JPH1120418A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improving dirt adhesion resistance of a tire side face during travel on the wet road surface so as to always present excellent side face appearance. SOLUTION: At least the surface layer part of rubber forming the outside of both side face part of a tire is formed of a rubber composition composed of one or more kinds of rubber selected from natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, acrylonitrile- butadiene copolymer rubber, isoprene-isobutylene copolymer rubber and ethylene- propylene-diene copolymer rubber, a reinforcing agent and a fluorinated additive containing a perfluoroalkyl group contained copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a tire side surface portion when a vehicle travels on a road surface covered with a water film or water having a depth exceeding the water film (hereinafter referred to as a wet road surface) in or immediately after rainy weather. The present invention relates to a pneumatic tire that prevents dirt such as mud from adhering to a pneumatic tire and that can clean dirt very easily even if some dirt adheres.

[0002]

2. Description of the Related Art In recent years, the quality of vehicles, especially of passenger cars, has been remarkably improved. In response to this quality improvement, it is desired that pneumatic tires to be mounted on vehicles be further enhanced in luxury. Naturally, especially in the case of tires for passenger cars, it is indispensable to remarkably improve luxury and appearance. In this regard, in particular, flat tires, which are easy to obtain large rigidity during cornering and are therefore advantageous for exhibiting excellent steering stability, that is, tires having a flattening ratio with a smaller value (flattening ratio) are sports type vehicles. And high-end vehicles, and this type of tire tends to emphasize appearance. Therefore, these tires have been variously devised, especially in the characters and decorative designs of the sidewall portions, to improve the appearance.

[0003]

However, as described above, there is no tire which has improved appearance in view of preventing appearance of dirt such as mud so far, and has excellent angle. Even with a tire having an appearance, the appearance is usually significantly impaired with the attachment of dirt. Further, it takes a lot of time and effort to completely clean the once adhered dirt up to the original clean surface, so that the cleaning work itself tends to be less sparse.

The cause of the adhesion of dirt is an internal factor and an external factor originating from the tire itself. The internal factor is a blooming phenomenon such as an antioxidant or wax compounded in the sidewall rubber or the tread rubber. This is due to the adhesion of dust coming out of the brakes, soil, mud, dust, muddy water running on rainy weather, etc., which is caused by rolling or rolling tires. Among them, sports-type cars and luxury cars are greatly influenced by external factors due to their vehicle characteristics.

Therefore, the inventions according to the first to thirteenth aspects of the present invention effectively and at a high rate prevent the attachment of dirt to the side surface of the tire due to the running of the vehicle, and even if the dirt once adheres to the tire. An object of the present invention is to provide a pneumatic radial tire having both side surfaces capable of efficiently and easily cleaning dirt and constantly maintaining the excellent appearance inherent in the tire.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a toroidal shape is formed between a pair of bead portions and a pair of sidewall portions, and both sidewall portions. In a pneumatic tire having a radial carcass that reinforces each of these portions and a belt that strengthens the tread portion at the outer periphery of the carcass, at least a surface layer of rubber that forms the outside of both side surfaces of the tire The part is selected from natural rubber, polyisoprene rubber, styrene / butadiene copolymer rubber, polybutadiene rubber, acrylonitrile / butadiene copolymer rubber, isoprene / isobutylene copolymer rubber, and ethylene / propylene / diene copolymer rubber 1
A pneumatic radial tire comprising a rubber composition containing at least one kind of rubber and a fluorine-based additive having a reinforcing agent and a perfluoroalkyl group-containing copolymer.

Here, the rubber forming the outer sides of both side portions of the tire includes not only the rubber of the sidewall portion but also the rubber at both end portions of the tread portion when the rubber at both end portions is located on the side portion. It shall include rubber. The styrene-butadiene copolymer rubber may be one produced by solution polymerization or one produced by emulsion polymerization.Solution-polymerized styrene-butadiene copolymer rubber is more resistant to pneumatic radial tires for passenger cars. The wet skid property and the pneumatic tire for racing are each better and preferable in terms of blowout resistance.

The above-mentioned copolymer is preferable as the fluorine-based additive to be added to the rubber composition, but PTFE (polytetrafluoroethylene, tetrafluoroethylene resin) or HF
TMS (heptadecafluorodecyltrimethoxysilane) may also be used. The amount of the fluorine-based additive is preferably in the range of 1 to 20 parts by weight, more preferably 5 parts by weight or more based on 100 parts by weight of rubber. The reason why the fluorine-based additive preferably has a perfluoroalkyl group-containing copolymer is that the copolymerized oligomer is entangled with the rubber (polymer) to form a bonding force between the fluorine-based additive and the rubber composition. Can be made strong.

In carrying out the invention as set forth in claim 1, with respect to the reinforcing agent, at least a part of the reinforcing agent is silica as in the invention as set forth in claim 2. As in the described invention, at least a part of the reinforcing agent is aluminum hydroxide, and as in the invention described in claim 4, the reinforcing agent contains carbon black, silica, and aluminum hydroxide. Fits.

In carrying out the invention as set forth in claim 1, one of the fluorine-based additives is a perfluoroalkyl group-containing copolymer in the rubber composition as in the invention as set forth in claim 5. Is a fluorine-based copolymer obtained by reacting an ethylenically unsaturated monomer X containing an acetoacetyl group and an ethylenically unsaturated monomer Y containing a perfluoroalkyl group, The second of the fluorine-based additives is such that the fluorine-based additive having a perfluoroalkyl group-containing copolymer in the rubber composition is an acetoacetyl group-containing ethylenically unsaturated monomer as described in claim 6. Is a fluorocopolymer obtained by reacting a monomer X, a perfluoroalkyl group-containing ethylenically unsaturated monomer Y, and an ethylenically unsaturated monomer Z copolymerizable therewith. Fit those two kinds of the case, in any case it is effective in achieving the objects the present invention. The fluorine-based additive is preferably in an oligomer form.

Further, the ethylenically unsaturated monomer X described in claims 5 and 6 is substantially the same as the ethylenically unsaturated monomer X containing acetoacetyl group as in the invention described in claim 7.
Is preferably an acetoacetyl group-containing (meth) acrylate, and the acetoacetyl group-containing (meth) acrylate is preferably acetoacetyl group-containing (meth) acrylate. It is practically preferable that the acrylate is at least one of acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate.

Here, (meth) acrylate is a notation including both acrylate and methacrylate. For example, an acetoacetyl group-containing (meth) acrylate means that it contains both an acetoacetyl group-containing acrylate and an acetoacetyl group-containing methacrylate.

Further, the ethylenically unsaturated monomer Y described in claims 5 and 6 is, as in the invention described in claim 9,
Perfluoroalkyl group-containing ethylenically unsaturated monomer Y
Has the following general formula (I)

Embedded image [However, R _f is a perfluoroalkyl group having 4 to 20 carbon atoms, R ₁ is -H or -CH ₃ , A is -Q-,-
_{CON (R 2) -Q -,} - SO 2 N (R 2) -Q-,
(However, -Q- is an alkylene group having 1 to 10 carbon atoms,
R ₂ is an alkyl group having 1 to 4 carbon atoms. )].

In practicing the invention as set forth in claim 6, the invention relates to the ethylenically unsaturated monomer Z as in the invention as set forth in claim 10. However, it is practically useful to use a linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms.

Further, according to the invention described in claim 10,
As for the details, as in the invention described in claim 11, a linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms is represented by the following general formula (II)

Embedded image (However, R ₁ is -H, -CH ₃ , R ₂ is a carbon number of 14 to ₂ )
4 is a linear or branched alkyl group. ) Is desirable.

The weight ratio between the ethylenically unsaturated monomer X and the ethylenically unsaturated monomer Y in the invention described in claim 5 has an optimum range. Preferably, the weight ratio of the ethylenically unsaturated monomer X containing an acetoacetyl group and the ethylenically unsaturated monomer Y containing a perfluoroalkyl group is 1 to 30:70 to 99.

In the same manner as described above, also in the invention described in claim 6, the triethylenically unsaturated monomer X, the ethylenically unsaturated monomer Y, and the ethylenically unsaturated monomer Z There exists an optimum range for the weight ratio of the acetoacetyl group-containing ethylenically unsaturated monomer X and the perfluoroalkyl group-containing ethylenically unsaturated monomer Y as in the invention described in claim 13. And an ethylenically unsaturated monomer Z copolymerizable therewith, in a weight ratio of 1 to 30:40 to 80:
It is preferably from 10 to 50.

In practicing the present invention, it is preferable that the fluorine-based additive is in the form of an oligomer, and that the rubber composition is mixed with a silicon oxide and a silane coupling agent. I do.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIG. FIG. 1 is a left half cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention taken along a plane including a tire rotation axis. In the figure, a pneumatic radial tire (hereinafter referred to as a tire)
It comprises a pair of bead portions (only one side is shown) 1, a pair of sidewall portions (only one side is shown) 2, and a tread portion 3 which is continuous between the two sidewall portions 2 in a toroidal shape. The right half from the tire equatorial plane E has the same configuration as the left half.

One or more ply (two ply in the illustrated example) radial carcass 5 which becomes a rubber-coated ply of an organic fiber cord, for example, a polyester cord or a nylon cord in a radial arrangement, is provided with a pair of bead cores 4 ( The above-mentioned parts 1 to 3 are reinforced over one another (only one side is shown), and the tread part 3 is reinforced by a belt 6 arranged on the outer periphery of the carcass 5. The belt 6 is composed of two or more layers (two layers in the illustrated example) of steel cord intersecting layers and one or more layers of organic fiber code, for example, a wide spiral wound layer of a nylon cord (so-called cap layer) disposed on the outer periphery thereof. ) And one or more narrow spiral wound layers (so-called layer layers) arranged on the outer periphery of the end of the layer according to the customary manner, but the cap layer is used alone or the layer layer is used alone. It is allowed.

A tread rubber 7 is disposed on the tread surface 3t side of the tread portion 3, and a sidewall rubber 8 is disposed outside the tire of the sidewall portion 2, and the tread rubber 7 and the sidewall rubber 8 are combined with a normal buttress. In the vicinity of the called position, they are joined to each other at the overlapping surface S as shown.
The inner surface of the tire is provided with an inner liner 9, and in the case of a tubeless tire, the inner liner 9 is made of an air-impermeable rubber and plays a role in maintaining air pressure. Tread rubber 7 is groove 1
1, 12 and 13, the grooves 11 and 12 are straight grooves extending along the circumference of the tread surface 3t in the illustrated example, and the groove 13 is a groove 1
It is an inclined groove which opens to 1 and 12.

Therefore, the rubber disposed on both sides of the tire shown in FIG. 1 on the outer side of the tire includes the end (buttress) rubber of the tread rubber 7, the sidewall rubber 8, and the bead portion 1.
And a rubber chafer (not shown). The tread rubber 7 in the illustrated example is composed of a composite rubber of the rubber 7b on the tread 3t that contacts the ground when a load is applied and the surface rubber 7c at both ends of the tread portion 3, and the sidewall rubber 8 is also formed of the tread rubber 7. Similarly, tire inner rubber 8b
It is an example of a composite rubber configuration of a rubber and a surface rubber 8c. In addition, the rubber chafer 10 is a tire applicable rim (1997 version JA
When it is located outside the tire beyond the flange of the rim specified by the TMA standard, it is preferable to use a composite rubber structure as described above.

Natural rubber, polyisoprene rubber, styrene / butadiene copolymer rubber, polybutadiene rubber, acrylonitrile / butadiene copolymer are used as at least the surface rubber 7c of the end rubber of the tread rubber 7 and at least the surface rubber 8c of the sidewall rubber 8. Rubber, one or more rubbers selected from isoprene / isobutylene copolymer rubber and ethylene / propylene / diene copolymer rubber, and a fluorine-based additive having a reinforcing agent and a perfluoroalkyl group-containing copolymer. It is necessary to apply a rubber composition.

Although not shown, the tread rubber 7 is not shown.
At least one of the end rubber and the side wall rubber 8 is formed as a single rubber, and the rubber composition can be applied to the single rubber. When the tire outer surface of the rubber chafer 10 exceeds the flange of the applicable rim, the rubber composition is applied to at least the surface rubber of the rubber chafer 10.

When the vehicle is running on rainy weather or on a wet road surface immediately after rainy weather, dirt such as mud or dust may be formed on the side surface of a tire that rolls on a wet road surface or a road surface covered with water having a depth exceeding a water film. As a result of observing the process in which the matter adheres in detail, water containing dirt components and mud rolled up from a wet road surface or a road surface covered with water deeper than a water film by the rolling tire adheres to the side surface of the tire. Naturally, it was found that after the wet road surface was finished, only the moisture on the side portion was evaporated and only the dirt component remained, and as the drying progressed, the dirt component adhered to the tire side portion. .

Therefore, in order to prevent the adhesion of dirt to the tire side surface, it is crucial to prevent the dirt-mixed water wound up by the tire from the road surface from adhering to the tire side surface. Recognize. It can also be seen that it is only necessary to be able to easily clean even if dust or brake dust adheres.

As a result of further intensive studies, it was found that there is a strong inverse correlation between the tendency of water containing dirt components to adhere to the tire side surface and the water repellency of the tire side surface. That is, if the water repellency of the surface of the side surface of the tire is increased, the amount of adhesion of the dirt component to the side surface of the tire is greatly reduced, and as a result, the fixation of the dirt component itself can be effectively prevented. This means that at least the surface layer portions 7c and 8c of the rubber forming the outer sides of both side portions of the tire have at least one rubber selected from the various rubbers described above, a reinforcing agent and a copolymer containing a perfluoroalkyl group. The reason is to apply a rubber composition having a fluorine-containing additive having the following formula:

Because the rubber composition has a unique property of extremely high water repellency, the side surface of the tire exhibits a property of preventing the adhesion of water containing a dirt component, and has a high degree of adhesion of the dirt-resistant substance. This is because the property can be obtained. As a result, since there are many chances of mounting as a radial tire for a passenger car on a sports type car or a luxury car, a flat tire requiring a high degree of appearance is required. In particular, a flat tire having a flat ratio of 70 specified by the JATMA standard (1997 version) is required. Appearance that satisfies requirements by applying the above rubber composition to the following tires and RV (Recreational Vehicle) tires, which are popular in recent years, have high fashionability, and often travel on uneven terrain, etc. Can be obtained.

Here, in a preferred embodiment, a silicon oxide, for example, silica is used as at least a part of the reinforcing material of the rubber composition, which utilizes a strong adsorption force of silica to a fluorine-based additive. More preferably, by adding a silane coupling agent, the bonding force of the fluorine additive in the rubber composition is further increased via silica, and the performance deterioration due to the fluorine-based additive is effectively prevented. It works.

In another preferred embodiment, aluminum hydroxide is used for at least a part of the reinforcing material of the rubber composition, and when the rubber composition is applied to both ends of the tread rubber 7, One of the ends 7c of the tread rubber 7 comes into contact with the ground at the time of vehicle operation such as cornering. Therefore, while maintaining the wear resistance of the end 7c of the tread rubber 7 at the time of cornering, not only the low temperature region but also the high temperature region is maintained. This has the effect of improving grip performance on wet road surfaces and semi-wet road surfaces.

In still another preferred embodiment, the reinforcing material of the rubber composition contains carbon black, silica and aluminum hydroxide. In this case, the workability at the time of kneading the rubber is impaired. And the effect of further improving the above performance can be obtained.

Hereinafter, preferred embodiments of the fluorine-based additive having a perfluoroalkyl group-containing copolymer will be described in detail. First, it is suitable that the fluorine-based additive is in an oligomer form as a whole image and has a molecular weight in the range of 7000 to 9000. The reason is that by setting the molecular weight of the additive within this range, the polymer becomes lower in polymer than the polymer of the rubber composition (generally, the molecular weight is several hundred thousand), and as a result, the degree of dispersion of the additive in the rubber composition is reduced. And strengthen the bonding force between the fluorine-based additive and the rubber composition through strong bonding force due to the copolymerized oligomer being entangled with the polymer in the rubber. Because you can do it.

Next, one of the fluorine-based additives having a perfluoroalkyl group-containing copolymer includes an acetoacetyl group-containing ethylenically unsaturated monomer X and a perfluoroalkyl group-containing ethylenically unsaturated monomer. Fluorine-based copolymers obtained by reacting isomer Y are suitable. This fluorine-based copolymer has an advantage of being excellent in low-temperature crosslinkability.

Examples of the acetoacetyl group-containing ethylenically unsaturated monomer X include acetoacetoxyethyl acrylate, acetoacetoxyethyl methacrylate, acetoacetoxyethyl crotonate, acetoacetoxypropyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxypropyl crotonate, 2-cyanoacetoacetoxyethyl methacrylate, N- (2
-Acetoacetoxyethyl) acrylamide, N- (2
-Acetoacetoxyethyl) methacrylamide, allyl acetoacetate, vinyl acetoacetate and the like. Of these, acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate are particularly preferred.

The acetoacetyl group-containing ethylenically unsaturated monomer is generally obtained by reacting a functional group-containing ethylenically unsaturated monomer with diketene or transesterifying the monomer with an acetoacetoxyalkyl ester. Manufactured by

The perfluoroalkyl group-containing ethylenically unsaturated monomer Y need not be particularly limited, and any known and commonly used one can be used. As the monomer Y, for example, the general formula (I)

Embedded image [However, R _f is a perfluoroalkyl group having 4 to 20 carbon atoms, R ₁ is -H or -CH ₃ , A is -Q-,-
_{CON (R 2) -Q -,} - SO 2 N (R 2) -Q-,
(However, -Q- is an alkylene group having 1 to 10 carbon atoms,
R ₂ is an alkyl group having 1 to 4 carbon atoms)]).

Specifically, Y-1: CF ₃ (CF ₂ ) _n CH ₂ CH ₂ OCOCH = CH ₂ (n = 5 to 11, average of n = 9) Y-2: CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ OCOC (CH ₃ ) = CH ₂ Y-3: CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ OCOC (CH ₃ ) = CH ₂ Y-4: (CF ₃ ) ₂ CF (CF ₂ ) ₆ (CH ₂ ) ₃ OCOCH = CH ₂ Y-5: (CF ₃ ) ₂ CF (CF ₂ ) ₁₀ (CH ₂ ) ₃ OCOCH = CH ₂ Y-6: CF ₃ (CF ₂ ) ₇ SO ₂ N (C _{2 H 7) CH 2 CH 2} OCOCH = CH 2 Y-7: CF 3 (CF 2) 7 SO 2 N (CH 3) CH 2 CH 2 OCOC (CH 3) = CH 2 Y-8: CF 3 (CF _{2) 7 SO 2 N (CH} 3) CH 2 CH 2 OCOCH = CH 2 Y-9: CF 3 (CF 2) 7 (CH 2) 4 OCOCH = CH 2 Y-10: CF 3 (CF 2) 6 COOCH _{= CH 2 Y-11: CF} 3 (CF 2) 7 SO 2 N (C 4 H 9) (CH 2) 4 OCOCH = CH 2 Y-12: CF 3 (CF 2) 7 CH 2 CH (OH) CH _{2 OCOCH = CH 2 Y-13} : CF 3 (CF 2) 5 CON (C 3 H 7) CH 2 CH 2 OCOC (CH 3) = CH 2 Y-14: CF 3 (CF 2) 7 CON (C 2 _{H 5) CH 2 CH 2 OCOCH} = CH monomers such as ₂ are exemplified.

Next, two of the fluorine-based additives having a perfluoroalkyl group-containing copolymer include an acetoacetyl group-containing ethylenically unsaturated monomer X and a perfluoroalkyl group-containing ethylenically unsaturated monomer. It is a fluorine-based copolymer obtained by reacting a polymer Y with an ethylenically unsaturated monomer Z copolymerizable with these.

Examples of the ethylenically unsaturated monomer Z copolymerizable with the acetoacetyl group-containing ethylenically unsaturated monomer X and the perfluoroalkyl group-containing ethylenically unsaturated monomer Y include ethylene, propylene, Vinyl chloride, vinylidene chloride, styrene, α-methylstyrene, vinyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso
-Butyl (meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, n
-Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate,
Dodecyl (meth) acrylate, hexadecyl (meth)
Acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, Methyl vinyl ether, propyl vinyl ether, octyl vinyl ether, butadiene, isoprene, chloroprene, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide, N-methylol (meth) acrylamide, 3-chloro-2-hydroxy Monomers such as (meth) acrylate and diacetone acrylamide are exemplified.

In the above copolymerizable ethylenically unsaturated monomer Z, a carboxyl group, an amino group, an amide group,
In those having a functional group such as a urethane group, those functional groups have an acetoacetyl group-containing ethylenically unsaturated monomer X
However, it is not preferable that the product reacts with acetoacetyl groups to form a gel during polymerization, or the reaction proceeds during storage to shorten the product life, but copolymerization is also possible if the amount is extremely small.

In order to improve the adhesion of dirt on the side surface of the tire, which is an object of the present invention, a linear or branched alkyl group having 14 to 24 carbon atoms represented by the following general formula (II) is contained. It is preferable to use (meth) acrylate.

Embedded image (However, R ₁ is -H, -CH ₃ , R ₂ is a carbon number of 14 to ₂ )
4 is a linear or branched alkyl group. )

Specific examples of the linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms include:
For example, n-cetyl (meth) acrylate, n-stearyl (meth) acrylate, n-behenyl (meth) acrylate, iso-stearyl (meth) acrylate and the like can be mentioned.

As the copolymerizable ethylenically unsaturated monomer Z, two or more of these may be used in combination. In order to obtain the above-described copolymer, various polymerization reactions and conditions can be arbitrarily selected, and bulk polymerization, solution polymerization, emulsion polymerization,
Any of various polymerization methods such as suspension polymerization, radiation polymerization, and photopolymerization can be employed.

The fluorine-based additive having the perfluoroalkyl group-containing copolymer may be prepared by solution polymerization or emulsion polymerization, and the organic solvent-type, emulsion-type or aerosol-type fluorine-containing additive and at least one of water and an organic solvent. Can be directly produced. For example, according to the manufacturing method disclosed in JP-A-7-228638.

The copolymerization ratio of the acetoacetoxy group-containing ethylenically unsaturated monomer X and the perfluoroalkyl group-containing ethylenically unsaturated monomer Y in the copolymer does not need to be particularly limited. Actually, in the case of a two-component system comprising an acetoacetoxy group-containing ethylenically unsaturated monomer X and a perfluoroalkyl group-containing ethylenically unsaturated monomer Y, an acetoacetoxy group-containing ethylenically unsaturated monomer is used. X is in the range of 1 to 30% by weight, while the perfluoroalkyl group-containing ethylenically unsaturated monomer Y is 70 to 9% by weight.
Preferably it is in the range of 9% by weight. Further, a three-component system comprising an acetoacetoxy group-containing ethylenically unsaturated monomer X, a perfluoroalkyl group-containing ethylenically unsaturated monomer Y, and an ethylenically unsaturated monomer Z copolymerizable therewith. In this case, the polymerization ratio is not limited as in the case of the two-component system, but in practice, the acetoacetoxy group-containing ethylenically unsaturated monomer X is in the range of 1 to 30% by weight, and the perfluoroalkyl group-containing 40 to 8 ethylenically unsaturated monomers Y
Preferably, the amount of the copolymerizable ethylenically unsaturated monomer Z is in the range of 0 to 50% by weight.

Not only in the case of the two-component system, but also in the case of producing a copolymer of the monomer X, the monomer Y and another copolymerizable ethylenically unsaturated monomer Z, an acetoacetoxy group-containing monomer is used. The copolymerization ratio between the ethylenically unsaturated monomer X and the perfluoroalkyl group-containing ethylenically unsaturated monomer Y is particularly important.

Among these monomers, preferable ones are as described above. However, from the viewpoints of availability of raw materials, water repellency and oil repellency, the ethylenically unsaturated monomer X containing an acetoacetoxy group is preferred. And at least one of acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate, as the perfluoroalkyl group-containing ethylenically unsaturated monomer Y, a perfluoroalkyl group-containing (meth) acrylate, a copolymerizable ethylenically unsaturated monomer As the body Z, a linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms is preferable.
As a commercially available product among the fluorine-based additives described above, for example, Daifen Ink Chemical Industry's Defenser MCF-323SF is suitably used.

It is preferable that the compounding amount of the above-mentioned fluorine-based additive is in the range of 1 to 20 parts by weight based on 100 parts by weight of the rubber. The reason that the fluorine-based additive is required to have a perfluoroalkyl group-containing copolymer is that a small amount of the additive exerts a remarkable effect on the adhesion of stains, and a mechanical change such as curing of a rubber matrix component. This is because the above-mentioned effects can be exhibited without or without deterioration of physical properties. This is a result in consideration of the fact that it is extremely difficult to achieve both water repellency and rubber physical properties in the case of a rubber composition to which a general fluorinated resin is simply added.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic radial tire for a passenger car having a size of 225 / 50R16 and a tread rubber 7 having a two-layer structure of two layers of rubber 7b and 7c at the end according to FIG. Reference numeral 8 has a configuration of a laminate of two layers of rubbers 8b and 8c. The contact width of the tread 3t is 176m
m, and the ground contact length was 122 mm. Carcass 5 is 10
Consisting of two plies of 00D / 2 polyester cord,
The belt 6 is composed of two layers of 1 × 5 steel cord cross layers, one layer of 1260D / 2 nylon cord cap layer, and one layer of the same cord layer. Table 1 shows the surface rubber 7 at the end of the tread rubber 7 in Examples 1 and 2.
The upper part of Table 2 shows the compounding contents of c and the surface rubber 8c of the side wall rubber 8 together with those of the comparative examples. Values are parts by weight. The middle row shows the physical property values of these tread rubbers.

[0050]

[Table 1]

The butadiene rubbers described in Table 1 are BR-01 manufactured by Nippon Synthetic Rubber Co., Ltd., styrene butadiene rubber has a styrene component content of 35%, and silica has
Nipsil VN3 AQ manufactured by Nippon Silica Co., a silane coupling agent is Si-69 manufactured by DEGUSSA, and a fluorine-based additive is a fluoroalkyl group-containing oligomer.
Defensor MCF-32 made by Dainippon Ink and Chemicals, Inc.
3SF and the vulcanization accelerator NS are Noxeller NS-F manufactured by Ouchi Shinko Chemical Industry Co., Ltd., and the vulcanization accelerator CZ is Noxeller CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Regarding the physical properties of the tread rubber described in the items of Table 1, the JIS hardness is JIS K6301.
According to the method specified in (1994), measured values at a temperature of 25 ° C., tensile strength T _B (MPa) and 100% modulus (MPa) using a spring-type hardness tester, type A, at a temperature of 25 ° C.
JIS K6301 (1), using a JIS No. 3 test piece, making the test piece a dumbbell shape with a sample that can be collected.
994), the contact angle (degree) measured at a temperature of 25 ° C. is such that a water drop having a size (about 1 mm in diameter) that is not easily affected by gravity is dropped on a horizontal rubber surface. The angle difference between the angle θ formed between the tangent of the water droplet surface on the rubber surface and the rubber surface on the side in contact with the water droplet with the contact angle meter and Comparative Example 1 (the greater the angle θ, the higher the water repellency) That is).

The tires of Examples 1 and 2 and Comparative Example were used as test tires. These tires were mounted on a test vehicle of a rear-wheel drive vehicle (domestic passenger car) of 2500 cc. After running 100 km each, the amount of dirt adhering to both sides of the tire was evaluated by sensory evaluation by three evaluators in a state where the tire was completely dried. The score was a full score of 10 points with the appearance having blackish gloss before the start of the test run, and the higher the degree of gray or white, the closer to blackish, the higher the score, and conversely, the higher the degree of gray or white, the lower the score. Was based on the average of the total scores of the three players. The higher the score, the closer to 10 points, the better. The evaluation results are shown in the lower part of Table 1 as stain resistance.

From the results in Table 1, it can be seen from the results of the comparative example tire that both ends of the tread rubber and the sidewall rubber are conspicuous, the appearance is significantly impaired, and the image is far from the image of a high-grade tire. On the other hand, in each of the tires of Examples 1 and 2, the water repellency of the surface rubber 7c at the end portion of the tread rubber 7 and the surface rubber 8c of the sidewall rubber 8 was actually exhibited, and the tires before the test run It can be seen that the tire has an excellent appearance close to that of the tire. Although not shown in Table 1, the tires of Examples 1 and 2 were restored to the original state having a blackish luster only by watering with a normal hose, whereas the comparative example required extra dirt removal work. there were. These facts demonstrate that the tires of Examples 1 and 2 have significantly improved stain resistance.

[0055]

According to the invention as set forth in claims 1 to 13 of the present invention, not only when traveling on rainy weather but also when traveling on a road surface covered with a water film or shallow water, mud, dust, etc., which are splashed with water, are not limited. Even if dirt is inevitably sprayed on the side of the tire, the amount of dirt attached can be suppressed to a very small amount, and even after the tire has dried, a small amount of dirt can be easily and completely washed away. It is possible to provide a pneumatic radial tire that is capable of maintaining excellent appearance that should always be provided as a luxury tire.

[Brief description of the drawings]

FIG. 1 is a left half sectional view of a tire showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 3t Tread surface 4 Bead core 5 Radial carcass 6 Belt 7 Tread rubber 7b Tread tread rubber 7c Tread rubber end surface layer rubber 8 Side wall rubber 8b Inner side wall rubber 8c Surface layer side wall rubber 9 Inner liner 10 Rubber chafer E Tire equatorial plane S Both rubber joint side

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 101/04 C08L 101/04

Claims (13)

[Claims] 1. A radial carcass comprising a pair of beads and a pair of sidewalls, and a tread portion connected in a toroidal shape between the two sidewalls, and a radial carcass for reinforcing these portions, and an outer periphery of the carcass. In a pneumatic radial tire having a belt for reinforcing a tread portion, at least a surface layer portion of a rubber forming the outside of both side portions of the tire is made of natural rubber, polyisoprene rubber, styrene / butadiene copolymer rubber, polybutadiene rubber, acrylonitrile.・
One or more rubbers selected from butadiene copolymer rubber, isoprene / isobutylene copolymer rubber and ethylene / propylene / diene copolymer rubber, and a fluorine additive having a reinforcing agent and a perfluoroalkyl group-containing copolymer. A pneumatic radial tire comprising a rubber composition as a component. 2. The tire according to claim 1, wherein at least a part of the reinforcing agent is silica. 3. The tire according to claim 1, wherein at least a part of the reinforcing agent is aluminum hydroxide. 4. The tire according to claim 1, wherein the reinforcing agent contains carbon black, silica and aluminum hydroxide. 5. The rubber composition as claimed in claim 1, wherein the fluorine-containing additive having a perfluoroalkyl group-containing copolymer comprises an acetoacetyl group-containing ethylenically unsaturated monomer (X) and a perfluoroalkyl group-containing ethylenically unsaturated monomer. Monomer (Y)
And a fluorine-based copolymer obtained by reacting
4. The tire according to any one of the above items 4. 6. The rubber composition according to claim 1, wherein the fluorine-containing additive having a perfluoroalkyl group-containing copolymer is an acetoacetyl group-containing ethylenically unsaturated monomer (X) and a perfluoroalkyl group-containing ethylenically unsaturated monomer. The fluorine-based copolymer obtained by reacting a saturated monomer (Y) with an ethylenically unsaturated monomer (Z) copolymerizable therewith, according to any one of claims 1 to 4. Tires. 7. The tire according to claim 5, wherein the acetoacetyl group-containing ethylenically unsaturated monomer (X) is an acetoacetyl group-containing (meth) acrylate. 8. The tire according to claim 7, wherein the (meth) acrylate containing an acetoacetyl group is at least one of acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate. 9. The perfluoroalkyl group-containing ethylenically unsaturated monomer (Y) is represented by the following general formula (I): [However, R _f is a perfluoroalkyl group having 4 to 20 carbon atoms, R ₁ is -H or -CH ₃ , A is -Q-,-
_{CON (R 2) -Q -,} - SO 2 N (R 2) -Q-,
(However, -Q- is an alkylene group having 1 to 10 carbon atoms,
R ₂ is an alkyl group having 1 to 4 carbon atoms. 7. The tire according to claim 5, which is a compound represented by the following formula: 10. The tire according to claim 6, wherein the copolymerizable ethylenically unsaturated monomer (Z) is a linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms. . 11. A linear or branched alkyl group-containing (meth) acrylate having 14 to 24 carbon atoms is represented by the following general formula (II): (However, R ₁ is -H, -CH ₃ , R ₂ is a carbon number of 14 to ₂ )
4 is a linear or branched alkyl group. The tire according to claim 10, which is a compound represented by the formula: 12. The acetoacetyl group-containing ethylenically unsaturated monomer (X) and the perfluoroalkyl group-containing ethylenically unsaturated monomer (Y) are in a weight ratio of 1 to 30:70.
The tire according to claim 5, wherein 13. An ethylenically unsaturated monomer containing an acetoacetyl group (X), an ethylenically unsaturated monomer containing a perfluoroalkyl group (Y), and an ethylenically unsaturated monomer copolymerizable therewith. Body (Z) is 1 to 30: 4 by weight ratio
The tire according to claim 6, wherein the ratio is from 0 to 80:10 to 50.