JPH07299497A - Scale preventing material - Google Patents

Abstract

PURPOSE:To prevent the effect of a scale preventing material caused by an anticorrosive or the like used in combination from decreasing by using the scale preventing material consisting of a copolymer, containing a polyoxyalkylene compound expressed by a specific formula and maleic anhydride as an essential monomer and obtained by a prescribed solution polymerization or bulk polymerization, and the hydrolyzed compound or the salt. CONSTITUTION:This scale preventing material consists of the copolymer containing the polyoxyalkylene compound (a) expressed by the formula and maleic anhydride (b) as a essential monomer and is obtained by the solution polymerization in a solvent inert to the acid anhydride group or the bulk polymerization in the absence of the solvent and the hydrolyzed compound or the salt. In the formula R<1> is a 2-5C alkenyl group, R<2> is a 1-4C hydrocarbon group, AO is a 2-4C oxyalkylene group in which oxyethylene group is 50-100mol% (n) is the average addition mol number and is 1-100. Where, the mol ratio of (a) to (b) is (3:7)-(7:3) and the number average molecular weight is 500-100000.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a scale inhibitor. More specifically, the present invention relates to a scale inhibitor that prevents the sparingly soluble salt from depositing in a boiler, a heating evaporator, a water-cooling heat exchanger, or the like.

[0002]

2. Description of the Related Art Natural water, tap water, industrial water or sea water is used for heating and evaporating system equipment such as boilers and seawater desalination equipment, and water cooling type heat exchangers such as cooling towers. In addition to cations such as calcium ions and magnesium ions contained in these water, anions such as carbonate ions, bicarbonate ions or sulfate ions, zinc ions derived from the corrosion inhibitor used in the system or Phosphate ions are deposited as a sparingly soluble salt on the heat transfer surface, etc.,
Scale is generated. The generated scale causes serious problems such as deterioration of thermal efficiency, localized corrosion of pipes and heat transfer surfaces, closure of circulation system, and breakage. Conventionally, various scale inhibitors such as phosphoric acid compounds (for example, JP-A-51-146341) and lignin compounds have been used for the purpose of preventing such scale disorders. However, phosphoric acid compounds are scale inhibitors that also have anticorrosion effects, but easily cause hydrolysis and reduce anticorrosion effects, and react with calcium ions, magnesium ions, etc. to form sparingly soluble salts and scale. Turn into. Further, if discharged to the outside of the system, it causes eutrophication and causes environmental pollution, which is not preferable. Further, since the lignin compound is a natural product, the quality is not constant and the performance varies. In order to solve such problems, poly (meta)
Acrylate salt [hereinafter, acrylic acid and methacrylic acid are collectively referred to as (meth) acrylic acid] (for example, Japanese Patent Publication No.
30914), polymers of hydroxyalkyl ester-based (meth) acrylic acid monomers (for example, JP-A-59-59).
196799), polymers of maleic acid-based monomers (for example, JP-A-47-11357 and JP-A-61-1).
178097, JP-A-62-91295), a copolymer of a maleic acid-based monomer and a (meth) acrylic acid-based monomer (for example, JP-A-50-26764,
JP-A-57-149312 and JP-A-58-216
796), a copolymer of a maleic acid-based monomer and a polyoxyalkylene monoallyl ether (see, for example, JP-A No.
9-176312, JP-A-58-6295, JP-A-59-12908) and the like have been proposed as scale inhibitors. However, the poly (meth) acrylic acid salt has a drawback in that the dispersive power is lowered at the time of high concentration and scale is easily generated. Polymers of hydroxyalkyl ester (meth) acrylic acid type monomers are not suitable for use in high temperature systems such as heating and evaporation system equipment because they hydrolyze because they contain ester bonds and their performance deteriorates. . Polymers of maleic acid-based monomers and copolymers of maleic acid-based monomers and acrylic acid-based monomers are effective in trapping cations such as calcium ions and magnesium ions that cause scale. However, the effect of suppressing the scale component dispersion action and crystal growth is insufficient. A copolymer of a maleic acid-based monomer and a polyoxyalkylene monoallyl ether is a scale inhibitor proposed to solve the above problem, but the effect of suppressing the scale component dispersing action and crystal growth is still insufficient. Not really.

[0003]

DISCLOSURE OF THE INVENTION The present invention has an excellent scale-preventing effect, exhibits scale-preventing performance even at high temperatures, does not cause a problem of environmental pollution, and is used as an anticorrosive agent in a system. Even when used in combination with a slime control agent or a chelating agent, it is an object of the present invention to provide a scale inhibitor capable of sufficiently exerting its effect.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the problems of the above scale inhibitors, the present inventors have found that a solution polymerization of a polyoxyalkylene compound having a specific structure and maleic anhydride is carried out. Further, it was found that a copolymer or a derivative thereof obtained by bulk polymerization has an excellent scale preventing effect, and the present invention has been completed based on the finding. That is, the present invention provides (1) (a) the following general formula [1] R ¹ O (AO) _n R ² ... [1] (wherein R ¹ is an alkenyl group having 2 to 5 carbon atoms). R ² is a hydrocarbon group having 1 to 40 carbon atoms, and A ²
Is an oxyalkylene group having 2 to 4 carbon atoms, and its 50 to 10
0 mol% is an oxyethylene group, and n is an average number of added moles of oxyalkylene of 1 to 100. ) And a (b) maleic anhydride as an essential monomer, obtained by solution polymerization using an organic solvent that does not react with an acid anhydride group or bulk polymerization using no solvent. A scale inhibitor comprising a polymer, a hydrolyzate thereof or a salt of the hydrolyzate, and (2) the molar ratio of (a) and (b) is (a) :( b) = 3: 7-
7: 3 and a number average molecular weight of 500 to 100,0
The scale preventive agent according to item (1) is 00.

In the general formula [1], the alkenyl group having 2 to 5 carbon atoms represented by R ¹ is vinyl group, allyl group, methallyl group, 1,1-dimethyl-2-propenyl group, 3-methyl- 3-butenyl group and the like. When the alkenyl group represented by R ¹ has 6 or more carbon atoms, the dispersing action of the scale component decreases, which is not preferable. In the general formula [1], the hydrocarbon group having 1 to 40 carbon atoms represented by R ² is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a secondary butyl group, a tertiary butyl group. Group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, isotridecyl group, tetradecyl group, hexadecyl group, isocetyl group, octadecyl group, isostearyl group Saturated aliphatic hydrocarbon groups such as octyldodecyl group, docosyl group and decyltetradecyl group; aliphatic unsaturated hydrocarbon groups such as allyl group and oleyl group; alicyclic saturated hydrocarbon groups such as cyclohexyl group and methylcyclohexyl group Group; alicyclic unsaturated hydrocarbon group such as cyclopentenyl group and cyclohexenyl group;
Aromatic hydrocarbon groups such as phenyl group, benzyl group, cresyl group, butylphenyl group, dibutylphenyl group, octylphenyl group, nonylphenyl group, dodecylphenyl group, dioctylphenyl group, dinonylphenyl group, styrenated phenyl group or There are substituted aromatic hydrocarbon groups, and these may be used alone or in combination of two or more. If the number of carbon atoms of the hydrocarbon group represented by R ² exceeds 40, the hydrophobicity becomes too strong, and the scale preventive effect of the copolymer decreases, which is not preferable. In the general formula [1], the oxyalkylene group having 2 to 4 carbon atoms represented by AO includes oxyethylene group, oxypropylene group, oxytrimethylene group, 1,2-oxybutylene group, 1,3
Examples include an -oxybutylene group, a 2,3-oxybutylene group and an oxytetramethylene group. When the oxyalkylene group represented by AO is an oxymethylene group having 1 carbon atom, harmful formaldehyde is generated by decomposition, which is not preferable. When the oxyalkylene group represented by AO has 5 or more carbon atoms, the hydrophilicity of the obtained copolymer is insufficient and the scale preventing effect is deteriorated, which is not preferable.
If 50 mol% or more of the oxyalkylene group represented by AO is an oxyethylene group, two or more kinds of oxyalkylene groups may be bonded in any block or random manner. The reason why 50 mol% or more of the oxyalkylene group is limited to the oxyethylene group is that if the oxyethylene group is less than 50 mol%, the water solubility becomes insufficient and the scale preventing effect is reduced. N represents the average number of moles of oxyalkylene added,
n = 1 to 100. When n exceeds 100, the viscosity of the polyoxyalkylene compound represented by the general formula [1] becomes high and the production becomes difficult, which is not preferable. The copolymer of the polyoxyalkylene compound represented by the general formula [1] and maleic anhydride does not react the polyoxyalkylene compound represented by the general formula [1] and maleic anhydride with an acid anhydride group. It can be easily obtained by copolymerizing in an organic solvent using a polymerization initiator in a system that does not use any solvent in some cases.

In producing the scale inhibitor of the present invention,
When performing solution polymerization, the organic solvent used is not particularly limited as long as it does not react with the acid anhydride group, and examples thereof include acetone, methyl ethyl ketone, ethyl acetate, dimethyl sulfoxide, N, N-dimethylformamide, cyclohexane, diisopropyl ether. , Benzene, toluene,
Organic solvents such as xylene, ethylbenzene, cumene, hexane, heptane, octane and the like can be mentioned. The amount used is not particularly limited, but is 200% by weight or less, preferably 10 to 10% with respect to the compound of the general formula [1] as a raw material.
It is 0% by weight, more preferably 20 to 50% by weight. When the amount of the organic solvent used exceeds 200% by weight, the subsequent treatment process becomes complicated, which is not preferable. Further, when the compound of the general formula [1] is liquid, it is possible to carry out bulk polymerization without using a solvent. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, and tert-butylperoxy-2.
-Organic peroxides such as ethylhexanoate or azo polymerization initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis-2,4,4-trimethylpentane To be The amount used is not particularly limited, but is preferably 0.1 to 20 mol% with respect to the compound of the general formula [1]. When the amount of the polymerization initiator is less than 0.1 mol% with respect to the compound of the general formula [1], the polymerization rate is slow and the polymerization takes a long time, which is not preferable. When the amount of the polymerization initiator exceeds 20 mol% with respect to the compound of the general formula [1], the molecular weight of the obtained copolymer does not increase, which is not preferable. Further, other copolymerizable monomers such as styrene, vinyl acetate, vinyl sulfonic acid and acrylic acid may be copolymerized within a range that does not affect the effects of the invention. The proportion of the other copolymerizable monomer is preferably 20 mol% or less with respect to the polyoxyalkylene compound represented by the general formula [1]. When the amount of the other copolymerizable monomer exceeds 20 mol%, the crystal growth suppressing action and the dispersing action of the sparingly soluble salt as a scale component are deteriorated, which is not preferable.

In the scale inhibitor of the present invention, the molar ratio of the polyoxyalkylene compound and maleic anhydride is 3:
It is preferably 7 to 7: 3. Even if the amount of polyoxyalkylene compound is small and the molar ratio of polyoxyalkylene compound and maleic anhydride is less than 3: 7, the amount of polyoxyalkylene compound is large and the molar ratio of polyoxyalkylene compound and maleic anhydride is 7: 3. If it exceeds the above range, the effect of preventing the scale of the copolymer decreases, which is not preferable. In the scale inhibitor of the present invention, the number average molecular weight of the copolymer is preferably 500 to 100,000,
More preferably, it is 1,000 to 20,000. When the number average molecular weight is less than 500, the dispersion effect and the effect of suppressing crystal growth are insufficient, which is not preferable. Further, a copolymer having a number average molecular weight of more than 100,000 is difficult to produce, and thus it is not preferable. The copolymer thus obtained can be used as it is as a scale inhibitor of the present invention, but a copolymer obtained by hydrolyzing the obtained copolymer, and a hydrolyzate thereof can be used. Copolymers neutralized to salts can also be used as the scale inhibitor of the present invention.

The hydrolysis of the copolymer of the polyoxyalkylene compound of the present invention and maleic anhydride can be carried out by using the copolymer as an aqueous solution or dispersion and using an acidic substance or a basic substance as a catalyst. It is preferable to use a volatile substance as a catalyst. Further, the hydrolyzate of the copolymer can be neutralized with a basic substance to form a salt. In the present invention, the basic substance used for hydrolysis and neutralization of the copolymer is not particularly limited, but examples thereof include ammonia, organic amines, alkali metal hydroxides, carbonates or heavy metals such as sodium and potassium. Carbonate etc. are mentioned. Examples of organic amines include methylamine, ethylamine,
Propylamine, hexylamine, ethanolamine,
Examples thereof include diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, aniline and the like. The scale preventive agent of the present invention has a relatively high pH which is likely to cause scale formation.
Even when the circulating water is high, or when the circulating water contains alkaline earth metals such as calcium and magnesium that easily form low-solubility salts, and when the circulating water temperature is high, It can be fully demonstrated. Further, the scale inhibitor of the present invention is sufficiently effective when used alone, but should be used in combination with other additives such as general anticorrosive agents, slime control agents or chelating agents used in the system. You can also At the time of use, it can be used in the same manner as a conventional scale inhibitor, such as continuous or intermittent addition to circulating water such as a boiler, a heating evaporator, and a water-cooling heat exchanger. At that time, the addition amount varies depending on each application, but usually 1 to 100 ppm with respect to water is sufficiently effective.

[0009]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Synthesis Example 1 In a four-necked flask equipped with a stirrer, a nitrogen gas inlet tube, a reflux condenser and a thermometer, 292 g of the polyoxyalkylene compound represented by a in Table 1 and 98 maleic anhydride.
g and 300 ml of toluene, and the temperature of the mixture was raised to 50 ° C. under a nitrogen gas atmosphere.
-Add 2.0 g of ethyl hexanoate and add 70 ° C.
The temperature was raised to, and a copolymerization reaction was carried out at the same temperature for 10 hours. Then, toluene was removed under reduced pressure at 50 ° C. to obtain a water-soluble copolymer A which was a reddish brown transparent viscous liquid. The number average molecular weight of the copolymer obtained by gel permeation chromatography was 3950.

[0010]

[Table 1]

Synthetic Examples 2 to 5 and 7 In the same manner as in Synthetic Example 1, the polyoxyalkylene compounds b to e and g shown in Table 1, maleic anhydride and the other monomer were mixed in the molar ratio shown in Table 2. To obtain the corresponding copolymers B to E and G, respectively.

[0012]

[Table 2]

Synthesis Example 6 Polyoxyalkylene compound f shown in Table 1 and maleic anhydride and styrene which is another monomer are prepared in the same manner as in Synthesis Example 1 except that the solvent toluene in Synthesis Example 1 is not used. And the corresponding copolymer F
Got Synthesis Example 8 Using the same reactor as in Synthesis Example 1, 278 g of the polyoxyalkylene compound represented by h in Table 1 and 10 parts of water were used.
0 g was added, and the mixture was stirred under a nitrogen gas atmosphere and heated to 95 ° C. Next, an aqueous solution obtained by dissolving 200 g of disodium maleate and 14 g of ammonium persulfate in 220 g of water was added dropwise over 120 minutes. 20% more after dropping
14 g of ammonium persulfate aqueous solution was added dropwise over 20 minutes. After completion of the dropping, the mixture was stirred at 95 ° C. for 100 minutes to complete the polymerization, and an aqueous solution of copolymer H was obtained. Synthetic Examples 9 and 10 In the same manner as in Synthetic Example 8, polyoxyalkylene compounds i and j shown in Table 1 and disodium maleate were secondarily mixed.
Copolymerization was carried out at the molar ratios shown in the table, and corresponding copolymers I and J were obtained. Synthetic Examples 11 to 13 Polyoxyalkylene compounds h, i and j shown in Table 1 were reacted with maleic anhydride in the same manner as in Synthetic Example 1, but all caused gelation. Example 1 In a 200 ml Erlenmeyer flask equipped with a ground-in stopper, 100 g of 0.067% by weight sodium hydrogen carbonate aqueous solution and 0.05 of calcium chloride.
100 g of 83% by weight aqueous solution (1 as calcium ion)
50 ppm) and 0.2 g of a 1.0 wt% aqueous solution of the copolymer A obtained in Synthesis Example 1 as a scale inhibitor (corresponding to 10 ppm as an effective component) were added, and a 0.1 wt% potassium hydroxide aqueous solution was added. The pH was adjusted to 8.5 to give a supersaturated solution of calcium carbonate. After sealing the Erlenmeyer flask tightly, the Erlenmeyer flask containing the solution was allowed to stand in a constant temperature bath at 60 ° C. for 12 hours. The solution was cooled and then filtered through a 0.45 μm membrane filter to quantify calcium ions in the filtrate by the EDTA titration method. Comparative Example 1 The procedure of Example 1 was repeated except that no copolymer was added, and the calcium ion in the filtrate was quantified. The scale inhibition rate was determined by the following formula, and the results are shown in Table 3.

[Equation 1] However, [C _o ]: the amount of Ca ²⁺ present in the solution before the heat treatment (=
150 ppm) [C _n ]: amount of Ca ²⁺ present in the filtrate after the heat treatment without addition of the copolymer (ppm) [C _f ]: of Ca ²⁺ present in the filtrate after the heat treatment Amount (pp
m) is shown.

[0014]

[Table 3]

Examples 2 to 7 Scale suppression was performed in the same manner as in Example 1 except that the copolymers A to B obtained in Synthesis Examples 2 to 7 were used instead of the copolymer A of Example 1. The rate was determined and shown in Table 3. Comparative Examples 2 to 4 The scale inhibition rate was obtained in the same manner as in Example 1 except that the copolymers H to J obtained in Synthesis Examples 8 to 10 were used instead of the copolymer A of Example 1. , Shown in Table 3. Comparative Example 5 Instead of the copolymer A of Example 1, a commercially available sodium polyacrylate (number average molecular weight 4,000) was used, and the scale inhibition rate was determined in the same manner as in Example 1 and shown in Table 3. It was As is clear from the results shown in Table 3, in the scale inhibitor of the present invention, Comparative Examples 2 and 3 using Copolymers H, I and J in which one end of the polyoxyalkylene compound is a hydroxyl group and Compared with No. 4, it shows an excellent scale prevention ability. Further, it can be seen that the scale inhibitor of the present invention is superior to Comparative Example 5 which uses sodium polyacrylate which is generally used. Furthermore,
As is clear from Synthesis Examples 11 to 13, h, i, and j in which one end of the polyoxyalkylene compound was a hydroxyl group could not undergo solution polymerization, but the polyoxyalkylene compound used in the present invention had no problem. The solution could be polymerized.

[0016]

EFFECT OF THE INVENTION Since the scale inhibitor of the present invention comprises a copolymer of a polyoxyalkylene compound having a hydrocarbon group at a branched end and maleic anhydride, it is excellent in hydrolysis resistance when heated and It is excellent in suppressing the crystal growth of the soluble salt and dispersing the salt.

Claims (2)

[Claims] (A) The following general formula [1] R ¹ O (AO) _n R ² ... [1] (wherein R ¹ is an alkenyl group having 2 to 5 carbon atoms, and R ² Is a hydrocarbon group having 1 to 40 carbon atoms, and AO
Is an oxyalkylene group having 2 to 4 carbon atoms, and its 50 to 10
0 mol% is an oxyethylene group, and n is an average number of added moles of oxyalkylene of 1 to 100. (B) a copolymer obtained by solution polymerization using an organic solvent that does not react with an acid anhydride group, or bulk polymerization that does not use any solvent, containing a polyoxyalkylene compound represented by the formula (4) and (b) maleic anhydride as essential monomers. A scale inhibitor comprising a polymer, a hydrolyzate thereof or a salt of the hydrolyzate. 2. The molar ratio of (a) and (b) is (a):
(B) = 3: 7 to 7: 3 and the number average molecular weight is 5
The scale preventive agent according to claim 1, which is from 0 to 100,000.