Development of improving processing HNBR

摘要

The hydrogenated nitrile elastomer (HNBR) is a new rubber consisting of methylene chain, cyano groups and a small number of C=C. This elastomer is produced by selection hydrogenation reaction of the olefin segments in NBR. During reaction, only the double bond should be selectively hydrogenated without the cynao groups which are essential for retaining the oil resistant properties of NBR. Present, the capacity of HNBR in total world is about 7500t/a[1],developed and commercialized by Bayer (Germany)and Zeon (Japan),trademark is THERBAN and ZETPOL respectively. In domestic, We (Lanzhou Petrochemical Company) has built a 100t/a HNBR pilot plant.As known, Mooney viscosity is a key factor in rubber processing, low Mooney viscosity will result in decreasing of strength, increasing of compression set, whereas high Mooney viscosity is hard to process, also must be plasticated. In order to overcome above problems, we designate and synthesize a base rubber as NBR-1 by modifying molecular weight distribution(MWD),its MWD is more than conventional NBR as NBR-2,correspondently their Mw, Mn and MWD are 14.9,2.2,6.78 and 13.9,4.3,3.23.Those hydrogenated product are quoted as HNBR-1 and HNBR-2.Their polymer Mooney viscosity (ML1+4 100℃) are 39 and 82.A solution of 3.5kg of NBR-1 containing 36% by weight of acrylonitrile,in 35kg of chlorobenzene and a solution of 5.5g of tris-(triphenylphosphane)-rhodium-chloride[2] in 2.5kg of chlorobenzene are introduced into a 50 liter autoclave blanketed with nitrogen. The nitrogen is replaced by hydrogen and hydrogenation is carried out for 8hr at 100℃-120℃,under a hydrogen pressure of 8 Mpa. The hydrogenation process of NBR-2 same as that of NBR-1.Their degrees of hydrogenation amount to ＞ 98%(as determined by iodine value).We find MWD of base NBR has a most effect on HNBR. Table 1 shows a comparison of physical properties of HNBR-1 and HNBR-2.As would be expected lower polymer Mooney viscosities yield lower compound Mooney viscosities.It is evident that HNBR-1 has almost the same properties in spite of lower polymer Mooney viscosities compared with HNBR-2.Table 1 Comparison of physicalproperties of HNBR-1 and HNBR-2**Compounding formulation(weight part):HNBR 100,ZnO 5.0,stearic acid 0.5,N770 carbon 50,polyester plasticizer 5.0,dicumyl peroxide 6.5,triallyl isocyanurate 1.75,styrenized diphenylamine 1.5,zinc salt of 2-mercaptobenzimidazole 0.5.