The invention relates to a tire having a circumferential tread of a cap/base configuration composed of an outer tread rubber cap layer with a running surface of the tread and an underlying tread rubber base layer, wherein said tread cap layer is composed of two longitudinal adjacent zones, namely a primary tread cap zone and a minor lateral outboard control element (zone). The primary tread cap zone and the lateral outboard tread cap element provide a significant gradation of cold dynamic storage moduli (G′) at −25° C. and hot tan delta values at 100° C., yet similar warm dynamic storage moduli (G′) at 60° C. The primary tread cap zone and lateral outboard control tread cap element are load bearing in the sense of extending from the running surface of the tread radially inward to the unitary (non-zoned) tread base rubber layer. The zoned rubber tread cap layer and unitary rubber tread base layer are an integral tread composite in a sense of being co-extruded. In one aspect of the invention, the primary tread cap zone rubber composition is silica-rich and the lateral, outboard element rubber composition is carbon black-rich and which furthermore provide a gradation of filler reinforcement content; provide a gradation of silica to carbon black ratio and provide a gradation of cis 1,4-polybutadiene rubber content.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the invention, drawings are provided. In particular,
FIG. 1 is provided as depicting a partial cross-sectional view of a cap/base configured tread portion of a pneumatic tire.
FIG. 2 is a graphical presentation of temperature sweep for dynamic storage modulus (G′) values.
Claims
1. A tire having a rubber tread of a cap/base construction comprised of an outer, zoned rubber tread cap layer having an outer running surface and an underlying internal rubber tread base layer of a unitary rubber composition, wherein said tread cap layer is comprised of two adjoining circumferential, longitudinal tread cap rubber zones of graduated physical properties, wherein said tread cap zones individually extend from the running surface of said tread cap layer radially inward to said tread base layer:
wherein said tread cap zones are comprised of a primary tread cap zone and a lateral, outboard control tread cap zone; wherein said primary tread cap zone spans from 70 to about 85 percent of the axial width of the free running surface of said tire tread cap layer and wherein said lateral, outboard control tread cap zone spans from about 15 to 30 percent of axial width of the free running surface of said tire tread cap layer and is positioned adjacent to and axially outward from said primary tread cap zone;wherein the storage modulus G′ at −25° C., 3 percent strain and 10 Hertz of the rubber composition of said primary tread cap zone is at least about 6 MPa less than such storage modulus G′ at −25° C. of said lateral, outboard control tread cap zone;wherein the storage modulus G′ at 60° C., 3 percent strain and 10 Hertz of the rubber composition of said primary tread cap zone is within about 2 MPa of such storage modulus G′ at 60° C. of said lateral, outboard control tread cap zone;wherein the tan delta value at 100° C., 3 percent strain and 10 Hertz of the rubber composition of said lateral, outboard tread cap zone is at least 10 percent greater than such tan delta value of the rubber composition of said primary tread cap zone.
2. The tire of claim 1:
wherein the rubber composition of said primary cap zone is comprised of, based on parts by weight per 100 parts by weight rubber (phr) and so long as said storage moduli G′ and tan delta values are met:(A) 100 phr of at least three conjugated diene-based elastomer(s) comprised of:
(1) about 40 to about 70 phr of cis 1,4-polybutadiene elastomer,(2) about 30 to about 60 phr of organic solution polymerization prepared styrene/butadiene elastomers having a bound styrene content in a range of from about 20 to about 40 percent and a vinyl 1,2-content in a range of from about 20 to about 55 percent comprised of a styrene/butadiene elastomer (SBR-1), and amine functionalized styrene/butadiene elastomer (SBR-2), with a weight ratio of said SBR-1 to said SBR-2 in a range of from about 70/30 to about 40/60;(B) reinforcing filler in a range of from about 90 to about 135 phr comprised of:
(1) precipitated silica in a range of from about 75 to about 120 phr, and(2) rubber reinforcing carbon black in a range of from about 5 to about 15 phr, and(C) coupling agent for said silica having a moiety reactive with hydroxyl groups contained on the surface of said precipitated silica another moiety interactive with diene-based elastomers;wherein the rubber composition of said lateral outboard tread cap zone is comprised of, based on parts by weight per 100 parts by weight rubber (phr) and so long as said storage modulus G′ values are met:(D) 100 phr of at least two conjugated diene-based elastomer(s);
(1) from zero to about 40 phr of cis 1,4-polybutadiene elastomer,(2) about 60 to about 100 phr of organic solution polymerization prepared styrene/butadiene elastomers having a bound styrene content in a range of from about 20 to about 40 percent and a vinyl 1,2-content in a range of from about 20 to about 55 percent comprised of a styrene/butadiene elastomer (SBR-1), and amine functionalized styrene/butadiene elastomer (SBR-2), with a weight ratio of said SBR-1 to said SBR-2 in a range of from about 70/30 to about 40/60;(E) reinforcing filler in a range of from about 50 to about 120 phr, wherein the content of said reinforcing filler is at least 10 phr less than the content of reinforcing filler of the rubber composition of said primary tread cap zone, comprised of:
(1) precipitated silica within a range of from zero to about 45 phr, and(2) rubber reinforcing carbon black within a range of from about 30 to about 120 phr, wherein the content of said rubber reinforcing carbon black content is at least 5 phr greater than the content of said aid precipitated silica, and(F) coupling agent for said silica having a moiety reactive with hydroxyl groups contained on the surface of said precipitated silica another moiety interactive with diene-based elastomers.
3. The tire of claim 1:
wherein the rubber composition of said primary tread cap zone has a dynamic storage modulus (G′) at −25° C., 3 percent strain and 10 Hertz in a range of about 10 to about 30 MPa and a dynamic storage modulus (G′) at 60° C., 3 percent strain and 10 Hertz in a range of from about 3.5 to about 5.5 MPa, andwherein the rubber composition of said lateral tread cap zone outboard control zone has a dynamic storage modulus (G′) at −25° C., 3 percent strain and 10 Hertz in a range of about 25 to about 45 MPa and dynamic storage modulus (G′) at 60° C., 3 percent strain and 10 Hertz in a range of from about 2 to about 4 MPa;
4. The tire of claim 1 wherein the tan delta (100° C.) property at 3 percent strain and 10 hertz of the rubber composition of said lateral outboard control tread cap zone is in a range of from about 0.15 to about 0.35 and the tan delta property of the rubber composition of said primary tread cap zone is in a range of from about 0.05 to about 0.25.
5. The tire of claim 4 wherein the tan delta (100° C.) property at 3 percent strain and 10 hertz of the rubber composition of said lateral outboard control tread cap zone is in a range of from about 0.15 to about 0.35 and the tan delta property of the rubber composition of said primary tread cap zone is in a range of from about 0.05 to about 0.25.
6. The tire of claim 2 wherein the rubber compositions of at least one of said primary tread cap zone and lateral outboard tread cap zones contain at least one additional conjugated diene-based elastomer so long as said dynamic storage moduli values at −25° C. and 60° C. and said tan delta (100° C.) values are met.
7. The tire of claim 6 wherein said additional elastomers for at least one of said primary tread cap zone and lateral outboard control tread cap zone are selected from at least one of, so long as said dynamic storage moduli (G′) at −25° C. and 60° C. and tan delta (100° C.) values are met, isoprene/butadiene rubber, trans 1,4-polybutadiene, low vinyl polybutadiene having vinyl content in a range of 5 to about 20 percent, high vinyl polybutadiene having a vinyl content in a range of from about 20 to about 90 percent and 3,4-polyisoprene rubber.
8. The tire of claim 2 wherein said amine functionalized styrene/butadiene elastomer (SBR-2) is functionalized with amine substituents comprised of at least one of primary and amine groups.
9. The tire of claim 8 wherein said amine substituents are comprised of at least one secondary amine comprised of an N-methyl amine
10. The tire of claim 1 wherein tire is designed to be positioned on a vehicle with said lateral, outboard control zone of said tread cap positioned axially outboard of the associated vehicle.
11. The tire of claim 2 wherein the rubber compositions of the tread cap layer composed of said primary tread cap zone and lateral outboard tread cap zone and said tread base rubber layer are an integral tread component in the sense of being co-extruded.
12. The tire of claim 1 wherein the junction of said primary tread cap zone and said lateral outboard control element tread cap zone is positioned within a circumferential grooves between said tread cap zones.
13. The tire of claim 1 wherein the axial span of the total running surface of the tread cap layer is up to 15 percent greater than the span of the free running surface of the tread.
14. The tire of claim 2 wherein at least one of said tread cap zones contains from about 1 to about 15 phr of short fibers selected from at least one of glass, polyester, nylon, aramid, carbon, rayon and cotton fibers.
15. The tire of claim 2 wherein at least one of said tread cap zones contains from about 1 to about 5 phr of at least one of particulate inorganic granules and organic granules, in addition to said rubber reinforcing carbon black and said precipitated silica, having an average diameter in a range of from about 50 to about 200 microns.
16. The tire of claim 2 wherein said tread base rubber layer is a single rubber composition comprised of at least one conjugated diene-based elastomer.
17. The tire of claim 16 wherein said tread base rubber layer is comprised of cis 1,4-polyisoprene rubber which contains carbon black in a range of from about 30 to about 70 phr and from zero to about 25 phr of precipitated silica.
18. The tire of claim 2 wherein said coupling agent is:
(A) a bis-(3-triethoxysilylpropyl)polysulfide having an average of from 2 to about 4 connecting sulfur atoms in its polysulfidic bridge, or(B) a bis-(3-triethoxysilylpropyl)polysulfide having an average of from about 2 to about 2.6 connecting sulfur atoms in its polysulfidic bridge and a bis-(3-triethoxysilylpropyl)polysulfide having an average of from about 3.4 to about 4 connecting sulfur atoms in its polysulfidic bridge, wherein said polysulfide having an average of from 2 to about 2.6 connecting sulfur atoms in its polysulfidic bridge (to the exclusion of such polysulfide having an average of from 3 to 4 connecting sulfur atoms in its polysulfidic bridge) is blended with said rubber composition in the absence of sulfur and sulfur vulcanization accelerator and wherein said polysulfide having an average of from about 3.4 to about 4 connecting sulfur atoms in its polysulfidic bridge is thereafter blended with said rubber composition in the presence of sulfur and at least one sulfur vulcanization accelerator, or(C) an organoalkoxymercaptosilane composition of the general Formula (I) represented as:
(X)n(R7O)3-n—Si—R8—SH (I)wherein X is a radical selected from chlorine, bromine, and alkyl radicals having from one through 4, carbon atoms; wherein R7 is an alkyl radical having from 1 through 18 carbon atoms; wherein R8 is an alkylene radical having from one 1 through 4 carbon atoms; and n is an average value of from zero through 3, and wherein in such cases where n is zero or 1, R7 may be the same or different for each (R7O) moiety in the composition, and(D) said organalkoxyomercaptosilane of the general Formula (I) capped with a moiety which uncaps the organoalkoxymercaptosilane upon heating to an elevated temperature.
19. The tire of claim 18 wherein said coupling agent is comprised of an organoalkoxymercaptosilane selected from at least one of triethoxy mercaptopropyl silane, trimethoxy mercaptopropyl silane, methyl dimethoxy mercaptopropyl silane, methyl diethoxy mercaptopropyl silane, dimethyl methoxy mercaptopropyl silane, triethoxy mercaptoethyl silane, tripropoxy mercaptopropyl silane and 3-octanoylthio-1-propyltriethoxysilane.
20. The tire of claim 2 wherein said coupling agent is composite of precipitated silica and said coupling agent.
Patent Application
20070175557
