JPH04312502A - Cleaning method - Google Patents

Abstract

PURPOSE:To clean and remove stain based on soft scale or slime by adding hydrogen peroxide and water soluble cationic polymer to water system and using hydrogen peroxide having low concentration. CONSTITUTION:(A) Hydrogen peroxide or hydrogen peroxide adduct (e.g. sodium percarbonate or sodium perborate) capable of producing hydrogen peroxide in water and (B) a polymer obtained by reaction of a water soluble cationic polymer, preferably alkylene polyamine and/or polyalkylene polyamine with epichlorohydrin or dichloroethyl ether and having 500-50000 molecular weight are added to a water system at amounts of the component A of 0.1-2wt.% and the component B of 0.01-0.5wt.%. A poly[2-hydroxyethylene(di-methylimino) ethylene(dimethylimino-)methylene dichloride expressed by formula I (n is 4-40) or poly[oxyethylene (dimethyl imino)-ethylene(dimethyl imino) ethylene chloride] expressed by formula II is preferably used as the component B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning soft scale, slime, etc. adhering to heat exchangers and piping systems. More specifically, the present invention relates to a method for washing and removing stains caused by soft scale and slime by adding a specific chemical to the water system of a heat exchanger or piping system.

0002

BACKGROUND OF THE INVENTION In recent years, with the development of the chemical industry and other industries, large amounts of industrial water have become necessary. In addition to industrial tap water, seawater, lake water, marsh water, river water, and groundwater are used as sources of industrial water. Various types of microorganisms grow in these industrial waters, and some of these microorganisms are dependent on the quality of the water in which they exist.
Many of them continue to proliferate depending on the environment and cause various disorders. For example, when water is used for cooling, microorganisms that live in the water proliferate, trapping suspended solids, etc., and clinging to the walls of water facilities, forming slime, or causing soft scale. This can cause problems such as a decrease in heat exchange efficiency and poor water flow. In particular, in the case of open-type water circulation using an open cooling tower, the circulating water is forcibly aerated in a part of the system and comes into contact with air, and is exposed to sunlight. The growth of aerobic microorganisms such as bacteria and algae is encouraged. Similar problems have also occurred in cooling water systems installed with small cooling towers in air conditioning and heating and cooling facilities in buildings and factories.

[0003] Conventionally, physical cleaning methods such as jet cleaning and pig cleaning, or chemical cleaning methods using chemicals have been used to remove problems caused by dirt such as slime and soft scale. In particular, chemical cleaning methods can be cleaned without removing or dismantling the equipment, and can clean complex structures that are difficult to clean using physical cleaning methods, and can clean processes such as cooling water circulation lines all at once. Can be washed. Furthermore, it has many advantages, such as being able to be cleaned even while the device is in operation, and is used in a wide variety of ways. Oxidizing agents such as sodium subzinc oxide and hydrogen peroxide are generally used as slime removers in this chemical cleaning method, and hydrogen peroxide in particular decomposes into oxygen gas. It is widely used because it has the advantage of turning into water and becoming harmless. However, when cleaning and removing slime using such an oxidizing agent, for example, sodium subzinc chloride has the disadvantage that it has a weak slime removal effect on its own, is corrosive to metal materials, and significantly decomposes in aqueous systems. be. Further, in the case of hydrogen peroxide, it is easily decomposed in an aqueous system, and in order to sufficiently remove slime and the like, it must be added at a relatively high concentration, which is economically disadvantageous. In order to eliminate this drawback,
Several methods have been proposed that use hydrogen peroxide in combination with other agents. For example, the special public interest rate of 1973-1020
No. 4 proposes a method of removing slime using hydrogen peroxide and hydrazine. This method itself is an effective prescription that can reduce the concentration of hydrogen peroxide required for slime removal, but it is difficult to use as a single agent, and it is difficult to combine hydrazine, a reducing agent, and peroxide, an oxidizing agent. It is a combination with hydrogen and is dangerous to work with. Other methods have been proposed in which hydrogen peroxide is used in combination with an enzyme (catalase) or some type of bactericide, but the reality is that none of these are practically effective formulations.

[0004] The present invention provides a chemical cleaning method in which a sufficient effect can be obtained by using hydrogen peroxide at a low concentration, a synergistic effect is exerted in combination with hydrogen peroxide, and moreover, it can be used as a single agent. It is an object of the present invention to provide a cleaning method for removing slime and soft scale using a chemical combination of a synergist that is easy to operate, and highly safe.

[0005]

[Means for Solving the Problems] The present inventors investigated a chemical cleaning method from various aspects to achieve the above-mentioned purpose, and used hydrogen peroxide and a certain type of water-soluble cationic polymer. It has been found that this method is extremely effective and fully achieves the object of the present invention. By the way, the water-soluble cationic polymer used in the present invention is a product obtained by reacting an alkylene polyamine and/or a polyalkylene polyamine with epichlorohydrin or dichloroethyl ether, and has a molecular weight of 500 to 5.
A range of 0,000 is preferred. Such water-soluble cationic polymers are disclosed in, for example, JP-A-2-16909.
6, Special Publication No. 53-23377, Special Publication No. 55-49042
It is manufactured by the method described in et al. The water-soluble cationic polymer used in the present invention is known to be effective as an agent for preventing abnormal phenomena and bulking of activated sludge, as shown in the above-mentioned publications. It is also known that a reaction product (polymer) using N,N,N',N'-tetramethylethylenediamine is effective as an algaecide.

[0006] As a result of various studies conducted by the present inventors from the viewpoint of cleaning and removing stains caused by slime and soft scale, it was found that the water-soluble cationic polymer itself has no effect on removing slime adhering to the inner walls of pipes, etc. Although it is so low that it is almost impossible to put it to practical use, it has been found that when used in combination with hydrogen peroxide, it exhibits an excellent slime removal effect even at a low concentration of hydrogen peroxide. That is, the present invention relates to a cleaning method in which hydrogen peroxide and a water-soluble cationic polymer are added to a water system.

The water-soluble cationic polymer used in the method of the present invention does not cause foaming, which is observed in quaternary ammonium compounds conventionally used as microbial growth inhibitors, and can be added to water systems. ease of handling,
It has good workability, has good compatibility with hydrogen peroxide, and does not cause phenomena such as separation, and can be used as a single agent.

Specific compounds as alkylene polyamines and polyalkylene polyamines used in the production of the water-soluble cationic polymer that can be used in the present invention include ethylenediamine, N,N-dimethylethylenediamine, N,N' -dimethylethylenediamine, N,N
-diethylethylenediamine, propylenediamine, N
, N-dimethylpropylene diamine, N, N, N', N
'-Tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, tetramethylenepentamine, and the like. Among the water-soluble cationic polymers that can be used in the present invention, the most preferable compounds from a performance standpoint are N
,N,N',N'-tetramethylethylenediamine and epichlorohydrin or dichloroethyl ether. Poly[2-hydroxyethylene (dimethylimino)ethylene (dimethylimino)]
Methylene dichloride or poly[oxyethylene (dimethylimino) ethylene (dimethylimino) ethylene chloride].

[0009]

[Chemical formula 1]

0010

[Case 2]

[0011] In the method of the present invention, hydrogen peroxide and water-soluble cationic polymer may be added to the water system individually, or they may be blended in advance and added. Normally, it is convenient to use a mixture of the two in advance. When used as a mixture of both, the blending ratio is generally in the range of 10 to 50% by weight of hydrogen peroxide and 1 to 10% by weight of the water-soluble cationic polymer. The concentration of hydrogen peroxide added to the water system is 0.1 to 2% by weight.
, the water-soluble cationic polymer is preferably in the range of 0.01 to 0.5% by weight.

[0012] As the hydrogen peroxide in the present invention, in addition to so-called hydrogen peroxide, hydrogen peroxide adducts capable of producing hydrogen peroxide in service water, such as compounds such as sodium percarbonate and sodium perborate, can also be used. However, hydrogen peroxide is preferred from the viewpoint of compatibility with water-soluble cationic polymers, handling, workability, etc.

There is no need to worry about the corrosivity of the chemicals used in the method of the present invention to metals, but in addition to the above-mentioned essential components, if necessary, azole-based agents such as benzotriazole may be added to protect the copper material. There is no problem in using compounds, quaternary ammonium salts, quaternary imidazole salts, etc. as disinfectants, and the use of azole compounds is a preferred embodiment from the viewpoint of protecting the copper material during cleaning. EXAMPLES Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

[0014]

[Example] Example 1 Industrial water was passed through a glass cooling tower with a length of about 50 cm and a diameter of about 10 cm for 30 days, and slime was adhered to the inner wall of the corrugated pipe to be used as a test material. The adhered slime was sticky, with zooglaia as its main component, and suspended solids such as diatoms and earth and sand. The cooling tube with the slime attached was connected to a 2 liter beaker containing a predetermined concentration of chemicals via a circulation pump and washed for 2 hours.The slime removed in the beaker was filtered and dried at 110℃ to reduce its weight. I asked for it. The amount of slime attached at the start of the test was about 2.8 g. As the water-soluble cationic polymer, a 50% aqueous solution of poly[2-hydroxyethylene (dimethylimino) ethylene (dimethylimino) methylene dichloride] molecular weight 6,000 (hereinafter referred to as compound A) represented by the general formula (1), Poly[oxyethylene (dimethylimino) ethylene (
dimethylimino)ethylene chloride] molecular weight 5,000
A 50% aqueous solution of (hereinafter referred to as Compound B) was used, and these were mixed in advance in the proportions shown in the table and subjected to the test. The results are shown in Table 1.

[0015]
Table 1 Test mixture
Sly number ─
────────────────── Addition amount
Moisture removal Hydrogen peroxide Water-soluble polymer
(%) Amount (g) ──────────
──────────────────── ───
─ 1 60% Hydrogen peroxide 80% by weight Compound A 20% by weight 1
2.3 2 Same as above
Same as above
3 2.8 3
60% Hydrogen peroxide 50% by weight Same as above 1 2.
0 4 60% Hydrogen peroxide 50% by weight Compound A 20% by weight 3
2.5 5 60% hydrogen peroxide 7
0% by weight Compound B30% by weight 1
2.3 6 60% Hydrogen peroxide 50% by weight Same as above
2 2.7 ──────
────────────────────────
──── 7 Untreated area

- 0.1 (Note) If the total number of parts by weight is less than 100 when preparing a compounding agent, the remainder is water.

Example 2 A test similar to Example 1 was conducted. In this example, in addition to Compounds A and B, the following compounds were also used as water-soluble cationic polymers, and 60% hydrated hydrazine was used and added individually. The results are shown in Table 2. Reaction product of water-soluble cationic polymer N,N-diethyldiethylenediamine and epichlorohydrin (molecular weight 30.0
00) (hereinafter referred to as compound C) reaction product of diethylenetriamine and epichlorohydrin (molecular weight 10,00
0) (hereinafter referred to as compound D), a reaction product of N,N-dimethylpropylene diamine and dichloroethyl ether (
Molecular weight 8,000) (hereinafter referred to as compound E) Reaction product of triethylenetetramine and dichloroethyl ether (molecular weight 6,000) (hereinafter referred to as compound F)

0017
]
Table 2 Test Hydrogen peroxide Water-soluble polymer
slime number
Addition amount (%) ────────────
─ Removal amount (g)
Additive compound Addition amount (%) ────────
──────────────────────────
─ 1 0.1
Compound A 0.02
1.4 2 0.2
Compound B 0.05
1.8 3 0.5
Compound C 0.1
2.0 4
1.0 Compound D
0.2 2.4 5
1.5 Compound E
0.3 2.7
6 2.0 Compound F 0.5 2.8

Comparative Example 1 A test similar to Example 1 was conducted using hydrogen peroxide alone or a water-soluble cationic polymer alone. The results are shown in Table 3. As is clear from Table 3, the slime removal effect is extremely low when used alone. (Margin below)

[0019]
Table 3 Test

slime number
Additive drug and amount (%)
Amount removed (g) ──── ────
────────── ────────
1 hydrogen peroxide 0
．． 5 0.6 2
Same as above 1.
0 1.3 3
Same as above 3.0
2.6 4
Same as above 5.0
2.8 5
Compound A 0.5
0.3 6
Same as above 1.0
0.3 7
Compound B 1.0
0.2 8
Same as above 3.0
0.4 (Note) Hydrogen peroxide was used as 60% hydrogen peroxide, water-soluble cationic polymer was used as a 50% aqueous solution, and the amount added was expressed in pure content.

[0020]

Effects of the Invention As is clear from the above description, the present invention uses hydrogen peroxide and a water-soluble cationic polymer in combination to remove and clean stains caused by slime and soft scale. When used, unexpected synergistic effects can be obtained, and furthermore, even when hydrogen peroxide is added at a low concentration, it exhibits remarkable effects and has high industrial utility value.

Claims (1)

[Claims] [Claim 1] A cleaning method characterized by adding hydrogen peroxide and a water-soluble cationic polymer to a water system [
2. The method according to claim 1, wherein the water-soluble cationic polymer is an alkylene polyamine and/or a reaction product of a polyalkylene polyamine and epichlorohydrin or dichloroethyl ether. The ionic polymer is poly[2-hydroxyethylene (dimethylimino) ethylene (dimethylimino) methylene dichloride] or poly[oxyethylene (dimethylimino) ethylene (dimethylimino)
ethylene chloride], the method according to claim 1.