PLASTICIZER SYSTEM AND RUBBER COMPOSITION FOR PNEUMATIC TIRE

Abstract

The invention relates to a plasticizer system for use in a tread rubber composition. The plasticizer system is partially derived from or devoid of petroleum-based oils and resins. The pneumatic tire has a tread of a rubber composition comprising, based on 100 parts by weight of elastomer (phr): from about 10 to about 60 phr of a solution polymerized styrene-butadiene rubber (SSBR) extended with an oil not derived from petroleum; and a plasticizer system comprised of (1) from about 4 to about 8 phr of a plasticizing oil not derived from petroleum, and (2) from about 10 to about 20 phr of a hydrocarbon plasticizing resin selected from styrene/α-methyl styrene resin and polyterpene plasticizing resin.

Claims

1. A pneumatic tire having a tread of a rubber composition comprising, based on 100 parts by weight of elastomer (phr): (A) conjugated diene-based elastomer comprised of: (1) from about 10 to about 60 phr of a solution polymerized styrene-butadiene rubber (SSBR) extended with an oil not derived from petroleum, and (2) from about 20 to about 100 phr of at least one additional conjugated diene-based elastomer comprised of at least one of polybutadiene, cis 1,4-polyisoprene rubber, and styrene/butadiene elastomer; and (B) a plasticizer system comprised of: (1) from about 4 to about 8 phr of a plasticizing oil not derived from petroleum, and (2) from about 10 to about 20 phr of a hydrocarbon plasticizing resin selected from a petroleum-derived hydrocarbon and a non-petroleum derived hydrocarbon.

2. The tire of claim 1, wherein the hydrocarbon plasticizing resin is styrene/α-methyl styrene resin.

3. The tire of claim 1, wherein the non-petroleum derived hydrocarbon resin is polyterpene plasticizing resin.

4. The tire of claim 1, wherein the plasticizing oil is a triglyceride vegetable oil comprised of at least one of soybean, sunflower, rapeseed, and canola oil.

5. The tire of claim 1, wherein the plasticizing oil is soybean oil.

6. The tire of claim 1, wherein the extending oil is a triglyceride vegetable oil.

7. The tire of claim 6, wherein the extending oil is soybean oil.

8. The tire of claim 1, wherein the at least one additional conjugated diene-based elastomer comprises from about 35 to about 50 phr of cis polybutadiene and from about 15 to about 35 phr of cis 1,4-polyisoprene rubber.

9. The tire of claim 1, wherein the solution polymerized styrene-butadiene rubber has a bound styrene content in a range of from about 9% to about 36% extended with 25 phr of soybean oil.

10. The tire of claim 1, wherein the hydrocarbon plasticizing resin has a Tg of from about +20° C. to about +60° C.

11. The tire of claim 1, wherein the polyterpene plasticizing resin has a Tg of from about +40° C. to about +80° C.

12. The tire of claim 1, wherein the plasticizer system is devoid of petroleum-derived resin and oil.

13. A plasticizer system for use with solution polymerized styrene-butadiene rubber (SSBR) extended with an oil not derived from petroleum, the system comprising, based on 100 parts by weight of elastomer (phr): (A) from about 4 to about 8 phr of a plasticizing oil not derived from petroleum; and (B) from about 10 to about 20 phr of a hydrocarbon plasticizing resin, the hydrocarbon plasticizing resin being one of a petroleum-derived hydrocarbon resin and a non-petroleum derived hydrocarbon resin.

14. The plasticizer system of claim 13, wherein the hydrocarbon plasticizing resin is styrene/α-methyl styrene resin.

15. The plasticizer system of claim 13, wherein the non-petroleum derived hydrocarbon resin is polyterpene plasticizing resin.

16. The plasticizer system of claim 13, wherein the plasticizing oil is a triglyceride vegetable oil comprised of at least one of soybean, sunflower, rapeseed, and canola oil.

17. The plasticizer system of claim 13, wherein the solution polymerized styrene-butadiene rubber (SSBR) is extended with a triglyceride vegetable oil.

18. The plasticizer system of claim 17, wherein the triglyceride vegetable oil is soybean oil.

19. A rubber composition comprising the plasticizer system of claim 17.

20. A pneumatic tire comprising a tread of the rubber composition of claim 19.

Description

EXAMPLE

[0051] In this example, the effect of the disclosed plasticizer system on the performance of a tread compound is illustrated. Rubber compositions were mixed in a multi-step mixing procedure following the recipes in Table 1. Standard amounts of curatives were also included. Rubber compounds were then cured in the tire and tested on vehicles for wet braking performance, rolling resistance (RR), and treadwear, with the results given in Table 2.

[0052] A Control rubber composition was prepared as Sample A with an emulsion polymerized SBR with petroleum oil.

[0053] For the Experimental rubber Sample B, the emulsion polymerized SBR was replaced with solution polymerized SSBR extended with soybean oil. The conventional petroleum-based rubber processing oil of Control Sample A was also replaced with soybean oil, with all other ingredients essentially being the same.

[0054] For the Experimental rubber Sample C, the composition of Sample B was modified by inclusion of polyterpene traction resin, with all other ingredients essentially being the same.

[0055] The basic formulations are illustrated in the following Table 1, which is presented in terms of parts per 100 parts by weight of rubber (phr).

TABLE-US-00001 TABLE 1 Samples Control Experimental A B C Polybutadiene.sup.1 45 45 40 Emulsion SBR.sup.2 28 0 0 Natural rubber 27 23 27 Solution SBR.sup.3 0 32 33 Petroleum oil 17.5 0 0 Soybean oil 0 6.4 6.6 Carbon Black 75 77 76 Antioxidant(s) 4.3 4.3 4.3 Stearic Acid 2 2 2 Traction Resin A.sup.4 3.5 15 0 Traction Resin B.sup.5 0 0 14 ZnO.sup.12 3.0 3.0 3.0 Sulfur.sup.13 1.7 1.7 1.7 Accelerator 1.1 1.2 1.2 .sup.1High cis polybutadiene, obtained as BUDENE1223 from The Goodyear Tire & Rubber Company. .sup.2Emulsion polymerized SBR obtained as Plioflex 1769 from The Goodyear Tire & Rubber Company. .sup.3Solution polymerized SBR with styrene content of 33%, extended with 25 phr soybean oil. .sup.4Copolymer of styrene and alpha-methylstyrene, Tg = +39° C., obtained as Sylvatraxx 4401 from Arizona Chemical. .sup.5Polyterpene resin, Tg = +60° C., obtained as Sylvatraxx 4150 from Arizona Chemical.

[0056] Various cured rubber properties of the Control A and Experimental Samples B-C are reported in the following Table 2 with the results for tires of treads formed from Control rubber composition A being normalized to values of 100 and results for experimental tires with treads of rubber compositions B and C being related to the normalized values.

[0057] The values of Control A tire are normalized to a value of 100 and the values for experimental Sample B and C tires are compared to the normalized values of 100 for Control A tire.

TABLE-US-00002 TABLE 2 Samples Control Experimental A B C Petroleum oil 7 0 0 Soybean oil 0 6.4 6.6 Traction Resin A.sup.1 3.5 15 0 Traction Resin B.sup.2 0 0 14 Wet braking (higher is better) 100 102 105 Rolling resistance (higher is 100 101 98 indication of beneficially lower rolling resistance) Treadwear (higher is better) 100 97 95 .sup.1Copolymer of styrene and alpha-methylstyrene, Tg = +39° C., obtained as Sylvatraxx 4401 from Arizona Chemical. .sup.2Polyterpene resin, Tg = +60° C., obtained as Sylvatraxx 4150 from Arizona Chemical.

[0058] As can be seen in Table 2, the overall performance properties of the rubber compositions B (partially devoid of petroleum-based plasticizer) and C (completely devoid of petroleum-based plasticizer) compared favorably with the performance properties of the Control Sample A.

[0059] It is further seen that the wet braking performance of Samples B (partially devoid of petroleum-based plasticizer) and C (completely devoid of petroleum-based plasticizer) improved over that of Control Sample A.

[0060] From Table 2, it is further seen that pneumatic tires with treads of Sample C (completely devoid of petroleum-based plasticizer) exhibited a wet braking performance value of 105, which is significantly improved over the normalized value of 100 for treads formed from the rubber composition of Control Sample A.

[0061] It is further seen that the rolling resistance of Sample B (partially devoid of petroleum-based plasticizer) improved over that of Control Sample A and the rolling resistance of Sample C is similar to that of Control Sample A.

[0062] It is further seen that the treadwear performances of Samples B and C are similar to that of Control Sample A.

[0063] It is hereby concluded that, for tire treads formed from rubber compositions partially or completely devoid of petroleum-based plasticizer, the overall balance of rubber performances is maintained or improved when the plasticizer includes a triglyceride vegetable oil (as extender oil in the solution SBR) and at least an aromatic hydrocarbon resin. It is further concluded that, for tire treads formed from rubber compositions partially or completely devoid of petroleum-based products, wet braking is significantly improved when the plasticizer includes a triglyceride vegetable oil (as extender oil in the solution SBR) and a hydrocarbon resin selected from an aromatic hydrocarbon and a non-petroleum derived hydrocarbon, such as polyterpene.

[0064] 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.