JPS5845475B2 - Suiyo Seihi Makugatabou Sabiso Seibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-soluble film type rust preventive composition used for temporary rust prevention on the surface of steel products.

Oil film type rust preventive agents have been widely used for temporary rust prevention on the surface of steel products.

This oil film-type rust preventive agent maintains its rust preventive effect for a relatively long period of time, but when it is removed, (a) it requires degreasing and cleaning treatment with an alkaline agent or solvent, and (0) it is emitted during the process. Deficiencies were pointed out, such as the necessity of post-treatment of the waste liquid, and (iii) the large number of man-hours and equipment costs involved.

In order to improve these defects, a water-soluble film-type rust preventive agent (Japanese Patent Application No. 48-20386) and a soft film-type water-soluble rust preventive composition (Japanese Patent Application No. 70584-1982) were proposed.

Not only do they have a long-term rust-preventing effect, but once they have temporarily served their rust-preventing purpose, they can be easily removed by simply washing with water. This shows the fruits of rationalization in rust prevention management of various types.

However, the above-mentioned rust preventive agents and rust preventive compositions have the following latent problems, and therefore face a situation where they lack practicality depending on the types of tanks and equipment.

The problems are: (1) It has poor moisture resistance and weakens in summer or in high humidity environments, and (0) It is a soft solid at room temperature, so it requires heating and liquefaction when painting. ←→ Even when liquefied, the viscosity is high, so special painting equipment such as an airless sprayer is required for painting.

This invention was made to improve the above-mentioned problems.It exhibits a moderately viscous liquid form at room temperature, and can be applied to the surface of steel products using an ordinary air spray machine, and the coating film is moisture resistant. It is a highly practical water-soluble film-type preventive material that is highly durable and exhibits long-term rust-preventing power, and can be easily removed by treatment with room-temperature water after temporarily preventing rust on the surface of steel products. A rust composition is provided.

That is, the present invention provides a water-soluble film-type rust preventive composition used for temporary rust prevention on the surface of steel products, which contains a homopolymer of acrylic acid or methacrylic acid, maleic anhydride, and a carbon number of 2.
It is characterized in that it is made by mixing one or more mixtures selected from the copolymers with olefinic hydrogen carbonates of 5 to 5 with an alkaline solution and subjecting the mixture to modification treatment.

The olefinic hydrocarbons used in this invention are propylene,
It is selected from those having 2 to 5 carbon atoms, such as butylene and isobutylene.

When the number of carbon atoms is 6 or more, the resulting anticorrosive composition tends to have unfavorable effects on viscosity and other aspects of practicality.

The degree of polymerization of the homopolymer or copolymer used in this invention is preferably about 300 to 3,000.

The reason for this is that if the degree of polymerization is extremely low, the film-forming ability of the resulting anticorrosive composition tends to be low, whereas if the degree of polymerization is significantly high, the viscosity of the composition becomes too high, making it difficult to Similarly, problems may arise in paintability.

Known polymerization reactions may be used to synthesize the above-mentioned homopolymers and copolymers.

For example, a method for synthesizing a copolymer of maleic anhydride and an olefinic hydrocarbon is disclosed in Japanese Patent Publication No. 16551/1983.

None of the thus obtained homopolymers, copolymers, or mixtures thereof can form a water-soluble film having antirust properties by itself.

In order to make this possible, a modification treatment using an alkaline solution such as an aqueous alkaline solution is required.

That is, when the above-mentioned polymer is mixed with an aqueous solution of an alkali metal salt such as sodium hydroxide, and this mixture is appropriately heat-treated at, for example, around 70°C, the mixture becomes a viscous liquid at room temperature. .

This mixture exhibits the performance as a water-soluble film-type antirust composition.

The details of what kind of changes occur in the polymer due to the above modification treatment are not necessarily clear, but at least some or all of the carboxylic acid groups in the polymer are converted to carboxylic acid salts. It is thought that it generates .

In addition, the alkaline agents necessary for the modification treatment are not limited to sodium hydroxide, but also include alkali metal salts such as lithium hydroxide and sodium carbonate, alkaline earth metal salts such as magnesium oxalate, calcium hydroxide, and barium carbonate, and ammonia. In addition to the above-mentioned inorganic alkaline agents, organic alkaline agents such as ethanolamine and hexylamine can also be used.

In this invention, a water-soluble film-type rust-preventing composition that exhibits a suitably viscous liquid form at room temperature can be obtained, so unlike conventional methods, heating and liquefying operations are not required when coating the surface of steel products. In addition, not only an airless spray machine but also a regular air spray machine can be used.

A dense resinous film is formed on the surface of the painted steel product.

This resinous film can exhibit long-term rust prevention properties even with a thin film thickness.

Moreover, unlike conventional coatings, this resinous coating is highly moisture resistant, and does not weaken even in summer or in high humidity environments.

On the contrary, since it exhibits drying properties, it is possible to shield the surface of the steel product from a corrosive atmosphere.

After it has served its purpose of temporarily preventing rust on the surface of the steel product, it can be easily removed from the surface of the steel product by a simple immersion treatment or cleaning treatment in room temperature water.

In addition, if it is desired to enhance the rust preventive power of the water-soluble film-type rust preventive composition of the present invention, a small amount of a known rust preventive agent may be added.

That is, to the above viscous mixture, one or more rust inhibitors selected from sodium nitrite, sodium phosphate, sodium borate, triethanolamine, dicyclohexylamine nitrite, petroleum sulfonate, etc. are added. Then, when it is applied to the surface of a steel product, the molecules of the added rust preventive agent are adsorbed to the surface of the steel product or become passivated there, so it lasts for a longer period of time than when no rust preventive agent is added. Demonstrates excellent rust prevention ability.

Next, this invention will be explained in detail.

Based on the compounding ratios shown in the left column of Table 1, water-soluble film-type rust preventive compositions ■, ■, ■, and ■ were prepared.

To explain one example of the preparation method, first, water is poured into a reaction vessel, then potassium hydroxide and magnesium hydroxide are charged, heated to 70°C, and then maleic anhydride-butylene copolymer is added and mixed uniformly. do.

The sample is obtained when this mixture turns transparent or translucent.

Samples (2) and (2) may also be prepared in the same manner as above.

For samples ① and ②, sodium nitrite and triethanolamine were added when the contents became transparent or translucent.

Rust prevention test I: ■ of the water-soluble film-type rust prevention composition prepared as described above.
, ■, ■, and ■ were respectively applied to a mild steel polishing plate (SPC-C) 150×70×3im using an air spray machine and dried.

This specimen was used as a test piece and was hung in an outdoor storage rust prevention tester to conduct a rust prevention test for 80 days.

Although this test device is open to the atmosphere, it is designed to prevent rain from falling on the test piece.

The results of the rust prevention test are as shown in the right column of Table 1, and none of the test pieces coated with the water-soluble film-type rust prevention compositions ■, ■, ■, ■, ■ developed rust.

Also, during the rust prevention test, the coating film on none of the test pieces softened.
After the test, it was completely removed by immersing it in room temperature water for about 10 minutes.

For comparison, a rust prevention test was conducted in the same manner as above using three types of commercially available rust prevention oils.

The results are shown in Table 2. The test pieces of both samples ① and ② developed rust, but the test pieces of sample ① did not.

After the rust prevention test, the coating film on each test piece was removed, but at that time, samples (■) and (2) required immersion treatment in a heated alkaline degreasing solution for around 20 minutes, followed by water washing treatment, and sample (■)
required the same operation twice.

Rust prevention test ■: The water-soluble film-type antirust compositions shown in Table 1 (■) and (■).

Using ■, ■, ■, condenser tube plate (4,
2x5. Om) was rust-proofed.

After cleaning the surface of the tube sheet by shot blasting, the above-mentioned anticorrosive composition was applied using an airless sprayer to a film thickness of approximately 60 μm.

Although the workshop is indoors, it is open to the atmosphere, and welding work is also carried out in the surrounding area, making it a more corrosive environment than ordinary tanks.

After completing the assembly of the condenser (takes approximately 3 months), we inspected the surface of the tube sheet and found that there was only a slight amount of rust on the tube sheet that had been coated with rust-preventing composition and ■, which was hardly a problem. Upon inspection, no rust was observed on the tube sheets of rust-preventing compositions ①, ②, and ②.

As detailed above, the water-soluble film-type rust preventive composition of the present invention exhibits a suitably viscous liquid state at room temperature, and when it is applied to the surface of a steel product, it can be sprayed as is using an air spray machine. Can be painted.

The coating film is highly moisture resistant, so there is no risk of weakening even in summer or in high humidity environments, and not only can it exhibit rust prevention properties for a long period of time, but after it has served its purpose as a temporary rust prevention,
Since it can be easily removed by immersion in room-temperature water or by washing, it is highly practical for temporary rust prevention of a wide range of steel products such as tanks and equipment, whether for land or marine use.

Claims (1)

[Claims] 1. In a water-soluble film-type rust preventive composition used for temporary rust prevention on the surface of steel products, a homopolymer of acrylic acid or methacrylic acid and a copolymer of maleic anhydride and an olefinic hydrocarbon having 2 to 5 carbon atoms are used. 1. A water-soluble film-type rust preventive composition, characterized in that it is obtained by mixing one or more mixtures selected from the following with an alkaline solution and undergoing a modification treatment.