Method and system for mixing rubber materials
By controlling the rotor speed to maintain a constant heating rate, the method stabilizes the thermal history of the rubber material, ensuring consistent quality in kneaded rubber production.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- THE YOKOHAMA RUBBER CO LTD
- Filing Date
- 2022-04-07
- Publication Date
- 2026-06-10
Smart Images
Figure 0007872484000001 
Figure 0007872484000002 
Figure 0007872484000003
Abstract
Description
Technical Field
[0001] The present invention relates to a kneading method and system for rubber materials, and more particularly to a kneading method and system for rubber materials capable of more stably producing kneaded rubber of target quality.
Background Art
[0002] Unvulcanized kneaded rubber is used to manufacture rubber products such as tires and rubber hoses. For example, as a rubber material, a primary kneaded rubber is produced by kneading a raw rubber, a non-vulcanizing compounding agent such as carbon black, a filler, an oil, etc. with a closed kneader. Thereafter, a final kneaded rubber is produced by kneading a vulcanizing compounding agent such as sulfur into the primary kneaded rubber.
[0003] In the kneading process for producing these kneaded rubbers, a shearing force is applied to the rubber material by a rotating rotor while dispersing the compounding agent in the raw rubber. To obtain a kneaded rubber of target quality, the compounding agent is sufficiently dispersed in the raw rubber and the viscosity is made appropriate. Various kneading methods for obtaining a kneaded rubber of target quality have been proposed (for example, see Patent Document 1). In the kneading method proposed in Patent Document 1, kneading is performed while controlling the temperature of the rubber material using a closed kneader.
[0004] The change in temperature over time (thermal history) of the rubber material being mixed is closely related to the reaction of the material and is therefore an important indicator during mixing. Since the temperature of the rubber material at the end of the mixing process will be higher than the temperature at the start, the mixing process includes a step to raise the temperature of the rubber material. In a pre-set heating process, if the heating rate at which the rubber material is raised from a predetermined temperature to a target temperature varies, the thermal history of the rubber material will change, which can cause variations in the quality of the mixed rubber. When the rotation speed of the rotor is controlled by PID to bring the temperature of the rubber material being mixed to a target temperature, as used in the mixing method of Patent Document 1, the difference between the temperature of the rubber material being mixed and the target temperature will be reduced more quickly. As a result, the rubber material will reach the target temperature before the end of the heating process, and the target temperature will be maintained thereafter until the end of the heating process. The time required for the rubber material to reach the target temperature depends on the sequentially detected temperature of the rubber material and is therefore prone to variation, and consequently, variations will occur in the thermal history of the rubber material during the pre-set heating process. Therefore, temperature control of such rubber materials is insufficient for the stable production of compounded rubber of the target quality, and there is room for improvement. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] Japanese Patent Publication No. 2020-100116 [Overview of the project] [Problems that the invention aims to solve]
[0006] The object of the present invention is to provide a method and system for compounding rubber materials that can more stably produce compounded rubber of target quality. [Means for solving the problem]
[0007] To achieve the above objective, the present invention provides a method for mixing rubber materials, in which a rubber material consisting of raw rubber and compounding agents is mixed batch by batch by rotating a rotor installed inside the mixing chamber of a closed-type mixer, wherein the target heating rate Vg of the rubber material during the heating process, in which the rubber material is heated from a predetermined temperature M1 to a target temperature Mg over a predetermined time T, is set by the following equation (1), and the rotation speed of the rotor is controlled based on the magnitude of the difference between the measured heating rate Vr of the rubber material detected sequentially during the heating process and the target heating rate Vg, thereby reducing the difference. Then, the measured heating rate Vr during the heating process is brought closer to the target heating rate Vg. It is characterized by the following: Target temperature increase rate Vg=(target temperature Mg-predetermined temperature M1) / predetermined time T...(1)
[0008] The rubber material mixing system of the present invention comprises a closed-type kneader for mixing rubber material consisting of raw rubber and compounding agents in batches, and a control device for controlling the rotational speed of a rotor installed inside the kneading chamber of the closed-type kneader. In the kneading process, in which the rubber material is kneaded by rotating the rotor, the target heating rate Vg of the rubber material during the heating process, in which the rubber material is heated from a predetermined temperature M1 to a target temperature Mg over a predetermined time T set in advance, is set by the following equation (1), and the system comprises a temperature sensor that sequentially detects the temperature of the rubber material during the heating process, and a calculation device to which the detection data from the temperature sensor is sequentially input, and the calculation device sequentially calculates the measured heating rate Vr of the rubber material during the heating process using the detection data, and sequentially calculates the magnitude of the difference between this measured heating rate Vr and the target heating rate Vg, and the control device reduces the difference by controlling the rotational speed of the rotor based on the magnitude of the difference. Then, the measured heating rate Vr during the heating process is brought closer to the target heating rate Vg. It is characterized by its structure. Target temperature increase rate Vg=(target temperature Mg-predetermined temperature M1) / predetermined time T...(1) [Effects of the Invention]
[0009] According to the present invention, the target heating rate Vg of the rubber material during the heating process of the kneading process is set to a constant value such that the temperature of the rubber material rises uniformly over a predetermined time T. Then, by controlling the rotation speed of the rotor so that the measured heating rate Vr of the rubber material during the heating process matches the target heating rate Vg, the measured heating rate Vr is brought closer to the target heating rate Vg, thereby suppressing variations in the thermal history of the rubber material throughout the entire heating process and making it easier to equalize the thermal history. As a result, it is advantageous to manufacture kneaded rubber of the target quality more stably. [Brief explanation of the drawing]
[0010] [Figure 1] This is an explanatory diagram illustrating the kneading system of the present invention, showing a closed kneader in a longitudinal cross-sectional view. [Figure 2] This is a cross-sectional view AA in Figure 1. [Figure 3] This is an explanatory diagram illustrating the process of mixing rubber materials using the mixing system shown in Figure 1. [Figure 4] This graph schematically illustrates a typical example of the temperature change of rubber material over time during the mixing process. [Figure 5] This graph schematically illustrates the target heating rate (temperature change over time) of the rubber material during the heating process according to the embodiment. [Figure 6] This graph schematically illustrates the change in temperature of a rubber material over time when the rotor rotation speed is controlled using PID to reduce the difference between the target temperature of the rubber material and the detected temperature of the rubber material during the heating process. [Modes for carrying out the invention]
[0011] The rubber material mixing method and system of the present invention will be described below based on the embodiments shown in the figures.
[0012] In the embodiment of the rubber material mixing system 1 illustrated in Figures 1 to 3, a mixed rubber Rn of a predetermined quality is produced by mixing a rubber material R consisting of raw rubber G and compounding agent N. This mixing system 1 can be applied to both the production of primary mixed rubber Rn1 without vulcanizing compounding agent and the production of final mixed rubber Rn2 with vulcanizing compounding agent. Primary mixed rubber Rn1 is produced by mixing raw rubber G and non-vulcanizing compounding agent N1. Final mixed rubber Rn2 is produced by mixing primary mixed rubber Rn1 and vulcanizing compounding agent N2.
[0013] As raw material rubber G, various known types of rubber can be used, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene, chloroprene rubber, butyl rubber, styrene-butadiene rubber (SBR), nitrile rubber (acrylonitrile rubber, hydrogenated nitrile rubber), and ethylene propylene diene rubber. Raw material rubber G can be used alone or in combination of two or more types. As non-vulcanizing compounding agent N1, appropriate compounds can be used from among various known compounding agents such as carbon black, silica, silane coupling agents, zinc oxide, and stearic acid. As vulcanizing compounding agent N2, appropriate compounds can be used from among known compounding agents such as sulfur, vulcanization accelerators, vulcanization accelerators, and vulcanization retarders.
[0014] This mixing system 1 comprises a sealed mixing machine 2 (hereinafter referred to as the mixing machine 2), a control device 12 that controls the movement of the mixing machine 2, a computing device 13, and a temperature sensor 14. The computing device 13 receives various data and performs various calculations. The control device 12 and the computing device 13 are connected via wired or wireless communication. The temperature sensor 14 and the computing device 13 are connected via wired or wireless communication.
[0015] The kneader 2 can use various known types. This kneader 2 has a kneading chamber 5a, a ram chamber 5b connected to the upper end opening of the kneading chamber 5a and extending upward, a pair of rotors 3 (3A, 3B) arranged in the kneading chamber 5a, and a ram 6 arranged to be movable up and down in the ram chamber 5b. An oil input part 7 is connected to the kneading chamber 5a, and a rubber input part 8 and a compounding agent input part 10 are connected to the ram chamber 5b. A hopper 9 is connected to the upper end of the compounding agent input part 10.
[0016] Each rotor 3A, 3B has a rotor shaft 3c and stirring blades 3d protruding from the rotor shaft 3c. The respective rotors 3A, 3B (rotor shafts 3c) are arranged opposite to each other, and each rotor shaft 3c is connected to a drive motor 4 via a speed changer 4a. The respective rotors 3A, 3B (rotor shafts 3c) are rotationally driven in opposite directions to each other by the drive motor 4. The rotational drive, stop, and rotational speed of the rotors 3A, 3B (rotor shafts 3c) are controlled by a control device 12.
[0017] An opening and closing discharge door 11 is provided on the bottom surface of the kneading chamber 5a. Further, a temperature sensor 14 is provided on the discharge door 11 with its tip exposed to the kneading chamber 5a. Since the temperature sensor 14 only needs to be able to sequentially detect the temperature of the rubber material R being kneaded in the kneading chamber 5a, it can be installed at a different position (such as the rotor shaft 3c, the stirring blades 3d, the inner wall of the kneading chamber 5a, the lower surface of the ram chamber 5b, etc.) not limited to the discharge door 11. The detection data (the temperature of the rubber material R) detected by the temperature sensor 14 is sequentially input into an arithmetic device 13.
[0018] The ram 6 is moved up and down by a lifting mechanism such as a hydraulic cylinder. The up and down movement (up and down position) of the ram 6 is controlled by the control device 12. When the ram 6 moves downward to the lower limit position illustrated in FIG. 3, the upper end opening of the kneading chamber 5a is blocked and the kneading chamber 5a is in a sealed state. In FIG. 3, the ram 6 in the standby position is shown by a two-dot chain line. In the kneading process, by appropriately moving the ram 6 up and down, the ram pressure applied to the rubber material R introduced into the kneading chamber 5a by the ram 6 is adjusted.
[0019] The control device 12 is equipped with a tachometer 12a and a wattmeter 12b. The tachometer 12a sequentially detects the rotational speed of the rotor 3, and the detected data is sequentially input into the arithmetic unit 13. The wattmeter 12b sequentially detects the instantaneous power amount P1 required to rotationally drive the rotor 3, and the detected data is sequentially input into the arithmetic unit 13. The arithmetic unit 13 calculates the integrated power amount P obtained by integrating the instantaneous power amount P1, and can grasp the integrated power amount P required to rotationally drive the rotor 3 during an arbitrary kneading period.
[0020] A computer is used as the control device 12 and the arithmetic unit 13. In this embodiment, the control device 12 and the arithmetic unit 13 are provided separately, but the control device 12 can also be used as the arithmetic unit 13. That is, it is also possible to adopt a configuration in which one computer functions as both the control device 12 and the arithmetic unit 13.
[0021] As illustrated in FIG. 4, the kneading process of one batch of rubber material R mainly includes a rubber pre-kneading stage (S1), a compounding agent incorporation stage (S2), and a uniform dispersion stage (S3). In the kneading process, the temperature of the kneaded rubber material R changes (is changed) as illustrated in FIG. 4.
[0022] In the rubber pre-kneading stage (S1), with the ram 6 held at the standby position in the ram chamber 5b as illustrated in FIG. 1, a preset predetermined amount of raw rubber G is introduced into the kneading chamber 5a through the rubber input section 8. Thereafter, the ram 6 is moved downward to the lower limit position of the ram chamber 5b. In this state, while introducing oil into the kneading chamber 5a through the oil input section 7, the rotor 3 is rotationally driven to knead the raw rubber G and the oil. In the rubber pre-kneading stage (S1), the temperature of the rubber material R (raw rubber G) is not stable due to the temperature of the introduced raw rubber G and oil, etc.
[0023] In the compounding agent intake stage (S2), the ram 6 is moved to the standby position in the ram chamber 5b, and a predetermined amount of compounding agent N of a set type is introduced from the hopper 9 through the compounding agent input section 10 into the kneading chamber 5a. Then, the ram 6 is moved downward to the lower limit position in the ram chamber 5b. In this state, the rotor 3 is rotated as illustrated in Figure 3 to knead the rubber material R. In the compounding agent intake stage (S2), the temperature of the rubber material R is raised from a predetermined temperature M1 to a target temperature Mg. That is, the compounding agent intake stage (S2) includes a heating process to raise the temperature of the rubber material R.
[0024] In Figure 4, there is a short period after the first heating process in which the temperature of the rubber material R becomes approximately constant, followed by a second heating process. To raise the temperature of the rubber material R from a predetermined temperature M1 to a target temperature Mg, one heating process may be set, or multiple heating processes (2 to 3) may be set. If two heating processes are set, for example, the mixing time for the first and second heating processes may be made the same, and the target temperature of the rubber material R at the end of the first process may be set to a temperature approximately midway between the predetermined temperature M1 and the target temperature Mg.
[0025] In the uniform dispersion stage (S3), the compounding agent N is uniformly dispersed throughout the raw rubber G. In this stage, as illustrated in Figure 3, the rotor 3 is rotated to knead the rubber material R while maintaining the temperature of the rubber material R at a roughly constant level.
[0026] In this embodiment, the target heating rate Vg of the rubber material R during the heating process, in which the rubber material R is heated from a predetermined temperature M1 to a target temperature Mg over a predetermined time T, is set by the following equation (1). Target temperature increase rate Vg=(target temperature Mg-predetermined temperature M1) / predetermined time T...(1)
[0027] In other words, as illustrated by the upward-sloping linear line in Figure 5, the target heating rate Vg of the rubber material R during the heating process is set to a constant value such that the temperature of the rubber material R rises uniformly from a predetermined temperature M1 to a target temperature Mg over a predetermined time T. This target heating rate Vg is input to the calculation device 13. When setting up multiple heating processes, the target heating rate Vg is set similarly for each heating process. Basically, the target heating rate Vg for each heating process should be the same.
[0028] Next, we will describe an example of a procedure for mixing rubber materials using this mixing system 1.
[0029] In the mixing process, as illustrated in Figure 1, a predetermined amount of one batch of rubber material R (raw rubber G, compounding agent N) is put into the mixing chamber 5a of the mixer 2. Next, as illustrated in Figure 3, the rubber material R is mixed by rotating the rotor 3, and mixed rubber Rn is produced through a series of steps S1, S2, and S3 as illustrated in Figure 4.
[0030] Once the mixing process for one batch of rubber material R is complete, the discharge door 11 is opened to discharge the mixed rubber Rn from the bottom of the mixing chamber 5a. The same mixing process is then performed on a new batch of rubber material R, and multiple batches of rubber material R are mixed continuously.
[0031] During the mixing process, the temperature of the rubber material R being mixed is continuously detected by a temperature sensor 14. The calculation unit 13, which receives the detection data from the temperature sensor 14 sequentially, uses this detection data to sequentially calculate the measured heating rate Vr of the rubber material R during the heating process. Then, it sequentially calculates the magnitude of the difference D between the sequentially calculated measured heating rate Vr and the target heating rate Vg.
[0032] The control device 12 reduces the difference D by controlling the rotational speed of the rotor 3 based on the magnitude of the difference D calculated sequentially. Basically, as the rotational speed of the rotor 3 increases, the heating rate of the rubber material R increases, and as the rotational speed of the rotor 3 decreases, the heating rate of the rubber material R decreases. Therefore, if the measured heating rate Vr is faster than the target heating rate Vg, the control device slows down the rotational speed of the rotor 3, and if the measured heating rate Vr is slower than the target heating rate Vg, the control device speeds up the rotational speed of the rotor 3.
[0033] In this way, the heating process of the rubber material R is set to a predetermined time T, and the difference D is reduced using the heating rate of the rubber material R as an indicator. That is, in this embodiment, the rotational speed of the rotor 3 is controlled so that the measured heating rate Vr of the rubber material R matches the target heating rate Vg, which is shown by the upward-sloping linear straight line illustrated in Figure 5. Since the measured heating rate Vr is brought closer to the target heating rate Vg in this way, the change in the temperature of the rubber material R over time during the heating process is generally as illustrated in Figure 5.
[0034] Integrating the upward-sloping linear line illustrated in Figure 5 over a predetermined time T during the heating process gives the thermal history of the rubber material R during this heating process. Therefore, according to this embodiment, variations in the thermal history of the rubber material R over the entire heating process are suppressed, making it easier to maintain a constant thermal history. In other words, it is advantageous to impart the necessary thermal history to the rubber material R without excess or deficiency within a predetermined time T. As a result, it is advantageous to more stably manufacture compounded rubber Rn of the target quality.
[0035] On the other hand, if the rotation speed of the rotor 3 is controlled by PID to reduce the difference between the target temperature Mg of the rubber material R and the sequentially detected temperature of the rubber material R during the heating process of the rubber material R, the change in the temperature of the rubber material R over time will be as illustrated in Figure 6. Figure 6 shows the data (three data points) for the mixing of three types of rubber material R, indicated by a thick solid line, a thick dashed line, and a thick dotted line.
[0036] As illustrated in Figure 6, reducing the difference between the target temperature Mg of the rubber material R and the sequentially detected temperature of the rubber material R will cause the difference to decrease more quickly. As a result, the rubber material R reaches the target temperature Mg before the end of the heating process, and the target temperature Mg is maintained thereafter until the end of the heating process. As illustrated in Figure 6, the time required for the rubber material R to reach the target temperature Mg is subject to variation as it depends on the sequentially detected temperature of the rubber material R. Integrating the temperature data of the rubber material R illustrated in Figure 6 over a predetermined time T of the heating process gives the thermal history of the rubber material R during this heating process. Therefore, this method is also prone to variation in the thermal history of the rubber material R during the heating process over a predetermined time T, making it less advantageous for stably producing compounded rubber Rn of the target quality compared to the embodiment described above.
[0037] In this embodiment, when controlling the rotational speed of the rotor 3 to reduce the difference D, it is preferable to use proportional control (P control) of the rotational speed based on the magnitude of the difference D. That is, the rotational speed is controlled according to the value obtained by multiplying the magnitude of the difference D by a predetermined coefficient K1. This allows for a smoother reduction of the difference D by changing the rotational speed more rapidly when the difference D is large, and changing the rotational speed more slowly when the difference D is small.
[0038] More preferably, the rotational speed is controlled proportionally and integrally (PI control) based on the magnitude of the difference D. That is, in addition to proportional control, the rotational speed is controlled according to a value obtained by multiplying the cumulative magnitude of the difference D by a predetermined coefficient K2. This makes it possible to suppress steady-state deviations of the difference D. However, since the heating rate of the rubber material R varies greatly in a short time, if the rotational speed is controlled by PID control (proportional, integral, and differential control), the fluctuation of the rotational speed becomes excessive. For this reason, it is desirable not to perform PID control when controlling the rotational speed of the rotor 3 in order to reduce the difference D.
[0039] The present invention is highly effective when it is required to strictly adhere to a target temperature Mg during the heating process of the rubber material R. For example, when the rubber material R to be kneaded is unvulcanized rubber that does not contain vulcanizing compounding agents, and contains silica and a silane coupling agent as compounding agents N, strictly adhering to the target temperature Mg is of great importance, and therefore, applying the present invention is particularly preferable. [Explanation of symbols]
[0040] 1. Mixing System 2. Closed-type kneader 3 (3A, 3B) rotors 3c rotor shaft 3D stirring blade 4. Drive motor 4a transmission 5a Mixing Room 5b Ram chamber 6 Ram 7 Oil input section 8 Rubber insertion section 9 Hoppa 10 Compounding agent input section 11 Discharge door 12 Control device 12a Tachometer 12b power meter 13 Arithmetic unit 14. Temperature sensor G Raw rubber N(N1, N2) combination preparation R Rubber Material Rn(Rn1, Rn2) compounded rubber
Claims
1. In a method for mixing rubber materials, in which a rubber material consisting of raw rubber and compounding agents is mixed batch by batch by rotating a rotor installed inside the mixing chamber of a closed-type kneader, A method for kneading a rubber material, wherein the target heating rate Vg of the rubber material during the heating process, in which the rubber material is heated from a predetermined temperature M1 to a target temperature Mg over a predetermined time T, is set by the following equation (1), and the rotation speed of the rotor is controlled based on the magnitude of the difference between the measured heating rate Vr of the rubber material, which is detected sequentially during the heating process, and the target heating rate Vg, thereby reducing the difference and bringing the measured heating rate Vr during the heating process closer to the target heating rate Vg. Target temperature increase rate Vg = (target temperature Mg - predetermined temperature M1) / predetermined time T... (1)
2. The method for kneading a rubber material according to claim 1, wherein the compounding agent is a non-vulcanizing compounding agent containing silica and a silane coupling agent, and the rubber material is unvulcanized rubber without a vulcanizing compounding agent.
3. A method for kneading a rubber material according to claim 1 or 2, wherein the rotation speed is proportionally controlled based on the magnitude of the difference.
4. A method for kneading a rubber material according to claim 1 or 2, wherein the rotation speed is controlled proportionally or integrally based on the magnitude of the difference.
5. A rubber material mixing system comprising a closed-type kneader for mixing rubber materials consisting of raw rubber and compounding agents in batches, and a control device for controlling the rotational speed of a rotor installed inside the mixing chamber of the closed-type kneader, In the kneading process, in which the rubber material is kneaded by rotating the rotor, the target heating rate Vg of the rubber material in the heating process, in which the rubber material is heated from a predetermined temperature M1 to a target temperature Mg over a predetermined time T, is set by the following equation (1): The system comprises a temperature sensor that sequentially detects the temperature of the rubber material during the heating process, and a computing device that sequentially receives the detection data from the temperature sensor. A rubber material mixing system configured such that, using the detection data, the calculation device sequentially calculates the measured heating rate Vr of the rubber material during the heating process, and the magnitude of the difference between this measured heating rate Vr and the target heating rate Vg is sequentially calculated, and the control device controls the rotation speed of the rotor based on the magnitude of the difference to reduce the difference and bring the measured heating rate Vr during the heating process closer to the target heating rate Vg. Target heating rate Vg = (target temperature Mag - set temperature M1) / set time T... (1)