Coating process with self-crosslinkable composition for electrical steel sheet

A process for the production of an electrical steel sheet core, the process comprising:

• applying a coating layer of a varnish composition onto a surface of the electrical steel sheet wherein the varnish composition comprises:
• (A) about 1 to about 95 wt % of a resin comprising nucleophilic groups selected from the group consisting of OH, NHR and SH, and electrophilic groups that can react with the nucleophilic groups, wherein the resin undergoes transacylation in its main chain and/or side chain(s) by reacting the nucleophilic groups with the electrophilic groups,
• (B) about 5 to about 75 wt % of an organic solvent and/or water,
• wherein the wt % is based on the total weight of the varnish composition and curing the applied at least one coating layer, wherein the curing is performed at curing temperatures in the range of about 200 to about 600° C. and the curing is done in a time period of about 10 seconds to about 1 minute,
• wherein the electrophilic groups are carbon atoms bound via double bonds to oxygen atoms in esters,
• punching out parts of the coated electrical steel sheet after curing,
• stacking and assembling the parts to form a sheet core by technical means chosen from welding, clamping, interlocking, aluminium die casting and riveting.

An electrical steel sheet coated with a coating process using a varnish composition, the coating process comprising the steps of:

• a) applying a coating layer of a varnish composition onto a surface of the electrical steel sheet wherein the varnish composition comprises:
• (A) about 1 to about 95 wt % of a resin comprising nucleophilic groups selected from the group consisting of OH, NHR and SH, and electrophilic groups that can react with the nucleophilic groups, wherein the resin undergoes transacylation in its main chain and/or side chain(s) by reacting the nucleophilic groups with the electrophilic groups,
• (B) about 5 to about 75 wt % of an organic solvent and/or water, wherein the wt % is based on the total weight of the varnish composition and
• b) curing the applied coating layer, wherein the curing is performed at curing temperatures in the range of about 200 to about 600° C. and the curing is done in a time period of about 10 seconds to about 1 minute,
• wherein the electrophilic groups are carbon atoms bound via double bonds to oxygen atoms in esters.