JP7724498B2 - Rust inhibitor for iron and method for preventing rust on iron structures - Google Patents

Description

The present invention relates to an iron rust inhibitor and a method for preventing rust on iron structures using the iron rust inhibitor.

Paints containing particulate zinc and particulate aluminum have traditionally been used as rust inhibitors for iron. However, in recent years, it has been proposed that instead of using particulate zinc and particulate aluminum, scale-like zinc and scale-like aluminum are used with a silicone resin as a binder component. This results in the zinc and aluminum scales being layered alternately in a tree ring pattern, providing superior rust prevention effects compared to anti-rust paints that use particulate zinc and particulate aluminum (see Patent Documents 1 and 2 below).

However, while the above-mentioned rust inhibitors, which use scale-like zinc and scale-like aluminum, have a relatively good adhesion strength (JISK5600-5-7) of approximately 2.5 MPa, there has been a demand in recent years for rust inhibitors with even better adhesion (adhesion).

In addition, rust inhibitors that use scale-like zinc and scale-like aluminum can form a rust-preventive layer by spraying using air sprays, airless sprays, or by brushing or dipping in a hot water bath. However, they have the problem that they cannot be applied with a roller, which is a relatively simple but efficient method of application. In other words, if you try to apply them with a roller, the result will be a crumbly coating that is completely unusable.

Patent No. 5207439 Patent No. 5159833

The present invention solves the above problems by providing a rust inhibitor for iron that has the same rust-preventing function as the rust inhibitors using scale-like zinc and scale-like aluminum, but has far superior adhesion (adhesion) to iron materials, and can be applied by spray coating (air spray, airless spray, etc.), brush application, dipping in a hot water bath, or even by roller; it also provides a method of rust prevention for iron structures using the above rust inhibitor for iron.

(1) The rust inhibitor for iron of the present invention is an iron rust inhibitor comprising (A) spherical particulate zinc, (B) aluminum powder, (C) carbon nanotubes, (D) a curable silicone compound containing an organoxysilyl group, and (E) bentonite,
The composition is characterized in that the ratio of the components (A), (B), and (C) is, in mass ratio, 0.125 to 20 of the component (B) and 0.0125 to 4 of the component (C) relative to 100 of the component (A); the mass ratio of [total of (A) + (B) + (C)] to the component (D) is 20 to 30 of the component (D) relative to 70 to 80 of the total of (A) + (B) + (C)], with the total of (A) + (B) + (C) + (D) being 100 as the reference; and the mass ratio of the component (E) is 0.5 to 1 relative to 100 of the total of (A) + (B) + (C) + (D)] .

(2) In the rust inhibitor for iron described in paragraph (1) above, it is preferable that (A) the average particle size of the spherical zinc particles is 15 μm or less, (B) the particle size of the aluminum powder is 150 mesh or less, and (C) the particle size of the carbon nanotubes is 50 nm or less.

The average particle size of (A) above was measured using a Blaine air permeability and particle size analyzer, the particle size of (B) above was measured in accordance with JIS Z 8801-1, and the particle size of (C) above was measured using a laser diffraction particle distribution analyzer.

(3) In the rust inhibitor for iron according to any one of (1) to (2) , the component (D) is
Chemical formula R ¹ _x Si(OR ² ) _4-x (1)
Here, x is preferably 1 or 2, R ¹ is a methyl group or a phenyl group, and R ² is a methyl group or an ethyl group, and the silane compound is preferably a partial (co)hydrolyzed condensate of such a silane compound.

(4) Furthermore, a method for preventing rust on an iron structure using the rust inhibitor for iron of the present invention is a method for preventing rust on an iron structure, characterized in that the rust inhibitor for iron according to any one of items (1) to (3) is applied to the iron structure and allowed to dry naturally.

(5) In the method for preventing rust on an iron structure described in (4) above, the method for applying the iron rust inhibitor to the iron structure is any one of spraying, brushing, dipping, and roller coating.

(1) The rust inhibitor for iron of the present invention has sufficient rust-preventing properties equivalent to those of the rust inhibitor using scale-like zinc and scale-like aluminum described above, and has far superior adhesion (adhesion) to iron materials compared to the rust inhibitor using scale-like zinc and scale-like aluminum described above, making it possible to provide a rust inhibitor for iron that can be applied simply with a roller. Furthermore, the rust inhibitor of the present invention is typically stored and transported in a container after production, but this prevents zinc and aluminum from settling and, in some cases, hardening and adhering to the bottom of the container, and also prevents paint dripping when applied, allowing the formation of a coating film in which the added particles are uniformly dispersed.
The ratio of the components (A), (B), and (C) is such that, relative to 100 masses of the component (A), the component (B) is 0.125 to 20 masses and the component (C) is 0.0125 to 4 masses, and the mass ratio of the total of (A) + (B) + (C) to the component (D) is such that the total of (A) + (B) + (C) + (D) is 100 masses. By adopting an embodiment in which the mass ratio of the (D) component is 20 to 30 relative to the total of [(A) + (B) + (C) + (D)] of 70 to 80, and the mass ratio of the (E) component is 0.5 to 1 relative to the total of [(A) + (B) + (C) + (D)] of 100, in addition to the effect described in the above item (1), the rust prevention function is sufficiently maintained, adhesion (adhesion) to iron materials and heat resistance can be sufficiently exhibited, and corrosion resistance against acidic and alkaline atmospheres can also be maintained, which is preferable.

(2) In the iron rust inhibitor described in item (2) of the section on means for solving the above problems, the iron rust inhibitor described in item (1) uses (A) spherical zinc particles with an average particle size of 15 μm or less, (B) aluminum powder with a particle size of 150 mesh or less, and (C) carbon nanotubes with a particle size of 50 nm or less, which allows the formation of a dense rust inhibitor film, sufficient adhesion (adhesion) to the iron material, and improved coating strength, making this preferable.

(3) In the rust inhibitor for iron according to the item (3) in the section on means for solving the problems, the component (D) is
Chemical formula R ¹ _x Si(OR ² ) _4-x (1)
In this case, by adopting a preferred embodiment in which x is 1 or 2, ^R1 is a methyl group or a phenyl group, and ^R2 is a methyl group or an ethyl group, and the silane compound is a partial (co)hydrolyzed condensate of such a silane compound, the silane compound is a versatile silane compound that is excellent in terms of cost, curability, and coating film properties, and is therefore preferred.

(4) In the method for preventing rust on iron structures using the rust inhibitor for iron of the present invention described in item (4) of the section on means for solving the above problems, the rust inhibitor for iron of the present invention can be applied to an iron material and left at room temperature to dry and form a rust-preventive coating film, which is preferable because it does not require energy costs and does not require heating and drying even for large steel structures that cannot be placed in a heating furnace, and it can provide a rust prevention method that can demonstrate the advantages of the rust inhibitor for iron described above.

(5) In the method for preventing rust on iron structures using the rust inhibitor for iron of the present invention described in item (5) of the section on means for solving the above problems, the method for applying the rust inhibitor may be any of a spray method, a brush method, a dipping method, and a roller method. Application by a roller is also possible, which is a relatively simple and efficient method of application, and is preferable because application by a roller also has sufficient adhesion and can form a rust-preventing film that can fully exhibit rust prevention properties.

The rust inhibitor for iron of the present invention is characterized by containing (A) spherical zinc particles, (B) aluminum powder, (C) carbon nanotubes, (D) a curable silicone compound containing organoxysilyl groups, and (E) bentonite.

Compared to rust inhibitors using flake zinc and flake aluminum, the iron rust inhibitor of the present invention has significantly improved adhesion to iron materials. To achieve this, it is necessary to use spherical particulate zinc powder as component (A), powdered aluminum (B), which may also contain granular or flake-like (thin foil) powder, and carbon nanotubes as component (C). However, to achieve sufficient rust prevention performance equivalent to these rust inhibitors without using the aforementioned combination of flake zinc and flake aluminum, and to enable application by roller, it is necessary to use spherical particulate zinc powder, aluminum powder, carbon nanotubes, the aforementioned curable silicone compound, and a small amount of bentonite. Using a small amount of carbon nanotubes instead of a large amount of aluminum increases the conductivity between the potential differences of iron, zinc, and aluminum, making steel structures more resistant to rust and improving the strength, heat resistance, and corrosion resistance in acidic and alkaline atmospheres of the coating.

The addition of bentonite prevents zinc and aluminum from precipitating and paint from dripping, as mentioned above, and allows the formation of a coating film in which the added particles are uniformly dispersed.
Bentonite also includes so-called organic bentonite (organically modified clay in which the layer surface of montmorillonite is reacted with quaternary ammonium ions).

(A) Spherical zinc particles should have an average particle size of 15 μm or less, (B) aluminum powder should be 150 mesh or less, and (C) carbon nanotubes should preferably be 50 nm or less. Using particles with too large a particle size can impair film-forming properties and tend to reduce rust prevention and adhesion (adhesion) to iron materials, so the above ranges are preferred.

More preferably, (A) is 1-5 μm and (B) is 200 mesh or less. There is no particular lower limit from the standpoint of rust prevention, but if it is too fine, measures to prevent hazards such as dust explosions will be necessary, so it is best to use around 400 mesh.

(C) Commercially manufactured carbon nanotubes can usually be used as is, so there is no particular lower limit, but commercially manufactured ones are generally between 0.4 and 50 nm, so this should be used.

The component (D) used is a curable silicone compound containing organoxysilyl groups. "Curable" here means that it cures with moisture in the air. Such silicone compounds are manufactured and sold by Shin-Etsu Chemical Co., Ltd. and other companies, so they are easily available.

Preferred silicone compounds include those represented by the formula R ¹ _x Si(OR ² ) _4-x
(1)
Here, x is preferably 1 or 2, R ¹ is a methyl group or a phenyl group, and R ² is a methyl group or an ethyl group, and the silane compound is preferably a partial (co)hydrolyzed condensate of such a silane compound.

These silicone compounds are general-purpose silane compounds that are preferable due to their cost, curability, and excellent coating properties. They are particularly preferable because they do not contain organic solvents and can be used as solvent-free, room-temperature curing silicone coating agents that can be cured at room temperature.

A few specific examples of these silicone compounds include, but are not limited to, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, partial (co)hydrolyzed condensates of the above triorganoxysilanes or mixed silanes of triorganoxysilanes and diorganoxysilanes, etc.

In the iron rust inhibitor of the present invention, the mass ratio of the (A), (B), and (C) components is preferably such that, for every 100 of the (A) component, the (B) component is 0.125 to 20 and the (C) component is 0.0125 to 4; the mass ratio of the (A) + (B) + (C) total to the (D) component is preferably such that, based on a (A) + (B) + (C) + (D) total of 100, the (D) component is 20 to 30 mass ratio to a (A) + (B) + (C) total of 70 to 80 mass ratio, such that the (A) + (B) + (C) + (D) total is 100; and the mass ratio of the (E) component is preferably 0.5 to 1 mass ratio to a (A) + (B) + (C) + (D) total of 100.

By using a blending ratio within this range, rust prevention functions are fully maintained, adhesion (adhesion) to iron materials is fully exhibited, and heat resistance and corrosion resistance in acidic and alkaline atmospheres are also maintained, which is preferable. Furthermore, precipitation of zinc and aluminum can be prevented, and paint dripping can be prevented when painting, and a coating film in which the added particles are uniformly dispersed can be formed, which is preferable.

Here, the mass ratio of 0.125 to 20 parts by weight of component (B) to 100 parts by weight of component (A) means that if the mass of component (A) is taken as 100, then the mass ratio of component (B) is 0.125 to 20 parts by weight. If component (A) is taken as 1, then the ratio of component (B) is 1/100 of 0.125 to 20, i.e., 0.00125 to 0.2. To give a more specific example, if 100 g of component (A) is used, then 0.125 to 20 g of component (B) is used. If 50 g of component (A) is used, then the ratio of component (B) is 1/2 of 0.125 to 20, i.e., 0.0625 to 10 g. The mass ratio has the same meaning for component (C).

Regarding the mass ratio of [(A) + (B) + (C) total]: (D), if [(A) + (B) + (C) + (D) total] is set to 100 and 100 is used as the base, then the mass ratio of the (D) component is 20-30 when [(A) + (B) + (C) total] is 70-80, means that when [(A) + (B) + (C) total] is 70, the mass ratio of the (D) component is 30 and [(A) + (B) + (C) + (D) total] is 100, and when [(A) + (B) + (C) total] is 80, the mass ratio of the (D) component is 20 and [(A) + (B) + (C) + (D) total] is 100. For example, when the total of [(A) + (B) + (C)] is 75, the mass ratio of component (D) is 25, which is the ratio with the total of [(A) + (B) + (C) + (D)] being 100. To explain further using an example, when the total of [(A) + (B) + (C)] is 76 parts by mass, the amount of component (D) used is 24 parts by mass, and the mass of the total of [(A) + (B) + (C) + (D)] is 100 parts by mass. To give an example where the units are grams instead of parts by mass, when the total of [(A) + (B) + (C)] is 40 g, the amount of component (D) used is 10 g, and the mass of the total of [(A) + (B) + (C) + (D)] is 50 g. Expressing this as a ratio of the above mass proportions, the ratio of [(A) + (B) + (C) total] is 40, and the amount of component (D) used is 10; if we double this without changing the ratio, the ratio of [(A) + (B) + (C) total] becomes 80, and the amount of component (D) used becomes 20, so the ratio of [(A) + (B) + (C) + (D) total] becomes 100.

The use ratio of component (E) is preferably 0.5 to 1 mass part per 100 parts by mass of the total of (A) + (B) + (C) + (D). This means that, for example, when the mass ratio is expressed in parts by mass, the use ratio of component (E) is 0.5 to 1 mass part per 100 parts by mass of the total of (A) + (B) + (C) + (D).

The method for applying the iron rust inhibitor of the present invention to iron materials is not particularly limited, but spray painting methods such as air spray and airless spray, brush application, and dipping in a hot water bath are possible, as well as application with a roller. The spray method is particularly preferred.

The iron materials to which the rust inhibitor of the present invention can be applied are not particularly limited, but include not only iron alone, but also ordinary steel for mechanical structures, steel for construction, high-tensile steel, electromagnetic steel plate, cast iron, stainless steel, deteriorated hot-dip galvanized steel plate, surface-treated steel plate that ensures electrical conductivity, and other iron materials that contain auxiliary additives such as carbon, silicon, manganese, phosphorus, or sulfur depending on the purpose, as well as iron materials that may develop red rust.

The viscosity of the rust inhibitor of the present invention is not particularly limited, but is typically around 550 to 750 mPa·s according to JIS K 5400 1990.

The amount of the rust inhibitor of the present invention to be applied to an iron material varies depending on the object to be coated, so it is difficult to define in general terms, but a standard amount is about 300 to 600 g/ ^m2 .

After applying the rust inhibitor of this invention to iron materials, it can be left to dry naturally at room temperature. It hardens with the moisture in the air. While this varies depending on the type of curable silicone compound used, suitable data show that according to JIS K 5600-1-1, it takes 2-3 hours for the compound to semi-harden (when no scratches are left when lightly rubbed with a fingertip) and 5-7 days for it to fully harden.

The objects to which the rust inhibitor of the present invention can be applied are not particularly limited, but to name a few examples, it can be suitably applied to structures and articles in harsh environments where rust is likely to occur, such as bridges, pedestrian bridges, various plant facilities (equipment, piping, steel frames, etc.), primer paints to prevent CUI (corrosion under insulation), power transmission towers, radio towers, coastal structures, river management facilities such as steel sluice gates and relief gates, gas tanks, wind power generation propeller towers, and oil storage bases, which are areas where iron materials are used, as well as structures and articles whose main parts are made of steel.

To facilitate understanding of the present invention, the present invention will be described in detail below using examples, but the present invention is not limited to these examples in any way.

Example 1
(A) 69.99 parts by mass of spherical zinc particles having an average particle size of 4 μm, (B) 2.52 parts by mass of 300 mesh aluminum powder, (C) 1.5 parts by mass of carbon nanotubes having a particle size of 0.5 to 50 nm mixed therein (D) component (D1) 16 parts by mass of "KR-400" partial condensate of organoalkoxysilane (containing an organoaluminum compound curing catalyst) manufactured by Shin-Etsu Chemical Co., Ltd. (D2) 7 parts by mass of "X40-9225" partial condensate of organoalkoxysilane manufactured by Shin-Etsu Chemical Co., Ltd. (D3) 1.5 parts by mass of "KBM-22" dimethyldimethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, 0.69 parts by mass of organic bentonite (organically modified clay in which the layer surface of montmorillonite is reacted with a quaternary ammonium ion) was prepared as component (E),
After each raw material was placed in a tank equipped with a pressure reducing device, it was stirred for 50 hours at room temperature under a reduced pressure of 0.08 to 0.04 MPa gauge pressure to avoid moisture in the air, to produce a rust inhibitor. The viscosity of the rust inhibitor was measured using a Toki Sangyo Co., Ltd. digital rotational viscometer VB-10M model rotor No. M3 at a rotation speed of 60 rpm (60 seconds) at a test temperature of 23±2°C, in accordance with JIS K 5400:1990 Viscosity 4.5.3 Rotational Viscometer Method, and was 667 mPa.

Comparative Example 1
(A) 69.99 parts by mass of scale-like zinc powder, (B) 2.52 parts by mass of scale-like 150 mesh aluminum, having a scale-like shape and a maximum diagonal length or maximum diameter of the planar portion of 30 to 60 μm and a thickness of 1 to 5 μm;
Component (D) (D1) "KR-400" 16 parts by mass of a partial condensate of organoalkoxysilane (containing an organoaluminum compound curing catalyst) manufactured by Shin-Etsu Chemical Co., Ltd. (D2) "X40-9225" 7 parts by mass of a partial condensate of organoalkoxysilane manufactured by Shin-Etsu Chemical Co., Ltd. (D3) "KBM-22" 1.5 parts by mass of dimethyldimethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, 0.69 parts by mass of organic bentonite (organically modified clay in which the layer surface of montmorillonite is reacted with a quaternary ammonium ion) was prepared as component (E),
After each raw material was placed in a tank equipped with a pressure reducing device, it was stirred for 50 hours at room temperature under a reduced pressure of 0.08 to 0.04 MPa gauge pressure to avoid moisture in the air, to produce a rust inhibitor. The viscosity of the rust inhibitor was measured using a Toki Sangyo Co., Ltd. digital rotational viscometer VB-10M model rotor No. M3 at a rotation speed of 60 rpm (60 seconds) at a test temperature of 23±2°C, in accordance with JIS K 5400:1990 Viscosity 4.5.3 Rotational Viscometer Method, and was 678 mPa.

The rust inhibitors obtained in Example 1 and Comparative Example 1 were applied to the surface of a typical SS400 steel plate (3 mm thick, 150 mm long, 75 mm wide) by blasting to clean the surface. Two test pieces were prepared, each coated by spraying to a dry film thickness of 80 μm (340 g/ ^m² ). The test pieces were then left at 25°C and 65% relative humidity for five days to form a hardened coating of the rust inhibitor. (Test Piece A is Example 1, and Test Piece B is Comparative Example 1.) Furthermore, for comparison, one hot-dip galvanized HDZ55 steel plate (manufactured by Nippon Test Panel Co., Ltd.; HDZ55 is a grade with 550 g/ ^m² of zinc deposited) (Test Piece C) was prepared. Test Pieces A, B, and C were subjected to an accelerated corrosion test (CAS test, JIS H 8502) for 13 days to examine the development of red rust.

The adhesion strength (adhesion) of the anti-rust coating was tested using JIS K 5600-5-7 (tensile test) on two test pieces, A and B.

No red rust was observed on either test piece A, which was coated with the rust inhibitor of the present invention, or test piece B, which was a comparative example. On the other hand, red rust was observed on almost 50% of the surface of test piece C.

The adhesion strength of the anti-rust coating was 9.77 MPa for Example 1 and 2.5 MPa for Comparative Example 1, demonstrating far superior adhesion (adhesion) to that of Comparative Example 1, which used the above-mentioned scale-like zinc and scale-like aluminum. When the anti-rust agent of Example 1 was similarly applied to the same test piece using the roller coating method and a coating was similarly formed, the surface was slightly less smooth, but roughly the same anti-rust function was achieved. On the other hand, when the anti-rust agent of Comparative Example 1 was similarly applied to the same test piece using the roller coating method and an attempt was made to form a coating in the same way, the coating became crumbly and was unsatisfactory as an anti-rust coating.

The rust inhibitor for iron of the present invention is useful for preventing the occurrence of rust in various iron products, and the method for preventing rust on iron structures using the rust inhibitor for iron of the present invention can be suitably applied to the rust prevention of structures and articles whose main parts are made of steel, as well as structures that are located in harsh environments where rust is likely to occur, such as bridges, pedestrian bridges, various plant facilities (equipment, piping, steel frames, etc.), primer paints to prevent CUI (corrosion under insulation), power transmission towers, radio towers, coastal structures, river management facilities such as steel sluice gates and undulating gates, gas tanks, propeller towers for wind power generation, and oil storage bases, where iron materials are used.

Claims (5)

A rust inhibitor for iron comprising (A) spherical particulate zinc, (B) aluminum powder, (C) carbon nanotubes, (D) a curable silicone compound containing an organoxysilyl group, and (E) bentonite ,
The rust inhibitor for iron, wherein the ratios of the components (A), (B), and (C) are, in mass ratio, 0.125 to 20 of the component (B) and 0.0125 to 4 of the component (C) relative to 100 of the component (A); the mass ratio of the [total of (A) + (B) + (C)] to the component (D) is 20 to 30 relative to 70 to 80 of the total of (A) + (B) + (C)], such that the total of (A) + (B) + (C) + (D) is 100, based on 100 of the total of (A) + (B) + (C) + (D); and the mass ratio of the component (E) is 0.5 to 1 relative to 100 of the total of (A) + (B) + (C) + (D) . The rust inhibitor for iron according to claim 1, wherein (A) the average particle size of the spherical zinc particles is 15 μm or less, (B) the particle size of the aluminum powder is 150 mesh or less, and (C) the particle size of the carbon nanotubes is 50 nm or less. The component (D) is
Chemical formula R ¹ _x Si(OR ² ) _4-x (1)
The rust ^inhibitor for iron according to any one of claims 1 to 2, which is a silane compound or a partial (co)hydrolyzed condensate of such a silane compound, wherein x is 1 or 2 , ^R1 is a methyl group or a phenyl group, and R2 is a methyl group or an ethyl group. A method for preventing rust on an iron structure, comprising applying the iron rust inhibitor according to any one of claims 1 to 3 to the iron structure and allowing it to dry naturally. 5. The method for preventing rust on an iron structure according to claim 4 , wherein the method for applying the iron rust inhibitor to the iron structure is any one of spraying, brushing, dipping, and roller coating.