JPH10118694A - Scale preventing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scale preventing agent which has excellent scale preventing function even at high temperature by adding a ternary copolymer comprising polyxyalkylene compound with a specified structure, a sulfuric acid compound, and malice acid type compound or its derivative to the agent. SOLUTION: This scale preventing agent is produced by adding polyoxyalkylene compound (A) expressed by formula I R<1> O(AO)n R<2> (in the formula, R<1> reprints an alkenyl group, R<2> a hydrocarbon group, AO an oxyalkylene group of which 50-100 mole % is oxyacetylene group, and n for average addition mole number of the oxyethylene and 1-100), a sulfuric acid compound (B) expressed by formula II R<3> SO3 M (in the formula, R<3> represents an alkyl group and M hydrogen atom, etc.), and a maleic acid type compound (C). In thus case, the composition of the ternary copolymer is adjusted to have mole ratio (A)+(B)}:(C)=(3:7)-(7:3), (A):(B)=(1:5)-(99:1) and 500-100,000 weight average molecular weight and is used as the agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scale inhibitor, and more particularly, to a scale inhibitor which prevents precipitation of a sparingly soluble salt in a boiler, a heating evaporator, a water-cooled heat exchanger and the like.

[0002]

2. Description of the Related Art Natural water, tap water, industrial water, seawater, and the like are used in water-cooled heat exchangers such as heating / evaporation equipment such as boilers and seawater desalination equipment, and cooling towers. Scales such as calcium salts, magnesium salts, and silica are formed on the walls of the vessel that come into contact with the water, particularly on the heat transfer surface. Particularly, in the open circulation cooling water system, when the operation is performed with less disposal of the cooling water outside the system, dissolved salts are highly concentrated, and calcium salts having low solubility are used.
Magnesium salts, silica, etc. are scaled. The formed scale causes serious problems such as a decrease in thermal efficiency, local corrosion of pipes and heat transfer surfaces, closure of the circulation system, breakage, and the like.

Heretofore, as a scale inhibitor for preventing or removing such scale, polyacrylates and polymethacrylates (hereinafter, acrylic acid and methacrylic acid have been combined to form (meth) acrylic acid). (For example, JP-B-49-30914) and a polymer of a maleic acid-based monomer (for example, JP-A-47-11375,
61-178097, JP-A-62-91295), a copolymer of a maleic acid monomer and a (meth) acrylic acid monomer (for example, JP-A-50-26764, JP-A-57-149312, JP-A-58-216796), polymers of hydroxyalkyl (meth) acrylate-based monomers (for example, JP-A-59-196799), polyoxyalkylene compounds and maleic anhydride Copolymer with acid (for example, JP-A-6-195538)
And the like. However, poly (meth) acrylate has a disadvantage that the dispersing power is reduced at the time of high concentration and scale is easily generated. Polymers of maleic acid monomers and copolymers of maleic acid monomers and (meth) acrylic acid monomers are useful for capturing cations such as calcium ions and magnesium ions that cause scale. Although effective, the effect of dispersing scale components and the effect of suppressing crystal growth are insufficient. A polymer of a (meth) acrylic acid hydroxyalkyl ester-based monomer is not suitable for use at a high temperature, such as a heating-evaporation apparatus, because it contains an ester bond and is hydrolyzed to lower its performance. A copolymer of a polyoxyalkylene compound and maleic anhydride is a scale inhibitor proposed to solve the above problem, but the dispersing effect of the scale component and the effect of suppressing crystal growth are not yet sufficient. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a scale inhibitor having an excellent scale preventing effect and exhibiting a scale preventing performance even at a high temperature.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that ternary polyoxyalkylene compounds, sulfonic acid compounds and maleic acid compounds having a specific structure are obtained. The inventors have found that a copolymer or a derivative thereof has an excellent scale preventing effect, and have completed the present invention based on the knowledge.

That is, the present invention provides (1) a polyoxyalkylene compound represented by the following formula [I]:
(2) a sulfonic acid compound represented by the following formula [II],
And (3) a maleic acid-based compound composed of maleic anhydride, maleic acid, or maleic acid salt as an essential monomer unit, and the composition is {(1) + (2)} in molar ratio:
(3) = 3: 7 to 7: 3, (1) :( 2) = 1: 5 to 9
9: 1 and a weight average molecular weight of 500 to 100,
It is a scale inhibitor consisting of a terpolymer of 000. R ¹ O (AO) _n R ² [I] (wherein, R ¹ is an alkenyl group having 2 to 5 carbon atoms;
R ² is a hydrocarbon group having 1 to 10 carbon atoms, AO is 2 to carbon atoms
In the oxyalkylene group 4, 50 to 100 mol% is an oxyethylene group, and n is an average number of moles of the added oxyalkylene of 1 to 100. R ³ SO ₃ M [II] (wherein, R ³ is an alkenyl group having 2 to 5 carbon atoms;
M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, or organic ammonium. )

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the formula [I], examples of the alkenyl group having 2 to 5 carbon atoms represented by R ¹ include vinyl, allyl, methallyl, 1,1-dimethyl-2-propenyl, 3- And a methyl-3-butenyl group. When the carbon number of the alkenyl group represented by R ¹ is 6 or more, the dispersing action of the scale component tends to decrease.

In the formula [I], the number of carbon atoms represented by R ² is 1
As the hydrocarbon group of 10 to 10, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group,
Aliphatic saturated hydrocarbon groups such as secondary butyl group, tertiary butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, and decyl group; fats such as allyl group and methallyl group Alicyclic unsaturated hydrocarbon groups such as cyclohexyl group and methylcyclohexyl group; alicyclic unsaturated hydrocarbon groups such as cyclopentenyl group and cyclohexenyl group; phenyl group, benzyl group, cresyl group, There is an aromatic hydrocarbon group such as a butylphenyl group or a substituted aromatic hydrocarbon group, and these may be used alone or in combination of two or more. If the carbon number of the hydrocarbon group represented by R ² exceeds 10, the hydrophobicity becomes too strong, and the scale prevention effect of the copolymer is undesirably reduced.

In the formula [I], the oxyalkylene group having 2 to 4 carbon atoms represented by AO includes oxyethylene group, oxypropylene group, oxytrimethylene group, oxybutylene group, oxytetramethylene group and the like. . These oxyalkylene groups are ethylene oxide,
This is a group obtained by addition polymerization of an alkylene oxide such as propylene oxide, 1,2-butylene oxide, and tetrahydrofuran. If the number of carbon atoms of the oxyalkylene group represented by AO is 5 or more, the resulting copolymer is not sufficiently hydrophilic and has a poor scale prevention effect, which is not preferable.
As long as 50 mol% or more of the oxyalkylene groups represented by AO is an oxyethylene group, two or more oxyalkylene groups may be bonded in a block or random manner. The reason that 50 mol% or more of the oxyalkylene group is limited to the oxyethylene group is that when the oxyethylene group is less than 50 mol%, the water solubility becomes insufficient and the scale preventing effect is reduced. Also,
n represents the average number of moles of oxyalkylene added, and n = 1
When n is larger than 100, the formula [I]
The viscosity of the polyoxyalkylene compound represented by the formula (1) becomes high, and the production becomes difficult.

In the formula [II], the alkenyl group having 2 to 5 carbon atoms represented by R ³ may be the same as R ¹ , such as vinyl, allyl, methallyl, 1,1-dimethyl-2-propenyl, And a 3-methyl-3-butenyl group. When the number of carbon atoms is 6 or more, the dispersing effect of the scale component tends to decrease.

In the formula [II], examples of the alkali metal represented by M include lithium, sodium and potassium, and examples of the alkaline earth metal include ＣａCa and ２Ca.
Examples of the organic ammonium include alkanolamines such as monoethanolammonium, diethanolammonium, and triethanolammonium; and alkylamines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, and triethylamine.

In the scale inhibitor of the present invention, a unit (1) of a polyoxyalkylene compound represented by the formula [I], a unit (2) of a sulfonic acid compound represented by the formula [II], and a maleic acid compound The composition of the unit (3) is {(1) + (2)} :( 3) = 3: 7 to 7: 3 in a molar ratio, and if it is outside this range, the scale preventing effect is reduced. Further, the composition of (1) and (2) is a molar ratio of (1):
(2) = 1: 5-99: 1, 1: 2 to 10: 1
It is preferred that Outside these ranges, the dispersing effect and the effect of suppressing crystal growth become insufficient. In the scale inhibitor of the present invention, the weight average molecular weight of the copolymer is from 500 to 100,000, and from 10,000 to 3
Preferably it is 000. Weight average molecular weight of 5
If it is less than 00, the dispersing effect and the effect of suppressing crystal growth are insufficient, and if it exceeds 100,000, it is difficult to manufacture.

Although the scale inhibitor of the present invention is sufficiently effective when used alone, it can be used in combination with other additives used in the system, such as general chelating agents, corrosion inhibitors or slime controlling agents. Can also be used. When used, it can be used in the same manner as a conventional scale inhibitor, for example, by adding it continuously or intermittently to circulating water such as a boiler, a heating evaporator, or a water-cooled heat exchanger. At this time, the amount of addition varies depending on the use, but usually 1 to 100 ppm with respect to water is sufficiently effective.

[0014]

The scale inhibitor of the present invention has an excellent scale inhibitory effect, and can exhibit its effect sufficiently even when the temperature of the circulating water is high.

[0015]

The present invention will be described below with reference to examples and comparative examples. Synthesis Examples 1 to 7 In a four-necked flask equipped with a stirrer, a nitrogen gas inlet tube, a reflux condenser and a thermometer, 204 g (1.0 mol) of the polyoxyalkylene compound represented by a in Table 1 and allyl sulfone 144 g (1.0 mol) of sodium silicate, 294 g (3.0 mol) of maleic anhydride and 40 g of ammonium persulfate as a polymerization initiator are weighed, 500 g of water is added as a solvent, and the mixture is heated to 60 ° C. under a nitrogen gas atmosphere. The polymerization reaction was performed for 10 hours at an elevated temperature to obtain a water-soluble copolymer A as a pale yellow transparent viscous liquid. The weight average molecular weight of the copolymer obtained by gel permeation chromatography was 15070. Hereinafter, in the same manner, the polyoxyalkylene compounds b to g shown in Table 1, sodium allyl sulfonate, and maleic anhydride were copolymerized in the molar ratio shown in Table 2 to obtain corresponding copolymers BG.

[0016]

[Table 1]

[0017]

[Table 2]

Synthesis Example 8 Using the same reactor as in Synthesis Example 1, 190 g (1.0 mol) of the polyoxyalkylene compound represented by h in Table 1 and 100 g of water were added and stirred under a nitrogen gas atmosphere. And heated to 95 ° C. Next, an aqueous solution in which 200 g (1.25 mol) of disodium maleate and 14 g of ammonium persulfate were dissolved in 220 g of water was added dropwise over 120 minutes. After completion of the dropwise addition, 14 g of a 20% aqueous ammonium persulfate solution was further added dropwise over 20 minutes. After dropping, 9
Stir at 5 ° C for 100 minutes to complete the polymerization and to obtain copolymer H
Was obtained.

Synthesis Example 9 Using the same reactor as in Synthesis Example 1, 204 g (1.0 mol) of the polyoxyalkylene compound represented by a in Table 1, 103 g (1.05 mol) of maleic anhydride, And 300 ml of toluene, the mixture was heated to 50 ° C. under a nitrogen gas atmosphere, 5.0 g of tertiary butyl peroxy-2-ethylhexanoate was added, and the temperature was further raised to 70 ° C., and the same temperature was maintained for 10 hours. The reaction was performed. Then, toluene was removed at 50 ° C. under reduced pressure to obtain a copolymer I.

Examples 1 to 7 In a 200 ml Erlenmeyer flask equipped with a stopper, 100 g of a 0.067% by weight aqueous solution of sodium hydrogencarbonate and 0.1 g of calcium chloride were added.
100 g of a 0.83% by weight aqueous solution (150 ppm as calcium ion) and Synthesis Example 1 as a scale inhibitor
0.2 g of a 1.0% by weight aqueous solution of copolymer A obtained in
(Equivalent to 10 ppm as an effective component) was added, and the pH was adjusted to 8.5 with a 0.1% by weight aqueous solution of potassium hydroxide to obtain a supersaturated solution of calcium carbonate. After sealing the Erlenmeyer flask, the Erlenmeyer flask containing the solution was allowed to stand in a thermostat at 60 ° C. for 12 hours. After cooling, the solution was filtered through a 0.45 μm membrane filter, and calcium ions in the filtrate were quantified by EDTA titration. Operations were performed using the copolymers B to G obtained in Synthesis Examples 2 to 7 in place of the copolymer A, and calcium ions in the filtrate were quantified in the same manner.

On the other hand, exactly the same operation was repeated except that no copolymer was added, and the calcium ion in the filtrate was determined to be 80 ppm. Table 3 shows the results obtained by using this numerical value to determine the scale suppression rate according to the following equation.

[0022]

(Equation 1)

Comparative Examples 1 and 2 The scale inhibition rate was the same as in Example 1 except that the copolymers H and I obtained in Synthesis Examples 8 and 9 were used instead of the copolymer A in the Examples. And the results are shown in Table 3.

Comparative Examples 3 and 4 In place of the copolymer A of Example 1, polymaleic acid (weight average molecular weight: 1,000) and sodium polyacrylate (weight average molecular weight: 4,000) were used.
The scale inhibition rate was determined in the same manner as described above, and the results are shown in Table 3.

[0025]

[Table 3]

As is clear from Table 3, the terpolymer of the present invention is superior to Comparative Examples 1 and 2 using copolymers H and I of a polyoxyalkylene compound and a maleic acid compound. The scale inhibition rate is shown. Also,
It can be seen that the present invention is superior to Comparative Examples 3 and 4 using commonly used polymaleic acid and sodium polyacrylate.

Claims (1)

[Claims] 1. A polyoxyalkylene compound represented by the following formula [I]: (2) a sulfonic acid compound represented by the following formula [II]:
And (3) a maleic acid-based compound composed of maleic anhydride, maleic acid, or maleic acid salt as an essential monomer unit, and the composition is expressed by a molar ratio of {(1) + (2)} :( 3) = 3:
A scale inhibitor comprising a terpolymer having a ratio of 7 to 7: 3, (1) :( 2) = 1: 5 to 99: 1, and a weight average molecular weight of 500 to 100,000. R ¹ O (AO) _n R ² [I] (wherein, R ¹ is an alkenyl group having 2 to 5 carbon atoms;
R ² is a hydrocarbon group having 1 to 10 carbon atoms, AO is 2 to carbon atoms
In the oxyalkylene group 4, 50 to 100 mol% is an oxyethylene group, and n is an average number of moles of the added oxyalkylene of 1 to 100. R ³ SO ₃ M [II] (wherein, R ³ is an alkenyl group having 2 to 5 carbon atoms;
M is a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, or organic ammonium. )