Impregnating coating layer for insulating sheetsand multilayer laminates

A method for producing a multilayer laminate having a first surface and a second surface, the multilayer laminate comprising at least three layers, characterized in that the method comprises the steps of:

• a) providing a first outer layer that is a first nonwoven backing sheet containing a crystalline silicate mineral powder, the first outer layer comprising a coating of an impregnating resin based on acrylate derivatives,
• b) providing an inner layer that comprises either:
• i) heat resistant floc and binder and being free of crystalline silicate mineral powder, or
• ii) heat resistant polymeric film being free of crystalline silicate mineral powder, and
• c) providing a second outer layer that is a second nonwoven backing sheet containing a crystalline silicate mineral powder, the second outer layer comprising a coating of an impregnating resin based on acrylate derivatives,
• d) binding the first outer layer, the inner layer, and the second outer layer together face-to-face, with the inner layer being between the first and second outer layers,
• wherein the multilayer laminate has a total of 15 to 80 weight percent crystalline silicate mineral powder, based on the total amount of said crystalline silicate mineral powder, floc, and binder in the multilayer laminate;
• wherein said crystalline silicate mineral powder comprises mica, and
• wherein each of the first and second outer layers comprises 15 to 80 weight percent crystalline silicate mineral powder, 5 to 25 weight percent heat-resistant floc, and 20 to 60 weight percent binder, based on the total amount of said crystalline silicate mineral powder, floc, and binder in each first and second outer layer, and
• wherein each of the first and second surfaces of the multilayer laminate is coated with the impregnating resin, and each of the first and second surfaces are stabilized by a region of the said impregnating resin that both covers and extends into each of the first and second outer layers forming said first and second surfaces of the multilayer laminate,
• the region of impregnating resin extending into each outer layer a distance of 10 to 50 micrometers from each of said first and second surfaces, and further, the region of impregnating resin having a thickness of impregnating resin of from 5 to 50 micrometers on each of said first and second surfaces.