Unsaturated polymers are admixed with compounding and cure ingredients, processed and formed into shapes, and cure to yield finished products. If cure starts during processing and forming operations, the polymer mixture (stock) gets tough and hard to work, and often is discarded. This toughening phenomenon, known as scorching, is caused by premature activation of the vulcanization accelerator(s). Vulcanization retarders are used to delay the action of the accelerators. However, many of the older known types of retarders such as salicyclic acid, benzoic acid, and N-nitrosodiphenylamine are only marginally effective when used with the so-called fast-acting accelerators such as 2-mercaptobenzothiazole and the like. The problem of scorching is even more serious when amine-based antioxidants and antiozonants or high pH carbon blacks, all of which make stocks more scorchy, are employed. New compounds are needed to impart safety to scorchy stocks. Compounds as vulcanization retarders are disclosed in U.S. Pat. Nos. 3,513,139; 3,539,538; 3,546,185; 3,562,225; 3,586,696; 3,637,844; and 3,640,976.
USPTO Backgrounds
USPTO Backgrounds