JPS5995998A - Scale preventing agent - Google Patents

Abstract

PURPOSE:To provide a scale preventing agent which suppresses effectively the formation of scale due to Zn<2+> ion with the concn. lower than for the case in which an acrylic acid polymer or its water soluble salt and >=1 kinds among phosphonic acid, alpha-aminocarboxylic acid or the water soluble salt thereof are used alone. CONSTITUTION:An acrylic acid polymer (e.g.; acrylic acid homopolymer) or its water-soluble salt (e.g.; Na salt) (component A) is prepd. The mol.wt. of the polymer is usually 500-300,000, more particularly 1,000-50,000. On the other hand, >=1 kinds among phosphoric acid (e.g.; aminotrimethyl phosphonic acid), alpha-aminocarboxylic acid or the water-soluble salt thereof (component B) are prepd. The component A and the component B are combined at a compounding ratio of 95:5wt%-5:95wt%, whereby an intended scale preventing agent is obtd. The formation of the scale due to Zn<2+> is effectively suppressed if such scale preventing agent is added to object water such as boiler feed water.

Description

[Detailed Description of the Invention] Conventionally, galvanized steel pipes (steel pipes whose inner surface is galvanized) have been used for water piping for the purpose of corrosion prevention, but recently they have been used for boiler restoration because they are easily available. It has also come to be widely used in water recovery systems.

However, when this piping is used in a boiler condensate recovery system, the following problems arise due to the action of zinc ions eluted into the water.

After the oil crisis, as part of energy-saving measures, increases in condensate recovery rate and concentration ratio (usually 1
0 to 15 times), but at this time, condensate containing a large amount of eluted zinc ions is supplied as water supply again, and the blow rate is set low (high concentration rate). Zinc ions react with silica and the like present in the water supply to produce scales such as zinc silicate, basic zinc carbonate, and zinc hydroxide, which adhere in large quantities to the inside of the boiler. As a result, there is a risk that all sorts of disadvantageous situations may occur, such as a reduction in heat exchange efficiency, blockage of piping, and explosion due to blockage of the heat exchanger. Similar problems have also been observed in boiler piping made of conventionally used zinc-containing alloys (eg, aluminum brass).

Therefore, when galvanized steel pipes or zinc-containing alloy steel pipes are applied to boiler condensate recovery systems, the above-mentioned disadvantages must be solved. The reality is that there are no effective drugs to suppress school outbreaks.

An object of the present invention is to provide a novel scale inhibitor that can be added to target water such as boiler feed water to suppress the formation of scale caused by zinc ions in the water system.

The present invention provides an acrylic acid polymer or a water-soluble salt thereof (5)
and one or more compounds selected from the group consisting of phosphonic acid, α-aminocarboxylic acid, or a water-soluble salt thereof This is a scale inhibitor for aqueous systems including piping.

The scale inhibitor according to the present invention comprises one or two selected compounds consisting of an acrylic acid polymer or a water-soluble salt thereof and a phosphonic acid, an α-aminocarboxylic acid, or a water bathable salt thereof. It is characterized in that by using these two or more compounds in combination, an effective scale prevention effect can be obtained at a lower concentration than when each is used alone.

Specific examples of the polymer of the present invention include acrylic acid homopolymer, acrylic acid-maleic acid copolymer, and acrylic acid-7-malic acid copolymer. Examples of these water-soluble salts include sodium salts, potassium salts, and ammonium salts. When the polymer is a copolymer, the amount of acrylic acid present in the molecule is usually 10% or more, preferably 30 to 7% in molar ratio to other structural units.
The range is 0%. If it is less than 10 inches, the dispersion effect on zinc-based scale deteriorates.

The molecular weight of the above polymer is usually 500 to 300.00.
0, preferably i,ooo to 50.000.

Especially in the case of acrylic acid homopolymer, 10D00~
50.000 is preferred. When the molecular weight is outside the above range, the dispersion effect on zinc-based scale deteriorates.

The phosphonic acid or its water-bathable salt of the present invention has the following formulas (1), (ff), (iii),
A compound or salt represented by (IV) is exemplified.

Formula (I): 20 11 (wherein, X1 to X3 and Y, to Y3 each may be the same or different and represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; Z1 to Zo are , each of which may be the same or different, including hydrogen atom, alkali metal atom, and ammonium. .

(1) Aminotrimethylphosphonic acid and its sodium, potassium, and ammonium salts (2) Aminodimethylphosphomonoethylphosphonic acid and its sodium, potassium, and ammonium salts Formula (■): [In the formula,) ζ, ■ (2 and melon , each λ, may be the same or different, and the following group (A): (X, , Y,
, Z, and Z2 have the same meanings as in the above formula (I). ); ■ (3 is the above-mentioned group (5), carbon number 1-5
represents a lower alkyl group; n represents all integers from 1 to 3; ] Examples of the phosphonic acid or water-soluble salt thereof represented by the above formula (n) include the following.

(1) Ethylenediaminetetramethylphosphonic acid and its sodium, potassium, and ammonium salts (2) Diethylenetriaminepentamethylphosphonic acid and its sodium, potassium, and ammonium salts (3) Triethylenetetraaminehexamethylphosphonic acid and its sodium, potassium, and ammonium salts Formula ( ill) : (In the formula, X represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; Y represents a hydrogen atom, a lower alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or ammonium; Z1 to Z4 are the above-mentioned It has the same meaning as in the case of formula (I).) Examples of the phosphonic acid or its water-soluble salt represented by the above formula (fit) include the following.

(1) Hydroxyethylidene diphosphonic acid and its sodium, potassium, ammonium salts (2) Hydroxypropylidene diphosphonic acid and its sodium,
Potassium, ammonium salt formula (~): 02゜ (wherein, Re may be the same or different, and represents a hydrogen atom, a lower alkyl group having 1 to 5 carbon atoms, or a carboxyl group: X1 to X3 and 2., 22 have the same meanings as in the above formula (I).) Examples of the phosphonic acid or water-soluble salt thereof represented by the above formula are as follows.

(1) 1,2.4-)lycarboxybutane-2-phosphonic acid and its sodium and potassium.

Ammonium salt (2) 1,2-dicarboxybutane-2-phosphonic acid and its sodium, potassium, and ammonium salts (3) 1,2,4-)dicarboxyhexane-1-phosphonic acid and its sodium, potassium, and ammonium salts Salts Examples of the α-aminocarboxylic acids or water-soluble salts thereof of the present invention include compounds or salts represented by the following formulas (V) and (Vl).

Formula (V): (wherein, Xl and X2 may be the same or different, H, -○) 12-CH2-OH or -CH2-
C00Z2 Fully clothed; Z, , Z, , is (1) above
It has the same meaning as the expression. > The α-aminocarboxylic acid represented by the above formula (V) or its water-soluble salt is aminoacetic acid.

Examples include iminodiacetic acid, N-(β-hydroxyethyl)-aminodiacetic acid, N,N-di(β-hydroxyethyl)-glycine, nitrilotriacetic acid, or their sulfur, lium, potassium, or ammonium salts.

Formula (Vl): (In the formula, X, , X, , X3 and X4 may be the same or different, and -CH2-CH2-OH
.

-CH2-C00Z, and n &-11~3 (
7) Represents an integer, and Zl has the same meaning as in the above formula (I). ) The α-aminocarboxylic acid represented by the above formula (Vl) or its water-bathable salt includes ethylenediaminetetraacetic acid, N-(β-hydroxyethyl)-ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, or the like. Examples include sodium, potassium, and ammonium salts.

Acrylic acid polymer or its water-soluble salt and phosphonic acid,
The blending ratio of one or more compounds selected from the group consisting of α-ami7carpone or their water-soluble salts is (A):(B) ~95:5% by weight ~5: 95% by weight
Preferably (to): (average = 95:5% by weight to 50:50
Weight%. If this blending ratio deviates from this range,
A desirable scale prevention effect may not be obtained.

These drugs are dissolved in water VC to form an aqueous solution, either individually or in combination, and added to the target aqueous system. Also, corrosion,
The inhibitor of the present invention may be added to an aqueous system to which additives commonly used to adjust scale, sludge, pH 1 hardness, etc., such as hydrazine, sodium hydroxide, and phosphoric acid, are added. Even in this case, the effect of the inhibitor of the present invention is not impaired in any way.

The inhibitor of the present invention exhibits a scale prevention effect when added in a predetermined amount to target water. The amount added varies depending on the zinc concentration in the water, but is usually 0.1 to 11,000 p1. Preferably it is set in the range of 10 to 100 degrees. If it is less than 0.14, the effect will be insufficient, and if it exceeds 100011, the scale prevention effect will hardly change and it will become uneconomical.

The inhibitory effect of the inhibitor of the present invention on scale formation is presumed to be mainly due to the dispersion effect of the acrylic acid polymer and the sequestration effect of zinc ions through chelate formation of phosphonic acid and α-aminocarboxylic acid. Ru.

The target water system of the present invention is a boiler water system, but it is obvious that it can be used in any other system as long as zinc is present in the water and zinc-based scale is a problem. Probably.

By using the scale inhibitor of the present invention, it becomes possible to sufficiently suppress the production of Seikool caused by zinc ions in an aqueous system. Moreover, even when used in the temperature range of 180 to 250°C, the effect of suppressing scale formation is stably exhibited, so even if energy-saving operation such as high concentration operation of the boiler is performed, various types of permanent installation due to scale will be prevented. This will be avoided, and its industrial value is extremely large.

Examples are given below to clarify the effects of the scale inhibitor of the present invention.

Example A test was conducted under the test boiler conditions of a pressure of 10 kyfβ, a temperature of 180°C in summer, a retained water volume of 4.75 kg, and a blowing water volume of 1-16 kg/hr. The amount of scale was measured.

All soft water is used as boiler water supply, and the water quality of boiler water is adjusted to pH.
1tO~11.5 (sodium hydroxide), total 7 concentration 330~390fQa, total zinc concentration 14~15111X
When the boiler was operated for 45 hours with the concentration set to 13 times and without adding scale inhibitor, the result was 62.7V1.
scale was adhered to the inside of the test tube. Analysis of this scale revealed that the majority of power Zn, (OH), 5
It's i207/H2O.

Next, the same test as above was conducted by adding 70 to 75 ppm of the school preventive agent according to the present invention listed in Table 1 to the aqueous system. The results are shown in Table IVC. As a comparative example, Table 2
A test similar to the above was performed by adding the school preventive agent described above alone to an aqueous system, and the amount of scale adhesion was approximately 3 nV;
(/i: The amount of addition required to maintain the concentration was determined. The results are shown in Table 2. However, A in the table is sodium polyacrylate (molecular weight approximately 25.000) B ht 7 lyric acid - maleic acid Cobo IJ Mer (molecular weight 4,000) C
is ethylenediaminetetramethylphosphonic acid, 2-hydroxyethyl 1゜2-diphosphonic acid, E is aminotrimethylphosphonic acid, F is ethylenediaminetetraacetic acid, G
represents nitrilotriacetic acid; H represents N-(β-hydroxyethyl)-aminodiacetic acid;

From Tables 1 and 2, it can be seen that the scale inhibitor of the present invention containing a blend of acrylic acid polymer and phosphonic acid or α-aminocarboxylic acid has a very remarkable synergistic effect despite the small amount of calories added. It can be seen that a good scale prevention effect can be obtained. Furthermore, it can be seen that if an attempt is made to obtain an effect equivalent to that obtained by the scale inhibitor of the present invention using each component alone, the amount to be added will exceed the practical limit.

Table-15 Ken-2 (ratio@) Patent applicant Kurita Industries Co., Ltd.

Claims (1)

[Claims] (1) Acrylic acid polymer or water-soluble salt thereof (8)
and one or more compounds (B) selected from the group consisting of phosphonic acid, α-aminocarboxylic acid, or a water-soluble salt thereof. An anti-scaling agent for water systems including piping. (2) The scale inhibitor according to claim 1, wherein the polymer is an acrylic acid homopolymer. (3) The scale inhibitor according to claim 1, wherein the polymer is a copolymer of acrylic acid and maleic acid or hexamaric acid. (4) The scale inhibitor according to any one of claims 1 to 3, wherein the polymer has a molecular weight of 500 to 300,000. (5) The scale inhibitor according to any one of claims 1 to 4, wherein the phosphonoic acid is aminotrimethylphosphonic acid. (6) The phosphonic acid is 2-hydroxyethyl-1
, 2-diphosphonic acid according to any one of claims 1 to 4. (7) The scale inhibitor according to any one of claims 1 to 4, wherein the phosphonic acid is ethylenediaminetetramethylphosphonic acid. (8) The scale inhibitor according to any one of claims 1 to 7, wherein the α-aminocarboxylic acid is ethylenediaminetetraacetic acid. (9) The scale inhibitor according to any one of claims 1 to 7, wherein the α-aminocarboxylic acid is nitrilotriacetic acid. (6) The scale inhibitor according to any one of claims 1 to 7, wherein the α-aminocarboxylic acid is N-(β-hydroxyethyl)-aminoacetic acid. (B) Claim 1 in which the water system is a boiler water system
The scale inhibitor according to any one of items 1 to 10.