SUMMARY OF THE INVENTION
The present invention is proposed in order to overcome the above-mentioned disadvantages of the prior art. The object of the present invention is to provide a solvent for polystyrene having an excellent dissolving ability and an excellent chemical stability, with no influence on the operating environment.
Another object of the present invention is to provide a method for reducing the volume of the polystyrene foam with the use of the above-mentioned solvent.
Still another object of the present invention is to provide a method for recycling the polystyrene foam with the use of the above-mentioned solvent.
The present invention provides a solvent for polystyrene comprising as its main ingredient at least one member selected from the group consisting of a glycol ether compound represented by the general formula (1) ##STR1## where m represents an integer of 1-4, n represents an integer of 0-4, and R represents a hydrogen atom or a methyl group,
and a fatty acid dialkyl ester compound represented by the general formula (2)
R1 OOC--(CH2)n --COOR2 ( 2)
where R1 and R2 each represents an alkyl group having 1-3 carbon atoms, and n represents an integer of 0-4.
As the above-mentioned glycol ether compound, it is preferable to use at least one member selected from the group consisting of diethylene glycol dimethyl ether, diethylene glycol diethyl ether and dipropylene glycol dimethyl ether.
In a preferred embodiment of the present invention, the above-mentioned solvent is selected from glycol ether compounds having a flash point of 100° C. or higher. The solvent is further added with water.
As the above-mentioned fatty acid dialkyl ester compound, it is preferable to use a fatty acid dimethyl ester compound, in particular, dimethyl succinate, dimethyl glutarate or dimethyl adipate,
In a preferred embodiment of the present invention, the solvent is the above-mentioned fatty acid dialkyl ester compound, with an addition of water.
A method for recycling the polystyrene foam in accordance with the present invention comprises the steps of dissolving the polystyrene foam in the above-mentioned solvent, and distilling the obtained solution at a temperature at which polystyrene does not decompose, thereby to separate the above-mentioned solvent from the polystyrene.
Another method for recycling the polystyrene foam in accordance with the present invention comprises the steps of dissolving the polystyrene foam in the above-mentioned solvent, precipitating polystyrene from the obtained solution by adding water to the solution, and separating the polystyrene from the solution.
Still another method for recycling the polystyrene foam in accordance with the present invention comprises the steps of dissolving the polystyrene foam in the above-mentioned solvent, precipitating polystyrene from the obtained solution by cooling the solution to a temperature lower than the temperature at which polystyrene dissolves, and separating the polystyrene from the solution.
In the above-mentioned method for recycling the polystyrene foam, it is preferable to perform a filtrating process for separating the precipitated polystyrene from the solution.
The present invention also provides a method for recycling the polystyrene foam, wherein the above-mentioned solvent is regenerated by distillation and used again as the solvent for the polystyrene foam.
While novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the preferred embodiments.