JP7854632B2 - Method for manufacturing an iron rust reduction rust inhibitor. - Google Patents

Description

The present invention relates to a technical field concerning rust prevention pretreatment for surface preparation before painting on steel substrates such as iron and stainless steel. It relates to an iron rust reduction rust prevention treatment agent that, when applied to the surface of a steel substrate, reduces existing red rust and brown rust ( _{Fe₂O₃ )} to black rust ( _{Fe₃O₄ )} , thereby enabling painting without mechanically removing the iron rust.

When painting steel substrates, if the iron rust present on the surface is not removed, the iron rust layer will expand due to the progression of oxidation of the steel, and the paint film will deteriorate and peel off due to reduced adhesion. Therefore, when painting steel substrates, it was essential to pre-treat the substrate by mechanically removing the iron rust present on the steel substrate using sandpaper, scraping, or sandblasting. This pre-treatment of the substrate before painting required a great deal of effort, and there was a strong demand for reducing this pre-treatment effort. As a countermeasure, it had been proposed to incorporate phosphoric acid compounds such as phosphoric acid and zinc phosphate into the primer paint, but their penetration into the iron rust and reducing power were small, and they were not satisfactory in terms of the rust prevention and durability of the paint film.

Prior Patent Documents

Japanese Patent Publication No. 2004-338236
Japanese Patent Publication No. 2005-105337
Japanese Patent Publication No. 2009-40929

The present invention relates to an iron rust reduction and rust prevention treatment agent that, in the pre-treatment of a steel substrate before painting, eliminates the need for conventional mechanical iron rust removal work. By directly applying the pre-treatment coating agent to the steel substrate, reducing substances in the paint penetrate into the iron rust and react with the red or brownish iron rust to convert it into black rust. At the same time, it forms a rust-preventive coating film with excellent rust prevention, water resistance, and weather resistance.

The first invention of the present invention is a two-component iron rust reduction and rust prevention treatment agent for paint on steel substrates, characterized in that it comprises an iron rust reduction and rust prevention treatment agent (Agent A) which contains a reducing mineral acid, tannic acid, and alcohols with 5 or fewer carbon atoms as reducing substances to reduce the iron rust on the substrate, and an iron rust reduction and rust prevention treatment agent (B) which consists of a water-soluble emulsion resin and a lower alcohol with 5 or fewer carbon atoms applied to the iron rust layer of the steel plate beneath the paint film to which Agent A has been applied, in order to promote conversion to black rust and reduction reaction. By incorporating alcohols with 5 or fewer carbon atoms into Agent A, the components of reducing phosphoric acid and tannic acid have high penetration into the iron rust layer and also have excellent reduction reactivity with iron rust. Furthermore _, by applying Agent B, the reduction reaction of iron rust (red rust or _brown rust: _Fe₂O₃ ) is further promoted, and the conversion to black rust (magnetite: _Fe₃O₄ ) proceeds more completely, forming a coating with high rust prevention and corrosion resistance.

The second invention of the present invention relates to a pre-treatment agent for a steel substrate used in painting, wherein hypophosphorous acid and phosphorous acid are preferred as reducing mineral acids contained as reducing substances for iron rust in the iron rust reduction rust prevention agent (Agent A), as they exhibit excellent reducing reactivity with iron rust, and the combination of hypophosphorous acid and phosphorous acid is particularly preferred. The present invention relates to the two-component iron rust reduction rust prevention agent of the present invention, characterized in that the iron rust reduction rust prevention agent (Agent A) contains at least one of hypophosphorous acid and phosphorous acid.

The third invention of the present invention has found that, in a pre-treatment agent for coating steel substrates, it is even more preferable, in terms of the reducing properties and durability of the coating film, to further incorporate a reducing phosphate compound (a compound of reducing phosphate such as zinc, aluminum, or calcium) along with a reducing mineral acid.

The fifth invention of this invention is a rust prevention treatment method for a steel substrate, in which a rust reduction rust prevention treatment agent (Agent A), which reduces iron rust on the steel substrate to prevent rust, and a rust reduction rust prevention treatment agent (Agent B), which further promotes the reduction reaction of iron rust, are applied to the substrate in two layers and two stages. This method is found to be superior in terms of the rust prevention ability, waterproofing, and corrosion resistance of the coating film.

The present invention's iron rust reduction rust-preventive treatment agent does not require any pre-treatment work to remove iron rust from the substrate. By applying the two-component iron rust reduction rust-preventive treatment agent to a substrate surface where iron rust has occurred, red rust is converted to black rust, forming a black rust-preventive and waterproof coating. Therefore, it can be used as is, like a normal paint, but a topcoat may also be applied.

Furthermore, this two-component iron rust reduction rust-preventive treatment agent has high penetration into the oxide film and iron rust layer of steel substrates, resulting in high rust prevention and waterproofing capabilities. Therefore, when applying a topcoat, it is possible to enhance the durability of the topcoat film.
The use of this two-component iron rust reduction rust inhibitor eliminates the need for pretreatment work to remove iron rust from steel substrates, significantly reducing the amount of painting work. Furthermore, the durability of the coating is greatly improved, resulting in a substantial reduction in painting and maintenance costs for the target substrates.

In the present invention, the reducing mineral acid in the iron rust reduction rust-preventive treatment agent (Agent A), which has the function of reducing iron rust (red rust, brown rust), is a reducing phosphoric acid and its compounds, which have high rust-preventive capabilities. Phosphorous acid and hypophosphorous acid are particularly preferred. These reducing phosphoric acid-based mineral acids react with iron rust to reduce iron oxide and also react with steel substrates to form reduced iron phosphate, thereby exhibiting rust prevention properties. The blending ratio of reducing phosphoric acid-based mineral acids is preferably 0.5 to 30% by weight in the paint. If the blending amount of reducing phosphoric acid-based mineral acids is less than 0.5% by weight, the rust prevention performance decreases, and if it exceeds 30% by weight, the coating film strength and water resistance decrease.

Regarding the reducing mineral acid in the above-mentioned iron rust reduction rust inhibitor (Agent A), reducing phosphoric acid may be added along with reducing phosphoric acid, or reducing phosphoric acid compounds may be added to enhance rust prevention ability. Preferred reducing phosphoric acid compounds include iron phosphate, calcium phosphate, magnesium phosphate, aluminum phosphate, iron hypophosphate, calcium hypophosphate, magnesium hypophosphate, and aluminum hypophosphate. It is preferable to include these reducing phosphoric acid compounds in the iron rust reduction rust inhibitor (Agent A) at an amount of 0.5 to 20% by weight.

The tannic acid used in the iron rust reduction rust inhibitor (Agent A) of the present invention can be persimmon tannin, bark extracts of acacia, mangium, radiata pine, etc., but it is preferable to use tannic acid extracted and purified from gallnuts. The amount of tannic acid in the iron rust reduction rust inhibitor (Agent A) is preferably 1 to 30% by weight. If the amount of tannic acid is less than 1% by weight, adhesion to rust and rust prevention will decrease. If it exceeds 30% by weight, the water resistance and coating performance will decrease significantly.

In the present invention, the iron rust reduction rust-preventive treatment agent (Agent A) preferably contains a lower alcohol with 5 or fewer carbon atoms to enhance the penetration of tannic acid and reducing phosphoric acid compounds. Examples of lower alcohols with 5 or fewer carbon atoms include methanol, ethyl alcohol, propanol, butanol, and pentanol, with ethanol and n-propanol being particularly preferred in terms of penetration and safety. The amount of alcohol with 5 or fewer carbon atoms is 1 to 50% by weight, and a concentration of 10 to 40% by weight is particularly desirable in terms of penetration and coating film strength.

In the present invention, the water-soluble emulsion resin to be contained in the iron rust reduction rust prevention agent (Agent B), which is used to promote the reduction reaction and enhance the waterproofness of the coating film after application of the iron rust reduction rust prevention agent (Agent A), can be acrylic resin emulsion, acrylic-vinyl acetate resin emulsion, acrylic-ethylene vinyl acetate resin emulsion, acrylonitrile-vinyl chloride-vinylidene chloride copolymer emulsion, acrylic urethane resin emulsion, acrylic epoxy resin emulsion, acrylic silicone resin emulsion, etc., and these can be used.

For the water-soluble emulsion resin used in the iron rust reduction rust inhibitor (Agent B), acrylic resin emulsion, acrylic urethane resin emulsion, and acrylic silicone resin emulsion are particularly preferred due to their ease of film formation, penetration into rust, and ease of application. These resins may be used individually or in combination of two or more. The amount of water-soluble emulsion resin in the paint is used in the range of 10 to 95% by weight, but a blend of 30 to 80% by weight is particularly preferred in terms of iron rust reduction reactivity, rust prevention ability, and paint film strength.

In the present invention, it is desirable to include a lower alcohol with 5 or fewer carbon atoms in the iron rust reduction rust-preventive treatment agent (Agent B). Examples of lower alcohols with 5 or fewer carbon atoms include methanol, ethyl alcohol, propanol, butanol, and pentanol, with ethanol and n-propanol being particularly preferred in terms of penetration and safety. The amount of alcohol with 5 or fewer carbon atoms is 1 to 40% by weight, and a concentration of 10 to 30% by weight is particularly desirable in terms of penetration and coating film strength.

The water-based rust-preventive paint of the present invention may contain various known paint additives to improve paint properties (viscosity, gloss, drying speed, film strength, water resistance, etc.) as needed. For example, paint additives such as dispersants like surfactants, leveling agents, viscosity modifiers, plasticizers, crosslinking agents, film strengthening fillers, and coloring pigments may be added.

The present invention's iron rust reduction rust inhibitor (Agent A) is manufactured by blending a reducing phosphoric acid, tannic acid, and a lower alcohol having 1 to 5 carbon atoms as raw materials, and the iron rust reduction rust inhibitor (Agent B) is manufactured by blending a water-soluble emulsion as the main raw material with water and a lower alcohol having 1 to 5 carbon atoms as raw materials, and mixing and dispersing them in a wet disperser.
Since the iron rust reduction rust inhibitor of the present invention is water-based, its concentration and viscosity can be adjusted by diluting it with pure water as needed.

The iron rust reduction rust-preventive treatment agent of the present invention can be applied to a steel substrate without removing the rust layer that has formed on the substrate surface. In other words, topcoat painting can be performed without surface preparation (cleaning), which is a pretreatment of the steel substrate, and it is characterized by reducing the rust layer on the substrate and forming a coating film with excellent rust prevention, corrosion resistance, weather resistance, and adhesion.

Specifically, by applying the iron rust reduction rust inhibitor (Agent A), the contained reducing phosphoric acid mineral acid reduces the red rust and brown rust ( _Fe₂O₃ ) of iron present on the steel substrate to black rust ( _magnetite : _Fe₃O₄ ) through a reduction reaction. At the same time, it reacts with the steel substrate to form a highly rust-preventive reducing iron phosphate film on the steel surface _, which is the interface with the coating film. Furthermore, by applying the iron rust reduction rust inhibitor (Agent B), the contained aqueous emulsion promotes the conversion reaction of iron rust to black rust (magnetite: _Fe₃O₄ ) and the polymerization and crosslinking reactions of the aqueous emulsion. This significantly improves the iron rust reduction reaction of the coating film _, the conversion to black rust, and adhesion, thereby forming a rust-preventive coating film with excellent water resistance, corrosion resistance, and weather resistance.

Furthermore, for the reasons stated above, the water-based rust-preventive paint of the present invention exhibits superior rust prevention and corrosion resistance compared to ordinary iron oxide (red iron oxide)-based primers, even on new steel substrates and steel structures that have not yet rusted.

The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

As an iron rust reduction rust inhibitor (Agent A), 50 g of phosphorous acid, 150 g of tannic acid, 150 g of ethanol, 50 g of n-propanol, and 600 g of pure water were placed in a wet disperser and mixed and dispersed to obtain the water-based rust inhibitor paint (Agent A) of Example 1. The mixing ratio of these raw materials is shown in Table 1.

As the iron rust reduction rust-preventive treatment agent (Part B), 650 parts by weight of acrylic resin marion (AP1350, manufactured by Showa Polymer Co., Ltd.), 100 g of ethanol, 50 g of n-propanol, and 200 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (Part B) of Example 1. The mixing ratio of these raw materials is shown in Table 2.

On rusted steel plates (Type 4 surface preparation) from which surface rust had been removed, 100 g/ ^m² each of the water-based rust-preventive paint (Part A) and (Part B) were applied, and the plates were left to stand and dry at 25°C for 5 days to prepare test specimens for evaluation.

As evaluation tests for the coated test specimens, a saltwater resistance test and an accelerated weathering test were conducted. In the saltwater resistance test, the test specimens were immersed in 50°C hot water for 1000 hours, after which they were removed and the appearance of the coating was observed for any abnormalities, and a grid tape peel test was also performed. Furthermore, in the accelerated weathering test, the specimens were treated for 3000 hours using a sunshine weatherometer, and the condition of the coating was observed thereafter. The results are shown in Table 4.

As an iron rust reduction rust inhibitor (Agent A), 50 g of calcium phosphite, 150 g of tannic acid, 150 g of ethanol, 50 g of n-propanol, and 600 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust inhibitor paint (Agent A) of Example 2. The formulation table is shown in Table 1.

As the iron rust reduction rust-preventive treatment agent (Part B), 650 parts by weight of acrylic resin emulsion (AP1350, manufactured by Showa Polymer), 100 g of ethanol, 50 g of n-propanol, and 200 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (Part B) of Example 2. The mixing ratio of these raw materials is shown in Table 2.

The two-component water-based rust-preventive coating obtained in Example 2 was applied to test pieces in which iron rust had been induced, in the same manner as in Example 1. A saltwater resistance test and an accelerated weathering test were then performed on this rust-preventive coating film in the same manner as in Example 1. The measurement results are shown in Table 4.

As an iron rust reduction rust inhibitor (Agent A), 50 g of aluminum phosphate, 150 g of tannic acid, 150 g of ethanol, 50 g of n-propanol, and 600 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust inhibitor paint (Agent A) of Example 3. The mixing ratio of these raw materials is shown in Table 1.

As the iron rust reduction rust-preventive treatment agent (Part B), 650 parts by weight of acrylic silicone resin emulsion (Nisshin Chemical Co., Ltd. E430), 100 g of ethanol, 50 g of n-propanol, and 200 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (Part B) of Example 3. The formulation table is shown in Table 2.

The two-component water-based rust-preventive coating obtained in Example 3 was applied to test pieces in which iron rust had been induced, in the same manner as in Example 1. Saltwater resistance tests and accelerated weathering tests were then performed on this rust-preventive coating film in the same manner as in Example 1. The measurement results are shown in Table 4.

As an iron rust reduction rust inhibitor (Agent A), 50 g of hypophosphorous acid, 150 g of tannic acid, 150 g of ethanol, 50 g of n-propanol, and 600 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust inhibitor paint (Agent A) of Example 4. The mixing ratio of these raw materials is shown in Table 1.

As the iron rust reduction rust-preventive treatment agent (Part B), 650 parts by weight of acrylic resin marion (AP1350, manufactured by Showa Polymer Co., Ltd.), 100 g of ethanol, 50 g of n-propanol, and 200 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (Part B) of Example 4. The formulation table is shown in Table 2.

The two-component water-based rust-preventive coating obtained in Example 4 was applied to test pieces in which iron rust had been induced, in the same manner as in Example 1. Saltwater resistance tests and accelerated weathering tests were then performed on this rust-preventive coating film in the same manner as in Example 1. The measurement results are shown in Table 4.

As an iron rust reduction rust inhibitor (Agent A), 50 g of calcium hypophosphite, 150 g of tannic acid, 150 g of ethanol, 50 g of n-propanol, and 600 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust inhibitor paint (Agent A) of Example 5. The mixing ratio of these raw materials is shown in Table 1.

As the iron rust reduction rust-preventive treatment agent (Part B), 650 parts by weight of acrylic silicone resin emulsion (Nisshin Chemical Co., Ltd. E430), 100 g of ethanol, 50 g of n-propanol, and 200 g of pure water were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (Part B) of Example 5. The formulation table is shown in Table 2.

The two-component water-based rust-preventive coating obtained in Example 5 was applied to test pieces in which iron rust had been induced, in the same manner as in Example 1. A saltwater resistance test and an accelerated weathering test were then performed on this rust-preventive coating film in the same manner as in Example 1. The measurement results are shown in Table 4.

Comparative Example

The following are comparative examples.

Comparative Example 1

Acrylic resin emulsion (AP1350, manufactured by Showa Polymer): 650 parts by weight, phosphoric acid: 50 g, tannic acid: 150 g, and pure water: 250 g were added to a wet disperser and mixed and dispersed to obtain the water-based rust-preventive paint (one-component type) of Comparative Example 1. The formulation table is shown in Table 3.
Then, similar to Example 1, 100 g/ ^m² of this water-based rust-preventive paint (one-component type) was applied to a rust-affected steel plate (Type 4 surface treatment) from which surface rust had been removed, and the plate was left to stand and dry at 25°C for 5 days to prepare the test specimens for evaluation. The applied coating was evaluated in the same manner as in Example 1, and the measurement results are shown in Table 5.

Comparative Example 2

Comparative Example 2, a water-based rust-preventive coating (one-component type), was prepared by blending 650 parts by weight of acrylic resin emulsion (AP1350, manufactured by Showa Polymer), 150 parts by weight of tannic acid, 50 parts by weight of calcium phosphate, and 250 parts by weight of pure water. The coating film was then evaluated in the same manner as in Example 1, and the measurement results are shown in Table 5.

Comparative Example 3

Acrylic silicone resin emulsion (AP1350, manufactured by Showa Polymer): 650 parts by weight, tannic acid: 150 parts by weight, aluminum phosphate: 50 parts by weight, and pure water: 250 parts by weight were added and mixed and dispersed to obtain Comparative Example 3, a water-based rust-preventive paint (one-component type). The coating film was then evaluated in the same manner as in Example 1, and the measurement results are shown in Table 5.

Claims (5)

A rust-reducing rust-preventive treatment agent (Agent A) for pre- treatment of iron rust in painting on steel substrates, characterized in that it contains a reducing substance that reduces iron rust on the substrate, a reducing phosphoric acid-based mineral acid, and further tannic acid and alcohols with 5 or fewer carbon atoms,
A rust reduction and rust prevention treatment agent (Agent B) containing a water- soluble emulsion resin and a lower alcohol with 5 or fewer carbon atoms, wherein the amount of the water-soluble emulsion resin is in the range of 30 to 80% by weight, thereby enhancing the waterproofness of the coating film and further promoting the reduction reaction of iron rust in the layer beneath the applied coating film,
A two-component iron rust reduction rust prevention treatment agent characterized by being applied by coating. The two-component iron rust reduction and rust prevention agent according to claim 1, characterized in that the reducing phosphoric acid mineral acid as the iron rust reducing substance in the iron rust reduction and rust prevention agent (Agent A) contains at least one of hypophosphorous acid and phosphorous acid. A two-component iron rust reduction and rust prevention agent according to claim 1 or 2, characterized in that, as a component of the iron rust reduction and rust prevention agent (Agent A), a reducing phosphoric acid-based mineral acid is combined with a reducing phosphoric acid compound, and the reducing phosphoric acid compound contains at least one compound of reducing phosphoric acid of zinc , aluminum, and calcium . A two-component iron rust reduction and rust prevention agent according to any one of claims 1 to 3, characterized in that the iron rust reduction and rust prevention agent (agent B) is formulated with at least one of acrylic emulsion and acrylic silicone emulsion as the water-soluble emulsion resin. A rust prevention method characterized by applying two layers of a rust-reducing rust-preventive treatment agent (Agent A), which reduces iron rust on the steel substrate to prevent rust, and a rust-reducing rust-preventive treatment agent (Agent B), which further promotes the reduction reaction of iron rust, to the substrate in a pretreatment of a steel substrate, wherein the rust prevention treatment is performed using a two-component rust-reducing rust-preventive treatment agent according to any one of claims 1 to 4.