Method for producing rubber composition
A two-step method for producing rubber compositions with diene rubber, silica, and a specific organic silane improves interface softening and dispersibility, addressing the trade-off in wet performance and fuel economy while enhancing abrasion resistance.
Patent Information
- Application Number
- JP2024013912
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-02-01
- Publication Date
- 2025-08-14
AI Technical Summary
Existing rubber compositions for tires face a trade-off between wet performance and fuel economy, and insufficient interface softening between diene rubber and silica, leading to inadequate abrasion resistance.
A method involving a two-step process where diene rubber, silica, and a sulfur-containing silane coupling agent are first mixed to form a pre-remilled composition, followed by mixing with an organic silane having a terpene skeleton and molecular weight of 200 to 1000, enhancing interface softening and dispersibility.
The resulting vulcanized rubber achieves a well-balanced improvement in wet performance, fuel economy, and abrasion resistance, particularly suitable for tire treads.
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for producing a rubber composition. [Background technology]
[0002] Pneumatic tires are expected to be driven in a variety of environments, and improving tire performance on wet roads (hereinafter also referred to as "wet performance") is essential. In addition, in response to recent demands for resource conservation, pneumatic tires are required to have low fuel consumption, and therefore, improved heat generation, which contributes to low fuel consumption, is also required. Additionally, from the perspective of improving durability, pneumatic tires are also required to have high wear resistance.
[0003] Patent Document 1 listed below describes a rubber composition for tires that contains a diene rubber, silica, a sulfur-containing silane coupling agent, and a specific alkyltriethoxysilane, in which 50% by mass or more of the diene rubber is a styrene-butadiene copolymer rubber, the sulfur-containing silane coupling agent has a mercapto group, the silica content is 5 to 150 parts by mass per 100 parts by mass of the diene rubber, the sulfur-containing silane coupling agent content is 3 to 15% by mass relative to the silica content, and the alkyltriethoxysilane content is 0.1 to 20% by mass relative to the silica content.
[0004] Patent Document 2 listed below describes a rubber composition obtained by compounding 100 parts by mass of diene rubber, 20 to 150 parts by mass of silica, and 2 to 20% by mass of an organic silane having a monosulfide bond (-CSC-) relative to the mass of the silica.
[0005] Patent Document 3 listed below describes a rubber composition obtained by compounding 100 parts by mass of a diene rubber containing a modified diene rubber modified with at least one functional group selected from the group consisting of an alkoxy group, a carbonyl group, a hydroxyl group, an amino group, and an epoxy group with 30 to 120 parts by mass of silica and 2 to 20% by mass of an organic silane having a low molecular weight terpene skeleton relative to the mass of the silica. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] Patent No. 4930661 [Patent Document 2] Patent No. 6018001 [Patent Document 3] Patent No. 6377476 Summary of the Invention [Problem to be solved by the invention]
[0007] The technologies described in Patent Documents 1 and 2 both address the issue of achieving both wet performance and fuel economy in a pneumatic tire. However, as a result of extensive research by the present inventors, it has been found that there is a trade-off between wet performance and fuel economy, and therefore there is room for further improvement.
[0008] In the technology described in Patent Document 3, an organic silane having a low molecular weight terpene skeleton is compounded into the rubber composition. However, as a result of extensive research by the present inventors, it has been found that there is room for further improvement, as described below.
[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a rubber composition that serves as a raw material for vulcanized rubber for tires, which has a well-balanced improvement in wet performance, fuel economy, and abrasion resistance. [Means for solving the problem]
[0010] The above problems can be solved by the following configuration: That is, the present invention relates to a method for producing a rubber composition containing a diene rubber, silica, an organosilane, and a sulfur-containing silane coupling agent other than the organosilane, wherein the organosilane is a compound having a terpene skeleton and a molecular weight of 200 to 1000, the method comprising: a first step of mixing at least the diene rubber, the silica, and the sulfur-containing silane coupling agent to obtain a pre-remilled rubber composition; and a second step of mixing the pre-remilled rubber composition with the organosilane.
[0011] In the method (1) for producing a rubber composition, the organic silane is represented by the following general formula (1): [ka] (In the above formula (1), R 1 , R 2 and R 3 are each independently an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, and R 1 , R 2 and R 3 wherein at least one of them is an alkoxy group. n is an integer of 2 to 4. X is a group having a terpene skeleton and a molecular weight of 200 to 1000, and the carbon-carbon double bond in the molecule of X may be saturated or unsaturated, and X may contain a hetero element.
[0012] In the method (1) or (2) for producing a rubber composition, the organosilane is represented by the following general formula (2): [ka] (In the above formula (2), R 1 , R 2 , R 3 and n are the same as in the above formula (1).) and a compound represented by the following general formula (3a): [ka] A compound represented by the following general formula (3b): [ka] and a compound represented by the following general formula (3c): [ka] A method (3) for producing a rubber composition is preferred, which is an ene-thiol reaction product with at least one compound selected from the group consisting of compounds represented by the following formula:
[0013] In any of the above methods (1) to (3) for producing a rubber composition, a method (4) for producing a rubber composition is preferred, in which, in the first step, when the total amount of the diene rubber is 100 parts by mass, 30 to 150 parts by mass of the silica is mixed, and 1 to 15% by mass of the sulfur-containing silane coupling agent is mixed with the silica, and in the second step, 10 to 300% by mass of the organic silane of the sulfur-containing silane coupling agent is mixed with the rubber composition before remilling. [Effects of the Invention]
[0014] When silica is compounded as a reinforcing material in a rubber composition, especially when the amount of silica compounded is large, the dispersibility of the silica in the rubber tends to deteriorate, resulting in insufficient filling effect of the silica. Therefore, various organic silanes (silane coupling agents) have been compounded to improve the dispersibility of silica in the rubber. However, as a result of extensive research by the present inventors, it has been found that the organic silanes that have been compounded so far, even when compounded with silica in the rubber, do not sufficiently soften the interface between the rubber and the silica, making it difficult to achieve a balanced improvement in the wet performance and fuel economy of the final vulcanized rubber.
[0015] On the other hand, in the method for producing a rubber composition according to the present invention, a compound having a terpene skeleton with a molecular weight of 200 to 1000 is blended into the rubber composition together with the diene rubber and silica. The terpene skeleton of the organosilane with a molecular weight of 200 to 1000 has a high affinity with the diene rubber, and when present at the interface between the diene rubber and silica, it can soften the interface to a high degree. In addition, the terpene skeleton with a molecular weight of 200 to 1000 can hydrophobize the silica surface to a high degree, thereby improving the dispersibility of silica in the diene rubber. As a result, the vulcanized rubber produced by the method for producing a rubber composition according to the present invention exhibits excellent silica dispersibility in the rubber while achieving a well-balanced improvement in wet performance and fuel economy due to the extremely soft interface between the diene rubber and silica. In addition, in the method for producing a rubber composition according to the present invention, the rubber composition further contains a sulfur-containing silane coupling agent other than the organosilane, in addition to the organosilane with a terpene skeleton with a molecular weight of 200 to 1000. This results in a balanced improvement in wet performance, fuel efficiency, and wear resistance.
[0016] However, after extensive research, the present inventors have found that when a rubber composition is produced by simultaneously mixing an organosilane having a terpene skeleton and a molecular weight of 200 to 1000 with silica and a sulfur-containing silane coupling agent other than the organosilane, the two react competitively with the hydroxyl groups on the silica surface, reducing the amount of bonding between the sulfur-containing silane coupling agent and the silica, which can result in an insufficient improvement in the abrasion resistance of the final vulcanized rubber. Therefore, further research has revealed that the abrasion resistance of the final vulcanized rubber can be sufficiently improved by performing the first step of mixing at least a diene rubber, silica, and a sulfur-containing silane coupling agent to obtain a pre-remill rubber composition, and the second step of mixing the pre-remill rubber composition with an organosilane having a terpene skeleton and a molecular weight of 200 to 1000.
[0017] Incidentally, the technology described in Patent Document 3, in which an organic silane having a low molecular weight terpene skeleton is compounded in a rubber composition, contributes to improving the dispersibility of silica in the rubber to some extent, but does not sufficiently soften the interface between the diene rubber and the silica. To the best of the inventor's knowledge, this is the first research that focuses on the flexibility of the interface between the diene rubber and the silica, and, of course, Patent Document 3 does not describe or suggest it. Furthermore, Patent Document 3 does not describe or suggest the use of an organic silane having a terpene skeleton and a molecular weight of 200 to 1000 in combination with silica and a sulfur-containing silane coupling agent other than the organic silane in separate processes.
[0018] The vulcanized rubber of the rubber composition obtained by the method for producing a rubber composition according to the present invention has a well-balanced improvement in wet performance, fuel economy, and abrasion resistance, and is therefore particularly useful for use in the tread of pneumatic tires. DETAILED DESCRIPTION OF THE INVENTION
[0019] In the method for producing a rubber composition according to the present invention, diene rubber, silica, an organic silane, and a sulfur-containing silane coupling agent other than the organic silane are used as raw materials.
[0020] The diene rubber is not particularly limited, and examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer, styrene-isoprene-butadiene copolymer rubber, etc. These may be used alone or in combination of two or more.
[0021] As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc., which are commonly used for rubber reinforcement, are used. Among them, wet silica is preferred. From the viewpoint of improving the wet performance and fuel economy of the vulcanized rubber in a well-balanced manner, the amount of silica blended is preferably 30 to 150 parts by mass, more preferably 50 to 120 parts by mass, when the total amount of diene rubber in the rubber composition is taken as 100 parts by mass.
[0022] The method for producing a rubber composition according to the present invention is characterized in that the rubber composition contains, as an organosilane, a compound having a terpene skeleton with a molecular weight of 200 to 1,000. If the molecular weight of the terpene skeleton of the organosilane is less than 200 or more than 1,000, the interface between the diene rubber and the silica will not be softened sufficiently, and improvements in wet performance and fuel economy tend to be insufficient. In the present invention, the amount of organosilane in the rubber composition is preferably 10 to 300% by mass of the sulfur-containing silane coupling agent used in combination, and more preferably 10 to 100% by mass of the sulfur-containing silane coupling agent used in combination.
[0023] In the present invention, the organosilane having a terpene skeleton and a molecular weight of 200 to 1000 is preferably an organosilane represented by the following general formula (1): [ka] (In the above formula (1), R 1 , R 2 and R 3 are each independently an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, and R 1 , R 2 and R 3 at least one of them is an alkoxy group. n is an integer of 2 to 4. X is a group having a terpene skeleton and a molecular weight of 200 to 1000, and the carbon-carbon double bond in the molecule of X may be saturated or unsaturated, and X may contain a hetero element.
[0024] The organosilane used in the present invention is not particularly limited as long as it is a compound having a terpene skeleton and a molecular weight of 200 to 1000, but more preferably, an ene-thiol reaction product of a silicon-containing thiol compound and a compound having a terpene skeleton and a molecular weight of 200 to 1000 can be used. Examples of silicon-containing thiol compounds include those represented by the following general formula (2):
[0025] [ka] (In the above formula (2), R 1 , R 2 , R 3 and n are the same as in the above formula (1). Examples of the silicon-containing thiol compound having a mercapto group represented by the general formula (2) include a silicon-containing thiol compound having a mercapto group represented by the general formula (2). The silicon-containing thiol compound having a mercapto group can be converted into a desired organosilane by an ene-thiol reaction between the mercapto group and a carbon-carbon double bond (C=C) in a compound having a terpene skeleton and a molecular weight of 200 to 1000. Specific examples of the compound of the general formula (2) include (3-mercaptopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)methyldimethoxysilane, (3-mercaptopropyl)dimethylmethoxysilane, and mercaptoethyltriethoxysilane.
[0026] The compound having a terpene skeleton and a molecular weight of 200 to 1000 is not particularly limited, but is preferably a compound represented by the following general formula (3a): [ka] A compound represented by the following general formula (3b): [ka] and a compound represented by the following general formula (3c): [ka] The general formula (3a), the general formula (3b), and the general formula (3c) may be each independently subjected to an ene-thiol reaction with a silicon-containing thiol compound having a mercapto group to produce an organosilanes, or at least two or all three of these may be mixed and subjected to an ene-thiol reaction with a silicon-containing thiol compound having a mercapto group to produce an organosilanes.
[0027] In the ene-thiol reaction, it is preferable to use a radical generator as a reaction catalyst. Radical reactions can also be carried out by irradiation with ultraviolet (UV) light. Examples of radical generators include azo compounds and organic peroxides, including those that generate radicals by heat or light irradiation. Examples of azo compounds include azobisisobutyronitrile (AIBN) and 1,1'-azobis(cyclohexanecarbonitrile) (ABCN). Examples of organic peroxides include di-tert-butyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and methyl ethyl ketone peroxide.
[0028] The ene-thiol reaction can be carried out by mixing, for example, a compound represented by general formula (2), a compound having a terpene skeleton and a molecular weight of 200 to 1000, and a radical generator together with an organic solvent such as toluene, and maintaining the mixture under conditions that generate radicals. The reaction temperature is preferably 50 to 120°C.
[0029] The organic silane having a terpene skeleton with a molecular weight of 200 to 1000 has a monosulfide bond (-CSC-) to improve its affinity with diene rubber. Furthermore, because the organic silane having a terpene skeleton with a molecular weight of 200 to 1000 has a high affinity between the terpene skeleton with a molecular weight of 200 to 1000 and diene rubber, when present at the interface between the diene rubber and silica, it can soften the interface to a high degree. Therefore, in the vulcanized rubber of the rubber composition according to the present invention, the dispersibility of silica in the rubber is excellent, and the interface between the two is very soft, resulting in a balanced improvement in wet performance and fuel economy.
[0030] In the present invention, it is preferable to use a compound represented by the general formula (1) as the organosilane having a terpene skeleton and a molecular weight of 200 to 1000, and a compound represented by the following general formula (4a): [ka] A compound represented by the following general formula (4b): [ka] or a compound represented by the following general formula (4c): [ka] Compounds represented by the following formula are particularly preferred.
[0031] In the method for producing a rubber composition according to the present invention, a sulfur-containing silane coupling agent other than the organosilane is used as a raw material together with an organosilane having a terpene skeleton and a molecular weight of 200 to 1000. This makes it possible to produce a rubber composition that has a good balance of improved wet performance, fuel economy, and abrasion resistance. Examples of sulfur-containing silane coupling agents other than the organosilane that are compounds having a terpene skeleton and a molecular weight of 200 to 1000 include bis(3-triethoxysilylpropyl)tetrasulfide (e.g., "Si69" manufactured by Evonik Japan Co., Ltd.), bis(3-triethoxysilylpropyl)disulfide (e.g., "Si75" manufactured by Evonik Japan Co., Ltd.), bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, and bis(3-trimethoxysilylpropyl)tetrasulfide. mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, and mercaptoethyltriethoxysilane; and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane.
[0032] In the present invention, the content of the sulfur-containing silane coupling agent in the rubber composition is preferably 1 to 15 mass %, more preferably 1 to 10 mass %, of the compounded amount of silica.
[0033] In the method for producing a rubber composition according to the present invention, in addition to the diene rubber, silica, organosilane which is a compound having a terpene skeleton and a molecular weight of 200 to 1000, and a silane coupling agent other than the organosilane, carbon black, a vulcanizing agent, a vulcanization accelerator, an antioxidant, stearic acid, a softener such as wax or oil, a processing aid, etc. may be compounded.
[0034] As the carbon black, for example, carbon blacks commonly used in the rubber industry such as SAF, ISAF, HAF, FEF, and GPF, as well as conductive carbon blacks such as acetylene black and ketjen black can be used.
[0035] As the vulcanizing agent, sulfur can be suitably used. The sulfur may be any ordinary sulfur for rubber, such as powdered sulfur, precipitated sulfur, insoluble sulfur, or highly dispersible sulfur. In the rubber composition for tires according to the present invention, the content of the vulcanizing agent is preferably 0.5 to 3.5 parts by mass when the total amount of the diene rubber is taken as 100 parts by mass.
[0036] As the vulcanization accelerator, vulcanization accelerators commonly used for rubber vulcanization, such as sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators and dithiocarbamate-based vulcanization accelerators, may be used alone or in appropriate mixtures.
[0037] As the antiaging agent, antiaging agents commonly used for rubber, such as aromatic amine antiaging agents, amine-ketone antiaging agents, monophenol antiaging agents, bisphenol antiaging agents, polyphenol antiaging agents, dithiocarbamate antiaging agents, and thiourea antiaging agents, may be used alone or in appropriate mixtures.
[0038] The method for producing a rubber composition according to the present invention is a method for producing a rubber composition containing a diene rubber, silica, an organic silane, and a sulfur-containing silane coupling agent other than the organic silane, wherein the organic silane is a compound having a terpene skeleton and a molecular weight of 200 to 1000, and the method includes a first step of obtaining a pre-remill rubber composition by mixing at least the diene rubber, silica, and sulfur-containing silane coupling agent, and a second step of mixing the pre-remill rubber composition with the organic silane.
[0039] In the first and second steps, kneading machines that are commonly used in the rubber industry, such as Banbury mixers, kneaders, and rolls, can be used.
[0040] In the first step, at least a diene rubber, silica, and a sulfur-containing silane coupling agent are mixed to obtain a pre-remill rubber composition. The conditions for carrying out the first step are not particularly limited, but examples include using the above-mentioned kneader and kneading at 100 to 200°C for 200 to 300 seconds.
[0041] In the second step, the rubber composition before remilling is mixed with an organic silane. The conditions for carrying out the second step are not particularly limited, but examples thereof include using the above-mentioned kneader and kneading at 100 to 200°C for 100 to 200 seconds.
[0042] The vulcanized rubber of the rubber composition produced by the method for producing a rubber composition according to the present invention has a well-balanced improvement in wet performance, fuel economy, and abrasion resistance, and is therefore particularly useful for use in the tread of pneumatic tires. [Example]
[0043] The present invention will be explained in more detail below by way of examples.
[0044] [Preparation of Rubber Composition and Vulcanized Rubber] Comparative Examples 1 to 12 According to the formulations (parts by mass) listed in Tables 1 to 10, the rubber components were masticated for 30 seconds using a Daihan lab mixer (300 cc). Then, silica, a sulfur-containing silane coupling agent, an organic silane, zinc oxide, stearic acid, and oil were added and kneaded for 240 seconds, after which the mixture was discharged. The discharged rubber composition was then added to a lab mixer, kneaded for 180 seconds, and then discharged. Furthermore, the discharged rubber composition, sulfur, and a vulcanization accelerator were added to the lab mixer, kneaded for 60 seconds, and then discharged. The resulting unvulcanized rubber composition was sheeted using a two-roll mill to a thickness of 2 mm, and then subjected to a vulcanization press at 160°C for 20 minutes to obtain a vulcanized sample. Examples 1 to 10 According to the formulation (parts by mass) listed in Tables 1 to 10, the rubber components were masticated for 30 seconds using a Daihan lab mixer (300 cc). Then, silica, a sulfur-containing silane coupling agent, zinc oxide, stearic acid, and oil were added, and the mixture was kneaded for 240 seconds before being discharged to obtain a pre-remill rubber composition (Step 1). Next, the discharged pre-remill rubber composition and organic silane were added to the lab mixer, kneaded for 180 seconds, and then discharged (Step 2). Furthermore, the discharged rubber composition, sulfur, and vulcanization accelerator were added to the lab mixer, kneaded for 60 seconds, and then discharged. The resulting unvulcanized rubber composition was sheeted using a two-roll mill to a thickness of 2 mm, and then subjected to a vulcanization press at 160°C for 20 minutes to obtain a vulcanized sample. The compounding ingredients listed in Tables 1 to 10 are listed below.
[0045] (Diene rubber) SBR: ENEOS Materials "HPR350", terminal amine-modified S-SBR (silica) Tosoh Corporation's "Nip Seal AQ" (Silane coupling agent (sulfur-containing silane coupling agent)) Evonik Japan "Si75"
[0046] (organosilane) Organic silane (1) (a compound having a terpene skeleton and a molecular weight of 200 to 1000): produced by the following synthesis method 1 (Synthesis method 1) 46.6 g of nerolidol (Tokyo Chemical Industry Co., Ltd.) represented by the general formula (3a), 50.0 g of (3-mercaptopropyl)triethoxysilane (Tokyo Chemical Industry Co., Ltd.), 3.4 g of 2,2'-azobis(isobutylnitrile) (Wako Pure Chemical Industries, Ltd.), and 100 mL of toluene were mixed in a recovery flask, and after bubbling with nitrogen gas for 30 minutes, the mixture was reacted at 70°C for 24 hours. The reaction solution was then concentrated, yielding 94.8 g of a pale yellow liquid (yield: 98% by mass). NMR analysis confirmed that the product was nerolidolsilane represented by the general formula (4a). This product was designated "organosilane (1)."
[0047] Organic silane (2) (a compound having a terpene skeleton and a molecular weight of 200 to 1000): produced by the following synthesis method 2 (Synthesis method 2) 60.9 g of geranylinalool (Tokyo Chemical Industry Co., Ltd.) represented by the general formula (3b), 50.0 g of (3-mercaptopropyl)triethoxysilane (Tokyo Chemical Industry Co., Ltd.), 3.4 g of 2,2'-azobis(isobutylnitrile) (Wako Pure Chemical Industries, Ltd.), and 100 mL of toluene were mixed in a recovery flask, and after bubbling with nitrogen gas for 30 minutes, the mixture was reacted at 70 ° C for 24 hours. The reaction solution was then concentrated, yielding 109.2 g of a pale yellow liquid (yield: 98% by mass). NMR analysis confirmed that the product was geranylinaloolsilane represented by the general formula (4b). This product was designated "organic silane (2)."
[0048] Organic silane (3) (a compound having a terpene skeleton and a molecular weight of 200 to 1000): produced by the following synthesis method 3 (Synthesis method 3) 62.2 g of isophytol (manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the general formula (3c), 50.0 g of (3-mercaptopropyl)triethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), 3.4 g of 2,2'-azobis(isobutylnitrile) (manufactured by Wako Pure Chemical Industries, Ltd.), and 100 mL of toluene were mixed in a recovery flask, and after bubbling with nitrogen gas for 30 minutes, the mixture was reacted at 70°C for 24 hours. The reaction solution was then concentrated to obtain 111.0 g of a pale yellow liquid (yield: 99% by mass). NMR analysis confirmed that the product was isophytolsilane represented by the general formula (4c). This product was designated "organosilane (3)."
[0049] (Other compounding agents) Zinc oxide: "Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Kao Corporation's "Lunac S-20" Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator (1): Sumitomo Chemical's "Soxinol CZ" Vulcanization accelerator (2): "Noccela D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
[0050] The obtained vulcanized rubber samples were evaluated under the following evaluation conditions. [WET performance (wet grip performance)] Using a viscoelasticity tester manufactured by Ueshima Seisakusho Co., Ltd., the loss factor tan δ was measured at a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 1%, and a temperature of 0°C. The value of Comparative Example 2 is shown in Table 1, the value of Comparative Example 3 in Table 2, the value of Comparative Example 4 in Table 3, the value of Comparative Example 5 in Table 4, the value of Comparative Example 6 in Table 5, the value of Comparative Example 7 in Table 6, the value of Comparative Example 8 in Table 7, the value of Comparative Example 10 in Table 8, the value of Comparative Example 11 in Table 9, and the value of Comparative Example 12 in Table 10, all expressed as an index with 100 as the index. The larger the index, the larger the tan δ, indicating better wet grip performance when made into a tire.
[0051] [Low fuel consumption (heat generation)] Using a viscoelasticity tester manufactured by Ueshima Seisakusho Co., Ltd., the loss factor tan δ was measured at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and a temperature of 60°C. The value for Comparative Example 2 is shown in Table 1, the value for Comparative Example 3 in Table 2, the value for Comparative Example 4 in Table 3, the value for Comparative Example 5 in Table 4, the value for Comparative Example 6 in Table 5, the value for Comparative Example 7 in Table 6, the value for Comparative Example 8 in Table 7, the value for Comparative Example 10 in Table 8, the value for Comparative Example 11 in Table 9, and the value for Comparative Example 12 in Table 10, all expressed as an index with 100 as the index. The smaller the index, the smaller the tan δ, indicating excellent heat buildup when made into a tire.
[0052] [Wear resistance] In accordance with JIS K6264, a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. was used to measure abrasion loss under conditions of a load of 40 N and a slip ratio of 30%, and the reciprocals of the measured values were expressed as an index, with the value for Comparative Example 2 in Table 1, the value for Comparative Example 3 in Table 2, the value for Comparative Example 4 in Table 3, the value for Comparative Example 5 in Table 4, the value for Comparative Example 6 in Table 5, the value for Comparative Example 7 in Table 6, the value for Comparative Example 8 in Table 7, the value for Comparative Example 10 in Table 8, the value for Comparative Example 11 in Table 9, and the value for Comparative Example 12 in Table 10 being set to 100. A larger index indicates better abrasion resistance.
[0053] [Table 1]
[0054] [Table 2]
[0055] [Table 3]
[0056] [Table 4]
[0057] [Table 5]
[0058] [Table 6]
[0059] [Table 7]
[0060] [Table 8]
[0061] [Table 9]
[0062] [Table 10]
[0063] The results in Tables 1 to 10 show that, in contrast to Comparative Examples 1 to 12 in which silica was simultaneously mixed with an organic silane having a terpene skeleton and a molecular weight of 200 to 1000 and a sulfur-containing silane coupling agent other than the organic silane, the vulcanized rubbers of Examples 1 to 10, which were produced by mixing at least a diene rubber, silica, and a sulfur-containing silane coupling agent in a first step to obtain a rubber composition before remilling, and a second step to mix the rubber composition before remilling with an organic silane having a terpene skeleton and a molecular weight of 200 to 1000, exhibit well-balanced improvements in wet performance, fuel economy, and abrasion resistance.
Claims
1. A method for producing a rubber composition containing a diene rubber, silica, an organic silane, and a sulfur-containing silane coupling agent other than the organic silane, comprising: The organosilane is a compound having a terpene skeleton and a molecular weight of 200 to 1000, a first step of obtaining a pre-remill rubber composition by mixing at least the diene rubber, the silica, and the sulfur-containing silane coupling agent; a second step of mixing the pre-remill rubber composition with the organic silane.
2. The organosilane is represented by the following general formula (1): 【Chemical 1】 (In the above formula (1), R 1 , R 2 and R 3 are each independently an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, and R 1 , R 2 and R 3 wherein at least one of the groups is an alkoxy group. n is an integer of 2 to 4. X is a group having a terpene skeleton and a molecular weight of 200 to 1000, and the carbon-carbon double bond in the molecule of X may be saturated or unsaturated, and X may contain a hetero element.
3. The organosilane is represented by the following general formula (2): 【Chemistry 2】 (In the above formula (2), R 1 , R 2 , R 3 and n are the same as in the above formula (1).) and a compound represented by the following general formula (3a): 【Chemistry 3】 a compound represented by the following general formula (3b): 【Chemistry 4】 and a compound represented by the following general formula (3c): 【Chemistry 5】 2. The method for producing a rubber composition according to claim 1, wherein the rubber composition is an ene-thiol reaction product with at least one compound selected from the group consisting of compounds represented by the formula:
4. 2. The method for producing a rubber composition according to claim 1, wherein in the first step, when the total amount of the diene rubber is 100 parts by mass, 30 to 150 parts by mass of the silica is mixed, and 1 to 15% by mass of the sulfur-containing silane coupling agent is mixed with the silica, and in the second step, 10 to 300% by mass of the organic silane of the sulfur-containing silane coupling agent is mixed with the rubber composition before remilling.
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