JPH0448514B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a cleaning method for steam cleaning thin objects having a small heat capacity such as metals, glass, plastics, etc., or objects having folds or recesses, using a methylene chloride solvent having a low boiling point. [Prior Art] Various oils adhere to the surfaces of materials such as metals, glass, and plastics, and in order to remove these oils, organic solvents such as halogenated hydrocarbons, alcohols, and ketones have traditionally been used. The solvent cleaning method used has been widely adopted. For example, when applying plating or painting to mechanical parts, etc., as a pretreatment, oil adhering to these mechanical parts is degreased and cleaned using the above-mentioned organic solvent. In this case, degreasing with an organic solvent is generally carried out after immersing the object to be cleaned in an organic solvent at room temperature (in addition,
If necessary, ultrasonic cleaning can be performed using an organic solvent at room temperature), and steam cleaning is often performed by bringing the object to be cleaned into contact with saturated vapor of an organic solvent.
As described above, the steam cleaning method is carried out for the purpose of finishing cleaning the object to be cleaned at the final stage of the solvent degreasing process and also drying the object. Here, in the steam cleaning method, the object to be cleaned, whose temperature is lower than the saturated vapor temperature (boiling point) of the organic solvent, is placed in the saturated steam zone of the solvent, so that the object to be cleaned absorbs heat from the solvent vapor. The vapor of the solvent condenses and liquefies on the surface of the object to be cleaned, and flows down as droplets while washing away the dirt adhering to the surface of the object to be cleaned, thereby cleaning the surface of the object to be cleaned. In this case, the cleaning action of the solvent vapor continues until the temperature of the object to be cleaned reaches the boiling point of the solvent, and when the temperature of the object to be cleaned reaches the boiling point of the solvent, the condensation of the vapor on the surface ends. do. Thereafter, when the object to be cleaned is taken out of the steam bath with the solvent attached and left in the atmosphere, the solvent evaporates into the atmosphere and the object to be cleaned dries. [Problem to be solved by the invention] However, the above-mentioned chikke cleaning method
During drying, the object to be cleaned is cooled by the heat of vaporization of the solvent, causing water vapor in the atmosphere to adhere to the surface of the object (condensation), causing stains, and dust in the atmosphere to re-adhere. May cause stains. If the object to be cleaned has a large heat capacity and is relatively simple in shape, this problem is relatively unlikely to occur, but if the object to be cleaned is thin and has a small heat capacity, this condensation may occur. is often a problem. In addition, even if the object to be cleaned has a relatively large heat capacity, parts with many folds or recesses may
When taking out the solvent from the steam tank after steam cleaning, a large amount of condensed solvent is taken out, so a large amount of heat is lost through evaporation, which often causes condensation, and moreover, solvent loss due to taking out also increases. This increases cleaning costs and also creates problems in the working environment. Such problems are particularly likely to occur when methylene chloride, which has a heat of vaporization of about 80 cal/g and a low boiling point (about 70° C.), is used. That is, as an organic solvent for cleaning, 1,1,1-
Trichloroethane, trichlorethylene, perchlorethylene, etc. are widely used, and their boiling point and latent heat of vaporization are 74.0℃ and 57.7cal/g for 1,1,1-trichloroethane, and 87.2℃ and 57.2cal for trichlorethylene. /g, perchlorethylene
121.2℃, 50.0cal/g. Furthermore, although Freon 113 has a boiling point of 47.6° C., it has a latent heat of vaporization of 35.1 cal/g and dries quickly, so when these solvents are used, condensation does not become a serious problem. However, methylene chloride has a boiling point of 40.4°C and a latent heat of vaporization of 78.7 cal/g, which is lower than the above solvents and has a large latent heat of vaporization. When the object to be cleaned is taken out at a later date, the object to be cleaned is cooled to below room temperature and tends to drop below the dew point temperature, causing dew condensation to become a serious problem. For this reason, if a thin object with a small heat capacity or an object with many folds or recesses is steam-cleaned using methylene chloride, which has a low boiling point and a relatively large latent heat of vaporization, the object will be exposed to the air when it is taken out into the atmosphere. To solve the problem that when methylene chloride adhering to an object to be cleaned evaporates, the object to be cleaned is cooled to below room temperature by the heat of vaporization, and water vapor in the atmosphere easily condenses on the surface of the object, causing dew condensation. was requested. Furthermore, in the conventional steam cleaning method,
When a cold object to be cleaned is brought into the vapor zone of solvent-saturated steam, the vapor zone descends as it is attracted to the object, condensation begins on the surface of the object, and the temperature of the object reaches the boiling point of the solvent. Condensation continues until the temperature is reached, then the vapor zone rises again,
Forming a steam zone at a predetermined location. This phenomenon in which the steam zone descends and rises and disturbs the steam zone (steam zone destruction phenomenon) is observed based on the difference between the temperature of saturated steam and the temperature of the object to be cleaned, and the size of the heat capacity of the object to be cleaned. Although this is a phenomenon, the disturbance of the vapor zone increases the loss of solvent vapor due to scattering. Therefore, the present invention prevents water vapor from condensing on the surface of the object after cleaning when degreasing and cleaning thin objects with small heat capacity or objects having folds or recesses with methylene chloride vapor. ,
Therefore, to provide a steam cleaning method that prevents the inconvenience of stains on objects to be cleaned, eliminates the loss of solvent carried out, reliably prevents the steam zone destruction phenomenon, and maintains the steam zone stably. The purpose is to Means for Solving the Problems] In order to achieve the above object, the present invention cleans a thin object having a small heat capacity or an object to be cleaned having folds or recesses using a methylene chloride solvent contained in a plurality of cleaning tanks. When performing sequential cleaning, the last cleaning tank is a methylene chloride vapor tank, and a superheating heater is provided in the methylene vapor region within this steam tank, and this heater superheats the methylene chloride vapor to a temperature 5 to 60°C higher than its boiling point. forming a superheated steam region in the upper part of the steam tank, and forming an outflow superheated steam region above the plurality of cleaning tanks by covering the plurality of cleaning tanks with superheated steam flowing out from the superheated steam region; The object to be cleaned is washed with methylene chloride in the washing tank, and the object heated in the outflow superheated steam area is heated by 5 to 60°C above the boiling point of the methylene chloride. Introducing the superheated steam region in a steam tank superheated to a high temperature without destroying the superheated steam region, cleaning the object to be cleaned in this superheated steam region, and heating and drying it until the superheated steam temperature reaches, The item to be cleaned is taken out. Here, as the material of the object to be cleaned, any material can be used as long as it is not attacked by organic solvents and can withstand the temperature of superheated steam, such as glass, plastic, and various metals. [Function] In the steam cleaning method according to the present invention, when an object to be cleaned is sequentially cleaned with methylene chloride solvent contained in a plurality of cleaning tanks, the saturated vapor of methylene chloride is heated to 50% above its boiling point in the last step. Cleaning is performed by bringing the object to be cleaned into contact with superheated steam obtained by heating the object to a high temperature of ~60°C. This prevents water vapor in the air from condensing on the surface of the object and prevents stains from forming. Ru. That is, in the present invention, when an object to be cleaned whose temperature is below the boiling point of methylene chloride comes into contact with the superheated vapor of methylene chloride, it receives heat from the superheated vapor and becomes superheated, and at the same time, the superheated vapor removes heat and is cooled. The liquid condenses and liquefies on the surface of the object to be cleaned. This washing continues until the temperature of the object to be washed reaches the boiling point of methylene chloride. Condensation ends when the object to be cleaned reaches the boiling point of methylene chloride, but since the surrounding area is superheated steam, it is heated further by the time it reaches the temperature of the steam, and at the same time, liquid methylene chloride condenses and adheres to the surface of the object to be cleaned. evaporates. Therefore, by the time the object to be cleaned reaches the temperature of the superheated vapor of methylene chloride, the surface of the object to be cleaned has already been well dried, and even if it is taken out into the atmosphere, it will adhere to the object in liquid form and cause the cleaning tank to become dry. There is no loss of methylene chloride carried outside, and inconveniences such as dirt and stains due to condensation of water vapor caused by vaporization of the adhering methylene chloride solution can be avoided. Further, in the present invention, a superheated steam region is formed in the steam tank, and this region is 55% higher than the boiling point of methylene chloride.
Since it is superheated to a high temperature of ~60°C, it is more stable and less turbulent than a normal steam zone, and an outflow superheated steam area is also formed above the multiple cleaning tanks by the superheated steam flowing out from this steam tank. Therefore, when an object to be cleaned that has been cooled to a temperature below the boiling point of methylene chloride is brought into the steam tank, it is immediately heated by the outflowing superheated steam, and the superheated steam region that has been formed in the steam tank is not destroyed. Therefore, the superheated steam area in the steam tank is not disturbed,
By maintaining a stable vapor zone, methylene chloride loss can be extremely reduced. That is, according to the present invention, even if the object to be cleaned has a small heat capacity or has many folds or recesses, it is steam-cleaned with methylene chloride, which has a low boiling point and a large latent heat of vaporization, and the object to be cleaned is sufficiently dried and the chloride is removed. Methylene does not adhere to the object to be cleaned and evaporate in the atmosphere, and a clean surface finish with no stains caused by condensation of water vapor in the atmosphere can be obtained. Since the superheated steam region of the tank is protected by the outflow superheated steam region, the superheated steam region in the steam tank is stabilized, preventing loss of methylene chloride and making stable cleaning possible. Next, embodiments of the present invention will be described with reference to the drawings. [Example] Fig. 1 shows an example of a cleaning device used in carrying out the present invention. It is configured in a tank type. Each of these tanks 1, 2, and 3 contains a methylene chloride solvent 4, and the object to be cleaned is first ultrasonically cleaned in the ultrasonic bath 1, and then washed with the solvent (methylene chloride) in the cold bath 2. and finally transported into the steam tank 3. Here, it is a known method to carry out ultrasonic cleaning, then wash in a cold bath, and finally carry it into a steam tank, but the present invention is characterized by the steam cleaning method after carrying into the steam tank. It is. That is, a heating heater 6 is installed at the bottom of this steam tank 3.
The heater 6 heats the solvent (methylene chloride) 4 in the steam tank 3 to generate saturated vapor of the solvent, and a saturated vapor region 4a is formed above the solvent 4. Furthermore, a steam superheating heater 7 for superheating the saturated steam is installed in the saturated steam region 4a, and the superheating heater 7 superheats the saturated steam region 4a to a temperature 5 to 60° C. higher than its boiling point. A superheated steam region 4b is formed in the upper part of the steam tank 3. In this case, the overheating heater 7 can be an electric heater, a heat circulation type heater, etc. If an electric heater is used, the slider 8 can be connected to an electric circuit so that the temperature can be adjusted to a desired temperature. . Note that the amount of heat of the heater 7 for superheating may be about 1/4 to 1/5 of the amount of heat of the heater 6 for generating saturated steam, and by providing this amount of heat, sufficient superheated steam can be obtained. In addition, since the purpose of the superheating heater 7 is to superheat the saturated steam region, fins etc. are provided to increase the heat transfer area, and baffles etc. are provided to improve contact with the steam 4a. It is preferable to increase efficiency. In this case, thermal efficiency can be increased by subjecting the outer wall of the steam tank 3 to heat insulation processing. In addition, the superheated steam temperature of the solvent can be easily adjusted to a desired temperature by adjusting the slider 8, etc., and can be adjusted as appropriate by considering the boiling point of the solvent, the heat resistance of the object to be cleaned, the solvent, etc. Although it can be determined, the temperature should be selected within a range of 5 to 60°C higher than the boiling point (approximately 40°C) of methylene chloride. Further, one side wall of the ultrasonic tank 1 and the other side wall of the steam tank 3 are each extended upward, and the space above each layer 1, 2, 3 surrounded by these both side walls is filled with superheated parts of the steam tank 3. Superheated steam flows from the steam region 4b,
Here, an outflow superheated steam region 4c is formed.
In this case, the temperatures in both superheated steam regions 4b and 4c are not the same, and the temperature distribution is such that the further away from the steam tank 3 toward the ultrasonic tank 1, the lower the superheated steam temperature becomes. Incidentally, a steam cooling pipe 9 is disposed at the upper part of the above-mentioned both side walls, and the superheated steam in the outflowing superheated steam region 4c is cooled by the steam cooling pipe 9, so that it is scattered upward from the position where the cooling pipe 9 is disposed. This will be prevented. Here, normal cooling methods can be used, such as supplying tap water or well water into the cooling pipe, or using a refrigerant cooled by a refrigerator if a low boiling point cleaning agent is used. can do. The solvent condensed by the cooling pipe 9 is collected into the cooling bath 2 via a water separator 10. The object to be cleaned, which has been washed in the cold bath 2 as described above, is washed and dried in the superheated steam area 4b in the steam bath 3, and in this way, the object to be cleaned is finally washed with methylene chloride. Since the cleaning is performed using superheated steam, condensation of water vapor on the surface of the object to be cleaned is prevented as much as possible after cleaning, thereby preventing the inconvenience of stains on the object to be cleaned, and reducing the loss of solvent carried out. can be reduced. Also,
In this way, not only the superheated steam region 4b is formed in the steam tank 3, but also the entire cleaning device is covered with the outflow superheated steam region 4c, so that the object to be cleaned that has been cooled to below the boiling point of the solvent can be cooled. Even when it is carried into the steam tank 3 from the bathtub 2, it is heated by the superheated steam in the outflow superheated steam region 4c, so that the superheated steam region 4b in the steam tank 3 that has been formed is not destroyed. Therefore, the superheated steam region 4b is not disturbed and a stable steam zone is maintained. Furthermore, Fig. 2 shows another example of a cleaning device used for carrying out the present invention, and this example is an example of a device that performs superheated steam cleaning after saturated steam cleaning in addition to the known saturated steam cleaning. be. That is, in this device, a saturated steam tank 11 and a superheated steam tank 3 are arranged in a state where they are communicated with each other at the lower part thereof, and a saturated steam region 4a formed in the upper part of the saturated steam tank 11 and a superheated steam tank 3 are connected to each other. A superheated steam region 4b formed above is partitioned by a partition part 12, and the saturated steam region 4a is filled with saturated vapor of the solvent 4, and the superheated steam region 4b is filled with superheated steam. Furthermore, both steam tanks 11 and 3
In the space above, an outflow superheated steam region 4c is formed by superheated steam flowing out from the superheated steam region 4b, as in the case of the apparatus shown in FIG. The apparatus shown in FIG. 2 also has a superheated steam tank 3.
Not only is a superheated steam region 4b formed within the cleaning device, but also the entire cleaning device is covered with an outflow superheated steam region 4c, so when an object to be cleaned that has been cooled to below the boiling point of methylene chloride is brought in, the outflow superheat steam area 4c
Although the temperature of the superheated steam decreases to some extent, it does not destroy the saturated steam region 4a of the saturated steam tank 11, and the superheated steam region 4b is not disturbed. Therefore, a stable superheated steam region 4b is maintained, solvent loss can be extremely suppressed, and stable cleaning can be performed. Next, an experimental example will be shown. Experimental Example 1 Using methylene chloride as a solvent, test samples washed with superheated steam and test samples washed with saturated steam using the steam tank of the apparatus shown in Figure 1 were tested to determine whether condensation occurred and whether the solvent was taken out. confirmed. The test results are shown in Table 1.

[Table] From the results in Table 1, it is found that the superheated steam cleaning method of the present invention does not cause dew condensation or liquid take-out, but the saturated steam cleaning method causes dew condensation or liquid take-out. Experimental Example 2 Using methylene chloride (boiling point 40°C) as a solvent, the amount of solvent consumed during operation using the three-tank cleaning equipment shown in Figure 1 was compared between the superheated steam cleaning method of the present invention and the conventional saturated steam cleaning method. Tested on the law. The results are shown in Table 2.

〔Effect of the invention〕

According to the present invention, when methylene chloride is used to clean a thin object with a small heat capacity or an object to be cleaned that has many folds or recesses, stains caused by water vapor condensing on the surface of the object are effectively suppressed. At the same time, there is no destruction of the superheated steam zone, the superheated steam zone can be maintained stably, and the loss of methylene chloride carried out is prevented.
In addition, stable cleaning can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one example of an apparatus used for carrying out the present invention, and FIG. 2 is a schematic diagram showing another example of the apparatus used for carrying out the present invention. 3... Steam tank, 4... Solvent, 4a... Saturated steam region, 4
b... Superheated steam area of the steam tank, 4c... Outflow superheated steam area, 7... Superheating heater.

Claims (1)

[Claims] 1. When cleaning thin objects with small heat capacity or objects having folds or recesses with methylene chloride solvent contained in multiple cleaning tanks, the last cleaning tank is a methylene chloride vapor tank, and this steam A superheating heater is provided in the methylene vapor region in the tank, and this heater superheats the methylene chloride vapor to a temperature 5 to 60°C higher than its boiling point to form a superheated vapor region in the upper part of the steam tank. Above the cleaning tank, superheated steam flowing out from the superheated steam area covers the plurality of cleaning tanks to form an outflow superheated steam area, and the object to be cleaned is cleaned with methylene chloride in the cleaning tank, and finally, By passing through the outflow superheated steam area, the object to be cleaned heated in the outflow superheated steam area is transferred to the superheated steam area in the steam tank which is superheated to 5 to 60 degrees Celsius higher than the boiling point of the methylene chloride. A steam cleaning method characterized in that the object to be cleaned is introduced without being destroyed, the object to be cleaned is cleaned in this superheated steam region, and the object to be cleaned is taken out after being heated and dried to the temperature of the superheated steam.