JPH10310886A - Anticorrosive for metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively inhibit corrosion on the surface of a metallic material coming in contact with water by using a compd. contg. a water-soluble polymer having N-vinylcarboxylic acid amide units as an anticorrosive for a metal. SOLUTION: This anticorrosive contains a water-soluble polymer having N-vinylcarboxylic acid amide units represented by the formula and at least one selected from among a heavy metallic salt, a phosphorus compd. and an anionic polymer. The water-soluble polymer is poly-N-vinylformamide, poly-N- vinylacetamide, a polymer obtd. by partially hydrolyzing poly-N-vinylformamide or poly-N-vinylacetamide, a polymer having vinylamine units, a polymer obtd. by partially hydrolyzing a copolymer of N-vinylformamide or N-vinylacetamide with another monomer or a polymer having cationic functional groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal corrosion inhibitor. More specifically, the present invention relates to a metal anticorrosive which can effectively suppress corrosion of a metal material surface in contact with water.

[0002]

2. Description of the Related Art Generally, in cooling water systems such as boilers, petroleum refining plants, various industrial plants including the chemical industry, buildings and air conditioning plants for district heating and cooling equipment, metal pipe surfaces such as heat transfer surfaces and water channel wall surfaces. Corrosion and scale may occur on the surface, reducing the efficiency of heat exchange and causing a plugging accident. For this reason, great care is always taken to prevent corrosion and scale formation. In a water system such as an open circulation cooling water system, a steel material such as carbon steel is mainly used for a base material such as a heat exchanger and a pipe. Steel immersed in cooling water is corroded by dissolved oxygen, chloride ions, sulfate ions, and the like in the water, and pitting occurs. Such pitting also occurs in corrosion-resistant materials such as copper, copper alloys and stainless steel. Therefore, conventionally, a metal anticorrosive has been used to suppress such corrosion of a metal material in contact with an aqueous system. In particular, the anticorrosive used in the cooling water system is soluble in water itself, but forms an oxide film or a water-insoluble or hardly soluble film on the metal surface to elute metal ions or reduce dissolved oxygen. By inhibiting the reaction, the corrosion reaction is suppressed.
Although various anticorrosives have been proposed, they have never been satisfactory. For example,
Heavy metal salts such as chromate and zinc salts have been widely used, but chromate salts have excellent anticorrosion effects,
When used at a low concentration, local corrosion is likely to occur and the effect is not stable. Further, zinc salts do not have a sufficient anticorrosion effect. Furthermore, all of them have problems in stability and regulation of drainage and are difficult to handle. Phosphorus compounds such as (poly) phosphate and phosphonic acid also have some anticorrosion effects and are used as anticorrosion agents, but their effects are not sufficient. In recent years, from the viewpoint of preventing eutrophication in closed water areas, the emission of phosphorus has been regulated, and its use may be restricted. As a metal corrosion inhibitor using an anionic organic polymer, JP-A-53-92349 proposes a corrosion inhibitor containing a water-soluble salt of a copolymer of isobutylene and maleic acid. Add a water-soluble polymer that is relatively easy to gel, such as polyacrylic acid, polyitaconic acid, a copolymer of acrylic acid and maleic anhydride, and an anticorrosive, and adjust the pH of the cooling water system to 6.5 or more. Anticorrosion methods have been proposed. However, such anionic organic polymers are subject to the conditions of the target water system such as water temperature, pH, and M alkalinity,
There is a problem in that calcium ions, magnesium ions, and the like dissolved in an aqueous system are adsorbed to carboxyl groups to form salts, and as a result, the polymer is crosslinked and wasted and wasted, and the anticorrosion effect is not stable.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a metal anticorrosive which can effectively suppress corrosion occurring on the surface of a metal material in contact with water.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a metal anticorrosive containing a water-soluble polymer having an N-vinylcarboxylic acid amide unit can be converted into water. The present inventors have found that the present invention is extremely effective in suppressing corrosion generated on the surface of a metal material in contact with, and have completed the present invention based on this finding. That is, the present invention provides (1) a metal anticorrosive comprising a water-soluble polymer having an N-vinylcarboxylic acid amide unit,
(2) It contains (A) a water-soluble polymer having an N-vinylcarboxylic acid amide unit, and (B) at least one compound selected from the group consisting of a heavy metal salt, a phosphorus compound and an anionic polymer. And (3) a water-soluble polymer having an N-vinylcarboxylic acid amide unit is poly-N-vinylformamide, poly-N-vinylacetamide, poly-N-vinylformamide or poly-N- A polymer having a vinylamine unit obtained by partially hydrolyzing vinylacetamide, a copolymer of N-vinylformamide or N-vinylacetamide and another monomer, or a copolymer of N-vinylformamide or N-vinylacetamide and another monomer Partially hydrolyzed more cationic functional groups Cationic functional group and an anionic first (1) is a polymer having a functional group claim or the (2) above, wherein the metal corrosion inhibitor is intended to provide.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The metal anticorrosive of the present invention contains a water-soluble polymer having an N-vinylcarboxylic acid amide unit represented by the general formula [1].

Embedded image The N-vinylcarboxylic acid amide unit represented by the general formula [1] can be introduced into a polymer by homopolymerizing or copolymerizing the N-vinylcarboxylic acid amide represented by the general formula [2]. it can. CH ₂ ＣＨCHNHCOR [2] In the general formulas [1] and [2], R is preferably hydrogen or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group,
Examples thereof include an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. Examples of the N-vinylcarboxylic acid amide unit represented by the general formula [1] include an N-vinylformamide unit, an N-vinylacetamide unit, an N-vinylpropionamide unit, an N-vinylbutylamide unit, and an N-vinylamide unit.
And vinyl valeramide units. When the number of carbon atoms of R in the N-vinylcarboxylic acid amide unit represented by the general formula [1] increases, the hydrophilicity of the N-vinylcarboxylic acid amide unit decreases, but another monomer having high hydrophilicity is copolymerized. By doing so, a water-soluble polymer can be obtained. Among the above N-vinylcarboxylic acid amide units, a polymer having an N-vinylformamide unit and an N-vinylacetamide unit can be particularly preferably used.

The method for producing the N-vinylcarboxylic acid amide represented by the general formula [2] is not particularly limited, and for example, N- (α-hydroxyethyl) carboxylic acid obtained by reacting acetaldehyde with a carboxylic acid amide. Reacting an acid amide with an alcohol to etherify it, and further thermally decomposing the etherified product at a high temperature in the gas phase, or pyrolyzing while evaporating the N-vinylcarboxylic amide formed by heating in the liquid phase. Can be manufactured.
The monomer copolymerizable with N-vinylcarboxylic acid amide used in the present invention can be used without particular limitation as long as the obtained copolymer or the copolymer obtained by hydrolysis has water solubility.
Such monomers include, for example, (meth) acrylamide, (meth) acrylonitrile, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, methyl (meth) acrylate, ethyl (meth) acrylate, styrene , Allyl alcohol, hydroxyethyl
Nonionic monomers such as (meth) acrylate, (meth)
Acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and their alkali metal salts, vinylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, hydroxyallyloxypropanesulfonic acid, isoprenesulfonic acid And anionic monomers such as alkali metal salts thereof, allylamine,
Examples thereof include quaternary ammonium salts or tertiary salts of dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, and cationic monomers such as diallyldimethylammonium chloride.

In the present invention, the method of homopolymerizing N-vinylcarboxylic acid amide or copolymerizing N-vinylcarboxylic acid amide with a monomer copolymerizable with N-vinylcarboxylic acid amide is not particularly limited. The raw material polymer used in the present invention, which is a water-soluble polymer having an N-vinylcarboxylic acid amide unit and a water-soluble polymer having an N-vinylcarboxylic acid amide unit by hydrolysis, is water-soluble or hydrophilic. Therefore, an aqueous polymerization method using water as a medium can be suitably used. In the aqueous polymerization method, an aqueous monomer solution or aqueous dispersion is prepared, the pH is adjusted as necessary, the atmosphere is replaced with an inert gas, and then the mixture is heated to 50 to 100 ° C., and a water-soluble polymerization initiator is added. By doing so, polymerization can be carried out. As the water-soluble polymerization initiator, for example, 2,2′-azobis (2
-Amidinopropane) dihydrochloride, azo compounds such as azobis-N, N'-dimethyleneisobutylamidine dihydrochloride, 4,4'-azobis (4-cyanovaleric acid) -2-sodium, ammonium persulfate, persulfate Persulfates such as sodium and potassium persulfate; peroxides such as hydrogen peroxide and sodium periodate; The polymerization is usually completed in 3 to 6 hours, and is allowed to cool.
An aqueous polymer solution or dispersion can be obtained. The polymerization can be carried out not only in an aqueous medium but also by a solution polymerization, a suspension polymerization, an emulsion polymerization or the like in a general organic solvent.

In the present invention, the water-soluble polymer having an N-vinylcarboxylic acid amide unit is poly-N-vinylformamide, poly-N-vinylacetamide, poly-N-vinylacetamide.
A polymer obtained by partially hydrolyzing N-vinylformamide or poly-N-vinylacetamide and further having a vinylamine unit, N-vinylformamide or N-vinylformamide;
A copolymer of vinylacetamide and another monomer, or a copolymer of N-vinylformamide or a copolymer of N-vinylacetamide and another monomer partially hydrolyzed, further having a cationic functional group or a cationic functional group and an anionic functional group Preferably it is a polymer. In the present invention, the method for partially hydrolyzing the homopolymer of N-vinylcarboxylic acid amide or the copolymer of N-vinylcarboxylic acid amide is not particularly limited.
-Ammonia, primary amine, secondary amine, etc. are added to an aqueous solution or aqueous dispersion of a vinyl carboxylic acid amide copolymer, and then sodium hydroxide is added thereto to hydrolyze under basic conditions, and the N- Some of the vinylcarboxylic acid amide units can be N-vinylamine units. Alternatively, a polymer is hydrolyzed under acidic conditions by adding a mineral acid such as hydrochloric acid to an aqueous solution or aqueous dispersion of a homopolymer of N-vinylcarboxylic amide or a copolymer of N-vinylcarboxylic amide and heating the polymer. The N-vinyl carboxylic acid amide unit therein can be an N-vinyl amine unit. Even when a homopolymer of N-vinylcarboxylic acid amide or a copolymer of a monomer copolymerizable with N-vinylcarboxylic acid amide is water-insoluble, a hydrophilic group is generated by hydrolyzing the polymer to form a water-soluble polymer. Can be used for the metal anticorrosive of the present invention. In the case of a copolymer, a part of the structure of the used monomer unit may be modified. For example, the (meth) acrylate unit becomes an anionic (meth) acrylic acid unit by hydrolysis, and
The nitrile group of the (meth) acrylonitrile unit hydrolyzes to an amide group and a carboxyl group,
In some cases, it further reacts with the primary amino group of the vinylamine unit generated by hydrolysis of the vinylcarboxylic acid amide unit to form an amidine ring. The water-soluble polymer containing these modified units may also be used as the metal anticorrosive of the present invention. Can be used for

[0009] In the present invention, the N-
The proportion of vinyl carboxylic acid amide units is preferably at least 5 mol%, more preferably at least 50 mol%. In the present invention, the molecular weight of the water-soluble polymer having an N-vinylcarboxylic acid amide unit is 2,000.
It is preferably from 1 to 1,000,000. 2,000 molecular weight
If it is less than the above range, a sufficient anticorrosion effect may not be obtained. On the other hand, if the molecular weight exceeds 1,000,000, the viscosity of the liquid at the time of use may be too high to make it difficult to handle. The molecular weight of the polymer can be determined by gel permeation chromatography. The metal anticorrosive of the present invention further comprises at least one compound selected from the group consisting of a heavy metal salt, a phosphorus compound and an anionic polymer, in addition to the water-soluble polymer having an N-vinylcarboxylic acid amide unit. Can be. Examples of the heavy metal salt include a chromate salt and a zinc salt. Examples of the phosphorus compound include (poly) phosphates such as sodium hexametaphosphate and phosphonic acids such as hydroxyethylidene diphosphonic acid. Examples of the anionic polymer include polymaleic acid and polyacrylic acid, and alkali metal salts thereof. The metal anticorrosive of the present invention can further enhance its corrosion inhibitory effect by incorporating these components. The type and content of the compound selected from the group consisting of the heavy metal salt, the phosphorus compound and the anionic polymer to be contained can be appropriately selected according to the water quality of the aqueous system to be added and the use conditions.

The use form of the metal anticorrosive of the present invention is not particularly limited. For example, it can be used as an aqueous solution containing a water-soluble polymer having an N-vinyl carboxylic acid amide unit, or it can be used as an aqueous solution. The water-soluble polymer having an acid amide unit can be dried once to form a powder, which can be used by dissolving it in water before use. The metal anticorrosive of the present invention can be added to an applied system as an aqueous solution adjusted to an arbitrary concentration. Usually, the concentration of the water-soluble polymer in the applied water is 1 to 100.
It is preferable to add it so that it becomes mg / liter. The metal anticorrosive of the present invention can be used in combination with other additives as necessary. Examples of the additive used in combination include a scale inhibitor, a bactericide, and the like. The scale inhibitor, bactericide and the like can be mixed and added to the same solution as the metal anticorrosive of the present invention, or these additives can be separately injected. There are no particular restrictions on the water quality conditions and the operating conditions of the boiler and heat exchanger when the metal anticorrosive of the present invention is applied, and the present invention can be applied to the operating conditions and water quality of ordinary boilers and heat exchangers. it can. The metal anticorrosive of the present invention can suppress metal corrosion in an oxidizing environment, and in particular, can effectively prevent corrosion of a metal material surface in contact with water. Although the detailed mechanism by which the metal anticorrosive of the present invention suppresses corrosion of the metal material surface in contact with water is unknown, the amide group of the N-vinylcarboxylic acid amide unit forms a hydrogen bond with the hydroxide layer on the metal surface. It is considered that a polymer film having anticorrosive properties is formed on the metal surface by being adsorbed.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In addition, in the Example and the comparative example, evaluation of the anticorrosive was performed by the following method. Table 1 shows the drugs used in Examples and Comparative Examples. [Evaluation method of anticorrosion agent] Water containing pure water and salts added to Atsugi-shi water is circulated through an open-circulation cooling water system having a heat exchanger with a heat transfer area of about 0.25 m ² and a water volume of 0.45 m ^3. Water and makeup water were added, a predetermined amount of the anticorrosive was added to the water system, and the system was operated for 30 days while controlling the water quality under the following conditions. The material of the heat exchanger tube is STB with mill scale.
35, an outer diameter of 19 mm, and a basic treatment with sodium hexametaphosphate for 1 day in advance. The circulating water inlet temperature is 30 ° C, the circulating water outlet temperature is 50 ° C, and the circulating water flow rate is 0.5.
m / s. The anticorrosive was evaluated by measuring the maximum pit depth of the heat exchanger tube 30 days later. Water quality: pH = 8.8, electrical conductivity 1,650 μS / cm, M alkalinity 180 mg / liter, calcium hardness 200 mg
/ L, magnesium hardness 130 mg / l, silica 100 mg / l, chloride ion 300 mg / l, sulfate ion 180 mg / l.

[0012]

[Table 1]

Example 1 Poly-N-vinylformamide (molecular weight 80,000,
Drug A) is added to a concentration of 10 mg / liter,
The test was performed. The maximum pit depth was 0.13 mm. Example 2 A test was performed by adding poly-N-vinylacetamide (molecular weight: 3,000, drug B) to a concentration of 10 mg / liter. The maximum pit depth was 0.13 mm. Example 3 A test was carried out by adding a 10 mol% hydrolyzate of poly-N-vinylformamide (molecular weight: 12,000, drug C) to a concentration of 10 mg / liter. The maximum pit depth was 0.14 mm. Example 4 A test was carried out by adding a copolymer of N-vinylformamide and sodium acrylate in a molar ratio of 85:15 (molecular weight: 8,000, drug D) to a concentration of 10 mg / liter. The maximum pit depth was 0.14 mm. Example 5 N-vinylformamide and allylamine molar ratio 90:
The test was performed by adding 10 copolymers (molecular weight 10,000, drug E) to a concentration of 10 mg / l. The maximum pit depth was 0.12 mm. Example 6 A polymer having a molar ratio of 85:15 of N-vinylformamide and sodium acrylate hydrolyzed in an amount of 20 mol% of N-vinylformamide units (molecular weight: 12,12)
000, drug F) was added to give a concentration of 10 mg / l and the test was carried out. The maximum pit depth is 0.13mm
Met. Example 7 Poly-N-vinylformamide (molecular weight 80,000,
The test was carried out by adding drug A) to a concentration of 10 mg / l and zinc chloride (drug G) as zinc at a concentration of 1 mg / l. Maximum pit depth is 0.12m
m. Example 8 Sodium hexametaphosphate (drug H) was used as a total phosphoric acid at a concentration of 3 mg so that poly-N-vinylacetamide (molecular weight: 3,000, drug B) had a concentration of 10 mg / liter.
Per liter, and the test was carried out. The maximum pit depth was 0.12 mm. Example 9 A polymer obtained by hydrolyzing 20 mol% of N-vinylformamide units of a copolymer of N-vinylformamide and sodium acrylate in a molar ratio of 85:15 (molecular weight: 12,12)
000, drug F) to a concentration of 10 mg / liter,
The test was performed by adding hydroxyethylidene diphosphonic acid (drug I) as a total phosphoric acid to a concentration of 3 mg / liter. The maximum pit depth was 0.11 mm. Example 10 Poly-N-vinylformamide (molecular weight 80,000,
The test was carried out by adding drug A), polymaleic acid (molecular weight 3,000, drug J) and polyacrylamide (molecular weight 5,000, drug K) to a concentration of 10 mg / liter, respectively. The maximum pit depth was 0.12 mm. Comparative Example 1 A test was conducted by adding zinc chloride (drug G) as zinc to a concentration of 1 mg / liter. The maximum pit depth is
It was 0.26 mm. Comparative Example 2 A test was carried out by adding sodium hexametaphosphate (drug H) as a total phosphoric acid to a concentration of 3 mg / liter. The maximum pit depth was 0.35 mm. Comparative Example 3 A test was carried out by adding sodium hexametaphosphate (drug H) as a total phosphoric acid to a concentration of 6 mg / liter. The maximum pit depth was 0.34 mm. Comparative Example 4 A test was carried out by adding hydroxyethylidene diphosphonic acid (drug I) as a total phosphoric acid to a concentration of 3 mg / liter. The maximum pit depth was 0.24 mm. Comparative Example 5 A test was conducted by adding polymaleic acid (molecular weight: 3,000, drug J) and polyacrylamide (molecular weight: 5,000, drug K) to a concentration of 10 mg / liter, respectively. The maximum pit depth was 0.27 mm. Table 2 shows the results of Examples 1 to 10 and Comparative Examples 1 to 5.

[0014]

[Table 2]

Example 1 in which poly-N-vinylformamide was added as an anticorrosive, Example 2 in which poly-N-vinylacetamide was added, Example 3 in which a partial hydrolyzate of poly-N-vinylformamide was added Examples 4 and 5 in which a copolymer of N-vinylformamide and sodium acrylate or allylamine was added, Example 6 in which a partial hydrolyzate of a copolymer of N-vinylformamide and sodium acrylate was added, Poly- Example 7, poly-N with addition of N-vinylformamide and zinc chloride
Example 8 in which vinylacetamide and sodium hexametaphosphate were added, Example 9 in which a partial hydrolyzate of a copolymer of N-vinylformamide and sodium acrylate and hydroxyethylidene diphosphonic acid were added, poly-N-vinylformamide and In Example 10 in which polymaleic acid and polyacrylamide were added, the maximum pitting depth was as small as 0.11 to 0.14 mm, and N
-It is understood that a metal anticorrosive containing a water-soluble polymer having a vinylcarboxylic acid amide unit has an excellent corrosion inhibiting effect. In contrast, in Comparative Examples 1 to 5 in which zinc chloride, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, polymaleic acid, and polyacrylamide, which have been conventionally used as metal anticorrosives, the maximum pitting depth is lower. It is as large as 0.24 to 0.35 mm.

[0016]

The metal anticorrosive of the present invention has an excellent inhibitory effect on corrosion of metal surfaces in contact with water.

Claims (3)

[Claims] 1. A metal anticorrosive comprising a water-soluble polymer having an N-vinylcarboxylic acid amide unit. 2. It contains (A) a water-soluble polymer having an N-vinylcarboxylic acid amide unit, and (B) at least one compound selected from the group consisting of heavy metal salts, phosphorus compounds and anionic polymers. A metal corrosion inhibitor characterized by the following. 3. A water-soluble polymer having an N-vinylcarboxylic acid amide unit partially hydrolyzes poly-N-vinylformamide, poly-N-vinylacetamide, poly-N-vinylformamide or poly-N-vinylacetamide. A polymer further having a vinylamine unit,
N-vinylformamide or a copolymer of N-vinylacetamide and another monomer or a copolymer of N-vinylformamide or N-vinylacetamide and another monomer partially hydrolyzed and further a cationic functional group or a cationic functional group The metal anticorrosive according to claim 1 or 2, which is a polymer having an anionic functional group.