Method for one-step recovery of polystyrene foam plastic by suspension method

Abstract

The invention provides a method for one-step recovery of polystyrene foam plastic by a suspension method. The method comprises the following steps: mixing and dissolving polystyrene and a good solvent to obtain a polystyrene solution; adding a foaming agent into the aqueous solution containing the emulsifier or the dispersant to obtain a mixed solution; adding the polystyrene solution in the step S1 into the mixed solution in the step S2, continuously stirring to form suspension or emulsion, and filtering to obtain the white polystyrene beads. According to the method, processing forming after precipitation is not needed, the suspension is prepared only by adjusting the proportion of all the components, polystyrene can be recycled in one step through dissolution and filtration, dissolution and granulation are completed synchronously, and high economic value is achieved. The particle size of the prepared spherical polystyrene beads is in a range of 0.1-2mm, and the spherical polystyrene beads can be directly used for a foam molding process.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmentally friendly waste plastic recycling, and particularly relates to a method for recycling polystyrene foam plastics by a suspension method in one step. Background Art

[0002] Waste polystyrene (such as foam packaging materials) is a common solid waste, which causes serious pollution to the environment due to its large volume and difficulty in natural degradation.

[0003] The main methods for recycling polystyrene include directly burning to utilize heat energy; dry distillation and cracking to recycle solvents or extract styrene; thermoplastic processing into molding plastics or blending modification; mechanical pulverization and then using as soil improvement materials, filtering materials for underground drainage channels, cement binders, lightweight thermal insulation materials, sound insulation materials, etc.; regenerating into expandable polystyrene. Among them, the added value of regenerating into expandable polystyrene is the highest.

[0004] The methods for regenerating expandable polystyrene include the melting method and the solvent method. The melting method will inevitably deteriorate the quality of polystyrene and has to be used at a lower grade. The solvent method does not require high-temperature heating and can maximize the preservation of its original properties and can even be used as polystyrene foam plastic packaging.

[0005] The solvent method for recycling polystyrene into spherical particles usually requires two steps. For example, the patents with publication numbers CN101502989A and CN101307150A, that is, dissolving and precipitating to make polystyrene solids, and then processing into the required shape, which requires additional heating. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the defects in the prior art and proposes a method for recycling polystyrene foam plastics by a suspension method in one step. By using a good solvent to dissolve polystyrene and combining with an aqueous solution of a dispersant to form a suspension or emulsion, high-purity polystyrene spherical beads are obtained by physical separation means. The recycling process of the present invention is environmentally friendly and does not produce secondary pollution. The formation and stirring steps of the suspension are simple and easy to control, and are suitable for industrial applications. The recycled polystyrene beads have high purity, can be directly used for the production of recycled materials, and the solvent can be recycled.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] In the first aspect, the present invention provides a method for recycling polystyrene foam plastics by a suspension method in one step, including the following steps:

[0009] S1: Mix and dissolve polystyrene with a good solvent to obtain a polystyrene solution;

[0010] S2: Add a foaming agent to an aqueous solution containing an emulsifier or a dispersant to obtain a mixed solution;

[0011] S3: Add the polystyrene solution from step S1 to the mixture from step S2, continuously stir to form a suspension or emulsion, and filter to obtain white polystyrene beads.

[0012] Preferably, the good solvent includes one or a mixture of several of ketone solvents, halogenated hydrocarbon solvents, aromatic hydrocarbon solvents, alcohol solvents, and alkane solvents.

[0013] More preferably, the ketone solvent is selected from acetone or methyl ethyl ketone, the ester solvent is selected from one or several of ethyl acetate, butyl acetate, and isopropyl acetate, the halogenated hydrocarbon solvent is selected from one or several of dichloromethane, dichloroethane, and chloroform, the aromatic hydrocarbon solvent is selected from one or several of benzene, toluene, and xylene, the alcohol solvent is selected from one or two of ethanol and isopropanol, and the alkane solvent is cyclohexane.

[0014] Preferably, the polystyrene content in the polystyrene solution is 0.1 - 1.0 g / mL.

[0015] Preferably, the foaming agent is one or a mixture of several of pentane, hexane, heptane, and petroleum ether.

[0016] Preferably, the dispersant is polyvinyl alcohol.

[0017] Preferably, the emulsifier is sodium dodecyl sulfonate and / or sodium dodecyl sulfate.

[0018] Preferably, the concentration of the aqueous solution containing the emulsifier or dispersant in step S2 is 1 - 30 g / L.

[0019] Preferably, the volume ratio of the polystyrene solution to the aqueous solution containing the emulsifier or dispersant is 1:10 - 1:1.

[0020] Preferably, the stirring speed in step S3 is above 300 rpm.

[0021] In a second aspect, the present invention also provides the white polystyrene beads prepared by the above preparation method, and the particle size of the white polystyrene beads is 0.1 - 2.0 mm.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The method of the present invention does not require post - precipitation processing. By only adjusting the ratio of each component to form a suspension, the dissolution and filtration can be used to recover polystyrene in one step, and the dissolution and granulation are completed simultaneously, achieving high economic value. The prepared polystyrene spherical beads have a particle size in the range of 0.1 - 2.0 mm and can be directly used in the foaming molding process.

[0024] (2) Under the condition of no heating or short-time heating, the method of the present invention can collect spherical polystyrene beads through simple filtration, and these beads can be directly used in the subsequent foaming molding process. Compared with the conventional solvent recovery method, the energy consumption is significantly reduced and the original quality of the material is maintained.

[0025] (3) The method of the present invention is environmentally friendly and hardly generates secondary pollution during the whole recycling process. It is a more efficient, economical and environmentally friendly polystyrene recycling solution. Detailed Embodiments

[0026] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention.

[0027] In this article, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0028] In this article, when a value is described as a range, it should be understood that such disclosure includes the disclosure of all possible sub-ranges within that range, as well as specific numerical values falling within that range, regardless of whether specific numerical values or specific sub-ranges are explicitly indicated.

[0029] In this article, when referring to "multiple", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0030] In this article, when referring to "preferred", "more preferred", they are only used to describe embodiments or examples with better effects, and it should be understood that they do not constitute a limitation on the protection scope of the present invention.

[0031] In this article, when referring to "further", etc., which are used for descriptive purposes, it represents a difference in content, but should not be construed as a limitation on the protection scope of the present invention.

[0032] In this article, the term "and / or" is a description of the association relationship of an object, indicating that three relationships can exist. For example, A and / or B means: A or B, or the three relationships of A and B.

[0033] In this article, the term "about" means + / - 10% of the specified value, preferably + / - 5%, more preferably + / - 1%.

[0034] In this article, the terms "comprising", "including", "having", "containing", etc. are all open-ended terms, that is, they are intended to include but not limited to.

[0035] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention.

[0036] The present invention will be described in detail below in conjunction with embodiments.

[0037] Example 1

[0038] (1) Use thermoplastic polystyrene waste recycled material as raw material, cut it into blocks with a diameter of less than 20 cm, and put it into a container filled with dichloromethane. The amount of dichloromethane is 100 mL, and the weight of the polystyrene recycled material is 30 g. Stir for about 15 min without heating.

[0039] (2) Dissolve 0.5 g of polyvinyl alcohol with a degree of alcoholysis of 54 - 56 mol% in 200 mL of deionized water, then add 2 g of foaming agent n-pentane, and stir for 10 minutes to form a uniformly suspended dispersant solution.

[0040] (3) Drop the polystyrene solution into the dispersant solution and continuously stir for 3 hours to ensure uniform distribution of the particles.

[0041] (4) Use a filtration separation device to separate the suspension to obtain white polystyrene beads with an average diameter of 0.1 mm, and dry them for later use.

[0042] Example 2

[0043] (1) Use thermoplastic polystyrene waste recycled material as raw material, simply crush it and put it into a container filled with dichloromethane and toluene. The amounts of dichloromethane and toluene are each 12.5 mL, and the weight of the polystyrene recycled material is 15 g. Let it stand for 15 min.

[0044] (2) Dissolve 1 g of polyvinyl alcohol with a degree of alcoholysis of 80 mol% in 250 mL of water, then add 0.2 g of foaming agent hexane, and stir for 5 minutes to form a uniformly dispersed dispersant solution.

[0045] (3) Drop the polystyrene solution into the dispersant solution and continuously stir for 3 hours to form a suspension.

[0046] (4) Use a filtration separation device to separate the suspension to obtain white polystyrene beads with an average diameter of 0.1 mm, and dry them for later use.

[0047] Example 3

[0048] (1) Use thermoplastic polystyrene waste recycled material as raw material. After simple crushing, put it into a container filled with acetone. The amount of acetone is 50 mL, and the weight of the polystyrene recycled material is 5 g. Stir for 30 min.

[0049] (2) Dissolve 0.5 g of polyvinyl alcohol with a degree of alcoholysis of 80 mol% in 400 mL of water, then add 1 g of foaming agent n - hexane, and stir for 15 minutes to form a uniform dispersant solution.

[0050] (3) Drop the polystyrene solution into the dispersant solution, heat to 60 °C, and continuously stir for 50 minutes to form a suspension.

[0051] (4) Use a filtration separation device to separate the suspension to obtain white polystyrene beads with an average diameter of 1.2 mm, and air - dry them for later use.

[0052] Example 4

[0053] (1) Use thermoplastic polystyrene waste recycled material as raw material. After simple crushing, put it into a container filled with ethyl acetate. The amount of ethyl acetate is 50 mL, and the weight of the polystyrene recycled material is 5 g. Let it stand for 15 min.

[0054] (2) Dissolve 1 g of polyvinyl alcohol with a degree of alcoholysis of 72 mol% in 400 mL of water, then add 1 g of foaming agent petroleum ether, and stir for 15 minutes to form a uniform dispersant solution.

[0055] (3) Drop the polystyrene solution into the dispersant solution, heat to 90 °C, and continuously stir for 60 minutes to form a suspension.

[0056] (4) Use a filtration separation device to separate the suspension to obtain white polystyrene beads with an average diameter of 1.2 mm, and air - dry them for later use.

[0057] Example 5

[0058] (1) Use thermoplastic polystyrene waste recycled material as raw material. After simple crushing, put it into a container filled with cyclohexane. The amount of cyclohexane is 50 mL, and the weight of the polystyrene recycled material is 10 g. Heat to 60 °C and stir for 30 min.

[0059] (2) Dissolve 12 g of polyvinyl alcohol with a degree of alcoholysis of 80 mol% in 400 mL of water, then add 1 g of foaming agent heptane, and stir for 15 minutes to form a uniform dispersant solution.

[0060] (3) Drop the polystyrene solution into the dispersant solution, heat to 90 °C, and continuously stir at high speed for 60 minutes to form a suspension.

[0061] (4) Use a filtration separation device to separate the suspension, obtaining white polystyrene beads with an average diameter of 1.5 mm, and air-dry them for later use.

[0062] Example 6

[0063] (1) Use recycled waste thermoplastic polystyrene as raw material. After simple crushing, put it into a container filled with 50 mL of dichloroethane. The weight of the polystyrene recycled material is 10 g, and let it stand for 15 min.

[0064] (2) Dissolve 1 g of polyvinyl alcohol with an alcoholysis degree of 80 mol% in 400 mL of water, then add 1 g of foaming agent heptane, and stir for 15 minutes to form a uniform dispersant solution.

[0065] (3) Drop the polystyrene solution into the dispersant solution, heat it to 90 °C, and continuously stir for 60 minutes to form a suspension.

[0066] (4) Use a filtration separation device to separate the suspension, obtaining white polystyrene beads with an average diameter of 1.0 mm, and air-dry them for later use.

[0067] Example 7

[0068] (1) Use polystyrene waste recycled from a waste recycling station as raw material. After simple crushing, put it into a container filled with 25 mL of dichloromethane. The weight of the polystyrene recycled material is 5 g. After filtration, let it stand for 10 min.

[0069] (2) Dissolve 1 g of sodium dodecyl sulfate in 200 mL of water, then add 0.5 g of foaming agent n-pentane, and stir for 15 minutes to form a uniform emulsifier solution.

[0070] (3) Drop the polystyrene solution into the emulsifier solution, heat it to 35 °C, and continuously stir for 60 minutes to form a suspension.

[0071] (4) Use a filtration separation device to separate the suspension, obtaining white polystyrene beads with an average diameter of 2.0 mm, and air-dry them for later use.

[0072] Example 8

[0073] (1) Use polystyrene waste recycled from a waste recycling station as raw material. After simple crushing, put it into a container filled with 25 mL of dichloromethane. The weight of the polystyrene recycled material is 2.5 g. After filtration, let it stand for 10 min.

[0074] (2) Dissolve 0.2 g of sodium dodecyl sulfate in 200 mL of water, then add 0.5 g of foaming agent n-pentane, and stir for 15 minutes to form a uniform emulsifier solution.

[0075] (3) Drop the polystyrene solution into the emulsifier solution and stir at high speed for 90 minutes to form a suspension.

[0076] (4) Separate the suspension using a filtration separation device to obtain white polystyrene beads with an average diameter of 0.1 mm, and air-dry them for later use.

[0077] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for one-step recycling of polystyrene foam by suspension method, characterized in that: It includes the following steps: S1: Mix and dissolve polystyrene with a good solvent to obtain a polystyrene solution; S2: Add a foaming agent to an aqueous solution containing an emulsifier or a dispersant to obtain a mixture; S3: Add the polystyrene solution in step S1 to the mixture in step S2, continuously stir to form a suspension or an emulsion, and filter to obtain white polystyrene beads.

2. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The good solvent includes one or a mixture of several of ketone solvents, ester solvents, halogenated hydrocarbon solvents, aromatic hydrocarbon solvents, and alkane solvents.

3. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The ketone solvent is selected from acetone or methyl ethyl ketone, the ester solvent is selected from one or several of ethyl acetate, butyl acetate, and isopropyl acetate, the halogenated hydrocarbon solvent is selected from one or several of dichloromethane, dichloroethane, and chloroform, the aromatic hydrocarbon solvent is selected from one or several of benzene, toluene, and xylene, and the alkane solvent is cyclohexane.

4. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The polystyrene content in the polystyrene solution is 0.1 - 1.0 g / mL.

5. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The foaming agent is one or a mixture of several of pentane, hexane, heptane, and petroleum ether.

6. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The dispersant is polyvinyl alcohol.

7. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The emulsifier is sodium dodecyl sulfonate and / or sodium lauryl sulfate.

8. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: In step S2, the concentration of the aqueous solution containing an emulsifier or a dispersant is 1 - 30 g / L.

9. The method for one-step recycling of polystyrene foam by suspension method according to claim 1, characterized in that: The volume ratio of the polystyrene solution to the aqueous solution containing an emulsifier or a dispersant is 1:10 - 1:

1.

10. The white polystyrene beads prepared by the method for recycling polystyrene foam plastics in one step by suspension method according to any one of claims 1-9, characterized in that: The particle size of the white polystyrene beads is 0.1 - 2 mm.