JPH07268666A - Metal corrosion preventive agent and metal corrosion preventive method - Google Patents

Abstract

PURPOSE:To develop a metal corrosion preventive agent consisting of a water- soluble copolymer having an excellent metal corrosion preventive effect with a small amt. of addition without having toxicity and causing environmental pollution by polymerizing a specific monomer forming a terpolymer or interpolymer. CONSTITUTION:A methacrylic acid expressed by formula IV or its salt at a ratio of 5 to 90wt.%, an acrylamidoalkylsulfonate or acrylamidoarylsulfonate, such as 2-acrylamido-2-methylpropanesulfonic acid expressed by formula V, etc., at 5 to 50wt.% and at least one kind among a vinyl ester and vinyl acetate expressed by formulas I, II and a substd. acrylamide expressed by formula III at 5 to 50wt.% are polymerized at 120 to 200 deg.C by using a polymn. initiator, such as hydrogen peroxide, in water or solvent, such as isopropanol. A water-soluble soln. of a concn. 0.1 to 1000mg/l of the polymer having an average mol. wt. 1500 to 25000 is prepd. and further, small amt. of various kinds of corrosion preventive agents for Cu, scale preventive agents, slime control agents and chelating agents may be compounded therewith.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a metal corrosion inhibitor comprising a low molecular weight and water-soluble copolymer and an improved method for preventing metal corrosion in an aqueous system by adding a small amount of the metal corrosion inhibitor. Regarding More specifically, the present invention relates to a metal anticorrosive agent and a metal anticorrosion method comprising a water-soluble copolymer obtained by polymerizing at least three kinds of monomers that form a terpolymer or an interpolymer. It is a thing.

[0002]

2. Description of the Related Art Chromates, nitrites, phosphates, zinc salts, and other inorganic salts have been conventionally used as anticorrosion agents for metallic corrosion of closed circulating cooling water or open circulating cooling water. Organic compounds such as acrylic acid polymers are also used to improve the anticorrosion effect. For example, the molecular weight is 1,000.
100 mg of the following acrylic acid homopolymers and salts thereof
A method of adding at least 1 / l is known (Japanese Patent Publication No. 58-2).
8348).

[0003]

However, although the above-mentioned anticorrosive inorganic salts such as chromate salts, nitrite salts, phosphate salts, and zinc salts are effective, they have various problems in their use.

That is, chromate has a strong toxicity,
Its use is avoided for pollution prevention measures. Nitrite shows an excellent effect in a closed circulating cooling water system, but in an open circulating cooling water system, it is easily decomposed into nitrate by a nitrite-oxidizing bacterium and loses its effect, so that its range of use is limited. Phosphate is said to cause eutrophication when the wastewater is discharged into the sea or rivers and cause red tide. Zinc salt is highly effective as a cathodic anticorrosive and is often used in combination with phosphates, but due to its toxicity, its use is gradually being restricted, so a nontoxic and harmless anticorrosive agent should be considered. Is being promoted.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The object of the present invention is that it is non-toxic, does not pollute the environment, and exhibits a metal corrosion-preventing effect with a small amount of addition. It is to provide a metal anticorrosive agent that can exert its effect.

[0006]

As a result of intensive studies to solve the above problems, the present inventors have found that a terpolymer or interpolymer obtained by polymerizing a specific monomer has an excellent metal anticorrosion effect. As a result, they have completed the present invention.

That is, the present invention provides (a) (meth) acrylic acid and / or its salt: 5 to 90% by weight, (b)
Acrylamide alkyl sulfonate or acryl amide aryl sulfonate: 5 to 50% by weight, at least one selected from the group consisting of (c) vinyl ester, vinyl acetate and substituted acrylamide: 5 to 50% by weight
The present invention relates to a metal anticorrosion agent comprising a water-soluble copolymer containing the unit of (1) and a metal anticorrosion method comprising adding the metal anticorrosion agent to an aqueous system.

The unit of (meth) acrylic acid and / or salt thereof of (a), which is one of the units of the metal anticorrosive agent of the present invention, has the general formula (4).

[0009]

[Chemical 5]

[In the formula, R ⁸ is hydrogen or a methyl group, X is hydrogen, a metal cation or N- (R ⁹ ) (in the formula, R ⁹ is hydrogen, a C ₁ -C ₄ alkyl group) , C ₁ -C ₄ hydroxyalkyl groups or mixtures thereof. ] It has a structural formula shown by.

Preferred compounds for (meth) acrylic acid and / or salts thereof include methacrylic acid, acrylic acid, and sodium salts thereof.

(A) in the water-soluble copolymer of the present invention
The proportion of the units of (meth) acrylic acid and / or its salt is 5 to 90% by weight.

The unit of (b) acrylamidoalkylsulfonate or acrylamidoarylsulfonate, which is another unit of the metal anticorrosive agent of the present invention, has the general formula (5).

[0014]

[Chemical 6]

[In the formula, R ¹⁰ is hydrogen or a methyl group, R ¹¹ is hydrogen or a C ₁ -C ₄ alkyl group,
R ¹² is a C _{1 to} C ₈ alkyl group or a C _{8 to} C ₁₀ aralkyl group, and X is the same as defined in the general formula (4). ] It has a structural formula shown by.

Preferred as the acrylamidoalkyl sulfonate or acrylamido aryl sulfonate is 2-acrylamido-2-methylpropane sulfonic acid.

The proportion of the unit (b) acrylamidoalkylsulfonate or acrylamidoarylsulfonate in the water-soluble copolymer of the present invention is 5 to 50% by weight.

Another one of the units of the metal anticorrosive agent of the present invention is at least one selected from the group consisting of (c) vinyl ester, vinyl acetate and substituted acrylamide. Among these, the unit of vinyl ester is , General formula (1)

[0019]

[Chemical 7]

[Wherein R ¹ is a halogen or a methyl group, R ² is a C ₁ -C ₆ alkyl group, a C ₆ -C ₁₀ aryl group, a C ₆ -C ₁₀ aralkyl group or a general Formula (2)

[0021]

[Chemical 9]

Wherein R ³ is hydrogen or a methyl group, R ⁴ is a C ₁ -C ₆ alkyl group or hydrogen,
n is an integer of 1 to 3), and the unit of the substituted acrylamide is represented by the general formula (3).

[0023]

[Chemical 10]

[Wherein R ⁵ is hydrogen or a methyl group, R ⁶ and R ⁷ are hydrogen, a C ₁ -C ₈ alkyl group, C 6
A cycloalkyl group having ₆ -C _8, a benzyl group or a group represented by formula (2)

[0025]

[Chemical 11]

(Wherein R ³ is hydrogen or a methyl group, R ⁴ is a C ₁ -C ₆ alkyl group or hydrogen,
n is an integer of 1 to 3), provided that both R ⁶ and R ⁷ are not hydrogen].

Among the units (c) of the water-soluble copolymer of the present invention, preferred are t-butyl acrylamide and t
-Substituted acrylamides such as octyl acrylamide.

The proportion of at least one unit selected from the group consisting of (c) vinyl ester, vinyl acetate and substituted acrylamide in the water-soluble copolymer of the present invention is 5
~ 50% by weight.

The weight average molecular weight of the water-soluble copolymer of the present invention is preferably in the range of 2000 to 10,000, and in the case of a terpolymer, the weight average molecular weight is 1500 to
The range of 25,000 is preferable.

As a method for producing the water-soluble copolymer of the present invention, a general synthesis method for a low molecular weight copolymer of (meth) acrylic acid may be adopted.

That is, for example, at least one selected from the group consisting of (a) (meth) acrylic acid and / or a salt thereof, (b) acrylamidoalkylsulfonate or acrylamidoarylsulfonate and (c) vinyl ester, vinyl acetate and substituted acrylamide. 1
The seed monomer is treated with a polymerization initiator such as hydrogen peroxide, ammonium persulfate, potassium persulfate or benzoyl peroxide in water or a solvent such as isopropanol,
Polymerization may be performed at a temperature of 0 to 200 ° C. and a polymer concentration of 25 to 50% by weight.

To prevent corrosion of metals in an aqueous system using the metal corrosion inhibitor of the present invention, the concentration of the polymer is 0.1 to 1,000.
It may be added in the range of mg / l, preferably 1-100 mg / l. That is, if it is less than 0.1 mg / l, the anticorrosive effect cannot be obtained, and even if it is added in excess of 1000 mg / l, the performance is almost constant, and the effect improvement due to the increase of the addition amount is small and it is economically unreasonable.

The metal anticorrosive agent of the present invention can be used as an anticorrosive agent for a closed circulation cooling water system or an open circulation cooling water system. In addition to the metal anticorrosion agent of the present invention, nitrous acid, phosphoric acid, silicic acid, molybdic acid or tungsten is used. Anticorrosive agents such as acids, oxy acids, amino acids, aliphatic organic acids, aliphatic amine acids, aromatic carboxylic acids, aluminates, boric acid, lignin sulfonic acid / or their water-soluble salts, tannins and lignins,
Benzotriazole, tolyltriazole and other azole-based or mercaptobenzothiazole-based anticorrosive agents for copper and copper alloys, acrylic acid-based polymers, maleic acid-based polymers, methacrylic acid-based polymers, sulfonic acid-based polymers, phosphoric acid-based Polymers, itaconic acid-based polymers, isobutylene-based polymers / or scale inhibitors such as water-soluble salts thereof,
Slime control agents such as ammonium compounds, amine compounds, chlorine compounds, bromine compounds, nitrogen-sulfur compounds, organometallic compounds, ethylenediamine,
Amine-based polymers such as diethylenetriamine or nitrilotriacetic acid, ethylenediaminetetraacetic acid salts, aminocarboxylic acid-based polymers such as diethylenetriaminepentaacid or gluconic acid, citric acid, oxalic acid, formic acid, tartaric acid, phytic acid, succinic acid, lactic acid, etc. It may be used in combination with or mixed with the organic carboxylic acid type chelating agent.

The metal anticorrosive agent of the present invention can also be used as a hot circulating water type or boiler water type anticorrosive agent. In this case, the metal anticorrosive agent of the present invention is hydrazine,
Sulfite, bisulfite, ascorbate, erythorbate, tannin, lignin, lignin sulfonate,
Deoxidizer such as glucose, p such as hydroxide and carbonate
Inorganic or organic phosphorus compounds such as H regulator, orthophosphate, hexametaphosphate, hydroxyethylidene diphosphonate, phosphonobutane tricarboxylate, acrylic acid-based polymer, maleic acid-based polymer, methacrylic acid-based compound Polymers, sulfonic acid-based polymers, phosphoric acid-based polymers, itaconic acid-based polymers, isobutylene-based polymers / or scale inhibitors such as water-soluble salts thereof, amine-based polymers such as ethylenediamine and diethylenetriamine, or nitrilo Triacetic acid, ethylenediaminetetraacetic acid salt, aminocarboxylic acid-based polymers such as diethylenetriaminepentanoic acid or gluconic acid, citric acid, oxalic acid, formic acid, tartaric acid, phytic acid, succinic acid, lactic acid and other organic carboxylic acid type chelating agents, Octadecylamine, cyclohexylamine, monoethanol Emissions, or in combination with amine vapor based anticorrosive such as morpholine, mixing was nothing like no problem will be used.

[0035]

The details of the anticorrosion mechanism of the metal anticorrosive agent of the present invention are not clear at present, but as shown in the examples below, by using an appropriate amount of this metal anticorrosive agent, excellent anticorrosion properties against metals can be obtained. Give effect.

[0036]

[Examples] Toda city water (referred to as "raw water" in the table below) and 3 times concentrated water of the city water were used as test water, and 1 liter of each test water contained each polymer salt as a solid content. The test liquid added quantitatively was kept at 35 ° C. using a thermostat. A metal test piece (material: SS-400, size: 5
(0x30x1mm) is suspended on a stirring bar and the rotation speed is 170r.
Soaking for 7 days while rotating at pm, corrosion rate (mg /
dm ² · day) was measured. The results are shown in Tables 1 and 2.

[0037]

[Table 1]

[0038]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the metal anticorrosive agent comprising the water-soluble copolymer of the present invention exhibits excellent anticorrosive power even when used in a small amount. Polymer and acrylic acid and 2-acrylamido-2-
The copolymer with methylpropanesulfonic acid had a poor anticorrosion effect.

[0040]

Industrial Applicability The metal anticorrosive agent of the present invention has excellent anticorrosion performance and is an organic compound of a terpolymer or an interpolymer, so that it has no toxicity and does not pollute the environment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Shibata 1-4-9 Kawagishi, Toda City, Saitama Organo Research Institute (72) Inventor Hiroshi Wakatsuki 1-4-9 Kawagishi, Toda City, Saitama Prefecture No. Organo Research Institute

Claims (7)

[Claims] 1. (a) (Meth) acrylic acid and / or its salt: 5 to 90% by weight, (b) acrylamidoalkylsulfonate or acrylamidoarylsulfonate: 5 to 50% by weight, (c) vinyl ester, vinyl acetate. And a metal anticorrosive comprising at least one selected from the group consisting of and substituted acrylamide: a water-soluble copolymer containing 5 to 50% by weight of a unit. 2. The water-soluble copolymer is 1500 to 2500.
The metal anticorrosive agent according to claim 1, having a weight average molecular weight in the range of 0. 3. The unit in the water-soluble copolymer is (a)
(Meth) acrylic acid and / or its salt: 5 to 90% by weight, (b) 2-acrylamido-2-methylpropanesulfonic acid: 5 to 50% by weight, (c) vinyl ester,
At least one selected from the group consisting of vinyl acetate and substituted acrylamide: 5 to 50% by weight, The metal anticorrosive agent according to claim 1. 4. The unit of vinyl ester in the water-soluble copolymer is represented by the general formula (1): [In the formula, R ¹ is halogen or a methyl group, and
² is a C _{1 to} C ₆ alkyl group, a C _{6 to} C ₁₀ aryl group,
C ₆ -C ₁₀ aralkyl group or general formula (2) (In the formula, R ³ is hydrogen or a methyl group, and R ⁴ is C
_{1 to} C ₆ alkyl group or hydrogen, and n is an integer of 1 to 3], and a metal compound according to claim 1 or claim 3. Anticorrosive. 5. The substituted acrylamide unit in the water-soluble copolymer is represented by the general formula (3): [In the formula, R ⁵ is hydrogen or a methyl group, and R ⁶ and R ⁷ are hydrogen, a C _{1 to} C ₈ alkyl group, a C _{6 to} C ₈ cycloalkyl group, a benzyl group or the general formula (2 ) [Chemical 4] (In the formula, R ³ is hydrogen or a methyl group, and R ⁴ is C
_{1 to} C ₆ alkyl group or hydrogen, and n is an integer of 1 to 3), provided that both R ⁶ and R ⁷ are not hydrogen]. The metal corrosion inhibitor according to claim 1 or 3, characterized in that 6. The water-soluble copolymer is 2000-1000.
The metal anticorrosive agent according to claim 1, which is a terpolymer having a weight average molecular weight of 0. 7. A metal anticorrosion method comprising adding an effective amount of the metal anticorrosive agent according to claim 1 to an aqueous system.