JP2003073499A - Method for separating and recovering thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently separating a flame-retardant and a thermoplastic resin from a molding comprising essentially a thermoplastic resin containing a flame-retardant without needing costly equipment. SOLUTION: Dissolving a molding comprising essentially a thermoplastic resin containing a flame-retardant into a first solvent capable of dissolving both the flame-retardant and the thermoplastic resin, adding a second solvent which dissolves the flame-retardant but does not dissolves the thermoplastic resin to the solution, and depositing the thermoplastic resin to be separated and recovered. Here it is preferable from the viewpoint of further reducing the amount of flame-retardant contained in the separated and recovered thermoplastic resin, that the weight ratio of (used amount of the first solvent)/(dissolved amount of the molding) is made >=10, or that the volume ratio (used amount of the second solvent)/(used amount of the first solvent) is made >=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and recovering a thermoplastic resin from a molded product mainly composed of a thermoplastic resin containing a flame retardant.

[0002]

2. Description of the Related Art While the production amount of products made from resins continues to increase year by year, environmental destruction such as global warming and acid rain, environmental pollution such as the generation and scattering of dioxins, and a shortage of garbage incinerators Therefore, reuse of waste has become an important and urgent issue. Under these circumstances, the Specified Household Appliance Recycling Law (Home Appliance Recycling Law) came into effect in April 2001, and household electric appliances such as TVs, washing machines, refrigerators, and air conditioners (hereinafter referred to as "home appliances"). 4 items are required to be recycled.

[0003] Waste recycling methods include thermal recycling by burning and recovering thermal energy, chemical recycling by burning or thermal decomposition to recover valuable materials such as inorganic fillers, oil components, and plastic raw materials, and crushing as they are. Material recycling, which involves remelting and processing into various molded products, is also possible. Among these, material recycling is desired from the viewpoint of preventing environmental pollution and effectively utilizing resources.

[0004] In order to improve flame retardancy, the housing of the household electric appliances including the above-mentioned four household appliances required to be recycled is mixed with a halogen-based flame retardant containing a halogen atom such as bromine or chlorine. A plastic resin is used as the material. Therefore, when these home electric appliances are recycled by the above-mentioned method, there is a problem that an organic halogen compound harmful to a human body is generated in the combustion process and the melting process.
Particularly, in the case of a decabro flame retardant (a specific odor flame retardant), there is a possibility that dioxins may be produced when it is burned or heated, and its use is limited.

Therefore, various methods have been proposed so far for the purpose of removing the flame retardant from the thermoplastic resin. For example, JP-A-6-144801 proposes a method of recovering bromine or antimony as a compound by chemically reacting a decomposition gas generated by thermally decomposing a heat-resistant resin containing bromine or antimony with an alkaline aqueous solution. There is. However, in this method, the component containing halogen or antimony in the decomposed gas is often an organic compound that is difficult to dissolve or dissociate in the aqueous solution, and thus it is difficult to efficiently separate the flame retardant.

Further, Japanese Patent Laid-Open No. 2001-19792 proposes a method in which carbon dioxide gas in a supercritical state is continuously contacted with a flame-retardant resin composition to extract and separate a halogen-based flame retardant. Further, in JP-A-2001-19794, a polystyrene composition containing a flame retardant / antimony compound is dissolved in a solvent, and the flame retardant / antimony compound is precipitated and separated by a centrifuge, and then a resin component is recovered from a residual resin solution. The method of doing is proposed. However, these methods require expensive equipment for processing such as supercritical state and centrifugation. Further, since the processing capacity of these is generally low, there is a problem in that the cost for separating the flame retardant is high in the above method.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and an object thereof is to obtain a flame retardant and a heat-resistant agent from a molded article mainly composed of a thermoplastic resin containing a flame retardant. It is an object of the present invention to provide a method for efficiently separating a plastic resin and an expensive equipment without requiring expensive equipment.

Another object of the present invention is to produce organic halogen compounds and dioxins harmful to the human body,
It is intended to provide a method capable of recovering a thermoplastic resin from a used product and recycling the material.

Another object of the present invention is to provide a molding resin raw material and a molding having high quality, which are produced from the separated and recovered thermoplastic resin.

[0010]

According to the present invention, a molded article mainly composed of a thermoplastic resin containing a flame retardant is dissolved in a first solvent which dissolves both the flame retardant and the thermoplastic resin. After that, a second solvent in which the flame retardant is dissolved but the thermoplastic resin is not dissolved is added to this solution, and the thermoplastic resin is precipitated to separate and collect the thermoplastic resin. Will be provided.

Here, from the viewpoint of further reducing the amount of the flame retardant contained in the separated and recovered thermoplastic resin, (the amount of the first solvent used) / (the amount of the molded product dissolved) is set to 10 or more by weight ratio. Alternatively, it is desirable that the volume ratio of (amount of second solvent used) / (amount of first solvent used) be 1 or more.

From the viewpoint of effective use of resources,
The flame retardant may be further recovered by evaporating the solvent from the solution after the thermoplastic resin is deposited and separated.

Further, according to the present invention, the step of separately collecting from the used product the parts mainly composed of the thermoplastic resin containing the flame retardant, the thermoplastic resin from the separated and collected parts by using the above separation and recovery method. There is provided a method for reusing a thermoplastic resin, which comprises a step of recovering the thermoplastic resin and a step of melting and molding the recovered thermoplastic resin.

Further, according to the present invention, there is provided a molding resin raw material characterized by being produced by melting and molding the thermoplastic resin recovered by the above-mentioned separation and recovery method.

According to the present invention, there is also provided a molded article characterized by being produced by melting and molding the thermoplastic resin recovered by the above-mentioned separation and recovery method.

Here, a recovered thermoplastic resin may be further mixed with an unused thermoplastic resin in accordance with the intended use and required characteristics of the molded product using the separated and recovered thermoplastic resin as a raw material. Good.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention efficiently separate a flame retardant and a thermoplastic resin from a molded article mainly composed of a thermoplastic resin containing a flame retardant without requiring expensive equipment. As a result of earnestly studying whether or not it is possible, the present invention has been accomplished by paying attention to the difference in solubility between the thermoplastic resin and the flame retardant in a solvent. That is, the major feature of the present invention is that
After dissolving in a first solvent that dissolves both the thermoplastic resin and the flame retardant, a second solvent that dissolves the flame retardant but not the thermoplastic resin is added to this solution to precipitate the thermoplastic resin. .

FIG. 1 is a process chart showing an example of the separation and recovery method of the present invention. A solvent C _{1 for} separately collecting and molding a molded product formed of a thermoplastic resin containing a flame retardant from waste products such as home electric appliances and dissolving the flame retardant A and the thermoplastic resin B ₁
This molded body is melted (step 101). Here, it is desirable that the temperature of the solvent C ₁ at the time of dissolution is room temperature. The time required for dissolution varies depending on the composition of the thermoplastic resin, the shape of the molded product, the amount of solvent used, etc., but generally it is possible to shorten the time by heating the solvent.

Then, a solvent C _{2 in} which the flame retardant A is dissolved but the thermoplastic resin B is not added is added to the solution in which the molded body is dissolved (step 102). As a result, the thermoplastic resin B is deposited and precipitated in the solution (step 103). The precipitated thermoplastic resin B is separated from the solution (step 104). As a separation method, a conventionally known solid such as filtration is used.
A liquid separation method may be used. The separated and recovered thermoplastic resin is reused as a raw material for the resin molded body as described later. On the other hand, the solvent is evaporated from the solution after the thermoplastic resin B has been separated and separated (step 105), and the flame retardant A is recovered (step 106).

The thermoplastic resin which can be separated and recovered by the method of the present invention is not particularly limited, and any conventionally known thermoplastic resin can be separated and recovered. Examples thereof include ABS resin, AS resin, polystyrene, polypropylene, polyethylene, polycarbonate, and methacrylic resin.

The flame retardant which can be separated by the method of the present invention is, for example, tetrabromobisphenol A (TBF).
A), halogenated flame retardants such as polybromobiphenyl (PBB), polybromodiphenyl oxide (PBDO), decabromodiphenyl oxide (DBDPO) and octabromodiphenyl oxide (OBDPO).

The first solvent and the second solvent used in the present invention are appropriately determined depending on the types of the thermoplastic resin and the flame retardant which are the main components of the molded product. For example, when the thermoplastic resin is polystyrene, examples of the first solvent (good solvent) include cyclohexane, benzene, toluene, chloroform, tetrahydrofuran (THF), methyl ethyl ketone (MEK), ethyl acetate, limonene, and pinene. Among these, terpene solvents such as limonene and pinene, which are natural organic compounds, are preferable from the viewpoint of environmental safety. Hexane is used as the second solvent (poor solvent),
Examples include ether, acetone, ethanol, methanol and the like.

The amount of the first solvent to be used may be appropriately determined according to the amount of the molded body to be dissolved, but according to the experiments conducted by the present inventors, it is 10 times or more the weight of the molded body to be dissolved. It has been found desirable to use a solvent of This is because if the amount of the first solvent used is less than 10 times the amount of the molded product dissolved, a large amount of the flame retardant may be mixed in the recovered thermoplastic resin. Details of the experiment will be described later (Example 2).

On the other hand, the amount of the second solvent used is preferably the same as or more than the amount of the first solvent used on a volume basis. According to the experimental results of the present inventors, when the amount of the second solvent used is smaller than the amount of the first solvent used, a large amount of the flame retardant may be mixed in the recovered thermoplastic resin. . Details of the experiment will be described later (Example 3).

The molded product used in the present invention is not particularly limited as long as it is mainly composed of a thermoplastic resin containing a flame retardant, and for example, discarded used TVs, washing machines, refrigerators, air conditioners, etc. Examples include the housing of home appliances.

Next, the reuse method of the present invention will be described. FIG. 2 is a process diagram showing an example of the recycling method of the present invention. Hereinafter, a television will be described as an example of a used product. First, used TVs discarded from homes and the like are collected (step 201), disassembled, and separated and collected for each part (step 202). Then, the separated and collected parts are finely crushed (step 203). Next, the flame-retardant-free thermoplastic resin is recovered from the component mainly composed of the flame-retardant-containing thermoplastic resin (for example, a TV housing) by using the separation and recovery method described above (step 204). The collected thermoplastic resin is washed to remove the adhering solvent and foreign substances (step 205). Next, the washed thermoplastic resin is mixed homogeneously (step 20).
6). And it heat-molds (step 207) and it is set as the pellet-shaped resin raw material for molding (step 208). The extruder used here may be a single-screw extruder, a twin-screw extruder or a multi-screw extruder. In order to prevent thermal deterioration of the thermoplastic resin, the heating temperature of the extruder is preferably in the range of the melting temperature (T) to (T + 120 ° C) of the thermoplastic resin. In addition, any of sheet cutting, strand cutting, hot air cutting, underwater cutting, etc. may be used to manufacture the pellets, but the resin raw material can be smoothly supplied in the injection molding of the subsequent process, and it can be used for large-scale processing. Water cutting is particularly preferable. Then, the pelletized resin raw material is put into an injection molding machine to produce a molded body (step 209).

In the recycling method of the present invention, it is not necessary to include all of the steps shown in FIG. 2, and a step of separately collecting from the used product a component mainly composed of a thermoplastic resin containing a flame retardant, It suffices to include at least a step of recovering the thermoplastic resin by using the separation and recovery method described above and a step of melting and molding the recovered thermoplastic resin. In addition, if these essential steps are provided, it goes without saying that steps not shown in FIG. 2 may be added as necessary.

In the process diagram shown in FIG. 2, the recovered thermoplastic resin is melt-kneaded by an extruder to form a pellet-shaped resin raw material for molding, but the form of the resin raw material is not limited to this. Absent. For example, it may be in any form such as a sheet, a film or a pipe, and may be appropriately determined depending on the type of molding machine.

Further, in order to further simplify the recycling process, the recovered thermoplastic resin is put into the molding machine as it is without producing a molding resin raw material such as pellets to directly produce a molded body. Of course it doesn't matter. Further, conventionally known additives such as a heat stabilizer, a light stabilizer, an antistatic agent, a lubricant, a filler, an anticorrosive agent for copper, an antibacterial agent, and a coloring agent are added to the recovered thermoplastic resin to impair the effects of the invention You may add as needed in the range which is not. The step of adding these additives is preferably when the raw materials are put into an extruder or an injection molding machine.

The unused thermoplastic resin may be further mixed with the recovered thermoplastic resin in accordance with the use and the required characteristics of the molded product using the separated and recovered thermoplastic resin as a raw material to form a molded product.

[0031]

The present invention will be further described based on the following examples, but the present invention is not limited to these examples.

Example 1 A television casing molded of polystyrene resin containing a decabromodiphenyl oxide / antimony oxide flame retardant was crushed to a size of about 10 mm, and 50 g of the crushed product was used as the first material.
The solvent was added to 1.1 l of THF (specific gravity 0.88) and dissolved. A second solvent, 2.5 l of ethanol (specific gravity 0.79), was added to this solution to precipitate / precipitate a polystyrene resin in the solution. The precipitated polystyrene resin was separated by filtration, and then molded with a hot press to a thickness of 1 mm. Then, the content of bromine was measured with an energy dispersive X-ray fluorescence analyzer. When the content of the flame retardant was determined from the intensity of Kα ray of bromine, 91% of the flame retardant contained in the housing was removed from the recovered polystyrene.

Example 2 Polystyrene was recovered from a molded product in the same manner as in Example 1 except that the mixing ratio of the crushed product of the TV casing and the first solvent was variously changed, and the polystyrene was contained in the recovered polystyrene. The flame retardant removal rate of the flame retardant was calculated by measuring the flame retardant. The result is shown in Figure 2.
Shown in. In FIG. 2, the vertical axis represents the flame retardant removal rate (%) and the horizontal axis represents the weight ratio of the first solvent and the molded body, and changes in the flame retardant removal rate depending on the weight ratio of the first solvent and the molded body. FIG. As is clear from this figure, when the weight ratio of the first solvent to the molded body exceeds 10, the flame retardant removal rate is dramatically increased to 80% or more.

Example 3 Polystyrene was recovered from a molded article in the same manner as in Example 1 except that the mixing ratio of THF (first solvent) and ethanol (second solvent) was variously changed, and the recovered polystyrene was used. The flame retardant contained in was measured and the removal rate of the flame retardant was calculated. The results are shown in Fig. 3. In FIG. 3, the vertical axis represents the flame retardant removal rate (%), the horizontal axis represents the volume ratio of the first solvent and the second solvent, and the flame retardant removal is performed by the volume ratio of the first solvent and the second solvent. It is a figure showing change of a rate. As is clear from this figure, when the volume ratio of the first solvent and the second solvent exceeds 1, the flame retardant removal rate dramatically increases to 80% or more.

[0035]

According to the separation and recovery method of the present invention, a molded article mainly containing a thermoplastic resin containing a flame retardant is dissolved in a first solvent which dissolves both the flame retardant and the thermoplastic resin,
A second solvent that dissolves the flame retardant but not the thermoplastic resin is added to this solution, and the thermoplastic resin is precipitated and separated and recovered, so that the thermoplastic resin can be efficiently used without requiring expensive equipment. Can be separated.

Further, the ratio of (the amount of the first solvent used) / (the amount of the molded product dissolved) is 10 or more by weight, or (the second amount)
When the volume ratio of (the amount of the solvent used) / (the amount of the first solvent used) is 1 or more, the amount of the flame retardant contained in the separated and recovered thermoplastic resin can be further reduced.

Further, the flame retardant can be further recovered by evaporating the solvent from the solution after the thermoplastic resin is deposited and separated.

In the method for recycling the thermoplastic resin of the present invention,
The step of separating and collecting parts mainly composed of a thermoplastic resin containing a flame retardant from a used product, the step of collecting the thermoplastic resin from the separated and collected parts by using the separation and collection method, and the collected thermoplastic resin Since it has a step of melting and molding, it is possible to material-recycle used products without producing organic halogen compounds and dioxins that are harmful to the human body.

The molding resin raw material and the molded product of the present invention have high quality because they are produced by melting and molding the thermoplastic resin recovered by the above-mentioned separation and recovery method, and are used as various resin parts. it can. Further, when the unused thermoplastic resin is mixed with the thermoplastic resin recovered by the above-mentioned separation and recovery method and used, the characteristics of the molded product can be variously changed and its application can be expanded.

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of a separation and recovery method of the present invention.

FIG. 2 is a process chart showing an example of a recycling method of the present invention.

FIG. 3 is a diagram showing the relationship between (amount of first solvent used) / (amount of molded product dissolved) and the flame retardant removal rate.

FIG. 4 is a diagram showing a relationship between (amount of second solvent used) / (amount of first solvent used) and a flame retardant removal rate.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 9/02 610 B01D 9/02 610Z 625 625C (72) Inventor Tetsuya Kadoma 22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture No.22 F-term in Sharp Corporation (reference) 4F301 AA12 AA15 AA20 AA26 CA04 CA09 CA12 CA14 CA53 CA71

Claims (8)

[Claims] 1. A flame-retardant-dissolving molded article mainly comprising a thermoplastic resin is dissolved in a first solvent that dissolves both the flame-retardant and the thermoplastic resin, and then the flame-retardant is dissolved. A method for separating and recovering a thermoplastic resin, which comprises adding a second solvent in which the thermoplastic resin is insoluble to the solution and precipitating the thermoplastic resin for separation and recovery. 2. The separation and recovery method according to claim 1, wherein (amount of the first solvent used) / (amount of the molded body dissolved) is 10 or more in a weight ratio. 3. The separation and recovery method according to claim 1 or 2, wherein (volume of second solvent) / (volume of first solvent) is 1 or more in volume ratio. 4. The separation and recovery method according to claim 1, wherein the flame retardant is further recovered by evaporating a solvent from the solution after the thermoplastic resin is deposited and separated. 5. A step of separately collecting from a used product a component mainly composed of a thermoplastic resin containing a flame retardant, and the separate collection method according to any one of claims 1 to 4. A method for reusing a thermoplastic resin, comprising: a step of recovering a thermoplastic resin from a part; and a step of melting and molding the recovered thermoplastic resin. 6. A resin raw material for molding, which is produced by melting and molding a thermoplastic resin recovered by the separation and recovery method according to any one of claims 1 to 4. 7. A molded article produced by melting and molding a thermoplastic resin recovered by the separation and recovery method according to any one of claims 1 to 4. 8. The molded article according to claim 7, wherein the thermoplastic resin recovered by the separation and recovery method according to any one of claims 1 to 4 is used as a mixture with an unused thermoplastic resin.