Plastic recovery method

Abstract

The present invention provides a plastic recovery method in which a solvent is combined with a heating step to dissolve a recovery target, and the solvent and the recovery target are separated by negative pressure. The plastic recovery method provided by the invention has high plastic recovery rate, and the solvent can be recycled, so that the cost is reduced, and the derivative environment problem can be avoided.

Description

Technical Field

[0001] The present invention relates to a method for plastic recycling, and particularly to a method for recycling polypropylene plastics. Background Art

[0002] The invention of plastics began in the 19th century. Due to the advantages of low production cost and high stability, plastics are widely used as the main materials for daily necessities. For example, polypropylene (PP) has the advantages of heat resistance, acid and alkali resistance, and good toughness, so it is widely used in beverage bottles, straws, microwaveable containers, trash cans, etc. In addition, the carcinogenic risk of PP is lower than that of other plastic materials, so it is more widely used in food containers.

[0003] Since plastics are not easily decomposed in nature, environmental problems have gradually arisen, especially for disposable plastic bags or containers such as PET bottles. Current plastic recycling methods include: (1) melt recycling method: re-shaping the clean scraps left by recycling processing plants, or obtaining post-consumer recycled plastics by recycling different plastic products; and (2) pyrolysis method: recycling specific plastics to make fuels. For example, the production method of decomposing waste plastics into liquid oil and combustible gas is disclosed in Taiwan Patent Publication No. TWI254115B.

[0004] Although countries are gradually implementing plastic reduction policies, the environmental problems caused by plastic waste still need to be solved urgently. Therefore, it is necessary to develop new plastic recycling methods. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for plastic recycling, comprising:

[0006] (1) Preparation step: providing a plastic-containing material, the plastic-containing material comprising a plastic component, and the plastic component comprising polypropylene (PP);

[0007] (2) Mixing step: mixing the plastic-containing material and a solvent to obtain a first mixture, wherein the plastic component is soluble in the solvent;

[0008] (3) Heating step: heating and stirring the first mixture at a temperature of 80°C to 140°C to dissolve the plastic component in the solvent to obtain a solution; and

[0009] (4) Separation step: placing the solution in a negative pressure environment to obtain the plastic component.

[0010] According to the present invention, first, a solvent is used to dissolve the plastic to be recycled, which has a high plastic recovery rate. Second, heating and stirring contribute to dissolution and can improve the plastic recovery rate. Third, by means of a negative pressure environment to evaporate the solvent, (1) the solvent and the plastic to be recycled can be effectively separated; (2) the solvent or the recycled plastic can be prevented from deteriorating due to excessive heating. Based on the fact that the solvent can be reused, solvent recovery can (1) further reduce the cost of plastic recycling and attract more manufacturers to invest in the plastic recycling industry; (2) avoid the cost increase and potential environmental problems caused by solvent emissions. Therefore, the present invention can reduce environmental problems in two aspects: encouraging recycling and reducing chemical waste liquid emissions.

[0011] The plastic-containing material of the present invention includes a polymer, a mixture, or a combination thereof.

[0012] According to the present invention, in this heating step, when heated to above 140 °C, the dissolution liquid will start to boil.

[0013] In one embodiment, in this separation step, it further includes: keeping the dissolution liquid warm, and the temperature is 70 °C to 100 °C. The present invention creates a negative pressure environment to lower the boiling point of the solvent and keeps the solvent continuously boiling through heat preservation, so as to facilitate the accelerated and stable recovery of the solvent and has the advantage of reducing energy consumption.

[0014] In one embodiment, in this separation step, the pressure of the negative pressure environment is greater than or equal to 0 mbar and less than or equal to 90 mbar, for example: 1 mbar, 10 mbar, 30 mbar, 50 mbar, 70 mbar, or 90 mbar. Preferably, the pressure of the negative pressure environment is greater than or equal to 0 mbar and less than or equal to 20 mbar.

[0015] In one embodiment, the time of this separation step is 5 minutes to 1 hour. Preferably, when the pressure of the negative pressure environment is greater than or equal to 0 mbar and less than or equal to 20 mbar, the time of this separation step is 10 minutes to 20 minutes; and / or when the pressure of the negative pressure environment is greater than 20 mbar and less than or equal to 80 mbar, the time of this separation step is 20 minutes to 40 minutes.

[0016] In one embodiment, the plastic recycling method of the present invention does not use a precipitating agent to separate out the plastic component.

[0017] In one embodiment, the solvent includes aromatic hydrocarbons, ketones, ethers, cycloalkanes, esters, or a combination thereof.

[0018] Preferably, the ester includes alkyl esters.

[0019] Preferably, the aromatic hydrocarbon includes benzene, toluene, xylene, tetralin, decalin, or a combination thereof.

[0020] The above xylene has the advantage of relatively low toxicity.

[0021] In one embodiment, in the mixing step, a non-solvent is further added, and the non-solvent includes an ether, a ketone, an ester, or a combination thereof.

[0022] Preferably, the ether includes tetrahydrofuran.

[0023] Preferably, the ketone includes cyclohexanone, acetone, or a combination thereof.

[0024] Preferably, the ester includes propylene glycol monomethyl ether acetate, butyl acetate, isopentyl acetate, or a combination thereof.

[0025] According to the present invention, the "non-solvent" is a liquid that can be miscible with the solvent, and the use of the non-solvent can reduce the amount of solvent used while maintaining a high recovery rate, which helps to reduce costs, toxicity, and improve environmental friendliness.

[0026] In one embodiment, the difference between the solubility parameter of the non-solvent and the solubility parameter of the solvent is greater than or equal to 0 and less than or equal to 2, for example: 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, or 2, to improve the dissolution effect. Preferably, the difference between the solubility parameter of the non-solvent and the solubility parameter of the solvent is greater than or equal to 0 and less than or equal to 0.5.

[0027] The above solubility parameter is a physical constant that measures the compatibility of liquid materials, and its physical meaning is the square root of the cohesive energy density of the material.

[0028] In one embodiment, the plastic component is hardly soluble in the non-solvent. Preferably, the plastic component is substantially insoluble in the non-solvent. More preferably, the plastic component is insoluble in the non-solvent.

[0029] The above "hardly soluble" means that the plastic component is substantially insoluble in the non-solvent at a temperature of 80°C to 140°C and a time of 40 minutes.

[0030] In one embodiment, based on the total volume of the solvent and the non-solvent, the solvent is 45% to 60% by volume, such as: 45% by volume, 48% by volume, 51% by volume, 53% by volume, 56% by volume, 59% by volume or 60% by volume; and the non-solvent is 40% to 55% by volume, such as: 40% by volume, 41% by volume, 44% by volume, 47% by volume, 49% by volume, 52% by volume or 55% by volume.

[0031] More preferably, based on the total volume of the solvent and the non-solvent, the solvent is 48% to 52% by volume, and the non-solvent is 48% to 52% by volume. Even more preferably, based on the total volume of the solvent and the non-solvent, the solvent is 50% by volume, and the non-solvent is 50% by volume.

[0032] In one embodiment, the ratio of the volume of the solvent to the volume of the non-solvent is 0.8 to 1.5; such as: 0.8, 1.0, 1.2, 1.4 or 1.5. For example, when the solvent is 100 ml and the non-solvent is 100 ml, the ratio of the volume of the solvent to the volume of the non-solvent is 1; or when the solvent is 120 ml and the non-solvent is 100 ml, the ratio of the volume of the solvent to the volume of the non-solvent is 1.2.

[0033] In one embodiment, there are multiple plastic-containing materials, and these plastic-containing materials have different specific gravities.

[0034] Before the preparation step, the plastic recycling method of the present invention further includes a classification step: preparing classification solutions with different specific gravities to float out multiple plastic-containing materials with different specific gravities.

[0035] More preferably, in the classification step, multiple plastic-containing materials are placed into multiple classification solutions and separated in ascending order of specific gravity. For example, a first classification solution with a specific gravity of 0.8, a second classification solution with a specific gravity of 1.0, and a third classification solution with a specific gravity of 1.2 are prepared. These plastic-containing materials are first placed into the first classification solution to obtain a first floating part and a first sediment part. The first sediment part is further placed into the second classification solution to obtain a second floating part and a second sediment part. Finally, the second sediment part is further placed into the third classification solution to obtain a third floating part and a third sediment part; wherein, the first floating part, the second floating part, the third floating part and the third sediment part each have different specific gravities.

[0036] In one embodiment, the specific gravity of these classification solutions is 0.8 to 1.6, for example: 0.8, 1.0, 1.2, 1.4 or 1.6. For example, a variety of plastic-containing materials are placed in multiple classification solutions and separated in the order of specific gravity of 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 and 1.6. More preferably, the specific gravity of these classification solutions is 0.8 to 1.0. Even more preferably, the specific gravity of these classification solutions is 0.8 to 0.9. Through the classification step, the present invention can effectively screen out materials that do not contain or hardly contain polypropylene, so as to improve the polypropylene recovery efficiency.

[0037] In one embodiment, the plastic-containing material is in granular form.

[0038] More preferably, the average diameter of the plastic-containing material is greater than 0 mm and less than or equal to 5 mm, for example: 1 mm, 2 mm, 3 mm, 4 mm or 5 mm.

[0039] The heating temperature of the heating step of the present invention is 80°C to 140°C, for example: 80°C, 100°C, 120°C or 140°C. More preferably, the heating temperature of this heating step is 130°C to 140°C, for example: 130°C, 133°C, 136°C, 139°C or 140°C.

[0040] In one embodiment, the stirring speed in this heating step is 15 rpm to 40 rpm, for example: 15 rpm, 20 rpm, 25 rpm, 30 rpm, 35 rpm or 40 rpm. The present invention can maintain the continuous suspension of the plastic-containing material in the solvent through stirring, so as to improve the dissolution efficiency and recovery rate.

[0041] In one embodiment, the stirring time in this heating step is 15 minutes to 60 minutes, for example: 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0042] In one embodiment, based on 100 ml of the solvent, the weight of the plastic-containing material is greater than 0 g and less than or equal to 2.2 g, for example: 0.05 g, 0.1 g, 0.15 g, 0.2 g, 0.25 g, 0.3 g, 0.35 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g, 0.9 g, 1.0 g, 1.1 g, 1.2 g, 1.3 g, 1.4 g, 1.5 g, 1.6 g, 1.7 g, 1.8 g, 1.9 g, 2.0 g, 2.1 g or 2.2 g. More preferably, based on 100 ml of the solvent, the weight of the plastic-containing material is 1.4 g to 1.6 g. According to the present invention, the ratio range of the volume of the solvent to the weight of the plastic-containing material has two advantages: (1) this weight ratio range makes the first mixture easy to stir; and (2) this weight ratio range improves the plastic recovery rate.

[0043] In one embodiment, based on the total volume of the solvent and the non-solvent being 100 milliliters, the weight of the plastic-containing material is greater than 0 grams and less than or equal to 2.2 grams. For example: 0.05 grams, 0.1 grams, 0.15 grams, 0.2 grams, 0.25 grams, 0.3 grams, 0.35 grams, 0.4 grams, 0.5 grams, 0.6 grams, 0.7 grams, 0.8 grams, 0.9 grams, 1.0 grams, 1.1 grams, 1.2 grams, 1.3 grams, 1.4 grams, 1.5 grams, 1.6 grams, 1.7 grams, 1.8 grams, 1.9 grams, 2.0 grams, 2.1 grams, or 2.2 grams. More preferably, based on the total volume of the solvent and the non-solvent being 100 milliliters, the weight of the plastic-containing material is 1.4 grams to 1.6 grams. According to the present invention, the ratio range of the total volume of the solvent and the non-solvent to the weight of the plastic-containing material has two advantages: (1) this weight ratio range makes the first mixture easy to stir; and (2) this weight ratio range improves the plastic recovery rate.

[0044] In one embodiment, (3) the heating step includes: (3-1): heating and stirring the first mixture at a temperature of 80°C to 140°C to dissolve the plastic component in the solvent to obtain a second mixture; and (3-2): filtering the second mixture through a filter screen to obtain a solution. The present invention can thereby remove impurities insoluble in the solvent to improve the purity of the recovered material.

[0045] In one embodiment, step (3-2) further includes a precipitation step. A. After obtaining the second mixture, let the second mixture stand to obtain a second mixture that has been allowed to stand; wherein, the temperature of the second mixture that has been allowed to stand is lower than the temperature of the second mixture, and the second mixture that has been allowed to stand includes a supernatant and a precipitate; and B. Filter the impurities in the supernatant through a filter screen to obtain the solution. In other words, the present invention can, through the precipitation step, that is, by allowing the second mixture to stand without heating, cooperate with the filter screen to remove undissolved components and suspended substances to remove impurities.

[0046] More preferably, in this precipitation step, the time for allowing the second mixture to stand is 2 hours to 3 hours. The present invention allows the second mixture to stand at room temperature. After obvious precipitation occurs in the second mixture that has been allowed to stand, that is, the second mixture that has been allowed to stand includes a supernatant and a precipitate, and then filter the supernatant through a filter screen. Compared with directly filtering the second mixture, filtering the supernatant can shorten the filtering time required and reduce the amount of impurities contained in the solution.

[0047] In summary, the plastic recycling method of the present invention has a high plastic recovery rate, and both the solvent and the non-solvent can be recycled and reused, which not only reduces costs but also avoids environmental problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 and Figure 2 is a flowchart of the plastic recycling method of the present invention. Detailed implementation manners

[0049] The following provides various operation modes to illustrate the implementation manners of the present invention; those skilled in the art can easily understand the advantages and effects that the present invention can achieve through the content of this specification, and make various modifications and changes without departing from the spirit of the present invention to implement or apply the content of the present invention.

[0050] As Figure 1 shown, first, the plastic recycling method of the present invention includes step S1: preparation step: prepare a plastic-containing material, the plastic-containing material includes a plastic component, and the plastic component includes polypropylene. Specifically, the plastic-containing material is a powder obtained by pulverizing and sieving industrial waste containing polypropylene, for example: sieving through a 10-mesh sieve to obtain plastic-containing material particles with a diameter of less than 2 mm.

[0051] Second, the plastic recycling method of the present invention includes S2: mixing step: mix the plastic-containing material and a solvent to obtain a first mixture, wherein the plastic component is soluble in the solvent. Specifically, the solvent is selected as xylene, and the plastic-containing material and xylene are mixed to obtain a first mixture.

[0052] Third, the plastic recycling method of the present invention includes S3: heating step: heat and stir the first mixture at a temperature of 80°C to 140°C to dissolve the plastic component in the solvent to obtain a solution. Specifically, the heating temperature of this heating step is 140°C, the stirring speed is 20 rpm to 30 rpm, and the time of this heating step is 20 minutes to 40 minutes. Specifically, the heating temperature of this heating step is 140°C, the stirring speed is 20 rpm to 30 rpm, and the time is 20 minutes to 40 minutes.

[0053] Finally, the plastic recycling method of the present invention includes S4: separation step: place the solution in a negative pressure environment to obtain the plastic component. Specifically, the solution is transferred to a decompression concentration device and sealed, and a negative pressure is formed by pumping air to make the solution boil and separate out xylene to obtain polypropylene in the form of flakes or particles.

[0054] Please refer to Figure 1 and Figure 2, when the plastic-containing material is industrial waste containing polypropylene, since it contains components insoluble in the solvent, the S3 heating step includes: S3-1: heating and stirring the first mixture at a temperature of 80°C to 140°C to dissolve the plastic components in the solvent to obtain a second mixture; and S3-2: filtering the second mixture through a filter screen to obtain a solution. Specifically, a filter screen is used to remove undissolved solids to remove impurities. In addition, before removing the undissolved solids with a filter screen, the second mixture can be left standing at room temperature first. After obvious precipitation occurs in the standing second mixture, the supernatant is taken for filtration.

[0055] Test Example 1 and Test Example 2: Solvent Recovery Condition Test

[0056] In step (4) of the present invention, the separation step is to place the solution in a negative pressure environment to obtain the plastic components. Therefore, the pressure required for the negative pressure environment and the corresponding recovery time are tested first, and the operation is as follows: Xylene is selected as the solvent, and 200 ml of xylene solution is poured into a sample bottle and then placed in a negative pressure environment, that is, a rotary evaporator, to simulate step (4) of the present invention, the separation step; wherein, the sample bottles in Test Example 1 and Test Example 2 are both subjected to water bath heating in the rotary evaporator, the temperature is set at 80°C, the rotation speed of the sample bottle is set at 20 rpm, and the pressure is measured according to the pressure gauge configured on the air pump, and the time required for the water bath heating to heat from room temperature to the complete evaporation of 200 ml of xylene solution is recorded. The results are shown in Table 1. In addition, the function of the air pump is to pump air, and it is difficult to accurately control the pressure of the negative pressure environment. Therefore, only based on 20 mbar, the pressure of two groups of negative pressure environments is distinguished for testing.

[0057] Table 1: Pressure of the negative pressure environment, evaporation time and solvent recovery rate used in Test Example 1 and Test Example 2

[0058]

[0059] As can be seen from Table 1, the pressure of the negative pressure environment in Test Example 1 is greater than 20 mbar to 80 mbar, about 2% to 8% of one atmosphere (1.013 bar), and the required evaporation time is about 30 minutes; the pressure of the negative pressure environment in Test Example 2 is 0 mbar to 20 mbar, about 0% to 2% of one atmosphere (1.013 bar), and the required evaporation time is about 15 minutes, and the solvent recovery rates of Test Example 1 and Test Example 2 are both greater than 98%. It can be seen that reducing the pressure of the negative pressure environment can significantly reduce the time required for step (4) of the present invention, the separation step, without affecting the solvent recovery rate, so as to improve the efficiency.

[0060] Examples 1 to 7

[0061] The plastic-containing materials, solvents, and non-solvents used in Examples 1 to 7 are shown in Table 2. First, the plastic-containing materials are crushed by a crushing device and sieved through a 10-mesh sieve to obtain plastic-containing material particles with a diameter of 2 mm or less. After adding 3 g of the plastic-containing material particles to a solvent (or a mixed solution containing a solvent and a non-solvent), a first mixture is obtained. Then, the first mixture is heated to 140 °C by an electric heating furnace, and during the heating process, the first mixture is stirred at a rotation speed of 20 rpm to 30 rpm and continuously stirred at 140 °C for 20 minutes to 40 minutes to dissolve the plastic-containing material particles and obtain a solution. The solution is transferred to a vacuum concentration device, and the solution is kept warm in a warm water bath at 90 °C, and the water flow switch of the condenser is turned on. After confirming that the vacuum concentration system is sealed, the air pump is turned on to reduce the pressure in the system to 0 mbar to 20 mbar, and after the solution starts to boil or evaporate, the air pump is turned off, and then the vapors of the solvent (and non-solvent) are condensed through the condenser to recover the solvent (and non-solvent), while keeping the pressure in the system from rising. Finally, after the solvent (and non-solvent) has completely evaporated, solid polypropylene in the form of flakes or particles is obtained, which is rinsed with clean water to remove the remaining xylene odor and then air-dried to obtain the recycled polypropylene. Then, it is weighed and its appearance is inspected. The results are shown in Table 3. The above-mentioned mixed solution containing a solvent and a non-solvent can be directly reused after recovery without separation; or it can be separated by utilizing the different boiling points of the solvent and the non-solvent respectively.

[0062] The above-mentioned recovered solvent (and non-solvent) is in a clear state and can be reused. In addition, in Examples 5 to 7 of the present invention, industrial waste containing polypropylene is used, so it contains components insoluble in the solvent. Therefore, between the heating step and the separation step, a filtration step is additionally carried out: filtration is carried out with a 500-mesh stainless steel filter screen to remove solids larger than 25 microns. In addition, before filtering the solution, the solution is left standing at room temperature for 2.5 hours. After it cools and obvious precipitation appears, the supernatant is taken for filtration. Finally, the industrial waste containing polypropylene used in Examples 5 to 7 is confirmed to contain polypropylene by an optical method before dissolution, and strong oxidants are used to remove the remaining organic substances and impurities.

[0063] Table 2: Plastic-containing materials, solvents, and non-solvents used in Examples 1 to 7

[0064]

[0065] Table 3: Polypropylene recovery weights and appearances of Examples 1 to 7

[0066]

[0067] From the comparison of Examples 1 to 4, it can be seen that the highest recovered weight of polypropylene is obtained using xylene as the solvent, reaching as high as 93.7% (the calculation formula is 2.81 / 3*100%). And when a non-solvent is used to replace a part of the solvent, the recovered weight of polypropylene only slightly decreases, indicating that the non-solvent can indeed replace the solvent and maintain a high polypropylene recovery rate, even though polypropylene is hardly soluble in the non-solvent. Secondly, the solvent recovery rates of Examples 1 to 4 are all higher than 90%, even higher than 95%, with extremely low losses. In addition, for the recovered products obtained in Examples 1 to 4, the FTIR test results are consistent with the signals of commercially available polypropylene, indicating that the present invention can indeed effectively recover polypropylene. Finally, since the polypropylene content of the industrial waste containing polypropylene in Examples 5 to 7 is unknown, it was tested 3 times in the same manner. Based on the fact that the colors of the recovered polypropylene obtained in Examples 5 to 7 are darker than those of commercially available polypropylene, it is judged that it is not pure polypropylene and may contain other components that are also soluble in xylene.

[0068] Examples 8 to 11

[0069] The plastic-containing materials, solvents, and non-solvents used in Examples 8 to 11 are shown in Table 4. Among them, the plastic-containing material particles in each group are commercially available polypropylene, and except that (1) the addition amount of commercially available polypropylene is 0.8 g; (2) the solvent in each group is 100 ml of xylene; and (3) the volume ratio of the solvent and non-solvent in each group is 1:1, the remaining experimental methods are the same as those in Examples 1 to 7.

[0070] Table 4: Solvents and Non-solvents Used in Examples 8 to 11

[0071]

[0072] As can be seen from Table 4, when the non-solvents are selected as propylene glycol methyl ether acetate, butyl acetate, isoamyl acetate, and cyclohexanone, the polypropylene recovery rates of Examples 8 to 11 are all higher than 94%. Furthermore, the polypropylene recovery rate of Example 9 using butyl acetate as the non-solvent is the best, reaching 96%, but the solvent and non-solvent recovery rates of Example 9 are the lowest, only 75%. In addition, cyclohexanone is used as the non-solvent in both Example 3 and Example 11. The volume ratio of xylene and cyclohexanone in both Example 3 and Example 11 is 1:1, and the total volume of the solvent and non-solvent in both Example 3 and Example 11 is 200 ml. The polypropylene recovery rate of Example 3 is 92.7%, slightly lower than 95% of Example 11. Based on the fact that the original amount of commercially available polypropylene in Example 3 is 3 g, which is much higher than 0.8 g in Example 11, it can be found that Example 3 shows a more cost-effective recovery result, that is, the recovered polypropylene in Example 3 is 2.78 g (3 g 92.7%), much higher than 0.076 g (0.8 g 95%). Therefore, when the weight percentage (W / V) of polypropylene is 2.78 g / 200 mL, which is close to 1.5 g / 100 mL, a higher polypropylene recovery can be obtained.

[0073] In summary, it can be seen that the plastic recycling method of the present invention indeed has a high plastic recovery rate, and both the solvent and the non-solvent can be recycled and reused, which not only reduces costs but also avoids the derivation of environmental problems.

Claims

1. A plastic recycling method, comprising: (1) Preparation step: Prepare a plastic-containing material, the plastic-containing material comprising a plastic component, and the plastic component comprising polypropylene; (2) Mixing step: Mix the plastic-containing material and a solvent to obtain a first mixture, wherein the plastic component is soluble in the solvent; (3) Heating step: Heat and stir the first mixture at a temperature of 80°C to 140°C to dissolve the plastic component in the solvent to obtain a solution; and (4) Separation step: Place the solution in a negative pressure environment to obtain the plastic component.

2. The plastic recycling method according to claim 1, wherein in the separation step, it further comprises: maintaining the temperature of the solution at 70°C to 100°C.

3. The plastic recycling method according to claim 1, wherein the solvent comprises aromatic hydrocarbons, ketones, ethers, cycloalkanes, esters or combinations thereof.

4. The plastic recycling method according to claim 3, wherein the aromatic hydrocarbons comprise benzene, toluene, xylene, tetralin, decalin or combinations thereof.

5. The plastic recycling method according to claim 1, wherein in the mixing step, a non-solvent is further added, and the non-solvent comprises ethers, ketones, esters or combinations thereof.

6. The plastic recycling method according to claim 5, wherein the ether comprises tetrahydrofuran; the ketone comprises cyclohexanone, acetone or combinations thereof; and the ester comprises propylene glycol monomethyl ether acetate, butyl acetate, isoamyl acetate or combinations thereof.

7. The plastic recycling method according to claim 5, wherein based on the total volume of the solvent and the non-solvent, the solvent is 45 volume percent to 60 volume percent, and the non-solvent is 40 volume percent to 55 volume percent.

8. The plastic recycling method according to claim 1, wherein the plastic-containing material is in granular form, and the average diameter of the plastic-containing material is greater than 0 mm and less than or equal to 5 mm, the stirring speed in the heating step is 15 rpm to 40 rpm, the time is 15 minutes to 60 minutes, and the pressure of the negative pressure environment is greater than or equal to 0 mbar and less than or equal to 90 mbar.

9. The plastic recycling method according to claim 1, wherein based on 100 ml of the solvent, the weight of the plastic-containing material is greater than 0 g and less than or equal to 2.2 g.

10. The plastic recycling method according to claim 5, wherein based on 100 ml of the total volume of the solvent and the non-solvent, the weight of the plastic-containing material is greater than 0 g and less than or equal to 2.2 g.

Images