Inorganic zinc primer

Abstract

This invention provides an inorganic zinc primer that prevents rusting of steel materials through painting, and also ensures that the processed area maintains the same level of corrosion resistance as the unprocessed area even after processing. [Solution] The solution comprises an inorganic binder, graphene, zinc powder, inorganic pigment, and solvent. The amount of zinc powder is within the range of 20 to 75 parts by mass, based on 100 parts by mass of paint solids. The amount of graphene is within the range of 0.01 to less than 3.0 parts by mass, based on 100 parts by mass of zinc powder. The inorganic pigment component contains silica powder, and the amount of the silica powder is within the range of 20 to 95 parts by mass, based on 100 parts by mass of zinc powder. Inorganic zinc primer.

Description

[Technical Field]

[0001] This invention relates to an inorganic zinc primer. [Background technology]

[0002] Because the sacrificial corrosion protection effect of zinc on iron has been well known for a long time, inorganic zinc-rich primers containing a large amount of zinc are widely used as rust-preventive coatings for various steel structures such as ships, bridges, tanks, and plants.

[0003] For example, Patent Document 1 discloses a primary rust-preventive coating for steel materials, characterized in that it contains tetraalkoxysilicate, alkyltrialkoxysilicate and / or initial hydrolysis condensates thereof (A), acidic water-dispersible colloidal silica (B), zinc powder (C), and powder (D) selected from silica powder, rutile powder, synthetic rutile powder, chromium powder, and zircon powder with a burn weight of 2% by weight or less, the weight ratio of (A) to (B) being 95:5 to 40:60, and the weight ratio of the sum of (A) and (B) to (C) and (D) being 100:100:50 to 100:1000:500.

[0004] Furthermore, Patent Document 2 describes an inorganic zinc powder primer composition comprising 9 to 19% by mass of an inorganic binder component (A), 61 to 79% by mass of zinc powder (B), and 8 to 23% by mass of an extender pigment (C), based on the total mass of the inorganic binder component (A) in terms of silica equivalent, wherein the inorganic binder component (A) comprises 64 to 95% by mass of silica equivalent, based on the total mass of the inorganic binder component (A) in terms of silica equivalent, and is based on the general formula: (R 1 ) n -Si-(OR 2 ) 4-n (In the formula, R 1 R is a C1-C18 alkyl group or phenyl group which may be substituted with an epoxy group or a mercapto group. 2An inorganic zinc shop primer composition is disclosed, characterized in that it comprises an organosilicate and / or condensate component (a1) represented by (a) an alkyl group having 1 to 6 carbon atoms, and n being an integer from 0 to 2, and 5 to 36% by mass of colloidal silica (a2) in terms of silica equivalent mass, wherein the average particle size of the zinc powder (B) is 0.5 to 10 μm, and the extender pigment (C) comprises 50 to 80% by mass of silica powder (c1) with an average particle size of 1 to 10 μm based on the total mass of the extender pigment (C), and 20 to 50% by mass of at least one extender pigment (c2) selected from the group consisting of feldspar and kaolin with an average particle size of 10 μm or less.

[0005] In recent years, with the soaring price of zinc powder and the prediction of future depletion, there has been growing interest in reducing the amount of zinc powder used in inorganic zinc-rich primers. Graphene is one method for reducing the amount of zinc powder in inorganic zinc-rich primers. Graphene has a thin-layer sheet structure and is electrically conductive, making it a promising material for application in inorganic zinc-rich primers.

[0006] Patent Document 3 discloses a primary anti-corrosion coating composition containing a siloxane-based binder (a) which is a condensate of at least one compound selected from alkyl silicates and alkyltrialkoxysilanes, zinc powder (b), and at least one carbon-based nanomaterial (c) selected from graphene, fullerenes, and carbon nanotubes.

[0007] Furthermore, Patent Document 4 discloses a coating composition comprising i. an inorganic binder, ii. a metallic pigment, iii. a filler, and iv. functionalized graphene for at least partially replacing a portion of the metallic pigment in the coating composition.

[0008] Furthermore, Patent Document 5 discloses a composition containing a curable resin and / or its precursor, inorganic particles, and graphene, wherein the average thickness of the graphene is 0.30 nm or more and 100 nm or less. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 3-079675 [Patent Document 2] WO2014 / 119784 [Patent Document 3] WO2020 / 262366 [Patent Document 4] Japanese Patent Publication No. 2022-540761 [Patent Document 5] WO2023 / 074652 issue [Overview of the project] [Problems that the invention aims to solve]

[0010] When steel materials are blast-treated, rust immediately occurs, so a primary rust-preventive coating is applied as soon as possible. These primary rust-preventive coated steel materials are then welded, processed, and assembled to construct ships and steel structures. To prevent rust from occurring during this processing and assembly period, a quick-drying primary rust-preventive primer is applied to the steel surface beforehand. After processing and assembly are completed, a secondary surface treatment is performed, followed by the application of a primer, intermediate coat, and topcoat.

[0011] The inorganic zinc primers described in Patent Documents 1 to 6 can suppress rust formation and provide coated steel with excellent cutting properties when applied to blast-treated steel. However, if the coated steel is left for a long period after processing, rust may form on the processed area, and the appearance of the processed area may be inferior to that of the unprocessed area (flat surface). Such coated steel presents problems in terms of durability.

[0012] This invention has been made in view of the above problems, and aims to provide an inorganic zinc primer that prevents rusting of steel materials by painting, and in which the processed area has the same corrosion resistance as the unprocessed area even after processing after painting. [Means for solving the problem]

[0013] The inventors of the present invention studied the above problems. As a result, it was found that by using graphene in an inorganic zinc primer and setting the inorganic pigment composition to a specific composition, the same corrosion resistance as the unprocessed part can be obtained even after processing after painting. The present invention mainly Item 1 An inorganic zinc primer containing an inorganic binder, graphene, zinc powder, an inorganic pigment component, and a solvent, where the amount of zinc powder is in the range of 20 to 75 parts by mass based on 100 parts by mass of the paint solid content, the amount of graphene is in the range of 0.01 or more and less than 3.0 parts by mass based on 100 parts by mass of zinc powder, the inorganic pigment component contains silica powder, and the amount of the silica powder is in the range of 20 to 95 parts by mass based on 100 parts by mass of zinc powder, an inorganic zinc primer. Item 2 The inorganic zinc primer according to Item 1, wherein the inorganic binder contains an organosilicate and / or its condensate, and colloidal silica. Item 3 The inorganic zinc primer according to Item 1 or 2, wherein the solid content of colloidal silica is in the range of 5 to 50 parts by mass based on 100 parts by mass of the inorganic binder solid content. Item 4 The inorganic zinc primer according to any one of Items 1 to 3, wherein the D / G ratio measured by Raman spectroscopy of graphene is 1.0 or more and 2.5 or less. Item 5 The inorganic zinc primer according to any one of Items 1 to 4, wherein the total amount of zinc powder and the inorganic pigment component is in the range of more than 60 parts by mass and 98 parts by mass or less based on 100 parts by mass of the paint solid content. Item 6 A multi-component inorganic zinc primer for preparing an inorganic zinc primer by mixing a main agent (I) and a pigment paste (II) before painting, a main agent (I) containing an inorganic binder and a solvent, and a pigment paste (II) containing graphene, zinc powder, an inorganic pigment component, and a solvent, and having the inorganic zinc primer according to any one of Items 1 to 5. Section 7 A multi-component inorganic zinc primer for preparing an inorganic zinc primer by mixing a main component (I) and a pigment paste (II) before painting, Main component (I) containing an inorganic binder, catalyst, and solvent, An inorganic zinc primer according to any one of claims 1 to 6, comprising a pigment paste (II) containing graphene, zinc powder, an inorganic pigment component, and a solvent. Section 8 A coating method comprising applying an inorganic zinc primer described in any one of items 1 to 7 to a substrate surface. Section 9 A coating substrate provided with a coating film formed from an inorganic zinc primer as described in any one of items 1 to 8. Section 10 A painted structure having a coating film formed from an inorganic zinc primer as described in any one of items 1 to 9. That is the case. [Effects of the Invention]

[0014] The inorganic zinc primer of the present invention can prevent rusting of steel plates when applied to them. Furthermore, even after processing a steel plate coated with this inorganic zinc primer, the corrosion resistance of the processed area remains the same as that of the unprocessed area. [Modes for carrying out the invention]

[0015] In one embodiment, the present invention comprises an inorganic binder, graphene, zinc powder, an inorganic pigment, and a solvent. The amount of zinc powder is within the range of 20 to 75 parts by mass, based on 100 parts by mass of paint solids. The graphene content is within the range of 0.01 to less than 3.0 parts by mass, based on 100 parts by mass of zinc powder. The present invention provides an inorganic zinc primer in which the inorganic pigment component contains silica powder, and the amount of the silica powder is in the range of 20 to 95 parts by mass based on 100 parts by mass of zinc powder. In the present invention, an inorganic zinc primer refers to a primer coating containing zinc powder.

[0016] [Inorganic binders] In the present invention, an inorganic binder is incorporated into the inorganic zinc primer to bind graphene, zinc powder, and inorganic pigment components within the coating film. In a preferred embodiment, the inorganic binder is a silicon-based binder, and preferably includes organosilicates and / or their condensates and colloidal silica.

[0017] Organosilicates and / or condensates thereof Examples of the organosilicate and / or its condensate components include organosilicates and / or their condensate components such as tetraalkoxysilicate, alkyltrialkoxysilicate, and dialkyldialkoxysilicate. Examples of the tetraalkoxysilicate include tetramethoxysilicate, tetraethoxysilicate, tetrapropoxysilicate, tetraisopropoxysilicate, tetrabutoxysilicate, and tetraisobutoxysilicate. Examples of the alkyltrialkoxysilicate include methyltrimethoxysilicate, methyltriethoxysilicate, methyltripropoxysilicate, ethyltrimethoxysilicate, and ethyltriethoxysilicate. Examples of the dialkyldialkoxysilicate include dimethyldimethoxysilicate, dimethyldiethoxysilicate, diethyldimethoxysilicate, diethyldiethoxysilicate, and combinations thereof. Furthermore, these organosilicates may also include those that have undergone a hydrolysis reaction followed by a condensation reaction to an arbitrary reaction rate.

[0018] Examples of commercially available condensation reaction products of such organosilicates include ethyl silicate 28 (manufactured by Nippon Colcoat Co., Ltd.), ethyl silicate 40 (manufactured by Nippon Colcoat Co., Ltd.), and ethyl silicate 48 (manufactured by Nippon Colcoat Co., Ltd.).

[0019] In the inorganic binder, the content of the organosilicate compound and / or its condensate is preferably in the range of 50 to 95 parts by mass, and particularly 60 to 90 parts by mass, based on 100 parts by mass of inorganic binder solids, from the viewpoint of corrosion resistance of the unprocessed and processed parts. Furthermore, in the embodiment of the multi-component inorganic zinc primer comprising a main component (I) and a pigment paste (II) described later, the content of the organosilicate compound and / or its condensate in the main component (I) is preferably in the range of 50 to 95 parts by mass, and particularly preferably in the range of 60 to 90 parts by mass, based on 100 parts by mass of inorganic binder solids. When using an inorganic binder that generates SiO2 while producing by-products during moisture curing, such as organosilicates and / or their condensate components (for example, tetraalkoxysilicate condensates produce alcohol as a by-product and generate SiO2 during moisture curing), the present invention calculates the solid content (inorganic binder solid content, paint solid content, etc.) of the portion containing the inorganic binder based on the remaining components (remaining SiO2, etc.) excluding the above-mentioned by-products.

[0020] In this specification, solid content refers to the residue obtained by removing volatile components such as water and organic solvents from the sample, and can be measured according to the JIS K 5601 1-2 (2008) standard (heating temperature: 125°C, heating time: 60 minutes).

[0021] [Colloidal Silica] The colloidal silica mentioned above refers to a state in which silica is finely dispersed in a liquid such as water, an organic solvent, or a mixture of water and an organic solvent. Colloidal silica is commercially available and comes in various forms, including sodium ion-stabilized, acidic, and ammonium ion-stabilized types. The average primary particle diameter of the colloidal silica is preferably in the range of 1 nm to 100 nm, and particularly in the range of 5 nm to 50 nm. The average primary particle diameter is a catalog value, and if the catalog value is unknown, it can be measured by the BET method (JIS Z 8830 (2013)). Examples of commercially available products include the "Snowtex" series from Nissan Chemical Industries, Ltd. and the "Adelite AT" series from Asahi Denka Kogyo Co., Ltd.

[0022] From the viewpoint of corrosion resistance of the unprocessed and processed parts, the solid content of colloidal silica is preferably in the range of 1 to 50 parts by mass, more preferably 5 to 50 parts by mass, and particularly preferably 10 to 40 parts by mass, based on 100 parts by mass of inorganic binder solids. Furthermore, in embodiments of a multi-component inorganic zinc primer containing a main component (I) and a pigment paste (II) as described later, the solid content of colloidal silica is preferably 5 to 50 parts by mass, and particularly preferably in the range of 10 to 40 parts by mass, based on 100 parts by mass of inorganic binder solids in the main component (I). Furthermore, in such embodiments, even when using 100 parts by mass of solids in the main component (I) as a reference, the solid content of colloidal silica is preferably 5 to 50 parts by mass, and particularly preferably in the range of 10 to 40 parts by mass.

[0023] [Graphene] The inorganic zinc primer of this embodiment contains graphene. In this embodiment, by including zinc powder along with a specific amount of graphene, the sacrificial corrosion protection effect of the zinc powder can be further improved. Furthermore, even if the surface is processed after painting, the sacrificial corrosion protection effect of the processed area is less likely to be impaired, thus improving corrosion resistance.

[0024] Generally, graphene, in the narrow sense, refers to a thickness of one atom of sp². 2 While the term "graphene" generally refers to a sheet of bonded carbon atoms (single-layer graphene), in this specification, the term also includes materials that have a layered, flaky form. Similarly, the term "graphene" also includes materials that have a layered, flaky form, as described later.

[0025] In this specification, materials with an O / C ratio (the atomic ratio of oxygen atoms to carbon atoms) greater than 0.4, as measured by X-ray photoelectron spectroscopy (XPS), are referred to as graphene oxide, while those with an O / C ratio of 0.4 or less are referred to as graphene. Furthermore, reduced graphene oxide obtained by reducing graphene oxide, with an O / C ratio of 0.4 or less, is also referred to as graphene.

[0026] Graphene may be manufactured by a physical exfoliation method or a chemical exfoliation method. When manufactured by a physical exfoliation method, it can be produced using graphite as a raw material by known methods involving heat treatment or the application of strong shear force. When manufactured by a chemical exfoliation method, graphene oxide is subjected to a reduction treatment to produce reduced graphene oxide. There are no particular limitations on the method for producing graphene oxide, and known methods can be used. Alternatively, commercially available graphene oxide may be purchased and used. From the viewpoint of higher exfoliation degree, superior dispersibility in inorganic zinc primer, and enhanced corrosion resistance, it is preferable to use graphene manufactured by a chemical exfoliation method.

[0027] The graphene of the present invention preferably has an elemental ratio of oxygen to carbon (O / C ratio) of 0.05 or more and 0.40 or less, as measured by X-ray photoelectron spectroscopy. The O / C ratio represents the amount of functional groups on the graphene, and the oxygen element originates from hydroxyl groups and carboxyl groups. Since these functional groups can form bonds with the aforementioned inorganic binder, they have the effect of maintaining corrosion protection, especially in processed areas. From the viewpoint of further improving dispersibility in inorganic zinc primer and superior bonding with the binder, an O / C ratio of 0.08 or more is more preferable. Furthermore, from the viewpoint of further enhancing the corrosion protection effect of graphene, 0.3 or less is more preferable, and 0.25 or less is even more preferable.

[0028] The O / C ratio of graphene is measured by X-ray photoelectron spectroscopy (XPS) after extracting graphene from an inorganic zinc primer, pulverizing it by vacuum drying, and then performing XPS analysis. The main C1s peak, based on carbon atoms, is assigned to 284.3 eV, and the O1s peak, based on oxygen atoms, is assigned to a peak around 533 eV. The O / C ratio is calculated from the area ratio of each peak, and the resulting value is rounded to two decimal places.

[0029] The O / C ratio of graphene can be easily adjusted to the aforementioned range by, for example, adjusting the degree of oxidation of the raw material graphene oxide and the degree of reduction due to the reduction reaction conditions when using a chemical exfoliation method. Alternatively, commercially available graphene oxide or graphene with the desired O / C ratio may be used.

[0030] The average thickness of the graphene in this invention is preferably 0.3 nm or more and 100 nm or less. An average thickness of 0.30 nm is the theoretical minimum for graphene and indicates that it is a single layer of graphene. On the other hand, by making the average thickness of the graphene 100 nm or less, the dispersibility of graphene in the inorganic zinc primer can be further improved. The average thickness of the graphene is more preferably 50 nm or less, even more preferably 20 nm or less, and even more preferably 10 nm or less.

[0031] The average thickness of graphene can be easily adjusted to the aforementioned range by adjusting the degree of dispersion of graphene oxide or reduced graphene using a disperser or kneader. Alternatively, commercially available graphene oxide or graphene with a desired average thickness may be used.

[0032] In this invention, the average thickness of graphene is measured by sampling graphene from an inorganic zinc primer and using an atomic force microscope. Using an atomic force microscope, the graphene is observed under magnification to a field of view of approximately 1 to 20 μm square so that it can be properly observed. Ten randomly selected graphene samples are measured, and their thicknesses are calculated by determining the arithmetic mean. The thickness of each graphene sample is the arithmetic mean of five randomly selected thickness measurements on that graphene sample.

[0033] In the present invention, the size of graphene in the direction parallel to the graphene layer is preferably 0.5 μm or more, more preferably 1.0 μm or more, from the viewpoint of further enhancing the corrosion resistance. On the other hand, from the viewpoints of further enhancing the dispersibility and further improving the corrosion resistance, it is preferably 100 μm or less, more preferably 50 μm or less, and still more preferably 20 μm or less. Therefore, in the present invention, graphene powder is preferably used as the graphene. The size of graphene in the direction parallel to the graphene layer can be easily adjusted to the above-mentioned range by applying a shearing force by a disperser or a crusher to graphene oxide or reduced graphene. Also, commercially available graphene oxide or graphene having a desired size may be used.

[0034] The size of graphene in the direction parallel to the graphene layer is measured using an electron microscope after collecting graphene from the inorganic zinc primer. Using an electron microscope, the observation is enlarged to a visual field range of about 5 μm to 200 μm square so that graphene can be appropriately observed, and for 10 randomly selected graphenes, the length (major axis) of the longest part and the length (minor axis) of the shortest part in the direction parallel to the graphene layer are measured respectively, and it is calculated by obtaining the arithmetic mean value of the numerical value obtained by (major axis + minor axis) / 2.

[0035] The graphene of the present invention preferably has a D / G ratio measured by Raman spectroscopy of 1.0 or more and 2.5 or less. In the present specification, the D / G ratio is an index of the amount of the defect structure of graphene and can be measured by Raman spectroscopy. The peak intensity ratio of Raman measurement is that when an argon ion laser is used as the excitation laser and the excitation wavelength is 514.5 nm. In Raman spectroscopy, graphene has peaks around 1580 cm -1 and around 1335 cm -1 and the peak intensity around 1580 cm -1 is G, and around 1335 cm -1Let D be the intensity of the nearby peak. In perfect graphite crystals, the D peak does not appear, and as the symmetry of the graphite structure is lost, the intensity of the D peak increases. Therefore, as the structural defects of graphene increase, the intensity ratio of the D peak to the G peak (D / G ratio) decreases. From the viewpoint of further improving dispersibility in inorganic zinc primer, a D / G ratio of 1.3 or higher is more preferable, and 1.4 or higher is even more preferable. Also, from the viewpoint of further improving corrosion resistance, a ratio of 2.2 or lower is more preferable.

[0036] The D / G ratio of graphene can be easily adjusted to the aforementioned range by, for example, adjusting the degree of oxidation of the raw material graphene oxide and the degree of reduction due to the reduction reaction conditions when using a chemical exfoliation method. Alternatively, commercially available graphene oxide or graphene with a desired D / G ratio may be used.

[0037] The graphene of the present invention has a specific surface area (hereinafter simply referred to as "specific surface area") of 80 m² as measured by the BET method. 2 / g or more 250m 2 It is preferable that the amount is less than or equal to / g. The specific surface area of ​​graphene reflects the degree of delamination of graphene, and within the above range, the higher the degree of delamination of graphene, the larger the specific surface area. From the viewpoint of further improving dispersibility in inorganic zinc primer and further improving corrosion resistance, the specific surface area of ​​graphene is 100m². 2 It is more preferable that it be 130m or more per gram. 2 It is more preferable that the amount is 200 m² or more. Furthermore, from the viewpoint of suppressing aggregation due to decreased dispersibility, the specific surface area of ​​graphene should be 200 m². 2 It is more preferable that the value be less than or equal to / g. The BET measurement method shall be performed according to the method described in JIS Z8830:2013, the amount of adsorbed gas shall be measured by the carrier gas method, and the adsorption data shall be analyzed by the single-point method.

[0038] In this embodiment, the graphene content is 0.01 or more and less than 3.0 parts by mass, based on 100 parts by mass of zinc powder as described later, and is particularly preferably in the range of 0.05 to 1.5 parts by mass.

[0039] If the graphene content is less than 0.01 parts by mass, the process resistance and corrosion resistance after processing are insufficient. On the other hand, if the content is 3.0 parts by mass or more, the process resistance and corrosion resistance after processing are insufficient, and the manufacturability is also reduced, which is undesirable.

[0040] Graphene is preferably mixed and dispersed together with inorganic pigments and zinc powder, as described later. In the mixed dispersion, graphene may be in powder form, paste form, or liquid dispersion form. From the viewpoint of further improving the dispersibility and corrosion resistance of graphene, it is preferable to use it in paste form or liquid dispersion form. When graphene is in paste form or liquid dispersion form, solvents described later can preferably be used, and it can be manufactured using known dispersion techniques. Mixing equipment used for dispersion includes, for example, bead mills, homodispers, homomixers, planetary mixers, sand mills, and other mixers and kneaders.

[0041] In this embodiment, since the total amount of zinc powder and inorganic pigment is excessive compared to the amount of graphene, the graphene in the coating film comes into contact with the surface of the zinc powder and inorganic pigment, and at least a portion of the surface of the zinc powder and inorganic pigment is coated with graphene.

[0042] [Zinc powder] The aforementioned zinc powder is a powder made of zinc, and is not particularly limited in shape, size, etc., and conventionally known types in the paint field can be used.

[0043] The zinc powder content is in the range of 20 to 75 parts by mass, based on 100 parts by mass of paint solids, and is particularly preferably in the range of 25 to 65 parts by mass.

[0044] If the zinc powder content is less than 15 parts by mass, the corrosion protection of both the unprocessed and processed parts is insufficient. On the other hand, if it exceeds 75 parts by mass, the corrosion protection of the processed part is insufficient, and the manufacturability also decreases, which is undesirable.

[0045] [Inorganic pigment content] The inorganic zinc primer of this embodiment contains silica powder as an inorganic pigment component. In this embodiment, by including a specific amount of silica powder relative to zinc powder along with a specific amount of graphene, rust formation of the steel plate is prevented, and the corrosion resistance of the processed area is equivalent to that of the unprocessed area even after processing following painting. The silica powder may be manufactured by any method and in any shape, and may be amorphous or crystalline.

[0046] The silica powder differs from colloidal silica in that its particle size is larger than that of colloidal silica. Therefore, in this invention, the term "silica powder" does not include colloidal silica. Examples of silica powder include crystalline silica and amorphous silica. In this invention, the terms "crystalline silica" and "amorphous silica" refer to materials other than colloidal silica. The average particle size of the silica powder is preferably in the range of 1 to 10 μm, and particularly in the range of 2 to 8 μm. The average particle size is the average particle size including not only the particle size of primary particles but also the particle size of secondary particles (aggregates), and is the D50 value of the volume-based particle size distribution. The D50 value is the particle size at which the cumulative particle size distribution from the small particle size side accounts for 50% of the volume-based particle size distribution. The measurement method is the laser diffraction scattering method, performed in accordance with JIS Z 8825 (2022). In this process, as a pretreatment, the sample is dispersed by adding it to a mixed solvent of acetone and isopropyl alcohol and applying ultrasound for 1 minute, adjusting the sample concentration to a concentration within a predetermined transmittance range set in the instrument. The transmittance range is, for example, 0.800 to 0.930.

[0047] The silica powder content is in the range of 20 to 95 parts by mass, based on 100 parts by mass of zinc powder, and is particularly preferably in the range of 30 to 90 parts by mass.

[0048] If the silica powder content is less than 20 parts by mass, the corrosion resistance after processing is insufficient. On the other hand, if it exceeds 90 parts by mass, the corrosion resistance of both the unprocessed and processed parts is insufficient, and the manufacturability also decreases, which is undesirable.

[0049] The inorganic pigment component may include inorganic pigments other than silica powder. Examples of the other inorganic pigments include extender pigments such as kaolin, clay, mica, talc, barium sulfate, calcium carbonate, aluminum hydroxide, zinc oxide, barite, zirconium oxide, zirconium silicate, potassium feldspar, wollastonite, and diatomaceous earth; coloring pigments such as titanium dioxide, graphite, red iron oxide, and cyanine-based coloring pigments; rust-preventive pigments such as phosphate-based metal compounds, phosphite-based metal compounds, metal silicate salts, metal ion exchange silica-based compounds, condensed phosphate-based metal compounds, vanadium-based metal compounds, and combinations thereof.

[0050] Furthermore, in this embodiment, from the viewpoint of suitability for manufacturing the inorganic zinc primer and corrosion resistance, it is preferable that the total amount of zinc powder and inorganic pigment is in the range of 60 to 98 parts by mass, more preferably more than 60 parts by mass and 98 parts by mass or less, and particularly preferably 70 to 95 parts by mass, based on 100 parts by mass of paint solids. Also, it is preferable that the amount of inorganic pigment is in the range of 5 to 60 parts by mass, more preferably more than 5 parts by mass and 60 parts by mass or less, and particularly preferably 10 to 45 parts by mass, based on 100 parts by mass of paint solids.

[0051] [solvent] Examples of the solvent include water and organic solvents. Examples of organic solvents include alcohol-based organic solvents, aromatic organic solvents, ether-based organic solvents, ketone-based organic solvents, and ester-based organic solvents.

[0052] Examples of the aforementioned alcoholic organic solvents include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and 3-methoxy-3-methyl-1-butanol; and polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, and trimethylolpropane.

[0053] Examples of aromatic organic solvents include benzene, toluene, and xylene.

[0054] Examples of the aforementioned ether-based organic solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether; tetrahydrofuran, 1,4-dioxane, anisole, and the like.

[0055] Examples of the ketone-based organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl-n-amyl ketone.

[0056] Examples of the ester-based organic solvents include methyl acetate, ethyl acetate, and butyl acetate.

[0057] [Inorganic zinc primer] The inorganic zinc primer of this embodiment may contain appropriate amounts of additives other than the inorganic binder, such as binders, catalysts, thickeners, defoamers, and dispersants.

[0058] [catalyst] Among these, catalysts that can promote the hydrolysis condensation of organosilicates, the reaction between organosilicates and surface hydroxyl groups of colloidal silica, etc., can be widely used. More specifically, catalysts include, for example, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, formic acid, and phosphoric acid; organotin compounds such as dioctyltin dilaurate, dioctyltin dimaleate, dioctyltin maleate, and tin octoate; phosphate esters such as monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, and didecyl phosphate; and di- Examples include organic titanate compounds such as sopropoxybis(acetylacetate)titanium and diisopropoxybis(ethylacetoacetate)titanium; organic aluminum compounds such as tris(ethylacetoacetate)aluminum and tris(acetylacetonate)aluminum; and organic zirconium compounds such as tetrabutylzirconate, tetrakis(acetylacetonate)zirconium, tetraisobutylzirconate, and butoxytris(acetylacetonate)zirconium.

[0059] From the viewpoint of corrosion resistance of the unprocessed and processed parts, the catalyst content is preferably 0.2 to 5.0 parts by mass, and particularly preferably in the range of 0.5 to 3.0 parts by mass, based on 100 parts by mass of inorganic binder solids. Furthermore, in embodiments of the multi-component inorganic zinc primer containing the main component (I) and pigment paste (II) described below, even when based on 100 parts by mass of solids of the main component (I), the catalyst content is preferably 0.01 to 5.0 parts by mass, and particularly preferably in the range of 0.05 to 3.0 parts by mass.

[0060] The inorganic zinc primer described above is not limited to a paint form as long as it is within the scope of the present invention, but preferably it is a multi-component system in which the main component (I) and pigment paste (II) are stored in separate containers and mixed before painting. For details, Main component (I) containing an inorganic binder and a solvent, This is an inorganic zinc primer comprising a pigment paste (II) containing graphene, zinc powder, inorganic pigment components, and a solvent.

[0061] Furthermore, in embodiments of a multi-component inorganic zinc primer comprising a main component (I) and a pigment paste (II), unless otherwise specified, "based on 100 parts by mass of paint solids" means that the total paint solids of the main component (I) and the pigment paste (II) are based on 100 parts by mass. Therefore, for example, "the amount of zinc powder is in the range of 20 to 75 parts by mass based on 100 parts by mass of paint solids" means that, in embodiments of a multi-component inorganic zinc primer, the amount of zinc powder is in the range of 20 to 75 parts by mass based on the total paint solids of the main component (I) and the pigment paste (II) are based on 100 parts by mass.

[0062] The amount of solvent contained in the main component is preferably in the range of 50 to 95 parts by mass, and particularly 60 to 90 parts by mass, based on 100 parts by mass of main component (I), from the viewpoint of miscibility with the pigment paste and ease of painting.

[0063] In this embodiment, from the viewpoint of corrosion protection of the unprocessed and processed parts, it is preferable that the solvent on the main component (I) side contains both water and an organic solvent. The solvent can be added at any stage of the production of the main component (I). For example, the solvent may be added as a diluent for viscosity adjustment, or raw materials such as colloidal silica may be provided containing the solvent and the solvent may be added when these raw materials are blended.

[0064] Furthermore, it is preferable that the catalyst is included in the main component (I). In other words, a part of this embodiment is Main component (I) containing an inorganic binder, catalyst and solvent, This is an inorganic zinc primer comprising a pigment paste (II) containing graphene, zinc powder, inorganic pigment components, and a solvent.

[0065] In these multi-component embodiments, the types and amounts of inorganic binders, graphene, zinc powder, inorganic pigments, solvents, etc., are the same as described above.

[0066] The amount of solvent contained in the pigment paste (II) is preferably in the range of 5 to 60 parts by mass, and particularly 10 to 50 parts by mass, based on 100 parts by mass of pigment paste (II), from the viewpoint of manufacturability. From the viewpoint of manufacturability, an organic solvent is preferred for the solvent in the pigment paste (II). The solvent can be added at any stage of the production of the pigment paste (II). For example, the solvent may be added as a diluent for viscosity adjustment, or raw materials such as graphene and additives may be provided with the solvent already contained, and the solvent may be added when these raw materials are blended.

[0067] In these multi-component systems, the main component (I) is preferably an organosilicate and / or a condensate thereof, colloidal silica, a catalyst, and a solvent.

[0068] [Base material] Substrates to which this inorganic zinc primer can be applied include steel, galvanized steel, stainless steel, magnesium alloy, aluminum, aluminum alloy, etc., with steel being the preferred choice.

[0069] [Painting method and painted substrate] This inorganic zinc primer can be applied by conventionally known methods such as air spraying, airless spraying, or brushing. It is preferable to remove rust from the substrate by blasting prior to application. Since the coating film made with this inorganic zinc primer has excellent corrosion resistance, the thickness of the coating on the substrate after application can be made thin. Specifically, it is in the range of 1 to 30 μm, and particularly 5 to 25 μm. The coating thickness can be measured with an electromagnetic film thickness meter.

[0070] For drying after painting, room temperature drying is preferable, but forced drying using heating equipment is also possible if necessary.

[0071] [Painted structures] Examples of structures to be painted in this embodiment include steel structures such as ships, offshore structures, plants, bridges, and tanks. This inorganic zinc primer has excellent workability as well as corrosion resistance, so it can be applied not only to the substrate before the construction of the structure, but also to the structure after its construction. [Examples]

[0072] The present invention will be described in more detail above with reference to examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" mean "parts by mass" and "% by mass," respectively.

[0073] [Production of inorganic zinc primers] Example 1 Nineteen parts of "Ethyl Silicate 40" (Note 1) and 37 parts of isopropyl alcohol were placed in a reaction vessel. The reaction vessel was kept at 50°C, and 0.1 parts of 2N hydrochloric acid and 7 parts of "Snowtex ST-O" (Note 2) were added dropwise over approximately 1 hour while stirring. After the dropwise addition was complete, stirring was continued for 1 hour to produce a solution of the inorganic binder. In a separate container, 26 parts isopropanol, 1 part graphite, 26 parts crystalline silica (Note 4), and 3.1 parts graphene dispersion (C) (Note 5) were charged. Glass beads were added, and the mixture was shaken in a paint shaker for 1 hour, after which the glass beads were filtered off. Next, 46 parts zinc powder was added and dispersed for 30 minutes to produce a pigment dispersion paste. Next, the inorganic binder and pigment dispersion paste were mixed according to the proportions shown in Table 1 below to produce an inorganic zinc primer. (Note 1) "Ethyl Silicate 40": Trade name, manufactured by Colcoat, condensate of tetraethoxysilane, silica residue 40% by mass (In this specification, the solid content of ethyl silicate 40 is considered to be 40% by mass) (Note 2) "Snowtex ST-O": Product name, manufactured by Nissan Chemical Corporation, acidic colloidal silica, average primary particle size 12 nm, solid content 20% by mass, water content (Note 3) Amorphous silica: Average particle size 5 μm (Note 4) Crystalline silica: Average particle size 3.7 μm (Note 5) Graphene solution (C): Reduced graphene oxide was produced in an aqueous solvent by chemical exfoliation. The aqueous slurry of the obtained reduced graphene oxide was filtered and concentrated using filter paper, and the concentrated slurry was recovered. The obtained concentrated slurry was mixed with twice the weight of isopropyl alcohol, and processed using a Homodisper 2.5 type (Primix) at a rotation speed of 3,000 rpm for 30 minutes, then filtered using filter paper to recover the graphene wet cake. The obtained graphene wet cake was processed using a Homodisper 2.5 type (Primix) at a rotation speed of 3,000 rpm for 30 minutes with a mixed solvent of 42.5% xylene and 57.5% isopropyl alcohol as the solvent to produce a graphene dispersion containing 1.5% by mass of graphene.

[0074] The properties of graphene were analyzed using the methods described in Preparation Examples 1 and 2, and Measurement Examples 1-5 below. The average thickness of the graphene was 3 nm, the size of the graphene in the direction parallel to the graphene layer was 10 μm, the O / C ratio of the graphene was 0.10, the D / G ratio of the graphene was 1.9, and the BET specific surface area of ​​the graphene was 160 m². 2 It was / g.

[0075] [Preparation Example 1: Preparation of Graphene Diluent] The pigment dispersion pastes prepared in each example and comparative example were diluted 10-fold with xylene and processed using a Homodisper 2.5 type (Primix) at 3,000 rpm for 30 minutes to prepare a paint diluent. The obtained paint diluent was operated in a centrifuge at 11,000 rpm for 20 minutes, and after removing the supernatant, the black slurry on top of the precipitate was collected. 10 times the weight of xylene was added to the obtained black slurry and processed again using a Homodisper 2.5 type (Primix) at 3,000 rpm for 30 minutes to redisperse it. The slurry was then passed through a mesh filter with a mesh size that could remove inorganic particles to remove them. The obtained filtrate was filtered using filter paper to recover graphene. The recovered graphene was washed 5 times with 20 mL of N-methylpyrrolidone. The washed graphene was diluted to 0.01% by weight using N-methylpyrrolidone and processed for 60 seconds at a rotation speed of 40 m / s (shear rate: 20,000 per second) using a "Filmix" (registered trademark) 30-30 model (Primix Corporation) to obtain a graphene dilution.

[0076] [Preparation Example 2: Preparation of Graphene Powder] The graphene dilution prepared in the same manner as in Preparation Example 1 was filtered using filter paper to recover the graphene. The recovered graphene was washed five times with 20 mL of deionized water. The washed graphene was diluted to 0.01% by weight using deionized water and processed for 60 seconds at a rotation speed of 40 m / s (shear rate: 20,000 per second) using a "Filmix" (registered trademark) 30-30 model (Primix Corporation) to obtain a graphene aqueous dilution. The obtained graphene aqueous dilution was frozen with liquid nitrogen and vacuum dried overnight using a freeze vacuum dryer to produce graphene powder.

[0077] [Measurement Example 1: Average Thickness of Graphene] The graphene dilution prepared in Preparation Example 1 was dropped onto a mica substrate and dried to deposit graphene onto the substrate. The graphene on the substrate was observed using an atomic force microscope (Dimension Icon; Bruker) under magnification to a field of view of approximately 1 to 10 μm square, and the thickness of 10 randomly selected graphenes was measured. The thickness of each graphene was calculated as the arithmetic mean of the thickness measurements taken at 5 randomly selected locations on each graphene. The average thickness of the graphene was calculated by determining the arithmetic mean of the thicknesses of the 10 graphenes.

[0078] [Measurement Example 2: Dimensions of graphene in the direction parallel to the graphene layer] A graphene diluent was prepared in the same manner as in Preparation Example 1, and the graphene diluent was dropped onto a mica substrate and dried in the same manner as in Measurement Example 1 to deposit graphene onto the substrate. The graphene on the substrate was observed at a magnification of 30,000x using an electron microscope S-5500 (manufactured by Hitachi High-Technologies Corporation). For 10 randomly selected graphenes, the length of the longest part (major axis) and the length of the shortest part (minor axis) in the direction parallel to the graphene layer were measured, and the size in the direction parallel to the graphene layer was calculated by taking the arithmetic mean of the values ​​obtained by (major axis + minor axis) / 2.

[0079] [Measurement Example 3: O / C ratio of graphene] Graphene powder was prepared in the same manner as in Preparation Example 2. The photoelectron spectrum of the graphene powder was measured using an X-ray photoelectron spectrometer Quantera SXM (manufactured by ULVAC-PHI, Inc.). The excitation X-rays were monochromatic AlKα1,2 lines (1486.6 eV), with an X-ray diameter of 200 μm and a photoelectron escape angle of 45°. The main C1s peak based on carbon atoms was assigned to 284.3 eV, and the O1s peak based on oxygen atoms was assigned to a peak around 533 eV. The O / C ratio was calculated from the area ratio of the O1s peak and the C1s peak, and the obtained value was rounded to two decimal places.

[0080] [Measurement Example 4: Graphene D / G Ratio] Graphene powder was prepared in the same manner as in Preparation Example 2. Raman measurements were performed on the graphene powder using a Ramanor T-64000 (Jobin Yvon / Atago Bussan). The beam diameter was 100 μm, and an argon ion laser (wavelength: 514.5 nm) was used as the light source. (1580 cm⁻¹) -1 The peak intensity in the vicinity is G, 1335 cm. -1 The intensity of the nearby peak was denoted as D, and the intensity ratio of the D peak to the G peak (D / G ratio) was calculated. The obtained value was then rounded to one decimal place by rounding to the second decimal place.

[0081] [Measurement Example 5: Specific Surface Area of ​​Graphene] Graphene powder was prepared in the same manner as in Preparation Example 2. The specific surface area of ​​the graphene powder was measured using an HM Model-1210 (Macsorb). The measurement principle was the BET flow method (single-point method) (as described in Z8830:2013). Degassing conditions were 100°C for 180 minutes. The equilibrium relative pressure was measured at 0.29.

[0082] Examples 2-12 and Comparative Examples 1-7 In Example 1, an inorganic zinc primer was prepared using the same procedure as in Example 1, except that the materials and their proportions were as shown in Table 1 below.

[0083] [Table 1]

[0084] [Painting onto the substrate] A steel plate measuring 300 mm in length, 100 mm in width, and 1.7 mm in thickness was shot-blasted. Both sides were then coated with various inorganic zinc primers using an air spray to achieve a dry film thickness of 10 μm. This coated steel plate was then left in an environment of 23°C and 50% RH for 7 days. Furthermore, the steel plate was bent at a position 120 mm from the longitudinal end face so that the angle was 120°, obtaining a test specimen with the convex bent portion and the remaining flat general portion as the evaluation surface. For accurate evaluation, the end faces and back surfaces of the test specimen were coated with epoxy resin paint to prevent corrosion.

[0085] [Evaluation Test] (*) Manufacturability Manufacturability was evaluated by checking the dispersion of each pigment paste produced in the examples and comparative examples using a particle gauge. The evaluation criteria are as follows. S: The result when evaluated with a particle gauge is less than 40 μm. A: The result when evaluated with a particle gauge was 40 μm to 50 μm. B: When evaluated with a particle gauge, the result is greater than 50 μm and less than or equal to 75 μm. C: When evaluated with a particle gauge, the result is greater than 75 μm and less than or equal to 00 μm. D: The result when evaluated with a particle gauge exceeds 100 μm. (*) Processing resistance The degree of cracking of the coating on the bent portion was evaluated according to the following criteria. S: No cracks in the paint film at the bent parts. A: Very slight cracks in the paint film that do not reach the base material are observed at the bent portion. B: Slight cracks in the paint film that do not reach the base material are observed at the bent area. C: Slight cracks in the paint film reaching the base material are observed at the bent portion. D: Significant cracking of the paint film reaching the base material is observed at the bent portion. (*) Corrosion resistance The test specimens after the bending process described above were exposed for 6 months at a location 10m from the shore on the coast of Sumoto City, Hyogo Prefecture, and the rust formation on the bent and flat sections was evaluated according to the following criteria. Red rust formed on both the bent and flat sections. In this experiment, the corrosion resistance of the flat section was considered equivalent to the corrosion resistance of the unprocessed section (before processing), and the corrosion resistance of the bent section was considered equivalent to the corrosion resistance of the processed section (after processing). ·Flat area corrosion resistance S: No white rust at all on the flat surfaces. A: The area percentage of white rust on the flat surface is greater than 0 and less than 5%. B: The area percentage of white rust on flat surfaces is 5% or more but less than 30%. C: The area percentage of white rust on flat surfaces is between 30% and 50%. D: The area percentage of white rust on flat surfaces exceeds 50%. • Corrosion resistance at the bent parts S: No red rust at all on the bent parts. A: The area percentage of red rust on the bent part is greater than 0 and less than 5%. B: The area percentage of red rust on the bent part is 5% or more but less than 30%. C: The area percentage of red rust on the bent part is between 30% and 50%. D: The area covered by red rust on the bent portion exceeds 50%.

Claims

1. It contains an inorganic binder, graphene, zinc powder, inorganic pigment, and solvent. The amount of zinc powder is within the range of 20 to 75 parts by mass, based on 100 parts by mass of paint solids. The amount of graphene is within the range of 0.01 or more and less than 3.0 parts by mass, based on 100 parts by mass of zinc powder. The inorganic pigment component contains silica powder, and the amount of the silica powder is within the range of 20 to 95 parts by mass, based on 100 parts by mass of zinc powder. Inorganic zinc primer.

2. The inorganic zinc primer according to claim 1, wherein the inorganic binder comprises organosilicate and / or a condensate thereof, and colloidal silica.

3. The inorganic zinc primer according to claim 1 or 2, wherein the solid content of colloidal silica is in the range of 5 to 50 parts by mass, based on 100 parts by mass of inorganic binder solids.

4. The inorganic zinc primer according to claim 1 or 2, wherein the graphene has a D / G ratio of 1.0 or more and 2.5 or less as measured by Raman spectroscopy.

5. The inorganic zinc primer according to claim 1 or 2, wherein the total amount of zinc powder and inorganic pigment is within the range of more than 60 parts by mass and 98 parts by mass or less, based on 100 parts by mass of paint solids.

6. A multi-component inorganic zinc primer for preparing an inorganic zinc primer by mixing a main component (I) and a pigment paste (II) before painting, Main component (I) containing an inorganic binder and a solvent, An inorganic zinc primer according to claim 1 or 2, comprising a pigment paste (II) containing graphene, zinc powder, an inorganic pigment component, and a solvent.

7. A multi-component inorganic zinc primer for preparing an inorganic zinc primer by mixing a main component (I) and a pigment paste (II) before painting, Main component (I) containing an inorganic binder, catalyst, and solvent, An inorganic zinc primer according to claim 1 or 2, comprising a pigment paste (II) containing graphene, zinc powder, an inorganic pigment component, and a solvent.

8. A coating method comprising coating a substrate surface with the inorganic zinc primer described in claim 1 or 2.

9. A coating substrate provided with a coating film formed from the inorganic zinc primer according to claim 1 or 2.

10. A painted structure provided with a coating film formed from the inorganic zinc primer described in claim 1 or 2.

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