JP2015221884A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition that improves its rolling resistance property, wet grip performance, performance on ice and snow, and wear resistance at high levels in a balanced manner, and a studless tire having a tread comprising the rubber composition.SOLUTION: A rubber composition comprises, based on 100 pts. mass of a rubber component comprising natural rubber 40-60 mass% and butadiene rubber 40-60 mass%, 10-35 pts. mass of a modified liquid butadiene rubber with a weight average molecular weight of 3000-40000, and more than 50 pts. mass to 80 pts. mass of silica.

Description

  The present invention relates to a rubber composition comprising a predetermined liquid component containing a modified liquid butadiene rubber and silica, and a studless tire having a tread made of the rubber composition.

  Conventionally, spike tires have been used as tires for running on snowy and snowy roads, and chains have been attached to tires. However, environmental problems such as dust problems occur, and studless tires have been developed as icy and snowy road running tires. Compared to the general road surface, the snowy and snowy road surface has a significantly reduced coefficient of friction and becomes slippery. Therefore, studless tires are required to perform on snow and snow, and the material and design are devised. In order to improve the low temperature characteristics of the studless tire, for example, a technique of using liquid butadiene rubber instead of oil has been studied (Patent Document 1).

  Recently, in consideration of the environment, low fuel consumption and durability (wear resistance) are also required for studless tires. However, it has been difficult to satisfy these characteristics in a balanced manner. In particular, when silica is used, it is difficult to mix the silica and the rubber component. Therefore, improving the dispersibility has been a problem in extracting the characteristics of silica.

JP 2008-50432 A

  The present invention provides a rubber composition in which rolling resistance characteristics, wet grip performance, performance on snow and snow, and wear resistance are improved in a well-balanced manner, and a studless tire having a tread composed of the rubber composition. Objective.

  As a result of intensive studies, the present inventor has found that the above-mentioned problems can be solved by blending a predetermined modified liquid butadiene rubber and silica with a predetermined rubber component. Was completed.

That is, the present invention is based on 100 parts by mass of a rubber component comprising 40 to 60% by mass of natural rubber and 40 to 60% by mass of butadiene rubber.
10 to 35 parts by weight of a modified liquid butadiene rubber having a weight average molecular weight of 3000 to 40000, and
The present invention relates to a rubber composition comprising more than 50 to 80 parts by mass of silica.

  In the above rubber composition, it is preferable that the modified liquid butadiene rubber has its terminal modified with an amino group and / or an alkoxysilyl group.

  The present invention also relates to a studless tire having a tread made of the rubber composition.

  According to the present invention, a rubber composition in which rolling resistance characteristics, wet grip performance, performance on snow and snow, and wear resistance are improved in a well-balanced manner and a studless tire having a tread composed of the rubber composition are obtained. Can do.

  Hereinafter, the configuration of the present invention will be described in detail.

<Rubber component>
The rubber component of the present invention is a rubber component comprising 40 to 60% by mass of natural rubber (NR) and 40 to 60% by mass of butadiene rubber (BR). When the content of the natural rubber in the rubber component of 100% by mass is less than 40% by mass or the content of the butadiene rubber exceeds 60% by mass, the wet grip performance tends to be low, while the content of the natural rubber is 60% by mass. If the content of super or butadiene rubber is less than 40% by mass, the performance on ice and snow tends to be lowered. The content of natural rubber is preferably 55% by mass or less, and more preferably 50% by mass or less. The content of butadiene rubber is preferably 45% by mass or more, and more preferably 50% by mass or more.

  In the present invention, the rubber component may be added with other rubber components in addition to the above-mentioned natural rubber and butadiene rubber. Examples of such rubber components include isoprene rubber (IR) and styrene butadiene rubber (SBR). ), Chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR) and the like. These rubber components may be used alone or in combination of two or more. In particular, natural rubber (NR) is preferred for reasons such as rolling resistance and wear performance.

<Modified liquid butadiene rubber>
In the modified liquid butadiene rubber (modified liquid BR) or liquid butadiene rubber (liquid BR) of the present invention, the liquid state means that it is in a liquid state at room temperature (25 ° C.).

  The weight average molecular weight (Mw) of the modified liquid BR is preferably 3000 or more, more preferably 5000 or more. If Mw is less than 3000, the rubber composition becomes hard due to the effect of the content decreasing with time, and the wet grip performance tends to decrease. On the other hand, Mw is preferably 40000 or less, more preferably 30000 or less. When Mw exceeds 40,000, grip performance tends to decrease. The weight average molecular weight (Mw) of the modified liquid BR was determined by gel permeation chromatography (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ- manufactured by Tosoh Corporation. It is a value determined by standard polystyrene conversion based on the measured value by M).

  In the present invention, the modified liquid BR refers to liquid BR by an amino group (including any of primary amino group, secondary amino group, and tertiary amino group), alkoxysilyl group, alkoxysilyl group by a conventional method. A group treated with a modifying group such as a combination of a group and an amino group. Liquid BR may be used independently and may use 2 or more types together.

  In addition, the modifying group introduced into the liquid BR may be bonded to any of the polymerization start terminal, polymerization end terminal, polymer main chain, and side chain of the liquid BR, but it suppresses energy loss from the polymer terminal. In view of improving the hysteresis loss characteristic, it is preferably introduced at the polymerization initiation terminal or the polymerization termination terminal.

  As the modified liquid BR in the present invention, in particular, a polymerized terminal (active terminal) of the liquid BR is modified with a compound represented by the following formula (1) (for example, a modification described in JP 2010-111753 A Those modified according to the SBR production method are preferred. In this case, it is easy to control the molecular weight of the polymer, and there are advantages that the low molecular weight component that increases tan δ can be reduced. In addition, the bond between the silica and the polymer chain is strengthened, and the rolling resistance characteristics and wear resistance are further improved. it can.

（式中、Ｒ¹、Ｒ²およびＲ³は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）またはこれらの誘導体を表す。Ｒ⁴およびＲ⁵は、同一若しくは異なって、水素原子またはアルキル基を表す。ｎは整数を表す。）

Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH) or a derivative thereof. R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or an alkyl group, and n represents an integer.)

Examples of the alkyl group or alkoxy group in R ¹ , R ² and R ³ include those having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably 1 to 4 carbon atoms. Examples of the alkyl group for R ⁴ and R ⁵ include those having 1 to 4 carbon atoms. n is preferably 1 to 5, more preferably 2 to 4, and still more preferably 3.

  Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-dimethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3 -Dimethylaminopropyltrimethoxysilane etc. are mentioned. These may be used alone or in combination of two or more.

  Examples of the method for modifying liquid BR with the compound (modifier) represented by the above formula (1) are described in JP-B-6-53768, JP-B-6-57767, JP-T2003-514078, and the like. Conventionally known methods such as the above method can be used. For example, liquid BR may be brought into contact with a modifying agent. After synthesizing liquid BR by anionic polymerization, a predetermined amount of modifying agent is added to the polymer rubber solution, and a polymerization terminal (active terminal) of liquid BR is added. Examples thereof include a method of reacting with a modifying agent and a method of reacting by adding a modifying agent to a liquid BR solution.

  One or more modified liquid BRs can be used.

  The blending amount of the modified liquid BR is 10 to 35 parts by mass with respect to 100 parts by mass of the rubber component. If it is less than 10% by mass, the contribution to the dispersion of silica is small, and the wet grip performance, the performance on ice and snow, and the wear resistance tend to decrease. On the other hand, if it exceeds 35 parts by mass, the wet grip performance tends to decrease. The blending amount of the modified liquid BR is preferably 34% by mass or less, more preferably 33% by mass or less, more preferably 32% by mass or less, more preferably 31% by mass or less, and further preferably 30% by mass or less.

<Filler>
Examples of the filler include fillers usually used in this field such as silica and carbon black.

(silica)
As the silica, any of those usually used in this field can be suitably used. For example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc. Can be mentioned. Of these, hydrous silica is preferred because it has many silanol groups. Specific examples of silica that can be used in the present invention include Ultrasil VN3, 115GR, 1115MP, 1165MP, and 165GR. One or two or more types of silica can be used.

N ₂ SA of silica is preferably 100 m ² / g or more, more preferably 120 m ² / g or more. If it is less than 100 m ² / g, the wet grip performance tends to decrease. On the other hand, N ₂ SA is preferably 200 m ² / g or less, more preferably 180 m ² / g or less. If it exceeds 200 m ² / g, the workability and dispersibility tend to be impaired. N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-81.

  The compounding quantity of a silica is 50 super mass parts-80 mass parts with respect to 100 mass parts of rubber components. If it is 50 parts by mass or less, the wet grip performance tends to be lowered, and if it exceeds 80 parts by mass, the fuel efficiency tends to be deteriorated. The blending amount of silica is more preferably 60 parts by mass or more.

(Silane coupling agent)
The rubber composition of the present invention preferably contains a silane coupling agent. As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4- Triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxy Silylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) ) Sulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3 -Trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxy Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthioca Sulfide systems such as vamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Mercapto type such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane Amino systems such as orchid; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri Chloro type such as ethoxysilane; and the like. These silane coupling agents may be used alone or in combination of two or more. Of these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide and the like are preferable from the viewpoint of good processability.

  When the silane coupling agent is contained, the blending amount is preferably 3 parts by mass or more, and more preferably 3.5 parts by mass or more with respect to 100 parts by mass of silica. When the amount of the silane coupling agent is less than 3 parts by mass, there is a tendency that effects such as improvement of dispersibility cannot be sufficiently obtained. Moreover, it is preferable that the compounding quantity of a silane coupling agent is 10 mass parts or less, and it is more preferable that it is 8 mass parts or less. When the compounding amount of the silane coupling agent exceeds 10 parts by mass, a sufficient coupling effect cannot be obtained and the reinforcing property tends to be lowered.

(Carbon black)
As carbon black, those generally used in tire production can be used, for example, SAF, ISAF, HAF, FF, FEF, GPF, etc., and these carbon blacks can be used alone, Two or more kinds may be used in combination. The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is 80 m ² / g or more, preferably 115 m ² / g or more. If N ₂ SA is less than 80 m ² / g, the wear properties tend to be reduced. On the other hand, N ₂ SA of carbon black is 200 m ² / g or less, and preferably 185 m ² / g or less. When N ₂ SA of carbon black is larger than 200 m ² / g, processability and dispersion tend to deteriorate. N ₂ SA of carbon black is determined in accordance with JIS K 6217-2: 2001.

  The compounding amount of carbon black is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and further preferably 9 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the wear performance tends to deteriorate. On the other hand, the amount is preferably 40 parts by mass or less, more preferably 30 parts by mass or less. When it exceeds 40 mass parts, there exists a tendency for rolling resistance to deteriorate.

  The total blending amount of the filler is preferably 50 parts by mass or more, more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 50 parts by mass, the wear performance tends to deteriorate. On the other hand, the amount is preferably 110 parts by mass or less, more preferably 100 parts by mass or less. If it exceeds 110 parts by mass, the rolling resistance tends to deteriorate.

<Oil>
In the present invention, it is preferable to blend a softener from the viewpoint of grip performance and the like. Although it does not specifically limit as a softening agent, Oils, such as mineral oil, are mentioned. Examples of the oil include process oils such as paraffinic process oil, aroma based process oil, and naphthenic process oil.

  The blending amount of the oil is preferably 5 parts by mass or more, more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the effect of addition may not be obtained. The blending amount of the oil is preferably 25 parts by mass or less, more preferably 20 parts by mass or less. When it exceeds 25 parts by mass, the wear resistance tends to deteriorate.

<Vulcanization accelerator>
Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, and guanidine-based vulcanization accelerators. Among them, in the present invention, sulfenamide-based and guanidine-based vulcanization accelerators are preferably used. Can be used.

  Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazylsulfenamide. Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and the like. Examples of the thiuram vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and the like. Examples of the guanidine vulcanization accelerator include N, N-diphenylguanidine. As a vulcanization accelerator, 1 type (s) or 2 or more types can be used.

  When the vulcanization accelerator is blended, the blending amount of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, a sufficient vulcanization rate cannot be obtained, and good grip performance and wear resistance tend to be not obtained. On the other hand, the amount is preferably 5 parts by mass or less, more preferably 4 parts by mass or less. If it exceeds 5 parts by mass, blooming may occur and grip performance and wear resistance may be reduced.

  In addition to the above components, the rubber composition of the present invention suitably contains compounding agents conventionally used in the rubber industry, such as zinc oxide, antioxidants, oils, waxes, sulfur, vulcanization accelerators and the like. be able to.

  The rubber composition of the present invention thus obtained has improved rolling resistance characteristics, wet grip performance, performance on snow and snow, and wear resistance in a highly balanced manner, and is therefore a tire, especially a studless tire that is a winter tire. Can be used for Moreover, it can use suitably especially for a tire tread from these characteristics.

  When used in a tire, the rubber composition of the present invention can be produced as a tire by an ordinary method. That is, if necessary, a mixture containing the above ingredients is kneaded, extruded in accordance with the shape of each member of the tire at an unvulcanized stage, and molded on a tire molding machine by a normal method. Thus, an unvulcanized tire is formed. A tire can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer, and air can be put into the tire to obtain a pneumatic tire.

In this specification, Mw and Mn are measured using a gel permeation chromatograph (GPC) and converted from standard polystyrene.
The glass transition temperature (Tg) is measured by a differential scanning calorimeter (DSC).
For example, “1-99 mass%” includes values at both ends.

  The present invention will be described based on examples, but the present invention is not limited to the examples.

  The various chemicals used in the present specification are collectively shown below. Various chemicals were purified according to conventional methods as needed.

<Various chemicals used in the production of rubber composition>
Natural rubber (NR): TSR20
Butadiene rubber (BR): Ubepol BR150B manufactured by Ube Industries (Tg: -114 ° C, cis content: 97% by mass)
Modified liquid BR (1): weight average molecular weight 30000
Modified liquid BR (2): weight average molecular weight 5000
Modified liquid BR (3): weight average molecular weight 50000
Carbon Black: Show Black N220 (N ₂ SA: 115 m ² / g) manufactured by Cabot Japan
Silica (hydrous silica): Ultrazil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si-69 manufactured by Degussa
Oil: JOMO process X140 manufactured by Japan Energy Co., Ltd.
Wax: Sunnock wax anti-aging agent manufactured by Ouchi Shinko Chemical Co., Ltd .: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-) manufactured by Ouchi Shinko Chemical Co., Ltd. Phenylenediamine)
Stearic acid: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd .: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator (TBBS) manufactured by Karuizawa Sulfur Co., Ltd .: Ouchi Shinsei Chemical Noxeller NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Kogyo Co., Ltd.
Vulcanization accelerator (DPG): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.

<Manufacture of rubber composition and tire>
In accordance with the formulation shown in Table 1, various chemicals (excluding sulfur and vulcanization accelerator) were kneaded at 160 ° C. for 2 minutes in a 1.7 L Banbury mixer to obtain a kneaded product. To the obtained kneaded product, sulfur and a vulcanization accelerator were added and kneaded at 80 ° C. for 3 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tire tread shape, bonded together with other tire members on a tire molding machine, and press vulcanized at 183 ° C. for 10 minutes to obtain a test tire ( Tire size: 205 / 65R15). In addition, when obtaining the vulcanized rubber composition used for various tests, it obtained by press vulcanizing the unvulcanized rubber composition molded into a predetermined shape under the same conditions as described above.

(Rolling resistance index)
About the vulcanized rubber composition (strip shape: 4 mm × 40 mm × 2 mm) obtained above, using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), temperature 70 ° C., initial strain 10%, dynamic strain 2 The tan δ of each formulation was measured under the condition of%, and the tan δ of Comparative Example 1 was taken as 100, and the index was expressed by the following formula. The larger the index, the better the rolling resistance characteristics.

(Rolling resistance index) = (tan δ of Comparative Example 1) ÷ (tan δ of each formulation) × 100

(Wet grip performance index)
The test tire was mounted on a traction test vehicle, and the vehicle was driven on a wet asphalt road test course. At this time, the vehicle was run at 40 km / h, the maximum friction coefficient (Maxμ) from when the brake was applied to when the vehicle was stopped was measured, and an index was displayed according to the following formula. The larger the index, the better the wet grip performance.

(Wet grip performance index) = (Maxμ of each formulation) / (Maxμ of Comparative Example 1)
× 100

(Abrasion resistance)
About the vulcanized rubber composition (ring shape, diameter 50 mm) obtained above, using a Lambone abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., surface rotation speed 50 m / min, load load 3.0 kg, sand fall amount 15 g / The amount of lamborn wear was measured under the conditions of min and a slip rate of 20%. Then, the volume loss amount was calculated from the measured lamborn wear amount, and the volume loss amount of Comparative Example 1 was set as 100, and the volume loss amount of each formulation was indicated by an index according to the following calculation formula. It shows that it is excellent in abrasion resistance performance, so that a numerical value is large.

(Abrasion resistance index) = (Volume loss amount of Comparative Example 1) / (Volume loss amount of each formulation) × 100

(Performance on ice and snow)
The test tire was attached to the mark X, and the vehicle was run on the Nayoro test course. The performance on ice and snow at that time was sensory evaluated by a test driver. The comparative example 1 was set to 100, and the index was displayed for each formulation.

  The results are shown in Table 1.

  According to the present invention, there are provided a rubber composition in which rolling resistance characteristics, wet grip performance, performance on snow and snow, and wear resistance are improved in a well-balanced manner, and a studless tire having a tread made of the rubber composition. be able to.

Claims (3)

For 100 parts by mass of a rubber component comprising 40 to 60% by mass of natural rubber and 40 to 60% by mass of butadiene rubber,
10 to 35 parts by weight of a modified liquid butadiene rubber having a weight average molecular weight of 3000 to 40000, and
A rubber composition comprising more than 50 to 80 parts by mass of silica. The rubber composition according to claim 1, wherein the modified liquid butadiene rubber has its terminal modified with an amino group and / or an alkoxysilyl group. A studless tire having a tread made of the rubber composition according to claim 1.