초록 ▼

This invention relates to a pneumatic tire having a built-in sealant layer and its preparation. The sealant layer precursor is a layer of a butyl rubber based composition which contains an organoperoxide. The butyl rubber of said precursor is a copolymer of isobutylene and isoprene containing from a

This invention relates to a pneumatic tire having a built-in sealant layer and its preparation. The sealant layer precursor is a layer of a butyl rubber based composition which contains an organoperoxide. The butyl rubber of said precursor is a copolymer of isobutylene and isoprene containing from about 0.5 to about 5, alternately less than 1, mole percent isoprene. The precursor composition contains carbon black and/or coal dust and may contain a dispersion of liquid conjugated diene polymer (e.g. liquid cis 1,4-polyisoprene polymer), short fibers and/or hollow glass microspheres. A layer of the sealant precursor is built into the tire between a sulfur vulcanized halobutyl rubber innerliner and conjugated diene-based rubber of the tire carcass. The butyl rubber of the sealant precursor is partially depolymerized by the organoperoxide during the elevated temperature vulcanization of the tire to form the built-in sealant layer. In one aspect of the invention, said uncured butyl rubber sealant precursor layer composition has a storage modulus G′ (80° C.) in a range of about 100 to about 400 kPa and said partially depolymerized butyl rubber sealant layer composition has a storage modulus G′ (80° C.) in range of about 5 to about 50 kPa.

대표청구항 ▼

1. A pneumatic tire having a built-in puncture sealing layer wherein said puncture sealing layer contains an at least partially organoperoxide-depolymerized butyl rubber-based sealant layer positioned between a sulfur vulcanized halobutyl rubber tire innerliner and a sulfur vulcanized diene-based vu

1. A pneumatic tire having a built-in puncture sealing layer wherein said puncture sealing layer contains an at least partially organoperoxide-depolymerized butyl rubber-based sealant layer positioned between a sulfur vulcanized halobutyl rubber tire innerliner and a sulfur vulcanized diene-based vulcanized conjugated diene-based tire carcass, wherein said sealant layer is a polymeric composition having a storage modulus (G′) in a range of from about 5 to about 50, alternately about 5 to about 30, kPa, which is exclusive of polyisobutylene additive, and is comprised of, based upon parts by weight per 100 parts by weight of said partially depolymerized butyl rubber:(A) a partially organoperoxide-depolymerized butyl rubber as a copolymer of isobutylene and isoprene, wherein said copolymer prior to such depolymerization contains from about 0.5 to about 5 percent units derived from isoprene, and correspondingly from about 95 to about 99.5 weight percent units derived from isobutylene, and, based upon parts by weight per 100 parts by weight partially depolymerized butyl rubber (phr) of: (B) particulate filler comprised of about 5 to about 90 phr of rubber reinforcing carbon black and coal dust, and, optionally at least one of: (1) from zero to about 6 phr of short fibers, and (2) from zero to about 20 phr of hollow glass microspheres; (C) from zero to about 20 phr of rubber processing oil having a maximum aromatic content of about 15 weight percent; (D) from 1 to about 10 phr of liquid polyisoprene having a weight average molecular weight in a range of from about 35,000 to about 65,000. 2. The tire of claim 1 wherein said particulate filler is additionally comprised of from about 0.5 to about 5 phr of short fibers selected from at least one of cotton fibers and synthetic fibers selected from at least one of rayon, aramid, nylon and polyester fibers, and their mixtures, wherein said cotton fibers have an average length of up to about 200 microns and said synthetic fibers have an average length of up to about 2,500 microns.3. The tire of claim 1 wherein said particulate filler is additionally comprised of from about 5 to about 15 phr of hollow glass microspheres having an average diameter in a range of from about 20 to about 40 microns.4. The tire of claim 1 wherein said partially depolymerized butyl rubber contains from about 4 to about 15 phr of said rubber processing oil which is comprised of about a 35 to about 45 weight percent naphthenic content, about a 45 to about 55 weight percent paraffinic content and an aromatic content of less than about 15 weight percent.5. A pneumatic tire having a puncture sealing ability comprised of an assembly of components comprised of an outer circumferential sulfur curable rubber tread, at least one sulfur curable rubber carcass ply supporting said tread and an inner sulfur curable halobutyl rubber tire innerliner layer, is prepared by:(A) positioning a layer of an uncured butyl rubber-based rubber composition, exclusive of sulfur curative, as a sealant layer precursor between said innerliner and rubber carcass, wherein said butyl rubber based composition has a storage modulus G′ (80° C.) in a range of from about 100 to about 400 kPa, wherein said sealant precursor butyl rubber composition is comprised of, based upon parts by weight per 100 parts of butyl rubber (phr): (1) 100 phr of butyl rubber as a copolymer of isobutylene and isoprene which contains about 0.5 to about 5 mole percent units derived from isoprene and, correspondingly about 95 to about 99.5 mole percent derived from isobutylene, and, based upon parts by weight per 100 parts of said butyl rubber (phr); (2) particulate filler comprised of about 5 to about 90 phr of rubber reinforcing carbon black and coal dust, and optionally (a) from zero to 6 phr of short fibers, and/or (b) from zero to about 20 phr of hollow glass microspheres; (3) from zero to about 20 phr of rubber processing oil, having a maximum aromatic content of about 15 weight percent; (4) from 1 to about 10 phr of liquid polyisoprene having a weight average molecular weight in a range of from about 35,000 to about 65,000; and (5) about 0.5 to about 10 phr of active organoperoxide compound; and (B) vulcanizing said tire assembly in a suitable mold at a temperature in a range of from about 150° C. to about 175° C. for a sufficient period of time to partially depolymerize said butyl rubber and thereby form a built-in sealant layer having a storage modulus property G′ (80° C.) in a range of from about 5 to about 50 kPa. 6. The tire of claim 5 wherein said organoperoxide is selected from at least one of tertbutyl perbenzoate, dialkylbenzene peroxides, 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane; 1,1-di-t-butyl peroxi-3,3,5-trimethyl cyclohexane; 2,5-dimethyl-2,5-di(t-butyl peroxy) hexyne-3; p-chlorobenzyl peroxide; 2,4-dichlorobenzyl peroxide; 2,2-bis-(t-butyl peroxi)-butane; di-t-butyl peroxide; benzyl peroxide; 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane, dicumyl peroxide; and 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane.7. The tire of claim 5 wherein said organoperoxide is comprised of dicumylperoxide.8. The tire of claim 5 wherein said filler is additionally comprised of about 0.5 to about 5 phr of short fibers selected from at least one of cotton fibers and synthetic fibers selected from at least one of rayon, aramid, nylon and polyester fibers, and their mixtures, wherein said cotton fibers have an average length of up to about 200 microns and said synthetic fibers have an average length of up to about 2,500 microns.9. The tire of claim 5 wherein said filler is additionally comprised of from about 5 to about 15 phr of hollow glass microspheres having an average diameter in a range of from about 20 to about 40 microns.