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

Abstract

The present invention relates to a monomer composition for synthesizing recycled plastic, which comprises an aromatic diol compound, wherein a color coordinate b* is 0.1 to 1, wherein the aromatic diol compound yield is more than 75%, and wherein the monomer composition for synthesizing recycled plastic is recovered from 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, the composition comprising an aromatic diol compound,
 wherein the composition has a color coordinate b* of 0.1 to 1,   wherein a yield of the aromatic diol compound measured according to Equation 1 is more than 75%, and   wherein the monomer composition for synthesizing recycled plastic is recovered from a polycarbonate-based resin;
   Yield (%)= W   1   /W   0   [Equation 1]
 
   in Equation 1, W 0  is the mass of the aromatic diol compound obtained during 100% decomposition, and W 1  is the mass of the aromatic diol compound actually obtained.   
     
     
         2 . The monomer composition for synthesizing recycled plastic according to  claim 1  wherein:
 the monomer composition for synthesizing recycled plastic has a color coordinate L* of 98 or more. 
 
     
     
         3 . The monomer composition for synthesizing recycled plastic according to  claim 1  wherein:
 the monomer composition for synthesizing recycled plastic has a color coordinate a* of 0 or less. 
 
     
     
         4 . The monomer composition for synthesizing recycled plastic according to  claim 1  wherein:
 the monomer composition for synthesizing recycled plastic has an aromatic diol compound purity level of 98% or more. 
 
     
     
         5 . The monomer composition for synthesizing recycled plastic according to  claim 1  wherein:
 an amount of sodium salt impurities contained in the monomer composition for synthesizing recycled plastic, as measured using ion chromatography, is less than 10 μg relative to 1 g of the monomer composition. 
 
     
     
         6 . The monomer composition for synthesizing recycled plastic according to  claim 1  wherein:
 the monomer composition for synthesizing recycled plastic contains diethyl carbonate as a by-product, and the diethyl carbonate is recovered from the polycarbonate-based resin. 
 
     
     
         7 . A method for preparing a monomer composition for synthesizing recycled plastic, the method comprising the steps of:
 depolymerizing a polycarbonate-based resin by a depolymerization reaction;   adding acid so that the pH of the depolymerization reaction product is 2 to 8 to form a depolymerization reaction product;   removing impurities from the depolymerization reaction product after the addition of acid; and   separating a carbonate precursor from the depolymerization reaction product.   
     
     
         8 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 in the step of adding acid so that the pH of the depolymerization reaction product is 2 to 8, converting a salt of an aromatic diol compound contained in the depolymerization reaction product into an aromatic diol compound. 
 
     
     
         9 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 the step of removing impurities after the addition of acid comprises separating; 
 a water layer containing the impurities from an organic solvent layer containing an aromatic diol compound and a carbonate precursor are separated. 
 
     
     
         10 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 the polycarbonate-based resin is depolymerized in the presence of a solvent containing ethanol. 
 
     
     
         11 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 10  wherein:
 the content of the ethanol is 10 to 15 moles relative to 1 mole of the polycarbonate-based resin. 
 
     
     
         12 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 the polycarbonate-based resin is depolymerized by reaction with a base in an amount of 0.5 moles or less relative to 1 mole of the polycarbonate-based resin. 
 
     
     
         13 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 an antioxidant is added to a reaction solution during the step of depolymerizing the polycarbonate-based resin. 
 
     
     
         14 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 in the step of separating the carbonate precursor from the depolymerization reaction product, 
 the method comprises a reduced pressure distillation step of the depolymerization reaction product. 
 
     
     
         15 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 7  wherein:
 after the step of separating the carbonate precursor from the depolymerization reaction product, 
 the method further comprises a purification step of the depolymerization reaction product from which the carbonate precursor has been separated. 
 
     
     
         16 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 15  wherein:
 the purification step of the depolymerization reaction product from which the carbonate precursor has been separated comprises, 
 a washing step of the depolymerization reaction product from which the carbonate precursor has been separated. 
 
     
     
         17 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 15  wherein:
 the purification step of the depolymerization reaction product from which the carbonate precursor has been separated comprises, 
 a recrystallization step of the depolymerization reaction product from which the carbonate precursor has been separated. 
 
     
     
         18 . The method for preparing a monomer composition for synthesizing recycled plastic according to  claim 15  wherein:
 the purification step of the depolymerization reaction product from which the carbonate precursor has been separated comprises 
 an adsorption purification step of the depolymerization reaction product from which the carbonate precursor has been separated. 
 
     
     
         19 . A recycled plastic comprising a reaction product of the monomer composition for synthesizing recycled plastic of  claim 1  and a comonomer. 
     
     
         20 . A molded product comprising the recycled plastic of  claim 19 .