Creaming of Rubber Latex

Abstract

Abstract The creaming of rubber latex was first observed as far back as 1824 when Hancock, working with what was probably Castilloa latex, observed that if this latex is well shaken with three or four times its volume of water and then allowed to stand, a separation into two layers will take place which thus effects a purification of the dispersion. This phenomenon, reported again by Faraday in 1825, is a spontaneous creaming which takes place with latices of large particle size. Latex of Hevea brasiliensis will not cream spontaneously in this manner and, although other methods of inducing creaming, such as the addition of caustic alkali, were previously known, it remained for Traube in 1924 to patent the first method which would prove satisfactory for commercial concentration. Rahn had reported in 1922 that the natural creaming of milk could be greatly accelerated and made more complete if small amounts of gelatin or of similar hydrophilic colloids, such as gum tragacanth, gum arabic, peptone or albumen, were added to the milk before allowing it to stand. Recognizing the similarity between milk and rubber latex, Traube applied this knowledge to the development of the creaming of latex. He found such substances as carrageen moss, Iceland moss, and other vegetable mucilages to be effective in causing separation of the latex dispersion into two layers—the upper one rich in rubber and the lower one, generally termed serum, almost free of rubber.