Rubber composition for coating organic fiber cord

Abstract

The present invention addresses the problem of providing a rubber composition for coating an organic fiber cord, the rubber composition being capable of increasing the proportion of a sustainable material in a tire while maintaining the performance of the tire. The means for solving the problem is a rubber composition for coating an organic fiber cord, the rubber composition containing a rubber component and a filler, wherein the filler includes recycled carbon black, the recycled carbon black has three or more lines (3) having a length of 10 mm or more as measured with a grind gauge (1), and the particle size of the third largest particle among particles that yield the lines (3) having a length of 10 mm or more is 20 μm or less.

Description

Rubber composition for covering organic fiber cords

[0001] This invention relates to a rubber composition for covering organic fiber cords.

[0002] Conventionally, a carcass layer containing reinforcing cords is arranged inside the tire to reinforce its strength and rigidity, and a belt layer containing reinforcing cords is arranged on the radially outer side of the carcass layer. Furthermore, a belt reinforcement layer (also called a "cap layer") containing reinforcing cords may be arranged on the radially outer side of the belt layer to reinforce the belt layer. Among these tire components, organic fiber cords such as polyamide (nylon) fiber cords and PET fiber cords are widely used as reinforcing cords in the carcass layer and belt reinforcement layer, and rubber-organic fiber cord composites, in which the organic fiber cords are coated with coating rubber, are widely used in the carcass layer and belt reinforcement layer. Here, in order to ensure the strength of the coating rubber, carbon black is usually added as a reinforcing filler to the rubber composition that serves as its raw material.

[0003] On the other hand, in recent years, from the perspective of social sustainability, there has been a demand for the use of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and recycled resources, for various components used in tires, and there is a demand for an increase in the proportion of sustainable materials in the rubber composition applied to such tires. For example, recycled carbon black is known as a material derived from recycled resources (see Patent Document 1 below).

[0004] European Patent Application Publication No. 3427975

[0005] However, the inventors found that when they applied a rubber composition containing recycled carbon black as a reinforcing filler to the coating rubber of organic fiber cords in order to improve the proportion of sustainable materials in tires, and further applied such a rubber-organic fiber cord composite to the carcass layer or belt reinforcement layer, the tire performance deteriorated.

[0006] Therefore, the object of the present invention is to provide a rubber composition for covering organic fiber cords that can improve the proportion of sustainable materials in tires while maintaining tire performance.

[0007] The gist of the rubber composition for covering organic fiber cords of the present invention, which solves the above problems, is as follows.

[0008] [1] A rubber composition for covering organic fiber cords, comprising a rubber component and a filler, wherein the filler contains recycled carbon black, and the recycled carbon black, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that give rise to the lines with a length of 10 mm or more is 20 μm or less.

[0009] [2] The rubber composition for covering organic fiber cords according to [1], wherein the paste for measuring the recycled carbon black with a grind gauge is prepared in accordance with JIS K 5101-1-5.

[0010] [3] The rubber composition for covering organic fiber cords according to [1] or [2], wherein the paste for measuring recycled carbon black with a grind gauge is prepared in accordance with JIS K 5101-1-5, with the applied load set to 0.4 to 0.5 kN and the rotation speed of the glass plate set to 90 to 110 r / min.

[0011] [4] The recycled carbon black comprises one or more metal atoms selected from the group consisting of Zn, Cu, and Fe, in the rubber composition for covering organic fiber cords according to any one of [1] to [3].

[0012] [5] The recycled carbon black comprises Zn, and is a rubber composition for covering organic fiber cords according to any one of [1] to [4].

[0013] [6] The recycled carbon black has a Zn content of 2.5% by mass or less, the rubber composition for covering organic fiber cords according to any one of [1] to [5].

[0014] [7] The recycled carbon black has an ash content of 20% by mass or less, the rubber composition for covering organic fiber cords according to any one of [1] to [6].

[0015] [8] A rubber composition for covering organic fiber cords according to any one of [1] to [7], wherein the loss tangent tanδ (24°C) measured under conditions of temperature 24°C, initial strain 6%, amplitude ±1%, and frequency 52Hz is 0.15 or less, and the loss tangent tanδ (60°C) measured under conditions of temperature 60°C, initial strain 1.5%, amplitude ±1%, and frequency 52Hz is 0.10 or less.

[0016] [9] The rubber composition for covering organic fiber cords according to [8], wherein the loss tangent tanδ (24°C) is 0.12 or less.

[0017]

[10] The rubber composition for covering organic fiber cords according to [8] or [9], wherein the loss tangent tanδ (60°C) is 0.07 or less.

[0018]

[11] The rubber composition for covering organic fiber cords according to any one of [1] to

[10] , wherein the rubber component comprises natural rubber and styrene-butadiene rubber, and the content of natural rubber in 100 parts by mass of the rubber component is 70 parts by mass or more.

[0019]

[12] The rubber composition for covering organic fiber cords according to

[11] , wherein the styrene-butadiene rubber is a non-oil-extractable styrene-butadiene rubber.

[0020]

[13] A rubber composition for covering organic fiber cords according to any one of [1] to

[12] , which does not contain polymer-derived oils.

[0021]

[14] An organic fiber cord coating rubber composition according to any one of [1] to

[13] , wherein the oil content is 0.2% by mass or less.

[0022] According to the present invention, it is possible to provide a rubber composition for coating an organic fiber cord that can improve the ratio of sustainable materials of the tire while maintaining tire performance.

[0023] It is an explanatory diagram of an example of the measurement result by a grind gauge. It is a schematic diagram for explaining how to calculate the elastic modulus at 7% elongation of the cord. It is a schematic diagram showing a cross section in the width direction of an example of an organic fiber cord. It is a diagram schematically showing a cross section of a rubber-organic fiber cord composite. It is a cross-sectional view of an embodiment of a tire.

[0024] Hereinafter, the rubber composition for coating an organic fiber cord of the present invention will be specifically illustrated and described based on its embodiments.

[0025] <Definition> The compounds described in this specification may be partially or entirely derived from fossil resources, may be derived from biological resources such as plant resources, or may be derived from recycled resources such as used tires. Further, it may be derived from a mixture of any two or more of fossil resources, biological resources, and recycled resources.

[0026] In this specification, the "ratio of sustainable materials" is the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) in the target rubber composition for coating an organic fiber cord.

[0027] In this specification, the biological resources (biomass resources) refer to carbon-neutral organic resources derived from organisms and are resources excluding fossil resources (such as petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but do not compete with food, and from the perspective of effective utilization of resources, it is preferably non-edible.

[0028] In this specification, the recycled resources (recycled resources) refer to resources obtained by recycling products that have been used once, collected without being used, or discarded. For example, recycled resources include resources obtained by recycling used rubber products such as used tires.

[0029] <Organic Fiber Cord Coating Composition> The rubber composition for coating an organic fiber cord according to this embodiment contains a rubber component and a filler. And in the rubber composition for coating an organic fiber cord according to this embodiment, the filler contains recycled carbon black, and the recycled carbon black has three or more lines with a length of 10 mm or more when measured by a grind gauge, and among the particles that result in the lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less.

[0030] In the rubber composition for coating an organic fiber cord according to this embodiment, recycled carbon black is blended as a filler. Since the recycled carbon black is a material derived from recycled resources, the ratio of sustainable materials in the rubber composition for coating an organic fiber cord according to this embodiment is improved. Therefore, by applying an organic fiber cord coated with the rubber composition for coating an organic fiber cord according to this embodiment to a tire, it is possible to improve the ratio of sustainable materials in the tire. However, when a general recycled carbon black is applied to the coating rubber of an organic fiber cord and disposed inside the tire, the tire performance deteriorates. In contrast, in the tire according to this embodiment, by applying recycled carbon black having three or more lines with a length of 10 mm or more when measured by a grind gauge, and among the particles that result in the lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less to the coating rubber of the organic fiber cord and disposing it inside the tire, the tire performance can be maintained. Therefore, the rubber composition for coating an organic fiber cord according to this embodiment can improve the ratio of sustainable materials in the tire while maintaining the tire performance by being applied to the tire.

[0031] The rubber composition for coating organic fiber cords in this embodiment preferably has a loss tangent tanδ (24°C) of 0.15 or less measured under the conditions of (i) a temperature of 24°C, initial strain of 6%, amplitude of ±1%, and frequency of 52Hz, and (ii) a loss tangent tanδ (60°C) of 0.10 or less measured under the conditions of (ii) a temperature of 60°C, initial strain of 1.5%, amplitude of ±1%, and frequency of 52Hz. By having the rubber composition for coating organic fiber cords have a loss tangent tanδ (24°C) of 0.15 or less measured under the conditions of (i) a temperature of 24°C, initial strain of 6%, amplitude of ±1%, and frequency of 52Hz, and (ii) a loss tangent tanδ (60°C) of 0.10 or less measured under the conditions of (ii) a temperature of 60°C, initial strain of 1.5%, amplitude of ±1%, and frequency of 52Hz, the hysteresis loss of the rubber composition (coating rubber) from near room temperature to near running temperature can be reduced, and when applied to a tire, heat generation inside the tire can be suppressed. Therefore, an organic fiber cord coating rubber composition having (i) a loss tangent tanδ (24°C) of 0.15 or less and (ii) a loss tangent tanδ (60°C) of 0.10 or less can be applied to a tire to improve the low heat generation of the tire.

[0032] The rubber composition for coating organic fiber cords preferably has a loss tangent tanδ (24°C) of 0.15 or less, and more preferably 0.12 or less. When the loss tangent tanδ (24°C) of the rubber composition for coating organic fiber cords (coating rubber) is 0.12 or less, when the rubber-organic fiber cord composite is applied to a tire, the heat generation inside the tire at around room temperature can be further suppressed. Therefore, when an organic fiber cord coating rubber composition has a loss tangent tanδ (24°C) of 0.12 or less is applied to a tire, the low heat generation of the tire can be further improved.

[0033] The rubber composition for coating organic fiber cords preferably has a loss tangent tanδ (60°C) of 0.10 or less, and more preferably 0.07 or less. When the loss tangent tanδ (60°C) of the rubber composition for coating organic fiber cords (coating rubber) is 0.07 or less, when the rubber-organic fiber cord composite is applied to a tire, it is possible to further suppress the heat generation inside the tire during driving and further suppress the temperature inside the tire. Therefore, when an organic fiber cord coating rubber composition has a loss tangent tanδ (60°C) of 0.07 or less is applied to a tire, the low heat generation properties of the tire can be further improved.

[0034] "Rubber component" The rubber composition for covering organic fiber cords of this embodiment contains a rubber component, which provides rubber elasticity to the composition. The sustainability rate of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component is the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources in the rubber component.

[0035] The rubber component is preferably derived from biological resources and recycled resources. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer component constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%. Similarly, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer component constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%.

[0036] The aforementioned rubber component is a component that contributes to crosslinking, and typically has a weight-average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 5,000,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) of the rubber component can be determined, for example, by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC).

[0037] The rubber component is preferably a diene-based rubber, and among the diene-based rubbers, isoprene-based rubber and butadiene-based rubber are preferred.

[0038] Examples of the isoprene-based rubber include natural rubber (NR) and synthetic isoprene rubber (IR). The origin of the natural rubber is not particularly limited, and examples include that derived from the Para rubber tree, guayule, or Russian dandelion. The natural rubber may be modified or altered, and the synthetic isoprene rubber may also be altered. These isoprene-based rubbers may be used individually or in combination of two or more types. Natural rubber is preferred as the isoprene-based rubber.

[0039] Examples of the aforementioned butadiene-based rubber include butadiene rubber (BR) and styrene-butadiene rubber (SBR). Here, it is preferable that the butadiene used as a raw material for the butadiene-based rubber is derived from biological resources or recycled resources.

[0040] Examples of the styrene-butadiene rubber include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR).

[0041] The isoprene-based rubber and the butadiene-based rubber preferably have a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0042] Furthermore, in order to keep the overall sustainability rate of the rubber component within the aforementioned range, it is preferable to use natural rubber (NR) as the rubber component, or to use polymers synthesized using monomer components derived from biological resources or recycled resources. It is also possible to use mass balance certified synthetic rubber to keep the sustainability rate within the aforementioned range.

[0043] The ratio of each monomer unit (for example, units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component can be appropriately adjusted depending on the member to which it is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the isoprene-based rubber and butadiene-based rubber mentioned above. The ratio of cis-bonded units in the butadiene-derived units can also be appropriately adjusted depending on the member to which it is applied. In this specification, "monomer unit" means a constituent unit of a polymer, "unit derived from isoprene" means a constituent unit in a polymer composed of isoprene, which is a monomer (including isoprene units in natural rubber), "unit derived from butadiene" means a constituent unit in a polymer composed of butadiene, which is a monomer, and "unit derived from aromatic vinyl compounds" means a constituent unit in a polymer composed of aromatic vinyl compounds, which are monomers. In this specification, the ratio of each monomer unit is measured by NMR.

[0044] In addition to the isoprene-based rubber, butadiene rubber (BR), and styrene-butadiene rubber (SBR) mentioned above, the rubber component may also include diene-based rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These rubber components may be used individually or in combination of two or more.

[0045] The rubber component may have functional groups that interact with fillers such as carbon black and silica introduced through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups. These functional groups may also have substituents. These functional groups may be introduced into the rubber component individually or in combination of two or more. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atoms of the amino group are replaced by alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are even more preferred.

[0046] The functional group can be introduced, for example, by reacting a compound having the functional group (modifier) ​​with the rubber component. The functional group is a modifying functional group that interacts with fillers such as silica and carbon black, and examples include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Examples of compounds having nitrogen-containing functional groups (modifiers) include amino group-containing compounds, examples of compounds having silicon-containing functional groups (modifiers) include silicon halides and hydrocarbyloxysilane compounds, and examples of compounds having oxygen-containing functional groups (modifiers) include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples include compounds described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used individually or in combination of two or more.

[0047] The aforementioned rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be manufactured, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources, in the same manner as conventional methods for manufacturing synthetic rubber derived from fossil resources.

[0048] For example, the method described in Japanese Patent Publication No. 2022-179158 can be used to prepare rubber derived from the above-mentioned biological resources.

[0049] As the butadiene obtained from the aforementioned biological resources, butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tigric acid) can be suitably used.

[0050] The rubber composition for coating organic fiber cords of this embodiment contains natural rubber and styrene-butadiene rubber as rubber components, and it is preferable that the content of natural rubber is 70 parts by mass or more per 100 parts by mass of the rubber components. More preferably, the content of natural rubber in the rubber composition is 70 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the rubber components. Furthermore, it is preferable that the content of styrene-butadiene rubber in the rubber composition is 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber components. When the rubber composition contains natural rubber and styrene-butadiene rubber as rubber components, and the content of natural rubber is 70 parts by mass or more per 100 parts by mass of the rubber components, the hysteresis loss of the rubber composition for coating organic fiber cords (coating rubber) is further reduced, and when the rubber-organic fiber cord composite is applied to a tire, heat generation inside the tire is further suppressed, and the temperature inside the tire can be more reliably suppressed. Therefore, when such a rubber composition for coating organic fiber cords is applied to a tire, the low heat generation properties of the tire can be further improved. The natural rubber may be modified. In the case of modified natural rubber, it is preferable that the nitrogen content is 0.1 to 0.3% by mass. Furthermore, it is preferable that the modified natural rubber has had its proteins removed by a centrifugal separation process, enzymatic treatment, or urea treatment. In addition, it is preferable that the phosphorus content of the modified natural rubber is greater than 200 ppm and less than or equal to 900 ppm.

[0051] It is preferable to use non-oil-exposed styrene-butadiene rubber as the styrene-butadiene rubber. By including non-oil-exposed styrene-butadiene rubber in the rubber composition, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, when an organic fiber cord coating rubber composition containing non-oil-exposed styrene-butadiene rubber is applied to a tire, it can further suppress heat generation inside the tire and further improve the low heat generation properties of the tire.

[0052] "Filler" The rubber composition for covering organic fiber cords of this embodiment contains a filler. The inclusion of a filler improves the reinforcing properties of the rubber composition for covering organic fiber cords.

[0053] (Recycled Carbon Black) The filler contains recycled carbon black. Since recycled carbon black is a material derived from recycled resources, incorporating recycled carbon black into the rubber composition as a filler can improve the proportion of sustainable materials in the tire to which the rubber composition is applied.

[0054] In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials submitted for recycling. Examples of such waste materials include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only rubber generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is fine rubber generated, for example, in the buffing process of retreading tires, where the tread portion remaining on the base tire is scraped off. Peeling rubber is long pieces of rubber, for example, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by scraping the surface of rubber products such as tires using a U-shaped or V-shaped knife like a peeler. Furthermore, waste rubber includes not only cross-linked rubber but also unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, and rubber parts or components at the manufacturing stage of final products. Used tires may include, for example, those that have been retreaded, as well as tires that have been discarded for any reason, such as those resulting from tire replacement or vehicle scrapping, and End-of-Life Tires (ELTs) that have reached the end of their lifespan. Waste oil is not limited to that generated when plastics and rubber are decomposed, but also includes used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oil that does not contain any composition other than organic matter, such as those derived from silicone rubber or polyvinyl chloride, is desirable. Furthermore, waste oil that is mixed with carbon black or rubber containing carbon black is desirable. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., carbon black that is not recycled. Note that "used" here includes not only those that have been discarded after being actually used, but also those that were manufactured but discarded without actually being used.

[0055] Furthermore, it is preferable that the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by thermal decomposition of a vulcanized rubber product containing carbon black is readily available because a large amount of vulcanized rubber products containing carbon black exist and it can be easily obtained by thermal decomposition. Moreover, it is preferable that the recycled carbon black is obtained from the solid residue generated by the thermal decomposition of the above-mentioned vulcanized rubber product containing carbon black. When a rubber product containing carbon black is thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from either. When recovering carbon black from volatile components, it is possible to recover oil with a specific gravity suitable for producing carbon black and use it to produce carbon black using an existing carbon black production method (for example, Japanese Patent Publication No. 2015-520259). In this case, unlike carbon black recovered from solid residue, there are advantages such as the absence of impurities and the absence of mixtures of different grades. Furthermore, in the production of environmentally friendly carbon black, there are various options besides the oil obtained by recovering volatile components from the thermal decomposition of rubber mentioned above, such as using vegetable oil or oil derived from waste plastics. However, edible resources such as vegetable oil present challenges in securing sufficient quantities due to other uses such as food, and the environmental impact associated with the expansion of cultivated land must also be considered. Similarly, oil derived from waste plastics is used for other purposes such as horizontal recycling of plastics, so supply issues are also a concern. On the other hand, when using volatile components (oil) produced by the thermal decomposition of vulcanized rubber products, particularly tires, the tire industry has a system for continuing to use existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire manufacturing, thereby contributing to reducing the environmental burden on the industry. The grade of carbon black is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0056] Furthermore, when the recycled carbon black is recovered from solid residue, it is more preferably carbon black that has undergone surface treatment or surface modification. Examples of surface treatment or surface modification include hydrofluoric acid treatment, hydrochloric acid, sulfuric acid, or other acids, or peroxides. Surface treatment or surface modification may be carried out at room temperature, preferably at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C to 100°C.

[0057] Furthermore, the recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent Publication No. 6856781 (Comparison of Surface Morphology and Chemistry of Pyrolysis Carbon Black and Commercial Carbon Black, Powder Technology 160 (2005) 190-193).

[0058] The recycled carbon black may lack functional groups on its surface, or it may have been treated to include functional groups on its surface. Treatment to include 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 thermal decomposition process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Japanese Patent Publication No. 6856781, carbon black obtained from a thermal decomposition 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 this embodiment also includes carbon black that has been treated to include functional groups on its surface.

[0059] Furthermore, for the thermal decomposition of cross-linked rubber products (vulcanized rubber products) such as used tires, one example is a thermal decomposition method at a temperature of 650°C or higher.

[0060] The cross-linked rubber products used in the aforementioned decomposition may be grouped by the type of rubber component they contain beforehand, and the decomposition process may be carried out for each group separately. Alternatively, they may be grouped by the type of filler they contain beforehand (for example, the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and the decomposition process may be carried out for each group separately. Furthermore, they may be grouped by both the type of rubber component and the type of filler, and the decomposition process may be carried out for each group separately. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again incorporated into the rubber component, a rubber composition with better performance can be obtained.

[0061] Furthermore, if the cross-linked rubber product used in the decomposition is derived from a tire, it may be grouped in advance by tire type (for example, for passenger cars, trucks and buses, heavy vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.) and then the decomposition process may be carried out for each group. Alternatively, it may be grouped in advance by tire component (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.) and then the decomposition process may be carried out for each group. Moreover, it may be possible to group by both tire type and tire component and then carry out the decomposition process for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again blended into the rubber component, a rubber composition with better performance can be obtained.

[0062] The recycled carbon black, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among those particles that produce lines of 10 mm or more is 20 μm or less. By incorporating recycled carbon black, which, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among those particles that produce lines of 10 mm or more is 20 μm or less, as a filler, the physical properties of the rubber composition are maintained, and the tire performance can be maintained even when the rubber composition is applied to a tire.

[0063] Methods for evaluating the dispersibility of carbon black using the aforementioned grind gauge are described in JIS K5101 (particularly regarding paste preparation) and JIS K5400 (particularly regarding evaluation methods based on the manner of linear mark formation). In evaluating recycled carbon black using a grind gauge, as described later, from the viewpoint of the durability of the rubber composition (high-temperature tensile strength after degradation, crack propagation resistance after thermal degradation, etc.), it is important whether the particle size of the third largest particle in the recycled carbon black being measured is 20 μm or less. Therefore, from the viewpoint of accurately measuring particle sizes around 20 μm and from the viewpoint of ease of measurement, it is preferable to use a grind gauge with a range of 0 to 25 μm. Note that any grind gauge with an upper limit of the range greater than 20 μm can be used, as it is possible to determine whether the particle size of the third largest particle is 20 μm or less. Furthermore, when used for other purposes (maintaining performance other than durability of rubber compositions containing recycled carbon black), the range of the grind gauge used can be appropriately selected according to the purpose.

[0064] As described above, JIS K5101-1-5 describes a method for preparing a paste of recycled carbon black as a measurement sample in grind gauge measurement. In this embodiment, it is preferable to prepare the paste of recycled carbon black in accordance with JIS K5101-1-5 as a measurement sample for measurement using a grind gauge. By using a paste of recycled carbon black prepared in accordance with JIS K5101-1-5, variations in measurement results can be further suppressed and measurement accuracy can be further improved. Furthermore, a rubber composition containing recycled carbon black evaluated using such a measurement sample can be applied to tires to more reliably maintain tire performance. In one embodiment, the accuracy of grind gauge measurement can be further improved by appropriately adjusting the viscosity of the paste. In one embodiment, it is preferable to prepare a paste (measurement sample) containing recycled carbon black by blending recycled carbon black and zinc oxide with epoxidized soybean oil. Here, the mixing ratio of the paste is not particularly limited, but it is preferable to use about 8 to 12 g of recycled carbon black and about 160 to 200 g of zinc oxide per 100 mL of epoxidized soybean oil.

[0065] Furthermore, in the evaluation of recycled carbon black using the grind gauge, when preparing the recycled carbon black paste according to JIS K5101-1-5, it is preferable to apply a load of 0.4 to 0.5 kN and rotate the glass plate at 90 to 110 r / min, from the viewpoint of improving evaluation accuracy. By using a recycled carbon black paste prepared with the applied load and glass plate rotation speed within the above range, variations in measurement results can be further suppressed and measurement accuracy can be further improved. In addition, a rubber composition containing recycled carbon black evaluated using such a sample can be applied to tires to more reliably maintain tire performance. Note that the method for preparing the recycled carbon black paste is not particularly limited, as long as it does not affect the measurement results, even if it is a method other than the one conforming to the JIS standard.

[0066] Figure 1 shows an explanatory diagram of an example of measurement results using a grind gauge. In the measurement using grind gauge 1, several lines attributable to particles in the measurement sample are observed. In this embodiment, in accordance with JIS standards, lines 2 with a length of less than 10 mm are not considered, and lines 3 with a length of 10 mm or more are considered. Furthermore, among the lines 3 with a length of 10 mm or more, line 31 attributable to the largest particle and line 32 attributable to the second largest particle are judged to be abnormal values, and in this embodiment, from the viewpoint of improving measurement accuracy, attention is focused on line 33 attributable to the third largest particle. The scale 4 at the location where line 33 attributable to the third largest particle appears is read, and this reading is taken as the particle size of the third largest particle. If the particle size of the third largest particle is 20 μm or less, even if recycled carbon black is added, the decrease in the durability of the rubber composition, particularly the high-temperature tensile strength after degradation and the crack propagation resistance after thermal degradation, can be suppressed. In this specification, the measurement of recycled carbon black using a grind gauge is performed by the method described in the examples.

[0067] In this embodiment, recycled carbon black in which, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that give rise to such lines of 10 mm or more is 20 μm or less, can be manufactured by various methods. For example, recycled carbon black with a particle size of 20 μm or less can be manufactured by further grinding the recycled carbon black produced by a general method from recycled waste by extending the grinding process for a longer time or increasing the grinding intensity.

[0068] The recycled carbon black may contain one or more metal atoms selected from the group consisting of Zn, Cu, and Fe. Since recycled carbon black is obtained from recycled waste as raw material, it contains various elements other than carbon (C), and zinc (Zn), copper (Cu), and iron (Fe) are elements that are easily contained in recycled carbon black. Therefore, recycled carbon black containing at least one of the elements of Zn, Cu, and Fe does not require any special removal operations, and rubber compositions for covering organic fiber cords containing such recycled carbon black are easy to manufacture.

[0069] The recycled carbon black may contain Zn. As mentioned above, recycled carbon black is obtained from recycled waste as a raw material, and therefore contains various elements other than carbon (C), with zinc (Zn) being a particularly common element in recycled carbon black. For this reason, recycled carbon black containing Zn does not require any special removal operations, and rubber compositions for covering organic fiber cords containing such recycled carbon black are easy to manufacture.

[0070] If the recycled carbon black contains Zn, the Zn content in the recycled carbon black is preferably 2.5% by mass or less. A lower Zn content in the recycled carbon black is preferable, but if the Zn content is 2.5% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. Furthermore, a rubber composition in which such deterioration of physical properties is suppressed is more likely to maintain tire performance when applied to tires. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Zn content in the recycled carbon black is more preferably 2.0% by mass or less, even more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. The Zn content in the recycled carbon black may also be 0.01% by mass or more, or 0.05% by mass or more. The upper and lower limits can be combined as appropriate.

[0071] Methods to keep the Zn content in recycled carbon black within the above range include, for example, acid treatment and analyzing the amount of Zn contained in the raw rubber to be recycled in advance, and using some or all of the raw rubber with a low Zn content.

[0072] The Fe content in the recycled carbon black is preferably 0% by mass or more and 0.1% by mass or less. A lower Fe content in the recycled carbon black is preferable, but if the Fe content is 0.1% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Fe content in the recycled carbon black is more preferably 0.09% by mass or less, even more preferably 0.08% by mass or less, still preferably 0.07% by mass or less, even more preferably 0.06% by mass or less, even more preferably 0.05% by mass or less, particularly preferably 0.04% by mass or less, and most preferably 0.03% by mass or less. Furthermore, the Fe content in the recycled carbon black may be 0.01% by mass or more, or 0.02% by mass or more. The upper and lower limits can be combined as appropriate.

[0073] The Cu content in the recycled carbon black is preferably 0% by mass or more and 0.05% by mass or less. A lower Cu content in the recycled carbon black is preferable, but a Cu content of 0.05% by mass or less can suppress a decrease in the physical properties of the rubber composition. From the viewpoint of suppressing a decrease in the physical properties of the rubber composition, the Cu content in the recycled carbon black is more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, and even more preferably 0.01% by mass or less. Furthermore, the Cu content in the recycled carbon black may be 0.01% by mass or more, or 0.02% by mass or more. The upper and lower limits can be combined as appropriate.

[0074] The recycled carbon black may contain components other than Zn, Fe, and Cu as described above. "Components other than Zn, Fe, and Cu" refers to components other than Zn, Fe, and Cu in the ash. Examples of components other than Zn, Fe, and Cu in the ash include Si (silicon), S (sulfur), Ca (calcium), K (potassium), Br (bromine), Mg (magnesium), Cl (chlorine), P (phosphorus), Co (cobalt), Na (sodium), and Al (aluminum).

[0075] The recycled carbon black may contain silicon (Si). Preferably, the Si content in the recycled carbon black is 0% by mass or more and 1.0% by mass or less. A Si content of 1.0% by mass or less suppresses a decrease in the physical properties of the rubber composition. From a similar viewpoint, a Si content of 0.5% by mass or less is more preferable, and 0.3% by mass or less is even more preferable. Furthermore, a Si content of 0% by mass, i.e., substantially Si-free, is also preferable. On the other hand, the Si content may be 0.01% by mass or more, or 0.05% by mass or more. The upper and lower limits can be combined as appropriate.

[0076] The recycled carbon black may contain sulfur (S). The S content in the recycled carbon black is preferably 0.4% by mass or more, more preferably 0.5% by mass or more. Furthermore, the S content is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The upper and lower limits can be combined as appropriate.

[0077] The recycled carbon black may contain Ca (calcium). In the recycled carbon black, the Ca content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and particularly preferably 0.8% by mass or more. Furthermore, the Ca content is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and even more preferably 1.1% by mass or less. The upper and lower limits can be combined as appropriate.

[0078] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m² obtained by the BET method. ２ It is preferable that the amount be / g, and 50 to 90 m ２ It is more preferable that the amount be / g, and 55 to 75 m ２ It is particularly preferable that the value be / g. Here, in this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black by the BET method is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556.

[0079] The recycled carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, the pH of the recycled carbon black is determined according to ASTM D1512.

[0080] The recycled carbon black preferably has a toluene staining transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, in this specification, the toluene staining transmittance of recycled carbon black is determined according to ASTM D1618.

[0081] The recycled carbon black preferably has a heating loss of 3% by mass or less at 125°C, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Hereinafter, the heating loss of the recycled carbon black at 125°C is determined according to ASTM D1509.

[0082] The recycled carbon black preferably has a 35-mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Here, in this specification, the 35-mesh sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0083] The recycled carbon black preferably has a 325-mesh (44 μm) sieve residue of 1,000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. Here, in this specification, the 325-mesh (44 μm) sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0084] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Hereinafter, the pellet hardness of the recycled carbon black is determined according to ASTM D5230.

[0085] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Hereinafter, the pellet fine powder content of the recycled carbon black is determined according to ASTM D1508.

[0086] The recycled carbon black preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Hereinafter, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size analyzer, with the refractive index of water being 1.33 and the refractive index of the filler being 1.75.

[0087] The recycled carbon black preferably contains 50% or more by volume of particles 5 μm or smaller, more preferably 70% or more by volume, and particularly preferably 80% or more by volume.

[0088] The recycled carbon black preferably has an ash content of 20% by mass or less, and more preferably 0.5% by mass or more and 20% by mass or less. If the ash content in the recycled carbon black exceeds 20% by mass, it may not be possible to obtain a tire with sufficient reinforcement. On the other hand, a rubber composition containing recycled carbon black with an ash content of 20% by mass or less is more likely to maintain tire performance when applied to a tire. Considering the reinforcement of the tire, the ash content is preferably 10% by mass or less, more preferably 6% by mass or less, more preferably 5% by mass or less, more preferably 4% by mass or less, more preferably 3% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less. In other words, the recycled carbon black preferably has an ash content of 0.5% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 6% by mass or less, even more preferably 0.5% by mass or more and 5% by mass or less, even more preferably 0.5% by mass or more and 4% by mass or less, even more preferably 0.5% by mass or more and 3% by mass or less, even more preferably 0.5% by mass or more and 2% by mass or less, and particularly preferably 0.5% by mass or more and 1% by mass or less.

[0089] The aforementioned ash content specifically includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from solid residue obtained by thermal decomposition of waste, a certain amount of ash remains even after various processes to remove it. In this embodiment, the presence of ash in recycled carbon black is permitted. The lower limit of the ash content of the recycled carbon black used in this embodiment may be 0.5% by mass. Hereinafter, the ash content of carbon black is determined according to ASTM D8474 / D1506.

[0090] The recycled carbon black preferably has an oil absorption rate (OAN) of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Hereinafter, the oil absorption rate (OAN) of the recycled carbon black is determined according to ASTM D2414.

[0091] The recycled carbon black preferably has an oil absorption rate (COAN) of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Hereinafter, the oil absorption rate (COAN) of the compressed sample of recycled carbon black is determined according to ASTM D3493.

[0092] The recycled carbon black content is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, even more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component. When the recycled carbon black content is 5 parts by mass or more per 100 parts by mass of the rubber component, it has a significant effect on improving the ratio of sustainable materials in the tire, and when it is 50 parts by mass or less, tire performance can be maintained more reliably.

[0093] (Carbon black other than recycled carbon black) The rubber composition for covering organic fiber cords of this embodiment may also contain carbon black other than recycled carbon black as a filler. The other carbon black is not particularly limited and examples include GPF, FEF, and HAF grade carbon black. These carbon blacks may be used individually or in combination of two or more.

[0094] Nitrogen adsorption specific surface area of ​​the other carbon black (N ２ SA) is 40m ２ It is preferable that it be less than or equal to 34m ２ It is more preferable that it be less than or equal to 30m ２It is particularly preferable that it is below / g. Further, the nitrogen adsorption specific surface area (N ２ SA) of the other carbon black can be 25 m ２ / g or more. Further, the content of the other carbon black is preferably 30 to 60 parts by mass, more preferably 40 to 50 parts by mass, based on 100 parts by mass of the rubber component. When the rubber composition for coating an organic fiber cord contains 30 to 60 parts by mass of carbon black other than recycled carbon black with respect to 100 parts by mass of the rubber component, and the nitrogen adsorption specific surface area (N ２ SA) of the other carbon black is 40 m ２ / g or less, the hysteresis loss of the rubber composition for coating an organic fiber cord (coating rubber) becomes smaller, and when a rubber-organic fiber cord composite is applied to a tire, heat generation inside the tire is further suppressed, and it is more surely possible to suppress the inside of the tire from becoming high temperature. Therefore, by applying such a rubber composition for coating an organic fiber cord, the low heat generation property of the tire can be further improved.

[0095] (Silica) The rubber composition for coating an organic fiber cord of the present embodiment may contain silica. The type of the silica is not particularly limited. For example, wet silica, colloidal silica, calcium silicate, aluminum silicate, etc. may be mentioned. Among the above, the silica is preferably wet silica, more preferably precipitated silica. These silicas may be used alone or in combination of two or more.

[0096] As the silica, from the viewpoint of reducing environmental load, silica derived from silicate plants is preferable. The silicate plants are present, for example, in mosses, ferns, toxics, cucurbitaceae, nettle family, and gramineous plants. Among these plants, gramineous plants are preferable. Among gramineous plants, silica derived from rice husk (hereinafter, also referred to as "rice husk silica") is particularly preferable from the viewpoint of easy availability. As the silica, further, end materials of silicon wafers that are raw materials for semiconductors, silica produced by recycling silicon components from glass bottles, etc. may also be mentioned.

[0097] The silica is not particularly limited, but for example, if its CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m² ２ / g or more, 250m ２ Silica of 0.35 nm or less can be used. The CTAB specific surface area refers to the value measured in accordance with ASTM D3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. ２ The specific surface area (m²) is calculated from the amount of adsorption of CTAB. ２ The CTAB specific surface area is defined as ( / g). The BET specific surface area of ​​the silica is 100 m². ２ / g or more, 250m ２ It can be less than or equal to / g. The BET specific surface area is the specific surface area obtained by the BET method, and in this invention, it can be measured in accordance with ASTM D4820-93.

[0098] Furthermore, the silica content is not particularly limited. For example, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less.

[0099] "Silane Coupling Agent" When the rubber composition for covering organic fiber cords of this embodiment contains silica, it is preferable that the rubber composition contains a silane coupling agent in order to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl- Examples include N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. These silane coupling agents may be used individually or in combination of two or more.

[0100] Furthermore, bioethanol can also be used as a raw material for silane coupling agents.

[0101] "Resin" The rubber composition for covering organic fiber cords of this embodiment may contain a resin. Examples of the resin include at least one resin selected from terpene resins, phenolic resins, coumarone-indene resins, xylene resins, rosin-based resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, polyurethane resins, acrylic resins, and the like. The above resins can be those described in Japanese Patent Application Publication No. 2022-132289 or International Publication No. 2019 / 116656.

[0102] The resin preferably has a softening point of 30°C or higher, more preferably 60°C or higher, more preferably 90°C or higher, more preferably higher than 110°C, and more preferably 120°C or higher. Furthermore, the resin preferably has a softening point of 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, and more preferably 140°C or lower. The softening point of the resin is measured in accordance with JIS-K2207-1996 (ring-sphere method).

[0103] The resin content is not particularly limited, but for example, the resin is preferably in the range of 1 to 100 parts by mass, and more preferably in the range of 5 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0104] "Other" In addition to the components described above, the rubber composition for covering organic fiber cords of this embodiment may further contain various additives used in rubber products, especially tires, such as antioxidants, zinc oxide (zinc oxide), sulfur, vulcanization accelerators, waxes, fillers such as stearic acid, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, organic peroxides, cellulose nanofibers, cellulose particles, solid fine particles such as eggshells, rice husks, and walnut powder, and rubber powder obtained by crushing used rubber products. Here, the amount of zinc oxide in the rubber composition is preferably more than 3 parts by mass and less than 5 parts by mass per 100 parts by mass of the rubber components. If the amount of zinc oxide is 5 parts by mass or more, aggregation may occur and dispersibility may deteriorate, and if it is 3 parts by mass or less, it may adversely affect the vulcanization reaction.

[0105] Preferably, the rubber composition for coating organic fiber cords does not contain polymer-derived oils. Here, "not containing polymer-derived oils" means that it does not contain oils that are indirectly incorporated into the rubber composition as components contained in polymers such as the rubber components. By making the polymer-derived oil content in the rubber composition for coating organic fiber cords zero, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, when an organic fiber cord coating rubber composition that does not contain polymer-derived oils is applied to a tire, the low heat generation properties of the tire can be further improved.

[0106] It is even more preferable that the oil content in the rubber composition for covering organic fiber cords is 0.2% by mass or less. By having an oil content of 0.2% by mass or less in the rubber composition for covering organic fiber cords, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, when an organic fiber cord coating rubber composition with an oil content of 0.2% by mass or less is applied to a tire, the low heat generation properties of the tire can be further improved.

[0107] "Method for Producing the Rubber Composition" The method for preparing the rubber composition for covering organic fiber cords according to this embodiment is not particularly limited, and known methods can be used. For example, it can be obtained by kneading each component, including the rubber component and recycled carbon black, using a kneader such as a Banbury mixer, roll mixer, or internal mixer. Alternatively, the components other than the crosslinking accelerator and crosslinking agent may be mixed in a non-production (non-pro) stage, and the crosslinking accelerator and crosslinking agent may be added to the mixture and mixed in a production (pro) stage to prepare the rubber composition. The rubber composition for covering organic fiber cords according to this embodiment can be crosslinked or vulcanized. The conditions for crosslinking or vulcanizing the rubber composition can be adjusted as appropriate, for example, the temperature can be 120 to 200°C and the heating time can be 1 minute to 900 minutes.

[0108] "Applications" The organic fiber cord coating rubber composition of this embodiment can be applied to various components of a tire, for example, as a coating rubber for the carcass, a coating rubber for the belt reinforcement layer, a coating rubber for the belt, etc.

[0109] <Organic Fiber Cords> The organic fiber cords to be coated with the rubber composition for covering organic fiber cords of this embodiment are not particularly limited. In a tire, the organic fiber cords can be used, for example, as carcass cords; belt reinforcing cords in the belt reinforcing layer (usually located on the radially outer side of the belt layer located in the tread portion); insert layer reinforcing cords in the insert layer (usually located on the tire widthwise outer side of the bead filler, extending from near the bead core in the bead portion to the sidewall portion); and so on.

[0110] The raw materials for the aforementioned organic fiber cord are not particularly limited and may be derived from synthetic products, biological resources such as plant resources, animal resources, or microbial resources, mechanically recycled materials obtained by crushing, melting, and respinning resin products, or chemically recycled materials obtained by depolymerizing and repolymerizing resin products.

[0111] The material of the organic fiber cord is not particularly limited and includes, for example, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethylene frangipane carboxylate (PEF); polyamides such as 6-nylon®, 6,6-nylon®, 4,6-nylon®, and aramid; cellulose such as rayon and lyocell; and the like.

[0112] Examples of polyethylene terephthalate (PET) include polyethylene terephthalate obtained by mechanically or chemically recycling PET products or clothing.

[0113] Examples of the aforementioned polyamides include polyamide 4 (PA4), polyamide 11 (PA11), polyamide 4,4 (PA44), polyamide 5,4 (PA54), polyamide 4,6 (PA46), polyamide 5,6 (PA56), polyamide 4,10 (PA410), polyamide 6 (PA6, also known as 6-nylon®), polyamide 6,6 (PA66, also known as 6,6-nylon®), polyamide 6,10 (PA610), and polyamide 10,10 (PA1010), which are polyamides derived from biological resources.

[0114] Here, we will describe the case where the organic fiber cord is applied to the belt reinforcing cord in the belt reinforcing layer. When applied to the belt reinforcing cord, it is preferable that the organic fiber cord has a cutting strength of 6.5 cN / dtex or more, an elongation at break of 10% or more, and an elastic modulus of 6.0 mN / (dtex・%) or more when stretched to 7%. The cutting strength, elongation at break, and elastic modulus of 7% stretch of the organic fiber cord are values ​​measured at room temperature (23°C). Furthermore, the various physical properties of the organic fiber cord can be measured according to JIS L 1013 "Test Method for Chemical Fiber Filament Yarn".

[0115] Furthermore, the modulus of elasticity at 7% elongation is calculated by converting the slope of the tangent line (N / %) at the point corresponding to 7% elongation of the load-elongation curve of the organic fiber cord into a value per dtex. The slope of the tangent line at the point corresponding to 7% elongation of the load-elongation curve refers to the slope of the tangent line S at the point corresponding to 7% elongation of the load-elongation curve C of the organic fiber cord, as shown in Figure 2.

[0116] Organic fiber cords with a cutting strength of 6.5 cN / dtex or higher, an elongation at cutting of 10% or higher, and an elastic modulus of 6.0 mN / (dtex·%) or higher at 7% elongation exhibit high cutting strength, high elongation at cutting, and a high elastic modulus at 7% elongation. By applying such organic fiber cords to a belt reinforcement layer, it is possible to improve the handling stability of the tire while maintaining the plunger durability of the tire.

[0117] Among the materials mentioned above, polyethylene terephthalate is preferred as the material for the organic fiber cord when applied to belt reinforcement cords. In other words, the organic fiber cord applied to the belt reinforcement cord in the belt reinforcement layer is preferably polyethylene terephthalate cord. Polyethylene terephthalate cord has higher rigidity than commonly used nylon cords, etc., and is excellent in improving the durability of the tire plunger and steering stability.

[0118] An example of the aforementioned organic fiber cord is an organic fiber cord having a core containing at least one core strand and a sheath containing at least one sheath strand, wherein the sheath strand is spirally wound around the outer circumference of the core to form the sheath, and the core strand is made of an organic fiber with an initial tensile resistance of 55 cN / dtex or higher, and the sheath strand is made of at least one selected from aliphatic polyamide fiber, polyester fiber, polyvinyl alcohol fiber, and cotton.

[0119] Figure 3 shows a schematic cross-sectional view in the width direction of an example of an organic fiber cord. The organic fiber cord 10 shown in Figure 3 has a core 13 containing at least one core strand 11 and a sheath 14 containing at least one sheath strand 12, with the sheath strand 12 being spirally wound around the outer circumference of the core 13 to form the sheath 14. More specifically, the organic fiber cord 10 shown in Figure 3 has a core 13 formed by further twisting three core strands 11, which are made of single-twist yarns obtained by under-twisting the raw yarn, and a sheath 14 made of 14 sheath strands 12, which are made of single-twist yarns obtained by under-twisting the raw yarn, with the sheath strand 12 being spirally wound around the outer circumference of the core 13 to form the sheath 14.

[0120] In the organic fiber cord 10, it is preferable that the core strands 11 constituting the core 13 are made of organic fibers having an initial tensile resistance of 55 cN / dtex or more. When the initial tensile resistance of the organic fibers constituting the core strands 11 is 55 cN / dtex or more, sufficient wear resistance of the tread portion can be ensured when applied to a tire. Preferably, the initial tensile resistance of the organic fibers constituting the core strands 11 is 3.0 × 10 ２ cN / dtex or more 1.1×10 ３ The value is less than or equal to cN / dtex. In this specification, the initial tensile resistance of organic fibers can be measured in accordance with JIS L 1017.

[0121] Furthermore, in the organic fiber cord 10, it is preferable that the sheath strands 12 constituting the sheath 14 consist of at least one selected from aliphatic polyamide fibers such as 6-nylon, 6,6-nylon, and 4,6-nylon, polyester fibers, polyvinyl alcohol (PVA) fibers, and cotton. Examples of polyester fibers include polyethylene terephthalate (PET) fibers.

[0122] By using highly rigid organic fibers that satisfy a predetermined initial tensile resistance as the core strands 11 constituting the core 13, the tire reinforcement layer can be made highly rigid. When the organic fiber cord 10 is applied to a tire, the in-plane rigidity of the tread portion can be improved, ensuring the wear resistance of the tread portion. On the other hand, by using a predetermined organic fiber with high wear fatigue resistance as the sheath strands 12 constituting the sheath 14, and arranging this sheath 14 on the outer circumference of the core 13, it is less likely that sheath strands will break due to contact or friction with each other when the cords come into contact with each other. As a result, a decrease in cord strength can be prevented, and cord durability can be improved.

[0123] In the organic fiber cord 10, the desired effect can be obtained by using organic fibers that satisfy a predetermined initial tensile resistance for the core strands 11 constituting the core 13, and by using predetermined organic fibers for the sheath strands 12 constituting the sheath 14. However, it is more preferable to configure it as follows.

[0124] Regarding the core strand 11, specific examples of organic fibers that satisfy the above-mentioned initial tensile resistance include aromatic polyamide fibers and rayon fibers, and preferably aromatic polyamide fibers are used. By using aromatic polyamide fibers, the wear resistance of the tread portion can be further improved when the organic fiber cord 5 is applied to a tire. Examples of aromatic polyamide fibers include aramid fibers.

[0125] Furthermore, the total fineness of the core 13 is preferably 1.4 × 10 ３ ~1.2 x 10 ４ It is dtex, and more preferably 1.0 × 10 ４ ~1.2 x 10 ４ It is dtex. By setting the total fineness of the core within the above range, the wear resistance of the tread portion can be further improved when the organic fiber cord 10 is applied to the tire.

[0126] Furthermore, it is preferable that the total fineness of the sheath strand 12 is lower than the total fineness of the core 13. This can further improve the wear resistance of the tread portion.

[0127] <Adhesive composition> The organic fiber cord is preferably treated with an adhesive composition.

[0128] Examples of the adhesive composition include a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially not containing addition-reactive carbon-carbon double bonds in its main chain structure, a heat-reactive aqueous urethane resin (B), and an epoxy compound (C), and optionally further containing rubber latex (D). By treating an organic fiber cord with such an adhesive composition, the adhesion between the organic fiber cord and the rubber composition for covering the organic fiber cord (covering rubber) at high temperatures can be improved.

[0129] Conventionally, the adhesive treatment of organic fiber cords has involved a so-called two-bath treatment, in which epoxy or isocyanate is applied to the cord surface, and then treated with a resin (hereinafter referred to as RFL resin) made by mixing resorcinol, formaldehyde, and latex. However, with this method, the resin used in the first bath becomes very hard, which can increase the strain input to the organic fiber cord and reduce the cord's fatigue resistance. Furthermore, while such RFL resin can exhibit sufficient cord-elastomer adhesion at room temperature, its adhesive strength can drastically decrease at high temperatures above 130°C. In contrast, by using a one-bath mixture (adhesive composition) containing a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially no addition-reactive carbon-carbon double bonds in its main chain structure, a heat-reactive aqueous urethane resin (B), and an epoxy compound (C), it is possible to ensure sufficient adhesion to the organic fiber cord coating rubber composition (coating rubber) even at high temperatures of 180°C or higher, without curing the organic fiber cord.

[0130] The main chain of the thermoplastic polymer (A) mainly has a linear structure, and the main chain is preferably an ethylenically modified polymer such as an acrylic polymer, a vinyl acetate polymer, or a vinyl acetate-ethylene polymer; or a urethane polymer. However, the thermoplastic polymer (A) only needs to have the function of suppressing resin fluidity at high temperatures and ensuring the fracture strength of the resin by crosslinking the functional groups of the pendant groups, and is not limited to the ethylenically modified polymers and urethane polymers mentioned above.

[0131] Furthermore, preferred functional groups for the pendant group of the thermoplastic polymer (A) include oxozaline groups, bismaleimide groups, (blocked) isocyanate groups, aziridine groups, carbodiimide groups, hydrazino groups, epoxy groups, epithio groups, and the like.

[0132] Furthermore, the thermoplastic polymer (A), heat-reactive aqueous urethane resin (B), epoxy compound (C), and rubber latex (D) described above can be those described in International Publication No. 2024 / 190799 and International Publication No. 2024 / 180857, respectively.

[0133] In the adhesive treatment of the aforementioned organic fiber cord (particularly polyethylene terephthalate cord), it is preferable to use a mixture of three components (adhesive composition) – the thermoplastic polymer (A), the heat-reactive aqueous urethane resin (B), and the epoxy compound (C) – as the first treatment solution, and a standard RFL resin solution as the second treatment solution. Alternatively, in the adhesive treatment described above, it is also possible to perform the treatment in only one bath using a mixture of the thermoplastic polymer (A), the heat-reactive aqueous urethane resin (B), the epoxy compound (C), and rubber latex (D).

[0134] In the above adhesive composition, the proportion of thermoplastic polymer (A) (dry mass ratio) is preferably 2 to 75%, the proportion of heat-reactive aqueous urethane resin (B) (dry mass ratio) is preferably 15 to 87%, the proportion of epoxy compound (C) (dry mass ratio) is preferably 11 to 70%, and the proportion of rubber latex (D) (dry mass ratio) is preferably 20% or less.

[0135] On the other hand, from the viewpoint of environmental protection, it is preferable to use a dipping solution that does not contain resorcinol and formalin as the adhesive composition for organic fiber cords. Examples of such dipping solutions include a composition containing (a) a rubber latex having an unsaturated diene and (b) one or more compounds selected from compounds containing a polyether skeleton structure and amine functional groups, compounds having an acrylamide structure, polypeptides, polylysine, and carbodiimide. Examples of such dipping solutions include a composition that, in addition to the above-mentioned rubber latex having an unsaturated diene (a) and compound (b), further contains one or more compounds selected from aqueous compounds having (thermally dissociable blocked) isocyanate groups (c), polyphenols (d), and polyvalent metal salts (e).

[0136] Other dipping solutions that do not contain resorcinol and formalin include compositions containing polyphenols (I) and aldehydes (II). In addition, such compositions may further contain at least one of isocyanate compounds (III) and rubber latex (IV) in addition to polyphenols (I) and aldehydes (II).

[0137] The adhesive composition used to treat (coat) the aforementioned organic fiber cord contains polyphenols (I) and aldehydes (II), which allows for good adhesion even when resorcinol is not used, taking into consideration the environmental impact.

[0138] "Polyphenols (I)" The adhesive composition can enhance its adhesion to organic fiber cords by containing polyphenols (I) as a resin component. Here, polyphenols (I) are typically water-soluble polyphenols and are not particularly limited as long as they are polyphenols other than resorcinol. In polyphenols (I), the number of aromatic rings or hydroxyl groups can be appropriately selected.

[0139] From the viewpoint of achieving better adhesion, the polyphenols (I) preferably have two or more hydroxyl groups, and more preferably have three or more hydroxyl groups. Having three or more hydroxyl groups in the polyphenols allows the polyphenols or polyphenol condensates to dissolve in the water-containing adhesive composition (dip treatment solution). This allows the polyphenols to be uniformly distributed within the adhesive composition, thereby achieving better adhesion. Furthermore, if the polyphenols (I) are polyphenols containing multiple (two or more) aromatic rings, each of these aromatic rings has two or three hydroxyl groups located at the ortho, meta, or para position.

[0140] As the aforementioned polyphenols (I), for example, those described as polyphenol compounds in International Publication No. 2022 / 130879 can be used. These polyphenols (I) may be used individually or in combination of two or more.

[0141] "Aldehydes (II)" The adhesive composition can achieve high adhesion together with the polyphenols (I) by containing aldehydes (II) as a resin component in addition to the polyphenols (I) described above. Here, aldehydes (II) are not particularly limited and can be appropriately selected according to the required performance. In this specification, aldehydes (II) also include aldehyde derivatives from which aldehydes are generated.

[0142] Examples of the aldehydes (II) include monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, chloral, butyraldehyde, caproaldehyde, and allylaldehyde; or aliphatic dialdehydes such as glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, and adipoaldehyde; aldehydes having an aromatic ring; and dialdehyde starch. These aldehydes (II) may be used individually or in combination of two or more.

[0143] The aldehyde (II) is preferably an aldehyde having an aromatic ring or contains an aldehyde having an aromatic ring, because better adhesion can be obtained. Furthermore, it is preferable that the aldehyde (II) does not contain formaldehyde. Here, "does not contain formaldehyde" means, for example, that the formaldehyde content in the total mass of the aldehydes is less than 0.5% by mass.

[0144] In the aforementioned adhesive composition, polyphenols (I) and aldehydes (II) are in a condensed state, and it is preferable that the mass ratio of polyphenols to aldehydes having aromatic rings (content of aldehydes having aromatic rings / content of polyphenols) is 0.1 or more and 3 or less. This is because in this case, the hardness and adhesiveness of the resin, which is the product of the condensation reaction that occurs between polyphenols and aldehydes having aromatic rings, becomes more suitable. From a similar viewpoint, it is more preferable that the mass ratio of polyphenols to aldehydes having aromatic rings (content of aldehydes having aromatic rings / content of polyphenols) in the aforementioned adhesive composition is 0.25 or more, and more preferably 2.5 or less. Note that the above mass ratio is the mass of the dry product (solid content ratio).

[0145] Furthermore, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass. This is because better adhesion can be ensured without worsening workability, etc. From a similar viewpoint, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is more preferably 5% by mass or more, and more preferably 25% by mass or less. Note that the above total content is the mass (solid content ratio) of the dry product.

[0146] "Isocyanate compound (III)" The adhesive composition preferably further contains an isocyanate compound (III) in addition to the polyphenols (I) and aldehydes (II) described above. In this case, the adhesive properties of the adhesive composition can be further enhanced by the synergistic effect with polyphenols (I) and aldehydes (II).

[0147] Here, the isocyanate compound (III) is a compound that promotes adhesion of the adhesive composition to a resin material (for example, a phenol / aldehyde resin obtained by condensing polyphenols (I) and aldehydes (II)), and is a compound having an isocyanate group as a polar functional group. These isocyanate compounds (III) may be used individually or in combination of two or more.

[0148] The isocyanate compound (III) is not particularly limited, but from the viewpoint of further improving adhesion, it is preferable to include an aromatic compound containing a (blocked) isocyanate group. By including an aromatic compound containing a (blocked) isocyanate group in the adhesive composition, the (blocked) isocyanate group-containing aromatic compound is distributed near the interface between the organic fiber cord and the adhesive composition, resulting in a further adhesion-enhancing effect, which can further improve the adhesion of the adhesive composition to the organic fiber cord.

[0149] As for the (blocked) isocyanate group-containing aromatic compounds, those described in International Publication No. 2024 / 190799 and those described in International Publication No. 2024 / 180857 may be used.

[0150] The content of isocyanate compound (III) in the adhesive composition is not particularly limited, but from the viewpoint of ensuring better adhesion more reliably, it is preferably 5 to 65% by mass. From the same viewpoint, the content of isocyanate compound (III) in the adhesive composition is more preferably 10% by mass or more, and more preferably 45% by mass or less. The above content is the mass (solid content ratio) of the dry product.

[0151] "Rubber latex (IV)" The adhesive composition may further substantially contain rubber latex (IV) in addition to the polyphenols (I), aldehydes (II), and isocyanate compounds (III) described above. This allows the adhesive composition to further enhance its adhesion to rubber members.

[0152] Here, the rubber latex (IV) is not particularly limited and includes natural rubber (NR), as well as synthetic rubbers such as polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonylitol-butadiene rubber (NBR), or vinylpyridine-styrene-butadiene copolymer rubber (Vp). These rubber latex (IV) may be used individually or in combination of two or more types.

[0153] When preparing the adhesive composition containing the rubber latex (IV), it is preferable to mix the rubber latex (IV) with phenols (I) and aldehydes (II) before incorporating the isocyanate compound (III).

[0154] The content of rubber latex (IV) in the adhesive composition is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 70% by mass or less, and more preferably 60% by mass or less.

[0155] The method for producing the adhesive composition is not particularly limited, but examples include a method of mixing raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV) and then aging them, or a method of mixing polyphenols (I) and aldehydes (II), aging them, and then adding rubber latex (IV) and aging it further. If the raw materials for producing the adhesive composition include isocyanate compounds (III), the method may also involve adding rubber latex (IV), aging it, and then adding isocyanate compounds (III).

[0156] <Rubber-Organic Fiber Cord Composite> By coating an organic fiber cord with the rubber composition for covering organic fiber cords of this embodiment, a rubber-organic fiber cord composite can be formed.

[0157] The rubber-organic fiber cord composite is preferably formed by coating an organic fiber cord 21 with a coating rubber (a rubber composition for covering organic fiber cords) 22, as shown in Figure 4.

[0158] Furthermore, an example of the rubber-organic fiber cord composite is a rubber-organic fiber cord composite that satisfies the following formula (1): (A / B) / total cord fineness ≥ 0.3 ... (1) Here, A in the above formula (1) represents "cord strength (N) × fiber occupancy". By increasing the value of A, the strength of the rubber-organic fiber cord composite can be increased. Also, the fiber occupancy in A represents "cross-sectional area of ​​the organic fiber cord (mm²)". ２ The formula is (A / B) / (thickness of the rubber-organic fiber cord composite (mm) × (diameter of the organic fiber cord (mm) + distance between organic fiber cords (mm))), and increasing this value allows for a thinner coating rubber 22, contributing to a reduction in rolling resistance. In addition, B in the above formula (1) is "tanδ of the coating rubber × rubber occupancy rate", and decreasing this value reduces the volume of rubber in the rubber-organic fiber cord composite, contributing to weight reduction and a reduction in rolling resistance. The rubber occupancy rate is "1 - fiber occupancy rate". Furthermore, the total cord fineness in the above formula (1) is the sum of the fineness of the organic fibers 23, and the larger this value, the thicker the organic fiber cord 21 becomes, indicating higher strength but also a larger mass. By setting the ratio of "A / B" to the "total cord fineness" to 0.3 or more, it is possible to increase the strength of the rubber-organic fiber cord composite even when using cords with low fineness (when the mass of the organic fiber cord is small).

[0159] From a similar viewpoint, it is preferable that the rubber-organic fiber cord composite satisfies the following formula (1'): (A / B) / total cord fineness ≥ 0.45 ... (1')

[0160] The cord strength of the organic fiber cord is preferably 160 N or higher, and more preferably 165 N or higher. This is because it allows for a greater increase in the strength of the rubber-organic fiber cord composite. The cord strength of the organic fiber cord can be controlled as appropriate by adjusting, for example, the total fineness of the cord, the number of twists, the yarn strength, etc.

[0161] Furthermore, the yarn strength of the organic fibers constituting the organic fiber cord is preferably 7.8 cN / dtex or higher, and more preferably 8.0 cN / dtex or higher. As a result of increasing the strength of the organic fiber cord, the strength of the rubber-organic fiber cord composite can be further increased. The yarn strength of the organic fibers can be increased by adjusting the molecular weight, crystallinity, and crystal orientation of the resin used for the organic fibers.

[0162] The tensile strength of the sheet-like rubber-organic fiber cord composite is preferably greater than 2300 N / cm. A tensile strength of greater than 2300 N / cm of the composite can be obtained. The strength of the composite (N / cm) is calculated by multiplying the tensile strength of a single cord measured by ASTM D885 by the number of cords per 10 cm of width.

[0163] The thickness of the sheet-like rubber-organic fiber cord composite is preferably 1.8 mm or less, more preferably 1.5 mm or less, even more preferably 1.2 mm or less, and particularly preferably 1.0 mm or less. This is because a thickness of 1.8 mm or less of the sheet-like composite promotes weight reduction of the rubber-organic fiber cord composite, thereby more reliably suppressing the deterioration of rolling resistance when applied to a tire. The thickness of the sheet-like composite is the thickness T of the composite when it is cut by a plane perpendicular to the direction in which the cords extend within the composite, as shown in Figure 4.

[0164] Furthermore, the total fineness of the organic fiber cord is preferably 1000 to 4800 dtex, and more preferably 2000 to 4000 dtex. A total fineness of 1000 dtex or more of the organic fiber cord can further increase the strength of the rubber-organic fiber cord composite. On the other hand, a total fineness of 4800 dtex or less of the organic fiber cord can more reliably suppress the deterioration of rolling resistance when the rubber-organic fiber cord composite is applied to a tire. Here, the total fineness of the organic fiber cord is the sum of the fineness of the organic fibers constituting the cord, and the total fineness can be controlled by adjusting the fineness of the organic fibers, the number of twists, etc.

[0165] Furthermore, from the viewpoint of maintaining plunger energy, the diameter of the organic fiber cord is preferably 0.45 mm or more, and more preferably 0.50 mm or more. Also, from the viewpoint of reducing rolling resistance, it is preferably 0.80 mm or less, and more preferably 0.70 mm or less.

[0166] Furthermore, the fineness of the organic fiber is preferably 550 to 2200 dtex, and more preferably 1100 to 1670 dtex. A fineness of 550 dtex or higher for the organic fiber allows for greater strength of the rubber-organic fiber cord composite. On the other hand, a fineness of 2200 dtex or lower for the organic fiber allows for more reliable suppression of deterioration in rolling resistance when the rubber-organic fiber cord composite is applied to a tire. The fineness of the organic fiber can be controlled by adjusting the type of fiber, manufacturing conditions, etc.

[0167] The fineness of the organic fiber cord is preferably 1100 / 2 to 2000 / 2 dtex. A fineness of 1100 / 2 dtex or higher allows for greater strength of the rubber-organic fiber cord composite. On the other hand, a fineness of 2000 / 2 dtex or lower allows for more reliable suppression of the deterioration of rolling resistance when the rubber-organic fiber cord composite is applied to a tire.

[0168] Furthermore, the weaving density of the organic fiber cord is preferably 120 cords / 10 cm or more, and more preferably 140 cords / 10 cm or more. This is because it can further increase the strength of the rubber-organic fiber cord composite. The weaving density of the organic fiber cord refers to the number of organic fiber cords per 10 cm in the direction in which the cords are arranged side by side in the rubber-organic fiber cord composite (the transverse direction in Figure 4).

[0169] Furthermore, the fiber occupancy rate in the rubber-organic fiber cord composite is preferably 30% or more and 40% or less, and more preferably 35% or more and 40% or less, in order to achieve a higher level of both strength and low rolling resistance when applied to a tire. The fiber occupancy rate refers to the cross-sectional area (mm²) of the organic fiber cord, as described above. ２ It is obtained by the formula: ) / (thickness of the rubber-organic fiber cord composite (mm) × (diameter of the organic fiber cord (mm) + distance between organic fiber cords (mm))).

[0170] Here, the diameter of the organic fiber cord is the diameter D in the cross-section of the organic fiber cord 21 constituting the rubber-organic fiber cord composite 20, as shown in Figure 4. In addition, the cross-sectional area of ​​the organic fiber cord is the area S in the cross-section of the organic fiber cord 21 constituting the rubber-organic fiber cord composite 20, as shown in Figure 4. Furthermore, the distance between the organic fiber cords is the shortest distance P between adjacent cords 21 in the cross-section of the organic fiber cord 21 constituting the rubber-organic fiber cord composite 20, as shown in Figure 4.

[0171] <Tires> The rubber-organic fiber cord composite constructed by coating an organic fiber cord with the organic fiber cord coating rubber composition of this embodiment can be suitably applied to the carcass layer, belt reinforcement layer, and the like of a tire.

[0172] Below, an embodiment of a tire to which the organic fiber cord coating rubber composition of this embodiment is applied will be described in detail with reference to the drawings.

[0173] Figure 5 is a cross-sectional view of one embodiment of a tire. The tire 100 shown in Figure 5 has a pair of bead portions 30 and a pair of sidewall portions 40 and a tread portion 50 connected to both sidewall portions 40, and comprises a carcass layer 70 extending in a toroidal shape between bead cores 60 embedded in the pair of bead portions 30, two belt layers 80A and 80B arranged on the radially outer side of the crown portion of the carcass layer 70, a belt reinforcement layer (also called a "cap layer") 90A arranged on the radially outer side of the belt layers 80A and 80B so as to cover the entire belt layers 80A and 80B, and a pair of belt reinforcement layers (also called "layer layers") 90B arranged so as to cover only both ends of the belt reinforcement layer 90A. In the tire 100 shown in Figure 5, at least one of the carcass layer 70 or the belt reinforcement layers 90A, 90B, or at least one of the carcass layer 70 and the belt reinforcement layers 90A, 90B, is a rubber-organic fiber cord composite to which the rubber composition for covering organic fiber cords of this embodiment described above is applied.

[0174] In the tire 100 shown in Figure 5, the carcass layer 70 is a single layer, but the number of carcass layers may be two or more. Also, in the tire 100 shown in Figure 5, the carcass layer 70 consists of a main body that extends in a toroidal shape between a pair of bead cores 60 embedded in the bead portion 30, and folded-over portions that are wound radially outward from the inside to the outside in the tire width direction around each bead core 60, but the shape and structure of the carcass layer 70 are not limited to this. Here, it is preferable that the carcass layer 70 is made of multiple organic fiber cords that extend in a direction substantially perpendicular to the tire circumferential direction (for example, extending at an angle of 70 to 90°) and are covered with coating rubber, that is, it is preferable that the carcass layer 70 is a radial carcass.

[0175] Furthermore, although the belt layers 80A and 80B of the tire 100 shown in Figure 5 consist of two layers, the number of belt layers may be one or three or more. In addition, in the tire 100 shown in Figure 5, each belt layer 80A and 80B is typically made of reinforcing cords that extend at an inclination with respect to the tire's equatorial plane (for example, at an angle of 15 to 40°) and are covered with coating rubber, preferably steel cords covered with coating rubber. Furthermore, the two belt layers 80A and 80B are stacked such that the reinforcing cords constituting the belt layers 80A and 80B intersect each other with the tire's equatorial plane in between, thereby forming the belt 80.

[0176] Furthermore, in the tire 100 shown in Figure 5, the belt reinforcement layers 90A and 90B are formed by covering reinforcing cords arranged substantially parallel to the tire circumferential direction (for example, at an angle of 0 to 5° with respect to the tire circumferential direction) with coating rubber. The belt reinforcement layers 90A and 90B are formed by continuously winding narrow strips, prepared by covering organic fiber cords with coating rubber, in a spiral shape in the tire circumferential direction. In this case, since there are no joints in the tire circumferential direction, the uniformity of the tire is good, and because there are no joints, strain concentration at joints can be prevented. Although the tire 100 shown in Figure 5 has belt reinforcement layers 90A and 90B, it is also possible to omit either belt reinforcement layer 90A or belt reinforcement layer 90B. Also, in the tire 100 shown in Figure 5, the belt reinforcement layer (cap layer) 90A and the belt reinforcement layer (layer layer) 90B are each one layer, but there may be two or more layers.

[0177] <Method for Manufacturing Tires> The tires can be manufactured by conventional methods using the above-described rubber composition for covering organic fiber cords. For example, depending on the type of tire to be applied, the tires may be obtained by molding and then vulcanizing an unvulcanized rubber composition or an unvulcanized treat (rubber-organic fiber cord composite), or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The components of the tire other than the carcass layer and belt reinforcement layer are not particularly limited, and known components can be used. The tires are preferably pneumatic tires, and as the gas to be filled into the pneumatic tires, in addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

[0178] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0179] <Preparation and Evaluation of Rubber Compositions in Reference Examples 1 and 2> Two types of rubber compositions having the compound compositions shown in Table 1 were prepared. The total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources was calculated for each rubber composition to determine the sustainable material ratio. Furthermore, the tensile strength of the obtained rubber compositions was evaluated using the following method.

[0180] (1) Method for evaluating breaking strength The rubber composition prepared as described above was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The obtained vulcanized rubber test pieces were punched out into JIS-3 dumbbells, and the resulting samples were subjected to tensile tests at room temperature according to JIS K 6251:2004, and the breaking strength (TB) before thermal degradation (initial) and after thermal degradation (100°C × 24 hours) was measured. The results are shown in Table 1. A higher value indicates better resistance to fracture.

[0181]

[0182] *1 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *2 New carbon black: Manufactured by Asahi Carbon, product name "N550", nitrogen adsorption specific surface area (N ２ SA) = 40m２ / g, OAN oil absorption = 121 mL / 100 g *3 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *4 Anti-aging agent 1: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 6C" *5 Anti-aging agent 2: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 224" *6 Oil: ENEOS, product name "A / Omix" *7 Fatty acid: Miyoshi Oil & Fat Co., Ltd., product name "MXST" *8 Other chemicals: Total amount of sulfur, vulcanization accelerator, resin, and wax, same ratio in each rubber composition

[0183] Table 1 shows that replacing new carbon black with recycled carbon black among the various materials contained in the rubber composition reduces the tensile strength before and after thermal degradation.

[0184] <Evaluation of Recycled Carbon Black> The physical properties of recycled carbon black were evaluated using the following method.

[0185] (2) Grind gauge measurement A mixture was obtained by mixing 3.75 g of zinc oxide, 0.20 g of the carbon black under test, and 2.00 mL of epoxidized soybean oil. The obtained mixture was kneaded for 5 to 10 minutes to form a paste, and sample pastes were prepared. In accordance with JIS K5101-1-5, pastes were prepared using a Toyo Seiki Co., Ltd. Huber Mahler (model: H3) under conditions of a load of 0.4536 kN and a glass plate rotation speed of 100 r / min. In accordance with JIS K5400, each sample paste was placed on a grind gauge and stretched with a scraper. A grind gauge with a range of 0 to 25 μm was used. It was confirmed that three or more continuous lines of 10 mm or more appeared, and the scale at the location where the line caused by the third largest particle among the particles that produced the continuous lines of 10 mm or more appeared was read, and this reading was taken as the particle size of the third largest particle. The average value of the particle size measured four times is shown in Table 2.

[0186] (3) Nitrogen adsorption specific surface area (N ２ SA) In accordance with ASTM D6556, the specific surface area (N) of nitrogen adsorption of the tested carbon black. ２ SA was measured.

[0187] (4) Elemental analysis: The content of zinc (Zn), copper (Cu), and iron (Fe) was confirmed by X-ray fluorescence analysis (XRF).

[0188] (5) Ash content The ash content of the carbon black sample was measured according to ASTM D8474 and D1506.

[0189]

[0190] <Preparation and Evaluation of Rubber Compositions in Example 1 and Comparative Example 1> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 3. Other chemicals included antioxidants, oils, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in Example 1 and Comparative Example 1. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were the amounts commonly used in the preparation of rubber compositions. The total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources was calculated for the rubber composition to determine the sustainable material ratio. Furthermore, the high-temperature tensile strength and crack propagation resistance after degradation were evaluated for the obtained rubber compositions using the following method.

[0191] (6) Method for evaluating high-temperature tensile strength after degradation Each rubber composition was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. The obtained vulcanized rubber was subjected to thermal degradation at 100°C for 48 hours in an air atmosphere. A tensile test was performed at 100°C in accordance with JIS K6251:2017 and the tensile strength was measured. With the tensile strength of the test piece from Example 1 set to 100, the high-temperature tensile strength (fracture resistance) after degradation was expressed as an index using the following formula: High-temperature tensile strength index after degradation = (Tensile strength of the test piece / Tensile strength of the test piece from Example 1) × 100 A higher high-temperature tensile strength index after degradation indicates that the vulcanized rubber is less prone to fracture and has superior performance (fracture resistance) after degradation.

[0192] (7) Method for evaluating crack propagation resistance after thermal degradation The test rubber composition was pre-treated by thermal degradation at 100°C for 24 hours in an air atmosphere. From the degraded rubber composition, a strip-shaped test piece was prepared with a 0.5 mm hole drilled in the lengthwise direction in the center. A dc / dn test was performed using this test piece (using a Shimadzu Servopulsa, repeated fatigue was applied at a frequency of 5 Hz and 80°C with a strain of 30-100%), and the tear energy [J / m] at 1950 cycles was determined. ２ The crack propagation rate was calculated when the common logarithm of [ ] was 3.9. In the crack propagation rate obtained by the above process, the formulation data of Example 1 was used as a control (index value 100), and the formula data of each example was normalized by the reciprocal of the formula data. A larger index value indicates a lower crack propagation rate and superior crack propagation resistance after thermal degradation.

[0193]

[0194] *9 Natural rubber: RSS#3 *10 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *11 New carbon black: Manufactured by Asahi Carbon, N550 *12 Recycled carbon black 1: Same as Table 2 *13 Recycled carbon black 2: Same as Table 2

[0195] Tables 2 and 3 show that even with rubber compositions containing recycled carbon black of the same ash content, the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition vary significantly depending on the particle size of the third largest particle measured by the grind gauge of the incorporated recycled carbon black. It can be seen that incorporating recycled carbon black in which the third largest particle size measured by the grind gauge is 20 μm or less improves the high-temperature tensile strength and crack propagation resistance after thermal degradation. These results indicate that applying a rubber composition containing recycled carbon black in which, when measured by grind gauge, there are three or more lines with a length of 10 mm or more, and the third largest particle size among the particles producing these lines is 20 μm or less, can improve the proportion of sustainable materials while maintaining tire performance.

[0196] <Preparation and Evaluation of Rubber Compositions for Standard and Reference Examples 3-5> Carbon black (CB) and styrene-butadiene rubber with different ash, Zn, and S content were kneaded according to the formulations shown in Table 4 to prepare the rubber compositions for each example. The methods for measuring the component amounts and ash content in the carbon black used in each example, and the methods for evaluating the tensile strength and viscoelasticity of the prepared rubber compositions are as follows. The results are shown in Table 4.

[0197] (8) Amount of components in carbon black The amounts of components such as Zn, Fe, and S in carbon black were measured by X-ray fluorescence analysis.

[0198] (9) Ash Content The ash content of carbon black was measured by thermogravimetric analysis (TGA, RIGAKU Corporation). The sample was heated from room temperature to 550°C under a nitrogen atmosphere, and then heated to maintain 550°C under an air atmosphere, and the loss on heating was measured. The loss on heating (mass%) when the sample was heated from room temperature to 550°C under a nitrogen atmosphere was defined as "Loss on Heating 1," and the loss on heating (mass%) when heated to maintain 550°C under an air atmosphere was defined as "Loss on Heating 2." The ash content was calculated using the following formula: Ash content (mass%) = 100 - Loss on Heating 1 - Loss on Heating 2

[0199] (10) The rubber compositions of the standard example and reference example were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. Tensile tests were performed on each vulcanized rubber at room temperature in accordance with JIS K6301-1995 to measure its tensile strength. The tensile strength of the standard example test specimen was set to 100, and the tensile strength was expressed as an index using the following formula: Tensile strength index = (Tensile strength of test specimens other than the standard example / Tensile strength of the standard example test specimen) × 100 A larger index indicates that the vulcanized rubber is less likely to break and has superior tensile strength.

[0200] (11) Viscoelasticity A viscoelasticity test was performed using "ARES-G2" manufactured by TA Instruments Inc. under the conditions of a frequency of 15 Hz, shear strain of 10%, and temperature of 50°C, and the storage modulus (G') of the rubber composition was measured. The evaluation results were indexed with the standard example as the control (index value 100). A higher index indicates a higher G', which in turn indicates superior rubber properties when applied to tires.

[0201]

[0202] *14 SBR: Styrene-butadiene rubber, manufactured by ENEOS Material Co., Ltd., product name "#1500" *15 CB1: Carbon Black 1, recycled carbon black equivalent to N330 *16 CB2: Carbon Black 2, recycled carbon black equivalent to N330 *17 CB3: Carbon Black 3, recycled carbon black equivalent to N330 *18 CB4: Carbon Black 4, new carbon black equivalent to N330

[0203] Table 4 shows that by using carbon black with a Zn content of 2.5% by mass or less, or an ash content of 6% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed.

[0204] <Preparation and Evaluation of Rubber Compositions in Reference Examples 6 and 7> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 5. The loss tangent tanδ (24°C) and loss tangent tanδ (60°C) of the obtained rubber compositions were measured using the following method. The results are shown in Table 5.

[0205] (12) Measurement of loss tangent tanδ of the rubber composition The rubber composition was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. Using a viscoelasticity measuring device (manufactured by Rheometrics), the loss tangent tanδ (24°C) was measured on the obtained vulcanized rubber test pieces under the conditions of (i) temperature 24°C, initial strain 6%, amplitude ±1%, and frequency 52 Hz, and (ii) loss tangent tanδ (60°C) was measured under the conditions of temperature 60°C, initial strain 1.5%, amplitude ±1%, and frequency 52 Hz.

[0206]

[0207] *19 NR: Natural rubber, TSR #20 *20 SBR(1): Styrene-butadiene rubber, solution polymerized SBR, non-oil-based (ENEOS Material 1500) *21 SBR(2): Styrene-butadiene rubber, emulsion polymerized SBR, 27.3% oil-based (ENEOS Material 1778) *22 Carbon black(1): GPF grade carbon black, N ２ SA (Specific surface area for nitrogen adsorption): 28 m² ２ / g, OAN absorption 89ml / 100g *23 Carbon black (2): HAF grade carbon black, N ２ SA (Specific surface area for nitrogen adsorption): 71 m² ２ / g, OAN absorption rate 103ml / 100g *24 Zinc oxide: Manufactured by Hakusui Tech Co., Ltd., 3 types of zinc oxide *25 Anti-aging agent: Manufactured by Seiko Chemical Co., Ltd., Nonflex RD *26 Sulfur: Manufactured by Tanaka Ai Co., Ltd., SULFUR (5% OIL-TREATED) *27 Vulcanization accelerator: SANCELER NS-G, SANCELER DM-TG

[0208] From the comparison of Reference Example 6 and Reference Example 7 in Table 5, it can be seen that non-oil-based styrene-butadiene rubber is incorporated, and the nitrogen adsorption specific surface area (N) ２ SA) is 40m ２ By incorporating carbon black at a concentration of 0.15 / g or less, the loss tangent tanδ (24°C) of the rubber composition, measured under conditions of 24°C, initial strain of 6%, amplitude ±1%, and frequency of 52Hz, can be reduced to 0.10 or less, and the loss tangent tanδ (60°C) can be reduced to 0.10 or less, measured under conditions of 60°C, initial strain of 1.5%, amplitude ±1%, and frequency of 52Hz. Such a rubber composition exhibits excellent low heat generation, and it is predicted that applying it to tires can improve the fuel efficiency performance of the tires.

[0209] The rubber composition for covering organic fiber cords of the present invention can be applied to various components of tires, for example, as a coating rubber for the carcass, a coating rubber for the belt reinforcement layer, a coating rubber for the belt, and so on.

[0210] 1: Grind gauge 2: Line less than 10 mm in length 3: Line 10 mm or longer 31: Line caused by the largest particle 32: Line caused by the second largest particle 33: Line caused by the third largest particle 4: Scale mark where the line caused by the third largest particle appears 10: Organic fiber cord 11: Core strand 12: Sheath strand 13: Core 14: Sheath 20: Rubber-organic fiber cord composite 21: Organic fiber cord 22: Coating rubber 23: Organic fiber T: Thickness of rubber-organic fiber cord composite D: Diameter of organic fiber cord P: Shortest distance between adjacent cords 30: Bead section 40: Sidewall section 50: Tread section 60: Bead core 70: Carcass layer 80A, 80B: Belt layer 80: Belt 90A: Belt reinforcement layer (cap layer) 90B: Belt reinforcement layer (layer layer) 100: Tire

Claims

1. A rubber composition for covering organic fiber cords, comprising a rubber component and a filler, wherein the filler contains recycled carbon black, and the recycled carbon black, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that give rise to the lines with a length of 10 mm or more is 20 μm or less.

2. The rubber composition for covering organic fiber cords according to claim 1, wherein the paste for measuring the recycled carbon black with a grind gauge is prepared in accordance with JIS K 5101-1-5.

3. The rubber composition for covering organic fiber cords according to claim 1, wherein the paste for measuring the recycled carbon black with a grind gauge is prepared in accordance with JIS K 5101-1-5, with the applied load set to 0.4 to 0.5 kN and the rotation speed of the glass plate set to 90 to 110 r / min.

4. The rubber composition for covering organic fiber cords according to claim 1, wherein the recycled carbon black contains one or more metal atoms selected from the group consisting of Zn, Cu, and Fe.

5. The rubber composition for covering organic fiber cords according to claim 1, wherein the recycled carbon black contains Zn.

6. The rubber composition for covering organic fiber cords according to claim 1, wherein the recycled carbon black has a Zn content of 2.5% by mass or less.

7. The rubber composition for covering organic fiber cords according to claim 1, wherein the recycled carbon black has an ash content of 20% by mass or less.

8. The rubber composition for covering organic fiber cords according to claim 1, wherein the loss tangent tanδ (24°C) measured under conditions of temperature 24°C, initial strain 6%, amplitude ±1%, and frequency 52Hz is 0.15 or less, and the loss tangent tanδ (60°C) measured under conditions of temperature 60°C, initial strain 1.5%, amplitude ±1%, and frequency 52Hz is 0.10 or less.

9. The rubber composition for covering organic fiber cords according to claim 8, wherein the loss tangent tanδ (24°C) is 0.12 or less.

10. The rubber composition for covering organic fiber cords according to claim 8, wherein the loss tangent tanδ (60°C) is 0.07 or less.

11. The rubber composition for covering organic fiber cords according to claim 1, wherein the rubber component comprises natural rubber and styrene-butadiene rubber, and the content of natural rubber in 100 parts by mass of the rubber component is 70 parts by mass or more.

12. The rubber composition for covering organic fiber cords according to claim 11, wherein the styrene-butadiene rubber is a non-oil-extractable styrene-butadiene rubber.

13. The rubber composition for covering organic fiber cords according to claim 1, which does not contain polymer-derived oils.

14. The rubber composition for covering organic fiber cords according to claim 1, wherein the oil content is 0.2% by mass or less.

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