JPS6246208B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a twin-screw continuous kneader for the purpose of improving the uniformity of a kneaded material and preventing fillers from being discharged without sufficient dispersion. It is about improvement.

Equipment for kneading polymeric substances such as synthetic resins includes
Broadly divided, there are continuous kneading machines equipped with a single-screw or twin-screw rotor in the chamber, batch-type kneading machines such as Banbury mixers, and screw extruders. The high shear rate plasticizes the material in a short time, enabling efficient kneading.

In other words, as shown qualitatively in the graph of Figure 1, the shear rate of the kneader and the kneading time required to obtain a kneaded product of a constant quality are inversely proportional, and the range represented by the block in the figure A is for a continuous kneader, B is for a batch kneader,
C shows each characteristic range in the case of a screw extruder. For twin-screw continuous kneading machines, the shear rate is maximum
1000sec ^-1 The kneading time is about 10 to 40 seconds, and the kneading is performed in a short time at a significantly higher shear rate than screw extruders, etc., so it is efficient and can be made smaller. It also exhibits excellent ability for kneading composite materials such as mixing inorganic fillers.

However, in recent years, with the development of the synthetic resin industry, the uses of resin have diversified, and in addition to a single type of synthetic resin, there are various types including blended polymers that are a mixture of two or more types of synthetic resins and composite materials that are a mixture of various additives. In response to this, even in continuous kneading machines, depending on the material to be kneaded, it may be necessary to extend the kneading time, and the residence time of the material inside the kneading machine may have to be extended over a wide range. It is required to be adjustable. In this case, according to the conventional continuous kneading machine of this type, the opening degree of the discharge orifice at the discharge port, the production volume, etc. can be considered as adjustment factors.
Problems still remain in adjusting the residence time over a range depending on the various materials.

In other words, the operation of this type of continuous kneading machine is generally performed based on the production volume, the rotation speed of the mixing rotor, the opening degree of the discharge orifice at the discharge port, the cooling conditions of the mixing chamber and the rotor, etc. When the number and cooling conditions are kept constant, the temperature and degree of kneading can be adjusted by the orifice opening, and the relationship between the orifice opening (θ) and the residence time (t) of the material inside the kneader is Second
The result will be as shown in the graph in the figure. That is, when the orifice opening becomes smaller, the material filling rate in the kneader increases due to the increase in discharge resistance, and the residence time becomes longer, thereby increasing the degree of kneading and increasing the temperature of the kneaded material. In addition, as shown in the same graph for the case of production volume Q1 and the case of production volume Q2 (Q1>Q2), the residence time can also be extended by reducing the production volume, but in this case, the residence time can be extended by reducing the production volume. This will reduce efficiency. In addition, lengthening the rotor will also increase the residence time, but this will also increase the temperature of the kneaded material, so if there is a limit to the temperature of the kneaded material, the orifice opening degree must be increased. It does not extend the residence time.

Furthermore, during kneading, in addition to improving the average degree of kneading of the kneaded product, it is often even more important to perform uniform kneading. In other words, for example, regarding the problem of film-grade polyolefin resins and the addition of carbon black, it is important to reduce the overall number of film-eyes and the number of undispersed particles of carbon black, but even in small amounts, If insufficiently kneaded materials are mixed in and fisheye or carbon particles larger than a certain size remain, the properties of the kneaded product will be adversely affected. To prevent this, it is necessary to equalize the residence time of the material in the kneader and prevent the so-called short pass, where the material partially passes through the kneader with little shearing work. In continuous seed kneading machines, short passes are difficult to avoid.
There is a large variation in the local residence time of the material,
The above problems could not be solved. In order to solve this problem, the applicant has proposed that a portion of the barrel corresponding to the kneading blade of the kneading rotor installed in the barrel be moved in the tangential direction to the rotor when moving toward the rotor. We proposed a continuous kneading machine with a constriction mechanism configured to change the gap, and the internal space of the barrel could be adjusted by the constriction mechanism (Japanese Patent Application Laid-open No. 139825/1982), and found a solution to this problem. Figure.

In the above-mentioned kneading machine, the residence time and degree of kneading of the kneaded materials can be adjusted over a wide range, and the average residence time can be extended, making it possible to prevent short passes of the kneaded materials. However, as a result of further research by the present inventors, a kneading machine that can improve the quality of the kneaded product compared to the previously proposed kneading machine has been developed. I found it.

In other words, in the above-mentioned kneading machine, when starting kneading, using only the squeezing mechanism causes problems such as seizure due to the metal contact between the rotor and the squeezing member, which causes resin leakage and reduces the quality of the material at the start of kneading. It was found that the loss of

The present invention was invented in view of the above points, and is characterized in that the kneading properties at the start of kneading and thereafter are controlled by main and sub-orifices. Describe.

Figure 1 is a graph showing the relationship between the kneading time and shear rate of the kneading machine, Figure 2 is a graph showing the relationship between the opening degree of the discharge orifice of the continuous kneader and material residence time, and Figures 3 to 10 The figures show an embodiment of the continuous kneading machine of the present invention, in which Fig. 3 is a longitudinal sectional view showing the entire continuous kneading machine, Fig. 4 is a sectional view taken along line A-A in Fig. 3, and Fig. 5 7 to 7 are cross-sectional views showing an embodiment of the sub-orifice mechanism, FIG. 8 is an enlarged cross-sectional view showing a cross section of the discharge part of the kneading rotor, FIGS. 9 and 10 are cross-sectional views showing the kneading blade portion, and FIG. The figure is a graph showing the relationship between the opening degree of the sub-orifice, the temperature of the kneaded extrudate, and the carbon dispersion index.

As shown in FIG. 3, 1, 1 is a biaxial mixing winged rotor, and 2 is a mixing barrel surrounding both rotors 1, 1. The rotor 1 has a screw part 1a for material transfer and a kneading blade part 1b,
Both rotors 1, 1 are configured to be rotated in mutually different directions by appropriate drive equipment. Further, the barrel 2 is formed by integrating two substantially cylindrical parallel chambers corresponding to the two rotors 1, 1 in communication with each other. A hopper 3 for supplying material is provided at the charging end of the barrel 2, and a discharge port 5 is provided at the other end, including a discharge orifice 4 which opens downward and whose opening degree can be adjusted.

Further, following the kneading blade portions 1b of the rotors 1, 1, there are provided a constriction portion 1c with a circular cross section and a discharge portion 1d with a circular cross section, each having a diameter equal to or smaller than the outer diameter of the rotor.

Reference numeral 6 denotes a movable body disposed in the barrel 2 corresponding to the constricted portion 1c of the rotor, and connects the rotors 1, 1 at right angles to the axial direction while maintaining a sealed state with other parts of the barrel 2. be able to move in the direction of
In other words, it is configured to be able to approach and separate from the rotors 1, 1.

The inner surface of the movable body 6 has a shape in which two arcuate portions are connected in the width direction, corresponding to the outer peripheries of both rotors.

7 is a hydraulic cylinder for opening and closing the orifice 4 in the main orifice mechanism described above.

It is preferable to provide the movable body 6 at the upper and lower parts of the barrel 2, as shown in FIGS. 4 to 7, in order to widen the aperture adjustment range.

That is, in the embodiment shown in FIG. 4, the throttle parts 6 are arranged as separate parts 6a and 6b at the upper and lower positions of the barrel 2, and flange parts 8 are formed at both ends of each movable body 6, and these flanges A fastening bolt 9 having a screw threaded only at the tip portion of the portion 8 and having a smooth portion on the other portion is passed through and attached to the barrel 2, and furthermore, the tips are attached to the upper and lower portions of the barrel 2 near the bolt 9. A distance adjusting bolt 10 is screwed so as to be in contact with each other, and these constitute a sub-orifice mechanism.

FIG. 5 shows movable bodies 6a, 6 of the sub-orifice mechanism.
This is an example where b is linked up and down at the same time,
Screws 11a are formed to move in opposite directions up and down only at the locations corresponding to the upper and lower movable bodies 6a and 6b, and smooth adjustment bolts 11 are inserted into both sides by passing through the upper and lower movable bodies 6a and 6b and the barrel 2. Pulleys 12, 12 are fixed to the upper ends of these adjustment bolts 11, 11, respectively, and a transmission band 13, such as a chain or belt, is stretched between these pulleys.

14 is a handle fixed to one side of the adjustment bolt 11, and by manually rotating the handle, the adjustment bolt 11 is rotated, and the movable bodies 6a, 6 are rotated.
Adjust the positional relationship of b.

15 is a scale attached to the side of the barrel 2, and is provided in a positional relationship corresponding to the pointer 16 attached to the end of the upper movable body 6a.

The embodiment shown in FIG. 6 has a structure in which the scale 15 and pointer 16 shown in FIG. 5 are added to the structure shown in the embodiment shown in FIG. 4, and the embodiment shown in FIG.
Hydraulic cylinders 17a and 17b are provided on the upper and lower sides of the barrel 2, respectively, so that the piston rods 18a and 18 of the cylinders can be adjusted individually or simultaneously.
It has a structure in which movable bodies 6a and 6b are screwed onto the tips of b, respectively.

The configuration of the sub-orifice mechanism is as described above, but in the kneading machine of the present invention, the discharge part 1 of the kneading rotor 1
As shown in Fig. 8 AB, at point d, a protrusion 1e having a height of α is provided with a predetermined tip clearance with the inner wall surface of the barrel 2, in order to avoid heat generation of the kneaded material to be discharged as much as possible. Figure B shows a configuration in which two protrusions 1e are provided at positions with a 180° phase difference.

Note that the cross-sectional shape of the winged portion of the rotor 1 is preferably a structure having wings 1b in two directions as shown in FIG. 9, or wings 1b' in three directions as shown in FIG. The winged part is made up of a combination of wings twisted in the direction of propulsion and wings twisted in the direction of pushing back or wings that do not twist.

Thus, the material continuously and quantitatively supplied through the hopper 3 is melted and kneaded by the rotation of the rotors 1, 1 while passing between the inner surface of the barrel 2 and the rotors 1, 1 in the barrel 2. After
The material is continuously discharged from the discharge orifice 4 of the discharge port 5, and in this case, generally, the longer the residence time of the material in the barrel 2, the better the kneading.

In the kneading machine of the present invention, the orifice mechanism 4 at the outlet location 5 is connected to the hydraulic cylinder 7 at the start of kneading.
It operates and closes completely. This is because the material supplied quantitatively from the hopper 3 is in the form of unmelted powder, so if the orifice 4 is left open, sufficient residence time cannot be secured in the kneading machine. This is because there is a high possibility that it will be discharged in a molten state, and this is to be prevented.

When the time has elapsed when it is considered that the materials supplied into the kneading machine at the start of kneading have been sufficiently kneaded, the orifice 4 of the above-mentioned discharge location 5 is opened, and the gap between the kneading blade 1c and the discharge portion 1d is opened. Manually adjust the movable body 6 of the auxiliary orifice provided in the constriction part 1c provided at change.

In this case, since the auxiliary orifice mechanism of the present invention has a constricted portion 1c of the rotor 1 having a substantially circular cross section,
Since the kneaded material is adjusted by the rotating body on the circumference of the constricted part 1c, there is little chance of the material passing unkneaded in the axial direction, considering the properties of the molten material.
By providing sufficient residence time, the phenomenon of shot passes in the kneader can be prevented and a uniform kneaded product can be obtained.

<Example> Barrel inner diameter 50mmφ High pressure polyethylene (MI=2)/carbon black=74/26 Production volume 60Kg/hr Rotor rotation speed 750RPM Main orifice fully open (27mm), sub orifice in continuous kneading machine When the temperature of the kneaded material and the relationship between the carbon dispersity index and the opening degree of the orifice were measured when the mechanism was operated, results as shown in the graph of FIG. 11 were obtained.

According to the graph in FIG. 11, it can be seen that by fully opening the main orifice mechanism and narrowing the opening of the auxiliary orifice, the temperature of the kneaded material increases and the dispersion of carbon improves.

This allows adjustment of the kneading of the kneaded material by adjusting the opening degree of the sub-orifice, improves carbon dispersion, and ultimately prevents shot passes, which is a problem with this type of kneader.

As described above, the continuous kneading machine of the present invention includes a constriction part with a circular cross section and a corresponding movable body between the kneading blade part of the rotor and the discharge part, separately from the orifice of the discharge part. Since the structure is equipped with an auxiliary orifice, the degree of filling of the kneaded material increases immediately before the discharge section, increasing the chance that the kneaded material will be bitten into the rotor tip, and undispersed particles will be mixed into the kneaded material. As a result, the quality of the kneaded product can be improved.

Furthermore, since the temperature of the kneaded material can be adjusted over a wide range, which was not sufficient with the orifice mechanism of the discharge section alone, the quality of the kneaded material can be further improved.

Further, since the protrusions are provided on the discharge portion of the rotor, it is possible to suppress heat generation of the kneaded material, which helps improve the quality of the kneaded material.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the kneading time and shear rate of the kneading machine, Figure 2 is a graph showing the relationship between the opening degree of the discharge orifice of the continuous kneader and material residence time, and Figures 3 to 10 The figures show an embodiment of the continuous kneading machine of the present invention, in which Fig. 3 is a longitudinal sectional view showing the entire continuous kneading machine, Fig. 4 is a sectional view taken along line A-A in Fig. 3, and Fig. 5 7 to 7 are cross-sectional views showing an embodiment of the sub-orifice mechanism, FIG. 8 is an enlarged cross-sectional view showing a cross section of the discharge part of the kneading rotor, FIGS. 9 and 10 are cross-sectional views showing the kneading blade portion, and FIG. The figure is a graph showing the relationship between the opening degree of the sub-orifice, the temperature of the kneaded extrudate, and the carbon dispersion index. 1...Kneading rotor, 2...Kneading machine barrel, 3...
...Hopper, 4...Discharge orifice, 5...Discharge port, 6...Aperture member, 7...Hydraulic cylinder, 1
0, 11...Adjustment bolt, 12...Pulley, 1
3...Transmission band, 14...Handle.

Claims (1)

[Claims] 1. A barrel that has a material supply port at one end and a material discharge port at the other end, and whose cross section is two circles communicating with each other.
, a screw section 1a for forwarding the material from the material supply port, and a kneading section 1b consisting of sending and returning blades.
and a rotor in which a discharge portion 1d for feeding the kneaded material toward the material discharge port is sequentially formed, and two rotors are arranged inside the barrel to rotate in different directions.
In a shaft-continuous kneading machine, the material discharge port of the barrel opens at right angles to the rotor axis direction, and this discharge port is provided with a first constriction part whose opening degree can be adjusted, and a first throttle part is provided between the kneading part and the discharge part of each rotor. A material passage section 1c with a circular cross section equal to or smaller than the rotor outer diameter is provided, and a movable body divided into two parts concentrically surrounding this material passage section and movable back and forth is attached to the barrel, and this material passage section and the movable body A two-screw continuous kneading machine characterized by forming a second constricted part. 2. The two-axis continuous system according to claim 1, wherein the discharge part of the rotor is configured to send material to the discharge port by one or more protrusions provided on the outer periphery of a substantially circular cross section. Type kneading machine.