JP2004358693A - Method for kneading silica compounded rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a kneading method capable of obtaining a silica compounded rubber composition having stable quality without causing a scorching of rubber. <P>SOLUTION: In this kneading method for obtaining the silica compounded rubber composition by mixing silica and a silane coupling agent with a diene rubber, the necessary reaction amounts of silica and the silane coupling agent having to be achieved by kneading operation are preliminarily determined experimentally and the temperature of the mixed rubber is calculated with the elapse of time on the basis of the charging quantity and discharge quantity of kneading energy from the start of kneading operation while the reaction amount of silica and the silane coupling agent are calculated with the elapse of time on the basis of the temperature of the mixed rubber. When the calculation values of the reaction amounts reach the necessary reaction amounts, kneading operation is completed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for kneading a silica-containing rubber composition, and more particularly, to a method for kneading a silica-containing rubber composition that enables production of a good-quality rubber composition in which silica is uniformly dispersed.
[0002]
[Prior art]
It is known that use of a rubber composition in which tread rubber is mixed with silica can improve fuel economy and wet grip of a tire. However, silica has a drawback that the particles are easily aggregated due to hydrogen bonds of silanol groups, which are surface functional groups, and therefore have poor dispersibility in rubber. Therefore, when silica is compounded in rubber, a silane coupling agent is compounded and a coupling reaction with silica is performed to reduce silanol groups on the silica surface and improve affinity for rubber (Patents). Reference 1).
[0003]
However, when the silane coupling agent is compounded as described above, if the amount of the coupling reaction between the silica and the silane coupling agent is insufficient, good dispersibility of the silica cannot be obtained, and the reaction is excessive. In addition, there is a problem that the quality is deteriorated due to rubber scorching. For this reason, in the conventional kneading method, the rubber temperature is constantly measured with a thermocouple or the like during the kneading operation, and the kneading operation is performed within an empirically set time while maintaining the rubber temperature within a certain range. Is not always constant for each batch, which causes a problem that the dispersibility of silica is not constant. Further, the rubber temperature may overshoot due to a delay in display of the thermocouple, resulting in burning due to overreaction.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H11-263878
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a kneading method which can solve the above-mentioned conventional problems and can obtain a silica-containing rubber composition having a stable quality without causing rubber scorching or the like.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a method for kneading a rubber composition in which silica and a silane coupling agent are mixed with a diene rubber, in which a required reaction amount of silica and a silane coupling agent to be achieved by a kneading operation is previously measured. The temperature of the mixed rubber is calculated over time based on the input and output of the kneading energy from the start of the kneading operation, and the reaction between the silica and the silane coupling agent is performed based on the temperature of the mixed rubber. The amount is calculated over time, and the kneading operation is terminated when the calculated value of the reaction amount reaches the required reaction amount.
[0007]
In this way, the required reaction amount between silica and the silane coupling agent is determined in advance by an experiment, and in the kneading operation, the rubber temperature is not measured by a thermocouple or the like, but the rubber temperature is determined by the input amount of the kneading energy. Since the calculation is performed from the discharge amount, the response time is not caused, and the reaction amount of the silane coupling is calculated from the rubber temperature of the calculated value, and the mixing operation is terminated when the calculated value matches the required reaction amount. As a result, it is possible to accurately control the amount of reaction between silica and the silane coupling agent, to uniformly disperse silica, and to obtain a high-quality silica-containing rubber composition without rubber scorch because there is no excessive reaction. it can.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
As the diene rubber used in the present invention, any of known rubbers conventionally used for tires can be used. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR) and the like can be mentioned. These rubber types may be used alone or as a blend of two or more types.
[0009]
The silica used in the present invention is not particularly limited, but for example, use of synthetic hydrated silica is preferable. The amount of silica in the silica-containing rubber composition is preferably from 10 to 200 parts by weight, more preferably from 20 to 80 parts by weight, per 100 parts by weight of rubber.
[0010]
As the silane coupling agent, any of those used in the rubber industry can be used and is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, γ-mercaptopropoxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β- (amino Ethyl) -γ-aminopropyltrimethoxysilane is preferred. The amount of the silane coupling agent may be 2 to 20% by weight, preferably 4 to 15% by weight based on the weight of silica.
[0011]
Further, the rubber composition of the present invention may be compounded with a compounding agent other than the above as long as the effects of the present invention are not impaired. For example, fillers such as carbon black, talc and clay, vulcanizing agents such as sulfur and peroxide, vulcanization accelerators, vulcanization aids such as stearic acid and zinc oxide, and antioxidants can be compounded. it can.
[0012]
The kneading method of the present invention may be carried out by blending at least silica and a silane coupling agent in the above-described diene rubber at a predetermined ratio, and using a conventionally used kneader such as a Banbury mixer or a kneader. . The rubber temperature during the kneading operation is preferably from 120 to 170C. Since the reaction between the silica and the silane coupling agent is an exothermic reaction, the kneading machine may be provided with a cooling jacket to circulate cooling water during the kneading process, in order to maintain such a rubber temperature range. preferable.
[0013]
In the present invention, in carrying out the above-mentioned kneading operation, it is necessary to determine in advance by experiment the necessary amount (target value) of the coupling reaction between silica and the silane coupling agent in the kneading operation per batch. As the required reaction amount, a reaction amount is set so that the dispersibility of the silica in the rubber is the most uniform and the rubber is not burned due to an excessive reaction.
[0014]
As shown in FIG. 1, the required reaction amount between silica and the silane coupling agent is set by performing a kneading operation while maintaining a constant rubber temperature and detecting the torque over time with a vulcanization degree measuring device. The reaction amount of the silica and the silane coupling agent reacted until the torque starts to rise is used.
[0015]
That is, when the torque is continuously detected by the vulcanization degree measuring device from the start of the kneading operation of the silica-containing rubber composition, the torque gradually decreases immediately after the start of the kneading operation as shown in FIG. , A time-torque curve that reverses and rises is obtained. A tangent line A is drawn at the minimum value of the time-torque curve obtained in this way, and a tangent line B is drawn at a straight line portion after the rise. Assuming that the elapsed time from the start of the kneading operation is the rising time t, the reaction amount in which the silica and the silane coupling agent have reacted during the elapse of the rising time t is determined as the required reaction amount from the following equation (1). is there.
Reaction amount = a∫exp ｛k1 / T (t)｝ dt (1)
Where a is a constant,
T (t) is the rubber temperature at time t elapsed from the start of mixing,
k1 is the rate constant of the coupling reaction.
[0016]
The coupling reaction rate constant k1 can be determined as follows. That is, the relationship between the rubber temperature obtained as shown in FIG. 1 and the rise time t is calculated for a plurality of rubber temperatures (for example, four points of 130 ° C., 140 ° C., 150 ° C., and 160 ° C. in FIG. 1). The rise time t was measured (rise time t at a rubber temperature of 130 ° C. was 35 minutes, t at 140 ° C. was 19 minutes, t at 150 ° C. was 9 minutes, and t at 160 ° C. was 4.5 minutes). As shown in FIG. 2, the relationship between the temperature and the rise time t is plotted on a graph showing the relationship between the reciprocal of the rubber temperature represented by the absolute temperature T (K) and the rise time t. The slope of a straight line obtained by connecting these plotted points corresponds to the coupling reaction rate constant k1. In the example shown in FIG. 2, k1 = 112030.
[0017]
On the other hand, the rubber temperature T (t) at the time t elapsed from the start of the kneading operation is sequentially calculated over time by the following equation (2), and based on the calculated value of the rubber temperature, the above equation (1) is used. The reaction amount is calculated sequentially over time. In the calculation of the expression (1) at this time, the constant a does not need to be obtained because the constant a is common in each calculation. Then, when the integrated value of the reaction amount of the silica and the silane coupling agent calculated from the start of the kneading operation reaches the required reaction amount set in advance, the kneading operation ends. .
[0018]
The kneading method of the present invention is capable of accurately controlling the reaction amount between silica and a silane coupling agent by performing the above-described kneading operation, and a high-quality silica compound rubber in which silica is uniformly dispersed in rubber. A composition can be obtained. Further, since the excess reaction does not occur by controlling the reaction amount, rubber scorch does not occur.
T (t) = To + {Qinput (t) −Qoutput (t)} / {W × ρ (t)} dt (2)
Here, T (t) is a calculated rubber temperature at an elapsed time t from the start of kneading,
To is the initial rubber temperature at the start of the kneading operation,
Qinput (t) is an energy input amount at an elapsed time t from the start of kneading,
Qoutput (t) is an energy emission amount at an elapsed time t from the start of kneading,
W is the mixing weight of the rubber composition,
ρ (t) is the rubber specific heat at the time t elapsed from the start of kneading.
[0019]
The energy input amount Qinput (t) at the elapsed time t in the above equation can be calculated from the electric power value (kw) when driving the kneader. Further, the energy discharge amount Qoutput (t) at the elapsed time t is proportional to the contact area between the rubber composition and the kneader casing and the rotor, and the difference between the temperature of the rubber composition and the cooling water temperature. It can be calculated from the following equation (3).
Qoutput (t) = C2 × W2 ^{/ 3} × {T (t) -Tc} (3)
Here, C2 is the parameter W of the heat exchange rate, the mixing weight T (t) of the rubber composition is the rubber temperature at the time t elapsed from the start of mixing, and is calculated from the initial temperature To and the input power (kw). Calculated value,
Tc is the temperature of the cooling water.
[0020]
FIG. 3 schematically illustrates an apparatus for performing the kneading method of the present invention.
[0021]
A kneader 1 for picking up a rubber composition has a pair of kneading blades 3 and 4 provided inside a casing 2. The kneading blades 3, 4 are rotationally driven in opposite directions by a drive motor 5, and knead a mixture of rubber, silica, a silane coupling agent and the like in the casing 2. Further, a cooling jacket 6 is provided around the outer periphery of the casing 2. The jacket 6 is provided with a cooling water supply port 6a and a discharge port 6b. The cooling water supplied from the supply port 6a exchanges heat with the rubber mixture in the casing while circulating through the jacket 6, and finally discharges. It is discharged from the outlet 6b.
[0022]
Reference numeral 7 denotes a controller for controlling the operation of the kneader 1, and reference numeral 8 denotes a start switch.
[0023]
In the above-described apparatus, when the start switch 8 is turned on, the kneading machine 1 is started, and a kneading operation start signal is transmitted to the controller 7. With this start signal, the controller 7 accumulates the elapsed time t from the start of kneading, calculates the rubber temperature T (t) at the time t elapsed from the start of kneading according to the above equation (2), and calculates the calculated rubber temperature T (t). Based on the above, the reaction amount of silica and the silane coupling agent is calculated by the above equation (1).
[0024]
The power consumption of the motor 5 is input to the controller 7 as an energy input Qinput (t) as a signal necessary for the calculation of the equations (1) and (2), and the calculation of the energy emission Qoutput (t) is performed. Therefore, the weight W of the rubber composition, the initial rubber temperature To, the cooling water temperature Tc of the cooling jacket 6, and the like are input.
[0025]
When the calculated reaction amount calculated by the controller 7 as described above reaches the required reaction amount set in advance by an experiment, a stop signal is transmitted from the controller 7 to the start switch 8 and the drive motor 5 Is stopped to end the kneading operation.
[0026]
The kneading method of the present invention can be generally applied to a kneading operation in which silica and a silane coupling agent are blended with a diene rubber, and can be preferably applied particularly when kneading a tread rubber of a tire.
[0027]
【The invention's effect】
As described above, according to the present invention, the required reaction amount between silica and a silane coupling agent is determined in advance by an experiment, and in the kneading operation, the rubber temperature is measured rather than actually measured with a thermocouple or the like. Is calculated from the input and output of the kneading energy, so that a response delay is not caused, and the silane coupling reaction amount is calculated from the rubber temperature of the calculated value, and the calculated value matches the required reaction amount. Since the mixing operation is terminated at the time, the amount of reaction between the silica and the silane coupling agent is accurately controlled, and the silica is uniformly dispersed. A rubber composition can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing a time-torque curve when kneading a rubber composition.
FIG. 2 is a graph showing a relationship between a reciprocal of a rubber temperature and a torque rise time when a rubber composition is kneaded.
FIG. 3 is a schematic view illustrating an apparatus for practicing the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Kneading machine 2 Casing 3, 4 Kneading blade 5 Drive motor 6 Cooling jacket 7 Controller 8 Start switch

Claims (3)

In a kneading method of a rubber composition in which silica and a silane coupling agent are mixed with a diene rubber, a necessary reaction amount of silica and a silane coupling agent to be achieved by a kneading operation is determined in advance by an experiment, and the kneading operation is performed. Along with calculating the temperature of the mixed rubber over time based on the input and output of the kneading energy from the start, the amount of reaction between the silica and the silane coupling agent is calculated over time based on the temperature of the mixed rubber. A method for kneading a silica-containing rubber composition, wherein the kneading operation is terminated when the calculated value of the reaction amount reaches the required reaction amount. 2. The method according to claim 1, wherein the amount of the silane coupling agent is 2 to 15% by weight based on the weight of the silica. The method for kneading a silica-containing rubber composition according to claim 1 or 2, wherein the silica-containing rubber composition is for a tire tread.

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