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

1 . A monomer composition for synthesizing recycled plastic, comprising:

terephthalic acid having a particle size of 10 μm or more and 400 μm or less,

wherein the monomer composition has a moisture content is 30% or less,

wherein the monomer composition is a recovered product from a (co)polymer synthesized from at least one monomer containing terephthalic acid, and

wherein the moisture content is calculated by the following Equation:

( a−b )÷ a× 100  [Equation]

in the above equation,

‘a’ is the weight of the monomer composition before drying at 140° C. for 10 minutes,

‘b’ is the weight of the monomer composition after drying at 140° C. for 10 minutes.

2 . The monomer composition according to claim 1 , further comprising an 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;

washing a depolymerization reaction product from which the diol component has been removed; and

cooling the washed depolymerization reaction product to a temperature of 100° C. or less,

wherein the washing step comprises:

a step of washing the depolymerization reaction product from which the diol component has been removed with a first 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 second 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 each of the first solvent and the second solvent is water.

9 . The method for preparing a monomer composition according to claim 7 , whereinafter the step of washing with the first solvent at a temperature of 20° C. or more and 100° C. or less, the depolymerization reaction product from which the diol component has been removed has a pH value of 3 to 4.

10 . The method for preparing a monomer composition according to claim 7 , wherein in the step of washing with the second solvent at a temperature of 200° C. or more and 300° C. or less, the second solvent is used in an amount of 5 parts by weight or more and 55 parts by weight or less based on 1 part by weight of the (co)polymer.

11 . The method for preparing a monomer composition according to claim 7 , wherein the washing step proceeds the step of washing with the second solvent at a temperature of 200° C. or more and 300° C. or less, after the step of washing with the first solvent at a temperature of 20° C. or more and 100° C. or less.

12 . 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 second solvent at a temperature of 200° C. or more and 300° C. or less and the temperature of the step of washing with the first solvent at a temperature of 20° C. or more and 100° C. or less is 150° C. or more and 200° C. or less.

13 . The method for preparing a monomer composition according to claim 7 , wherein in the cooling step, the cooling rate is from 1° C./min to 10° C./min.

14 . 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.

15 . 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 water or alkylene glycol solvent.

16 . 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.

17 . A recycled plastic, comprising:

a reaction product of the monomer composition of claim 1 and a comonomer.

18 . A molded product, comprising:

the recycled plastic of claim 17 .

19 . A plasticizer composition, comprising:

a reaction product of the monomer composition of claim 1 and an alcohol.