JP6984124B2 - Manufacturing method of rubber composition for tires and rubber composition for tires - Google Patents

Description

The present invention relates to a method for producing a rubber composition for a tire and a rubber composition for a tire obtained by the production method.

In recent years, in response to increasing environmental awareness, it has been required to reduce the rolling resistance of tires in order to improve the fuel efficiency of automobiles, and a method of using silica as a filler has been proposed.

However, the silica compound has a high Mooney viscosity after kneading, and the processability is lowered. In addition, silica is a hydrophilic material whose surface is covered with silanol groups and is difficult to mix with diene rubber, but when used in combination with a silane coupling agent, it is bonded by polycondensation with silica to make the silica surface hydrophobic. It can be dispersed in diene-based rubber (see Patent Document 1 and the like).

More recently, with the enforcement of the tire labeling system, not only fuel efficiency but also fracture characteristics that contradict this are required to be compatible, and good silica dispersibility, workability, fuel efficiency performance, fracture characteristics, etc. have been improved. It is desired.

Japanese Unexamined Patent Publication No. 2002-363346

The present invention solves the above problems and provides a method for producing a rubber composition for a tire, which is excellent in silica dispersibility, fuel efficiency, fracture characteristics and workability, and a rubber composition for a tire obtained by the production method. The purpose is.

In the present invention, a rubber component, silica and a silane coupling agent are added and kneaded with a Banbury mixer to obtain a first kneaded product, and the first kneaded product is further kneaded with a Banbury mixer to obtain a second kneaded product. The second step of obtaining the unvulcanized rubber composition and the third step of adding and kneading the second kneaded product and the vulcanizing chemical to obtain the unvulcanized rubber composition are included, and after the first step and / or after the second step, The present invention relates to a method for producing a rubber composition for a tire, which adjusts the alcohol concentration in the kneading chamber of a Banbury mixer to 20% LEL or less.

In the above-mentioned production method, it is preferable to adjust the alcohol concentration in the kneading chamber of the Banbury mixer to 20% LEL or less after the second step.
In the above-mentioned production method, it is preferable to measure the alcohol concentration in real time in the first step and / or the second step.

The present invention also relates to a rubber composition for a tire obtained by the above-mentioned production method.
The rubber composition preferably has a silica content of 40 parts by mass or more with respect to 100 parts by mass of the rubber component, and the silane coupling agent is bis (3-triethoxysilylpropyl) disulfide.

According to the present invention, it is a method for producing a rubber composition for a tire that adjusts the alcohol concentration in the kneading chamber of the Banbury mixer to 20% LEL or less after the first step and / or after the second step, and thus has silica dispersibility. It is possible to provide a rubber composition for a tire, which is excellent in fuel efficiency, breakage characteristics and processability.

It is a figure which shows the reaction of silica and a silane coupling agent (bis (3-triethoxysilylpropyl) disulfide). It is a schematic cross-sectional view which shows an example of a Banbury mixer, and shows the state which measures the alcohol concentration in a kneading chamber (the kneading chamber is a substantially closed state). It is a schematic cross-sectional view which shows an example of a Banbury mixer, and shows the state which measures the alcohol concentration in a kneading chamber (the kneading chamber is an open state).

[Manufacturing method of rubber composition for tires]
In the method for producing a rubber composition for a tire of the present invention, a first step of adding a rubber component, silica and a silane coupling agent and kneading them with a Banbury mixer to obtain a first kneaded product, and further Banbury the first kneaded product. It includes a second step of kneading with a mixer to obtain a second kneaded product and a third step of adding a second kneaded product and a vulcanizing chemical and kneading to obtain an unvulcanized rubber composition, after the first step. And / or after the second step, the alcohol concentration in the kneading chamber of the Banbury mixer is adjusted to 20% LEL or less.

As shown in the schematic diagram of FIG. 1, the silane coupling agent is hydrolyzed using the adsorbed water on the silica surface, and finally binds to silica by a dehydration condensation reaction with a silanol group on the silica surface. .. Alcohol such as ethanol and water are generated in this process, but these reactions are equilibrium reactions, and the presence of alcohol and water in the kneaded product is a factor that inhibits the reaction between silica and the silane coupling agent. ..

In the present invention, the alcohol (ethanol, etc.) in the kneading chamber of the Banbury mixer after the first step and the second step is kneaded with silica until the concentration of alcohol (ethanol, etc.) becomes 1/5 (20% LEL) or less of the lower explosive limit. The reaction of the silane coupling agent proceeds sufficiently, and a kneaded product having stable rubber physical properties is produced. As a result, the surface of the silica becomes hydrophobic, and the hydrophobicized silica can be highly dispersed in the rubber. Therefore, a rubber composition for a tire can be obtained in which good silica dispersibility is obtained and fuel efficiency, fracture characteristics and workability are improved in a well-balanced manner.

As the kneading progresses, the amount of generated alcohol decreases, the silica dispersity is made constant at a high level, and the rubber physical characteristics are also made constant. Therefore, the alcohol concentration can be used as an index for completing the coupling reaction between silica and the silane coupling agent. Since it is possible to measure the alcohol concentration in real time, it can also be used as a process control index at the production site.

Hereinafter, details of each step will be described.

(First step)
The first step is a step of adding a rubber component, silica and a silane coupling agent and kneading them with a Banbury mixer to obtain a first kneaded product.

2 and 3 are schematic cross-sectional views showing an example of a Banbury mixer used in the first step. The Banbury mixer 1 shown in FIGS. 2 and 3 includes a kneading chamber (mixing chamber) 10 and a ram (floating weight) 11 configured to substantially seal the kneading chamber 10.

A tubular hopper 12 is connected to the kneading chamber 10, and materials are charged from the charging port 13 provided on the side surface of the hopper 12. The charged material is kneaded by rotating a pair of rotors 14a and 14b provided in the kneading chamber 10 in opposite directions, and then discharged from a drop door 15 provided in the lower part of the kneading chamber 10. .. Further, the Banbury mixer 1 is provided with an alcohol sensor 16 capable of measuring the concentration of alcohol such as ethanol in the kneading chamber 10.

The ram 11 is configured to be movable up and down in the hopper 12 by an air cylinder or the like, and the kneading chamber 10 can be substantially sealed or opened (substantially unsealed) by lowering or ascending the ram 11. The kneading is usually carried out in a state where the ram 11 is lowered and the kneading chamber 10 is substantially sealed.

FIG. 2 shows a state in which the ram 11 is lowered and the kneading chamber 10 is substantially sealed. From this state, as shown in FIG. 3, the kneading chamber 10 can be opened by raising the ram 11 and communicating the inside of the kneading chamber 10 with the outside air.

In the first step, after the first step, it is preferable to adjust the alcohol concentration in the kneading chamber of the Banbury mixer to 20% LEL or less (kneading until the alcohol concentration in the kneading chamber of the Banbury mixer becomes 20% LEL or less). Is preferable). 15% LEL or less is more preferable, and 10% LEL or less is further preferable. The lower limit is not particularly limited. When two or more kinds of alcohols such as ethanol and methanol are generated, it is preferable to adjust the concentration of each alcohol kind within the above range.

Such a first step can be carried out, for example, by measuring the alcohol concentration in the kneading chamber 10 after kneading in the kneading of the first step and confirming that the alcohol concentration is 20% LEL or less. .. It can also be carried out by measuring the alcohol concentration in the kneading chamber 10 in real time during kneading in the first step and kneading until the alcohol concentration becomes 20% LEL or less.

FIGS. 2 and 3 show a method in which the alcohol sensor 16 is provided as a method for measuring the alcohol concentration, but other methods capable of measuring the alcohol concentration can also be used.

In the first step, the discharge temperature of the first kneaded product is preferably 170 ° C. or lower, more preferably 165 ° C. or lower, still more preferably 160 ° C. or lower. When the temperature is 170 ° C. or lower, good workability tends to be ensured. The discharge temperature is preferably 140 ° C. or higher, more preferably 145 ° C. or higher, and even more preferably 150 ° C. or higher. When the temperature is 140 ° C. or higher, the reaction of the silane coupling agent tends to be sufficiently promoted.

In the first step, the kneading time is preferably 3 to 10 minutes.

The rubber component, silica, and silane coupling agent added in the first step may be the total amount or a part thereof, but the total amount is preferable.
The other components are not particularly limited as long as they are components other than vulcanization chemicals, but for example, carbon black; softeners such as oil; antiaging agents; waxes; vulcanization aids such as stearic acid and zinc oxide. Can be mentioned.

It is preferable to use a diene-based rubber as the rubber component to be added in the first step. Natural rubber (NR) and diene synthetic rubber can be used as the diene rubber, and examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and acrylonitrile butadiene rubber. (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like can be mentioned. These may be used alone or in combination of two or more. Among them, NR, BR and SBR are preferable, and BR and SBR are more preferable because they show fuel efficiency, fracture characteristics and workability in a well-balanced manner.

The silica to be added in the first step is not particularly limited, and examples thereof include silica prepared by a dry method (anhydrous silica) and silica prepared by a wet method (hydrous silica), and there are many silanol groups on the surface. Silica prepared by a wet method is preferable because it has many reaction points with a silane coupling agent. Only one type of silica may be used, or two or more types of silica may be used in combination. Examples of commercially available silica products include Ultrasil VN3 manufactured by Evonik Industries, Inc.

In the first step, the amount of silica blended with respect to 100 parts by mass of the rubber component to be kneaded in the step is preferably 21 to 74 parts by mass. By adjusting within the above range, the alcohol concentration is adjusted within the measurement range of the alcohol sensor, and there is a tendency that appropriate data can be obtained. Moreover, since the alcohol concentration can be measured, it can be used as a process control index.

Nitrogen adsorption specific surface area _(N 2 SA) of silica is preferably ^90m 2 / g or more, more preferably ^{95 m} 2 / g or more, further preferably 100 m ² / g or more. Sufficient fracture characteristics tend to be obtained by setting the content to 90 m ^{2 / g or more.} The N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 240 m ² / g or less. By setting the content to 300 m ² / g or less, good dispersibility tends to be obtained.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

As the silane coupling agent to be added in the first step, bis (3-triethoxy) is used because it is easy to control the temperature during the reaction treatment in the first step and it is excellent in the effect of improving the reinforcing property of the rubber composition. A sulfide-based silane coupling agent such as silylpropyl) disulfide, bis (3-triethoxysilylpropyl) tetrasulfide, and 3-trimethoxysilylpropylbenzothiazolyltetrasulfide is preferable, and bis (3-triethoxysilylpropyl) disulfide is preferable. Is more preferable. These silane coupling agents may be used alone or in combination of two or more.

(Second step)
The second step is a step of further kneading the first kneaded product obtained in the first step with a Banbury mixer to obtain a second kneaded product. By providing the second step, silica dispersion is further promoted. In the second step, only the first kneaded product may be further kneaded, or other components may be added and kneaded together with the first kneaded product.

The kneading in the second step can be carried out under the same conditions and methods as in the first step. In the present invention, it is particularly preferable to adjust the alcohol concentration in the kneading chamber of the Banbury mixer to 20% LEL or less after the second step (kneading until the alcohol concentration in the kneading chamber of the Banbury mixer becomes 20% LEL or less). Is preferable). As a result, the reaction between silica and the silane coupling agent proceeds sufficiently, and as a result, good silica dispersibility, rubber physical characteristics and the like can be obtained. 15% LEL or less is more preferable, and 10% LEL or less is further preferable. The lower limit is not particularly limited. When two or more kinds of alcohols such as ethanol and methanol are generated, it is preferable to adjust the concentration of each alcohol kind within the above range.

(Third step)
The third step is a step of adding the second kneaded product and the vulcanizing chemical obtained in the second step and kneading them to obtain an unvulcanized rubber composition.

In the third step, in order to prevent scorch from being generated due to an increase in the rubber temperature during kneading, kneading is terminated when the rubber temperature reaches a predetermined temperature (preferably 60 to 120 ° C.), and vulcanization is not performed. It is preferable to discharge the rubber composition from the kneader. The kneading time of the third step is not particularly limited, but is preferably about 1 to 15 minutes.

The kneader used in the third step may be a closed type Banbury mixer or an open roll as in the first step.

Examples of the vulcanization chemical to be added in the third step include a vulcanizing agent and a vulcanization accelerator, and it is preferable to use a vulcanizing agent and a vulcanization accelerator in combination.

As the vulcanizing agent, an organic peroxide, a sulfur-based vulcanizing agent, or the like can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, and the like. 5-Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexin- 3, 1,3-bis (t-butylperoxypropyl) benzene and the like can be mentioned. Examples of the sulfur-based vulcanizing agent include sulfur and morpholine disulfide. These may be used alone or in combination of two or more. Among them, a sulfur-based vulcanizing agent is preferable, and sulfur is more preferable, because the effect of the present invention can be obtained satisfactorily.

Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerator. Can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based and guanidine-based are preferable, and sulfenamide-based and guanidine-based are more preferable, because the effects of the present invention can be obtained satisfactorily.

(Other processes)
The unvulcanized rubber composition obtained in the third step is extruded according to the shape of the tire member (cap tread, etc.), molded by a normal method on a tire molding machine, and together with other tire members. Tires can be manufactured by laminating, forming unvulcanized tires, and then heating and pressurizing in a vulcanizer.

(Rubber composition for tires)
In the rubber composition obtained by the production method of the present invention, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more because low fuel consumption, breakage characteristics and processability can be obtained in a well-balanced manner. , More preferably 15% by mass or more, preferably 70% by mass or less, and more preferably 50% by mass or less.

In the rubber composition obtained by the production method of the present invention, the content of SBR in 100% by mass of the rubber component is preferably 30% by mass or more because low fuel consumption, fracture characteristics and processability can be obtained in a well-balanced manner. , More preferably 50% by mass or more, preferably 95% by mass or less, and more preferably 85% by mass or less.

In the rubber composition obtained by the production method of the present invention, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. Is. By increasing the amount to 5 parts by mass or more, the reinforcing property required for the tire tends to be obtained. The content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 100 parts by mass or less. When the content is 200 parts by mass or less, good workability tends to be obtained.

In the rubber composition obtained by the production method of the present invention, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. By using 1 part by mass or more, good workability tends to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. By setting the amount to 20 parts by mass or less, there is a tendency that an effect commensurate with the cost can be obtained.

In the rubber composition obtained by the production method of the present invention, the content of the vulcanizing agent is preferably 100 parts by mass of the rubber component, because low fuel consumption, fracture characteristics and processability can be obtained in a well-balanced manner. It is 0.1 part by mass or more, more preferably 0.5 part by mass or more, preferably 8 parts by mass or less, and more preferably 5 parts by mass or less.

In the rubber composition obtained by the production method of the present invention, the content of the vulcanization accelerator is preferably 100 parts by mass of the rubber component because low fuel consumption, fracture characteristics and processability can be obtained in a well-balanced manner. Is 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, preferably 10 parts by mass or less, and more preferably 8 parts by mass or less.

The present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
SBR: NS616 manufactured by Zeon Corporation
BR: BR1220 manufactured by Nippon Zeon Corporation (cis content: 96% by mass)
Carbon Black: Seest N220 manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 manufactured by Evonik (N ₂ SA: 175m ² / g)
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries, Inc.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunknock N manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: Stearic acid "Camellia" manufactured by NOF CORPORATION
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ (N-cyclohexyl-2) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. − Benzothiazolylsulfenamide)
Vulcanization accelerator D: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

[Examples / Comparative Examples]
(First step)
In accordance with the formulation shown in Tables 1 and 2, materials other than sulfur and the vulcanization accelerator are added to the Banbury mixer and kneaded until the rubber temperature (temperature of the kneaded product) reaches the discharge temperature shown in Tables 1 and 2. The first kneaded product was obtained (kneading time: Tables 1 and 2).
(Second step)
The first kneaded product was put into a Banbury mixer and further kneaded to obtain a second kneaded product (discharge temperature, kneading time: Tables 1 and 2).
(Third step)
The obtained second kneaded product, sulfur and a vulcanization accelerator were put into an open roll and kneaded to obtain an unvulcanized rubber composition (kneading conditions: 80 ° C., kneading time: 5 minutes).
(Vulcanization process)
The obtained unvulcanized rubber composition was vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition.

The unvulcanized rubber composition and the vulcanized rubber composition obtained above were evaluated as follows. The results are shown in Tables 1 and 2. Table 1 uses Comparative Example 1 and Table 2 uses Comparative Example 3 as a reference comparative example.

(Ethanol sensor)
The ethanol sensors used are as follows.
Measuring machine: New Cosmos Electric Co., Ltd. XP-3110 (flammable gas detector)
(specification)
Detection principle: Contact combustion type Detection range: 0 to 100% LEL
Instruction accuracy: ± 5% of full scale
Response speed: Within 30 seconds An ethanol sensor was installed in the lower part of the kneading chamber, and the generated ethanol concentration was measured for the first kneaded product after the first step and the second kneaded product after the second step. The ethanol concentration was measured 20 seconds after the kneading of the first kneaded product and the second kneaded product. This is because in the case of measurement immediately after kneading, the measured values are not stable and appropriate data cannot be obtained, and it is necessary to wait 20 seconds for measurement in a state where the atmosphere in the kneading chamber (chamber) is uniform. ..

(Reactivity of silica and silane coupling agent (Pain effect))
Using RPA2000 (manufactured by Alpha Technologies), G * of the unvulcanized rubber composition at 100 ° C. and 0.5% strain and G * at 100 ° C. and 64% strain were measured, and the difference ΔG * was measured. Calculated. The results are expressed exponentially with the reference comparison example as 100. The larger the index, the better the dispersibility of the filler, and the better the reactivity between silica and the silane coupling agent.

(Processability (Moony viscosity))
The Mooney viscosity of the unvulcanized rubber composition was measured at 130 ° C. according to JIS K 6300. The results are expressed exponentially with the reference comparison example as 100. The larger the index, the better the workability.

(Fuel efficiency performance)
Using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., the tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 60 ° C. The results are expressed exponentially with the reference comparison example as 100. The larger the index, the lower the rolling resistance and the better the fuel efficiency.

(destruction strength)
In accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties", a tensile test was carried out using a No. 3 dumbbell with a thickness of 2 mm formed from the above vulcanized rubber composition, and the breaking strength (TB) was obtained. And elongation at break (EB) were measured, respectively. Then, the fracture energy defined by the product of TB and EB is exponentially displayed with the reference comparative example as 100. The larger the index, the better the fracture characteristics (fracture strength).

From Tables 1 and 2, in the examples in which the alcohol concentration in the kneading chamber of the Banbury mixer was adjusted to 20% LEL or less after the first step and / or after the second step, silica was used as compared with the comparative example having a high alcohol concentration. The reactivity of the silane coupling agent was high, and the performance balance of silica dispersibility, fuel efficiency, fracture characteristics and processability was excellent.

1 Banbury mixer 10 Kneading chamber 11 Lamb 12 Hopper 13 Input port 14a, 14b Rotor 15 Drop door 16 Alcohol sensor

Claims (4)

The first step of adding the rubber component, silica and silane coupling agent and kneading with a Banbury mixer to obtain the first kneaded product,
The second step of further kneading the first kneaded product with a Banbury mixer to obtain the second kneaded product,
Including the third step of adding a second kneaded product and a vulcanizing chemical and kneading to obtain an unvulcanized rubber composition.
The silane coupling agent is bis (3-triethoxysilylpropyl) disulfide,
A method for producing a rubber composition for a tire, which adjusts the alcohol concentration in the kneading chamber of a Banbury mixer to 20% LEL or less after the first step and / or after the second step. The method for producing a rubber composition for a tire according to claim 1, wherein after the second step, the alcohol concentration in the kneading chamber of the Banbury mixer is adjusted to 20% LEL or less. The method for producing a rubber composition for a tire according to claim 1 or 2, wherein the alcohol concentration is measured in real time in the first step and / or the second step. Method for producing a rubber composition for a tire according to claim 1, the content of silica to 100 parts by mass of the rubber component is 40 parts by mass or more.

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