Rubber mixing method and sealed rubber mixer

Abstract

To provide a rubber mixing method and a sealed rubber mixer which improve a variation in quality of a rubber mixture caused by a waiting time before mixing and enable homogenization of rubber mixtures obtained in multiple batches.SOLUTION: In a rubber mixing method in which raw rubber and compounding ingredients are mixed batch by batch in a chamber 10 of a sealed rubber mixer equipped with a temperature control function using temperature-controlling water, when a waiting time before mixing reaches a preset threshold value or when a mixer temperature of the sealed rubber mixer during standby drops to a preset threshold value, a temperature control condition is changed so that a flow rate of the temperature-controlling water is reduced until a designated time has elapsed or until a designated mixer temperature is reached or until the mixing step immediately after standby is completed.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a rubber mixing method for mixing raw rubber and compounding ingredients batch by batch and an internal rubber mixer for carrying out the method. More specifically, the present invention relates to a rubber mixing method and an internal rubber mixer which improve the variation in quality of the rubber mixture caused by the waiting time before mixing and enable homogenization of the rubber mixture obtained in multiple batches. [Background technology]

[0002] When manufacturing rubber products such as tires and rubber hoses, for example, raw rubber and various compounding agents such as carbon black and silica are charged into an internal rubber mixer and mixed (see, for example, Patent Document 1). This mixing allows the various compounding agents to be uniformly dispersed in the raw rubber, and a rubber mixture with an appropriate viscosity is obtained. The internal rubber mixer is equipped with a pair of rotors arranged in parallel within a chamber. As the rubber mixture rotates around the rotors, it is kneaded by applying a shear force between the rotors and the inner wall surface of the chamber.

[0003] In the rubber mixing process described above, heat is generated because the rubber is repeatedly subjected to shear forces. In contrast, closed-type rubber mixers are equipped with a temperature control device that circulates temperature-controlled water around the chamber, so that the heat of the rubber in the chamber is transferred to the temperature-controlled water. It is known that such heat transfer during rubber mixing has a significant effect on the unvulcanized physical properties of the rubber.

[0004] However, when mixing the same lot of rubber in multiple batches, the history of heat transfer from the rubber varies depending on the waiting time before mixing, which can cause variations in the quality of the rubber mixture between batches. For example, when the waiting time before mixing is long, the viscosity of the rubber mixture obtained in the batch immediately after the waiting time decreases.

[0005] In response to this problem, when mixing the same lot of rubber in multiple batches, it is possible to homogenize the rubber mixtures obtained in multiple batches by blending them together. However, from the viewpoint of traceability, blending rubber mixtures obtained in multiple batches is not necessarily desirable, and an alternative method is being sought. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-214119 A 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 and an internal rubber mixer which improve the variation in quality of the rubber mixture caused by the waiting time before mixing and enable homogenization of the rubber mixture obtained in a plurality of batches. [Means for solving the problem]

[0008] In order to achieve the above object, the rubber mixing method of the present invention uses an internal rubber mixer equipped with a temperature control function using temperature-controlling water, and mixes raw rubber and compounding ingredients in a chamber of the internal rubber mixer in batches, comprising the steps of: When the waiting time before mixing reaches a preset threshold value, the temperature control conditions are changed so that the flow rate of the temperature-controlled water is reduced until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing process immediately after the waiting period is completed.

[0009] In order to achieve the above object, the present invention provides an internal rubber mixer comprising a chamber into which raw rubber and compounding ingredients are fed, a pair of rotors which rotate within the chamber, a temperature control device which circulates temperature-controlled water around the chamber, and a control device which controls the flow rate of the temperature-controlled water, The control device is characterized in that when the waiting time before mixing reaches a preset threshold value, it changes the temperature control conditions so that the flow rate of the temperature-controlled water is reduced until a specified time has elapsed, until a specified mixer temperature is reached, or until the mixing process immediately after waiting is completed.

[0010] Another rubber mixing method of the present invention for achieving the above object is a rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature-controlling water, in which raw rubber and compounding ingredients are mixed in a chamber of the internal rubber mixer in batches, comprising the steps of: When the mixer temperature of the internal rubber mixer during standby drops to a preset threshold value, the temperature control conditions are changed so that the flow rate of the temperature-controlled water is reduced until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing process immediately after standby is completed.

[0011] Another closed type rubber mixer of the present invention for achieving the above object is a closed type rubber mixer comprising a chamber into which raw rubber and compounding ingredients are fed, a pair of rotors which rotate within said chamber, a temperature control device which circulates temperature-controlled water around said chamber, and a control device which controls the flow rate of said temperature-controlled water, The control device is characterized in that, when the mixer temperature of the internal rubber mixer during standby drops to a preset threshold value, it changes the temperature control conditions so as to reduce the flow rate of the temperature-controlled water until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing process immediately after standby is completed. Effect of the Invention

[0012] In the present invention, when the waiting time before mixing reaches a preset threshold, the temperature control conditions are changed to reduce the flow rate of temperature-controlled water until a designated time has elapsed, or until a designated mixer temperature is reached, or until the mixing step immediately after waiting is completed, thereby suppressing a drop in the mixer temperature, thereby improving the variation in the quality of the rubber mixture caused by the waiting time and homogenizing the rubber mixtures obtained in multiple batches. In this case, the rubber mixture for each batch can be supplied as it is to the manufacturing process of the rubber product, ensuring traceability.

[0013] Alternatively, in the present invention, when the mixer temperature of the internal rubber mixer during standby drops to a preset threshold, the temperature control conditions are changed to reduce the flow rate of temperature-controlled water until a designated time has elapsed, or until the designated mixer temperature is reached, or until the mixing process immediately after standby is completed, thereby suppressing the drop in mixer temperature, thereby improving the variation in quality of the rubber mix caused by the standby time and homogenizing the rubber mixes obtained in multiple batches. In this case, the rubber mix for each batch can be supplied as it is to the manufacturing process of the rubber product, ensuring traceability.

[0014] In the present invention, when the temperature control conditions are controlled using the mixer temperature as an index, it is preferable to use the temperature detected by a temperature sensor installed in at least one of the end plates, the casing, and the drop door surrounding the chamber as the mixer temperature. The temperature detected by the temperature sensor installed in such a position sufficiently reflects the temperature of the rubber mixture. [Brief description of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing an internal rubber mixer according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a front view showing an internal rubber mixer according to an embodiment of the present invention. [Diagram 3]FIG. 2 is a circuit diagram showing a pump and a control device for a temperature adjustment device in the internal rubber mixer according to the embodiment of the present invention. [Figure 4] 1 is an example of a flowchart of a rubber mixing method according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram showing various control patterns in the rubber mixing method according to an embodiment of the present invention. [Figure 6] 2 is a graph showing the Mooney viscosity of rubber mixtures obtained by the rubber mixing method of the present invention for each batch. [Figure 7] 1 is a graph showing the Mooney viscosity of rubber mixtures obtained by a conventional rubber mixing method for each batch. [Figure 8] FIG. 2 is a cross-sectional view showing an internal rubber mixer according to another embodiment of the present invention. [Figure 9] FIG. 2 is a front view showing an internal rubber mixer according to another embodiment of the present invention. [Figure 10] FIG. 4 is a circuit diagram showing a pump and a control device for a temperature adjustment device in an internal rubber mixer according to another embodiment of the present invention. [Figure 11] 2 is an example of a flowchart of a rubber mixing method according to another embodiment of the present invention. [Figure 12] FIG. 4 is a diagram showing a control pattern in a rubber mixing method according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1 and 2 show an internal rubber mixer according to an embodiment of the present invention, and Figure 3 shows a pump and a control device for the temperature control device.

[0017] 1 and 2, this closed rubber mixer includes a cylindrical casing 1 that forms a chamber 10 that is a mixing space for materials to be mixed, a pair of rotors 2, 2 arranged to extend horizontally within the casing 1, a pair of end plates 3, 3 arranged at both ends of the casing 1 and supporting the pair of rotors 2, 2, a drive unit 4 that rotates the pair of rotors 2, 2, a cylinder 5 connected to the top of the casing 1 and extending vertically, an upper cover 6 configured to be movable vertically within the cylinder 5, a material input section 7 provided midway through the cylinder 5, a drop door 8 arranged at the bottom of the casing 1 that can be opened and closed, and a temperature control device 9 including piping for circulating temperature-controlled water that is embedded in the casing 1 and the drop door 8. The pair of rotors 2, 2 are configured to rotate in opposite directions to each other, and the rotation mixes a rubber mixture R consisting of raw rubber and compounding agents that is input into the chamber.

[0018] As shown in FIG. 3, a pump 11 for circulating temperature-controlled water (cooling water) in a temperature control device 9 (cooling device) is connected to a power source 13 via an inverter 12. The inverter 12 is connected to a control device 14, and adjusts the voltage and frequency of the power supplied to the pump 11 based on a control signal supplied from the control device 14. Therefore, the output of the pump 11 (i.e., the flow rate of the temperature-controlled water per unit time) can be adjusted, for example, in the range of 0% to 100%. That is, the control device 14 generates a control signal under a predetermined condition, and controls the flow rate of the temperature-controlled water based on the control signal. The temperature of the temperature-controlled water is not particularly limited, but is set, for example, in the range of 30°C to 60°C, preferably in the range of 40°C to 50°C.

[0019] When a rubber mixture R is to be obtained using the closed rubber mixer configured as described above, first, the drop door 8 is closed and the top cover 6 is moved above the cylinder 5, and raw rubber and compounding agents are charged into the chamber 10 from the material charging section 7. As compounding agents, various compounding agents such as reinforcing agents such as carbon black and silica, oil, anti-aging agents, processing aids, softeners, plasticizers, vulcanizing agents, vulcanization accelerators, and vulcanization retarders are appropriately used. After the raw rubber and compounding agents are charged into the chamber 10 and the top cover 6 is closed, the pair of rotors 2, 2 are rotated to knead the raw rubber and compounding agents. As a result, the compounding agents are uniformly dispersed in the raw rubber, and a rubber mixture R adjusted to an appropriate viscosity is obtained. The rubber mixture R thus obtained is discharged from the drop door 8. In this way, the mixing process for one batch is completed.

[0020] In the above-mentioned mixing process, the rubber mixture R generates heat as it is kneaded while being subjected to shear force between the rotor 2 and the inner wall surface of the chamber 10 as it rotates around the rotor 2. For this reason, in the closed-type rubber mixer, temperature-controlled water is constantly circulated by the temperature control device 9 to control the temperature of the chamber 10, and the heat of the rubber mixture R in the chamber 10 is transferred to the temperature-controlled water. Such heat transfer during rubber mixing has a significant effect on the unvulcanized physical properties of the rubber mixture R.

[0021] Usually, when mixing one lot of materials, the mixing work is performed in multiple batches (e.g., 5 batches) in consideration of the capacity of the internal rubber mixer. Therefore, for example, if the waiting time before mixing the first batch is long, the mixer temperature may be excessively lowered due to the temperature control effect of the temperature control device 9, and the physical properties of the rubber mixture R obtained in the first batch may differ from the physical properties of the rubber mixture R obtained in the remaining batches.

[0022] Therefore, in the above-mentioned rubber mixing method, the waiting time before mixing is measured, and when the waiting time before mixing reaches a preset threshold, the temperature control conditions are changed so that the flow rate of the temperature control water is reduced until the specified time has elapsed, until the specified mixer temperature is reached, or until the mixing process immediately after waiting is completed. That is, when the waiting time before mixing reaches a preset threshold, the control device 14 changes the temperature control conditions so that the flow rate of the temperature control water by the pump 11 is reduced until the specified time has elapsed, until the specified mixer temperature is reached, or until the mixing process immediately after waiting is completed. For example, when the waiting time before mixing reaches a preset threshold, the flow rate of the temperature control water can be changed to 75% of the normal flow rate. When the temperature control conditions are changed until the specified time has elapsed, it is desirable to measure the specified time from the start of the mixing process immediately after waiting. The specified time can be set, for example, within a range of 1 minute to 10 minutes.

[0023] FIG. 4 is an example of a flowchart of a rubber mixing method according to an embodiment of the present invention. When the mixing process is repeatedly performed for multiple batches, the waiting time before mixing is measured (step S1), and when the waiting time reaches a preset threshold value (step S2), the flow rate change of the temperature control water is started (step S3) and the flow rate change time is measured (step S4). Then, when the mixing process is completed (step S5), or when the flow rate change time reaches a designated time (step S6), or when the designated mixer temperature is reached (step S7), the flow rate change of the temperature control water is terminated (step S8). In the above flowchart, the flow rate change of the temperature control water is terminated using all of the judgment results of steps S5 to S7 as the judgment criterion, but the flow rate change of the temperature control water can be terminated using at least one of the judgment results of steps S5 to S7 as the judgment criterion.

[0024] FIG. 5 shows various control patterns in the rubber mixing method according to the embodiment of the present invention. In FIG. 5, when the mixing process of multiple batches is repeatedly performed, the threshold of the waiting time is set to 10 minutes, and the designated time for changing the flow rate of the temperature-controlled water is set to 10 minutes from the start of the mixing process immediately after the waiting. In the control pattern A, the flow rate is changed so that the flow rate of the temperature-controlled water is reduced from the time when the waiting time has elapsed 10 minutes until the mixing process immediately after the waiting is completed. In the control pattern B, the flow rate is changed so that the flow rate of the temperature-controlled water is reduced from the time when the waiting time has elapsed 10 minutes until the mixing process immediately after the waiting is completed, and such a flow rate change is performed whenever the waiting time reaches the threshold. In the control pattern C, the flow rate change is started so that the flow rate of the temperature-controlled water is reduced from the time when the waiting time has elapsed 10 minutes, and the flow rate change is completed when the designated time (10 minutes) has elapsed from the start of the mixing process immediately after the waiting. In addition, the flow rate change can be completed when the designated mixer temperature is reached.

[0025] In the above-mentioned rubber mixing method, when the waiting time before mixing reaches a preset threshold, the temperature control conditions are changed to reduce the flow rate of the temperature-controlled water until a specified time has elapsed, or until a specified mixer temperature is reached, or until the mixing process immediately after waiting is completed, thereby suppressing a drop in the mixer temperature, thereby improving the variation in quality of the rubber mixture R caused by the waiting time and homogenizing the rubber mixture R obtained in multiple batches. Moreover, since the rubber mixture R for each batch can be supplied as it is to the manufacturing process for rubber products, traceability can be ensured, unlike the method of blending rubber mixtures R obtained in multiple batches.

[0026] Figure 6 shows the Mooney viscosity of the rubber mixture obtained by the rubber mixing method of the present invention for each batch, and Figure 7 shows the Mooney viscosity of the rubber mixture obtained by the conventional rubber mixing method for each batch. As shown in Figure 7, in the conventional rubber mixing method, the Mooney viscosity of the rubber mixture obtained in the first batch, which had a long waiting time, is significantly lower than the Mooney viscosity of the rubber mixture obtained in the other batches. In contrast, as shown in Figure 6, in the rubber mixing method of the present invention, the Mooney viscosity of the rubber mixture obtained in the first batch, which had a long waiting time, is close to the Mooney viscosity of the rubber mixture obtained in the other batches.

[0027] Fig. 8 and Fig. 9 show an internal rubber mixer according to another embodiment of the present invention, and Fig. 10 shows a pump and a control device for the temperature adjustment device. In this embodiment, the same parts as those in the embodiment of Fig. 1 to Fig. 3 are given the same reference numerals, and detailed description of those parts is omitted.

[0028] As shown in Figs. 8 and 9, in the closed rubber mixer of this embodiment, temperature sensors 21, 22, and 23 are respectively disposed in the casing 1, the end plate 2, and the drop door 8 surrounding the chamber 10. Thermocouples are preferably used as the temperature sensors 21, 22, and 23. More specifically, a hole that does not penetrate from the outside into the chamber 10 is provided in the side of the casing 1, and the temperature sensor 21 is inserted into the hole. The temperature sensor 21 detects the temperature of the chamber 10 (casing temperature) without contacting the rubber mixture R. In addition, a hole that penetrates from the outside into the chamber 10 is provided in the end plate 2, and the temperature sensor 22 is inserted into the hole. The temperature sensor 22 detects the temperature of the chamber 10 (end plate temperature) while contacting the rubber mixture R. In addition, a hole that penetrates from the outside into the chamber 10 is provided in the drop door 8, and the temperature sensor 23 is inserted into the hole. The temperature sensor 23 detects the temperature of the chamber 10 (drop door temperature) while contacting the rubber mixture R.

[0029] 10, the temperatures detected by the temperature sensors 21, 22, and 23 are input to the control device 14. The control device 14 refers to at least one of the temperatures detected by the temperature sensors 21, 22, and 23 as a mixer temperature, and controls the output of the pump 11 of the temperature adjustment device 9 based on the mixer temperature.

[0030] Specifically, in the above-mentioned rubber mixing method, when the mixer temperature of the closed rubber mixer on standby drops to a preset threshold, the temperature control conditions are changed so that the flow rate of the temperature control water is reduced until a specified time has elapsed, or until the designated mixer temperature is reached, or until the mixing process immediately after standby is completed. That is, when the mixer temperature (casing temperature, end plate temperature, and / or drop door temperature) of the closed rubber mixer on standby drops to a preset threshold, the control device 14 changes the temperature control conditions so that the flow rate of the temperature control water by the pump 11 is reduced until a specified time has elapsed, or until the designated mixer temperature is reached, or until the mixing process immediately after standby is completed. For example, when the mixer temperature of the closed rubber mixer on standby drops to a preset threshold, the flow rate of the temperature control water can be changed to 75% of the normal flow rate. When the temperature control conditions are changed until a specified time has elapsed, it is desirable to measure the specified time from the start of the mixing process immediately after standby. The specified time can be set, for example, within a range of 1 minute to 10 minutes. Note that the casing temperature, end plate temperature, and drop door temperature do not necessarily coincide with each other, so the thresholds can be set arbitrarily according to the measurement points.

[0031] FIG. 11 is an example of a flow chart of a rubber mixing method according to another embodiment of the present invention. When the mixing process of multiple batches is repeatedly performed, the mixer temperature of the closed rubber mixer on standby is measured (step S11), and when the mixer temperature falls to a preset threshold value (step S12), the flow rate change of the temperature control water is started (step S13) and the flow rate change time is measured (step S14). Then, when the mixing process is completed (step S15), or when the flow rate change time reaches a designated time (step S16), or when the designated mixer temperature is reached (step S17), the flow rate change of the temperature control water is terminated (step S18). In the above flow chart, the flow rate change of the temperature control water is terminated using all of the judgment results of steps S15 to S17 as the judgment criterion, but the flow rate change of the temperature control water can be terminated using at least one of the judgment results of steps S15 to S17 as the judgment criterion.

[0032] FIG. 12 shows various control patterns in a rubber mixing method according to another embodiment of the present invention. In FIG. 12, when the mixing process of multiple batches is repeatedly performed, the threshold value of the mixer temperature is set to 40°C, and the designated time for changing the flow rate of the temperature-controlling water is set to 10 minutes from the start of the mixing process immediately after standby. In control pattern D, the flow rate is changed so that the flow rate of the temperature-controlling water is reduced from the time when the mixer temperature drops to 40°C (the time when the standby time is about 10 minutes) until the end of the mixing process immediately after standby. In control pattern E, the flow rate is changed so that the flow rate of the temperature-controlling water is reduced from the time when the mixer temperature drops to 40°C (the time when the standby time is about 10 minutes) until the end of the mixing process immediately after standby, and such a flow rate change is performed whenever the mixer temperature drops to the threshold value. In control pattern F, the flow rate change is started so that the flow rate of the temperature-controlling water is reduced from the time when the mixer temperature drops to 40°C (the time when the standby time is about 10 minutes), and the flow rate change is ended at the time when the designated time (10 minutes) has elapsed from the start of the mixing process immediately after standby. Alternatively, the flow rate change can be terminated when the specified mixer temperature is reached.

[0033] In the above-mentioned rubber mixing method, when the mixer temperature of the internal rubber mixer during standby drops to a preset threshold value, the temperature control conditions are changed to reduce the flow rate of temperature-controlled water until a designated time has elapsed, or until a designated mixer temperature is reached, or until the mixing process immediately after standby is completed, thereby suppressing the drop in mixer temperature, thereby improving the variation in quality of the rubber mixture R caused by the standby time and homogenizing the rubber mixture R obtained in multiple batches. Moreover, since the rubber mixture R for each batch can be supplied as it is to the manufacturing process for rubber products, traceability can be ensured, unlike the method of blending rubber mixtures R obtained in multiple batches. EXAMPLES

[0034] In a rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature-control water, raw rubber and silica-based compounding agents are mixed in batches in the chamber of the internal rubber mixer. When the waiting time before mixing reaches a preset threshold (10 minutes), the temperature control conditions are changed so that the flow rate of the temperature-control water is reduced until a specified time has elapsed, until a specified mixer temperature is reached, or until the mixing process immediately after waiting is completed (Examples 11 and 12). In addition, in Standard Example 11 and Comparative Example 11, the same mixing process was carried out with the temperature control conditions kept constant.

[0035] In Standard Example 11, Comparative Example 11, and Examples 11 and 12, one lot was divided into five batches for the mixing process, and the waiting time between batches was 1 minute in principle, with only the waiting time for the first batch being different. The temperature-controlled water flow rate, waiting time, mixing time, and time for changing the temperature-controlled conditions when the temperature-controlled conditions were changed are shown in Table 1. The temperature-controlled water flow rate when the temperature-controlled conditions were changed is the ratio to the standard time.

[0036] For the rubber mixtures obtained in each batch of Standard Example 11, Comparative Example 11, and Examples 11 and 12, the Mooney viscosity, storage shear modulus G' at 0.28% strain, and storage shear modulus G' at 300% strain were measured, and the coefficient of variation of the rubber mixture obtained in the first batch was calculated. The results are also shown in Table 1. A smaller coefficient of variation means less variation in quality.

[0037] [Table 1]

[0038] As can be seen from Table 1, in Comparative Example 11, as a result of the longer waiting time, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were larger and the quality variation was larger than in Standard Example 11. In contrast, in Examples 11 and 12, even when the waiting time was longer, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were smaller and the quality variation was smaller.

[0039] Next, in a rubber mixing method in which raw rubber and carbon-based compounding agents are mixed in batches in a chamber of an enclosed rubber mixer equipped with a temperature control function using temperature-control water, when the waiting time before mixing reaches a preset threshold value (10 minutes), the temperature control conditions are changed so that the flow rate of temperature-control water is reduced until a specified time has elapsed, until a specified mixer temperature is reached, or until the mixing process immediately after waiting is completed (Examples 21 and 22). Also, in Standard Example 21 and Comparative Example 21, the same mixing process was carried out with the temperature control conditions kept constant.

[0040] In Standard Example 21, Comparative Example 21, and Examples 21 and 22, one lot was divided into five batches for the mixing process, and the waiting time between batches was 1 minute in principle, with only the waiting time for the first batch being different. The temperature-controlled water flow rate, waiting time, mixing time, and time for changing the temperature-controlled conditions when the temperature-controlled conditions were changed are shown in Table 2. The temperature-controlled water flow rate when the temperature-controlled conditions were changed is the ratio to the standard time.

[0041] For the rubber mixtures obtained in each batch of Standard Example 21, Comparative Example 21, and Examples 21 and 22, the Mooney viscosity, storage shear modulus G' at 0.28% strain, and storage shear modulus G' at 300% strain were measured, and the coefficient of variation of the rubber mixture obtained in the first batch was calculated. The results are also shown in Table 2. A smaller coefficient of variation means less variation in quality.

[0042] [Table 2]

[0043] As can be seen from Table 2, in Comparative Example 21, as a result of the longer waiting time, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were larger than those of Standard Example 21, and the quality variation was larger. In contrast, in Examples 21 and 22, even when the waiting time was longer, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were smaller, and the quality variation was smaller. Note that the effect was more remarkable when the above-mentioned silica-based compounding agent was mixed than when a carbon-based compounding agent was mixed.

[0044] Next, in a rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature-control water, raw rubber and silica-based compounding agents are mixed in batches in the chamber of the internal rubber mixer. When the mixer temperature (end plate temperature) of the internal rubber mixer during standby falls to a preset threshold value (80°C), the temperature control conditions are changed so that the flow rate of the temperature-control water is reduced until a specified time has elapsed, until the specified mixer temperature is reached, or until the mixing process immediately after standby is completed (Examples 31 and 32). In addition, in Standard Example 31 and Comparative Example 31, the same mixing process was carried out with the temperature control conditions kept constant.

[0045] In Standard Example 31, Comparative Example 31, and Examples 31 and 32, one lot was divided into five batches for the mixing process, and the waiting time between batches was 1 minute as a rule, with only the waiting time for the first batch being different, resulting in different mixer temperatures in the internal rubber mixer during standby. The temperature control water flow rate, end plate temperature, mixing time, and time for changing the temperature control conditions when the temperature control conditions were changed are shown in Table 3. The temperature control water flow rate when the temperature control conditions were changed is the ratio to the standard time.

[0046] For the rubber mixtures obtained in each batch of Standard Example 31, Comparative Example 31, and Examples 31 and 32, the Mooney viscosity, storage shear modulus G' at 0.28% strain, and storage shear modulus G' at 300% strain were measured, and the coefficient of variation of the rubber mixture obtained in the first batch was calculated. The results are also shown in Table 3. A smaller coefficient of variation means less variation in quality.

[0047] [Table 3]

[0048] As can be seen from Table 3, in Comparative Example 31, as a result of the decrease in the mixer temperature (end plate temperature), the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were larger and the quality variation was larger than in Standard Example 31. In contrast, in Examples 31 and 32, even when the mixer temperature (end plate temperature) was decreased, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were smaller and the quality variation was smaller.

[0049] Next, in a rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature control water, raw rubber and silica-based compounding agents are mixed in batches in the chamber of the internal rubber mixer. When the mixer temperature (casing temperature) of the internal rubber mixer during standby drops to a preset threshold value (45°C), the temperature control conditions are changed so that the flow rate of temperature control water is reduced until a specified time has elapsed, until the specified mixer temperature is reached, or until the mixing process immediately after standby is completed (Examples 41 and 42). In addition, in Standard Example 41 and Comparative Example 41, the same mixing process was carried out with the temperature control conditions kept constant.

[0050] In Standard Example 41, Comparative Example 41, and Examples 41 and 42, one lot was divided into five batches for the mixing process, and the waiting time between batches was 1 minute in principle, with only the waiting time for the first batch being different, resulting in different mixer temperatures in the internal rubber mixer during standby. The temperature control water flow rate, casing temperature, mixing time, and time for changing the temperature control conditions when the temperature control conditions were changed are shown in Table 4. The temperature control water flow rate when the temperature control conditions were changed is the ratio to the standard time.

[0051] For the rubber mixtures obtained in each batch of Standard Example 41, Comparative Example 41, and Examples 41 and 42, the Mooney viscosity, storage shear modulus G' at 0.28% strain, and storage shear modulus G' at 300% strain were measured, and the coefficient of variation of the rubber mixture obtained in the first batch was calculated. The results are also shown in Table 4. A smaller coefficient of variation means less variation in quality.

[0052] [Table 4]

[0053] As can be seen from Table 4, in Comparative Example 41, as a result of the decrease in the mixer temperature (casing temperature), the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were larger and the quality variation was larger than in Standard Example 41. In contrast, in Examples 41 and 42, even when the mixer temperature (casing temperature) was decreased, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were smaller and the quality variation was smaller.

[0054] Next, in a rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature control water, raw rubber and silica-based compounding agents are mixed in batches in the chamber of the internal rubber mixer. When the mixer temperature (drop door temperature) of the internal rubber mixer during standby falls to a preset threshold value (70°C), the temperature control conditions are changed so that the flow rate of temperature control water is reduced until a specified time has elapsed, until the specified mixer temperature is reached, or until the mixing process immediately after standby is completed (Examples 51 and 52). In addition, in Standard Example 51 and Comparative Example 51, the same mixing process was carried out with the temperature control conditions kept constant.

[0055] In Control Example 51, Comparative Example 51, and Examples 51 and 52, one lot was divided into five batches for the mixing process, and the waiting time between batches was 1 minute in principle. Only the waiting time for the first batch was varied, and as a result, the mixer temperature of the internal rubber mixer during standby was varied. The temperature control water flow rate, drop door temperature, mixing time, and time for changing the temperature control conditions when the temperature control conditions were changed are shown in Table 5. The temperature control water flow rate when the temperature control conditions were changed is the ratio to the standard time.

[0056] For the rubber mixtures obtained in each batch of Standard Example 51, Comparative Example 51, and Examples 51 and 52, the Mooney viscosity, storage shear modulus G' at 0.28% strain, and storage shear modulus G' at 300% strain were measured, and the coefficient of variation of the rubber mixture obtained in the first batch was calculated. The results are also shown in Table 5. A smaller coefficient of variation means less variation in quality.

[0057] [Table 5]

[0058] As can be seen from Table 5, in Comparative Example 51, as a result of the decrease in the mixer temperature (drop door temperature), the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were larger and the quality variation was larger than that of Standard Example 51. In contrast, in Examples 51 and 52, even when the mixer temperature (drop door temperature) was decreased, the coefficients of variation of the Mooney viscosity and storage shear modulus G' (0.28%, 300%) of the rubber mixture obtained in the first batch were smaller and the quality variation was smaller. [Explanation of symbols]

[0059] 1 Casing 2 Rotors 3 End Plate 4. Drive unit 5 Cylinder 6 Top lid 7 Material input section 8. Drop Door 9 Temperature control device 11 Pump 12 Inverter 13 Power supply 14 Control device 21,22,23 Temperature Sensor R Rubber mixture

Claims

1. A rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature-controlling water, in which raw rubber and compounding ingredients are mixed in a chamber of the internal rubber mixer for each batch, A rubber mixing method characterized in that, when a waiting time before mixing reaches a preset threshold, the temperature control conditions are changed so that the flow rate of the temperature control water is reduced until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing step immediately after the waiting is completed.

2. A closed-type rubber mixer including a chamber into which raw rubber and compounding ingredients are introduced, a pair of rotors that rotate within the chamber, a temperature control device that circulates temperature-controlled water around the chamber, and a control device that controls the flow rate of the temperature-controlled water, the control device changes the temperature control conditions so as to reduce the flow rate of the temperature-controlled water when a waiting time before mixing reaches a preset threshold value, until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing process immediately after waiting is completed.

3. A rubber mixing method using an internal rubber mixer equipped with a temperature control function using temperature-controlling water, in which raw rubber and compounding ingredients are mixed in a chamber of the internal rubber mixer for each batch, A rubber mixing method characterized in that, when the mixer temperature of an internal rubber mixer during standby drops to a preset threshold value, the temperature control conditions are changed so that the flow rate of the temperature-controlled water is reduced until a designated time has elapsed, until a designated mixer temperature is reached, or until the mixing process immediately after standby is completed.

4. 4. The rubber mixing method according to claim 3, wherein the mixer temperature is a temperature detected by a temperature sensor installed in at least one of an end plate, a casing, and a drop door surrounding the chamber.

5. A closed-type rubber mixer including a chamber into which raw rubber and compounding ingredients are introduced, a pair of rotors that rotate within the chamber, a temperature control device that circulates temperature-controlled water around the chamber, and a control device that controls the flow rate of the temperature-controlled water, the control device, when the mixer temperature of the internal rubber mixer on standby drops to a preset threshold value, changes the temperature control conditions so as to reduce the flow rate of the temperature-controlled water until a designated time has elapsed, until the mixer temperature reaches a designated value, or until the mixing process immediately after standby is completed,

6. 6. The internal rubber mixer according to claim 5, wherein the mixer temperature is a temperature detected by a temperature sensor installed in at least one of an end plate, a casing, and a drop door surrounding the chamber.

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