Dry-peelable temporary protective coatings

Abstract

A dry-strippable coating composition can be incorporated into a composite article and comprises a dried water-borne polyurethane dispersion including a release additive comprising a releasing co-solvent or other selected release material. When water is removed from the polyurethane dispersion of the composite article and when the article comprises a thermoformable substrate, the article can be thermoformed to provide a shaped article. Dry-stripping the coating composition from the substrate provides a thermoformed substrate and a thermoformed protective layer. The dry-strippable coatings provide temporary protection for the surface of various products and components during manufacture, assembly, shipping, installation, painting, and refinishing operations.

It is claimed:  
     
         1 . A process comprising the step of: 
 providing a composite article comprising 
 1) a nonporous substrate having on at least one surface thereof  
 2) a strippable protective dried water-borne polyurethane coating composition, said polyurethane being free of polymerizable acrylate functionality, said composition comprising a release additive including one or both of (a) a releasing co-solvent having a boiling point greater than 100° C., and (b) a dispersion of a metal salt of stearic acid or a dispersion of a wax.  
   
     
     
         2 . The process according to  claim 1  further comprising the step of removing said protective layer by stripping it from said substrate in the absence of a stripping solvent.  
     
     
         3 . The process according to  claim 1  wherein said polyurethane comprises one or both of a polyurethane-urea and a sulfopoly(ester-urethane) all of which optionally are terminated with one or more silyl groups.  
     
     
         4 . The process according to  claim 1  wherein said polyurethane comprises a carboxylate or sulfonate functional polyurethane urea.  
     
     
         5 . The process according to  claim 1  wherein said release additive comprises a hydrophilic polyol.  
     
     
         6 . The process according to  claim 5  wherein said hydrophilic polyol comprises glycerol or an oligomer of glycerol.  
     
     
         7 . The process according to  claim 5  wherein said hydrophilic polyol is selected from the group consisting of ethers and esters of ethylene glycol, polyethylene glycol, ethers and esters of polyethylene glycol, and pentaerythritol ethoxylate.  
     
     
         8 . The process according to  claim 1  wherein said releasing co-solvent is selected from the group consisting of castor oil, sulfonated castor oil, and ethoxylated polydimethylsiloxanes.  
     
     
         9 . The process according to  claim 1  wherein said release additive is present in said coating composition in an amount in the range of 0.5 to 20 weight percent relative to the weight of solids in said polyurethane dispersion.  
     
     
         10 . The process according to  claim 9  wherein the amount of release additive is present in the range of 5 to 10 weight percent relative to the weight of solids in said polyurethane dispersion.  
     
     
         11 . The process according to  claim 1  wherein said substrate is selected from the group consisting of plastic, metal, glass, and ceramic.  
     
     
         12 . The process according to  claim 1  wherein said substrate comprises a thermoplastic film.  
     
     
         13 . The process according to  claim 1  wherein said substrate comprises a thermoformable material.  
     
     
         14 . The process according to  claim 13  wherein said thermoformable material comprises a plastic material.  
     
     
         15 . The process according to  claim 12  wherein said thermoplastic film comprises one or more of acrylonitrile butadiene styrene polymer, high impact polystyrene, polyethylene, polypropylene, poly(ethylene terephthalate) and copolymers thereof, polymethylmethacrylate, poly(ethylene naphthalenedicarboxylate), polycarbonate, polycarbonate-polyetherimide, and polyvinyl chloride.  
     
     
         16 . The process according to  claim 13  further comprising the step of thermoforming said composite article into a desired shape.  
     
     
         17 . The process according to  claim 16  further comprising the step of dry-stripping said protective layer from said substrate to produce a thermoformed substrate.  
     
     
         18 . A coating composition comprising an aqueous polyurethane dispersion, said polyurethane being free of acrylate functionality, said polyurethane including a release additive comprising one or both of (a) a releasing co-solvent having a boiling point greater than 100° C., and (b) a dispersion of a metal salt or a dispersion of a wax.  
     
     
         19 . The coating composition according to  claim 18  wherein said release additive is selected from the group consisting of glycerol, oligomers of glycerol, ethers and esters of ethylene glycol, polyethylene glycol, ethers and esters of polyethylene glycol, pentaerythritol ethoxylate, castor oil, sulfonated castor oil, dispersions of metal salts of stearic acid, ethoxylated polydimethylsiloxanes, and dispersed waxes.  
     
     
         20 . The coating composition according to  claim 18  from which water has been removed to provide a dry-strippable polyurethane coating.  
     
     
         21 . The polyurethane coating according to  claim 18  wherein said polyurethane is selected from the group consisting of a) a polyurethane-urea or a sulfopoly(ester-urethane) all of which optionally are terminated with one or more silyl groups, and b) a carboxylate or sulfonate functional polyurethane urea.  
     
     
         22 . The polyurethane coating according to  claim 19  wherein said release additive comprises glycerol or an oligomer of glycerol.  
     
     
         23 . A composite article comprising 
 a) a nonporous substrate having on at least one surface thereof    b) a strippable protective dried water-borne polyurethane coating composition, said polyurethane being free of acrylate functionality, said composition comprising a release additive including one or both of (a) a releasing co-solvent having a boiling point greater than 100° C., and (b) a dispersion of a metal salt of stearic acid or a dispersion of a wax.    
     
     
         24 . The composite article according to  claim 23  wherein said substrate comprises a thermoformable material.  
     
     
         25 . The composite article according to  claim 24  which has been thermoformed to produce a shaped article.  
     
     
         26 . The composite article according to  claim 25  wherein said thermoforming comprises one or more of heating, pressing, stretching, and application of vacuum.  
     
     
         27 . The composite article according to  claim 23  wherein said polyurethane is selected from the group consisting of a) a polyurethane-urea or a sulfopoly(ester-urethane) all of which optionally are terminated with one or more silyl groups, and b) a carboxylate or sulfonate functional polyurethane-urea.  
     
     
         28 . The composite article according to  claim 23  wherein said release additive is selected from the group consisting of glycerol or an oligomer thereof, ethers and esters of ethylene glycol, polyethylene glycol, ethers and esters of polyethylene glycol, pentaerythritol ethoxylate, castor oil, sulfonated castor oil, metal salts of stearic acid, ethoxylated polydimethylsiloxanes, and dispersed waxes.  
     
     
         29 . The composite article according to  claim 23  wherein said substrate is selected from the group consisting of plastic, metal, glass, sealed wood, and ceramic.  
     
     
         30 . The composite article according to  claim 25  wherein said substrate comprises a plastic material.  
     
     
         31 . A process comprising the step of: 
 a) providing a composite article comprising 
 1) a nonporous substrate having on at least one surface thereof  
 2) a strippable protective dried water-borne polyurethane coating composition comprising a release additive including one or both of (a) a releasing co-solvent having a boiling point greater than 100° C., and (b) a dispersion of a metal salt of stearic acid or a dispersion of a wax, and  
   b) thermoforming said composite article into a desired shape.    
     
     
         32 . A coating composition comprising an aqueous polyurethane dispersion including a release additive comprising one or both of (a) a releasing co-solvent having a boiling point greater than 100° C., and (b) a dispersion of a metal salt or a dispersion of a wax, wherein said polyurethane comprises a sulfopoly(ester-urethane) which optionally is terminated with one or more silyl groups.