JPH054096A - Calcium-based scale preventive - Google Patents

Abstract

PURPOSE:To use a calcium-based scale preventive even in a river system having a heat transfer part by preparing a preventive for preventing generation of calcium carbonate scale formed in the various river systems having calcium hardness by organophosphonic acid and a water-soluble acrylic acid-based copolymer or the like. CONSTITUTION:This calcium-based scale preventive is prepared by (a) organophosphonic acid or its salt having scale inhibiting action, (b) a binary or more water-soluble acrylic acid-based or maleic acid-based copolymer which is constituted of vinyl monomer having carboxyl group or of at least two kinds of monomer units consisting of both vinyl monomer having the other polar group and the same and (c) citric acid or its salt. As the blending rate (as weight ratio) of the above respective components (a)-(c), when the component (a) is set to 1, the component (b) is set to 0.4-20. When the total amount of the components (a) and (b) is set to 1, the component (c) is set to 0.3-3.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a calcium-based scale inhibitor. More specifically, it relates to agents useful for preventing the formation of calcium carbonate-based scale that can occur in various water systems having calcium hardness.

[0002]

2. Description of the Related Art In various industrial water systems, especially boiler water systems and cooling water systems, calcium-based scales mainly composed of calcium carbonate produced by hardness components and dissolved carbonates in water, especially such calcium-based scales, are used for heat transfer in the various water systems. Since it is deposited on the surface and causes a decrease in its heat transfer efficiency, it is desired to prevent or suppress it as much as possible. From this point of view, conventionally, agents that are added to the above water system to prevent or suppress the generation of calcium-based scale are known as so-called scale inhibitors. Further, as such scale inhibitors, various chemical agents including, for example, polyacrylic acid type copolymers, organic phosphonic acids, organic chelating agents and the like have been proposed for a long time.
Then, recently, focusing on the scale prevention efficiency, it has been proposed to use a certain organic phosphonic acid in combination with a specific water-soluble organic binary copolymer having a carboxyl group and a sulfonate group. 1-41400).

[0003]

In an industrial water system such as a cooling water system, recently, from the viewpoint of effective use of water, the frequency of circulation and reuse increases, that is, a higher concentrated water is used. There is a tendency. And in such highly concentrated water, the calcium hardness becomes extremely high,
It often happens that the concentration exceeds 0 ppm. (Hereinafter,
Hardness is expressed in ppm in terms of calcium carbonate. ) In such highly concentrated water, when the above-mentioned conventional scale inhibitor is added, the scale-preventing effect is likely to be insufficient, and in particular, the addition of calcium of the order of several ppm to several tens of ppm is usually used. It was difficult to effectively prevent scale in a concentrated water system having a hardness exceeding 300 ppm.

On the other hand, in the cooling water system and the boiler water system, the amount of heat transfer in the heat transfer section tends to be increased in order to improve the heat exchange efficiency. Then, as the amount of heat transfer increases, the amount of calcium carbonate-based scale generated also significantly increases, increasing the frequency of scale failure. And such a system with a large amount of heat transfer (for example, 300,000 Kcal / m ² ·
(h or more), even when water having a relatively low calcium hardness was used, the scale preventive effect of the conventional scale inhibitors was lowered, and it was difficult to prevent scale disorders. The present invention has been made under such circumstances, and in particular, a scale capable of exhibiting an excellent scale-preventing effect even in a water system using highly concentrated water and a water system having a large heat transfer portion. It is intended to provide an inhibitor.

[0005]

Thus, according to the present invention, (a) an organic phosphonic acid having a scale-inhibiting action or a salt thereof, and (b) a vinyl monomer having a carboxyl group or another polar group are contained. A binary or more water-soluble acrylic acid-based or maleic acid-based copolymer composed of two or more kinds of monomer units composed of a vinyl monomer,
(C) A calcium-based scale inhibitor comprising citric acid or a salt thereof is provided.

According to the present invention, when an organic phosphonic acid-based scale inhibitor is used in combination with a water-soluble acrylic acid-based or maleic acid-based copolymer, by further adding citric acid, the scale-preventing effect is remarkably improved. However, it is based on the discovery of the fact that an excellent scale preventing effect can be stably exhibited even under a severe environment such as the above-mentioned high hardness and high heat transfer. Since citric acid itself does not have a scale-preventing action, the above findings are surprising.

Examples of the organic phosphonic acid or its salt (a) used in the present invention include ethylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid, methylenediphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, 1 , 1-aminoethanediphosphonic acid, 1,1-hydroxypropanediphosphonic acid, 1,1-hydroxybutanediphosphonic acid, 1,1-aminobutanediphosphonic acid,
Aminotrimethylenephosphonic acid, aminotriethylenephosphonic acid, ethylenediaminetetramethylphosphonic acid,
Hexamethylenediamine tetramethylphosphonic acid, diethylenetriamine-pentamethylphosphonic acid, 2-phosphonoacetic acid, 2-phosphonopropionic acid, 2-phosphonosuccinic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid and the like can be mentioned. As a particularly preferred example, 2-
Examples include phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid or aminotrimethylenephosphonic acid. As the salt, alkali metal salts such as sodium salt and potassium salt, ammonium salt and the like are suitable.

The water-soluble acrylic acid-based or maleic acid-based copolymer used in the present invention is composed of two or more kinds of monomer units consisting of a vinyl monomer having a carboxyl group or a vinyl monomer having another polar group. It is a binary or more copolymer. Here, as the vinyl monomer having a carboxyl group, the following formula (I):

[0009]

[Chemical 1] (In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a hydrogen atom,
A methyl group or a carboxyl group; when R ₂ is a carboxyl group, it may combine with an adjacent carboxyl group to form an anhydride ring).
Specific examples of these monomers include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and fumaric acid. These may be in the form of salts such as sodium salts.

On the other hand, as the vinyl monomer having another polar group, the following formula (II):

[0011]

[Chemical 2] Wherein, R ₃ is a hydrogen atom or a methyl group, R _{4 is: -COOR 5 SO 3 H, -COOR} 5 OH -CONHR 5 SO 3 H, -CONHR 5 OH, -R 5 SO 3 H, -C 6 H ₄ —SO ₃ H, or —R ₅ O (R ₆ O) _n H (wherein, R ₅ is a C _1-6 alkylene group, and R ₆ is C _1-3.
Alkylene group: n is 0 to 100)]. These may also be in the form of salts, for example sodium salts. Specific examples of the monomer of formula (II) include sulfoethyl acrylate,
Examples thereof include methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, polyethylene glycol monoallyl ether, styrene sulfonic acid, 2-hydroxyethyl acrylate, and N-methylol acrylamide.

The water-soluble acrylic acid-based or maleic acid-based copolymer (b) used in the present invention is a copolymer comprising two or more kinds of the above-mentioned monomer of the formula (I) or the monomer of the formula (I) and the formula: A copolymer composed of two or more kinds of the monomer (II) is included. Specific examples thereof include (meth) acrylic acid-sulfoethyl acrylate copolymer, (meth) acrylic acid-methallyl sulfonic acid copolymer, (meth) acrylic acid-2-acrylamido-2-
Methyl propane sulfonic acid copolymer, (meth) acrylic acid-polyethylene glycol monoallyl ether copolymer, acrylic acid-methacrylic acid copolymer, maleic acid-
Styrene sulfonic acid copolymer, acrylic acid-acrylic acid 2-hydroxyethyl copolymer, methacrylic acid-N-
Methylol acrylamide etc. are mentioned. The molecular weight of these is not particularly limited, but usually about 500 to 20,000 is suitable, and the copolymerization ratio may be adjusted so that the carboxyl group-containing unit is contained at least 30 mol% or more.

On the other hand, as the salt of citric acid as the component (c) used in the present invention, alkali salts such as sodium, potassium and ammonium are suitable. The scale inhibitor of the present invention contains the organic phosphonic acid component (a), the water-soluble acrylic acid-based or maleic acid-based copolymer (b) and the citric acid component (c), and these components are usually added. It is prepared as an aqueous solution containing. However, it may be in the form of powder. Of course, other known additives (for example, other scale-inhibiting components, corrosion-inhibiting components, slime-inhibiting components) may be contained as long as the effects of the present invention are not impaired.

Here, the blending ratio (as a weight ratio) of the above components (a) to (c) is 0.4 to 20 (more preferably 1.0 to 1.0) for the component (a) with 1 being the component (a). 10), and the component (c) is 0.3 to 3.0 (more preferably 0.5 to 2.0) with the total amount of the components (a) and (b) being 1.
It is preferable to adjust so as to obtain a synergistic effect. Particularly considering the synergistic effect and the economic effect, a particularly preferable mixing ratio of the component (a) and the component (b) is 1: 1.0 to 3.
It is 0.

When the component (a) is 1 and the component (b) is less than 0.4 or greater than 20, or the total amount of the components (a) and (b) is 1, the component (c) is mixed. If it is less than 0.3 or greater than 3, a synergistic effect is not exhibited and the scale preventing effect is not sufficient, which is not preferable.

Also, in place of the citric acid or the salt thereof as the component (c), tartaric acid, gluconic acid, malic acid or a salt thereof, which is another oxycarboxylic acid, may be used in the above-mentioned blending ratio to obtain a good scale preventing effect. I can't get it.

The addition amount of the scale inhibitor of the present invention is not particularly limited, but it is usually suitable to select it in the range of 5 to 100 ppm as the total amount of the active ingredients.
For example, an aqueous system with Ca hardness exceeding 300 ppm (usually
Even in highly concentrated water), a sufficient scale-inhibiting effect can usually be obtained with an addition amount of about 20 to 60 ppm, and in an aqueous system having a heat transfer amount of more than 300,000 Kcal / m ² · hr, usually 5 to A desired scale preventing effect can be obtained with an addition amount of about 50 ppm. The scale inhibitor of the present invention is particularly suitable for a highly concentrated cooling water system having a Ca hardness of more than 300 ppm and a heat transfer amount of 300,000 Kcal / m ² ·.
It is used to prevent adhesion of calcium-based scales such as cooling water heat exchangers that exceed hr and cooking cattle in pulp and paper mills.

【Example】

Example 1

[0019]

[Table 1] As the component (a) of the present invention, 2-phosphonobutane-
1,2,4-tricarboxylic acid (hereinafter, PBTC), 1-
Hydroxyethylidene-1,1-diphosphonic acid (hereinafter H
EDP) or aminotrimethylene phosphonic acid (hereinafter referred to as A
MP), the water-soluble acrylic acid or maleic acid copolymer shown in Table 1 above as the component (b), and citric acid or sodium citrate as the component (c). Dissolve in pure water with the mixing ratio shown in the example,
An aqueous solution having a solid content of 30%, which is an example of the present invention, was prepared. In addition, as a comparative example, each component shown in the comparative example of Table 3 was dissolved in pure water in each mixing ratio to prepare an aqueous solution agent of the comparative example. A prescribed amount of the above-mentioned preparation was added to each test water, and the effect of preventing calcium carbonate scale was evaluated by a double tube test using the inner tube as a heat transfer surface. The results are shown in Comparative Example and Table 3. In the table, mcm is the scale adhesion rate (mg / c
m ² · month). Table 2 shows the water quality of the test water used.

[0020]

[Table 2] *: Converted to calcium carbonate The test conditions are as follows. ○ Test water water temperature 40 ° C ○ Heat transfer amount 30,000 Kcal / m ² · hr ○ Test water flow rate 0.5 m / s ○ Test period 120 hr The results are shown in Table 3 together with the comparative examples. In the table, mc
m means a scale deposition rate (mg / cm ² · month).

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

[Table 6] Note) PBTC: 2-phosphonobutane-1,2,4-tricarboxylic acid HEDP: 1-hydroxyethylidene-1,1-diphosphonic acid AMP: aminotrimethylenephosphonic acid

As described above, it is understood that the scale inhibitor of the present invention exhibits an excellent scale inhibiting effect. In particular, since the effects of Comparative Examples 14 to 16 in which other oxycarboxylic acid is used instead of citric acid are insufficient, the effect of the present invention by using citric acid is recognized as a selective and exceptional effect. .

Example 2 The scale inhibitor of Example No. 4 in Table 3 was used, the same test conditions as in Example 1 and the following water quality were used, except that the Ca hardness was 100, 200, 300, 400, 500 and 600.
The scale adhesion test was carried out by changing to ppm.

[0027]

[Table 7] * Converted to calcium carbonate Test conditions ○ Test water temperature 40 ℃ ○ Heat transfer 30,000Kcal / m ² · hr Test water flow rate 0.5m / s Test period 120hr

The results are shown in FIG. In the figure, ● is blank, ○ is HEDP only (30 ppm), ☆ is P
BTC (30 ppm) and Δ are data for the scale inhibitor of the present invention (30 ppm).

As described above, it can be seen that the scale preventive agent of the comparative example has an insufficient scale preventive effect from the time when the Ca hardness exceeds 200 ppm, and the scale preventive effect is halved in the range exceeding 300 ppm. On the other hand, according to the scale inhibitor of the present invention, 300 pp
It can be seen that the excellent calcium-based scale prevention effect continues to be expressed even in high hardness water exceeding m.

Example 3 In the same manner as in Example 1, a scale adhesion test was carried out by a heater-type circulation device in a system with a high heat transfer surface under the water quality shown in Table 5 and the following conditions.

[0031]

[Table 8] * Converted to calcium carbonate Test conditions ○ Test water temperature 50 ℃ ○ Heat transfer amount 500,000 Kcal / m ² · hr Test water flow rate 0.5 m / s Test period 120 hr

The results are shown in Table 6 together with the comparative examples.
As described above, it is understood that the excellent scale preventive effect of the scale inhibitor of the present invention is obtained even in an aqueous system having a large amount of heat transfer.

[0033]

[Table 9]

[0034]

[Table 10]

[0035]

[Table 11] * PAa: sodium polyacrylate * PMa: polymaleic acid Note) PBTC: 2-phosphonobutane-1,2,4-tricarboxylic acid HEDP: 1-hydroxyethylidene-1,1-diphosphonic acid AMP: aminotrimethylenephosphonic acid

Example 4 In the same manner as in Example 3, a scale adhesion test was conducted under the water quality shown in Table 7 and the following conditions.

[0037]

[Table 12] * Converted to calcium carbonate Test conditions ○ Test water temperature 50 ° C 〇By changing the temperature of the heater, the scale deposition rate at various heat transfer rates was measured. Test water flow rate 0.5m / s Test period 120hr

The results are shown in FIG. In the figure, ● indicates blank, ○ indicates HEDP alone, ☆ indicates PBTC alone, and Δ indicates scale inhibitor of Example No. 14 in Table 6. Thus, the amount of heat transfer is 200,000 Kcal / m ² · h
In a system having a high heat transfer area for r, the scale preventive effect by HEDP or PBTC is insufficient, but the scale inhibitor of the present invention has an excellent calcium scale preventive effect even in such a severe system. It can be seen that is stably expressed.

[0039]

According to the calcium-based scale inhibitor of the present invention, it is possible to prevent the generation of calcium scale in a harsh water system having a high Ca hardness or a high heat transfer amount. Therefore, according to the calcium-based scale inhibitor of the present invention, it is possible to easily prevent damage due to calcium scale in various water systems.

[Brief description of drawings]

FIG. 1 is a graph showing a scale prevention effect of various kinds of Ca hardness by the calcium scale inhibitor of the present invention in comparison with a comparative example.

FIG. 2 is a graph showing a scale prevention effect of the calcium scale inhibitor of the present invention at various heat transfer amounts, in comparison with a comparative example.

[Explanation of symbols]

● Blank HEPD ☆ PBTC △ Scale inhibitor of the present invention

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location C08K 5/42 C08L 33/02 LHR 7242-4J 33/14 LHY 7242-4J 35/00 LHY

Claims (9)

[Claims] 1. Two or more kinds of monomer units each comprising (a) an organic phosphonic acid having a scale-inhibiting action or a salt thereof, and (b) a vinyl monomer having a carboxyl group or a vinyl monomer having another polar group. A calcium-based scale inhibitor comprising a binary or more water-soluble acrylic acid-based or maleic acid-based copolymer composed of (c) and (c) citric acid or a salt thereof. 2. The blending ratio (as a weight ratio) of the components (a), (b) and (c) is such that the component (a) is 1 and the component (b) is the same.
Is 0.4 to 20, and the component (c) is 0.3 to 3.0 with the total amount of the components (a) and (b) being 1, and the scale inhibitor according to claim 1. 3. The blending ratio (as a weight ratio) of the components (a), (b) and (c) is such that the component (a) is 1 and the component (b) is the same.
Is 1.0 to 10, and the component (c) is 0.3 to 3.0 with the total amount of the components (a) and (b) being 1, and the scale inhibitor according to claim 1. 4. The blending ratio of the components (a), (b) and (c) (as a weight ratio) is such that the component (a) is 1 and the component (b) is 1.
Is 1.0 to 3.0, and the component (c) is 0.5 to 2.0 with the total amount of the component (a) and the component (b) being 1, and the scale inhibitor according to claim 1. 5. The organic phosphonic acid having a scale inhibiting effect is 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid or aminotrimethylenephosphonic acid. Scale inhibitor. 6. The copolymer of component (b) has an average molecular weight of about 500 to 100,000, and the carboxyl group-containing unit of the copolymer is at least 30 mol% or more. The scale inhibitor described in. 7. The copolymer of component (b) is acrylic acid-sulfoethyl acrylate, acrylic acid-methallyl sulfonic acid, acrylic acid-2-acrylamido-2-methylpropane sulfonic acid, acrylic acid-polyethylene glycol monoallyl. The scale inhibitor according to any one of claims 1 to 6, which is ether, acrylic acid-methacrylic acid, maleic acid-styrene sulfonic acid, acrylic acid-2-hydroxyethyl acrylate or methacrylic acid-N-methylol acrylamide. 8. The scale inhibitor according to claim 1, which is used in an aqueous system having a calcium hardness of 300 ppm or more. 9. The scale inhibitor according to claim 1, which is used in a cooling water system having a heat transfer surface having a heat transfer amount of 300,000 Kcal / m ² · hr or more.