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 that has high acid value while recovering from a (co)polymer synthesized from monomers containing terephthalic acid, 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 having   an acid value measured by KS M ISO 2114 of 670 mgKOH/g or more, 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 , further comprising
 isophthalic acid having a molar ratio of less than 0.85 mol % based on 100 mol % of a total monomer compounds contained in the monomer composition.   
     
     
         3 . 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. 
     
     
         4 . The monomer composition according to  claim 1 , wherein
 the terephthalic acid has a molar ratio of more than 99.15 mol % based on 100 mol % of a total monomer compounds contained in the monomer composition.   
     
     
         5 . The monomer composition according to  claim 2 , wherein
 the isophthalic acid is recovered from the (co)polymer.   
     
     
         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; and   washing a depolymerization reaction product from which the diol component has been removed,   wherein the washing step comprises:
 a step of washing the depolymerization reaction product from which the diol component has been removed with a protic polar solvent at a temperature of 20° C. or more and 100° C. or less; and 
 a step of washing the depolymerization reaction product from which the diol component has been removed with a washing solvent containing an aprotic polar solvent at a temperature of 20° C. or more and 110° C. or less. 
   
     
     
         8 . The method for preparing a monomer composition according to  claim 7 , wherein
 the protic polar solvent comprises water or alcohol.   
     
     
         9 . The method for preparing a monomer composition according to  claim 7 , wherein
 the aprotic polar solvent comprises tetrahydrofuran or acetonitrile.   
     
     
         10 . The method for preparing a monomer composition according to  claim 7 , wherein
 the washing solvent comprises one of the aprotic polar solvent, or a mixture of the aprotic polar solvent and the protic polar solvent.   
     
     
         11 . The method for preparing a monomer composition according to  claim 7 , wherein
 in the step of washing with the protic polar solvent at a temperature of 20° C. or more and 100° C. or less,   the protic polar solvent is used in an amount of 5 parts by weight or more and 30 parts by weight or less based on 1 part by weight of the (co)polymer synthesized from the monomer containing terephthalic acid.   
     
     
         12 . The method for preparing a monomer composition according to  claim 7 , wherein
 in the step of washing with the washing solvent containing the aprotic polar solvent at a temperature of 20° C. or more and 110° C. or less,   the washing solvent is used in an amount of 5 parts by weight or more and 30 parts by weight or less based on 1 part by weight of the (co)polymer.   
     
     
         13 . The method for preparing a monomer composition according to  claim 7 , wherein
 the washing step proceeds the step of washing with the washing solvent containing the aprotic polar solvent at a temperature of 20° C. or more and 110° C. or less, after the step of washing with the protic polar solvent at a temperature of 20° C. or more and 100° C. or less.   
     
     
         14 . The method for preparing a monomer composition according to  claim 7 , wherein
 a difference value between the temperature of the step of washing with the protic polar solvent at a temperature of 20° C. or more and 100° C. or less, and the temperature of the step of washing with the washing solvent containing the aprotic polar solvent at a temperature of 20° C. or more and 110° C. or less is 30° C. or more and 100° C. or less.   
     
     
         15 . 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 2.3 moles or less relative to 1 mole of the (co)polymer.   
     
     
         16 . The method for preparing a monomer composition according to  claim 7 , wherein
 the depolymerization reaction of the (co)polymer synthesized from the at least one monomer containing terephthalic acid is carried out in the presence of an alkylene glycol solvent.   
     
     
         17 . The method for preparing a monomer composition according to  claim 7 , wherein
 before the step of washing the depolymerization reaction product from which the diol component has been removed,   the method further comprises neutralizing the depolymerization reaction product from which the diol component has been removed with an acid.   
     
     
         18 . A recycled plastic, comprising:
 a reaction product of the monomer composition of  claim 1  and a comonomer.   
     
     
         19 . A molded product, comprising:
 the recycled plastic of  claim 18 .   
     
     
         20 . A plasticizer composition, comprising:
 a reaction product of the monomer composition of  claim 1  and an alcohol.