Dissolving and removing composition and cleaning method using same

Abstract

To provide a dissolution removal composition capable of removing a scale in a shorter time more than ever, in cleaning of dissolution removal of a scale containing a metal oxide, and a cleaning method.SOLUTION: A dissolution removal composition includes: a main agent for dissolving and removing scales containing metal oxides attached to a base material; a base material reactant-generating component that reacts with the base material to generate a reactant; and a base material reactant dissolving component that dissolves and removes the reaction product. In cleaning using this dissolution removal composition, the scales can be peeled and removed from the base material side while dissolving and removing the scales from a surface side.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a dissolving and removing composition and a cleaning method using the same. [Background technology]

[0002] In heat transfer tubes of thermal power plants, etc., scale consisting mainly of iron oxide (Fe2O3, Fe3O4, etc.) adheres to the inner surface during operation. If the scale grows over a certain period of operation, it may cause damage due to an increase in the differential pressure of the fluid flowing inside the heat transfer tube, a decrease in heat transfer efficiency, and an excessive rise in the metal temperature of the heat transfer tube due to heat transfer obstruction.

[0003] To prevent such trouble from occurring, the amount of iron oxide and other scale buildup is monitored during maintenance inspections, and chemical cleaning is performed periodically to remove the scale.

[0004] Patent Document 1 discloses a method for dissolving and removing scale such as iron oxide adhering to a base material using a cleaning liquid whose main component is a scale-dissolving agent that contains metal oxides.

[0005] The dissolving and removing composition (cleaning liquid) described in Patent Document 1 can dissolve and remove both hematite (Fe2O3) and magnetite (Fe3O4) scales. Magnetite is a self-oxidizing scale, while hematite is a powder scale generated by oxygen treatment in the management of boiler feedwater. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-84304 A Summary of the Invention [Problem to be solved by the invention]

[0007] The concept of Patent Document 1 is to gradually dissolve and remove the scale starting from the surface side, so it takes time to dissolve and remove the scale. For example, cleaning at 40°C takes about 100 hours.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a dissolving and removal composition and a cleaning method that can remove scale containing metal oxides in a shorter time than conventional methods. [Means for solving the problem]

[0009] In order to solve the above problems, the dissolving and removing composition and the cleaning method using the same of the present disclosure employ the following measures.

[0010] The present disclosure relates to a method for manufacturing a ceramic material comprising: a base material that dissolves and removes scale containing metal oxides attached to a base material; a base material reactant generating component that reacts with the base material to generate a reactant; and a base material reactant dissolving component that dissolves and removes the reactant. the main agent is selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof, and is contained in an amount of 11% by weight to 25% by weight based on the total weight; the base reactant generating component is a thiadiazole-based compound having 1,3,4-thiadiazole as a planar skeleton, and is contained in an amount of 0.003% by weight or more based on the total weight; the base reactant dissolving component is selected from the group consisting of 3-mercaptopropionic acid, thiolactic acid, and salts thereof, which are C3 compounds having a thiol group and a carboxylic acid group, and is contained in an amount of 0.7% by weight to 5% by weight based on the total weight; and the pH is 5 to 7. A dissolving and removing composition is provided.

[0011] The present disclosure relates to a method for cleaning an object to be cleaned, the object to be cleaned including a base material having attached thereto scale containing a metal oxide, the method comprising: cleaning the object to be cleaned with a cleaning solution including a base material, a base material reactant generating component, and a base material reactant dissolving component; dissolving and removing at least a portion of the scale from the base material by the base material; reacting the base material reactant generating component with the base material to generate a reactant between the base material and the scale; and dissolving and removing the reactant by the base material reactant dissolving component. the base agent is selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof, and is contained in an amount of 11% by weight to 25% by weight based on the total weight of the cleaning solution; the base reactant generating component is a thiadiazole-based compound having 1,3,4-thiadiazole as a planar skeleton, and is contained in an amount of 0.003% by weight or more based on the total weight of the cleaning solution; the base reactant dissolving component is selected from the group consisting of 3-mercaptopropionic acid, thiolactic acid, and salts thereof, which are C3 compounds having a thiol group and a carboxylic acid group, and is contained in an amount of 0.7% by weight to 5% by weight based on the total weight of the cleaning solution; and the pH of the cleaning solution is 5 to 7. , a cleaning method is provided. Effect of the Invention

[0012] In the above disclosure, in addition to dissolving and removing at least a portion of the scale from the scale surface using the main agent, a base material reactant generating component is reacted with the base material surface exposed after the scale has been dissolved and removed to generate a base material reactant between the base material surface and the scale, and this base material reactant is dissolved by the base material reactant dissolving component, thereby creating a gap between the scale and the base material, and even if the scale is in the process of being dissolved, the fluid force of the cleaning liquid can be used to peel and remove the scale from the base material.

[0013] In the above disclosure, by removing scale using two removal mechanisms, cleaning can be completed in a shorter time than with the conventional method in which scale is dissolved and removed using a base agent. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an image showing how a base material reactant is generated. [Diagram 2] FIG. 2 is a more specific image diagram of a base material reactant. [Diagram 3] FIG. 1 is an image of the scale removal (peeling) mechanism. [Figure 4] This is a more specific image diagram of scale removal (peeling). [Diagram 5] FIG. 1 is an evaluation chart of scale removability. [Figure 6] FIG. [Figure 7] FIG. 1 is a diagram showing the effects of the presence or absence of a base agent, a base metal reactant-generating component, and a base metal reactant-dissolving component on scale removal properties and corrosion prevention properties. [Figure 8] FIG. 13 is a diagram showing the results when the content of the main agent was changed. [Figure 9] FIG. 4 is a diagram showing the relationship between the content of the base agent and the scale removal area ratio. [Figure 10] FIG. 13 shows the effect of varying the content of the matrix reactant product components. [Figure 11] FIG. 1 is a diagram showing the relationship between the content of base material reactant product components and the scale removal area ratio. [Figure 12] FIG. 13 is a diagram showing the results of varying the content of the base material reactant dissolved component. [Figure 13] FIG. 1 is a diagram showing the relationship between the content of base material reactant dissolved components and the scale removal area ratio. [Figure 14] FIG. 1 is a graph showing the relationship between the content of dissolved components of base material reactants and the amount of corrosion. [Figure 15] FIG. 4 is a diagram showing the relationship between the content of dissolved components in the base reactant and the remaining amount of sulfur. [Figure 16] FIG. 13 is a graph showing the results when the pH of the test liquid was changed. [Figure 17] FIG. 1 is a graph showing the relationship between the pH of a test liquid and the scale removal area ratio. [Figure 18] FIG. 13 is a diagram showing the results when the type of base agent is changed. [Figure 19] FIG. 13 shows the results of varying the type of matrix reactant product component. [Figure 20] FIG. 13 is a diagram showing the results of changing the type of base material reactant dissolution component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The object to be cleaned in this embodiment has a structure in which scale containing metal oxide is attached to a base material. The base material is made of metal. The base material contains iron. The base material may contain molybdenum. The metal oxide is iron oxide (Fe2O3 and Fe3O4) or the like.

[0016] [Dissolution and removal composition] The dissolving and removing composition according to this embodiment includes (A) a base material, (B) a component for generating a base material reactant, and (C) a component for dissolving the base material reactant.

[0017] The base agent (A) is a component capable of dissolving scale containing metal oxides, and may be selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof.

[0018] More specifically, the main agents are 1-hydroxyethane-1,1-diphosphonic acid, aminotris(methylenephosphonic acid), and ethylenediaminetetraacetic acid.

[0019] The base agent may be contained in an amount of 11% by weight or more and 25% by weight or less, and preferably 15% by weight or more and 20% by weight or less, based on the total weight of the dissolving and removing composition. If the base agent is too little or too much, the scale removing properties will be insufficient.

[0020] (B) The base metal reactant generating component is a component that reacts with the base metal to generate a reactant. The reactant has anticorrosive properties.

[0021] The matrix reactant product components are thiazole-based compounds having planar backbones.

[0022] The planar framework of the matrix reactant product component comprises a 1,3,4-thiadiazole as shown in formula (1). [ka]

[0023] X1 can be substituted with a thiol group (mercaptan group) or an amino group. X2 can be substituted with a hydrogen atom, a methyl group, a methylthio group, or a thiol group (mercaptan group).

[0024] More specifically, the matrix reactant product component can be, for example, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-methylthio-1,3,4-thiadiazole, 1,3,4-thiadiazole-2-thiol, 2-amino-5-mercapto-1,3,4-thiadiazole, or 5-methyl-1,3,4-thiadiazole-2-thiol.

[0025] The base material reactant generating component is preferably contained in an amount of 0.003% by weight to 0.1% by weight based on the total weight of the dissolving and removing composition. If the base material reactant generating component is too small, the generation rate of the base material reactant generated between the base material and scale slows down, resulting in insufficient scale removal properties.

[0026] (C) The base material reactant dissolving component is a component that dissolves the base material reactant and can impart corrosion resistance to the base material.

[0027] The base reactant dissolving component is a C3 compound containing a thiol group and a carboxylic acid group. In a C3 compound, the longest carbon chain number is 3. If the number of carbon chains is small, the molecular structure is small, so the steric hindrance ability is low, and the corrosion prevention ability after dissolution is reduced. If the number of carbon chains is large, the molecular structure is large, so the frequency factor for the reactant is small, and the reactant dissolving ability is reduced.

[0028] More specifically, the matrix reactant dissolving component may be selected from the group consisting of 3-mercaptopropionic acid, thiolactic acid, and salts thereof.

[0029] The base material reactant soluble component may be contained in an amount of 0.7% by weight or more and 5% by weight or less based on the total weight of the dissolving and removing composition. If the base material reactant soluble component is too small, the scale removal performance is reduced and the amount of corrosion increases. In addition, if the base material reactant soluble component is too small or too large, the amount of sulfur remaining in the base material after cleaning increases. Residual sulfur is a cause of corrosion during boiler operation, so it is preferable to have a small amount.

[0030] The dissolving and removing composition may include (D) a corrosion inhibitor, (E) a reducing agent, and (F) an antifoaming agent.

[0031] (D) The corrosion inhibitor is an anticorrosive component that inhibits rust formation in the base material. The corrosion inhibitor includes a surfactant. The surfactant is an amphoteric surfactant or a nonionic surfactant.

[0032] Examples of amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, 2-alkyl-N-carboxyethyl-N-hydroxyethyl imidazolinium betaine, alkali metal salts of β-alkylamino carboxylic acids (e.g., sodium β-alkylamino propionate), and alkali metal salts of alkylamino dicarboxylic acids (e.g., sodium 3-[lauryl[3-(sodiooxy)-3-oxopropyl]amino]propionate). One type of amphoteric surfactant may be used alone, or two or more types may be used in combination. The amphoteric surfactants have a carboxylic acid group and a nitrogen atom, and these substituents allow the amphoteric surfactant to be adsorbed to the surface of the metal base material. This can reduce the amount of metal sulfide produced by the reaction of the exposed surface of the metal base material with sulfur.

[0033] The content of the amphoteric surfactant is from 0.001 to 10% by weight, preferably from 0.005 to 5% by weight, more preferably from 0.01 to 2% by weight, based on the total mass of the dissolving and removing composition.

[0034] Examples of the nonionic surfactant include polyoxyalkylene glycol fatty acid esters, polyalkylene glycol fatty acid esters, and polyoxyalkylene alkyl ethers. As the nonionic surfactant, one type may be used alone, or two or more types may be used in combination. For example, from the viewpoint of removing scale containing metal oxides and inhibiting corrosion of metal base material, the nonionic surfactant is preferably polyethylene glycol monooleate, polyethylene glycol monolaurate, or polyethylene glycol monostearate.

[0035] The content of the nonionic surfactant is from 0.001 to 10% by weight, preferably from 0.005 to 5% by weight, and more preferably from 0.01 to 2% by weight, based on the total mass of the dissolving and removing composition.

[0036] (E) The reducing agent is a component that promotes dissolution of scale components through its reducing action. The reducing agent may be a sulfur compound with strong reducing properties. Examples of sulfur compounds with strong reducing properties include thiourea compounds and dithionites. Thiourea compounds include thiourea dioxide and guanylthiourea. The sulfur atoms contained in the sulfur compound are adsorbed to the metal and strengthen the protective film.

[0037] The content of the strongly reducing sulfur compound is 0.01% by weight or more and 1% by weight or less, preferably 0.01% by weight or more and 0.1% by weight or less, more preferably 0.02% by weight or more and 0.08% by weight or less, based on the total mass of the dissolving and removing composition. If it is less than 0.01% by weight, the scale removing ability is insufficient. If it exceeds 1% by weight, the corrosion prevention ability is insufficient.

[0038] The reducing agent may contain an organic acid having oxygen reducing properties. The organic acid having oxygen reducing properties may be selected from components having excellent oxygen removing properties and durability. Examples of such organic acids include ascorbic acid and erythorbic acid.

[0039] The content of the organic acid having oxygen reducing properties is 0.01% by weight or more and 8% by weight or less, preferably 0.1% by weight or more and 5% by weight or less, more preferably 0.5% by weight or more and 3% by weight or less, based on the total mass of the dissolving and removing composition. If it is less than 0.01% by weight, the scale removing property is insufficient. If it exceeds 8% by weight, the corrosion prevention property is insufficient.

[0040] The (F) antifoaming agent is a component that suppresses foaming of the dissolving and removing composition. The antifoaming agent may be, for example, a silicone-based antifoaming agent.

[0041] The pH of the dissolving and removing composition is from 5 to 7. The pH can be adjusted with sodium hydroxide (NaOH), potassium hydroxide (KOH), or the like.

[0042] [Cleaning method] The above-mentioned dissolving and removing composition is used as a cleaning liquid to clean an object to be cleaned, thereby removing scale adhering to a base material.

[0043] The cleaning time can be appropriately set depending on the nature and amount of scale. For example, when the amount of scale containing iron oxide is 10 to 20 mg / cm 2 If present, cleaning time is approximately 20 to 50 hours.

[0044] The temperature of the cleaning liquid may be about 15 to 55° C. The temperature of the cleaning liquid may be higher than 55° C.

[0045] For example, when the object to be cleaned is a heat transfer tube of a power plant, the object to be cleaned is cleaned by circulating the cleaning liquid inside the heat transfer tube (circulation cleaning), or by filling the inside of the heat transfer tube with the circulating liquid and leaving it to stand (immersion cleaning). When performing circulation cleaning, the cleaning liquid is preferably pulsated (swing blow). Pulsating the cleaning liquid generates varying fluid forces of the cleaning liquid, which allows the scale to be effectively peeled off and removed.

[0046] The dissolving and removing composition and cleaning method according to the present embodiment are suitable for removing scale (particularly iron rust) that adheres to the inside of iron-based piping in power plants, etc. The dissolving and removing composition according to the present embodiment and the cleaning method using the same can also be widely used for removing iron-based oxides and / or hydroxides that adhere to heat exchangers in power plants and chemical plants, cooling jackets of internal combustion engines, etc.

[0047] 1 to 4 are conceptual diagrams showing cleaning using the dissolving and removing composition of the present embodiment. FIG. 1 is a conceptual diagram showing the generation of a base material reactant. FIG. 2 is a more specific conceptual diagram showing the base material reactant. FIG. 3 is a conceptual diagram showing a scale removal (peeling) mechanism. FIG. 4 is a more specific conceptual diagram showing scale removal (peeling).

[0048] In cleaning using the dissolving and removing composition according to this embodiment as a cleaning liquid, scale (iron oxide scale in FIG. 1) is dissolved and removed from the base material by the main agent contained in the cleaning liquid.

[0049] The scale adhering to the object to be cleaned has an uneven thickness and may have cracks.

[0050] In the gaps in the scale or in the areas where the scale has been dissolved by the base material, the base material is exposed as shown in Figure 1. In the exposed areas of the base material, the reactant-generated components of the base material are mixed with the MoFe component (Mo n+ and Fe 2+ ) and base metal reactants are generated between the scale and the base metal. The base metal reactants are extremely thin films, but they can suppress base metal corrosion.

[0051] The base metal reactant generating component has a planar skeleton containing a heteroatom in an organic ring. The unshared electron pair of this heteroatom exhibits high reactivity with the base metal, and a strong layered reactant (base metal reactant) as shown in Figure 2 is generated between the scale and the base metal.

[0052] The base material reactant dissolving component dissolves the base material reactant. When the base material reactant generated between the scale and the base material is dissolved, a gap is generated between the scale and the base material as shown in Figure 3, and the scale becomes easy to peel off.

[0053] As shown in Fig. 4, the base material reactants dissolved by the base material reactant dissolving components are removed from the base material surface. At this time, the scale on the base material reactants can be peeled off and removed by the fluid force of the cleaning liquid. The base material reactant dissolving components are adsorbed to the exposed base material, providing the base material with anticorrosive properties.

[0054] By using a dissolving and removing composition in which a main agent, a component that generates a reactant from the base material, and a component that dissolves the reactant from the base material are coexistent, it is possible to prevent corrosion of the base material while removing scale.

[0055] The cleaning method according to this embodiment may include a step of collecting the peeled scale.

[0056] Next, the basis for selecting the components in the dissolving and removing composition will be explained.

[0057] The base composition of the dissolving and removing composition (test liquid) was as follows, and tests were conducted to evaluate the scale removing ability, corrosion prevention ability, and amount of sulfur remaining after cleaning of the dissolving and removing composition by changing the content or type of each component as appropriate.

[0058] 1. Test solution 1.1 Base composition (pH 5.5) Component A: 1-hydroxyethane-1,1-diphosphonic acid 15% by weight Ingredient B: 2,5-dimercapto-1,3,4-thiadiazole (MTD) 0.00 4 weight% Component C: 3-mercaptopropionic acid 1.5% by weight Component D-1: 3-[lauryl[3-(sodiooxy)-3-oxopropyl]amino]propionic acid 0.5% by weight Component D-2: Polyoxyalkylene oleyl ether 0.1% by weight Component E: Sodium dithionite 0.1% by weight Component F: Silicone-based defoamer 0.015% by weight

[0059] 1.2 Manufacturing method The test solution was prepared by sequentially adding and mixing (A) the main agent, (B) the base material reactant generating component, (C) the base material reactant dissolving component, (D-1) the amphoteric surfactant, (D-2) the nonionic surfactant, (E) the reducing agent, and (F) the defoaming agent to pure water at room temperature, and adjusting the pH with potassium hydroxide (KOH).

[0060] 2. Scale removal 2.1 Creation of test specimen First, a boiler furnace tube with magnetite (Fe3O4) and hematite (Fe2O3) attached to its inner surface was cut to a length of 24 mm and then cut in half lengthwise. Next, the parts other than the part with scale attached, i.e., the outer circumference and cut surface of the tube, were coated with epoxy resin.

[0061] The surface area of ​​the scale-adhering portion of the test specimen (two half-cut tubes) is 12.1 cm 2The amount of scale attached to the test specimen was 18 mg / m of magnetite. 2 , hematite 0.6mg / cm 2 It was.

[0062] 2.2 Cleaning test As shown in Figure 5, the rotor was placed in an acrylic beaker with a diameter of 30 mm, and a 26 mm diameter stand with holes was placed over the rotor. Two halved tubes (test specimens) were placed on the stand so that the scale-adhered surface was on the inside. The ratio of the scale-adhered area to the surface area was 1.3 (mL / cm 2 ) 15.7 mL of the test liquid was poured into the acrylic beaker.

[0063] The acrylic beaker was sealed with a rubber stopper in an atmospheric environment and placed in a thermostatic bath equipped with a stirrer. The liquid temperature in the thermostatic bath was set to 40° C. After reacting for 30 hours while stirring with the stirrer, the test specimen was removed from the acrylic beaker.

[0064] The test specimens were taken out, washed with water for a few seconds, and then subjected to rust prevention treatment in an aqueous hydrazine solution (0.05% by weight) heated to 80° C. for 30 minutes.

[0065] After the rust prevention treatment, the test specimens were visually inspected for the remaining scale area, and the scale removal area rate (%) was calculated using the following formula (2).

[0066] Scale removal area rate (%) = (initial scale area - remaining scale area) / initial scale area × 100 (2)

[0067] 3.Corrosion resistance 3.1 Creation of test specimen A boiler tube (STBA23) without scale was cut in half lengthwise and then cut into 5 cm pieces widthwise. After polishing with #150 sandpaper, the tube was degreased with toluene and then acetone to prepare a test specimen. The surface area of ​​the test specimen was 26 cm 2 It was.

[0068] 3.2 Corrosion test As shown in Figure 6, a rotor was placed in a glass container, a stand with holes was placed over the rotor, and a test specimen was placed on the stand. 2 ) 104 mL of the test liquid was poured into the glass container.

[0069] The reagent iron oxide powder was added to the test solution so that the total iron content when dissolved was 2.25% by weight, and the glass container was sealed with a lid in an air environment. The reagent iron oxide powder contained reagent magnetite powder and reagent hematite powder in a ratio of 9:1.

[0070] After leaving the mixture at 40°C for 20 hours while stirring with a stirrer, the test specimen was removed from the glass container. The test specimen was washed with water for a few seconds and then subjected to rust prevention treatment in an aqueous hydrazine solution (0.05% by weight) heated to 80°C for 30 minutes.

[0071] The amount of corrosion (mg / cm2) was calculated from the weight change of the test specimen before and after the test. 2 ) was calculated.

[0072] 4. Residual sulfur The test specimen was washed in the same manner as in 2.2 above, removed from the acrylic beaker, and rinsed with water for several seconds, after which the following treatment (rinsing treatment) was performed.

[0073] First, the test specimen was immersed in hydrogen peroxide (2% by weight). After stirring for 1 hour in a thermostatic chamber at 50°C, the test specimen was transferred to a 2% by weight aqueous solution of citric acid. The amount of the 2% by weight aqueous solution of citric acid was 1.3 times the surface area of ​​the test specimen.

[0074] After stirring for 1 hour in a constant temperature bath at 50°C, the test specimen was transferred to a hydrazine aqueous solution for rust prevention treatment. The test specimen was thoroughly dried and subjected to elemental analysis (EDX) using a scanning electron microscope (SEM). Measurements were taken at three different measurement positions at a voltage of 20 kV and a magnification of 200 times, and the average was calculated to determine the weight percentage of sulfur element.

[0075] The residual sulfur content may be greater than or equal to 0.4% by weight and less than 0.8% by weight, and is preferably less than 0.4% by weight.

[0076] 5.Results 5.1 Effects of ingredients A, B, and C FIG. 7 shows the effect of the presence or absence of component A (main agent), component B (component that generates base metal reactants), and component C (component that dissolves base metal reactants) on scale removal properties and corrosion prevention properties.

[0077] When cleaning was performed using the test solution with the base composition, the scale removal area rate was 90%, and the amount of corrosion was 2.6 mg / cm 2 It was.

[0078] The scale removal area ratio may be 40% or more, and is preferably 70% or more. Even if the pass criterion for the scale removal area ratio is 70%, the test solution of the base composition meets the pass criterion.

[0079] The amount of corrosion is 5-10mg / cm 2 and 5 mg / cm 2 The pass criterion for the amount of corrosion (corrosion resistance) is 5 mg / cm 2 Even if the concentration is less than 100%, the test solution of the base composition still meets the pass criteria.

[0080] The test solution that did not contain component A had a low scale removal area ratio and did not meet the pass criteria. This result confirmed that the presence or absence of component A affects scale removal performance.

[0081] In the test liquid that did not contain component B, the scale removal area rate was 20%. In the test liquid that did not contain component C, the scale removal area rate was 90%. In the test liquid that did not contain components B and C, the scale removal area rate was 90%. This suggests that when component C is not included, component A alone shows high scale removal properties due to the corrosion reaction, but when component C is included, the presence or absence of component B affects scale removal properties.

[0082] In the test solution that did not contain component A and the test solution that did not contain component B, the corrosion amount was 5mg / cm 2On the other hand, in the test solution that did not contain component C, the amount of corrosion was 46.1 mg / cm 2 This did not satisfy the pass criteria. This confirmed that the presence or absence of component C affects corrosion resistance.

[0083] According to the above results, the test liquid containing components A, B, and C had the highest scale removal property and excellent corrosion prevention. If the amount of attached scale is the same, the cleaning time can be shortened by using the dissolving and removing composition according to the above embodiment.

[0084] 5.2 Content of main ingredient Figure 8 shows the results when the content of the main agent (component A) in the test liquid was changed from 0 to 28% by weight. Figure 9 shows the relationship between the content of the main agent and the scale removal area ratio. In this figure, the horizontal axis is the content of the main agent in the test liquid (% by weight), and the vertical axis is the scale removal area ratio (%).

[0085] 8 and 9, the scale removal area ratio was low whether the content of the base agent was too low or too high. This is presumably because a low content of the base agent slows down the scale dissolution rate, while a high content of the base agent reduces the viscosity and water content of the test liquid, slowing down the scale dissolution rate.

[0086] In the test solutions (Nos. 4 to 6) with a base content of 11% by weight or more and 25% by weight or less, the scale removal area rate was 70% or more. When the base content was 15% by weight or more and 20% by weight or less, the scale removal area rate was about 90%.

[0087] 9, it can be seen that the scale removal area ratio changes significantly between the test solution with a base content of 10% by weight (No. 3) and the test solution with a base content of 11% by weight (No. 4). The scale removal area ratio also seemed to change significantly after the test solution with a base content of 25% by weight (No. 6).

[0088] The amount of corrosion was 5mg / cm for all test solutions No. 1 to 7.2 This was below the pass criteria (see Figure 8).

[0089] 5.3 Content of reactant components in base material Figure 10 shows the results when the content of the base material reactant product component (component B) in the test liquid was changed from 0 to 0.004 wt%. Figure 11 shows the relationship between the content of the base material reactant product component and the scale removal area ratio. In this figure, the horizontal axis is the content (wt%) of the base material reactant product component in the test liquid, and the vertical axis is the scale removal area ratio (%).

[0090] 10 and 11, the scale removal area ratio increased as the content of the base material reactant product components increased. Fig. 11 shows that the scale removal area ratio was 70% or more in test liquids with a base material reactant product content of 0.003 wt% or more.

[0091] The amount of corrosion was 5mg / cm for all test solutions No. 8 to 11. 2 (See Figure 10.)

[0092] 5.4 Content of dissolved components in base material reactants FIG. 12 shows the results when the content of the base metal reactant soluble component (component C) in the test liquid was changed from 0 to 5.5% by weight. FIG. 13 is a diagram showing the relationship between the content of the base metal reactant soluble component and the scale removal area ratio. In this figure, the horizontal axis shows the content (wt%) of the base metal reactant soluble component in the test liquid, and the vertical axis shows the scale removal area ratio (%). FIG. 14 is a diagram showing the relationship between the content of the base metal reactant soluble component and the amount of corrosion. In this figure, the horizontal axis shows the content (wt%) of the base metal reactant soluble component in the test liquid, and the vertical axis shows the amount of corrosion (mg / cm 2 15 is a diagram showing the relationship between the content of the component dissolved in the base material reactant and the remaining amount of sulfur. In this figure, the horizontal axis represents the content (wt%) of the component dissolved in the base material reactant in the test liquid, and the vertical axis represents the remaining amount of sulfur (wt%).

[0093] 12 and 13, the scale removal area ratio was 90% in the test liquid (No. 12) that did not contain any dissolved components of the base material reactant. When dissolved components of the base material reactant were added, the scale removal area ratio temporarily decreased to 45%, but then started to increase, and in the test liquids (Nos. 15 to 17) that contained 0.7 wt% or more of dissolved components of the base material reactant, the scale removal area ratio was 85% or more.

[0094] According to Figures 12 and 14, the amount of corrosion was 10 mg / cm2 in the test solution (No. 12) that did not contain any dissolved components of the base metal reactant. 2 However, this decreased as the content of the base metal reactant soluble components increased. In the test solutions (No. 15 to 17) with a content of the base metal reactant soluble components of 0.7 wt% or more, the corrosion amount was 5 mg / cm 2 It became lower than that.

[0095] 12 and 15, the amount of sulfur remaining after the rinsing process decreased once as the content of the soluble components of the base material reactant increased, but then started to increase when the content of the soluble components of the base material reactant increased too much. In the test solutions (Nos. 15 and 16) in which the content of the soluble components of the base material reactant was 0.7% by weight or more and 5% by weight or less, the amount of sulfur remaining after the rinsing process was kept below 0.4% by weight.

[0096] pH 5.5 Figure 16 shows the results when the pH of the test liquid was changed in the range of 5.5 to 9.0. Figure 17 shows the relationship between the pH of the test liquid and the scale removal area ratio. In this figure, the horizontal axis is the pH of the test liquid, and the vertical axis is the scale removal area ratio (%).

[0097] When the pH of the test liquid was high, the scale removal area ratio decreased. According to Fig. 17, when the pH was 7 or less, the scale removal area ratio was 70% or more.

[0098] The amount of corrosion increases as the pH increases, and at pH 7 or less, the amount of corrosion is 5 mg / cm 2 was thought to be below.

[0099] 5.6 Types of base agent FIG. 18 shows the results when the type of main agent (ingredient A) was changed. In the test solution using 1-hydroxyethane-1,1-diphosphonic acid, aminotris(methylenephosphonic acid), and ethylenediaminetetraacetic acid as component A, the scale removal area rate was 80% or more and the corrosion amount was 5mg / cm 2 and the sulfur residue was less than 0.4 wt.%.

[0100] On the other hand, in the test solution using citric acid as component A, the scale removal area rate was low and the amount of corrosion was 5 mg / cm 2 It became higher than that.

[0101] 5.7 Types of reactant components in the base material FIG. 19 shows the results of varying the type of base reactant product component (component B). In the test solution using 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-methylthio-1,3,4-diadiazole, 1,3,4-thiadiazole-2-thiol, 2-amino-5-mercapto-1,3,4-thiadiazole, or 5-methyl-1,3,4-thiadiazole-2-thiol as component B, the scale removal area rate was 80% or more and the corrosion amount was 5 mg / cm 2 and the sulfur residue was less than 0.4 wt.%.

[0102] On the other hand, in the test solution using benzotriazole as component B, the corrosion amount was 5mg / cm 2 The residual sulfur content was less than 0.4 wt%, while the scale removal area rate was low at 20%.

[0103] 5.8 Types of dissolved components in the base material reactants FIG. 20 shows the results when the type of base material reactant soluble component (component C) was changed. In the test solution using 3-mercaptopropionic acid and thiolactic acid as component C, the scale removal area rate was 85% or more and the corrosion amount was 5mg / cm 2 and the sulfur residue was less than 0.4 wt.%.

[0104] On the other hand, in the test solution using thiomalic acid as component C, the scale removal area rate was 85% or more and the corrosion amount was 5mg / cm 2 The sulfur content was less than 0.8 wt. %.

[0105] Thiomalic acid is a C4 compound with a large molecular structure, which gives it a high steric hindrance ability and high corrosion prevention properties after dissolution. However, it is presumed that the large molecular structure reduces the frequency factor of the thiol group in the base material reactant, which reduces its solubility in the base material reactant.

[0106] In the test solution using thioglycolic acid as component C, the scale removal area rate was 85% or more, and the sulfur residue was less than 0.4% by weight, but the corrosion amount was 10 mg / cm 2 It was higher than that.

[0107] Thioglycolic acid has a strong ability to dissolve reactants in the base material. However, because thioglycolic acid is a C2 compound and has a small molecular structure, it has a low steric hindrance ability, and it is presumed that the corrosion prevention ability after dissolution was poor.

[0108] In the test solution using thioacetic acid as component C, the scale removal area rate was 20% or more and the corrosion amount was 10mg / cm 2 exceeded.

[0109] It is presumed that thioacetic acid, like thioglycolic acid, had poor anticorrosive ability after dissolution because of its small molecular structure, and that thioacetic acid had poor scale removal ability because it does not have a carboxylic acid group that is thought to dissolve the base material reactant.

[0110] <Additional Notes> The dissolving and removing composition and cleaning method described in the above-described embodiment can be understood, for example, as follows.

[0111] The present disclosure provides a dissolving and removing composition that includes a base agent that dissolves and removes scale including metal oxides adhered to a base material, a base material reactant generating component that reacts with the base material to generate a reactant, and a base material reactant dissolving component that dissolves and removes the reactant.

[0112] The present disclosure provides a method for cleaning an object to be cleaned, which includes a base material having scale containing a metal oxide attached thereto, the method including cleaning the object to be cleaned with a cleaning solution containing a main agent, a base material reactant generating component, and a base material reactant dissolving component, dissolving and removing at least a portion of the scale from the base material by the main agent, reacting the base material reactant generating component with the base material to generate a reactant between the base material and the scale, and dissolving and removing the reactant by the base material reactant dissolving component.

[0113] The scale containing metal oxides is dissolved and removed from the surface side by the base agent.

[0114] In areas where the scale has dissolved or where the base material is exposed in gaps in the scale, the base material components react with the base material reactant generating components to generate base material reactants. The base material reactants impart corrosion protection to the base material.

[0115] The base material reactant dissolving component dissolves the base material reactant, which causes the scale to be peeled off and removed.

[0116] In the above disclosure, by removing scale using two removal mechanisms, cleaning time can be shortened compared to the conventional method in which scale is dissolved and removed using a base agent.

[0117] In the absence of the base metal reactant dissolving component, the scale peeling proceeds, but the amount of corrosion increases. In the above disclosure, the base metal reactant dissolving component is included, so that the amount of corrosion of the base metal is suppressed, the scale peeling is promoted, and the cleaning time can be shortened.

[0118] In one embodiment of the above disclosure, the matrix reactant dissolving component may be a C3 compound or a salt thereof having a thiol group and a carboxylic acid group.

[0119] A C3 compound having a thiol group and a carboxylic acid group or a salt thereof has the ability to dissolve reactants and has a suitable corrosion inhibitory ability after dissolution.

[0120] In one embodiment of the above disclosure, the base reactant soluble component may be included in an amount of 0.7% by weight or more and 5% by weight or less based on the total weight.

[0121] If the amount of the base metal reactant dissolved component is too small, the scale removal and corrosion prevention properties will be reduced and the amount of sulfur remaining after rinsing will be large, whereas if the amount of the base metal reactant dissolved component is too large, the amount of sulfur remaining after rinsing will be large.

[0122] In one embodiment of the above disclosure, the base agent may be selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof.

[0123] In one embodiment of the above disclosure, the base material may be contained in an amount of 11% by weight or more and 25% by weight or less based on the total weight.

[0124] If the content of the base agent is too high or too low, the scale removal performance decreases. If the content of the base agent is within the above range, the scale removal performance is high.

[0125] In one embodiment of the above disclosure, the pH of the dissolution removal composition may be from 5 to 7.

[0126] In one aspect of the above disclosure, the matrix reactant product component can be a thiadiazole-based compound having a planar backbone.

[0127] By having a planar skeleton, a layered and strong matrix reactant can be produced. The layered and strong matrix reactant can have good peelability.

[0128] In one embodiment of the above disclosure, the planar scaffold may be a 1,3,4-thiadiazole.

[0129] In one embodiment of the above disclosure, the matrix reactant product component may be present in an amount of 0.003% by weight or more based on the total weight.

Claims

1. A base agent that dissolves and removes scale containing metal oxides that adhere to the base material; a matrix reactant generating component that reacts with the matrix to generate a reactant; A base material reactant dissolving component that dissolves and removes the reactant; Including, the main ingredient is selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof, and is contained in an amount of 11% by weight or more and 25% by weight or less based on the total weight of the composition; the base reactant product component is a thiadiazole-based compound having 1,3,4-thiadiazole as a planar skeleton, and is included in an amount of 0.003 wt % or more based on the total weight of the base reactant; The base reactant dissolving component is selected from the group consisting of 3-mercaptopropionic acid, thiolactic acid, and salts thereof, which are C3 compounds having a thiol group and a carboxylic acid group, and is contained in an amount of 0.7% by weight or more and 5% by weight or less based on the total weight of the base reactant; A dissolving and removing composition having a pH of 5 to 7.

2. A method for cleaning an object to be cleaned, the method comprising: cleaning the object to be cleaned with a cleaning solution containing a base material, a base material reactant generating component, and a base material reactant dissolving component; Dissolving and removing at least a portion of the scale from the base material by a base material; reacting a base material reactant generating component with the base material to generate a reactant between the base material and the scale; Dissolving and removing the reactants using a base material reactant dissolving component; the main ingredient is selected from the group consisting of aminocarboxylic acids, phosphonic acids, and salts thereof, and is contained in an amount of 11% by weight or more and 25% by weight or less based on the total weight of the cleaning solution; the base reactant product is a thiadiazole-based compound having 1,3,4-thiadiazole as a planar skeleton, and is contained in an amount of 0.003 wt % or more based on the total weight of the cleaning solution; the base material reactant dissolving component is selected from the group consisting of 3-mercaptopropionic acid, thiolactic acid, and salts thereof, which are C3 compounds having a thiol group and a carboxylic acid group, and is contained in an amount of 0.7% by weight or more and 5% by weight or less based on the total weight of the cleaning solution; The cleaning method, wherein the cleaning solution has a pH of 5 to 7.

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