When applying water based adhesives by hand spray techniques or automated/machine controlled spray techniques for assembly of cushioning materials, such as for the furniture and bedding industries, there is a problem with adhesive overspray. The overspray presents itself as a fog in the factory that can carry long distances from the actual application area of the factory. This fog also creates a nuisance dust health hazard for the employees. Lastly, the fog or overspray is wasteful of resources as the adhesive is lost and not used for its intended purpose. This overspray not only gets onto the employees that apply the adhesive, but also contaminates nearby equipment, finished product, or raw materials in inventory, and contaminates air conditioners, heaters, and lighting.
One solution has been to set up air extraction hoods in the spray area. This works relatively well when the filters are maintained and the types of parts that are being assembled are small. However when making larger items such as mattresses, large sofa cushions, and the like, the usefulness of an air extraction hoods is negated because of the impracticality of extraction hoods that are sized for large items.
Also there have been attempts to control the overspray fog by using low fogging air atomized guns such as the DUX or EasyFlow Laminair spray gun. Although these spray devices minimize the over spray when adjusted properly, they are dependent on the spray operators not adjusting the settings as they can easily be misadjusted and create fog.
Another solution has been to use different types of adhesive bases other than water base. Solvent based adhesives and hot melt adhesives when sprayed do not create a fog. These types of adhesives work well to eliminate the overspray but have other problems.
Solvent based adhesives contain hazardous materials and often are flammable. They require air extraction equipment to reduce the flammability hazard as well as the health hazards to employees. Also solvent adhesives do not adhere some types of visco-elastic foams.
Hot melt adhesives typically do not bond foam cushion substrates as well as water based or solvent based products. Hot melts also require melt tanks and heated hose and this equipment is more expensive on a per gun basis than water based or solvent adhesives.
Another solution is the roll coating of water based adhesive rather than spray application. Roll coating eliminates the over spray, but suffers additional problems because the rollers are exposed to the atmosphere. As such, during any down time at all, the adhesive on the rollers can coagulate, causing inconsistent application of the adhesive. In addition, at the end of a shift, the workers must clean the rollers, adding to the system downtime and taking away working time from the workers. Further still, rollers do not allow a control of the application rate over a surface. Although roll coating provides a consistent application of adhesive across an entire surface, sometimes it is advantageous to vary the application rate of the adhesive. For example, it may be advantageous to use more adhesive in one area, and less in another, thereby using less adhesive overall.