JP4634780B2 - Scale inhibitor and scale prevention method - Google Patents

Description

  The present invention relates to an aqueous scale inhibitor and a scale prevention method. More particularly, the present invention relates to a scale inhibitor and a scale prevention method that are excellent in scale prevention effects such as cooling water systems and boiler water systems, and that are particularly effective for preventing silica-based scales.

Scale failure occurs in water such as cooling water systems, boiler water systems, geothermal water systems, washing water systems, and metal surfaces that are in contact with water, particularly heat transfer surfaces. In particular, in an open-circulation cooling water system, from the standpoint of resource and energy savings, waste water (blow) is reduced outside the system and highly concentrated operation is performed, so that salts that dissolve in water are concentrated. Heat transfer surfaces and the like are easily corroded, and scales such as calcium salt, magnesium salt, and silica are generated. Conventionally, various acrylic acid polymers, various maleic acid polymers, and the like have been proposed as scale inhibitors for preventing or removing these scales (Patent Document 1).
JP 2002-102886 A

However, the effects of conventional scale inhibitors are not always satisfactory, and the effect of suppressing silica-based scales is particularly insufficient.
That is, the object of the present invention is to provide a scale inhibitor that is excellent in scale prevention effects such as cooling water systems, boiler water systems, geothermal water systems, and washing water systems, and that is particularly effective in suppressing silica-based scales, and a scale prevention method that uses the scale inhibitor. It is to be.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a scale inhibitor having a specific structure achieves the above-mentioned goal, and have reached the present invention. That is, the present invention provides a scale inhibitor comprising an alkylene oxide adduct (A) of a compound (a) having three or more active hydrogen atom-containing groups, and the scale inhibitor is added to a high silica concentration aqueous system to obtain a silica-based A scale prevention method characterized in that scale generation is prevented.

  The scale inhibitor according to the present invention exhibits the effect of suppressing silica-based scales such as cooling water systems, boiler water systems, geothermal water systems, and washing water systems.

  (A) in the present invention is an alkylene oxide adduct of the compound (a) having three or more active hydrogen atom-containing groups. The active hydrogen atom-containing group (a) includes a hydroxyl group, a carboxyl group, 1 Examples include a secondary amino group, a secondary amino group, an imino group, and a thiol group.

  (A) is a compound having three or more, preferably 3-8, of one or more of these active hydrogen atom-containing groups. Examples thereof include the following compounds.

(A1) a compound having 3 or more hydroxyl groups;
(A11) polyhydric alcohols;
For example, a trihydric alcohol having 3 to 24 carbon atoms (such as glycerin and trimethylolpropane), a tetrahydric alcohol (such as pentaerythritol and sorbitan), a pentavalent alcohol (such as dipentaerythritol, glucose, and fructose) and a hexahydric alcohol (such as Sorbitol).
(A12) polyhydric phenols;
Examples thereof include monocyclic polyhydric phenols (such as pyrogallol) and polycyclic polyhydric phenols (such as trihydroxynaphthalene) having 6 to 24 carbon atoms.
(A2) a compound having 3 or more primary and / or secondary amino groups;
Examples of the polyalkylene polyamines include C2-C24 triamine (diethylenetriamine and the like), tetraamine (triethylenetetramine and the like), and pentaamine (tetraethylenepentamine and the like).
(A3) a compound having three or more carboxyl groups;
Polycarboxylic acids such as trivalent carboxylic acids having 3 to 36 carbon atoms (such as trimers of linoleic acid), tetravalent carboxylic acids (such as dimers of itaconic acid and maleic acid), and pentavalent carboxylic acids (acrylic) Acid pentamers, etc.).
(A4) a compound having three or more thiol groups;
Polythiols, for example, polythiol corresponding to the above polyhydric alcohol (all of OH replaced with thiol groups), polythiol obtained by reaction of a compound containing 3 or more glycidyl groups with hydrogen sulfide, and the like.
Among (a), (a1) and (a2) are preferable from the viewpoint of silica scale prevention property, (a11) is more preferable, and sorbitol is particularly preferable.

As the alkylene oxide constituting (A) (hereinafter abbreviated as AO), AO having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, and more preferably 2 or 3 carbon atoms from the viewpoint of solubility in water. Can be mentioned.
Examples of AO include ethylene oxide (hereinafter abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), butylene oxide, styrene oxide, and the like.

  (A) in the present invention is not particularly limited as long as it is an AO adduct of (a), but from the viewpoint of preventing silica scale, EO and / or PO adducts of (a1) or (a2) are preferred. More preferable is an adduct of 4 to 100 EO and 0 to 50 PO on average per active hydrogen atom-containing group, and more preferable is the following general formula (1) or (2) AO adduct represented by

In the general formula (1), R ¹ represents an ethylene group, R ² represents a propylene group, and / indicates that they are bonded in a random form and / or a block form, preferably both a random form and a block form It is a combined use.
m is an integer of 1 or more that averages 4 to 100, preferably 4 to 50, and more preferably 10 to 40. n is an integer of 0 or 1 or more which averages from 0 to 50, preferably from 0 to 20, and more preferably from 0 to 10. A plurality of m and n may be the same or different, and p is an integer of 1 to 10, preferably 3 to 6.

  Specific examples of the AO adduct represented by the general formula (1) include EO (30 to 120 mol) · PO (0 to 30 mol) random adduct of glycerin and EO (60 to 240 mol) · PO of sorbitol. (0-60 mol) Block adducts and the like can be mentioned.

In the formula, X is — (R ¹ O) m / (R ² O) n—H, R ¹ represents an ethylene group, R ² represents a propylene group, and / binds in a random and / or block form. Preferably, both random and block combinations are used.
m is an integer of 1 or more which averages 4 to 100, preferably 10 to 80, and more preferably 10 to 70. n is 0 or an integer of 1 or more which averages 0 to 50, preferably 1 to 30, and more preferably 1 to 20. q is an integer of 1 to 100, preferably 1 to 50, more preferably 1 to 20.
M and n in the plurality of X may be the same or different.

  Specific examples of the AO adduct represented by the general formula (2) include EO (30 to 210 mol) · PO (3 to 60 mol) random adduct of diethylenetriamine and EO (40 to 280 mol) of triethylenetetramine. -PO (4-80 mol) block adducts etc. are mentioned.

The scale inhibitor of the present invention comprises (A) itself or an aqueous solution of (A).
(A) is usually solid or liquid, and the melting point in the case of solid is usually 30 to 80 ° C. When (A) is a liquid, the viscosity is usually 1,000 to 80,000 mPa · s at 25 ° C., preferably 1,000 to 30,000 mPa · s.
When the scale inhibitor is the aqueous solution of (A), the concentration of (A) is usually 10 to 90% by mass, preferably 30 to 80% by mass.

  As a production method of (A), for example, (a) includes a method in which AO is randomly and / or block-added in the presence of a catalyst, preferably at a temperature of 30 to 120 ° C., preferably at a pressure of 0 to 0.6 MPa. .

A conventionally known catalyst can be used as the catalyst. Lewis acids such as BF ³ , BCl ³ , AlCl ³ , FeCl ³ and SnCl ³ and their complexes [eg BF ³ ether complex, BF ³ tetrahydrofuran complex (BF ³ · THF)]; H ² SO ⁴ , HClO ⁴ Protic acids such as: alkali metal perchlorates such as KClO ⁴ and NaClO ⁴ ; alkaline earth metal perchlorates such as Ca (ClO ⁴ ) ² and Mg (ClO ⁴ ) ² ; Al (ClO ⁴ ) Alkali metal or alkaline earth metal hydroxides such as perchlorates of other metals such as ³ [KOH, NaOH, CsOH, Ca (OH) ² etc.]; Alkali metal or alkaline earth metal oxides (K ² O, CaO, BaO, etc.), alkali metal (Na, K, etc.), and their hydrides (NaH, KH, etc.); triethylamine, trimethylamine And amines such as emissions and the like. Of these, BF ³ ether complex and BF ³ tetrahydrofuran complex (BF ³ · THF), KOH, NaOH or CsOH are preferred.

  The number average molecular weight of (A) (hereinafter abbreviated as Mn, measured by GPC) is not particularly limited, but is preferably 3,000 to 100,000, and 4,000 to 50,000. More preferable from the viewpoint of water solubility.

  The amount of the scale inhibitor of the present invention added to the target aqueous system varies depending on the water quality of the target aqueous system, but (A) is preferably about 1 to 200 mg / L as a standard.

The scale inhibitor of the present invention may be used in combination with other additives as long as the performance is not impaired. Other additives include anticorrosives (phosphorus compounds such as phosphates, polymerized phosphates, phosphates and phosphonates, salts of polyvalent metals such as zinc, aluminum and nickel, benzotriazole, tolyltriazole , Azoles such as mercaptobenzothiazole and hydrazine), slime control agents (quaternary ammonium salts such as alkyldimethylbenzylammonium chloride, chloromethyltrithiazoline, chloromethylisothiazoline, methylisothiazoline and ethylaminoisopropylaminomethylthiatriazine) , Enzymes, fungicides, colorants, fragrances, hydrophilic solvents (such as methanol, ethanol, isopropyl alcohol, ethylene glycol and propylene glycol), and antifoaming agents (Silico System antifoaming agent, such as Pluronic-based or polyoxyalkylene defoamer and mineral oil-based antifoaming agent), and the like.
Based on the mass of (A), the combination ratio is usually 10 to 200 mass% for the anticorrosive agent, 5 to 100 mass% for the slime control agent, the enzyme and the bactericidal agent, and 0.01 to 10 mass for the colorant and the fragrance. The mass%, the hydrophilic solvent is 1 to 100 mass%, and the antifoaming agent is 1 to 100 mass%.

  The aqueous system that is the target of the scale inhibitor in the present invention may be any aqueous system as long as there is a possibility of scale failure, but as an aqueous system in which the scale inhibitor of the present invention sufficiently exhibits the effect. Examples thereof include high salt water systems, particularly high silica water systems having a silica concentration of 150 mg / L or more. Examples of such water systems include open / cooling water systems, boiler water systems, steel dust collection water systems, and geothermal water systems. In addition, particularly in areas where the silica concentration of tap water and well water is high, there are places where it is partially concentrated by an automatic dishwasher / dryer etc., and there is a problem of scale generation. These scale inhibitors are effective, but are not limited thereto.

    The scale prevention method of the present invention is a scale prevention method characterized by adding the above scale inhibitor to a high silica concentration aqueous system to prevent the formation of silica scale.

[Example]
The present invention will be described in detail by the following examples, but the present invention is not limited thereto.

Example 1
After charging and mixing 182 parts of sorbitol and 13 parts of powdered potassium hydroxide in a stainless steel pressure vessel equipped with a stirrer, heating / cooling device, thermometer and dropping tank, the space in the system was replaced with nitrogen At a temperature of 120 to 130 ° C. and a pressure of −0.1 MPa to 3 MPa, a mixture of EO8,244 parts and PO2,175 parts was added dropwise with stirring, and the reaction was continued until the pressure reached equilibrium. Subsequently, 2,400 parts of PO was added dropwise and reacted until the pressure reached equilibrium to obtain a PO41.3 mol block adduct of sorbitol EO (187.4 mol) / PO (37.5 mol) random adduct. The scale inhibitor A-1 of the present invention was used.

Example 2
As AO to be added, except that only 8,712 parts of EO was used, a sorbitol EO (198 mol) adduct was obtained in the same manner as in Example 1 and used as scale inhibitor A-2 of the present invention.

Example 3
A pressure vessel similar to Example 1 was charged with 103 parts of diethylenetriamine and 13 parts of powdered potassium hydroxide, mixed, and after replacing the space inside the system with nitrogen, the temperature was 120 to 130 ° C. and the pressure was −0.1 MPa. Under stirring, a mixture of EO 7,920 parts and PO 3,480 parts was added dropwise and reacted until the pressure reached equilibrium to obtain a diethylenetriamine EO (180 mol) / PO (60 mol) random adduct. The scale inhibitor A-3 of the present invention was used.

<Evaluation of silica-based scale prevention>
Using the scale inhibitors A-1 to A-3 described above and the scale inhibitors of Comparative Examples 1 to 3 below, silica-based scale inhibitory properties were evaluated.

Comparative Example 1; Carribbon L-400 (sodium polyacrylate, Mn about 10,000, manufactured by Sanyo Chemical Industries, Ltd.)
Comparative Example 2; PEG-10,000 (polyethylene glycol, Mn about 10,000)
Comparative Example 3; PEG-20,000 (polyethylene glycol, Mn about 20,000)
[Evaluation methods]
In a 200 ml Erlenmeyer flask made of glass, 240 ml / L of MgSO ₄ .7H ₂ O is added to 95 ml of ion-exchanged water, 1420 mg / L of Na ₂ SiO ₃ .9H ₂ O is used as a silica-based scale source compound, and NaHCO ₃ is used. Add to a concentration of 420 mg / L and adjust the pH to 9 ± 0.02, then add the scale inhibitor from Table 1 to a concentration of 50 ppm, and further ion exchange so that the total is 100 ml. The test solution was prepared with water. This test solution was allowed to stand in a constant temperature bath at 30 ° C. and 70 ° C., and filtered with a 0.1 μm filter after 3 days. The test solution was diluted 15 times with ion-exchanged water, and then at 30 ° C. by molybdenum yellow absorptiometry. The dissolved silica concentration and the dissolved silica concentration at 70 ° C. were determined, and the precipitation amount (%) was calculated from the following formula.
Silica precipitation (%) = {(BA) / B} × 100
A: Molybdenum yellow spectrophotometric measurement results after 3 days (absorbance, unit: abs)
B: Molybdenum yellow spectrophotometric measurement result (absorbance, unit: abs) before the test
The results are shown in Table 1.

  From the results in Table 1, it was confirmed that the scale inhibitor of the present invention has a large effect of suppressing silica-based scale.

  Since the scale inhibitor of the present invention has an excellent effect of preventing silica-based scale, it is extremely suitable as a scale inhibitor for cooling water systems, boiler water systems, washing water systems, and the like.

Claims (4)

Alkylene oxide adduct of compound (a) having 3 or more active hydrogen atom-containing groups (
A) an aqueous scale inhibitor comprising A), wherein (A) is per active hydrogen atom-containing group.
An average of 4-100 ethylene oxide and an average of 0-50 propylene oxide
Scale inhibitor, a random adduct of The scale inhibitor according to claim 1, wherein the active hydrogen atom-containing group is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, a primary amino group, a secondary amino group, an imino group, and a thiol group. The scale inhibitor according to claim 1 or 2, wherein (A) is an adduct of an alkylene oxide having 2 and / or 3 carbon atoms. The scale prevention method characterized by adding the scale inhibitor in any one of Claims 1-3 to a high silica concentration aqueous system, and preventing the production | generation of a silica type scale.