JP2021161313A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

To solve problems for example, in a low fuel consumption tire which is on the market because of labeling regime and awareness of environmental issues, therefore, a method of blending high silica or blending silica with small diameter, is used, however, a non-reacted silanol group is left therefore a desired effect cannot be acquired.SOLUTION: There is provided a rubber composition obtained by, to 100 mass parts of a diene rubber, blending 30-200 mass parts of silica, and 0.7-2.5 mass% of an inorganic filler with respect to the silica.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly to a rubber composition having an improved viscoelastic balance without reducing wear resistance and a pneumatic tire using the same. It is a thing.

In recent years, fuel-efficient tires have been put on the market in the industry in response to increasing environmental awareness and labeling system. Conventionally, the rolling resistance of pneumatic tires has been indexed by tan δ (60 ° C). In order to reduce this tan δ (60 ° C) and achieve both wet performance and wear resistance, high silica content and small particles are used. Techniques such as blending silica with a diameter are used.
Silica has a poor affinity for rubber, and it is important to improve its dispersibility. Therefore, as shown in FIG. 1, there is a method of adding a silane coupling agent to rubber and reacting a silanol group on the silica surface with a silane coupling agent to disperse silica during rubber mixing, but an unreacted silanol group. There is a problem that the desired effect cannot be obtained because the residue remains.

Further, as shown in FIG. 2, when an additive such as a fatty acid zinc salt is added, it reacts with the silanol group to reduce the OH group, but the amount of zinc is increased to eliminate most of the silanol groups on the silica surface. Since it is necessary, there is a concern that it will have an adverse effect during rubber vulcanization.

The following Patent Document 1 discloses the calcified seaweed used in the examples of the present invention. However, Patent Document 1 relates to an external preparation for skin, and its technical field is different from that of the present invention. Further, no technical idea is disclosed in which calcified seaweed is blended into a rubber composition to improve the viscoelastic balance without lowering the wear resistance.

Japanese Unexamined Patent Publication No. 2016-141646

An object of the present invention is to provide a rubber composition having an improved viscoelastic balance without lowering wear resistance, and a pneumatic tire using the same.

As a result of diligent research, the present inventors have found that the above problems can be solved by blending silica and an inorganic filler in a specific amount with the diene rubber, and have completed the present invention.

That is, the present invention is characterized in that, with respect to 100 parts by mass of diene rubber, 30 to 200 parts by mass of silica and 0.7 to 2.5% by mass of an inorganic filler are mixed with respect to the silica. It provides a composition.
The present invention also provides the rubber composition, wherein the inorganic filler comprises at least two selected from the group consisting of calcium, magnesium, potassium, iron and aluminum.
The present invention also provides the rubber composition, wherein the inorganic filler is a calcified seaweed.
The present invention also provides a pneumatic tire using the rubber composition.

The rubber composition of the present invention is characterized by blending 30 to 200 parts by mass of silica and 0.7 to 2.5% by mass of an inorganic filler with respect to 100 parts by mass of the diene rubber. Therefore, it is possible to provide a rubber composition having an improved viscoelastic balance and a pneumatic tire using the same without lowering the wear resistance.
In the present invention, the mineral content contained in the inorganic filler can cap the unreacted silanol groups on the silica surface as shown in FIG. 1, thereby improving the dispersibility of the silica in the rubber, which is desired. Can exert the effect of.
Further, according to the form in which the inorganic filler contains at least two kinds selected from the group consisting of calcium, magnesium, potassium, iron and aluminum, the cap of the unreacted silanol group on the silica surface is further performed better. At the same time, when a zinc compound as shown in FIG. 2 is added, zinc is ion-exchanged with at least two kinds of the element to release zinc, which is involved in cross-linking of rubber and has the above-mentioned effect of the present invention. It is presumed that it will further increase.
Further, according to the form in which the inorganic filler is a calcified seaweed, the seaweed contains a large amount of at least two species selected from the group consisting of calcium, magnesium, potassium, iron and aluminum. It is possible to better cap the unreacted silanol groups on the surface of the silica.

It is a schematic diagram for demonstrating the unreacted silanol group of the silica surface in rubber. It is a schematic diagram for demonstrating the state in which the unreacted silanol group of the silica surface in rubber is capped by zinc.

Hereinafter, the present invention will be described in more detail.

(Diene rubber)
As the diene-based rubber used in the present invention, any diene-based rubber that can be blended in the rubber composition can be used, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR). , Styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-dienter polymer (EPDM) and the like. These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and the terminal may be denatured with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.

(silica)
Specific examples of the silica used in the present invention include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, aluminum silicate, and the like, and these are used alone. Or two or more of them may be used in combination.
From the viewpoint of improving wet performance, silica preferably has a CTAB adsorption specific surface area of 100 to 300 m ² / g, and more preferably 120 to ²⁰⁰ m 2 / g.
The CTAB adsorption specific surface area is a value obtained by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed on the silica surface according to JIS K6217-3: 2001 "Part 3: How to obtain the specific surface area-CTAB adsorption method". Is.

(Inorganic filler)
The inorganic filler used in the present invention preferably contains at least two types selected from the group consisting of calcium, magnesium, potassium, iron and aluminum, and examples of the inorganic filler satisfying this condition include clay and the following. Examples include the calcified seaweed described in.

As an example of clay component analysis (SEM-EDX), as the main component (mass%),
C: 15%
O: 56%
Si: 14%
K: 3.6%
Al: 10%
Fe: 1.3%
Containing at least two species selected from the group consisting of calcium, magnesium, potassium, iron and aluminum.

Further, as the calcified seaweed, as disclosed in Patent Document 1, the seaweed is obtained by adsorbing a mineral component in the sea, and is, for example, a calcareous residue of a red algae seaweed, preferably. It is a calcareous residue of corallinoideae seaweed.

Examples of the corallinoideae seaweed include Lythothermnium corallioides, Phymaaturison calcareum, and Lithothamnium glacial. These coral seaweeds are abundant in cold and calm seas, and the calcareous residue remaining after the coral seaweeds die is 90% by mass or more inorganic and mainly consists of calcium carbonate and magnesium carbonate. ..

Calcified seaweed can be used even when dredged from the seabed, but since it contains impurities such as sand and shells, some or all of these may be washed with seawater or fresh water, or sieved. , The method for removing the contaminants such as manual sorting is preferably used alone or in combination of two or more to remove the contaminants. Further, it is more preferable that the calcified seaweed is, for example, dried by removing impurities from the dredged state from the seabed, sterilizing by hydrogen peroxide solution treatment or heat treatment, and the like. From the viewpoint of processability, the calcified seaweed is more preferably crushed and powdered.

The means for drying the calcified seaweed to obtain the powder is not particularly limited, and for example, a dried product can be obtained by drying the calcified seaweed containing water by sun-drying or hot air drying. The degree of drying may be such that it is confirmed that the water content of the calcified seaweed is sufficiently reduced, for example, until the water content is 10 wt% or less, preferably 5 wt% or less. Degree.

Examples of the powdering method include, but are not limited to, a method of crushing and pulverizing calcified seaweed by a ball mill, a hammer mill, a roller mill or the like which are usually used by those skilled in the art. It is also possible to change the order of drying and pulverization, crush the calcified seaweed before drying in advance, and dry the pulverized product into powder.

Such calcified seaweed powder may be commercially available, and examples thereof include AQUAMIN (MARIGOT), seaweed calcium IT-1 (manufactured by Taiyo Kagaku Co., Ltd.), and aquamineral (manufactured by Nippon Biocon Co., Ltd.). Can be mentioned.

The specific surface area of the powder of calcified seaweed is preferably 4.0~13.0m ² / g, more preferably 6.0~12.0m ² / g. Having such a specific surface area has the effect that the powder further disintegrates during kneading of the rubber composition and becomes more likely to become finer, and the unreacted silanol groups on the silica surface can be satisfactorily capped. The particle size of the powder is preferably 0.05 μm to 50 μm.

As an example of component analysis (SEM-EDX) of calcified seaweed, for example, Aqua Mineral (Nippon Biocon), as the main component (mass%),
C: 16%
O: 53%
Ca: 28%
Mg: about 3%
Containing at least two species selected from the group consisting of calcium, magnesium, potassium, iron and aluminum.

In the inorganic filler used in the present invention, at least two kinds selected from the group consisting of calcium, magnesium, potassium, iron and aluminum are preferably contained in an amount of 11 to 45% by mass, preferably 14 to 45% by mass. It is more preferably included.

(Rubber composition blending ratio)
The rubber composition of the present invention is characterized by blending 30 to 200 parts by mass of silica and 0.7 to 2.5% by mass of an inorganic filler with respect to 100 parts by mass of diene rubber. And.
If the blending amount of silica is less than 30 parts by mass with respect to 100 parts by mass of the diene rubber, the mechanical properties and wear resistance of the rubber composition deteriorate, and conversely, if it exceeds 200 parts by mass, the workability deteriorates.
If the blending amount of the inorganic filler is less than 0.7% by mass with respect to silica, the addition amount is too small to achieve the effect of the present invention, and conversely, if it exceeds 2.5% by mass, wear resistance is achieved. Decreases. In particular, when calcified seaweed is used as the inorganic filler, if the blending amount exceeds 2.5% by mass with respect to silica, good dispersion in rubber cannot be obtained.

The blending amount of the silica is preferably 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
The blending amount of the inorganic filler is preferably 0.9 to 2.5% by mass with respect to silica.

(Other ingredients)
In addition to the above-mentioned components, the rubber composition in the present invention includes a rubber composition such as a vulcanization or cross-linking agent; a vulcanization or cross-linking accelerator; zinc oxide; carbon black; various fillers; an antiaging agent; a plasticizer. Various additives generally blended in can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or cross-linking. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.
When blending a silane coupling agent, it is preferable to knead the diene rubber and the silane coupling agent, and then blend and knead the inorganic filler.

In the present invention, under normal kneading conditions, at least two selected from the group consisting of calcium, magnesium, potassium, iron and aluminum contained in the inorganic filler cap the unreacted silanol groups on the silica surface. It becomes possible.

Further, the rubber composition of the present invention is suitable for producing a pneumatic tire according to a conventional method for producing a pneumatic tire, and is preferably applied to a tread of a pneumatic tire, particularly a cap tread.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

Examples 1 to 4 and Comparative Examples 1 to 3
Sample Preparation In the formulation (parts by mass) shown in Table 1, the components excluding the inorganic filler, vulcanization accelerator and sulfur are kneaded in a 1.7 liter closed rubbery mixer for 5 minutes, and then the inorganic filler is added thereto. It was charged and kneaded, and the rubber was discharged to the outside of the mixer and cooled to room temperature. Then, the rubber was put into the same mixer again, a vulcanization accelerator and sulfur were added, and the mixture was further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the test method shown below.

E'(20 ° C): Based on JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, the storage elastic modulus at 20 ° C under the conditions of initial strain of 10%, amplitude of ± 2%, and frequency of 20 Hz E'( 20 ° C.) was determined. The results are shown exponentially with Comparative Example 1 as 100. The larger the index, the higher the storage elastic modulus.

tan δ (60 ° C.): Tested at 60 ° C. according to JIS K6394. The results are shown exponentially with Comparative Example 1 as 100. The smaller the index, the lower the rolling resistance.

The larger the value of E'(20 ° C.) / tan δ (60 ° C.), the better the viscoelastic balance, and it means that both high hardness and low rolling resistance can be achieved at the same time.

Abrasion resistance: Using a Ramborn wear tester manufactured by Iwamoto Seisakusho Co., Ltd., the amount of abrasion was determined by measuring under the conditions of a load of 5 kg (49N), a slip ratio of 25%, a time of 4 minutes, and room temperature. The results are shown exponentially with Comparative Example 1 as 100. The larger the index, the better the wear resistance.

The results are also shown in Table 1.

* 1: SBR (Nipol 1739 manufactured by Nippon Zeon Corporation, styrene amount 40% by mass, oil spread amount = 37.5 parts by mass per 100 parts by mass of SBR)
* 2: BR (Nipol BR1220 manufactured by Zeon Corporation)
* 3: Silica (Zeosil 1165MP manufactured by Rhodia, CTAB specific surface area = 159m ² / g)
* 4: Carbon black (Show Black N339 manufactured by Cabot Japan Co., Ltd.)
* 5: Calcified seaweed (Aqua Mineral T manufactured by Nippon Biocon Co., Ltd., average particle size = 5 μm, specific surface area = 8.1 m ² / g)
* 6: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 7: Stearic acid (beaded stearic acid manufactured by NOF CORPORATION)
* 8: Anti-aging agent (Santoflex 6PPD manufactured by Solutia Europe)
* 9: Wax (paraffin wax manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
* 10: Aroma oil (Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.)
* 11: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis (3-triethoxysilylpropyl) tetrasulfide)
* 12: Sulfur (fine powder sulfur with Jinhua stamp oil manufactured by Tsurumi Chemical Industry Co., Ltd.)
* 13: Vulcanization accelerator 1 (Noxeller CZ-G manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
* 14: Vulcanization accelerator 2 (Soxinol DG manufactured by Sumitomo Chemical Co., Ltd.)
* 15: Clay (Catalupo Y-K manufactured by Sanyo Clay)

From the results in Table 1, the rubber compositions of Examples 1 to 4 contained 30 to 200 parts by mass of silica and 0.7 to 2.5 parts of inorganic filler with respect to 100 parts by mass of diene rubber. Since it is characterized by being blended in mass%, it can be seen that the viscoelastic balance is improved without lowering the wear resistance as compared with Comparative Example 1.
On the other hand, in Comparative Example 2, since the blending amount of the inorganic filler was less than the lower limit specified in the present invention, various properties were not improved.
In Comparative Example 3, since the blending amount of the inorganic filler exceeded the upper limit specified in the present invention, the dispersibility in the rubber was deteriorated, and the tan δ (60 ° C.) and the abrasion resistance were not improved.

Claims (4)

A rubber composition characterized by blending 30 to 200 parts by mass of silica and 0.7 to 2.5% by mass of an inorganic filler with respect to 100 parts by mass of the diene rubber. The rubber composition according to claim 1, wherein the inorganic filler contains at least two kinds selected from the group consisting of calcium, magnesium, potassium, iron and aluminum. The rubber composition according to claim 1 or 2, wherein the inorganic filler is a calcified seaweed. A pneumatic tire using the rubber composition according to any one of claims 1 to 3.

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