JPS6226283B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber mixing method and apparatus for obtaining a rubber mixture with excellent carbon dispersion. In order to uniformly distribute the carbon black within the rubber mixture, it is necessary to generate as high a shear force as possible in the mixer. However, there is a limit to the shearing force that can be applied to the rubber mixture in the mixer due to viscosity reduction due to deformation from the rotor and oil added to strengthen and improve workability. The force changes during mixing, especially as the viscosity decreases. Conventionally,
In this type of mixing method, the oil input time was determined by a specified time, the electrical energy consumed in mixing, the temperature level, or a combination thereof. In these methods, the rubber bite in the mixer and the crushing energy of the rubber blocks change for each mixing batch due to variations in the plasticity of the raw rubber, the temperature, the temperature of the mixer, etc., which causes a large change in the mixing torque. It was not possible to stabilize the carbon dispersion in the rubber mixture at a high level. In addition, in order to eliminate variations in these mixing conditions, temperature control equipment for the mixer, mastication of raw rubber,
This had the disadvantage of requiring heat insulation equipment and complicating the equipment. The present invention detects the movement of the ram during rubber mixing and switches the oil input or ram pressure at a specific level of this ram position, thereby increasing the degree of dispersion of carbon black in the rubber mixture and reducing the variation between mixed batches. It is an object of the present invention to provide a rubber mixing method and apparatus that eliminates this problem and allows a uniform rubber mixture to be obtained. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a rubber mixer (Banbury mixer) used in the present invention, in which 1 is a chamber, 2 is a jacket, and 3 is a rotor provided in the chamber 1. The lower part of the chamber 1 is provided with a ridge 5 forming part of a mixture discharge door 4. Reference numeral 6 designates a raw rubber inlet, 7 a carbon black inlet, and 8 an oil inlet nozzle facing the chamber 1. Reference numeral 9 denotes a ram for applying pressure to the material in the chamber 1, and is connected via a piston rod 11 to a piston (not shown) in a cylinder 10 disposed above. Reference numeral 12 denotes a stopper rod extending outside the cylinder 10, which connects the ram 9 (piston rod 1) to the outside of the cylinder 10.
1). A permanent magnet 13 is attached to the telltale rod 12. A ram motion sensor 14 (hereinafter referred to as a sensor) is provided at a position facing the permanent magnet 13. An example of the sensor 14 is shown in FIG. In FIG. 2, 15 is a power supply terminal, 16 is a rectifier, 17 is a constant current generating circuit, 18 is a voltage dividing circuit, 19 is a limit switch, 20 is a reed relay, and 21 is an output terminal. The voltage dividing circuit 1
8 consists of reed switches 22 arranged along the moving direction of the permanent magnet 13 and resistors 23 connected between each reed switch 22 . When AC power is supplied to the power supply terminal 15, it is rectified by the constant current generating circuit 17, and a stable DC current is supplied to the voltage dividing circuit 18. The limit switch 19 is normally in an off state. When the permanent magnet 13 moves up and down in this state, the reed switch 22 at the position facing the permanent magnet 13 is turned on, and an output proportional to the division ratio of the resistor 23 is generated at the output terminal 21. When the permanent magnet 13 comes out of the area of the reed switch 22, the limit switch 19 is turned on by the permanent magnet 13 (a separate kicker may be provided on the telltale rod 12), thereby turning on the reed relay 20 and outputting. A constant voltage is output from the terminal 21. The above-mentioned ram motion sensor 14 is merely an example, and a well-known linear sensor or angle sensor may be used. FIG. 3 shows an electric circuit for processing the signal from the sensor 13 to control the oil supply timing, in which 24 is a filter, 25 is a voltage reduction detection section, 2
Reference numeral 6 indicates a level setting section, and 27 indicates a comparison section. Next, the rubber mixing operation will be explained with reference to FIG. In Fig. 4, A is the movement of the ram 9 during rubber mixing (ram motion), and B is the rotor 3.
This figure shows the temporal change in torque. With the ram 9 raised to the top dead center, raw rubber and carbon black are charged from the raw rubber input port 6 and carbon black input port 7, respectively, and after closing each of the input ports 6 and 7, the cylinder 10 The ram 9 is lowered and the raw rubber is pressurized with an appropriate pressure. As the roller 3 rotates, the raw rubber is crushed and mixed with carbon black. As the raw rubber is crushed, the apparent volume of the rubber mixture expands,
Ram 9 is gradually pushed upward. Then, a state is reached where the repulsive force accompanying the volumetric expansion of the rubber mixture and the pressure exerted by the cylinder 10 are balanced (fourth
Figure P). As the mixing further progresses, the rebound elasticity of the mixture decreases, so the ram 9 gradually descends and reaches the bottom dead center (Q in FIG. 4). This movement of the ram 9 is expressed as a vertical movement of the permanent magnet 13 via the telltale rod 12, thereby causing an electrical signal to be output from the output terminal 21 of the sensor 14 as described above. In Fig. 3, the output of sensor 13 is
4, unnecessary frequency band signals are removed by the filter 24, and the signal is output as a voltage waveform signal as shown in FIG. 4C. The filter 24
The output is applied to the voltage decrease detection section 25 and the comparison section 27. The voltage decrease detection unit 25 detects that the voltage is at the maximum level.
This circuit outputs an output when it reaches P' and begins to decrease. Such a circuit is well known, but to give an example, by adding the output from the filter 24 to the terminal of the OP amplifier and applying the output from the filter 24 to the terminal via a delay circuit, the voltage at the terminal can be lowered. When the voltage is higher than the voltage on the side, that is, when the voltage decreases, the OP amp outputs an output. or
Using a comparator instead of the OP amplifier, similarly adding the output of the filter 24 to one of the two input terminals and the output of the filter 24 to the other via a delay circuit,
A circuit may also be used in which the comparator outputs an output only when the other voltage is higher than the one voltage. The output of the voltage decrease detection section 25 is given to the comparison section 25, which causes the comparison section 27 to be in an operating state.
The output of the filter 24 and the output of the level setting section 26 are compared. The level setting unit 26 is electrically set with a ram position H (ram level) that determines the timing of oil injection.
When the output from the filter 24 matches the output from the filter 24 (T in FIG. 4), the comparison section 27 makes a level determination and outputs a signal. Based on this signal, oil is supplied from the oil supply nozzle 8. Thereafter, after a certain period of time has elapsed or after a certain amount of electrical energy has been consumed, the door 4 is opened and the rubber mixture is taken out. The timing of adding oil varies depending on the type of rubber to be mixed, weight, etc., so ram level H depends on the type of rubber, weight, etc.
The optimal value is selected depending on the weight. As an example
The table below shows the results of testing the relationship between ram level and carbon dispersion (non-pro mixture) when rubber with a total weight of 187 kg having a mixing ratio of NR:SBR:IR=2:1:1.5 was mixed.

[Table] In the above mixture, a high degree of carbon dispersion can be obtained by setting the ram level in the range of 1.5 to 2.0 cm. In the above-mentioned embodiment, an example was shown in which oil is supplied based on the output signal of the comparison section 27, but it is also possible to perform only switching of the ram pressure without supplying oil. That is, as described above, after the ram 9 reaches the highest point P as the rubber mixture expands in volume, as mixing progresses, the viscosity of the mixture decreases and the rebound properties gradually decline. Ram 9 then begins to descend. By reducing the ram pressure at a certain level when the ram is lowering, or by raising the ram for a short period of time, the declining rebound resilience can be recovered, and when the ram is pressurized again, the shearing force applied to the rubber mixture can be reduced by the ram. You can recover to the same extent as at the highest point P. The switching timing for reducing the ram pressure or increasing the ram pressure coincides with the timing for adding oil when adding oil. Therefore, by reducing the ram pressure or increasing the ram pressure using the output signal of the comparison section 27, the degree of carbon dispersion can be similarly increased. The temperature inside the rubber mixing machine, the plasticity of the raw rubber, the temperature, etc. change seasonally, and some raw rubbers change from batch to batch. It brings about a major change in the mixing process that grinds the raw rubber and disperses the carbon black into the rubber. The output waveform of the ram motion represents changes in these mixing conditions depending on its shape and time lag, so
For homogeneous rubbers, the specific level, which determines the oil input or ram switching time, is always constant. Therefore, according to the present invention, (1) By performing oil injection at a specific level of ram motion, carbon dispersion can be stabilized at a high level despite changes in mixing conditions. (2) At a certain level of ram motion, the rubber and carbon mixture has a certain apparent volume, so if oil is introduced at this time, subsequent electrical energy can be stably added to the rubber mixture. . (3) When the ram pressure is reduced or the ram is lifted at a certain level of ram motion, as the viscosity of the rubber mixture decreases, the rebound resilience, which has been declining, recovers to the same extent, and when the ram is pressurized again. , the shearing force applied to the rubber mixture can be recovered to the same extent, and the degree of carbon dispersion can be stabilized at a high level even when no oil is added. (4) The equipment is simplified because the mixer does not require special equipment such as temperature control equipment or equipment for masticating and insulating raw rubber. There is an effect.

[Brief explanation of the drawing]

Fig. 1 is a vertical side view of a rubber mixer used in the present invention, Fig. 2 is a circuit showing an example of a ram motion sensor, Fig. 3 is a signal processing circuit diagram for carrying out the present invention, and Fig. 4 The figure is a graph showing temporal changes in ram position, torque, and filter output. 3: rotor, 9: ram, 14: ram motion sensor, 24: filter, 25: voltage reduction detection section, 26: level setting section, 27: comparator.

Claims (1)

[Claims] 1. In a method of mixing carbon black with raw rubber using a rubber mixer, the position of the ram during mixing is continuously detected, and the position of the ram is continuously detected while the ram moves from the highest point to the lowest point. A rubber mixing method characterized in that a level determination signal is output when a specific level is reached, and oil injection or ram pressure switching is performed based on this signal. 2. A ram motion sensor attached to the rubber mixing machine, a voltage reduction detection section that outputs an output when the output of the ram motion sensor reaches a maximum level and begins to decrease, and a level at which a specific level of the ram is set in advance. a setting section; a comparator that compares the output of the level setting section and the output of the ram motion sensor and outputs a level determination signal under the condition that the two match and the output of the voltage reduction detection section is output; A rubber mixing device characterized by comprising: