A method for separating and purifying cycloolefin resin material from recycled plastics

Abstract

The application provides a method for separating and purifying cycloolefin resin material, which comprises maintaining recycled plastics in a solvent at a certain temperature and time, the temperature and time satisfying the following defined relationship, so that the cycloolefin resin material in the recycled plastics is sufficiently dissolved in the solvent; n >= 0; wherein T0 and T n are a certain specific temperature and the next increased temperature respectively; t0 and t n are the residence time corresponding to the specific temperature T0 and T n , T0 is 60 DEG C, and t0 is 40 min. The scheme of the application can separate and purify COC and COP plastics in recycled plastics, the solvent used does not contain carcinogenic solvents such as toluene and benzene, has good green environmental protection, and the regenerated COC and COP products have excellent transparency without adding additional additives, have high application value, and can be used in high-end fields such as food packaging and medical packaging. In addition, the application can simultaneously satisfy the separation and purification of COC or COP material, and improve the added value of the recycled cycloolefin resin material.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials technology and plastic recycling, and in particular to a method and application for separating and purifying cyclic olefin resin materials. Background Technology

[0002] The disposal of waste plastics and the corresponding environmental problems have received widespread attention from the public and professionals. Therefore, the recycling of waste plastics has become an important direction, especially since polyolefin materials are widely used in food packaging, with a large volume used and discarded annually, causing serious environmental pollution. Therefore, the recycling of film packaging materials is the most important way to solve plastic pollution, which can also save energy, reduce the consumption of fossil fuels, and effectively address the environmental pollution and ecological crisis. Cycloolefin resin materials include cycloolefin copolymers (COC) and cycloolefin polymers (COP). As a class of high-end polyolefin resins in the polyolefin material family, they are widely used in many packaging fields due to their excellent properties such as water vapor barrier properties, aroma retention, high permeability, and wrinkle resistance. Therefore, the recycling and reuse of cycloolefin resin materials has become crucial.

[0003] As is well known, there are different ways to recycle plastics, including mechanical recycling, advanced physical or solvent recycling, and chemical processing (such as thermochemical recycling like pyrolysis or gasification and solvent decomposition). Mechanical recycling refers to the process of directly blending, melt blending, and extrusion granulation of waste polyolefin plastics to obtain recycled polyolefin materials. However, in this process, polyolefin plastics often degrade, leading to significant yellowing, a sharp decrease in transparency, and severe degradation of mechanical properties, making them unsuitable for high-end applications and limiting their use to low-value products. High-temperature chemical depolymerization involves the pyrolysis of polyolefin plastics under heating and the action of a catalyst, causing the polymer chains to break indiscriminately, forming low-molecular-weight compounds. However, it produces relatively few monomers, which cannot be used as monomers in subsequent polyolefin synthesis. Furthermore, chemical depolymerization is a complex process, requiring extremely high industrialization standards, resulting in high carbon emissions, enormous energy consumption, and high costs.

[0004] Solvent-based recycling avoids the significant degradation of material properties caused by mechanical recycling, as well as the complex and energy-intensive high-temperature pyrolysis process. Patent CN107810226B reports the use of short-chain aliphatic hydrocarbon solvents to dissolve polyolefin plastics under high temperature and pressure, but the process is demanding, requiring high temperature and pressure conditions and high energy consumption. Patent CN114133618B reports the use of a compound solvent (toluene / limonene) to dissolve low-density polyethylene resin, while COC remains insoluble. After filtration, high-purity COC recycled material is obtained. However, toluene is highly toxic, pollutes the environment, and long-term exposure can affect human health, making it impossible to use the recycled COC material in high-end fields such as food packaging and medical packaging. Furthermore, this method is only suitable for recycling COC material and cannot be used to recycle COP material.

[0005] In summary, there is an urgent need in this field to develop a simple, efficient, green, environmentally friendly, and low-energy-consumption method for purifying cyclic olefin resin materials, which is applicable to both the separation and purification of COC materials and the purification of COP materials, thereby meeting the demand for recycled cyclic olefin resin material products in high-end fields. Summary of the Invention

[0006] To address the aforementioned shortcomings in existing technologies, the present invention aims to provide a method for separating and purifying cyclic olefin resin materials, particularly suitable for separating and purifying recycled plastics primarily composed of COC or COP. It provides a method for using solvents to separate and purify cyclic olefin resins and cleverly establishes a relationship between temperature and time, controlling the residence time based on temperature. This method not only leverages the advantage of high recovery rates but also ensures high purity of the recycled plastics, representing an improvement over other cyclic olefin resin recyclables. It offers high application value and possesses advantages such as simplicity, efficiency, environmental friendliness, low energy consumption, and low cost.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for separating and purifying cyclic olefin resin materials from recycled plastics, the method comprising maintaining the recycled plastics in a solvent at a certain temperature and time, wherein the temperature and time satisfy the following defined relationship, such that the cyclic olefin resin materials in the recycled plastics are fully dissolved in the solvent; n≥0;

[0009] Where T0 and T n These represent a specific temperature and the next temperature increase; t0 and t n These correspond to specific temperatures T0 and T, respectively. n The duration of stay.

[0010] In this invention, when T0 is 60℃, t0 is 40min; when T1 = 70℃, When T2 = 80℃ When T3 = 90℃, 0.833 × [40 / (e 2 min≤t3≤40 / (e) 2 )min, when T4=100℃,

[0011] In this invention, the cyclic olefin resin material is a cyclic olefin copolymer (COC) or a cyclic olefin polymer (COP).

[0012] In this invention, when T0 = 60℃, t0 = 40min; the heating temperature T is controlled between 60 and 100℃, for example, 60, 70, 80, 90, or 100℃; and the residence time t is controlled between 2.3 and 40min, for example, 2.3, 10, 20, 30, or 40min.

[0013] In this invention, the solvent is a mixed solvent selected from decahydronaphthalene and dimethyl sulfoxide or tetrahydronaphthalene and dimethyl sulfoxide.

[0014] In this invention, the volume fraction of the decahydronaphthalene is 68-80% of the total volume of the mixed solvent, and the volume fraction of the tetrahydronaphthalene is 53-63% of the total volume of the mixed solvent.

[0015] In one specific embodiment, the method of the present invention for separating and purifying cyclic olefin resin materials includes the following specific steps:

[0016] ② The recycled plastic is washed, dried, and cryogenically crushed to obtain waste powder;

[0017] ② Mix the waste powder with the solvent, heat it to a certain temperature under stirring conditions, and then let it stand for a specific time;

[0018] ③ Add an adsorbent to the mixture from step ② for adsorption, and then collect the purified cyclic olefin resin solution.

[0019] ④ Add a precipitant to the purified cyclic olefin resin solution from step ③ and carry out a precipitation reaction under stirring. Then, filter, wash, and dry to obtain a highly transparent cyclic olefin resin material.

[0020] In this invention, the recycled plastic in step ① is waste plastic containing cyclic olefin copolymers (COC) and / or cyclic olefin polymers (COP);

[0021] Preferably, the recycled plastic further comprises linear low-density polyethylene (LLDPE) and / or low-density polyethylene (LDPE).

[0022] Preferably, the sum of the mass percentages of the cyclic olefin copolymer (COC) and / or cyclic olefin polymer (COP) and linear low-density polyethylene (LDPE) and / or LDPE is 98 wt% or more, for example, 98.1, 98.3, 98.5, 98.7, 99, 99.2, 99.5, 99.7, or 99.9 wt%; wherein the mass percentage of the cyclic olefin copolymer (COC) and / or cyclic olefin polymer (COP) is 70 to 85 wt% of the total mass of the recycled plastic, for example, 70, 75, 80, or 85 wt%.

[0023] The specific source of the recycled plastic is not limited, but it is preferably recycled material from easy-tear film granules used in packaging.

[0024] In step ① of this invention, the cleaning agent is at least one of nonionic surfactant cleaning agent, amphoteric cleaning agent, alkaline cleaning agent, and biological enzyme cleaning agent. It can be diluted with water before use. After cleaning, it can be rinsed with water. This is a routine operation in the field. The specific process, such as temperature and time, is not specifically limited. The goal is to clean the dirt.

[0025] In this invention, the cryogenic crushing process described in step ① is carried out at a temperature of -50 to -78°C; for example, -50, -55, -60, -65, -70, -75, or -78°C.

[0026] Preferably, the average particle size of the waste powder after crushing is below 1000 μm, for example, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, or 50 μm, and more preferably 300–600 μm. Processing the recycled waste into powder of the aforementioned preferred particle size results in higher processing efficiency during subsequent dissolution and adsorption processes, and more effectively removes small molecule impurities and insoluble substances from the waste.

[0027] In this invention, the mass ratio of the waste powder to the volume ratio of the solvent in step ② is 1g:(20-40)mL, for example 1g:20mL, 1g:25mL, 1g:30mL, 1g:35mL, 1g:40mL, preferably 1g:(20-25)mL.

[0028] Heating temperature and residence time can affect the dissolution effect of waste materials. The temperature and time must satisfy the following defined relationship so that the cyclic olefin resin material in the recycled plastic is fully dissolved in the solvent. When T0 = 60℃ and t0 = 40min, under the conditions described in this invention, the selectivity of COC or COP in the dissolved waste powder can be improved, resulting in high-purity regenerated COC or COP products.

[0029] In this invention, the adsorbent in step ③ is at least one of activated carbon, bentonite, montmorillonite, activated clay, and alumina.

[0030] In this invention, the mass ratio of the adsorbent in step ③ to the waste powder in step ② is 1:(50-100), for example 1:50, 1:60, 1:70, 1:80, 1:90, or 1:100.

[0031] Preferably, the adsorption temperature is 70–90°C, for example, 70, 80, or 90°C, and the adsorption time is 0.5–2 hours, for example, 0.5, 1, 1.5, or 2 hours. Under these conditions, COC or COP in the waste powder can be fully dissolved in the mixed solvent, and impurities such as antioxidants and colorants that leach out or are insoluble can be fully removed by the adsorbent, thereby improving the purity of the recycled COC or COP material.

[0032] In this invention, the precipitant in step ④ is an acidified ethanol solution.

[0033] Preferably, the acid used for acidification in the acidified ethanol solution is one or more of hydrochloric acid, phosphoric acid, acetic acid, and formic acid. More preferably, the volume percentage content of the acid in the acidified ethanol solution is 5-15%, for example, 5, 7, 9, 11, 13, or 15%.

[0034] In this invention, the volume ratio of the cyclic olefin resin solution to the precipitant in step ④ is 1:(0.5~1.5), for example 1:0.5, 1:1, or 1:1.5.

[0035] In this invention, the drying in step ④ is vacuum drying, with a temperature of 80-120℃, a vacuum degree of ≤0.1kPa, and a time of 8-12h.

[0036] The glass transition temperature (Tg) of the high-transparency cyclic olefin copolymer (COC) described in this invention is 60–180 °C.

[0037] The glass transition temperature (Tg) of the highly transparent cyclic olefin polymer (COP) of this invention is 100–160 °C.

[0038] The light transmittance of the high-transparency cyclic olefin resin material described in this invention is not less than 90%, for example, 90, 91, 92, 93, 94, 95, or 97%.

[0039] The purity of the high-transparency cyclic olefin resin material described in this invention is ≥98.5wt%.

[0040] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0041] (1) The empirical formula proposed in this invention achieves an effective balance between high purity and high recovery efficiency of cyclic olefin resin by cleverly adjusting the relationship between heating temperature and residence time. At the same time, it can meet the requirements for separation and purification of COC and COP materials, thereby improving the recycling value of cyclic olefin resin materials.

[0042] (2) The method provided in this invention is simple and efficient. Without adding any additional additives, the resulting product has excellent transparency, high application value, and wide application range. At the same time, the solvent can be recycled and reused, realizing the transformation of waste into treasure and saving costs. It provides a solution for the recycling of COC or COP plastics. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] The main raw materials used in the embodiments and comparative examples of this invention are shown below. Unless otherwise specified, all other raw materials were obtained through ordinary commercial channels.

[0045] Easy-tear film granule recycled material a: COC content is 85wt% (Polyplastics TOPAS8007, Japan), glass transition temperature Tg is 78℃; low density polyethylene content is 15wt% (Maoming Petrochemical LDPE 2420H), melting point is 109℃.

[0046] Easy-tear film granule recycled material b: COC content is 80wt% (Polyplastics TOPAS5013, Japan), glass transition temperature Tg is 134℃; low density polyethylene content is 20wt% (Maoming Petrochemical LDPE 2420H), melting point is 109℃.

[0047] Easy-tear film granule recycled material c: COP content is 70wt% (Japan Zeon 1020R), glass transition temperature Tg is 102℃; low density polyethylene content is 30wt% (Maoming Petrochemical LDPE 2420H), melting point is 109℃.

[0048] The easily tearable film granules recycled materials a, b, and c are self-made. Based on the compositional analysis of existing easily tearable film products, they are prepared using a film blow molding process according to conventional processing operations in this field. Specifically, the process involves mixing cyclic olefin resin materials with low-density polyethylene in a specific ratio, then adding the mixture to a screw extruder for melt extrusion, and finally directly blow molding it into a film using a blown film machine to obtain the self-made recycled materials. The processing temperature is controlled at 260℃, the blown film ratio is 2, the traction speed is 30 m / min, and the screw speed is 25 r / min.

[0049] Adsorbent (activated carbon): Shanghai Maclean Biochemical Technology Co., Ltd., 20-50 mesh;

[0050] Adsorbent (bentonite): Shanghai Maclean Biochemical Technology Co., Ltd., density 2-3 g / cm³ 3 ;

[0051] Cleaning agent: Guangdong Sanpin Technology Co., Ltd., SP-288, nonionic surfactant;

[0052] Decahydronaphthalene: Beijing Innocare Technology Co., Ltd., analytical grade;

[0053] Tetrahydronaphthalene: Beijing Innocare Technology Co., Ltd., analytical grade;

[0054] Dimethyl sulfoxide: Beijing Innocare Technology Co., Ltd., analytical grade.

[0055] The performance test parameters and corresponding test methods used in the various embodiments of the present invention are as follows:

[0056] (1) The formula for calculating the purity (wt%) of COC or COP in recycled plastics is as follows: The purity of recycled plastics was determined using a Bruker Avance III 600MHz nuclear magnetic resonance spectrometer. 13 The purity of COC or COP in recycled plastics was calculated by analyzing the C NMR spectrum, using deuterated tetrachloroethane as the solvent, and the measurement temperature was 120℃.

[0057] (2) The formula for calculating the recovery rate (wt%) is: 100 × (mass of COC or COP in recycled plastic ÷ mass of COC or COP in waste plastic).

[0058] (3) Light transmittance: Refer to GB 2410-2008 and test on a light transmittance tester.

[0059] (4) The glass transition temperature Tg of recycled COC or COP plastics was determined by differential scanning calorimetry (DSC) at a heating rate of 10℃ / min and a cooling rate of 10℃ / min, with a scanning range of 30~280℃, using a two-stage heating curve.

[0060] Example 1

[0061] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0062] ① Wash 10g of easily tearable film granules with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in an 80℃ oven (vacuum degree ≤0.1kPa) for 12h, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 300μm;

[0063] ② Add the waste powder to a mixed solvent of 106 mL tetrahydronaphthalene and 94 mL dimethyl sulfoxide, mix, heat to 60 °C under stirring and hold for 40 min to allow COC to dissolve completely;

[0064] ③Then 0.2g of adsorbent bentonite is added to adsorb impurities. After adsorption at 70℃ for 2 hours, the solid residue is removed by filtration to obtain a purified COC solution.

[0065] ④ Add 210 mL of purified COC solution to a mixture of 250 mL of ethanol and 25 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 80℃ (vacuum degree ≤ 0.1 kPa) for 12 h to obtain highly transparent COC material.

[0066] Example 2

[0067] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0068] ① Wash 20g of easily tearable film granules with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 90℃ oven (vacuum degree ≤0.1kPa) for 10h, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 400μm;

[0069] ② Add the waste powder to a mixed solvent of 294 mL decahydronaphthalene and 126 mL dimethyl sulfoxide, mix, heat to 70 °C under stirring and hold for 19 min to allow COC to dissolve completely;

[0070] ③Then 0.2g of adsorbent bentonite is added to adsorb impurities. After adsorption at 80℃ for 1 hour, the solid residue is removed by filtration to obtain a purified COC solution.

[0071] ④ Add 440 mL of purified COC solution to a mixture of 500 mL of ethanol and 50 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 90℃ (vacuum degree ≤ 0.1 kPa) for 10 h to obtain highly transparent COC material.

[0072] Example 3

[0073] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0074] ① Wash 15g of easily tearable film granules (b) with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 100℃ oven (vacuum degree ≤0.1kPa) for 9 hours, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 500μm;

[0075] ② Add the waste powder to a mixed solvent of 264 mL decahydronaphthalene and 66 mL dimethyl sulfoxide, heat to 80 °C under stirring and hold for 9 min to allow COC to dissolve completely;

[0076] ③Then 0.25g of adsorbent bentonite is added to adsorb impurities. After adsorption at 90℃ for 0.5h, the solid residue is removed by filtration to obtain a purified COC solution.

[0077] ④ Add 345 mL of purified COC solution to a mixture of 475 mL of ethanol and 25 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 100℃ (vacuum degree ≤ 0.1 kPa) for 9 h to obtain highly transparent COC material.

[0078] Example 4

[0079] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0080] ① Wash 12g of easily tearable film granules (b) with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 120℃ oven (vacuum degree ≤0.1kPa) for 8 hours, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 600μm;

[0081] ② Add the waste powder to a mixed solvent of 144 mL decahydronaphthalene and 36 mL dimethyl sulfoxide, mix, heat to 90 °C under stirring and hold for 5 min to allow COC to dissolve completely;

[0082] ③Then 0.125g of adsorbent bentonite was added to adsorb impurities. After adsorption at 70℃ for 2 hours, the solid residue was removed by filtration to obtain a purified COC solution.

[0083] ④ Add 312 mL of purified COC solution to a mixture of 180 mL of ethanol and 20 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 120℃ (vacuum degree ≤ 0.1 kPa) for 8 hours to obtain highly transparent COC material.

[0084] Example 5

[0085] The specific steps for preparing highly transparent cyclic olefin polymers (COPs) from recycled plastics are as follows:

[0086] ① Wash 2.5g of easily tearable film granules with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 120℃ oven (vacuum degree ≤0.1kPa) for 8 hours, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 500μm;

[0087] ② Add the waste powder to a mixed solvent of 36 mL tetrahydronaphthalene and 24 mL dimethyl sulfoxide, mix, heat to 100°C under stirring and hold for 2.5 min to allow COP to dissolve completely;

[0088] ③Then 0.04g of adsorbent bentonite was added to adsorb impurities. After adsorption at 70℃ for 1.5h, the solid residue was removed by filtration to obtain a purified COP solution.

[0089] ④ Add 62.5 mL of purified COP solution to a mixture of 65 mL of ethanol and 10 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 120℃ (vacuum degree ≤ 0.1 kPa) for 8 hours to obtain highly transparent COP material.

[0090] Example 6

[0091] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0092] ① Wash 75g of easily tearable film granules with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 100℃ oven (vacuum degree ≤0.1kPa) for 9h, and then crush it in a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 100μm;

[0093] ② Add the waste powder to a mixed solvent of 1890 mL tetrahydronaphthalene and 1110 mL dimethyl sulfoxide, mix, heat to 70 °C under stirring and hold for 19 min to allow COC to dissolve completely;

[0094] ③Then add 1g of adsorbent bentonite to adsorb impurities. After adsorption at 80℃ for 1h, filter to remove solid residue and obtain purified COC solution.

[0095] ④ Add 3075 mL of purified COC solution to a mixture of 2000 mL of ethanol and 200 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 100℃ (vacuum degree ≤ 0.1 kPa) for 9 h to obtain highly transparent COC material.

[0096] Example 7

[0097] The specific steps for preparing highly transparent cyclic olefin copolymers (COCs) from recycled plastics are as follows:

[0098] ① Wash 75g of easily tearable film granules (b) with cleaning agent SP-288 and water, rinse with clean water, dry the recycled plastic in a 100℃ oven (vacuum degree ≤0.1kPa) for 9 hours, and then crush it using a cryogenic crusher at -50~-78℃ (including liquid nitrogen cooling) to obtain waste powder with an average particle size of 800μm;

[0099] ② Add the waste powder to a mixed solvent of 1530 mL decahydronaphthalene and 720 mL dimethyl sulfoxide, mix, heat to 80 °C under stirring and hold for 9 min to allow COC to dissolve completely;

[0100] ③Then 0.9g of adsorbent bentonite is added to adsorb impurities. After adsorption at 80℃ for 1 hour, the solid residue is removed by filtration to obtain a purified COC solution.

[0101] ④ Add 2325 mL of purified COC solution to a mixture of 1500 mL of ethanol and 150 mL of hydrochloric acid, stir to carry out precipitation reaction, filter and wash, and dry in an oven at 100℃ (vacuum degree ≤0.1 kPa) for 9 h to obtain highly transparent COC material.

[0102] Comparative Example 1

[0103] The method is the same as in Example 2, except that the dwell time in step ② is 23 minutes, while other conditions remain unchanged.

[0104] Comparative Example 2

[0105] The method is the same as in Example 2, except that the dwell time in step ② is 15 minutes, while other conditions remain unchanged.

[0106] Comparative Example 3

[0107] The method is the same as in Example 3, except that the dwell time in step ② is 13 minutes, while other conditions remain unchanged.

[0108] Comparative Example 4

[0109] The method is the same as in Example 4, except that the dwell time in step ② is 11 minutes, while other conditions remain unchanged.

[0110] Comparative Example 5

[0111] The method is the same as in Example 1, except that the solvent in step ② is dimethyl sulfoxide, while other conditions remain unchanged.

[0112] Comparative Example 6

[0113] The method is the same as in Example 5, except that in step ② the solvent is tetrahydronaphthalene, while other conditions remain unchanged.

[0114] Comparative Example 7

[0115] Referring to the method in Example 2, the only difference is that the solvent in step ② is decahydronaphthalene, while other conditions remain unchanged.

[0116] Comparative Example 8

[0117] The recycled plastic is processed using easy-tear film granules (a) without the processing method of this invention, but only through a simple extrusion process.

[0118] The cyclic olefin resin materials prepared in the above examples and comparative examples were subjected to performance tests, and the test data are shown in Table 1:

[0119] Table 1. Performance test results of cyclic olefin copolymers in Examples 1-7 and Comparative Examples 1-8

[0120]

[0121] As can be seen from Comparative Examples 1, 3 and 4, excessively long residence time will cause some LDPE to dissolve after accelerated swelling, resulting in excessively low purity of recycled COP plastic.

[0122] As shown in Comparative Example 2, if the residence time is too short, the solvent will not be able to fully dissolve the COC, and the purity of the recycled COC plastic will be too low.

[0123] As can be seen from Comparative Examples 5-7, replacing the mixed solvent with a single solvent will result in the solvent being unable to fully dissolve the COC, leading to excessively low purity of the recycled COC plastic.

[0124] As shown in Comparative Example 8, when other methods are used to recycle plastics, low-density polyethylene and COC cannot be completely separated, resulting in excessively low purity of recycled COC plastics.

Claims

1. A method for separating and purifying cyclic olefin resin materials from recycled plastics, the method comprising maintaining the recycled plastics in a solvent at a certain temperature and for a certain time, wherein the temperature and time satisfy the following defined relationship, such that the cyclic olefin resin materials in the recycled plastics are fully dissolved in the solvent; , n≥0; where T0 and T n These represent a specific temperature and the next temperature increase; t0 and t n These correspond to specific temperatures T0 and T, respectively. n The residence time is 40 min at T0 = 60°C. The cyclic olefin resin material is a cyclic olefin copolymer (COC) or a cyclic olefin polymer (COP). The solvent is a mixed solvent selected from decahydronaphthalene and dimethyl sulfoxide or tetrahydronaphthalene and dimethyl sulfoxide. The volume fraction of decahydronaphthalene in the mixed solvent of decahydronaphthalene and dimethyl sulfoxide is 68-80% of the total volume of the mixed solvent, and the volume fraction of tetrahydronaphthalene in the mixed solvent of tetrahydronaphthalene and dimethyl sulfoxide is 53-63% of the total volume of the mixed solvent.

2. The method as described in claim 1, characterized in that, The method includes the following specific steps: ① The recycled plastic is washed, dried, and cryogenically crushed to obtain waste powder; ② Mix the waste powder with the solvent, heat it to a certain temperature under stirring conditions, and then let it stand for a specific time; ③ Add an adsorbent to the mixture from step ② for adsorption, and then collect the purified cyclic olefin resin solution. ④ Add a precipitant to the purified cyclic olefin resin solution from step ③ and carry out a precipitation reaction under stirring. Then, filter, wash, and dry to obtain a highly transparent cyclic olefin resin material.

3. The method as described in claim 2, characterized in that, The recycled plastic in step ① is waste plastic containing cyclic olefin copolymers (COC) and / or cyclic olefin polymers (COP); the recycled plastic also contains linear low-density polyethylene (LLDPE) and / or low-density polyethylene (LDPE); the total mass percentage of the cyclic olefin copolymers (COC) and / or cyclic olefin polymers (COP) to linear low-density polyethylene and / or low-density polyethylene is more than 98 wt%; and / or, the mass percentage of the cyclic olefin copolymers (COC) and / or cyclic olefin polymers (COP) is 70-85 wt% of the total mass of the recycled plastic.

4. The method as described in claim 2, characterized in that, The cryogenic crushing process described in step ① involves a processing temperature of -50 to -78°C; the average particle size of the waste powder after crushing is below 1000 μm.

5. The method according to any one of claims 2-4, characterized in that, The mass ratio of the waste powder to the volume ratio of the solvent in step ② is 1g:(20~40)mL.

6. The method as described in claim 5, characterized in that, The mass ratio of the waste powder to the volume ratio of the solvent in step ② is 1g:(20~25)mL.

7. The method according to any one of claims 2-4, characterized in that, The adsorbent in step ③ is at least one of activated carbon, bentonite, montmorillonite, activated clay, and alumina; and / or, the mass ratio of the adsorbent in step ③ to the waste powder in step ② is 1:(50-100); and / or, the adsorption temperature is 70-90℃ and the adsorption time is 0.5-2h.

8. The method according to any one of claims 2-4, characterized in that, The precipitant in step ④ is an acidified ethanol solution; the acid used for acidification in the acidified ethanol solution is one or more of hydrochloric acid, phosphoric acid, acetic acid, and formic acid, and the acid volume percentage content in the acidified ethanol solution is 5-15%.

9. The method according to any one of claims 2-4, characterized in that, The volume ratio of the cyclic olefin resin solution to the precipitant in step ④ is 1:(0.5~1.5); and / or, the drying in step ④ is vacuum drying, with a temperature of 80~120℃, a vacuum degree ≤0.1kPa, and a time of 8~12h.

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