JP7377098B2 - Method for manufacturing rubber composition and method for manufacturing pneumatic tire - Google Patents

Description

The present invention relates to a method for producing a rubber composition, which includes a step of kneading a rubber composition containing a rubber component, silica, and a silane coupling agent, and a method for producing a pneumatic tire obtained using the rubber composition as a raw material. It is.

In recent years, silica has come to be used instead of carbon black as a rubber reinforcing filler. However, silica has weaker reinforcing properties for rubber than carbon black, so in order to increase this reinforcing properties, a silane coupling agent is generally added when silica is blended into a rubber component. By adding a silane coupling agent as a compounding agent, the silane coupling agent is immobilized on silica through a coupling reaction, and the rubber component further reacts with the silane coupling agent, improving the dispersibility of silica into rubber. This increases reinforcing properties.

By the way, in order to efficiently perform the reaction between silica and silane coupling agent, it is desirable to knead a rubber composition containing a rubber component, silica, and silane coupling agent at a specific temperature for a long time. A coupling reaction between silica and a silane coupling agent is difficult to occur in a low-temperature environment, but if the temperature is too high, a crosslinking reaction of the rubber occurs, causing a rapid increase in viscosity and gelation.

When kneading is performed in the kneading chamber of a closed kneader in the presence of the rubber component, silica, and silane coupling agent, heat generation due to the viscous flow of the rubber and heat generation due to the coupling reaction occurs. The temperature inside the kneading chamber increases. For this reason, there is a problem in that the temperature rises to a temperature at which gelation occurs within a short period of time, and sufficient time is not available for the coupling reaction.

Patent Document 1 below describes a kneading process in which a rubber component, silica, and a silane coupling agent are kneaded using an internal kneader, and subsequent to the kneading process, the rubber mass obtained by the kneading is heated at a high temperature below the internal kneader. A method for producing a rubber composition is described, which includes a holding step of holding the rubber mass in an atmosphere for a predetermined period of time to supply the rubber mass with the amount of heat necessary for the reaction between silica and a silane coupling agent.

Patent Document 2 below describes 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. The temperature was set within the range of 150 to 170°C in the first step. A method for producing a tire rubber composition is described in which a reaction treatment of kneading a rubber component, silica, and a silane coupling agent while maintaining a reaction temperature is carried out until specific conditions are met.

Patent Document 3 below describes 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. The temperature was set within the range of 110 to 130°C in the first step. While maintaining the reaction temperature, the reaction treatment of kneading the rubber component, silica, and silane coupling agent is carried out for 90 seconds or more when the reaction temperature is 110°C or more and less than 120°C, and for 30 seconds or more when the reaction temperature is 120 to 130°C. A method for producing a rubber composition for tires is described, which is carried out for more than a second.

Japanese Patent Application Publication No. 2012-184289 JP 2018-70753 Publication Japanese Patent Application Publication No. 2018-104586

However, in all of the techniques described in the above-mentioned patent documents, it is necessary to carry out the kneading step multiple times in order to improve the dispersibility of silica in the rubber composition and further to reduce the viscosity of the rubber composition. For this reason, it has been found that while the power consumption throughout the rubber composition manufacturing process increases, there is still room for further improvement in the dispersibility of silica.

The present invention aims to solve the above problems, and aims to provide a method for producing a rubber composition that has excellent dispersibility of silica and can reduce power consumption throughout the production process.

The above problem can be achieved by the following configuration. The present invention provides a method for producing a rubber composition, comprising a kneading step of kneading a rubber composition containing at least a rubber component, silica, and a silane coupling agent in a kneading chamber provided in a closed kneader, the method comprising: The kneading machine is located above the kneading chamber and has a neck portion having a cylindrical space inside, and is movable up and down within the cylindrical space of the neck portion, and when kneading the rubber composition, a ram capable of pressing the rubber composition in the kneading chamber from above, and the kneading step includes maintaining the ram in a non-pressing state for a certain period of time while keeping the rubber composition within a predetermined temperature range. The present invention relates to a method for producing a rubber composition, characterized by a step of kneading under controlled temperature.

In the method for producing a rubber composition, the kneading chamber is a kneading chamber equipped with a kneading rotor whose rotational speed can be automatically controlled by a control section and capable of detecting and outputting an internal temperature, and Before the step, there is a preparatory step of setting the control time and target temperature in the control section, and the kneading step includes information about the measured temperature in the kneading chamber and information on the actual temperature in the kneading chamber until the control time elapses. Preferably, the step is to knead the inside of the kneading chamber while automatically controlling the rotational speed by PID control to set the actually measured temperature to the target temperature by the control unit based on the target temperature.

In the method for producing a rubber composition, the kneading step includes at least a rubber component, the silica, and the silane coupling agent, while the temperature is controlled below the lower limit temperature at which the coupling reaction between the silica and the silane coupling agent proceeds. A first step of kneading a rubber composition containing the above, and a second step of kneading the rubber composition while allowing the coupling reaction to proceed while the temperature is controlled to be higher than the lower limit temperature at which the coupling reaction proceeds. It is preferable that the second step is a step of kneading the ram in a non-pressed state for a certain period of time while controlling the temperature within a predetermined temperature range.

In the method for producing a rubber composition, the kneading chamber is a kneading chamber equipped with a kneading rotor whose rotational speed can be automatically controlled by a control section and capable of detecting and outputting an internal temperature, and Before the step, there is a preparation step in which settings regarding a control time and a target temperature are made to the control section, and both the first step and the second step included in the kneading step are performed until the control time elapses. During the kneading process, the control unit automatically controls the rotational speed by PID control to set the measured temperature to the target temperature based on information regarding the measured temperature in the kneading chamber and the target temperature, while kneading in the kneading chamber. Preferably, it is a step.

The present invention also provides a material process for producing a rubber composition by any of the methods for producing a rubber composition described above, and a process for producing an unvulcanized tire using the rubber composition produced in the material process. The present invention relates to a method for manufacturing a pneumatic tire, including a process.

The method for producing a rubber composition according to the present invention includes a kneading step of kneading the rubber composition while keeping the ram in a non-pressed state for a certain period of time while controlling the temperature within a predetermined temperature range. In such a kneading step, the rubber composition is kneaded in a state where the ram is not pressed against the rubber composition, that is, in a state where at least a part of the kneading chamber is open, so volatile substances such as moisture are removed. The rubber composition can be kneaded with fresh oxygen mixed therein. Therefore, the rubber composition has an excellent viscosity reducing effect and a silica dispersing effect. In particular, when the kneading process includes a first step and a second step that have different controlled temperature ranges, and when the rotation speed of the kneading rotor provided in the kneading chamber is automatically controlled by the control unit by PID control, each In each step, the temperature in the kneading chamber can be kept within a certain range for a certain period of time. This allows kneading to be carried out in the kneading chamber for a certain period of time while maintaining the temperature, which improves the dispersibility of silica compared to the conventional structure in which the rubber compound is discharged once it reaches a certain temperature. Excellent rubber compounds can be produced. Furthermore, since it is possible to reduce the number of man-hours in the kneading process, it is possible to reduce power consumption during the entire manufacturing process. In particular, when silica, which is ultimately included in the rubber composition, is added all at once during the kneading process, the number of man-hours in the kneading process can be significantly reduced, making it possible to significantly reduce power consumption during the entire manufacturing process. Become.

This is an example of an internal kneader that can be used in the manufacturing method according to the present invention.

The method for producing a rubber composition according to the present invention includes a kneading step of kneading a rubber composition containing at least a rubber component, silica, and a silane coupling agent in a kneading chamber provided in a closed kneader, the kneading step However, it is characterized in that it is a process of kneading while keeping the ram in a non-pressing state for a certain period of time and controlling the temperature within a predetermined temperature range. Such temperature control may be performed in one step in which the temperature range to be controlled is one stage, but in the present invention, the temperature range to be controlled is two stages in particular in the present invention. It is preferable to include a two-step kneading process including a first step and a second step.

[First step]
In the first step, a rubber composition containing at least a rubber component, silica, and a silane coupling agent is kneaded at a temperature below the lower limit temperature at which the coupling reaction between the silica and the silane coupling agent proceeds.

As the rubber component, diene rubber can be suitably used. Examples of diene rubber include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), butadiene rubber (SPB) containing syndiotactic-1,2-polybutadiene, Examples include chloroprene rubber (CR) and nitrile rubber (NBR), and these can be used alone or as a blend of two or more. These exemplified diene rubbers may have terminals modified (for example, terminal-modified BR, terminal-modified SBR, etc.) or modified to impart desired properties (for example, modified NR) can also be used. As this end-modified diene rubber, a diene rubber whose polymer end has been modified with various modifiers can be used, and various known modification methods can be used. Specifically, modifiers include tin compounds, aminobenzophenone compounds, isocyanate compounds, diglycidylamine compounds, cyclic imine compounds, halogenated alkoxysilane compounds, glycidoxypropylmethoxysilane compounds, neodymium compounds, alkoxysilane compounds, and amines. Examples include combination use of a compound and an alkoxysilane compound. In the case of synthetic rubber, there are no particular restrictions on its polymerization method or molecular weight, and the combination of rubber type and blending ratio can be selected as appropriate depending on the site and application where the rubber composition is used. Regarding polybutadiene rubber (BR), in addition to those synthesized using cobalt (Co) catalysts, neodymium (Nd) catalysts, nickel (Ni) catalysts, titanium (Ti) catalysts, and lithium (Li) catalysts, WO2007 It is also possible to use one synthesized using a polymerization catalyst composition containing a metallocene complex described in Japanese Patent Application No. 129670. Among these diene rubbers, use of BR and/or SBR is preferred, use of SBR is more preferred, and use of modified SBR modified with amine and alkoxysilane is particularly preferred.

As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc., which are commonly used for rubber reinforcement, are used. Among these, wet silica is preferred.

The silane coupling agent is not particularly limited as long as it contains sulfur in its molecule, and various silane coupling agents that are mixed with silica in a rubber composition can be used. For example, bis(3-triethoxysilylpropyl)tetrasulfide (for example, "Si69" manufactured by Degussa), bis(3-triethoxysilylpropyl) disulfide (for example, "Si75" manufactured by Degussa), bis(2-triethoxysilylpropyl)tetrasulfide (for example, "Si75" manufactured by Degussa), Sulfide silanes such as ethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)disulfide, and γ-mercaptopropyltrisulfide. Mercaptosilanes such as methoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltriethoxysilane, etc. Protected mercaptosilanes such as methoxysilane are included.

In the method for producing a rubber composition according to the present invention, at the time of the first step of the kneading process, the amount of silica blended is preferably 30 to 150 parts by mass when the total amount of the rubber component is 100 parts by mass. Conventionally, when setting the amount of silica in a rubber composition within this range, in order to improve the dispersibility of silica, the silica was kneaded in multiple steps, or the rubber composition that had been kneaded once was kneaded again. However, in the present invention, in the first step, the silica is highly filled, more preferably, the silica contained in the final rubber composition is added all at once in the kneading process. can be carried out. Furthermore, by performing the second step (described later) following the first step (without discharging the rubber composition), the silica in the rubber composition can be added all at once, the dispersibility of silica can be improved, and multiple Since multiple kneading is not necessary, it is possible to reduce power consumption in the kneading process.

In the method for producing a rubber composition according to the present invention, the amount of silica blended in the rubber composition in the kneading step is 30 to 150 parts by mass, and 80 to 130 parts by mass, when the total amount of the rubber component is 100 parts by mass. Preferably. Further, the amount of the silane coupling agent blended is preferably 2 to 15 parts by weight, more preferably 6 to 13 parts by weight, based on 100 parts by weight of silica.

In the first step, the lower limit temperature at which the coupling reaction between the silica and the silane coupling agent proceeds is appropriately determined depending on the combination of the silica and the silane coupling agent. In this case, the lower limit temperature at which the coupling reaction proceeds is within the range of 135 to 145°C, more specifically approximately 140°C. Therefore, in the first step, it is preferable to knead the rubber composition while controlling the temperature within the range of 90 to 130°C, and more preferably to knead the rubber composition while controlling the temperature within the range of 100 to 120°C. preferable. An example of a method for temperature control within such a temperature range is a PID control method, which will be described later.

In the first step of the kneading process, it is preferable that the fill factor, which indicates the volume of the rubber composition relative to the capacity of the kneading chamber provided in the internal kneader, is 70 to 80%. Even if kneading is carried out in a state where the fill factor is less than 70%, the viscosity of the rubber composition will be low and the temperature will tend to rise, making temperature control difficult in some cases. On the other hand, if the fill factor exceeds 80%, mixing of the rubber composition becomes insufficient, and it may be difficult to improve the dispersibility of silica.

In the present invention, the fill factor can be specifically calculated using the following formula.
[Fill factor] = ([Volume of rubber composition] / [Capacity of kneading chamber provided in internal kneader]) x 100

The method for producing a rubber composition according to the present invention improves the dispersibility of silica while adding silica in the rubber composition at once, even in a high fill factor mixture with a fill factor of about 70 to 80%. Moreover, since multiple kneading is not necessary, it is possible to reduce power consumption in the kneading process.

[Second step]
In the second step, the rubber composition is kneaded while allowing the coupling reaction to proceed while the temperature is controlled to be higher than the lower limit temperature at which the coupling reaction proceeds. As mentioned above, for example, when a sulfide bond is formed by a coupling reaction, the lower limit temperature at which the coupling reaction proceeds is within the range of 135 to 145°C, more specifically approximately 140°C. In the second step, it is preferable to knead the rubber composition while controlling the temperature within the range of 140 to 170°C, and more preferably to knead the rubber composition while controlling the temperature within the range of 145 to 165°C. As a method for controlling the temperature within such a temperature range, for example, the PID control method can be mentioned, as in the first step.

In the present invention, since the first step is performed subsequent to the first step (without discharging the rubber composition), the blending ratio of silica to the rubber component and fill factor in the second step are the same as in the first step. .

The present invention is characterized in that the kneading step is a step of kneading while keeping the ram in a non-pressing state for a certain period of time and controlling the temperature within a predetermined temperature range. When the kneading process includes two steps including a first step and a second step, the second step is kneading while keeping the ram in a non-pressed state for a certain period of time and controlling the temperature within a predetermined temperature range. Preferably, the step is: This point will be discussed later.

In the present invention, a PID control method can preferably be used in both the first step and the second step. Specifically, the following manufacturing method;
The kneading chamber is equipped with a kneading rotor whose rotational speed can be automatically controlled by the control unit, and is capable of detecting and outputting the internal temperature. It has a preparation process for making settings related to time and target temperature, and both the first and second steps included in the kneading process are updated with information about the measured temperature in the kneading chamber and the target temperature until the control time elapses. Based on this, it is possible to suitably carry out a method for producing a rubber composition, which is a step of kneading in a kneading chamber while automatically controlling the rotational speed by PID control to set the actually measured temperature to the target temperature by the control unit.

In the method for producing the rubber composition according to the present invention, for example, an internal kneader can be used. As such an internal kneader, an intermeshing intermix type mixer, a tangential Banbury type mixer, a pressure kneader, etc. can be used, and an intermeshing intermix type mixer is particularly suitable.

The internal kneading machine 1 shown in FIG. 1 is an internal mixer, and includes a cylinder 2 used for raising and lowering a ram 4, and a cylinder 2 for charging a rubber composition containing at least a rubber component, silica, and a silane coupling agent. It is provided with a port 3, a kneading chamber 5 for kneading the rubber composition, and a drop door 7 for discharging the kneaded rubber composition. The ram 4 is arranged to adjust the pressure within the kneading chamber 5 by moving up and down.

In a state where the ram 4 is pressed against the rubber composition in the kneading chamber while descending (pressing state), the rubber composition is kneaded while the inside of the kneading chamber is kept in a sealed state. In the present invention, the kneading step is performed while the ram is kept in a non-pressing state for a certain period of time and the temperature is controlled within a predetermined temperature range. That is, by raising the ram 4 for a certain period of time during the kneading process, the kneading chamber 5 is maintained in an open state (non-pressed state). For this reason, the rubber composition is kneaded in a state where fresh oxygen is mixed while removing volatile substances such as moisture from the rubber composition.

The kneading chamber 5 is equipped with a pair of kneading rotors 6 for kneading materials, and the kneading rotors 6 are driven to rotate around a rotating shaft 12 by a motor (not shown). Further, the kneading chamber 5 is equipped with a temperature sensor 13 for detecting the temperature within the same chamber. This temperature sensor 13 may be installed inside the drop door 7, for example.

The rotational speed of the motor that rotates the kneading rotor 6 is adjusted based on a control signal from the control unit 11. The control unit 11 controls the rotation speed of the motor based on temperature information inside the kneading chamber 5 sent from the temperature sensor 13. The motor may be configured as long as its rotational speed can be freely changed by the control unit 11, and may be configured as an inverter motor, for example.

More specifically, the rotational speed of the motor is determined by a PID calculation processing section provided inside the control section 11 in proportion to the deviation between the actual temperature Tp in the kneading chamber 5 detected by the temperature sensor 13 and the target temperature Ts. (P), integral (I), and differential (D) operations are executed. That is, the PID arithmetic processing unit performs a proportional (P) operation in which a control amount is calculated in proportion to the difference (deviation e) between the actual temperature Tp in the kneading chamber 5 detected by the temperature sensor 13 and the target temperature Ts. Each control amount obtained by the integral (I) operation that calculates the controlled amount from the integral value of e in the time axis direction, and the differential (D) operation that calculates the controlled amount from the slope of the change in deviation e, that is, the differential value. The total value determines the rotation speed of the motor.

The flow of a method for producing a rubber composition using a PID control method in a kneading process including a first step and a second step is shown below. When the rubber component, silica, and silane coupling agent are introduced into the internal kneading machine 1, in the first step, the temperature is increased based on the values of the target temperature T _s1 and the control setting time t _m1 inputted in advance in the preparation process. , the control unit 11 starts PID control of the motor. That is, the rotational speed of the motor is determined based on the control signal from the control section 11, and thereby the rotational speed of the kneading rotor 6 is determined. As described above, the target temperature T _s1 in the first step is 90 to 130° C., and the control setting time t _m1 is preferably 10 to 150 seconds, more preferably 40 to 90 seconds.

Regarding the method of charging the rubber component, silica, and silane coupling agent, the rubber component, silica, and silane coupling agent may each be separately charged into the internal kneading machine 1, or the rubber component and After adding silica, a certain kneading treatment may be performed, and then the silane coupling agent may be added.

The control unit 11 performs PID control on the rotational speed of the motor until the elapsed time t from the control start time becomes equal to or greater than the control setting time t _m1 . As for the specific control content, as described above, the rotation speed is controlled based on the deviation between the measured temperature Tp and the target temperature _Ts in the kneading chamber 5 sent from the temperature sensor 13, the integral value of the deviation, and the differential value of the deviation. Make small changes.

Then, when the control time t becomes equal to or greater than the control set time _tm1 , the control unit 11 ends the PID control of the motor, and then increases the temperature of the rubber composition until the target temperature _Ts1 in the second step is reached. let The subsequent steps are the same as the first step, and in the second step, PID control of the motor is started by the control unit 11 based on the values of the target temperature T _s2 and the control setting time t _m2 that have been input in advance. The control setting time t _m2 is set to a time that exceeds the minimum time required for the coupling reaction between silica and the silane coupling agent. As described above, it is preferable that the target temperature T _s2 in the second step is 140 to 170° C., and the control setting time t _m2 is 30 to 300 seconds.

In the case of a method for manufacturing a rubber composition using a PID control method in the kneading process including the first step and the second step, preferably in the second step, while holding the ram in a non-pressed state for a certain period of time, It is preferable to knead while the temperature is controlled within a predetermined temperature range. In the second step, the time for holding the ram in the non-pressed state is preferably 5 seconds or more, preferably 30 seconds or more, and preferably 60 seconds or more. However, if the ram is raised to a non-pressing state immediately after reaching the control temperature in the second step, the temperature control of the rubber composition tends to become unstable. It is preferable to bring it into a non-pressed state in the middle or end of the step.

After the kneading process including the first and second steps is completed, the rubber composition is discharged from the drop door 7. Thereafter, a rubber composition is manufactured through a step of adding vulcanization compounding agents such as sulfur and a vulcanization accelerator to the cooled rubber composition and kneading the mixture.

In the method for producing a rubber composition according to the present invention, even if the fill factor is a high fill factor mixture of about 70 to 80%, the power consumption in the kneading process is reduced while adding silica in the rubber composition at once. In addition, a rubber composition with excellent silica dispersibility can be produced. The method for producing a pneumatic tire according to the present invention includes a material step of producing a rubber composition by the method for producing a rubber composition, and a step of producing an unvulcanized tire using the rubber composition produced in the material step. including. The pneumatic tire manufactured in the present invention has excellent silica dispersibility, and therefore has excellent wet grip performance and rolling resistance. Specific examples will be described below.

The following materials were used in each Example and Comparative Example.
(material)
・SBR; Product name “SBR1502”, manufactured by JSR Corporation ・Modified S-SBR; Product name “HPR350”, manufactured by JSR Corporation ・Silica; Product name “Nipseal AQ”, manufactured by Tosoh Corporation ・Silane coupling agent; Product name “Si75” ”, manufactured by Degussa Corporation, stearic acid; “Lunac S-20”, manufactured by Kao Corporation, carbon black (N339); product name “SEAST KH”, manufactured by Tokai Carbon Co., Ltd., oil; product name “Process NC-140”, JX Manufactured by Nippon Oil & Energy Co., Ltd., Zinc oxide; Product name: "Zinc oxide type 2", Mitsui Mining & Mining Co., Ltd., Wax; Product name: "OZOACE355", Manufactured by Nippon Seirin Co., Ltd., Sulfur; Product name: "5% oil treated powdered sulfur ”, manufactured by Tsurumi Chemical Industry Co., Ltd., vulcanization accelerator 1; trade name: “Suncellar DM-G”, manufactured by Sanshin Chemical Industry Co., Ltd., vulcanization accelerator 2; trade name: “Soxeal CZ”, manufactured by Sumitomo Chemical Co., Ltd.

Comparative example 1
The formulation described in "1st" in Table 1 was put into a Banbury mixer, which is an internal kneading machine, and the kneading process was carried out without PID control, and the rubber composition was discharged when the temperature reached 160°C. During the kneading process, kneading was carried out while maintaining the descending state of the ram (pressing state). After that, in order to improve the dispersibility of silica and reduce the viscosity, the rubber composition obtained in "1st" is kneaded without PID control, and the rubber composition is discharged when the temperature reaches 160°C. was carried out twice. Finally, the vulcanization compounding agents (sulfur and vulcanization accelerator) described in "Final" are added, the kneading process is carried out without PID control, and the rubber composition is discharged when the temperature reaches 160 ° C. In this way, a rubber composition was produced.

Table 1 shows the energy consumption (power amount) and Mooney viscosity of the obtained rubber composition, as well as the wet road surface properties and fuel efficiency of the pneumatic tire manufactured using the obtained rubber composition as a raw material.

[Energy consumption (power amount) of rubber composition]
The amount of power consumed from the 1st to Final steps was expressed as an index evaluation with Comparative Example 1 set as 100. The lower the number, the lower the energy consumption (power amount).

[Mooney viscosity]
Mooney viscosity ML ₍₁₊₄₎ at 100° C. was measured according to JIS K6300, and expressed as an index with Comparative Example 1 set as 100. The smaller the index, the lower the viscosity and the better the processability.

[WET grip performance]
Four 205/65R15 radial test tires were installed, the vehicle was run on a road surface sprinkled with water at a depth of 2 to 3 mm, and the friction coefficient was measured at 100 km/h to evaluate wet grip performance. Comparative Example 1 is set as 100 and expressed as an index, and the larger the index, the better the wet grip performance.

[Rolling resistance]
Using the same 205/65R15 test radial tires as in the wet grip performance test above, in accordance with JISD4234:2009, the rim (15 x 6 JJ), internal pressure (230 kPa), load (3.43 kN), and speed (80 km/h) were used. The rolling resistance during running was measured and expressed as an index with Comparative Example 1 set as 100. The smaller the index, the better.

Comparative example 2
The formulation listed in "1st" in Table 1 was put into a Banbury mixer, which is an internal kneading machine, and the kneading process was carried out while performing PID control with a control temperature range of 1 stage (1 step) until the temperature reached 160°C. At this stage, the rubber composition was discharged. During the kneading process, kneading was carried out while maintaining the descending state of the ram (pressing state). After that, in order to improve the dispersibility of silica and reduce the viscosity, the rubber composition obtained in "1st" is kneaded without PID control, and the rubber composition is discharged when the temperature reaches 160°C. was carried out once. Finally, the vulcanization compounding agents (sulfur and vulcanization accelerator) described in "Final" are added, the kneading process is carried out without PID control, and the rubber composition is discharged when the temperature reaches 160 ° C. In this way, a rubber composition was produced.

Example 1
The formulation listed in "1st" in Table 1 was put into a Banbury mixer, which is an internal kneading machine, and the kneading process was carried out while performing PID control with a control temperature range of 1 stage (1 step) until the temperature reached 160°C. At this stage, the rubber composition was discharged. During the final 60 seconds of the 120 seconds of PID control, kneading was carried out while raising the ram (in a non-pressing state). After that, in order to improve the dispersibility of silica and reduce the viscosity, the rubber composition obtained in "1st" is kneaded without PID control, and the rubber composition is discharged when the temperature reaches 160°C. was carried out once. Finally, the vulcanization compounding agents (sulfur and vulcanization accelerator) described in "Final" are added, the kneading process is carried out without PID control, and the rubber composition is discharged when the temperature reaches 160 ° C. In this way, a rubber composition was produced.

Example 2
The formulation described in "1st" in Table 1 was put into a Banbury mixer, which is an internal kneading machine, and the kneading process was carried out while performing PID control with a two-step control temperature range, until the temperature reached 160°C. At this stage, the rubber composition was discharged. During the final 60 seconds of the second control time of 120 seconds in the second step of the kneading process, kneading was carried out while raising the ram (in a non-pressing state). After that, in order to improve the dispersibility of silica and reduce the viscosity, the rubber composition obtained in "1st" is kneaded without PID control, and the rubber composition is discharged when the temperature reaches 160°C. was carried out once. Finally, the vulcanization compounding agents (sulfur and vulcanization accelerator) described in "Final" are added, the kneading process is carried out without PID control, and the rubber composition is discharged when the temperature reaches 160 ° C. In this way, a rubber composition was produced.

Example 3
A rubber composition was prepared in the same manner as in Example 2, except that kneading was carried out while raising the ram (in a non-pressing state) for the final 5 seconds of the second control time of 120 seconds in the second step of the kneading process. was manufactured.

Example 4
A rubber composition was prepared in the same manner as in Example 2, except that kneading was carried out while raising the ram (in a non-pressing state) for the final 100 seconds of the second control time of 120 seconds in the second step of the kneading process. was manufactured.

Example 5
Of the second control time of 120 seconds in the second step of the kneading process, kneading was performed while raising the ram (non-pressing state) for the middle 60 seconds (30 seconds in pressing state → 60 seconds in non-pressing state → pressing state) A rubber composition was produced in the same manner as in Example 2, except that the heating time was 30 seconds).

Example 6
Except for the fact that during the second control time of 120 seconds in the second step of the kneading process, the ram was repeatedly lowered (pressed state) and raised (non-pressed state), and kneaded while keeping the non-pressed state for a total of 60 seconds. A rubber composition was produced in the same manner as in Example 2.

The rubber compositions obtained in Comparative Examples 1 to 2 and Examples 1 to 6 were applied to tire treads to produce test tires, and wet grip performance and rolling resistance were measured.

From the results in Table 1, the rubber compositions obtained in Examples 1 to 6 have excellent silica dispersibility, and therefore, pneumatic tires equipped with tire treads obtained using the rubber compositions as raw materials have excellent wet grip performance and rolling performance. It can be seen that it has excellent resistance.

Claims (3)

A method for producing a rubber composition, comprising a kneading step of kneading a rubber composition containing at least a rubber component, silica, and a silane coupling agent in a kneading chamber provided in an internal kneader, the method comprising:
The closed kneading machine has a neck portion that is located above the kneading chamber and has a cylindrical space inside, and is movable up and down within the cylindrical space of the neck portion, and is configured to mix the rubber composition. A ram capable of pressing the rubber composition in the kneading chamber from above during kneading,
The kneading step is a step of kneading while keeping the ram in a non-pressing state for a certain period of time while controlling the temperature at 150 to 170 ° C. ,
The kneading chamber is a kneading chamber equipped with a kneading rotor whose rotation speed can be automatically controlled by a control unit, and whose internal temperature can be detected and output.
Before the kneading step, a preparation step of setting the control time and target temperature for the control section,
In the kneading process, the rotation is controlled by the control unit by PID control to set the measured temperature to the target temperature based on information regarding the measured temperature in the kneading chamber and the target temperature until the control time elapses. A method for producing a rubber composition , comprising the step of kneading in the kneading chamber while automatically controlling the speed . A method for producing a rubber composition, comprising a kneading step of kneading a rubber composition containing at least a rubber component, silica, and a silane coupling agent in a kneading chamber provided in an internal kneader, the method comprising:
The closed kneading machine has a neck portion that is located above the kneading chamber and has a cylindrical space inside, and is movable up and down within the cylindrical space of the neck portion, and is configured to mix the rubber composition. A ram capable of pressing the rubber composition in the kneading chamber from above during kneading,
The kneading step is a step of kneading while keeping the ram in a non-pressing state for a certain period of time while controlling the temperature at 150 to 170 ° C. ,
In the kneading step, a rubber composition containing at least a rubber component, the silica, and the silane coupling agent is kneaded in a state where the temperature is controlled to be below the lower limit temperature at which the coupling reaction between the silica and the silane coupling agent proceeds. The first step and
a second step of kneading the rubber composition while allowing the coupling reaction to proceed in a state where the temperature is controlled to be higher than the lower limit temperature at which the coupling reaction proceeds;
The second step is a step of kneading while maintaining the ram in a non-pressing state for a certain period of time and controlling the temperature within a predetermined temperature range,
The kneading chamber is a kneading chamber equipped with a kneading rotor whose rotation speed can be automatically controlled by a control unit, and whose internal temperature can be detected and output.
Before the kneading step, a preparation step of setting the control time and target temperature for the control section,
In both the first step and the second step included in the kneading process, the actually measured temperature is controlled by the controller based on the information regarding the actually measured temperature in the kneading chamber and the target temperature until the control time elapses. A method for producing a rubber composition , comprising the step of kneading in the kneading chamber while automatically controlling the rotational speed by PID control to achieve the target temperature. A material step of producing a rubber composition by the method for producing a rubber composition according to claim 1 or 2 , and a step of producing an unvulcanized tire using the rubber composition produced in the material step. Method of manufacturing pneumatic tires.

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