Production of emulsion-polymerized butadiene rubber in powder form

Abstract

There is disclosed a simple economical method of producing butadiene rubber, particularly NBR, in dry powder form free of extraneous material influencing its utility in rubber products manufacture. The method consists of preparing the butadiene rubber in latex form in the usual manner but using sodium lauryl sulfate or equivalent as emulsifier and then coagulating the latex with a combination of magnesium sulfate and aluminum sulfate, or their equivalents, in a molar ratio of Mg to Al in the range of 0.3 to 1 to 2 to 1. The coagulum wet cake obtained contains powder size particles of the rubber and is dried to give a dry free-flowing rubber powder, preferably after addition of zinc stearate or equivalent which functions as an anticake agent and prevents agglomeration of the powder size particles during drying. The zinc stearate can be added to the wet cake as dry powder or as a wet paste or produced in situ.