Process for the recovery of polymers from mixed plastic waste

1 . A process for the recovery of polymers from mixed plastic waste, said process comprising the following steps:

a) shredding mixed plastic waste to a predetermined particle size followed by mixing with water and separating a floating top layer of light material containing light plastic and a settled bottom layer of heavy material containing heavy plastic;

b) separately drying said light material containing light plastic and said heavy material containing heavy plastic in a dryer to obtain a dried light plastic and a dried heavy plastic;

c) sequentially separating polymers selected from polystyrene (PS), polyvinyl chloride (PVC), ethyl vinyl alcohol (EVOH), nylon, polycarbonate (PC) and polyethylene terephthalate (PET) from said dried heavy plastic by:

I. mixing said dried heavy plastic in a first fluid medium capable of solubilizing polystyrene under stirring at a first predetermined temperature to obtain a first crude mixture followed by separating said first crude mixture to obtain a first filtrate and first solids containing undissolved plastic material; and subjecting said first filtrate to a predetermined method to obtain polystyrene and said first fluid medium, wherein said first predetermined temperature is in the range of 30° C. to 50° C.;

II. mixing said first solids in a second fluid medium capable of solubilizing polyvinyl chloride under stirring at a second predetermined temperature to obtain a second crude mixture followed by separating said second crude mixture to obtain a second filtrate and second solids containing undissolved plastic material; and subjecting said second filtrate to a predetermined method to obtain polyvinyl chloride and said second fluid medium, wherein said second predetermined temperature is in the range of 40° C. to 60° C.;

III. mixing said second solids in a third fluid medium capable of solubilizing ethyl vinyl alcohol (EVOH) under stirring at a third predetermined temperature to obtain a third crude mixture followed by separating said third crude mixture to obtain a third filtrate and third solids containing undissolved plastic material; and subjecting said third filtrate to a predetermined method to obtain ethyl vinyl alcohol (EVOH) and said third fluid medium, wherein said third predetermined temperature is in the range of 60° C. to 80° C.;

IV. mixing said third solids in a fourth fluid medium capable of solubilizing nylon under stirring at a fourth predetermined temperature to obtain a fourth crude mixture followed by separating said fourth crude mixture to obtain a fourth filtrate and fourth solids containing undissolved plastic material; and subjecting said fourth filtrate to a predetermined method to obtain nylon and said fourth fluid medium, wherein said fourth predetermined temperature is in the range of 90° C. to 110° C.;

V. mixing said fourth solids in a fifth fluid medium capable of solubilizing polycarbonate (PC) under stirring at a fifth predetermined temperature to obtain a fifth crude mixture followed by separating said fifth crude mixture to obtain a fifth filtrate and fifth solids containing undissolved plastic material; and subjecting said fifth filtrate to a predetermined method to obtain polycarbonate (PC) and said fifth fluid medium, wherein said fifth predetermined temperature is in the range of 110° C. to 130° C.; and

VI. mixing said fifth solids in a sixth fluid medium capable of solubilizing polyethylene terephthalate (PET) under stirring at a sixth predetermined temperature to obtain a sixth crude mixture followed by separating said sixth crude mixture to obtain a sixth filtrate and sixth solids containing residual plastic material; and subjecting said sixth filtrate to a predetermined method to obtain polyethylene terephthalate (PET) and said sixth fluid medium, wherein said sixth predetermined temperature is in the range of 140° C. to 160° C.; and

d) sequentially separating polymers selected from polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE) from said dried light plastic by solubilizing said dried light plastic in a seventh fluid medium under stirring at a seventh predetermined temperature to obtain a seventh crude mixture, wherein said seventh predetermined temperature is in the range of 110° C. to 130° C. followed by:

I. cooling said seventh crude mixture to a temperature in the range of 110° C. to 120° C. followed by filtering to obtain polypropylene and a seventh filtrate;

II. cooling said seventh filtrate to a temperature in the range of 90° C. to 100° C. followed by filtering to obtain high density polyethylene and an eighth filtrate; and

III. cooling said eighth filtrate to a temperature in the range of 75° C. to 85° C. followed by filtering to obtain low density polyethylene and said seventh fluid medium; and

wherein said predetermined method is selected from the group consisting of cooling, adding an antisolvent, distillation, centrifugation, skimming, and settling and filtration.

2 . The process as claimed in claim 1 , wherein polypropylene, high density polyethylene, low density polyethylene, polystyrene (PS), polyvinyl chloride (PVC), ethyl vinyl alcohol (EVOH), nylon, polycarbonate (PC) and polyethylene terephthalate (PET) are independently dried.

3 . The process as claimed in claim 1 , wherein said first crude mixture, said second crude mixture, said third crude mixture, said fourth crude mixture, said fifth crude mixture, said sixth crude mixture and said seventh crude mixture are independently passed in an activated carbon bed to remove color impurities.

4 . The process as claimed in claim 1 , wherein said first fluid medium, said second fluid medium, said third fluid medium, said fourth fluid medium, said fifth fluid medium and said sixth fluid medium are independently recycled for solubilizing said dried heavy plastic, said first solids, said second solids, said third solids, said fourth solids, and said fifth solids, respectively.

5 . The process as claimed in claim 1 , wherein said seventh fluid medium is recycled to step d) for solubilizing said dried light plastic.

6 . The process as claimed in claim 1 , wherein said cooling is carried out at a temperature in the range of 25° C. to 30° C.

7 . The process as claimed in claim 1 , wherein said predetermined particle size is in the range of 0.1 mm to 10 mm.

8 . The process as claimed in claim 1 , wherein

said first fluid medium is selected from the group consisting of ethyl methyl ketone (EMK), tetrahydrofuran (THF), toluene, xylene, N-methyl-2-pyrrolidone (NMP), valeronitrile, trichloroacetic acid, 1-Naphthol, 1,2-dihydroxybenzene (Catechol), dimethyl formamide (DMF), N,N-dimethyl acetamide, cyclohexanone, N-methyl-2-pyrrolidone (NMP), cyclopentanone, and mesityl oxide;

said second fluid medium is selected from the group consisting of THF, toluene, 2,3-dihydropyran, pyridine, chlorobenzene, ethyl acetoacetate, diethyleneglycol, propylene carbonate, 1-butanol, dimethyl formamide (DMF), N,N-dimethyl acetamide, cyclohexanone, morpholine, N-methyl-2-pyrrolidone (NMP), valeronitrile, cyclopentanone, and dimethyl sulfoxide (DMSO);

said third fluid medium is at least one selected from the group consisting of isopropyl alcohol (IPA), water, dimethyl sulfoxide (DMSO), propanediol (PDO), pyridine, diethyleneglycol, hydrogen peroxide, chloro acetic acid, dimethyl formamide (DMF), acrylic acid, N,N-dimethyl acetamide, phenol, cyclohexylamine, ethyl amine, morpholine, and N-Methyl-2-pyrrolidone (NMP);

said fourth fluid medium is selected from the group consisting of formic acid, propanediol (PDO), dimethyl sulfoxide (DMSO), hydrogen peroxide, acetic acid, formic acid, chloro acetic acid, acrylic acid, benzoic acid, propionic acid, butyric acid, methacrylic acid, and isobutyric acid;

said fifth fluid medium is selected from the group consisting of dimethyl sulfoxide (DMSO), ethyl methyl ketone (EMK), toluene, 2,3-dihydropyran, pyridine, and butanone;

said sixth fluid medium is selected from the group consisting of dimethyl formamide (DMF), gamma-valerolactone (GVL), dimethyl formamide, dimethyl sulfoxide (DMSO), pyridine, N,N-dimethyl acetamide, phenol, N-Methyl-2-pyrrolidone (NMP), valeronitrile, trichloroacetic acid, 1-Naphthol, and 1,2-dihydroxybenzene (Catechol); and

said seventh fluid medium is selected from the group consisting of o-xylene, p-xylene, mixed xylene, toluene, dodecane, camphene, 1-butanol, tetrahydrofuran (THF), 1-octene, ethyl benzene and di-n-butyl ether.

9 . The process as claimed in claim 1 , wherein said antisolvent is selected from the group consisting of water, hexane, acetone, isopropyl alcohol (IPA), methanol, and ethanol.

10 . The process as claimed in claim 1 , wherein said step (c) comprises parallel and simultaneous separation of polymers selected from polystyrene (PS), polyvinyl chloride (PVC), ethyl vinyl alcohol (EVOH), nylon, polycarbonate (PC) and polyethylene terephthalate (PET) from said dried heavy plastic.