CN118406282B - A method for preparing recycled polymer from waste mixed plastics and recycled polymer - Google Patents
A method for preparing recycled polymer from waste mixed plastics and recycled polymer Download PDFInfo
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- CN118406282B CN118406282B CN202410474565.7A CN202410474565A CN118406282B CN 118406282 B CN118406282 B CN 118406282B CN 202410474565 A CN202410474565 A CN 202410474565A CN 118406282 B CN118406282 B CN 118406282B
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
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- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/60—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from the reaction of a mixture of hydroxy carboxylic acids, polycarboxylic acids and polyhydroxy compounds
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- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
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Abstract
本发明提供一种废弃混合塑料中回收制再生聚合物的方法，包括以下步骤：S1、将废弃混合塑料中的聚合物与反应单体在催化剂的作用下进行常压可逆反应，获得第一前驱物；S2、对步骤S1获得的第一前驱物进行过滤、纯化，去除杂质，获得第二前驱物；S3、将第二前驱物在150‑300℃、绝对压力1‑1000Pa下，在催化剂的作用下进行可逆反应0.5‑48h，得到反应单体和再生的聚合物，同时将反应单体回收；所述废弃混合塑料中的聚合物包括聚酯、聚碳酸酯、聚酰胺中的一种。本发明提供的废弃混合塑料中回收制再生聚合物的方法，能够实现不经过人工分拣，可以选择性地回收废弃混合塑料中的聚酯、聚碳酸酯或聚酰胺。
The present invention provides a method for recycling a regenerated polymer from waste mixed plastics, comprising the following steps: S1, subjecting a polymer in the waste mixed plastics to a reversible reaction with a reaction monomer under the action of a catalyst at normal pressure to obtain a first precursor; S2, filtering and purifying the first precursor obtained in step S1, removing impurities, and obtaining a second precursor; S3, subjecting the second precursor to a reversible reaction for 0.5-48h at 150-300°C and an absolute pressure of 1-1000Pa under the action of a catalyst to obtain a reaction monomer and a regenerated polymer, and recycling the reaction monomer at the same time; the polymer in the waste mixed plastics includes one of polyester, polycarbonate, and polyamide. The method for recycling a regenerated polymer from waste mixed plastics provided by the present invention can achieve the polyester, polycarbonate, or polyamide in the waste mixed plastics to be selectively recycled without manual sorting.
Description
Technical Field
The invention belongs to the technical field of polymer recovery, and particularly relates to a method for recovering and preparing regenerated polymer from waste mixed plastics and the regenerated polymer.
Background
The general-purpose plastic has excellent properties of chemical resistance, high strength, light weight, low preparation cost and the like, and the market scale is rapidly increased. However, mass production and excessive use of plastic products have led to large-scale production of plastic waste, and plastic pollution has become increasingly serious. China is one of the largest plastic producing countries and consuming countries in the world, and in recent years, green low-carbon and circular economy are greatly promoted, so that urgent demands are made on waste plastic recovery. At present, polyester, polycarbonate and polyamide are widely existing in mixed waste plastics, and are important points for plastic recycling at present. The polyester is mainly a thermoplastic polymer compound formed by polycondensation of dibasic acid and dihydric alcohol, represented by polyethylene terephthalate (PET), is one of the most widely used polymer materials in the world, the polycarbonate is used as a multifunctional engineering polymer, when the product is abandoned, the product is mainly regarded as a highly polluted material through landfill or incineration treatment, the polyamide is also called nylon, is a generic name of thermoplastic resin with repeated amide groups on a molecular main chain, and is initially used as a raw material for preparing fibers, and is a widely used engineering plastic in the industry at present due to the characteristics of toughness, wear resistance, self lubrication, wide use temperature range and the like.
The recycling method of waste plastics mainly comprises a physical recycling method and a chemical conversion method, specifically, (1) the physical recycling method involves the steps of treating waste plastics through physical means such as crushing, washing, sorting and weighing, and then processing the waste plastics into usable materials, wherein the method has the limitations of degraded performance, low recycling efficiency, high recycling cost and the like of regenerated products, and (2) the chemical recycling method utilizes chemical conversion (including the manners of an alcoholysis method, a phenolysis method, a hydrolysis method, an acidolysis method, an ammonolysis method and the like) to convert waste polyesters, polycarbonates or polyamides into monomer or oligomer products for recycling. For example, CN114773197a discloses a method for recycling PET mixed plastics, which adopts a multifunctional metal zinc catalyst to catalyze the alcoholysis of the PET mixed plastics, and obtains high-purity monomers after purification. However, since the depolymerization process can produce both monomers and oligomers, the method of using only high purity monomers not only significantly reduces the utilization rate of waste plastics, but also increases the difficulty of purification and results in final monomer product costs exceeding those of virgin monomers upstream of chemical engineering. Thus, this depolymerization process to monomers is not economically desirable.
In comparison, the depolymerization of waste plastics into oligomers has a higher utilization rate. For example, CN116003767a discloses a method for recycling waste polycarbonate to prepare recycled polycarbonate, which first depolymerizes waste polycarbonate into low molecular weight polycarbonate short chains using phenol, and then re-obtains new polycarbonate material by polymerizing it with bisphenol a, diphenyl carbonate at high temperature. For another example, CN115850794a discloses a method for recycling waste nylon, in which the waste nylon is depolymerized by small molecular acid containing ether-oxygen bond structure to obtain carboxyl-terminated oligomeric nylon chain segment, and then the carboxyl-terminated oligomeric nylon chain segment is reacted with polyether component to prepare polyether-polyamide elastomer. However, since waste polyesters, polycarbonates or polyamides generally contain various other plastic components and impurities, conventional depolymerization processes are only suitable for single types of plastics or require manual sorting of the mixed waste plastics in advance, and cannot cope with the separation problem in the case of mixed plastics. Meanwhile, the chemical recovery of the waste polyester, the polycarbonate or the polyamide is carried out by adopting different types of depolymerizing agents respectively, and cannot be treated by adopting a universal method.
In order to solve these problems, there is a need to develop a low-cost general-purpose method for recycling waste plastics, which is capable of directly recycling polyester, polycarbonate or polyamide from waste mixed plastics without sorting.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for recycling and preparing a regenerated polymer from waste mixed plastics, which can directly recycle polyester, polycarbonate or polyamide from the waste mixed plastics without sorting, and the prepared regenerated polyester, regenerated polycarbonate or regenerated polyamide has adjustable mechanical properties and biodegradability.
In order to achieve the above object, the present invention provides a method for recycling and preparing a recycled polymer from waste mixed plastics, comprising the steps of:
S1, under normal pressure, reacting a reactant in waste mixed plastics with a reaction monomer under the action of a catalyst to obtain a first precursor;
S2, dissolving, separating and removing impurities from the first precursor obtained in the step S1 to obtain a second precursor;
s3, reacting the second precursor for 0.5-48 hours under the action of a catalyst at 150-300 ℃ and under the absolute pressure of 1-1000Pa to obtain a reaction monomer and a regenerated polymer;
the reactant in the waste mixed plastic is one of polyester, polycarbonate or polyamide.
In the method for producing a regenerated polymer according to the present invention, the reaction in step S1 and the reaction in step S3 are reversible, in the present invention, the reaction in step S1 is defined as a positive reaction, the reaction in step S3 is defined as a reverse reaction, the reaction in step S3 proceeds in the direction of the reverse reaction when the pressure is reduced and the temperature is increased, and in step S3, the pressure is gradually reduced from the normal atmospheric pressure (101.325 kPa), preferably to 100Pa to 10 Pa, so that the reaction proceeds more thoroughly, and a regenerated polymer having a high molecular weight is obtained.
In the invention, reactants (polyester, polycarbonate or polyamide) in waste mixed plastics can selectively react with reactive monomers in a reversible way under the action of a catalyst, other types of plastics or impurities keep chemical inertness and do not react with the reactive monomers, and the process inserts units of the reactive monomers into molecular chains of the polyester, the polycarbonate or the polyamide to obtain a soluble first precursor. The first precursor is oligomer and is easy to dissolve in conventional low-cost solvent at normal temperature, then the first precursor is filtered and purified under the action of solvent, adsorbent and precipitant to remove other plastics and impurities to obtain a second precursor, then the second precursor is subjected to high-temperature and reduced-pressure conditions to remove reaction monomers in the second precursor through the reverse reaction process of reversible reaction and is recovered, and the polymerization reaction is continued to obtain the regenerated polyester, the regenerated polycarbonate or the regenerated polyamide of the invention, so that the aim of directly recovering the polyester, the polycarbonate or the polyamide from waste mixed plastics without sorting is realized.
In the present invention, the reaction monomer obtained in step S3 increases as the degree of reaction increases. Meanwhile, the structure of the polyester, polycarbonate or polyamide molecular chain is changed by the reaction monomer, so that the mechanical property and the thermal property of the regenerated polymer are changed, and the regenerated product is easier to hydrolyze under the action of biology (enzyme) and the like by the reaction monomer with higher proportion, so that the regenerated polymer has the biodegradation characteristic. Therefore, according to the present invention, the mechanical properties, the biodegradability and the like of the final recycled polyester, the recycled polycarbonate or the recycled polyamide can be selectively controlled by controlling the conditions of the reaction in the step S3 according to the purpose of use of the recycled product.
Further, the reaction monomer in S1 includes at least one of five-membered or six-membered cyclic esters, cyclic thioesters, cyclic carbonates, cyclic anhydrides, and cyclic lactams, and the structures of the five-membered or six-membered cyclic esters and the cyclic thioesters are as follows:
the cyclic carbonate has the structure shown in the following formula (IV) and formula (V):
The cyclic anhydride has the following structures (VI) and (VII):
The structure of the cyclic lactam is shown in the following formula (VIII) and formula (IX):
Wherein ,R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11、R12、R13、R14、R15、R16、R17、R18、R19、R20、R21、R22、R23、R24、R25 and R 26 are independent of each other and are each hydrogen or alkyl.
In the present invention, when R 1-R26 is an alkyl group, the number of carbon atoms in the alkyl group is not particularly limited, and the number of carbon atoms in the alkyl group is preferably 10 or less.
In the present invention, since the ring tension of the five-membered and six-membered ring molecules is smaller, the ring closing reaction is more easily completed in step S3, thereby removing the reaction system in the reverse reaction, which is advantageous for forming recycled polyester, recycled polycarbonate or recycled polyamide.
In the invention, the reaction monomer in the step S1 can be selectively and reversibly reacted with polyester, polycarbonate or polyamide in the mixed plastic, wherein the reversible reaction equations of the polyester and cyclic ester, cyclic thioester, cyclic carbonate and cyclic anhydride are shown in figure 1;
The reversible reaction equations of the polycarbonate and cyclic esters, cyclic thioesters, cyclic carbonates and cyclic anhydrides are shown in figure 2;
The reversible reaction equations of the polyamide with cyclic anhydride and cyclic lactam are shown in figure 3.
Further, the polyester comprises at least one of polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, cyclohexane dimethanol terephthalate, polyethylene furandicarboxylate, polybutylene succinate, polybutylene adipate/terephthalate copolyester, and polylactic acid;
The polycarbonate comprises at least one of bisphenol A polycarbonate and polypropylene carbonate;
The polyamide comprises at least one of polyhexamethylene adipamide, polycaprolactam, poly omega-aminoundecanoyl, polydodecanoyl, polybutylene adipamide, polyhexamethylene dodecanoyl diamine and polydecanoyl sebacamide.
Further, the catalyst is at least one of oxides, hydroxides, alkoxides, carboxylates and halogen salts of tin, zinc, magnesium, antimony, manganese and cadmium.
Further, the weight of the catalyst is 0.05-1% of the total weight of reactants in the waste mixed plastic, and the catalyst can be ensured to have a sufficient catalytic effect in the dosage range.
Further, the molar ratio of the repeating units of the reactants to the reactive monomers in the waste mixed plastic is related to the reaction equilibrium constant between the polymer-reactive monomers and the solubility of the first precursor. The greater the reaction equilibrium constant (i.e., the more readily reactive) the greater the solubility of the first precursor in the corresponding solvent, the less reactive monomer is required, and therefore the molar ratio of repeat units of reactant to the reactive monomer in the waste mixed plastic is 1 (0.1-10), and even more preferably 1:5.
Further, the reaction in the step S1 is carried out at a temperature of 100-250 ℃ for 0.5-48 hours.
In the reaction in step S1, a gas flow of an inert gas such as nitrogen or argon is introduced, and a reflux reaction is performed.
Further, the specific step of the step S2 is that the first precursor obtained in the step S1 is dissolved by a solvent, part of unreacted and insoluble plastics is removed by filtration, then pigments and impurities are removed by silica gel adsorption, a precipitator is added, and after precipitation occurs, the solvent is evaporated to dryness, so that a second precursor is obtained.
Further, when the reactant in the waste mixed plastic is polyester or polycarbonate, the solvent is at least one of chloroform, tetrahydrofuran, acetone and methylene dichloride;
When the reactant in the waste mixed plastic is polyamide, the solvent is hexafluoroisopropanol.
Further, the precipitating agent is at least one of diethyl ether, methanol and ethanol.
Further, the adsorbent is at least one of silica gel, activated carbon, alumina and molecular sieve.
In a second aspect, the present invention provides a recycled polymer produced by the method for recycling recycled polymer from waste mixed plastics, wherein the recycled polymer is one of recycled polyester, recycled polycarbonate or recycled polyamide.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the method for recycling the recycled polymer from the waste mixed plastic, provided by the invention, the recycled polyester, the recycled polycarbonate or the recycled polyamide is obtained through the reversible reaction of the polymer in the mixed plastic and the unique reaction monomer, so that the purpose of selectively recycling the polyester, the polycarbonate or the polyamide in the waste mixed plastic without manual sorting can be realized.
(2) The method for recycling the regenerated polymer from the waste mixed plastic provided by the invention solves the limitation that only a single plastic can be utilized for depolymerization in the traditional chemical conversion method, and the mixed plastic conversion effect is poor.
(3) According to different purposes of the product, the recycling method can selectively regulate and control the mechanical properties, the biodegradability and other properties of the final recycled polyester, the recycled polycarbonate and the recycled polyamide by controlling the conditions of the reverse reaction.
(4) The recovery method is simple and controllable, and the reaction monomer can be recovered and recycled, so that the method accords with the principle of green chemical atom economy.
Drawings
FIG. 1 is an equation for the reversible reaction of polyesters with cyclic esters, cyclic thioesters, cyclic carbonates, cyclic anhydrides, respectively;
FIG. 2 is an equation for the reversible reaction of polycarbonate with cyclic esters, cyclic thioesters, cyclic carbonates, cyclic anhydrides, respectively;
FIG. 3 is an equation for the reversible reaction of a polyamide with a cyclic anhydride, a cyclic lactam, respectively;
FIG. 4 is a nuclear magnetic resonance hydrogen spectrum of the first precursor prepared in example 1;
FIG. 5 is a nuclear magnetic resonance spectrum of the first precursor prepared in example 1;
FIG. 6 is a nuclear magnetic resonance hydrogen spectrum of the recycled polyester product prepared in example 1;
FIG. 7 is a nuclear magnetic resonance spectrum of the recycled polyester product prepared in example 1.
Detailed Description
The present invention will be further described in detail with reference to the following specific examples, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent, but the scope of the present invention is not limited to the examples.
The raw materials used in the following examples are all commercially available unless otherwise specified.
Examples
Example 1
S1, adding 27.4g of mixed plastic from film packaging into a 250mL reaction kettle, wherein the mixed plastic contains 25g of polyethylene terephthalate (PET), polypropylene, polyvinyl chloride and other plastic materials. Wherein PET has an intrinsic viscosity of 0.63kDa and a number average molecular weight of 26.5kDa (the test solvent is phenol at a mass ratio of 60/40
1, 2-Tetrachloroethane, as defined herein, was added, followed by 66.4g of propylene carbonate (molar ratio of the repeating unit of PET to the propylene carbonate 1:5) and 0.046g of ethylene glycol antimony, and an inert argon gas flow was introduced for oxidation protection, and the mixture was heated to 200℃under normal pressure and stirring conditions, and was subjected to a reverse reaction by condensation reflux for 3 hours to obtain a first precursor. The first precursor was detected to have an intrinsic viscosity of 0.09dL/g and a number average molecular weight of 1.80kDa.
S2, dissolving the first precursor obtained in the step S1 by using chloroform, filtering to remove part of unreacted insoluble plastics such as polypropylene, polyvinyl chloride and the like, adsorbing by silica gel to remove pigments and impurities, adding precipitator diethyl ether to precipitate, removing the precipitate, and evaporating the solvent to obtain a second precursor.
And S3, vacuumizing and decompressing the second precursor obtained in the step S2 to 100Pa in a reaction kettle, and stirring and reacting for 2 hours at the rotating speed of 150r/min at the temperature of 230 ℃ to obtain a pure white regenerated polyester product A1. The intrinsic viscosity was found to be 0.61dL/g, the number average molecular weight was found to be 25.3kDa, and the nuclear magnetic resonance spectroscopy measurements of FIGS. 6-7 showed that the molar content of propylene carbonate units was found to be 5.0%.
Example 2
Example 2 referring to example 1, the only difference from example 1 is that the PET derived from the bottled water packaging mixed plastic in example 1 was replaced with bisphenol A polycarbonate (PC, the intrinsic viscosity was 0.32dL/g, the number average molecular weight was 15.1kDa, and the solvent was chloroform) derived from bottled water packaging, and other plastic materials were contained therein, and finally a colorless transparent recycled polycarbonate product was obtained and designated as A2.
The first precursor obtained in step S1 was found to have an intrinsic viscosity of 0.05dL/g and a number average molecular weight of 1.57kDa.
Finally, a colorless transparent regenerated polycarbonate product was obtained, which had an intrinsic viscosity of 0.35dL/g, a number average molecular weight of 16.8kDa, and a molar content of propylene carbonate units of 4.8% as determined by nuclear magnetic resonance spectroscopy.
Example 3
Example 2 referring to example 1, the only difference from example 1 is that the PET derived from the bottled water packaging mixed plastic in example 1 was replaced with poly (adipic acid)/butylene terephthalate copolyester (PBAT) for packaging, which had an intrinsic viscosity of 1.01dL/g, a number average molecular weight of 35.6kDa, and chloroform as the solvent), and other plastic materials were contained therein, and finally a pure white recycled polyester product was obtained and designated as A3.
The first precursor obtained in step S1 was found to have an intrinsic viscosity of 0.66dL/g and a number average molecular weight of 1.9kDa.
The detection shows that the pure white regenerated polyester product has an intrinsic viscosity of 1.26dL/g, a number average molecular weight of 49.0kDa and a molar content of propylene carbonate units of 3.8 percent.
Example 4
S1, adding 27.4g of mixed plastic from bottled water package into a 250mL reaction kettle, wherein the mixed plastic contains 25g of polyhexamethylene adipamide (PA 66, the intrinsic viscosity of which is 1.16dL/g through separation detection, the number average molecular weight of which is 24.7kDa, and the solvent of which is hexafluoroisopropanol), and other plastic materials such as polypropylene, polyvinyl chloride and the like. 47.07g of butyrolactam (molar ratio of PA66 recurring units to butyrolactam 1:5) and 0.036g of ethylene glycol antimony (in an amount of 0.05% relative to the total mass of PA66 and butyrolactam) were additionally charged. And (3) introducing inert argon gas flow to perform oxidation protection, heating to 200 ℃ under normal pressure and stirring conditions, and performing condensation reflux to perform reversible reaction for 3 hours to obtain a first precursor. The first precursor was tested to have an intrinsic viscosity of 0.25dL/g and a number average molecular weight of 2.16kDa.
S2, dissolving the first precursor obtained in the step S1 by using hexafluoroisopropanol, and filtering to remove part of unreacted and insoluble plastics such as polypropylene, polyvinyl chloride and the like. Removing pigment and impurities through silica gel adsorption, adding precipitator diethyl ether, precipitating, removing the precipitate, evaporating the solvent, and evaporating the solvent to obtain a second precursor.
And S3, vacuumizing and decompressing the two precursors obtained in the step S2 to be less than 100Pa in a reaction kettle, and reacting for 2 hours under the stirring of the rotating speed of 150r/min at the temperature of 250 ℃ to obtain pure white regenerated polyamide which is marked as A4.
The pure white recycled polyamide has an intrinsic viscosity of 1.21dL/g, a number average molecular weight of 26.4kDa, and a molar content of butyrolactam units of 3.5% as determined by nuclear magnetic resonance spectroscopy.
Examples 5 to 6
Referring to example 1, the preparation of examples 5-6 was identical to example 1 except that the antimony glycol of example 1 was replaced with stannous chloride of example 5, the antimony glycol of example 1 was replaced with magnesium oxide of example 6, wherein the catalyst was still used in an amount of 0.05% relative to the total mass of PET and propylene carbonate, and the products of examples 5-6 were designated A5 and A6, respectively.
The first precursor obtained in step S1 of example 5 was tested to have an intrinsic viscosity of 0.08dL/g and a number average molecular weight of 1.57kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.65dL/g, a number average molecular weight of 27.6kDa and a molar content of propylene carbonate units of 4.7% as determined by nuclear magnetic resonance spectroscopy.
The first precursor obtained in step S1 of example 6 had an intrinsic viscosity of 0.11dL/g and a number average molecular weight of 2.43kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.63dL/g, a number average molecular weight of 26.5kDa and a molar content of propylene carbonate units of 4.8% as determined by nuclear magnetic resonance spectroscopy.
Examples 7 to 9
Referring to example 1, the preparation of examples 7-9 was identical to example 1 except that propylene carbonate from example 1 was replaced with gamma-butyrolactone from example 7, propylene carbonate from example 1 was replaced with D, L-lactide from example 8, propylene carbonate from example 1 was replaced with succinic anhydride from example 9, wherein the molar ratio of repeat units to reactive monomers in PET was still 1:5, and the products from examples 7-9 were designated A7, A8 and A9, respectively.
The precursor obtained in step S1 of example 7 was examined to have an intrinsic viscosity of 0.13dL/g and a number average molecular weight of 3.05kDa;
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.67dL/g, a number average molecular weight of 28.8kDa and a molar content of gamma-butyrolactone units of 4.6% as determined by nuclear magnetic resonance spectroscopy.
The precursor obtained in step S1 obtained in example 8 had an intrinsic viscosity of 0.10dL/g and a number average molecular weight of 2.13kDa.
The step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.62dL/g and a number average molecular weight of 25.9kDa, and which shows a molar content of D, L-lactide units of 9.5% as determined by nuclear magnetic resonance spectroscopy.
The precursor obtained in step S1 of example 9 had an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.60dL/g, a number average molecular weight of 24.8kDa and a molar content of succinic anhydride units of 8.7% as determined by nuclear magnetic resonance spectroscopy.
Examples 10 to 12
Referring to example 1, the procedure for the preparation of example 10 was the same as in example 1 except that the molar ratio of PET to propylene carbonate in example 10 was 2:1, the molar ratio of PET to propylene carbonate in example 11 was 1:1, the molar ratio of PET to propylene carbonate in example 12 was 1:10, and the products of examples 10-12 were designated A10, A11 and A12, respectively.
The first precursor obtained in step S1 of example 10 was examined to have an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.64dL/g, a number average molecular weight of 27.2kDa and a molar content of propylene carbonate units of 0.5% as determined by nuclear magnetic resonance spectroscopy.
The first precursor obtained in step S1 of example 11 had an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.63dL/g and a number average molecular weight of 26.7kDa,
And the nuclear magnetic resonance spectrum detection shows that the molar content of the propylene carbonate unit is 2.1 percent.
The first precursor obtained in step S1 of example 12 had an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa. Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.61dL/g, a number average molecular weight of 25.5kDa and a molar content of propylene carbonate units of 8.9% as determined by nuclear magnetic resonance spectroscopy.
Example 13
Referring to example 1, the procedure of example 13 was the same as that of example 1 except that the temperature of the reaction in step S1 in this example was 250℃and the product of example 13 was designated as A13.
The precursor obtained in step S1 of example 13 was found to have an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.61dL/g, a number average molecular weight of 25.1kDa and a molar content of propylene carbonate units of 7.8% as determined by nuclear magnetic resonance spectroscopy.
Example 14
Referring to example 1, the procedure for the preparation of example 14 was the same as in example 1 except that the temperature of the reaction in step S3 in this example was 250℃and the product of example 14 was designated as A14.
The precursor obtained in step S1 of example 14 was found to have an intrinsic viscosity of 0.07dL/g and a number average molecular weight of 1.31kDa.
Step S3 gives a pure white recycled polyester product having an intrinsic viscosity of 0.64dL/g, a number average molecular weight of 27.1kDa and a molar content of propylene carbonate units of 3.9% as determined by nuclear magnetic resonance spectroscopy.
Examples 15 to 17
Referring to example 1, the preparation process of examples 15 to 17 was the same as that of example 1 except that the reaction time of step S3 in example 15 was 1h, the reaction time of step S3 in example 16 was 4h, and the reaction time of step S3 in example 17 was 8h, and the products of examples 15 to 17 were designated as A15, A16 and A17, respectively.
Step S3 of example 15 gave a pure white recycled polyester product having an intrinsic viscosity of 0.55dL/g, a number average molecular weight of 23.4kDa and a molar content of propylene carbonate units of 6.3% as determined by nuclear magnetic resonance spectroscopy.
Example 16 gives a pure white recycled polyester product having an intrinsic viscosity of 0.66dL/g, a number average molecular weight of 28.1kDa and a molar content of propylene carbonate units of 3.6% as determined by nuclear magnetic resonance spectroscopy.
Example 17 gives a pure white recycled polyester product having an intrinsic viscosity of 0.71dL/g, a number average molecular weight of 31.2kDa and a molar content of propylene carbonate units of 2.3% as determined by nuclear magnetic resonance spectroscopy.
Examples 18 to 19
The procedure for the preparation of examples 18 to 19 was the same as in example 1, except that the reaction pressure in step S3 of example 18 was 50Pa, the reaction pressure in step S3 of example 19 was 10Pa, and the products of examples 18 to 19 were designated as A18 and A19, respectively, with reference to example 1.
Step S3 of example 18 gave a pure white recycled polyester product having an intrinsic viscosity of 0.67dL/g, a number average molecular weight of 28.8kDa and a molar content of propylene carbonate units of 4.2% as determined by nuclear magnetic resonance spectroscopy.
Example 19 gives a virgin, white recycled polyester product having an intrinsic viscosity of 0.72dL/g, a number average molecular weight of 31.8kDa and a molar content of propylene carbonate units of 2.8% as determined by nuclear magnetic resonance spectroscopy.
Comparative example
Comparative example 1
The pre-reaction polyethylene terephthalate (PET) raw material from the film package of example 1, which had been physically separated, was designated as B1.
Comparative example 2
S1, adding 27.4g of mixed plastic from bottled water package into a 250mL reaction kettle, wherein the mixed plastic contains 25g of polyethylene terephthalate (PET, the intrinsic viscosity of which is 0.80kDa and the number average molecular weight of which is 37.0kDa through separation detection), polypropylene, polyvinyl chloride and other plastic materials. 66.4g of propylene carbonate (molar ratio of PET to propylene carbonate 1:5) and 0.0457g of ethylene glycol antimony (amount 500ppm relative to the total mass of PET and propylene carbonate) were additionally charged. And (3) introducing inert argon gas flow to perform oxidation protection, heating to 200 ℃ under normal pressure and stirring conditions, and performing condensation reflux to perform reversible reaction for 3 hours to obtain a first precursor. The intrinsic viscosity of the precursor was found to be 0.59dL/g and the number average molecular weight was found to be 25.4kDa.
S2, no step is carried out.
And S3, vacuumizing and decompressing the obtained precursor in a reaction kettle to be less than 100Pa, wherein the reaction temperature is 250 ℃, the mechanical stirring rotating speed is 150r/min, and reacting for 2 hours to obtain a dark ink product which is marked as B2. The intrinsic viscosity is 0.52dL/g, the number average molecular weight is 20.3kDa, and the nuclear magnetic resonance spectrum detection shows that the molar content of the propylene carbonate unit is 5.1 percent.
Comparative example 3
S1, adding 27.4g of mixed plastic from bottled water package into a 250mL reaction kettle, wherein the mixed plastic contains 25g of polyethylene terephthalate (PET, the intrinsic viscosity of which is 0.80kDa and the number average molecular weight of which is 37.0kDa through separation detection), polypropylene, polyvinyl chloride and other plastic materials. 66.4g of propylene carbonate (molar ratio of PET to propylene carbonate 1:5) and 0.0457g of ethylene glycol antimony (amount 500ppm relative to the total mass of PET and propylene carbonate) were additionally charged. And (3) introducing inert argon gas flow to perform oxidation protection, heating to 250 ℃ under normal pressure and stirring, and performing condensation reflux to perform reversible reaction for 3 hours to obtain a first precursor. The intrinsic viscosity of the precursor was found to be 0.59dL/g and the number average molecular weight was found to be 25.1kDa.
S2, dissolving the first precursor obtained in the step S1 by using chloroform, filtering to remove part of unreacted insoluble polypropylene, polyvinyl chloride and other plastics, adsorbing by silica gel to remove pigments and other impurities, adding precipitator diethyl ether to precipitate, and finally evaporating the solvent to obtain a final product, namely B3.
Performance test examples
Performance test example 1
The recycled polyester, recycled polycarbonate or recycled polyamide products A1-A19 of examples 1-19 and the recycled products B1-B3 of comparative examples 1-3 were each injection molded into corresponding test strips according to a unified procedure, and performance tests were conducted according to the following test standards and conditions, and the results are recorded in Table 1 below.
Tensile strength measured according to the measurement method specified in the ISO 527-2 plastic tensile property test method, wherein the tensile rate is 50mm/min;
Elongation at break measured according to the measurement method specified in the ISO 527-2 plastic tensile property test method, wherein the tensile rate is 50mm/min;
TABLE 1 test results for examples 1-19 and comparative examples 1-3
Performance test example 2
Testing of the final aerobic biological decomposing ability of the materials under controlled composting conditions (according to the test criteria:
GB/T19277.1-2011/ISO 14855-1:2005) the recycled polyester, recycled polycarbonate or recycled polyamide products A1-A19 of examples 1-19 and the recycled products B1-B2 of comparative examples 1-2 are each injection molded according to a unified procedure into a corresponding test strip, mixed with an inoculum and placed in a composting vessel prepared in advance, the dry weight of the inoculum to the dry weight of the material being 6:1 and the volume of the mixture being not more than 3/4 of the volume of the composting vessel, the content of carbon dioxide in the exhaust gas of each composting vessel being measured periodically during the test with a total organic carbon analyzer, the ratio to the theoretical release amount being calculated to obtain the biological decomposition rate (%). The test results are shown in table 2 below.
TABLE 2 composting biodegradability test results for examples 1-19 and comparative examples 1,2
As can be seen from the data of examples 1-19 of tables 1 and 2, the present invention can achieve the adjustment of the mechanical and biodegradation properties of the recycled polyester, recycled polycarbonate or recycled polyamide products by the selection of the catalyst, the difference of the reversible reactive monomers, the difference of the temperature, the pressure and the reaction time, thereby obtaining recycled plastic products which can be used in different occasions.
The data of comparative example 1 and comparative example 1 shows that the recycled polyester obtained by inserting the units of the reactive monomer into the polyester molecular chain is better in mechanical properties and biodegradability than the original polyethylene terephthalate (PET).
The data of comparative example 1 and comparative example 2 show that the properties of the final product, mechanical and biodegradation, are much worse than those of example 1 without the process of filtering, purifying and removing impurities.
The data of comparative examples 1 and 3 show that the products obtained without the reversible reaction have poor tensile strength and elongation at break.
Compared with the traditional recycling mode of mixed plastics, the recycling method of the invention realizes no need of manual sorting and can selectively recycle polyester, polycarbonate or polyamide products. Secondly, the polyester, polycarbonate and polyamide products prepared by the method have certain advantages. In general, compared with the prior art, the recycling method has the advantages that manual sorting is not needed, different plastics are recycled chemically and selectively, the limitation of the traditional chemical recycling method on the treatment of mixed plastics is overcome, the performance of a final product can be adjusted by controlling the reaction time, meanwhile, the method is simple and controllable, and the reversible reactive monomer can be recycled and reused, so that the method accords with the green chemistry principle.
The embodiments of the present invention are described in detail above. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the core concepts of the invention. It should be noted that it will be apparent to those skilled in the art that the present invention may be modified and adapted without departing from the principles of the present invention, and that such modifications and adaptations are intended to be within the scope of the appended claims.
Claims (8)
1. A method for recycling and preparing regenerated polymer from waste mixed plastic, which is characterized by comprising the following steps:
S1, under normal pressure, reacting a reactant in waste mixed plastics with a reaction monomer under the action of a catalyst to obtain a first precursor;
S2, dissolving, separating and removing impurities from the first precursor obtained in the step S1 to obtain a second precursor;
S3, reacting the second precursor for 0.5-48 hours under the action of a catalyst at 150-300 ℃ and under the absolute pressure of 1-1000Pa to obtain a reaction monomer and a regenerated polymer;
the reactant in the waste mixed plastic is one of polyester, polycarbonate or polyamide,
The reaction monomer in the S1 comprises at least one of five-membered or six-membered cyclic ester, cyclic thioester, cyclic carbonate, cyclic anhydride and cyclic lactam, and the structures of the five-membered or six-membered cyclic ester and the cyclic thioester are shown in the following formulas (I) - (III):
The cyclic carbonate has the following structural formula (IV) and formula (V):
The cyclic anhydride has the following structures (VI) and (VII):
The structure of the cyclic lactam is shown in the following formula (VIII) and formula (IX):
wherein ,R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11、R12、R13、R14、R15、R16、R17、R18、R19、R20、R21、R22、R23、R24、R25 and R 26 are each, independently of one another, hydrogen or alkyl,
The polyester is respectively reacted with the cyclic ester, the cyclic thioester, the cyclic carbonate and the cyclic anhydride, the polycarbonate is respectively reacted with the cyclic ester, the cyclic thioester, the cyclic carbonate and the cyclic anhydride, and the polyamide is respectively reacted with the cyclic anhydride and the cyclic lactam.
2. The method for recycling recycled polymer from waste mixed plastics according to claim 1, wherein the polyester comprises at least one of polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, cyclohexane dimethanol terephthalate, polyethylene furandicarboxylate, polybutylene succinate, polybutylene adipate/terephthalate copolyester, polylactic acid;
The polycarbonate comprises at least one of bisphenol A polycarbonate and polypropylene carbonate;
The polyamide comprises at least one of polyhexamethylene adipamide, polycaprolactam, poly omega-aminoundecanoyl, polydodecanoyl, polybutylene adipamide, polyhexamethylene dodecanoyl diamine and polydecanoyl sebacamide.
3. The method for recycling and preparing regenerated polymer in waste mixed plastics according to claim 1, wherein the catalyst is at least one of oxides, hydroxides, alkoxides, carboxylates, and halogen salts of tin, zinc, magnesium, antimony, manganese, and cadmium.
4. The method for recycling and preparing recycled polymer from waste mixed plastics according to claim 1, wherein the weight of the catalyst is 0.05-1% of the total weight of reactants in the waste mixed plastics.
5. The method for recycling and preparing recycled polymer from waste mixed plastic according to claim 1, wherein the mole ratio of the repeating unit of reactant to the reactive monomer in the waste mixed plastic is 1 (0.1-10).
6. The method for recycling and preparing recycled polymer from waste mixed plastics according to claim 1, wherein the reaction is performed at 100-250 ℃ for 0.5-48 hours in step S1.
7. The method for recycling and preparing regenerated polymer in waste mixed plastic according to claim 1, wherein the specific process of step S2 is that the first precursor obtained in step S1 is dissolved by solvent, part of unreacted and insoluble plastic is removed by filtration, pigment and impurities are removed by silica gel adsorption, a precipitator is added, precipitation occurs, and after precipitation is removed, the solvent is evaporated to dryness, so as to obtain the second precursor.
8. A recycled polymer produced by the method for recycling recycled polymer from waste mixed plastics according to any one of claims 1 to 7, wherein the recycled polymer is one of recycled polyester, recycled polycarbonate or recycled polyamide.
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