JPS6210683B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for producing and dispensing high quality aqueous solutions, such as, for example, ammonia, hydrogen chloride, hydrogen fluoride, etc. BACKGROUND OF THE INVENTION In recent years, in fields such as the electronic industry and analysis, higher quality products have been desired for aqueous solutions such as aqueous ammonia, hydrochloric acid, and hydrofluoric acid. In such an aqueous solution, impurities that should be particularly strictly controlled are metals and fine particles. Conventionally, these high-quality aqueous solutions have been obtained by distilling the raw material aqueous solution and absorbing the generated steam into purified water to obtain an aqueous solution of a predetermined concentration.Then, this solution is passed through another precision sieve, and a predetermined amount is poured into reagent bottles. It was supplied in small portions. However, in conventional methods, even if a distillation operation is performed, trace amounts of metals and fine particles in the raw material aqueous solution cannot be avoided due to droplet entrainment. Furthermore, during the process of filling and removing reagent bottles from the reagent bottles, there is a possibility that fine particles and metals may be mixed in from the air, and during storage in the reagent bottles, trace amounts of impurities may be eluted from the bottles. . Furthermore, the operations for producing and supplying the aqueous solution as described above require the wearing of clean gloves and, preferably, must be performed with great care, such as in a clean room. In addition, reagent bottles are usually collected and reused in order to reduce the elution of impurities as much as possible, and these operations require a great deal of labor and complexity. However, even with these points in mind, the possibility of impurity contamination as described above essentially exists, so the impurity concentration in current high-quality aqueous solutions is lower than that in, for example, hydrochloric acid.
Taking Fe as an example, it remains at around 200 ppb. OBJECTS OF THE INVENTION The primary object of the present invention is to provide a method for producing and delivering high quality aqueous solutions with significantly reduced impurity concentrations by eliminating the possibility of contamination with these impurities. Furthermore, it is an object of the present invention to solve the above-mentioned difficulties when handling these aqueous solutions. Structure of the Invention According to the present invention, the total amount of metals contained is
Fine particles with a particle size of 0.5ppm or less and 0.2μ or more
A method is provided for producing and supplying a high-quality aqueous solution with a concentration of 200 particles/ml or less, which method involves vaporizing a liquefied gas with a purity of 99.5% or higher at the point of use to substantially eliminate impurities. This vapor is absorbed into pure water that has a specific resistance of 5 MΩ or more and contains 200 particles/ml or less with a particle size of 0.2 μ or more, and the aqueous solution obtained in this way is used as it is. It is characterized by being served. Detailed Description of the Structure of the Invention In other words, the method of the present invention vaporizes a solute component of a target aqueous solution, for example, a liquefied gas such as ammonia, hydrogen chloride, or hydrogen fluoride, to substantially eliminate impurities at the place of use. In this method, a high-quality aqueous solution with a predetermined concentration is obtained by obtaining vapor-free vapor and absorbing it into high-purity water. Here, steam that does not contain substantially impurities is defined as steam containing substantially no impurities.
Fine particles with a particle size of 200ppb or less and a particle size of 0.2μ or more
Steam containing 100 particles/ml or less. In addition, in the present invention, metals include Ag, Al, Ba, Ca, Cd,
Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni,
Refers to metals such as Pb, Sr, and Zn, and fine particles refer to particles with a particle size of approximately 10μ or less (JIS Z
8122). Highly pure water refers to pure water that has a specific resistance of 5 MΩ or more and contains 200 particles/ml or less with a particle size of 0.2 μ or more. Furthermore, an aqueous solution is a high-purity water containing 2 to 90% by weight, that is, a solute concentration of 10 to 98% by weight.
It refers to something. The target solute component is usually liquefied and held in a cylinder, and by vaporizing it, the vapor of the component can be easily obtained. Most of the impurities (metals, particulates) in the liquid in the cylinder remain in the liquid during vaporization, and hardly ever flow out into the vapor, but if droplets are accompanied, impurities can be expected to be mixed in. To prevent this, the speed of steam outflow should be controlled, and mist catchers and filters should be installed as necessary.
Furthermore, it is desirable to maintain the purity of the liquefied gas used at a higher level, preferably at 99.5% or higher. Also,
When carrying out the method of the present invention, the liquefied gas in the cylinder is preferably replaced with the liquefied gas in a new cylinder while about 5 to 10% of the gas still remains. If the residual amount of liquefied gas in the cylinder becomes too small, the purity of the liquefied gas may drop sharply, leading to a decrease in the purity of the resulting aqueous solution. The pure water used in the method of the present invention has a specific resistance of
It is so-called high-purity water that has a resistance of 5 MΩ or more and contains 200 particles/ml or less with a particle size of 0.2 μ or more, and the quality of such high-purity water is determined by the desired quality of the resulting aqueous solution. The specific resistance
It is more preferable to use so-called ultrapure water, which has a resistance of 16 MΩ or more and contains 50 particles/ml or less with a particle size of 0.2 μ or more. At the place of use, liquefied gas with a purity of 99.5% or higher is vaporized and the outflow rate is controlled to prevent entrainment of droplets during vaporization, and in some cases, filters are installed, and further The liquefied gas is 5
Steam containing virtually no impurities, that is, the total amount of metals, is produced by a method that leaves about 10% of the gas.
Fine particles with a particle size of 200ppb or less and a particle size of 0.2μ or more
Obtain steam of 100 pieces/ml or less. If the quality of this steam is high, the amount of impurities in the absorbed pure water is defined as the quality of high-pure water, and the impurities will not be leached from the container of a device that produces a high-quality aqueous solution with a predetermined concentration, such as the device shown in Figure 1. Even if the amount is small, in the present invention, a high quality aqueous solution is produced and supplied in which the total amount of metals contained is 0.5 ppm or less and the number of fine particles with a particle size of 0.2 μ or more is 200 particles/ml or less. . Methods for always obtaining an aqueous solution with a constant concentration include a method in which a predetermined amount of vapor of the target solute component is absorbed into a predetermined amount of high-purity water, or a method in which a predetermined concentration is obtained by simultaneously flowing a predetermined amount of high-purity water and steam. As an example, an apparatus that can be used in the former case is shown in FIG. In FIG. 1, vapor of a solute component is introduced from a liquefied gas cylinder 1, preferably through a filter 7, at a well-controlled predetermined flow rate into an absorber 3 filled with a predetermined amount of high-purity water. This high purity water is supplied from a high purity water supply line 2. The gas supply line is provided with a backflow prevention pressure equalization line 5, and the absorber 3 is provided with a heat of solution cooler 4 and a level gauge 6. By introducing gas for a predetermined period of time in this way, an aqueous solution of a predetermined concentration is prepared in the absorber, and this can be taken out from the pot 8 and used directly. These methods and devices can be automated, if desired, such that a predetermined amount of a liquid of a predetermined concentration can be obtained at any time, for example, by simply pressing a button. The material of the device includes materials that cannot be immersed in the target aqueous solution, such as Teflon or Teflon coating, tantalum or its lining, and can be selected depending on the type of target aqueous solution. According to the method of the present invention, it is possible to prepare the desired aqueous solution at the place where it will be used, and it is possible to eliminate the possibility of subsequent contamination with impurities caused by the use of reagent bottles. easily obtain aqueous solutions of much higher quality than
can be used. Examples Hereinafter, the present invention will be further explained with reference to Examples. Example 1 Liquefied ammonia with a purity of 99.999% or higher and a Fe content of 100 ppb is evaporated from a cylinder and absorbed into ultrapure water with a resistivity of 18 MΩ and 20 particles/ml of 0.2 μ or higher using a device as shown in Figure 1. Aqueous ammonia with a concentration of 29% was prepared. The gas flow rate from the cylinder was set at 3/min, and the gas was passed through 280 g of ultrapure water for about 1 hour. At that time, the entire absorber was cooled in an ice bath to maintain the temperature of the absorber below room temperature. Fe in the obtained ammonia water was 1 ppb,
The number of dust particles with a particle size of 0.2μ or more was 30 pieces/ml. For comparison, the analytical values of ammonia water obtained below and the analytical values of ammonia water currently used in the electronics industry are shown below.

[Table] Example 2 Liquefied hydrogen chloride with a purity of 99.999% or higher and a Fe content of 120 ppb was evaporated, and in the same manner as in Example 1, it was absorbed into ultrapure water of the same quality used in Example 1, and hydrochloric acid with a concentration of 35% was added. Prepared. The flow rate of gas from the cylinder is 0.9/
min, and passed through 650 g of ultrapure water for about 4 hours. The entire absorber was cooled in an ice bath to maintain the absorber temperature below ambient temperature. The obtained hydrochloric acid was of much higher quality than commercially available high-purity hydrochloric acid for use in the electronic industry, as described below.

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating an example of an apparatus useful for carrying out the method of the present invention. In the figure, 1 is a liquefied gas cylinder, 2 is an ultrapure water supply line, 3 is an absorber, 4 is a melt heat cooler, 5 is a backflow prevention pressure equalization line, 6 is a level gauge, 7 is a filter, and 8 is a pot. .

Claims (1)

[Claims] 1. A method for producing and supplying a high-quality aqueous solution containing 0.5 ppm or less of metals in total and 200 particles/ml with a particle size of 0.2 μ or more, which has a purity of 99.5 at the place of use. % or more of liquefied gas is evaporated to produce a vapor containing virtually no impurities, and this vapor is converted into pure water that has a specific resistance of 5 MΩ or more and contains 200 particles/ml or less with a particle size of 0.2 μ or more. A method characterized in that the aqueous solution thus obtained is used as it is.