A prepreg can be obtained by impregnating a base paper with a heat-curing resin free from formaldehyde, the prepreg exhibiting a residual moisture content of 2 to 4% by weight after drying, the resin of the prepreg being non-crosslinked and exhibiting a degree of crosslinking of maximum about 85% in the case of thermal treatment of the prepreg over a period of about 40 seconds at about 132.degree. C.