RUBBER COMPRISED OF PRODUCT OF DIENE-BASED ELASTOMER, BRANCHED POLYETHYLENIMINE OLIGOMER AND REINFORCING FILLER, AND TIRE WITH COMPONENT

Abstract

The invention relates to rubber comprised of a reaction product of at least one diene-based elastomer, branched polyethylenimine oligomer and filler reinforcement comprised of at least one of rubber reinforcing carbon black and precipitated silica. The invention further relates to a tire with a component comprised of such rubber composition.

Claims

1. A method of preparing a rubber composition is provided wherein said rubber composition is comprised of, based on parts by weight per 100 parts by weight rubber (phr): (A) 100 phr of at least one conjugated diene-based elastomer, (B) about 0.05 to about 1 phr of branched polyethylenimine oligomer, (C) about 30 to about 130 phr of reinforcing filler comprised of combination of rubber reinforcing carbon black and precipitated silica, (D) 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 elastomer(s), and (E) about 0.1 to about 8 phr of zinc oxide and from about 0.5 to about 8 phr of fatty acid, wherein said method comprises blending said elastomer(s), reinforcing filler, branched polyethylenimine oligomer, coupling agent for said precipitated silica reinforcing filler, zinc oxide and fatty acid in at least two preparatory (non-productive) sequential mixing steps followed by a blending sulfur curative and at least one sulfur vulcanization accelerator in a subsequent final (productive) mixing step; wherein said zinc oxide and fatty acid are blended in preparatory mixing step subsequent to a preparatory mixing step in which the said polyethylenimine oligomer is blended with said rubber composition.

2. The method of claim 1 wherein the weight ratio of zinc oxide to fatty acid is in a range of from about 1/5 to about 1/1,

3. The method of claim 1 wherein the silica coupler and precipitated silica are added to the rubber composition to interact together in situ within the rubber composition.

4. The method of claim 1 wherein the silica coupler is pre-reacted with the precipitated silica to form a composite thereof which is added to the rubber composition.

5. The method of claim 1 wherein said fatty acid is comprised of at least one of stearic acid, palmitic acid and oleic acid any mixture thereof.

6. The method of claim 1 wherein at least one additive selected from carboxylic acid which contains a phenolic moiety, salicylic acid and methylated salicylic acid is blended with said rubber composition in a said preparatory and/or productive mixing step.

7. The method of claim 6 wherein said additive is a carboxylic acid which contains a phenolic moiety.

8. The method of claim 7 wherein said additive is comprised of p- or m-hydroxy benzoic acid.

9. The method of claim 6 wherein said additive is salicylic acid.

10. The method of claim 6 wherein said additive is methylated salicylic acid.

11. The method of claim 1 wherein salicylic acid is blended with said rubber composition in a said preparatory mixing step in a weight ratio of from about 1/1 to about 1/3 of said polyethylenimine to salicylic acid

12. A rubber composition prepared by the method of claim 1.

13. A rubber composition prepared by the method of claim 2.

14. A rubber composition prepared by the method of claim 3.

15. A rubber composition prepared by the method of claim 4.

16. A rubber composition prepared by the method of claim 5.

17. A rubber composition prepared by the method of claim 6.

18. A rubber composition prepared by the method of claim 7.

19. A tire having a tread comprised of the rubber composition of claim 12.

20. A tire having a tread comprised of the rubber composition of claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0028] The drawing is provided to illustrate a prospective branched polyethylenimine oligomer and to illustrate a prospective composite of a branched polyethylenimine oligomer, elastomer as a diene-based polymer and precipitated silica particles.

[0029] The Drawing

[0030] FIG. 1 (FIG. 1) of the drawing presents a prospective chemical structure of a highly branched polyethylenimine oligomer.

[0031] FIG. 2 (FIG. 2) of the drawing presents a prospective composite comprised of a highly branched polyethylenimine oligomer which couples an elastomer (polymer chain) composed of a diene-based elastomer (the diene-portion of the elastomer not shown) to precipitated silica reinforcing filler particles (silica particles) through an interaction of amine groups of the polyethylenimine oligomer with hydroxyl groups contained on the precipitated silica filler particles.

[0032] The precipitated silica, rubber reinforcing carbon black and PEI (oligomer) can be mixed with the rubber composition in one or more non-productive mix stages. Zinc oxide and salicylic acid are preferably added subsequent to the branched PEI oligomer addition and, more preferably, in a subsequent non-productive mixing stage to minimize their premature interaction with the branched PEI oligomer. In a subsequent and final mixing stage, sulfur curative and cure accelerator(s) are then mixed with the rubber composition. The terms “non-productive” and “productive” mix stages are well known to those having skill in the rubber mixing art.

[0033] The following Example is presented to illustrate one aspect of the invention and is not intended to be limiting. The parts and percentages are by weight unless otherwise designated.

EXAMPLE I

[0034] An exemplary Control rubber Sample A and exemplary Experimental rubber Samples B, C and D are provided to illustrate preparation of rubber compositions.

[0035] Control rubber Sample A is composed of diene-based elastomers and reinforcing filler as precipitated silica with a minimal content of carbon black.

[0036] Experimental rubber Sample B is similar to Control rubber Sample A except that it contains the branched polyethylenimine oligomer and the salicylic acid as a vulcanization retarder (scorch retarder).

[0037] For this Example, both zinc oxide and fatty acid were blended subsequent to (in a mixing step subsequent to) addition of the branched polyethylenimine oligomer to minimize a pre-mature interaction of the polyethylenimine oligomer with the zinc oxide and fatty acid and to therefore maximize reactions of the branched polyethylenimine oligomer with the diene-based elastomers, precipitated silica and carbon black.

[0038] Experimental rubber Samples C and D are similar to Experimental rubber Sample B except for higher loadings of the branched polyethylenimine oligomer and the salicylic acid.

[0039] The basic formulation for the Control rubber Sample A and Experimental rubber Samples B, C and D are illustrated in the following Table 1 where the ingredients are expressed in terms of parts by weight per 100 parts of rubber (phr) unless otherwise indicated.

[0040] The rubber compositions may be prepared, for example, by mixing the ingredients in at least two sequential preparatory (non-productive) mixing steps (e.g. NP1 and NP2) at an elevated temperature without sulfur and sulfur cure accelerators which are thereafter added in a final (productive) mixing step (PR) usually at a lower mixing temperature. The rubber composition may then sheeted out and cooled to below 50° C. between each of the non-productive mixing steps and prior to the productive mixing step. Rubber mixing steps involving non-productive and productive mixing steps are generally well known to those having skill in such art.

[0041] For this Example the branched polyethylenimine oligomer, zinc oxide and fatty acid are blended in non-productive mixing steps with the rubber composition in a mixing step separate from and subsequent to the addition of the is branched polyethylenimine oligomer.

TABLE-US-00001 TABLE 1 Non-Productive Parts (phr) Mixing Step (NP1) Control A Exp B Exp C Exp D SSBR rubber 67 67 67 67 (styrene/butadiene rubber).sup.1 Cis 1,4-polybutadiene rubber.sup.2 33 33 33 33 Carbon black, rubber reinforcing 5 5 5 5 (N330).sup.3 Precipitated silica.sup.4 95 95 95 95 Silica coupler.sup.5 7.6 7.6 7.6 7.6 Wax, crystalline and paraffin 1.5 1.5 1.5 1.5 Rubber processing oil 28 28 28 28 Antioxidant(s) 3 3 3 3 Branched polyethylenimine 0 0.2 0.4 0.6 oligomer Zinc oxide 2 0 0 0 Fatty acid.sup.6 5 0 0 0 Non-Productive Mixing Step (NP2) Zinc oxide 0 2 2 2 Fatty acid.sup.6 0 5 5 5 Salicylic acid 0 0.4 0.8 1.2 Productive Mixing Step (PR) Sulfur 1.6 1.6 1.6 1.6 Accelerator(s).sup.8 2.8 2.8 2.8 2.8 .sup.1Styrene/butadiene elastomer (SSBR) prepared by solvent solution polymerization and end-functionalized with what is understood to be alkoxy and a combination of amine and thiol functional groups and having a styrene content of about 21 percent rubber as SLR4606 ™ from Trinseo .sup.2Cis 1,4-polybutadiene rubber as BUD1223 ™ from The Goodyear Tire & Rubber Company .sup.3Rubber reinforcing carbon black as N330, an ASTM designation .sup.4Precipitated silica as Zeosil 1165MP ™ from Solvay .sup.5Silica coupler comprised of a bis(3-triethoxysilylpropyl) polysulfide containing an average from about 2 to about 2.6 connecting sulfur atoms in its polysulfidic bridge as Si266 ™ from Evonik .sup.6Mixture of fatty acids comprised of stearic, palmitic and oleic acids .sup.7Polyethylenimine oligomer as a branched polyethylenimine oligomer from Sigma Aldridge .sup.8Sulfenamide sulfur cure accelerator

[0042] The following Table 2 represents the uncured and cured behavior and various physical properties of the rubber compositions based upon the basic formulation of Table 1 and reported for Control rubber Sample A and Experimental rubber Samples B, C and D.

TABLE-US-00002 TABLE 2 Non-Productive Samples (phr) Mixing Step (NP1) Control A Exp B Exp C Exp D SSBR elastomer 67 67 67 67 Cis 1,4-polybutadiene rubber 33 33 33 33 Rubber reinforcing carbon black 5 5 5 5 Precipitated silica 95 95 95 95 Polyethylenimine, branched 0 0.2 0.4 0.6 oligomer Salicylic acid 0 0.4 0.8 1.2 Properties RPA test (Rubber Process Analyzer), 10% strain, 11 Hertz, 100° C. Storage modus G′ (MPa) 2.2 1.9 2.1 2.2 Tan delta 0.13 0.11 0.12 0.12 Rebound (60° C.), (higher is 51 58 56 53 better) (percent) DIN abrasion (lower is better).sup.1 123 101 106 109 Stress-strain Tensile strength (MPa) 14.1 14.9 14.2 13.7 Elongation at break (%) 376 367 348 335 300% modulus, ring, (MPa) 12 13 13.1 13.5 Cure: MDR test, 150° C. Delta torque (dN-m) 20.7 17 17.7 17.6 T25 (minutes) 9.2 7.5 6.6 5.9 T90 (minutes) 16.8 13.9 12.2 10.8 .sup.1DIN53516, relative volume loss

[0043] It can be seen from Table 2 that the addition of 0.2 phr of the branched polyethylenimine oligomer significantly and beneficially reduced the hysteresis of the rubber composition as evidenced by the increased 60° C. rebound value of 58 percent which is about a 14 percent beneficial improvement for Experimental rubber Sample B as compared to a value of 51 percent for Control rubber Sample A which is believed be an indication of better elastomer/silica filler interaction via the branched PEI oligomer.

[0044] It can further be seen from Table 2 that the addition of 0.2 phr of the branched polyethylenimine oligomer significantly and beneficially increased the DIN abrasion resistance to a value of 101 for Experimental rubber Sample B as compared to a value of 123 for Control rubber Sample A which is about an 18 percent improvement which is believed be an indication of better bonding of the elastomer to the precipitated silica filler via the PEI.

[0045] Therefore, it is concluded that rather minimal amount of addition of the branched polyethylenimine oligomer (0.2 phr) to the rubber composition (prior to addition of zinc oxide and fatty acid) can significantly and beneficially improve (reduce) predictive rolling resistance for a tire with tread of Experimental rubber Sample B composition as well as improve (reduce) its predictive tread wear.

[0046] The increase in amounts of branched polyethylenimine oligomer and salicylic acid for Experimental rubber Samples C and D also resulted in a beneficial increase in rebound values and beneficial decrease in abrasion values.

EXAMPLE II

[0047] This Example is provided to illustrate preparation of a precipitated silica reinforced rubber composition in which a branched polyethylenimine oligomer is blended together in the same mixing stage (step) with zinc oxide and fatty acid in a non-productive mixing step with the rubber composition.

[0048] An exemplary Control rubber Sample A from Example I and Experimental rubber Samples E, F and F provided in this Example II are presented to illustrate prior experimental work relating to methodology of use of the branched polyethylenimine oligomer for the precipitated silica reinforced rubber composition.

[0049] Control rubber Sample A contains diene-based elastomers and reinforcing filler.

[0050] Experimental rubber Sample E is similar to Control rubber Sample A except that it contained the branched polyethylenimine oligomer and the salicylic acid as a vulcanization retarder.

[0051] Experimental rubber Samples F and G are similar to Experimental rubber Sample E except for higher loadings of the branched polyethylenimine oligomer and the salicylic acid.

[0052] The basic formulation for the Control rubber Sample A and Experimental rubber Samples E, F and G are illustrated in the following Table 3 where the ingredients are expressed in terms of parts by weight per 100 parts of rubber (phr) unless otherwise indicated.

[0053] The rubber compositions were prepared in the manner of Example I except that, for Experimental Samples E, F and G, the branched polyethylenimine oligomer, zinc oxide and fatty acid are blended together in the same mixing non-productive mixing step.

TABLE-US-00003 TABLE 3 Non-Productive Mixing Step (NP1) Parts (phr) SSBR rubber (styrene/butadiene rubber).sup.1 67 Cis 1,4-polybutadiene rubber.sup.2 33 Carbon black, rubber reinforcing (N330).sup.3 5 Precipitated silica.sup.4 95 Silica coupler.sup.5 7.6 Wax, crystalline and paraffin 1.5 Rubber processing oil 28 Antioxidant(s) 3 Branched polyethylenimine oligomer 0.2 to 0.6 Zinc oxide 2 Fatty acid.sup.6 5 Non-Productive Mixing Step (NP2) Salicylic acid 0.4 to 1.2 Productive Mixing Step (PR) Sulfur 1.6 Accelerator(s).sup.8 2.8

[0054] The following Table 4 represents the uncured and cured behavior and various physical properties of the rubber compositions based upon the basic formulation of Table 1, and reported for Control rubber Sample A (copied from Table 2 of Example I and Experimental rubber Samples E, F and G of this Example II.

TABLE-US-00004 TABLE 4 Cntrl A Samples (phr) from Ex. I Exp E Exp F Exp G SSBR elastomer 67 67 67 67 Cis 1,4-polybutadiene rubber 33 33 33 33 Rubber reinforcing carbon black 5 5 5 5 Precipitated silica 95 95 95 95 Polyethylenimine, branched 0 0.2 0.4 0.6 oligomer Salicylic acid 0 0.4 0.8 1.2 Properties RPA test (Rubber Process Analyzer), 10% strain, 11 Hertz, 100° C. Storage modus G′ (MPa) 2.2 1.9 2.1 2.2 Tan delta 0.13 0.13 0.12 0.13 Rebound (60° C.) (Higher is 51 51 50 50 better) (percent) DIN abrasion_ (lower is better).sup.1 123 124 122 120 Cure: MDR test, 150° C. Delta torque (dN-m) 20.7 20 19.7 19.2 T25 (minutes) 9.2 7.9 6.9 5.7 T90 (minutes) 16.8 14.6 12.8 10.5 .sup.1DIN53516, relative volume loss

[0055] It can be seen from Table 4 that the benefit achieved in Example I (illustrated in its Table 3) in beneficially increasing the rubber composition's rebound and beneficially decreasing its abrasion loss (increasing its abrasion resistance) was not obtained for rubber Samples E, F and G where the zinc oxide and fatty acid were mixed together with the branched polyethylenimine oligomer in the same non-productive mixing step for the rubber composition (instead of mixing the zinc oxide and fatty acid subsequent to and separate from the branched polyethylenimine oligomer as previously illustrated in Example I for its Samples B, C and D).

[0056] It is concluded that the results observed in this Example II verify the beneficial discovery of addition of the zinc oxide and fatty acid subsequent to and separate from the branched polyethylenimine oligomer to the rubber composition in a non-productive mixing stage.

[0057] While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made within the scope of the invention.