Carbon black, rubber composition, and rubber article

Abstract

The present invention addresses the problem of providing carbon black capable of suppressing deterioration of the physical properties of a rubber composition when applied to the rubber composition. The problem is solved by carbon black containing one or more selected from the group consisting of Zn, Fe, and Cu, the Zn content being 0 mass% to 2.5 mass%.

Description

Carbon black, rubber compositions, and rubber products

[0001] This invention relates to carbon black, rubber compositions, and rubber products.

[0002] In recent years, research on recycling and sustainable materials has been actively pursued in order to realize a sustainable society. Research on recycling and effective utilization of used tires is also progressing. In particular, recovering carbon black from used tires as a useful material is becoming increasingly important.

[0003] Incidentally, carbon black recovered through recycling (hereinafter referred to as "recycled carbon black") contains impurities such as metal, inorganic, and organic components that were originally contained in tires. When recycled carbon black is used in the manufacture of rubber, it is known that various mechanical properties such as reinforcing properties and fracture resistance are reduced compared to non-recycled carbon black (so-called "new" carbon black) due to the influence of these impurities. Various studies have been conducted to suppress this reduction in physical properties. For example, Patent Document 1 below examines the ash content and statistical thickness specific surface area of ​​recycled carbon black.

[0004] International Publication No. 2024 / 116832

[0005] While carbon black as described in Patent Document 1 can suppress the deterioration of the physical properties of a rubber composition when applied, only the ash content has been considered, and the amounts of each component in the ash have not been examined. Therefore, there is still room for further research into carbon black that can suppress the deterioration of physical properties when applied to a rubber composition.

[0006] Therefore, the present invention aims to solve the problems of the above-mentioned prior art and to provide a carbon black that can suppress the deterioration of the physical properties of a rubber composition when applied to it. A further objective of the present invention is to provide a rubber composition containing such carbon black and a rubber product using such a rubber composition.

[0007] The essential structure of the carbon black, rubber composition, and rubber product of the present invention, which solves the above problems, is as follows.

[0008] [1] Carbon black comprising one or more selected from the group consisting of Zn, Fe, and Cu, wherein the content of Zn is 0% by mass or more and 2.5% by mass or less.

[0009] [2] Carbon black comprising one or more elements selected from the group consisting of Zn, Fe, and Cu, wherein the Fe content is 0% by mass or more and 0.1% by mass or less.

[0010] [3] Carbon black containing 0.5% by mass or more of S, and optionally containing Zn, wherein the Zn content is 0% by mass or more and 2.5% by mass or less.

[0011] [4] Carbon black containing 0.5% by mass or more of S, and optionally containing Fe, wherein the Fe content is 0% by mass or more and 0.1% by mass or less.

[0012] [5] The carbon black according to [1] or [2], further comprising 0.4% by mass or more of S.

[0013] [6] The carbon black according to any one of [1] to [5], wherein the Zn content is 1.0% by mass or less.

[0014] [7] The carbon black according to any one of [1] to [6], wherein the Fe content is 0.06% by mass or less.

[0015] [8] Carbon black according to any one of [1] to [7], wherein the Si content is 0% by mass or more and 1.0% by mass or less.

[0016] [9] Carbon black according to any of [1] to [8], wherein the ash content is 6.0% by mass or less.

[0017]

[10] A rubber composition comprising carbon black as described in any of [1] to [9].

[0018]

[11] A rubber product selected from the group consisting of tires, rubber tracks, and hoses, using the rubber composition described in

[10] .

[0019] According to the present invention, it is possible to provide a carbon black that can be easily manufactured by simplifying processing steps such as purification, and that can suppress the deterioration of the physical properties of a rubber composition when applied to it. According to the present invention, it is possible to provide a rubber composition containing such carbon black, and a rubber product using such a rubber composition.

[0020] The present invention will be described in detail below based on its embodiments.

[0021] The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, or recycled resources.

[0022] <Carbon Black> The carbon black of the first embodiment of the present invention comprises one or more elements selected from the group consisting of Zn, Fe, and Cu, and is characterized in that the content of Zn is 0% by mass or more and 2.5% by mass or less.

[0023] Furthermore, the carbon black of the second embodiment of the present invention contains one or more elements selected from the group consisting of Zn, Fe, and Cu, and is characterized in that the Fe content is 0% by mass or more and 0.1% by mass or less. The carbon black of the first embodiment and the carbon black of the second embodiment can suppress the deterioration of physical properties when applied to a rubber composition. In addition, these carbon blacks can maintain the physical properties of the rubber composition while leaving components that may affect the deterioration of the physical properties of the rubber composition, thus simplifying processing steps such as purification to completely remove components that may affect the deterioration of the physical properties of the rubber composition.

[0024] Furthermore, the carbon black of the third embodiment of the present invention is characterized by containing 0.5% by mass or more of S, optionally containing Zn, and having a Zn content of 0% by mass or more and 2.5% by mass or less.

[0025] Furthermore, the carbon black of the fourth embodiment of the present invention contains 0.5% by mass or more of S, optionally contains Fe, and is characterized in that the Fe content is 0% by mass or more and 0.1% by mass or less. The carbon black of the third embodiment and the carbon black of the fourth embodiment can suppress the deterioration of physical properties when applied to a rubber composition. In addition, these carbon blacks can maintain the physical properties of the rubber composition while leaving components that may lead to a deterioration of physical properties, thus simplifying processing steps such as purification to completely remove components that may affect the deterioration of the physical properties of the rubber composition.

[0026] The carbon black of the present invention is preferably recycled carbon black. In the present invention, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials that have been recycled. The waste materials that have been recycled include rubber products containing carbon black, such as used rubber and used tires. "Recycled carbon black" is different from carbon black that is manufactured directly from hydrocarbons such as petroleum and natural gas as raw materials, i.e., carbon black that is not recycled. Here, "used" includes not only those that have been discarded after being actually used, but also those that were manufactured but discarded without actually being used.

[0027] The recycled carbon black described above is preferably recycled carbon black obtained from solid residue produced by thermally decomposing rubber products containing carbon black. When rubber products containing carbon black are thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from both.

[0028] Furthermore, the carbon black of the present invention is more preferably carbon black that has undergone surface treatment or surface modification. Examples of surface treatment and surface modification include hydrofluoric acid treatment, acids such as hydrochloric acid and sulfuric acid, and peroxides. Surface treatment and surface modification may be carried out at room temperature, preferably at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C to 100°C.

[0029] Carbon black that is not recycled and is manufactured using hydrocarbons as raw materials (hereinafter sometimes referred to as "ordinary carbon black") has a high carbon content. The carbon content of these carbon blacks is approximately 98% by mass or more (excluding adsorbed water). As will be described later, the carbon black of the present invention may differ from ordinary carbon black because the carbon content may vary.

[0030] (Ash Content) Solid residues obtained by thermally decomposing waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash originates from non-volatile components contained in rubber and tires. Specifically, the ash includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, etc. The amount of ash in carbon black varies depending on the amount of non-volatile components contained in used rubber and used tires. In the case of carbon black produced from solid residues obtained by thermally decomposing waste materials, a certain amount of ash remains even after various processes to remove it. For this reason, carbon black obtained from such solid residues tends to have a high ash content and a relatively low carbon black content.

[0031] As described above, the carbon black of the present invention may contain ash. The carbon black of the present invention allows for the inclusion of ash, while controlling the amount of each component (e.g., Zn, Fe, etc.) in the ash. In other words, by controlling the amount of each component in the ash, the carbon black of the present invention suppresses the deterioration of the physical properties of the rubber composition when the carbon black is applied to the rubber composition. A higher ash content indicates a lower carbon content, so a lower ash content is preferable in terms of the physical properties of the carbon black. However, considering the limitations and costs of ash removal, an ash content that does not deteriorate the physical properties of the rubber composition is acceptable.

[0032] The carbon black of the present invention preferably has an ash content of 0.5% by mass or more and 10% by mass or less. When the ash content in the carbon black exceeds 10% by mass, it may not be possible to obtain a tire having sufficient reinforcing properties. Considering the reinforcing properties of the tire, the ash content is preferably 6.0% by mass or less, more preferably 5.0% by mass or less, still more preferably 4.0% by mass or less, further preferably 3.0% by mass or less, and particularly preferably 2.0% by mass or less. That is, the carbon black of the present invention preferably has an ash content of 0.5% by mass or more and 6.0% by mass or less, more preferably 0.5% by mass or more and 5.0% by mass or less, still more preferably 0.5% by mass or more and 4.0% by mass or less, further preferably 0.5% by mass or more and 3.0% by mass or less, and particularly preferably 0.5% by mass or more and 2.0% by mass or less.

[0033] [Zn, Fe, and Cu] The carbon black of the first embodiment and the second embodiment contains one or more selected from the group consisting of Zn, Fe, and Cu. Zn, Fe, and Cu are components in the ash. Further, the carbon black of the third embodiment optionally contains Zn, and the carbon black of the fourth embodiment optionally contains Fe.

[0034] -Zn- The carbon black of the present invention may contain Zn (zinc). Zn in the carbon black is derived from, for example, zinc white used as a vulcanization aid. When the content of Zn in the carbon black exceeds a certain amount, the physical properties of the rubber composition deteriorate, but if it is below a certain amount, the deterioration of the physical properties of the rubber composition can be suppressed.

[0035] In the first embodiment of the present invention, the Zn content in the carbon black is preferably 0% by mass or more and 2.5% by mass or less. Furthermore, in the second embodiment of the present invention, the Zn content in the carbon black is preferably 0% by mass or more and 2.5% by mass or less. Furthermore, in the third embodiment, the Zn content in the carbon black is preferably 0% by mass or more and 2.5% by mass or less. Furthermore, in the fourth embodiment of the present invention, the Zn content in the carbon black is preferably 0% by mass or more and 2.5% by mass or less. A lower Zn content in the carbon black is preferable, but if the Zn content is 2.5% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing a decrease in the physical properties of the rubber composition, the Zn content is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, still preferably 0.5% by mass or less, even more preferably 0.4% by mass or less, even more preferably 0.3% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.1% by mass or less. The Zn content may also be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate.

[0036] Methods to keep the Zn content in carbon black within the above range include, for example, analyzing the amount of Zn contained in the raw rubber to be acid-treated and recycled in advance, and using some or all of the raw rubber with a low Zn content.

[0037] -Fe- The carbon black of the present invention may contain Fe (iron). The Fe is derived, for example, from the steel cords of tires. If the Fe content in the carbon black exceeds a certain amount, the physical properties of the rubber composition will deteriorate, but if it is below a certain amount, the deterioration of the physical properties of the rubber composition can be suppressed.

[0038] In the first embodiment of the present invention, the content of Fe in the carbon black is preferably 0% by mass or more and 0.1% by mass or less. Also, in the second embodiment of the present invention, the content of Fe in the carbon black is 0% by mass or more and 0.1% by mass or less. Furthermore, in the third embodiment of the present invention, the content of Fe in the carbon black is preferably 0% by mass or more and 0.1% by mass or less. Furthermore, in the fourth embodiment of the present invention, the content of Fe in the carbon black is 0% by mass or more and 0.1% by mass or less. The lower the content of Fe in the carbon black, the more preferable it is. However, if the content of Fe is 0.1% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the content of Fe is more preferably 0.09% by mass or less, even more preferably 0.08% by mass or less, further preferably 0.07% by mass or less, even further preferably 0.06% by mass or less, even further more preferably 0.05% by mass or less, particularly preferably 0.04% by mass or less, and most preferably 0.03% by mass or less. Also, the content of Fe may be 0.01% by mass or more, or may be 0.02% by mass or more. The above upper and lower limit values can be combined as appropriate.

[0039] As a method for making the content of Fe in the carbon black within the above range, for example, acid treatment, and analyzing in advance the amount of Fe contained in the recycled raw rubber and applying a part or all of the raw rubber with a small amount of Fe can be mentioned.

[0040] -Cu- The carbon black of the present invention may contain Cu (copper). Cu may be derived from plating such as steel cord.

[0041] The Cu content in the carbon black is preferably 0% by mass or more and 0.05% by mass or less. A lower Cu content in the carbon black is preferable, but a Cu content of 0.05% by mass or less can suppress the deterioration of the physical properties of the rubber composition. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Cu content is more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, and even more preferably 0.01% by mass or less. The Cu content may also be 0.01% by mass or more, or 0.02% by mass or more. The above upper and lower limits can be combined as appropriate.

[0042] Methods for adjusting the Cu content in carbon black to the above range include, for example, analyzing the amount of Cu contained in the raw rubber to be acid-treated and recycled in advance, and using some or all of the raw rubber with a low Cu content.

[0043] [Components other than Zn, Fe, and Cu] The carbon black of the present invention may contain components other than the above-mentioned Zn, Fe, and Cu. "Components other than Zn, Fe, and Cu" refers to components other than Zn, Fe, and Cu in the ash. Examples of components other than Zn, Fe, and Cu in the ash include Si (silicon), S (sulfur), Ca (calcium), K (potassium), Br (bromine), Mg (magnesium), Cl (chlorine), P (phosphorus), Co (cobalt), Na (sodium), Al (aluminum), etc.

[0044] -Si- The carbon black of the present invention may contain Si (silicon). In the carbon black of the present invention, the Si content is preferably 0% by mass or more and 1.0% by mass or less. A Si content of 1.0% by mass or less suppresses the deterioration of the physical properties of the rubber composition. From a similar viewpoint, the Si content is more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. It is also preferable that the Si content is 0% by mass, that is, substantially Si-free. On the other hand, the Si content may be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate.

[0045] Methods for adjusting the Si content in carbon black to the above range include, for example, hydrofluoric acid treatment and base treatment.

[0046] -S- The carbon black of the first and second embodiments of the present invention may contain sulfur (S). In the carbon black of the first and second embodiments of the present invention, the S content is preferably 0.4% by mass or more, and more preferably 0.5% by mass or more. Furthermore, in the carbon black of the first and second embodiments of the present invention, the S content is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The above upper and lower limits can be combined as appropriate. The carbon black of the third and fourth embodiments of the present invention contains 0.5% by mass or more of sulfur (S). If the S content is less than 0.5% by mass, the processing steps such as refining may become complicated, high-precision processing equipment may be required, making it difficult to manufacture easily, and a large amount of energy may be required, potentially increasing the environmental burden. In the carbon black of the third and fourth embodiments of the present invention, the S content is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The above upper and lower limits can be combined as appropriate. In other words, in the carbon black of the third and fourth embodiments of the present invention, the S content is preferably in the range of 0.5% by mass or more and 2.0% by mass or less, more preferably in the range of 0.5% by mass or more and 1.8% by mass or less, and even more preferably in the range of 0.5% by mass or more and 1.0% by mass or less.

[0047] Methods for adjusting the sulfur content in carbon black to the above range include, for example, acid treatment.

[0048] -Ca- The carbon black of the present invention may contain Ca (calcium). In the carbon black of the present invention, the Ca content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and particularly preferably 0.8% by mass or more. Furthermore, the Ca content is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and even more preferably 1.1% by mass or less. The above upper and lower limits can be combined as appropriate.

[0049] Methods for adjusting the Ca content in carbon black to the above range include, for example, acid treatment.

[0050] -K, Br, Mg, Cl, P, Co, Na, and Al- The carbon black of the present invention may contain K, Br, Mg, Cl, P, Co, Na, and Al. Preferably, the content of K, Br, Mg, Cl, P, Co, Na, and Al is 0% by mass or more and 0.2% by mass or less. More preferably, the content of P, Co, Na, and Al is 0% by mass, that is, P, Co, Na, and Al are substantially not contained in the carbon black.

[0051] (Carbon Content) The carbon black of the present invention preferably has a carbon content of 85% by mass or more and 97% by mass or less. Note that the above carbon content does not include adsorbed water. If the carbon content in the carbon black of the present invention is less than 85% by mass, there is a risk that physical properties such as reinforcing properties will decrease. Considering the suppression of the decrease in physical properties of the rubber composition to which the carbon black is applied, a higher carbon content is preferable. Specifically, the carbon content is preferably 85% by mass or more, more preferably 87% by mass or more, even more preferably 89% by mass or more, and still more preferably 91% by mass or more. Accordingly, the carbon black of the present invention preferably has a carbon content of 85% by mass or more and 97% by mass or less, more preferably 87% by mass or more and 97% by mass or less, even more preferably 89% by mass or more and 97% by mass or less, and still more preferably 91% by mass or more and 97% by mass or less.

[0052] [Characteristics of Carbon Black] The carbon black of the present invention has a statistical thickness specific surface area (STSA) of 65 m². ２ It is preferable that the amount is 65 m² or more. Generally, the smaller the particle size of carbon black, the larger the statistical thickness specific surface area tends to be. ２ If the value is less than / g, it may not be possible to sufficiently improve the tire's reinforcing properties. Statistical thickness specific surface area is 65 m². ２ By using carbon black with a high density of 1 / g or more, it is possible to significantly improve the reinforcing properties compared to using ordinary carbon black. Considering the reinforcing properties, the statistical thickness specific surface area is 70 m². ２ It is preferable that the amount is 1 / g or more. While there is no particular upper limit on the statistical thickness specific surface area, considering the physical properties required for tires, such as rolling resistance, the statistical thickness specific surface area of ​​the carbon black of the present invention is 90 m². ２ It is preferable that the amount is less than or equal to / g. That is, the statistical thickness specific surface area of ​​the carbon black of the present invention is 65 m². ２ / g or more 90m ２ It is preferable that it be less than or equal to 70m ２ / g or more 85m２ It is more preferably below / g. The statistical thickness specific surface area (STSA) is a value measured in accordance with ISO CD 4652-2 / 3.

[0053] Further, the carbon black of the present invention has a nitrogen adsorption specific surface area (N ２ SA) of preferably 75 m ２ / g or more and 110 m ２ / g or less. When the nitrogen adsorption specific surface area is 75 m ２ / g or more, a rubber composition having sufficient fracture resistance can be obtained. Considering the fracture resistance, the nitrogen adsorption specific surface area (N ２ SA) is preferably 80 m ２ / g or more. Usually, the smaller the particle size of carbon black, the larger the nitrogen adsorption specific surface area tends to be. By using carbon black with a large nitrogen adsorption specific surface area, it becomes possible to obtain a rubber composition excellent in fracture resistance. However, when the nitrogen adsorption specific surface area of carbon black exceeds 110 m ２ / g and becomes too high, the rolling resistance of the tire to which the rubber composition is applied tends to deteriorate. The nitrogen adsorption specific surface area of carbon black is preferably 100 m ２ / g or less. The nitrogen adsorption specific surface area of the carbon black of the present invention is more preferably 80 m ２ / g or more and 100 m ２ / g or less. The nitrogen adsorption specific surface area (N ２ SA) is a value measured in accordance with ISO 4652-1.

[0054] Further, the carbon black of the present invention preferably has a specific coloring power of 55 or more measured in accordance with JIS K 6217-5. The specific coloring power is one of the parameters related to the particle size and specific surface area of carbon black. When the specific coloring power is 55 or more, sufficient fracture resistance can be obtained. The specific coloring power is preferably 60 or more, more preferably 65 or more, further preferably 70 or more, and particularly preferably 80 or more.

[0055] (Another Embodiment) In addition to the carbon black of the above-described embodiment, the present invention further includes the carbon black of the following embodiment. The carbon black of the other embodiment comprises one or more elements selected from the group consisting of Zn, Fe, and Cu, characterized in that the Zn content is 0% by mass or more and 2.5% by mass or less, or the Fe content is 0% by mass or more and 0.1% by mass or less.

[0056] In yet another embodiment, the carbon black is characterized by containing 0.5% by mass or more of S, optionally containing Zn, wherein the Zn content is 0% by mass or more and 2.5% by mass or less, or optionally containing Fe, wherein the Fe content is 0% by mass or more and 0.1% by mass or less.

[0057] [Method for producing carbon black] The carbon black of the present invention is produced from solid residue generated by thermally decomposing a rubber product containing carbon black. The method for producing carbon black of the present invention includes the steps of thermally decomposing a rubber product containing carbon black and obtaining carbon black from the solid residue.

[0058] In the present invention, the rubber product containing carbon black as a raw material is, for example, a used tire. Preferably, the used tire is recovered from a large vehicle such as a truck or bus, or from a passenger car. The rubber product may be pre-crushed before the thermal decomposition process.

[0059] In the pyrolysis process, known apparatus can be used to pyrolyze rubber products containing carbon black. For example, fuel, nitrogen, and the rubber product are introduced into a pyrolysis furnace, and pyrolysis is carried out. As a result of this pyrolysis process, solid residue and volatile components are produced from the rubber product.

[0060] After the thermal decomposition process, the solid residue and volatile components are separated by a known method. The volatile components are converted into oil (decomposition oil) upon cooling.

[0061] The solid residue after separation is collected. If necessary, impurities such as zinc oxide, silica, and iron compounds (iron oxide) are removed from this solid residue to recover recycled carbon black. Known methods can be used to remove impurities. By performing such an impurity removal process, even if the amount of ash in the obtained solid residue is large, carbon black that satisfies the above-mentioned amount of ash and the amount of components in the ash can be obtained.

[0062] Furthermore, in the process of treating the above-mentioned impurities, hydrofluoric acid treatment or high-temperature acid treatment is preferred. For example, the method described in Japanese Patent Publication No. 2021-521323 can be used for high-temperature acid treatment.

[0063] <Rubber Composition> The rubber composition of the present invention contains the above-mentioned carbon black. Because the rubber composition contains the above-mentioned carbon black, the deterioration of physical properties is suppressed. The rubber composition of the present invention is not particularly limited other than containing the above-mentioned carbon black, and can be any carbon black that is commonly used in the manufacture of tires. Each component is described below.

[0064] (Rubber component) In the rubber composition of the present invention, the type of rubber is not particularly limited. Examples include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butyl rubber (IIR), ethylene-propylene-diene copolymer (EPDM), acrylonitrile-butadiene copolymer (NBR), and rubbers that are combinations thereof.

[0065] (Filler) The rubber composition of the present invention may contain a filler that reinforces the rubber composition. In the present invention, the rubber composition contains the carbon black described above (hereinafter also referred to as "carbon black of the present invention"). The amount of carbon black blended in the rubber composition can be appropriately adjusted depending on the part of the tire to which the resulting rubber will be applied. For example, the amount of carbon black blended in the present invention can be adjusted within the range of 1 to 150 parts by mass per 100 parts by mass of the rubber component. By using the carbon black of the present invention in the rubber composition, a decrease in physical properties can be suppressed.

[0066] In the present invention, the rubber composition may contain ordinary carbon black in addition to the carbon black of the present invention. When ordinary carbon black is used, the grade is not particularly limited. From the viewpoint of promoting the use of recycled materials, it is preferable that the amount of ordinary carbon black included is as small as possible, and it is particularly preferable that it is not included at all. Furthermore, it is preferable that the amount of ordinary carbon black included is less than the amount of carbon black of the present invention. However, depending on the specifications required for the rubber product, the amount of ordinary carbon black may be increased relative to the carbon black of the present invention. The amount of ordinary carbon black included can be adjusted, for example, within the range of 0 to 150 parts by mass per 100 parts by mass of the rubber component. In this case, it is preferable that the mass ratio of ordinary carbon black to the carbon black of the present invention (ordinary carbon black / carbon black of the present invention) be within the range of 95 / 5 to 0 / 100.

[0067] Furthermore, the rubber composition of the present invention may contain silica and other inorganic fillers as fillers. The types of fillers other than carbon black, and the amounts of each filler, can be appropriately selected depending on the part of the tire to which they are applied.

[0068] In the present invention, there are no particular restrictions on the type of silica, and examples include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, aluminum silicate, etc., with wet silica being preferred among these. These silicas may be used individually or in combination of two or more types. Furthermore, in the present invention, the physical properties of the silica used, such as the BET specific surface area and the cetyltrimethylammonium bromide specific surface area (CTAB), are not particularly limited and can be appropriately selected according to the performance of the tire obtained from the rubber composition. In addition, the amount of silica blended in the rubber composition is not particularly limited and can be appropriately selected according to the performance required of the tire.

[0069] In the present invention, there are no particular restrictions on the type of inorganic filler; for example, clay, talc, calcium carbonate, aluminum hydroxide, etc., can be used. These inorganic fillers can be appropriately selected considering their various physical properties.

[0070] (Various Components) The rubber composition of the present invention may contain various components commonly used in the rubber industry, as necessary, to the extent that the effects of the present invention are not impaired. Examples of such components include stearic acid, antioxidants, zinc oxide, vulcanizing agents, vulcanization accelerators, resins, oils, silane coupling agents, and the like.

[0071] <Rubber Products> The rubber products of the present invention are selected from the group consisting of tires, rubber tracks, and hoses, using the rubber composition described above. Because the rubber products of the present invention use the rubber composition described above and, consequently, contain the carbon black described above, the deterioration of physical properties is suppressed.

[0072] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0073] <Measurement Method and Evaluation Method> (1) Amount of Components in Carbon Black The amounts of components such as Zn, Fe, and S in carbon black were measured by X-ray fluorescence analysis.

[0074] (2) Ash Content The ash content of carbon black was measured by thermogravimetric analysis (TGA, RIGAKU Corporation). The sample was heated from room temperature to 550°C under a nitrogen atmosphere, and then heated to maintain 550°C under an air atmosphere, and the loss on heating was measured. The loss on heating (mass%) when the sample was heated from room temperature to 550°C under a nitrogen atmosphere was defined as "Loss on Heating 1," and the loss on heating (mass%) when heated to maintain 550°C under an air atmosphere was defined as "Loss on Heating 2." The ash content was calculated using the following formula: Ash content (mass%) = 100 - Loss on Heating 1 - Loss on Heating 2

[0075] (3) The rubber compositions of the standard example, examples, and comparative examples were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. Tensile tests were performed on each vulcanized rubber at room temperature in accordance with JIS K6301-1995 to measure its tensile strength. The tensile strength of the standard example specimen was set to 100, and the tensile strength was expressed as an index using the following formula: Tensile strength index = (Tensile strength of specimens other than the standard example / Tensile strength of the standard example specimen) × 100 A larger index indicates that the vulcanized rubber is less prone to breakage and has superior tensile strength.

[0076] (4) Viscoelasticity A viscoelasticity test was conducted using "ARES-G2" manufactured by TA Instruments Inc. under the conditions of a frequency of 15 Hz, shear strain of 10%, and temperature of 50°C, and the storage modulus (G') of the rubber composition was measured. The evaluation results were indexed with the standard example as the control (index value 100). A higher index indicates a higher G', which in turn indicates superior rubber properties when applied to products such as tires.

[0077] <Evaluation of physical properties based on Zn content in carbon black> Carbon black (CB) and styrene-butadiene rubber with different ash content, Zn content, and sulfur content were kneaded in the formulations shown in Table 1 below to prepare rubber compositions for each example. Each rubber composition was evaluated using the evaluation method described above. The evaluation results are shown in Table 1.

[0078]

[0079] *1 SBR: Styrene-butadiene rubber, product name "#1500" *2 CB1: Carbon Black 1, recycled carbon black equivalent to N330 *3 CB2: Carbon Black 2, recycled carbon black equivalent to N330 *4 CB3: Carbon Black 3, recycled carbon black equivalent to N330 *5 CB5: Carbon Black 5, new carbon black equivalent to N330

[0080] Table 1 shows that the deterioration of the physical properties of the rubber composition is suppressed in the examples.

[0081] <Evaluation of physical properties based on Fe content in carbon black> Carbon black (CB) and styrene-butadiene rubber with different ash, Zn, Fe, and S content were kneaded in the formulations shown in Table 2 below to prepare rubber compositions for each example. Each rubber composition was evaluated using the evaluation method described above. The evaluation results are shown in Table 2.

[0082]

[0083] *6 CB4: Carbon Black 4, Enrestec recycled carbon black

[0084] Table 2 shows that the deterioration of the physical properties of the rubber composition is suppressed in the examples.

[0085] According to the present invention, it is possible to provide a carbon black that can suppress the deterioration of the physical properties of a rubber composition when applied to it.

Claims

1. Carbon black comprising one or more elements selected from the group consisting of Zn, Fe, and Cu, wherein the Zn content is 0% by mass or more and 2.5% by mass or less.

2. Carbon black comprising one or more elements selected from the group consisting of Zn, Fe, and Cu, wherein the Fe content is 0% by mass or more and 0.1% by mass or less.

3. Carbon black containing 0.5% by mass or more of sulfur, and optionally containing Zn, wherein the Zn content is 0% by mass or more and 2.5% by mass or less.

4. Carbon black containing 0.5% by mass or more of S, and optionally containing Fe, wherein the Fe content is 0% by mass or more and 0.1% by mass or less.

5. The carbon black according to claim 1 or 2, further comprising 0.4% by mass or more of S.

6. The carbon black according to any one of claims 1 to 4, wherein the Zn content is 1.0% by mass or less.

7. The carbon black according to any one of claims 1 to 4, wherein the Fe content is 0.06% by mass or less.

8. The carbon black according to any one of claims 1 to 4, wherein the Si content is 0% by mass or more and 1.0% by mass or less.

9. The carbon black according to any one of claims 1 to 4, wherein the ash content is 6.0% by mass or less.

10. A rubber composition comprising the carbon black described in any one of claims 1 to 4.

11. A rubber product selected from the group consisting of tires, rubber tracks, and hoses, using the rubber composition described in claim 10.

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