A method of degrading a polyolefin

Abstract

The application provides a polyolefin degradation method, comprising the following steps: mixing polyolefin, heteropoly acid quaternary ammonium salt, chlorinated alkane and oxidant, and obtaining polyolefin wax after reaction. The degradation method has mild reaction conditions, controllable product and excellent raw material adaptability. Experimental results show that under mild conditions, by controlling the reaction temperature, reaction time, catalyst dosage and the addition rate of oxidant, the number average molecular weight Mn of the degradation product is controlled in 0.3kDa-12kDa, and the PDI is less than 3.0; further, by using different waste polyolefins without pretreatment as raw materials, efficient degradation of various polyolefins is also achieved, fully illustrating the applicability of the degradation method. At the same time, the degradation method can greatly reduce energy consumption and equipment investment, and is suitable for industrial large-scale popularization and application.

Description

Technical Field

[0001] This application relates to the field of plastic degradation and recycling technology, and in particular to a method for degrading polyolefins. Background Technology

[0002] Polyolefins are currently the most widely used and applied synthetic plastics in the world. They have advantages such as light weight, low price, readily available raw materials, high chemical stability, and good insulation properties. However, because they are often used in short-life packaging materials, they are discarded after use, and their good stability makes them difficult to degrade in nature, leading to their large-scale accumulation in the environment. Therefore, the efficient high-value conversion of polyolefin waste has become a very urgent global project.

[0003] Currently, the main methods for recycling polyolefins include mechanical recycling, energy recovery, and chemical recycling. While mechanical recycling is the most convenient method, it leads to irreversible degradation of polyolefin properties. Energy recovery (such as incineration) can recover heat energy, but it generates large amounts of carbon dioxide, dioxins, furans, polychlorinated biphenyls (PCBs), and ash containing heavy metals. Chemical recycling, by converting polyolefins into low-molecular-weight chemicals or high-value-added materials, is considered one of the most promising recycling strategies. Existing chemical recycling technologies mainly include thermal cracking, catalytic cracking, and hydrocracking. Thermal cracking is usually carried out at high temperatures (>400℃), resulting in high energy consumption, complex product composition, and poor controllability. Catalytic cracking can lower the reaction temperature, but it often relies on precious metals or zeolite catalysts, leading to high costs and strict requirements for raw material purity. Hydrocracking requires a high-pressure hydrogen atmosphere, posing significant equipment requirements and safety risks. Summary of the Invention

[0004] In view of this, this application provides a method for degrading polyolefins. The degradation method provided by this application can achieve efficient degradation of polyolefins under mild conditions without the need for high temperature, precious metal catalysts and high pressure environment.

[0005] This application provides a method for degrading polyolefins, comprising the following steps: Polyolefins, heteropolyacid quaternary ammonium salts, chlorinated alkanes, and oxidants are mixed and reacted to obtain polyolefin waxes.

[0006] In some specific implementations, the polyolefin is selected from one or more of polyethylene, polypropylene, and polyolefin elastomers.

[0007] In some specific implementations, the molecular weight of the polyolefin is 15kDa to 200kDa.

[0008] In some specific implementations, the heteropolyacid quaternary ammonium salt has the molecular formula of formula (Ⅰ): Q a Zb M p O q (H2O) m Equation (I); Wherein, Q is [R1R2R3R4N] + R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C1. 20 The alkyl group, wherein the substituent is C6~C6. 20 aryl; Alternatively, Q can be [R5R6R7N]. + R 5 R 6 and R 7 Any two groups in the ring, together with the nitrogen atom they occupy, form an alicyclic or aromatic ring, and the remaining groups are selected from substituted or unsubstituted C1~C1 groups. 20 The alkyl group, wherein the substituent is C6~C6. 20 aryl; Z is selected from P, As, Si, Ge, B, or Co; M is selected from W, Mo, V, Nb, or Ta; a, b, m, p, and q are integers, where a = 1~5, b = 1~4, p = 1~8, q = 5~40, and m = 0~4.

[0009] In some specific implementations, the heteropolyacid quaternary ammonium salt has the structure of formula (I-1), (I-2), (I-3), (I-4), (I-5), or (I-6): [(C3H7)4N]3[PO4(WO3)4] Equation (Ⅰ-1); [C 18 H 37 N(CH2Ph)(CH3)2]3[PO4(WO3)4] Equation (Ⅰ-2); [π-C5H5NC 16 H 33 Equation (Ⅰ-3) of [PO4(WO3)4] [(C3H7)4N]3[PO4(MoO3)4] Equation (Ⅰ-4); [N( n -Bu)4]3[(AsO4){MoO(O2)2}{[MoO(O2)2](H2O)}] Formula (I-5); [π-C5H5NC 16 H 33 Equation (Ⅰ-6) 3[PO4(MoO3)4].

[0010] In some specific implementations, the chlorinated alkane is selected from one or more of 1,1,2-trichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrachloroethane, 1-chlorohexane, and 1,1,1,2-tetrachloroethane.

[0011] In some specific implementations, the oxidant is selected from one or more of hydrogen peroxide, m-chloroperoxybenzoic acid, and peracetic acid; The concentration of the oxidant is 1 wt% to 60 wt%.

[0012] In some specific implementations, the mass ratio of the polyolefin, heteropolyacid quaternary ammonium salt and chlorinated alkane is (1~10): (0.1~1): (100~400).

[0013] In some specific implementations, the reaction temperature is 110℃~150℃ and the reaction time is 1h~48h.

[0014] In some specific implementations, the oxidant is added at a rate of 0.01 mL / min to 0.2 mL / min.

[0015] The degradation method provided in this application uses polyolefins as raw materials, chlorinated alkanes as solvents, and heteropolyacid quaternary ammonium salts as catalysts. Under the combined action of an oxidant, an oxidative degradation system is formed that can achieve efficient degradation of polyolefins under mild conditions. The degradation method described in this application features mild reaction conditions, controllable products, and excellent raw material adaptability. Experimental results show that, under mild conditions, by adjusting the reaction temperature, reaction time, catalyst dosage, and oxidant addition rate, the number-average molecular weight (Mn) of the degradation products can be controlled within the range of 0.3 kDa to 12 kDa, with a PDI less than 3.0. Furthermore, efficient degradation of various polyolefins has been achieved using different untreated waste polyolefins as raw materials, fully demonstrating the applicability of the degradation method provided in this application. Simultaneously, the degradation method can significantly reduce energy consumption and equipment investment, making it suitable for large-scale industrial application. Attached Figure Description

[0016] Figure 1 This is a gas chromatography-mass spectrometry analysis result of the degraded end-functionalized polyethylene wax product of Example 10 of this application; Figure 2 This is the carbon NMR spectrum of the end-functionalized polyolefin wax product after degradation in Example 10 of this application. Detailed Implementation

[0017] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0018] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0019] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0020] The use of any and all instances or exemplary language such as “e.g.” or “including” herein is merely intended to better illustrate the application and does not constitute a limitation on the scope of the application unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0021] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0022] This application provides a method for degrading polyolefins, comprising the following steps: Polyolefins, heteropolyacid quaternary ammonium salts, chlorinated alkanes, and oxidants are mixed and reacted to obtain polyolefin waxes.

[0023] This application uses polyolefins as the degradation substrate and combines chlorinated alkanes, heteropolyacid quaternary ammonium salt catalysts, and oxidant solutions to form a highly efficient oxidative degradation system. This synergistic oxidative degradation system provided by this application is key to achieving efficient degradation of polyolefins under mild conditions. Furthermore, the degradation method provided by this application has no special requirements for the polyolefin substrate and can directly process virgin polyolefins as well as untreated waste polyolefins, significantly simplifying the recycling process.

[0024] Specifically, a first solution is obtained by mixing and dissolving a polyolefin, a heteropolyacid quaternary ammonium salt, and a chlorinated alkane; the first solution is then mixed with an oxidant, and the reaction yields a terminal-functionalized polyolefin wax.

[0025] This application first mixes a polyolefin, a heteropolyacid quaternary ammonium salt, and a chlorinated alkane to obtain a first solution. This application does not have specific limitations on the type and molecular weight of the polyolefin used as the degradation substrate. In some specific implementations, the polyolefin includes, but is not limited to, polyethylene, polypropylene, polyolefin elastomers, etc., and may be one or more of these. In some specific implementations, the polyethylene includes, but is not limited to, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, etc., and may be one or more of these. In some specific implementations, the polyethylene products include, but are not limited to, polyethylene bags, polyethylene films, polyethylene plastic bottles, etc. In some specific implementations, the molecular weight of the polyolefin is 15kDa to 200kDa, preferably 17kDa to 150kDa.

[0026] The heteropolyacid quaternary ammonium salt described in this application has the molecular formula of formula (I): Q a Z b M p O q (H2O) m Equation (I); Wherein, Q is [R1R2R3R4N] + R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C1. 20 Alkyl groups, preferably substituted or unsubstituted C1-C2. 18 The alkyl group; the substituent is C6~C6. 20 The aryl group is preferably C6~C 10 aryl; Alternatively, Q can be [R5R6R7N]. + R 5 R 6 and R 7 Any two groups in the compound, together with the nitrogen atom they contain, form an alicyclic or aromatic ring, preferably an aromatic ring, and more preferably pyridine; the remaining groups are selected from substituted or unsubstituted C1~C1 groups. 20 Alkyl groups, preferably substituted or unsubstituted C4 groups. 10 ~C 20 The alkyl group, wherein the substituent is C6~C6. 20 The aryl group is preferably C6~C 10 aryl; Z is a heteroatom selected from P, As, Si, Ge, B or Co, preferably P or As; M is a metal atom selected from W, Mo, V, Nb or Ta, preferably W or Mo; a, b, m, p, and q are integers, where a = 1 to 5, preferably 2 to 4; b = 1 to 4, preferably 1 to 2; p = 1 to 8, preferably 2 to 4; q = 5 to 40, preferably 10 to 20, more preferably 14 to 17; and m = 0 to 4, preferably 0 to 1.

[0027] In some specific implementations, the heteropolyacid quaternary ammonium salt has the structure of formula (I-1), (I-2), (I-3), (I-4), (I-5), or (I-6): [(C3H7)4N]3[PO4(WO3)4] Equation (Ⅰ-1); [C 18 H 37 N(CH2Ph)(CH3)2]3[PO4(WO3)4] Equation (Ⅰ-2); [π-C5H5NC 16 H 33 Equation (Ⅰ-3) of [PO4(WO3)4] [(C3H7)4N]3[PO4(MoO3)4] Equation (Ⅰ-4); [N( n -Bu)4]3[(AsO4){MoO(O2)2}{[MoO(O2)2](H2O)}] Formula (I-5); [π-C5H5NC 16 H 33 Equation (Ⅰ-6) 3[PO4(MoO3)4].

[0028] This application does not impose any special restrictions on the source of heteropolyacid quaternary ammonium salts, which can be prepared according to the following methods: The M source, Z source, and hydrogen peroxide are mixed and reacted to obtain an aqueous solution of peroxy metal acid; the quaternary ammonium salt solution is mixed with the above aqueous solution of peroxy metal acid and reacted to obtain a heteropoly acid quaternary ammonium salt catalyst.

[0029] In some specific implementations, the M source is a compound containing an M metal atom, selected from one or more of tungstic acid, molybdic acid, vanadic acid, niobic acid, and tantalic acid, preferably tungstic acid or molybdic acid. In some specific implementations, the Z source is a compound containing a Z heteroatom, selected from one or more of phosphoric acid, arsenic acid, silicic acid, germanic acid, boric acid, and cobalt acid, preferably phosphoric acid or arsenic acid. In some specific implementations, the molar ratio of the M source to the Z source is 1:0.1~0.5, preferably 1:0.2~0.3, and the reaction time is 0.5h~3h, preferably 0.5h~1.5h. In some specific implementations, the solvent of the quaternary ammonium salt solution is preferably dichloromethane, and the quaternary ammonium salt is preferably one or more of hexadecylpyridine chloride, tetrapropylammonium bromide, and octadecylbenzyldimethylammonium chloride. In some specific implementations, the reaction of the quaternary ammonium salt solution with the aqueous solution of the peroxymetallic acid is preferably carried out under stirring conditions, the reaction temperature is room temperature, and the reaction time is 1h~5h, preferably 2h~3h. Some specific implementations also include separating the reaction solution, drying the organic phase, and obtaining the heteropolyacid quaternary ammonium salt after drying.

[0030] In some specific implementations, the chlorinated alkane is selected from one or more of 1,1,2-trichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrachloroethane, 1-chlorohexane, and 1,1,1,2-tetrachloroethane, preferably 1,1,2-trichloroethane, 1,3-dichloropropane, or 1,1,2,2-tetrachloroethane. In some specific implementations, the mass ratio of the polyolefin, the heteropolyacid quaternary ammonium salt, and the chlorinated alkane is (1~10):(0.1~1):(100~400), preferably (2~6):(0.1~0.6):(150~350). In some specific implementations, the dissolution is preferably carried out under stirring conditions, and the stirring temperature is 110℃~150℃, preferably 120℃~140℃.

[0031] After obtaining the first solution, the first solution is mixed with an oxidant, and the reaction yields an end-functionalized polyolefin wax. In some specific implementations, the oxidant is selected from one or more of hydrogen peroxide, m-chloroperoxybenzoic acid, and peracetic acid. In some specific implementations, the concentration of the oxidant is 1 wt% to 60 wt%, preferably 10 wt% to 40 wt%. In some specific implementations, the mixing is preferably performed by adding the oxidant to the first solution under stirring conditions. In some specific implementations, the addition rate of the oxidant is 0.01 mL / min to 0.15 mL / min, preferably 0.04 mL / min to 0.12 mL / min, more preferably 0.8 mL / min. In some specific implementations, the reaction temperature is 110℃ to 150℃, preferably 120℃ to 140℃, and the reaction time is 1 h to 48 h, preferably 8 h to 30 h, more preferably 10 h to 25 h.

[0032] In some specific implementations, the obtained reaction solution is further post-treated, such as by cooling, sedimentation, filtration, and drying. This application does not impose any particular limitations on the methods of cooling, sedimentation, filtration, and drying; any method that can be implemented by those skilled in the art is acceptable.

[0033] The degradation method provided in this application uses polyolefins as raw materials, chlorinated alkanes as solvents, and heteropolyacid quaternary ammonium salts as catalysts. Under the combined action of an oxidant, an oxidative degradation system is formed that can achieve efficient degradation of polyolefins under mild conditions. The degradation method described in this application features mild reaction conditions, controllable products, and excellent raw material adaptability. Experimental results show that, under mild conditions, by adjusting the reaction temperature, reaction time, catalyst dosage, and oxidant addition rate, the number-average molecular weight (Mn) of the degradation products can be controlled within the range of 0.3 kDa to 12 kDa, with a PDI less than 3.0. Furthermore, efficient degradation of various polyolefins has been achieved using different untreated waste polyolefins as raw materials, fully demonstrating the applicability of the degradation method provided in this application. Simultaneously, the degradation method can significantly reduce energy consumption and equipment investment, making it suitable for large-scale industrial application.

[0034] The present invention is further illustrated below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0035] In the following embodiments and comparative examples, the symbols are explained as follows: HDPE: High-density polyethylene; LDPE: Low-density polyethylene; LLDPE: Linear low-density polyethylene; PP: Polypropylene; PS: Polystyrene; POE: Polyolefin elastomer; Mn: Number-average molecular weight (unit: kDa, kilodaltons); PDI: Polydispersity Index; wt%: Mass fraction, used to express the concentration of the oxidant solution; mol%: Mole Percent, used to indicate the amount of heteropolyacid quaternary ammonium salt catalyst used.

[0036] In the following embodiments and comparative examples: The raw material, high-density polyethylene (HDPE), has Mn=31.1kDa and PDI=5.8.

[0037] The preparation method of the heteropolyacid quaternary ammonium salt catalyst is as follows: [(C3H7)4N]3[PO4(WO3)4] Equation (Ⅰ-1); 4.0 mmol of tungstic acid was dissolved in hydrogen peroxide, and 1.0 mmol of phosphoric acid was added and reacted for 1 h to obtain an aqueous solution of peroxyphosphotungstic acid. 3.0 mmol of tetrapropylammonium bromide was dissolved in dichloromethane, and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a white powder was obtained after drying.

[0038] [C 18 H 37 N(CH2Ph)(CH3)2]3[PO4(WO3)4] Equation (Ⅰ-2); 4.0 mmol of tungstic acid was dissolved in hydrogen peroxide, and 1.0 mmol of phosphoric acid was added and reacted for 1 h to obtain an aqueous solution of peroxyphosphotungstic acid. 3.0 mmol of octadecylbenzyldimethylammonium chloride was dissolved in dichloromethane, and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a white solid was obtained after drying.

[0039] [π-C5H5NC 16 H 33 Equation (Ⅰ-3) of [PO4(WO3)4] 4.0 mmol of tungstic acid was dissolved in hydrogen peroxide, and 1.0 mmol of phosphoric acid was added and reacted for 1 h to obtain an aqueous solution of peroxyphosphotungstic acid. 3.0 mmol of hexadecylpyridine chloride was dissolved in dichloromethane, and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a white powder was obtained.

[0040] [(C3H7)4N]3[PO4(MoO3)4] Equation (Ⅰ-4); 4.0 mmol of molybdic acid was dissolved in hydrogen peroxide, and 1.0 mmol of phosphoric acid was added and reacted for 1 h to obtain an aqueous solution of peroxyphosphomolybdic acid. 3.0 mmol of tetrapropylammonium bromide was dissolved in dichloromethane, and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a light yellow powder was obtained after drying.

[0041] [N( n -Bu)4]3[(AsO4){MoO(O2)2}{[MoO(O2)2](H2O)}] Formula (I-5); 2.0 mmol of molybdic acid was dissolved in hydrogen peroxide, and 1.0 mmol of arsenic acid was added and reacted for 1 h to obtain an aqueous solution of peroxyarsenicmolybdic acid. 3.0 mmol of tetrabutylammonium bromide was dissolved in dichloromethane, and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a pale yellow solid was obtained after drying.

[0042] [π-C5H5NC 16 H 33 ]3[PO4(MoO3)4] Equation (Ⅰ-6); 4.0 mmol of molybdic acid was dissolved in hydrogen peroxide, and 1.0 mmol of phosphoric acid was added and reacted for 1 h to obtain an aqueous solution of peroxyphosphomolybdic acid. 3.0 mmol of hexadecylpyridine chloride was dissolved in dichloromethane and added to the above solution. The mixture was stirred at room temperature for 2 h. The liquid was separated, the organic phase was dried under vacuum, and a light yellow powder was obtained after drying.

[0043] Example 1

[0044] 2g HDPE, 0.24g catalyst of formula (Ⅰ-1) and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until HDPE was completely dissolved. While stirring, 115mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out under normal pressure air atmosphere for 24h. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.05g of small molecule polyethylene wax product was obtained.

[0045] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=6.3kDa and PDI=2.0.

[0046] Example 2

[0047] 2g HDPE, 0.33g catalyst of formula (Ⅰ-2) and 150mL 1,3-dichloropropane were added to the reaction vessel. The reaction system was heated to 130℃ and stirred until HDPE was completely dissolved. While stirring, 48mL of 30wt% peracetic acid aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 1.99g of small molecule polyethylene wax product was obtained.

[0048] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=11.5kDa and PDI=2.3.

[0049] Example 3

[0050] 4g of HDPE, 0.30g of catalyst of formula (Ⅰ-3), and 150mL of 1,3-dichloropropane were added to a reaction vessel. The reaction system was heated to 130℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration, and drying, 2.07g of small molecule polyethylene wax product was obtained.

[0051] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=8.8kDa and PDI=2.4.

[0052] Example 4

[0053] 2g HDPE, 0.19g catalyst of formula (Ⅰ-4) and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until HDPE was completely dissolved. While stirring, 115mL of 15wt% peracetic acid aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out under normal pressure air atmosphere for 24h. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.06g of small molecule polyethylene wax product was obtained.

[0054] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=3.8kDa and PDI=2.2.

[0055] Example 5

[0056] 6g of HDPE, 0.19g of catalyst (Ⅰ-5), and 150mL of 1,1,2,2-tetrachloroethane were added to a reaction vessel. The reaction system was heated to 140℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of a 30wt% solution of 1,1,2,2-tetrachloroethane containing m-chloroperoxybenzoic acid was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal atmospheric pressure. After the reaction was completed, the product was cooled, settled, filtered, and dried to obtain 2.00g of small molecule polyethylene wax.

[0057] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=2.2kDa and PDI=2.5.

[0058] Example 6

[0059] 2g HDPE, 0.24g catalyst of formula (Ⅰ-6) and 150mL 1,3-dichloropropane were added to the reaction vessel. The reaction system was heated to 130℃ and stirred until HDPE was completely dissolved. While stirring, 48mL of 30wt% peracetic acid aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.00g of small molecule polyethylene wax product was obtained.

[0060] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=7.5kDa and PDI=2.6.

[0061] Example 7

[0062] 2g HDPE, 0.3g catalyst of formula (Ⅰ-1) and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until HDPE was completely dissolved. While stirring, 115mL of 15wt% m-chloroperoxybenzoic acid in 1,1,2-trichloroethane was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously in air at normal pressure for 24h. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.00g of small molecule polyethylene wax product was obtained.

[0063] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product has Mn=5.4kDa and PDI=2.6.

[0064] Example 8

[0065] 2g HDPE, 0.3g catalyst of formula (Ⅰ-4) and 150mL 1,3-dichloropropane were added to the reaction vessel. The reaction system was heated to 130℃ and stirred until HDPE was completely dissolved. While stirring, 48mL of 30wt% m-chloroperoxybenzoic acid in 1,3-dichloropropane solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously in air atmosphere at normal pressure for 10h. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.10g of small molecule polyethylene wax product was obtained.

[0066] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product has Mn=10.4kDa and PDI=2.4.

[0067] Example 9

[0068] 2g of HDPE, 0.3g of catalyst (I-3) (0.84mol%), and 150mL of 1,1,2,2-tetrachloroethane were added to a reaction vessel. The reaction system was heated to 140℃ and stirred until the HDPE was completely dissolved. While stirring, 24mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.04mL / min. The degradation reaction was carried out continuously for 10h under normal atmospheric pressure. After the reaction was completed, the product was cooled, settled, filtered, and dried to obtain 2.14g of small molecule polyethylene wax.

[0069] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product had Mn=0.32kDa and PDI=2.2.

[0070] Example 10

[0071] 2g HDPE, 0.3g catalyst of formula (Ⅰ-3) and 150mL 1,1,2,2-tetrachloroethane were added to a reaction vessel. The reaction system was heated to 140℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 3.5g of end-functionalized polyethylene wax product was obtained.

[0072] The product obtained in this embodiment was a brown oily substance, which was characterized and analyzed by gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis results are shown below. Figure 1 , Figure 1This is a gas chromatography-mass spectrometry (GC-MS) analysis result of the degraded end-functionalized polyethylene wax product from Example 10 of this application. Figure 1 It can be seen that the degradation products are mainly small molecule alkanes with ≤10 carbon atoms and oxygen-containing functionalized derivatives.

[0073] The end-functionalized polyethylene wax product was analyzed by carbon nuclear magnetic resonance spectroscopy. The results are shown in [reference needed]. Figure 2 , Figure 2 This is the carbon NMR spectrum of the end-functionalized polyethylene wax product after degradation in Example 10 of this application. Figure 2 It is known that the polyethylene wax end group prepared in this embodiment contains carboxyl or acyl chloride functional groups.

[0074] Example 11

[0075] 2g HDPE, 0.3g catalyst of formula (Ⅰ-3) (0.84mol%), and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the HDPE was completely dissolved. While stirring, 24mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.04mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration, and drying, 2.01g of small molecule polyethylene wax product was obtained.

[0076] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=10.7kDa and PDI=2.6.

[0077] Example 12

[0078] 2g HDPE, 0.3g of catalyst (I-3) (0.84mol%), and 150mL of 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, the product was cooled, settled, filtered, and dried to obtain 2.07g of small molecule polyethylene wax product.

[0079] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product has Mn=4.4kDa and PDI=2.5.

[0080] Example 13

[0081] 2g HDPE, 0.3g catalyst of formula (Ⅰ-3) (0.84mol%) and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 130℃ and stirred until the HDPE was completely dissolved. While stirring, 72mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.12mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.06g of small molecule polyethylene wax product was obtained.

[0082] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product had Mn=4.2kDa and PDI=2.1.

[0083] Example 14

[0084] 2g HDPE, 0.1g of catalyst (I-3) (0.14mol%) and 150mL of 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.05g of small molecule polyethylene wax product was obtained.

[0085] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=10.7kDa and PDI=2.0.

[0086] Example 15

[0087] 2g HDPE, 0.3g of catalyst (I-3) (0.42mol%) and 150mL of 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out continuously for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.07g of small molecule polyethylene wax product was obtained.

[0088] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. In this example, the small molecule polyethylene wax product has Mn=4.4kDa and PDI=2.5.

[0089] Example 16

[0090] 2g HDPE, 0.6g catalyst of formula (Ⅰ-3) (0.84mol%) and 150mL 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the HDPE was completely dissolved. While stirring, 48mL of 30wt% hydrogen peroxide aqueous solution was added to the reaction system at a rate of 0.08mL / min. The degradation reaction was carried out for 10h under normal pressure air atmosphere. After the reaction was completed, after cooling, sedimentation, filtration and drying, 2.07g of small molecule polyethylene wax product was obtained.

[0091] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=4.1kDa and PDI=1.9.

[0092] Comparative Example 1

[0093] The difference from Examples 11-13 is that no oxidant was added, but the other steps were the same, and 2.04g of small molecule polyethylene wax product was obtained.

[0094] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=26.7kDa and PDI=3.5.

[0095] Comparative Example 2

[0096] The difference from Examples 14-16 is that no catalyst was added, but the other steps are the same, and 2.01g of small molecule polyethylene wax product is obtained.

[0097] The above-mentioned small molecule polyethylene wax product was subjected to gel permeation chromatography (GPC) to test the molecular weight and molecular weight distribution of the polymer. The small molecule polyethylene wax product described in this example has Mn=13.4kDa and PDI=1.9.

[0098] As shown in Examples 1-16 and Comparative Examples 1-2, compared to Comparative Examples 1-2, this application achieves a highly efficient oxidative degradation system through the synergistic effect of chlorinated alkanes, heteropolyacid quaternary ammonium salt catalysts, and oxidant solutions. Simultaneously, by controlling the reaction temperature, reaction time, catalyst dosage, and oxidant addition rate, the number-average molecular weight (Mn) of the degradation products is controlled within the range of 0.3 kDa to 12 kDa, and the PDI is less than 3.0.

[0099] Table 1. Effect of hydrogen peroxide aqueous solution addition rate on degradation efficiency

[0100] As shown in Examples 11-13, the degradation efficiency gradually increased with the increase of the hydrogen peroxide aqueous solution addition rate, as shown in Table 1. However, when the addition rate exceeded 0.08 mL / min, the change in Mn tended to level off, and the improvement in degradation efficiency was no longer significant.

[0101] Table 2 Effect of catalyst dosage on degradation efficiency

[0102] As shown in Examples 14-16, the degradation efficiency gradually increases with the increase of the catalyst concentration of formula (Ⅰ-3), as shown in Table 2. However, when the catalyst concentration of formula (Ⅰ-3) exceeds 0.84 mol%, the change in molecular weight tends to level off, and the improvement in degradation efficiency is no longer significant.

[0103] Example 17

[0104] This embodiment examines the degradation effect of the degradation method described in this application on different polyolefin raw materials and polystyrene.

[0105] Polystyrene (PS), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), polyolefin elastomer (POE), polyethylene bags (PE bag1, PE bag2, PE bag3), polyethylene bottles (PE bottle), and polyethylene cling film (PE cling film) were used as degradation substrates. 2g of each substrate, 0.3g of catalyst (Ⅰ-3), and 150mL of 1,1,2-trichloroethane were added to a reaction vessel. The reaction system was heated to 120℃ and stirred until the substrates were completely dissolved. Then, 230mL of 30wt% hydrogen peroxide aqueous solution was added at a rate of 0.08mL / min. The reaction was carried out under normal atmospheric pressure for 48h. After the reaction was completed, the degradation products were obtained after cooling, sedimentation, filtration, and drying. The results are shown in Table 3.

[0106] Table 3 Degradation effect of Example 17 of this application

[0107] As shown in Table 3, the degradation method described in this application, using different untreated waste polyolefins as raw materials, achieved efficient degradation of various polyolefins under mild conditions of normal air pressure, fully demonstrating the applicability of the degradation method provided in this application.

[0108] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for degrading polyolefins, characterized in that, Includes the following steps: Polyolefins, heteropolyacid quaternary ammonium salts, chlorinated alkanes, and oxidants are mixed and reacted to obtain polyolefin waxes.

2. The degradation method according to claim 1, characterized in that, The polyolefin is selected from one or more of polyethylene, polypropylene, and polyolefin elastomers.

3. The degradation method according to claim 1 or 2, characterized in that, The molecular weight of the polyolefin is 15kDa to 200kDa.

4. The degradation method according to claim 1, characterized in that, The heteropolyacid quaternary ammonium salt has the molecular formula of formula (Ⅰ): Q a Z b M p O q (H2O) m Equation (I); Wherein, Q is [R1R2R3R4N] + R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C1. 20 The alkyl group, wherein the substituent is C6~C6. 20 aryl; Alternatively, Q can be [R5R6R7N]. + R 5 R 6 and R 7 Any two groups in the ring, together with the nitrogen atom they occupy, form an alicyclic or aromatic ring, and the remaining groups are selected from substituted or unsubstituted C1~C1 groups. 20 The alkyl group, wherein the substituent is C6~C6. 20 aryl; Z is selected from P, As, Si, Ge, B, or Co; M is selected from W, Mo, V, Nb, or Ta; a, b, m, p, and q are integers, where a = 1~5, b = 1~4, p = 1~8, q = 5~40, and m = 0~4.

5. The degradation method according to claim 4, characterized in that, The heteropolyacid quaternary ammonium salt has the structure of formula (I-1), (I-2), (I-3), (I-4), (I-5), or (I-6): [(C3H7)4N]3[PO4(WO3)4] Equation (Ⅰ-1); [C 18 H 37 N(CH2Ph)(CH3)2]3[PO4(WO3)4] Equation (Ⅰ-2); [π-C5H5NC 16 H 33 3[PO4(WO3)4] of formula (I-3); [(C3H7)4N]3[PO4(MoO3)4] Equation (Ⅰ-4); [N( n -Bu)4]3[(AsO4){MoO(O2)2}{[MoO(O2)2](H2O)}]in(Ⅰ-5)? [π-C5H5NC 16 H 33 3[PO4(MoO3)4] Formula (I-6).

6. The degradation method according to claim 1, characterized in that, The chlorinated alkane is selected from one or more of 1,1,2-trichloroethane, 1,3-dichloropropane, 1,1,2,2-tetrachloroethane, 1-chlorohexane, and 1,1,1,2-tetrachloroethane.

7. The degradation method according to claim 1, characterized in that, The oxidant is selected from one or more of hydrogen peroxide, m-chloroperoxybenzoic acid, and peracetic acid; The concentration of the oxidant is 1 wt% to 60 wt%.

8. The degradation method according to any one of claims 1 to 7, characterized in that, The mass ratio of the polyolefin, heteropolyacid quaternary ammonium salt and chlorinated alkane is (1~10): (0.1~1): (100~400).

9. The degradation method according to claim 8, characterized in that, The reaction temperature is 110℃~150℃, and the reaction time is 1h~48h.

10. The degradation method according to claim 9, characterized in that, The oxidant is added at a rate of 0.01 mL / min to 0.2 mL / min.

Images