Ameripol SN—A Cis-,4-Polyisoprene

Abstract

HE important observation, made by Katz ( 6 ) in 1925 using T x-ray diffraction technique, showed that the mere stretching of crude or soft vulcanized Hevea rubber caused a t least a portion of the polymer to undergo crystallization. This and the subsequent experiments of Hock ( 4 ) emphasized the point that ~uccesaful attempts to synthesize a polymer resembling Hevea rubber mould have to take regularity into account. The situation is complicated in isoprene polymers by the variety of ways the monomer can enter the growing polymer chain.The four isomeric forms of polyisoprene are shown in Figure 1.Since head-to-tail orientations must be considered because of the asymmetry of the isoprene molecule, there are eight possible arrangements of the units that can occur in polymerized isoprene. Sodium, potassium, emulsion, and alfin polyisoprenes have been shown to contain all four forms of the repeating units (8). All of these uncured polymers have poor tack and their pure gum vulcanizates shorn poor physical properties. They do not crystallize when stretched or cooled. It has long been recognized that polymers of conjugated hydrocarbon dienes would have to be very regular in structure before their properties would approach those of Hevea rubber.Looking back over the last 15 to 20 years, there has been a elow development, almost iniperceptible at first, of catalyst systems m-hich produce polymers that in some degree shox-an oriented structure. This orientation could result if the monomer, during the propagation phase of the polymerization, is held in a definite position with respect to the growing chain, as by cybotactic forces where polymerization is initiated a t the melting point of the monomer or as by adsorption of the monomer onto a solid surface-perhaps to the surface of the catalyst itself.The woik reported here deals primarily mith the properties of a rubber made by directed polymerization. POLYMER STRUCTURE AND PROPERTIESCatalyst. Catalyst systems, based on polyolefin information purchased from Karl Ziegler, hare been applied to isoprene mononler systems. and modifications have been developed such that either cis-1,4-polyisoprene or trans-l,4-polyisoprene can now be prepared at n 111 Infrared Absorption Spectra. The effect of one of these catalyst modifications was first recognized when a modified olefin polymerization yielded an isolable unstabilized rubbery component n~liich showed an infrared absorption spectrum (2-to 25micron range) almost identical to that of Hevea rubber except for peaks due to oxidation at 2.8, 5.6, and 5.8 microns and, additionally, a slightly higher intensity in the peak at 11.25 microns. Subsequent samples of this rubber, a cis-1,4-poly-I The B. F. Goodrich Go., Tire and Equipment Division, Akron, Ohio.isoprene, now called Ameripol SN, when protected by age resistors did not show these oxidation peaks (Figure 2).Infrared absorption spectra indicate low ma,ximum concentrations of 1,2-and 3,4-addition products in Bmeripol SN. For these two isomeric units the discrimination in the presen...

Hexamethylene-N,N1 bis (tertbutyl peroxycarbamate) as crosslinking agent in elastomers

“…Several other factors affect the final vu1canizate structure. Such factors are the presence of nitrogenous bases (30,31), the type of accelerator system and accelerator to sulphur ratio (25,26).…”

“…It is also possible during "maturing" that di-and polysulphidic crosslinks undergo dynamic interchange with like crosslinks and with similar sulphidic chains present in pendent groups or intramolecular loops. Such interchange may be facilitated by high 31 temperature or by nucleophilic reagents such as sulphenyl and persulphenyl anions derived from the accelerator complex:…”

Historical Development of Synthetic Rubbers

“…The second method 14 uses a catalyst of the so-called 'Ziegler-Natta' type, that is, a complex formed by reacting an organometallic compound with a transition-metal compound. (Of almost equal interest is the discovery of methods of manufacturing stereospecific polybutadienes.)…”

Von der stereospezifischen Polymerisation zur asymmetrischen autokatalytischen Synthese von Makromolekülen Nobel-Vortrag am 12. Dezember 1963

“…-HC -CH- Die beiden geometrischen Polyisopren-lsomeren waren bereits aus der Natur bekannt : Naturlicher Kautschuk ist das cis-1 .CPolymere, Guttapercha und Balata sind trans-1.4-Polymere. Beide Typen wurden durch stereospezifische Polymerisation auch synthetisch erhalten, das cis-1 .CPolymere erstmals durch Chemiker der Firma Goodrich in den USA [94], und das trans-1.4-Polymere Anfang 1955 von uns [95]. Die anderen Stereoisomeren mit 1.2-oder 3.4-Verknupfung konnten bisher noch nicht in so holier sterischer Reinheit dargestellt werden, als daB kristalline Produkte erhalten worden waren.…”