Method for recovering waste polycarbonate

Abstract

The invention discloses a waste polycarbonate recovery method which comprises the following steps: crushing and cleaning polycarbonate to obtain polycarbonate flocculus, and cleaning the polycarbonate flocculus by adopting a flowing phase to obtain pretreated polycarbonate; dissolving the pretreated polycarbonate in a first organic solvent to obtain a mixed solution; adding a second organic solvent into the mixed solution for separating out polycarbonate, and then filtering, drying and crushing to obtain the polycarbonate, the recovery method is a solvent method, can be applied to recovery of polycarbonate in waste polycarbonate containing a coating and toner, is wide in adaptive object range, free of degradation of molecular chain length and capable of keeping mechanical properties and chromaticity, and has the advantages of being easy to operate, low in cost and the like.

Description

Technical Field

[0001] This invention relates to the field of polycarbonate recycling technology, and more specifically to a method for recycling waste polycarbonate. Background Technology

[0002] Currently, the main methods for recycling waste polycarbonate are mechanical recycling and chemical solvent recycling. The chemical method is further divided into two directions: chemical pyrolysis recycling and chemical solvent recycling. The mechanical recycling process involves cleaning, crushing, removing the coating, and granulating the waste PC before it can be directly used in new product production. Applicable scenarios: pure waste materials (such as Nongfu Spring water bottles and car headlight covers); the technology is mature and low-cost. Limitations: performance degrades after multiple cycles; it cannot handle waste materials with coatings, waste materials of different colors, or PC alloy waste. This leads to many problems, such as the polycarbonate having to be downgraded for reuse.

[0003] Chemical (depolymerization) recycling principle: PC is decomposed into monomers such as bisphenol A, and then repolymerized into virgin PC, achieving "molecular-level regeneration". Teijin Chemical (Japan): Atmospheric pressure alkaline catalytic degradation method, bisphenol A recovery rate >95%, purity 99.9%. Covestro: Chemical dissolution process, treating waste containing >50% PC, directly producing monomers for high-transparency applications such as automotive lights and electronic screens. Advantages: Performance comparable to virgin materials, capable of handling complex waste; Limitations: High cost and the need for novel catalysts; the development of novel catalysts requires a long time cycle.

[0004] Chemical solvent recovery involves pre-treating PC waste to remove surface stains and functional additives, then dissolving the PC, and finally adding a poor solvent to the PC solution to precipitate the PC, resulting in brand-new PC. This achieves a cycle from 'polymer' to 'polymer', with the same performance as brand-new PC. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recycling waste polycarbonate. This recycling method is a chemical solvent method, which can be applied to the recycling of polycarbonate in waste polycarbonate containing coatings and pigments. It has a wide range of applications, does not degrade the molecular chain length, maintains mechanical properties and color, and has the advantages of simple operation and low cost.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] The first aspect of this invention provides a method for recycling waste polycarbonate, the recycling method comprising the following steps:

[0008] (a) The polycarbonate is crushed and washed to obtain polycarbonate flakes, and then the polycarbonate flakes are washed with a mobile phase to obtain pretreated polycarbonate, wherein the mobile phase is selected from any one of ethyl acetate, N,N-dimethylformamide, benzene, m-xylene, o-xylene, dimethyl sulfoxide and mesitylene;

[0009] (b) Dissolve the pretreated polycarbonate in a first organic solvent to obtain a mixture;

[0010] (c) A second organic solvent is added to the mixture to precipitate polycarbonate, which is then filtered, dried and pulverized to obtain the polycarbonate.

[0011] Preferably, in step (a), the flow rate of the mobile phase per minute is 0.05 to 2 times the mass of the polycarbonate flocs; and the temperature of the mobile phase is 10 to 100°C.

[0012] Preferably, in step (a), the amount of mobile phase used is 6 to 15 times the mass of the polycarbonate flocs.

[0013] Preferably, in step (b), the first organic solvent is selected from any one of ethyl acetate, N,N-dimethylformamide, chloroform, dichloromethane, carbon tetrachloride, N-methylpyrrolidone, and mesitylene.

[0014] Preferably, in step (b), the amount of the first organic solvent is 5 to 10 times the mass of the polycarbonate.

[0015] Preferably, in step (b), the temperature of the first organic solvent is 10~30°C.

[0016] Preferably, in step (c), the second organic solvent is selected from any one of xylene, trimethylbenzene, cyclohexane, n-heptane, methanol, ethanol, 95% ethanol, and petroleum ether.

[0017] Preferably, in step (c), the amount of the second organic solvent added is 6 to 20 times the mass of the polycarbonate.

[0018] Preferably, in step (c), the drying temperature is 110~120℃, the drying time is 3~5h, and the pulverized particle size is 100~300μm.

[0019] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0020] The present invention relates to a solvent-based recycling method, which can be applied to the recycling of polycarbonate from waste polycarbonate containing coatings and colorants. It has a wide range of applicability, does not degrade the molecular chain length, and maintains mechanical properties and color. It also has the advantages of simple operation and low cost. It solves the problems of downgraded use in physical and mechanical recycling of waste polycarbonate with coatings and colorants and high energy consumption in chemical recycling. Detailed Implementation

[0021] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0022] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] This invention provides a method for recycling waste polycarbonate, the method comprising the following steps:

[0024] (a) The polycarbonate is crushed and washed to obtain polycarbonate flakes, and then the polycarbonate flakes are washed with a mobile phase to obtain pretreated polycarbonate, wherein the mobile phase is selected from any one of ethyl acetate, N,N-dimethylformamide, benzene, m-xylene, o-xylene, dimethyl sulfoxide and mesitylene;

[0025] (b) Dissolve the pretreated polycarbonate in a first organic solvent to obtain a mixture;

[0026] (c) A second organic solvent is added to the mixture to precipitate polycarbonate, which is then filtered, dried and pulverized to obtain the polycarbonate.

[0027] The present invention relates to a solvent-based recycling method, which can be applied to the recycling of polycarbonate from waste polycarbonate containing coatings and colorants. It has a wide range of applicability, does not degrade the molecular chain length, and maintains mechanical properties and color. It also has the advantages of simple operation and low cost. It solves the problems of downgraded use in physical and mechanical recycling of waste polycarbonate with coatings and colorants and high energy consumption in chemical recycling.

[0028] In one embodiment, in step (a), the flow rate of the mobile phase per minute is 0.05 to 2 times the mass of the polycarbonate flakes; the temperature of the mobile phase is 10 to 100°C.

[0029] In one embodiment, in step (a), the amount of mobile phase used is 6 to 15 times the mass of the polycarbonate flocs.

[0030] In one embodiment, in step (b), the first organic solvent is selected from any one of ethyl acetate, N,N-dimethylformamide, chloroform, dichloromethane, carbon tetrachloride, N-methylpyrrolidone, and mesitylene.

[0031] In one embodiment, in step (b), the amount of the first organic solvent is 5 to 10 times the mass of the polycarbonate.

[0032] In one embodiment, in step (b), the temperature of the first organic solvent is 10~30°C.

[0033] In one embodiment, in step (c), the second organic solvent is selected from any one of xylene, trimethylbenzene, cyclohexane, n-heptane, methanol, ethanol, 95% ethanol, and petroleum ether.

[0034] In one embodiment, in step (c), the amount of the second organic solvent added is 6 to 20 times the mass of the polycarbonate.

[0035] In one embodiment, in step (c), the drying temperature is 110~120℃, the drying time is 3~5h, and the pulverized particle size is 100~300μm.

[0036] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0037] All raw materials used in this invention were purchased commercially.

[0038] Example 1

[0039] This embodiment is a method for recycling waste polycarbonate, which includes the following steps:

[0040] (a) Polycarbonate containing coating and pigment is crushed and washed with water to obtain polycarbonate flakes. 150g of polycarbonate flakes are loaded into a column with a jacket and agitator, and room temperature xylene is continuously introduced at a flow rate of 15mL / min for 1.5h. After removing the coating and pigment, pretreated polycarbonate is obtained.

[0041] (b) Pour the pretreated polycarbonate into a flask, add 750g of dichloromethane at room temperature to dissolve the pretreated polycarbonate and obtain a mixture;

[0042] (c) Add 1000g of methanol to the mixture to precipitate polycarbonate, filter it, dry the precipitated polycarbonate solid under vacuum at 120°C for 4h, after drying, crush the polycarbonate solid with a pulverizer to obtain powdered polycarbonate.

[0043] Example 2

[0044] This embodiment is a method for recycling waste polycarbonate, which includes the following steps:

[0045] (a) Polycarbonate containing coating and pigment is crushed and washed with water to obtain polycarbonate flakes. 200g of polycarbonate flakes are loaded into a column with a jacket and agitator. Room temperature xylene is continuously introduced at a flow rate of 20mL / min for 2h. After removing the coating and pigment, pretreated polycarbonate is obtained.

[0046] (b) Pour the pretreated polycarbonate into a flask, add 2000g of dichloromethane at room temperature to dissolve the pretreated polycarbonate and obtain a mixture;

[0047] (c) Add 3000g of methanol to the mixture to precipitate polycarbonate, filter it, dry the precipitated polycarbonate solid under vacuum at 120°C for 4h, after drying, crush the polycarbonate solid with a pulverizer to obtain powdered polycarbonate.

[0048] Comparative Example 1

[0049] This comparative example illustrates a method for recycling waste polycarbonate, which includes the following steps:

[0050] (a) Polycarbonate containing coating and pigment is crushed and washed with water to obtain polycarbonate flakes. 200g of polycarbonate flakes are loaded into a column with a jacket and agitator. Room temperature xylene is continuously introduced at a flow rate of 20mL / min for 2h. After removing the coating and pigment, pretreated polycarbonate is obtained.

[0051] (b) Pour the pretreated polycarbonate into a flask, add 2000g of dichloromethane at room temperature to dissolve the pretreated polycarbonate and obtain a mixture;

[0052] (c) Add 3000g of n-heptane to the mixture to precipitate polycarbonate, filter it, dry the precipitated polycarbonate solid under vacuum at 120°C for 4h, after drying, crush the polycarbonate solid with a pulverizer to obtain powdered polycarbonate.

[0053] Experimental Example

[0054] Polycarbonate was recovered according to the recovery methods of Examples 1-2 and Comparative Example 1, respectively;

[0055] The mechanical properties and color of the above-mentioned polycarbonate were tested, and the recovery rate was calculated. The results are shown in Table 1.

[0056] Table 1

[0057] Group Recovery rate chromaticity Mechanical properties Example 1 95% L: 70.1, a: -1.2, b: 8.0 Notched impact strength of cantilever beam: 65.2 kJ / m²; tensile strength: 63 MPa; tensile fracture strain: 115%; flexural strength: 90 MPa; flexural modulus: 2350 MPa Example 2 95% L: 70.5, a: -0.98, b: 8.5 Notched impact strength of cantilever beam: 65.2 kJ / m²; tensile strength: 65 MPa; tensile fracture strain: 115.5%; flexural strength: 90.5 MPa; flexural modulus: 2280 MPa. Comparative Example 1 80% L: 65.5, a: -0.2.0, b: 10.5 Notched impact strength of cantilever beam: 64 kJ / m²; tensile strength: 58 MPa; tensile fracture strain: 90.5%; flexural strength: 89.2 MPa; flexural modulus: 2180 MPa.

[0058] As shown in Table 1:

[0059] Compared to the comparative example, the waste polycarbonate recovered in this application embodiment has superior performance.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for recycling waste polycarbonate, characterized in that, The recycling method includes the following steps: (a) The polycarbonate is crushed and washed to obtain polycarbonate flakes, and then the polycarbonate flakes are washed with a mobile phase to obtain pretreated polycarbonate, wherein the mobile phase is selected from any one of ethyl acetate, N,N-dimethylformamide, benzene, m-xylene, o-xylene, dimethyl sulfoxide and mesitylene; (b) Dissolve the pretreated polycarbonate in a first organic solvent to obtain a mixture; (c) A second organic solvent is added to the mixture to precipitate polycarbonate, which is then filtered, dried and pulverized to obtain the polycarbonate.

2. The recycling method according to claim 1, characterized in that, In step (a), the flow rate of the mobile phase per minute is 0.05 to 2 times the mass of the polycarbonate flocs; the temperature of the mobile phase is 10 to 100°C.

3. The recycling method according to claim 1, characterized in that, In step (a), the amount of mobile phase used is 6 to 15 times the mass of the polycarbonate flocs.

4. The recycling method according to claim 1, characterized in that, In step (b), the first organic solvent is selected from any one of ethyl acetate, N,N-dimethylformamide, chloroform, dichloromethane, carbon tetrachloride, N-methylpyrrolidone, and mesitylene.

5. The recycling method according to claim 1, characterized in that, In step (b), the amount of the first organic solvent used is 5 to 10 times the mass of the polycarbonate.

6. The recycling method according to claim 1, characterized in that, In step (b), the temperature of the first organic solvent is 10~30℃.

7. The recycling method according to claim 1, characterized in that, In step (c), the second organic solvent is selected from any one of xylene, trimethylbenzene, cyclohexane, n-heptane, methanol, ethanol, 95% ethanol, and petroleum ether.

8. The recycling method according to claim 1, characterized in that, In step (c), the amount of the second organic solvent added is 6 to 20 times the mass of the polycarbonate.

9. The recycling method according to claim 1, characterized in that, In step (c), the drying temperature is 110~120℃, the drying time is 3~5h, and the particle size is 100~300μm.