Inner liner for pneumatic tires comprising biochar

Abstract

A rubber composition for improving butyl elastomer tire liners, the rubber composition comprising biochar filler, wherein the tire liner exhibits improved oxygen permeability while displaying a nominal elastic change compared to a tire liner composed of carbon black as filler. The rubber composition comprises butyl rubber, a vulcanization system, and in some embodiments further comprises zinc oxide, fatty acids, and resin.

Description

Technical Field

[0001] The subject of this invention relates to a tire liner and a tire comprising such a liner, the tire liner having a rubber composition comprising a butyl rubber-based elastomer matrix and containing biochar. Background Technology

[0002] Tubeless tires have an inner surface composed of a low-permeability composition to prevent air leakage and protect the tire's oxidation-sensitive internal components from oxygen and water penetration. For example, the tire's ply layers are made of oxidation-sensitive metal cords. The protection provided by the tire liner allows for improved tire durability and reduced need for repeated inflation. Protection of the tire's inner surface is typically achieved through a liner composed of an elastomer composition based on butyl rubber. In fact, the air impermeability of butyl rubber is associated with a non-negligible minimum thickness (in millimeters). Reducing this thickness by improving the performance of the air-impermeable liner reduces tire weight and hysteresis, thereby improving the overall efficiency and environmental impact of both the tire and the vehicle.

[0003] With fuel conservation and environmental protection becoming priorities, there is a desire to produce liners that are less air-permeable and exhibit the lowest possible weight and hysteresis to achieve improved tire rolling resistance and overall vehicle efficiency. Furthermore, environmental concerns have motivated consumers and product manufacturers to seek products that utilize renewable materials and reduce reliance on non-renewable materials such as petroleum derivatives.

[0004] Other publications (such as EP1939015A2) demonstrate that permeability is improved by using high-surface-area activated carbon as a filler to absorb oxygen. This publication employs multiple layers to block air permeation and individually absorb the oxygen that does permeate, as disclosed in paragraphs [0009-0010]. The addition of these layers increases weight and increases the tire's hysteresis characteristics, thereby reducing its overall environmental impact.

[0005] There is a need for a tire liner with reduced permeability to reduce liner thickness and thus improve the overall environmental impact of tires. Summary of the Invention

[0006] Aspects and advantages of the invention will be set forth in part in the description which follows, or will be apparent from the specific embodiments, or may be learned by practice of the invention.

[0007] In one exemplary embodiment, the tire liner for a tire comprises butyl rubber, a vulcanization system, and biochar filler per 100 parts by weight of rubber, and the tire liner is prepared to have improved permeability compared to the same formulation using carbon black.

[0008] In another exemplary embodiment, the tire liner utilizes a 50m 2 / g to 600m 2 / g surface area of ​​biochar filler.

[0009] In another exemplary embodiment, the tire liner utilizes a 400m 2 / g to 600m 2 / g surface area of ​​biochar filler.

[0010] In another exemplary embodiment, the tire liner utilizes a diameter greater than 500m 2 / g surface area of ​​biochar filler.

[0011] In another exemplary embodiment, the tire liner of any of the above-mentioned items also contains zinc oxide.

[0012] In another exemplary embodiment, the tire liner of any of the above embodiments further comprises a fatty acid. In at least one embodiment, the fatty acid is stearic acid.

[0013] In another embodiment, the tire liner of any of the above embodiments further comprises a resin. In at least one embodiment, the resin for the pneumatic tire liner is an octylphenol-formaldehyde resin.

[0014] In another embodiment, the tire liner of any of the above embodiments further comprises a vulcanization system consisting of sulfur and an accelerator. In at least one embodiment, in the pneumatic tire liner, the accelerator is selected from the group consisting of benzothiazole disulfide, 2-mercaptobenzothiazole, and benzothiazolyl-2-sulfenylmorpholine.

[0015] In another embodiment of the invention, the tire comprises any of the tire liners described herein.

[0016] In another exemplary embodiment, the tire liner for a tire comprises butyl rubber; a vulcanization system; and biochar filler, wherein the pneumatic tire liner has 50% biochar filler particles with an average particle size in the range of 0.1 µm to 2.0 µm.

[0017] According to the aforementioned implementation scheme, 50% of the biochar filler particles have an average particle size in the range of 0.2µm to 1.0µm.

[0018] According to the aforementioned implementation scheme, 50% of the biochar filler particles have an average particle size of less than 1.0 µm.

[0019] In another exemplary embodiment, the tire liner for a tire comprises butyl rubber; a vulcanization system; and biochar filler, wherein the pneumatic tire liner has 50% biochar filler particles with an average particle size of less than 2.0 µm.

[0020] These and other features, aspects, and advantages of the invention will become more readily understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the detailed description, serve to explain the principles of the invention. Detailed Implementation

[0021] Specific embodiments of the invention include a liner and a tire having such a liner, the liner having improved transfer rate and permeability properties. This improvement in transfer rate and permeability has been achieved by forming a unique rubber composition containing biochar as a filler. Such tires are particularly suitable for passenger cars and / or light trucks, and while some embodiments are limited to this type of use, others are broader and can include tires suitable for other vehicles including heavy trucks, aircraft, etc.

[0022] For the purposes of describing the invention, specific reference will now be made to embodiments and examples of the invention. Each example is provided as an explanation of the invention and not as a limitation thereof. In fact, those skilled in the art will appreciate that various modifications and changes can be made to the invention without departing from its scope or spirit. For example, a feature or step described as part of one embodiment may be used with another embodiment or step to produce yet another embodiment or method. Therefore, it is intended that the invention cover such modifications and variations as if they were within the scope of the appended claims and their equivalents.

[0023] It has been found that combining butyl rubber (such as bromobutyl elastomer) with milled biochar produces a surprisingly improved rubber with superior impermeability and transfer rate compared to compositions containing carbon black.

[0024] In one implementation, the liner forms the innermost layer of the tire.

[0025] The inner butyl rubber liner is composed of a bromobutyl rubber-based rubber composition containing a dispersion of milled biochar. In one embodiment, the liner contains no other reinforcing agents. In another embodiment, trace amounts of another reinforcing carbon black may be present. In yet another embodiment, equivalent amounts of carbon black and biochar are present. In yet another embodiment, 10 phr of biochar is present.

[0026] Any butyl rubber used for the lining can be used in the present invention, including halogenated butyl rubbers (such as chlorobutyl rubber, bromobutyl rubber) and non-halogenated butyl rubbers (such as conventional butyl rubber), such as mixtures of isobutylene rubber and isoprene. Similarly, combinations of butyl rubbers can be used without departing from the present invention.

[0027] vulcanization system For specific implementations, the vulcanization system is preferably a sulfur- and accelerator-based system, but other vulcanizing agents known to those skilled in the art may also be useful. As used herein, vulcanizing agents are those materials that cause rubber crosslinking and can therefore be added only to the production mixture to prevent premature curing. Such agents include, for example, elemental sulfur, sulfur donors, and peroxides. Any compound capable of acting as an accelerator for elastomer vulcanization in the presence of sulfur can be used, specifically those selected from the group consisting of: 2-mercaptobenzothiazolyl disulfide (abbreviated “MBTS”), N-cyclohexyl-2-benzothiazolyl sulfonamide (abbreviated “CBS”), N,N-dicyclohexyl-2-benzothiazolyl sulfonamide (abbreviated “DCBS”), N-tert-butyl-2-benzothiazolyl sulfinylimide (abbreviated “TBBS”), N-tert-butyl-2-benzothiazolyl sulfinylimide (abbreviated “TBSI”), and mixtures of these compounds. Preferably, a sulfinyl amide-type main accelerator is used.

[0028] The rubber composition may also include a vulcanization retarder, a vulcanization system based on, for example, sulfur or peroxide, a vulcanization accelerator, a vulcanization activator, etc.

[0029] The vulcanization system may also include various known auxiliary accelerators or vulcanization activators, such as zinc oxide, stearic acid and guanidine derivatives (specifically diphenylguanidine).

[0030] mix

[0031] The rubber composition, as an embodiment of the present invention, can be prepared in a suitable mixer in a manner known to those skilled in the art. Typically, mixing can be carried out in two consecutive preparation stages, the first stage being a thermomechanical process at a high temperature, followed by a second stage being a mechanical process at a lower temperature.

[0032] The rubber composition, as an embodiment of the present invention, can be prepared in a suitable mixer in a manner known to those skilled in the art. Typically, mixing can be carried out in two consecutive preparation stages, the first stage being a thermomechanical process at a high temperature, followed by a second stage being a mechanical process at a lower temperature.

[0033] The first stage (sometimes referred to as the "non-productive stage") involves thoroughly mixing the various components of the composition, typically by kneading, but excluding some components of the vulcanization system, such as vulcanizing agents, accelerators, and retarders. This is carried out in a suitable kneading apparatus (such as a Banbury-type internal mixer) until a maximum temperature, typically between 120°C and 190°C, is reached under mechanical work and high shear applied to the mixture, indicating adequate dispersion of the components.

[0034] Following the cooling of the mixture, a second stage of mechanical processing is carried out at a lower temperature. Sometimes referred to as the “productive” stage, this finishing stage involves incorporating some of the aforementioned vulcanization system (including vulcanizing agents, accelerators, and retarders) that were not added in the “non-productive” stage into the rubber composition using suitable equipment such as an open mill. This is performed at a sufficiently low temperature (i.e., below the vulcanization temperature of the mixture) for an appropriate time (typically, for example, between 1 and 30 minutes or between 2 and 10 minutes) to prevent premature vulcanization.

[0035] Example 1

[0036] An exemplary, illustrative oxygen-barrier rubber composition comprising a dispersion of bromobutyl rubber containing milled biochar is presented as samples A, B, and C.

[0037] The biochar used was commercially available Rogue BioChar, available at Oregon Biochar Solutions 2350 Ave G.; White City, OR 97503; USA. Rogue BioChar has a 553m³ / h content. 2 / g surface area and less than 3% ash content. The biochar was milled to an average diameter of 0.32µm by SEM examination of the particles in the rubber compound. Particle "diameter" should be understood as the maximum diameter of the particles. Those skilled in the art will understand that this results in the same size range of biochar particles as expected from such milling processes, with 50% of the particles (by particle count) falling within the particle size range of 0.1µm to 2.0µm average diameter.

[0038] In this embodiment, the grinding of samples A, B, and C is shown to be performed without solvent, which is otherwise referred to as “dry grinding.” Alternatively, grinding may occur in a solvent. Such solvents may include methanol, ethanol, acetone, or isopropanol. Grinding may also occur in the presence of a grinding aid, such as a proton acceptor, such as diphenylguanidine (“DPG”), polyethylene glycol (“PEG”), rosin amine, or polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (“TMQ”). Grinding can be performed by methods known to those skilled in the art, such as those shown in PCT Publication WO 2022 / 146432.

[0039] The biochar used in this invention will have a high surface area, measured as 50 m² / g to 600 m² / g, as determined by BET surface area measurement. In other embodiments, the biochar will have a surface area of ​​400 m² / g to 600 m² / g. In other embodiments, the biochar will have a surface area greater than 500 m² / g. In other embodiments, the biochar will have a surface area of ​​500 m² / g to 600 m² / g. Rubber compositions containing high-surface-area biochar have been found to have advantageous permeability properties compared to N722 carbon black, which has a lower surface area. Although carbon black with a high surface area similar to that of the milled biochar used would result in a high elastic modulus in the rubber, thus adversely affecting the usefulness of the resulting rubber composition, the high surface area of ​​the milled biochar results in the rubber composition having an elastic modulus similar to that of the N772 carbon black formulation used in witness sample "W".

[0040] It was found that the biochar used had a content of 1.5 g / cm³. 3 Up to 1.7 g / cm 3 The density and total surface energy (polar; dispersed 29.2 mJ / m2 to 29.3 mJ / m2) of the composition “W” shown in Table 1 below are 40 mJ / m2 to 42 mJ / m2, 11 mJ / m2 to 13 mJ / m2 of polar surface energy and 29.2 mJ / m2 to 29.3 mJ / m2 of dispersed surface energy, which are otherwise substantially similar to the carbon black witness N772 used in the composition “W” shown in Table 1 below.

[0041] Table 1. Properties of biochar and carbon black N772 .

[0042]

[0043] In one embodiment, the biochar is wet-milled in ethanol. In another embodiment, the biochar is dry-milled.

[0044] The witness material W is composed of bromobutyl rubber containing N772 carbon black dispersion.

[0045] The composition of the rubber is shown in Table 2 below. All exemplary compositions consist of the following: 100 phr of bromobutyl rubber; 1.5 phr of zinc oxide; 1.5 phr of fatty acid, here stearic acid; 2.5 phr of resin, here octylphenol formaldehyde resin; 1.5 phr of sulfur; 1.2 phr of accelerator; and 50 phr of filler. The accelerator is selected from the group consisting of benzothiazole disulfide (MBTS), 2-mercaptobenzothiazole (MBT), and benzothiazole-2-sulfenylmorpholine (MBS).

[0046] Table 2. Rubber Sample Compositions .

[0047]

[0048] For witness material W, the accelerator used is MBTS, and the filler is N772 carbon black.

[0049] For comparative samples A, B, and C, the same reinforcing agent (ground biochar) was used, but different accelerators were used for each. For comparative sample A, the accelerator was MBTS; for comparative sample B, the accelerator was MBT; and for comparative sample C, the accelerator was MBS.

[0050] The rubber composition, as an embodiment of the present invention, can be prepared in a suitable mixer in a manner known to those skilled in the art. A rubber sample is prepared by mixing the elastomer with reinforcing fillers and other rubber compounding components in a non-productive mixing stage within an internal rubber mixer for, for example, about 4 minutes, to a temperature, for example, less than 110°C. The rubber composition and curing agent are then ground and cooled between the non-productive and productive mixing steps.

[0051] Samples with a thickness (T) of 1.1 mm to 1.4 mm were prepared. Permeability values ​​were measured at 40 °C using a Mocon Oxtran 2 / 60 permeability "tester". Cured samples in the form of a disc with a predetermined thickness (approximately 1.1 mm to 1.4 mm) were assembled into the apparatus and sealed with vacuum grease. One side of the disc was kept under 10 psi of nitrogen, while the other side was kept under 10 psi of oxygen. An oxygen detector was used to monitor the increase in oxygen concentration on the side kept under nitrogen. The oxygen concentration on the side kept under nitrogen was recorded, ensuring a constant value for determining oxygen permeability.

[0052] The result shows that it is in cc / m 2 The permeability is calculated per day, which reports the gas volume in cubic centimeters divided by the rubber surface area in square meters, and in cc-mm (m²) permeability. 2The permeation rate (measured in cubic centimeters) was reported by multiplying the gas volume in cubic centimeters by the rubber thickness in millimeters and dividing by the rubber surface area in square meters to illustrate the thickness variation for each sample. The test results are shown in Table 3 below.

[0053] Table 3. Permeability of rubber samples .

[0054]

[0055] The results showed that the permeability of all samples containing biochar as a filler was significantly improved.

[0056] Example 2

[0057] Sixteen test samples were produced, each containing the mixture used in Sample A of Example 1 above. The increased duration was tested for two samples respectively, indicating that absorption alone was not the cause of the increased decrease in oxygen permeability through the sample.

[0058] Prepare a sample with a thickness (T) of 1.1 mm. Measure the permeability at 40 °C using a Mocon Oxtran 2 / 60 permeability "tester". Assemble the cured sample, in the form of a disc with a predetermined thickness (approximately 1.1 mm), into the apparatus and seal it with vacuum grease. One side of the disc is held under 10 psi of nitrogen, while the other side is held under 10 psi of oxygen. Monitor the increase in oxygen concentration on the side held under nitrogen using an oxygen detector. Record the oxygen concentration on the side held under nitrogen, ensuring a constant value for determining oxygen permeability.

[0059] The result shows that it is in cc / m 2 The permeability is calculated per day, which reports the gas volume in cubic centimeters divided by the rubber surface area in square meters, and in cc-mm (m²) permeability. 2 The permeation rate (measured in cubic centimeters) was reported by multiplying the gas volume in cubic centimeters by the rubber thickness in millimeters and dividing by the rubber surface area in square meters to illustrate the thickness variation for each sample. The test results are shown in Table 4 below.

[0060] Table 4. Sample testing conducted during the eight-day test. .

[0061]

[0062] The stability of the sample's permeability over time indicates that the improvement in permeability is due to some factor other than adsorption.

[0063] As used herein, “phr” means “parts in 100 parts by weight of rubber” and is a common measure in the art, where a component of a rubber composition is measured relative to the total weight of the rubber in the composition, that is, the weight parts of that component in 100 parts by weight of total rubber in the composition.

[0064] As used herein, elastomers and rubbers are synonymous terms.

[0065] The selected combinations of aspects of the disclosed technology correspond to various different embodiments of the invention. It should be noted that each of the exemplary embodiments presented and discussed herein should not imply limitation on the subject matter. Features or steps described or illustrated as part of one embodiment may be combined with aspects of another embodiment to produce yet another embodiment. Furthermore, certain features may be interchanged with similar, unstated means or features that perform the same or similar function.

[0066] The terms “a,” “one,” and the singular form of the word should be treated as the plural form containing the same word, such that these terms imply the provision of one or more of something. The terms “at least one” and “one or more” are used interchangeably. A range described as “between a and b” includes the values ​​of both “a” and “b.”

[0067] No reference to any document constitutes prior art to any invention disclosed or claimed herein, nor does it imply that the document, alone or in combination with any other one or more referenced documents, teaches, suggests, or discloses any such invention. Furthermore, in the event of any conflict between the meaning or definition of any term in this document and any meaning or definition of the same term in a document incorporated herein by reference, the meaning or definition given to that term in this document shall prevail.

Claims

1. A pneumatic tire liner, wherein the pneumatic tire liner comprises, based on 100 parts by weight of rubber: Butyl rubber; Vulcanization system; and Biochar packing material.

2. The pneumatic tire innerliner of claim 1, wherein the biochar filler has a surface area of 50 m 2 / g to 600 m 2 / g.

3. The pneumatic tire innerliner of claim 2, wherein the biochar filler has a surface area of 400 m2 / g to 600 m2 / g. 2 2 / g to 600 m2 / g.​ 4. The pneumatic tire liner according to claim 3, wherein the biochar filler has a density of 500 m³. 2 / g to 600m 2 / g of surface area.

5. The pneumatic tire liner according to claim 1, wherein the biochar filler has a density greater than 500 μm 2 / g of surface area.

6. The pneumatic tire liner according to any one of the preceding claims, wherein the pneumatic tire liner further comprises zinc oxide.

7. The pneumatic tire liner according to any one of the preceding claims, wherein the pneumatic tire liner further comprises fatty acids.

8. The pneumatic tire liner according to any one of the preceding claims, wherein the pneumatic tire liner further comprises resin.

9. The pneumatic tire liner according to claim 7, wherein the fatty acid is stearic acid.

10. The pneumatic tire liner according to any one of the preceding claims, wherein the vulcanization system comprises: Sulfur and Accelerator.

11. The pneumatic tire liner according to claim 7, wherein the accelerator is selected from the group consisting of benzothiazole disulfide, 2-mercaptobenzothiazole and benzothiazolyl-2-sulfonylmorpholine.

12. A pneumatic tire liner, the pneumatic tire liner comprising: Butyl rubber; sulfur; Accelerator; Zinc oxide; Resin; and Biochar packing material, wherein the biochar packing material has a density of 500m 2 / g to 600m 2 / g of surface area.

13. The pneumatic tire liner according to claim 9, wherein the accelerator is selected from the group consisting of benzothiazole disulfide, 2-mercaptobenzothiazole and benzothiazolyl-2-sulfonylmorpholine.

14. The pneumatic tire liner according to claim 12 or claim 13, wherein the pneumatic tire liner further comprises fatty acids.

15. The pneumatic tire liner of claim 14, wherein the fatty acid is stearic acid.

16. The pneumatic tire liner according to any one of claims 12 to 15, wherein the resin is octylphenol formaldehyde.

17. A tire comprising an inner liner according to any one of the preceding claims.

18. The pneumatic tire liner according to any one of the preceding claims, wherein 50% of the biochar filler particles have an average particle size in the range of 0.1 µm to 2.0 µm.

19. The pneumatic tire liner according to any one of the preceding claims, wherein 50% of the biochar filler particles have an average particle size in the range of 0.2 µm to 1.0 µm.

20. The pneumatic tire liner according to any one of the preceding claims, wherein 50% of the biochar filler particles have an average particle size of less than 1.0 µm.

21. The pneumatic tire liner according to any one of the preceding claims, wherein 50% of the biochar filler particles have an average particle size of less than 2.0 µm.

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