JP6958006B2 - Manufacturing method of rubber composition for tires - Google Patents

Description

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

In rubber compositions for tires, a technique of blending silica is widely used for the purpose of improving fuel efficiency and wet grip in a well-balanced manner.

Since silica has high cohesiveness and is difficult to disperse uniformly in rubber, it is generally used in combination with a silane coupling agent that binds to silica and promotes dispersion of silica. Conventionally, various methods for increasing the reactivity of a silane coupling agent have been studied in order to improve the dispersibility of silica. For example, in Patent Document 1, a method of blending a hydroxy acid and an itaconic acid into a rubber composition. Is disclosed. Further, as another method for increasing the reactivity of the silane coupling agent, a method in which the vulcanization accelerator, which is usually added in the finish kneading process, is added together with the rubber component, silica and the silane coupling agent in the base kneading process is also known. ing. However, in recent years, further improvement in the dispersibility of silica has been required.

International Publication No. 2011/06202099

The present invention solves the above problems, improves the dispersibility of silica while obtaining good workability, and provides a rubber composition for tires having improved fuel efficiency and wet grip performance in a well-balanced manner. It is an object of the present invention to provide a method for producing a composition.

The present invention is a first base kneading step of kneading a rubber component, silica and a silane coupling agent, and a second base kneading step of kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step. And the second kneading product obtained in the second base kneading step and the finishing kneading step of kneading the vulcanizing agent, and the third kneading product obtained in the finishing kneading step by an extruder equipped with a cylinder and a screw. The extrusion step comprises a method for producing a rubber composition for a tire, which is carried out by adjusting the temperature difference between the cylinder and the screw to 7 to 28 ° C.

According to the present invention, a first base kneading step of kneading a rubber component, silica and a silane coupling agent, and a second base of kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step. The kneading step, the finish kneading step of kneading the second kneaded product and the vulcanizing agent obtained in the second base kneading step, and the third finish kneading step obtained in the finish kneading step by an extruder equipped with a cylinder and a screw. The extrusion step includes an extrusion step of extruding the kneaded product, and the extrusion step is a method for producing a rubber composition for a tire, which is performed by adjusting the temperature difference between the cylinder and the screw to 7 to 28 ° C., and therefore has good workability. A rubber composition for a tire can be obtained in which the dispersibility of silica is improved and the fuel efficiency and wet grip performance are improved in a well-balanced manner.

The present invention is a first base kneading step of kneading a rubber component, silica and a silane coupling agent, and a second base kneading step of kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step. And the second kneading product obtained in the second base kneading step and the finishing kneading step of kneading the vulcanizing agent, and the third kneading product obtained in the finishing kneading step by an extruder equipped with a cylinder and a screw. The extrusion step is a method for producing a rubber composition for a tire, which is carried out by adjusting the temperature difference between the cylinder and the screw to 7 to 28 ° C., including an extrusion step of extruding.

When the kneaded product obtained in the kneading step is kneaded by an extruder, the reaction rate of the coupling agent can be further increased by raising the temperature of the screw to improve the dispersion of silica. Further, as the temperature difference between the screw and the cylinder increases, the discharge amount also increases. With ordinary compounds, there is a problem that burning is likely to occur when the temperature of the screw is raised.
In the present invention, the vulcanization accelerator is added and kneaded by the second base kneading to improve the silica dispersion and reduce the compound viscosity. The dispersion of silica is remarkably improved while obtaining good processability.

This is because a low-viscosity compounded rubber can be obtained by adding a vulcanization accelerator as a base kneading, so that heat generation can be suppressed. Therefore, it is difficult to burn even under high share conditions, so the temperature difference between the screw and the cylinder is increased. This is due to the fact that the reaction rate of the coupling agent can be further increased under high temperature conditions, and it is presumed that this synergistically improves the silica dispersion while obtaining good processability. Therefore, it is possible to synergistically improve the performance balance between fuel efficiency and wet grip performance while preventing discoloration during kneading and obtaining good workability (kneading workability, extrusion workability).

The details of each step will be described below.
(First base kneading process)
In the first base kneading step, the rubber component, silica and the silane coupling agent are kneaded.

Examples of the rubber component include diene rubbers such as natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). These may be used alone or in combination of two or more. Of these, SBR and BR are preferable, and the combined use of SBR and BR is more preferable.

The silane coupling agent is not particularly limited, and examples thereof include sulfide-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, and chloro-based silane coupling agents. These may be used alone or in combination of two or more. Of these, a sulfide-based silane coupling agent is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

The silica is not particularly limited, and those commonly used in the tire industry can be used. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 to 250 m ² / g, more preferably 120 to ²⁰⁰ m 2 / g.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

In the first base kneading step, the input amount of the rubber component, silica and the silane coupling agent may be the total amount (total amount used in the whole process) or a part thereof.
Since the dispersion of silica can be further promoted, it is preferable to add the entire amount of the rubber component in the first base kneading step and knead it, and to add a part of the silica and the silane coupling agent in the first base kneading step. It is preferable to knead the mixture and add the rest in the second base kneading step to knead.

In the first base kneading step, in addition to the above-mentioned rubber component, silica, and silane coupling agent, other components may be added and kneaded. The other components are not particularly limited as long as they are not the vulcanization accelerator added in the second base kneading step and the vulcanization agent added in the finish kneading step, and examples thereof include carbon black and oil.

The kneading of the first base kneading step can be carried out using a known kneading machine, and is preferably carried out using, for example, a closed type Banbury mixer. The shape of the rotor of the Banbury mixer may be either a tangential type or a meshing type.

In the first base kneading step, the discharge temperature of the first kneaded product is preferably 130 to 160 ° C. from the viewpoint of the reaction promoting effect of the silica and the silane coupling agent.

(Second base kneading process)
In the second base kneading step, the first kneaded product and the vulcanization accelerator obtained in the first base kneading step are kneaded.

The vulcanization accelerator is not particularly limited, and examples thereof include guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamate salts, thioureas, and xanthogenates. These may be used alone or in combination of two or more. Of these, guanidines, sulfenamides, thiazoles, and thiurams are preferable because the effects of the present invention can be obtained satisfactorily.

Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholbolate, and 1,3-di-o-. Examples thereof include cumenyl guanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine and the like. These may be used alone or in combination of two or more. Of these, 1,3-diphenylguanidine and 1,3-di-o-tolylguanidine are preferable.

Examples of sulfenamides include N-cyclohexyl-2-benzothiazolyl sulfenamide, N, N-dicyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide, Examples thereof include N-oxydiethylene-2-benzothiazolyl sulfenamide and N-methyl-2-benzothiazolyl sulfenamide. These may be used alone or in combination of two or more. Of these, N-cyclohexyl-2-benzothiazolyl sulfeneamide is preferable.

Examples of thiazoles include 2-mercaptobenzothiazole (MBT), dibenzothiazil disulfide (MBTS), 2- (2,4-dinitrophenyl) mercaptobenzothiazole, and 2- (2,6-diethyl-4-moriholinothio) benzo. Thiazole and the like can be mentioned. These may be used alone or in combination of two or more. Of these, 2-mercaptobenzothiazole and dibenzothiazyl disulfide are preferable.

Examples of thiurams include tetrakis (2-ethylhexyl) thiuram disulfide, tetrabenzyl thiuram disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, dipentamethylene thiuram tetrasulfide and the like. These may be used alone or in combination of two or more. Of these, tetrakis (2-ethylhexyl) thiuram disulfide and tetrabenzyl thiuram disulfide are preferable.

In the second base kneading step, the input amount of the vulcanization accelerator may be the total amount (total amount used in the whole process) or a part, but it is said that the dispersion of silica can be further promoted. For this reason, it is preferable that a part is charged in the second base kneading process and kneaded, and the rest is charged in the finishing kneading process and kneaded.
Further, from the viewpoint of the reaction promoting effect of the silane coupling agent and silica, the amount of the vulcanization accelerator added is preferably set to 0.1 to 10 parts by mass with respect to 100 parts by mass of the added amount of silica.

In the second base kneading step, other components may be added and kneaded in addition to the above-mentioned first kneaded product and vulcanization accelerator. The other components are not particularly limited as long as they are not vulcanizing agents added in the finish kneading step, and examples thereof include silica, silane coupling agents, oils, stearic acid, and antiaging agents.

The kneading of the second base kneading step can be carried out using a known kneader, for example, using a closed type Banbury mixer similar to the first base kneading step.

In the second base kneading step, the discharge temperature of the second kneaded product is preferably 130 to 160 ° C. from the viewpoint of the reaction promoting effect of the silica and the silane coupling agent.

(Finishing process)
In the finish kneading step, the second kneaded product and the vulcanizing agent obtained in the second base kneading step are kneaded.

The kneading method in the finish kneading step is not particularly limited, and for example, a known kneading machine such as an open roll can be used. The discharge temperature of the third kneaded product is preferably 80 to 120 ° C.

The vulcanizing agent to be added in the finish kneading step is not particularly limited as long as it is a chemical capable of cross-linking the rubber component, and examples thereof include sulfur and the like. Further, the hybrid cross-linking agent (organic cross-linking agent) can also be used as the vulcanizing agent in the present invention. These may be used alone or in combination of two or more. Of these, sulfur is preferable.

In the finish kneading step, other components may be added and kneaded in addition to the above-mentioned vulcanizing agent. Examples of other components include vulcanization accelerators, zinc oxide and the like.

As the vulcanization accelerator added in the finish kneading step, the same vulcanization accelerator added in the base kneading step can be used, but guanidines, thiazoles and sulfenamides are preferable, and guanidines and thiazoles are preferable. , Sulfenamides are more preferable in combination.

(Extrusion process)
In the extrusion step, an extruder equipped with a cylinder and a screw is used to extrude the third kneaded product obtained in the finish kneading step into a sheet shape. In the extrusion process, an extruder having a cylinder and a screw known in the rubber field can be used.

The extrusion process is performed by adjusting the temperature difference between the cylinder and the screw to 7 to 28 ° C. By setting the temperature difference to the lower limit or higher, the compound viscosity tends to be lowered and the silica dispersion tends to be improved. By setting the content below the upper limit, the texture of the rubber sheet tends to be improved and the silica dispersion tends to be improved. The temperature difference is preferably 10 to 25 ° C. Normally, the cylinder is adjusted to a higher temperature than the screw.

In the extrusion step, the temperature of the cylinder is preferably adjusted to 30 to 100 ° C., more preferably 35 to 80 ° C., still more preferably 40 to 70 ° C. from the viewpoint of silica dispersibility and processability. The temperature of the screw is preferably adjusted to 40 to 120 ° C., more preferably 45 to 100 ° C., and even more preferably 50 to 90 ° C. from the viewpoint of silica dispersibility and workability.

The temperature of the cylinder and screw of the extruder can be adjusted by using a temperature adjusting device including a jacket for circulating hot water, a cooling device, a circulation pump, a heating device, a temperature sensor, and the like. For example, a temperature control device is installed on each part of the screw part and the cylinder part, and the cooling device and the heating device are operated based on the result of the temperature measurement of the hot water by the temperature sensor to supply the hot water to the jacket of each part. By adjusting the temperature, the temperature of the screw part and the cylinder part can be adjusted individually.

(Vulcanization process)
The kneaded product (unvulcanized rubber composition) produced in the above step is usually vulcanized afterwards. For example, an unvulcanized rubber composition is extruded according to the shape of a tire member such as a tread, molded by a normal method on a tire molding machine, and bonded together with other tire members to form an unvulcanized tire. The tire can be manufactured by heating and pressurizing in a vulcanizer after forming the tire. The vulcanization temperature is preferably 130 to 200 ° C., and the vulcanization time is preferably 5 to 15 minutes.

In the rubber composition obtained by the production method of the present invention, the silica content is preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component because low fuel consumption and wet grip performance can be obtained in a well-balanced manner. , More preferably 60 parts by mass or more, preferably 200 parts by mass or less, and more preferably 100 parts by mass or less.

In the rubber composition obtained by the production method of the present invention, the content of the silane coupling agent is preferably 5 parts by mass with respect to 100 parts by mass of silica because fuel efficiency and wet grip performance can be obtained in a well-balanced manner. It is more than parts, more preferably 8 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 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: Nippon Zeon Co., Ltd. Nipol NS210 (S-SBR)
BR: BR150B manufactured by Ube Industries, Ltd.
Silica: Ultrasil VN3 manufactured by Evonik Degussa (N ₂ SA: 175m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Carbon black: Diamond black N220 (N ₂ SA: ^{114m 2} / g) manufactured by Mitsubishi Chemical Corporation
Oil: X140 (aroma oil) manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: Beads made by NOF CORPORATION Stearic acid Tsubaki vulcanization accelerator D: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazolyl sulfeneamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator MP: Noxeller MP (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator TOT-N: Noxeller TOT-N (Tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator TBZTD: Sunseller TBZTD (Tetrabenzyl thiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator MBTS: Noxeller DM (dibenzothiazil disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization Accelerator NS: Noxeller NS (Nt-Butyl-2-benzothiazolysulfurene amide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

(Examples and comparative examples)
(1) First base kneading process When the materials listed in the items of the first base kneading process in Tables 1 to 5 are kneaded using a Banbury mixer and the rubber temperature (temperature of the kneaded product) reaches about 150 ° C. It was discharged at.
(2) Second base kneading process Using a rubbery mixer, the first kneaded product obtained in the first base kneading process and the materials listed in the items of the second base kneading process in Tables 1 to 5 are kneaded. It was discharged when the rubber temperature reached about 150 ° C.
(3) Finish kneading process Using an open roll, the second kneaded product obtained in the second base kneading process and the materials listed in the items of the finish kneading process in Tables 1 to 5 are kneaded, and the rubber temperature is about. It was discharged when the temperature reached 110 ° C.
(4) Extrusion process Using an extruder (screw diameter: φ80 mm, L / D: 50, die gap width: 40 mm), the third kneaded product obtained in the finish kneading process has a screw rotation speed of 80 RPM and an extrusion speed. A ribbon-shaped sheet was extruded at about 9 m / min to obtain an unvulcanized rubber composition. The cylinder temperature and screw temperature of each example and comparative example are as described in each table.
(5) Vulcanization Step The unvulcanized rubber composition obtained in the extrusion step was press-vulcanized at 170 ° C. for 10 minutes with a mold having a thickness of 0.5 mm to obtain a vulcanized rubber composition.

The obtained vulcanized rubber composition and unvulcanized rubber composition were evaluated as follows. The results are shown in Tables 1-5. The standard formulations in each table are as follows.
Table 1: Comparative Example 1-1
Table 2: Comparative Example 2-1
Table 3: Comparative Example 3-1
Table 4: Comparative Example 4-1
Table 5: Comparative Example 5-1

(Fabric skin)
The unvulcanized rubber composition was extruded into a rubber sheet having a thickness of 1.0 mm with a roll, and the state of the obtained rubber sheet dough was confirmed. Those with no cuts in the ears and no problems with the skin of the fabric are marked with ○, those with some problems are marked with △, and those without problems are marked with ×.

(Moony Viscosity Index)
The obtained unvulcanized rubber composition was measured at 100 ° C. according to the method for measuring Mooney viscosity according to JIS K6300. The value of the reference compound was set as 100 and displayed as an index. The larger the index, the lower the viscosity and the better the workability.

(Silica dispersion index)
Using RPA2000 manufactured by Alfer Technology Co., Ltd., the strain dependence of the storage elastic modulus of the vulcanized rubber composition was measured under the conditions of a measurement temperature of 110 ° C. (preheating 1 minute), a frequency of 6 cpm, and an amplitude of 0.28 to 10%. The value of the storage elastic modulus when the strain amount was 0.56% was obtained, and the value of the reference compound was set as 100 and displayed as an index. The larger the index, the less the silica is poorly dispersed, indicating that the silica is well dispersed.

(RR index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition under the conditions of a temperature of 30 ° C., a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. Was measured, and the reference composition was set as 100 and displayed as an index. The larger the index, the lower the rolling resistance and the better the fuel efficiency.

(WET index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition was obtained under the conditions of a temperature of 0 ° C., a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. Was measured, and the reference composition was set as 100 and displayed as an index. The larger the index, the larger the coefficient of friction on the wet road surface, indicating that the wet grip performance is excellent.

From Tables 1 to 5, in the examples in which the vulcanization accelerator was kneaded by the base kneading and the temperature difference between the cylinder and the screw of the extruder was adjusted within a predetermined range, the dispersibility of silica was remarkably improved and the fuel consumption was low. It was also clarified that the wet grip performance was improved in a well-balanced manner. In addition, good workability (kneading workability, extrusion workability) was also obtained.

Claims (5)

The first base kneading process of kneading the rubber component, silica and silane coupling agent,
The first base kneading step of kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step, and the second base kneading step of kneading the vulcanization accelerator.
A finishing kneading step of kneading the second kneaded product and the vulcanizing agent obtained in the second base kneading step, and a finishing kneading step.
The third kneaded product obtained in the finish kneading step includes an extrusion step in which the third kneaded product containing a vulcanizing agent is put into an extruder equipped with a cylinder and a screw and extruded.
The extrusion step is a method for producing a rubber composition for a tire, which is carried out by adjusting the temperature difference between the cylinder and the screw to 7 to 28 ° C. Contains styrene butadiene rubber, butadiene rubber and silica
The method for producing a rubber composition for a tire according to claim 1, wherein the rubber composition having a silica content of 75 parts by mass or more with respect to 100 parts by mass of the rubber component is produced. The second base kneading step is at least one selected from the group consisting of N-cyclohexyl-2-benzothiazolyl sulfeneamide, 2-mercaptobenzothiazole, tetrakis (2-ethylhexyl) thiuram disulfide and tetrabenzyl thiuram disulfide. The method for producing a rubber composition for a tire according to claim 1 or 2, wherein the above is kneaded. The first base kneading step kneads styrene-butadiene rubber and butadiene rubber.
The method for producing a rubber composition for a tire according to any one of claims 1 to 3, wherein the finishing kneading step kneads zinc oxide. The first base kneading step kneads styrene-butadiene rubber and butadiene rubber.
The method for producing a rubber composition for a tire according to any one of claims 1 to 4, wherein the finishing kneading step kneads dibenzothiazil disulfide.