JP2020131061A - Slime peeling agent for water system, and method of peeling slime in water system - Google Patents

Abstract

To efficiently peel and remove slime in a water system without using hydrazine.SOLUTION: There is provided a slime peeling agent for a water system, comprising carbohydrazide and an isothiazolone compound. A preferable isothiazoline compound is 5-chloro-2-methyl-4-isothiazoline-3-one. It is preferable to circulate water in the water system for 20 hours or longer subsequent to adding carbohydrazide and an isothiazolone compound into a water system.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water-based slime stripping agent and a water-based slime stripping method. Specifically, the present invention provides a slime stripping agent and stripping agent for efficiently stripping slime adhering to a water system, particularly a cooling water system or a heat exchanger, when a new plant is started up (flushing) or when the plant is restarted. The present invention relates to a slime stripping agent and a stripping method that do not use hydrazine for the purpose of complying with environmental regulations.

In the cooling water process, paper making process, and membrane treatment process of various factories and buildings, slime (biofilm) is generated in the system by microorganisms such as bacteria, which causes problems such as deterioration of thermal efficiency, deterioration of quality, and blockage of membranes and pipes. .. As a method for preventing such damage caused by slime, a slime release agent is added.

Conventionally, hydrazine has been widely used as a slime stripping agent because it has a high slime stripping effect. However, hydrazine is a substance subject to PRTR, and there is a possibility that it will shift to a Class 2 Specified Chemical Substance under the Chemical Substances Control Law in the future. Therefore, a non-hydrazine-based slime remover is desired from the viewpoint of environmental regulation.

The carbohydrazide used in the present invention is known as an anticorrosive agent for boilers (Japanese Patent Laid-Open No. 2010-236788) and a patina inhibitor (Japanese Patent Laid-Open No. 2012-12698). However, there is no application example as a slime release agent in an aqueous system.
Further, Cl-MIT (5-chloro-2-methyl-4-isothiazolin-3-one) used in the present invention is known as a cooling water-based disinfectant. However, the slime peeling effect is low, and it is necessary to use it at a high concentration in order to obtain a sufficient effect with Cl-MIT alone.

Japanese Unexamined Patent Publication No. 2010-236788 Japanese Unexamined Patent Publication No. 2012-12698

The present invention solves the above-mentioned conventional problems, and is an aqueous slime remover and an aqueous slime remover capable of efficiently removing slime adhering to a cooling water system, a heat exchanger, etc. without using hydrazine for the purpose of environmental harmony. It is an object of the present invention to provide a slime peeling method.

As a result of diligent studies to solve the above problems, the present inventors have been able to efficiently exfoliate and remove aqueous slime without using hydrazine by using carbohydrazide and an isothiazolone compound in combination. I found.
That is, the gist of the present invention is as follows.

[1] An aqueous slime stripper containing carbohydrazide and an isothiazolin compound.

[2] The aqueous slime stripper according to [1], wherein the isothiazolin compound is 5-chloro-2-methyl-4-isothiazolin-3-one.

[3] The water-based slime stripper according to [1] or [2], wherein the content of the isothiazolin compound is 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the carbohydrazide.

[4] An aqueous slime exfoliation method in which carbohydrazide and an isothiazolin compound are added to an aqueous system.

[5] The method for stripping an aqueous slime according to [4], wherein the isothiazolin compound is 5-chloro-2-methyl-4-isothiazolin-3-one.

[6] The method for stripping an aqueous slime according to [4] or [5], wherein the amount of the isothiazolone compound added is 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the amount of carbohydrazide added. ..

[7] The method for exfoliating an aqueous slime according to any one of [4] to [6], wherein the carbohydrazide is added so that the concentration of the carbohydrazide in the aqueous system becomes 20 to 100 mg / L.

[8] The method for exfoliating an aqueous slime according to any one of [4] to [7], wherein the isothiazolone compound is added so that the concentration of the isothiazolone compound in the aqueous system becomes 0.5 to 3.0 mg / L. ..

[9] The method for exfoliating an aqueous slime according to any one of [4] to [8], wherein after adding the carbohydrazide and the isothiazolone compound, the water in the aqueous system is circulated for 20 hours or more.

According to the present invention, it is possible to obtain a high slime exfoliation effect equivalent to that of the current hydrazine treatment without using hydrazine due to the high synergistic effect of the combined use of carbohydrazide and the isothiazolone compound.

It is a schematic block diagram which shows the structure of the test apparatus used in an Example.

Embodiments of the present invention will be described in detail below.

[Aqueous slime stripper]
The water-based slime stripper of the present invention contains carbohydrazide and an isothiazolone compound.

Examples of the isothiazolinone compound include 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT), 2-methyl-4-isothiazolin-3-one (MIT), and 4,5-dichloro-2-methyl. -4-isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one , 5-Chloro-2-t-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-cyclohexyl-4 -Isothiazolin-3-one, 1,2-benzothiazolin-3-one and the like can be mentioned. These isothiazolin compounds may be used alone or in combination of two or more. Of these isothiazolone compounds, Cl-MIT is preferable from the viewpoint of slime peeling effect.

The content of carbohydrazide and isothiazolone compound in the aqueous slime stripper of the present invention is 0.5 to 15.0 parts by mass, preferably 0.6 to 10.0 parts by mass, based on 100 parts by mass of carbohydrazide. The amount may be parts, more preferably 1.0 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass.
When the ratio of the isothiazolone compound to the carbohydrazide is within the above range, a good slime peeling effect can be obtained by an excellent synergistic effect by using these in combination.

The aqueous slime remover of the present invention may contain carbohydrazide and an isothiazolone compound as essential components, and other components other than carbohydrazide and the isothiazolone compound, for example, low molecular weight polymers (molecular weight 500 to 20, 000) and the like may be contained, but it is preferable that the carbohydrazide and the isothiazolone compound are contained in an amount of 1.0% by mass or more as the main components excluding water.

The carbohydrazide and isothiazolone compounds may be added simultaneously or separately as described below. Therefore, the water-based slime stripper of the present invention may be a single agent of carbohydrazide and an isothiazolone compound, or may be provided as two agents containing each separately. When carbohydrazide and Cl-MIT as the isothiazolone compound are used, it is preferable to provide them as two agents containing them separately.

The water-based slime stripper of the present invention may be provided as a powder of carbohydrazide, an isothiazolone compound or a mixture thereof, or may be provided as an aqueous solution. In the case of an aqueous solution, for example, it is provided as an aqueous solution having a carbohydrazide concentration of 5 to 15% by mass, an isothiazolone compound concentration of 5 to 50% by mass, or a total concentration of carbohydrazide and an isothiazolone compound of 10 to 65% by mass.

[Aqueous slime peeling method]
The water-based slime exfoliation method of the present invention is characterized by adding carbohydrazide and an isothiazolone compound to the water-based system. The carbohydrazide and the isothiazolone compound may be added simultaneously to the same location in the aqueous system, or may be added separately. When added at the same time, the carbohydrazide and the isothiazolone compound may be added as a premixed mixed drug, or separate drugs may be added. Further, when they are added separately, they may be added separately to the same place or added to different places.
The types of carbohydrazide and isothiazolone compounds are as described above.

The amount of carbohydrazide added to the water system may be such that the carbohydrazide concentration in the water system is 20 to 500 mg / L, preferably 20 to 100 mg / L, and particularly preferably about 30 to 60 mg / L.
The amount of the isothiazolone compound added to the aqueous system is such that the concentration of the isothiazolone compound in the aqueous system is 0.3 to 5.0 mg / L, preferably 0.5 to 3.0 mg / L, and particularly preferably about 0.5 to 1.0 mg / L. The amount may be such that
The addition amount ratio of the carbohydrazide to the isothiazolone compound to the aqueous system is such that the addition amount of the isothiazolone compound is 0.5 to 15.0 parts by mass, preferably 0.6 to 10.0 parts by mass, based on 100 parts by mass of the carbohydrazide addition amount. The ratio may be parts by mass, more preferably 1.0 to 8.0 parts by mass, particularly preferably 1.0 to 5.0 parts by mass, and the total addition of carbohydrazide and isothiazolone compound to the aqueous system. The amount may be about 20.3 to 505.0 mg / L.
With the above addition amount, a good slime peeling effect can be obtained under an excellent synergistic effect while securing the necessary and sufficient amounts of the carbohydrazide and the isothiazolone compound.

As described above, the carbohydrazide and the isothiazolone compound may be added as a powder or as an aqueous solution.

In the water-based slime peeling method of the present invention, it is preferable to circulate the water-based water after adding the carbohydrazide and the isothiazolone compound to the water-based system or while adding the carbohydrazide and the isothiazolone compound. The circulation time is preferably 20 hours or more after reaching the above-mentioned suitable addition concentrations of the carbohydrazide and isothiazolone compounds, and more preferably the circulation time is 24 to 48 hours. By circulating the drug in the water system after the addition of the drug in this way, the peeling action of the drug can be sufficiently spread throughout the system to obtain a good slime peeling effect.
After the above circulation treatment, the operation of the water system is started or restarted.

In the water-based slime stripping method of the present invention, in addition to the carbohydrazide and the isothiazolone compound, other than the carbohydrazide and the isothiazolone compound exemplified as other components which may be contained in the water-based slime stripper of the present invention described above. Drugs may be added.

[Water system to be treated]
The water-based slime stripping agent of the present invention and the water system to be treated by the slime stripping method are not particularly limited as long as they are water systems that generate slime, and are, for example, plant cooling water systems of various factories, scrubbers, paper and pulp water systems, wastewater treated water systems, etc. Examples include wastewater treatment water systems, steel water systems, cutting oil water systems, and film process water systems that use separation films such as back-penetration films. According to the present invention, these devices comply with environmental regulations without using hydrazine. , The slime adhering to the water flow pipe can be efficiently peeled off and removed.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 4, Comparative Examples 1 to 4]
<Experimental conditions>
An experiment was conducted to investigate the slime peeling effect using the test apparatus shown in FIG.

First, the test water tank 1 of 50L volume, at the water pump _{P 1} from the pipe 11 dechlorinated water (calcium hardness: 40mgCaCO ₃ / L, total hardness: 60mgCaCO ₃ / L, acid consumption: 40mgCaCO ₃ / L) introduced to pooled, medium (activated sludge) was batch added by a water pump P ₂ from the pipe 12. Pipe 13 dechlorinated water and the medium by the water pump P _3, it was circulated in the order of transparent column 2 and a pipe 14. A SUS tube was inserted into the transparent column 2 so that the slime adhering to the SUS tube could be visually observed. The flow velocity in the column 2 was 5.0 L / min.
After visually confirming the adhesion of slime to the SUS tube in the column 2, the agents shown in Table 1 were added in batches to the concentrations shown in Table 1 and circulated for another 24 hours. After that, the peeling state of the slime of the SUS tube was visually confirmed.
The following evaluation criteria are used to evaluate the slime peeling effect of each drug based on the ratio of the slime peeling amount by the drug treatment (the amount obtained by subtracting the adhesion amount after the drug treatment from the adhesion amount before the drug treatment) to the slime adhesion amount before the drug treatment. Was evaluated by. In the following evaluation criteria, the larger the number of +, the better the slime peeling effect. When the evaluation is ++ or more, it has a high slime peeling effect equivalent to that of hydrazine.
(Evaluation criteria)
Evaluation: Slime peeling amount +: 0 to 15%
++: 16-45%
+++: 46-100%

<Results / Discussion>
The results of the above experiment are shown in Table 1.
As shown in Table 1 below, the peeling effect was insufficient with each of carbohydrazide or Cl-MIT alone, but by using carbohydrazide and Cl-MIT in combination, a high slime peeling effect equivalent to that of hydrazine can be obtained. It was.

1 Test water tank 2 Transparent column

Claims (9)

An aqueous slime stripper containing carbohydrazide and an isothiazolin compound. The water-based slime stripper according to claim 1, wherein the isothiazolin compound is 5-chloro-2-methyl-4-isothiazolin-3-one. The water-based slime stripper according to claim 1 or 2, wherein the content of the isothiazoline compound is 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the carbohydrazide. An aqueous slime exfoliation method in which carbohydrazide and an isothiazolin compound are added to an aqueous system. The water-based slime stripping method according to claim 4, wherein the isothiazolin compound is 5-chloro-2-methyl-4-isothiazolin-3-one. The method for stripping an aqueous slime according to claim 4 or 5, wherein the amount of the isothiazolone compound added is 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the amount of carbohydrazide added. The method for exfoliating an aqueous slime according to any one of claims 4 to 6, wherein the carbohydrazide is added so that the concentration of the carbohydrazide in the aqueous system is 20 to 100 mg / L. The method for stripping an aqueous slime according to any one of claims 4 to 7, wherein the isothiazolone compound is added so that the concentration of the isothiazolone compound in the aqueous system is 0.5 to 3.0 mg / L. The method for exfoliating an aqueous slime according to any one of claims 4 to 8, wherein after adding the carbohydrazide and the isothiazolone compound, the water in the aqueous system is circulated for 20 hours or more.

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