Waste ABS plastic recovery method and system

Abstract

The invention relates to the technical field of waste ABS (Acrylonitrile Butadiene Styrene) plastic recovery, in particular to a waste ABS plastic recovery method and system. The method comprises the following steps: (1) enabling waste ABS plastic to be in contact with a solvent for dissolving to obtain a liquid-phase component and a solid-phase component; the solvent comprises a solvent A and a solvent B, the solvent A is selected from one or more of dichloromethane, trichloromethane and carbon tetrachloride, and the solvent B is selected from one or more of N-methyl pyrrolidone, tetrahydrofuran, dimethylformamide and butanone; (2) contacting the liquid-phase component with an adsorbent for adsorption to obtain a desorption solution; the adsorbent comprises acidic activated carbon and activated clay; and (3) evaporating the desorption liquid to obtain the ABS. The recovery method of the waste ABS plastic has the advantages of being short in technological process, low in energy consumption and high in separation efficiency, the recovery rate of the ABS can be remarkably increased, the color of the recovered ABS is reduced, and the use value of the recovered ABS is increased.

Description

Technical Field

[0001] The invention relates to the technical field of waste ABS plastic recycling, and in particular to a waste ABS plastic recycling method and system. Background Art

[0002] ABS plastic generally includes acrylonitrile-butadiene-styrene polymer and various organic additives and non-agent additives used to improve the performance of acrylonitrile-butadiene-styrene polymer. It is a material with good toughness, hard texture, strong rigidity and rich colors. It is widely used in manufacturing industries such as automobiles.

[0003] At present, with the widespread popularity of new energy battery vehicles, the use of ABS plastics is increasing, which has also led to the generation of a large amount of waste ABS plastics, causing serious pollution. At present, the solvent dissolution method is usually used to recover ABS from waste ABS plastics to achieve the reuse of ABS. However, this method generally has problems such as high energy consumption, low recovery rate, heavy color of the recycled products, and low use value.

[0004] CN1908041A discloses a production method for recycling high-purity ABS from waste ABS plastics. First, ethylene glycol and propylene glycol are mixed (4:1) and then reacted with a certain amount of concentrated phosphoric acid and dehydrated to produce an MP solvent. A certain amount of waste ABS plastic fragments are added to a dissolving kettle, and MP solvent (material to solvent ratio 2:1 to 4:1) is added to the kettle. All are dissolved at 50-90°C and normal pressure. The dissolved solution is then filtered from the dissolving kettle into a special filter, and the filtrate is pumped into an evaporating kettle. Distillation is performed at a vacuum degree between 0.01MPa-0.06MPa and 60-150°C, and the MP solvent evaporated is pumped into a storage tank for recycling. The semi-fluid ABS in the distilling kettle is sent to an extruder to be extruded into strips, and after water cooling, it is pelletized into high-purity ABS raw materials. This method has the characteristics of good product quality, high economic benefits, reasonable process, and no pollution. However, the high-purity ABS raw materials produced are light yellow opaque particles.

[0005] CN110511332A discloses a recycling process for waste ABS plastics. The specific recycling process is as follows: waste ABS plastics are treated with acid and alkali to obtain secondary treatment products, the secondary treatment products and nitrile rubber are added to butanone at the same time, stirred and dissolved, benzoyl peroxide is added thereto, the temperature is raised to 95-100°C, hexafluorobutyl acrylate and silanization agent are added thereto, the temperature is raised to 120-125°C for constant temperature reaction for 1-2h, and then the temperature is raised to reflux reaction for 4-5h, and then the acetone solution and unreacted hexafluorobutyl acrylate are removed by reduced pressure distillation to obtain modified ABS. Although this process can realize the recycling of waste ABS plastics, this recycling process has the problems of long time and complicated process flow.

[0006] Therefore, there is an urgent need to provide a method for recycling waste ABS plastics with simple process, low energy consumption, light color of recycled ABS and high use value. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of the prior art in that the waste ABS plastic recycling process is long, the energy consumption is high, the recycled ABS has a heavy color, and the use value is low, and to provide a waste ABS plastic recycling method and system.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for recycling waste ABS plastics, wherein the method comprises the following steps:

[0009] (1) contacting waste ABS plastic with a solvent to dissolve it, thereby obtaining a liquid phase component and a solid phase component; wherein the solvent comprises a solvent A and a solvent B, wherein the solvent A is selected from one or more of dichloromethane, chloroform, and carbon tetrachloride, and the solvent B is selected from one or more of N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, and butanone;

[0010] (2) contacting the liquid phase component with an adsorbent for adsorption to obtain a desorption liquid; wherein the adsorbent includes acidic activated carbon and activated clay;

[0011] (3) Evaporating the desorption liquid to obtain ABS.

[0012] The second aspect of the present invention provides a waste ABS recovery system, wherein the system comprises a dissolving device, an adsorption device and an evaporation device connected in sequence; wherein the dissolving device is used to dissolve the waste ABS plastic and the solvent to obtain a liquid component and a solid component; the adsorption device is used to adsorb the liquid component and the adsorbent to obtain a desorption liquid; and the evaporation device is used to evaporate the desorption liquid to obtain ABS.

[0013] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0014] 1) The method for recycling waste ABS plastics provided in the present invention utilizes solvent to achieve efficient dissolution of ABS, which can significantly improve the recovery rate of ABS, so that the recovery rate of ABS is ≥95%;

[0015] 2) The method for recycling waste ABS plastics provided by the present invention can significantly reduce the color of the recycled ABS and improve the use value of the recycled ABS through the synergistic effect of the solvent and the adsorbent;

[0016] 3) The method for recycling waste ABS plastics provided in the present invention can reduce the amount of additives added when the recycled ABS is reused, and has high use value;

[0017] 4) The method for recycling waste ABS plastics provided in the present invention solves the problems of long separation process, high energy consumption, low separation efficiency, etc. in the prior art, fills the technical gap of efficiently recycling ABS using organic solvents, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is an appearance diagram of the crushed waste battery shell material in the present invention;

[0019] Figure 2 is an appearance diagram of the ABS recovered in Example 1 of the present invention;

[0020] Figure 3 is the infrared characterization spectrum of the ABS recovered in Example 1 of the present invention;

[0021] Figure 4 It is the appearance picture of the ABS recovered in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0022] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0023] A first aspect of the present invention provides a method for recycling waste ABS plastics, wherein the method comprises the following steps:

[0024] (1) contacting waste ABS plastic with a solvent to dissolve it, thereby obtaining a liquid phase component and a solid phase component; wherein the solvent comprises a solvent A and a solvent B, wherein the solvent A is selected from one or more of dichloromethane, chloroform, and carbon tetrachloride, and the solvent B is selected from one or more of N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, and butanone;

[0025] (2) contacting the liquid phase component with an adsorbent for adsorption to obtain a desorption liquid; wherein the adsorbent includes acidic activated carbon and activated clay;

[0026] (3) Evaporating the desorption liquid to obtain ABS.

[0027] In step (1):

[0028] In a preferred embodiment of the present invention, the present invention does not specifically limit the source of waste ABS plastics, and the waste ABS plastics can be waste battery casings, mechanical parts (pipes, pipe fittings, battery slots, and power tool casings, etc.), and auto parts (glove boxes, glove boxes, upper and lower door sill trims, etc.), preferably waste battery casings.

[0029] Wherein, in the present invention, taking the waste battery shell as an example, the content of ABS in the waste battery shell is ≥60wt%, preferably 60-90wt%. In addition to ABS, the waste battery shell also contains various organic and / or inorganic additives for changing the physical and chemical properties and color of ABS. The inventor of the present invention has found through research that the waste ABS plastic is first dissolved by a solvent containing solvent A and solvent B, and then adsorbed by an adsorbent, which can significantly improve the recovery rate of ABS, reduce the color depth of the ABS recovered, and obtain white ABS with high use value and good quality.

[0030] In a preferred embodiment of the present invention, the particle size of the waste ABS plastic is 1-100 mm, preferably 10-50 mm.

[0031] Among them, in the present invention, in order to increase the dissolution rate of waste ABS plastic in the solvent, the waste ABS plastic can be cleaned, dried and crushed before dissolution. Moreover, impurities such as sand, gravel and soil in the waste ABS plastic can also be removed by cleaning and drying.

[0032] In a preferred embodiment of the present invention, the solvent A is dichloromethane, and the solvent B is N-methylpyrrolidone and / or tetrahydrofuran.

[0033] Among them, in the present invention, the inventors have found through research that when a mixture of dichloromethane and N-methylpyrrolidone, or dichloromethane and tetrahydrofuran, is used as a solvent, the solvent has better solubility in waste ABS plastics, which not only helps to improve the recovery rate of ABS, but also helps to further reduce the color depth of the recycled ABS.

[0034] In a preferred embodiment of the present invention, the mass ratio of the solvent A to the solvent B is 1:0.1-2, preferably 1:0.5-1.

[0035] In a preferred embodiment of the present invention, the dissolution operating conditions include: the mass ratio of waste ABS plastic to solvent is 1:1-15, preferably 1:5-10; the dissolution temperature is 20-100°C, preferably 30-70°C; the dissolution time is 10-150min, preferably 20-100min.

[0036] Among them, in the present invention, by controlling the dissolution conditions, the colored substances in the waste ABS can be minimized from entering the solvent while promoting the dissolution of ABS as much as possible, which helps to further reduce the color of the recovered ABS solvent.

[0037] In a preferred embodiment of the present invention, after the dissolution is completed, a solid-liquid separation operation is performed to obtain a liquid phase component and a solid phase component.

[0038] Among them, in the present invention, ABS and part of the colored substances are dissolved in the solvent and enter the liquid phase component, and the solid phase component is mainly inorganic additives, mechanical impurities and organic additives insoluble in the solvent in the waste ABS.

[0039] In step (2):

[0040] In a preferred embodiment of the present invention, the preparation method of the acidic activated carbon comprises: placing the activated carbon in an acid treatment liquid for acid treatment to obtain the acidic activated carbon; wherein the acid treatment liquid is selected from one or more of hydrogen peroxide, hydrochloric acid, nitric acid, and sulfuric acid, preferably hydrogen peroxide; the acid treatment is carried out at room temperature, and the acid treatment time is 6-48h, preferably 12-36h.

[0041] Among them, in the present invention, the acid treatment liquid refers to a solution that can make the modified activated carbon acidic. The acid treatment liquid can be not only an acidic solution, but also hydrogen peroxide. This is because after the activated carbon is treated with hydrogen peroxide, the functional groups such as carboxyl groups on the surface of the activated carbon can be significantly increased, making the modified activated carbon acidic. After research, the inventor found that using acidic activated carbon and activated clay as adsorbents can improve the selective adsorption of the adsorbent to colored substances in the liquid phase component, reduce the adsorption amount of ABS, and help to further improve the recovery rate of ABS.

[0042] In a preferred embodiment of the present invention, the mass ratio of the acidic activated carbon to the activated clay is 1:0.1-1.5, preferably 1:0.5-1.

[0043] Among them, in the present invention, appropriately increasing the amount of activated white clay can further improve the adsorption effect of the adsorbent, so that the color of the recycled ABS plastic is closer to white.

[0044] In a preferred embodiment of the present invention, the operating conditions of the adsorption include: the mass ratio of the liquid phase component to the adsorbent is 1:0.5-10, preferably 1:1-8; the adsorption temperature is 25-100°C, preferably 30-50°C; the adsorption time is 10-150min, preferably 20-100min.

[0045] In a preferred embodiment of the present invention, after the adsorption is completed, a solid-liquid separation operation is performed again to obtain a desorbed liquid and a deactivated adsorbent. The deactivated adsorbent can be regenerated according to a known method and then returned to step (2) for recycling.

[0046] In step (3):

[0047] In a preferred embodiment of the present invention, the evaporation is carried out under vacuum, the evaporation temperature is 50-150° C., preferably 60-100° C., and the evaporation time is 10-48 h, preferably 20-30 h.

[0048] In the present invention, evaporation is performed under vacuum, so that the solvent can be recovered at low temperature, which can prevent ABS from deteriorating at high temperature and help obtain high-quality ABS. The recovered solvent separated during the evaporation process can be returned to step (1) for recycling after cooling.

[0049] The second aspect of the present invention provides a recycling system for waste ABS plastics, wherein the system comprises a dissolving device, an adsorption device and an evaporation device connected in sequence; wherein the dissolving device is used to dissolve the waste ABS plastics with a solvent to obtain a liquid component and a solid component; the adsorption device is used to adsorb the liquid component with an adsorbent to obtain a desorbed liquid; and the evaporation device is used to evaporate the desorbed liquid to obtain ABS.

[0050] In a preferred embodiment of the present invention, the recovery system further comprises a separation device, wherein the separation device is used to separate the mixed liquid from the dissolution device and the mixed liquid from the adsorption device.

[0051] The present invention does not specifically limit the dissolving device, adsorption device, evaporation device and separation device, and they can be conventionally selected according to actual needs. For example, the dissolving device and adsorption device can be a reactor with stirring and heating functions, the evaporation device can be a vacuum dryer, an evaporator, etc., and the separation device can be a centrifuge or a filter.

[0052] In a preferred embodiment of the present invention, the recovery system further comprises a condensing device, wherein the condensing device is used to cool the recovered solvent from the evaporating device.

[0053] The present invention will be described in detail by way of examples below: The waste ABS plastic is the crushed material of the waste battery shell from Xiaodao electric vehicles, the ABS content is 78wt%, and after washing, drying and crushing, the average particle size is 30mm.

[0054] Preparation of acidic activated carbon: The activated carbon was placed in 30% by mass hydrogen peroxide and stirred for 24 hours, then washed with deionized water until the filtrate was neutral, and then dried.

[0055] Activated white clay: purchased from Leping Clean Bleaching Clay Co., Ltd.

[0056] Example 1

[0057] (1) 50 g of waste battery shells were contacted with 500 g of solvent (a mixture of dichloromethane and N-methylpyrrolidone, with a mass ratio of 1:1) in a dissolving and stirring device, mixed at 30° C. for 30 min, and then transported to a filter with a pore diameter of less than 50 nm for filtration to obtain a liquid phase component;

[0058] (2) the liquid phase components and the adsorbent (a mixture of acid activated carbon A and activated clay, with a mass ratio of 1:1) were mixed in an adsorption device at a mass ratio of 1:5, adsorbed at 30°C, and transported to a high-speed centrifuge for centrifugal separation after 30 minutes to obtain a desorption liquid;

[0059] (3) The desorbed liquid is transported to a vacuum dryer for evaporation and treated at 80° C. and 200 mbar for 24 hours to obtain ABS and a recovered solvent; wherein the recovered solvent is condensed by a condensing device and then returned to step (1) for recycling.

[0060] The ABS obtained is a white solid with a recovery rate of 99%. Figure 1 As shown, the appearance of the obtained ABS is as Figure 2 By comparison Figure 1 and Figure 2It can be seen that the present invention can recycle white ABS from dark-colored waste battery shells. The whiter the recycled ABS is, the higher its quality and the higher its use value.

[0061] The obtained ABS was characterized by infrared spectroscopy. Figure 3 As shown. Figure 3 It can be seen that the wave number is 2234cm -1 The -C≡N stretching vibration in acrylonitrile is 1494cm -1 、1451cm -1 It is the -C=C- bending vibration of the benzene ring, 756cm -1 、698cm -1 It is the out-of-plane deformation of the monosubstituted benzene ring -C=C-. The above are all characteristic absorption peaks of ABS plastic, confirming that the recycled material is ABS.

[0062] Example 2

[0063] The same as Example 1, except that in step (1), an equal amount of N-methylpyrrolidone was replaced with tetrahydrofuran, and the mixture was mixed at 45° C. for 45 min. The obtained ABS was white, and the recovery rate was 97%.

[0064] Example 3

[0065] The same as Example 1, except that: in step (2), the mass ratio of acidic activated carbon to activated clay is 1:0.5. The obtained ABS is light white, and the recovery rate is 96%.

[0066] Among them, the color of the ABS recycled in Example 1 is whiter than the color of the ABS recycled in Example 3. By comparing Example 1 and Example 3, it can be seen that within the scope defined by the present invention, appropriately increasing the amount of activated white clay can further improve the adsorption effect of the adsorbent, so that the color of the recycled ABS plastic is closer to white.

[0067] Comparative Example 1

[0068] The same as Example 1, except that the solvent in step (1) is 500 g of dichloromethane. The obtained ABS is white, and the recovery rate is 84%.

[0069] Comparative Example 2

[0070] The same as Example 1, except that the solvent in step (1) is 500 g of N-methylpyrrolidone. The obtained ABS is white, and the recovery rate is 82%.

[0071] By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that, compared with using dichloromethane and N-methylpyrrolidone alone, the combined effect of dichloromethane and N-methylpyrrolidone can significantly improve the recovery rate of ABS.

[0072] Comparative Example 3

[0073] The same as Example 1, except that in step (2), the acidic activated carbon is replaced by activated carbon that has not been treated with acid. The obtained ABS is gray-green, such as Figure 4 As shown, the recovery rate was 95%.

[0074] Among them, Figure 4 It can be seen that the ABS recovered in Comparative Example 3 is white with a dark gray color and has a distinct dark gray-green color. Moreover, the recovery rate of ABS in Comparative Example 3 is 4% less than that in Example 1. By comparing Example 1 and Comparative Example 3, it can be seen that compared with activated carbon that has not been treated with acid, the acid activated carbon and activated white clay used as adsorbents can not only significantly improve the selective adsorption of the adsorbent to the colored substances in the liquid phase component, reduce the adsorption amount of ABS, but also help to increase the recovery rate of ABS.

[0075] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for recycling waste ABS plastics, characterized in that: The method comprises the following steps: (1) contacting waste ABS plastic with a solvent to dissolve it, thereby obtaining a liquid phase component and a solid phase component; wherein the solvent comprises a solvent A and a solvent B, wherein the solvent A is selected from one or more of dichloromethane, chloroform, and carbon tetrachloride, and the solvent B is selected from one or more of N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, and butanone; (2) contacting the liquid phase component with an adsorbent for adsorption to obtain a desorption liquid; wherein the adsorbent includes acidic activated carbon and activated clay; (3) Evaporating the desorption liquid to obtain ABS.

2. The recycling method according to claim 1, wherein: The waste ABS plastic is a waste battery shell; Preferably, the particle size of the waste ABS plastic is 1-100 mm, preferably 10-50 mm.

3. The recovery method according to claim 1 or 2, wherein: The solvent A is dichloromethane, and the solvent B is N-methylpyrrolidone and / or tetrahydrofuran.

4. The recovery method according to any one of claims 1 to 3, wherein: The mass ratio of the solvent A to the solvent B is 1:0.1-2, preferably 1:0.5-1.

5. The recovery method according to any one of claims 1 to 4, wherein: The dissolution operating conditions include: the mass ratio of waste ABS plastic to solvent is 1:1-15, preferably 1:5-10; the dissolution temperature is 20-100°C, preferably 30-70°C; and the dissolution time is 10-150min, preferably 20-100min.

6. The recovery method according to any one of claims 1 to 5, wherein: The method for preparing the acidic activated carbon comprises: placing the activated carbon in an acid treatment liquid for acid treatment to obtain the acidic activated carbon; The acid treatment liquid is selected from one or more of hydrogen peroxide, hydrochloric acid, nitric acid and sulfuric acid, preferably hydrogen peroxide; the acid treatment is carried out at room temperature, and the acid treatment time is 6-48h, preferably 12-36h.

7. The recovery method according to any one of claims 1 to 6, wherein: The mass ratio of the acidic activated carbon to the activated clay is 1:0.1-1.5, preferably 1:0.5-1.

8. The recovery method according to any one of claims 1 to 7, wherein: The adsorption operating conditions include: the mass ratio of liquid phase component to adsorbent is 1:0.5-10, preferably 1:1-8; the adsorption temperature is 25-100°C, preferably 30-50°C; the adsorption time is 10-150min, preferably 20-100min.

9. The recovery method according to any one of claims 1 to 8, wherein: The evaporation is carried out under vacuum, the evaporation temperature is 50-150° C., preferably 60-100° C., and the evaporation time is 10-48 h, preferably 20-30 h.

10. A waste ABS recycling system, characterized in that: The system comprises a dissolving device, an adsorption device and an evaporation device which are connected in sequence; wherein the dissolving device is used to dissolve waste ABS plastic and a solvent to obtain a liquid phase component and a solid phase component; the adsorption device is used to adsorb the liquid phase component and an adsorbent to obtain a desorption liquid; and the evaporation device is used to evaporate the desorption liquid to obtain ABS.

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