The Deresination of Guayule: A Physical Model. Part I: Effect of Water and Temperature on the Diffusion Coefficients

Abstract

Abstract 1. The nature of the static deresination of guayule worms is complicated by the presence of moisture. In analogy with hevea latex coagulum, the moisture occurs in pockets and channels between the rubber agglomerates which contain the solubilized resin, and it enhances desorption of the resin into a solvent. At moisture above a critical level (around 10 wt.%), the pockets are likely to be interconnecting, thus providing easy access for the water-miscible solvent to the interior of the worms through an interchange process with the moisture. 2. Assuming minimal resistance at the surface of the worms, the static deresination is thought to take place in four consecutive steps: (a) the penetration of solvent into the pores of the worms made up of moisture pockets and channels, (b) the absorption (swelling) of the solvent into the rubber phase and subsequent transfer of the solubilized resin from the rubber phase to the solvent, (c) diffusion of the resin as a solute in the solvent through the swollen rubber phase to the internal surface in the pores, and (d) diffusion of the resin solute through the pores to the surface of the worms. 3. The deresination performance of acetone is much better than that of 95% ethanol. 4. The diffusion coefficient of acetone in the rubber phase is shown to be almost one order of magnitude greater than the diffusion coefficient for overall desorption of resin into acetone. This indicates that the rate-limiting step is the diffusion of the resin through the rubber phase to the internal surface of rubber agglomerates inside the pores.