Patent ID: 7297721

Claim:
A process for the preparation of a high molecular weight food grade polyethyleneterephthalate, said process comprising the steps of: (a) processing by adding PCRPET flakes to the paste form of virgin PTA, isophthalic acid(IPA), monoethylene glycol(MEG) and additives in the esterification reactor to obtain an esterified material, (b) retaining about 20-30% of the esterified material of step (a) in the esterification reactor as a prepolymer heel, and filtering the rest of the esterified prepolymer material to obtain a prepolymer material filtrate of uniform quality, (c) transferring the filtrate of step (b) into a prepoly reactor while maintaining a temperature in the range of 240-255° C. for a maximum period of 60 minutes to achieve an I.V. of about 0.3 dl/g, (d) charging the material of step (c) into an autoclave at a temperature in the range of 284-300° C. to achieve a degree of polymerization in the range of 100-110 to obtain an amorphous polymer resin/melt, (e) subjecting the amorphous polymer resin/melt of step (d) to solid state polymerization to obtain food grade crystalline PET, and (f) preferably continuing the process cycle by adding an appropriate quantity of PCRPET flakes, PTA IPA and MEG to the retained prepolymer heel of step (b) and performing steps (c) to (e) to obtain continuous production of crystalline food grade PET resin.