![]() These gels or fisheyes reduce product quality. A small number of solid particles never completely dissolve.Nitrogen blowing or blanketing may be required to reduce oxygenation.Long processing times at high temperature can also lead to discoloration of the oil.Oxidation can occur during extended processing at high temperature, degrading the polymer.These are not easily dispersed by conventional mixers, and can build up on the vessel wall, behind baffles or on the liquid surface. Poor in-tank agitation can lead to re-agglomeration of polymer particles.Conventional agitators do not produce sufficient shear to reduce the polymer particles larger particles take longer to solubilize as a smaller surface area is exposed to the surrounding oil.With conventional agitation, many hours are required to completely solubilize the polymer.Polymer is predispersed into base oil in bulk by the polymer supplier, leading to additional costs in respect of the base oil itself and the costs of processing and bulk transport.This is the most expensive form of polymer.Good in-tank agitation is required to disperse the polymer, and maintain vigorous movement within the vessel.Mixing is continued for several hours to allow the polymer to become solubilized.The polymer is added to the oil and dispersed by the agitator.The bales of polymer are shredded, chopped or granulated into small pieces before addition to the base oil.The hot oil penetrates the polymer, which softens and gradually becomes solubilized into the oil.Good in-tank agitation is required to disperse the polymer, and to maintain vigorous movement within the vessel.Polymer supplied in pellet or crumb form is added directly to the heated base oil. ![]() The liquid polymer is weighed/metered into heated base oil and blended by simple agitation.It is easy to use and requires no special mixing equipment or processing. Polymer may be predissolved by the supplier, and is supplied in liquid form.Each of these types has a different processing requirement: Liquid Polymer Polymer is available in liquid, crumb, pellet and solid bale form. VI improvers make up around 10% of the content of a typical multigrade luboil, and increase the raw material costs of the finished product. 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. 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:
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