JPS6314037B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cleaning agent for neutralizing acid cleaning liquid for piping, and particularly to a neutralizing cleaning agent suitable for neutralizing acid cleaning liquid for various factories, air conditioning equipment piping, etc. [Prior Art] Conventionally, for the purpose of removing mill scale etc. generated during manufacturing and processing of a new plant or removing scale such as iron oxide generated during plant operation after operation,
Acid cleaning is being carried out on various factories and air conditioning equipment piping. When the acid cleaning solution used is neutralized after completion of the acid cleaning, an alkali such as caustic soda, caustic potash, or soda carbonate has conventionally been used. As a neutralization method, in-system neutralization is generally carried out while the cleaning liquid remains in the system to be cleaned. [Problems to be solved by the invention] However, in conventional system neutralization, iron ions, copper ions, etc. generated by acid cleaning corrode the steel or copper material of the cleaning system in the following reaction. This cannot be suppressed, 2Fe ³⁺ +Fe→3Fe ²⁺ 2Fe ³⁺ +Cu→2Fe ²⁺ +Cu ²⁺ Cu ²⁺ +Fe→Cu+Fe ²⁺ Cu ²⁺ +Cu→2Cu ⁺ calcium hydroxide generated by neutralization. , Iron hydroxide, etc., accumulate and adhere to the inside of the pipes, causing new scale damage. If neutralized products such as calcium hydroxide, iron hydroxide, etc. accumulate in narrow pipes within the system, There were drawbacks such as inability to perform sufficient neutralization and difficulty in discharging accumulated neutralization products. The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to suppress corrosion of steel or copper materials caused by iron ions or copper ions, and to prevent hydration caused by neutralization. It prevents calcium, iron hydroxide, etc. from accumulating or adhering to the inside of the piping, making neutralization work easy and complete, and cleaning after neutralization is easy and the inside of the system is extremely clean after cleaning. The purpose of the present invention is to provide a cleaning agent for neutralizing acid cleaning liquid for piping. [Means for Solving the Problem] In order to achieve this objective, the cleaning agent for neutralizing the pickling solution for piping of the present invention adds a chelating agent, a reducing agent, and a dispersing agent to the alkali for acid neutralization. It contains an alkali metal hydroxide and/or an alkali metal carbonate, and further contains a chelating agent consisting of gluconic acid and/or its salt, 1 selected from the group consisting of erythorbic acid, erythorbate and hydrazine. A reducing agent containing one or more species, and a dispersing agent containing one or more species selected from the group consisting of carboxylic acid-based low molecular weight polymers, salts of carboxylic acid-based low molecular weight polymers, phosphonic acids, and phosphonates. The present invention provides a cleaning agent for neutralizing acid cleaning liquid for piping, which is characterized by the following. The present invention will be explained in detail below. The neutralizing detergent of the present invention contains an alkali metal hydroxide and/or an alkali metal carbonate for neutralizing acids. As the alkali metal hydroxide and alkali metal carbonate, those commonly used for acid neutralization may be used, and examples thereof include caustic soda, caustic potash, and soda carbonate. The neutralizing detergent of the present invention further contains a chelating agent, a reducing agent, and a dispersing agent. The chelating agent consists of gluconic acid and/or its salt, and its content is 1 of the total weight of the chelating agent, reducing agent, and dispersing agent (hereinafter referred to as "auxiliary agent weight").
A range of 99% by weight is suitable. The reducing agent is erythorbic acid or a salt thereof, or hydrazine, and these may be used alone or in combination of two or more. The content of the reducing agent is suitably in the range of 1 to 99% by weight of the auxiliary agent. The dispersant is a carboxylic acid-based low molecular weight polymer such as polyacrylic acid, polymethacrylic acid, or polymaleic acid, or a salt thereof, or a phosphonic acid or a salt thereof, and these may be used alone or in combination of two or more. It may also be used as The content of the dispersant is suitably in the range of 0.1 to 99% by weight based on the weight of the auxiliary agent. The neutralizing detergent of the present invention contains the above-mentioned chelating agent, reducing agent, and dispersing agent such that the total amount thereof is 0.1 to 100% by weight based on the weight of the alkali metal hydroxide and/or alkali metal carbonate. It is preferable to contain it. It is preferable that the neutralizing detergent of the present invention further contains a copper anticorrosive agent to prevent corrosion of copper materials. Examples of the anticorrosive agent for copper include tolyltriazole, benzotriazole, and salts thereof, and these may be used alone or in combination of two or more. The content of the copper anticorrosive agent is preferably in the range of 0.1 to 99% by weight of the total weight of the chelating agent, reducing agent, dispersant, and copper anticorrosive agent. The neutralizing detergent of the present invention may contain other commonly used surfactants such as ABS and sodium oleate, moisturizing agents, and the like. Such a neutralizing detergent of the present invention may be used in a state in which an alkali and an auxiliary agent are mixed in advance and prepared in a liquid, powder, pellet, or other solid form such as a tablet. Alternatively, the alkali and the auxiliary agent may be formulated separately, added to the neutralization system during neutralization, and mixed within the system. Excellent effects can be obtained in either case. [Effect] The effects of various auxiliary agents contained in the neutralizing detergent of the present invention will be explained below. Gluconic acid or its salt forms a passive oxide film of iron gluconate on the surface of the steel material, thereby suppressing corrosion of the surface of the steel material. The reducing agent is eluted by acid cleaning and produces Fe ³⁺ ions, which have a negative effect on steel and copper materials due to corrosion.
Cu ²⁺ ions and Fe ²⁺ ions, which do not participate in corrosion, respectively.
By reducing to ions and Cu ⁺ ions, it suppresses corrosion of steel and copper materials. Dispersants neutralize calcium ions, iron ions, etc. eluted by acid cleaning, prevent them from precipitating crystals, suppress the growth of precipitated crystals, and disperse them, thereby improving piping. Prevent scale from adhering to metal surfaces such as The anticorrosive agent for copper forms a passive precipitated film of a copper chelate compound on the surface of the copper material, thereby suppressing corrosion of the surface of the copper material. Therefore, it is preferable to include a copper anticorrosive agent especially when the neutralization system is made of copper material. In addition, the cleaning effect of neutralization can be further improved by incorporating a surfactant or the like into the neutralizing cleaning agent of the present invention, if necessary. [Examples] The present invention will be described in more detail below with reference to experimental examples, working examples, and comparative examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. Experimental Example 1 In a 1-volume beaker, take 1 aqueous hydrochloric acid solution containing 1000 ppm each of Fe ³⁺ and Cu ²⁺ ions, and add 10 g of caustic soda and various chemicals in the amounts shown in Tables 1 to 3. Neutralized. At this time, pure copper (TCUP) (Table 1) is added to the neutralization system (i.e. in the beaker).
Test specimens of aluminum brass (BSTF) (Table 2) and carbon steel (SPCC) (Table 3) (both have a surface area of 31
cm ² ) was immersed in the test piece, stirred with a magnetic stirrer, and the corrosion loss of the test piece after 2 hours was measured to determine the corrosion rate. The results are shown in Tables 1 to 3. From Tables 1 to 3, sodium gluconate,
It is also clear that corrosion of copper or steel materials is significantly suppressed by adding a reducing agent such as sodium erythorbate or hydrazine. Furthermore, it is clear that corrosion of copper materials is also suppressed by anticorrosive agents for copper such as benzotriazole and tolyltriazole.

【table】

【table】

【table】

[Table] Experimental Example 2 Take aqueous hydrochloric acid solution 1 containing 1000 ppm each of Fe ³⁺ , Cu ²⁺ , and Ca ²⁺ ions in a 1-volume beaker, add the amount of chemicals shown in Table 4, and then add 10 g of caustic soda. was added and stirred to perform neutralization treatment, and the appearance of each solution after neutralization was observed. The results are shown in Table 4. Table 4 shows that addition of a dispersant such as sodium polyacrylate or sodium phosphonate prevents scale from adhering to the neutralization treatment system.

[Table] Example 1 A process cooling water heat exchanger (material STB-35) of a petrochemical factory was cleaned with an acid cleaning solution containing 3% by weight of hydrochloric acid and 0.2% by weight of an amine anticorrosive agent IBIT (manufactured by Asahi Chemical Co., Ltd.) After washing with sodium carbonate, a neutralizing detergent consisting of sodium carbonate, sodium gluconate, sodium erythorbate, and sodium polyacrylate was added to the system at a concentration of 3.3% of each of sodium carbonate,
Sodium gluconate 0.1%, sodium erythorbate 0.1%, sodium polyacrylate 0.1%
(all percentages by weight) to perform in-system neutralization. After neutralization, the neutralized solution was discharged and washed with water, and it took 25 minutes from the start of washing until the washing wastewater became clear. In addition, after the cleaning work was completed, the heat exchanger was opened and the inside of the tube was observed. No sludge or rust was found inside the heat exchanger, and the inner wall surface of the system had a metallic luster. It turned out that it had been cleaned. Comparative Example 2 After acid cleaning, neutralization was carried out in the same manner as in Example 1 except that only caustic soda was added instead of the neutralizing detergent so that the concentration in the system was 3.3% by weight.
I washed it with water. As a result, it took 40 minutes from the start of washing until the washing waste water became clear. In addition, when the inside of the tube was observed after the cleaning work, a large amount of sludge mainly composed of calcium carbonate, calcium hydroxide, and iron hydroxide was deposited inside, and red rust was observed on the entire inside surface of the tube. It was found that the material was corroded. From the results of Example 1 and Comparative Example 1, it was found that the neutralizing detergent of the present invention can prevent scale formation in the neutralization system and corrosion of the material, and can also facilitate cleaning after neutralization. It is clear that it can be done. In addition, in Example 1, even when hydrazine was added in the same proportion in place of sodium erythorbate, the same excellent effects as in Example 1 were exhibited. Example 2 The cooling system of an air conditioner in a building was cleaned with an acid cleaning solution containing 2% by weight of hydrochloric acid and 0.2% by weight of the same amine anticorrosive agent used in Example 1. After completing the acid cleaning, apply a 100% aqueous neutralizing detergent solution consisting of the following composition:
Neutralization was performed with Kg, followed by washing with water. :Blend: Caustic soda 10% by weight Sodium gluconate 8% by weight Sodium erythorbate 5% by weight Sodium polyacrylate 2% by weight Water 75% by weight As a result, the time required from the start of neutralization to the end of washing with water was 1 hour. In addition, test pieces of SS41 and TCUP were immersed in order to test their corrosive properties, but no corroded areas were observed in any of them, and they had a metallic luster. Comparative Example 2 Acid cleaning, neutralization, and water washing were performed in the same manner as in Example 2, except that neutralization was performed with about 20 kg of a 48% by weight aqueous solution of caustic soda, and the corrosivity of the test piece was examined. As a result, the immersed test piece lost its metallic luster and took on a brown color. In addition, reddish-brown turbidity, thought to be caused by iron hydroxide, was observed in the washing wastewater several hours later. [Effects of the Invention] As detailed above, the cleaning agent for neutralizing the pickling solution for piping of the present invention prevents corrosion of steel materials and copper materials by neutralizing the system, and can be used in various factories and air conditioners. Prevents damage due to corrosion of equipment piping, etc. Prevents rescaling of calcium ions, iron ions, etc. generated by neutralization within the system, Prevents scale adhesion and accumulation within the system, and reduces scale failure. It has excellent effects such as making neutralization work easier, increasing neutralization efficiency, making neutralization complete, making cleaning after neutralization easier, and making the inside of the system extremely clean after cleaning. obtain. Therefore, according to the neutralizing detergent of the present invention, it is possible to neutralize the system efficiently in a short time, which is extremely advantageous industrially.

Claims (1)

[Scope of Claims] 1. A chelating agent containing an alkali metal hydroxide and/or an alkali metal carbonate and further consisting of gluconic acid and/or its salt, 1 selected from the group consisting of erythorbic acid, erythorbate and hydrazine. A reducing agent containing one or more species, and a dispersing agent containing one or more species selected from the group consisting of carboxylic acid-based low molecular weight polymers, salts of carboxylic acid-based low molecular weight polymers, phosphonic acids, and phosphonates. A cleaning agent for neutralizing acid cleaning liquid for piping. 2 The content of the chelating agent, reducing agent, and dispersing agent is
The neutralizing detergent according to claim 1, characterized in that the content of the alkali metal hydroxide and/or alkali metal carbonate is 0.1 to 100% by weight.