Rubber composition, tire, rubber crawler, and hose

Abstract

The present invention addresses the problem of providing a rubber composition which can give rubber products having an improved sustainable-material proportion while retaining durability, especially after-deterioration performance. This rubber composition contains recycled carbon black, and is characterized in that the recycled carbon black, when examined with a grind gauge (1), shows three or more lines (3) each having a length of 10 mm or longer and the third largest particle among the particles which have caused the lines (3) each having a length of 10 mm or longer has a particle size of 20 μm or less.

Description

Rubber compositions, tires, rubber tracks, and hoses

[0001] This invention relates to rubber compositions, tires, rubber tracks, and hoses.

[0002] Conventionally, various rubber compositions have been used in rubber products such as tires, rubber tracks, and hoses. Furthermore, in order to ensure the strength of these rubber products, carbon black is usually added as a reinforcing filler to the rubber compositions that serve as their raw materials.

[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 in rubber products, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources. Therefore, there is a need to increase the proportion of sustainable materials in the rubber compositions applied to these rubber products. 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, if recycled carbon black is used as a reinforcing filler instead of unused carbon black to increase the proportion of sustainable materials in rubber products, a problem arises where the post-degradation performance of the rubber composition deteriorates depending on the condition of the recycled carbon black, leading to a decrease in the durability of the rubber product.

[0006] Therefore, the present invention aims to solve the problems of the above-mentioned prior art and provide a rubber composition that can improve the proportion of sustainable materials in rubber products while maintaining durability, particularly performance after degradation. Furthermore, the present invention aims to provide tires, rubber tracks, and hoses that have an improved proportion of sustainable materials while maintaining durability, particularly performance after degradation.

[0007] The gist of the rubber composition, tire, rubber crawler, and hose of the present invention, which solve the above problems, is as follows.

[0008] [1] A rubber composition comprising recycled carbon black, wherein 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 according to [1], wherein the paste for measurement using a grind gauge of recycled carbon black is prepared in accordance with JIS K 5101-1-5.

[0010] [3] The rubber composition according to [1] or [2], wherein the paste for measurement using a grind gauge of recycled carbon black 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 rubber composition according to any one of [1] to [3], wherein the recycled carbon black comprises at least one of the elements Zn, Cu, and Fe.

[0012] [5] The recycled carbon black has a nitrogen adsorption specific surface area (N ２ SA) 40-100m ２ A rubber composition according to any one of [1] to [4], wherein the composition is / g.

[0013] [6] The rubber composition according to any one of [1] to [5], wherein the recycled carbon black has an oil absorption capacity (OAN) of 70 to 120 mL / 100 g.

[0014] [7] A rubber composition according to any one of [1] to [6], for use in tires.

[0015] [8] A rubber composition according to any one of [1] to [6], for use with rubber tracks.

[0016] [9] A rubber composition according to any one of [1] to [6], which is for use in hoses.

[0017]

[10] A tire characterized by comprising a rubber member made of the rubber composition described in any one of [1] to [7].

[0018]

[11] A rubber crawler comprising a rubber member made of the rubber composition according to any one of [1] to [6] and [8].

[0019]

[12] A hose comprising a rubber member made of the rubber composition according to any one of [1] to [6] and [9].

[0020] According to the present invention, it is possible to provide a rubber composition capable of improving the ratio of sustainable materials in rubber products while maintaining durability. Further, according to the present invention, it is possible to provide a tire, a rubber crawler, and a hose in which the ratio of sustainable materials is improved while maintaining durability.

[0021] It is an explanatory view of an example of measurement results by a grind gauge.

[0022] Hereinafter, the rubber composition, tire, rubber crawler, and hose of the present invention will be exemplified and described in detail based on their embodiments.

[0023] <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.

[0024] 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 and tire.

[0025] In this specification, the biological resources (biomass resources) refer to carbon-neutral organic resources derived from organisms, and include, for example, those stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants and animals. It is a resource excluding fossil resources (oil, coal, natural gas, etc.). The biological resources may be edible or inedible, but preferably inedible so as not to compete with food and from the viewpoint of effective use of resources.

[0026] Specific examples of the aforementioned biological resources include, for example, cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residue, etc.), wood, charcoal, compost, food waste, vegetable oil residue, fishery product residue, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.). Examples of biological resources include oat oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., residue after sugarcane juicing), soybeans, okara (soy pulp), essential oils (pine root oil, orange oil, eucalyptus oil, etc.), black pulp liquor, algae, etc. Processed versions of these biological resources (i.e., biological resource-derived materials) can also be used. Processing methods include, for example, biological processing methods utilizing the functions of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as micronization, compression, microwave processing, and electromagnetic wave processing. Furthermore, extracted and purified materials (i.e., biological resource-derived materials) from the biological resources or biological resources that have undergone the processing can also be used. For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the aforementioned biological resources can also be used. Examples of the aforementioned sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, growth, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., all derived from biological resources. Examples of the aforementioned proteins include compounds formed by linking amino acids (preferably L-amino acids) derived from biological resources, and also include oligopeptides such as dipeptides. Examples of the aforementioned amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., all derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred among these.The amino acid may be an L-amino acid or a D-amino acid, but from the perspective of abundance in nature and ease of availability, L-amino acids are preferred. Examples of the fatty acid include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc. derived from biological resources. Examples of the fatty acid ester include vegetable oils, animal oils, modified products of oils and fats derived from biological resources, etc. These biological resources may contain various materials and impurities.

[0027] In this specification, the recycled resource refers to a resource obtained by recycling a product that has 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.

[0028] <Rubber Composition> The rubber composition of this embodiment contains recycled carbon black. In the rubber composition of this embodiment, the recycled carbon black is characterized in that when measured by grind gauge, there are three or more lines with a length of 10 mm or more, 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.

[0029] In the rubber composition of this embodiment, recycled carbon black is a material derived from recycled resources. Therefore, by incorporating recycled carbon black into the rubber composition, the proportion of sustainable materials in the rubber product to which the rubber composition is applied can be improved. However, as described above, if recycled carbon black is incorporated instead of ordinary unused carbon black, depending on the condition of the recycled carbon black, the durability of the rubber composition, particularly its performance after degradation, may decrease, leading to a problem of reduced durability of the rubber product. In response to this problem, the inventors have diligently studied and found that by using recycled carbon black to be incorporated into the rubber composition, 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 the particles that produce such lines of 10 mm or more is 20 μm or less, the decrease in the durability of the rubber composition, particularly its performance after degradation, can be suppressed. In addition to grind gauge measurement, various methods are known for evaluating the dispersibility of carbon black. However, with methods other than grind gauge measurement, the correlation between the dispersibility of recycled carbon black and the durability of the rubber composition, particularly its performance after degradation, is low. In contrast, grind gauge measurements show a high correlation between the dispersibility of recycled carbon black and the durability of the rubber composition, particularly its performance after degradation. By using recycled carbon black that is judged to have good dispersibility by grind gauge measurements, that is, recycled carbon black in which the particle size of the third largest particle is 20 μm or less, the deterioration of the rubber composition, particularly its performance after degradation, can be suppressed. Therefore, according to the rubber composition of this embodiment, it is possible to improve the proportion of sustainable materials in rubber products while maintaining durability, particularly performance after degradation.

[0030] (Recycled Carbon Black) In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials used for recycling. Examples of such waste materials include waste rubber and used tires. 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 tire replacements, scrapped vehicles, or End-of-Life Tires (ELTs) that have reached the end of their lifespan. "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. In this context, "used" includes not only tires that have been discarded after being actually used, but also tires that were manufactured but discarded without actually being used.

[0031] 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 product containing carbon black exists 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 vulcanized rubber product containing carbon black.

[0032] The solid residue obtained by thermal decomposition of waste materials such as used rubber and used tires contains ash in addition to carbon black. The ash originates from non-volatile components contained in rubber and tires. Therefore, the recycled carbon black obtained from this solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, a higher carbon content in recycled carbon black is preferable. In the recycled carbon black, the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content in the recycled carbon black is preferably 97% by mass or less, may be 95% by mass or less, or 92% by mass or less. Note that the carbon content does not include adsorbed water.

[0033] 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. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The rubber composition of this embodiment contains recycled carbon black. Since recycled carbon black is a material derived from recycled resources, incorporating recycled carbon black into the rubber composition can improve the proportion of sustainable materials in rubber products to which the rubber composition is applied.

[0040] In the rubber composition of this embodiment, 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 produce such lines of 10 mm or more is 20 μm or less. Methods for evaluating the dispersibility of carbon black using a grind gauge are described in JIS K5101 (particularly concerning the preparation of paste) and JIS K5400 (particularly concerning methods for evaluation by the manner in which linear marks are generated). In measurements according to these JIS standards, the recycled carbon black has three or more lines with a length of 10 mm or more in the grind gauge measurement, and the particle size of the third largest particle among the particles that produce such lines of 10 mm or more is 20 μm or less.

[0041] It is preferable to use a grind gauge with a range of 0 to 25 μm. As described later, from the viewpoint of the durability of the rubber composition, it is important whether or not 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 a grind gauge with an upper limit of the range greater than 20 μm can be used as it is possible to determine whether or not the particle size of the third largest particle is 20 μm or less. Furthermore, when used for other purposes (performance other than the durability of the rubber composition containing recycled carbon black), the range of the grind gauge used can be appropriately selected according to the purpose.

[0042] 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 that has undergone such measurement can more reliably maintain its durability, especially its performance after degradation. 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.

[0043] Furthermore, in the evaluation of recycled carbon black using the grind gauge, when preparing the paste of recycled carbon black in accordance with JIS K5101-1-5, it is preferable to apply a load of 0.4 to 0.5 kN and rotate the glass plate at a speed of 90 to 110 r / min, from the viewpoint of improving evaluation accuracy. By using a paste of recycled carbon black prepared with the applied load and glass plate rotation speed within the above range, it is possible to further suppress variations in measurement results and further improve measurement accuracy. In addition, a rubber composition containing recycled carbon black that has undergone such measurement can more reliably maintain its durability, especially its performance after degradation. Note that the method for preparing the paste of recycled carbon black 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.

[0044] 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, the deterioration of the durability of the rubber composition, particularly its performance after degradation, can be suppressed even when recycled carbon black is added. In this specification, the measurement of recycled carbon black using a grind gauge is performed by the method described in the examples.

[0045] In this embodiment, recycled carbon black having three or more lines of 10 mm or longer in length, as measured by a grind gauge, and the particle size of the third largest particle among the particles that give rise to these lines of 10 mm or longer being 20 μm or less, can be produced by various methods. For example, recycled carbon black with a particle size of 20 μm or less can be produced 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.

[0046] The recycled carbon black may contain at least one of the elements Zn, Cu, and Fe. Since the recycled carbon black is obtained using waste materials subjected to recycling as raw materials, it contains various elements other than carbon (C), and zinc (Zn), copper (Cu), and iron (Fe) are elements that are likely to be contained in the recycled carbon black. Therefore, there is no need to perform special removal operations or the like on the recycled carbon black containing at least one of the elements Zn, Cu, and Fe, and a rubber composition containing such recycled carbon black is easy to manufacture. The content of Zn in the recycled carbon black is usually 0.01 to 5% by mass, preferably 0.05 to 3% by mass. The content of Cu in the recycled carbon black is usually 0 to 0.5% by mass, preferably 0.01 to 0.1% by mass. The content of Fe in the recycled carbon black is usually 0.01 to 0.5% by mass, preferably 0.01 to 0.3% by mass.

[0047] The recycled carbon black may contain sulfur (S). Since sulfur (S) is also an element that is likely to be contained in the recycled carbon black, there is no need to perform special removal operations or the like on the recycled carbon black containing sulfur (S), and a rubber composition containing such recycled carbon black is easy to manufacture. The content of sulfur (S) in the recycled carbon black is preferably usually 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less. Also, the sulfur content may be 0.5% by mass or more, or may be 1% by mass or more. [[ID=​​​​​​​​​​​​​​​​SA) 40-100m ２ A rubber composition containing recycled carbon black at a concentration of 1 / g is easy to manufacture and has sufficient durability. Herein, the nitrogen adsorption specific surface area of ​​recycled carbon black is determined by the BET method and is the statistical thickness specific surface area (STSA), according to ASTM D6556.

[0049] The recycled carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Hereinafter, the pH of the recycled carbon black is determined according to ASTM D1512.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the various physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, in this specification, the ash content of the recycled carbon black is determined according to ASTM D8474 / D1506.

[0056] The recycled carbon black preferably has an oil absorption capacity (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. If the recycled carbon black has an oil absorption capacity (OAN) of 70 mL / 100 g or more, the rubber composition will have sufficient reinforcing properties. Furthermore, recycled carbon black with an oil absorption capacity (OAN) of 70 to 120 mL / 100 g does not require any special treatment. Therefore, a rubber composition containing recycled carbon black with an oil absorption capacity (OAN) of 70 to 120 mL / 100 g is easy to manufacture and has sufficient durability. Hereinafter, the oil absorption capacity (OAN) of the recycled carbon black is determined according to ASTM D2414.

[0057] 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.

[0058] 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 described later. 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 great effect in improving the ratio of sustainable materials in the rubber product to which the rubber composition is applied, and when it is 50 parts by mass or less, the crack resistance and other fracture resistance of the rubber composition can be maintained more reliably.

[0059] (Rubber component) The rubber composition of this embodiment typically contains a rubber component, which provides the composition with rubber elasticity. 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 refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources in the rubber component.

[0060] The rubber component is preferably a diene-based rubber, and of the diene-based rubber, isoprene-based rubber and butadiene-based rubber are preferred. Here, isoprene-based rubber refers to rubber that contains units derived from isoprene as monomer units, and butadiene-based rubber refers to rubber that contains units derived from butadiene as monomer units.

[0061] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). As for natural rubber (NR), for example, those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20), can be used.

[0062] Examples of the butadiene-based rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. 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.

[0063] Examples of the butadiene rubber (BR) include high-cis content butadiene rubber, low-cis content butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available butadiene rubber (BR) can be used, and examples of such commercially available butadiene rubber include products from UBE Elastomer Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation. These butadiene rubbers may be used individually or in combination of two or more types.

[0064] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion polymerized styrene-butadiene rubber (E-SBR)) and solution polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution polymerized styrene-butadiene rubber (S-SBR)). In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds may be used individually or in combination of two or more.

[0065] In addition to the isoprene-based rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., 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.

[0066] (Carbon Black Other Than Recycled Carbon Black) The rubber composition of this embodiment may contain carbon black other than recycled carbon black. By combining carbon black other than recycled carbon black with recycled carbon black, the durability of the rubber composition, particularly its performance after degradation, can be maintained more reliably. Examples of carbon black other than recycled carbon black include new carbon black manufactured by conventional methods, carbon black manufactured by heating polymer materials and carbonizing them, and carbon black manufactured from vegetable oil or waste oil. Examples of carbon black derived from vegetable oil include those derived from castor oil and pine resin oil. The grade of the carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. As carbon black other than the recycled carbon black mentioned above, commercially available products can be used. Examples of commercially available carbon black other than recycled carbon black include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Birla Carbon, and others. These carbon blacks may be used individually or in combination of two or more types.

[0067] Nitrogen adsorption specific surface area (N) of carbon black other than the aforementioned recycled carbon black ２ SA) is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the specific surface area (N) of nitrogen adsorption of carbon black other than recycled carbon black. ２ SA) is 20m ２ Preferably 50 m ２ More preferably 70 m ２ More preferably 90 m ２ More preferably 200m ２ Preferably less than / g, and 150m ２ More preferably less than / g, and 130m ２ A value of less than or equal to / g is even more preferable.

[0068] Carbon black other than the recycled carbon black preferably has an oil absorption capacity (OAN) of 50 to 150 mL / 100 g. Furthermore, carbon black other than recycled carbon black has an oil absorption capacity (OAN) of 50 to 150 mL / 100 g and a nitrogen adsorption specific surface area (N ２ SA) 20-130m ２ It is even more preferable that the amount of oil absorbed (OAN) is 80 to 130 mL / 100 g, and the nitrogen adsorption specific surface area (N ２ SA) is 20-60m ２ It is even more preferable that the oil absorption capacity (OAN) is 50 to 150 mL / 100 g, and the nitrogen adsorption specific surface area (N ２ SA) 20-130m ２ By combining carbon black with the recycled carbon black, the durability of the rubber composition, particularly its performance after degradation, can be maintained even more reliably. Furthermore, the oil absorption capacity (OAN) is 80 to 130 mL / 100 g, and the nitrogen adsorption specific surface area (N) is also high. ２ SA) is 20-60m ２ By combining carbon black at a concentration of / g with the recycled carbon black, the durability of the rubber composition, particularly its performance after degradation, can be maintained even more reliably.

[0069] The content of carbon black other than recycled carbon black is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of carbon black other than recycled carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 100 parts by mass or less, per 100 parts by mass of the rubber component.

[0070] The proportion of recycled carbon black in the total amount of recycled carbon black and other carbon black (i.e., the total amount of carbon black) is preferably 1 to 100% by mass, more preferably 1 to 99% by mass, and even more preferably 10 to 99% by mass. When the proportion of recycled carbon black in the total amount of carbon black is 10% by mass or more, it has a great effect on improving the ratio of sustainable materials in the rubber composition and rubber products using it, and when the proportion of recycled carbon black in the total amount of carbon black is 99% by mass or less, the fracture resistance of the rubber composition can be maintained more reliably. Therefore, a rubber composition in which the proportion of recycled carbon black in the total amount of carbon black is 1 to 100% by mass, preferably 1 to 99% by mass, has a great effect on improving the ratio of sustainable materials and can maintain durability, especially post-degradation performance, more reliably.

[0071] (Resin) The rubber composition of this embodiment may contain a resin. The resin may be a terpene resin, a rosin resin, or C ５ based resin, C ５ -C ９ based resin, C ９ Examples include resins such as cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used individually or in combination of two or more types.

[0072] The resin content is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the resin content is preferably in the range of 5 to 100 parts by mass, and more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0073] (Silica) The rubber composition of this embodiment may contain silica. Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred because it has a large amount of silanol groups. These silicas may be used individually or in combination of two or more. Commercially available silica can be used, and examples of commercially available silica include products from Tosoh Silica Co., Ltd., Evonik, Solvay, Solvay Japan Ltd., Tokuyama Corporation, etc.

[0074] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferred. These silicate plants include, for example, mosses, ferns, horsetails, plants of the Cucurbitaceae family, Urticaceae family, and grasses. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo grass, and sugarcane, and among these, rice is preferred.

[0075] The silica has a nitrogen adsorption specific surface area (N ２ SA) is 50m ２ It is preferable that it be 100m or more per gram. ２ It is more preferable that the amount is 150m or more per gram. ２ It is even more preferable that it be 350m or more ２ It is preferable that the amount is less than or equal to 250m ２ It is more preferable that it be less than or equal to 230m ２ It is even more preferable that it be less than or equal to 200m ２ It is even more preferable that it be less than or equal to / g. In this specification, the specific surface area of ​​silica for nitrogen adsorption (N ２ SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0076] The silica content can be adjusted as appropriate depending on the tire category, tire material, target performance, etc., for example. For example, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, even more preferably 100 parts by mass or more, particularly preferably 110 parts by mass or more, and also preferably 300 parts by mass or less, more preferably 200 parts by mass or less, even more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less.

[0077] (Silane coupling agent) If the rubber composition 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. The silane coupling agent may be 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-N, Examples include 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. Commercially available silane coupling agents can be used, and examples of such commercially available silane coupling agents include products from Evonik, Momentive, Shin-Etsu Silicone Co., Ltd., Toray Dow Corning Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used individually or in combination of two or more types.

[0078] The content of the silane coupling agent can be adjusted as appropriate depending on, for example, the tire category, tire components, target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, even more preferably 8 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of silica.

[0079] (Rubber Powder) The rubber composition of this embodiment may contain rubber powder. The rubber powder may be obtained by crushing used rubber products such as used tires, and optionally removing reinforcing materials such as steel materials and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for the purpose of producing rubber powder and crushing it. It is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0080] The content of the rubber powder is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of the rubber powder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and also preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0081] (Liquid Softener) The rubber composition of this embodiment may contain a liquid softener. Here, "liquid softener" refers to a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid softener is not particularly limited and includes oils, liquid polymers, etc., and among these, oils are preferred. These liquid softeners may be used individually or in combination of two or more.

[0082] The content of the liquid softener is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component.

[0083] (Anti-aging agent) The rubber composition of this embodiment may contain an anti-aging agent. Examples of the anti-aging agent include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available products can be used as the aforementioned anti-aging agents. Examples of commercially available anti-aging agents include those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Corporation, and Flexis Co., Ltd. These anti-aging agents may be used individually or in combination of two or more types.

[0084] The content of the anti-aging agent is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of the anti-aging agent is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2 parts by mass or more, and preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component.

[0085] (Wax) The rubber composition of this embodiment may contain wax. Examples of the wax include natural waxes such as plant-based waxes and animal-based waxes; petroleum-based waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as polymers of ethylene and polymers of propylene. Commercially available waxes can be used, and examples of commercially available waxes include those from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., and Ouchi Shinko Chemical Industry Co., Ltd. These waxes may be used individually or in combination of two or more types.

[0086] The amount of wax is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the amount of wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0087] (Stearic Acid) The rubber composition of this embodiment may contain stearic acid. Commercially available stearic acid can be used, and examples of commercially available stearic acid include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries Ltd., Chiba Fatty Acid Co., Ltd., etc. These commercially available stearic acid products may be used individually or in combination of two or more types.

[0088] The stearic acid content is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the stearic acid content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0089] (Zinc Oxide) The rubber composition of this embodiment may further contain zinc oxide (zinc oxide). Preferably, the zinc oxide is obtained not only from zinc ingots but also from recycled zinc or zinc dross (i.e., obtained through recycling). Commercially available zinc oxide can be used, and examples of commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., etc. These commercially available zinc oxide products may be used individually or in combination of two or more types.

[0090] The zinc oxide content is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the zinc oxide content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or less, per 100 parts by mass of the rubber component. When the zinc oxide content is 3 parts by mass or less per 100 parts by mass of the rubber component, the various physical properties of the rubber composition are improved.

[0091] (Sulfur) The rubber composition of this embodiment preferably contains sulfur. The sulfur can be derived from fossil resources, recycled resources, or materials derived from biological resources, and from the viewpoint of reducing environmental impact, it is particularly preferable to use sulfur obtained from waste derived from biological resources. An example of a method for obtaining sulfur from waste derived from biological resources is the method described in the aforementioned International Publication No. 2024 / 048141. In addition, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used as crosslinking agents in the rubber industry. Commercial products can be used as the sulfur, and examples of commercially available sulfur include products from Tsurumi Chemical Industries, Ltd., Hosoi Chemical Industries, Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Ltd., Flexis Co., Ltd., etc. These sulfurs may be used individually or in combination of two or more.

[0092] The sulfur content is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 0.8 parts by mass or more, and preferably 8 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0093] (Vulcanization Accelerator) The rubber composition of this embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator can be derived from fossil resources, recycled resources, or biological resources, but from the viewpoint of reducing environmental impact, it is preferable that it be derived from biological resources. A vulcanization accelerator derived from biological resources can be obtained, for example, by the method disclosed in Japanese Patent Application Publication No. 2005-139239. The vulcanization accelerator may be a sulfenamide-based vulcanization accelerator such as N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide; or 1,3-diphenylguanidine (DPG), 1,3-di Examples of vulcanization accelerators include guanidine-based vulcanization accelerators such as -o-tollguanidine and o-tollbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, and examples of commercially available vulcanization accelerators include those from Ouchi Shinko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., and others. These vulcanization accelerators may be used individually or in combination of two or more.

[0094] The content of the vulcanization accelerator is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and also preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, per 100 parts by mass of the rubber component.

[0095] (Other) In addition to the components described above, the rubber composition of this embodiment may further contain various additives commonly used in the tire industry, such as fillers like calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; organic peroxides; etc. The content of these additives is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, a range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component is preferred.

[0096] (Method for manufacturing the rubber composition) The method for manufacturing the rubber composition of this embodiment is not particularly limited, but for example, it can be manufactured by blending the rubber component with recycled carbon black and various components selected as needed, and then kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized by vulcanization.

[0097] There are no particular restrictions on the mixing conditions, and various conditions such as the input volume of the mixing device, the rotation speed of the rotor, the ram pressure, as well as the mixing temperature, mixing time, and the type of mixing device can be appropriately selected according to the purpose. Examples of mixing devices include Banbury mixers, intermixes, kneaders, and rolls, which are commonly used for mixing rubber compositions.

[0098] There are no particular restrictions on the heat treatment conditions, and various conditions such as heat treatment temperature, heat treatment time, and heat treatment equipment can be appropriately selected according to the purpose. Examples of such heat treatment equipment include heat treatment roll machines commonly used for heat treatment of rubber compositions.

[0099] There are no particular restrictions on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature can be appropriately selected according to the purpose. Examples of extrusion equipment include extruders typically used for extruding rubber compositions. The extrusion temperature can be determined as appropriate.

[0100] There are no particular restrictions on the apparatus, method, and conditions for performing the vulcanization, and they can be appropriately selected according to the purpose. Examples of vulcanization apparatus include molding vulcanizers that use molds for vulcanizing rubber compositions. As for the vulcanization conditions, the temperature is, for example, around 100 to 190°C.

[0101] (Applications) The rubber composition of this embodiment can be applied to various components of rubber products such as tires, rubber tracks, and hoses. In addition to tires, rubber tracks, and hoses, the rubber composition of this embodiment can also be applied to seismic isolation rubber and the like.

[0102] While tires require sufficient durability, particularly performance after degradation, the rubber composition of this embodiment maintains durability, especially performance after degradation, as described above. Therefore, the rubber composition of this embodiment is useful for tires. For example, the rubber composition of this embodiment can be used in tire treads (cap tread, base tread, under tread), cushioning rubber, shoulders, sidewalls, clinch, bead filler, carcass coating rubber, belt reinforcement layer coating rubber, belt layer coating rubber, insulation, chafer, inner liner, etc., and can also be used in the side reinforcement layer of run-flat tires, etc.

[0103] Furthermore, while rubber tracks and hoses require sufficient durability, particularly performance after degradation, the rubber composition of this embodiment maintains durability, especially performance after degradation, as described above. Therefore, the rubber composition of this embodiment is useful for both rubber tracks and hoses. The rubber composition of this embodiment can also be used, for example, in the guide rubber and inner layer rubber of rubber tracks, the inner rubber layer, intermediate rubber layer, and outer rubber layer of hoses.

[0104] <Tire> The tire of this embodiment is characterized by comprising a rubber member made of the above-described rubber composition. Because the tire of this embodiment comprises a rubber member made of the above-described rubber composition, the proportion of sustainable materials is improved while maintaining durability. In the tire of this embodiment, the rubber member may include the tread (cap tread, base tread, under tread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, belt reinforcement layer coating rubber, belt layer coating rubber, insulation, chafer, inner liner, etc., as well as the side reinforcement layer of a run-flat tire.

[0105] The tire of this embodiment can be manufactured by conventional methods using the rubber composition described above. For example, depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process and then performing full vulcanization. The tire of this embodiment is preferably a pneumatic tire, and as the gas used to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

[0106] <Rubber Crawler> The rubber crawler of this embodiment is characterized by comprising a rubber member made of the above-described rubber composition. Because the rubber crawler of this embodiment comprises a rubber member made of the above-described rubber composition, the proportion of sustainable materials is improved while maintaining durability. Examples of rubber members in the rubber crawler of this embodiment include guide rubber and inner layer rubber.

[0107] In one embodiment, the rubber crawler comprises an inner layer rubber forming the inner circumferential surface of the rubber crawler, and guide rubber provided at a predetermined pitch in the circumferential direction at the center of the inner layer rubber in the width direction. In one embodiment, the above-described rubber composition can be used for at least one of the guide rubber and the inner layer rubber.

[0108] <Hose> The hose of this embodiment is characterized by comprising a rubber member made of the above-described rubber composition. Because the hose of this embodiment comprises a rubber member made of the above-described rubber composition, the proportion of sustainable materials is improved while maintaining durability. In the hose of this embodiment, examples of rubber members include an inner rubber layer, an intermediate rubber layer, an outer rubber layer, etc.

[0109] In one embodiment, the hose comprises an inner rubber layer (inner tube rubber) located radially inward, an outer rubber layer located radially outward, and, if necessary, a reinforcing layer located between the inner rubber layer and the outer rubber layer. In one embodiment, the above-described rubber composition can be used in at least one of the inner rubber layer and the outer rubber layer. The above-described rubber composition can also be used in a hose consisting of a single rubber layer.

[0110] 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.

[0111] <Evaluation of Carbon Black> The physical properties of carbon black were evaluated using the following method.

[0112] (1) Grind gauge measurement: 3.75 g of zinc oxide, 0.20 g of the carbon black under test, and 2.00 mL of epoxidized soybean oil were mixed to obtain a mixture. 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 1.

[0113] (2) Nitrogen adsorption specific surface area (N２ SA) In accordance with ASTM D6556, the specific surface area (N) of nitrogen adsorption of the tested carbon black. ２ SA was measured.

[0114] (3) Elemental analysis: The content of zinc (Zn), copper (Cu), and iron (Fe) was confirmed by X-ray fluorescence analysis (XRF).

[0115] (4) Ash content The ash content of the carbon black sample was measured according to ASTM D8474 and D1506.

[0116]

[0117] <Preparation and Evaluation of Rubber Compositions> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 2. Other chemicals included antioxidants, oils, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in the comparative examples and examples. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were also the amounts commonly used in the preparation of rubber compositions. The durability of the obtained rubber compositions was evaluated by the high-temperature tensile strength after degradation using the following method.

[0118] (5) 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.

[0119] (6) 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.

[0120]

[0121] *1 Natural rubber: RSS#3 *2 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *3 New carbon black: Manufactured by Asahi Carbon, N550 *4 Recycled carbon black 1: Same as Table 1 *5 Recycled carbon black 2: Same as Table 1

[0122] Tables 1 and 2 clearly show that even for rubber compositions containing recycled carbon black with 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 in the blended carbon black. In other words, the rubber compositions of the examples according to the present invention are able to maintain their performance, especially after degradation, while increasing the proportion of sustainable materials.

[0123] The rubber composition of the present invention can be used in rubber products such as tires, rubber tracks, and hoses.

[0124] 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 at the location where the line caused by the third largest particle appeared

Claims

1. A rubber composition containing recycled carbon black, wherein 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 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 according to claim 1, wherein the paste for measurement using a grind gauge of recycled carbon black 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 according to claim 1, wherein the recycled carbon black comprises at least one of the elements Zn, Cu, and Fe.

5. The recycled carbon black has a nitrogen adsorption specific surface area (N ２ SA) 40-100m ２ The rubber composition according to claim 1, wherein the weight is / g.

6. The rubber composition according to claim 1, wherein the recycled carbon black has an oil absorption capacity (OAN) of 70 to 120 mL / 100 g.

7. The rubber composition according to claim 1, for use in tires.

8. The rubber composition according to claim 1, which is for use with rubber tracks.

9. The rubber composition according to claim 1, which is for use in hoses.

10. A tire characterized by comprising a rubber member made of the rubber composition described in any one of claims 1 to 7.

11. A rubber crawler characterized by comprising a rubber member made of the rubber composition described in any one of claims 1 to 6 and 8.

12. A hose comprising a rubber member made of the rubber composition described in any one of claims 1 to 6 and 9.

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