JP2007008112A - Kneading method and kneading apparatus for rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a kneading method and a kneading apparatus for a rubber composition, which increase an operation efficiency of a mixer, and at the same time, enables the efficient reaction of a silane coupling agent while suppressing an increase of the equipment cost when the rubber composition prepared by blending silica and the silane coupling agent is kneaded. <P>SOLUTION: After the rubber composition prepared by blending silica and the silane coupling agent is kneaded by the mixer 1 at temperatures of 160°C or less, the rubber composition R is transferred on a pair of kneading rolls 6a and 6b while held at temperatures of 120°C or more, and the rubber composition R is self-heated with a shearing force given from the kneading rolls 6a and 6b to maintain a temperature of 140-160°C. A sheet of the rubber composition R passing through a gap between the kneading rolls 6a and 6b is returned on the kneading rolls 6a and 6b through a plurality of conveyors 8a-8b, and a temperature fall from the discharge of the sheet from the kneading rolls 6a and 6b to the again-returning to the kneading rolls 6a and 6b is set to be 10°C or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and equipment for kneading a rubber composition comprising silica and a silane coupling agent. More specifically, the present invention relates to a silane cup while improving the operation efficiency of a mixer and suppressing an increase in equipment cost. The present invention relates to a kneading method and a kneading equipment for a rubber composition capable of efficiently performing a reaction of a ring agent.

  In recent years, silica has been used as a filler for rubber reinforcement in place of carbon black. Further, when silica is blended in a rubber composition, a silane coupling agent is generally added to improve the dispersion of silica particles in the rubber. When kneading such a rubber composition containing silica, the reaction control of the silane coupling agent is important (see, for example, Patent Document 1).

  By the way, as a kneading equipment for the rubber composition, a closed mixer including a pair of rotors is widely used (for example, see Patent Document 2). Therefore, it is desirable that a closed mixer can be used for kneading the rubber composition containing silica. Therefore, in order to sufficiently perform the reaction of the silane coupling agent, the rotor speed of the closed mixer is made variable, and the rotor speed is adjusted so as to keep the temperature constant, or while using the closed mixer. Combining the kneading step for dispersion and the kneading step for reaction is performed. However, in a closed mixer, the measurement accuracy of the internal temperature is low and the temperature distribution is non-uniform, so that temperature adjustment based on the rotor speed is extremely difficult. Further, when a dispersion kneading step and a reaction kneading step are combined in a closed mixer, the kneading time becomes long, and the production cost of the rubber composition containing silica increases.

On the other hand, while the dispersion kneading step is performed by a closed mixer, the reaction kneading step is performed by another mixer, an extruder, a temperature-controlled indoor roll, or the like, thereby dispersing the kneading step. It has been proposed to efficiently perform the reaction of the silane coupling agent while increasing the operating efficiency of the mixer that performs the above (see, for example, Patent Document 3). However, when other mixers are prepared or an extruder, a temperature-controlled indoor roll, or the like is used to perform the kneading step for reaction, there is a problem that the equipment cost is greatly increased. Therefore, it is desired to efficiently perform the reaction of the silane coupling agent with an inexpensive facility.
Japanese Patent Laid-Open No. 10-175208 Japanese Patent Laid-Open No. 10-71613 JP 2004-352831 A

  The object of the present invention is to increase the operation efficiency of the mixer and knead the reaction of the silane coupling agent efficiently while suppressing the increase in equipment cost when kneading the rubber composition comprising silica and the silane coupling agent. It is an object of the present invention to provide a kneading method and a kneading equipment for a rubber composition that can be carried out.

  In order to achieve the above object, the rubber composition of the present invention is kneaded with a rubber composition containing silica and a silane coupling agent at a temperature of 160 ° C. or lower by a mixer and then kneaded with the mixer. The rubber composition is conveyed onto a pair of kneading rolls while maintaining a temperature of 120 ° C. or higher, and the rubber composition is self-heated by a shearing force applied from these kneading rolls to maintain a temperature of 140 ° C. to 160 ° C. The sheet of the rubber composition that has passed through the gap of the kneading roll is returned to the kneading roll via a plurality of conveyors, and the sheet is discharged from the kneading roll to return to the kneading roll again. The temperature drop is made 10 ° C. or less.

  Further, the kneading equipment for the rubber composition of the present invention for achieving the above object includes a mixer for kneading a rubber composition containing silica and a silane coupling agent, and a rubber composition kneaded by the mixer. A pair of kneading rolls having a function of maintaining a temperature of 140 ° C. to 160 ° C. by causing the product to self-heat, and a circulation path for returning the sheet of the rubber composition that has passed through the gap between the kneading rolls to the kneading rolls are formed. And a plurality of conveyors.

  In the present invention, a pair of kneading rolls and a plurality of conveyors are installed as a device for controlling the reaction of the silane coupling agent in the next step of the mixer for kneading the rubber composition comprising silica and the silane coupling agent. To do. Then, the rubber composition self-heats with a shearing force applied from the kneading roll to maintain a temperature of 140 ° C. to 160 ° C., and the rubber composition sheet that has passed through the gap of the kneading roll is kneaded through a plurality of conveyors. The temperature of the sheet is reduced to 10 ° C. or less until the sheet is discharged from the kneading roll and then returned to the kneading roll, so that the reaction of the silane coupling agent is efficiently performed. To do.

  Thus, the apparatus composed of a pair of kneading rolls and a plurality of conveyors can adjust the temperature by utilizing the self-heating of the rubber composition, and does not require large-scale temperature control equipment. Equipment costs are relatively low. Therefore, in addition to increasing the operating efficiency of the mixer carrying the kneading step for dispersion, it becomes possible to efficiently perform the reaction of the silane coupling agent while suppressing an increase in equipment cost.

  In the rubber composition kneading method of the present invention, it is preferable that the conveying time from the rubber composition mixer to the kneading roll is 90 seconds or less. Further, it is preferable to process the rubber composition into a sheet-like intermediate having a thickness of 4 mm to 20 mm in the course of conveying the rubber composition from the mixer to the kneading roll.

  In the rubber composition kneading facility of the present invention, the volume of the mixer is preferably 70 L to 620 L. The length of the kneading roll is preferably 1000 mm to 2400 mm, and the diameter of the kneading roll is preferably 400 mm to 800 mm. The length of the circulation path is preferably 3 m to 30 m. It is preferable that the distance between the pair of stock guides defining the stock region of the rubber composition on the kneading roll is variable, and the gap amount of the kneading roll is variable in the range of 2 mm to 10 mm.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a kneading facility for a rubber composition according to an embodiment of the present invention. In FIG. 1, the hermetic mixer 1 includes a pair of rotors 3 and 3 in a kneading unit 2. At the upper part of the kneading part 2, there is an inlet for the rubber composition, which is closed by the ram 4. On the other hand, there is a kneaded rubber composition outlet at the bottom of the kneading section 2, and a lid 5 that can be opened and closed is provided at the outlet. The kneaded rubber composition R discharged from the mixer 1 is conveyed onto a pair of kneading rolls 6a and 6b.

  The pair of kneading rolls 6a and 6b are arranged in the horizontal direction so that the rotation axes thereof are parallel to each other, and rotate in opposite directions so as to entrain the rubber composition R by a driving means (not shown), and by the shearing force The rubber composition R has a function of self-heating to maintain a temperature of 140 ° C. to 160 ° C. The gap between the kneading rolls 6a and 6b is adjusted by a position control device 7 connected to the rotating shaft of the kneading roll 6a.

  The sheet of the rubber composition R that has passed through the gap between the kneading rolls 6a and 6b returns to the kneading rolls 6a and 6b again through a circulation path formed by the plurality of conveyors 8a, 8b, 8c, and 8d. Yes. That is, the conveyor 8a receives the sheet of the rubber composition R at the lower position of the kneading rolls 6a and 6b, the conveyors 8b and 8c sandwich the sheet of the rubber composition R transferred by the conveyor 8a and send it upward, and the conveyor 8d A sheet of the rubber composition R transferred by the conveyors 8b and 8c is dropped onto the kneading rolls 6a and 6b.

  Around the kneading roll 6a, a thermometer 9a for measuring the temperature of the sheet of the rubber composition R discharged from the kneading roll 6a, 6b, and the temperature of the sheet of the rubber composition R returning to the kneading roll 6a, 6b And a thermometer 9b for measuring. The detection results of these thermometers 9 a and 9 b are input to the control circuit 10. The control circuit 10 controls the speed and gap amount of the kneading rolls 6a and 6b based on the detection results of the thermometers 9a and 9b.

  When the kneading operation is performed using the rubber composition kneading equipment described above, first, the rubber composition R containing silica and the silane coupling agent is kneaded with the mixer 1 and then the rubber kneaded with the mixer 1. The composition R is transferred to a reaction control device composed of kneading rolls 6a and 6b and conveyors 8a to 8d, and the reaction of the silane coupling agent is performed in this reaction control device.

  In the mixer 1, a rubber composition containing silica and a silane coupling agent is kneaded at a temperature of 160 ° C. or lower. If the temperature in the mixer 1 exceeds 160 ° C., the physical properties of the rubber composition containing silica are impaired. After kneading by the mixer 1, the rubber composition R is conveyed onto the pair of kneading rolls 6a and 6b while maintaining the temperature at 120 ° C. or higher. When the temperature of the rubber composition R is less than 120 ° C., the temperature recovery time becomes longer than necessary. In order to maintain the temperature, the conveyance time of the rubber composition R from the mixer 1 to the kneading rolls 6a and 6b is preferably 90 seconds or less. However, if a windproof cover or the like is installed, the conveyance time can be extended.

  Further, the rubber composition R may be processed into a sheet-like intermediate Rm having a thickness of 4 mm to 20 mm in the process of transporting the rubber composition R from the mixer 1 to the kneading rolls 6a and 6b. The sheet-like intermediate Rm may be directly fed into the kneading rolls 6a and 6b, or may be led in the middle of a circulation path composed of the conveyors 8a to 8d.

  In the kneading rolls 6a and 6b, the rubber composition R is self-heated by a shearing force to maintain a temperature of 140 ° C to 160 ° C. By maintaining this temperature range, the silane coupling agent can be reacted efficiently. Moreover, since the sheet | seat of the rubber composition R which passed the gap of the kneading rolls 6a and 6b is returned on the kneading rolls 6a and 6b via the plurality of conveyors 8a to 8d, the silane coupling agent in the rubber composition R It is possible to efficiently discharge the gas generated in response to the reaction. Furthermore, the temperature drop of the rubber composition R from the time when the sheet of rubber composition R is discharged from the kneading rolls 6a and 6b to the time when the sheet returns to the kneading rolls 6a and 6b again is 10 ° C. or less. That is, the temperature immediately before the sheet of the rubber composition R returns to the kneading rolls 6a and 6b is 130 ° C to 150 ° C. Thereby, it becomes possible to perform reaction of a silane coupling agent efficiently.

  In the above kneading equipment, the volume of the mixer 1 is preferably 70L to 620L. If the volume of the mixer 1 is too small, heat radiation from the rubber composition to be kneaded increases, so that it is difficult to maintain a temperature of 140 ° C. to 160 ° C. due to natural heat generation. Combination with 6b becomes difficult.

  The length of the kneading rolls 6a and 6b is 1000 mm to 2400 mm, and the diameter is preferably 400 mm to 800 mm. The kneading rolls 6a and 6b having such dimensions form a relatively large bank, which is advantageous in maintaining the rubber composition R at a relatively high temperature.

  The length of the circulation path of the rubber composition R is preferably 3 m to 30 m. If the length of the circulation path is less than 3 m, it is disadvantageous for discharging the gas generated in the rubber composition R out of the system, and conversely if it exceeds 30 m, the sheet of the rubber composition R is excessively cooled. Therefore, it becomes difficult to keep the rubber composition R on the kneading rolls 6a and 6b at 140 ° C. or higher due to self-heating. The length of the circulation path is the length of the sheet portion of the rubber composition R. Moreover, the transfer speed by the conveyors 8a to 8d is preferably set to 30 m / min to 60 m / min.

  On the kneading rolls 6a and 6b, a pair of stock guides 11 that define the stock region of the rubber composition R are disposed in the same manner as a general kneading roll, but the interval between these stock guides 11 is variable. It is desirable. By adjusting the distance between the stock guides 11, the bank amount of the kneading rolls 6a and 6b can be adjusted, and the temperature of the rubber composition R can be adjusted. Generally, it is possible to increase the temperature of the rubber composition R by increasing the bank amount.

  The gap amount between the kneading rolls 6a and 6b is preferably variable in the range of 2 mm to 10 mm. If the gap amount is less than 2 mm, the cooling of the sheet of the rubber composition R becomes excessive, and it becomes difficult to keep the temperature of the rubber composition R on the kneading rolls 6 a and 6 b at 140 ° C. or higher. Exceeding this requires a great amount of time to raise the temperature of the rubber composition R, and the exhaust of gas from the rubber composition R becomes inefficient.

  As a control other than the above, the temperature of the rubber composition R is continuously measured, the temperature drop due to the viscosity drop accompanying the progress of kneading is sensed, the surface speed and the gap amount of the kneading rolls 6a and 6b are adjusted, and the rubber composition It is also effective to maintain the temperature of the object R within a predetermined range. Thereby, the temperature of the rubber composition R on the kneading rolls 6a and 6b can be controlled to 140 ° C. to 160 ° C. without providing an external heating device.

  According to the rubber composition kneading method and the kneading apparatus described above, the temperature can be adjusted by utilizing the self-heating of the rubber composition R, and no large-scale temperature control equipment is required. Cost is relatively low. Therefore, in addition to increasing the operating efficiency of the mixer carrying the kneading step for dispersion, it becomes possible to efficiently perform the reaction of the silane coupling agent while suppressing an increase in equipment cost.

It is sectional drawing which shows roughly the kneading | mixing equipment of the rubber composition which consists of embodiment of this invention.

Explanation of symbols

1 Mixer 6a, 6b Kneading roll 8a, 8b, 8c, 8d Conveyor 11 Stock guide R Rubber composition

Claims (8)

  A rubber composition obtained by blending silica and a silane coupling agent is kneaded with a mixer at a temperature of 160 ° C. or lower, and then the rubber composition kneaded with the mixer is kept at a temperature of 120 ° C. or higher with a pair of kneading rolls. A plurality of sheets of the rubber composition that are conveyed to the top and maintain the temperature of 140 ° C. to 160 ° C. by self-heating the rubber composition by the shearing force applied from these kneading rolls and passing through the gap of the kneading rolls. The rubber composition is returned to the top of the kneading roll via the conveyor of the rubber composition, and the temperature decrease of the sheet from when the sheet is discharged from the kneading roll to returning to the kneading roll is 10 ° C. or less. Kneading method.   The method for kneading a rubber composition according to claim 1, wherein a conveying time of the rubber composition from the mixer to the kneading roll is 90 seconds or less.   The kneading of the rubber composition according to claim 1 or 2, wherein the rubber composition is processed into a sheet-like intermediate having a thickness of 4 mm to 20 mm in a process of conveying the rubber composition from the mixer to the kneading roll. Method.   A mixer for kneading a rubber composition comprising silica and a silane coupling agent, and a pair having a function of maintaining a temperature of 140 ° C. to 160 ° C. by self-heating the rubber composition kneaded by the mixer And a plurality of conveyors for forming a circulation path for returning the sheet of the rubber composition that has passed through the gap between the kneading rolls back to the kneading roll.   The rubber composition kneading facility according to claim 4, wherein the mixer has a capacity of 70L to 620L.   The rubber composition kneading equipment according to claim 4 or 5, wherein the kneading roll has a length of 1000 mm to 2400 mm, and the kneading roll has a diameter of 400 mm to 800 mm.   The rubber composition kneading facility according to any one of claims 4 to 6, wherein the circulation path has a length of 3 m to 30 m. The gap between the pair of stock guides defining the stock region of the rubber composition on the kneading roll is variable, and the gap amount of the kneading roll is variable in the range of 2 mm to 10 mm. A kneading facility for the rubber composition.

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