Transition from titanium catalyzed polyisoprene
to neodymium catalyzed polyisoprene
The current information letter covers the SKI-3 production transition to neodymium catalyzed polyisoprene SKI-5. Neodymium rubbers both polybutadiene and polyisoprene are enable to satisfy the high-level requirements, specified by tire manufacturers to raw materials. Modern tires should help to reduce fuel consumption, air pollution and noise, to improve stability and handling of the car (by reducing the braking distance, improving traction with mushy, snowy and icy roads). Neodymium catalyzed rubbers meet all these challenges. The group of scientists from the state institute of synthetic rubbers in St. Petersburg and R&D center of JSC "Synthez-Kauchuk" is the first in the world who has developed an industrial process for manufacture of neodymium catalyzed polyisoprene rubber, which was regarded as a strong competitor to natural rubber and nowadays replaces it successfully in the domestic market of tire and rubber industries, it was named as SKI-5 for tire industry and as SKI-5PM for general rubber goods. Rubber SKI-5, unlike SKI-3, doesn't contain gel fraction, mixed valence metals, dimers and trimers (oligomers) of isoprene as well as has higher average molecular weight. The microstructure of the neodymium catalyzed polyisoprene differs from the microstructure of titanium catalyzed polyisoprene by higher stereo and regioselectivity - it has no trans-1,4 and 1,2-isoprene units. This provides stability of quality and better fluidity of the rubber itself and compounded mixes thereof. Having resembling plasto-elastic characteristics of rubber compounds, the tensile stress @ 300% elongation and tear strength of the vulcanizates based on SKI-5 are higher than that of similar vulcanizates based on SKI-3. Furthermore, fatigue strength of vulcanizates based on neodymium catalyzed polyisoprene exceeds fatigue strength of vulcanizates based on titanium polyisoprene. Absence of isoprene oligomers gives SKI-5 ecological advantage over SKI-3 at all stages of its production, processing and application of products based on it. Absence of mixed valence metals gives a high thermal stability to the rubber and goods thereof. SKI-5 testing in the tread rubbers for solid metal cord tires has shown that rubbers based on SKI-5 have greater Mooney viscosity (84 units) than rubbers based on SKI-3 (75 units) and natural rubber (68 units). Premature vulcanization resistance (time before starting of vulcanization) in the rubber based on SKI-5 is higher than in the rubber based on natural rubber and is on the same level as in the rubber based on SKI-3. Vulcanization rate and reversal resistance of rubbers based on SKI-5 are similar to rubbers based on natural rubber and excel those based on SKI-3 (it has higher optimum vulcanization time and lower reversal time). Related to the degree of vulcanization (conventional stress at 300 % elongation) rubbers based on SKI-5 and SKI-3 are similar. Rubbers based on natural rubber have a higher degree of vulcanization. Related to tension strength, experimental and standard rubbers are similar. Relative hysteresis effect of SKI-5 at 100°C is the same as of SKI-3 and is better than of natural rubber. Retention factor of longitudinal strength and breaking elongation characterizing heat-ageing resistance is higher in rubbers based on SKI-5 than in rubbers based on SKI-3 and natural rubber. Related to fatigue endurance at flexing rubbers based on SKI-5 also dominate those based on SKI-3 and natural rubber. Crispness temperature range of SKI-5 based rubber is the same as of rubbers based on SKI-3 and natural rubber. All the above-mentioned indicators define SKI-5 as the 21" century rubber and future belongs to it. Therefore polyisoprene production unit is currently undergoing the large construction and installation works, the completion of which in 2014 will let us make the transition from the production of titanium catalyzed polyisoprene to neodymium catalyzed polyisoprene. The following grades will be produced: SKI-5 with staining antioxidant and SKI¬5PM with nonstaining antioxidant for medical and food industries.
Technical Data Sheets