Patent ID: 6021831
Filing Date: 2000-02-08
Classification: B60C,C08K

Abstract:
A pneumatic tire for using on snow and icy road surfaces comprising a tire tread which substantially contacts at least a road surface and includes a foamed rubber layer, and wherein said foamed rubber layer has closed cells whose average diameter is about 1 um to about 120 um and has an expansion ratio of about 1% to about 100%, and a solid-phase rubber portion having a rubber composition comprising a mixture of at least both of a diene-based rubber and silica, with said silica present in an amount of from about 10 to about 80 parts by weight based on 100 parts by weight of said diene-based rubber;(a) wherein a thin film layer of a non-foamed rubber covers the surface of the tread when the tire is new so that the foamed rubber layer is exposed after the vehicle has been run-in slightly;(b) wherein said diene-based rubber comprises about 30 parts by weight or more of cis-1,4-polybutadiene in 100 parts by weight of said diene-based rubber;(c) wherein said silica and cis-1,4-polybutadiene in the foamed rubber layer are present in amounts that satisfy the following equation:{(parts by weight of B)-30 parts by weight}<{1.5.times.(parts by weight of S)};whereinB represents cis-1,4-polybutadiene;S represents silica;parts by weight of B represents an amount of B in parts by weight in 100 parts by weight of said diene-based rubber; and parts by weight of S represent an amount of S in parts by weight based on 100 parts by weight of said diene-based rubber;(d) wherein said rubber composition includes a silane coupling agent, and the amount of said silane coupling agent is about 3% to about 20% by weight based on said silica;(e) wherein said rubber composition also includes carbon black;(f) wherein said rubber composition includes about 5 to about 50 parts by weight of said carbon black based on 100 parts by weight of said diene-based rubber, said carbon black having a nitrogen absorption specific surface area (N.sub.2 SA) of about 105 m.sup.2 or more per gram and having a dibutyl phthalate absorption number (DBP) of about 110 ml or more per 100 grams,(g) wherein said rubber composition includes a vulcanizing agent and a vulcanization accelerator which is at least one of a thiazole vulcanization accelerator and a sulfenamide vulcanization accelerator; and(h) wherein said vulcanization accelerator and said vulcanizing agent are present in amounts which satisfy the following equation:1.2<(parts by weight of overall amount of vulcanization accelerator/parts by weight of amount of vulcanizing agent)<4.0wherein parts by weight represents an amount based on 100 parts by weight of said diene-based rubber.