Rubber composition and tire

Abstract

To provide a rubber composition capable of increasing the ratio of sustainable materials in rubber products while suppressing shrinkage, and a tire having an increased sustainable material ratio while maintaining dimensional accuracy.SOLUTION: The present invention provides a rubber composition that comprises a rubber component (A) comprising modified natural rubber (A1) having a total nitrogen content of 0.1-0.3 mass%, and reclaimed carbon black (B), as well as a tire comprising a rubber member composed of the rubber composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a tire. [Background technology]

[0002] Conventionally, various rubber compositions have been used in rubber products such as tires, various hoses, rubber crawlers, seismic isolation rubber, etc. In order to ensure the strength of these rubber products, the rubber compositions that are the raw materials thereof usually contain carbon black as a reinforcing filler.

[0003] On the other hand, in recent years, from the viewpoint of social sustainability, it has been required to use so-called sustainable materials such as materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) in rubber products, and it has also been required to increase the ratio of sustainable materials in rubber compositions applied to said rubber products. For example, recycled carbon black is known as a material derived from recycled resources (recycled resources). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Application Publication No. 3427975 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when recycled carbon black is used as a reinforcing filler instead of virgin carbon black in order to increase the proportion of sustainable materials in rubber products, there is a problem that the shrinkage of the rubber composition increases and the dimensional accuracy of the rubber product deteriorates.

[0006] Therefore, an object of the present invention is to provide a rubber composition that can solve the above-mentioned problems of the conventional technology and increase the proportion of sustainable materials in rubber products while suppressing shrinkage. Another object of the present invention is to provide a tire that improves the proportion of sustainable materials while maintaining dimensional accuracy. [Means for solving the problem]

[0007] The rubber composition and tire of the present invention that solve the above problems are outlined below.

[0008] [1] A rubber component (A) containing a modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3 mass%, A rubber composition comprising: (B) recycled carbon black. The rubber composition of the present invention described in [1] above can increase the proportion of sustainable materials in rubber products while suppressing shrinkage.

[0009] [2] The rubber composition according to [1], wherein the modified natural rubber (A1) has been subjected to at least one deproteinization treatment selected from the group consisting of centrifugation, enzyme treatment, and urea treatment. The rubber composition described in [2] above has excellent workability and abrasion resistance.

[0010] [3] The rubber composition according to [1] or [2], wherein the modified natural rubber (A1) has a phosphorus content of more than 200 ppm by mass. The rubber composition described in [3] above has good abrasion resistance.

[0011] [4] The rubber composition according to any one of [1] to [3], wherein the recycled carbon black (B) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. In the rubber composition described in [4] above, the recycled carbon black (B) is easily available.

[0012] [5] The rubber composition according to any one of [1] to [4], wherein the recycled carbon black (B) has an ash content of 20 mass % or less. The rubber composition described in the above item [5] can improve various physical properties of a rubber product to which the rubber composition is applied.

[0013] [6] A tire comprising a rubber member made of the rubber composition according to any one of [1] to [5]. The tire of the present invention described in [6] above has an improved proportion of sustainable materials while maintaining dimensional accuracy. Effect of the Invention

[0014] According to the present invention, it is possible to provide a rubber composition that can increase the proportion of sustainable materials in rubber products while suppressing shrinkage. Furthermore, according to the present invention, it is possible to provide a tire that maintains dimensional accuracy while improving the proportion of sustainable materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The rubber composition and tire of the present invention will be described in detail below with reference to examples based on embodiments thereof.

[0016] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0017] In this specification, the "proportion of sustainable materials" refers to the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the target rubber composition and tire.

[0018] In this specification, the biological resources (biomass resources) refer to carbon-neutral organic resources derived from living 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 or animals, and are resources other than fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible from the viewpoint of not competing with food and of effective resource utilization.

[0019] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock waste, 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 ... Examples of the biological resources include crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue after squeezing juice from sugarcane), soybeans, soybean pulp, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, algae, etc. The biological resources may be processed (i.e., biological resource-derived substances). Examples of the processing methods include biological processing methods that utilize the functions of microorganisms, plants, animals, and tissue cultures thereof; chemical processing methods that utilize acids, alkalis, catalysts, thermal energy, light energy, etc.; physical processing methods such as micronization, compression, microwave processing, and electromagnetic wave processing; and the like. The biological resources may also be extracted and refined from the biological resources or biological resources that have been processed (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the biological resources can be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, and among these, valine, leucine, isoleucine, arginine, and phenylalanine are preferred.The amino acid may be either an L-amino acid or a D-amino acid, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. The fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. The fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may be contaminated with various materials and impurities.

[0020] In this specification, the term "recycled resources" refers to resources obtained by regenerating (recycling) products that have been used once, or that have been collected without being used, or that have been discarded. For example, recycled resources include resources obtained by regenerating (recycling) used rubber products such as used tires.

[0021] <Rubber composition> The rubber composition of the present embodiment is characterized by containing a rubber component (A) including a modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3 mass %, and recycled carbon black (B).

[0022] In the rubber composition of the present embodiment, the recycled carbon black (B) is a material derived from a renewable resource (recycled resource). Therefore, by blending the recycled carbon black (B) into the rubber composition, the ratio of sustainable materials in the rubber product to which the rubber composition is applied can be increased. However, as mentioned above, when recycled carbon black is compounded in place of normal virgin carbon black, there is a problem that the shrinkage of the rubber composition increases and the dimensional accuracy of the rubber product deteriorates. To address this issue, the rubber composition of the present embodiment contains a modified natural rubber (A1) with a total nitrogen content of 0.1 to 0.3% by mass as the rubber component (A). In general, when a rubber component with a high degree of polymer chain entanglement is compounded in a rubber composition, the rubber composition tends to shrink more. In contrast, the modified natural rubber (A1) has a total nitrogen content of 0.1 to 0.3% by mass and the polymer chain branches are released, so that the polymer chains are less entangled. By compounding the modified natural rubber (A1) in the rubber composition, the shrinkage of the rubber composition can be suppressed. In addition, since the modified natural rubber (A1) is a material derived from biological resources (biomass resources), by blending the modified natural rubber (A1) into a rubber composition, the ratio of sustainable materials in rubber products to which the rubber composition is applied can be further increased. Therefore, according to the rubber composition of this embodiment, it is possible to increase the proportion of sustainable materials in rubber products while suppressing shrinkage.

[0023] (Rubber component (A)) The rubber composition of the present embodiment includes a rubber component (A) containing a modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3 mass%, and the rubber component (A) provides rubber elasticity to the composition. The rubber component (A) preferably has a sustainability rate of 30 mass% or more, more preferably 40 mass% or more, more preferably 50 mass% or more, more preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, even more preferably 90 mass% or more, and particularly preferably 100 mass%. Here, the "sustainability rate" of the rubber component (A) refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component (A).

[0024] As the rubber component (A), the rubber derived from biological resources and the rubber derived from recycled resources are preferred. Here, the proportion of the monomer components derived from biological resources in 100 mol% of the monomer components 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, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. The proportion of monomer components derived from recycled resources in 100 mol% of monomer components 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, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0025] The rubber component (A) is a component that contributes to crosslinking, and usually has a weight average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and preferably 5,000,000 or less, more preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,300,000 or less. In this specification, the weight average molecular weight (Mw) of the rubber component (A) can be determined, for example, by converting the weight average molecular weight (Mw) into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0026] The rubber component (A) of the rubber composition of this embodiment contains a modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3% by mass. The modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3% by mass has less entanglement of polymer chains, so that even if the rubber composition is compounded with recycled carbon black (B) described later, the rubber composition can be prevented from shrinking. In addition, since the modified natural rubber (A1) is a sustainable rubber derived from nature, compounding the modified natural rubber (A1) in the rubber composition can improve the ratio of sustainable materials in the rubber product to which the rubber composition is applied, and further reduce the environmental load. Furthermore, the modified natural rubber (A1) is also excellent in the effect of improving the workability of the rubber composition in kneading, extrusion, rolling, etc., compared to normal natural rubber.

[0027] The modified natural rubber (A1) has a total nitrogen content of 0.1% by mass or more, preferably 0.15% by mass or more, and 0.3% by mass or less, preferably 0.25% by mass or less. When the total nitrogen content of the modified natural rubber (A1) is within the range of 0.1 to 0.3% by mass, the modified natural rubber (A1) does not contain an excessive amount of protein, suppressing gelation, and promoting interactions between polymer chains in the modified natural rubber (A1), improving abrasion resistance and low heat build-up. In this specification, the total nitrogen content of the modified natural rubber (A1) is specifically measured using "TruSpec CHN" (manufactured by LECO Corporation). In this measurement, a calibration curve for determining the total nitrogen content is first prepared using EDTA as a standard substance, and then about 10 mg of the sample (modified natural rubber) is weighed and the average value is calculated from three measurement results to determine the total nitrogen content of the sample.

[0028] The modified natural rubber (A1) preferably has a phosphorus content of more than 200 ppm by mass, and more preferably not more than 900 ppm by mass, and more preferably not more than 700 ppm by mass. When the modified natural rubber (A1) has a phosphorus content of more than 200 ppm by mass, the interaction between polymer chains in the modified natural rubber (A1) is promoted to increase the molecular weight, thereby improving the abrasion resistance of the rubber composition. In this specification, the phosphorus content of the modified natural rubber (A1) is determined by decomposing a sample (modified natural rubber) in a wet ashing apparatus and then performing inductively coupled plasma optical emission spectrometry (ICP analysis). More specifically, the phosphorus content of the modified natural rubber (A1) is determined using an ICP optical emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).

[0029] The modified natural rubber (A1) is preferably subjected to at least one deproteinization treatment selected from the group consisting of centrifugation, enzyme treatment, and urea treatment. By using a modified natural rubber from which proteins have been removed as the rubber component (A), it is possible to greatly improve the workability during kneading, extrusion, rolling, etc., of a rubber composition containing the modified natural rubber, as well as the abrasion resistance.

[0030] The centrifugation is a process for deproteinizing natural rubber latex, which is the raw material of natural rubber, by centrifugation. The conditions for centrifugation (rotation speed, time, etc.) are not particularly limited, and the conditions can be appropriately changed depending on the protein content to be removed. After the centrifugation, washing and drying treatments can be carried out to obtain the modified natural rubber (A1).

[0031] The enzyme treatment is a treatment for selectively decomposing proteins in natural rubber latex, which is a raw material for natural rubber. The enzyme used in the enzyme treatment is not particularly limited as long as it is an enzyme that can decompose proteins, and examples thereof include proteases.

[0032] Proteases can be classified according to the location of degradation, for example, into exopeptidases (which cut off approximately 1 to 2 amino acid residues from the ends of protein / peptide chain sequences) and endopeptidases (which cut in the center of protein / peptide chain sequences). In terms of classification by substrate, examples include proteinases (which break down proteins) and (in the narrow sense) peptidases (which break down synthetic peptides with smaller molecular weights). Furthermore, from the perspective of classification based on catalytic mechanism, examples include serine proteases such as chymotrypsin and subtilisin; aspartic acid proteases (acid proteases) such as pepsin, cathepsin D, and HIV protease; metalloproteases such as thermolysin; cysteine ​​proteases such as papain and caspase; and N-terminal threonine proteases and glutamic acid proteases that have become known in the proteasome. Furthermore, from the viewpoint of the decomposition site, it is preferable to use an endopeptidase. In addition, a protease that is highly active at about pH 10.5 when ammonia is added, i.e., an alkaline protease, is preferable, and from the viewpoint of suppressing the coagulation of natural rubber latex, a protease that is highly active at an optimum temperature of 10 to 40°C, preferably at about room temperature (e.g., 20°C) is preferable. The protease may be one of the above-mentioned types, or may be a composition containing two or more of the above-mentioned types. Furthermore, the protease may be a main component containing an enzyme other than the protease, or a main component other than the protease may contain the protease as a side activity.

[0033] The urea treatment is a treatment in which proteins in natural rubber latex, the raw material of natural rubber, are denatured with a urea-based compound and then removed. Here, the urea-based compound refers to urea, urea derivatives, and urea complex salts.

[0034] Examples of the urea derivative include methylurea, ethylurea, n-propylurea, i-propylurea, n-butylurea, i-butylurea, and n-pentylurea, and preferred urea derivatives include methylurea and ethylurea. The urea complex salt can be prepared by, for example, HNO 3 CO(NH 2 ) 2 , H 3 PO 4CO(NH 2 ) 2 , H 2 C 2 O 4 2CO(NH 2 ) 2 , Ca(NO 3 ) 2 4CO(NH 2 ) 2 , CaSO 4 4CO(NH 2 ) 2 , Mg(NO 3 ) 2 CO(NH 2 ) 2 2H 2 O, CaSO 4 (5~6)CO(NH 2 ) 2 2H 2 Examples include O.

[0035] The natural rubber latex that has been subjected to the urea treatment is then subjected to separation and removal of natural rubber and proteins by means of mechanical separation, coagulation of the rubber component, ultrafiltration, etc. The natural rubber latex that has been subjected to the protein modification treatment is refined by such removal treatment to become modified natural rubber (highly purified natural rubber).

[0036] The natural rubber latex used in the centrifugation, enzyme treatment, or urea treatment is not particularly limited. For example, field latex collected from rubber trees or concentrated natural rubber latex obtained by treating the field latex may be used. The dry rubber content in the natural rubber latex is also not particularly limited, and from the viewpoint of obtaining better abrasion resistance, it is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more.

[0037] The proportion of the modified natural rubber (A1) in the rubber component (A) may be 100% by mass, but may contain other rubber components within a range that does not impair the object of the present invention. Furthermore, the natural rubber (NR) may be a mixture of not only the modified natural rubber (A1) but also normal natural rubber. From the viewpoint of further improving abrasion resistance, the proportion of the modified natural rubber (A1) in the rubber component (A) is preferably 10% by mass or more, more preferably 20 to 90% by mass, and particularly preferably 40 to 70% by mass.

[0038] The rubber component (A) of the rubber composition of the present embodiment contains at least a modified natural rubber (A1) and may consist solely of the modified natural rubber (A1), or may contain a rubber component (A2) other than the modified natural rubber.

[0039] The rubber component (A2) other than the modified natural rubber is preferably a diene rubber, and the diene rubber is preferably an isoprene rubber other than the modified natural rubber and a butadiene rubber. Here, the isoprene rubber refers to a rubber containing a unit derived from isoprene as a monomer unit, and the butadiene rubber refers to a rubber containing a unit derived from butadiene as a monomer unit.

[0040] The proportion of the rubber component (A2) other than the modified natural rubber in the rubber component (A) is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and may be 0% by mass (i.e., the rubber component (A) may consist only of the modified natural rubber (A1). When the proportion of the rubber component (A2) other than the modified natural rubber in the rubber component (A) is 90% by mass or less, shrinkage of the rubber composition can be more reliably suppressed.

[0041] Examples of isoprene-based rubbers other than the modified natural rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Natural rubber (NR) may be, for example, RSS#3, TSR20 (for example, SIR20 or STR20), or other rubbers commonly used in the tire industry. The origin of natural rubber (NR) is not particularly limited, and examples include rubbers derived from Hevea brasiliensis, guayule, and Russian dandelion. Synthetic isoprene rubber (IR) is not particularly limited, and examples include rubbers commonly used in the tire industry such as IR2200. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0042] The isoprene-based rubber other than the modified natural rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to set the sustainability ratio of the isoprene-based rubber other than the modified natural rubber within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from renewable resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.).

[0043] Examples of the butadiene rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene rubber, is preferably derived from biological resources or recycled resources.

[0044] 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 products can be used as the butadiene rubber (BR), and examples of commercially available butadiene rubbers include products from UBE Elastomers Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Co., Ltd., and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0045] 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)), solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)), and the like. In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, divinylnaphthalene, and the like. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, the aromatic vinyl compound-butadiene copolymer rubber is preferably SBR. The styrene may have a substituent. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of the commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Nippon Zeon Corporation, Sumitomo Chemical Co., Ltd., and the like. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0046] The butadiene-based rubber has a sustainability rate of preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to make the sustainability rate of the butadiene-based rubber fall within the above range, for example, a polymer synthesized using butadiene derived from biological resources, butadiene derived from renewable resources, aromatic vinyl compounds derived from biological resources (e.g., styrene derived from biological resources), and aromatic vinyl compounds derived from renewable resources (e.g., styrene derived from renewable resources) as monomer components may be used. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.). In addition, the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (e.g., styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene, etc. according to a conventional method, but also rubber obtained by reactions or enzyme reactions caused by microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.").

[0047] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to increase the proportion of modified natural rubber (A1) in rubber component (A), use natural rubber (NR) in addition to modified natural rubber (A1) as rubber component (A), or use a polymer synthesized using monomer components derived from biological resources or monomer components derived from renewable resources as monomer components.

[0048] Generally, materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment for their production, and are therefore usually produced in large factories in specific regions, and a lot of energy is required for the storage and transportation of raw materials and products. In contrast, materials derived from biological resources (biomass resources) are derived from agricultural products, forests, etc. in each region, and can be produced on a small scale by fermentation of microorganisms and catalytic reactions, so by utilizing products and waste from each region, the energy required for the transportation and storage of raw materials can be reduced, and further the energy required for the transportation and storage of the produced materials to tire factories can also be reduced, making them environmentally friendly. In addition, materials derived from regenerated resources (recycled resources) can be obtained, for example, by dismantling, downsizing, and pyrolyzing used tires to extract materials that constitute tires, such as rubber, fillers, and steel cords.

[0049] As a means of obtaining materials derived from recycled resources, a process of "dismantling and downsizing" may be performed on collected rubber products such as tires, or a process of "dismantling and downsizing" may be further performed on rubber products such as tires manufactured using the rubber composition of the present embodiment. Dismantling and downsizing is a series of processes in which rubber products such as tires are crushed and separated into individual materials. Dismantling and downsizing may further include the processes of "separation," "cutting," "chipping," "crushing," and "pulverization" in this order. Separation is a process in which a rubber product is separated into individual materials (rubber and metal, etc.). Cutting is a process in which a rubber product is cut into pieces into individual parts (tread and sidewall, etc.). Chipping is a process in which a rubber product is scraped or perforated. Crushing is a process in which a rubber product is crushed into chips of several inches in size. Crushing is a process in which a rubber product is crushed into granules.

[0050] The separation methods include pulling out, induction heating, punch cutting, magnetic separation, cutting separation, mechanical separation, cooling, and water jet. Pulling out is a method of hooking a bead using a hook or the like and pulling it out of the tire. Induction heating is a method of reducing the adhesive force between the metal of the bead and the rubber by induction heating, and separating the metal and the rubber. Punch cutting is a method of removing the bead from the tire by making a series of overlapping punch cuts (holes) in the sidewall of the tire around the bead. Magnetic separation is a method of separating the metal of the bead from the rubber using magnetic force. Cutting separation is a method of cutting and separating the metal of the bead and the rubber using a blade, cutter blade, knife, or rotary milling machine. Mechanical separation is a method of separating the metal and the rubber by applying a mechanical force sufficient for separation. Cooling is a method of cooling using liquid nitrogen or the like to embrittle the rubber before separating it. Water jet is a method of separating the rubber and the metal by spraying water at high pressure.

[0051] The cutting methods include rotary blades, blade cutters, L-knives, water jets, and pneumatic cutting. Rotary blades are a method of cutting by applying a rotating blade (including blades, circular saws, etc.) to the object. Blade cutters are a method of cutting using a blade or cutter blade. L-knives are a method of cutting using an L-shaped knife. Water jets are a method of cutting by spraying water (including water containing sand) at high pressure. Pneumatic cutting is a method of cutting using compressed air.

[0052] The chipping method includes punch cutting and filing. Punch cutting is a method of making holes using a punch blade. File filing is a method of scraping the tire using a file.

[0053] The crushing method includes a rotating blade, a blade cutter, and a cutting wheel. The rotating blade is a method of crushing an object by applying a rotating blade (including a blade, a circular saw, etc.) to the object. The blade cutter is a method of crushing an object by using a blade or a cutter blade. The cutting wheel is a method of crushing an object by placing a cutting blade on a wheel-shaped crushing part and applying it to the object.

[0054] The crushing techniques include roller mills, pin mills, and water jets. Roller mills crush materials by a "grinding and grinding action" that combines the compressive force caused by the centrifugal force of the rollers and the shearing force caused by the rotation of the rollers. Pin mills crush materials by attaching dozens of pins to the surfaces of two opposing disks and rotating them at high speed. Water jets crush materials by spraying water at high speed and colliding it with the target material.

[0055] Furthermore, the following separation methods may be selected for the separation according to the object to be separated. When the object to be separated is metal, magnetic separation, "pulling, peeling, tearing", melting, crushing, punching, high-pressure jet, cutting / machining, sedimentation, and centrifugal classification may be selected. Magnetic separation is a method of separating metal and rubber using magnetic force. Pulling, peeling, and tearing are methods of separating metal such as bead wires from rubber by pulling them out, peeling them off, and tearing them off. Melting includes vibration melting, heated steam, and induction heating. Vibration melting is a method of separating metal parts while vibrating the tire with ultrasonic waves or the like and melting them. Heated steam is a method of melting the rubber by blowing heated steam and separating the metal cord. Induction heating is a method of heating the tire by electromagnetic induction and separating the metal cord. Crushing is a method of separating the metal cord from the rubber by crushing the tire with a roller or the like. Punching is a separation technique that removes metal cords from tires by making a series of overlapping punching cuts in a circumferential pattern on the tire sidewall around the bead. High-pressure jetting is a technique that separates metal and rubber by spraying water or other materials at high pressure. Cutting and milling is a technique that separates metal and rubber parts by mechanical cutting and milling. Sedimentation is a technique that separates rubber and wires that settle to the bottom by placing them in a water-soluble polyol for several to several tens of hours at temperatures exceeding 160°C. Centrifugal classification is a type of air classification that separates metal and rubber using centrifugal force.

[0056] When the material to be separated is fiber, the following methods may be selected: sieving, vibrating screen, melting, air classification, centrifugal classification, gravity classification, friction, "pulling, peeling, tearing", high pressure jet, electrostatic separation, mechanical heat control, and cutting / cutting. Sieving is a method of separating fiber and rubber using a sieve. Vibrating screen is a separation method in which sieving is performed by vibrating a sieve up and down. Melting includes heated steam and induction heating. Heated steam is a method of melting rubber by blowing heated steam and separating metal cords. Induction heating is a method of heating tires by electromagnetic induction and separating metal cords. Air classification is a method of separating fiber and rubber powder by utilizing the difference in the hydrodynamic behavior of particles (centrifugal force, gravity, inertia force, etc.). Centrifugal classification is a type of air classification, and is a method of separating fiber and rubber powder using centrifugal force. Gravity classification is a type of wind classification, and is a method that uses gravity to separate the fiber and rubber. Friction is a method of applying pressure to the tire to generate friction, forming aggregates from the fiber, and separating the aggregates and rubber granules using a sieve or other method. Pulling, peeling, and tearing are methods of pulling, peeling, and tearing the fiber reinforcement parts from the rubber. High-pressure jetting is a method of spraying water or other water at high pressure to separate the fiber and rubber. Electrostatic separation is a method of charging particles using electrostatic forces, and separating the fiber and rubber due to the difference in the charge or electric field strength. Mechanical heat control is a method of separating rubber from fiber reinforcement elements under controlled thermal conditions. Cutting and cutting is a method of separating the fiber and rubber parts by mechanical cutting and cutting.

[0057] When the object to be separated is a sealant, mechanical lubrication after solidification or the use of a processing aid may be selected. Mechanical lubrication after solidification is a separation technique in which the sealant layer is removed by mechanical lubrication after solidification using liquid nitrogen or the like. The use of a processing aid is a separation technique in which the sealant layer is removed using water or a soap solution.

[0058] When the object to be separated is resin, crushing, cutting, melting, or peeling may be selected. Crushing is a method of separating the resin from the rubber by crushing the tire with a roller or the like. Cutting is a method of cutting along the boundary surface between the rubber layer and the resin to separate the resin. Melting includes vibration melting. Vibration melting is a method of vibrating the tire with ultrasound or the like to separate the resin while melting it. Peeling is a separation method in which unfoamed rubber is foamed by heating, and a peeling force is applied between the rubber and the resin component to peel the resin component from the rubber.

[0059] In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization process in which biological resources or processed products of biological resources are desulfurized and sulfur-containing substances are removed from the biological resources or processed products of biological resources, a recovery process in which sulfur is recovered from the desulfurization residue generated in the desulfurization process, and a processing process in which the recovered sulfur is processed into sulfur for vulcanization (for example, the method described in Patent Application No. 2022-140390), and raw materials for rubber compositions for tires can be obtained from various waste materials and used items.

[0060] In this way, by using sustainable materials (materials derived from biological resources or renewable resources), it is possible to reduce the overall environmental impact of tire manufacturing, such as reducing carbon dioxide emissions over the entire life cycle (LCCO2), reducing energy consumption over the entire life cycle (LCE), reducing costs incurred over the entire life cycle (LCC), and reducing the use of fossil resources.

[0061] In addition, when producing the rubber composition, the ratio of the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be appropriately selected according to the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food), and the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be polymerized to obtain rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) having performance equivalent to that of conventional synthetic rubber. When using monomer components derived from renewable resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomer. In that case, the impact on the environment can be evaluated by adopting the concept of mass balance.

[0062] The ratio of each monomer unit (e.g., unit derived from isoprene, unit derived from butadiene, unit derived from aromatic vinyl compound) in the entire rubber component (A) can be adjusted appropriately depending on the component to which it is applied. The ratio of each monomer unit in the entire rubber component (A) can be adjusted, for example, by appropriately combining the above-mentioned modified natural rubber (A1), isoprene-based rubber other than the modified natural rubber, and butadiene-based rubber. In addition, the ratio of cis-bond units in the butadiene-derived units can also be adjusted appropriately depending on the component to which it is applied. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "unit derived from isoprene" refers to a structural unit in a polymer constituted based on the monomer isoprene (including the isoprene unit in natural rubber), the term "unit derived from butadiene" refers to a structural unit in a polymer constituted based on the monomer butadiene, and the term "unit derived from an aromatic vinyl compound" refers to a structural unit in a polymer constituted based on the monomer aromatic vinyl compound. In this specification, the ratio of each monomer unit is measured by NMR.

[0063] The rubber component (A) may contain diene rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc., in addition to the above-mentioned modified natural rubber (A1), isoprene-based rubbers other than modified natural rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR). These rubber components may be used alone or in combination of two or more.

[0064] The rubber component (A) may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, and thiocarbonyl groups, and these functional groups may have a substituent. These functional groups may be introduced into the rubber component alone or in combination of two or more. Among these, an amino group, an alkoxy group, and an alkoxysilyl group are preferred, and a substituted amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxysilyl group having 1 to 6 carbon atoms are more preferred.

[0065] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component (A). The functional group is a modified functional group having an interactive property with a filler such as silica or carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds, and examples of compounds (modifiers) having a silicon-containing functional group include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having an oxygen-containing functional group include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds include those described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0066] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) can be produced in the same manner as conventional synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from renewable resources, and, if necessary, monomer components derived from fossil resources. The rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions with microorganisms or enzyme reactions.

[0067] Regarding the method for preparing rubber derived from biological resources from the above-mentioned biological resources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from biological resources as a monomer component, it is possible to obtain butadiene rubber (B-BR) derived from biological resources (biomass resources), and by using styrene obtained from biological resources and butadiene obtained from biological resources as monomer components, it is possible to obtain styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources). Here, methods for obtaining B-BR and B-SBR from biological resources include, in addition to artificial polymerization methods, methods of polymerization in vivo, and methods of polymerization with biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods according to the target tire performance.

[0068] As the butadiene obtained from the 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 tiglic acid) can be suitably used. Two or more of these butadienes may be used in combination. As the styrene obtained from the biological resources, styrene obtained from a plant (preferably a plant belonging to the family Hamamelidaceae, Styraxaceae, or Apocynaceae, more preferably a plant belonging to the genera Liquidamus, Styrax, or Catharanthus, and even more preferably Sweetgum, Styrax rosa, or Catharanthus roseus) or a microorganism (preferably a microorganism belonging to the genera Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may be used in combination.

[0069] Recently, biomass combinat mainly using bioethanol, bioethylene, etc. are planned, but bioethanol and bioethylene are mainly produced using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of monomer components derived from biological resources as the monomer components derived from the biological resources, or to use monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources in combination, and further to appropriately adjust the ratio of these monomer components. This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and to stably supply rubber derived from sustainable materials, and further to consider the environment depending on the situation at the time of production. In addition, when using multiple types of monomer components derived from biological resources, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadiene derived from multiple types of biological resources with different origins as the butadiene derived from biological resources, and / or to use a mixture of styrene derived from multiple types of biological resources with different origins as the styrene derived from biological resources. This allows multiple types of biological resources to be effectively utilized.

[0070] (Recycled Carbon Black (B)) The rubber composition of the present embodiment contains recycled carbon black (B). The recycled carbon black (B) is a material derived from a renewable resource (recycled resource), and therefore, by blending the recycled carbon black (B) in the rubber composition, the ratio of sustainable materials in the rubber product to which the rubber composition is applied can be increased.

[0071] In this specification, "recycled carbon black" refers to carbon black obtained by recovering raw materials that are waste materials provided for recycling. Examples of the waste materials include waste rubber, used tires, waste oil, and the like. Waste rubber refers to all discarded rubber, including unnecessary scraps generated from the production or repair of rubber products, and is not limited to that generated from rubber products. Examples of the scraps include buffing powder, peeled rubber, and the like. Buffing powder is fine rubber generated in a buffing process for scraping the tread portion remaining on the base tire, for example, in tire retreading. Peeling rubber is a long piece of rubber, for example, 1 to 2 cm wide, peeled off from the surface of a rubber product such as a tire. Peeling rubber is generated by scraping the surface of a rubber product such as a tire using a knife with a U-shaped or V-shaped tip like a peeler. In addition, waste rubber is not limited to crosslinked rubber, but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, and rubber parts or components in the manufacturing stage of the final products. The used tires may be tires to be retreaded, or may be tires discarded for some reason, such as waste tires generated from tire replacement, scrapping, etc., and ELT (End-of-Life Tire) that has reached the end of its life as a tire. Waste oil is not limited to oil generated when decomposing plastics and rubber, but may include, for example, used oil discharged from industry, such as animal and vegetable oils, lubricating oil, insulating oil, cutting oil, etc. Among them, the waste oil is preferably one that does not have any composition other than organic matter, such as one derived from silicone rubber or polyvinyl chloride. In addition, the waste oil is preferably one that is mixed with carbon black or rubber containing carbon black. "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 does not only include carbon black that has been actually used and then discarded, but also carbon black that has been manufactured but not actually used and then discarded.

[0072] The recycled carbon black (B) is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. The recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is easily available because there are a large number of vulcanized rubber products containing carbon black and it is easily obtained by pyrolysis. Furthermore, the recycled carbon black (B) is preferably obtained from a solid residue generated by pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and the recycled carbon black can be recovered from either of them. When recovering carbon black from volatile components, it is possible to recover an oil fraction with a specific gravity suitable for producing carbon black and use it to produce carbon black by an existing carbon black production method (for example, JP 2015-520259 A). In this case, unlike carbon black recovered from solid residues, there are advantages such as no impurities and no mixing of different grades. In addition, in the production of carbon black with low environmental impact, there are various options such as using vegetable oil, oil derived from waste plastic, etc., in addition to the oil obtained by recovering the volatile components obtained by the above-mentioned rubber pyrolysis. However, edible resources such as vegetable oil have needs for other uses such as food, so there are issues with securing sufficient amounts, and it is necessary to consider the impact on the environment due to the expansion of cultivated land. In addition, oil derived from waste plastics, etc. is also used for other purposes such as horizontal recycling of plastics, so there are also issues on the supply side. On the other hand, when using volatile components (oil) generated by thermal decomposition of vulcanized rubber products, especially tires, it is possible to continue using existing materials because of the system of continuing to use existing materials within the tire industry, and it is possible to reduce the consumption of new materials in new tire production and contribute to reducing the environmental burden of the industry. The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0073] The solid residue obtained by pyrolysis of wastes such as used rubber and used tires contains ash in addition to carbon black. The ash is derived from non-volatile components contained in rubber and tires. Therefore, the recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, in consideration of the various physical properties required for tires manufactured using the recycled carbon black, the higher the carbon content in the recycled carbon black, the better. In the recycled carbon black (B), the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, more preferably 87% by mass or more, and even more preferably 89% by mass or more. The carbon content in the recycled carbon black (B) is preferably 97% by mass or less. The carbon content is a value that does not include adsorbed moisture.

[0074] Specific examples of ash include 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 pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black (B) is allowed to contain ash. The lower limit of the ash content of the recycled carbon black (B) may be 0.5 mass %. On the other hand, in consideration of the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black (B) is preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 5.0 mass % or less. When the ash content of the recycled carbon black (B) is 20 mass % or less, the various physical properties of the rubber product to which the rubber composition is applied can be improved. In this specification, the ash content of carbon black is calculated from the mass of unburned components (ash content) obtained by burning carbon black at 550° C.±25° C. to convert it to incineration.

[0075] The recycled carbon black (B) can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, referring to "Rubber Chemistry and Technology", Vol. 85, No. 3, pp. 408-449 (2012), in particular pp. 438, 440, and 442, describes that the recycled carbon black (B) can be obtained by pyrolysis of organic materials at 550-800°C with the exclusion of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

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

[0076] The regenerated carbon black (B) may lack a functional group on its surface, or may be treated to include a functional group on its surface. The treatment to include a functional group on the surface of the regenerated carbon black can be carried out by a conventional method. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black having hydroxyl and / or carboxyl groups on its surface. In Japanese Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The regenerated carbon black according to this embodiment also includes carbon black that has been treated to include a functional group on its surface.

[0077] Moreover, examples of the thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0078] The crosslinked rubber products used for the decomposition may be grouped according to the type of rubber component previously blended, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped according to the type of filler previously blended (e.g., the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped according to the type of rubber component and the type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties is obtained, and therefore, when the recycled carbon black is blended again with the rubber component, a rubber composition with better performance is obtained.

[0079] In addition, when the crosslinked rubber product used for the decomposition is derived from a tire, the tire may be grouped in advance by type (for example, for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and then the decomposition step may be performed for each group. In addition, the tire may be grouped in advance by tire components (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 step may be performed for each group. Furthermore, the tire may be grouped by type and by tire components, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties is obtained, so that when it is blended again into the rubber component, a rubber composition with better performance is obtained.

[0080] The regenerated carbon black (B) used in this embodiment has a nitrogen adsorption specific surface area (N 2 SA) is 20 to 150m 2 / g, and the DBP oil absorption is preferably 50 to 150 mL / 100 g. In this embodiment, a commercially available product can be used as the recycled carbon black. An example of such a commercially available product is "PB365" manufactured by Enrestec. PB365 is a recycled carbon black produced by pyrolysis of used tires, and has a N 2 SA is 73.6m 2 / g. PB365 also contains about 17% by mass of ash. In this specification, the nitrogen adsorption specific surface area (N 2 SA) is determined according to JIS K 6217-2:2017 (ISO 4652:2012). In this specification, the DBP oil absorption of carbon black is determined according to JIS K 6217-4:2017.

[0081] The regenerated carbon black (B) preferably has a pH of 4-12, more preferably 5-11, and particularly preferably 6-10. Herein, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0082] The recycled carbon black (B) preferably has a toluene coloring transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. In this specification, the toluene color transmission of the recycled carbon black is determined in accordance with ASTM D1618.

[0083] The heat loss of the recycled carbon black (B) at 125° C. is preferably 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Herein, the heat loss of recycled carbon black at 125° C. is determined in accordance with ASTM D1509.

[0084] The recycled carbon black (B) preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0085] The recycled carbon black (B) 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. In this specification, the 35 mesh screen residue of recycled carbon black is determined in accordance with ASTM D1514.

[0086] The recycled carbon black (B) preferably has a 325 mesh (44 μm) sieve residue of 1000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. In this specification, the 325 mesh (44 μm) sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0087] The recycled carbon black (B) preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0088] The recycled carbon black (B) 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. In this specification, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0089] The recycled carbon black (B) preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. In this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming that the refractive index of water is 1.33 and the refractive index of the filler is 1.75.

[0090] The recycled carbon black (B) preferably contains particles of 5 μm or less in volume percentage of 50% or more, more preferably 70% or more, and particularly preferably 80% or more.

[0091] The regenerated carbon black (B) preferably has a compressed dibutyl phthalate (24M4DBP) absorption of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption of recycled carbon black is determined in accordance with ASTM D3493.

[0092] The content of the recycled carbon black (B) is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, and even more preferably 5 to 50 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the recycled carbon black (B) is 5 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving the ratio of sustainable materials in the rubber product to which the rubber composition is applied is large, and when the content is 50 parts by mass or less, the shrinkage of the rubber composition can be more reliably suppressed.

[0093] (resin) The rubber composition of the present embodiment may contain a resin. Examples of the resin include terpene-based resins, rosin-based resins, C 5 Resin, C 5 -C 9 Resin, C 9Examples of the resins include cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene resins, rosin resins, C 5 Resin, C 5 -C 9 Resin, C 9 Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins and aromatic resins, and particularly preferred are terpene-based resins and rosin-based resins. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins, and therefore can reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry road surfaces, wet road surfaces, snowy road surfaces, and frozen road surfaces. 5 Resin, C 9 Resin, C 5 -C 9 The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve abrasion resistance and fuel economy in a well-balanced manner, while the aromatic resin can improve grip performance, abrasion resistance and rubber strength in a well-balanced manner.

[0094] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). In addition, the resin may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group include an amino group, an amide group, an isocyanate group, an imino group, an imidazole group, a urea group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, an ether group, a carbonyl group, an oxycarbonyl group, a silyl group, an alkoxysilyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, and a thiocarbonyl group.

[0095] The terpene resin is a solid resin obtained by blending turpentine obtained at the same time when rosin is obtained from pine trees, or a polymerization component separated therefrom, and polymerizing it using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. The terpene resin also includes terpene-aromatic compound resin, and representative examples of the terpene-aromatic compound resin include terpene-phenol resin and styrene-terpene resin. The terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing with formalin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes as the raw material are not particularly limited, and are preferably monoterpene hydrocarbons such as α-pinene and limonene, more preferably those containing α-pinene, and particularly preferably α-pinene.

[0096] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil. Examples of modified rosin, rosin derivatives, and modified rosin derivatives include polymerized rosin, partially hydrogenated rosin thereof, glycerin ester rosin, partially hydrogenated rosin thereof, and fully hydrogenated rosin thereof, pentaerythritol ester rosin, partially hydrogenated rosin thereof, and polymerized rosin, etc.

[0097] Said C 5 As for the resin, C is obtained by thermal cracking of naphtha in the petrochemical industry. 5 Examples include aliphatic petroleum resins obtained by (co)polymerizing the fraction. 5 The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene, and the like.

[0098] Said C 5 -C9 The resin is C 5 -C 9 C refers to synthetic petroleum resin. 5 -C 9 As a type of resin, for example, petroleum-derived C 5 -C 11 The fraction was dissolved in AlCl 3 , B.F. 3 More specifically, copolymers mainly composed of styrene, vinyl toluene, α-methyl styrene, indene, etc., can be mentioned. 5 -C 9 As for the resin, 9 Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. 9 "Less than 100% of the total resin content" means that 9 This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0099] Said C 9 The resin is C 9 This refers to synthetic petroleum resins, such as AlCl 3 Or BF 3 Using Friedel-Crafts type catalysts such as C 9 It refers to the solid polymer obtained by polymerizing the fraction. 9 Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, or the like as a main component.

[0100] The cyclopentadiene resin refers to a resin containing a unit derived from a cyclopentadiene monomer as a monomer unit. Examples of the cyclopentadiene resin include a homopolymer of a cyclopentadiene monomer, a copolymer of two or more cyclopentadiene monomers, and a copolymer of a cyclopentadiene monomer and another monomer. Examples of the cyclopentadiene monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred, that is, the cyclopentadiene resin is preferably a dicyclopentadiene resin. The dicyclopentadiene resin is, for example, AlCl 3 Or BF 3 It refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as . Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C 9 Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0101] The aromatic resin refers to a resin containing a unit derived from an aromatic monomer as a monomer unit. Examples of the aromatic resin include a homopolymer of an aromatic monomer, a copolymer of two or more aromatic monomers, and a copolymer of an aromatic monomer and another monomer. Examples of the aromatic monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenolic monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0102] The softening point of the resin is preferably 30° C. or higher, more preferably 60° C. or higher, more preferably 80° C. or higher, more preferably higher than 110° C., more preferably 116° C. or higher, more preferably 120° C. or higher, more preferably 123° C. or higher, and even more preferably 127° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160° C. or lower, more preferably 150° C. or lower, more preferably 145° C. or lower, more preferably 141° C. or lower, and even more preferably 136° C. or lower. In this specification, the softening point of the resin is the temperature at which the ball drops when the softening point defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0103] As the resin, commercially available products can be used, and examples of commercially available resin products that can be used include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Clayton, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton Polymers, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0104] The content of the resin is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, tire components, target performance, etc. For example, the content of the resin 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, relative to 100 parts by mass of the rubber component (A).

[0105] (silica) The rubber composition of the present embodiment may contain silica. Examples of the 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 number of silanol groups. These silicas may be used alone or in combination of two or more. As the silica, a commercially available product may be used, and examples of the commercially available silica include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, Tokuyama Corporation, etc.

[0106] As the silica, silica derived from silicic acid plants is preferred from the viewpoint of reducing environmental load. The silicic acid plants are present, for example, in mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, Gramineae plants are preferred. In addition, the Gramineae plants include rice, bamboo grass, sugarcane, and the like, among which rice is preferred. Since rice is widely cultivated for food, it can be procured locally in a wide area, and since rice husks are generated in large quantities as industrial waste, it is easy to secure the amount. Therefore, from the viewpoint of easy availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. By using the rice husk silica, rice husks that become industrial waste can be effectively utilized, and since the raw material can be procured locally near the tire manufacturing plant, the energy and cost of transportation and storage can be reduced, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet method using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali and extracting the rice husk ash with an alkali silicate aqueous solution. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husks can be pyrolyzed by steaming them in a kiln to obtain rice husk charcoal. The rice husk charcoal thus obtained is pulverized using a known pulverizer (for example, a ball mill), and then sorted and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by the method described in JP 2019-38728 A. From the viewpoint of reducing the environmental load, it is also preferable to use, as the silica, silica obtained by extracting silicic acid components from scraps of silicon wafers, which are the raw material for semiconductors, glass bottles, etc., and recycling the extracted silica for use in the production.

[0107] The silica has a nitrogen adsorption specific surface area (N 2 SA) is 50m 2 / g or more, and 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 2 / g or less, and 2 / g or less is more preferable, 2 / g or less is more preferable, 2 It is even more preferable that the molecular weight is not more than 1 / g. In this specification, the nitrogen adsorption specific surface area (N 2 SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0108] The content of the silica can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the silica 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, still more preferably 100 parts by mass or more, particularly preferably 110 parts by mass or more, and 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, relative to 100 parts by mass of the rubber component (A).

[0109] (Silane coupling agent) When the rubber composition of the present embodiment contains silica, in order to improve the effect of the silica, the rubber composition preferably contains a silane coupling agent. 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-N, Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. As the silane coupling agent, a commercially available product can be used, and examples of the commercially available silane coupling agent include products from Evonik, Momentive, Shin-Etsu Silicone Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0110] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced mainly using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of ethanol (bioethanol) derived from biological resources as the raw material for the silane coupling agent, or to use ethanol (bioethanol) derived from biological resources, ethanol derived from renewable resources, and ethanol derived from fossil resources in combination, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (for example, the demand for biomass resources as food). This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and also to consider the environment depending on the situation at the time of production.

[0111] The content of the silane coupling agent can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the 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, and even more preferably 8 parts by mass or more, and is 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, relative to 100 parts by mass of the silica.

[0112] (Other carbon blacks) The rubber composition of the present embodiment may contain carbon black other than the above-mentioned recycled carbon black (B). As the other carbon black, carbon black derived from plants is particularly preferable. Examples of carbon black derived from plants include those derived from castor oil and rosin oil. The grade of the other carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. As the other carbon black, commercially available products can be used, and examples of the other carbon black commercially available products 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 Co., Ltd., and the like. These other carbon blacks may be used alone or in combination of two or more.

[0113] The nitrogen adsorption specific surface area (N 2 SA) is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the nitrogen adsorption specific surface area (N 2 SA) is 20m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable.

[0114] The content of the other carbon black is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the tire components, the target performance, etc. For example, the content of the other carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component (A).

[0115] The proportion of silica in the total content of silica and carbon black is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category, tire components, target performance, etc. of the tire to which it is applied. For example, in the case of tread rubber for passenger car tires, the proportion of silica in the total content of silica and carbon black is preferably 50% 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 95% by mass or more. In addition, the proportion of silica in the total content of silica and carbon black may be 100% by mass, but is preferably 98% by mass or less.

[0116] (rubber powder) The rubber composition of the present embodiment may contain rubber powder. The rubber powder may be obtained by crushing used rubber products such as used tires, and removing reinforcing materials such as steel materials and fibers, dust, glass, sand, stones, etc., as desired, or by preparing a new vulcanized rubber composition to produce rubber powder and crushing it. For example, rubber powder can be obtained from vulcanized rubber by the method described in "Rubber Chemistry And Technology". In the process of crushing vulcanized rubber to obtain rubber powder, mechanical treatment or low-temperature treatment may be used. For example, in the mechanical treatment, various crushing devices such as a cracker mill and a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In the low-temperature treatment, the finely chopped vulcanized rubber is frozen at a very low temperature and then crushed into fine particles. In addition, a magnetic separator or the like can be used to remove steel materials, and an air separator or the like can be used to remove fibers. As the rubber powder, a commercially available product can be used, and examples of the commercially available rubber powder include products from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental load, 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 kinds.

[0117] The composition of the rubber powder is not particularly limited, and depends on the composition of the vulcanized rubber of the raw material, such as used rubber products (used tires). In one embodiment, the rubber powder contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber powder may be the same as or different from the rubber component, carbon black, silica, etc. that may be contained in the rubber composition of the present embodiment described above.

[0118] The rubber powder has a volume average particle size of preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle size of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle size is measured by a laser diffraction particle size distribution measuring device, for example, "CAPA500" manufactured by Horiba, Ltd.

[0119] The rubber powder has a 60 mesh sieve residue of preferably less than 1 mass%, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, with no particular lower limit. Also, the rubber powder has an 80 mesh sieve residue of preferably less than 10 mass%, more preferably 1 mass% or less, and even more preferably 0.5 mass% or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0120] The rubber powder has an acetone extractable content of preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractables in the rubber powder refer to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0121] The content of the rubber powder is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber component is applied, the tire components, the 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, and even more preferably 3 parts by mass or more, and is 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, relative to 100 parts by mass of the rubber component (A).

[0122] (liquid softener) The rubber composition of the present embodiment may contain a liquid softener. Here, the "liquid softener" is 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 examples thereof include oil and liquid polymer, among which oil is preferable. These liquid softeners may be used alone or in combination of two or more.

[0123] The oil is a general term for the extender oil contained in the rubber component and the liquid oil added as a compounding agent of the rubber composition, and examples thereof include vegetable oil, process oil, oil obtained by recycling vegetable oil or process oil, or a mixture thereof. From the viewpoint of reducing the environmental load, the oil is preferably vegetable oil or oil obtained by recycling. Examples of the vegetable oil include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc. Examples of the process oil include paraffin-based process oil, aromatic process oil, naphthene-based process oil, etc. The oil may be a commercially available product, and examples of the commercially available oil include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0124] The liquid polymer is preferably a liquid diene polymer. Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or the terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0125] The content of the liquid softener is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and is 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, relative to 100 parts by mass of the rubber component (A).

[0126] (Anti-aging agent) The rubber composition of the present embodiment may contain an antioxidant, such as 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. As the antiaging agent, commercially available products can be used, and examples of the commercially available antiaging agent include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antiaging agents may be used alone or in combination of two or more.

[0127] The content of the antiaging agent is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the antiaging agent is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is 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, relative to 100 parts by mass of the rubber component (A).

[0128] (wax) The rubber composition of the present embodiment may contain a wax. Examples of the wax include natural waxes such as vegetable wax and animal wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of the commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0129] The content of the wax is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0130] (Stearic acid) The rubber composition of the present embodiment may contain stearic acid. Commercially available stearic acid may be used, and examples of the commercially available stearic acid include products from NOF Corp., Kao Corp., Fujifilm Wako Pure Chemical Corp., Chiba Fatty Acid Corp., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0131] The content of the stearic acid is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0132] (Zinc Oxide) The rubber composition of the present embodiment may contain zinc oxide (zinc white). The zinc oxide may be obtained not only from zinc metal but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available products can be used as the zinc oxide, and examples of the 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., and the like. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0133] The content of the zinc oxide is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0134] (sulfur) The rubber composition of the present embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or materials derived from biological resources. From the viewpoint of reducing the environmental load, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of a method for obtaining sulfur from waste derived from biological resources include the method described in the above-mentioned Japanese Patent Application No. 2022-140390. In addition, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used as crosslinking agents in the rubber industry. As the sulfur, commercially available products can be used, and examples of commercially available sulfur products include products from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., etc. These sulfurs may be used alone or in combination of two or more types.

[0135] The sulfur content is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the 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, and even more preferably 0.8 parts by mass or more, and is preferably 8 parts by mass or less, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0136] (Vulcanization accelerator) The rubber composition of the present embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, recycled resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing environmental load. The vulcanization accelerator derived from biological resources can be obtained by, for example, the method disclosed in JP-A-2005-139239. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; 1,3-diphenylguanidine (DPG), 1,3-diphenylguanidine (DPG), and 1,3-diphenylguanidine (DPG). Examples of the vulcanization accelerator include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available products can be used as the vulcanization accelerator, and examples of the commercially available vulcanization accelerators include products from Ouchi Shinko Chemical Industry Co., Ltd. and Sumitomo Chemical Co., Ltd. These vulcanization accelerators may be used alone or in combination of two or more.

[0137] The content of the vulcanization accelerator is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the 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, and even more preferably 3 parts by mass or more, and is 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, relative to 100 parts by mass of the rubber component (A).

[0138] (Cellulose nanofiber) The rubber composition of the present embodiment may contain cellulose nanofibers (CNF). The cellulose nanofibers can reinforce the rubber composition by blending them with the rubber composition. The cellulose nanofibers are preferably modified cellulose nanofibers, which are fine fibers made from modified cellulose. The fiber diameter of the cellulose nanofibers is not particularly limited, but is about 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofibers can be obtained by averaging the fiber diameters and fiber lengths obtained from the results of observing each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofibers can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment and defibration treatment.

[0139] The raw material for the cellulose nanofibers is not particularly limited as long as it contains cellulose, and examples thereof include plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. These cellulose raw materials may be used alone or in combination of two or more.

[0140] The content of the cellulose nanofibers is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the tire components, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by weight, and even more preferably in the range of 10 to 40 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0141] (Porous cellulose particles) The rubber composition of the present embodiment may contain porous cellulose particles. The porous cellulose particles are preferably cellulose particles having a porous structure with a porosity of 75 to 95%, and by compounding them with the rubber composition, the performance on ice can be improved. When the porosity of the porous cellulose particles is 75% or more, the effect of improving the performance on ice is excellent, and when the porosity is 95% or less, the strength of the particles can be increased. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a certain mass of a sample (i.e., the porous cellulose particles) with a measuring cylinder, calculating the bulk density, and using the following formula. Porosity (%) = {1-[bulk specific gravity of sample (g / mL)] / [true specific gravity of sample (g / mL)]} x 100 Here, the true specific gravity of cellulose is 1.5.

[0142] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, the average particle size is preferably 1000 μm or less. The lower limit of the average particle size is not particularly limited, but is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and further preferably 200 to 800 μm. The porous cellulose particles are preferably spherical particles having a major axis / minor axis ratio of 1 to 2. By using particles having such a spherical structure, the dispersibility in the rubber composition is improved, which contributes to improving performance on ice and maintaining abrasion resistance, etc. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and the long axis / short axis ratio of the porous cellulose particles are obtained as follows: That is, the porous cellulose particles are observed under a microscope to obtain an image, and the long axis and short axis of the particles (when the long axis and short axis are the same, the length in a certain axis direction and the length in an axis direction perpendicular to the long axis) are measured for 100 particles using the image, and the average particle size is obtained by calculating the average value, and the long axis / short axis ratio is obtained by averaging the values ​​obtained by dividing the long axis by the short axis.

[0143] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopearl" and are described in JP-A-2001-323095, JP-A-2004-115284, etc., and these can be suitably used.

[0144] The content of the porous cellulose particles is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the porous cellulose particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by weight, and further preferably in the range of 3 to 15 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0145] (solid fine particles) The rubber composition of the present embodiment may contain solid fine particles. The solid fine particles can improve the performance on ice by blending them with the rubber composition. The solid fine particles preferably have an average particle diameter of 1 μm or more, and more preferably 1000 μm or less, and more preferably 300 μm or less. Examples of the solid fine particles include powders derived from plants such as rice husks, walnut powder, and walnut shells; powders derived from animals such as eggshells (eggshell powder) and bone powder; powders derived from natural minerals such as whitebait; inorganic fine particles such as graphite and zinc oxide whiskers; water-soluble metal salt fine particles such as magnesium sulfate and metal salts of lignin sulfonate; non-metallic fibers such as glass fibers; and the like. Among these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0146] The content of the solid fine particles is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, tire components, target performance, etc. For example, the content of the solid fine particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by weight, and further preferably in the range of 3 to 15 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0147] (others) In addition to the above-mentioned components, the rubber composition of the present embodiment may further contain various additives commonly used in the tire industry, such as fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; organic peroxides; etc. The content of these additives is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc., and is preferably in the range of 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component (A).

[0148] (Method of manufacturing rubber composition) The method for producing the rubber composition of the present embodiment is not particularly limited, but for example, the rubber composition can be produced by blending recycled carbon black (B) and various components appropriately selected as necessary with a rubber component (A) containing the modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3 mass%, followed by kneading, heating, extrusion, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0149] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0150] The conditions of the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, heat-in equipment, etc. can be appropriately selected depending on the purpose. Examples of the heat-in equipment include a heat-in roller machine usually used for heat-in of a rubber composition.

[0151] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder that is usually used for extruding a rubber composition. The extrusion temperature can be appropriately determined.

[0152] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As the vulcanization apparatus, a molding vulcanizer using a mold used for vulcanizing a rubber composition can be mentioned. As the vulcanization condition, the temperature is, for example, about 100 to 190°C.

[0153] (Application) The rubber composition of the present embodiment can be applied to various components of a tire, for example, tread (cap tread, base tread, under tread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, belt reinforcing layer coating rubber, belt layer coating rubber, insulation, chafer, inner liner, etc., and can also be used for side reinforcing layers of run-flat tires. In addition to tires, the rubber composition of the present embodiment can also be applied to various hoses, rubber crawlers, seismic isolation rubber, etc. These tires and other rubber products can improve the ratio of sustainable materials while maintaining dimensional accuracy by using the rubber composition of the present embodiment.

[0154] When the rubber composition of this embodiment is applied to the coating rubber of the belt reinforcing layer, the belt reinforcing layer may be a member obtained by, for example, covering reinforcing cords (organic fiber 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 the rubber composition of this embodiment (reinforcing layer rubber, elastomer). The belt reinforcing layer may be formed by continuously winding a narrow strip prepared by covering an organic fiber cord with the rubber composition (elastomer) of this embodiment in a spiral shape in the tire circumferential direction.

[0155] The organic fiber cord applied to the belt reinforcing layer may be, for example, an organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more.

[0156] An organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more has high strength at break, large elongation at break, and a high elastic modulus at 7% elongation. Therefore, when an organic fiber cord with such physical properties is used in a belt reinforcing layer, it is possible to improve the steering stability of the tire while ensuring the plunger durability of the tire.

[0157] The material of the organic fiber cord is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethylene furan dicarboxylate (PEF); nylons such as 6-nylon, 6,6-nylon, 4,6-nylon, and 4,10-nylon; and celluloses such as rayon and lyocell. Among these, polyethylene terephthalate is preferred, that is, the organic fiber cord as the reinforcing material of the belt reinforcing layer is preferably a cord made of polyethylene terephthalate (hereinafter, sometimes simply referred to as "polyethylene terephthalate cord"). The polyethylene terephthalate cord has higher rigidity than commonly used nylon cords and is excellent in improving the plunger durability and steering stability of the tire. In addition, the raw material of the organic fiber cord is not particularly limited, and may be derived from synthetic products, biological products, mechanical recycling derived from crushing, melting, and re-spinning PET products such as PET bottles, or chemical recycling derived from depolymerizing and repolymerizing PET products such as PET bottles.

[0158] In addition, when the rubber composition of the present embodiment is applied to the coating rubber of the belt layer, typically, a plurality of belt cords are arranged in parallel in the belt layer. Such belt cords are generally steel cords. The structure of such belt cords is not particularly limited. However, from the viewpoint of effectively achieving both improved durability and reduced rolling resistance of the tire, the belt cord may have a 1×N structure (N is an integer of 2 or more) formed by twisting together N filaments, an M+N structure in which N sheath filaments (here, N is an integer greater than 1) are twisted in a spiral shape around M core filaments (here, the core filaments may be twisted or may be bundled without twisting), or a multi-twist structure in which a plurality of the 1×N structure or M+N structure are twisted together. In addition, it is also preferable that the cord is a monofilament that is twisted in parallel without being twisted together.

[0159] The filaments constituting the belt cord have a diameter of X (mm) and a tensile strength of Y (MPa) that satisfies the following formula: 4000-2000X≦Y≦4500-2000X By using filaments satisfying the above formula in the belt layer, the strength of the belt layer can be improved, the plunger level can be improved, and the cut resistance of the tire can be supplemented. Here, the tensile strength of the filaments is determined in accordance with the provisions of ISO 17832:2009.

[0160] From the viewpoint of fatigue resistance, the hardness of the surface layer of the filament constituting the belt cord is preferably 90 to 110% of the hardness of the inner layer, and particularly preferably 100%. The hardness can be measured, for example, by Vickers hardness. The surface layer of the filament means a layer from the outermost surface to a depth of 0.01 mm, and the inner layer means the inner layer of the filament. The hardness can be measured in a region 0.005 mm deep from the outermost surface for the surface layer, and 0.04 mm deep for the inner layer.

[0161] There is no particular limitation on the method for producing the filaments constituting the belt cord. For example, the filaments may be obtained by refining iron ore and wire drawing, or may be obtained by refining scrap iron and wire drawing, or may be obtained by recycling steel extracted from tires.

[0162] <Tires> The tire of the present embodiment is characterized by including a rubber member made of the above-mentioned rubber composition. The tire of the present embodiment includes a rubber member made of the above-mentioned rubber composition, and therefore has an improved ratio of sustainable materials while maintaining dimensional accuracy.

[0163] The tire of this embodiment can be manufactured by a normal method using the above-mentioned rubber composition. For example, 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 been subjected to a pre-vulcanization process or the like and then further vulcanizing it, depending on the type of tire to be applied. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. EXAMPLES

[0164] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0165] <Preparation and Evaluation of Rubber Composition> Rubber compositions of the examples and comparative examples are prepared according to the compounding recipes shown in Table 1. For the obtained rubber compositions, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) is calculated to calculate the sustainable material ratio. The results are shown in Table 1.

[0166] [Table 1]

[0167] *1 Modified conjugated diene polymer: See the following section for details *2 Polyisoprene rubber: ENEOS Materials Corporation, product name "IR2200" *3 Modified natural rubber: See the following section for details *4 Aromatic oil: Manufactured by Fuji Kosan Co., Ltd., trademark "Aromax #3" *5 Unused carbon black: ISAF-HS *6 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *7 Silica: manufactured by Tosoh Silica Corporation, trademark "Nipsil AQ" *8 Silane coupling agent: Bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Degussa, trademark "Si69" *9 Antioxidant 6C: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by Seiko Chemical Co., Ltd., trademark "Ozonone 6C" *10 Vulcanization accelerator DPG: Diphenyl guanidine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trademark "Noccela D" *11 Vulcanization accelerator DM: Dibenzothiazyl disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trademark "Noccela DM" *12 Vulcanization accelerator NS: Nt-butyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trademark "Noccela NS"

[0168] The modified conjugated diene copolymer (*1) is prepared as follows. <Production Example of Modified Conjugated Diene Copolymer> Under a nitrogen atmosphere, 41 g of 3-aminopropyltriethoxysilane (Gelest) was added as an aminosilane moiety to 400 ml of dichloromethane solvent in a glass flask equipped with a stirrer, and 48 ml of trimethylsilane chloride (Aldrich) and 53 ml of triethylamine were further added as protective moieties to the solution. The mixture was stirred at room temperature for 25 hours, and then the reaction solution was put into an evaporator to remove the solvent to obtain a composition reaction solution. The reaction solution thus obtained was then subjected to reduced pressure distillation under 5 mmHg conditions to obtain a complete condensation product of N,N-bis(trimethylsilyl)aminopropyltriethoxysilane as a 150-200°C fraction.

[0169] In a dried, nitrogen-purged 800 mL pressure-resistant glass vessel, add a cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene so that the amounts are 60 g of 1,3-butadiene and 15 g of styrene, add 0.70 mmol of 2,2-ditetrahydrofurylpropane, and further add 0.70 mmol of n-butyllithium (BuLi), and then carry out a polymerization reaction in a warm water bath at 50°C for 1.5 hours. Next, the complete condensate of N,N-bis(trimethylsilyl)aminopropyltriethoxysilane obtained above is added to the polymerization reaction system in an amount equivalent to the amount of lithium (Li) in moles, and the modification reaction is carried out at 50° C. for another 30 minutes. After that, 1.5 ml of dilute hydrochloric acid is added little by little to the polymerization reaction system, then water is added in an amount three times the molar amount of lithium (Li) and stirred for 30 minutes. Next, an isopropanol solution of 2,6-di-tert-butyl-p-cresol is added to the polymerization reaction system to terminate the polymerization reaction. After that, water vapor is blown in to reduce the partial pressure of the solvent (steam stripping) to remove the solvent, and the mixture is vacuum dried to obtain a modified conjugated diene copolymer.

[0170] Modified natural rubber (*3) is produced as follows. <Modified natural rubber manufacturing example> (1) Enzyme treatment process of natural rubber latex Water is added to natural rubber latex of clone GT-1, the dry rubber content (DRC) is adjusted to 15% by mass, and ammonia is further added to adjust the pH to 8.0. Then, 0.2% by mass of 1,2-benzisothiazolin-3-one is added as a preservative and stirred to disperse uniformly. 1.5 g of Levenol WX [manufactured by Kao Corporation] is added as a surfactant to 1000 g of the obtained preservative-containing natural rubber latex, and stirred to disperse thoroughly. Next, 0.15 g of protease [Alcalase 2.5L Type DX, manufactured by Novozymes] is added to the mixture, and stirred to disperse thoroughly. The obtained mixture is then left to stand at 40°C for 15 hours.

[0171] (2) Coagulation and drying process of modified natural rubber latex The modified natural rubber latex obtained as above is coagulated by adding formic acid to adjust the pH to 4.7. The solid matter thus obtained is treated with a scraper five times, crumbed through a shredder, and then dried in a hot air dryer at 110°C for 210 minutes to obtain modified natural rubber.

[0172] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention have an improved ratio of sustainable materials. [Industrial Applicability]

[0173] The rubber composition of the present invention can be used for rubber products such as tires, various hoses, rubber crawlers, and seismic isolation rubber.

[0174] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 12_Responsible Consumption and Production" and "No. 13_Concrete measures against climate change."

Claims

1. A rubber component (A) containing a modified natural rubber (A1) having a total nitrogen content of 0.1 to 0.3 mass%, A rubber composition comprising:

2. The rubber composition according to claim 1, wherein the modified natural rubber (A1) has been subjected to at least one deproteinization treatment selected from the group consisting of centrifugation, an enzyme treatment, and a urea treatment.

3. The rubber composition according to claim 1, wherein the modified natural rubber (A1) has a phosphorus content of more than 200 ppm by mass.

4. 2. The rubber composition according to claim 1, wherein the recycled carbon black (B) is obtained by pyrolysis of a vulcanized rubber product containing carbon black.

5. The rubber composition according to claim 1 , wherein the recycled carbon black (B) has an ash content of 20 mass % or less.

6. A tire comprising a rubber member made of the rubber composition according to claim 1.

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