JPH10130873A - Metal corrosion inhibitor, metal corrosion inhibiting solution and metal corrosion inhibiting method using the solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive metal corrosion inhibitor exhibiting a high corrosion inhibiting performance even under high-temp. conditions where metal ions are present and capable of preventing the aggregation and precipitation in the presence of metal ions, a metal corrosion inhibiting soln. contg. the inhibitor and a metal corrosion inhibiting method using the soln. SOLUTION: This metal corrosion inhibitor consists of the sulfurcontg. compd. having at least two structural units shown by -O-R1 -S- (where O is oxygen atom, S is sulfur atom, and R1 is a bivalent saturated hydrocarbon residue). The metal corrosion inhibiting soln. contains an acidic soln. consisting of an aq. soln. contg. an inorg. acid and/or an org. acid and the metal corrosion inhibitor. The corrosion of a metal is inhibited by treating the metal with the metal corrosion inhibiting soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the prevention of metal corrosion, and more particularly to the removal of various scales of metal such as black scale, red rust, scale and oxide films of non-ferrous metals adhering to ferrous metals. Acid pickling, plant pot cleaning,
The present invention relates to a metal corrosion inhibitor which is added to a cleaning solution to prevent corrosion of a metal caused during cleaning of a cooling system piping, that is, elution of a base metal, a metal corrosion inhibitor containing the same, and a metal corrosion inhibitor method using the same. It is.

[0002]

2. Description of the Related Art Generally, during chemical cleaning of various steel plates, chemical plants, large boilers, various heat exchangers, cooling pipes, etc., hydrochloric acid,
Aqueous solutions of inorganic acids such as sulfuric acid, phosphoric acid, hydrofluoric acid and oxalic acid,
A treatment with an aqueous solution of an organic acid such as citric acid or succinic acid has been performed. The purpose of this chemical cleaning is to use Fe ₂ O ₃ , Fe
₃ O ₄ , various iron oxides such as FeO (rust), calcium compounds called scales, magnesium compounds, or
The purpose is to remove the oxide film of the nonferrous metal. At the time of this chemical cleaning, a metal corrosion inhibitor is added to the pickling solution at a concentration of about 0.01 to several percent in order to minimize dissolution of the base metal, that is, corrosion of the metal.

[0003] As metal corrosion inhibitors, generally, N,
An organic compound containing a hetero atom such as O, S, P, or a composition containing the same is used. And conventionally,
Long-chain amines such as laurylamine and stearylamine;
Polyalkyleneamines such as polyethyleneimine; thioureas such as diethylthiourea, dibutylthiourea and diphenylthiourea; benzothiazoles such as 2-mercaptobenzothiazole; benzoyl such as 1-hydroxy-1,2,3-benzotriazole Triazoles; unsaturated compounds such as propargyl alcohol; polyoxyalkylenes such as polyethylene glycol; polyamides such as vinylpyrrolidone and acrylamide copolymer compositions; organic compounds such as polyhydric alcohols such as polyvinyl alcohol inhibit corrosion. It is known that it has an effect and can be used as a metal corrosion inhibitor.

[0004]

However, as can be seen from the results of the comparative examples described below, known metal corrosion inhibitors have insufficient corrosion inhibiting effects. Polyethyleneimines and benzothiazoles have excellent corrosion inhibiting effect, but when metal corrosion inhibitor is used repeatedly, coagulation precipitates due to chelation with metal ions dissolved in the metal corrosion inhibitor. For example, precipitates generated during pickling of various steel sheets contaminate the steel sheet surface. Therefore, there may be a case where the metal forming process or the coating process after treatment is adversely affected.

The present invention has been made to solve the above problems, and an object of the present invention is to exhibit high corrosion inhibition performance even under conditions where metal ions are present at high temperatures, and to prevent coagulation and precipitation in the presence of metal ions. An object of the present invention is to provide an inexpensive metal corrosion inhibitor that can be prevented, a metal corrosion inhibitor containing the same, and a metal corrosion inhibitor method using the same.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies and found that the following general formula (1):-(OR ₁ -S)-(1) (wherein O is an oxygen atom , R ₁ represents an aliphatic hydrocarbon residue, and S represents a sulfur atom.) A metal corrosion inhibitor comprising a sulfur-containing compound containing at least two or more structural units represented by Among them, it is possible to maintain a high corrosion inhibitory effect even at high temperatures under pickling conditions of iron-based metals, and to prevent the formation of precipitates even under pickling conditions containing iron ions, and And found that corrosion can be controlled at low cost.
The present invention has been completed. It has never been known that the above sulfur-containing compound alone has a very high corrosion inhibiting effect.

That is, the metal corrosion inhibitor according to the first aspect of the present invention has the following general formula (1):-(O-R ₁ -S) -... (1) (where O is an oxygen atom, R ₁ is a divalent saturated hydrocarbon residue, and S represents a sulfur atom), and is characterized by comprising a sulfur-containing compound containing at least two or more structural units represented by the following formula:

[0008] The metal corrosion inhibitor of the invention according to claim 2 is:
According to claim 1, wherein the metal corrosion inhibitor, the sulfur-containing compound represented by the following general formula _{(2): R 2 - (} O-R 1) n -O-R 3 ... (2) ( In the formula, R ₁ Is a divalent saturated hydrocarbon residue, R ₂ , R
₃ each independently represents a hydrocarbon residue or a hydrogen atom, and n represents a positive integer of 3 or more. The polyoxyalkylene compound represented by the formula (1) is characterized in that at least two or more of the oxygen atoms contained in the polyoxyalkylene compound have a structure replaced with a sulfur atom.

The metal corrosion inhibitor according to the third aspect of the present invention comprises:
It is characterized by comprising an acidic solution comprising an aqueous solution containing an inorganic acid and / or an organic acid, and a metal corrosion inhibitor according to claim 1 or 2.

According to a fourth aspect of the present invention, there is provided a method for inhibiting metal corrosion, comprising treating a metal using the metal corrosion inhibiting solution according to the third aspect.

According to the above method, even at high temperatures, metal corrosion can be efficiently suppressed, and metal corrosion can be suppressed at low cost.

Hereinafter, the present invention will be described in detail. Metal corrosion inhibitor according to the present invention have the general formula (1) - (O-R 1 -S) - ... (1) ( In the formula, O is an oxygen atom, R ₁ is a divalent saturated hydrocarbon residues , S represents a sulfur atom) (hereinafter simply referred to as a sulfur-containing compound).

The divalent saturated hydrocarbon residue represented by R ₁ may be linear or branched.
It may be a cycloalkylene group. As the divalent saturated hydrocarbon residue represented by R ₁ , a saturated hydrocarbon residue having 1 to 8 carbon atoms is preferable. When the carbon number is 9 or more,
There is a possibility that the solubility in the metal corrosion inhibitor is reduced.

Specific examples of the divalent saturated hydrocarbon residue having 1 to 8 carbon atoms include, for example, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, and octamethyl group. Methylene group, 1-
Methylethylene group, 2-methylethylene group, 1-methyltrimethylene group, 2-methyltrimethylene group, 3-methyltrimethylene group, 1-methyltetramethylene group, 2-
Methyltetramethylene group, 3-methyltetramethylene group, 4-methyltetramethylene group, 1-methylpentamethylene group, 2-methylpentamethylene group, 3-methylpentamethylene group, 4-methylpentamethylene group, 5-methyl Pentamethylene group, 1-methylhexamethylene group,
2-methylhexamethylene group, 3-methylhexamethylene group, 4-methylhexamethylene group, 5-methylhexamethylene group, 6-methylhexamethylene group, 1-methylheptamethylene group, 2-methylheptamethylene group, 3 −
C2-C2 groups such as methylheptamethylene, 4-methylheptamethylene, 5-methylheptamethylene, 6-methylheptamethylene, and 7-methylheptamethylene;
An alkylene group of 8, 1,2-cyclohexylene group, 1,
Examples thereof include cycloalkylene groups such as a 3-cyclohexylene group and a 1,4-cyclohexylene group.

The sulfur-containing compound is represented by the general formula (2): R _2- (OR ₁ ) _n -OR ₃ (2) (wherein R ₁ is a divalent saturated hydrocarbon residue; R ₂ , R
₃ each independently represents a hydrocarbon residue or a hydrogen atom, and n represents a positive integer of 3 or more. In the polyoxyalkylene compound represented by the formula (1), it is preferable that at least two or more of the oxygen atoms of the polyoxyalkylene compound have a structure replaced with a sulfur atom.

The hydrocarbon residue represented by R ₂ includes a hydrocarbon group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group and a butyl group. Also,
As the hydrocarbon residue represented by R ₃ ,
And 4 hydrocarbon groups, for example, a methyl group, an ethyl group, a propyl group, and a butyl group.

The sulfur-containing compounds include, for example, mercaptoalkanol and / or thiodialkanol, alkylene glycol and / or
Or a condensate with a polyalkylene glycol (hereinafter referred to as a condensate (A)); a product obtained by hemiacetalization and / or acetalization of an adduct of mercaptoalkanol with acrolein and / or methacrolein;
Condensates of mercaptoalkanol and / or thiodialkanol with monoalkanolamine and / or dialkanolamine (hereinafter referred to as condensate (B)) and the like.

Specific examples of the mercaptoalkanol include 2-mercaptoethanol, 2-mercaptopropanol, 3-mercaptopropanol,
Examples thereof include 2,3-dimethyl-2-mercaptoethanol and 2-mercaptocyclohexanol. These mercaptoalkanols may be used alone,
Further, two or more kinds may be appropriately mixed and used. Also,
Specific examples of the thiodialkanol include thiodiethanol, thiodipropanol, and thiodibutanol. One of these thiodialkanols may be used alone, or two or more of them may be used as an appropriate mixture.

Specific examples of the alkylene glycol include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. Can be One of these alkylene glycols may be used alone, or two or more thereof may be appropriately mixed and used.

The above polyalkylene glycol includes:
Any glycol having two or more oxyalkylene structures may be used. Specific examples include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having various molecular weights and various molecular weight distributions, dipropylene glycol, and tripropylene glycol. , Tetrapropylene glycol, polypropylene glycol having various molecular weights and various molecular weight distributions, and the like. One of these polyalkylene glycols may be used alone, or two or more of them may be appropriately mixed and used.

Specific examples of the above monoalkanolamine include monoethanolamine and monopropanolamine. One of these monoalkanolamines may be used alone, or two or more of them may be appropriately mixed and used. Specific examples of the dialkanolamine include diethanolamine and dipropanolamine. One of these dialkanolamines may be used alone, or two or more of these dialkanolamines may be appropriately mixed and used.

The condensate (A) can be obtained by dehydrating and condensing a mixture containing mercaptoalkanol and / or thiodialkanol and alkylene glycol and / or polyalkylene glycol in the presence of a catalyst.

The catalyst used for producing the condensate (A) is a starting material, mercaptoalkanol and / or
Alternatively, any compound may be used as long as it can dehydrate and condense the thiodialkanol and the terminal alcohol moiety of the alkylene glycol and / or polyalkylene glycol. Specifically, any acidic catalyst may be used, and examples thereof include phosphoric acid, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and a polymer having a sulfonic acid group. However, when the condensate (A) is used as the metal corrosion inhibitor according to the present invention, it is not preferable that an acidic substance remains in the condensate (A). A converted catalyst is preferably used. As a catalyst in which an acidic component is immobilized on a carrier,
Specifically, a polymer having a sulfonic acid group is preferable, and among them, a cation exchange resin having a sulfonic acid group in a side chain, a sulfonic acid group-containing fluororesin, and the like are particularly preferable. As long as the catalyst does not elute into the reaction solution during the reaction, the catalyst is not limited thereto.

The ratio of the charged amount of mercaptoalkanol and / or thiodialkanol to the charged amount of alkylene glycol and / or polyalkylene glycol in the production of the condensate (A) is defined in claims 1 to 2. Is a ratio in which the number of structural units is guaranteed, that is, in the polyoxyalkylene compound represented by the general formula (2), at least two or more of the oxygen atoms of the polyoxyalkylene compound have a sulfur atom Containing an unusual structure and having the general formula (1)
The ratio is not particularly limited as long as a sulfur-containing compound containing at least two or more structural units represented by is obtained.

In the production of the above-mentioned condensate (A), it is preferable to remove the water generated during the reaction out of the reaction system in order to promote the reaction. If necessary, a solvent having an azeotropic property with water may be used in order to make the reaction proceed more smoothly. Examples of the solvent used include aliphatic hydrocarbons and aromatic hydrocarbons, and specifically, hexane, cyclohexane, benzene, toluene, xylene,
Mesitylene and the like can be exemplified. The amount of the solvent used is not limited as long as it is necessary to remove water generated in the reaction system during the reaction.

The reaction temperature for producing the above condensate (A) is not particularly limited as long as the substrate to be condensed is a temperature at which the condensed substrate can be condensed. Is determined as appropriate. The reaction mode for producing the above condensate (A) is not particularly limited, but the produced water and the solvent are distilled out of the reaction system, and the water and the solvent can be separated in two phases, and In addition, a method in which the solvent is refluxed to the reaction system can be more preferably used.

The above condensate (B) is obtained by dehydrating and condensing a mixture containing a mercaptoalkanol and / or a thiodialkanol and a monoalkanolamine and / or a dialkanolamine in the presence of a catalyst. Can be The reaction conditions such as the type of catalyst, the type and amount of the solvent, the mixing ratio of the raw materials, the reaction temperature, and the reaction type when producing the condensate (B) are the same as the reaction conditions for producing the condensate (A). Is fine.

The amount of mercaptoalkanol used in producing the adduct of mercaptoalkanol with acrolein and / or methacrolein (hereinafter referred to as (meth) acrolein) is 0 to 1 mol of (meth) acrolein. Preferably in the range of 0.5 to 3.0 moles,
More preferably, it is in the range of 0.9 to 1.1 mol. (Meta)
If mercaptoalkanol is used in excess with respect to acrolein, (meth) acrolein is promptly converted to the target compound, and the amount of remaining unreacted (meth) acrolein can be reduced. However, even if more than 3 mol of mercaptoalkanol is used per 1 mol of (meth) acrolein, the above effect is not improved, and the amount of mercaptoalkanol recovered after the reaction is increased, which is not economical. When less than 0.5 mol of mercaptoalkanol is used per 1 mol of (meth) acrolein, a large amount of unreacted (meth) acrolein remains and a side reaction such as polymerization of (meth) acrolein occurs. Absent.

Since the reaction between mercaptoalkanol and (meth) acrolein proceeds without a catalyst, it is possible to carry out the reaction without a catalyst. However, if necessary, the reaction rate is controlled by using a catalyst. It is possible. The catalyst that can be used is not particularly limited, but a base catalyst is preferably used. The base catalyst may be an inorganic substance or an organic substance. That is, examples of the inorganic base catalyst include: alkaline earth metal oxides such as magnesium oxide and calcium oxide; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; magnesium hydroxide and calcium hydroxide. Alkaline earth metal hydroxides; alkali metal carbonates such as sodium carbonate and potassium carbonate; magnesium carbonate;
And alkaline earth metal carbonates such as calcium carbonate. Further, as the base catalyst of the organic substance, liquid organic compounds having at least one functional group selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium salt may be used. Any solid can be used.

Since the reaction between mercaptoalkanol and (meth) acrolein is an exothermic reaction, it is necessary to remove heat from the reaction system during the reaction in order to suppress an increase in the reaction temperature. Therefore, in the production method of the present invention, a solvent can be used as necessary in order to enhance the effect of heat removal. The solvent that can be used is not particularly limited as long as it is inert to the reaction, and examples thereof include water; an organic solvent such as hexane; and a mixed solvent thereof.
The amount of the solvent used is not particularly limited, and may be appropriately adjusted so that the reaction temperature becomes a desired temperature. still,
In the production method of the present invention, the reaction can be performed without a solvent.

The reaction temperature is important and ranges from 20 ° C to 60 ° C.
Is preferably within the range. When the reaction temperature is lower than 20 ° C., the reaction rate is reduced, and it takes too much time for the reaction to proceed, so that it is not economical. When the reaction temperature is 60
If the temperature is higher than ° C, side reactions such as polymerization of (meth) acrolein occur, and the yield of the adduct decreases. In addition, when the reaction is performed at a high temperature of 60 ° C. or more, as described later, the generated sulfur-containing aldehyde is acetalized, and an acetalized product is formed as a by-product.

The reaction time is not particularly limited, but is preferably 0.5 to 24 hours from the viewpoint of productivity. In the production method of the present invention, the reaction can be performed under normal pressure, but the reaction can be promoted by performing the reaction under pressure.

In the production method of the present invention, a polymerization inhibitor such as a benzoquinone compound or a nitro compound can be used to suppress the polymerization of (meth) acrolein which is a side reaction.

Further, mercaptoalkanol and (meth)
The reaction with acrolein may be carried out by employing any of a batch system, a semi-batch system, and a continuous system. When the batch system or the semi-batch system is employed, the method for supplying the mercaptoalkanol and (meth) acrolein is not particularly limited, and various methods are possible. Specifically, for example, a method in which mercaptoalkanol and (meth) acrolein are charged in advance in a reaction vessel in a lump and the reaction is started; after charging mercaptoalkanol in the reaction vessel, (meth) acrolein is supplied. A method in which mercaptoalkanol and a solvent are charged and mixed in a reaction vessel,
A method of performing the reaction while supplying (meth) acrolein;
After charging mercaptoalkanol to the reaction tank, a method of performing a reaction while supplying a mixed solution of (meth) acrolein and a solvent can be used.

As described above, the general formula (3)

[0036]

Embedded image

(Wherein, R ₄ represents a saturated hydrocarbon residue having 2 or more carbon atoms, and R ₅ represents a hydrogen atom or a methyl group). Since the above sulfur-containing aldehyde has both a hydroxyl group and an aldehyde group in the molecule, it reacts with each other between the molecules to produce a (hemi) acetal compound as a by-product. The generation of this (hemi) acetal compound proceeds more smoothly in an acidic solution due to an acid-catalyzed reaction. In general, it is widely known in the field of organic chemistry that an alcohol and an aldehyde react by acid catalysis to be converted into (hemi) acetal. Therefore, when the sulfur-containing aldehyde is added as a metal corrosion inhibitor to an acidic liquid (for example, a pickling solution), the above-mentioned (hemi) acetal is generated, thereby exhibiting a metal corrosion inhibitory effect. It is considered something. Therefore, as a metal corrosion inhibitor according to the present invention,
It is also possible to use a mixture in which (hemi) acetal is originally contained in the sulfur-containing aldehyde, that is, a mixture in which a part of the sulfur-containing aldehyde is converted to (hemi) acetal.

The metal corrosion inhibitor comprising the above sulfur-containing compound can exhibit a sufficient corrosion inhibitory effect by itself, but can be used in combination with a known corrosion inhibitor and / or a surfactant. Good. The amount of the known corrosion inhibitor and / or surfactant used is not particularly limited, but is desirably controlled within a range that does not impair the excellent corrosion inhibitory effect of the sulfur-containing compound according to the present invention.

The metal corrosion inhibitor according to the present invention comprises the above metal corrosion inhibitor and an acid solution comprising an aqueous solution containing an inorganic acid and / or an organic acid.

The above-mentioned inorganic acids include hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, sulfamic acid and the like, and the above-mentioned organic acids include methanesulfonic acid, oxalic acid, citric acid, succinic acid and the like. The concentration of the inorganic acid and / or the organic acid in the acidic liquid is not particularly limited. Also, the pH of the acidic liquid is not particularly limited.

The amount of the metal corrosion inhibitor to be used is preferably 0.001% by weight or more, more preferably in the range of 0.001 to 5% by weight, and more preferably in the range of 0.01 to 1% by weight, based on the acid solution. Is more preferred. The amount of the sulfur-containing compound used is 0.0
If it is less than 01% by weight, the effect of inhibiting metal corrosion is reduced. On the other hand, even if the use amount of the sulfur-containing compound exceeds 5% by weight, the effect of inhibiting corrosion is not so much improved and it is not economical.

The above-mentioned metal corrosion inhibitor is suitably used as an acid pickling solution used for pickling various metals, but the use thereof is not particularly limited.

In the method for inhibiting metal corrosion according to the present invention, a metal is treated using the above-mentioned metal corrosion inhibitor. The metal may be an iron-based metal or a non-ferrous metal, but an iron-based metal is particularly preferred. In addition, the temperature of the above treatment is not particularly limited as long as it does not decompose the sulfur-containing compound. The method of the above treatment is not particularly limited, either. For example, a plate-like metal may be immersed in a metal corrosion inhibitor.

The use of the metal corrosion inhibitor according to the present invention is not limited to the use in which the metal corrosion inhibitor is mixed with an acid solution. Can be applied to applications. That is, the metal corrosion inhibitor may be used in addition to the pickling solution and used in the cleaning solution at the time of plant cleaning, or may be used in the circulating fluid of a radiator of an automobile or the like. It may be used by adding it to cooling water or a cleaning liquid of a heat exchanger such as a boiler.

[0045]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 First, 30.5 g (0.25 mol) of thiodiethanol and 15.5 g of ethylene glycol (0.25 mol) were placed in a three-necked flask equipped with a thermometer, a Dean-Stark trap, and a reflux condenser. .25 mol), 54 g of toluene as a solvent, and 4.6 g (10% by weight based on the total amount of thiodiethanol and ethylene glycol) of a dehydration catalyst (trade name: “Dowex 650CH”, manufactured by Dow Chemical Co., Ltd.). The mixture was heated while stirring with a magnetic stirrer to reflux toluene. When 4.5 g (0.25 mol) of water was distilled off, a part of the reaction mixture was collected and analyzed by gas chromatography. As a result, unreacted thiodiethanol and ethylene glycol were not confirmed. The water was distilled off while further heating, and the heating was stopped when 10 g (about 0.5 mol) of water was distilled off. Then
After the catalyst was filtered and separated, the solvent was distilled off from the reaction solution under reduced pressure to obtain 30.2 g of a pale yellow viscous liquid. When the obtained viscous liquid was analyzed by high performance liquid chromatography, a single peak was observed, indicating that the liquid was the target sulfur-containing polyethylene glycol.

Next, the above sulfur-containing polyethylene glycol as a metal corrosion inhibitor, that is, a thiodiethanol / ethylene glycol condensate is added in an amount of 0.1% to an aqueous hydrochloric acid solution with respect to an 18% by weight aqueous hydrochloric acid solution as an acidic liquid.
1% by weight was added to obtain a metal corrosion inhibitor.

Next, a corrosion test was performed. That is, first, a cold-rolled steel plate (JIS G3141, 1 mm × 30 mm × 50 m) as a metal to be treated with the metal corrosion inhibitor.
m) was washed with acetone under ultrasonic irradiation, weighed after drying, and taken as the weight before immersion.

Next, the cold-rolled steel sheet was immersed in the metal corrosion inhibitor at room temperature for 5 hours. Thereafter, the cold-rolled steel sheet was taken out, washed with distilled water to wash away hydrochloric acid, washed with acetone, and dried. The weight of the dried cold-rolled steel sheet was measured, and the amount of corrosion in the corrosion test was calculated from the weight loss before and after immersion.

The amount of corrosion during blanking was measured in the same manner as in the case of using the above-mentioned metal corrosion inhibitor except that only the 18% by weight aqueous hydrochloric acid solution was used instead of the above-mentioned metal corrosion inhibitor. Then, the corrosion inhibition rate was calculated from the corrosion amount in the corrosion test using the metal corrosion inhibitor and the corrosion amount at the time of blanking according to the following equation. Corrosion inhibition rate = (corrosion amount of blank test−corrosion amount of corrosion test) / corrosion amount of blank test × 100 In this example, as shown in Table 1, the corrosion inhibition rate was 93.1%.

After the completion of the corrosion test, the presence or absence of a precipitate was visually observed. As shown in Table 1, no precipitate (agglomerated precipitate) was observed.

Example 2 First, 13.4 g of water as a solvent and 7.8 g of 2-mercaptoethanol as a mercaptoalkanol were placed in a three-necked flask equipped with a thermometer, a reflux condenser and a dropping funnel. 0.1 mol) to prepare a reaction solution. Then, 5.6 g (0.1 mol) of acrolein was dropped into the reaction solution from the dropping funnel over 45 minutes while stirring the reaction solution. still,
While the acrolein was being added dropwise, the temperature of the reaction solution was controlled not to exceed the boiling point of acrolein by cooling the flask with water.

Further, after stirring the reaction solution for 5 hours, a part of the reaction solution was collected and analyzed by high performance liquid chromatography. As a result, the conversion of 2-mercaptoethanol was 98.5%, and the conversion of acrolein was 99.5%. In addition, a single product was confirmed, and the yield of the product was 98.5%. Elemental analysis, ¹ H-NMR, and infrared absorption spectrum of the obtained product were measured to confirm that the product was 3-[(2-hydroxyethyl) thio] propionaldehyde. Then, the above aldehyde compound, ie, 3-
[(2-Hydroxyethyl) thio] propionaldehyde was treated with hydrochloric acid to obtain a mixture of (hemi) acetal of the aldehyde compound. The formation of the (hemi) acetal mixture was confirmed by measuring ¹ H-NMR.

Next, in place of the thiodiethanol / ethylene glycol condensate in Example 1,
A metal corrosion inhibitor was obtained in the same manner as in Example 1, except that a (hemi) acetal mixture of [(2-hydroxyethyl) thio] propionaldehyde was used. Using the above metal corrosion inhibitor, a corrosion test was performed in the same manner as in Example 1, and the corrosion inhibition rate was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 1 shows the results.

Comparative Example 1 A comparative metal corrosion inhibitor was obtained in the same manner as in Example 1 except that thiourea was used instead of the thiodiethanol / ethylene glycol condensate in Example 1. Next, a corrosion test was performed in the same manner as in Example 1 using the above-described comparative metal corrosion inhibitor,
The corrosion inhibition rate was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, the precipitate was observed. Table 1 shows the results.

Comparative Example 2 A comparative metal corrosion inhibitor was obtained in the same manner as in Example 1 except that polyethylene glycol was used instead of the thiodiethanol / ethylene glycol condensate in Example 1. Using the above comparative metal corrosion inhibitor, a corrosion test was performed in the same manner as in Example 1, and the corrosion inhibition rate was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 1 shows the results.

[0057]

[Table 1]

Example 3 5 parts by weight of FeCl 2 per 100 parts by weight of an 18% by weight aqueous hydrochloric acid solution as an acidic liquid
₂ , 1 part by weight of FeCl ₃ .6H ₂ O, and 0.1 part by weight of the thiodiethanol / ethylene glycol condensate synthesized in Example 1 were added to obtain a metal corrosion inhibitor.

On the other hand, the same metal piece (cold rolled steel sheet) as in Example 1 was washed and weighed in the same manner as in Example 1. Next, the metal piece was immersed in the metal corrosion inhibitor at 50 ° C. for 1 hour. After that, take out the immersed metal piece,
As in Example 1, the weight after washing with distilled water and acetone and drying was measured, and the corrosion inhibition rate was calculated.

The amount of corrosion in the blank for calculating the corrosion inhibition rate was determined by using a mixed solution of the above-mentioned metal corrosion inhibiting solution excluding the thiodiethanol / ethylene glycol condensate at 50 ° C. The metal piece immersed for one hour was washed with distilled water and acetone, and dried as described in Example 1, and the weight after drying was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 2 shows the results.

Example 4 In the same reactor as in Example 1, 61 g (0.5 mol) of thiodiethanol, 53 g (0.5 mol) of diethylene glycol, about 100 g of toluene as a solvent, and a dehydration catalyst (commercially available) 6.8 g (6% by weight based on the total amount of thiodiethanol and diethylene glycol) of the name "Diaion PK208" (manufactured by Mitsubishi Kasei Corporation) was charged, heated, refluxed, and subjected to dehydration condensation. When almost the theoretical amount (1 mol) of water was distilled off, the heating was stopped, and thiodiethanol /
The diethylene glycol condensate was isolated.

Next, corrosion was performed in the same manner as in Example 3 except that the thiodiethanol / diethylene glycol condensate synthesized as described above was used instead of the thiodiethanol / ethylene glycol condensate synthesized in Example 1. The inhibition rate was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 2 shows the results.

Example 5 In the same reactor as in Example 1, 61 g (0.5 mol) of thiodiethanol, 52.5 g (0.5 mol) of diethanolamine, about 120 g of toluene as a solvent, and a dehydration catalyst (Product name "Diaion PK208", manufactured by Mitsubishi Chemical Corporation) Approx. 60 g
(Equimolar amount or more with respect to the amine value of diethanolamine), heated, refluxed, and subjected to dehydration condensation. When almost the theoretical amount (1 mol) of water was distilled off, the heating was stopped.
In the same manner as in Example 1, a thiodiethanol / diethanolamine condensate was isolated.

Next, the corrosion inhibition rate was measured in the same manner as in Example 3 except that the above thiodiethanol / diethanolamine condensate was used instead of the thiodiethanol / ethylene glycol condensate. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 2 shows the results.

Example 6 In the same reactor as in Example 1, thiodiethanol 61 g (0.5 mol), 1,4-
45 g (0.5 mol) of butanediol, about 100 g of toluene as a solvent, and 5.3 g of a dehydration catalyst (trade name "Diaion PK208", manufactured by Mitsubishi Kasei Corporation)
(5% by weight based on the total amount of thiodiethanol and 1,4-butanediol) was charged, heated, refluxed, and subjected to dehydration condensation. The heating was stopped when almost the theoretical amount (1 mol) of water was distilled off, and the thiodiethanol / 1,4-butanediol condensate was isolated in the same manner as in Example 1.

Next, instead of the thiodiethanol / ethylene glycol condensate, the above thiodiethanol / 1,
Except for using the 4-butanediol condensate, the corrosion inhibition rate was measured in the same manner as in Example 3. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 2 shows the results. From the results of Examples 3 to 6, the condensate of thiodiethanol with various alkylene glycols and the condensate of thiodiethanol with alkanolamine have a very high corrosion inhibiting power and form a precipitate. It turns out not to be.

Example 7 In Example 3, instead of the thiodiethanol / ethylene glycol condensate, a compound having two oxyalkylenethio structures, 3,6
-Except that dithia-1,8-octanediol is used
The corrosion inhibition rate was measured in the same manner as in Example 3. Also,
When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 2 shows the results.

Comparative Example 3 In Example 3, a compound having one oxyalkylenethio structure was used instead of the thiodiethanol / ethylene glycol condensate.
The corrosion inhibition rate was measured in the same manner as in Example 3 except that methyl [(2-hydroxyethyl) thio] propionate was used. After the completion of the corrosion test, the presence or absence of a precipitate was visually observed. Table 2 shows the obtained results.

As described above, in Comparative Example 3, since a compound having one oxyalkylenethio structure was used as a metal corrosion inhibitor, a clear decrease in performance was observed as compared with Example 7. This indicates that compounds having two or more oxyalkylenethio structures are very effective as metal corrosion inhibitors.

Comparative Example 4 Example 3 was repeated except that polyethyleneimine (trade name “Epomin SP-300”, manufactured by Nippon Shokubai Co., Ltd.) was used instead of the thiodiethanol / ethylene glycol condensate. The corrosion inhibition rate was measured in the same manner as described above. After the test, the presence or absence of a precipitate was visually observed. Table 2 shows the obtained results. The above-mentioned polyethyleneimine has a high corrosion inhibition rate of 87.3%, but the formation of precipitates was observed, indicating that it was not suitable as a corrosion inhibitor.

[Comparative Example 5] In Example 3, 2-thiodiethanol / ethylene glycol condensate was used instead of 2-
The corrosion inhibition rate was measured in the same manner as in Example 3, except that the sodium salt of mercaptobenzothiazole was used.
Table 2 shows the obtained results. The sodium salt of 2-mercaptobenzothiazole has a corrosion inhibition rate of 66.
Although it was 0%, formation of a precipitate was also observed, indicating that it was not suitable as a corrosion inhibitor. .

[0072]

[Table 2]

Example 8 In Example 3, the amount of the thiodiethanol / ethylene glycol condensate was changed to 0.1
Example 3 except that the weight% was changed to 0.05% by weight.
The corrosion inhibition rate was measured in the same manner as described above. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 3 shows the obtained results. From comparison with Example 3, it can be seen that the thiodiethanol / ethylene glycol condensate does not decrease the corrosion inhibition rate even when the concentration is low.

Example 9 In Example 4, the amount of the thiodiethanol / diethylene glycol condensate was set to 0.1.
The corrosion inhibition rate was measured in the same manner as in Example 4 except that the weight was changed from 1% by weight to 0.05% by weight. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 3 shows the obtained results.
Shown in From the comparison with Example 4, it can be seen that the thiodiethanol / diethylene glycol condensate does not lower the corrosion inhibition rate even when the concentration decreases.

[0075]

[Table 3]

Example 10 The corrosion inhibition rate was measured in the same manner as in Example 3, except that a 10% by weight aqueous solution of methanesulfonic acid, which is an organic acid, was used instead of the 18% by weight aqueous hydrochloric acid solution. did. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 4 shows the obtained results.

Example 11 The corrosion inhibition rate was measured in the same manner as in Example 4, except that a 10% by weight aqueous solution of methanesulfonic acid was used instead of the 18% by weight aqueous hydrochloric acid solution. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 4 shows the obtained results.

[0078]

[Table 4]

From these results, it can be seen that the thiodiethanol / ethylene glycol condensate and the thiodiethanol / diethylene glycol condensate exhibit sufficient corrosion inhibitory power even when added to an organic acid.

Example 12 The corrosion inhibition rate was measured in the same manner as in Example 3 except that an aqueous solution of 10% by weight of sulfuric acid was used instead of the aqueous solution of 18% by weight of hydrochloric acid. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 5 shows the obtained results.

Example 13 The corrosion inhibition rate was measured in the same manner as in Example 4 except that a 10% by weight aqueous sulfuric acid solution was used instead of the 18% by weight aqueous hydrochloric acid solution. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 5 shows the obtained results.

[0082]

[Table 5]

Example 14 The procedure of Example 3 was repeated, except that a 10% by weight aqueous solution of sulfamic acid generally used as a scale remover was used instead of the 18% by weight aqueous hydrochloric acid solution. The corrosion inhibition rate was measured. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed.
Table 6 shows the obtained results.

Example 15 The corrosion inhibition rate was measured in the same manner as in Example 4, except that a 10% by weight aqueous solution of sulfamic acid was used instead of the 18% by weight aqueous solution of hydrochloric acid. When the presence or absence of a precipitate was visually observed after the completion of the corrosion test, no precipitate was observed. Table 6 shows the obtained results.

[0085]

[Table 6]

From the results shown in Tables 5 and 6, the thiodiethanol / ethylene glycol condensate and the thiodiethanol / diethylene glycol condensate exhibited sufficient corrosion inhibiting power even when added to an aqueous solution of an inorganic acid other than hydrochloric acid. You can see that

[0087]

According to the metal corrosion inhibitor of the present invention, high corrosion inhibiting performance is exhibited even under conditions where metal ions are present at high temperatures, coagulation and precipitation in the presence of metal ions can be prevented, and the cost is low. This has the effect of being

According to the metal corrosion inhibitor of the present invention,
Metal corrosion can be efficiently suppressed even at high temperatures, and it is possible to prevent the formation of precipitates even when metal ions such as iron ions are dissolved when used repeatedly, and it is inexpensive. This has the effect of suppressing metal corrosion.

Further, according to the metal corrosion suppressing method of the present invention, there is an effect that the metal corrosion can be efficiently suppressed even at a high temperature and the metal corrosion can be suppressed at a low cost.

Claims (4)

[Claims] 1. The following general formula (1):-(O-R ₁ -S)-(1) (wherein O is an oxygen atom, R ₁ is a divalent saturated hydrocarbon residue, and S is A metal corrosion inhibitor comprising a sulfur-containing compound containing at least two structural units represented by a sulfur atom). 2. The method according to claim 1, wherein the sulfur-containing compound is represented by the following general formula (2): R _2- (OR ₁ ) _n -OR ₃ (2) wherein R ₁ is a divalent saturated carbon Hydrogen residue, R ₂ , R
₃ each independently represents a hydrocarbon residue or a hydrogen atom, and n represents a positive integer of 3 or more. 2. The metal according to claim 1, wherein the polyoxyalkylene compound represented by the formula (1) contains a structure in which at least two or more of the oxygen atoms of the polyoxyalkylene compound are replaced by sulfur atoms. Corrosion inhibitors. 3. A metal corrosion inhibitor comprising an acidic solution comprising an aqueous solution containing an inorganic acid and / or an organic acid, and the metal corrosion inhibitor according to claim 1 or 2. 4. A method for inhibiting metal corrosion, comprising treating a metal with the metal corrosion inhibitor according to claim 3.