JP2845672B2 - Metal corrosion inhibitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal anticorrosive,
More specifically, the present invention relates to a metal anticorrosive comprising a copolymer of caffeic acid and unsaturated sulfonic acid.

[0002]

2. Description of the Related Art In order to suppress corrosion of metals, particularly carbon steel, in a boiler water system or a high-temperature water system of a heating or cooling circulation system, various anticorrosive agents such as oxygen scavengers have been conventionally used. Such anticorrosives suppress the corrosion of metals by removing dissolved oxygen in water, which is the main cause of corrosion, and forming an insoluble film on the surface of the metal, and isolating the metal from an environment containing a corrosive factor. Commonly used anticorrosives include hydrazine, sodium sulfite, sodium bisulfite, glucose, tannin, lignin and the like.

[0003]

In recent years, there has been an increasing interest in safety as well as effects on water treatment chemicals, and water treatment in high-temperature water systems is no exception. In high-temperature water systems, in order to prevent corrosion on heat transfer surfaces such as metal pipes, heat exchangers, and boilers, water that uses a deoxidizer to remove dissolved oxygen in water, which is the main cause of corrosion, is used. Processing is taking place.

Hydrazine and sodium sulfite are the main oxygen scavengers used for such purposes. However, when hydrazine is used, the generated steam or high-temperature water can come into direct contact with the human body or products due to its toxicity. It cannot be used in hospitals or food factories that have potential.

Although sodium sulfite has no problem in safety, it does not always exert a sufficient effect because it reacts with oxygen to produce sulfate ions which cause corrosion. As a result of significantly increasing the concentration and the electric conductivity, the amount of blow is increased, and there are disadvantages such as an increase in energy cost.

On the other hand, natural anticorrosives such as tannin have no problem of safety or excessive increase in the concentration of dissolved solids and electric conductivity of boiler water, but their physical properties are not constant. In addition, there is a drawback that a stable effect is hardly obtained because of being easily modified by an external environment.

The present invention solves the problems of these conventional methods, and provides a metal anticorrosive which has no problem in safety, suppresses energy loss to a low level, and effectively suppresses corrosion. With the goal.

[0008]

The metal anticorrosive according to the present invention made to achieve the above object is caffeic acid (C
(Affective Acid) and an unsaturated sulfonic acid. The weight average molecular weight of the copolymer of the present invention is preferably 1,000 to 2,000 from the viewpoint of exhibiting an excellent anticorrosion effect on metals.
0000, more preferably 50,000 to 800,
000.

Examples of the unsaturated sulfonic acid used in the synthesis of the copolymer of the present invention include styrene sulfonic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and the like. From the viewpoint of exhibiting an excellent anticorrosion effect, styrenesulfonic acid or an alkali metal salt thereof is preferable.

The weight ratio of caffeic acid to unsaturated sulfonic acid is caffeic acid / unsaturated sulfonic acid = 95/5 to 5/95.
Is more preferable, and more preferably 85/15 to 15
/ 85.

The above-mentioned copolymer contained in the metal anticorrosive of the present invention can be converted into a salt, if necessary. The kind of the salt is not particularly limited, but examples thereof include alkali metal salts, ammonium salts and amine salts.

The copolymer used in the metal anticorrosive of the present invention is prepared by mixing caffeic acid and unsaturated sulfonic acid with sodium hydrogen sulfite, a reducing agent of a redox catalyst, using a mixture of ion-exchanged water and ethanol as a solvent. 40 to 150 ° C., preferably 50 to 150 ° C. using ammonium persulfate
5 minutes to 5 hours under a constant temperature condition of 90 ° C., preferably 1
It is produced by a polymerization reaction for 5 minutes to 2 hours.

The amount of the metal anticorrosive of the present invention added to water is from 1 to 5,000 mg / l, preferably from 10 to 500 mg / l, as the above copolymer, so that the corrosion of the metal can be effectively suppressed. Can be.

Further, the metal anticorrosive of the present invention is useful as a metal corrosion inhibitor in a boiler water system or a heating or cooling circulating water system having a remarkably high heat load.

Further, the metal anticorrosive of the present invention is an alkali agent such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, morpholine, cyclohexylamine, phosphate, organic acid salt, tannin, lignin, glucose, octadecyl. Use with an anticorrosive such as an amine and a dispersant such as polyacrylic acid, polymaleic acid, polymethacrylic acid or an alkali metal salt thereof, or in combination with the dispersant may be used at all.

The "weight average molecular weight" of the copolymer in the present specification is a value determined by gel permeation chromatography (GPC), and the measurement conditions are as follows.

GPC Measurement Condition Equipment Tosoh Corporation 8000 Series Detector RI-8000 Range 16 UV-8000 Range 0.08 Wavelength λ 220 nm Column Tosoh Guard column, TSKgel 2500 + 4000
+6000 PW _XL Column temperature 40 ° C Eluent H ₂ O Pump flow rate 1 ml / min Standard substance Polyethylene oxide Mn = 6 × 10, 1 × 10, 3 × 10, 7.5 × 10, 2 × 10,5
× 10 ⁴ (where Mn is the number average molecular weight)

[0018]

The mechanism of the anticorrosive function of the metal anticorrosive agent of the present invention is determined by removing dissolved oxygen in water, which is a major cause of corrosion, to suppress the cathodic reaction, and to provide an insoluble adsorption film with excellent stability on the metal surface. Alternatively, it is conceivable that this is achieved by forming an oxide film and isolating the metal from an environment containing a corrosive factor.

[0019]

EXAMPLES The present invention is described below by way of examples (production examples of copolymers).
The present invention will be described in detail with reference to a deoxidation test and a corrosion test in comparison with Comparative Examples, but it goes without saying that the present invention is not limited to the Examples.

Production Example 1 (Production of Copolymer) Into a reaction vessel, 250 g of ion-exchanged water and 200 g of ethanol were placed as solvents, and 25 g of caffeic acid, 25 g of sodium styrenesulfonate, and hydrogen sulfite as a reducing agent for a redox catalyst were added thereto. 12.5 g of sodium was added.
This was heated to 60 ° C. while being stirred in a hot water bath, and a solution obtained by dissolving 25 g of ammonium persulfate as a catalyst in 50 g of ion-exchanged water was charged all at once. The reaction was further carried out for 1 hour while the temperature was kept constant while stirring, and then the reaction vessel was placed in an ice bath and cooled to obtain a reaction product. The weight average molecular weight of the obtained copolymer was 451,000.

Production Example 2 (Production of Copolymer) Into a reaction vessel, 300 g of ion-exchanged water and 150 g of ethanol were placed as solvents, and 12.5 g of caffeic acid, 37.5 g of sodium styrenesulfonate and a reducing agent for a redox catalyst were added thereto. 6.25 g of sodium bisulfite. This was heated to 60 ° C. while being stirred in a hot water bath, and a solution obtained by dissolving 12.5 g of ammonium persulfate as a catalyst in 50 g of ion-exchanged water was charged all at once. The reaction was further carried out for 1 hour while the temperature was kept constant while stirring, and then the reaction vessel was placed in an ice bath and cooled to obtain a reaction product. The weight average molecular weight of the obtained copolymer is 14
It was 1,000.

Production Example 3 (Production of Copolymer) Into a reaction vessel were placed 250 g of ion-exchanged water and 200 g of ethanol as solvents, 25 g of caffeic acid, 25 g of sodium styrenesulfonate, and hydrogen sulfite as a reducing agent for a redox catalyst. 6.25 g of sodium were charged.
This was heated to 60 ° C. while stirring in a hot water bath, and 12.5 g of ammonium persulfate as a catalyst was added to 50 parts of ion-exchanged water.
g, and then the solution was added all at once. The reaction was further carried out for 1 hour while the temperature was kept constant while stirring, and then the reaction vessel was placed in an ice bath and cooled to obtain a reaction product. The weight average molecular weight of the obtained copolymer is 783,00
It was 0.

[Deoxygenation Test] The amount of oxygen that can be reduced by the respective aqueous solutions (pH: 11) obtained when the anticorrosive of the present invention and the existing anticorrosive are added in predetermined amounts to the synthetic water having the quality shown in Table 1 ( The oxygen consumption was measured using a pressure detection type OD meter (where OD means oxygen demand) (temperature: 25 ° C., measurement period: 3 days). Table 2 shows the results.
Shown in

[0024]

[Table 1]

[0025]

[Table 2]

[Corrosion Test] A mild steel test tube (inner diameter 50 mm, length 50) was placed in a 10-liter test boiler.
0mm) and mild steel test piece (20 × 80 × 2m)
m) was installed and a corrosion test was performed. The soft water shown in Table 3 was used as the make-up water of the boiler, and the anticorrosive of the present invention or the existing anti-corrosive was mixed with the make-up water in the amount shown in Table 4 and supplied to the test boiler.

The makeup water has a pH of 10.
A small amount of caustic soda was added so as to be 5 or more. The test boiler was continuously operated at a pressure of 1 MPa, a temperature of 183 ° C. and a 10-fold concentration for 150 hours.

After the test was completed, the test tube and the test piece were taken out, the state of occurrence of corrosion was observed, and the corrosion rate and corrosion inhibition rate of the test piece were measured by the following equations.

[0029]

(Equation 1)

[0030]

(Equation 2)

The results are shown in Table 4.

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

The copolymer constituting the metal anticorrosive of the present invention is an oligomer or a polymer, and therefore has no volatility and is highly safe. Even when it reacts with oxygen, the concentration of dissolved solids in boiler water and the electric conductivity are high. Is not excessively increased, and the amount of blow can be reduced to reduce the energy cost.

Since the above copolymer is a synthetic product,
Quality control is easy and lot-to-lot variation in composition and chemical properties can be minimized.

Further, the metal anticorrosive of the present invention forms a stable insoluble film or oxide film on the metal surface together with the removal of dissolved oxygen in water. Non-metallic metal anticorrosion treatment can also be realized.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuhiko 3-124-1, Kabone, Edogawa-ku, Tokyo (56) References JP-A 1-132344 (JP, A) JP-A 1-275552 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) C23F 11 / 00,11 / 16,11 / 173 C08F 220 / 02,220 / 04 C09K 15 / 06,15 / 08 F28F 19/00 JICST file ( JOIS)

Claims (4)

(57) [Claims] 1. A boiler-based or heated boiler comprising a copolymer of caffeic acid and unsaturated sulfonic acid.
High-temperature water-based metal anticorrosive for heat or cooling circulation system . 2. The metal anticorrosive according to claim 1, wherein the unsaturated sulfonic acid is styrenesulfonic acid or an alkali metal salt thereof. 3. A polymer having a weight average molecular weight of 1,000.
The metal anticorrosive according to claim 1, wherein the amount is from 0 to 2,000,000. 4. adding a metal corrosion inhibitor according to claim 1 or 2 in water so that 1~5,000mg / l, Bo
Irrigation water system or high temperature water system of heating or cooling circulation system
A method to control metal corrosion.