JP4223022B2 - Rubber material kneading control method - Google Patents

Description

  The present invention relates to a rubber material kneading control method, and more particularly to a rubber material kneading control method capable of efficiently obtaining a kneaded rubber having a stable viscosity when the rubber material is kneaded by a roll kneader. is there.

  Conventionally, rubber materials used as materials for rubber products such as tires are made by mixing a predetermined amount of raw rubber such as natural rubber, carbon, and compounding chemicals into a closed mixer called a Banbury mixer and kneading them uniformly. A method of mixing and kneading so as to reduce the viscosity to a certain level has been used.

  However, there is a problem that the kneaded rubber rises to a predetermined temperature or more due to friction during the kneading process or the heat generated by the compounded chemicals, and vulcanization proceeds. After that, it was necessary to carry out kneading again, which was inefficient.

  In order to solve such problems, various methods have been proposed in which kneaded rubber kneaded with a closed mixer is kneaded with a roll kneader having an open structure (see, for example, Patent Documents 1 and 2). In Patent Document 1, by defining the thickness of a rubber sheet that passes through a roll of a roll kneader to be equal to or less than a predetermined thickness, a strong shearing force can be applied to the kneaded rubber to reliably reduce the plasticity (viscosity). I can do it. However, unlike the roll interval, it is difficult to control the thickness of the rubber sheet, and there is a problem that it takes time to obtain a desired viscosity only by the thickness of the rubber sheet.

In Patent Document 2, the temperature range of the kneaded rubber when being charged from the closed mixer to the roll kneader is specified, but it is necessary to cool the kneaded rubber to this temperature range before being charged into the roll kneader. This causes a loss of time and energy, so a more efficient method has been demanded.
JP-A 63-56407 Japanese Patent Laid-Open No. 4-125112

  An object of the present invention is to provide a rubber material kneading control method capable of efficiently obtaining a kneaded rubber having a stable viscosity when a rubber material is kneaded by a roll kneader.

In order to achieve the above object, the rubber material kneading control method of the present invention comprises kneading rubber material discharged from a closed mixer to kneaded rubber material having a target viscosity by kneading with at least one roll kneader. the control method, the roll gap of the roll kneader and 0.5 mm to 3.0 mm, to control the temperature of the rubber kneading rubber in the kneading machine so as to target viscosity 40 ° C. to 90 ° C. for a predetermined time The increase or decrease of the amount of the kneaded rubber bank on the roll of the roll kneader is circulated through the roll kneader to feed the kneaded rubber, or the conveyor belt feed speed or the circulation of the kneaded rubber circulated to the roll kneader. The kneading is controlled by changing at least one of the lengths of the paths .

Here, the viscosity is calculated based on the rubber temperature of the kneaded rubber in the roll kneader, the roll drive torque of the roll kneader, the roll gap, the roll surface speed, and the bank amount by using a preset viscosity estimation formula. It is also possible to control the rubber temperature and the bank amount of the kneaded rubber so as to correct the difference between the estimated rubber viscosity and the target viscosity .

In addition, as the rubber temperature and roll driving torque used for estimating the viscosity, estimated values set in advance in a monotonically decreasing function form can be used .

  According to the rubber material kneading control method of the present invention, in the rubber material kneading control method, the kneaded rubber discharged from the closed mixer is kneaded with at least one roll kneader to obtain a kneaded rubber having a target viscosity. By controlling the roll gap of the roll kneader to 0.5 mm to 3.0 mm, which is effective for reducing the viscosity, a large shearing force can be applied to the kneaded rubber, and the viscosity can be efficiently reduced. In addition to this, since the rubber temperature of the kneaded rubber in the roll kneader is controlled to 40 ° C. to 90 ° C. effective in reducing the viscosity, the viscosity reduction can be promoted. Thus, kneading rubber having a stable viscosity can be obtained efficiently by kneading the two conditions of the roll cap and the rubber temperature.

In addition to controlling the temperature of the kneaded rubber, setting an appropriate roll gap, etc. in order to make the kneaded rubber have a predetermined viscosity , the kneaded rubber can be increased or decreased by increasing or decreasing the bank amount of the kneaded rubber on the roll of the roll kneader. By controlling at least one of the conveying speed of the conveyor belt to be circulated into the roll or the length of the circulation path for circulating the kneaded rubber to the roll kneader, the kneaded rubber having a predetermined viscosity that is more accurate and stable can be obtained. Can be obtained .

The rubber material kneading control method of the present invention will be described below based on the embodiments shown in the drawings. FIG. 1 illustrates an overall outline of a basic roll kneader.

  This roll kneader 1 has a pair of left and right rolls 2 that are rotationally driven by electric motors 5 in opposite directions, and has an open structure. The kneaded rubber R is repeatedly and continuously supplied to the roll 2 and kneaded by the reversing conveyor belt 4 for supplying the kneaded rubber R to the roll 2 from above and the transfer conveyor belt 10 in which one end is lifted. .

  One roll 2 is provided with an actuator 6 so that the roll gap can be changed by moving the roll 2. A roll gap sensor 8 is disposed below the rolls 2, and a temperature sensor 7 that detects the temperature of the kneaded rubber R and a cooling fan 3 that cools the kneaded rubber R are disposed above the transfer conveyor belt 10.

  Each data of the electric power level P (drive torque), roll surface speed V, roll gap h, and rubber temperature T of the electric motor M is transmitted to the arithmetic unit 9.

  When the kneaded rubber R discharged from the hermetic mixer is kneaded by the roll kneader 1, the roll gap is detected by the roll gap sensor 8, and the roll gap is set to 0.5 mm or more and 3.0 mm or less by the actuator 6. While controlling, the rubber temperature T of the kneaded rubber R is detected by the temperature sensor 7, the degree of cooling is adjusted by the cooling fan 3, and the temperature is controlled in the range of 40 ° C. or higher and 90 ° C. or lower, and the kneaded rubber R is repeatedly kneaded. This control is performed via the arithmetic unit 9.

  This control range is illustrated inside the rectangle of FIG. If the roll gap h is less than 0.5 mm, the amount of rubber that can be kneaded in a given time cannot be increased, and it becomes difficult to control the gap. If the roll gap h exceeds 3.0 mm, sufficient shearing force cannot be applied and viscosity is effective. Cannot be reduced.

  On the other hand, if the rubber temperature T exceeds 90 ° C., sufficient shearing force cannot be given even if it is repeatedly kneaded, and the viscosity cannot be lowered. Further, when the temperature is lower than 40 ° C., the load on the roll or the like is increased, resulting in problems such as insufficient mechanical strength, and the rubber sheet is easily cut due to a decrease in the fluidity of rubber, thereby increasing the risk of occurrence of trouble.

  Therefore, by kneading the roll gap h and the rubber temperature T simultaneously within this range, a kneaded rubber having an efficient and stable viscosity can be obtained.

  In particular, when the roll gap h and the rubber temperature T are controlled within the control range within the rectangular shape, and within the range within the parallelogram, it is possible to further accelerate the viscosity reduction.

Viscosity control when carrying out the above kneading operation is to estimate and calculate the viscosity over time based on the rubber temperature, roll drive torque, roll gap and roll surface speed, so that the estimated viscosity becomes the target viscosity in a predetermined time. And kneading while controlling. Although it does not specifically limit as a calculation formula used for estimation of a rubber viscosity in the kneading | mixing operation process, following (1) Formula can be illustrated.
η _MV = P / [K · exp [Ea / R (1 / T-1 / 373)] · (V / 2h) ^A ] (1)
Here, η _MV : Viscosity index (reference temperature is 100 ° C. and shear rate is 2 [1 / s])
P: Roll drive power level (corresponding to drive torque)
K: Coefficient Ea: Activation energy R: Gas constant T: Rubber temperature V: Roll surface speed h: Roll gap size A: 0.3 to 1.0 (coefficient determined by kneaded rubber)

  FIG. 2 illustrates this control flow, which will be described with reference to this figure. First, at a certain point when the kneaded rubber R discharged from the hermetic mixer is kneaded to some extent by the roll kneader 1, the power level P (drive torque) of the electric motor M, the roll surface speed V, the roll gap h, and the rubber temperature T Each data is acquired and the viscosity of the kneaded rubber R is estimated by the arithmetic unit 9 using the above equation (1).

  Thereafter, the target viscosity at the time set in advance and the estimated viscosity are compared. If the estimated viscosity is within the allowable range of the target viscosity, the kneading is continued without changing the kneading conditions. If the estimated viscosity is higher than the target viscosity, the cooling temperature of the cooling fan 3 is increased to increase the number of cooling fans 3 to be operated, the fan rotation speed is increased, etc., and the rubber temperature T is decreased to promote the viscosity decrease. In addition, the roll gap h can be reduced to promote viscosity reduction.

  If the estimated viscosity is lower than the target viscosity, it is difficult to reduce the viscosity by decreasing the number of cooling fans 3 to operate, slowing down the fan rotation speed, etc. To do. Also, the roll gap h can be increased to suppress the viscosity reduction.

  The means for controlling the rubber temperature is not limited to the cooling fan 3, and a fluid may be circulated inside the roll 2 to exchange heat. The kneading time can be adjusted by controlling and changing the roll surface speed V.

  This control is repeatedly carried out by appropriately determining the number of times within a predetermined kneading time. Then, when the target viscosity is reached within a predetermined kneading time, the control is terminated as indicated by the dotted line. This control process is illustrated in FIG. 3, and the viscosity E estimated at the time of measurement of T1 to T4 gradually approaches the target viscosity G set in advance by this control, and the target viscosity ηf is set at the predetermined kneading time Tf. Can do.

In this control method, when the estimated viscosity is calculated by the above equation (1) or the like, instead of using actually measured values that vary greatly for the rubber temperature T and the power level P (driving torque), a monotonously decreasing function type is used in advance. It is preferable to use the estimated value set in. The monotonic decreasing function form is a function form represented by, for example, Y = AlogX + B, Y = AexpX + B, Y = AX ^B (where X is an actual measurement value, Y is an estimated value, and A and B are constants). An approximate curve is continuously calculated based on real values, and the representative rubber temperature and representative power level (torque) at the time of measurement are obtained as estimated values. In addition, the moving average value of the measured value for the most recent predetermined time can also be used.

  In FIG. 5 and FIG. 6, as an example of the estimated values of the rubber temperature and the power level obtained in a monotonously decreasing function form, the measured values and the moving average values of the measured values for each minute are displayed. It can be seen that the estimated value obtained in the monotonically decreasing function form and the moving average value per minute are more stable than the actually measured values, and in particular, the estimated value obtained in the monotonically decreasing function form is more stable.

FIG. 7 shows the relationship between the final viscosity index (η _MV ) and the actually measured final viscosity when the estimated viscosity is calculated and controlled based on the estimated values of the rubber temperature and power level obtained in a monotonically decreasing function form, and 1 minute. The relationship between the final viscosity index (η _MV ) and the actually measured final viscosity when the estimated viscosity is calculated and controlled based on each moving average value is shown. In FIG. 7, the data plotted with circles shows the former monotonically decreasing function form, and the data plotted with triangles shows the latter moving average value per minute. From this result, it is possible to obtain a kneaded rubber having a stable viscosity with a certain degree of variation by the control method based on both estimated values, and in particular, according to the estimated value obtained by the monotonically decreasing function form, the relationship is closer to the actually measured viscosity. It can be seen that a kneaded rubber having a stable viscosity with little variation in viscosity from batch to batch can be obtained. This makes it possible to obtain a kneaded rubber having a stable viscosity with little variation in viscosity for a predetermined time.

FIG. 8 illustrates an overall outline of a roll kneader 1 that implements the rubber material kneading control method of the present invention . The roll kneading machine 1 is obtained by adding a bank amount sensor 11 to the roll kneading machine 1 shown in FIG.

  In roll kneading, the shearing force applied to the kneaded rubber R by the roll 2 varies depending on the so-called bank amount B of the kneaded rubber R on the roll 2. When the bank amount B is large, the narrow gap between the rolls 2 and 2 is pushed from a wider state, so that the shearing force increases and the viscosity decreases. Therefore, the viscosity of the kneaded rubber R varies depending on the bank amount B.

  In the roll kneader 1, a bank amount sensor 11 is provided to suppress such a variation in viscosity. As the bank amount sensor 11, the bank amount B is detected using an infrared camera, an optical sensor, or the like. Specifically, for example, the height H from the top surface of the roll 2 to the top surface of the kneaded rubber R on the roll 2 is detected, and the bank amount B is calculated by the arithmetic unit 9 connected using the detection data. presume.

  As an example of a method for estimating the bank amount B, a method for estimating the bank amount B by approximating it with a cylindrical body will be described with reference to FIG. A line segment CL in the figure is a center line between the rolls 2 and 2.

  The bank amount sensor 11 detects the height H from the top surface of the roll 2 to the top surface of the kneaded rubber R on the roll 2, and the intersection C between the horizontal line and the center line CL from the top surface of the roll 2 to the height H. And the area of a circle that touches the surface of both rolls 2 through the intersection C is calculated. Then, the length of the kneaded rubber R in the roll width direction is detected by the bank amount sensor 11 or another means, and the volume of the cylindrical body is obtained by multiplying the calculated circle area and the length in the roll width direction of the kneaded rubber R, This is the bank amount B.

  By inputting data such as the center coordinates of the roll 2, the outer diameter, the distance between the two rolls 2, and the like into the arithmetic device 9, the bank amount B can be estimated in real time by the arithmetic device 9. The estimation of the bank amount B is not limited to this, and may be approximated by another method.

  When the viscosity of the kneaded rubber R is higher than the predetermined viscosity, the bank amount B is controlled to be increased. In order to increase the bank amount B, the conveyor conveyance speed CV of the transfer conveyor belt 10 and the reversing conveyor belt 4 is increased, or the height position of the recirculating conveyor belt 4 is decreased to shorten the circulation path of the kneading rubber R. .

  On the other hand, when the viscosity of the kneaded rubber R is lower than the predetermined viscosity, the bank amount B is controlled to decrease. In order to reduce the bank amount B, the conveyor conveyance speed CV of the transfer conveyor belt 10 and the reversing conveyor belt 4 is decreased, or the height position of the recirculating conveyor belt 4 is increased to extend the circulation path of the kneading rubber R. That's fine.

  For example, the viscosity when the same kneaded rubber R is roll-kneaded with only the bank amount B changed is as shown in FIG. The bank amount (index) in FIG. 10 is an index of the volume of the kneaded rubber R on the roll 2 with respect to the reference volume, and the larger this index is, the larger the bank amount B is. The viscosity index is an index with respect to the reference viscosity. The larger the index, the higher the viscosity, and the viscosity index before roll kneading (the number of roll passes is 0) is 10.

  From this result, it can be seen that as the bank amount B increases, the viscosity can be quickly reduced, and as the number of roll passes increases, the difference in the effect increases. Such measurement is performed to collect and accumulate data, and the relationship between the bank amount B and the decrease in viscosity is grasped in advance and used for increase / decrease control of the bank amount B.

As the viscosity control by the roll kneader 1, the viscosity is estimated and calculated over time based on the rubber temperature, the roll drive torque, the roll gap, the roll surface speed, and the bank amount, and the estimated viscosity becomes the target viscosity in a predetermined time. Knead while controlling. As a calculation formula used for estimating the rubber viscosity in the kneading operation process, for example, the following formula (2) in which the item of bank amount B is added to the formula (1) described above can be exemplified.
η _MV = P / [K · exp [Ea / R (1 / T−1 / 373)] · (V / 2h−1 / B) ^A ]
(2)
Here, B is the bank amount, and other symbols are the same as in equation (1).

  In this way, in addition to controlling the temperature of the kneaded rubber R and setting an appropriate roll gap in order to make the kneaded rubber R have a predetermined viscosity, the bank amount sensor 11 detects the bank amount B, and the delivery conveyor belt 10 and By adjusting the conveyor conveyance speed CV of the kneaded conveyor belt 4 and the circulation path of the kneaded rubber R to control the increase / decrease in the bank amount B, it is possible to obtain the kneaded rubber R having a predetermined viscosity that is more accurate and stable.

It is explanatory drawing which illustrates the outline | summary of the basic roll kneader . It is a control flowchart which shows an example of the kneading | mixing control method of a rubber material . It is a graph which shows an example of the control progress by the control flow of FIG. It is a graph which shows the control range of the kneading | mixing rubber temperature and roll gap in the kneading | mixing control method of a rubber material . It is a graph which shows the relationship between the kneading | mixing time and rubber | gum temperature in the kneading | mixing process of a rubber material. It is a graph which shows the relationship between the kneading | mixing time and electric power level in the kneading | mixing process of a rubber material. It is a graph which shows the relationship between the viscosity index of an estimated value, and the last viscosity of measurement. It is explanatory drawing which illustrates the outline | summary of the roll kneader which implements the kneading | mixing control method of the rubber material of this invention. FIG. 9 is an explanatory diagram illustrating a method for enlarging the main part of FIG. It is a graph which shows the influence which the bank amount and the frequency | count of a roll pass in the kneading | mixing process of a rubber material have on a viscosity fall.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 roll kneader 2 roll 3 cooling fan 4 kneading conveyor belt 5 electric motor 6 actuator 7 temperature sensor 8 roll gap sensor 9 arithmetic device 10 delivery conveyor belt 11 bank amount sensor R kneading rubber G target viscosity curve E estimated viscosity curve

Claims (3)

In a kneading control method of a rubber material in which a kneaded rubber discharged from a closed mixer is kneaded with at least one roll kneader to obtain a kneaded rubber having a target viscosity, the roll gap of the roll kneader is set to 0.5 mm to 3 mm. The rubber temperature of the kneaded rubber in the roll kneader is controlled to 40 ° C. to 90 ° C. so that the target viscosity is reached in a predetermined time, and the increase / decrease in the bank amount of the kneaded rubber on the roll of the roll kneader is increased. The kneaded rubber is kneaded in a controlled manner by changing at least one of the conveying speed of the conveyor belt to be circulated and fed to the roll kneader or the length of the circulation path through which the kneaded rubber is circulated to the roll kneader. Rubber material kneading control method. Using a viscosity estimation formula set in advance, the viscosity is estimated based on the rubber temperature of the kneaded rubber in the roll kneader, the drive torque of the roll of the roll kneader, the roll gap, the roll surface speed, and the bank amount, The rubber material kneading control method according to claim 1 , wherein the rubber temperature and bank amount of the kneaded rubber are controlled so as to correct a difference between the estimated rubber viscosity and the target viscosity. The rubber material kneading control method according to claim 2 , wherein an estimated value set in advance in a monotonically decreasing function form is used as the rubber temperature and roll driving torque used for estimating the viscosity.

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