TW201348150A - Processing method of cooling water system - Google Patents

Abstract

A processing method of a cooling water system of the invention is the processing method of the cooling water system which a processing agent formed by containing a (meth)acrylic acid copolymer is added to the cooling water system in which a calcium hardness is 300 mg/L or more by CaCO3, and a concentration of a chloride ion and/or a sulfate ion is 1000 mg/L or more, and the (meth)acrylic acid copolymer contains a structure unit (a) derived from a (meth)acrylic acid monomer (A) and a structure unit (b) derived from a specific (meth)allyl ether monomer (B). Further, in all structure units 100 mol% derived from the monomers, a content of the structure unit (a) ranges from 80 mol% to 90 mol% and a content of the structure unit (b) ranges from 10 mol% to 20 mol%. At least one end of a main chain of the (meth)acrylic acid copolymer is a sulfonic acid group or its salt.

Description

Cooling water system treatment method

The present invention relates to a method for treating a cooling water system. In particular, the present invention relates to a method for preventing adhesion or deposition of calcium scales in pipes or heat exchangers in a cooling water system having a high calcium hardness. A method of treating a cooling water system that causes heat transfer failure, reduced flow, and metal corrosion on the heat transfer surface.

In the open-circuit cooling water system, scale defects occur on the heat transfer surfaces and pipes that come into contact with water. Further, in terms of resource saving and energy saving, in the case of performing a high concentration operation, the dissolved salts are concentrated to form a sparingly soluble salt and become scale. The scale generated in the heat exchange portion causes a heat transfer disorder, and scale adhering to the pipe causes a decrease in flow rate. In addition, it is known that the generated scale is peeled off and circulated in the system, whereby the pump, the piping, and the heat exchange unit are clogged, and the piping and the scale exchange in the heat exchange unit are promoted with clogging.

The scales to be produced include calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, calcium citrate, magnesium citrate, magnesium hydroxide, zinc phosphate, zinc hydroxide, and basic zinc carbonate.

In order to prevent the generation of such scale, a scale inhibitor can be used. The scale inhibitor is usually used: inorganic polyphosphoric acid such as sodium hexametaphosphate or sodium tripolyphosphate, hydroxy ethylidene phosphonic acid or phosphonobutane tricarbolic acid, etc. Phosphonic acid, a raw material containing a carboxyl group such as maleic acid, acrylic acid or itaconic acid, if necessary, with vinylsulfonic acid, allylsulfonic acid, 2-methylpropenylamine-2-methylpropanesulfonic acid, etc. A copolymer of a vinyl monomer having a sulfonic acid group or a nonionic vinyl monomer such as acrylamide.

Further, the metal member provided in the open-circuit cooling water system, for example, a heat exchanger made of carbon steel, copper or a copper alloy, or a reaction vessel or a pipe is corroded by contact with cooling water, and therefore is usually implemented by adding a chemical agent. Anti-corrosion treatment.

As the chemical agent, a phosphorus compound such as orthophosphate, hexametaphosphate, hydroxyethylidenephosphonate or phosphinium butane tricarboxylate is usually added to the cooling water. Heavy metal salts such as zinc salts or dichromates are sometimes added singly or in combination.

Furthermore, in recent years, due to the global environmental load reduction and the trend of efficient use of resources, the cooling water for reclaimed water (reprocessed water) for replenishing water has been increasing. The recovered water is characterized by high calcium hardness, phosphorus concentration, chloride ion, and sulfate ion concentration. Since the recovered water has a high calcium hardness, it is a problem in the case where the recovered water is used for replenishing water, and even if the above-described scale inhibitor is added, the generation of scale cannot be prevented. Therefore, in order to reduce the concentration of the salt of the cooling water, it is necessary to increase the blow water amount, and it is difficult to reduce the water.

Another problem is the accelerated metal corrosion of the cooling water system caused by the high concentration of chloride ions and sulfate ions. Therefore, the recycled water is used as a supplement to the cooling water. The problem in water is to achieve scale and corrosion resistance in water with high concentration of scale components and corrosive ions.

From the viewpoint of water-repellent scale, there is a method of injecting an acid such as sulfuric acid to lower the pH of the cooling water. However, this method further increases the concentration of chloride ions or sulfate ions as corrosive ions by adding an acid, so actually Application is difficult.

A method of removing the hardness of calcium in the make-up water by a water softener and adjusting the total alkalinity and the pH value has been disclosed (Patent Document 1). However, it is necessary to frequently regenerate the water softener, which is difficult to apply.

In addition, as a reason why the effect of the scale inhibitor is not exhibited in the water system having a high calcium hardness, Patent Document 2 cites a gelation reaction between a polymer and calcium, and it is explained that the polymer loses solubility and precipitates. Waterproof scale. As a countermeasure against this, a (meth)acrylic polymer having a sulfonic acid group at the end of the main chain has been proposed, and it has been described that the gel resistance is improved, and an excellent scale resistance effect is exhibited in a water system having a high calcium concentration. .

According to this technique, even in the case of water having high calcium hardness, it is possible to prevent scale. However, even if the anti-corrosion treatment which is usually used is used in combination, it may not be possible to use the recovered water having a high concentration of corrosive ions as the makeup water. Get a full anti-corrosion effect. In addition, in actuality, even if it is desired to improve the corrosion resistance and increase the concentration of the corrosion inhibitor, it itself becomes scale in the form of phosphate or zinc hydroxide, and thus the effect cannot be obtained.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent No. 3918182

[Patent Document 2] Japanese Patent No. 3650724

The present invention has been made under such circumstances, and an object of the present invention is to provide a method for treating a cooling water system in which water (reprocessed water) is used to replenish water with a scale component and a water having a high corrosive ion concentration. It prevents the adhesion of calcium scale to pipes or heat exchangers, prevents obstacles such as heat transfer failure and flow rate reduction, and prevents corrosion of metals such as pipes and heat exchangers.

The inventors of the present invention have conducted intensive studies in order to achieve the above object, and as a result, have found that the above object can be attained by adding a treating agent to a cooling water system having a high calcium hardness and a high concentration of chloride ions or sulfate ions. Thus, the present invention has been completed, and the treatment agent is a (meth)acrylic copolymer containing a specific (meth)acrylic monomer in a specific ratio. The structural unit (a) and the structural unit (b) derived from a specific (meth)allyl ether-based monomer, and at least one main chain terminal is a sulfonic acid group or a salt thereof.

That is, the present invention provides a method for treating a cooling water system, which is a cooling water having a calcium hardness of 300 mg/L or more in terms of CaCO ₃ and a chloride ion and/or a sulfate ion concentration of 1000 mg/L or more. In the system, a method of treating a cooling water system containing a treatment agent containing a (meth)acrylic copolymer, and the (meth)acrylic copolymer is derived from the following formula (1) ( The structural unit (a) of the (meth)acrylic monomer (A) and the structural unit (b) derived from the (meth)allyl ether monomer (B) represented by the following general formula (2), And in all the monomer units derived from the monomer 100 mol% (% by mole), the content of the structural unit (a) is 80 mol% to 90 mol%, and the content of the structural unit (b) is 10 mol% to 20 mol. %, at least one main chain end of the above (meth)acrylic copolymer is a sulfonic acid group or a salt thereof,

(wherein R ¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group),

(wherein R ² represents a hydrogen atom or a methyl group, and Y and Z each independently represent a hydroxyl group, a sulfonic acid group or a salt thereof, and at least one of Y and Z represents a sulfonic acid group or a salt thereof).

According to the present invention, it is possible to provide a method for treating a cooling water system, which uses the recovered water (reprocessed water) for the scale component of the supplementary water and the water having a high corrosive ion concentration to prevent the calcium scale from being piped or heat exchanged. Adhesion of the device prevents obstacles such as heat transfer barriers and flow reduction, and prevents corrosion of metals such as pipes or heat exchangers.

The method for treating a cooling water system according to the present invention is characterized by cooling water having a calcium hardness of 300 mg/L or more in terms of CaCO ₃ and having a chloride ion and/or a sulfate ion concentration of 1000 mg/L or more. In the water system, a treating agent is added to prevent scale disorder of the cooling water system and to suppress corrosion of the metal, and the treating agent contains a (meth)acrylic copolymer having a specific structure.

[(Meth)acrylic copolymer]

The (meth)acrylic copolymer contained in the treatment agent used in the treatment method of the cooling water system of the present invention is a copolymer containing the structural unit (a) and the structural unit (b), and the above structural unit (a) is derived from In the (meth)acrylic monomer (A) represented by the following formula (1), the structural unit (b) is derived from a (meth)allyl ether represented by the following formula (2). Body (B).

(wherein R ¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group)

(wherein R ² represents a hydrogen atom or a methyl group, and Y and Z are each independently a hydroxyl group, a sulfonic acid group or a salt thereof, and at least one of Y and Z represents a sulfonic acid group or a salt thereof)

Specifically, each of the structural unit (a) and the structural unit (b) is a structural unit represented by the following general formula (3) or (4).

(wherein R ¹ and X are the same as the above formula (1))

(wherein R ² , Y and Z are the same as the above formula (2))

((meth)acrylic monomer (A))

The (meth)acrylic monomer (A) is represented by the above formula (1), and specific examples of the metal atom of X in the formula (1) include lithium, sodium, potassium, and the like, and an organic amine. Specific examples of the group include monoethanolamine, diethanolamine, triethanolamine, and the like.

Specific examples of the (meth)acrylic monomer (A) include acrylic acid, methacrylic acid, and the like (for example, a sodium salt, a potassium salt, an ammonium salt, etc.), and among these, acrylic acid is particularly preferred. Sodium acrylate, methacrylic acid. These may be used alone or in combination of two or more.

In addition, the above "(meth)acrylic type" means both an acrylic type and a methacryl type. Other similar terms are the same.

((meth)allyl ether monomer (B))

The (meth)allyl ether-based monomer (B) is represented by the above formula (2), and in the formula (2), as a sulfonic acid group of Y and Z or a salt thereof, a specific example of the metal salt For example, a salt such as sodium, potassium or lithium may be mentioned, and specific examples of the salt of the organic amine group include monoethanolamine, diethanolamine and triethanolamine.

Specific examples of the (meth)allyl ether-based monomer (B) include 3-(methyl)allyloxy-2-hydroxy-1-propanesulfonic acid and a salt thereof, and 3-(methyl group). Alkenyloxy-1-hydroxy-2-propanesulfonic acid and salts thereof, particularly preferably sodium 3-(methyl)allyloxy-2-hydroxy-1-propanesulfonate. These may be used alone or in combination of two or more.

In addition, the above "(meth)allyl ether system" means both an allyl ether type and a methyl allyl ether type. Other similar terms are the same.

<Morbi>

The (meth)acrylic copolymer is a structural unit containing a structural unit (a) derived from a (meth)acrylic monomer (A) and a (meth)allyl ether-based monomer (B). The copolymer of (b), the content of the structural unit (a) is 80 mol% to 90 mol%, and the content of the structural unit (b) is 10 mol% in 100 mol% of all structural units derived from the monomer. ~20 mol% ratio. When the content of the structural unit (a) exceeds 90 mol%, the affinity with calcium becomes too strong, and when applied to a water system having a high calcium hardness, the polymer tends to gel and precipitate, and the performance is not exhibited. When the content of the structural unit (a) is less than 80 mol%, the proportion of the carboxyl group contributing to the corrosion prevention is small, so that the corrosion resistance is lowered.

<molecular weight>

The weight average molecular weight of the (meth)acrylic copolymer is preferably from about 1,000 to 40,000. When the weight average molecular weight of the (meth)acrylic copolymer exceeds 40,000, the gel resistance is lowered, and when the weight average molecular weight of the (meth)acrylic copolymer is less than 1,000, the scale resistance is lowered. Further, the (meth)acrylic copolymer preferably has a weight average molecular weight of 5,000 to 38,000.

Further, the above weight average molecular weight is a value in terms of standard polyacrylic acid obtained by gel permeation chromatography (GPC method).

(Other monomer (C))

The (meth)acrylic copolymer may contain the structural unit (a) and the structural unit (b) at least in the above ratio, and may include There is a structural unit (c) derived from other monomers copolymerizable with the (meth)acrylic monomer (A) or the (meth)allyl ether monomer (B) (C) ). In this case, the ratio of the structural unit (c) is preferably 10 mol% or less, more preferably 5 mol% or less, relative to 100 mol% of all the structural units derived from the monomer.

Examples of the other monomer (C) include 2-propenylamine-2-methylpropanesulfonic acid, (meth)allylsulfonic acid, vinylsulfonic acid, styrenesulfonic acid, and methacrylic acid-2- a sulfonic acid group-containing unsaturated monomer such as sulfonic acid ethyl ester and the like; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinyl-N- N-vinyl monomer such as methylformamide, N-vinyl-methylacetamide, N-vinyl oxazolidone; (meth) acrylamide, N, N a nitrogen-containing nonionic unsaturated monomer such as dimethyl methacrylamide or N-isopropyl acrylamide; 3-(methyl)allyloxy-1,2-dihydroxypropane, (methyl a hydroxyl group-containing unsaturated monomer such as allyl alcohol or isoprenol; adding 1 mole to 200 moles on 3-(methyl)allyloxy-1,2-dihydroxypropane a compound obtained by ethylene oxide on the left and right sides of the ear (3-(methyl)allyloxy-1,2-di(poly)oxyethyl ether propane), and addition to (meth)allyl alcohol a compound containing a polyoxyethylene group such as a compound having a molar content of about 100 moles of ethylene oxide; methyl (meth)acrylate or (meth)acrylic acid (Meth) acrylate ester, (meth) acrylate, butyl (meth) acrylate and the like; an unsaturated dicarboxylic acid monomer is itaconic acid; unsaturated aromatic monomers such as styrene and the like.

These monomers (C) may be used alone or in combination of two or more.

(Production method)

The method for producing the (meth)acrylic copolymer includes exemplifying the monomer A method of polymerizing (A), a monomer (B), and a monomer mixture of the monomer (C) (hereinafter simply referred to as "monomer mixture") in the presence of a polymerization initiator.

<Polymerization initiator>

A known initiator can be used as the polymerization initiator. For example, preferred are: hydrogen peroxide; persulfate such as sodium persulfate, potassium persulfate or ammonium persulfate; dimethyl-2,2'-azobis(2-methylpropionate), 2,2 '-Azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2, 2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyrate) dimethyl ester, 4,4'-azobis ( 4-cyanovaleric acid), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2- Methylpropionamidine]n hydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2) -Imidazoline-2-yl)propane disulfate dihydrate, azo compound such as 1,1'-azobis(cyclohexane-1-carbonitrile); benzamidine peroxide, lauric peroxide An organic peroxide such as hydrazine, peracetic acid, di-tert-butyl peroxide or cumene hydroperoxide. Among these polymerization initiators, from the viewpoint of improving the gel resistance of the obtained polymer, it is preferred to use a persulfate described later.

The amount of the polymerization initiator to be used is not particularly limited as long as it is such that the copolymerization of the monomer mixture can be initiated. It is preferably one mole per monomer mixture, except for the case described below. 15 g or less, more preferably 1 g to 12 g.

<chain transfer agent>

In the method for producing the (meth)acrylic copolymer, a chain transfer agent may be used as the molecular weight of the polymer, as needed, insofar as it does not adversely affect the polymerization. Conditioner.

Specific examples of the chain transfer agent include mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, octyl thioglycolate, and 3 a mercaptan chain transfer agent such as octyl cyanopropionate, 2-mercaptoethanesulfonic acid, n-dodecyl mercaptan, octyl mercaptan, or butyl thioglycolate; carbon tetrachloride, dichloromethane ( Methylene chloride), halides such as bromoform and bromotrichloroethane; secondary alcohols such as isopropanol and glycerol; phosphorous acid, hypophosphorous acid and salts thereof (sodium hypophosphite, potassium hypophosphite) Or) sulfuric acid, bisulfurous acid, dithionous acid, metabisulfurous acid and salts thereof (hereinafter also referred to as "heavy sulfites"). Lower oxides such as sodium sulfite, potassium bisulfite, sodium disulfite, potassium disulfite, sodium metabisulfite, potassium metabisulfite, etc., and salts thereof. The above chain transfer agents may be used alone or in combination of two or more.

When the chain transfer agent is used, the copolymer to be produced can be inhibited from being polymerized to a required degree or more, and a low molecular weight copolymer can be efficiently produced. Among these, in the copolymerization reaction of the present invention, it is preferred to use bisulfite. Thereby, a sulfonic acid group can be efficiently introduced into the main chain end of the obtained copolymer, and gel resistance can be improved. Further, it is preferred to use a heavy sulfite (salt) as a chain transfer agent to improve the color tone of the copolymer (composition).

The amount of the chain transfer agent to be added is not particularly limited as long as it is a good amount of the monomer mixture to be polymerized, and is preferably 1 g to 20 g with respect to the monomer mixture, except for the case described below. More preferably, it is 2 g~15 g.

<starting agent system>

In the method for producing the (meth)acrylic copolymer, it is preferred to use one or more of persulfate and bisulfite (salt) as a starting agent (polymerization initiator and chain transfer agent). The combination). Thereby, the sulfonic acid group can be efficiently introduced at the end of the polymer main chain, and a low molecular weight water-soluble polymer excellent in gel resistance in addition to the dispersing ability or the chelate ability can be obtained, and the present invention can be effectively exhibited. The effect of the effect. By adding a bisulfite (salt) to the initiator in addition to the persulfate, it is possible to suppress the obtained polymer from being polymerized to a required degree or more, and to efficiently produce a polymer having a low molecular weight.

Specific examples of the persulfate salt include sodium persulfate, potassium persulfate, and ammonium persulfate.

Further, in the present invention, the heavy sulfite (salt) is as described above, and among them, sodium metabisulfite, potassium bisulfite, and ammonium bisulfite are preferable.

In the case where the above-mentioned persulfate and bisulfite (salt) are used in combination, the amount of the bisulfite is preferably 0.1 part by mass to 5 parts by mass, more preferably 1 part by mass of the persulfate. It is in the range of 0.2 parts by mass to 3 parts by mass, and more preferably 0.2 parts by mass to 2 parts by mass. When the amount of the sulfite (salt) is less than 0.1 part by mass based on 1 part by mass of the persulfate, the effect of the bisulfite (salt) tends to be small. Therefore, the introduction amount of the sulfonic acid group at the terminal of the polymer decreases, and the gel resistance of the copolymer tends to decrease. Further, the weight average molecular weight of the (meth)acrylic copolymer tends to be high. On the other hand, when the amount of the bisulfite (salt) is more than 5 parts by mass based on 1 part by mass of the persulfate, there is a tendency that the effect of the bisulfite (salt) cannot be obtained in accordance with the addition ratio. Next, heavy sulfite (salt) is supplied (depletedly consumed) in the polymerization reaction system. Therefore, excess bisulfite (salt) is decomposed in the polymerization system, and a large amount of sulfurous acid gas (SO ₂ gas) is generated. In addition, a large amount of impurities in the (meth)acrylic copolymer tend to be formed, and the performance of the obtained (meth)acrylic copolymer tends to be lowered. Further, there is a tendency that impurities are easily precipitated at the time of low temperature retention.

Regarding the case of using the above persulfate and bisulfite (salt) The amount of addition, relative to the monomer mixture 1 mole, the total amount of persulfate and bisulfite (salt) is preferably 2 g to 20 g, more preferably 2 g to 15 g, and further preferably 3 g~ 10 g, and more preferably 4 g to 9 g. When the amount of the persulfate and bisulfite (salt) added is less than 2 g, the molecular weight of the obtained polymer tends to increase. In addition to this, there is a tendency that the sulfonic acid group introduced into the terminal of the obtained (meth)acrylic copolymer is reduced. On the other hand, when the amount added exceeds 20 g, there is a tendency that the effects of persulfate and bisulfite (salt) cannot be obtained in accordance with the added amount, and the obtained (meth)acrylic copolymer is obtained instead. The purity is reduced.

The persulfate salt may also be dissolved in a solvent described below, preferably dissolved in water. It is added in the form of a persulfate solution (preferably an aqueous solution). The concentration in the case of using the persulfate solution (preferably an aqueous solution) is preferably from 1% by mass to 35% by mass, more preferably from 5% by mass to 35% by mass, and even more preferably from 10% by mass to 30% by mass. quality%. Here, when the concentration of the persulfate solution is less than 1% by mass, the concentration of the product is lowered, and transportation and storage become troublesome. On the other hand, when the concentration of the persulfate solution exceeds 35% by mass, the handling becomes difficult.

The above bisulfite (salt) may be dissolved in a solvent described below, preferably dissolved. The solution is added in the form of a solution of a bisulfite (preferably aqueous solution) in water. The concentration in the case of using the bisulfite-based solution (preferably an aqueous solution) is preferably 10% by mass to 42% by mass, more preferably 20% by mass to 42% by mass, and still more preferably 32% by mass. Mass%~42% by mass. Here, when the concentration of the heavy sulfite solution is less than 10% by mass, the concentration of the product is lowered, and transportation and storage become troublesome. On the other hand, when the concentration of the heavy sulfite solution is more than 42% by mass, the handling becomes difficult.

<Other additives>

In the method for producing the (meth)acrylic copolymer, as an additive other than the initiator or the chain transfer agent which can be used in the polymerization reaction system when the monomer mixture is polymerized in an aqueous solution, the present invention may be omitted. Appropriate additives such as heavy metal concentration adjusters and pH adjusters may be added in an appropriate amount within the range of effects.

The heavy metal concentration adjusting agent is not particularly limited, and for example, a polyvalent metal compound or a monomer can be used. Specific examples thereof include: vanadium trichloride oxide, vanadium trichloride, vanadyl oxalate, vanadyl sulfate, anhydrous vanadic acid, ammonium metavanadate, ammonium sulfate hypovanadas [(NH ₄ ) ₂ SO ₄ . VSO ₄ . 6H ₂ O], ammonium sulfate vanadium [(NH ₄ )V(SO ₄ ) ₂ . 12H ₂ O], copper (II) acetate, copper (II), copper (II) bromide, copper (II) acetate, copper (II) chloride, copper ammonium chloride, copper carbonate, copper chloride (II), copper (II) citrate, copper (II) hydride, copper (II) hydroxide, copper nitrate, copper naphthenate, copper (II) oleate, copper maleate, copper phosphate, copper sulfate ( II), cuprous chloride, copper (I) cyanide, copper iodide, copper (I) oxide, copper thiocyanate, acetamidine Iron, ferric ammonium citrate, ferric ammonium oxalate, ferrous ammonium sulfate, ferric ammonium sulfate, ferric citrate, fumaric acid Iron, ferric ironate, ferric nitrate, ferric nitrate, ferric phosphate, ferric pyrophosphate a polyvalent metal oxide such as vanadium, copper (II) oxide, ferrous oxide or ferric oxide; a polyvalent metal sulfide such as iron (III) sulfide, iron sulfide (II) or copper sulfide; Copper powder, iron powder, and the like.

In the method for producing a (meth)acrylic copolymer, since the obtained (meth)acrylic copolymer preferably has a heavy metal ion concentration of 0.05 ppm to 10 ppm, it is preferred to add the above amount as needed. Heavy metal concentration adjuster.

(polymerization solvent)

In the production of the (meth)acrylic copolymer, the monomer mixture is usually polymerized in a solvent, and the solvent used in the polymerization system is preferably water, alcohol, glycol, glycerin or polyethylene. An aqueous solvent such as an alcohol is particularly preferably water. These may be used alone or in combination of two or more. Moreover, in order to improve the solubility of the monomer mixture in a solvent, an organic solvent may be appropriately added in a range that does not adversely affect the polymerization of each monomer.

Specifically, the organic solvent may be appropriately selected from the following compounds: one or two or more kinds of lower alcohols such as methanol and ethanol; guanamines such as dimethylformaldehyde; and ethers such as diethyl ether and dioxane.

The amount of the solvent used is preferably from 40% by mass to 200% by mass, more preferably from 45% by mass to 180% by mass, even more preferably from 50% by mass to 150% by mass based on the total amount of the monomer mixture. When the amount of the solvent used is less than 40% by mass, the molecular weight becomes high. On the other hand, when the amount of the solvent used exceeds 200% by mass, the concentration of the produced (meth)acrylic copolymer becomes low, and it may be necessary to remove the solvent depending on the case. Further, a majority or a total amount of the solvent may be added to the reaction vessel at the initial stage of polymerization. For example, a part of the solvent may be appropriately added (dropped) to the reaction system alone in the polymerization, and the monomer mixture may also be used. The form in which the component, the starter component, or other additives are previously dissolved in the solvent is appropriately added (dropped) to the reaction system together with the components.

(polymerization temperature)

The polymerization temperature of the above monomer mixture is not particularly limited. The polymerization temperature is preferably 50 ° C or higher, more preferably 70 ° C or higher, or preferably 99 ° C or lower, and even more preferably 95 ° C or lower from the viewpoint of efficiently producing the polymer. When the polymerization temperature is lower than 50 ° C, the polymerization time is too long, and the productivity is lowered, in addition to an increase in molecular weight and an increase in impurities. On the other hand, when the polymerization temperature is set to 99 ° C or lower, when bisulfuric acid (salt) is used as the initiator system, decomposition of bisulfite (salt) can be suppressed and a large amount of sulfurous acid gas can be generated. Therefore, it is better. The polymerization temperature herein means the temperature of the reaction solution in the reaction system.

In particular, in the case of a method of starting polymerization from room temperature (room start method), for example, when polymerization is carried out for 180 minutes per batch (180 minutes of prescription), it is preferably within 70 minutes, preferably In 0 minutes to 50 minutes, More preferably, the temperature is set to be from 0 minutes to 30 minutes (as long as it is within the range of the above polymerization temperature, preferably from 70 ° C to 90 ° C, more preferably from about 80 ° C to 90 ° C). Thereafter, it is desirable to maintain the set temperature until the end of the polymerization. When the temperature rise time deviates from the above range, the obtained (meth)acrylic copolymer has a high molecular weight. Further, although the example in which the polymerization time is 180 minutes is shown, when the prescription of the polymerization time is different, it is preferable to refer to this example and set the temperature rise time so that the ratio of the temperature rise time to the polymerization time is the same.

(Reaction system pressure, reaction environment)

In the polymerization of the above monomer mixture, the pressure in the reaction system is not particularly limited, and may be any pressure at normal pressure (atmospheric pressure), under reduced pressure, or under pressure. When bisulfuric acid (salt) is used as the initiator system, it is preferred to prevent the release of sulfurous acid gas during the polymerization to achieve low molecular weight, so that it is preferably carried out under normal pressure or within the reaction system. It is sealed and pressurized. Further, when the polymerization is carried out under normal pressure (atmospheric pressure), it is not necessary to provide a pressurizing device or a pressure reducing device, and it is not necessary to use a reaction container or a pipe which is resistant to pressing. Therefore, from the viewpoint of production cost, it is preferably atmospheric pressure (atmospheric pressure). In other words, the optimum pressure conditions may be appropriately set depending on the purpose of use of the obtained (meth)acrylic copolymer.

The environment within the reaction system can maintain an air environment, but is preferably set to an inert environment. For example, it is preferred to replace the inside of the reaction system with an inert gas such as nitrogen before the start of the polymerization. Thereby, it is possible to prevent the ambient gas (for example, oxygen or the like) in the reaction system from being dissolved in the liquid phase to function as a polymerization inhibitor. As a result, it is possible to prevent the initiator (persulfate or the like) from being deactivated and reduced, and it is possible to achieve a lower molecular weight.

(degree of neutralization in polymerization)

In the method for producing the (meth)acrylic copolymer, the polymerization reaction of the monomer mixture is preferably carried out under acidic conditions. By carrying out the reaction under acidic conditions, the viscosity of the aqueous solution of the polymerization reaction system can be suppressed from increasing, and the low molecular weight (meth)acrylic copolymer can be favorably produced. Further, since the polymerization reaction can be carried out under conditions of a higher concentration than before, the production efficiency can be greatly improved. In particular, by reducing the degree of neutralization in the polymerization to 0 mol% to 25 mol%, the effect of the above-mentioned reduction in the initial dose can be doubled, and the effect of reducing impurities can be particularly enhanced. Further, it is preferred to adjust the pH of the reaction solution in the polymerization at 25 ° C to 1 to 6. By carrying out the polymerization reaction under such acidic conditions, the polymerization can be carried out at a high concentration and in one stage, so that the concentration step can be omitted. Therefore, the productivity is greatly improved, and the increase in manufacturing cost can also be suppressed.

In the above acidic conditions, the pH of the reaction solution in the polymerization at 25 ° C It is preferably 1 to 6, more preferably 1 to 5, and further preferably 1 to 4. In the case where the pH is less than 1, for example, when bisulfuric acid (salt) is used as the initiator system, sulfurous acid gas may be generated to cause corrosion of the apparatus. On the other hand, when the pH exceeds 6, when bisulfite (salt) is used as the initiator system, the efficiency of the bisulfite (salt) is lowered and the molecular weight is increased.

Examples of the pH adjuster for adjusting the pH of the reaction solution include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, hydroxides of alkaline earth metals such as calcium hydroxide and magnesium hydroxide, ammonia, monoethanolamine, and the like. An organic amine salt such as triethanolamine. These may be used alone or in combination of two or more. Among these, sodium hydroxide and hydrogen are preferred. An alkali metal hydroxide such as potassium oxide is particularly preferably sodium hydroxide. In the present specification, these may be simply referred to as "pH adjusters" or "neutralizers".

The degree of neutralization in the polymerization is preferably from 0 mol% to 25 mol%, more preferably 1 Mol%~15 mol%, and preferably in the range of 2 mol% to 10 mol%. When the degree of neutralization in the polymerization is within this range, the copolymer can be optimally copolymerized, and impurities can be reduced to produce a polymer having good gel resistance. Further, the low molecular weight polymer can be favorably produced without increasing the viscosity of the aqueous solution of the polymerization reaction system. Further, since the polymerization reaction can be carried out under conditions of a higher concentration than before, the production efficiency can be greatly improved.

On the other hand, when the degree of neutralization in the polymerization exceeds 25 mol%, the chain transfer efficiency of bisulfite (salt) may decrease and the molecular weight may increase. In addition to this, as the polymerization progresses, the viscosity of the aqueous solution of the polymerization reaction increases. As a result, the molecular weight of the obtained polymer is increased to the extent necessary, and a low molecular weight polymer cannot be obtained. Further, the effect obtained by the above-described reduction in the degree of neutralization may not be sufficiently exhibited, and it may be difficult to greatly reduce impurities.

The neutralization method herein is not particularly limited. For example, (meth) propylene A (meth) acrylate such as sodium is used as a part of the raw material, and a hydroxide of an alkali metal such as sodium hydroxide or the like may be used as a neutralizing agent to neutralize the polymerization, or may be used in combination. Further, the addition form of the neutralizing agent at the time of neutralization may be a solid or an aqueous solution dissolved in a suitable solvent, preferably an aqueous solution dissolved in water.

The concentration of the aqueous solution in the case of using an aqueous solution is preferably 10% by mass to 60% by mass, more preferably 20% by mass to 55% by mass, and still more preferably 30% by mass to 50% by mass. When the concentration of the aqueous solution is less than 10% by mass, the concentration of the product is lowered, and the transportation and storage become cumbersome. When the concentration of the aqueous solution exceeds 60% by mass, precipitation may occur and the viscosity may become high. The liquid becomes complicated.

(addition conditions of raw materials)

In the polymerization, the monomer mixture, the starter, the chain transfer agent and other additives are preferably dissolved in a suitable solvent (preferably the same solvent as the solvent used for the drip solution). Forming a monomer mixture solution, a starter solution, and a chain transfer agent solution and other additive solutions, facing the (aqueous) solvent that has been added to the reaction vessel (if necessary, adjusted to a predetermined temperature) to a predetermined drop The polymerization was carried out while continuously adding dropwise the respective solutions. Further, a part of the aqueous solvent may be added dropwise after the initial addition of the solvent previously added to the container in the reaction system. However, it is not limited to this manufacturing method.

For example, regarding the dropping method, it may be continuously dropped, or may be added dropwise in a small amount intermittently. It is also possible to initially add a part or a total amount of one or two or more kinds of monomers. In addition, the dropping rate (drop amount) of one or two or more kinds of monomers may be fixedly fixed (a certain amount) from the beginning to the end of the dropwise addition, or the dropping rate may be made according to the polymerization temperature or the like ( The amount of addition) varies with time. Further, even if all the dropping components are added in the same manner, the dropping components can be shifted at the beginning or at the end, or the dropping time can be shortened or lengthened.

In the case where bisulfite (salt) is used as the initiator, the molecular weight at the initial stage of polymerization has a large influence on the final molecular weight. Therefore, in order to lower the initial molecular weight, it is preferably within 60 minutes from the start of the polymerization, more preferably 30. Within 5 minutes, it is preferable to add (drop) 5% by mass to 20% by mass of heavy sulfite (salt) or a solution thereof within 10 minutes. In particular, as will be described later, it is effective in the case of starting polymerization from room temperature.

Further, in the dropwise addition component during the polymerization, the dropping time of the bisulfite (salt) or the solution thereof in the case where bisulfuric acid (salt) is used as the initiator is preferably a monomer ( The end of the dropwise addition of the A) and the monomer (B) is preferably from 1 minute to 30 minutes, more preferably from 1 minute to 20 minutes, and further preferably from 1 minute to 15 minutes. Thereby, the amount of bisulfite (salt) after the completion of the polymerization can be reduced, and the generation of sulfurous acid gas or the formation of impurities by the bisulfite (salt) can be effectively and efficiently suppressed. Therefore, after the completion of the polymerization, the impurities in which the sulfurous acid gas in the gas phase portion is dissolved in the liquid phase can be particularly reduced. When bisulfite (salt) remains after the completion of the polymerization, impurities are generated to cause deterioration of the performance of the polymer or precipitation of impurities at the time of low temperature retention. Therefore, it is desirable that the initiator containing a heavy sulfite (salt) at the end of the polymerization is consumed without remaining.

Here, when the end time of the dropwise addition of the heavy sulfite (solution) is shorter than the end time of the addition of the monomer (A) or the monomer (B), it may be less than one minute earlier. The heavy sulfite (salt) remains after the end of the polymerization. Such a case includes the case where the dropwise addition of the heavy sulfite (salt) or the solution thereof is completed simultaneously with the completion of the dropwise addition of the monomer (A) or the monomer (B), or the heavy sulfite (salt) (solution) The completion of the dropwise addition is completed later than the completion of the dropwise addition of the monomer (A) and the monomer (B). In such a case, it is difficult to effectively and efficiently suppress the generation of sulfurous acid gas or the formation of impurities, and the residual initiator may cause adverse effects on the thermal stability of the obtained polymer. ring. On the other hand, when the end time of the dropwise addition of the heavy sulfurous acid (salt) or its solution is earlier than the end time of the dropwise addition of the monomer (A) or the monomer (B), the heavy sulfurous acid (salt) The class is consumed until the end of the aggregation. Therefore, there is a tendency for the molecular weight to increase. In addition, the dropping rate of heavy sulfite (salt) in the polymerization is faster than that of the monomer (A) and the monomer (B), and is dripped in a short time, so that a large amount is generated during the dropwise addition period. The tendency of impurities or sulfurous acid gas.

In addition, in the dripping component at the time of polymerization, bisulfite (salt) is used. In the case of the initiator system, the dropwise addition end time of the persulfate (solution) is preferably from 1 minute to 30 minutes from the end time of the dropwise addition of the monomer (A) and the monomer (B). More preferably, it is 1 minute to 25 minutes, and further preferably 1 minute to 20 minutes. Thereby, the amount of the monomer component remaining after the completion of the polymerization can be reduced, and the impurities caused by the residual monomer can be particularly reduced.

Here, the end time of the addition of the persulfate (solution) is shorter than that of the monomer (A), When the completion time of the dropwise addition of the monomer (B) can be delayed only for less than 1 minute, the monomer component may remain after the completion of the polymerization. In this case, the end of the dropwise addition of the persulfate (solution) is the same as the end of the dropwise addition of the monomer (A) or the monomer (B), or the dropwise addition of the persulfate (solution) is earlier than the single The case where the dropwise addition of the body (A) and the monomer (B) is completed. In such a case, there is a tendency that it is difficult to effectively and efficiently suppress the formation of impurities. On the other hand, when the end time of the dropwise addition of the persulfate (solution) is delayed by more than 30 minutes from the end time of the dropwise addition of the monomer (A) or the monomer (B), the persulfate or the persulfate thereof after the end of the polymerization may be used. The decomposition product remains to form impurities.

(aggregation time)

In the case of polymerization, when the polymerization temperature is lowered and bisulfuric acid (salt) is used as the initiator system, it is more important to suppress the generation of sulfurous acid gas and prevent the formation of impurities. Therefore, the total dropping time at the time of polymerization is desirably as long as preferably from 150 minutes to 600 minutes, more preferably from 160 minutes to 450 minutes, and even more preferably from 180 minutes to 300 minutes.

When the total dropping time is less than 150 minutes, the effect of the persulfate solution and the bisulfite solution added as the initiator is lowered, so that the obtained (meth)acrylic copolymer is copolymerized. The amount of the sulfur-containing group such as a sulfonic acid group introduced into the end of the main chain tends to decrease. As a result, there is a tendency that the weight average molecular weight of the polymer becomes high.

Further, by dropwise addition to the reaction system in a short period of time, there is a possibility that excess bisulfite (salt) is present. Therefore, sometimes such excess bisulfite (salt) is decomposed to generate sulfurous acid gas, which is released to the outside of the system or forms impurities. However, the above can be improved by performing the dropwise addition in a specific range in which the polymerization temperature and the starting dose are low.

On the other hand, when the total dropping time exceeds 600 minutes, the generation of sulfurous acid gas is suppressed, so that the performance of the obtained polymer is good, but the productivity is sometimes lowered, and the use is limited. The total dropping time herein refers to the time from the start of the dropwise addition of the first dropping component (not limited to one component) to the end of the dropping of the last dropping component (not limited to one component).

(polymerized solid content concentration of monomer)

When the dropwise addition of the total amount of the above monomer, polymerization initiator and chain transfer agent is completed, the solid content concentration in the aqueous solution (ie, the concentration of the polymerized solid component of the monomer) is higher. The content is preferably 35 mass% or more, more preferably 40 mass% to 70 mass%, and further preferably 45 mass% to 65 mass%. When the solid content concentration at the end of the polymerization reaction is 35% by mass or more, the polymerization can be carried out at a high concentration and in a single step, so that a low molecular weight (meth)acrylic copolymer can be efficiently obtained, and for example, the concentration step can be omitted. Therefore, the manufacturing efficiency and productivity can be greatly improved, and the manufacturing cost can be suppressed.

When the solid content concentration is increased in the polymerization reaction system, the viscosity of the reaction solution increases with the progress of the polymerization reaction, and the weight average molecular weight of the obtained polymer tends to be greatly increased. However, by carrying out the polymerization reaction on the acidic side (pH of 1 to 6 at 25 ° C and the degree of neutralization of the carboxylic acid in the range of 0 mol% to 25 mol %), the reaction accompanying the polymerization reaction can be suppressed. The viscosity of the solution rises. Therefore, even if the polymerization reaction is carried out under a high concentration condition, a polymer having a low molecular weight can be obtained, and the production efficiency of the polymer can be greatly improved.

(maturing step)

In the method for producing the (meth)acrylic copolymer, after the addition of all the raw materials used, the ripening step can be provided for the purpose of increasing the polymerization rate of the monomers and the like. The aging time is usually from 1 minute to 120 minutes, preferably from 5 minutes to 90 minutes, more preferably from 10 minutes to 60 minutes. When the aging time is less than 1 minute, the aging may be insufficient to cause the monomer component to remain, and impurities due to the residual monomer may be formed to deteriorate the performance. On the other hand, the polymer solution may be colored when the aging time exceeds 120 minutes.

The temperature of the preferred polymer solution in the ripening step is the same range as the above polymerization temperature. Therefore, the temperature here is also at a certain temperature (preferably The temperature is maintained at the time of the beam, and the temperature can be varied with time during aging.

(step after polymerization)

In the method for producing the (meth)acrylic copolymer, the polymerization is preferably carried out under acidic conditions as described above. Therefore, the degree of neutralization of the carboxylic acid of the obtained (meth)acrylic copolymer (the final degree of neutralization of the carboxylic acid) may be set after the completion of the polymerization, if necessary, by appropriately adding an appropriate alkali component as a post-treatment. Within the established range. Examples of the alkali component include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; hydroxides of alkaline earth metals such as calcium hydroxide and magnesium hydroxide; and organic amines such as ammonia, monoethanolamine, diethanolamine and triethanolamine. Wait.

The final degree of neutralization differs depending on the intended use, and is not particularly limited.

The final degree of neutralization of the carboxylic acid in the case of use as an acidic polymer is preferably from 0 mol% to 75 mol%, more preferably from 0 mol% to 70 mol%. The final degree of neutralization of the carboxylic acid in the case of use as a neutral or basic polymer is preferably from 75 mol% to 100 mol%, more preferably from 85 mol% to 99 mol%. Further, in the case where the final degree of neutralization in the case of being used as a neutral or basic polymer exceeds 99 mol%, the aqueous polymer solution may be colored.

Further, in the case where it is not used for neutralization and is intended to be used as an acid, since the reaction system is acidic, toxic sulfurous acid gas may remain in the reaction system and in the environment. In such a case, it is desirable to decompose the peroxide by adding a peroxide such as hydrogen peroxide, or to preliminarily introduce (blowing) air or nitrogen to drive it out.

Further, the method for producing the (meth)acrylic copolymer may be a batch type or a continuous type.

The (meth)acrylic copolymer thus obtained exerts the following effects: Stops the scale of the cooling water system and inhibits corrosion of the metal. Though the mechanism is not necessarily clear, the carboxyl group derived from the structural unit (a) of the (meth)acrylic monomer (A) has a strong affinity with calcium ions as a scale component, and is adsorbed to the growth of crystals. Point, thus hindering growth. Further, it is also known that a raw material containing a carboxyl group has an anticorrosive property, and by setting the structural unit (a) to a mol% or more, it is possible to have both a scale and an anticorrosive effect.

In order to prevent gelation, it is necessary to set the structural unit (b) derived from the (meth)allyl ether-based monomer (B) having a small interaction with calcium ions and having high solubility to a certain amount or more. The number must be such that the end of the main chain is a sulfonic acid group to improve gel resistance.

Next, the treatment method of the cooling water system of the present invention will be described.

[Processing method of cooling water system]

In the treatment method of the cooling water system of the present invention, the treatment agent containing the above (meth)acrylic copolymer is added to a cooling water system having the following water quality, preventing scale disorder of the cooling water system, and suppressing metal corrosion.

As described above, the (meth)acrylic copolymer is particularly preferably a copolymer comprising a structural unit (a) derived from acrylic acid (AA) or methacrylic acid (a) and a structural unit (b). One or two or more (meth)acrylic monomers (A) in MAA) and sodium acrylate (SA), the above structural unit (b) is derived from 3-allyloxy-2-hydroxy-1-propene Sodium sulfonate (HAPS). More specifically, the (meth)acrylic copolymer is AA/HAPS, MAA/HAPS, AA/SA/HAPS, Copolymer such as AA/MAA/HAPS.

Furthermore, the operating conditions in the case of applying the treatment method of the present invention are not particularly limited.

(water quality of cooling water system)

The treatment method of the cooling water system of the present invention is applied to a cooling water system having a water hardness of 300 mg/L or more in terms of CaCO ₃ and a chloride ion and/or a sulfate ion concentration of 1000 mg/L. the above.

Addition method of a scale inhibitor/corrosion inhibitor (hereinafter also referred to as "copolymer type scale inhibitor/anticorrosive agent") containing the (meth)acrylic copolymer described above added to such a cooling water system It is not particularly limited and may be added to a portion to be protected from corrosion or scale, or directly in front of it.

Further, the amount of the addition is not particularly limited and may be appropriately selected depending on the water quality of the cooling water system to be added. It is preferred that the concentration of the copolymer scale inhibitor/anticorrosant is usually 0.01 mg/L to 100 mg. /L, preferably 2 mg/L to 50 mg/L.

The copolymer is a scale inhibitor/anti-corrosion agent which can be used in combination with other scale inhibitors or corrosion inhibitors, slime control agents, if desired.

(Can be used together with anti-corrosion agent)

Examples of the corrosion inhibitor which can be used in combination include hydroxyethylidene diphosphonic acid or phosphinium butane tricarboxylic acid, ethylenediaminetetramethylenephosphonic acid, nitrilo trimethyl phosphonic acid, and the like. Phosphonic acid, orthophosphate, polymeric phosphate, phosphate, zinc salt, nickel salt, molybdenum salt, tungsten salt, oxycarboxylate, triazole, amine, and the like.

(waterproofing agent that can be used together)

Examples of the scale inhibitor which can be used in combination include a hydroxyethylidene diphosphonic acid or a phosphonium butane tricarboxylic acid, an ethylene diamine tetramethylene phosphonic acid, a phosphonic acid such as a nitrogen trimethylphosphonic acid, and an orthophosphoric acid. Salt, polymeric phosphate, polymaleic acid, polyacrylic acid, maleic acid copolymer, maleic acid/acrylic acid, maleic acid/isobutylene, maleic acid/sulfonic acid, acrylic acid/sulfonic acid, acrylic acid/nonionic A copolymer of a monomer, a trimer of an acrylic acid/sulfonic acid/nonionic group-containing monomer, and the like.

Examples of the sulfonic acid in the above scale inhibitor include vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, isoprenesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and 2 - acrylamide-2-methylpropanesulfonic acid, 2-methylpropenylamine-2-methylpropanesulfonic acid, allyloxybenzenesulfonic acid, methylallyloxybenzenesulfonic acid, and the like Metal salts, etc.

Further, examples of the nonionic group-containing monomer in the above scale inhibitor include a alkylguanamine (C1 to C5 alkylguanamine), hydroxyethyl methacrylate, and an addition molar number of 1 to 30. (poly)ethylene oxide/propane mono(meth)acrylate, monomethyl ether oxide/propane having a molar number of 1 to 30, and the like.

(Complex mud control agent can be used together)

Examples of the slime control agent which can be used together include a quaternary ammonium salt such as alkyldimethylbenzylammonium chloride, chloromethyltrithiazoline, chloromethylisothiazoline, methylisothiazoline or ethyl. A mixture of amino isopropylaminomethyl thiazolidine, hypochlorous acid, hypobromous acid, hypochlorous acid and sulfamic acid, etc., may also contain an enzyme, sterilizing Agents, colorants, perfumes, water-soluble organic solvents, defoamers, and the like.

The above-described scale inhibitor, corrosion inhibitor, and slime control agent may be used alone or in combination of two or more.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited by the examples.

In addition, the corrosion resistance test and the calcium phosphate scale precipitation suppression test were performed by the following methods, and the measurement of the molecular weight and the presence or absence of the terminal sulfonic acid group were confirmed by the following methods.

(1) Corrosion resistance test

A low carbon steel (Japanese Industrial Standards (JIS) G3141 SPSS-SB) having a size of 50 mm × 30 mm × 1 mm and a surface area of 0.31 dm ² was subjected to #400 grinding and toluene degreased test piece as a test piece. As such, the mass is determined and the mass is taken as the mass before the test.

In a 5000 ml polymer container, water obtained by dechlorinating wild wood water from 5000 ml minus the amount of each reagent added is added, and sodium hydrogencarbonate aqueous solution, sodium citrate aqueous solution, polymer solution, sulfuric acid is added. After a magnesium aqueous solution, a sodium chloride aqueous solution, a phosphoric acid solution, a calcium chloride aqueous solution, a sodium sulfate aqueous solution, or a zinc sulfate aqueous solution, the pH was adjusted with a small amount of a sodium hydroxide aqueous solution and a sulfuric acid aqueous solution to prepare test water. About 1000 ml of test water was transferred to a 1000 ml beaker, placed in a thermostatic chamber of a corrosion test apparatus maintained at 40 ° C, and the test piece was screwed to a rotating shaft and immersed in test water, and rotated at 170 rpm. The residual liquid of the test water was continuously injected into a 1000 ml beaker at 0.8 ml/min using a roller pump.

Three days after the immersion test piece, the test piece was taken out, and the surface of the test piece was washed with acid to remove the adhered corrosion product, and the mass after drying was measured, and the mass was taken as the mass after the test. Thereafter, the corrosion resistance (mdd) was calculated from the mass change of the test piece by the following formula, and the corrosion resistance was evaluated.

Corrosion rate (mdd) = {pre-test mass (mg) - mass after test (mg)} / {surface area of the test piece (dm ² ) × test days (days)}

The case where the etching rate was less than 10 mdd was evaluated as ◎, the case where the etching rate was 10 mdd or more and less than 20 mdd was evaluated as ○, and the case where the etching rate was 20 mdd or more and less than 30 mdd was evaluated as Δ, and the etching rate was The case of 30 mdd or more was evaluated as ×. The water quality conditions are shown in Table 1.

(2) Calcium phosphate scale precipitation inhibition test

In a 500 ml conical beaker, an amount of ultrapure water obtained by subtracting 500 ml of each reagent addition amount, an aqueous solution of sodium hydrogencarbonate, an aqueous solution of sodium citrate, a polymer solution, an aqueous solution of magnesium sulfate, After a sodium chloride aqueous solution, a phosphoric acid solution, an aqueous calcium chloride solution, and a sodium sulfate aqueous solution, the pH was adjusted with a small amount of a sodium hydroxide aqueous solution and a sulfuric acid aqueous solution, and after sealing, it was allowed to stand in a thermostat at 60 ° C for 20 hours. Thereafter, the phosphoric acid concentration of the filtrate was measured using a 0.1 μm filter paper, and the detection rate of phosphoric acid was calculated according to the following formula.

Phosphoric acid detection rate (%) = (phosphoric acid concentration after test / phosphoric acid concentration before test) ×100

When the detection rate of phosphoric acid was 90% or more, it was evaluated as ◎, and when the detection rate of phosphoric acid was 80% or more and less than 90%, it was evaluated as ○, and when the detection rate of phosphoric acid was 50% or more and less than 80%. When it is Δ, the case where the detection rate of phosphoric acid is less than 50% is evaluated as ×. The water quality conditions are shown in Table 1.

(3) Molecular weight

The weight average molecular weight was measured using a gel permeation chromatography ("HLC-8320GPC" manufactured by Tosoh Corporation) under the following conditions.

Detector: Differential refractometer RI

Pipe column: manufactured by Showa Denko Co., Ltd., Shodex Asahipak GF-310-HQ, Shodex Asahipak GF-710-HQ, Shodex Asahipak GF-1G

Eluent: 0.1 N sodium acetate solution

Flow rate: 0.5 ml/min

Column temperature: 40 ° C

Standard curve: Polyacrylic acid standard (POLYACRYLIC ACID STANDARD) (manufactured by Chuanghe Science Co., Ltd.)

(4) terminal sulfonic acid group

The copolymer (aqueous solution) adjusted to a pH of 1 was dried under reduced pressure at room temperature to distill off water, and then heavy water was used as a solvent to carry out ¹ H nuclear magnetic resonance (NMR) measurement. The terminal sulfonic acid group was confirmed based on the presence or absence of a peak of 2.7 ppm caused by introduction of a sulfonic acid group at the terminal of the polymer main chain.

Example 1 to Example 8 and Comparative Example 1 to Comparative Example 9

The polymers in the polymer solutions used in Examples 1 to 8 and Comparative Examples 1 to 9 were respectively copolymers obtained by polymerizing monomers in the ratios shown in Tables 2 and 3, and the weight average molecular weight. The presence or absence of the terminal sulfonic acid group is shown in Table 2 and Table 3, respectively.

Further, the corrosion rate (mdd) obtained by the corrosion resistance evaluation test using the copolymer and the phosphoric acid detection rate (%) obtained by performing the calcium phosphate scale inhibition test are shown in Tables 2 and 3, respectively.

According to Tables 2 and 3, in the calcium phosphate inhibition test in which the water quality of the recovered water is envisaged, if the phosphoric acid detection rate is compared, the comparison is in Comparative Example 4, Comparative Example 5, Comparative Example 1 to Comparative Example 3, and Comparative Example 6. Comparative Example 7 <Example, Comparative Example 8, and Comparative Example 9. From the results, it is known that a polymer having a structural unit derived from acrylic acid (AA) and sodium 3-allyloxy-2-hydroxy-1-propanesulfonate (HAPS) has a sulfonic acid group at the terminal end of the main chain. In the examples, the comparative examples 8, and the comparative examples 9, the water-repellent effect of the water was considered to be excellent in the water quality of the water. The reason for this is considered to be that it is less likely to cause gelation with calcium ions by introducing a sulfonic acid group at the end of the main chain.

It is known that Comparative Example 1 to Comparative Example 5 have no sulfonic acid group, so calcium phosphate scale is prevented. The effect is poor. It is found that Comparative Example 6 and Comparative Example 7 have a structural unit derived from HAPS, but do not have a sulfonic acid group at the end of the main chain. Therefore, in the case of water quality in which the recovered water is supplemental water, the scale resistance effect is deteriorated. As described above, in Comparative Examples 1 to 7, it was considered that the sulfonic acid group was not contained at the end of the main chain, so that gelation with calcium ions was caused, and the scale resistance effect was inferior to that of Examples, Comparative Example 8, and Comparative Example 9.

In the corrosion resistance evaluation test, when the corrosion rate was compared, the following were Comparative Example 8, Comparative Example 9> Comparative Example 6, Comparative Example 7> Comparative Example 1 to Comparative Example 5>Example. From the results, it was found that the examples having a large number of carboxyl groups and the comparative examples 1 to 5 had high anti-corrosion effects. This is considered to be because when the carboxyl group is large, it is easily adsorbed on the etching surface, so that the progress of corrosion can be suppressed.

Although Comparative Example 8 and Comparative Example 9 were found to have excellent scale-preventing effects similar to those of the Examples, the corrosion resistance was inferior to that of the Examples. From the results, it is found that if the proportion of the sulfonic acid exceeds 20 mol%, the anticorrosive effect is lowered, and it is impossible to suppress corrosion in the water quality of the recovered water, and it is impossible to have both the scale preventing effect and the anticorrosive effect.

From the above results, it is known that a polymer having a sulfonic acid group at the terminal end of the polymer having AA and HAPS and a ratio of HAPS of 10 mol% to 20 mol% is shown in the water quality in which the recovered water is supplemented with water. Excellent anti-scaling effect and anti-corrosion effect.

[Industrial availability]

The treatment method of the cooling water system of the present invention can use the recovered water (reprocessed water) to replenish the scale component of the water and the water having high corrosive ions, thereby preventing the adhesion of the calcium scale to the piping or the heat exchanger and preventing the transmission. Heat barrier, flow reduction, etc. It is a problem and prevents corrosion of metals such as pipes or heat exchangers.

Claims (2)

A method for treating a cooling water system, which is added to a cooling water system having a calcium hardness of 300 mg/L or more and a chloride ion and/or a sulfate ion concentration of 1000 mg/L or more in terms of CaCO ₃ A method of treating a cooling water system of a treatment agent (meth)acrylic copolymer, wherein the (meth)acrylic copolymer contains a (meth)acrylic acid represented by the following formula (1) The structural unit (a) of the monomer (A) and the structural unit (b) derived from the (meth)allyl ether monomer (B) represented by the following general formula (2), and all derived from the single The content of the structural unit (a) is 80 mol% to 90 mol%, and the content of the structural unit (b) is 10 mol% to 20 mol%, and the above (meth)acrylic acid is 100 mol% of the structural unit of the bulk. At least one main chain end of the copolymer is a sulfonic acid group or a salt thereof, (wherein R ¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group), (wherein R ² represents a hydrogen atom or a methyl group, and Y and Z each independently represent a hydroxyl group, a sulfonic acid group or a salt thereof, and at least one of Y and Z represents a sulfonic acid group or a salt thereof). The method for treating a cooling water system according to claim 1, wherein the (meth)acrylic copolymer is the structural unit (a) and the structural unit (b), wherein the structural unit (a) It is derived from one or two or more (meth)acrylic monomers (A) selected from the group consisting of acrylic acid, methacrylic acid and sodium acrylate, and the above structural unit (b) is derived from 3-(methyl)allyloxy group. Sodium 2-hydroxy-1-propane sulfonate.