Geopolymer coatings

Abstract

This invention provides a geopolymer coating material, which is primarily composed of geopolymers, and which protects the coated object with the coating film formed thereon and improves its aesthetic appeal. [Solution] A coating material mainly composed of a geopolymer consisting of an active filler and an alkaline solution, and containing a coloring pigment, wherein the average particle size of the coloring pigment is 0.1 μm or more, so that the coating film formed from this coating material is durable and has an aesthetic appeal.

Description

[Technical Field]

[0001] This invention relates to a coating material applied to wall surfaces such as the interior and exterior walls of structures such as buildings, and more specifically to a geopolymer coating material that uses a geopolymer as its binder component. [Background technology]

[0002] Traditionally, there have been many types of coatings applied to the interior and exterior walls of buildings and other structures, including those primarily composed of organic binders such as synthetic resin emulsions, and those using inorganic binders such as cement. The coatings formed by these materials are used to improve the durability and aesthetic appeal of wall surfaces.

[0003] Among these, for surfaces to be painted, such as concrete, inorganic binders such as cement, or mixtures of cement and synthetic resin emulsions are sometimes used. On the other hand, in recent years, geopolymers have attracted attention as an alternative material to cement, which emits large amounts of carbon dioxide during its manufacturing process.

[0004] For example, Patent Document 1 proposes a geopolymer for repairing cracks or restoring the cross-section of concrete. This document describes a novel geopolymer that can ensure high injectability and filling properties, appropriate pot life, and excellent strength development at room temperature for crack repair and cross-section restoration.

[0005] Furthermore, Patent Document 2 proposes a geopolymer composition, as well as mortar and concrete using the same. This document describes a geopolymer composition that exhibits good strength development and expansion properties when cured, has low drying shrinkage, and has a good aesthetic appearance when cured. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-163196 [Patent Document 2] Japanese Patent Publication No. 2020-55696 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, these were proposed as mortar, concrete, or cross-section repair materials, and were not intended to be applied to wall surfaces to improve their durability or aesthetic appeal. This invention provides a geopolymer coating material, which is mainly composed of geopolymers, and which can protect the coated object with the coating film formed thereby and improve its aesthetic appeal. [Means for solving the problem]

[0008] A coating material primarily composed of a geopolymer consisting of an active filler and an alkaline solution, and containing a coloring pigment, wherein the average particle size of the coloring pigment is 0.1 μm or larger, resulting in a durable and aesthetically pleasing coating film formed from this material. Because the geopolymer coating material has an L value of 50 or more for the active filler, the coating film formed from this material can be given vivid colors and has excellent design properties.

[0009] Because the active filler is a geopolymer coating material made of blast furnace slag, a coating film can be formed even at room temperature, and because blast furnace slag is white, it is easy to color the coating material. Furthermore, by including titanium dioxide in the coating material in a range of 0.1 to 20.0% by weight, it is possible to give the coating material a variety of colors. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described. The present invention relates to a coating material containing a geopolimer composed of an active filler and an alkaline solution as a main component and a coloring pigment, and is a geopolimer coating material in which the average particle diameter of the coloring pigment is 0.1 μm or more.

[0011] The active filler contained in the coating material of the present invention is stimulated by the alkalinity of an alkaline compound such as an alkaline solution and hardens. This is because the active filler soluble in the alkaline solution destabilizes its surface by the alkaline compound, and as the moisture of the alkaline stimulant disappears, the active fillers approach each other and bond.

[0012] Examples of this active filler include blast furnace slag, fly ash, silica fume, rice husk ash, etc., but those having an L value of 50 or more are preferred. Here, the L value refers to the L * a * b * It is the L value (lightness) in the L*a*b* color system. When the L value of the active filler is 50 or more, when the coating material containing this active filler contains a coloring pigment, the coating film formed from this coating material can be given a vivid color. More preferably, the L value is 70 or more, and even more preferably, the L value is 80 or more.

[0013] It is preferable to use blast furnace slag as the active filler contained in the coating material of the present invention. Since blast furnace slag has high reactivity, it has good curability, is likely to form a coating film even at room temperature, and has good initial water resistance. In addition, since it is white in color, it is easy to color the coating material, so it can protect the coated object and form a coating film that can also impart designability.

[0014] The active filler is preferably contained in the coating material at 10 to 40% by weight. When it is more than 40% by weight, the bonding force of the coating film becomes strong, and cracks often occur in the coating film. When it is less than 10% by weight, the strength of the coating film and the adhesion to the substrate often deteriorate. More preferably, the content of the active filler is within the range of 10 to 35% by weight, and the coating film has good strength and adhesion to the substrate, and the coating film is less likely to crack. Further, if the content of the active filler is within the range of 15 to 30% by weight, the coating film can achieve a balance between cracking, strength, and adhesion.

[0015] The alkali solution contained in the coating material of the present invention may be any solution in which the active filler is soluble and can destabilize its surface. As this alkali solution, aqueous solutions such as sodium hydroxide, potassium hydroxide, and sodium metasilicate, those showing alkalinity among colloidal silica, solutions and dispersions such as water glass, lithium silicate, and alumina sol are preferably used.

[0016] By using the alkali solution, it reacts with the active filler, gives strength to the coating film formed by the coating material of the present invention, has good adhesion to the substrate, and can protect the coated object. These alkali solutions may be used alone or in combination of two or more. Among these alkali solutions, colloidal silica is preferably used. This colloidal silica is easy to handle, can increase the surface strength, has good adhesion to the substrate, can make the coating film hydrophilic, and forms a good coating film, so it is preferably used because it is less likely to get raindrop stains.

[0017] The average particle diameter of the silica fine particles dispersed in this colloidal silica is preferably 4 to 100 nm, more preferably 6 to 50 nm, and even more preferably 10 to 20 nm. When the average particle diameter of the silica fine particles is within this range, it is easy to adjust the hydrophilicity, and the binding force between the silica fine particles becomes optimal.

[0018] When the average particle diameter of the silica fine particles is less than 4 nm, the binding force between the silica fine particles is too strong, and there is a risk of shrinkage cracks occurring in the coating film. Conversely, when it exceeds 100 nm, the binding force between the silica fine particles is weak, and the strength of the coating film may be weakened. These silica microparticles can take various shapes, including spherical, pearl necklace-like, needle-like, and rod-like, with spherical particles being preferred. This is because, when the silica microparticles dry and become a dry gel, they can form a close-packed structure, thereby improving the strength of the coating film.

[0019] The coating material of the present invention contains a coloring pigment, the average particle size of which is 0.1 μm or larger. Either inorganic or organic pigments may be used as the coloring pigment. For example, metal oxides, complex oxides, chromates, sulfides, phosphates, metal complexes, carbon black, metal powder pigments, pearlescent pigments, azo pigments, and condensed polycyclic pigments can be used in general coating materials. By adding coloring pigments to the coating material, the material can be colored, and the resulting coating film will also be colored, resulting in a stable color and adding aesthetic appeal to the coated object. Without the addition of coloring pigments, the color of the raw materials (mainly the color of the active filler) will determine the color of the coating film, and the color may vary depending on the batch of raw materials.

[0020] Furthermore, the average particle size of this coloring pigment is 0.1 μm or larger. This average particle size of 0.1 μm or larger makes it less likely for the coloring pigment to leach out of the coating, resulting in less color change in the colored coating over time. This is because the coating film formed from the coating material of the present invention has many fine pores, and if the particle size of the coloring pigment is small, it is thought that it will be washed away over time due to the effects of rain, etc., causing the color of the coating film to change. The average particle size is the D50 value calculated from the volume-based particle size distribution measured by laser diffraction.

[0021] The content of colored pigments, excluding white pigments, is preferably in the range of 0.01 to 1.0% by weight in the coating material. Including colored pigments within this range allows for the formation of a vividly colored coating film, which has good weather resistance. If the content of colored pigments, excluding white pigments, is less than 0.01% by weight, the coating material will hardly be colored. If it is greater than 1.0% by weight, the colored pigments tend to leach out of the coating film, leading to greater color changes over time.

[0022] Furthermore, it is preferable to include titanium dioxide, a white pigment, in the coating material of the present invention in an amount ranging from 0.1 to 20.0% by weight. By including titanium dioxide, the L value can be increased, making it easier to color the coating material in various colors. Furthermore, because titanium dioxide particles are relatively hard and nearly spherical in shape, fewer cracks occur on the surface of the resulting coating, forming a relatively hard coating that can protect the coated object.

[0023] In addition to the raw materials mentioned above, the coating material of the present invention may contain, as needed, various additives commonly used in coating materials, such as synthetic resins, fillers, surfactants used as defoamers, dispersants, and wetting agents, thickeners and leveling agents for adjusting viscosity and viscosity, preservatives, anti-algal agents, antifungal agents, and pH adjusters. Synthetic resins include acrylic resins, silicone resins, acrylic silicone resins, fluororesins, polyurethane resins, styrene resins, epoxy resins, melamine resins, alkyd resins, vinyl chloride resins, vinyl acetate resins, polyester resins, polyether resins, phenolic resins, and ketone resins. These synthetic resins may be used individually or in mixtures of two or more types.

[0024] These synthetic resins are often dispersed in water to form synthetic resin emulsions. These synthetic resin emulsions can be those commonly used in coating material formulations, as long as they are well miscible with alkaline compounds. Fillers include calcium carbonate, kaolin, talc, clay, diatomaceous earth, bentonite, white carbon, glass beads, aluminum hydroxide, magnesium hydroxide, and silica sand.

[0025] The coating material of the present invention, composed of the above-mentioned raw materials, is applied to a substrate (a covering) and forms a coating film after drying and hardening, and it is preferable that the thickness of the coating film is in the range of 100 to 3000 μm. If the coating thickness is less than 100 μm, it may not adequately cover the substrate, and the coated object may not be fully protected. If it is thicker than 3000 μm, the weight of the coating becomes heavy, making efficient application on vertical surfaces difficult, and sagging or cracking may occur during the curing process, resulting in an unsatisfactory coating.

[0026] The coating material of the present invention can be applied to the following types of surfaces: concrete, mortar, ALC panels, siding boards, extruded panels, gypsum boards, slate, ceramics, plastics, wood, stone, tiles, etc., which make up the walls of buildings. Among these coatings, those with a pH in the range of 7 to 14 are preferred. This is because, in the case of coatings mainly composed of geopolymers, if the pH of the substrate is in the range of 7 to 14, the reaction curing at the interface with the substrate proceeds easily, resulting in good adhesion and sufficient strength for the coating film as a whole.

[0027] The coating material of the present invention can be applied using painting tools commonly used in painting work, such as sprayers, paint rollers, and brushes, and can be applied on-site. Furthermore, in the case of line painting where the material is pre-painted in a factory using painting machinery, such as for painted exterior wall panels, painting can also be done using reciprocating sprayers, roll coaters, or curtain flow coaters.

[0028] The coating material of the present invention, constructed in this manner, has the following characteristics. Because it is an inorganic coating material mainly composed of geopolymers consisting of active fillers and alkaline solutions, the resulting coating film has better durability compared to coating films formed from conventional coating materials mainly composed of organic binders, and can protect the covered object.

[0029] Because the coating material of the present invention contains coloring pigments, the coating film formed from this material is colored, and the color remains stable, thus providing aesthetic appeal to the coated object. Furthermore, because the average particle size of the coloring pigments is 0.1 μm or larger, the coloring pigments are less likely to leach out of the coating film, and the colored coating film undergoes less color change over time. Furthermore, because it is primarily composed of geopolymers, it does not exhibit efflorescence compared to inorganic coatings that use cement as a binder, resulting in less color change over time.

[0030] The L value of the active filler contained in the coating material of the present invention is 50 or higher, which allows the coating film formed from this material to have vivid colors and improves the aesthetic appearance of the covered object. More preferably, the L value is 70 or higher, and even more preferably, the L value is 80 or higher, which allows for more vivid colors and further improves the aesthetic appeal of the covering.

[0031] Because the active filler contained in the coating material of the present invention is blast furnace slag, it easily forms a coating film even at room temperature. Therefore, even when applied on-site, a durable coating film is formed, which can protect the covered object. Furthermore, because blast furnace slag is white in color, it is easy to color the coating material, allowing for the formation of brightly colored coatings and improving the aesthetic appeal of the covered object.

[0032] Furthermore, by including titanium dioxide in a range of 0.1 to 20.0% by weight, it is possible to impart various colors to the coating material and form a vividly colored coating film, thereby improving the aesthetic appeal of the covered object. The coating film formed from the coating material of the present invention has a thickness in the range of 100 to 3000 μm, resulting in a durable coating film that can protect the covered object.

[0033] The coating material of the present invention is preferably applied to a coating having a pH in the range of 7 to 14. This is because the reaction curing at the interface with the coating material proceeds easily, adhesion is good, and sufficient strength can be obtained for the coating film as a whole, thus providing better protection for the coating material. [Examples]

[0034] The coating material configured as described above will be explained using a more specific embodiment. The raw materials shown in Table 1 were uniformly mixed to prepare the coating material. Blast furnace slag, fly ash, and silica fume were used as the activated fillers.

[0035] Furthermore, when the L values ​​of the active fillers were measured by placing a colorless, transparent glass plate on top of each active filler and measuring it using a Konica Minolta spectrophotometer (CM-600d), the L value of blast furnace slag was 88, the L value of fly ash was 65, and the L value of silica fume was 77. Colloidal silica with a pH of 11 was used as the alkaline solution.

[0036] The following coloring pigments were used: titanium dioxide (average particle size: 0.3 μm), red iron oxide (average particle size: 0.2 μm), black iron oxide (average particle size: 0.2 μm), and carbon black (average particle size: 0.03 μm). The average particle size is the D50 value calculated from the volume-based particle size distribution measured by laser diffraction. In addition, calcium carbonate was used as a filler, and defoaming agents, dispersants, and thickeners were added as additives.

[0037] [Table 1]

[0038] The prepared coating material was applied to slate boards using a wool roller to create test specimens with a film thickness of approximately 200 μm. The curing properties, appearance, and weather resistance of the coating film were then examined. The results are shown in Table 2. The test specimens were prepared in a laboratory with a temperature of 23°C and a humidity of 50%.

[0039] [Table 2]

[0040] (Curing properties of the coating film) The curability of the coating film was confirmed by touch to check the time until the coating material was applied and the coating film was cured. In Example 3 using silica fume, the curing time was longer compared to the coating materials using blast furnace slag or fly ash, but all the test specimens were cured.

[0041] (Appearance of the coating film) The appearance of the coating film was visually confirmed for the coating film formed from the coating material to evaluate the designability. All the test specimens to which coloring pigments were added formed stable colored coating films. The coating film of Example 2 using fly ash became a slightly dull-colored coating film because the color of the fly ash was gray. In addition, the coating film of Comparative Example 1 to which no coloring pigment was added became a gray coating film with the color of the fly ash, and the color might differ depending on the lot of the fly ash, and a stable-colored coating film was not obtained.

[0042] (Weather resistance of the coating film) The weather resistance of the coating film was measured by exposing the test specimen outdoors at 60 degrees south facing in Gamagori City, Gifu Prefecture for 6 months, and measuring the color difference (ΔE) after 6 months using a spectrophotometer (CM-600d) manufactured by Konica Minolta. This color difference (ΔE) is the color difference in the L * a * b * color system, and ΔL * = L * (reference) - L * (target), Δa * = a * (reference) - a * (target), Δb * = b * (reference) - Δb * (target), and when ΔE = (ΔL *2 + Δa *2 + Δb *2 ) 0.5 is represented, and it is a value representing the change in color before exposure (reference) and after exposure (target).

[0043] For the test specimen of Comparative Example 2 using carbon black as the coloring pigment, the color faded and became white, and the value of ΔE became larger compared to Examples 1 and 4.

Claims

1. A geopolymer coating material comprising a geopolymer composed mainly of an active filler and an alkaline solution, and containing a coloring pigment, wherein the average particle size of the coloring pigment is 0.1 μm or larger.

2. The geopolymer coating material according to claim 1, wherein the L value of the active filler is 50 or more.

3. The geopolymer coating material according to claim 2, wherein the active filler is blast furnace slag.

4. Furthermore, the geopolymer coating material according to claims 1 to 3, wherein it contains titanium dioxide, and the amount of titanium dioxide in the coating material is in the range of 0.1 to 20.0% by weight.

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