Control of Alfin Rubber Molecular Weight

Abstract

Control of molecular weight of alfin catalyzed diene polymers has been demonstrated for polymers of butadiene, isoprene, styrene, piperylene and combinations of these. The 1,4-dihydro derivatives of benzene and naphthalene are effective molecular weight moderators. The known microstructure of alfin polymers remains unchanged with the use of these agents. Molecular weight controlled alfin gums process readily on standard rubber machinery. Oil extenders or softeners, although not necessary, are easily incorporated. The feasibility of continuous processing has been demonstrated for the production of catalyst, moderators and polymers on pilot plant scale. A wide series of polymers and copolymers at predetermined molecular weights and compositions have been produced in the same pilot plant. Alfin polybutadiene with limited amounts of styrene is essentially a solution type SBR. Alfin copolymers with styrene and/or isoprene have undergone preliminary road tests in tires. Wear and heat build-up data indicate performance to be intermediate between SBR and polybutadiene.

Synthetic Polyisoprene Rubber as a Mimic of Natural Rubber: Recent Advances on Synthesis, Nanocomposites, and Applications

“…When isoprene is polymerized using an alfin catalyst, a great amount of trans-1,4configuration is obtained with about 20% of double bonds. The molecular weight is controlled by small amounts of 1,4-dihydrobenzene or 1,4-dihydronaphtalene; these do not affect the microstructure of the resulting polyisoprenes [73]. Such polymers are processed readily on standard rubber machinery.…”

The Formation of Gel in Alfin-Plus Polymerization

“…For with alfin rubber, the prime problem appears to be quality more than the extremely high molecular weight that has so often been credited [6][7][8][9][10] as causing failures. An extremely high molecular weight within a minute has been a feature since the discovery of the catalyst, but only lately has good quality been attainable by giving attention to the better utilization of the surface (that is, more of the surface being used for polymerization and less for side reactions [3] and to the condition of the surface -freedom from propylene -where the extraordinary rapid chain growth is taking place.…”