Conveyor belt cover compound

Abstract

Graphene is an allotrope or one of the several physical forms of carbon, other examples being graphite, fullerenes, and diamond. At the atomic level, it is in the form a sheet with a thickness nominally under 1.0 nanometer and up to 1 micron in diameter. Sheets of such dimensions when added to other composites facilitate increases in thermal and electrical conductivity and in the case of elastomer nanocomposites, improvements in hysteresis, compounding ingredient dispersion, aging resistance, and reductions in permeability. In the case of conveyor belt cover compounds, natural rubber based formulations are preferred due to high tensile strength, tear strength and damage resistance, and high resistance to abrasion. Graphene as a performance additive enables further improvement in these critical properties.

Claims

1. A conveyor belt comprising: natural rubber; a peptizer; carbon black; 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 ?m, and contains greater than about 95% carbon; aliphatic hydrocarbon resin; treated distillate aromatic extract; N-(1,3-dimethylbutyl)-N-phenyl-1,4-benzenediamine; 2,2,4-trimethyl-1,2-dihydroquinoline; paraffinic wax; microcrystalline wax; zinc oxide; stearic acid; N-tert-butyl-benzothiazole sulfonamide; sulfur; and pre vulcanization inhibitor.

2. The conveyor belt of claim 1, wherein the graphene is pristine graphene.

3. A conveyor belt comprising: rubber; carbon black; 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 ?m, and contains greater than about 95% carbon.

4. The conveyor belt of claim 3, wherein the graphene is a graphene plate, wherein the graphene plate is present in the amount of between about 0.5 PHR and about 10.0 PHR.

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

6. The conveyor belt of claim 5, wherein the graphene plate has an oxygen content of less than about 1%.

7. The conveyor belt of claim 4, wherein the graphene plate is present in the amount of between about 0.5 PHR and about 8.0 PHR.

8. The conveyor belt of claim 7, wherein the graphene plate is present in the amount of between about 1.0 PHR and about 2.0 PHR, wherein the composition has no clay fillers.

9. The conveyor belt of claim 7, wherein the graphene plate is present in the amount of between about 3.0 PHR and about 5.0 PHR.

10. The conveyor belt of claim 3, wherein the thickness of the graphene plate is less than about 1 nm and the aspect ratio of the graphene plate is about 1000.

11. The conveyor belt of claim 3, wherein the conveyor belt further comprises carbon black.

12. The conveyor belt of claim 11, wherein the conveyor belt further comprises: a peptizer; aliphatic hydrocarbon resin; treated distillate aromatic extract; an antiozonant; and, an antioxidant.

13. The conveyor belt of claim 12, wherein the conveyor belt further comprises: paraffinic wax; microcrystalline wax; zinc oxide; stearic acid; an accelerator; sulfur; and a pre vulcanization inhibitor.

14. The conveyor belt of claim 13, wherein the antiozonant is N-(1,3-dimethylbutyl)-N-phenyl-1,4-benzenediamine and the antioxidant is 2,2,4-trimethyl-1,2-dihydroquinoline.

15. The conveyor belt of claim 14, wherein the accelerator is N-tert-butyl-benzothiazole sulfonamide and the peptizer is 2,2-dibenzamido-diphenyldisulphide, wherein the rubber is natural rubber or butyl rubber.

16. The conveyor belt of claim 3, wherein the graphene is pristine graphene.

Description

III. BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present teachings are described hereinafter with reference to the accompanying drawings.

(2) FIG. 1 shows graphene forms;

(3) FIG. 2 shows a belt construction;

IV. DETAILED DESCRIPTION

(4) FIG. 1 shows three forms of graphene. FIG. 2 shows a schematic of a conveyor belt construction, showing upper cover 10, fabric reinforcement friction 12, 14, and lower cover 16. Among the many aspects of a conveyor belt cover compound are high tear strength, adhesion between the cover compound and the layer of rubber below it such as the friction of tie gum, and excellent abrasion resistance. A high performance conveyor belt cover compound will therefore consist of natural rubber compounded with abrasion resistance carbon black and other compound ingredients to ensure durability in service. These ingredients will include an antioxidant, antiozonant, compound process oil, and a vulcanization system consisting of zinc oxide, stearic acid, sulfur, and an accelerator such t-butyl benzothiazole disulfide (TBBS). A simplified model compound is illustrated in Table I.

(5) Graphene is also added to the rubber and mixed as noted above. Graphene will be added to a rubber formulation, such as one based on natural rubber, at levels from about 0.1 PHR to about 50.0 PHR, including about 0.5 PHR to about 8.0 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. Graphene in this invention is described as in Table II.

(6) TABLE-US-00001 TABLE I Simplified Model Conveyor Belt Cover Compound Based in Natural Rubber PHR (parts per hundred rubber) Natural Rubber (TSR10) 100.00 Carbon Black (HAF N330) 50.00 Process Oil (aromatic type) 8.00 Antioxidant (TMQ) 2.50 Antiozonant (6PPD) - Optional 2.50 Zinc Oxide 3.0 Stearic Acid 2.0 Accelerator 1 (CBS) 1.00 Accelerator 2 (TMTD) - optional 0.10 Sulfur 2.00 Retarder (PVI) - optional 0.15 TSRtechnical specified rubber HAFhigh abrasion furnace TMQ2,2,4-Trimethyl-1,2-Dihydroquinoline polymer PPDN-(1,3-dimethylbutyl)-N-phenyl-1,4-benzenediamine CBSN-cyclohexyl-2- benzothiazole sulfenamide TMTDTetramethylthiuram disulfide PVIpre vulcanization inhibitor

(7) The particle size range of graphene used in the present teachings can range from about 50 nm to about 10 ?m. In one aspect, the particle size range is from about 100 nm to about 5 ?m. 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 ?m, greater than about 2 ?m, greater than about 3 ?m, greater than about 4 ?m, greater than about 5 ?m, greater than about 6 ?m, greater than about 7 ?m, greater than about 8 ?m, or greater than about 9 ?m. In one aspect, the particle size range is less than about 10 ?m, less than about 9 ?m, less than about 8 ?m, less than about 7 ?m, less than about 6 ?m, less than about 5 ?m, less than about 4 ?m, less than about 3 ?m, less than about 2 ?m, less than about 1 ?m, 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 that 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 would 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.

(8) TABLE-US-00002 TABLE II Typical Properties of Graphene Form Powder, dark grey, odorless Carbon >95% Particle size 50 nm to 10 ?m 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

Measurement of Properties of Rubber Compositions

(9) 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. Tear strength and adhesion were measured following ASTM D624.

Example 1

(10) Natural rubber based high performance conveyor belt compounds can be typically described as shown in Table III. This compound contains super abrasion resistance furnace carbon black (SAF-super abrasion furnace) with the ASTM designation of N121. Pristine graphene is added at various levels to demonstrate an optimum loading or content, in this case from 0.0 PHR to 10.00 PHR.

(11) TABLE-US-00003 TABLE III Conveyor Belt Cover Compound Compound Grade 1 Natural Rubber TSR20 100.00 Peptizer (Renecit 11) 0.10 Carbon Black N121 50.00 Graphene 0.00 Escorez 1102 2.00 TDAE (aromatic oil) 3.00 6PPD 2.50 TMQ 1.50 Paraffin wax 1.00 Microcrystalline wax 1.00 Zinc Oxide 4.00 Stearic acid 2.00 TBBS 1.00 Sulfur 1.00 PVI 0.20

(12) The reference compound in this instance (Table III) is considered representative of compounds for such applications.

Example 2

(13) There are three grades of pristine graphene considered in the study whose properties are described on Table IV. The grade, #2 or PS100 (particle size), was selected for study as it represented the center point of the range of properties for the three available grades.

(14) TABLE-US-00004 TABLE IV Graphene Under the Trade Name Prophene? Grade Number PS100 PS100 PS150 Form Light powder Light powder Light powder Dark grey/ Dark grey/ Dark grey/ Color Black Black Black Odor None None None Carbon wt % 99.50 99.00 95.00 H2O wt % 0.35 0.50 0.75 O2 wt % <1.0 <1.0 <2.0 Ash wt % <0.1 <0.5 <4.5 Resistivity ohm (Powder) cm <50 <100 <150 Resistivity <10 <20 <30 (Sheet) Particle size nm 50 nm-5 ?m 100 nm-5 ?m 150 nm- 10 ?m Mono, bi- >83% >70% >65% tri-layers Particle max 1.7 nm 2.5 nm 2.8 nm thickness Layer count < 10.00 <15 <16 Density g/cm3 2.200 2.200 2.200 Specific m2/g 250.0 180.0 100.0 surface area

Example 3

(15) Graphene identified under the name PS100 was added to the natural rubber conveyor belt cover compound at the following increments, 0.5, 1.0, 2.0, 4.0, and 10.0 PHR. The compounds were mixed and Mooney viscosity and vulcanization kinetics determined (Table V). The following was noted 1. Graphene had no impact or effect on compound viscosity, suggesting no impact on compound factory processing properties 2. Addition of graphene did not shift compound vulcanization kinetics 3. Tensile strength, compound elongation at tensile strength breaking point and modulus and 300% strain were not affected by graphene content

(16) It is evident that addition of pristine graphene as a compounding ingredient not requiring any reformulation to correct loss in fundamental properties as is typical for many other compounding materials.

(17) TABLE-US-00005 TABLE V Addition of Graphene to Conveyor Belt Cover Compound Compound Grade 1 2 3 4 5 6 Natural Rubber TSR20; RSS2 100.00 100.00 100.00 100.00 100.00 100.00 Peptizer (Renecit 11) 0.10 0.10 0.10 0.10 0.10 0.10 Carbon Black 50.00 50.00 50.00 50.00 50.00 50.00 (N12:N121, Alter: N Pristine Graphene 0.00 0.50 1.00 2.00 4.00 10.00 Escorez 1102 2.00 2.00 2.00 2.00 2.00 2.00 TDAE (aromatic oil) 3.00 3.00 3.00 3.00 3.00 3.00 6PPD 2.50 2.50 2.50 2.50 2.50 2.50 TMQ 1.50 1.50 1.50 1.50 1.50 1.50 Paraffinic was 1.00 1.00 1.00 1.00 1.00 1.00 Microcrystalline wax 1.00 1.00 1.00 1.00 1.00 1.00 Zinc Oxide 4.00 4.00 4.00 4.00 4.00 4.00 Stearic acid 2.00 2.00 2.00 2.00 2.00 2.00 TBBS 1.00 1.00 1.00 1.00 1.00 1.00 Sulfur 1.00 1.00 1.00 1.00 1.00 1.00 PVI 0.20 0.20 0.20 0.20 0.20 0.20 Total PHR 169.30 169.80 170.30 171.30 173.30 179.30 Mooney Viscosity ML1 + 4 ML1 + 4 100? C. 61.63 61.66 62.20 62.20 61.06 61.69 MDR Rheometer Temperature 160? C. 160? C. 160? C. 160? C. 160? C. 160? C. MH 9.67 9.56 9.89 9.77 9.67 10.05 ML 1.85 1.75 1.9 1.81 1.78 1.86 Delta Torque 7.82 7.81 7.99 7.96 7.89 8.19 t10 2.55 2.45 2.65 2.52 2.45 2.66 t50 4.47 4.53 4.51 4.50 4.48 4.51 t90 6.73 6.76 6.81 6.67 6.88 6.91 Tensile Strength MPa 26.00 27.00 26.00 26.60 26.70 25.00 Elongation % 568 565 577 593 583 519 100% modulus MPa 2.10 2.00 2.10 2.20 2.50 3.10 200% modulus MPa 5.90 5.90 5.90 5.80 6.50 7.40 300% modulus MPa 11.30 11.40 11.50 11.00 11.90 13.00

Example 4

(18) Tear strength and abrasion resistance were measured on the six compounds illustrated in Table V (see Table VI). At very low levels of pristine graphene, i.e., at 0.5 to 1.0 PHR tear strength improved considerably. Similarly, abrasion resistance demonstrated significant improvement up to 2.0 PHR.

(19) These improvements are achieved with no trade off in any other properties, such as tensile strength, compound processing, and vulcanization properties.

(20) TABLE-US-00006 TABLE VI Effect of Pristine Graphene on Conveyor Belt Compound Tear Strength and Abrasion Resistance Compound Grade 1 2 3 4 5 6 Natural Rubber TSR20; RSS2 100.00 100.00 100.00 100.00 100.00 100.00 Peptizer (Renecit 11) 0.10 0.10 0.10 0.10 0.10 0.10 Carbon Black 50.00 50.00 50.00 50.00 50.00 50.00 (N12:N121, Alter: N Pristine Graphene 0.00 0.50 1.00 2.00 4.00 10.00 Tear Strength KN/m 112.85 153.4 129.67 109.91 94.07 84.37 Abrasion (DIN) mm.sup.3 180 174 143 141 181

(21) 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.