Aqueous inorganic zinc-rich coating composition

Abstract

To provide an aqueous inorganic zinc-rich paint composition which hardly causes cracking of a coated film and redissolution of a coated film due to rain fall and condensation shortly after application even when applied at outdoor.SOLUTION: There is provided an aqueous inorganic zinc-rich paint composition which comprises an alkali silicate represented by the general formula, M2O nSiO2 (wherein, M is Na, K, Li or Cs, n is a number of 2.5 to 4), a water-retaining agent, a porous material carrying a compound having an amino group and / or an ammonium ion source, a vehicle containing water and a zinc powder, wherein the amount of the alkali silicate is 10 to 50 pts.mass based on 100 pts.mass of the vehicle, the amount of the water-retaining agent is 4.0 to 20.0 pts.mass based on 100 pts.mass of the alkali silicate and the amount of the zinc powder is 80 to 95 pts.mass based on 100 pts.mass of the solid content of the aqueous inorganic zinc-rich paint composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous inorganic zinc-rich paint composition, and in particular to an aqueous inorganic zinc-rich paint composition that is resistant to cracking of the coating film and re-dissolution of the coating film due to rainfall or condensation soon after application, even when applied outdoors. [Background technology]

[0002] Zinc-rich paints, which utilize the sacrificial anticorrosive properties of zinc against iron, are widely used to protect steel structures from corrosion. Among these, paints using inorganic binders can produce coatings with excellent weather resistance and long-term corrosion protection. In addition, considering the impact on the environment, there is a demand for a shift from solvent-based to water-based paints, and water-based inorganic zinc-rich paints containing alkali silicate as a binder component have long been studied.

[0003] Japanese Patent Laid-Open Publication No. 2009-249490 (Patent Document 1) describes a water-based inorganic zinc-rich paint composition that uses a water-based inorganic material with excellent corrosion resistance as a vehicle to reduce VOCs. The water-based inorganic zinc-rich paint composition is characterized by comprising a vehicle made of an aqueous solution containing 10 to 50 mass% alkali silicate represented by the general formula MO·nSiO (wherein M is Na, K, Li, or Cs, and n is a number from 2 to 4), 0.01 to 0.1 M ammonium ions, and 0.01 to 1 M halogen ions, and zinc dust, so that when the paint film is dried, the binder solids content is 5 to 20 mass% and the zinc dust content is 80 to 95 mass%.

[0004] Japanese Patent Laid-Open Publication No. 106271 / 1980 (Patent Document 2) describes an invention for an aqueous inorganic zinc-rich primer, which is made by blending zinc powder into a vehicle containing an aqueous solution of alkali silicate represented by the general formula MO·mSiO·nHO (where M is an alkali metal belonging to Group 1A of the Periodic Table, m is an integer, and n is 0 or an integer) and a synthetic resin emulsion in a solids ratio of 1:0.01 to 0.5. According to this invention, the drawbacks of inorganic zinc-rich primers are eliminated by modifying the alkali silicate with a synthetic resin emulsion such as an acrylic emulsion. Furthermore, the addition of the synthetic resin emulsion gives the paint film organic properties, which improves adhesion to steel sheets, flexibility, and recoatability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-249490 [Patent Document 2] Japanese Patent Application Publication No. 55-106271 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have studied aqueous inorganic zinc-rich paint compositions and found that aqueous inorganic zinc-rich paints containing alkali silicate as a binder component are prone to cracking in the resulting paint film when applied outdoors due to the rapid evaporation of water during drying. Furthermore, because the reaction between alkali silicate and zinc powder is slow (for example, it takes about a week after application for these to become insoluble in water), there is also the drawback that the paint film can re-dissolve due to rainfall or condensation within a short period after application.

[0007] Therefore, an object of the present invention is to provide an aqueous inorganic zinc-rich paint composition that is less likely to cause cracking of the paint film or re-dissolution of the paint film due to rainfall or condensation soon after application, even when applied outdoors. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the present inventors have discovered that by blending a specific amount of a water-retaining agent with the alkali silicate used, it is possible to prevent rapid evaporation of water during drying and prevent cracking of the paint film even when applied outdoors, and that by blending a porous material carrying a compound having an amino group and / or an ammonium ion source, it is possible to promote the reaction between the alkali silicate and zinc dust and prevent re-dissolution of the paint film due to rainfall or condensation soon after application, thereby completing the present invention.

[0009] Therefore, the aqueous inorganic zinc-rich paint composition of the present invention is an aqueous inorganic zinc-rich paint composition comprising a porous material carrying an alkali silicate represented by the general formula MO·nSiO (wherein M is Na, K, Li, or Cs, and n is a number of 2.5 to 4), a water retention agent, a compound having an amino group, and / or an ammonium ion source, as well as a vehicle containing water, and zinc powder, the amount of the alkali silicate is 10 to 50 parts by mass relative to 100 parts by mass of the vehicle; the amount of the water retention agent is 4.0 to 20.0 parts by mass per 100 parts by mass of the alkali silicate; The aqueous inorganic zinc-rich paint composition is characterized in that the amount of the zinc dust is 80 to 95 parts by mass per 100 parts by mass of the solid content of the aqueous inorganic zinc-rich paint composition.

[0010] In a preferred embodiment of the aqueous inorganic zinc-rich paint composition of the present invention, the water retention agent contains at least one selected from polyacrylic acid, carboxymethyl cellulose, hyaluronic acid, and alginic acid.

[0011] In another preferred embodiment of the aqueous inorganic zinc-rich paint composition of the present invention, a part of the alkali silicate is neutralized with an inorganic acid.

[0012] In another preferred embodiment of the aqueous inorganic zinc-rich paint composition of the present invention, the compound having an amino group is at least one compound selected from polyethylene polyamine compounds, polyamide resins, polyamine resins, and modified polyamine resins, and the amount of the compound having an amino group is 0.05 to 3.0 parts by mass per 100 parts by mass of the aqueous inorganic zinc-rich paint composition. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an aqueous inorganic zinc-rich paint composition that is less likely to cause cracking of the paint film or re-dissolution of the paint film due to rainfall or condensation soon after application, even when applied outdoors. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. The present invention relates to an aqueous inorganic zinc-rich paint composition. In this specification, the aqueous inorganic zinc-rich paint composition of the present invention is also referred to as the "paint composition of the present invention."

[0015] A water-based paint is a paint that contains water as the main solvent.

[0016] The inorganic paint is a paint containing an inorganic material such as an alkali silicate as a binder component.

[0017] Zinc-rich paint is a paint that contains a large amount of metallic zinc powder. Not only does the zinc provide sacrificial corrosion protection, but it also forms an oxide film with high barrier properties in corrosive environments to prevent corrosion of steel materials. For this reason, it is used in a wide range of applications, such as as a shop primer for steel materials used in ships and bridges, or as an undercoat paint for bridges and large steel structures.

[0018] The coating composition of the present invention is an aqueous inorganic zinc-rich coating composition, which contains water as the main solvent, an alkali silicate as a binder component, and zinc dust in an amount sufficient to provide anticorrosion properties.

[0019] In the present invention, the components other than zinc are collectively referred to as the “vehicle.” That is, the coating composition of the present invention can be described as a coating composition containing a vehicle containing water and an alkali silicate, and zinc powder.

[0020] The water used in the coating composition of the present invention is not particularly limited, but suitable examples include tap water, ion-exchanged water, distilled water, and other pure water, with water having a relatively low Ca hardness being preferred. Furthermore, when storing the coating composition for a long period of time, water that has been sterilized by ultraviolet irradiation or the like may be used to prevent the growth of mold and bacteria. In the coating composition of the present invention, the amount of water is preferably 5 to 30 parts by mass, more preferably 10 to 20 parts by mass, per 100 parts by mass of the coating composition.

[0021] In the coating composition of the present invention, the alkali silicate is an alkali silicate represented by the general formula MO·nSiO (wherein M is Na, K, Li, or Cs, and n is a number from 2.5 to 4). The alkali silicate reacts with zinc powder during drying to form a network polymer, which functions as a binder. The alkali silicate is preferably sodium silicate.

[0022] In the coating composition of the present invention, the amount of alkali silicate represented by the general formula MO·nSiO is 10 to 50 parts by mass, preferably 15 to 40 parts by mass, per 100 parts by mass of vehicle. The alkali silicate may be used alone or in combination of two or more.

[0023] In the coating composition of the present invention, it is preferable that the alkali silicate is partially neutralized with an inorganic acid. Examples of inorganic acids that can be used include hydrohalic acids such as hydrochloric acid, hydrofluoric acid, and hydrobromic acid, and nitric acid. However, it is particularly preferable to use a hydrohalic acid, especially hydrochloric acid. By using an alkali silicate partially neutralized with an inorganic acid, it is possible to suppress the consumption of zinc dust in a corrosive environment. Furthermore, by using an alkali silicate partially neutralized with an inorganic acid, it is possible to prevent the coating film from redissolving due to rainfall or condensation soon after application.

[0024] In the coating composition of the present invention, the amount of inorganic acid used to neutralize the alkali silicate is preferably 0.5 to 4.5 parts by mass per 100 parts by mass of the alkali silicate represented by the general formula MO·nSiO. If the amount of inorganic acid used is less than 0.5 parts by mass per 100 parts by mass of the alkali silicate, the effect of suppressing zinc dust consumption in a corrosive environment will not be sufficiently achieved, and if it exceeds 4.5 parts by mass, the coating composition may gel.

[0025] When the coating composition of the present invention contains an alkali silicate represented by the general formula MO·nSiO2 and a modified alkali silicate obtained by neutralizing the alkali silicate represented by the general formula MO·nSiO2 with an inorganic acid, the amount of alkali silicate represented by the general formula MO·nSiO2 per 100 parts by mass of vehicle can be determined from the amount of alkali silicate before neutralization with inorganic acid. For example, the alkali silicate solution B used in Example 5 described below is sodium silicate in which the sodium silicate has been partially neutralized, and the amount of alkali silicate in alkali silicate solution B is the amount used multiplied by 21.24% by mass. Note that "21.24% by mass" here refers to the mass content of pure alkali silicate (represented by the general formula MO·nSiO2) contained in the neutralized alkali silicate solution B. This allows the amount of alkali silicate represented by the general formula MO·nSiO2 per 100 parts by mass of vehicle to be determined.

[0026] In the coating composition of the present invention, the zinc dust is a fine powder of metallic zinc. Zinc dust is classified into types according to particle size, and the average particle size of zinc dust used in zinc-rich coatings is preferably 2 μm to 20 μm, and more preferably 3 μm to 15 μm.

[0027] In the present invention, the average particle size of zinc powder is the 50% particle size (D 50 ) and can be determined from the particle size distribution measured using a particle size distribution analyzer (for example, a laser diffraction / scattering particle size analyzer). The particle size here is expressed as the spherical equivalent diameter measured by the laser diffraction / scattering method.

[0028] In the coating composition of the present invention, the amount of zinc dust is 80 to 95 parts by mass, preferably 85 to 95 parts by mass, per 100 parts by mass of the solid content of the coating composition.

[0029] In the present invention, the solid content refers to the components excluding volatile components such as solvents, and is the component that will ultimately form the coating film. The solid content may also be referred to as the non-volatile content or the coating film-forming component, but the solid content in the present invention refers to the components remaining after heating 1 g of a sample at 110°C for 60 minutes. The amount of solid content contained in the coating composition of the present invention is preferably 70 to 95 parts by mass, more preferably 75 to 90 parts by mass, per 100 parts by mass of the coating composition.

[0030] In the paint composition of the present invention, the vehicle contains a water retention agent. The inventors have discovered that incorporating a large amount of water retention agent prevents rapid evaporation of water during drying and prevents cracking of the paint film, even when applied outdoors. Water retention agents are generally handled in a high-viscosity, low-nonvolatile state and are typically diluted (used) with large amounts of water to dissolve them in the vehicle. Therefore, the use of a water retention agent significantly reduces the solids content of the paint, raising concerns about reduced performance as a zinc-rich paint. However, the inventors have discovered that in inorganic zinc-rich paint compositions containing alkali silicate as a binder component, gradually adding an alkali silicate solution to a highly concentrated aqueous water retention agent solution allows for the incorporation of a large amount of water retention agent without reducing the solids content. This makes it possible to prevent cracking of the paint film without reducing the performance of the zinc-rich paint, such as paint workability and corrosion resistance. The reason that large amounts of water are not required to dissolve the water retention agent in the paint composition of the present invention is thought to be due to the neutralization of the water retention agent by the alkali silicate. In the coating composition of the present invention, the amount of the water retention agent is 4.0 to 20.0 parts by mass, and preferably 5.0 to 17.0 parts by mass, per 100 parts by mass of the alkali silicate represented by the above general formula M2O·nSiO2.

[0031] The water retention agent used in the coating composition of the present invention is a polymeric water retention agent, such as a water-soluble polymer or an alkali-soluble polymer. Here, a water-soluble polymer is a polymer that dissolves in water, and an alkali-soluble polymer is a polymer that dissolves in an alkaline aqueous solution. Alkali-soluble polymers are often used in the form of an emulsion before the addition of alkali. From the viewpoint of incorporating a large amount of water retention agent without reducing the solid content in the coating, an alkali-soluble polymer is preferred as the water retention agent. Specific examples of water retention agents include polysaccharides such as cellulose, starch, alginic acid, and hyaluronic acid; polymers of unsaturated carboxylic acid monomers (e.g., acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, etc.); and polymers of unsaturated carboxylic acid monomers and monomers copolymerizable with unsaturated carboxylic acid monomers (e.g., acrylate, methacrylate, styrene, etc.). The water retention agents may be used alone or in combination of two or more. In the coating composition of the present invention, the water retention agent preferably contains at least one selected from polyacrylic acid, carboxymethyl cellulose, hyaluronic acid, and alginic acid.

[0032] In one embodiment of the coating composition of the present invention, the vehicle contains a compound having an amino group. The inventors have discovered that the use of a compound having an amino group accelerates the reaction between alkali silicate and zinc dust, making it possible to form a coating film that is resistant to redissolution due to rainfall or condensation soon after application. Conventionally, the use of ammonium ions to accelerate the reaction between alkali silicate and zinc dust has been known, but their effect is so strong that the presence of ammonium ions has caused gelation in inorganic zinc-rich coating compositions containing alkali silicate as a binder component. On the other hand, compounds having an amino group can accelerate the reaction between alkali silicate and zinc dust while suppressing gelation of the alkali silicate, making them preferable reaction accelerators.

[0033] An amino group refers to a functional group having an -NH structure or a functional group in which one or two hydrogen atoms of -NH are substituted with an organic group (e.g., a hydrocarbon group). A compound having an amino group refers to a compound having an amino group bonded to a carbon atom. Examples of compounds having an amino group include polyethylene polyamine compounds, polyamide resins, polyamine resins, modified polyamine resins, silane coupling agents having an amino group, alkanolamines, and alkylamines. In the coating composition of the present invention, the compound having an amino group is preferably at least one compound selected from polyethylene polyamine compounds, polyamide resins, polyamine resins, and modified polyamine resins.

[0034] Polyethylene polyamine compounds are compounds in which multiple amino groups are linked in a linear or branched manner via ethylene chains, and examples include diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), and hexaethyleneheptamine (HEHA).

[0035] Polyamide resins, which are compounds containing amino groups, are resins that contain multiple amide bonds in addition to amino groups. Examples include resins produced by condensation of amines with carboxylic acids or by the Mannich reaction of amines with formaldehyde and ketones or phenols. Polyamine resins are resins that contain at least two amino groups per molecule. Examples include resins produced by condensation polymerization of amines with aldehydes, etherification of amines with alcohols, or ring-opening polymerization of amines with heterocyclic structures (e.g., ethyleneimine). Etherification of amines with alcohols can be achieved by ring-opening polymerization of alkylene oxides such as ethylene oxide and propylene oxide. Modified polyamine resins are polyamine resins in which some of the amino groups have been modified. Modification of amino groups can be achieved by known methods, such as amidation of amino groups, the Mannich reaction of amino groups with carbonyl compounds, or the addition reaction of amino groups with epoxy groups. Epoxy adduct-type polyamine resins, in which epoxy resins are added to amino groups, are preferred.

[0036] When an epoxy adduct-type polyamine resin is used, the molecular weight is increased by modifying a portion of the polyamine resin, which has an amine value in the range of 100 to 250 mgKOH / g, with an epoxy resin having a weight-average molecular weight of about 500 to 1000, thereby improving physical properties such as coating strength. The amount of epoxy resin used for modification is preferably 5 to 20 parts by mass in solids relative to the polyamine resin. If the amount of epoxy resin used for modification is less than 5 parts by mass, the effect of improving coating strength is low, while if it exceeds 20 parts by mass, the viscosity of the paint may increase, reducing coating workability.

[0037] The amine value refers to the number of milligrams of potassium hydroxide (unit: mg KOH / g) required to neutralize the amino groups contained in 1 g of sample, equivalent to the amount of hydrochloric acid or perchloric acid, and can be measured using the method specified in the total amine value test method for amine-based curing agents for epoxy resins specified in JIS K 7237:1995.

[0038] The weight-average molecular weight of the resin is a value measured by gel permeation chromatography (GPC), using polystyrene as the standard substance and tetrahydrofuran as the mobile phase.

[0039] Examples of amines that can be used in the production of polyamide resins, polyamine resins, and modified polyamine resins include aliphatic polyamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, triaminopropane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, and 1,3-bisaminomethylcyclohexane; aromatic polyamines such as phenylenediamine, metaxylylenediamine, paraxylylenediamine, and diaminodiphenylmethane; and amines having a heterocyclic structure such as ethyleneimine.

[0040] Examples of silane coupling agents having an amino group include silane coupling agents having a functional group having an -NH2 structure at the terminal or a functional group in which one hydrogen atom of -NH2 is substituted with an organic group (for example, a hydrocarbon group). Specific examples of silane coupling agents having an amino group include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldiethoxysilane. Silane, N-β-(aminoethyl)-γ-aminopropyltriisopropoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-8-aminooctyltrimethoxysilane, γ-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and the like.

[0041] Examples of alkanolamines include ethanolamine, N-methylethanolamine, N,N-dimethylethanolamine, diethanolamine, etc. Examples of alkylamines include diethylamine, diisopropylamine, dibutylamine, ethylamine, isopropylamine, butylamine, etc.

[0042] In the coating composition of the present invention, the amount of the amino group-containing compound is preferably 0.05 to 3.0 parts by mass, more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the coating composition. The amino group-containing compound may be used alone or in combination of two or more types. If the amount of the amino group-containing compound is less than 0.05 parts by mass per 100 parts by mass of the coating composition, the effect of promoting the reaction between the alkali silicate and zinc dust is not sufficiently achieved, making the coating more susceptible to re-dissolution due to rainfall or condensation soon after application. If the amount exceeds 3.0 parts by mass, the amino group-containing compound likely acts as a plasticizer, reducing the cohesive strength of the coating film.

[0043] In another embodiment of the coating composition of the present invention, the vehicle contains a porous material supporting an ammonium ion source, preferably ammonium chloride (NH4Cl), instead of or in addition to the amino group-containing compound. Ammonium ions are known to function as an activator of alkali silicates, promoting the reaction between alkali silicates and zinc dust. Ammonium chloride is sometimes used as an ammonium ion source. However, controlling the reaction between alkali silicates and zinc dust using ammonium chloride is difficult, and even a small amount can cause gelation of inorganic zinc-rich coating compositions containing alkali silicates as binder components. Therefore, the present inventors have conducted research and found that supporting an ammonium ion source, preferably ammonium chloride, on a porous material can promote the reaction between alkali silicates and zinc dust while suppressing gelation of inorganic zinc-rich coating compositions, thereby forming coating films that are resistant to redissolution due to rainfall or condensation soon after application. It is believed that the use of a porous material carrying an ammonium ion source, preferably ammonium chloride, allows ammonium ions to be gradually eluted into the coating material, thereby preventing gelation of the inorganic zinc-rich coating composition. In addition to ammonium chloride, inorganic salts such as ammonium fluoride can be used as the ammonium ion source. The porous material carrying ammonium chloride can also be used in combination with the above-mentioned compound having an amino group.

[0044] A porous material carrying an ammonium ion source can be prepared by, for example, impregnating a porous material with an ammonium ion source such as ammonium chloride (NH4Cl). Specifically, powdered ammonium chloride is dissolved in water, and then the solution is mixed with a porous material to prepare a slurry. The resulting slurry is dried in an oven, and the dried material is pulverized into powder in a mortar and pestle. The pulverized material is then classified to prepare a porous material carrying ammonium chloride.

[0045] The porous material preferably supports 5 to 30 parts by mass, and more preferably 10 to 20 parts by mass, of the ammonium ion source relative to 100 parts by mass of the porous material.

[0046] The porous material supporting the ammonium ion source has a particle diameter (D 99 ) is preferred.

[0047] In the present invention, the particle diameter (D 99 ) is the 99% particle size of the volume-based particle size distribution (D 99 ) and can be determined from the particle size distribution measured using a particle size distribution analyzer (for example, a laser diffraction / scattering particle size analyzer). The particle size here is expressed as the spherical equivalent diameter measured by the laser diffraction / scattering method.

[0048] The porous material is preferably a molecular sieve, and preferably has a surface pore size of 10 Å or less, more preferably 5 Å or less. If the surface pore size exceeds 10 Å, the amount of ammonium ion source eluted increases, making it difficult to control the reaction between zinc dust and alkali silicate.

[0049] In the coating composition of the present invention, the amount of the porous material supporting the ammonium ion source is preferably 0.3 to 5.0 parts by mass, more preferably 0.3 to 3.0 parts by mass, per 100 parts by mass of the coating composition.

[0050] In the coating composition of the present invention, the vehicle preferably contains ammonium ions, which function as an activator for the alkali silicate and contribute to promoting the reaction between the alkali silicate and zinc dust.

[0051] Suitable ammonium ion sources include inorganic salts such as ammonium chloride and ammonium fluoride, with ammonium chloride being particularly preferred. The concentration of ammonium ions contained in the vehicle is preferably 0.01 to 0.1 M (mol / L).

[0052] However, as mentioned above, the presence of ammonium ions can cause gelation of inorganic zinc-rich paint compositions containing alkali silicate as a binder component, so it is preferable to use the ammonium ion source supported on a porous material (e.g., molecular sieve, etc.).

[0053] In the coating composition of the present invention, the vehicle preferably contains halogen ions, which function as a catalyst for the reaction between the alkali silicate and zinc dust, thereby contributing to the promotion of the reaction between the alkali silicate and zinc dust.

[0054] The halogen ion is preferably a chloride ion or a fluoride ion, with chloride ion being particularly preferred. The halogen ion source is preferably a chloride or fluoride of an inorganic compound such as a metal (e.g., Na, K, Ca, Al, or Mg) or ammonia, with Na salt being particularly preferred. The concentration of halogen ion in the vehicle is preferably 0.01 to 1.0 M (mol / L).

[0055] In the paint composition of the present invention, other components such as pigments (excluding zinc dust), flexibility imparting agents, surface conditioners, wetting agents, pigment dispersants, emulsifiers, viscosity modifiers, anti-settling agents, anti-skinning agents, anti-dripping agents, defoaming agents, anti-color separation agents, leveling agents, drying agents, plasticizers, film-forming aids, neutralizing agents, paint film reinforcing materials (for example, fibrous materials such as barium titanate whiskers), electrostatic lubricants, antistatic agents, and conductivity imparting agents can be appropriately blended into the vehicle depending on the purpose, within the range that does not impair the performance of the zinc-rich paint.

[0056] Examples of pigments that do not fall under the category of zinc powder include pigments that are commonly used in the paint industry, such as extender pigments, color pigments, and anti-rust pigments.

[0057] Examples of extender pigments include talc, barium sulfate, silica, calcium carbonate, kaolin, alumina, alum, clay, magnesium hydroxide, and magnesium oxide. Examples of coloring pigments include inorganic pigments such as titanium oxide, red iron oxide, and yellow iron oxide. Examples of rust-preventive pigments include aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, zinc calcium phosphate, zinc aluminum phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, and vanadate / phosphate mixed pigments.

[0058] The coating composition of the present invention preferably does not contain any other pigments other than zinc dust, but if it contains a pigment that does not fall under the category of zinc dust, the amount of the pigment that does not fall under the category of zinc dust is preferably 10 parts by mass or less per 100 parts by mass of the solids content of the coating composition. The pigment that does not fall under the category of zinc dust may be used alone or in combination of two or more types.

[0059] The coating composition of the present invention can be prepared by mixing various components appropriately selected as needed. The coating composition of the present invention is preferably a two-component, one-powder type. A two-component, one-powder type coating composition is, for example, a coating composition prepared by mixing a liquid containing an alkali silicate and a water retention agent, a liquid containing a compound having an amino group, and zinc powder immediately before use. A preferred method for preparing a two-component, one-powder type coating composition is a method in which a liquid containing an alkali silicate and a water retention agent is mixed with a liquid containing a compound having an amino group to prepare a vehicle, and zinc powder is added to the vehicle to prepare the coating composition. In addition, when a material carrying an ammonium source is used instead of a compound having an amino group, a method of preparing a coating composition includes mixing a liquid containing an alkali silicate, a material carrying an ammonium source, and a water retention agent with zinc powder immediately before use.

[0060] In the coating composition of the present invention, the viscosity of the vehicle measured at 25°C and 6 rpm using a Brookfield viscometer is preferably 1 to 200 poise, and more preferably 0.1 to 20 poise using a Brookfield viscometer at 25°C and 60 rpm. The viscosity of the vehicle referred to here refers to the viscosity of the vehicle before being mixed with zinc dust. Furthermore, the viscosity of the coating composition of the present invention when applied is preferably 1 to 200 poise as measured with a Brookfield viscometer (25°C, 6 rpm), and more preferably 1 to 200 poise as measured with a Brookfield viscometer (25°C, 60 rpm). The viscosity of the coating composition referred to here refers to the viscosity of the coating composition containing a vehicle and zinc dust.

[0061] The means for applying the coating composition of the present invention is not particularly limited, and known coating means such as brush coating, roller coating, trowel coating, spatula coating, and spray coating (e.g., air spray coating, airless spray coating, etc.) can be used.

[0062] The means for drying the coating composition of the present invention is not particularly limited, and may be either natural drying at ambient temperature or forced drying using a dryer or the like.

[0063] The coating composition of the present invention is a zinc-rich coating composition and is capable of forming a coating film with excellent corrosion resistance, so the substrate to be coated is preferably a metal substrate or a composite substrate made of a metal and another material.

[0064] The substrate to be coated with the coating composition of the present invention may have various shapes, such as two-dimensional substrates in the form of a film, sheet, or plate, or three-dimensional substrates that are complex three-dimensional objects. The surface of the substrate may be smooth or may have irregularities. Specific examples of the substrate include steel materials such as steel plates, steel pipes, and steel bars, as well as steel structures such as steel towers, bridge facilities, chimneys, pipelines, plants, and tanks. The surface of the substrate may be subjected to pretreatments such as degreasing, chemical conversion treatment, and polishing, or may be coated with a sealer or primer, or at least a portion of the surface may have an old paint film present. The old paint film refers to a paint film already present on the substrate when painting, particularly repair, is performed.

[0065] The coating composition of the present invention can be applied to painting structures when they are newly constructed, and can also be applied to painting structures when they are repainted or repaired, and is particularly suitable for use in painting zinc-plated structures when they are repainted or repaired. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0067] The raw materials used in the following examples and comparative examples are as follows. The solid content of each raw material was calculated by taking a 1g sample, storing it in a hot air oven set at 110°C for 60 minutes, and calculating the mass of the remaining components relative to the mass of the raw material before heating. <Alkali silicate> Alkali silicate solution A (J sodium silicate No. 3, solid content: 50% by mass, alkali silicate content: 40% by mass, manufactured by Nippon Chemical Industry Co., Ltd.) (Alkali silicate solution A is an aqueous solution containing an alkali silicate represented by Na2O·nSiO2 (wherein n is a number from 3 to 3.3).) Alkali silicate solution B (sodium silicate neutralized with hydrochloric acid, solid content: 26.55% by mass, alkali silicate content: 21.24% by mass) (Alkali silicate solution B is an aqueous solution containing an alkali silicate represented by Na2O·nSiO2 (wherein n is a number between 3 and 3.3), and the alkali silicate is partly neutralized with hydrochloric acid.) Alkali silicate solution C (sodium silicate containing NH4Cl, solid content: 38 mass%, alkali silicate content: 30.40 mass%) (Alkali silicate solution C is an aqueous solution containing an alkali silicate represented by Na2O·nSiO2 (wherein n is a number from 3 to 3.3) and NH4Cl.) <Water retention agent> Water-retaining agent solution A (PRIMAL ASE-60, polyacrylic acid type, solid content 28% by mass, manufactured by Dow Chemical Japan Co., Ltd.) Water-retaining agent solution B (prepared by the method described below, polyacrylic acid type, solid content 2.8% by mass) Water retention agent C (alginic acid powder, solid content 100% by mass, manufactured by Kouhara of Maikon Co., Ltd.) <Compounds containing an amino group> Diethanolamine (Kanto Chemical Co., Ltd.) Diethylamine (Kanto Chemical Co., Ltd.) Tetraethylenepentamine (Kanto Chemical Co., Ltd.) Water-based polyamide resin solution (product name: WD-11M-60, amine value 50-65, solid content 60% by mass, manufactured by Mitsubishi Chemical Corporation) Water-based polyamine resin solution (product name: Fujicure FXH-927, amine value 150-170, solids content 80% by mass, manufactured by T&K TOKA) Water-based modified polyamine resin solution (epoxy-modified Fujicure FXH-927, amine value 100-120, solid content 70% by mass) Silane coupling agent A (KBM-603, N-2(aminoethyl)-3-aminopropylmethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) Silane coupling agent B (KBM-903, 3-aminopropylethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) <Porous material supporting ammonium chloride> Porous material A (molecular sieve supporting NH4Cl, surface pore diameter approximately 10 Å) Porous material B (molecular sieve supporting NH4Cl, surface pore diameter approximately 5Å) Porous material C (molecular sieve supporting NH4Cl, surface pore diameter approximately 3Å) <Zinc powder> Zinc powder (F-500, average particle size 7.5 μm, manufactured by Honjo Chemical Co., Ltd.) <Other> NH4Cl powder (Kanto Chemical Co., Ltd.) Coating reinforcement material (Tismo D, barium titanate whiskers, manufactured by Otsuka Chemical Co., Ltd.) Defoamer (Nopco 8034L, solid content 88% by mass, manufactured by San Nopco Ltd.)

[0068] [Method for preparing alkaline silicate solution B] After adding a predetermined amount of water to 100 parts by mass of alkali silicate solution A to dilute it, 18 parts by mass of 1M (mol / L) hydrochloric acid was gradually added dropwise with mechanical stirring to neutralize part of the alkali silicate, preparing alkali silicate solution B. At this time, the amount of alkali silicate in alkali silicate solution B was 21.24% by mass.

[0069] [Method for preparing alkaline silicate solution C] To 100 parts by mass of alkaline silicate solution A, 5.3 parts by mass of 1 M (mol / L) NH4Cl solution was slowly added dropwise with mechanical stirring to prepare alkaline silicate solution C containing NH4Cl at a concentration of 0.05 M (mol / L). At this time, the amount of alkaline silicate in alkaline silicate solution C was 30.4 mass%.

[0070] [Preparation method of water retention agent aqueous solution B] 10 parts by mass of the water retention agent aqueous solution A was diluted with 83 parts by mass of water, and then 7 parts by mass of a 1 M (mol / L) sodium hydroxide aqueous solution was added to form a uniform aqueous solution, thereby preparing the water retention agent aqueous solution B. At this time, the solid content of the water retention agent aqueous solution B was 2.96% by mass, and the polyacrylic acid content was 2.8% by mass.

[0071] [Method for preparing porous material A] Six parts by mass of NH4Cl powder (manufactured by Kanto Chemical Co., Ltd.) was dissolved in 60 parts by mass of tap water, and then 40 parts by mass of molecular sieve 13X (manufactured by Resonac Universal Co., Ltd., surface pore size 10 Å) was mixed to form a slurry, which was then dried in an oven at 100°C for 180 minutes, and then crushed into powder in a mortar. The powder passed through a 100-mesh wire net was used as porous material A. At this time, the particle diameter (D 99 ) was 150 μm.

[0072] [Method for preparing porous material B] Porous material B was obtained in the same manner as porous material A, except that molecular sieve 5A (manufactured by Resonac Universal Co., Ltd., surface pore diameter 5 Å) was used instead of molecular sieve 13X. At this time, the particle diameter (D 99 ) was 150 μm.

[0073] [Method for preparing porous material C] Porous material C was obtained in the same manner as porous material A, except that molecular sieve 3A (manufactured by Resonac Universal Co., Ltd., surface pore diameter 3 Å) was used instead of molecular sieve 13X. At this time, the particle diameter (D 99 ) was 150 μm.

[0074] <Method of preparing coating compositions in examples and comparative examples> [Comparative Example 1] In Comparative Example 1, 15 parts by mass of alkali silicate solution A was mixed with 8.9 parts by mass of water to obtain a uniform aqueous solution, and then 1.0 part by mass of a coating film reinforcing material was added with mechanical stirring to obtain an aqueous dispersion. Next, 2.0 parts by mass of an aqueous polyamide resin solution was added and mixed, and finally 85 parts by mass of zinc powder was added and mixed to obtain an aqueous inorganic zinc-rich coating composition.

[0075] [Examples 1 to 3, 5 to 11, and Comparative Examples 2 to 3] In Example 1, 15 parts by weight of alkali silicate solution A was mixed with 7.8 parts by weight of water, and 1.1 parts by weight of water-retaining agent solution A was gradually added and stirred while mechanically stirring to obtain a uniform solution. Then, 1.0 parts by weight of coating film reinforcement material and 0.1 parts by weight of antifoaming agent were added while further stirring mechanically to obtain an aqueous dispersion. Next, 2.0 parts by weight of aqueous polyamide resin solution was added and mixed, and finally, 90 parts by weight of zinc powder was added and mixed to obtain an aqueous inorganic zinc-rich paint composition. The vehicle of the aqueous inorganic zinc-rich paint composition of Example 1 was a composition consisting of alkali silicate solution A, water, water-retaining agent solution A, coating film reinforcement material, antifoaming agent, and aqueous polyamide resin solution, i.e., a composition consisting of components other than zinc powder. For Examples 2, 3, and 5-11 and Comparative Examples 2 and 3, aqueous inorganic zinc-rich paint compositions were prepared according to the formulations shown in Tables 1-3.

[0076] [Example 4] In Example 4, 15 parts by weight of alkali silicate solution A was mixed with 3.0 parts by weight of water, and while mechanically stirring, 6.0 parts by weight of water retention agent aqueous solution B was gradually added and stirred to obtain a uniform solution. Then, while further stirring mechanically, 1.0 part by weight of coating film reinforcement material was added to obtain an aqueous dispersion. Next, 2.0 parts by weight of aqueous polyamide resin solution was added and mixed, and finally, 95 parts by weight of zinc dust and 1.0 part by weight of water retention agent C, which had been previously mixed, were added and mixed to obtain an aqueous inorganic zinc-rich paint composition. The vehicle of the aqueous inorganic zinc-rich paint composition of Example 4 was a composition consisting of alkali silicate solution A, water, water retention agent aqueous solution A, coating film reinforcement material, aqueous polyamide resin solution, and water retention agent C, i.e., a composition consisting of components other than zinc dust.

[0077] Comparative Example 4 In Comparative Example 4, 15 parts by mass of alkali silicate solution A was mixed with 6.9 parts by mass of water, and 2.0 parts by mass of water retention agent solution A was gradually added and stirred with mechanical stirring to obtain a uniform aqueous solution. Then, 1.0 part by mass of coating film reinforcing agent and 0.1 part by mass of antifoaming agent were added with further mechanical stirring to obtain an aqueous dispersion. Next, 75 parts by mass of zinc powder was added and mixed to obtain an aqueous inorganic zinc-rich paint composition.

[0078] [Examples 12 to 14] For Example 12, 15 parts by weight of alkali silicate solution A was mixed with 6.9 parts by weight of water, and 2.0 parts by weight of water-retaining agent solution A was gradually added and stirred while mechanically stirring to obtain a uniform solution. Then, 1.0 parts by weight of coating film reinforcement material and 0.1 parts by weight of antifoaming agent were added while further stirring mechanically to obtain an aqueous dispersion. Next, 80 parts by weight of zinc powder was added and mixed, and immediately before application, 0.5 parts by weight of silane coupling agent A was added and mixed to obtain an aqueous inorganic zinc-rich paint composition. The vehicle for the aqueous inorganic zinc-rich paint composition of Example 12 was a composition consisting of alkali silicate solution A, water, water-retaining agent solution A, coating film reinforcement material, antifoaming agent, and silane coupling agent A, i.e., a composition consisting of components other than zinc powder. For Examples 13 and 14, aqueous inorganic zinc-rich paint compositions were prepared according to the formulations shown in Table 3.

[0079] [Examples 15 to 17] For Example 15, 15 parts by weight of alkali silicate solution C was mixed with 6.9 parts by weight of water, and 2.0 parts by weight of water-retaining agent aqueous solution A was gradually added and stirred while mechanically stirring to obtain a uniform solution. Then, 1.0 parts by weight of coating film reinforcement material and 0.1 parts by weight of antifoaming agent were added while further stirring mechanically to obtain an aqueous dispersion. Next, 2.0 parts by weight of aqueous polyamide resin solution and 105 parts by weight of zinc powder were added and mixed, and 1.0 part by weight of silane coupling agent B was added and mixed just before coating to obtain an aqueous inorganic zinc-rich paint composition. The vehicle for the aqueous inorganic zinc-rich paint composition of Example 15 was a composition consisting of alkali silicate solution C, water, water-retaining agent aqueous solution A, coating film reinforcement material, antifoaming agent, aqueous polyamide resin solution, and silane coupling agent B, i.e., a composition consisting of all components except zinc powder. For Examples 16 and 17, aqueous inorganic zinc-rich paint compositions were prepared according to the formulations shown in Table 4.

[0080] [Examples 18 to 20] For Example 18, 15 parts by weight of alkali silicate solution A was mixed with 6.9 parts by weight of water, and 2.0 parts by weight of water-retaining agent solution A was gradually added and stirred while mechanically stirring to obtain a uniform aqueous solution. Then, 1.0 parts by weight of coating film reinforcement material and 0.1 parts by weight of antifoaming agent were added while further stirring mechanically to obtain an aqueous dispersion. Finally, 75 parts by weight of zinc powder and 0.5 parts by weight of porous material A, which had been previously mixed, were added and mixed to obtain an aqueous inorganic zinc-rich paint composition. The vehicle for the aqueous inorganic zinc-rich paint composition of Example 18 was a composition consisting of alkali silicate solution A, water, water-retaining agent solution A, coating film reinforcement material, antifoaming agent, and porous material A, i.e., a composition consisting of components other than zinc powder. For Examples 19 and 20, aqueous inorganic zinc-rich paint compositions were prepared according to the formulations shown in Table 4.

[0081] Comparative Example 5 For Comparative Example 5, 15 parts by weight of alkali silicate solution A was mixed with 6.9 parts by weight of water, and while mechanically stirring, 2.0 parts by weight of water retention agent aqueous solution A was gradually added and stirred to obtain a uniform aqueous solution. Then, while further stirring mechanically, 1.0 part by weight of coating film reinforcement agent and 0.1 part by weight of antifoaming agent were added to obtain an aqueous dispersion. Next, 75 parts by weight of zinc powder was added and mixed, and just before painting, 0.1 part by weight of NH4Cl powder was added and mixed to obtain an aqueous inorganic zinc-rich paint composition.

[0082] <Measurement and evaluation methods> [Painting workability] Each water-based inorganic zinc-rich paint composition was applied at a rate of 700 g / m to a galvanized steel sheet (150 x 70 x 3.2 mm) that had been water-sprayed and cured outdoors, and the surface had deteriorated to the extent that white rust of the zinc had formed. 2 After drying for 30 minutes in a sunny outdoor location, the same water-based inorganic zinc-rich paint composition was applied to 2 / 3 of the surface of the galvanized steel sheet in an amount of 700 g / m. 2 The coating was applied in layers with a brush so that the coating was smooth and the results were evaluated according to the following criteria. For samples in which the coating workability was evaluated as ×, no other evaluations were made. ◎: No problems with brush painting, and painting can be done without problems even in areas where multiple coats have been applied. ○: The viscosity is high and it is difficult to move the brush, or when applying multiple coats, it tends to be absorbed into the first coat, making it difficult to move the brush. ×: Viscosity increased significantly, making brush application difficult, or when applying multiple coats, the paint was absorbed into the first coat, making brush application difficult.

[0083] [Appearance of coating film when dried outdoors] The galvanized steel sheets for which the paint workability was evaluated were left to dry for one day in a sunny outdoor location, after which the paint surface was visually inspected and rated according to the following criteria. Paint films rated as ⊚ or ◯ are deemed to be less susceptible to cracking. ◎: No defects such as cracks or lifting on the surface of the coating film. ◯: Although some small cracks were observed on the edges of the coating surface and in the overlapping areas, no large cracks that would affect the coating performance were observed, and there was no significant effect on the coating performance. ×: Significant cracks or lifting were observed on the coating surface.

[0084] [Whether or not the coating dissolves] The galvanized steel sheets used to evaluate the appearance of the coating film when dried outdoors were immersed horizontally in a vat filled with tap water at 23°C for 2 hours, and the galvanized steel sheets removed from the vat were used as test specimens. The state of dissolution of the coating film was confirmed visually, and then the moisture on the surface of the test specimen was wiped off with a Kimwipe (manufactured by Nippon Paper Crecia). It was confirmed that the paint was attached to the Kimwipe, and the results were evaluated according to the following criteria. Coatings rated as ⊚ or ◯ were deemed to be coatings that were unlikely to re-dissolve soon after application. ⊚: The coating film is not dissolved and almost no paint is found adhering to the Kimwipe. ○: A small amount of paint is attached to the Kimwipe, and the coating film is slightly dissolved. Dissolution to the extent that it affects the coating film performance is not observed. ×: The coating film is dissolved and a large amount of paint is attached to the Kimwipe.

[0085] [Saltwater resistance (corrosion prevention)] Each water-based inorganic zinc-rich coating composition was applied at a rate of 700 g / m to a sandblasted steel plate (SPCC-SB, 150 x 70 x 2.3 mm). 2 After drying for 3 days in a 23°C, 50% RH environment, an epoxy resin-based paint (Eponics #30 Primer HB, manufactured by Dai Nippon Toryo Co., Ltd.) was applied to the surface not coated with the aqueous inorganic zinc-rich paint composition to a thickness of 120 μm, and then dried for another 4 days in a 23°C, 50% RH environment to prepare a test specimen. The obtained test specimen was immersed in a 3 wt% saline solution up to 110 mm in the longitudinal direction of the test plate, and the condition of the coating after 30 days was visually inspected and evaluated according to the following criteria. ⊚: No cracking or peeling was observed in the coating film in the immersed area. ○: Peeling was observed in several places on the coating film in the immersed area. ×: Cracks and peeling were observed in the coating film of the immersed area, and the corrosion prevention performance could not be maintained.

[0086] <Examples and Comparative Examples> According to the formulations shown in Tables 1 to 4, coating compositions were prepared by the above-mentioned <Method for preparing coating compositions in Examples and Comparative Examples>, and the coating properties and coating film performance were evaluated. The results are shown in Tables 1 to 4. The numerical values ​​of each component in the formulations shown in the tables are expressed in "parts by mass."

[0087] [Table 1]

[0088] [Table 2]

[0089] [Table 3]

[0090] [Table 4]

[0091] Regarding the "amount of alkali silicate per 100 parts by mass of vehicle" in the table, the vehicle refers to a composition consisting of components other than zinc dust. Furthermore, with regard to the "amount of water retention agent per 100 parts by mass of alkali silicate," water retention agent aqueous solution A and water retention agent aqueous solution B are aqueous solutions containing polyacrylic acid as a water retention agent. Therefore, in examples where water retention agent aqueous solution A or water retention agent aqueous solution B is used, the "water retention agent" refers to the polyacrylic acid contained in water retention agent aqueous solution A or water retention agent aqueous solution B.

Claims

1. General formula M ２ O.nSiO ２ (wherein M is Na, K, Li or Cs, and n is a number from 2.5 to 4), a water-retaining agent, a compound having an amino group and / or a porous material carrying an ammonium ion source, a vehicle containing water, and zinc powder, the amount of the alkali silicate is 10 to 50 parts by mass relative to 100 parts by mass of the vehicle; the amount of the water retention agent is 4.0 to 20.0 parts by mass per 100 parts by mass of the alkali silicate; The amount of the zinc powder is 80 to 95 parts by mass per 100 parts by mass of the solid content of the aqueous inorganic zinc-rich coating composition.

2. 2. The aqueous inorganic zinc-rich paint composition according to claim 1, wherein the water retention agent comprises at least one selected from the group consisting of polyacrylic acid, carboxymethyl cellulose, hyaluronic acid, and alginic acid.

3. 3. The aqueous inorganic zinc-rich paint composition according to claim 1, wherein a part of the alkali silicate is neutralized with an inorganic acid.

4. The aqueous inorganic zinc-rich coating composition according to any one of claims 1 or 2, characterized in that the compound having amino group is at least one compound selected from polyethylene polyamine compounds, polyamide resins, polyamine resins and modified polyamine resins, and the amount of the compound having amino group is 0.05 to 3.0 parts by mass relative to 100 parts by mass of the aqueous inorganic zinc-rich coating composition.

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