The present invention broadly relates to gas scrubbing devices for extracting contaminating particulate matter entrained in a gas stream employing a liquid washing medium. More particularly, the present invention is directed to an improved composition and process for denaturing high solids paint particles captured and entrained in an aqueous wash solution to effect a coagulation thereof and a flotation of the coagulated paint particles facilitating a separation and recovery from the aqueous wash solution.
Gas scrubbing devices of the various types well known in the art are extensively employed in paint spray chambers or booths for extracting particulate contaminating matter such as paint overspray particles during a paint spray operation from the recirculating air stream in order to provide an environmentally acceptable effluent for discharge to the atmosphere. Typical of such paint spray booth scrubbing devices are those such as described and illustrated in U.S. Pat. Nos. 3,119,675 and 3,782,080 the teachings of which are incorporated herein by reference. In essence, such air scrubbing devices employ various baffles, flood sheets, curtainous streams and/or spray patterns for extracting and capturing entrained particulated paint overspray particles from the air stream which become entrained in the aqueous wash water solution. In the spray application of conventional solvent-thinned coating compostions it has been conventional practice to incorporate various water soluble alkaline metal salts in the aqueous wash water to effect a denaturing or "killing" of the captured paint particles converting them from sticky substances to relatively dry putty-like agglomerates which tend to float in the recovery section of the apparatus facilitating removal or extraction thereof such as by skimming or the like. If the captured paint particles are not denatured, their sticky characteristics result in a progressive adherence and accumulation on the various surfaces of the water scrubbing apparatus and within the pipelines employed for recirculating the wash solution causing a progressive restriction in the flow of air and liquid through the apparatus significantly reducing the efficiency thereof and necessitating frequent shutdowns for cleaning and rejuvenation.
While such alkaline additive compounds of the types heretofore known have been satisfactory for denaturing conventional solvent-thinned coating formulations of the types heretofore known, such additives have been found ineffective and at times completely unsatisfactory for denaturing so-called "high-solids paints" which have been commercially introduced within the past few years for further reducing solvent emmissions in paint spray operations. The more stringent air regulations imposed by the Environmental Protection Agency (EPA) has occasioned the replacement of conventional solvent-thinned paint formulations usually containing less than about 45 percent by volume solids with the so-called high solids (or low-solvent) solvent-thinned coating compositions usually containing greater than 50 percent by volume solids, and more usually 60 percent or more by volume solids thereby attaining a substantial reduction in the quantity of organic solvent emissions to the atmosphere. In order to provide a sprayable viscosity at such lower solvent contents, such high-solid paint formulations contain polymers which are of a substantially smaller molecular weight in comparison to the molecular weight of polymers in conventional paint systems making them particularly tacky and difficult to denature employing additive agents of the types heretofore employed.
The present invention provides for a new additive agent for use in aqueous wash solutions of air or gas scrubbing devices and to a novel process for denaturing or killing captured high-solids paint particles entrained in such wash solutions thereby avoiding a progressive buildup of the contaminating paint on the structural sections of such scrubbing devices and further facilitating an extraction of the scrubbed paint constituents from the wash water facilitating a recirculation thereof.