JP7252754B2 - Method for producing rubber composition and method for producing tire - Google Patents

Description

The present disclosure relates to a method of manufacturing a rubber composition and a method of manufacturing a tire.

Silica, which is used as a reinforcing filler for rubber, has a silanol group and therefore tends to aggregate due to hydrogen bonding. Therefore, it is not easy to disperse silica well. In particular, it is difficult to disperse silica well when the silica is highly filled or when silica with a small particle size is used.

Good dispersion of silica can reduce Mooney viscosity, an index of processability.

JP 2013-18890 A

An object of the present disclosure is to provide a method for producing a rubber composition capable of reducing Mooney viscosity.

In the method for producing a rubber composition according to the present disclosure, at least rubber, silica, and a silane coupling agent are charged into an internal kneader so as to satisfy the first formula, and the reaction between silica and the silane coupling agent is suppressed. a step of kneading while controlling the kneading temperature; and a step of kneading in an internal kneader while controlling the kneading temperature so that the reaction between silica and the silane coupling agent proceeds.
The first formula is
5<volume of silica to be put in × fill factor<30
is. In the first formula, the volume of silica is expressed in cubic decimeters.
The fill factor is calculated by the second formula, and the second formula is
Fill factor = (volume of object to be kneaded/capacity of kneading chamber of internal kneader) x 100
is.

The method for manufacturing a tire according to the present disclosure includes the steps of manufacturing a rubber composition by the method for manufacturing a rubber composition according to the present disclosure, and manufacturing an unvulcanized tire using the rubber composition.

1 is a conceptual diagram showing the configuration of a closed kneader that can be used in Embodiment 1. FIG.

A method for producing a rubber composition according to one aspect of the present disclosure includes charging at least rubber, silica and a silane coupling agent into an internal kneader so as to satisfy the first formula, and reacting the silica and the silane coupling agent ( A step of kneading while controlling the kneading temperature so as to suppress the silane reaction (hereinafter referred to as “silane reaction”) (hereinafter referred to as “step K1”) and controlling the kneading temperature so that the silane reaction proceeds and a step of kneading with a closed type kneader (hereinafter referred to as “step K3”). The method for producing a rubber composition of this embodiment may include a step of kneading while increasing the kneading temperature (hereinafter referred to as “step K2”) between steps K1 and K3. .
The first formula is
5<volume of silica to be put in × fill factor<30
is. In the first formula, the volume of silica is expressed in cubic decimeters. In addition, hereinafter, "the volume of charged silica×fill factor" may be referred to as "α".
The fill factor is calculated by the second formula, and the second formula is
Fill factor = (volume of object to be kneaded/capacity of kneading chamber of internal kneader) x 100
is.

The method for producing a rubber composition of this aspect can reduce the Mooney viscosity. The mechanism leading to such effects is presumed as follows.

In order to suppress the silane reaction (reaction of silica and silane coupling agent), at least rubber, silica and silane coupling agent are kneaded while controlling the kneading temperature, so before the silane reaction actively progresses , silica can be effectively dispersed. Therefore, a state in which silica is dispersed can be created before the silane reaction proceeds actively. After that, since the kneading is performed while controlling the kneading temperature so that the silane reaction proceeds, the silane reaction can proceed actively while the silica is dispersed. Therefore, the efficiency of the silane reaction can be increased, and the cohesive force of silica can be effectively reduced. As a result, it is considered that silica is finely dispersed and the Mooney viscosity is lowered.

Moreover, since α exceeds 5, it can be said that the volume of silica in the kneading chamber is not excessively low and the fill factor is not excessively low. Therefore, it is possible to effectively shear the object to be kneaded. Therefore, the Mooney viscosity can be effectively reduced.

Moreover, since α is less than 30, it can be said that the ratio of silica in the kneading chamber is not excessively high and the fill factor is not excessively high. Therefore, it is possible to effectively shear the object to be kneaded. Therefore, the Mooney viscosity can be effectively reduced.

According to the method for producing a rubber composition of this aspect, when the rubber mixture discharged from the internal kneader is formed into a sheet, it may be possible to obtain a sheet-like rubber in good condition. It is believed that this is because the method for producing a rubber composition according to this embodiment can improve the dispersion of silica.

Step K1 may comprise kneading such that the kneading temperature is kept constant. With this configuration, it is possible to suppress the kneading temperature from rising as the kneading progresses, so that the silane reaction can be effectively suppressed. Thus, silica can be dispersed more effectively in step K1.

Step K3 may comprise kneading such that the kneading temperature is kept constant. According to this configuration, it is possible to suppress the kneading temperature from rising as the kneading progresses, so that the silane reaction can be promoted while suppressing gelation.

The fill factor may be from 50% to 66%. According to this configuration, since the fill factor is 50% or more, the material to be kneaded can be effectively sheared. Therefore, when it is desired to raise the kneading temperature to a predetermined temperature, the temperature can be raised without any problem. Moreover, since the fill factor is 66% or less, shear can be effectively applied to the object to be kneaded.

<<Embodiment 1>>
From here, Embodiment 1 which is an example of this mode is described.

<1. Closed kneader>
First, a closed kneader that can be used in Embodiment 1 will be described.

As shown in FIG. 1, the closed kneader 1 includes a kneading section 4 having a casing 2 and a rotor 3, a neck section 5 located above the kneading section 4 and having a cylindrical space therein, and a neck section. 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 portion 4.

An opening 2 a is provided in the central portion of the upper surface of the casing 2 . A neck portion 5 having a cylindrical space inside is provided above the opening portion 2a. A side face of the neck portion 5 is provided with an inlet 6 into which rubber and a compounding agent can be introduced. Two or more inlets 6 may be provided in order to charge the rubber and the compounding agent through separate inlets. The rubber and compounding agent charged from the charging port 6 pass through the cylindrical space of the neck portion 5 and are charged into the casing 2 from the opening 2 a of the casing 2 .

The ram 7 has a shape capable of closing the opening 2 a of the casing 2 . The ram 7 can move vertically in the cylindrical space of the neck portion 5 by means of a shaft 8 connected to its upper end. The ram 7 can push and pressurize the rubber existing in the casing 2 by its own weight or the pressing force from the shaft 8 .

The drop door 9 is closed during kneading. The drop door 9 is opened after the kneading is finished.

A rotation speed of a motor (not shown) that rotates the rotor 3 is adjusted based on a control signal from the control section 11 . The control unit 11 controls the rotation speed of the motor based on the temperature information (specifically, the actually measured temperature Tp) in the kneading unit 4 sent from the temperature sensor 13 . The rotation speed of the motor can be freely changed by the control unit 11 . The motor can be, for example, an inverter motor.

In order to determine the rotation speed of the motor, the PID calculation processing section provided inside the control section 11 proportionally ( P), integration (I) and differentiation (D). Specifically, the PID calculation processing unit performs a proportional (P) operation for calculating the control amount in proportion to the difference (deviation e) between the measured temperature Tp and the target temperature Ts, and an integral operation for integrating the deviation e along the time axis. The rotational speed of the motor is determined by the total value of each control amount obtained by the integration (I) operation for calculating the control amount from the value and the differentiation (D) operation for calculating the control amount from the gradient of the change of the deviation e, that is, the derivative value. to decide. PID is an abbreviation for Proportional Integral Differential.

<2. Each step of the method for producing a rubber composition>
Next, some steps included in the method for producing a rubber composition in Embodiment 1 will be described.

The method for producing a rubber composition according to Embodiment 1 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 compounding agent to obtain a rubber composition. (hereinafter referred to as “step S2”).

<2.1. Step S1 (Step of Producing Rubber Mixture)>
In step S1, at least rubber, silica, and a silane coupling agent are charged into the internal kneader 1 so as to satisfy the first formula, and the silane reaction (reaction between silica and the silane coupling agent) is suppressed. A step K1 of kneading while controlling the kneading temperature, then a step K2 of kneading while increasing the kneading temperature, and then a step of kneading while controlling the kneading temperature so that the silane reaction proceeds. K3.

<2.1.1. Step K1 (Step of kneading to suppress silane reaction)>
In step K1, at least rubber, silica and a silane coupling agent are charged into the internal kneader 1 so as to satisfy the first formula, and the silane reaction (reaction between silica and the silane coupling agent) is suppressed. These are kneaded while controlling the kneading temperature.

The first formula is
5 <Volume of silica charged into closed kneader 1 × fill factor <30
is. In the first formula, the volume of silica is expressed in cubic decimeters. The volume of silica can be obtained, for example, based on the mass of silica and the specific gravity of silica. 1.95 kg/dm ³ is adopted as the specific gravity of silica.

Regarding the first formula, “the volume of silica charged into the internal kneader 1×fill factor” (α) is preferably 6 or more, more preferably 7 or more. α is preferably 28 or less, more preferably 27 or less.

The fill factor is calculated by the second formula.
Fill factor = (volume of object to be kneaded/capacity of kneading chamber of internal kneader 1) x 100
In the second formula, the volume of the object to be kneaded can be expressed in cubic decimeters. The volume of the object to be kneaded can be obtained based on the mass of the object to be kneaded and the density of the object to be kneaded. Here, the mass of the object to be kneaded can be the sum of the mass of compounding agents excluding vulcanization compounding agents (for example, sulfur and vulcanization accelerator) and the mass of rubber. In the second formula, the kneading chamber volume can also be expressed in cubic decimeters. The capacity of the kneading chamber is not particularly limited. The capacity of the kneading chamber can be, for example, from 150 dm ³ to 450 dm ³ . Note that 1 cubic decimeter corresponds to 1 L.

The fill factor is preferably 50% or higher, more preferably 52% or higher, still more preferably 54% or higher, and even more preferably 56% or higher. The fill factor is preferably 66% or less, more preferably 64% or less, even more preferably 62% or less, still more preferably 60% or less.

Examples of rubber 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 rubber.

Modified rubber may be used as the rubber. Examples of modified rubber include modified SBR and modified BR. The modified rubber can have functional groups containing heteroatoms. The functional group may be introduced at the end of the polymer chain or into the polymer chain, preferably at the end. Functional groups include amino groups, alkoxyl groups, hydroxyl groups, carboxyl groups, epoxy groups, cyano groups, halogen groups and the like. Among them, an amino group, an alkoxyl group, a hydroxyl group, and a carboxyl group are preferred. The modified rubber can have at least one of the exemplified functional groups. Amino groups include primary amino groups, secondary amino groups, and tertiary amino groups. Alkoxyl groups include methoxy, ethoxy, propoxy, 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 due to chemical reaction with silanol groups of silica. The amount of modified rubber in 100% by mass of rubber used in step K1 may be 10% by mass or more, 20% by mass or more, or 30% by mass or more. The amount of modified rubber in 100% by mass of rubber used in step K1 may be 90% by mass or less, 80% by mass or less, or 70% by mass or less.

Examples of silica include wet silica and dry silica. Among them, wet silica is preferable. Wet silica may include precipitated silica. The specific surface area of silica measured by a nitrogen adsorption method may be, for example, 80 m ² /g or more, 120 m ² /g or more, 140 m ² /g or more, or 160 m ² /g or more. may be The specific surface area of silica may be, for example, 300 m ² /g or less, 280 m ² /g or less, 260 m ² /g or less, or 250 m ² /g or less. good. Here, the specific surface area of silica is measured according to the multi-point nitrogen adsorption method (BET method) described in JIS K-6430.

In step K1, the amount of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, relative to 100 parts by mass of rubber. The amount of silica may be 30 parts by mass or more, 40 parts by mass or more, or 60 parts by mass or more. The amount of silica is preferably 160 parts by mass or less, more preferably 140 parts by mass or less, and still more preferably 120 parts by mass or less with respect to 100 parts by mass of rubber. The amount of silica may be 100 parts by mass or less, or may be 90 parts by mass or less.

Silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilyl) butyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)disulfide and other sulfidesilanes, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyl Mercaptosilanes such as dimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane may be mentioned. One or any combination of these can be selected and used.

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 still more preferably 5 parts by mass or more with respect to 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 with respect to 100 parts by mass of silica.

In step K1, carbon black, antioxidant, stearic acid, wax, zinc oxide, oil and the like can be kneaded together with rubber, silica and silane coupling agent. One or any combination of these can be selected and used.

Examples of carbon black that can be used include furnace blacks such as SAF, ISAF, HAF, FEF and GPF, as well as conductive carbon blacks such as acetylene black and ketjen black. The carbon black may be agglomerated carbon black that is agglomerated in consideration of its handleability, or may be non-agglomerated carbon black. 1 type, or 2 or more types can be used among these.

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. An anti-aging agent etc. can be mentioned. Antiaging agents can be used by selecting one or any combination from these.

In step K1, kneading is performed so that the kneading temperature is kept constant. "The kneading temperature is kept constant" includes that the kneading temperature is kept within a certain range. Specifically, in step K1, kneading is performed so that the actually measured temperature Tp is maintained at the target temperature Ts. At this time, the measured temperature Tp can be kept within ±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, still more preferably 115° C. or higher, and even more preferably 120° C. or higher. If it is too low, it tends to take longer to disperse the silica. Note that the target temperature Ts can be appropriately set in consideration of the composition, particularly the type of silane cup agent.

In step K1, kneading is carried out for 10 seconds or more so that the kneading temperature is kept within a certain range. It is preferably 20 seconds or longer, more preferably 30 seconds or longer, and even more preferably 40 seconds or longer. It 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. may

The kneading temperature is maintained by adjusting the rotation speed of the rotor 3. Specifically, the kneading temperature is maintained by adjusting the rotation speed of the rotor 3 by PID control. Here, the rotation speed of the rotor 3 is adjusted by PID control for making the actually measured temperature Tp the target temperature Ts. PID control may be started from the beginning of kneading, or may be started when the actually measured temperature Tp reaches a predetermined temperature.

<2.1.2. Step K2 (Step of kneading while increasing the kneading temperature)>
In step K2, kneading is performed while increasing the kneading temperature. In step K2, the kneading temperature is raised to a temperature (for example, 140° C. or higher) at which the silane reaction proceeds actively. Specifically, the kneading temperature is raised to the target temperature Ts of step K3.

<2.1.3. Step K3 (Step of kneading to promote silane reaction)>
In step K3, kneading is performed while controlling the kneading temperature so that the silane reaction (reaction of silica and the silane coupling agent) proceeds.

In step K3, kneading is performed so that the kneading temperature is kept constant. "The kneading temperature is kept constant" includes that the kneading temperature is kept within a certain range. Specifically, in step K3, kneading is performed so that the actually measured temperature Tp is maintained at the target temperature Ts. At this time, the measured temperature Tp can be kept within ±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 to proceed with the silane reaction. 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 this is too high, gels may occur.

In step K3, kneading is performed for 20 seconds or longer so that the kneading temperature is kept within a certain range. It is preferably 40 seconds or longer, more preferably 60 seconds or longer, and even more preferably 80 seconds or longer. It 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. may

The kneading temperature is maintained by adjusting the rotational speed of the rotor 3, as in step K1.

After that, if necessary, kneading is continued up to a predetermined discharge temperature, and the drop door 9 is opened to discharge the rubber mixture.

<2.1.4. Other>
The rubber mixture can be further kneaded as required. For example, silica and a silane coupling agent can be optionally added to the rubber mixture and further kneaded. The silica added in this step may be of the same type as the silica charged in step K1, or may be of a different type. The silane coupling agent added in this step may be of the same type as the silane coupling agent introduced in step K1, or may be of a different type.

A rubber mixture can be obtained by the procedure described above.

<2.2. Step S2 (Step of kneading the rubber mixture and the vulcanization compounding agent to obtain a rubber composition)>
In step S2, at least the rubber mixture and the vulcanizing compounding agent are kneaded to obtain a rubber composition. Examples of vulcanization compounding agents include vulcanization agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization accelerator auxiliaries, vulcanization retarders, and the like. One or any combination of these vulcanizing compounding agents can be selected and used. Examples of sulfur include powdered sulfur, precipitated sulfur, insoluble sulfur, and highly dispersible sulfur. Sulfur can be used by selecting one or any combination from these. Vulcanization accelerators include sulfenamide vulcanization accelerators, thiuram vulcanization accelerators, thiazole vulcanization accelerators, thiourea vulcanization accelerators, guanidine vulcanization accelerators, and dithiocarbamate vulcanization accelerators. etc. can be mentioned. Vulcanization accelerators can be used by selecting one or any combination thereof. Kneading can be performed with a kneader. Examples of the kneader include a closed kneader and an open roll. A Banbury mixer, a kneader, etc. can be mentioned as a closed type kneader.

In the rubber composition, the amount of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, relative to 100 parts by mass of rubber. The amount of silica may be 30 parts by mass or more, 40 parts by mass or more, or 60 parts by mass or more. The amount of silica is preferably 160 parts by mass or less, more preferably 140 parts by mass or less, and still more preferably 120 parts by mass or less with respect to 100 parts by mass of rubber. The amount of silica may be 100 parts by mass or less, or may be 90 parts by mass or less.

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 still more preferably 5 parts by mass or more with respect to 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 with respect to 100 parts by mass of silica.

The rubber composition may further include carbon black, antioxidants, stearic acid, waxes, zinc oxide, oils, sulfur, vulcanization accelerators, and the like. The rubber composition can 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 with respect to 100 parts by mass of rubber. The amount of vulcanization accelerator is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of rubber.

The rubber composition can be used in making tires. Specifically, it can be used for producing a tire member that constitutes a tire. For example, the rubber composition can be used to make tread rubbers, sidewall rubbers, Cheha rubbers, bead filler rubbers, and the like. The rubber composition can be used to make one or any combination of these tire components.

<3. Each step of tire manufacturing method>
Next, some of the steps included in the tire manufacturing method according to Embodiment 1 will be described. Of these steps, the step of producing the rubber composition has already been explained.

A method for manufacturing a tire in Embodiment 1 includes a step of manufacturing an unvulcanized tire using a rubber composition. This process includes making a tire component that includes the rubber composition and making an unvulcanized tire comprising the tire component. Examples of tire components include tread rubber, sidewall rubber, chaha rubber, and bead filler rubber. Among them, tread rubber is preferred.

The tire manufacturing method in Embodiment 1 can further include a step of vulcanizing and molding the unvulcanized tire. The tire obtained by the method of Embodiment 1 can be a pneumatic tire.

<Various modifications can be made to Embodiment 1>
Various modifications can be made to the method for manufacturing the rubber composition and the method for manufacturing the tire in Embodiment 1. For example, one or more of the following modifications can be selected to modify the first embodiment.

In the first embodiment described above, the configuration in which the kneading temperature is controlled by the rotation speed of the rotor 3 in step K1 has been described. However, Embodiment 1 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 kneader 1 or by the pressing force of the ram 7 . Any combination of these may be used to control the kneading temperature.

In the first embodiment described above, the configuration in which the kneading temperature is controlled based on PID control in step K1 has been described. However, Embodiment 1 is not limited to this configuration. The kneading temperature may be controlled based on a control method other than PID control.

In the first embodiment described above, the configuration in which the kneading temperature is controlled by the rotational speed of the rotor 3 in step K3 has been described. However, Embodiment 1 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 kneader 1 or by the pressing force of the ram 7 . Any combination of these may be used to control the kneading temperature.

In the first embodiment described above, the configuration in which the kneading temperature is controlled based on PID control in step K3 has been described. However, Embodiment 1 is not limited to this configuration. The kneading temperature may be controlled based on a control method other than PID control.

In the first embodiment described above, the configuration of obtaining the rubber composition by kneading the rubber mixture and the vulcanization compounding agent has been described. However, Embodiment 1 is not limited to this configuration. For example, a rubber mixture may be considered a rubber composition.

Examples of the present disclosure are described below.

Raw materials and chemicals used in the examples are shown below.
SBR1 “SBR1502” manufactured by JSR SBR2 “SBR1723” (oil content 27% by mass) NR RSS#3 manufactured by JSR
Carbon black “SEAST KH” Silica “9100GR” (BET=235m ² /g) manufactured by Tokai Carbon Co., Ltd. Oil “Process NC140” manufactured by Evonik Silane coupling agent manufactured by JX Nikko Nippon Oil “Si75” Anti-aging agent manufactured by Degussa “ Nocrac 6C” Zinc oxide manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. “Type 2 zinc oxide” Wax manufactured by Mitsui Kinzoku Co., Ltd. “OZOACE0355” Stearic acid manufactured by Nippon Seiro Co., Ltd. “Industrial stearic acid” Sulfur manufactured by Kao Corporation “5% oil-treated powder Sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator “Noccellar NS-P” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Calculation of fill factor The fill factor was calculated by the following formula.
Fill factor = (volume of object to be kneaded/capacity of kneading chamber of B-type Banbury mixer) x 100
The volume of the object to be kneaded was obtained based on the mass of the object to be kneaded and the density of the object to be kneaded. Here, the mass of the object to be kneaded was obtained by summing the mass of the compounding agents excluding sulfur and the vulcanization accelerator and the mass of the rubber. The kneading chamber volume was 260 cubic decimeters.

Calculation of α α was calculated by the following formula.
α=Volume of silica fed into the B-type Banbury mixer×Fill factor In this formula, the volume of silica is expressed in cubic decimeters. The volume of silica was obtained based on the mass of silica and the specific gravity of silica. 1.95 kg/dm ³ was adopted as the specific gravity of silica.

Preparation of unvulcanized rubber in Comparative Examples 1, 2, 4, 6 and 7 According to Table 1, the compounding agents excluding sulfur and the vulcanization accelerator and the rubber were put into a B-type Banbury mixer, and the target temperature Ts = The mixture was kneaded at 150°C and discharged at 160°C to obtain a rubber mixture. The rubber mixture, sulfur and vulcanization accelerator were charged into a B-type Banbury mixer to obtain unvulcanized rubber.

Preparation of unvulcanized rubber in Examples 1 to 3 and Comparative Examples 3 and 5 According to Table 1, the compounding agents excluding sulfur and the vulcanization accelerator and rubber were put into a B-type Banbury mixer, and the target temperature Ts = The mixture was kneaded at 130° C., then kneaded at the target temperature Ts=150° C., and discharged at 160° C. to obtain a rubber mixture. The rubber mixture, sulfur and vulcanization accelerator were then charged into a B-type Banbury mixer to obtain an unvulcanized rubber.

Mooney Viscosity The Mooney viscosity of the unvulcanized rubber was measured according to JIS K-6300 using a rotorless Mooney measuring machine manufactured by Toyo Seiki Seisakusho. To measure the Mooney viscosity, the unvulcanized rubber was preheated at 100° C. for 1 minute, then the rotor was rotated, and the torque value was recorded in Mooney units 4 minutes after the rotor started to rotate. Table 1 shows the Mooney viscosities of each example, with the Mooney viscosities of Comparative Example 1 being 100. The smaller the index, the lower the Mooney viscosity and the better the workability.

State of unvulcanized rubber sheet The unvulcanized rubber was formed into a sheet with an 8-inch roll, and the state of the surface and both ends was observed. When the surface and both ends were in a smooth state, it was judged as "good", and when the surface was rough and both ends were jagged, it was judged as "poor".

In Table 1, the first temperature control means PID control started when the measured temperature Tp reaches the target temperature Ts. The first temperature control time is the time (length of time) during which the first temperature control is performed. The second temperature control also means PID control started when the measured temperature Tp reaches the target temperature Ts. The second temperature control time is the time (length of time) during which the second temperature control is performed.

In the first temperature control of Examples 1 to 3 and Comparative Examples 3 and 5, the measured temperature Tp fell within the range of plus or minus 5°C of the target temperature Ts. Also in the second temperature control of Examples 1 to 3 and Comparative Examples 3 and 5, the measured temperature Tp fell within the range of plus or minus 5° C. of the target temperature Ts. Also in the temperature control of Comparative Examples 1, 2, 4, 6 and 7, the temperature fell within the range of plus or minus 5°C of the target temperature Ts.

The silane coupling agent (“Si75” manufactured by Degussa) hardly reacts with silica at 130°C, but reacts with silica at 150°C. Next, by following the procedure of kneading at 150° C. (second temperature control), the Mooney viscosity could be reduced (see, for example, Comparative Example 1 and Example 1). This procedure also improved the condition of the unvulcanized rubber sheet (see, for example, Comparative Example 1 and Example 1).

The effect of improving the reaction rate by this procedure (the procedure of kneading at 130° C. and kneading at 150° C.) was greater when α=21 than when α=4 and α=31. Specifically, when α=21, the improvement effect was −15 points (see Comparative Example 1 and Example 1). On the other hand, when α=4, the improvement effect was −2 points (see Comparative Examples 2 and 3). In the case of α=31, the improvement effect was −7 points (see Comparative Examples 4 and 5). Moreover, the effect of improving the reaction rate by this procedure was greater when α=8 and when α=27 than when α=4 and when α=31.

Claims (3)

At least rubber, silica, and a silane coupling agent are put into an internal kneader equipped with a rotor so as to satisfy the first formula, and the kneading temperature is controlled so as to suppress the reaction between the silica and the silane coupling agent. A process of kneading while
A step of kneading with the internal kneader while controlling the kneading temperature so that the reaction proceeds,
The first formula is
5<Volume of the silica to be introduced × fill factor <30
and
In the first formula, the volume of silica is expressed in cubic decimeters,
The fill factor is calculated by a second formula, wherein the second formula is
Fill factor = (volume of object to be kneaded/capacity of kneading chamber of internal kneader) x 100
and
In the first formula, a numerical value represented by a ratio based on 1 is substituted for the fill factor,
In the step of kneading so as to suppress the reaction, the rotation speed of the rotor is controlled by Proportional Integral Differential control in order to set the kneading temperature to the target temperature,
In the step of kneading so that the reaction proceeds, the rotation speed of the rotor is controlled by Proportional Integral Differential control in order to set the kneading temperature to the target temperature.
A method for producing a rubber composition. The method for producing a rubber composition according to claim 1, wherein the fill factor is 50% to 66%. A step of producing a rubber composition by the method for producing a rubber composition according to claim 1 or 2;
and making an unvulcanized tire using the rubber composition.
How tires are made.

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