JP3445081B2 - Rubber composition and pneumatic tire using the rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having improved workability, 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, generally, when a wet method hydrous silicic acid (hereinafter, simply referred to as "hydrous silicic acid") is compared with carbon black, the reinforcing property and abrasion resistance are poor. As a means for improving the reinforcing property and wear resistance, it is well known in carbon black that the filler has a fine particle size (high specific surface area), but if the hydrous silicic acid is similarly made into a fine particle size, Dispersion of hydrous silicic acid becomes insufficient, the Mooney viscosity of the rubber composition increases, and the processability deteriorates significantly.

Generally, it is desired that both workability and reinforcing property are excellent, but these physical properties are contradictory to each other. However, practically, due to the diversification and sophistication of the uses of rubber products, hydrous silicic acid that gives a rubber composition having both improved processability and reinforcement is desired.
However, none of the conventional hydrous silicic acid has provided satisfactory rubber physical properties. As described above, there is a demand for hydrous silicic acid as a highly reinforced filler having an excellent overall balance of both workability and reinforcement.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a rubber composition which can reduce the viscosity of the rubber composition to improve the processability and is excellent in the reinforcing property and abrasion resistance, and the rubber thereof. It is intended to provide a pneumatic tire using the composition.

[0008]

Means for Solving the Problems In using the above-mentioned hydrous silicic acid in a rubber composition, the present inventors have prepared a rubber composition containing the above-mentioned hydrous silicic acid having specific physical properties.
The present invention succeeded in obtaining a rubber composition of the above purpose and a pneumatic tire using the rubber composition, and completed the present invention. That is, the present invention resides in the following (1) to (6). (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 200 to 300 m ² / g,
The Hg method specific surface area (hereinafter, simply referred to as “Hg-SA”) is 150 m ² / g or less, and the ratio of the amount of adsorbed dibutylamine (hereinafter, simply referred to as “DBA”) / N ₂ —SA is 1.4.
Hereinafter, and the and the ratio of Hg-SA / N ₂ -SA 0.6
A rubber composition comprising 10 to 90 parts by weight of the following hydrous silicic acid. (2) Hg-SA of hydrous silicic acid is 50 to 150 m ² / g, DBA / N ₂ -SA ratio is 0.8 to 1.4, and Hg-SA / N ₂ -SA ratio. Is 0.2 to 0.6
The rubber composition according to (1) above, which is (3) The rubber composition as described in (1) or (2) above, which contains a silane coupling agent in an amount of 1 to 15% by weight of hydrous silicic acid. (4) The following formulas (I) to (II
The rubber composition according to (3) above, which contains at least one of I).

[Chemical 4]

[Chemical 5]

[Chemical 6] (5) Carbon black of 5 to 80 is used as a reinforcing filler.
(1) to (4), 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. (6) A pneumatic tire using the rubber composition according to any one of (1) to (5) above in a tire tread portion.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail. The mechanism of the rubber reinforcement of the filler is generally said to be due to the reactivity and structure characteristic of the filler and the dispersing function. More specifically, it is known that, as a major factor involved in the reinforcing performance of rubber, the primary particle size and the aggregate size of hydrous silicic acid and the resulting dispersion in the rubber composition are greatly involved. Therefore, it is important to control the physical properties of these hydrous silicic acids in order to obtain the desired rubber reinforcing performance. Regarding the structural properties of hydrous silicic acid, the particle size, the pore volume, etc. are used as indexes. However, with regard to the diversification function, no definite index has been found yet.

The present inventors not only have these structural characteristics,
Focusing on the dispersive function, we conducted repeated research on rubber reinforcement with hydrous silicic acid. The reinforcing performance of a hydrous silicic acid composition is roughly proportional to N ₂ -SA of hydrous silicic acid, and the higher the N ₂ -SA, the higher the reinforcing performance. However, the viscosity of the rubber composition tends to increase as the hydrous silicic acid having a higher specific surface area. Furthermore, if the specific surface area is too high, poor dispersion is caused, conversely the reinforcing performance is lowered, and at the same time workability is impaired. It is considered that this is due to the following reasons. Many silanol (Si-OH) groups are present on the surface of hydrous silicic acid. These silanol groups provide a reinforcing effect, but on the other hand, the self-aggregation force due to hydrogen bonds between particles acts too strongly, which makes dispersion within the rubber difficult. Therefore, it is understood that even if the specific surface area is high, only a part of the high specific surface area comes into contact with the rubber, which conversely reduces the reinforcing effect.

That is, an increase in the specific surface area of hydrous silicic acid as a filler (smaller diameter of primary particles) leads to an increase in silanol groups on the particle surface. As a result, it is presumed that dispersion failure occurs inside the rubber and the reinforcing effect decreases.
From such a viewpoint, the present inventor, with respect to the conventional hydrous silicic acid having a uniform primary particle diameter, those having different primary particle sizes are mixed, and the silicic acid hydrous is adjusted by adjusting the degree of mixing. By adjusting the specific surface area, even with hydrous silicate particles having a high specific surface area, good dispersion in the rubber composition can be obtained, and at the same time, low viscosity and easy processability can be achieved. I thought I could do it. The inventors of the present invention have conducted extensive research from such a viewpoint, and have found that a rubber composition containing the hydrous silicic acid in the above-specified range has an excellent reinforcing effect, and completed the present invention.

The hydrous silicic acid used in the present invention is N _2-
SA is in the range of 200 to 300 m ² / g. N ₂ -SA
Is less than 200 m ² / g, the reinforcing property is poor, and conversely 300 m
If it exceeds ² / g, the self-cohesive force is too strong, which causes poor dispersion and leads to a decrease in reinforcing property and an increase in viscosity. N
The range of _2- SA is preferably 230 to 280 m ² / g.
Is. The hydrous silicic acid used in the present invention further comprises H
g-SA is 150 m ² / g or less. Hg-SA is a value calculated from the size of pores formed by agglomerated particles of hydrous silicic acid and the agglomerated particles. The calculation method is 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), and r = average pore radius (μm). The hydrated silicic acid having a small Hg-SA value has a small pore volume, is mixed with primary particles of large and small hydrated silicic acid, and is in a state close to close packing, or an aggregate of hydrated silicic acid ( It is presumed that aggregated particles) are mixed in size and are close to close packing. Hg-SA
Of more than 150 m ² / g behaves similar to a rubber composition containing a highly active hydrous silicic acid, and since the reinforcing property is high but the rubber viscosity is also high at the same time, it is not preferable. Is 150 m ² / g or less. Hg-S
A is preferably in the range of 50 to 150 m ² / g, more preferably in the range of 100-150 ² / g.

Further, the hydrous silicic acid used in the present invention is
The DBA / N ₂ -SA ratio is 1.4 or less. DBA (m
・ Mol / kg-SiO ₂ ) (R. Meyer: Kautschuk und Gummi 7 (8), 1
80-182WT (1954)) indicates the amount of acidic points and is said to be proportional to the external surface area of hydrous silicic acid. If the external surface area becomes too large, problems such as poor dispersion and reduced workability will occur as described above. Generally N ₂ −
Those with a large SA tend to have a high DBA, and are often said to have high activity. The present invention uses this DBA and N ₂
-The balance relationship with -SA is adjusted to improve the reinforcing performance of the rubber composition. That is, in the present invention, DBA / N ₂ −
By setting the ratio of SA to 1.4 or less, improvement in workability and improvement in reinforcement are both achieved. The DBA / N ₂ -SA ratio is preferably in the range 0.8 to 1.4.

Further, the hydrous silicic acid used in the present invention is
The ratio of Hg-SA / N ₂ -SA is 0.6 or less. Hg
The ratio of -SA / N ₂ over the SA, preferably 0.2 to 0.6
Is more preferable, and more preferably 0.3 to 0.5.
The ratio of Hg-SA / N ₂ -SA is an index of the mixed state of different primary particles of hydrous silicic acid, and by setting it to be 0.6 or less, the increase of the viscosity of the rubber composition is suppressed and at the same time, it is added. Sulfur properties can be improved. However, if Hg-SA is too small or the ratio of Hg-SA / N ₂ -SA is too small, the viscosity of the rubber composition is lowered and the workability is improved, but the reinforcing property is deteriorated, so be careful. It costs.

From the viewpoints 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 reinforcing effect and abrasion resistance effect are small, and when it exceeds 90 parts by weight, the viscosity of the rubber composition becomes high and the processability is impaired, which 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 compounding amount of the silane coupling agent is 1 to 15% by weight, preferably 1 to 12% by weight based on the weight of hydrous silicic acid. If the amount of the silane coupling agent is less than 1% by weight, the coupling effect is small, and if it exceeds 15% by weight,
Reinforcing property and wear 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-mentioned 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 suitably applied to rubber products such as tires, conveyor belts and hoses, and the finished rubber products such as tires, conveyor belts and hoses can be processed and reinforced. It has excellent wear resistance and the like. Further, since the pneumatic tire of the present invention is one in which the rubber composition is used in the tire tread portion, it is possible to obtain a pneumatic tire excellent in workability, reinforcement property and high wear resistance of the tire tread portion. Becomes

[0024]

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 E 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 E are hydrous silicic acids having physical properties within the scope of the present invention. Sample D ~
Regarding E, it was obtained by the following Production Examples 1 and 2.

The physical properties of the hydrous silicic acids of Samples A to E were measured by the following methods. (1) Adsorption amount of dibutylamine (DBA) A certain amount of excess n was added to hydrous silicic acid in a petroleum benzine solution.
-Add and adsorb dibutylamine, and back titrate the remaining amine with acetic acid solution of perchloric acid to subtract the amount of adsorbed amine to determine the amount of silanol groups. Unit: m · mol
/ Kg (2) BET method specific surface area (N ₂ -SA) Measured by a one-point method with AMS-8000 (manufactured by Okura Riken Co., Ltd.). Unit: m ² / g

(3) 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 = pore volume (cc / g), r = average radius (μm))

(Production Example 1, Sample D) 2 equipped with a stirrer
In a stainless steel container with a 00 liter jacket, water 91
Liter and sodium silicate aqueous solution [SiO ₂ 150
g / l, SiO ₂ / Na ₂ O weight ratio 3.3] 0.7 liter were charged and heated to a temperature of 85 ° C. P at this time
H was 9.4 and SiO ₂ concentration was 1.2 g / l.
A similar aqueous solution of sodium silicate and sulfuric acid (18.4 mol / l) were simultaneously added to the above aqueous solution while maintaining the pH at 9.5 ± 0.5, and the solution was stopped at 55 minutes. S at this time
The iO ₂ concentration was 38 g / l. Subsequently, an aqueous solution of sodium silicate similar to the above containing 3% of sodium silicate in an amount of 155% of the sodium silicate consumed in this reaction was added.
Added in 5 minutes. The SiO ₂ concentration at this time is 68 g / l
Met. Subsequently, the same addition of sulfuric acid as described above was performed for 20 minutes, the acidification at pH 3 was completed, and a precipitate was obtained. The reaction temperature of all steps was kept at 85 ± 1 ° C. After that, the obtained reaction product was filtered with a filter press and washed with water, and the obtained wet cake was dried with a box dryer to obtain hydrous silicic acid by a wet precipitation method.

(Production Example 2, Sample E) Using the same container and the same raw material as in Production Example 1, 102 liters of water and 0.6 liter of an aqueous sodium silicate solution were charged and heated to 80 ° C. At this time, the pH was 9.2 and the SiO ₂ concentration was 0.9.
It was g / l. Thereafter, simultaneous addition was carried out for 95 minutes in the same manner as in Production Example 1. The silica concentration at this time was 34 g / l. Subsequently, an aqueous sodium silicate solution similar to the above containing sodium silicate in an amount of 140% of the sodium silicate consumed in the simultaneous addition was added in 30 minutes. At this time, the SiO ₂ concentration was 61 g / l. Then, acid addition was carried out with sulfuric acid for 30 minutes, and the pH was adjusted to 3 to obtain hydrous silicic acid in the same manner as in Example 1. The reaction temperature is 80 in all steps.
The temperature was kept at ± 1 ° C.

[0029]

[Table 1]

(Examples 1 to 6 and Comparative Examples 1 to 8) Using the hydrous silicic acid (Samples A to E) having the physical properties shown in Table 1 above, the compounding compositions shown in Tables 2 and 3 below were used. A rubber composition was prepared. Examples 1 to 6 and Comparative Examples 1 to 1
For the rubber composition of No. 8, Mooney viscosity (workability), reinforcing property and abrasion resistance were evaluated by the following measuring methods. The results are shown in Tables 2 and 3 below and FIG. In addition, the compounding unit of the compounding composition of Table 2 and Table 3 is a weight part.

(1) Mooney viscosity Preheating at 125 ° C. according to JIS K6300 1
Start the test after 5 minutes and compare the value after 4 minutes with the control. The smaller the better. (2) Reinforcing property According to JIS K6251, a tensile strength at the time of performing a tensile test at 25 ° C using a dumbbell-shaped No. 3 sample is compared with that of a control. Larger is better. (3) Wear resistance 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.

[0032]

[Table 2]

[0033]

[Table 3]

(Discussion of Tables 2 to 3 and FIG. 1) In Examples 1 to 4 and Comparative Examples 1 to 6, Comparative Example 1 was used as a control, Example 5 was used as Comparative Example 7, and Example 6 was used as a comparison. Example 8 was used as a control. Examples 1 to 6 using hydrous silicic acid having physical properties falling within the scope of the present invention (Samples D to E) are comparisons using hydrous silicic acid having physical properties falling outside the scope of the present invention (Samples A to C). It was found that the Mooney viscosity (workability), the reinforcing property and the wear resistance can be significantly improved as compared with Examples 1 to 8. This is
It is also clear from.

[0035]

EFFECTS OF THE INVENTION According to the present invention, there is provided a rubber composition capable of greatly improving workability, reinforcing property and abrasion resistance. Further, since the pneumatic tire of the present invention uses the rubber composition in the tire tread portion,
A pneumatic tire having excellent workability, reinforcing property and high wear resistance of the tire tread portion can be obtained.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between Mooney viscosity (index) and abrasion resistance (index) for Examples 1 to 6 and Comparative Examples 1 to 8.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C08L 9/00 C08K 5/54

Claims (6)

(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
Is in the range of 200 to 300 m ² / g, Hg method specific surface area (Hg-SA) is 150 m ² / g or less, and dibutylamine adsorption amount (DBA) / BET method specific surface area (N ₂ −
SA) is 1.4 or less, and the Hg method specific surface area (Hg-SA) / BET method specific surface area (N ₂ -SA) ratio is 0.6 or less. A rubber composition containing 90 parts by weight. 2. The Hg method specific surface area (H
g-SA) is 50 to 150 m ² / g, and the amount of adsorbed dibutylamine (DBA) / BET specific surface area (N ₂ -S)
Claim ratio of A) is 0.8 to 1.4, and the ratio of Hg method specific surface area (Hg-SA) / BET method specific surface area (N ₂ -SA) is 0.2 to 0.6 The rubber composition according to 1. 3. The rubber composition according to claim 1 or 2, which contains a silane coupling agent in an amount of 1 to 15% by weight based on the wet process silicic acid. 4. The rubber composition according to claim 3, which comprises at least one of the following formulas (I) to (III) as a silane coupling agent. [Chemical 1] [Chemical 2] [Chemical 3] 5. A reinforcing filler containing 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. 6. A pneumatic tire using the rubber composition according to claim 1 for a tire tread portion.