JP2018197286A - Method of producing rubber composition for tire - Google Patents

Abstract

To provide a method of producing a rubber composition for a tire, which improves dispersibility of silica while suppressing occurrence of scorch and gives a rubber composition for a tire excellent in fuel economy.SOLUTION: The present invention relates to the method of producing a rubber composition for a tire, which includes: a first base kneading step of kneading a rubber component, silica, and a silane coupling agent; a second base kneading step of kneading a first kneaded product obtained in the first base kneading step and a vulcanization accelerator; and a finishing kneading step of kneading a second kneaded product obtained in the second base kneading step and a vulcanizing agent. The kneading in the second base kneading step is performed by a Banbury mixer which includes a kneading chamber and a drop door for discharging the content of the kneading chamber and in which the temperature of the drop door is adjusted to 20-40°C.SELECTED DRAWING: None

Description

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

In the rubber composition for tires, a technique of blending silica is widely used for the purpose of improving the fuel efficiency and wet grip with a good balance.

Since silica is highly cohesive and 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, in order to improve the dispersibility of silica, various techniques for increasing the reactivity of the silane coupling agent have been studied. For example, in Patent Document 1, a technique of adding hydroxy acid and itaconic acid to a rubber composition Is disclosed. In addition, as another method for increasing the reactivity of the silane coupling agent, a method is also known in which a vulcanization accelerator that is usually added in the finishing kneading step is added in the base kneading step together with the rubber component, silica, and the silane coupling agent. ing. However, in recent years, further improvement in the dispersibility of silica has been demanded.

International Publication No. 2011-062099

The present invention provides a method for producing a tire rubber composition that solves the above-mentioned problems and improves the dispersibility of silica while suppressing the occurrence of scorch, and that provides a tire rubber composition having excellent fuel efficiency. The purpose is to do.

The present invention includes a first base kneading step for kneading a rubber component, silica and a silane coupling agent, and a second base kneading step for kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step. And a final kneading step for kneading the second kneaded product and the vulcanizing agent obtained in the second base kneading step, and kneading in the second base kneading step is performed in a kneading chamber and the contents of the kneading chamber It is related with the manufacturing method of the rubber composition for tires implemented by the Banbury mixer which is provided with the drop door which discharges | emits, and the temperature of the said drop door is adjusted to 20-40 degreeC.

According to the present invention, the base kneading step is performed in at least two stages of the first base kneading step and the second base kneading step, and in the second base kneading step in which the vulcanization accelerator is added, Since the method for producing a rubber composition for a tire that adjusts the drop door to a predetermined set temperature, the dispersibility of silica is improved while suppressing the occurrence of scorch, and the rubber composition for a tire excellent in fuel efficiency is obtained. Can be provided.

It is a schematic sectional drawing which shows an example of the Banbury mixer used at a 2nd base kneading process.

The present invention includes a first base kneading step for kneading a rubber component, silica and a silane coupling agent, and a second base kneading step for kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step. And a final kneading step for kneading the second kneaded product and the vulcanizing agent obtained in the second base kneading step, and kneading in the second base kneading step is performed in a kneading chamber and the contents of the kneading chamber And a drop door for discharging the tire, and the temperature of the drop door is adjusted to 20 to 40 ° C.

The Banbury mixer is a device that discharges the contents of the kneading chamber from the drop door after kneading the material in a state where the kneading chamber is substantially sealed by a ram. In order to suppress the adhesion of the contents to the drop door, the drop door is usually adjusted to a temperature of about 41 to 80 ° C. In this temperature range, when the vulcanization accelerator is added in the second base kneading step. , There is a tendency that scorch is likely to occur (the scorch time is shortened).
In contrast, in the present invention, by adjusting the temperature of the drop door to 20 to 40 ° C., even when the vulcanization accelerator is added in the second base kneading step, the generation of scorch is suppressed (the scorch time is increased). can do. In addition, the reaction between silica and the silane coupling agent is promoted by the vulcanization accelerator, so that the contents do not easily adhere to the drop door even though the temperature of the drop door is lower than usual. .

In addition, the kneaded product after the finish kneading step is usually sent to an extrusion step in which the kneaded product is extruded into a sheet using an extruder. In this extrusion process, increasing the extrusion speed (rotational speed of the screw of the extruder) and increasing the moving speed (line speed) of the extruded sheet improves the dispersibility of the silica, but tends to cause scorch. is there.
On the other hand, in the present invention, in the method of adding the vulcanization accelerator in the second base kneading step, the generation of scorch in the extrusion step can be suppressed by adjusting the temperature of the drop door to 20 to 40 ° C. This makes it possible to increase the line speed, improve the dispersibility of silica, and obtain a rubber composition for tires with improved fuel economy. In addition, improvement in productivity can be expected by increasing the line speed.

Details of each step will be described below.

(First base kneading process)
In the first base kneading step, the rubber component, silica and 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.

Although it does not specifically limit as a silane coupling agent, For example, a sulfide type, a vinyl type, an amino type, a glycidoxy type, a nitro type, a chloro type silane coupling agent etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, sulfide-based silane coupling agents are 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 silane coupling agent may be the total amount (total amount used in all steps) or a part thereof.
The rubber component is preferably added and kneaded in the first base kneading step because silica dispersion can be further promoted, and part of the silica and silane coupling agent is added in the first base kneading step. Then, it is preferable to knead and the remaining part is charged in the second base kneading step and kneaded.

In the first base kneading step, in addition to the 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 other than the vulcanization accelerator added in the second base kneading step and the vulcanizing agent added in the finishing kneading step, and examples thereof include carbon black and oil.

The kneading method in the first base kneading step is not particularly limited, and a Banbury mixer or the like used in the second base kneading step described later can be used.

In the first base kneading step, the discharge temperature is preferably 130 to 160 ° C. from the viewpoint of the reaction promoting effect of 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, dithiocarbamates, thioureas, and xanthates. These may be used individually by 1 type and may use 2 or more types together. Of these, guanidines, sulfenamides, thiazoles and thiurams are preferred 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, dicatechol borate di-o-tolylguanidine salt, 1,3-di-o- Examples thereof include cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine and the like. These may be used individually by 1 type and may use 2 or more types together. Of these, 1,3-diphenylguanidine is preferable.

Examples of sulfenamides include N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide and the like can be mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, N-cyclohexyl-2-benzothiazolylsulfenamide and Nt-butyl-2-benzothiazolylsulfenamide are preferable.

Thiazoles include 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzo. Examples include thiazole. These may be used individually by 1 type and may use 2 or more types together. Of these, 2-mercaptobenzothiazole and dibenzothiazyl disulfide are preferable.

Examples of thiurams include tetrakis (2-ethylhexyl) thiuram disulfide, tetrabenzylthiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, dipentamethylenethiuram tetrasulfide and the like. These may be used individually by 1 type and may use 2 or more types together. Of these, tetrakis (2-ethylhexyl) thiuram disulfide and tetrabenzylthiuram disulfide are preferable.

In the second base kneading step, the amount of the vulcanization accelerator to be introduced may be the total amount (total amount used in all steps) or may be a part, but the silica dispersion can be further promoted. For this reason, it is preferable to add a part in the second base kneading process and knead, and to add the remaining part in the finishing kneading process.
Moreover, from the viewpoint of the reaction promoting effect between the silane coupling agent and silica, the amount of the vulcanization accelerator is preferably set to 0.1 to 10 parts by mass with respect to 100 parts by mass of the silica.

In the second base kneading step, in addition to the first kneaded product and the vulcanization accelerator, other components may be added and kneaded. The other components are not particularly limited as long as they are other than the vulcanizing agent added in the finish kneading step, and examples thereof include silica, silane coupling agent, oil, stearic acid, anti-aging agent and the like.

FIG. 1 is a schematic cross-sectional view showing an example of a Banbury mixer used in the second base kneading step. A Banbury mixer 1 shown in FIG. 1 includes a kneading chamber (mixing chamber) 10, a ram (floating weight) 11 that is configured to substantially seal the kneading chamber 10, and a drop door 15 that discharges the contents of the kneading chamber. With.

A cylindrical hopper 12 is connected to the kneading chamber 10, and material is charged from a charging port 13 provided on the side surface of the hopper 12. The charged material is kneaded by a pair of rotors 14 a and 14 b provided in the kneading chamber 10 rotating in opposite directions, and then discharged from a drop door 15 provided in the lower part of 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 switched between substantially sealed and opened (substantially sealed release) by the lowering and rising of the ram 11. The kneading is usually performed in a state where the ram 11 is lowered and the kneading chamber 10 is substantially sealed.

In the second base kneading step, the temperature of the drop door 15 is adjusted to 20 to 40 ° C. By setting it as 20 degreeC or more, adhesion of the content to the drop door 15 can be suppressed notably, and generation | occurrence | production of scorch can be suppressed notably by setting it as 40 degreeC or less.
Note that the temperature of the drop door 15 may be adjusted by a method similar to that of a normal Banbury mixer. For example, the temperature can be adjusted by attaching a jacket for circulating hot water or cooling water to the drop door.

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

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

It does not specifically limit as a kneading method of a finish kneading process, For example, well-known kneading machines, such as an open roll, can be used. The discharge temperature is preferably 80 to 120 ° C.

The vulcanizing agent is not particularly limited as long as it is a chemical capable of crosslinking the rubber component, and examples thereof include sulfur. Moreover, a hybrid crosslinking agent (organic crosslinking agent) can also be used as a vulcanizing agent in the present invention. These may be used individually by 1 type and may use 2 or more types together. Of these, sulfur is preferable.

In the final kneading step, in addition to the second kneaded product and the vulcanizing agent, other components may be added and kneaded. Examples of other components include a vulcanization accelerator and zinc oxide.

As the vulcanization accelerator to be added in the final kneading step, the same vulcanization accelerator as in the second base kneading step can be used, but guanidines, thiazoles and sulfenamides are preferable, guanidines, The combined use of thiazoles and sulfenamides is more preferable.

(Extrusion process)
In the extrusion step, the kneaded product (third kneaded product) obtained in the finish kneading step is extruded into a sheet using an extruder.

The extruder usually includes a cylinder, a screw, and a pin protruding from the inner surface of the cylinder (a pin attached to protrude from the inner surface of the cylinder). In this extruder, the kneaded material supplied from the material supply section of the extruder is sequentially moved by the rotation of the screw in the kneading chamber in which a predetermined number of pins in the cylinder protrude and is kneaded by the joint work of the pin and the screw. , Plasticized, injected into the mold of the injection nozzle at the tip, and formed into a sheet shape.

What is necessary is just to adjust suitably the extrusion speed (rotation speed of a screw) of an extruder according to the moving speed (line speed) of the sheet | seat extruded from an extruder.
The line speed of the sheet is preferably 35 m / min or more, more preferably 40 m / min or more from the viewpoint of productivity, and preferably 65 m / min or less, more preferably 55 m / min from the viewpoint of scorch suppression. It is as follows.
Note that the line speed of the sheet can be adjusted by the speed of a conveyor, a roll, or the like that conveys the sheet.

(Vulcanization process)
The kneaded product (unvulcanized rubber composition) prepared in the above-described process is usually vulcanized thereafter. 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, and an unvulcanized tire After forming the tire, the tire can be manufactured by heating and pressing in a vulcanizer. 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 content of silica is preferably 30 parts by mass or more, more preferably 100 parts by mass with respect to 100 parts by mass of the rubber component, because good fuel economy can be obtained. It is 60 parts by mass or more, preferably 200 parts by mass or less, 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 or more with respect to 100 parts by mass of silica because good fuel efficiency is obtained. Preferably it is 8 mass parts or more, Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less.

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: Nipol NS210 (S-SBR) manufactured by Nippon Zeon Co., Ltd.
BR: BR150B manufactured by Ube Industries, Ltd.
Silica: Ultrasil VN3 manufactured by Evonik Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Carbon black: Diamond black N220 (N ₂ SA: 114 m 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 Shinsei Chemical Co., Ltd.
Stearic acid: beads manufactured by NOF Corporation Tsubaki stearate vulcanization accelerator D: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator MP: Noxeller MP (2-mercaptobenzothiazole) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator TOT-N: Noxeller TOT-N (tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator TBZTD: Sunseller TBZTD (tetrabenzylthiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator MBTS: Noxeller DM (dibenzothiazyl disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator NS: Noxeller NS (Nt-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.

(Examples and Comparative Examples)
(1) First base kneading step When the materials described in the items of the first base kneading step in Tables 1 to 5 were kneaded using a Banbury mixer, and the rubber temperature (temperature of the kneaded product) reached about 150 ° C. Was discharged. The set temperature of the drop door of the Banbury mixer is as shown in Tables 1-5.
(2) Second base kneading step Using a Banbury mixer, the first kneaded product obtained in the first base kneading step and the materials described in the items of the second base kneading step in Tables 1 to 5 are kneaded. The rubber was discharged when the rubber temperature reached about 150 ° C. The set temperature of the drop door of the Banbury mixer is as shown in Tables 1-5.
(3) Finish kneading process Using an open roll, the second kneaded product obtained in the second base kneading process and the materials described in the items of the finishing kneading process in Tables 1 to 5 are kneaded, and the rubber temperature is about It discharged | emitted when it became 110 degreeC.
(4) Extrusion process The third kneaded product obtained in the finishing kneading step was subjected to Table 1 using an extruder (screw diameter: φ80 mm, L / D: 50, die gap width: 40 mm, cylinder temperature: 220 ° C.). A ribbon-like sheet was extruded so as to achieve the line speed described in ˜5 to obtain an unvulcanized rubber composition.
(5) Vulcanization Step The unvulcanized rubber composition obtained in the extrusion step was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 10 minutes to obtain a vulcanized rubber composition.

The following evaluation was performed about the obtained unvulcanized rubber composition and vulcanized rubber composition. The results are shown in Tables 1-5. In addition, the reference | standard mixing | blending in each table | surface is 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

(Scorch index)
In accordance with JIS K 6300, the scorch time (t10) of the unvulcanized rubber composition measured at 130 ° C. was displayed as an index with the reference compounding as 100. The smaller the index, the longer the scorch time, and the less scorch occurs.

(Silica dispersion index)
Using RPA2000 manufactured by Alpha Technology, 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 at a strain amount of 0.56% was determined, and the index value was expressed with the value of the reference blend as 100. The larger the index, the less the silica is poorly dispersed and the better the silica is dispersed.

(RR index)
Loss tangent (tan δ) of the vulcanized rubber composition using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) 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 indicated as an index with a reference blend of 100. The larger the index, the lower the rolling resistance and the better the fuel efficiency.

(productivity)
As a productivity index, the ratio of the line speed of each formulation to the line speed: 25 m / min at which scorch is hardly generated was calculated.

From Tables 1 to 5, the vulcanization accelerator was added in the second base kneading process, and the example in which the drop door of the Banbury mixer used in the second base kneading process was adjusted to a predetermined set temperature, While suppressing, the dispersibility of silica was improved, and the fuel efficiency was improved. In addition, by increasing the line speed, it was possible to secure a sufficient scorch time even though good productivity was obtained.

Although not shown in the table, scorch occurred in the extrusion process when the set temperature of the drop door was 41 to 80 ° C. and the line speed was 40 m / min.

DESCRIPTION OF SYMBOLS 1 Banbury mixer 10 Kneading chamber 11 Ram 12 Hopper 13 Inlet 14a, 14b Rotor 15 Drop door

Claims (1)

A first base kneading step of kneading a rubber component, silica and a silane coupling agent;
A second base kneading step for kneading the first kneaded product and the vulcanization accelerator obtained in the first base kneading step;
A final kneading step of kneading the second kneaded product and the vulcanizing agent obtained in the second base kneading step,
A tire that is kneaded in the second base kneading step by a Banbury mixer that includes a kneading chamber and a drop door that discharges the contents of the kneading chamber, and the temperature of the drop door is adjusted to 20 to 40 ° C. For producing a rubber composition for use.

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