New Generation of Stereoregular cis-1,4-Polybutadiene Produced by NIZHNEKAMSKNEFTEKHIM PJSC Part II. Synthesis of «Neodimium» Polybutadienes of Improved Characteristics

Abstract

Continuation of the work, the results are set out in report I. At the first stage, to improve performance properties of vulcanizates, a high-molecular grade SKD 563 of a viscosity of 60–70 Mooney units was developed; however, it is inferior to the standard grade SKDN in terms of processability due to the high viscosity of rubber compounds. Further research at PJSC Nizhnekamskneftekhim was aimed at improving the hysteresis properties of «neodymium» cis-1,4-polybutadienes (SKDN) while maintaining the level of technological properties of rubber compounds, similar to rubber with a standard viscosity group of 40–49 Mooney units. This was achieved by improving the molecular-mass characteristics of SKDN. For this purpose, a catalytic system has been developed with the preservation of neodymium carboxylate as the central component of the catalyst. The production of a new grade of rubber SKD 544NP has been mastered, the reduction of its polydispersity is achieved by reducing the proportion of the high-molecular fraction, at the same time the content of fractions with an average level of molecular weights (MW) is growing without much change in the low MW range. A comparison of SKD 544NP with a foreign analogue was carried out. The improved level of physical and mechanical properties of filled rubbers according to a set of parameters: rebound resilience at 23 and 70 °C, heat generation, the value of loss tangent tgδ at 60 °C was shown. Their behavior is the same during processing, as indicated by the close value of the Payne effect. In terms of the complex properties, rubber based on SKD 544NР are superior to rubbers based on serial «neodymium» butadiene rubbers and are not yield to the modern import analog. In terms of performance properties of vulcanizates based on SKD 544NP and SKD 563, they are superior to rubbers based on serial «neodymium» butadiene rubbers and are not inferior to modern imported analogues, while SKD 544NP is distinguished by good processability.