JP2001323110A - Tread rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tread rubber composition which has a high abrasion resistance, is excellent in wet performances, e.g. braking performance and hydroplaning performance, in the rain, and is suitable for treads of pneumatic tires, etc. SOLUTION: This tread rubber composition contains a water-repellent rubber composition having a contact angle with water at 25 deg.C of 90 deg. or higher, preferably 100 deg. or higher, at a ground contact point and a hydrophilic rubber composition having a contact angle with water at 25 deg.C of 70 deg. or lower, preferably 50 deg. or lower, still preferably 30 deg. or lower, at a non-ground contact point. Preferably, the water-repellent rubber composition contains at least one water-repellent agent selected from among fluororesins, silane compounds, and silicone oils; the hydrophilic rubber composition contains at least one hydrophilicizing agent selected from among nonionic surfactants; the gauge of the hydrophilic rubber is at least 0.1 mm; and the area of the water-repellent rubber composition accounts for at least 50% of the ground contact surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a tread rubber composition having good wear resistance, excellent wet performance such as braking performance in rainy weather and hydroplaning performance, and suitable for treads of pneumatic tires and the like. The present invention relates to a pneumatic tire using the tread rubber composition and having excellent WET performance and wear resistance.

[0002]

2. Description of the Related Art Conventionally, wet performance such as braking performance in rainy weather has been known.
The development of tread rubber compositions for pneumatic tires having excellent performance has been actively conducted. Conventionally, the W
As a tread rubber composition having excellent ET performance, those having a hydrophilic surface or a water-repellent surface are known, but none of them have sufficient WET performance. On the other hand, tread rubber compositions are required to have excellent abrasion resistance as basic performance, but at present, tread rubber compositions having excellent abrasion resistance and the WET performance have not yet been provided. .

[0003]

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 has good abrasion resistance and WET such as braking performance in wet weather and hydroplaning performance.
An object of the present invention is to provide a tread rubber composition having excellent performance and suitable for a tread such as a pneumatic tire, and a pneumatic tire using the tread rubber composition and having the above-mentioned wet performance and wear resistance.

[0004]

In order to solve the above-mentioned problems, the present inventors have made intensive studies on the contact angles of water with respect to the surface of the block of the tire tread, the groove side surface and the groove bottom surface. It has been found that the WET performance can be significantly improved by controlling the contact angle of water with each part to be in different ranges. The present invention is based on such findings by the present inventors, and the means for solving the above problems are as follows. That is, <1> a water-repellent rubber composition having a contact angle with respect to water at 25 ° C. of 90 ° or more in a contact portion, and a hydrophilic rubber composition of 70 ° or less in a non-contact portion. Tread rubber composition. <2> The water-repellent rubber composition having a contact angle with water at 25 ° C. of 100 ° or more at the ground contact portion.
> The tread rubber composition described in <1>. <3> The above-mentioned <1 containing a hydrophilic rubber composition having a contact angle with water at 25 ° C of 50 ° or less in a non-ground portion.
> Or <2>. <4> The above-mentioned <1 which contains a hydrophilic rubber composition having a contact angle with water at 25 ° C of 30 ° or less in a non-ground portion.
> Or <2>. <5> The tread rubber composition according to any one of <1> to <4>, wherein the water-repellent rubber composition contains at least one water-repellent selected from a fluororesin, a silane compound, and a silicone oil. Things. <6> The tread rubber composition according to any one of <1> to <5>, wherein the hydrophilic rubber composition contains at least one hydrophilic agent selected from nonionic surfactants. . <7> The tread rubber composition according to any one of <1> to <6>, wherein the gauge of the hydrophilic rubber composition is 0.1 mm or more. <8> The area occupied by the water-repellent rubber composition on the ground contact surface is 50.
% Of the tread rubber composition according to any one of <1> to <7>. <9> The area occupied by the water-repellent rubber composition on the ground contact surface is 70.
% Of the tread rubber composition according to any one of <1> to <7>. <10> A pneumatic tire using the tread rubber composition according to any one of <1> to <9> for at least a tread.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION (Tread Rubber Composition) The tread rubber composition of the present invention comprises a water-repellent rubber composition in a grounded portion and a hydrophilic rubber composition in a non-grounded portion.

-Water-Repellent Rubber Composition- The water-repellent rubber composition must have a contact angle with water at 25 ° C. of 90 ° or more, and preferably 100 ° or more. When the water-repellent rubber composition has a contact angle with water at 25 ° C. of less than 90 °, a force for repelling a water film interposed at an interface between a road surface and the surface of the water-repellent rubber composition to the outside of the interface is small. , The effect of improving the WET performance may not be sufficient. In the tread of a general pneumatic tire, the contact angle with water is 70 ° or more and 90 ° or more.
Is less than. In the present invention, the water contact angle is also preferably a lower limit of any of the above numerical ranges or a range having a lower limit of any of the water contact angles employed in Examples described later. The water contact angle is, for example,
It can be measured as follows. That is, water is dropped on the surface of a rubber sample at room temperature, the contact angle of the water droplet is measured using a known contact angle meter, and the measured value can be used as the contact angle with water.

The area occupied by the water-repellent rubber composition on the grounding surface is preferably at least 50%, more preferably at least 70%. When the area occupied by the water-repellent rubber composition in the ground plane is less than 50%,
Since the occupation ratio of the surface having excellent water repellency is low, the force of repelling the water film interposed between the road surface and the surface of the water repellent rubber composition to the outside of the interface is small, and the effect of improving the WET performance is not sufficient. Sometimes.

The water-repellent rubber composition preferably contains at least one water-repellent selected from a fluororesin, a silane compound and a silicone oil. Examples of the fluororesin include ethylene tetrafluoride resin. Examples of the silane compound include a silane coupling agent. Examples of the silicone oil include dimethyl silicone oil. In addition, the said water-repellent agent may be used individually by 1 type, may use 2 or more types together, and may use a commercial item.

The water-repellent rubber composition preferably contains the water-repellent, but the components other than the water-repellent are not particularly limited, and are known as components for compounding the rubber composition. One. The water-repellent rubber composition contains, for example, a rubber component and other components appropriately selected as necessary.

The rubber component contains at least one type of diene rubber, and may further contain another rubber if necessary. Examples of the diene rubber include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, chloroprene rubber, and ethylene / propylene / diene copolymer rubber. These may be used alone or in combination of two or more. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene / butadiene rubber are preferred. As the other rubber, for example, fluorine rubber, butyl rubber,
Examples include ethylene-propylene copolymer rubber, silicone rubber, epichlorohydrin rubber, polysulfide rubber, and urethane rubber. The content of the diene rubber in the rubber component is preferably 90% by weight or more.
% By weight or more, and particularly preferably 100% by weight.

The other components can be appropriately selected according to the purpose within a range that does not impair the effects of the present invention, and commercially available products can be suitably used. As the other components, for example, a reinforcing filler, a vulcanizing agent such as sulfur, a vulcanization accelerator such as dibenzothiazyl disulfide,
Vulcanization aid, N-cyclohexyl-2-benzothiazyl-
Antioxidants such as sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid, antiozonants, coloring agents, antistatic agents,
In addition to dispersants, lubricants, antioxidants, softeners, foaming agents, foaming aids, additives such as inorganic fillers, and the like, various compounding agents ordinarily used in the rubber industry are exemplified.

The reinforcing filler is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include carbon black, silica, and short fibers.

There is no particular limitation on the carbon black, and commercial products can be suitably used. The content of the carbon black in the rubber composition is preferably 5 to 60 parts by weight based on 100 parts by weight of the rubber component.

[0014] The silica is not particularly limited, and commercially available silica can be suitably used. As the content of the silica in the rubber composition, the rubber component 100
It is preferably 5 to 60 parts by weight based on parts by weight.

The short fibers are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include organic fibers such as polyamide fibers, polyolefin fibers, and polyester fibers, and inorganic fibers such as glass fibers. .

-Hydrophilic Rubber Composition- The hydrophilic rubber composition must have a contact angle with water at 25 ° C. of 70 ° or less, preferably 50 ° or less, and more preferably 30 ° or less. Is more preferable. When the contact angle of water of the hydrophilic rubber composition at 25 ° C. exceeds 70 °, the flow rate of water on the surface of the hydrophilic rubber composition does not increase, and the hydrophilic rubber composition is not sufficiently hydrophilic. In some cases, the effect of improving the wet performance may not be exhibited. In the present invention, the water contact angle is preferably an upper limit of any of the above numerical ranges or a range having an upper limit of any of the water contact angles employed in the examples described later.

It is preferable that the hydrophilic rubber composition contains at least one hydrophilic agent selected from nonionic surfactants.

[0018] The content of the nonionic surfactant in the hydrophilic rubber composition may be as follows:
The amount is preferably 0.5 to 10 parts by weight based on part by weight. When the content of the nonionic surfactant is less than 0.5 part by weight, the surface of the hydrophilic rubber composition may not be sufficiently hydrophilized, and when the content exceeds 10 parts by weight, The abrasion resistance of the hydrophilic rubber composition may decrease.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, Glycerin fatty acid esters, polyethylene glycol fatty acid esters, and the like. These may be used alone or in combination of two or more, and commercially available products can be suitably used.

Examples of the polyoxyethylene alkyl ether include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene higher alcohol ether. As the sorbitan fatty acid ester, for example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,
Sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan sesquioleate, and the like.

Examples of the polyoxyethylene sorbitan fatty acid ester include polyoxyethylene sorbitan monococo fatty acid ester, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and polyoxyethylene sorbitan monostearate. Ethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan triisostearate, and the like. Examples of the polyoxyethylene sorbitol fatty acid ester include polyoxyethylene sorbite tetraoleate.

The glycerin fatty acid ester includes:
For example, glycerol monostearate, glycerol monooleate, self-emulsifying glycerol monostearate, molecular distilled monoglyceride stearin, molecular distilled monoglyceride vegetable stearin, molecular distilled monoglyceride vegetable olein, medium-purity monoglyceride / stearin, medium Monoglyceride-stearin-olein-based, medium-purity monoglyceride-olein-based, and medium-purity monoglyceride-self-emulsifying stearin-based.

Examples of the polyethylene glycol fatty acid ester include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, and polyethylene glycol monooleate. In addition to these, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylamine, alkylalkanolamide, and the like are further included.

The gauge of the hydrophilic rubber composition is as follows:
It is preferably 0.1 mm or more and less than 3.0 mm. When the gauge of the hydrophilic rubber composition is less than 0.1 mm, formation of a surface film by the nonionic surfactant as a hydrophilizing agent becomes incomplete, and in the hydrophilic rubber composition, The desired hydrophilicity may not be obtained,
When the thickness is 3.0 mm or more, the hydrophilic rubber composition layer is thickly arranged on the ground contact surface. Therefore, the number of steps for removing the layer of the hydrophilic rubber composition may be increased due to wear caused by running-in or buffing.

The above-mentioned hydrophilic rubber composition preferably contains the above-mentioned hydrophilizing agent. The components other than the above-mentioned hydrophilizing agent are not particularly limited, and include those known as rubber components. The hydrophilic rubber composition contains, for example, the rubber component and the other components in the description of the water-repellent rubber composition.

-Production of tread rubber composition-The tread rubber composition of the present invention is produced according to a known method. For example, the hydrophilic rubber composition is laminated on the water-repellent rubber composition, and vulcanized. It is manufactured by performing molding or the like.

The vulcanization molding apparatus, system, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As an apparatus for performing the vulcanization molding, for example, a molding vulcanizer using a mold usually used for vulcanization of a rubber composition for a tire may be mentioned. The temperature for the vulcanization molding is usually about 120 to 190 ° C.

The water-repellent rubber composition and the hydrophilic rubber composition are appropriately kneaded with the respective components.
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 depending on 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, in order to control the fluidity of the water-repellent rubber composition and the hydrophilic rubber composition, plasticizers such as aroma oils, naphthene oils, paraffin oils, ester oils, etc. A processability improver such as a liquid polymer such as a liquid polyisoprene rubber and a liquid polybutadiene rubber can be appropriately added to the tread 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.

-Applications- Although the tread rubber composition of the present invention can be suitably used for tire treads of various vehicles, it can be particularly preferably used for the following pneumatic tire treads of the present invention.

(Pneumatic Tire) The pneumatic tire of the present invention comprises at least the tread rubber composition of the present invention, and is preferably used at least for a tread. The pneumatic tire of the present invention is not particularly limited except that the tread 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 a 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, it is preferable that at least the cap portion is formed of the tread rubber composition of the present invention.

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 tread rubber composition of the present invention (the water-repellent rubber composition laminated with the hydrophilic rubber composition) is prepared, and the tread rubber composition is added to the crown portion of a fresh pneumatic tire case. On the unvulcanized base previously attached to And it can be manufactured by vulcanization molding under a predetermined temperature and a predetermined pressure in a predetermined mold.

In the pneumatic tire of the present invention, when not used, the entire surface including the tread block is covered with the hydrophilic rubber composition. Although the water-repellent rubber composition is not exposed, the hydrophilic rubber composition on the surface of the tread block is worn due to initial use or buffing of the surface, and the water-repellent rubber composition is worn away from the surface of the tread block. Thereafter, the water-repellent rubber composition is exposed. In the pneumatic tire of the present invention, the water-repellent rubber composition is exposed on the surface of the tread block that is a ground contact surface, and the hydrophilic rubber composition is exposed on the groove side surface and the groove bottom surface that are non-ground surfaces. ing.

The generally required wet braking performance is considered to be a problem when the water film on the road surface is about 1 to 2 mm. In this case, hydroplaning does not occur, and the water-repellent rubber composition in the tread block is used. The exposed surface of the object
This greatly contributes to the wet braking performance. On the other hand, the hydroplaning performance is problematic when the water depth is deep such as a rut (when the water film is about 5 to 20 mm). In this case, the macro drainage effect greatly contributes to the hydroplaning performance. .

In the pneumatic tire of the present invention, the water film present at the interface between the road surface and the tread block is immediately exposed to the block groove by the exposed surface of the water-repellent rubber composition in the tread block. It is possible to increase the effective contact area. As a result, wet braking performance such as braking performance in rainy weather is improved. On the other hand, hydroplaning is a phenomenon that is likely to occur with the increase in speed and the thickness of the water film, and it is important how quickly a large amount of water film intervening at the interface flows out of the interface. Groove side and groove bottom in tread block,
That is, since the exposed surface of the hydrophilic rubber composition has low convection water resistance, the water flowing into the groove easily flows and is easily removed. For this reason, the hydrophilic rubber composition allows a large amount of the water film existing at the interface to flow efficiently out of the interface. As a result, WET characteristics such as hydroplaning performance in rainy weather are improved.

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.

[0042]

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

(Examples 1 to 25 and Comparative Examples 1 to 8) Table 1
Tread rubber (Nos. 1 to 19) having compositions shown in FIGS.
Was manufactured. Each tread rubber was laminated in a combination shown in Tables 3 and 4, and each tread rubber composition and a pneumatic tire using the tread rubber (size: 205 / 60R15)
Was manufactured, and the following evaluation was performed. Tables 3 and 4 show the results.
It was shown to.

<Hydroplaning performance> 2000c
A passenger car of class c is equipped with a pneumatic tire, and the straight road of the test course is a wet road surface having a water depth of 20 mm.
After entering at km / h, while stepping on the accelerator,
The rotational speed of the drive wheels and the actual vehicle speed were measured. At this time, the vehicle initially accelerates, but hydroplaning occurs at a certain speed, and the driving wheel rotation speed increases, but the vehicle speed does not increase. The speed at which the drive wheel rotational speed and the vehicle speed dissociated was defined as the limit speed, and was expressed as an index. The larger the value, the better the result.

<WET Braking Performance> A 2000cc class passenger car was equipped with pneumatic tires, and the straight road on the test course was used as a WET road surface with a depth of 2mm, and the passenger car was entered there at a speed of 60km / h. Braking,
The braking distance was measured and displayed as an index. The larger the value, the better the result.

<Wear Resistance> The amount of wear loss was measured using a Lambourn abrasion tester, and was calculated by the following equation. Abrasion resistance index = {(weight after test of tread rubber composition of comparative example as control) / (weight before test of tread rubber composition of comparative example as control)} × 100 The control shown in Tables 3 and 4 The tread rubber composition of the comparative example was indexed as 100. That is, the larger the numerical value, the better the wear resistance.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

In Table 1, numerical values (quantities) represent "parts by weight". "SBR # 1500" is a styrene-butadiene rubber (manufactured by JSR Corporation, SBR # 150
0). “BR01” means cis-1,4-polybutadiene (BR01, manufactured by JSR Corporation). “NR” is natural rubber (Tech BeeH
ang, RSS # 3). "Carbon Black HA
F "is a product of Asahi Carbon Co., Ltd., # 70, carbon N22
0 means “silica”, manufactured by Nippon Silica Industry Co., Ltd.
Nipsil AQ is meant. “Aroma oil” means Diana Process Oil AH-24 manufactured by Idemitsu Kosan Co., Ltd. "Stearic acid" is available from Kao Corporation, LUNA
CRS beads). The “silane coupling agent” is a silane coupling agent (bis-3-triethoxysilylpropyl-tetrasulfide: manufactured by Degussa AG,
Si69 (trademark)). "Anti-aging agent" means Nocrack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
The upper "promoter" means a vulcanization accelerator (diphenylguanidine (manufactured by Sumitomo Chemical Co., Ltd., Succinol DG)), and the middle "promoter" means a vulcanization accelerator (N-cyclohexyl-2-benzothiazyl). -1-sulfenamide (Nouchira CZ, manufactured by Ouchi Shinko Chemical Co., Ltd.), and the lower “accelerator” means a vulcanization accelerator (dibenzothiazyl disulfide (Noxeller DM, manufactured by Ouchi Shinko Chemical Co., Ltd.)). I do.

From the results in Tables 3 and 4, the following is clear. That is, as compared with Comparative Examples 1 to 8 which are tread rubber compositions containing silica in the related art, Examples 1 to 25 which are tread rubber compositions of the present invention have good abrasion resistance and braking performance in rainy weather. And WET performance such as hydroplaning performance and the like, and their balance was also good.

[0053]

According to the present invention, the above-mentioned conventional problems can be solved, the abrasion resistance is good, the braking performance in rainy weather, the wet planing performance such as hydroplaning performance, etc., the pneumatic tire, etc. A tread rubber composition suitable for a tread of the present invention, and a pneumatic tire having excellent WET performance and abrasion resistance can be provided by using the tread rubber composition.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 83/04 C08K 5/54

Claims (10)

[Claims] 1. A water-repellent rubber composition having a contact angle with respect to water at 25 ° C. of 90 ° or more in a grounded portion, and a hydrophilic rubber composition of 70 ° or less in a non-grounded portion. Tread rubber composition. 2. The tread rubber composition according to claim 1, comprising a water-repellent rubber composition having a contact angle with respect to water at 25 ° C. of 100 ° or more at a ground contact portion. 3. The tread rubber composition according to claim 1, comprising a hydrophilic rubber composition having a contact angle with water at 25 ° C. of 50 ° or less in a non-ground portion. 4. The tread rubber composition according to claim 1, comprising a hydrophilic rubber composition having a contact angle with water at 25 ° C. of 30 ° or less in a non-ground portion. 5. The water-repellent rubber composition comprises at least one selected from a fluororesin, a silane compound and a silicone oil.
The tread rubber composition according to any one of claims 1 to 4, comprising a kind of water repellent. 6. The tread rubber composition according to claim 1, wherein the hydrophilic rubber composition contains at least one hydrophilic agent selected from nonionic surfactants. 7. The gauge of the hydrophilic rubber composition is 0.1 mm.
The tread rubber composition according to any one of claims 1 to 6, which is the above. 8. The tread rubber composition according to claim 1, wherein the area of the water-repellent rubber composition occupying the ground contact surface is 50% or more. 9. The tread rubber composition according to claim 1, wherein the area occupied by the water-repellent rubber composition on the ground contact surface is 70% or more. 10. A pneumatic tire using the tread rubber composition according to claim 1 for at least a tread.