High-toughness plastic master batch prepared by regenerating waste PVC (polyvinyl chloride) and preparation method of high-toughness plastic master batch

Abstract

The invention discloses a high-toughness plastic master batch prepared by regenerating waste PVC and a preparation method thereof, belongs to the technical field of plastic master batch processing, and aims to solve the technical problem that the toughness of a plastic master batch prepared by regenerating waste PVC needs to be further improved in the prior art. The regenerated PVC composite material specifically comprises the following components in parts by weight: 60-80 parts of regenerated PVC powder, 10-15 parts of a modified toughening agent, 3-5 parts of modified carbon nanotubes and 6-8 parts of an auxiliary additive, the regenerated PVC powder, the modified flexibilizer, the modified carbon nanotubes and the auxiliary additive are mixed, melted, extruded and granulated to obtain the high-toughness plastic master batch, so that the toughness of the plastic master batch is improved, and the mechanical property and the high-temperature resistance of the plastic master batch are also improved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic masterbatch processing, and in particular to high-toughness plastic masterbatch prepared by recycling waste PVC and a preparation method thereof. Background Art

[0002] With the extensive application of polyvinyl chloride (PVC) in cable sheathing, pipes, building materials and other fields, the recycling and reuse of waste PVC materials has gradually become an important direction of resource recycling and environmental protection. At present, plastic masterbatches prepared from recycled waste PVC are mostly used as modified raw materials and widely used in low-end products. However, due to the degradation of the recycled PVC molecular chain and incomplete structure, its toughness is much lower than that of the original material, which limits its promotion in medium and high-performance applications.

[0003] In order to improve its toughness, toughening agents or elastomer blends are usually introduced for modification. At the same time, there are also studies using nanofillers or coupling agents to improve its mechanical properties and interface compatibility. These modification methods can improve the tensile elongation and impact properties of recycled PVC masterbatch to a certain extent by enhancing the energy absorption capacity and crack propagation resistance of the material, and have been initially applied in functional films, cable sheaths, non-structural parts and other fields.

[0004] Although the above materials and modification methods have improved the toughness of recycled PVC masterbatch to a certain extent, there are still many shortcomings:

[0005] On the one hand, traditional toughening agents have limited polarity matching with recycled PVC, which easily leads to phase separation or uneven dispersion in the matrix, resulting in unstable modification effects and difficulty in balancing tensile properties and elongation at break.

[0006] On the other hand, conventional elastomers are prone to thermal degradation or migration during high-temperature processing, affecting the thermal stability and long-term performance of the final product;

[0007] In addition, although inorganic nanofillers can improve rigidity and thermal stability, they often sacrifice the flexibility of the material, making it difficult to achieve a synergistic improvement in toughness and strength.

[0008] The fundamental reason for the above-mentioned shortcomings is that the recycled PVC itself has problems such as chain segment breakage, thermal oxidation residues, poor interface compatibility and severe stress concentration. It is difficult to achieve systematic improvement in performance through a single toughening method or filler system. For this reason, a solution is now proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a high-toughness plastic masterbatch prepared by recycling waste PVC and a preparation method thereof, so as to solve the technical problem in the prior art that the toughness of the plastic masterbatch prepared by recycling waste PVC needs to be further improved.

[0010] The object of the present invention can be achieved by the following technical solution: a high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following components by weight: 60-80 parts of recycled PVC powder, 10-15 parts of a modified toughening agent, 3-5 parts of modified carbon nanotubes and 6-8 parts of auxiliary additives;

[0011] The modified toughening agent is prepared by the following steps:

[0012] A1. Place acrylonitrile, styrene, fatty acid soap and cumene hydroperoxide in a reaction kettle and stir at room temperature for 5-10 minutes to obtain a prepolymer solution;

[0013] A2. Place polybutadiene latex in a reactor and stir. Heat the reactor to 50-60°C, add sodium pyrophosphate, glucose and ferrous sulfate aqueous solution, stir for 15-30 minutes, slowly add prepolymer solution dropwise, heat the reactor to 65-75°C, keep the temperature for reaction for 0.5-1.5 hours, and post-treat to obtain a modified toughening agent.

[0014] The preparation reaction principle of the modified toughening agent is:

[0015] During the reaction process, acrylonitrile and styrene monomers form monomer droplets under the emulsification effect of fatty acid soap. Further, an aqueous ferrous sulfate solution and isopropyl benzene hydroperoxide initiate a free radical polymerization reaction through redox, wherein sodium pyrophosphate is a complexing agent to prevent precipitation of trivalent iron ions, and glucose is an auxiliary reducing agent. Under the initiation of the above-mentioned redox system, in the presence of polybutadiene latex, the acrylonitrile and styrene monomer free radicals attack the surface of the polybutadiene latex particles, undergo graft copolymerization, and form a coating, thereby obtaining a modified toughening agent with polybutadiene latex as a core and acrylonitrile and styrene as a shell.

[0016] Furthermore, in step A1, the weight ratio of acrylonitrile, styrene, fatty acid soap and isopropyl benzene hydroperoxide is 3-5:2-4:0.5-1:0.05-0.1; in step A2, the amount ratio of the polybutadiene latex, sodium pyrophosphate, glucose, ferrous sulfate aqueous solution and prepolymer solution is 20-25g:0.05-0.1g:0.1-0.2g:2-4mL:10-15mL, the concentration of the ferrous sulfate aqueous solution is 40-50wt%, and the post-treatment step is as follows: after the reaction is completed, the reaction system is cooled to room temperature, 2-4g of sodium chloride is added for demulsification, and the mixture is allowed to stand for 20-30min, filtered, and the filter cake is washed 2-4 times with deionized water, transferred to an oven at a temperature of 50-60°C, and dried to constant weight to obtain a modified toughening agent.

[0017] Furthermore, the modified carbon nanotubes are prepared by the following steps:

[0018] B1. Place carbon nanotubes and a mixed acid solution in a reaction kettle and stir. Heat the reactor to 135-145° C., keep the temperature for 1-2 hours, and perform post-treatment to obtain activated carbon nanotubes.

[0019] The preparation reaction principle of activated carbon nanotubes is:

[0020] During the reaction, under high temperature conditions, concentrated sulfuric acid and nitric acid in the mixed acid solution attack surface defects of carbon nanotubes, triggering carboxylation reaction of the carbon nanotube walls to obtain activated carbon nanotubes with carboxyl groups on the surface.

[0021] B2. Place activated carbon nanotubes and 1,2-dichloroethane in a nitrogen atmosphere-protected reactor and stir. Place the reactor in an ice bath at 0-5°C, slowly add acryloyl chloride, and keep the reaction warm for 2-4 hours. Post-process to obtain crude modified carbon nanotubes.

[0022] The preparation reaction principle of modified carbon nanotube crude product is:

[0023] During the reaction, under ice bath conditions, acryloyl chloride reacts with the carboxyl groups in the activated carbon nanotubes to undergo chlorination reaction, thereby obtaining crude modified carbon nanotubes modified with olefin unsaturated double bonds.

[0024] B3. Place the crude modified carbon nanotubes and 1,2-dichloroethane in a reactor and stir, add antimony trichloride and liquid bromine, heat the reactor to 40-50°C, keep the temperature for reaction for 2-4 hours, and perform post-treatment to obtain modified carbon nanotubes.

[0025] The preparation reaction principle of modified carbon nanotubes is:

[0026] During the reaction, under the action of heating and catalyst, the unsaturated double bonds of olefins in the crude modified carbon nanotubes undergo electrophilic addition reaction with liquid bromine to obtain modified carbon nanotubes modified with bromine atoms.

[0027] Furthermore, in step B1, the amount ratio of the carbon nanotubes and the mixed acid solution is 1-2g:150-200mL, and the mixed acid solution is composed of 95-98wt% concentrated sulfuric acid and 60-65wt% nitric acid in a volume ratio of 100-150:30-50. The post-treatment step is as follows: after the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 6-10h to obtain activated carbon nanotubes; in step B2, the amount ratio of the activated carbon nanotubes, 1,2-dichloroethane and acryloyl chloride is 2-4g:50-70mL:1-2 mL, the post-treatment step: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed with deionized water until neutral, transferred to an oven at a temperature of 50-60°C, and dried to constant weight to obtain a crude modified carbon nanotube; in step B3, the amount ratio of the crude modified carbon nanotube, 1,2-dichloroethane, antimony trichloride and liquid bromine is 2-4g:60-80mL:0.2-0.4g:1-2mL, the post-treatment step: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 6-10h to obtain modified carbon nanotubes.

[0028] Furthermore, the recycled PVC powder is prepared by the following steps:

[0029] C1. Place waste PVC powder, potassium hydroxide, and dimethyl sulfoxide in a reactor and stir. Heat the reactor to 75-85° C., keep the temperature for 4-6 hours, and perform post-processing to obtain pyrolyzed PVC powder.

[0030] The preparation reaction principle of pyrolysis PVC powder is:

[0031] During the reaction, there are a large number of -CH2-CHCl- units in the structure of PVC. Potassium hydroxide will cause the C-Cl bond to break and remove it together with the adjacent β-hydrogen to form a conjugated double bond, releasing chloride ions and water, and finally obtaining pyrolyzed PVC powder.

[0032] C2. Place the pyrolyzed PVC powder and the repair agent in a reactor, mix them evenly, and then perform post-processing to obtain recycled PVC powder.

[0033] The preparation reaction formula of recycled PVC powder is:

[0034]

[0035] The preparation reaction principle of recycled PVC powder is:

[0036] During the reaction, the conjugated double bond structure in the pyrolyzed PVC powder undergoes a DA reaction with N,N'-ethylenebis(maleamic acid) to generate a cyclic stable structure, shorten the conjugated chain, and increase the flexibility of the molecule. Local cross-linking can enhance the interaction between chains, thereby obtaining recycled PVC powder with repaired mechanical properties.

[0037] Furthermore, in step C1, the amount ratio of the waste PVC powder, potassium hydroxide and dimethyl sulfoxide is 4-6g:130-150mL:8-10g, and the post-treatment step includes: after the reaction is completed, adding 200-250mL of anhydrous ethanol to the reaction solution, after precipitation, filtering, washing the filter cake with ethanol and deionized water 2-4 times, transferring it to an oven at a temperature of 50-60°C, and drying it to constant weight to obtain regenerated PVC powder; in step C2, the weight ratio of the pyrolyzed PVC powder and the repair agent is 5-10:0.4-0.6, the repair agent is N,N'-ethylenebis(maleamic acid), and the post-treatment step includes: after mixing evenly, transferring the product to an oven at a temperature of 50-60°C, and drying it for 2-4h to obtain regenerated PVC powder.

[0038] The present invention also provides a method for preparing high-toughness plastic masterbatch by regenerating waste PVC, comprising the following steps:

[0039] S1, placing recycled PVC powder, modified toughening agent, modified carbon nanotubes and auxiliary additives in a high-speed mixer, and mixing them at high speed to obtain a mixture;

[0040] S2. Add the mixed material into a twin-screw extruder, melt-extrude, and granulate to obtain high-toughness plastic masterbatch.

[0041] Further, in step S1, the auxiliary additives are composed of an ultraviolet absorber, a plasticizer, a lubricant and an antioxidant in a mass ratio of 2:5:3:1, the ultraviolet absorber is one or more of 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, p-tert-butylphenyl salicylate and 2-hydroxy-4-n-octyloxybenzophenone, the plasticizer is one or more of dioctyl phthalate, dibutyl phthalate and diisononyl phthalate, the lubricant is one or more of fatty acid amide, oleic acid and stearic acid, and the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,4'-thiobis(6-tert-butyl-3-methylphenol) and 2,6-di-tert-butyl-4-methylphenol;

[0042] Furthermore, the temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 150°C, 150°C, 155°C, 160°C, 165°C, 165°C, 170°C, and 170°C, respectively. The main engine speed of the twin-screw extruder is 120-160rpm, and the pressure is 80-120bar.

[0043] The present invention has the following beneficial effects:

[0044] 1. The present invention is to prepare a modified toughening agent with polybutadiene latex as the core and acrylonitrile and styrene as the shell through a reduction-oxidation initiation system. When the rubber core of the modified toughening agent is subjected to stress in the plastic masterbatch, it can deform, produce silver streaks and shear yield, thereby effectively passivating the crack tip, consuming impact energy, and improving the elongation at break and impact strength of the material. The shell has good polar compatibility with the PVC matrix and can achieve effective bonding at the interface, avoiding the modified toughening agent from forming large dispersed phase agglomerations in the plastic masterbatch matrix and weakening the mechanical strength of the overall material, which is beneficial to the regeneration of the plastic masterbatch. For PVC powder, the flexible rubber phase of the modified toughening agent can play a buffering and bridging role in the stress transfer process, reducing the negative impact of recycled PVC segment defects. At the same time, the hard shell part combines with the repaired recycled PVC powder interface, which helps to restore and improve the continuity and overall mechanical properties of the recycled PVC. In addition, the polarity matching of the modified toughening agent shell and the PVC matrix also helps to uniformly disperse carbon nanotubes in the matrix, because good interfacial wettability can reduce the agglomeration of modified carbon nanotubes, further improving the thermal stability and mechanical properties of the plastic masterbatch.

[0045] 2. The present invention also activates carbon nanotubes through a mixed acid system and further introduces bromine atoms to modify them to obtain modified carbon nanotubes. Under high temperature conditions, the weak C-Br bonds on the modified carbon nanotubes and the weak C-Cl bonds of the regenerated PVC break and entangle, and these entanglement points serve as crosslinking points to toughen the regenerated PVC. The carbon nanotubes themselves have extremely high strength, modulus and aspect ratio, but in the untreated state, the surface is highly inert and easily agglomerated, making it difficult to disperse evenly in the polymer matrix. Modifying the surface of the structure not only improves the wettability and interfacial bonding of the carbon nanotubes in the PVC matrix and toughening agent phase, but also allows them to be firmly embedded through chemical bonding or physical entanglement. The modified carbon nanotubes can form a uniformly dispersed nano-reinforced network in the plastic masterbatch, which can block and deflect crack propagation, bear and disperse stress in the local stress area, and alleviate the stress concentration effect, thereby improving the strength, toughness and fatigue life of the recycled PVC powder, and further improving the mechanical properties and toughness of the plastic masterbatch. At the same time, the high thermal conductivity of carbon nanotubes helps to quickly transfer and evenly distribute heat during the processing process, reduce the risk of thermal degradation of recycled PVC in the melt extrusion stage, improve the thermal stability of the plastic masterbatch, and synergize with the modified toughening agent to improve the toughness, thermal stability and mechanical properties of the plastic masterbatch.

[0046] 3. The present invention is to remove the residual plasticizer and aging by-products of waste PVC powder under alkaline conditions by high-temperature pyrolysis to generate a conjugated double bond structure, which is then reacted with the repair agent N, N'-ethylenebis (maleamic acid) to generate a cyclic stable structure through DA reaction, shorten the conjugated chain, increase the flexibility of the molecule, and locally cross-link to improve the interaction between the chains to obtain recycled PVC powder with repaired mechanical properties, thereby restoring the mechanical properties and interface compatibility of the recycled PVC. After the modified carbon nanotubes are acidified and activated and the surface functional groups are grafted, their surface polarity is improved. They are more compatible with the polar sites of recycled PVC and can be firmly embedded in the PVC matrix through hydrogen bonds, dipole-dipole interactions, and even chemical bonding. During the PVC processing and molding process, carbon nanotubes can construct a uniformly dispersed three-dimensional network structure within the matrix, blocking and deflecting crack propagation that is prone to occur in the recycled PVC powder due to segment defects. They also enhance its thermal conductivity and improve processing thermal stability to a certain extent. The modified toughening agent adopts a core-shell structure. The rubber core can deform and absorb energy under impact loads, while the hard shell has good polar compatibility with the PVC matrix. In a system containing recycled PVC powder, the hard shell can bind to the polar sites and residual active groups of the recycled PVC, increasing interfacial bonding strength and reducing phase separation. Therefore, the recycled PVC powder not only serves as the skeleton of the high-toughness plastic masterbatch, but also forms a ternary synergistic relationship with the modified carbon nanotubes and modified toughening agent, jointly improving the toughness, impact resistance, and thermal stability of the plastic masterbatch. DETAILED DESCRIPTION

[0047] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all 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.

[0048] The specific name of the fatty acid soap used in the present invention is potassium laurate soap, and its molecular weight is 238.41;

[0049] The polybutadiene latex used in the present invention has a pH of 3-8, an effective content of 56%, and is a milky white liquid.

[0050] The sodium pyrophosphate used in the present invention has a pH of 9.9-10.7, a content of (Na4P2O7) ≥ 96.5%, and is in the form of white granules;

[0051] The glucose used in the present invention is in the form of white crystalline powder, specifically glucose monohydrate, with a particle size of 60-80 meshes.

[0052] Example 1

[0053] This embodiment provides a method for preparing recycled PVC powder for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0054] Step I: Preparation of pyrolysis PVC powder

[0055] Weigh: 40 g of waste PVC powder, 1300 mL of potassium hydroxide and 80 g of dimethyl sulfoxide, place them in a reactor and stir, heat the reactor to 75°C, and keep the reaction for 4 hours. After the reaction is completed, add 2000 mL of anhydrous ethanol to the reaction solution, precipitate, filter, wash the filter cake twice with ethanol and deionized water, transfer it to an oven at 50°C, and dry it to constant weight to obtain pyrolyzed PVC powder.

[0056] Step II: Preparation of recycled PVC powder

[0057] Weigh: 50 g of pyrolysis PVC powder and 4 g of N,N'-ethylenebis(maleamic acid) are placed in a reactor and mixed evenly. The product is then transferred to an oven at 50°C and dried for 2 hours to obtain regenerated PVC powder.

[0058] Example 2

[0059] This embodiment provides a method for preparing recycled PVC powder for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0060] Step I: Preparation of pyrolysis PVC powder

[0061] Weigh: 50 g of waste PVC powder, 1400 mL of potassium hydroxide and 90 g of dimethyl sulfoxide, place them in a reactor and stir, heat the reactor to 80°C, and keep the reaction for 5 hours. After the reaction is completed, add 2250 mL of anhydrous ethanol to the reaction solution, precipitate, filter, and wash the filter cake with ethanol and deionized water three times, transfer it to an oven at 55°C, and dry it to constant weight to obtain pyrolyzed PVC powder.

[0062] Step II: Preparation of recycled PVC powder

[0063] Weigh: 75 g of pyrolysis PVC powder and 5 g of N,N'-ethylenebis(maleamic acid) were placed in a reactor and mixed evenly. The product was then transferred to an oven at 55°C and dried for 3 hours to obtain regenerated PVC powder.

[0064] Example 3

[0065] This embodiment provides a method for preparing recycled PVC powder for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0066] Step I: Preparation of pyrolysis PVC powder

[0067] Weigh: 60 g of waste PVC powder, 1500 mL of potassium hydroxide and 100 g of dimethyl sulfoxide, place them in a reactor and stir, heat the reactor to 85°C, and keep the reaction for 6 hours. After the reaction is completed, add 2500 mL of anhydrous ethanol to the reaction solution, precipitate, filter, and wash the filter cake with ethanol and deionized water 4 times, transfer it to an oven at 60°C, and dry it to constant weight to obtain pyrolyzed PVC powder.

[0068] Step II: Preparation of recycled PVC powder

[0069] Weigh: 100 g of pyrolysis PVC powder and 6 g of N,N'-ethylenebis(maleamic acid) were placed in a reactor and mixed evenly. The product was then transferred to an oven at 60°C and dried for 4 hours to obtain regenerated PVC powder.

[0070] Example 4

[0071] This embodiment provides a method for preparing modified carbon nanotubes for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0072] Step ①: Preparation of activated carbon nanotubes

[0073] 95 wt % of concentrated sulfuric acid and 60 wt % of nitric acid were mixed in a volume ratio of 100:30 to obtain a mixed acid solution for later use;

[0074] Weigh: 10 g of carbon nanotubes and 1500 mL of mixed acid solution are placed in a reactor and stirred. The reactor is heated to 135°C and kept warm for 1 hour. After the reaction is completed, the reaction system is cooled to room temperature and filtered. The filter cake is washed with deionized water until neutral, transferred to a freeze dryer at -60°C, and dried for 6 hours to obtain activated carbon nanotubes.

[0075] Step ②: Preparation of crude modified carbon nanotubes

[0076] Weigh: 20 g of activated carbon nanotubes and 500 mL of 1,2-dichloroethane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is ice-bathed to 0°C, 10 mL of acryloyl chloride is slowly added, and the reaction is kept warm for 2 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to an oven at a temperature of 50°C, and dried to constant weight to obtain a crude modified carbon nanotube.

[0077] Step 3: Preparation of modified carbon nanotubes

[0078] Weigh: 20 g of crude modified carbon nanotubes and 600 mL of 1,2-dichloroethane are placed in a reactor and stirred, 2 g of antimony trichloride and 10 mL of liquid bromine are added, the reactor is heated to 40°C, and the reaction is kept warm for 2 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 6 hours to obtain modified carbon nanotubes.

[0079] Example 5

[0080] This embodiment provides a method for preparing modified carbon nanotubes for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0081] Step ①: Preparation of activated carbon nanotubes

[0082] 96 wt % of concentrated sulfuric acid and 62 wt % of nitric acid were mixed in a volume ratio of 125:40 to obtain a mixed acid solution for later use;

[0083] Weigh: 15 g of carbon nanotubes and 1700 mL of mixed acid solution are placed in a reactor and stirred. The reactor is heated to 140°C and kept warm for 1.5 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at -60°C, and dried for 8 hours to obtain activated carbon nanotubes.

[0084] Step ②: Preparation of crude modified carbon nanotubes

[0085] Weigh: 30 g of activated carbon nanotubes and 600 mL of 1,2-dichloroethane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is ice-bathed to 3°C, 15 mL of acryloyl chloride is slowly added, and the reaction is kept warm for 3 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to an oven at a temperature of 55°C, and dried to constant weight to obtain a crude modified carbon nanotube.

[0086] Step 3: Preparation of modified carbon nanotubes

[0087] Weigh: 30 g of crude modified carbon nanotubes and 700 mL of 1,2-dichloroethane are placed in a reactor and stirred, 3 g of antimony trichloride and 15 mL of liquid bromine are added, the reactor is heated to 45°C, and the reaction is kept warm for 3 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 8 hours to obtain modified carbon nanotubes.

[0088] Example 6

[0089] This embodiment provides a method for preparing modified carbon nanotubes for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0090] Step ①: Preparation of activated carbon nanotubes

[0091] 98 wt % concentrated sulfuric acid and 65 wt % nitric acid were mixed in a volume ratio of 150:50 to obtain a mixed acid solution for later use;

[0092] Weigh: 20 g of carbon nanotubes and 2000 mL of mixed acid solution are placed in a reactor and stirred. The reactor is heated to 145°C and kept warm for 2 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 10 hours to obtain activated carbon nanotubes.

[0093] Step ②: Preparation of crude modified carbon nanotubes

[0094] Weigh: 40 g of activated carbon nanotubes and 700 mL of 1,2-dichloroethane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is ice-bathed to 5°C, 20 mL of acryloyl chloride is slowly added, and the reaction is kept warm for 4 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to an oven at a temperature of 60°C, and dried to constant weight to obtain a crude modified carbon nanotube.

[0095] Step 3: Preparation of modified carbon nanotubes

[0096] Weigh: 40 g of crude modified carbon nanotubes and 800 mL of 1,2-dichloroethane are placed in a reactor and stirred, 4 g of antimony trichloride and 20 mL of liquid bromine are added, the reactor is heated to 50°C, and the reaction is kept warm for 4 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed with deionized water until neutral, transferred to a freeze dryer at a temperature of -60°C, and dried for 10 hours to obtain modified carbon nanotubes.

[0097] Example 7

[0098] This embodiment provides a method for preparing a modified toughening agent for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0099] Step (1): preparing prepolymer solution

[0100] Weigh 30 g of acrylonitrile, 20 g of styrene, 5 g of fatty acid soap and 0.5 g of cumene hydroperoxide, place them in a reactor, and stir at room temperature for 5 minutes to obtain a prepolymer solution.

[0101] Step (2): preparing a modified toughening agent

[0102] Weigh: 200 g of polybutadiene latex is placed in a reactor and stirred. The reactor is heated to 50°C, 0.5 g of sodium pyrophosphate, 1 g of glucose and 20 mL of ferrous sulfate aqueous solution are added, and the mixture is stirred for 15 minutes. 100 mL of prepolymer solution is slowly added dropwise, the reactor is heated to 65°C, and the reaction is kept warm for 0.5 hours. After the reaction is completed, the reaction system is cooled to room temperature, 20 g of sodium chloride is added for demulsification, and the mixture is allowed to stand for 20 minutes. The filter cake is washed twice with deionized water, transferred to an oven at 50°C, and dried to constant weight to obtain a modified toughening agent.

[0103] Example 8

[0104] This embodiment provides a method for preparing a modified toughening agent for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0105] Step (1): preparing prepolymer solution

[0106] Weigh 40 g of acrylonitrile, 30 g of styrene, 7 g of fatty acid soap and 0.7 g of cumene hydroperoxide into a reaction kettle and stir at room temperature for 7 minutes to obtain a prepolymer solution.

[0107] Step (2): preparing a modified toughening agent

[0108] Weigh: 225 g of polybutadiene latex is placed in a reactor and stirred. The reactor is heated to 55°C, 0.7 g of sodium pyrophosphate, 1.5 g of glucose and 30 mL of ferrous sulfate aqueous solution are added, stirred for 20 minutes, 125 mL of prepolymer liquid is slowly added dropwise, the reactor is heated to 70°C, and the reaction is kept warm for 1 hour. After the reaction is completed, the reaction system is cooled to room temperature, 30 g of sodium chloride is added for demulsification, and the mixture is allowed to stand for 25 minutes. The filter cake is washed three times with deionized water, transferred to an oven at 55°C, and dried to constant weight to obtain a modified toughening agent.

[0109] Example 9

[0110] This embodiment provides a method for preparing a modified toughening agent for high-toughness plastic masterbatch prepared by recycling waste PVC, comprising the following steps:

[0111] Step (1): preparing prepolymer solution

[0112] Weigh 50 g of acrylonitrile, 40 g of styrene, 10 g of fatty acid soap and 1 g of cumene hydroperoxide into a reaction kettle and stir at room temperature for 10 min to obtain a prepolymer solution.

[0113] Step (2): preparing a modified toughening agent

[0114] Weigh: 250g of polybutadiene latex is placed in a reactor and stirred. The reactor is heated to 60°C, 1g of sodium pyrophosphate, 2g of glucose and 40mL of ferrous sulfate aqueous solution are added, and stirred for 30min. 150mL of prepolymer liquid is slowly added dropwise, the reactor is heated to 75°C, and the reaction is kept warm for 1.5h. After the reaction is completed, the reaction system is cooled to room temperature, 40g of sodium chloride is added for demulsification, and the mixture is allowed to stand for 30min. The filter cake is washed 4 times with deionized water, transferred to an oven at 60°C, and dried to constant weight to obtain a modified toughening agent.

[0115] Example 10

[0116] This embodiment provides a method for preparing high-toughness plastic masterbatch from recycled waste PVC, comprising the following steps:

[0117] Step ⑴, prepare mixture

[0118] Evenly mix p-tert-butylphenyl salicylate, dibutyl phthalate, stearic acid, and 4,4'-thiobis(6-tert-butyl-3-methylphenol) in a mass ratio of 2:5:3:1 to obtain an auxiliary additive, which is set aside;

[0119] Weigh by weight: 60 parts of the recycled PVC powder prepared in Example 1, 10 parts of the modified toughening agent prepared in Example 7, 3 parts of the modified carbon nanotubes prepared in Example 4 and 6 parts of auxiliary additives, place them in a high-speed mixer at 800 rpm, and mix them evenly at high speed to obtain a mixture.

[0120] Step ⑵, preparation of high toughness plastic masterbatch

[0121] The mixed material is added into a twin-screw extruder, melt-extruded, and granulated to obtain a high-toughness plastic masterbatch;

[0122] The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 150°C, 150°C, 155°C, 160°C, 165°C, 165°C, 170°C, and 170°C, respectively. The main engine speed of the twin-screw extruder is 120rpm and the pressure is 80bar.

[0123] Example 11

[0124] This embodiment provides a method for preparing high-toughness plastic masterbatch from recycled waste PVC, comprising the following steps:

[0125] Step ⑴, prepare mixture

[0126] Evenly mix p-tert-butylphenyl salicylate, dibutyl phthalate, stearic acid, and 4,4'-thiobis(6-tert-butyl-3-methylphenol) in a mass ratio of 2:5:3:1 to obtain an auxiliary additive, which is set aside;

[0127] Weigh by weight: 70 parts of the recycled PVC powder prepared in Example 2, 12 parts of the modified toughening agent prepared in Example 8, 4 parts of the modified carbon nanotubes prepared in Example 5 and 7 parts of auxiliary additives, place them in a high-speed mixer at 1000 rpm, and mix them at high speed to obtain a mixture.

[0128] Step ⑵, preparation of high toughness plastic masterbatch

[0129] The mixed material is added into a twin-screw extruder, melt-extruded, and granulated to obtain a high-toughness plastic masterbatch;

[0130] The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 150°C, 150°C, 155°C, 160°C, 165°C, 165°C, 170°C, and 170°C, respectively. The main engine speed of the twin-screw extruder is 140rpm and the pressure is 100bar.

[0131] Example 12

[0132] This embodiment provides a method for preparing high-toughness plastic masterbatch from recycled waste PVC, comprising the following steps:

[0133] Step ⑴, prepare mixture

[0134] Evenly mix p-tert-butylphenyl salicylate, dibutyl phthalate, stearic acid, and 4,4'-thiobis(6-tert-butyl-3-methylphenol) in a mass ratio of 2:5:3:1 to obtain an auxiliary additive, which is set aside;

[0135] Weigh 80 parts by weight of the recycled PVC powder prepared in Example 3, 15 parts of the modified toughening agent prepared in Example 9, 5 parts of the modified carbon nanotubes prepared in Example 6, and 8 parts of auxiliary additives, place them in a high-speed mixer at 1200 rpm, and mix them evenly at high speed to obtain a mixture.

[0136] Step ⑵, preparation of high toughness plastic masterbatch

[0137] The mixed material is added into a twin-screw extruder, melt-extruded, and granulated to obtain a high-toughness plastic masterbatch;

[0138] The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 150°C, 150°C, 155°C, 160°C, 165°C, 165°C, 170°C, and 170°C, respectively. The main engine speed of the twin-screw extruder is 160rpm and the pressure is 120bar.

[0139] Comparative Example 1

[0140] The difference between this comparative example and Example 12 is that when preparing the high-toughness plastic masterbatch, an equal amount of waste PVC powder is used instead of recycled PVC powder.

[0141] Comparative Example 2

[0142] The difference between this comparative example and Example 12 is that when preparing the high-toughness plastic masterbatch, an equal amount of activated carbon nanotubes is used instead of the modified carbon nanotubes.

[0143] Comparative Example 3

[0144] The difference between this comparative example and Example 12 is that the addition of the modifying toughening agent is omitted when preparing the high-toughness plastic masterbatch.

[0145] Performance testing:

[0146] The tensile strength, Vicat softening temperature, and elongation at break of the plastic masterbatches prepared in Examples 10-12 and Comparative Examples 1-3 were tested with reference to the standard GB / T 40006.11-2024 "Plastics - Recycled Plastics - Part 11: Polyvinyl Chloride (PVC) Materials";

[0147] The simply supported beam notched impact strength of the plastic masterbatches prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard GB / T 40006.6-2021 "Plastics Recycled Plastics Part 6: Polystyrene (PS) and High-Impact Polystyrene (PS-I) Materials". The specific data are shown in Table 1.

[0148] Table 1 - Performance test data of each sample

[0149]

[0150] Data Analysis:

[0151] Comparative analysis of the data in Table 1 shows that the plastic masterbatch prepared by the present invention has a tensile strength of 35.9 MPa, a Vicat softening temperature of 87.2°C, an elongation at break of 197.3%, and a simply supported beam notched impact strength of 12.6 kJ·m -2 , all data are better than those of the comparative example;

[0152] This shows that the present invention prepares a modified toughening agent with polybutadiene latex as the core and acrylonitrile and styrene as the shell through a reduction-oxidation initiation system, activates carbon nanotubes through a mixed acid system, and further introduces bromine atoms to modify the carbon nanotubes, and generates a conjugated double bond structure by pyrolysis of waste PVC powder under alkaline conditions to remove residual plasticizers and aging by-products, and then reacts with the repair agent N,N'-ethylenebis(maleamic acid) to generate a cyclic stable structure through a DA reaction, shorten the conjugated chain, and increase the flexibility of the molecule. Local cross-linking can improve the interaction between chains to obtain recycled PVC powder with repaired mechanical properties, and the recycled PVC powder, modified toughening agent, modified carbon nanotubes and auxiliary additives are mixed, melt-extruded, and granulated to obtain a high-toughness plastic masterbatch, which not only improves the toughness of the plastic masterbatch, but also improves its mechanical properties and high-temperature resistance.

[0153] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. High-toughness plastic masterbatch prepared by recycling waste PVC, characterized in that: The invention comprises the following components by weight: 60-80 parts of recycled PVC powder, 10-15 parts of modified toughening agent, 3-5 parts of modified carbon nanotubes and 6-8 parts of auxiliary additives; The modified toughening agent is prepared by the following steps: A1. Place acrylonitrile, styrene, fatty acid soap and cumene hydroperoxide in a reaction kettle and stir at room temperature for 5-10 minutes to obtain a prepolymer solution; A2. Place polybutadiene latex in a reactor and stir. Heat the reactor to 50-60°C, add sodium pyrophosphate, glucose and ferrous sulfate aqueous solution, stir for 15-30 minutes, slowly add prepolymer solution dropwise, heat the reactor to 65-75°C, keep the temperature for reaction for 0.5-1.5 hours, and post-treat to obtain a modified toughening agent.

2. The high-toughness plastic masterbatch prepared by recycling waste PVC according to claim 1, characterized in that: In step A1, the weight ratio of acrylonitrile, styrene, fatty acid soap and isopropyl benzene hydroperoxide is 3-5:2-4:0.5-1:0.05-0.1; in step A2, the amount ratio of the polybutadiene latex, sodium pyrophosphate, glucose, ferrous sulfate aqueous solution and prepolymer solution is 20-25g:0.05-0.1g:0.1-0.2g:2-4mL:10-15mL, and the concentration of the ferrous sulfate aqueous solution is 40-50wt%.

3. The high-toughness plastic masterbatch prepared by recycling waste PVC according to claim 1, characterized in that: The modified carbon nanotubes are prepared by the following steps: B1. Place carbon nanotubes and a mixed acid solution in a reaction kettle and stir. Heat the reactor to 135-145° C., keep the temperature for 1-2 hours, and perform post-treatment to obtain activated carbon nanotubes. B2. Place activated carbon nanotubes and 1,2-dichloroethane in a nitrogen atmosphere-protected reactor and stir. Place the reactor in an ice bath at 0-5°C, slowly add acryloyl chloride, and keep the reaction warm for 2-4 hours. Post-process to obtain crude modified carbon nanotubes. B3. Place the crude modified carbon nanotubes and 1,2-dichloroethane in a reactor and stir, add antimony trichloride and liquid bromine, heat the reactor to 40-50°C, keep the temperature for reaction for 2-4 hours, and perform post-treatment to obtain modified carbon nanotubes.

4. The high-toughness plastic masterbatch prepared by recycling waste PVC according to claim 3, characterized in that: In step B1, the carbon nanotubes and the mixed acid solution are used in a ratio of 1-2 g:150-200 mL, and the mixed acid solution is composed of 95-98 wt% concentrated sulfuric acid and 60-65 wt% nitric acid in a volume ratio of 100-150:30-50; in step B2, the activated carbon nanotubes, 1,2-dichloroethane and acryloyl chloride are used in a ratio of 2-4 g:50-70 mL:1-2 mL; in step B3, the modified carbon nanotube crude product, 1,2-dichloroethane, antimony trichloride and liquid bromine are used in a ratio of 2-4 g:60-80 mL:0.2-0.4 g:1-2 mL.

5. The high-toughness plastic masterbatch prepared by recycling waste PVC according to claim 1, characterized in that: The recycled PVC powder is prepared by the following steps: C1. Place waste PVC powder, potassium hydroxide, and dimethyl sulfoxide in a reactor and stir. Heat the reactor to 75-85° C., keep the temperature for 4-6 hours, and perform post-processing to obtain pyrolyzed PVC powder. C2. Place the pyrolyzed PVC powder and the repair agent in a reactor, mix them evenly, and then perform post-processing to obtain recycled PVC powder.

6. The high-toughness plastic masterbatch prepared by recycling waste PVC according to claim 5, characterized in that: In step C1, the usage ratio of the waste PVC powder, potassium hydroxide and dimethyl sulfoxide is 4-6g:130-150mL:8-10g; in step C2, the weight ratio of the pyrolyzed PVC powder and the repair agent is 5-10:0.4-0.6, and the repair agent is N,N'-ethylenebis(maleamic acid).

7. The method for preparing high-toughness plastic masterbatch by regenerating waste PVC according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, placing recycled PVC powder, modified toughening agent, modified carbon nanotubes and auxiliary additives in a high-speed mixer, and mixing them at high speed to obtain a mixture; S2. Add the mixed material into a twin-screw extruder, melt-extrude, and granulate to obtain high-toughness plastic masterbatch.

8. The method for preparing high-toughness plastic masterbatch by regenerating waste PVC according to claim 7, characterized in that: In step S1, the auxiliary additives are composed of an ultraviolet absorber, a plasticizer, a lubricant, and an antioxidant in a mass ratio of 2:5:3:1.

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