STYRENE/BUTADIENE RUBBER EXTENDED WITH LOW UNSATURATED SOYBEAN OIL AND TIRE WITH COMPONENT

Abstract

The invention relates to styrene/butadiene elastomer extended with a specialized soybean oil comprised of a low unsaturation containing soybean oil. The specialized soybean oil is a vegetable triglyceride soybean oil containing a high concentration of oleic acid ester and thereby a low unsaturation soybean oil. The invention relates to preparation of styrene/butadiene rubber extended with such specialized soybean oil, a prepared rubber composition and tires with component thereof. Such styrene/butadiene rubber is comprised of an organic solvent solution polymerization prepared styrene/butadiene elastomer.

Claims

1. A method of preparing an oil extended styrene/butadiene rubber (SSBR) comprised of blending a specialized soybean triglyceride oil with a cement comprised of organic solvent and styrene/butadiene rubber and recovering a composite from said cement comprised of said specialized soybean oil and SSBR, wherein said specialized soybean oil is comprised of mixed saturated and unsaturated fatty acid esters wherein the unsaturated ester portion of said specialized soybean oil is comprised of at least 65 percent of oleic acid ester.

2. The method of claim 1 for preparing a triglyceride vegetable oil extended organic solution polymerization prepared styrene/butadiene elastomer which comprises, based on parts by weight per 100 parts by weight of elastomer (phr): (A) anionically initiating polymerization of monomers comprised of styrene and 1,3-butadiene in an organic solvent solution to form a synthetic styrene/butadiene elastomer (SSBR) contained in a cement comprised of said SSBR and said solvent; (B) terminating said polymerization of said monomers in said cement; (C) blending from about 5 to about 60 phr of specialized soybean oil with said cement, and (D) recovering said SSBR as a composite comprised of said SSBR and said specialized soybean oil, wherein said specialized soybean oil is a vegetable triglyceride oil comprised of mixed mixed saturated, mono-unsaturated and polyunsaturated triglyceride esters of fatty acids having its unsaturated ester content comprised of at least about 65 percent of mono-unsaturated oleic acid.

3. The method of claim 1 wherein said unsaturated ester portion of said specialized soybean oil contains about 75 to about 95 percent mono-unsaturated oleic acid ester component and at least 1 percent linolenic acid ester component.

4. The method of claim 1 wherein said unsaturated ester portion of said specialized soybean oil contains about 75 to about 95 percent mono-unsaturated oleic acid ester and from about 1.5 to about 5 percent linolenic acid ester component.

5. The method of claim 1 wherein said SSBR is a tin or silicon coupled SSBR.

6. The method of claim 1 wherein said SSBR is a functionalized SSBR containing at least one functional group comprised of at least one of amine, siloxy, carboxyl and hydroxyl groups.

7. The method of claim 6 wherein said SSBR is a tin or silicon coupled SSBR.

8. The method of claim 2 wherein said SSBR is the product of an anionic initiated polymerization of styrene and 1,3-butadiene employing n-butyllithium as an initiator in the presence of an inert solvent.

9. A composite of said SSBR extended with specialized soybean oil wherein said specialized soybean oil is a vegetable triglyceride oil comprised of mixed saturated, mono-unsaturated and polyunsaturated triglyceride esters of fatty acids having its unsaturated ester content comprised of at least about 65 percent of mono-unsaturated oleic acid.

10. The rubber composition of claim 9 which contains a styrene/butadiene rubber (SSBR) extended with a specialized soybean oil.

11. The rubber composition of said claim 10 wherein said SSBR is an anionically initiated polymerization product of styrene and 1,3-butadiene monomers.

12. The rubber composition of claim 10 wherein said rubber composition contains at least one additional vegetable triglyceride oil comprised of at least one of sunflower oil, rapeseed oil, corn oil canola oil and additional soybean oil where the unsaturated ester of said additional soybean oil has a mono-unsaturated oleic acid ester content in a range of from about 15 to about 30 percent.

13. A tire having a component comprised of the rubber composition of claim 10.

14. A tire having a component comprised of the rubber composition of claim 11.

15. A tire having a component comprised of the rubber composition of claim 12.

16. A rubber composition comprised of, based upon parts by weight per 100 parts by weight rubber (phr): (A) conjugated diene-based elastomers comprised of: (1) about 50 to about 100 phr of specialized soybean oil extended SSBR composite of claim 10, and correspondingly (2) from about zero to about 50 phr of at least one additional elastomer comprised of at least one of polymers of at least one of isoprene and 1,3-butadiene and copolymers of styrene and at least one of isoprene and 1,3-butadiene; (B) about 40 to about 110 phr of reinforcing filler comprised of: (1) amorphous synthetic silica (e.g. precipitated silica), or (2) rubber reinforcing carbon black, or (3) combination of precipitated silica and rubber reinforcing carbon black; (C) silica coupling agent for said precipitated silica where said reinforcing filler contains precipitated silica having a moiety reactive with hydroxyl groups on said precipitated silica and another different moiety interactive with carbon-to-carbon double bonds of said conjugated diene-based elastomers, wherein said specialized soybean oil is a vegetable triglyceride oil comprised of mixed saturated, mono-unsaturated and polyunsaturated triglyceride esters of fatty acids having its unsaturated ester content comprised of at least about 65 percent of mono-unsaturated oleic acid.

17. A tire having a component of the rubber composition of claim 16 wherein said reinforcing filler is rubber reinforcing carbon black.

18. A tire having a component of the rubber composition of claim 16 where said reinforcing filler is a combination of rubber reinforcing carbon black and precipitated silica containing from about 20 to about 99 weight percent of said precipitated silica.

19. A tire having a component of the rubber composition of claim 16 where said reinforcing filler is a combination of rubber reinforcing carbon black and precipitated silica containing from about 20 to about 45 weight percent of said precipitated silica.

20. The rubber composition which contains a styrene/butadiene rubber (SSBR) extended with a specialized soybean oil of claim 9, wherein said specialized soybean oil is a vegetable triglyceride oil comprised of mixed saturated, mono-unsaturated and polyunsaturated triglyceride esters of fatty acids having its unsaturated ester content comprised of about 75 to about 95 percent of mono-unsaturated oleic acid and wherein the combination of saturated and unsaturated fatty acids is comprised of about 65 to about 90 percent of the mono-unsaturated oleic acid ester, with the remainder of the unsaturated fatty acid esters being comprised of poly-unsaturated fatty acid esters.

Description

EXAMPLE I

[0078] In this example, the effect of extending an organic solution anionic polymerized styrene and 1,3-butadiene monomers (SSBR) with a vegetable triglyceride soybean oil as a specialized soybean oil having a high mono-unsaturated oleic acid ester component is evaluated and compared to a more conventional soybean oil containing a significantly lower oleic acid ester component content.

[0079] Experiments were conducted to evaluate the effect of employing the specialized soybean oil for extension of an SSBR. By the term extension or extended it is meant that the soybean oil is added to and mixed with a low viscosity polymerization solvent cement of the soybean oil following which composite of the SSBR elastomer and soybean oil is recovered from the cement. The composite is then blended with rubber compounding ingredients to prepare the rubber composition. It is in contrast to simply mixing the SSBR and the soybean oil with rubber compounding ingredients in a rubber mixer to prepare the rubber composition.

[0080] Control rubber Sample A contained the SSBR extended by a more conventional soybean oil. (soybean oil pre-blended with the SSBR cement to form a composite thereof).

[0081] Experimental rubber Sample B contained the SSBR extended by the specialized soybean oil. (soybean oil pre-blended with the SSBR cement to form a composite thereof).

[0082] The rubber Samples were prepared by mixing the elastomers with reinforcing filler as rubber reinforcing carbon black without precipitated silica together in a first non-productive mixing stage (NP1) in an internal rubber mixer for about 4 minutes to a temperature of about 160 C. The resulting mixture was subsequently mixed in a second sequential non-productive mixing stage (NP2) in an internal rubber mixer to a temperature of about 160 C. with no additional ingredients added. The rubber composition was subsequently mixed in a productive mixing stage (P) in an internal rubber mixer with a sulfur cure package, namely sulfur and sulfur cure accelerator(s), for about 2 minutes to a temperature of about 115 C. The rubber composition is removed from its internal mixer after each mixing step and cooled to below 40 C. between each individual non-productive mixing stage and before the final productive mixing stage.

[0083] The basic formulation for the Control rubber Sample A using conventional soybean oil extended SSBR and Experimental rubber Sample B using specialized soybean oil extended SSBR. is presented in the following Table 1 expressed in parts by weight per 100 parts of rubber (phr) unless otherwise indicated.

TABLE-US-00001 TABLE 1 Parts by weight (phr) Non-Productive Mixing Stage (NP) Conventional soybean oil extended 110 or 0 (80 SSBR, SSBR.sup.1 30 soybean oil)* Specialized soybean oil extended 110 or 0 (80 SSBR, SSBR.sup.2 30 soybean oil)** Cis 1,4-polybutadiene elastomer.sup.3 20 Carbon black.sup.4 85 Wax, microcrystalline 1.5 Zinc oxide 2 Fatty acid.sup.5 3 Antioxidant 2 Productive Mixing Stage (P) Sulfur 1.4 Sulfur cure accelerator(s).sup.6 2.4 Antioxidant 0.7 *80 parts by weight SSBR, 30 parts by weight conventional soybean oil extension **80 parts by weight SSBR, 30 parts by weight specialized soybean oil extension .sup.1Composite of solution polymerization prepared styrene/butadiene rubber (SSBR) having a Tg of about 18 C., 30 percent bound styrene, 41 percent vinyl content for its butadiene portion and for this Example, extended with (thereby containing) 37.5 parts conventional soybean oil per 100 parts SSBR. The conventional soybean oil was a soybean plant-derived triglyceride oil from Cargill Dressings comprised of saturated and unsaturated fatty acid esters with a minor portion of its unsaturated fatty acid esters being mono-unsaturated oleic fatty acid ester comprised of about 32 percent oleic acid ester, about 68 percent poly-unsaturated fatty acid esters such as for example linoleic acid ester and linolenic acid ester. The saturated fatty acid esters may be, for example palmitic and stearic acid esters. .sup.2Composite of solution polymerization prepared styrene/butadiene rubber (SSBR) having a Tg of about 18 C., about 30 percent bound styrene, 41 percent vinyl content for its butadiene portion and, for this Example, extended with (thereby containing) 37.5 parts specialized soybean oil per 100 parts SSBR. The specialized soybean oil was a soybean oil obtained as Plenish soybean oil from DuPont as a blend of saturated and unsaturated fatty acid esters with the unsaturated fatty acid esters having a mono-unsaturation oleic acid ester content of about 89 percent, a di-unsaturation linoleic acid ester content of about 8 percent and a tri-unsaturation linolenic acid ester content of about 3 percent. .sup.3Cis 1,4-polybutadiene rubber as BUD1207 from The Goodyear Tire & Rubber Company .sup.4N330 rubber reinforcing carbon black, ASTM identification .sup.5Primarily comprised of stearic, palmitic and oleic acids .sup.6Sulfenamide and diphenylguanidine accelerators

[0084] The following Table 2 illustrates cure behavior and various physical properties of rubber compositions based upon the basic recipe of Table 1 and reported herein as a Control rubber Sample A and Experimental rubber Sample B. Where cured rubber samples are examined, such as for the stress-strain, hot rebound and hardness values, the rubber samples were cured for about 14 minutes at a temperature of about 160 C.

TABLE-US-00002 TABLE 2 Samples Control A Experimental B Materials (phr) Conventional soybean oil extended SSBR 110 (80 0 SSBR) Specialized soybean oil extended SSBR 0 110 (80 SSBR) Cis 1,4-polybutadiene rubber 20 20 Properties RPA.sup.1 (100 C.), Storage Modulus G, MPa Predictive Rubber Processing Uncured storage modulus G, 15% strain, 273 277 0.83 Hertz (kPa) Stiffness (greater is better for predictive tread rubber performance) (11 Hertz (kPa) Cured storage modulus G, 1% strain 2590 2735 Cured storage modulus G, 10% strain 1286 1378 Cured storage modulus G, 15% strain 1140 1224 Hysteresis Indication (lower is better for predictive hysteresis reduction) Tan delta at 1% strain 0.23 0.21 Tan delta at 10% strain 0.24 0.23 Tan delta at 15% strain 0.23 0.22 Rebound value of cured rubber, (%), 23 C. 30 31 Rebound value of cured rubber, (%), 100 C. 54 57 (higher rebound value is better for predictive hysteresis reduction) .sup.1Rubber Process Analyzer (RPA) instrument

[0085] In Table 2 it is seen that Experimental rubber Sample B containing the composite of SSBR extended with specialized soybean oil contain a high oleic acid ester component content (70 percent) thereby being of a significantly low unsaturation, yielded a rubber composition of a stiffness value (cured rubber storage modulus G value) of, for example at a 15 percent strain, 1224 kPa, which was a beneficial increase of the stiffness value (modulus G) compared to a value of 1140 kPa for the Control rubber composition A containing the composite of SSBR extended with the more conventional soybean oil containing a low oleic acid ester component content, thereby being a significantly higher unsaturation soybean oil.

[0086] In Table 2 it is also seen that Experimental rubber Sample B containing the low unsaturation specialized soybean oil yielded a rubber composition having a tan delta value of, for example, at a 15 percent strain, 0.22 which was beneficial reduction from a value of 0.23 for the Control rubber composition A containing significantly higher unsaturation conventional soybean oil. Therefore, the rubber composition of Experimental rubber Sample B was of a beneficially lower predictive hysteresis than the rubber composition of Control rubber Sample A which, in turn, was of a beneficially lower predictive internal heat generation for the rubber composition (Experimental rubber Sample B) during its dynamic use (service) and predictive of a beneficially lower rolling resistance (increased energy savings) for a tire with tread of such rubber composition.

[0087] It is concluded that, although the mechanism might not be fully understood, a significant and beneficial discovery was made for soybean oil extension of the SSBR with a specialized soybean oil of a high oleic acid ester content (89 percent of its unsaturated fatty acid content) compared to a more conventional soybean oil having a significantly lower (about 30 percent) oleic acid ester content of its unsaturated fatty acid ester. Such discovery may be a result of the high oleic acid ester content of the unsaturated ester portion of the specialized soybean oil and/or of the correspondingly lower unsaturation content of unsaturated ester portion of the specialized soybean oil.

[0088] 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.