JPH0132081B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for rapidly filling containers with bulky powder at high density. Powder products generally have a problem in that they are bulky, leading to an increase in logistics costs. The above problem is particularly serious in bulky powder products. Conventionally, in order to solve the above-mentioned problems, a method has been proposed in which the powder is filled while alternately reducing the pressure inside the container and applying gas shock to the powder in the container. For example, there is a method of filling powder into bags using an apparatus as shown in FIG. The apparatus shown in FIG. 1 includes a closed chamber 1 having an opening for a powder supply nozzle 2 inside and a pressure reducing device 7.
It is connected to the closed chamber 1 via an atmospheric switching valve 5. A porous frame 1' is provided within the closed chamber for holding the bag. Powder filling using the above device is carried out by inserting a breathable bag 3 having a powder filling port 4 into the porous chamber 1 such that the opening of the powder supply nozzle 2 is inserted into the powder filling port 4. The powder is loaded into the powder chamber 1', and the vacuum/atmosphere switching valve 5 is operated to reduce the pressure inside the bag in the chamber, and the powder is exposed to the atmosphere by applying a gas shock to the powder inside the bag, which are alternately repeated. Hopper 8 in the bag
Powder is introduced from the inside, and degassing and impact compression of the powder are alternately repeated. Another method for solving the above problem is to deaerate the gas present between the powder particles and then fill the powder into a container using a screw packer or the like. However, the above-mentioned method uses fine powder hydrated silicic acid,
Currently, when applied to bulky powders such as finely divided calcium silicate, finely divided magnesium carbonate, and carbon black, the effect of improving the packing density and filling speed of the powder is hardly apparent. The inventors of the present invention have conducted extensive research on a method for rapidly filling containers with bulky powder at high density. As a result, after deaerating the gas existing between particles of bulky powder in advance to increase the bulk specific gravity of the powder, the powder with increased bulk specific gravity is placed in a breathable container. We found that filling the container while alternately reducing the pressure inside the container and applying gas shock to the powder in the container by alternately switching the external space between a reduced pressure state and an open state to the atmosphere was more effective than expected. Heading This has led us to propose the present invention. That is, the present invention increases the bulk specific gravity of a bulky powder by compressing or degassing the gas existing between the particles of the powder, and then increases the air permeability of the powder with the increased bulk specific gravity. Filling a container with powder by alternately switching the external space of the container between a reduced pressure state and an atmosphere open state, thereby alternately reducing the pressure inside the container and applying gas shock to the powder in the container. This is a method for filling bulky powder. The filling method of the present invention is effective for bulky powders. It is particularly effective in filling powders with a bulk specific gravity of less than 0.07, such as inorganic and organic fine powders such as fine hydrated silicic acid, fine magnesium carbonate, ultrafine silicic acid, fine aluminum silicate, carbon black, and starch. Further, the container used in the present invention is not particularly limited as long as it has air permeability.
In addition, in the present invention, a container having air permeability refers to a form in which the material of the container has air permeability equal to or higher than that of kraft paper, and a form in which the material of the container does not have air permeability but a ventilation hole is provided in the container. This includes aspects. Specifically, for example, kraft bags, other breathable bags, drums, flexible container bags, etc. are commonly used. In the present invention, the method for degassing the gas existing between the particles of the powder may be any known method without particular limitation. For example, a vacuum drum whose surface is covered with an air-permeable sheet is combined into a roll format, and the powder is passed through the gap between the rolls to perform compression deaeration, or a vacuum deaeration device as shown in Figure 2 is used. All you have to do is degas it. The apparatus shown in FIG. 2 has a damping type screw whose pitch is attenuated toward the powder outlet 9 in a casing 8, and a decylinder 11 made of a porous body with a filter attached between the damping type screw and the casing. is provided, and a gas suction port 12 is provided in the casing where the desorption cylinder is located. In the above device, powder is supplied from the input port 13,
The damping screw 10 compresses the inside of the casing and transports it. During this time, by sucking the gas in the atmosphere outside the desorption cylinder 11 through the suction port 12, the gas between the particles of the powder is degassed, and the bulk specific gravity increases. The rate of increase in the bulk specific gravity of the powder by the above degassing method is advantageous to a large extent in filling the powder into the container described above. In particular, in the case of powder having a bulk specific gravity of less than 0.07, it is necessary to deaerate the powder so that the bulk specific gravity at the time of filling into the container is 0.08 or more, preferably 0.10 or more. This is preferable because the filling speed can be further improved. Incidentally, the bulk specific gravity at the time of filling into the container does not necessarily match the bulk specific gravity immediately after performing the above degassing method, and the bulk specific gravity is usually slightly lower than the bulk specific gravity of the powder immediately after degassing. .
Therefore, the rate of increase in the bulk specific gravity of the powder due to the degassing method may be determined by taking into account the decrease in the bulk specific gravity of the degassed powder until it is filled into a container. The powder whose bulk specific gravity has been increased by the deaeration method is
By alternately switching the external space of the air-permeable container to a reduced pressure state and an open state to the atmosphere, the container is filled while alternately reducing the pressure inside the container and applying gas shock to the powder inside the container. be done. In the present invention, it is extremely important to perform the deaeration method and the container filling method in combination. In other words, if the container is filled without performing the degassing method, it will be difficult to fill the container with powder at a sufficient packing density, and even if it is possible to fill the container with a sufficient packing density. Filling speed will be significantly slower. Furthermore, even if the degassing method is combined with other filling methods, such as filling a container with a screw packer, the packing density of the powder cannot be sufficiently increased. That is, by performing the above two methods in combination, it is possible to significantly improve the packing density and filling speed of the powder into the container. The method of filling the powder with increased bulk specific gravity into a breathable container is to alternately switch the external space of the container to a reduced pressure state and an open state to the atmosphere to reduce the pressure inside the container and to inject gas into the powder in the container. The method is not particularly limited as long as it is a method of filling the powder while repeating the introduction of the powder into the container, the vacuum degassing of the powder, and the impact compression by alternately repeating the application of impact. For example, when filling powder into a breathable bag, a device as shown in FIG. 1 and a device as shown in FIG. 3 in which a screw feeder 18 is attached to the device in FIG. 1 as a feeding device are used. The method is preferred. In the above method, the operating conditions such as the depressurization rate and degree of vacuum when reducing the pressure inside the container, and the switching cycle for applying gas shock to the powder inside the container when the container is opened to the atmosphere are determined by the bulk specific gravity of the powder at the time of filling, It may be determined as appropriate depending on the strength, size, etc. of the container used.
For example, in a method using the apparatus shown in Fig. 1 above, when a closed chamber forming the external space of a breathable container has an internal volume of about 300, the pressure inside the chamber is reduced at a rate of 15 to 50 mmHg/sec.
Generally, the operation is repeated by reducing the pressure to a degree of vacuum of 200 to 300 mmHg, maintaining that state for about 25 to 30 seconds, then switching to the open state to the atmosphere, and maintaining that state for about 3 to 5 seconds. FIG. 4 shows a preferred embodiment of an apparatus for filling bags with powder in the method of the present invention. The apparatus shown in FIG. 4 is a combination of the powder degassing device 15 shown in FIG. 2 and the filling device using the closed chamber 1 shown in FIG. The filling apparatus shown in FIG. 4 is provided with a screw feeder 18 that operates to supply powder from the powder supply nozzle when the pressure inside the closed chamber is reduced.
In FIG. 4, the powder is supplied from the hopper 16 to the deaerator 15, where it is degassed under reduced pressure and its bulk specific gravity increases. The powder whose bulk specific gravity has increased reaches the powder supply nozzle 2 from the screw feeder 18 via the hopper 17. The hopper 17 may be of any type as long as it connects the deaerator 15 and the screw feeder 18 and has the function of storing powder. Inside the closed chamber 1, the bag is filled with powder by the above-described operation of alternately maintaining the vacuum state and the atmosphere open state. As explained above, the filling method of the present invention can quickly and densely fill a container with bulky powder, and can reduce packaging capacity and logistics costs for the powder. EXAMPLES Below, Examples and Comparative Examples will be shown to specifically explain the present invention, but the present invention is not limited to these Examples. In the Examples and Comparative Examples, the bulk specific gravity and pressure reduction rate of the powder were measured by the following method. Measurement method 1 Bulk specific gravity of powder Powder is dropped from a height of 20 cm into a container with an internal volume of 100 ml (50φm/m x 50 m/m), filled to the angle of repose, the surface of the powder is scraped, and the Weigh it using a dish balance to find the bulk specific gravity. 2 Pressure increase rate V _B of closed chamber Pressure increase rate V _B was determined by the following formula. V _B =△P/△T [mmHg/sec], △P represents the ultimate pressure of the Prudhon tube type pressure detector, and △T represents the time until the ultimate pressure is reached. Example Fine powder hydrated silicic acid having the bulk specific gravity shown in Table 1 was filled into a breathable bag using the apparatus shown in FIG. The degassing device 15 has a degassing cylinder with an inner diameter of 20 cm, a length of 120 cm, and a pitch damping ratio of 7/10, and the closed chamber 1 has an internal volume of 300 and a perforated frame volume of 200.
I used the one from In the above apparatus, the fine powder hydrated silicic acid was supplied from the hopper 16 to the deaerator 15, and degassed under reduced pressure under the vacuum degree and screw rotation speed conditions shown in Table 1. Table 1 shows the bulk specific gravity after degassing under reduced pressure. On the other hand, a three-layer kraft bag having an internal volume of 98 and having a powder filling port was loaded into the porous frame 1' in the closed chamber 1. Next, the vacuum/atmosphere switching valve 5 is operated to reduce the pressure inside the closed chamber at the pressure reduction rate shown in Table 1 to the degree of vacuum shown in Table 1,
This state was maintained for 25 seconds, then opened to the atmosphere and held for 3 seconds, which was repeated. During this time, when the inside of the closed chamber was in a reduced pressure state, the screw feeder 18 was driven at a constant rotation speed, and the fine powder hydrated silicic acid was supplied from the powder supply nozzle 2 to perform filling. Table 1 shows the bulk specific gravity of the fine powder hydrated silicic acid at the outlet of the powder supply nozzle. Using the above method, the time required to fill a kraft bag with 20 kg of finely powdered hydrated silicic acid was measured. The results are also shown in Table 1.

[Table] Comparative Example 1 Filling into a kraft bag was carried out in the same manner as in Example No. 1, except that fine hydrated silicic acid with a bulk specific gravity of 0.04 was used and deaeration under reduced pressure using a deaerator was not performed. The time was measured. As a result, it took 400 seconds to fill 20 kg of finely powdered hydrated silicic acid. Comparative Example 2 The fine hydrated silicic acid taken out from the deaerator in Example No. 1 was made into three layers with an internal volume of 98 using a screw-type packer having the same performance as the screw feeder used in Example. A kraft bag was filled at the same rotation speed as in the example. As a result, the time required to fill the kraft bag was 600 seconds.

[Brief explanation of drawings]

Figures 1 and 3 are schematic diagrams of a powder filling device;
FIG. 2 is a schematic diagram of a degassing device, and FIG. 4 is a schematic diagram of one embodiment of the device used to carry out the present invention. In the figure, 1 is a closed chamber, 1' is a porous frame, 2 is a powder supply nozzle, 3 is a porous bag, 4 is a powder filling port, 5 is a vacuum/atmosphere switching valve, 6 is a hopper, and 7 is a pressure reducing device, 8 is a casing, 9 is a powder outlet, 10
11 is a damping screw, 11 is a decylinder, 12 is a suction port, 13 is an inlet port, 15 is a deaerator, 16, 17
18 indicates a hopper, and 18 indicates a screw feeder.

Claims (1)

[Claims] 1. After increasing the bulk specific gravity of a bulky powder by compressing and degassing the gas present between the particles of the powder or degassing under reduced pressure, the powder with the increased bulk specific gravity is placed in a breathable container, The powder is filled while alternately reducing the pressure inside the container and applying gas shock to the powder in the container by alternately switching the external space of the container between a reduced pressure state and an atmosphere open state. How to fill bulky powder.