CN114015112A - PET waste recycling and regenerating method and polyester material prepared by same - Google Patents
PET waste recycling and regenerating method and polyester material prepared by same Download PDFInfo
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- CN114015112A CN114015112A CN202111223764.3A CN202111223764A CN114015112A CN 114015112 A CN114015112 A CN 114015112A CN 202111223764 A CN202111223764 A CN 202111223764A CN 114015112 A CN114015112 A CN 114015112A
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- 229920000728 polyester Polymers 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 55
- 239000000463 material Substances 0.000 title claims abstract description 43
- 238000004064 recycling Methods 0.000 title claims abstract description 31
- 230000001172 regenerating effect Effects 0.000 title claims abstract description 22
- 239000002904 solvent Substances 0.000 claims abstract description 48
- 150000002736 metal compounds Chemical class 0.000 claims abstract description 20
- 238000001556 precipitation Methods 0.000 claims abstract description 20
- 238000007711 solidification Methods 0.000 claims abstract description 17
- 230000008023 solidification Effects 0.000 claims abstract description 16
- 239000003463 adsorbent Substances 0.000 claims abstract description 15
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- 239000000843 powder Substances 0.000 claims description 37
- 239000000047 product Substances 0.000 claims description 24
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 15
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000006243 chemical reaction Methods 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
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- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 150000001335 aliphatic alkanes Chemical group 0.000 claims description 7
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 5
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 4
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 4
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims description 4
- 229910052901 montmorillonite Inorganic materials 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 2
- 229960000892 attapulgite Drugs 0.000 claims description 2
- 239000000440 bentonite Substances 0.000 claims description 2
- 229910000278 bentonite Inorganic materials 0.000 claims description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims description 2
- 229910052791 calcium Inorganic materials 0.000 claims description 2
- 239000011575 calcium Substances 0.000 claims description 2
- 229910001622 calcium bromide Inorganic materials 0.000 claims description 2
- WGEFECGEFUFIQW-UHFFFAOYSA-L calcium dibromide Chemical compound [Ca+2].[Br-].[Br-] WGEFECGEFUFIQW-UHFFFAOYSA-L 0.000 claims description 2
- 125000004432 carbon atom Chemical group C* 0.000 claims description 2
- 239000004927 clay Substances 0.000 claims description 2
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- 239000003153 chemical reaction reagent Substances 0.000 abstract description 14
- 238000011084 recovery Methods 0.000 abstract description 9
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- 238000011282 treatment Methods 0.000 abstract description 8
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 abstract description 5
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- 230000000052 comparative effect Effects 0.000 description 23
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- 238000000605 extraction Methods 0.000 description 9
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 9
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- 239000007789 gas Substances 0.000 description 7
- 238000002834 transmittance Methods 0.000 description 7
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- 238000012360 testing method Methods 0.000 description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 5
- 229910001424 calcium ion Inorganic materials 0.000 description 5
- 239000012459 cleaning agent Substances 0.000 description 5
- 239000005995 Aluminium silicate Substances 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 4
- 235000012211 aluminium silicate Nutrition 0.000 description 4
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 4
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- LQNUZADURLCDLV-UHFFFAOYSA-N nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1 LQNUZADURLCDLV-UHFFFAOYSA-N 0.000 description 4
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- 239000008367 deionised water Substances 0.000 description 2
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- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 description 2
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
- C08J11/08—Recovery or working-up of waste materials of polymers without chemical reactions using selective solvents for polymer components
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/16—Halogen-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/28—Nitrogen-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/16—Halogen-containing compounds
- C08K2003/162—Calcium, strontium or barium halides, e.g. calcium, strontium or barium chloride
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/28—Nitrogen-containing compounds
- C08K2003/287—Calcium, strontium or barium nitrates
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/10—Transparent films; Clear coatings; Transparent materials
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/14—Gas barrier composition
-
- 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
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
Abstract
The invention discloses a method for recycling and regenerating PET waste and a polyester material prepared by the method, and belongs to the field of plastic recycling. The recovery and regeneration method of the PET waste material extracts the primarily treated PET waste material to remove small molecular impurities in the waste material, then the waste material is fully heated and dissolved by good solvent NMP, an adsorbent is adopted for decoloration and purification, a metal compound is introduced to be complexed with PET terminal carboxyl, and a poor solvent with specific type and temperature is adopted to carry out solidification and precipitation treatment on the solution, so that the obtained polyester material has higher crystallinity, the intrinsic gas isolation performance and high transparency of the polyester material are improved under the condition of not introducing a filler, and meanwhile, the PET waste material has good appearance effect and high transparency; the method has no high energy consumption step, uses less reagents, is safe and environment-friendly, and the obtained product has high application value and wide application field. The invention also discloses the polyester material prepared by the method and a plastic product for food packaging further obtained.
Description
Technical Field
The invention relates to the field of plastic recycling, in particular to a PET waste recycling and regenerating method and a polyester material prepared by the PET waste recycling and regenerating method.
Background
PET (dimethyl terephthalate) is an important engineering plastic, has good mechanical properties, wear resistance, creep resistance, chemical resistance and the like, is widely used in the fields of food packaging, fibers, films and the like, wherein a large market share is concentrated in the food packaging industry, and common mineral water, carbonated beverages and functional beverage bottles are made of the material due to the non-toxicity, tastelessness, low price and permeation resistance, so that the annual waste amount is huge, and serious environmental pollution is caused. The recycling of plastics is the most important way to solve the plastic pollution, and in the field of plastic recycling, PET beverage bottle recycling is the product with the highest recovery rate, but a huge gap still exists in high-end PET reclaimed materials in the market; more importantly, the domestic high-end recycled PET industry is still in the starting stage, the recycling system is incomplete, the recycling process is extensive, most recycled PET products are poor in quality and performance, the product performance is greatly attenuated, the functionalization level is low, the recycled PET products can only be applied to the low-valued field, and the high-end recycled PET products are very rare.
At present, two methods for recycling PET in China are mainly used: chemical depolymerization and mechanical recovery.
The chemical depolymerization method is that PET is subjected to depolymerization reaction under the action of heating and a catalyst to generate a low-molecular-weight product or a synthetic monomer, and then the product or the synthetic monomer can be used as a monomer to participate in polyester synthesis again to obtain high-purity and high-performance regenerated PET. In the prior art disclosed in CN107459788A, polyester reclaimed materials and polyester oligomer melts are subjected to reactive melt blending, ethylene glycol is added for mixing and alcoholysis reaction to obtain depolymerized melts, and then the depolymerized melts are filtered, purified and subjected to polycondensation to obtain regenerated polyester melts, and cooled and granulated to obtain regenerated polyester chips; the technical scheme of CN102532815A is to depolymerize waste polyester textiles by using ethylene glycol, purify depolymerized monomers and then carry out polymerization reaction to obtain regenerated polyester; in the technical scheme of CN110734578A, waste polyester materials are first foamed and granulated to obtain waste ester granules containing a microporous structure inside, and after other easily soluble impurities are removed by using a solvent, the waste ester granules are depolymerized and repolymerized by using ethylene glycol to obtain recycled polyester. However, as described in the above-mentioned conventional techniques, the chemical depolymerization method requires a complicated process, and a step such as high-temperature depolymerization or high-temperature melting is required in the process, which results in high energy consumption and high cost.
The mechanical recovery method is to obtain the regenerated PET by directly mixing, melting and blending, extruding and granulating the waste PET material through simple physical mechanical treatment, and the recovery process is generally simpler than the chemical depolymerization method, but the PET in the process of the scheme is generally degraded, has more impurities and poor performance, and can only be applied to low-value products for recycling. In order to realize the functionalization of products prepared by the methods, for example, for a PET material with a high barrier property requirement, people generally use a modifier to compound or compound a film layer in the preparation process, for example, CN105622974A covers a PET substrate film with a coating layer so as to realize the effects of high barrier property and high transparency, however, the method has certain requirements on the shape of the substrate, and the coating layer and the PET substrate have the possibility of falling off, so that the application range is narrow; CN109467895A is that PEN resin and modified filler are added in PET material matrix, so that the prepared composite material has intrinsic high barrier property, but the product is not high in transparency, light gray in color and poor in appearance effect.
Disclosure of Invention
Based on the defects in the prior art, the invention aims to provide a PET waste recovery and regeneration method, which is different from the traditional chemical depolymerization method and mechanical recovery method, and is used for purifying, recovering and regenerating the PET waste by an extraction-dissolution-solidification precipitation method without introducing high-temperature melting and other high-energy-consumption steps, so that the recovery and regeneration cost is saved, and the PET high-molecular chain is prevented from being degraded; introducing a metal compound to be complexed with PET terminal carboxyl before the solidification precipitation process, so that the crystallinity of the interior of PET is obviously improved during solidification precipitation, and further high gas barrier property is obtained; the recycled product is not realized by introducing the barrier filler to improve the gas barrier property, and the obtained product has good appearance performance and high transparency.
In order to achieve the purpose, the invention adopts the technical scheme that:
a PET waste recycling and regenerating method comprises the following steps:
(1) cleaning and drying PET waste, and then crushing to obtain waste powder A;
(2) heating and extracting the waste powder A by using an organic solvent, and then filtering and drying to obtain waste powder B;
(3) adding the waste material powder B into a good solvent, heating to 60-120 ℃, mixing and dissolving, introducing an adsorbent to adsorb impurities, and filtering to obtain a purified polyester solution C; the good solvent is N-methylpyrrolidone (NMP);
(4) adding a metal compound into the purified polyester solution C, mixing and dissolving to obtain a modified polyester solution D; the metal compound is a soluble calcium-containing compound;
(5) adding the modified polyester solution D into a poor solvent, carrying out a solidification precipitation reaction, and filtering the precipitate to obtain the polyester material; the poor solvent is alkane with 5-6 carbon atoms, and the temperature of the poor solvent during the solidification precipitation reaction is 30-50 ℃.
Preferably, the metal compound includes at least one of calcium chloride, calcium nitrate, and calcium bromide.
In the method for recovering and regenerating the PET waste, firstly, the PET waste after primary treatment is extracted to remove small molecular impurities in the waste, then the waste is fully heated and dissolved by using a good solvent NMP (without depolymerization, the macromolecular chain structure of the PET is kept, and the molecular chain or chemical bond of the PET is not broken), an adsorbent is adopted to remove insoluble impurities (decoloration and purification) and then a metal compound is introduced, calcium ions in the metal compound can be connected with two terminal carboxyl groups in the PET through complexation, so that the interaction between the macromolecular chains of the PET is stronger, and then a specific poor solvent alkane is adopted to carry out solidification and precipitation treatment on the solution, so that the obtained polyester material has remarkable high crystallinity, and further shows excellent gas isolation; the method is low in application cost, under the condition that no filler is introduced, part of degraded micromolecules and impurities which influence the appearance of the raw materials are further removed through decoloring and purifying, and the obtained product is good in appearance and high in transparency.
In addition, the poor solvent alkane is required to be liquid and have strong fluidity under the processing conditions, and the alkane with high carbon number is mostly viscous and has poor fluidity; the alkanes with low carbon number are mostly gaseous, and the mixed polyester solution is difficult to infiltrate under the process condition of the invention.
Preferably, the alkane is any one of hexane, pentane, petroleum ether (a mixture of pentane and hexane).
In addition, the inventor also discusses the parameters of the dissolving and solidifying precipitation processes in the process of the method, when the waste powder is added into a good solvent for dissolving, the waste powder needs to be heated to a certain temperature, if the temperature is too low, the dissolution rate of the waste powder is low and the waste powder cannot be fully dissolved, the subsequent decoloration and purification cannot be well carried out, and the recovery rate of the PET waste is low; if the dissolution temperature is too high, the PET in the waste powder undergoes aging degradation upon dissolution, resulting in a significant reduction in the appearance properties of the final product.
Preferably, the temperature of the poor solvent during the solidification precipitation reaction is 40-45 ℃.
When the temperature of the poor solvent in solidification precipitation directly influences the non-isothermal crystallization kinetic process in the PET precipitation process, the crystallization rate and the crystallinity of PET are further changed; when the temperature of the poor solvent is too high, the PET precipitation efficiency is low, the yield is low, and when the temperature is too low, the polymer is precipitated too fast, and the crystallization effect of the polymer is influenced, so that the cost performance is optimal when the temperature is 40-45 ℃ within the range of 30-50 ℃ in comprehensive consideration.
Preferably, the PET waste material in the step (1) is cleaned by at least one of a zwitterion cleaning agent, an alkaline cleaning agent and a biological enzyme cleaning agent.
Preferably, the vacuum degree during drying in the step (1) is less than or equal to 0.1kPa, the temperature is 45-70 ℃, and the time is 1-4 h.
Preferably, the average particle size of the waste powder A after the crushing treatment in the step (1) is 10 to 300 μm.
After the PET waste is processed into the powder with the optimal particle size, the processing efficiency can be improved in the subsequent extraction process, and meanwhile, small molecular impurities and insoluble substances in the waste are removed more effectively.
More preferably, the crushing treatment is cryogenic crushing treatment, and the temperature of the PET waste in the crushing treatment is-50 to-78 ℃.
Preferably, the organic solvent in step (2) is extracted by heating: sequentially using methanol, acetone and cyclohexane as organic solvents to respectively heat and extract waste powder A, wherein the volume ratio of the mass of the waste powder A to the organic solvent added each time is 1 g: (5-30) mL, the temperature is 70-100 ℃, and the time for heating and extracting each time when the organic solvent is added is 0.5-4 h.
Under the condition, small molecular impurities in the material can be fully extracted by using a specific organic solvent, and meanwhile, the solvent cannot be excessively wasted or PET in the material cannot be degraded due to improper conditions.
Preferably, the ratio of the volume of the good solvent in the step (3) to the mass of the waste powder B is (5 to 10) mL: 1g, and the dissolving time is 0.5-4 h.
Preferably, the adsorbent comprises at least one of activated carbon, bentonite, montmorillonite, activated clay, medical stone and attapulgite powder, and the mass ratio of the adsorbent to the waste powder B is 1: (3-40).
Under the condition, PET in the extracted waste powder can be fully dissolved in NMP (N-methyl pyrrolidone) which is a good solvent, and impurities which are seeped or insoluble and can influence the stability or the appearance of waste such as an antioxidant, a coloring agent and the like can be fully removed through an adsorbent, so that the purity is improved.
Preferably, the mass ratio of the volume of the purified polyester solution C in the step (4) to the added metal compound is 1 mL: (0.0025 to 0.005) g.
Calcium ions in the metal compound can improve the binding force between PET molecular chains through complexation with terminal carboxyl groups of two PETs, however, the crosslinking degree of the PET cannot be effectively improved if the calcium ions are not added enough, and the processability of the material can be influenced if the calcium ions are added too much.
Preferably, the volume ratio of the modified polyester solution D in the step (5) to the poor solvent is 1: (10-20).
The use of the poor solvent is the key of the solidification precipitation reaction, if the amount of the poor solvent is too small, PET in the polyester solution cannot be fully precipitated, so that the yield of a final product is not high, and if the amount of the poor solvent is too much, the difficulty in recovering subsequent waste liquid and separating precipitated solids in a system is increased.
The invention also aims to provide the polyester material prepared by the PET waste recycling and regenerating method.
Still another object of the present invention is to provide a plastic product for food packaging, which is prepared from a raw material comprising the polyester material of the present invention.
Preferably, the plastic product for food packaging comprises a food preservative plastic film, a food packaging bag and a beverage packaging bottle.
The PET waste recycling and regenerating method has the advantages that the polyester material prepared by the method is high in performance and low in production energy consumption under the condition that no filler is introduced; the PET reclaimed material has higher intrinsic barrier property and transparency and good appearance effect, has wider application range compared with the PET reclaimed material prepared by the prior art, and is particularly suitable for preparing plastic products in the field of food packaging with higher requirements on appearance, transparency and insulation.
The method has the beneficial effects that the method extracts the primarily treated PET waste to remove small molecular impurities in the waste, then fully heats and dissolves the waste by using a good solvent NMP, adopts an adsorbent to decolor and purify, introduces a metal compound, and adopts a poor solvent with specific type and temperature to carry out solidification and precipitation treatment on the solution, so that the obtained polyester material has higher crystallinity, the intrinsic gas isolation performance of the polyester material is improved under the condition of not introducing a filler, and meanwhile, the PET waste has good appearance effect and high transparency; the method has no high energy consumption step, uses less reagents, is safe and environment-friendly, and the obtained product has high application value and wide application field. The invention also provides the polyester material prepared by the method and a plastic product for food packaging further obtained.
Detailed Description
In order to better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples and comparative examples, which are intended to be understood in detail, but not intended to limit the invention. All other embodiments obtained by a person skilled in the art without making any inventive step are within the scope of protection of the present invention. The experimental reagents and instruments designed for the practice of the present invention and the comparative examples are common reagents and instruments unless otherwise specified.
The reagents used in the examples of the invention and the comparative examples are as follows:
PET waste: a recycled material of a beverage bottle sheet is obtained by Hongyu textile technology limited company in Dongguan city, and the PET content is about 97-99%;
methanol: the Guangzhou chemical reagent factory analyzes and purifies;
acetone: the Guangzhou chemical reagent factory analyzes and purifies;
cyclohexane: the Guangzhou chemical reagent factory analyzes and purifies;
n-methylpyrrolidone (NMP): chemical reagent, Inc., Guangdong Wengjiang, analytically pure;
nitrobenzene: the Guangzhou chemical reagent factory analyzes and purifies;
adsorbent (activated carbon): 20-50 meshes of Shanghai Mielin Biochemical technology Co., Ltd;
adsorbent (montmorillonite): 200-300 meshes of Shanghai Mielin Biochemical technology, Inc.;
commercial PET regrind: guangzhou Mingming packaging materials Co., Ltd, model PETG 80;
kaolin: kaolin is purchased from Shanghai Michelin Biotechnology, Inc. of 200-300 meshes.
N-hexane: the Guangzhou chemical reagent factory analyzes and purifies;
petroleum ether: guangzhou chemical reagent works, industrial purity;
calcium nitrate: the Guangzhou chemical reagent factory analyzes and purifies;
calcium chloride: guangzhou chemical reagent factory, analytically pure.
Example 1
The invention discloses a PET waste recycling and regenerating method and an embodiment of a polyester material prepared by the PET waste recycling and regenerating method, wherein the method comprises the following steps:
(1) cleaning 100g of PET waste with an alkaline cleaning agent, drying in a 65 ℃ oven (the vacuum degree is less than or equal to 0.1kPa) for 2h, and then crushing with a cryogenic crusher at-50 to-78 ℃ (cooling with liquid nitrogen) to obtain waste powder A with the average particle size of 200 mu m;
(2) adding the waste powder A into a first-stage high-temperature autoclave, introducing 700mL of methanol, heating and stirring at 80 ℃ for 2h for extraction, and filtering; 700mL of acetone is introduced, heated and stirred at 90 ℃ for 2h for extraction, and filtered; introducing 1000mL of cyclohexane, heating and stirring at 100 ℃ for 3 hours for extraction, and filtering; drying to obtain waste powder B;
(3) transferring the waste powder B into a second-stage high-temperature high-pressure reaction kettle, adding 800mL of good solvent NMP, heating to 80 ℃, mixing and stirring for 2h until the waste powder B is fully dissolved, introducing 5g of adsorbent active carbon to adsorb impurities, transferring the impurities into a filter, and filtering to obtain a purified polyester solution C;
(4) adding 3.0g of calcium chloride into the purified polyester solution C, mixing and dissolving to obtain 800mL of modified polyester solution D;
(5) and adding the modified polyester solution D into 8L of poor solvent n-hexane with the temperature of 40 ℃, maintaining the temperature of the poor solvent to perform a solidification precipitation reaction, and filtering and precipitating to obtain the polyester material.
Example 2
This example is different from example 1 only in that the temperature of the poor solvent at the time of the solidification precipitation reaction is 50 ℃.
Example 3
This example is different from example 1 only in that the temperature of the poor solvent at the time of the solidification precipitation reaction is 30 ℃.
Example 4
This example differs from example 1 only in that the metal compound is calcium nitrate.
Example 5
This example differs from example 1 only in that the amount of the metal compound added was 3.6 g.
Example 6
This example differs from example 1 only in that the metal compound was added in an amount of 2.0 g.
Example 7
This example differs from example 1 only in that the amount of the metal compound added was 4.0 g.
Example 8
The difference between the present example and example 1 is only that the addition amount of the good solvent is 750 mL; the adsorbent is 10g of montmorillonite, and the poor solvent is petroleum ether.
Example 9
The difference between the embodiment and the embodiment 1 is only that the addition amount of the methanol is 500mL, the extraction temperature is 80 ℃, and the extraction time is 1.5 h; the addition amount of the acetone is 500mL, the extraction temperature is 80 ℃, and the extraction time is 1.5 h; the adding amount of cyclohexane is 1000mL, the temperature is 120 ℃, and the extraction time is 3 h; the addition amount of the good solvent is 1000mL, and the heating temperature of the waste powder B when the waste powder B is dissolved in the good solvent is 90 ℃; the adsorbent is 15g of activated carbon.
Comparative example 1
The method for recycling and regenerating the PET waste material comprises the following steps:
(1) cleaning 100g of PET waste with an alkaline cleaning agent, drying for 2h at 65 ℃ (vacuum degree is less than or equal to 0.1kPa), and crushing with a cryogenic crusher at-50 to-78 ℃ (cooling with liquid nitrogen) to obtain waste powder A with average particle size of 500 μm;
(2) and adding the waste powder A into a double-screw extruder, filtering and purifying by a filter screen, mixing with kaolin filler, and performing melt extrusion granulation to obtain the polyester material.
Comparative example 2
The comparative example is different from example 1 only in that the temperature of the poor solvent is 60 ℃.
Comparative example 3
The comparative example differs from example 1 only in that the process does not add metal compounds.
Comparative example 4
The comparative example differs from example 1 only in that the heating temperature at which the scrap powder B in step (3) is dissolved in the good solvent is 150 ℃.
Comparative example 5
The comparative example differs from example 1 only in that the heating temperature at which the scrap powder B in step (3) is dissolved in the good solvent is 50 ℃.
Comparative example 6
This comparative example differs from example 1 only in that the good solvent NMP is replaced by nitrobenzene.
Comparative example 7
The polyester material used in this comparative example was a commercial PET regrind, which was not treated and tested subsequently.
Comparative example 8
The comparative example differs from example 1 only in that the poor solvent used was replaced with deionized water.
Effect example 1
In order to verify the performance of the polyester material prepared by the PET waste recycling and regenerating method, the polyester materials obtained in examples 1-5 and comparative examples 1-8 are subjected to a performance test, and the test method comprises the following steps:
gas barrier test: the product was prepared into a uniform size sheet of 50mm by 50mm with a thickness of 0.5mm and tested according to JIS-K7126-1-2006 pressure difference methodCO of2A transmittance;
and (3) testing light transmittance: testing according to standard GB 2410-2008; wherein the greater the transmittance value, the greater the sample transparency;
and (3) testing the chroma b value: testing according to the standard GB/T17931 and 2003; wherein the lower the value, the better the appearance of the sample.
The test results are shown in table 1.
TABLE 1
As can be seen from Table 1, the polyester material obtained by the PET scrap recycling and regenerating method of the present invention has high gas barrier property, high transparency and good appearance, and CO is a product2The transmittance is less than 50cm3V (m2.24h.0.1MPa), the chromaticity b value is less than or equal to 1.5, the light transmittance is more than or equal to 80 percent, and the transparency is far superior to that of the similar PET reclaimed material product sold in the prior market of a comparative example 7. In contrast, the polyester material prepared in comparative example 1 uses kaolin as a filler to improve the gas barrier properties of the product, whereas CO2The transmittance still reaches 51cm3V (m2.24h.0.1MPa) and the chroma b value is as high as 4.6, and the light transmittance is as low as 43 percent; compared with the embodiment 1, the technical scheme of the comparative examples 2 to 6 selects the technical parameters which are not in the protection range of the invention, and the performance of the obtained polyester material is far inferior to that of the embodiments 1 to 9; the poor solvent in the comparative example 8 is replaced by deionized water, and the metal compound is dissolved in the poor solvent while the polyester material is precipitated in the reaction process, so that the connectivity of calcium ions and two terminal carboxyl groups in PET is weakened, and the performance of the obtained polyester material is obviously weakened.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. A PET waste material recycling and regenerating method is characterized by comprising the following steps:
(1) cleaning and drying PET waste, and then crushing to obtain waste powder A;
(2) heating and extracting the waste powder A by using an organic solvent, and then filtering and drying to obtain waste powder B;
(3) adding the waste material powder B into a good solvent, heating to 60-120 ℃, mixing and dissolving, introducing an adsorbent to adsorb impurities, and filtering to obtain a purified polyester solution C; the good solvent is N-methylpyrrolidone (NMP);
(4) adding a metal compound into the purified polyester solution C, mixing and dissolving to obtain a modified polyester solution D; the metal compound is a soluble calcium-containing compound;
(5) adding the modified polyester solution D into a poor solvent, carrying out a solidification precipitation reaction, and filtering the precipitate to obtain the polyester material; the poor solvent is alkane with 5-6 carbon atoms, and the temperature of the poor solvent during the solidification precipitation reaction is 30-50 ℃.
2. The method for recycling and regenerating PET waste according to claim 1, wherein the metal compound is at least one of calcium chloride, calcium nitrate and calcium bromide.
3. The method for recycling and regenerating PET waste according to claim 1, wherein the temperature of the poor solvent in the solidification precipitation reaction is 40 to 45 ℃.
4. The method for recycling and regenerating PET waste according to claim 1, characterized in that the organic solvent in step (2) is extracted by heating: sequentially using methanol, acetone and cyclohexane as organic solvents to respectively heat and extract waste powder A, wherein the volume ratio of the mass of the waste powder A to the organic solvent added each time is 1 g: (5-30) mL, the temperature is 70-100 ℃, and the time for heating and extracting each time when the organic solvent is added is 0.5-4 h.
5. The method for recycling and regenerating PET scraps according to claim 1, wherein the ratio of the volume of the good solvent in the step (3) to the mass of the scrap powder B is (5-10) mL: 1g of the total weight of the composition.
6. The method for recycling and regenerating the PET waste according to claim 1, wherein the adsorbent is at least one of activated carbon, bentonite, montmorillonite, activated clay, maifanite, and attapulgite powder, and the mass ratio of the adsorbent to the waste powder B is 1: (3-40).
7. The method for recycling and reusing PET waste according to claim 1, wherein the ratio of the volume of the purified polyester solution C to the mass of the added metal compound in the step (4) is 1 mL: (0.0025 to 0.005) g.
8. The method for recycling and reusing PET waste according to claim 1, wherein the volume ratio of the modified polyester solution D to the poor solvent in the step (5) is 1: (10-20).
9. The polyester material obtained by the method for recycling and regenerating PET scrap as claimed in any one of claims 1 to 8.
10. A plastic product for food packaging, characterized in that a raw material for producing the plastic product for food packaging comprises the polyester material according to claim 9.
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