Rubber Mixing Method

Abstract

To provide a rubber mixing method capable of reliably determining the mixed state of an unvulcanized rubber and an additive.SOLUTION: A rubber mixing method kneads an unvulcanized rubber R with an additive X by a roll kneader 1 with a pair of rolls 2 and 2 and conveys a rubber sheet S that has passed a gap between the pair of rolls 2 and 2 by conveyors 3 and 4 to circulate on the pair of rolls 2 and 2. In the rubber mixing method, the method measures a temperature of the rubber sheet S conveyed by the conveyor 4 in a width direction of the rubber sheet S. On the basis of temperature distribution in the width direction of the rubber sheet S, the method determines that the additive X has introduced into the unvulcanized rubber R, and the mixed state of the unvulcanized rubber R and the additive X.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber mixing method using a roll mixer and a circulating conveyor, and more particularly to a rubber mixing method that makes it possible to reliably determine the mixing state of unvulcanized rubber and additives. [Background technology]

[0002] When producing rubber products such as tires and rubber hoses, unvulcanized rubber is prepared by kneading raw rubber with non-vulcanization compounding agents such as carbon black and oil, and then further kneading vulcanization compounding agents such as sulfur into the unvulcanized rubber.

[0003] In such a kneading process, a rubber mixing device is used that includes a roll kneader with a pair of rolls that kneads unvulcanized rubber together with additives, and a conveyor that transports a rubber sheet that passes through the gap between the pair of rolls and circulates it over the pair of rolls (see, for example, Patent Document 1).

[0004] A rubber mixing device using an open roll mixer and a circulating conveyor can mix unvulcanized rubber with vulcanization compounding ingredients while preventing excessive temperature rise. Also, unvulcanized rubber scraps (returned materials) may be added to the roll mixer and kneaded into the mixer.

[0005] However, when unvulcanized rubber is mixed with additives using the above-mentioned rubber mixing device, it is necessary to uniformly disperse additives such as vulcanization compounding agents and unvulcanized rubber scraps in the rubber sheet, but the mixing operation may end with these additives unevenly distributed in the rubber sheet. If additives such as vulcanization compounding agents and unvulcanized rubber scraps are unevenly distributed in the rubber sheet, there is a risk of degrading the quality of rubber products made from it. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-35007 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a rubber mixing method that makes it possible to reliably determine the mixing state of unvulcanized rubber and additives. [Means for solving the problem]

[0008] In order to achieve the above object, the rubber mixing method of the present invention comprises kneading unvulcanized rubber together with additives using a roll kneader equipped with a pair of rolls, conveying a rubber sheet that has passed through a gap between the pair of rolls by a conveyor and circulating it over the pair of rolls, measuring the temperature of the rubber sheet being conveyed by the conveyor along the width direction of the rubber sheet, and determining whether the additives have been added to the unvulcanized rubber and the mixed state of the unvulcanized rubber and the additives based on the temperature distribution in the width direction of the rubber sheet. 1. A rubber mixing method comprising: The temperature distribution in the width direction of the rubber sheet is used as reference information, and when a part in the width direction of the rubber sheet has a temperature lower than a preset threshold, it is determined that the additive has been added to the unvulcanized rubber. If there is a part in the width direction of the rubber sheet where the temperature is lower than the threshold, it is determined that the unvulcanized rubber and the additive are not mixed properly. It is characterized by the following. [Effects of the Invention]

[0009] In the present invention, in a rubber mixing method in which unvulcanized rubber and additives are mixed in a roll mixer equipped with a pair of rolls, and a rubber sheet that passes through a gap between the pair of rolls is transported by a conveyor and circulated over the pair of rolls, the temperature of the rubber sheet being transported by the conveyor is measured along the width direction of the rubber sheet. Because additives such as vulcanization-related compounding agents and unvulcanized rubber scraps (returned materials) are added at a relatively low temperature compared to the unvulcanized rubber that serves as the matrix, their influence is reflected in the temperature distribution along the width direction of the rubber sheet. Therefore, based on the temperature distribution along the width direction of the rubber sheet, it is possible to determine whether the additives have been added to the unvulcanized rubber and the mixing state of the unvulcanized rubber and the additives. In particular, because the temperature distribution along the width direction of the rubber sheet is used as reference information, the mixing state of the unvulcanized rubber and the additives can be reliably determined even in cases where it is difficult to determine visually.

[0010] In the present invention, it is preferable to determine that an additive has been added to unvulcanized rubber when a portion in the width direction of the rubber sheet has a temperature lower than a preset threshold, and then determine that the unvulcanized rubber and the additive are not sufficiently mixed when a portion in the width direction of the rubber sheet has a temperature lower than the threshold. By comparing with such a threshold, the mixing state can be determined more accurately.

[0011] In addition to determining the mixing state of the unvulcanized rubber and the additives, it is preferable to adjust the mixing conditions of the unvulcanized rubber and the additives based on the results of the determination of the mixing state, thereby improving the mixing state of the unvulcanized rubber and the additives and ultimately improving the quality of the rubber product.

[0012] Furthermore, when determining the mixed state of the unvulcanized rubber and the additives, it is preferable to take into account the timing of adding the unvulcanized rubber and the additives and the operating conditions of the roll mixer and the conveyor. The timing of adding the unvulcanized rubber and the additives and the operating conditions of the roll mixer and the conveyor have a significant effect on the mixed state, so by reflecting these in the determination of the mixed state, the mixed state can be determined more accurately. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a side view showing an example of a rubber mixing device used in the present invention. [Figure 2] 2 is a plan view showing a rubber sheet being conveyed by a conveyor in the rubber mixing device of FIG. 1. FIG. [Figure 3] 4 is a graph showing a temperature distribution in the width direction of a rubber sheet. DETAILED DESCRIPTION OF THE INVENTION

[0014] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows an example of a rubber mixing apparatus used in the present invention, and Fig. 2 shows a rubber sheet being transported by a conveyor in the rubber mixing apparatus of Fig. 1.

[0015] As shown in FIG. 1, this rubber mixing device includes a roll mixer 1 having a pair of rolls 2, 2 for mixing unvulcanized rubber R with additives X, and conveyors 3, 4 for transporting a rubber sheet S that has passed through the gap between the pair of rolls 2, 2 and circulating it over the pair of rolls 2, 2. The pair of rolls 2, 2 have their rotation axes arranged parallel to each other along the horizontal direction and are driven to rotate in opposite directions under the control of a control unit 5. An actuator 6 is connected to one of the pair of rolls 2, 2 for displacing the position of the rotation axis, and the gap dimension between the pair of rolls 2, 2 is adjusted by driving this actuator 6. The driving of the actuator 6 is controlled by the control unit 5. The unvulcanized rubber R that is fed onto the pair of rolls 2, 2 passes through the gap between the rolls 2, 2 and is discharged downward as a rubber sheet S.

[0016] The conveyor 3 is configured to transport the rubber sheet S horizontally after passing through the gap between the rolls 2, 2, and then guide the rubber sheet S upward. On the other hand, the conveyor 4 is configured to transport the rubber sheet S received from the conveyor 3 upward, and then transport the rubber sheet S horizontally and guide it to the area directly above the pair of rolls 2, 2. Therefore, the rubber sheet S that has passed through the gap between the pair of rolls 2, 2 is returned to the bank above the pair of rolls 2, 2 via the conveyors 3, 4 and kneaded repeatedly. The driving of the conveyors 3, 4 is controlled by a control unit 5.

[0017] A non-contact temperature measuring device 11 is disposed along the transport path of the rubber sheet S. The temperature measuring device 11 measures the temperature of the rubber sheet S transported by the conveyor 4 along the width direction of the rubber sheet S. That is, as shown in FIG. 2, the temperature of the rubber sheet S is continuously sampled along a measurement line L across at least the entire width of the rubber sheet S. For example, an infrared thermograph can be used as this temperature measuring device 11. The infrared thermograph continuously captures temperature information in the width direction of the rubber sheet R3 as images or videos as the rubber sheet S is transported. Information to be referenced is extracted from the temperature information thus captured. Of course, other devices can also be used as the temperature measuring device 11. The measurement results of the temperature measuring device 11 are input to a determination unit 12. The determination unit 12 determines the mixing state of the unvulcanized rubber R and the additive X based on the temperature distribution in the width direction of the rubber sheet S. The determination result of the determination unit 12 is input to the control unit 5.

[0018] Next, a rubber mixing method using the above-described apparatus will be described. First, as shown in FIG. 1, unvulcanized rubber R is placed on a pair of rolls 2, 2 of a roll mixer 1. A rubber sheet S that passes through the gap between the pair of rolls 2, 2 is transported by conveyors 3, 4 and circulated over the pair of rolls 2, 2. The unvulcanized rubber R is unvulcanized rubber obtained by kneading raw rubber with non-vulcanization compounding agents such as carbon black and oil. Next, an additive X is placed on the pair of rolls 2, 2 of the roll mixer 1 and kneaded into the unvulcanized rubber R. Examples of the additive X include vulcanization compounding agents such as sulfur, as well as unvulcanized rubber scraps (returned materials). Such additive X circulates with the rubber sheet S and is dispersed throughout the rubber sheet S by being repeatedly kneaded by the roll mixer 1. It is also possible to simultaneously place the unvulcanized rubber R and additive X on the pair of rolls 2, 2.

[0019] In the rubber mixing process described above, the temperature of the rubber sheet S transported by the conveyors 3 and 4 is measured along the width direction of the rubber sheet S by a temperature measuring device 11. The determination unit 12 determines whether the additive X has been added to the unvulcanized rubber R and the mixing state of the unvulcanized rubber R and the additive X based on the temperature distribution along the width direction of the rubber sheet S. Because the additive X, such as a vulcanization compounding agent or unvulcanized rubber scrap (return material), is added at a relatively low temperature compared to the unvulcanized rubber R that serves as the matrix, the effect of the addition of the additive X is apparent in the temperature distribution. Therefore, the addition of the additive X can be determined based on the temperature distribution along the width direction of the rubber sheet S, and if there is no temperature drop, it can be determined that the additive X has not been added. As mixing progresses and the additive X is mixed with the unvulcanized rubber R, the temperature distribution along the width direction of the rubber sheet S becomes uniform. However, if the mixing state is insufficient, this will be apparent in the temperature distribution along the width direction of the rubber sheet S. Therefore, the mixing state of the unvulcanized rubber R and the additive X can be determined based on the temperature distribution along the width direction of the rubber sheet S. In particular, since the temperature distribution in the width direction of the rubber sheet S is used as reference information, the mixing state of the unvulcanized rubber R and the additive X can be reliably determined even in cases where it is difficult to determine visually.

[0020] In the rubber mixing process, when at least a portion of the rubber sheet S in the width direction has a temperature lower than a predetermined threshold, it is determined that the additive X has been added to the unvulcanized rubber R. If thereafter, at least a portion of the rubber sheet S in the width direction has a temperature lower than the threshold, it is determined that the unvulcanized rubber R and the additive X are insufficiently mixed. More specifically, the temperature distribution in the width direction of the rubber sheet S may be as shown in FIG. 3. In FIG. 3, the vertical axis represents temperature (°C) and the horizontal axis represents the widthwise position (mm) of the conveyor 4. Since the width of the rubber sheet S is narrower than the width of the conveyor 4, for example, the central side of the widthwise direction of the conveyor 4 is designated as a judgment region M, and the temperature distribution in this judgment region M is used as an index. The judgment region M can be determined based on mixing specifications such as the amount of rubber in the unvulcanized rubber R, the guide width and roll gap of the roll mixer 1, and conveyor settings. The width of the judgment region M can be set arbitrarily, for example, within a range of 30% to 90% of the overall width of the conveyor 4. If the determination region M is too wide, noise increases during determination, and conversely, if it is too narrow, the determination accuracy decreases.

[0021] As shown in FIG. 2, when there is a portion in the rubber sheet S where additive X is unevenly distributed, and a portion in the judgment region M in the width direction of the rubber sheet S has a temperature lower than a preset threshold T, it is determined that additive X has been added to the unvulcanized rubber R. If there is a portion whose temperature is lower than the threshold T even after mixing has progressed, it is determined that the mixing state is insufficient. The threshold T can be arbitrarily selected using as an index the local temperature of the rubber sheet S when a mass of additive X is formed due to insufficient mixing. By comparing the temperature distribution in the width direction of the rubber sheet S with the threshold T in this way, the mixing state of the unvulcanized rubber R and the additive X can be more accurately determined. The threshold T is not particularly limited, but can be set to, for example, 80% or less of the average temperature of the rubber sheet S in the judgment region M.

[0022] In the rubber mixing process described above, in addition to determining the mixing state of the unvulcanized rubber R and the additive X, it is preferable to adjust the mixing conditions for the unvulcanized rubber R and the additive X based on the determination result of the mixing state. For example, based on the determination result of the determination unit 12, the control unit 5 controls the driving conditions of the roll mixer 1 and the conveyors 3 and 4. More specifically, if the mixing state is determined to be insufficient, it is possible to extend the driving time of the roll mixer 1 and the conveyors 3 and 4, narrow the gap between the rolls 2 and 2 to increase the shear force, increase the driving speed of the roll mixer 1 and the conveyors 3 and 4, or apply a combination of these controls. This improves the mixing state of the unvulcanized rubber R and the additive X, and ultimately improves the quality of the rubber product.

[0023] Furthermore, when determining the mixed state of the unvulcanized rubber R and the additive X, it is advisable to take into consideration the timing of feeding the unvulcanized rubber R and the additive X and the operating conditions of the roll mixer 1 and the conveyors 3 and 4. For example, it is clear that the unvulcanized rubber R and the additive X are not sufficiently mixed immediately after feeding the unvulcanized rubber R and the additive X and immediately after starting the operation of the roll mixer 1 and the conveyors 3 and 4, and therefore such periods can be excluded from the determination process. [Explanation of symbols]

[0024] 1 Roll mixer 2 rolls 3,4 Conveyor 5. Control section 6 Actuators 11 Temperature measuring device 12 Judgment section R Unvulcanized rubber S rubber sheet X additives

Claims

1. A rubber mixing method comprising kneading unvulcanized rubber together with additives using a roll kneader equipped with a pair of rolls, conveying a rubber sheet that has passed through a gap between the pair of rolls by a conveyor and circulating it over the pair of rolls, measuring the temperature of the rubber sheet being conveyed by the conveyor along the width direction of the rubber sheet, and determining whether the additives have been added to the unvulcanized rubber and the mixed state of the unvulcanized rubber and the additives based on the temperature distribution in the width direction of the rubber sheet, A rubber mixing method characterized by using the temperature distribution in the width direction of the rubber sheet as reference information, and when a part in the width direction of the rubber sheet has a temperature lower than a predetermined threshold, determining that the additive has been added to the unvulcanized rubber, and if there is then a part in the width direction of the rubber sheet where the temperature is lower than the threshold, determining that the unvulcanized rubber and the additive are not sufficiently mixed.

2. 2. The rubber mixing method according to claim 1, wherein mixing conditions for the unvulcanized rubber and the additives are adjusted based on the result of the determination of the mixed state.

3. The rubber mixing method according to any one of claims 1 to 2, characterized in that when determining the mixed state of the unvulcanized rubber and the additives, the timing of adding the unvulcanized rubber and the additives and the driving conditions of the roll kneader and the conveyor are taken into consideration.

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