A method for reducing the content of acetaldehyde in a pet material, a foam filter and a method for preparing the same

Abstract

The application relates to the technical field of polymer material preparation processes, and discloses a method for reducing the content of acetaldehyde in PET material, a foam filter screen and a preparation method thereof. The preparation of the foam filter screen comprises the following steps: step 1, a stainless steel filter screen is immersed in a dopamine solution to adhere dopamine; step 2, copper nano precursor is loaded on the surface of the filter screen; step 3, spiral carbon fibers are grown on the stainless steel filter screen by a chemical vapor deposition method; step 4, the filter screen is treated by oxidation with a strong acid solution; and step 5, the foam filter screen after oxidation is treated by amination to obtain the foam filter screen. The spiral nanofibers are grown in situ on the surface of the stainless steel filter screen by the CVD method, and primary amino groups or secondary amino groups are grafted on the surface of the fibers, so that the acetaldehyde in the PET melt can be adsorbed on the filter screen to reduce the content of acetaldehyde in the PET. The foam filter screen does not need to be added into the PET melt, and will not affect any performance of the base body, and the method for removing acetaldehyde is simple, fast and efficient.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation technology, specifically to a method for reducing the acetaldehyde content in PET materials, a foam filter and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET) possesses good film-forming properties, optical transparency, mechanical properties, and impermeability, making it widely used in packaging materials. During the granulation process, PET flakes undergo degradation and oxidation under the high-temperature shearing of a twin-screw extruder, generating high levels of acetaldehyde. Currently, for safety reasons, the government strictly controls the acetaldehyde content in PET particles; therefore, it is necessary to strictly control the acetaldehyde content in recycled PET particles.

[0003] Currently, the method to reduce the acetaldehyde content in recycled PET particles is to remove the internal acetaldehyde gas through solid-phase polycondensation (SSP) technology. This method involves pre-crystallizing the recycled PET particles, then placing them in a high-temperature drum under high vacuum or nitrogen protection for high-temperature baking to remove the acetaldehyde from the PET particles.

[0004] For example, CN112111054A discloses a method for producing low-acetaldehyde PET, including melt polymerization, crystallization, preheating, and polycondensation thickening. Although this process can reduce the acetaldehyde content in PET particles to less than 1 ppm, it is time-consuming, generally requiring more than 12 hours, and places high demands on the equipment. Currently, SSP equipment is basically dependent on imports, and domestically produced equipment is difficult to meet production needs.

[0005] In addition, there are methods that use acetaldehyde removal agents, such as CN111234474A which discloses an acetaldehyde removal agent for PET bottles and a method for removing acetaldehyde from PET bottles. By adding anthranilic acid and / or anthranilamide to react with acetaldehyde, the problem of high acetaldehyde value in PET packaging is effectively solved. However, the acetaldehyde removal effect varies, and the added new additives are very likely to affect the mechanical properties and thermal properties of the matrix resin itself, producing side effects. Summary of the Invention

[0006] This invention addresses the issue of excessively high acetaldehyde content during PET material preparation by providing a foam filter that rapidly reduces the acetaldehyde content of PET materials without the addition of acetaldehyde removal agents. This foam filter contains amination-modified helical nanofibers, which can quickly and effectively absorb acetaldehyde from the PET melt, resulting in PET materials with low acetaldehyde content.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a foam filter screen that reduces the acetaldehyde content in PET material, comprising the following steps:

[0009] Step 1: Immerse the stainless steel filter screen in a dopamine solution, adjust the pH of the solution to alkaline, and then wash and dry the filter screen.

[0010] Step 2: Add the stainless steel filter screen treated in Step 1 to a mixed solution of copper chloride and magnesium oxide, add potassium sodium tartrate aqueous solution to the mixed solution for reaction, remove the stainless steel filter screen, wash and dry it to obtain a stainless steel filter screen loaded with nano copper precursor.

[0011] Step 3: The stainless steel filter screen loaded with the nano-copper precursor is grown with helical carbon fibers by chemical vapor deposition (CVD) in a carbon source environment to obtain a foam filter screen loaded with helical fibers.

[0012] Step 4: Place the foam filter screen with spiral fibers in a strong acid solution for oxidation treatment, and wash and dry the filter screen to obtain an oxidized foam filter screen;

[0013] Step 5: Immerse the oxidized foam filter in a polyamine treatment solution for amination treatment, and then wash and dry to obtain the foam filter.

[0014] This invention utilizes CVD to grow helical nanofibers in situ on the surface of a stainless steel filter screen. During the production process, the helical nanofibers entangle with each other to form a porous three-dimensional foam covering the filter screen surface, significantly increasing the filtration area while maintaining good mechanical strength. Furthermore, the surface of the helical carbon nanofibers in this filter screen is grafted with primary or secondary amine structures, enabling them to react with acetaldehyde gas in the PET melt as it passes through, causing acetaldehyde to be adsorbed onto the filter screen and thus reducing the acetaldehyde content in the PET. This foam filter screen is installed together with the stainless steel filter screen at the die head of the extruder, requiring no additional equipment or devices. The PET melt passes through the filter screen during granulation and extrusion without affecting any properties of the matrix itself. Compared to solid-phase thickening methods for acetaldehyde removal, this method is simpler, faster, and more efficient.

[0015] The stainless steel filter screen mentioned in step 1 is a stainless steel woven mesh or a round hole mesh, such as 304 stainless steel, with a mesh size of 10 to 100 mesh, and more preferably 20 to 80 mesh.

[0016] The concentration of the dopamine solution in step 1 is 0.01-0.1 mol / L, more preferably 0.03-0.06 mol / L; the dopamine soaking in step 1 is to adhere dopamine to the surface of the filter screen, and use its viscosity to uniformly bond the copper tartrate catalyst precursor in step 2, so that more helical carbon nanofibers can be grown on the surface of the filter screen.

[0017] In step 1, the pH of the solution is adjusted using Tris buffer or NaOH to 8-8.5. Under alkaline conditions, dopamine exists in the form of phenol-ketone and amine. The OH and NH bonds in these two forms can react with other electrophilic functional groups, thus making them easy to polymerize. Moreover, the amine group can increase the interaction force between the polymer and metal ions, forming a more stable complex.

[0018] The soaking time in step 1 is 10-30 hours, and the soaking temperature is room temperature;

[0019] In step 2, the concentration of copper chloride in the mixed solution is 0.001-10 mol / L, more preferably 0.005-1 mol / L; the mass ratio of copper chloride to magnesium oxide is 1:1-10:1, more preferably 1:1-5:1; the ratio of the two will affect the morphology of the spiral fiber. If it exceeds the appropriate range, the spiral fiber will transition into a straight fiber, resulting in an uneven spiral fiber morphology.

[0020] In step 2, the concentration of potassium sodium tartrate in the aqueous solution is 0.001-1 mol / L, more preferably 0.005-1 mol / L; if the concentration is too low, nanofibers cannot be generated; if the concentration is too high, the generated catalyst nano-copper will accumulate, the catalytic efficiency will decrease, and the growth of helical fibers will also be affected.

[0021] In step 2, the molar ratio of potassium sodium tartrate to copper chloride is 1:1 to 1:5;

[0022] In step 2, after adding potassium sodium tartrate, the reaction lasts for 30–120 minutes, and the temperature throughout the process is 25–40°C.

[0023] In step 3, the carbon source includes one or more of acetylene, ethylene, and methane;

[0024] Step 3 involves growing helical carbon fibers by heating to 250-300℃ and holding for 30-90 minutes, followed by high-temperature carbonization treatment at 800-1000℃ for 30-60 minutes.

[0025] Step 3, the chemical vapor deposition method for growing helical carbon fibers, specifically includes: placing the dried copper nanoparticle precursor-loaded stainless steel filter screen in a ceramic boat; purging the air in the tube furnace with argon gas; slowly heating the tube furnace to 250-300℃; then switching the gas to carbon source gas; reacting for 30-90 minutes; stopping the reaction by turning off the carbon source gas and purging with argon gas; then raising the furnace temperature to 800-1000℃ and holding it at that temperature for 30-60 minutes; turning off the heating after the reaction; and cooling the sample to room temperature with the furnace to obtain the helical fiber-loaded foam filter screen.

[0026] In step 3, the spiral carbon nanofibers grown on the stainless steel filter screen have a diameter of 10-100 nm and a length of 10-50 μm, more preferably a diameter of 10-30 nm and a length of 30-45 μm.

[0027] In step 4, the strong acid solution is a mixture of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated HNO3 to concentrated H2SO4 is 1:1 to 1:5, more preferably 1:2 to 1:3. This process involves oxidizing carbon nanofibers using a strong acid, utilizing the strong oxidizing properties of concentrated HNO3 and concentrated H2SO4 to graft oxygen-containing groups such as carboxyl and hydroxyl groups onto the fiber surface.

[0028] In step 4, the oxidation treatment temperature is 35-45℃ and the oxidation treatment time is 0.5-2h; the higher the oxidation treatment temperature, the longer the reaction time.

[0029] In step 5, the polyamine treatment agent is a polyamine containing two or more primary or secondary amino groups.

[0030] Preferably, the polyamine treatment agent comprises one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine;

[0031] Preferably, the molar concentration of the polyamine treatment agent solution is 0.01–5 mol / L, more preferably 0.1–1 mol / L. The degree of amination of the fiber depends on the amount of reactive groups between the filter and acetaldehyde; theoretically, a higher degree of amination is better, but it also results in higher acetaldehyde adsorption efficiency.

[0032] In step 5, the amination temperature is 60-90℃ and the amination time is 1-6h. The higher the amination temperature and the longer the amination time, the greater the amount of amine grafts on the fiber surface, the higher the degree of amination, and the higher the acetaldehyde adsorption efficiency.

[0033] Preferably, after soaking or reaction in steps 1, 2, 4, and 5, the filter screen is cleaned by washing it 1-3 times with any one or more solvents, including anhydrous ethanol and water, to remove impurities such as solvents from each step and unreacted raw materials.

[0034] Preferably, the drying process after cleaning in steps 1, 2, 4, and 5 is carried out at 80-120°C for 10-36 hours to remove water, solvents, etc.

[0035] Preferably, the soaking in steps 1, 2, 4, and 5 is carried out with a solution volume sufficient to completely submerge the stainless steel filter screen or foam filter screen.

[0036] Preferably, the solvents used in the solutions in each step are conventional solvents that can dissolve the corresponding raw materials. For example, the solvent used in the dopamine solution in step 1 includes water; the solvent used in the mixed solution of copper chloride and magnesium chloride in step 2 includes water; and the solvent used in the polyamine treatment agent solution in step 5 includes water.

[0037] The present invention also provides a foam filter screen for reducing the acetaldehyde content in PET material prepared according to the preparation method.

[0038] This invention also provides a method for reducing the acetaldehyde content in PET materials, comprising the steps of:

[0039] Step 1: Embed the foam filter screen in the stainless steel filter screen groove and place it at the twin-screw extruder head; for example, the foam filter screen is a circle with a diameter of 130mm and a thickness of 2-5mm;

[0040] Step 2: Use a twin-screw extruder with the twin-screw die head to melt-extrude PET raw material to obtain PET material with low acetaldehyde content.

[0041] This invention places a foam filter screen loaded with amination-modified helical carbon nanofibers at the die head of PET raw material melt extrusion. When the PET melt passes through, the primary and secondary amino groups on the fibers can react with acetaldehyde molecules in the PET, adsorbing acetaldehyde molecules and leaving them on the foam filter screen, thereby reducing the acetaldehyde content in the melt and causing the acetaldehyde content in the PET to decrease rapidly.

[0042] Preferably, the foam filter screen after adsorbing acetaldehyde is calcined in a high-temperature furnace at 500-800℃ under argon protection to remove acetaldehyde. After oxidation treatment (step 4) and amination treatment (step 5), it can be recycled and reused.

[0043] The PET raw materials include virgin PET and recycled PET, which includes all forms of recycled PET, such as PET film, PET sheet, PET bottle flakes, etc.

[0044] The melt extrusion temperature is 240-300℃, and the screw speed is 200-350rpm.

[0045] The acetaldehyde content in the PET material obtained by the method of this invention is below 1 ppm.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The present invention grows spiral nanofibers in situ on the surface of stainless steel filter screen by CVD method, and grafts primary or secondary amino groups on the surface of the screen after ammoniation treatment. The resulting foam filter screen is used for acetaldehyde removal from PET melt, which is highly efficient and has no effect on PET substrate, and can obtain PET material with low acetaldehyde content.

[0048] (2) In this invention, the spiral nanofibers entangle with each other during the production process to form porous three-dimensional foam that covers the filter screen surface, significantly increasing the filter area and providing good mechanical strength. After high-temperature carbonization, the spiral nanofibers are further transformed into spiral carbon nanofibers. After carbonization, nanopores appear on the surface of the carbon fibers, further increasing their specific surface area and fiber strength. The product is less prone to breakage and damage when used at the die head of PET melt extrusion.

[0049] (3) The foam filter prepared in this invention is used to remove small acetaldehyde molecules in PET melt. After adsorbing acetaldehyde gas, it can be placed in a high-temperature furnace for calcination to remove acetaldehyde. After surface modification, it can be reused. Attached Figure Description

[0050] Figure 1 This is a SEM image of the spiral fiber foam prepared by CVD in Example 1. Detailed Implementation

[0051] 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.

[0052] All raw materials used in the following specific embodiments were purchased from the market. The PET 3A bottle flakes were purchased from Zhejiang Haili Environmental Protection Technology Co., Ltd., with an intrinsic viscosity of 0.82 dl / g. The stainless steel filter screen was purchased from Wenzhou Xuzhan Chemical Fiber Equipment Factory, with a mesh size of 200.

[0053] Example 1

[0054] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0055] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0056] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0057] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0058] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times with water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen for removing acetaldehyde. Its microstructure is as follows. Figure 1 As shown.

[0059] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0060] Example 2

[0061] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0062] Step 2: Prepare 100 parts of 0.02 mol / L copper chloride solution and add 60 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.02 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on nano-copper precursor.

[0063] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0064] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0065] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0066] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0067] Example 3

[0068] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0069] Step 2: Prepare 100 parts of 0.01 mol / L copper chloride solution and add 30 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.02 mol / L potassium sodium tartrate solution dropwise to the solution. After allowing it to react fully, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and then place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on nano-copper precursor.

[0070] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0071] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0072] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0073] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0074] Example 4

[0075] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0076] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0077] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, then purge the air from the tube furnace with argon gas (50 mL / min); then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 60 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0078] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0079] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0080] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0081] Example 5

[0082] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0083] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0084] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, then purge the air from the tube furnace with argon gas (50 mL / min); then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 120 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0085] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0086] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0087] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0088] Example 6

[0089] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0090] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0091] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0092] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0093] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.0 mol / L ethylenediamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0094] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0095] Example 7

[0096] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0097] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0098] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0099] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0100] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 0.8 mol / L diethylenetriamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0101] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0102] Example 8

[0103] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0104] Step 2: Prepare 100 parts of 0.03 mol / L copper chloride solution and add 120 parts of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution, allowing it to react fully. Then, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on the nano-copper precursor.

[0105] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0106] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0107] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 0.8 mol / L triethylenetetramine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0108] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0109] Comparative Example 1

[0110] Without placing a foam filter screen in the die head of the twin-screw extruder, PET melt extrusion is performed using a conventional die head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, and the screw speed is 300 rpm. After extrusion, the melt is cooled, granulated, and dried to finally obtain recycled PET particles.

[0111] Comparative Example 2

[0112] Step 1: Prepare 150 portions of 0.01 mol / L dopamine solution. Place a stainless steel filter template in the solution and react at room temperature for 24 hours, then remove it. After washing with water and ethanol, dry it in an oven at 100°C for 12 hours.

[0113] Step 2: Prepare 100 parts of 0.0005 mol / L copper chloride solution and add 1 part of MgO. After stirring thoroughly for 10 min, add the stainless steel filter screen treated in Step 1. Slowly add 100 parts of 0.01 mol / L potassium sodium tartrate solution dropwise to the solution. After allowing it to react fully, remove the stainless steel filter screen template, wash it repeatedly with water and anhydrous ethanol three times, and then place it in an oven for thorough drying (100℃, 24 h) to obtain a stainless steel filter screen supported on nano-copper precursor.

[0114] Step 3: Place the dried stainless steel filter screen from Step 2 into a ceramic boat, and then purge the air from the tube furnace with argon gas (50 mL / min). Then switch the gas to acetylene (30 mL / min), and slowly heat the tube furnace to 271℃ (<1℃ / min) for 30 min. Stop the reaction by turning off the acetylene and argon gas. Subsequently, slowly increase the furnace temperature (heating rate 5℃ / min) to 800℃ and hold for 30 min. After the holding time, turn off the heating and continue purging with argon gas to cool the sample to room temperature in the furnace, obtaining a foam filter screen loaded with helical carbon fibers.

[0115] Step 4: Prepare 100 portions of concentrated HNO3 / H2SO4 mixed solution (v / v = 1:2), which contains concentrated sulfuric acid (HNO3, 63%) and concentrated nitric acid (H2SO4, 98%). Place the foam filter screen loaded with spiral carbon fibers obtained in Step 3 into the strong acid mixture and react it at a constant temperature of 40°C in a water bath for 1 hour. After that, take it out, wash it three times with water and three times with ethanol respectively, and then dry it (100°C, 24 hours) to obtain an oxidized foam filter screen.

[0116] Step 5: The foam filter screen oxidized in Step 4 is completely immersed in a 1.5 mol / L tetraethylenepentamine solution for amination treatment for 3 hours at a temperature of 90℃. After treatment, the foam is washed three times in water and ethanol to remove excess reactants, and then dried in an oven (100℃, 24 hours) to finally obtain the foam filter screen used for removing acetaldehyde.

[0117] Step 6: The foam filter prepared in Step 5 is embedded in a stainless steel filter groove in a circular shape with a diameter of 130 mm and a thickness of 2-5 mm, and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes are added to the twin-screw extruder for melt extrusion. The temperatures of each section of the extruder are set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, with a screw speed of 300 rpm. After extrusion, the melt is cooled, granulated, and dried to obtain recycled PET particles.

[0118] Comparative Example 3

[0119] Following the preparation process of Example 1, the amination process in step 5 was omitted. The foam filter screen oxidized in step 4 was directly embedded in a stainless steel filter screen groove and placed at the twin-screw extruder head. 100 parts of recycled PET bottle flakes were added to a twin-screw extruder for melt extrusion. The temperatures of each section of the extruder were set to 220℃, 230℃, 235℃, 235℃, 240℃, 240℃, 240℃, 240℃, and 250℃, respectively, and the screw speed was 300 rpm. After extrusion, the melt was cooled, granulated, and dried to finally obtain recycled PET particles.

[0120] The acetaldehyde content of the recycled PET particles prepared in the examples and comparative examples was determined according to SH / T 1817-2017, and the results are shown in Table 1.

[0121] Table 1. Acetaldehyde content in recycled PET particles prepared in the examples and comparative examples.

[0122]

[0123] As can be seen from the data in Table 1, the acetaldehyde content in Examples 1-8 was significantly reduced compared to Comparative Examples 1-3. In Comparative Example 2, the insufficient amount of carbon fiber precursor and the lack of amination process both significantly reduced the acetaldehyde removal efficiency. In Examples 1-3, the amounts of copper chloride and magnesium oxide were gradually reduced, and the amount of carbon fiber produced also decreased, thus reducing the acetaldehyde removal rate.

[0124] As can be seen in Examples 1, 4, and 5, the longer the carbon fiber deposition time, the more carbon fiber is loaded on the surface of the stainless steel filter, which is more conducive to improving the removal effect of acetaldehyde.

[0125] As can be seen in Examples 1, 6, 7, and 8, using more diverse amine treatment agents during amination treatment yields better results, enabling the loading of more amino groups onto the spiral carbon fibers and resulting in better acetaldehyde removal.

Claims

1. A method for the production of a foam filter for reducing the acetaldehyde content in PET material, characterized in that, The preparation method comprises the following steps: Step 1, immerse the stainless steel filter screen in a dopamine solution, adjust the pH of the solution to be alkaline, and then wash and dry the filter screen after soaking; Step 2, add the stainless steel filter screen treated in step 1 to a mixed solution of copper chloride and magnesium oxide, add a potassium sodium tartrate aqueous solution dropwise to the mixed solution to react, and then take out the stainless steel filter screen and wash and dry it to obtain a nano-copper precursor loaded stainless steel filter screen; Step 3, grow helical carbon fibers on the nano-copper precursor loaded stainless steel filter screen by chemical vapor deposition in a carbon source environment to obtain a helical fiber loaded foam filter screen; Step 4, oxidize the helical fiber loaded foam filter screen in a strong acid solution, wash and dry the filter screen to obtain an oxidized foam filter screen; Step 5, immerse the oxidized foam filter screen in a polyamine treatment agent solution for amination treatment, and then wash and dry it to obtain the foam filter screen. In step 2, the mass ratio of copper chloride to magnesium oxide is 1:1-10:

1.

2. The method of claim 1, wherein the foam filter is prepared by the steps of: a) providing a PET material; b) adding a reducing agent to the PET material; c) adding a blowing agent to the PET material; d) heating the PET material to a temperature of 200 °C to 300 °C; and e) forming a foam filter from the PET material. In step 1, the concentration of the dopamine solution is 0.01-0.1 mol / L; And / or, in step 1, the pH of the solution is adjusted by using a Tris buffer solution, and the pH of the solution is adjusted to 8-8.5; And / or, in step 1, the soaking time is 10-30 h, and the soaking temperature is room temperature.

3. The method of claim 1, wherein the foam filter is prepared by the steps of: a) providing a PET material; b) adding a reducing agent to the PET material; c) adding a blowing agent to the PET material; d) heating the PET material to a temperature of 200 °C to 300 °C; and e) forming a foam filter from the PET material. In step 2, the concentration of copper chloride in the mixed solution is 0.001-10 mol / L; And / or, in step 2, the concentration of potassium sodium tartrate in the potassium sodium tartrate aqueous solution is 0.001-1 mol / L; And / or, in step 2, the molar ratio of potassium sodium tartrate to copper chloride is 1:1-1:5; And / or, in step 2, after the potassium sodium tartrate is added dropwise, the reaction is carried out for 1-3 h at room temperature.

4. The method of claim 1, wherein the foam filter is prepared by the steps of: a) providing a PET material; b) adding a reducing agent to the PET material; c) adding a blowing agent to the PET material; d) heating the PET material to a temperature of 200 °C to 300 °C; and e) forming a foam filter from the PET material. In step 3, the carbon source includes one or more of acetylene, methane, and ethylene; And / or, in step 3, the growth of helical carbon fibers includes heating to 250-300℃ for 30-90 min, and then heating to 800-1000℃ for carbonization treatment for 30-60 min.

5. The method for preparing a foam filter screen for reducing acetaldehyde content in PET material according to claim 1, characterized in that, In step 4, the strong acid solution is a mixed solution of concentrated nitric acid and concentrated sulfuric acid, and the volume ratio of concentrated HNO3 to concentrated H2SO4 is 1:1-1:5; And / or, in step 4, the oxidation treatment temperature is 35-45℃, and the oxidation treatment time is 0.5-2 h.

6. The method for preparing a foam filter screen for reducing acetaldehyde content in PET material according to claim 1, characterized in that, In step 5, the polyamine treatment agent is a polyamine containing two or more primary or secondary amino groups; And / or, the molar concentration of the polyamine treatment agent solution is 0.01-5 mol / L.

7. The method of claim 1 or 6, wherein the method is characterized by, In step 5, the polyamine treatment agent includes one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; And / or, in step 5, the amination treatment temperature is 60-90℃, and the amination treatment time is 1-6 h.

8. A foam filter screen with reduced acetaldehyde content in PET material prepared by the preparation method of any one of claims 1-7.

9. A method of reducing the content of acetaldehyde in a PET material, characterized in that, The preparation method comprises the following steps: Step 1, embed the foam filter screen of claim 8 in a stainless steel filter screen slot, and place it at a double screw machine head; Step 2, melt and extrude PET raw materials by using a double screw extruder containing the double screw machine head to obtain a PET material with low acetaldehyde content.

10. The method of claim 9, wherein the PET material is a PET bottle. 10 The melt extrusion temperature is 240-300℃, and the screw rotation speed is 200-350 rpm.

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