TIRE WITH TREAD CONTAINING VEGETABLE OIL EXTENDED HIGH TG STYRENE/BUTADIENE ELASTOMER AND TRACTION RESIN

Abstract

This invention relates to a tire with high performance tread of rubber composition for promoting tread durability and traction. For such purpose, a tread rubber composition is provided which contains a high Tg solvent solution polymerization prepared styrene/butadiene elastomer (SSBR) together with precipitated silica reinforcement and traction resin. The invention includes extension of the uncured high Tg SSBR by triglyceride vegetable oil instead of petroleum based oil.

Claims

1. A pneumatic tire is provided having a rubber tread intended to be ground-contacting, where said tread is comprised of a rubber composition comprised of, based on parts by weight per 100 parts by weight elastomer (phr): (A) conjugated diene-based elastomers comprised of: (1) from about 25 to 60 phr of high Tg styrene/butadiene elastomer (SSBR) pre-extended with vegetable triglyceride oil, wherein said SSBR has a Tg in a range of from about −20° C. to about +10° C. and a bound styrene content in a range of from about 25 to about 50 percent; (2) from 75 to 40 phr of at least one additional conjugated diene-based elastomer comprised of at least one of polybutadiene and cis 1,4-polyisoprene rubber; (B) about 50 to about 200 phr of reinforcing filler comprised of a combination of rubber reinforcing carbon black and precipitated silica where the reinforcing filler is comprised of from about 50 to about 100 weight percent precipitated silica, where said reinforcing filler further contains silica coupler for said precipitated silica having a moiety reactive with hydroxyl groups on said precipitated silica and another different moiety interactive with said diene-based elastomers; and (C) about 5 to about 50 phr of traction promoting resin comprised of at least one of styrene/alphamethylstyrene copolymer resin, terpene-phenol resin, coumarone-indene resin, petroleum hydrocarbon resin, terpene polymer resin, and rosin derived resin and modified rosin acid resin, desirably comprised of styrene/alphamethylstyrene resin.

2. The tire of claim 1 where said high Tg SSBR is extended with about 5 to about 40 parts by weight vegetable triglyceride oil per 100 parts by weight of said high Tg SSBR.

3. The tire of claim 1 wherein said vegetable triglyceride oil is soybean oil.

4. The tire of claim 1 wherein said high Tg SSBR has a vinyl 1,2-content in a range of from about 10 to about 80 percent based on butadiene content.

5. The tire of claim 1 wherein said coupling agent is comprised of bis(3-triethoxysilylpropyl) polysulfide having an average of connection sulfur atoms in its polysulfide bridge in a range of from about 2 to about 4 sulfur atoms, or organoalkoxymercaptosilane or combination thereof.

6. The tire of claim 1 wherein said precipitated silica is pre-treated with at least one of said coupling agents.

7. The tire of claim 1 wherein said traction promoting resin for said tread rubber composition is comprised of at least one of said styrene/alphamethylstyrene resin and terpene-phenol resin.

8. The tire of claim 1 where said triglyceride vegetable oil is comprised of at least one of sunflower oil, rapeseed oil, canola oil, palm oil and soybean oil.

9. The tire of claim 1 wherein said SSBR is an end-functionalized styrene/butadiene elastomer with functional groups reactive with hydroxyl groups on said precipitated silica comprised of at least one of alkoxy, amine, siloxy and thiol groups.

10. The tire of claim 1 wherein said SSBR is tin or silicon coupled.

Description

EXAMPLE 1

[0044] In this example, four rubber compositions are evaluated. Rubber compounds were mixed in a multistep mix procedure following the formulations as given in Table 1, with all amounts in phr. Mixed samples were cured and tested for various physical properties, as given in Table 2. In Table 2 various physical properties of the rubber compositions of Control rubber Sample C-1 and Experimental rubber Samples E-1, E-2 and E-3 are reported. The rubber samples were cured at a temperature of about 170° C. for about 10 minutes.

TABLE-US-00001 TABLE 1 C-1 E-1 E-2 E-3 ESBR.sup.1 60 0 0 0 Polybutadiene.sup.2 30 40 45 45 Natural Rubber 10 10 0 0 SSBR.sup.3 0 50 55 55 Soybean oil (as extension oil in SSBR) 0 10 11 11 Soybean oil (freely added to mixer) 0 12.5 5.5 0 Petroleum oil (as extension in ESBR) 22.5 0 0 0 Hydrocarbon traction resin.sup.4 24 24 30 30 Precipitated silica 80 80 80 80 Silane coupling agent 7.4 7.4 6.4 6.4 Carbon black 11 11 10 10 Antidegradants 4.5 4.5 4.5 4.5 Stearic acid 3 3 3 3 Sulfur 1.2 1.5 1.4 1.4 Zinc oxide 1.75 1.75 1.75 1.75 Cure Accelerators 3.5 4.0 3.9 3.9

[0045] .sup.1Emulsion polymerization prepared styrene/butadiene elastomer (ESBR), extended with 37.5 parts by weight petroleum based rubber processing oil per 100 parts by weight of SSBR, where the ESBR has a moderate Tg of about −55° C. as PLF1763.

[0046] .sup.2Cis 1,4-polybutadiene rubber having a cis 1,4-content of at least about 95 percent and a Tg of about −104° C. as BUD1223™ from The Goodyear Tire & Rubber Company prepared by neodymium based catalysis of 1,3-butadiene monomer.

[0047] .sup.3Solution polymerization prepared styrene/butadiene elastomer (SSBR), extended with 20 parts by weight soybean oil per 100 parts by weight of SSBR, where the SSBR has a high Tg of about −14° C. and a styrene content of about 33 percent and a vinyl 1,2-content based on its polybutadiene component of about 54 percent as SLF33SOY from The Goodyear Tire & Rubber Company. The SSBR is reported in Table 1 in terms of the dry elastomer SSBR with the extension soybean oil reported on a separate line.

[0048] .sup.4Traction promoting resin as styrene-alphamethylstyrene copolymer having a softening point in a range of about 80° C. to 90° C. (ASTM E28) obtained as Sylvatraxx4401 from Arizona Chemicals.

TABLE-US-00002 TABLE 2 Sample C-1 E-1 E-2 E-3 Wet predictive properties Rebound at 0° C. (lower is better) 18 15 11 11 TanDelta at 0° C. (higher is better) 0.40 0.40 0.55 0.58 Winter predictive properties G′ at −20° C. (MPa) (lower is better) 14.0 12.4 19.6 27.8 Lab abrasion properties DIN volume loss (lower is better) 76 80 83 71
E-1 vs. C-1

[0049] When replacing ESBR with a higher Tg SSBR for improved wet performance, use of low Tg soybean oil in place of petroleum oil allows for simultaneous improvement in winter predictive properties without a significant change in lab abrasion.

E-2 and E-3 vs. E-1

[0050] Reducing soybean oil loading while holding all other ingredients constant results in a substantial decline in predicted winter performance while offering only a slight improvement in predicted wet performance and similar lab abrasion properties.

EXAMPLE 2

[0051] In this example, four rubber compositions are evaluated. Rubber compounds were mixed in a multistep mix procedure following the formulations as given in Table 3, with all amounts in phr. Mixed samples were cured and tested for various physical properties, as given in Table 4. In Table 2 various physical properties of the rubber compositions of Control rubber Sample C-2 and Experimental rubber Samples E-4 and E-5 are reported. The rubber samples were cured at a temperature of about 170° C. for about 10 minutes.

TABLE-US-00003 TABLE 3 C-2 E-4 E-5 ESBR.sup.1 35 0 0 Polybutadiene.sup.2 45 50 55 Natural Rubber 20 20 15 SSBR.sup.3 0 30 30 Soybean oil (as extension oil in SSBR) 0 6 6 Petroleum oil (as extension in ESBR) 13 0 0 Hydrocarbon traction resin.sup.4 9 9 15 Precipitated silica 70 70 70 Silane coupling agent 5.6 5.6 5.6 Carbon black 22 17 17 Antidegradants 4.5 4.5 4.5 Stearic acid 3 3 3 Sulfur 1.2 1.4 1.4 Zinc oxide 1.75 1.75 1.75 Cure Accelerators 2.5 2.7 2.7
.sup.1Emulsion polymerization prepared styrene/butadiene elastomer (ESBR), extended with 37.5 parts by weight petroleum based rubber processing oil per 100 parts by weight of SSBR, where the ESBR has a moderate Tg of about −55° C. as PLF1763.

[0052] .sup.2Cis 1,4-polybutadiene rubber having a cis 1,4-content of at least about 95 percent and a Tg of about −104° C. as BUD1223TM from The Goodyear Tire & Rubber Company prepared by neodymium based catalysis of 1,3-butadiene monomer.

[0053] .sup.3Solution polymerization prepared styrene/butadiene elastomer (SSBR), extended with 20 parts by weight soybean oil per 100 parts by weight of SSBR, where the SSBR has a high Tg of about −14° C. and a styrene content of about 33 percent and a vinyl 1,2-content based on its polybutadiene component of about 54 percent as SLF33SOY from The Goodyear Tire & Rubber Company. The SSBR is reported in Table 1 in terms of the dry elastomer SSBR with the extension soybean oil reported on a separate line.

[0054] .sup.4Traction promoting resin as styrene-alphamethylstyrene copolymer having a softening point in a range of about 80° C. to 90° C. (ASTM E28) obtained as Sylvatraxx4401 from Arizona Chemicals.

TABLE-US-00004 TABLE 4 Sample C-2 E-4 E-5 Wet predictive properties Rebound at 0° C. (lower is better) 30 27 24 TanDelta at 0° C. (higher is better) 0.31 0.33 0.34 Winter predictive properties G′ at −20° C. (MPa) (lower is better) 14.0 14.4 14.5 Lab abrasion properties DIN volume loss (lower is better) 31 31 31
E-4 and E-5 vs. C-2

[0055] When replacing ESBR with a higher Tg SSBR for improved wet performance, use of low Tg soybean oil in place of petroleum oil allows for improvement in wet predictive properties without a significant change in winter predictive property and lab abrasion.

[0056] Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.