JPH0427314B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a corrosion inhibitor that is stable in hard water and contains as an active ingredient a reaction product of a compound having a succinic anhydride group and an α-amino acid salt. BACKGROUND OF THE INVENTION Inorganic and organic corrosion inhibitors have been used to prevent corrosion of metals in systems where aqueous media and metal surfaces are in contact. Among inorganic corrosion inhibitors, chromic acid compounds such as dichromate have excellent corrosion prevention effects but are toxic, and nitrites, which are effective in closed circulating water systems, can be used as they are or after being reduced to form nitroso compounds. In addition, phosphates are undesirable because they cause eutrophication of lakes, lakes, and rivers. Basically, organic corrosion inhibitors that have a polar functional group in their molecules that can coordinate to the metal surface are used, such as fatty acid salts, oxycarboxylic acid compounds, benzoates, diethanolamine, and mercapto. Although there are benzothiazoles, there are very few that show satisfactory corrosion prevention effects as single products.
Usually a combination of several drugs is used. Among these, fatty acid salts have particularly excellent anti-corrosion properties, but have the drawbacks of being prone to foaming, poor hard water resistance, and precipitation of calcium soap, magnesium soap, and the like. Japanese Patent Application Publication No. 56-58978, No. 57-
No. 39177 describes the use of special acylated amino acid salts as a countermeasure to these problems, but these compounds are a combination of acid chloride and amino acid salt. Since it must be manufactured by the Baumann reaction, not only is it a big problem to remove a large amount of by-product salt (generally sodium chloride), but in order to prevent foaming, it is necessary to use special substances such as branched fatty acids. However, it has the disadvantage of requiring the use of expensive acid chlorides. On the other hand, a reaction product of a compound having a succinic anhydride group in the molecule and an alkali or amine also has an excellent antirust effect, but similarly has the drawback of insufficient hard water stability. OBJECT OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a corrosion inhibitor that is stable against hard water. Structure of the Invention As a result of intensive research, the present inventors discovered that the reaction product of a compound having a succinic anhydride group in the molecule and an α-amino acid salt has extremely good stability in hard water and has low foaming. Completed the invention. The above reaction product is expressed by the general formula:

Take an imide structure as shown in [Formula], or

As shown in the formula, only one carboxyl group of succinic acid has an amide structure. _{where , 2} is an alkali metal,
Represents a hydrogen atom or an ammonium group. It goes without saying that the reaction product includes a mixture of both. Compounds with a succinic anhydride group in the molecule include (1) Maleic anhydride is a compound with a double bond in the molecule. Alder addition or ene reaction addition, such as maleated rosin,
Contains maleopimaric acid, maleated fatty acids, maleated oils, maleated petroleum resins, maleated polybutadiene, alkenylsuccinic anhydrides, etc. (2)
α-olefin, a copolymer of one or more vinyl compounds and maleic anhydride, such as ethylene, propylene, n-butylene, i-butylene, n-pentene, i-pentene, isoprene, 1.3-pentadiene, 2.3-dimethylbutadiene, 2.5 -Heptadiene, 2-methyl-1,3-hexadiene, 1,3-octadiene, cyclohexene, styrene, vinyl acetate, acrylonitrile, vinyl chloride, acrylic acid, acrylic acid esters, butyl vinyl ether, i-butyl vinyl ether, etc. and maleic anhydride. Examples include polymers, but the compound is not necessarily limited to the above compound group as long as it polymerizes with maleic anhydride, and also includes polymaleic anhydride. α-amino acids include glycine, alanine, valine, leucine, isoleucine, methionine, cystine, cysteine, α-aminobutyric salt, phenylalanine, tyrosine, tryptophan, threonine, serine, glutamic acid, aspartic acid, oxyglutamic acid, and γ-methylglutamic acid. , cysteic acid, homocysteic acid, lysine, ornithine, histidine, etc., and the N-
Alkyl derivatives include α-methylalanine,
Examples include α-methylvaline and sarcosine. Next, bases that neutralize amino acids include alkali metal hydroxides (NaOH, KOH, etc.), alkaline earth metal hydroxides (Ca(OH) ₂ , Mg(OH) ₂ , etc.), and trivalent bases such as aluminum. A metal hydroxide, ammonia, and substituted ammonia (amine, alkanolamine, diamine, dialkanolamine, polyamine, morpholine, etc.) are appropriately selected and used. The above compounds () and () are the above-mentioned compound having a succinic anhydride group in the molecule, and the above-mentioned α
An imidocarboxylic acid salt or an amide carboxylic acid salt can be easily produced by reacting an amino acid salt with water or water and a solvent other than water at about 70°C to 95°C. Among the corrosion inhibitors of the present invention, imidocarboxylic acid salts and amidocarboxylic acid salts derived from maleic anhydride polymers and copolymers of maleic anhydride and other monomers have particularly effective scale prevention effects. It is worth noting that this method will further increase its usefulness. The corrosion inhibitor of the present invention is mainly added to systems in which an aqueous medium and metal come into contact, such as water for cooling systems, hydraulic water for tanks, water stored at full capacity, machining fluid for electrical discharge machining, or water-soluble grinding fluid. It is used as a rust inhibitor or as a known rust preventive agent. Examples Eight types of typical corrosion inhibitors of the present invention (A to A below)
Table 1 shows the test results for H) and two comparative samples (I and J below). A Reaction product between the sodium salt of glycine and maleopimaric acid B Reaction product between the potassium salt of alanine and maleopimaric acid C Reaction product between the sodium salt of glutamic acid and maleopimaric acid D Reaction between the sodium salt of sarcosine and maleopimaric acid Product E Reaction product of sodium salt of glutamic acid and styrene-maleic anhydride copolymer F Triethylamine salt of glutamic acid and Isoban (isobutylene-maleic anhydride copolymer)
G Reaction product between triethanolamine salt of methionine and isobutyl vinyl ether-maleic anhydride copolymer H Reaction product between sodium salt of glutamic acid and maleated fatty acid I Sodium salt of maleopimaric acid J Maleation Potassium salt of tall oil fatty acids The test results obtained are shown in Table 1. However, the test method is as follows. (1) Stability against hard water A 0.2% aqueous solution (PH9-10) of the test sample was mixed with equivalent amounts of 400ppm and 10000ppm hard water made with calcium chloride to make solutions of 200ppm and 5000ppm, respectively, and the presence or absence of precipitates was examined. Ta. (2) Foaming property: 0.2% of the sample in a 100ml graduated cylinder with a stopper.
25 ml of an aqueous solution (adjusted to pH 9-10) was added, vigorously shaken up and down 80 times, allowed to stand, and the foam height was measured after 10 minutes. (3) Rust prevention test (mild steel plate immersion method) Pour 100ml of test water into a 100ml wide-mouth bottle and test the treated mild steel plate (JISG3141, SPCC-B, size 70 x 30
×0.8 (mm) polished with sandpaper, washed sequentially with toluene, acetone, and water, and dried)
After putting the lid on and leaving it at room temperature for 3 days, the appearance of the test piece was observed. Effects of the Invention From the above description and examples, it can be seen that the corrosion inhibitor of the present invention has good stability against hard water, little foaming, and excellent rust prevention ability. Moreover, the corrosion inhibitor of the present invention is an amino acid derivative, has low toxicity to humans and animals, and can be called a so-called low-pollution corrosion inhibitor, and should be widely used.

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Claims (1)

[Claims] 1. A compound having a succinic anhydride group in the molecule and α
Reaction product with amino acid salt General formula and general formula (In the formula, X is a residue of a molecule having a succinic anhydride group in the molecule, excluding the succinic anhydride group, R ₁ is an alkyl group, Y is an amino acid residue, and M ₁ is an alkali metal or ammonium group. , _M2 is an alkali metal,
Represents a hydrogen atom or an ammonium group. ) A corrosion inhibitor stable in hard water, characterized in that it contains one or more compounds selected from the group consisting of: