Tire sealant and tire with sealant containing silica and balanced organoperoxide depolymerized butyl rubber

A tire sealant precursor composition is disclosed comprising a butyl rubber and a combination of organoperoxides comprising 4,4-di-(tertiary butylperoxy) valerate and dicumyl peroxide. The ratio of dicumyl peroxide to 4,4-di-(tertiary butylperoxy) valerate is in a range of from 3/1 to 30/1. The composition further comprises a reinforcing filler comprising silica. Also a pneumatic tire with such a partially depolymerized composition as a built-in sealant layer is disclosed as well as a method of manufacturing.