CN117086066A - Method for treating and recycling homo-polypropylene based on solvent - Google Patents
Method for treating and recycling homo-polypropylene based on solvent Download PDFInfo
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- CN117086066A CN117086066A CN202311053579.3A CN202311053579A CN117086066A CN 117086066 A CN117086066 A CN 117086066A CN 202311053579 A CN202311053579 A CN 202311053579A CN 117086066 A CN117086066 A CN 117086066A
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- 238000000034 method Methods 0.000 title claims abstract description 50
- 239000002904 solvent Substances 0.000 title claims abstract description 45
- 229920005629 polypropylene homopolymer Polymers 0.000 title claims abstract description 23
- 238000004064 recycling Methods 0.000 title abstract description 8
- 239000004743 Polypropylene Substances 0.000 claims abstract description 70
- -1 polypropylene Polymers 0.000 claims abstract description 63
- 229920001155 polypropylene Polymers 0.000 claims abstract description 58
- 239000000463 material Substances 0.000 claims abstract description 56
- 239000004033 plastic Substances 0.000 claims abstract description 47
- 229920003023 plastic Polymers 0.000 claims abstract description 47
- 238000000605 extraction Methods 0.000 claims abstract description 37
- 238000011084 recovery Methods 0.000 claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 238000000926 separation method Methods 0.000 claims abstract description 10
- 230000008569 process Effects 0.000 claims description 27
- 239000012535 impurity Substances 0.000 claims description 21
- 239000013502 plastic waste Substances 0.000 claims description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 claims description 9
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 7
- 238000005516 engineering process Methods 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 claims description 6
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 4
- 239000000284 extract Substances 0.000 claims description 4
- SCYULBFZEHDVBN-UHFFFAOYSA-N 1,1-Dichloroethane Chemical compound CC(Cl)Cl SCYULBFZEHDVBN-UHFFFAOYSA-N 0.000 claims description 3
- 239000000356 contaminant Substances 0.000 claims description 3
- 238000007667 floating Methods 0.000 claims description 3
- 238000010907 mechanical stirring Methods 0.000 claims description 3
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 3
- 239000002699 waste material Substances 0.000 abstract description 10
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- 239000000126 substance Substances 0.000 abstract description 8
- 238000000746 purification Methods 0.000 abstract description 7
- 239000003344 environmental pollutant Substances 0.000 abstract description 6
- 231100000719 pollutant Toxicity 0.000 abstract description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 4
- 238000003912 environmental pollution Methods 0.000 abstract description 4
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 abstract description 4
- 239000001569 carbon dioxide Substances 0.000 abstract description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 2
- 238000006116 polymerization reaction Methods 0.000 abstract description 2
- 238000002474 experimental method Methods 0.000 description 14
- 239000011347 resin Substances 0.000 description 12
- 229920005989 resin Polymers 0.000 description 12
- 239000000243 solution Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 239000004698 Polyethylene Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000012855 volatile organic compound Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 229920000573 polyethylene Polymers 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 150000005215 alkyl ethers Chemical class 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 230000001877 deodorizing effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000011978 dissolution method Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000000855 fermentation Methods 0.000 description 2
- 230000004151 fermentation Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000000813 microbial effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010411 cooking Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 239000005337 ground glass Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000007603 infrared drying Methods 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002667 nucleating agent Substances 0.000 description 1
- 235000014593 oils and fats Nutrition 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000012047 saturated solution Substances 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000012745 toughening agent Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/30—Destroying solid waste or transforming solid waste into something useful or harmless involving mechanical treatment
- B09B3/35—Shredding, crushing or cutting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/80—Destroying solid waste or transforming solid waste into something useful or harmless involving an extraction step
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/04—Disintegrating plastics, e.g. by milling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B2101/00—Type of solid waste
- B09B2101/75—Plastic waste
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0213—Specific separating techniques
- B29B2017/0279—Optical identification, e.g. cameras or spectroscopy
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0213—Specific separating techniques
- B29B2017/0293—Dissolving the materials in gases or liquids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
The application discloses a method for treating and recycling homo-polypropylene based on a solvent, which comprises the steps of pretreating to obtain polypropylene crushed materials; fully contacting the polypropylene crushed material with an extraction solvent, pressurizing and heating, and selectively extracting pollutants; performing solid-liquid separation on the polypropylene crushed material and the extraction solvent, and performing devolatilization treatment to obtain purified polypropylene; the method provided by the scheme of the application has the advantages that the purification efficiency of plastic wastes in the takeaway cutlery box is high, the whole flow is simple, the production process is totally closed, the discharge of three wastes is avoided, the environmental pollution is avoided, the production cost is low, the discharge amount of carbon dioxide is low, the regenerated plastic with high purity is obtained, the odor, various volatile and semi-volatile substances and the residues of n-hexane soluble substances are greatly reduced in the recovery process, the physical and mechanical properties are basically consistent with those of new materials, and the waste plastic can be directly added into petrochemical final polymerization reaction equipment without pelleting.
Description
Technical Field
The application relates to the technical field of solid waste plastic treatment, in particular to a method for treating and recycling homopolypropylene based on a solvent.
Background
The development of the plastic industry makes a great contribution to the social development, and the annual plastic production of China is up to about 1.2 hundred million tons at present, and most of the plastic is discarded into the environment after one-time use. According to statistics, the yield of waste plastics in China is about 240-480 ten thousand tons/year; by 2035, about 80 hundred million tons of waste plastics exist in the natural environment, and the continuous accumulation of waste plastics not only causes serious environmental pollution, but even affects the ecological balance in the natural environment because the plastic needs 200 to 500 years to be completely degraded.
PP (polypropylene) is the most used single plastic package due to its melting point and strong load bearing capacity. Only in 2010, 50 million pounds of polypropylene were produced in the united states. Unfortunately, the american chemical committee (American Chemistry Council) discloses that PP is the lowest recovery of post-consumer plastics, with less than 1% recovery of post-consumer PP foam, and that recovery of polypropylene is of great importance.
In the prior art, a solvent recovery method (Solvent Purification/solvent-based) is adopted for recovering polypropylene, a dissolution principle is utilized to selectively separate target plastics from other plastics or pollutants, plastic waste is washed and crushed and then is put into a solvent with high solubility to the target plastics and low solubility to other components, the other components are kept in a solid state and are separated from a solution of the target plastics, so that the target plastics solution is purified, and after the purification process is finished, the target plastics can be extracted from the solution by a precipitation method. The recovery method is a physical method in nature, and the dissolution method is taken as a physical recovery method with mild reaction conditions, so that the original molecular structure of the target plastic can be effectively maintained, and the purity of the resin is improved: compared with a physical mechanical method, the dissolution method is a deeper purification technology, can ensure that the recovered resin has higher purity, can separate target plastics from other plastics through selection and collocation of different solvents and continuous optimization of separation processes (dissolution temperature/pressure, precipitation of saturated solution, precipitation, solvent removal and the like), and is a method capable of obtaining relatively single resin, but can be limited by factors such as waste gas emission requirements, economic cost and the like.
Disclosure of Invention
The application aims to provide a method for treating and recycling homopolypropylene based on a solvent, which adopts an extraction mechanism to extract and remove impurities, and can remove impurities more accurately without dissolving target plastics.
In order to achieve the above object, the present application provides a solvent-based process for treating and recovering homo-polypropylene comprising:
pretreating to obtain polypropylene crushed materials;
the polypropylene crushed material is fully contacted with an extraction solvent to perform extraction and impurity removal;
and (3) carrying out solid-liquid separation on the crushed polypropylene material subjected to impurity removal and the extraction solvent, and carrying out devolatilization treatment to obtain purified polypropylene.
Optionally, the pretreatment includes performing a preliminary selection and performing a sorting.
Optionally, the initial selection process includes: and (3) performing primary selection on the plastic waste, and performing machine primary selection, crushing, cleaning, drying and impurity removal on the plastic waste to obtain plastic crushed materials.
Optionally, the machine begining includes: the machine utilizes an image recognition technology and an automatic learning technology to screen the plastic waste according to the characteristics of polypropylene.
Optionally, the sorting process includes: sorting the plastic crushed materials, immersing the plastic crushed materials into a 47.3% ethanol water solution, fully oscillating and stirring, selecting solids floating on the 47.3% ethanol water solution, and carrying out solid-liquid separation to obtain the polypropylene crushed materials.
Optionally, the extraction solvent comprises one or more of methanol, ethanol, acetone, dichloroethane, n-butane, ethyl acetate, cyclohexanone and methyl ethyl ketone.
Optionally, pressurizing and heating are carried out in the process of extracting and removing impurities, and pollutants are selectively extracted; the extraction temperature is 60-120 ℃ and the extraction time is 20-60 min.
Optionally, the extraction includes the following steps: ultrasonic vibration and/or mechanical stirring are/is adopted.
Optionally, the devolatilization process includes: the polypropylene crushed materials are sucked in vacuum through a negative pressure fan and subjected to infrared heating in devolatilization equipment, and the polypropylene crushed materials are pumped to the top of the devolatilization equipment, dispersed and fallen and simultaneously subjected to infrared heating to be dried.
Optionally, the devolatilization temperature is 70-90 ℃ and the devolatilization time is 50-70 min.
Compared with the prior art, the method for treating and recycling the homopolypropylene based on the solvent provided by the application adopts an extraction mechanism, selectively extracts and removes impurities, and can remove impurities more accurately without dissolving target plastics; the method has high purification efficiency on plastic wastes in the takeaway cutlery box, the whole flow is simple, the production process is totally closed, the discharge of three wastes is avoided, the environmental pollution is avoided, the production cost is low, the recovery efficiency is high, and the purity of the obtained regenerated plastic is high.
Detailed Description
The present application will be described in more detail below, wherein preferred embodiments of the application are shown, it being understood that one skilled in the art may modify the application herein described while still achieving the beneficial results of the present application. Accordingly, the following description is to be construed as broadly known to those skilled in the art and not as limiting the application.
The application is more specifically described by way of example in the following paragraphs. The advantages and features of the present application will become more apparent from the following description.
The embodiment of the application provides a method for treating and recycling homopolypropylene based on a solvent, which comprises the following steps of:
s1, preprocessing to obtain a polypropylene crushed material.
S2, fully contacting the polypropylene crushed material with an extraction solvent to extract and remove impurities.
S3, carrying out solid-liquid separation on the purified polypropylene crushed material and the extraction solvent, and carrying out devolatilization treatment to obtain purified polypropylene.
The pretreatment comprises the steps of firstly selecting plastic waste to obtain plastic crushed materials and separating the plastic crushed materials to obtain polypropylene crushed materials.
The process for initially selecting the plastic waste comprises the following steps: the plastic waste is subjected to machine primary selection, crushing, cleaning, drying and impurity removal to obtain plastic crushed materials.
Wherein, the sieve pore size of the crusher is 15-20 mm, and the preferred sieve pore size of the crusher is 18mm.
The polypropylene plastic waste is mainly a plastic cutlery box, and the plastic cutlery boxes circulated in the market are relatively fixed in shape and are mostly transparent rectangular cutlery boxes, so that target plastics can be primarily screened out from the plastic waste according to colors and shapes.
The machine beginnings include: the machine utilizes an image recognition technology and an automatic learning technology to perform primary selection on the plastic waste, and colorless target plastic is selected from the plastic waste according to the color and the shape of the plastic waste.
The density of PP (polypropylene) pure resin is the lowest in the manufacturing materials of colorless transparent cutlery box, even all plastic materials in daily contact, and the density range is about 0.89-0.91 g/cm 3 The resin with similar density is polyethylene with the density of about 0.912 to 0.965g/cm 3 。
Thus, the plastic crushed material was classified by PP resin density, and the plastic crushed material was completely immersed in a 47.3% ethanol aqueous solution with a solid-to-liquid ratio of 1:1.5 to 1:3.5 An aqueous solution of 47.3% ethanol having a density of 0.92g/cm 3 After full shaking and stirring, selecting solid floating in 47.3% ethanol water solution, and separating solid from liquid to obtain polypropylene crushed material.
The components precipitated in the 47.3% ethanol aqueous solution may have a small amount of pure PP resin, or may have a small amount of PP resin added with high-density filler (such as calcium carbonate), and the main material of the bottom is non-PP resin in consideration of the actual manufacturing raw material condition and liquid tension of the cutlery box.
In the process of primary selection of plastic waste, according to the color and shape or other preset data about the characteristics of polypropylene, the machine cannot accurately identify PE (polyethylene) and PP composite plastic and PP resin added with additives such as toughening agents, so that the density of the PP resin can be utilized to effectively select polypropylene broken materials in the process of further selecting the PP resin density, and the selecting efficiency is high.
In some embodiments, after obtaining the polypropylene crushed material, the method may further comprise the steps of: color screening is performed manually, and further white polypropylene crushed materials are screened out.
Further, in S2, the process of extraction and impurity removal may achieve selective extraction, where the extraction solvent is selected from solvents that cannot dissolve polypropylene (including low molecular weight distribution portion), but have higher solubility for the contaminants that permeate and anchor in the amorphous region (amorphous state) of the takeaway cutlery box, and have an insignificant extraction effect on antioxidants, acid absorbers (such as calcium stearate), and nucleating agents contained in polypropylene; wherein the contaminants include oils and fats and microbial fermentation products thereof; the extraction solvent comprises: one or more of methanol, ethanol, acetone, dichloroethane, n-butane, ethyl acetate, cyclohexanone and methyl ethyl ketone.
Pressurizing and heating are carried out in the process of extracting and removing impurities, and pollutants such as grease, microbial fermentation products and the like are selectively extracted; the extraction time is 20-60 min, the heating temperature range is 60-120 ℃, and the heating temperature range is 100-120 ℃ preferably; the high pressure and high temperature cooking can quickly extract pollutants, and can also achieve the effect of high temperature sterilization.
Furthermore, in step S2, ultrasonic vibration or/and mechanical stirring may be used to avoid stacking of the crushed polypropylene particles while removing impurities by extraction, so as to achieve the purpose of improving the extraction effect.
The oscillating frequency of the ultrasonic oscillating device is higher than 2000kHz, tiny bubbles can be continuously generated in the liquid of the cleaning tank of the ultrasonic oscillating device under the action of high-frequency oscillation, the liquid is continuously closed after the tiny bubbles are generated, strong impact can be generated in the process, dirt on the surface of the polypropylene crushed material is impacted and stripped, and the cleaning and decontaminating effects are achieved.
In addition, in the process of extraction and impurity removal, a Soxhlet extractor is selected, the extraction solvent is removed from the extraction reactor and subjected to continuous separation, wherein the fraction with high boiling point, namely the pollutant, is continuously enriched, and the fraction with low boiling point, namely the extraction solvent, is returned to the extraction reactor, so that the polypropylene crushed material is continuously extracted by the pure solvent, and the extraction solvent is purified and recycled.
Further, in step S3, after the extraction and impurity removal, the mixture of the polypropylene crushed material and the extraction solution is subjected to solid-liquid separation, and then subjected to devolatilization treatment to obtain a purified polypropylene crushed material.
The devolatilization process comprises: the polypropylene crushed material is sucked in vacuum through a negative pressure fan and subjected to infrared heating in devolatilization equipment, the material is vacuumized to the tank top of the devolatilization equipment, then falls down in a dispersing cover to obtain a larger contact area, the falling down is simultaneously subjected to infrared heating to dry the material, VOC (volatile organic compound) is carried away, and gas is released from the devolatilization equipment, so that the deodorizing is further realized.
In the embodiment, devolatilization is realized through an infrared drying system, infrared radiation with specific wavelength is used for continuously heating crushed materials, the crushed materials enter a vacuum module after reaching a preset temperature, and the release of components such as water molecules, volatile organic compounds and the like is accelerated by a vacuum environment, so that devolatilization drying is realized, the materials can be uniformly heated without additional stirring, and the temperature is accurately controlled, so that the devolatilization is thorough, the devolatilization efficiency is high, and the deodorizing effect is good; the material is heated from inside to outside, the uniformity is better, the energy consumption is lower (compared with the preheating energy consumption, the energy is saved by 60%), and meanwhile, compared with the conventional hot air heat transfer, the treatment effect is improved.
In addition, inert gas is introduced to carry out partial pressure in the devolatilization process, the devolatilization temperature is 70-90 ℃, and the devolatilization time is 50-70 min.
In this example, seven sets of experiments were provided to examine samples treated by the solvent-based treatment and recovery method of homo-polypropylene as described above, respectively, in terms of recovery purity, sample odor, total Volatile Organic Compound (TVOC), alkaline substance (sodium hydroxide, alkaline detergent, surfactant, etc.) residue, and the like.
Experiment one
The content of the polypropylene crushed material obtained by pretreatment in the step S1 is detected to be more than 99.6%, and the content of polyethylene mixed in the plastic crushed material obtained by treatment is about 3-5% when ethanol solution separation and purification are not adopted in the traditional recovery process, so that the purity of the recovered polypropylene is higher by adopting the solvent-based method for treating and recovering the homo-polypropylene.
Experiment two
The recovered polypropylene sample was subjected to odor detection by reference to the artificial nasal method of 6.14 in GB/T24149.2-2017, with class 1 being the best of the class 6 odor ratings.
A20 g weight sample of polypropylene was placed in a 1L ground glass bottle, sealed, placed at (80.+ -. 3) C for 2 hours, cooled to (60.+ -. 3) C and odor grade was identified by a discriminator.
Conclusion of experiment: the odor is greatly reduced, and the odor of the polypropylene sample is 3-3.8 according to the evaluation of six grades of odor, so that the range of virgin homo-polypropylene new materials is basically reached.
Experiment three
TVOC testing was performed according to VDA277, and a 20g weight sample of polypropylene was taken to test the TVOC content before and after devolatilization, respectively.
Conclusion of experiment: after the devolatilization treatment, the TVOC of the sample is reduced from 50-70 mu gC/g to 20-30 mu gC/g before the devolatilization treatment, the improvement is obvious, and the devolatilization treatment method provided in the scheme has a great improvement on the emission characteristic.
Experiment four
And (3) carrying out an alkaline substance residue detection experiment on the recycled polypropylene sample, mixing and stirring the polypropylene sample with distilled water, and testing the pH value of the distilled water to characterize the residual pH value of the crushed material.
The specific experimental steps are as follows:
1. calibrating the acidometer with a buffer solution;
2. weighing 100g of the recycled polypropylene sample, putting the polypropylene sample into a 1000mL beaker, adding 500mL of distilled water with pH value of 6-8, and stopping stirring after stirring the polypropylene sample for 10min under the condition of complete infiltration;
3. after the solution is stable, the test electrode is gently placed in a beaker, the electrode to be tested is completely immersed, and the result is recorded when the value is stable, namely the residual pH value of the crushed material is accurate to 0.1pH value.
Conclusion of experiment: the pH is less than 7.2 and is basically neutral.
Experiment five
The recovered polypropylene sample was subjected to an experiment for detecting the residue of n-hexane soluble substances, and the precipitation amount was greatly reduced from 0.75% to about 0.2% at 60℃for 2 hours.
Experiment six
BPA residue: free (derived mainly from ink)
The content was reduced from 0.2ppm to 0.05ppm or less due to the cleaning effect.
Experiment seven
Detergent residue: free (PEG alkyl ether, PPG alkyl ether, APEO alkylphenol polyoxyethylene, etc.)
The content is reduced from 0.2ppm to less than 0.05ppm due to the cleaning effect.
Seven sets of experiments showed that: the polypropylene sample treated and recovered by the solvent-based method for treating and recovering the homopolypropylene provided by the scheme has high polypropylene content, high recovery purity, greatly reduced odor, various volatile and semi-volatile substances in the recovery process, and basically neutral pH value of the crushed material.
In summary, the method for treating and recycling the homopolypropylene based on the solvent provided by the application adopts an extraction mechanism to selectively extract and remove impurities, so that impurities can be removed more accurately without dissolving target plastics; the method has high purification efficiency on plastic wastes in the takeaway cutlery box, the whole flow is simple, the production process is totally closed, no three wastes are discharged, no environmental pollution is caused, the regenerated plastic with high purity can be obtained with lower production cost and lower carbon dioxide discharge, the odor, various volatile and semi-volatile substances are greatly reduced in the recovery process, the physical and mechanical properties are basically consistent with those of new materials, and petrochemical final polymerization reaction equipment can be directly added without granulation.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. A process for solvent-based treatment and recovery of homo-polypropylene comprising:
pretreating to obtain polypropylene crushed materials;
the polypropylene crushed material is fully contacted with an extraction solvent to perform extraction and impurity removal;
and (3) carrying out solid-liquid separation on the crushed polypropylene material subjected to impurity removal and the extraction solvent, and carrying out devolatilization treatment to obtain purified polypropylene.
2. The solvent-based process for treating and recovering a homopolypropylene of claim 1, wherein said pretreatment comprises a preliminary selection and a sorting.
3. The solvent-based process for treating and recovering homo-polypropylene according to claim 2, wherein the preliminary selection process comprises: and (3) performing primary selection on the plastic waste, and performing machine primary selection, crushing, cleaning, drying and impurity removal on the plastic waste to obtain plastic crushed materials.
4. A solvent-based process for treating and recovering homo-polypropylene as claimed in claim 3, wherein said machine beginnings comprise: the machine utilizes an image recognition technology and an automatic learning technology to screen the plastic waste according to the characteristics of polypropylene.
5. A solvent-based process for treating and recovering homo-polypropylene as claimed in claim 3, wherein the sorting process comprises: sorting the plastic crushed materials, immersing the plastic crushed materials into a 47.3% ethanol water solution, fully oscillating and stirring, selecting solids floating on the 47.3% ethanol water solution, and carrying out solid-liquid separation to obtain the polypropylene crushed materials.
6. The method for treating and recovering a homopolypropylene based on a solvent according to claim 1, wherein the extraction solvent comprises one or a combination of two or more of methanol, ethanol, acetone, dichloroethane, n-butane, ethyl acetate, cyclohexanone, and methyl ethyl ketone 。
7. The solvent-based process for treating and recovering a homopolypropylene as defined in claim 1, wherein the process of removing impurities by extraction is performed by heating under pressure to selectively extract contaminants; the heating temperature is 60-120 ℃, and the extraction time is 20-60 min.
8. The solvent-based process for treating and recovering homo-polypropylene according to claim 1, wherein said extraction is accompanied by the steps of: ultrasonic vibration and/or mechanical stirring are/is adopted.
9. The solvent-based process for treating and recovering homo-polypropylene of claim 1, wherein the devolatilization process comprises: the polypropylene crushed materials are sucked in vacuum through a negative pressure fan and subjected to infrared heating in devolatilization equipment, and the polypropylene crushed materials are pumped to the top of the devolatilization equipment, dispersed and fallen and simultaneously subjected to infrared heating to be dried.
10. The solvent-based process for treating and recovering a homo-polypropylene as claimed in claim 9, wherein the devolatilization temperature is 70 to 90℃and the devolatilization time is 50 to 70min.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311053579.3A CN117086066A (en) | 2023-08-21 | 2023-08-21 | Method for treating and recycling homo-polypropylene based on solvent |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311053579.3A CN117086066A (en) | 2023-08-21 | 2023-08-21 | Method for treating and recycling homo-polypropylene based on solvent |
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| CN202311053579.3A Pending CN117086066A (en) | 2023-08-21 | 2023-08-21 | Method for treating and recycling homo-polypropylene based on solvent |
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