Monomer composition for synthesizing recycled plastic, preparation method thereof, recycled plastic, and molded product using the same

Abstract

The present disclosure relates to a monomer composition for synthesizing recycled plastic that contains a high-purity aromatic diol compound recovered through recycling by chemical decomposition of a polycarbonate-based resin, a method for preparing the same, and a recycled plastic and molded product using the same. Also, the present disclosure relates to a monomer composition for synthesizing recycled plastic that contains a by-product with a high added value recovered through recycling by chemical decomposition of a polycarbonate-based resin, a method for preparing the same, and a recycled plastic and molded product using the same.

1 . A monomer composition for synthesizing recycled plastic, comprising:
 an aromatic diol compound,   wherein the monomer composition has a color coordinate L* of more than 95, and a color coordinate a* of −0.06 to 0.10, and   wherein the monomer composition is a recovered product from a polycarbonate-based resin.   
     
     
         2 . The monomer composition according to  claim 1 , wherein the monomer composition for synthesizing recycled plastic has a color coordinate b* of less than 2. 
     
     
         3 . The monomer composition according to  claim 1 , wherein the aromatic diol compound has a purity of more than 99%. 
     
     
         4 . The monomer composition according to  claim 1 , further comprising two or more compounds selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate,
 wherein the dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate are recovered products from the polycarbonate-based resin.   
     
     
         5 . A monomer composition for synthesizing recycled plastic, comprising:
 two or more compounds selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate,   wherein the dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate are recovered products from a polycarbonate-based resin.   
     
     
         6 . The monomer composition according to  claim 5  wherein
 the monomer composition comprises the dimethyl carbonate at a ratio of 1% to 30%, the diethyl carbonate at a ratio of 10% to 65%, and the ethylmethyl carbonate at a ratio of 30% to 60%. 
 
     
     
         7 . A method for preparing a monomer composition for synthesizing recycled plastic, the method comprising the steps of:
 depolymerizing a polycarbonate-based resin in the presence of a solvent containing methanol and ethanol; and   separating a carbonate precursor from the depolymerization reaction product.   
     
     
         8 . The method for preparing a monomer composition according to  claim 7 , wherein
 ethanol is contained in an amount of 1 mole to 15 moles relative to 1 mole of methanol.   
     
     
         9 . The method for preparing a monomer composition according to  claim 7 , wherein
 a content of the methanol and ethanol is 10 moles to 15 moles relative to 1 mole of the polycarbonate-based resin.   
     
     
         10 . The method for preparing a monomer composition according to  claim 7 , wherein
 the depolymerization reaction of the polycarbonate-based resin is carried out by reacting a base in an amount of 0.5 moles or less relative to 1 mole of the polycarbonate-based resin.   
     
     
         11 . The method for preparing a monomer composition according to  claim 7 , wherein
 the solvent further comprises at least one organic solvent selected from the group consisting of tetrahydrofuran, toluene, methylene chloride, chloroform, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate and dipropyl carbonate.   
     
     
         12 . The method for preparing a monomer composition according to  claim 11 , wherein
 a content of the organic solvent is 16 to 20 moles relative to 1 mole of the polycarbonate-based resin.   
     
     
         13 . The method for preparing a monomer composition according to  claim 11 , wherein
 a content of the organic solvent is 1.5 moles to 2 moles relative to 1 mole of a total of methanol and ethanol.   
     
     
         14 . The method for preparing a monomer composition according to  claim 7 , wherein the step of depolymerizing a polycarbonate-based resin in the presence of a solvent containing methanol and ethanol comprises:
 adding a base to a mixed solvent of methanol and ethanol and an organic solvent to prepare a catalyst solution; and   adding the polycarbonate-based resin to the catalyst solution and stirring a mixture.   
     
     
         15 . The method for preparing a monomer composition according to  claim 7 , wherein the step of separating a carbonate precursor from the depolymerization reaction product comprises:
 a reduced pressure distillation step of the depolymerization reaction product.   
     
     
         16 . The method for preparing a monomer composition according to  claim 7 , further comprising:
 a purification of the depolymerization reaction product from which the carbonate precursor has been separated.   
     
     
         17 . The method for preparing a monomer composition according to  claim 7 , further comprising a neutralization reaction step of the depolymerization reaction product with an acid, before the separating step. 
     
     
         18 . A recycled plastic, comprising:
 a reaction product of the monomer composition of  claim 1  and a comonomer.   
     
     
         19 . A recycled plastic, comprising:
 a reaction product of the monomer composition of  claim 5  and a comonomer.   
     
     
         20 . A molded product comprising the recycled plastic of  claim 18 .