JP5823075B1 - Pitting corrosion inhibitor composition and pitting corrosion suppression method - Google Patents

Abstract

[PROBLEMS] To provide a pitting corrosion inhibitor composition and a pitting corrosion suppression method excellent in low-temperature stability, which are applied to a carbon steel heat exchanger of an open circulation type cooling water system. An anticorrosive film forming component and a dispersant component are included as active ingredients, the anticorrosive film forming component contains a maleic acid polymer, an itaconic acid polymer, and a compound that releases zinc ions, and the dispersant component is It contains a copolymer of monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid, and the weight ratio of the blending amount of the dispersant component to the blending amount of the anticorrosive film forming component is 0.4 to 0.8. The weight ratio of the added amount of the dispersant component to the added amount of the anticorrosive film-forming component in the circulating water of the pitting corrosion inhibitor composition and the open circulation type cooling water system is 0.4 to 0.8. A pitting corrosion suppression method comprising adding an anticorrosion film forming component and a dispersant component to an open circulation type cooling water system. [Selection figure] None

Description

  The present invention relates to a composition for suppressing corrosion of iron-based metals such as carbon steel in contact with water, particularly pitting corrosion, and a method for suppressing pitting corrosion in an open circulation type cooling water system. The present invention also relates to the composition having excellent low-temperature stability.

  In an open circulation type cooling water system, iron-based metal such as carbon steel is generally used as a material for heat transfer tubes and piping of heat exchangers in the system. Since these iron-based metals undergo significant corrosion when they come into contact with water, various corrosion inhibitors are used to prevent corrosion of the iron-based metals. These corrosion inhibitors prevent corrosion by forming a thin anticorrosive film on the surface of the ferrous metal.

  Conventionally, it is generally known that phosphoric acid or condensed phosphate is used for cooling water as a method of preventing corrosion in an open circulation cooling water system, and phosphorus-based compounds such as condensed phosphate and phosphonic acid. Corrosion inhibitors that use zinc and zinc compounds are also frequently used.

  However, heavy metals such as zinc compounds and phosphoric acids are concerned about toxicity to aquatic organisms and effects on eutrophication of lakes and rivers. Regulations came into effect. Accordingly, there is a need for a corrosion inhibitor and a corrosion inhibition method that can reduce the amount of heavy metals and phosphoric acids used.

  On the other hand, in an open-circulation cooling water system, metal corrosion occurs on the anode surface. Therefore, by suppressing the anode, the corrosion rate on the entire metal surface can be reduced, but the formation of the anticorrosion coating is made uniform. If not, the corrosion current flowing through the anode, which is a missing portion of the coating, becomes excessive, and local corrosion called pitting corrosion that progresses in the form of holes toward the inside of the metal occurs. If pitting corrosion occurs in the heat exchanger during system operation, leakage to the cooling water to the process side or leakage from the process side, etc., will have a great impact on the operation of the system, sometimes at the process side plant It may lead to an unexpected shutdown.

  The life of the heat exchanger tube of the heat exchanger is the period until the heat transfer tube is pierced by pitting corrosion or the maximum pitting corrosion depth reaches a safety tolerance. Contributes to longer life.

  In general, seamless steel pipes are used as carbon steel pipes for multi-tube heat exchangers, and cold-finished seamless steel pipes with high dimensional accuracy are used because the accuracy of the outer diameter is particularly required. In cold-finished seamless steel pipes, mill scale generated by heat treatment after cold working, carbide of lubricant during cold working, residue of ground treatment, etc. adhere unevenly to the steel surface. Tends to cause pitting corrosion due to the formation of oxygen concentration cells. However, even though the conventional corrosion suppression method can suppress the overall corrosion rate, the pitting corrosion rate cannot be sufficiently suppressed.

For example, Patent Document 1 states that “in the case of a very common water quality, if a phosphorus-based compound of about 10 mg / L or more as PO ₄ is added, a certain degree of corrosion suppression effect can be obtained, but pitting corrosion is surely achieved. In order to suppress it, it is necessary to add a high concentration of about 100 mg / L. ”Patent Document 2 describes that“ a large amount of anticorrosive is added to prevent the progress of local corrosion of metal in an aqueous system. It may also cause damage ", indicating the difficulty of suppressing pitting corrosion.

  In Patent Document 1, a method for suppressing pitting corrosion of a metal that reduces the amount of phosphorus compound added by using an operation of removing corrosive ions involved in pitting corrosion by bringing water supplied to the target aqueous system into contact with an anion exchange resin. Has proposed. However, in this method, it is necessary to add equipment filled with anion exchange resin, and maintenance and management of the equipment and anion exchange resin are also required, so that the management operation of the water system becomes complicated and the cost also increases. To do.

  Patent Document 2 proposes a method of adding microcapsules containing an anticorrosive to an aqueous system as a method of suppressing the progress of local corrosion. Examples of the anticorrosive contained in the microcapsule include phosphoric acid, chromic acid, tungstic acid, water-soluble salts of molybdic acid, and the like. Patent Document 3 proposes a pitting corrosion inhibitor characterized by containing molybdic acid, tungstic acid or a salt thereof and sodium carbonate or potassium carbonate. However, in these proposals, a microcapsule preparation process is required, or a relatively expensive heavy metal such as tungsten or molybdenum is applied as a main component, so that a pitting corrosion inhibitor that can reduce the amount of heavy metal used and The pitting corrosion prevention method cannot be sufficiently met, and the cost increases.

  In addition, it has been disclosed that phosphonic acid derivatives such as ethanolamine bisphosphonomethyl-N-oxide and hydroxyiminobis (methylphosphonic acid) (see Patent Document 4) also have a local corrosion inhibiting effect. There is a problem that a high concentration is necessary to obtain it.

  On the other hand, Patent Document 5 discloses isoprenesulfonic acid / acrylic acid / acrylic acid-2-hydroxyethyl terpolymer and isoprenesulfonic acid / acrylic acid / as a water treatment agent that does not contain phosphorus and has an effect of preventing local corrosion. Acrylamide-2-methylpropanesulfonic acid-based terpolymers and the like are disclosed, but the same applicant described in Patent Document 6 that the single use of these polymers may cause pitting corrosion depending on the conditions of the target aqueous system. Point out. Patent Document 6 proposes a corrosion inhibitor containing silicic acid or a salt thereof and a sulfonic acid polymer as a corrosion inhibitor that is non-phosphorus and non-metallic and has an excellent pitting corrosion prevention effect. However, since this corrosion inhibitor is added so that the silica concentration of the target aqueous system is 50 to 100 mg / L, it is difficult to adjust the amount of the chemical added in an aqueous system in which the increase or decrease in the silica concentration is large.

  As described above, there is still a high demand for an iron-based metal pitting corrosion inhibitor and pitting corrosion suppression method that can reduce the amount of zinc compound and phosphorus compound used and that is highly effective.

Japanese Patent Laid-Open No. 11-029885 JP 2004-353025 A JP 2007-023370 A Japanese Patent Laid-Open No. 10-165987 JP-A-9-248555 JP 2008-088475 A

  In the open circulation type cooling water system, the present inventors can reduce the amount of zinc compound and phosphorus compound used, and are made of carbon steel in contact with water, which has a high effect of suppressing pitting corrosion in ferrous metals, particularly carbon steel. As a result of research on the pitting corrosion inhibitor composition of the heat exchanger material, even if it is a composition with a high pitting corrosion suppression effect of carbon steel, the storage stability as a composition, especially the low temperature stability is bad and may not be practical. It turns out that there is. Therefore, the present invention can reduce the amount of zinc compound and phosphorus compound used in an open-circulation cooling water system, has a high effect of suppressing pitting corrosion of carbon steel, and is stable when the composition is stored at a low temperature. It is an object of the present invention to provide a pitting corrosion inhibitor composition and a pitting corrosion suppression method for a carbon steel heat exchanger material that is excellent in properties and in contact with water.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the suppression of pitting corrosion of ferrous metals that come into contact with water in an open circulation cooling water system. Combined with an anticorrosive film-forming component containing a compound, a specific itaconic acid polymer and a compound that releases zinc ions, a dispersant component containing a copolymer of monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid As a result, the formation of the anticorrosion coating on the surface of the iron-based metal is made uniform, and the anticorrosion coating is prevented from being scaled by thickening, and a reliable and stable excellent pitting corrosion suppression effect can be achieved. Furthermore, by optimizing the ratio of each component, a composition blend having excellent stability when stored at a low temperature was found, and the present invention was achieved.

That is, the invention according to claim 1 is a method for producing a pitting corrosion inhibitor composition for suppressing pitting corrosion of a carbon steel heat exchanger material in contact with water,
The pitting corrosion inhibitor composition contains an anticorrosion film-forming component and a dispersant component as active ingredients, and the anticorrosion film-forming component has a maleic acid polymer having no phosphono group and phosphino group, and has a phosphono group and a phosphino group. An itaconic acid-based polymer and a compound that releases zinc ions, the dispersant component contains a copolymer of a monoethylenically unsaturated carboxylic acid and a monoethylenically unsaturated sulfonic acid, The weight ratio of the blending amount of the dispersant component to the blending amount (here, the maleic acid polymer and the itaconic acid polymer are calculated in terms of polymer solids, and the compound that releases zinc ions is calculated in terms of zinc) is 0. A method for producing a pitting corrosion inhibitor composition, wherein the pitting corrosion inhibitor composition is 4-0.8.
The method for producing the maleic acid polymer and the itaconic acid polymer comprises producing the itaconic acid polymer with the maleic polymer remaining in the same reaction vessel after the maleic acid polymer is produced. The polymerization initiator addition interval from the end of the first polymerization initiator addition during the production of the maleic acid polymer to the start of the second polymerization initiator addition during the production of the itaconic acid polymer is in the range of 15 to 120 minutes. a method of manufacturing a two polymers mixtures are directly
Under stirring, the polymer mixture as the anticorrosive film forming component, the compound that releases zinc ions, and the copolymer of the monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid as the dispersant component in water. It is a manufacturing method of the pitting corrosion inhibitor composition manufactured by adding and dissolving .

The invention according to claim 2 is directed to a maleic acid-based polymer having no phosphono group and phosphino group, an itaconic acid-based polymer having no phosphono group and phosphino group, and zinc ions in the circulating water of an open circulation type cooling water system. Addition amount of anticorrosive film-forming component containing a compound that releases a compound (wherein maleic polymer and itaconic acid polymer are calculated in terms of polymer solids, and compounds that release zinc ions are calculated in terms of zinc And the anti-corrosion film forming component and the dispersion so that the weight ratio of the added amount of the dispersant component containing the copolymer of the monoethylenically unsaturated carboxylic acid and the monoethylenically unsaturated sulfonic acid is 0.4 to 0.8. A pitting corrosion suppression method for suppressing pitting corrosion of a carbon steel heat exchanger material in contact with water by adding an agent component to an open circulation type cooling water system,
The method for producing the maleic acid polymer and the itaconic acid polymer is the production of an itaconic acid polymer with the maleic polymer still contained in the same reaction vessel after the maleic acid polymer is produced. To produce a mixture of two types of polymers directly or to produce an itaconic acid polymer, and then to produce a maleic acid polymer with the itaconic acid polymer still contained in the same reaction vessel. Directly producing a mixture of two polymers,
It is a pitting corrosion suppression method characterized in that the zinc concentration in the circulating water of the open circulation type cooling water system is in the range of 0.5 to 2 mg / L in terms of Zn.

The invention according to claim 3 includes the anticorrosion film-forming component and the dispersant component as active ingredients, and the compounding amount of the anticorrosion film-forming component (wherein the maleic acid polymer and the itaconic acid polymer are polymers) Open-circulate a pitting corrosion inhibitor composition in which the weight ratio of the amount of the dispersant component to 0.4 to 0.8 is calculated in terms of solid content and the compound that releases zinc ions is calculated in terms of zinc) It adds to a type | formula cooling water system, It is a pitting corrosion suppression method of Claim 2 characterized by the above-mentioned.

  By applying the pitting corrosion inhibitor composition and pitting corrosion suppression method of a carbon steel heat exchanger material in contact with water according to the present invention to an open circulation cooling water system, the process side due to pitting corrosion occurring in the heat exchanger material Failures such as leakage to the cooling water or leakage from the process side are reduced. In an unscheduled shutdown of a plant caused by these leaks, it takes a considerable period of time to heat up and start up each device of the plant after repairing the leaked part, and the heat exchanger reaches a steady state. Therefore, the present invention that contributes to stable operation of the plant has a great resource saving and energy saving effect. Further, the pitting corrosion inhibitor composition and the pitting corrosion suppression method of the present invention can reduce the concentration of zinc compound and phosphorus compound added to the open circulation type cooling water system as compared with the conventional pitting corrosion inhibitor. Can also reduce the effect.

It is a systematic diagram which shows the test apparatus used for the Example.

  The open circulation type cooling water system that is the subject of the present invention is an oil refining factory, chemical factory, thermal power plant, steel mill, pulp and paper manufacturing industry, automobile factory, semiconductor manufacturing industry, etc. Includes cooling water system for air conditioning.

  The type of heat exchanger to which the present invention is applied is not particularly limited. For example, a shell-and-tube multi-tube heat exchanger, a double-tube heat exchanger, a spiral heat exchanger, a plate heat exchanger, a spiral Examples of the heat exchanger include a tube heat exchanger, a spiral plate heat exchanger, a coil heat exchanger, and a jacket heat exchanger.

  In the present invention, the ferrous metal surface of the heat exchanger in contact with water refers to the heat transfer surface of the heat exchanger, the tube plate, the inner surface of the partition, the inner surface of the trunk, the baffle plate, and the water side of the piping surface. In particular, a carbon steel pipe for a heat exchanger is an object of the present invention. The carbon steel pipe for heat exchanger to which the pitting corrosion inhibitor composition and the pitting corrosion suppression method of the present invention can be applied is, for example, STB340, STB410, STB510, etc. of carbon steel pipe for boiler / heat exchanger specified in JIS G3461: 2012. Including cold-finished seamless pipes and hot-finished seamless pipes. The pitting corrosion inhibitor composition and the pitting corrosion suppressing method of the present invention are particularly effective for pitting corrosion suppression of cold-finished seamless steel pipes generally used as carbon steel pipes for heat exchangers.

  Pitting corrosion in the present invention is a local part where corrosion progresses from a defective portion of a metal as defined in JIS Z0103: 1996 “Anti-corrosion prevention terminology” and progresses into a hole (pit shape) toward the inside of the metal. Means corrosion.

  The anticorrosion film forming component in the present invention is a component that forms an anticorrosion film on the metal surface of an iron-based metal that comes into contact with water. In the present invention, a maleic acid polymer, an itaconic acid polymer, and zinc ions are released. Further, phosphorus compounds such as phosphoric acid, polymerized phosphoric acid, organic phosphonic acid, phosphonocarboxylic acid, phosphinopolycarboxylic acid and water-soluble salts thereof can be mentioned.

  The dispersant component in the present invention is a component that disperses and stabilizes an excessive anticorrosion film forming component in water in order to prevent thickening and scaling of the anticorrosion film formed on the surface of the iron-based metal in contact with water. And in this invention, the copolymer of a monoethylenically unsaturated carboxylic acid and a monoethylenically unsaturated sulfonic acid is mentioned.

  The maleic acid polymer used in the present invention is a polymer containing maleic acid as a main constituent unit, and the polymer contains a maleic acid monomer, or a maleic monomer and other monomers copolymerizable with maleic acid. Produced by polymerization.

  The constituent ratio of maleic acid in the polymer is in the range of 70 to 100% by weight, but preferably in the range of 80 to 100% by weight. The maleic acid polymer of the present invention may be a maleic acid homopolymer or a maleic acid copolymer containing less than 30% by weight of other monomers copolymerizable with maleic acid.

  The itaconic acid polymer used in the present invention is a polymer containing itaconic acid as a main constituent unit, and the polymer contains an itaconic acid monomer, or an itaconic acid monomer and another monomer copolymerizable with itaconic acid. Produced by polymerization.

  The composition ratio of itaconic acid in the polymer is in the range of 70 to 100% by weight, but preferably in the range of 80 to 100% by weight. The itaconic acid polymer of the present invention may be an itaconic acid homopolymer or an itaconic acid copolymer containing less than 30% by weight of other monomers copolymerizable with itaconic acid.

  Examples of the maleic monomers include maleic acid and neutralized salts thereof, maleic anhydride, maleic esters and mixtures thereof. Examples of the neutralized salt include alkali metal salts (specifically, potassium salts, sodium salts, and the like), ammonium salts, and the like, and one or more of these may be used.

  Examples of other monomers copolymerizable with maleic acid include unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; (meth) acrylic acid alkyl esters; (meth) acrylic acid hydroxyl alkyl esters; (Meth) acrylamide; N-alkyl-substituted (meth) acrylamides; Ethylene, propylene, isopropylene, butylene, isobutylene, hexene, 2-ethylhexene, pentene, isopentene, octene, isooctene and other olefins; vinyl alkyl methyl ethers Two or more of these may be used.

  Examples of the itaconic acid monomer include itaconic acid and neutralized salts thereof, itaconic anhydride, itaconic acid esters, and mixtures thereof. The neutralized salt is the same as that exemplified for the maleic monomer. The other monomer copolymerizable with itaconic acid is the same as the other monomer copolymerizable with maleic acid.

  The molecular weight of the maleic acid polymer used in the present invention is usually 300 to 5000, preferably 400 to 3000. When the molecular weight is out of this range, the pitting corrosion suppressing effect and the scale suppressing effect are reduced, which is not preferable. The copolymer may be either a block or a random copolymer.

  The molecular weight of the itaconic acid polymer used in the present invention is usually 300 to 5000, preferably 400 to 3000. When the molecular weight is out of this range, the pitting corrosion suppressing effect and the scale suppressing effect are reduced, which is not preferable. The copolymer may be either a block or a random copolymer.

  In addition, after the production of the maleic acid polymer, which will be described later, the itaconic acid polymer is produced with the maleic acid polymer still contained in the same reaction vessel, or vice versa. In the case where the coalescence is produced in the same reaction vessel, the molecular weights of the maleic acid polymer and the itaconic acid polymer cannot be measured separately, and therefore are measured as the average molecular weight of these mixtures. That is, the weight average molecular weight of the mixture of the maleic acid polymer and the itaconic acid polymer is usually 300 to 3000, preferably 400 to 2000. When the molecular weight is out of this range, the pitting corrosion suppressing effect and the scale suppressing effect are reduced, which is not preferable.

  The maleic acid polymer and itaconic acid polymer used in the present invention can be produced by known methods. That is, a maleic acid monomer or an itaconic acid monomer in an aqueous solution or an organic solvent such as xylene, toluene, isopropyl alcohol, hydrogen peroxide, benzoyl peroxide, persulfate, di-t-butyl peroxide, etc. In the presence of a polymerization initiator, it is produced by adding a polymerization regulator as necessary and heating. The maleic acid polymer is produced by, for example, adding 2 to 10% by weight of maleic anhydride to an aromatic solvent and heating / dissolving it, and 5 to 12% by weight of the polymerization initiator with respect to maleic anhydride. %, And a method of polymerizing at a temperature of 100 to 200 ° C. (Japanese Patent No. 2964154) is disclosed. As a method for producing an itaconic acid polymer, for example, a method of adding an initiator to an itaconic acid aqueous solution neutralized with a water-soluble base and maintaining the temperature at 80 to 120 ° C. (Japanese Patent Laid-Open No. 5-86129) is disclosed. Has been.

  If the solvent used in the production of these polymers is a non-aqueous organic solvent such as toluene or xylene, maleic anhydride or maleic esters instead of maleic acid, itaconic esters or itaconic anhydride instead of itaconic acid A monomer that is soluble in an organic solvent such as benzoyl peroxide and di-t-butyl peroxide is used, and a polymerization initiator that is soluble in an organic solvent is used. After producing a polymer containing an anhydride or ester, the organic solvent is removed by decantation or evaporation, and the ester or anhydride is hydrolyzed while heating by adding water to heat the desired water-soluble maleic acid-based polymer. A coalescence or itaconic acid polymer can be obtained. However, since polymerization in a non-aqueous solvent requires an organic solvent removal step and hydrolysis step, not only is the operation complicated, but the heating energy cost and solvent cost used in these steps are large. Not economical. In addition, the effects on the environment and human body when harmful organic solvents are released into the atmosphere, waste water, soil, etc. cannot be ignored. For this reason, in the manufacturing method of the maleic acid type polymer and the itaconic acid type polymer used by this invention, it is preferable to manufacture by the aqueous polymerization method which does not use an organic solvent. In the case of water-based polymerization using mainly water as a solvent, monomers that are soluble in water such as maleic acid, maleic anhydride, itaconic acid, itaconic anhydride are used, and hydrogen peroxide, persulfate, water-soluble azo It is produced using a polymerization initiator that is soluble in water, such as a system catalyst.

  A preferred method for producing the maleic acid polymer and the itaconic acid polymer used in the present invention is a method for continuously producing the maleic acid polymer and the itaconic acid polymer in the same reaction vessel. That is, after the maleic acid polymer is produced, itaconic acid polymer is produced in the same reaction vessel with the maleic acid polymer still contained, and the mixture of the two polymers is directly produced. Well, after producing an itaconic acid polymer, it is possible to produce a maleic acid polymer with the itaconic acid polymer still contained in the same reaction vessel to directly produce a mixture of two kinds of polymers. However, a more preferable production method is that after the maleic acid polymer is produced, the itaconic acid polymer is produced with the maleic acid polymer still contained in the same reaction vessel. It is a method for producing the mixture directly.

  By producing a mixture of maleic acid-based polymer and itaconic acid-based polymer in the same reaction vessel, the amount of steam used for heating can be reduced. Not only can the manpower be reduced, but the production method can improve the monomer reaction rate and improve the pitting corrosion suppression effect.

  A specific example of a preferred method for producing a mixture of a maleic acid polymer and an itaconic acid polymer in the same reaction vessel is obtained by adding maleic acid or maleic anhydride or both, and an alkali metal hydroxide to water. First, a monomer solution of maleic acid prepared by dissolving or dissolving an alkali metal salt of maleic acid in water is heated to a predetermined temperature, and the polymerization initiator solution is added over a predetermined time while maintaining the temperature. A maleic acid polymer solution was prepared by adding a polymerization initiator, and then itaconic acid (or itaconic anhydride) was added to the maleic acid polymer solution and dissolved, and then heated to a predetermined temperature. Mixing the maleic acid polymer and the itaconic acid polymer by adding the polymerization initiator solution for the second time, adding the polymerization initiator solution over a certain period of time while maintaining The solution is a method for preparing.

  Here, the polymerization initiator addition interval from the end of the first polymerization initiator addition at the time of maleic acid polymerization to the start of the second polymerization initiator addition at the time of itaconic acid polymerization was produced according to the monomer reaction rate and the production method. It affects the pitting corrosion inhibitory effect of the composition blended with the polymer mixture. When the polymerization initiator addition interval is in the range of 20 to 100 minutes, it shows a high monomer reaction rate and an excellent pitting corrosion inhibitory effect. The effect of suppressing pitting corrosion when the addition interval is outside this range is reduced. The reason for this is not necessarily clear, but when the addition interval of the polymerization initiator is less than 20 minutes, itaconic acid monomer is further polymerized to the residual radicals of the maleic acid polymer, which is not preferable in terms of performance, and is a block copolymer of itaconic acid and maleic acid. May be generated. Since the residual radical of the maleic acid polymer disappears when the polymerization initiator addition interval is 20 to 100 minutes, it is presumed that independent maleic acid polymer and itaconic acid polymer are formed. When the polymerization initiator addition interval exceeds 100 minutes, it is presumed that the monomer reaction rate is lowered because the polymerization initiator activity is lowered, and the advantage of producing in the same reaction vessel is lost. As for the method of adding itaconic acid, it is preferable to add it all at once within the polymerization initiator addition interval from the end of the first polymerization initiator addition to the start of the second polymerization initiator addition.

  In the method for producing a mixture of a maleic acid polymer and an itaconic acid polymer in the same reaction vessel, in addition to maleic acid and itaconic acid, other monomers copolymerizable with the maleic acid and itaconic acid may be included. The amount is preferably less than 30% by weight based on the total amount of maleic acid and itaconic acid, and the timing of addition is not particularly limited, but is usually performed simultaneously with the addition of maleic acid or itaconic acid.

  In the method for producing a mixture of a maleic acid polymer and an itaconic acid polymer in the same reaction vessel, the amount of alkali metal hydroxide such as sodium hydroxide or potassium hydroxide added is maleic acid, itaconic acid and other It is preferable to add at a molar ratio of 0.2 to 2 with respect to the total number of moles of unsaturated carboxylic acid. Here, the alkali metal hydroxide may be added all at once before the start of polymerization, or may be added separately at each polymerization step, but it is preferably a method of adding all at once before the start of polymerization.

  The polymerization initiator used in the method for producing a mixture of maleic acid polymer and itaconic acid polymer in the same reaction vessel may be hydrogen peroxide, persulfate, etc. A persulfate is preferably used in combination, and the polymerization initiator is added in an amount of 0.3 to 30% by weight of hydrogen peroxide and 0.1 to 0.1% of persulfate with respect to the total amount of maleic acid and itaconic acid. A range of 5% by weight is preferred. It is further preferred to add a redox catalyst with the polymerization initiator, the preferred redox catalyst is a reducible cation, a metal obtained from iron, zinc, cobalt, molybdenum, chromium, nickel, vanadium and cesium and combinations thereof. More preferred redox catalysts containing ions are ferrous ammonium sulfate, ferrous sulfate, ferrous chloride, cobalt salts (eg, cobalt sulfate hexahydrate), vanadium salts, and combinations thereof. The amount of the redox catalyst is preferably in the range of 0.001 to 0.5% by weight in terms of metal with respect to the total amount of maleic acid and itaconic acid.

  If any of the amount of the alkali metal hydroxide, the amount of the polymerization initiator, or the amount of the redox catalyst is out of the above range, the monomer reaction rate is not sufficiently increased, and a considerable amount of unreacted monomer remains. Therefore, it is difficult to obtain a sufficient pitting corrosion suppression effect and scale suppression effect. Here, the total amount of the above maleic acid and itaconic acid is calculated in terms of maleic acid when maleic anhydride is used, and in terms of itaconic acid when itaconic anhydride is used.

  Regardless of the polymerization method, the molecular weight of the maleic acid polymer or itaconic acid polymer can be adjusted by appropriately changing the amount of polymerization initiator, polymerization temperature, polymerization time, monomer concentration, and the like. Alternatively, the molecular weight can be adjusted by adding a polymerization regulator and changing its concentration. As the polymerization regulator, secondary compounds such as isopropyl alcohol and 2-butyl alcohol, and known compounds such as bisulfite and sulfite can be used.

  The temperature of the polymerization reaction varies depending on the polymerization method, the type of polymerization initiator, the type of solvent, etc., but is usually controlled to a reflux temperature or a temperature lower than the reflux temperature, and is usually in the range of 40 to 200 ° C. The preferred reaction temperature is in the range of 60-140 ° C. If the reaction temperature is too low, a sufficient reaction rate cannot be obtained, and conversely, if the reaction temperature is too high, a decarboxylation reaction of the polymer occurs and the pitting corrosion suppression effect and the scale suppression effect are reduced. Absent.

  In the polymerization process of itaconic acid, foaming is likely to occur if the ratio of itaconic acid is high. Therefore, it is preferable to add an antifoaming agent before charging itaconic acid. The antifoaming agent used here is a polyethylene glycol type nonionic surfactant having a cloud point of 20 ° C. or higher, such as polyoxyethylene polyoxypropylene glycol, higher alcohol ethylene oxide adduct, higher alcohol ethylene oxide / propylene oxide adduct, This is preferable because separation in an aqueous solution does not occur at room temperature.

  The mixture of the two polymers thus produced can be diluted with water as required for handling.

  When maleic acid polymer and itaconic acid polymer are separately polymerized and mixed, the monomer reactivity of maleic acid and itaconic acid is low, and a considerable amount of unreacted maleic acid monomer and itaconic acid monomer remains. Therefore, although it is difficult to obtain a sufficient pitting corrosion inhibiting effect and a scale inhibiting effect, in the above production method for producing a mixture of two kinds of polymers, a maleic acid polymer and an itaconic acid polymer, in the same reaction vessel It is presumed that a high monomer reaction rate can be obtained, and as a result, good low temperature stability and an excellent pitting corrosion suppression effect can be obtained. For example, in the homopolymerization of maleic acid in aqueous polymerization, the reaction rate generally does not exceed 90%, but the reaction rate of maleic acid of 90% or more can be obtained by the two-polymer mixed production method using the same container. .

  The content weight ratio of the maleic acid polymer and the itaconic acid polymer in the anticorrosive film forming component of the present invention is in the range of 90:10 to 10:90, preferably in the range of 70:30 to 30:70.

  The compound that releases zinc ions used as the anticorrosive film forming component of the present invention refers to a compound that releases zinc ions in the water of the target water system, and the compound includes inorganic zinc compounds and organic zinc compounds. Examples of the inorganic zinc compound include zinc chloride, zinc sulfate, and zinc nitrate. Examples of the organic zinc compound include zinc acetate and zinc gluconate. The organic zinc compound increases COD and BOD in waste water. Therefore, an inorganic zinc compound is preferable. When zinc nitrate is used as the inorganic zinc compound, the concentration of nitrogen in the waste water is increased and eutrophication is caused. Therefore, zinc chloride and zinc sulfate are preferable. Here, zinc oxide may be dissolved with hydrochloric acid or sulfuric acid instead of zinc chloride or zinc sulfate.

  In the pitting corrosion inhibitor composition of the present invention, when an azole compound is further blended as a copper anticorrosive agent, since zinc chloride is poorly compatible with the azole compound, the content of the azole compound in the composition is 0.2. In the case of exceeding%, it is preferable to use zinc sulfate or a mixture of zinc oxide and sulfuric acid instead of zinc chloride.

  Of the phosphoric acid, polymerized phosphoric acid, organic phosphonic acid, phosphonocarboxylic acid, phosphinopolycarboxylic acid and their water-soluble salts selected from the phosphoric acid, polymerized phosphoric acid, organic phosphonic acid, and water-soluble salts thereof used as the anticorrosive film forming component of the present invention Examples include inorganic phosphoric acid, orthophosphoric acid and water-soluble salts thereof, and polymerized phosphoric acid includes pyrophosphoric acid, metaphosphoric acid, hexametaphosphoric acid and water-soluble salts thereof. Examples of the water-soluble salt include sodium salt, potassium salt, ammonium salt and the like.

  The organic phosphonic acid is an organic compound having one or more phosphono groups in the molecule, specifically, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylene. Examples include phosphonic acid, diethylenetriaminepentamethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, and the like, preferably 1-hydroxyethylidene-1,1-diphosphonic acid (abbreviation: HEDP).

  The phosphonocarboxylic acid is an organic compound having one or more phosphono groups and one or more carboxyl groups in the molecule. Specifically, 2-phosphonobutane-1,2,4-tricarboxylic acid, hydroxyphosphonic acid is used. Examples include acetic acid, phosphonopolymaleic acid, phosphonic succinic acid, and the like, preferably 2-phosphonobutane-1,2,4-tricarboxylic acid (abbreviation: PBTC) and phosphonopolymaleic acid. Here, phosphonocarboxylic acid is commercially available from Rhodia under the trade name BRICORRR288 and from BWA under the trade name BELCOR585. The phosphonocarboxylic acid can be produced, for example, by heating phosphorous acid and monoethylenically unsaturated carboxylic acid in a neutral to alkaline aqueous solvent in the presence of a free radical initiator (for example, special (See Kaihei 4-334392). The phosphonocarboxylic acid can be obtained by reacting a reaction product of hypophosphorous acid with a carbonyl compound or an imine compound with an unsaturated carboxylic acid in the presence of a reaction initiator (see Japanese Patent No. 3284318). ).

  The phosphinopolycarboxylic acid is a compound having one or more phosphino groups and two or more carboxyl groups in the molecule. Specifically, it is a bis-- obtained by reacting acrylic acid and hypophosphorous acid. Poly (2-carboxyethyl) phosphinic acid, bis-poly (1,2-dicarboxyethyl) phosphinic acid obtained by reacting maleic acid with hypophosphorous acid, reacting maleic acid with acrylic acid and hypophosphorous acid Bis-poly [2-carboxy- (2-carboxymethyl) obtained by reacting poly (2-carboxyethyl) (1,2-dicarboxyethyl) phosphinic acid, itaconic acid and hypophosphorous acid Ethyl] phosphinic acid, acrylic acid, a reaction product of 2-acrylamido-2-methylpropanesulfonic acid and hypophosphorous acid, etc., preferably acrylic acid The reaction product of maleic acid and hypophosphorous acid is the reaction product of itaconic acid and maleic acid and hypophosphorous acid. The production of phosphinopolycarboxylic acid is usually carried out by heating hypophosphorous acid and monoethylenically unsaturated carboxylic acid in the presence of a free radical initiator in an aqueous solvent. No. 29316, Japanese Patent Publication No. 5-57992 and Japanese Patent Publication No. 6-47113. Further, phosphinopolycarboxylic acids are commercially available from Bio Labs under trade names such as BELCLENE500, BELPERSE164, and BELCLENE400.

  The content ratio of each component in the anticorrosive film forming component of the present invention is 25 to 85% by weight as the total amount of the maleic acid polymer and the itaconic acid polymer, and the compound that releases zinc ions is 15 to 35% in terms of zinc. %, Phosphorus compound is 0 to 45 wt%.

  The copolymer of monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid used as the dispersant component of the present invention is a copolymer of monoethylenically unsaturated sulfonic acid and monoethylenically unsaturated carboxylic acid, and Copolymers of monoethylenically unsaturated sulfonic acids, monoethylenically unsaturated carboxylic acids and other copolymerizable monoethylenically unsaturated monomers are included. Monoethylenically unsaturated sulfonic acids such as 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, conjugated diene sulfonated products such as butadiene sulfonic acid and isoprene sulfonic acid, styrene sulfone One or more of acid, sulfoalkyl (meth) acrylate ester, sulfoalkyl (meth) allyl ether, sulfopheno (meth) allyl ether, (meth) allylsulfonic acid, and the like are used. As the monoethylenically unsaturated carboxylic acid, one or more of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride and the like are used. Other copolymerizable monoethylenically unsaturated monomers include (meth) acrylic acid esters (meth) acrylic acid alkyl esters, (meth) acrylic acid hydroxyl alkyl esters; (meth) acrylamides (meth) ) Acrylamide, N-alkyl substituted (meth) acrylamide; olefins having 2 to 8 carbon atoms such as ethylene, propylene, isopropylene, butylene, isobutylene, hexene, 2-ethylhexene, pentene, isopentene, octene, isooctene, etc .; vinyl alkyl ether Vinyl methyl ether, vinyl ethyl ether; maleic acid alkyl ester and the like, and one or more of them are used. Among these, preferred specific compounds include a copolymer of 2-acrylamido-2-methylpropanesulfonic acid (abbreviation: AMPS) and (meth) acrylic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid and ( Examples include a copolymer of (meth) acrylic acid, and a copolymer of conjugated diene sulfonated product and (meth) acrylic acid.

  The molecular weight of the copolymer of monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid is usually 1,000 to 100,000, preferably 4,000 to 20,000 as a weight average molecular weight. It is.

  The weight ratio of the blending amount of the dispersant component to the blending amount of the anticorrosion film forming component in the pitting corrosion inhibitor composition of the present invention is 0.4 to 0.8. In this weight ratio, the amount of the anticorrosive film forming component is as follows: the polymer solid content of the maleic acid polymer, the polymer solid content of the itaconic acid polymer, and the zinc equivalent amount of the compound releasing zinc ions, and further the composition When the phosphorus compound is contained in the product, it is calculated as the total weight including the amount of the active ingredient of the phosphorus compound, and the dispersant component is a monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid. The weight ratio is calculated using the polymer solids weight of the polymer.

  When this weight ratio is smaller than 0.4, the formed anticorrosion film is likely to be thickened and scaled, so that the film is likely to be lost and the possibility of reducing the pitting corrosion suppression may be increased. . In addition, when this weight ratio is larger than 0.8, there is a possibility that the anticorrosive film forming component necessary and sufficient for forming the film is not supplied to the surface of the iron-based metal, and the formation of the anticorrosion film may be incomplete. Since it increases, there is a possibility that the possibility that the pitting corrosion suppression effect is reduced is increased.

  The method for producing the pitting corrosion inhibitor composition of the present invention can be produced by adding each component of the anticorrosive film and the dispersant component to water under stirring and dissolving them, and the order of addition of each component is not particularly limited. When the compound that releases ions is zinc sulfate, the pH is adjusted with sulfuric acid so that the pH of the composition is in the range of 1.5 to 2.0. In the case of zinc chloride, the pH of the composition is 0 or less. It is preferable to adjust the pH with hydrochloric acid so as to be in the range of -2.0.

  The pitting corrosion inhibitor composition of the present invention does not inhibit the effects of the present invention other than the anticorrosive film forming component and the dispersant component described above, and also provides the product stability of the pitting corrosion inhibitor composition of the present invention. As long as they are not impaired, a known corrosion inhibitor, scale inhibitor, scale dispersant, microbial disorder inhibitor, antifoaming agent, and the like may be blended. In particular, when copper or a copper alloy is present in a part of the aqueous facility targeted by the pitting corrosion inhibitor composition of the present invention, it is preferable to add an azole compound. Examples of the azole compound include tolyltriazole, benzotriazole, substituted benzotriazole, mercaptobenzothiazole and the like. In addition, when an azole compound cannot be mix | blended with the pitting corrosion inhibitor composition of this invention, it is preferable to use an azole compound together separately.

The method for inhibiting pitting corrosion according to the present invention includes a maleic acid polymer having no phosphono group and phosphino group, an itaconic acid polymer having no phosphono group and phosphino group, and zinc in the circulating water of an open circulation cooling water system. Addition amount of anticorrosive film-forming component including ion-releasing compound (wherein maleic acid polymer and itaconic acid polymer are calculated in terms of polymer solids, and compounds releasing zinc ions are calculated in terms of zinc) to) monoethylenically unsaturated carboxylic acids and monoethylenically unsaturated sulfonic corrosion protective coating forming component so that the weight ratio of the addition amount is 0.4 to 0.8 of the dispersant component comprising a copolymer of acid to A pitting corrosion suppression method for suppressing pitting corrosion of a carbon steel heat exchanger material in contact with water by adding a dispersant component to an open circulation cooling water system,
The method for producing the maleic acid polymer and the itaconic acid polymer is the production of an itaconic acid polymer with the maleic polymer still contained in the same reaction vessel after the maleic acid polymer is produced. To produce a mixture of two types of polymers directly or to produce an itaconic acid polymer, and then to produce a maleic acid polymer with the itaconic acid polymer still contained in the same reaction vessel. Directly producing a mixture of two polymers,
Is pitting suppression method of the addition concentration of zinc in the circulation water of the open circulating cooling water system, wherein the range der Rukoto of 0.5 to 2 mg / L of Zn terms

  In the method for inhibiting pitting corrosion of the present invention, the method for adding the anticorrosive film forming component and the dispersant component to the open circulation type cooling water system includes the method for adding the pitting corrosion inhibitor composition of the present invention, and the formation of the anticorrosive film. A method of adding the component and the dispersant component separately, and further adding each component contained in the anticorrosive film forming component and the dispersant component in an appropriate combination, for example, a maleic acid polymer and an itaconic acid polymer Two types of compositions are added: a combined composition and a phosphorus compound, a compound that releases zinc ions, and a composition that combines a copolymer of a monoethylenically unsaturated carboxylic acid and a monoethylenically unsaturated sulfonic acid. There is a way. The effect of the present invention can be obtained by any addition method. In particular, when the pitting corrosion inhibitor composition of the present invention is used, only one addition device is required, and the anticorrosive film forming component in the composition is used. When the composition is added to the circulating water of the open circulation type cooling water system, the dispersing agent with respect to the added amount of the anticorrosive film forming component in the circulating water is 0.4 to 0.8. The weight ratio of the component addition amounts is preferably 0.4 to 0.8. In other addition methods, a plurality of addition devices are required, and in order to carry out the pitting corrosion suppression method of the present invention, it is necessary to adjust the addition ratio of each addition device. Therefore, unless there is a special reason, the pores of the present invention. An addition method using a food inhibitor composition is recommended.

  In the pitting corrosion suppression method of the present invention, the anticorrosion film forming component and the dispersant component are preferably added continuously by a chemical injection pump to the target open circulation cooling water system, and intermittent if the required chemical concentration can be maintained. Addition can also be selected.

In the pitting corrosion suppression method of the present invention, the zinc addition concentration in the circulating water of the target open circulation type cooling water system is preferably 2 mg / L or less in terms of Zn based on the drainage standard, and more preferably 0. It is in the range of 5 to 2.0 mg / L. When the calcium hardness in the circulating water is less than 100 mg CaCO ₃ / L, the concentration of the phosphorus compound added is in the range of 1 to 3 mg / L in terms of PO ₄ , and the calcium hardness in the circulating water exceeds 100 mg CaCO ₃ / L and is 300 mg CaCO _3. When less than / L, the addition concentration of the phosphorus compound is in the range of 0 to ₃ mg / L in terms of PO ₄ , and when the calcium hardness in the circulating water exceeds 300 mg CaCO ₃ / L, the addition concentration of the phosphorus compound is in terms of PO ₄ The range is 0 to 2 mg / L.

  In the method for inhibiting pitting corrosion of the present invention, the anticorrosive film forming component and the dispersant component of the present invention are added in the case where each component is added separately even when the pitting corrosion inhibitor composition of the present invention is added. Even so, there is no particular limitation as long as the added chemicals are quickly stirred at a uniform concentration and there is no particular limitation, and an appropriate part of the target water system can be selected.

  Microbial damage as well as corrosion and scale are major obstacles in water systems. It is preferable to add a microbial disorder inhibitor to the pitting corrosion inhibitor composition of the present invention or to use it together when it cannot be added. Examples of microbial disorder inhibitors include sodium hypochlorite, calcium hypochlorite, liquefied chlorine, bromine chloride, reaction products of hypochlorite and bromide, chloroisocyanuric acids, chlorodimethylhydantoic acids, bromodimethylhydantoic acids , Compounds such as chlorobromodimethylhydantoic acid, which dissolve in water to produce hypochlorous acid and / or hypobromite; hydrazine; 2-methylisothiazolin-3-one, 2-methyl-4-chloroisothiazoline- 3-one, 2-methyl-5-chloroisothiazolin-3-one, 2-methyl-4,5-dichloroisothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octyl-4 -Isothiazoline-3-one, 4,5-dichloro-2-n-octyl-3 (2H) isothiazoline, etc. An azoline compound; an organic bromide compound such as 2,2-dibromo-2-nitroethanol, 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-3-nitrilopropionamide; a methylenebisthiocyanate; Bis- (1,4-dibromoacetoxy) -2-butene, benzyl bromacetate, sodium bromide, α-bromocinnamaldehyde, sodium 2-pyridinethiol-1-oxide, bis (2-pyridinethiol-1-oxide) ) Zinc, 2- (4-thiazolyl) benzimidazole, hexahydro-1,3,5-tris- (2-hydroxyethyl) -S-triazine, bis (trichloromethyl) sulfone, dithiocarbamate, 3,5-dimethyltetrahydro -1,3,5,2H-thiadiazin-2-thione , Bromoacetic acid ethylthiophenyl ester, α-chlorobenzoaldoxime acetate, 2,4,5,6-tetrachloroisophthalonitrile, 1,2-dibromo-2,4-dicyanobutane, 3-iodo-2-propenyl Examples include butyl carbamate, salicylic acid, sodium salicylate, paraoxybenzoic acid ester and p-chloro-m-xylenol.

In the pitting corrosion inhibitor composition and the pitting corrosion suppression method of the present invention, the microbial disorder inhibitor preferably mixed or used in combination with the pitting corrosion inhibitor composition is hypochlorous acid and / or hypobromite. Although it is a compound to be produced, its addition amount is usually 0.05 to ₂ mg / L (in terms of Cl ₂ ) as the free halogen concentration (total of free chlorine and free bromine) in the circulating water of the target open circulation cooling water system. is there.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example. In addition, various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

(Test equipment)
The test apparatus and test method used for evaluating the pitting corrosion inhibitory effect of the pitting corrosion inhibitor composition and the pitting corrosion suppression method of the present invention is to heat a carbon steel pipe STB340SC (JIS G3461: 2012) for boiler / heat exchanger. Except that it can be installed in the exchanger, it conforms to the on-site test method of JIS G0593-2002 “Testing method for corrosion and scale prevention of water treatment agent”. An outline of the test apparatus is shown in FIG.
HE-1, HE-4, HE-5, and HE-6 of the heat exchanger 7 are double pipe heat exchangers conforming to JIS G0593-2002, and the outer diameter of the inner pipe is 12.7 mm. A heat transfer tube made of 510 mm stainless steel tube SUS304 (JIS G3459) was installed, a cartridge heater was inserted into the tube and heated, and cooling water was passed outside the tube.
In addition, HE-2 and HE-3 are installed with a cold-finished seamless carbon steel tube STB340SC (JIS G3461) having an outer diameter of 19.0 mm and a length of 600 mm as test heat transfer tubes. Cooling water was passed through the tube, and the outside of the tube was heated by an electric heater block.

The water capacity of the entire system including the water tank 2 and the piping was 62 L, and the water temperature of the water tank 2 was controlled by the water temperature control device 9 so as to be 35 ° C. Water was passed through the circulation pump 3 while being controlled by the flow rate adjusting valve 5 so that the flow rate was 210 L / h corresponding to a linear flow rate of 0.3 m / s in the test heat transfer tube evaluation unit, and the heat flux of the heat exchanger 7 was 40. It was set to -70 kW / m < ² >. The cooling tower 1 used was an induced draft counterflow contact type having a cooling capacity of 1.8 cooling tons. The temperature difference between the circulating water at the inlet and outlet of the cooling tower was 15 ° C. The electrical conductivity of the circulating water is continuously measured by the electrical conductivity measuring cell 4 so that the electrical conductivity corresponding to a predetermined concentration is obtained from the electrical conductivity input signal using the electrical conductivity control device 11. The blowdown pump 10 was controlled.

(Production Example 1) Production example of maleic acid polymer and itaconic acid polymer in the same reaction vessel 18.3 wt. Of maleic anhydride in a 500 mL four-necked flask equipped with a glass reflux tube, a nitrogen vent tube, a dropping funnel and a stirrer Parts (21.6 parts by weight in terms of maleic acid), 0.012 parts by weight of ferrous sulfate heptahydrate and 31.0 parts by weight of water were added, and 11.9 parts by weight of a 48% aqueous potassium hydroxide solution was added thereto. It was. While this liquid was heated to 90 ° C. and the liquid temperature was maintained at 90 to 95 ° C., 7.3 parts by weight of 35% hydrogen peroxide and 0.25 parts by weight of sodium persulfate were dissolved in 1.0 part by weight of water. The first polymerization initiator solution was added dropwise over 50 minutes. After completion of the dropwise addition, 18.4 parts by weight of itaconic acid and 0.012 parts by weight of ferrous sulfate heptahydrate were added to the reaction solution all at once. Since the temperature decreased due to the addition of itaconic acid, the reaction solution was reheated to 90 ° C. to maintain the solution temperature at 90 to 95 ° C., and 35% hydrogen peroxide 6 minutes after the completion of the first polymerization initiator solution addition. A second polymerization initiator solution in which 11.0 parts by weight and 0.4 parts by weight of sodium persulfate were dissolved in 1.5 parts by weight of water was added dropwise over 50 minutes. After completion of the second addition of the polymerization initiator solution, add 0.012 part by weight of ferrous sulfate heptahydrate, further heat at 90 ° C. for 2 hours, and then add water to make a total of 100 parts by weight. As a result, an aqueous solution containing 21.6% by weight of a maleic acid polymer having a weight average molecular weight of 1100 and 18.4% by weight of an itaconic acid polymer was obtained. In addition, nitrogen was continuously bubbled with stirring during the entire reaction process. As a result of measuring the residual monomer in the reaction solution by high performance liquid chromatography, the reaction rate of maleic acid was 85% and the reaction rate of itaconic acid was 98%.

(Production Example 2)
15. In the same manner as in Production Example 1, except that the second polymerization initiator solution was added 15 minutes after the completion of the first polymerization initiator solution addition, 21.6 wt% maleic acid polymer and itaconic acid polymer 18. An aqueous solution containing 4% by weight was prepared. The reaction rate of maleic acid was 90%, and the reaction rate of itaconic acid was 98%.

(Production Example 3)
In the same manner as in Production Example 1, except that the second polymerization initiator solution addition was performed 50 minutes after the completion of the first polymerization initiator solution addition, 21.6 wt% maleic acid polymer and itaconic acid polymer 18. An aqueous solution containing 4% by weight was obtained. The reaction rate of maleic acid was 95%, and the reaction rate of itaconic acid was 99%.

(Production Example 4)
In the same manner as in Production Example 1, except that the second polymerization initiator solution addition was performed 70 minutes after the completion of the first polymerization initiator solution addition, 21.6 wt% maleic acid polymer and itaconic acid polymer 18. An aqueous solution containing 4% by weight was obtained. The reaction rate of maleic acid was 95%, and the reaction rate of itaconic acid was 98%.

(Production Example 5)
In the same manner as in Production Example 1, except that the second polymerization initiator solution was added 120 minutes after the completion of the first polymerization initiator solution addition, 21.6 wt% maleic acid polymer and itaconic acid polymer 18. An aqueous solution containing 4% by weight was obtained. The reaction rate of maleic acid was 90%, and the reaction rate of itaconic acid was 94%.

(Production Example 6)
In the same manner as in Production Example 1, except that the second polymerization initiator solution addition was performed 22 hours after the completion of the first polymerization initiator solution addition, 21.6 wt% maleic acid polymer and itaconic acid polymer 18. An aqueous solution containing 4% by weight was obtained. The reaction rate of maleic acid was 84%, and the reaction rate of itaconic acid was 88%.

(Production Example 7)
To the same four-necked flask as in Production Example 1, 18.4 parts by weight of itaconic acid, 0.012 parts by weight of ferrous sulfate heptahydrate and 22 parts by weight of water were added. 9 parts by weight were added. While continuously ventilating nitrogen, this liquid was heated to 90 ° C. and the liquid temperature was maintained at 90 to 95 ° C., while 9.2 parts by weight of 35% hydrogen peroxide and 0.32 parts by weight of sodium persulfate were added to water. The first polymerization initiator solution dissolved in 1.0 part by weight was added dropwise over 50 minutes. After completion of the dropwise addition, 21.3 parts by weight of maleic anhydride (21.6 parts by weight in terms of maleic acid) and 0.012 parts by weight of ferrous sulfate heptahydrate were added all at once, and the liquid temperature was maintained at 90 to 95 ° C. However, 50 minutes after the completion of the first polymerization initiator solution addition, the second polymerization start in which 9.2 parts by weight of 35% hydrogen peroxide and 0.32 parts by weight of sodium persulfate were dissolved in 1.0 part by weight of water. The agent solution was added dropwise over 50 minutes. After the addition of the second polymerization initiator solution was completed, the mixture was further heated at 90 ° C. for 2 hours, and then water was additionally added so that the total amount was 100 parts by weight. 21.6% by weight of maleic acid polymer and itaconic acid polymer An aqueous solution containing 18.4% by weight was obtained. The reaction rate of maleic acid was 79%, and the reaction rate of itaconic acid was 95%.
Thus, after manufacturing an itaconic acid type polymer, when manufacturing a maleic acid type polymer with the itaconic acid type polymer still contained in the same reaction vessel, the maleic acid type polymer of Production Example 1 is obtained. After the production, the reaction rate of maleic acid was low as compared with the method of producing an itaconic acid polymer with the maleic acid polymer still contained in the same reaction vessel.

(Production Example 8)
5.9 parts by weight of maleic anhydride (7.0 parts by weight in terms of maleic acid) and 33.0 parts by weight of itaconic acid were added, and the second polymerization initiator solution was added 50 minutes after the completion of the first polymerization initiator solution addition. An aqueous solution containing 7.0% by weight of a maleic acid polymer and 33.0% by weight of an itaconic acid polymer was obtained in the same manner as in Production Example 1 except that addition was performed. The reaction rate of maleic acid was 95%, and the reaction rate of itaconic acid was 99%.

(Production Example 9)
Maleic anhydride (11.4 parts by weight (maleic acid equivalent: 13.5 parts by weight)) and itaconic acid (26.5 parts by weight) were added, and the second polymerization initiator solution was added 50 minutes after the completion of the first polymerization initiator solution addition. An aqueous solution containing 13.5% by weight of maleic acid polymer and 26.5% by weight of itaconic acid polymer was obtained in the same manner as in Production Example 1 except that addition was performed. The reaction rate of maleic acid was 95%, and the reaction rate of itaconic acid was 99%.

(Production Example 10)
22.4 parts by weight of maleic anhydride (26.5 parts by weight in terms of maleic acid) and 13.5 parts by weight of itaconic acid were added, and the second polymerization initiator solution was added 50 minutes after the completion of the first polymerization initiator solution addition. An aqueous solution containing 26.5% by weight of maleic acid polymer and 13.5% by weight of itaconic acid polymer was obtained in the same manner as in Production Example 1 except that the addition was performed. The reaction rate of maleic acid was 92%, and the reaction rate of itaconic acid was 98%.

(Production Example 11)
27.9 parts by weight of maleic anhydride (33.0 parts by weight in terms of maleic acid) and 7.0 parts by weight of itaconic acid were added, and the second polymerization initiator solution was added 50 minutes after the completion of the first addition of the polymerization initiator solution. An aqueous solution of 33.0% by weight of maleic acid polymer and 7.0% by weight of itaconic acid polymer was obtained in the same manner as in Production Example 1 except that addition was performed. The reaction rate of maleic acid was 90%, and the reaction rate of itaconic acid was 98%.

Production Example 12 Production Example of Maleic Acid and Itaconic Acid Copolymer In the same four-necked flask as in Production Example 1, maleic anhydride 18.3 parts by weight (maleic acid equivalent 21.6 parts by weight) and itaconic acid 18. 4 parts by weight, 0.022 parts by weight of ferrous sulfate heptahydrate and 31.0 parts by weight of water were added, and 11.9 parts by weight of a 48% aqueous potassium hydroxide solution was added thereto. The solution was heated to 95 ° C. while continuously ventilating nitrogen, and then 18.3 parts by weight of 35% hydrogen peroxide and 0.65 parts by weight of sodium persulfate were added to water 2. A polymerization initiator solution dissolved in 5 parts by weight was added dropwise over 100 minutes, followed by further heating at 95 ° C. for 2 hours. The reaction rate of maleic acid was 62%, and the reaction rate of itaconic acid was 98%.

(Production Example 13) Production Example of Maleic Acid Polymer by Aqueous Polymerization Method In the same four-necked flask as in Production Example 1, maleic anhydride 40 parts by weight (0.40 mol), ferrous sulfate heptahydrate 0.02 Part by weight and 40 parts by weight of water were added, and 11.9 parts by weight (0.10 mol) of a 48% aqueous potassium hydroxide solution was added thereto. The solution was heated to 95 ° C. while continuously bubbling nitrogen, and then 18.3 parts by weight of 35% hydrogen peroxide and 0.65 parts by weight of sodium persulfate were added to water 2 while maintaining the solution temperature at 95 ° C. A polymerization initiator solution dissolved in 5 parts by weight was added dropwise over 120 minutes. After completion of the dropping, 0.02 part by weight of ferrous sulfate heptahydrate was added all at once, and further heated at 95 ° C. for 2 hours to obtain an aqueous solution of a maleic acid polymer having a weight average molecular weight of 1000. The reaction rate of maleic acid was 88%.
Furthermore, although the maleic acid polymer was produced by changing the reaction temperature, the amount of the polymerization initiator and the reaction time, the reaction rate of maleic acid did not exceed 90%.

(Production Example 14) Production Example of Itaconic Acid Polymer by Aqueous Polymerization Method In the same four-necked flask as in Production Example 1, itaconic acid 40 parts by weight (0.3 mol), ferrous sulfate heptahydrate 0.02 weight And 40 parts by weight of water were added, and 11.9 parts by weight (0.1 mol) of a 48% aqueous potassium hydroxide solution was added thereto. The liquid was heated to 90 ° C. while continuously ventilating nitrogen, and then 20 parts by weight of 35% hydrogen peroxide and 0.3 parts by weight of sodium persulfate were added to 1.2 parts by weight of water while maintaining the liquid temperature at 95 ° C. The polymerization initiator solution dissolved in the part was added dropwise over 120 minutes. After completion of dropping, 0.02 part by weight of ferrous sulfate heptahydrate was added all at once, and further heated at 95 ° C. for 2 hours to obtain an aqueous solution of an itaconic acid polymer having a weight average molecular weight of 1200. The reaction rate of itaconic acid was 99%.

1. Examples 2-5 , 8-11 , Reference Examples 1, 6, 7, 12 , 13 and Comparative Examples 1-4
(Low temperature stability test of pitting corrosion inhibitor composition)
The pitting corrosion inhibitor composition No. After freezing the glass bottles containing a1 to a16 in a freezer set at −20 ° C. for one day, transfer these glass bottles to a thermostat set at 0 ° C., and set them to −5 ° C. Left in the incubator for 1 week. This operation was repeated three times to examine the presence / absence of precipitation / separation and crystal precipitation. The results are shown in Table 1.

(Evaluation test of pitting corrosion suppression effect)
Using the test apparatus, the pitting corrosion inhibitor composition No. 1 having the composition shown in Table 1 was used. The evaluation of the pitting corrosion inhibitory effect of a1 to a16 was tested. Yokkaichi city water was used as makeup water 12 for the test apparatus shown in FIG. The water quality of Yokkaichi city water at this time is pH: 7, electrical conductivity: 10 mS / m, Ca hardness: 35 mg-CaCO ₃ / L, Mg hardness: 7 mg-CaCO ₃ / L, M alkalinity: 35 mg-CaCO ₃ / L, chloride ion: 7 mg / L, sulfate ion: 7 mg / L, silica: 11 mg / L.
As an initial treatment, Yokkaichi City water was sprinkled in the water tank 2, 200 mg / L of the composition to be tested and 12.5 mg / L of sodium hexametaphosphate (average degree of condensation 40) were added and circulated at room temperature for 48 hours. After adding 40 mg / L of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid [copolymerization ratio (weight) 60:40, average molecular weight 10,000], the heat load is started and the heat load is started. Since the specified concentration reached after 3 days, the blowdown was started immediately and the conductivity was automatically adjusted so that the concentration was about 4.3 times and the Ca hardness in the circulating water was 150 mg-CaCO ₃ / L. Controlled. Simultaneously with the start of blowdown, 45 mg / L of the composition to be tested with respect to the blowdown amount was added by the water treatment agent injector 13. The addition concentration of zinc in the circulating water was 1.7 mg / L in terms of Zn, and the addition concentration of the phosphorus compound was 1.0 mg / L in terms of PO ₄ . The test period was one month. After completion of the test, the heat transfer tubes made of ST-2340SC made of HE-2 and HE-3 were removed and vertically divided, and the pitting corrosion depth in the tube was measured with a micro gauge to obtain the maximum value of the pitting corrosion depth. As a composition for a test of Examples 2-5 , 8-11 , Reference Examples 1, 6, 7, 12 , 13 and Comparative Examples 1-3, pitting corrosion inhibitor composition No. a1 to a16 were used. Comparative Example 4 is an example in which no composition to be tested was added. The results are shown in Table 1.

The definitions of terms, symbols and abbreviations in Table 1 are as follows.
(1) Acrylic acid-AMPS copolymer: A copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid [copolymerization ratio (weight) 60:40, average molecular weight 10,000]
(2) Component ratio: The weight ratio of the dispersant component and the anticorrosive film forming component blended in each composition, the (dispersant component / anticorrosive film forming component) ratio (3) MAL: maleic acid polymer . However, composition No. a14 represents maleic acid.
(4) ITA: Itaconic acid polymer. However, composition No. a14 represents itaconic acid.
(5) MAL: ITA weight ratio: Indicates the weight ratio of maleic acid polymer to itaconic acid polymer contained in each composition. However, Composition No. In a14, the weight ratio of maleic acid to itaconic acid in the copolymer of maleic acid and itaconic acid is shown.
(6) Mixing method:
(6-1) Same container: A maleic acid polymer and an itaconic acid polymer were continuously produced in the same reaction container to obtain a mixture of two polymers.
(6-2) Separate mixing: Maleic acid polymer and itaconic acid polymer produced separately were mixed to obtain a mixture of two kinds of polymers.
(6-3) (MAL + ITA copolymer); copolymer of maleic acid and itaconic acid (7) polymerization sequence:
(7-1) MAL⇒ITA; In the same reaction vessel, after the maleic acid polymer was produced, an itaconic acid polymer was continuously produced.
(7-2) ITA =>MAL; In the same reaction vessel, a maleic acid polymer was continuously produced after the itaconic acid polymer was produced.
(8) Polymerization initiator addition interval: Time from the end of the first polymerization initiator addition to the start of the second polymerization initiator addition (9) Polymaleic acid A: BELCLENE200LA (trade name, manufactured by BWA)

Examples 2 to 5 , 8 to 11 and Reference Examples 1, 6, and 7 are examples in which the mixing method is the same container, and Reference Examples 12 and 13 are examples in which the mixing method is separate mixing. Examples 2 to 5 and Reference Examples 1 and 6 are examples in which the polymerization initiator interval was changed, Reference Example 7 was an example in which the polymerization order was changed from ITA to MAL, and Examples 8 to 11 were MAL: ITA. This is an example in which the weight ratio is changed.
Comparative Example 1 is an example in which a copolymer of maleic acid and itaconic acid was used in place of the mixture of maleic acid polymer and itaconic acid polymer. The maleic acid polymer of the anticorrosive film forming component of the present invention has a maleic acid composition ratio in the range of 70 to 100% by weight, and the itaconic acid polymer in the composition ratio of itaconic acid in the range of 70 to 100% by weight. In the copolymer of maleic acid and itaconic acid used in Comparative Example 1, the constituent ratio of maleic acid and itaconic acid is 56% by weight and 46% by weight. It does not correspond to either a polymer or itaconic acid polymer, and Comparative Example 1 is not an example of the present invention.
Further, the anticorrosive film forming component of the present invention includes both a maleic acid polymer and an itaconic acid polymer, but Comparative Examples 2 and 3 include only one of a maleic acid polymer or an itaconic acid polymer. It is.

  According to the results of the low temperature stability and pitting corrosion inhibitory effect test of the pitting corrosion inhibitor composition shown in Table 1, the excellent low temperature stability of the pitting corrosion inhibitor composition of the present invention and the pitting corrosion suppression method of the present invention. Excellent anti-pitting effect was revealed.

2. Examples 14-17 and Comparative Examples 5-14
Pitting corrosion inhibitor composition Nos. Shown in Tables 2-4. About b1-b14, the low-temperature stability test of the said pitting corrosion inhibitor composition and the evaluation test of the said pitting corrosion inhibitory effect were done, and the result is shown to Tables 2-4. The addition concentration of zinc in the circulating water in the evaluation test of the pitting corrosion inhibitory effect was 1.6 to 1.8 mg / L in terms of Zn except for Comparative Example 12, and was 5.8 mg / L in terms of Zn in Comparative Example 12. It was. The definitions of terms, symbols, and abbreviations in Table 2 are the same as in Table 1. In addition, HEDP is 1-hydroxyethylidene-1,1-diphosphonic acid, PBTC is 2-phosphonobutane-1,2,4-tricarboxylic acid, and phosphinopolycarboxylic acid is acrylic acid-maleic acid-hypophosphorous acid ( Molar ratio 2: 1: 1) copolymer (average molecular weight 1500), which was produced according to the method described in JP-B-6-47113.

  Examples 14-17 are the examples which changed the component ratio of the pitting corrosion inhibitor composition within the range of 0.4-0.8. Comparative Examples 5-8, 10, and 11 are examples in which the component ratio is outside the range of 0.4 to 0.8. Comparative Example 9 is an example that does not contain a dispersant component, and Comparative Examples 12 to 14 are examples that do not contain a maleic acid-based polymer and an itaconic acid-based polymer that are anticorrosive film forming components.

  According to the results of the low temperature stability and pitting corrosion inhibitory effect test of the pitting corrosion inhibitor composition shown in Tables 2 to 4, the excellent low temperature stability of the pitting corrosion inhibitor composition of the present invention and the pitting corrosion suppression of the present invention. The excellent anti-pitting effect of the method was revealed.

3. Reference Examples 18-29
The pitting corrosion inhibitory effect described above except that the pitting corrosion inhibitor composition and the addition amount shown in Table 5 were used, and the calcium hardness (Ca hardness) in the circulating water was set to 70, 150, 250, and 350 mg-CaCO ₃ / L, respectively. The test was performed using the same test apparatus and test method as in the evaluation test. The addition concentration of zinc in the circulating water in this test was 1.6 to 1.8 mg / L in terms of Zn. The results are shown in Table 5.

The definitions of terms, symbols and abbreviations in Table 5 are as follows.
(1) Composition No. : Same composition No. shown in Tables 1 and 2 The pitting corrosion inhibitor composition was used.
(2) Composition addition amount: addition concentration of pitting corrosion inhibitor composition in circulating water (3) Phosphorus compound addition concentration: addition concentration of phosphorus compound in circulating water (4) Ca hardness: calcium hardness

From the results of Table 5, the relationship between the calcium hardness in the circulating water and the addition concentration of the phosphorus compound is such that when the calcium hardness in the circulation water is less than 100 mg CaCO ₃ / L, the addition concentration of the phosphorus compound is 1 to 3 mg in terms of PO _4. / L in the range of the addition concentration of the phosphorus compound when 300mgCaCO less than ₃ / L calcium hardness of the circulating water exceeds 100MgCaCO ₃ / L is in the range of 0～3Mg / L in PO ₄ terms, the circulating It was revealed that when the calcium hardness in water exceeds 300 mg CaCO ₃ / L , an excellent pitting corrosion inhibitory effect can be obtained when the concentration of addition of the phosphorus compound is in the range of 0 to 2 mg / L in terms of PO ₄ .

  The pitting corrosion inhibitor composition and the pitting corrosion suppression method of the present invention include a cooling water system for various manufacturing industries such as an oil refinery factory, a chemical factory, a thermal power plant, an iron mill, a paper pulp manufacturing industry, an automobile factory, and a semiconductor manufacturing industry. Applicable to cooling water systems for air conditioning.

DESCRIPTION OF SYMBOLS 1 Cooling tower 2 Water tank 3 Circulation pump 4 Electrical conductivity measurement cell 5 Flow rate adjustment valve 6 Flowmeter 7 Heat exchanger 8 Test piece holder 9 Water temperature control device 10 Blow down pump 11 Electrical conductivity control device 12 Supply water 13 Water treatment Agent Injection Device 14 Liquid Level Control Device

Claims (3)

A method for producing a pitting corrosion inhibitor composition for suppressing pitting corrosion of a carbon steel heat exchanger material in contact with water,
The pitting corrosion inhibitor composition contains an anticorrosion film-forming component and a dispersant component as active ingredients, and the anticorrosion film-forming component has a maleic acid polymer having no phosphono group and phosphino group, and has a phosphono group and a phosphino group. An itaconic acid-based polymer and a compound that releases zinc ions, the dispersant component contains a copolymer of a monoethylenically unsaturated carboxylic acid and a monoethylenically unsaturated sulfonic acid, The weight ratio of the blending amount of the dispersant component to the blending amount (here, the maleic acid polymer and the itaconic acid polymer are calculated in terms of polymer solids, and the compound that releases zinc ions is calculated in terms of zinc) is 0. A method for producing a pitting corrosion inhibitor composition, wherein the pitting corrosion inhibitor composition is 4-0.8.
The method for producing the maleic acid polymer and the itaconic acid polymer comprises producing the itaconic acid polymer with the maleic polymer remaining in the same reaction vessel after the maleic acid polymer is produced. The polymerization initiator addition interval from the end of the first polymerization initiator addition during the production of the maleic acid polymer to the start of the second polymerization initiator addition during the production of the itaconic acid polymer is in the range of 15 to 120 minutes. a method of manufacturing a two polymers mixtures are directly
Under stirring, the polymer mixture as the anticorrosive film forming component, the compound that releases zinc ions, and the copolymer of the monoethylenically unsaturated carboxylic acid and monoethylenically unsaturated sulfonic acid as the dispersant component in water. The manufacturing method of the pitting corrosion inhibitor composition manufactured by melt | dissolving in addition . Anti-corrosion coating comprising maleic acid-based polymer having no phosphono group and phosphino group, itaconic acid-based polymer having no phosphono group and phosphino group, and a compound capable of releasing zinc ions in the circulating water of an open circulation cooling water system Monoethylenically unsaturated carboxylic acid with respect to the amount of forming component added (wherein maleic acid polymer and itaconic acid polymer are calculated in terms of polymer solids, and compounds that release zinc ions are calculated in terms of zinc) The anti-corrosion film forming component and the dispersant component are separated from the open circulation cooling water so that the weight ratio of the added amount of the dispersant component containing the copolymer of the acid and the monoethylenically unsaturated sulfonic acid is 0.4 to 0.8. A pitting corrosion suppression method for suppressing pitting corrosion of a carbon steel heat exchanger material that comes into contact with water by adding to the system,
The method for producing the maleic acid polymer and the itaconic acid polymer is the production of an itaconic acid polymer with the maleic polymer still contained in the same reaction vessel after the maleic acid polymer is produced. To produce a mixture of two types of polymers directly or to produce an itaconic acid polymer, and then to produce a maleic acid polymer with the itaconic acid polymer still contained in the same reaction vessel. Directly producing a mixture of two polymers,
The method for inhibiting pitting corrosion, wherein the addition concentration of zinc in the circulating water of the open circulation cooling water system is in the range of 0.5 to 2 mg / L in terms of Zn. The anticorrosive film-forming component and the dispersant component are contained as active ingredients, and the blending amount of the anticorrosive film-forming component (wherein the maleic acid polymer and the itaconic acid polymer are calculated in terms of polymer solids, Add a pitting corrosion inhibitor composition having a weight ratio of the amount of the dispersant component to 0.4 to 0.8 to the open circulation cooling water system. The pitting corrosion suppression method according to claim 2 .

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