ELECTRO-INSULATING VARNISH Russian patent published in 2012 - IPC C09D5/25 H01B3/42 

FIELD: chemistry.

SUBSTANCE: varnish contains a varnish base, a functional additive which increases coating hardness, siccative HF and methyl ethyl ketoxime radical polymerisation inhibitor. The varnish base is an oligomer with strongly polar chromane rings. The oligomer is obtained by reacting tung oil and 101L phenol-formaldehyde resin, taken in equivalent ratio of 1:0.15-0.18, respectively, while heating said mixture for 60 minutes at temperature 160°C. After extracting water, temperature is raised to 182°C until achieving viscosity of 25-36 s. The oligomer is added to the composition in 50% xylene solution. The functional additive used is rosin ester with glycerine. Components are in the following ratio, wt %: oligomer - 31.0-36.2, rosin ester with glycerine - 9.0-3.8, siccative HF - 2.00, methyl ethyl ketoxime - 0.60, xylene - the balance.

EFFECT: wider raw material base, replacing molten amber, which is not produced on an industrial scale, with rosin ester with glycerine, high content of non-volatile substances, elasticity and electrical strength of the coating.

1 tbl, 2 ex