Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K13/00—Use of mixtures of ingredients not covered by one single of the preceding main groups, each of these compounds being essential
  • C08K13/02—Organic and inorganic ingredients
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/548—Silicon-containing compounds containing sulfur
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons

Definitions

• the present invention relates to compounding agents for diene rubber and rubber compositions.
• Silica-filled tires offer excellent performance for automotive applications, particularly in terms of wear resistance, rolling resistance, and wet grip. These performance improvements are closely related to improving tire fuel economy, and so they have recently been the subject of vigorous research, particularly in the passenger car tire industry, where solution-polymerized styrene-butadiene rubber (S-SBR) is used.
• S-SBR solution-polymerized styrene-butadiene rubber
• Silica-filled rubber compositions reduce the rolling resistance of tires and improve wet grip performance, but have problems with workability because they have high unvulcanized viscosity and require multi-stage kneading or the like. Therefore, in rubber compositions in which inorganic fillers such as silica are simply compounded, the filler dispersion is insufficient, resulting in problems such as a significant decrease in fracture strength and abrasion resistance. Therefore, sulfur-containing organosilicon compounds are essential to improve the dispersion of the inorganic filler in the rubber and to chemically bond the filler to the rubber matrix.
• Sulfur-containing organosilicon compounds used as rubber compounding agents include compounds containing alkoxysilyl groups and polysulfide silyl groups within the molecule, such as bis-triethoxysilylpropyl tetrasulfide and bis-triethoxysilylpropyl disulfide (see Patent Documents 1 to 4).
• Patent Document 5 proposes a method of improving hardness and tensile properties by adding a silicone resin containing a silanol group to an organic elastomer, but further improvements in hardness, tensile properties, and durability are desired.
• the present invention has been made in consideration of the above circumstances, and aims to provide a rubber compounding agent that, when added to a rubber composition, results in a rubber composition that can achieve the desired hardness, tensile properties, and durability without compromising the processability, wear resistance, or fuel economy of the composition; a rubber composition containing this rubber compounding agent; and a tire formed from this rubber composition.
• R1 's each independently represent a hydrogen atom, or an alkyl group, aralkyl group, or aryl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, at least 50 mol% of R1 's are methyl groups
• R2 's represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, or an acetyl group, at least 20 mol% of R2 's are hydrogen atoms, a, b, c, and d are numbers which satisfy 0 ⁇ a
• R1 's each independently represent a hydrogen atom, or an alkyl group, aralkyl group, or aryl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, at least 50 mol% of R1 's are methyl groups
• R2 's represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, or an acetyl group, at least 20 mol% of R2 's are hydrogen atoms
• a, b, c, and d are numbers which satisfy 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1
• the compounding agent for rubber of the present invention contains the following component (A).
• R 1 's each independently represent a hydrogen atom, or an alkyl group, aralkyl group, or aryl group having 1 to 8 carbon atoms, which may be substituted with a halogen atom.
• the alkyl group having 1 to 8 carbon atoms for R 1 may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, and n-octyl groups.
• an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group, an ethyl group, or a propyl group is more preferred.
• the aralkyl group is preferably an aralkyl group having 7 to 20 carbon atoms, and specific examples thereof include a benzyl group and a phenylethyl group.
• the aryl group is preferably an aryl group having 6 to 18 carbon atoms, and specific examples thereof include unsubstituted aryl groups such as phenyl and naphthyl groups; and alkylaryl groups having 7 to 18 carbon atoms such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, with a phenyl group being preferred.
• R2 represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, or an acetyl group, and is preferably a hydrogen atom. At least 20 mol% of R2 are hydrogen atoms, preferably 50 mol% or more, and more preferably 60 mol% or more.
• the silicone resin (A) may be a single composition or a mixture of multiple compounds with different compositions.
• the weight-average molecular weight of the silicone resin (A) of the present invention is not particularly limited, but is preferably 500 to 500,000, and more preferably 1,000 to 300,000, as calculated using polystyrene standards by gel permeation chromatography (GPC). If the weight-average molecular weight is less than 500, the hardness and tensile properties may not improve.
• the silicone resin (A) is preferably solid at 25° C. Being solid makes it easier to mix into the tire composition.
• the softening point of the (A) silicone resin is preferably 60 to 120° C.
• the softening point is a value measured by the ring and ball method in accordance with JIS K2207:2006. From the viewpoint of safety during kneading of the rubber composition, it is preferable that the silicone resin (A) has a non-volatile content excluding solvents and the like of 95 mass % or more.
• the compounding agent for rubber of the present invention can also contain (B) an organosilicon compound having at least one group selected from a polysulfide group, a thioester group, and a mercapto group, and an alkoxysilyl group.
• the component (B) is not particularly limited as long as it is a compound having such a functional group, and for example, any conventionally known silane coupling agent that is compounded in rubber compositions for use in tires and the like can be used.
• silane coupling agent examples include polysulfide-based organosilicon compounds such as bis-(3-bistriethoxysilylpropyl)tetrasulfide and bis-(3-bistriethoxysilylpropyl)disulfide; mercapto-based organosilicon compounds such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane; and thioester-based organosilicon compounds such as 3-octanoylthiopropyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane.
• polysulfide-based organosilicon compounds such as bis-(3-bistriethoxysilylpropyl)tetrasulfide and bis-(3-bistriethoxysilylpropyl)disulfide
• mercapto-based organosilicon compounds such as 3-mercaptopropyltrimeth
• reaction products of the above-mentioned organosilicon compounds having sulfur atoms with alcohols containing polyether groups hydrolysis condensates of these organosilicon compounds, and co-hydrolysis condensates of these organosilicon compounds with other organosilicon compounds having alkoxysilyl groups.
• the component (B) may be used alone or in combination of two or more.
• the compounding ratio of component (A) to component (B) is not particularly limited, but a mass ratio of (B)/(A) of 10/90 to 95/5 is preferred, and 30/70 to 95/5 is even more preferred.
• composition containing the silicone resin (A) of the present invention described above can be used by itself as a rubber compounding agent, but the composition may also be mixed with at least one type of powder and used as a rubber compounding agent.
• powders include carbon black, talc, calcium carbonate, stearic acid, silica, aluminum hydroxide, alumina, and magnesium hydroxide.
• silica and aluminum hydroxide are preferred from the viewpoint of reinforcing properties, and silica is more preferred.
• the compounding agent for rubber of the present invention may be a mixture with an organic polymer or rubber such as a fatty acid, a fatty acid salt, polyethylene, polypropylene, polyoxyalkylene, polyester, polyurethane, polystyrene, polybutadiene, polyisoprene, natural rubber, or a styrene-butadiene copolymer, or may be a mixture with various additives that are commonly used for tires or other general rubbers, such as a vulcanizing agent, a crosslinking agent, a vulcanization accelerator, a crosslinking accelerator, various oils, an antioxidant, a filler, or a plasticizer.
• the form of the agent may be liquid or solid, and may be diluted with an organic solvent or emulsified.
• any rubber that has conventionally been generally used in various rubber compositions can be used.
• diene rubbers such as various isoprene rubbers (IR) such as natural rubber, various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), and acrylonitrile-butadiene copolymer rubbers (NBR), and these may be used alone or in combination of two or more.
• non-diene rubbers such as butyl rubber (IIR) and ethylene-propylene copolymer rubber (EPR, EPDM) may also be used in combination.
• Component (D) examples include those commonly used in the tire industry, such as silica, carbon black, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc, and clay. These may be used alone or in combination of two or more.
• the rubber composition of the present invention preferably contains silica and carbon black.
• the blending amount of component (D) in the rubber composition of the present invention is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass, and even more preferably 20 to 130 parts by mass per 100 parts by mass of component (C).
• the amount added is preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 3.0 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, per 100 parts by mass of component (C). Within the above range, a good balance between tensile properties and abrasion resistance is achieved.
• Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-5 Using a 4 L internal mixer (MIXTRON, manufactured by Kobe Steel, Ltd.), the natural rubber shown in Table 1 was kneaded for 60 seconds. Next, carbon black, silica, silicone resin, stearic acid, antioxidant, resin, and wax shown in Table 1 were added, the internal temperature was raised to 150°C, and the mixture was discharged. Thereafter, the mixture was stretched using rolls. The obtained rubber composition was again kneaded using an internal mixer (MIXTRON, manufactured by Kobe Steel, Ltd.) until the internal temperature reached 145°C, discharged, and then stretched using rolls. Zinc oxide, vulcanization accelerator, and sulfur shown in Table 1 were added to the mixture and kneaded to obtain a rubber composition.
• MIXTRON manufactured by Kobe Steel, Ltd.
• Natural rubber RSS#3 Carbon black: Seast 9H (manufactured by Tokai Carbon Co., Ltd.)
• Silica Nipsil AQ (manufactured by Tosoh Silica Corporation)
• Silicone resin (A-1) A silicone resin represented by the formula (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.21 , in which R 1 is a methyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), with a weight-average molecular weight of 3,000, a softening point of 75°C, and a solid state at 25°C.
• Silicone resin (A-2) A silicone resin represented by the formula (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.12 , in which R 1 is a methyl group (80 mol %) and a phenyl group (20 mol %), and R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), with a weight-average molecular weight of 3,500, a softening point of 77°C, and a solid state at 25°C.
• Silicone resin (A-3) A silicone resin represented by the formula (R 1 SiO 3/2 Silicone resin (A-4): (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.12 , where R 1 is a methyl group (80 mol %) or an n-propyl group (20 mol %), R 2 is a hydrogen atom (60 mol %) or a methyl group (40 mol %) , the weight average molecular weight is 3,500 , the softening point is 77°C, and the silicone resin is a solid at 25° C .
• Silicone resin (A-7) (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.61 , wherein R 1 is a phenyl group (70 mol %) and an n-propyl group (30 mol %), R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), the weight average molecular weight is 4,500, the softening point is 75°C, and the silicone resin is a solid at 25° C .
• Silicone resin (A-8) (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.12 , wherein R 1 is an n-propyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) or a methyl group (40 mol %), the weight average molecular weight is 3,000 , the softening point is 70°C, and the silicone resin is a solid at 25°C .
• Silicone resin (A-10) (R 1 SiO 3/2 ) 0.60 (R 1 2 SiO 2/2 ) 0.40 (R 2 O 1/2 ) 0.21 , wherein R 1 is a methyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), the weight-average molecular weight is 3,000, and the silicone resin is solid at 60°C and 25°C.
• Stearic acid industrial stearic acid (manufactured by Kao Corporation).
• Antioxidant Nocrac 6C (Ouchi Shinko Chemical Industry Co., Ltd.) Resin: T-REZ RA-100 (manufactured by ENEOS Corporation) Wax: Ozoace 0355 (manufactured by Nippon Seiro Co., Ltd.) Zinc oxide: Zinc oxide No.
• the test specimen was a sheet having a thickness of 0.2 cm and a width of 0.5 cm, with a clamping distance of 2 cm and an initial load of 1 N.
• the tan ⁇ (60 ° C) value was expressed as an index, with Comparative Example 1-1 being 100. The smaller the index value of tan ⁇ (60 ° C), the better the rolling resistance.
• the vulcanized products of the rubber compositions obtained in Examples 1-1 to 1-6 have improved hardness, tensile properties, and durability while maintaining wear resistance, compared to the vulcanized products of the rubber compositions obtained in Comparative Examples 1-1 to 1-5.
• Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-5 The SBR and BR shown in Table 2 were mixed for 30 seconds using a 4 L internal mixer (MIXTRON, manufactured by Kobe Steel, Ltd.). Next, the oil components, carbon black, silica, sulfide silane, silicone resin, stearic acid, antioxidant, and wax shown in Table 2 were added, the internal temperature was raised to 150°C, and the mixture was held at 150°C for 2 minutes, after which it was discharged. It was then stretched using a roll. The resulting rubber was again kneaded using an internal mixer (MIXTRON, manufactured by Kobe Steel, Ltd.) until the internal temperature reached 140°C, discharged, and then stretched using a roll. To this was added zinc oxide, a vulcanization accelerator, and sulfur as shown in Table 2, and the mixture was kneaded to obtain a rubber composition.
• MIXTRON manufactured by Kobe Steel, Ltd.
• SBR SLR-4602 (manufactured by Trinseo)
• BR BR-01 (manufactured by JSR Corporation)
• Oil AC-12 (manufactured by Idemitsu Kosan Co., Ltd.)
• Carbon black Seast 3 (manufactured by Tokai Carbon Co., Ltd.)
• Silica Nipsil AQ (manufactured by Tosoh Silica Corporation)
• Sulfide silane KBE-846 (manufactured by Shin-Etsu Chemical Co., Ltd., bis(triethoxysilylpropyl)tetrasulfide)
• Silicone resin (A-1) A silicone resin represented by the formula (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.21 , in which R 1 is a methyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), with a weight-average mo
• Silicone resin (A-2) A silicone resin represented by the formula (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.12 , in which R 1 is a methyl group (80 mol %) and a phenyl group (20 mol %), and R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), with a weight-average molecular weight of 3,500, a softening point of 77°C, and a solid state at 25°C.
• Silicone resin (A-8) (R 1 SiO 3/2 ) 1.00 (R 2 O 1/2 ) 0.12 , wherein R 1 is an n-propyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) or a methyl group (40 mol %), the weight average molecular weight is 3,000 , the softening point is 70°C, and the silicone resin is a solid at 25°C .
• Silicone resin (A-10) (R 1 SiO 3/2 ) 0.60 (R 1 2 SiO 2/2 ) 0.40 (R 2 O 1/2 ) 0.21 , wherein R 1 is a methyl group (100 mol %), R 2 is a hydrogen atom (60 mol %) and a methyl group (40 mol %), the weight-average molecular weight is 3,000, and the silicone resin is solid at 60°C and 25°C.
• Stearic acid industrial stearic acid (manufactured by Kao Corporation).
• Antioxidant Nocrac 6C (Ouchi Shinko Chemical Industry Co., Ltd.) Wax: Ozoace 0355 (manufactured by Nippon Seiro Co., Ltd.) Zinc oxide: Zinc oxide No. 3 (manufactured by Mitsui Mining & Smelting Co., Ltd.)
• Vulcanization accelerator (a): Noccela D (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
• Vulcanization accelerator (b): Noccela DM-P (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
• Vulcanization accelerator c): Noccela CZ-G (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
• Sulfur 5% oil-treated sulfur (Hosoi Chemical Industry Co., Ltd.)
• the unvulcanized and vulcanized physical properties of the rubber compositions obtained in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-5 were measured using the methods described below. The results are also shown in Table 2. Regarding the vulcanized physical properties, the obtained rubber compositions were press-molded (160°C, 10 to 40 minutes) to produce vulcanized rubber sheets (2 mm thick).
• the test specimen was a sheet having a thickness of 0.2 cm and a width of 0.5 cm, with a clamp distance of 2 cm and an initial load of 1 N.
• the values of tan ⁇ (0°C) and tan ⁇ (60°C) are expressed as indexes with Comparative Example 2-1 being 100.
• the vulcanized rubber compositions obtained in Examples 2-1 to 2-6 have significantly improved hardness, tensile properties, and durability while maintaining their abrasion resistance, compared to the vulcanized rubber compositions obtained in Comparative Examples 2-1 to 2-5.

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