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

Abstract

The present disclosure relates to a monomer composition for synthesizing recycled plastic which is capable of recovering from a (co)polymer synthesized from a monomer containing terephthalic acid, extremely reducing the content of isophthalic acid, which is an impurity, and securing terephthalic acid having increased particle size, a method for preparing the same, and a recycled plastic, molded product, and plasticizer composition using the same.

1 . A monomer composition for synthesizing recycled plastic, comprising:
 terephthalic acid; and   isophthalic acid having a molar ratio of less than 0.5 mol % based on 100 mol % of the monomer composition,   wherein the terephthalic acid has a particle size of 10 μm or more and 300 μm or less, and   wherein the monomer composition is a recovered product from a (co)polymer synthesized from at least one monomer containing terephthalic acid.   
     
     
         2 . The monomer composition according to  claim 1 , wherein the at least one monomer containing terephthalic acid further comprises aliphatic diols, polyalkylene oxides, fatty acids, fatty acid derivatives, or a combination thereof. 
     
     
         3 . The monomer composition according to  claim 1 , wherein
 the terephthalic acid is contained in the monomer composition in an amount of more than 99.5 mol % based on 100 mol % of a total monomer compounds contained in the monomer composition.   
     
     
         4 . The monomer composition according to  claim 1 ,
 further comprising:   an organic solvent having a weight ratio of less than 10 ppm based on 100% by weight of the monomer composition.   
     
     
         5 . The monomer composition according to  claim 4 , wherein
 the organic solvent comprises N-methyl-2-pyrrolidone or dimethylacetamide.   
     
     
         6 . The monomer composition according to  claim 1 , wherein
 the (co)polymer comprises at least one (co)polymer selected from the group consisting of polyalkylene terephthalate, polyalkylene terephthalate-based copolymer, and thermoplastic polyester elastomer.   
     
     
         7 . A method for preparing a monomer composition for synthesizing recycled plastic, comprising the steps of:
 subjecting a (co)polymer synthesized from at least one monomer containing terephthalic acid to a depolymerization reaction and removing a diol component;   dissolving a depolymerization reaction product from which the diol component has been removed in an organic solvent and then recrystallizing the depolymerization reaction product; and   washing the recrystallized depolymerization reaction product with a solvent at a temperature of 200° C. or more and 300° C. or less.   
     
     
         8 . The method for preparing a monomer composition according to  claim 7 , wherein
 the solvent used in the washing step comprises water.   
     
     
         9 . The method for preparing a monomer composition according to  claim 7 , wherein
 in the washing step, 5 parts by weight or more and 10 parts by weight or less of the solvent is used based on 1 part by weight of the recrystallized depolymerization reaction product.   
     
     
         10 . The method for preparing a monomer composition according to  claim 7 , wherein
 the organic solvent used in the recrystallization step comprises N-methyl-2-pyrrolidone or dimethylacetamide.   
     
     
         11 . The method for preparing a monomer composition according to  claim 7 , wherein
 in the recrystallization step, 4 parts by weight or more and 10 parts by weight or less of the organic solvent is used based on 1 part by weight of the depolymerization reaction product from which the diol component has been removed.   
     
     
         12 . The method for preparing a monomer composition according to  claim 7 , wherein
 the recrystallization step comprises:
 dissolving the depolymerization reaction product from which the diol component has been removed in the organic solvent at a temperature of 50° C. or more and 130° C. or less; and 
 cooling a solution in which the depolymerization reaction product dissolved in the organic solvent to a temperature of 10° C. or less. 
   
     
     
         13 . The method for preparing a monomer composition according to  claim 7 , wherein
 the depolymerization reaction of the (co)polymer is carried out by reacting a base and the (co)polymer with a molar ratio of the base in an amount of 1.5 moles or more and 2.5 moles or less relative to 1 mole of the (co)polymer.   
     
     
         14 . The method for preparing a monomer composition according to  claim 7 , wherein
 the depolymerization reaction of the (co)polymer is carried out in the presence of an alkylene glycol solvent.   
     
     
         15 . The method for preparing a monomer composition according to  claim 7 , wherein
 before the dissolving and recrystallizing step,   the method further comprises:   neutralizing the depolymerization reaction product from which the diol component has been removed with an acid.   
     
     
         16 . The method for preparing a monomer composition according to  claim 7 , wherein
 after the step of subjecting the (co)polymer synthesized from the monomer containing terephthalic acid to a depolymerization reaction and removing the diol component,   the method further comprises:
 purifying the depolymerization reaction product from which the diol component has been removed. 
   
     
     
         17 . A recycled plastic, comprising:
 a reaction product of the monomer composition of  claim 1  and a comonomer.   
     
     
         18 . The recycled plastic according to  claim 17 , wherein
 the recycled plastic has a melt flow index of 15 g/10 min or more and 27 g/10 min or less as measured by ASTM D1238.   
     
     
         19 . A molded product, comprising:
 the recycled plastic of  claim 17 .   
     
     
         20 . A plasticizer composition, comprising:
 a reaction product of the monomer composition of  claim 1  and an alcohol.