| abstract |
Addition of oxidation inhibitor (antioxidant) or other additive to lubricating oil as in a working engine is effected by placing into the oil a container, e.g., a polyolefin container or capsule, for example, a polypropylene capsule containing said additive which permeates through the container wall into the oil gradually. A polypropylene capsule containing zinc dialkyldithiophosphate is described. Other container materials and other polyolefin, e.g., polyethylene and copolymers of monoolefins such as ethylene-propylene copolymers can be used. The container or capsule is found to release increasing quantities of additive as the oil temperature surrounding the same increases, with container rupture at extreme operating conditions of temperature to release remaining additives to further protect the oil under such conditions. |