JPS6128034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a washing and drying method for removing water adhering to the surface of an article.

Various plated products, optical lenses, semiconductor materials, etc. need to be washed with water and dried quickly and completely after the required surface treatment. In order to dry articles containing adhered water, a so-called washing and dehydrating method is known in which the articles are immersed in a non-aqueous liquid to remove water. As this non-aqueous liquid, chlorofluorohydrocarbon liquid, especially trichlorotrifluoroethane, has a low interfacial tension and is excellent in desorption effect of water, as well as low corrosivity to plastic materials, chemical stability, and nonflammability. It has favorable properties such as low toxicity and is used as an excellent cleaning solution, but as it lacks the water removal effect as it is, various surfactants are added or it is mixed with a water-soluble organic liquid. Used as a boiling mixture. When using a surfactant, the non-volatile surfactant remains on the surface of the product after washing, and it is difficult to completely remove water from minute cracks and small pores on the surface of the product. In contrast, cleaning liquids made of azeotropic mixtures with water-soluble organic liquids do not have the problem of surface contamination of articles, as is the case with the addition of surfactants, and do not cause microcracks or inside small pores. It has the advantage of being able to remove water well.

Several proposals have been made for cleaning techniques using azeotropic mixtures of trichlorotrifluoroethane and water-soluble organic liquids as the cleaning liquid (e.g.
(Special Publication No. 49-36867, Japanese Patent Publication No. 49-101955). A washing device using this type of washing liquid consists of a dehydration tank that immerses the article to remove water, and a washing liquid containing the removed water overflowing from the dehydration tank, which separates the layers based on the difference in specific gravity, and removes the upper aqueous phase. It basically consists of a water separation tank for removing water, and a means for circulating the washing liquid from which water has been separated in the water separation tank to the dehydration tank. However, in this process, the water separated from the surface of the article is dissolved in the water-soluble liquid, so in the water separation tank, the water-soluble organic liquid is also removed along with the water, resulting in an immediate decrease in the concentration of the water-soluble liquid in the washing liquid. However, it cannot be used as it is. Regarding this, in a previous patent application (Japanese Patent Application No. 54-39008), the present inventors introduced the water separated in the water separation tank into a rectifier, separated the water-soluble liquid by rectification, The problem of liquid composition fluctuation was solved by returning the water to the dehydration tank or water separation tank.

However, even with this prior application method, if the water adhering to the surface of the article contains electrolyte substances or colloidal substances, the above-mentioned stains in the water microscopically remaining after treatment will remain on the surface of the article. There is a problem.

The present invention has been completed with the aim of solving the above problems and achieving more precise cleaning and dehydration.The present invention is accomplished by immersing the article to be washed in trichlorotrifluoroethane containing a water-soluble organic liquid, which is the first washing liquid. and then immersed in a second washing solution consisting of trichlorotrifluoroethane and about 20 to 50% (by weight) of a water-soluble organic liquid, with or without steam bath washing. The present invention provides a washing and drying method characterized in that the material is pulled up and further subjected to steam bath washing in a fluorocarbon-based organic solvent mainly consisting of trichlorotrifluoroethane.

The present invention will be explained in detail below.

The article to be treated is first immersed in a first washing liquid, that is, a washing liquid consisting of trichlorotrifluoroethane mixed with a water-soluble organic liquid. Methanol, ethanol, isopropanol, acetone, etc. are used as the water-soluble organic liquid. Among these various liquids, ethanol in particular has the best water desorption effect when coexisting with trichlorotrifluoroethane. As the ethanol, denatured ethanol, such as one containing 6.5% or less methanol, may be used.

If the mixing ratio of water-soluble organic liquid to trichlorotrifluoroethane is too low, the dehydration effect of the washing liquid will not be sufficient, while if it is too high, the flammability of the water-soluble organic liquid aqueous solution produced will increase as described below.
Due to the risk of fire, etc., it should be limited to a few percent (by weight).
Preferably it is about 2.5-8.0% (by weight).

Although the content of the water-soluble organic liquid in the first washing liquid is as low as a few percent (by weight), its specific gravity is greater than that of water, so buoyancy acts on the water on the surface of the article immersed therein. At the same time, the water-soluble organic liquid in the washing liquid dissolves into the adhered water, and an aqueous solution of the water-soluble organic liquid is formed on the surface of the article. Since this aqueous solution has a low surface tension, the adhesion of water is weakened, and the water cannot resist the buoyant force and floats and separates.

Although most of the water adhering to the surface of the article is removed in this way, a very thin film of the aqueous solution of the water-soluble organic liquid remains on the surface. This coating is not removed because it is in equilibrium with the first wash solution and remains after the article is lifted from the wash solution. For this reason,
If the initially deposited water contains dirt, this dirt will remain on the surface of the article after drying.

As mentioned above, the present invention aims to remove the aqueous solution of water-soluble organic liquid remaining on the surface of the article and completely remove the remaining stains. The article treated with the liquid is then subjected to a second washing liquid, that is, a fluorocarbon-based organic solvent containing about 20 to 50% (by weight) of a water-soluble organic liquid, with or without steam bath cleaning of the washing liquid. immerse in it. As this water-soluble organic liquid, methanol, ethanol, isopropanol, butanol, acetone, etc. are used. Among these, isopropanol is preferably used because it has an excellent draining effect and is easy to handle. As the fluorocarbon-based organic solvent, trichlorotrifluoroethane is preferred, but tetrachlorodifluoroethane, trichlorofluoroethane, etc. may also be used.

The reason why the mixing ratio of the water-soluble organic liquid to the fluorocarbon organic solvent is about 20% (by weight) or more is because the coating removal effect of the water-soluble organic liquid aqueous solution is insufficient, and on the other hand, the upper limit is about 50%. (weight) because if the concentration of the water-soluble liquid exceeds this value, the washing liquid becomes flammable and fire prevention measures are required.

This second washing liquid has a higher concentration of water-soluble organic liquid than the first washing liquid, and therefore has high water solubility.For example, in a washing liquid in which ethanol is mixed with trichlorotrifluoroethane as the water-soluble organic liquid, When the ethanol concentration is 4%, the solubility of water is as low as 0.26%, but when the ethanol concentration is increased to 35%, the solubility of water increases to 6.3%. Therefore,
When the article is immersed in the second washing liquid, the film of the water-soluble organic liquid aqueous solution remaining on the surface loses its equilibrium, dissolves in the washing liquid, and is removed. In this way, any trace amount of moisture remaining after washing with the first washing liquid is almost completely removed.

Since the second cleaning liquid remains on the surface of the article that has been treated with the second cleaning liquid, the article is further subjected to steam cleaning using a fluorocarbon-based organic solvent to remove the second cleaning liquid. Trichlorotrifluoroethane is preferably used as the vapor, but tetrachlorodifluoroethane, trichlorofluoroethane, etc. may also be used, or a mixture of these vapors may be used. In the case of mixed vapor, it is desirable that the composition be azeotropic. Through this steam bath cleaning, the articles are completely cleaned and dehydrated.

FIG. 1 [] is a schematic vertical cross-sectional view showing one embodiment of the washing and dehydrating device used for carrying out the method of the present invention;
The figure [ ] is a schematic plan view thereof. 1 is a dehydration tank filled with trichlorotrifluoroethane containing several percent (by weight) of a water-soluble organic liquid as the first washing liquid;
6 is an evaporation tank forming a steam bath of the first washing liquid;
18 is the second washing liquid, which is a water-soluble organic liquid of about 20 to 50
% (by weight) of a fluorocarbon organic solvent, and 22 is an evaporation tank containing vapor of a fluorocarbon organic solvent mainly consisting of trichlorotrifluoroethane. The dehydration tank 1 is connected with a water separation tank 2 that separates the water separated from the surface of the article in the dehydration tank from the washing liquid based on the difference in specific gravity, and a storage tank 7 that stores the washing liquid from which water has been separated. The washing liquid in the storage tank 7 is sent to the dehydration tank 1 and the distillation tank 16 as described later. Also,
The water containing the water-soluble organic liquid separated in the water separation tank 2 is sent to the rectifier 4, where the water-soluble organic liquid is separated, and the water is transferred to the dehydration tank 1 and/or the water separation tank 2.
It is starting to return to . These dehydration tank, evaporation tank, and means for returning water-soluble organic liquid to the dehydration tank, etc., work together to maintain the composition of the first washing liquid in the dehydration tank, etc. within a certain range, as described later. have

When washing and dehydrating articles according to the present invention, the washing with the first washing liquid does not necessarily need to be carried out by the above-mentioned apparatus, but the above-mentioned apparatus can keep the composition of the trichlorotrifluoroethane washing liquid containing a water-soluble organic liquid constant. It is extremely effective for maintaining

The processing process by this device will be explained below. That is, in the above-mentioned apparatus, the article to be washed is first immersed in the first washing liquid in the dehydration tank 1 to remove water adhering to the surface. The water released from the surface of the article floats to the surface of the washing liquid, overflows the tank wall 1a, and enters the water separation tank 2. Here too, the water in the washing liquid rises to the surface due to the difference in specific gravity.
The aqueous phase 2a formed at the top of the tank is introduced into the rectifier 4 through the drain pipe 3 from the opening 3a. In the rectifier, the water-soluble organic liquid in the waste water is separated from water and returned as vapor or liquid to the upper space of the dehydration tank 1 and the water separation tank 2 or into these liquids through the pipe 5, while the water-soluble organic liquid is separated from the water. The water from which the liquid has been removed is discharged from the system through the take-out pipe 6. In addition, water separation tank 2
The washing liquid from which water has been separated is temporarily stored in a storage tank 7.
A part of it is passed through pump 8 to pipes 9a and 9b.
The remaining portion is sent to the steam tank 16 via a pipe line 17.

Incidentally, when the water separated in the water separation tank 2 is rectified in the rectifier 4 to recover a water-soluble organic liquid, a small amount of the water-soluble organic liquid is not hydrated but is lost with the waste water. Furthermore, since the upper spaces 11 of the dehydration tank 1 and the water separation tank 2 are open to the atmosphere, the washing liquid in these tanks may be reduced due to vapor diffusion, or may be entrained when the items to be washed are brought in and out. be lost. This first wash must therefore be replenished with a mixture of trichlorotrifluoroethane and a water-soluble organic liquid of a certain composition. In this case, the composition of the first washing liquid cannot be maintained within a certain range even if a mixed solution containing a high concentration of water-soluble organic liquid is replenished in consideration of replenishment of the water-soluble organic liquid that is lost with drainage. For example, when the water-soluble organic liquid is ethanol, the vapor-liquid equilibrium of a mixture of ethanol and trichlorotrifluoroethane is shown in Figure 2 in terms of ethanol concentration, and when the ethanol concentration in the liquid phase exceeds 4%, The ethanol concentration in the gas phase is almost constant. Therefore, the washing liquid vaporized from the dehydration tank and the like in the apparatus shown in FIG. 1 is lost to the atmosphere as vapor having an ethanol concentration of 4%. However, if we replenish the washing liquid with a high ethanol concentration to compensate for the ethanol lost with drainage, the ethanol concentration of the replenishing washing liquid will be equal to the ethanol concentration of the washing liquid vapor dissipated into the atmosphere ( Approximately 4
%), the ethanol concentration of the first washing liquid in the dehydration tank is gradually concentrated, and a change in liquid composition is unavoidable. The device shown in Figure 1 solves this problem.
A portion of the washing liquid from which water has been separated is transferred from the storage tank 7 to the steam tank 16.
This makes it possible to maintain the composition of the washing liquid within a certain range. In other words, a part of the washing liquid from which water has been separated in the water separation tank 2 is sent to the evaporation tank 1, so even if the concentration of the washing liquid to be replenished is somewhat high, the water-soluble organic liquid is concentrated in the steam tank. It will only happen in 16. The water-soluble organic liquid concentration of the washing liquid vapor generated by heating with the heater 15 in the steam tank 16 is:
Depending on the concentration of the water-soluble organic liquid in the washing liquid, it is determined according to the vapor-liquid equilibrium curve as shown in Figure 2. For example, when the water-soluble organic liquid is ethanol, the ethanol concentration in the liquid phase is up to 50%. Even if the temperature rises, the ethanol concentration in the vapor generated is only about 7.8%.
Since the washing liquid supplied to the dehydration tank etc. is cooled by this steam, it has the same concentration and will never become abnormally high.

The concentration of the water-soluble organic liquid in the washing liquid to be refilled must be higher than the concentration at which the vapor generated in the evaporation tank 16 has an azeotropic composition.
4.0% or more, and considering the amount carried away with wastewater, 4.5% or more, more preferably about 5.0%.
% or more. On the other hand, if the ethanol concentration in the vapor phase exceeds about 8%, the vapor becomes flammable, so the ethanol concentration in the replenishing washing liquid should be determined according to Figure 2.
The gas phase ethanol concentration corresponding to the liquid phase ethanol concentration of 50% is 7.8% or less, more preferably about
6.5% or less.

Note that the water that floats and separates in the water separation tank 2 dissolves a large amount of water-soluble organic liquid and is generally flammable, posing a fire risk. , upper space 11 of the water separation tank
The vapor is nonflammable if filled with
The above dangers can be prevented.

By the way, since the space 11 communicates with the atmosphere, in order to prevent the washing liquid vapor from escaping, a cooler 12 is provided in this communication path, and the washing liquid vapor is cooled and liquefied here. The liquefied washing liquid is sent to dehydration tank 1 or gutter 2.
1 and returned to the water separation tank 2. As shown in the figure, the gutter 21 is connected to a liquid reservoir 14 provided at the upper part of the water separation tank through a return pipe 13a, and the gutter 21
If the washing liquid collected in the above is led to the liquid reservoir 14 and the vapor generated from this liquid reservoir covers the upper surface of the aqueous phase 2a, the above-mentioned fire prevention effect becomes even more reliable. The washing liquid in the liquid reservoir 14 is returned to the water separation tank 12 through the return pipe 13b.

The article is dehydrated with the first washing liquid in the dehydration tank 1 in which the liquid composition is maintained within a certain range as described above.
In the evaporation tank 16, the water-soluble organic liquid is subjected to steam bath cleaning or not, and then in the cleaning phase 18, the water-soluble organic liquid, which is the second cleaning liquid, is in a fluorocarbon-based organic solvent containing about 20 to 50% (by weight). immersed in. At this point, the film of the aqueous solution remaining on the surface of the article is removed. The amount of moisture that adheres to the surface of the article and is brought into the cleaning tank 18 is usually negligible and does not affect the composition of the second cleaning liquid in the cleaning tank. Further, since the concentration of the water-soluble organic liquid in the second washing liquid is about 50% or less, no special precautions for fire prevention are required.

The articles treated with the second cleaning liquid are further subjected to steam bath cleaning in a fluorocarbon-based organic solvent in the next evaporation tank 22. Since the upper space of the evaporation tank 22 communicates with the atmosphere, a cooler 24 is provided to prevent vapor from escaping into the atmosphere, and the liquefied solvent is collected in the evaporation tank 22. Ru. By this steam bath cleaning, the second washing liquid adhering to the surface of the article is removed, and thus the article to be treated is completely washed and dried.

Although the washing tank 18 and the evaporation tank 22 may be provided separately from the devices constituting the dehydration tank 1 and the like, it is convenient for manufacturing to provide them integrally as shown. In this case, the vapors in both evaporation tanks 16 and 22 sandwiching the washing tank 18 have a low concentration of water-soluble organic liquid, and when these vapors come into contact with the second washing in the washing tank 18, the concentration of water-soluble organic liquid in the washing liquid decreases. In order to prevent this, partition walls 18a and 1
8b needs to be higher than the upper surface of the vapor in each evaporator (the interface between the atmosphere and the vapor) to prevent vapor from entering from each evaporator.

In addition, if pipes 20a and 20b are provided at the bottom of the washing tank 18 via a valve 19 so that the second washing liquid in the washing tank can be transferred to the evaporation tank 16, the dehydration tank 1 and the evaporation tank Even if the concentration of the water-soluble organic liquid in the washing liquid 16 decreases, it can be replenished by opening the valve 19, and even if the water concentration of the washing liquid itself increases, this operation can reduce it. can.

Using the apparatus shown in FIG. 1, the mirror glass after washing was dehydrated and washed. In the same device, when only immersion in the dehydration tank 1 and evaporation tank 16 was performed, the dehydration and cleaning effect was insufficient, and there were parts of the glass surface that did not have the aluminum vapor deposited film after cleaning. In the method of the present invention, immersion was performed in sequence into a dehydration tank 1, a washing tank 18 filled with a trichlorotrifluoroethane-ethanol mixture containing 35% ethanol, and an evaporation tank 22 filled with trichlorotrifluoroethane vapor. It is completely dehydrated and washed, has no defects such as those mentioned above, and can form a uniform aluminum vapor deposition film over the entire surface.

As described above, the method of the present invention can stably wash and dry an article for a long time, and can achieve precise washing and drying without leaving even the slightest stain on the surface of the article.

[Brief explanation of the drawing]

FIG. 1 [] is a schematic vertical cross-sectional view showing one embodiment of the washing and drying apparatus used in carrying out the method of the present invention;
The figure [ ] is a schematic plan view thereof, and FIG. 2 is a graph showing the vapor-liquid equilibrium of a trichlorotrifluoroethane-ethanol mixture in terms of ethanol concentration. 1: Dehydration tank, 2: Water separation tank, 4: Rectification equipment,
7: Storage tank, 12, 24: Cooler, 15, 23: Heater, 16: Evaporation tank, 18: Washing tank, 22: Evaporation tank.

Claims (1)

[Claims] 1. The article to be washed is immersed in the first washing solution, trichlorotrifluoroethane containing a water-soluble organic liquid, and then pulled out, and then subjected to the vapor bath cleaning of the above washing solution, or without being subjected to the second washing solution. A washing and drying method characterized by immersing in a fluorocarbon-based organic solvent containing 20 to 50% (by weight) of a water-soluble organic liquid, pulling it up, and further subjecting it to steam cleaning of the fluorocarbon-based organic solvent.