Two-component adhesives Spraying

In order to eliminate harmful solvents which are flammable and sometimes noxious, adhesives manufacturers have developed water-based adhesives, based on rubber latex or polymer dispersions, which set quickly due to the addition of an activator that reacts quickly with the base polymer and induces its quick coagulation. But the mixing should be done during the spraying in order to avoid any coagulation and clogging into the gun. 

Therefore, the manufacturers of spray guns have developed special guns such as the one shown in Fig. 29. The injector valve injects the activator through a special air baffle where it is then distributed from the air cap horn holes. The activator is then proportionately blended with atomized adhesive within the spray pattern. 

For instance, the De Vilbiss Probond MSV-2K gun is a high-volume, low-pressure spray gun, which limits atomizing air cap pressure to a maximum of 0.7 bar with a 4 to 6 bars air inlet pressure. 

For an air cap pressure of 5 bars, the air consumption is only 18 1/min. The flow of adhesive is controlled by pressure in the tank and by the adjustment of the fluid tip and the needle, the spray fineness may be controlled with the atomization air, the width of the stream and the spray pattern are adjusted by changing the 

These two-component adhesives are usually formulated with a 10/1 ratio of adhesive to activator. The add-ons may vary from 50 to 200 g/m, depending on the job and the materials to be bonded. 

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