JP2006022288A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition superior in rolling resistance performance, wet breaking performance and processability without electrostatic troubles such as a radio noise, and a pneumatic tire using it. <P>SOLUTION: This rubber composition comprises a rubber component including a rubbery polymer (A) of 20-60 wt.% of a conjugated diene polymer or a conjugated diene-styrene copolymer modified by a multifunctional compound having a diglycidylamino group and a rubbery polymer (B) of 20-60 wt.% of a conjugated diene polymer or a conjugated diene-styrene copolymer having a primary amino group and an alkoxysilyl group combined to a polymer chain, and a reinforcing material including carbon black and an inorganic filler, wherein its volume resistivity is less than 10<SP>9</SP>Ωcm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  Recently, with increasing interest in the environment and safety, tires are also strongly required to improve fuel economy by reducing rolling resistance, and improve road surface graspability, especially braking performance on wet road surfaces (wet braking performance). became. However, these characteristics are generally contradictory, and in order to achieve both, for example, a modified polymer that interacts with the filler (for example, Patent Document 1 below) or silica as a filler is blended. (Patent Document 2 below).

  However, polymers modified with modifiers such as silicon tetrachloride and tin tetrachloride described in Patent Document 1 meet recent high demands in terms of improving rolling resistance performance and wet braking performance. It ’s difficult.

  In addition, when trying to further improve rolling resistance performance and wet braking performance with only silica compounding, there is a limit to the total amount as a reinforcing agent, so the amount of silica is increased by suppressing the amount of carbon black There is a need. Therefore, the resistance value of the rubber composition increases, and static electricity trouble such as radio noise occurs.

  Incidentally, recently, as a new technology, it has been proposed to use a styrene-butadiene copolymer rubber modified with a polyfunctional compound having a diglycidylamino group (Patent Document 3 below). When this modified rubber is used, the effect is recognized compared with the above-mentioned conventional one in terms of both rolling resistance performance and wet braking performance, but it can be said that it is sufficiently satisfactory for the recent higher required level. Absent.

Patent Document 4 below proposes using a modified styrene-butadiene copolymer rubber having a primary amino group and an alkoxysilyl group. When this modified rubber is used, an excellent effect can be obtained in terms of both rolling resistance performance and wet braking performance. That is, the amino group and the alkoxysilyl group improve the interaction with the filler and improve the dispersibility of the filler, whereby the rolling resistance performance can be greatly improved. However, in this case, since the interaction is too strong, there is a problem that the viscosity of the rubber composition increases, the handling as a rubber sheet is difficult, and the processability is poor.
JP-A-57-55912. JP2003-155383A. JP 2002-284934 A. JP2003-171418A.

  The present invention has been made in view of the above points, and has a good balance between rolling resistance performance and wet braking performance without causing trouble due to static electricity such as radio noise, and also has excellent workability. It aims at providing a composition and a pneumatic tire using the same.

The rubber composition according to the present invention is a conjugated diene polymer or a conjugated diene-styrene copolymer, and is a rubbery polymer (A) 20 to 20 that is modified with a polyfunctional compound having a diglycidylamino group. 60% by weight, a conjugated diene polymer or a conjugated diene-styrene copolymer, and a rubber-like polymer (B) 20-60 having a primary amino group and an alkoxysilyl group bonded to the polymer chain A rubber composition comprising: a rubber component comprising: wt%; and a reinforcing agent comprising carbon black and an inorganic filler, characterized in that the volume resistivity value is less than 10 ⁹ Ω · cm. To do.

  In the rubber composition of the present invention, other diene polymer may be contained in an amount of 20% by weight or less as the rubber component, and in this case, it is preferable to use natural rubber as the other diene polymer.

  The pneumatic tire according to the present invention has a tread composed of these rubber compositions.

According to the present invention, the polymer (A) modified with a polyfunctional compound having a diglycidylamino group and the polymer (B) having an amino group and an alkoxysilyl group are used in combination, thereby impairing workability. In addition, the rolling resistance performance and the wet braking performance can be achieved at a higher level than before, and the volume specific resistance value is less than 10 ⁹ Ω · cm. Can be eliminated. Therefore, it is possible to provide a rubber composition that is extremely useful in practice as a rubber composition for a tire tread.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

1. Polymer (A)
In the rubber composition of the present invention, the polymer (A) used as the rubber component is a conjugated diene polymer or a conjugated diene-styrene copolymer, which is modified with a polyfunctional compound having a diglycidylamino group. A rubbery polymer.

  Such a polymer (A) can be produced by the method described in JP-A No. 2002-284934. That is, a conjugated diene system having an active terminal obtained by anionic polymerization of a conjugated diene or a conjugated diene and styrene in a hydrocarbon solvent using an organic alkali metal and / or organic alkaline earth metal as a polymerization initiator. It can be obtained by reacting a polymer or a conjugated diene-styrene copolymer with a polyfunctional compound having a diglycidylamino group at its active terminal.

  As the conjugated diene, 1,3-butadiene and isoprene are preferable, and the styrene to be copolymerized is preferably a random copolymerized one. Moreover, you may copolymerize another copolymerizable monomer as needed. Preferably, styrene-butadiene copolymer rubber is used as the polymer (A).

  Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as toluene. As the polymerization initiator, n-butyl lithium is preferably used.

  Examples of the polyfunctional compound having a diglycidylamino group used as a modifier include diglycidylaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, and diglycidylaminomethyl. Examples include diglycidylamino compounds such as cyclohexane and tetraglycidyl-1,3-bisaminomethylcyclohexane. The polyfunctional compound is preferably reacted at an epoxy group / active terminal ratio of the polymer in an amount ratio of more than 1 equivalent and 10 equivalents or less. As a result, a modified polymer in which an unreacted epoxy group in a polyfunctional compound molecule bonded to the polymer is present together with a hydroxyl group generated by a reaction between an active terminal of the polymer and an epoxy group, In the case of the above polyfunctional compound, an amino group is also introduced. In the polymer (A), the higher the modification rate by such a polyfunctional compound, the better. However, the modification rate actually has a certain limit, and in the present invention, the polymer (A) is a polyfunctional compound. It is preferable to contain more than 60% by weight of the modified component obtained by the reaction.

  When the polymer (A) is a styrene-butadiene copolymer rubber, the styrene content is preferably 20 to 45% by weight, more preferably 30 to 40% by weight. Further, the vinyl content in the butadiene portion is preferably 15 to 50% by weight, more preferably 25 to 45% by weight.

2. Polymer (B)
In the rubber composition of the present invention, the polymer (B) used as the rubber component is a conjugated diene polymer or a conjugated diene-styrene copolymer, which is a primary amino group bonded to a polymer chain. And a rubbery polymer having an alkoxysilyl group.

  Such a polymer (B) can be produced by the method described in JP-A No. 2003-171418. That is, (1) Anionic polymerization of a conjugated diene, or a conjugated diene and styrene, using an organic alkali metal and / or an organic alkaline earth metal as a polymerization initiator in a hydrocarbon solvent, and having an active terminal obtained thereby. To a conjugated diene polymer or conjugated diene-styrene copolymer, a compound having a protected primary amino group and an alkoxysilyl group is added and reacted at the active end, and then deprotected (hydrolyzed). Or (2) Anionic polymerization of a conjugated diene or a conjugated diene and styrene in a hydrocarbon solvent using a lithium amide with a primary amino group protected as a polymerization initiator. Alkoxysilane compound for conjugated diene polymer or conjugated diene-styrene copolymer with active terminal It reacted to active terminals by adding, then process according deprotection (hydrolysis), the obtained.

  As the conjugated diene, 1,3-butadiene and isoprene are preferable, and the styrene to be copolymerized is preferably a random copolymerized one. Moreover, you may copolymerize another copolymerizable monomer as needed. Preferably, styrene-butadiene copolymer rubber is used as the polymer (B). In addition, as a hydrocarbon solvent, the thing similar to the case of the above-mentioned polymer (A) can be used.

  In the production method of (1) above, as the compound having a protected primary amino group and alkoxysilyl group used as a modifier, an amino group-containing alkoxysilane compound protected with an alkylsilyl group is preferably used. , N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, N, N-bis (trimethylsilyl) aminopropyltrimethoxysilane, N, N -Bis (trimethylsilyl) aminopropylmethyldiethoxysilane and the like. In addition, when 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane is used as a modifier, the silacyclopentane can react with the active ends of two molecules of polymer. As the polymerization initiator, n-butyl lithium is preferably used. Furthermore, the hydrolysis for deprotecting the protected primary amino group is carried out by adding at least twice the mole of water or acidic water of the compound used as the modifier within the temperature range of 80 to 150 ° C. It can be performed by reacting for 10 minutes or more. A known coupling agent such as silicon tetrachloride or tin tetrachloride may be used in combination with the amino group-containing alkoxysilane compound.

  In the production method (2), as the lithium amide initiator, lithium amide having a primary amino group protected with an alkylsilyl group is preferably used. For example, 3- [N, N-bis (trimethylsilyl)]- 1-propyllithium, 3- [N, N-bis (trimethylsilyl)]-2-methyl-1-propyllithium, 4- [N, N-bis (trimethylsilyl)]-1-butyllithium, 3- (2, 2,5,5-tetramethyl-2,5-disila-1-azacyclopentane) -1-propyllithium, 2-methyl-3- (2,2,5,5-tetramethyl-2,5-disila -1-azacyclopentane) -1-propyllithium and the like. Moreover, as an alkoxysilane compound made to react with the active terminal after superposition | polymerization, various alkoxysilane compounds, such as tetramethoxysilane and tetraethoxysilane, can be used. In addition, the hydrolysis for deprotecting the protected primary amino group is performed within a temperature range of 80 to 150 ° C. by adding water or acid water at least twice as much as the lithium amide initiator, It can be performed by reacting for 10 minutes or more.

  When the polymer (B) is a styrene-butadiene copolymer rubber, the styrene content is preferably 30% by weight or less, more preferably 10 to 25% by weight. Moreover, it is preferable that the vinyl content in a butadiene part is 50 weight% or more, More preferably, it is 50 to 70 weight%. Further, when both the polymers (A) and (B) are styrene-butadiene copolymer rubber, the polymer (A) has a higher styrene content and a lower vinyl content in the butadiene portion. preferable.

3. Rubber component In the rubber composition of the present invention, the rubber component comprises 20 to 60% by weight of the polymer (A) and 20 to 60% by weight of the polymer (B). If the ratio of the polymer (A) is less than 20% by weight, the ratio of the polymer (B) increases, the viscosity of the rubber composition increases, and the processability is inferior. The ratio of the coalesced (B) is reduced, and the effect of improving the rolling resistance performance and the wet braking performance is inferior. Further, when the ratio of the polymer (B) is less than 20% by weight, the rolling resistance performance and the wet braking performance are inferior. Conversely, when it exceeds 60% by weight, the viscosity of the rubber composition is increased and the processability is inferior. In addition, it is preferable that a polymer (A) and a polymer (B) are 80 weight% or more of a rubber component with a total amount.

  The rubber component can be composed only of the above polymers (A) and (B), but together with these polymers (A) and (B), other diene polymers (C) are added in an amount of 0 to 20 wt. The total amount of the polymers (A), (B), and (C) is 100% by weight (A + B + C = 100% by weight). That is, the other diene polymer (C) is not essential, but when used in combination, it is preferably 20% by weight or less. If the other diene polymer (C) exceeds 20% by weight, the rolling resistance performance and wet braking performance are not improved. The blending ratio of the other diene polymer (C) is more preferably 10 to 20% by weight.

  Here, the other diene polymer (C) is not particularly limited, and besides natural rubber, isoprene rubber and nitrile rubber, butadiene rubber other than the above polymers (A) and (B), and styrene-butadiene copolymer. Examples include polymer rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and these may be used alone or in combination of two or more. . Among these, natural rubber and butadiene rubber are preferable, and natural rubber is more preferably used in combination. When natural rubber is used in combination, the volume resistivity of the rubber composition is decreased as shown in the examples below. This is presumed that impurities in natural rubber have a conductive effect.

4). Reinforcing Agent In the rubber composition of the present invention, the reinforcing agent blended together with the rubber component is composed of carbon black and an inorganic filler. Here, silica (hydrous silicic acid) is preferably used as the inorganic filler. The compounding amount of carbon black is preferably 20 to 50 parts by weight with respect to 100 parts by weight of the rubber component, and the volume fraction of carbon black with respect to the entire rubber composition is 10 to 15 vol%. Is preferred. When the amount of carbon black is less than this, it is difficult to ensure conductivity. Moreover, as a compounding quantity of an inorganic filler, it is preferable that it is 20-50 weight part with respect to 100 weight part of rubber components. When the amount of the inorganic filler is less than this, the balance between the rolling resistance performance and the wet braking performance is deteriorated. The total amount of carbon black and inorganic filler is preferably 50 to 100 parts by weight based on 100 parts by weight of the rubber component in order to ensure the reinforcing properties required for rubber for tire treads. The ratio of carbon black to inorganic filler is, by weight, carbon black / inorganic filler = 1/2 to 2/1, so that both conductivity and rolling resistance performance / wet braking performance are achieved. Preferred above. Conversely speaking, in the present invention, the balance between the rolling resistance performance and the wet braking performance can be greatly improved by the combination of the polymers (A) and (B) used as the rubber component. The blending amount of the inorganic filler can be reduced, and therefore the carbon black can be increased without increasing the total amount as a reinforcing agent to ensure conductivity, and thus the predetermined reinforcing property and conductivity are ensured. Above, rolling resistance performance and wet braking performance can be improved.

5. Other components In addition to the above-described components, the rubber composition of the present invention includes tire rubbers such as silane coupling agents, anti-aging agents, zinc white, stearic acid, softeners, vulcanizing agents, and vulcanization accelerators. Various additives generally used in the composition can be blended. In addition, 2-25 weight part of silane coupling agents are normally mix | blended with respect to 100 weight part of inorganic fillers.

6). Volume Specific Resistance Value In the rubber composition of the present invention, the volume specific resistance value needs to be less than 10 ⁹ Ω · cm. When the volume resistivity is 10 ⁹ Ω · cm or more, when the rubber composition is used as a rubber for a tire tread, the electric conductivity of the tire is inferior, the static electricity is easily charged, and radio noise is generated during running. This may cause discomfort such as static electricity shock when getting on and off. Such volume specific resistance value can be set within the above range by adjusting the amount of carbon black described above or by using natural rubber in combination with the rubber component.

7). Action The rubber composition comprising the above has the above-mentioned special functional group in the polymer (B) having a problem in workability, although it has an excellent balance between rolling resistance performance and wet braking performance. By using together with the polymer (A), it is possible to achieve both rolling resistance performance, wet braking performance, and workability, and furthermore, as shown in the examples described later, the rolling resistance performance has also been improved. It can be greatly improved. In addition, by setting the volume resistivity to less than 10 ⁹ Ω · cm, troubles due to static electricity such as radio noise can be eliminated, so that it can be preferably used as a rubber for forming a tread of a pneumatic tire. it can.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Preparation of rubber composition)
Using a Banbury mixer, a rubber composition was prepared according to the formulation shown in Table 1 below. The details of each component in Table 1 are as follows.

SBR1: Styrene-butadiene rubber synthesized by the method described in JP-A No. 2002-284934 using tetraglycidyl-1,3-bisaminomethylcyclohexane as a modifying agent (corresponding to the above polymer (A). Styrene) Content = 35% by weight, vinyl content in the butadiene part = 35% by weight, glass transition point = −26 ° C., weight average molecular weight = 950,000).

SBR2: Styrene-butadiene rubber synthesized using SiCl ₄ as a modifier (styrene content = 35 wt%, vinyl content in butadiene portion = 35 wt%, glass transition point = −26 ° C., weight average molecular weight = 1 million).

SBR3: styrene-butadiene rubber synthesized by the method described in JP-A No. 2003-171418 using 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane as a modifier Corresponding to coalescence (B): styrene content = 20% by weight, vinyl content in butadiene part = 60% by weight, glass transition point = −30 ° C., weight average molecular weight = 450,000).

SBR4: Styrene-butadiene rubber synthesized using SnCl ₄ as a modifier (styrene content = 20% by weight, vinyl content in the butadiene part = 60% by weight, glass transition point = −30 ° C., weight average molecular weight = 650,000).

・ NR: Natural rubber (RSS # 3)
・ HISIS BR: JSR butadiene rubber “BR01”
・ Carbon black: N234 "Seast 7H" manufactured by Tokai Carbon
・ Silica: “Ultra Gil VN3” manufactured by Degussa
Coupling agent: “Si75” manufactured by Degussa
In addition, each rubber composition contains, as a common compound, 30 parts by weight of an aroma-based process oil (“Process X-140” manufactured by Japan Energy), 2 parts by weight of stearic acid (“Lunac S-20” manufactured by Kao), zinc 2 parts by weight of Hana (Mitsui Mining & Mining “Zinc Hua 1”), 2 parts by weight of anti-aging agent (“Antigen 6C” by Sumitomo Chemical), 2 parts by weight of wax (“Ozoace 0355” by Nippon Seiki), vulcanized An accelerator (Sumitomo Chemical "Soccinol CZ") 1.5 parts by weight and sulfur (Tsurumi Chemical "powder sulfur") 2.1 parts by weight were blended.

(Evaluation)
Each rubber composition obtained was measured for Mooney viscosity (processability) and volume resistivity (electric resistance). A pneumatic tire was produced using each rubber composition. The tire was manufactured by applying each rubber composition to a cap tread of a 205 / 65R15 94H radial tire for a passenger car having a tread with a cap / base structure, and vulcanizing and molding the rubber composition according to a conventional method. And about each obtained tire, wet braking performance, rolling resistance, and radio noise were evaluated. Each evaluation method is as follows.

Mooney viscosity (workability): Mooney viscosity was measured in accordance with JIS K6300, and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index is, the lower the viscosity is, that is, the better the workability is, and 105 or more means that it is not suitable for actual use.

・ Wet braking: Four tyre tires are mounted on a 2000cc FF vehicle, run on a wet road with a depth of 2-3mm, and the ABS is operated at a speed of 90km / h to decelerate to 20km / h. Was measured (average value of n = 10). The value of Comparative Example 1 is expressed as an index, which is 100. The larger the index, the shorter the braking distance and the better the wet braking performance.

・ Rolling resistance (low fuel consumption): When using a tire with a rim of 15 × 6.5-JJ and running at 23 km and 80 km / h on a rolling resistance measuring drum with an air pressure of 230 kPa and a load of 450 kgf. The rolling resistance was measured. The value of Comparative Example 1 is expressed as an index, and the smaller the index is, the smaller the rolling resistance is, and thus the better the fuel efficiency is.

-Electric resistance (volume specific resistance value): A rubber sheet having a thickness of 2 mm was vulcanized and molded from the rubber composition, and each of the obtained rubber sheets was used at 500V, 23 ° C, 65RH using "High Lester UP" manufactured by Mitsubishi Chemical. The volume resistivity was measured in%.

Radio noise: The pneumatic tire was mounted on the FF vehicle, and the presence or absence of noise during normal driving and AM radio viewing was evaluated.

  As shown in Table 1, when the rubber compositions of Examples 1 to 4, compared with Comparative Example 1, the Mooney viscosity and electrical resistance are not increased, and the wet resistance performance is equal to or higher, and the rolling resistance performance is higher. It was remarkably improved.

  On the other hand, in Comparative Example 2, since SBR2 was used instead of the polymer (A), there was no problem in the balance between the rolling resistance performance and the wet braking performance, but the Mooney viscosity was high and the workability was poor. . In Comparative Example 3, since the reinforcing agent was all carbon black, the balance between rolling resistance performance and wet braking performance was poor. In Comparative Example 4, since the reinforcing agent was all silica, the balance between the rolling resistance performance and the wet braking performance was good, but the Mooney viscosity was high, the electrical resistance was high, and the occurrence of radio noise was also observed. In Comparative Example 5, since SBR4 was used instead of the polymer (B) in Example 3, the balance between the rolling resistance performance and the wet braking performance was insufficient. In Comparative Example 6, since SBR2 was used instead of the polymer (A) in Example 3, the viscosity was high and the processability was poor. In Comparative Example 7, compared with Example 4, SBR4 was used instead of the polymer (B), so that the balance between rolling resistance performance and wet braking performance was insufficient. In Comparative Example 8, since SBR2 was used instead of the polymer (A) in Example 4, the viscosity was high and the processability was poor. In Comparative Example 9, since BR was used excessively, the balance between rolling resistance performance and wet braking performance was inferior. In Comparative Example 10, since SBR1 was used alone, the cost for improving the rolling resistance performance and the wet braking performance was insufficient. In Comparative Example 11, since SBR3 was used alone, the balance between the rolling resistance performance and the wet braking performance was excellent, but the viscosity was high and the workability was poor.

  FIG. 1 shows the relationship between the wet braking performance and the rolling resistance performance of Examples and Comparative Examples. As shown in the figure, in the example, there was a tendency to be clearly superior to the comparative example in that the rolling resistance was lowered without impairing the wet braking performance. On the other hand, Comparative Examples 2, 6, and 8 having high viscosity tended to be relatively close to Examples, but those having low viscosity and satisfying practical processing conditions were compared with Examples. There was clearly a different tendency, and the improvement effect of wet braking performance and rolling resistance performance was inferior.

It is a graph which shows the relationship between wet braking performance and rolling resistance performance about each rubber composition of an Example and a comparative example.

Claims (4)

A conjugated diene polymer or a conjugated diene-styrene copolymer, 20 to 60% by weight of a rubbery polymer (A) modified with a polyfunctional compound having a diglycidylamino group;
A conjugated diene polymer or a conjugated diene-styrene copolymer, comprising 20 to 60% by weight of a rubbery polymer (B) having a primary amino group and an alkoxysilyl group bonded to a polymer chain. A rubber component consisting of
A reinforcing agent comprising carbon black and an inorganic filler;
A rubber composition comprising:
A rubber composition having a volume resistivity value of less than 10 ⁹ Ω · cm.   The rubber composition according to claim 1, wherein the rubber component contains 20% by weight or less of another diene polymer.   The rubber composition according to claim 2, wherein the other diene polymer is natural rubber.   A pneumatic tire having a tread made of the rubber composition according to claim 1.

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