JPH11246706A - Rubber composition and pneumatic tire using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. having excellent static and dynamic ozone resistance over a wide temp. range and to provide a pneumatic tire using it. SOLUTION: A rubber compsn. comprises a blend of 100 pts.wt. of a natural rubber or a diene-based synthetic rubber and 0.1-10 pts.wt. of a hydrocarbon- based wax; said hydrocarbon-based wax has a componential compsn. comprising 30-65 totaled wt.% of a 29-39C nonlinear component and a 28-36C linear component at a componential ratio of the former to the latter of 20-55 wt.%, 7-30 totaled wt.% of 20-25C linear and nonlinear components, 15-35 totaled wt.% of a 38-53C linear component and a 42-51C nonlinear component, and 60 totaled wt.% or less of a 32-46C linear component and a 38-46C nonlinear component. A pneumatic tire uses this rubber compsn. as the outer skin parts material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly to a rubber composition having excellent ozone resistance (ozone deterioration prevention property) over a wide temperature range from a low temperature to a high temperature. Rubber composition that is excellent in and can maintain their performance for a long time,
Also, the present invention relates to a high performance pneumatic tire using the same as an outer cover member.

[0002]

2. Description of the Related Art Conventionally, it has been known to mix a rubber with a wax in order to prevent a rubber product from cracking due to air or sunlight and to maintain a good appearance. When the wax is mixed with rubber, the wax oozes on the surface to form a thin film, and this thin film blocks the contact between the rubber and ozone, thereby preventing the deterioration of the rubber. Various waxes (ie, wax-based antioxidants) for preventing such rubber deterioration or aging have been known in the art. The phenomenon in which the thin film peels off and falls off is significantly different depending on the temperature. Therefore, several proposals have been made to develop a wax exhibiting stable performance over a wide temperature range from a low temperature to a high temperature. For example, a wax-based antioxidant having a wide range of carbon numbers of 16 to 41 (U.S. Pat. No. 3,423,348), or a 25 to 24 carbon atoms.
25 to 70% of 29 linear hydrocarbons and 34 to 34 carbon atoms
Wax-based antioxidants each containing 35 to 75% of 40 linear hydrocarbons (JP-B-54-25062) have been proposed.

Further, JP-A-48-91141 and JP-A-63-145346 disclose that the content of linear hydrocarbons having 26 to 29 carbon atoms and 34 to 40 carbon atoms is large, and that the content of linear hydrocarbons having 30 to 33 carbon atoms is high. A wax-based antioxidant having a small number of linear hydrocarbons and having a low carbon number distribution is disclosed. Further, JP-A-1-230648 discloses a wax-based antioxidant capable of improving the ozone resistance at a relatively high temperature by increasing the content of a linear saturated hydrocarbon having 36 to 51 carbon atoms. . In addition, JP-A-5-43744 discloses that
A wax-based antiaging agent having a content of a linear saturated hydrocarbon having 58 or more carbon atoms of 1% by weight or less and a content of a linear saturated hydrocarbon having 48 to 57 carbon atoms of 3 to 30% by weight. JP-A-7-70375 discloses a wax-based antioxidant in which the average content of non-linear saturated hydrocarbons having 36 to 44 carbon atoms per carbon number is 1.5% by weight or more. Is disclosed. The former can prevent blooming of the wax without impairing the static ozone resistance of the rubber product, and the latter is said to improve the dynamic ozone resistance of the rubber product. However, these conventional wax-based antioxidants have advantages and disadvantages, and have good appearance of rubber products, particularly tires, and good static and dynamic ozone resistance over a wide temperature range, and have long-term performance. It was difficult to keep everything at a sufficiently high level.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is intended to provide a rubber article, particularly an automobile tire, which has an appearance and a static dynamic ozone resistance in a low to high temperature range. It is an object of the present invention to provide a rubber composition which is excellent in dynamic ozone resistance, can maintain these properties for a long time, and provides good workability, and a pneumatic tire using the same.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies from such a viewpoint, and found that a linear saturated hydrocarbon component and a non-linear saturated hydrocarbon component having a predetermined carbon number range are It has been found that a rubber composition obtained by compounding a rubber with a hydrocarbon wax having a component composition designed to satisfy various relationships can achieve the object. The present invention has been completed based on such findings. That is, the present invention provides a rubber composition comprising 0.1 to 10 parts by weight of a hydrocarbon wax with respect to 100 parts by weight of a natural rubber and / or a diene-based synthetic rubber. The component composition is such that the ratio (I ₁ / N ₁ ) of the non-linear saturated hydrocarbon component (I ₁ ) having 29 to 39 carbon atoms to the linear saturated hydrocarbon component (N ₁ ) having 28 to 36 carbon atoms is 20-55
% By weight, the ratio of the total amount of the linear saturated hydrocarbon component (N ₁ ) having 28 to 36 carbon atoms and the non-linear saturated hydrocarbon component (I ₁ ) having 29 to 39 carbon atoms to the whole wax (T) ((N ₁ + I ₁ ) / T) is 30 to 65% by weight, a linear saturated hydrocarbon component (N ₂ ) having 20 to 25 carbon atoms and a non-linear saturated hydrocarbon component having 20 to 25 carbon atoms ( Ratio of total amount of I ₂ ) to total wax (T) ((N ₂ + I ₂ )
/ T) is 7 to 30% by weight of the total amount of the linear saturated hydrocarbon component (N ₃ ) having 38 to 53 carbon atoms and the non-linear saturated hydrocarbon component (I ₃ ) having 42 to 51 carbon atoms. The ratio ((N ₃ + I ₃ ) / T) to the entire wax (T) is 15 to 3
5% by weight and the total amount of the total amount of the linear saturated hydrocarbon component (N ₄ ) having 32 to 46 carbon atoms and the non-linear saturated hydrocarbon component (I ₄ ) having 38 to 46 carbon atoms (T) (N ₄ + I ₄ ) / T) is 60% by weight or less. The present invention also provides a pneumatic tire using the above rubber composition for a skin member.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention comprises a natural rubber and / or a diene-based synthetic rubber and a hydrocarbon-based wax. Here, as the diene-based synthetic rubber, for example, polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (S
BR), acrylonitrile butadiene rubber (NBR),
Chloroprene rubber (CR), butyl rubber (IIR) and the like can be mentioned. Natural rubber or diene-based synthetic rubber as the rubber component may be used alone or in combination of two or more.

On the other hand, in the rubber composition of the present invention,
The component composition of the hydrocarbon wax compounded in the rubber is as follows.
It is necessary to have the characteristics shown below. First, the tire
And other rubber products have excellent appearance at room temperature.
(That is, it has a strong blackness and a glossy appearance)
To achieve this, the bleeding
If the total amount of
It is desirable that the wax be as transparent as possible. So
According to standards such as
The non-linear saturated hydrocarbon component of the number 29 to 39 (I₁) Charcoal
A linear saturated hydrocarbon component having a prime number of 28 to 36 (N₁) To
Rate (I₁/ N ₁) Is 20 to 55% by weight.
Is required, preferably 25 to 50% by weight, more preferably
Or 30 to 45% by weight. Here, the above ratio (I
₁/ N₁) Is less than 20% by weight, various rubbers such as tires
If the appearance of the product is not sufficient and exceeds 55% by weight, it is weighed
Workability is extremely reduced.

Next, the operating temperature range (tire surface temperature) of a tire is generally -10 to 60 ° C.
It is desired that the hydrocarbon wax compounded in the rubber composition can maintain a thin film formed by blooming on the tire surface in this temperature range to a certain thickness or more. The wax component that blooms in this temperature range has 20 to 5 carbon atoms.
5, and among them, the linear and non-linear ones have different blooming temperature ranges. From such criteria, in order to control the film thickness at room temperature (in particular, to develop ozone resistance at room temperature), the component in the wax contains 28 to 36 carbon atoms.
Of a linear saturated hydrocarbon component (N ₁ ) having from 29 to 39 carbon atoms
The ratio ((N ₁ + I ₁ ) / T) of the total amount of the non-linear saturated hydrocarbon component (I ₁ ) to the entire wax (T) is 3
0 to 65% by weight, preferably 3% by weight.
It is 3 to 60% by weight, more preferably 35 to 55% by weight. If the ratio ((N ₁ + I ₁ ) / T) is less than 30% by weight, the static ozone resistance at room temperature is not sufficient,
If it exceeds 65% by weight, the appearance will be insufficient.

Further, in order to control the film thickness at a low temperature (around -10 to 0 ° C.), in the components in the wax, a linear saturated hydrocarbon component having 20 to 25 carbon atoms (N
₂ ) The ratio ((N ₂ + I ₂ ) / T) of the total amount of the non-linear saturated hydrocarbon component (I ₂ ) having 20 to 25 carbon atoms to the whole wax (T) is 7 to 30% by weight. And it is preferably 10 to 25% by weight, more preferably 11 to 20% by weight. Here, the above ratio ((N
_{If 2} + I ₂ ) / T) is less than 7% by weight, the static ozone resistance at low temperatures is not sufficient, and if it exceeds 30% by weight, the appearance becomes insufficient.

In order to control the film thickness at a high temperature (around 50 ° C.), the components in the wax are a straight-chain saturated hydrocarbon component (N ₃ ) having 38 to 53 carbon atoms and 42 to 51 carbon atoms. Of the total amount of the non-linear saturated hydrocarbon component (I ₃ ) to the whole wax (T) ((N ₃ +
I ₃₎ / T) is required to be 15 to 45 wt%, preferably 18 to 40 wt%, more preferably 20
~ 35% by weight. Here, the above ratio ((N ₃ +
If I ₃ ) / T) is less than 15% by weight, the static ozone resistance at high temperatures is not sufficient, and if it exceeds 45% by weight, the dynamic ozone resistance and appearance are insufficient.

By the way, a wax film on a tire surface
Presence is effective in increasing static ozone resistance
However, when rolling tires, the ozone resistance is low.
It can also cause it to fall. Therefore, the temperature range during tire rolling
Surrounding (usually around 30 to 50 ° C), more than necessary
It is desired to control so that a film is not formed. So
According to standards such as
A linear saturated hydrocarbon component having a number of 32 to 46 (N_Four) And carbon
A non-linear saturated hydrocarbon component represented by _Four)
The ratio of the measurement to the total wax (T) ((N_Four+
I_Four) / T) must be not more than 60% by weight.
Preferably 55% by weight or less, more preferably 20 to
55% by weight. Here, the above ratio ((N_Four+ I_Four)
/ T) exceeds 60% by weight, the dynamic ozone resistance is sufficient.
Absent.

The component composition of the hydrocarbon wax in the present invention may be any one satisfying the above conditions (1) to (3).
Or those satisfying the conditions of-are more desirable. That is, various types of rubber products such as tires are generally used over a long period of time, and for that purpose, products that can maintain various performances (appearance, ozone resistance, etc.) of wax for a long period of time are suitable. In order to maintain such various performances for a long period of time, the present invention employs two techniques.One of the techniques is to exist in rubber without blooming on the rubber product surface and to bloom. The purpose is to introduce a wax component (so-called microwax) that holds the wax component easily and delays the bloom speed at a constant rate. From such criteria, the total of ₅ of the components in the wax, the linear saturated hydrocarbon component (N ₅ ) having 55 or more carbon atoms and the non-linear saturated hydrocarbon component (I ₅ ) having 55 or more carbon atoms, was used. preferably a percentage of the total wax _{(T) ((N 5 +} I 5) / T) is 0.01 to 15 wt%, more preferably from 0.05 to 13% by weight,
Particularly preferably, the content is 0.1 to 12% by weight. If the ratio ((N ₅ + I ₅ ) / T) is less than 0.01% by weight, the effect of maintaining ozone resistance and appearance may not be sufficient.
If it exceeds 15% by weight, the ozone resistance may be insufficient.

As another method for maintaining various performances for a long period of time, a non-linear saturated hydrocarbon component having a lower bloom speed than that of a linear saturated hydrocarbon component is increased to delay the bloom speed. It is to make it. From such criteria, the components in the wax have 20 to 55 carbon atoms.
The ratio (I ₆ / T) of the non-linear saturated hydrocarbon component (I ₆ ) to the whole wax (T) is preferably less than 35% by weight, more preferably less than 30% by weight, particularly preferably 25% by weight. % By weight. Here, when the above ratio (I ₆ / T) is 35% by weight or more, the weighing workability may decrease.

In addition, when kneading wax with rubber, it is generally desirable that the wax be solid and finely granular in consideration of workability. However, when the amount of the non-linear saturated hydrocarbon component increases, solidification (blocking or agglomeration) tends to occur when the wax is used alone, making it difficult to weigh. Similarly, when the oil content is high, the solidification is also likely to occur, which causes inconvenience. From such a standard, the oil (O)
Is preferably 2% by weight or less, more preferably 1.5% by weight or less, and particularly preferably 1% by weight or less, based on the total wax (T). here,
If the above ratio (O / T) exceeds 2% by weight, weighing workability may be impaired.

The hydrocarbon wax of the present invention having such properties can be produced by various methods, and any one obtained by any of the methods can be used without any particular limitation. Can be. For example,
From the conventionally known petroleum wax or synthetic wax, desired properties can be obtained directly by appropriately combining vacuum distillation, solvent deoiling, sweating, press deoiling, or the like, or various waxes are appropriately blended. Can be obtained by: Here, in order to confirm that the component composition of the wax is in a desired range, a capillary gas chromatograph method or the like may be used. In addition, a specific method of obtaining a petroleum wax is a method of obtaining a petroleum wax as a by-product when producing a lubricating base oil from crude oil. That is, the crude oil is distilled under normal pressure, the bottom oil is further distilled under reduced pressure, and the distillate is subjected to solvent extraction with phenol, furfural or the like to remove aromatic components, preferably hydrorefining, and further ketone, Solvent dewaxing is performed with an aromatic mixed solvent to obtain a dewaxed oil as a lubricating base oil, and a crude wax can be obtained as a by-product at that time. This crude wax can be further deoiled with a solvent to remove low-boiling waxes to obtain a deoiled wax.
Further, the coarse wax may be sweat-deoiled to obtain a deoiled wax. Each of the deoiled waxes can be refined by treating it with sulfuric acid, clay or the like.

In the rubber composition of the present invention, the mixing ratio of the hydrocarbon wax is 0.1 to 10 parts by weight, preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of natural rubber and / or diene synthetic rubber. 8 parts by weight, more preferably 0.5 to 5 parts by weight. Here, the compounding ratio of the hydrocarbon wax is 0.1.
If the amount is less than 10 parts by weight, the effect of blending the wax is not sufficiently exhibited. If the amount is more than 10 parts by weight, inconvenience such as poor appearance occurs.

The rubber composition of the present invention may contain various chemicals usually used in the rubber industry, such as carbon black, a vulcanizing agent, and the like, as long as the object of the present invention is not impaired.
It can contain vulcanization accelerators, anti-aging agents, anti-scorch agents, softeners, other fillers, zinc white, stearic acid, and the like. The rubber composition of the present invention is widely used as a rubber member for industrial products such as tires, belts, hoses and rubber rollers, and is particularly suitably used for outer skin members of tires, for example, tread rubber and sidewall rubber. Can be The pneumatic tire of the present invention is manufactured by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition according to the present invention containing various chemicals as described above is extruded into a predetermined member in an unvulcanized stage, and is pasted and formed by a normal method on a tire molding machine. Then, the obtained green tire is vulcanized and molded to obtain a tire.

[0018]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Measurement of Component Composition of Hydrocarbon Wax First, ten types of hydrocarbon waxes were prepared, and their component compositions (however, linear saturated hydrocarbon components and non-linear saturated hydrocarbon components) were tested according to the following test methods. Was measured by Table 1 shows the results. That is, 1 microliter of a sample obtained by dissolving 5 mg of a wax sample in 100 microliter of cyclohexane was injected into gas gammagraphy (GC) using a microsyringe and analyzed. The models and conditions of the used GC are as follows. The obtained data was evaluated based on the peak area. GC model: HP5890 Column: HT5 (SGE INTERNATIONAL)
PTY. LTD. ) Flow rate: 29.5 cm / sec Carrier gas: Helium Column temperature: Maintain at 180 ° C for 2 minutes, then 15 ° C /
The temperature was raised to 400 ° C. in min and maintained at 400 ° C. for 20 minutes. Further, the content of the oily substance in the hydrocarbon wax was measured by the following method. That is, 100c
5 g of a wax sample was placed in the acetone of Example c, left standing overnight, cooled to −10 ° C., left standing for 2 hours, filtered to obtain a filtrate, and acetone was removed from the filtrate by a vacuum pump. Was evaluated as an oil. The results are also shown in Table 1.

Examples 1 to 4 and Comparative Examples 1 to 6 (1) Preparation of rubber composition test piece 50.0 parts by weight of natural rubber (RSS # 4) and 50.000 parts by weight of polybutadiene rubber (BR01, manufactured by JSR Corporation) 0 parts by weight, F
EF Carbon (Seast F, manufactured by Tokai Carbon Co., Ltd.) 5
0.0 parts by weight, a high aromatic softener (Aromax # 3,
15.0 parts by weight, manufactured by Fujikosan Co., Ltd., 1.5 parts by weight of various hydrocarbon waxes having the properties shown in Table 1, stearic acid (B
2.0 parts by weight of R-stearic acid, manufactured by NOF Corporation, 3.0 parts by weight of zinc oxide (No. 1 zinc flower, manufactured by Hakusui Chemical Co., Ltd.),
Anti-aging agent (N- (1,3-dimethylbutyl) -N′-
Phenyl-p-phenylenediamine) (Nocrack 6
C, Ouchi Shinko Chemical Co., Ltd.) 3.0 parts by weight, vulcanization accelerator (dibenzothiazyl disulfide) (Noxeller D
M, Ouchi Shinko Chemical Co., Ltd.) 1.0 part by weight, vulcanization accelerator (diphenylguanidine) (Noxeller DPG, Ouchi Shinko Chemical Co., Ltd.) 0.5 part by weight, and sulfur (Karuizawa Refining) (Made by Toshosho Co., Ltd.) using a kneader, and then formed into a sheet using a roll having a surface temperature of 70 ° C.
Thereafter, this was filled in an appropriate mold, vulcanized under the conditions of a temperature of 160 ° C., a pressure of 30 kg / cm ² , and a heating time of 15 minutes, and then demolded to prepare a predetermined rubber composition test piece.

(2) Evaluation of Physical Properties of Rubber Composition Specimen (i) Evaluation of Appearance 100 mm × 150 mm ×
After a 5-mm test piece was left indoors for 2 weeks, a visual sensory test was performed. Table 1 shows the results. In addition,
The meaning of each symbol in the table is as follows. ◎: Black and glossy ○: Blackness is slightly inferior but glossy △: Black but not glossy X: Inferior to black and not glossy

(Ii) Evaluation of static ozone resistance (JIS K)
(Based on 6301-1995) 150mm × 150mm ×
A 2 mm test piece was cut into a 60 mm × 10
A rectangular strip of mm × 2 mm with a smooth surface was prepared. The strip-like test piece was stimulated under the following conditions, and the generated cracks were visually evaluated. Table 1 shows the results. The meaning of each symbol in the table is as follows. ：: Small number of cracks or none ×: Many cracks or countless number of cracks Static ozone resistance at low temperature Pretreatment condition: 0 ° C. × 1 week Specimen elongation rate: 30% Ozone concentration: 50 ± 5 pphm Temperature: 0 ° C. Exposure time: Static ozone resistance pretreatment conditions at room temperature for 5 days: room temperature x 1 week Test piece elongation rate: 30% Ozone concentration: 50 ± 5 pphm Temperature: room temperature Exposure time: static ozone resistance pretreatment conditions at high temperature for 2 days : 50 ° C x 1 week Specimen elongation rate: 30% Ozone concentration: 50 ± 5 pphm Temperature: 50 ° C Exposure time: 6 hours

(Iii) Evaluation of dynamic ozone resistance (JIS K)
(Based on 6301-1995) 150mm × 150mm ×
A 2 mm test piece was 80 mm × 20 using a punching die.
A rectangular strip of mm × 2 mm with a smooth surface was prepared. The strip-like test piece was stimulated under the following conditions, and the generated cracks were visually evaluated. Table 1 shows the results. The meaning of each symbol in the table is as follows. ：: few or no cracks ×: many or no cracks Pretreatment conditions: 40 ° C. × 1 week Specimen elongation: 0 to 30% (30 reciprocations / minute) Ozone concentration: 50 ± 5 pphm Temperature: 40 ° C. Exposure time : 6 hours

(Iv) Evaluation of solidification properties (weighing workability) 100 g of a hydrocarbon wax was put in a bag, sealed, put on a 5 kg weight, left for 48 hours, and then visually observed. Table 1 shows the results. The meaning of each symbol in the table is as follows. ：: good (not solidified), ×: solidified

(V) Evaluation of persistence of the effect After exposing the test piece prepared by the method of the above (ii) outdoors for 3 months, the attached matter on the surface was wiped off with a gauze to which acetone was applied, and then the above (ii) Was evaluated for static ozone resistance at room temperature. Table 1 shows the results. The meaning of each symbol in the table is as follows. ○: few or no cracks ×: many or countless cracks

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

* The properties are as follows. : A non-linear saturated hydrocarbon component having 29 to 39 carbon atoms (I
₁ ) a linear saturated hydrocarbon component having 28 to 36 carbon atoms (N
Ratio _{1) (I 1 / N)} : the total amount of linear saturated hydrocarbon component of 28 to 36 carbon atoms (N ₁₎ and the non-linear saturated hydrocarbon component of 29 to 39 carbon atoms (I ₁₎ Of the total wax (T) ((N ₁ + I ₁ ) / T): a linear saturated hydrocarbon component (N ₂ ) having 20 to 25 carbon atoms and a non-linear saturated hydrocarbon component having 20 to 25 carbon atoms Ratio of total amount of component (I ₂ ) to total wax (T) ((N ₂ + I ₂ ) / T): linear saturated hydrocarbon component (N ₃ ) having 38 to 53 carbon atoms and 42 to 51 carbon atoms Of the total amount of the non-linear saturated hydrocarbon component (I ₃ ) to the whole wax (T) ((N ₃ + I ₃ ) / T): the linear saturated hydrocarbon component having 32 to 46 carbon atoms (N the total amount of percentage of the total wax (T) of ₄₎ and the non-linear saturated hydrocarbon component of 38 to 46 carbon atoms (I ₄₎ ( _{N 4 + I 4) / T} ): carbon atoms more than 55 linear saturated hydrocarbon component (N ₅₎
And a non-linear saturated hydrocarbon component having 55 or more carbon atoms (I ₅ )
Fraction of the full sum of the wax _{(T) ((N 5 +} I 5) / T): Non-linear saturated hydrocarbon component of 20 to 55 carbon atoms (I
₆ ) Ratio of total wax (T) (I ₆ / T): ratio of oil (O) to total wax (T) (O / T)

[0029]

The rubber composition of the present invention is obtained by blending a natural rubber or a diene-based synthetic rubber with a hydrocarbon wax having a specific property. Not only appearance, but also excellent static ozone resistance and dynamic ozone resistance over a wide temperature range, and their performance can be maintained at a high level for a long period of time. Therefore, the rubber composition of the present invention is expected to be effectively used as a material for various rubber products such as automobile tires, and has high practical value.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 9:00 91:06)

Claims (4)

[Claims] 1. Natural rubber and / or diene synthetic rubber 1
A rubber composition comprising 0.1 to 10 parts by weight of a hydrocarbon wax with respect to 00 parts by weight, wherein the hydrocarbon wax has a component composition of 29 to 39 carbon atoms. ratio (I ₁ / N ₁₎ 20 to 55 wt% with respect to a straight chain saturated hydrocarbon moiety having a carbon number of 28 to 36 (N ₁₎ of hydrocarbon component (I _1), linear 28 to 36 carbon atoms The ratio ((N ₁ + I ₁ ) / T) of the total amount of the saturated hydrocarbon component (N ₁ ) and the non-linear saturated hydrocarbon component (I ₁ ) having 29 to 39 carbon atoms to the whole wax (T) is 30. To 65% by weight, a linear saturated hydrocarbon component having 20 to 25 carbon atoms (N
₂ ) and the ratio of the total amount of the non-linear saturated hydrocarbon component (I ₂ ) having 20 to 25 carbon atoms (I ₂ ) to the whole wax (T) ((N ₂ + I ₂ ) / T) is 7 to 30% by weight; Number 3
8 to 53 linear saturated hydrocarbon components (N ₃ ) and 4 carbon atoms
The ratio ((N ₃ + I ₃ ) / (N ₃ + I ₃ ) / total wax (T) of the total amount of 2 to 51 non-linear saturated hydrocarbon components (I ₃ )
T) is 15 to 35% by weight, and the total amount of the linear saturated hydrocarbon component (N ₄ ) having 32 to 46 carbon atoms and the non-linear saturated hydrocarbon component (I ₄ ) having 38 to 46 carbon atoms is A rubber composition, wherein a ratio ((N ₄ + I ₄ ) / T) to the whole wax (T) is 60% by weight or less. 2. The hydrocarbon wax has a component composition of a linear saturated hydrocarbon component (N ₅ ) having 55 or more carbon atoms and a non-linear saturated hydrocarbon component (I ₅ ) having 55 or more carbon atoms. Ratio of total amount to total wax (T) ((N ₅ + I
_5. The rubber composition according to claim 1, wherein ₅ ) / T) is 0.01 to 15% by weight. 3. The composition of the hydrocarbon wax is such that the ratio of the non-linear saturated hydrocarbon component (I ₆ ) having 20 to 55 carbon atoms to the whole wax (T) (I ₆ / I)
3. The rubber composition according to claim 1, wherein T) is less than 35% by weight, and a ratio (O / T) of the oil (O) to the whole wax (T) is 2% by weight or less. 4. A pneumatic tire using the rubber composition according to claim 1 for a skin member.