MANUFACTURING METHOD FOR PERACETIC ACID SOLUTION USING COLUMN-TYPE REACTOR AND COIL- TUBE-TYPE AGING REACTOR

Technical Field

[1] The present invention relates to a method for preparing a disinfectant cleansing solution containing peracetic acid, which is superior in sterilizing, cleansing or disinfecting medical devices and is highly stable. The disinfectant cleansing solution may be used to cleanse, disinfect or sterilize dialysis equipments, specialized endoscope equipments, surgical instruments, anesthetic equipments, obstetric and gynecologic instruments, dental instruments, and other general medical devices. Background Art

[2] The development of electronic devices has led to the development in the medical field, providing more convenient and effective medical care for patients. The conventional medical equipments having simple structure can be easily sterilized and disinfected without having to consider the environment, heat or toxicity issue of the related disinfectant. However, recently, as the medical equipments adopt more complicated and various materials, the right use and thorough post-management of the medical equipments are critical in improving the quality of medical care. Accordingly, hospitals are hiring experts and having them managing the medical equipments. The importance of cleansing, sterilization and disinfection of machines and devices is appreciated a lot recently. In addition to the fact that they determine the quality of medical care, use of stable and superior cleansing disinfectants is essential in that the use of improperly disinfected or cleansed medical instruments may result in a fatal secondary infection.

[3] Examples of disinfectants for medical devices include sodium hypochlorite, formaldehyde, glutaraldehyde and acetic acid. However, glutaraldehyde and formaldehyde have a pungent odor and are irritant to skin and eyes. And, sodium hypochlorite and acetic acid may result in corrosion of the medical devices. For these reasons, a neglected maintenance of medical devices often results in a fatal consequence during medical care, as well as secondary infections.

[4] Because peracetic acid solution has few corrosion problems and provides good disinfecting ability, it is used in cleansing and disinfecting of various medical equipments as an alternative to the aforesaid disinfectants. Since it exhibits broad activities on microorganisms, it is also widely used for disinfecting water for cooling towers, water for food processing, water for pulp- and papermaking, etc., in addition to sterilization, dis- infection and cleansing of medical equipments.

[5] Peracetic acid-based disinfectant cleansing solutions for medical devices containing peracetic acid, acetic acid and hydrogen peroxide are disclosed in WO 88/08667, WO 93/07909, WO 94/14321, EP 193,426, EP 596,493, USP 6,168,808, KR 2000-49667, or the like. Those peracetic acid-based disinfectant cleansing solutions further include a stabilizer such as phosphoric acid, phosphonic acid, etc., a non-ionic surfactant such as sorbitan monopalmitate, poly oxy ethylene cetyl ether, etc., an amine oxide, or the like, in addition to the main components - peracetic acid, acetic acid, hydrogen peroxide and purified water. With quick sterilizing ability, the peracetic acid-based disinfectant cleansing solutions are suitable for general cleansing or automatic cleansing, but they have some problems in practical applications. For example, a disinfectant cleansing solution with a low peracetic acid content (in general, less than 1 wt%) may not effectively cope with the contamination by the patient's mucus. Further, general- use disinfectant cleansing solutions containing peracetic acid are usually used for endoscope equipments, forceps, surgical instruments, or the like. In case of medical devices made, for example, with copper- or zinc-containing compounds the peracetic acid-based disinfectant cleansing solutions may result in a corrosion problem.

[6] Recently, a method for preparing a disinfectant composition comprising a first aqueous solution comprising peracetic acid and a second aqueous solution comprising a corrosion inhibitor and a peracetic acid stabilizer has been developed. According to USP 5,624,634, since it has remarkably improved corrosion inhibiting ability, the two- component peracetic acid composition may be used to cleanse and disinfect medical equipments wherein corrosion- susceptible metals are used.

[7] Also, methods for preparing high-concentration peracetic acid solutions are reported.

According to USP 3,264,345, UK 789,016, UK 1,014,361, EP 296,328, EP 789,016 and EP 1,004,576, high-concentration peracetic acid solutions are prepared by distilling peracetic acid at relatively low concentration obtained from the reaction of hydrogen peroxide and acetic acid in the presence of an acid catalyst.

[8] An example of the most frequently employed method for the preparation of peracetic acid aqueous solutions is to mix acetic acid, hydrogen peroxide and a stabilizer at various proportions in the presence of an inorganic acid catalyst. This method results in various products adequate for various purposes, with significantly improved stability and functionality. However, the method is problematic in that the use of the inorganic acid such as phosphoric acid or sulfuric acid may cause severe corrosion of metallic materials. In consequence, the characteristic advantages of peracetic acid such as environment-friendliness and low toxicity are deteriorated and the production cost increases remarkably. In particular, the method of preparing high-concentration peracetic acid solutions by distilling peracetic acid produced in the presence of the inorganic acid catalyst is disadvantageous in the aspects of environment and production cost due to excessive use of the inorganic acid catalyst.

[9] For these reasons, a method for preparing a peracetic acid solution without using an inorganic acid was developed. UK 776,758 discloses a method for preparing a peracetic acid solution using a cation-exchange resin as catalyst instead of an inorganic acid such as sulfuric acid or phosphoric acid. And, US 4,647,678 discloses a method for preparing a peracetic acid solution using a strongly acidic cation-exchange resin as catalyst for use as disinfectant and bleach.

[10] According to the aforesaid methods for preparing peracetic acid solutions using ion- exchange resins, (1) an ion-exchange resin is added to a mixture solution of acetic acid and hydrogen peroxide, and then stirred for several hours, or (2) a reaction mixture is continuously passed through a tubular reactor filled with an ion-exchange resin by means of pumping and pressure control. However, these methods are problematic in that the mixing proportion of acetic acid and hydrogen peroxide is not precisely controlled in real time so as to be adequate for various purposes, and in that a long time of aging reaction is required. Therefore, it was difficult to obtain peracetic acid solutions with stabilized peracetic acid concentration in real time for various purposes.

[11] In addition, the existing methods for preparing peracetic acid solutions are problematic in that a swelling inhibitor or a stabilizer is used to maintain the catalytic property of the ion-exchange resin and thereby to attain stabilized peracetic acid concentration. The use of such compounds results in deterioration of the properties of the peracetic acid solutions, as well as environmental problems. Disclosure of Invention

Technical Problem

[12] When producing peracetic acid by reacting acetic acid and hydrogen peroxide, inorganic acid such as sulfuric acid or phosphoric acid is typically used as catalyst. Accordingly, the peracetic acid solution used for the cleansing of medical devices contains a small amount of inorganic acid, which has the problems of corrosion and irritation to the human body. Technical Solution

[13] One of the methods to solve the problems caused by the use of inorganic acid as catalyst is to use a cation-exchange resin instead of the inorganic acid. The methods for producing peracetic acid using an ion-exchange resin as catalyst are disclosed in several literatures, but they are not applied widely. The reason is that the concentration of acetic acid, hydrogen peroxide and peracetic acid in the produced peracetic acid solution is unstable and that the productivity is not high as compared to the method using the inorganic acid. Specifically, according to the method for preparing peracetic acid using an ion-exchange resin as catalyst disclosed in the literature, a very long aging time is necessary to stabilize the peracetic acid concentration and it is difficult to maintain the mixing proportion of acetic acid and hydrogen peroxide constant in real time. Besides, exposure of the reactants and product before and after the production of peracetic acid to outside, as well as purification of the reactants, also acts as a factor making the final peracetic acid product unstable.

[14] To overcome the problems of the existing techniques, the inventors of the present invention developed an apparatus for the preparation of a peracetic acid solution capable of preparing a peracetic acid solution continuously by means of flow injection in an integrated space cut off from the air, and a method for preparing a peracetic acid solution using the same. According to the preparation method, the reactants acetic acid and hydrogen peroxide are continuously purified at a constant flow rate and mixed with each other at an accurate concentration ratio. Then, they react while passing through a tubular reactor filled with a strongly acidic ion-exchange resin at 20-50 ⁰ C. After passing through a first coil tube type aging reactor, the product is mixed with purified water. Then, after passing through a second coil tube type aging reactor, it may be used in real time or stored for later use.

[15] More specifically, the method for preparing a peracetic acid solution according to the present invention includes: a preliminary stage of purifying the reactants acetic acid and hydrogen peroxide using a first cation-exchange resin as an adsorbent; a mixing stage of mixing the reactants by means of flow injection while controlling the relative and absolute injection amount to continuously prepare a reactant solution having a acetic acid/hydrogen peroxide mixing proportion adequate for an intended use; a main reaction stage of injecting the reactant solution to a column type reactor in which a second cation-exchange resin is filled as a reaction catalyst to produce peracetic acid; a first aging stage of aging the reaction product that has passed through the main reaction stage in a first coil tube type aging reactor; a dilution stage of mixing the reaction product that has passed through the first aging stage with purified water to prepare diluted peracetic acid solution; and a second aging stage of aging the diluted peracetic acid solution again in a second coil tube type aging reactor. The respective stages may be performed consistently and interconnectedly in an integrated space cut off from the air. The method for preparing a peracetic acid solution according to the present invention is characterized by an integrated preparation process of a peracetic acid solution. Differently from the existing production method wherein disinfectant cleansing solutions are produced in batches according to uses, peracetic acid solutions with a stabilized equilibrium concentration of peracetic acid can be prepared easily and conveniently, while changing the mixing proportion of acetic acid and hydrogen peroxide in real time depending on various required uses. Advantageous Effects

[16] Differently from the existing batch type method, the peracetic acid disinfectant prepared according to the method of the present invention is advantageous in that the control of peracetic acid concentration and the change of the mixing proportion of acetic acid and hydrogen peroxide may be carried out continuously. Specifically, for example, the relative amount of acetic acid in the reaction mixture of acetic acid and hydrogen peroxide is increased first to remove hardly soluble carbonates (scales). Immediately thereafter, the relative amount of hydrogen peroxide and peracetic acid is increased to make it easier to remove, sterilize or disinfect biofilms. As a result, descaling and sterilization of medical devices can be performed effectively through cleansing and disinfection using a relatively small amount of disinfectant cleansing solution.

[17] The cleansing disinfectant prepared in accordance with the present invention may comprise 1.0-35 wt% of acetic acid, 1.0-35 wt% of hydrogen peroxide, 0.1-20 wt% of peracetic acid and 10-97.9 wt% of reverse-osmosed water. The method for preparing a peracetic acid solution according to the present invention is particularly advantageous in that a stable cleansing disinfectant with an adequate composition for various uses can be prepared continuously and that a peracetic acid solution capable of maintaining a sufficient stability can be prepared without adding a swelling inhibitor or a stabilizer to the reactants since the reactants are purified in advance. Brief Description of Drawings

[18] The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawing in which:

[19] Fig. 1 schematically illustrates an integrated manufacturing system for realizing the continuous preparation method of a peracetic acid solution according to the present invention. Best Mode for Carrying out the Invention

[20] Exemplary embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth therein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments.

[21] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms a, an, etc. does not denote a limitation of quantity, but rather denotes the presence of at least one of the referenced item. The use of the terms "first", "second", and the like does not imply any particular order, but they are included to identify individual elements. Moreover, the use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. It will be further understood that the terms "comprises" and/or "comprising", or "includes" and/ or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

[22] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[23] Fig. 1 schematically illustrates an integrated manufacturing system for realizing the continuous preparation method of a peracetic acid solution according to the present invention.

[24] As seen in Fig. 1, all the reaction apparatuses excluding storage tanks 1, 2 for acetic acid and hydrogen peroxide may be disposed inside an isolated space cut off from the air (enclosed by a square box in the figure). The temperature of the isolated space and all the apparatuses disposed therein may be controlled within 20 and 5O ⁰ C.

[25] The method for preparing a peracetic acid solution according to the present invention comprises a preliminary stage, a mixing stage, a main reaction stage, a first aging stage, a dilution stage and a second aging stage.

[26] In the preliminary stage, acetic acid and hydrogen peroxide supplied from first and second storage tanks 1, 2 are passed through column type purifiers 3, 6 to remove metallic impurities including divalent and trivalent cations and to preheat the reactants for reaction. The flow rate of acetic acid and hydrogen peroxide may be effectively controlled using flow meters 4, 5 in the range from 0.1 to 50 mL/min.

[27] In the mixing stage, the acetic acid and hydrogen peroxide that have passed through the flow meters 4, 5 are mixed at a molar ratio determined by the controlled flow rate to prepare a reactant solution.

[28] In the main reaction stage, the reactant solution is passed through a column type reactor 7 filled with a cation-exchange resin to prepare a reaction product containing peracetic acid. The cation-exchange resin may be an ion-exchange resin having sulfonate groups.

[29] In the first aging stage, the reaction product is aged as it passes through a first coil tube type aging reactor 8 maintained at a constant temperature until the peracetic acid reaction reaches an equilibrium state. As a result, the peracetic acid concentration of the reaction product may be maintained constant.

[30] In the mixing stage, the reaction product is mixed with purified water 10 the supply of which is controlled by a purified water flow meter 9, thereby preparing a diluted peracetic acid stock solution. The purified water 10 may be nearly pure water. For example, reverse-osmosed water or deionized distilled water may be used.

[31] In the second aging stage, the diluted peracetic acid stock solution is subjected again to an equilibrium reaction as it passed through a second coil tube type aging reactor 11. As a result, a final peracetic acid solution the peracetic acid concentration of which is maintained stably at a desired level is obtained. The final peracetic acid solution may be used as a cleansing disinfectant immediately after the preparation. Alternatively, it may be stored in a storage container equipped outside the integrated reaction apparatus for later use.

[32] The composition of the components of the peracetic acid solution for cleansing and disinfection prepared according to the preparation method of the present invention comprising the aforesaid stages may be adjusted for different uses to be provided for cleansing of various medical devices. For example, when removing scales whose main component is calcium carbonate, it is preferable to treat with a peracetic acid solution containing less than 0.1 mol of hydrogen peroxide per 10 mol of acetic acid at first, and then gradually use a peracetic acid solution with a higher hydrogen peroxide content. For another example, when disinfection or sterilization is the main purpose, it will be effective to use a peracetic acid solution having a molar ratio of acetic acid to hydrogen peroxide of 2:1. For another example, when cleansing medical devices to which biofilms or excess organic substances are adhered, it will be effective to use a peracetic acid solution having a molar ratio of acetic acid to hydrogen peroxide of about 1:2 to 1:11. For practical use, peracetic acid solution it may be the most effective not to fix the composition of the components but to perform cleansing or disinfection while gradually changing the composition. Mode for the Invention

[33] The examples and experiments will now be described. The following examples and experiments are for illustrative purposes only and not intended to limit the scope of this disclosure. [34] Example 1 : Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 11 : 1

[35] The temperature of an isolated space in which an integrated reaction system for preparation of peracetic acid is located is maintained at 35 ⁰ C. Acetic acid and hydrogen peroxide are respectively passed through a tube type purifier filled with a sulfonate ion-exchange resin. Using flow meters for acetic acid and hydrogen peroxide, acetic acid is passed at a flow rate of 9.5 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 1.3 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 11:1. The resultant reactant solution is injected into a column type reactor filled with a sulfonate ion-exchange resin at a rate of 10 mL/min to produce peracetic acid by means of a continuous reaction. A reaction product flowing out of the column type reactor is passed through a first coil tube type aging reactor, so that the production of peracetic acid reaches nearly an equilibrium state. The reaction product flowing out of the first coil tube type aging reactor is mixed with reverse-osmosed water supplied from a purified water flow meter at a rate of 89.2 mL/ min to prepare a diluted peracetic acid solution. The diluted peracetic acid solution is passed through a second coil tube type aging reactor, so that the production of peracetic acid reaches nearly an equilibrium state again.

[36] Example 2: Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 5: 1

[37] The procedure of Example 1 is repeated, except that acetic acid is passed at a flow rate of 9 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 2.9 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 5 : 1 , and that reverse-osmosed water is mixed at a rate of 88.1 mL/min in the dilution stage.

[38] Example 3: Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 2: 1

[39] The procedure of Example 1 is repeated, except that acetic acid is passed at a flow rate of 7.8 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 6.3 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 2: 1 , and that reverse-osmosed water is mixed at a rate of 86.1 mL/min in the dilution stage.

[40] Example 4: Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 1:2

[41] The procedure of Example 1 is repeated, except that acetic acid is passed at a flow rate of 4.7 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 15 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 1:2, and that reverse-osmosed water is mixed at a rate of 80.3 mL/min in the dilution stage.

[42] Example 5: Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 1:5 [43] The procedure of Example 1 is repeated, except that acetic acid is passed at a flow rate of 2.6 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 21 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 1:5, and that reverse-osmosed water is mixed at a rate of 76.4 mL/min in the dilution stage.

[44] Example 6: Preparation of peracetic acid solution with molar ratio of acetic acid to hydrogen peroxide of 1 : 11 [45] The procedure of Example 1 is repeated, except that acetic acid is passed at a flow rate of 1.3 mL/min and hydrogen peroxide (35% aqueous solution) is passed at a flow rate of 24.9 mL/min, so that the mixing molar ratio of acetic acid to hydrogen peroxide is 1:11, and that reverse-osmosed water is mixed at a rate of 73.8 mL/min in the dilution stage.

[46] Table 1 summarizes the preparation of peracetic acid solutions with different molar proportions of acetic acid and hydrogen peroxide according to Examples 1 to 6. [47] Table 1 [Table 1] [Table ]

[48] As seen in Table 1, by controlling the flow rate of acetic acid and hydrogen peroxide injected to the integrated reaction system, the equilibrium concentration of hydrogen peroxide and peracetic acid in the final peracetic acid solution may be changed variously. [49] Example 7: Change of equilibrium concentration depending on addition of swelling inhibitor [50] In order to measure the effect of the swelling of the sulfonate ion-exchange resin on the equilibrium of the peracetic acid production reaction, etidronic acid is added as a swelling inhibitor at 0, 0.5 and 1 wt%, and the result is monitored. The experiment is carried out with the molar ratio of acetic acid to hydrogen peroxide fixed at 2: 1 (as in Example 3). The initial total volume of acetic acid, hydrogen peroxide, the swelling inhibitor and water is set as 50 mL.

[51] Table 2 summarizes the measurement of the equilibrium concentration depending on the addition of the swelling inhibitor. [52] Table 2 [Table 2] [Table ]

[53] As seen in Table 2, the peracetic acid concentration of the final peracetic acid solution in the equilibrium state does not show significant change depending on the addition amount of the swelling inhibitor. In addition, no significant instability of peracetic acid production is observed when the swelling inhibitor is not added.

[54] Example 8: Peracetic acid production depending on aging of reaction product following main reaction stage [55] Reaction products are obtained as in Examples 1 to 6 through the preliminary stage, mixing stage and main reaction stage, but without the aging stage, with the weight proportion of the reactants acetic acid and hydrogen peroxide (35% aqueous solution) at 20: 17. The reaction products are aged using either a stirring type aging reactor or a coil tube type aging reactor. The concentration of hydrogen peroxide and peracetic acid in the resultant final peracetic acid solutions are determined. Aging using the stirring type aging reactor is carried out while stirring in a sealed reactor at 45 ⁰ C using a magnetic bar. Aging using the coil tube type aging reactor is carried out while circulating the reaction product in a sealed coil tube type aging reactor (coil with diameter 1 mm or less) at 45 ⁰ C.

[56] Table 3 summarizes stability of the peracetic acid solutions obtained by aging the stirring type aging reactor and the coil tube type aging reactor. [57] Table 3 [Table 3] [Table ]

[58] H ₂ O ₂ : hydrogen peroxide; PAA: peracetic acid [59] As seen in Table 3, the peracetic acid concentration increases significantly faster when the coil tube type aging reactor is used as compared to when the stirring type aging reactor. Specifically, for example, after 1 hour of aging, the coil tube type aging reactor produces 13.7 wt% of peracetic acid, whereas the stirring type aging reactor produces 10.5 wt% of peracetic acid.

[60] This suggests that the rate of decrease of the hydrogen peroxide concentration in the aged peracetic acid solution due to the production of peracetic acid or simple decomposition and/or evaporation may be different depending on the aging method. This may be quantitatively analyzed by the following equations considering the molecular weights of hydrogen peroxide and peracetic acid.

[61] (1) Decrease of hydrogen peroxide due to production of peracetic acid (wt%) = increase of peracetic acid (wt%) x 34 ÷ 76 [62] (2) Decrease of hydrogen peroxide due to decomposition and/or evaporation (wt%) = experimentally determined decrease of hydrogen peroxide (wt%) - decrease of hydrogen peroxide due to production of peracetic acid (wt%) [63] When the stirring type aging reactor is used, the experimentally determined decrease of hydrogen peroxide is 7.58 wt% and the decrease of hydrogen peroxide due to production of peracetic acid is 6.03 wt%. Therefore, it can be seen that the decrease of hydrogen peroxide due to decomposition and/or evaporation is 1.55 wt%. In contrast, when the coil tube type aging reactor is used, the experimentally determined decrease is 7.48 wt% and the decrease due to production of peracetic acid is 6.89 wt%. Thus, the decrease of hydrogen peroxide due to decomposition and/or evaporation is only 0.59 wt%.

[64] When the stirring type aging reactor is used, the decomposition rate of hydrogen peroxide relatively increases even when the stirring is performed in a sealed state. As a result, generation of oxygen foams increases and, consequently, the hydrogen peroxide in the solution decreases. This results in a decreased peracetic acid concentration in the peracetic acid solution in the equilibrium state. In contrast, when the coil tube type aging reactor is used, generation of the foams may be suppressed as much as possible since the reaction product flows through a path provided by the thin coil tube having a uniform temperature distribution. The experimental results reveal the advantage of the coil tube type aging reactor as an apparatus capable of minimizing hydrogen peroxide loss during aging due to decomposition and/or evaporation. Likewise, by diluting the reaction product that has passed through the first aging stage by means of the first coil tube type aging reactor with purified water to considering the intended use, and then performing the second aging stage using the second coil tube type aging reactor, peracetic acid concentration in the equilibrium state may be maximized while minimizing loss of hydrogen peroxide.

[65] Example 9: Descaling ability of peracetic acid solution depending on composition

[66] In order to evaluate the ability of removing scales from an artificial kidney that has been used for a long time, samples taken from the artificial kidney machine and the tube are analyzed by X-ray diffractometry. The main components of the scales are calcium carbonate and calcium sulfate. In order to measure the descaling ability of the peracetic acid solutions prepared according to Examples 1 to 6, 0.1 g of artificially prepared calcium carbonate powder is added to 10 mL of each peracetic acid solution of Examples 1 to 6, and the time required for the calcium carbonate powder to be completely dissolved is measured.

[67] Table 4 summarizes the descaling ability of the peracetic acid solutions.

[68] Table 4 [Table 4] [Table ]

[69] As seen in Table 4, the descaling ability of the peracetic acid solutions prepared by increasing the molar ratio of the reactants acetic acid to hydrogen peroxide from 11:1 to 1:11 increases in proportion to the molar ratio.

[70] Example 10: Biofilm removal ability of peracetic acid solution depending on composition

[71] In order to evaluate the biofilm removal ability of peracetic acid solutions with different compositions, a stainless steel plate is cut to a size of 1 cm x 1 cm and sterilized, and an adherent microcolony is prepared thereon. The microcolony is observed after cleansing and disinfecting with the peracetic acid solutions prepared according to Examples 1 to 6. As a result, it is revealed that the peracetic acid solution prepared according to Example 6 exhibits the most superior biofilm removal ability.

[72] Example 11 : Sterilizing power of peracetic acid solution depending on composition

[73] In order to measure the sterilizing power of the peracetic acid solutions with different compositions, the sterilizing power of the peracetic acid solutions prepared according to Examples 1 to 6 against bacteria and fungi is tested. Specifically, 0.1 mL of bacterial solution incubated for 24 hours in nutrient broth and tryptic soy broth is added to 10 mL of the peracetic acid solutions prepared according to Examples 1 to 6, each diluted 10 times with purified water. After mixing by agitation for 30 seconds, followed by allowing to stand for 1 minute, 1 mL of the reaction solution is taken and immediately added a test tube containing 9 mL of a neutralizer (4.26% sodium phosphate dibasic, 3% Tween, 0.5% sodium thiosulfate pentahydrate, 0.3% L-α-lecithin and 0.1% L- histidine). Then, 1 mL is taken from the test tube and diluted 10 times with peptone water. For comparative experiment depending on concentration, each 0.1 mL of the solution from the test tube and the 10x diluted solution thereof are applied on a previously prepared plate medium. The samples are incubated in a 30-35 ⁰ C incubator for 3 days. After counting the number of colonies in all samples, the number is divided by the number of plates to calculate the average number of colonies per plate.

[74] Table 5 summarizes the sterilizing power of the peracetic acid solutions with different compositions.

[75] Table 5 [Table 5] [Table ]

Industrial Applicability

[76] According to the present invention, a peracetic acid solution appropriate for the purpose of cleansing or sterilization may be prepared safely and quickly. The preparation method enables a continuous preparation of peracetic acid solutions with desired mixing proportion of hydrogen peroxide and acetic acid and peracetic acid concentration, appropriate for various uses, while changing them in real time. Accordingly, an effective cleansing and disinfection is possible by using a disinfectant cleansing solution the composition of which is adjusted in real time depending on the desired environmental factors of medical devices or equipments or depending on the required cleansing or sterilization requirements. In addition, the peracetic acid aqueous solution prepared in accordance with the present invention is an environment-friendly disinfectant in the true sense of the word, since it exhibits a desired cleansing and disinfection effect without using a commonly used catalyst such as phosphoric acid, a stabilizer or a swelling inhibitor, which are added to improve stability of the peracetic acid concentration, or other chemical substances.

[77] While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of this disclosure as defined by the appended claims.

[78] In addition, many modifications can be made to adapt a particular situation or material to the teachings of this disclosure without departing from the essential scope thereof. Therefore, it is intended that this disclosure not be limited to the particular exemplary embodiments disclosed as the best mode contemplated for carrying out this disclosure, but that this disclosure will include all embodiments falling within the scope of the appended claims.