JPH08327226A - Vacuum drying method and vacuum dryer - Google Patents

Abstract

PURPOSE: To improve the defect of prior art of insufficient drying when the quantity of material to be dried is small. CONSTITUTION: The vacuum dryer, comprising a hermetically sealable tank 10, exhaust means 40 for exhausting the tank 10, a centrifugal dehydrating mechanism 30 having a turntable 33 rotatably installed in the tank 10 and a basket member 34 placed on the turntable 33, and a gas supply pipeline 85 for introducing inert gas or the air into the tank 10, is provided with water pouring means 90 for supplying water to the tank 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum drying device and a vacuum drying method for drying precision electronic parts, metal parts, plastic molded parts and the like after cleaning.

[0002]

2. Description of the Related Art Conventionally, Freon-113 or 1,1,1-for cleaning precision electronic parts, metal parts, plastic molded parts, etc.
Although detergents such as trichloroethane have been used, in recent years, due to problems of ozone layer depletion and effects on the human body, the use of the above detergents has been restricted, and cleaning with alternative detergents is being started. Water-based, alcohol-based or hydrocarbon-based ones are used as the alternative cleaning agents. Especially, in the case of the water-based cleaning agents, Freon-113, 1,1,
Unlike 1-trichloroethane, there is a problem that a rinsing step with pure water or city water is required, and a subsequent drying step requires time. Therefore, in order to shorten the time of the drying process, a vacuum drying method with high drying efficiency is adopted.

Materials to be dried, such as precision electronic parts, metal parts, and plastic molded parts, have a large amount of attached water after the rinsing step. Therefore, if they are suddenly vacuum dried, the water may freeze and remain due to the latent heat of evaporation of the water. Yes, the drying is insufficient. Therefore, the basket member accommodating the material to be dried is rotated and drained by centrifugal force, and then the residual moisture is vacuum dried. Furthermore, in the vacuum drying method,
The drying of residual water requires the supply of heat necessary for evaporation, and the drying device used in this method is equipped with heating means.

The applicant of the present invention has previously developed the vacuum drying apparatus described in Japanese Utility Model Publication No. 7-2877. As shown in FIG. 3, the outline of the apparatus is composed of a centrifugal dehydration mechanism 30, a vacuum pump 40, and a tank 10 equipped with a heater 70. The tank 10 is composed of a lid 12 that can be opened and closed, and a storage portion 11 that stores a basket member that stores an object to be dried. The storage portion 11 is connected to a gas supply pipeline 85 and a vacuum exhaust pipe 41. . The basket member 34 is provided on the outer wall surface 80b of the housing portion 11 in which the basket member 34 is housed.
A heater 70 is attached so as to surround the wall of the housing portion 11, and the wall surface 80 of the housing portion 11 is heated by the heater 70 to 100 ° C. or higher, preferably 100 to 300 ° C.

Next, as an example of a method for drying the moisture adhering to the material to be dried by using the vacuum drying apparatus shown in FIG.
The case where the material to be dried is a metal that easily rusts will be described. First, the lid 12 is closed, the first opening / closing valve 42 and the second opening / closing valve 86 are closed, and power is supplied to the heater 70 so that the wall surface 80 of the housing portion 11 is 100 ° C. or higher, preferably 100 to 300 ° C. Heat to. Then open the lid 12,
The basket member 34 accommodating the material to be dried 50 to which moisture is attached is fixed on the turntable 33. Close the lid 12, drive the drive motor 31, turntable 33
The upper basket member 34 is rotated, and the attached water is dehydrated by the centrifugal force. The water that has been dehydrated and scattered here comes into contact with the heated inner wall surface 80a of the housing portion 11, becomes superheated steam, evaporates, and is diffused into the housing portion 11. The superheated steam that has been vaporized and diffused fills the housing portion 11 and the heat is quickly transmitted, and the article to be dried 50 in the basket member 34 is also heated. Then, the first opening / closing valve 42 is opened, the vacuum pump 40 is operated, the exhaust pipe 41 is evacuated, the tank 10 is evacuated, and the residual water adhering to the material to be dried 50 is vacuum dehydrated. To dry completely. Finally, the first opening / closing valve 42 is closed, the second opening / closing valve 86 is opened, and the inert gas is introduced from the gas supply pipe line 85 to bring the inside of the tank 10 to the atmospheric pressure. The basket member 34 accommodating the dried product 50 is removed from the turntable 33 and taken out. In addition, if the material to be dried is an article that is difficult to rust,
The gas introduced into the gas supply line 85 may be air instead of the inert gas.

[0006]

The feature of the conventional vacuum drying apparatus is that water is scattered from the material to be dried by centrifugal separation and collides against a wall surface heated to 100 ° C. or more to be heated to become superheated steam. When it evaporates, the volume of the liquid expands significantly from gas to liquid, and this superheated steam immediately disperses and fills the storage unit to quickly transfer heat to the material to be dried and raise the temperature of the material to be dried. This is to accelerate vacuum drying. However, when carrying out the drying operation with the vacuum dryer, the drying may be insufficient. As a result of diligent pursuit of the cause, it was found that the drying was insufficient when the amount of the material to be dried in the basket member was small. Further, in that case, it was also found that the temperature of the material to be dried in the basket member taken out from the apparatus after all the operations were completed was low. That is, normally, the material to be dried, which has been washed, is placed in a vacuum drying device at room temperature, and when sufficiently dried, the temperature of the material to be dried at the end of drying is raised to 70 ° C. or higher. However, in the case of poor drying, the temperature of the material to be dried at the end of vacuum drying was low and was 50 ° C. or lower.

The present invention has been made in view of the above circumstances, and provides a vacuum drying apparatus and a vacuum drying method capable of overcoming the disadvantage of the prior art that the drying is insufficient when the amount of the material to be dried is small. It is an object.

[0008]

The vacuum drying method of the present invention comprises a centrifugal dehydration step in which a material to be dried with moisture adhered thereto is heated from the surroundings and a centrifugal force is applied to disperse the adhered moisture. A vacuum drying method comprising: placing a material to be dried under a reduced pressure atmosphere, evaporating residual water to dry the material to be dried, and heating the periphery of the material to be dried during the centrifugal dehydration step. It is characterized by pouring water into the part and raising the temperature of the material to be dried by the generated steam.

The vacuum drying apparatus of the present invention includes an airtight tank, exhaust means for exhausting the inside of the tank, a turntable rotatably installed in the tank, and a basket member mounted on the turntable. In a vacuum drying apparatus comprising a centrifugal dehydration mechanism including: a heating means for heating the basket member housed in the tank from the surroundings; and a gas introducing means for introducing an inert gas or air into the tank. A water injection means for supplying water is provided in the tank. In the vacuum drying apparatus of the present invention, the water injection means is a water storage tank,
A water supply conduit for guiding the water in the water storage tank into the tank, a pump interposed in the conduit, and a nozzle portion provided at the tip of the conduit may be provided. The nozzle portion may be an annular nozzle arranged above the basket member or a nozzle capable of pouring water into the inner bottom portion of the tank. The vacuum drying apparatus of the present invention may be configured to include a pressure valve that releases the pressure generated during water injection to the outside.

[0010]

In the conventional vacuum drying apparatus having no water injection means, when the amount of the material to be dried is small, the amount of water attached to the material to be dried is small. Therefore, since the dehydration amount by centrifugal dehydration is small, the amount of water vapor generated by contact with the heating unit in the tank is also small. Therefore, it is considered that a sufficient amount of heat to raise the temperature of the material to be dried cannot be transmitted to the material to be dried. Therefore, in the present invention, in a centrifugal dehydration step in which centrifugal force acts to scatter the adhering water while heating the material to be dried to which the water has adhered from the surroundings, water is poured into the heating portion around the material to be dried, The temperature of the material to be dried is raised by the steam. When the amount of the material to be dried is small, the amount of dehydration during centrifugal dehydration is small, so a sufficient amount of water is replenished by appropriately pouring water. The injected water contacts the heating part heated to 100 ° C. or higher and immediately evaporates to replenish the amount of water vapor in the tank, so that the tank is filled with a sufficient amount of water vapor.
With this superheated steam, a sufficient amount of heat is effectively transmitted to the material to be dried, the temperature of the material to be dried is raised, and the subsequent vacuum drying is promoted.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the vacuum drying apparatus of the present invention. This vacuum drying device includes a tank 10 and a tank 1.
No. 0 heater 20, a centrifugal dehydration mechanism 30 for rotating a turntable 33 arranged in the tank 10, a vacuum pump 40 connected to the tank 10, and water injection for spraying water into the tank 10. And means 90. The tank 10 is composed of a storage portion 11 for storing a basket member 34 for storing the material to be dried 50 and an openable / closable lid 12. A gas supply pipe line 85 for supplying an inert gas or air to the inside of the housing portion 11 is connected,
An on-off valve 86 is interposed in this conduit 85. Further, a safety valve 87 is provided in the pipe line 85 to open to the outside air when the internal pressure of the tank 10 exceeds a set pressure.
An inert gas supply source such as nitrogen gas or argon gas is connected to the pipe line 85, or its tip is open to the atmosphere so that air can be supplied into the tank 10. The container 11 of the tank 10 has a bottomed cylindrical shape, and a heater 70 is provided in contact with or close to the outer periphery and the bottom of the container 11. Further, a cover 75 that covers the heater 70 is provided outside the housing portion 11.

The centrifugal dewatering mechanism 30 has a motor 31 arranged below the tank 10 and a rotary shaft 32 extending from the motor 31 into the housing 11 through the central portion of the bottom of the housing 11.
And the turntable 3 provided at the tip of the rotary shaft 32
3 and the dried object 50 placed on the turntable 33.
And a basket member 34 for storing the.
The housing 11 is provided with a bearing that airtightly supports the rotary shaft 32.

The water injection means 90 is a storage tank 9 containing pure water 91.
2, a water injection conduit 93 for guiding pure water 91 from the storage tank 92 into the tank 10, and a pump 94 interposed in the water injection conduit 93.
And an annular nozzle 95 connected to the tip of the water injection pipe 93 and arranged above the basket member 34 in the tank 10. Further, an open / close valve 96 is interposed between the pump 94 and the annular nozzle 95 of the water injection pipe 93. As shown in FIG. 2, the annular nozzle 95 has an inner diameter dimension into which the basket member 34 can be inserted, and a large number of water injection holes 96 are formed on the side surface and the lower surface thereof.

Next, as an example of the vacuum drying method of the present invention, a case of drying an article to be dried using the above-mentioned vacuum drying apparatus will be described. The material to be dried 50 is placed in the basket member 3
4 is placed on the turntable 33, the lid 12 of the tank 10 is closed, and the motor 31 is rotated to rotate the basket member 34. At this time, the heater 70 of the tank 10
The wall surface of the housing portion 11 is heated to 100 ° C. or higher. Along with the start of this centrifugal dehydration, a predetermined amount of pure water 91 is introduced into the housing portion 11 by the water injection means 90 into the annular nozzle 95.
Water is sprayed from the water injection hole 96 of.

The pure water 91 sprinkled from the annular nozzle 95 of the water injection means 90 comes into contact with the heated wall surface 80 of the accommodating portion 11 and instantly evaporates to become superheated steam to fill the accommodating portion 11. When the injected pure water and the water scattered from the material to be dried 50 by centrifugal dehydration evaporate, the pressure in the tank 10 rapidly rises due to volume expansion from liquid to gas.
When the pressure in the tank 10 exceeds a predetermined value, the gas supply line 85
It is possible to prevent the abnormal increase in the internal pressure in the tank 10 by operating the safety valve 87 attached to the valve to release the gas in the tank 10 to the outside.

The water vapor is filled in the containing portion 11 and the heat is rapidly transmitted, and the article to be dried 50 in the basket member 34 is also heated. Then, the first on-off valve 42 is opened, the vacuum pump 40 is operated, the exhaust pipe 41 is evacuated, the tank 10 is evacuated, and the residual water adhering to the material to be dried 50 is vacuum dehydrated. Allow to dry completely. Finally, the first opening / closing valve 42 is closed, the second opening / closing valve 86 is opened, and an inert gas such as nitrogen gas or argon gas is supplied to the gas supply line 85.
After introducing into the tank 10 to bring the inside of the tank 10 to the atmospheric pressure, the lid 12 is opened, and the basket member 34 accommodating the material to be dried 50 is removed from the turntable 33 and taken out. If the material to be dried is an article that is difficult to rust, the gas introduced into the supply pipeline 85 may be air instead of the inert gas.

Since the vacuum drying apparatus according to this embodiment is provided with the water injection means 90 for supplying water into the tank 10,
Even when the amount of the material to be dried 50 is small and the amount of water scattered during centrifugal dehydration is small, pure water 91 is sprinkled in the tank 10 by the water injection means to generate a sufficient amount of water vapor to appropriately dry the material to be dried 50. The temperature can be raised to, and the residual water can be completely dried by vacuum drying.

In the above embodiment, the basket member 3
4 is configured to inject water into the tank 10 by an annular nozzle 95 arranged above 4, but instead of the annular nozzle 95,
A configuration in which a nozzle capable of pouring water is used in the inner bottom portion of the housing portion 11 may be used. Further, in the above embodiment, the gas supply line 85
Although a safety valve 87 that opens when a pressure exceeding a certain pressure is attached to the tank is configured to prevent a rapid pressure increase in the tank 10 at the time of water injection, the safety valve may be mounted to the lid 12 or the housing portion 11 of the tank 10. . In addition, in the above-described embodiment, the housing portion 11
Although the heater 70 is attached to the outer surface of the housing to heat the wall surface 80 of the housing portion 11, a closed heater such as a sheath heater may be arranged on the inner wall surface of the housing portion 11. Hereinafter, the effects of the present invention will be clarified by Examples 1 and 2 and Comparative Examples 1 to 6.

(Embodiment 1) A vacuum drying apparatus having the same components as the apparatus shown in FIG. 1 and equipped with an accommodating portion 11 (internal volume of about 90 liters) having an inner diameter of 400 mm and a height of 500 mm was prepared. A short tube made of stainless steel (outer diameter: 5 mm, length: 5 mm) was housed in the basket member 34 as the article to be dried 50 in this apparatus, and a drying test was performed under the following conditions. Weight of material to be dried (dry material) 1000 g Adhered water content 200 g Temperature of the wall surface of the storage unit 200 ° C Temperature when the material to be dried is stored in the tank 30 ° C Basket member rotation speed 300 rpm Centrifugal dehydration time 30 seconds Water injection amount 80 ml Vacuum exhaust Time 3 minutes When the water injection was started together with the centrifugal dehydration, the pressure in the tank rose momentarily, and the safety valve 87 actuated. After vacuum evacuation for 3 minutes, air was supplied from the gas supply pipe 85 to complete the drying. When the lid 12 was opened and the temperature of the material to be dried 50 was immediately measured by a thermocouple, it was about 8
5 ° C. When the basket member 34 was taken out from the housing portion 11 and weighed, the weight of the dried object was 1
It was 000 g, and it was confirmed that it was completely dried.

(Example 2) As a material to be dried, a width of 30 m
Using a pure iron magnetic head of m, height of 40 mm, and length of 100 mm, the same vacuum drying apparatus as in Example 1 was used, and a drying test was conducted under the following conditions. Weight of material to be dried (dry material) 2000 g Adhered water content 200 g Temperature of the wall surface of the storage unit 200 ° C Temperature when the material to be dried is stored in the tank 30 ° C Basket member rotation speed 200 rpm Centrifugal dehydration time 30 seconds Water injection amount 80 ml Vacuum exhaust Time: 2 minutes While pouring water into the tank, the basket member containing the material to be dried is centrifugally dehydrated, followed by vacuum drying for 2 minutes, and then nitrogen gas is supplied from the gas supply line 85 to dry the basket member. finished. The temperature of the material to be dried was about 70 ° C. As a result of measuring the weight of the dried substance taken out, it was 2000 g, and it was confirmed that the substance was completely dried.

(Comparative Example 1) Except that water was not injected,
A drying test was conducted in the same manner as in Example 1. As a result, the temperature of the material to be dried when taken out of the tank after the completion of drying was about 40 ° C., and the weight was 1100 g. It was found that the temperature of the material to be dried was lower than that in Example 1, and only about half of the attached water amount of 200 g was dried.

(Comparative Example 2) Therefore, the same vacuum test as in Comparative Example 1 was conducted except that the vacuum evacuation time was extended to 6 minutes. As a result, the temperature of the material to be dried is about 45 ° C and the weight is 1
It was 070 g. Compared with Comparative Example 1, the temperature of the material to be dried is slightly elevated and the dehydration amount is slightly increased, but the drying is insufficient. That is, compared to the case of Example 1, the temperature of the material to be dried is low, and the amount of attached water is still 70 g.

(Comparative Example 3) Except that water was not injected,
The same drying test as in Example 2 was performed. As a result, the temperature of the material to be dried was about 30 ° C. and the weight was 2100 g. Comparing with the results in Example 2, it can be seen that the temperature of the material to be dried is the same as that before being stored in the tank, and only half of the attached water amount of 100 g is dehydrated.

(Comparative Example 4) Therefore, the same vacuum test as in Comparative Example 3 was conducted except that the vacuum evacuation time was extended to 8 minutes. As a result, the temperature of the material to be dried is about 40 ° C and the weight is 2
It was 100 g. Compared with Comparative Example 3, the temperature of the material to be dried was slightly increased, but the amount of attached water was unchanged.

(Comparative Example 5) The same material to be dried as in Example 1 was used, and the capacity was 6000 g (1200 g of attached water).
The test was conducted under the same conditions as in Example 1 except that water was not injected. After drying, the temperature of the material to be dried was about 80 ° C. and the weight was 6000 g, which confirmed that the material was completely dried.

(Comparative Example 6) A test was conducted under the same conditions as in Example 2 except that the same material to be dried as in Example 2 was used, the contained amount was 6000 g (adhered water content was 600 g), and no water was injected. After drying, the temperature of the material to be dried is about 70 ° C and the weight is 6
It was 000 g, and it was confirmed to be completely dried.

The results of the tests of the above Examples and Comparative Examples are summarized in Table 1.

[0028]

[Table 1]

As is clear from the results summarized in Table 1, this occurs when the amount of the material to be dried is large and the amount of water scattered from the material to be dried during centrifugal dehydration (Comparative Examples 5 and 6). By increasing the amount of water vapor and raising the temperature of the material to be dried sufficiently, and subsequently performing vacuum drying, the material to be dried can be completely dried. However, when the amount of the material to be dried decreases, as shown in Comparative Examples 1 to 4, due to the decrease in water vapor generated from the water scattered during centrifugal dehydration,
It becomes impossible to sufficiently raise the temperature of the material to be dried, and as a result, vacuum drying is not sufficiently performed, and complete drying cannot be performed. Then, as shown in Examples 1 and 2, when the amount of the material to be dried is small, by supplying an appropriate amount of water into the tank during centrifugal dehydration and increasing the amount of water vapor generated, It was possible to raise the temperature of the dried product sufficiently, and the drying efficiency of the subsequent vacuum drying became extremely high. As a result, it was possible to completely dry the dried product. Therefore, by supplying an appropriate amount of water to the tank during centrifugal dehydration and increasing the amount of water vapor generated, the material to be dried can be completely dried in a short time regardless of the amount of the material to be dried. it can.

[0030]

As described above, according to the present invention,
By supplying an appropriate amount of water to the tank during centrifugal dehydration and increasing the amount of water vapor generated, even if the amount of water to be dried is small and the amount of water scattered during centrifugal dehydration is small The amount of water vapor can be generated to sufficiently heat the material to be dried, and since the material to be dried can be sufficiently heated, the drying efficiency of the subsequent vacuum drying becomes extremely high,
It is possible to completely dry the material to be dried. Therefore, according to the present invention, by supplying an appropriate amount of water to the tank during centrifugal dehydration and increasing the amount of water vapor generated, the dried substance can be completely removed in a short time regardless of the stored amount of the dried substance. Can be dried.

Further, in the vacuum drying apparatus according to the present invention, a water storage tank, and a water supply conduit for guiding the water in the water storage tank into the tank.
By providing a water injection means including a pump interposed in the conduit and a nozzle portion provided at the tip of the conduit,
An appropriate amount of water can be easily supplied into the tank, and the vacuum drying device can be automated.

Further, as the nozzle portion, an annular nozzle arranged above the basket member or a nozzle capable of pouring water into the inner bottom portion of the tank is adopted, so that the heating portion of the tank can be heated without sprinkling water on the material to be dried. Since water can be evenly poured and steam can be efficiently generated, it is possible to raise the temperature of the material to be dried with a small amount of water.

Further, by providing the pressure valve for releasing the pressure generated at the time of water injection to the outside, it is possible to prevent the troubles such as the device damage or the sudden opening of the lid due to the rapid pressure increase in the tank caused at the time of water injection. It is possible to improve safety.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a vacuum drying apparatus of the present invention.

FIG. 2 is a bottom view of the annular nozzle of the apparatus of FIG.

FIG. 3 is a schematic sectional view showing a conventional vacuum drying apparatus.

[Explanation of symbols]

10 ... Tank, 33 ... Turntable, 34 ... Basket member, 30 ... Vacuum dehydration mechanism, 40 ... Vacuum pump, 50 ... Dried object, 70 ... Heater, 80 ... Wall surface (heating part) , 90 ... water injection means, 95 ... annular nozzle.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F26B 21/00 F26B 21/00 P 25/06 25/06 Z

Claims (5)

[Claims] 1. A centrifugal dehydration step of heating a material to be dried to which moisture is attached from the surroundings while applying a centrifugal force to scatter the water to be attached, and subsequently placing the material to be dried under a reduced pressure atmosphere,
A vacuum drying method comprising: a vacuum drying step of evaporating residual water to dry the material to be dried, wherein during the centrifugal dehydration step, water is poured into a heating part around the material to be dried, and the water vapor generated by the water vapor is generated. A vacuum drying method characterized by increasing the temperature of a dried product. 2. Centrifugal dehydration comprising an airtight tank, an exhaust means for exhausting the inside of the tank, a turntable rotatably installed in the tank, and a basket member mounted on the turntable. In a vacuum drying apparatus equipped with a mechanism, a heating means for heating the basket member housed in the tank from the surroundings, and a gas introducing means for introducing an inert gas or air into the tank, water is introduced into the tank. An evacuation device characterized in that it is provided with water injection means for supplying water. 3. A water injection means, a water storage tank, a water supply conduit for guiding the water in the water storage tank into the tank, and a pump interposed in the conduit.
The vacuum exhaust device according to claim 2, further comprising a nozzle portion provided at a tip of the conduit. 4. The vacuum exhaust device according to claim 3, wherein the nozzle portion is an annular nozzle arranged above the basket member or a nozzle capable of pouring water into the inner bottom portion of the tank. 5. The vacuum evacuation device according to claim 2, further comprising a pressure valve that releases the pressure generated during water injection to the outside.