JP2019019182A - Production method of rubber composition for tire - Google Patents

Abstract

To provide a production method of a rubber composition for a tire, by which a rubber composition for tire can be obtained that is improved in dispersibility of silica and improved in high mileage property and wet grip performance in a balanced manner, while achieving good processability.SOLUTION: The production method of a rubber composition for a tire includes: a base kneading step of kneading a rubber component, silica, a silane coupling agent and a vulcanization accelerator; a finish kneading step of kneading a kneaded material 1 obtained in the base kneading step with a vulcanizer; and an extrusion step of extruding a kneaded material 2 obtained in the finish kneading step by use of an extruder. The extruder includes a cylinder, a screw and pins disposed to protrude on an inner surface of the cylinder, in which the pins are arranged as protruding in an average number of 8 to 15 per the pitch of the screw.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 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 solves the above-mentioned problems, improves the dispersibility of silica while obtaining good processability, and provides a tire rubber composition having improved fuel economy and wet grip performance in a well-balanced manner. It aims at providing the manufacturing method of a composition.

The present invention includes a base kneading step for kneading a rubber component, silica, a silane coupling agent, and a vulcanization accelerator, a kneaded product 1 obtained in the base kneading step and a finishing kneading step for kneading the vulcanizing agent, and extrusion. An extrusion process for extruding the kneaded material 2 obtained in the finishing kneading process by a machine, the extruder comprising a cylinder, a screw, and a pin protruding from the inner surface of the cylinder, and the pin is screw pitched The present invention relates to a method for producing a rubber composition for tires, which is an average of 8 to 15 protrusions.

According to the present invention, a base kneading step for kneading a rubber component, silica, a silane coupling agent and a vulcanization accelerator, and a final kneading step for kneading the kneaded material 1 obtained in the base kneading step and the vulcanizing agent, And an extruding step of extruding the kneaded product 2 obtained in the finishing kneading step by an extruder, the extruder comprising a cylinder, a screw, and a pin protruding from the inner surface of the cylinder, and the pin Since it is a method for producing a rubber composition for tires that is projected in an average of 8 to 15 for each screw pitch, the dispersibility of silica is improved while obtaining good processability, fuel efficiency and wet grip performance. Thus, a rubber composition for tires with improved balance can be obtained.

An example of the schematic diagram of the extruder used at an extrusion process. An example of the schematic diagram of the peripheral surface in the schematic diagram of an extruder, and a pin protrusion location.

The present invention includes a base kneading step for kneading a rubber component, silica, a silane coupling agent, and a vulcanization accelerator, a kneaded product 1 obtained in the base kneading step and a finishing kneading step for kneading the vulcanizing agent, and extrusion. An extrusion process for extruding the kneaded material 2 obtained in the finishing kneading process by a machine, the extruder comprising a cylinder, a screw, and a pin protruding from the inner surface of the cylinder, and the pin is screw pitched It is a manufacturing method of the rubber composition for tires which protrudes 8-15 on average every time.

When the kneaded product obtained in the kneading step is kneaded with an extruder, the higher the pin density (number of pins) provided in the cylinder or the like, the more effective kneading can be realized, and the silica dispersibility becomes higher. However, on the other hand, there is a problem that burns occur in a normal formulation. In the present invention, the silica dispersion improvement effect by adding and kneading the vulcanization accelerator in the base kneading, and the silica dispersion improvement effect by optimizing the pin density of the extruder can be obtained synergistically, Silica dispersion can be significantly improved.

This is because by adding a vulcanization accelerator in the base kneading, a low-viscosity compounded rubber can be obtained, so heat generation can be suppressed, and therefore it is difficult to burn even under high shear conditions. It can be assumed that the silica dispersion is synergistically improved. Accordingly, it is possible to synergistically improve the performance balance between low fuel consumption and wet grip performance while preventing burns during kneading and obtaining good processability (kneading processability, extrusion processability).

Details of each step will be described below.

(Base kneading process)
In the base kneading step, the rubber component, silica, silane coupling agent and vulcanization accelerator 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.

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 and 1,3-di-o-tolylguanidine are preferable.

Examples of the sulfenamides include N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-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 is 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 base kneading step, the amount of the vulcanization accelerator to be input is set to 0.1 to 10 parts by mass with respect to 100 parts by mass of silica from the viewpoint of the reaction promoting effect of the silane coupling agent and silica. Is preferred.

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

In the base kneading step, the input amount of the rubber component, silica, silane coupling agent and vulcanization accelerator may be the total amount (total amount used in all steps) or a part thereof.
For the reason that the dispersion of silica can be further promoted, the rubber component, the silica and the silane coupling agent are preferably added and kneaded in the base kneading step, and the vulcanization accelerator is partially incorporated in the base kneading step. It is preferable to add and knead, and to add the remainder in the final kneading step and knead.

As the kneader used in the base kneading step, a closed Banbury mixer is preferable. The shape of the rotor of the Banbury mixer may be tangential or meshing.

In the base kneading step, the discharge temperature of the kneaded product 1 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 kneaded material 1 and the vulcanizing agent obtained in the base kneading step are added and 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 of the kneaded material 2 is preferably 80 to 120 ° C.

Although it will not specifically limit if it is a chemical | medical agent which can bridge | crosslink a rubber component as a vulcanizing agent thrown in at a finishing kneading process, For example, sulfur etc. are mentioned. 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, other components may be added and kneaded in addition to the above vulcanizing agent. 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 to be added in the base kneading step can be used, but guanidines, thiazoles and sulfenamides are preferable, guanidines and thiazoles. The combined use of sulfenamides is more preferred.

(Extrusion process)
In the extrusion process, the kneaded product 2 obtained in the finish kneading process is extruded into a sheet shape.
In the extrusion process, an extruder having a cylinder, screws, and pins protruding from the inner surface of the cylinder (pins attached so as to protrude from the inner surface of the cylinder) and an average number of pins per screw pitch within a predetermined range is provided. Using, the kneaded material 2 is extruded.

FIG. 1 shows an example of a schematic diagram of an extruder used in an extrusion process. The extruder 1 in FIGS. 1A and 1C includes a cylinder 11, a screw 12, and a pin 13 protruding from the inner surface of the cylinder 11, and FIG. It is a form that has not been done. The screw 12 has a flight 121 spirally around the shaft, and is inserted into the cylinder 11 and installed. Since the pins 13 in FIGS. 1A and 1C project from the material conveyance space in the cylinder 11, the flight 121 is provided with a notch 122 to prevent interference with the pins 13. ing.

FIG. 2 shows an example of a schematic diagram of an extruder and a schematic diagram of a circumferential surface at a projecting portion of a pin. The left view of FIG. 2 shows a mode in which the pin 13 and the notch 122 are provided, as in FIGS. 1 (a) and 1 (c). The right figure (i), (ii), (iii) has shown the form which protruded the pin 13 in the notch part 122 by six, eight, and ten in the circumference, respectively. Especially, the form which protruded 6-8 pins 13 per notch part 122 is preferable.

The extruder 1 has an average of 8 to 15 pins 13 protruding from each screw pitch P, and from the viewpoint of silica dispersibility, an average of 10 to 12 pins are preferably protruded. As shown in FIGS. 1 and 2, the screw pitch P is a distance (lead) by which the screw 12 advances in the axial direction when the screw 12 rotates 360 degrees.

For example, in the case of the extruder 1 in FIG. 1 (a) (number of pins per screw pitch P: 1 row) and FIG. 2 (iii) (number of pins 13 in the circumference: 10), the screw pitch The average number of pins 13 for each P is 10 (= 1 row × 10). In the case of the extruder 1 in FIG. 1 (c) (number of pins per screw pitch P: 1.5 rows) and FIG. 2 (ii) (number of pins 13 in the circumference: 8), the screw pitch The average number of pins 13 for each P is 12 (= 1.5 rows × 8).

It is desirable that the pins 13 be projected uniformly at each screw pitch P. For example, as shown in FIGS. 1A, 1C, and 2, the circumferential pins 13 (notches It is preferred that the part 122) be installed uniformly in the screw axis direction. Moreover, it is preferable that the number of each circumferential pin 13 installed in each notch portion 122 is the same number in each notch portion 122 (a set of one circumferential pin 13).

In the extrusion process, the kneaded material 2 supplied from the material supply unit (not shown) of the extruder 1 is sequentially moved by the rotation of the screw 12 in the kneading chamber in which a predetermined number of pins 13 in the cylinder 11 protrude. It is kneaded and plasticized by the pin 13 and the screw 12 and injected into a die of an injection nozzle (not shown) at the tip and formed into a sheet shape.

(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 silica content is preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component because the fuel efficiency and wet grip performance can be obtained in a balanced manner. More preferably, it is 60 parts by mass or more, and 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 masses with respect to 100 mass parts of silica because low fuel consumption and wet grip performance can be obtained in a balanced manner. Part or more, more preferably 8 parts by weight or more, and preferably 20 parts by weight or less, more preferably 15 parts by weight 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 DT: Noxeller DT (1,3-di-o-tolylguanidine) manufactured by Ouchi Shinsei Chemical Industry 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-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical 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) Base kneading step The materials described in the items of the base kneading step in Tables 1 to 5 were kneaded using a Banbury mixer, and discharged when the rubber temperature (kneaded material temperature) reached about 150 ° C.
(2) Finish kneading process Using an open roll, the kneaded product 1 obtained in the base kneading process and the materials described in the items of the finishing kneading process in Tables 1 to 5 are kneaded so that the rubber temperature is about 110 ° C. It was discharged at that time.
(3) Extrusion process The kneaded product 2 obtained in the finishing kneading process is converted into an extruder (screw diameter: φ80 mm, L / D: 20, cylinder temperature: 75) shown in FIGS. ), A flat sheet was extruded at a screw rotation speed of 25 RPM and an extrusion speed of about 25 m / min to obtain an unvulcanized rubber composition. The specifications of the extruder used in each example and comparative example are as described in each table.
(4) 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 vulcanized rubber composition and the unvulcanized 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

(Dough skin)
The unvulcanized rubber composition was extruded and formed into a rubber sheet having a thickness of 1.0 mm with a roll, and the state of the resulting rubber sheet was confirmed. The case where no ear breakage occurred and there was no problem in the fabric skin was indicated by ○, the case having a slight problem was indicated by △, and the case where it was not indicated by ×.

(Mooney viscosity index)
About the obtained unvulcanized rubber composition, it measured at 130 degreeC according to the measuring method of the Mooney viscosity based on JISK6300. The index was displayed with the value of the reference blend as 100. The larger the index, the lower the viscosity and the better the workability.

(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.

(WET 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 temperature 0 ° C., frequency 10 Hz, initial strain 10% and dynamic strain 2%. Was measured and indicated as an index with a reference blend of 100. The larger the index, the greater the coefficient of friction on the wet road surface, indicating better wet grip performance.

From Tables 1 to 5, the examples in which the vulcanization accelerator was kneaded with the base kneading and the pin density of the extruder was adjusted, the silica dispersibility was remarkably improved, and the fuel economy and wet grip performance were well balanced. It became clear that it improved. Also, good processability (kneading processability, extrusion processability) was obtained.

1 Extruder 11 Cylinder 12 Screw 13 Pin 121 Flight 122 Notch P Screw Pitch

Claims (1)

A base kneading step for kneading the rubber component, silica, silane coupling agent and vulcanization accelerator;
A final kneading step of kneading the kneaded material 1 and the vulcanizing agent obtained in the base kneading step;
An extrusion process for extruding the kneaded product 2 obtained in the finishing kneading process by an extruder,
The said extruder is a manufacturing method of the rubber composition for tires which is equipped with the cylinder, the screw, and the pin protruded on the inner surface of the said cylinder, and protruded the average of 8-15 said pins for every screw pitch.

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