JPH0231894A - Agent for preventing scaling in cooling water system - Google Patents

Abstract

PURPOSE:To prevent the occurrence of scaling and to facilitate and operation at a high concn. by combining polyethylene glycol having mol.wt. in a specified range and an agent for preventing calcium scale. CONSTITUTION:Especially in a water-treating agent for open-type cooling water circulating system, phosphonic acid ester or salt of polyethylene glycol having 1,000-100,000mol.wt., 1-hydroxyethyliden-1, etc., and(or) carboxylic acid polymer having <= 100,000mol.wt. such as hydrolysate of maleic anhydride are contained. By this combination, the agent has remarkable synergistic effect on both calcium and silica scales in a cooling water system and prevents the occurrence of scaling even in the operation at a high concn.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a composite water treatment agent that has effects such as a scale inhibitor for a cooling water system, as well as anticorrosion and slime prevention, particularly for water treatment of an open circulation type cooling water system. Regarding drugs.

[Conventional technology]

With the development of industry in recent years, more and more water is being used, and it is particularly desirable to conserve cooling water, which is in high demand.

Therefore, an increasing number of water systems are forced to circulate cooling water in the chemical industry, petrochemical industry, etc., and cooling water in building air conditioners, etc., and are performing so-called highly concentrated operation to minimize the amount of blowdown water.

In such an open circulation cooling water system, calcium ions, magnesium ions, (bi)carbonate ions, silicate ions, etc. accumulate in the water, deposit and adhere to the pipes of the heat exchanger, and reduce heat exchange efficiency. This causes scale problems such as deterioration and blockage problems.

In general, the scales that occur in open circulation cooling water systems are calcium carbonate scale (hereinafter referred to as calcium scale), which is a combination of calcium ions and (bi)carbonate ions in water, and calcium scale, which is a combination of silica ions in water and mainly magnesium ions. It is broadly classified into silicic acid scale (hereinafter referred to as silica scale).

Conventional agents for preventing such scale damage include polymerized phosphates such as sodium hexametaphosphate, phosphonic acids such as -hydroxyethylidene-1,1-diphosphonic acid, hydrolysates of polymaleic anhydride, and polyacrylic acid. Carboxylic acid-based low molecular weight polymers such as soda are known.

Although these drugs have a considerable effect on calcium scale, they have almost no effect on silica scale, or may even have the opposite effect depending on the drug.

Furthermore, these drugs have the disadvantage that their effectiveness against calcium scale decreases when silicate ions are present in large amounts.

On the other hand, although no practically effective silica scale inhibitor has yet been published, several patents have been reported.

For example, JP-A-59-39397 proposes a compound having an alkylene oxide chain such as a polyethylene oxide chain or a polyethylene oxide-polypropylene oxide block polymer chain represented by the following formula.

General formula (A) General formula (B) HO-(C2H40) p-(CJJ), l-(C2
H3O), -H general formula (C) RO-(CzH40) p-H Furthermore, in JP-A-61-107997, molecular weight 2
Polyacrylamide or polymethacrylamide of 00 to io, ooo is described.

Furthermore, in Japanese Patent Publication No. 62-43758, General 2RI
-0-(RZ-0-). Polyoxyethylene esters and ethers represented by R3 are described.

All of these compounds are water-soluble nonionic polymers, but cationic compounds such as quaternary ammonium salts are also proposed in JP-A-57-11039 and JP-A-62-289297. has been done.

The reasons why the above-mentioned compounds have not yet reached the stage of practical use in cooling water systems are: (1) their effectiveness is insufficient; (2) they require a large amount to have a sufficient practical effect;
This is presumed to be due to the following reasons: (1) Even if silica scale alone is effective, its effectiveness decreases when calcium scale coexists.

Therefore, in the current concentration operation of the cooling water system, the amount of silicate ions in the circulating water is approximately 150pp, depending on the heat load of the heat exchanger.
The upper limit is m.

However, the water quality in Japan has a relatively high concentration of silicate ions, and especially when groundwater is used as a water source, the silicate ions in makeup water often reach 50 ppm or more. In cooling water systems that use such make-up water, highly concentrated operation cannot be performed to avoid silica scale problems, and the system is usually operated at a concentration factor of about 3, which poses problems in terms of water conservation. is the current situation.

[Problems to be solved by the present invention]

The present invention provides an agent that sufficiently prevents the formation of scale even when calcium ions and silicate ions are maintained at high concentrations in cooling water systems where both calcium scale and silica scale precipitate, and enables highly concentrated operation. The purpose is to provide.

[Means to solve the problem]

As a result of extensive research into water treatment chemicals that do not cause scale damage even when operating highly concentrated cooling water systems, the present inventors discovered that polyethylene glycol in a specific molecular weight range and conventional calcium scale inhibitors The present invention was created based on the recognition that a synergistic effect can be exerted by combining the two, and a remarkable effect can be obtained on both calcium scale and silica scale.

That is, the present invention relates to a cooling water-based scale inhibitor containing polyethylene glycol having a molecular weight of 1000 to 100,000, phosphonic acid or its salt, and/or a carboxylic acid polymer having a molecular weight of 100,000 or less. In addition, we have added anti-corrosion agents, anti-slime agents, etc.
It relates to a composite water treatment agent that also has effects such as preventing slime.

The molecular weight of the polyethylene glycol used in the present invention is preferably from i, ooo to ioo, ooo, and particularly preferably from 3,000 to 60,000.

If the molecular weight is less than 1,000, the desired effect will be extremely reduced. On the other hand, those having a molecular weight of 100,000 or more, for example, those having a molecular weight of 150,000 to 400,000, show considerable effects, but their high viscosity causes problems in formulation and is unsuitable for practical use.

As the phosphonic acid or its salt or the carboxylic acid polymer having a molecular weight of 100,000 or less used in the present invention, those conventionally used as calcium scale inhibitors can be used as they are.

For example, as phosphonic acids, amino(trimethylene)phosphonic acid, ■-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, 2-phosphonobutane-1,2,4- Examples include t-ricarboxylic acid and salts thereof.

In addition, examples of carboxylic acid polymers include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid,
Polymers of ethylene hydrocarbons having carboxyl groups such as fumaric anhydride, itaconic acid, and crotonic acid, or between these monomers or these monomers and other polymerizable vinyl monomers, such as acrylonitrile and acrylamide. , methacrylamide, vinyl acetate, styrene, styrene derivatives, ethylene, n-butylene, isobutylene and other copolymers, and hydrolysates or water-soluble salts of the above polymers or copolymers.

Particularly preferred are 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2
, 4-tricarboxylic acid, polymaleic anhydride hydrolyzate, and sodium bis(poly-2-carboxyethyl)phosphinate represented by the following general formula, etc.
When used in combination with polyethylene glycol, it exhibits a surprisingly excellent synergistic effect.

General Formula When adding the scale inhibitor of the present invention to a cooling water system, polyethylene glycol, phosphonic acids, and carboxylic acid-based polymers may be added separately, but they are usually added after blending these components in advance. It is convenient.

In the present invention, the blending ratio of the drug components depends on the concentration of calcium ions and silicate ions in the cooling water system, but usually the weight ratio of polyethylene glycol:phosphonic acids and/or carboxylic acid polymers is 0:90 to 90. 90:
10, preferably in the range of 2o:80 to 8o:20. This blending ratio is the same whether the phosphonic acids or carboxylic acid polymers are used alone or in combination. When phosphonic acids and carboxylic acid polymers are used together, the phosphonic acids and carboxylic acid polymers are each arbitrarily selected within the commonly used concentration range, but in the present invention, the weight ratio of the phosphonic acids and carboxylic acid polymers is usually 20:80-80:
It may be in the range of 20.

In the present invention, the amount of the scale inhibitor of the present invention as well as the composite water treatment agent that also has effects such as corrosion prevention and slime prevention added to the cooling water system depends on the water quality and operating conditions of the cooling water system, but -i. polyethylene glycol is 1 to 10
The amount is 0 ppm, preferably 5 to 20 ppm, and there is almost no effect at 1 ppI or less (20 ppm).
It has a remarkable effect up to about 20 ppm.
If it exceeds , a corresponding effect is observed, but no significant improvement in effect is observed. Furthermore, even if the amount exceeds 100 ppm, the effect remains unchanged and it is economically disadvantageous.

Phosphonic acids and carboxylic acid polymers may be added in amounts commensurate with the usual concentration of each drug.
Generally, the amount is 1 to 20 ppm, but due to its synergistic effect with polyethylene glycol, a considerable effect can be recognized even with a small amount added.

Generally, it is necessary for scale inhibitors to continuously maintain the effective concentration in an aqueous system, and even in the case of the scale inhibitor of the present invention, operational management is necessary to continuously maintain the above-mentioned effective concentration. It is preferable to do this.

The scale inhibitor of the present invention can be further added with agents having other functions to form a composite water treatment agent having the respective functions. For example, hydrazine hydrate, hydrazine salts, and other hydrazine compounds, and organic N-hydrazine compounds such as dimethyldithiocarbamate, which provide a slime-preventing effect.
3-based compounds, or azole compounds such as benzotriazole as a copper-based anticorrosive agent to impart anticorrosive effects, water-soluble zinc salts as an iron-based anticorrosive agent, etc., can be further blended to prevent various problems in cooling water systems with a single solution. It can be made into a composite water treatment agent that can prevent.

(Effects of the Invention) The scale inhibitor of the present invention exhibits remarkable effects on both calcium scale and silica scale in cooling water systems, enables high-concentration operation, and is a complex compound with other functions. It can also be used as a water treatment agent, and has extremely high industrial utility value.

〔Example] Next, the present invention will be specifically explained using examples.

In each example, the test was conducted using synthetic water equivalent to cooling water during high concentration operation, and the effect of preventing scale precipitation and scale adhesion was investigated.

Calcium chloride (CaCl z 2H□O) 6
Calcium hardness 2 using Fta magnesium (MgSO47H20), sodium hydrogen carbonate (Na) 1cOx), and sodium metasilicate (NazSiO39HzO)
80 ppm, magnesium hardness 280 ppm, H7
nt force') degree 600 ppm, SIJ force 350p
It was adjusted so that it was pm.

Scale precipitation prevention effect Test solution containing each drug added to the specified concentration was heated at 50°
After being allowed to stand for 48 hours at C, the solution was filtered and the dissolved calcium hardness and silica concentration in the filtrate were analyzed to determine the scale precipitation suppression rate.

Calcium scale precipitation Wk (ppm) = 280
(ppm) - Dissolved calcium hardness (ppm) Silica scale precipitation amount (ppm) = 350 (ppm) - Dissolved silica concentration (ppm) -
B Scale precipitation suppression rate (%) = X], OO
A = Amount of scale precipitation when no drug is added (ppm) B = Amount of scale precipitation when a drug is added (ppm) - Force! Two animals + L sound prevention test Test solution No. 32 containing each drug added to a predetermined concentration was placed in a beaker and stirred with a magnetic cooler.

A 300W copper pipe heater (heat transfer area: 1
4.4 cm”) to deposit scale on the heater surface.

The test liquid was circulated through cooling water so that the temperature inside the beaker was 35°C.

The test liquid was supplied and blown at a rate of 1β/hr to prevent the liquid from becoming cloudy, and the test time for one bite was 5 hours.

To remove attached scale, soak the heater in 5% hydrochloric acid.
The dissolved content was analyzed to calculate the calcium scale content, and the undissolved bone was scraped off and weighed to determine the silica scale content.
The scale adhesion prevention rate was calculated by converting the amount of adhesion per cm2.

X - Amount of adhesion when no drug is added (g/100cm") Y - Adhesion ffi when drug is added (g/100cm2) Example 1
and Comparative Example 1 The results of testing the combination effect of the polyethylene glycol of the present invention and phosphonic acids are shown in Table 1 (Part 1). For comparison, the effects of using polyethylene glycol or phosphonic acids alone were also tested, and the results are shown in Table 1 (Part 2).

The following compounds were used as phosphonic acids in this test.

Compound (A) -Amino (trimethylene)phosphonic acid compound (B) -4-hydroxyethylidene-1,1
-diphosphonic acid compound (C) - ethylenediaminetetramethylenephosphonic acid compound (D) -2-phosphonobutane-L2,4-
As is clear from Table 1 (Part 1) and Table 1 (Part 2) of tricarboxylic acids, although polyethylene glycol or phosphonic acids have almost no effect on silica scale when used alone, they have a significant effect when used together. A synergistic effect is demonstrated,
It can be seen that the effect on calcium scale is also significantly improved.

In addition, the molecular weight of polyethylene glycol is 3,000
It also turns out that a range of .about.60,000 is particularly suitable.

Example 2 and Comparative Example 2 The effect of the combination of the polyethylene glycol and carboxylic acid polymer of the present invention was tested. For comparison, the effect of using a carboxylic acid polymer alone was also tested. These results are shown in Table 2 (Part 1) and Table 2 (Part 2).

The carboxylic acid polymer used in this test was the following compound.

As is clear from Table 2 (Part 1) and Table 2 (Part 2) and Comparative Example 1 listed above, it can be seen that a remarkable synergistic effect is exerted by using polyethylene glycol and carboxylic acid polymer together. .

Comparative Example 3 The effect of combining polyethylene glycol with a phosphonic acid or a carboxylic acid polymer when the molecular weight was less than 1.000 and more than 100,000 was tested. The results are shown in Table 3.

As can be seen from Table 3, when the molecular weight of polyethylene glycol is less than 1,000, almost no effect is observed, and when the molecular weight exceeds 100,000, it is somewhat effective, but the effect tends to decrease. I can see that.

In addition, high molecular weight materials have high viscosity, making them difficult to handle and impractical.

Example 3 The combined effect of polyethylene glycol, phosphonic acids, and carboxylic acid-based polymers was tested. This result is the fourth
Shown in the table.

As is clear from the results in the table, it can be seen that the combined use of polyethylene glycol, phosphonic acids, and carboxylic acid polymers also exhibits remarkable effects.

Claims (1)

Scope of Claims: (1) Cooling water system scale prevention characterized by containing polyethylene glycol with a molecular weight of 1000 to 100,000, phosphonic acid or its salt, and/or a carboxylic acid polymer with a molecular weight of 100,000 or less agent. (2) Polyethylene glycol with a molecular weight of 1000 to 100,000 and phosphonic acid or its salt and/or a carboxylic acid-based polymer with a molecular weight of 100,000 or less,
The scale inhibitor according to claim 1, which is blended in a blending ratio of 10:90 to 90:10 (weight ratio). (3) Phosphonic acid or its salt is 1-hydroxyethylidene-
1,1-diphosphonic acid, 2-phosphonobutane-1,2,
The scale inhibitor according to claim 1, which is 4-tricarboxylic acid or a salt thereof. (4) Claim 1, wherein the carboxylic acid polymer is a hydrolyzate of polymaleic anhydride, sodium bis(poly-2-carboxyethyl)phosphonate represented by the following general formula:
The scale inhibitor according to Items 1 and 2. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (5) Polyethylene glycol with a molecular weight of 1,000 to 100,000 at a concentration of 1 to 100 ppm, phosphonic acid or its salt and/or a molecular weight of 100,000
1. A method for preventing scaling in a cooling water system, which comprises causing a carboxylic acid polymer having a concentration of 1 to 20 ppm to exist in the cooling water. (6) It is characterized by blending polyethylene glycol with a molecular weight of 1,000 to 100,000, a phosphonic acid or its salt and/or a carboxylic acid polymer with a molecular weight of 100,000 or less, and a slime inhibitor and/or anticorrosion agent. A cooling water-based composite water treatment agent.