JPS584567B2 - Kneading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called internal mixer, which is capable of sufficiently kneading materials regardless of their type.

An internal mixer is a batch-type kneading machine suitable for kneading rubber and plastics, and is especially suitable for masticating rubber, mixing carbon master batches, or mixing vulcanizing agents, which is usually called professional mixing, and is used for tires. It is an indispensable mechanical equipment for the rubber industry such as manufacturing.

A conventional internal mixer includes a pair of parallel rotors 2 rotating in opposite directions in a chamber 1, as shown in FIGS.
. It is in the opposite direction.

The material inputted from a hopper (not shown) is press-fitted into the mixing chamber 7 through the supply port 16 by the biting action of the rotor and the pushing action of the floating weight, where it is subjected to rolling action by the rotor and then transferred to the kneading chamber 7 by the rotor. It passes while being crushed between the tip of the blade and the inner wall of the casing (tip clearance 6), and is sent in the axial direction of the rotor.

This action takes place on each of the long and short blades, which have opposite winding directions so that the material is transferred from the ends to the center for each rotor, and the kneaded material is removed from the lower part of the chamber.

Further, as shown in FIGS. 4 to 6, there is a so-called four-blade rotor in which each rotor has two long blades and two short blades, for a total of four blades.

This configuration has almost the same effect, but since it has twice the number of chips compared to a two-blade rotor, micro-dispersion of the additives progresses and the kneading efficiency is generally high.

On the other hand, in order to obtain a homogeneous mixture, micro-dispersion is performed, and the concentration of the added chemicals and additives is constant no matter which part of the kneaded material is taken, and the concentration of the kneaded material is also kept constant. The so-called macro-dispersion effect, which involves uniform mixing, is also important.

For example, if the vulcanizing agent is not mixed uniformly during the professional mixing process in the tire manufacturing industry, the physical properties of the final product will vary.
It becomes difficult to manufacture tires of consistent quality.

In particular, the proportion of recent tires that use steel radial tires, which have steel cords inside them, has been increasing in order to improve safety during high-speed driving. However, materials tend to be much harder and more difficult to mix and disperse uniformly.

For this reason, conventional internal mixers sometimes have problems such as insufficient strength of the kneading machine and insufficient uniform dispersion of chemicals.

In view of these points, the present invention focuses on the movement of materials in the mixer when kneading with an internal mixer, and aims to provide a kneading and kneading device that can perform macroscopically sufficient mixing regardless of the type of material. This is the purpose.

As shown in FIGS. 1 to 6, the rotor of the internal mixer has spiral blades to feed the material in the axial direction of the rotor.

Therefore, the movement of the material inside the kneading chamber is divided into a flow in the axial direction of the rotor and a flow between the left and right kneading chambers housing the rotor.

In order to obtain a uniform kneaded product, it is necessary to activate the flow in the axial direction and the flow between the kneading chambers to prevent material from stagnation in the kneading chambers.

Internal mixer with 4-blade rotor (inner volume 236
When hard rubber was professionally kneaded in step 1), it was found that in certain types of rubber, the distribution of chemicals was extremely uneven, and that the uniform dispersion of additives was significantly inferior to that of the two-blade rotor.

In order to find out the reason for this, we created a model testing machine and observed the state of material flow inside the mixer.

The barrel of the model testing machine is made of acrylic resin, and has a structure that allows direct observation of the flow of material inside.

In addition, in order to quantitatively evaluate the quality of dispersion, a certain amount of colored plastic beads (polystyrene) was added.
After kneading, repeat the number of beads contained in a certain sample (n
The model test machine has the same dimensions as an internal mixer with an internal volume of 17 liters, and the material exhibits flow behavior similar to the hard rubber in a practical mixer. It was discovered that a 30% aqueous solution of CMC (carboxymethylcellulose) was suitable, and this was used.

The results of kneading experiments of model substances using the two-blade rotor and four-blade rotor using the above model test machine are shown in Figure 7 A and B, where A is for a kneading time of 40 seconds and B is for a kneading time of 60 seconds. This shows the variation in beads.

In the case of the two-blade rotor, 11 has a filling rate (volume ratio of the material occupying the kneading chamber space) of 0.
The beads are well dispersed over a wide range of 4 to 1.0, and uniform dispersion progresses even if the kneading time is short.
With a four-blade rotor, dispersion deteriorates significantly as the filling rate increases, and dispersion is not improved even if the kneading time is extended.

The reason why the four-blade rotor has such poor dispersion is that each rotor has two long blades and two short blades that are twisted in a direction that pushes the material toward the center. At the center where the short blades contact the blades, the tips of each blade are shifted in phase by 90 degrees as shown in Figure 6, and are arranged to improve the flow of material. After the material has left the end of the long blade, it does not have enough room to move to the other end of the mixer, and is forced back toward the long blade by the short blade, which is twisted in the opposite direction to the long blade. It became clear that the materials were pushed back and pressed together in the center of the rotor, resulting in a lack of axial flow of the material necessary for uniform mixing.

On the other hand, in the case of a two-blade rotor, as shown in Figure 1, the ends of the long blades and the ends of the short blades are arranged so that they partially overlap in the center of the rotor. The material flowing in the direction of the center of the shaft is released at the end of the long wing, flows into the space behind the short wing, and is swept back into the long wing section.

Therefore, the movement of the material itself is similar to a four-blade rotor, but there are only one long blade and one short blade, so there is a lot of space for the material to move, and the axial flow increases, making it difficult to mix the kneaded material uniformly. It turned out to be moving forward.

A four-blade rotor has been proposed by David Zett Tyson et al. in Japanese Patent Publication No. 27032/1983 to solve the problem of uneven kneading caused by insufficient flow of materials.

That is, the cross-sectional shapes of the long blades and short blades are designed to reduce the bulge of the rotor at the ends near the center of the rotor and reduce the cross-sectional area, thereby improving the flow of the material and achieving uniform dispersion.

Therefore, the inventor of the present invention attempted to knead hard rubber using this method, but the method did not have a sufficient effect on hard rubber and yielded results that were unsatisfactory in practical terms.

Therefore, the present inventor developed a CM that behaves similar to hard rubber.
In order to use C aqueous solution and take advantage of the high kneading efficiency of the four-blade rotor, various studies were conducted on the blade shape.

First, we examined the material flow using a model test machine, and determined the rotor shape, which had shown excellent results, using a small internal mixer (
After confirming the effectiveness with a mixer (with an internal volume of 4.3 liters), it was scaled up to a practical mixer (with an internal volume of 236 liters) and its practical performance was confirmed.

The reason why the dispersion of the four-blade rotor is poor is due to the poor axial flow of the material, so in order to improve the axial flow, the twist angle and cross-sectional shape of the blades were changed from the conventional standard in a model test machine. The effect on uniform dispersion of plastic beads in the CMC was investigated by fixing the same value as that of the rotor and varying the ratio of the lengths of the short blades to the long blades (blade span ratio) Ls<Ll.

As a result, it was found that in the configuration shown in FIG. 8, when the blade span ratio was set below a certain value, the variation in the plastic beads in the kneaded material was reduced and the uniformity was significantly improved.

In other words, by changing the ratio of the axial lengths of the short blades and long blades, the uniformity of the mixture is significantly improved, resulting in good dispersion that could never be achieved with the conventional standard blade length ratio of 0.49. It has become clear that it is possible to produce a four-blade rotor with

In addition, in the configuration of the first product shown as a conventional example, the blade span ratio is 0.
50. In the configuration shown in FIG. 4, the blade span ratio is 0.58, and in all conventional rotors of this type, the blade span ratio is set to about 0.5.

Figure 9 shows the relationship between bead variation and wingspan ratio.
No. 4 shows the characteristics when the kneading time is 40 seconds, and No. 15 shows the characteristics when the kneading time is 60 seconds.

As is clear from this figure, when the blade length ratio reaches 0.4, the dispersion increases rapidly, and it can be seen that the smaller the blade length ratio is, the better the dispersion is performed.

In order to achieve uniform dispersion, it is preferable to use a rotor consisting of only continuous long blades with the length of the short blades being 0, but with a rotor consisting of only long blades, the thrust load that the rotor receives when kneading materials is There are also drawbacks such as excessive compression and the effect of strongly compressing the material on the side wall of the mixer, causing local heating.

It has been confirmed through experiments that in order to prevent such defects from occurring, it is necessary to set the blade span ratio to 0.1 or more.

Therefore, the blade span ratio is set to 0.4 to 0.1, preferably 0.3 to 0.
．． Set within the range of 15.

That is, the present invention is a kneading device in which a pair of parallel rotors rotating in opposite directions are arranged in a mixing chamber sealed by a casing and an end frame, and each rotor has a pair of long blades. These wings extend in a spiral around the center line of the rotor, and the winding direction of the spiral is such that the long wings and the short wings are in opposite directions, and the long wings of one rotor are connected to the long wings of the other rotor. The long blades of the rotor are in the same direction, and the lengths of the long and short blades in the rotor axial direction are set so that the span ratio of the short blades to the long blades is in the range of 0.4 to 0.1.

Further, the shape of the rotor according to the present invention is such that each rotor has a pair of long blades 4 and short blades 5, as shown in FIG. is formed.

The cross-sectional shape of each blade is similar to that shown in FIGS. 4 to 6, but the blade span ratio is different from the conventional one and is set in the range of 0.4 to 0.1.

In the example of FIG. 8, Ls/Ll is approximately 0.31.

The results of the kneading experiment using the model material when the blade span ratio is 0.4 are as shown by curve 3 in FIG. 7, which shows good results comparable to the conventional two-blade rotor.

(Example) The blade length ratio (Ls/
A standard rotor with Ll) of 0.49 and a blade span ratio of 0.23.
Using the rotor of the present application, a professional kneading test for masticating natural rubber and dispersing a vulcanizing agent was conducted.

The results are shown in Table 1, and it can be seen that even compared to the two-blade rotor, which is said to have excellent chemical dispersibility in professional kneading, the rotor of the present invention achieves more uniform chemical dispersion.

As explained above, the present invention improves macro and micro kneading by improving the rotor blades, and is applicable not only to professional kneading but also to mastication, carbon masterbatch kneading, and other rubber kneading. It can also exhibit excellent effects in kneading.

In addition, in the above embodiment, only an example of four blades was shown, but two
Of course, other numbers of wings may be used.

In addition, in this application, the above-mentioned Japanese Patent Publication No. 4
Unlike the rotor described in Japanese Patent No. 2-27032, there is no need to make the center part thinner, so there are advantages of excellent strength and durability.

[Brief explanation of the drawing]

Figure 1 is a plan view of the rotor of a conventional internal mixer.
2 and 8 are sectional views taken along the lines ■-■ and ■-■ in FIG. 1, FIG. 4 is a plan view of another conventional rotor, and FIGS. 5 and 6 are -V line and VI-VI line sectional views, Figure 7A and Figure 7 are comparative characteristic diagrams of crosstalk states of the present invention and conventional devices, Figure 8 is a plan view of the rotor of the present invention, and Figure 9 is a diagram of the rotor. FIG. 3 is a relationship diagram between blade length ratio and kneading state. 2, 3...Rotor, 4...Long blade, 5...Short blade, 6...Tip clearance, 13, 14, 15...Characteristic curve of the present application, Ll...Long blade length, Ls...Short blade wing length.

Claims (1)

[Claims] 1. A kneading and kneading device comprising a pair of parallel rotors rotating in opposite directions arranged in a mixing chamber operated and closed by a casing and an end frame, each rotor having a pair of long blades. These blades extend in a spiral around the center line of the rotor, and the winding direction of the spiral is such that the long blade and the short blade are in opposite directions, and the long blade of one rotor is connected to the long blade of the other rotor. The long blades of the rotor are in the same direction, and the lengths of the long and short blades in the rotor axis direction are such that the blade length ratio of the short blades to the long blades is 0.4 to 0.
A kneading device characterized by being set to fall within the first range. 2. The kneading and kneading device according to claim 1, characterized in that the blade length ratio of the short blades to the long blades is set in the range of 0.3 to 0.15.