Method for producing rubber composition, method for manufacturing tire, and apparatus for producing rubber composition

Abstract

To provide a method for producing a rubber composition which can improve low heat generation and abrasion resistance of a tire, and a method for manufacturing a tire, and to provide an apparatus for producing a rubber composition.SOLUTION: A method for producing a rubber composition includes the steps of: charging at least a rubber component, silica and a silane coupling agent into a kneader (1), and kneading the mixture in a kneading chamber (74); and moving a first mixture formed by the step of kneading the mixture in the kneading chamber (74) to a kneading chamber (94), and kneading the mixture in the kneading chamber (94), and compressed gas is sent into the kneading chamber (94) in the step of kneading in the kneading chamber (94). By sending the compressive gas into the kneading chamber (94), a volatile matter, for example, moisture and alcohol can be discharged to outside of the kneading chamber (94). Accordingly, a coupling reaction can be efficiently progressed, and a degree of silica dispersion can be enhanced. As a result, low heat generation and abrasion resistance of a tire can be improved.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a rubber composition, a method for producing a tire, and an apparatus for producing a rubber composition. [Background technology]

[0002] Silica, which is used as a reinforcing filler for rubber, has a tendency to aggregate due to hydrogen bonds due to the presence of silanol groups. Therefore, it is not easy to disperse silica well. In particular, it is not easy to disperse silica well when it is highly loaded or when small particle size silica is used.

[0003] It is known to use a silane coupling agent to reduce the cohesive force of silica. The silane coupling agent can react with silica during kneading, so that it can prevent the silica from coagulating. In addition, the silane coupling agent can react with the double bond of the rubber component during vulcanization, so that it can bond the silica and the rubber component.

[0004] As a method for reducing the cohesive force of silica, that is, as a method for increasing the degree of silica dispersion, kneading is performed under proportional integral differential control (hereinafter sometimes referred to as "PID control") of the rotor rotation speed to set the kneading temperature to a target temperature (see, for example, Patent Document 1). Specifically, it is known to perform kneading after setting the target temperature to 150°C, that is, a temperature at which the reaction between silica and a silane coupling agent (hereinafter sometimes referred to as "coupling reaction") actively proceeds.

[0005] There is also a method in which kneading is performed with the ram held in a non-pressing state under PID control of the rotor (see Patent Document 2). With this method, it is possible to discharge volatile substances (such as water and alcohol generated during the coupling reaction) to the outside of the kneading chamber, so that the coupling reaction can be efficiently promoted. Therefore, the cohesive force of silica can be further reduced.

[0006] In the methods described in Patent Documents 1 and 2, mixing is performed under PID control of the rotor, so the mixing time per mixing stage is longer than when mixing is performed without PID control. Note that a mixing stage is a cycle from when materials are fed into the mixer to when they are discharged.

[0007] On the other hand, a method using a kneader equipped with two kneading chambers is known (see, for example, Patent Document 3). In this method, kneading is performed in the first kneading chamber, and the mixture formed by the kneading is transferred to the second kneading chamber, where kneading is performed so that the coupling reaction proceeds actively. According to this method, since kneading in the first kneading chamber and kneading in the second kneading chamber can be performed in parallel, it is possible to improve the production amount per unit time. In other words, it is possible to improve productivity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-18890 A [Patent Document 2] JP 2021-102721 A [Patent Document 3] US6828361B2 Summary of the Invention [Problem to be solved by the invention]

[0009] In such a method using a kneader, there is room for improvement in terms of low heat build-up and wear resistance, which are important properties of tires.

[0010] The present invention aims to provide a method for producing a rubber composition capable of improving the low heat build-up property and abrasion resistance of a tire, and a tire production method, and also aims to provide an apparatus for producing the rubber composition. [Means for solving the problem]

[0011] In order to solve this problem, the method for producing a rubber composition of the present invention comprises the steps of: A step of feeding at least a rubber component, silica, and a silane coupling agent into a kneader including a first kneading chamber, a first rotor rotatable in the first kneading chamber, a second kneading chamber downstream of the first kneading chamber, and a second rotor rotatable in the second kneading chamber, and kneading the rubber component, silica, and a silane coupling agent in the first kneading chamber; a step of transferring the first mixture formed by the step of kneading in the first kneading chamber to the second kneading chamber and kneading in the second kneading chamber; In the step of kneading in the second kneading chamber, compressed gas is fed into the second kneading chamber.

[0012] In the method for producing a rubber composition of the present invention, a kneader including a first kneading chamber and a second kneading chamber downstream of the first kneading chamber is used, so that kneading in the first kneading chamber and kneading in the second kneading chamber can be performed in parallel. Therefore, productivity can be improved compared to the case where a kneader with one kneading chamber (hereinafter sometimes referred to as a "single machine") is used. In other words, the production amount per unit time can be improved.

[0013] Moreover, in the process of kneading the first mixture containing the rubber component, silica, and silane coupling agent in the second kneading chamber, compressed gas is fed into the second kneading chamber, so that volatile substances, such as water and alcohol (specifically, alcohol produced in the course of the coupling reaction), can be discharged to the outside of the second kneading chamber. Therefore, it is possible to reduce slippage of the second rotor caused by water, and it is possible to efficiently advance the coupling reaction, and it is possible to reduce the cohesive force of silica. Therefore, it is possible to increase the degree of silica dispersion. As a result, it is possible to improve the low heat generation and wear resistance of the tire.

[0014] In the above-mentioned manufacturing method, The kneader further includes a hole opening on a wall surface of the second kneading chamber, It is preferable that, when the compressed gas is fed into the second kneading chamber, the compressed gas is fed into the second kneading chamber through the hole in the second kneading chamber.

[0015] In any of the above-mentioned manufacturing methods, The kneader further comprises a hole opening in a wall of a channel between the first kneading chamber and the second kneading chamber. It is preferred that, at least during the time that the compressed gas is fed into the second kneading chamber, the gas in the second kneading chamber is exhausted through at least the holes in the channel. This structure allows volatile substances (such as water and alcohol) to be discharged through the holes in the channels, which makes it possible to more efficiently promote the coupling reaction and further reduce the cohesive force of the silica, thereby further improving the low heat generation and wear resistance of the tire.

[0016] In any of the above-mentioned manufacturing methods, the compressed gas is preferably compressed air. This configuration reduces costs since compressed air is inexpensive to produce.

[0017] In any of the above-mentioned manufacturing methods, in the step of kneading in the second kneading chamber, it is preferable to perform proportional integral differential control (hereinafter sometimes referred to as "PID control") of the rotation speed of the second rotor so that the kneading temperature in the second kneading chamber is set to a target temperature. When kneading is performed without performing any PID control of the second rotor (i.e., when kneading is performed at a constant rotation speed of the second rotor), in some formulations, the kneading temperature may not reach a temperature at which the coupling reaction actively proceeds, and in other formulations, the kneading temperature may rise to a temperature at which gelation actively proceeds. In contrast, according to this configuration, the kneading temperature can be stabilized by controlling the rotation speed of the second rotor using PID control, so that a decrease in the reaction rate of the coupling reaction and gelation can be suppressed.

[0018] The method for producing a tire of the present invention includes the steps of: A step of preparing a rubber composition by any one of the methods for producing a rubber composition described above; and producing an unvulcanized tire using the rubber composition.

[0019] The apparatus for producing the rubber composition of the present invention is A kneader including a first kneading chamber, a first rotor rotatable in the first kneading chamber, a second kneading chamber downstream of the first kneading chamber, a second rotor rotatable in the second kneading chamber, and a hole opened in a wall surface of the second kneading chamber; a compressor for generating compressed gas for feeding into said second kneading chamber through said bores in said second kneading chamber.

[0020] According to the rubber composition manufacturing apparatus of the present invention, the compressed gas generated by the compressor can be sent to the second kneading chamber through the hole in the second kneading chamber. Therefore, since volatile substances (such as water and alcohol) can be discharged outside the second kneading chamber, the coupling reaction can be efficiently promoted and the cohesive force of silica can be reduced. Therefore, the degree of silica dispersion can be increased. As a result, the low heat generation property and wear resistance of the tire can be improved. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a conceptual diagram showing a configuration of a rubber composition production apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described.

[0023] <1. Rubber composition manufacturing equipment> First, a rubber composition production apparatus, that is, a kneading system, that can be used in this embodiment will be described.

[0024] As shown in FIG. 1, a rubber composition manufacturing apparatus 30 in this embodiment includes a kneader 1 and a compressor 21 that generates compressed gas to be sent to the kneader 1. The manufacturing apparatus 30 further includes a pipe 26 for compressed gas that is fixed to the kneader 1. The manufacturing apparatus 30 may include other devices, such as an aftercooler, a tank, a main life filter, and an air dryer, between the compressor 21 and the pipe 26 in relation to the path of the compressed gas. Of course, the manufacturing apparatus 30 may include a pipe connecting these. The manufacturing apparatus 30 further includes a suction device 85 that can suck gas in the kneader 1 (specifically, gas in the kneading chamber 94 of the kneader 1).

[0025] The compressor 21 can generate compressed gas. The compressor 21 includes a housing 25. In the housing 25, the compressor 21 includes, for example, a motor (not shown), a compressor body (not shown) that is driven by the motor and compresses gas (for example, air), and a tank (not shown) that stores the compressed gas compressed by the compressor body. In such a compressor 21, the compressed gas discharged from the compressor body can flow into the tank via a pipe (not shown). Meanwhile, the compressed gas stored in the tank can exit the compressor 21 via a pipe (not shown). The compressor 21 may further include, for example, an aftercooler, a tank, a main life filter, and an air dryer.

[0026] Examples of the compressed gas include compressed air and compressed inert gases (e.g., nitrogen gas, helium gas, neon gas, and argon gas). Of these, compressed air is preferred because it can be produced at low cost.

[0027] The compressed gas coming out of the compressor 21 is sent to the kneading chamber 94 of the kneader 1 via a piping 26 after passing through an aftercooler, a tank, a main life filter, an air dryer, etc. as necessary. The piping 26 is provided with a pressure gauge (not shown) for measuring the pressure of the compressed gas.

[0028] The kneading machine 1 includes a kneading chamber 74, a rotor 73 rotatable in the kneading chamber 74, a cylindrical neck 5 located above the kneading chamber 74, an inlet 6 provided in the neck 5, a ram 7 that can move up and down in the space within the neck 5, a kneading chamber 94 downstream of the kneading chamber 74, and a rotor 93 rotatable in the kneading chamber 94.

[0029] The casing 72 forming the kneading chamber 74 is provided with an inlet and an outlet below the inlet. The kneading chamber 74 communicates with the space inside the neck 5 via the inlet. On the other hand, the kneading chamber 74 communicates with the channel, i.e., the space between the kneading chamber 74 and the kneading chamber 94 via the outlet.

[0030] The kneader 1 includes a pair of rotors 73 that are rotatable within a casing 72. The pair of rotors 73 may be of an intermeshing type or a tangential type.

[0031] The kneader 1 further includes a drop door 79 capable of opening and closing the outlet of the casing 72 .

[0032] An inlet 6 through which rubber components and compounding ingredients can be fed is provided on the side surface of the neck 5. Two or more inlets 6 may be provided.

[0033] The kneader 1 may include a hopper door 6a that can open and close the feed port 6.

[0034] Ram 7 is shaped so as to be able to close the entrance of casing 72. Ram 7 can move up and down in the space within neck 5 by means of shaft 8 connected to its upper end. Ram 7 can press the rubber components and compounding agents present within casing 72 by its own weight or by the pressing force from shaft 8. In other words, it can apply pressure.

[0035] In the kneader 1, a channel is provided between the casing 72 and a casing 92 downstream of the casing 72. That is, in the kneader 1, a channel connecting the kneading chamber 74 and the kneading chamber 94 is provided.

[0036] A hole that opens on the wall surface of the channel is provided in the kneader 1. Through this hole, gas in the kneading chamber 94 is sucked and discharged by the suction device 85. Even in the absence of the suction device 85, gas in the kneading chamber 94 is discharged through this hole.

[0037] The kneader 1 includes a casing 92 below the casing 72. Thus, the kneader 1 is provided with a kneading chamber 94 below the kneading chamber 74. The casing 92 forming the kneading chamber 94 is provided with an inlet and an outlet below the inlet. The kneading chamber 94 is connected to a channel (i.e., a space connecting the kneading chamber 74 and the kneading chamber 94) via the inlet.

[0038] The capacity of the kneading chamber 94 is larger than the capacity of the kneading chamber 74. The capacity of the kneading chamber 94 is preferably larger than the capacity of the kneading chamber 74 by 20% or more and 60% or less.

[0039] The kneader 1 includes a hole that opens into the wall surface of the kneading chamber 94. In other words, the casing 92 of the kneader 1 includes a hole that opens into the kneading chamber 94. This hole penetrates from the outer surface to the inner surface of the casing 92. Compressed gas generated by the compressor 21 is sent into the kneading chamber 94 from this hole.

[0040] The kneader 1 includes a pair of rotors 93 that are rotatable within a casing 92. The pair of rotors 93 may be of an intermeshing type or a tangential type.

[0041] The kneader 1 further includes a drop door 99 capable of opening and closing the outlet of the casing 92 .

[0042] The rotation speed of a motor (not shown) that rotates the rotor 73 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 (specifically, the measured temperature Tp) of the kneading chamber 74 sent from the temperature sensor 76. The rotation speed of the motor can be freely changed by the control unit 11. The motor can be, for example, an inverter motor.

[0043] In order to determine the rotation speed of the motor, the PID calculation processing unit provided inside the control unit 11 performs proportional (P), integral (I) and differential (D) calculations based on the deviation between the actual temperature Tp of the kneading chamber 74 detected by the temperature sensor 76 and the target temperature Ts. Specifically, the PID calculation processing unit determines the rotation speed of the motor based on the sum of the control amounts obtained by the proportional (P) operation that calculates a control amount proportional to the difference (deviation e) between the actual temperature Tp and the target temperature Ts, the integral (I) operation that calculates a control amount from an integral value obtained by integrating the deviation e in the time axis direction, and the differential (D) operation that calculates a control amount from the gradient of the change in the deviation e, i.e., the differential value. Note that PID is an abbreviation for Proportional Integral Differential.

[0044] The rotation speed of a motor (not shown) that rotates the rotor 93 is also 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 (specifically, the measured temperature Tp) of the kneading chamber 94 sent from the temperature sensor 96. The rotation speed of the motor can be freely changed by the control unit 11. The motor can be, for example, an inverter motor.

[0045] In order to determine the rotation speed of the motor, the PID calculation processor provided inside the control unit 11 performs proportional (P), integral (I) and differential (D) calculations based on the deviation between the actual temperature Tp of the kneading chamber 94 detected by the temperature sensor 96 and the target temperature Ts. Specifically, the PID calculation processor determines the rotation speed of the motor based on the sum of the control amounts obtained by the proportional (P) operation that calculates a control amount proportional to the difference (deviation e) between the actual temperature Tp and the target temperature Ts, the integral (I) operation that calculates a control amount from an integral value obtained by integrating the deviation e in the time axis direction, and the differential (D) operation that calculates a control amount from the gradient of the change in the deviation e, i.e., the differential value.

[0046] In the kneader 1, the rubber component and compounding ingredients fed from the feed port 6 pass through the neck 5 into the casing 72, i.e., into the kneading chamber 74, and are kneaded in the kneading chamber 74. In the kneading chamber 74, the rubber component and compounding ingredients can be kneaded in a state where they are pressed by the ram 7, i.e., under pressure. The first mixture formed in the kneading chamber 74 passes through a channel into the casing 92, i.e., into the kneading chamber 94, and is kneaded in the kneading chamber 94. The ram 7 does not reach the first mixture in the kneading chamber 94, and therefore the mixture is kneaded without being pressed.

[0047] <2. Method for producing rubber composition> Next, a method for producing the rubber composition according to the present embodiment will be described.

[0048] The method for producing a rubber composition in this embodiment includes a step of preparing a rubber mixture (hereinafter referred to as "step S1") and a step of kneading at least the rubber mixture and vulcanization-related compounding ingredients to obtain a rubber composition (hereinafter referred to as "step S2").

[0049] <2.1. Step S1 (step of preparing rubber mixture)> Step S1 includes a step of feeding at least a rubber component, silica, and a silane coupling agent into the kneader 1 and kneading them in the kneading chamber 74 (hereinafter referred to as "step K1"), and a step of transferring the first mixture formed in step K1 to the kneading chamber 94 and kneading them in the kneading chamber 94 (hereinafter referred to as "step K2"). In this embodiment, since the kneader 1 is used, kneading in the kneading chamber 74 and kneading in the kneading chamber 94 can be performed in parallel. Therefore, productivity can be improved compared to the case of using a single machine. In other words, the production amount per unit time can be improved.

[0050] The steps K1 and K2 constitute one kneading stage. The kneading stage is a cycle from the input of materials into the kneader 1 to the discharge of the materials out of the kneader 1.

[0051] <2.1.1. Step K1 (Step of Kneading in the Kneading Chamber 74)> In the step K1, at least the rubber component, silica, and silane coupling agent are charged into the kneader 1, and at least the rubber component, silica, and silane coupling agent are kneaded in the kneading chamber 74.

[0052] Examples of the rubber component include natural rubber, polyisoprene rubber, styrene butadiene rubber (SBR), polybutadiene rubber (BR), nitrile rubber, and chloroprene rubber. One or any combination of these may be selected and used. The rubber component is preferably a diene rubber.

[0053] Modified rubber may be used as the rubber component. Examples of modified rubber include modified SBR and modified BR. The modified rubber may have a functional group containing a heteroatom. The functional group may be introduced to the end of the polymer chain or may be introduced into the polymer chain, but is preferably introduced to the end. Examples of the functional group include amino groups, alkoxyl groups, hydroxyl groups, carboxyl groups, epoxy groups, cyano groups, and halogen groups. Among these, amino groups, alkoxyl groups, hydroxyl groups, and carboxyl groups are preferred. The modified rubber may have at least one of the exemplified functional groups. Examples of the amino group include primary amino groups, secondary amino groups, and tertiary amino groups. Examples of the alkoxyl group include methoxy groups, ethoxy groups, propoxy groups, and butoxy groups. The exemplified functional groups interact with the silanol groups (Si-OH) of silica. Here, the interaction means, for example, chemical bonding or hydrogen bonding by chemical reaction with the silanol groups of silica. The amount of the modified rubber in 100% by mass of the rubber component used in step K1 may be 10% by mass or more, 20% by mass or more, or 30% by mass or more. The amount of the modified rubber in 100% by mass of the rubber component used in step K1 may be 90% by mass or less, 80% by mass or less, or 70% by mass or less.

[0054] Examples of silica include wet silica and dry silica. Of these, wet silica is preferred. Examples of wet silica include precipitated silica. The specific surface area of ​​silica measured by the nitrogen adsorption method is, for example, 80 m 2 / g or more, 2 / g or more, 2 / g or more, 2 The specific surface area of ​​silica may be, for example, 300 m 2 / g or less, and 2 / g or less, and 2 / g or less, and 2 / g or less. Here, the specific surface area of ​​silica is measured in accordance with the multipoint nitrogen adsorption method (BET method) described in JIS K-6430.

[0055] In step K1, the amount of silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more, based on 100 parts by mass of the rubber component. The amount of silica is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, even more preferably 130 parts by mass or less, and even more preferably 120 parts by mass or less, based on 100 parts by mass of the rubber component.

[0056] Examples of the silane coupling agent include sulfur-containing silane coupling agents. For example, sulfide silanes such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, and bis(2-trimethoxysilylethyl)disulfide; mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, and mercaptoethyltriethoxysilane; and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. One or any combination of these can be selected and used.

[0057] In step K1, the amount of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, based on 100 parts by mass of silica. The upper limit of the amount of the silane coupling agent is, for example, 20 parts by mass or 15 parts by mass, based on 100 parts by mass of silica.

[0058] In step K1, the rubber component, silica, and silane coupling agent can be kneaded with carbon black, antioxidants, stearic acid, wax, zinc oxide, oil, etc. Any one or any combination of these can be selected and used.

[0059] As the carbon black, for example, furnace black such as SAF, ISAF, HAF, FEF, GPF, etc., as well as conductive carbon black such as acetylene black and ketjen black, etc., can be used. The carbon black may be granulated carbon black, which is granulated in consideration of its handling properties, or may be ungranulated carbon black. One or more of these may be used.

[0060] Examples of the antiaging agent include aromatic amine-based antiaging agents, amine-ketone-based antiaging agents, monophenol-based antiaging agents, bisphenol-based antiaging agents, polyphenol-based antiaging agents, dithiocarbamate-based antiaging agents, thiourea-based antiaging agents, etc. The antiaging agent may be used alone or in any combination selected from these.

[0061] In the step K1, the rotation speed of the rotor 73 may be PID-controlled. Specifically, the rotation speed of the rotor 73 may be PID-controlled so as to set the kneading temperature in the kneading chamber 74, i.e., the measured temperature Tp, to the target temperature Ts. The PID control may be started from the beginning of kneading in the kneading chamber 74, or may be started when the measured temperature Tp reaches a predetermined temperature (for example, the target temperature Ts or a temperature somewhat lower than the target temperature Ts).

[0062] The target temperature Ts may be, for example, 100° C. or more, 120° C. or more, 130° C. or more, 140° C. or more, or 145° C. or more. The target temperature Ts may be, for example, 160° C. or less, 155° C. or less, or 150° C. or less.

[0063] The PID control may be performed for, for example, 10 seconds or more, 30 seconds or more, 60 seconds or more, 80 seconds or more, or 100 seconds or more. The PID control may be performed for, for example, 1000 seconds or less, 800 seconds or less, 600 seconds or less, 400 seconds or less, or 200 seconds or less.

[0064] In addition, in the step K1, the compressed gas is not fed into the kneading chamber 74.

[0065] <2.1.2. Step K2 (Step of Kneading in the Kneading Chamber 94)> In step K2, the first mixture formed in step K1 is transferred to the kneading chamber 94 and kneaded in the kneading chamber 94. In order to transfer the first mixture to the kneading chamber 94, the drop door 79 can be opened and the first mixture can be dropped into the kneading chamber 94.

[0066] In step K2, compressed gas is fed into the kneading chamber 94. That is, the first mixture is kneaded in the kneading chamber 94 while the compressed gas is fed into the kneading chamber 94. By feeding compressed gas into the kneading chamber 94, volatile substances such as water and alcohol (specifically, alcohol produced in the course of the coupling reaction) can be discharged outside the kneading chamber 94. Therefore, slippage of the rotor 93 due to water can be reduced, the coupling reaction can be efficiently promoted, and the cohesive force of silica can be reduced. Therefore, the degree of silica dispersion can be increased. As a result, the low heat generation and wear resistance of the tire can be improved.

[0067] By feeding compressed gas into the kneading chamber 94 in step K2, the loss of silica can also be avoided. This will be explained. If compressed gas were fed into the kneading chamber 74 in step K1 instead of feeding compressed gas into the kneading chamber 94 in step K2, silica may scatter due to the feeding of compressed gas. This is because silica is not sufficiently incorporated into the rubber component in the kneading chamber 74. In contrast, in this embodiment, compressed gas is fed into the kneading chamber 94 in step K2. That is, compressed gas is fed when kneading the first mixture in which silica is sufficiently or to some extent incorporated into the rubber component. Therefore, scattering of silica can be suppressed. Therefore, loss of silica can be avoided.

[0068] When the compressed gas is fed into the kneading chamber 94, the compressed gas is fed into the kneading chamber 94 through holes in the kneading chamber 94 (specifically, holes opening in the wall surface of the kneading chamber 94).

[0069] The compressed gas may be fed continuously or intermittently, with the continuous feeding of the compressed gas being preferred.

[0070] Kneading while feeding compressed gas, i.e., kneading under compressed gas, may be performed throughout step K2 or may be performed for only a portion of step K2. When kneading under compressed gas is performed halfway through step K2, kneading under compressed gas may be started, for example, 10 seconds or more, 20 seconds or more, or 30 seconds or more after the start of step K2.

[0071] The kneading time under compressed gas is preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 30 seconds or more. The kneading time under compressed gas may be 60 seconds or more, 120 seconds or more, or 180 seconds or more. In addition, when the compressed gas is fed intermittently, the kneading time under compressed gas is the total time of feeding the compressed gas.

[0072] The pressure of the compressed gas sent to the kneading chamber 94 may be 0.2 MPa or more, 0.3 MPa or more, or 0.4 MPa or more. If the pressure is 0.2 MPa or more, volatile substances (such as moisture and alcohol) can be more effectively discharged to the outside of the kneading chamber 94. Note that the "pressure of the compressed gas" may be the pressure of the compressed gas in the pipe 26. This pressure can be measured by a pressure gauge provided in the pipe 26.

[0073] The discharge rate of the compressed gas (specifically, the discharge rate of the compressed gas discharged from the compressor 21) may be, for example, 300 L / min or more, or 700 L / min or more. On the other hand, the discharge rate may be, for example, 1500 L / min or less, 1200 L / min or less, or 1000 L / min or less.

[0074] The temperature of the compressed gas sent to the kneading chamber 94 may be, for example, 15° C. or higher, 20° C. or higher, or 25° C. or higher. On the other hand, the temperature of the compressed gas may be, for example, 160° C. or lower, 150° C. or lower, or 100° C. or lower. The "temperature of the compressed gas" may be, for example, the temperature of the compressed gas leaving an air dryer. Here, the air dryer may be an air dryer built into the compressor 21, or an air dryer provided between the compressor 21 and the kneader 1.

[0075] While compressed gas is being fed into the kneading chamber 94, the gas in the kneading chamber 94 is discharged from the hole in the channel. At this time, the gas in the kneading chamber 94 may be sucked by the suction device 85 through this hole. That is, suction may be performed for the purpose of discharging. On the other hand, the gas in the kneading chamber 94 may be discharged from this hole without suction. Regardless of whether suction is performed or not, the gas in the kneading chamber 94 may be discharged from the hole in the channel and also from other holes.

[0076] In step K2, PID control of the rotation speed of the rotor 93 may be performed. Specifically, PID control of the rotation speed of the rotor 93 may be performed to set the kneading temperature in the kneading chamber 94, i.e., the measured temperature Tp, to the target temperature Ts. The PID control may be started from the beginning of kneading in the kneading chamber 94, or may be started when the measured temperature Tp reaches a predetermined temperature (for example, the target temperature Ts or a temperature somewhat lower than the target temperature Ts). By controlling the rotation speed of the rotor 93 by PID control, the kneading temperature can be stabilized, so that a decrease in the reaction rate of the coupling reaction and gelation can be suppressed.

[0077] The target temperature Ts may be, for example, 140°C or higher, 142°C or higher, 145°C or higher, 148°C or higher, or 150°C or higher. If it is 140°C or higher, the coupling reaction tends to proceed actively. The target temperature Ts is preferably 170°C or lower, more preferably 165°C or lower, even more preferably 160°C or lower, even more preferably 155°C or lower, and even more preferably 153°C or lower. If it is 170°C or lower, gelation tends to be suppressed.

[0078] The PID control may be performed for, for example, 10 seconds or more, 30 seconds or more, 60 seconds or more, 80 seconds or more, 100 seconds or more, or 120 seconds or more. The PID control may be performed for 1000 seconds or less, 800 seconds or less, 600 seconds or less, 500 seconds or less, 400 seconds or less, or 300 seconds or less.

[0079] When PID control is performed, it is preferable to feed compressed gas in parallel with the PID control. The compressed gas may be fed throughout the entire PID control or only for a portion of the time during which the PID control is performed.

[0080] The rubber mixture formed by kneading in the kneading chamber 94 can be discharged from the kneading chamber 94 by opening a drop door 99 .

[0081] <2.1.3.Other> If necessary, the rubber mixture can be further kneaded, i.e., re-kneaded, in order to improve the dispersibility of the silica or reduce the Mooney viscosity. Re-kneading may be performed multiple times.

[0082] By the above procedure, a rubber mixture can be obtained.

[0083] <2.2. Step S2 (Step of kneading the rubber mixture and the vulcanization compounding ingredients to obtain a rubber composition)> In step S2, at least the rubber mixture and the vulcanization compounding agents are kneaded to obtain a rubber composition. Examples of the vulcanization compounding agents include sulfur, organic peroxides and other vulcanizing agents, vulcanization accelerators, vulcanization accelerator assistants, and vulcanization retarders. The vulcanization compounding agents can be selected from these or any combinations. Examples of sulfur include powdered sulfur, precipitated sulfur, insoluble sulfur, and highly dispersible sulfur. The sulfur can be selected from these or any combinations. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. The vulcanization accelerator can be selected from these or any combinations. The kneading can be performed with a kneader. Examples of the kneader include a kneader 1, an open roll, a Banbury mixer, and a kneader.

[0084] In the rubber composition, the amount of silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more, based on 100 parts by mass of the rubber component. The amount of silica is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, even more preferably 130 parts by mass or less, and even more preferably 120 parts by mass or less, based on 100 parts by mass of the rubber component.

[0085] In the rubber composition, the amount of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more, based on 100 parts by mass of silica. The upper limit of the amount of the silane coupling agent is, for example, 20 parts by mass or 15 parts by mass based on 100 parts by mass of silica.

[0086] The rubber composition may further include carbon black, antioxidants, stearic acid, wax, zinc oxide, oil, sulfur, vulcanization accelerators, etc. The rubber composition may include one or any combination of these. The amount of sulfur is preferably 0.5 to 5 parts by mass in terms of sulfur content per 100 parts by mass of the rubber component. The amount of vulcanization accelerator is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component.

[0087] The rubber composition can be used to manufacture tires. Specifically, the rubber composition can be used to manufacture tire components that constitute tires. For example, the rubber composition can be used to manufacture tread rubber, sidewall rubber, chafer rubber, bead filler rubber, etc. The rubber composition can be used to manufacture one or any combination of these tire components.

[0088] <3. Tire manufacturing method> Next, the method for producing a tire according to the present embodiment will be described. Among the steps included in the method for producing a tire according to the present embodiment, the step of preparing the rubber composition has already been described.

[0089] The tire manufacturing method in this embodiment includes a step of producing an unvulcanized tire using the rubber composition. This step includes producing a tire component including the rubber composition, and producing an unvulcanized tire including the tire component. Examples of the tire component include tread rubber, sidewall rubber, chafer rubber, and bead filler rubber. Among them, tread rubber is preferable.

[0090] The tire manufacturing method of the present embodiment may further include a step of vulcanizing and molding the unvulcanized tire. The tire obtained by the method of the present embodiment may be a pneumatic tire.

[0091] <4. Various modifications can be made to the above-described embodiment> The above-described embodiment may be modified in various ways. For example, the above-described embodiment may be modified by selecting one or more of the following modifications.

[0092] In the above embodiment, a configuration has been described in which compressed gas is sent into the kneading chamber 94 from holes opening in the wall surface of the kneading chamber 94. However, the above embodiment is not limited to this configuration. For example, compressed gas may be sent into the kneading chamber 94 from holes opening in the wall surface of the channel. At this time, gas within the kneading chamber 94 may be discharged from holes opening in the wall surface of the kneading chamber 94.

[0093] In the above embodiment, the manufacturing apparatus 30 includes the suction device 85. However, the above embodiment is not limited to this configuration. In other words, the manufacturing apparatus 30 does not have to include the suction device 85.

[0094] In the above embodiment, the gas in the kneading chamber 94 is discharged from the holes of the channel. However, the above embodiment is not limited to this configuration. For example, the gas in the kneading chamber 94 may be discharged from the inlet 6 after the hopper door 6a and the drop door 79 are opened to some extent.

[0095] In the above embodiment, in the step K1, a configuration has been described in which compressed gas is not fed into the kneading chamber 74 when at least the rubber component, the silica, and the silane coupling agent are kneaded in the kneading chamber 74. However, the above embodiment is not limited to this configuration. That is, compressed gas may be fed into the kneading chamber 74 in the step K1 as well.

[0096] In the above embodiment, the kneading machine 1 is configured such that the kneading chamber 94 is provided below the kneading chamber 74. However, the above embodiment is not limited to this configuration. For example, the kneading chamber 94 may be provided at the same height as the kneading chamber 74. In this case, the kneading machine 1 may include a belt conveyor between the kneading chamber 74 and the kneading chamber 94 for transferring the first mixture formed in the kneading chamber 74 to the kneading chamber 94.

[0097] In the above embodiment, the kneader 1 including only the kneading chamber 74 and the kneading chamber 94 is used as the kneading chamber in the steps K1 and K2. However, the above embodiment is not limited to this configuration. For example, the kneader 1 may further include a third kneading chamber below the kneading chamber 94.

[0098] In the above embodiment, the kneader 1 includes the control unit 11. However, the above embodiment is not limited to this configuration. In other words, the kneader 1 does not have to include the control unit 11.

[0099] In the above embodiment, the entire amount of silica is added in the kneading stage including steps K1 and K2. However, the above embodiment is not limited to this configuration. For example, silica may be added in a plurality of kneading stages.

[0100] In the above embodiment, the rubber mixture and the vulcanization compounding agent are kneaded to obtain the rubber composition. However, the above embodiment is not limited to this configuration. For example, the rubber mixture may be treated as the rubber composition. EXAMPLES

[0101] The following describes an embodiment of the present invention.

[0102] <Comparative Examples 1 to 5 and Examples 1 to 7> The raw materials and chemicals used in these examples are as follows: SBR "SBR1502" manufactured by JSR Modified solution polymerized SBR "HPR350" manufactured by JSR Corporation Silica "Nipsil AQ" manufactured by Tosoh Corporation Silane coupling agent "Si75" manufactured by Degussa Stearic acid "Lunac S-20" manufactured by Kao Corporation Carbon black "N339 Seast KH" manufactured by Tokai Carbon Co., Ltd. Oil "Process NC140" manufactured by ENEOS Zinc oxide "Zinc oxide No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent "Antigen 6C" manufactured by Sumitomo Chemical Sulfur "5% oil treated sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1 "Suncerer DM-G" manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2 "Sokushinol CZ" manufactured by Sumitomo Chemical Co., Ltd.

[0103] [Table 1]

[0104] Preparation of unvulcanized rubber in Comparative Example 1 - Single machine assumed mixing According to Table 1, the rubber components and compounding ingredients were fed into a tandem mixer (i.e., a mixer having a similar structure to mixer 1 shown in FIG. 1), and mixed without PID control in the first mixer (i.e., the upstream mixer. Hereinafter, this may be referred to as the "upper mixer"), and the mixture was discharged (first mixing stage). The mixture obtained in the first mixing stage was re-kneaded (second mixing stage). The mixture obtained in the second mixing stage was re-kneaded (third mixing stage). The mixture obtained in the third mixing stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0105] Preparation of unvulcanized rubber in Comparative Example 2 - Single machine assumed mixing According to Table 1, the rubber components and compounding ingredients were put into a tandem mixer, and the upper mixer was kneaded with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 360 seconds), and the mixture was discharged (first kneading stage). The mixture obtained in the first kneading stage was kneaded again (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0106] Preparation of Unvulcanized Rubber in Comparative Example 3 According to Table 1, the rubber components and compounding ingredients were charged into a tandem mixer, and the mixture was mixed in the upper mixer without PID control, and mixed in the lower mixer (i.e., the second mixer) without PID control, and the mixture was discharged (first mixing stage). The mixture obtained in the first mixing stage was mixed again (second mixing stage). The mixture obtained in the second mixing stage was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0107] Preparation of Unvulcanized Rubber in Comparative Example 4 According to Table 1, the rubber components and compounding ingredients were put into a tandem mixer, and the upper mixer mixed them without PID control, and the lower mixer mixed them with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 360 seconds), and the mixture was discharged (first mixing stage). The mixture obtained in the first mixing stage was mixed again (second mixing stage). The mixture obtained in the second mixing stage was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0108] Preparation of Unvulcanized Rubber in Comparative Example 5 According to Table 1, the rubber components and compounding ingredients were put into a tandem mixer, and the mixture was kneaded in the upper mixer with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 130 seconds), and in the lower mixer with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 230 seconds), and the mixture was discharged (first kneading stage). The mixture obtained in the first kneading stage was re-kneaded (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0109] Preparation of unvulcanized rubber in Example 1 According to Table 1, the rubber components and compounding ingredients were fed into a tandem mixer, and the mixture was kneaded in the upper mixer without PID control, and in the lower mixer without PID control, and then discharged (first kneading stage). For kneading in the lower mixer, compressed air generated by a compressor was sent into the lower mixer through holes formed in the wall of the lower mixer for only 30 seconds from the time when the kneading temperature, i.e., the measured temperature, reached 150°C. The mixture obtained in the first kneading stage was kneaded again (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0110] Preparation of unvulcanized rubber in Example 2 According to Table 1, the rubber components and compounding ingredients were put into a tandem mixer, and the mixture was kneaded in the upper mixer without PID control, and in the lower mixer with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 360 seconds), and the mixture was discharged (first kneading stage). For kneading in the lower mixer, compressed air generated by a compressor was sent into the lower mixer through a hole formed in the wall of the lower mixer for only 30 seconds from the start of control during the 360-second control time. The mixture obtained in the first kneading stage was kneaded again (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0111] Preparation of unvulcanized rubber in Example 3 According to Table 1, the rubber components and compounding ingredients were put into a tandem mixer, and the mixture was kneaded in the upper mixer with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 130 seconds), and in the lower mixer with PID control (specifically, PID control with a control start temperature of 150°C, a target temperature of 150°C, and a control time of 230 seconds), and the mixture was discharged (first kneading stage). For kneading in the lower mixer, compressed air generated by a compressor was sent into the lower mixer from a hole formed in the wall of the lower mixer only for 30 seconds from the start of control during the control time of 230 seconds. The mixture obtained in the first kneading stage was re-kneaded (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0112] Preparation of unvulcanized rubber in Example 4 Regarding the kneading in the lower mixer, an unvulcanized rubber was produced in the same manner as in Example 3, except that compressed air was fed into the lower mixer for only 80 seconds from the start of control out of the 230 second control time.

[0113] Preparation of unvulcanized rubber in Example 5 Regarding the kneading in the lower mixer, an unvulcanized rubber was produced in the same manner as in Example 3, except that compressed air was fed into the lower mixer for only 130 seconds from the start of control out of the 230 seconds of control time.

[0114] Preparation of unvulcanized rubber in Example 6 Regarding the kneading in the lower mixer, an unvulcanized rubber was produced in the same manner as in Example 3, except that compressed air was fed into the lower mixer for only 180 seconds from the start of control out of the 230 seconds of control time.

[0115] Preparation of unvulcanized rubber in Example 7 Regarding the kneading in the lower mixer, an unvulcanized rubber was produced in the same manner as in Example 3, except that compressed air was fed into the lower mixer throughout the control time of 230 seconds.

[0116] Preparation of vulcanized rubber The unvulcanized rubber was vulcanized at 150°C for 30 minutes to obtain a vulcanized rubber.

[0117] Mooney Viscosity The Mooney viscosity of the unvulcanized rubber was measured in accordance with JIS K-6300 using a rotorless Mooney measuring instrument manufactured by Toyo Seiki Seisakusho. To measure the Mooney viscosity, the unvulcanized rubber was preheated at 100°C for 1 minute, and then the rotor was rotated, and the torque value 4 minutes after the start of the rotor rotation was recorded in Mooney units. The Mooney viscosity of each example is shown in Table 2, with the Mooney viscosity of Comparative Example 1 set as an index of 100. The smaller the index, the lower the Mooney viscosity and the better the processability.

[0118] Abrasion resistance The amount of wear was measured using a Lambourn abrasion tester in accordance with JIS K6264 under a load of 3 kg, a slip rate of 20%, and a temperature of 23° C. The reciprocal of the amount of wear in Comparative Example 1 is set as an index of 100, and the reciprocal of the amount of wear in each example (the reciprocal of the amount of wear) is shown in Table 2. The larger the index, the more excellent the abrasion resistance.

[0119] Wet road braking performance The rebound resilience (%) was measured in accordance with JIS K6255 at 23° C. using a Lübke rebound resilience tester. The reciprocal of the rebound resilience in Comparative Example 1 is set as an index of 100, and the reciprocal of each example (the reciprocal of the rebound resilience) is shown in Table 2. The higher the index, the better the wet road braking performance.

[0120] Low fuel consumption The tan δ of the vulcanized rubber was measured in accordance with JIS K-6394 using a viscoelasticity tester manufactured by Toyo Seiki Seisakusho. The tan δ was measured under the conditions of a frequency of 10 Hz, a dynamic strain of 1.0%, a temperature of 60°C, and a static strain (initial strain) of 10%. The tan δ of each example is shown in Table 2 as an index, with the tan δ of Comparative Example 1 taken as 100. The smaller the index, the lower the tan δ and the better the fuel economy.

[0121] [Table 2] The "discharge temperature" in Table 2 is the discharge temperature of the upper mixer and also the discharge temperature of the lower mixer in Comparative Examples 3 to 5 and Examples 1 to 7. In Comparative Examples 3 to 5 and Examples 1 to 7, during kneading in the lower mixer, gas in the lower mixer was sucked by a suction device through holes provided in the wall of the channel between the lower mixer and the upper mixer. "Injection of compressed air" in Table 2 means that compressed air with a discharge rate of 950 L / min and a pressure of 0.6 MPa was sent into the lower mixer through a hole formed in the wall of the lower mixer. This pressure was measured by a pressure gauge attached to an air hose attached to the tandem mixer. Incidentally, although the temperature of the compressed air was not measured, it is assumed that it was around room temperature.

[0122] By injecting compressed air into the lower mixer during mixing in the lower mixer, it was possible to improve the wear resistance and fuel economy (see Comparative Example 3 and Example 1; Comparative Example 4 and Example 2; Comparative Example 5 and Examples 3 to 7). In addition, it was possible to improve the wet road braking performance. It was also possible to reduce the Mooney viscosity.

[0123] <Comparative Example 6 and Examples 8 to 10> The raw materials and chemicals used in these examples are as follows: NR RSS#3 SBR "SBR1502" manufactured by JSR Solution Polymerization SBR "Tuf1834" manufactured by Asahi Kasei Corporation Silica "Nipsil AQ" manufactured by Tosoh Corporation Silane coupling agent "Si75" manufactured by Degussa Stearic acid "Lunac S-20" manufactured by Kao Corporation Carbon black "N339 Seast KH" manufactured by Tokai Carbon Co., Ltd. Oil "Process NC140" manufactured by ENEOS Zinc oxide "Zinc oxide No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent "Antigen 6C" manufactured by Sumitomo Chemical Sulfur "5% oil treated sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1 "Suncerer DM-G" manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2 "Sokushinol CZ" manufactured by Sumitomo Chemical Co., Ltd.

[0124] [Table 3]

[0125] Preparation of Unvulcanized Rubber in Comparative Example 6 According to Table 3, the rubber components and compounding ingredients were put into a tandem mixer, and the mixture was kneaded in the upper mixer with PID control (specifically, PID control with a control start temperature of 155°C, a target temperature of 155°C, and a control time of 40 seconds), and in the lower mixer with PID control (specifically, PID control with a control start temperature of 155°C, a target temperature of 155°C, and a control time of 200 seconds), and the mixture was discharged (first kneading stage). The mixture obtained in the first kneading stage was re-kneaded (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0126] Preparation of unvulcanized rubber in Example 8 According to Table 3, the rubber components and compounding ingredients were put into a tandem mixer, and the mixture was kneaded in the upper mixer with PID control (specifically, PID control with a control start temperature of 155°C, a target temperature of 155°C, and a control time of 40 seconds), and in the lower mixer with PID control (specifically, PID control with a control start temperature of 155°C, a target temperature of 155°C, and a control time of 200 seconds), and the mixture was discharged (first kneading stage). For kneading in the lower mixer, compressed air generated by a compressor was sent into the lower mixer from a hole formed in the wall of the lower mixer only for 20 seconds from the start of control during the control time of 200 seconds. The mixture obtained in the first kneading stage was re-kneaded (second kneading stage). The mixture obtained in the second kneading stage was kneaded with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0127] Preparation of unvulcanized rubber in Example 9 Unvulcanized rubber was produced in the same manner as in Example 8, except that compressed air was fed into the lower mixer for only 120 seconds from the start of control out of the 200 second control time.

[0128] Preparation of unvulcanized rubber in Example 10 An unvulcanized rubber was produced in the same manner as in Example 8, except that, for the kneading in the lower mixer, compressed air was fed into the lower mixer throughout the control time of 200 seconds.

[0129] Preparation of vulcanized rubber The unvulcanized rubber was vulcanized at 150°C for 30 minutes to obtain a vulcanized rubber.

[0130] evaluation Mooney viscosity, abrasion resistance, wet road braking performance, and fuel economy were measured by the above-mentioned method. The Mooney viscosity of each example is shown in Table 4 as an index with the Mooney viscosity of Comparative Example 6 set to 100. The smaller the index, the lower the Mooney viscosity and the better the processability. Regarding abrasion resistance, the inverse of the abrasion amount of each example is shown in Table 4 as an index with the inverse of the abrasion amount of Comparative Example 6 set to 100. The larger the index, the better the abrasion resistance. Regarding wet road braking performance, the inverse of the rebound resilience of each example is shown in Table 4 as an index with the inverse of the rebound resilience of Comparative Example 6 set to 100. The larger the index, the better the wet road braking performance. The tan δ of each example is shown in Table 4 as an index with the tan δ of Comparative Example 6 set to 100. The smaller the index, the lower the tan δ and the better the fuel economy.

[0131] [Table 4] The "discharge temperature" in Table 4 is the discharge temperature of the upper mixer and also the discharge temperature of the lower mixer. In Comparative Example 6 and Examples 8 to 10, during kneading in the lower mixer, gas in the lower mixer was sucked by a suction device through holes provided in the wall of the channel between the lower mixer and the upper mixer. "Injection of compressed air" in Table 4 means that compressed air with a discharge rate of 950 L / min and a pressure of 0.6 MPa was sent into the lower mixer through a hole formed in the wall of the lower mixer. This pressure was measured by a pressure gauge attached to an air hose attached to the tandem mixer. Incidentally, although the temperature of the compressed air was not measured, it is assumed that it was around room temperature.

[0132] By injecting compressed air into the lower mixer during mixing in the lower mixer, it was possible to improve the wear resistance and fuel economy (see Comparative Example 6 and Examples 8 to 10). In addition, it was possible to improve the wet road braking performance. It was also possible to reduce the Mooney viscosity. [Explanation of symbols]

[0133] 1... kneader, 5... neck, 6... inlet, 6a... hopper door, 7... ram, 8... shaft, 11... control section, 21... compressor, 25... housing, 26... piping, 30... rubber composition manufacturing apparatus, 72... casing, 73... rotor, 74... kneading chamber, 76... temperature sensor, 79... drop door, 85... suction device, 92... casing, 93... rotor, 94... kneading chamber, 96... temperature sensor, 99... drop door

Claims

1. A step of feeding at least a rubber component, silica, and a silane coupling agent into a kneader including a first kneading chamber, a first rotor rotatable in the first kneading chamber, a second kneading chamber downstream of the first kneading chamber, and a second rotor rotatable in the second kneading chamber, and kneading the rubber component, silica, and a silane coupling agent in the first kneading chamber; a step of transferring the first mixture formed by the step of kneading in the first kneading chamber to the second kneading chamber and kneading in the second kneading chamber; In the step of kneading in the second kneading chamber, a compressed gas is fed into the second kneading chamber. A method for producing a rubber composition.

2. The kneader further includes a hole opening on a wall surface of the second kneading chamber, When feeding the compressed gas into the second kneading chamber, the compressed gas is fed into the second kneading chamber through the hole in the second kneading chamber. A method for producing the rubber composition according to claim 1.

3. The kneader further comprises a hole opening in a wall of a channel between the first kneading chamber and the second kneading chamber. The method for producing a rubber composition according to claim 1 , wherein the gas in the second kneading chamber is discharged from at least the holes in the channel while the compressed gas is being fed into at least the second kneading chamber.

4. The method for producing a rubber composition according to claim 1 , wherein the compressed gas is compressed air.

5. 2. The method for producing a rubber composition according to claim 1, wherein in the step of kneading in the second kneading chamber, proportional integral differential control of the rotation speed of the second rotor is performed so that a kneading temperature in the second kneading chamber is set to a target temperature.

6. A step of preparing a rubber composition by the method for producing a rubber composition according to any one of claims 1 to 5; and producing an unvulcanized tire using the rubber composition. A method for manufacturing tires.

7. A kneader including a first kneading chamber, a first rotor rotatable in the first kneading chamber, a second kneading chamber downstream of the first kneading chamber, a second rotor rotatable in the second kneading chamber, and a hole opened in a wall surface of the second kneading chamber; a compressor for generating compressed gas for pumping into the second kneading chamber through the hole in the second kneading chamber; Rubber composition manufacturing equipment.

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