JP7028069B2 - Kneading method and equipment for rubber materials - Google Patents

Description

The present invention relates to a method and an apparatus for kneading a rubber material, and more specifically, a closed-type kneader can be used to obtain a stable rubber material having a good quality in which a compounding agent is well dispersed in a raw material rubber. It relates to a kneading method and an apparatus for rubber materials.

When manufacturing rubber products such as tires, there is a kneading step in which various compounding agents are dispersed in raw rubber and kneaded to obtain an unvulcanized rubber material. In this kneading step, for example, a closed type kneader is used. A rotor is installed internally in the kneading chamber of the closed kneader, and a ram weight that moves up and down is arranged above the kneading chamber. After the raw rubber and various compounding agents are put into the kneading chamber, the upper opening of the kneading chamber is closed by a ram weight and kneaded by a rotating rotor (see, for example, Patent Document 1).

During this kneading, the ram weight functions as a lid of the kneading chamber to prevent the compounding agent from being ejected from the kneading chamber. Immediately after the compounding agent is put into the kneading chamber, the apparent volume in the kneading chamber is large, and when the ram weight drops to the lower limit position, excessive pressure is applied to the rubber material (raw rubber and compounding agent) in the kneading chamber. It works. Along with this, the easily scattered compounding agent may be ejected from the gap between the kneading chamber and the ram weight to the outside of the kneading chamber. When the compounding agent is ejected from the kneading chamber, the quality of the kneaded rubber material varies because the amount of the compounding agent is insufficient. Further, when the powdery compounding agent is excessively pressed by the ram weight, it becomes agglomerates and becomes difficult to disperse in the raw rubber.

On the other hand, if the kneading step is performed in a state where the ram weight is arranged above the lower limit position for a long time, the compounding agent is sufficiently dispersed in the raw rubber and it becomes difficult to knead. Further, since it takes a long time to sufficiently disperse the compounding agent in the raw rubber and knead it, there is also a problem that the productivity is lowered.

Japanese Unexamined Patent Publication No. 9-254148

An object of the present invention is to provide a method and an apparatus for kneading a rubber material, which can obtain a rubber material with stable quality in which a compounding agent is well dispersed in a raw rubber, with good productivity, using a closed-type kneader. It is in.

The method for kneading a rubber material of the present invention for achieving the above object is a state in which a rubber material composed of a raw material rubber and a compounding agent is kneaded in a kneading chamber of a closed type kneader, and the upper opening of the kneading chamber is closed with a ram weight. In a method of kneading a rubber material in which the rubber material is kneaded by rotating an internal rotor facing the kneading chamber, a pressure sensor installed on the lower surface of the ram weight is used to knead the rubber material in the kneading chamber. The detected pressure is preset by sequentially detecting the contact pressure between the rubber material and the lower surface of the ram weight and controlling a predetermined kneading condition by the control unit based on the detected pressure by the pressure sensor. It is characterized in that the rubber material is kneaded while adjusting so as to be within the target range.

The rubber material kneading device of the present invention has a rotor installed in the kneading chamber opposite to the kneading chamber, a ram weight arranged so as to be movable up and down above the kneading chamber, and a control unit for controlling the kneading conditions. Then, in the kneading chamber in which the upper opening is closed by the ram weight, the rubber material composed of the raw material rubber and the compounding agent is kneaded by the rotating rotor, and the rubber material is provided with a closed kneader. The kneading device has a pressure sensor installed on the lower surface of the ram weight, and the contact pressure between the rubber material in the kneading chamber and the lower surface of the ram weight is sequentially detected by the pressure sensor, and the pressure sensor is used. By controlling a predetermined kneading condition by the control unit based on the detected pressure by the above, the rubber material is kneaded while the detected pressure is adjusted to be within a preset target range. It is characterized by.

According to the present invention, the contact pressure between the rubber material in the kneading chamber of the closed kneader and the lower surface of the ram weight can be directly and sequentially detected by the pressure sensor installed on the lower surface of the ram weight. Therefore, by controlling a predetermined kneading condition by the control unit based on the pressure detected by the pressure sensor, it is possible to accurately adjust the detected pressure so as to be within a preset target range. Along with this, the rubber material can be kneaded while being appropriately pressed by the ram weight without excess or deficiency, so that a rubber material with stable quality in which the compounding agent is well dispersed in the raw rubber can be obtained with good productivity. ..

It is explanatory drawing which illustrates the kneading apparatus of the rubber material of this invention in the vertical cross-sectional view of the inside of the closed type kneader. FIG. 1 is a cross-sectional view taken along the line AA of FIG. It is explanatory drawing which illustrates the kneading apparatus of FIG. 1 in a plan view. It is a perspective view which illustrates the ram weight and the pressure sensor of FIG. It is explanatory drawing which shows the modification of the pressure sensor of FIG. It is explanatory drawing which illustrates the state which the rubber material is kneaded by the kneading apparatus of FIG. It is a graph which schematically exemplifies the time-dependent change of the detection pressure in a certain kneading progress stage. It is explanatory drawing which illustrates another embodiment of a kneading apparatus in a plan view.

Hereinafter, the method and apparatus for kneading the rubber material of the present invention will be described based on the embodiment shown in the figure.

The rubber material kneading apparatus 1 of the present invention exemplified in FIGS. 1 to 3 kneads the unvulcanized rubber material R. The rubber material R is composed of a raw material rubber G and a plurality of types of compounding agents N, and the compounding agent N is evenly dispersed in the raw material rubber G by kneading to obtain an appropriate viscosity. In this embodiment, a case where the raw rubber G and the non-vulcanized compounding material N are kneaded to produce the rubber material R is illustrated, but the raw material rubber G and the non-vulcanized compounded material N are kneaded. The present invention can also be applied to the case where the vulcanization-based compounding agent N is kneaded with the rubber material R to produce the rubber material R.

The raw material rubber G includes natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene, chloroprene rubber, butyl rubber, styrene-butadiene rubber (SBR), and nitrile rubber (acrylic nitrile rubber, Nitrile hydride rubber), ethylene propylene diene rubber and the like can be exemplified. These may be used alone or in combination of two or more. As the non-vulcanized compounding agent N, for example, carbon black, silica, a silane coupling agent, zinc oxide, stearic acid and the like are appropriately used. Examples of the vulcanization-based compounding agent N include sulfur, a vulcanization activator, and a vulcanization accelerating aid.

The kneading device 1 includes a closed type kneader 2 such as a Banbury mixer, a pressure sensor 13, and a control unit 12 in which the pressure detected by the pressure sensor 13 is sequentially input. The control unit 12 controls various kneading conditions as described later.

The closed type kneader 2 includes a kneading chamber 4a, a ram weight chamber 4b connected to the upper opening of the kneading chamber 4a and extending upward, and a ram weight 8 arranged in the ram weight chamber 4b. A pair of rotors 3 arranged to face each other are provided in the kneading chamber 4a. A blade 3b is projected from the rotating shaft 3a of each rotor 3, and the rotating shafts 3a arranged in parallel are rotationally driven by the drive motors 2a and 2b. A transmission 2c is interposed between the drive motors 2a and 2b and the respective rotary shafts 3a. The rotation of the rotor 3 is controlled by the control unit 12.

An oil charging section 5 is provided on the side surface of the kneading chamber 4a. A discharge door 10 that opens and closes is provided on the bottom surface of the kneading chamber 4a, and a temperature sensor 11 is provided with its tip exposed to the kneading chamber 4a. The temperature sensor 11 sequentially detects the temperature of the rubber material R kneaded in the kneading chamber 4a. The temperature detected by the temperature sensor 11 is sequentially input to the control unit 12.

The ram weight chamber 4b is provided with a rubber charging unit 6 into which the raw rubber G is charged and a compounding agent charging unit 9 into which the compounding agent N is charged. A hopper 7 is connected to the upper end of the compounding agent charging portion 9.

The ram weight 8 that moves up and down inside the ram weight chamber 4b can close the upper opening of the kneading chamber 4a when it moves downward to a predetermined position. The ram weight 8 is moved up and down by an elevating mechanism 8a such as a hydraulic cylinder. The vertical movement (vertical position) of the ram weight 8 is controlled by the control unit 12.

The pressure sensor 13 is installed on the lower surface of the ram weight 8. The pressure sensor 13 sequentially detects the contact pressure P between the rubber material R charged into the kneading chamber 4a and the lower surface of the ram weight 8 as the detection pressure P. In this embodiment, as illustrated in FIG. 4, a sheet-shaped pressure-sensitive element is used as the pressure sensor 13. This pressure sensitive element outputs the detected pressure P as an electric signal, and the magnitude of the detected pressure P is grasped. By moving the ram weight 8 up and down (changing the vertical position), the magnitude of the detection pressure P (that is, the contact pressure P between the rubber material R and the lower surface of the ram weight 8) can be adjusted.

As long as the pressure sensor 13 can detect the contact pressure P, various types and shapes can be adopted, not limited to the form shown in FIG. For example, a diaphragm type pressure sensitive element as shown in FIG. 5 can be used as the pressure sensor 13. In FIG. 5, a large number of circular pressure sensors 13 are embedded in the lower surface of the ram weight 8.

The pressure sensor 13 may be installed so as to be able to detect the detection pressure P within a range covering 70% or more, more preferably 80% or more, still more preferably 90% or more of the total area of the lower surface of the ram weight 8. As the area detected by the pressure sensor 13 is increased, it becomes advantageous to detect even when a locally high contact pressure P is generated without overlooking it.

The target range AR preset for the detection pressure P is input and stored in the control unit 12. This target range AR is an allowable range including the target value M of the detected pressure P. Since the appropriate detection pressure P differs depending on the progress stage of kneading, pre-kneading or the like is performed to grasp the target range AR for each kneading progress stage. The target value M (target range AR) is set based on the detection pressure P in the kneading step when the rubber material R having the characteristics (viscosity and the like) satisfying the standard can be kneaded.

Further, a power meter 12a is attached to the control unit 12. The instantaneous power required to drive the rotation of the rotor 3 is sequentially detected by the power meter 12a. The instantaneous power detected by the power meter 12a is input to the control unit 12. The control unit 12 calculates the integrated electric power amount obtained by integrating the instantaneous power, and can grasp the electric energy amount (load acting on the rotor 3) required for rotationally driving the rotor 3 in an arbitrary kneading period. In addition, the rotation speed of the rotor 3 and the like are input to the control unit 12.

Hereinafter, an example of the procedure of the method for kneading the rubber material of the present invention will be described.

First, a predetermined amount of raw rubber G is charged into the kneading chamber 4a through the rubber charging unit 6, and kneading is performed by rotating the rotor 3. After appropriately kneading the raw material rubber G, a predetermined amount of the required type of compounding agent N is charged into the kneading chamber 4a through the compounding agent charging unit 9.

After that, as illustrated in FIG. 6, the ram weight 8 is moved downward to close the upper opening of the kneading chamber 4a, and each rotor 3 is rotated to rotate the rubber material R (raw rubber G and compounding agent). Knead N). When the rubber material R of the kneading chamber 4a comes into contact with the lower surface (pressure sensor 13) of the ram weight 8, the pressure sensor 13 detects the contact pressure P as the detection pressure P. When the rubber material R of the kneading chamber 4a does not come into contact with the lower surface (pressure sensor 13) of the ram weight 8, the pressure sensor 13 detects the contact pressure P as the detection pressure P is zero.

The pressure P detected by the pressure sensor 13 changes with time as illustrated in FIG. Since the rubber material R rotates inside the kneading chamber 4a together with the rotor 3, the detection pressure P of this embodiment has a waveform having a period for each rotation of the rotor 3. It can be determined that the rubber material R is filled in the upper part of the kneading chamber 4a during the time period when the detected pressure P is maintained at a high value. It can be determined that a cavity (gap between the rubber material R and the rubber material R) exists in the upper part of the kneading chamber 4a during the time period when the detection pressure P is low and drops.

The solid thin line M shown in FIG. 7 indicates a preset target value with respect to the detected pressure P. The target range AR sandwiched above and below by the broken line thin line indicates an allowable range including the target value M of the detected pressure P.

The volume of the compounding agent N may be excessive at the stage where the compounding agent N is not kneaded into the raw material rubber G, such as immediately after the powdered compounding agent N is put into the kneading chamber 4a. In this case, the lower surface of the ram weight 8 (pressure sensor 13) comes into contact with the compounding agent N at a position where the ram weight 8 has moved downward to some extent. When the ram weight 8 is moved downward to the lower limit position as it is, the compounding agent N is ejected from the gap between the kneading chamber 4a and the ram weight 8 to the outside of the kneading chamber 4a by the pressing by the ram weight 8, or is pressed by the ram weight 8. May cause the compounding agent N to become agglomerates.

Therefore, when the detected pressure P (that is, the contact pressure P) by the pressure sensor 13 is likely to be larger than the target range AR, the downward movement of the ram weight 8 is stopped or the ram weight 8 is moved upward so that the detected pressure P is the target. Adjusted to range AR. In this way, the upper opening of the kneading chamber 4a is closed by the ram weight 8, and the rotor 3 is rotated to knead the rubber material R inside the kneading chamber 4a. During kneading, oil is appropriately supplied to the rubber material R from the oil charging section 5.

On the other hand, if the volume of the rubber material R charged into the kneading chamber 4a is not excessive, the rubber material R does not come into contact with the lower surface of the ram weight 8 even if the ram weight 8 is moved downward to the lower limit position, or slightly. It is only in contact with. Therefore, the ram weight 8 is moved downward to the lower limit position so that the upper opening of the kneading chamber 4a is closed. Since the volume of the rubber material R is not excessive, even if the ram weight 8 is moved downward to the lower limit position, the compounding agent N does not spout out of the kneading chamber 4a or becomes an agglomerate. Therefore, the rubber material R is kneaded inside the kneading chamber 4a by rotating the rotor 3 in this state.

By kneading, the compounding agent N is kneaded into the raw rubber G to some extent and dispersed, and the volume of the rubber material R is reduced. Along with this, the rubber material R is less likely to come into contact with the lower surface of the ram weight 8, and the pressure P detected by the pressure sensor 13 becomes smaller. Therefore, by moving the ram weight 8 downward based on the detected pressure P by the pressure sensor 13, the detected pressure P is increased and maintained in the target range AR.

Further, the detection pressure P varies depending on the position of the rubber material R that rotates together with the rotor 3 inside the kneading chamber 4a. Therefore, the detected pressure P is adjusted to be within the target range AR by moving the ram weight 8 up and down based on the detected pressure P by the pressure sensor 13. The detection pressure P can be decreased by moving the ram weight 8 upward, and the detection pressure P can be increased by moving the ram weight 8 downward.

That is, in this embodiment, the rubber material is adjusted so that the detected pressure P becomes the preset target range AR by controlling the vertical position of the ram weight 8 by the control unit 12 based on the detected pressure P. Knead R. For example, based on the detected pressure P, the maximum value of the detected pressure P for each rotation of the rotor 3 is adjusted to be within the target range AR. The amount of vertical movement of the ram weight 8 at this time is, for example, about 3% of the outer diameter of the rotor 3.

By using the pressure sensor 13 installed on the lower surface of the ram weight 8, the contact pressure P between the rubber material R kneaded in the kneading chamber 4a and the lower surface of the ram weight 8 can be sequentially detected directly and accurately. Therefore, the detected pressure P can be accurately adjusted to be within the target range AR by controlling the predetermined kneading conditions by the control unit 12 based on the detected pressure P by the pressure sensor 13.

Therefore, the rubber material R can be kneaded while being appropriately pressed by the ram weight 8 without excess or deficiency. That is, it is possible to avoid a problem that the powdery compounding agent L is excessively pressed by the ram weight 8 and the compounding agent N is ejected from the gap between the kneading chamber 4a and the ram weight 8 to the outside of the kneading chamber 4a. In addition, it is possible to prevent the powdery compounding agent L from being excessively pressed to form agglomerates. Therefore, it is advantageous to disperse the required amount of the compounding agent L evenly in the raw material rubber G.

Further, since the pressing by the ram weight 8 against the powdery compounding agent L is not excessive, the compounding agent L can be sufficiently kneaded into the raw material rubber G. Since the time for kneading the compounding agent L does not become excessively long, it is possible to obtain a rubber material R having a stable quality in which the compounding agent L is well dispersed and with good productivity.

In this embodiment, the detected pressure P is sequentially detected by the pressure sensor 13 over a wide area on the lower surface of the ram weight 8. Therefore, even when a very high contact pressure P is locally generated, it can be detected without overlooking. Then, when a very high detection pressure P is detected, the detection pressure P is adjusted to be lowered to the target range AR. When a very high contact pressure P is generated locally, the compounding agent L tends to form agglomerates at the position where the contact pressure P is generated. It will be very effective.

The downward movement speed of the ram weight 8 can also be adjusted based on the pressure P detected by the pressure sensor 13. For example, when the detection pressure P is zero, the downward movement speed of the ram weight 8 is made faster. On the other hand, when the detected pressure P exceeds zero, the downward moving speed of the ram weight 8 is further slowed down. By controlling the downward movement speed of the ram weight 8 in this way, the kneading chamber 4a is quickly closed by the ram weight 8 while preventing the powdery compounding agent N from being ejected to the outside of the kneading chamber 4a. The kneading can be started.

The kneading device 1 illustrated in FIG. 8 is different from the kneading device 1 of the previous embodiment only in that the facing interval of the rotor 3 can be changed as a kneading condition. In this kneading device 1, an inter-axis changing mechanism 3c provided with an eccentric ring or the like is interposed between one rotor and the transmission 2c. By operating the shaft-to-axis changing mechanism 3c by the control unit 12, one of the rotating shafts 3a moves and the facing interval of the rotor 3 changes.

When the distance between the rotors 3 is increased in the state illustrated in FIG. 6, the pressure P detected by the pressure sensor 13 becomes smaller. On the other hand, when the facing interval of the rotor 3 becomes smaller, the pressure P detected by the pressure sensor 13 becomes larger.

Therefore, in this embodiment, the detected pressure P can be adjusted to be within the target range AR by changing the facing interval of the rotor 3 by the control unit 12 based on the detected pressure P by the pressure sensor 13. The detection pressure P can be adjusted to be within the target range AR by changing the facing interval of the rotor 3 by the control unit 12 and changing the vertical position of the ram weight 8.

Using the same kneading device as the kneading device 1 exemplified in FIG. 1, the rubber materials were kneaded under the same conditions except that the control of the vertical position of the ram weight was different (conventional example and embodiment). .. In the conventional example, after the rubber material was put into the kneading chamber, kneading was performed while maintaining the ram weight at the lower limit position. In the embodiment, the present invention is applied to sequentially detect the contact pressure between the rubber material and the lower surface of the ram weight 8 by a pressure sensor installed on the lower surface of the ram weight. Then, the rubber material was kneaded while adjusting the detected pressure to a preset target range by changing the vertical position of the ram weight by the control unit based on the detected pressure P by the pressure sensor.

As a result, it was confirmed that the time required to knead the entire amount of the compounding agent into the raw rubber was about 1/3 of that of the conventional example in the example. In addition, the rubber material after kneading was analyzed to measure the RPA value (index), which is a measure of the dispersibility of the compounding agent. The smaller the index, the better the dispersibility of the compounding agent. It was confirmed that the RPA value (index) was 79 in the example with respect to 100 in the conventional example.

1 Kneading device 2 Sealed kneader 2a, 2b Drive motor 2c Transmission 3 Rotor 3a Rotating shaft 3b Blade 3c Axis-to-axis change mechanism 4a Kneading chamber 4b Ram weight chamber 5 Oil charging section 6 Rubber loading section 7 Hopper 8 Ram weight 8a Lifting and lowering Mechanism 9 Compounding agent input section 10 Discharge door 11 Temperature sensor 12 Control section 13 Pressure sensor G Raw material rubber N Blending agent R Rubber material

Claims (6)

In the kneading chamber of the closed-type kneader, the rubber material consisting of the raw rubber and the compounding agent is placed in a state where the upper opening of the kneading chamber is closed by a ram weight, and the rotor installed in the kneading chamber is rotated to face the kneading chamber. In the method of kneading the rubber material, which kneads the rubber material by allowing the rubber material to be kneaded.
The pressure sensor installed on the lower surface of the ram weight sequentially detects the contact pressure between the rubber material in the kneading chamber and the lower surface of the ram weight, and the control unit determines the pressure based on the pressure detected by the pressure sensor. A method for kneading a rubber material, which comprises kneading the rubber material while adjusting the detection pressure so as to be within a preset target range by controlling the kneading conditions. The method for kneading a rubber material according to claim 1, wherein the maximum value of the detected pressure is used as the detected pressure adjusted so as to be within the target range. The method for kneading a rubber material according to claim 1 or 2, wherein the pressure sensor detects the contact pressure within a range covering 70% or more of the total area of the lower surface of the ram weight. The method for kneading a rubber material according to any one of claims 1 to 3, wherein the predetermined kneading condition is a vertical position of the ram weight. The method for kneading a rubber material according to any one of claims 1 to 4, wherein the predetermined kneading condition is a facing interval of the rotor. It has a rotor installed inward facing the kneading chamber, a ram weight arranged so as to be vertically movable above the kneading chamber, and a control unit for controlling the kneading conditions, and the upper opening is opened by the ram weight. In the kneading device of the rubber material provided with the closed type kneader in which the rubber material composed of the raw rubber and the compounding agent is kneaded by the rotating rotor in the kneaded chamber in the closed state.
It has a pressure sensor installed on the lower surface of the ram weight, and the contact pressure between the rubber material in the kneading chamber and the lower surface of the ram weight is sequentially detected by the pressure sensor, and is based on the pressure detected by the pressure sensor. The rubber is characterized in that the rubber material is kneaded while the detection pressure is adjusted to be within a preset target range by controlling a predetermined kneading condition by the control unit. Material kneading device.

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