JPS6331365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber mixing method in which rubber mixing is completed by keeping the mixing time constant from the time when a ram reaches a specific position during kneading until the end of mixing.

Conventionally, in order to eliminate variations in the plasticity of the mixture due to variations in the degree of shear force generated in the mixer during mixing from batch to batch, mixing methods have been used in which the electrical energy consumed from the start of mixing to the end of mixing is constant. However, if the same type of rubber is mixed and the amount of power required for mixing is constant,
It is well known that variations in the plasticity of the raw material rubber introduced lead to variations in the plasticity of the resulting mixture. In other words, assuming that the amount of power consumed for mixing is constant, if the raw rubber has a high plasticity, the electric energy required to mechanically crush the raw rubber is at a high level immediately after the raw rubber is added, and the rubber mixture will not reach the specified level. This is because the amount of power consumption reaches a predetermined value and the mixing ends before the plasticity level decreases to . Conventionally, attempts have been made to use this type of rubber mixing method to detect the plasticity of the raw rubber at the initial stage of mixing and use it to correct the standard power consumption value during mixing. There is a method of detecting and using the peak value of raw rubber, but the peak power level immediately after raw rubber is introduced changes depending on the shape of raw rubber and the timing of raw rubber input.

As is well known, the two rotors of a general rubber mixing machine rotate at a certain ratio to increase the kneading efficiency, so raw rubber may be introduced when the rotational phase of both rotors matches. The penetration of the raw material rubber differs from when it is not used, and a large change appears in the peak power value. In a normal rubber mixer (Banbury mixer), the time interval during which the rotational phases match is approximately 10 seconds, and it is practical to use this peak power value to detect the degree of plasticity of raw rubber during mixing. isn't it. In addition, in order to detect the degree of plasticity of raw rubber by applying the electric signal provided by the mixer during mixing, it is necessary to obtain the empirical formula for both by performing a relatively large number of test mixtures. When mixing other rubbers with different amounts, the empirical formula cannot generally be used as is. Furthermore, when modifying the reference power consumption value during mixing, the amount of modification must generally be determined for each type of rubber with a different composition.

An object of the present invention is to provide a rubber mixing method that reduces variations in the plasticity of a mixture due to differences in the plasticity of raw rubbers.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a rubber mixer (Banbury mixer) used in the method of the present invention, in which 1 is a chamber, 2 is a cooling jacket, and 3 is a rotor provided within the chamber 1. A door 4 is provided at the bottom of the chamber 1 for releasing the mixture. 6 is a raw rubber inlet, 7 is a carbon black inlet, and 8 is a nozzle for injecting oil into 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 located above. Reference numeral 12 denotes a stopper rod extending outside the cylinder 10 and connected to the ram 9 (which may also be the piston rod 11). A permanent magnet 13 is attached to the rotor rod 12.
A ram motion sensor 14 is provided at a position facing this permanent magnet 13. The ram motion sensor 14 has a structure that can extract an electric signal according to the height of the vertical movement of the permanent magnet 13. It is connected to the reed switch.

Figure 2 is an example of a chart observed during rubber mixing, where A represents the temporal change in electric power consumed in the mixer, and B represents the temporal change in the movement of the ram 9 (ram motion). It is taken out as an output signal of the sensor 14.

A typical rubber mixing operation is performed as follows. With the ram 9 raised to the top dead center, a predetermined weight of raw rubber and carbon black are loaded into the raw rubber inlet 6 and the carbon black inlet 7, respectively.
Input time T ₁ , each input port 6, 7
After closing, the ram 9 is lowered by the cylinder 10, and the raw rubber is pressurized at a predetermined pressure. The raw rubber is crushed by the rotation of the rotor 3 and the chamber 1
The raw rubber is coated with carbon within the chamber, and so-called mechanical mixing progresses during this period. As the raw rubber is crushed into pieces, the apparent volume of the rubber mixture expands, and the ram 9 is gradually pushed upward despite being pressurized with a predetermined pressure. Then, a state is reached where the repulsive force due to the volumetric expansion of the rubber mixture and the pressure exerted by the cylinder 10 are balanced. This state is the maximum value P of the ram motion, and this period is represented by _T2 . As the mixing further progresses, mechanical mixing shifts to chemical mixing, dispersing carbon black and reducing the plasticity of the mixture.As the repulsive force of the entire mixture decreases, the ram descends. Ram motion B forms a chevron. Thereafter, at time _T3 determined from various conditions, other additives such as oil are added, and the mixing ends at time _T4 .

FIG. 3 is a plot of how the plasticity of a rubber mixture changes depending on the mixing time from the maximum ram motion time _T2 to the end of mixing time _T4 in a certain type of rubber mixing. The square, triangle, and circle marks in the graph indicate the level of plasticity of the raw material rubber used for mixing. From this figure, it is clear that the plasticity of the obtained rubber mixture can be determined by the mixing time from the maximum ram motion time T ₂ to the mixing end time T ₄ , and does not depend on the plasticity of the raw rubber. be. Therefore, in the method of the _present invention, _the chemical The mixing end time T ₄ is controlled so that the time required for the target mixing (time from time T ₂ to time T ₄ ) is always constant when mixing the same type of rubber.

FIG. 4 is an example of an electric circuit used in carrying out the present invention, and shows the ram motion sensor 1.
The output of No. 4 is applied to a filter 15, which removes signals in unnecessary frequency bands and outputs it as a signal with a voltage waveform as shown in FIG. 2B. The output of the filter 15 is input to a peak detection section 17. The peak detection unit 17 generates a signal at a time _T2 when the maximum value P of the ram motion B is detected after a time period determined by the timer 16 has elapsed from the raw rubber input time _T1 . The reason for using the timer 16 is to avoid detecting the peak value of the ram motion before time _T2 .
The signal from the peak detector 17 is sent to the mixing time counter 1.
Activate 8. When the count value of the time counter 18 reaches a certain value preset in the setting section 19 according to the type of rubber mixture, the time counter 18 outputs a mixing end command.

In this embodiment, the ram motion is extracted as an analog signal, and the maximum point P of this signal is used as the reference point for determining the time count until the end of mixing.
The invention is not limited to this, but for example, if a detector such as a reed switch or a limit switch is provided at a location where the position where the ram 9 reaches its maximum point can be detected, the signal from this detector becomes the signal at time _T2 . So,
If this signal is input to the time counter 18, exactly the same effect can be obtained. Also, in principle, the shape of ram motion B rises and falls whenever rubber is mechanically cut in the rubber mixing machine, so it is possible to mix rubber without adding additives during mixing, only raw rubber, or similar rubbers. Even when only the mixture is kneaded (massured), the mixing method of the present invention can be applied.

As explained above, by determining the mixing end time so that the mixing time from the maximum ram motion time is constant, the following effects can be obtained.

(1) Even if there is variation in the plasticity of the raw rubber, there is almost no variation in the plasticity of the mixture, and a uniform rubber mixture can be obtained.

(2) In order to determine the mixing time of the rubber mixer to obtain a rubber mixture with a predetermined plasticity, regardless of the degree of plasticity of the raw rubber, the plasticity of the raw rubber and the electric power chart during mixing can be determined. It is not necessary that the relational expression for

(3) When correcting and controlling the overall mixing time reference value using the above relational expression in order to eliminate variations in the plasticity of the rubber mixture, there is no need for test mixing, data analysis, etc. to determine the amount of correction. , a control circuit for performing correction calculations, etc. is not required.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the rubber mixer used in the method of the present invention, Figure 2 is a power chart and ram motion chart during rubber mixing, and Figure 3 is the plasticity of the rubber mixture obtained by mixing. FIG. 4 is an electrical circuit diagram used to carry out the method of the present invention. 14: Ram motion sensor, 17: Peak detection section, 18: Time counter, 19: Setting section.

Claims (1)

[Claims] 1. A method of kneading raw rubber using a rubber mixer, which is characterized by detecting the highest value of ram motion during kneading and keeping the mixing time constant from the time when this highest value is reached until the end of mixing. Law.