JP2001247718A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having high processability and excellent rolling friction resistance (mileage) and abrasion resistance. SOLUTION: The objective rubber composition contains 100 pts.wt. of a natural rubber and/or a synthetic diene rubber, 5-100 pts.wt. of silica, 2-20 wt.% silane coupling agent based on the silica and 1-20 wt.% sodium salt based on the silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition containing silica and a silane coupling agent, and more particularly to a rubber composition excellent in rolling friction resistance (fuel consumption characteristics) and abrasion resistance without lowering workability. About things.

[0002]

2. Description of the Related Art In recent years, there has been a demand for safety and low fuel consumption of automobiles, and it has been desired to simultaneously improve wet skid characteristics, fuel consumption characteristics and wear resistance of rubber materials for tires. It is well known that there is a trade-off.

Conventionally, as a method of solving such a problem, a method of using silica as a low heat generation filler has been known. Silica tends to agglomerate with each other because the silanol groups that are its surface functional groups are hydrogen-bonded, and the silane coupling agent binds with these silanol groups to prevent agglomeration of the silicas and improve processability. It is thought to improve. On the other hand, in terms of performance, it is considered that the silica and the polymer are chemically bonded to the silane coupling agent, so that the rolling resistance is reduced and the abrasion is improved. However, in order to achieve these objects, it is necessary to knead the silica and the silane coupling agent and chemically react them during processing. It is better to knead it. However, a part of the functional group that reacts with the rubber in the silane coupling agent partially reacts with the rubber due to the temperature applied during processing such as kneading, so that a rubber burning phenomenon called gelation occurs. However, if kneading is performed at such a low temperature that rubber scorching does not occur, there occurs a contradiction that the reaction between the silica and the silane coupling agent becomes insufficient.

[0004]

SUMMARY OF THE INVENTION The present invention provides a rubber composition containing a specific amount of silica and a silane coupling agent with respect to natural rubber and / or diene-based synthetic rubber without reducing the processing characteristics of the rubber composition. Performance (fuel efficiency characteristics)
Another object of the present invention is to provide a rubber composition having improved abrasion resistance.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to improve the above-mentioned problems, and as a result, have efficiently promoted (assisted) the reaction between silica and a silane coupling agent without causing rubber scorch. By using a specific compound as obtained, a method for satisfying the rolling resistance characteristics and the wear resistance without lowering the workability was found, and the present invention was completed.

That is, according to the present invention, 5 to 100 parts by weight of silica, 2 to 20% by weight of silane coupling agent and 2 to 20% by weight of sodium based on 100 parts by weight of natural rubber and / or diene synthetic rubber are used. A rubber composition (claim 1) comprising a salt in an amount of 1 to 20% by weight based on the weight of silica.

Further, the present invention is the rubber composition according to claim 1, wherein the sodium salt is an oxyacid salt or an organic acid salt (claim 2).

Further, the present invention is the rubber composition according to claim 1 or 2, wherein the sodium salt is a hydrous salt having water of crystallization.

The present invention also provides the rubber composition according to any one of claims 1, 2 and 3, wherein the sodium salt is a phosphate.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The rubber composition of the present invention contains a natural rubber (NR) and / or a diene-based synthetic rubber as a rubber component.
Examples of the diene synthetic rubber used in the present invention include styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene. Rubber (NB
R) and the like, and one or more kinds may be contained in the rubber component used in the present invention.

[0012] The rubber composition of the present invention contains silica as a filler. The silica is not particularly limited, and examples thereof include dry silica (silicic anhydride) and wet silica (hydrous silicic acid), with wet silica being preferred. Preferred examples of wet-process silica include Ultrasil VN3 manufactured by Degussa.
(Trade name), Nippon Silica Co., Ltd. Nip Seal VN3A
Q (product name) and the like. As the silica, for example, silica having a nitrogen adsorption specific surface area of 100 to 300 m ² / g can be used. With silica having a small nitrogen adsorption specific surface area, a sufficient elastic modulus cannot be obtained, and abrasion resistance tends to be deteriorated. With silica having a large nitrogen adsorption specific surface area, kneading workability tends to be reduced without improving grip power.

The amount of silica is 5 to 100 parts by weight, preferably 10 to 85 parts by weight, more preferably 20 to 65 parts by weight, based on 100 parts by weight of the rubber component. If the silica content is less than 5 parts by weight, the reinforcing effect is small, and
Exceeding the weight part is not preferable because heat generation increases and workability deteriorates. From the viewpoint of both low heat generation and workability, the amount of silica is preferably 20 to 65 parts by weight.

The rubber composition of the present invention contains a silane coupling agent in order to strengthen the bond between the filler and the rubber component and to improve abrasion resistance. As a silane coupling agent,
Any silane coupling agent conventionally used in combination with the silica filler can be used.

Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, and bis (3-trimethoxysilylpropyl) tetrasulfide. , Bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane,
2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloropropyltrimethoxysilane Chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N,
N-dimethylthiocarbamoyl tetrasulfide, 3-
Triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzo Thiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-
Trimethoxysilylpropyl methacrylate monosulfide; and bis (3-triethoxysilylpropyl)
Tetrasulfide is preferred.

The amount of the silane coupling agent is 2 to 20% by weight based on the weight of the silica. If the amount of the silane coupling agent is less than 2% by weight, the coupling effect is small, and if it exceeds 20% by weight, the coupling effect is not obtained although the cost is increased. The amount of the silane coupling agent is preferably 4 to 15% by weight from the viewpoint of both the coupling effect and the dispersion effect.

[0017] The rubber composition of the present invention contains a sodium salt. The sodium salt that can be used in the present invention is, for example, an oxyacid salt or an organic acid salt, preferably a phosphate,
Alternatively, a hydrate salt having water of crystallization, more preferably a hydrate salt having water of crystallization of an oxyacid salt or an organic acid salt, still more preferably a phosphate salt having water of crystallization.

Specific examples of the sodium salt include disodium hydrogen phosphate, sodium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphite, disodium dihydrogen diphosphate, sodium phosphinate, carbonate Sodium, sodium bicarbonate, sodium sulfate, sodium sulfite, sodium disulfate, sodium disulfite,
Examples include sodium acetate, trisodium citrate, sodium oxalate, disodium succinate and the like. Examples of the hydrated salt include disodium hydrogen phosphate heptahydrate, disodium hydrogen phosphate dodecahydrate, sodium dihydrogen phosphate dodecahydrate, trisodium phosphate dodecahydrate, Disodium hydrogen phosphite pentahydrate, sodium carbonate decahydrate, sodium sulfate decahydrate, sodium sulfite hemihydrate, sodium acetate trihydrate, trisodium citrate dihydrate Hydrate, disodium succinate hexahydrate and the like.

The amount of the sodium salt is from 1 to 20% by weight, preferably from 2 to 15% by weight, based on the weight of the silica. If the amount of the sodium salt is less than 1% by weight, the reaction promoting effect between silica and the silane coupling agent is small,
If it exceeds 0% by weight, the reinforcing property is deteriorated, which is not preferable. The amount of the sodium salt is preferably 2 to 15% by weight from the viewpoint of the effect of promoting the coupling reaction.

The rubber composition of the present invention can contain carbon black as a filler in addition to the above silica. Examples of the carbon black include HAF, I
Examples include SAF and SAF, but are not particularly limited. The compounding amount of carbon black is preferably 80 parts by weight or less based on 100 parts by weight of the rubber component. If the amount of carbon black exceeds 80 parts by weight, the heat buildup tends to increase. The amount of the carbon black is 25 to 65 from the viewpoint of reinforcing properties and low heat generation.
Parts by weight are preferred.

The rubber composition of the present invention may contain an inorganic filler other than silica and carbon black. Examples of the inorganic filler other than silica and carbon black include clay, aluminum hydroxide, calcium carbonate, and alumina.

The rubber composition of the present invention comprises, in addition to the above rubber component, filler (inorganic filler such as silica and carbon black), a silane coupling agent and a sodium salt,
If necessary, compounding agents used in the ordinary rubber industry, such as a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator, can be appropriately contained.

[0023] The rubber composition of the present invention comprises a tire, a hose,
It can be used as a rubber composition requiring mechanical properties and abrasion resistance of belts and other various industrial products.

[0024]

EXAMPLES The present invention will be described below in detail with reference to examples, but this does not limit the purpose of the present invention.

Examples 1 to 6 and Comparative Example 1 100 parts by weight of a diene-based synthetic rubber, 55 parts by weight of silica, 4.4 parts by weight of a silane coupling agent (8% by weight based on the weight of silica), 2 parts by weight of a sodium salt Or 4 parts by weight (3.64% by weight or 7.27% by weight based on the weight of silica), 2 parts by weight of stearic acid, 3 parts by weight of zinc oxide, 1 part by weight of an antioxidant, 1.5 parts by weight of sulfur, TBBS (Vulcanization accelerator) 1 part by weight and DPG (vulcanization accelerator) 0.5 part by weight were kneaded and blended to obtain each rubber composition.

Each of the obtained rubber compositions was press-vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized product. Each of the obtained vulcanizates was tested for the following properties. Table 1 shows the type and amount of sodium salt compounded and the test results of each characteristic for each rubber composition. Comparative Example 1 was a case where no sodium salt was added.

In Table 1, sodium salt (1) is disodium hydrogen phosphate dodecahydrate, sodium salt (2) is trisodium phosphate dodecahydrate, and sodium salt (3) is dihydrogen phosphate. Sodium dihydrate, sodium salt (4)
Represents sodium sulfate decahydrate, and sodium salt (5) represents sodium acetate trihydrate.

Description of Various Chemicals The following commercial products were used as various chemicals. Diene-based synthetic rubber: SBR manufactured by JSR Corporation
1502 (styrene-butadiene copolymer) Silica: Ultrasil VN3 manufactured by Degussa Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide manufactured by Degussa) Anti-aging agent: manufactured by Ouchi Shinko Chemical Co., Ltd. No crack 6C
(N- (1,3-dimethylbutyl) -N′-phenyl-
(p-phenylenediamine) Vulcanization accelerator (TBBS): Noxeller NS (Nt-butyl-2-benzothiazyl sulfenamide) manufactured by Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator (DPG): Ouchi Emerging Noxeller D (N, N'-diphenylguanidine) manufactured by Chemical Co., Ltd.

Description of Test Method (Mooney Viscosity) According to the Mooney viscosity measurement method specified in JIS K6300, the Mooney viscosity (ML) of each vulcanizate was measured at a temperature of 130 ° C. for 1 minute and a measurement of 4 minutes.
_{1 + 4} ) was measured. The lower the Mooney viscosity, the better the processability.

(T90) Evaluation was made using a curastometer. That is, the time required to reach 90% of the difference between the maximum value and the minimum value of the torsion torque measured by the curast meter + the minimum value was defined as T90. The measurement temperature was measured at 170 ° C. The shorter the value of T90, the faster the vulcanization rate.

(Tensile Stress) The tensile stress (300% modulus) at 300% elongation of each vulcanizate was measured according to JIS K6301. The higher the value, the better the tensile stress.

(Abrasion Index) The volume loss of each vulcanizate was measured using a Lambourn abrasion tester at a temperature of 20 ° C., a slip ratio of 20% and a test time of 5 minutes. Comparative Example 1
Was set to 100, and the wear index of each example was calculated by the following formula. The higher the wear index, the better the wear resistance. Wear index of each example = volume loss of comparative example 1 例 volume loss of each example × 100

(Rolling Resistance Index) Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho), a temperature of 70 ° C.
The tan δ of each vulcanizate was measured under the conditions of an initial strain of 10% and a dynamic strain of 2%. The rolling resistance index of Comparative Example 1 was 10
The rolling resistance index of each example was calculated by the following formula. The higher the index, the better the rolling resistance characteristics. Rolling resistance index of each example = tan δ of comparative example 1 tan δ of each example × 100

(Wet skid index) ASTM E3 using a portable skid tester manufactured by Stanley.
Each sulfide was subjected to a wet skid test according to the method of 03-83. The wet skid index of Comparative Example 1 was set to 100, and the wet skid index of each example was calculated by the following formula. The greater the wet skid index, the better the wet skid performance. Wet skid index of each example = measurement result of each example (numerical value) ÷ measurement result of comparative example 1 (numerical value) × 100

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to provide a rubber composition having high workability, and excellent in rolling friction resistance (fuel consumption characteristics) and abrasion resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/098 C08K 5/098 5/544 5/544 5/548 5/548 C08L 7/00 C08L 7 / 00

Claims (4)

[Claims] 1 to 100 parts by weight of natural rubber and / or a diene-based synthetic rubber, 5 to 100 parts by weight of silica;
The silane coupling agent is 2 to 20% by weight based on the weight of silica, and the sodium salt is 1 to 20% based on the weight of silica.
A rubber composition characterized by containing by weight. 2. The rubber composition according to claim 1, wherein the sodium salt is an oxyacid salt or an organic acid salt. 3. The rubber composition according to claim 1, wherein the sodium salt is a hydrated salt having water of crystallization. 4. The rubber composition according to claim 1, wherein the sodium salt is a phosphate.