Reclaimed rubber-containing rubber composition

Abstract

To provide a rubber composition which hardly generates heat and has excellent cut resistance, while containing a reclaimed rubber.SOLUTION: The rubber composition is obtained by blending a diene rubber, carbon black and / or silica, and a cellulose-containing reclaimed rubber. The rubber composition contains 30-100 pts.mass of the total of the carbon black and the silica and 5-25 pts.mass of the cellulose-containing reclaimed rubber based on 100 pts.mass of the diene rubber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rubber composition containing reclaimed rubber, and a tire using the rubber composition containing reclaimed rubber. [Background technology]

[0002] From the viewpoint of reducing the environmental load, used rubber products (waste rubber products) such as waste tires are turned into waste rubber powder, which is then devulcanized and processed into reclaimed rubber, which is then blended with new rubber components (virgin rubber components) into a rubber composition for reuse. However, since the physical properties of this reclaimed rubber after vulcanization are inferior to those of new rubber (virgin rubber), there is an issue that the physical properties of the rubber composition blended with the reclaimed rubber are poor, failing to reach a practical level, or that the targets of use are limited.

[0003] In response to this, various studies have been conducted. For example, Patent Document 1 discloses a method in which waste rubber products are crushed and then subjected to desulfurization and functionalization treatments under specified conditions to increase the reactivity of the reclaimed rubber itself and improve the physical properties of the rubber after vulcanization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-212377 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, even in rubber compositions containing recycled rubber that has been subjected to such treatment, there have been many cases where sufficient performance such as mechanical properties has not been obtained. In particular, rubber compositions used in the manufacture of tires for construction vehicles and the like are required to have both cut resistance and low heat generation (the property of being less likely to generate heat), but when recycled rubber is used in such rubber compositions, it is extremely difficult to achieve both cut resistance and low heat generation (particularly, maintaining low heat generation is difficult), and the industry has been required to develop a recycled rubber-containing rubber composition that is suitable for the manufacture of tires for construction vehicles and the like and that has both cut resistance and low heat generation.

[0006] Therefore, an object of the present invention is to provide a rubber composition which contains reclaimed rubber and yet is resistant to heat generation and has excellent cut resistance. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors conducted extensive research and discovered that a rubber composition which contains a diene rubber, carbon black and / or silica, and cellulose-containing reclaimed rubber in a total amount of 30 to 100 parts by mass of the carbon black and silica and 5 to 25 parts by mass of the cellulose-containing reclaimed rubber per 100 parts by mass of the diene rubber, is resistant to heat generation and has excellent cut resistance, despite containing reclaimed rubber, and thus completed the present invention.

[0008] That is, the present invention provides the following <1> ~ <7> It is. <1> A rubber composition containing a diene rubber, carbon black and / or silica, and cellulose-containing reclaimed rubber, the rubber composition containing 30 to 100 parts by mass of the carbon black and the silica in total, and 5 to 25 parts by mass of the cellulose-containing reclaimed rubber, per 100 parts by mass of the diene rubber. <2> The cellulose-containing regenerated rubber contains 0.5 to 16% by mass of cellulose. <1> The rubber composition according to claim 1. <3> The cellulose contained in the cellulose-containing regenerated rubber is powdered cellulose. <1> or <2> The rubber composition according to claim 1. <4> The cellulose contained in the cellulose-containing regenerated rubber is cellulose nanofiber and / or cellulose nanocrystal. <1> or <2> The rubber composition according to claim 1. <5> The cellulose-containing reclaimed rubber is a cellulose-containing reclaimed rubber containing petroleum-derived oil. <1> ~ <4> The rubber composition according to any one of the above. <6> The cellulose-containing reclaimed rubber is a cellulose-containing reclaimed rubber containing a non-petroleum-derived and naturally-derived oil. <1> ~ <4> The rubber composition according to any one of the above. <7> <1> ~ <6> A tire using the rubber composition according to any one of claims 1 to 5. Effect of the Invention

[0009] According to the present invention, a rubber composition which is resistant to heat generation and has excellent cut resistance while containing reclaimed rubber can be obtained. [Brief description of the drawings]

[0010] [Figure 1] 1 is a partial cross-sectional schematic view of a tire showing an example of an embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will now be described. The present invention relates to a rubber composition which contains a diene rubber, carbon black and / or silica, and cellulose-containing reclaimed rubber, and contains 30 to 100 parts by mass of the carbon black and silica in total and 5 to 25 parts by mass of the cellulose-containing reclaimed rubber per 100 parts by mass of the diene rubber, and a tire using this rubber composition. Hereinafter, these are also referred to as the "rubber composition of the present invention" and the "tire of the present invention".

[0012] In the present invention, unless otherwise specified, a numerical range expressed using "~" means a numerical range having the numerical value before "~" as the lower limit and the numerical value after "~" as the upper limit.

[0013] The components and materials contained in the rubber composition of the present invention, their contents, etc. will be described in detail below.

[0014] [Diene rubber (diene rubber with new rubber component)] The diene rubber of the new rubber component (virgin rubber component) compounded in the rubber composition of the present invention is a rubber component having a double bond in the polymer main chain, and specific examples thereof include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), synthetic isoprene rubber (IR), etc. These diene rubbers can be used alone or in combination of two or more kinds.

[0015] In particular, in the rubber composition of the present invention, it is preferable that the diene rubber of the new rubber component contains NR and / or IR. Furthermore, from the viewpoint of use in tires for construction vehicles, it is more preferable that the diene rubber contains NR and / or IR in total at preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, and even more preferably 90 mass% or more, and may be a diene rubber consisting of NR and / or IR. It is particularly preferable that the diene rubber of the new rubber component consists of NR.

[0016] The weight average molecular weight of each of these diene rubbers is preferably 50,000 to 3,000,000, and more preferably 100,000 to 2,000,000. Furthermore, each of these may be graft-modified with a vinyl monomer or epoxidized with an organic peracid. In the present invention, the "weight average molecular weight" refers to a value measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent. The GPC measurement is performed at 40°C using a column (MIXED-B, manufactured by Polymer Laboratories) as a measuring instrument.

[0017] The rubber composition of the present invention may contain new rubber components other than diene-based rubber, but it is preferable that the new rubber components contained therein are 90% by mass or more of diene-based rubber, more preferably 95% by mass or more of diene-based rubber, and even more preferably that the new rubber components contained therein consist of diene-based rubber (100% by mass of diene-based rubber).

[0018] [Carbon black] The carbon black to be blended in the rubber composition of the present invention is not particularly limited, and any known carbon black used in applications such as tires can be used. For example, specific examples of carbon black that can be used include various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF, FT, and MT. The carbon black may be used alone or in combination of two or more types. The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 70 to 145 m, particularly from the viewpoint of use in tires for construction vehicles. 2 / g, and 85 to 130m 2 It is more preferable that the nitrogen adsorption specific surface area (N2SA) of this carbon black is 70 m 2 When the nitrogen adsorption specific surface area (N2SA) of the carbon black is less than 145 m 2 If it exceeds 1 / g, it tends to become difficult to maintain the low heat build-up property of the rubber composition. The term "carbon black" means fine carbon particles consisting of primary particles with a diameter of about 3 to 500 nm, which are industrially produced under quality control. The nitrogen adsorption specific surface area (N2SA) of carbon black is the amount of nitrogen adsorbed on the carbon black surface, measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0019] In the rubber composition of the present invention, from the viewpoint of use in tires for construction vehicles, it is preferable to contain 30 to 60 parts by mass of this carbon black per 100 parts by mass of the diene rubber of the new rubber component. Furthermore, this amount is more preferably 35 parts by mass or more per 100 parts by mass of this diene rubber, and more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. If the amount of this carbon black is less than 30 parts by mass per 100 parts by mass of the diene rubber, it tends to be difficult to maintain the cut resistance of the rubber composition. If the amount of this carbon black exceeds 60 parts by mass per 100 parts by mass of the diene rubber, it tends to be difficult to maintain the low heat generation property of the rubber composition. Here, this amount is the amount of carbon black described above, and even if the above-mentioned specific carbon black is contained in the cellulose-containing reclaimed rubber described below, it is preferable to set the amount within the above range from the viewpoint of fully exerting the action of the specific carbon black in the rubber composition of the present invention. However, while the amount of the compounding satisfies the above, the total amount including the amount derived from the cellulose-containing reclaimed rubber (and the amount of the compounding) may also be within the above range.

[0020] [silica] The silica to be compounded in the rubber composition of the present invention is not particularly limited, and any known silica compounded in rubber compositions for use in tires and the like can be used. Specific examples include wet silica, dry silica, fumed silica, diatomaceous earth, and the like, and such silica can be used alone or in combination of two or more kinds. In particular, from the viewpoint of use in tires for construction vehicles, it is preferable that the CTAB specific surface area of ​​the silica contained in the rubber composition of the present invention is 110 to 200 m2 / g is more preferable, and 150 to 180m 2 It is even more preferred that the weight ratio is / g. The term "silica" means a particulate material made of silicon dioxide (SiO2) or containing silicon dioxide as the main component (e.g., 80% by mass or more, or even 90% by mass or more). The CTAB specific surface area of ​​silica is a value measured according to "ISO5794 / 1".

[0021] In the rubber composition of the present invention, from the viewpoint of use in tires for construction vehicles, it is preferable that the silica is contained in an amount of 10 to 40 parts by mass per 100 parts by mass of the diene rubber of the new rubber component. Furthermore, this amount is more preferably 20 parts by mass or more, and more preferably 30 parts by mass or less, per 100 parts by mass of the diene rubber. If the amount of silica is less than 10 parts by mass or more than 40 parts by mass per 100 parts by mass of the diene rubber, it tends to be difficult to maintain the cut resistance of the rubber composition. Here, this amount is also the amount of silica blended as described above, and even if silica is contained in the cellulose-containing reclaimed rubber described later, it is preferable to make the blended amount within the above range from the viewpoint of fully exerting the effect of silica in the rubber composition of the present invention. However, while the blended amount satisfies the above, the total amount including the amount derived from the cellulose-containing reclaimed rubber (and the blended amount) may also be within the above range.

[0022] The rubber composition of the present invention contains at least one of the above carbon black and silica, and contains 30 to 100 parts by mass of the carbon black and silica in total relative to 100 parts by mass of the diene rubber of the new rubber component. Furthermore, this amount is more preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more relative to 100 parts by mass of the diene rubber. Also, it is more preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less. If this amount is less than 30 parts by mass relative to 100 parts by mass of the diene rubber, the cut resistance of the rubber composition is not sufficient. Also, if this amount exceeds 100 parts by mass relative to 100 parts by mass of the diene rubber, the low heat generation property of the rubber composition cannot be maintained. Furthermore, it is more preferable that the total content of carbon black and silica satisfies the above range, and the content of carbon black and / or the content of silica is within the above range.

[0023] [Rosin-based resin] The rubber composition of the present invention is preferably blended with a rosin-based resin, particularly from the viewpoint of use in construction vehicle tires. Examples of the rosin-based resin blended in the rubber composition of the present invention include modified rosins such as gum rosin, wood rosin, tall rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleic rosin, and fumaric rosin, ester derivatives of these rosins such as glycerin ester, pentaerythritol ester, methyl ester, and triethylene glycol ester, and rosin-modified phenolic resins, and such rosin-based resins can be used alone or in combination of two or more kinds. Among these, polymerized rosin or rosin ester derivatives are more preferred. In particular, from the viewpoint of use in construction vehicle tires, the softening point of the rosin-based resin contained in the rubber composition of the present invention is more preferably 90 to 120°C, and even more preferably 95 to 115°C. For the same reason, the acid value of the rosin resin contained in the rubber composition of the present invention is more preferably 80 to 130 KOHmg / g, and further preferably 90 to 120 KOHmg / g. The softening point of the rosin-based resin is a value measured by a method conforming to JIS K6220-1: 2015. The acid value of the rosin-based resin is the amount of potassium hydroxide required to neutralize the acid contained in 1 g of the resin, expressed in milligrams, and is a value measured by potentiometric titration (JIS K 0070: 1992).

[0024] In the rubber composition of the present invention, the rosin resin is preferably contained in an amount of 0.2 to 10 parts by mass per 100 parts by mass of the diene rubber of the new rubber component. Furthermore, this amount is more preferably 1 part by mass or more, more preferably 2 parts by mass or more, more preferably 3 parts by mass or more, more preferably 4 parts by mass or more, more preferably 9 parts by mass or less, and more preferably 8 parts by mass or less per 100 parts by mass of the diene rubber. If the amount of the rosin resin is less than 0.2 parts by mass per 100 parts by mass of the diene rubber, it tends to be difficult to maintain the cut resistance of the rubber composition. If the amount of the rosin resin is more than 10 parts by mass per 100 parts by mass of the diene rubber, it tends to be difficult to maintain the low heat generation property of the rubber composition. Here, this amount is also the blending amount of the rosin-based resin described above, and even when the rosin-based resin is contained in the cellulose-containing reclaimed rubber described below, it is preferable to set the blending amount within the above range from the viewpoint of fully exerting the effect of the rosin-based resin in the rubber composition of the present invention. However, while the blending amount satisfies the above, the total amount including the amount derived from the cellulose-containing reclaimed rubber (and the blending amount) may also be within the above range.

[0025] [Regenerated rubber containing cellulose] The rubber composition of the present invention is blended with cellulose-containing reclaimed rubber, which is a reclaimed rubber containing cellulose. That is, the rubber composition of the present invention is a rubber composition containing reclaimed rubber. The rubber composition of the present invention contains this cellulose-containing reclaimed rubber as reclaimed rubber in a predetermined composition, and thus has excellent cut resistance and low heat generation properties while containing reclaimed rubber. The cellulose-containing reclaimed rubber is a reclaimed rubber obtained by recycling waste rubber products and contains cellulose, and is substantially unvulcanized before being blended into the rubber composition of the present invention. Although not limited thereto, for example, waste rubber powder (waste tire rubber powder, etc.) obtained by crushing, separating foreign matter, classifying, finely crushing, separating foreign matter, and classifying waste rubber products such as waste tires in this order is added with cellulose, oil, and a desulfurizing agent (e.g., dibenzamide diphenyl disulfide (Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.), etc.), mixed with heat, and desulfurized to obtain desulfurized rubber powder, and the cellulose-containing reclaimed rubber (reclaimed rubber powder, etc.) formed using the desulfurized rubber powder can be exemplified.

[0026] The cellulose content in the cellulose-containing reclaimed rubber is preferably 0.5 to 16% by mass, since this makes it easier for the effects of the present invention to be fully exhibited. The lower limit is more preferably 1% by mass or more, even more preferably 2% by mass or more, even more preferably 3% by mass or more, even more preferably 4% by mass or more, and even more preferably 5% by mass or more. The upper limit is more preferably 14% by mass or less, even more preferably 12% by mass or less, even more preferably 10% by mass or less, even more preferably 9% by mass or less, and even more preferably 8% by mass or less.

[0027] The cellulose contained in the cellulose-containing regenerated rubber may be, for example, powdered cellulose. This allows for a relatively inexpensive cellulose-containing regenerated rubber. Here, the powdered cellulose does not include nanocellulose powder (such as cellulose nanocrystal powder) described later. Examples of the powdered cellulose include Viscopal (a product of Rengo Co., Ltd.) as a roughly spherical (uncontrolled shape) powdered cellulose, and KC Flock (a product of Nippon Paper Industries Co., Ltd.) as a fibrous powdered cellulose, but are not limited thereto. The average particle diameter of this powdered cellulose (D 50 ) is not limited, but is preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, even more preferably 400 μm or less, even more preferably 250 μm or less, and even more preferably 100 μm or less. The lower limit may be 5 μm or more, and may further be 10 μm or more. Here, this "average particle diameter (D 50 "The volume-based average particle diameter (50% volume cumulative distribution diameter (D 50 )).

[0028] The cellulose contained in the cellulose-containing regenerated rubber is preferably cellulose nanofiber and / or cellulose nanocrystal. This is because the cellulose-containing regenerated rubber containing these is particularly likely to improve the cut resistance of the rubber composition of the present invention. These are collectively called "nanocellulose", and nanocellulose containing amorphous, which is an ultrafine fiber with an average fiber diameter of 1 to 1000 nm and an average fiber length of 0.5 to 5 μm, is cellulose nanofiber (CNF, for example, Cellenpia manufactured by Nippon Paper Industries Co., Ltd.), which is also called microfibrillated cellulose. In addition, crystalline (for example, needle-shaped crystals or spherical crystals) nanocellulose that is an ultrafine fiber with an average fiber diameter of 1 to 1000 nm and an average fiber length of 0.1 to 0.5 μm is cellulose nanocrystal (CNC, for example, Cellulose Nanocrystal manufactured by Fillerbank Co., Ltd.).

[0029] As described above, the average fiber diameter of the cellulose nanofibers and cellulose nanocrystals is 1 to 1000 nm, but it is preferably 1 to 200 nm. The average aspect ratio (average fiber length / average fiber diameter) is preferably 10 to 1000, more preferably 50 to 500. If the average fiber diameter is less than the above range and / or the average aspect ratio exceeds the above range, the dispersibility in the reclaimed rubber tends to be low. If the average fiber diameter exceeds the above range and / or the average aspect ratio is less than the above range, the reinforcing performance tends to be easily reduced.

[0030] Here, the "average fiber diameter" and "average fiber length" refer to the average fiber diameter and fiber length values ​​obtained by obtaining an electron microscope image by TEM or SEM observation at a magnification appropriately set according to the size of the constituent fibers, and measuring at least 50 or more fibers in the image. The average aspect ratio is calculated from the average fiber length and average fiber diameter thus obtained.

[0031] In addition, these celluloses (cellulose as a raw material in the case of nanocellulose) may be derived from wood or non-wood (bacteria, algae, cotton, etc.), and are not particularly limited. In addition, examples of the above-mentioned method for producing nanocellulose include a method in which water is added to the raw cellulose, processed with a mixer, etc. to prepare a slurry in which cellulose is dispersed in water, and this is directly defibrated by applying mechanical shear force using a high-pressure or ultrasonic device, and a method in which this slurry is subjected to chemical treatment such as oxidation treatment, alkali treatment, acid hydrolysis, etc. to modify the cellulose to make it easier to defibrate, and then defibrated by applying mechanical shear force using a disperser, etc. By performing such chemical treatment before defibration, the cellulose can be defibrated more finely and uniformly with low energy, and chemically modified nanocellulose (chemically modified nanocellulose) can be easily obtained. Examples of chemical treatments include treatments using chemical treatment agents such as 2,2,6,6-tetramethylpiperidine-1-oxyl (hereinafter referred to as "TEMPO"), 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-amino-TEMPO, 4-hydroxy-TEMPO, 4-phosphonooxy-TEMPO, phosphoric esters, periodic acid, alkali metal hydroxides, and carbon disulfide. Chemical treatments may also be performed after mechanical defibration of cellulose. In addition to the above-mentioned chemical treatments, in order to further increase the affinity with waste rubber powder, cellulase treatment, carboxymethylation, esterification, and treatment with cationic polymers may also be performed after the defibration step.

[0032] Furthermore, the cellulose-containing reclaimed rubber is preferably a cellulose-containing reclaimed rubber containing oil as described above. In particular, by adding oil together with the cellulose during devulcanization of waste rubber powder, the dispersibility of cellulose in the reclaimed rubber is further increased. The oil content in the cellulose-containing reclaimed rubber is preferably 4 to 50% by mass, since the effects of the present invention are easily exerted. The lower limit is more preferably 8% by mass or more, more preferably 12% by mass or more, more preferably 15% by mass or more, more preferably 18% by mass or more, and even more preferably 20% by mass or more. The upper limit is more preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

[0033] This cellulose-containing reclaimed rubber may contain, for example, petroleum-derived oil. This petroleum-derived oil is oil obtained from petroleum, and examples thereof include process oils such as TDAE (Treated Distillate Aromatic Extract) oil (a product of Shell Lubricants Japan), but is not limited thereto.

[0034] Alternatively, the cellulose-containing regenerated rubber preferably contains a non-petroleum-derived and natural oil. In other words, it is preferable that the cellulose-containing regenerated rubber is not derived from petroleum and contains an oil obtained from animals, plants, microorganisms, or a part thereof. This is because it has a higher affinity with the above-mentioned cellulose and is easy to increase its dispersibility. In particular, from this viewpoint, wood-derived oils are more preferable among the non-petroleum-derived and natural oils. The wood-derived oil is exemplified as a preferred example, such as tall oil (crude tall oil obtained during the manufacture of kraft pulp from wood such as pine, tall oil fatty acid, tall rosin, distilled tall oil, etc.), but is not limited thereto. It is more preferable that the wood-derived oil contains more than 50 mass% of fatty acid and resin acid (for example, one or more selected from the group consisting of abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, and dehydroabietic acid) in total, and the mass ratio of resin acid to fatty acid (resin acid / fatty acid) is 0.9 or more, further 1.0 or more, and further 1.1 or more. The upper limit is more preferably 2.0 or less, even more preferably 1.8 or less, and even more preferably 1.5 or less.

[0035] In addition to the above, the cellulose-containing regenerated rubber may contain components derived from waste rubber products (waste rubber powder, etc.). For example, it may contain polymer components (rubber components, resin components, etc.) derived from waste rubber products, and inorganic fillers (carbon black, silica, etc.) derived from waste rubber products. An example of waste rubber powder obtained from a waste rubber product is waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than carbon black of 15% by mass or less, and an oil content of less than 10% by mass. A preferred example is cellulose-containing regenerated rubber that has been desulfurized by adding cellulose, oil, etc. to the waste rubber. The main component of the polymer component (75% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more of the polymer component) is a rubber component, but may also contain a resin component. The lower limit of the polymer component content of the waste rubber powder is more preferably 42% by mass or more. The upper limit is 80% by mass or less, and more preferably 75% by mass or less. Also, the carbon black content is more preferably 20 to 30% by mass. Furthermore, the upper limit of the total content of inorganic materials other than carbon black is more preferably 12% by mass or less, and even more preferably 10% by mass or less. Examples of inorganic materials other than carbon black include silica, clay, calcium carbonate, magnesium carbonate, mica, talc, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, barium sulfate, and zinc oxide (zinc oxide). Furthermore, the upper limit of the oil content (oil content in the waste rubber powder) is more preferably 8% by mass or less, and even more preferably 5% by mass or less. In addition to the components derived from waste rubber products (waste rubber powder), this cellulose-containing reclaimed rubber may also contain materials used in the production of the reclaimed rubber, such as unreacted devulcanizing agents, etc. Also, it is preferable that the main part of the rubber component contained in this cellulose-containing reclaimed rubber (75% by mass or more, preferably 80% by mass or more of the rubber component) is diene-based rubber (reclaimed diene-based rubber), and it is more preferable that the main part is natural rubber (reclaimed natural rubber).

[0036] The carbon black content in the cellulose-containing reclaimed rubber is preferably 30% by mass or less, more preferably 25% by mass or less, and the silica content in the cellulose-containing reclaimed rubber is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

[0037] The rubber composition of the present invention contains such cellulose-containing reclaimed rubber in an amount of 5 to 25 parts by mass per 100 parts by mass of the diene rubber of the new rubber component. This makes it possible to improve cut resistance while suppressing heat generation while containing reclaimed rubber (both of these can be increased). This content is more preferably 6 parts by mass or more per 100 parts by mass of this diene rubber, more preferably 7 parts by mass or more, more preferably 8 parts by mass or more, more preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and even more preferably 15 parts by mass or less. If the content of this cellulose-containing reclaimed rubber is less than 5 parts by mass or more than 25 parts by mass per 100 parts by mass of the diene rubber, it is not preferable because the low heat generation property of the rubber composition cannot be maintained. In addition, there is a possibility that other mechanical properties and the like will not be sufficient. Here, even if the above-mentioned carbon black, silica, oil, etc. are contained in the cellulose-containing regenerated rubber, the compounding amount of the cellulose-containing regenerated rubber is within the above-mentioned range. In other words, in the case of the cellulose-containing regenerated rubber containing the above-mentioned carbon black, silica, or oil, the content of the cellulose-containing regenerated rubber is the content of the cellulose-containing regenerated rubber including the carbon black, silica, or oil contained therein.

[0038] [Other ingredients] The rubber composition of the present invention may further contain appropriate amounts of various additives that are generally used in rubber compositions, such as inorganic fillers other than those mentioned above (e.g., clay, calcium carbonate, magnesium carbonate, mica, talc, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, barium sulfate, etc.), resin components other than those mentioned above, process oil, wax, zinc oxide (zinc oxide), stearic acid, lecithin, antioxidants, plasticizers, curing agents, vulcanizing agents (e.g., sulfur, etc.), vulcanization accelerators, and vulcanization acceleration aids, within the range that does not significantly affect the effects of the present invention, and these additives can be kneaded by a known method to form a rubber composition. However, the rubber composition of the present invention does not contain any material containing cellulose other than the cellulose-containing reclaimed rubber. In other words, the rubber composition of the present invention does not substantially contain any cellulose other than the cellulose derived from the cellulose-containing reclaimed rubber. Here, "substantially not contained" means that the content is less than 0.1% by mass.

[0039] For example, the content of the process oil in the rubber composition of the present invention is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the diene rubber of the new rubber component. This allows the hardness of the rubber composition of the present invention to be adjusted, and the processability of the rubber composition to be improved. The contents of the stearic acid, zinc oxide, and antioxidant in the rubber composition of the present invention are each preferably 1 to 5 parts by mass per 100 parts by mass of the diene rubber of the new rubber component. The content of the vulcanizing agent in the rubber composition of the present invention is preferably 0.3 to 3.0 parts by mass, more preferably 0.5 to 2.5 parts by mass, based on 100 parts by mass of the diene rubber of the new rubber component. The content of the vulcanization accelerator in the rubber composition of the present invention is preferably 0.3 to 3.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, based on 100 parts by mass of the diene rubber of the new rubber component ....

[0040] When the rubber composition of the present invention contains silica, it may further contain a silane coupling agent in order to further increase the dispersibility of the silica. The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The hydrolyzable group is also not limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxy group, and an alkenyloxy group, and more preferably an alkoxysilyl group in which the alkoxy group is bonded to a silicon atom. When the hydrolyzable group is an alkoxysilyl group, the number of carbon atoms in the alkoxy group is preferably 1 to 16, and more preferably 1 to 4. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

[0041] The organic functional group is not limited, but may be any group capable of forming a chemical bond with an organic compound, such as an epoxy group, a vinyl group, an acryloyl group, a methacryl group, an amino group, a sulfide group (particularly, a polysulfide group (-S n - (n is an integer of 2 or more), mercapto group, blocked mercapto group (protected mercapto group) (for example, octanoylthio group), etc., and among these, sulfide group (particularly disulfide group, tetrasulfide group), mercapto group, and blocked mercapto group are preferred. Such silane coupling agents may be used alone or in combination of two or more. The silane coupling agent is preferably a sulfur-containing silane coupling agent.

[0042] The rubber composition of the present invention preferably contains 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass, of the silane coupling agent relative to 100 parts by mass of silica.

[0043] [Manufacturing method etc.] The method for producing the rubber composition of the present invention may be a conventional method and is not particularly limited. As an example of the production method, the rubber composition of the present invention can be produced by kneading and mixing the diene rubber of the new rubber component, carbon black or silica, cellulose-containing regenerated rubber, and other components as necessary at room temperature or high temperature using a kneading machine such as a Banbury mixer, kneader, or roll at a predetermined ratio. When using a vulcanization-based component (sulfur, vulcanization accelerator, vulcanization accelerator assistant, etc.), it is preferable to first mix the other components at high temperature and then cool and mix the vulcanization-based component.

[0044] The rubber composition of the present invention obtained as described above has excellent cut resistance while containing reclaimed rubber. At the same time, it is less likely to generate heat, i.e., it has excellent low heat generation properties.

[0045] The tire of the present invention, which is less susceptible to heat generation and has excellent cut resistance, can be obtained by using the rubber composition for tires of the present invention. The tire of the present invention is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire can be, for example, air, inert gas such as nitrogen, argon, helium, or other gas.

[0046] In particular, by using the rubber composition of the present invention at least in the cap tread portion (e.g., the portion indicated by reference numeral 3 in FIG. 1) that contacts the road surface of the tire and / or the sidewall portion (e.g., the portion indicated by reference numeral 2 in FIG. 1) that constitutes the side surface of the tire, an excellent tire for construction vehicles can be obtained. Furthermore, it is more preferable to use the rubber composition of the present invention at least in the cap tread portion to make a tire for construction vehicles. The rubber composition of the present invention may be partially used in a part of the cap tread portion and / or the sidewall portion (e.g., the surface layer thereof). Furthermore, the tire of the present invention may be constructed by using the rubber composition of the present invention in members other than these (e.g., the bead portion indicated by reference numeral 1 in FIG. 1), or the entire tire of the present invention (the entire portion constituted by the rubber composition) may be constituted by the rubber composition of the present invention.

[0047] Hereinafter, examples of the present invention will be described, however, the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention. EXAMPLES

[0048] (Preparation and Evaluation of Rubber Compositions) Rubber compositions having the ingredients shown in Table 1 below were prepared.

[0049] Specifically, first, the components (except for the vulcanization accelerator and sulfur) in the mass parts shown in the upper part of Table 1 below were mixed for 5 minutes after heating to about 150°C using a 1.7-liter closed Banbury mixer, and then the mixture was discharged from the mixer and cooled to room temperature to obtain a master batch. Furthermore, using the Banbury mixer, a predetermined amount of the vulcanization accelerator and sulfur were mixed and kneaded with each of the obtained master batches, and the mixture was press-vulcanized at 170°C for 10 minutes in a predetermined mold to produce the rubber compositions (vulcanized rubber test pieces) of the standard example, comparative examples 1 to 3, and examples 1 to 3.

[0050] The rubber compositions (vulcanized rubber test pieces) obtained in the Standard Example, Comparative Examples 1 to 3, and Examples 1 to 3 were evaluated for heat build-up and cut resistance as follows.

[0051] <Fever> For each of the obtained vulcanized rubber test pieces, tan δ(60°C) was measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho under conditions of initial strain of 10%, amplitude of ±2%, frequency of 20 Hz and temperature of 60°C. The results are shown in the lower part of Table 1 below. The results are expressed as an index with the standard example value being 100, and the index was converted so that the lower the heat generation property, the higher the index. In other words, the higher the index, the more difficult it is to generate heat.

[0052] <Cut resistance> For each of the obtained vulcanized rubber test pieces, flex crack growth resistance was measured in accordance with JIS K6260. The results are also shown in the lower part of Table 1. The results are expressed as an index, with the crack length of the standard example after 30,000 flexions taken as 100. A higher index value indicates better cut resistance.

[0053] [Table 1]

[0054] The details of each component in Table 1 above are as follows: NR: Natural rubber (TSR20, glass transition temperature (Tg): -62°C) Reclaimed rubber: Reclaimed rubber formed from devulcanized rubber powder obtained by adding 1 part by mass of a desulfurizing agent (dibenzamide diphenyl disulfide: Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.) to 100 parts by mass of waste tire rubber powder (PolyDyne80: rubber powder with 105 μm mesh pass of 30% or more by mass, polymer component content of 42% or more by mass, carbon black content of 25 to 30% by mass, total content of inorganic materials other than carbon black of 8% or less by mass, oil content of 5% or less by mass, manufactured by Lehigh Technologies Co., Ltd.), heating and mixing, and desulfurizing the desulfurized rubber powder. Cellulose-containing regenerated rubber 1: 100 parts by mass of waste tire rubber powder (PolyDyne80) and powdered cellulose (Viscopal D-30: average particle size (D 50 A cellulose-containing regenerated rubber was formed from devulcanized rubber powder by adding 10 parts by mass of cellulose ether (20-40 μm, manufactured by Rengo Co., Ltd.), 30 parts by mass of TDAE (Treated Distillate Aromatic Extract) oil (Extract No. 4; petroleum-derived, manufactured by Shell Lubricants Japan Co., Ltd.), and 1 part by mass of a desulfurizing agent (dibenzamide diphenyl disulfide: Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.), heating and mixing the mixture, and desulfurizing the rubber powder. Cellulose-containing regenerated rubber 2: 100 parts by mass of waste tire rubber powder (PolyDyne80) are mixed with 10 parts by mass of oxidized cellulose nanofiber (CNF; Nippon Paper Industries, Cellenpia), 30 parts by mass of TDAE (Treated Distillate Aromatic Extract) oil (Extract No. 4; petroleum-derived, Shell Lubricants Japan), and 1 part by mass of a desulfurizing agent (dibenzamide diphenyl disulfide: Noctizer SS, Ouchi Shinko Chemical), and then heated and mixed to form a cellulose-containing regenerated rubber from the desulfurized rubber powder (CNF is added after being dispersed in water). Cellulose-containing regenerated rubber 3: 100 parts by mass of waste tire rubber powder (PolyDyne80) and powdered cellulose (Viscopal D-30: average particle size (D 50 A cellulose-containing regenerated rubber was formed from devulcanized rubber powder by adding 10 parts by mass of cellulose ether (20-40 μm, manufactured by Rengo Co., Ltd.), 30 parts by mass of tall oil (crude tall oil), and 1 part by mass of a desulfurizing agent (dibenzamide diphenyl disulfide: Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.), heating and mixing the mixture, and desulfurizing the devulcanized rubber powder. *Crude tall oil: A mixture of fatty acids and resin acids, obtained by neutralizing black liquor obtained during the manufacture of kraft pulp from pine wood (alkaline cooking), with an acid. The mass ratio of resin acids to fatty acids (resin acids / fatty acids) is approximately 1.2, and the resin acids include at least abietic acid, neoabietic acid, and palustric acid. Carbon black: Show Black N339 (Nitrogen adsorption specific surface area (N2SA): 88m 2 / g, manufactured by Gabot Japan) ·Silica: Zeosil 1165MP (CTAB adsorption specific surface area: 159m 2 / g, manufactured by Rhodia) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik Degussa) Process oil: Extract No. 4S (Shell Lubricants Japan) Rosin-based resin: Rosin-modified resin (Haritac AQ-90A, rosin ester, manufactured by Harima Chemical Group Co., Ltd.) Stearic acid: Stearic acid YR (NOF Corporation) Zinc oxide: Zinc oxide (ZnO, manufactured by Seido Chemical Industry Co., Ltd.) Anti-aging agent: Ozonone 6C (Seiko Chemical Co., Ltd.) Vulcanization accelerator: Noccela NS-P (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sulfur: Myucron OT-20 (manufactured by Shikoku Chemical Industry Co., Ltd.)

[0055] From these results, it was shown that in a rubber composition containing natural rubber, carbon black, silica, and cellulose-containing reclaimed rubber, by configuring the composition to contain 40 parts by mass of carbon black, 25 parts by mass of silica, and 10 parts by mass of cellulose-containing reclaimed rubber (containing about 7% by mass of cellulose) per 100 parts by mass of natural rubber (Examples 1 to 3), a rubber composition containing reclaimed rubber and having excellent low heat generation properties and cut resistance was obtained, as compared with the standard example. In particular, Example 3, which contains cellulose-containing reclaimed rubber containing natural product-derived oil, was less likely to generate heat and had better cut resistance. These were recognized to be rubber compositions particularly suitable for use in the cap tread and sidewall parts of tires for construction vehicles. On the other hand, the rubber composition containing recycled rubber that does not contain cellulose did not have sufficient low heat buildup (Comparative Example 1). Also, when the amount of cellulose-containing recycled rubber was outside the range, the low heat buildup was also insufficient (Comparative Examples 2 and 3). [Explanation of symbols]

[0056] 1 Bead section 2 Sidewall 3 Cap tread section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Rim cushion

Claims

1. A rubber composition containing a diene rubber, carbon black and / or silica, and cellulose-containing reclaimed rubber, A rubber composition comprising 30 to 100 parts by mass of the carbon black and the silica in total, and 5 to 25 parts by mass of the cellulose-containing reclaimed rubber, per 100 parts by mass of the diene rubber.

2. The rubber composition according to claim 1, wherein the cellulose-containing reclaimed rubber contains 0.5 to 16 mass % of cellulose.

3. 3. The rubber composition according to claim 1, wherein the cellulose contained in the cellulose-containing reclaimed rubber is powdered cellulose.

4. The rubber composition according to claim 1 or 2, wherein the cellulose contained in the cellulose-containing reclaimed rubber is cellulose nanofiber and / or cellulose nanocrystal.

5. 3. The rubber composition according to claim 1, wherein the cellulose-containing reclaimed rubber contains a petroleum-derived oil.

6. 3. The rubber composition according to claim 1, wherein the cellulose-containing reclaimed rubber is a cellulose-containing reclaimed rubber containing a non-petroleum-derived and naturally-derived oil.

7. A tire using the rubber composition according to claim 1 or 2.

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