Process for removing a coating from a substrate

Abstract

A process of stripping a coating according to the invention comprises subjecting a coated substrate to an aqueous medium containing a peroxide and an interfacial mixing agent, and to heating preferably by either ultraviolet (UV) and/or infrared (IR) radiation. The substrate is completely stripped of the coating and suffers no damage to itself as a result of the paint debonding/dislodging process. No toxic wastes are generated from this process, nor are particulates associated with air pollution generated. The metal substrates being stripped also do not undergo corrosion or other damage as a result of the described process.

1 . A process for removing a coating from a substrate, comprising:
 (a) heating the coated substrate;   (b) applying a stripping solution containing a peroxide and an interfacial mixing agent to the coated substrate;   (c) waiting for waiting for separation of the coating from the substrate to occur; and   (d) then stripping the separated coating off of the substrate.   
   
   
       2 . The process of  claim 1 , wherein step (a) comprises exposing the coated substrate to effective wavelengths of electromagnetic radiation. 
   
   
       3 . The process of  claim 2 , wherein the electromagnetic radiation comprises one or both of infrared light and ultraviolet light. 
   
   
       4 . The process of  claim 1 , wherein the substrate is a vehicle or part thereof. 
   
   
       5 . The process of  claim 5 , wherein the coating comprises one or more layers of paint. 
   
   
       6 . The process of  claim 1 , wherein the substrate is steel or aluminum. 
   
   
       7 . The process of  claim 1  wherein the substrate is a composite material. 
   
   
       8 . The process of  claim 7 , wherein the substrate is a carbon-based honeycomb or laminate. 
   
   
       9 . The process of  claim 1 , wherein the coating on the substrate comprises polyurethane or acrylic resin. 
   
   
       10 . The process of  claim 1 , wherein step (b) comprises spraying the stripping solution onto an exposed surface of the coated substrate, the substrate further having a non-exposed surface that spraying of the stripping solution does not effectively reach; and
 the process further comprises the steps of:   (e) repositioning the substrate so that the non-exposed surface can be sprayed with the stripping solution; and   (f) then repeating steps (a) to (d) on the repositioned substrate.   
   
   
       11 . The process of  claim 1 , wherein step (b) is carried out over a period of time sufficient to permit blisters to form in step (c). 
   
   
       12 . The process of  claim 1 , wherein step (b) comprises intermittently spraying the stripping solution onto the coated substrate. 
   
   
       13 . The process of  claim 12 , wherein step (b) comprises spraying the stripping solution as often as needed to maintain the substrate at a temperature not exceeding a target maximum temperature, whereby evaporative cooling is used to control the temperature of the substrate. 
   
   
       14 . The process of  claim 12 , wherein step (b) is carried out at least every 10 minutes for from 30 minutes to 6 hours. 
   
   
       15 . The process of  claim 1 , wherein the stripping solution consists essentially of:
 5 to 50 wt. % of hydrogen peroxide;   2 to 75 wt. % of an alkoxy polymer effective as an interfacial mixing agent;   0 to 2 wt. % of a surfactant effective as a wetting agent;   and the balance is essentially water.   
   
   
       16 . A stripping solution effective for removing paint from a painted substrate under infrared or ultraviolet light, consisting essentially of:
 5 to 50 wt. % of hydrogen peroxide;   2 to 75 wt. % of an alkoxy polymer effective as an interfacial mixing agent;   0 to 2 wt. % of a surfactant effective as a wetting agent;   and the balance is essentially water.   
   
   
       17 . The stripping solution of  claim 16 , wherein the amount of the alkoxy polymer is in the range of 2 to 50 wt. % and the amount of hydrogen peroxide is in the range of 5 to 30 wt. %. 
   
   
       18 . The stripping solution of  claim 16 , wherein the alkoxy polymer is a polyethylene glycol with a molecular weight in the range of 200 to 600. 
   
   
       19 . An apparatus for carrying out a process for removing a coating from a substrate, comprising:
 a chamber having an access opening into which a coated substrate is placed;   means for heating the coated substrate inside the chamber;   means for spraying a stripping solution onto the coated substrate in an amount and concentration effective to form gas pockets in situ at a coating-substrate boundary, whereby the coating is dislodged from the substrate; and   a reservoir containing a supply of the stripping solution.   
   
   
       20 . The apparatus of  claim 19 , wherein the heating means comprises an IR lamp, the spraying means comprises a nozzle which is operatively connected to the reservoir.