JPS5827347B2 - The first year of the year - Google Patents

Description

[Detailed description of the invention] The present invention relates to an anticorrosive agent for highly concentrated water in the circulating system.

More specifically, the present invention has a molecular weight of 1,000 to 10,00.
0 and at least one kind of a substantially water-soluble homopolymer of acrylic acid or methacrylic acid, or a copolymer of acrylic acids or methacrylic acids and maleic acids or fumaric acids, and zinc molybdate as main components. This invention relates to an anticorrosive agent for highly concentrated water in the circulating system.

Recently, the problem of pollution caused by water pollution has become very important, and as one of the countermeasures, attempts are being made to minimize blow-up and reuse water used in cooling systems in factories and other facilities.

The water used in such cooling systems has an increased concentration of salts among its components, and in many cases has recently tripled in concentration.
It is expected that it will soon be used up to about five times as many.

Furthermore, when the blowing of the cooling water is substantially stopped, the salt concentration of the water increases by about 100 times.

As a result, equipment in which highly concentrated water in a so-called water circulation system is used is subject to harsh conditions and is prone to corrosion, and it is unclear or unlikely that known anticorrosives can be used for other purposes.

On the other hand, it is well known that highly concentrated water has a high salt concentration and calcium salts, magnesium salts, etc. precipitate and form scale, promoting corrosion.

To address these problems, an anticorrosive agent made of a water-soluble low molecular weight polymer and zinc was already developed in the Japanese Patent Publication No. 50-21950.
It has been proposed in the issue.

However, the polymer disclosed herein has a molecular weight of about 1,000
It is said that the anticorrosion effect is weak when it is 0 or more.

On the other hand, it is known that water-soluble salts of molybdic acid are used as anticorrosive agents, but for example, when sodium molybdate and zinc chloride are used together, sodium chloride is produced as a by-product, which may adversely affect the anticorrosion effect in highly concentrated water systems. It's considered undesirable.

The inventors of the present invention have conducted various studies in this field, and have found that when a water-soluble zinc salt is added to an acrylic or methacrylic acid monopolymer with a molecular weight of about i, ooo to io, ooo, it has an anticorrosion effect. However, the addition of zinc molybdate, which was conventionally thought to be insoluble in water and unusable, surprisingly provided an extremely good anticorrosive effect, as well as acrylic acid or methacrylic acid and fumaric acid or maleic acid. The copolymer has a molecular weight of about i, o o o ~ 10,
The present inventors discovered that adding zinc molybdate, which is insoluble in water, to 000 not only has an excellent anticorrosive effect, but also has no adverse effect on highly concentrated water systems, and has completed the present invention.

Further, conventional anticorrosive agents having an anticorrosion effect against soft water have been limited, but the anticorrosive agent according to the present invention has a characteristic of exhibiting an excellent effect against soft water.

Molecular weight used in the present invention: 1,000 to 10.0
Copolymers of 00 and substantially water-soluble acrylic acids or methacrylic acids and maleic acids or fumaric acids are copolymers of acrylic acids and maleic acids or fumaric acids, or copolymers of methacrylic acids and maleic acids or fumaric acids. A copolymer of a mixture of acrylic acids and methacrylic acids with maleic acids or fumaric acids, and has a molecular weight of 1,000 to 10.
000 and substantially water-soluble.

In forming this copolymer, the acrylic acids and methacrylic acids used may be amide forms or ester forms in addition to free carboxylic acids.

In addition to free acids, maleic acids and fumaric acids may also be in the form of esters.

However, the copolymer used in this invention must be substantially water-soluble, and if an amide or ester monomer is used as the raw material monomer, the copolymer produced may be partially hydrated. It may be decomposed to make it water-soluble.

In short, it is sufficient as long as it has the molecular weight specified above and is water-soluble.
The carboxyl group may be in the form of a salt.

Furthermore, the respective raw materials used for producing the homopolymer of acrylic acids or methacrylic acids include the same materials as those explained for the above copolymer.

Zinc molybdate used in the present invention is sparingly soluble in water, and the anticorrosive agent according to the present invention is usually added to circulating water as an aqueous dispersion or powder formulation of the polymer and zinc molybdate.

In the case of a powder preparation, it is preferable to use it as a fine powder as much as possible.

The blending ratio of the polymer used in the present invention and zinc molybdate is preferably about 1:4 to 3:2, and more preferably about 1:1.

The added amount of the anticorrosive agent according to the present invention is such that the maintenance concentration in the circulating water is about 10 to 100p, preferably about 30 to 501) IXI
It is added as appropriate so that it becomes I.

Note that the anticorrosive agent according to the present invention may include additives to anticorrosive agents used in this field.

For example, triazoles; benzotriazole; 4-phenyl-1,2,3-triazole; 1,2-naphthotriazole; and 4-nitrobenzotriazole and similar substances; thiazoles; thiazole, 2-
Compounds such as mercaptothiazole; 2-mercaptobenzothiazole, penduthiazole and the like are added to provide more effective corrosion protection in aqueous systems where both steel and copper or alloys thereof are present in the same system. It can be done in a specific manner.

Furthermore, a polymerized phosphate salt may be added to the anticorrosive agent according to the present invention.

Next, preferred formulation examples will be given.

Formulation example 1 [Dispersion formulation] 40% acrylic acid maleic acid copolymer (molecular weight 2000-3000) Zinc molybdate water (Active ingredient formulation example 2 [Powder formulation] Sodium polyacrylate (molecular weight s, ooo) Zinc molybdate ( Active ingredient: 1:1) Next, the present invention will be explained with reference to Examples, but is not limited thereto.

Example 1 We prepared water that was 5 times more concentrated than Osaka city water.

The quality of this water is as follows.

[Water quality analysis]

Osaka city water 5 times concentrated water p! (8,2 Electrical conductivity 901.5 P Alkalinity O M tt 69.5 Total hardness 236.0 Chlorine ion 94.5 Sulfate ion 171, O Silicic acid 29.0 Total iron 0.62 Lucium hardness 188.0 The tt test solution was prepared by adjusting the pH of the above 5-fold concentrated water with 0.1 N-sodium carbonate.
It was adjusted to 8.5 and used.

As a test piece, an iron piece 88-41 (manufactured by Minato Metal) with a size of 50 x 30 + z A fixed amount of the drug was added and the test piece was rotated at 1100 rpm for 5 days at 60'C.

After completion of the test, the test piece was taken out and its corrosion loss was measured to calculate MD D (/72!/dm2/day) (ie, corrosion loss per unit area per day).

The (mixing ratio), concentration, corrosion loss, corrosion rate, and scale adhesion status on the test piece surface for each chemical are shown below in order.

Example 2 The same Osaka cloth 5 times concentrated water as in Example 1 was passed through a cation exchange resin to soften it and used as a test liquid.

Below are the (mixing ratio), concentration, corrosion loss, and
Corrosion rate and scale adhesion status on the test piece surface are shown in order.

The test method was the same as in Example 1.

Claims (1)

[Claims] 1 At least one type of substantially water-soluble homopolymer of acrylic acids or methacrylic acids or copolymers of acrylic acids or methacrylic acids and maleic acids or fumaric acids with a molecular weight of 1,000 to io, ooo, and zinc molybdate. An anticorrosive agent for highly concentrated water in the circulating system, characterized by containing as a main component.