JP3445080B2 - Rubber composition and pneumatic tire using the rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition having improved reinforcement and abrasion resistance, and a pneumatic tire using the rubber composition.

[0002]

2. Description of the Related Art Conventionally, carbon black has been used as a reinforcing filler for rubber. This is because carbon black has high reinforcement and excellent wear resistance as compared with other fillers, but in recent years, energy saving,
Under the social demand for resource saving, in particular, in order to save fuel consumption of automobiles, lower heat generation of rubber compositions has been required at the same time.

In order to reduce the heat generation of the rubber composition by carbon black, it is possible to fill a small amount of carbon black or use carbon black having a large particle size. It is well known that there is a trade-off with abrasion.

On the other hand, as a low heat-generating filler for a rubber composition, hydrous silicic acid (silica) is known, and many patents have been filed up to the present, such as JP-A-3-252431. ing.

However, the rubber composition containing the wet-process hydrous silicic acid is inferior to the rubber composition containing carbon black in terms of processability, reinforcement and abrasion resistance among the general rubber physical properties. There is. To eliminate these drawbacks,
Combination use of silane coupling agents and other organic compounds has been performed. However, satisfactory physical properties have not yet been obtained, and further modification is strongly desired.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and uses a rubber composition having improved reinforcement and abrasion resistance, and a rubber composition thereof. To provide a pneumatic tire.

[0007]

SUMMARY OF THE INVENTION In view of the problems of the prior art, the inventors of the present invention have conducted extensive studies and made natural rubber and diene synthetic rubber compounded with a wet range hydrous silicic acid in a specific range. The inventors have found that the composition can exhibit excellent reinforcing effect and abrasion resistance, and have completed the present invention.
That is, the present invention resides in the following (1) to (7). (1) 100 parts by weight of natural rubber and / or diene-based synthetic rubber, BET specific surface area (hereinafter simply referred to as "N ₂ -S
A)) is in the range of 170 to 300 m ² / g,
A rubber composition comprising 10 to 90 parts by weight of a wet process hydrous silicic acid having a Hg method specific surface area (hereinafter, simply referred to as “Hg-SA”) / N ₂ -SA ratio of 1.08 or more. (2) N ₂ -SA of wet method hydrous silicic acid is 170 to 250 m
² / g in the range of, and Hg-SA / N ₂ above ratio -SA it is in the range of 1.1 to 1.2 (1) rubber composition. (3) The above-mentioned (1) or (2), in which the pore volume with a radius of 1000 Å or less is 1.6 cc / g or more by the Hg method pore volume measurement method.
The rubber composition described. (4) The silane coupling agent is 1 to 2 of wet method hydrous silicic acid.
The rubber composition as described in any one of (1) to (3) above, which contains 0% by weight. (5) The following formulas (I) to (II
The rubber composition according to (4) above, which contains at least one of I).

[Chemical 4]

[Chemical 5]

[Chemical 6] (6) Carbon black of 5 to 80 is used as a reinforcing filler.
(1) to (5), wherein the total amount of wet-process hydrous silicic acid and carbon black is 120 parts by weight or less.
The rubber composition according to any one of 1. (7) A pneumatic tire using the rubber composition according to any one of (1) to (6) above in a tire tread portion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in more detail below. The mechanism of rubber reinforcement is considered to be the dispersion function and structural properties of the filler. With respect to the structural properties, the particle diameter of the filler, the pore volume, and a higher-order structure called a structure in which particles are connected to each other can be mentioned. Generally, carbon black has a well-developed structure, and various functional groups on the surface of particles are present. Since it has a strong bond with polymer molecules and is suitable as a rubber reinforcing agent, it has been widely used to date.

On the other hand, wet-process hydrous silicic acid (hereinafter, simply referred to as "hydrous silicic acid") has silanol groups (Si-O) on its surface.
H) is present and brings about a reinforcing effect, but on the other hand, it has a weak point that it hinders dispersion and lowers the effect of the drug. As described above, hydrous silicic acid has only a siloxane group and a silanol group on the particle surface, and does not have a functional group like carbon black, and thus has low reactivity with a polymer.
Therefore, the reinforcing effect is enhanced by supplementing with a silane coupling agent or the like. Although such a method is in the present situation, this method alone is not sufficient as a hydrous silicic acid for tires. Therefore,
It is necessary to raise the level of structural properties of hydrous silicic acid, which is discussed in terms of pore volume and surface area.

In particular, the structural properties of hydrous silicic acid are considered to be important for improving the wear resistance. The strong entanglement between the hydrous silicic acid and the polymer should be an important factor together with the chemical bond strength with the polymer molecule. For that purpose, it is necessary to further increase the pore volume of hydrous silicic acid. That is, the rubber molecules enter the pores to form a strong structure (bond or entanglement). Therefore, it should be possible to supplement the weak bond between the hydrous silicic acid and the rubber molecule to enhance the reinforcing effect. The inventors of the present invention have conducted repeated research from this viewpoint.
With respect to natural rubber and diene-based synthetic rubber, it was found that a rubber composition containing hydrous silicic acid in the above specific range can exhibit excellent reinforcing effect and abrasion resistance, and completed the present invention. .

It is already well known that the mechanism of rubber reinforcement depends largely on N ₂ -SA of hydrous silicic acid as a filler. Hydrous silicic acid generally used as a conventional rubber-reinforcing filler has N ₂ -SA of 220 m ² / g.
It is as follows. In addition, such hydrous silicic acid generally has an Hg-SA of 200 m ² / g or less, and Hg-SA /
The ratio of N ₂ -SA is less than 1.0.

On the other hand, the hydrous silicic acid used in the present invention is
N ₂ -SA is in the range of 170 to 300 m ² / g, and the ratio of Hg-SA / N ₂ -SA is 1.08 or more.
If N ₂ -SA is less than 170 m ² / g, the reinforcing property will be low. On the other hand, when N ₂ -SA exceeds 300 m ² / g, the dispersion during rubber kneading is hindered, as a result, the reinforcing property is lowered, and the viscosity of the rubber composition becomes too high, which deteriorates the processability. N ₂ -SA is preferably 170 to 250 m ^2.
The range is / g.

The hydrous silicic acid used in the present invention is Hg-
The ratio of SA / N ₂ -SA is 1.08 or more and has high structural properties. This ratio is preferably 1.1 or higher, and even more preferably 1.15 or higher. Hg
The upper limit of the ratio of -SA / N ₂ -SA are Practically, 1.2
It is a degree.

The Hg-SA / N ₂ -SA ratio of 1.08 or more, which is characteristic of the hydrous silicic acid used in the present invention, means that the structure is high, that is, the volume of fine pores is rich. A large N ₂ -SA means a small primary particle, and it is expected that the aggregate is small and the contact area with rubber is large. The calculation method of Hg-SA can be expressed as Hg-SA = 2V / r, assuming that the pores are cylindrical. (However, Hg-SA = surface area (m ² / g), V = total pore volume (cc / g), r = average pore radius (μm)) It can be said that the larger the volume, the larger the surface area. Since the conventional general hydrous silicic acid has a Hg-SA / N ₂ -SA ratio of less than 1, the hydrous silicic acid of the present invention is clearly different from these conventional products.

The hydrous silicic acid used in the present invention preferably has a pore volume of 1.6 cc / g or more with a radius of 1000 Å or less measured by the Hg method pore volume measurement method. The reinforcing effect of the rubber can be enhanced by increasing the volume of the Hg method pore volume having a radius of 1000 Å or less. Radius 100
The pore volume of 0 Å or less is preferably 1.6 to 1.9 cc
/ G range. As described above, it was found that the hydrated silicic acid having a high structural property can improve the reinforcing property and abrasion resistance of the rubber.

From the viewpoint of reinforcement, abrasion resistance and workability, the content of hydrous silicic acid is from 10 to 100 parts by weight of rubber.
90 parts by weight, preferably 15 to 80 parts by weight is desirable. When the content of hydrous silicic acid is less than 10 parts by weight, the effect of reinforcement and abrasion resistance is small, and when it exceeds 90 parts by weight, it is difficult to obtain a good dispersion of hydrous silicic acid, resulting in deterioration of reinforcement and abrasion resistance. However, it is not preferable.

As the rubber used in the present invention, natural rubber (NR) or diene-based synthetic rubber can be used alone or in a blended form thereof. As synthetic rubber,
For example, synthetic polyisoprene rubber (IR), polybutadiene rubber (BR) and styrene butadiene rubber (SBR)
Etc.

The silane coupling agent used in the present invention is
At least one represented by the following formulas (I) to (III) can be mentioned.

[Chemical 7]

[Chemical 8]

[Chemical 9]

Specifically, bis (3-triethoxysilylpropyl) polysulfide, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane,
γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N, N- Examples include dimethylcarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, and the like.

The content of the silane coupling agent is 1 to 20% by weight, preferably 2 to 15% by weight based on the weight of hydrous silicic acid.
% By weight. When the amount of the silane coupling agent is less than 1% by weight, the coupling effect is small, and when it exceeds 20% by weight, both the reinforcing property and the abrasion resistance are deteriorated, which is not preferable.

In the present invention, carbon black can be further compounded as a reinforcing filler. As the carbon black, SAF, ISAF and HAF can be preferably used, but the carbon black is not particularly limited. The amount of carbon black compounded is 5 to 80 with respect to 100 parts by weight of the rubber.
It is preferable that the total amount of hydrous silicic acid and carbon black is 120 parts by weight or less. Reinforcing properties and abrasion resistance can be further improved by setting the blending amount of carbon black within the above range.

In the present invention, in addition to the above rubber, hydrous silicic acid, silane coupling agent, and carbon black, if necessary, a softening agent (wax, oil), an antioxidant, a vulcanizing agent, a vulcanizing agent, Compounding agents usually used in the rubber industry, such as a vulcanization accelerator and a vulcanization accelerating aid, can be appropriately mixed.

The rubber composition of the present invention comprises the above rubber component, hydrous silicic acid, silane coupling agent, carbon black,
The rubber compounding agent and the like to be compounded as necessary can be prepared with a kneading machine such as a Banbury mixer.

The rubber composition of the present invention can be preferably applied to rubber products such as tires, conveyor belts and hoses. The rubber products used as products such as tires, conveyor belts and hoses are reinforced and have high resistance. It has excellent abrasion resistance. Further, since the pneumatic tire of the present invention uses the above rubber composition in the tire tread portion, a pneumatic tire excellent in reinforcement of the tire tread portion and high wear resistance can be obtained.

[0025]

EXAMPLES The present invention will be described below in detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples. The hydrous silicic acid used in Examples and Comparative Examples is
The hydrous silicic acids of Samples A to F having the physical properties shown in Table 1 below were used. Samples A to C are hydrous silicic acids having physical properties outside the scope of the present invention, and Samples D to F are hydrous silicic acids having physical properties within the scope of the present invention. Sample D ~
F was obtained according to the following Production Examples 1 to 3.

The physical properties of the hydrous silicic acids of Samples A to F were measured by the following methods. (1) BET method specific surface area (N ₂ -SA) Measured by a one-point method using Kantasorb (manufactured by Quantachrome, USA). (2) Hg method specific surface area (Hg-SA) Measured with a porosimeter 2000 type (manufactured by Carlo Erba, Italy). Calculation method; Hg-SA = 2V / r (Hg-SA = specific surface area (m ² / g), V = total pore volume (cc / g), r = average radius (μm)) (3) Hg method fineness Pore volume porosimeter 2000 type.

(Production Example 1, Sample D) A 240 liter jacketed stainless steel container equipped with a stirrer was placed in a sodium silicate aqueous solution (SiO ₂ / Na ₂ O weight ratio: 3.
3, SiO ₂ concentration 150 g / l) and water were added so that the SiO ₂ concentration was 60 g / l, and the temperature was raised to 80 ° C. by heating with steam. Next, 98 wt% concentrated sulfuric acid in an amount corresponding to 25% of the total amount required for neutralizing the added sodium silicate was added over 5 minutes. Immediately after the addition was completed, the mixture was heated with steam to 96 ° C. for 20 minutes. Next, 20% of the neutralization equivalent was added with the same sulfuric acid as above for 5 minutes, followed by aging for 20 minutes, which was repeated 3 times. Next, about 10% of the neutralization equivalent of sulfuric acid was added for 5 minutes. The pH at that time was 9.
It was 3. During this time, the temperature was maintained at 96 ± 1 ° C. Then, aging was carried out for 60 minutes while maintaining the temperature. Then, the same sulfuric acid was further added for 10 minutes to stop the reaction at pH 3 to complete the reaction. The obtained reaction product was filtered, washed with water and spray-dried by a commonly used method to obtain a hydrous silicic acid as a sample D by a wet precipitation method. The properties of the obtained hydrous silicic acid were as follows. ^{_{· N 2 -SA = 192m 2 /}} g · Hg-SA = 222m 2 / g · Hg-SA / N 2 -SA = 1.16 · Hg pore volume (hereinafter radius 1000Å) = 1.65cc / g

(Production Example 2, Sample E) Using the same container and the same raw material as in Production Example 1, 80 liters of an aqueous sodium silicate solution and water were added so that the SiO ₂ concentration was 60 g / l, and the temperature was 80. ℃ was made. Then, an acid equivalent to 35% of the neutralization equivalent was added for 10 minutes. It was then heated to a temperature of 96 ° C. in 20 minutes. Then add 5% acid equivalent to 5
The aging and aging were repeated 3 times for 15 minutes each. Subsequently, an acid equivalent to about 13% of the neutralization equivalent was added for 5 minutes.
The pH at that time was 9.5. Then temperature 96 ± 1 ℃
Was maintained for 60 minutes for aging. After that, acidification was performed for 10 minutes to complete the reaction at pH 3. After that, a hydrous silicic acid as a sample E was obtained in the same manner as in Production Example 1. The properties of the obtained hydrous silicic acid were as follows. ^{_{· N 2 -SA = 241m 2 /}} g · Hg-SA = 281m 2 / g · Hg-SA / N 2 -SA = 1.17 · Hg pore volume (hereinafter radius 1000Å) = 1.83cc / g

(Production Example 3, Sample F) First, 97 liters of an aqueous solution of sodium silicate and water were charged to obtain SiO 2.
_A hydrous silicic acid as a sample F was obtained in the same manner as in Production Example 2 except that the ₂ concentration was 76 g / l. The properties of the obtained hydrous silicic acid were as follows.・ N ₂ -SA = 175 m ² / g ・ Hg-SA = 190 m ² / g ・ Hg-SA / N ₂ -SA = 1.08 ・ Hg pore volume (radius 1000 Å or less) = 1.73 cc / g

[0030]

[Table 1]

(Examples 1 to 9 and Comparative Examples 1 to 8) Using the hydrous silicic acid (Samples A to F) having the physical properties shown in Table 1 above, rubbers were prepared according to the compounding compositions shown in Tables 2 to 4 below. A composition was prepared. The rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 8 were evaluated for reinforcement and wear resistance by the following measuring methods. In addition, the compounding unit of the compounding composition in Tables 2-4 is a weight part.

(1) Reinforcing property According to JIS K6251, a dumbbell-shaped No. 3 sample was used to conduct a tensile test at 25 ° C., and the tensile strength was compared with that of a control. Larger is better. (2) Using a wear-resistant Lambourn abrasion tester, BS (British Standar
d) Measured at a ground pressure of 5 kg / cm ² and a slip ratio of 40% by a method according to the standard 903 (part A) D method, and calculated by the following formula. Abrasion resistance = (weight loss of control / weight loss of test specimen) × 100 The larger the value, the better the abrasion resistance.

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

(Consideration of Tables 2 to 4) In Examples 1 to 7 and Comparative Examples 1 to 6, Comparative Example 1 was used as a control, Example 8 was used as Comparative Example 7, and Example 9 was used as Comparative Example 8. It is a control. Example 1 using hydrous silicic acid (Samples D to F) having physical properties within the scope of the present invention
Nos. 9 to 9 were found to be able to significantly improve the reinforcing property and abrasion resistance as compared with Comparative Examples 1 to 8 using hydrous silicic acid (Samples A to C) having physical properties outside the scope of the present invention. .

[0037]

[Effects of the Invention] According to the inventions of claims 1 to 6, there is provided a rubber composition capable of greatly improving the reinforcing property and the abrasion resistance. According to the invention of claim 7, since the above rubber composition is used for the tire tread portion, a pneumatic tire excellent in reinforcement of the tire tread portion and high wear resistance is provided.

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Claims (7)

(57) [Claims] 1. Natural rubber and / or diene-based synthetic rubber 1
BET specific surface area (N ₂ -SA) relative to 100 parts by weight
There is a range of 170~300m ² / g, and Hg method specific surface area (Hg-SA) / BET method specific surface area (N ₂ -S
A wet method hydrous silicic acid having a ratio of A) of 1.08 or more is 10
A rubber composition containing about 90 parts by weight. 2. The wet method hydrous silicate has a BET method specific surface area (N ₂ -SA) in the range of 170 to 250 m ² / g, and a Hg method specific surface area (Hg-SA) / BET method specific surface area (N The rubber composition according to claim 1, wherein the ratio of ( _2- SA) is in the range of 1.1 to 1.2. 3. A radius of 10 according to the Hg method pore volume measurement method.
The rubber composition according to claim 1 or 2, which has a pore volume of not more than 00Å and is not less than 1.6 cc / g. 4. The rubber composition according to claim 1, which contains a silane coupling agent in an amount of 1 to 20% by weight based on the wet process silicic acid. 5. The rubber composition according to claim 4, which contains at least one of the following formulas (I) to (III) as a silane coupling agent. [Chemical 1] [Chemical 2] [Chemical 3] 6. The reinforcing filler contains 5 to 80 parts by weight of carbon black, and the total blending amount of wet-process hydrous silicic acid and carbon black is 120 parts by weight or less. The rubber composition according to item 4. 7. A pneumatic tire using the rubber composition according to any one of claims 1 to 6 in a tire tread portion.