosphere and stirred. The reaction vessel was heated to 120-130℃ and stirred for 2-4 hours. The flame-retardant modified eugenol was obtained after post-treatment.

2. The flame-retardant and high-temperature resistant CPVC cable protection conduit according to claim 1, characterized in that, In step A1, the ratio of eugenol, potassium carbonate, acetone, tetrabutylammonium bromide, and epichlorohydrin is 1-2 g. 1.6-1.8g:15-25mL:0.03-0.05g:1-2g; In step A2, the weight ratio of the epoxy-modified eugenol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine is 1.6-2.6:1.6-2.6:0.05-0.

10.

3. The flame-retardant and high-temperature resistant CPVC cable protection conduit according to claim 1, characterized in that, The thiol-modified graphene oxide was prepared by the following steps: B1. Place graphene oxide and tetrahydrofuran in a reaction vessel at 0-5℃ and stir for 30-60 min. Add cyanuric chloride and sodium carbonate and stir at low temperature for 3-5 h. After post-treatment, obtain cyanuric chloride-grafted graphene oxide. B2. Place cyanuric chloride-grafted graphene oxide and N,N-dimethylformamide in a nitrogen-protected reactor and stir. Add sodium hydrosulfide and triethylamine. Heat the reactor to 50-60℃ and maintain the temperature for 4-6 hours. Post-treatment yields thiol-modified graphene oxide.

4. The flame-retardant and high-temperature resistant CPVC cable protection conduit according to claim 3, characterized in that, In step B1, the ratio of graphene oxide, tetrahydrofuran, cyanuric chloride, and sodium carbonate is 2-4g:400-500mL:10-12g:4-6g; in step B2, the ratio of cyanuric chloride-grafted graphene oxide, N,N-dimethylformamide, sodium hydrosulfide, and triethylamine is 4.5-5.5g:250-350mL:1-2g:0.2-0.7g.

5. The flame-retardant and high-temperature resistant CPVC cable protection conduit according to claim 1, characterized in that, The modified reactive anti-aging agent is prepared by: placing salicylaldehyde and ethanol in a reaction vessel and stirring evenly, slowly adding allylamine, heating the reaction vessel to 50-60℃, keeping it at the temperature and stirring for 2-4 hours, and then processing to obtain the modified reactive anti-aging agent.

6. The flame-retardant and high-temperature resistant CPVC cable protection conduit according to claim 5, characterized in that, The ratio of salicylaldehyde, ethanol and allylamine used is 1-2g:5-15mL:0.4-0.9g.

7. A method for preparing the flame-retardant and high-temperature resistant CPVC cable protection conduit as described in any one of claims 1-6, characterized in that, The process includes the following steps: CPVC, flame-retardant modified eugenol, mercapto-modified graphene oxide, modified reactive anti-aging agent and additives are added to a high-speed mixer and premixed at 120-140℃ for 10-20 minutes. Then, the mixture is transferred to a twin-screw extruder for melt extrusion, pelletizing and extrusion molding to obtain CPVC cable protection pipe.

8. The method for preparing a flame-retardant and high-temperature resistant CPVC cable protection pipe according to claim 7, characterized in that, The processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 160-170℃, plasticizing section 170-180℃, homogenizing section 180-190℃, die head temperature 185-195℃, screw speed 30-50 r / min, and the auxiliary materials are lubricant, heat stabilizer and initiator in a mass ratio of 1:1:0.2.

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