GRAPHENE AS ADDITIVE FOR RUBBER COMPOUNDS AND PRODUCTS

Abstract

The introduction of graphene as an additive in rubber compounds is disclosed. The product shows increased barrier protection for tire innerliners, with no tradeoffs in other characteristics. A rubber compound is disclosed herein including butyl rubber and graphene plate, wherein the graphene plate has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

Claims

1. A composition comprising: butyl rubber; carbon black; naphthenic oil; aromatic hydrocarbon resin; aliphatic hydrocarbon resin; phenolic tackifier; accelerator; stearic acid; zinc oxide; sulfur; and graphene, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

2. A composition comprising: butyl rubber; and graphene plate, wherein the graphene plate has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

3. The composition of claim 2, wherein the graphene plate is between about 0.1 PHR and about 50.0 PHR.

4. The composition of claim 3, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

5. The composition of claim 4, wherein the graphene plate has an oxygen content of less than about 1%.

6. The composition of claim 2, wherein the thickness is less than about 1 nm and the aspect ratio is about 1000.

7. The composition of claim 3, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

8. The composition of claim 2, wherein the composition further comprises carbon black.

9. The composition of claim 8, wherein the composition further comprises: naphthenic oil; aromatic hydrocarbon resin; aliphatic hydrocarbon resin; phenolic tackifier; accelerator; stearic acid; zinc oxide; and, sulfur.

10. The composition of claim 7, wherein the graphene plate is between about 1.0 PHR and about 2.0 PHR, wherein the composition has no clay fillers.

11. A method of compounding rubber, the method comprising the steps of: blending butyl rubber with graphene, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon; exfoliating the graphene into plates, wherein the graphene plates as carboxylic acid, ketone, aldehyde, or hydroxyl groups on the graphene plate surface or graphene plate edges; and aligning the graphene plates into perpendicular alignment, such that the graphene plates provide a barrier to migration oxygen, nitrogen, moisture, or water vapor molecules.

12. The method of claim 11, wherein the graphene plate is between about 0.1 PHR and about 50.0 PHR.

13. The method of claim 12, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

14. The method of claim 13, wherein the graphene plate has an oxygen content of less than about 1%.

15. The method of claim 11, wherein the thickness is less than about 1 nm and the aspect ratio is about 1000.

16. The method of claim 12, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

17. The method of claim 12, wherein the method further comprises the step of blending in carbon black.

18. The method of claim 17, wherein the method further comprises the step of: blending in naphthenic oil, aromatic hydrocarbon resin, aliphatic hydrocarbon resin, phenolic tackifier, accelerator, stearic acid, zinc oxide, and sulfur.

19. The method of claim 16, wherein the graphene plate is between about 1.0 PHR and about 2.0 PHR, wherein no clay fillers are added.

Description

III. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present teachings are described hereinafter with reference to the accompanying drawings.

[0024] FIG. 1 depicts a graph showing rapid reduction in permeability;

[0025] FIG. 1A depicts the structure of graphene;

[0026] FIG. 2 depicts the structures of graphene oxide and reduced graphene oxide;

[0027] FIG. 3 depicts a tire; and

[0028] FIG. 4 is a graphical representation of the graphene plates acting as a barrier to gas flow.

IV. DETAILED DESCRIPTION

[0029] FIG. 3 shows tire having a tread 10, sidewall 12, belt plies 14, inner liner 16, bead filler 18, beads 20, and radial cord body 22. With reference to FIGS. 1-4, in one aspect of the present teaching, a tire innerliner 16 is a calendered halobutyl rubber sheet compounded with additives that result in low air permeability. The innerliner assures that the tire will hold high-pressure air inside, without an inner tube, minimizing diffusion through the rubber structure. Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component. Mixing is the process of applying mechanical work to the ingredients in order to blend them into a homogeneous substance. Internal mixers are often equipped with two counter-rotating rotors in a large housing that shear the rubber charge along with the additives. The mixing is done in two or three stages to incorporate the ingredients in the desired order. The shearing action generates considerable heat, so both rotors and housing are water-cooled to maintain a temperature low enough to assure that vulcanization does not begin.

[0030] With continuing reference to FIGS. 1-4, the graphene is added to the rubber and mixed as noted above. Graphene will be added to a rubber formulation, such as one based on bromobutyl, at levels from about 0.1 PHR to about 50.0 PHR, including about 0.5 PHR to about 45.0 PHR, about 0.5 PHR to about 40.0 PHR, about 0.5 PHR to about 35.0 PHR, about 0.5 PHR to about 30.0 PHR, about 0.5 PHR to about 25.0 PHR, about 0.5 PHR to about 20.0 PHR, about 0.5 PHR to about 15.0 PHR, and from 0.5 PHR to 10.0 PHR. In another aspect of the present teachings, the graphene is added at less than about 50.0 PHR, less than about 45.0 PHR, less than about 30.0 PHR, less than about 25.0 PHR, less than about 20.0 PHR, less than about 15.0 PHR, and less than about 10.0 PHR. In another aspect of the present teachings, the graphene is added at greater than about 0.5 PHR, greater than about 1.0 PHR, greater than about 5.0 PHR, greater than about 10.0 PHR, greater than about 15.0 PHR, greater than about 20.0 PHR, greater than about 25.0 PHR, greater than about 30.0 PHR, greater than about 35.0 PHR, greater than about 40.0 PHR, and greater than about 45.0 PHR. With continuing reference to FIGS. 1-4, the graphene is added to the rubber and mixed as noted above. Graphene in this aspect is described as in Table 1.

TABLE-US-00001 TABLE 1 Typical Properties of Graphene Form Powder, dark grey, odorless Carbon >95% Particle size 50 nm to 10 μm Moisture, Oxygen, Ash <0.75 wt. %, <2.0 wt. %, <4.5 wt. %, respectively Resistivity <150 ohm cm Particle (sheet) thickness) <3.2 nm Particle layers <16 Specific gravity 2. gm/cubic centimeter Surface area (specific) 180 square m.sup.2/gm

[0031] The particle size range of graphene used in the present teachings can range from about 50 nm to about 10 μm. In one aspect, the particle size range is from about 100 nm to about 5 μm. In one aspect, the particle size range is greater than about 50 nm, greater than about 100 nm, greater than about 150 nm, greater than about 200 nm, greater than about 250 nm, greater than about 300 nm, greater than about 350 nm, greater than about 400 nm, greater than about 450 nm, greater than about 500 nm, greater than about 550 nm, greater than about 600 nm, greater than about 650 nm, greater than about 700 nm, greater than about 750 nm, greater than about 800 nm, greater than about 850 nm, greater than about 900 nm, greater than about 950 nm, greater than about 1 μm, greater than about 2 μm, greater than about 3 μm, greater than about 4 μm, greater than about 5 μm, greater than about 6 μm, greater than about 7 μm, greater than about 8 μm, or greater than about 9 μm. In one aspect, the particle size range is less than about 10 μm, less than about 9 μm, less than about 8 μm, less than about 7 μm, less than about 6 μm, less than about 5 μm, less than about 4 μm, less than about 3 μm, less than about 2 μm, less than about 1 μm, less than about 950 nm, less than about 900 nm, less than about 850 nm, less than about 800 nm, less than about 750 nm, less than about 700 nm, less than about 650 nm, less than about 600 nm, less than about 550 nm, less than about 500 nm, less than about 450 nm, less than about 400 nm, less than about 350 nm, less than about 300 nm, less than about 250 nm, less than about 200 nm, less than about 150 nm, or less than about 100 nm. The form is plate-like rather than cylindrical or fibrous. To further define the material, carbon content is greater than 95%, and in one aspect greater than 99%. The carbon content can be greater than 96%, greater than 97%, or greater than 98% as well. Ash and oxygen content is less than 1% in one aspect of the present teachings. In one aspect, the average particle thickness is about 2.5 nm and the number of layers in a particle is less than 15, thus allowing attainment of a near exfoliated condition when compounded. Specific surface area of the graphene plate will range from 100 m.sup.2/gram to 250 m.sup.2/gram and in one aspect is about 180 m.sup.2/gram. In one aspect, the surface area of the graphene plate is greater than 150 m.sup.2/gram, greater than 100 m.sup.2/gram, less than 250 m.sup.2/gram, less than 200 m.sup.2/gram, or less than 150 m.sup.2/gram.

[0032] Graphene is added to the rubber compound formulations at between about 0.0 PHR and about 50.00 PHR, including in the range of about 0.5 PHR to about 8.00 PHR. Reductions in compound permeability initially show a large decrease (as shown in FIG. 1), tapering as graphene levels increase. Gas-permeability decreases with increasing graphene loading of about 0.4 vol % in rubber composites. The percolation threshold is about 40 times lower than that for clay-based composites. According to the Nielsen model on gas permeability, the thickness of an individual graphene based sheet dispersed in the graphene styrene-butadiene rubber (SBR) composite with 2.0 vol. % of GO was predicted to be 1.47 nm.

[0033] Graphene, when added to a bromobutyl rubber compound formulation, can be in various forms and which can be part of the present teaching, such as a powder, in pastilles or pellets using wax as a carrier, aiding dust suppression, in pre-weight sealed, low-melt temperature polyethylene bags, and melt or solution blended with a compatible polymer, such as butyl rubber or halobutyl rubber and then compounded as part of the total rubber hydrocarbon content.

[0034] Graphene has an aspect ratio of near 1000, assuming the graphene plate thickness is about 1 nm. The plate length/diameter can be up to about 1 micron. The graphene can thus function as a barrier. The graphene exfoliates into sheets when added to the rubber compound, which improves the barrier properties when perpendicular alignment to the sheet direction is achieved. The graphene plates provide a barrier to oxygen and nitrogen migration, and moisture or water vapor molecules migrating through the liner compound of the tire or other product requiring such properties. Such gas molecule transport phenomenon is described as a “tortuous path” as shown in FIG. 4. With continuing reference to FIGS. 1-4, with the addition of graphene as a filler, there is no trade-off or loss in conventional processing and mechanical properties. Graphene has a very high aspect ratio. Small amounts have a large impact on reducing permeability. The nominal aspect ratio of graphene of up to 1000 compares with the typical aspect ratio of 20 for kaolin clay fillers. The clay fillers have to be added at about 40 PHR and also need a surfactant for compatibility. Due to the relatively large size of the graphene plates versus inorganic fillers, graphene can be added at about 1 PHR to about 2 PHR.

Measurement of Properties of Rubber Compositions

[0035] Mooney viscosity (ML1+4) at 100° C. measured in accordance with ASTM D1646. Vulcanization kinetics and associated properties was measured by following the procedure in ASTM D5289. Tensile strength and associated data generated through measurement of tensile strength was determined following ASTM D412. Shore-A Hardness was measured following the method in ASTM D2240. Tear strength and adhesion were measured following ASTM D624. Oxygen permeability was measured using an Ametek Mocon OX-TRAN 2/22 permeability tester and following ASTM D3985. Air permeability determined according to the method in ASTM D1434.

EXAMPLE 1

[0036] In this example, tire model innerliner compounds were prepared containing graphene levels, ranging from about 0.00 PHR to about 20.00 PHR. The graphene was first blended with bromobutyl rubber and then added as a master-batch to the compounds. The amount of free bromobutyl polymer added to the formulation was adjusted with the graphene master-batch to ensure the total polymer content is 100.00 PHR as described earlier. Graphene was added at 0.5 PHR, 2.0 PHR, 5.00 PHR, 8.00 PHR, and 20.0 PHR. Compounds were prepared using a laboratory internal mixer, using a two-stage mixing procedure. The first stage is referred to as non-productive, followed by the final stage or productive phase, where the vulcanization chemicals are added. The formulations are shown in Table 2. In Table 2, ERTNB10-53-MB is a masterbatch of bromobutyl rubber and graphene. The specific grade of bromobutyl is Bromobutyl 2222 supplied by ExxonMobil Chemical, wherein the formulations is Bromobutyl 2222 at 100.00 PHR and graphene at 37.50 PHR. The blend was prepared by mixing and blending in a banbury, mixing the blends up to 100° C., and then sheeting the blend for later compounding work. Though not necessary, in Table 1 a re-mill is illustrated which can be included in the mixing procedure should it be desired. A re-mill is a procedure where the compound is passed through a mixer for a short period of time so as to optimized final compound viscosity.

[0037] The mechanical properties illustrated in Table 3 are equivalent to innerliners with no graphene. This is the case for compounds containing graphene at levels up to about 10 PHR. It is noted that industrial levels of graphene usage will be in the range of about 0.5 PHR to about 10.0 PHR. There is no shift in tensile strength, Mooney viscosity, modulus, tack, green strength, or tear strength. However, there is direction improvement in adhesion, consistent with results from other compound classes.

EXAMPLE 2

[0038] This example shows the excellent reduction in permeability achieved with small amounts of graphene in the bromobutyl innerliner compound. Permeability was measured and two sets of results are reported, (i) permeation of oxygen through the innerliner compounds and (ii) permeation of air. In both instances there is a sharp reduction in permeability with very small amounts of graphene added to the bromobutyl compounds, followed by a less steep drop than would be predicted by computational models proposed by Neilson.

[0039] Addition of graphene to the bromobutyl compound shows a very rapid drop in permeability which is required for tire innerliner applications. This drop is considered significantly greater than that possible using other plate-like additives, such as kaolin clays, other clays, or talc nanocompo sites. It is noted that this reduced tire liner permeability is useful for electric vehicle tires, truck tires, bus tires, off road tires, farm equipment tires, and aircraft tires. Graphene has an aspect ratio of near 1000, assuming the graphene plate thickness is about 1 nm. The plate length/diameter can be up to about 1 micron. The graphene thus functions as a barrier or creation of the tortuous path noted above (FIG. 4). The graphene exfoliates into sheets when added to the rubber compound, which improves the barrier properties. The graphene plates provide a barrier to oxygen and nitrogen migration through the liner compound of the tire.

TABLE-US-00002 TABLE 2 Compound 3 (control) 1 2 4 5 6 ERTNB ERTNB ERTNB ERTNB ERTNB ERTNB Number 10-54-03 10-54-01 10-54-02 10-54-04 10-54-05 10-54-06 BIIR 2222 100.00 98.67 94.67 86.67 78.67 46.70 Carbon Black N660 60.00 60.00 60.00 60.00 60.00 60.00 ERTNB10-53-MB 0.00 1.83 7.33 18.33 29.33 73.30 Naphthenic oil 8.00 8.00 8.00 8.00 8.00 8.00 Struktol 40MS 7.00 7.00 7.00 7.00 7.00 7.00 Koresin 2.00 2.00 2.00 2.00 2.00 2.00 Escorez 1102 2.00 2.00 2.00 2.00 2.00 2.00 Stearic Acid 1.00 1.00 1.00 1.00 1.00 1.00 Zinc Oxide 1.00 1.00 1.00 1.00 1.00 1.00 MBTS 1.25 1.25 1.25 1.25 1.25 1.25 Sulfur 0.50 0.50 0.50 0.50 0.50 0.50 Total 182.75 183.25 184.75 187.75 190.75 202.75 Graphene 0.00 0.50 2.00 5.00 8.00 20.00 1st Pass or Non-Productive Set-up Start Temp. 65° C., 65 RPM, & 50 Ram pressure  0′ add elastomers and ertnb10-53-MB  0.25′ add carbon black  2′ add others  3′ sweep  3.5′ adjust (increase) rotor speed, ramp temperature to 150° C. at 5′  5′ (try to reach 150° C. at 5′) Re-mill if required Set-up Start Temp. = RT, 65 RPM, & 50 Ram pressure  0′ ADD 1st Pass MB  3′ DUMP MILL 1′ on mill with mill rolls at R.T.  5′ (try to reach 150° C. at 5′) Final Pass Productive Set-Up SANDWICH IN CURES  0′ ADD ⅔ of 2nd pass MB 15″ ADD Sulfur, Accelerator pocket, & ⅓ of 2nd pass MB  1 SWEEP  5′ (try to reach 150° C. at 5′)

TABLE-US-00003 TABLE 3 Compound 3 1 2 4 5 6 ERTNB ERTNB ERTNB ERTNB ERTNB ERTNB Number 10-54-03 10-54-01 10-54-02 10-54-04 10-54-05 10-54-06 BIIR 2222 PHR 100.00 100.00 100.00 100.00 100.00 100.00 Graphene PHR 0.00 0.50 2.00 5.00 8.00 20.00 Mooney Viscosity ML1 + 4 57.80 57.50 57.60 58.70 58.60 60.40 100° C. MDR Rheometer 160° C. Delta Torque in-lb 2.59 2.67 2.75 2.58 2.74 3.18 Ts1 min 5.08 5.15 5.04 5.10 4.78 5.52 T50 min 6.15 6.32 6.24 6.12 5.90 5.52 T90 min 12.63 12.86 12.86 12.14 11.80 12.49 Tack [Tel Tack] 3.86 2.88 3.31 3.10 3.67 5.12 Tensile Strength MPa 9.47 9.76 9.63 9.49 9.04 8.54 Elongation % 833 836 854 804 785 708  50% Modulus MPa 0.72 0.73 0.75 0.93 0.91 1.28 100% Modulus MPa 1.04 1.05 1.15 1.40 1.46 2.26 200% Modulus MPa 2.05 2.11 2.32 2.66 2.80 4.02 300% Modulus MPa 3.39 3.51 3.66 4.04 4.09 5.21 Shore A 54.00 54.00 53.00 56.00 57.00 60.00 Tear Strength KN/m 53.34 51.33 52.37 52.12 51.96 51.12 Trouser Tear Str. lbf/in 147.00 153.00 142.00 149.00 157.00 169.00 Peel Adhesion 79.00 71.00 73.00 73.00 86.00 46.00

TABLE-US-00004 TABLE 4 Compound 3 1 2 4 5 6 ERTNB ERTNB ERTNB ERTNB ERTNB ERTNB Number 10-54-03 10-54-01 10-54-02 10-54-04 10-54-05 10-54-06 BIIR 2222 PHR 100.00 100.00 100.00 100.00 100.00 100.00 Graphene PHR 0.00 0.50 2.00 5.00 8.00 20.00 Oxygen Permeability using (40.sup.o C., 100% O.sub.2) Ametek Mocon (ASTM D3985) Permeation cc*mm/(m.sup.2*day) 220 201 168 146 152 101 Permeability cc*mm/(m.sup.2*day*mmHg) 0.289 0.264 0.221 0.192 0.200 0.133 Rating (Lower is better) 100 91 76 73 69 46 Air Permeability to ASTM D1434 60° C. Permeability cc STP-cm/cm2-s-atm 2.455 1.249 1.495 1.668 1.745 1.610 Rating (Lower is better) 100 51 61 68 71 66 Note: Permeation and Permeability coefficients taken from the industry reference formulation (#3) in the text Tire Engineering, CRC Press 2021

[0040] Clause 1—A composition including butyl rubber, carbon black, naphthenic oil, aromatic hydrocarbon resin, aliphatic hydrocarbon resin, phenolic tackifier, accelerator, stearic acid, zinc oxide, sulfur, and graphene, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

[0041] Clause 2—A composition including butyl rubber and graphene plate, wherein the graphene plate has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon.

[0042] Clause 3—The composition of clause 2, wherein the graphene plate is between about 0.1 PHR and about 50.0 PHR.

[0043] Clause 4—The composition of clauses 2 or 3, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

[0044] Clause 5—The composition of clauses 2-4, wherein the graphene plate has an oxygen content of less than about 1%.

[0045] Clause 6—The composition of clauses 2-5, wherein the thickness is less than about 1 nm and the aspect ratio is about 1000.

[0046] Clause 7—The composition of clauses 2-6, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

[0047] Clause 8—The composition of clauses 2-7, wherein the composition further includes carbon black.

[0048] Clause 9—The composition of clauses 2-8, wherein the composition further includes naphthenic oil, aromatic hydrocarbon resin, aliphatic hydrocarbon resin, phenolic tackifier, accelerator, stearic acid, zinc oxide, and sulfur.

[0049] Clause 10—The composition of clauses 2-9, wherein the graphene plate is between about 1.0 PHR and about 2.0 PHR, wherein the composition has no clay fillers.

[0050] Clause 11—A method of compounding rubber, the method including the steps of blending butyl rubber with graphene, wherein the graphene has a thickness of less than about 3.2 nm, a particle size of between about 50 nm and about 10 μm, and contains greater than about 95% carbon, exfoliating the graphene into plates, wherein the graphene plates as carboxylic acid, ketone, aldehyde, or hydroxyl groups on the graphene plate surface or graphene plate edges, and aligning the graphene plates into perpendicular alignment, such that the graphene plates provide a barrier to migration oxygen, nitrogen, moisture, or water vapor molecules.

[0051] Clause 12—The method of clause 11, wherein the graphene plate is between about 0.1 PHR and about 50.0 PHR.

[0052] Clause 13—The method of clauses 11 or 12, wherein the graphene plate has a surface area from about 100 m.sup.2/gram to about 250 m.sup.2/gram.

[0053] Clause 14—The method of clauses 11-13, wherein the graphene plate has an oxygen content of less than about 1%.

[0054] Clause 15—The method of clauses 11-14, wherein the thickness is less than about 1 nm and the aspect ratio is about 1000.

[0055] Clause 16—The method of clauses 11-15, wherein the graphene plate is between about 0.5 PHR and about 8.0 PHR.

[0056] Clause 17—The method of clauses 11-16, wherein the method further includes the step of blending in carbon black.

[0057] Clause 18—The method of clauses 11-17, wherein the method further includes the step of blending in naphthenic oil, aromatic hydrocarbon resin, aliphatic hydrocarbon resin, phenolic tackifier, accelerator, stearic acid, zinc oxide, and sulfur.

[0058] Clause 19—The method of clauses 11-18, wherein the graphene plate is between about 1.0 PHR and about 2.0 PHR, wherein no clay fillers are added.

[0059] Clause 20—The method and composition of clauses 1-19, wherein the butyl rubber can be chlorobutyl or bromobutyl, or a combination of both.

[0060] Non-limiting aspects have been described, hereinabove. It will be apparent to those skilled in the art that the above methods and apparatuses may incorporate changes and modifications without departing from the general scope of the present subject matter. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.