JP2003313358A - Resolvent of polystyrene foam and treatment method of polystyrene foam using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safer resolvent of polystyrene foam (hereinafter, abbreviated to EPS) excellent in solubility (volume reducibility and contractibility) of EPS, a method for treating EPS efficiently at a lower cost using a method which does not cause the environmental pollution followed by recovering PS, and a method for recycling and reuse of PS obtained by treatment of EPS. <P>SOLUTION: The resolvent of the polystyrene foam comprises N,N-dimethyl formamide and/or N,N-dimethyl acetamide. A dissolving method of the polystyrene foam makes EPS contact with the resolvent. The recovering method and the recycling method of PS are also provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dissolving and recovering expanded polystyrene (hereinafter abbreviated as EPS), which is widely used as packing materials, and polystyrene (hereinafter referred to as "polystyrene").
Abbreviated as PS. ) Concerning the recycling method.

[0002]

2. Description of the Related Art EPS is lightweight, easy to mold,
In addition, since it has good heat insulation properties, it is widely used in industry, general households, etc. as a packaging material for containers for transportation, shock absorbing materials during transportation, heat insulating materials, etc. After use, industrial waste of EPS is generated.

However, the used EPS is reused only for a part, and most of the EPS has a large volume and is disposed of by incineration as industrial waste, but the EPS has a large volume. In addition, it has problems such as poor degradability in soil and generation of high heat and toxic gas when incinerated.

Recently, the EPS after use has been recycled, and it is returned to the industrial waste contractor and the EPS maker side. For example, limonene (Japanese Patent Laid-Open No. 5-263065, Japanese Patent Laid-Open No. 6-63065).
No. 298992, JP-A-8-134254, etc.) and an EPS solvent such as toluene (JP-A-8-85734, JP-A-8-253621, etc.) to facilitate disposal. Development of PS recovery system is progressing. However, since the commonly used EPS shrinking agent and dissolving agent are non-aqueous solvents, there is a risk in EPS processing, and a special system is required for separating EPS and solvent and recovering PS. . On the other hand, the recovered solvent also requires special treatment such as recovery (purification) and combustion disposal in the end.

Limonene, which is often used as the EPS shrinkage agent, can reduce the volume of EPS, but is expensive and requires a special recovery process because it is a non-aqueous solvent. Toluene can dissolve EPS, but it is difficult to collect PS, and since it is also a non-aqueous solvent, the standards for wastewater treatment are strict, and special recovery treatment is required. It wasn't good enough.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and the object of the present invention is to provide an EPS.
EPS with excellent solubility (volume reduction and shrinkage)
Is to provide a solubilizer. Another object of the present invention is to
E efficiently and at low cost without causing environmental pollution
It is an object of the present invention to provide a method for treating PS and recovering PS. Still another object of the present invention is to provide a method for recycling and reusing PS obtained by treating EPS.

[0007]

In order to solve the above problems, the present invention has the following constitution. (1) N, N-dimethylformamide (hereinafter abbreviated as DMF) and / or N, N-dimethylacetamide (hereinafter,
It is abbreviated as DMA. EP) characterized by containing
S solubilizer. (2) A method for dissolving EPS, which comprises contacting EPS with a solubilizer containing DMF and / or DMA. (3) E containing EPS, DMF and / or DMA
A method for recovering PS, which comprises contacting with and dissolving a PS solubilizer, and then separating PS and the EPS solubilizer from the obtained PS solution. (4) A method of producing granular PS by dropping the PS solution obtained by the present invention into water. (5) A method in which the PS solution obtained by the present invention is brought into contact with water to prepare a thread-shaped, plate-shaped, or rod-shaped PS. (6) A method for producing a PS film, which comprises applying the PS solution obtained by claim 2 to the surface of an object and then removing the EPS dissolving agent.

[0008] That is, the inventors of the present application have conducted intensive studies to achieve the above-mentioned object, and as a result, DMF and DMA are excellent as EPS solubilizers, and DMF and DMA are water-soluble and also treat waste water. It has been found that an effective EPS dissolution and treatment method which solves the above-mentioned problems can be obtained by using these as an EPS dissolution agent because they are simple and have completed the present invention.

The EPS dissolving agent according to the present invention may be any one containing DMF and / or DMA (hereinafter sometimes abbreviated as the EPS dissolving agent of the present invention), and its purity is also particularly high. There is no need at all. Also, DMF and DM
When the mixed solubilizer of A is used, the mixing ratio is not particularly limited.

Further, the EPS dissolving agent of the present invention is, for example, acetone, acetonitrile, methanol, ethanol, 1-
It may contain other solvents such as propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol. For example, when acetone is mixed, the mixing ratio is preferably about 0 to 75 v / v% of the volume of DMF and / or DMA.

When other solvents are mixed, the mixing ratio is 0 to 50 v / d of the volume of DMF and / or DMA.
It is preferably about v%, preferably about 0 to 40 v / v%. When the mixing ratio of other solvents is 40v / v% or higher (less than about 75v / v%), EPS is not completely dissolved but its volume is reduced to about 1/20 of the original volume. When it becomes about 75 v / v% or more, EPS can be dissolved using the mixed solvent.
It is also difficult to reduce the volume. However, in the case of a mixed solvent of DMF and / or DMA and 1-butanol, 1-
Even when the concentration of butanol is about 75 v / v%, the property of reducing the volume of EPS can be seen.

[0012] It should be noted that DMF and / or DMA which has the property of not completely dissolving EPS but reducing its volume.
And a mixed solvent of other solvent as described above is used, E
PS having a reduced volume of PS can be easily recovered, and the mixed solvent can also be recovered and reused, which is one of the preferable modes for recycling EPS.

The method for dissolving EPS according to the present invention is
May be contacted with the EPS dissolving agent of the present invention. The method is not particularly limited, but specifically, for example, E of the present invention is used.
An appropriate amount of EPS may be placed in the container containing the PS dissolving agent.

Although the EPS dissolves naturally in the EPS dissolving agent of the present invention even if it is left as it is, the dissolution rate becomes slower as the dissolution progresses, so the EPS should be lightly pressed from above.
It may be dissolved by kneading. It is more preferable to add EPS while stirring the EPS dissolving agent of the present invention. Furthermore, it is preferable that the EPS is cut into a small size or finely crushed before being brought into contact with the EPS dissolving agent of the present invention.

The EPS may be dissolved in the container as it is, or may be cut into a small size or finely crushed, and the EPS dissolving agent of the present invention may be added as it is or by spraying.

When the EPS dissolving agent of the present invention is brought into contact with EPS, the amount of EPS to be treated from the beginning is the EP of the present invention.
The S solubilizer may be contacted, or a certain amount of EPS may be first contacted with the EPS solubilizer of the present invention to be dissolved, and then EPS may be added in a stepwise manner.
S may be brought into contact with the EPS dissolving agent of the present invention.

Since DMF and DMA are volatile,
The above operation and the storage of the solution in which EPS is dissolved (PS solution) are more preferably performed under sealed conditions.

According to the above method, the EPS is used as the EP of the present invention.
A PS solution dissolved in the S-solvent is obtained. Although it depends on the specific gravity of EPS, the volume of EPS is reduced to about 1/2 to 1/60 of the volume before treatment, and to 1/2 to 1/100 in the case of EPS of low specific gravity. . Since the PS solution increases in viscosity as the PS concentration increases and contains bubbles, it is not always completely transparent.

From the PS solution obtained by the present invention, P
As a method for separating S from the EPS dissolving agent of the present invention,
A method of bringing the PS solution into contact with water, a method of subjecting the PS solution to a dry treatment as it is, and a method of contacting the PS solution with a solvent that weakens the EPS dissolving power of the EPS solution of the present invention used in the solution. Etc.

In the above method, in order to bring the PS solution into contact with water, for example, if the PS solution is put into water, P
A solid substance of S (which still contains a solvent such as DMF or DMA; hereinafter abbreviated as PS intermediate) is obtained. Also, contrary to the above method, a PS intermediate can be obtained by a method of adding water to the PS solution. In addition, when contacting with water, the water may be stationary or under stirring, but it is generated.
In order to prevent the PS intermediates from sticking to each other and overlapping with each other, it is preferable to carry out the stirring at an appropriate speed.

Next, water is stirred, so that E in the PS intermediate is
The PS solubilizer can be transferred to the aqueous phase. After that, it is optional to change the water several times and further carry out the stirring process.

The water used in the above operation does not need to be of high purity and may be tap water, but distilled water or deionized water may be used without problems.

Finally, the PS solid matter is taken out of the water tank,
When dried by natural drying, air drying, heat drying (room temperature to about 130 ° C), etc., P containing no solvent such as DMF and DMA
S solid matter can be recovered. Here, EP
S becomes a PS solid substance whose volume is reduced to about 1/2 to 1/100 before the treatment.

The PS solids from which the EPS dissolving agent is removed can also be obtained by the above method, that is, a method in which the PS dissolving solution is directly dried without contact with water.

Used in carrying out the above method,
As the solvent for weakening the dissolving power of the EPS dissolving agent of the present invention,
Acetone, cetonitrile, methanol, ethanol, 1-
Examples of the solvent include water-soluble solvents such as propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol, or mixed solvents thereof, with acetonitrile, methanol or ethanol being particularly preferable. Further, the mixing ratio of these may be any ratio as long as PS is precipitated from the PS solution.

The PS solution was used for the solution,
In order to precipitate PS from the PS solution by mixing a solvent that weakens the EPS dissolving power of the EPS dissolving agent of the present invention, the PS solution and the solvent may be mixed. The order of mixing these may be either addition of a solvent to PS dissolution or addition of a PS solution to the solvent. Also, adding the other while stirring the PS solution or solvent is optional.

Since the PS intermediate is precipitated in the PS solution by the above operation, the precipitated PS intermediate is collected,
The EPS dissolving agent of the present invention may be removed from the PS intermediate by the above-mentioned method of contacting with water, or the PS solid may be recovered by washing with water and then drying by the above-mentioned method. Good.

To prepare the granular PS solid matter according to the present invention, the PS solution may be dropped into water by an appropriate means such as using a thin tube. The size of the grain is P
By appropriately adjusting the concentration of the S solution, the diameter and shape of the thin tube, the dropping rate of the PS solution, the dropping amount, etc., the desired size can be obtained.

Further, a method of appropriately selecting the diameter of the injection pipe for pouring the PS solution into water and injecting it into a thread form from a thin pipe, and further changing the diameter or shape of the injection pipe appropriately, continuously or Intermittently inject the PS solution into the aqueous phase through the injection tube,
By separating the EPS dissolving agent of the present invention, PS solids having various shapes and sizes such as thin strips, sticks, lumps, and rods can be produced.

In the method for producing a PS film on the surface of an object according to the present invention, as a method for applying the PS solution on the surface of the object, for example, a brush or the like is used to apply PS to the surface of the object. PS using the method of applying the solution or the atomizer
There are a method of spraying the solution on the surface of the object and a method of immersing the object in the PS solution.

For example, the method of immersing the target product in the PS solution will be described as an example. First, the target product for forming a film, such as a glass tube, is immersed in the PS solution and then taken out. Then, the PS solution is adhered around the object to form a thin film. Then, when this is gently immersed in water, the color of the film becomes white. After being immersed in water for a while, the EPS dissolving agent of the present invention is transferred to the aqueous phase (that is, after the EPS dissolving agent of the present invention is removed), and then dried to form PS around the target substance. A film can be prepared. At this stage, the film obtained is opaque. When performing this operation, stirring the water, replacing the water, or the like is optional for the time for immersing the target product in the water. In addition, in this operation, even after the PS film is formed on the outer surface of the target object and dried as it is without being immersed in water, the EPS dissolving agent of the present invention is removed and the PS film is formed. Can be made.

The drying temperature is preferably room temperature to 130 ° C.
A transparent film is obtained by heating at about 130 ° C. 1
If the temperature is higher than 30 ° C, PS is melted, which is not preferable.

By the above operation, it is possible to easily secure a simple test tube having a PS film, which has a light-shielding property and a heat insulating property. A PS film of various shapes and thicknesses can be obtained by appropriately adjusting the shape of the target product, the time for immersing the target product in the PS solution, the time for drawing the target product from the PS solution, and the concentration of the PS solution. Can be formed.

The concentration of the PS solution used for producing each PS solid is not particularly limited, but considering the ease of molding, in order to obtain a granular PS solid,
EPS of the present invention so that the EPS becomes about 5 to 50 w / v%
Those dissolved in a dissolving agent are preferred.

For example, in order to obtain a filamentous PS solid, the E of the present invention is adjusted so that the EPS is about 30 to 80 w / v%.
Those dissolved in PS solubilizer are preferred.

For example, in order to obtain a plate-shaped or rod-shaped PS solid, it is preferable that EPS is dissolved in the EPS dissolving agent of the present invention so as to be about 30 to 80 w / v%.

When the PS solution is prepared using a widely used EPS (general-purpose EPS) having a specific gravity of about 0.015, the following method may be used.

For example, a PS solution for obtaining a granular or thread-like PS solid is 1/10 to 1 volume of general-purpose EPS.
It may be obtained by dissolving in an EPS solubilizer of the present invention of about / 20 volume.

The PS solution used to obtain a plate-shaped or rod-shaped PS solid is about 1/20 to 1/60 volume, preferably 1/20 to 1 / volume for 1 volume of general-purpose EPS. 40
It may be dissolved in a volume of the EPS dissolving agent of the present invention to obtain a paste-like or gum-like PS solution.

The concentration of the PS solution used for forming the PS film in the present invention is not particularly limited.

It is also possible to obtain a PS solid matter by dissolving a general-purpose EPS in 1/1 to 2/5 volume of the EPS dissolving agent of the present invention with respect to 1 volume of EPS and then contacting it with water. it can. In this case, at the moment of contact with water, PS disperses and spreads on the cloudy thin film.

On the other hand, a general-purpose EPS is dissolved in a small amount of the EPS dissolving agent of the present invention up to about 1/40 volume to about 1/60 volume with respect to 1 volume of EPS, and then contacted with water. A method for obtaining a PS solid material is also possible. In the PS solid thus obtained, the solubilizer is encapsulated (PS intermediate). By doing so, the volume of EPS is 1/40 to 1/60. And can be made smaller. In order to remove the EPS dissolving agent of the present invention from the PS intermediate thus obtained, for example, PS
The intermediate may be further contacted with water, the PS intermediate may be subjected to a dry treatment as it is, the PS intermediate may be contacted with a solvent that weakens the dissolving power of the dissolving agent used in the solution. Alternatively, the PS solution obtained by the above method may be brought into contact with a solvent that weakens the dissolving power of the solubilizer instead of water, and the PS intermediate obtained may be subjected to a drying treatment.

Since all the solvents used in the present invention are water-soluble solvents, the water containing the solvent generated during the process of the present invention can be decomposed by a biological activated sludge method in a factory wastewater treatment facility. Good. In addition, DMF, DMA, and the solvents that weaken the PS dissolving power of these are water-soluble, so if they meet the requirements of chemical oxygen demand (COD value), they may be discarded as they are through a factory wastewater treatment facility. The COD value may be diluted so as to be equal to or less than the required value and then discarded.
That is, since the conventional EPS condensing agent or EPS dissolving agent uses a solvent insoluble in water, the treatment after use is troublesome, but since the EPS dissolving agent of the present invention is water-soluble, it cannot be used after use. Thus, the treatment of is also extremely simple as compared with the conventional method.

According to the present invention, EPS can be recycled for various purposes, for example:

(1) A test tube, a beaker, a volumetric flask or the like having a complicated shape can be used to form a film having a heat insulating effect. Also, PS molded products such as a test tube type, a beaker type, and a volumetric flask type can be obtained by the method of forming a film. (2) A cushioning material having an arbitrary size can be manufactured. (3) By using the method of extruding the PS solution through the pores, various shapes insoluble in water can be prepared. (4) By adding a dye in advance to the PS solution, a molded product of any desired color and shape can be obtained. (5) By adding an additive such as a strength enhancer to the PS solution, for example, a film having high strength and difficult to peel off,
A target functional product can be manufactured. (6) If the EPS dissolving agent of the present invention or a component easily soluble in water is added to the PS dissolving liquid, the added component is transferred to the EPS dissolving agent-water phase in the production process of PS solids. , P
Since it escapes from the S intermediate, a PS film having pores can be produced.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0047]

EXAMPLES In the following examples, expanded polystyrene (EPS) rectangular parallelepiped has a volume of 2.5 × 2.67 × 15 cm.
= 100 cm ³ , weight 1.5 g, specific gravity 0.015 means a rectangular EPS. Moreover, a series of operations were all performed at room temperature.

Example 1. Dissolution of EPS 1 (1) N, N-dimethylformamide (DM) in a 100 ml beaker of 1/10 volume PS solution
F, Wako Pure Chemical Industries, Ltd., for chemistry) 10ml, EP
One S rectangular parallelepiped was lightly pushed in from above and dissolved. EP
S was easily soluble in DMF and could be completely dissolved (colloidal form). The obtained polystyrene (PS)
The volume of the solution was about 10 ml. This gives a volume of 1
This means that the EPS can be made into a PS solution having a volume of about 1/10.

(2) 1/8 volume of PS solution The 1/10 volume of PS solution obtained in (1) was left for 30 minutes, and then a new EPS rectangular parallelepiped was lightly weighted as in (1). Pressed down and dissolved. EPS dissolved relatively easily.
The volume of the PS solution obtained was about 11 ml.
As a result, EPS with a volume of 1 could be made into a PS solution with a volume of about 1/18.

(3) 1/25 volume PS solution 1/18 volume PS solution obtained in (2) was stored for 1 hour, and then a new EPS rectangular parallelepiped was used in the same manner as (1). It was lightly pressed into and dissolved with stirring with a glass rod. Although the solubility was a little poor, it dissolved relatively easily. The volume of the PS solution obtained was about 12 ml. As a result, 1 volume of EPS could be made into PS solution of about 1/25 volume.

(4) 1/33 volume of PS solution The 1/25 volume of PS solution obtained in (3) was stored for 1 hour, and then a new EPS rectangular parallelepiped was used as in (1). It was lightly pressed into and dissolved with stirring with a glass rod. Although the solubility was a little poor, it dissolved relatively easily. The volume of the PS solution obtained was about 12 ml. As a result, the EPS having a volume of 1 could be made into a PS solution having a volume of about 1/33.

(5) 1/38 volume of PS solution The 1/33 volume of PS solution obtained in (4) was stored for 1 hour, and then a new EPS rectangular parallelepiped was used as in (1). It was lightly pressed into and dissolved with stirring with a glass rod. Solubility slightly deteriorated. The volume of the PS solution obtained was 1
It was about 3 ml. This will reduce the volume of EPS to about 1
This means that we were able to make a PS solution of / 38 volume.

In the first embodiment, instead of DMF, N,
N-dimethylformamide (DMA, Wako Pure Chemical Industries, Ltd.
The same result was obtained by using (for manufacturing, chemical). That is, EPS is easily soluble in DMA, and is about 1/10 volume, about 1/18 volume, about 1/25 volume, about 1/33 volume and about 1/38 volume.
A volume of PS solution could be obtained.

Example 2. Preparation of PS solids Put 5 ml of DMF in a 100 ml beaker and dissolve it in the beaker while pushing lightly into one EPS rectangular parallelepiped.
A solution was obtained. Then 200 ml of the PS solution obtained
Pour into 100 ml of water with stirring in a beaker. Injection is carried out intermittently in small amounts, and the PS intermediate (PS
A solid containing an EPS dissolving agent, here DMF.
same as below. ) Was generated. After stirring for 10 minutes,
The water was discarded, the PS intermediate was lightly crushed with a spatula, 100 ml of fresh water was added, and the mixture was further stirred for 10 minutes. This operation was repeated 3 times to wash with water to transfer the DMF in the PS intermediate into the aqueous phase. Obtained PS solid (PS
A solid substance that does not contain an EPS dissolving agent. ) Was removed from the beaker, the surface was washed with water on a Nutsche, filtered, and then naturally dried to obtain a PS solid. The volume of the obtained PS solid is about 5 to 6 v / v% of the volume of EPS before treatment.
Was reduced to.

In the second embodiment, D is used instead of DMF.
Similar results were obtained with MA. That is, EPS
Was readily soluble in DMA, and the volume of the obtained PS solid was reduced to about 5 to 6 v / v% of the volume of EPS before treatment.

Example 3. Preparation of filamentous PS solids Put 5 ml of DMF in a 100 ml beaker and dissolve it in the beaker while pressing one EPS rectangular parallelepiped lightly.
A solution was obtained. The PS solution thus obtained was put into an injection cylinder, and after the needle was attached, it was extruded into water through a needle through 100 ml of water that was stirred in a 200 ml beaker to form a filamentous PS intermediate. After stirring for 10 minutes, the water was discarded, 100 ml of fresh water was added, and the mixture was stirred for another 10 minutes. This operation was repeated 3 times to wash with water to transfer the DMF in the PS intermediate into the aqueous phase. The obtained filamentous PS solid was taken out of the beaker, the surface was washed with water on a nutche, filtered, and then naturally dried to obtain a filamentous PS solid.

In the third embodiment, D is used instead of DMF.
A filamentous PS solid was similarly obtained using MA.

Example 4. Preparation of granular PS solids An EPS rectangular parallelepiped with a rectangular parallelepiped of 2.5 × 2.67 × 1.5 cm 1
Cut into 0 pieces. Put these 10 pieces together in a 200 ml beaker, sprinkle 5 ml of DMF from above with a measuring pipette, stir and mix with a stainless steel spatula,
It melt | dissolved and the PS solution was obtained. 5 ml of the obtained PS solution
Using a volumetric pipette, drop into 100 ml of water with stirring in a 200 ml beaker to form a granular PS intermediate. After stirring for 10 minutes, the water was discarded, 100 ml of fresh water was added, and the mixture was stirred for another 10 minutes. This operation was repeated 3 times to wash with water to transfer the DMF in the PS intermediate into the aqueous phase. The obtained PS solid was taken out of the beaker, the surface was washed with water on a Nutsche, filtered, and then naturally dried to obtain a granular PS solid. The volume of the obtained PS solid is about 5 to 6 v / v% of the volume of EPS before treatment.
Was reduced to.

In the fourth embodiment, D is used instead of DMF.
Similar results were obtained with MA. That is, EPS
Was readily soluble in DMA and the volume of the resulting granular PS solids was reduced to about 5-6 v / v% of the volume of EPS before treatment.

Example 5. Preparation of PS solid material In the same manner as in Example 1, EPS 4.5 g (300 cm ³ )
Is dissolved in 20 ml of DMF, and it is about 1/1 of the original EPS volume.
A PS solution of 5 was prepared. Separately, prepare 9 50 ml beakers, and use water-soluble solvents such as acetone, methanol,
50 ml each of ethanol, 1-propanol, 2-propanol, acetonitrile, 1-butanol, 2-butanol, and t-butanol was dispensed into each of 9 beakers. While stirring the beaker containing the solvent with a stirrer, 3 ml of the obtained polystyrene solution was added dropwise from above using a 5 ml pipette to insolubilize the polystyrene with each of 9 solvents to obtain a PS intermediate. . Each solid was taken out, washed with water, and then dried by heating to obtain a PS solid. The volume of the obtained PS solid is about 5 to 6 v / v% of the volume of EPS before treatment.
Was reduced to.

Example 6. Preparation of PS coating 25 ml of DMF was placed in a 50 ml beaker, 5 EPS rectangular parallelepipeds were added in sequence and dissolved in the same manner as in Example 1. A glass test tube (inner diameter 10 mm, outer diameter 13 m) was added to the obtained PS solution.
m, length 13 cm) was immersed for about 5 cm, immediately taken out and immersed in water. Immediately, the film became a white opaque film. After dipping in water for a while to transfer DMF to an aqueous phase, the test tube was taken out and naturally dried.

In the sixth embodiment, D is used instead of DMF.
Similar results were obtained with MA. That is, EPS
The same operation was performed by using DMA as a dissolving agent of the above, and a white opaque film could be formed on the outer surface of the glass test tube.

Example 7. A mixed solvent was prepared by mixing EPS dissolved DMA using a mixed solvent with various solvents such that the concentration was 75, 50, 40, 30, 25 v / v% with respect to DMA. EPS 0.1 g (1 x 1 x 6.6 c in a 100 ml beaker)
m, specific gravity 0.015) and 1 ml of the mixed solvent prepared above were mixed and dissolved. The results are shown in Table 1 below.

[0064]

[Table 1]

◯: Completely dissolved Δ: Not dissolved in mixed solvent, EPS volume contracted to 0.3 cm ³ ×: Insoluble As is clear from Table 1, it was found that the mixed solvent of DMA and acetone can dissolve EPS. It was When a mixed solvent of DMA and acetonitrile is used, EPS does not dissolve at a concentration of acetonitrile of 40 to 75 v / v%, and about 1/20.
Volume reduced to ~ 1/22. Also, a mixed solvent of DMA and methanol (methanol concentration 40 to 50 v / v%), DMA
And ethanol mixed solvent (ethanol concentration 50v / v%),
Mixed solvent of DMA and 1-butanol (1-butanol concentration
Similar results were obtained when 75 v / v%) was used. On the other hand, when the concentration of the solvent mixed with DMA is decreased, the EP
It was found that S became soluble.

Next, 1 ml of each PS solution obtained in Table 1 above when the solubility is ◯ was sampled with a whole pipette and
When dropped into 80 ml of water which was stirred in a 00 ml beaker, it became granular regardless of which PS solution was dissolved in any mixed solvent, and granular polystyrene could be recovered.

[0067]

INDUSTRIAL APPLICABILITY The EPS dissolving agent of the present invention is a high molecular weight organic compound, even though it is a water-soluble solvent.
Can be dissolved and the volume of EPS can be reduced very effectively. Further, any solvent that weakens the dissolving power of the EPS dissolving agent of the present invention is a water-soluble solvent and is excellent in handling and safety. For example, the used water can be decomposed by a factory wastewater treatment facility or a biological activated sludge method. Also, the water after use may be further diluted with water so that the COD value becomes less than the required value and then discarded.
The method can be easily carried out by a factory or a general consumer who desires to process a small amount of expanded polystyrene.

Since the EPS dissolving agent of the present invention and the solvent that weakens the dissolving power of the EPS dissolving agent are water-soluble solvents,
If the PS solution is treated with water or dried, PS can be easily recovered, and it can be expected to install a safe and low-cost PS recovery system.

Further, the PS solid thus obtained can be reused as a raw material for a foamed or non-foamed molded product or as a raw material for miscellaneous products, volatile oil, tar and the like.

The PS solution obtained by the present invention can be supplied to an industrial waste supplier or a PS or EPS maker for recycling.

According to the present invention, compared with the conventional method of treating and recovering using a non-aqueous solvent, it is safer and takes less time.
There is no need to install new equipment, and environmental measures, recycling measures, and safety measures can now be taken at low cost.

Claims (9)

[Claims] 1. N, N-dimethylformamide and / or N, N-
A foamed polystyrene dissolving agent characterized by containing dimethylacetamide. 2. A method for dissolving expanded polystyrene, which comprises contacting expanded polystyrene with an expanded polystyrene dissolving agent containing N, N-dimethylformamide and / or N, N-dimethylacetamide. 3. Expanded polystyrene is contacted with an expanded polystyrene dissolving agent containing N, N-dimethylformamide and / or N, N-dimethylacetamide and dissolved therein, and then polystyrene and the expanded polystyrene are obtained from the obtained polystyrene solution. A method for recovering polystyrene, which comprises separating a polystyrene dissolving agent. 4. The method according to claim 3, wherein the polystyrene and the expanded polystyrene dissolving agent are separated by bringing the polystyrene dissolved liquid into contact with water. 5. The separation of the polystyrene and the expanded polystyrene dissolving agent is carried out by bringing the polystyrene dissolving solution into contact with a solvent that weakens the polystyrene dissolving power of the dissolving agent to precipitate polystyrene from the polystyrene dissolving solution. 3. The method for recovering polystyrene according to 3. 6. A solvent which weakens the dissolving power of a polystyrene foam dissolving agent is acetone, acetonitrile, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol or a mixed solvent thereof. The recovery method according to claim 5. 7. A method for producing a thread-shaped, plate-shaped or rod-shaped polystyrene by bringing the polystyrene solution obtained in claim 2 into contact with water. 8. A method for producing granular polystyrene by dropping the polystyrene solution obtained according to claim 2 into water. 9. A method for producing a polystyrene coating, which comprises applying the polystyrene dissolving solution obtained in claim 2 on the surface of an object and then removing the polystyrene dissolving agent.