JP6707979B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition which is improved in workability and tensile elongation at break to a level not higher than conventional levels, and a pneumatic tire using the same.

In recent years, pneumatic tires have been required to have high wet grip performance and low rolling resistance. In order to satisfy these requirements, a technique is known in which a reinforcing composition such as a styrene-butadiene copolymer or silica is blended with a rubber composition constituting a tire tread. Further, in order to improve the wear resistance, rubber hardness and impact resilience of the rubber composition, it has been proposed to blend, for example, polybutadiene or highly reactive silica, but in this case the rubber strength and tensile elongation at break are reduced. However, there were problems such as deterioration of workability.

Patent Document 1 discloses a pneumatic tire using a rubber composition in which a styrene-butadiene copolymer in which an arrangement of styrene units is specified and silica are blended in a tread has wet skid resistance, rolling resistance and abrasion resistance at the same time. State that you are satisfied. However, this rubber composition was not able to sufficiently improve the tensile elongation at break and the workability, so that it was not possible to sufficiently satisfy the demands of consumers.

In Patent Document 2, an ozone decomposition product of a styrene-butadiene copolymer is analyzed by gel permeation chromatography (GPC), and a long chain styrene block content ratio to the total styrene content, a single chain containing one styrene unit are contained. State that the proportion is measured. The long-chain styrene block is 5% by weight or less, the single chain having one styrene unit is 50% by weight or more, and the total styrene content is styrene-butadiene based on the total styrene content in the styrene-butadiene copolymer. Styrene-butadiene copolymers having from 10 to 30% by weight of the copolymer are described. However, the rubber composition comprising this styrene-butadiene copolymer could not always sufficiently improve its rubber strength, tensile elongation at break and workability. Further, the analysis by GPC of Patent Document 2 shows that the ozone decomposition product of the styrene-butadiene copolymer can be fractionated based on the number of styrene units and the chain consisting of only styrene units. ,2-The number of units derived from the bond could not be identified. Furthermore, the analysis by GPC was to calculate the ratio of the amount of styrene in the decomposed product to the total amount of styrene, and was not to accurately quantify the amount of each decomposed product.

JP, 03-239737, A JP 57-179212 A

An object of the present invention is to provide a rubber composition whose workability and tensile elongation at break are improved to a level not higher than conventional levels.

The rubber composition of the present invention which achieves the above object is a rubber composition comprising a diene rubber containing at least one styrene-butadiene copolymer and a reinforcing filler, wherein the at least one styrene-butadiene is used. A styrene-butadiene copolymer component composed of a copolymer is characterized by having the following properties (1) to (4).
(1) The content of bound styrene is 5 to 50% by weight
(2) Among the components obtained by ozonolysis, one 1,2-bonded butadiene-derived unit is present in 100 mol% of the total of decomposition components containing styrene-derived units and/or 1,2-bonded butadiene-derived units. The decomposed component V1 containing is not less than 19.5 mol% and less than 25 mol% (3) Of the components obtained by ozonolysis, a total of 100 mol of decomposed components containing a styrene-derived unit and/or a 1,2-bonded butadiene-derived unit %, the decomposition component S2V1 containing two styrene-derived units and one 1,2-bonded butadiene-derived unit is 5 mol% or more (4) The vinyl content of the butadiene portion is 50% or more.

The rubber composition of the present invention has (1) a content of bound styrene of 5 to 50% by weight, and (2) a styrene-derived unit and/or 1,2-bonded component among components obtained by ozonolysis. Decomposition component V1 containing one 1,2-bonded butadiene-derived unit in the total of 100 mol% of the decomposition components containing butadiene-derived units is 19.5 mol% or more and less than 25 mol%, and is obtained by (3) ozone decomposition. Among the components, two styrene-derived units and one 1,2-bonded butadiene-derived unit are contained in 100 mol% in total of the decomposition components containing the styrene-derived unit and/or the 1,2-bound butadiene-derived unit. Since the decomposition component S2V1 contains 5 mol% or more and (4) the vinyl content of the butadiene portion satisfies 50% or more, a diene rubber composed of a styrene-butadiene copolymer component and a reinforcing filler are contained, And tensile elongation at break can be improved to levels higher than conventional levels.

The diene rubber may include at least one diene rubber other than the above-mentioned styrene-butadiene copolymer. The reinforcing filler is preferably at least one selected from silica and carbon black.

The rubber composition described above is preferably used for a pneumatic tire, and particularly preferably for a cap tread. This pneumatic tire has excellent tire durability over the conventional level, and also has excellent productivity and stable production of high-quality tires.

It is an example of a calibration curve showing the correlation between the concentration of a standard sample and ionic strength. It is an example of another calibration curve showing the correlation between the concentration of the standard sample and the ionic strength. It is explanatory drawing which shows the relationship between a chain component and the inclination of a calibration curve, and the inclination of the estimated calibration curve. It is explanatory drawing which shows the relationship of another chain component and the inclination of a calibration curve, and the inclination of the estimated calibration curve. It is explanatory drawing which shows the relationship between another chain component and the inclination of a calibration curve, and the inclination of the estimated calibration curve.

The rubber composition of the present invention comprises a diene rubber and a reinforcing filler. The diene rubber always contains at least one styrene-butadiene copolymer. In the present specification, a polymer component composed of at least one styrene-butadiene copolymer may be referred to as "styrene-butadiene copolymer component". In the present invention, the styrene-butadiene copolymer component satisfies all the following characteristics (1) to (4).
(1) The content of bound styrene is 5 to 50% by weight
(2) Among the components obtained by ozonolysis, one 1,2-bonded butadiene-derived unit is present in 100 mol% in total of the decomposition components containing styrene-derived units and/or 1,2-bonded butadiene-derived units. Less than 25 mol% of the decomposition component V1 containing (3) Of the components obtained by ozone decomposition, a styrene-derived unit is contained in 100 mol% in total of the decomposition components containing a styrene-derived unit and/or a 1,2-bonded butadiene-derived unit. 5 mol% or more of the decomposition component S2V1 containing two butadiene and one 1,2-bonded butadiene-derived unit (4) The vinyl content of the butadiene portion is 50% or more

When the styrene-butadiene copolymer component is composed of a single styrene-butadiene copolymer, the styrene-butadiene copolymer must satisfy all the above-mentioned properties (1) to (4).

When the styrene-butadiene copolymer component is composed of a blend of a plurality of styrene-butadiene copolymers, the styrene-butadiene copolymer component as a whole has all the above-mentioned characteristics (1) to (4). Need to meet. As long as the styrene-butadiene copolymer component as a whole satisfies all the characteristics (1) to (4), each of the styrene-butadiene copolymers constituting the blended product is the above-mentioned (1) to (4). All characteristics may or may not be satisfied. It is preferable that the styrene-butadiene copolymer constituting the blend satisfy all of the characteristics (1) to (4). By constructing the styrene-butadiene copolymer component with two or more kinds of styrene-butadiene copolymers satisfying all the characteristics (1) to (4), the processability of the rubber composition and the tensile elongation at break were excellent. Can be something.

In the present invention, the styrene-butadiene copolymer component has a content of (1) bound styrene of 5 to 50% by weight, preferably 10 to 40% by weight. By setting the styrene content of the styrene-butadiene copolymer component within such a range, it is possible to improve the balance between the moldability of the rubber composition and the tensile elongation at break. When the styrene content of the styrene-butadiene copolymer component is less than 5% by weight, wet skid characteristics, abrasion resistance and rubber strength are deteriorated. When the styrene content of the styrene-butadiene copolymer component exceeds 50% by weight, the glass transition temperature (Tg) of the styrene-butadiene copolymer component increases, the balance of viscoelastic properties deteriorates, and heat generation becomes large. .. That is, the balance between hysteresis loss and wet skid characteristics deteriorates. The styrene content of the styrene-butadiene copolymer component shall be measured by ¹ H-NMR.

The styrene-butadiene copolymer component used in the present invention is measured by a mass spectrometer after the decomposition component obtained by ozone decomposition is fractionated by a liquid chromatogram in two stages using two columns having different characteristics. (Hereinafter, it may be described as “LC×LCMS analysis”). By this LC×LCMS analysis, the composition and amount of the ozone decomposing component can be analyzed in more detail, and in addition to the styrene-derived unit in the ozone decomposing component, the 1,2-bonded butadiene-derived unit can be quantified.

The styrene-butadiene copolymer is a copolymer of styrene and butadiene, and comprises a repeating unit of styrene (styrene unit) and a repeating unit of butadiene (butadiene unit). The butadiene unit is a portion in which butadiene is polymerized with 1,2-bonds (a repeating unit of ethylene having a vinyl group in a side chain) and a portion with 1,4-bonds (a repeating unit of a 2-butylene divalent group). Consists of. The portion polymerized by the 1,4-bond is composed of a repeating unit having a trans-2-butylene structure and a repeating unit having a cis-2-butylene structure.

When styrene-butadiene copolymer is decomposed by ozonolysis, the butadiene portion polymerized by 1,4-bond is cleaved. Further, the vinyl group on the side chain of the butadiene portion polymerized by the 1,2-bond is oxidized to a hydroxymethyl group. As a result, in the styrene-butadiene copolymer, a repeating unit sandwiched between two adjacent 1,4-bond-polymerized butadiene units is produced as an ozone decomposing component. For example, when only one 1,2-bonded butadiene unit in the main chain is sandwiched by two 1,4-bond-polymerized butadiene units, the compound represented by the following general formula (I) is decomposed by ozonolysis. To generate. In the present specification, the compound represented by the general formula (I) is referred to as "ozone decomposing component V1". In the present specification, the direction in which adjacent units are linked may be a head-to-tail bond or a head-to-head bond, and the head-to-tail bond/head-to-head bond represented by the chemical formula are to be mutually replaced. .

Further, in the main chain, when a portion sandwiched between two styrene units and one 1,2-bond-polymerized butadiene unit and a neighboring 1,4-bond-polymerized butadiene unit undergoes ozonolysis, the following general formula (II) A compound represented by In the present specification, the decomposition component composed of two styrene-derived units and one 1,2-bond-polymerized butadiene-derived unit is referred to as "ozone decomposition component S2V1".

The compound represented by the general formula (II) is selected from the order of arrangement of two styrene-derived units and one 1,2-bonded butadiene-derived unit, head-to-tail bond/head-to-head bond and their arrangement order. Also included are compounds in which at least one of them is different.

As described above, the portion sandwiched between two adjacent 1,4-bond-polymerized butadiene units is a styrene-derived unit and/or a 1,2-bonded butadiene-derived unit formed by a hydroxyethyl group at both ends by ozonolysis. It is generated as a decomposition component sandwiched between. Further, 1,4-butanediol is produced from a repeating portion in which two or more butadiene units polymerized by 1,4-bonds are continuous.

The styrene-butadiene copolymer component used in the present invention is a styrene-derived unit and/or 1 among the components obtained by (2) ozonolysis when the decomposition component obtained by ozonolysis is measured by LC×LCMS analysis. The decomposition component V1 containing one 1,2-bonded butadiene-derived unit is less than 25 mol% in a total of 100 mol% of the decomposition components containing the 1,2-bonded butadiene-derived unit. The decomposition component containing one 1,2-bonded butadiene-derived unit means the ozone decomposition component V1 containing only one 1,2-bonded butadiene-derived unit as described above. The number of moles of each decomposition component can be obtained by measuring the ozone decomposition component by LC×LCMS analysis. Next, the total number of moles of decomposition components containing styrene-derived units and/or 1,2-bonded butadiene-derived units produced by ozonolysis is calculated, and this is defined as 100 mol% of ozonolysis components. The amount of the decomposition component V1 containing one 1,2-bonded butadiene-derived unit is less than 25 mol% and preferably 10 mol% or more and less than 25 mol% in 100 mol% of the ozone decomposition component. When the ozonolysis component V1 is less than 25 mol %, the rubber composition can have excellent tensile elongation at break. Further, it is possible to reduce the viscosity of the rubber composition and make it excellent in moldability.

In addition to the above, the styrene-butadiene copolymer component used in the present invention has two (3) styrene-derived units and 1,2-bond when the decomposition component obtained by (3) ozone decomposition is measured by LC×LCMS analysis. The decomposition component S2V1 containing one butadiene-derived unit is 5 mol% or more, preferably 6 to 12 mol %. Here, the ozone decomposing component S2V1 is an ozone decomposing component containing only two styrene-derived units and one 1,2-bonded butadiene-derived unit as described above, and is the same as the decomposing component represented by the general formula (II). Equivalent to. The number of moles of the decomposition component represented by the general formula (II) can be obtained by measuring the ozone decomposition component by LC×LCMS analysis. When the total number of moles of the decomposition component containing the styrene-derived unit and/or the 1,2-bonded butadiene-derived unit is calculated to be 100 mol% of the ozone decomposition component, two styrene-derived units and 1,2 The ozonolysis component S2V1 consisting of one unit of butadiene-derived units must be 5 mol% or more. By doing so, the tensile elongation at break of the rubber composition can be made excellent. Further, it is possible to reduce the viscosity of the rubber composition and to improve the molding processability.

In the present specification, the method of ozone decomposing a styrene-butadiene copolymer component and the measurement of ozone degradants are described in Tanaka et al. [Polymer, 22, 1721 (1981)] and [Macromolecules, 16, 1925 (1983)]. It shall be carried out according to the specified method. In the analysis method described in Tanaka et al., the ozone decomposition component S1 containing only one styrene-derived unit and the ozone decomposition component S1Vn(n containing one styrene-derived unit and one or more 1,2-bonded butadiene-derived units are included. Is called a "styrene single chain". On the other hand, in the present invention, as described above, the number of moles of the ozone decomposing component S1 containing only one styrene-derived unit and the ozone decomposing component S2V1 containing two styrene-derived units and one 1,2-bonded butadiene-derived unit. Focusing on, the analysis is individually performed by LC×LCMS analysis.

In the present specification, the conditions for measuring the ozone decomposing component by LC×LCMS analysis can be as follows.
Liquid chromatograph: Comprehensive two-dimensional LC Nexera-e (manufactured by Shimadzu Corporation)
Mass spectrometer: LCMS-8040 or LCMS-8050 (both manufactured by Shimadzu Corporation)
First-dimensional column: Two columns (A) in which the stationary phase is a polymer gel (Shodex Mspak GF-310 2D manufactured by Showa Denko KK, inner diameter: 2.0 mm, length 150 mm, particle size 5 μm) and the stationary phase is a polymer One column (B) that is a gel (Super HZ 1000 manufactured by Tosoh Corporation, inner diameter: 2.0 mm, length 250 mm, particle size 3 μm) is used by connecting three in series Injection volume: 1 μL (sample solution (Concentration: 10 mg/mL)
Mobile phase: THF
Flow rate: 0.02 mL/min
Second-dimensional column: Column (A) in which the stationary phase is a core-shell polymer gel modified with an octadecyl group (Kinetex C18 manufactured by Phenomenex, inner diameter: 3.0 mm, length 50 mm, particle diameter 2.6 μm)
Mobile phase A: water:methanol=1:1
Mobile phase B: Methanol flow rate: 2.0 mL/min
Time program: B conc. 20% (0 minutes) → 100% (0.75 minutes) → 20% (0.76 minutes) → STOP (1 minute)
Interface temperature: 350℃
Desolvation temperature: 200°C
Interface voltage: 4.5V
Interface (Ionization method): (APCI positive mode)
Mass analysis conditions: SIM measurement 9event (ev1: S1~S1V10, ev2: S2~S2V10, ev3: S3~S3V10, ev4: S4~S4V10, ev5: S5~S5V10, ev6: S6~S6V10, ev7: S7~S7V10, ev8: S8 to S8V10, ev9: V1 to V10) Total 98 ch SIM+ SIM for each minute 98 event (for making calibration curve) Total 107 event
Detection ion: Proton-added ion (m/z=[M+H]+)

Here, a commercially available sample may be used as the standard sample, or a sample obtained by separating and collecting from the ozone decomposition product of SBR and calculating the purity by NMR or the like may be used. For example, a standard sample can be prepared as follows.

Solution-polymerized SBR having a styrene content of 36% by weight and a vinyl content of 42% in butadiene was subjected to ozonolysis treatment, and LC-9104 (preparative GPC) manufactured by Japan Analytical Industry Co., Ltd. and four low molecular weight columns (JAIGEL-1H, JAIGEL) were used. -2H (two each), and a total of 7 components of S1, S1V1, S2, S2V1, S3, S3V1, and V1 were collected in a chloroform solvent, and the purity was calculated by NMR to obtain a standard sample.

Polybutadiene having a vinyl content of 70% was subjected to ozonolysis treatment, and a column (VP-ODS 150 mm×4.6 mm) was used in an HPLC system Prominence manufactured by Shimadzu Corporation, using mobile phase A as water and mobile phase B as methanol. First, by confirming the elution time of the components by mass spectrometry ionization condition APCI+ by a gradient measurement of 20%B-100%B for 40 minutes with a flow rate of 1 mL/min and an injection amount of 0.2 μL, V1, V2, and V3 are set to time. Was collected and the purity was calculated by NMR to obtain a standard sample.

LC×LCMS analysis can be performed by the following operations.
For the analysis, LCMS-8040 (product name) or LCMS-8050 (product name) manufactured by Shimadzu Corporation is used, and the standard sample obtained above is measured by the APCI positive MS mode.

A correlation diagram (calibration curve) between the concentration and ionic strength of each standard sample was created based on the detection results of the mass spectrometer. The created correlation diagrams are shown in FIGS. 1 and 2. 1 and 2, symbols such as "S1V1", "V1", and "S2" represent the number of 1,2-bonded butadiene-derived units and the number of styrene-derived units of the compound showing the calibration curve. For example, the symbol "S1V1" indicates that the compound has one 1,2-bonded butadiene-derived unit and one styrene-derived unit. As can be seen from FIGS. 1 and 2, the calibration curve differs depending on the number of styrene-derived units and the number of 1,2-bonded butadiene-derived units contained in the compound.

<Estimation of calibration curve>
In the case of SBR whose structure is unknown, there are various types of ozone decomposing components, and it is not possible to perform quantitative analysis of all decomposing components only with the calibration curves of the compounds shown in FIGS. 1 and 2. Therefore, from the calibration curve obtained for the above-mentioned standard sample, a calibration curve for the decomposition product component whose mass-to-charge ratio is unknown was estimated.

Specifically, for the chain component Sn of styrene only, the amount of change in the slope of the calibration curve when the number of chains of styrene increases by 1 is calculated from the calibration curves of S1 to S3, and the chain component Sn( The slope of n≧4) was estimated. The slope of the calibration curve was estimated in the same manner for the chain component (Vm) composed of 1,2-bonded butadiene-derived units. The slope of the estimated calibration curve is shown in FIG.

On the other hand, regarding the chain component (SnVm) composed of a styrene-derived unit and a 1,2-bonded butadiene-derived unit, the slope when the number of 1,2-bonded butadiene chains is changed while fixing the number of styrene chains From the styrene and 1,2-bonded butadiene derived units with respect to the slope of the calibration curve from the change amount of the slope of the calibration curve when the number of styrene chains is changed by fixing the number of 1,2-bonded butadiene chains. Was calculated, and the slope of the calibration curve of the chain component SnVm was estimated from the contribution of styrene and the unit derived from 1,2-bonded butadiene and the number of chains. 3 to 5 show the slope of the calibration curve of the chain component obtained from the actually measured results and the slope of the calibration curve estimated by the above method.

<Creation of two-dimensional chromatogram>
Next, the ozonolysis product component was analyzed by LCxLCMS. The apparatus and analysis conditions used for the analysis are the same as those used for creating the calibration curve.

The detection results of the mass spectrometer were analyzed using analysis software ChromSquare (manufactured by Shimadzu Corporation), and the elution time of the primary column was represented by the horizontal axis, the elution time of the secondary column by the vertical axis, and the signal intensity was represented by contour lines. A two-dimensional chromatogram was created. By using LCxLC, it is possible to separate components such as S2V1 and S1V1 whose elution times are very close to each other, so that the chain structure of the styrene-derived unit and the 1,2-bonded butadiene-derived unit contained in the sample can be identified. Became possible.

The styrene-butadiene copolymer component used in the present invention has a vinyl content of (4) butadiene moiety of 50% or more, preferably 50 to 65%. By setting the vinyl content of the butadiene portion in the styrene-butadiene copolymer component to 50% or more, it is possible to suppress the Mooney viscosity from becoming excessively small and improve the moldability. Further, by setting the vinyl content in the butadiene portion to 50% or more, it is possible to secure rubber strength and wear resistance and suppress an increase in hysteresis loss. The vinyl content of the butadiene portion shall be measured by ¹ H-NMR.

The content of the styrene-butadiene copolymer component having the characteristics (1) to (4) is preferably 40% by weight or more, more preferably 60 to 100% by weight, further preferably 100% by weight of the diene rubber. It is 80 to 100% by weight. By containing 40% by weight or more of the styrene-butadiene copolymer component specified by the properties (1) to (4), the rubber composition has excellent tensile elongation at break and improved molding processability. can do.

The rubber composition of the present invention may contain a diene rubber other than the styrene-butadiene copolymer component that satisfies all the characteristics (1) to (4). Examples of other diene rubbers include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (low cis BR), high cis BR, high trans BR (trans bond content of butadiene part 70 to 95%), styrene. -Isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution polymerization random styrene-butadiene-isoprene copolymer rubber, emulsion polymerization random styrene-butadiene-isoprene copolymer rubber, emulsion polymerization styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile- Examples thereof include butadiene copolymer rubber, high vinyl SBR-low vinyl SBR block copolymer rubber, polyisoprene-SBR block copolymer rubber, polystyrene-polybutadiene-polystyrene block copolymer and the like.

The content of the other diene rubber is 100% by weight of the diene rubber, preferably 60% by weight or less, more preferably 0 to 40% by weight, and further preferably 0 to 20% by weight. By containing other diene rubber, various physical properties such as abrasion resistance can be improved.

The rubber composition of the present invention contains a diene rubber and a reinforcing filler. As the reinforcing filler, for example, carbon black, silica, clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, inorganic filler such as barium sulfate, cellulose, lecithin, lignin, An organic filler such as a dendrimer can be exemplified. Above all, it is preferable to blend at least one selected from carbon black and silica.

By adding carbon black to the rubber composition, the rubber composition can have excellent abrasion resistance and rubber strength. The blending amount of carbon black is not particularly limited, but is preferably 10 to 100 parts by weight, and more preferably 25 to 80 parts by weight with respect to 100 parts by weight of the diene rubber.

As the carbon black, furnace black, acetylene black, thermal black, channel black, carbon black such as graphite may be blended. Of these, furnace black is preferable, and specific examples thereof include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, and FEF. These carbon blacks can be used alone or in combination of two or more. Further, surface-treated carbon black obtained by chemically modifying these carbon blacks with various acid compounds can also be used.

Further, by adding silica to the rubber composition, the rubber composition can have low heat build-up and excellent wet grip performance. The amount of silica is not particularly limited, but is preferably 10 to 150 parts by weight, and more preferably 40 to 100 parts by weight, based on 100 parts by weight of the diene rubber.

As silica, silica usually used in rubber compositions for tire treads, for example, wet process silica, dry process silica, or carbon-silica (dual phase filler) having silica supported on the surface of carbon black, silane coupling It is possible to use silica or the like which has been surface-treated with a compound which is reactive or compatible with both silica and rubber such as an agent or polysiloxane. Among these, wet process silica containing hydrous silicic acid as a main component is preferable.

In the present invention, the compounding amount of the reinforcing filler containing silica and/or carbon black is preferably 10 to 150 parts by weight, and more preferably 40 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. If the compounding amount of the reinforcing filler is less than 10 parts by weight, the reinforcing performance cannot be sufficiently obtained, and the rubber hardness and the tensile breaking strength are insufficient. On the other hand, if the amount of the reinforcing filler compounded exceeds 150 parts by weight, the exothermic property increases and the tensile breaking elongation decreases. In addition, the wear resistance deteriorates and the workability also deteriorates.

The rubber composition of the present invention is preferable because the low heat buildup property and abrasion resistance are further improved by blending a silane coupling agent together with silica. By blending a silane coupling agent with silica, the dispersibility of silica is improved and the reinforcing property with a diene rubber is further enhanced. The silane coupling agent is preferably added in an amount of 2 to 20% by weight, more preferably 5 to 15% by weight, based on the amount of silica. If the blending amount of the silane coupling agent is less than 2% by weight based on the weight of silica, the effect of improving the dispersibility of silica cannot be sufficiently obtained. On the other hand, if the silane coupling agent exceeds 20% by weight, the diene rubber component tends to gel, and the desired effect cannot be obtained.

The silane coupling agent is not particularly limited, but a sulfur-containing silane coupling agent is preferable, and examples thereof include bis-(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)trisulfide. , Bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-trimethoxysilylethyl) tetrasulfide, 3- Mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and VP Si363 manufactured by Evonik Co., Ltd. No. 2,490,69, such as mercaptosilane compounds, 3-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-tri Methoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, 3-octa Noylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxy Propylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β- Aminoamino)-γ-aminopropylmethyldimethoxysilane and the like. Wear. Further, the silane coupling agent is an organosilicon compound, and as the organosilicon compound, a polysiloxane, a side chain or both ends of the polysiloxane, one end or both side chains and both ends have an amino group, an epoxy group, a carbinol group, or a mercapto group. Group, carboxyl group, hydrogen group, polyether group, phenol group, silanol group, acryl group, methacryl group, long-chain alkyl group, or other silicone group having one or more organic groups introduced, and one or more organosilanes condensed Examples thereof include silicone oligomers obtained by the reaction. Of these, bis-(3-triethoxysilylpropyl) tetrasulfide and bis(3-triethoxysilylpropyl) disulfide are preferable.

In addition to the above-mentioned components, the rubber composition of the present invention has a vulcanization or cross-linking agent, a vulcanization accelerator, an antioxidant, a processing aid, a plasticizer, a liquid polymer, a thermosetting resin, and a thermoplastic resin according to a conventional method. Various compounding agents generally used in rubber compositions for tire treads such as resins can be compounded. Such a compounding agent can be kneaded by a general method into a rubber composition, which can be used for vulcanization or crosslinking. The compounding amount of these compounding agents can be a conventional general compounding amount as long as the object of the present invention is not violated. The rubber composition for tire tread can be prepared by mixing the above components using a known rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

The vulcanizing or crosslinking agent is not particularly limited, but examples thereof include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur; halogens such as sulfur monochloride and sulfur dichloride. Sulfurized oxide; organic peroxides such as dicumyl peroxide, ditertiary butyl peroxide and the like. Among these, sulfur is preferable, and powdered sulfur is particularly preferable. These vulcanizing or crosslinking agents may be used alone or in combination of two or more. The compounding ratio of the vulcanizing agent is usually 0.1 to 15 parts by weight, preferably 0.3 to 10 parts by weight, and more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the diene rubber. is there.

The vulcanization accelerator is not particularly limited, and examples thereof include N-cyclohexyl-2-benzothiazylsulfenamide, Nt-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfamide. Sulfenamide vulcanization accelerators such as phenamide, N-oxyethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, dioltotolylguanidine, ortho Guanidine vulcanization accelerators such as tolylbiguanidine; Thiourea vulcanization accelerators such as diethylthiourea; Thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and 2-mercaptobenzothiazole zinc salt; Thiuram-based vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; Dithiocarbamate-based vulcanization accelerators such as sodium dimethyldithiocarbamate and zinc diethyldithiocarbamate; Sodium isopropylxanthate, zinc isopropylxanthate, butylxanthogen A vulcanization accelerator such as a xanthogenic acid-based vulcanization accelerator such as zincate. Among them, those containing a sulfenamide vulcanization accelerator are particularly preferable. These vulcanization accelerators may be used alone or in combination of two or more. The compounding amount of the vulcanization accelerator is preferably 0.1 to 15 parts by weight, and more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the diene rubber.

The antiaging agent is not particularly limited, but is 2,2,4-trimethyl-1,2-dihydroquinoline polymer, p,p'-dioctyldiphenylamine, N,N'-diphenyl-p-phenylenediamine, N- Amine-based antioxidants such as phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, 2,6-di-t-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-) 6-t-butylphenol) and other phenolic antiaging agents. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the diene rubber.

The processing aid is not particularly limited, for example, higher fatty acid such as stearic acid, higher fatty acid amide such as stearic acid amide, aliphatic higher amine such as stearylamine, aliphatic higher alcohol such as stearyl alcohol, Partial esters of fatty acids and polyhydric alcohols such as glycerin fatty acid esters, fatty acid metal salts such as zinc stearate, zinc oxide and the like can be used. The blending amount is appropriately selected, but the blending amount of the higher fatty acid, the aliphatic higher amide, the higher alcohol, and the fatty acid metal salt is preferably 0.05 to 15 parts by weight, more preferably 100 parts by weight of the diene rubber. Is 0.5 to 5 parts by weight. The blending amount of zinc oxide is preferably 0.05 to 10 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the diene rubber.

The plasticizer used as a compounding agent is not particularly limited, but, for example, an aroma-based, naphthene-based, paraffin-based or silicone-based extender oil is selected according to the application. The amount of the plasticizer used is usually 1 to 150 parts by weight, preferably 2 to 100 parts by weight, and more preferably 3 to 60 parts by weight per 100 parts by weight of the diene rubber. When the amount of the plasticizer used is within this range, the dispersing effect of the reinforcing agent, tensile strength, abrasion resistance, heat resistance, etc. are balanced to high values. Other plasticizers include diethylene glycol, polyethylene glycol, silicone oil and the like.

The thermosetting resin is not particularly limited, but examples thereof include resorcin-formaldehyde resin, phenol-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin, phenol derivative-formaldehyde resin, and specifically m-3. , 5-xylenol-formaldehyde resin, 5-methylresorcinol-formaldehyde resin and other thermosetting resins that cure or become high molecular weight by heating or by applying heat and a methylene donor, and other guanamine resins, diallyl phthalate Examples thereof include resins, vinyl ester resins, phenol resins, unsaturated polyester resins, furan resins, polyimide resins, polyurethane resins, melamine resins, urea resins, epoxy resins and the like.

The thermoplastic resin is not particularly limited, for example, polystyrene resin, polyethylene resin, polypropylene resin, polyester resin, polyamide resin, polycarbonate resin, polyurethane resin, polysulfone resin, as a general-purpose resin, Examples thereof include polyphenylene ether-based resins and polyphenylene sulfide-based resins. In addition, aromatic hydrocarbon resins such as styrene-α-methylstyrene resin, indene-isopropenyltoluene resin, coumarone-indene resin, dicyclopentadiene resin, main raw materials are 1,3-pentadiene, pentene, methylbutene, etc. Examples include hydrocarbon resins such as petroleum resins, alkylphenol resins, modified phenol resins, terpene phenol resins, terpene-based resins, and aromatic modified terpene resins.

Since the rubber composition of the present invention is designed to improve the workability and the tensile elongation at break above the conventional level, it improves the durability of the pneumatic tire above the conventional level and also provides a high-quality tire with excellent productivity. It can be stably produced.

The rubber composition of the present invention is a cap tread portion of a pneumatic tire, an undertread portion, a sidewall portion, a bead filler portion, and a cord covering rubber such as a carcass layer, a belt layer and a belt cover layer, and a cross section in a run flat tire. It can be suitably used for a crescent-shaped side reinforcing rubber layer, a rim cushion portion, and the like.

Hereinafter, the present invention will be further described with reference to examples, but the scope of the present invention is not limited to these examples.

Eight types of styrene-butadiene copolymers were blended at the compounding ratio shown in Table 1 to prepare a styrene-butadiene copolymer component, and (1) content of bound styrene (% by weight), (2) 1,2 -Mol% of the ozonolysis component V1 containing one bonded butadiene-derived unit, (3) mol% of the ozonolysis component S2V1 containing two styrene-derived units and one 1,2-bonded butadiene-derived unit, and (4) The vinyl content (% by weight) of the butadiene portion was measured. Further, since the styrene-butadiene copolymer NS570, Tuffden E581, and HP755B are oil-extended products, the actual blending amount is shown in parentheses together with the actual blending amount.

The (1) bound styrene content of the styrene-butadiene copolymer component and the (4) vinyl content of the butadiene moiety were measured by ¹ H-NMR.

The conditions for ozonolysis of the styrene-butadiene copolymer component were as described above. Further, (2) mol% of the ozone decomposing component V1 containing one 1,2-bonded butadiene-derived unit, (3) ozonolysis containing two styrene-derived units and one 1,2-bonded butadiene-derived unit. The mol% of the component S2V1 was measured based on the conditions described above by LC×LCMS analysis.

Eight types of rubber compositions comprising the compounding agents shown in Table 2 as a common compounding agent and compounding the styrene-butadiene copolymer component (blend of a plurality of styrene-butadiene copolymers) shown in Table 1 and another diene rubber The materials (Examples 1 , 3, 5, Reference Examples 2, 4 and Comparative Examples 1 to 3) were mixed with the components excluding sulfur and the vulcanization accelerator for 6 minutes using a 1.7 L closed Banbury mixer. After discharging from the mixer at 150° C., it was cooled to room temperature. Then, the mixture was mixed again for 3 minutes using a 1.7 liter closed Banbury mixer, and after discharging, sulfur and a vulcanization accelerator were mixed with an open roll to prepare a rubber composition. The Mooney viscosity of the obtained rubber composition was evaluated by the following measuring method. The obtained rubber composition was vulcanized at 160° C. for 30 minutes using a predetermined mold to prepare a vulcanized rubber test piece. Using the obtained vulcanized rubber test piece, the tensile elongation at break was evaluated by the following measuring method.

Mooney viscosity The Mooney viscosity (ML ₁₊₄ ) of the rubber composition was measured using a Mooney viscometer in accordance with JIS K6300 using an L-shaped rotor, preheating time 1 minute, rotor rotation time 4 minutes, temperature 100°C. It was measured under the condition of 2 rpm. The obtained results are shown in the column of "Mooney viscosity" in Table 1 as an index with Comparative Example 1 being 100. The smaller the index of "Moonie viscosity", the lower the Mooney viscosity and the better the moldability.

Tensile Break Elongation Using the obtained vulcanized rubber test piece, a dumbbell JIS No. 3 type test piece was prepared according to JIS K6251 and a tensile test was performed at room temperature (20° C.) at a pulling speed of 500 mm/min. The tensile breaking elongation at break was measured. The obtained results are shown in the "Tensile breaking elongation" column of Table 1 as an index for setting the value of Comparative Example 1 to 100. The larger the index of "tensile breaking elongation", the greater the tensile breaking elongation.

In Table 1, the types of raw materials used are as follows.
-NS116: Nippon Zeon NS116, bound styrene amount 20.9% by weight, vinyl content 63.8%, non-oil extended product NS570: Nippon Zeon NS570, bound styrene amount 40.6% by weight, An oil-extended product having a vinyl content of 19.0% and 37.5 parts by weight of an oil component added to 100 parts by weight of SBR. 3%, oil-extended product in which 37.5 parts by weight of oil component is added to 100 parts by weight of SBR. Extend product HP755B: HPR 755B made by JSR, bound styrene amount 39.6% by weight, vinyl content 39.4%, oil extended product 37.5 parts by weight added to SBR 100 parts by weight HPR850: made by JSR HPR850, bound styrene content 27.0% by weight, vinyl content 58.8%, non-oil extended product NR: natural rubber, TSR20
BR: polybutadiene, Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.
・Oil: Extract No. 4S manufactured by Showa Shell Sekiyu KK

The types of raw materials used in Table 2 are shown below.
・Silica: Nip seal AQ manufactured by Nippon Silica Co., Ltd.
-Silane coupling agent: sulfide-based silane coupling agent, Si69VP manufactured by Degussa
-Carbon black: Show black N339M manufactured by Showa Cabot
Zinc oxide: 3 types of zinc oxide manufactured by Shodo Kagaku Kogyo Co., Ltd.-Stearic acid: stearic acid manufactured by NOF CORPORATION Anti-aging agent: Santoflex 6PPD manufactured by Solutia Euro
・Wax: Paraffin wax manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. ・Sulfur: Sulfur vulcanization accelerator from Karuizawa Smelter & Refinement-1: Sanshin Chemical Co., Ltd. CM-PO (CZ)
・Vulcanization accelerator -2: Sanshin Chemical Co., Ltd. Sancellar DG (DPG)

As is clear from Table 1 , the rubber compositions of Examples 1 , 3, and 5 were confirmed to improve Mooney viscosity and tensile elongation at break.

The rubber composition of Comparative Example 2 contained 25 mol% or more of the ozonolysis component V1 containing one 1,2-bonded butadiene-derived unit, two styrene-derived units and one 1,2-bonded butadiene-derived unit. Since the ozone decomposing component S2V1 contained therein is less than 5 mol %, the Mooney viscosity is large and the moldability is poor.

In the rubber composition of Comparative Example 3, the styrene-butadiene copolymer component contained 25 mol% or more of the ozone decomposing component V1 containing one 1,2-bonded butadiene-derived unit, two styrene-derived units and 1,1. Since the ozone decomposing component S2V1 containing one 2-bonded butadiene-derived unit is less than 5 mol %, the Mooney viscosity is large, the moldability is poor, and the tensile elongation at break is small.

Claims (6)

A rubber composition comprising a diene rubber containing at least one styrene-butadiene copolymer and a reinforcing filler, wherein the styrene-butadiene copolymer component comprising at least one styrene-butadiene copolymer is A rubber composition having the following characteristics (1) to (4).
(1) The content of bound styrene is 5 to 50% by weight
(2) Among the components obtained by ozonolysis, one 1,2-bonded butadiene-derived unit is present in 100 mol% of the total of decomposition components containing styrene-derived units and/or 1,2-bonded butadiene-derived units. The decomposed component V1 containing is not less than 19.5 mol% and less than 25 mol% (3) Of the components obtained by ozonolysis, a total of 100 mol of decomposed components containing a styrene-derived unit and/or a 1,2-bonded butadiene-derived unit %, the decomposition component S2V1 containing two styrene-derived units and one 1,2-bonded butadiene-derived unit is 5 mol% or more (4) The vinyl content of the butadiene portion is 50% or more. The rubber composition according to claim 1, wherein the decomposition component S2V1 described in (3) above is 8.6 mol% or more and 9.9 mol% or less. The rubber composition according to claim 1 or 2 , wherein the diene rubber further contains at least one diene rubber other than the styrene-butadiene copolymer. The reinforcing filler is silica, the rubber composition according to any one of claims 1-3, characterized in that it consists of at least one selected from carbon black. A pneumatic tire characterized by using the rubber composition according to any one of claims 1-4. The pneumatic tire according to claim 5 , wherein the rubber composition is used for a cap tread.

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