CN104203842A - Method for treating cooling water system - Google Patents

Abstract

A method for treating a cooling water system with CaCO as calcium hardness₃A treatment agent comprising a (meth) acrylic copolymer having a structural unit (a) derived from a (meth) acrylic monomer (A) and a structural unit (B) derived from a specific (meth) allyl ether monomer (B), wherein the content of the structural unit (a) is 80 to 90 mol%, the content of the structural unit (B) is 10 to 20 mol% in 100 mol% of all the structural units derived from the monomers, and wherein at least one of the main chain ends of the (meth) acrylic copolymer is a sulfonic acid group or a sulfonic acid group salt, is added to a cooling water system having a chloride ion and/or sulfate ion concentration of 1000mg/L or more.

Description

Treatment method of cooling water system

technical field

The present invention relates to a cooling water system treatment method, in particular to a cooling water system with high calcium hardness to prevent heat transfer obstruction, flow rate drop, The treatment method of metal corrosion cooling water system.

Background technique

In an open circulating cooling water system, fouling will occur on the heat transfer surface in contact with water and in the piping. In addition, when a high-concentration operation is performed from the viewpoint of resource saving and energy saving, dissolved salts are concentrated to form insoluble salts, resulting in fouling. Scale generated in the heat exchange part will hinder heat transfer, and the fouling attached to the piping will cause the flow rate to drop. In addition, it is known that when the generated scale falls off and circulates in the system, it clogs the pump, piping, and heat exchange unit, and that fouling of the piping and heat exchange unit is accelerated due to clogging.

Examples of the type of stain to be generated include calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide, and basic zinc carbonate.

In order to prevent the occurrence of such stains, a stain preventive agent can be used. As the antifouling agent, generally, inorganic polyphosphoric acids such as sodium hexametaphosphate or sodium tripolyphosphate; phosphonic acids such as hydroxyethylene diphosphonic acid or phosphonobutane tricarboxylic acid; maleic acid, Carboxyl group-containing materials such as acrylic acid and itaconic acid; A vinyl monomer, or a copolymer composed of nonionic vinyl monomers such as acrylamide.

In addition, metal parts installed in an open circulating cooling water system, such as heat exchangers, reactors, and piping made of carbon steel, copper, or copper alloys, are corroded by contact with cooling water. Anti-corrosion treatment by chemical addition.

As the agent, generally, phosphorus compounds such as orthophosphate, hexametaphosphate, hydroxyethylidene phosphonate, phosphorobutanetricarboxylate, etc. are added to the cooling water. There are also heavy metal salts such as zinc salt or dichromate added alone or in combination.

In recent years, the cooling water that uses recovered water (reprocessed water) as make-up water has increased in response to the worldwide trend of reducing environmental load and effectively utilizing resources. Recycled water has the characteristics of high calcium hardness, phosphorus concentration, chloride ion and sulfuric acid ion concentration. This recovered water has high calcium hardness. Therefore, as a problem when using the recovered water as make-up water, for example, the addition of the above-mentioned anti-fouling agent cannot prevent the occurrence of fouling. Therefore, in order to reduce the concentration of salts in cooling water, it is necessary to increase the amount of blowwater, but it is difficult to save water.

Another problem is the acceleration of metal corrosion in the cooling water system due to the high concentration of chloride ions and sulfuric acid ions. Therefore, when the recycled water is used as the makeup water of the cooling water, the problem is to perform both fouling prevention and corrosion prevention in water quality with a high concentration of fouling components and a high concentration of corrosive ions.

From the point of view of preventing fouling, there is a method of injecting acid such as sulfuric acid to lower the pH of cooling water, but this method adds acid, thereby further increasing the concentration of chloride ions or sulfate ions as corrosive ions, Therefore, there are difficulties in practical application.

A method of removing calcium hardness in make-up water with a water softener and adjusting total alkalinity and pH has been disclosed (Patent Document 1). However, since the water softener needs to be frequently regenerated, practical application is difficult.

In addition, as the reason why the effect of the antifouling agent cannot be exerted in the water system with high calcium hardness, Patent Document 2 cites a gelation reaction between the polymer and calcium, and explains that the polymer loses solubility and precipitates, Therefore it becomes impossible to prevent dirt. As a countermeasure against this, a (meth)acrylic polymer having a sulfonic acid group at the end of the main chain has been proposed, thereby improving gel resistance and exhibiting excellent performance even in water systems with high calcium concentrations. A prevention of dirt effect.

This technology can prevent fouling even in water with high calcium hardness. However, even if commonly used anti-corrosion treatment is used in combination, it may not necessarily be obtained in a cooling water system that uses recovered water with a high concentration of corrosive ions as makeup water. Full anti-corrosion effect. In addition, even if the concentration of the anticorrosion agent is increased in order to improve the anticorrosion performance, the anticorrosion agent itself becomes phosphate, zinc hydroxide, etc. and becomes fouled, so the effect is not actually obtained.

prior art literature

patent documents

Patent Document 1: Japanese Patent No. 3928182

Patent Document 2: Japanese Patent No. 3650724

Contents of the invention

The problem to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a cooling water system treatment method that uses recovered water (reprocessed water) for make-up water with high concentrations of fouling components and corrosive ions In the water quality, it prevents the adhesion of calcium-based dirt in the piping or heat exchangers, prevents heat transfer obstruction, flow reduction, etc., and prevents corrosion of metals such as piping or heat exchangers.

Solution to the problem

As a result of careful research by the present inventors in order to achieve the aforementioned object, it was found that the aforementioned object can be achieved by adding a treatment agent having the following composition to a cooling water system having a high calcium hardness and a concentration of chloride ions or sulfuric acid ions, thereby completing the invention. The treatment agent is formed by containing a (meth)acrylic copolymer containing a structural unit (a) derived from a specific (meth)acrylic monomer and a structural unit (a) derived from a specific In the structural unit (b) of the (meth)allyl ether-based monomer, at least one of the main chain terminals is a sulfonic acid group or a sulfonic acid salt.

That is, the present invention provides a treatment method of a cooling water system, in which the calcium hardness is calculated as CaCO ₃₀₀ mg/L or more, and the concentration of chloride ions and/or sulfate ions is more than 1000 mg/L in a cooling water system, adding (formazan base) a treatment agent made of acrylic copolymer, wherein,

The aforementioned (meth)acrylic copolymer has a structural unit (a) derived from a (meth)acrylic monomer (A) represented by the following general formula (1), and a structural unit (a) derived from ( Structural unit (b) of methyl) allyl ether monomer (B),

And, in 100 mol% of all monomer-derived structural units, the content of the structural unit (a) is 80 to 90 mol%, and the content of the structural unit (b) is 10 to 20 mol%,

In addition, in the aforementioned (meth)acrylic copolymer, at least one of main chain terminals is a sulfonic acid group or a sulfonic acid salt.

In the general formula ( ¹ ), R represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group, or an organic amino group;

In the general formula ( ² ), R Represents a hydrogen atom or a methyl group, Y and Z independently represent a hydroxyl group, a sulfonic acid group, or their salts, at least one of Y and Z represents a sulfonic acid group or a sulfonic acid group Salt.

The effect of the invention

According to the present invention, it is possible to provide a cooling water system treatment method that prevents calcium-based scale from adhering to piping or heat exchange in water with a high concentration of fouling components and corrosive ions that use recovered water (retreated water) as make-up water. It prevents the obstruction of heat transfer, flow rate drop, etc., and prevents the corrosion of metals such as pipes and heat exchangers.

Detailed ways

The treatment method of the cooling water system of the present invention is characterized in that, in the cooling water system having a calcium hardness of 300 mg/L or more in terms of CaCO ₃ and a chloride ion and/or sulfate ion concentration of 1000 mg/L or more, by adding A treatment agent containing a (meth)acrylic copolymer having a specific structure can prevent fouling of a cooling water system and suppress metal corrosion.

(Meth)acrylic copolymer:

The (meth)acrylic copolymer contained in the treatment agent used in the cooling water treatment method of the present invention is a structure derived from a (meth)acrylic monomer (A) represented by the following general formula (1): A copolymer of a unit (a) and a structural unit (b) derived from a (meth)allyl ether-based monomer (B) represented by the following general formula (2).

In the general formula ( ¹ ), R represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a metal atom, an ammonium group, or an organic amino group;

In the general formula ( ² ), R Represents a hydrogen atom or a methyl group, Y and Z independently represent a hydroxyl group, a sulfonic acid group, or their salts, at least one of Y and Z represents a sulfonic acid group or a sulfonic acid group Salt.

The above-mentioned structural unit (a) and structural unit (b) specifically refer to structural units represented by the following general formulas (3) and (4), respectively.

In the general formula, R ¹ and X are the same as the aforementioned general formula (1).

In the general formula, R ² , Y, and Z are the same as those in the aforementioned general formula (2).

((meth)acrylic monomer (A))

The (meth)acrylic monomer (A) is represented by the aforementioned general formula (1), wherein specific examples of the metal atom of X in the general formula (1) include lithium, sodium, potassium, etc.; Specific examples of the organic amino group include monoethanolamine, diethanolamine, triethanolamine, and the like.

Specific examples of the (meth)acrylic monomer (A) include: acrylic acid, methacrylic acid, and their salts (for example, sodium salts, potassium salts, ammonium salts, etc.), among which acrylic acid is particularly preferred. , sodium acrylate, methacrylic acid. These can be used individually by 1 type or in combination of 2 or more types.

In addition, the said "(meth)acryl type" means both an acryl type and a methacryl type. The same applies to other similar terms.

((Methyl)allyl ether monomer (B))

The (methyl) allyl ether monomer (B) is represented by the aforementioned general formula (2), wherein, in the general formula (2), among the sulfonic acid groups or sulfonic acid group salts of Y and Z, as the metal Specific examples of salts include salts such as sodium, potassium, and lithium, and specific examples of salts of organic amino groups include monoethanolamine, diethanolamine, and triethanolamine.

Specific examples of the aforementioned (meth)allyl ether-based monomer (B) include: 3-(methyl)allyloxy-2-hydroxy-1-propanesulfonic acid and its salts, 3- (Meth)allyloxy-1-hydroxy-2-propanesulfonic acid and its salts, among them, sodium 3-(meth)allyloxy-2-hydroxy-1-propanesulfonate is particularly preferred. These can be used individually by 1 type or in combination of 2 or more types.

In addition, the said "(meth)allyl ether system" means both an allyl ether system and a methallyl ether system (methallyl ether system). The same applies to other similar terms.

<molar ratio>

This (meth)acrylic copolymer contains a structural unit (a) derived from a (meth)acrylic monomer (A) and a structural unit derived from a (meth)allyl ether monomer (B) In the copolymer of (b), the content of the structural unit (a) is 80 to 90 mol%, and the content of the structural unit (b) is 10 to 20 mol% in 100 mol% of all monomer-derived structural units. When the content of the structural unit (a) exceeds 90 mol%, the affinity with calcium becomes too strong, and when it is applied to a water system with high calcium hardness, the polymer gels and easily precipitates, making it impossible to perform; When it is less than 80 mol%, the ratio of the anticorrosion-imparting carboxyl group is small, and anticorrosion performance falls.

<Molecular Weight>

The weight average molecular weight of this (meth)acryl-type copolymer is preferably about 1,000 to 40,000. When the weight average molecular weight of this (meth)acryl-type copolymer exceeds 40,000, gel-resistant performance falls, and when it is less than 1,000, stain prevention ability falls. Moreover, it is more preferable that the weight average molecular weight of this (meth)acryl-type copolymer is 5000-38000.

In addition, the said weight average molecular weight is the value of standard polyacrylic acid conversion measured by the gel permeation chromatography (GPC method).

(Other monomers (C))

The (meth)acrylic copolymer may have at least the aforementioned structural unit (a) and the aforementioned structural unit (b) in the aforementioned proportions, but may also contain, in addition to these, a A structural unit (c) of another monomer (C) copolymerized with a body (A) or a (meth)allyl ether-based monomer (B). In this case, the ratio of the structural unit (c) is preferably 10 mol% or less, more preferably 5 mol% or less, based on 100 mol% of all monomer-derived structural units.

Examples of other monomers (C) include: 2-acrylamide-2-methylpropanesulfonic acid, (meth)allylsulfonic acid, vinylsulfonic acid, styrenesulfonic acid, methacrylic acid 2- Unsaturated monomers containing sulfonic acid groups such as ethyl sulfonate (2-sulfonate) and their salts; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N- N-vinyl monomers such as vinyl-N-methylformamide, N-vinyl-methylacetamide, N-vinyloxazolidinone, etc.; (meth)acrylamide, N,N-dimethyl Nitrogen-containing non-ionic unsaturated monomers such as methacrylamide and N-isopropylacrylamide; 3-(meth)allyloxy-1,2-dihydroxypropane, (meth)allyl alcohol, Hydroxyl-containing unsaturated monomers such as isoprenol; 3-(methyl)allyloxy-1,2-dihydroxypropane with 1 to 200 moles of ethylene oxide added Compound (3-(meth)allyloxy-1,2-di(poly)oxyethylene ether propane), a compound in which about 1 to 100 moles of ethylene oxide is added to (meth)allyl alcohol Unsaturated monomers containing polyoxyethylene groups; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate, etc. (meth) ) acrylates; unsaturated dicarboxylic acid monomers such as itaconic acid; aromatic unsaturated monomers such as styrene, etc.

These monomers (C) can be used individually by 1 type or in combination of 2 or more types.

(Preparation)

As a method for producing the (meth)acrylic copolymer, for example, a monomer mixture (hereinafter, sometimes simply referred to as is a "monomer mixture"), a method of polymerizing it in the presence of a polymerization initiator.

<polymerization initiator>

As the polymerization initiator, known initiators can be used. For example, hydrogen peroxide; persulfates of sodium persulfate, potassium persulfate, ammonium persulfate, etc.; 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-methylpropane Amidine] n-hydrate, 2,2'-Azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-Azobis[2-(2-imidazoline -2-yl)propane]disulfate dihydrate, 1,1'-azobis(cyclohexane-1-carbonitrile) and other azo compounds; benzoyl peroxide, lauroyl peroxide, peroxide Organic peroxides such as acetic acid, di-tert-butyl peroxide, and cumene hydroperoxide are suitable. Among these polymerization initiators, it is preferable to use persulfates described later from the viewpoint of improving the gel resistance of the obtained polymer.

The amount of the polymerization initiator used is not particularly limited as long as it is an amount capable of initiating copolymerization of the monomer mixture, but it is preferably 15 g or less with respect to 1 mole of the monomer mixture, except for the cases described below. More preferably, it is 1 to 12 g.

<Chain transfer agent>

In the production method of this (meth)acryl-type copolymer, if necessary, a chain transfer agent can be used as a molecular weight regulator of a polymer in the range which does not adversely affect superposition|polymerization.

As the chain transfer agent, specifically, mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptosuccinic acid, octyl thioglycolate, octyl 3-mercaptopropionate, 2-Mercaptoethanesulfonic acid, N-dodecyl mercaptan, octyl mercaptan, mercapto butyl acetate, etc.; carbon tetrachloride, dichloromethane, bromoform, bromotrichloromethane (Bromotrichloromethane) ) and other halides; secondary alcohols such as isopropanol and glycerin; phosphorous acid, hypophosphorous acid, and their salts (sodium hypophosphite, potassium hypophosphite, etc.) Methyl bisulfite, and their salts (hereinafter, sometimes referred to as "bisulfite (salt)". For example, sodium bisulfite, potassium bisulfite, sodium dithionite, potassium dithionite, sodium methylbisulfite , Potassium methylbisulfite, etc.) and other lower oxides and their salts. The above-mentioned chain transfer agents may be used alone or in combination of two or more.

By using this chain transfer agent, it is possible to suppress the phenomenon that the copolymer to be produced becomes higher than necessary in molecular weight, and it is possible to efficiently produce a low-molecular-weight copolymer. Among them, bisulfites (salts) are preferably used in the copolymerization reaction of the present invention. Thereby, a sulfonic acid group can be efficiently introduced at the main chain terminal of the obtained copolymer, and gel resistance can be improved. Moreover, since the color tone of a copolymer (composition) can be improved by using bisulfite (salt) as a chain transfer agent, it is preferable.

The amount of the chain transfer agent added is not limited as long as it is an amount capable of favorably polymerizing the monomer mixture, but it is preferably 1 to 20 g per mole of the monomer mixture, except for the cases described below. , more preferably 2 to 15 g.

<Initiator system>

In the method for producing the (meth)acrylic copolymer, it is preferable to use one or more of persulfate and bisulfite (salt) in combination as the initiator system (a combination of a polymerization initiator and a chain transfer agent). . Thus, the sulfonic acid group can be effectively introduced at the end of the main chain of the polymer, and a low molecular weight water-soluble polymer having excellent gel resistance in addition to excellent dispersing ability and chelating ability can be obtained, thereby effectively embodying Effect of the present invention. By adding bisulfites (salts) other than persulfates to the initiator system, it is possible to suppress the phenomenon that the obtained polymer becomes higher than necessary in molecular weight, thereby enabling efficient production of low molecular weight polymers .

As said persulfate, specifically, sodium persulfate, potassium persulfate, ammonium persulfate, etc. are mentioned.

Moreover, the bisulfite (salt) of this invention is as above-mentioned, Among them, sodium bisulfite, potassium bisulfite, and ammonium bisulfite are preferable.

The addition ratio when the aforementioned persulfate and bisulfite (salt) are used in combination is preferably 0.1 to 5 parts by mass of bisulfite (salt) with respect to 1 part by mass of persulfate, more preferably 0.2 to 3 parts by mass, More preferably, it exists in the range of 0.2-2 mass parts. When bisulfite (salt) is less than 0.1 mass part with respect to 1 mass part of persulfates, the effect which bisulfite (salt) exerts tends to become weak. Therefore, the introduction amount of the sulfonic acid group at the terminal of the polymer decreases, and the gelation resistance of the copolymer tends to decrease. Moreover, there exists a tendency for the weight average molecular weight of a (meth)acryl-type copolymer to become high. On the other hand, when bisulfite (salt) exceeds 5 mass parts with respect to 1 mass part of persulfate, there is a polymerization reaction in a state where the effect of bisulfite (salt) cannot be obtained more depending on the addition ratio. Bisulfite (salt) in the system tends to be excessively supplied (uselessly consumed). Therefore, excess bisulfite (salt) is decomposed in the polymerization reaction system, and a large amount of sulfurous acid gas (SO ₂ gas) is generated. In addition, there exists a tendency for many impurities in a (meth)acrylic-type copolymer to generate|occur|produce, and the performance of the obtained (meth)acryl-type copolymer to fall. In addition, there is a tendency for impurities to be easily precipitated during low-temperature maintenance.

When using the aforementioned persulfate and bisulfite (salt), the total amount of persulfate and bisulfite (salt) is preferably 2 to 20 g, more preferably 2 to 15 g, based on 1 mole of the monomer mixture. , more preferably 3-10 g, even more preferably 4-9 g. When the addition amount of the said persulfate and bisulfite (salt) is less than 2 g, there exists a tendency for the molecular weight of the polymer obtained to increase. In addition, there exists a tendency for the sulfonic acid group introduced to the terminal of the obtained (meth)acrylic-type copolymer to reduce. On the other hand, when the addition amount is greater than 20 g, the effect of persulfate and bisulfite (salt) cannot be obtained more with the addition amount, and on the contrary, there is a possibility that the purity of the obtained (meth)acrylic copolymer decreases. tendency.

The aforementioned persulfate can be added in the form of a solution (preferably an aqueous solution) of the persulfate dissolved in a solvent described later, preferably water. The concentration when used as the persulfate solution (preferably an aqueous solution) is preferably 1 to 35% by mass, more preferably 5 to 35% by mass, still more preferably 10 to 30% by mass. However, when the concentration of the persulfate solution is less than 1% by mass, the concentration of the product decreases, and transportation and storage become cumbersome. On the one hand, when the concentration of the persulfate solution exceeds 35% by mass, handling becomes difficult.

The aforementioned bisulfite (salt) can be added in the form of a solution (preferably an aqueous solution) of bisulfite (salt) dissolved in a solvent described later, preferably water. The concentration when used as the bisulfite (salt)-based solution (preferably an aqueous solution) is preferably 10 to 42% by mass, more preferably 20 to 42% by mass, and still more preferably 32 to 42% by mass. Among them, when the concentration of the bisulfite (salt)-based solution is less than 10% by mass, the concentration of the product decreases, and transportation and storage become cumbersome. On the one hand, when the concentration of the bisulfite (salt) solution exceeds 42% by mass, handling becomes difficult.

<Other additives>

In the preparation method of this (meth)acrylic copolymer, other additives other than initiators and chain transfer agents that can be used in the polymerization reaction system when the aforementioned monomer mixture is polymerized in an aqueous solution can be added without affecting the present invention. Appropriate additives are added within the scope of the effect, for example, heavy metal concentration regulators, pH regulators, etc. can be added in proper amounts.

The aforementioned heavy metal concentration regulator is not particularly limited, and for example, polyvalent metal compounds or monomers can be used. Specifically, vanadyl trichloride, vanadium trichloride, vanadyloxalate, vanadyl sulfate, vanadic anhydride, ammonium metavanadate, ammonium hypovanadous sulfate (NH ₄ ) ₂ SO ₄ ·VSO ₄ ·6H ₂ O), ammonium vanadous sulfate (ammonium vanadous sulfate: (NH ₄ )V(SO ₄ ) ₂ ·12H ₂ O), copper(Ⅱ) acetate, copper(Ⅱ), Copper(II) bromide, copper(II) acetoacetate (copper(II) アセチルアセテート), ammonium cupric chloride, ammonium copper chloride, copper carbonate, copper(II) chloride ), copper(II) citrate, copper(II) formate, copper(II) hydroxide, copper nitrate, copper naphthenate, copper(II) oleate, copper maleate, copper phosphate, copper(II) sulfate , cuprous chloride, copper(I) cyanide, copper iodide, copper(I) oxide, copper thiocyanate, iron acetylacetate, ammonium ferric citrate, ammonium ferricoxalate, sulfuric acid Water-soluble multivalent metals such as ammonium ferric, ammonium ferric sulfate, ferric citrate, ferric fumarate, ferric maleate, ferrous lactate, ferric nitrate, iron pentacarbonyl, ferric phosphate, ferric pyrophosphate, etc. Salt; multivalent metal oxides such as vanadium pentoxide, copper(Ⅱ), ferrous oxide, ferric oxide, etc.; multivalent metal sulfides such as iron(Ⅲ), iron(Ⅱ), copper sulfide, etc.; copper powder, iron powder, etc.

In the method for producing the (meth)acrylic copolymer, the obtained (meth)acrylic copolymer preferably has a heavy metal ion concentration of 0.05 to 10 ppm. Therefore, it is preferable to add an appropriate amount of the heavy metal concentration regulator as necessary.

<polymerization solvent>

In the preparation of the (meth)acrylic copolymer, the above-mentioned monomer mixture is generally polymerized in a solvent, but at this time, the solvent used for the polymerization reaction system is preferably water, ethanol, ethylene glycol, glycerin, polyethylene glycol Aqueous solvents such as the like, water is particularly preferable. These can be used individually by 1 type or in combination of 2 or more types. In addition, in order to increase the solubility of the monomer mixture in the solvent, an organic solvent may be added appropriately within a range that does not adversely affect the polymerization of each monomer.

As the aforementioned organic solvents, specifically, one or more of them are suitably selected from lower alcohols such as methanol and ethanol; amides such as dimethylformamide; ethers such as diethyl ether and dioxane, etc. .

The usage-amount of the said solvent is preferably 40-200 mass % with respect to the whole monomer mixture, More preferably, it is 45-180 mass %, More preferably, it is the range of 50-150 mass %. When the usage-amount of this solvent is less than 40 mass %, molecular weight will become high. On the one hand, when the usage-amount of this solvent exceeds 200 mass %, the density|concentration of the (meth)acrylic-type copolymer to manufacture will become low, and a solvent needs to be removed in some cases. In addition, most or the whole amount of the solvent may be placed in the reaction container in advance in the initial stage of polymerization, but, for example, a part of the solvent may be added (dropped) to the reaction system appropriately during the polymerization, or may be Bulk mixture components, initiator components, and other additives are dissolved in a solvent in advance, and these components are appropriately added (dropped) to the reaction system during polymerization.

<polymerization temperature>

The polymerization temperature of the aforementioned monomer mixture is not particularly limited. From the viewpoint of efficiently producing the polymer, the polymerization temperature is preferably 50°C or higher, more preferably 70°C or higher, or preferably 99°C or lower, more preferably 95°C or lower. When the polymerization temperature is lower than 50° C., in addition to an increase in the molecular weight and an increase in impurities, the polymerization time required is too long, thereby reducing productivity. On the one hand, when the polymerization temperature is 99° C. or lower, it is preferable to suppress the decomposition of bisulfite (salt) to generate a large amount of sulfurous acid gas when bisulfite (salt) is used as the initiator. Here, the polymerization temperature refers to the reaction solution temperature in the reaction system.

In particular, in the method of starting the polymerization from room temperature (room temperature start method), for example, when the polymerization is carried out for 180 minutes per batch (180-minute treatment method), within 70 minutes, preferably 0 to 50 minutes, more preferably 0 The set temperature is reached within ~ 30 minutes (it may be within the range of the above-mentioned polymerization temperature, but preferably 70 to 90°C, more preferably about 80 to 90°C). Then, it is preferable to maintain the set temperature until the polymerization is terminated. When the temperature rise time exceeds the above-mentioned range, the obtained (meth)acrylic copolymer may become high in molecular weight. In addition, although an example of a polymerization time of 180 minutes was given, if the method of handling the polymerization time is different, it is preferable to refer to this example and set the temperature raising time at the same ratio as the temperature raising time to the polymerization time.

(pressure of reaction system, reaction environment)

When the aforementioned monomer mixture is polymerized, the pressure in the reaction system is not particularly limited, and the reaction can be carried out under any pressure such as normal pressure (atmospheric pressure), reduced pressure, or increased pressure. Preferably, when bisulfurous acid (salt) is used as the initiator system, in order to prevent the release of sulfurous acid gas during polymerization and realize low molecular weight, the reaction can be carried out under normal pressure conditions, or in a closed reaction system and add The reaction was carried out under pressure conditions. In addition, when polymerization is carried out under normal pressure (atmospheric pressure), it is not necessary to install a pressurizing device or a decompressing device, and it is not necessary to use a pressure-resistant reaction vessel or piping. Therefore, normal pressure (atmospheric pressure) is preferable from the viewpoint of production cost. That is, what is necessary is just to set optimum pressure conditions according to the use purpose of the obtained (meth)acryl-type copolymer.

The environment in the reaction system may be an air environment or an inactive environment. For example, it is preferable to replace the inside of the system with an inert gas such as nitrogen before starting the polymerization. Thereby, the atmospheric gas (for example, oxygen etc.) in a reaction system can be prevented from being dissolved in a liquid phase and functioning as a polymerization inhibitor. As a result, deactivation and reduction of the initiator (persulfate, etc.) can be prevented, and further reduction in molecular weight can be achieved.

(degree of neutralization in aggregation)

In the production method of this (meth)acrylic-type copolymer, it is preferable to carry out the polymerization reaction of the said monomer mixture under acidic conditions. By carrying out the reaction under acidic conditions, the viscosity increase of the aqueous solution of the polymerization reaction system can be suppressed, and a low molecular weight (meth)acrylic copolymer can be prepared favorably. In addition, since the polymerization reaction can be carried out at a higher concentration than before, the production efficiency can be greatly improved. In particular, when the degree of neutralization during polymerization is set as low as 0 to 25 mol%, the aforementioned effect of reducing the amount of initiator can be synergistically enhanced, and the effect of reducing impurities can be particularly enhanced. In addition, it is preferable to adjust the pH of the reaction solution during polymerization to 1-6 at 25°C. By carrying out the polymerization reaction under such acidic conditions, the polymerization can be carried out at a high concentration in one step, and therefore, the concentration step can be omitted. Thereby, productivity improves significantly, and the increase of manufacturing cost can be suppressed.

In the above-mentioned acidic conditions, the pH of the reaction solution during polymerization is preferably 1-6, more preferably 1-5, and still more preferably 1-4 at 25°C. When the pH is less than 1, for example, when bisulfurous acid (salt) is used as an initiator, generation of sulfurous acid gas and corrosion of equipment may be caused. On the other hand, when the pH exceeds 6, when bisulfite (salt) is used as the initiator, the efficiency of bisulfite (salt) decreases and the molecular weight increases.

As a pH regulator for adjusting the pH of the reaction solution, there may be mentioned: hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; hydroxides of alkaline earth metals such as calcium hydroxide and magnesium hydroxide; Ammonia, organic amine salts such as monoethanolamine and triethanolamine, etc. These can be used individually by 1 type or in combination of 2 or more types. Among them, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable, and sodium hydroxide is more preferable. In this specification, the above substances may be referred to simply as "pH adjuster" or "neutralizer".

The degree of neutralization during polymerization is preferably within a range of 0 to 25 mol%, more preferably 1 to 15 mol%, and still more preferably 2 to 10 mol%. When the degree of neutralization in the polymerization is within the corresponding range, the copolymerization can be carried out best, impurities can be reduced, and a polymer with better gel resistance can be prepared. In addition, the viscosity of the aqueous solution of the polymerization reaction system does not increase, and a low-molecular-weight polymer can be prepared favorably. In addition, since the polymerization reaction can be carried out at a higher concentration than before, the production efficiency can be greatly improved.

On the other hand, when the degree of neutralization during polymerization exceeds 25 mol%, the chain transfer efficiency of bisulfites (salts) may decrease and the molecular weight may increase. In addition, as the polymerization proceeds, the viscosity of the aqueous solution of the polymerization reaction system increases significantly. As a result, the molecular weight of the obtained polymer increases more than necessary, and a low molecular weight polymer cannot be obtained. In addition, the above-mentioned effect of lowering the degree of neutralization may not be fully exhibited, and it may be difficult to significantly reduce impurities.

The neutralization method is not particularly limited. For example, a salt of (meth)acrylic acid such as sodium (meth)acrylate can be used as a part of the raw material, and an alkali metal hydroxide such as sodium hydroxide can also be used as a neutralizing agent. And, these can also be used together. In addition, the addition form of the neutralizing agent at the time of neutralization may be a solid or an aqueous solution dissolved in an appropriate solvent, preferably water.

The aqueous solution concentration when using an aqueous solution is preferably 10 to 60% by mass, more preferably 20 to 55% by mass, still more preferably 30 to 50% by mass. When the concentration of the aqueous solution is less than 10% by mass, the concentration of the product decreases, making transportation and storage cumbersome, and when it exceeds 60% by mass, precipitation may occur, and the viscosity becomes high, so liquid delivery becomes cumbersome.

(addition conditions of raw materials)

During polymerization, it is preferred that the above-mentioned monomer mixture, initiator, chain transfer agent and other additives be dissolved in an appropriate solvent (preferably the same solvent as the solvent to be dripped), as a monomer mixture solution and an initiator solution. And the chain transfer agent solution and other additive solutions are polymerized while being continuously dropped for a predetermined dropping time into the (aqueous) solvent (adjusted to a predetermined temperature if necessary) charged into the reaction vessel. Furthermore, with respect to a part of the aqueous solvent, it is also possible to drop it separately thereafter, differently from the initially charged solvent which was previously charged into the container in the reaction system. However, it is not limited to this production method.

For example, as for the dropping method, continuous dropping may be used, or intermittent dropping may be performed by subdividing several times. One type or two or more types of monomers may be initially added in part or in total. In addition, one or two or more kinds of dropping speeds (dropping amounts) of the monomers are always (constantly) dropped in a constant (constant amount) form from the beginning to the end of the dropping, or can be changed over time according to the polymerization temperature or the like. The dropping speed (dropping amount) was changed. In addition, it is not necessary to perform the same dripping on all the dripping components, and the start time or the end time may be shifted for each dripping component, or the dropping time may be shortened or extended.

When bisulfite (salt) is used as the initiator system, the molecular weight at the initial stage of polymerization has a great influence on the final molecular weight. Therefore, in order to reduce the initial molecular weight, preferably within 60 minutes, more preferably within 30 minutes, and still more preferably within 10 minutes, 5 to 20% by mass of bisulfite (salt) or its solution is added (dropped) from the start of polymerization. In particular, as described later, it is effective to start polymerization from room temperature.

In addition, in the dropping component at the time of polymerization, in the case of using bisulfite (salt) as the initiator system, the dropping time of bisulfite (salt) or its solution is different from that of the monomer (A), (B ), preferably 1 to 30 minutes, more preferably 1 to 20 minutes, even more preferably 1 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 caused by the bisulfite (salt) can be effectively and efficiently suppressed. Therefore, after the polymerization is terminated, the sulfurous acid gas in the gas phase is dissolved in the liquid phase, and impurities can be significantly reduced. If the bisulfite (salt) remains after the polymerization is terminated, it may lead to the formation of impurities to reduce the performance of the polymer or the precipitation of impurities during low temperature maintenance. Therefore, it is preferable that the initiator containing bisulfite (salt) is consumed and does not remain at the end of the polymerization.

Wherein, relative to the dropping termination time of the monomers (A), (B), when the dropping termination time of bisulfite (salt) (solution) is only accelerated for less than 1 minute, there is a reaction of bisulfite (salt) after the termination of polymerization. residual condition. Such a case includes: the case where the dropping of bisulfite (salt) or its solution is stopped and the dropping of monomers (A) and (B) are stopped at the same time; the dropping of bisulfite (salt) (solution) is stopped Compared with the case where the droplet termination of the monomers (A) and (B) is slow. In this case, it tends to be difficult to effectively and efficiently suppress the generation of sulfurous acid gas or the formation of impurities, and the remaining initiator may adversely affect the thermal stability of the obtained polymer. On the one hand, when the dropping termination time of bisulfite (salt) or its solution is greater than 30 minutes in advance with respect to the dropping termination time of monomer (A), (B), before polymerization terminates, bisulfite (salt) has already It is consumed. Therefore, there is a tendency for the molecular weight to increase. In addition, during the polymerization, the dropping rate of bisulfite (salt) is faster than that of the monomers (A) and (B), and a large amount drops in a short time. Therefore, impurities or A tendency to generate a large amount of sulfurous acid gas.

In addition, in the dropping component at the time of polymerization, when bisulfite (salt) is used as the initiator, the drop stop time of persulfate (solution) is relative to the drop stop of monomers (A) and (B). The time is preferably delayed for 1 to 30 minutes, more preferably for 1 to 25 minutes, and still more preferably for 1 to 20 minutes. Thereby, the amount of monomer components remaining after the polymerization is terminated can be reduced, and impurities due to the remaining monomers can be significantly reduced.

However, when the dropping end time of the persulfate (solution) is delayed by less than 1 minute from the dropping end time of the monomers (A) and (B), monomer components may remain after the polymerization is terminated. Such a case includes: the case where the dropping of the persulfate (solution) is stopped and the dropping of the monomers (A) and (B) are stopped at the same time; the dropping of the persulfate (solution) is stopped relative to the monomers (A), (B) The case where the dropping is terminated quickly. In this case, it tends to be difficult to effectively and efficiently suppress the formation of impurities. On the one hand, when the dropping termination time of persulfate (solution) is delayed more than 30 minutes relative to the dropping termination time of monomer (A), (B), residual persulfate or its decomposed product may be left behind the polymerization termination, and form Impurities.

(polymerization time)

During polymerization, when the polymerization temperature is lowered and bisulfurous acid (salt) is used as the initiator, it is more important to suppress the generation of sulfurous acid gas and prevent the formation of impurities. Therefore, the total dropping time during polymerization is preferably as long as 150 to 600 minutes, more preferably 160 to 450 minutes, still more preferably 180 to 300 minutes.

When the total dropping time is less than 150 minutes, there is a tendency that the effect of the persulfate solution and the bisulfite (salt) solution added as the initiator system will be reduced. Therefore, there is a tendency that the obtained (meth)acrylic acid Copolymer, the amount of sulfur-containing groups such as sulfonic acid groups introduced in the main chain terminal is reduced. As a result, there exists a tendency for the weight average molecular weight of this polymer to become high.

In addition, in the method of dropping in a short period of time in the reaction system, bisulfite (salt) may exist in excess. Therefore, such excess bisulfurous acid (salt) decomposes to generate sulfurous acid gas, which is discharged outside the system or forms impurities. However, the above-mentioned situation can be improved by performing the polymerization temperature and the amount of the initiator in a low specific range.

On the one hand, when the total dropping time exceeds 600 minutes, since the generation of sulfurous acid gas is suppressed, the performance of the obtained polymer is good, but the productivity may be lowered and the usage may be limited. The total dropping time refers to the time from the start of dropping the first dropping component (not limited to one component) to the completion of dropping of the last dropping component (not limited to one component).

(Polymerized solid content concentration of monomer)

The solid content concentration in the aqueous solution (that is, the polymerization solid content concentration of the monomer) at the time when the dropping of the total amount of the aforementioned monomer, polymerization initiator, and chain transfer agent is terminated is preferably 35% by mass or more, more preferably 40 to 70% by mass. % by mass, more preferably 45 to 65% by 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 in a high-concentration and one-step manner, so that a low-molecular-weight (meth)acrylic copolymer can be efficiently obtained. For example, the Concentration process. Therefore, the production efficiency and productivity can be greatly improved, and the production cost can be suppressed.

Among them, when the solid content concentration in the polymerization reaction system is increased, there is a tendency that the viscosity of the reaction solution increases significantly as the polymerization reaction progresses, and the weight average molecular weight of the polymer obtained also tends to increase significantly. However, by carrying out the polymerization reaction on the acid side (pH at 25° C. is 1 to 6, and the neutralization degree of carboxylic acid is in the range of 0 to 25 mol%), it is possible to suppress the increase in the viscosity of the reaction solution accompanying the progress of the polymerization reaction. Therefore, even if the polymerization reaction is carried out under high-concentration conditions, a low-molecular-weight polymer can be obtained, and the production efficiency of the polymer can be greatly improved.

(ripening process)

In the production method of this (meth)acryl-type copolymer, after the addition of all the raw materials used is terminated, an aging process may be set for the purpose of raising the polymerization rate of a monomer, etc. as well. The aging time is usually 1 to 120 minutes, preferably 5 to 90 minutes, more preferably 10 to 60 minutes. If the aging time is less than 1 minute, monomer components remain due to insufficient aging, and impurities caused by residual monomers may be formed, resulting in a decrease in performance. On the one hand, when the aging time is longer than 120 minutes, coloring of the polymer solution may occur.

The preferred temperature of the polymer solution in the aging step is the same as the above-mentioned polymerization temperature range. Therefore, the temperature may be maintained at a constant temperature (preferably, the temperature at the time when the dropping is terminated), or the temperature may be changed over time during aging.

(process after polymerization)

In the production method of this (meth)acryl-type copolymer, it is preferable to superpose|polymerize under the above-mentioned acidic conditions. Therefore, the degree of neutralization of the carboxylic acid of the obtained (meth)acrylic copolymer (the final degree of neutralization of the carboxylic acid) can be adjusted by appropriately adding an appropriate basic component as a post-treatment after the polymerization is terminated. set within the specified range. Examples of the basic 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; ammonia, monoethanolamine, and diethanolamine , organic amines such as triethanolamine, etc.

The final degree of neutralization varies depending on the intended use, so it is not particularly limited.

In particular, the final neutralization degree of carboxylic acid when used as an acidic polymer is preferably 0 to 75 mol%, more preferably 0 to 70 mol%. The final neutralization degree of carboxylic acid when used as a neutral or basic polymer is preferably 75 to 100 mol%, more preferably 85 to 99 mol%. In addition, when the final neutralization degree exceeds 99 mol % when used as a neutral or basic polymer, the polymer aqueous solution may be colored.

In addition, when using acid without neutralization, the inside of the reaction system is acidic, and therefore toxic sulfurous acid gas may remain in the reaction system and its environment. At this time, it is preferable to decompose by adding a peroxide such as hydrogen peroxide, or to introduce (blow out) air or nitrogen to discharge.

In addition, the production method of this (meth)acrylic-type copolymer may be a batch method or a continuous method.

The (meth)acrylic copolymer obtained as described above has the effect of preventing fouling of the cooling water system and suppressing corrosion of metals. The mechanism is not yet clear, but it is thought that the carboxyl group derived from the structural unit (a) of the (meth)acrylic monomer (A) has a strong affinity with calcium ions, which are dirt components, and grows through the growth of crystals. Adsorption on the spots inhibits growth. In addition, it is known that carboxyl group-containing materials have anticorrosion properties, and by setting the structural unit (a) to a certain mole % or more, both fouling prevention and anticorrosion effects can be exhibited.

However, in order to prevent gelation, it is necessary to set a certain amount of At the same time, it is necessary to use the end of the main chain as a sulfonic acid group to improve gel resistance.

Next, the processing method of the cooling water system of this invention is demonstrated.

<Treatment method of cooling water system>

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

The (meth)acrylic acid-based copolymer is as described above, but it is particularly preferably composed of one or more ( Copolymer of structural unit (a) derived from meth)acrylic monomer (A) and structural unit (b) derived from sodium 3-allyloxy-2-hydroxy-1-propanesulfonate (HAPS) . More specifically, copolymers of AA/HAPS, MAA/HAPS, AA/SA/HAPS, AA/MAA/HAPS and the like.

In addition, there are no particular limitations on the operating conditions when the treatment method of the present invention is applied.

(Water quality of cooling water system)

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

Regarding the addition method of the antifouling agent/anticorrosion agent (hereinafter also referred to as "copolymer system antifouling agent/anticorrosion agent") composed of the above-mentioned (meth)acrylic copolymer to be added to the cooling water system, and It is not particularly limited, and it may be added to the site where corrosion and fouling are to be prevented, or before the site, or the like.

In addition, the addition amount is not particularly limited, and can be appropriately selected according to the water quality of the cooling water system to be added. However, the concentration of the copolymer system antifouling agent/anticorrosion agent is usually added to reach 0.01 to 100 mg/L. It is preferable to add so that it may become 2-50 mg/L.

If necessary, this copolymer system antifouling agent/anticorrosion agent can be used in combination with other antifouling agents, anticorrosive agents, and slime controlling agents.

(corrosion inhibitors that can be used together)

As anticorrosion agents that can be used together, for example, hydroxyethylene diphosphonic acid or phosphoryl butane tricarboxylic acid, ethylenediamine tetramethylene phosphonic acid, nitrilotrimethylphosphonic acid (nitrilotrimethylphosphonic acid) ) and other phosphonic acids, orthophosphates, polymeric phosphates, phosphoric acid esters, zinc salts, nickel salts, molybdenum salts, tungsten salts, oxycarboxylates, triazoles, amines, etc.

(prevention of dirt available for use together)

As the antifouling agent that can be used in combination, for example, hydroxyethylene diphosphonic acid or phosphorobutanetricarboxylic acid, ethylenediaminetetramethylenephosphonic acid, nitrilotrimethylphosphonic acid (nitrilotrimethylphosphonic acid) acid) such as phosphonic acid, orthophosphate, polymeric phosphate, polymaleic acid, polyacrylic acid, maleic acid copolymer, maleic acid/acrylic acid, maleic acid/isobutylene, maleic acid/sulfonic acid, acrylic acid/ Sulfonic acid, copolymer of acrylic acid/monomer containing nonionic group, terpolymer of acrylic acid/sulfonic acid/monomer containing nonionic group, etc.

As the sulfonic acid in the aforementioned antifouling agent, for example, vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, isoprenesulfonic acid, 3-allyloxy-2-hydroxypropyl Sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 4-sulfobutyl methacrylate, allyloxybenzenesulfonic acid, methyl Allyloxybenzenesulfonic acid and their metal salts, etc.

In addition, as the nonionic group-containing monomer in the above-mentioned antifouling agent, for example, alkylamide (C1-C5 alkylamide), hydroxyethyl methacrylate (hydroxyethyl methacrylate), additional mole number 1 Mono(meth)acrylate of (poly)ethylene/propylene oxide of ~30, monovinyl ether ethylene/propylene oxide of 1~30 moles added, etc.

(Slime control agent that can be used together)

As a slime control agent that can be used in combination, for example, quaternary ammonium salts such as alkyldimethylbenzyl ammonium chloride, chloromethyltrithiazoline, chloromethylisothiazoline, methylisothiazoline, or ethylaminoisopropylaminomethylthiatriazine (Ethylaminoisopropylaminomethylthiatriazine: エリルアミノイソプロピルモノメチチルチリテリジン), hypochlorous acid, hypobromous acid, a mixture of hypochlorous acid and sulfamic acid (sulfamic acid), etc., enzymes , fungicides, colorants, fragrances, water-soluble organic solvents, and defoamers, etc.

For the above-mentioned antifouling agent, anticorrosion agent, and slime control agent, one kind can be used alone or two or more kinds can be used in combination.

Example

Hereinafter, the present invention will be described in more detail through examples, but the present invention is not limited to these examples.

In addition, a corrosion resistance test and a calcium phosphate scale-out inhibition test were performed by the following methods, and molecular weight measurement and confirmation of the presence or absence of terminal sulfonic acid groups were performed by the following methods.

(1) Corrosion resistance test

For the low-carbon steel (JISG3141SPSS-SB) with a size of 50mm×30mm×1mm and a surface area of ^0.31dm2 , the test piece was ground to #400 and degreased with toluene as a sample, and the mass was measured, and the mass was taken as the mass before the test .

Put the dechlorinated water of Nogi-cho water in a 5000ml plastic container (ポリ container). The amount of the dechlorinated water is the amount obtained by subtracting the amount of each reagent added from 5000ml, and then add sodium bicarbonate aqueous solution and sodium silicate. After aqueous solution, polymer solution, magnesium sulfate aqueous solution, sodium chloride aqueous solution, phosphoric acid solution, calcium chloride aqueous solution, sodium sulfate aqueous solution, and zinc sulfate aqueous solution, the pH is adjusted by a small amount of sodium hydroxide aqueous solution and sulfuric acid aqueous solution, thereby serving as test water. About 1000ml of test water was transferred to a 1000ml beaker and placed in a constant temperature tank of a corrosion test device maintained at 40°C. The test piece was fixed to the rotating shaft with screws for immersion and rotated at 170 revolutions (rpm). The residual liquid of the test water was continuously injected into a 1000ml beaker at a speed of 0.8ml/minute (min) by a roller pump.

Three days after the immersion of the test piece, the test piece was taken out, the surface of the test piece was washed with acid to remove adhering corrosion products, the mass after drying was measured, and this amount was taken as the mass after the test. After that, based on the mass change of the test piece, the corrosion rate (mdd) was calculated by the following formula, and the anticorrosion performance was evaluated.

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

A corrosion rate of less than 10mdd is marked as ◎; a corrosion rate of more than 10mdd and less than 20mdd is marked as ○; a corrosion rate of more than 20mdd and less than 30mdd is marked as △; and a corrosion rate of more than 30mdd is marked as ×. Water quality conditions are shown in Table 1.

(2) Calcium phosphate scale precipitation inhibition test

Add ultrapure water to a 500ml conical beaker. The amount of ultrapure water is to subtract the amount of each reagent added from 500ml, and then add sodium bicarbonate aqueous solution, sodium silicate aqueous solution, polymer solution, magnesium sulfate aqueous solution, After sodium chloride aqueous solution, phosphoric acid solution, calcium chloride aqueous solution, and sodium sulfate aqueous solution, the pH was adjusted with a small amount of sodium hydroxide aqueous solution and sulfuric acid aqueous solution, and after plugging, it was left to stand in a constant temperature bath at 60°C for 20 hours. Thereafter, the phosphoric acid concentration of the filtrate filtered through 0.1 μm filter paper was measured, and the detection rate of phosphoric acid was calculated based on the following formula.

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

A phosphoric acid detection rate of 90% or more was marked as ◎; 80% or more and less than 90% was marked as ○; 50% or more and less than 80% was marked as Δ; and less than 50% was marked as ×. Water quality conditions are shown in Table 1.

Table 1

Recycled water A: Water quality assuming recycled water as make-up water

Recycled water B: water quality assuming recycled water as make-up water

(3) Molecular weight

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

Detector: RI

Column: Showa Denko Co., Ltd. Shodex Asahipak GF-310-HQ, GF-710-HQ, GF-1G

Eluent: 0.1N sodium acetate aqueous solution

Flow rate: 0.5ml/min

Column temperature: 40°C

Calibration curve: Polyacrylic acid standard (POLYACRYLIC ACID STANDARD) (manufactured by Sowa Scientific Co., Ltd.)

(4) Terminal sulfonic acid group

After the copolymer (aqueous solution) adjusted to pH 1 was dried under reduced pressure at room temperature and water was distilled, heavy water was used as a solvent, and ¹ HNMR measurement was performed to confirm whether the peak at 2.7 ppm originating from the sulfonic acid group introduced at the end of the polymer main chain was exist.

Examples 1-8 and Comparative Examples 1-9

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

In addition, Table 2 and Table 3 respectively show the corrosion rate (mdd) of the results of the anticorrosion performance evaluation test using the copolymer and the phosphoric acid detection rate (%) of the results of the calcium phosphate fouling inhibition test.

Table 2

AA: Acrylic

HAPS: Sodium 3-allyloxy-2-hydroxy-1-propanesulfonate

table 3

AA: Acrylic

MA: maleic acid

HAPS: Sodium 3-allyloxy-2-hydroxy-1-propanesulfonate

Based on Table 2 and Table 3, when comparing the detection rate of phosphoric acid based on the calcium phosphate inhibition test performed in the water quality assumed to be replenished with recycled water, the order of them is Comparative Example 4, 5<Comparative Example 1-3, Comparative Example 6 , 7<Example, Comparative Example 8,9. From the results, it can be seen that among polymers having structural units derived from acrylic acid (AA) and 3-allyloxy-2-hydroxyl-1-propanesulfonate (HAPS), examples in which a sulfonic acid group is present at the end of the main chain , Comparative Examples 8 and 9 exhibited an excellent fouling prevention effect in severe water quality in which recycled water was assumed to be make-up water. The reason for this is considered to be that gelation with Ca ions hardly occurs due to the introduction of the main chain terminal sulfonic acid group.

From the result, since Comparative Examples 1-5 did not have a sulfonic acid group, it turned out that the calcium phosphate fouling prevention effect was inferior. From the results, it can be seen that Comparative Examples 6 and 7 have structural units derived from HAPS, but have no sulfonic acid group at the end of the main chain, so the fouling prevention effect is poor in the water quality assuming that the recycled water is the make-up water. Similarly, since Comparative Examples 1 to 7 did not have a sulfonic acid group at the end of the main chain, gelation with Ca ions occurred, and the stain prevention effect was inferior to that of Examples and Comparative Examples 8 and 9.

According to the anticorrosion performance evaluation test, when comparing the corrosion rates, their order is Comparative Examples 8 and 9>Comparative Examples 6 and 7>Comparative Examples 1-5>Examples. From the results, it can be seen that the anticorrosion effect is high in Examples and Comparative Examples 1-5 having many carboxyl groups. The reason for this is considered to be that, when there are many carboxyl groups, it is easy to be adsorbed on the corrosion surface, and therefore, progress of corrosion can be suppressed.

From the results, it can be seen that Comparative Examples 8 and 9 showed the same excellent antifouling effect as the Examples, but the anticorrosion performance was inferior to the Examples. From the results, it can be seen that when the proportion of sulfonic acid exceeds 20 mol %, the anti-corrosion effect is reduced, and the corrosion cannot be suppressed in the water quality of the recovered water, and the anti-fouling effect and the anti-corrosion effect cannot be obtained at the same time.

From the above results, it can be seen that in the water quality assuming that the recovered water is makeup water, polymers having AA and HAPS at the end of the main chain of the polymer having a sulfonic acid group and having a HAPS ratio of 10 to 20 mol% show Excellent anti-fouling effect and anti-corrosion effect.

Industrial Applicability

The cooling water system treatment method of the present invention can prevent calcium-based scales from adhering to pipes or heat exchangers to prevent heat transfer obstruction in recycled water (retreated water) that is used as make-up water with high scale components and corrosive ions. , flow rate drop, etc., and can prevent corrosion of metals such as piping and heat exchangers.

Claims (2)

1. a treatment process for cooling water system, its in calcium hardness with CaCO ₃count that 300mg/L is above, chloride ion and/or sulfate ion concentration is in cooling water system more than 1000mg/L, add and contain the treatment agent that (methyl) acrylic copolymer forms, wherein,

Aforementioned (methyl) acrylic copolymer, (methyl) allyl ethers that has the structural unit (a) of (methyl) acrylic monomer (A) representing from following general formula (1), represent from following general formula (2) is the structural unit (b) of monomer (B)

And in all from 100 % by mole of the structural units of monomer, the content of structural unit (a) is that 80～90 % by mole, the content of structural unit (b) are 10～20 % by mole,

And aforementioned (methyl) acrylic copolymer, is sulfonic group or sulfonic group salt at least one of main chain end,

In general formula (1), R ¹represent hydrogen atom or methyl, X represents hydrogen atom, atoms metal, ammonium or organic amino group;

In general formula (2), R ²represent hydrogen atom or methyl, Y and Z represent respectively hydroxyl, sulfonic group or their salt independently, and at least one in Y and Z represents sulfonic group or sulfonic group salt.

2. the treatment process of cooling water system as claimed in claim 1, wherein, (methyl) acrylic copolymer, be by from be selected from vinylformic acid, methacrylic acid and sodium acrylate one or more (methyl) acrylic monomer (A) structural unit (a) and form from the structural unit (b) of 3-(methyl) allyloxy-2-hydroxyl-1-propanesulfonate.