A New Additive for Improving the Thermal Aging Characteristics of Kraft Insulating Paper

Kraft paper is used for insulation in oil-immersed equipment such as transformers. The reason is that Kraft paper has given satisfactory performance on electrical and mechanical properties. As for life, however, thermal degradation occurs due to temperature rise in operation. Examples of these kinds of the Kraft paper are cyanoethylated Kraft paper and amine modified Kraft paper. Kraft paper containing morpholine, oxyalkylamine, aromatic polyamine, para-toluene-sulfone, etc., are well known. This paper describes a method for thermally upgrading Kraft paper using carbamate compound. The results obtained are summarized as follows. 1) n-Butyl carbamate is effective for thermally upgrading Kraft paper. 2) n-Butyl carbamate modified paper does not contaminate transformer oil.