JPS636680Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a critical point drying device used for preparing samples for scanning electron microscopes and the like.

In the critical point drying device, a sample that has been dehydrated, fixed, and replaced with an appropriate reagent is stored in a pressure vessel, into which a mediating solvent such as liquid carbonic acid is injected.
This device heats the mediating solvent so that it passes through a mixed state of a liquid phase and a gas phase and then changes to a gas phase, thereby drying the sample. In such a device, it is necessary to maintain the temperature of the pressure vessel at around 10° C. or lower in order to easily inject liquefied gas (liquid carbon dioxide, etc.) as a mediating solvent. However, once processing has been completed, the container reaches a high temperature of around 40°C, and must be forcibly cooled to allow continuous processing. For this reason, conventional methods have been to provide air cooling means such as a fan outside the container, or to inject the liquefied gas or its evaporated gas directly into the container, and to rapidly release the gas, thereby utilizing adiabatic expansion of the gas for cooling. is being carried out.

However, the former requires a large-scale cooling means and is not very efficient. In addition, in the latter case, the sample cannot be placed in the container before the cooling operation, so the container lid must be opened and closed to insert the sample after cooling, but at this time, the inside of the container is exposed to the atmosphere, so the inner wall of the cooled container It is not possible to prevent moisture condensation from occurring, which is the most hated thing in the world. If the sample is placed in the container before being cooled, the sample will be damaged by the rapid drop due to adiabatic expansion of the gas in the container and by the rapid flow of gas.

This invention is intended to solve the above drawbacks.
The details will be explained below based on the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. Reference numeral 1 denotes a pressure vessel which is robustly constructed to withstand an internal pressure of more than 100 atmospheres. The upper surface of the container is a removable lid 2, and a transparent window 3 is provided in the center for observing the inside. A heater 4 is provided at a suitable location in the container and is used to heat the container and vaporize the mediator solvent injected into the container. Reference numeral 5 designates a source of mediating solvent, ie a tank of liquid carbonic acid, for example, which is introduced into the container 1 through a pipe 8 equipped with a tap 6 and an inlet valve 7. The vaporized gas within the pressure vessel is discharged to the outside via a pipe 9 and a discharge valve 10.
Reference numeral 11 denotes a tank provided outside the container 1, which has a double structure with the container serving as an inner tank, with a gap formed between them to form a cooling jacket 12. This jacket has a pipe 14 with an inlet valve 13.
is connected to the liquid carbon dioxide tank 5 via the main valve 6. As a result, liquid carbon dioxide or its vaporized gas is introduced into the jacket 12 as a refrigerant. 15 is a discharge pipe, and 16 is a discharge valve.

In such a device, to dry the sample, close all valves and main valves and close the lid 2.
Open the container 1 and store the sample in the container 1. Next, the main valve 6
and valves 7 and 10 to replace the air in the container with carbon dioxide gas. After that, valves 7 and 1
0 is closed, valves 13 and 16 are opened, and the solvent in the tank 5 or its evaporated gas is allowed to flow into the jacket to pre-cool the container 1. When the container reaches a predetermined temperature (for example, 5° C.), valves 13 and 16 are closed, and valves 7 and 10 are then opened to inject liquid carbonic acid into container 1. Specified amount (approximately 90% of the contents in the container)
After injecting, close the main tap 6 and valve 7 and turn off the heater 4.
Heat container 1 to around 50°C. This heating causes the liquid carbonic acid to evaporate, maintaining the temperature and pressure above the critical point.

When all of the liquid carbon dioxide is vaporized and the gas is discharged by opening the valve 10, the drying of the sample is completed.

With the above configuration, the container 1 is cooled by flowing a refrigerant into the jacket 12, and the refrigerant uses a mediating solvent used for drying processing, so the structure is extremely simple and compact, and the sample can be placed inside the container. The container can be pre-cooled while stored in the container, and therefore a satisfactory drying process can be performed without any moisture condensation on the container wall.

Note that the above is an example of the present invention, and various modifications can be made. For example, although liquefied gas for drying processing or its evaporated gas is used as the refrigerant, a completely separate refrigerant source may be used. Further, the cooling jacket is not limited to the case where the container is a double tank, but may be one in which a cavity or hole is provided in the container 1 as shown in FIG. 2, for example. In FIG. 2, 1a, 1b, 1c and 1d are cavities symmetrically provided in the container wall, communicating with each other at the top and bottom, into which the refrigerant flows. 4a and 4b are heaters for heating, and 17a and 17b are sensors for temperature display and temperature control.

[Brief explanation of drawings]

FIG. 1 is a view showing one embodiment of the present invention, and FIG. 2 is a sectional view of the main part showing another embodiment. 1... Container, 2... Lid, 3... Window, 4... Heater, 5... Tank, 6... Main valve, 7, 10, 1
3 and 16... valves, 8, 9, 14 and 15...
...Pipe, 11...Outer tank, 12...Cooling jacket.

Claims (1)

[Scope of claims for utility model registration] 1. Dehydration using a reagent. The sample that has been fixed and replaced is stored in a pressure vessel, a mediating solvent such as liquid carbonic acid or liquid Freon is injected, and the mediating solvent is heated to change from a liquid phase to a mixed state of liquid and gas phases, and then to a gas phase. A critical point drying apparatus for drying the sample by transferring the pressure vessel to the pressure vessel, wherein the pressure vessel is provided with a cooling jacket, and a means for supplying a refrigerant to the jacket is provided. 2. The critical point drying apparatus according to claim 1, wherein the refrigerant supplied to the jacket is a medium solvent injected into the container or its evaporated gas. 3. The critical point drying apparatus according to claim 1 or 2, wherein the cooling jacket is a hole or cavity provided in a pressure vessel. 4. The critical point drying device according to claim 1 or 2, wherein the cooling jacket is a space formed by a double tank including an inner tank and an outer tank.