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
  • B60C1/0016—Compositions of the tread
• • 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
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • 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
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/016—Additives defined by their aspect ratio
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• the present invention relates to a rubber composition and a pneumatic tire.
• silica has been employed together with various coupling agents, a dispersing agent, a surface modifier and the like.
• a silane coupling agent is considered to prevent silica particles from coagulating each other due to bonding with silanol groups on the surface of silica and to improve processability of the rubber composition.
• no rubber composition in which dry grip performance can be improved besides rolling resistance is lowered has been put into practical use yet.
• JP-A-8-337687 discloses a rubber composition lowering rolling resistance by compounding particulate silica and a silane coupling agent, however, the rubber composition is insufficient in the improvement effects of wet grip performance and dry grip performance, and thus, it still has a scope to be improved.
• An object of the present invention is to provide a rubber composition in which both wet grip performance and dry grip performance are improved, while rolling resistance is maintained, and a pneumatic tire using the same.
• the present invention relates to a rubber composition
• a rubber composition comprising 5 to 150 parts by weight of silica having an aspect ratio of 2 to 20 based on 100 parts by weight of a rubber component containing a diene rubber.
• the present invention also relates to a pneumatic tire, wherein the rubber composition is used for a tread.
• the rubber composition of the present invention comprises a rubber component and silica.
• the rubber component contains a diene rubber since it can improve wet grip performance and abrasion resistance.
• a diene rubber examples are rubbers generally used in the rubber industry such as a natural rubber (NR), a styrene butadiene rubber (SBR), a butadiene rubber (BR), an isoprene rubber (IR), a butyl rubber (IIR), an acrylonitrile butadiene rubber (NBR), an ethylene propylene diene rubber (EPDM) and a chloroprene rubber (CR), these are not particularly limited, and they may be used alone or in combination of at least two kinds.
• NR natural rubber
• SBR styrene butadiene rubber
• BR butadiene rubber
• IR isoprene rubber
• IR butyl rubber
• NBR acrylonitrile butadiene rubber
• EPDM ethylene propylene diene rubber
• CR chloroprene rubber
• a combined styrene amount of SBR is preferably at least 20% by weight, and more preferable at least 21% by weight. When a combined styrene amount is less than 20% by weight, it tends that adequate improvement effect of grip performance can not be obtained. Also, the combined styrene amount is preferably at most 60% by weight, and more preferably at most 50% by weight. When the combined styrene amount is more than 60% by weight, a rubber becomes hard and wet grip performance tends to be lowered.
• an amount of SBR is preferably at least 3 parts by weight, and more preferably at least 5 parts by weight from the viewpoint that sufficient grip performance can be obtained.
• the amount of SBR is the most preferably 100 parts by weight.
• silica contained in the rubber composition can improve wet grip performance but it can not achieve both lowering of rolling resistance and improvement of dry grip performance.
• silica contained in the rubber composition several pieces of silica are combined to be silica having a chain structure (hereinafter, referred to as structure silica) so that at low tensile elongation (at low strain) such as at rolling with a low slip ratio, the number of stress concentration caused on the interface between a rubber and silica is reduced, and the ratio of stress that rubber matrix is shared is increased, thereby hysteresis loss is reduced and rolling resistance is lowered, and at high tensile elongation (at high strain) such as sudden brake and sharp curve, structure silica is oriented to a direction along a tread circumference to increase hysteresis loss and enhance dry grip performance.
• structure silica is oriented to a direction along a tread circumference to increase hysteresis loss and enhance dry grip performance.
• An average diameter (D) of structure silica is preferably at least 3 nm, and more preferably at least 4 nm.
• D is preferably at most 500 nm, and more preferably at most 400 nm.
• An average length (L) of structure silica is preferably at least 6 nm, and more preferably at least 10 nm.
• L is less than 6 nm, no effect to increase hysteresis loss due to the orientation of silica in a high tensile elongation area is obtained, and it tends that dry grip performance can not be increased.
• L is preferably at most 10,000 nm, and more preferably at most 7,000 nm.
• D is more than 10,000 nm, since stress is increased in a low tensile elongation area, hysteresis loss is increased, and it tends that rolling resistance is increased.
• An aspect ratio (L/D) of structure silica is at least 2, and preferably at least 2.5.
• L/D is less than 2
• L/D is at most 20, and preferably at most 17.5.
• L/D is more than 20, since stress is increased in a low tensile elongation area, hysteresis loss is increased and rolling resistance is increased.
• D, L and L/D are measured by observing silica dispersed in a vulcanized rubber composition by a transmission electron microscope.
• examples are organosilica sol IPA-ST-UP (available from Nissan Chemical Industries, Ltd.), high purity organo sol (available from Fuso Chemical Co., Ltd.), and Fine Cataloid F-120 (available from Catalysts & Chemicals Industries Co., Ltd.).
• An amount of structure silica is at least 5 parts by weight, preferably at least 10 parts by weight, and more preferably at least 15 parts by weight based on 100 parts by weight of the rubber component. When an amount of structure silica is less than 5 parts by weight, adequate improvement effects of rolling resistance, wet grip performance and dry grip performance due to containing structure silica can not be obtained. Also, an amount of structure silica is at most 150 parts by weight, preferably at most 120 parts by weight, and more preferably at most 100 parts by weight when an amount of structure silica is more than 150 parts by weight, rigidity of the rubber composition becomes high, and processability and wet grip performance are lowered.
• a silane coupling agent is compounded together with structure silica in the rubber composition of the present invention.
• the silane coupling agent there is no particular limitation as the silane coupling agent, those which have been used together with silica in the tire industry may be used, and examples are bis(3-triethoxysilylpropyl) polysulfide, bis(2-triethoxysilylethyl) polysulfide, bis(3-trimethoxysilylpropyl) polysulfide, bis(2-trimethoxysilylethyl) polysulfide, bis(4-triethoxysilylbutyl) polysulfide, and bis(4-trimethoxysilylbutyl) polysulfide, and these silane coupling agents may be used alone or in combination of at least two kinds.
• such a silane coupling agent as bis(3-triethoxysilylpropyl) disulfide is favorably used from the viewpoint of having both an
• An amount of a silane coupling agent is preferably at least 1 part by weight, and more preferably at least 2 parts by weight based on 100 parts by weight of structure silica.
• an amount of the silane coupling agent is less than 1 part by weight, since structure silica is hardly oriented to a direction along a circumference of a tread at high tensile elongation, and hysteresis loss is hardly increased, it tends that dry grip performance is lowered.
• an amount of the silane coupling agent is preferably at most 20 parts by weight, and more preferably at most 15 parts by weight. When an amount of the silane coupling agent is more than 20 parts by weight, improvement effects due to compounding a silane coupling agent can not be obtained, and cost thereof is increased.
• compounding agents generally used in the rubber industry such as various softening agents, various antioxidants, stearic acid, zinc oxide, a vulcanizing agent such as sulfur, and various vulcanization accelerators can be compounded into the rubber composition of the present invention.
• a kneaded article is obtained by kneading chemicals other than sulfur and vulcanization accelerators, for example, by a Banbury mixer (step 1). Then, sulfur and the vulcanization accelerators are added to the kneaded article and the mixture is kneaded by using, for example, a roller to obtain an unvulcanized rubber composition (step 2). Further, the rubber composition of the present invention is obtained by vulcanizing the unvulcanized rubber composition (step 3).
• step 1 a process of mixing chemicals other than sulfur and vulcanizing accelerators in toluene which is an excellent solvent of a rubber is known, however, in the case of this process, the number of silica particles constituting structure silica becomes excessively large, and it tend that rolling resistance is increased. As a result, L/D of structure silica becomes excessively large and rolling resistance tends to be increased.
• the rubber composition of the present invention is used for tires, and particularly, from the viewpoints that rolling resistance can be maintained at low tensile elongation and dry grip performance can be improved at high tensile elongation at the same time as excellent in wet grip performance, the rubber composition of the present invention is preferably used for a tread among tire parts, and more preferably used for a tread for tires of such as bus and truck for heavy load, general automobile tires, and racing-car tires.
• silica dispersed in vulcanized rubber compositions was observed by a transmission electron microscope, and a long diameter and a short diameter of arbitrary 30 particles were measured, and average values of these are respectively referred to as D and L, and L/D is calculated from D and L.
• Rubber test pieces formed into a cylindrical shape having a length of 20 mm and a diameter of 100 mm are prepared from the prepared vulcanized rubber compositions, and using a flat belt abrasion tester (FR5010) manufactured by Ueshima Seishakusho Co., Ltd., under the conditions of a speed at 20 km/h, a load of 4 kgf, an outside air temperature at 30° C., and a water temperature at 25° C., the maximum value of friction coefficient is read, which is detected at the time when a slip ratio of a sample for a wet road surface is changed from 0 to 70%.
• FR5010 flat belt abrasion tester manufactured by Ueshima Seishakusho Co., Ltd.
• Pneumatic tires of Example 1 and Comparative Examples 1 and 2 (tire size: 195/65R15) are prepared by forming the prepared unvulcanized rubber compositions into a tread shape, laminating with other tire parts, and vulcanizing under the condition at 170° C. for 20 minutes.
• Example 1 containing silica within the range of L/D from 2 to 20, both a vulcanized rubber composition and a pneumatic tire can improve both wet grip performance and dry grip performance without increasing rolling resistance property.
• both a vulcanized rubber composition and a pneumatic tire can improve dry grip performance, but wet grip performance and rolling resistance property were degenerated.
• a rubber composition in which wet grip performance and dry grip performance can be improved while rolling resistance is maintained by containing silica having a specific aspect ratio in the rubber composition, and a pneumatic tire using the same for a tread can be provided.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Tires In General (AREA)

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• 2006
  • 2006-10-03 US US11/541,643 patent/US20070112121A1/en not_active Abandoned
  • 2006-10-12 JP JP2006279010A patent/JP4790562B2/ja active Active
  • 2006-10-18 DE DE602006001625T patent/DE602006001625D1/de active Active
  • 2006-10-18 EP EP06021824A patent/EP1790501B1/en not_active Ceased
  • 2006-10-19 US US11/583,159 patent/US7411016B2/en active Active
  • 2006-11-08 CN CN2006101484248A patent/CN1966556B/zh not_active Expired - Fee Related
  • 2006-11-13 RU RU2006139788/04A patent/RU2338761C2/ru not_active IP Right Cessation

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