JPH09254148A - Rubber kneading method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restore the uniformity of plastification in an early stage at a time of rubber clogging and to form kneaded rubber excellent in the dispersion of additives by selecting a predetermined first pressure kneading process when there is no possibility of rubber clogging and selecting a predetermined auxiliary kneading process when there is possibility. SOLUTION: A rubberr kneading process 30 in an emergency is automatically changed over when there is the possibility of rubber clogging in a guide hole and an auxiliary kneading process 31 is performed in place of a first pressure kneading process. Changeover is judged based on whether the elapse time T on the way of the falling of a ram wt. reaching the 20% height position Y3 upwardly separated from a lower limit position Y2 over a distance of 20% of the height between an upper limit position Y1 and the lower limit position Y2 from the start of falling is 10 sec or more and, when 10 sec or more is required, the auxiliary kneading process 31 is performed. In the auxiliary kneading process, the guide hole is once reduced in pressure by a pressure reducing auxiliary step 31A and the upward movement of clogged rubber is made smooth and the clogged rubber can be certainly dropped into a mixing chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber kneading method and apparatus capable of increasing the plasticity of a raw rubber and the uniformity of dispersion of a rubber additive.

[0002]

2. Description of the Related Art In order to improve the processability of a rubber material and to impart desired properties after vulcanization, a kneading operation of plasticizing a raw material rubber by cutting rubber molecules and uniformly dispersing additives is carried out. It is necessary and, for that reason, a closed kneading device is frequently used. This one, as shown schematically in FIG.
A ram weight b is placed on a mixing chamber provided with a pair of rotors a and a.
Is arranged so that it can be moved up and down, and the rotor a is rotated in a pressurized state due to the lowering of the ram weight b, whereby a higher shearing force is generated and the kneading efficiency is improved.

[0003]

However, in the closed type kneading device, as shown in the figure, at the initial stage when the raw material rubber is charged, sometimes part of the raw material rubber is ram sliding portion c above the mixing chamber. However, since the kneading state cannot be visually confirmed by the operator, the rubber c1 in this portion is not kneaded, resulting in a poor plasticized state.
There is a problem that the dispersion of the rubber additive becomes uneven. When this rubber clogging is detected, generally, the kneading time is extended, but once the rubber is clogged,
Since it moves in bulk in other rubber having a low viscosity, it is difficult to apply a shearing force, and thus it is difficult and time-consuming to restore the uniformity of plasticization.

In view of this, the present invention identifies the possibility of rubber clogging by measuring the elapsed time during which the ram weight is descending by detecting the height position of the ram weight, and determines when there is no possibility of rubber clogging. Based on the selection of the first pressure kneading process of No. 1 and the predetermined auxiliary kneading process including the depressurization auxiliary step when there is a possibility, the uniformity of plasticization at the early stage of rubber clogging can be achieved at an early stage. It is an object of the present invention to provide a rubber kneading method and an apparatus for the same, capable of stably forming a high-quality kneaded rubber excellent in dispersion of an additive and capable of improving kneading efficiency itself.

[0005]

In order to achieve the above object, the invention according to claim 1 of the present invention is such that a mixing chamber having a rotor and a ram weight for pressurizing the mixing chamber are set from an upper limit position to a lower limit position. A lifting device that holds it so that it can be raised and lowered to a position,
The raw material rubber and the rubber additive to be charged into the mixing chamber at the upper limit position of the ram weight of the mixer including the detector for detecting the height position of the ram weight, the ram weight from the upper limit position to the lower limit position. The first pressure kneading step in which the rotor is rotated at the number of revolutions RA for kneading for a time of TA seconds from the start of descending, and after this step, the ram weight is moved from the lower limit position to the upper limit. A first reduced pressure kneading step in which the rotor is rotated to a rotational speed RB slower than the rotational speed RA and kneaded for a time of TB seconds shorter than the time TA from the start of this rising. In the rubber kneading method, at the time of the first pressure kneading step, a distance of 20% of the height H between the upper limit position and the lower limit position is separated from the lower limit position upward from the start of the descent of the ram weight. Barrel 2 When the elapsed time T during the descent of the ram weight to reach the% height position requires 10 seconds or more, the ram weight is raised from the descent position to the upper limit position instead of the first pressure kneading step and 1 from the start of climb
The rotor is rotated at the rotational speed R for a time T1 of 0 to 30 seconds.
A pressure reduction assisting step of rotating at a low rotational speed R1 of 90 to 70% of A, and the ram weight after this step is lowered from the upper limit position to the lower limit position and T2 shorter than the time difference TA-T1 from the start of the lowering. The rubber kneading method is characterized by performing an auxiliary kneading process including a pressure assisting step of rotating the rotor at a rotation speed RA for a time of 2 seconds.

The invention according to claim 2 is a rubber kneading method characterized in that the time T2 of the pressure assisting step is TA- (T + T1).

According to a third aspect of the present invention, a mixing chamber having a rotor, an elevating tool for holding a ram weight for pressurizing the mixing chamber so as to be able to ascend and descend from an upper limit position to a lower limit position, and a height position of the ram weight are continuous. 2. The rubber kneading method according to claim 1, further comprising a detector for detecting the rotation speed of the rotor and a raising / lowering operation of the ram weight according to a detection signal of the height position by the detector. It is a rubber kneading device that is characterized by performing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the rubber kneading device 1 elevates a device main body 4 having a mixing chamber 3 in which a pair of left and right rotors 2 and 2 are rotatably accommodated, and a ram weight 5 which pressurizes the mixing chamber 3. Lifting tool 6 that can be held
And a detector 7 for continuously detecting the height position of the ram weight 5, and a controller 9 for controlling the rotation speed of the rotor 2 and the raising / lowering operation of the ram weight 5 by a detection signal of the detector 7. It is equipped with

A guide hole 11 is formed in the main body 4 of the apparatus, the lower end of which communicates with the mixing chamber 3 and the inlet 10 of the raw rubber and the rubber additive which can be opened and closed.
The ram weight 5 is guided from the upper limit position Y1 to the lower limit position Y2 along the guide hole 11. The rotor 2 is
The wing portion 2 is provided at each central position of the mixing chamber 3 having a lateral cross section of a figure 8.
The apparatus main body 4 is arranged horizontally with the phase angles of A different from each other.
Are driven to rotate in opposite directions by an electric motor M such as a servomotor.

The elevating tool 6 is formed of, for example, an air cylinder attached to the upper part of the apparatus main body 4, and the raw material rubber in the mixing chamber 3 is pressed at the lower limit position Y2 to the tip of the rod extending downward. The ram weight 5 for applying pressure is provided.

In the present embodiment, the detector 7 is, for example, a rotatably supported disc-shaped rotating body 13 for generating pulse signals, which has slits or the like formed on its outer periphery at equal intervals, and the rotating body 13. One end is connected to the outer circumference of the device and the other end is connected to the device body 4
A cord body 1 such as a wire for converting the up-and-down movement of the ram weight 5 into the rotational movement of the rotating body 13 by being connected to the ram weight 5 through a protection tube 14 standing upright.
5 and a sensor 16 for optically or electromagnetically detecting the passage of a slit or the like of the rotating body 13 associated with the rotating motion. Therefore, when the ram weight 5 moves between the upper limit position Y1 and the lower limit position Y2 due to the expansion and contraction of the rod of the elevating tool 6, the sensor 16 counts the number of passages of the slit or the like of the rotating body 13 to cause the ram to move. Weight 5
The height position of can be continuously detected. The string 15 is held by a pulley, a spring or the like so that the up-and-down movement can be smoothly converted into a rotation movement.

As described above, the detector 7 of the present embodiment detects the ascending / descending movement of the ram weight 5 by replacing it with the pulse signal of the rotating body 13. Therefore, the detector 7 operates smoothly as compared with the detector having a structure for directly reading the ascending / descending movement. It has the advantages that the durability can be improved, the number of sensors can be significantly reduced, and the structure can be simplified and made compact. However, it is also possible to raise the detection axis to the ram weight 5 and the like and detect the up-and-down movement of this detection axis using a plurality of known switches.

The controller 9 comprises a rotor control section for controlling the number of revolutions of the rotor 2 according to the detection signal of the detector 7, and a ram control section for controlling the raising / lowering operation of the ram weight 5. An automatic rubber kneading step 20 schematically shown in FIG. 6 having a pressure kneading step 21 and an emergency rubber kneading step 30 schematically shown in FIG. 7 having a depressurization assisting step 3A are automatically performed. Select and execute.

Here, the regular rubber kneading step 20 is
First pressure kneading step 21 and first reduced pressure kneading step 2
2 and, in the present example, a second pressure kneading step 23
And a second reduced pressure kneading step 24 and a third pressure kneading step 25.

The first press-kneading step 21 is performed as shown in FIG.
6, a step of kneading the raw material rubber and the rubber additive charged into the mixing chamber 3 from the charging port 10 at the upper limit position Y1 of the ram weight 5 in a pressurized state shown in FIGS. The ram weight 5 from the upper limit position Y1 to the lower limit position Y2, and
The rotor 2 is rotated at the number of revolutions RA from the start of falling P1 to TA seconds. It should be noted that in the usual molding of rubber for tires, the process time TA is 25 to 35 seconds, and in this example, 3
It takes about 0 seconds, and the rotor speed RA is 45 to 35.
The rpm is set to about 40 rpm in this example.

In this example, the first pressure kneading step 2
Prior to 1, the main purpose of introducing the raw material rubber or the like to be introduced into the mixing chamber 3 is to close the inlet 10 and then rotate the rotor 2 at a speed higher than the rotational speed RA at the upper limit position Y1 of the ram weight 5. A preliminary process 26 shown in FIGS. 3 and 6 is performed in which the motor is driven at the rotation speed R0 for a time T0 of about 10 seconds.
The difference between the rotor rotation speed R0 and the rotor rotation speed RA in the preliminary step 26 is 5 to 15 rpm, and in this example, 10 rpm.
It is a degree.

In the first vacuum kneading step 22, as shown in FIGS. 5 and 6, the ram weight 5 is raised from the lower limit position Y2 to the upper limit position Y1, and during the rising start P2 to TB seconds. This is a step of kneading by rotating the rotor 2 at a rotation speed RB, and this rotor rotation speed RB is lower than the rotor rotation speed RA by 5 to 15 rpm, in this example 10
It is set to a low speed of about rpm. Also, the process time TB is 5 to 1
It is 5 seconds, which is shorter than the process time TA, and is about 10 seconds in this example.

The second and third pressure kneading steps 23 and 25
Then, the ram weight 5 is lowered from the upper limit position Y1 to the lower limit position Y2, respectively, and the rotor 2 is rotated at the rotational speeds RC and RE during the respective TC seconds and TE seconds from the start of the descent of the ram weight 5 P3 and P5, respectively. Let In the second reduced pressure kneading step 24, the ram weight 5 is raised from the lower limit position Y2 to the upper limit position Y1 and the rotor is rotated at the rotation speed RD for TD seconds from the start P4 of the rise.

The rotor speed RC in the pressure kneading step 23 is the rotor speed RB in the pressure kneading step 22.
The process time TC is shorter than the process time TA and longer than the process time TB, which is about 20 seconds in this example. Also, the rotor rotation speed RD in the reduced pressure kneading step 24
Is approximately equal to the rotor rotational speed RE in the pressure kneading step 25, and is 5 to 1 from the rotor rotational speed RC in the pressure kneading step 23.
The low speed is 5 rpm, and the low speed is 10 rpm in this example. The process time TD of the reduced pressure kneading process 24 is substantially equal to the process time TB of the reduced pressure kneading process 22, and the product RE · T of the rotor rotational speed RE and the process time TE of the pressure kneading process 25.
E is substantially equal to the product RC · TC of the rotor speed RC and the process time TC in the pressure kneading process 23.

That is, the rotor rotational speeds R0 to RE and the process times T0 to TE in the respective steps 20 to 25 are, in this example, R0>RA>RB≈RC> RD≈RE TA>TC> T0≈TB≈TD RE.・ TE≈RC ・ TC.

Here, in general, the viscosity of rubber generally decreases gradually as kneading proceeds, and the impact resilience gradually decreases, so that the shearing force decreases and the cutting efficiency of rubber molecules decreases. However, when the pressure in the mixing chamber 3 is reduced, the impact resilience of the rubber is recovered, and when the pressure is applied again, the shearing force received by the rubber is recovered and the kneading efficiency is enhanced. Therefore, in the present application, the pressure kneading steps 21, 23, 25 and the reduced pressure kneading steps 22, 24 are alternately repeated. Also in the pressure kneading steps 21, 23, and 25, since RA>RC> RE and the rotor speed is reduced as the viscosity decreases, the shearing force on the rubber can be kept high.

The lifting / lowering tool 6 normally moves the ram weight 5 up and down between the upper limit position Y1 and the lower limit position Y2 for about 1 to 2 seconds. Done between.

Next, the rubber kneading step 30 in an emergency will be described. The emergency rubber kneading step 30 is a step of automatically switching when there is a possibility of rubber clogging in the guide hole 11, and as shown in FIG. 7, the first pressure kneading step is performed. An auxiliary kneading step 31 is performed instead of the step 21. It should be noted that, in the switching, during the first pressure kneading step 21, a distance of 20% of the height H between the upper limit position Y1 and the lower limit position Y2 is moved upward from the lower limit position Y2 from the descending start P1. It is judged whether or not the elapsed time T during the descent of the ram weight 5 to reach the separated 20% height position Y3 requires 10 seconds or more. When it takes 10 seconds or more, the auxiliary kneading step 31 is performed.

In the auxiliary kneading step 31, the ram weight 5 is raised again to the upper limit position Y1 from the middle of the lowering, and the rotor 2 is rotated at the rotational speed RA for a time T1 of 10 to 30 seconds from the start P6. Depressurization assisting step 31A of rotating at a low rotational speed R1 of 90 to 70%, and after this step 31A, the ram weight 5 is lowered again from the upper limit position Y1 to the lower limit position Y2, and the downward start time P7 to T2 seconds. In the meantime, the pressurization assisting step 31B for rotating the rotor 2 at a rotation speed R2 equal to the rotation speed RA is configured.

In the auxiliary kneading step 31, as described above, the decompression auxiliary step 31A temporarily reduces the pressure to smooth the upward movement of the clogged rubber, and the mixing chamber 3 accompanying the rotation of the rotor due to the decrease in the rotation speed. Since the internal pressure fluctuation of the rubber inside is easily transmitted to the clogged rubber, the clogged rubber can be reliably dropped into the mixing chamber when the next pressurization is performed. Moreover, the depressurization and the rotation speed reduction in the depressurization assisting step 31A can suppress an excessive viscosity difference between the rubber and the clogged rubber due to the progress of the kneading of the rubber in the mixing chamber 3, and the uniform plasticization. Can be recovered early.

The intermediate elapsed time T, which is the criterion for switching, is preferably set as close to 10 seconds as possible within a range of 10 seconds or more for early recovery of uniformity, and therefore, in this example, about 10 seconds. Set.

The process time T2 of the pressurization assisting step 31B is the process time difference T determined from the overall kneading efficiency.
It may be shorter than A-T1, especially T2 = TA- (T + T
When 1), the rubber kneading step 2 is always / emergency
The process times of 0 and 30 can be substantially matched, and the subsequent work such as vulcanization molding can be facilitated.

After the auxiliary kneading step 31, the first reduced pressure kneading step 2 is carried out in the same manner as the above-mentioned usual rubber kneading step 20.
2, the second pressure kneading step 23, the second reduced pressure kneading step 24, and the third pressure kneading step 25 are sequentially performed.

[0029]

[Examples] Using the kneading device shown in FIG. 1, kneading the raw rubber and the additives shown in Table 1 was performed, and only the regular rubber kneading step was performed regardless of whether or not rubber clogging occurred. Compare the uniformity of dispersion of additives in the kneaded rubber of Comparative Example with the uniformity of dispersion of additives in the kneaded rubber of Example of the present application in which the kneading process is selected for normal / emergency rubber kneading The results are shown in Table 2. Table 3 shows the rotor rotation speed and process time in the rubber kneading process.

The homogeneity of the dispersion of the additives was measured by using a rheometer as a torque while vulcanizing the kneaded rubber at a constant temperature of 160 ° C., and the standard deviation of the maximum torque value in each of the 12 samples was measured. Comparison was made with σ.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

As shown in Table 2, in the case of the comparative example, the standard deviation σ
Is large and the quality of the vulcanized rubber varies greatly depending on the presence or absence of rubber clogging, whereas in the example product of the present application,
It can be seen that vulcanized rubber of substantially constant quality is obtained regardless of whether or not rubber is clogged, and the uniformity is greatly improved.

[0035]

Since the present invention is configured as described above,
When the rubber is clogged, the uniformity of plasticization can be recovered at an early stage, a high-quality kneaded rubber excellent in dispersion of the additive can be stably formed, and the kneading efficiency itself can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing an embodiment of a rubber kneading device of the present invention.

FIG. 2 is a partial cross-sectional view of the main part thereof.

FIG. 3 is a schematic cross-sectional view of an apparatus for explaining a preliminary process.

FIG. 4 is a schematic sectional view of an apparatus for explaining a pressure kneading step.

FIG. 5 is a schematic cross-sectional view of an apparatus for explaining a reduced pressure kneading step.

FIG. 6 is a process diagram showing the relationship between the lifting / lowering operation of a ram weight and time in a regular rubber kneading process.

FIG. 7 is a process diagram showing the relationship between the raising / lowering operation of a ram weight and time in an emergency rubber kneading process.

FIG. 8 is a schematic cross-sectional view of an apparatus for explaining the problems of the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixer 2 Rotor 3 Mixing chamber 5 Ram weight 6 Lifting device 7 Detector 21 First pressure kneading step 22 First depressurizing kneading step 31 Auxiliary kneading step 31A Depressurizing auxiliary step 31B Pressurizing auxiliary step P1, P3, P5, P7 Start of descending P2, P4, P6 Start of rising Y1 Upper limit position Y2 Lower limit position Y3 20% height position

Claims (3)

[Claims] 1. A mixing chamber having a rotor, an elevating tool for holding a ram weight for pressurizing the mixing chamber so as to be able to ascend and descend from an upper limit position to a lower limit position, and a detector for detecting a height position of the ram weight. A raw material rubber and a rubber additive charged into a mixing chamber at the upper limit position of the ram weight of the mixer provided, the ram weight is lowered from the upper limit position to the lower limit position, and during the time of TA seconds from the start of lowering, A first pressure kneading step of kneading by rotating the rotor at a rotation speed RA, and after this step, the ram weight is raised from a lower limit position to an upper limit position and is shorter than the time TA from the start of the raising. A first vacuum kneading step of kneading by rotating the rotor at a rotational speed RB slower than the rotational speed RA for a time of TB seconds; During the kneading process, the descending start of the ram weight, height H between the upper position and the lower limit position 20
When the elapsed time T of the ram weight descending from the lower limit position to the 20% height position which is separated from the lower limit position by 10 seconds or more requires 10 seconds or more, the ram weight is replaced with the first pressure kneading step. A pressure-reducing auxiliary step of raising the rotor from the mid-descent position to the upper limit position and rotating the rotor at a low rotation speed R1 of 90 to 70% of the rotation speed RA for a time T1 of 10 to 30 seconds from the start of the increase, After this step, the ram weight is lowered from the upper limit position to the lower limit position, and the pressurization assisting step of rotating the rotor at the rotation speed RA for a time T2 seconds shorter than the time difference TA-T1 from the start of the lowering. A rubber kneading method comprising performing an auxiliary kneading step consisting of 2. The time T2 of the pressurization assisting step is TA
-(T + T1), a rubber kneading method. 3. A mixing chamber having a rotor, an elevator for holding a ram weight for pressurizing the mixing chamber so as to be capable of moving up and down from an upper limit position to a lower limit position, and a detector for continuously detecting the height position of the ram weight. 2. A rubber kneading apparatus for carrying out the rubber kneading method according to claim 1, further comprising a controller for controlling the rotation speed of the rotor and the lifting and lowering operation of the ram weight according to a height position detection signal from the detector.