JP7453528B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

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

In recent years, fuel-efficient tires have been put on the market in this industry in response to increased environmental awareness and labeling systems. Conventionally, tan δ (60°C) has been used as an index for the rolling resistance of pneumatic tires, and in order to reduce this tan δ (60°C) and achieve both wet performance and wear resistance, high silica content and small particle Techniques such as blending silica with a certain diameter have been used.
Silica has poor affinity for rubber, so it is important to improve its dispersibility. Therefore, as shown in Figure 1, there is a method in which a silane coupling agent is added to the rubber and the silanol groups on the silica surface react with the silane coupling agent during rubber mixing to disperse the silica, but the unreacted silanol groups remains and the desired effect cannot be obtained.

Additionally, as shown in Figure 2, when additives such as fatty acid zinc salts are added, they react with silanol groups and reduce the number of OH groups, but in order to eliminate most of the silanol groups on the silica surface, the amount of zinc must be increased. Since this is necessary, there is a concern that it may have an adverse effect during rubber vulcanization.

Note that Patent Document 1 below discloses calcified seaweed used in Examples of the present invention. However, Patent Document 1 relates to an external skin preparation, and is in a different technical field from the present invention. Moreover, no technical idea is disclosed in which calcified seaweed is blended into a rubber composition to improve the viscoelastic balance without reducing wear resistance.

Japanese Patent Application Publication No. 2016-141646

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

As a result of extensive research, the present inventors have found that the above problems can be solved by blending specific amounts of silica and inorganic filler into diene rubber, and have completed the present invention.

That is, the present invention provides a rubber characterized in that 30 to 200 parts by mass of silica and 0.7 to 2.5 parts by mass of inorganic filler are blended with respect to 100 parts by mass of diene rubber. A composition is provided.
The present invention also provides the rubber composition, wherein the inorganic filler contains 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 calcified seaweed.
The present invention also provides a pneumatic tire using the rubber composition.

The rubber composition of the present invention is characterized in that it contains 30 to 200 parts by mass of silica and 0.7 to 2.5 parts by mass of inorganic filler to 100 parts by mass of diene rubber. Therefore, it is possible to provide a rubber composition with improved viscoelastic balance without reducing abrasion resistance, and a pneumatic tire using the same.
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. It is possible to express the effect of
Further, according to an embodiment in which the inorganic filler contains at least two selected from the group consisting of calcium, magnesium, potassium, iron, and aluminum, unreacted silanol groups on the silica surface are more effectively capped. In addition, when a zinc compound as shown in FIG. 2 is added, zinc and at least two of the elements undergo ion exchange and zinc is released, which participates in crosslinking of the rubber and achieves the above-mentioned effects of the present invention. It is assumed that this will further increase the
Moreover, according to the form in which the inorganic filler is calcified seaweed, the seaweed contains a large amount of at least two selected from the group consisting of calcium, magnesium, potassium, iron, and aluminum, so that the above-mentioned ingredients can be added in small amounts. It becomes possible to more effectively cap unreacted silanol groups on the silica surface.

FIG. 2 is a schematic diagram for explaining unreacted silanol groups on the surface of silica in rubber. FIG. 2 is a schematic diagram for explaining a state in which unreacted silanol groups on the surface of silica in rubber are capped with zinc.

The present invention will be explained in more detail below.

(Diene rubber)
The diene rubber used in the present invention can be any diene rubber that can be blended into the rubber composition, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR). , styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), and the like. These may be used alone or in combination of two or more. Moreover, its molecular weight and microstructure are not particularly limited, and it may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized.

(silica)
Specific examples of the silica used in the present invention include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. may be used, or two or more types 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, more preferably 120 to 200 m ² /g.
The CTAB adsorption specific surface area is the value obtained by measuring the adsorption amount of n-hexadecyltrimethylammonium bromide on the silica surface in accordance with JIS K6217-3:2001 "Part 3: How to determine specific surface area - CTAB adsorption method" It is.

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

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

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

Examples of the coralline algae include Lithothamnium corallioides, Phymatolithon calcareum, and Lithothamnium glaciale. These coralline algae are abundant in cold, calm seas, and the calcareous residue that remains after the coralline algae withers is over 90% by mass inorganic, mainly consisting of calcium carbonate and magnesium carbonate. .

Calcified seaweed can be used even if it has been dredged from the seabed, but since it contains impurities such as sand and shells, some or all of it must be washed with seawater or fresh water, or sieved. It is preferable that the above-mentioned impurities are removed by one method or a combination of two or more methods for removing the above-mentioned impurities, such as manual sorting. Further, it is more preferable that the calcified seaweed be dredged from the seabed, remove impurities, further sterilized by hydrogen peroxide treatment, heat treatment, etc., and then dried. 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, but, for example, a dried product can be obtained by drying the calcified seaweed containing water by sun-drying, hot air drying, or the like. The degree of drying may be as long as it is confirmed that the water content of the calcified seaweed has been sufficiently reduced, for example, until the water content is 10 wt% or less, preferably 5 wt% or less. That's about it.

Methods of powdering include, but are not limited to, methods commonly used by those skilled in the art, such as grinding and powdering the calcified seaweed using a ball mill, hammer mill, roller mill, etc. It is also possible to reverse the order of drying and powdering, and grind the calcified seaweed before drying, and then dry the ground material to produce a powder.

Such calcified seaweed powder may be commercially available, such as AQUAMIN (MARIGOT), Seaweed Calcium IT-1 (Taiyo Kagaku Co., Ltd.), Aqua Mineral (Nippon Biocon Co., Ltd.), etc. Can be mentioned.

The specific surface area of the calcified seaweed powder is preferably 4.0 to 13.0 m ² /g, more preferably 6.0 to 12.0 m ² /g. Having such a specific surface area makes it easier for the powder to further disintegrate and become finer during kneading of the rubber composition, and has the effect of successfully capping unreacted silanol groups on the silica surface. Note that 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, such as Aqua Mineral (Nippon Biocon), the main components are (mass%),
C: 16%
O: 53%
Ca: 28%
Mg: about 3%
It contains at least two selected from the group consisting of calcium, magnesium, potassium, iron and aluminum.

In the inorganic filler used in the present invention, at least two 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 even more preferable that it be included.

(Ratio of rubber composition)
The rubber composition of the present invention is characterized in that it contains 30 to 200 parts by mass of silica and 0.7 to 2.5 parts by mass of inorganic filler to 100 parts by mass of diene rubber. shall be.
If the amount of silica blended is less than 30 parts by mass with respect to 100 parts by mass of diene rubber, the mechanical properties and abrasion resistance of the rubber composition will deteriorate, and if it exceeds 200 parts by mass, processability will deteriorate.
If the amount of the inorganic filler added to the silica is less than 0.7% by mass, the amount added is too small to achieve the effects of the present invention, and on the other hand, if it exceeds 2.5% by mass, the wear resistance will decrease. decreases. In particular, when calcified seaweed is used as an inorganic filler, if the amount exceeds 2.5% by mass based on silica, good dispersion in the rubber cannot be obtained.

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

(Other ingredients)
In addition to the above-mentioned components, the rubber composition of the present invention includes a vulcanization or crosslinking agent; a vulcanization or crosslinking accelerator; zinc oxide; carbon black; various fillers; anti-aging agents; and plasticizers. Various additives that are commonly blended in can be blended, and such additives can be kneaded by a common method to form a composition and used for vulcanization or crosslinking. The blending amounts of these additives can also be set to conventional and general blending amounts as long as they do not contradict the purpose of the present invention.
In addition, when blending a silane coupling agent, it is preferable to mix the diene rubber and the silane coupling agent, then mix and knead the inorganic filler.

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

Furthermore, the rubber composition of the present invention is suitable for manufacturing pneumatic tires according to conventional pneumatic tire manufacturing methods, and is preferably applied to treads, particularly cap treads, of pneumatic tires.

The present invention will be further explained below 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
Preparation of sample In the formulation (parts by mass) shown in Table 1, the components excluding the inorganic filler, vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7 liter closed Banbury mixer, and then the inorganic filler was added thereto. The rubber was added and kneaded, and the rubber was discharged from the mixer and cooled to room temperature. Next, 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 using the test method shown below.

E' (20℃): Storage modulus E'( 20°C). The results were expressed as an index with Comparative Example 1 set as 100. The larger the index, the higher the storage modulus.

tan δ (60°C): Tested at 60°C in accordance with JIS K6394. The results were expressed as an index with Comparative Example 1 set as 100. The smaller the index, the lower the rolling resistance.

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

Abrasion resistance: Using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., measurement was performed under the conditions of a load of 5 kg (49 N), a slip ratio of 25%, a time of 4 minutes, and room temperature to determine the abrasion loss. The results were expressed as an index with Comparative Example 1 set 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 Co., Ltd., styrene content 40% by mass, oil extension amount = 37.5 parts by mass per 100 parts by mass of SBR)
*2: BR (Nipol BR1220 manufactured by Zeon Corporation)
*3: Silica (Rhodia Zeosil 1165MP, CTAB specific surface area = 159 m 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 Seido Kagaku Kogyo Co., Ltd.)
*7: Stearic acid (bead 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 (Kinka-in oil-filled fine powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)
*13: Vulcanization accelerator 1 (Noxeler CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
*14: Vulcanization accelerator 2 (Soccinol DG manufactured by Sumitomo Chemical Co., Ltd.)
*15: Clay (Katalpo Y-K manufactured by Sanyo Clay Co., Ltd.)

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

Claims (3)

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

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