RUBBER COMPOSITION FOR PROMOTING ELECTRICAL CONDUCTIVITY, AND TIRE WITH COMPONENT

Abstract

The invention relates to a rubber composition and its preparation for providing a path of least electrical resistivity through an electrically resistive rubber composition for a tire with a component of such rubber composition, particularly a tire tread.

Claims

1. A method of providing a rubber composition wherein said method comprises: (A) providing a first electrically conductive rubber composition comprised of at least about 50 parts by weight of rubber reinforcing carbon black per 100 parts by weight rubber in said first rubber composition, wherein the elastomer(s) thereof is comprised of at least 50 weight percent cis 1,4-polyisoprene rubber with the remainder comprised of cis 1,4-polybutadiene rubber, (B) providing a second electrically resistive rubber composition in said first electrically conductive rubber phase comprised of diene-based elastomer(s) and of from about 40 to about 80 parts by weight precipitated silica per 100 parts by weight of rubber of said second electrically resistive rubber phase together with silica coupler for said precipitated silica having a moiety reactive with hydroxyl groups of said precipitated silica and another different moiety interactive with said diene-based elastomer(s), wherein the elastomer(s) thereof are comprised of at least 50 weight percent cis 1,4-polybutadiene rubber with the remainder comprised of cis 1,4-polyisoprene rubber, (C) blending the first and second rubber compositions together to form a phased rubber composition comprised of a continuous electrically conductive first rubber phase comprised of said first rubber composition and a second rubber phase as dispersed rubber domains in said first rubber phase where said dispersed rubber domains are comprised of said second electrically resistive rubber composition wherein said phased rubber composition blend contains a maximum of 35 parts by weight rubber reinforcing carbon black and about 20 to about 50 parts of precipitated silica per 100 parts by weight of elastomers contained in said phased rubber composition blend.

2. The method of claim 1 wherein said method further comprises blending sulfur and at least one sulfur cure accelerator with said phased rubber composition followed by sulfur curing said phased rubber composition.

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

4. The method of claim 2 wherein, for said second dispersed rubber phase, said precipitated silica and silica coupler are reacted together in situ within the rubber composition to form a composite thereof.

5. The method of claim 2 wherein, for said second dispersed rubber phase, said precipitated silica and silica coupler are pre-reacted together prior to introduction into the rubber composition to form a composite thereof.

6. The method of claim 2 comprised of: (A) providing a first electrically conductive rubber composition comprised of at least 80 parts by weight of rubber reinforcing carbon black per 100 parts by weight rubber in said first rubber composition, wherein the elastomer(s) thereof is comprised of about 50 weight percent natural cis 1,4-polyisoprene rubber with the remainder comprised of cis 1,4-polybutadiene rubber, (B) providing a second electrically resistive rubber composition in said first electrically conductive rubber phase comprised of diene-based elastomer(s) and of from about 40 to about 80 parts by weight precipitated silica per 100 parts by weight of rubber of said second electrically resistive rubber phase together with silica coupler for said precipitated silica having a moiety reactive with hydroxyl groups of said precipitated silica and another different moiety interactive with said diene-based elastomer(s), wherein the elastomer(s) thereof are comprised of about 80 weight percent cis 1,4-polybutadiene rubber with the remainder comprised of cis 1,4-polyisoprene rubber.

7. A sulfur cured rubber composition prepared by the method of claim 6.

8. The rubber composition of claim 6 wherein, for said second dispersed rubber phase, said precipitated silica and silica coupler are reacted together in situ within the rubber composition to form a composite thereof.

9. The rubber composition of claim 6 wherein, for said second dispersed rubber phase, said precipitated silica and silica coupler are pre-reacted together prior to introduction into the rubber composition to form a composite thereof.

10. A phased rubber composition comprised of: (A) a continuous electrically conductive cis 1,4-polyisoprene based rubber phase containing at least 50 phr of rubber reinforcing carbon black in said first rubber composition, wherein the elastomer(s) thereof is comprised of at least 50 weight percent cis 1,4-polyisoprene rubber with the remainder comprised of cis 1,4-polybutadiene rubber, and (B) dispersed domains contained in said continuous rubber phase comprised of a cis 1,4-polybutadiene based rubber phase containing about 40 to about 80 phr of precipitated silica together with silica coupler for said precipitated silica having a moiety reactive with hydroxyl groups of said precipitated silica and another different moiety interactive with said diene-based elastomer(s), wherein the elastomer(s) thereof are comprised of at least 50 weight percent cis 1,4-polybutadiene rubber with the remainder comprised of cis 1,4-polyisoprene rubber, wherein the blend of phased rubber compositions contains a maximum of 35 phr of rubber reinforcing carbon black.

11. The rubber composition of claim 10 wherein, for said second dispersed rubber phase, said precipitated silica is provided as a reaction product of precipitated silica and silica coupler reacted together in situ within the rubber composition.

12. The rubber composition of claim 10 wherein, for said second dispersed rubber phase, said precipitated silica is provided as a reaction product of precipitated silica and silica coupler pre-reacted together prior to introduction into the rubber composition.

13. A tire having a composite comprised of the rubber composition of claim 3.

14. The tire of claim 13 where said composite is a tire tread.

15. A tire having a composite comprised of the rubber composition of claim 7.

16. The tire of claim 15 where said composite is a tire tread.

17. A tire having a composite comprised of the sulfur cured rubber composition of claim 10.

18. The tire of claim 17 where said composite is a tire tread.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0047] Processes of preparing rubber compositions are illustrated by FIG. 1 (FIG. 1) and FIG. 2 (FIG. 2). A phased rubber product prepared by the process shown as FIG. 2 is illustrated by FIG. 3 (FIG. 3).

[0048] FIG. 1 illustrates a conventional step-wise method of preparation of a rubber composition.

[0049] FIG. 2 illustrates a process of preparation of a phased rubber composition relating to the process of this invention.

[0050] FIG. 3 illustrates a a phased rubber product prepared by the process shown as FIG. 2 comprised of a continuous rubber phase containing a dispersed rubber phase.

THE DRAWINGS

[0051] In FIG. 1, a process of preparation of a rubber composition, is illustrated by conventional blending of natural rubber and cis 1,4-polybutadiene rubber with a combination of rubber reinforcing carbon black and precipitated silica to form a rubber composition comprised of a natural rubber based rubber phase and a cis 1,4-polybutadiene rubber based rubber phase which contain rubber reinforcing carbon black and precipitated silica dispersed equally in each of the rubber phases.

[0052] In FIG. 2, an inventive process is illustrated of non-productive blending of masterbatch No 1 comprised of a non-productive mixed electrically conductive natural rubber based rubber phase containing filler reinforcement comprised of rubber reinforcing carbon black with masterbatch No. 2 comprised of a non-productive electrically resistive cis 1,4-polybutadiene based rubber phase containing filler reinforcement comprised of precipitated silica and coupling agent (silica coupler) for the precipitated silica. In FIG. 2, an optional further mixing of the already mixed non-productive mixed rubber blend is also shown. In FIG. 2, mixing of sulfur curatives with the rubber mixture in a productive rubber mixing step is also shown. In FIG. 2, a resultant rubber composition prepared by such mixing is shown.

[0053] In FIG. 3, the phased rubber composite is presented to illustrate the blend prepared by the process presented by FIG. 2, namely a blend of the aforesaid continuous electrically conductive phase, namely the electrically conductive rubber phase as masterbatch No. 1 of FIG. 2 comprised of the natural rubber based rubber phase containing the rubber reinforcing carbon black filler reinforcement, which contains domains dispersed therein of an electrically resistive phase, namely the electrically resistive rubber phase as masterbatch No. 2 of FIG. 2 comprised of the cis 1,4-polybutadiene based rubber phase containing the precipitated silica with silica coupler.

[0054] In this manner, for FIG. 3, a rubber composite, or composition, is illustrated with an electrically conductive path (path of least electrical resistance) provided through the rubber composite by the continuous electrically conductive phase, namely masterbatch No. 1.

[0055] The following examples are provided to further illustrate the invention. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I

[0056] Rubber compositions are prepared containing rubber reinforcing carbon black.

[0057] Control rubber Sample A contains 34 parts by weight rubber reinforcing carbon black.

[0058] Experimental rubber Sample B comprised of a first electrically conductive rubber composition (referred to herein as masterbatch MB 1) contains 68 parts by weight rubber reinforcing carbon black.

[0059] Experimental rubber Sample C comprised of a second electrically resistive rubber composition (referred to herein as masterbatch MB2) contains no (zero parts by weight) rubber reinforcing carbon black.

[0060] A blend is provided comprised of a blend of said first electrically conductive rubber composition (a continuous rubber phase) and said second electrically resistive rubber composition (a dispersed rubber phase within said continuous rubber phase).

[0061] The weight ratio of the MB1 and MB2 rubber compositions was 50/50 to yield a blend having the same rubber and reinforcing filler content as Control rubber Sample A.

[0062] The following Table 1 is a summary of materials for Control rubber Sample A, individual masterbatches MB1 and MB2 and a blend of masterbatches MB1 and MB2 (blend) where the parts are by weight (phr) unless otherwise indicated.

TABLE-US-00001 TABLE 1 Control Exp. B Exp. C Blend Materials A MB1 MB2 MB1 + MB2 Non-productive Mixing Step(s) Cis 1,4-polybutadiene 75 50 100 75 rubber1 Natural Rubber.sup.2 25 50 0 25 Precipitated silica.sup.3 32 0 65 32 Silica coupling agent.sup.4 3.2 0 6.4 3.2 Carbon black.sup.5 34 68 0 34 Fatty acid.sup.6 2 2 2 2 Zinc oxide 3 3 3 3 Productive Mixing Step - after mixing the Masterbatches Sulfur 1 1 1 1 Sulfur cure accelerators(s).sup.7 3 3 3 3 1Cis 1,4-polybutadiene rubber having a Tg (glass transition temperature) of about 104 C. as BUD1223 from The Goodyear Tire & Rubber Company .sup.2Cis 1,4-polyisoprene rubber comprised of natural rubber .sup.3Precipitated silica as Zeosil 1165 MP from Solvay .sup.4Silica coupling agent as Si266 from Evonik .sup.5Rubber reinforcing carbon black as N110, an ASTM designation .sup.6Fatty acid comprised of stearic, palmitic and oleic acids .sup.7Sulfur cure accelerators comprised of a combination of sulfenamide and diphenyl guanidine.

[0063] Various cured and uncured rubber properties of the rubber compositions are reported in the following Table 2.

TABLE-US-00002 TABLE 2 Control Blend Properties A MB1 + MB2 Tire Tread Predictive Handling Properties, Cured storage modulus (G).sup.1 at 100 C., 11 Hertz (RPA).sup.1 1 percent strain (KPa) 2620 2650 10 percent strain (KPa) 1310 1350 Tire Tread Rolling Resistance Predictive Properties (higher values for rebound and lower values for tan delta are predictive of beneficial reduction in tire rolling resistance) Rebound (100 C.) 47 46 Tan delta, (100 C., 0.259 0.254 10% strain, 11 Hertz) Tire Tread Predictive Wet Performance Properties Rebound, 0 C. 20.1 20.8 Tire Treadwear Predictive Property, Abrasion Resistance (rate of abrasion, lower is better) Grosch abrasion.sup.2, 1034 1148 high, mg/km Tear Strength.sup.3, (peal adhesion) N At 95 C. for testing 70 53 Electrical Resistivity (Mega ohm*cm) At 23 C. 4500 0.19

[0064] From Table 2 it can be seen that the handling, rolling resistance, wet traction, abrasion and tear properties of the Sample A (Control) and Sample B (Blend 1) are not markedly different.

[0065] From Table 2 it can also be seen that the electrical resistivity of the Control rubber Sample A is more than 20,000 times more resistive than the blend of masterbatches.

[0066] Therefore, it is concluded that the aforementioned masterbatch processing of a compound can have a drastic positive influence on compound resistivity with little to no tradeoff in the other indicated rubber composition mechanical properties.

[0067] 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 therein without departing from the spirit or scope of the invention.