A polyvinyl chloride sealing strip material prepared by using red mud and tire waste and a preparation method thereof

Abstract

The present invention provides a polyvinyl chloride sealing strip material prepared by red mud and tire waste, which is composed of the following raw materials by mass: 100 parts of polyvinyl chloride resin, 1-3 parts of heat stabilizer, 10-40 parts of red mud, 5-20 parts of tire waste, 5-15 parts of plasticizer, 0-3 parts of lubricant, and 1-5 parts of coupling agent. Red mud and tire waste are used as combined fillers to fill the modified PVC resin matrix, red mud can act as a rigid filler, brown colorant, heat stabilizer and acid gas neutralizer, and waste tire waste can act as a toughness filler, and the synergistic effect of the two improves the thermal stability, mechanical properties and aging resistance of the matrix. The sealing strip prepared by the method of the present invention has excellent performance, not only reduces production costs, but also provides an effective way for the value-added utilization of red mud and tire waste, and protects the ecological environment.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of industrial solid waste, and specifically relates to a high-temperature resistant brown polyvinyl chloride (PVC) sealing strip material prepared by utilizing red mud (RM) and tire waste, and a preparation method thereof. Background Art

[0002] Red mud is a strongly alkaline solid waste produced in the process of producing alumina using bauxite as raw material. Because it is rich in iron oxide, it has a red mud or powdery appearance. my country is the world's largest producer of alumina. In 2021, my country's alumina production was about 77.47 million tons, accounting for 55% of the world's total production, and red mud emissions were about 100 million tons. Up to now, the comprehensive utilization rate of red mud in my country is about 5%, and the cumulative stockpile exceeds 1.1 billion tons. The large-scale stockpiling of red mud not only occupies land, but also poses a risk of pollution to the soil and groundwater. Therefore, it is urgent to promote the clean and efficient utilization of red mud in my country. Studies have shown that red mud is rich in high-melting-point dicalcium silicate, perovskite, hematite and other metal oxides. If used as a plastic filler, it can greatly improve the mechanical properties, thermal stability and aging resistance of the material.

[0003] With the rapid development of the automobile industry, my country has become the world's largest automobile producer and consumer. As a by-product of the automobile industry, waste tires have been increasing year by year. In 2019 alone, China's automobile tire production reached 650 million. The long-term open-air storage of more and more waste tires not only occupies a large amount of land, but also easily breeds mosquitoes and spreads diseases, seriously deteriorates the natural environment, and may cause fires, seriously threatening people's lives and property safety. It is called "black pollution". "Black pollution" and the serious waste of rubber resources caused by it have attracted global attention. Studies have shown that waste tires have the characteristics of high strength, high toughness, etc., and can be used as good toughness fillers in plastic products to improve their mechanical properties and processing characteristics.

[0004] Plastics have been listed as one of the four major engineering materials along with steel, cement and wood, and the output of resin materials as plastic raw materials has been growing at a high speed for many years. Taking China alone as an example, the annual output of synthetic resins in 2022 is expected to exceed 100 million tons. According to statistics, an average of 1.6 tons of standard oil is consumed to manufacture 1 ton of plastic products, which will cause 3.5 tons of CO2 emissions. In 2019, the plastics industry consumed 8% of the world's oil and caused 1.29 billion tons of carbon emissions. PVC is a typical resin material, and its global sales volume is second only to polyethylene. It is a non-toxic, odorless white powder with excellent properties such as flame retardancy, insulation, wear resistance and corrosion resistance. However, PVC molecules contain unstable structures such as allyl chloride, which are not easy to process and have poor flow properties. In addition, PVC is prone to generate HCl gas under oxygen, high temperature or light conditions, and aging and degradation occur, resulting in poor thermal stability.

[0005] Chinese invention patent CN 103131214 B discloses a process for producing PVC filler using red mud, a byproduct of alumina. The method requires firstly to subject the red mud slurry to composite dealkalization; then it needs to be washed by a vacuum washer and activated by carbon dioxide; finally, it needs to be baked, ground, graded and sent to the powder bin. Its disadvantages are long production process, low efficiency, high cost, and multiple use of chemicals to dealkalize the red mud, and waste materials and waste liquid will cause secondary pollution to the environment. Chinese invention patent CN 115197488 A discloses a method for manufacturing special materials for sealing strips using waste tires. The method first grinds the waste tires into rubber powder; then the obtained rubber powder is mixed with ethylene-octene polymer, diisopropylbenzene peroxide, triallyl isocyanurate and antioxidant, and added to a banbury mixer for mixing to obtain special materials for sealing strips. Its disadvantage is that the use of waste tire rubber powder as the main material to prepare sealing strips will decompose sulfur-containing acidic gas due to high temperature in the banbury mixer, which will cause damage to human health and the environment. Chemical reagents must be used again to treat these sulfur-containing gases, which will undoubtedly greatly increase production costs.

[0006] It can be seen from the above-mentioned improved technologies that whether using red mud alone as plastic filler or directly using waste tire rubber powder as the main material to prepare sealing strips, it will cause pollution and damage to human health and the environment, increase production costs, and have little market prospects. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of high cost and pollution of the prior art for the reuse of red mud and waste tires, as well as poor thermal stability of PVC sealing strips, thereby providing a high-temperature resistant brown polyvinyl chloride sealing strip material prepared by using red mud and tire waste and a preparation method thereof. The alkalinity in red mud is mainly used to neutralize the acidic gas generated by waste tire rubber powder and PVC at high temperature; the high melting point metal oxides contained in red mud are used to improve the thermal stability and aging resistance of the PVC matrix; the rich iron oxide contained in red mud is used as a brown colorant for the PVC matrix; the rigidity and toughness of red mud and waste tires are used to synergistically enhance the mechanical properties and processing characteristics of the PVC matrix; at the same time, the synergistic use of red mud and tire waste as PVC resin matrix fillers greatly reduces the production cost of sealing strips and the emission of acidic gases, and protects the ecological environment.

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

[0009] A polyvinyl chloride sealing strip material prepared by using red mud and tire waste is composed of the following raw materials in parts by mass: 100 parts of polyvinyl chloride (PVC) resin, 1-3 parts of heat stabilizer, 10-40 parts of red mud, 5-20 parts of tire waste, 5-15 parts of plasticizer, 0-3 parts of lubricant and 1-5 parts of coupling agent.

[0010] The present invention utilizes the synergistic effect of red mud and tire waste, and requires that the red mud and tire waste are within an appropriate dosage range. If the red mud content is too much, it will affect the toughness of the product, and if the tire waste content is too much, it will affect the hardness and thermal stability of the product; on the contrary, if the dosage of the two is too small, the synergistic modification effect is limited, and the performance improvement of the polyvinyl chloride product sealing strip is not obvious enough.

[0011] Preferably, a polyvinyl chloride sealing strip material prepared by using red mud and tire waste is composed of the following raw materials in parts by mass: 100 parts of polyvinyl chloride (PVC) resin, 1-3 parts of heat stabilizer, 20-35 parts of red mud, 8-15 parts of tire waste, 5-10 parts of plasticizer, 0-2 parts of lubricant, and 1-3 parts of coupling agent.

[0012] Furthermore, the raw materials are mixed according to the ratio, and then subjected to supercritical CO2 treatment, plasticization, granulation, plasticization again, extrusion molding, cooling, and cutting molding to obtain a PVC sealing strip.

[0013] The supercritical CO2 treatment conditions are: 30°C to 120°C, 7.5MPa to 30MPa, and treatment for 1 hour to 4 hours.

[0014] Preferably, the red mud is surface-modified with polyvinyl chloride (PVC).

[0015] The surface modification method comprises: a) preparing a tetrahydrofuran solution of PVC; b) mixing the PVC solution with red mud and water, and reacting at 100-120° C. for 20-40 minutes; c) stirring, filtering and drying to obtain red mud with the surface modified with PVC.

[0016] The mass ratio of PVC to red mud is (0.5-3):10.

[0017] Red mud contains Si-OH, Al-OH, etc., which can undergo condensation reaction with PVC under high temperature (greater than 100°C) to achieve surface grafting modification, which not only improves the interfacial compatibility between the two and enhances the mechanical properties, but also facilitates subsequent mixed coupling.

[0018] Red mud contains a variety of metal oxides. First, PVC resin is used to modify its surface to form a coating-like structure, which can form more active sites on the red mud surface and more forces between it and the PVC resin, thereby improving the interfacial compatibility between red mud and PVC and making the mixing more uniform. At the same time, since the red mud surface contains a small amount of PVC, under the action of the hydroxyl, amino and other functional groups of the coupling agent (such as titanate), more forces can be formed between the red mud, the surface-modified PVC and the matrix PVC resin, further improving the interfacial properties of the red mud and the matrix PVC resin and other materials, improving the coupling efficiency of the materials, improving the effect of red mud and tire waste as fillers to modify the PVC resin, and improving the mechanical properties and stability of PVC sealing strip products.

[0019] The heat stabilizer is selected from one or more of tribasic lead sulfate, dust-free composite lead salt heat stabilizer, zinc stearate, calcium stearate, rare earth stabilizer, and octanoic acid.

[0020] The plasticizer is selected from one or more of di(2-ethylhexyl) phthalate, di(2-ethylhexyl) adipate, and tri-n-butyl acetyl citrate.

[0021] The lubricant is selected from one or more of polyethylene wax, paraffin wax and stearic acid.

[0022] The coupling agent is selected from one or more of titanate coupling agent, silane, titanate, and aluminate.

[0023] The active functional groups (such as hydroxyl and amino) in the coupling agent connect the red mud to the PVC matrix through chemical bonds during the curing process, thereby densifying the overall structure of the composite material and improving the mechanical and thermal stability of the product.

[0024] The present invention also provides a method for preparing a polyvinyl chloride sealing strip material by using red mud and tire waste, comprising the following steps:

[0025] (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder;

[0026] The red mud raw material has a mesh size of ≥800, and its main chemical components are Al2O3: 20% to 35%, SiO2: 20% to 30%, CaO: 15% to 25%, Na2O: 10% to 20%, Fe2O3: 10% to 20%, and TiO2: 3% to 10%;

[0027] The waste tire has a mesh size of ≥400, and its main components are rubber, carbon black, vulcanizing agent and other chemical additives.

[0028] Preferably, the red mud powder is surface-modified with polyvinyl chloride (PVC).

[0029] The surface modification method is as follows: a) preparing a tetrahydrofuran solution of PVC; b) mixing the PVC solution with ground red mud powder and water, and reacting at 100-120° C. for 20-40 minutes; c) stirring, filtering, and drying to obtain the red mud powder with PVC surface modification for later use. The mass ratio of PVC for surface modification to red mud is (0.5-3):10.

[0030] PVC can modify the surface of red mud powder to produce more active sites on the surface of red mud, and generate more forces with the PVC resin matrix during the curing process; at the same time, with the help of the coupling agent, the red mud and PVC resin can be more closely combined, thereby improving the coupling efficiency and the effect of red mud filling and modifying the PVC resin matrix. Ultimately, the PVC sealing strip product has higher stability and does not require the introduction of other modifier materials.

[0031] (2) mixing the ground red mud powder and tire rubber powder with polyvinyl chloride (PVC) resin, heat stabilizer, plasticizer, lubricant, and coupling agent, and treating with supercritical CO2;

[0032] The supercritical CO2 treatment process is as follows: the raw materials are mixed and put into a reactor, supercritical carbon dioxide fluid is introduced into the reactor, and after treating for 1 to 4 hours at 30°C to 120°C and 7.5MPa to 30MPa, the pressure is slowly reduced to normal pressure and taken out.

[0033] During the supercritical CO2 treatment process, under the action of supercritical CO2 solvent, micro-fusion occurs on the surface of the polymer mixture. When the CO2 is removed by decompression, the micro-fusion part of the mixture surface will solidify and cross-link, thereby improving the mechanical properties of the mixture.

[0034] (3) plasticizing and granulating the taken-out material to obtain sealing strip pellets;

[0035] Wherein, step (3) adopts a twin-screw extruder for plasticization; the mixing and plasticizing temperature of the twin-screw extruder is 120-160°C, and the granulation extrusion temperature of the twin-screw extruder is 110-140°C.

[0036] (4) The sealing strip pellets obtained in step (3) are plasticized again and extruded to obtain a semi-finished sealing strip;

[0037] The sealing strip pellets obtained in step (4) are plasticized again by a single screw extruder; the body temperature of the single screw extruder is 130-170°C, and the temperature of the extrusion molding mold is 150-180°C.

[0038] (5) After molding, the semi-finished sealing strip is cooled and cut to obtain a high temperature resistant polyvinyl chloride sealing strip.

[0039] Wherein, the cooling is air cooling or water cooling, and the cooling water temperature during the water cooling process is 8-15°C.

[0040] Beneficial effects of the present invention:

[0041] (1) Red mud and waste tire waste are used as combined fillers to fill and modify the PVC resin matrix. Red mud can act as a rigid filler, brown colorant, heat stabilizer and acid gas neutralizer, and waste tires can act as a tough filler. The synergistic effect of the two improves the thermal stability, mechanical properties and aging resistance of the matrix. The alkalinity in red mud can neutralize the harmful acidic gases produced by waste tire rubber powder and PVC at high temperatures; the high melting point metal oxides contained in red mud can improve the thermal stability and aging resistance of the PVC matrix; the combination of rigid filler red mud and tough filler waste tire rubber powder can synergistically enhance the mechanical properties and processing characteristics of the PVC matrix.

[0042] (2) The rich iron oxide contained in red mud can act as a brown colorant for the PVC matrix, beautifying the appearance of the prepared sealing strip product.

[0043] (3) The reuse of industrial solid waste red mud and waste tires in the PVC resin matrix reduces greenhouse gas emissions, protects the ecological environment, and greatly reduces production costs, with significant economic and environmental benefits.

[0044] (4) The present invention utilizes supercritical CO2 surface treatment during the material mixing process to cause micro-fusion, curing and cross-linking on the surface of the PVC-based mixture, thereby improving the final mechanical properties of the material.

[0045] (5) Red mud is surface-modified or modified with a small amount of PVC resin to form a coating-like structure. With the help of a small amount of PVC on the surface of the red mud, more active sites are generated and more forces are formed. Under the action of the coupling agent, the density of the interface structure between the red mud and the PVC resin can be further improved, and the thermal stability of the product can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a technical flow chart of Embodiment 1 of the present invention;

[0047] Figure 2 The high temperature resistant brown polyvinyl chloride sealing strip material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0049] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0050] Example 1

[0051] A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste:

[0052] (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder;

[0053] (2) preparing the required raw materials of polyvinyl chloride resin 100 parts, heat stabilizer zinc stearate 1 part, red mud powder 10 parts, tire rubber powder 8 parts, plasticizer di(2-ethylhexyl) phthalate 8 parts, lubricant paraffin 1 part, titanate coupling agent 1 part, mixing and putting into a reactor, introducing supercritical carbon dioxide fluid into the reactor, treating at 60° C. and 8 MPa for 3 hours, slowly reducing to normal pressure, and taking out;

[0054] (3) adding the taken-out material into a twin-screw extruder, fully plasticizing it at 130° C., and granulating it at 120° C. to obtain sealing strip granules;

[0055] (4) The sealing strip pellets are plasticized again at 150° C. through a single screw extruder, and extruded through a mold at 160° C. to obtain a semi-finished sealing strip;

[0056] (5) After molding, the semi-finished sealing strip is cooled and cut to obtain a high temperature resistant brown polyvinyl chloride sealing strip.

[0057] Example 2

[0058] The other experimental steps and conditions were the same as those in Example 1, except that the content of tire rubber powder was increased to 15 parts, and a high temperature resistant brown polyvinyl chloride sealing strip material was prepared.

[0059] Example 3

[0060] The other experimental steps and conditions were the same as those in Example 1, except that the content of tire rubber powder was increased to 20 parts, and a high temperature resistant brown polyvinyl chloride sealing strip material was prepared.

[0061] Example 4 (Changes in red mud content)

[0062] The other experimental steps and conditions were the same as those in Example 1, except that the content of red mud powder was increased to 20 parts, and a high-temperature resistant brown polyvinyl chloride sealing strip material that met the requirements was prepared.

[0063] Example 5

[0064] The other experimental steps and conditions were the same as those in Example 1, except that the content of the red mud powder was increased to 35 parts, and a high-temperature resistant brown polyvinyl chloride sealing strip material that met the requirements was prepared.

[0065] Example 6

[0066] A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste,

[0067] (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder;

[0068] The red mud powder is subjected to surface modification, comprising steps a) to c):

[0069] a) preparing a tetrahydrofuran solution of PVC: dissolving PVC resin in tetrahydrofuran to form a PVC solution;

[0070] b) mixing the PVC solution with red mud powder and water, and reacting at 120° C. for 30 min; wherein the weight ratio of the PVC resin in step a) to the red mud powder in step b) is 1:10;

[0071] c) stirring the mixture obtained in step b), filtering and drying at 50° C. for 1 hour to obtain PVC surface-modified red mud powder.

[0072] (2) preparing the required raw materials of polyvinyl chloride resin 100 parts, heat stabilizer zinc stearate 1 part, surface modified red mud powder 10 parts, tire rubber powder 8 parts, plasticizer di(2-ethylhexyl) phthalate 8 parts, lubricant paraffin 1 part, titanate coupling agent 1 part, mixing and putting into a reactor, introducing supercritical carbon dioxide fluid into the reactor, treating at 60° C. and 8 MPa for 3 hours, slowly reducing to normal pressure, and taking out;

[0073] Steps (3) to (5) are the same as in Example 1 to obtain a high temperature resistant brown polyvinyl chloride sealing strip.

[0074] Example 7

[0075] A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste,

[0076] (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder;

[0077] The red mud powder is subjected to surface modification, comprising steps a) to c):

[0078] a) preparing a tetrahydrofuran solution of PVC: dissolving PVC resin in tetrahydrofuran to form a PVC solution;

[0079] b) mixing the PVC solution with red mud powder and water, and reacting at 120° C. for 40 min; wherein the weight ratio of the PVC resin in step a) to the red mud powder in step b) is 3:10;

[0080] c) stirring the mixture obtained in step b), filtering and drying at 50° C. for 1 hour to obtain PVC surface-modified red mud powder.

[0081] The remaining steps (2)-(5) are the same as in Example 6 to obtain a high temperature resistant brown polyvinyl chloride sealing strip.

[0082] Embodiment 8 (other parameters)

[0083] A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste:

[0084] (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder;

[0085] (2) preparing the required raw materials of 100 parts of polyvinyl chloride resin, 2 parts of heat stabilizer calcium stearate, 24 parts of red mud powder, 12 parts of tire rubber powder, 10 parts of plasticizer tri-n-butyl acetyl citrate, 1 part of lubricant polyethylene wax, and 2 parts of silane coupling agent, mixing them and putting them into a reactor, introducing supercritical carbon dioxide fluid into the reactor, treating them at 70° C. and 8 MPa for 2.5 hours, slowly reducing the pressure to normal pressure, and taking them out;

[0086] (3) adding the taken-out material into a twin-screw extruder, fully plasticizing it at 140° C., and granulating it at 140° C. to obtain sealing strip granules;

[0087] (4) The sealing strip pellets are plasticized again at 160° C. through a single screw extruder, and extruded through a mold at 160° C. to obtain a semi-finished sealing strip;

[0088] (5) After molding, the semi-finished sealing strip is cooled and cut to obtain a high temperature resistant brown polyvinyl chloride sealing strip.

[0089] Comparative Example 1 (without red mud)

[0090] A method for preparing polyvinyl chloride sealing strip material using tire waste:

[0091] (1) collecting waste tire materials, grinding them to obtain tire rubber powder;

[0092] (2) preparing the required raw materials of polyvinyl chloride resin 100 parts, heat stabilizer zinc stearate 1 part, tire rubber powder 8 parts, plasticizer di(2-ethylhexyl) phthalate 8 parts, lubricant paraffin 1 part, titanate coupling agent 1 part, mixing and putting into a reactor, introducing supercritical carbon dioxide fluid into the reactor, treating at 60° C. and 8 MPa for 3 hours, slowly reducing to normal pressure, and taking out;

[0093] Steps (3)-(5) are the same as in Example 1.

[0094] Comparative Example 2 (without tire powder)

[0095] A method for preparing polyvinyl chloride sealing strip material using red mud:

[0096] (1) collecting and grinding waste red mud materials to obtain red mud powder;

[0097] (2) preparing the required raw materials of 100 parts of polyvinyl chloride resin, 1 part of heat stabilizer zinc stearate, 10 parts of red mud powder, 8 parts of plasticizer di(2-ethylhexyl) phthalate, 1 part of lubricant paraffin, and 1 part of titanate coupling agent, mixing them and putting them into a reactor, introducing supercritical carbon dioxide fluid into the reactor, treating them at 60° C. and 8 MPa for 3 hours, then slowly reducing the pressure to normal pressure and taking them out;

[0098] Steps (3)-(5) are the same as in Example 1.

[0099] Comparative Example 3 (non-supercritical)

[0100] A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste:

[0101] (1) collecting waste red mud and tire materials, grinding them to obtain red mud powder and tire rubber powder;

[0102] (2) Prepare the required raw materials of polyvinyl chloride resin 100 parts, heat stabilizer zinc stearate 1 part, red mud powder 10 parts, tire rubber powder 8 parts, plasticizer di (2-ethylhexyl) phthalate 8 parts, lubricant paraffin 1 part, and titanate coupling agent 1 part and mix them;

[0103] (3) adding the mixed material into a twin-screw extruder, fully plasticizing it at 130° C., and granulating it at 120° C. to obtain sealing strip granules;

[0104] Steps (4)-(5) are the same as in Example 1.

[0105] Performance testing:

[0106] The hardness, tensile impact strength, heating weight loss and heating shrinkage of the polyvinyl chloride sealing strip products prepared in the examples and comparative examples were tested. The hardness was measured according to the national standard GB / T 2411-2008 "Standard for Determining Indentation Hardness (Shore Hardness) of Plastics and Hard Rubber Using a Hardness Tester"; the tensile impact strength was measured according to the national standard GB / T 13525-1992 "Test Method for Tensile Impact Properties of Plastics"; the heating weight loss was measured according to the national standard GB / T 7141-2008 "Test Method for Thermal Aging of Plastics"; the heating shrinkage was measured according to the national standard GB / T 12002-1989 "Sealing Strips for Plastic Doors and Windows". The test results are shown in Table 1.

[0107] Table 1 Test results of high temperature resistant brown sealing strips obtained from different comparative examples and embodiments

[0108]

[0109]

[0110] From the data in the above table, it can be seen that the amount of tire waste is adjusted in Examples 1-3, and the impact strength of the PVC sealing strip is improved to a certain extent by utilizing the toughness of the tire waste; the amount of red mud waste is adjusted in Examples 4-5, and the rigidity of red mud can be used to improve the hardness and thermal stability of the PVC sealing strip, and other properties of the product (such as impact strength) are not affected. In Examples 6-7, which use red mud surface modification, the hardness, tensile impact strength, and stability of the PVC sealing strip products are significantly improved, and the heating weight loss and heating shrinkage rate are significantly reduced. This may be because the surface modification of red mud using the same PVC resin as the resin matrix can significantly improve the coupling efficiency with the PVC resin matrix and the compactness of the structure, so that the PVC sealing strip product formed is more stable, so the product heating weight loss and heating shrinkage rate are low, and the high temperature resistance is good.

[0111] It can be seen from Example 1 and Comparative Examples 1 and 2 that when only a single tire waste or red mud waste is used as a raw material, the hardness, tensile strength and thermal stability cannot be taken into account. Compared with Comparative Example 1, the hardness and thermal stability data of Comparative Example 1 are reduced (the heating weight loss rate reaches 3.2%, and the heating shrinkage rate reaches 3.0%). This is because the presence of red mud in Example 1 can neutralize the acidic HCl gas generated during the heating process of tire rubber powder, which is beneficial to improving the thermal stability of the product. At the same time, the rigidity of red mud can improve the hardness of the PVC sealing strip.

[0112] Compared with Comparative Example 2, Example 1 has a lower tensile impact strength of the PVC sealing strip product due to the lack of tire rubber powder in Comparative Example 2.

[0113] In Examples 1-8 of the present invention, tire waste and red mud waste are used as raw materials, and the synergistic effect of the two can be fully exerted. Red mud and tire waste are used as combined fillers to fill the modified PVC resin matrix, wherein red mud can act as a rigid filler, brown colorant, heat stabilizer and acid gas neutralizer, and discarded tire waste can act as a tough filler. The synergistic effect of the two improves the thermal stability, mechanical properties and aging resistance of the matrix.

[0114] Because the comparative example 3 did not adopt supercritical treatment, the hardness and tensile strength were reduced, and the thermal stability of the product also decreased slightly. This also shows that the present invention can make the surface of the PVC-based mixture undergo micro-fusion-cross-linking by means of supercritical CO2 surface treatment, and combine the synergistic effect of tire waste and red mud waste to achieve the technical effect of improving the mechanical properties of the material.

[0115] Those skilled in the art should understand that the above embodiments are only for the purpose of clearly illustrating the present disclosure, and are not intended to limit the scope of the present application. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. A method for preparing polyvinyl chloride sealing strip material using red mud and tire waste, characterized in that: The invention is composed of the following raw materials in parts by weight: 100 parts of polyvinyl chloride resin, 1-3 parts of heat stabilizer, 10-40 parts of red mud, 5-20 parts of tire waste, 5-15 parts of plasticizer, 0-3 parts of lubricant, and 1-5 parts of coupling agent; The red mud is surface-modified with polyvinyl chloride (PVC); the surface modification method comprises: a) preparing a tetrahydrofuran solution of PVC; b) mixing the PVC solution with red mud and water, and reacting at 100-120° C. for 20-40 minutes; c) stirring, filtering and drying to obtain the red mud with the surface modified with PVC; The polyvinyl chloride sealing strip material is prepared by mixing various raw materials according to a proportion, and then undergoing supercritical CO2 treatment, plasticization, granulation, re-plasticization, extrusion molding, cooling, and cutting molding to obtain the PVC sealing strip.

2. The polyvinyl chloride sealing strip material according to claim 1, characterized in that: The heat stabilizer is selected from one or more of tribasic lead sulfate, dust-free composite lead salt heat stabilizer, zinc stearate, calcium stearate, and rare earth stabilizer; The plasticizer is selected from one or more of di(2-ethylhexyl) phthalate, di(2-ethylhexyl) adipate, and tri-n-butyl acetyl citrate; The lubricant is selected from one or more of polyethylene wax, paraffin wax, and stearic acid; The coupling agent is selected from one or more of a titanate coupling agent, a silane coupling agent, and an aluminate coupling agent.

3. The polyvinyl chloride sealing strip material according to claim 1, characterized in that: The supercritical CO2 treatment conditions are: 30°C ~ 120°C, 7.5MPa ~ 30MPa, and the treatment time is 1 hour ~ 4 hours.

4. The method for preparing polyvinyl chloride sealing strip material using red mud and tire waste according to any one of claims 1 to 3, characterized in that: The steps include: (1) collecting waste red mud and tire waste, grinding them to obtain red mud powder and tire rubber powder; (2) mixing the ground red mud powder and tire rubber powder with PVC resin, heat stabilizer, plasticizer, lubricant and coupling agent, and treating with supercritical CO2; (3) plasticizing and granulating the material taken out in step (2) to obtain sealing strip pellets; (4) The sealing strip pellets obtained in step (3) are plasticized again and extruded to obtain a semi-finished sealing strip; (5) After molding, the semi-finished sealing strip is cooled and cut to obtain a high temperature resistant PVC polyvinyl chloride sealing strip.

5. The preparation method according to claim 4, characterized in that: In step (1), the mesh number of the red mud raw material is ≥800, and the mesh number of the tire rubber powder is ≥400; in step (3), a twin-screw extruder is used for plasticization; the mixing and plasticization temperature of the twin-screw extruder is 120-160° C., and the granulation extrusion temperature of the twin-screw extruder is 110-140° C.; in step (4), the obtained sealing strip pellets are plasticized again by a single-screw extruder; the body temperature of the single-screw extruder is 130-170° C., and the temperature of the extrusion molding mold is 150-180° C.

6. The preparation method according to claim 4, characterized in that: The mass ratio of PVC for surface modification to red mud powder is (0.5-3):10.

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