JP2018104586A - Production method of rubber composition for tire and production method of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a rubber composition for a tire having low fuel consumption property, fracture property and workability which are improved in a balanced manner.SOLUTION: The production method of a rubber composition for a tire is provided, including a first step of charging a rubber composition, silica and a silane coupling agent and kneading them to obtain a first kneaded article, a second step of further kneading the first kneaded article to obtain a second kneaded article, and a third step of charging the second kneaded article and a vulcanization agent and kneading them to obtain an unvulcanized rubber. In the first step, a reaction processing for kneading the rubber component, the silica and the silane coupling agent while maintaining a reaction temperature set in the range of 110 to 130°C, is conducted for 90 sec. or more when the reaction temperature is 110°C or more and less than 120°C, and for 30 sec. or more when the reaction temperature is 120 to 130°C.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a tire rubber composition and a method for producing a pneumatic tire.

In recent years, in response to increasing environmental awareness, there is a demand for reducing rolling resistance of tires in order to improve the fuel efficiency of automobiles.

Generally, in order to reduce rolling resistance, a method of blending silica with tread rubber is used. However, when silica is blended, there is a problem that Mooney viscosity after kneading increases and processability decreases. . Silica is a hydrophilic material whose surface is covered with silanol groups, and it is difficult to mix with diene rubber used in tire rubber compositions, but when used in combination with a silane coupling agent, silica and silane cups are used. Since the ring agent is bonded by polycondensation and the surface of the silica is hydrophobized, it can be easily dispersed in a diene rubber (see, for example, Patent Document 1).

Also, recently, with the enforcement of tire labeling systems in each country, tread rubber is required to have not only low fuel consumption but also high level of compatibility with fracture characteristics that are contrary to low fuel consumption. The current technology is insufficient to achieve this requirement.

JP 2002-363346 A

An object of the present invention is to solve the above-mentioned problems and to provide a method for producing a tire rubber composition and a method for producing a pneumatic tire in which fuel economy, fracture characteristics and processability are improved in a well-balanced manner.

The present invention includes a first step in which a rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product, and a second step in which the first kneaded product is further kneaded to obtain a second kneaded product. And a third step in which the second kneaded product and the vulcanized chemical are added and kneaded to obtain an unvulcanized rubber composition. In the first step, the temperature is set within a range of 110 to 130 ° C. While maintaining the reaction temperature, the reaction treatment for kneading the rubber component, the silica, and the silane coupling agent is 90 seconds or more when the reaction temperature is 110 ° C. or more and less than 120 ° C., and the reaction temperature is 120 to 130. In the case of ° C., the present invention relates to a method for producing a rubber composition for tires that is carried out for 30 seconds or more.

The present invention also relates to a method for manufacturing a pneumatic tire in which a pneumatic tire is manufactured using the tire rubber composition obtained by the manufacturing method.

According to the present invention, for a tire in which fuel efficiency, fracture characteristics, and workability are improved in a well-balanced manner by performing a reaction process for kneading a rubber component, silica, and a silane coupling agent at a predetermined temperature for a predetermined time. A rubber composition can be produced.

The present invention includes a first step in which a rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product, and a second step in which the first kneaded product is further kneaded to obtain a second kneaded product. And a third step in which the second kneaded product and the vulcanized chemical are added and kneaded to obtain an unvulcanized rubber composition. In the first step, the temperature is set within a range of 110 to 130 ° C. While maintaining the reaction temperature, the reaction treatment for kneading the rubber component, the silica, and the silane coupling agent is 90 seconds or more when the reaction temperature is 110 ° C. or more and less than 120 ° C., and the reaction temperature is 120 to 130. In the case of ℃, it is a manufacturing method of the rubber composition for tires carried out for 30 seconds or more.

In order to disperse a filler such as silica in the rubber composition, it is first necessary to plasticize the rubber component (polymer) so that the filler can be easily taken up. In the present invention, since the rubber component can be sufficiently plasticized by carrying out the reaction treatment in the first step, the filler is well dispersed, and the fuel economy, fracture characteristics and processability are well balanced. An improved rubber composition for tires can be produced.

In addition, modified polymers that have been developed in recent years tend to be less plasticized than ordinary polymers, and thus the present invention is particularly effective.

First, each component used in the present invention will be described.

(Rubber component)
As the rubber component, diene rubber is preferably used. As the diene rubber, natural rubber (NR) or diene synthetic rubber can be used. 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. These may be used alone or in combination of two or more. Of these, NR, BR, and SBR are preferable, and BR and SBR are more preferable because they exhibit low fuel consumption, fracture characteristics, and processability in a well-balanced manner.

In the rubber composition obtained by the production method of the present invention, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more because the fuel efficiency, fracture characteristics and processability can be obtained in a good balance. More preferably, it is 15 mass% or more, preferably 70 mass% or less, more preferably 50 mass% or less.

In the rubber composition obtained by the production method of the present invention, the SBR content in 100% by mass of the rubber component is preferably 30% by mass or more because the fuel efficiency, fracture characteristics, and processability can be obtained in a good balance. More preferably, it is 50 mass% or more, preferably 95 mass% or less, more preferably 85 mass% or less.

(silica)
Silica is not particularly limited, but includes silica prepared by a dry process (anhydrous silica) and silica prepared by a wet process (hydrous silica), and has many silanol groups on the surface. Silica prepared by a wet method is preferred because it has many reactive sites with the ring agent. Silica may be used alone or in combination of two or more. Examples of commercially available silica include Ultrasil VN3 manufactured by Evonik.

Nitrogen adsorption specific surface area _(N 2 SA) of the silica, from the viewpoint of fracture properties, preferably ^90m 2 / g or more, more preferably ^{95 m} 2 / g or more, further preferably 100 m ² / g or more. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 240 m ² / g or less, from the viewpoint of dispersibility of silica.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

In the rubber composition obtained by the production method of the present invention, the content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and more preferably 10 parts by mass or more, from the viewpoint of reinforcing properties. Preferably it is 50 mass parts or more. The silica content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and still more preferably 100 parts by mass or less, from the viewpoint of processability.

(Silane coupling agent)
As the silane coupling agent, bis (3-triethoxysilylpropyl) disulfide, bis (bis) is preferable because it is easy to control the temperature during the reaction treatment in the first step and is excellent in the reinforcing effect of the rubber composition. Sulfide-based silane coupling agents such as (3-triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide are preferable, and bis (3-triethoxysilylpropyl) disulfide is more preferable. These silane coupling agents may be used alone or in combination of two or more.

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 from the viewpoint of reinforcing properties. It is. In addition, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, from the viewpoint of cost effectiveness.

(Vulcanized chemicals)
Examples of vulcanizing chemicals include vulcanizing agents and vulcanization accelerators, and it is preferable to use vulcanizing agents and vulcanization accelerators in combination.

As the vulcanizing agent, organic peroxides, sulfur-based vulcanizing agents and 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, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- Examples include 3,1,3-bis (t-butylperoxypropyl) benzene. Examples of the sulfur vulcanizing agent include sulfur and morpholine disulfide. These may be used alone or in combination of two or more. Especially, since the effect of this invention is acquired favorably, a sulfur type vulcanizing agent is preferable and sulfur is more preferable.

In the rubber composition obtained by the production method of the present invention, the content of the vulcanizing agent is preferably based on 100 parts by mass of the rubber component, because low fuel consumption, destructive properties and processability can be obtained in a good balance. It is 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less.

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

In the rubber composition obtained by the production method of the present invention, the content of the vulcanization accelerator is preferably based on 100 parts by mass of the rubber component because the fuel efficiency, fracture characteristics and processability can be obtained in a good balance. Is 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

(Other ingredients)
In addition to the above components, the rubber composition obtained by the production method of the present invention includes a compounding agent generally used in the production of a rubber composition, such as carbon black; an anti-aging agent; a softening agent such as oil; and stearic acid. Vulcanization aids such as zinc oxide; and the like can be blended.

Next, each kneading step in the production method of the present invention will be described.

(First step)
The first step is a step in which a rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product.

In this step, a reaction process for kneading the rubber component, silica, and silane coupling agent is performed for a predetermined time while maintaining a reaction temperature set within a range of 110 to 130 ° C. As a result, the rubber component is sufficiently plasticized, and a filler such as silica can be well dispersed.

By setting the reaction temperature to 110 ° C. or higher, the rubber component can be efficiently plasticized. If the reaction temperature is too high, the reaction between the silane coupling agent and silica proceeds in a state where the rubber component is not sufficiently plasticized, and the dispersibility of the silica may deteriorate. By setting it as 130 degrees C or less, plasticization of a rubber component can be advanced, suppressing reaction with a silica and a silane coupling agent.

When the reaction temperature is 110 ° C. or more and less than 120 ° C., the time for performing the reaction treatment may be 90 seconds or more, and when the reaction temperature is 120 to 130 ° C., the time for performing the reaction treatment is 30 seconds or more. I just need it. In either case, the upper limit is not particularly limited, but is preferably 300 seconds or less from the viewpoint of production efficiency.

As the procedure of the first step, for example, when the reaction temperature is set to 110 ° C., when the rubber temperature reaches 110 ° C. during the kneading, the rotation speed of the mixer, the ram dropping pressure, Kneading is performed while adjusting the temperature in the chamber (reaction treatment). By carrying out this reaction treatment for a predetermined time, the rubber component can be plasticized.

The rubber temperature during the reaction treatment (temperature of the kneaded product) is preferably as constant as possible from the viewpoint of stabilizing the quality of the resulting rubber composition, and specifically, ± 3 ° C. of the set reaction temperature. It is preferable that it is the range of these.

In the first step, after carrying out the reaction treatment, it is preferable to perform further kneading and discharge when the rubber temperature reaches 140 to 170 ° C. Thus, after carrying out the reaction treatment, the reaction between silica and the silane coupling agent can proceed after the rubber component is sufficiently plasticized by increasing the rubber temperature. In the first step, the kneading time excluding the reaction treatment is not particularly limited, but is preferably about 1 to 15 minutes.

The kneading machine used in the first step is preferably a closed Banbury mixer. The shape of the rotor of the Banbury mixer may be tangential or meshing.

The rubber component, silica, and silane coupling agent to be added in the first step may be all or part of them, but the total amount is preferable.

In the first step, in addition to the rubber component, silica, and silane coupling agent, other components may be added and kneaded. Other components are not particularly limited as long as they are components other than vulcanized chemicals, and examples thereof include carbon black, oil, anti-aging agent, wax, stearic acid, and zinc oxide.

(Second step)
The second step is a step of further kneading the first kneaded product obtained in the first step to obtain a second kneaded product. By providing the second step, dispersion of silica is 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.

In the second step, kneading is preferably performed using the same kneader as in the first step, and the rubber is preferably discharged when the rubber temperature reaches 140 to 170 ° C. The kneading time in the second step is not particularly limited, but is preferably about 1 to 15 minutes.

(Third process)
The third step is a step in which the second kneaded product and vulcanized chemical obtained in the second step are added and kneaded to obtain an unvulcanized rubber composition.

In the third step, in order to prevent scorch from being generated due to an increase in rubber temperature during kneading, kneading is terminated when the rubber temperature reaches a predetermined temperature (preferably 100 to 120 ° C.), and unvulcanized. The rubber composition is preferably discharged from the kneader. The kneading time in the third step is not particularly limited, but is preferably about 1 to 15 minutes.

As in the first step, the kneader used in the third step may be a closed Banbury mixer or an open roll.

(Other processes)
The unvulcanized rubber composition obtained in the third step is extruded according to the shape of the tire member (preferably cap tread), molded by a normal method on a tire molding machine, and other tire members The tire can be manufactured by pasting together and forming an unvulcanized tire, followed by heating and pressing in a vulcanizer.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: NS616 manufactured by Nippon Zeon Co., Ltd.
BR: BR1220 manufactured by Nippon Zeon Co., Ltd. (cis 1, 4 content: 96% by mass)
Carbon black: Seast N220 manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 manufactured by Evonik (average primary particle size: 17 nm, N ₂ SA: 175 m ² / g)
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl manufactured by Ouchi Shinsei Chemical Co., Ltd.) -2-Benzothiazolylsulfenamide)
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Examples and Comparative Examples)
(First step)
In accordance with the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were put into a Banbury mixer and kneaded to obtain a first kneaded product. The kneading is carried out while adjusting the rubber temperature to be within ± 3 ° C. of the reaction temperature after the rubber temperature reaches the set reaction temperature, and after a predetermined time (reaction time) has elapsed, It was discharged when the temperature reached 165 ° C. The reaction temperature and reaction time in each example are as shown in Tables 2-6. The kneading time excluding the reaction treatment was 10 minutes.
(Second step)
The obtained first kneaded product was put into a Banbury mixer and further kneaded, and discharged when the rubber temperature reached 165 ° C. The kneading time was 5 minutes.
(Third process)
The obtained second kneaded product, sulfur and vulcanization accelerator were put into an open roll and kneaded to obtain an unvulcanized rubber composition. The kneading was finished when the rubber temperature reached 110 ° C. The kneading time was 2 minutes.
(Vulcanization process)
The obtained unvulcanized rubber composition was vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.

The following evaluation was performed about the 1st kneaded material and vulcanized rubber composition which were obtained above. The results are shown in Tables 2-6.
In the following evaluation, the reference comparative example of Table 2 is Comparative Example 1, the reference comparative example of Table 3 is Comparative Example 7, the reference comparative example of Table 4 is Comparative Example 10, the reference comparative example of Table 5 is Comparative Example 11, The reference comparative example in Table 6 was set as Comparative Example 12.

(Mooney viscosity)
According to JIS K6300, the Mooney viscosity of the first kneaded product was measured at 130 ° C. The results are shown as an index with the reference comparative example being 100 (VIS index after the first step). The smaller the index, the better the workability.

(Tan δ)
Using a spectrometer manufactured by Ueshima Seisakusho, 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 were expressed as an index with the reference comparative example being 100 (tan δ index). The smaller the index, the lower the rolling resistance and the better the fuel efficiency.

(Destructive energy)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, a tensile test was conducted using a No. 3 dumbbell with a thickness of 2 mm formed from the above vulcanized rubber composition. And elongation at break (EB) were measured. Then, the breaking energy defined by the product of TB and EB was displayed as an index (breaking energy index) with the reference comparative example being 100. The larger the index, the better the fracture characteristics.

(Performance index)
In order to comprehensively evaluate the performance of each example, a performance index was calculated by the following formula.
Performance index = ((100 / VIS index after first step) × 100 + (100 / tan δ index) × 100 + fracture energy index) / 3

As shown in Tables 2 to 6, in the first step, Examples 1 to 13 in which the reaction temperature was set within the range of 110 to 130 ° C. and the reaction treatment was performed for a predetermined time are shown in the respective standards. Compared with the comparative example, fuel efficiency, fracture characteristics, and processability were significantly improved.
In Comparative Examples 1 to 6 and 12 to 17 in which the reaction temperature was set outside the range of 110 to 130 ° C., even if the reaction time was increased, sufficient performance improvement was not observed.
From these results, it became clear that the dispersibility of silica can be improved by a simple method of adjusting the kneading method by paying attention to the plasticization of the rubber component without changing the kind of compounding chemical.

Claims (2)

A rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product;
A second step of further kneading the first kneaded product to obtain a second kneaded product;
Adding the second kneaded product and the vulcanized chemical and kneading to obtain a non-vulcanized rubber composition,
In the first step, a reaction process in which the rubber component, the silica, and the silane coupling agent are kneaded while maintaining a reaction temperature set within a range of 110 to 130 ° C, the reaction temperature is 110 ° C or higher. A method for producing a rubber composition for a tire, which is carried out for 90 seconds or more when the reaction temperature is less than 120 ° C, and for 30 seconds or more when the reaction temperature is 120 to 130 ° C. The manufacturing method of the pneumatic tire which produces a pneumatic tire using the rubber composition for tires obtained by the manufacturing method of Claim 1.