. . "Such phenol-aldehyde resins can be produced from phenol itself or the various phenols that are substituted, for example, with hydroxyl groups or with halogen atoms such as fluorine, chlorine or bromine, or with hydrocarbyl radicals, such as alkyl and alkenyl groups of l to 18 carbon atoms, alicyclic groups of five to 18 carbon atoms and aryl or aralkyl groups of six to 18 carbon atoms." . . . . . .