Pneumatic tire having puncture sealing feature and method of making same

A method of preparing a pneumatic tire having a puncture sealing feature by applying a sealant composite to the inner surface of a cured rubber tire, the improvement which comprises applying the composite sealant to the inner surface of the cured tire in the form of a relatively narrow individual strip, having dimensional stability and resistance to flow, adhered circumferentially around the inner surface of the crown portion of the tire in a spiral fashion with sufficient revolutions to achieve a desired width of the sealant composite, utilizing the sequential steps of (A) optionally cleaning or preparing the inner surface of the tire by (i) cleaning with an aqueous detergent solution or hydrocarbon solvent and allowing it to dry and/or (ii) buffing or abrading the surface to roughen it, (B) optionally heating the tire to a temperature in the range of about 40.degree. C. to about 80.degree. C., (C) optionally applying a thin coating of a cement to the prepared inner tire surface and (D) applying and adhering said strip of sealant composite to the inner surface of the tire or to the optional cement coat;

• wherein said sealant composite, as applied to the inner surface of said cured rubber tire, consists essentially of an admixture of
• (A) 100 parts by weight of a partially crosslinked butyl rubber, said butyl rubber having been partially crosslinked prior to mixing with the remainder of the following ingredients (B), (C) and (D), and characterized by being partially crosslinked to an extent characterized by being about 20 to about 80 percent soluble in cyclohexane at about 80.degree. C. and having a molecular weight in the range of about 200,000 to about 400,000;
• (B) about 25 to about 150 parts by weight (i) oil selected from at least one of paraffinic, naphthenic, or aromatic oils and (ii) polyisobutylene characterized by being a semi-solid at 40.degree. C.;
• (C) about 2 to about 50 parts by weight tackifying resin for said rubber having a softening point in the range of about 80.degree. C. to about 120.degree. C. selected from at least one of the group consisting of thermoplastic olefin/diolefin polymerizate resins and phenolformaldehyde resins;
• (D) about 10 to about 150 parts by weight of carbon black having a particulate size in the range of about 200 to about 400 U.S. Standard Sieve Size.