tire

Abstract

To provide a tire that offers excellent wear resistance and can contribute to increasing the proportion of sustainable materials. [Solution] A tire is provided comprising a tire belt and a tire tread portion in contact with the outer radial side of the tire belt, wherein the amount of recycled material contained in the rubber composition of the tire tread portion varies in the width direction.

Description

[[Technical Field]]

[0001] The present disclosure relates to a tire. [[Background Art]]

[0002] The tread of a tire is required to have abrasion resistance, and performance is improved by optimizing the material used for producing the tread. For example, Patent Document 1 discloses that abrasion resistance can be improved by blending predetermined amounts of a reinforcing filler, a tetrazine-based compound, and a hydrocarbon resin respectively into a predetermined rubber component. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] International Publication No. 2018 / 190427 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In recent years, from the perspective of social sustainability, the use of so-called sustainable materials such as materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) has been required for businesses and products, and improvement of the ratio of sustainable materials (hereinafter, also sometimes referred to as "sustainable ratio") is also required for various members used in tires.

[0005] Furthermore, in order to increase the sustainability rate and reduce environmental impact, the use of recycled resources such as recycled carbon black, powdered rubber, and recycled rubber in tire rubber formulations is being considered. However, recycled materials are more susceptible to the inclusion of impurities and deterioration of the material itself compared to unused materials, and as a result, their quality may be inferior to unused materials. From the perspective of rubber abrasion resistance, using low-quality recycled materials generally reduces abrasion resistance, making simple substitution difficult. This may necessitate limiting the amount used in the formulation, obtaining high-performance recycled materials at a cost, or requiring additional processing.

[0006] Furthermore, while it is desirable for the tire tread to wear evenly as it wears down, from the standpoint of tire life and performance, the wear rate may differ between parts of the tread, such as near the center line (center section) and near the shoulder (shoulder section), due to the load on the tire and the influence of the road surface. In this case, uneven wear occurs on the tread surface, which may affect the expected performance and how the tire is used.

[0007] This disclosure is made in view of the above points, and aims to provide a tire that is excellent at suppressing uneven wear and can contribute to improving the proportion of sustainable materials. [Means for solving the problem]

[0008] A tire according to a first aspect of this disclosure comprises a tire belt and a tire tread portion in contact with the radially outer side of the tire belt, wherein the amount of recycled material contained in the rubber composition of the tire tread portion varies in the width direction.

[0009] A tire according to a second aspect of this disclosure is a tire according to the first aspect, wherein the rubber composition uses rubber in which more recycled material is incorporated in the shoulder portion than in the center portion.

[0010] A tire according to a third aspect of this disclosure is a tire according to the first aspect, wherein the rubber composition uses rubber in which more recycled material is compounded in the center portion than in the shoulder portion.

[0011] A tire according to a fourth aspect of this disclosure is a tire according to a first aspect, wherein the recycled material is powdered rubber, reclaimed rubber, or recycled carbon black.

[0012] The tire according to the fifth aspect of this disclosure is the tire according to the first aspect, wherein the tire is a retreaded tire.

[0013] The tire according to the sixth aspect of this disclosure is the tire according to the first aspect, wherein the tire is a mining tire.

[0014] A tire according to a seventh aspect of this disclosure is a tire according to a first aspect, wherein the amount of recycled material contained in the rubber composition of the tire tread is determined based on wear data when driving on a road surface.

[0015] The eighth aspect of this disclosure is the tire according to the first aspect, wherein the amount of recycled material contained in the rubber composition of the tire tread is determined based on data relating to the effect of the recycled material on the wear resistance rate. [Effects of the Invention]

[0016] This disclosure provides a tire that excels at suppressing uneven wear and can contribute to increasing the proportion of sustainable materials. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows an example of the configuration of a tire 20 in which recycled resources are used according to an embodiment of the disclosed technology, as a cross-sectional view. [Figure 2] This figure shows examples of formulations with and without recycled resources. [Figure 3]Figure 2 shows a graph illustrating the wear results of tire 20 manufactured using the compound shown in Figure 2. [Modes for carrying out the invention]

[0018] Hereinafter, an example of an embodiment of this disclosure will be described with reference to the drawings. In each drawing, identical or equivalent components and parts are given the same reference numerals. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0019] In this specification, recycled resources refer to resources obtained by recycling products that have been used, collected without being used, or discarded. For example, recycled resources include recycled carbon black, powdered rubber, and recycled rubber obtained by recycling used rubber products such as used tires. Recycled carbon black refers to carbon black recovered from raw materials that are waste materials used for recycling. Examples of waste materials used for recycling include rubber products containing carbon black (especially vulcanized rubber products), such as used rubber and used tires, and waste oil. Recycled carbon black is different from carbon black that is manufactured directly from hydrocarbons such as petroleum and natural gas as raw materials, i.e., carbon black that is not recycled. Here, "used" includes not only products that have been used and then discarded, but also products that were manufactured but discarded without actually being used.

[0020] The recycled carbon black used in the present embodiment is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. In this case, raw materials used in the manufacture of rubber products can be recycled within the industry, which is preferable from the viewpoint of sustainability. Furthermore, the recycled carbon black used in the present embodiment is preferably obtained from a solid residue produced by pyrolysis of the vulcanized rubber product containing the above carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either.

[0021] In addition, recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 mentions "Rubber Chemistry and Technology", Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440 and 442, and describes that it can be obtained by pyrolysis of organic materials at 550 to 800°C with exclusion of oxygen, or by vacuum pyrolysis at a relatively low temperature (paragraph

[0027] ). As mentioned in paragraph

[0004] of Japanese Patent No. 6856781, carbon black obtained from such a pyrolysis process generally lacks functional groups on its surface (Comparison of surface morphology and chemistry of pyrolytic carbon black and commercial carbon black, Powder Technology 160 (2005) pp. 190-193).

[0022] The recycled carbon black may be free of functional groups on its surface, or may be treated to include functional groups on its surface. The treatment for including functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Further, in Japanese Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to the present embodiment also includes these carbon blacks treated to contain functional groups on their surfaces.

[0023] FIG. 1 is a cross-sectional view illustrating an example of the configuration of a tire 20 in which recycled resources are used. FIG. 1 shows a tire tread portion TR, a tire belt BL, and a carcass CS as representative tire constituent members of the tire 20. In the present specification, the direction toward the center portion in the width direction of the tire tread portion TR is also referred to as the center direction, and the direction toward the shoulder portion of the tire 20 opposite to the center direction is also referred to as the shoulder direction.

[0024] The rubber composition for a tire tread used for the tire tread portion TR in the present embodiment contains a rubber component, a resin component, and a filler.

[0025] In this embodiment, the amount of recycled material contained in the rubber composition of the tire tread TR of the tire 20 is characterized by varying in the width direction. That is, the amount of recycled material contained in the rubber composition of the tire tread TR is not uniform, but differs depending on the location. Because the amount of recycled material contained in the rubber composition of the tire tread TR differs depending on the location, it is possible to achieve a superior effect in suppressing uneven wear of the tire tread TR compared to the case where the amount of recycled material is uniform, and to contribute to improving the proportion of sustainable materials. Generally, recycled materials are inferior to unused materials in terms of wear resistance, so by making the amount of recycled material in the rubber composition used in the parts where wear progresses quickly 0 or small, and the amount of recycled material in the rubber composition used in the parts where wear progresses relatively slowly, the wear rate of the entire tread can be made uniform, which leads to the suppression of uneven wear.

[0026] More specifically, in the rubber composition of the tire tread section TR, rubber is used in which more recycled material is blended in the shoulder section than in the center section. Furthermore, in the rubber composition of the tire tread section TR, rubber is used in which more recycled material is blended in the center section than in the shoulder section. By using rubber blended with recycled material in this way, the wear resistance of the tire tread section TR is improved compared to when the amount of recycled material is uniform, and it can also contribute to improving the proportion of sustainable materials.

[0027] Furthermore, the tire tread portion TR may exhibit different wear conditions from the center towards the shoulder, and uneven wear is particularly undesirable from the standpoint of tire life and performance. Therefore, it is desirable for the tire tread portion TR to have a uniform wear rate from the center towards the shoulder. A uniform wear rate from the center towards the shoulder can be achieved by having the amount of recycled material contained in the rubber composition of the tire tread portion TR not uniform, but varying depending on the location.

[0028] The amount of recycled material included in the rubber composition of the tire tread portion TR may be determined based on data regarding the wear of the tire tread portion TR when driven on the target road surface. For example, data regarding the wear of the tire tread portion TR after driving a predetermined distance may be collected, and the amount of wear with recycled material included may be compared with the amount of wear without recycled material included, and the amount of recycled material included may be determined such that the increase in wear is kept within a predetermined amount. Alternatively, the amount of recycled material included in the rubber composition of the tire tread portion TR may be determined based on data regarding the effect of recycled material on the wear resistance rate. For example, data regarding the wear of the tire tread portion TR after driving a predetermined distance may be collected, and the wear resistance rate with recycled material included may be compared with the wear resistance rate with recycled material included, and the amount of recycled material included may be determined such that the increase in wear resistance rate is kept within a predetermined amount.

[0029] Generally, the materials for tire rubber compositions (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment for production, and are typically produced in large factories in specific regions, requiring significant energy for the storage and transportation of raw materials and finished products. In contrast, materials derived from recycled resources can be obtained, for example, by dismantling and thermally decomposing used tires to extract materials that make up the tire, such as rubber, fillers, and steel cords. By using sustainable materials (materials derived from recycled resources) in this way, the environmental burden in tire manufacturing can be comprehensively reduced, including a reduction in carbon dioxide emissions (LCCO2) throughout the entire lifecycle, a reduction in energy consumption (LCE) throughout the entire lifecycle, a reduction in costs incurred throughout the entire lifecycle (LCC), and a reduction in the use of fossil resources.

[0030] Rubber derived from sustainable materials (materials derived from recycled resources) can be manufactured, for example, using monomer components derived from recycled resources, and optionally using monomer components derived from fossil resources, in the same manner as conventional methods for manufacturing synthetic rubber derived from fossil resources.

[0031] The method for manufacturing the rubber composition of this embodiment is not particularly limited, but for example, it can be manufactured by blending various components appropriately selected with the rubber component, then kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce vulcanized rubber. There are no particular restrictions on the kneading conditions, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, etc., as well as the kneading temperature, kneading time, and type of kneading device can be appropriately selected according to the purpose. Examples of kneading devices include Banbury mixers, intermixes, kneaders, rolls, etc., which are usually used for kneading rubber compositions. There are also no particular restrictions on the heating conditions, and various conditions such as the heating temperature, heating time, and heating device can be appropriately selected according to the purpose. Examples of heating devices include heating roll machines, etc., which are usually used for heating rubber compositions. There are also no particular restrictions on the extrusion conditions, and various conditions such as the extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected according to the purpose. Extrusion equipment typically includes extruders used for extruding rubber compositions. The extrusion temperature can be determined as appropriate. There are no particular restrictions on the vulcanization equipment, methods, and conditions, and they can be selected as appropriate according to the purpose. Vulcanization equipment typically includes mold vulcanizers used for vulcanizing rubber compositions. The vulcanization temperature is, for example, around 100 to 190°C.

[0032] The tire 20 can be manufactured by conventional methods using the rubber composition described above. For example, depending on the type, the tire 20 may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process and then performing full vulcanization. Preferably, the tire is a pneumatic tire, and as the gas used to fill the pneumatic tire, in addition to normal air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

[0033] This disclosure is applicable to applications other than tires. Examples include passenger car tires, truck and bus tires, aircraft tires, and mining vehicle tires. It is particularly effective for tires used under conditions where uneven wear is likely to occur, and is especially effective for tires used on vehicles that travel on unpaved roads, such as mining vehicles.

[0034] Furthermore, this disclosure can also be applied to retread tires. Pneumatic tires are made by attaching tread rubber, which contacts the road surface, to a base tire, and the base tire can often still be used even after the lifespan of the tread rubber has ended. For this reason, the worn tread rubber is sometimes replaced with new tread rubber (retreading), and the tire is reused as a retread tire (reconditioned tire). By applying this disclosure to retread tires, uneven wear of retread tires can be suppressed.

[0035] This section describes a comparative example of wear rates between cases where recycled resources are not used and cases where they are used. Figure 2 shows examples of formulations with and without recycled resources. Ctrl indicates the amounts of NR (natural rubber), BR (butadiene rubber), and carbon black when recycled resources are not used, while Examples 1-6 show the amounts when recycled rubber, powdered rubber, or recycled carbon black (rCB) is added in addition to NR, BR, and carbon black. Although not listed in the table, samples were also prepared by adding other common rubber compounds: sulfur: 1.3 phr, vulcanization accelerator: 1.5 phr, zinc oxide: 3.9 phr, antioxidant: 1.4 phr, and wax: 1.0 phr. These compounds are commercially available and can be appropriately selected according to the desired rubber properties. Example 1 is an example in which recycled rubber 1 (tire lic red line mark from Muraoka Rubber Industry Co., Ltd.) was used, Example 2 is an example in which a different recycled rubber 2 (high-strength recycled rubber from Asahi Recycled Rubber Co., Ltd.) was used, Examples 3 and 4 are examples in which the amount of recycled rubber 2 was varied, Example 5 is an example in which powder rubber (42 mesh powder rubber from Asahi Recycled Rubber Co., Ltd.) was used, and Example 6 is an example in which rCB (manufactured by Enrestec, trade name PB365) was used. Recycled rubber 1 was recycled wheel tire rubber from Muraoka Rubber Industry Co., Ltd., and recycled rubber 2 was recycled tire tread rubber from Muraoka Rubber Industry Co., Ltd.

[0036] Figure 3 is a graph showing the results of wear on rubber manufactured using the formulation shown in Figure 2. The vertical axis represents the amount of wear measured in the Lambourn test, with higher values ​​indicating lower wear resistance. The test was conducted using an FPS testing machine from Ueshima Seisakusho Co., Ltd., with a load of 50N and a slip ratio of 25%, by dropping test sand at a constant speed between the sample and the worn road surface. The horizontal axis represents the 300% modulus (M300) measured at 20°C in accordance with JIS K6251. A smaller DF wear value shown on the vertical axis indicates superior wear resistance. Line 30 in Figure 3 shows the value when M300 is adjusted by the amount of sulfur, and line 31 shows the value when M300 is adjusted by the amount of carbon black. These lines show the effect of changes in elastic modulus on the amount of wear. Note that Ctrl S- shows the value when the amount of sulfur in Ctrl is reduced, and by connecting it to Ctrl, a line can be drawn showing the change when the amount of sulfur is changed. Similarly, Ctrl CB- indicates the value when the amount of carbon black in Ctrl is reduced, and by connecting it to Ctrl, a line can be drawn showing the change when the amount of carbon black is changed. If the value is above these lines, it indicates that the wear rate is faster than the effect of controlling the elastic modulus on the wear rate, and if it is below these lines, it indicates that the wear rate is slower than the effect of controlling the elastic modulus on the wear rate. In other words, the higher the value is above lines 30 and 31, the faster the wear rate is compared to the standard formulation.

[0037] As shown in Figure 3, Examples 1-6 exhibit a faster wear rate than Ctrl. Based on this, by increasing or decreasing the amount of recycled material in the tire width direction, the wear rate can be made more uniform, and the amount of recycled material used can be increased. Specifically, the compound can be selected for the center, right shoulder, and left shoulder sections.

[0038] Comparing Ctrl with Example 1, it can be seen that Ctrl wears about 12% faster. Based on this, if a tire 20 is worn down to the point where the center of the tire tread TR is 1.2 times more worn than the shoulder, using Ctrl in the center and the rubber from Example 1 in the shoulder can reduce the impact on tire life while preventing uneven wear of the tire tread TR of tire 20.

[0039] As described above, this embodiment provides a tire 20 in which a predetermined amount of recycled resources are incorporated into the tire tread portion TR. Furthermore, in the tire 20 of this embodiment, the amount of recycled material contained in the rubber composition of the tire tread portion varies in the width direction. Because a predetermined amount of recycled resources is incorporated into the tire tread portion TR, the tire 20 of this embodiment has superior wear resistance and can contribute to an improvement in the proportion of sustainable materials compared to the case in which the amount of recycled material contained in the rubber composition of the tire tread portion is uniform.

[0040] While embodiments of the present disclosure have been described in detail above with reference to the attached drawings, the technical scope of the present disclosure is not limited to these examples. It is clear that a person with ordinary skill in the art of the present disclosure may conceive of various modifications or alterations within the scope of the technical idea set forth in the claims, and these modifications or alterations are also understood to fall within the technical scope of the present disclosure.

[0041] Furthermore, the effects described in the above embodiments are descriptive or illustrative, and are not limited to those described in the above embodiments. In other words, the technology relating to this disclosure may produce other effects that would be obvious to a person of ordinary skill in the art of this disclosure from the descriptions in the above embodiments, in addition to or in lieu of the effects described in the above embodiments. [Explanation of Symbols]

[0042] 20 tires TR Tire Tread Section BL Tire Belt CS Carcass

Claims

1. A tire comprising a tire belt and a tire tread portion that contacts the outer side of the tire in the radial direction of the tire, A tire in which the amount of recycled material contained in the rubber composition of the tire tread portion varies in the width direction.

2. The tire according to claim 1, wherein the rubber composition uses rubber in which more recycled material is blended in the shoulder portion than in the center portion.

3. The tire according to claim 1, wherein the rubber composition uses rubber in which more recycled material is blended in the center portion than in the shoulder portion.

4. The tire according to claim 1, wherein the recycled material is powdered rubber, recycled rubber, or recycled carbon black.

5. The tire according to claim 1, wherein the tire is a retreaded tire.

6. The tire according to claim 1, wherein the tire is a mining tire.

7. The tire according to claim 1, wherein the amount of recycled material contained in the rubber composition of the tire tread is determined based on data regarding wear when driving on a road surface.

8. The tire according to claim 1, wherein the amount of recycled material contained in the rubber composition of the tire tread is determined based on data relating to the effect of the recycled material on the wear resistance rate.

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