Method for producing a rubber composition and method for producing a tire

Abstract

To provide a method for producing a rubber composition that can improve low heat generation and wet road braking performance of tires.SOLUTION: The method for producing rubber composition of the present invention includes a process of kneading at least rubber, silica and a silane coupling agent in the closed kneader 1 while controlling the kneading temperature so that the coupling reaction of silica and silane coupling agent is suppressed, and, at least the rubber, silica and silane coupling agent are kneaded in a state where the ram 7 of the closed kneader 1 is not pressed for at least a part of the time during the process.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a rubber composition and a method for producing a tire.

Background Art

[0002] Silica used as a reinforcing filler for rubber has silanol groups and thus tends to aggregate by hydrogen bonding. Therefore, it is not easy to disperse silica well. In particular, it is not easy to disperse silica well when silica is highly filled or when silica with a small particle size is used.

[0003] In order to reduce the cohesive force of silica, it is known to use a silane coupling agent. Since the silane coupling agent can react with silica during kneading, it can prevent the aggregation of silica. In addition, since the silane coupling agent can react with the double bond of rubber during vulcanization, it can also bond silica and rubber.

[0004] In order to enhance the dispersion of silica, it is described in Patent Document 1 that rubber, silica, a silane coupling agent, etc. are kneaded in a closed kneader while controlling the kneading temperature so that the reaction of silica and the silane coupling agent (specifically, the coupling reaction) is suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The method described in Patent Document 1 enhances the dispersion of silica, thereby improving the low heat generation of tires and braking performance on wet roads (hereinafter referred to as "wet road braking performance"). However, there is still room for improvement in this method.

[0007] The present invention aims to provide a method for producing a rubber composition that can improve the low heat generation and wet road surface braking performance of tires. [Means for solving the problem]

[0008] To solve this problem, the method for producing the rubber composition of the present invention is as follows: The process includes a step of kneading at least rubber, the silica, and the silane coupling agent in a closed-type kneader while controlling the kneading temperature, so as to suppress the coupling reaction between silica and the silane coupling agent. The aforementioned closed-type kneader comprises a kneading chamber, a neck portion located above the kneading chamber, and a ram that can move up and down within the space of the neck portion. During at least a portion of the above process, the ram is not pressed while at least the rubber, the silica, and the silane coupling agent are kneaded together. Here, "the state in which the ram is not pressed" includes a state in which the ram is raised to such an extent that at least a part of the kneading chamber becomes an open system.

[0009] According to the present invention, by controlling the mixing temperature while mixing in a way that suppresses the coupling reaction, silica can be effectively dispersed before the coupling reaction proceeds actively. As a result, when the coupling reaction is carried out in subsequent steps, the efficiency of the coupling reaction can be increased, thereby effectively reducing the cohesive force of silica. Therefore, the low heat generation and wet road surface braking performance of the tire can be improved.

[0010] Furthermore, by kneading in a non-pressure state (which includes a state where at least a portion of the kneading chamber is open) for at least a portion of the process (specifically, the process of kneading while controlling the kneading temperature to suppress the coupling reaction), volatile substances such as water can be discharged outside the kneading chamber, thereby reducing rotor slip caused by moisture. As a result, the degree of silica dispersion before the coupling reaction actively proceeds can be further increased. In addition, since water is generated as a by-product during the coupling reaction process, if the coupling reaction proceeds after that process (specifically, the process of kneading while controlling the kneading temperature to suppress the coupling reaction), the coupling reaction can proceed with reduced moisture, thus allowing the coupling reaction to proceed more efficiently. As a result, the low heat generation and wet road surface braking performance of the tire can be improved.

[0011] The present invention can effectively improve the low heat generation and wet road braking performance of tires, particularly when the rotor rotation speed is PID controlled during the process (specifically, the process of kneading while controlling the kneading temperature so as to suppress the coupling reaction). This will be explained below. If kneading is performed only in a pressing state (specifically, a state in which the material being kneaded is pressed down by a ram) while the rotor is PID controlled, it is likely to cause a temperature rise due to shear heating, which tends to lower the rotor rotation speed, and therefore silica dispersion (specifically, the dispersion of silica before the coupling reaction proceeds) does not proceed easily. In contrast, in the present invention, by kneading in a non-pressing state, kneading can be performed in a state in which the temperature rise is less likely to occur compared to the pressing state, and thus the decrease in rotor rotation speed can be suppressed. As a result, the degree of silica dispersion before the coupling reaction proceeds actively can be further increased. Therefore, when the coupling reaction proceeds in subsequent steps (specifically, the step of kneading while controlling the kneading temperature to suppress the coupling reaction), it is possible to increase the efficiency of the coupling reaction, and as a result, the cohesive force of silica can be effectively reduced. Consequently, the low heat generation and wet road braking performance of the tire can be effectively improved.

[0012] In the method for producing the rubber composition of the present invention, it is preferable that the time for the aforementioned part is 10 seconds or more. That is, it is preferable that the kneading is performed in a non-pressing state for 10 seconds or more during that step (specifically, the step of kneading while controlling the kneading temperature so as to suppress the coupling reaction).

[0013] By kneading for 10 seconds or more, the moisture content in the kneading chamber can be effectively reduced. Therefore, the dispersion of silica (specifically, the dispersion of silica before the coupling reaction proceeds) can be effectively improved. In addition, if the coupling reaction proceeds in subsequent steps (specifically, the step of kneading while controlling the kneading temperature to suppress the coupling reaction), the efficiency of the coupling reaction can be effectively increased.

[0014] In the method for producing the rubber composition of the present invention, it is preferable that the enclosed kneader is equipped with a rotor in the kneading chamber, and in the process (specifically, the process of kneading while controlling the kneading temperature so as to suppress the coupling reaction), the rotation speed of the rotor is controlled by PID control in order to make the kneading temperature a target temperature.

[0015] This configuration, that is, the PID control of the rotor's rotational speed, effectively improves the tire's low heat generation and wet road braking performance. This will be explained. If mixing were performed only under a pressing state (specifically, with the material being mixed pressed down by a ram) while the rotor's PID control was active, it would easily lead to a temperature rise due to shear heating, causing the rotor's rotational speed to decrease, and therefore the silica dispersion (specifically, the dispersion of silica before the coupling reaction proceeds) would not progress easily. In contrast, in this invention, mixing is performed under a non-pressing state, which allows mixing to be performed under conditions where the temperature rise is less likely compared to the pressing state, thus suppressing the decrease in rotor rotational speed. As a result, the dispersion of silica (specifically, the dispersion of silica before the coupling reaction proceeds) can be effectively increased. Therefore, the tire's low heat generation and wet road braking performance can be improved.

[0016] The present invention's method for producing the rubber composition preferably further includes a step of kneading while controlling the kneading temperature so that the coupling reaction proceeds.

[0017] By controlling the mixing temperature during the mixing process to facilitate the coupling reaction, the silica can be dispersed and the coupling reaction can be actively promoted. This increases the efficiency of the coupling reaction, and as a result, the cohesive force of the silica can be effectively reduced. Therefore, since the dispersion of silica can be effectively improved, the low heat generation and wet road braking performance of the tire can be improved.

[0018] The tire manufacturing method of the present invention includes the steps of producing a rubber composition using the rubber composition manufacturing method of the present invention, and producing an unvulcanized tire using the rubber composition. [Brief explanation of the drawing]

[0019] [Figure 1] This is a conceptual diagram showing the configuration of a closed-type kneader that can be used in this embodiment.

Best Mode for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described.

[0021] <1. Closed Kneader> First, a closed kneader that can be used in this embodiment will be described.

[0022] As shown in FIG. 1, the closed kneader 1 includes a kneading chamber 4 having a casing 2 and a rotor 3, a neck portion 5 located above the kneading chamber 4 and having a cylindrical space inside, an inlet 6 provided in the neck portion 5, a ram 7 capable of moving up and down in the cylindrical space of the neck portion 5, and a drop door 9 located on the lower surface of the kneading chamber 4. Examples of the closed kneader 1 include an intermeshing closed kneader and a tangential closed kneader.

[0023] An opening 2a is provided at the central portion of the upper surface of the casing 2. Above the opening 2a, a neck portion 5 having a cylindrical space inside is provided. An inlet 6 through which rubber and compounding agents can be introduced is provided on the side surface of the neck portion 5. Two or more inlets 6 may be provided. The rubber and compounding agents introduced through the inlet 6 pass through the cylindrical space of the neck portion 5 and are introduced into the casing 2 through the opening 2a of the casing 2.

[0024] The ram 7 has a shape capable of closing the opening 2a of the casing 2. The ram 7 can move up and down in the cylindrical space of the neck portion 5 by a shaft 8 connected to the upper end thereof. The ram 7 can press and pressurize the rubber present in the casing 2 by its own weight or the pressing force from the shaft 8.

[0025] The drop door 9 is closed during kneading. After kneading is completed, the drop door 9 is opened.

[0026] The rotational speed of the motor (not shown) that rotates the rotor 3 is adjusted based on a control signal from the control unit 11. The control unit 11 controls the rotational speed of the motor based on temperature information (specifically, the measured temperature Tp) inside the kneading chamber 4 sent from the temperature sensor 13. The motor's rotational speed can be freely changed by the control unit 11. The motor can be, for example, an inverter motor.

[0027] To determine the motor's rotational speed, the PID calculation unit located inside the control unit 11 performs proportional (P), integral (I), and differential (D) calculations based on the deviation between the measured temperature Tp and the target temperature Ts detected by the temperature sensor 13 in the kneading chamber 4. Specifically, the PID calculation unit determines the motor's rotational speed by the sum of the control variables obtained through a proportional (P) operation, which calculates a control variable in proportion to the difference (deviation e) between the measured temperature Tp and the target temperature Ts; an integral (I) operation, which calculates a control variable from the integral value obtained by integrating the deviation e in the time axis direction; and a differential (D) operation, which calculates a control variable from the slope of the change in the deviation e, i.e., the differential value. PID stands for Proportional Integral Differential.

[0028] <2. Each step in the manufacturing method of the rubber composition> Next, some of the steps included in the method for producing the rubber composition in this embodiment will be described.

[0029] The method for producing the 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 a vulcanizing compounding agent to obtain a rubber composition (hereinafter referred to as "step S2").

[0030] <2.1. Process S1 (Process for producing rubber mixture)> Step S1 includes a step of kneading at least rubber, silica, and a silane coupling agent in a closed-type kneader 1 while controlling the kneading temperature so as to suppress the coupling reaction (reaction of silica and silane coupling agent) (hereinafter referred to as "step K1"), a step of kneading in a closed-type kneader 1 while increasing the kneading temperature (hereinafter referred to as "step K2"), and a step of kneading in a closed-type kneader 1 while controlling the kneading temperature so as to allow the coupling reaction to proceed (hereinafter referred to as "step K3").

[0031] Processes K1 to K3 constitute a single mixing stage. The mixing stage is a cycle from the input of materials to the discharge of materials into the closed-type mixer 1. Therefore, when transitioning from process K1 to process K2, materials such as rubber, silica, and silane coupling agent are not discharged from the closed-type mixer 1, and when transitioning from process K2 to process K3, the materials are also not discharged from the closed-type mixer 1.

[0032] <2.1.1. Process K1 (Process of kneading in a way that suppresses coupling reactions)> In step K1, at least rubber, silica, and a silane coupling agent are placed in a closed-type kneader 1, and these are kneaded while controlling the kneading temperature so as to suppress the coupling reaction (reaction of silica and silane coupling agent). Step K1 allows for effective dispersion of silica before the coupling reaction proceeds actively. In addition, step K1 can also reduce the amount of electricity consumed for the production of the rubber composition. This will be explained. If the kneading temperature were not controlled in step K1, the kneading time would be limited by the temperature rise due to shear heating, making it highly necessary to perform multiple re-kneading cycles (especially in silica-heavy formulations). In contrast, in this embodiment, by controlling the kneading temperature in step K1, the limitation on kneading time due to temperature rise can be removed, allowing for a longer kneading time and thus reducing the number of re-kneading cycles. As a result, the amount of electricity consumed for the production of the rubber composition can be reduced.

[0033] Examples of rubbers include natural rubber, polyisoprene rubber, styrene-butadiene rubber (SBR), polybutadiene rubber (BR), nitrile rubber, and chloroprene rubber. One or any combination of these can be selected and used. The rubber is preferably a diene-based rubber.

[0034] Modified rubber may be used as the rubber. Examples of modified rubber include modified SBR and modified BR. Modified rubber may have functional groups containing heteroatoms. Functional groups may be introduced at the ends of the polymer chain or introduced within the polymer chain, but are preferably introduced at the ends. Examples of functional groups include amino groups, alkoxy groups, hydroxyl groups, carboxyl groups, epoxy groups, cyano groups, halogen groups, etc. Among these, amino groups, alkoxy groups, hydroxyl groups, and carboxyl groups are preferred. Modified rubber may have at least one of the exemplified functional groups. Examples of amino groups include primary amino groups, secondary amino groups, and tertiary amino groups. Examples of alkoxy groups include methoxy groups, ethoxy groups, propoxy groups, and butoxy groups. The exemplified functional groups interact with the silanol groups (Si-OH) of silica. Here, interaction means, for example, chemical bonding or hydrogen bonding through a chemical reaction with the silanol groups of silica. The amount of modified rubber in 100% by mass of rubber used in process K1 may be 10% by mass or more, 20% by mass or more, or 30% by mass or more. The amount of modified rubber in 100% by mass of rubber used in process K1 may be 90% by mass or less, 80% by mass or less, or 70% by mass or less.

[0035] Examples of silica include wet silica and dry silica. Wet silica is preferred. As an example of wet silica, sedimentation silica can be used. The specific surface area of ​​silica obtained by nitrogen adsorption is, for example, 80 m². 2 It may be more than / g, 120m 2 It may be more than / g, 140m 2It may be more than / g, 160m 2 It may be more than / g. The specific surface area of ​​silica is, for example, 300m². 2 It may be less than / g, 280m 2 It may be less than / g, and 260m 2 It may be less than / g, and 250m 2 The amount may be less than or equal to / g. Here, the specific surface area of ​​silica is measured in accordance with the multipoint nitrogen adsorption method (BET method) described in JIS K-6430.

[0036] 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, per 100 parts by mass of rubber. 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, per 100 parts by mass of rubber.

[0037] Examples of silane coupling agents include sulfidesilanes 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.

[0038] In step K1, the amount of 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, per 100 parts by mass of silica. The upper limit of the amount of silane coupling agent is, for example, 20 parts by mass or 15 parts by mass, per 100 parts by mass of silica.

[0039] In step K1, carbon black, antioxidants, stearic acid, wax, zinc oxide, oil, etc., can be mixed together with rubber, silica, and silane coupling agents. One or any combination of these can be selected and used.

[0040] As carbon black, furnace blacks such as SAF, ISAF, HAF, FEF, and GPF can be used, as well as conductive carbon blacks such as acetylene black and Ketjen black. The carbon black may be granulated carbon black, which is processed with handling in mind, or it may be ungranulated carbon black. One or more of these types can be used.

[0041] Examples of anti-aging agents include aromatic amine-based anti-aging agents, amine-ketone-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, polyphenol-based anti-aging agents, dithiocarbamate-based anti-aging agents, and thiourea-based anti-aging agents. Anti-aging agents can be selected individually or in any combination from these.

[0042] In step K1, the mixture is kneaded so that the kneading temperature is kept constant. "Keeping the kneading temperature constant" includes keeping the kneading temperature within a certain range. Specifically, in step K1, the mixture is kneaded so that the measured temperature Tp is maintained at the target temperature Ts. At this time, the measured temperature Tp may be kept within plus or minus 5°C of the target temperature Ts. The target temperature Ts may be less than 140°C, 138°C or less, 135°C or less, 132°C or less, or 130°C or less. The target temperature Ts is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, and even more preferably 120°C or higher. If it is too low, it tends to take a long time to disperse the silica. Note that the target temperature Ts can be set appropriately considering the formulation, and especially considering the type of silane coupling agent.

[0043] In step K1, the mixture is kneaded for at least 10 seconds so that the kneading temperature is maintained within a certain range. Preferably, this is 20 seconds or more, more preferably 40 seconds or more, even more preferably 60 seconds or more, and even more preferably 70 seconds or more. This may be 1000 seconds or less, 800 seconds or less, 600 seconds or less, 400 seconds or less, 200 seconds or less, or 100 seconds or less.

[0044] The mixing temperature is maintained by adjusting the rotational speed of rotor 3. Specifically, the mixing temperature is maintained by adjusting the rotational speed of rotor 3 using PID control. Here, the rotational speed of rotor 3 is adjusted by PID control to set the measured temperature Tp to the target temperature Ts. PID control may be started from the beginning of mixing, or it may be started when the measured temperature Tp reaches a predetermined temperature.

[0045] During at least a portion of the time in process K1, the ram 7 is in a non-pressing state (i.e., a non-pressing state, which includes a state in which at least a portion of the mixing chamber 4 is an open system) while at least the rubber, silica, and silane coupling agent are mixed. This (specifically, mixing in a non-pressing state) allows volatile substances such as water to be discharged outside the mixing chamber 4, thereby reducing rotor 3 slippage caused by moisture. As a result, the degree of silica dispersion before the coupling reaction proceeds actively can be further increased. In addition, since water is generated as a by-product during the coupling reaction in process K3, the coupling reaction can proceed more efficiently because the moisture content is reduced. As a result, the low heat generation and wet road surface braking performance of the tire can be improved.

[0046] The non-pressure state may be continuous or intermittent. A continuous non-pressure state can be created, for example, by maintaining the ram 7 in an elevated position. An intermittent non-pressure state can be created, for example, by repeatedly lowering and raising the ram 7.

[0047] Non-pressing kneading is performed in the middle and / or final stages of process K1. That is, kneading is performed in the middle and / or final stages of process K1 in a non-pressing state. This is because the temperature tends to rise more easily in the middle and final stages of process K1 compared to the beginning of process K1, and the rotational speed of rotor 3 tends to decrease. By kneading in the non-pressing state in the middle and / or final stages of process K1 (i.e., by kneading in a state where the temperature does not rise easily), the decrease in the rotational speed of rotor 3 can be suppressed. On the other hand, it is preferable to perform kneading in the pressing state in the beginning of process K1.

[0048] The non-pressing time is preferably 10 seconds or more, more preferably 30 seconds or more, and even more preferably 50 seconds or more. By having a non-pressing time of 10 seconds or more, the moisture content in the kneading chamber 4 can be effectively reduced. Therefore, the dispersion of silica (specifically, the dispersion of silica before the coupling reaction proceeds) can be effectively improved, and the efficiency of the coupling reaction in step K3 can be effectively increased. If the non-pressing time is intermittent, "non-pressing time" refers to the total non-pressing time.

[0049] As already explained, in process K1, the rotational speed of rotor 3 is controlled by PID control to set the mixing temperature to the target temperature Ts. This (specifically, controlling the rotational speed of rotor 3 by PID control) effectively improves the low heat generation and wet road braking performance of the tire. This will be explained. If mixing were performed only in a pressed state (specifically, with the ram 7 pressing down on the material being mixed) during PID control of rotor 3, it would easily lead to a temperature rise due to shear heating, causing the rotational speed of rotor 3 to decrease, and therefore the silica dispersion (specifically, the dispersion of silica before the coupling reaction proceeds) would not proceed easily. In contrast, in this embodiment, by mixing in a non-pressed state, mixing can be performed in a state where the temperature rise is less than in the pressed state, thus suppressing the decrease in the rotational speed of rotor 3. As a result, the dispersion of silica (specifically, the dispersion of silica before the coupling reaction proceeds) can be effectively increased. Therefore, the low heat generation and wet road braking performance of the tire can be improved.

[0050] <2.1.2. Process K2 (Process of kneading while increasing the kneading temperature)> In step K2, the mixture is kneaded while increasing the kneading temperature. In step K2, the kneading temperature is raised to a temperature at which the coupling reaction proceeds actively (for example, 140°C or higher). Specifically, the kneading temperature is raised to the target temperature Ts of step K3. In step K2, the ram 7 can be used to press down on the material during kneading, i.e., to knead in a pressed state.

[0051] <2.1.3. Process K3 (Process for mixing to facilitate the coupling reaction)> In step K3, the mixture is kneaded while controlling the kneading temperature to allow the coupling reaction (reaction of silica and silane coupling agent) to proceed. Step K3 allows the coupling reaction to proceed actively with the silica dispersed, thereby increasing the efficiency of the coupling reaction and effectively reducing the cohesive force of the silica. Therefore, it is possible to effectively improve the dispersion of silica, which can improve the low heat generation and wet road braking performance of the tire. In addition, step K3 can also reduce the amount of electricity consumed for the manufacture of the rubber composition. This will be explained. If the kneading temperature were not controlled in step K3, the kneading time would be limited by the temperature rise due to shear heating, making it highly necessary to perform multiple re-kneadings (especially in silica-high-fill formulations). In contrast, in this embodiment, by controlling the kneading temperature in step K3, the limitation of kneading time due to temperature rise can be removed, allowing the kneading time to be extended and thus reducing the number of re-kneadings. As a result, the amount of electricity consumed for the manufacture of the rubber composition can be reduced. Furthermore, in step K3, the materials being kneaded can be kneaded in a pressed state using the ram 7.

[0052] In step K3, the mixture is kneaded so that the kneading temperature is kept constant. "Keeping the kneading temperature constant" includes keeping the kneading temperature within a certain range. Specifically in step K3, the mixture is kneaded so that the measured temperature Tp is kept at the target temperature Ts. At this time, the measured temperature Tp may be kept within plus or minus 5°C of the target temperature Ts. The target temperature Ts may be 140°C or higher, 142°C or higher, 145°C or higher, 148°C or higher, or 150°C or higher. If it is too low, it tends to take too long for the coupling reaction to proceed. 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 too high, gel may form.

[0053] In step K3, the mixture is kneaded for at least 20 seconds so that the kneading temperature is maintained within a certain range. Preferably, this is 40 seconds or more, more preferably 60 seconds or more, and even more preferably 80 seconds or more. This may be 2000 seconds or less, 1500 seconds or less, 1000 seconds or less, 500 seconds or less, 300 seconds or less, or 200 seconds or less.

[0054] Furthermore, maintaining the mixing temperature is done by adjusting the rotation speed of rotor 3, just as in process K1.

[0055] Then, if necessary, continue mixing until the predetermined discharge temperature is reached, open the drop door 9, and discharge the rubber mixture.

[0056] <2.1.4. Others> If necessary, the rubber mixture can be further kneaded to improve silica dispersibility or reduce Mooney viscosity. In other words, it can be re-kneaded.

[0057] A rubber mixture can be obtained by following the procedure described above.

[0058] <2.2. Step S2 (Step to obtain a rubber composition by kneading the rubber mixture and vulcanizing compounding agent)> In step S2, a rubber composition is obtained by kneading at least a rubber mixture and a vulcanizing compound. Examples of vulcanizing compounds include sulfur, organic peroxides and other vulcanizing agents, vulcanization accelerators, vulcanization accelerator aids, and vulcanization retarders. One or any combination of these can be selected and used as the vulcanizing compound. Examples of sulfur include powdered sulfur, precipitated sulfur, insoluble sulfur, and highly dispersible sulfur. One or any combination of these can be selected and used as the sulfur. Examples of vulcanization accelerators 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. One or any combination of these can be selected and used as the vulcanization accelerator. Kneading can be carried out in a kneader. Examples of kneaders include closed-type kneaders and open-roll kneaders. Examples of closed-type kneaders include Banbury mixers and kneaders.

[0059] 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, per 100 parts by mass of rubber. 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, per 100 parts by mass of rubber.

[0060] In the rubber composition, the amount of 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, per 100 parts by mass of silica. The upper limit of the amount of silane coupling agent is, for example, 20 parts by mass or 15 parts by mass, per 100 parts by mass of silica.

[0061] The rubber composition may further contain carbon black, an antioxidant, stearic acid, wax, zinc oxide, oil, sulfur, a vulcanization accelerator, and the like. The rubber composition may contain 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 rubber. The amount of vulcanization accelerator is preferably 0.1 to 5 parts by mass per 100 parts by mass of rubber.

[0062] The rubber composition can be used in the manufacture of tires. Specifically, it can be used in the manufacture of tire components. For example, the rubber composition can be used in the manufacture of tread rubber, sidewall rubber, chaff rubber, bead filler rubber, etc. The rubber composition can be used to manufacture one or any combination of these tire components.

[0063] <3. Each step in the tire manufacturing process> Next, some of the steps included in the tire manufacturing method of this embodiment will be described. Of these steps, the step of preparing the rubber composition has already been described.

[0064] The tire manufacturing method in this embodiment includes a step of producing an unvulcanized tire using a rubber composition. This step includes producing tire components containing the rubber composition, and producing an unvulcanized tire equipped with the tire components. Examples of tire components include tread rubber, sidewall rubber, chaff rubber, and bead filler rubber. Among these, tread rubber is preferred.

[0065] The tire manufacturing method in this embodiment may further include a step of vulcanizing and molding an unvulcanized tire. The tire obtained by the method of this embodiment may be a pneumatic tire.

[0066] <Various modifications can be made to the above-described embodiments.> Various modifications can be made to the embodiments described above. For example, one or more of the following modifications can be selected to modify the embodiments described above.

[0067] In the above-described embodiment, a configuration was explained in which the entire amount of silica is added in a kneading stage including steps K1 to K3. However, the above-described embodiment is not limited to this configuration. For example, the silica may be added in multiple kneading stages.

[0068] In the above-described embodiment, a configuration was explained in which the kneading temperature is controlled by the rotational speed of the rotor 3 in step K1. However, the above-described embodiment is not limited to this configuration. For example, the kneading temperature may be controlled by the temperature of the heating / cooling medium flowing through the jacket (not shown) of the closed-type kneader 1.

[0069] In the above-described embodiment, a configuration was explained in which the kneading temperature is controlled based on PID control in step K1. However, the above-described embodiment is not limited to this configuration. The kneading temperature may be controlled based on a control method other than PID control.

[0070] In the above-described embodiment, a configuration was explained in which the mixture is kneaded in a pressed state at the beginning of step K1, and kneaded in a non-pressed state in the middle and / or final stages. However, the above-described embodiment is not limited to this configuration. For example, the mixture may be kneaded in a non-pressed state from the beginning to the end of step K1.

[0071] In the above-described embodiment, a configuration was explained in which the kneading temperature is controlled in step K3. However, the above-described embodiment is not limited to this configuration. For example, it is not necessary to control the kneading temperature in step K3.

[0072] In the above-described embodiment, a configuration was explained in which the kneading temperature is controlled by the rotational speed of the rotor 3 in step K3. However, the above-described embodiment is not limited to this configuration. For example, the kneading temperature may be controlled by the temperature of the heating / cooling medium flowing through the jacket (not shown) of the closed-type kneader 1.

[0073] In the above-described embodiment, a configuration was explained in which the kneading temperature is controlled based on PID control in step K3. However, the above-described embodiment is not limited to this configuration. The kneading temperature may be controlled based on a control method other than PID control.

[0074] The above-described embodiment explains a configuration in which a rubber mixture and a vulcanizing compounding agent are kneaded together to obtain a rubber composition. However, the above-described embodiment is not limited to this configuration. For example, a rubber mixture may be considered as a rubber composition. [Examples]

[0075] Examples of the present invention are described below.

[0076] The raw materials and chemicals used in the examples are as follows. SBR "SBR1502" manufactured by JSR Corporation Modified Solution Polymerized SBR "HPR350" manufactured by JSR Corporation Silica "Nipseal AQ" manufactured by Tosoh Corporation Silane coupling agent "Si75" manufactured by Degussa. Stearic acid "Lunaq S20" manufactured by Kao Corporation Carbon Black "N339 Seast KH" manufactured by Tokai Carbon Co., Ltd. Oil "Process NC140" manufactured by JX Nippon Oil & Energy Corporation Zinc Oxide "Zinc Oxide Type 2" Manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd. Sulfur "5% Oil-Treated Sulfur" Manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: "Sunceller DM-G" manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2 "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd.

[0077] [Table 1]

[0078] Preparation of unvulcanized rubber in Comparative Example 1 The rubber and compounding agents were placed in a Banbury mixer according to Table 1 and mixed without PID control, and the mixture was discharged at 160°C (first mixing stage). In the first mixing stage, mixing was performed with downward force applied by the ram, i.e., under pressure. The mixture obtained in the first mixing stage was remixed in a Banbury mixer without PID control and discharged at 160°C (second mixing stage). The mixture obtained in the second mixing stage was remixed in a Banbury mixer without PID control and discharged at 160°C (third mixing stage). The mixture obtained in the third mixing stage was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0079] Preparation of unvulcanized rubber in Comparative Example 2 The rubber and compounding agents were placed in a Banbury mixer according to Table 1, and mixed with a single-stage PID control according to Table 2, with the mixture discharged at 160°C (first mixing stage). That is, the mixture was mixed at a target temperature of 150°C for 180 seconds, and the mixture was discharged at 160°C. In the first mixing stage, mixing was performed with downward force applied by the ram, i.e., under pressure. The mixture obtained in the first mixing stage was remixed in the Banbury mixer without PID control and discharged at 160°C (second mixing stage). The remixed mixture was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0080] Preparation of unvulcanized rubber in Comparative Example 3 The rubber and compounding agents were placed in a Banbury mixer according to Table 1, and mixed with a single-stage PID control according to Table 2, with the mixture discharged at 160°C (first mixing stage). That is, the mixture was mixed at a target temperature of 130°C for 80 seconds, and the mixture was discharged at 160°C. In the first mixing stage, mixing was performed with downward force applied by the ram, i.e., under pressure. The mixture obtained in the first mixing stage was remixed in the Banbury mixer without PID control and discharged at 160°C (second mixing stage). The remixed mixture was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0081] Preparation of unvulcanized rubber in Comparative Example 4 The rubber and compounding agents were placed in a Banbury mixer according to Table 1, and mixed using a two-stage PID control according to Table 2, with the mixture discharged at 160°C (first mixing stage). Specifically, the mixture was mixed at a target temperature of 130°C for 80 seconds, then at a target temperature of 150°C for 100 seconds, and the mixture was discharged at 160°C. In the first mixing stage, mixing was performed with downward force applied by the ram, i.e., under pressure. The mixture obtained in the first mixing stage was remixed in the Banbury mixer without PID control and discharged at 160°C (second mixing stage). The remixed mixture was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0082] Preparation of unvulcanized rubber in Example 1 The rubber and compounding agents were added to the Banbury mixer according to Table 1, and mixed using a two-stage PID control according to Table 2, with the mixture discharged at 160°C (first mixing stage). Specifically, mixing was performed at a target temperature of 130°C for 80 seconds, then at a target temperature of 150°C for 100 seconds, and the mixture was discharged at 160°C. During the first control time of 80 seconds in the first mixing stage, mixing was performed with the ram raised (i.e., non-pressed) for only the last 50 seconds. Otherwise, mixing was performed with downward force applied by the ram, i.e., in a pressed state. The mixture obtained in the first mixing stage was remixed in the Banbury mixer without PID control and discharged at 160°C (second mixing stage). The remixed mixture was mixed with sulfur and a vulcanization accelerator to obtain unvulcanized rubber (final stage).

[0083] Preparation of unvulcanized rubber in Example 2 Unvulcanized rubber was obtained using the same method as in Example 1, except that during the first 80-second control time of the first mixing stage, the ram was raised (i.e., in a non-pressing state) for only the last 10 seconds of the mixing process.

[0084] Preparation of unvulcanized rubber in Example 3 Unvulcanized rubber was obtained using the same method as in Example 1, except that during the first 80-second control time of the first mixing stage, the ram was raised (i.e., in a non-pressing state) for only the last 70 seconds of the mixing process.

[0085] Preparation of unvulcanized rubber in Example 4 Unvulcanized rubber was obtained using the same method as in Example 1, except that during the first 15 seconds and the last 15 seconds of the first control time of the first mixing stage, mixing was performed with downward force applied by the ram, i.e., in a pressing state, and during the middle 50 seconds, mixing was performed with the ram raised (i.e., in a non-pressing state).

[0086] Preparation of unvulcanized rubber in Example 5 Unvulcanized rubber was obtained in the same manner as in Example 1, except that a non-pressing state was intermittently created by repeatedly lowering and raising the ram during the first control time of 80 seconds in the first mixing stage. Of the 80-second first control time, a total of 50 seconds was spent in a non-pressing state.

[0087] Production of vulcanized rubber Unvulcanized rubber was vulcanized at 150°C for 30 minutes to obtain vulcanized rubber.

[0088] Energy consumption (electricity) Table 2 shows the amount of electricity consumed from the first mixing stage to the final stage, using an index where the amount of electricity in Comparative Example 1 is set to 100. A smaller index indicates lower electricity consumption and lower energy consumption.

[0089] Mooney viscosity The Mooney viscosity of unvulcanized rubber was measured in accordance with JIS K-6300 using a rotorless Mooney viscosity analyzer 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. The torque value in Mooney units was recorded 4 minutes after the start of rotor rotation. Table 2 shows the Mooney viscosity of each example, with the Mooney viscosity of Comparative Example 1 set to 100 as an index. A smaller index indicates lower Mooney viscosity and superior processability.

[0090] Braking performance on wet surfaces Using a Lübke rebound elasticity tester, the rebound elasticity (%) was measured in accordance with JIS K6255 at a temperature of 23°C. Table 2 shows the reciprocals (reciprocals of rebound elasticity) for each example, with the reciprocal of the rebound elasticity in Comparative Example 1 set to 100. A higher index indicates superior braking performance on wet road surfaces.

[0091] Fuel efficiency The tanδ of vulcanized rubber was measured using a viscoelasticity tester manufactured by Toyo Seiki Seisakusho Co., Ltd., in accordance with JIS K-6394. Tanδ was measured under the following conditions: frequency 10 Hz, dynamic strain 1.0%, temperature 60°C, and static strain (initial strain) 10%. Table 2 shows the tanδ of each example, with the tanδ of Comparative Example 1 set to 100. A smaller index indicates a lower tanδ and superior fuel efficiency.

[0092] [Table 2]

[0093] In Table 2, the one- or two-stage PID control performed in the first mixing stage refers to PID control that begins when the measured temperature reaches the target temperature. This PID control controls the rotational speed of the rotor.

[0094] The silane coupling agent ("Si75," manufactured by Degussa) hardly reacts with silica at 130°C, but reacts with silica at 150°C. By creating a state where the ram is not pressed for a predetermined time during kneading at 130°C or 125°C, it was possible to improve low heat generation and wet road braking performance, as well as reduce Mooney viscosity (see Comparative Example 4 and Examples 1-5, in particular Comparative Example 4 and Examples 1-3). In addition, it was possible to reduce the energy consumption (specifically, electrical energy) required for the manufacture of the rubber composition (see Comparative Example 4 and Examples 1-5, in particular Comparative Example 4 and Examples 1-3). This is thought to be because less torque was applied in the non-pressed state compared to the pressed state.

[0095] Furthermore, by employing at least one stage of PID control, the mixing time could be extended, reducing the number of re-mixing cycles. As a result, the energy consumption (specifically, electrical energy) required for manufacturing the rubber composition could be reduced. [Explanation of symbols]

[0096] 1...Closed kneader, 2...Casing, 2a...Opening, 3...Rotor, 4...Kneading chamber, 5...Neck section, 6...Inlet, 7...Ram, 8...Shaft, 9...Drop door, 11...Control unit, 13...Temperature sensor

Claims

1. kneading at least rubber, the silica, and the silane coupling agent in an internal kneader while controlling the kneading temperature so as to suppress a coupling reaction between the silica and the silane coupling agent; The internal mixer includes a mixing chamber, a neck portion located above the mixing chamber, and a ram that can move up and down in a space within the neck portion. kneading at least the rubber, the silica, and the silane coupling agent in a state where the ram is not pressing for at least a portion of the time during the process; A method for producing a rubber composition.

2. The method for producing a rubber composition according to claim 1 , wherein the partial time is 10 seconds or more.

3. The internal mixer is provided with a rotor in the mixing chamber, In the step, the rotation speed of the rotor is controlled by PID control so that the kneading temperature is set to a target temperature. A method for producing the rubber composition according to claim 1 or 2.

4. The method for producing a rubber composition according to any one of claims 1 to 3, further comprising a step of kneading while controlling the kneading temperature so as to promote the coupling reaction.

5. A step of producing a rubber composition by the method for producing a rubber composition according to any one of claims 1 to 4; and producing an unvulcanized tire using the rubber composition. Tire manufacturing method.

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