JPH1024270A - Cleaning method using supercritical fluid as cleaning fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently clean a material to be cleaned by extracting a contaminant soluble in a supercritical fluid among the contaminants depositing on the material surface in a mixed state with the supercritical fluid and washing away the contaminants insoluble in the supercritical fluid with liq. and gas. SOLUTION: The liq. carbon dioxide from a liq. carbon dioxide storage tank 10 is pressurized with a carbon dioxide pump 11 to the supercritical pressure, heated to the supercritical temp. by a first heat exchanger 12 and supplied to a first cleaning tank 20 to clean a first material to be cleaned in the tank 20. The supercritical carbon dioxide discharged from the tank 20 and contg. a contaminant soluble in the supercritical carbon dioxide is depressurized, cooled and supplied to a second cleaning tank 30, the liq. carbon dioxide used in the cleaning and discharged from the first to third cleaning tanks 20 to 40 is depressurized, controlled in temp. and supplied to a separation tank 50 to separate the contaminants.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method using a supercritical fluid capable of satisfactorily cleaning a contaminant that is dissolved or not dissolved in a supercritical fluid adhering in a mixed state to the surface of an object to be cleaned.

[0002]

2. Description of the Related Art Precision cleaning technology greatly contributes to the improvement of quality and productivity in the fields of electronics-related parts, optical equipment, and precision mechanical parts, such as surface treatment, vapor deposition, bonding, and other pre-processes and final finishing processes. doing. Cleaning methods such as immersion method using water, chemicals, and organic solvent as a cleaning medium, rocking method, ultrasonic method, spraying method, and vapor cleaning method using organic solvent such as chlorofluorocarbon are developed. Various combinations have been put to practical use. However, the use of the chlorofluorocarbon-based solvent used as a cleaning fluid is restricted due to problems such as destruction of the ozone layer. In addition, as products have higher performance, there is a demand for higher levels of detergency. Based on these facts, a new cleaning method which is an alternative to the conventional method is being studied, and one of the methods being researched and developed is a cleaning method using a supercritical fluid. The supercritical cleaning method has the unique properties of supercritical fluids, low viscosity like gas, and high diffusivity, while having the density and large solubility like a liquid. Is a method that utilizes the property that the property of fluctuates greatly. As the supercritical fluid, carbon dioxide is most used from the viewpoint of handling properties and economy.

[0003]

However, the supercritical cleaning method can extract and remove contaminants such as oils, fats, water, and organic solvents adhering in a mixed state to the surface of the object to be cleaned. Since the critical fluid has low viscosity and its diffusion coefficient is much higher than that of liquid, it can easily penetrate into the area where liquid-based cleaning agents cannot enter, and it has fine grooves and pores with complicated geometric structures. Contaminants existing inside the polymer material and dissolved in the supercritical fluid can be easily removed. However, even if it is washed over a long period of time, it removes contaminants that do not dissolve in supercritical fluids, such as inorganic compounds and polymer compound powders and exfoliated substances that adhere in a mixed state to the surface of the cleaning object. There is a problem that cannot be done. The present invention has been made in view of the conventional problems,
An object of the present invention is to provide a cleaning method using a supercritical fluid capable of satisfactorily cleaning a contaminant that is dissolved or not dissolved in a supercritical fluid adhered in a mixed state to the surface of an object to be cleaned.

[0004]

According to a first aspect of the present invention, there is provided a cleaning method using a supercritical fluid as a cleaning fluid, wherein the supercritical fluid dissolves in a supercritical fluid such as an oil, a water, an organic solvent or the like attached to an object to be cleaned. A first step of extracting contaminants, and powders and particles, exfoliated substances, etc. remaining on the surface of the object to be cleaned by a liquid or gas obtained by depressurizing and / or cooling the supercritical fluid discharged in the first step A second step of washing out contaminants that do not dissolve in the supercritical fluid.

Further, the cleaning method using a supercritical fluid as a cleaning fluid according to the second aspect of the present invention is characterized in that a contaminant dissolved in a supercritical fluid such as fats, oils, water and an organic solvent and a supercritical fluid such as powders and exfoliated substances. A supercritical fluid is supplied to a first cleaning tank containing a first cleaning object to which a contaminant that does not dissolve in the fluid is attached, and is dissolved in the supercritical fluid from the surface of the first cleaning object. A first step of extracting contaminants; a second step of depressurizing and / or cooling the supercritical fluid discharged from the first washing tank to obtain a liquid or a gas after the first step; The liquid or gas thus obtained is supplied to a second cleaning tank containing a second object to be cleaned from which contaminants previously dissolved in the supercritical fluid are extracted and removed, and remains on the surface of the second object to be cleaned. The third step of washing out contaminants that do not dissolve in the supercritical fluid, and after the third step A fourth step of removing the liquid or gas from the second cleaning tank and taking out the washed second object to be cleaned, and after the fourth step, contaminants that dissolve in the supercritical fluid and do not dissolve in the supercritical fluid A fifth step of storing the third object to be cleaned to which the contaminant is attached in the second cleaning tank,
By repeating these operations in the first and second cleaning tanks sequentially, a predetermined number of objects to be cleaned are cleaned.

Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to a third aspect of the present invention, three or more cleaning tanks are provided in advance, and a first cleaning tank is provided with a supercritical fluid such as oil, water, or an organic solvent. A first cleaning object to which a contaminant dissolved in a critical fluid and a contaminant insoluble in a supercritical fluid such as a granular material and an exfoliated substance are stored, and in a second cleaning tank,
A second cleaning object from which contaminants dissolved and removed in the supercritical fluid are extracted and removed, and a contaminant soluble in the supercritical fluid and a contaminant insoluble in the supercritical fluid after the third cleaning tank The third and subsequent objects to be cleaned to which are adhered are stored and prepared, and a supercritical fluid is supplied to the first cleaning tank.
A first step of extracting contaminants dissolved in the supercritical fluid from the surface of the first object to be cleaned, and after the first step, the supercritical fluid discharged from the first cleaning tank is depressurized and / or cooled. A second step of obtaining a liquid or gas; and supplying the liquid or gas obtained in the second step to a second cleaning tank to contaminate the supercritical fluid remaining on the surface of the second object to be cleaned. A third step of washing away the substance, after the third step, a liquid or gas is removed from the second washing tank, and a fourth step of taking out the washed second object to be washed, and after the fourth step, a supercritical fluid And a fifth step in which a new object to be cleaned, to which a contaminant that dissolves in water and a contaminant that does not dissolve in the supercritical fluid adheres, is stored in the second cleaning tank and is on standby. A supercritical fluid is supplied to the third cleaning tank, and the supercritical fluid adhering to the stored third object to be cleaned is supplied. A sixth step of extracting and removing contaminants dissolved in the fluid, and after the sixth step, a seventh step of depressurizing and / or cooling the supercritical fluid discharged from the third washing tank to obtain a liquid or gas; An eighth step of supplying the liquid or gas obtained in the seventh step to the first cleaning tank to wash out contaminants insoluble in the supercritical fluid remaining in the first object to be cleaned, and after the eighth step Ninth step of removing the liquid or gas from the first cleaning tank and taking out the first cleaned object to be cleaned, and after the ninth step, contaminants dissolved in the supercritical fluid and dissolved in the supercritical fluid A tenth step of storing a new object to be cleaned to which no contaminants are attached in the first cleaning tank and waiting, and performing the operations of the above steps sequentially in three or more cleaning tanks. By repeating, a predetermined number of objects to be cleaned are continuously cleaned.

The cleaning method using a supercritical fluid as a cleaning fluid according to claim 4 is a cleaning method using a supercritical fluid as a cleaning fluid according to claim 2 or 3, In the meantime, a step of separating a contaminant dissolved in the supercritical fluid from a liquid or a gas by a separation tank is provided. Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 5, the contaminants dissolved in the supercritical fluid such as oils, fats, water, and organic solvents and the supercritical fluid such as powders and particles are separated. A first step of supplying a supercritical fluid to a single cleaning tank containing an object to be cleaned to which contaminants not to be adhered and extracting contaminants dissolved in the supercritical fluid from the surface of the object to be cleaned; After the first step, a second step of supplying a liquid or gas to the cleaning tank to wash away contaminants that are not dissolved in the supercritical fluid remaining on the surface of the object to be cleaned, and after the second step,
Remove the liquid or gas from the cleaning tank, remove the cleaned object, and remove the next cleaning object with contaminants that dissolve in the supercritical fluid and contaminants that do not dissolve in the supercritical fluid. In the third step of storing in the
A fourth step of supplying a supercritical fluid to the cleaning tank and extracting contaminants dissolved in the supercritical fluid from the surface of the next object to be cleaned in the cleaning tank, and sequentially repeating the above steps. Accordingly, the contaminants that are dissolved and do not dissolve in the supercritical fluid from each of the objects to be cleaned in one cleaning tank are intermittently removed.

Further, the cleaning method using a supercritical fluid as a cleaning fluid according to claim 6 is a cleaning method using a supercritical fluid as a cleaning fluid according to any one of claims 2 to 5, wherein This is to separate and remove contaminants from the liquid or gas after washing away the contaminants that do not dissolve in water. The cleaning method using a supercritical fluid as a cleaning fluid according to claim 7 is the cleaning method using the supercritical fluid as a cleaning fluid according to claim 6, wherein the supercritical fluid and a liquid or gas are supplied to the cleaning tank. It has a fluid storage tank, and a liquid or gas, which has been cleaned by separating and removing contaminants, is cooled and returned to the liquid fluid storage tank for circulating use. Further, the cleaning method using a supercritical fluid as a cleaning fluid according to claim 8 uses supercritical carbon dioxide as the supercritical fluid in claims 1 to 7.

The cleaning fluid in the present invention includes fluids in a supercritical state, such as ethane, propane, butane, ammonia, nitrogen suboxide, or carbon dioxide. It is preferable to use supercritical carbon dioxide from the viewpoint of safety. The object to be cleaned in the present invention includes, for example, electronic parts, optical equipment, precision mechanical parts, and the like made of glass, ceramics, and synthetic resin. Here, the surface of the object to be cleaned includes the surface on the front side and the surface on the back side of the object to be cleaned, and also includes fine grooves and holes on the surface. The contaminants dissolved in the supercritical fluid attached to the surface of the object to be cleaned in the present invention include, for example, cutting oils, polishing oils, rust preventive oils, oils and fats such as lubricating oils, and mineral oils, animal and vegetable oils as raw materials. And organic solvents such as alcohols, ketones, ethers and esters, and unreacted monomers, oligomers and release agents such as silicone resins and polycarbonate resins. Examples of contaminants that do not dissolve in the supercritical fluid attached to the surface of the object to be cleaned include, for example, powders and particles derived from the object to be cleaned such as metals, ceramics, and polymers, and materials for processing equipment. Derived powder and dust in the air.

Hereinafter, a supercritical fluid such as supercritical carbon dioxide in the present invention will be described. It is known that nature has three states: gas, liquid, and solid. For example, in the case of carbon dioxide, the gas is carbon dioxide, the liquid is liquid carbon dioxide, and the solid is dry ice. By the way, when liquid carbon dioxide is put in one pressure vessel, liquid and gas form two phases of gas and liquid while maintaining equilibrium with each other. From this state, when the pressure and temperature are gradually increased, the state where the gas-liquid interface disappears and a single phase can be observed. The pressure and temperature at this time are defined as critical pressure (73.8 kg / cm ² G) and critical temperature (31.1 ° C.), respectively.
I'm calling The supercritical fluid refers to a fluid under conditions that exceed the critical pressure and critical temperature. In other words, the supercritical fluid is in the fourth state.

Incidentally, ethane, propane, ammonia,
The supercritical states of nitrogen suboxide and carbon dioxide are:
Critical pressure is 48.8, 42.6, 38.0, 112.
8, 71.7, 73.8 kg / cm ² G, critical temperature 3
2.3, 96.9, 152.0, 132.4, 36.
5, 31.1 ° C. The properties and characteristics of supercritical fluids are that while supercritical fluids have a density close to that of liquids, their viscosity is close to that of gases, and their diffusion coefficient is much higher than that of liquids, they can facilitate mass transfer to fine parts. is there. In general,
It is known that a fluid having a high density such as a liquid dissolves a substance well, and a fluid having a low density such as a gas has a low dissolving power. The dissolving power of a supercritical fluid is proportional to its density, but the density changes greatly with a slight pressure and temperature change.
Large solubility differences are obtained. The supercritical cleaning method using a supercritical fluid conceptually only replaces the water or organic solvent cleaning medium with a supercritical fluid, but has the following characteristics compared to the CFC-based cleaning method and the water-based cleaning method. Have.

(1) Since the supercritical fluid has a low viscosity and a high diffusivity, it can easily penetrate into the portion where the liquid cleaning agent is not put. Therefore, contaminants existing inside fine grooves, pores having a complicated geometric structure, and a polymer material can be easily removed. (2) In the liquid-based cleaning method, the general process is cleaning → rinsing → drying. However, in the supercritical method, when the cleaning fluid is taken out of the cleaning tank, the cleaning fluid is immediately vaporized from the surface of the object, and thus the drying process after cleaning. Is unnecessary. (3) In the liquid cleaning method, when contaminants are reused,
A step of separating from water or an organic solvent by distillation or the like is required.
However, in the supercritical cleaning method, the contaminants and the cleaning fluid are completely separated in the separation tank, so that the contaminants having utility value can be recovered and reused as they are. (4) The solubility of the supercritical fluid is greatly reduced by reducing the pressure, and the dissolved contaminants and the cleaning fluid can be separated. Therefore, cyclic reuse is possible.

Next, application fields of the supercritical cleaning method will be described. The selection of the cleaning method largely depends on the material and shape of the object to be cleaned. The characteristics of the object suitable for the supercritical cleaning method are as follows. (1) Those having a complicated geometric structure and a structure that does not allow a cleaning medium to enter. (2) Those sensitive to water or heat. (3) Those requiring long processing time for washing and drying. Of these, in the field of precision machine assemblies, the interiors of micromachines, bearing assemblies, computer disk drive components, and the like often have complicated geometric structures. Supercritical cleaning methods are believed to be effective in removing contaminants present in these hard-to-find spaces. The bearing portion of a helicopter blade is composed of a bearing and a housing, but it is necessary to completely remove moisture from a minute space in the housing in order to prevent rust. The supercritical cleaning method is considered to be suitable for this purpose, and is under study.

In the field of aerospace, cleaning of a gyroscope is most studied. The first reason is the recovery of the expensive anti-vibration fluid used in the gyroscope.When the anti-vibration fluid is cleaned by the supercritical cleaning method, the anti-vibration fluid dissolves well in the supercritical fluid. This is because even the vibration-proof fluid existing in the hole can be taken out and can be recovered and reused as it is. The second reason is that water induces corrosion in beryllium-based alloys used as gyroscope component materials, and is easily damaged. Corrosion inhibitors are also used in water-based cleaning methods, but are susceptible to damage in multi-stage cleaning and rinsing steps. However, because supercritical cleaning does not use water, it does not cause corrosion and is considered more suitable than aqueous cleaning.

In textile products, harmful organic solvents,
Construction of a system to wash and recycle fiber waste such as work clothes, cotton swabs, rags, and paper towels contaminated with oil, blood, etc. Supercritical cleaning is being considered as an alternative to removing oils and chemicals from newly woven fabrics. For example, cotton cloth and the like contaminated with motor oil of automobiles can be washed and used as an alternative to dry cleaning. In addition, the supercritical cleaning method uses not only the mechanism described above, but also a method that utilizes the increase in fluidity due to a sudden change in pressure of the supercritical fluid, a method that combines the supercritical cleaning method with the ultrasonic method or the pulsation method, etc. It is also conceivable that the cleaning effect is increased by this. The rapid depressurization method can be used, for example, for removing particulate matter blocking the entrance of fine grooves or pores.Put the object to be cleaned in a pressure vessel and bring the inside of the system to a high density supercritical state. Thereafter, when the pressure is rapidly reduced by an operation such as opening a valve, the supercritical fluid that has permeated into the deep portion of the groove or the pores is instantaneously vaporized, and a rapid fluid flow is generated. This is a method that uses the force of this rapid flow to block and remove particulate matter. Furthermore, a supercritical cleaning method combining an ultrasonic method can be applied. In this method, an ultrasonic generator is attached to a cleaning tank, and a single-frequency acoustic wave is generated to generate a partial pressure fluctuation in a supercritical fluid, and a plurality of gas regions and a supercritical region are alternately arranged. This is a method for increasing the cleaning effect by creating a state on the cleaning object.

When carbon dioxide is used as the cleaning fluid, the conditions for extracting contaminants with a supercritical fluid are as follows:
0-500 kg / cm ² G, especially 100-400 kg /
cm ² G is preferred, and if it is less than 80 kg / cm ² G, contaminants of fats and oils hardly dissolve, making cleaning difficult,
If it exceeds 500 kg / cm ² G, the construction cost of the apparatus and the cleaning treatment cost increase, which is economically undesirable. Further, the washing temperature is preferably from 31 to 80 ° C., particularly preferably from 35 to 70 ° C., and if it is less than 31 ° C., the washing effect is greatly reduced.
This is because if the temperature exceeds ℃, the substrate to be cleaned may be deteriorated in an object to be cleaned having a polymer material or the like as a substrate. If necessary, a lower alcohol such as methanol or an aliphatic hydrocarbon such as hexane may be added as an extraction aid at 30% by weight or less, particularly at 10% by weight or less. No matter how much the addition amount exceeds 30% by weight, improvement in the dissolution cleaning efficiency cannot be expected.

The solubility of supercritical carbon dioxide has the following characteristics. (1) Alcohols, ketones, esters and ethers having about 1 to 5 carbon atoms easily dissolve even at low pressure. (2) A substance having the second highest solubility next to that described in the above (1) is a hydrocarbon-based compound such as alkane, alkene, and terpene having a slightly higher carbon number. (3) Non-polar substances such as machine oils, lubricating oils, and edible oils may have high molecular weights and are slightly soluble. (4) Carbon dioxide does not destroy the ozone layer unlike the CFC-based solvent. In addition, since it is recycled and recycled, it does not significantly affect global warming and the like, so it is safe for workers and the environment. (5) Since carbon dioxide is used as a cleaning medium, there is no corrosion by water. Further, since the operating temperature is about 35 to 70 ° C., the present invention can be applied to an object which is weak to heat. (6) Polar substances such as inorganic compounds, phospholipids and amino acids hardly dissolve.

These properties are the factors that make the precision cleaning by the supercritical cleaning method more efficient than the liquid cleaning method. However, in supercritical carbon dioxide, polar substances such as indefinite compounds, phospholipids, and amino acids hardly dissolve, and therefore, in the conventional supercritical cleaning method, the above-mentioned polar substances remain on the surface of the object to be cleaned. The present invention proposes a method for greatly improving this.

As described above, in the cleaning method using the supercritical fluid as the cleaning fluid according to any one of the first to eighth aspects, the contaminants that are dissolved or do not dissolve in the supercritical fluid adhering in a mixed state to the surface of the object to be cleaned are removed. First, the contaminants that dissolve in the supercritical fluid are extracted with the supercritical fluid, and then the contaminants that do not dissolve in the supercritical fluid are washed away with a liquid with a high density or blown off with a gas. Can be cleaned well.

According to the first aspect of the present invention, in the cleaning method using a supercritical fluid as a cleaning fluid, the supercritical fluid from which contaminants dissolved in the supercritical fluid are extracted is decompressed and / or cooled to dissolve in the supercritical fluid. Since liquid or gas is obtained to wash away contaminants that do not dissolve in the supercritical fluid, two tasks must be performed in succession: extraction and removal of contaminants that dissolve in the supercritical fluid, and washing and removing contaminants that do not dissolve in the supercritical fluid. Can be. Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 2, cleaning of a contaminant and a supercritical fluid which alternately dissolve in a supercritical fluid of each object to be cleaned in two cleaning tanks. By repeating the cleaning of the contaminants that do not dissolve in the water, the workability of the cleaning operation of the object to be cleaned can be improved.
Furthermore, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 3, cleaning of contaminants that are alternately and continuously dissolved in the supercritical fluid of each object to be cleaned in three or more cleaning tanks. And cleaning of contaminants that do not dissolve in supercritical fluids
By sequentially repeating the cleaning operation, the cleaning operation can be continuously performed without interrupting the cleaning operation, and the workability of the cleaning operation of the object to be cleaned can be improved.

Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to the present invention, a supercritical fluid is extracted from a liquid or a gas from which a contaminant dissolved in the supercritical fluid attached to an object to be cleaned is removed. Contaminants that dissolve in the critical fluid
Separation by the separation tank allows the purified liquid or gas to be used for cleaning contaminants that do not dissolve in the supercritical fluid remaining on the surface of another object to be cleaned in the next process, and is a useful pollutant. Can be collected and reused. Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 5, a contaminant dissolved in the supercritical fluid from each of the objects to be cleaned in one cleaning tank and a contaminant not dissolved in the supercritical fluid. By intermittently removing the substance, the equipment cost can be reduced.

In the cleaning method using the supercritical fluid as the cleaning fluid according to the sixth and seventh aspects, the contaminants are separated and removed from the liquid or the gas after washing away the contaminants that do not dissolve in the supercritical fluid. By doing so, it is possible to collect and reuse contaminants that do not dissolve in a supercritical fluid having a use value. In particular, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 7, the supercritical fluid and the liquid or gas supplied to the cleaning tank are subjected to a supercritical treatment on the way or a liquid fluid storage tank as it is. The liquid or gas supplied to the washing tank from which the contaminants are separated and removed is cleaned and returned to the liquid fluid storage tank after cooling, so that the liquid or gas is safe for workers and the environment. In addition, running costs can be reduced. Furthermore, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 8, since supercritical carbon dioxide or the like is employed as the supercritical fluid, it is economical and safe for workers and the environment. It is preferable because the property is secured.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. Although the present embodiment uses supercritical carbon dioxide as the cleaning fluid, the same operation is performed for a case where ethane, propane, butane, ammonia, or nitrogen suboxide is used as the cleaning fluid. Form. First, a cleaning method using supercritical carbon dioxide as a cleaning fluid according to Embodiment 1 of the present invention will be described based on the cleaning device shown in FIGS.
In the cleaning apparatus of FIG. 1, 10 is a liquid carbon dioxide storage tank, 20 is a first cleaning tank, 30 is a second cleaning tank, 40
Denotes a third washing tank. In the middle of the first flow path a connected to the liquid carbon dioxide storage tank 10 and the first to third cleaning tanks 20 to 40, a carbon dioxide pump 11, a first heat exchanger 12, and valves 13 to 15 are provided. The first to third cleaning tanks 2 are provided between the upper and lower sides of the first to third cleaning tanks 20 to 40, respectively.
The supercritical carbon dioxide discharged from 0 to 40 is cooled and decompressed to be a liquid or a gas, and then the other
A second flow path b to be supplied to the third cleaning tanks 20 to 40 is connected. Valves 16 to 18 are provided in the vicinity of one end of the second flow path b which is branched into three, and thereafter, the supercritical carbon dioxide is sequentially decompressed to a downstream part collectively collected. A first pressure holding valve 19 and a second heat exchanger 21 for cooling supercritical carbon dioxide are provided. Further, downstream therefrom, the valve is branched into three parts, and near the other end, the valves 22 to 22 are provided.
24 are provided.

Further, a third flow path c of an external discharge system is also connected to each of the first to third cleaning tanks 20 to 40. Third
In the flow path c, the valves 25 to 2 are arranged in order from the branched upstream portion.
7, a second pressure-holding valve 28, a third heat exchanger 29, a separation tank 50 such as a cyclone for separating contaminants dissolved or insoluble in supercritical carbon dioxide from liquid carbon dioxide after washing, Pressure holding valve 31 is provided. FIG.
, 32 to 34 are first to third cleaning tanks 20 to 40, respectively.
An air release valve 35 is connected to the lower portion of the separation tank 50.

Next, a cleaning method using supercritical carbon dioxide as a cleaning fluid according to the first embodiment using the cleaning device using supercritical carbon dioxide as a cleaning fluid will be described with reference to FIGS. The first cleaning tank 20 contains an uncleaned first cleaning object in advance, and the second cleaning tank 30
Contains a second object to be cleaned from which only contaminants dissolved in supercritical carbon dioxide have been extracted and removed.
In the cleaning tank 40, the third object to be cleaned is being set. FIG.
The liquid carbon dioxide drawn from the liquid carbon dioxide storage tank 10 to the first flow path a
After the pressure is increased to a predetermined pressure equal to or higher than the critical pressure, the temperature is increased to a predetermined temperature equal to or higher than the critical temperature by the first heat exchanger 12 to become supercritical carbon dioxide. It is supplied to the cleaning tank 20. In the first cleaning tank 20, an uncleaned first cleaning object is stored, and contaminants dissolved in the supercritical carbon dioxide attached to the surface of the first cleaning object are sent. Extracted and removed by supercritical carbon dioxide.

Next, the supercritical carbon dioxide dissolved in the supercritical carbon dioxide after the extraction of the contaminants flows from the opened valve 16 into the second flow path b and is depressurized by the first pressure holding valve 19. Liquid carbon dioxide is cooled by the second heat exchanger 21 and supplied to the second cleaning tank 30 via the valve 23. In the second cleaning tank 30, the contaminants insoluble in the supercritical carbon dioxide adhering to the surface of the second object to be cleaned, from which only the contaminants soluble in the supercritical carbon dioxide have been extracted, are sent to the liquid carbon dioxide Or cooled and re-liquefied by the liquid carbon dioxide storage tank 10
Return to Then, the washed liquid carbon dioxide flows into the third flow path c via the opened valve 26,
After the pressure is reduced by the pressure holding valve 28, the contaminants which are dissolved or insoluble in the supercritical carbon dioxide are controlled by the temperature adjustment by the third heat exchanger 29, and then supplied to the separation tank 50, where the supercritical carbon dioxide is removed. Dissolved or undissolved contaminants are separated, then depressurized by a third pressure holding valve 31, and then released to the atmosphere. On the other hand, as shown in FIG.
The inside of the cleaning tank 30 is set to the atmospheric pressure by opening the air release valve 33, the second cleaned object to be cleaned is taken out from the atmospheric pressure, and a new uncleaned fourth object to be cleaned is stored. You.

Next, supercritical carbon dioxide is supplied from the liquid carbon dioxide storage tank 10 to the third cleaning tank 40 via the carbon dioxide pump 11 and the valve 15 of the first flow path a. The supercritical carbon dioxide after washing the contaminants dissolved in the carbon flows into the second flow path b via the valve 18, and is depressurized by the first pressure-holding valve 19, and the second heat exchanger 21
And is supplied to the first washing tank 20 through the valve 22. Here, as described above, the liquid carbon dioxide is fed into the surface of the first object to be cleaned from which the contaminants soluble in the supercritical carbon dioxide have been extracted, and the contaminants that do not dissolve in the supercritical carbon dioxide are washed away. It is. Subsequently, the liquid carbon dioxide after the cleaning flows into the third flow path c via the opened valve 25,
After the pressure is reduced by the pressure holding valve 28, the contaminants which are dissolved or insoluble in the supercritical carbon dioxide are controlled by the temperature adjustment by the third heat exchanger 29, and then supplied to the separation tank 50, where the supercritical carbon dioxide is removed. Dissolved or undissolved contaminants are separated, then depressurized by a third pressure holding valve 31, and then released to the atmosphere.

On the other hand, the inside of the first cleaning tank 20 is set to the atmospheric pressure by opening the air release valve 32, from which the first cleaned object to be cleaned is taken out.
Are stored. Thereafter, the operations of these steps are sequentially repeated in the first to third cleaning tanks 20 to 30, so that the supercritical carbon dioxide adhered to the object to be cleaned in each of the first to third cleaning tanks 20 to 40. The removal of contaminants that are dissolved or not dissolved in water is performed alternately and continuously. Thus, contaminants that are dissolved or do not dissolve in supercritical carbon dioxide adhering in a mixed state to the surface of the object to be cleaned can be satisfactorily cleaned.

FIG. 4 shows a cleaning apparatus to which a cleaning method using supercritical carbon dioxide as a cleaning fluid according to a second embodiment of the present invention is applied. As shown in FIG.
Is to deal with a large amount of contaminants dissolved in supercritical carbon dioxide, such as oil, attached to the surface, and is located downstream of the second heat exchanger 21 in the second flow path b. In this example, a separation tank 60 exclusively for removing contaminants dissolved in supercritical carbon dioxide is arranged. First to third washing tanks 20 to 4
From 0 to a large amount of supercritical carbon dioxide containing contaminants dissolved in supercritical carbon dioxide,
The pressure of the liquid carbon dioxide 9 and the cooling of the liquid carbon dioxide by the second heat exchanger 21 are supplied to the separation tank 60, so that the contaminants dissolved in the mixed supercritical carbon dioxide are separated. , Another first to third washing tanks 20 to 4
0. In FIG. 4, reference numeral 36 denotes a separated material discharge valve. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 shows a cleaning apparatus to which a cleaning method using supercritical carbon dioxide as a cleaning fluid according to Embodiment 3 of the present invention is applied. As shown in FIG.
Is an example in which a contaminant dissolved or insoluble in supercritical carbon dioxide from each object to be cleaned is intermittently removed in one cleaning tank 70. 11, valve 37, first heat exchanger 1
A flow path d connected to the cleaning tank 70 through the second tank 2, a first pressure-holding valve 19 from the cleaning tank 70, contaminants dissolved in supercritical carbon dioxide in supercritical carbon dioxide discharged from the cleaning tank 70, A separation tank 80 for separating and removing contaminants insoluble in supercritical carbon dioxide mixed in the liquid carbon dioxide after cleaning discharged from the cleaning tank 70 in another step;
And a flow path e connected to the liquid carbon dioxide storage tank 10 via the heat exchanger 21 of FIG. In addition, a bypass d ′ is provided in the flow path d to communicate between the carbon dioxide pump 11 and the valve 37 and between the first heat exchanger 12 and the cleaning tank 70. The separated matter discharge valve 39 is connected.

Next, a cleaning method using supercritical carbon dioxide as a cleaning fluid using this cleaning apparatus will be described. As shown in FIG. 5, the liquid carbon dioxide guided from the liquid carbon dioxide storage tank 10 to the flow path d is raised to a predetermined pressure equal to or higher than the critical pressure by the carbon dioxide pump 11 and then opened.
7, the temperature is raised to a predetermined temperature equal to or higher than the critical temperature by the first heat exchanger 12, and is converted into supercritical carbon dioxide.
0. Here, by supercritical carbon dioxide,
Contaminants dissolved in the supercritical carbon dioxide attached to the surface of the uncleaned object to be cleaned that has been stored in advance are extracted, and then the supercritical carbon dioxide mixed with the contaminants dissolved in the supercritical carbon dioxide is: After entering the flow passage e and being depressurized by the first pressure holding valve 19, the separation tank 80 separates and removes contaminants dissolved in the supercritical carbon dioxide. The contaminants dissolved in the separated supercritical carbon dioxide are discharged from the separated material discharge valve 39. Then, fats and oils,
The carbon dioxide from which contaminants such as water and organic solvents have been separated is cooled by the second heat exchanger 21 to become liquid carbon dioxide, and then the liquid carbon dioxide storage tank 10
And used for circulation.

Next, the flow path d from the liquid carbon dioxide storage tank 10
Liquid carbon dioxide supplied to the carbon dioxide pump 11
, The valve 38 flows into the opened bypass passage d ', and is returned to the flow passage d. Here, the contaminants that do not dissolve in the supercritical carbon dioxide are washed away from the surface of the object to be cleaned from which the contaminants that dissolve in the supercritical carbon dioxide are extracted. The liquid carbon dioxide containing the contaminants that do not dissolve in the supercritical carbon dioxide flows into the flow path e, and the first pressure holding valve 1
After the pressure is reduced by 9, the contaminants insoluble in the supercritical carbon dioxide are separated and removed in the separation tank 70, and then cooled again by the second heat exchanger 21, and then to the liquid carbon dioxide storage tank 10. Will be returned. These steps, in order,
The repetition allows intermittent removal of contaminants that are dissolved or insoluble in supercritical carbon dioxide from the object to be cleaned in one cleaning tank, thereby reducing equipment costs. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

Although the first and second embodiments show an example using three cleaning tanks, and the third embodiment shows an example using one cleaning tank, the present invention is not limited to this. 2
In the cleaning tank of the tank, a predetermined number of objects to be cleaned are washed by repeating the cleaning of contaminants that are mutually soluble in supercritical carbon dioxide and the cleaning of contaminants that are not soluble in supercritical carbon dioxide. Also, while using three or more washing tanks, taking out the washed object to be washed from the washed washing tank and storing a new object to be washed, the other washing tank in a standby state is used. By performing the cleaning operation of the object to be cleaned, the object to be cleaned may be continuously washed without interrupting the cleaning operation.

[0034]

EXAMPLES Examples of the present invention will be described below. Needless to say, the present invention is not limited to these examples. Example 1 Here, the object to be cleaned was continuously cleaned using the cleaning apparatus shown in FIGS. 1 to 3 under the following conditions. That is, by using the carbon dioxide pump 11, the liquid carbon dioxide from the liquid carbon dioxide storage tank 10 is supplied at 200 kg / cm ^2.
G to a supercritical pressure of G, and after raising the temperature to a supercritical temperature of 45 ° C. by the first heat exchanger 12, the internal volume is 2,000 cm.
³ first to the cleaning tank 20 by supplying supercritical carbon dioxide, washing the first object to be cleaned of unwashed first cleaning tank 20.

Thereafter, supercritical carbon dioxide containing contaminants dissolved in the supercritical carbon dioxide discharged from the first cleaning tank 20 is 65 kg / cm ² G by the first pressure holding valve 19.
The pressure is reduced to 20 ° C. by the second heat exchanger 21 and supplied to the second washing tank 30 having an internal volume of 2,000 cm ³ (the same applies hereinafter). First to third washing tanks 2
The washed liquid carbon dioxide discharged from 0 to 40 is decompressed to 30 kg / cm ² G by the second pressure holding valve 28, and then temperature-controlled to 15 ° C. by the third heat exchanger 29, It is supplied to a separation tank 50 having a volume of 500 cm ³ to separate contaminants that are dissolved or not dissolved in supercritical carbon dioxide. The liquid carbon dioxide after the separation is further reduced to the atmospheric pressure by the third pressure holding valve 31. As a result, contaminants dissolved or not dissolved in supercritical carbon dioxide adhering in a mixed state to the surface of the object to be cleaned were successfully cleaned.

Example 2 Here, the object to be cleaned was continuously cleaned using the cleaning apparatus shown in FIG. 4 under the following conditions. That is, an experiment was performed in the same manner as in Example 1 except that a separation tank 60 having an internal volume of 500 cm ³ was arranged downstream of the second heat exchanger 21 in the second flow path b. As a result, even if the amount of contaminants dissolved in supercritical carbon dioxide, such as oil, is large on the surface of the object to be cleaned, it is dissolved or dissolved in supercritical carbon dioxide adhering to the surface of the object to be cleaned in a mixed state. The clean contaminants could be cleaned well.

Example 3 Here, the object to be cleaned was continuously cleaned using the cleaning apparatus shown in FIG. 5 under the following conditions. That is, the flow path d to be looped by joining, to the e, a cleaning tank 70 having an internal volume of 2,000 cm ^3, inner volume 500 cm ³
An experiment was conducted in substantially the same manner as in Example 1 except that the separation tank 80 was provided. As a result, although it took more time and labor than in the case of Example 1, similarly, contaminants dissolved or insoluble in supercritical carbon dioxide adhering in a mixed state to the surface of the object to be cleaned could be cleaned well.

Comparative Example 1 An experiment was performed in the same manner as in Example 3 except that the uncleaned object stored in the cleaning tank 70 was cleaned only with supercritical carbon dioxide from the liquid carbon dioxide storage tank 10 side. . As a result, only the liquid adhering to the surface of the object to be cleaned in a mixed state could be cleaned, but the contaminants that did not dissolve in supercritical carbon dioxide remained adhered to the object to be cleaned, as compared with those of Example 3. .

[0039]

As described above, in the cleaning method using the supercritical fluid as the cleaning fluid according to claims 1 to 8 of the present invention,
Among the contaminants that dissolve or do not dissolve in the supercritical fluid that adhere to the surface of the object to be cleaned in a mixed state, the contaminants that dissolve in the supercritical fluid are first extracted by the supercritical fluid, and then the contaminants that do not dissolve in the supercritical fluid Is washed away with a liquid or a gas, so that the object to be cleaned can be cleaned well. As a result, the supercritical fluid easily penetrates into the area where the liquid cleaning agent does not enter, and contaminants existing inside fine grooves, pores with complicated geometric structures, polymer materials, etc. Contaminants that are easily extracted and do not dissolve in the supercritical fluid can be cleaned with a denser liquid state fluid or blown off with a gaseous state fluid to remove almost all contaminants attached to the object to be cleaned. it can. And, by using carbon dioxide, without destroying the ozone layer like a CFC-based solvent, and easily corroded by water, it can be applied to heat-sensitive objects,
No drying step after washing is required.

According to the first aspect of the present invention, in the cleaning method using a supercritical fluid as a cleaning fluid, the supercritical fluid obtained by extracting a contaminant dissolved in the supercritical fluid is depressurized and / or cooled to obtain a supercritical fluid. As a liquid or gas is obtained to wash away contaminants that do not dissolve in the supercritical fluid, the two tasks of extracting and removing contaminants that dissolve in the supercritical fluid and rinsing and removing contaminants that do not dissolve in the supercritical fluid are continuously performed. It can be carried out. Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 2, cleaning of a contaminant and a supercritical fluid which alternately dissolve in a supercritical fluid of each object to be cleaned in two cleaning tanks. Since the cleaning of the contaminants that do not dissolve in the water is repeated, the workability of the cleaning operation of the object to be cleaned can be improved. Furthermore, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 3, cleaning of contaminants that are alternately and continuously dissolved in the supercritical fluid of each object to be cleaned in three or more cleaning tanks. Since the cleaning of contaminants that do not dissolve in the supercritical fluid is sequentially repeated, the cleaning operation can be performed continuously without interrupting the cleaning operation, and the workability of the cleaning operation of the object to be cleaned can be improved.

Further, in the cleaning method using a supercritical fluid as a cleaning fluid according to a fourth aspect of the present invention, a supercritical fluid is extracted from a liquid or a gas from which a contaminant dissolved in the supercritical fluid attached to an object to be cleaned is removed. Contaminants that dissolve in the critical fluid
Since the separation is performed by the separation tank, the purified liquid or gas can be used for cleaning contaminants that do not dissolve in the supercritical fluid remaining on the surface of another object to be cleaned in the next step,
Can collect and reuse valuable pollutants. In a cleaning method using a supercritical fluid as a cleaning fluid according to a fifth aspect, removal of liquid and contaminants that are not dissolved in the supercritical fluid from each of the objects to be cleaned is performed intermittently in one cleaning tank. As a result, the equipment cost can be reduced.

Further, in the cleaning method using the supercritical fluid as the cleaning fluid according to the sixth and seventh aspects, the contaminants are separated and removed from the liquid or gas after flushing out the contaminants that do not dissolve in the supercritical fluid. As a result, contaminants can be collected and reused. In particular, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 7, the supercritical fluid and the liquid or gas supplied to the cleaning tank are subjected to a supercritical treatment on the way or to a liquid carbon dioxide as it is. The liquid or gas supplied from the storage tank to the cleaning tank, and the contaminants are separated and removed and cleaned, are returned to the liquid carbon dioxide storage tank after cooling, so that they can be circulated and used. Is safe and running costs can be reduced. Furthermore, in the cleaning method using a supercritical fluid as a cleaning fluid according to claim 8, since supercritical carbon dioxide is employed as the supercritical fluid, it is economical and secures safety for workers and the environment. Is preferred.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a cleaning apparatus to which a cleaning method using a supercritical fluid (supercritical carbon dioxide) as a cleaning fluid according to Embodiment 1 of the present invention is applied.

FIG. 2 is a main part configuration diagram illustrating a part of a cleaning process using a supercritical fluid (supercritical carbon dioxide) as a cleaning fluid using the cleaning apparatus according to the first embodiment of the present invention;

FIG. 3 is a main part configuration diagram showing another part of a cleaning process using a supercritical fluid (supercritical carbon dioxide) as a cleaning fluid using the cleaning apparatus according to the first embodiment of the present invention;

FIG. 4 is an overall configuration diagram of a cleaning apparatus to which a cleaning method using a supercritical fluid (supercritical carbon dioxide) as a cleaning fluid according to Embodiment 2 of the present invention is applied.

FIG. 5 is an overall configuration diagram of a cleaning apparatus to which a cleaning method using a supercritical fluid (supercritical carbon dioxide) as a cleaning fluid according to Embodiment 3 of the present invention is applied.

[Explanation of symbols]

 Reference Signs List 10 Liquid carbon dioxide storage tank 20 First cleaning tank 30 Second cleaning tank 40 Third cleaning tank 50 Separation tank 60 Separation tank 70 Cleaning tank 80 Separation tank

Claims (8)

[Claims] 1. A first step of extracting contaminants dissolved in a supercritical fluid such as fats, oils, water, and organic solvents attached to an object to be cleaned by a supercritical fluid, and a step of extracting the supercritical fluid discharged in the first step. A second step of washing out contaminants remaining on the surface of the object to be cleaned, which are not dissolved in a supercritical fluid, such as powders and particles, by a liquid or a gas obtained by decompression and / or cooling. A cleaning method using a supercritical fluid as a cleaning fluid. 2. A first object to be cleaned in which a contaminant soluble in a supercritical fluid such as oil, fat, water, and an organic solvent and a contaminant insoluble in a supercritical fluid such as a granular material and an exfoliated substance are adhered. A first step of supplying a supercritical fluid to a first cleaning tank containing the object and extracting contaminants dissolved in the supercritical fluid from the surface of the first object to be cleaned; The supercritical fluid discharged from the washing tank is decompressed and / or cooled to obtain a liquid or gas.
And supplying the liquid or gas obtained in the second step to a second cleaning tank containing a second object to be cleaned in which contaminants previously dissolved in the supercritical fluid have been extracted and removed. A third step of washing out contaminants that do not dissolve in the supercritical fluid remaining on the surface of the object to be cleaned, and after the third step, removing the liquid or gas from the second cleaning tank to thereby clean the second object to be cleaned. A fourth step of taking out an object, and after the fourth step, a third object to be cleaned to which a contaminant dissolved in the supercritical fluid and a contaminant insoluble in the supercritical fluid are attached is placed in the second cleaning tank. A supercritical fluid characterized by washing a predetermined number of objects to be washed by sequentially repeating the operations of these steps in the first and second washing tanks. A cleaning method using a cleaning fluid. 3. A washing tank having three or more washing tanks in advance,
Among them, the first cleaning tank has a first contaminant which dissolves in a supercritical fluid such as oil, water, and organic solvent, and a first contaminant which does not dissolve in a supercritical fluid such as a granular material and a separated substance. Is stored in the second cleaning tank, and a second cleaning object from which contaminants dissolved in the supercritical fluid are extracted and removed is stored in the second cleaning tank. A third cleaning object or later to which a contaminant that dissolves in the fluid and a contaminant that does not dissolve in the supercritical fluid adhere are prepared and stored, and the supercritical fluid is supplied to the first cleaning tank. A first step of extracting contaminants dissolved in the supercritical fluid from the surface of the object to be cleaned, and after the first step, depressurizing and / or cooling the supercritical fluid discharged from the first cleaning tank to obtain a liquid Or the second to get gas
A third step of supplying the liquid or gas obtained in the second step to the second cleaning tank to wash away contaminants insoluble in the supercritical fluid remaining on the surface of the second object to be cleaned; After the third step, a fourth step of removing the liquid or gas from the second cleaning tank and taking out the second cleaned object to be cleaned, and after the fourth step, a contaminant dissolved in the supercritical fluid, A fifth step in which a new object to be cleaned to which a contaminant that does not dissolve in the critical fluid adheres is stored in the second cleaning tank and is on standby; A sixth step of supplying a fluid and extracting and removing contaminants dissolved in the supercritical fluid adhering to the stored third object to be cleaned; and after the sixth step, the contaminants are discharged from the third cleaning tank. Decompressing and / or cooling the supercritical fluid to obtain a liquid or gas.
An eighth step of supplying the liquid or gas obtained in the seventh step to the first cleaning tank to wash away contaminants insoluble in the supercritical fluid remaining in the first object to be cleaned; After the eighth step, a ninth step of removing the liquid or gas from the first cleaning tank and taking out the washed first object to be cleaned, a contaminant dissolved in the supercritical fluid after the ninth step, A tenth step of storing a new object to be cleaned to which contaminants insoluble in the fluid are attached in the first cleaning tank and waiting, and performing the operations of the above steps in three or more cleaning tanks. A cleaning method using a supercritical fluid as a cleaning fluid, wherein a predetermined number of objects to be cleaned are continuously cleaned by repeating the cleaning process sequentially. 4. The supercritical system according to claim 2, further comprising a step of separating a contaminant soluble in the supercritical fluid from a liquid or a gas by a separation tank between the second step and the third step. A cleaning method using a fluid as a cleaning fluid. 5. A cleaning object containing contaminants dissolved in a supercritical fluid such as fats, oils, water, and organic solvents and contaminants insoluble in a supercritical fluid such as powders and exfoliated substances are stored. A first step of supplying a supercritical fluid to the one cleaning tank and extracting contaminants dissolved in the supercritical fluid from the surface of the object to be cleaned; and supplying a liquid or gas to the cleaning tank after the first step. A second step of washing out contaminants insoluble in the supercritical fluid remaining on the surface of the object to be cleaned; and after the second step, removing the liquid or gas from the cleaning tank, taking out the cleaned object to be cleaned, A third step of newly storing a contaminated substance dissolved in the supercritical fluid and a contaminant insoluble in the supercritical fluid in the cleaning tank; and a third step of storing the supercritical fluid in the cleaning tank after the third step. Supply the supercritical fluid from the surface of the next cleaning object in the cleaning tank And a fourth step of extracting contaminants that dissolve in the supercritical fluid from each of the objects to be cleaned in one cleaning tank by sequentially repeating the above steps. Cleaning method using a supercritical fluid as a cleaning fluid, wherein the cleaning is performed intermittently. 6. The supercritical fluid according to any one of claims 2 to 5, wherein the contaminants are separated and removed from a liquid or a gas after washing out the contaminants that do not dissolve in the supercritical fluid. Cleaning method. 7. A liquid fluid storage tank for supplying a supercritical fluid and a liquid or a gas to a cleaning tank, and a liquid or a gas that has been cleaned by separating and removing contaminants is cooled, and is then supplied to the liquid fluid storage tank. The cleaning method according to claim 6, wherein the supercritical fluid is returned and circulated for use. 8. The cleaning method according to claim 1, wherein supercritical carbon dioxide is used as the supercritical fluid.