An abrasive for cleaning waste plastics, its preparation method and application

Abstract

This invention relates to the field of waste plastic recycling technology, and discloses a friction agent for cleaning waste plastics, its preparation method, and its application. The method includes the following steps: mixing zirconia microspheres of at least two particle sizes with an alkaline dopamine solution and allowing it to stand to obtain dopamine-modified zirconia microspheres; mixing these with a trivalent iron source, a metal salt, water, and a solvent, allowing the mixture to stand, and then subjecting it to an alcoholic reaction and a reduction reaction to obtain zirconia microparticles modified with Fe3O4 nanosheets. This invention uses zirconia microspheres as a friction medium, loading sheet-like nano-Fe3O4 onto the surface of the microspheres to increase the scraping effect on the surface of recycled plastics. Using this friction medium, high-performance recycled plastic products can be obtained in ordinary cleaning equipment.

Description

Technical Field

[0001] This invention relates to the field of waste plastic recycling technology, specifically to a friction agent for cleaning waste plastics, its preparation method, and its application. Background Technology

[0002] Compared to metals and inorganic non-metallic materials, plastics are easier to process and manufacture, lighter in weight, have stable performance, lower manufacturing costs, and higher plasticity, making them widely used in packaging, building materials, daily chemicals, and other fields. Directly discarding waste plastic products after consumption causes environmental pollution and resource waste. Effective recycling, transforming low-value waste plastic products into high-value-added recycled plastic products, can not only reduce the environmental burden but also effectively promote the recycling of waste plastics. The surface of consumer plastic products often contains many strongly adhering contaminants. If not properly cleaned, these contaminants will remain in the recycled plastic during later processing, significantly negatively impacting its overall performance and limiting its downstream applications.

[0003] Patent CN 115648485 A discloses a plastic product recycling and cleaning equipment and method. The equipment includes an abrasive washing tank, a conveying device, a cleaning frame, and an abrasive supply device. The conveying device is used to input the cleaning frame into the abrasive washing tank and output it out of the tank. A first impact component is installed inside the abrasive washing tank. This component includes a rising impact member, a first drive unit for driving the rising impact member to move up and down, a falling impact member, and a second drive unit for driving the falling impact member to move up and down. The cleaning frame passes between the rising and falling impact members. A through hole is provided at the bottom of the cleaning frame for the rising impact member to pass through. The abrasive supply device is used to convey abrasive into the cleaning frame. Plastic products and abrasive are placed into the cleaning frame sequentially. The first impact component impacts the frame, loosening the dirt. After the dirt is loosened, the impact force combined with the huge frictional force generated by the abrasive carries the dirt away. Loosening the dirt first and then generating high frictional force achieves efficient and high-quality cleaning of the plastic products. This patented method uses an impact component to loosen dirt from plastic products, then uses friction to carry the dirt away. This method requires sophisticated equipment, and the impact is not very effective at cleaning stubborn impurities such as paint.

[0004] Patent CN 218890928 U discloses a recyclable plastic scrap washing device, belonging to the technical field of scrap processing equipment. It includes a washing drum with several filter holes at its lower part. A drive mechanism is installed inside the washing drum, and an anti-clogging component is installed inside the washing drum between the drive mechanism and the filter holes. A guide pipe is connected to the top of the washing drum. This invention incorporates the anti-clogging component. During the washing process, the filter screen prevents plastic scraps from falling into the filter holes and causing blockage. The vibration generated by the vibrator is transmitted to the mounting box, and then through the mounting box to the filter screen, causing the filter screen to vibrate and accelerating the falling of washing water mixed with the plastic scraps. During this falling process, some washing water falls onto the guide shroud and flows down along it, exiting through the filter holes along with washing water falling from other locations. While this drum washing device can increase the contact area between the washing water and the plastic, improving washing efficiency, it is not effective in removing strongly adsorbed impurities. Summary of the Invention

[0005] This invention addresses the problems of complex waste plastic cleaning equipment and poor cleaning effect by providing a method for preparing a friction agent for waste plastic cleaning. Zirconia microspheres are used as the friction medium, and sheet-like nano-iron oxide is loaded on the surface of the microspheres to increase the scraping effect on the surface of recycled plastic. With this friction medium, high-performance recycled plastic products can be obtained in ordinary cleaning equipment.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing an abrasive for cleaning waste plastics, comprising the following steps:

[0008] Step 1: Mix zirconia microbeads of at least two particle sizes with an alkaline dopamine solution, let stand, remove, wash and dry to obtain dopamine-modified zirconia microbeads.

[0009] Step 2: Dopamine-modified zirconia microspheres, ferric iron source, metal salt, water and solvent are mixed and allowed to stand. After alcoholic reaction, zirconia microparticles modified with Fe2O3 nanosheets are obtained.

[0010] Step 3: The zirconia microparticles modified with Fe2O3 nanosheets are reduced in a tube furnace to obtain zirconia microparticles modified with Fe3O4 nanosheets.

[0011] This invention uses zirconium beads of different sizes as a friction medium. During stirring, the strong friction between the microbeads and the plastic fragments effectively removes contaminants and foreign matter from the plastic surface. To further increase the friction between the zirconium beads and the plastic fragments, flake-like nano-ferric oxide is modified on the surface of the microbeads. During the cleaning process, the flake-like nano-ferric oxide acts like blades, scraping the plastic fragments as the zirconium beads roll, effectively removing paint and other impurities from the surface of the plastic fragments. Simultaneously, the nano-ferric oxide possesses a certain degree of magnetism, effectively adsorbing metallic foreign matter or metal shavings trapped inside the plastic fragments. This combined effect significantly improves the cleaning efficiency of waste plastic sheets, eliminating the need for large and complex cleaning equipment.

[0012] In step 1, the zirconia microspheres have a particle size of 0.01-6 mm; the particle size difference between zirconia microspheres of different sizes is 0.05-5 mm; preferably, the zirconia microspheres are a combination of 0.5 mm, 1.5 mm, and 5 mm particle sizes. A reasonable ratio of zirconia microspheres of different sizes can effectively fill the gaps between them and plastic fragments of different sizes, thereby effectively increasing the contact area and improving friction efficiency.

[0013] More preferably, the mass ratio of 0.5mm, 1.5mm, and 5mm zirconia microspheres is 5–15:20–40:40–60. The combination of zirconia microspheres of different sizes in a specific mass ratio allows for effective friction against the surfaces and edges of plastic fragments of varying sizes, achieving deep cleaning.

[0014] The molar concentration of dopamine in the alkaline dopamine solution is 0.001–1 mol / L; the pH of the solution is adjusted to 8–10 by adding Tris buffer; under alkaline conditions, dopamine can polymerize more fully and be coated on the surface of zirconia microspheres.

[0015] The mass ratio of dopamine to zirconium oxide microspheres is 1-5:100.

[0016] In step 1, the standing time is 10-40℃ for 10-30 hours.

[0017] The trivalent iron source includes one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric bromide;

[0018] The metal salt includes one or more of sodium acetate, sodium carbonate, sodium bicarbonate, potassium acetate, potassium carbonate, and potassium bicarbonate, used to adjust the pH value of the solution.

[0019] The solvent in step 2 includes one or more of methanol, ethanol, and n-propanol.

[0020] The mass ratio of the dopamine-modified zirconia microspheres, the ferric iron source, and the metal salt is 3-20:0.5-10:1-10;

[0021] The molar ratio of water to iron ions in the trivalent iron source is (10-100):1; the molar ratio of water to iron ions will regulate the morphology of Fe2O3 nanosheets. Preferably, the molar ratio of water to iron ions in the trivalent iron source is (10-30):1.

[0022] The mass ratio of the solvent to dopamine-modified zirconia microspheres is 1 to 5:1.

[0023] In step 2, the standing time is 12-36 h at 10-40℃; the alcohol thermal reaction is 160-200℃ for 12-24 h.

[0024] In step 3, the reduction reaction is carried out under a hydrogen atmosphere at 400–600°C for 2–8 hours.

[0025] The present invention also provides a friction agent for cleaning waste plastics prepared by the aforementioned preparation method.

[0026] The present invention also provides a method for cleaning waste plastics, comprising the steps of: stirring the abrasive, waste plastic fragments and water in a mixer; after the stirring is completed, removing the plastic fragments, washing them with clean water and drying them to obtain recycled plastics.

[0027] The mass of the friction agent is 20-60% of the waste plastic fragments;

[0028] Preferably, the stirring speed is 30-100 r / min, and the stirring time is at least 20 minutes.

[0029] The cleaning equipment uses a standard stainless steel agitator.

[0030] Preferably, after stirring, the plastic fragments are removed, and a certain amount of calcium chloride can be added to adjust the density of the aqueous solution. The amount of calcium chloride is determined according to the density of the plastic fragments to ensure that the density of the aqueous solution is greater than the density of the plastic fragments, but less than the density of the cleaning agent. This achieves the purpose of separating the plastic fragments and the cleaning agent through the aqueous solution. The waste plastic fragments include, but are not limited to, waste plastic fragments made of materials such as polysulfone, polyetheretherketone, polyphenylene sulfide, polyimide, and polybenzimidazole.

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

[0032] (1) In this invention, zirconium oxide microspheres are used as friction medium. The strong friction of microspheres with different particle sizes is used to remove contaminants and foreign matter from the surface of plastic fragments. Reduced iron oxide nanosheets are modified on the surface of the microspheres. The nanosheets can be used to scrape like blades, and the magnetic adsorption of iron oxide can be used to remove metallic impurities, which greatly improves the cleaning effect of plastic fragments.

[0033] (2) In this invention, zirconium oxide microspheres modified with iron oxide nanosheets are mixed and cleaned with waste plastic fragments by ordinary stirring. Without the need for complicated cleaning equipment, a high-efficiency cleaning effect can be achieved, and the mechanical properties of the recycled plastic products are good. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0035] All raw materials used in the following specific implementation methods were purchased from the market.

[0036] Example 1 (Particle size ratio: 15:30:55)

[0037] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 15:30:55) to the dopamine solution. Adjust the pH of the solution to 9 by adding Tris buffer. After standing at room temperature for 24 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0038] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 170℃ and reacted for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0039] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0040] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of polysulfone (PPSU) bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The PPSU fragments on the surface were collected, washed with clean water, dried, and then used for extrusion granulation. The washed PPSU fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0041] Example 2 (Particle size ratio: 10:35:55)

[0042] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 10:35:55) to the dopamine solution. Adjust the pH of the solution to 10 by adding Tris buffer. After standing at room temperature for 10 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0043] Twenty parts of the above-mentioned zirconia microspheres were added to 30 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The prepared mixed solution was then poured into a stainless steel reactor, and the temperature was raised to 170℃, and the reaction was carried out for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0044] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0045] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0046] Example 3 (Particle size ratio: 5:35:60)

[0047] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 5:35:60) to the dopamine solution. Adjust the pH of the solution to 9.5 by adding Tris buffer. After standing at room temperature for 24 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0048] Twenty parts of the above-mentioned zirconia microspheres were added to 60 parts of ethanol solution, along with 10 parts of trivalent FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the trivalent iron source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 200℃ and reacted for 18 hours. After the reaction was completed, the zirconia microspheres were washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0049] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0050] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0051] Example 4 (FeCl3 content)

[0052] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.1 mm: 1.5 mm: 5 mm = 15:30:55) to the dopamine solution. Adjust the pH of the solution to 9 by adding Tris buffer. After standing at room temperature for 18 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0053] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 7 parts of trivalent FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the trivalent iron source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The prepared mixed solution was then poured into a stainless steel reactor, and the temperature was raised to 180℃, and the reaction was carried out for 24 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0054] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0055] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0056] Example 5 (FeCl3 content)

[0057] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 15:30:55) to the dopamine solution. Adjust the pH of the solution to 8.5 by adding Tris buffer. After standing at room temperature for 12 hours, remove the zirconia beads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0058] Twenty parts of the above-mentioned zirconia beads were added to 50 parts of ethanol solution, along with 4 parts of trivalent FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the trivalent iron source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 190℃ and reacted for 12 hours. After the reaction was completed, the zirconia microbeads were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microbeads modified with Fe2O3 nanosheets.

[0059] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0060] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0061] Example 6 (Water Content)

[0062] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 15:30:55) to the dopamine solution. Adjust the pH of the solution to 9 by adding Tris buffer. After standing at room temperature for 24 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0063] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 10:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 170℃ and reacted for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0064] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0065] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0066] Example 7 (Water Content)

[0067] Prepare 1000 portions of 0.01 mol / L dopamine solution. Add 100 portions of zirconia microbeads of different sizes (0.5 mm: 1.5 mm: 5 mm = 15:30:55) to the dopamine solution. Adjust the pH of the solution to 9 by adding Tris buffer. After standing at room temperature for 24 hours, remove the zirconia microbeads. Wash them three times each with water and ethanol, and then dry them in an oven.

[0068] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 2:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The prepared mixed solution was then poured into a stainless steel reactor, and the temperature was raised to 170℃, and the reaction was carried out for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0069] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0070] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0071] Comparative Example 1 (without Fe3O4)

[0072] Fifty parts of zirconia microspheres of different particle sizes (0.5 mm: 1.5 mm: 5 mm = 15:30:55), 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with clean water, dried, and then used for extrusion granulation. The washed PPSU fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, finally yielding regenerated polysulfone particles.

[0073] Comparative Example 2 (Single Particle Size)

[0074] Prepare 1000 portions of 0.01 mol / L dopamine solution, add 100 portions of 0.5 mm zirconia microbeads to the dopamine solution, add Tris buffer to adjust the pH of the solution to 9, let it stand at room temperature for 24 hours, and then remove the zirconia microbeads. Wash them three times with water and three times with ethanol, and then dry them in an oven.

[0075] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 170℃ and reacted for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0076] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0077] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0078] Comparative Example 3 (Single Large Particle Size)

[0079] Prepare 1000 portions of 0.01 mol / L dopamine solution, add 100 portions of 5 mm zirconia microbeads to the dopamine solution, add Tris buffer to adjust the pH of the solution to 9, let it stand at room temperature for 24 hours, and then remove the zirconia microbeads. Wash them three times with water and three times with ethanol, and then dry them in an oven.

[0080] Twenty parts of the above-mentioned zirconia microspheres were added to 45 parts of ethanol solution, along with 10 parts of FeCl3, 10 parts of sodium acetate, and an appropriate amount of water (the molar ratio of water to iron ions in the ferric source was 20:1). After stirring and mixing thoroughly, the mixture was allowed to stand at room temperature (25℃) for 24 hours to obtain a mixed solution. The entire prepared mixed solution was poured into a stainless steel reactor, and the temperature was then raised to 170℃ and reacted for 12 hours. After the reaction was completed, the zirconia microspheres were removed, washed three times each with ethanol and water, and finally dried to obtain zirconia microspheres modified with Fe2O3 nanosheets.

[0081] Zirconia microspheres modified with Fe2O3 nanosheets were subjected to high-temperature reduction in a CVD tube furnace (600℃, 8h, H2 5sccm, Ar 95sccm) to convert Fe2O3 nanosheets into magnetic Fe3O4 nanosheets, ultimately obtaining zirconia microspheres modified with Fe3O4 nanosheets.

[0082] 50 parts of Fe3O4 nanosheet-modified zirconia microspheres, 100 parts of PPSU baby bottle fragments, and 300 parts of water were added to a stainless steel stirrer and stirred for 40 minutes at a speed of 50 rpm. The stirred mixture was then added to a 30% CaCl2 aqueous solution. The polysulfone fragments on the surface were collected, washed with water, dried, and then used for extrusion granulation. The washed polysulfone fragments were fed into a twin-screw extruder for granulation extrusion at extrusion temperatures of 300 / 310 / 320 / 340 / 350 / 350 / 350 / 350 / 340℃ and a speed of 300 rpm, ultimately yielding regenerated polysulfone particles.

[0083] The recycled polysulfone particles prepared in the examples and comparative examples were used to prepare test strips according to GB / T1040-2006 and GB / T1043-2008 standards. Mechanical properties were tested. For the black spot test, 10g of particles were taken and visually observed under a 5x magnifying glass. The size and number of black spots were confirmed using a film card for comparison. The test results are shown in Table 1.

[0084] Table 1. Properties of recycled polysulfone particles in the examples and comparative examples.

[0085]

[0086] As can be seen from Table 1, compared with Examples 1-3 and Comparative Examples 2-3, the mixture of zirconia microspheres with different particle sizes can significantly improve the mechanical properties of regenerated polysulfone compared with zirconia microspheres of a single particle size, and the black spots of impurities in the regenerated product are also less and smaller.

[0087] The results of Examples 1 and 4-5 show that the amount of iron precursor affects the amount of iron nanosheets, and therefore also affects the cleaning effect on waste plastics. Comparative Example 1 shows that when there is no scraping action from Fe3O4 nanosheets, the cleaning effect is significantly reduced, and the mechanical properties of the recycled product are also significantly reduced.

[0088] As can be seen from the results of Examples 1 and 6-7, reducing the amount of water increases the concentration of iron salts, causing the Fe2O3 nanosheets to deposit too quickly in the alcohol thermal reaction, resulting in agglomeration, which reduces the cleaning effect and affects the performance of recycled plastic products.

Claims

1. A method for preparing an abrasive for cleaning waste plastics, characterized in that, Including the following steps: Step 1: Mix zirconia microbeads of at least two particle sizes with an alkaline dopamine solution, let stand, remove, wash and dry to obtain dopamine-modified zirconia microbeads. Step 2: Dopamine-modified zirconia microspheres, ferric iron source, metal salt, water and solvent are mixed and allowed to stand, and then subjected to alcohol thermal reaction to obtain zirconia microparticles modified with Fe2O3 nanosheets; the mass ratio of dopamine-modified zirconia microspheres, ferric iron source and metal salt is 3-20:0.5-10:1-10; Step 3: The zirconia microparticles modified with Fe2O3 nanosheets are reduced in a tube furnace to obtain zirconia microparticles modified with Fe3O4 nanosheets. The mass ratio of the zirconia microspheres with particle sizes of 0.5 mm, 1.5 mm, and 5 mm is 5–15: 20–40: 40–60.

2. The method for preparing the abrasive for cleaning waste plastics according to claim 1, characterized in that, The molar concentration of dopamine in the dopamine solution was 0.001–1 mol / L; the pH of the solution was adjusted to 8–10 by adding Tris buffer. And / or, the mass ratio of dopamine to zirconium oxide microbeads is 1-5:100; And / or, in step 1, the standing time is 10-40℃ for 10-30 hours.

3. The method for preparing the abrasive for cleaning waste plastics according to claim 1, characterized in that, The trivalent iron source includes one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric bromide; And / or, the metal salt includes one or more of sodium acetate, sodium carbonate, sodium bicarbonate, potassium acetate, potassium carbonate, and potassium bicarbonate; And / or, the solvent includes one or more of methanol, ethanol and n-propanol; And / or, the molar ratio of water to iron ions in the trivalent iron source is (10-100):1; And / or, the mass ratio of the solvent to dopamine-modified zirconia microspheres is 1 to 5:

1.

4. The method for preparing the abrasive for cleaning waste plastics according to claim 1, characterized in that, In step 2, the standing time is 12-36 h at 10-40℃; the alcohol thermal reaction is 160-200℃ for 12-24 h.

5. The method for preparing the abrasive for cleaning waste plastics according to claim 1, characterized in that, In step 3, the reduction reaction is carried out under a hydrogen atmosphere at 400–600°C for 2–8 hours.

6. The abrasive for cleaning waste plastics prepared by the preparation method according to any one of claims 1-5.

7. A method for cleaning waste plastics, characterized in that, The process includes the following steps: mixing the abrasive as described in claim 6, waste plastic fragments, and water in a mixer; after mixing, removing the plastic fragments, rinsing them with clean water, and drying them to obtain recycled plastic.

8. The waste plastic cleaning method according to claim 7, characterized in that, The mass of the friction agent is 20-60% of the waste plastic fragments; and / or, the stirring speed is 30-100 r / min, and the stirring time is at least 20 min.

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