Rust inhibitor, method for manufacturing the same, and method for coating metal surfaces

Abstract

To provide a rust inhibitor that is less likely to run off the target object after application, is easy to remove, and has a low environmental impact, as well as a method for manufacturing the same and a method for coating metal surfaces. [Solution] An emulsion containing an oily component, an emulsifier, and water, wherein the oily component content is 5 to 45% by mass, the emulsifier content is 0.5 to 10% by mass, and the water content is 50 to 90% by mass, and the water is a rust inhibitor containing a phosphate as a rust-preventive component. This rust inhibitor is obtained by mixing a rust-preventive component or an aqueous solution of a rust-preventive component with an emulsion base containing an oily component, an emulsifier, and water. The rust inhibitor of the present invention is less likely to run off the object after application, is easy to remove, and has a low environmental impact. The rust inhibitor of the present invention is particularly suitable for temporary surface rust prevention after surface polishing in metal surface painting, and furthermore, it can be used to provide a painting method with a low environmental impact.

Description

Technical Field

[0001] The present invention relates to a rust preventive agent, a method for producing the same, and a method for coating a metal surface using the rust preventive agent.

Background Art

[0002] Conventionally, in the field of steel members such as reinforcing bars and steel frames, a rust prevention treatment is performed by applying a rust preventive oil to the surface of the members to prevent the occurrence of rust. The rust preventive oil is generally a mixture containing rust preventive components such as metal sulfonates and amines, and there is also provided a rust preventive oil further blended with wax, petrolatum, heavy base oil, etc. in order to maintain the rust preventive effect for a long time (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, such a rust preventive oil may not be suitable for temporarily preventing rust of steel members during processing. For example, when repairing a steel structure composed of reinforcing bars and steel frames, due to process convenience, etc., after performing scarifying grinding to remove old paint films, rust, dirt, etc. on the surface and prepare the base, it cannot be painted immediately, and it is often the case that a rust prevention treatment is performed only for a period of several days to several weeks. When the rust preventive oil is applied at this time, good painting cannot be performed unless the oil film is completely removed before painting. Therefore, it is necessary to remove the oil film using an organic solvent or the like, which has a high environmental load. In addition, since the rust preventive oil has high fluidity and flows down after application, depending on the shape of the object, the rust preventive effect cannot be exerted for a long time and it is necessary to add the rust preventive oil as needed, which has also been a cause of increasing the environmental load.

[0005] Therefore, the present invention aims to provide a rust inhibitor that is less likely to run off the target object after application, is easy to remove, and has a low environmental impact, a method for manufacturing the same, and a method for painting a metal surface using this rust inhibitor. [Means for solving the problem]

[0006] The above problems are solved by the invention having the configuration shown below. [1] An oil-in-water emulsion comprising an oily component, an emulsifier, and water, wherein the oily component content is 5 to 45% by mass, the emulsifier content is 0.5 to 10% by mass, the water content is 50 to 90% by mass, and the water contains a phosphate as a rust-preventive component. [2] The rust inhibitor according to [1], characterized in that the oily component content is 10 to 45% by mass, the water content is 50 to 65% by mass, and the rust inhibitor is in a creamy state. [3] A rust inhibitor as described in [1] or [2], used to suppress corrosion between the time a metal surface is polished and painted. [4] A method for producing a rust inhibitor, characterized by mixing a phosphate or an aqueous solution of the rust inhibitor with an oil-in-water emulsion base material containing an oily component, an emulsifier, and water. [5] A method for painting a metal surface, characterized by applying a rust inhibitor described in [1] or [2] to a metal surface that has been scraped, wiping off the applied rust inhibitor, and then applying an oil-based or water-based paint. [Effects of the Invention]

[0007] The rust inhibitor of the present invention is an oil-in-water emulsion with a certain viscosity and does not easily run off the target object after application. Furthermore, the rust inhibitor of the present invention can be removed to an extent that does not affect subsequent painting simply by wiping or scraping it off with a cloth after application. Therefore, it is easy to remove and contributes to reducing the environmental burden. Furthermore, due to its ease of wiping, the rust inhibitor of the present invention is suitable for rust prevention on metal surfaces before painting, and can be suitably used to suppress corrosion between the time of surface preparation and painting. After wiping, a good coating film with excellent adhesion can be easily and efficiently formed regardless of whether an oil-based or water-based paint is applied, eliminating the need to remove the rust inhibitor using organic solvents, thus providing a painting method with a low environmental impact. [Brief explanation of the drawing]

[0008] [Figure 1] This is a photograph showing the results of the rust prevention test in the example. [Modes for carrying out the invention]

[0009] Because the rust inhibitor of the present invention is an oil-in-water emulsion, it has a higher viscosity than conventional rust-preventive oils and is less likely to run off after application. Furthermore, it is easy to remove after application, and a good coating can be obtained in the subsequent painting process with simple removal work such as wiping. Due to these properties, it is particularly suitable for applications requiring temporary rust prevention, such as rust prevention between surface preparation and painting, especially when repairing steel structures. Surface preparation refers to preparing the surface by scraping off old paint, rust, dirt, etc., using power tools or hand tools before painting or repair.

[0010] (Rust inhibitor) The rust inhibitor of the present invention is an oil-in-water emulsion comprising an oily component, an emulsifier, and water containing a rust inhibitor. The oily component content is 5 to 45% by mass, the emulsifier content is 0.5 to 10% by mass, the water content is 50 to 90% by mass, and the pre-rust inhibitor is a phosphate salt. In this invention, the water content in the rust inhibitor refers to the percentage of pure water, expressed by mass, from the water contained in the rust inhibitor, excluding solutes such as rust inhibitors and other additives.

[0011] Examples of oily components include vegetable oils, hydrocarbon oils, and ester oils, which may be naturally derived or synthetic. It is preferable to use components that are low in irritation and toxicity to the human body and have a low environmental impact, and which are also used in existing cosmetic creams. Specifically, although not limited to these, examples of vegetable oils include jojoba seed oil, meadowfoam oil, macadamia seed oil, corn oil, hydrogenated coconut oil, and olive oil. Fatty acids such as stearic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, and squalane, which can also be produced from such animal and vegetable oils, may also be used. Examples of hydrocarbon oils include squalane, mineral oil (liquid paraffin), isohexadecane, isododecane, and hydrogenated polyisobutene. Examples of ester oils include ethylhexyl palmitate, isopropyl myristate, octyldodecanol, trimethylolpropane triisostearate, neopentyl glycol dicaprate, diisostearyl malate, isononyl isononanoate, cetyl lactate, cholesteryl stearate, and decyl oleate, among others.

[0012] The oily component of the present invention may be one of the above components or two or more of them.

[0013] As emulsifiers, various synthetic and natural surfactants can be used, as long as they do not contradict the objectives of the present invention. While not limited to these, specific examples of synthetic surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Among these, nonionic surfactants are preferred due to their low irritancy to the human body. Specific examples of nonionic surfactants include ethylene oxide condensate type surfactants such as polyoxyethylene alkyl ethers, polysorbate 80, and laureth-7, and polyhydric alcohol ester type surfactants such as glyceryl stearate and sorbitan stearate. Among these, those with an HLB value (hydrophile-lipophile-balance) of approximately 8 to 18 are preferred for forming an oil-in-water emulsion, specifically polysorbate 80, laureth-7, and glyceryl stearate.

[0014] The rust inhibitor of the present invention contains water containing a rust-preventive component. A phosphate salt is used as the rust-preventive component. When the rust inhibitor is applied to a metal surface, a passive film mainly composed of phosphate compounds produced by the reaction of phosphate ions with the metal is formed on the metal surface, exhibiting a rust-preventive effect. Therefore, the rust inhibitor of the present invention can be used on various metals in addition to iron, such as zinc.

[0015] Various phosphates can be used as rust inhibitors. Examples include sodium dihydrogen phosphate (NaH2PO4), potassium dihydrogen phosphate (KH2PO4), ammonium dihydrogen phosphate (NH4H2PO4), disodium hydrogen phosphate (Na2HPO4), dipotassium hydrogen phosphate (K2HPO4), ammonium hydrogen phosphate ((NH4)2HPO4), trisodium phosphate (Na2PO4), and tripotassium phosphate (K3PO4). Other polyphosphates may also be used. Among these, sodium dihydrogen phosphate (NaH2PO4) and potassium dihydrogen phosphate (KH2PO4) are preferred because they have low irritancy and environmental impact, high solubility in water, and are easy to prepare at high concentrations regardless of the water content in the emulsion. One type of these phosphate may be used, or two or more types may be used, depending on the type of metal being treated. The amount of phosphate dissolved in water should be approximately 1 to 15% by mass of the total amount of rust inhibitor, but this is not the only option; it should be selected appropriately according to the desired strength of rust prevention.

[0016] In the rust inhibitor of the present invention described above, the oily component, emulsifier, and water content is preferably 5 to 45% by mass for the oily component, 0.5 to 10% by mass for the emulsifier, and 50 to 90% by mass for the water. This results in a stable emulsion with high viscosity that is less likely to run off.

[0017] To increase viscosity further, the oil component should be approximately 10-45% by mass, the emulsifier 0.5-10% by mass, and the water 50-65% by mass. This will result in a creamy rust inhibitor that is less likely to run off for several weeks, even when applied to vertical or downward-facing surfaces. It also improves weather resistance, maintaining its rust-preventive effect even when exposed to wind, rain, and sea breeze. In this specification, the term "cream-like" refers to a cream shape that is not liquid, that is, it has no fluidity at room temperature or has very little fluidity. Specifically, it preferably has a viscosity of 5 Pa·s or more at room temperature (20°C). More preferably, it is about 10 to 1000 Pa·s from the viewpoints of ease of application and ease of removal. In addition to the above composition, a thickening agent may be used to increase the viscosity.

[0018] The rust inhibitor of the present invention has the above oil component, emulsifier, water and rust prevention component as essential components, but additives may be appropriately added to adjust the properties of the rust inhibitor in addition to these. Examples of additives include moisturizing agents, pH adjusters, thickening agents, emulsion stabilizers, preservatives, and the like. Any of these additives may be water-soluble or oil-soluble.

[0019] Examples of the moisturizing agent include glycerin and butylene glycol. Examples of the pH adjuster include potassium hydroxide, sodium hydroxide, acetic acid, and the like. Examples of the thickening agent include polysaccharides such as cellulose, proteins such as collagen, synthetic thickening agents such as polyacrylamide, polyethylene glycol, sodium polyacrylate, carbomer, and emulsion thickening agents such as polyacrylamide / (C13,C14) isoparaffin / laureth-7 (manufactured by Seppic, SEPIGEL305). Examples of the emulsion stabilizer include behenyl alcohol, cetyl alcohol, and the like. Examples of the preservative include paraoxybenzoic acid esters such as propyl paraben and methyl paraben, benzoic acid, salicylic acid, phenol, phenoxyethanol, and the like.

[0020] Any of these additives can be used alone or in combination of two or more. Also, the content of any additive is preferably 0 to 15% by mass. In particular, for the thickener, since it greatly affects the viscosity of the rust preventive agent, when adding, the content is preferably 0.1 to 5% by mass. If the concentration exceeds this, the viscosity may become extremely high and coating may be difficult. Considering the ease of coating during the coating operation, it is more preferable to be about 0.1 to 2.5% by mass.

[0021] The rust preventive agent of the present invention having the above configuration is difficult to flow down from the coated surface and can prevent the contact between the metal surface coated with the rust preventive agent and external water and air. And, a passive film composed of a compound of a metal and phosphoric acid can be formed on the surfaces of various metals including steel materials, and the rust preventive effect can be maintained even after the removal of the rust preventive agent.

[0022] Also, before painting the object coated with the rust preventive agent of the present invention, it is only necessary to wipe off the applied rust preventive agent until visual removal can be confirmed. Even if the rust preventive agent of the present invention is removed as simply as this, it does not adversely affect the subsequent painting of oil-based / water-based paints. Therefore, processes such as complete degreasing using an organic solvent and rinsing with a cleaning agent are not required, and it can contribute to reducing the environmental load. Furthermore, combined with the effect of forming a passive film with high coating film adhesion, a good coating film with excellent adhesion can be easily and efficiently formed.

[0023] Due to the above effects, the rust preventive agent of the present invention can be particularly preferably used for rust prevention for several days to several weeks from after chipping grinding of the metal surface to painting, such as when repairing metal structures such as steel structures. Also, when painting the metal surface, by using the rust preventive agent of the present invention for rust prevention after chipping grinding, there is no need to remove the rust preventive agent using an organic solvent or the like, and a painting method for a metal surface with a low environmental load can be provided.

[0024] (Method for manufacturing rust preventive agent) The rust inhibitor of the present invention can be manufactured by mixing a rust inhibitor component or an aqueous solution of a rust inhibitor component with an oil-in-water emulsion base material comprising an oily component, an emulsifier, and water.

[0025] The emulsion base is an oil-in-water emulsion containing approximately 5-45% by mass of oily components, 0.5-10% by mass of emulsifiers, and 50-90% by mass of water. However, the content of each component is not limited to these amounts and can be adjusted as appropriate to achieve the desired concentration after mixing with the rust inhibitor or its aqueous solution. Specific examples of the oily components and emulsifiers used are as described above. The emulsion base may be prepared by thoroughly mixing these components, or a commercially available cosmetic cream or other base with a similar composition may be used.

[0026] After preparing the emulsion base material, the aforementioned phosphate or an aqueous solution thereof is prepared as a rust inhibitor component and added to the emulsion base material in a predetermined amount and mixed. As a result, the phosphate dissolves in the water contained in the emulsion base material, and the rust inhibitor of the present invention is obtained.

[0027] If additives such as humectants or thickeners are to be added, they may be mixed into the emulsion base material beforehand, or they may be mixed at the same time as or after the mixing of the rust-preventive components. [Examples]

[0028] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0029] 1. Preparation of rust inhibitor (Example 1) Each raw material was weighed and thoroughly mixed to obtain base material 1, which is a creamy oil-in-water emulsion, to achieve the composition shown in Table 1. 6 g of sodium dihydrogen phosphate was dissolved in a small amount of water and mixed with base material 1 to obtain the rust inhibitor of Example 1. (Example 2) In the same manner as in Example 1, base material 2 was obtained to have the composition shown in Table 1, and 6 g of sodium dihydrogen phosphate was dissolved in a small amount of water and mixed to obtain the rust inhibitor of Example 2. (Example 3) In the same manner as in Example 1, base material 3 was obtained to have the composition shown in Table 1, and 6 g of sodium dihydrogen phosphate was dissolved in a small amount of water and mixed to obtain the rust inhibitor of Example 3. (Comparative Example 1) The same substrate 1 used in Example 1 was used as Comparative Example 1.

[0030] [Table 1]

[0031] The compositions of the rust inhibitors in Examples 1-3 are shown in Table 1. They were prepared to contain approximately 50-65% by mass of water, 10-30% by mass of oily components, and 2-4% by mass of emulsifiers. In addition, approximately 8-11% by mass of butylene glycol and glycerin were added as humectants, and 1-2% by mass of polyacrylamide was added as a thickener. The rust inhibitors in Examples 1-3 were all in cream form.

[0032] 2. Rust prevention test After polishing the surface of an iron plate (50 mm long, 50 mm wide, 2 mm thick), 2 mL of the rust inhibitor from the example or comparative example was applied uniformly. After 48 hours, the rust inhibitor was wiped off, and the surface condition was observed visually and with a scanning electron microscope equipped with an energy-dispersive fluorescent X-ray analyzer. Subsequently, the iron plate was placed outdoors to observe further changes in the surface.

[0033] As a result, after 48 hours, pinpoint rust was visible to the eye on the iron plate coated with comparative example substrate 1. On the other hand, no rust was observed on the iron plates coated with the rust inhibitors of Examples 1 to 3. When the surface of the iron plates was observed with a scanning electron microscope, no surface changes were observed on the iron plate coated with the comparative example cream, but it was confirmed that a passivation film consisting of iron phosphate had formed on the surface of the iron plate coated with the rust inhibitor of Example 1.

[0034] After placing the iron plates outdoors, no rust was observed in the iron plates treated with the rust inhibitor of Example 1 for 18 days (Figure 1, top). The same was true for Examples 2 and 3. On the other hand, when the comparative cream was used, numerous pinpoint rust spots appeared after 4 days of being placed outdoors, and then red rust developed over the entire surface (Figure 1, bottom).

[0035] From the above results, it was confirmed that the rust inhibitors of the present invention in Examples 1 to 3 not only exhibit rust-preventive effects during application, but also maintain their rust-preventive effect even after removal due to the formation of a passive film.

[0036] 3. Painting Test After sanding the surface of a steel plate (50mm long, 50mm wide, 2mm thick), the rust inhibitor from Example 1 was applied to the surface. It was then left outdoors for one week. Afterward, the rust inhibitor was wiped off with a cloth, and the surface was painted with water-based paint (Taiho Kohzai Co., Ltd., Water-based Automotive Chassis Rust Inhibitor, Chassis Black W). As a result, no paint repulsion, color unevenness, or unevenness was observed during painting. Furthermore, no defects such as blistering or peeling of the paint film were observed after drying. Similarly, no painting defects were observed when painting with oil-based paint (Top Stars Co., Ltd., EML-containing Shield Black). These results show that the rust inhibitor of the present invention is easy to remove, and that a good coating with excellent adhesion can be obtained even when painting after the rust inhibitor has been removed.

Claims

1. An oil-in-water emulsion comprising an oily component, an emulsifier, and water, The content of the oily component is 5 to 45% by mass. The emulsifier content is 0.5 to 10% by mass. The water content is 50 to 90% by mass. The aforementioned water is a rust inhibitor characterized by containing phosphate as a rust-preventive component.

2. The content of the oily component is 10 to 45% by mass. The water content is 50 to 65% by mass. The rust inhibitor according to claim 1, characterized in that it is in a creamy state.

3. A rust inhibitor according to claim 1 or 2, used to suppress corrosion between the time of surface preparation (scaling and polishing) of a metal surface and the time of painting.

4. A method for producing a rust inhibitor, characterized by mixing a phosphate or an aqueous solution of the rust inhibitor with an oil-in-water emulsion base material containing an oily component, an emulsifier, and water.

5. A method for painting a metal surface, characterized by applying a rust inhibitor according to claim 1 or 2 to a metal surface after surface polishing, wiping off the applied rust inhibitor, and then applying an oil-based or water-based paint.

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