Method for producing rubber composition, and method for manufacturing tire

Abstract

To provide a method for producing a rubber composition which can improve productivity, and can prevent separation of a rubber composition discharged from a kneader, and a method for manufacturing a tire.SOLUTION: A method for producing a rubber composition includes a step of charging at least a modified polymer, silica and a silane coupling agent into a kneader (1), kneading the mixture in a kneading chamber (74) and then kneading the mixture in the kneading chamber (94) and controls rotation speed of a rotor (73) so that a kneading temperature of the kneading chamber (74) is set at 140°C or lower. Productivity can be improved by using the kneader (1). PID control is performed on rotation speed of the rotor (73) so that a kneading temperature of the kneading chamber (74) is set at 140°C or lower, which can avoid occurrence of scorch in the kneading chamber (74), accordingly can prevent separation of the kneaded object by kneading of the kneading chamber (94).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 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, which can react with silica during kneading and thus prevent the silica from coagulating.

[0004] Meanwhile, a method is known in which silica, a silane coupling agent, a rubber component, etc. are fed into a kneader equipped with two kneading chambers and then kneaded (see, for example, Patent Document 1). In this method, kneading is performed in the first kneading chamber, and the kneaded product formed by the kneading is transferred to the second kneading chamber, and kneading is also performed in the second kneading chamber. 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]

[0005] [Patent Document 1] US6828361B2 Summary of the Invention [Problem to be solved by the invention]

[0006] If silica, a silane coupling agent, and a modified polymer are added and kneaded without adding zinc oxide or an amine-based antiaging agent to a kneader such as that described above (i.e., a kneader equipped with two kneading chambers), the kneaded product may be broken into pieces, i.e., disintegrated, by kneading in the second kneading chamber. If the kneaded product disintegrates by kneading in the second kneading chamber, problems may occur in the subsequent process. For example, in the tire manufacturing process, a process is generally performed in which the kneaded rubber, i.e., the rubber composition, is extruded by an extruder, and the surface of the extruded product (hereinafter, sometimes referred to as the "rubber surface") may become excessively rough. In other words, the rubber surface may deteriorate. If the extruded product is in the form of a sheet, the sheet may break.

[0007] An object of the present invention is to provide a method for producing a rubber composition and a method for producing a tire, which are capable of improving productivity (specifically, production amount per unit time) and preventing the rubber composition from breaking apart when discharged from a kneader. [Means for solving the problem]

[0008] In order to solve this problem, the method for producing a rubber composition of the present invention comprises the steps of: A step of introducing at least a modified polymer, 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; kneading at least the modified polymer, the silica, and the silane coupling agent in the first kneading chamber; The kneaded material formed by the step of kneading in the first kneading chamber is transferred to the second kneading chamber and kneaded in the second kneading chamber, In the step of kneading in the first kneading chamber, the rotation speed of the first rotor is controlled so that the kneading temperature in the first kneading chamber is 140° C. or lower. Here, the expression "in the step of kneading in the first kneading chamber, the rotation speed of the first rotor is controlled so that the kneading temperature in the first kneading chamber is 140° C. or less" allows the control of the rotation speed of the first rotor to be further controlled in the step so that the kneading temperature in the first kneading chamber exceeds 140° C., but does not allow the control (i.e., the control of the rotation speed of the first rotor to make the kneading temperature in the first kneading chamber exceed 140° C.) to be performed for a certain period of time (specifically, 20 seconds or more). In other words, this expression allows the control (i.e., the control of the rotation speed of the first rotor to make the kneading temperature in the first kneading chamber exceed 140° C.) to be performed for less than 20 seconds. Note that the control (i.e., the control of the rotation speed of the first rotor to make the kneading temperature in the first kneading chamber exceed 140° C.) may be performed for 10 seconds or less, and of course, it does not have to be performed.

[0009] In the method for producing a rubber composition of the present invention, a kneader including a first kneading chamber and a second 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 a 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.

[0010] Moreover, since the rotation speed of the first rotor is controlled to keep the kneading temperature in the first kneading chamber at 140°C or less, it is possible to prevent premature vulcanization, i.e., scorch, from occurring in the first kneading chamber (for example, when the silane coupling agent has a sulfur group, the sulfur in the silane coupling agent reacts with the double bond of the rubber component, causing scorch). Therefore, the kneaded material can be given a certain degree of plasticity by kneading in the second kneading chamber downstream of the first kneading chamber. Therefore, it is possible to prevent the kneaded material from breaking apart due to kneading in the second kneading chamber.

[0011] In the above-mentioned manufacturing method, It is preferable that, in the step of feeding at least the modified polymer, the silica, and the silane coupling agent into the kneader, neither zinc oxide nor an amine-based antiaging agent is fed. According to this configuration, since neither zinc oxide nor an amine-based antiaging agent is added, scorch is likely to occur in the first kneading chamber. However, since the rotation speed of the first rotor is controlled to keep the kneading temperature in the first kneading chamber at 140°C or lower, it is possible to prevent scorch from occurring in the first kneading chamber.

[0012] In any of the above-mentioned manufacturing methods, In the step of kneading in the second kneading chamber, it is preferable that the rotation speed of the second rotor is controlled so that the kneading temperature in the second kneading chamber exceeds 140°C. According to this configuration, the rotation speed of the second rotor is controlled to make the kneading temperature in the second kneading chamber exceed 140°C, so that it is possible to stabilize the kneading temperature in the second kneading chamber, thereby suppressing gelation.

[0013] 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. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a conceptual diagram showing the configuration of a kneader in the present embodiment. [Figure 2A] 1 is a photograph of a kneaded product formed by kneading in an upper mixer in Comparative Example 1. [Figure 2B] 3 is a photograph of a mixture after kneading in a lower mixer in Comparative Example 1. [Diagram 3] 1 is a photograph of a mixture after kneading in an upper mixer in Comparative Example 2. [Figure 4A]1 is a photograph of a kneaded product formed by kneading in an upper mixer in Comparative Example 3. [Figure 4B] 1 is a photograph of a kneaded product after kneading in a lower mixer in Comparative Example 3. [Figure 5A] 2 is a photograph of a kneaded product formed by kneading in an upper mixer in Example 1. [Figure 5B] 3 is a photograph of the kneaded product after kneading in the lower mixer in Example 1. [Figure 6A] 4 is a photograph of a kneaded product formed by kneading in an upper mixer in Example 2. [Figure 6B] 1 is a photograph of the kneaded product after kneading in the lower mixer in Example 2. [Figure 7A] 1 is a photograph of a kneaded product formed by kneading in an upper mixer in Example 3. [Figure 7B] 1 is a photograph of the kneaded product after kneading in the lower mixer in Example 3. [Figure 8A] 1 is a photograph of a kneaded product formed by kneading in an upper mixer in Example 4. [Figure 8B] 1 is a photograph of the kneaded product after kneading in the lower mixer in Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described.

[0016] <1. Mixing machine> First, a kneader that can be used in this embodiment will be described.

[0017] As shown in FIG. 1, the kneading machine 1 of this embodiment includes a kneading chamber 74, a rotor 73 that can rotate 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 that can rotate in the kneading chamber 94.

[0018] 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.

[0019] 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.

[0020] The kneader 1 further includes a drop door 79 capable of opening and closing the outlet of the casing 72 .

[0021] 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.

[0022] The kneader 1 may include a hopper door 6a that can open and close the feed port 6.

[0023] 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.

[0024] 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.

[0025] The kneader 1 may be provided with holes opening into the wall surface of the channel. Through these holes, gas in the kneading chamber 94 can be sucked in and discharged by a suction device (not shown). Even in the absence of a suction device, gas in the kneading chamber 94 can be discharged through these holes.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The kneader 1 further includes a drop door 99 capable of opening and closing the outlet of the casing 92 .

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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., 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 kneaded material formed in the kneading chamber 74 passes through a channel into the casing 92, i.e., the kneading chamber 94, and is kneaded in the kneading chamber 94. The ram 7 does not reach the kneaded material in the kneading chamber 94, and therefore the kneading is performed without pressure.

[0035] <2. Method for producing rubber composition> Next, a method for producing the rubber composition according to the present embodiment will be described.

[0036] 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").

[0037] <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 kneading machine 1 and kneading them in the kneading chamber 74 (hereinafter referred to as "step K1"), and a step of transferring the kneaded product formed by 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 kneading machine 1 is used, it is possible to perform kneading in the kneading chamber 74 and kneading in the kneading chamber 94 in parallel. Therefore, it is possible to improve productivity compared to the case where a single machine is used. In other words, it is possible to improve the production amount per unit time. Moreover, in this embodiment, since the silica and the silane coupling agent are kneaded, it is possible to fix the silane coupling agent to the silica, and therefore the cohesive force of the silica can be reduced. Furthermore, as described later, since a rubber component containing a modified polymer is also kneaded, the cohesive strength of the silica can be further reduced (specifically, it is possible to reduce the silanol groups of the silica, and therefore the cohesive strength of the silica can be further reduced) and the modified polymer can be bound to the silica.

[0038] 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.

[0039] <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.

[0040] The rubber component includes a modified polymer. The modified polymer may have a functional group. The modified polymer may be modified by a modifying agent having a functional group. Examples of the functional group include an amino group, an alkoxyl group, a hydroxyl group, a carboxyl group, an epoxy group, a cyano group, and a halogen group. Among them, an amino group, an alkoxyl group, a hydroxyl group, and a carboxyl group are preferred, and an amino group and an alkoxyl group are more preferred. This is because the amino group can be adsorbed to the silanol group of silica. This is because the alkoxy group can chemically react with the silanol group of silica to form a Si-O-Si bond. The modified polymer may have one or more types of functional groups. Examples of the amino group include a primary amino group, a secondary amino group, and a tertiary amino group. Examples of the alkoxyl group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. The functional group may be introduced at the end of the polymer chain or may be introduced into the polymer chain, but is preferably introduced at the end. The modified polymer may be used alone or in combination. Examples of the modified polymer include modified SBR and modified BR. Among them, modified SBR is preferred.

[0041] The amount of the modified polymer in 100% by mass of the rubber component used in step K1 may be 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more. The amount of the modified polymer 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.

[0042] The rubber component may contain a rubber component other than the modified polymer. Examples of such rubber components include natural rubber, polyisoprene rubber, styrene butadiene rubber (SBR), polybutadiene rubber (BR), nitrile rubber, and chloroprene rubber. Any one or any combination of these may be selected and used.

[0043] 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.

[0044] 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 80 parts by mass or more, even more preferably 100 parts by mass or more, even more preferably 110 parts by mass or more, and even more preferably 120 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 145 parts by mass or less, and even more preferably 140 parts by mass or less, based on 100 parts by mass of the rubber component.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The amount of the antiaging agent added in step K1 is preferably as small as possible. The amount of the antiaging agent added in step K1 is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, based on 100 parts by mass of the rubber component added in step K1. It is particularly preferable that no antiaging agent is added to the kneader 1 in step K1.

[0051] Examples of amine-based antiaging agents include N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, alkylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, p-(p-toluenesulfonylamide)diphenylamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, and 2,2,4-trimethyl-1,2-dihydroquinoline polymers. Any one or any combination of these may be selected and used.

[0052] The amount of the amine-based antiaging agent added in step K1 is preferably as small as possible. The amount of the amine-based antiaging agent added in step K1 is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, based on 100 parts by mass of the rubber component added in step K1. It is particularly preferable that no amine-based antiaging agent is added to the kneader 1 in step K1.

[0053] The amount of zinc oxide added in step K1 is preferably as small as possible. The amount of zinc oxide added in step K1 is preferably 0.2 parts by mass or less, and more preferably 0.1 parts by mass or less, relative to 100 parts by mass of the rubber component added in step K1. It is particularly preferable that no zinc oxide is added to the kneader 1 in step K1.

[0054] In the step K1, PID control is performed on the rotation speed of the rotor 73. Specifically, PID control is performed on the rotation speed of the rotor 73 so that the kneading temperature in the kneading chamber 74, i.e., the measured temperature Tp, becomes 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 slightly lower than the target temperature Ts).

[0055] The target temperature Ts is 140°C or less, preferably 135°C or less, more preferably 130°C or less, more preferably 125°C or less, and even more preferably 120°C or less. Since the target temperature Ts is 140°C or less, it is possible to avoid premature vulcanization, i.e., scorching, in the kneading chamber 74, and therefore it is possible to prevent the kneaded material from breaking apart due to kneading in the kneading chamber 94 downstream of the kneading chamber 74. This will be explained. If the kneading temperature in the kneading chamber 74 is controlled to exceed 140°C, premature vulcanization, i.e., scorching, is likely to occur in the kneading chamber 74, and it is difficult to give the kneaded material a certain degree of plasticity due to kneading in the kneading chamber 94 downstream of the kneading chamber 74, and as a result, the kneaded material breaks apart. In contrast, in the method for producing a rubber composition according to the present embodiment, since the target temperature Ts is 140° C. or lower, it is possible to prevent premature vulcanization, i.e., scorching, from occurring in the kneading chamber 74, and therefore the kneaded material can be given a certain degree of plasticity by kneading in the kneading chamber 94 downstream of the kneading chamber 74. Therefore, it is possible to prevent the kneaded material from breaking apart due to kneading in the kneading chamber 94. On the other hand, the target temperature Ts may be, for example, 100° C. or higher, 105° C. or higher, or 110° C. or higher.

[0056] The PID control time can be set appropriately depending on, for example, the target temperature Ts and the type of silane coupling agent. The PID control may be performed for, for example, 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, 300 seconds or less, or 200 seconds or less.

[0057] <2.1.2. Step K2 (Step of Kneading in the Kneading Chamber 94)> In step K2, the kneaded material formed in step K1 is transferred to the kneading chamber 94 and kneaded in the kneading chamber 94. In order to transfer the kneaded material to the kneading chamber 94, the drop door 79 is opened, and the kneaded material can be dropped into the kneading chamber 94.

[0058] In step K2, PID control is performed on the rotation speed of the rotor 93. Specifically, PID control is performed on the rotation speed of the rotor 93 so that the kneading temperature in the kneading chamber 94, i.e., the measured temperature Tp, becomes 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 slightly lower than the target temperature Ts). By controlling the rotation speed of the rotor 93, it is possible to stabilize the kneading temperature in the kneading chamber 94, and therefore gelation can be suppressed.

[0059] The target temperature Ts is preferably higher than 140°C, more preferably 145°C or higher, even more preferably 148°C or higher, and even more preferably 150°C or higher. If it is higher than 140°C, 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.

[0060] 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, or 500 seconds or less.

[0061] 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. In other words, the rubber mixture (which can also be called a kneaded product) can be discharged from the kneader 1.

[0062] <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.

[0063] By the above procedure, a rubber mixture can be obtained.

[0064] <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.

[0065] 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 80 parts by mass or more, even more preferably 100 parts by mass or more, even more preferably 110 parts by mass or more, and even more preferably 120 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 145 parts by mass or less, and even more preferably 140 parts by mass or less, based on 100 parts by mass of the rubber component.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] <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.

[0070] 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.

[0071] 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.

[0072] <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.

[0073] 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 mixture formed in the kneading chamber 74 to the kneading chamber 94.

[0074] 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.

[0075] In the above embodiment, the configuration in which the rotation speed of the rotor 93 is PID-controlled in the step K2 has been described. However, the above embodiment is not limited to this configuration. Therefore, in the step K2, kneading may be performed in the kneading chamber 94 without PID-controlling the rotation speed of the rotor 93.

[0076] In the above embodiment, the target temperature Ts of the process K2 is higher than 140° C. However, the above embodiment is not limited to this configuration. The target temperature Ts of the process K2 may be 140° C. or lower.

[0077] 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.

[0078] 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

[0079] The following describes an embodiment of the present invention.

[0080] The raw materials and chemicals used are as follows: BR “BR730” Manufactured by JSR Modified solution polymerized SBR (i.e. modified S-SBR) "HPR840" manufactured by JSR Corporation Silica "Nipsil AQ" manufactured by Tosoh Corporation Silane coupling agent "Si75" manufactured by Degussa Carbon black "Diablack N234" manufactured by Mitsubishi Chemical Corporation Oil "Process NC140" manufactured by ENEOS Wax "OZOACE0355" manufactured by Nippon Seiro Co., Ltd. Stearic acid "Lunac S-20" manufactured by Kao Corporation

[0081] [Table 1]

[0082] Preparation of Unvulcanized Rubber in Comparative Example 1 According to Table 1, the rubber components (i.e. BR or modified S-SBR) and compounding ingredients were charged into a tandem mixer and mixed 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 300 seconds), then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded material was discharged from the tandem mixer. Note that the PID control of the lower mixer was started when the kneaded material formed in the upper mixer was transferred to the lower mixer.

[0083] Preparation of unvulcanized rubber in Comparative Example 2 - Single machine assumed mixing The rubber components and compounding ingredients were charged into a tandem mixer according to Table 1, and mixed 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 720 seconds), and the mixed material was discharged from the tandem mixer. In Comparative Example 2, mixing in the lower mixer was not performed.

[0084] Preparation of Unvulcanized Rubber in Comparative Example 3 According to Table 1, the rubber components and compounding ingredients were charged into the tandem mixer, mixed in the upper mixer with PID control, and then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded product was discharged from the tandem mixer. As the PID control of the upper mixer, the first PID control of the upper mixer with a control start temperature of 130°C, a target temperature of 130°C, and a control time of 120 seconds, and the second PID control of the upper mixer with a target temperature of 150°C and a control time of 180 seconds were performed. The second PID control of the upper mixer was started when the first PID control of the upper mixer was completed. The PID control of the lower mixer was started when the kneaded product formed in the upper mixer was transferred to the lower mixer.

[0085] Preparation of unvulcanized rubber in Example 1 The rubber components and compounding ingredients were fed into a tandem mixer according to Table 1, and mixed in the upper mixer with PID control (specifically, PID control with a control start temperature of 140°C, a target temperature of 140°C, and a control time of 300 seconds), and then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded product was discharged from the tandem mixer. Note that the PID control of the lower mixer was started when the kneaded product formed in the upper mixer was transferred to the lower mixer.

[0086] Preparation of unvulcanized rubber in Example 2 The rubber components and compounding ingredients were fed into a tandem mixer according to Table 1, and mixed in the upper mixer with PID control (specifically, PID control with a control start temperature of 130°C, a target temperature of 130°C, and a control time of 300 seconds), and then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded product was discharged from the tandem mixer. Note that the PID control of the lower mixer was started when the kneaded product formed in the upper mixer was transferred to the lower mixer.

[0087] Preparation of unvulcanized rubber in Example 3 The rubber components and compounding ingredients were fed into a tandem mixer according to Table 1, and mixed in the upper mixer with PID control (specifically, PID control with a control start temperature of 120°C, a target temperature of 120°C, and a control time of 300 seconds), and then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded product was discharged from the tandem mixer. Note that the PID control of the lower mixer was started when the kneaded product formed in the upper mixer was transferred to the lower mixer.

[0088] Preparation of unvulcanized rubber in Example 4 The rubber components and compounding ingredients were fed into a tandem mixer according to Table 1, and mixed in the upper mixer with PID control (specifically, PID control with a control start temperature of 110°C, a target temperature of 110°C, and a control time of 300 seconds), and then mixed in the lower mixer with PID control (specifically, PID control with a target temperature of 150°C and a control time of 420 seconds), and the kneaded product was discharged from the tandem mixer. Note that the PID control of the lower mixer was started when the kneaded product formed in the upper mixer was transferred to the lower mixer.

[0089] [Table 2]

[0090] As shown in FIG. 2B, when the upper mixer was used for mixing under PID control with a target temperature of 150° C. and a control time of 300 seconds, and then the lower mixer was used for mixing, most of the mixture discharged from the tandem mixer was in the form of granules of approximately 10 mm or less (see Comparative Example 1).

[0091] As shown in FIG. 4B, even when the material was mixed in the upper mixer under first PID control of the upper mixer with a target temperature of 130° C. and a control time of 120 seconds and second PID control of the upper mixer with a target temperature of 150° C. and a control time of 180 seconds, and then mixed in the lower mixer, most of the mixed material discharged from the tandem mixer was in the form of granules of approximately 10 mm or less (see Comparative Example 3).

[0092] As shown in Fig. 5B, when the upper mixer was used for mixing under PID control with a target temperature of 140°C and a control time of 300 seconds, and then the lower mixer was used for mixing, about 40-50% (by volume) of the mixture discharged from the tandem mixer was solidified (see Example 1). Among the remaining mixture, several lumps of several cm (typically about 5 cm) were observed.

[0093] As shown in FIG. 6B, when the upper mixer was used for mixing under PID control with a target temperature of 130° C. and a control time of 300 seconds, and then the lower mixer was used for mixing, approximately 80% (by volume) of the mixture discharged from the tandem mixer was consolidated (see Example 2).

[0094] As shown in FIG. 7B, when the upper mixer was used for mixing under PID control with a target temperature of 120° C. and a control time of 300 seconds, and then the lower mixer was used for mixing, approximately 90% (by volume) or more of the mixture discharged from the tandem mixer was consolidated (see Example 3).

[0095] As shown in FIG. 8B, when the upper mixer was used for mixing under PID control with a target temperature of 110°C and a control time of 300 seconds, and then the lower mixer was used for mixing, approximately 90% (by volume) or more of the mixture discharged from the tandem mixer was consolidated (see Example 4). [Explanation of symbols]

[0096] Reference Signs List 1... kneader, 5... neck, 6... inlet, 6a... hopper door, 7... ram, 8... shaft, 11... control section, 72... casing, 73... rotor, 74... kneading chamber, 76... temperature sensor, 79... drop door, 92... casing, 93... rotor, 94... kneading chamber, 96... temperature sensor, 99... drop door

Claims

1. A step of introducing at least a modified polymer, 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; kneading at least the modified polymer, the silica, and the silane coupling agent in the first kneading chamber; The kneaded material formed by the step of kneading in the first kneading chamber is transferred to the second kneading chamber and kneaded in the second kneading chamber, In the step of kneading in the first kneading chamber, the rotation speed of the first rotor is controlled so that the kneading temperature in the first kneading chamber is 140° C. or less. A method for producing a rubber composition.

2. 2. The method for producing a rubber composition according to claim 1, wherein in the step of feeding at least the modified polymer, the silica, and the silane coupling agent into the kneader, neither zinc oxide nor an amine-based antioxidant is added.

3. The method for producing a rubber composition according to claim 1 , wherein in the step of kneading in the second kneading chamber, a rotation speed of the second rotor is controlled so that a kneading temperature in the second kneading chamber exceeds 140° C.

4. A step of preparing a rubber composition by the method for producing a rubber composition according to any one of claims 1 to 3; and producing an unvulcanized tire using the rubber composition. A method for manufacturing tires.

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