Vapor phase assisted post-consumer polymer processing apparatus and method

Abstract

Embodiments of the invention provide a process for processing post-consumer polymer. The polymer is contacted with a control medium having a carrier gas and a reactive vapor. Such a process is useful for processing post-consumer polymers with lower energy and reactants than with liquid reactants, and also promotes decontamination of the recycled polymer during the reaction.

What is claimed is: 
     
         1 . A process for processing post-consumer polymers comprising the steps of:
 a) conveying post-consumer polymer feed material to a reaction vessel;   b) heating the polymer feed material to a temperature sufficient to initiate and sustain reaction in a solid state;   c) contacting the heated polymer with a control medium comprising a carrier gas and a reactive vapor;   d) performing a solid state reaction (SSR) between the polymer and control medium, to provide a product;   e) discharging the product.   
     
     
         2 . A process according to  claim 1 , wherein the polymer comprises PET. 
     
     
         3 . A process according to  claim 2 , wherein the reactive vapor is selected from the group consisting of ethylene glycol, methanol, and water. 
     
     
         4 . A process according to  claim 3 , wherein the reactive vapor comprises ethylene glycol. 
     
     
         5 . A process according to  claim 1 , wherein the process permits the recovery of product having a number average molecular weight in the range of 3000 to 115,000 and an intrinsic viscosity in the range of 0.15 to 1.30 dl/g. 
     
     
         6 . A process according to  claim 5 , wherein the product is discharged to an extruder to produce a food grade product. 
     
     
         7 . A process according to  claim 1 , wherein the reactive vapor is present in the carrier gas at a concentration of about 0 to about 400,000 ppm. 
     
     
         8 . A process according to  claim 1 , wherein a residence time for the reaction is about 2 to about 8 hours. 
     
     
         9 . A process according to  claim 1 , wherein a temperature of the polymer during the reaction is about 190 to about 220° C. 
     
     
         10 . A process according to  claim 1 , wherein a molecular weight of the polymer is decreased in the solid state reaction. 
     
     
         11 . A process according to  claim 1 , wherein a molecular weight of the polymer is held constant in the solid state reaction. 
     
     
         12 . A process according to  claim 1 , wherein a rate of polymer molecular weight increase is decreased in the solid state reaction. 
     
     
         13 . A process according to  claim 1 , wherein a molecular weight of the polymer is increased in the solid state reaction without a decrease in a reaction rate. 
     
     
         14 . A process according to  claim 1 , wherein the discharged product of step e) has contaminant levels below 0.22 ppm. 
     
     
         15 . A process according to  claim 1 , wherein the discharged product of step e) has an intrinsic viscosity between 0.78 and 0.82 dl/g. 
     
     
         16 . A process according to  claim 1 , wherein the carrier gas is nitrogen. 
     
     
         17 . A process according to  claim 1 , wherein the carrier gas is carbon dioxide. 
     
     
         18 . A process according to  claim 1 , further comprising removing contaminants from the polymer with the control medium. 
     
     
         19 . A process according to  claim 18 , further including recovering the control medium, separating the contaminants from the control medium, and reintroducing the control medium to the polymer. 
     
     
         20 . A recycled polymeric product obtained by the process of  claim 1 . 
     
     
         21 . A process for processing post-consumer polymers comprising the steps of:
 a) conveying post-consumer polymer feed material to a reaction vessel;   b) heating the polymer feed material to a temperature sufficient to initiate and sustain reaction in a solid state;   c) contacting the heated polymer with a control medium comprising a carrier gas and a reactive vapor;   d) performing a solid state reaction (SSR) between the polymer and control medium, to provide a product;   e) simultaneously with step (d), reducing the level of contaminants within the polymer with the control medium; and   f) discharging the product.   
     
     
         22 . The method of  claim 21 , wherein the contaminates are selected from the group consisting of organic volatile polar, organic volatile non-polar, organic non-volatile polar, organic non-volatile polar contaminants, and any combination thereof. 
     
     
         23 . The method of  claim 21 , wherein the contaminates are selected from the group consisting of toluene, benzophenone, lindane, chlorobenzene, phenyl cyclohexane, methyl salycilate, methyl stearate, chloroform, and any combination thereof. 
     
     
         24 . The method of  claim 21 , wherein steps (d) and (e) are done under atmospheric pressure.