Degradable and recyclable plastic as well as preparation method and application thereof

Abstract

The invention discloses degradable and recyclable plastic as well as a preparation method and application thereof, and belongs to the technical field of polymer preparation. 3-cyclopentene-1-formate is subjected to ring opening polymerization to obtain poly (3-cyclopentene-1-formate), then the poly (3-cyclopentene-1-formate) and biomass high-grade linear fatty alcohol are subjected to transesterification under the action of a catalyst, a polyolefin-like high polymer material with side chain crystallization is obtained, the main chain of the polyolefin-like high polymer material contains carbon-carbon double bonds, a polymer can be depolymerized back to a monomer, and degradation and recycling are achieved. Due to side chain crystallization, the polymer has mechanical properties similar to that of low-density polyethylene, and can be applied to the field of preparation of low-density polyethylene. As the polymerization on-line temperature of cyclopentene is relatively low, the degradable plastic prepared by the invention can be degraded to original monomers or other cyclopentenyl monomers under mild conditions, and 100% recovery of carbon resources is realized. The obtained monomer can be polymerized again to obtain a corresponding polymer, so that closed-loop recycling is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer preparation, and in particular relates to a degradable, recyclable plastic and a preparation method and application thereof. Background Art

[0002] Plastic products are currently the most manufactured and used polymer materials, and are widely used in fields such as packaging, bottles, pipes and high-performance fibers. After years of development, the relevant production technology has matured, industrial manufacturing is simple, and mechanical properties are good. Plastics developed from petroleum-based materials have always been difficult to completely replace. Polyolefins (polyethylene and polypropylene) are the most commonly used types of plastic products, accounting for about 36%. They are completely composed of chemical bonds such as CH, CC, and CO. They are difficult to break and degrade under natural conditions, which has caused many environmental and social problems, such as "white pollution" and "microplastics", which pose potential threats to the ecology. Therefore, it is very necessary to prepare degradable and even recyclable alternative plastic products.

[0003] Cyclopentene is a type of cycloolefin monomer, which is a cheap and easily available category in petrochemical products. The ceiling temperature of polymerization of cyclopentene monomer is relatively low (~29°C, 1 mol / L concentration condition), which is very suitable for the preparation of depolymerizable polymer materials. 3-cyclopentene-1-carboxylic acid esters derived from cyclopentene (including 3-cyclopentene-1-carboxylic acid methyl ester and 3-cyclopentene-1-carboxylic acid ethyl ester) have also been commercialized. However, the polymers obtained by polymerization of this type of monomer are not crystalline and have a low glass transition temperature, making it difficult to achieve the mechanical properties of polyolefin plastics. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention provides a degradable and recyclable plastic and a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention: a method for preparing a degradable and recyclable plastic, comprising the following steps: ring-opening metathesis polymerization of 3-cyclopentene-1-carboxylate to obtain poly(3-cyclopentene-1-carboxylate), and then using biomass linear fatty alcohol and poly(3-cyclopentene-1-carboxylate) to undergo an ester exchange reaction under the action of a catalyst to obtain a side chain crystalline polyolefin-like degradable and recyclable plastic.

[0007] As a preferred embodiment of the present invention, the 3-cyclopentene-1-carboxylate includes one of 3-cyclopentene-1-carboxylic acid methyl ester and 3-cyclopentene-1-carboxylic acid ethyl ester.

[0008] As a preferred embodiment of the present invention, the biomass linear fatty alcohol includes one or more of n-octanol, n-nonanol, n-decanol, undecyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, eicosyl alcohol, docosyl alcohol, tetracosyl alcohol, hexacosyl alcohol, octacosyl alcohol, triacontyl alcohol, and dotriacontyl alcohol.

[0009] As a preferred embodiment of the present invention, the solvent for the ring-opening metathesis polymerization of 3-cyclopentene-1-carboxylate includes one or more of dichloromethane, tetrahydrofuran, toluene, chlorobenzene, and dichlorobenzene. The transesterification reaction may not use a solvent. If a solvent is used, it includes one or more of decalin, xylene, and toluene.

[0010] As a preferred embodiment of the present invention, the catalyst for the ring-opening metathesis polymerization includes Grubbs first-generation catalyst, Grubbs second-generation catalyst, Grubbs third-generation catalyst, Hoveyda-Grubbs first-generation catalyst, or Hoveyda-Grubbs second-generation catalyst; the catalyst for the transesterification reaction includes 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), tetrabutyl titanate, sulfuric acid, hydrochloric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, sodium hydroxide, potassium hydroxide, carbonate, aluminum chloride, zinc chloride, titanium tetrachloride, zinc acetate, sodium methoxide, sodium ethoxide, dichlorotitanocene, dibutyltin oxide, or butyltin chloride.

[0011] As a preferred embodiment of the present invention, the temperature of the ring-opening metathesis polymerization is -10 to 5 °C.

[0012] The second technical solution of the present invention: A degradable and recyclable plastic prepared by the preparation method described above.

[0013] The third technical solution of the present invention: An application of the degradable and recyclable plastic described above in packaging bags, greenhouse films, and mulch films.

[0014] The fourth technical solution of the present invention: A degradation method of the degradable and recyclable plastic described above, adding the degradable and recyclable plastic to a solvent and degrading it to obtain monomers under the action of a catalyst.

[0015] As a preferred embodiment of the present invention, the solvent includes tetrahydrofuran, dichloromethane, toluene, chlorobenzene, dichlorobenzene or chloroalkane; the catalyst includes Grubbs first-generation catalyst, Grubbs second-generation catalyst, Grubbs third-generation catalyst, Hoveyda-Grubbs first-generation catalyst or Hoveyda-Grubbs second-generation catalyst; the degradation temperature is 23 to 100 °C. The specific degradation temperature can be selected according to the boiling point of the selected solvent and the applicable activity of the catalyst, etc.

[0016] Temperature is a key factor affecting monomer polymerization and polymer degradation, that is, ring-opening polymerization of monomers is favored at low temperatures, and degradation of polymers into monomers is favored at high temperatures.

[0017] In the present invention, a crystallizable component is introduced into 3-cyclopentene-1-carboxylates derived from cyclopentene (including methyl 3-cyclopentene-1-carboxylate and ethyl 3-cyclopentene-1-carboxylate), and the position suitable for introducing it into the polymer molecular chain is the side chain. Linear fatty alcohols, especially those with longer chain lengths, have strong crystallization ability, are derived from biomass, can be extracted from plants, and have the ability to be renewable. Since it is ecologically beneficial in nature, the corresponding degradation products will not harm the environment. In the present invention, it is used as a side chain and introduced by transesterification with the polymer obtained by polymerizing the above-mentioned cyclopentenyl monomers, thereby preparing a degradable and recyclable plastic.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention selects 3-cyclopentene-1-carboxylate, which is relatively abundant in the petrochemical industry, as the matrix raw material to synthesize the corresponding depolymerizable polymer. The present invention performs transesterification on the ester groups in such polymers with biomass linear fatty alcohols to obtain a polyolefin-like polymer material with side-chain crystallization. The crystallization behavior of this polymer material is related to the amount of biomass linear fatty alcohol added in the transesterification reaction. Therefore, the crystallization behavior of the material can be regulated by adjusting the input amount of biomass linear fatty alcohol in the transesterification reaction, thereby regulating the mechanical properties of the material.

[0020] (2) The degradable plastic prepared by the present invention is close to low-density polyethylene (LDPE) in mechanical properties and can be used to make packaging bags, greenhouse films, mulch films, etc., thereby replacing the difficult-to-degrade LDPE in the corresponding fields.

[0021] (3) Since the upper polymerization temperature of cyclopentene is relatively low, the degradable plastic prepared by the present invention can be degraded into polymerizable monomers under mild conditions, realizing 100% recovery of carbon resources. The obtained monomers can be re-polymerized to obtain the corresponding polymers, realizing closed-loop recycling. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 Among them, A is the synthesis route of the depolymerizable polymer and the side-chain crystalline polymer of the present invention; B is the structural formulas of three types of polymers CP32-1, CP30-1, and CP28-1 obtained after the complete conversion of biomass linear fatty alcohol to methyl in the transesterification reactions of Example 3 and Examples 8-9; C is the schematic diagram of the depolymerization and closed-loop utilization of the degradable and recyclable plastics of the present invention.

[0024] Figure 2 It is a graph of the tensile deformation test results of low-density polyethylene LDPE and polymer products CP32-1, CP32-2, CP32-3, CP32-4 with different degrees of transesterification obtained by transesterification using n-dotriacontanol in Examples 3-7.

[0025] Figure 3 It is a graph of the tensile deformation test results of low-density polyethylene LDPE and polymer products CP30-1, CP30-2, CP30-3, CP30-4, CP30-5 with different degrees of transesterification obtained by transesterification using n-triacontanol in Example 8 and Examples 14-17.

[0026] Figure 4 It is a graph of the tensile deformation test results of low-density polyethylene LDPE and polymer products CP28-1, CP28-2, CP28-3, CP28-4, CP28-5 with different degrees of transesterification obtained by transesterification using n-octacosanol in Example 9 and Examples 22-25.

[0027] Figure 5 Among them, A is the degradation and recycling route of CP32-3 (62% transesterification of n-dotriacontanol) prepared in Example 5; B and C are the nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography spectrum of 3-cyclopentene-1-carboxylic acid dotriacontyl ester, methyl 3-cyclopentene-1-carboxylate, and poly(methyl 3-cyclopentene-1-carboxylate) after repolymerization in the route, respectively. Detailed Embodiments

[0028] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only used to describe specific implementation modes and are not used to limit the present invention.

[0029] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0031] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0032] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0033] In the following examples, normal temperature refers to 20 - 35 °C, and the raw materials used are all commercially available conventional raw materials without special limitations. This will not be repeatedly described hereinafter.

[0034] Example 1

[0035] Synthesis of poly(methyl 3-cyclopentene-1-carboxylate) (CPMt), and the synthesis route is as follows:

[0036]

[0037] The synthesis steps are as follows:

[0038] A depolymerizable polymer was obtained by ring-opening metathesis polymerization (ROMP) of methyl 3-cyclopentene-1-carboxylate. At room temperature and under a nitrogen atmosphere, methyl 3-cyclopentene-1-carboxylate (20 g, 158.5 mmol) was dissolved in dichloromethane (31.7 mL, 5 M) in a 100 mL flame-dried Schlenk flask. Then the catalyst (Hoveyda-Grubbs second-generation catalyst, 248 mg, 0.4 mmol) was quickly added to the mixture, and the mixture was stirred at room temperature for 30 minutes and then cooled to 0 °C. After two hours, 5 mL of ethyl vinyl ether was added to quench the reaction for 30 minutes. The solution was poured into 300 mL of methanol to precipitate the product. The pale yellow viscous solid product was dissolved in dichloromethane and reprecipitated into another 300 mL of methanol. Then the product was collected by centrifugation and dried in vacuo until the weight remained constant. Yield: 16.2 g (81%).

[0039] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.35 (d, J = 18.5 Hz, 2H), 3.64 (s, 3H), 2.37 (dd, J = 17.7, 11.5 Hz, 1H), 2.33–2.04 (m, 4H). 13C NMR (101 MHz, CDCl3, ppm): δ = 175.36 (s), 129.28 (s), 128.29 (s), 51.41 (s), 45.62 (s), 34.57 (s). GPC data (THF vs polystyrene standards): Mn = 23.3 kDa, Mw = 36.5 kDa (PDI = 1.57). DSC: Glass transition temperature Tg -25 °C.

[0040] Example 2

[0041] Synthesis of poly(ethyl 3-cyclopentene-1-carboxylate) (CPEt), the synthesis route is as follows:

[0042]

[0043] The synthesis steps are as follows:

[0044] By ring-opening metathesis polymerization (ROMP) of ethyl 3-cyclopentene-1-carboxylate, a depolymerizable polymer was obtained. At room temperature and under a nitrogen atmosphere, ethyl 3-cyclopentene-1-carboxylate (14 g, 100 mmol) was dissolved in dichloromethane (20 mL, 5 M) in a 100 mL flame-dried Schlenk flask. Then the catalyst (Hoveyda-Grubbs second-generation catalyst, 248 mg, 0.4 mmol) was quickly added to the mixture, and the mixture was stirred at room temperature for 30 minutes and then cooled to 0 °C. After two hours, 5 mL of ethyl vinyl ether was added to quench the reaction for 30 minutes. The solution was poured into 500 mL of methanol to precipitate the product. The pale yellow viscous solid product was dissolved in dichloromethane and reprecipitated into another 300 mL of methanol. Then the product was collected by centrifugation and dried in vacuo until the weight remained constant. Yield: 11.2 g (80%).

[0045] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.34 (d, J = 18.7 Hz, 2H), 4.11 (dq, J = 14.2, 7.1 Hz, 2H), 2.34 (dd, J = 16.0, 8.4 Hz, 1H), 2.18 (dd, J = 47.9, 10.8 Hz, 4H), 1.25 (dt, J = 14.2, 7.1 Hz, 3H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.92 (s), 129.31 (s), 60.17 (s), 45.56 (s), 34.53 (s), 14.36 (s). GPC data (THF vs. polystyrene standards): Mn = 32.8 kDa, Mw = 55.3 kDa (PDI = 1.69). DSC: Glass transition temperature Tg -42 °C.

[0046] Example 3

[0047] Synthesis of the degradable and recyclable polymer CP32-1, and the synthetic route is as follows:

[0048]

[0049] The crystalline degradable and recyclable polymer CP32-1 was prepared by a complete transesterification reaction of n-docosanol with poly(3-cyclopentene-1-carboxylic acid methyl ester), and the synthesis steps are as follows:

[0050] In an N2 environment, in a Schlenk flask equipped with a Teflon-coated stir bar, poly(3-cyclopentene-1-carboxylic acid methyl ester) (4 g, 31.7 mmol repeating units) and n-dotriacontanol (16.3 g, 35 mmol) (taking complete transesterification as an example) were added. The catalyst TBD (44.5 mg, 0.32 mmol, 1 mol%) was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 180 °C under vacuum to remove the by-product methanol (for 12 hours). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 hour. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we used ethyl acetate to extract them through a Soxhlet extractor at 60 °C. Yield: Polymer CP32-1, 15.9 g (yield 90%).

[0051] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.48–5.26 (m, 2H), 4.01 (q, J = 6.9 Hz, 2H), 2.26 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 2H), 1.25 (s, 58H), 0.88 (t, J = 6.7 Hz, 3H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.77, 129.28, 64.35, 45.83, 34.73, 31.95, 29.79, 29.77, 29.74, 29.72, 29.70, 29.65, 29.41, 29.37, 28.75, 26.01, 22.73, 14.11. GPC data (THF vs polystyrene standard): M n = 106.6 kDa, DSC: Melting point T m = 93 °C.

[0052] Example 4

[0053] Synthesis of the degradable and recyclable polymer CP32-2, and the synthesis route is as follows:

[0054]

[0055] A crystalline degradable and recyclable polymer CP32-2 was prepared by the partial transesterification reaction of n-dotriacontanol with poly(3-cyclopentene-1-carboxylic acid methyl ester). The steps are as follows:

[0056] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated stir bar, poly(3-cyclopentene-1-carboxylic acid methyl ester) (4 g, 31.7 mmol repeating units) and n-dotriacontanol (13 g, 28 mmol) (taking 80% transesterification as an example) were added. Catalyst TBD (44.5 mg, 0.32 mmol, 1 mol%) was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 180 °C under vacuum to remove by-product methanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we extracted them with ethyl acetate at 60 °C using a Soxhlet extractor. Yield: Polymer CP32-2, 13.5 g (yield 95%). Transesterification: 79%.

[0057] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.48–5.25 (m, 2H), 4.01 (q, J = 6.9 Hz, 1.58H), 3.65 (s, 0.58H), 2.25 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 1.58H), 1.25 (s, 55H), 0.88 (t, J = 6.7 Hz, 2.36H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.77, 129.28, 64.35, 51.45, 45.83, 34.73, 31.95, 29.79, 29.77, 29.74, 29.72, 29.70, 29.65, 29.41, 29.37, 28.75, 26.01, 22.73, 14.11. GPC data (THF vs polystyrene standard): M n = 92.6 kDa, DSC: Melting point T m = 90 °C.

[0058] Example 5

[0059] Synthesis of degradable and recyclable polymer CP32-3, and the synthesis route is as follows:

[0060]

[0061] Crystalline degradable and recyclable polymer CP32-3 was prepared by partial transesterification reaction of n-dotriacontanol with poly(3-cyclopentene-1-carboxylic acid methyl ester), and the steps are as follows:

[0062] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated magnetic stir bar, poly(methyl 3-cyclopentene-1-carboxylate) (4 g, 31.7 mmol repeating units) and n-dotriacontanol (9.8 g, 21 mmol) (taking the target 60% transesterification as an example) were added. The catalyst TBD (44.5 mg, 0.32 mmol, 1 mol%) was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 180 °C under vacuum to remove the byproduct methanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we used ethyl acetate to extract them through a Soxhlet extractor at 60 °C. Yield: Polymer CP32-3, 9.3 g (85% yield). Transesterification: 62%.

[0063] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.47–5.24 (m, 2H), 4.02 (q, J = 6.9 Hz, 1.24H), 3.65 (s, 1.14H), 2.26 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 1.24H), 1.25 (s, 34.3H), 0.88 (t, J = 6.7 Hz, 1.86H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.75, 129.28, 64.35, 51.45, 45.83, 34.73, 31.95, 29.79, 29.78, 29.74, 29.72, 29.70, 29.65, 29.41, 29.37, 28.75, 26.01, 22.74, 14.11. GPC data (THF vs polystyrene standard): M n = 65.6 kDa, DSC: Melting point T m = 91 °C.

[0064] Example 6

[0065] Synthesis of the degradable and recyclable polymer CP32-4, and the synthetic route is as follows:

[0066]

[0067] The crystalline degradable and recyclable polymer CP32-4 was prepared by the partial transesterification reaction of n-dotriacontanol with poly(methyl 3-cyclopentene-1-carboxylate), and the steps are as follows:

[0068] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated magnetic stir bar, poly(3-cyclopentene-1-carboxylate methyl ester) (4 g, 31.7 mmol repeating units) and n-dotriacontanol (6.5 g, 14 mmol) (taking 40% transesterification as an example) were added. The catalyst TBD (44.5 mg, 0.32 mmol, 1 mol%) was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 180 °C under vacuum to remove the by-product methanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we used ethyl acetate to extract them through a Soxhlet extractor at 60 °C. Yield: polymer CP32-4, 6.2 g (88% yield). Transesterification: 43%.

[0069] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.46–5.24 (m, 2H), 4.02 (q, J = 6.9 Hz, 0.86H), 3.64 (s, 1.71H), 2.26 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 0.86H), 1.26 (s, 24.1H), 0.89 (t, J = 6.7 Hz, 1.26H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.75, 129.29, 64.35, 51.46, 45.83, 34.74, 31.95, 29.79, 29.75, 29.74, 29.72, 29.70, 29.65, 29.41, 29.38, 28.75, 26.01, 22.74, 14.11. GPC data (THF vs polystyrene standard): M n n = 42.6 kDa, DSC: melting point T m m = 87 °C.

[0070] Example 7

[0071] Synthesis of degradable and recyclable polymer CP32-5, the synthetic route is as follows:

[0072]

[0073] Crystalline degradable and recyclable polymer CP32-5 was prepared by partial transesterification reaction of n-dotriacontanol with poly(3-cyclopentene-1-carboxylate methyl ester), and the steps are as follows:

[0074] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated magnetic stir bar, poly(methyl 3-cyclopentene-1-carboxylate) (4 g, 31.7 mmol repeating units) and n-dotriacontanol (3.3 g, 7 mmol) (taking 20% transesterification as an example) were added. Catalyst TBD (44.5 mg, 0.32 mmol, 1 mol%) was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 180 °C under vacuum to remove the by-product methanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we extracted them with ethyl acetate at 60 °C using a Soxhlet extractor. Yield: Polymer CP32-5, 2.9 g (yield 91%). Transesterification: 19%.

[0075] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.46–5.25 (m, 2H), 4.01 (q, J = 6.9 Hz, 0.38H), 3.64 (s, 2.43H), 2.26 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 0.38H), 1.24 (s, 1.19H), 0.89 (t, J = 6.7 Hz, 0.57H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.75, 129.29, 64.35, 51.46, 45.83, 34.74, 31.95, 29.79, 29.76, 29.74, 29.72, 29.70, 29.65, 29.41, 29.38, 28.75, 26.01, 22.74, 14.12. GPC data (THF vs polystyrene standard): M n n = 21.5 kDa, DSC: Melting point T m m = 80 °C.

[0076] Example 8

[0077] Synthesis of degradable and recyclable polymer CP30-1, the synthetic route is as follows:

[0078]

[0079] Crystalline degradable and recyclable polymer CP30-1 was prepared by the complete transesterification reaction of n-triacontanol with poly(ethyl 3-cyclopentene-1-carboxylate). The steps are as follows:

[0080] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated magnetic stir bar, poly(ethyl 3-cyclopentene-1-carboxylate) (4.5 g, 32 mmol repeating units) and n-triacontanol (15.4 g, 35 mmol) (taking complete transesterification as an example) were added. Tetrabutyl titanate (108.8 mg, 0.32 mmol, 1 mol%) as the catalyst was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 160 °C under vacuum to remove the by-product ethanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we used ethyl acetate to extract them through a Soxhlet extractor at 60 °C. Yield: Polymer CP30-1, 16.8 g (yield 98%).

[0081] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.46–5.25 (m, 2H), 4.01 (q, J = 6.9 Hz, 2H), 2.25 (dd, J = 51.6, 37.0 Hz, 5H), 1.57 (s, 2H), 1.25 (s, 58H), 0.89 (t, J = 6.7 Hz, 3H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.77, 129.29, 64.35, 45.83, 34.74, 31.95, 29.79, 29.77, 29.74, 29.72, 29.70, 29.65, 29.42, 29.37, 28.75, 26.01, 22.73, 14.12. GPC data (THF vs polystyrene standard): M n = 125.9 kDa, DSC: Melting point T m = 84 °C.

[0082] Example 9

[0083] Synthesis of degradable and recyclable polymer CP28-1, the synthetic route is as follows:

[0084]

[0085] Crystalline degradable and recyclable polymer CP28-1 was prepared by the complete transesterification reaction of n-octacosanol with poly(methyl 3-cyclopentene-1-carboxylate), and the steps are as follows:

[0086] Under N2 atmosphere, in a Schlenk flask equipped with a Teflon-coated magnetic stir bar, poly(methyl 3-cyclopentene-1-carboxylate) (4 g, 31.7 mmol repeating units) and n-octacosanol (14.35 g, 35 mmol) (taking complete transesterification as an example) were added. Tetrabutyl titanate (108.8 mg, 0.32 mmol, 1 mol%) as the catalyst was weighed and transferred to the Schlenk flask in the glove box. The mixture was heated to 160 °C under vacuum to remove the by-product methanol (for 12 h). After the reaction, toluene was added to dissolve the polymer. The mixture was precipitated in hexane and stirred for at least 1 h. The polymer precipitate was collected by filtration and washed with ethanol, and then dried in a vacuum oven. To completely remove the unreacted alcohol, we used ethyl acetate to extract them through a Soxhlet extractor at 60 °C. Yield: Polymer CP28-1, 12 g (yield 92%).

[0087] Characterization: 1 1H NMR (400 MHz, CDCl3, ppm): δ = 5.47–5.26 (m, 2H), 4.02 (q, J = 6.9 Hz, 2H), 2.25 (dd, J = 51.6, 37.0 Hz, 5H), 1.58 (s, 2H), 1.25 (s, 58H), 0.89 (t, J = 6.7 Hz, 3H). 13 13C NMR (101 MHz, CDCl3, ppm): δ = 174.77, 129.29, 64.35, 45.83, 34.74, 31.96, 29.79, 29.77, 29.74, 29.73, 29.70, 29.66, 29.42, 29.37, 28.76, 26.01, 22.73, 14.12. GPC data (THF vs polystyrene standard): M n = 75.8 kDa, DSC: Melting point T m = 75 °C.

[0088] Other examples are listed in a table, see Table 1.

[0089] Table 1 Preparation of crystalline degradable plastics using poly(methyl 3-cyclopentene-1-carboxylate) (4 g) as an example

[0090]

[0091]

[0092] Figure 1In it, A is the synthetic route of the depolymerizable polymer and the side-chain crystalline polymer of the present invention; B is the structural formulas of three types of polymers CP32-1, CP30-1, and CP28-1 obtained after the complete conversion of biomass linear fatty alcohol to methyl in the transesterification reactions of Example 3 and Examples 8-9; C is the schematic diagram of the depolymerization and closed-loop utilization of the degradable and recyclable plastics of the present invention.

[0093] Figure 2 is the tensile deformation test result diagram of low-density polyethylene LDPE (0.92 g / cm 3 ), and the polymer products CP32-1, CP32-2, CP32-3, CP32-4 with different degrees of transesterification obtained by transesterification using n-dotriacontanol in Examples 3-7. It can be seen that the mechanical properties of some products (CP32-1, CP32-2) are close to those of LDPE.

[0094] Figure 3 is the tensile deformation test result diagram of low-density polyethylene LDPE (0.92 g / cm 3 ), and the polymer products CP30-1, CP30-2, CP30-3, CP30-4, CP30-5 with different degrees of transesterification obtained by transesterification using n-triacontanol in Example 8 and Examples 14-17. It can be seen that the mechanical properties of some products (CP30-1, CP30-2, CP30-3) are close to those of LDPE.

[0095] Figure 4 is the tensile deformation test result diagram of low-density polyethylene LDPE (0.92 g / cm 3 ), and the polymer products CP28-1, CP28-2, CP28-3, CP28-4, CP28-5 with different degrees of transesterification obtained by transesterification using n-octacosanol in Example 9 and Examples 22-25. It can be seen that the mechanical properties of some products (CP28-1, CP28-2) are close to those of LDPE.

[0096] The degradation and cyclic recycling of CP32-3 (62% transesterification of n-docosanol) prepared in Example 5 were carried out as follows: At room temperature, under a nitrogen atmosphere, CP32-3 (5 g, 20.53 mmol C═C bonds) was dissolved in toluene (90 mL, 0.1 M) in a 250 mL flame-dried Schlenk flask. Then Grubbs first-generation catalyst (13.4 mg, 16.2 μmol) was quickly added to the mixture, and then the mixture was heated to 100 °C. After refluxing for 2 hours, the mixture was poured into 300 mL of acidic methanol. Methyl cyclopent-3-ene carboxylate (1.7 g, recovery rate 89%) was collected by vacuum distillation. Then the CP32-RM product (3 g, recovery rate 97%) was collected by filtration and purified by washing with methanol (100 mL). Yield: 4.7 g (total monomer recovery rate 94%).

[0097] Figure 5 In Figure 4, A is the degradation and cyclic recycling route of CP32-3 (62% transesterification of n-docosanol) prepared in Example 5. Under the action of a catalyst, it can be depolymerized into docosanyl cyclopent-3-ene-1-carboxylate and methyl cyclopent-3-ene-1-carboxylate. The former can undergo a transesterification reaction with methanol to obtain the latter. The latter can be further polymerized as a monomer to obtain poly(methyl cyclopent-3-ene-1-carboxylate). Poly(methyl cyclopent-3-ene-1-carboxylate) can undergo a transesterification reaction with n-docosanol to obtain the initial crystalline depolymerizable polymer, thus completing the closed-loop recycling. B and C are the 1H NMR spectra and gel permeation chromatography spectra of docosanyl cyclopent-3-ene-1-carboxylate, methyl cyclopent-3-ene-1-carboxylate, and poly(methyl cyclopent-3-ene-1-carboxylate) after repolymerization in the route, respectively, which all indicate that the target product was obtained according to the route and the good feasibility of the route.

[0098] The polymers prepared in other examples of the present invention can also be degraded according to the above route.

[0099] The above is only the preferred specific embodiment of the present invention, and the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A method for preparing degradable and recyclable plastics, characterized in that: The following steps are involved: 3-cyclopentene-1-carboxylate is ring-opening metathesis polymerized to obtain poly(3-cyclopentene-1-carboxylate), and then biomass linear fatty alcohol is used to undergo an ester exchange reaction with poly(3-cyclopentene-1-carboxylate) under the action of a catalyst to obtain a side chain crystalline polyolefin-like biodegradable and recyclable plastic.

2. The method for preparing degradable and recyclable plastic according to claim 1, characterized in that: The 3-cyclopentene-1-carboxylate includes one of 3-cyclopentene-1-carboxylic acid methyl ester and 3-cyclopentene-1-carboxylic acid ethyl ester.

3. The method for preparing degradable and recyclable plastic according to claim 2, characterized in that: The biomass linear fatty alcohol includes one or more of n-octanol, n-nonanol, n-decanol, undecyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecanol, octadecyl alcohol, eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol, triacontanol and tridocontanol.

4. The method for preparing degradable and recyclable plastic according to claim 1, characterized in that: The solvent for the ring-opening metathesis polymerization of 3-cyclopentene-1-carboxylate includes one or more of dichloromethane, tetrahydrofuran, toluene, chlorobenzene and dichlorobenzene, and the solvent for the transesterification reaction includes one or more of decahydronaphthalene, xylene and toluene.

5. The method for preparing degradable and recyclable plastic according to claim 1, characterized in that: The catalyst for the ring-opening metathesis polymerization reaction includes Grubbs first-generation catalyst, Grubbs second-generation catalyst, Grubbs third-generation catalyst, Hoveyda-Grubbs first-generation catalyst or Hoveyda-Grubbs second-generation catalyst; the catalyst for the ester exchange reaction includes 1,5,7-triazabicyclo[4.4.0]deca-5-ene, tetrabutyl titanate, sulfuric acid, hydrochloric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, sodium hydroxide, potassium hydroxide, carbonate, aluminum chloride, zinc chloride, titanium tetrachloride, zinc acetate, sodium methoxide, sodium ethoxide, dichlorotantalum, dibutyltin oxide or butyltin chloride.

6. The method for preparing degradable and recyclable plastic according to claim 1, characterized in that: The temperature of the ring-opening metathesis polymerization is -10 to 5°C.

7. A degradable and recyclable plastic prepared according to the preparation method according to any one of claims 1 to 6.

8. Use of the degradable and recyclable plastic according to claim 7 in packaging bags, greenhouse films and ground films.

9. A method for degrading recyclable plastics according to claim 7, characterized in that: The degradable and recyclable plastic is added into a solvent and degraded under the action of a catalyst to obtain a monomer.

10. The method for degrading recyclable plastics according to claim 9, characterized in that: The solvent includes tetrahydrofuran, dichloromethane, toluene, chlorobenzene, dichlorobenzene or chlorinated alkane; the catalyst includes Grubbs first-generation catalyst, Grubbs second-generation catalyst, Grubbs third-generation catalyst, Hoveyda-Grubbs first-generation catalyst or Hoveyda-Grubbs second-generation catalyst; and the degradation temperature is 23-100°C.

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