Metallized polymer film capacitor having a high viscosity polyurethane oil insulating fluid

A metallized polymer film capacitor comprising:

• a container having a pair of terminals adapted for connection to an electrical circuit;
• a capacitive element formed from a pair of tightly co-rolled metallized polymer films disposed in the container;
• a pair of electrical leads electrically and operatively connected between the pair of metallized polymer films and the pair of terminals;
• and
• a polyurethane oil insulating fluid having a viscosity in the range of about 500 to about 3000 poise at 25.degree. C. disposed in the container surrounding at least a portion of the capacitive element, the polyurethane oil being produced by reacting an organic polyisocyanate with a primary polyol selected from the group consisting of castor oil, ricinoleic acid derivatives of castor oil, and mixtures thereof, in the presence of a secondary polyol chain extender, wherein the ratio of NCO groups of the organic polyisocyanate to OH groups of the primary and secondary polyols is in the range of about 0.1 to 1 to about 0.6 to 1.

A metallized polymer film capacitor comprising:

• a container having a pair of terminals adapted for connection to an electrical circuit;
• a capacitive element formed from a pair of tightly co-rolled zinc metallized polypropylene films disposed in the container;
• a pair of electrical leads electrically and operatively connected between the pair of zinc metallized polypropylene films and the pair of terminals;
• and
• a polyurethane oil insulating fluid having a viscosity in the range of about 1900 to about 2500 poise at 25.degree. C. disposed in the container completely surrounding the capacitive element, the polyurethane oil being produced by reacting an organic polyisocyanate selected from the group consisting of aliphatic polyisocyanates, cycloliphatic polyisocyanates, aromatic polyisocyanates, polymethyleneisocyanates, polyphenylisocyanates, methylenediisocyanates and organic polyisocyanates that are a prepolymer prepared by reacting an excess of a polyisocyanate compound and a polyol with a primary polyol selected from the group consisting of castor oil, ricinoleic acid derivatives of castor oil, and mixtures thereof in the presence of a hydroxy-terminated polybutadiene diol chain extender, wherein the ratio of NCO groups of the organic polyisocyanate to OH groups of the primary polyol and diol is in the range of about 0.1 to 1 to about 0.6 to 1.