JP2001316527A - Rubber composition and pneumatic tire produced by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition free from the lowering of initial elastic modulus and the shortening of Mooney scorch time, having excellent thermal curing retarding property, capable of suppressing the hardening by thermal history and especially suitable for a pneumatic tire. SOLUTION: The rubber composition contains 100 pts.wt. of a rubber component composed of at least one kind of diene rubber, 0.5-5.0 pts.wt. of a vulcanization accelerator, 1.0-3.5 pts.wt. of sulfur and 0.65-1.80 pts.wt. of zinc element in the form of a composite zinc white as the zinc source of the zinc element. The composite zinc white preferably has a zinc oxide layer on the surface and/or contains an inorganic metal salt in the zinc white.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition particularly suitable for pneumatic tires, which does not reduce the initial elastic modulus or shortens the Mooney scorch time, is excellent in heat curing inhibition, can suppress curing due to heat history, and is excellent in rubber composition. Thing, and using the rubber composition,
Driving stability (hereinafter, sometimes referred to as “maneuverability”) and vibration riding comfort (hereinafter, “ride comfort”) from the beginning to the end of driving
And pneumatic tires.

[0002]

2. Description of the Related Art In recent years, with the advancement of high horsepower, high functionality, and long life of automobiles, pneumatic tires of such automobiles have a high balance between the above-mentioned maneuverability and the above-mentioned ride comfort, and have been developed in the middle of running. It is required to maintain these performances from the end to the end. In pneumatic tires of passenger cars that have transitioned from bias tires to radial tires, there has been a problem that, with the development of flattening, the maneuverability has been greatly improved, but the ride comfort has not always been sufficiently improved. For this reason, in the radial tire, it is particularly required that these performances be highly compatible.

[0003] The rubber composition used for the tread in the pneumatic tire has a large effect on the maneuverability and the riding comfort. It is known that these properties vary greatly depending on the hysteresis loss, viscoelasticity, modulus, hardness, Poisson's ratio, temperature dependency, and the like of the rubber composition. However, the details are unknown, the polymer contained in the rubber composition, a softener,
The mechanism of the synergistic effect of each of the materials such as the vulcanizing agent and the vulcanization accelerator and of the combination is unknown.

On the other hand, as the energy loss when the rubber composition used for the tread is deformed due to the unevenness of the road surface increases, the coefficient of friction between the rubber composition and the road surface increases,
It is known that the maneuverability is improved. Further, as the energy loss increases, the rubber composition easily absorbs the impact from the unevenness of the road surface like a damper,
It is known that the ride comfort is improved. Then, in order to increase the energy loss in the rubber composition, a styrene-butadiene rubber (SB) capable of utilizing the cohesive energy of styrene is used for the rubber composition.
It is known to use R) and aromatic softeners.

[0005] In a pneumatic tire using a rubber composition having a large energy loss in a tread, the energy absorption of the rubber composition is reduced by running, and the maneuverability and the riding comfort are deteriorated. There is a problem. It is considered that the decrease in the energy absorbing power is caused by the rubber composition being cured during running.

[0006] For this reason, in order to achieve a high balance between the maneuverability and the ride comfort, it is necessary to suppress the curing of the rubber composition during traveling.

[0007] Rubber compositions used in treads of pneumatic tires are generally cross-linked by sulfur. However, in the rubber composition cross-linked by the sulfur,
In the early stage of use, there is a crosslinked chain crosslinked with a relatively long polysulfide, but as the heat history increases due to use, the crosslinked chain is rearranged, and the polysulfide is converted into a shorter crosslinked chain such as disulfide, monosulfide. There is a problem that the crosslinking density increases with the change, and the resin gradually cures.

[0008] In addition to the sulfur as a crosslinking agent, a vulcanization accelerator, zinc white, stearic acid and the like are generally added to the rubber composition. The vulcanization accelerator may be added at the time of compounding the rubber composition with the help of stearic acid and / or
Alternatively, it reacts with the zinc white at the time of vulcanization to produce a zinc salt having a function as an accelerator for substantially accelerating a crosslinking reaction with polysulfide. However, in a rubber composition in which the zinc salt remains unreacted after vulcanization, the zinc salt also promotes crosslinking by polysulfide or unreacted free sulfur present as a crosslinking chain, and gradually cures. Problem.

In order to solve these problems, Japanese Patent Application Laid-Open No. Hei 10-77365 discloses a vulcanization accelerator and an accelerator such as bis (4-methylbenzothiazolyl-2) -disulfide.
It is disclosed to be applied to the aroma compounding of BR rubber. In this case, although the thermosetting inhibition of the rubber composition is certainly improved, and the maneuverability and the ride comfort at the end of running of the pneumatic tire are improved, the accelerator used here is expensive. There is a practical problem that the synthesis is difficult and the versatility is poor.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention does not reduce the initial elastic modulus or shorten the Mooney scorch time, and is excellent in heat-curing suppression properties,
A rubber composition that can suppress curing due to heat history and is particularly suitable for pneumatic tires, and using the rubber composition, steering stability (hereinafter sometimes referred to as “steerability”) and vibration riding from the beginning to the end of running. An object of the present invention is to provide a pneumatic tire having excellent comfort (hereinafter, sometimes referred to as “ride comfort”).

[0011]

Means for Solving the Problems As a result of intensive studies by the present inventors, the following findings were obtained. In the conventional rubber composition, zinc white was added to sulfur and vulcanization accelerator added in optional amounts. On the other hand, immediately after vulcanization, the amount was more than the amount required to obtain the maximum elastic modulus. However, in the case of this conventional rubber composition, since the zinc element is added in a necessary amount or more with respect to the amount of the sulfur and the vulcanization accelerator, it is formed by the reaction with the accelerator even after vulcanization. A large amount of zinc salt and unreacted zinc white remain, adversely affecting the curing reaction of the rubber composition during use. Therefore, it is a finding that by controlling the total amount of zinc element added to the rubber composition, the curing reaction during the use period of the rubber composition can be effectively suppressed. Further, even if the total amount of zinc element added to the rubber composition is controlled, when the main zinc source is zinc white, zinc white slightly remains in the vulcanized rubber without reacting, The zinc white and the accelerator react during the period of use to form a zinc salt, which adversely affects the suppression of the curing reaction, and lowers the initial elastic modulus and Mooney
It is a finding that the scorch time is shortened.

The present invention is based on the above findings of the present inventors, and the means for solving the above problems are as follows. <1> zinc containing 100 parts by weight of a rubber component composed of at least one diene rubber, 0.5 to 5.0 parts by weight of a vulcanization accelerator, and 1.0 to 3.5 parts by weight of sulfur; A rubber composition comprising 0.65 to 1.80 parts by weight of an element as a total weight, and a composite zinc white as a zinc source of the zinc element. <2> The rubber composition according to <1>, wherein the composite zinc white has a layer of zinc oxide on the surface. <3> The rubber composition according to <2>, wherein the composite zinc white contains an inorganic metal salt therein. <4> The vulcanization accelerator is a benzothiazole, a benzothiazolylsulfenamide, a benzothiazolylsulfenimide, a thiourea, a guanidine, an aldehydeamine, a dithiophosphate, a dithiocarbamate, or a xanthate. <1> to <3>, which are at least one selected from the group consisting of: and thiurams
A rubber composition according to any one of the above. <5> the vulcanization accelerator is at least one selected from the group consisting of zinc dithiophosphates, polysulfides dithiophosphates, zinc dithiocarbamates and thiurams, and benzothiazoles, benzothiazolylsulfenamides and The rubber composition according to any one of <1> to <3>, wherein the rubber composition is used in combination with at least one selected from the group consisting of benzothiazolylsulfenimides. <6> A pneumatic tire using the rubber composition according to any one of <1> to <5>. <7> The pneumatic tire according to <6>, wherein the rubber composition is used for at least a tread.

The rubber composition of the present invention comprises 100 parts by weight of a rubber component comprising at least one diene rubber, 0.5 to 5.0 parts by weight of a vulcanization accelerator, and 1.0 to 3.5 parts by weight of sulfur. And the total weight of elemental zinc is 0.65 to 0.65.
Contains 1.80 parts by weight. By controlling the total amount of zinc element to a low level, the amount of zinc salt and unreacted zinc white remaining in the rubber composition after vulcanization can be suppressed as much as possible. As a result, the curing reaction during the use period of the rubber composition is effectively suppressed. Further, in the rubber composition of the present invention,
The composition contains a complex zinc white as a zinc source of the zinc element. The composite zinc white is finely divided at the time of compounding, vulcanization, or the like, and is widely dispersed in the rubber composition. As a result, in the rubber composition after vulcanization, unreacted zinc white does not remain, and the zinc white does not react with the accelerator during the use period to form a zinc salt, and the curing does not occur. It does not adversely affect the suppression of the reaction and does not cause a decrease in the initial elastic modulus or a shortening of the Mooney scorch time.

[0014] The pneumatic tire of the present invention uses the rubber composition of the present invention. Therefore, in the pneumatic tire, the maneuverability and the maneuverability caused by the curing of the rubber composition are maintained until the end of running. The ride comfort is less deteriorated, and both performances are compatible at a high level.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Rubber Composition) In the rubber composition of the present invention, the total weight of zinc element is from 0.65 to 0.65.
It is necessary to contain 1.80 parts by weight.
It is preferable to contain 1.60 parts by weight, and 0.80 to 1.
More preferably, the content is 45 parts by weight. In the present invention, as a numerical range of the total weight of the zinc element, a lower limit or an upper limit of any of the numerical ranges or a numerical value of any of the examples described below as a lower limit, and any of the numerical ranges described above. It is also preferable that the lower limit or the upper limit of the above or the numerical range whose upper limit is any numerical value of the embodiment described later. When the total weight of the zinc element is less than 0.65 parts by weight, a decrease in the initial elastic modulus before deterioration of the vulcanized rubber, that is, a decrease in the initial elastic modulus is observed, while the total weight of the zinc element is 1.80 parts by weight. If it exceeds, the effect of the remaining zinc element is inferior in thermosetting inhibition, and both are not preferred.

The total weight of the zinc element is zinc white,
It can be calculated by summing the weight of the zinc element in the zinc compound contained in the vulcanization accelerator, other additives and the like. The reason why the total weight of the zinc element is used as an index in the rubber composition of the present invention is that the problem of curing in the rubber composition depends on the amount of all zinc elements in the rubber composition.

In the rubber composition of the present invention, it is necessary to contain at least a complex zinc white as a zinc source of the zinc element. In addition to the above, a zinc salt used as the vulcanization accelerator and other zinc salts may be used. It may contain an ionic compound containing zinc element or the like.

The composite zinc white is not particularly limited as long as it has a form that can be finely divided during compounding or vulcanization and can be widely dispersed in the rubber composition, and can be appropriately selected depending on the purpose. For example, those having a zinc oxide layer on the surface are preferable. As the composite zinc white, JP-A-49-29300 and JP-A-60-29300
Preferred are those described in JP-A-264324 and the like.

When the composite zinc white has a layer of zinc oxide (zinc white) on its surface, it preferably contains an inorganic metal salt as a core component. The inorganic metal salt can be appropriately selected from those known as inorganic fillers in the rubber industry, for example, calcium carbonate,
A combination of calcium sulfate and calcium carbonate may be mentioned, but the present invention is not limited thereto.

The ratio of zinc white to other components in the composite zinc white and the thickness of the zinc white layer on the surface of the composite zinc white can be appropriately selected according to the purpose. By the selection, the properties of the composite zinc white can be arbitrarily controlled. The particle size of the composite zinc white is not particularly limited and may be appropriately selected depending on the intended purpose.However, when the particle size is large, the wear resistance and the like of the rubber composition may be deteriorated. preferable.

The zinc source of the zinc element is not particularly limited except for the composite zinc white, and examples thereof include oxides (eg, zinc white) and zinc salts of vulcanization accelerators (eg, zinc dithiophosphate, Zinc dithiocarbamate, zinc xanthate, etc.), oxo acid salts (eg, zinc stearate, zinc carbonate, zinc sulfate, zinc nitrate, zinc benzenesulfinate, etc.), hydroxides, halides and the like. These may be used alone or in combination of two or more. Among them, oxides and zinc salts as vulcanization accelerators are preferred because they have little effect on other physical properties. Preferably
Zinc white, zinc carbonate, zinc dithiophosphate, zinc dithiocarbamate, and the like as oxides are particularly preferred.

The rubber composition of the present invention contains a rubber component, a vulcanization accelerator, and sulfur.

The rubber component comprises at least one diene rubber. Examples of the diene rubber include natural rubber and synthetic rubber such as isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and nitrile rubber. These may be used alone or in combination of two or more. Among them, styrene-butadiene rubber is preferable, and when the styrene-butadiene rubber contains 50% by weight or more, the It is preferable in terms of maneuverability when the rubber composition is used for a pneumatic tire.

The rubber component includes a rubber component other than the diene rubber as long as the effects of the present invention are not impaired.
For example, a modified copolymer obtained by halogenating a copolymer of an isomonoolefin and a p-alkylstyrene is used in an amount of 20 to
It may contain rubber containing 30% by weight.

The vulcanization accelerator is not particularly limited and may be appropriately selected from known ones. Examples thereof include benzothiazoles, benzothiazolylsulfenamides, benzothiazolylsulfenimides, and the like. Thioureas, guanidines, aldehyde amines, dithiophosphates, dithiocarbamates, xanthates, thiurams and the like are preferred. These may be used alone or in combination of two or more.

In the present invention, as the vulcanization accelerator, at least one selected from the group consisting of zinc dithiophosphates, polysulfides dithiophosphate, zinc dithiocarbamates and thiurams, benzothiazoles, benzothia It is preferable to use a combination of at least one selected from the group consisting of zolylsulfenamides and benzothiazolylsulfenimides, and zinc dithiophosphates and thiurams are preferred in that higher curing inhibition is obtained. It is more preferable to use at least one selected from the group consisting of at least one selected from benzothiazoles and benzothiazolylsulfenamides and at least one selected from guadinines.

The zinc dithiophosphates include, for example, zinc O, O'-diisopropyldithiophosphate,
Preferable examples include zinc O'-di-n-butyldithiophosphate and zinc O, O'-di-isobutyldithiophosphate. Preferred examples of the dithiophosphoric acid polysulfides include bis (O, O'-di-isopropylthiophosphoryl) disulfide, bis (O, O'-di-isobutylthiophosphoryl) disulfide, and the like.
Examples of the zinc dithiocarbamates include zinc dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethyldithiocarbamate, zinc dibenzyldithiocarbamate,
And the like. Examples of the thiurams include tetrabenzylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, and the like.

The benzothiazoles, benzothiazolylsulfenamides and benzothiazolylsulfenimides include, for example, dibenzothiazyl disulfide, N-tert-butyl-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-
Preferred examples include tert-butyl-di (2-benzothiazothiazolylsulfen) imide, bis (4-methylbenzothiazolyl-2) -disulfide, and the like.

Specific examples of the combined use of the vulcanization accelerator include:
Dibenzothiazyl disulfide, N-tert-butyl-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide,
Consists of N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-di (2-benzothiazolylsulfen) imide, and bis (4-methylbenzothiazolyl-2) -disulfide At least one member selected from the group consisting of zinc O, O'-diisobutyldithiophosphate, zinc zinc O, O'-diisopropyldithiophosphate, tetrabenzylthiuram disulfide,
And at least one selected from the group consisting of tetrakis (2-ethylhexyl) thiuram disulfide;
Combination with 1,3-diphenylguanidine is preferred.

The content of the vulcanization accelerator in the rubber composition is based on 100 parts by weight of the rubber component.
0.5 to 5.0 parts by weight.
-3.0 parts by weight is preferred. When the content of the vulcanization accelerator is less than 0.5 part by weight, when the rubber composition is used for a pneumatic tire, the effect of improving the maneuverability and the riding comfort is not sufficient, and the effect is 5.0. Exceeding the parts by weight does not provide a corresponding effect, and is economically disadvantageous, and it is not easy to control the total weight of the zinc element.

The content of the sulfur in the rubber composition is 1.0 to 1.0 part by weight based on 100 parts by weight of the rubber component.
It is necessary to contain 3.5 parts by weight. If the sulfur content is less than 1.0 part by weight, the breaking strength and abrasion resistance of the vulcanized rubber are undesirably reduced. If it exceeds 3.5 parts by weight, rubber elasticity may be impaired. This is not preferable in some respects.

The rubber composition of the present invention may further comprise, in addition to the above components, carbon black, silica, stearic acid, an antioxidant, a wax, a softener, a silane coupling agent and the like which are generally used as additives for the rubber composition. May be appropriately contained within a range that does not impair the effects of the present invention.

The rubber composition of the present invention can be produced by a conventional method. For example, the above-mentioned components are appropriately kneaded,
It is obtained by heating and extruding.

The conditions for the kneading are not particularly limited, and various conditions such as the volume to be charged into the kneading apparatus, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, and the type of the kneading apparatus are used. Can be appropriately selected according to the purpose. Examples of the kneading apparatus include a Banbury mixer, an intermix, and a kneader that are usually used for kneading a rubber composition.

The heating conditions are not particularly limited, and various conditions such as a heating temperature, a heating time, and a heating device can be appropriately selected according to the purpose. As the warming device, for example, a roll machine usually used for warming a rubber composition can be used.

The conditions for the extrusion are not particularly limited, and various conditions such as an extrusion time, an extrusion speed, an extrusion apparatus, and an extrusion temperature can be appropriately selected according to the purpose. As the extruder, for example, an extruder or the like usually used for extruding a rubber composition for a tire can be used. The extrusion temperature can be appropriately determined.

At the time of the extrusion, a plasticizer such as an aroma oil, a naphthene oil, a paraffin oil, an ester oil, a liquid polyisoprene rubber, a liquid polybutadiene rubber or the like is used for the purpose of controlling the fluidity of the rubber composition. A processability improver such as a liquid polymer can be appropriately added to the rubber composition. In this case, the viscosity of the rubber composition before vulcanization can be reduced, the fluidity thereof can be increased, and extrusion can be performed very well.

The rubber composition of the present invention can be suitably used for tire treads of various vehicles, and can be suitably used for the following pneumatic tires of the present invention.

(Pneumatic Tire) The pneumatic tire of the present invention comprises at least the rubber composition of the present invention, preferably at least a tread. In the pneumatic tire, the site to which the rubber composition of the present invention is applied other than the tread is not particularly limited, but, for example, carcass coating rubber, belt coating rubber, side rubber, bead filler, rubber chafer rubber And inner liner rubber. The pneumatic tire of the present invention is not particularly limited except that the rubber composition of the present invention is used, and the configuration of a known pneumatic tire can be employed as it is.

An example of the pneumatic tire is a pneumatic tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt for tightening a crown portion of the carcass, and a tread. Preferable examples include tires. The pneumatic tire of the present invention may have a radial structure or a bias structure.

The tread generally includes an upper cap portion directly in contact with the road surface and a lower base portion disposed adjacent to the inside of the pneumatic tire of the cap portion. It has a base structure. In the present invention, part or all of the cap / base structure may be formed of the rubber composition of the present invention, but at least the cap portion is formed of the rubber composition of the present invention. Is preferred.

The pneumatic tire of the present invention is not particularly limited in its production method, but can be produced, for example, as follows. That is, first, the rubber composition of the present invention is prepared, and the rubber composition is pasted on an unvulcanized base portion previously pasted on a crown portion of a fresh pneumatic tire case. And it can be manufactured by vulcanization molding under a predetermined temperature and a predetermined pressure in a predetermined mold.

The pneumatic tire of the present invention can be suitably applied not only to so-called passenger cars but also to various vehicles such as trucks and buses. Since the pneumatic tire of the present invention uses the rubber composition of the present invention, curing over time due to heat history is effectively suppressed, and in particular, the rubber composition is applied to a tread that greatly affects running performance. When used, it achieves both high maneuverability and ride comfort at a high level, and is excellent in its durability over time.

[0044]

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

(Examples 1 to 3 and Comparative Examples 1 to 11) -Preparation and Evaluation of Rubber Composition- For a rubber component shown in Table 1 containing carbon black, a Labo Plastomill (500 ml) and a 3-inch roll were used. Examples 1-3 and Comparative Example 1
To 11 were prepared (unvulcanized rubber). The following (1) Mooney scorch test was performed on these rubber compositions, and after vulcanization of each of these rubber compositions, the elastic modulus at 300% elongation and the rate of change of measured values before and after aging were determined as follows. It was measured by (2) tensile test and (3) air aging test. The results are shown in Table 2.

(1) Mooney scorch test The test was performed based on JIS K6300-1974. The Mooney Scorch test was measured at 130 ° C. In addition, the result was shown as an index with the result of Comparative Example 1 being 100. The MST (Mooney scorch time, index display) in the Mooney scorch test evaluates the ease of burning of rubber at the time of rubber molding such as extrusion and calendering. Means worse.

(2) Tensile test JIS K6301-197 after vulcanization at 145 ° C. for 40 minutes
5, a tensile test was performed, and the elastic modulus at 300% elongation (described as “M300” in Table 2) was measured.

(3) Aging test by air aging The rubber composition was aged by a gear type aging tester at a test temperature of 100 ± 1 ° C. for a predetermined time shown in Table 2 and left at room temperature for 5 hours or more. The sample was subjected to the tensile test (2) in the same manner as for the sample of the rubber composition immediately after compounding and before the aging test (described as “before aging”). The rate of change of the measured value before and after the aging test was calculated by the following equation. Table 2 shows the results. Change rate = (actual measured value of rubber after aging / actual measured value of compounded rubber before aging) × 1
00

All data are shown as indices with the measured value of the rubber composition of Comparative Example 1 containing 3.5 parts by weight of zinc white as 100.

[0050]

[Table 1]

[0051]

[Table 2]

As is clear from the results in Table 2, Example 1
The rubber compositions of Comparative Examples 1 and 6 showed a remarkable improvement in the rate of change after aging and were excellent in the heat-curing inhibitory properties as compared with the rubber compositions of Comparative Examples 1 and 6. Also, simply optimizing the total weight of the elemental zinc does not shorten the Mooney scorch time in the rubber compositions of Examples 1, 2 and 3 compared to the rubber compositions of Comparative Examples 2, 7 and 9. In addition, the rate of change after aging was improved without lowering the elastic modulus before aging. On the other hand, when the total weight of the zinc element is not within the predetermined range even when the composite zinc white is used, the rate of change after aging is large as in the rubber compositions of Comparative Examples 4, 5, 10 and 11, The improvement effect is not enough.

-Manufacture of Pneumatic Tire and Evaluation of Drivability and Ride Comfort-For the pneumatic tire using the rubber composition, drivability and ride comfort were evaluated by the following methods. Using the rubber compositions of Example 2 and Comparative Examples 6 and 7, which were kneaded and compounded according to the composition shown in Table 1, as a tread, 18
A 5 / 70R14 size pneumatic tire of one layer tread was prototyped, and the performance of the pneumatic tire was evaluated.

(1) Drivability On a test course, an FF4 door sedan was used to drive the actual vehicle on dry asphalt road surface, and the test driver integrated the driving, braking, steering response, and steering control. After the evaluation, the maneuverability of the new tire was evaluated. Further, the same tire was run in a general market at 20,000 km, and the maneuverability after running was evaluated.

(2) Ride Comfort On a test course, a real vehicle was run on a dry asphalt road surface using an FF 4-door sedan, and the overall evaluation was made based on the feeling of a test driver. This was also evaluated using a new tire and a tire after traveling 20,000 km.

It should be noted that both the maneuverability and the riding comfort are:
In Example 2, the difference from the control was indicated by a numerical value of ± using Comparative Example 6 as a control as a standard. The larger the value of +, the better the performance. The evaluation results were the same as those of the pneumatic tire of Example 2 and Comparative Example 6.
The difference from the control pneumatic tire is "+",
The value was indicated by the numerical value of "-". The larger the value of “+”, the better the performance. ± 0: The condition that the test driver cannot detect the difference in performance with the control pneumatic tire +1: The condition that the test driver is sufficiently superior to detect the difference in performance with the control pneumatic tire +2: The test driver Is in such a state that the performance difference with the control pneumatic tire can be clearly detected. Table 3 shows the results.

[0057]

[Table 3]

The pneumatic tire of Example 2 in which the rubber composition of the present invention was used as a tread rubber was characterized in that the pneumatic tire had excellent handling properties before running.
Riding comfort was also good, and it was clarified that maneuverability and riding comfort at the end of running could be maintained at a high level.

[0059]

According to the present invention, the above-mentioned problems in the prior art can be solved, the initial elastic modulus is not reduced, and the Mooney scorch time is not shortened. A rubber composition that is particularly suitable for a pneumatic tire, and a steering stability (hereinafter, sometimes referred to as “steering”) and a vibration riding comfort (hereinafter, “ride”) from the beginning to the end of running using the rubber composition. Pneumatic tires with excellent "comfort").

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Claims (7)

[Claims] 1. A rubber composition comprising 100 parts by weight of a rubber component comprising at least one diene rubber, 0.5 to 5.0 parts by weight of a vulcanization accelerator, and 1.0 to 3.5 parts by weight of sulfur. A rubber composition comprising 0.65 to 1.80 parts by weight of a zinc element as a total weight and a composite zinc white as a zinc source of the zinc element. 2. The rubber composition according to claim 1, wherein the composite zinc white has a layer of zinc oxide on the surface. 3. The rubber composition according to claim 2, wherein the composite zinc white contains an inorganic metal salt therein. 4. A vulcanization accelerator comprising benzothiazoles, benzothiazolylsulfenamides, benzothiazolylsulfenimides, thioureas, guanidines, aldehydeamines, dithiophosphates, dithiocarbamates, xanthogens 4. At least one member selected from the group consisting of acid salts and thiurams.
The rubber composition according to any one of the above. 5. The vulcanization accelerator is at least one selected from the group consisting of zinc dithiophosphates, polysulfides dithiophosphates, zinc dithiocarbamates and thiurams, and benzothiazoles and benzothiazolylsulfenamides. The rubber composition according to any one of claims 1 to 3, which is used in combination with at least one member selected from the group consisting of benzothiazolylsulfenimides and benzothiazolylsulfenimides. 6. A pneumatic tire using the rubber composition according to any one of claims 1 to 5. 7. The pneumatic tire according to claim 6, wherein the rubber composition is used at least for a tread.