AbstractPreemulsifying modifiers, or their solutions in monomers, with soap and water prior to charging the remaining ingredients of an emulsion polymerization system markedly changes the reactivity of high molecular weight modifiers. The increased reactivity of a mercaptan is seen in a higher regulating index as measured by the rate of depletion of the mercaptan. The regulating index oftert‐hexadecyl mercaptan for a styrene‐butadiene copolymerization (SBR) increased from 0.3 for the control to 3.0 after preagitation, and thus approached thetert‐dodecyl mercaptan control in efficiency on a molar basis. The regulating index ofn‐dodecyl mercaptan increased from 1.0 for the control to 16 for the experimental. The latter value is too high for efficient modification of SBR systems. This technique permits the attainment of a continuous range of regulating index values within limits based on the reactivity of the modifier and intensity and duration of preagitation. This paper presents solutions for two of the problems associated with the preagitation technique and proposes a mechanism to account for the changes in modification arising from preagitating modifiers in the soap solution. This report develops a variable in emulsion polymerization that has been little used and incompletely und
展开▼
