FOOTWEAR AND RUBBER SOLE CONTAINING CORNCOB GRANULES

Abstract

The invention relates to footwear with a rubber sole where such sole is comprised of a rubber composition which contains corn cob granules.

Claims

1. A footwear rubber sole intended for ground engagement comprised of a rubber composition which contains a dispersion of corncob granules and where the outer surface of said rubber sole intended for ground engagement contains micro-protrusions of the corncob granules, wherein said rubber composition contains, based on parts per 100 parts by weight rubber (phr): (A) at least one conjugated diene-based rubber, and (B) about 0.1 to about 30 phr of corncob granules.

2. The footwear rubber sole of claim 1 wherein its outer surface contains micro-cavities created by release of a portion of said micro-protrusions of said corncob granules.

3. The footwear rubber sole of claim 1 wherein said rubber composition contains reinforcing filler comprised of: (A) rubber reinforcing carbon black, or (B) precipitated silica together with silica coupler having a moiety reactive with hydroxyl groups on said precipitated silica and another different moiety interactive with said diene-based rubber, or (C) a combination of said rubber reinforcing carbon back and precipitated silica together with said silica coupler.

4. The footwear rubber sole of claim 1 comprised of a rubber composition which contains from about 2 to about 40 phr of rubber processing oils comprised of: (A) petroleum based rubber processing oil, (B) triglyceride vegetable oil, or (C) combination of a petroleum based rubber processing oil and triglyceride vegetable oil.

5. The footwear rubber sole of claim 4 wherein said triglyceride vegetable oil is comprised of at least one of soybean oil, sunflower oil, palm oil and rapeseed oil.

6. The footwear rubber sole of claim 1 wherein said rubber sole rubber composition is provided as being sulfur cured.

7. The footwear rubber sole of claim 1 wherein said conjugated diene-based elastomer is comprised of at least one of cis 1,4-polyisoprene rubber, cis 1,4-polybutadiene rubber, styrene/butadiene copolymer rubber, styrene/isoprene/butadiene terpolymer rubber, isoprene/butadiene rubber and block polymers comprised of styrene-isoprene-styrene and of styrene-butadiene-styrene polymer blocks.

8. The footwear rubber sole of claim 1 wherein said conjugated diene based elastomer is comprised of at least one of cis 1,4-polyisoprene rubber, cis 1,4-polybutadiene rubber and styrene/butadiene rubber, where said styrene/butadiene rubber is comprised of at least one of: (A) organic solution polymerization prepared styrene/butadiene rubber (SSBR), and (B) aqueous emulsion polymerization prepared styrene/butadiene rubber (ESBR) containing from about 2 to about 3 parts by weight residual rosin acid per 100 parts by weight ESBR.

9. The footwear rubber sole of claim 1 wherein said elastomer also includes up to about 25 phr of at least one of ethylene/propylene/non-conjugated diene terpolymer rubber, butyl rubber, halobutyl rubber and brominated copolymers of paramethylstyrene and isobutylene and their mixtures.

10. The footwear rubber sole of claim 9 wherein said elastomer is an ethylene/propylene/non-conjugated diene terpolymer where said non-conjugated diene is comprised of at least one of ethylidene norbornadiene, trans 1,4-hexadiene and dicyclopentadiene.

11. The footwear rubber sole of claim 1 wherein said rubber composition contains from about 10 to about 120 phr of particulate reinforcing fillers comprised of: (A) carbon black, or (B) precipitated silica, or (C) a combination of rubber reinforcing carbon black and precipitated silica.

12. The footwear rubber sole of claim 1 which contains at least one of clay, talc, and calcium carbonate.

13. The footwear rubber sole of claim 11 which contains a silica coupler for said precipitated silica having a moiety reactive with hydroxyl groups contained on the precipitated silica and another moiety interactive with the conjugated diene-based elastomer(s).

14. The footwear rubber sole of claim 13 wherein said silica coupler is comprised of: (A) a bis-(3-trialkloxysilylalkyl) polysulfide having an average of from 2 to about 4 connecting sulfur atoms in its polysulfidic bridge, or (B) an organoalkoxymercaptosilane composition.

15. The footwear rubber sole of claim 14 wherein said silica coupler is a bis(3-trialkoxysilylalkyl) polysulfide comprised of bis(3-triethoxysilylpropyl) polysulfide.

16. The footwear rubber sole of claim 1 wherein said rubber composition also contains about 1 to about 10 phr of zinc soap comprised of zinc rosinate as a product formed in situ within the rubber composition of zinc oxide and freely added rosin acid.

17. The footwear rubber sole of claim 14 wherein said particulate reinforcing filler is comprised of precipitated silica,

18. The footwear rubber sole of claim 17 wherein said precipitated silica is provided as a product of precipitated silica and silica coupler comprised of bis(3-triethoxysilylpropyl) polysulfide having an average of from about 2 to about 4 connecting sulfur atoms in its polysulfidic bridge and of an alkoxyorganomercaptosilane.

19. The footwear rubber sole of claim 5 where said rubber composition of said rubber sole contains a combination of petroleum based rubber processing oil and vegetable oil.

20. An article of footwear containing the rubber sole of claim 1.

Description

EXAMPLE I

[0071] This Example, derived from Example I of U.S. Pat. No. 7,249,621, relates to providing corncob granules in a rubber composition for a tire tread which is presented here for said evaluation of providing corncob granules in a footwear rubber sole rubber composition.

[0072] Samples of diene hydrocarbon based rubber compositions were prepared and are identified herein as Samples 1 through 5, with Sample 1 being a control sample.

[0073] Control Sample 1 contains cis 1,4-polyisoprene natural rubber having a Tg (glass transition temperature) of about 65 C. and an emulsion polymerization prepared styrene/butadiene copolymer elastomer (E-SBR) having a Tg of about 55 C.

[0074] Samples 2 through 5 are similar to the control Sample 1 except that they contain various amounts of corncob granules.

[0075] The compositions were prepared by mixing the ingredients in several stages, namely, two sequential non-productive mixing steps (without the curatives, namely the sulfur and accelerators) followed by a productive mix stage (in which the curatives are added), and the resulting composition was cured under conditions of elevated pressure and temperature.

[0076] For the non-productive mixing stages, the ingredients are mixed in an internal rubber mixer for about 4 minutes each to a temperature of about 160 C. following which the rubber composition is removed from the mixer, roll milled, sheeted out and allowed to cool to a temperature below 40 C. after each non-productive mixing stage.

[0077] In a subsequent productive mixing stage, the curatives are mixed with the rubber composition in an internal rubber mixer for about 2 minutes to a temperature of about 110 C. following which the rubber composition is removed from the mixer, roll milled, sheeted out and allowed to cool to a temperature below 40 C.

[0078] The rubber compositions are illustrated in the following Table 1 derived from the aforesaid U.S. patent.

TABLE-US-00001 TABLE 1 Samples Control 1 2 3 4 5 First Non-Productive Mixing Step E-SBR.sup.1 85 85 85 85 85 Natural rubber.sup.2 15 15 15 15 15 Carbon black.sup.3 49 49 49 49 45 Processing aids.sup.4 18 18 18 18 18 Antidegradant.sup.5 3.5 3.5 3.5 3.5 3.5 Zinc oxide 0.9 0.9 0.9 0.9 0.9 Corncob granules.sup.6 0 2.5 5 10 10 Second Non-Productive Mixing Step Carbon black.sup.3 16 16 16 16 16 Processing aids.sup.4 12.5 12.5 12.5 12.5 12.5 Productive Mixing Step Zinc oxide 2.1 2.1 2.1 2.1 2.1 Antidegradant.sup.5 1.2 1.2 1.2 1.2 1.2 Accelerator(s).sup.7 2.7 2.7 2.7 2.7 2.7 Sulfur 1.6 1.6 1.6 1.6 1.6 Retarder 0.5 0.5 0.5 0.5 0.5 .sup.1Styrene/butadiene copolymer elastomer as PLF1502 from The Goodyear Tire & Rubber Company containing about 23.5 percent bound styrene and having a Tg of about 55 C. .sup.2Cis 1,4-polyisoprene natural rubber (TSR20) .sup.3N550 rubber reinforcing carbon black, ASTM designation .sup.4Rubber processing oil and microcrystalline wax as processing aids and fatty acid as primarily stearic acid .sup.5Of the quinoline and amine types .sup.6Corncob granules as 60 Grit-O' cobs from The Andersons, Inc. .sup.7Benzothiazyl disulfide and tetramethyl thiuram disulfide

[0079] The following Table 2 derived from the aforesaid U.S. patent reports physical data for various physical properties of the samples. For cured rubber samples, the respective samples were cured for about 60 minutes to a temperature of about 160 C.

TABLE-US-00002 TABLE 2 Samples Control 1 2 3 4 5 Carbon black 65 65 65 65 61 Corncob granules 0 2.5 5 10 10 Rheometer, 170 C. (MDR).sup.1 Maximum torque (dNm) 13.3 13.6 13.6 13.5 13 Minimum torque (dNm) 1.9 2 1.7 2 1.9 Delta torque (dNm) 11.4 11.6 11.9 11.5 11.1 T90, minutes 7.5 7.7 7.8 8.1 8.1 Stress-strain (ATS).sup.2 Tensile strength (MPa) 17.6 15.5 15 13.2 13.3 Elongation at break (%) 577 531 533 526 540 300% modulus, ring (MPa) 8.1 8 7.9 7.2 6.7 Rebound (%) 23 C. 30 29 30 30 31 100 C. 42 41 42 42 42 Hardness (Shore A).sup.3 23 C. 71 71 73 73 73 100 C. 57 58 59 59 58 Tear strength, 95 C. (N).sup.4 193 165 138 113 65 Pierced groove flex (mm 0.54 0.55 0.64 0.62 0.69 @120 minutes).sup.5 DIN abrasion (2.5N) 132 145 156 183 190 relative cc loss.sup.6 RPA, 100 C..sup.7 G at 10% strain (kPa) 970 1004 1004 964 905 Tan delta at 10% strain 0.254 0.259 0.259 0.261 0.246 Sample surface visual 1 2 3 5 5 observation ratings.sup.8 .sup.1Data obtained according to moving die rheometer instrument, model MDR-2000 by Alpha Technologies, used for determining cure characteristics of elastomeric materials, such as for example torque, T90 etc. .sup.2Data obtained according to automated testing system instrument by the Instron Corporation which incorporates six tests in one system. Such instrument may determine ultimate tensile, ultimate elongation, modulii, etc. Data reported in the Table is generated by running the ring tensile test station which is an Instron 4201 load frame. .sup.3Shore A hardness according to ASTM D-1415 .sup.4Data obtained according to a peel strength adhesion (tear strength) test to determine interfacial adhesion between two samples of a rubber composition. In particular, such interfacial adhesion is determined by pulling one rubber composition away from the other at a right angle to the untorn test specimen with the two ends of the rubber compositions being pulled apart at a 180 angle to each other using an Instron instrument. .sup.5Pierced groove flex values were determined by continuous dynamic flexing and measuring the extent of crack growth and expressed in terms of millimeters (mm) at 240 minutes of flexing at 23 C. .sup.6DIN abrasion (relative to a control) according to DIN 53516 .sup.7Data obtained according to rubber process analyzer as RPA 2000 instrument by Alpha Technologies, formerly the Flexsys Company and formerly the Monsanto Company. References to an RPA-2000 instrument may be found in the following publications: H. A. Palowski, et al, Rubber World, June 1992 and January 1997, as well as Rubber & Plastics News, Apr. 26, 1993 and May 10, 1993. .sup.8Sample surface roughness using a graduated visual observation rating of from 1 to 5 with a rating of 1 for a smooth rubber surface and a rating of 5 for a relatively very rough rubber surface (caused by the corncob granules of which the majority are covered by a relatively thin rubber membrane).

[0080] From Table 2 it is observed that the rebound and hardness properties remained fairly constant with the addition of 2.5 to 10 phr of the corncob granules. However, tensile strength, tear strength and DIN abrasion properties became somewhat worse than those for the control sample, particularly at the 10 phr level of corncob granule addition.

[0081] From Table 2 it is also observed that the cured samples exhibited very small overall micro protrusions of the corncob granules, with the majority being covered by thin rubber membrane at the surface and also that abraded and torn portions of the respective samples exhibited numerous micro-cavities resulting from the displacement of individual protruded corncob granules. The resulting increase of the surface area and edges due to the presence of both the micro protrusions and micro-cavities are considered herein to provide increased traction particularly for winter driving conditions for a tire having a tread of the rubber composition.

[0082] Accordingly, it is concluded herein that a footwear rubber sole of a rubber composition containing corncob granules can aid in promoting traction the footwear sole's surface upon engagement of a substrate (e.g. ground) surface.

EXAMPLE II

[0083] This Example, derived from Example II of U.S. Pat. No. 7,249,621, relates to providing corncob granules in a rubber composition for a tire tread which is presented here for said evaluation of providing corncob granules in a footwear rubber sole rubber composition.

[0084] Samples of diene hydrocarbon based rubber compositions were prepared and are identified herein as Samples 6 through 9, with Sample 6 being a control sample.

[0085] Control Sample 6 contains cis 1,4-polyisoprene natural rubber having a Tg of about 65 C. and a cis 1,4-polybutadiene rubber having a Tg of about 103 C.

[0086] Samples 7 through 9 are similar to control Sample 6 except that they contain various amounts of corncob granules.

[0087] The compositions were prepared in the manner of Example I.

[0088] The rubber compositions are illustrated in the following Table 3 derived from the aforesaid U.S. patent.

TABLE-US-00003 TABLE 3 Samples Control 6 7 8 9 Non-Productive Mixing Step Natural rubber.sup.1 55 55 55 55 Cis 1,4-polybutadiene rubber.sup.2 45 45 45 45 Carbon black.sup.3 48 48 48 48 Processing aids.sup.4 14.8 14.8 14.8 14.8 Antidegradant.sup.5 5.3 5.3 5.3 5.3 Zinc oxide 2 2 2 2 Corncob granules.sup.6 0 2.5 5 10 Productive Mixing Step Zinc oxide 3 3 3 3 Antidegradant.sup.5 1 1 1 1 Accelerators.sup.7 2.6 2.6 2.6 2.6 Sulfur 0.7 0.7 0.7 0.7 .sup.1Cis 1,4-polyisoprene natural rubber (TSR20) .sup.2Cis 1,4-polybutadiene rubber as BUD1207 from The Goodyear Tire & Rubber Company having a Tg of about 103 C. .sup.3N550 rubber reinforcing carbon black, ASTM designation .sup.4Rubber processing oil and microcrystalline wax as processing aids and fatty acid as primarily stearic acid .sup.5Of the quinoline and amine types .sup.6Corncob granules as 60 Grit-O' Cobs from The Andersons, Inc. .sup.7Benzothiazyl disulfide and tetramethyl thiuram disulfide

[0089] The following Table 4 reports physical data for various physical properties of the samples. For cured rubber samples, the respective samples were cured for about 60 minutes to a temperature of about 160 C.

TABLE-US-00004 TABLE 4 Samples Control 6 7 8 9 Corncob granules 0 2.5 5 10 Rheometer, 160 C. (MDR).sup.1 Maximum torque (dNm) 16.2 16.7 16.8 17.4 Minimum torque (dNm) 2.1 2.3 2.3 2.6 Delta torque (dNm) 14.1 14.4 14.5 14.8 T90, minutes 12.3 11.7 11.7 11 Stress-strain (ATS).sup.2 Tensile strength (MPa) 17.5 15.6 14.6 12.9 Elongation at break (%) 528 499 488 473 300% modulus, ring (MPa) 7.5 7.5 7.3 7 Rebound (%) 23 C. 49 48 49 48 100 C. 59 58 58 57 Hardness (Shore A).sup.3 23 C. 60 61 62 63 100 C. 57 58 58 60 Tear strength, 95 C. (N).sup.4 92 95 94 102 Pierced groove flex (mm at 0.59 0.74 0.55 0.6 240 minutes).sup.5 Sample surface visual observation.sup.8 1 2 3 5 Static ozone test 50 pphm at 23 C., 25% strain No visual surface cracks Dynamic ozone test 50 pphm, 13 C., 25% strain Edge cracks only

[0090] From Table 4 it is observed that the addition of the corncob granules at a level of from 2.5 to 10 phr had a small effect on cured properties except for a reduction of tensile strength at the 10 phr level.

[0091] Accordingly, it is concluded herein that a footwear rubber sole of a rubber composition containing corncob granules can aid in promoting traction the footwear sole's surface upon engagement of a substrate (e.g. ground) surface.

EXAMPLE III

A Control

[0092] This Example, derived from an example presented in U.S. Pat. No. 9,163,126, relates to providing zinc rosinate in a rubber composition as a product of zinc oxide with rosin acid formed in situ within the rubber composition and thereby relates to the aforesaid evaluation of providing such zinc rosinate in a footwear rubber sole rubber composition. Tables 1 and 2 have been re-labeled herein as Tables 5 and 6, and Samples G through L have been re-labeled 10 through 15, to present a chronological order of tables and samples.

[0093] For this Example, rosin acid was introduced in a rubber composition in combination with zinc oxide to enable an in situ formation of zinc rosinate within the rubber composition,

[0094] Silica-rich rubber compositions were prepared as rubber Samples 10 through 15. Rubber Sample 10 was a control rubber sample formulated with 3 phr of zinc oxide and 1 phr of fatty acids comprised of stearic, palmitic and oleic acids to form salts of such fatty acids in situ within the rubber composition. Rubber Samples 11 and 12 were formulated with 3 phr and 6 phr of the fatty acids, respectively, while maintaining 3 phr of zinc oxide. Rubber Samples 13, 14, and 15 were formulated with 3 phr zinc oxide and rosin acid (instead of the aforesaid fatty acids) in amounts of 1, 3 and 6 phr of rosin acid, respectively, to form zinc rosinate in situ within the rubber composition.

[0095] The following Table 5 derived from the aforesaid US Patent illustrates a summary of the formulations.

TABLE-US-00005 TABLE 5 phr Non-Productive Mixing Stage (4 min to 170 C. drop temperature) Solution styrene/butadiene rubber (SBR).sup.1 74 Cis 1,4-polybutadiene rubber.sup.2 26 Precipitated silica.sup.3 73 Carbon black 10 Processing oil, wax 9 Silane coupling agent.sup.4 6.5 Antidegradant.sup.5 3 Zinc oxide 3 Traction resin.sup.6 5 Fatty acids (10-12) or rosin acid.sup.7 (13-15) 1, 3 and 6 Second Non-productive mixing stage (3 minutes to 160 C. drop temperature) No additional ingredients added Productive mixing stage (2 minutes to 120 C. drop temperature) Sulfur 1.9 Sulfenamide accelerator 1.7 Diphenyl guanidine accelerator 1.5 .sup.1SLF31X22 from The Goodyear Tire & Rubber Company .sup.2Budene 1207 from The Goodyear Tire & Rubber Company .sup.3Z1165MP from Rhone-Poulenc .sup.4NXT from GE Silicones .sup.5Amine type .sup.6Coumarone-indene resin .sup.7Gum rosin

[0096] The rubber composition samples were prepared by mixing the elastomers together with the identified rubber compounding ingredients in a first non-productive mixing stage (NP) in an internal rubber mixer for about 4 minutes at a temperature of about 170 C. The mixture was then further sequentially mixed in a second non-productive mixing stage (NP) in an internal rubber mixer, with no additional ingredients added, for about 3 more minutes at a temperature of about 160 C. The resulting mixture was then mixed in a productive mixing stage (P) in an internal rubber mixer with curatives for about 2 minutes at a temperature of about 120 C. The rubber composition was cooled to below 40 C. between the non-productive mixing steps and between the second non-productive mixing step and the productive mixing step.

[0097] The following Table 6 derived from the aforesaid U.S. patent illustrates the cure behavior and various physical properties of the silica-rich rubber compositions based on the basic recipe of Table 3 and reported herein as rubber Samples 10 through 15.

TABLE-US-00006 TABLE 6 Samples Control 10 11 12 13 14 15 Fatty acids, (phr) 1 3 6 0 0 0 Rosin acid (phr) 0 0 0 1 3 6 Processing Uncured (G).sup.1 256 203 184 249 224 187 Wet.sup.2 0 C. rebound 19 18 19 18 17 15 23 C. rebound 36 38 34 34 31 28 Handling.sup.3 G @ 10% 2261 1854 1598 2157 2100 1477 Modulus at 300% 10.4 9.1 8.3 10.6 9.1 7.4 Hot hardness 60 59 59 59 59 60 RR.sup.4 Rebound, 100 C. 56 58 61 55 52 51 TD (tan delta) at 100 C., RPA 0.14 0.12 0.11 0.14 0.14 0.13 Wear.sup.5 DIN abrasion 108 137 135 115 131 143 COF.sup.6 Dry 1.54 1.53 1.57 1.62 1.56 1.64 Wet 0.32 0.34 0.33 0.35 0.43 0.52 Tear Original 82 77 76 81 97 135 .sup.1Uncured G was measured using ASTM D6601 on an RPA 2000 .sup.2Rebound was measured using ASTM D1054 .sup.3Modulus at 300 percent was measured using ASTM D1042 .sup.4Rebound at 100 C. was measured using ASTM D1415 .sup.5DIN abrasion was measured using ASTM 596.3 .sup.6Coefficient of friction (COF) measured using ASTM D1894. COF value for a rubber sample may be measured, for example, on a Model SP-200 Slip/Peel tester from IMASS, Inc. at six inches (about 15.2 cm) per minutes using a 200 g sled against a substrate surface such as, for example, a polished aluminum surface

[0098] From Table 6 it can be seen in Samples 10 through 12, the increase of fatty acid provides no appreciable change in either of the dry or wet coefficient of friction (COF) values.

[0099] However, the coefficient of friction values for Samples 13, 14 and 15 (which contained the zinc rosinate formed in situ within the rubber compositions as a product of rosin acid, instead of the fatty acid, and zinc oxide) were dramatically improved for wet substrate conditions as compared to Samples 10, 11 and 12 and also showed a small improvement for dry COF.

[0100] Accordingly, it is concluded herein that a footwear sole of a rubber composition containing corncob granules which also contains a zinc soap in the form of zinc rosinate as a product of zinc oxide and freely added rosin acid, which may be in addition to any residual rosin acid which might be contained in an elastomer in the rubber composition can promote a coefficient of friction of the footwear sole's surface intended for contacting or engaging a substrate surface.

[0101] 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.