JP2005264190A - Corrosion inhibitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion inhibitor exhibiting an excellent anticorrosive effect for a metal in contact with water.
A corrosion inhibitor contains a (meth) acrylic acid copolymer. The (meth) acrylic acid copolymer is composed of a structural unit (a) derived from the (meth) acrylic acid monomer A) and a structural unit derived from the monoethylenically unsaturated monomer (B) ( b) The structural unit (b) comprises at least a structural unit (b1) derived from the (meth) allyl ether monomer (B1).
[Selection figure] None

Description

  The present invention relates to a corrosion inhibitor that exhibits an excellent anticorrosive effect on a metal in contact with water.

  In chemical reaction plants such as oil refining plants and cooling water systems such as air conditioning equipment, metal materials that come into contact with water are prone to corrosion, so phosphates, polymerized phosphates, and phosphonic acids can be used as corrosion inhibitors. Phosphorus compounds such as salts and heavy metal compounds such as zinc salts are used. However, corrosion inhibitors containing phosphorus compounds and heavy metal compounds are problematic in that their use is restricted or some treatment is required when cooling water is discharged because there is concern about the impact on the environment.

  As a corrosion inhibitor that does not contain a phosphorus compound or a heavy metal compound, for example, Patent Document 1 discloses a metal anticorrosive containing a polymer having a carboxyl group. Patent Document 2 describes a metal anticorrosive containing an acrylic acid copolymer obtained by copolymerizing acrylic acid or an alkali metal salt or ammonium salt of acrylic acid and methyl acrylate. .

  Furthermore, Patent Document 3 describes that an acrylic acid polymer having a sulfonic acid group at a terminal and having a weight average molecular weight of 500 to 2800 is preferably used as an aqueous corrosion inhibitor.

  Patent Document 4 contains a copolymer obtained by copolymerizing a monomer having a sulfonic acid group and a monomer having a carboxyl group, and polyacrylic acid having a weight average molecular weight of 2000 or less. It is described that the composition for preventing corrosion shows an excellent anticorrosive effect on metals.

On the other hand, in Patent Document 5, a (meth) acrylic acid monomer and a monoethylenically unsaturated monomer are copolymerized, contain a predetermined structure at a specific ratio, and have a sulfone at the terminal. It has been disclosed that a (meth) acrylic acid-based copolymer having an acid group is suitably used for applications such as aqueous dispersants, scale inhibitors, and detergent builders.
JP 2001-254191 A (publication date: September 18, 2001) JP 2001-329386 A (publication date: November 27, 2001) JP 2002-294273 A (publication date: October 9, 2002) JP 2002-371387 A (publication date: December 26, 2002) JP 2002-3536 A (publication date: January 9, 2002)

  However, the polymer contained in the metal anticorrosive of Patent Document 1 is limited to a relatively small weight average molecular weight having a weight average molecular weight of less than 3000, as shown in Examples of the document. . Production of a polymer having a small weight average molecular weight is industrially uneconomical because it requires a large amount of polymerization initiator or a lower polymerization concentration than production of a high molecular weight polymer. There is a problem that.

  Moreover, the acrylic acid type copolymer contained in the metal anticorrosive of the said patent document 2 does not have a sulfonic acid group. Therefore, when added to water with high hardness, gelation and precipitation are likely to occur, and it may be difficult to obtain a more excellent corrosion prevention effect.

  Furthermore, the acrylic acid polymer used as the aqueous corrosion inhibitor described in Patent Document 3 is limited to a relatively small weight average molecular weight of 500 to 2800, as in Patent Document 1. Production of such a low weight average molecular weight acrylic acid polymer requires a larger amount of polymerization initiator or lower polymerization concentration than production of a high molecular weight acrylic acid polymer. Therefore, there is a problem that it is industrially uneconomical.

  Moreover, in order to obtain an excellent anticorrosion effect using the composition for preventing corrosion described in Patent Document 4, there is a problem that two types of polymers need to be used in combination.

  In Patent Document 5, a (meth) acrylic acid monomer and a monoethylenically unsaturated monomer are copolymerized, contain a predetermined structure in a specific ratio, and have a terminal. The use of a (meth) acrylic acid copolymer having a sulfonic acid group as an anticorrosive is not disclosed.

  Therefore, it is economically advantageous for industrial production, and even when added to high-hardness water, it does not cause gelation or precipitation and exhibits excellent corrosion inhibition effects on metals. There is a need for agents.

  The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to exhibit an excellent anticorrosive effect on a metal in contact with water without precipitation even in high-hardness water. It is to provide a corrosion inhibitor that can be used.

  As a result of intensive studies in view of the above problems, the present inventors have (meth) acrylic acid copolymer obtained by copolymerizing a (meth) acrylic acid monomer and a monoethylenically unsaturated monomer. Since the corrosion inhibitor containing a polymer exhibits excellent anticorrosion properties against metals, this corrosion inhibitor is used for the purpose of preventing corrosion of pipes of water-based equipment such as oil refining plants and air conditioning equipment. Has been found to be suitable for use, and the present invention has been completed.

  That is, the corrosion inhibitor according to the present invention is a corrosion inhibitor comprising a (meth) acrylic acid-based copolymer in order to solve the above-described problems, and the (meth) acrylic acid-based copolymer. Is the general formula (1)

(Wherein R1 represents a hydrogen atom or a methyl group, and X represents any one of a hydrogen atom, a metal atom, an ammonium group, and an organic amine group) (meth) acryl having a structure represented by The structural unit (a) derived from the acid monomer (A) and the structural unit (b) derived from the monoethylenically unsaturated monomer (B) have the structural unit (b) General formula (2)

(In the formula, R2 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 is a sulfone group. The structural unit (b1) derived from the (meth) allyl ether monomer (B1) having a structure represented by an acid group or a salt thereof, and comprising the above (meth) acrylic acid copolymer The content of the structural unit (a) with respect to the total amount of the structural unit (a) and the structural unit (b1) in the coalescence is 86 mol% or more and 99.5 mol% or less, and the structural unit with respect to the total amount. The content of (b1) is 0.5 mol% or more and 14 mol% or less.

  In the corrosion inhibitor according to the present invention, in the above-described corrosion inhibitor, the (meth) acrylic acid copolymer preferably has a sulfonic acid group or a salt thereof at least one of the ends of the main chain.

  In the corrosion inhibitor according to the present invention, the (meth) acrylic acid copolymer preferably has a weight average molecular weight of 3000 or more and 20000 or less.

  As described above, the corrosion inhibitor of the present invention includes the structural unit (a) derived from the (meth) acrylic acid monomer (A) having the structure represented by the general formula (1), and the general Structural unit (b) derived from monoethylenically unsaturated monomer (B) containing at least structural unit (b1) derived from (meth) allyl ether monomer (B1) represented by formula (2) And the content of the structural unit (a) with respect to the total amount of the structural unit (a) and the structural unit (b1) is 86 mol% or more and 99.5%. The content of the structural unit (b1) is 0.5 mol% or more and 14 mol% or less with respect to the total amount.

  Even when the acrylic acid copolymer is added to water having high hardness, it can exhibit an excellent corrosion prevention effect without precipitation. Therefore, even when cooling water that circulates water-based equipment such as oil refining plants and air conditioning equipment is used repeatedly, the concentration of inorganic substances such as salts contained in these waters increases and hardness increases. The acrylic acid copolymer does not gel or precipitate.

  Therefore, the acrylic acid copolymer has an effect that it can be used as a corrosion inhibitor exhibiting an excellent anticorrosive effect on a metal surface in a pipe or the like that contacts the cooling water or the like. Moreover, if the corrosion inhibitor of this invention is used, it will become possible to suppress the renewal frequency of a water-system apparatus, and the replacement frequency of the component of this apparatus, and to improve the service life of an apparatus. Furthermore, it is possible to contribute to driving these devices safely.

  In the corrosion inhibitor of the present invention, the (meth) acrylic acid copolymer is preferably a sulfonic acid group or a salt thereof at least one of the ends of the main chain. Therefore, even when added to water of higher hardness, the effect of exhibiting an excellent corrosion prevention effect can be obtained without causing gelation or precipitation of the (meth) acrylic acid copolymer.

  An embodiment of the present invention will be described as follows. That is, the corrosion inhibitor of the present invention comprises at least a (meth) acrylic acid copolymer. The (meth) acrylic acid copolymer is composed of a structural unit (a) derived from the (meth) acrylic acid monomer (A) and a structural unit derived from the monoethylenically unsaturated monomer (B). (B).

  The (meth) acrylic acid monomer (A) has the general formula (1)

(Wherein R1 represents a hydrogen atom or a methyl group, and X represents any one of a hydrogen atom, a metal atom, an ammonium group, and an organic amine group).

  In the general formula (1), examples of the metal atom represented by X include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as magnesium and calcium. Examples of the organic amine group represented by X include monoethanolamine, diethanolamine, and triethanolamine.

  Therefore, specifically as said (meth) acrylic-acid type monomer (A), acrylic acid, methacrylic acid, and these salts (For example, alkali metal salt, alkaline-earth metal salt, ammonium salt etc.), etc. Can be mentioned. Among these compounds, acrylic acid and sodium acrylate are particularly preferable. As the (meth) acrylic acid monomer (A), only one of the above compounds may be used, or two or more may be used in combination.

  In addition, as the monoethylenically unsaturated monomer (B), the structural unit (b) has at least the general formula (2).

(In the formula, R2 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 is a sulfone group. A (meth) allyl ether monomer (B1) having a structure represented by an acid group or a salt thereof.

  That is, the monoethylenically unsaturated monomer (B) is copolymerizable with the (meth) acrylic acid monomer (A) and has at least a structure represented by the general formula (2). (Meth) allyl ether monomer (B1) having In general formula (2) representing the structure of the (meth) allyl ether monomer (B1), at least one of Y and Z is a sulfonic acid group or a salt thereof, and the other is a hydroxyl group. Also good.

  Examples of the sulfonic acid group salts represented by Y and Z include monovalent metal salts, divalent metal salts, ammonium salts, and salts of organic amine groups. Examples of the monovalent metal salt include salts of alkali metals such as sodium, potassium, and lithium. Examples of the divalent metal salt include salts of alkaline earth metals such as magnesium and calcium. it can. Examples of the organic amine group salt include monoethanolamine, diethanolamine, and triethanolamine.

  Specifically, as the (meth) allyl ether monomer (B1), 3- (meth) allyloxy-2-hydroxypropanesulfonic acid and its salt, 3- (meth) allyloxy-1-hydroxy-2 -Propanesulfonic acid and its salt can be mentioned, and among these, sodium 3-allyloxy-2-hydroxypropanesulfonate is particularly preferable. As the (meth) allyl ether monomer (B1), only one of these compounds may be used, or two or more may be used in combination.

Further, the monoethylenically unsaturated monomer (B) includes monoethylenically unsaturated monomers other than the (meth) allyl ether monomer (B1) (hereinafter referred to as other monoethylenically unsaturated monomers). (Described as a monomer). Examples of other monoethylenically unsaturated monomers include 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) allylsulfonic acid, vinylsulfonic acid, styrenesulfonic acid, and 2-sulfoethyl (meth). Acrylic acid, sulfonic acid monomers such as conjugated dienesulfonic acid such as 2-methyl-1,3-butadiene-1-sulfonic acid, and salts thereof; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide N-vinyl monomers such as N-vinyl-N-methylformamide, N-vinyl-N-methylacetamide, N-vinyloxazolidone; (meth) acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, etc. Amide monomers; unsaturated dicarbohydrates such as itaconic acid, fumaric acid and maleic acid Acid; 3- (meth) allyloxy-1,2-dihydroxypropane, 3-allyloxy-1,2-dihydroxypropane, 3-allyloxy-1,2-dihydroxy propane (meth) allyloxy propane compounds, and, Compounds obtained by adding 1 to 200 mol of ethylene oxide to 1 mol of these compounds (3-allyloxy-1,2-di (poly) oxyethylene ether propane, etc.); (meth) allyl alcohol, and (meta ) Allyl ether monomers such as compounds in which 1 to 100 mol of ethylene oxide is added to 1 mol of allyl alcohol; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (Meth) acrylic acid ester monomers such as hydroxyethyl (meth) acrylate; Prenol, and isoprene monomer such as compounds obtained by 1 mole to 100 moles of ethylene oxide addition respect isoprenol 1 mol, and the like can be given.

  As described above, the (meth) acrylic acid copolymer of the present invention is obtained by copolymerizing the (meth) acrylic acid monomer (A) and the monoethylenically unsaturated monomer (B). Become. Therefore, the (meth) acrylic acid copolymer is a structural unit (a) derived from the (meth) acrylic acid monomer (A) having the structure represented by the general formula (1), and (Meth) allyl ether having a structural unit (b) derived from a monoethylenically unsaturated monomer (B), and the structural unit (b) having a structure represented by the general formula (2) It comprises at least the structural unit (b1) derived from the system monomer (B1).

  The content ratio of the structural unit (a) to the total amount of the structural unit (a) and the structural unit (b1) in the (meth) acrylic acid copolymer is the (meth) acrylic acid copolymer. The upper limit of the content of the structural unit (a) is 99.5 mol% or less, more preferably 95 mol% or less. It is good to be. Moreover, the lower limit of the content rate of the said structural unit (b1) with respect to the total amount of a structural unit (a) and a structural unit (b1) in a (meth) acrylic-acid type copolymer is 0.5 mol% or more. Yes, more preferably 5 mol% or more, and the upper limit of the content of the structural unit (b1) is 14 mol% or less, more preferably 10 mol% or less.

  When the structural unit (a) is less than 86 mol% and the structural unit (b1) exceeds 14 mol%, the corrosion inhibiting effect is lowered. Further, when the structural unit (b1) is less than 0.5 mol% and the structural unit (a) exceeds 99.5 mol%, the gel resistance is lowered, and used as, for example, cooling water or the like. Thus, when the inorganic substance concentration in the cooling water increases, it becomes gelled and it becomes difficult to exhibit the corrosion inhibition effect.

  When the monoethylenically unsaturated monomer (B) contains another monoethylenically unsaturated monomer, the structural unit of the other monoethylenically unsaturated monomer is ( It is preferably 20 mol% or less, more preferably 10 mol% or less, and still more preferably based on the total amount of the structural unit (a) and the structural unit (b1) in the (meth) acrylic acid copolymer. Is preferably 5 mol% or less. When the structural unit of the other monoethylenically unsaturated monomer with respect to the total amount of the structural unit (a) and the structural unit (b1) exceeds 20 mol%, the corrosion inhibiting effect is lowered, which is not preferable.

  The (meth) acrylic acid copolymer obtained by copolymerizing the monomer component containing the (meth) acrylic acid monomer (A) and the monoethylenically unsaturated monomer (B) is: It is preferable that at least one of the ends of the main chain is a sulfonic group or a salt thereof. In this case, the (meth) acrylic acid copolymer includes a sulfonic acid group contained in the structural unit (b1) derived from the (meth) allyl ether monomer (B1) and a sulfonic acid group at the end of the main chain. Thus, the gel resistance can be remarkably improved. Thereby, even when added to water with high hardness, it is possible to exert an excellent corrosion prevention effect without causing gelation or precipitation.

  The (meth) acrylic acid copolymer has a lower limit of the weight average molecular weight Mw of 3000 or more, more preferably 4000 or more, and an upper limit of 20000 or less, more preferably 18000 or less. . If the weight average molecular weight Mw is outside the above range, the corrosion inhibiting effect is lowered, which is not preferable.

  The method for producing the (meth) acrylic acid copolymer of the present invention is a monomer component containing the (meth) acrylic acid monomer (A) and the monoethylenically unsaturated monomer (B). Is copolymerized. In the copolymerization of the monomer components, it is preferable to use sulfite as a chain transfer agent. Thereby, a sulfonic acid group can be introduce | transduced into the principal chain terminal of the (meth) acrylic-acid type copolymer obtained.

  Examples of the sulfite include sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite, sodium sulfite, potassium sulfite, and ammonium sulfite. Among these, sodium hydrogen sulfite is particularly preferable. These sulfites may be used alone or in combination of two or more.

  The amount of the sulfite used is preferably 2 to 15 g, more preferably 4 to 11 g per mole of all monomer components. If the amount of sulfite used is less than 2 g with respect to 1 mol of all monomer components, it is not preferable because sulfonic acid groups cannot be quantitatively introduced into the main chain ends of the polymer. On the other hand, if it exceeds 15 g, surplus sulfite is decomposed in the reaction system, and sulfite gas is generated, and sulfite is wasted, which is disadvantageous economically. .

  Further, in the copolymerization, examples of the polymerization initiator include 2,2′-azobis (2-aminopropane) hydrochloride, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propion Amide compounds]; peroxides such as hydrogen peroxide and tert-butylhydroxyperoxide; one or more selected from persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate. That's fine. Among these, as the polymerization initiator, it is particularly preferable to use a persulfate because the polymerization rate can be improved and the amount of residual monomer can be reduced. In general, the addition amount of the polymerization initiator is preferably 0.1 g to 1000 g per 1 mol of all monomer components.

  In the copolymerization, a polymerization aid may be used in combination with the chain transfer agent and the polymerization initiator. As a polymerization aid, for example, transition metal compounds such as iron and moor salts (ferrous ammonium sulfate hexahydrate), mercapto compounds such as mercaptoethanol and mercaptopropionic acid; ascorbate and the like can be used. This polymerization aid may be prepared in advance in the reaction system, and the addition amount is usually 0.1 ppm to 50 ppm for transition metal compounds, and for mercapto compounds and ascorbates with respect to all monomer components. 0.1 wt% to 5 wt% is preferable.

  In the copolymerization, the monomer components, the chain transfer agent, and the polymerization initiator are preferably continuously dropped or dividedly added separately over a predetermined dropping time. The dropping time may be set as appropriate, but is preferably 30 minutes to 480 minutes, and more preferably 45 minutes to 240 minutes. If the dropping time is too long, productivity is lowered, which is not preferable. If the dropping time is too short, introduction of a sulfonic acid group to the main chain terminal of the (meth) acrylic acid copolymer can be effectively performed. This is not preferable because it becomes difficult. In addition, the dropping speed of each of the above components may be a constant speed from the start to the end of the dropping, or the dropping speed may be changed as time passes as necessary.

  As a polymerization method for copolymerizing the monomer components, for example, known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be used. Although the reaction temperature in the case of the said copolymerization is not specifically limited, Preferably it is 50 to 150 degreeC, More preferably, it is 70 to 120 degreeC, Most preferably, it is good to set it as 80 to 110 degreeC. If the reaction temperature is less than 50 ° C., the reactivity in copolymerization tends to decrease and the amount of unreacted monomers increases, and if it exceeds 150 ° C., side reactions increase and reaction control becomes difficult. This is not preferable. In addition, the said copolymerization reaction may be performed in inert gas atmosphere, such as nitrogen and argon, and may be performed in air | atmosphere.

  The solvent used in carrying out the copolymerization reaction may be any solvent in which the copolymerization reaction proceeds, such as water; alcohols having 1 to 4 carbon atoms such as methanol, ethanol, isopropyl alcohol; amides such as dimethylformamide. And ethers such as diethyl ether and dioxane can be preferably used. These solvents may be a single solvent using only one kind or a mixed solvent obtained by mixing two or more kinds. Of the above solvents, water containing no organic solvent is most preferably used.

  In order to improve productivity in the copolymerization reaction, it is preferable that all solid components to be charged into the reaction system have a concentration of 10% by weight or more, more preferably 20% by weight. The above concentration is most preferable, and the concentration is 40% by weight or more. That is, it is preferable that the solid content concentration at the time when the polymerization reaction is completed is 10% by weight or more.

  The corrosion inhibitor of the present invention comprising the (meth) acrylic acid copolymer is added to water in contact with a metal such as cooling water used in water-based equipment such as an oil refinery plant or an air conditioner. It shows the effect of inhibiting the corrosion of metals. Therefore, if the corrosion inhibitor of the present invention is used, corrosion of a metal that comes into contact with water can be suppressed, which can contribute to safe operation of water-based equipment. Further, by using the corrosion inhibitor, it is possible to improve the service life of the equipment by suppressing the frequency of renewal of water-based equipment due to corrosion and the frequency of replacement of parts of the equipment.

  Furthermore, the corrosion inhibitor of the present invention can be suitably used even in high hardness water. Therefore, when it is assumed that the concentration of inorganic substances contained in water is gradually increased by reducing the amount of water supply or discharge water, such as cooling water that is repeatedly used by circulating in the apparatus. In addition, it is possible to obtain a metal corrosion inhibiting effect.

  That is, when cooling is performed by evaporating a part of the cooling water in an open circulation type cooling water system or the like, the inorganic substances contained in the water replenished to compensate for the evaporation are gradually concentrated. . Therefore, in the cooling water system, the concentration of the inorganic substance is usually adjusted by discharging a part of the cooling water used in a circulating manner. Accordingly, when the amount of water supplied to the cooling water system is reduced or the amount of cooling water discharged is reduced, the concentration of inorganic substances in the cooling water increases. Therefore, even when the concentration of the inorganic substance in the cooling water is high, if the corrosion inhibitor of the present invention that can be suitably used without causing gelation or precipitation of the inorganic substance is added to the cooling water, the amount of industrial water used And the amount of industrial wastewater can be reduced. Thereby, it is possible to consider environmental problems that have become social problems in recent years.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this. In addition, the measurement of the weight average molecular weight Mw and the anticorrosion performance test were measured as follows.

[Measurement of weight average molecular weight Mw]
The weight average molecular weight Mw of the polymer was measured by GPC (gel permeation chromatography). The GPC measurement was performed under the following conditions using a GPC apparatus (Shodex SYSTEM-21 (detector; RI, UV (detection wavelength: 220 nm))) manufactured by Showa Denko K.K. That is, a column in which Asahipak GF-710 HQ and Asahipak GF-310 HQ were connected in this order was used. As an eluent, a solution obtained by adding 670 g (reagent special grade) of acetonitrile to a sodium acetate aqueous solution in which deionized water was added to 27.22 g sodium acetate trihydrate (special grade reagent) to make the total amount 2000 g was used. The flow rate of the eluent was 0.5 mL / min, and the temperature was 40 ° C. The calibration curve was prepared using a polyethylene glycol standard sample (manufactured by GL Sciences).

[Anti-corrosion performance test]
The anticorrosion performance test of the corrosion inhibitor and the comparative corrosion inhibitor described later was performed as follows. That is, a test in which a low carbon steel (JIS G3141SPCC-SB) having a size of 40 mm × 25 mm × 1 mm and a surface area of 0.213 dm ² is polished by # 400 and further subjected to nitric acid treatment to remove the oxide film on the surface of the low carbon steel. The piece was degreased with toluene and weighed, and the weight was taken as the pre-test weight. Next, in an open container, 200 mL of water quality test water shown in Table 1 and a corrosion inhibitor or a comparative corrosion inhibitor so as to have an addition concentration shown in Table 3 in terms of solid content are placed, and the test piece is placed therein. It was immersed and kept at 40 ° C. for 2 days with gentle stirring.

  Two days after the test piece is immersed, the test piece is taken out, and the weight of the test piece is measured after the corrosion product adhering to the surface of the test piece is removed by washing with acid and dried. Was the weight after the test. Thereafter, the corrosion rate (mdd) was calculated from the weight change of the test piece by the corrosion test by the following formula, and the anticorrosion performance was evaluated.

  A 2.5L SUS separable flask equipped with a reflux condenser and a stirrer was charged with 328.5 g of deionized water and refluxed at the boiling point while stirring (hereinafter, this state is referred to as the boiling point reflux state). The temperature was raised to obtain a polymerization reaction system. Next, 20.7 g of an 80% by weight aqueous acrylic acid solution (hereinafter referred to as 80% AA) and an aqueous 37% by weight sodium acrylate solution (hereinafter described as 37% SA) were added to the polymerization reaction system in a boiling point reflux state with stirring. ) 412.9 g mixed aqueous solution (total weight 433.6 g), 25 wt% sodium 3-allyloxy-2-hydroxypropanesulfonate aqueous solution (hereinafter referred to as 25% HAPS) 131.2 g, 35 wt% peroxidation 28.7 g of hydrogen aqueous solution (hereinafter referred to as 35% HP) (corresponding to 5 g with respect to 1 mol of the monomer in the monomer component), 15% by weight sodium persulfate aqueous solution (hereinafter referred to as 15% NaPS) 41.5 g (equivalent to 3.1 g with respect to 1 mol of the monomer in the monomer component) and 47.4 g of deionized water were dropped from separate nozzles to prepare a reaction solution. The charge composition ratio (mol%) of each monomer with respect to all monomer components contained in the reaction solution is as shown in Table 2.

  The dropping time of each of the above aqueous solutions and deionized water was set to 120% for the mixed aqueous solution of 80% AA and 37% SA, 90 minutes for 25% HAPS, 120 minutes for 35% HP, 15% NaPS and deionized water were each 140 minutes. The dropping speed of each aqueous solution and deionized water was constant, and the dropping of each aqueous solution and deionized water was continuously performed.

  After completion of the dropwise addition of the 15% NaPS and deionized water, the reaction solution was kept at the boiling point reflux state (ripening) for another 60 minutes to complete the polymerization reaction. Thus, an aqueous solution of a copolymer (hereinafter referred to as copolymer P1 ') having a solid content concentration of 20% by weight and a final neutralization degree of 92 mol% was obtained. The results of measuring the weight average molecular weight Mw of the copolymer P1 'are shown in Table 2.

  Further, an anticorrosion performance test was performed using the aqueous solution of the copolymer P1 'as a corrosion inhibitor (hereinafter referred to as a corrosion inhibitor P1). The results are shown in Table 3.

  A 2.5 L SUS separable flask equipped with a reflux condenser and a stirrer was charged with 260 g of deionized water and 0.0293 g of Mole salt, and the temperature was raised to 90 ° C. while stirring to obtain a polymerization reaction system. . Next, 182.9 g of 35% by weight aqueous sodium hydrogen sulfite solution (hereinafter, 35% SBS) was added to the above polymerization reaction system maintained at about 90 ° C. with stirring (based on 1 mol of the monomer in the monomer component). (Equivalent to 8 g). Subsequently, 10 minutes after the start of dropwise addition of the 35% SBS, 80% AA (695.9 g), 40% sodium 3-allyloxy-2-hydroxypropanesulfonate (hereinafter referred to as 40% HAPS) 146. 1 g and 15% NaPS (106.7 g; equivalent to 2 g with respect to 1 mol of the monomer in the monomer component) were dropped from separate dropping nozzles to prepare a reaction solution. The charge composition ratio (mol%) of each monomer with respect to all monomer components contained in the reaction solution is as shown in Table 2.

  The dropping time of each of the aqueous solutions was 35 minutes SBS and 80% AA for 180 minutes, 40 minutes HAPS for 170 minutes, and 15% NaPS for 190 minutes. The dropping rate of each aqueous solution was constant, and the dropping of each aqueous solution was continuously performed.

  After completion of the dropwise addition of 15% NaPS, the reaction solution was maintained at 90 ° C. for 30 minutes (ripening) to complete the polymerization reaction. After completion of the polymerization, the reaction solution was allowed to cool, and while stirring the reaction solution, 613.3 g of a 48 wt% aqueous sodium hydroxide solution (hereinafter referred to as 48% NaOH) was gradually added dropwise to bring the reaction solution into the middle. It was summed up. Thus, an aqueous solution of a copolymer (hereinafter referred to as copolymer P2 ') having a solid content concentration of 50% by weight and a final neutralization degree of 97 mol% was obtained. The results of measuring the weight average molecular weight Mw of the copolymer P2 'are shown in Table 2.

  Further, an anticorrosion performance test was performed using the aqueous solution of the copolymer P2 'as a corrosion inhibitor (hereinafter referred to as a corrosion inhibitor P2). The results are shown in Table 3.

  A 2.5 L SUS separable flask equipped with a reflux condenser and a stirrer was charged with 156 g of deionized water and 0.0265 g of Mole salt, and the temperature was raised to 90 ° C. while stirring to obtain a polymerization reaction system. . Subsequently, dropwise addition of 35% SBS (182.9 g; equivalent to 8 g with respect to 1 mol of the monomer in the monomer component) was started in the polymerization reaction system maintained at about 90 ° C. with stirring. . Subsequently, 10 minutes after the start of dropwise addition of the 35% SBS, a mixed aqueous solution of 80% AA (689.4 g) and 37% SA (56 g) (total weight 745.4 g), 40% HAPS (65.4 g) 15% NaPS (106.7 g; equivalent to 2 g with respect to 1 mol of the monomer in the monomer component) was dropped from separate dropping nozzles to prepare a reaction solution. The charge composition ratio (mol%) of each monomer with respect to all monomer components contained in the reaction solution is as shown in Table 2.

  In addition, the dropping time of each of the above aqueous solutions is such that the dropping time of the above mixed aqueous solution of 80% AA and 37% SA and 35% SBS is 180 minutes, 40% HAPS is 170 minutes, and 15% NaPS is 190 minutes. It was. The dropping rate of each aqueous solution was constant, and the dropping of each aqueous solution was continuously performed.

  After completion of the dropwise addition of 15% NaPS, the reaction solution was maintained at 90 ° C. for 30 minutes (ripening) to complete the polymerization reaction. After completion of the polymerization, the reaction solution was allowed to cool, and while stirring the reaction solution, 48% NaOH (613.4 g) was gradually added dropwise to neutralize the reaction solution. Thus, an aqueous solution of a copolymer (hereinafter referred to as copolymer P3 ') having a solid content concentration of 50% by weight and a final neutralization degree of 97 mol% was obtained. The results of measuring the weight average molecular weight Mw of the copolymer P3 'are shown in Table 2.

  Further, an anticorrosion performance test was conducted using the aqueous solution of the copolymer P3 'as a corrosion inhibitor (hereinafter referred to as a corrosion inhibitor P3). The results are shown in Table 3.

  A SUS separable flask having a capacity of 2.5 L equipped with a reflux condenser and a stirrer was charged with 516 g of deionized water, and the temperature was raised to a boiling point reflux state while stirring to obtain a polymerization reaction system. Next, a mixed aqueous solution (total weight 335.1 g) of 80% AA (15.9 g) and 37% SA (319.2 g), 25% HAPS (112 g) was added to the polymerization reaction system under boiling reflux condition with stirring. ), 35% HP (23.2 g; equivalent to 5 g with respect to 1 mol of monomer in the monomer component), 15% NaPS (32.4 g; with respect to 1 mol of monomer in the monomer component) In this case, 204.5 g of deionized water was dropped from separate dropping nozzles to obtain a reaction solution. The charge composition ratio (mol%) of each monomer with respect to all monomer components contained in the reaction solution is as shown in Table 2.

  The dropping time of each of the above aqueous solutions and deionized water is such that the above mixed aqueous solution of 80% AA and 37% SA and 35% HP are 120 minutes, 25% HAPS is 90 minutes, 15% NaPS and deionized water. Ionized water for 140 minutes each. The dropping speed of each aqueous solution and deionized water was constant, and the dropping of each aqueous solution and deionized water was continuously performed.

  After completion of the dropwise addition of the 15% NaPS and deionized water, the reaction solution was held (ripened) at the boiling point reflux state for an additional 60 minutes to complete the polymerization reaction. Thus, an aqueous solution of a copolymer (hereinafter referred to as copolymer P4 ') having a solid content concentration of 14% by weight and a final neutralization degree of 95 mol% was obtained. The results of measuring the weight average molecular weight Mw of the copolymer P4 'are shown in Table 2.

  Further, an anticorrosion performance test was performed using the aqueous solution of the copolymer P4 'as a corrosion inhibitor (hereinafter referred to as a corrosion inhibitor P4). The results are shown in Table 3.

[Comparative Example 1]
A 2.5 L SUS separable flask equipped with a reflux condenser and a stirrer was charged with 106.4 g of deionized water and 0.1253 g of a Mole salt, and the temperature was raised to 90 ° C. while stirring to polymerize the reaction system. It was. Subsequently, dropwise addition of 35% SBS (457.1 g; equivalent to 25 g with respect to 1 mol of the monomer in the monomer component) was started in the polymerization reaction system maintained at about 90 ° C. with stirring. . Subsequently, 10 minutes after the start of dropping of the 35% SBS, 80 g AA (576 g), 48% NaOH (26.7 g), 25 wt% sodium persulfate aqueous solution (hereinafter referred to as 25% NaPS) 128 g (simple (Corresponding to 5 g with respect to 1 mol of the monomer in the monomer component) was dropped from separate dropping nozzles to prepare a reaction solution. The charge composition ratio (mol%) of the monomer component contained in the reaction solution is as shown in Table 2.

  The dropping time of each of the above aqueous solutions was set to 180 minutes for each of the 35% SBS, 80% AA, and 48% NaOH, and 190 minutes for 25% NaPS. The dropping rate of each aqueous solution was constant, and the dropping of each aqueous solution was continuously performed.

  After the completion of the dropwise addition of 25% NaPS, the reaction solution was maintained at 90 ° C. for 30 minutes (ripening) to complete the polymerization reaction. After completion of the polymerization, the reaction solution was allowed to cool, and while stirring the reaction solution, 48% NaOH (485.3 g) was gradually added dropwise to neutralize the reaction solution. Thus, an aqueous solution of sodium polyacrylate (hereinafter referred to as comparative polymer p1 ') having a solid content concentration of 45% by weight and a final neutralization degree of 96 mol% was obtained. The results of measuring the weight average molecular weight Mw of the comparative polymer p1 'are shown in Table 2.

  Further, an anticorrosion performance test was conducted using the aqueous solution of the comparative polymer p1 'as a comparative corrosion inhibitor (hereinafter referred to as a comparative corrosion inhibitor p1). The results are shown in Table 3.

[Comparative Example 2]
A 2.5 L SUS separable flask equipped with a reflux condenser and a stirrer was charged with 635.3 g of deionized water and heated to a boiling point reflux state while stirring to obtain a polymerization reaction system. Next, 37% SA (762.5 g), 15% NaPS (25 g; 1.3 g with respect to 1 mol of the monomer in the monomer component), Deionized water 82.3 was dropped from separate dropping nozzles to prepare a reaction solution. The charge composition ratio (mol%) of the monomer component contained in the reaction solution is as shown in Table 2.

  In addition, as for the dropping time of each of the above aqueous solutions and deionized water, the dropping time of 37% SA was 200 minutes, and 15% NaPS and deionized water were each 205 minutes. The dropping speed of each aqueous solution and deionized water was constant, and the dropping of each aqueous solution and deionized water was continuously performed.

  After completion of the dropwise addition of 15% NaPS and deionized water, the reaction solution was kept (ripened) at the boiling point for 30 minutes to complete the polymerization. Thus, an aqueous solution of sodium polyacrylate (hereinafter referred to as comparative polymer p2 ') having a solid content concentration of 19% by weight and a final neutralization degree of 100 mol% was obtained. The results of measuring the weight average molecular weight Mw of the comparative polymer p2 'are shown in Table 2.

  Further, an anticorrosion performance test was conducted using the aqueous solution of the comparative polymer p2 'as a comparative corrosion inhibitor (hereinafter referred to as a comparative corrosion inhibitor p2). The results are shown in Table 3.

[Comparative Example 3]
The anticorrosion performance of the test piece was evaluated by the above-described anticorrosion performance test method, except that the corrosion inhibitor or the comparative corrosion inhibitor was not used. The results are shown in Table 3.

  The corrosion inhibitor of the present invention suppresses corrosion of metals such as pipes that come into contact with water in water-based equipment that uses cooling water, such as chemical reaction plants such as petroleum refining plants and air conditioning equipment. Therefore, it can be preferably used.

Claims (3)

A corrosion inhibitor comprising a (meth) acrylic acid copolymer,
The (meth) acrylic acid copolymer has the general formula (1)

(Wherein R1 represents a hydrogen atom or a methyl group, and X represents any one of a hydrogen atom, a metal atom, an ammonium group, and an organic amine group) (meth) acryl having a structure represented by The structural unit (a) derived from the acid monomer (A) and the structural unit (b) derived from the monoethylenically unsaturated monomer (B)
The structural unit (b) has the general formula (2)

(In the formula, R2 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 is a sulfone group. Comprising at least a structural unit (b1) derived from a (meth) allyl ether monomer (B1) having a structure represented by an acid group or a salt thereof,
The content rate of the said structural unit (a) with respect to the total amount of the structural unit (a) and a structural unit (b1) in the said (meth) acrylic-acid type copolymer is 86 mol% or more and 99.5 mol% or less. A corrosion inhibitor, wherein the content of the structural unit (b1) with respect to the total amount is 0.5 mol% or more and 14 mol% or less.   2. The corrosion inhibitor according to claim 1, wherein at least one of the ends of the main chain of the (meth) acrylic acid copolymer is a sulfonic acid group or a salt thereof.   The corrosion inhibitor according to claim 1 or 2, wherein the (meth) acrylic acid copolymer has a weight average molecular weight of 3000 or more and 20000 or less.