High Speed Dissolving of Viscosity Index Improvers in Luboils
Luboils, in common with most fluids, experience reduced viscosity at high operating temperatures. This results in a poorer hydrodynamic film and poorer lubrication. Heavier base oil can be used to overcome this, but problems arise with cold starting and pumping at low temperatures. Multigrade oils were developed to achieve the optimum viscosity across a full range of operating temperatures in those applications where it is required.
The Process
The problems of temperature/viscosity instability are solved in multigrade luboils by the addition of Viscosity Index Improvers, made from various types of polymer, including:
- Polymethacrylates
- Styrene Butadiene copolymer
- Styrene Isoprene copolymer
- Ethylene Propylene copolymer
These provide a more stable viscosity and allow the formulation of oils with lower viscosity base oil (for easier cold starting) and yet which have adequate high temperature viscosity for engine protection.
VI improvers make up around 10% of the content of a typical multigrade luboil, and increase the raw material costs of the finished product. Polymer is available in liquid, crumb, pellet and solid bale form. Each of these types has a different processing requirement: