Rubber composition and pneumatic tire

Abstract

To provide a rubber composition comprising a diene-based rubber and silica, which is rubber composition meeting SDGs 12-5 especially involving the recycling and reuse of waste materials and to provide a pneumatic tire having at least a vulcanized rubber of a sustainable rubber composition and having particularly excellent rolling resistance and WET grip performance.SOLUTION: There is provided a rubber composition comprising a diene-based rubber and silica, wherein the rubber composition comprises recycled silica as silica. The recycled silica is preferably recycled silica derived from products used as a semiconductor wafer or a solar wafer.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Not only pneumatic tire manufacturers but also companies are required to work on SDGs (Sustainable Development Goals), which mean sustainable development goals. There are 17 goals in the SDGs, and one of them is SDGs 12-5 (By 2030, significantly reduce waste generation through prevention, reduction, recycling and reuse of waste).

[0003] Patent Document 1 below describes, with respect to 100 parts by mass of a diene rubber composed of 30 to 70 parts by mass of an isoprene rubber and 30 to 70 parts by mass of a styrene-butadiene rubber, 30 to 150 parts by mass of silica having a CTAB adsorption specific surface area of 100 m 2 / g to 250 m 2 / g, 5 to 150 parts by mass of powdered recycled rubber, and 5 to 90 parts by mass of a modified recycled rubber functionalized with a thiuram sulfide compound, a rubber composition for tires.

[0004] Patent Document 2 below describes a micronized elastomer powder blend for use in manufacturing a vulcanized elastomer product, including a plurality of cured elastomer particles, wherein the plurality of cured elastomer particles include particles having a size of less than 1 wt% of 40 mesh, at least 7 wt% of 60 mesh, at least 19 wt% of 80 mesh, at least 35 wt% of 120 mesh, at least 11 wt% of 140 mesh, and at least 20 wt% of less than 140 mesh, and further includes a non-cured elastomer material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technology described in the above Patent Document 1 is a technology using recycled rubber and is not a technology related to recycled silica that has been once used as a product and then recycled. Also, the technology described in the above Patent Document 2 is a technology using recycled elastomer and is not a technology related to recycled silica.

[0007] In addition, precipitated silica distributed in the market is usually produced by manufacturing sodium silicate (water glass) from silica sand (SiO2) and sodium hydroxide (NaOH) or sodium carbonate (Na2CO3), and then reacting water glass with sulfuric acid, and filtering, washing with water, drying, and pulverizing the resulting silicon dioxide precipitate. However, the silica produced in this way cannot be said to be sustainable, let alone meet SDGs 12-5.

[0008] Also, although bio-derived silica such as rice husk silica exists in the market, from the perspective of working towards SDGs 12-5 which aims at recycling and reuse of waste, bio-derived silica is insufficient.

[0009] The present invention has been made in view of the above circumstances, and its object is to provide a rubber composition containing a diene rubber and silica, particularly a rubber composition that meets SDGs 12-5 which aims at recycling and reuse of waste. Further, an object of the present invention is to provide a pneumatic tire having at least a vulcanized rubber of a sustainable rubber composition and particularly excellent in rolling resistance and WET grip performance.

Means for Solving the Problems

[0010] The above problems can be solved by the following configuration. That is, the present invention relates to a rubber composition containing a diene rubber and silica, characterized in that the silica contains recycled silica, and is a rubber composition (1).

[0011] In the rubber composition (1), a rubber composition (2) is preferable, wherein the recycled silica is recycled silica derived from products used as semiconductor wafers or solar wafers.

[0012] In the rubber composition (1) or (2), when the total amount of the diene rubber is 100 parts by mass, a rubber composition (3) containing 20 to 80 parts by mass of the silica is preferable.

[0013] In any of the compositions (1) to (3), as the silica, a rubber composition (4) is preferable, which contains non-recycled new silica in addition to the recycled silica, and the ratio of the recycled silica to the new silica is 1:3 to 1:0.

[0014] The present invention also relates to a pneumatic tire (5) comprising at least a vulcanized rubber of any of the rubber compositions (1) to (4).

Advantages of the Invention

[0015] In rubber compositions, especially in rubber compositions for pneumatic tires, silica is often compounded as a raw material. In the present invention, since recycled silica is used as the silica, it is in line with SDGs 12-5, which aims at recycling and reuse of waste. In the present invention, "recycled silica" means silica obtained by recycling silica that has been used as a product at least once. In particular, in the present invention, when recycled silica derived from products used as semiconductor wafers or solar wafers is compounded into the rubber composition, a pneumatic tire provided with the vulcanized rubber is preferable because it has excellent rolling resistance and WET grip performance.

Embodiments for Carrying out the Invention

[0016] The rubber composition according to the present invention contains a diene rubber and silica, and contains recycled silica as at least a part of the silica.

[0017] Recycled silica is silica obtained by recycling silica that has been used as a product at least once, and there are many products on the market that serve as raw materials for recycled silica. In the present invention, in particular, when recycled silica derived from a product used as a semiconductor wafer or a solar wafer is blended in a rubber composition, a pneumatic tire provided with the vulcanized rubber is preferable because it has excellent rolling resistance and WET grip performance. As an example, recycled silica derived from a product used as a semiconductor wafer will be described below.

[0018] In the semiconductor manufacturing process, there are steps of grinding and polishing semiconductor wafers (silicon wafers), and the waste materials generated in these steps contain a large amount of silicon. By collecting this waste material and subjecting it to a chemical recycling process of synthesis and oxidation, recycled silica can be produced. Regarding solar wafers as well, recycled silica can be produced by collecting waste materials containing silicon provided in solar wafers used as products and subjecting them to a chemical recycling process of synthesis and oxidation. The produced recycled silica can be pulverized to have a desired particle size and blended into a rubber composition.

[0019] The recycled silica used in the present invention preferably has the following physical properties. · SiO2 content: 94% by mass or more · DBP absorption: 170 - 210 (measured in accordance with ASTM D2424) · Specific surface area (m 2 / g): 140 - 220 (measured in accordance with ISO 9277)

[0020] The rubber composition according to the present invention contains recycled silica as at least a part of the silica, but may also contain non-recycled new silica in addition to the recycled silica. As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc. that are usually used for rubber reinforcement are used. Among them, wet silica is preferable.

[0021] The rubber composition according to the present invention contains recycled silica alone or both recycled silica and non-recycled new silica as the silica. When the total amount of the diene rubber is 100 parts by mass, it is preferable to contain 60 to 100 parts by mass of silica, and more preferably 70 to 90 parts by mass. Further, when the rubber composition according to the present invention contains both recycled silica and non-recycled new silica as the silica, the ratio of the recycled silica to the new silica is preferably 1:3 to 1:0.

[0022] The rubber composition according to the present invention preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents blended with silica in the rubber composition can be used. For example, sulfide silanes such as bis(3-triethoxysilylpropyl)tetrasulfide (e.g., "Si69" manufactured by Degussa), bis(3-triethoxysilylpropyl)disulfide (e.g., "Si75" manufactured by Degussa), bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)disulfide; mercapto silanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane; protected mercapto silanes such as 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane. The blending amount of the silane coupling agent is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of silica.

[0023] The rubber composition according to the present invention contains a diene rubber as a rubber component. Examples of the diene rubber include solution-polymerized styrene-butadiene rubbers such as emulsion-polymerized polystyrene-butadiene rubber (hereinafter also referred to as "E-SBR") and solution-polymerized polystyrene-butadiene rubber (hereinafter also referred to as "S-SBR") obtained by an emulsion polymerization method (radical polymerization method) in water, natural rubber, isoprene rubber, butadiene rubber, and the like.

[0024] The rubber composition for pneumatic tires according to the present invention may contain carbon black as a filler. As the carbon black, in addition to carbon black commonly used in the normal rubber industry such as SAF, ISAF, HAF, FEF, GPF, etc., conductive carbon black such as acetylene black and ketjen black can be used. When the total amount of the rubber component is 100 parts by mass, the rubber composition for pneumatic tires according to the present invention preferably contains 5 to 20 parts by mass of carbon black, and more preferably contains 5 to 10 parts by mass.

[0025] In addition to the diene rubber, silica, silane coupling agent and carbon black, the rubber composition for pneumatic tires according to the present invention can be blended with vulcanization system compounding agents, anti-aging agents, stearic acid, softening agents such as wax and oil, processing aids and the like.

[0026] As the anti-aging agent, anti-aging agents such as aromatic amine-based anti-aging agents, amine-ketone-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, polyphenol-based anti-aging agents, dithiocarbamate-based anti-aging agents, thiourea-based anti-aging agents, etc., which are usually used for rubbers, can be used alone or in appropriate mixtures.

[0027] Examples of the vulcanization system compounding agents include vulcanizing agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization accelerator aids, vulcanization retarders, and the like.

[0028] The sulfur as the vulcanization system compounding agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur, etc. can be used. Considering the physical properties and durability of the rubber after vulcanization, when the total amount of the rubber component is 100 parts by mass, the compounding amount of sulfur is preferably 1 to 10 parts by mass in terms of sulfur content, and more preferably 1 to 5 parts by mass.

[0029] As the vulcanization accelerator, vulcanization accelerators such as sulfenamide - type vulcanization accelerators, thiuram - type vulcanization accelerators, thiazole - type vulcanization accelerators, thiourea - type vulcanization accelerators, guanidine - type vulcanization accelerators, and dithiocarbamate - type vulcanization accelerators, which are commonly used for rubber vulcanization, can be used alone or appropriately mixed.

[0030] The rubber composition for a pneumatic tire according to the present invention is obtained by kneading, in addition to a diene - based rubber, silica, a silane coupling agent, and carbon black, vulcanization - system compounding agents, anti - aging agents, stearic acid, softening agents such as wax and oil, processing aids, etc., using a kneader used in ordinary rubber industries such as a Banbury mixer, a kneader, or a roll.

[0031] In addition, the compounding method of each of the above components is not particularly limited. A method of pre - kneading compounding components other than vulcanization - system compounding agents such as a sulfur - based vulcanizing agent and a vulcanization accelerator to form a masterbatch, adding the remaining components and further kneading, a method of adding and kneading each component in an arbitrary order, a method of adding all components simultaneously and kneading, etc. may all be used.

[0032] Since the rubber composition according to the present invention uses recycled silica as the silica, it is useful for pneumatic tire applications with environmental awareness. In addition, a pneumatic tire comprising at least the vulcanized rubber of the rubber composition for a pneumatic tire according to the present invention is excellent in rolling resistance and WET grip performance in addition to sustainability. Therefore, the rubber composition according to the present invention is particularly useful for tread applications of pneumatic tires.

Examples

[0033] Hereinafter, examples showing the configuration and effects of the present invention will be described. The evaluation items in the examples, etc. were evaluated based on the following evaluation conditions for rubber samples obtained by heating and vulcanizing each rubber composition at 160 ° C for 20 minutes.

[0034] (Rolling resistance of vulcanized rubber (low fuel consumption)) Using a UBM Rheometer E4000, the loss factor tanδ was measured under the conditions of a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 60°C, and it was expressed as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the rolling resistance of the tire, indicating excellent low fuel consumption performance.

[0035] (WET grip performance of vulcanized rubber) Using a UBM Rheometer E4000, the loss factor tanδ was measured under the conditions of a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 0°C, and it was expressed as an index with the value of Comparative Example 1 being 100. The larger the index, the larger the tanδ, indicating excellent WET grip performance.

[0036] (Preparation of rubber composition) According to the formulation in Table 1, the rubber compositions of Examples 1-3 and Comparative Examples 1-2 were compounded and kneaded using a normal Banbury mixer to adjust the rubber compositions. Each compounding agent described in Table 1 is shown below (in Table 1, the compounding amount of each compounding agent is shown as the number of parts by mass relative to 100 parts by mass of the rubber component).

[0037] · SBR1 (solution-polymerized styrene-butadiene rubber (end-modified): "HPR350" manufactured by ENEOS MATERIALS · SBR2 (emulsion-polymerized styrene-butadiene rubber): "SBR1502" manufactured by ENEOS MATERIALS · Carbon black: "Seast 3" manufactured by Tokai Carbon Co., Ltd. · Oil: "Process NC-140" manufactured by ENEOS · Zinc oxide: "Zinc Oxide Type 2" manufactured by Mitsui Mining & Smelting Co., Ltd. · Stearic acid: "Lunac S-20" manufactured by Kao Corporation · Antioxidant: "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd. · Silane coupling agent: "Si69" manufactured by Evonik Degussa · Silica 1 (non-regenerated new silica): "Nipsil AQ" manufactured by Tosoh Silica Corporation · Silica 2 (bio-derived silica): "K160" manufactured by Wilmar · Silica 3 (Recycled silica from semiconductor wafers or solar wafers containing Si and SiOx): "Semisils 180Y" manufactured by Semisils Note that Silica 3 has the following properties. · SiO2 content: 94% by mass or more · DBP absorption: 170 - 210 (measured in accordance with ASTM D2424) · Specific surface area (m 2 / g): 140 - 220 (measured in accordance with ISO 9277) · Vulcanization accelerator 1: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd. · Vulcanization accelerator 2: "Nocceler D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. · Sulfur: "5% oil-in powder sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

[0038]

Table 1

[0039] From the results in Table 1, in Comparative Example 2 where a part of the new silica in Comparative Example 1 was replaced with bio-derived Silica 2, the physical properties of the vulcanized rubber (rolling resistance and WET grip performance) hardly changed. On the other hand, in Examples 1 - 3 where a part of the new silica in Comparative Example 1 was replaced with recycled Silica 3, among the physical properties of the vulcanized rubber the WET grip performance showed an effect equal to or better than that, and the rolling resistance was significantly improved.

Claims

1. A rubber composition containing a diene rubber and silica, characterized in that the silica contains recycled silica.

2. The rubber composition according to Claim 1, wherein the recycled silica is recycled silica derived from products used as semiconductor wafers or solar wafers.

3. The rubber composition according to Claim 1, wherein when the total amount of the diene rubber is 100 parts by mass, the silica is contained in an amount of 20 to 80 parts by mass.

4. The rubber composition according to Claim 1, wherein the silica contains non-recycled new silica in addition to the recycled silica, and the ratio of the recycled silica to the new silica is 1:3 to 1:

0.

5. A pneumatic tire comprising at least a vulcanized rubber of the rubber composition according to Claim 1. ​

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