Rubber composition, rubber product, and tire

Abstract

Provided is a rubber composition that exhibits superior low-exothermic property and cut resistance.　The present invention is characterized by comprising: a rubber component containing natural rubber; and a cyclic polyol compound (A) represented by the following formula [in the formula, A represents -H or an alkyl group having 1-20 carbon atoms, X1, X2, X3, X4, and X5 each independently represent -OH or -R (here, -R represents -H or -CH2OH), and at least two of X1, X2, X3, X4, and X5 represent -OH].

Description

Rubber compositions, rubber products, and tires

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

[0002] Various components are used as additives to rubber compositions to improve the functionality of rubber compositions and the crosslinked rubber obtained by crosslinking them. For example, a technique is disclosed to improve the adhesion in vulcanization bonding with steel cords and the hardness of the rubber by blending (B) 0.5 to 10 parts by weight of carbohydrates, (C) 0.5 to 10 parts by weight of methoxylated methylol melamine resin, and (D) 0.05 to 1 part by weight of cobalt salt of a cobalt carboxylate with 100 parts by weight of rubber selected from (A) natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, acrylonitrile butadiene copolymer rubber, chloroprene rubber, butyl rubber, and halogenated butyl rubber. Furthermore, a technique is disclosed to achieve both abrasion resistance and wet performance and ice performance by including a specific diene rubber and silica with a glass transition temperature and CTAB adsorption specific surface area specified within a specific range in the rubber composition.

[0003] However, the conventional technologies described above were inferior in terms of cut resistance and wear resistance under harsh conditions (high-visibility conditions), and further improvements were desired when considering their application to rubber products such as tires.

[0004] Therefore, in recent years, a technology has been developed to improve the cut resistance of rubber compositions by adding compounds having a polyol structure to them (see, for example, Patent Document 1). This technology makes it possible to improve cut resistance compared to conventional methods without degrading physical properties such as low heat generation.

[0005] Japanese Patent Publication No. 2022-184189

[0006] As described above, it has been found that by adding a compound having a polyol structure to a rubber composition, a certain effect of improving cut resistance can be obtained. However, with regard to cut resistance, further improvement has been desired so that it can be achieved at a high level even under severe conditions such as the tread and sidewall portions of tires for construction vehicles and trucks and buses. In addition to the above-described cut resistance, it has also been desired to improve the low heat generation property of the rubber composition.

[0007] Therefore, an object of the present invention is to provide a rubber composition excellent in low heat generation property and cut resistance. Another object of the present invention is to provide a rubber product and a tire excellent in low heat generation property and cut resistance.

[0008] The present inventors have conducted intensive studies to solve the above problems. As a result, by incorporating a cyclic polyol compound having a specific structure into a rubber composition containing a large amount of natural rubber as a rubber component, the cut resistance of the rubber composition can be greatly improved, and self-aggregation in the rubber composition can also be suppressed. As a result, it has been found that deterioration of the low heat generation property of the rubber composition can be suppressed.

[0009] That is, the rubber composition of the present invention comprises a rubber component containing natural rubber and a cyclic polyol compound (A) represented by the following formula: [In the formula, A is -H or an alkyl group having 1 to 20 carbon atoms, and X １ , X ２ , X ３ , X ４ and X ５ are each independently -OH or -R (where -R is -H or -CH ２ OH), provided that at least two of X １ , X ２ , X ３ , X ４ and X ５ are -OH]. By having the above configuration, excellent low heat generation property and cut resistance can be realized.

[0010] The vulcanized rubber composition of the present invention is characterized by being obtained by vulcanizing the above-described rubber composition. By having the above configuration, excellent low heat generation and cut resistance can be achieved.

[0011] The rubber product of the present invention is a rubber product using the above-described rubber composition, characterized in that the rubber product is a tire or a rubber crawler. By having the above configuration, excellent low heat generation and cut resistance can be achieved.

[0012] The tire of the present invention is characterized by using the above-described rubber composition in at least one of the tread portion and the sidewall portion. By having the above configuration, excellent low heat generation and cut resistance can be achieved.

[0013] According to the present invention, it is possible to provide a rubber composition with excellent low heat generation and cut resistance. Furthermore, according to the present invention, it is also possible to provide rubber products and tires with excellent low heat generation and cut resistance.

[0014] The embodiments of the present invention are described below in detail. <Rubber Composition> The rubber composition of the present invention is a rubber composition comprising a rubber component containing natural rubber and a cyclic polyol compound (A).

[0015] (Rubber component) As described above, the rubber component included in the rubber composition of the present invention contains at least natural rubber. When natural rubber is used together with the cyclic polyol compound (A) described later, excellent cut resistance and low heat generation can be obtained.

[0016] Here, the content ratio of natural rubber in the rubber component is not particularly limited, but it is preferably 50% by mass or more, more preferably 55% by mass or more, and particularly preferably 60% by mass or more. This is because by setting the content ratio of natural rubber in the rubber component to 50% by mass or more, when used together with the cyclic polyol compound (A) described later, improvements in cut resistance and low heat generation can be more reliably achieved.

[0017] Furthermore, the rubber component may contain any synthetic rubber in addition to the natural rubber. For example, it is preferable that the rubber component contains diene-based synthetic rubber in order to obtain excellent cut resistance and low heat generation.

[0018] Examples of the diene-based synthetic rubber include synthetic polyisoprene (IR) and styrene-butadiene copolymer rubber (SBR). The diene-based synthetic rubber in the rubber component may be contained alone or as a blend of two or more types. Furthermore, the rubber component may also contain non-diene-based synthetic rubber depending on the required performance.

[0019] Furthermore, the rubber component, including the natural rubber, may be modified with a modifying agent. Examples of modifying agents used for modification include compounds containing nitrogen, oxygen, and silicon.

[0020] (Cyclic polyol compound (A)) In addition to the rubber components described above, the rubber composition of the present invention comprises the following formula: [In the formula, A is -H or an alkyl group having 1 to 20 carbon atoms, X １ , X ２ , X ３ , X ４ and X ５ These are independently -OH or -R (where -R is -H or -CH). ２ OH) and however X １ , X ２ , X ３ , X ４ and X ５ The compound includes a cyclic polyol compound (A) represented by [at least two of which are -OH].

[0021] The cyclic polyol compound (A) contained in the rubber composition can significantly improve the cut resistance of the rubber composition of the present invention. Furthermore, by enhancing the interaction between the rubber molecules of the rubber component and the agent described later, the physical properties of the crosslinked rubber can be homogenized, resulting in improvements in low heat generation, reinforcing properties, abrasion resistance, etc. Moreover, because the cyclic polyol compound (A) has few hydrophilic parts, self-aggregation in the rubber composition can be suppressed, resulting in good maintenance of the low heat generation properties of the rubber composition.

[0022] Here, the content of the cyclic polyol compound (A) is preferably 0.1 to 8 parts by mass per 100 parts by mass of the natural rubber. If the content is less than 0.1 parts by mass per 100 parts by mass of the natural rubber, the amount of the cyclic polyol compound is insufficient to improve cut resistance, and the effect of low heat generation is also insufficient. On the other hand, if the content of the cyclic polyol compound (A) exceeds 8 parts by mass per 100 parts by mass of the natural rubber, the amount of the cyclic polyol compound becomes too large, which may cause self-aggregation in the rubber composition and lead to deterioration of physical properties such as tensile fatigue resistance. Also, from a similar viewpoint, the content of the cyclic polyol compound (A) is preferably 0.1 to 6 parts by mass, and more preferably 0.3 to 4 parts by mass, per 100 parts by mass of the natural rubber.

[0023] Here, in the cyclic polyol compound (A), A in the formula is -H or an alkyl group. The alkyl group of A has 1 to 20 carbon atoms, preferably 1 to 10. This is because the compatibility with rubber changes depending on the length of the alkyl group.

[0024] For the cyclic polyol compound (A) mentioned above, X in the formula １ , X ２ , X ３ , X ４ and X ５ However, each is independently -OH or -R (where -R is -H or -CH). ２ OH) and however X １ , X ２ , X ３ , X ４and X ５ At least two of them are -OH. This allows for excellent cut resistance. From a similar perspective, X １ , X ２ , X ３ , X ４ and X ５ Preferably, at least three of them are -OH groups.

[0025] The cyclic polyol compound (A) is preferably a cyclic polyol compound having a hydrocarbyl ether group. This is because it can achieve better extension fatigue resistance and cut resistance.

[0026] Examples of the cyclic polyol compound (A) include inositol monomethyl ether and inositol. These compounds may be used individually or in combination of two or more. Among these compounds, inositol monomethyl ether is preferred as the cyclic polyol compound (A) from the viewpoint of achieving a higher level of both low heat generation and cut resistance.

[0027] (Filler) The rubber composition of the present invention preferably further contains a filler in addition to the rubber components and cyclic polyol compounds described above. By including a filler together with the rubber components, properties such as cut resistance, abrasion resistance, and low heat generation of the vulcanized rubber composition can be further enhanced.

[0028] - Carbon Black The filler preferably contains at least carbon black. Including carbon black as a filler can further improve the cut resistance and abrasion resistance of the vulcanized rubber composition. The carbon black content is not particularly limited, but it is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component. If the carbon black content is 30 parts by mass or more per 100 parts by mass of the rubber component, the abrasion resistance and cut resistance can be further improved. Furthermore, the carbon black content is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less. By setting the carbon black content to 80 parts by mass or less per 100 parts by mass of the rubber component, the deterioration of low heat generation can be more reliably suppressed.

[0029] Furthermore, the carbon black can reinforce the rubber composition and improve its abrasion resistance. Preferred carbon blacks include plant-derived carbon black and carbon black obtained through recycling (also referred to as "recycled carbon black" or "regenerated carbon black"). Examples of plant-derived carbon black include those derived from castor oil and pine resin oil. Recycled carbon black will be described in detail below.

[0030] In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials submitted for recycling. Examples of such waste materials include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only that generated from rubber products, but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is fine rubber generated, for example, in the buffing process of retreading tires, where the tread portion remaining on the base tire is scraped off. Peeling rubber is long pieces of rubber, for example, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by scraping the surface of rubber products such as tires using a U-shaped or V-shaped knife like a peeler. Furthermore, waste rubber includes not only cross-linked rubber, but also unvulcanized rubber. Rubber products include, for example, final products such as tires, rubber hoses, and rubber conveyor belts, as well as rubber parts or components at the manufacturing stage of final products. Used tires may include, for example, tires that have been retreaded, tires generated from tire replacement or vehicle scrapping, and End-of-Life Tires (ELTs) that have reached the end of their lifespan, or any other type of tire that has been discarded for any reason. Waste oil is not limited to that generated when plastics and rubber are decomposed, but also includes used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oil that does not contain any non-organic composition, such as those derived from silicone rubber or polyvinyl chloride, is preferable. Furthermore, waste oil that is mixed with carbon black or rubber containing carbon black is preferable. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., carbon black that is not recycled. Note that "used" here includes not only those that have been actually used and then discarded, but also those that were manufactured but discarded without actually being used.

[0031] Furthermore, it is preferable that the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by thermal decomposition of a vulcanized rubber product containing carbon black is readily available because a large amount of vulcanized rubber product containing carbon black exists and it can be easily obtained by thermal decomposition. Moreover, it is preferable that the recycled carbon black is obtained from the solid residue generated by the thermal decomposition of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from either. When recovering carbon black from volatile components, it is possible to recover oil with a specific gravity suitable for producing carbon black and use it to produce carbon black using an existing carbon black production method (for example, Japanese Patent Publication No. 2015-520259). In this case, unlike carbon black recovered from solid residue, there are advantages such as the absence of impurities and the absence of mixtures of different grades. Furthermore, in the production of environmentally friendly carbon black, there are various options besides the oil obtained by recovering volatile components from the thermal decomposition of rubber mentioned above, such as using vegetable oil or oil derived from waste plastics. However, edible resources such as vegetable oil present challenges in securing sufficient quantities due to other uses such as food, and the environmental impact associated with the expansion of cultivated land must also be considered. Similarly, oil derived from waste plastics is used for other purposes such as horizontal recycling of plastics, so supply issues are also a concern. On the other hand, when using volatile components (oil) produced by the thermal decomposition of vulcanized rubber products, particularly tires, the tire industry has a system for continuing to use existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire manufacturing, thereby contributing to reducing the environmental burden on the industry. The grade of carbon black is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

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

[0033] The aforementioned ash content specifically includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from solid residue obtained by thermal decomposition of waste, a certain amount of ash remains even after various processes to remove it. In this embodiment, the presence of ash in recycled carbon black is permitted. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0034] Furthermore, the recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

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

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

[0035] The recycled carbon black may lack functional groups on its surface, or it may have been treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a thermal decomposition process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Japanese Patent Publication No. 6856781, carbon black obtained from a thermal decomposition process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black that has been treated to include functional groups on its surface.

[0036] Furthermore, for the thermal decomposition of cross-linked rubber products (vulcanized rubber products) such as used tires, one example is a thermal decomposition method at a temperature of 650°C or higher.

[0037] The cross-linked rubber products used in the aforementioned decomposition may be grouped by the type of rubber component they contain beforehand, and the decomposition process may be carried out for each group separately. Alternatively, they may be grouped by the type of filler they contain beforehand (for example, the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and the decomposition process may be carried out for each group separately. Furthermore, they may be grouped by both the type of rubber component and the type of filler, and the decomposition process may be carried out for each group separately. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again incorporated into the rubber component, a rubber composition with better performance can be obtained.

[0038] Furthermore, if the cross-linked rubber product used in the decomposition is derived from a tire, it may be grouped in advance by tire type (for example, for passenger cars, trucks and buses, heavy vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.) and then the decomposition process may be carried out for each group. Alternatively, it may be grouped in advance by tire component (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.) and then the decomposition process may be carried out for each group. Moreover, it may be possible to group by both tire type and tire component and then carry out the decomposition process for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again blended into the rubber component, a rubber composition with better performance can be obtained.

[0039] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m² obtained by the BET method. ２ It is preferable that the amount be / g, and 50 to 90 m ２ It is more preferable that the amount be / g, and 55 to 75 m ２ It is particularly preferable that the value be / g. Here, in this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black by the BET method is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556.

[0040] The recycled carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, in this specification, the pH of the recycled carbon black is determined according to ASTM D1512.

[0041] The recycled carbon black preferably has a toluene staining transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, in this specification, the toluene staining transmittance of recycled carbon black is determined according to ASTM D1618.

[0042] The recycled carbon black preferably has a heating loss of 3% by mass or less at 125°C, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Hereinafter, the heating loss of the recycled carbon black at 125°C is determined according to ASTM D1509.

[0043] The recycled carbon black 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.

[0044] The recycled carbon black preferably has a 35-mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Here, in this specification, the 35-mesh sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0045] The recycled carbon black preferably has a 325-mesh (44 μm) sieve residue of 1,000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. Here, in this specification, the 325-mesh (44 μm) sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0046] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Hereinafter, the pellet hardness of the recycled carbon black is determined according to ASTM D5230.

[0047] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Hereinafter, the pellet fine powder content of the recycled carbon black is determined according to ASTM D1508.

[0048] The recycled carbon black preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Hereinafter, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size analyzer, with the refractive index of water being 1.33 and the refractive index of the filler being 1.75.

[0049] The recycled carbon black preferably contains 50% or more by volume of particles 5 μm or smaller, more preferably 70% or more by volume, and particularly preferably 80% or more by volume.

[0050] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the various physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, in this specification, the ash content of the recycled carbon black is determined according to ASTM D8474 / D1506.

[0051] The recycled carbon black preferably has an oil absorption rate (OAN) of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Hereinafter, the oil absorption rate (OAN) of the recycled carbon black is determined according to ASTM D2414.

[0052] The recycled carbon black preferably has an oil absorption rate (COAN) of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Hereinafter, the oil absorption rate (COAN) of the compressed sample of recycled carbon black is determined according to ASTM D3493.

[0053] Commercially available recycled carbon black can be used. Examples of such commercially available products include "PB365" manufactured by Enrestec. PB365 is recycled carbon black produced by the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m² by the BET method. ２ It is 1 / g and also contains approximately 17% by mass of ash.

[0054] The recycled carbon black content is preferably 1 to 80 parts by mass, more preferably 5 to 70 parts by mass, even more preferably 5 to 50 parts by mass, even more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of rubber component. When the recycled carbon black content is 1 part by mass or more per 100 parts by mass of rubber component, it has a great effect in improving the ratio of sustainable materials in rubber products to which the rubber composition is applied, and when it is 80 parts by mass or less, the fracture resistance of the rubber composition can be maintained more reliably.

[0055] - Silica Furthermore, it is preferable that the filler contains silica. This is because it is possible to obtain better cut resistance, abrasion resistance, and low heat generation. The silica content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component. By setting the silica content to 20 parts by mass or less per 100 parts by mass of the rubber component, deterioration of the processability and low heat generation of the rubber composition can be suppressed.

[0056] The type of silica is not particularly limited. Examples include wet silica, colloidal silica, calcium silicate, and aluminum silicate. Among the above, wet silica is preferred, and precipitated silica is more preferred. These silicas may be used individually or in combination of two or more types.

[0057] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferred. Silica derived from silicate plants can be derived from plants such as mosses, ferns, horsetails, cucurbits, nettles, and grasses (rice, wheat, barley, oats, rye, millet, foxtail millet, barnyard millet, corn, sugarcane, adlay, Japanese pampas grass, Erianthus, etc.). Silica derived from silicate plants can also be produced using biomass such as rice husks, rice straw, wheat straw, and bagasse. Among these plants, grasses are preferred. Among grasses, silica derived from rice husks (hereinafter also called "rice husk silica") is particularly preferred from the viewpoint of availability. These raw materials may be ash produced by combustion treatment or carbonized treatment. These silicate plants may be used individually or in combination of two or more types. The silica mentioned above can also include silica recycled from semiconductor wafers (silicon wafers) and solar wafer waste, glass bottles, waste sand (such as casting sand), mining waste, construction waste, waste glass, waste rubber such as waste tires, etc., and used in manufacturing. These silicas may be used individually or in combination of two or more types. The silica derived from silicate plants and the silica recycled from silicon components can be used in any ratio. Furthermore, from the viewpoint of promoting the reduction of environmental burden throughout the entire lifecycle of manufacturing, use, and disposal, silica supplied by a mass balance method can also be used as the silica. Silica supplied by this mass balance method is silica to which biological resource-derived characteristics or recycled resource-derived characteristics are assigned in any ratio by the mass balance method.

[0058] The silica is not particularly limited, but for example, if its CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m² ２ / g or more, 250m ２ Silica of 0.35 nm or less can be used. The CTAB specific surface area refers to the value measured in accordance with ASTM D3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. ２The specific surface area (m²) is calculated from the amount of adsorption of CTAB. ２ The CTAB specific surface area is defined as ( / g). The BET specific surface area of ​​the silica is 100 m². ２ / g or more, 250m ２ It can be less than or equal to / g. The BET specific surface area is the specific surface area obtained by the BET method, and in this invention, it can be measured in accordance with ASTM D4820-93.

[0059] • Other fillers In addition to the carbon black and silica mentioned above, the fillers may also be the following general formula (XX): nM・xSiO ｙ ・zH ２ O ... (XX) [wherein M is at least one selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, oxides or hydroxides of these metals, hydrates thereof, or carbonates of these metals; n, x, y, and z are integers from 1 to 5, integers from 0 to 10, integers from 2 to 5, and integers from 0 to 10, respectively] may also include inorganic compounds represented by the general formula (XX). Examples of inorganic compounds of the general formula (XX) include alumina (Al) such as γ-alumina and α-alumina. ２ O ３ Alumina monohydrate (Al) such as boehmite and diaspore. ２ O ３ • Aluminum hydroxide [Al(OH)] such as H2O, gibbsite, and bayerite ３ ], aluminum carbonate [Al ２ (CO ３ ) ３ ], magnesium hydroxide [Mg(OH) ２ ], magnesium oxide (MgO), magnesium carbonate (MgCO2) ３ ), talc (3MgO・4SiO ２ H2O), attapulgite (5MgO・8SiO ２ 9H ２ O), Titanium White (TiO2), Titanium Black (TiO2) ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ ], magnesium aluminum oxide (MgO・Al ２ O３ ), clay (Al ２ O ３ ·2SiO ２ ), kaolin (Al ２ O ３ ·2SiO ２ ·2H ２ O), pyrophyllite (Al ２ O ３ ·4SiO ２ ·H2O), bentonite (Al ２ O ３ ·4SiO ２ ·2H ２ O), aluminum silicate (Al ２ SiO ５ , Al ４ ·3SiO ４ ·5H ２ O, etc.), magnesium silicate (Mg ２ SiO ４ , MgSiO ３ , etc.), calcium silicate (Ca ２ SiO ４ , etc.), calcium aluminum silicate (Al ２ O ３ ·CaO·2SiO ２ , etc.), calcium magnesium silicate (CaMgSiO ４ ), calcium carbonate (CaCO ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ ·nH ２ O], zirconium carbonate [Zr(CO ３ ) ２ , and crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals that correct charges, such as various zeolites. From the perspective of the balance between abrasion resistance and wet performance, the inorganic compound of the general formula (XX) preferably has an average particle size of 0.01 to 10 μm, more preferably 0.05 to 5 μm.

[0060] Here, the total content of the filler is not particularly limited, but is preferably 30 to 150 parts by mass, and more preferably 40 to 120 parts by mass, per 100 parts by mass of the rubber component. This is because optimizing the amount of the filler can further improve tire characteristics such as wear resistance, cut resistance, and low loss.

[0061] (Other Components) In addition to the rubber component, cyclic polyol compound (A), and filler described above, the rubber composition of the present invention may contain other components such as compounding agents commonly used in the rubber industry. These other components may include, for example, silane coupling agents, crosslinking agents, vulcanization accelerators, polyethylene glycol, softeners, resins, antioxidants, zinc oxide, etc., selected as appropriate within a range that does not impair the objectives of the present invention. Commercially available compounding agents can be suitably used. Furthermore, if the rubber composition of the present invention contains silica, it is preferable that the rubber composition of the present invention also contains a silane coupling agent to enhance the effect of the silica. The silane coupling agent includes bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, Examples include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide.Commercially available silane coupling agents can be used, and examples of such commercially available silane coupling agents include products from Evonik, Momentive, Shin-Etsu Silicone Co., Ltd., Toray Dow Corning Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used individually or in combination of two or more types.

[0062] The content of the silane coupling agent can be adjusted as appropriate depending on, for example, the tire category, tire components, target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, even more preferably 8 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of silica.

[0063] Furthermore, bioethanol can also be used as a raw material for silane coupling agents. Bioethanol is produced using mainly sugars and / or celluloses as biological resources, and does not allow for the effective utilization of other biological resources such as proteins, lipids, and amino acids. Moreover, sugars compete with food, and excessive use of celluloses leads to deforestation. For this reason, in addition to the supply situation of various biological resources, it is preferable to use multiple types of monomer components derived from biological resources, or to use a combination of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, depending on the supply situation of various biological resources, the supply situation of recycled resources, the supply situation of fossil resources, and market demands (for example, the demand for biomass resources as food). This allows for the effective utilization of a wide range of biological resources such as sugars, proteins, and lipids, as well as recycled resources, without relying on a single type of biological resource, and also allows for environmental considerations depending on the circumstances during production.

[0064] There are no particular restrictions on the crosslinking agent, and it can be appropriately selected depending on the purpose. Examples include sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, oxime-nitrosamine-based crosslinking agents, etc. Among these crosslinking agents, sulfur-based crosslinking agents (vulcanizing agents) are more preferred for rubber compositions for tires. There are no particular restrictions on the content of the crosslinking agent, and it can be appropriately selected depending on the purpose, but it is preferably 0.1 to 20 parts by mass per 100 parts by mass of the rubber component.

[0065] Furthermore, when sulfur is used as the crosslinking agent, it is preferable to include a vulcanization accelerator. Conventional vulcanization accelerators can be used and are not particularly limited, but examples include sulfenamide-based vulcanization accelerators such as CBS (N-cyclohexyl-2-benzothiadylsulfenamide), TBBS (N-t-butyl-2-benzothiadylsulfenamide), and TBSI (N-t-butyl-2-benzothiadylsulfenimide); guanidine-based vulcanization accelerators such as DPG (diphenylguanidine); thiram-based vulcanization accelerators such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; and zinc dialkyldithiophosphate. The content of the vulcanization accelerator is preferably less than the content of sulfur, and more preferably about 1 to 10 parts by mass per 100 parts by mass of the rubber component.

[0066] The rubber composition of the present invention preferably further contains glycerol monostearate, as this can shorten the scorch time and further improve workability, such as increasing the vulcanization speed during tire manufacturing.

[0067] The glycerol monostearate content is 0.1 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. If the content is less than 0.1 parts by mass, the effects of the present invention may not be obtained favorably. The content is 3.5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. If it exceeds 3.5 parts by mass, the scorch time tends to become too short.

[0068] Furthermore, the polyethylene glycol content is 0.1 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. If it is less than 0.1 parts by mass, the effects of the present invention may not be obtained favorably. The content is 3.5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. If it exceeds 3.5 parts by mass, the scorch time tends to become too short.

[0069] Furthermore, the rubber composition of the present invention may also contain a softening agent, as this enhances the flexibility of the rubber and enables superior wet and ice performance. The softening agent can be any conventionally known agent and is not particularly limited, but examples include petroleum-based softening agents such as aroma oils, paraffin oils, and naphthenic oils, and plant-based softening agents such as palm oil, castor oil, cottonseed oil, and soybean oil. When using these, one or more may be appropriately selected and used. When a softening agent is included, from the viewpoint of ease of handling, it is preferable to include a softening agent that is liquid at room temperature, such as 25°C, for example, a petroleum-based softening agent such as aroma oils, paraffin oils, or naphthenic oils.

[0070] Furthermore, the rubber composition of the present invention may contain a resin in order to enhance the flexibility of the rubber and achieve superior wet performance and ice performance. Various natural resins and synthetic resins can be used as the resin, and specifically, it is preferable to use rosin-based resins, terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, xylene-based resins, etc. These resins may be used individually or in combination of two or more.

[0071] The method for producing the rubber composition of the present invention is not particularly limited. For example, the rubber composition of the present invention can be produced by compounding, kneading, heating, extruding, etc., the rubber component described above, a filler containing at least silica, a cyclic polyol compound (A), and other optionally added components, etc., using known methods.

[0072] There are no particular restrictions on the mixing conditions, and various conditions such as the input volume of the mixing device, the rotation speed of the rotor, the ram pressure, as well as the mixing temperature, mixing time, and the type of mixing device can be appropriately selected according to the purpose. Examples of mixing devices include Banbury mixers, intermixes, kneaders, and rolls, which are commonly used for mixing rubber compositions.

[0073] There are no particular restrictions on the heat treatment conditions, and various conditions such as heat treatment temperature, heat treatment time, and heat treatment equipment can be appropriately selected according to the purpose. Examples of such heat treatment equipment include heat treatment roll machines commonly used for heat treatment of rubber compositions.

[0074] There are no particular restrictions on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature can be appropriately selected according to the purpose. Examples of extrusion equipment include extruders typically used for extruding rubber compositions. The extrusion temperature can be determined as appropriate.

[0075] <Vulcanized Rubber Composition> The vulcanized rubber composition of the present invention is obtained by vulcanizing the rubber composition of the present invention described above. The obtained vulcanized rubber composition of the present invention has excellent low heat generation and cut resistance. There are no particular restrictions on the apparatus, method, conditions, etc., for performing the vulcanization, and they can be appropriately selected according to the purpose. There are also no particular restrictions on the apparatus for performing the vulcanization, and a molding vulcanizer using a mold, etc., which is normally used for vulcanizing rubber compositions, can be used. As for the vulcanization conditions, the temperature is, for example, about 100 to 190°C.

[0076] <Rubber Products> The rubber products of the present invention are characterized by using the rubber composition or vulcanized rubber composition of the present invention described above. By applying the rubber composition or vulcanized rubber composition of the present invention to rubber products, excellent low heat generation and cut resistance can be achieved. Examples of rubber products of the present invention include tires, rubber tracks, seismic isolation rubber, hoses, etc., and among these, tires or rubber tracks are preferred. This is because the excellent low heat generation and cut resistance offer significant advantages when used as tires or rubber tracks.

[0077] <Tire> The tire of the present invention is characterized in that the rubber composition or vulcanized rubber composition of the present invention described above is used in at least one of the tread portion and the sidewall portion. By applying the rubber composition of the present invention to the tread portion and / or sidewall portion, excellent low heat generation and cut resistance can be achieved. The tire of the present invention can be used, for example, as a tire for construction vehicles, a tire for trucks and buses, a tire for aircraft, or a tire for passenger cars, and is particularly preferred as a tire for passenger cars, a tire for trucks and buses, or a tire for construction vehicles. This is because the rubber composition used as the material for the tread portion and sidewall portion has excellent cut resistance, which offers significant advantages when used as the tire described above.

[0078] When using the vulcanized rubber composition of the present invention described above in the tread portion, the tread structure can be, for example, the structure described in the following publications: Japanese Patent Publication No. 2016-203842, Japanese Patent Publication No. 2009-196527, Japanese Patent Publication No. 2000-225815, Japanese Patent Publication No. 2000-264019, Japanese Patent Publication No. 2003-211921, and International Publication No. 2014 / 196409.

[0079] Furthermore, the tire of the present invention is not particularly limited except that the vulcanized rubber composition of the present invention described above is used in at least one of the tread portion and the sidewall portion of the tire, and can be manufactured according to conventional methods. In addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas to fill the tire.

[0080] 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.

[0081] (Examples and Comparative Examples) For Examples 1-4, Comparative Examples 1-2, and Comparative Example 4, rubber composition samples were prepared by compounding and kneading according to the formulations shown in Table 1 using conventional methods. For Comparative Example 3, a rubber composition sample was prepared by compounding and kneading according to the formulations shown in Table 1 using conventional methods. Each of the obtained samples was subjected to vulcanization treatment (145 °C, 33 minutes), followed by the following evaluations (1) and (2).

[0082] (Evaluation) (1) Low heat generation (tanδ index) For Examples 1-4, Comparative Examples 1-2, and Comparative Example 4, the loss tangent (tanδ) was measured using a viscoelasticity measuring device [manufactured by TA Instruments] on the vulcanized rubber composition of each sample at a temperature of 50°C, a strain of 5%, and a frequency of 15 Hz. For Comparative Example 3, the loss tangent (tanδ) was measured using a viscoelasticity measuring device [manufactured by TA Instruments] on the vulcanized rubber composition of the sample at a temperature of 50°C, a strain of 5%, and a frequency of 15 Hz. The measured tanδ was taken as the reciprocal and multiplied by 100. For Examples 1-3 and Comparative Examples 1-3, the index value is shown when the reciprocal value of the tanδ of Comparative Example 1 multiplied by 100 is set to 100. For Examples 4 and Comparative Example 4, the index value is shown when the reciprocal value of the tanδ of Comparative Example 4 multiplied by 100 is set to 100 (Table 1). Furthermore, a higher index value indicates superior low heat generation, and a value of 95 or higher indicates that the required performance is met.

[0083] (2) Cut Resistance For Examples 1-4, Comparative Examples 1-2, and Comparative Example 4, after vulcanizing the rubber composition of each sample, a pure shear type test specimen was prepared, and a cut was made in the test specimen while it was under tension using a tensile testing apparatus (Shimadzu Corporation). The propagation of the crack was observed, and the energy release rate (transition energy) at which the crack propagation rate increased discontinuously was measured. For Comparative Example 3, after vulcanizing the rubber composition of each sample, a pure shear type test specimen was prepared, and a cut was made in the test specimen while it was under tension using a tensile testing apparatus (Shimadzu Corporation). The propagation of the crack was observed, and the energy release rate (transition energy) at which the crack propagation rate increased discontinuously was measured. The evaluation is performed by calculating the reciprocal of the transition energy of each measured sample. For Examples 1-3 and Comparative Examples 1-3, the index value is shown when the reciprocal of the transition energy of the sample in Comparative Example 1 is set to 100. For Examples 4 and Comparative Example 4, the index value is shown when the reciprocal of the transition energy of the sample in Comparative Example 4 is set to 100 (Table 1). A higher index value indicates superior cut resistance, and a value of 105 or higher indicates that the required performance is met.

[0084]

[0085] *1 Natural rubber: RSS#3 *2 Butadiene rubber: BR01 (manufactured by ENEOS Material Co., Ltd.) *3 Carbon black: HAF grade carbon black *4 Sugar: D(+)-glucose (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *5 Cyclic polyol: Monomethyl ether of inositol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) *6 Others: Total amount of antioxidants, sulfur, vulcanization accelerators, zinc oxide, etc.

[0086] The results in Table 1 show that the rubber composition of the example has a superior balance of low heat generation and cut resistance compared to the rubber composition of the comparative example.

[0087] According to the present invention, it is possible to provide a rubber composition with excellent low heat generation and cut resistance. Furthermore, according to the present invention, it is also possible to provide rubber products and tires with excellent low heat generation and cut resistance.

Claims

1. A rubber component containing natural rubber and a cyclic polyol compound (A) represented by the following formula: [In the formula, A is -H or an alkyl group having 1 to 20 carbon atoms, and X ５ , X ２ , X ３ , X ４ , and X ５ are each independently -OH or -R (where -R is -H or -CH ２ OH), provided that at least two of X １ , X ２ , X ３ , X ４ , and X ５ are -OH], a rubber composition characterized by comprising the same.

2. The rubber composition according to claim 1, characterized in that the content of the cyclic polyol compound (A) is 0.1 to 8 parts by mass per 100 parts by mass of the rubber component.

3. The rubber composition according to claim 1 or 2, characterized in that the content ratio of natural rubber in the rubber component is 50% by mass or more.

4. The rubber composition according to claim 1 or 2, characterized in that the cyclic polyol compound (A) is a monomethyl ether of inositol.

5. The rubber composition according to claim 1 or 2, further comprising a filler, wherein the total content of the filler is 30 to 150 parts by mass per 100 parts by mass of the rubber component.

6. The rubber composition according to claim 5, characterized in that the filler contains carbon black, and the amount of carbon black is 30 parts by mass or more per 100 parts by mass of the rubber component.

7. The rubber composition according to claim 5, characterized in that the filler contains silica, and the silica content is 20 parts by mass or less per 100 parts by mass of the rubber component.

8. The rubber composition according to claim 6, characterized in that the carbon black contains recycled carbon black.

9. The rubber composition according to claim 7, characterized in that the silica contains silica derived from silicic acid plants.

10. A vulcanized rubber composition characterized by being obtained by vulcanizing the rubber composition described in claim 1 or 2.

11. A rubber product using the rubber composition described in claim 1 or 2, characterized in that the rubber product is a tire or a rubber crawler.

12. A tire characterized in that the rubber composition described in claim 1 or 2 is used in at least one of the tread portion and the sidewall portion.

Images