Rust-preventive paint compositions, rust-preventive coatings, and articles, as well as zinc-based composite particles and compositions containing zinc-based composite particles.

Abstract

Provided are a rust preventive pigment capable of achieving both high stability in water or an aqueous medium, and excellent rust preventive capability and adhesion of an obtained rust preventive film, and a rust preventive coating composition with which a rust preventive film can be obtained that excels in stability of a rust preventive pigment and that excels in rust preventive capability and adhesion. The rust preventive coating composition of the present invention contains a rust preventive pigment comprising one or more among particles of zinc or a zinc alloy that has had at least a portion of the surface thereof treated with phosphoric acid.

Description

[Technical Field]

[0001] This invention relates to rust-preventive paint compositions, rust-preventive coatings, and articles. It also relates to zinc-based composite particles useful for water-based paints and the like, and to compositions containing zinc-based composite particles. [Background technology]

[0002] Conventionally, to prevent corrosion of metals or alloys such as iron, rust-preventive paint compositions containing zinc or zinc alloy particles, or zinc or zinc alloy particles with modified surfaces, have been widely known and used as rust-preventive pigments.

[0003] For example, Patent Document 1 discloses a zinc-rich paint (a rust-preventive paint containing a high concentration of zinc powder in an inorganic or organic binder) whose main components are a pigment slurry obtained by mixing zinc flakes with alcohol and / or ketones, and a silicate-based binder for binding the zinc flakes.

[0004] Patent Document 2 discloses a coated zinc-containing metal flake having a colloidal silica film on its surface that exhibits excellent rust prevention, and a paint containing this coated zinc-containing metal flake.

[0005] Patent Document 3 discloses modified metal particles for corrosion-preventive coatings, which are metal particles based on zinc or a zinc alloy having silicon dioxide, and a corrosion-preventive coating composition containing these modified metal particles.

[0006] Furthermore, Patent Documents 4 and 5 also disclose rust-preventive coating compositions (corrosion-preventive coating compositions) containing particulate metal including zinc or a zinc alloy, a silane-based binder (silane-based binder), and water.

[0007] Furthermore, Patent Document 6 discloses a rust-preventively painted metal product having a coating formed by applying a non-chromium aqueous metal rust-preventive paint to the surface of a metal product to be painted, which is made by mixing flaky metallic zinc powder containing 6 to 35% by weight of flaky metallic aluminum powder as a rust-preventive pigment in an aqueous binder solution containing an aqueous resin emulsion and a water-soluble silane coupling agent as binder components, and a coating formed by applying a non-chromium surface treatment agent mainly composed of silane oligomers with a weight-average molecular weight of 1,000 to 10,000, obtained by hydrolysis and condensation polymerization of alkoxysilanes using alcohols as a solvent, onto the coating. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-73778 [Patent Document 2] Japanese Patent Application Publication No. 6-9897 [Patent Document 3] Japanese Patent Publication No. 2018-70999 [Patent Document 4] Special Publication No. 2007-534794 [Patent Document 5] Japanese Patent Publication No. 2008-280538 [Patent Document 6] Japanese Patent Publication No. 2005-238001 [Overview of the project] [Problems that the invention aims to solve]

[0009] Water-based paint compositions are in demand due to their low environmental impact, but achieving both high stability of anti-corrosion pigments in water or aqueous media, and excellent anti-corrosion performance and adhesion of the resulting anti-corrosion film, is extremely difficult. For example, if the anti-corrosion pigment is zinc or zinc alloy particles, or zinc or zinc alloy particles with a thin silica (silicon dioxide) film on the surface, the stability of the anti-corrosion pigment in water or aqueous media is low. On the other hand, if the anti-corrosion pigment is zinc or zinc alloy particles with a thick silica (silicon dioxide) film on the surface, the stability of the anti-corrosion pigment in water or aqueous media is high, but sufficient anti-corrosion performance cannot be obtained. Furthermore, if the anti-corrosion pigment is zinc or zinc alloy particles, or zinc or zinc alloy particles with a silica (silicon dioxide) film, the adhesion of the resulting anti-corrosion film tends to be low.

[0010] The present invention aims to provide a rust-preventive pigment capable of achieving both high stability in water or an aqueous medium and excellent rust-preventive performance and adhesion of the resulting rust-preventive film. Furthermore, the present invention aims to provide a rust-preventive paint composition, particularly an aqueous paint composition containing water as a solvent, that yields a rust-preventive film with excellent stability of the rust-preventive pigment and excellent rust-preventive performance and adhesion.

[0011] Furthermore, the present invention also aims to provide zinc-based composite particles that have high stability in water or aqueous media, and compositions containing these zinc-based composite particles. [Means for solving the problem]

[0012] The present invention relates to the following items. [1] A rust-preventive paint composition characterized by containing a rust-preventive pigment consisting of one or more zinc or zinc alloy particles whose surface is treated with phosphoric acid. [2] A rust-preventive paint composition characterized by containing a rust-preventive pigment consisting of one or more zinc or zinc alloy particles having a film on at least a portion of its surface containing at least one selected from inorganic phosphoric acid and inorganic phosphate. [3] The rust-preventive paint composition according to [1] or [2] above, characterized in that the zinc or zinc alloy particles are substantially spherical or flake-shaped. [4] The rust-preventive paint composition according to any one of [1] to [3] above, characterized in that the phosphoric acid is orthophosphoric acid. [5] A rust-preventive paint composition according to any one of the above [1] to [4], characterized in that it further contains water. [6] The rust-preventive paint composition according to any one of [1] to [5] above, further comprising a binder. [7] The rust-preventive paint composition according to [6] above, characterized in that the binder contains at least one selected from silane-based binders and organic binder resins. [8] The rust-preventive paint composition according to any one of the above [1] to [7], characterized in that it further contains a hydrophilic organic solvent in addition to water. [9] The rust-preventive paint composition according to any one of [1] to [8] above, further comprising particles of aluminum or an aluminum alloy as other metallic pigments.

[10] A rust-preventive coating characterized by being obtained by drying or heat-treating any of the rust-preventive coating compositions described in any of [1] to [9] above.

[11] An article having a rust-preventive coating on its surface obtained by drying or heat-treating any of the rust-preventive coating compositions described in [1] to [9] above.

[0013]

[12] A device comprising flake-shaped zinc-containing particles and a coating on its surface containing at least one selected from inorganic phosphoric acid and inorganic phosphate, A zinc-based composite particle characterized in that the phosphorus element content in the coating is 0.05 to 2.5 parts by mass per 100 parts by mass of the flake-shaped zinc-containing particles.

[13] The zinc-based composite particle according to

[12] above, characterized in that the inorganic phosphoric acid is at least one selected from orthophosphate, pyrophosphate, triphosphate, tetraphosphate, and phosphite.

[14] A zinc-based composite particle-containing composition characterized by containing the zinc-based composite particle described in

[12] or

[13] above and an amine compound.

[15] The zinc-based composite particle-containing composition described in

[14] above, wherein the amine compound is a primary amine.

[16] The zinc-based composite particle-containing composition described in

[14] or

[15] above, further characterized by containing a surfactant.

[17] The zinc-based composite particle-containing composition described in

[16] above, wherein the surfactant is a nonionic surfactant. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a rust preventive pigment capable of achieving both high stability in water or an aqueous medium and excellent rust preventive performance and adhesion of the resulting rust preventive film. Further, according to the present invention, it is also possible to provide a rust preventive paint composition having excellent stability of the rust preventive pigment and capable of obtaining a rust preventive film excellent in rust preventive performance and adhesion, particularly an aqueous paint composition containing water as a solvent.

[0015] Furthermore, according to the present invention, it is also possible to provide zinc-based composite particles having high stability even in water or an aqueous medium, and a composition containing such zinc-based composite particles. These zinc-based composite particles can be particularly preferably used as a rust preventive pigment for an aqueous rust preventive paint composition. [Brief Description of the Drawings]

[0016] [[ID=B24]] [Figure 1] FIG. 1 is a graph showing the change over time in the gas generation amount indicating the decomposition in water of the rust preventive pigments (phosphate-treated zinc flakes, untreated zinc flakes, or silica-treated zinc flakes) of Examples 1 to 2 and Comparative Examples 1 to 3. [Figure 2] FIG. 2 is a graph showing the change over time in the gas generation amount indicating the decomposition of the rust preventive pigments (phosphate-treated zinc flakes, untreated zinc flakes, or silica-treated zinc flakes) contained in the paint compositions of Examples 1 to 2 and Comparative Examples 1 to 3. [Figure 3]Figure 3 shows photographs of iron plates coated with the paint compositions of Examples 1-2 and Comparative Examples 1-3, taken 500 hours after the start of the salt spray test. [Figure 4] Figure 4 is a photograph showing the appearance of coating films with different thicknesses formed from the coating compositions of Example 2 and Comparative Examples 1 and 3. [Figure 5] Figure 5 shows photographs of iron plates coated with the paint compositions of Example 3 and Comparative Example 4, taken 24 hours and 72 hours after the start of the salt spray test. [Modes for carrying out the invention]

[0017] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0018] Furthermore, in this specification, terms marked with "abbreviated" indicate the meaning of the term without the "abbreviated" designation, within the scope of common technical knowledge for those skilled in the art, and shall also include the meaning of the term without the "abbreviated" designation.

[0019] <Rust-preventive pigment> The rust-preventive pigment of this embodiment consists of one or more particles of zinc or zinc alloy whose surface is treated with phosphoric acid, preferably all of it. Here, the rust-preventive pigment is used in the rust-preventive paint composition of this embodiment and is not limited to the zinc-based composite particles described later.

[0020] The zinc alloy is not particularly limited and may be any alloy containing zinc. Examples include alloys containing zinc and at least one selected from magnesium, aluminum, nickel, manganese, cobalt, tin, and chromium. The zinc content in the zinc alloy is not particularly limited, but is usually preferably 50% by mass or more, and more preferably 55% by mass or more.

[0021] In this embodiment, zinc particles and zinc-aluminum alloy particles (Zn-Al alloys) are preferred as zinc or zinc alloy particles.

[0022] The shape of the zinc or zinc alloy particles used in this embodiment is not particularly limited and may include, for example, approximately spherical, flake-shaped, flaky, plate-shaped, or laminar-shaped particles. However, it is generally preferable that the particles be approximately spherical or flake-shaped, and more preferably flake-shaped. It is also possible to use a combination of two or more zinc or zinc alloy particles with different shapes.

[0023] When zinc or zinc alloy particles are substantially spherical in shape, their average particle size is generally preferably 15 μm or less, and more preferably 1 to 10 μm, although this is not particularly limited. The average particle size of substantially spherical zinc or zinc alloy particles can be measured using a general laser diffraction particle size distribution analyzer. Examples include the LA-960V2 laser diffraction / scattering particle size distribution analyzer manufactured by Horiba, Ltd., and the Microtrac® MT3000II manufactured by Microtrac-Bell, Inc.

[0024] When the zinc or zinc alloy particles are in flake form, the average major axis is preferably 2 to 50 μm, more preferably 3 to 30 μm, and the average thickness is preferably 5 μm or less, more preferably 0.1 to 3 μm, although this is not particularly limited. The average aspect ratio (major axis / thickness) is preferably in the range of 1.5 to 500, more preferably in the range of 10 to 200. The average major axis and average thickness of flake-shaped zinc or zinc alloy particles can be measured using a general laser diffraction particle size distribution analyzer. Examples include the LA-960V2 laser diffraction / scattering particle size distribution analyzer manufactured by Horiba, Ltd., and the Microtrac® MT3000II manufactured by Microtrac-Bell, Inc.

[0025] The zinc or zinc alloy particles may have a smooth surface or not; for example, the surface may have irregularities such as ridges or bumps. The surface condition of the zinc or zinc alloy particles is not particularly limited. The zinc or zinc alloy particles may have undergone physical treatments such as surface roughening or rolling, or chemical treatments such as oxidation. By performing such physical or chemical treatments, the physical properties of the particles can be modified, changing their color (such as blackening) or imparting gloss.

[0026] In this embodiment, the rust-preventive pigment is characterized by having at least a portion, preferably all, of the surface of zinc or zinc alloy particles treated with phosphoric acid, and a film containing a phosphoric acid-modified layer, such as at least one selected from inorganic phosphoric acid and inorganic phosphate, is formed on at least a portion, preferably all, of the surface. However, "treated with phosphoric acid" here means treated with phosphoric acid or phosphate ions, and the compound used for treatment is not limited to phosphoric acid, but may be a phosphate compound that hydrolyzes to produce phosphate ions.

[0027] This surface treatment can also be carried out using an organic or inorganic phosphate compound (such as a phosphate salt) that hydrolyzes to produce phosphate ions, but it is preferable to use inorganic phosphate. As the inorganic phosphate, any of the following can be preferably used, such as orthophosphate, pyrophosphate, triphosphate, tetraphosphate, metaphosphate, or phosphite, but orthophosphate is more preferable. One type of inorganic phosphate may be used alone, or two or more types may be used in combination.

[0028] The rust-preventive pigment of this embodiment, which consists of zinc or zinc alloy particles whose surface is treated with phosphoric acid (preferably all of it), can be suitably manufactured by surface-treating the zinc or zinc alloy particles, for example, by uniformly kneading the zinc or zinc alloy particles with inorganic phosphoric acid, preferably orthophosphoric acid, a hydrophilic organic solvent, a small amount of water, an amine compound, and a surfactant. However, the method for manufacturing the rust-preventive pigment of this embodiment is not limited to this method.

[0029] In this embodiment, surface treatment with phosphoric acid is preferable to be performed in the presence of a small amount of water. However, if water alone is used as the solvent, it may not be possible to perform the surface treatment well and stably. Furthermore, by using an amine compound, the generation of hydrogen due to the reaction between zinc and water can be suppressed, allowing for more stable surface treatment of zinc or zinc alloy particles with phosphoric acid. Additionally, by using a surfactant, particle aggregation can be prevented, resulting in better dispersibility and allowing for more effective surface treatment of zinc or zinc alloy particles with phosphoric acid.

[0030] The hydrophilic organic solvent used has an SP value of 8-12 (cal / cm³) determined by the Fedors method. 3 ) 1 / 2 It is preferable that the hydrogen bonding force term δh of the SP value determined by the Hansen method is 6 (cal / cm²). 3 ) 1 / 2 It is preferable that the above conditions are met.

[0031] The hydrophilic organic solvents that can be used are not particularly limited, but examples include propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, diacetone alcohol, amyl alcohol, isoamyl alcohol, polyoxyethylene glycol, and polyoxypropylene glycol. The hydrophilic organic solvent may be used alone or in combination of two or more types.

[0032] The amine compound used is preferably a primary amine, and more preferably an aliphatic amine. It is more preferable that the amine compound used is an aliphatic primary amine. The amine compounds that can be used are not particularly limited, but examples include ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, dodecylamine (laurylamine), tridecylamine, tetradecylamine, hexadecylamine, octadecylamine (stearylamine), isopropylamine, isobutylamine, 2-ethylhexylamine, isotridecylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dioctylamine, dilaurylamine, ditridecylamine, distearylamine, diisopropylamine, diisobutylamine, di(2-ethylhexyl)amine, Diisotridecylamine, methylbutylamine, ethylbutylamine, ethylhexylamine, ethyl laurylamine, ethyl stearylamine, isopropyloctylamine, isobutyl 2-ethylhexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tritridecylamine, tristearylamine, triisopropylamine, triisobutylamine, tris(2-ethylhexyl)amine, triisotridecylamine, dimethyloctylamine, dimethyllaurylamine, dimethylstearylamine, diethyllaurylamine, allylamine, diallylamine, triallylamine, N,N-dimethylallylamine, cyclohexylamine, 2-methylcyclohexylamine, benzylamine, 4-methylbenzylamine, dicyclohexylamine, di-2-methylcyclohexylamine, dibenzylamine, di-4-methylbenzylamine, cyclohexyl-2-ethylhexylamine, cyclohexylbenzylamine, stearylbenzylamine, 2-ethylhexylbenzylamine, dimethylbenzylamine, dimethylcyclohexylamine, tricyclohexylamine, tribenzylamine, tri-4-methylbenzylamine, morpholine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-butoxypropylamine, 3-decyloxypropylamine, 3-lauryloxypropylamine, monoethanolamine, diethanolamine, monoisopropanolamine, monopropanolamine, butanolamine, triethanolamine, N,N-dimethylethanolamine, N-methyl N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-cyclohexyl-N-methylaminoethanol, N-benzyl-N-propylaminoethanol, N-hydroxyethylpyrrolidine, N-hydroxyethylpiperazine, N-hydroxyethylmorpholine, ethylenediamine, 1,2-propanediamine, 1,3-propylethanolamine Examples include ropanediamine, N,N-dimethyl-1,3-propanediamine, N-cyclohexyl-1,3-propanediamine, N-decyl-1,3-propanediamine, N-isotridecyl-1,3-propanediamine, N,N-dimethylpiperazine, N-methoxyphenylpiperazine, N-methylpiperidine, N-ethylpiperidine, quinuclidine, diazabicyclo[2,2,2]octane, and 1,8-diazabicyclo[5,4,0]-7-undecene. Amine compounds may be used individually or in combination of two or more.

[0033] The surfactant used is preferably a nonionic surfactant, preferably with an HLB value of 8 or higher, and more preferably between 8 and 13. While not particularly limited, examples of surfactants that can be used include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkylamide, polyoxyethylene higher alcohol ether, polyoxyalkylene alkyl ether, polyoxyethylene polyoxypropylene glycol, polyethylene glycol fatty acid ester, glycerin fatty acid ester, propylene glycol fatty acid ester, alkyl glyceryl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. A single surfactant may be used, or two or more may be used in combination.

[0034] The amount of inorganic phosphoric acid (preferably orthophosphoric acid) added is not particularly limited and can be selected as appropriate, but is usually preferably 0.1 to 10 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 0.5 to 5 parts by mass per 100 parts by mass of zinc or zinc alloy particles. Furthermore, the phosphorus content in the coating formed on the surface of the zinc or zinc alloy particles, which contains at least one selected from inorganic phosphoric acid and inorganic phosphate, is not particularly limited, but is usually preferably 0.05 to 2.5 parts by mass, and more preferably 0.2 to 1.5 parts by mass per 100 parts by mass of zinc or zinc alloy particles.

[0035] The amount of hydrophilic organic solvent added is not particularly limited and can be selected as appropriate, but is generally preferably 5 to 100 parts by mass, and more preferably 10 to 60 parts by mass, per 100 parts by mass of zinc or zinc alloy particles.

[0036] The amount of water added is not particularly limited and can be selected as appropriate, but is generally preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of zinc or zinc alloy particles.

[0037] The amount of amine compound added is not particularly limited and can be selected as appropriate, but is generally preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of zinc or zinc alloy particles.

[0038] The amount of surfactant added is not particularly limited and can be selected as appropriate, but is generally preferably 0.1 to 20 parts by mass, and more preferably 0.3 to 10 parts by mass, per 100 parts by mass of zinc or zinc alloy particles.

[0039] During the mixing process, the mixed product may further contain hydrophilic organic solvents and solvents other than water (non-hydrophilic organic solvents), but generally, the lower the content, the better. Specifically, it is preferable that the content be 50 parts by mass or less per 100 parts by mass of zinc or zinc alloy particles. Commercially available zinc or zinc alloy particles (compositions) dispersed in a dispersion medium such as aliphatic or aromatic hydrocarbon oil can be used as is, or, if necessary, the solvent in the dispersion medium can be removed, to produce the rust-preventive pigment of this embodiment.

[0040] The mixing process can be carried out using known equipment such as a mixer or kneader.

[0041] The mixing time and temperature are not particularly limited and can be selected as appropriate. The surface treatment (mixing) with phosphoric acid in this embodiment does not need to be performed at high temperatures and can be carried out at relatively low temperatures such as 10-40°C or room temperature.

[0042] Flake-shaped zinc or zinc alloy particles (zinc flakes or zinc alloy flakes) are industrially manufactured by using fatty acids such as stearic acid as a lubricant and smoothing out roughly spherical zinc or zinc alloy particles. After the zinc or zinc alloy particles are made into flakes, it is difficult to completely remove the fatty acids used as a lubricant, and conventional surface treatments that form silica films may be inhibited. However, in the phosphoric acid surface treatment of this embodiment, fatty acids are efficiently removed from the surface of the zinc or zinc alloy particles, so this problem does not occur.

[0043] In this way, the rust-preventive pigment of this embodiment, which consists of zinc or zinc alloy particles whose surface is treated with phosphoric acid at least a portion, preferably all, of the surface, can be obtained in the form of a paste or composition containing the rust-preventive pigment of this embodiment, a hydrophilic organic solvent, and water. The rust-preventive pigment of this embodiment may be separated from the obtained paste or composition by filtration or the like, but the paste or composition containing the obtained rust-preventive pigment of this embodiment can be used as is, or if necessary, the solvent can be removed, or a new solvent can be added, to manufacture a rust-preventive paint composition.

[0044] <Rust-preventive coating composition> The rust-preventive paint composition of this embodiment contains the rust-preventive pigment of this embodiment as described above.

[0045] The rust-preventive coating composition of this embodiment may contain only one or more organic solvents, but it is preferable that the solvent is water, or a mixture of water and one or more organic solvents (aqueous solvent), which is an aqueous coating composition. That is, the rust-preventive coating composition of this embodiment preferably contains water as a solvent, and may further contain an organic solvent, preferably a hydrophilic organic solvent, in addition to water.

[0046] When the solvent is a mixture of water and an organic solvent (aqueous solvent), the organic solvent used is preferably a hydrophilic organic solvent. The organic solvent contained in the rust-preventive paint composition of this embodiment may be a hydrophilic organic solvent used in the production of the rust-preventive pigment of this embodiment and contained in the resulting paste or composition. The organic solvent contained in the rust-preventive paint composition of this embodiment also has an SP value of 8 to 12 (cal / cm³) as determined by the Fedors method. 3 ) 1 / 2 Preferably, the hydrogen bonding force term δh of the SP value determined by the Hansen method is 6 (cal / cm²). 3 ) 1 / 2 It is preferable that the above conditions are met.

[0047] The organic solvents that can be used in the rust-preventive coating composition of this embodiment are not particularly limited, but examples include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol; glycol ethers such as monomethyl ether, monoethyl ether, dimethyl ether, and diethyl ether of these glycols; alcohols such as ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, and diacetone alcohol; and ketones such as acetone and methyl ethyl ketone. Among the organic solvents used, glycols and glycol ethers are preferred. The organic solvents may be used individually or in combination of two or more.

[0048] The content of water or aqueous solvent in the rust-preventive coating composition of this embodiment is not particularly limited, but is usually preferably 30% by mass or more, and more preferably 50 to 85% by mass. In the case of an aqueous solvent, it is preferable that the water content in the solvent is 50% by mass or more, and the organic solvent content is 50% by mass or less.

[0049] The rust-preventive coating composition of this embodiment typically further contains a binder.

[0050] The binder is not particularly limited, and either inorganic or organic binder resins can be used. One type of binder may be used alone, or two or more types may be used in combination.

[0051] The inorganic binder is not particularly limited, but examples include silane compounds such as silane coupling agents, silicates such as sodium silicate, potassium silicate, and lithium silicate, metal alkoxides such as tetraethoxysilane, tetraethoxytitanium, tetraisopropoxytitanium, tetrapropoxyzirconium, triisopropoxyaluminum, and dimethoxyzinc, and silicone resins. Examples of silane coupling agents include vinylsilane coupling agents such as vinyltrimethoxysilane, acrylicsilane coupling agents such as methacrylateoxypropyltrimethoxysilane, aminosilane coupling agents such as 3-aminopropyltrimethoxysilane, and epoxysilane coupling agents such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane. Other inorganic binders that can be used include titanium-based coupling agents such as isopropyltriisostearoyl titanate, aluminum-based coupling agents such as acetalkoxyaluminum diisopropylate, and zirconium-based coupling agents such as zirconium tributoxymonoacetylacetonate.

[0052] Among inorganic binders, silane-based binders such as silane-based coupling agents are preferred.

[0053] The organic binder resin is not particularly limited, but examples include acrylic resin, epoxy resin, phenolic resin, polystyrene resin, polyurethane resin, oxazoline group-containing polymer, and polyvinylpyrrolidone.

[0054] The binder content in the rust-preventive coating composition of this embodiment is not particularly limited and can be appropriately selected depending on the type of binder. When a silane-based binder is used, the silane-based binder content in the rust-preventive coating composition of this embodiment is not particularly limited, but is usually preferably 3 to 20% by mass, and more preferably 4 to 16% by mass.

[0055] The rust-preventive paint composition of this embodiment contains one or more rust-preventive pigments of this embodiment, i.e., zinc or zinc alloy particles whose surface is treated with phosphoric acid, but may further contain other metal pigments.

[0056] The metal pigments other than the rust-preventive pigments of this embodiment (hereinafter also referred to as "other metal pigments") are not particularly limited, but examples include particles of aluminum or aluminum alloys, manganese or manganese alloys, nickel or nickel alloys, titanium or titanium alloys, tin or tin alloys, iron or iron alloys, magnesium or magnesium alloys, cobalt or cobalt alloys, tungsten or tungsten alloys, vanadium or vanadium alloys, molybdenum or molybdenum alloys, tantalum or tantalum alloys, niobium or niobium alloys, stainless steel, and other metal or alloy particles. The other metal pigments may be used individually or in combination of two or more types.

[0057] The shape of the metal or alloy particles, which are other metal pigments, is not particularly limited, but is generally preferably approximately spherical or flake-shaped, and more preferably flake-shaped. Furthermore, at least a portion of the surface of the other metal pigments may be treated with, for example, silica or an aliphatic carboxylic acid.

[0058] In one embodiment, the rust-preventive paint composition of this embodiment preferably further contains aluminum or aluminum alloy particles in addition to the rust-preventive pigment of this embodiment.

[0059] The content of the rust-preventive pigment (the rust-preventive pigment of this embodiment and other metal pigments) in the rust-preventive paint composition of this embodiment is not particularly limited, but is usually preferably 10 to 50% by mass. When aluminum or aluminum alloy particles are used in combination as other metal pigments, the content ratio of the rust-preventive pigment of this embodiment to the aluminum or aluminum alloy particles (rust-preventive pigment:(aluminum or aluminum alloy particles)) in the rust-preventive paint composition is not particularly limited, but is usually preferably 9:1 to 5:5 by mass ratio.

[0060] The rust-preventive paint composition of this embodiment may further contain metal oxide pigments and organic pigments.

[0061] Examples of metal oxide pigments are not particularly limited, but include manganese oxide particles, molybdenum oxide particles, tungsten oxide particles, tin oxide particles, antimony oxide particles, iron oxide particles, aluminum oxide particles, zinc oxide particles, magnesium oxide particles, niobium oxide particles, vanadium oxide particles, tantalum oxide particles, silica particles, titania particles, zirconia particles, silica-alumina particles, silica-titania particles, and silica-magnesia particles.

[0062] Organic pigments are not particularly limited, but examples include β-naphthol pigments, β-oxynaphthoe pigments, pyrazolone pigments, acetoacetate allylide monoazo pigments, acetoacetate allylide disazo pigments, benzimidazolon monoazo pigments, isoindolinone pigments, styrene pigments, isoindoline pigments, and phthalocyanine pigments.

[0063] The rust-preventive paint composition of this embodiment may optionally contain additives such as surfactants, thickeners, inhibitors, lubricants, dispersants, wetting agents, leveling agents, rheology modifiers, pH adjusters, pH stabilizers, film-forming aids, stabilizers, thixotropes, defoamers, UV absorbers, flame retardants, preservatives, antistatic agents, and colorants. Furthermore, the rust-preventive paint composition of this embodiment may also contain amine compounds used in the production of the rust-preventive pigment of this embodiment and contained in the resulting paste or composition. While the rust-preventive pigment of this embodiment exhibits excellent dispersibility and usually does not require the addition of a dispersant, it may be preferable to use a dispersant to stably disperse other metal pigments and additives.

[0064] By adding a surfactant to the rust-preventive coating composition of this embodiment, the adhesion and leveling properties of the resulting rust-preventive film can be improved.

[0065] The surfactants are not particularly limited, but examples include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkylamides, polyoxyethylene higher alcohol ethers, polyoxyalkylene alkyl ethers, polyoxyethylene polyoxypropylene glycol, polyethylene glycol fatty acid esters, glycerin fatty acid esters, propylene glycol fatty acid esters, alkyl glyceryl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; cationic surfactants such as mono, di, or trialkylamine salts, alkyltrimethylammonium halide, dialkyldimethylammonium halide, and alkyldimethylbenzylammonium chloride; and anionic surfactants such as mono or dialkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates, and dialkyl sulfosuccinates. Among these, nonionic surfactants are preferred. One surfactant may be used alone, or two or more may be used in combination. The surfactant contained in the rust-preventive paint composition of this embodiment may be a surfactant used in the production of the rust-preventive pigment of this embodiment and contained in the resulting paste or composition.

[0066] The amount of surfactant in the rust-preventive coating composition of this embodiment is not particularly limited, but is usually preferably 0.01 to 10% by mass.

[0067] A thickening agent can also be added to the rust-preventive paint composition of this embodiment for the purpose of adjusting the viscosity.

[0068] The thickening agent is not particularly limited, but examples include cellulose-based thickening agents such as ethers (cellulose ethers) including methylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, methylethylcellulose, and hydroxypropylcellulose, as well as cellulose nanofibers, xanthan gum, urethane-based thickening agents, acrylic-based thickening agents, modified clay, fatty acid salts, and fatty acid amides. Among the thickening agents used, cellulose ethers are preferred. The thickening agent may be used alone or in combination of two or more types.

[0069] The content of the thickener in the rust-preventive coating composition of this embodiment is not particularly limited, but is usually preferably 0.005 to 2% by mass.

[0070] The rust inhibitor that can be added to the rust-preventive paint composition of this embodiment is a compound that reacts with the exposed metal or alloy surface when the rust-preventive pigment or other metal pigment of this embodiment is damaged in the composition, exposing the metal or alloy surface, and can form a film or modify (repair) the surface.

[0071] The repair agent is not particularly limited, but examples include boron compounds such as boric acid, aluminum compounds such as aluminum hydroxide, gallium compounds such as gallium hydroxide, silicon compounds such as sodium silicate, indium compounds such as indium hydroxide, tin compounds such as tin hydroxide, bismuth compounds such as bismuth hydroxide, vanadate compounds such as lithium vanadate, tungstate compounds such as lithium tungstate, molybdate compounds such as potassium molybdate, cerium compounds such as cerium nitrate, phosphates such as potassium phosphate, amine compounds such as polyethyleneimine, and silicon compounds such as tetraethoxysilane and silane coupling agents. Among the repair agents used, phosphoric acid compounds and bismuth compounds are preferred. The repair agent may be used alone or in combination of two or more. In addition, it may be added in the form of a rust-preventive pigment containing the above compounds, or the above compounds impregnated or supported on zeolite or cellulose nanofiber, or the above compounds encapsulated and contained within, and the method of addition is not particularly limited.

[0072] Furthermore, any excess phosphoric acid or phosphoric acid compound used in the production of the rust-preventive pigment in this embodiment and contained in the resulting paste or composition also functions as a repair agent in the rust-preventive paint composition.

[0073] The content of the repair agent in the rust-preventive coating composition of this embodiment is not particularly limited and can be selected as appropriate, but is generally preferably 10% by mass or less.

[0074] To adjust the coefficient of friction of the rust-preventive coating surface obtained from the rust-preventive coating composition of this embodiment, a lubricant may also be added to the rust-preventive coating composition of this embodiment.

[0075] Lubricants are not particularly limited, but examples include polyolefins and modified polyolefins (polyethylene, modified polyethylene, polypropylene, modified polypropylene, etc.), waxes such as paraffin, carnauba waxes, fluororesins, melamine cyanurate, and hexagonal boron nitride. One lubricant may be used alone, or two or more may be used in combination.

[0076] The lubricant content in the rust-preventive coating composition of this embodiment is not particularly limited and can be appropriately selected to obtain a desired surface friction coefficient, but is generally preferably 20% by mass or less.

[0077] The rust-preventive paint composition of this embodiment can be manufactured by uniformly stirring and mixing the rust-preventive pigment of this embodiment, or a paste or composition containing the rust-preventive pigment of this embodiment, with paint components such as water and / or an organic solvent and a binder, using commonly known methods. The paste or composition containing the rust-preventive pigment of this embodiment used here may also be a paste or composition obtained by uniformly kneading zinc or zinc alloy particles, inorganic phosphoric acid, a hydrophilic organic solvent, and a small amount of water during the manufacture of the rust-preventive pigment of this embodiment.

[0078] <Rust-preventive coatings and articles with rust-preventive coatings> The rust-preventive coating of this embodiment is obtained by drying or heat-treating the rust-preventive paint composition of this embodiment as described above. Furthermore, an article having the rust-preventive coating of this embodiment has the rust-preventive coating obtained by drying or heat-treating the rust-preventive paint composition of this embodiment as described above on its surface, for example, by applying the rust-preventive paint composition of this embodiment to an object to be coated and then drying or heat-treating it.

[0079] The anti-corrosion coating composition of this embodiment can be applied to metal or alloy materials, but is not particularly limited. Examples include aluminum, aluminum alloys, iron, iron alloys, carbon steel, alloy steel, and stainless steel. It can also be applied to metal or alloy surfaces that have undergone surface treatments such as plating, chemical conversion treatments such as oxidation, nitriding, or carbide, or dry plating. In particular, when the object to be coated contains iron or an iron alloy, or has a film or layer containing iron or an iron alloy on its surface, an excellent improvement in corrosion resistance can be obtained, and it can be applied particularly favorably. The object to be coated, or the object to be coated, may be the raw material (metal or alloy material itself), an intermediate product, or a final product, and is not particularly limited.

[0080] The method for applying the rust-preventive coating composition of this embodiment to the object to be coated is not particularly limited and can be carried out by any known method, but it is preferable to use methods such as the dip method (immersion method), dip-spin method (immersion method with centrifugal shaking), spray coating method, or spin coating method. It can also be applied using a roller, doctor blade, bar coater, brush, etc. The application conditions are also not particularly limited and can be selected as appropriate.

[0081] After applying the rust-preventive coating composition of this embodiment to the object to be coated, it is dried or heat-treated to form the rust-preventive coating of this embodiment. After drying at a relatively low temperature, heat treatment may be performed at a higher temperature.

[0082] The drying and heat treatment methods and conditions are not particularly limited and can be selected as appropriate, but it is generally preferable to heat the rust-preventive coating composition applied to the object to be coated to 60 to 400°C to remove the solvent and form a rust-preventive film. The heating method is not particularly limited and can be any known method such as convection heating, infrared heating, or induction heating. The heat treatment conditions, such as heat treatment time and heat treatment atmosphere, are also not particularly limited and can be selected as appropriate. For example, the heat treatment may be carried out in the atmosphere or in an inert gas such as nitrogen gas.

[0083] Before applying the rust preventive paint composition of this embodiment to the object to be coated, if necessary, the object to be coated may be degreased and washed with water or the like. Such degreasing and washing treatments can be performed by known methods. As the degreasing and washing treatments, for example, solvent degreasing using a hydrocarbon-based degreaser or the like, water washing treatment using an alkaline aqueous degreaser or the like, cleaning treatment using supercritical water or the like can be appropriately selected and performed.

[0084] The coating amount of the rust preventive paint composition of this embodiment is not particularly limited, but usually, it is preferable that the average film thickness of the rust preventive film after drying is 1 to 50 μm, and more preferably 5 to 30 μm. Also, in terms of the amount of zinc in the rust preventive film after drying, it is preferably 3 to 200 g / m 2 and more preferably 20 to 120 g / m 2

[0085] <Zinc-based composite particles, and zinc-based composite particle-containing composition> The zinc-based composite particles of this embodiment have flaky zinc-containing particles and a film containing at least one selected from inorganic phosphoric acid and inorganic phosphates on the surface thereof, and the content of phosphorus element contained in this film is 0.05 to 2.5 parts by mass with respect to 100 parts by mass of the flaky zinc-containing particles. The zinc-based composite particle-containing composition of this embodiment contains such zinc-based composite particles of this embodiment and an amine compound.

[0086] The film containing at least one selected from inorganic phosphoric acid and inorganic phosphates is preferably formed on the entire surface of the flaky zinc-containing particles, but may be partially formed on a part of the surface of the flaky zinc-containing particles as long as the effects of this embodiment are not impaired.

[0087] ​A coating formed on the surface of flake-shaped zinc-containing particles, containing at least one selected from inorganic phosphoric acid and inorganic phosphates, contains inorganic phosphoric acid adsorbed on the surface of the flake-shaped zinc-containing particles, and / or inorganic phosphates such as zinc phosphate compounds produced by the reaction of zinc (Zn) contained in the flake-shaped zinc-containing particles with inorganic phosphoric acid.

[0088] As the inorganic phosphoric acid, at least one selected from orthophosphate, pyrophosphate, triphosphate, tetraphosphate, and phosphorous acid can be used, with orthophosphate being preferred. As the inorganic phosphate salt, examples include, but are not limited to, zinc phosphate compounds produced by the reaction of zinc (Zn) contained in flake-shaped zinc-containing particles with inorganic phosphoric acid.

[0089] In the zinc-based composite particles of this embodiment, the phosphorus content in the coating formed on the surface of the flake-shaped zinc-containing particles, which contains at least one selected from inorganic phosphoric acid and inorganic phosphate, is preferably 0.05 to 2.5 parts by mass, and particularly preferably 0.2 to 1.5 parts by mass, per 100 parts by mass of the flake-shaped zinc-containing particles. If the phosphorus content in the coating is less than 0.05 parts by mass per 100 parts by mass of the zinc-containing particles, the zinc-based composite particles may not be sufficiently stable in water or an aqueous medium. Furthermore, if the phosphorus content in the coating exceeds 2.5 parts by mass per 100 parts by mass of the zinc-containing particles, aggregates of the zinc-based composite particles may form, and the color tends to deteriorate.

[0090] Furthermore, the thickness of the coating is not particularly limited as long as the phosphorus content in the coating is within the above range.

[0091] The flake-shaped zinc-containing particles consist mainly of zinc or a zinc alloy. The zinc alloy typically has a zinc content of 50% by mass or more. Examples include, but are not limited to, alloys of zinc with at least one element selected from aluminum, manganese, magnesium, chromium, etc.

[0092] The average major axis of the flake-shaped zinc-containing particles is not particularly limited, but is usually preferably 2 to 50 μm, and more preferably 3 to 30 μm. The average thickness of the flake-shaped zinc-containing particles is not particularly limited, but is usually preferably 5 μm or less, and more preferably 0.1 to 3 μm. Furthermore, the average aspect ratio (major axis / thickness) is not particularly limited, but is usually preferably in the range of 1.5 to 500, and more preferably in the range of 10 to 200.

[0093] The zinc-based composite particles of this embodiment are manufactured in the form of a composition containing zinc-based composite particles and a solvent, preferably in the form of a zinc-based composite particle-containing composition of this embodiment containing zinc-based composite particles and an amine compound.

[0094] The zinc-based composite particles of this embodiment can be suitably manufactured, for example, by a method that includes mixing and kneading flake-shaped zinc-containing particles with a solution in which inorganic phosphoric acid is dissolved in an organic solvent. This process allows for the formation of a coating containing at least one selected from inorganic phosphoric acid and inorganic phosphates on the surface of the flake-shaped zinc-containing particles.

[0095] The organic solvent used is not particularly limited, but hydrophilic organic solvents are preferred because they readily dissolve inorganic phosphoric acid. Examples of hydrophilic organic solvents include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, diacetone alcohol, amyl alcohol, isoamyl alcohol, ethyl cellosolve, butyl cellosolve, polyoxyethylene glycol, and polyoxypropylene glycol. A single hydrophilic organic solvent may be used, or two or more may be used in combination.

[0096] The amount of hydrophilic organic solvent added is usually preferably 5 to 100 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of flake-shaped zinc-containing particles.

[0097] Flake-shaped zinc-containing particles are commercially available, and some commercially available products contain aliphatic or aromatic hydrocarbon oils such as mineral spirits or solvent naphtha as a dispersion medium. Such commercially available products can be used as is in the production of the zinc-based composite particles and zinc-based composite particle-containing compositions of this embodiment. However, generally, the lower the hydrocarbon oil content (amount used), the better. Specifically, it is preferable to have 70 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of flake-shaped zinc-containing particles. Commercially available flake-shaped zinc-containing particles containing aliphatic or aromatic hydrocarbon oils as a dispersion medium can also be used in the production of the zinc-based composite particles and zinc-based composite particle-containing compositions of this embodiment after removing the solvent from the dispersion medium if necessary.

[0098] In the process of mixing and kneading flake-shaped zinc-containing particles with a solution of inorganic phosphoric acid dissolved in an organic solvent, the solution of inorganic phosphoric acid dissolved in an organic solvent may further contain a small amount of water. The amount of water added is usually preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of flake-shaped zinc-containing particles.

[0099] In this embodiment, it is preferable to mix and knead flake-shaped zinc-containing particles with a solution of inorganic phosphoric acid dissolved in an organic solvent in the presence of a surfactant and / or an amine compound. The surfactant plays a role in preventing the aggregation of the zinc-based composite particles of this embodiment by adsorbing onto or interposing on the surface of a film containing at least one selected from inorganic phosphoric acid and inorganic phosphate. The amine compound also exhibits a function of suppressing hydrogen generation.

[0100] The surfactant used is not particularly limited, but nonionic surfactants such as polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ether, polyethylene glycol fatty acid ester, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester can be suitably used. One surfactant may be used alone, or two or more may be used in combination.

[0101] The amount of surfactant added is not particularly limited, but is usually preferably 0.3 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of flake-shaped zinc-containing particles.

[0102] The amine compounds used are not particularly limited, but examples include ethylamine, propylamine, butylamine, hexylamine, octylamine, laurylamine, tridecylamine, stearylamine, isopropylamine, isobutylamine, 2-ethylhexylamine, isotridecylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dioctylamine, dilaurylamine, ditridecylamine, distearylamine, diisopropylamine, diisobutylamine, di(2-ethylhexyl)amine, diisotridecylamine, methylbutylamine, ethylbutylamine, ethylhexylamine, ethyllaurylamine, ethylstearylamine, isopropyloctylamine, isobutyl2-ethylhexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tritridecylamine, tristearylamine, triisopropylamine, triisobutylamine, tris(2-ethylhexyl)amine, triisotridecylamine Silamine, dimethyloctylamine, dimethyllaurylamine, dimethylstearylamine, diethyllaurylamine, allylamine, diallylamine, triallylamine, N,N-dimethylallylamine, cyclohexylamine, 2-methylcyclohexylamine, benzylamine, 4-methylbenzylamine, dicyclohexylamine, di-2-methylcyclohexylamine, dibenzylamine, di-4-methylbenzylamine, cyclohexyl-2-ethylhexylamine, cyclohexylbenzylamine, stearylbenzylamine Dylamine, 2-ethylhexylbenzylamine, dimethylbenzylamine, dimethylcyclohexylamine, tricyclohexylamine, tribenzylamine, tri-4-methylbenzylamine, morpholine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-butoxypropylamine, 3-decyloxypropylamine, 3-lauryloxypropylamine, monoethanolamine, diethanolamine, monoisopropanolamine, monopropanolamine, butanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-cyclohexyl-N-methylaminoethanol, N-benzyl-N-propylaminoethanol, N-hydroxyethylpyrrolidine, N-hydroxyethylpiperazine, N-hydroxyethylmorpholine, ethylenediamine, 1,2-propanedi Examples include amines, 1,3-propanediamine, N,N-dimethyl-1,3-propanediamine, N-cyclohexyl-1,3-propanediamine, N-decyl-1,3-propanediamine, N-isotridecyl-1,3-propanediamine, N,N-dimethylpiperazine, N-methoxyphenylpiperazine, N-methylpiperidine, N-ethylpiperidine, quinuclidine, diazabicyclo[2,2,2]octane, and 1,8-diazabicyclo[5,4,0]-7-undecene. Amine compounds may be used individually or in combination of two or more.

[0103] Among the amine compounds used, primary amines such as ethylamine, propylamine, and laurylamine are preferred. By using primary amines, the amount of hydrogen generated can be further reduced.

[0104] The mixing and kneading of flaky zinc-containing particles with a solution of inorganic phosphoric acid dissolved in an organic solvent can be carried out using known equipment such as a mixer or kneader.

[0105] The mixing and kneading of flake-shaped zinc-containing particles and a solution of inorganic phosphoric acid dissolved in an organic solvent can be carried out, for example, at a relatively low temperature of about 10 to 40°C under normal pressure, and can also be carried out at room temperature and normal pressure, but is not limited to these conditions. Furthermore, the time for mixing and kneading the flake-shaped zinc-containing particles and the solution of inorganic phosphoric acid dissolved in an organic solvent should be sufficient to form a coating containing at least one selected from inorganic phosphoric acid and inorganic phosphates on the surface of the flake-shaped zinc-containing particles, and can be appropriately selected.

[0106] In this way, the zinc-based composite particles of this embodiment can be obtained in the form of a composition containing zinc-based composite particles and an organic solvent, preferably in the form of a zinc-based composite particle-containing composition of this embodiment that further contains an amine compound. The organic solvent may be removed from the obtained composition to separate the zinc-based composite particles of this embodiment in the form of a dry powder or the like, or the obtained composition can be used as is, or with other components added as necessary, for various applications.

[0107] The zinc-based composite particles of this embodiment can be suitably used as a rust-preventive pigment for rust-preventive paint compositions, particularly for water-based rust-preventive paint compositions. Furthermore, the zinc-based composite particle-containing composition of this embodiment can also be suitably used for rust-preventive paint compositions, particularly for water-based rust-preventive paint compositions, by adding various additives as needed. The zinc-based composite particles and the zinc-based composite particle-containing composition of this embodiment can also be suitably used for the rust-preventive paint composition of this embodiment described above. [Examples]

[0108] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0109] <Example S-1> (Manufacturing of zinc-based composite particle-containing composition) 1000g of commercially available zinc flakes (Mitsui Mining & Smelting Co., Ltd.'s "Zinc Flakes MA-ZA-F"; 100% solids) was washed with propylene glycol monomethyl ether, then placed in a mixer and kneaded to obtain a cake with 88% solids. Next, 10g of laurylamine and 42g of nonionic surfactants (Kao Corporation's "Emulgen 105" and "Emulgen LS-106") were added. A solution of 7.5g of orthophosphoric acid dissolved in propylene glycol monomethyl ether was then added, and the mixture was kneaded at 30°C for 30 minutes to obtain 1394g of a composition containing zinc-based composite particles (1060g solids). The phosphorus content in this composition was 0.24 parts by mass per 100 parts by mass of zinc flakes (calculated from the amount of orthophosphoric acid added).

[0110] (Measurement of free phosphate levels) The amount of free phosphate in the obtained zinc-based composite particle-containing composition was measured using an ICP emission spectrometer (Thermo Fischer ICP-OES iCAP6000, manufactured by Thermo Fisher Scientific Co., Ltd.). As a result, the amount of free phosphate was less than 0.01% by mass relative to the mass of zinc flakes, in terms of phosphorus element.

[0111] (Evaluation of the stability of zinc-based composite particles in aqueous media) 22.5 g of the obtained zinc-based composite particle-containing composition was dispersed in 90 g of butyl cellosolve. Then, 90 g of deionized water was added and stirred, and a 10% by mass aqueous solution of dimethylethanolamine was further added to adjust the pH to 10.5 to prepare the sample. The prepared sample was then held at 40°C for 7 days, and the generated gas was collected and its volume measured. As a result, the amount of gas generated was 0 mL.

[0112] <Example S-2> A composition containing zinc-based composite particles was obtained in the same manner as in Example S-1, except that the amount of orthophosphate added was 10.0 g. The phosphorus content in this composition is 0.32 parts by mass per 100 parts by mass of zinc flakes (calculated from the amount of orthophosphate added).

[0113] (Measurement of free phosphate levels) The amount of free phosphate in the obtained zinc-based composite particle-containing composition was measured using an ICP emission spectrometer (Thermo Fischer ICP-OES iCAP6000, manufactured by Thermo Fisher Scientific Co., Ltd.). As a result, the amount of free phosphate was less than 0.01% by mass relative to the mass of zinc flakes, in terms of phosphorus element.

[0114] (Evaluation of the stability of zinc-based composite particles in aqueous media) 22.5 g of the obtained zinc-based composite particle-containing composition was dispersed in 90 g of butyl cellosolve. Then, 90 g of deionized water was added and stirred, and a 10% by mass aqueous solution of dimethylethanolamine was further added to adjust the pH to 10.5 to prepare the sample. The prepared sample was then held at 40°C for 7 days, and the generated gas was collected and its volume measured. As a result, the amount of gas generated was 0 mL.

[0115] <Comparative Example S-1> Except for adding 6.0 g of orthophosphate, the same procedure as in Example S-1 was used to obtain 1392 g (1058 g solids) of a composition containing zinc-based composite particles. The phosphorus content in this composition is 0.19 parts by mass per 100 parts by mass of zinc flakes (calculated from the amount of orthophosphate added).

[0116] (Measurement of free phosphate levels) The amount of free phosphate in the obtained zinc-based composite particle-containing composition was measured using an ICP emission spectrometer (Thermo Fischer ICP-OES iCAP6000, manufactured by Thermo Fisher Scientific Co., Ltd.). As a result, the amount of free phosphate was less than 0.01% by mass relative to the mass of zinc flakes, in terms of phosphorus element.

[0117] (Evaluation of the stability of zinc-based composite particles in aqueous media) 22.5 g of the obtained zinc-based composite particle-containing composition was dispersed in 90 g of butyl cellosolve. Then, 90 g of deionized water was added and stirred, and 10% dimethylethanolamine was further added to adjust the pH to 10.5 to prepare the sample. The prepared sample was then held at 40°C for 7 days, and the generated gas was collected and its volume measured. As a result, the amount of gas generated was 14 mL.

[0118] <Example 1> (Production of 0.3% by mass phosphate-treated zinc flakes) 100 parts by mass of zinc flakes ("Zinc Flakes MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) were placed in a mixer, and then 1 part by mass of laurylamine and 4 parts by mass of a nonionic surfactant ("Emulgen 105" manufactured by Kao Corporation) were added. A solution of 0.3 parts by mass of orthophosphate and 1 part by mass of deionized water mixed with 30 parts by mass of propylene glycol monomethyl ether was added, and the mixture was kneaded at 25°C for 30 minutes to obtain a paste of 0.3% by mass phosphate-treated zinc flakes (solid content: approximately 73% by mass).

[0119] (Evaluation of the water stability of 0.3% by mass phosphate-treated zinc flakes) 20 g (solid content) of a paste of 0.3% by mass phosphate-treated zinc flakes was mixed with 2 g of surfactant (Emulgen 108, manufactured by Kao Corporation), and this mixture was added to 200 g of deionized water and mixed for 5 minutes. Then, 200 g of the prepared dispersion was placed in a gas washing bottle and the amount of gas generated was measured over time using the water displacement method while maintaining a temperature of approximately 20°C. The results are shown in Figure 1. The amount of gas generated is thought to be the amount of hydrogen generated by the reaction between zinc and water, and an increase in the amount of gas generated is thought to indicate the decomposition of the phosphate-treated zinc flakes, which are a rust-preventive pigment, in water.

[0120] With 0.3% by mass phosphate-treated zinc flakes, the amount of gas generated was 10 mL or less even after 48 hours, and 30 mL or less even after 312 hours.

[0121] (Preparation of paint composition using 0.3% by mass of phosphate-treated zinc flakes) Using the prepared 0.3% by mass phosphate-treated zinc flakes, a paint composition was prepared by uniformly mixing the following components with a high-speed stirrer (PRIMIX Homodisper 2.5 type). 0.3% by mass phosphate-treated zinc flakes 20% by mass (on a solids basis) Aluminum flakes (WXM5660, manufactured by Toyo Aluminum Co., Ltd.) 10% by mass Silane coupling agent (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) 8% by mass Surfactant (Emulgen 108, manufactured by Kao Corporation) 2% by mass Thickening agent (CELLOSIZE® QP-4400H, manufactured by DOW Corporation) 0.1% by mass Deionized water (remaining portion)

[0122] (Evaluation of the stability of a paint composition using 0.3% by mass of phosphate-treated zinc flakes) 500 g of a paint composition using the prepared 0.3% by mass phosphate-treated zinc flakes was placed in a gas washing bottle, and the amount of gas generated was measured over time using the water displacement method while maintaining a temperature of approximately 20°C. The results are shown in Figure 2. The amount of gas generated is thought to be the amount of hydrogen produced by the reaction between zinc and water, and an increase in the amount of gas generated is thought to indicate the decomposition of the phosphate-treated zinc flakes, which are the rust-preventive pigment.

[0123] The paint composition using 0.3% by mass of phosphate-treated zinc flakes produced less than 2 mL of gas even after 7 days, and less than 30 mL of gas even after 30 days.

[0124] (Evaluation of rust prevention performance of a paint composition using 0.3% by mass of phosphate-treated zinc flakes) Using a bar coater, a paint composition using 0.3% by mass phosphate-treated zinc flakes was applied to an iron plate to a dry film thickness of approximately 8 μm, and then heated at 250°C for 10 minutes to form a coating film. A salt spray test was then performed on the iron plate coated with this 0.3% by mass phosphate-treated zinc flake coating in accordance with JIS Z-2371 to evaluate its rust prevention performance. Figure 3 shows a photograph of the iron plate 500 hours after the start of the salt spray test. The coating film of the 0.3% by mass phosphate-treated zinc flake coating is the first photograph from the left in Figure 3.

[0125] A steel plate coated with a paint composition using 0.3% by mass of phosphate-treated zinc flakes showed almost no red rust even after 500 hours, with only slight red rust observed in the X-shaped cuts made after the coating was formed. Furthermore, the accumulation of zinc-derived white rust due to sacrificial corrosion was observed in the X-shaped cuts. The accumulation of zinc-derived white rust indicates that the corrosion-preventive effect of zinc was achieved.

[0126] <Example 2> (Production of 0.6% by mass phosphate-treated zinc flakes) 100 parts by mass of zinc flakes ("Zinc Flakes MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) were placed in a mixer, and then 1 part by mass of laurylamine and 4 parts by mass of a nonionic surfactant ("Emulgen 105" manufactured by Kao Corporation) were added. A solution of 0.6 parts by mass of orthophosphate and 1 part by mass of deionized water mixed with 30 parts by mass of propylene glycol monomethyl ether was added, and the mixture was kneaded at 25°C for 30 minutes to obtain a paste of 0.6% by mass phosphate-treated zinc flakes (solid content: approximately 73% by mass).

[0127] (Evaluation of the water stability of 0.6 mass% phosphate-treated zinc flakes) Instead of using 0.3% by mass phosphate-treated zinc flakes, the prepared 0.6% by mass phosphate-treated zinc flakes were used, and a dispersion was prepared in the same manner as in Example 1. The amount of gas generated at approximately 20°C was measured over time. The results are shown in Figure 1.

[0128] With 0.6% by mass phosphate-treated zinc flakes, the amount of gas generated was 0 mL even after 300 hours.

[0129] (Preparation of paint composition using 0.6% by mass of phosphate-treated zinc flakes) A paint composition was prepared in the same manner as in Example 1, except that the prepared 0.6% by mass phosphate-treated zinc flakes were used instead of the 0.3% by mass phosphate-treated zinc flakes.

[0130] (Evaluation of the stability of a paint composition using 0.6% by mass of phosphate-treated zinc flakes) The amount of gas generated at approximately 20°C over time was measured for the paint composition using the prepared 0.6% by mass phosphate-treated zinc flakes, in the same manner as in Example 1. The results are shown in Figure 2.

[0131] The paint composition using 0.6% by mass of phosphate-treated zinc flakes produced less than 3 mL of gas even after 7 days, and less than 30 mL of gas even after 30 days.

[0132] (Evaluation of rust prevention performance of a paint composition using 0.6% by mass of phosphate-treated zinc flakes) A coating film of the paint composition using the prepared 0.6% by mass phosphate-treated zinc flakes was formed on a steel plate in the same manner as in Example 1, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate the rust prevention performance. Figure 3 shows a photograph of the steel plate 500 hours after the start of the salt spray test. The coating film of the paint composition using 0.6% by mass phosphate-treated zinc flakes is the second photograph from the left in Figure 3.

[0133] A steel plate coated with a paint composition using 0.6% by mass of phosphate-treated zinc flakes showed no red rust even after 500 hours. Furthermore, in the X-shaped cuts made after the coating was formed, the accumulation of zinc-derived white rust due to sacrificial corrosion was observed.

[0134] (Evaluation of adhesion of paint composition using 0.6% by mass phosphate-treated zinc flakes) Using a bar coater, paint compositions using the prepared 0.6% by mass phosphate-treated zinc flakes were applied to iron plates to achieve dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm. The plates were then heated at 250°C for 10 minutes to form the coating films. Photographs of the coating films with different thicknesses are shown in Figure 4. The rightmost photograph in Figure 4 shows the coating films of the paint composition using 0.6% by mass phosphate-treated zinc flakes, with dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm from top to bottom.

[0135] The paint composition using 0.6% by mass of phosphate-treated zinc flakes produced good film formation without peeling, regardless of the film thickness.

[0136] <Comparative Example 1> (Evaluation of the water stability of untreated zinc flakes) Instead of 0.3 mass% phosphoric acid-treated zinc flakes, untreated zinc flakes ("Zinc Flake MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) were used to prepare a dispersion in the same manner as in Example 1, and the amount of gas generated at approximately 20°C was measured over time. The results are shown in Figure 1.

[0137] Untreated zinc flakes that had not undergone surface treatment generated more than 40 mL of gas after 24 hours, and more than 150 mL of gas after 204 hours.

[0138] (Manufacturing of paint compositions using untreated zinc flakes) A paint composition was prepared in the same manner as in Example 1, except that untreated zinc flakes that had not undergone surface treatment were used instead of 0.3% by mass of phosphoric acid-treated zinc flakes.

[0139] (Evaluation of the stability of paint compositions using untreated zinc flakes) The amount of gas generated at approximately 20°C over time was measured for the paint composition using the prepared untreated zinc flakes, in the same manner as in Example 1. The results are shown in Figure 2.

[0140] The paint composition using untreated zinc flakes produced more than 70 mL of gas after one day, and more than 300 mL of gas after six days.

[0141] (Evaluation of rust prevention performance of paint compositions using untreated zinc flakes) A coating film of the paint composition using the prepared untreated zinc flakes was formed on a steel plate in the same manner as in Example 1, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate its rust prevention performance. Figure 3 shows a photograph of the steel plate 500 hours after the start of the salt spray test. The coating film of the paint composition using untreated zinc flakes is the third photograph from the left in Figure 3.

[0142] After 500 hours, red rust was observed on iron plates coated with a paint composition using untreated zinc flakes. Furthermore, zinc-derived white rust was observed not only in the X-shaped cuts made after the coating was formed, but across the entire surface of the iron plate.

[0143] (Evaluation of adhesion of paint compositions using untreated zinc flakes) In the same manner as in Example 2, the paint compositions using the prepared untreated zinc flakes were applied to iron plates to achieve dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm, and then heated at 250°C for 10 minutes to form the coating films. Photographs of the coating films with different thicknesses are shown in Figure 4. The leftmost photograph in Figure 4 shows the coating films of the paint composition using untreated zinc flakes, with dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm from top to bottom.

[0144] When the paint composition using untreated zinc flakes reached a dry film thickness of approximately 35 μm or more, delamination of the paint film from the steel plate occurred.

[0145] <Comparative Example 2> (Manufacturing of 2% by mass silica-treated zinc flakes) Ten parts by mass of zinc flakes ("Zinc Flakes MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) were placed in a mixer, and while mixing, 65 parts by mass of ethanol, 20 parts by mass of deionized water, and 2 parts by mass of 25% by mass aqueous ammonia solution were added and mixed at approximately 25°C for 30 minutes. Then, 2 parts by mass of tetraethoxysilane ("Ethyl Silicate 28" manufactured by Colcoat Co., Ltd.) were added and mixed at 25°C for 2 hours. After that, the mixture was heated to 80°C while mixing and dried until the water content was 1% by mass to obtain 2% by mass silica-treated zinc flakes (solid content: approximately 99% by mass).

[0146] (Evaluation of the water stability of 2% by mass silica-treated zinc flakes) Instead of 0.3% by mass phosphate-treated zinc flakes, the prepared 2% by mass silica-treated zinc flakes were used, and a dispersion was prepared in the same manner as in Example 1. The amount of gas generated at approximately 20°C was measured over time. The results are shown in Figure 1.

[0147] After 24 hours, the amount of gas generated by the 2% by mass silica-treated zinc flakes was 7 mL or more, and after 240 hours, the amount of gas generated was 70 mL or more.

[0148] (Preparation of paint composition using 2% by mass silica-treated zinc flakes) A paint composition was prepared in the same manner as in Example 1, except that 2% by mass silica-treated zinc flakes were used instead of 0.3% by mass phosphoric acid-treated zinc flakes.

[0149] (Evaluation of the stability of a paint composition using 2% by mass silica-treated zinc flakes) The amount of gas generated at approximately 20°C over time was measured for the paint composition using the prepared 2% by mass silica-treated zinc flakes, in the same manner as in Example 1. The results are shown in Figure 2.

[0150] The paint composition using 2% by mass silica-treated zinc flakes produced more than 9 mL of gas after 1 day, and more than 255 mL of gas after 30 days.

[0151] (Evaluation of rust prevention performance of a paint composition using 2% by mass silica-treated zinc flakes) A coating film of the paint composition using the prepared 2% by mass silica-treated zinc flakes was formed on a steel plate in the same manner as in Example 1, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate the rust prevention performance. Figure 3 shows a photograph of the steel plate 500 hours after the start of the salt spray test. The coating film of the paint composition using 2% by mass silica-treated zinc flakes is the fourth photograph from the left in Figure 3.

[0152] After 500 hours, red rust was observed on an iron plate coated with a paint composition using 2% by mass silica-treated zinc flakes. In addition, zinc-derived white rust was observed not only in the X-shaped cuts made after the coating was formed, but also across the entire surface of the iron plate.

[0153] <Comparative Example 3> (Manufacturing of 4% by mass silica-treated zinc flakes) Ten parts by mass of zinc flakes ("Zinc Flakes MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) were placed in a mixer, and while mixing, 65 parts by mass of ethanol, 20 parts by mass of deionized water, and 2 parts by mass of 25% by mass aqueous ammonia solution were added and mixed at approximately 25°C for 30 minutes. Then, four parts by mass of tetraethoxysilane ("Ethyl Silicate 28" manufactured by Colcoat Co., Ltd.) were added and mixed at 25°C for 2 hours. After that, the mixture was heated to 80°C while mixing and dried until the water content reached 1% by mass, yielding 4% by mass silica-treated zinc flakes (solid content: approximately 99% by mass).

[0154] (Evaluation of the water stability of 4 mass% silica-treated zinc flakes) Instead of 0.3% by mass phosphate-treated zinc flakes, the prepared 4% by mass silica-treated zinc flakes were used, and a dispersion was prepared in the same manner as in Example 1. The amount of gas generated at approximately 20°C was measured over time. The results are shown in Figure 1.

[0155] The 4% by mass silica-treated zinc flakes produced less than 1 mL of gas even after 48 hours, and less than 2 mL of gas even after 280 hours.

[0156] (Preparation of paint composition using 4% by mass silica-treated zinc flakes) A paint composition was prepared in the same manner as in Example 1, except that the prepared 4% silica-treated zinc flakes were used instead of 0.3% by mass phosphoric acid-treated zinc flakes.

[0157] (Evaluation of the stability of a paint composition using 4% by mass silica-treated zinc flakes) The amount of gas generated at approximately 20°C over time was measured for the paint composition using the prepared 4% by mass silica-treated zinc flakes, in the same manner as in Example 1. The results are shown in Figure 2.

[0158] The paint composition using 4% by mass silica-treated zinc flakes produced 0 mL of gas even after 2 days, and less than 20 mL of gas even after 28 days.

[0159] (Evaluation of rust prevention performance of a paint composition using 4% by mass silica-treated zinc flakes) A coating film of the paint composition using the prepared 4% by mass silica-treated zinc flakes was formed on a steel plate in the same manner as in Example 1, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate the rust prevention performance. Figure 3 shows a photograph of the steel plate 500 hours after the start of the salt spray test. The coating film of the paint composition using 4% by mass silica-treated zinc flakes is the fifth photograph from the left (first from the right) in Figure 3.

[0160] After 500 hours, a steel plate coated with a paint composition containing 4% by mass silica-treated zinc flakes showed red rust across its entire surface. However, no white rust originating from zinc was observed. This indicates that the rust-preventive effect of zinc was not achieved.

[0161] (Evaluation of adhesion of paint compositions using 4% by mass silica-treated zinc flakes) In the same manner as in Example 2, the coating compositions using the prepared 4% by mass silica-treated zinc flakes were applied to iron plates to achieve dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm, and then heated at 250°C for 10 minutes to form the coating films. Photographs of the coating films with different thicknesses are shown in Figure 4. The coating films of the coating composition using 4% by mass silica-treated zinc flakes are shown in the center photograph of Figure 4, with dry film thicknesses of approximately 15 μm, 25 μm, 35 μm, 45 μm, and 55 μm from top to bottom.

[0162] In a paint composition using 4% by mass silica-treated zinc flakes, delamination of the paint film from the steel plate occurred when the dry film thickness reached approximately 35 μm or more.

[0163] As is clear from Figures 1 and 2, 0.3% by mass phosphate-treated zinc flakes and 0.6% by mass phosphate-treated zinc flakes exhibited sufficient stability both in water and as a paint composition. On the other hand, 4% by mass silica-treated zinc flakes exhibited sufficient stability both in water and as a paint composition, but 2% by mass silica-treated zinc flakes exhibited insufficient stability both in water and as a paint composition. Untreated zinc flakes, without any surface treatment, exhibited very low stability both in water and as a paint composition.

[0164] Furthermore, as is clear from Figure 3, the paint compositions using 0.3% by mass phosphate-treated zinc flakes and 0.6% by mass phosphate-treated zinc flakes exhibited excellent rust prevention performance. On the other hand, the paint compositions using 2% by mass silica-treated zinc flakes and 4% by mass silica-treated zinc flakes, as well as the paint composition using untreated zinc flakes without surface treatment, exhibited insufficient rust prevention performance. In particular, the paint composition using 4% by mass silica-treated zinc flakes, which exhibited high stability both in water and as a paint composition, had poor rust prevention performance.

[0165] Furthermore, as is clear from Figure 4, the paint composition using phosphate-treated zinc flakes exhibited excellent adhesion of the resulting coating film. Whether thick or thin, the coating film did not peel off the substrate, resulting in a well-formed film. On the other hand, while the paint composition using silica-treated zinc flakes and the paint composition using untreated zinc flakes did not peel off the substrate in thin films, peeling occurred in thick films of approximately 35 μm or more, resulting in an unsuccessful film formation. It should be noted that as the film thickness increases, the shrinkage of the coating film due to heating during film formation increases, making peeling from the substrate more likely.

[0166] <Example 3> (Preparation of a paint composition using 0.3% by mass of phosphate-treated zinc flakes and an organic binder resin) A paint composition was prepared by uniformly mixing the following components using 0.3% by mass phosphate-treated zinc flakes prepared in the same manner as in Example 1, with a high-speed stirrer (PRIMIX Homodisper 2.5 type). Note that the epoxy resin is replaced with an organic binder resin. 0.3% by mass phosphate-treated zinc flakes 5% by mass (on a solids basis) Aluminum flakes (WXM5660, manufactured by Toyo Aluminum Co., Ltd.) 1% by mass Epoxy resin (Arakawa Chemical Co., Ltd.'s "Modepix 301") 30% by mass Surfactant (Emulgen 108, manufactured by Kao Corporation) 2% by mass Lubricant (BASF Japan's "Polygen WE6") 10% by mass Rust-preventive pigment ("Silomask" manufactured by Fuji Silysia Chemical Co., Ltd.) 3% by mass Black pigment (Mikuni Pigment Co., Ltd. "SA Black 3111") 5% by mass Thickening agent (Kelzan AR, manufactured by Sansho Co., Ltd.) 0.5% by mass Deionized water (remaining portion)

[0167] (Evaluation of rust prevention performance of a paint composition using 0.3% by mass of phosphate-treated zinc flakes and an organic binder resin) Using a bar coater, a paint composition made from 0.3% by mass phosphate-treated zinc flakes and an organic binder resin was applied to a steel plate to a dry film thickness of approximately 4 μm. The plate was then heated at 100°C for 20 minutes to form a coating film. A salt spray test was then performed on the steel plate coated with this paint composition in accordance with JIS Z-2371 to evaluate its rust prevention performance. Photographs of the steel plate 24 hours and 72 hours after the start of the salt spray test are shown in Figure 5. The second photograph from the left in Figure 5 is a photograph of the coating film made from 0.3% by mass phosphate-treated zinc flakes and an organic binder resin 24 hours after the start of the salt spray test, and the fourth photograph from the left in Figure 5 is a photograph of the coating film made from 0.3% by mass phosphate-treated zinc flakes and an organic binder resin 72 hours after the start of the salt spray test.

[0168] When a steel plate coated with a paint composition using 0.3% by mass of phosphate-treated zinc flakes and an organic binder resin was applied, only slight red rust was observed after 24 hours. In addition, in the X-shaped cuts made after the paint film was formed, the accumulation of zinc-derived white rust due to sacrificial corrosion of zinc was observed. Furthermore, even after 72 hours, the steel plate coated with the paint composition using 0.3% by mass of phosphate-treated zinc flakes and an organic binder resin showed sufficient prevention of red rust formation.

[0169] <Comparative Example 4> (Manufacturing of a paint composition using an organic binder resin without the use of 0.3% by mass of phosphate-treated zinc flakes) A paint composition was prepared in the same manner as in Example 3, except that 0.3% by mass of phosphate-treated zinc flakes were not used.

[0170] (Evaluation of rust prevention performance of a paint composition using an organic binder resin without 0.3% by mass of phosphate-treated zinc flakes) In the same manner as in Example 3, a coating film of the prepared paint composition, which does not use 0.3% by mass phosphate-treated zinc flakes and uses an organic binder resin, was formed on a steel plate, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate its rust prevention performance. Photographs of the steel plate 24 hours and 72 hours after the start of the salt spray test are shown in Figure 5. The first photograph from the left in Figure 5 is a photograph of the coating film of the paint composition that does not use 0.3% by mass phosphate-treated zinc flakes 24 hours after the start of the salt spray test, and the third photograph from the left in Figure 5 is a photograph of the coating film of the paint composition that does not use 0.3% by mass phosphate-treated zinc flakes 72 hours after the start of the salt spray test.

[0171] Even after 24 hours, red rust was observed across the entire surface of iron plates coated with a paint composition that did not use phosphate-treated zinc flakes.

[0172] <Example 4> (Production of 1.5% by mass phosphate-treated zinc powder) 1.5 parts by mass of orthophosphoric acid, 1.5 parts by mass of deionized water, 5 parts by mass of nonionic surfactant ("Nonion ID-206" manufactured by NOF Corporation), 30 parts by mass of triethylene glycol, and 70 parts by mass of ethylene glycol monobutyl ether were placed in a reaction vessel and mixed. Then, 100 parts by mass of zinc powder ("Zinc Powder #1" manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the mixture was stirred and kneaded at 40°C for 24 hours. The resulting slurry was filtered to separate the phosphate-treated zinc powder, washed with acetone, and dried at 60°C for 3 hours to obtain 1.5% by mass of phosphate-treated zinc powder.

[0173] (Evaluation of the water stability of 1.5% by mass phosphate-treated zinc powder) Instead of 0.3% by mass phosphate-treated zinc flakes, the prepared 1.5% by mass phosphate-treated zinc powder was used, and a dispersion was prepared in the same manner as in Example 1. The amount of gas generated at approximately 20°C was measured over time.

[0174] With 1.5% by mass phosphate-treated zinc powder, the amount of gas generated was 30 mL or less even after 300 hours.

[0175] <Comparative Example 5> (Evaluation of the water stability of untreated zinc powder) Instead of 0.3% by mass phosphate-treated zinc flakes, untreated zinc powder ("Zinc Powder #1" manufactured by Sakai Chemical Industry Co., Ltd.) was used, and a dispersion was prepared in the same manner as in Example 1. The amount of gas generated at approximately 20°C was measured over time.

[0176] In untreated zinc powder that had not undergone surface treatment, the amount of gas generated exceeded 10 mL after 24 hours, and was 90 mL after 204 hours.

[0177] <Example 5> (Preparation of a paint composition using 0.3% by mass of phosphate-treated zinc flakes and 1.5% by mass of phosphate-treated zinc powder) A paint composition was prepared in the same manner as in Example 1, except that instead of 20% by mass of 0.3% by mass of phosphate-treated zinc flakes, 12% by mass of 0.3% by mass of phosphate-treated zinc flakes (prepared in the same manner as in Example 1) and 8% by mass of 1.5% by mass of phosphate-treated zinc powder (prepared in the same manner as in Example 4) were used.

[0178] (Evaluation of rust prevention performance of paint compositions using 0.3% by mass of phosphate-treated zinc flakes and 1.5% by mass of phosphate-treated zinc powder) A coating film of a paint composition using 0.3% by mass phosphate-treated zinc flakes and 1.5% by mass phosphate-treated zinc powder, prepared in the same manner as in Example 1, was formed on a steel plate, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate its rust prevention performance.

[0179] A steel plate coated with a paint composition using 0.3% by mass of phosphate-treated zinc flakes and 1.5% by mass of phosphate-treated zinc powder showed no red rust even after 500 hours. Furthermore, in the X-shaped cuts made after the coating was formed, the accumulation of zinc-derived white rust due to sacrificial corrosion was observed.

[0180] <Comparative Example 6> (Manufacturing of paint compositions using untreated zinc flakes and untreated zinc powder) A paint composition was prepared in the same manner as in Example 1, except that 12% by mass of untreated zinc flakes ("Zinc Flake MA-ZA-F" manufactured by Mitsui Mining & Smelting Co., Ltd.) and 8% by mass of untreated zinc powder ("Zinc Powder #1" manufactured by Sakai Chemical Industry Co., Ltd.) were used instead of 20% by mass of 0.3% by mass of phosphate-treated zinc flakes.

[0181] (Evaluation of rust prevention performance of paint compositions using untreated zinc flakes and untreated zinc powder) A coating film of the paint composition using the prepared untreated zinc flakes and untreated zinc powder was formed on a steel plate in the same manner as in Example 1, and a salt spray test was performed in accordance with JIS Z-2371 to evaluate the rust prevention performance.

[0182] Iron plates coated with a paint composition using untreated zinc flakes and untreated zinc powder showed signs of red rust after 500 hours. Furthermore, zinc-derived white rust was observed not only in the X-shaped cuts made after the coating was formed, but across the entire surface of the iron plate.

[0183] This application is based on Japanese Patent Application No. 2020-200323, filed with the Japan Patent Office on December 2, 2020, the contents of which are incorporated herein by reference. [Industrial applicability]

[0184] According to the present invention, it is possible to provide a rust-preventive pigment that can achieve both high stability in water or an aqueous medium and excellent rust-preventive performance and adhesion of the resulting rust-preventive film. Furthermore, according to the present invention, it is also possible to provide a rust-preventive paint composition, particularly an aqueous paint composition containing water as a solvent, that yields a rust-preventive film with excellent stability of the rust-preventive pigment and excellent rust-preventive performance and adhesion.

[0185] Furthermore, the present invention also provides zinc-based composite particles and compositions containing zinc-based composite particles that have high stability even in water or aqueous media. These zinc-based composite particles can be particularly suitably used as rust-preventive pigments for aqueous rust-preventive paint compositions.

Claims

1. It contains a rust-preventive pigment consisting of one or more zinc or zinc alloy particles whose surface is treated with phosphoric acid, and a hydrophilic organic solvent. The aforementioned phosphoric acid is orthophosphate, The zinc or zinc alloy particles are surface-treated with the orthophosphoric acid using the hydrophilic organic solvent. The aforementioned hydrophilic organic solvent is characterized by comprising glycols or glycol ethers in the rust-preventive coating composition.

2. A rust-preventive pigment comprising one or more zinc or zinc alloy particles having a coating on at least a portion of its surface containing at least one selected from inorganic phosphoric acid and inorganic phosphate, and a hydrophilic organic solvent, The inorganic phosphoric acid is orthophosphate, The zinc or zinc alloy particles are surface-treated with the orthophosphoric acid using the hydrophilic organic solvent. The aforementioned hydrophilic organic solvent is characterized by comprising glycols or glycol ethers in the rust-preventive coating composition.

3. The rust-preventive paint composition according to claim 1 or 2, characterized in that the zinc or zinc alloy particles are substantially spherical or flake-shaped.

4. A rust-preventive paint composition according to any one of claims 1 to 3, characterized in that it further contains water.

5. A rust-preventive paint composition according to any one of claims 1 to 4, further comprising a binder.

6. The rust-preventive coating composition according to claim 5, characterized in that the binder contains at least one selected from silane-based binders and organic binder resins.

7. The rust-preventive paint composition according to any one of claims 1 to 6, further comprising aluminum or aluminum alloy particles as other metallic pigments.

8. A rust-preventive coating characterized by being obtained by drying or heat-treating the rust-preventive coating composition according to any one of claims 1 to 7.

9. An article characterized by having a rust-preventive coating on its surface obtained by drying or heat-treating a rust-preventive coating composition according to any one of claims 1 to 7.

10. It has flake-shaped zinc-containing particles and a coating on its surface containing at least one selected from inorganic phosphoric acid and inorganic phosphate, The phosphorus content in the aforementioned film is 0.05 to 2.5 parts by mass per 100 parts by mass of the flake-shaped zinc-containing particles. The zinc-containing particles consist of zinc or a zinc alloy. The inorganic phosphoric acid is orthophosphate, The zinc-based composite particles are characterized in that the flake-shaped zinc-containing particles are surface-treated with orthophosphoric acid using a hydrophilic organic solvent containing glycols or glycol ethers.

11. A zinc-based composite particle-containing composition characterized by containing zinc-based composite particles as described in claim 10 and an amine compound.

12. The zinc-based composite particle-containing composition according to claim 11, characterized in that the amine compound is a primary amine.

13. The zinc-based composite particle-containing composition according to claim 11 or 12, further comprising a surfactant.

14. The zinc-based composite particle-containing composition according to claim 13, characterized in that the surfactant is a nonionic surfactant.

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