Process for removing coating from polymeric substrate

Abstract

A process for removing the coating and any metals from polymeric substrates such as compact discs (CDs) and digital video discs (DVDs) by applying high shear conditions to fluidized particulates of the polymeric substrate optionally in the presence of an accelerant.

1 . A process for removing a coating from a polymeric substrate having a coating thereon, said process comprising the steps of: 
 (a) fragmenting said polymeric thermoplastic substrate into relatively small polymeric substrate particles;    (b) delivering said polymeric substrate particles to a mechanical shearing apparatus;    (c) fluidizing said polymeric substrate particles in said mechanical shearing apparatus;    (d) shearing said fluidized particles at a relatively high rate of shear to remove the coating from the polymeric substrate; and    (e) recovering the cleaned polymeric particles.    
     
     
         2 . A process as defined in  claim 1  wherein said polymeric substrate particles are fluidized with fluidizing medium selected from the group consisting of air and water.  
     
     
         3 . A process as defined in  claim 1  wherein said fluidizing medium comprises water.  
     
     
         4 . A process as defined in  claim 1  wherein said polymeric substrate comprises a polycarbonate.  
     
     
         5 . A process as defined in  claim 2  wherein said polycarbonate substrate comprises an optical media.  
     
     
         6 . A process as defined in  claim 2  wherein said optical media comprises compact disk, digital video disk or mixtures thereof.  
     
     
         7 . A process as defined in  claim 1  wherein said polymeric substrate particles comprise particles ranging in size from about 2 to about 20 millimeters in the longest direction.  
     
     
         8 . A process as defined in  claim 1  wherein an accelerant selected from the group consisting of carboxylic acids, carboxylic acid esters and mixtures thereof are further added to said shearing process.  
     
     
         9 . A process as defined in  claim 8  wherein said accelerant comprises aqueous acetic acid.  
     
     
         10 . A process as defined in  claim 9  wherein the concentration of acetic acid ranges from about 0.1% to about 20% by weight based on the weight of the aqueous acetic acid.  
     
     
         11 . A process as defined in  claim 10  wherein the concentration of acetic acid ranges from about 0.1 to about 10 weight percent.  
     
     
         12 . A process as defined in  claim 11  wherein the concentration of acetic acid ranges from about 0.25 to 1 weight percent.  
     
     
         13 . A process as defined in  claim 8  wherein said accelerant comprises a lactate.  
     
     
         14 . A process as defined in  claim 1  wherein the mixture in the shearing apparatus comprises from about 10 to about 60 weight percent solids.  
     
     
         15 . A process as defined in  claim 14  wherein the mixture in the shearing apparatus comprises from about 50 to about 60 weight percent solids.  
     
     
         16 . A process as defined in  claim 1  wherein the temperature of shearing is less than about 95° C.  
     
     
         17 . A process as defined in  claim 16  wherein the temperature of shearing ranges from about 50 to about 95° C.  
     
     
         18 . A process as defined in  claim 1  wherein said shearing apparatus comprises a rotary blade mixer operating at a mixing speed of at least about 1000 rpm.  
     
     
         19 . A process as defined in  claim 1  wherein step (d) comprises washing said sheared polymeric particles.  
     
     
         20 . A process as defined in  claim 19  wherein said washing step comprises water washing.  
     
     
         21 . A process as defined in  claim 20  wherein said washing step comprising water washing in the presence of an organic acid, a surfactant or a mixture thereof.  
     
     
         22 . A process as defined in  claim 5  further comprising the step of recovering aluminum from the mixing effluent.  
     
     
         23 . A process as defined in  claim 6  further comprising the step of recovering gold from the mixing effluent.  
     
     
         24 . A process for demetallizing and removing a coating from a polymeric substrate having a metal-containing coating thereon, said process comprising the steps of: 
 (a) fragmenting said polymeric thermoplastic substrate into relatively small polymeric substrate particles;    (b) delivering said polymeric substrate particles to a mechanical shearing apparatus;    (c) fluidizing said polymeric substrate particles in said mechanical shearing apparatus;    (d) shearing said fluidized particles at a relatively high rate of shear to remove the coating from the polymeric substrate, optionally in the presence of an accelerant selected from the group consisting of a carboxylic acid, a carboxylic acid ester and mixtures thereof; and    (e) recovering the cleaned polymeric particles.    
     
     
         25 . A process as defined in  claim 24  wherein said fluidizing medium comprises water.