Hydrogenated styrene-diene copolymer (HSD) viscosity index improver

Hydrogenated styrene-diene copolymer (HSD) is a copolymer of styrene with isoprene or butadiene, followed by hydrogenation to saturate the remaining double bonds in the diene monomer to improve thermo-oxidative stability. The relative molecular mass of HSD is generally (5-50)*10^4, its thickening ability and shear stability are better, and it can meet the requirements of multi-grade internal combustion engine oil, especially for the preparation of large-span multi-grade internal combustion engine oil. Due to (HSD) good thickening ability and shear stability, its use is increasing. At present, the commonly used ones are SV260 of Infineum, KY6161 of Kunvii, etc.

Structural characteristics of HSD class

HSD-type viscosity index improvers have good thickening ability and shear stability at the same time, because of the rationality of the raw rubber structure. The raw material has a large molecular weight and a small degree of dispersion. In addition, it is found from NMR analysis that they are star-shaped polymers, and divinylbenzene is cross-linked and polymerized into a dense core. Since the monomer has 2 vinyl groups, the core provides many polyisoprene arms. The chance of coupling, each core can have many arms, so the molecular weight of the arms does not need to be very large, 1*10^4-5*10^4, and the total molecular weight of such a copolymer reaches 10^5~10^6 , After fully hydrogenated after polymerization, more than 98% of the double bonds on the non-benzene ring are eliminated, so it has good thickening ability and high shear stability. Commonly used viscosity index improvers are diblock copolymers of type A-B, where A is a monoalkenyl aromatic compound (such as styrene) and B is a conjugated diene (such as butadiene and isoprene), which can be used at high speed. In the case of shearing, the star-shaped molecule with multi-arm can reduce the breaking of the chain, and the star-shaped molecule with the same molecular weight as the linear molecule can avoid the sharp drop of molecular weight, so as to better maintain the viscosity of the lubricating oil.


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